some studies on inorganic ion exchangers ^^ based on … · indian j. ghem., 22a, 721, 1983 2. a...
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SOME STUDIES ON INORGANIC ION EXCHANGERS ^^ BASED ON LEAD, ANTIMONY AND SILICON
SXJIVIMARY THESIS SUBMITTED FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY IN CHEMISTRY
YETURU SUNANDAMMA
DEPARTMENT OF CHEMISTRY
ALIGARH MUSLIM UNIVERSITY
ALIGARH
JUNE, 1986
1
SUM4ARY
Some s t u d i e s on i n o r g a n i c i o n e x c h a n g e r s b a s e d on l e a d ,
an t imony and s i l i c o n a r e d e s c r i b e d i n t h e p r e s e n t t h e s i s . I t
c o n t a i n s s i x c h a p t e r s .
I o n exchan^je h a s grown i n t o a p o v ; e r I u l t e c l m i q u e ^'ur
t h e s e p a r a t i o n of m e t a l i o n s and i s one of t h e most i m p o r t a n t
t o o l s f o r t h e a n a l y t i c a l c h e m i s t s . I n o r g a n i c i o n oAclnmc^^rB
owing t o t h e i r r e s i s t a t i c e t o w a r d s h i g h t e m p e r a t u r e s and
i o n i s i n g r a d i a t i o n s have been u s e d f o r t h e s e p a r a t i ^ j n of i o n i c
componen t s i n r a d i o a c t i v e W a s t e s . The e a s e w i t h which t h e
i n o r g a n i c i o n e x c h a n g e r s can be s y n t h e s i z e d and t h e sjv c i f i c
s e l e c t i v i t y e x h i b i t e d by them make t h e s t u d i e s on t h e s e
m a t e r i a l s v e r y i n t e r e s t i x i g .
GIIAPTKR I (IMTRU L'U(JTIOM )
T h i s G h a i t e r i s i n t r o d u c t o r y mm d i s c u s s e s b r i i i i y t h e
r e c e n t s t u d i e s on a r e p r e s e n t a t i v e s y n t h e t i c inoL-ganic ion
e x c h a n g e r , z i r c o n i u m p h o s p h a t e on wh ich e x t e n s i v e r e s e a r c h ht-.s
been c a r r i e d o u t . These s t u d i c ; - i n c l u d e (1) s y n t h e s i s oC
d i f f e r e n t phaf.. s of z i r c o n i u m phos j jha tc . ;uid s i m i l a r iiiiteri-jLls
(2) k i n e t i c s t u d i e s (3) c a t a l y t i c s t u ' j i e s (4) i oGA s t u i l i c s
(5) Mechanism of i o n exchan, e on z i r c o n i u m p h o s p h a t e . Z i r con ium
2
phosphate has been s i n g l e d out Tor d e t a i l e d treai^iaont as i t i s
a ijOOd model compouna f o r t h e o r e t i c a l i j tuo ios . In a d d i t i o i .
some impor t an t a n a l y t i c a l a ] ) p l i c a t i o n s of i n o r g a n i c ion
exchangers based on l e a d , antiraony and s i l i c o n a re suumariscd
i n TaDle 5»
CHAH'ER I I ( A SIMPLi AI^-^UACH TU Tlii; ION iiXOlLUTl E BEHAVloUil
03? GRYbTALLll i. LKAU .^. - xilUiJ ATE Il4 TERiib Ui'' 'i'Hii pYROOifLu.iii
STRUCTURE Oi' iU.TinUiUO AOID)
I n t t i i s Chapter v a r i o u s samples of c r y s t t a l l i n e l e a d
aJitimonate have been s y n t h e s i z e d and s t u d i e d f o r t h e i r ion
exchange p r o p e r t i e s u s ing ant imonic a c i d as one of t h e pa ren t
r e a g e n t s . Among t h e samples p r e p a r e d , t h e one vJith a laole r a t i o
01 /pb = 2.5 "Was taken f o r d e t a i l e d s t u d i e s . The excht^nger i s
monofunctional ii^ n a t u r e and shows good thermal and che.iiical
s t a b i l i t i e s .
Antimonic ac id has r e c e n t l y been shown to hjivc a pyrocb^ore o
s t r u c t u r e . I t i s cubic wi th a 10.565 A . The da t a on l e a d
ant imonate in d i f f e r e n t i o n i c forms a re i d e n t i c a l wi th in
expe r imen ta l e r r o r , as most of t h e H^O" in ant imonic aciei were + 2
r e p l a c e d by Pb wnen l e a d n i t r a t e Was ro f luxed wi th j i t i t iuonic
ac id t o form l e a d ai:itj monate .
Some p r o p e r t i e s such as IR s p e c t r a l da t a of ot l ier ; i n t i -
monate ion exchangers has been compared on t h e ba^.i'J of t h e
3
p y r o c l i l o r c B t r u c t u r e o£ a n t i m o n i c a c i d . D i s t r i b u t i o n
c o e f l ' i c i t n t s ( l v d ) h a v e been measu red f o r v a r i o u s c a t i o n s i n
f o r m i c a c i d sodium f o r m a t e s o l v e n t s y s t e m s . The a n a l y t i c a l
u t i l i t y of tajLS excht \ i iger h a s been d e m o n s t r a t e d by t h e
+ 2 +2 4-2 +2 +2 s e p a r a t i o n of ilg q u a j i t i t a t i v e l y f rom Zn , Go , Gu , Ga , p +2 „ +2 +2 , ,^+2 , . . + 2 „ ,+5 ^ c- +5 Ba , Sr , i-in , j.-'b , Ni , Al and Fe .
GHAl'Tiiii IlKGLitUilAfOGKAPIIIG BKIlAVIuUK OF 31 CATIONS ON SILICA
GEL-G IN r Oxti'IEG AGli>-ACi:TONE SULVENT SYSTE14S)
Thin 1 xyer chromatOii;raphy, t h e s econd moot p o p u l a r method
of s e p a r a t i o n a f t e r IIPLG i s r e c e i v i n g i n c r e a s i n g a t t e n t i o n a s a
s e p a r a t i o n t e c i i n i q u e . I n t h i s C h a p t e r t h e c h r o m a t o g r a p h i c
b e h a v i o u r of 51 m e t a l i o n s h a s been s t u d i e d i n f o r m i c a c i d -
a c e t o n e s o l v e n t s y s t e m s .
The i(^ v a l u e s of m e t a l i o n s i n f o r m i c a c i d - a c e t o n e
( 5 : 5 , "^/v) f o r m i c a c i d - a c e t o n e ( 6 : 4 , " ^ / y ) , f o r m i c a c i d - a c e t o n e
( 8 : 2 , "^/y) f f o r m i c a c i d - a c e t o n e ( 1 0 : 0 0 , "^/y) a r e sum^aarized i n
T a b l e 1 5 . C h r o m a t o g r a p h i c s p e c t r a have been p l o t t e d f o r a l l t h e
s o l v e n t ayLitems anu t h e r e s u l t s show t h a t t h e f o r m i c a c i d - a c e t o n e
s o l v e n t syi,;tcm i i j i;uj Lab le f o r numerous s e p a r a t i o n s . Some of
t h e i m p o r t , a i l s e p a r a t i o n s a c a i e v u d i n t h e s e s y s t e m s a r e a s
f o l l o w s , pb and VO from numerous m e t a l i o n s i n ( 4 : 6 , ^Z-^)
f o r m i c a c i d - a c c t o n e s y s t e m , Tl"*" f rom Tl"^^ ajid Ti"*^ f rom Sn +2
+4- / +^ and Sa i n ( 5 : 5 , "^/v) formic a c i d - a c e t o n e system, La from
U02^ and Or'*''' from Mo and M i n ( 6 : 4 , V v ) formic a c i d -+4 4-3 +3 +2 +2 +2
ace tone system, Ti from Or '^, Fe , Go , Ni and Hg from
Cd"*" in ( 8 : 2 , V y ) fo rmic a c i d - a c e t o n e system, Th"* from U02^
and La"*" , Th"^, Zr**^, Nb"^^, Ti"*^, Ta"^^, Mo"^ and \J"*" from
t h e o t h e r metal i o n s i n ( I O J O O , "^/V) fo rmic a c i d - a c e t o n e system.
CHAPTER IV (STUDIES ON A NiW ADSORBEMT lOW EXCHANGE
MATERIAI ; HYDROUS ANTIMONY SULPHIDE)
Most of t h e work on i n o r g a n i c ion exchangers has been
done on zirconium phosphate type m a t e r i a l s . I t was f i r s t
recognised by Kraus t h a t the sulphides of Cd(I I ) , Ag(I), f e ( I I ) ,
C u ( l l ) , Zn( I I ) , Pb(II) and As(III) have favourable adsorption
p r o p e r t i e s and they can be used as adsorbents for metal ions
which form more inso lub le su lph ides . A survey of l i t e r a t u r e
shows t h a t the sulphides are the l e a s t i nves t iga ted ma te r i a l s .
This Chapter deals with the synthes is and ion exchange p roper t i e s
of hydrous antimony sulphide(HAS) .
The composition r e s u l t s i nd i ca t e tha t the mole r a t i o of
antimony to sulphur i s 1.86. The higher mole r a t i o of lintimony
has been a t t r i b u t e d to the formation of hydrolysed antimony
sulphide due to the change in ac id i ty upon adding the sodium
sulphide solution to the antimony so lu t ion . Hence the decii^nation
Hyd2X)US jintimony Sulphide (HAS) . I n f r a r e d s t u d i e s confirm t h e
above r e s u l t s . Kd v a l u e s f o r some of t h e metal i o n s i n IMti and
t h e i r co r re spond ing pk^ ( - l o g K , K = s o l u b i l i t y p roduc t )
s u l p h i d e s a re given i n Table 1 8 . HAS shows t h e h i g h e s t
+2 p r e f e r e n c e f o r t h e Hg i o n . The a n a l y t i c a l u t i l i t y of t h i s
exchanger has been demons t ra ted by removing an impor t an t +2 p o l l u t i n g ion i . e . Hg from p o l l u t e d watero
CHAPTER V(PRELIMINARY STUDIES ON THE SYNTHESIS QJI'
SOI IE NEVJ INOitGANIG ION EXCHANGEiiS)
The a n a l y t i c a l impor tance of s y n t h e t i c i n o r g a n i c ion
exchangers i n t h e f i e l d s of medic ine , energy r e s o u r c e s recovery
and p o l l u t i o n abatement a re now w e l l known. Heteropoly t u n g s t a t e s
have r e c e n t l y been used as c a t a l y s t s f o r t h e photochemical
r e d u c t i o n of oxygen and w a t e r . Therefore t h e i n v e s t i g a t i o n of
t h e s e m a t e r i a l s has become t h e c u r r e n t f i e l d of r e s e a r c h . In
t h i s Chapter an a t tempt has been made t o s y n t h e s i z e some new
i n o r g a n i c ion exchangers based on some common c a t i o n s which may
prove t o be i n e x p e n s i v e . Some p r e l i m i n a r y s t u d i e s have been
c a r r i e d out on an t imona tes of i ' e ( I I ) and Ag( I ) , Uranyl t u n g s t a t e ,
B a s i c t a n t a l u m s u l p h a t e and Niobium t u n g s t o a r s e n a t e . The
c o n d i t i o n s f o r t h e s y n t h e s i s of t h e s e m a t e r i a l s a r e sumuiai-'izea in
Table 20. The ion exchange c a p a c i t i e s e x h i b i t e d by t h e s e m a t e r i a l s
a r e inqpress ive . The e f f e c t of d i f f e r e n t f a c t o r s such as (1) the
n a t u r e of t h e s t a r t i n g m a t e r i a l s f o r t h e s y n t h e s i s (2) t h e
c o n c e n t r a t i o n of t h e s o l u t i o n s of t h e pa r en t r e a g e n t s (5) mixing
r a t i o s of t h e s o l u t i o n s (4) t h e o r d e r of mixing of t h e pa r en t
r e a g e n t s (5) p r e c i p i t a t i o n pH (6) t h e chemica l s used to maintain
t h e p r e c i p i t a t i o n pH and (5) r e f l u x i n g t h e p r e c i p i t a t e s on the
ion exchange c a p a c i t y of t h e s e i n o r g a n i c ion exchangers has been
d i s c u s s e d .
CHAPTER VI iM Eij'i'UitT AT THE CORRELATION OF Kd VAlUES ».ITH THE BASIC PROPERTIES OE SOI-iE IlJORGAinC ION EXGHMGERS)
I n t h i s Chapter an e f f o r t has been made t o a r r i v e a t a
u s e f u l c o r r e l a t i o n of t h e b a s i c p r o p e r t i e s such as ion exchange
c a p a c i t y , i o n i c r a d i u s , i o n i c charge and atomic number wi th t h e
Kd Values of i n o r g a n i c ion exchangers i n t h e form of s u i t a b l e
p l o t s .
A p l o t of l o g Kd vs atomic number f o r metal i o n s on va r ious
an t imona tes r e v e a l s t h a t t h e Kd v a l u e s depend upon t h e i n t e r a c t i o n
of t h e counte r i o n s wi th t h e anion m a t r i x . I t has a l so been
n o t e d t h a t whi le t h e c r y s t a l l i n e form of l e a d an t imonate shows a
r e g u l a r t r e n d , t h e amorphous one shows an e r r a t i c b e h a v i o u r . I
A p l o t of l o g iLd vs i o n i c r a d i u s r e v e a l s t h a t a s t h e i o n i c r a d i u s
i n c r e a s e s t h e r e i s a r e g u l a r i n c r e a s e i n t h e Kd v a l u e s and t h i s i s
because t h e i o n s a re exchanged a s hydra t ed o n e s . A p l o t of Ion
exchange capacity vs hydrated ion ic r t d i u s shows tha t the ion
exchange capacity decreases as the hydrated ion ic rad ius
increases as the exchange now becomes more d i f i ' i c u l t . An
i n t e r e s t i n g fea ture of the p l o t s of log average Kd vs Charge
on the exchanging ion i s tha t the antimonate of chromium shows
the l a r g e s t JLd va lues f o r metal ions of 2,5 and 4 va lenc ies ,
where as the antimonate of cerium shows the minimum. In
general the re i s an increase in the Kd values with the increase
in the Charge on the exchanging ion .
SOME STUDIES ON INORGANIC ION EXCHANGERS ^"^ BASED ON LEAD, ANTIMONY AND SILICON
THESIS SUBXWtf^D-10^ f H K DEGREE OF
DOCTOR OF WtkOS l^ l+^ fM CHEMISTRY
YETURU SUNANDAMMA
DEPARTMENT OF CHEMISTRY
ALIGARH MUSLIM UNIVERSITY
ALIGARH
JUNE, 1986
^ S E C j ^
il
T3318 I
•
2 1 MAY 1587 I ^ O ^
M.S., Ph. D. (Lrunsiana)
EMERITUS SCIENTIST
Rer- No
CHEMISTRY SECTION Z. K. COLLEGE OF ENCG. & TECH.
ALIGARH MUSLIM UNIVERSITY ALIGARH-2020C1 (INDIA)
Dated.
C E R T I F I C A T E
This is to certify that the work embodied
in this thesis is the original work of the candidate
and is suitable for submission for the award of
Doctor of Philosophy in Chemistry of- the Aligarh
Muslim University, Aligarh.
(MOHSIN QURESHI)
SUPERVISOR
AQMO\<L£DGEi^MMT
I express W deep sense of g r a t i t ude to Professor
Mohsin Qureshi, Emeritus S c i e n t i s t , under •whose guidance
t h i s work has been car r ied out . I am thankful to
Professor A.U.Malik, Chairman, Chemistry Section, Z.H.College
of Engineering and Technology and Professor M.S.Ahmad,
Chairman, Department of Chemistry, Aligarh Muslim Univers i ty ,
Aligarh fo r providing research f a c i l i t i e s .
I am thankful to Dr.K.G.Varshney, Dr.Nairn Fatima,
Dr. Rifaqat A.E.Rao and Dr.AoP.Gupta fo r t h e i r constant
encouragement and fo r the i n t e r e s t they have taken in my vjork.
I am indebted to my col leagues 14r. Nas i r A. Rizvi ,
Mr.Sajid A. Khan, Dr. Anees Ahmad, Mr. ftishi K. Varshney,
Miss Nusrat Iqbal and Miss. Hina Khan fo r t h e i r unfa i l ing
co-opera t ion .
My specia l thanks are here for the Non-teaching staff
of the Chemistry Section, the Typist Mx. M.Nasir Z. Qureshi and
the Ar t i s t Mr. Nadeem Ahmad.
Pinancia l support by the Department of Science and
Technology and the Univers i ty Graats Commission are g ra te fu l ly
acknowledged.
(YETURU SUNAi^IDAi'li'lA)
CONTMTS
Page
i
1 . DEDICATION
2 . ACKNOVyLEDGEi ffiiJT
5 . LIST OP PAPERS PUBIISHED/COlMJlillGATED ^^
4 . LIST OF TABLES iii-iv
5 . LIST OP PIGUHES ^'^^
6 . CHAPTER I
INTRODUCTION 1
REFERENCES 42
7 . CHAPTER I I
A SIflPLE APPROACH TO THE ION EXCHANGE BEHAVIOUR OF CRYSTALLINE LEAD ANTIl'D-NATB IN TERMS OF THE PYROCHLORB STRUCTURE OF ANTIiVJONIC ACID •
INTRODUCTION "
EXPERT IffiNTAL 5®
RESULTS AND DISCUSSION ^^
REFERENCES 88
8 . CHAPTER I I I
CHROIUTOGRAPHIC BEHAVIOUR OF 51 CATIONS ON SILICA GEL-G IN FORMIC ACID-ACETONE SOLVENT SYSTEMS
JNTROIAJCTION 93
EXPERIMENTAL 95
RESULTS AND DISCUSSION 98
REFERENCES ^^8
Page
9 . CHAPTER IV
STUDIES ON A NEVk ADSORBENT ION EXCHjiNGE lUTEBIAL : HYDROUS ANTItDNY SULPHIDE
PHElIMINAaY STUDIES ON THE SYl^THESIS OP SOME NEW INORGANIC ION EXCHANGERS
114 INTRODUCTION
EXPERIMENTAL •'•• ^
RESIXLTS AND DISCUSSION ^^^
REPERENCES ^^"^
1 0 . CHAPTER V
129 INTRODUCTION
BXPERIMNTAL ^^^
RESULTS AND DISCUSSION 138
REEERENGES ^^^
1 1 . CHAPTER YI
AN EPEORT AT THE CORRELATION OE Kd VALUES WITH THE BASIC PROPERTIES OE SOi'IE INO.tGiUaC 150 ION EXCHANGERS
11
LIST Oi?' PUBLI OATIONS/GQMi IUNI CATIONS
1 . S t u d i e s on a new adsorben t ion exchange m a t e r i t a :
Hydrous Antimony Su lph ide .
Mohsin Quresh i , Anek Pa l Gupta and Yeturu Sunandamma
I n d i a n J . Ghem., 22A, 721 , 1983
2 . A simple approach to t h e ion exchange behav iour of c r y s t a l l i n e l e a d ajatimonate i n t e rms of t h e p y r o c t a o r e
s t r u c t u r e of an t imonic a c i d ,
Mohsin Quresh i , Nairn Fat ima aJid Yeturu Sunandamma
Communicated to Reac t ive Polymers(USA) comments have been r e c e i v e d .
5 . Chromatographic behav iour of 31 c a t i o n s on s i l i c a gel-G
i n formic a c i d - a c e t o n e s o l v e n t s y s t e m s .
Mohsin Quresh i , Kr i shna &opal Varshney and Yeturu
Sunan damma. To be communicated.
4 . Some new i n e x p e n s i v e s y n t h e t i c i n o r g a n i c ion exchangers
f o r chemical a n a l y s i s . Mohsin Quresh i , Kr i shna Gopal- Varshney and Yeturu
Sunandamma. To be communicated.
5 . Aa e f f o r t a t t h e c o r r e l a t i o n of d i s t r i b u t i o n c o e f f i c i e n t values(Kd) w i t h t h e b a s i c p r o p e r t i e s of some i n o r g a n i c ion exchange r s .
Mohsin Qureshi and Yeturu Sunandamuia. To be communicated.
i i i
LIST Qg TAHLES
Table 1 C r y s t a l l i n e Zirconium phospha te phases which e x h i b i t ion exchange p r o p e r t i e s .
Table 9 T e n t a t i v e band ass ignments i n t h e IR spectrum of c r y s t a l l i n e l e a d an t imona te ,
Page
3
Table 2 Some of E i senman ' s sequences f o r a l k a l i 21 metal i o n s .
Table 3 A n a l y t i c a l a p p l i c a t i o n s of i n o r g a n i c 28 ion exchangers based on l e a d , antimony and s i l i c o n .
Table 4 S y n t h e s i s of c r y s t a l l i n e l e a d a n t i m o n a t e . 58
Table 5 Ion exchange c a p a c i t i e s (lEC) of c r y s t a l - ^^ l i n e l e a d an t imonate f o r v a r i o u s c a t i o n s .
Table 6 Ef fec t of t e m p e r a t u r e on t h e ion exchange ^^
c a p a c i t y of c r y s t a l l i n e l e a d a n t i m o n a t e .
Table 7 S o l u b i l i t y of c r y s t a l l i n e l e a d a n t i m o n a t e . 72
Table 8 T e n t a t i v e band ass ignments i n t h e IR j . spectrum of c r y s t a l l i n e an t imonic a c i d .
78
Table 10 T e n t a t i v e band ass ignments i n t h e IR ^^ s p e c t r a of an t imonic a c i d and v a r i o u s metal a n t i m o n a t e s .
Table 11 A comparison of d - spac ings f o r niobium 81 an t imonate and an t imonic a c i d .
Table 12 Ed v a l u e s on l e a d an t imonate i n formic 82 ac id -sod ium formate media .
Table 13 S e p a r a t i o n s of metal i o n s on t h e columns 85 of c r y s t a l l i n e l e a d a n t i m o n a t e .
Table 14 X-ray s t u d i e s : Cry s t a l i o g r a p h i c i n d i c e s 07 and l a t t i c e p a r a m e t e r s of l e a d ant imonate in hydrogen and sodium fo rms .
Table 15 Rf v a l u e s of metal i o n s in formic a c i d - 99 ace tone so lven t sy s t ems .
i v
Table 16 Sepa ra t ion of metal i o n s i n fo rmic J^Q3 a c i d - a c e t o n e so lven t sys t ems .
Table 17 T e n t a t i v e band ass ignments i n t h e IR Spectrum of Hydrous itotimony Sulphide 121 (HAS).
Table 18 D i s t r i b u t i o n c o e f f i c i e n t s f o r some metal i o n s i n d e m i n e r a l i s e d wa te r on hydrous 124 antimony s u l p h i d e and pKgp v a l u e s of t h e i r co r r e spond ing s u l p h i d e s .
Table 19 Sepa ra t ion f a c t o r (qSf) of Hg"*" ion w i t h r e s p e c t to o t h e r metal i o n s on hydrous 125 antimony s u l p h i d e in d e m i n e r a l i s e d w a t e r .
Table 20 Exper imenta l c o n d i t i o n s f o r t h e s y n t h e s i s of P e ( I I ) an t imona t e , Ag(I) an t imona te , 139 Uranyl t u n g s t a t e , Bas i c t a n t a l u m s u l p h a t e and Niobium t u a g s t o a r s e n a t e .
V
LIST OJ;' flOURES
Page
Fig, 1 jin idealized portion of a layer of 4 oC-Zirconium phosphate.
+2 Fig. 2 Relative position of Cfu in anhydrous lo Zirconium phosphate showing trigonal coordination.
Fig. 3 Relative position of the [Cu(NH^).] H complex in anhydrous zirconium - • phosphate.
Fig. 4 Idealized structure of mixed-component pillared zirconium phosphate derivatives: ^^ p-phenylene diphosphonate/phosphate.
Fig. 5 Idealized structure of mixed-component pillared zirconium phosphate derivatives: -'• 4-4'-hiphenyl diphosphonate/phosphate.
16 Fig. 6 pH as a function of amount of hydroxide
added for Li+, Na+, K+, Rb+ and Gs+ ions on zirconium phosphate.
Fig. 7 Standard heats of partial exchange as a function of metal ion loading on "" oC-Zirconium phosphate for Li"*", Wa"**, K"*", Rb"*" and Gs"*" ions.
Fig. 8 pH t i t ra t ion curves on crystalline lead antimonate for Li" , Na"*" and K." ions. " 3
Fig. 9 IR spectra of lead antimonate at various 77 temperatures.
Fig. 10 A plot of log Kd Ga+2/Mg+2(e< ,separation 54
factor) for various inorganic ion exchangers.
Figs .11 -15 Plots of Rf vs. atomic number for metal ions in formic acid-acetone solvent 104-108 systems.
Fig.16 Plot of Rf vs. mole fraction of formic acid for 51 metal ions. - ^^
v i
P g ^
P ig . 17 A plo t of log Kd v s . pksp for metal ions on Hydrous Antimony sulphide . 12 3
Figs.18-27 P lo t s of log Kd v s . atomic number fo r metal ions on var ious antimonates. 151-160
F ig . 28 A Plot of log average KdCave.Kd) v s . atomic number fo r metal ions on 161 Various antimonate exchangers.
F i g . 29 A plot of log Kd v s . atomic number fo r a lka l ine ear th metal ions on var ious 162 antimonates and a plot of log average Kd(ave.Kd) v s . atomic number in a group.
Figs.50-39 P l o t s of log Kd v s . ion ic r a d i i fo r 169-178 metal ions on various antimonates.
F i g . 40 A p lo t of log average Kd(ave.Kd) v s . i on ic r a d i i fo r metal ions on var ious 179 antimonate exchangers and a p lo t of log average Kd(ave. Kd) v s . i on ic r a d i i for metal ions in a group.
F i g . 41 A p lo t of log Kd v s . ion ic r a d i i f o r a lka l ine ear th metal ions on var ious ant imonates .
F i g . 43 Plot of log average Kd (ave.Kd) v s . charge on the ion fo r var ious antimonate exchangers.
182
Fig . 4 2 P lo t s of hydrated ionic r a d i i v s . ion , „ -exchange capacity (lEC) fo r a l k a l i and a lka l ine ear th metal ions on various ant imonates.
195
C H A P T E R
1
INTROLUQTION
I n o r g a n i c ion exchangers a r e r e c e i v i n g i n c r e a s i n g
a t t e n t i o n owing t o t h e f a c t t h a t t h e s e m a t e r i a l s a r e
r e s i s t a n t t o hea t and r a d i a t i o n . They can be used f o r t h e
h igh t e m p e r a t u r e s e p a r a t i o n of i o n i c components i n
r a d i o a c t i v e w a s t e s , a s s o l i d e l e c t r o l y t e s and as c a t a l y s t s
[ 1 , 2 ] . The a c i d s a l t s w i th l a y e r e d s t r u c t u r e have been
found t o behave as very good hos t m a t e r i a l s f o r i n t e r c a l a t i n g
Lewis b a s e s [ 2 ] . I n a d d i t i o n t o t h e s e a p p l i c a t i o n s z i rconium
phospha te has been used f o r d e s a l i n a t i o n [ 5 , 4 ] , h y d r o g e n -
oxygen f u e l c e l l s [ 5 - 7 J and f o r use i n a r t i f i c i a l k idneys[8] .
When z i rconium phospha te i s used in conjunc t ion wi th u r e a s e ,
i t has t h e c a p a b i l i t y of removing a l l t h e ammonium i o n s from
t h e h y d r o l y s i s of u r e a d i a l y s e d from blood by e n a b l i n g t h e
c o n t r o l of o t h e r s a l t s i n t h e blood s t r e am.
The i n o r g a n i c ion exchangers may be c l a s s i f i e d
acco rd ing t o Pekarek a s f o l l o w s [ 9 ] .
1• Hydrous ox ides
2» Acid ic s a l t s of m u l t i v a l e n t m e t a l s '
3 . S a l t s of h e t e r o p o l y a c i d s
4« I n s o l u b l e f e r r o c y a n i d e s
5. Synthetic aluminosilicates
6 . Certain other substances e .g . . Synthetic apat i tes ,
sulphides, alkaline earth sulphates .
E a r l i e r work on the chemistry and app l i ca t ions of these
mate r ia l s has been summarised by Afliphlett [ lo] , Pekarek[9] ,
Marinsky[ll] and Vlalton[l2] . According to Marinsky zirconium
phosphates [ZrP] as a group are probably the ion exchangers
most extensively s tud ied . I t i s the re fo re pe r t i nen t to give
the bas ic f ea tu r e s of ZrP as a r ep resen ta t ive of the c lass -2
of the Pekarek c l a s s i f i c a t i o n .
ZrP has been prepared in the form of amorphous and also
in the form of c r y s t a l l i n e ma te r i a l . The composition and the
behaviour of the ge l s depend upon the condi t ions of preparat ion,
The c r y s t a l l i n e zirconium phosphates which exhibi t ion exchange
p r o p e r t i e s have been designated as oC^ )^ /X ^ , £ , ^ '^ , ® , J ,
K e t c . [13-24] . The formulae, the designation and the method
of prepara t ion ar6 summarised in Table-1 .
ZrP has a layered s t ruc tu re and a por t ion of t h i s
s t ruc tu re i s shown in P i g . 1 .
Recent Studies on Zirconium Phosphate
I t i s now worthwhile to summarise more recent s tudies
on ZrP. The following top i c s w i l l be considered.
1, ^ n t h e s i s of d i f fe ren t phases of ZrP
2 . K i n e t i c s t u d i e s
5« C a t a l y t i c s t u d i e s
H EH Ct! pq
P4
W o
o H
6H
pq
o
0 CO
P4
a o ??
a H !2i
8 H
SZ5 H ^^
en CO
o
o H
o (U u <0
«H 0
Pi
0) ra o P o J4
o •H -P a
• H CO o
P H t J
03 H
i o
^ i n i n c o c o c n c r i ^ c v j ^ O O O T - T - T - T - ^ T - - r - c \ J C M o ; j r M O J C v i
^ ^ ^ ^ ^ ^ ^ C M CM
a •H
•H -H o o R5 n5 CVJ
ri o •H
+> cd
P (D ? P
=H O
1:$ o si
S
o cd o •H M o xi Pi 03 O
PH
T o T —
.3 H 0) 5 0
1 ^ f-)
tsj
M =J H 0) «
PM U tS3 I
>-
1
O
tH o rt o
4^ US
H o CQ
O
a
.g H 0) tya P4 M
CS3 a> + j Oj
M j : l d H
ft CQ
«H O 0) si « P4
o • H U
o xl P4 CQ
o xi Pi
-ici Q)
o
rt QJ
H (U M P4 M
t>3
M :3 H
rt
O
o ^
P I 03 O Si P I
nd CU
O
ri 0)
.3 H 0) t;0
P4 (4
!S3
X : i H
CU 04
o o o ^ 1
o o
P4 fH IS3 1 .
V -P
Cd 0 W
o o o o 1
o en CM
P^ M ts) 1
V +> cd 0) W
•xi •H o cd
•p •H * O
CO
• ^ - v
-^ o PM
v ^
.,-^ "^
o ^ fe2J
^ CS3
Si CQ
:^
T S
•H O Cd
•p •H l5
•« td
CO
cd ^
P I
• CM
^-^ •^
O
^ 1: ^ N]
^ CO cd
:3:
o • H CQ
T S - d Cd
T J
%
H •H O
•v
^ W
•rl
A< f-l
t>q
V <D > H o CQ CO
O O o — I o o
+> cd
-^ o P4 l-M
Ti 0) CQ =5
' H
+ O
C\J W 00 • CM
H O
^ tS3
O O
LTV CO
•P Cd
•^ o
tc\ W I d
CQ :s
V I
+ , ^
• 'vi
^ ^ ^~.^
CM H O
? ^3
o o
O l >
+5 Cd
• ^
o
^ T j <D CO
^
+ o
CM w 03 • CM
H O
<g i>q
I
PM P4
t>3 tSJ I I
P4
I
?1 PM J4
NJ I
u 03
I
PM U tsj
I V c Q - > - u > l t > * - « C C D
P4
f-l
I •H
I
CM •
CM II J4
tSl
2
P EH
NJ I
V ':a.
a CM
^OJ
^ ^ "
O CM
w CM
CM CM
O <15 CM X !
W " 00
CM CM CM CM
CO
-^ ^ '^ ft ft AH W W W
?4 tS3 Nl
o ft w tS3
o ft W
2 w tsj
o ft W
(SJ
CM Si
•^ Cd
j ^ i f O ft W
u tS3
CO
- p o
CO • H
-p CQ QJ
+3 O
I d
CO • H H
c3 +3 CO CD
- P o
CM CM
o o ft ft
CM CM
o o ft W
tsj
ft W
cs3
4
Fig.l . An idealised portion of a layer of ©(-zirconium phosphate.
5
4 . ESCA s tud ies
5 . Mechanism of ion exchange on ZrP
1. Synthesis of d i f fe ren t phases of ZrP and s imi la r
ma te r i a l s ; The inorganic ion exchangers belonging to
the c lass of layered inso lub le acid s a l t s of t e t r a v a l e n t metals
may be obtained with two d i f fe ren t s t r u c t u r e s usual ly known
as oC o^ j 3 - s t r u c t u r e s . >f'--Zr(HPO,) p.ZHpO was f i r s t obtained
by Glearfield[25] . Y-^^'^a^^^"' phosphate( ^ - T i P ) was next
prepared by A lbe r t i , iULluli and Kobayashi[26-28] . iU-berti
prepared c r y s t a l l i n e TiP by slow decomposition of t i t an ium
chlorocomplexes in the presence of phosphoric acid[26]» From
the formation of i n t e r c a l a t i o n compounds. X-ray powder
p a t t e r n s , densi ty measurements as well as from comparison with
several acid s a l t s of t e t r a v a l e n t metals i t was concluded that
the c rys t a l s t ruc tu re of Ti(HPO^) P.2H2O synthesized by Albert!
i s analogous to t ha t of Y-Zr(HPO.) 2»2H20.
Alber t i not only s y n t h e s i z e d Y - T i P , but he also
s tudied the hydrogen-aminonium exchange on t h i s material[29] •
As a r e s u l t of i n t e r c a l a t i o n of ammines and other polar mole
- cu l e s in oC-ZrCHPO.)^ and Y-TiCHPO,)^, a s trong evidence was
found fo r the hypothesis tha t the s t r uc tu r e of Y~2ia ter ia l s i s
a layered one. As demonstrated by density measurements the
s t ruc tu re of the Y""J^c3?o-anion i s more compact than the
«>C-macro-anion. I t was also found tha t ammonia was taken up
at a high r a t e from aqueous solut ion vJith the formation of
a half and fu l ly exchanged NH. forms. Thus the use of Y -TiP
in the removal of ammonia or NIL ions from waste so lu t ions or
in kidney machines seems to be p o s s i b l e .
The synthes i s of a new inorganic ion exchanger
ZrHPO, oHPO^ Was repor ted recent ly by Albert i [30] . I t was found
tha t the Zirconium phosphate phosphite possesses a layered
s t ruc tu re s imi la r to tha t of oC-ZrP. I t i s poss ib le tha t ,
phosphate and phosphite groups are homogenously d i s t r i b u t e d
on both s ides of each l aye r , thus the f r e e area associa ted with
each P-OH i s much higher than in oC-Zr(HPO.) 2 .H20.<-Zr HPO. .HPO,
shows promise fo r i n t e r c a l a t i o n and exchange of l a rge ion ic and
polar spec ie s .
2 . Kine t ic s tud ie s ; Kine t ic ion exchange experiments have
been performed by A l b e r t i [ 3 l ] , who showed t h a t i t i s poss ib le
to replace the exchangeable protons present on the surface of
Zr(HP0^)2»H20 mic ro -c rys ta l s with several divalent and t r i v a l e n t
ca t ions without exchanging the inner p ro tons . Large differences
in the separat ion f a c t o r s were observed and t h i s shows tha t the
ZrP c r y s t a l s can be used for i n t e r e s t i n g separa t ions of micro
eimounts of ca t ions by th in l a y e r or column chromatography.
Clearf ie ld determined the k i n e t i c s of gas - so l id reac t ions
in oC-ZrP[32]. He measured the r a t e s of r eac t ions hetveen gaseous
HGl and sodium ion exchanged phases of ©C-ZrP. He found that
the r eac t i ons are diffusion cont ro l led and he determined
the diffusion coe f f i c i en t s in the temperature range of 25°G-
220 C. The dehydrated phases of ©C-ZrP are capable of
undergoing s o l i d - s o l i d ion exchange. Heating a mixture of
metal hal ide and oC-ZrP r e s u l t s in the displacement of protons
by metal ha l ide ca t ions as shown by the following equation.
Zx{KP0^)2+ XNaCl(s) = ^^B^2-X^^^A^ 2'^ ^ HGl(g) - ( e q . 1 ) .
¥hen t h i s reac t ion i s ca r r ied out above 200 0, i n i t i a l l y
Zr Nao,2^i ,8^-^^4^ 2 ^^^ l a t e r on Zr ^^,Q^] ,2^'^^A^ 2 ^^^ formed.
The hydrogen in ©C-ZrP i s covalently bonded to the phosphate
oxygen [35,34] . Thus the covalent bond must breal^ and H jumps
occur as the reac t ion proceeds. The r eac t ions were found to
be r e v e r s i b l e . Contact of the dehydrated Na ion exchanged
phases with gaseous HCl r e s u l t s in the formation of NaCl which
deposi t s on the surface of t he c r y s t a l s . This i n d i c a t e s tha t
the diffusion processes must occur as the reac t ion proceeds
and tha t these compounds behave as so l id ion conductors.
Indeed a membrane prepared from Zr(NaPO.)p was shown to add in
t ha t fashion in a sodium-sulphur bat tery[35] .
3 . Ca ta ly t i c s t ud i e s : In recent years the re has been
increased i n t e r e s t in proton conduction in so l id s in view of
poss ib le p r a c t i c a l a p p l i c a t i o n s . In p a r t i c u l a r , the recent
development of new c a t a l y s t s such as Sr-doped LaCoO^, which
8
at high temperatures operates b e t t e r than platinum black for
the reduction of oxygen by hydrogen, opens new prospects for
the app l ica t ion of proton conductors in fuel c e l l s operat ing
at temperatures 1 50*^-300^0[36j . Several orgajaic and inorganic
compounds have been examined, but fo r most of them, conducti-
v i t i e s of l e s s than lo" Xi-cm" at 25 C were found, i 'ast
proton conduction with conduc t iv i t i e s g rea te r than 10 A. cm
have been observed in r e l a t i v e l y few compounds. Typical
examples are percl i lor ic acid monohydrate, hydrogen uranylphosphate
t e t r a h y d r a t e , antimonic acid, phosphomolybdic acid,phosphotungstic
acid and inso lub le acid s a l t s of t e t r a v a l e n t meta ls . Albert i
determined the conduc t iv i t i e s of V-bydrogen t i t an ium phosphate
dihydrate and of anhydrous Y~Tip[37] . I t was found tha t the
anhydrous compounds have more conduc t iv i t i e s ( cr-300 G = 10 -
10 n cm ) than those of the corresponding hydrated ones
( d-25°0 = 10"^ - 10"^ n cm"'').
The heterogenizat ion of homogenous c a t a l y s t s i s an area
of in tense current i n t e r e s t [38,39] • Recently bulky complexes
have been incorporated between the l a y e r s of smectite clay,
h e c t o r i t e by an ion exchange process and these products have
exhibi ted i n t e r e s t i n g c a t a l y t i c behav iour [40 ,4 l j .
The ion exchange method of ca ta lys t immobilization on
layered compounds i s simple when compared to the procedures
required for the attachment of complexes to polymers. The
a t t r a c t i v e n e s s of the method i s fu r the r increased by providing
temperature- and so lven t - s t ab le inorganic layered exchcmgers
of known s t r u c t u r e s as suppor ts . The group IVB phosphates
form layered compounds of two types , those with a r e l a t i v e l y o
small i n t e r l aye r spacing ( ' ' ^ 7 . 6 A ) , the so ca l led ^C-type and
another with a l a r g e r i n t e r l a y e r spacing ('->-12A), or Y - t y p e .
oC -ZrP i s the best known of the group. I t ' s ion exchange
p rope r t i e s have been examined in de ta i l [42-44] and in the
hydrogen form i t i s known to be an acid ca ta lys t [4 5,46] ,
Clear f ie ld prepared complexes and cat ions supported on the
surface a;nd between the l a y e r s of ZrP[47] • They found tha t
Gu(II)-aquo and Gu(II)-ammine complexes were formed on the
layered inorganic ion exchaziger oC-ZrP (F ig s . 2&3) , The semi-
c r y s t a l l i n e and the c r y s t a l l i n e oC-ZrP supports appeared to
provide s imi la r environments for Gu(I I ) . The Gu(II) species
are r i g id ly f ixed at spec i f i c s i t e s and unlike the case of Cu(II)
on the amorphous support, the e f fec t s of rapid tumbling at room
temperature are not observed in the ESR.
Metals dispersed on supports represent an important
c l a s s of c a t a l y s t s . They are general ly prepared by impregnating
the support with a s a l t solut ion or ion exchanging the required
Cation onto the surface followed by reduction' with hydrogen at
elevated temperatures[48,49] . The nature of the r e su l t an t
metal d ispers ions s t rongly depends upon the experimental
condi t ions . In many ins tances the mechanism of the reduction
react ion i s in doubt and the na ture of t he dispersed metal
.10
Fig. Z . Relative position of Cu^'''in anhydrous zirconium phosphate showing trigonal coordination.
11
Fig. 3 . Relative position of the CCu{NH 3)4^ ^* complex in anhydrous zirconium phosphate.
12
poorly charac te r ized . This i s espec ia l ly t r ue of cation
reduct ions in zeo l i t es [50] . Therefore the study of a simple
ion exchange system in which f a c i l e reduction to metals occurs
might prove to be useful in shedding l i g h t on these quest ions .
In t h i s connection the hydrogen reduction of ce r t a in cat ions
on the ion exchanger «<.-ZrP i s i n t e r e s t i n g .
Cu(II) exchanged ZrP(eq.2) exh ib i t s high s e l e c t i v i t y
fo r the a i r oxidat ion of carbon monoxide[51j and the oxidat ive
hydrogenation of cyclohexene[52] .
Zr(HP04)2.H20+Cu'^^(aq) — ZrGuCPO^) 2.4H20+2H'^(aq) - (eq.2)
However, in the absence of oxygen, cyclohexene reduces
Gu to Cu and the Gu metal forms a reddish brown coating on
the surface of the ZrP. This reduction process i s accompanied
by a decrease in c a t a l y t i c a c t i v i t y fo r oxidat ive dehydrogenation,
No copper remains i n s ide the exchanger, because the X-ray
p a t t e r n s reveal only the presence of ZrCHPO^)^ along with the
copper[53,54] .
When the f reshly reduced so l id s are allowed to stand in + 2
a i r , reoxidat ion of the metal on the surface to Gu followed +2
by the diffusion of the Cu ions back in to the exchanger takes +2 p l ace . The reduct ion of Gu by hydrogen in Cu-exchanged
eC-ZrP, ZrGu(PO.)p has been found to proceed in two stages by
Glea r f i e ld [55 j . Below about 150 t o r r the product i s ZrGu(P0^)2
13
which in turn reacts further with hydrogen above hydrogen
pressures of 150 to r r to yield metal and "Y-^rP.
Supported metals are widely used as ca ta lys t s . Metal
i s usually introduced into the support as cation ei ther from
aqueous solutions or from suspensions by one of the several
processes such as impregnation, ion exchange, deposition or
co-precipitation followed by drying and hydrogen reduction.
Such catalysts which contain very sm^ill metal c ry s t a l l i t e s
have certain definite advantages over the bulk metals v/hich
can be in the form of films, wires or powders because the high
dispersion of the metal leads to a high surface area and to
increased resistance to s in ter ing. However, the dispersion of
metal par t ic les and the act ivi ty of catalyst strongly depend
on conditions under which the ca ta lys ts have been prepared and
on the par t icular support adopted[56] • Many efforts have been
made to develop finely dispersed metal par t i c les by reduction
of t rans i t ion metal ions in zeoli tes[50,57]• The possibi l i ty
of these catalysts being used as highly active and/or
bifunctional catalysts makes t h i s work very in te res t ing . Kinetic
and physico-chemical studies have been reported on the formation
of metal par t i c les in zeolites[58-6o] . Heverthless incomplete
characterization i s found in t h i s case owing to the l imitat ions
of analytical methods employed.
14
There i s t h e o r e t i c a l aJid p r a c t i c a l i n t e r e s t in studying
the redox behaviour oi t r a n s i t i o n metal ions in zirconium
phosphates. They iorm synthe t ic hydro^ien containing anaLOtjuey
of clays and possess cages akin to those of z e o l i t e s .
Therefore a f t e r studying the hydrogen reduction of Cu-
exchanged oC-ZrP, Clear f ie ld s tudied the hydrogen reduction
of Ag(l)-exchanged <<,-ZrP[6l] . He found tha t the reduction
proceeds under r e l a t i v e l y mild condi t ions . The time dependence
of the percentage of the Ag ions reduced in t h i s react ion i s
always expressed by an S-shaped curve v/ith a maximum react ion
r a t e at about ^^% conversion.
Clear f ie ld s tudied the decomposition of methyl alcohol
catalysed by ©C-Zr-and oC-Ti phosphates and t h e i r organic
der iva t ives[62] . The i dea l i s ed s t r u c t u r e s of mixed component
p i l l a r e d ZrP de r iva t i ve s are given in i' 'igs. 4 & 5. Dimethyl-
e ther Was found to be the precursor fo r hyurocarbon formation.
However, strong a c i d i t i e s of the phosphate compounds enhance
methane lbrmation. The phenyl group bridged de r iva t ives were
found to have a remarkably higher c a t a l y t i c a c t i v i t y and
s e l e c t i v i t i e s fo r the conversion of methanol to low molecular
weight hydrocarbons. These p i l l a r e d compounds were found to
provide pore s t ruc tu re for shape s e l e c t i v e products .
Orthophosphates of aluminium and boron are knov/n to
ca ta lyse r eac t ions such as dehydration, isomcrizat ion and
15
• Zr
• C
o P
o 0
Fig.4-Idealised structure of mixed-component pillared zirconium d«rivatives:p-phenylenediphosphonate/ phosphate.
• Zr
• C
o P
o 0
Fi^ . 5-Idealised structure of mixed-component pillared zirconium derivatives: 4 ,4 - biphenyldiphosphonate / phosphate.
16
dehydrogenation[63J . The c a t a l y t i c a c t i v i t y of these compounds
stems from t h e i r ac id ic nature and a great deal of effor t has
been expended in characterizing: the ac t ive s i t e s . In contrai'-t
very l i t t l e i s known about the ac id ic p rope r t i e s of the yrouj)
IVB orthophosphates of general formula M. (HPO^)p. These
compounds have layered s t r u c t u r e s anu behave as ion exchangers
[64] . Th e i r ion exchange behaviour does not depend upon the
pK of the contained protons but i s governed more by the
i n t e r l a y e r dis tance and the geometry of the f ixed groups[45,64] .
However, these compounus do exhibi t c a t a l y t i c a c t i v i t y e i the r
in the hydrogen or in the cation exchanged forms. Therefore
i t i s of i n t e r e s t to explore the acid s i t e s in these compounas.
Hat tor i et al[65) employing the butyl amine t i t r a t i o n
method, determined tha t Zr(HPO^)p contained both weak and strong
acid s i t e s and tha t Brji(nsted acid s i t e s were responsible for
the dehy'..ration of 1-Butanol. Clearf ie ld and Thakur[4 5]
confirmed the d i s t r i b u t i o n of acid s i t e s found by Hat tor i and
showed tha t the r a t e of dehydration of cyclohexanol was
d i r ec t l y propor t ional to the number of P-OH groups on the
su r face[66] . This r a t e deviated from l i n e a r i t y only for
c a t a l y s t s with low surface a r e a s .
<=<-Tip i s isomorphous with^C-ZrP and also exh ib i t s
s imi la r ionexchange behaviour and ac id i c p rone r t i e s in i t ' s
c a t a l y t i c behaviour. Therefore, Clenrf ie ld and i''riaiicza
prepared crys ta l l iz ie oC-TiP and sol id so lu t ions of Ti-Zr
phosphates and exaujj_ni. d t h e i r a c t i v i t y in the deiiydration oil
17
cyclohexane[67] . The c<.-phaGes were found to iooe one mole
of water at s l i g h t l y above 100°G and convert to ^ - p h a s e .
A second r e v e r s i b l e phase change to form f^-^hase occurs
at about 250°G while condensation of the hydrogenphosphate
groups takes place from 300 -400 0. lohen suf f ic ien t OH
groups are l o s t , the r^-phases do not rever t to ^ - p h a s e s on
cooling. However, the alcohol dehydration reac t ion catalysed
by the r\ -phases apparently r e s t o r e s su f f ic ien t hyuroxyl
groups to allow the c a t a l y s t s to reform the low teapera turc
C-ph.ases. There seems to be no co r re l a t ion of c a t a l y t i c
a c t i v i t y with e i t h e r the t i t an ium content of the ca ta lys t
or t h e i r surface a r ea s . Hov.'ever, a l l of them were founa to
be more r eac t ive than «<,-ZrP.
4 . ESCA Studies; A knowledge of chemical and physical
p rope r t i e s on the surface of an ion exchanger i s very importfint
since several such as c a t a l y t i c a c t i v i t y , ion exchange of la rge
cat ions or acid-base r eac t ions with l a rge basic molecules
strongly depend on the surface ion exchange groups, i'urtheriuore
a kaowledge ox d i s t r i b u t i o n of charge density on the surface
or in the bulk as well as of the eventual presence of a i f ferent
p a r t i c u l a r s i t e s \.itli d i f ferent e l t . c t r o s t a t i c po ten t ia l ; , i s
also importai^t in order to understand the ion exchjuigc mechaniGm
18
and ion ic tr^uicport [68] . 'I'he EUGA technique ir; p a r t i c u l a r l y
su i t ab le for obtainin^s iniormation on the chcuiical s t a t e oi
the surface of the c r y s t a l s anci of p rope r t i e s r e l a t ed to the
charge d i s t r i b u t i o n in the ne tvork . ^Uberti has carx-ied out
an i n t e r e s t i n g study of mic ro -c rys t a l l i ne oC-and ^ - Z r acid
phosphates by the EbGA technique[26j . He found tha t the
binding energies of zirconium and phosphorus e l ec t rons in
ZrP are s l i gh t l y higher thaji those reported for zirconium
de r iva t ives and t r i v n l e n t metal phosphates indicatin^; a
s t ronger po la r i za t ion of Zr-0 and P-0 bonds.
In h i s l a t e r s tud ies Albert i deterLiinod JJ)SGA spectra of
Zr(lV) and Ti(IV) acid phosphates in d i f ferent crystrJ-l ine
phases [69] . He found tha t two types of molecular o r b i t a l s
are mainly involved. One i s r e l a t e d to P-0 bonds and i t i s
affected by the c r y s t a l l i n e phase and the other r e l a t eu to
M(IV)-0 bonds i s l e s s sens i t ive to the c r y s t a l l i n e environment,
5 . Mechanism of Ion exchanr.e on ZrP; Ko other aspect of
ion exchange on ZrP has been soudieu more thoroughly thfan the
mechanism of ion exchange. In fac t Glearf ie ld and co-\.orliers
have published more than 55 papers on the d i f ferent asuocts
of the mechanism of ion exchange on ZrP. I t i s not poss ible
to summarize a l l the work repor tea by them and by other
19
co-'WorkerSo However, the more s ign i f i can t f ea tu re s w i l l be
presented in the following pages.
ZrP i s e i t h e r in the gel form (amorphous) or in the
c r y s t a l l i n e form (oc^ p,^Y, ^ J^ , t ,'^ , 6 , l , k ® ^ ° ' ) •
The mechanistic s tud ies of Clear f ie ld are mostly on the
°C-phase . I t i s the re fore proposed to present the basic
f ea tu r e s of t h e i r work f i r s t on amorphoun(gel ) ZrP, then
on oC~2rP and f i n a l l y on Y~2rP.
Eisenman has shown[TO] tha t the spec i f i c i t y \/hich an
anionic group containing fixed s i t e s exh ib i t s fo r a l k a l i
metal ions in aqueous solut ion can be accounted for solely
in terms of hydration and e l e c t r o s t a t i c ion bin (tin energ ies .
He assumes tha t the ca t ion ic and the anionic s i t e s form ion-pa i r s
with no Water in terposed between the ca t ions and the s i t e s .
Thus i f a cation exchanger i s placed in an aqueous solution of + +
two ca t ions A and B , the preference of the exchanger fo r ion + +
A or B depends on whether the difference in hydration free
energies or t h e i r e l e c t r o s t a t i c energies of i n t e r a c t i o n v;ith
the f ixed anion exchange s i t e s predominates. For the case of
a f ixed grouping of low f i e l d s t rength (Large r a d i i of the
f ixed anions) , the f i r s t term predominates giving a s e l e c t i v i t y
sequence of Gs > Rb > K > i a > Li . For a f ixed grouping
of high f i e l d streiigth( small r a d i i of the anions) the
e l e c t r o s t a t i c energy term w i l l be more iupor tant tnan tae
20
hydration f ree ener£^ term. Thia r e s u l t s in a completely
reversed aiJ-'inity sequence, i . e . , Li > Ka > I > ill >Gs .
By varying; the f i e l d Btrent;th(the rad ius of the anion)
Eisenman was able to j^)rcuict that cation exchraiigers should
exhibi t eleven sequences of preference for alkrJ.i motal ions
out of a t o t a l poss ib le 120 sequences. Some of the Eisenman's
sequences are ([jivon in Table 2.
Clearf ie ld and Kullber^^ studied the thermodynamics of
a l k a l i metal ion exchantje on amorphous ZrP over a wide load in j
range[^71J « S e l e c t i v i t i e s for the amomhous exohnnser i;eve
i n i t i a l l y Cs'''> Rb"*'> K' > na''"> L i t This soT-ics changed with
loadings u n t i l complete reversa l to the s e r i e s Li >iJ:i > xv >
Rb > Us Was observed at high l o a d s .
+ 2 r -I
the a lka l ine ear th metals and Cu ionsl_72j . In both case!
Glearf ie lu has studied the ion exchange of oC-ZrP with
iS
i r r e v e r s i b l e exchange was no t i ced . This i s probably due to
s i t e b inding.
Direct measurement of thermodynaiJiic qu^tntitlerj as a
function of cryL;tal l ini ty and loading i s iraportarib in
understanding the ion exchange process atid v/ere carri ' ju out b ,
Glearfield[73f74] . For the ion exchange reac t ion the observt,d
en t ropies Z^ o can be divided in to twu terms as
where, (S - S ) i s the difference in en t ropies of the
exchanging ions and^2:^S represen t s the entropy aif ference
21
CO
o H
0 o
D
m
H H
M W
H
o
o
B
3 CO H
o
P—4
0) H
EH
> u 0)
ra
o O
o
• p •rl > •ri
o
H 0) CO
+ Hi A
+
A +
A +
A + o
+ + + •H -H -rH H) HJ (^
A A A + + + oJ ra 01
A A A
+ + + O 13 A ^
+ +
A A + +
M M
A +
A +
+ + ra ra o o A A + + • H rQ
Hi «
A A + +
A A + +
A A + +
P4 M
+ o A
+
A +^
+ CQ
O
A + Pi
M •H Hi
+ ra o
A +
A + M A + a)
A A + +
I25 ^25
+ A
Hi
22
•between the cat ion and hydrogen ion forms of the exchanger,
i . e . , 2: 3 r e f l e c t s changes in the hydration of the exchanger
and difference in the l a t t i c e d i s t o r t i o n of the tv/o forms of
the exchanger.
Clearf ie ld studied[75] the Wo -E exchange and found
tha t (Sj° - SJJ) = 16.5 eu. They fu r the r found tha t Rb" - H"
exchange react ion on c r y s t a l l i n e ©C-ZrP up to 755 of exchange
i s accompanied by an entropy chatige of -36.4 eu. i'or most
c r y s t a l l i n e exchangers Clearf ie ld found tha t the react ion i s
exothermic \vith v i r t u a l l y constant heat changes up to TSJ** BJo
load ing . In the case of nearly amorphous exchanger the
reac t ion i s i n i t i a l l y exothenuic but then the heat function
passes through a broad maximum and becomes progress ively more
endothermic.
Clear f ie ld then studied the Ag ion exchange foroC-ZrP
[76] • Ag ion i s in termedia te in s ize to Na and K ions
and has a hydration number about equal to tha t of Na i o n s .
However, the water molecules are somewhat more strongly bound.
Clearf ie ld found tha t Ag ion exchange f o r < - Z r P as remarkable
fo r the following reasons .
1. Unlike a l k a l i metal ca t ions only a s ingle phase i s
formed over the e n t i r e range of Ag"*" ion loadin:;o
+ 2. Ag ion exh ib i t s a hi,:';h aJTfinity f o r o C - Z r P . Thus the
Ag ion i s more highly prefer red than any of the a l k a l i
metal c a t i o n s .
23
Ti t ra t ion curves of c r y s t a l l i n e acia sal^^J ol t e t r ava l en t
metals shovj a decrease in pH oi the supernatant solut ion with an
inc reas ing addit ion of laetal hydroxide. This i s a very unusual
phenomenon for common ion exchangers, but as i i lber t i showed i t i s
qu i te general for inorganic ion exchangers with a layered
s t ruc ture[77] «. Por a d i s t i n c t minimum in a t i t r a t i o n curve three
condi t ions are necessa ry .
1 . High ac t iva t ion energy fo r H /-.+ exchange.
2. i'ormation of so l id solut ion having high M-contcnt.
3 . Formation of a phase with a l a rge i n t e r l a y e r distajace
in the external p a r t s of the c r y s t a l s .
Some of the bas ic f ea tu r e s of the mechanism of exchange
have been recent ly summarised by Clearf ield[78] and they are
presented below.
©C-ZrP has a layered s t r u c t u r e . Each l a y e r cons i s t s of
zirconium atoms ly ing very near ly in a plane aJid bridged
through phosphate groups, loca ted a l t e r n a t i v e l y above and below
the p lane . Three oxygen atoms of each phosphate group are
bonded to th ree metal atoms composing a t r ian ig le . The fourth
oxygen atom po in t s aWay from the l aye r and bonds to a hydrogen
atom. The pacMng of the l aye r "is such as to c rea te the
c a v i t i e s that are connected by openings. A water molecule
s i t s in the centre of each cav i ty . There i s one such cavity for
<<.-ZrP formula in the c r y s t a l . The ion exchange behaviour of
oC-ZrP i s conditioned by two f ea tu re s oi^ i t s s t ruc tu re ; the
24
s i t e oi' the openings in to the cav i t i co ahd the \^eai- Turci'-d
holding- the l a y e r s toge the r . The l;ii'|.'jeGt ion tha t c;iii
diffuse unobstructed in to the c a v i t i e s has a diaiuetcr of 0 .L .1. A,
2.61A« Thus Li , Na , K ions do exchan^;c in acic soLation + +
but Rb and Gs ions do n o t . The raechanisia of exchant:;e the re fo re i s probably the followin^j.
At the surface of the c r y s t a l , the hydrated cation {jives
up most of i t s vJater and diffuses i n to the cavity as e i t he r
an unhydrated or atraost a p a r t i a l l y hydrated species replacin^^
a phosphate proton. The i n i t i a l process may be followed b/
diffusion of v/ater molecules in to the c rys ta l l a t t i c e and
subsequent rehydrat ion of the ca t i ons . This w i l l lead to an
increase in the interl;%yer dis tance and the formation of a
new phase. ALkali metal ion exchange on ©C-ZrP i s unique
towards each ion and does not depend upon the a c t i v i t y of
p ro tons . The phases formed depend upon the solution composition
and upon the way in which the exchanger cati accommodate the
d i f fe ren t ca t ions in the c a v i t i e s . For the exchati^;e on the
amorphous ZrP smoothly curved isotherms and enthalpy functions
were observed, supporting the view tha t the exchang s i t e s are
of continuously varying s i z e . In cont ras t exchange on crys ta l
- l i n e oC-ZrP gives r e c t i l i n e a r isotherms and enthalpy curves
cons is t ing of l i n e a r p a r t s of d i f fe ren t slopes which r e f l e c t s
the phase t r a n s i t i o n s occurrin{'; upon exchtingo and also the
25
uniformity of the exchange s i t e s within each phase
(Pigsc 6 & 7 ) .
Clearf ie ld and Garces[79] synthesized the "Y-ZrP v:ith an o
i n t e r l a y e r spacing of 12.2 A and a composition of Zr(Hi^O. )p . They examined the ion exchange of Li , Na , K , Rh and Gs
+ + ions . Li and Na ions y ie lded r eve r s ib l e t i t r a t i o n curves
+ + but K and Rb did n o t .
Zirconium phosphate is^-agoud laouel compound fur
t h e o r e t i c a l s t u d i e s . However, i t i s des i rab le to develop neiJ
inexpensive inorgjinic ion exchangers. Hence ion exchangers
based on some common elements such as Pb, Sb and Si provide an
a t t r a c t i v e a l t e r n a t i v e . The a n a l y t i c a l app l i ca t ions of
inorganic ion exchangers based on Pb, Sb and Si are given in
Table 3 . Since s i l i c a i s the simplest of the s i l i con-based
inorganic ion exchangers and th in l aye r chromatography i s a
simple separat ion technique, only the TLG on s i l i c a gel of
inorganic compounds has been included in t h i s Table, The
foregoing l i t e r a t u r e shov7s tha t very l i t t l e \.'ork has been
done on c r y s t a l l i n e lead antimonate and antimony sulphide as
inorganic ion exchangers. There i s only one study on the TLG
of cat ions in Formic acid-acetone systems oh s i l i c a g e l . In
t h i s work only th ree systems have been studied and no separat ions
have been repor ted . The present work was there fore undertaken
to study the ion exchange behaviour of c r y s t a l l i n e lead
antimonate and antimony sulphide and to develop the foriflio
acid-acetone systems for the TLG separat ion of ca t i ons . m
26
1 2 3 4 5 6 7 meq 0H7g a-ZrP
Fig.6.pH as a function of amount of hydroxide added for Li' 'Na' K"*' Rb'*"and Cs"*" ions;Zirconium phosphate.
27
0.8 1.0 • 0.4 0.6
Fig. 7. Standard heats of partial exchange as a function of metal ion loading on a -ZrP fo r Li"*", Na-'K'"Rb"*'andCs+.
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effort has also been made for the synbheLiis or couc ncvj
inorganic ion exchciigers and for the corrcln.tion o± the ion
exchange p rope r t i e s of come antimon;Ltes. 'fhis approach has
been developed in the follov/in^^- chaptorfj.
42
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Sep. Scio Techno l . , 14, 355, 1979.
140. Abe. Me; Chem.Let t . , 56 I -64 , 1979.
1 4 1 . Abe, Mo and K a s a i , K.
S e p . B c i . T e c h n o l . , 14 , 895, 1979.
C H ^ P T E R - I l
57
QflY ST ALLUDE LEAU AX' 'TII DIUTE Hi TERi-IS O-b' TIIE PYROGHLOiiE aTRUGTUilE OF AI4TIiMlIQ ACID
In r e c e n t years s t u d i e s on inor^-ojiic ion exchancerc have
a t t r a c t e d much a t t e n t i o n owing t o t h e i r widespread a p p l i c a t i o n s
i n medic ina l aiid envi ronmenta l r i e l d s [ l - 4 ] . I n o r g a n i c ion
exchangers a re s u p e r i o r t o orgai i ic r e s i n s because o! t h e i r easy
s y n t h e s i s , h igh s e l e c t i v i t y and r e s i s t j ^ i c e t o hea t said
r a d i a t i o n s .
Zirconium phospha te s a r e probably t h e most e x t e n s i v e l y
s t u d i e d s y n t h e t i c i n o r g a n i c ion exchangers [5] . I t "v-jas shown
by Kraus[6] t h a t z i rconium ajit imonate has unusual s e l e c t i v i t i e s
towards a l k a l i met.'vl.s, a l k a l i n e e a r t h me ta l s and r a r e e a r t h s
as compared t o z i rcon ium phospha te , z i rconium t u n g s t a t e and
z i r con ium molybdate . VJe have t h e r e f o r e been i n t e r e s t e d in a
s y s t e m a t i c study of v a r i o u s i n s o l u b l e axitiinonates as ion
exchange r s .
Antimonates of p e n t a v a l e n t [7-9] , t e t r a v a l e n t [10-1 5] ,
t r i v a l e n t [1 6-18] and d i v a l e n t [1 9, 20] m e t a l s have been syn thes i zed
and t h e i r ion excha^ige p r o p e r t i e s have been i n v e s t i g a t e d , ll 'iobiun
an t imonate[7] s y n t h e s i z e d a t room t empora tu re vras amorphous but
a c r y s t a l l i n e produc t Was o b t a i n e d when t h e m a t e r i a l was r e f luxed
58
f o r s e v e r a l hours wi th t h e mother l i q u o r , Antimonic ac id i n
v a r i o u s forms has a l s o been s y n t h e s i z e d as on ino rga t i i c ion
exchanger [ 2 1 - 2 6 ] . I t was observed t h a t t h e c r y s t a l l i n e form
of an t imonic ac id o b t a i n e d ( j rea t ly depends not up on t h e type
of antimony compound t aken as t h e s t a r t i n g m a t e r i a l but on t h e
t e m p e r a t u r e of c r y s t a l l i z a t i o n [ 2 3 ] .
P r e l im ina ry s t u d i e s showed t h a t s i l v e r an t imona te could
be o b t a i n e d only in t h e form of a powder. The mercury ant imonate
could no t be c r y s t a l l i z e d [ 2 7 ] o I t was cons ide red t h e r e f o r e
wor thwhi le t o i n v e s t i g a t e t h e ion exchange behav iour of
c r y s t a l l i n e l e a d a n t i m o n a t e . E a r l i e r s t u d i e s showed t h a t
amorphous l e a d an t imonate was not s t a b l e i n minera l aGids[20] •
Pormic a c i d was t h e r e f o r e chosen f o r t h e s e s t u d i e s o For.iiic
ac id i s ail unusual a c i d i n laany ways. I t i s s u f f i c i e n t l y a c i d i c
t o p reven t the- h y d r o l y s i s of s a l t s ( p k = 3.75) r.ind y e t a t t h e
same t ime i t i s noi; s u f f i c i e n t l y a c i d i c to d i s s o l v e t h e inorgfmic
ion exchangers s i g n i f i c a n t l y . I t ' s r educ ing p r o p e r t i e s do not
permit t h e o x i d a t i o n of c a t i o n s dur ing t h e a n a l y s i s . I t i s
t h e r e f o r e s u r p r i s i n g t h a t very fev/ s t u d i e s have been r e p o r t e d
on the behav iour of c a t i o n s i n t h i s medium[28-34] o
E^PEiai-MlTAb
Keais:ents;
Lead n i t r a t e (BL)H, P o o l ) , po tass ium py roan t imona tc ( r t i edc l ,
Germany), DUVEX 50W XB(Ma ) were used f o r t h e s y n t h e s i s of l e a d
59
ajitimonate. All o ther rea^^entrj used wore ol Annlaii ij^rade.
Apparatus;
Spectropliotoiaetric, pil-metric, X-ray and In ! r a red s tua ios
were ca r r i ed out with a Bausch L Lomb Spcctronic-20 Colo i-inetcr,
axid Elico pli meter (Model L^-10), P h i l i p s X-ray Unit imd a
Perkin-Eliaer spectrophotoueter(xiOdcl 6 21) r e s p e c t i v e l y .
Synthesis;
Antimonic aciu Wac prepared by passin£; OoOlH aqueous
solut ion oi potassium pyroantimonate through a colujin oi
DOWEX 50lfJX8(H ) . Lead ajitimonate samples were prepared by
adding O.OIH metal ion solut ion to a OoOlH solut ion of antimonic
acid in the volume r a t i o 1;2 respec t ive ly with constant s t i r r i n , , .
The samples were prepared at varying pll values I'rom 2 to 4 .
The p r e c i p i t a t e so obtained was allovjed to ston.d fo r 24 hours at
room temperature and then re i luxed fo r d i f ferent time i n t e r v a l s
with the mother l i q u o r and also with 0 . 5H n i t r i c ac id . I t was
f i l t e r e d , washed several t imes with d i s t i l l e d Water and then
dried at 40 -50 C. After complete dryint; the mater ia l was
immersed in 0.1 W n i t r i c acid for 24 hours with in t en .d t t e i i t
shalcing to convert i t to the II form. Grackinj of the ey.choj.gcr
Was observed durin.j; t h i s nrocosno The excess acid was rouovod
60
by repeated "washings with d i s t i l l e d water and the exchruiKcr
Was dried at 50 C. The r e s u l t s are summarised in Table 4 .
Ion exchan/^e capacity (lEC);
The ion exchange capac i t i e s ol the samples were deter dnea
by the column method[35j . A speci f ied amount (0 .5 g) of the
exchanger in the H form was packed in a column \.'ith a L'lasc
wool support . The packed column was washed witli d i s t i l l e d
Water. The hydrogen ions were then eluted v/ith 1H solut ion of
the e l e c t r o l y t e . The eff luent co l lec ted in each case at a r a t e
of 15-20 drops/min. was about 200 ral. The l i b e r a t e d II"*" was
t i t r a t e d against a standard sodium hydroxide so lu t ion . The
r e s u l t s of ion exchange capac i t i e s with respect to soi-ie
monovalent an-d divalent ca t ions are summarised in Table 5«
Qhemical QomDOsition;
Lead in the exchanger was p r e c i p i t a t e d as lead sulphate
and estimated[20] . A specif ied amount (0 .2 .g) of the Sample was
heated with concentrated HpSO, on a loiJ temperature hot ])late
u n t i l t h i ck fumes evolved f r e e l y . A c lea r solut ion x-'as obtained.
I t Was cooled and d i lu ted with about 100 ml of d i s t i l l e d water.
The prec ipated lead sulphate was then kept overnight . I t was
then f i l t e r e d through a previously wci{';hed s in te red gl, '' " o (^ <"' , -L >A t-J »->
61
c r u c i b l e o The p r e c i p i t o t o watJ washed wi th 'j'yollJltj. oxi^- i r i o d
a t 130 C t o a coiUjt.Uio \;eii,hoo The i jLi ' . r . i te \;ab c o i l u c t u u
a long ^fith washings aii' J. i t s volume \Jaf' Made upto 250 nil \. 'ilh
d i s t i l l e d watero Antimony was dcter^rilnod voluixci;:"ically 03
t h e po tass ium i o d i a e method [36] ^
Thermal Trea tuenx;
Lead sxitLnon . tc vc.o hea teo to d^.Tt'erent tcuporai^i-^rc&
in an e l e c t r i c i.u i iace in o rde r t o o::'j,..inc t h e e f l r c t oJ
h e a t i n g on t h e ion e-cch^inuC capac i ty« The ion o :chiui ,0 c i ac iLio;
a t d i f f e r e n t drying, t e m p e r a t u r e s aro cno\/n i n Taole 60
Chemical S t a u i l i t y ;
The chemical s t a o i l i t ^ of l ead aLi'L '-ion t c Mas ("etcr.dxit
in a l a r g e number of so iv x i t s . A s p e c i f i e r amount (0<.2 ^) o-i
V: 0 exchanger was e q u i l i b r a t e a ^fioh [^0 i-i of "ohe so lven t a^ r^^m
t empera tu re wi th o c c a s i o n a l shaking-. The exchanger was then
sepa ra t ed froiu t h e s o l u t i o n by f u t r a t j o n o Leau arid antimon, r.
t h e f i l t r a t e ^-ere cc t im, . teJ S' eel :opho^.o i .e t r i ja l ly aj i th i : :o: .e
ex t rac t ion[ ;p7j oji' - lu tass iu i . iu 1 'o, arco^'.^io ac id WL L.- ...[j ]
r e s p e c t i v e l y , fht r e s u l t s a rc shown in ' i ' ible 7 .
62
p H - t i t r a t i u n s ;
pII-tixr;LCioii:: were perxuriiea usiii^ Lhe mcthofi ^.i xOp
and Pepper[P9] . 'i hc Gv^teiiG in \/hich xitrabioiiG \/cre c;„rL"ie.j
out are LiOH-LiCl, KUn-kCl ciid Havd-UaOlc A cpi.cii-'icn a - oiuj t
(0 .2 g) 01 the exchaxiger \/ac kcDt in contact with varyij i j
volumes oi the base aiid the SaLc solutionG xor at>out 12 liourc
"With in ter i i i i t tcnt shaking, ilie ph oi the solutioi-c Ma.:: vhc.i
noted . The r e s u l t s are p lo t t ed in i''ig. 8,
In f ra red s tud ies ;
In l r a rod spect ra ol leau antiiai-nate a^ vai-'iouG
temperatures were recorded using the ivBr pe l l e t tech: i iuae.
P i g . 9.
X-raY ana lys i s ;
X-ray ana lys i s ol the exchanger was performed for
d i f fe ren t ionic forms of the exchanger using h i cke l f i l t o r e d
OuKp ^ r a d i a t i o n . The r e s u l t s are given in Table 14 .
Dis t r ibu t ion Coeff ic ients :
Dic t r ibut ion coef f i c i onto (kd) foe a number OL nctcU. i^n;
Were determineu in DL'M, formic acid, oouiuiu formate and in
mixtures of varyin^; volumes of foriaic acid and sodium fo-jmate.
63
Kd Values v/ere ca.lculated, usin^' the equa'tion
Kd = X mlA F Oo2
(eq .4)
"Where I i s the i n i t i a l volume of EDTA concumed by the
so lu t ion ; P, the f i n a l volume of EDTA consumed by the solut ion
a f t e r e q u i l i b r a t i o n . A]-l the ca t ions were estimated by
t i t r a t i o n s v'ith iiDTA[40] . Gomnlcte aosorption was found to
occur in some of the solvent systems studied for some metal
i ons . Resul ts arc shown in Table 12.
Quant i ta t ive Separat ions;
Por separat ion s tud ies a ^';lass column of 50 c a lonv and
0.6 cm in diameter Was used, A specif ied amount (1 .5 u) of
the exchanger in the H form was packed in the column with a
g la s s wool support . A solut ion of metal ions Was then t rans fe r red
to the column at a slow r a t e . The eff luent was then slowly
recycled through the column 8-10 t imes . The e lu t ion of metal
ions Was s t a r t e d a f t e r 30 minutes of loading.. The flow r a t e
of eff luent Was maintained at 1 ml/min. throughout the elut iun
process . MetaJ. ions in 10 ml f r a c t i o n s were then co l lec ted and
determined t i t r i m e t r i c a l l y with LLiTA. ;^ep;irations achieved on
lead antimonate columns are given in Taole 13.
64
RESULTS Mi) DISQUSSIUN
The ion exchange behaviour of c r y s t a l l i n u l e a d aiitimonute
has been s t u d i e d in a sea rch f o r i n e x p e n s i v e inor^janic iun exchan
g e r s . I t has a small exchange c a p a c i t y but i t shows s u f f i c i e n t
chemical and the rmal s t a b i l i t y to be of use as an ion exchange
m a t e r i a l . S tud i e s on amor^jhous l e a d an t imonate have been r e p o r t e d
e a r l i e r [ 2 0 ] . However, s i n c e t h e amorphous materiaJ-S do not show
r e p r o d u c i b l e p r o p e r t i e s e f f o r t s were made t o c r y s t a l l i z e and
c h a r a c t e r i z e i t .
Lead an t imonate when p repa red by mixing t h e so luLiuns of
po tass ium pyroat i t imunate and l e a d n i t r a t e was amorphous and \:;i,s
l e s s s t a b l e c h e m i c a l l y , "rte have atbeuipted t h e r e f o r e to s y n t h e s i z e
t h e m a t e r i a l by mixing the s o l u t i o n s of ant imunio aoi^ I'jia l end
n i t r a t e . The samples o b t a i n e d by us ing :urtimonic ac iu in pla-ce of
po tas s ium pyro^uitimonate were sho^^n t o ha.ve b e t t e r iiU'ch.-nicjil -aid
chemical s t a b i l i i i e s .
I n o r g a n i c ion exch,-.mgers a r e usUrvLly ob t a ined froi.i j^ol^roasic
a c i d s by pa r t i a J - ly r e p l a c i n g the p r o t o n s . This pa ' : t i ; j j , rej ' lacement
has two f u n c t i o n s ,
1 . I t makes t h e ac id i n s o l u b l e ( I f i t i s not a l r cauy so)
2 . I t pei:mits t h e i n s o l u b l e network to work as an exciianger.
Antimonic ac id i s an i n s o l u b l e ac id and t h e r e f o r e i t func t io i i s as
an exchanger a l s o . fho s a l t s of an t imonic a c i d i n \ /hich the p ro tons
65
have been p a r t i a l l y r e p l a c e d can a l c o ac t as ion exchan^^ers.
I t i s t h e r e f o r e wor thwhi le to c o r r e l a t e the p r o p e r t i e s oi"
c r y s t a l l i n e l e a d an t imonate and o t h e r laetal ant imonate; j wi lh
t h o s e of an t imonic a c i d .
Antimonic ac id has r e c e n t l y been shown to have a r n °
p y r o c h l o r e s t r u c t u r e [ 4 1 j . I t i s cubic \. ' i th a = 10.563 A . The d a t a f o r l e a d an t imona te i n d i f f e r e n t i o n i c forms a r e
i d e n t i c a l w i t h i n exper imen ta l e r r o r . These da ta g ive a u n i t o o , -
c e l l of 5.14 A or doubl ing t h i s 10.56^ A» Abe|_4 2j a l s o found
t h a t an t imonic a c i d gave l a t t i c e c o n s t a n t s of v a r i o u s forms as
10 .30 , 10 .53 , 10 .37 , 10 .40 , 10.47 f o r ila"*", Kb"*", Li"*", H"*", Cs"*" and
K forms wi thou t any change i n c r y s t a l s t r u c t u r e . The da ta on
l e a d ant imonate may be i n t e r p r e t e d as f o l l o w s . When l e a d n i t r a t e
i s r e f l u x e d wi th ant imonic ac id ion exchange occu r s t o t h e ex ten t +2 +
t h a t Pb r e p l a c e s most of t h e IrUO to form l e a d a n t i m o n a t e . The r a t i o of Sb/Pb f o r l e a d an t imonate i s 2o!:J : 1 anu can be
J.
interpreted on the basis that 80/^ of the H ion has been replaced,
(H^0''")2Sb20g.2H20+Pb'*"^ {ll^O'^) ^^2^^'^^QSb^0^.2ii^0 (eq.5)
C o r r e l a t i o n of t h e p r o p e r t i e s of o t h e r metal an t imona te s ^s ion exchanp:er3 on t h e ba,sis of p y r o c h l o r e h y n o t h e s i s :
The p y r o c h l o r e h y p o t h e s i s can be used t o exp l a in the
ion exchange p r o p e r t i e s of o t h e r an t imonate exchangers which
have been r e p o r t e d e a r l i e r [ 7 - 2 0 ] .
66
The unusual p rope r t i e s ol" airconium antimonate \;ere x i ro t
pointed out by Kraus and Ph i l l i p s [6 ] who shovfed tha t
antimonate exhibi ted a reversaJ- of Kd valuetj. They v;crc unable
to explain t h i s phenomenon. Later Abe and I t o synthesized
antimonic acid and s tudied i t s ion exchcai^^e behaviour. They
showed tha t c r y s t a l l i n e axitimonic acid possesses ion excha;tige
p rope r t i e s s imi la r to those of zirconium antimonate and concluded
tha t the reversa l in Kd values i s due to the presence of excess of
ajitimonic acid in zirconium antimonate. They also found that \.hen
the mater ia l had an Sb/Zr r a t i o l a r g e r than 1 i t containeu a
considerable amount of antimonic ac id[2 l j . Beatsle and HuyG[42]
a l so confirmed tha t the ion exchance behciviour of antiiionic acid
i s s imi la r to tha t of zirconium antimonateo I t i s tiiercfojx;
poss ib le t ha t in the zirconium antimonate of Kraus and P h i l l i p s
a l l the H O had not been replaced by zirconium(aJitimonic acj \;ar;
found in excess) and therefore zirconium antimon ite shov^ea
p rope r t i e s s imi la r to aJitimonic acido
Niobium antimonate Was prepared in an amorphous as v;cll
as in the c r y s t a l l i n e s t a t e . The c r y s t a l l i n e niobium ;vntiimunaCe
has the same d-spacini2;s as tha t of antijiionic-acid. Thus
niobium antimonate was probably formed by the replacement of
the protons in antimonic acid by niobium. A comparison of the
d-vaJ-Ues for niobium at^timonjite and antimonic acid cy : : t , J i i s e ,
by Abe[2l] and i3catsle[4 2] are (jiven in Table 11 -
67
Tatile 4 d e c c r i t e s t h e c o n d i t i o n s i o r t h e s y n t h e s i s oi
c r y s t a l l i n e l e a d an t i inona te . Of t h e v a r i o u s Samples p r epa red ,
t h e one (aq) t h a t was p r e p a r e d a t pH-4 and r e f l u x e d f o r 10 hours
i n t h e mother l i q u o r was found t o be t h e most s u i t a b l e one .
F u r t h e r s t u d i e s were c a r r i e d out on t h i s sample f o r which
Sh J Pb r a t i o i s 2o5 : 1 .
The exchange c a p a c i t y of l e a d an t imonate assuming; t h a t
only H O exchanges i s 0 .68 meq/g. This a g r e e s wel l v;ith the
c a p a c i t i e s shovjn i n Table 5» The l e a d becomes f i x e d in the ion
exchange s i t e s and t h u s does not exchan^;e out even in moderately
s t rong a c i d s o l u t i o n s . The ion exchange capp.city v a r i e s w i th
t h e metal ion and t h e maximum c a p a c i t y was foun i to be 0 .58 meq/ +2
g f o r Ga i o n . The sequence of a d s o r p t i o n of some of t h e metcJ.
i o n s on amorphous and c r y s t a l l i n e l e a d an t imona tes d i f f e r s from
ant imonic ac id i n t h e fo l l owing maimer,.
K > Sr > Ha > Ga > Mg on a - l e a d an t imonate ( a: amorphous) +2 +2 + +2 +
Ca > 3r > K > Mg > Li on G-lead antimono.tc( c: c r y s t a l l i n e )
L i < K < Os < Rb < ila. and i ig < lia < Ga < - r
on c -an t imonic a c i d .
Table 6 sho\;s t h e e f f e c t of d ry ing t e m p e r a t u r e on t h e ion
exchange c a p a c i t y of t h e m a t e r i a l . \'Jhen hea ted t o d i f f e r e n t
t empe ra tu r e s t h e ion exchange c a p a c i t y of c r y s t a l l i n e l o a d
ant imonate was not cu'fectcd much up t o 200 G. however the re was
a g radua l dec rease i n the ion exchange c a p a c i t y auovc 200 G oxm
reached a n e g l i g i b l e va lue , a t aoo G.
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T a b l e 5 IQH EXaHiU;&i^ QAPACI'i'IKS Oi;' CiiYbTiiLLIME LEAl^
MTIHONATi^ i'OR VAHIOUb GATI0N3
M e t a l i o n s
1 1 *
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5.4
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70
T a b l e 6 EiiTEQ'X Ox'' TEI-lPERATUit£ ON THE ION EXQiIjUjaE GAP API TY
Oi ' OxlY^TALLIITE LEAI> iUri'l riJN ATE
T e m p e r a t u r e ( G) IEG(meq/g)
40 0.40
100 0o38
200 0.38
500 0.10
400 0.03
600 0.05
800 0,03
71
The chemical sta"bili ty of lead antiiaonate was exa^iiined
in Various mineral ac ids (^liable ?) o Crys ta l l ine lead antimonate
Was found to be f a i r l y s t au le in mineral acids aiid was com])letely
s tab le in nIW and in 2i'I Formic ac id . The chemical s t a b i l i t y data
for Various antimonates j^repared so f a r roveal tha t in .jenerjil the
antimonates of pentavalent metals are more s tab le thai'i those of
t e t r a v a l e n t , t r i v a l e n t (and divalent meta ls . I t was also observed
tha t the c r y s t a l l i n e lead antimohate exh ib i t s hit;her s t a b i l i t y
when compared to the other divalent met;il antimonates.
Antimonates of var ious metals vihen t r e a t e d vrith hydrocliloric acid
re lease appreciable amounts of antimony and t h i s was explained
by the formation of chlorocomplexes of antimony, llovjever
antimonic acid behaves in a d i f ferent way. The s o l u b i l i t y of
c r y s t a l l i n e antimonic acid i s much lower than those of i t s
glassy ot amorphous forms. Crys ta l l ine lead antimonate also
behaves in a s imi la r wa ^ vjhere the amount of antimony released
i s much lower.
pH measurements performed by the added s a l t metliod
show tha t the c r y s t a l l i n e lead antimonate exh ib i t s monofunctional
behaviour(i ' ig . 8) . Ion exchaiige capacity ca lcu la ted from the pH
curves i s in good agreement with the obtained va lue .
The IR spectrum of lead antimonate can also be exTjlainod
on the bas i s of the pyrochlore hypothes i s . The t e n t a t i v e b:i;id
assignments in the IB. spectrum of antimonic acid a.re given in -1 -1
Table 8 . The absorDt ion band between 2800 Gm and 3800 Cm \Ji th
72
T a b l e 7 SOLUBILITY Oi ' Q.^Y^TALLIiiE L'^AU iUJTIl'DNAl'E
S o l v e n t
0.1M HGOOH
IM HOOOH
3M HOOOH
6M HGOOH
O.IM HNO^
IM HNO^
3M HNO^
O.IH HGl
1 M H d
3M HGl
APiount oX r e l e a s e d ( m
0 . 0 0
0 . 0 0
0 .01 1
0 . 2 5
0 . 0 0
0 . 0 2
0 . 1 8
0 . 0 0
0 .111
0 . 4 3
Pb 5 / 5 0 ml)
^moun I of Sb r e l e a G e d ( 1112/50 ml)
0 .00
0 . 0 0
0 . 0 1 5
0 .31
0 . 0 0
0u08
1 .24
0 . 0 0
1 o4
2o2
73
2 3 4 5 6
[0H"]added(meq/0.5g) Fig. 8-pH titration curves on Lead antimonate.
74
T a b l e 8 TEIITA'i'IYE Bl\xiD ASLJI(llU-iEIT'J3 IK 'i'lIE Id bPaOTRUM Ox''
CRYSTALLINE jUrfllCIIIQ ACID
«
BandCCm"''') I n t e n s i t y Specilic { roup vibration iioi'erence
3550
2450
1650
1280
750
S, shp
VW,shp
W , B
W , B
IS, B
VOH, V H^O
Overtone of Sb-OH
6 H2O
6 ;jb-OH
VSb-O
[25 ]
[ 4 4 ]
[44] -
75
_1
a msiximum at 3550 Cm io c h a r a c t e r i s t i c oi i n t e r s t i t i a l water
and OH groups. A s imi la r absorption band was found in the lit
spectrum of oC-Zirconium phosphate and Was i n t e r p r e t e d by
Clear f ie ld as or i i j ina t ing with the Water molecule[4 3] . The band -1 -1 ' -1
between 1500 Cm and 17^0 Cm with a maximum at 16':50 Cm i s due to the deformation v ibra t ion of i n t e r s t i t i a l water . The
-1 band at 750 Cm was i n t e r p r e t e d as due to the stretchin,:; v ibrat ion of Sb-0. The c r y s t a l l i n e antimonic acid showed bands havin^
-1 -1
maximum at 24 *0 Cm aJid 1280 Cm . I t was sugcestod by
Siebert[44] tha t the bmid at 1280 Cm" i s due to the Sb-OH defer
-mation v ibra t ion of the antimonyl group and the maximum in t ens i t y
at 24 30 Cm" due t o an overtone of Sb-OH deformation v i b r a t i o n .
If one compares t h i s assignment with t ha t ofoC-Zr(H ^OA)^ then
the following conclusions seem reasonable ,
(1) In oC-Zr(HP0.)2 the re are two peaks at 3590 Cm" and
3510 Cm" which are a t t r i b u t e d by ueabridgcs[45] to the OH s t re tch
of ac id ic phosphate group. The fac t t ha t the two peaks do not
coincide was taken as an ind ica t ion tha t the two monohydrogon
phosphates d i f fe r in ac id i ty as shown by the t i t r a t i o n curves.
Since in the case of antimonic acid we have only one absorption
band at 3350 Cm i t shows tha t the antimoriate groups are
probably equiva lent . This i s confirmed by the t i t r a t i o n curve of
antimonic acid which shows a monobasic behaviour. The absorption
band at 1250 Cm" i s assigned to the P-0 v ibra t ion inoC'-Zr(nPO. ) p.
In the Case of antimonic acid the Sb-OH v ib ra t i ons are found at
1280 Gm" .
76
(5) In oC-Zr(HP0^)2 the -band 2350 Cm"'' i s aasigned to OH
acid ic (s t rong H bond). However in the case oi antimonic acid
t h i s i s assigned as the overtone of Sb-OII (1280 Cm ) v i b r a t i o n s .
This assignment needs fu r the r inves t iga t iono
The IR spectrum of lead antimonate i s very s imi la r to the
spectrum of ant iuonic acid (]?igo9) shovring thereby t h a t the lead
antimonate i s only a p a r t i a l l y replaced antimonic ac id . The
Sb-0 band at 750 Cm i s present in both of them (Table 9) » The
1280 Cm band due to Sb-OH in antimonic acid i s sh i f ted to a
lower frequency i . e . 1230 Cm in the lead antimonateo The
2430 Cm band of antimonic acid i s not present in lead antimonate, +2
as most of the protons have been replaced by Pb groups.
The in f ra red band assignments fo r other antimonate exchangers
(Table 10) are in good agreement ^Jith the above o'bservations. The
following points may however be no t cc .
(1) The Sb-OH frequency at 1280 Cm i s s ens i t i ve to the
replacement of H i o n s . Thus in l ead antimonate i t s h i f t s to -1 -1
1230 Cm and in sodium antimonate to 1100 Cm . In the case of + —1
stannic antimonate (H form) i t i s found at 1280 Cm which in + 1
s tannic antimonate (Na form) i t i s sh i f ted to 1240 Cm o There
are however a few exceptions to t h i s t r e n d . In s t ann ic antimonate
(Rb form) and (Gs form) there i s no sh i f t from 1280 Cm" , In
the case of chromium antimonate ana tantalum antimonate i l sh i f t s -1 -1
to higher frequency i . e . 1380 cm and 1480 Cm r e s p e c t i v e l y .
77
o o
s> ^ ^^ uo J
CO "v, ^ nklyY
^tik\^u J _ \ . ^ o "^T^ t
;
\
r 1 /{ O o 00 vo
-j-i-i—1
c/o) aoNViiiwsNvyi
-
-
-
o
o - o
o • o
u>
o o CO o o o o o N .
O
§i si o ui o > 00 <
o o o rJ
O O m
o o o rO
1 E
O O
o — - I ^ o
' \^
-»'
/
CO
n •j-j
a> Q . E
• M
- M
ci! <+-"t3 4J
a* •4->
c o e
j - j
c OJ
T3
t 4 -
o
• M O a> C L
Q: 1—1
1 0^
• r - ^ N > , ^ ^ o /r-7 >^.^
78
Table 9 TENTATIVl BMib ASuIUlillEiri' III THE l i t oi^iitJTKiJl-l
OP QRYSTALLIME LEAU AimMOIU'i'li;
Band(Cm"') I n t e n s i t y Spec ix i c groujj v i b r a t i o n » • — ^ — • — ^ — • ' • • • • I H I • • • • • ! • • > | W I | M ^ M l i a i ! • • • • H I — H I M I 11 • • ^ Ml .—. • • ! • • m . • • • • » l l l l g I I I l l
5220 S, B V OH, 1/ H2O
1650 ^ , shp 6 n^O
1 230 ^ , shp 6 Sb-on
750 S, B IT Sb-O
^
CO
% SI 6H
i
o
o
H
en
o
rt Pi •H O
- p ai CD U U rQ
CQ >
« L CD a
w o f ^ ^
?? ^ ^
a---
rHM
s o •H +3 d
a u o
tH O
id o
^ ? O rQ FH
'Ci > 5
• r l ^ -P
ri U
1
^ ' H rQ +5 0)
« •H >
<U
a
&:5
vO
ra PH : : i - . o M fc.0
r a o
pl O rf CvJ O -H W
•rl rf-P ^ +3 O - r l l O C - r l - P - - ^ a -P CQ M 03 M ^^ O M QJ <D - r -
Cj-H ^ +3 ^J ; I
Q) -ri rt d a
^
-P
ra +3 M to
^ M
> - p
• H ^ H ^ O O
+5 02 (D ri ?4 O
- P
a
o
o -Tj C\J
CD - P
ft
O cd ^
W - P IS W
CD
o
o M
m •> CO
>
o LOi ir~
pn *«
• ^
o 03 OJ
0)
o U O
> a
o i A
^
ft
^ m
* k
^ f -
FQ CO
o o o
o C O
t o o KO
o CO ^o^
fA *•
•*
o
8
+3
0
ca ^
o
m
C O
o
CM
O
•H O rj
o •H id
o a
ft P) si si ra ra
a " CO
o o o •<^ •>- LA MD U 5 VO
pq
o o
CTi x - ' ^
pq m m *» •« t^
CO C O C O
pq
1,0
o o o o C— •^ r t •^ [— IT- D- ir-
Pi ft Si si pq CT ram * ^ •> ^ = —
3: :s ^ t>
o o o o 0 0 ' ^ LPv t r \ C\J (AJ CM CVJ
P J ft
ra "ra pq pq
o o o o -r- 00 OD - ^ VO i n LPv VO
rq pq ;c3 ^ ^ ra pq pq
OJ CO ^ •. " >• > CO ; - i r:£j
o o o o o o Lpv ,c- m rj
VO VO c— t r - t r -
f-l Q <D <:; > o O - P
pq pq
'^ ^ :^ CM
P I
Si O O M CO 0 0 CM CM CO
^ " ^ O
o
PI m pq
pq pq pq pq
CO*" w en CO
ft xi ra
pq pq •«
CO CO >
o CO 0)
4-J
a o 3
•ri -P
H 0)
o •H
c 3
0) -p ci
o
a
a 3
c 3
0)
Cj
o
o •H
O
o
i n
oj
0
cj
s •H •P
a O
a O
+ C53 + ;TH
M Is; M 12
M O o q^
+ - + +
a a o o
s^ ra PH O
1 _)
' c d
o cj
o a
^ ^ +3 C O CO
a
o C O
pq
>
s\ CO
o o ITS O
P^ P< ^ ci
m ra
o o o o o T- - - i n o O VO VO VO VO VO
pq pq
CO 03
o LTv CM <
o o K^ t<
o ir\ ^f^ t<
o o ^
o in ' d-tn
o o i n '
o i n ;n tn
O O tn tn
o Q. CM tn
i r - C3^
CO
- p Co r-*
O
a •H P
i a
•H o
•H is;
(D - P
J
o
§
p
O
P ' 1
o
-p ra
CO
ra 'J o
^
p>
c:>
79
n 'r-l -H O ' d a. c) 3 a
>
1 ^ 0) ,/3
~0 13
(1)
• H r 4
p J
ft U
Si ra
o n
so
These exceptionti need fu r t h e r study. The diferences may be due
to tJie fac t tha t the chromium and Tantalum antimonateG v/ere not
c r y s t a l l i n e but only amorphous.
-1 (2) The 2450 Gm band i s present only in antimonic acid and
-1 sodium antimonate where i t s h i f t s to 2145 Gm , In no other
antimonate t h i s band i s found.
Since lead antimonate was found to be s tab le an effort + + + +
Was made for X-ray analys ic of the samples in II , Na , K , Li , + 2 +2
Ga and llg f o r m s . The r e s u l t s show t h a t t h e ion exchani^;e
occurs by the replacement of surface protons of the c r y s t a l l i n e
lead antimonate. The r e s u l t s are shown in Table 14-.
The d i s t r i b u t i o n coe f f i c i en t s for var ious metal ions were
found to be very high in JMtl and in sodium formate systems (Table 12)
I t i s in teres t in^j to note tha t the adsorption of most of the metal
ions i s very high on c r y s t a l l i n e lead antimonate compared to the
amorphous one. A general t rend tha t i s common to both the
amorphous and c r y s t a l l i n e lead antimonates i s t h e i r low ai"finity + 2
towards Mg i o n s .
As the uptake of most of the metal ions i s very high on
c r y s t a l l i n e lead antimonate except f o r Mg ion, a general
procedure for separat ing the blg*'^ ion from some of i t s clocely
r e l a t e d as wel l as other metal ions i s of ,_,reat import;ince.
Table 1 1 A COi JPAKia;! OF d° SPACII^GS(A) JJ'UR
NlOBIUi4 Al TII'lONATE AND AMTimHilQ ACII>[7]
81
]>Ji n"bium an t imonate
d° I / I o
5.97 42
3 .15 55
3.01 54
2.60 16
2.40 17
2.04 16
1.84 24
1.76 19
1.57 18
1.50 18
1.467 12
1.350 10
Afitimonic a c i d
l / l o
6.00
3.128
2.995
2.594
1 .998
1 .835
lo754
1 .565
loo
80
75
15
17
31
22
U
m
o P4
H
o H p:! O
H
EH
g M EH
Hi
o
OJ
CD H
6H
S o
+ d o o
SSoo
O O
+ cd
O O
o o t< W W ••
• • ao
+ a o o
88: W W
• « O O
+ a ws O O
88P w w •• T— - r -
• • O O + cd W ^ ^ O O * 88'S' ww^ ^ ^ ,
O O
I o
O O
d a <a (^ ^
T- O
K o O O O f^ -. _ o o
cd LA £d 05 cd 00 - ^
CM T- O ^ CO C J T - O CM t r - LTN LA LfN VD
cd t A
^ VD tfA VO VO 00 P CD OO cTi t r - tr~ CM c\i
LTv CM 00 t<A
O O U > Q O 0 0 O O V O ^ C M O S O J ^ O O
cd cn ^ o tA 00 -vi-
CTv e n Lr> LA t A O O 'd- t - ^ 00 CO Lf\ - ; i - t<^ ^O -r- cd CTN
O O O ^ C M l A O O O L A COtOv O V O K ^ O U 5 C r > C M L A t O s C M COtO i - ^ O ' v h C-V£> L A ^ f - T - C T v T- cd Cd cd T- cd
O O O O v D O ^ ~ 0 CMvOvD C 0 > ^ - « ; i - ' ^ O 00 Cn ^ CO M3 CM CO T - Cd
o o en LA
cd
r \ LA T - c^ LA CO
o
cd
O l A LA CM tA CM ^ ^
cd Cd ^ CO
O Lf) O I>- CM o
o en
CM LA
o cd lov cd
o o CM O
CO
O t A O O ^ O O O C O L A O O L A ^ L A O •s^CM C d C X 3 L A C M C M T - C 0 cd tA CO
O -"J^ O O O O tA
CM cn cd c~-
o cd cd cd cd en
o o ^ o O cd o o cd
O o
cd o cd cd cd cd cd
^ ^ r * ' ? ' * ^ ^ ' ^ ' ^ ' ^ C M C M ^ C M C \ J t < > , C M
P4 O <S fJH O O tiO cj M cd
^ eg O pq O
82
H
o
cu
>
>
cd I—i
8 w
o
rf W o o
+3 8 P, W • l
:> : : 1 ra ••-'J • cd o
0) H
o
o
o •H
cd
II II
cd *
83
The separat ion f a c t o r f o r Ca/Mg was found to bu very
l a rge on c r y s t a l l i n e l ead a;ntiiiionate(Fic, 10) . Therefore
t h i s mater ia l can best be u t i l i z e d at room temperature for the
d i f f i c u l t separat ion of Ga from jyig and of I'lg from numerous
metal i o n s . Some of the separa t ions achieved on the coluiim.s of
c r y s t a l l i n e lead antimonate are given in Table 1 3 .
84
+ en
4 > <vj
O T3
en o
+3-
+Z-
+ 1
0
-1
- 2
- 3 -L. -L. -L. _!_ J . J L J - JL JL i J
Fig.10-AplotoflogkdCa^*/Mg^* {o<,separation factor) for various inorganic ion exchangers.
85
T a b l e 15 SKPAiCATIOHo 01'' I-IlJ'i'AL L^x\lj ul 'i'lIJJ COLoR^bJ
M e t a l i o n s s e p a r a t e d
1 0 Mg+2
Zn
+2 2 . Mg*^
00^2
3 . Ms"^^
Gu+2
4 . tlg"*"^
XL-5
5 . 14g'*'2
Ca^2
6 . Mg"*"
S r ^ 2
7 . Mg"*"
Ba-^2
Oij" GiilaTALLINi) LfiAJJ
Amount l o a d e d
1300
1 250
1300
1190
1300
1 208
1300
1 900
1300
1180
1300
1060
1300
1307
Amount f o u n d
(;ie)
1274
11 28
1325
1380
13 26
1278
1274
2533
1325
1156
1274
1108
1092
14 98
AilTU'DilATE
T o t a l e l u t i o n volume (ml)
70
80
70
70
70
50
70
60
70
40
70
40-
70
40
E l u e n t s uced
III HC00H+
0.11'l iillO^
IH iIC00H+
OolH M O j
IH 1IC00II+
0 .1H M O j
III IIC!00H+
OolM ffiiO,
II'I HCOOH
IM H000H+
o.iH mro^ 3
li'l HGOOH
IH KCI00H+
3
Ui nooou
li'l HG00H+
0 .1 ii lilfOv
86
(Table 15 contd.)
M e t a l i o n s s e p a r a t e d
8 . 1-Ig "
Jin-*-2
9 . Mg"^^
Pb-*-2
10.Mg"*"^
11.Mg"^^
Fe-^5
Amount l o a d e d
(MS)
1500
1000
1500
1660
1500
1450
1500
8011
Amount f oun d (MC)
1144
1154
1 248
1760
1274
1502
1525
104 9
I ' o t a l e l u t i o n volume (ml )
70
70
70
50
70
50
70
70
l i l u o n t y u s e d
1H IIGOOH
1 H HC00H+
0 . 1 ii HlTOj
IM riCX)OH
1 H HG00H+
0 , 1 H MO^
1I'I HCOOH
1H IIC0UII+
0 . 1 H m^O^ 5
IM HCOOH
0.1M ffiI0„ 5
87
T a b l e 1 4 X-RAY bTbijlES : aia;i'i'jll.LUui{itPHIQ lIiiJiQlJb i^.U
LATl'lCri P;utiUIoT£HB 01' LEAo^ Ail i'liiUlIia'E 11
PIYLitOGMl mi) SQjjIUM x-'URl'IS
2 - 6 d(A) l / l o h i a a (A°)
30 2.970 100 111 5o1442
34.8 2.6706 30.25 200 5.141
50 1.818 55.88 220 5o141
59.4 1.5562 31o25 310 4o92 l l
62.4 1 o4859 10.41 311 4.9215
Na form
2.9
30
34.8
50
59 .2
62.4
d(A°)
2.97
2.5705
1 .818
1 .5562
1 .4839
l / l o
100
35
37
30
12.5
hX l
111
200
220
"310
311
a(A°)
5o1441
5o l4 l
5ol421
4.9211
4 0921 5
ss
1 . Walton, HoF; Anal . Ghem. Rev . , 50, 40K, 197n.
2 . Sl idgetom, Y . , Hatsomoto, IL., ITaCoshi, K aiid
l a raesh ige , '2,
Nippon Kagaku K a i s h i , po619, 1976.
3 . Akaivfa, H . , KovJamoto, II. and Osuiai, H.
T a l o n t a . , 29, 63^^, 1982.
4 . Gunini , M., Lagona, A., P e t r o n i , B.M. and liuqno, i-IoV.
T a l a n t a . , 27, 4 5 , 1980.
5« G l e a r f i e l d , A., iNancol las , G. and B l e s s i n ^ , ii«ll.
"Ion exchange and so lven t e x t r a c t i o n " , e d i t e d
by Har insky , I 'Iarcel-Dekl:er, ITew YorL, 1975.
6 . P h i l l i p s , H .P . and i'Lraus, K.A.
J .Amer .Ghem.Soc. ,84, 2267, 1962o
7 . Quresh i , H. , Gupta, A»P. and Khan, T.
J .Ghromatogr . , 144, 251, 1977.
8 . Qureshi , M., Gupta, J . P o , IJowell , D.V. and Gupta, A.P.
Anal . Ghem., 4 0 , 54 5 , 1978.
9 . Quresh i , H . , Gupta, J . P . aJici bharuia, V.
Anal . Ghem., 4 5 , 1901, 1973.
89
1 0 . Quresh i , M. and Kumar, V.
J .Chem.30G. (A) . , p . 1 4 8 8 , 1970.
1 2 . Ta^don, S.H. and G i l l , J . i i .
T a l a J i t a . , 19 , 1555, 1972.
1 K 'randon, SoH. and ^ i l l , J . 3 .
J . I i a d i o a n a l . Ghem., 20, 5 , 1974.
1 5 . Quresh i , H . , Kumar, Y. ajid Zehra, H.
J .Ghroraa togr . , 67 , 351 , 1972.
14 . Hat hew, J . and Tandoii, S.li.
J . K a d i o a n a l . Ghem., 27, 515 , 1975.
1 5 . Mat hew, J . and Tan don, S.N.
Ac ta . Ghim.(Budaj)es t ) . , 92, 1, 1977.
1 6 . Quresh i , H. , Kumar Ro aJiti i i a tho re , U .S .
i 'o la i i ta , 19, 1577, 1972c
1 7 . Haw a t , J . P . and Singh, D.K.
i ina l . Ghim. A c t a . , 84 , 157, 1976.
1 8 . Rawat, J . P . and Singh, J . P .
Ghromatographia . , 10, 205, 1977.
1 9 . Quresh i , M., Varsimc7 , K.a» ^iiid P a t i u a , N,
J .Ghroma tog r . , I 6 9 , 565, 1979.
90
20, Th ind , P.;:^. and B i n d a l , T.iU
J . L i q . Ohromato^a.-., ^5, 57':5, 1 9 8 0 .
21 . Abe, n . jmd I t o , T.
B u l l . Ghem.Soc. j p n . , 4 0 , 1 0 1 3 , 1 9 6 7 .
2 2 . Abe, M. aJid I t o , T.
B u l l . G h e m . 3 o G . J p n . , 4 1 , 3 5 3 , 1968c
2 3 . Abe, H. and I t o , T.
B u l l . Ghem.Soc. J p n . , 4 1 , 2366 , 1 9 6 8 .
2 4 . Abe, M. and I t o , T.
B u l l . Ghera.Soc. J p n . , 4 2 , 2683 , 1 9 6 9 .
2 5 . Abe, Wc
J . I n o r f i . N u c l . Gheia., 4 1 , 8 5 , 1 9 7 9 .
2 6 . Abe, M. and I t o , T.
J . I n o r g . Nuc lo Ghein., 4 1 , 1 0 5 1 , 1 9 8 0 .
27» Sunandamma, Y .
M . P h i l , t h e s i s , March , 1 9 8 4 .
2 8 . Q u r e s h i , H . , H u s a i n , M . and I s r a e l i , A.II.
T a l a j i t a , ' ' 5 , 7 8 7 , 1 9 6 8 .
2 9 . Q u r e s h i , Ma and HusGaLn, W„
T a l a n t a . , 1 8 , 3 9 9 , 1971 .
91
30. Quroshi , 1-1. and Hussa in , K.
Ajinl. Ghem., 4 3 , U 4 7 , 1971 .
3 1 . Quresh i , H. and Hussa in , K.
Anal . Chim. A c t a . , 57 , 383, 1971 .
32o Quresh i , Mo, Varshney, K.G. and Kaushik , R.C.
Ana l . Ghem., 4 5 , 2433, 1973.
3 3 . Qure sh i , M., Thakur, J . S . and Quresh i , P.M.
J . L i q . Ghroiaato^r . , 3 , 6 0 5 , 1980.
3 4 . Quresh i , M. and Hussa in , V.
Anal . Ghem., 4 7 , 1710, 1975.
3 5 . Samuelson, 0 .
"Ion exchanfi-e s e p a r a t i o n s i n a n a l y t i c a l Chemistry"
John Wiley and S o n s . , New York, p . 3 7 , 1963.
3D . Purman , i<[.H.
"Standard methods of chemical a n a l y s i s " Van Nostrond,
New York, 6 th ed . p . 9 6 , 1962.
3 7 . S a n d e l l , E . B . ,
"Go lo r ime t r i c d e t e r m i n a t i o n of t r a c e s of M e t a l s " .
I n t e r s c i e i i c e : London, 5rd edn. 1959.
92
38 . Voge l , A . I .
"Text book of q u a n t i t a t i v e i n o r c a i i i c an; i l . /oio"
lon:;iiian aiid Co. , London, p.701 , 1978.
39 . '^opp, i'^'ii' and Pepper , i^ow.
J«Chem.Soc . ,p .9932 , 1964c
4 0 . R e i l l y , N . , b t imid , H.W. and Sadak, K . b .
J .Ghem.edn . , 30, 555, 1959.
4 1 . England, ¥ . A . , Gross, i-I.G., l l a ime t t . A., V^isexaa", P . J
aiid Good enough.
So l id l i ta te l o n i c G . , 1 (3-4 ) , 231, 19^0.
4 2. B e a t s l e , L.II . and l luys, DC
J . Ine r t ;» Wuclv Chem., 30, 6 39, 1968o
4 3 . C l e a r f i e l d , A.
Unpubliched researcl , Ohio University, 1964.
44. Siebert, H.
Z.iijiorti-. Allcem. Chem., 501, 161, 1959.
45. Deabridge, J.
i'l.S.Thesis, btrasburg University, I969.
C H l £ T E a - i n .
93
QHKQi-iATOLrii;u?IiIC BJillAVIOUil Oi?' 31 QAl'IUiJb Oil bli^XJA
IHTiJQLUQTIUlI
Thin l a y e r chromatotiraphy i s receivin^^^ in-jreacin^-
a t t e n t i o n as a s e p a r a t i o n t e c i m i q u e . I n f a c t i t rna ^ be
cons ide red t o be t h e second most popu la r method ox su,-ciration
aT te r HPIG. ThiL; i s probably due t o the f a c t t l ia t t h i n i . j o r
chromatography i s compara t ive ly i nexpens ive and a t t h e Sca ie
t ime t h e tec l in ique has s e n s i t i v i t y , c en t r a ] . a p p l i c a b i l i L y and
f l e x i b i l i t y [ l ] . The t ec imique has been used e. i toncavcly f o r
t h e s e p a r a t i o n of o r g a n i c compounv.D in f o r e n s i c l a b o r a t u r i c e ,
medical l a b o r a t o r i e s and chei-iical i n d u s t r y . However, l e s u \.'orL
has been done on t h e s e p a r a t i o n of c a t i o n s by t h i n In^^cr
chromatography. «ork done upto 1972 has been suiaiuariaca by
Brinkman in a r ev i ev e n t i t l e d "Thin l a y e r ChromatojrapJ ' ic da l r
f o r I n o r g a n i c Sub3tanGes"[2] . Recenc work has been revie^;ed by
Joseph Sherma and Bernard F r i e d [ 3 ] o
The s y s t e m a t i c s tudy of q u a n t i t a t i v e s e p a r a t i o n jf metal
i o n s has been c a r r i e d out liy Qureshi and Thakaj.- i n s o j i u u
c h l o r i d e - a c e t o n e so lven t rys tems[4] . They have a l so Sou i.^d th(.
e f f ec t of v a r i o u s f a c t o r s such as Sample c o n c e n t r a t i o i , eJ U'jnt
c o n c e n t r a t i o n , pH and i o n i c s t r e n c t h [ 5 ] . A sea rch of t h e
94
l i t e r a t u r e shov/s tha t very few s tuu ies have been r epor t e r on
the formic acid-acetone solvent system. There i s only one
study on t h i s system where formic acld-acetone systems(OOj10),
( 1 J 9 ) , (5:7) have "been used and the R^ values of metal ions
given[6] . This study i s incomplete in tvjo r e s p e c t s ( l ) very few
systems have been s tud ied . (2) No separa t ions have been actual ly
car r ied out . This system has therefore been re inves t i : ;a tcd by
varying the formic acid-acetone r a t i o and by developin;; some
possible sepa ra t ions . The r e s u l t s of t h i s study are given
below.
'JO
Thin Layer Chromatography apparatus( Tonlmiwal, India)
"Was used for the preparat ion oi s i l i c a ^cl p la tec on
20 X 3.5 cm glas;.. p l a t e s . Temperature cont ro l led e l e c t r i c
oven Was used to dry the p l a t e s . The p l a t e s \rere developea m
24 X 6 cm glass j a r s .
Rea^scents:
S i l i c a L"el G-(E.Herck), N i t r a t e s of Gad-.dum, Lea< , .icrGury(1),
ThalliuiQ(l), Uranyl, Thorium and lanthanum \/ere ox BDil. Zirconium
oxychloride (Blfrl, I n d i a ) , S i lver n i t r a t e (E.i-IercL) , Liobiuii and
Tantalum pentoxiaes were oi BDII. Soaiuu oungstate(BL/iI) , LooiuJi
a rsenate (J .T.Baker, USA) , Antimony pentachloride(Bi;J) , Acetoi.e
(E.Merck), Formic acid(B.i'-Ierck) . All other reagents useu vero oi"
i^aalaR grade.
Te^t s o l u t i o n s :
0.1M so lu t ions of the metal n i t r a t e s and ch lor ides \Jere
prepared in 0.01M solut ion oL" t h e i r oonxspondin,^ a c id s . Antimony
pentachlor idc solut ion was preitarea in An hydrochloric aoido
Niobium ana tanxalum ^cntoxid^s wert aissolvoa \ ' i th anuoniuu
96
s u l p h a t e i n c o n c e n t r a t e d s u l p h u r i c a c i d . Sodium tun^ju ta te ,
Sodium molybdate and Sodium a r s e n a t e s o l u t i o n s vjere p r epa red
i n "Mater. A s o l u t i o n of e e r i e s u l p h a t e was p r e p a r e d in 3.611
s u l p h u r i c a c i d . Stannous c h l o r i d e s o l u t i o n was p r e p a r e d in
4M h y d r o c h l o r i c a c i d . Mercurous n i t r a t e s o l u t i o n Was p repa red
i n 1»6N n i t r i c a c i d .
Detect ionJ
,+2 n,,+2 ^^+2 ^r^+2 0.+3 . +5 Ag-*- , T1+ , Hg^+ , Gd+2 , Gu+2 , pb+2^ ^^+2 ^ Q^+:?^ ^ H
+5 and Sb were d e t e c t e d wi th yel low ammonium su lph ide c o l u t i u n .
0.1?^ a l c h o l i c s o l u t i o n of A l i z a r i n r e d - S was used t o d e t e c t
L a • ' ^ Zr-^ , Th-^ , Ge+^ , Sn+2 , sn^^^ a,,d N h + ^ Zia''^ and Gr ^
+ 2 were d e t e c t e d w i t h a 1? s o l u t i o n oi d iphenyl c a r b a z i d e . hi
and Go were d e t e c t e d wi th a 2<> aqueous po tass ium f e r r o c y a n i d e
s o l u t i o n . A 1? a l c o h o l i c s o l u t i o n of p y r o g a l l o l vJas used t o
de t ec t Ta"*" and \i . 0.1M s tannous c h l o r i d e s o l u t i o n in 41\f HGl +6 +4
Was used t o d e t e c t Mo and Se o Aqueous po tass ium f e r r i c y a t i i d e +2
s o l u t i o n Was used t o d e t e c t Fe . A 1 ?» a l c o h o l i c chromotropic +4 ac id s o l u t i o n was used t o d e t e c t Ti .
P r e p a r a t i o n of S i l i c a G-el P l a t e s ;
S i l i c a ge l s l u r r y Was p repa red by mixing s i l i c a ge l wi th
c o n d u c t i v i t y wa te r i n 1 j 5 r a t i o by shaking c o n s t a n t l y f o r about
W-
5 minutes. The slurry uas immediately used to coat the cleaji
g lass p l a t e s v;il;h the help of an app l i ca to r . The p l a t e s with a
l aye r of Oo25 mm tiiiclmess were thus prepared and dried at room
temperature at f i r s t and then in an e l e c t r i c a l l y control led
oven at 100 + 1 G for 2 h rs for complete dry inc . They were
then s tored in aJi oven at room temperature u n t i l used.
Procedure;
The t e s t so lu t ions were applied on s i l i c a gel p l a t e s with
the help of c a p i l l a r i e s . The spots were then allowed to dry
"before carryings out the chromatography in glass j a r s containintj
the so lvent . The solvent was allowed to ascend 10 cm from the
s t a r t i n g l i n e on the p l a t e in a l l the cases , j tf ter the development
Was over the p l a t e s were dried in an a i r oven and the ions were
detected with the usual r eagen t s .
98
RESULTS MiD DIi:.CU!:3bl0H
The chr0matographic behav iour of 31 c a t i o n s ^^as s t u d i e d
i n formic a c i d - a c e t o n e so lven t system mixed i n d i f f e r e n t r a t i o s .
The Rf v a l u e s of metal i o n s in formic a c i d - a c e t o n e ( 4 : 6 ) , l o rmic
a c i d - a G e t o n e ( 5 J 5 ) , fo rmic a c i d - a c e t o n e ( 6 : 4 ) , formic a c i d -
a c e t o n e ( 8 : 2 ) , formic a c i d - a c e t o n e (10:00) a r e given i n Table 15*
The r e s u l t s show t h a t t h e formic a c i d - a c e t o n e so lven t system
i s s u i t a b l e f o r numerous s e p a r a t i o n s . Some of t h e metal i o n s t a i l
i n t h e v a r i o u s systems s t u d i e d as given below.
Solvent system
Pormic ac id -Ace tone (4 :6 )
Formic ac id -Ace tone (5 :5 )
Formic ac id -Ace tone (6 :4 )
Formic aGid-Acetone(8:2)
Formic acid-Acetone(lOjOO)
Ga,tions vfhich t a i l
Kb'*"^, Mo +6
Gd+2 ^ Mo+6
Ag^ , V0"*"2 , Nb'*'5 , Mo"^
Ag"*" , VO"**
'On+4 fn.+5 In general Pb^^-^ La^"^ , Vo''^ , Ti"^ , Zr"^ , Th^^ , Ta"
and W are strongly adsorbed in t h i s solvent and have an ^
value of 0 .00 . m other ca t ions s tudied have H v.dues ^^roater
than 0 .00 . Henc. t h i s solvent can be used for the separation
of these cat ions or any of these ca t ions from numerous meta2 ions .
In addit ion some binary and ternary separa t ions have bee., achieved
experimentally.
CO
oa
^
8
PH
\r\
H
-^ EH
' d +3 o
O O O o (i4 05 '^T-
O
o 0)
•H • • o
a Td +3 CM
o o oco
o t i -p ^
O O OKD
o
0 ?:! o
T J -p i r \ M -H 0) •» o o oin
P4 Oj <>i
O
o •H . . O a Tii -PMD
O O 0.5;J-pc< OJ «}
O •rj . . O a Tb -p ir-
O O OtOk PH oj -=^
Q)
-- O ^ Xi +3 CTi FH -H a> , » O O O T -
!3H 05 <«5
o
o o
o
o
CD
I LP. CM
o
M3 00
o o
CO
0
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0 •
o o
g
d +3 (D
S rt o •H
CM CM
+ + xi d o o
CM
+ (^
CM
+ ^
CM
+ O o
CM
+ •H 12;
o P i I o o •
o
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I O
o o o
o »r I
o o •
o
o
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o
o o o
o
o
CTi
o
o
o
o
o en
00
CM 03
00
o
CM
oo
o
CM
o
9. o o
CM
O O
00
cc
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cr, 00 i n
00 CO 00 00
o o
CD 00 03 00
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8 o
o
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00 0
o
CO
o
00 00 o 00
VD
+ CM CM t<^ CM w -+ +CM+ + + + qf.
M M tiD CD 03 d rt <=? t d M f i , fi4 (53 ! ^
CM 00
CO C O
o
ITS
o
9:9
cn
O
CM CO
cn
CM
CO
o
CM
O
+ + H H S-l C-l
o o
LTV
0) H
EH
(0
i: -P O
o o q o p6< Cj -aj T -
o •rl . . O g Tzi +sc\j ^ -H CD . . o o qcD
PH cd « !
o 0)
•rj . . O
O O OKO
o T J + i LfN
M -H a> . . o o o Lr\
PH d •=!<
o
•H . . o
o o o ^ |J4 C(3 -flJ
O •H . . O a t i -P [r-
o o o t< P nj oj
o •H . . O a T:* -p CTi ^1 -H (U . . o o o ^
P4 cd <«!
'^ •p Pi CD O
CD M3
CO
o
en
in 03
CM CO
8 o
co CO
o o
CO
* O
o CO
o EH
I o o •
o o ^^ • o
o vo •
o EH
Pi I o o o
o • • o
o o
e
o
o o
o o
o
o
o o
o o
o oT o I •
o o o
0
o
o o
o o
o o
o o
o
o o
o o
o o o o
o o o
o o
co
O " ^ O CO
• • o o
CO
O CTi
en
o
o o o
o o
o o
o o
o
o
o o
9, o
o o
o o
o o
o o
o o
o
o
CM CO
o
o
CO
o o o
CO
o
o CO EH O 00 00 OH O l >
0 I • O o o o o
o o
o o
• • o o
00
00 o o 00
o
g o J-" o OH O I • o o o •
o 0^
CO 00
in o 00 — • •
o o
o o o
LTv
en
100 o o
o to
i n C3
• o
en CO •
o
o o
0
o i n
• o
EH
I O o •
o ^
o o •
o
o o 0
o
VO CO
0
o
Cvl 00
4
o
o EH
1 o o •
o
i n CM
• o oT
o o •
o
o o •
o I o o
«
o CM
o o
o
I o o o • o
o
o CM
o
I • o o o o
o o
o o o
ro CM 9
o
o i n •
o
o CM 0
o 1
o o o ' -
CM C-
• o
i n o o o
o 00 «
o
K^
c~ • o
Ll^
o • o
o o • O 1
03 o • o
CM O
• o
+ o
t < ^ t < ^ C M < ^ ^ ^ ^ ^ u ^ L n , x ^ L n c M ^ . + ^ + . + + ^ + , + + + + + + + + CM + VO H - H c U ^ p x l CD C D - H U O X> ^ C t i o 0 +
« H q > e H o c o c - t N j o j t O h ^ E H ^ S : ^
lot
I t i s in te res t i r i i , : t o c o n s i d e r t h a t Pb , La , (Je "
Zr** , Ti"^ , Th"^ , Nb" '- aiid Ta"^^ a re s t a t i o n a r y i n a l l t h e
so lven t systems i n c l u d i n g t h e one in pure i o rmic ac id with an
iL, of OoOO. I t i s p o s s i b l e t h a t t h e s e i o n s except Aij and
Pb a r e stronj^ly adsorbed owin^ t o t h e i r hi^ii c h a r g e s . Pb
has a low R^ va lue because l e a d formate has a very smal l
s o l u b i l i t y i n Water and thereio2:e w i l l have even a lovjer s o l u b i l i t y
in formic a c i d .
I t Was founa i n axi e a r l i e r s tudy [7 ] t h a t a t h igh + "5 +2
c o n c e n t r a t i o n of formate i o n s i'e axtd Gu migra te towards anode i . e . t h e i r complexes aru ai'iionio in n a t u r e axid lience t h e i r h i^h
++ +2 R- v a l u e s . Hgp ion has a lower iU v a l u e than t h e Hg ion
++ r 1 +2 because Hg„ formate i s l e s s soluoleLSJ than t h e Hg f o r m a t e .
Ahrland, Granthe and UoraiifS] found t h a t hydrous s i l i c a e x h i b i t s
Cation exchange p r o p e r t i e s o n l y . S t u d i e s on t h e r a t e of uptake
showed t h a t t h e c a t i o n s may be grouped i n t o two c l a s s e s . Those
With charges upto +5(Gd'*'^, Gu^^, Zn'^^, Co"^2, Ni'^^^ EgV', Hg' ^^
Fe'*"^, Fe+^ , Sa^^^, T1+ , Tl^^^, Gr^^, Bi+^) a re r a p i d l y exchanged
while more h i g i a y charged i o n s a re adsorbed slowly,, Thus Zr''"'
and Nb"*" had a very h igh kd va lue wh i l e Ga"^ , -Sr"*" and Ba"*" have
low Kd v a l u e s . Our s t u d i e s a l so show t h a t Zr"*^, ub"*" ana o t h e r
h ighly charged i o n s have low a^ v a l u e s whi le c a t i o n s wi th charges
upto +3 have h igh il ., v a l u e s . Jig"*" aiid pb"*" a re e x c e p t i o n s probably
because they form i n s o l u b l e x o r m a t e s .
102
The chroiiiatOtj,rapii.i(-; spec t ra have been piol'^ud in
i!'igs. 11-16. ito ana lys ic oi' these Ii£;ures showc thai there are
four types ol spec t ra . 1 . Those which have a coxictttnt hi^.a K^
e .g . , Hg2 , Cd , Cu , Za , Mi , Oo , i l , i J- ,
Sn" ^ , Sn"* , ISe"* , UO^^ and Sb"*" . 2. Those in viiieh the ic . i s
i n i t i a l l y low but inc reases with increase in formic acid cncenl ; -
ra t ion e .g . Tl" "* , Pe"*" and Hg"*" . 5- Those in which the t
value i s constant and low e.:ja A - , Pb , l a , Ce ,
Zr*** , Th"* , Nb"*" , Ta" ^ a;nd Mo . 4 . So.ae exceptiuncu behaviour
which does not f i t any one of these types . This ic exhibited by
Cr"*" , VO" ^ and Ti"*^. The reasons for the shape of the
chromatographic spect ra have been described e a r l i e r [ l o ] . however,
the re are some po in t s which s t i l l need a t t e n t i o n . They are +3 1 , The behaviour of Cr i on . Here the lU f i r s t increases and
+ +2 then decreases . 1. In the case of Ag and VO the lU decreases as the mole f r ac t ion of formic acid inc reases from 0.2 to
0 . 6 .
P lo t s of R Values versus atomic number are {jiveu in
P ig s . 11-15. The in te res t ing ; aspect of these cujves i s ohat tlie
H values are e i t he r below 0.1 or above 0 . 6 . The onl- exceptions +1 +1
are Tl in 4 J 6 (Pormic ac id -ace tone) , Tl in 5:5(Po'.'aic ac id-
acetone), As in 6;4 (P'ormic acid-acetone) sys teus . As a reoul t
numerous separation;.- of one ion from intjjiy ions arc pos;;j 'uie. ^o.ac
of these have been t r i e d as shown in Table 16. However-, soue
ternary separa t ions ar« OIBO poss ib le which have not been
i:Q:3
Table 16 SEPiU^ATIUJ Oi- MTAh lOi^b Tu i-Udi-^C AQli>-AOhj:uLh
SOLViiHT bYSTEKB
Solvent system Heta l i o n s s e p a r a t e d
+ 2 1 . Formic acid.-Acetoiie(4:6) 1 , Pb from numerous metal i o n s
+2 2 . YO from numerous metal i o n s 3 . As"*" from Cu"*" , Ilg "*" and Hg"^^
2 . Formic a c i d - A c e t o n e ( 5 : 5 ) 1 . Tl"*" from Tl"**'"
2 . U02^ from Zr* " , Oe"* and La"*"
5 . Ti"^ from ai"*"^ and 3n"^
4"^ 4»'5 4-'^
3 . Formic a c i d - A c e t o n e ( 6 : 4 ) 1 . As from Fe , Cr ,
Bi"*" and be"^
2 . La"^^ from UOg^
3 . Gr"^^ from Mo"* and \i'^
4 . Formic ac id~Ace tone(8 : 2) 1 . Ti"^ from Cr"*" , Fe"*"
Go"*" and Ni"^^
2. HgJ"*" from Gd" ^
5 . Formic ac id -Ace tonc ( lO:00) U Th"^ from Uot^
2 , La-*- , Th-*^ , Zr-* - , T i " ^ , Nb+5^
Ta"*" , Mo"^ and W+ from
numerous metal i o n s
104
1.0
0.9
0.8
0.7
0.6
Cr+3
DC 0.5
0.4
0.3
0.2
0.1
-
-
• •
-
± -. .Im
U02*
Hg +2 11*3
.Bi*3
i-i£Ltr' Tjw:!i.l il!i!l 10 20 30 40 50 60 70 80 90 100
Atomic number Fig 11 - A plot of Rf vs Atomic number for metal ions in formic
acid-acetone (4;6V/v) solvent system.
10.5
1.0|
0.9
0.8
0.7
0.6
Cr*3<
F»*2
Co' ,•2
a: 0.5
0.4
0.3
0.2
0.1
-
-
-
-
-
' Ti*4
10 20 30 40 50 60 70 80
Atomic number Fig. 12 -A plot of Rf vs Atomic number for metal ions in formic
acid -acetone (5:5 v/v) solvent system.
106
1.0
0.9
0.8
0.7
0.6
Qc'o.ef-
0.4
0.3
0.2
0.1 h
Ce*3 Ta*5/^^ — • - # — — I 1=: LJi^ij^. . ^w " , II
10 20 30 40 50 60 70 80 90 100 Atomic number
Fig. 13 - A plot of Rf vs Atomic number for metal ions in formic acid-acetone (6:4V/v)solvent system.
107
cr
10 20 30 40 50 60 70 80 90 100
Atomic number
Fig. 14 -A plot of Rf vs Atomic number for metal ions in formic acid-acetone (8:2.v/v) solvent system.
1Q8
1.0
0.9
0.8
0.7-
0.6-
cr 0.5
0.4-
0.3 h
0.2-
0.1 -
Fe*3f ACu+2 Tr3 ,
Hg2*
|Ti*^ . Zr^4 JNb^S , La*3Ut*3 Tf*^w*6. ^ Pb*2 JTh*
95 10 20 30 40 50 60 70 80
Atomic number Fig.1 5-A plot of Rf vs Atomic number for metal ions in formic
acid-acetone (10 ;00v/v)solvent system.
109
+ 0 +0 +0 +]}
experiraentally t r i e d , i'or example La troia i-'e , Cr , 'I'l
aJid Bi"*"^.
About 12 ca t ions have aJi % value l e s s e r thrtfi 0.1 ai d
about 19 ca t ions have R^ values g rea t e r than 0 . 5 . There i s
hardly any effect on the R of the 12 cat ions v/ith increase in
formic acid concent ra t ion . However, the iL. of the 19 cat ions
inc reases with the increase in fomdc acid concentrat ion
(P ig .16) .
Ill)
1
8
.6
.4
Z
CC
Cu*2
\Z/
• • ' I I
^O^
-I L.
Fig.1
•4 .6 .8 1 .2 .4 .6 8 1 Z A .6 .8 1
Mole fraction of Formic acid.
6 -A plot of Rf vs mole fraction of Formic acid for 31 metal ions.
I l l
a:
1
.8
.6
.4
.2
1
• 8
6
.4
.Z
1
•8
.6
.4
•Z
1 .8
6
.4
.2
Sn*2
_1 L
Zr • *
• • • • • I • •
W*'
Bi :4'3
Pb ^2
J I L.
Th + 4 Ct • 3
J I I I I
-I I I I I
C0*2
J L. -I I
.2 .4 .6 .8 1 2 .4 .6 .8 1 -2 .4 .6 8 1
Cont'd ' °^^ fraction of Formic acid. Fig. 16 -A plot of Rf vs mole fraction of Formic acid for 31
metal ions.
112
1
.8-
•6
.4
.2
La • 3
• I * * ' • •
-'•'r\
' ' ' ' I
Ta*5
1 -.8
<4-.6 a:
.4
Aq*
Nb «s
Mo *6
_1 J = i * — I I • 2 .4 .6 .8 1 2 .4 .6 .8 1
1
8
.6
.4
.2
V(f2
.2 .4 6 .8 1
Mole fraction of Formic acid.-Cont'd. Fig. 16-A plot of Rf vs mole fraction of Formic acid for 31
metal ions.
113
1 . Macek, K.
J.GhrOmatoc-r. L i b r . , 22A, 1 6 1 , 1905.
2 . Brinkman, U.A. Tho, Yrieo G.D. ajid Kauroda, R.
J .Ghromatogr . , 8 5 , 187, 1973 .
5o Sherma, J» and i ' r i e d , B.
i inal .Ghem.aev. 56 , 48 H, 1 984 o
4 . Quresl i i , Mo a;ad Thakur, J .bo
Sep. S c i . 1 1 ( 5 ) , 4 6 7 , 1976.
5 . Quresh i , Mo and Thakur, J ^ S .
Chromatograpli ia, 1 1 , 7 , 1970o
6 . Quresh i , M., Thakur, J o S . and Quresh i , PoM.
J .L iqo Ghromatogro, 3 ( 4 ) , 6 0 5 , 1980.
7 . Mukherjee,- HoGo and Liebi, A.
J . I n d i a n Ghem.Soc , VLIZ, N o . 7 , 908, 1982.
8 . "GRG hand book of P h y s i c s and Chemist ry" 8 t h ed.
ORG P r e s s , 1 983.
9 . Alirland, So, G-rj3Xith, I and Noren . B.
Acta . Ghim. Scan . , 14 , 1077, I 9 6 0 .
G H ^ P T E R - I V
11.4
STU.UIES OH A DfM'i AlJaOiOSMIT lOI^ EXQIIMaE MATEUAL;
HYDROUS ANTIMDNY bmPHILE
TWTROlUCTIOIiJ
Most of t h e work on i n o r g a n i c ion exchangers has been done
on z i rcon ium phospha te type m a t e r i a l s . The a n t i m o n a t e s , a r s e n a t e s ,
ox ide s a»d o t h e r i n s o l u b l e s a l t s of m u l t i v a l e n t metal ione have
been found u s e f u l f o r many d i f f i c u l t s e p a r a t i o n s . I t was f i r s t
r e cogn i sed by Kraus t h a t t h e s u l p h i d e s of C d ( I I ) , Ag( I ) , P e ( I I ) ,
G u ( I I ) , Z n ( I I ) , P b ( I I ) and A s ( I I I ) have f a v o u r a b l e a d s o r p t i o n
p r o p e r t i e s and they can be used as a d s o r b e n t s f o r metal i o n s which
form more i n s o l u b l e 8 u l p h i d e s [ l , 2 j . The r e a c t i o n s of v a r i o u s heavy
metal i o n s w i t h cadmium su lph ide showed t h a t when d i l u t e ( e . g . ,
t r a c e r ) or c o n c e n t r a t e d ( e . g . , 1M) s o l u t i o n s of s i l v e r , copper o r
mercury n i t r a t e s w i t h o r w i thou t s u p p o r t i n g electrolyte(NaJN'0:,,mJO,)
Were pas sed th rough columns of cadraium su lph ide q u a n t i t a t i v e
removal of t h e i o n s from t h e s o l u t i o n was o b t a i n e d [ 2 ] .
A survey of t h e l i t e r a t u r e shows t h a t p i r o r t o t h e s y s t e m a t i c
work of Kraus some p r e l i m i n a r y s t u d i e s were r e p o r t e d on t h e
adso rp t ion p r o p e r t i e s of Zirconium s u l p h i d e [ 5 ] . Su lph ides of Ag( I ) ,
P e ( I I ) , G u ( l l ) , Z n ( I I ) , P b ( I i ) , C d ( I I ) , l l i ( I I ) , A s ( l I I ) and Sb(V)
have a l s o been s t u d i e d a s ion exchange m a t e r i a l s [ 4 - 1 1 ] . L a t e r on
Qureshi and coworkers s t u d i e d t h e a d s o r p t i o n p r o p e r t i e s of Sn(IV)
115
s u l p h i d e [ l 2 ] . However as f a r as could be ascer ta ined from the
l i t e r a t u r e no systematic v/ork has been reported on antimony
sulphide . In t h i s chapter are given the r e s u l t s of the s tudies
on antimony sulphide as an inorganic ion exchanger.
116
EXPERIiffiNTiilj
Reagents :
Uitimony p e n t a c h l o r i d e (BEH, P o o l e , Eng land) , Sodium
su lph ide (Jflakes, I n d i a ) and a l l o t h e r r e a g e n t s used were of
r eagen t g r a d e .
Apparatus;
Bausoh & Lomb Spec t ron i c -20 spec t ropho tome te r , P h i l l i p s
pH meter , Pe rk in -Elmer spec t ropho tome te r were u s e d .
S y n t h e s i s of Hydrous Antimony Su lph ide :
Hydrous antimony su lph ide (HAS) was p r e p a r e d by mixing
0.1M SbGlc i n 4M HCl and 0»5M sodium s u l p h i d e s o l u t i o n s i n volume
r a t i o 1:2 r e s p e c t i v e l y . HAS Was p r e c i p i t a t e d in an o r a n g e - r e d d i s h
co lou r from t h e h i g h l y a c i d i c m i x t u r e . I t was then al lowed to
s e t t l e down and was s u b j e c t e d t o r e f l u x i n g i n t h e mother l i q u o r
f o r 6 h o u r s . The p r e c i p i t a t e was f i l t e r e d under a reduced
p r e s s u r e of 25-50 Kg/Cm and washed w i t h d i f f e r e n t c o n c e n t r a t i o n s
of h y d r o c h l o r i c a c i d and f i n a l l y wi th d e m i n e r a l i s e d w a t e r . The
washed p r e c i p i t a t e was d r i e d a t 40-6o°G. I t broke down i n t o small
g r a n u l e s wi th immersion of t h e d r i e d sample in Water . The antimony
su lphide was t h u s o b t a i n e d i n two p h a s e s . The o C - p h a s e which was
117
in white colour and in the form oi' f ine powder Was reuoved witii
continuous washing with Dm. The p - p h a s e was oranrje in coloui:
with a p a r t i c l e s ize of 50-200 mesh. I t was then convertud to the
H" form using 0.1M HNO .
Ion ExchanjS e Gap a c i ty ;
The ion exchange capacity was determined "by the column method
[l3j . 0.5g of the exchanger in the hydrogen form was pacLed in a
column with a g l a s s wool support . The packed column was washed
with d i s t i l l e d water . The hydrogen ions were then e lu ted with
1M solut ion of sodium n i t r a t e . The eff luent Was col lec ted at a
r a t e of 15-20 drops/min. I t was about 200 ml. The l i b e r a t e d II"*"
ions were t i t r a t e d against a standard sodium hydroxide so lu t ion .
The ion exchange 'capacity was found to be 0.66 meq/g fo r Ra
ions .
Ghemical Composition:
0,5 g of t he sample was heated with the fusion mixture (1.5 g
of Wa No, and 1 .5 g NapGo^) and the melt was dissolved in water .
After reduction antimony was determined using the pyrogal lo l
method[l4] . The sulphur was oxidized with HNO and Was deteriained
as BaSO. gravimetr ica l ly[15] . The mole r a t i o of Sb to 3 was found
to be 1 .86,
118
Ghemical S t a b i l i t y ;
0 .2 g of the Sample was shaken in a number of minernl acid
so lu t ions for 6 hours and the antimony was determined spectrophoto-
met r i caLly [ l6 ] . Sulphur Was determined t i t r i m e t r i c a l l y [ 1 7 ] .
IR Spectrum;
I t Was recorded by the KBr disc method, and the data are
given in Table 17.
Dis t r ibut ion Qoeff ic ients ;
The d i s t r i b u t i o n coefficients(Kd) fo r some of the ca t ions
were determined by the batch process in DMl, Kd values were
Calculated using the equation,
I - P 50 Kd = X ml/g.
P 0 . 2
where I i s the i n i t i a l volume of EDTA consumed by the so lu t ion ,
I the f i n a l volume of EDTA consumed a f t e r e q u i l i b r a t i o n . All
the cat ions were est imated by t i t r a t i o n s with EDTA[18] . The
r e s u l t s are given in Table 18.
lU
Separg.tions;
Por separat ion s tud ies a 50 cm g la s s column with a
0.6 cm diameter was used, 1,5 g of the exchanger in the H
form Was packed in the column with a g la s s wool suppor t . A
solut ion of metal ions Was then t r ans f e r r ed to the column and
was passed through at a slow r a t e and the process of recycl ing
was ca r r i ed out . The e lu t ion of metal ions was s t a r t e d a f t e r
30 minutes of load ing . The flow r a t e was maintained at 1 ml/
min. throughout the e lu t ion p rocess . Metal ions in 10 ml
f r a c t i o n s were then co l lec ted and determined t i t r i m e t r i c a l l y
with EDTA. The r e s u l t s are summarised in Table 19.
120
A number of samples were prepared with d i f ferent mixin{^
r a t i o s of antimony pentachlor ide stnd sodium su lph ide . However,
the sample of HAS under study was found best regardinj^' the
mechanical s t a b i l i t y , p a r t i c l e s i ze and other column operation
q u a l i t i e s . The composition r e s u l t s i n d i c a t e t h a t the mole
r a t i o of Sb in the mater ia l i s hi{^her than tha t of S. This may
be due to the hydrolys is of antimony pentacii lorido besides the
formation of the sulphide because the ac id i ty of antimony
solut ion changes upon the addi t ion of sodium sulphide so lu t ion .
The change in ac id i ty leads to the i'oruiation of iiydrolycod
antimony sulphide and therefore the p r e c i p i t a t e so obtained i s
designated as hydrous antimony su lphide .
The Inf rared data (Table 17) of ilA^ show maxima at 5100 Cm , -1 -1 -1
1580 Cm , 1230 Cm and at 94-0 Cm which correspond to the
deformation v ibra t ion of the coordinated water ((HpO) Go-ord),
deformation v ibra t ion of i n t e r s t i t i a l water and of hydroxyl
groups [ 62(1-120)
i n t ^^^ (C*!!)] , deformation v ibra t ion of M-OII
groups [S^Csb-OH)] and s t r e t ch ing v ib r a t i ons of i-I-S ["Yj(i>b-S)3
r e spec t ive ly . A very sraall peak appears at 7^0 Cm which
corresponds to the s t r e t cn ing v ibra t ion of M-0[ "Yp( Sb-0)] bonds.
This study supports the contention tha t the mater ia l i s not only
the sulphide of antimony but i t i c hydrous antimony sulphide .
121
T a b l e 17 TENTATIVE BANU Al.3iaiJMEI^T!J IN T m I R
aPECTilUM Ux'' ilYJjROUo Al' l'Ii'DNY oULPiajjE
Band (Cm-"') I n t e n s i t y S p e c i r i c g r o u p v i b r a t i o n
3100
1580
1250
S, B
3 , B
3 , Shp
6^ HpOCdeformat ion
v i b r a t i o n of Go-ord.HpO)
6pH20 and OH ( d e f o r m a t i o n
v i b r a t i o n of i n t e r s t i t i a l
H^O ajnd OH) .
6 „M-OH ( def 0 rmat ion
v i b r a t i o n of H-OH)
940 M, 3hp ^ ^ S b - S ( 3 t r e t c h i n e
v i b r a t i o n of 3b-30
780 W, B V Sb-0 ( S t r e t c h i n g
v i b r a t i o n of 3b-0)
S : S t r o n g ; M : Medium; W : Meak; B : B road ; Shp : Sharp
122
Heat treatment of the samples at var ious temperatures
shows tha t HAS loses i t ' s t o t a l ion exchange capacity at 350 G,
The d i s t r i b u t i o n coe f f i c i en t s f o r some metal ions in iMi
•were determined and are presented in Table 18. The pKg (- log Kg ,
£„ = s o l u t b i l i t y product) of the corresponding metal sulphides bp
are also shovm in the Same t ab l e and a p lo t of p^g^ vs log Kd
in ? i g . l 7 i s also g iven . Kd values in U^lii vary v i t h the pKg
values i o e . the Kd value inc reases with increase in the pKg
va lue . Mg(II), Ca( I I ) , Sr ( I I ) and Ba(II) have low Kd values
because they form water soluble su lphides . This behaviour of
HAS revea l s tha t the uptake of the ion from water i s mainly
through adsorpt ion . Therefore the ions whose sulphides have
high pKo values form highly s t ab le p r e c i p i t a t e s during
adsorption over the surface of HAS. The low uptaJie of the ions
whose sulphides are soluble i s mainly due to the ion exch^mge
process .
I t i s c l e a r from Table 18 tha t the mater ia l shows the
highest preference for the Hg(II) i on . The separat ion f a c t o r s
(Qjy[ ) for Hg(ll) with respect to other ions have been calculated
and l i s t e d in Table 19. A number of metal ion p a i r s with Hg(II)
have been separated succescful ly .
I t i s c l ea r from the above that hydrous antimony sulphide
can be used for the removal of an important pol lut tui t i . e . Hg(ll}
from pol lu ted water . Jj'urther work i s necessary for the characteri-
123
Fig.l 7-A plot of log kd vs pksp for metal ions on Hydrous Antimony Sulphide
124
Table 18 uis'i'iaiiui'ioB (;ui:;i''m:XLi]'i's i^va soi ffi iiLTij. lun^ IN Dh\i on HAIJ £iD pK VALUEIJ Qi'' TIIMK auKi(i:;b-
POKiJii-IG iiULi'lilDE^i
Cation Kd va lueCml /g ) pk bp
Mg "^
Ga^^
Sr2^
Ba^^
Mn2+
Fe^^
Co2-
11x2+
Cd2+
Hg2-
5 5 . 2 0
680OO
9 2 . 0 0
8 8 . 6 0
1 6 0 . 0 0
182o00
1 9 4 . 8 0
2 0 8 . 0 0
264 .60
10917.00
15.15
18.40
26.72
27.00
28.29
55.00
125
T a b l e 1 9 SEP.UUTIOIJ i-'ACTOR io^^^) Of IIA^"^ ION
VjITH RhBPLCT I'O Ol'ilEK METAL I ON a ON
HAS li^ Dm
S e p a r a t e d p a i r Va lue
•^Sr
'^Ba
%\?
197.
160
118
124
68
59,
56.
.90
.40
.60
cOO
.19
.94
.0 2
52.44
4 1 . • 32
126
z a t i o u 01 ilAli aJiLi i 'or ytiulyin^j t h e Kiecluitii^jiii ol" adoo^-'ptiuii
of t h e variouG i o n s .
1 r -1
REFEREI^QES
1. Kraus , K.A. firid P h i l l i p s , H.O.
J . Ajner. Chem. S o c , 85 , 486 , I 9 6 3 .
2 . P h i l l i p s , H.O. and Kraus , K.A.
J .Ghromatogr . , 17, 549, 1965.
3 . B r a s l e r , S .E. , Sinochkin Yu,D. , Egorov, A . I . and
Perumov, D.A.
Radiokhimiya . , 11 , 507, 1959.
4 . Tyagai , V.A., P e t r o v a , N.A. a;nd Treskunova, l i .L .
E l e c t r o k h i m i y a . , 4 , 179, 1968.
5 . Che l i shchev , N . P .
Dokl.Akad.Hauk(USaR), 192, 1127, 1970.
6 . Lvovich, B . I . and Volkhin, V.V.
Zh. NeorgaJi.Khim., 15 , 520, 1970.
7 . Eremenko, B.A. , S i d l y a r , L.M. and Uskova, E .T .
l o n i t y l o n n y i Obmen, Akad. Nauk(USSR)
S b . S t a t e i , 76 , 1966.
8 . Volkhin, V.V. tmd Luovich, J J . l .
Zh .p r i i a .kh im(Lonin i i r ad ) . , 4 0 , 988, I 9 6 7 .
ns
9. Yolkhin, V.V. and Luovich, B . I .
S i n . Svo i s tva lonoobmen, H a t e r . , p . 7 3 , I z d .
Wauka, Moscow, 1968.
10 . G e o r l i c h , Z.
Zeszyty Nauk Univ. J a g i e l , Ser .Nauk.Ghem. ,7 ,5 ,196 2.
1 1 . Lvovich, B . I . and Yolkhin , V.V.
Zh. Neorgan. Khim., 13 , 570, 1968.
12 . Quresh i , M., EaWat, J . P . and Gupta, A.P.
I n d . J . TeGhnol . ,15 , 8 0 , 1977.
1 3« Samuelcon, 0 .
"Ion exchc'inge s e p a r a t i o n s i n a n a l y t i c a l C h e m s t r y "
John Wiley and Sons, New York, p . 3 7 , 1963 .
H . Vogel , A . I .
"Text book oi" q u a n t i t a t i v e i n o r g a n i c a i i a l y - i c "
Longman and Co., London, 4 t h e d . , p . 4 5 1 , 1978.
15 . Idem, I b i d . p.504
16. Idem. I b i d , p.731
17 . Idem. I b i d , p .385
18. R e i l l y , N., S t i aud , KM. and Sadak, K .S .
J .Ghem.Edu., 50, 555, 1959.
G H A P T E R - V
129
Pfi£LIl€HAiiY STUDIES ON THE SYNTHESIS OF SOi-IE NEW
INOKGiUTIC ION EXCHANGERS
INTJi DUCTION
The a n a l y t i c a l impor tance of s y n t h e t i c i n o r g a n i c ion
exchangers i s now f i r m l y e s t a ' b l i s h e d due t o t h e i r h igh
s e l e c t i v i t y , t he rma l s t a b i l i t y and r e s i s t a n c e t o r a d i a t i o n s .
They a r e f i n d i n g i n c r e a s i n g use i n t h e f i e l d s of medic ine ,
energy r e s o u r c e s recovery and p o l l u t i o n aba tement . Therefore ,
t h e i n v e s t i g a t i o n of t h e s e m a t e r i a l s has become a c u r r e n t
f i e l d of r e s e a r c h . A l a r g e number of i n s o l u b l e s a l t s of
p o l y b a s i c a c i d s have been i n v e s t i g a t e d a s inorgajxic ion
exchangers and have proved t o be an e x c e l l e n t a l t e r n a t i v e t o
o rgan i c r e s i n s .
U n f o r t u n a t e l y i t i s not y e t p o s s i b l e t o p r e d i c t t h e
p r o p e r t i e s of i n o r g a n i c ion exchange r s . An i n t e r e s t i n g at tempt
has been made t o f i n d an e m p i r i c a l r e l a t i o n between t h e c h e m i c ^
s t a b i l i t y and t h e chemical s t r u c t u r e of an ion exchanger [ 1] .
According to t h i s s tudy t h e chemical s t a b i l i t y of an i n o r g a n i c
ion exchanger depends up on t h e anion p r e s e n t and i s i n t h e
f o l l o w i n g o r d e r ,
molybdate < a r s e n a t e <, s e l e n a t e <. an t imonate <_ p h o s p h a t e <
t u n g s t a t e .
130
iijfiother important c h a r a c t e r i s t i c oi an ion exchanger i s i t o
ion exchange capac i ty . I t i s therel 'ore vforthv/hile to synthesize
new inorganic ion exchangers and to determine t h e i r ion exchange
c a p a c i t i e s . For t h i s purpose Fe( I l ) antimonate, HgpCH)
ajitimonate, Ag(I) antimonate, Uranyl t u n g s t a t e , bas ic tantalum
sulphate and niobium tungs toarsenate were synthesized and t h e i r
ion exchange capac i t i e s determined. The f i r s t th ree exchangers
are based on comuion ca t ions and may prove to be inexpensive.
Uranyl phosphates have been sys temat ica l ly studied[2-4] but
very l i t t l e work has been done on Uranyl t ungs t a t e s as ion
exchange m a t e r i a l s .
Oxides of tantalum and niobium are noted for t h e i r cheraical
i n e r t n e s s and hence t h e i r s a l t s are expected to have good
thermal a;nd chemical s t a b i l i t i e s . While repor t ing a de ta i led
inves t iga t ion on tantalum t u n g s t a t e , Qureshi e t . a l . reported[5]
some preliminary s tud ies on bas ic tantalum sulphate as an ion
exchange m a t e r i a l . Me have synthesized bas ic tantalum sulphate .
I t ' s anion exchange p r o p e r t i e s were found to be more in t e re s t in : ,
than i t s cation exchange p r o p e r t i e s .
The cation exchange behaviour of the s a l t s of heteropoly
acids and t h e i r de r iva t ives i s well known. I t i s an i n t e r e s t i n g
fea tu re of the heteropoly acid de r iva t ives tha t t h e i r p rope r t i e s
are d i f ferent from tiiose of the simple s a l t s from which they are
derived. Heteropoly tun/ :s ta tes have been used as c a t a l y s t s for
131
the photochemical reduction ol' oxygen and water r e c e n t l y [ 6 ] .
Various molybdophosphates, tungstophosphates and other
heteropoly acid s a l t s used as ion exchaagers v;ere reviewed by
Pekarek and Vese ly[7] .
Vihile studying the ion exchange p rope r t i e s of a var ie ty of
heteropoly acid s a l t s the Vaa K. Sroits group reported[8] the
synthes is of ammonium-1 2-tungsto a r sena te , (NH.) , ( As W pO/n) X HpO
but found tha t i t e i t h e r dissolved or i t formed a co l lo ida l
solut ion when used for absorption s t u d i e s . La te r on with some
improvements the same mater ia l was reported to have a high cation
exchange capacity and Was found su i t ab l e fo r the separat ion of
ab" , Gs , K , Tl and Ag [9J . Tung sto arsenate s a l t s were
fu r the r improved by replac ing the ammonium ions with organic base
anions such as the pyridinium i o n [ l o ] .
The exchanger pyridinium tungstoarsenate was found to be + +
highly se l ec t ive for Ag and Gs . Heterogenous membranes of s a l t s
of tungsto a rsena tes of Rb(I) and C u ( I I ) [ l l ] and Gs(I) and T1(I)
[12] were used as ion se l ec t ive e l e c t r o d e s .
Extensive l i t e r a t u r e survey revea l s t ha t l e s s a t t e n t i o n has
been paid to the development of niobium based_ exchangers and even
l e s s e r a t t en t ion to i t s heteropoly acid d e r i v a t i v e s . Woven and
Ghizdovn[l5] synthesized heteropoly acid compounds of niobium such
as niobio t ungs to s i l i ca te , Hg(3i " i ^NhpO^Q) and the s t ruc tu re of
the phase was es tab l i shed on the bas i s of i t s composition, Ifi and
polarographic s t u d i e s . Kato e t . a l [ l 4 ] reported the synthesis 01
132
niobium molybdophosphate and found tha t i t Was a su i t ao le
ca ta lys t l o r the oxidation oi' unsaturated aldehydes. Thoujh a
considerable work has been reported on the polybasic acid s a l t s
of niobium such as phosphate, t u n g s t a t e , a r sena te , molybdate,
antimonate and niobium hydroxide none of i t s heteropoly acid
s a l t s have been explored for i t s ion exchange p rope r t i e s so f a r .
iSfiobium tungstoarsenate i s expected to be a s tab le and se lec t ive
ion exchange and hence these samples were synthesized under a
Variety of experimental condit ions and t h e i r ion exchange
Capacit ies were determined.
Our s tud ies on the synthes is and ion exchange p roper t i e s
of fer rous antimonate, s i l v e r antimonate, uranyl tungsLate ,basic
tantalum sulphate and niobium tungstoarsenate are presented in
t h i s Chapter.
Synthesis of Ferrous antimonate;
Ferrous ammonium sulphate (Sarabhai Chemicals, I n d i a ) ,
potassium pyroantimonate(Riedel, G-ermany), Dowex 50 WX8 (Ka ) ,
antimony pentachlor ide (BDH, Poole) . All other reagents used
were of AnalaR grade.
133
procedure;
jijatimoniG acid was prepared as described e a r l i e r .
O.OIM so lu t ions fe r rous amjuonium sulphate and antimony
pentachlor ide were prepared in 0.01M su l fu r i c acid and 4M
hydrochloric acid r e s p e c t i v e l y . Samples of fe r rous antimonate
were prepared using both antimonic acid and antimony
pen tach lor ide . i'ormic acid was added to prevent the oxidation +2
of Pe ion during p r e c i p i t a t i o n . The samples were then -I-
refluxed and were converted to H form as described previously.
The ion exchange c a p a c i t i e s , determined as described e a r l i e r ,
are summarised in Table 20.
Synthesis of S i lver Antimonatet
Reagents;
S i lver n i t r a t e (E Merck), Potassium pyroantimonate (Riedel ,
Germany), Dowex 50 \i ZBCNa" form). All o ther reagents used were
of AnalaR grade.
Procedure;
O.OlM antimonic acid was prepared as before , 0.1M
solut ion of s i l v e r n i t r a t e was prepared in O.OlM n i t r i c ac id .
134
Si lver antimonate samples v/ere obtained by mixing the two
so lu t ions in 1:2 r a t i o ( s i l v e r n i t r a t e : antimonic acid) at
d i f ferent pH va lues . The p r e c i p i t a t e so obtained was allowed
to stand for 24 hrs at room temperature . I t was then refluxed
with the mother l i q u o r , f i l t e r e d , washed and then dried at
40° - 50°C. The mater ia l was converted to the hydrogen form
as before . S i lver antimonate thu^ obtained was in the form of
powder and was unsui table for column opera t ion .
Synthesis of Uranyl tungs ta te ;
Rea<g:ents;
Uranyl n i t r a t e (BDh, Poole) , Sodium tungstate(B]jH)
All other reagents used were of AnalaR grade.
Procedure;
0.05M, 0.1M and 0.3M so lu t ions of Uranyl n i t r a t e (were
prepared in the corresponding concentra t ions of n i t r i c acid)
and Sodium tungs ta te were prepared. The so lu t ions were mixed
in d i f ferent r a t i o s at various pH va lues . The p r e c i p i t a t e s
were then f i l t e r e d and washed several times with d i s t i l l e d
Water. The samples were dried and were then converted to
the hydrogen form as described e a r l i e r . The ion exchange
capac i t i e s of the samples, determin.-;d as described before, are
su miaari s e d in T a bl e 20 .
135
Synthesis of Basic tantalum sulphate;
Reagents;
Tantalum pentoxide(Bl}[i, Poole) , Potassium carbonate.
Potassium n i t r a t e and Sulfuric acid were of E.i'lerck, All
other reagents used were of Analafi g rade .
Apparatus;
Real e l e c t r i c fU2::nace(Real S c i e n t i f i c Corporation, Calcutta,
India) to maintain the required temperature, platinum crucible for
fusion purpose.
Procedure:
A new procedure fo r the d i sso lu t ion of tantalum pentoxide
Was devised by Qureshi e t . a l . [ l 5 ] and i s adopted here for the
purpose. A mixture of welx powdered tantalum pentoxide(1g),
potassium n i t r a t e (2 .5 g) and potassium carbonate (2 .5 g) in
15 ml platinum cruc ib le was heated in a furnace at 740-760°C
for 15 min. The temperature was careful ly cont ro l led as at
higher temperature e .g . 840°C i t g ives a product inso lub le in
concentrated H2S0^. The cooled melt was then t r ans fe r r ed to a
b o r o s i l i c a t e g la s s beaker with not more than 25 ml of concentrated
HpSO. ajad the contents of the beaker were heated on an e l e c t r i c
136
heater for 30 min. IMring t h i s treatment brovjn fumes were
evolved with vigorous effervescence. A c lear solut ion was
obtained in su l fu r i c ac id , i'ollowing t h i s procedure 10g of
tantalum pentoxide was dissolved in 500 ml of concentrated
su l fu r i c acid and d i lu t ed to 5 l i t r e s with d i s t i l l e d water,
50 ml of concentrated n i t r i c acid was added and the solut ion
Was boiled for two hours . The p r e c i p i t a t e so obtained was
allowed to stand fo r 24 hrs at room temperature . I t was
then Washed repeatedly with d i s t i l l e d water and dried at
60°Q. The mater ia l broke down to small p a r t i c l e s on immersion
in Water.
Ion £xchan!g:e Capacity;
Por the determination of Ion exchange capacity 100 ml of
1M HCa. Was passed through a column packed with 0.5 g of the
exchanger in sulphate form. The eff luent Was then co l lec ted
and the sulphate ion concentrat ion in i t Was determined
v o l u m e t r i c a l l y [ l 6 ] . The anion exchange capacity was found to
be 0.88 meq/g fo r Cl7
137
Synthesis of Niobium tuns toarsena te ;
Reagents;
Hiobium pentoxide (BLH, Poole) , Sodium tungsta te(BIi i ) ,
Sodium arsenate( J.T.Baker,USA) and Ammonium sulphate(BJJH) .
All other reagents used were of AnalaR grade.
Procedure;
15.291 g of Niobium pentoxide was heated with 400 ml of
concentrated HpSO. containing 135 g of Ammonium sulphate u n t i l
a c l ea r solut ion was obta ined. The solut ion was then cooled and
200 ml of concentrated HpSO. was added to make a 6o?^ acid
concentra t ion. The solut ion was then d i lu ted to 1 l i t . with
d i s t i l l e d water to give a 0.01M niobium so lu t ion . 0.1M
so lu t ions of sodium tungs ta t e and sodium arsenate were prepared
in d i s t i l l e d water . The so lu t ions of sodium tungs ta t e and sodium
arsenate were mixed before adding them to niobium so lu t ion . The
samples were prepared by mixing the so lu t ions in d i f ferent
r a t i o s and the pH was adjusted to 1 with Ammonia. The
p r e c i p i t a t e s were then kept for 24 h r s . at room temperature,
l i l t e r e d and washed several times with d i s t i l l e d water . They
were then dried at 60°C. Conversion to the H"*" form was carr ied
out as described e a r l i e r . Their ion exchange capac i t i e s are
given in Table 20.
138
UlbCUbSluH
During the l a s t f i f t een years many new inorganic ion
exchangers have "been synthesized and t h e i r ion exchange
p rope r t i e s have been s tud ied . They have been found to be
s e l ec t i ve fo r some inorganic i o n s . I t has also been observed
that the s e l e c t i v i t y of an ion exchanger can be var ied by
changing the condi t ions of p repa ra t ion . In cont inuat ion of
our systematic x/ork on some new inorganic ion exchange materials
a few preliminary s tud ies have been ca r r i ed out on the synthesis
and ion exchange p rope r t i e s of i"e(II) antimonate, Ag(I) antimonate
Uranyl t u n g s t a t e , Basic tantalum sulphate and Niobium tungsto
a r sena t e . The condi t ions for the synthes is of these ion
exchangers are summarised in Table 20.
A study of the d i f fe ren t f a c t o r s such as the nature of the
s t a r t i n g ma te r i a l s ! e . g . , subs t i t u t i on of ajitimonic acid for
potassium pyroantimonate as a source of the antimonate ions) for
the synthes is , the concentrat ion of the solut ion of the s t a r t i n g
ma te r i a l s , mixing r a t i o s of the so lu t ions , order of mixing of the
parent reagents , p r e c i p i t a t i o n pH, the chemicals used to maintain
the p r e c i p i t a t i o n pH(e.g. NH.OH or HaOH) and ref luxing the
p r e c i p i t a t e s on the ion exchange capacity of the inorgatiic ion
exchangers makes an i n t e r e s t i n g study.
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Efl'ect of the nature ox the litgrtin,, ugtcj-j.-i^ls:
The convention^il metaod oi' p r e c i r a t a t i o n \.iU put Si ium
pyroantimonate for the pre])aration oi' antimon;itos oi vj riouc;
metals gave products v.'hich v/ere unsui table i o r colUi.Tn operat ion.
During systematic s tud ies on the ion exctujige p rope r t i e s of
antimonates prepared with azitimonic acid i t was found th;xt the
mater ia ls exhibi t b e t t e r mechanical s t r eng ths , abtain a l a rge r
p a r t i c l e s ize and show an increase in the ion exchange ca aci ty
as compared to the mater ia l s obtained from potassium Tjy ro
antimonate. Such an inves t iga t ion was extended to i ' e ( l i )
antimonate. I t y ie lded samples with higher ion exchange
capac i t i e s compared to the sa^^^plos prepared by using pot ^s:^lum
pyroantimonate and antimony pentachlor idc . \i e have attci-irited to
synthesize niobium tungsto arsenate samples using tungs to -
arsenic aoid in place of sodium tungs toa r sena te . However there
Was l i t t l e success in our e f fo r t s to synthes ise tuugs toarsenic
acid by t r a d i t i o n a l methods, i 'ur ther i n v e s t i g a t i o n s are to be
car r ied out to f ind an a l t e r n a t i v e method for the synthes is
of tungsto a rsenic acid and use i t as one of the parent reagents
f o r ' t h e synthes is of niobium tungLitoarsenate.
Effect of the Concentrations of the mixing so lu t ions ;
In the case of Uranyl tungs ta te the samples obtained frou
0.05M and 0.1M so lu t ions of the parent reagents were in the form
of greenish yellow opaque p a r t i c l e s with low ion exchange
144
c a p a c i t i e s . As the concentrat ion of the reagents was increased
to 0.3M the Samples obtained were yellow shiny p a r t i c l e s \ / i th
higher ion exchaiiije c a p a c i t i e s . O.OlH concentrat ion of i ; 'e( l l) ,
Ag(I) and antiiaonic acid so lu t ions vfere used for the preparat ion
of a l l the Samples of ]?e(II) and ^lg(I) antinionates. Our
previous experience on antimonatcc showed tha t the saiflplGs
obtained are moL'e su i t ab le fo r column operat ions vJhen the
concentrat ions of the mixing'-; reagents are lov/ered, OolH
concentrat ions of niobium, tun^s t a t e nnd arsenate so lu t ions
were used for the preparat ion of a l l the samulos oi niobium
tungsto a r sena te . While synthesizing the inso luble s a l t s of
niobium(e.g. Niobium phosphate) i t Wac observed tha t the sampi c
obtained with 0.1H concentra t ions of the reagents exhibited
b e t t e r ion exchange p rope r t i e s compared to the samples rreuareu
with higher con cent r a t i^^ns of the r eagen t s .
Effeot of the mixing r a t i o s and the order of mixing
of the parent rea.'^':ents;
In the case of uranyl t ungs t a t e and Kiobium tungsto
arsenate there was a gradual improvement in the physical
p rope r t i e s ( e . g . , cracking) ana the ion exchange capacity oi
the samples wilh increase xn the mcttU-anion r a t i o . ;ji mcre.-'.se
in the volume r a t i o of sodium tuncistate and sudiuia a r so ia t e
•145
so lu t ions r e su l t ed in e i t h e r co l lo ida l so lu t ions or i ~ave a
mater ia l which dissolved at pH 1 . There Was not much dif-t'erezice
in the ion exchati^'e c apac i t i e s hov/ever.
I t i s in teres t ing; t o note the v a r i a h i l i t y exhibitou. hy
the samples following the order of mixing of t h e parent reagents .
The samples prepared by adding the solut ion of sodium tungs ta te
dropwise to a solut ion of uranyl n i t r a t e showed higher capac i t i e s
while the samples prepared by adding uranyl n i t r a t e solution
dropwise to a solut ion of sodium tunjgstate showed lower
c a p a c i t i e s . Mxing r a t i o s of 1:2(M:Sb) for ]?e(II) antimonate,
1j1 (i'I:\^) fo r uranyl tungs ta t e and 1:2:2 (Nb:\j;As) for Kiobium
tungsto arsenate were found to give good samples v/ith higher
ion exchange c a p a c i t i e s .
Effect of p r e c i p i t a t i o n pH ai d the na ture of the bases used to maintain the p r e c i p i t a t i o n ull;
The ion exchsmge capacity of i' 'e(II) antimonate inoroaces
with increase in the p r e c i p i t a t i o n pH for the samples prepared
with antimonic ac id . In the case of Uranyl t ungs t a t e the saiuples
obtained were greenish yellow opaque mate r i a l s at 1O\J p rec ip i t a t ion
pH Values and exhibi ted l i t t l e cracking on immersion in water.
The samples showed improved physical p rope r t i e s and mechanical
s t rengths with an increase in the p r e c i p i t a t i o n pH. V(hen
p r e c i p i t a t e d at higher pH values shiny p a r t i c l e s were obtainua
146
which, cracked s igni i iccja t ly on iiainersion in water . Ion exchange
capac i t i e s are hi^lier xor these Samples. A prcc i^u ta t ion pH
of 4 Was found to be su i ta t ' l e for the Uranyl tungsfcate synthcc is .
Two types of niohium tun^joooarseni^te samples were prepared.
The condit ions for the synthes i s of the tvjo types were iden t i ca l
in a l l r espec t s except tha.t in one case NILOII Was used to maintain
the p r e c i p i t a t i o n pli at 1 while in the other case sciium hydroxide
Was used l o r t h i s purpose. The p r e c i p i t a t e s obtained by
adjust ing the p r e c i p i t a t i o n pH with sodium hydroxide were
d i f f i c u l t to f i l t e r ahd produced samples with very small p a r t i c l e
s i z e . Sample S-144 dissolved when the pH was adjusted with
NaOH to 1. The samples were >^rey in colour aJid opaque. They
showed l i t t l e cracking- on immersion in water . However there
Was a remarkable improvement in the physical p rope r t i e s and
mechanical s t r eng ths of the samples when the p r e c i p i t a t i o n pPI
Was adjustod with aiimonium hydroxide. The sa^uples were white
shiny p a r t i c l e s which broke down vit;orously on iuuuersion in
Water. The p r e c i p i t a t e of sample a-144 could also be obtained
when the p r e c i p i t a t i o n pll Was adjusted with ammonium h^'droxiae
where as i t dissolved with the addi t ion of sodium hydroxide.
Xnspite of the fac t t ha t the re ex i s t s ' a d r a s t i c difference
in physical p rope r t i e s ol t he two types of the samples there i s
l i t t l e dif ierenvu in thei.- ion exchange c a p a c i t i e s .
147
Effect of refluxin;!-:; the Drec ip i t a tos ;
The ion exchconge capac i t i e s of the refluxed sam;)lbc vore
alviays l e s s in the case oi' Fe ( l l ) c-aitiiaonate samolet: coiaparco. to
the unrefluxed ones. This was a t t r i b u t e d to the surface area of
the unrefluxed saiaples. Aa'(I) oiitimonate wac obtained iii the
form of a povjder and remained in ohe po'k.'der forra oven p l t c r
refluxint;^ the p r e c i p i t a t e s v.'ith the mother l i q u o r . Hence no
fu r the r s tud ies could be carr ied out on t h i s jua te r ia l .
Basic tantalum sulphate i s a white hard glassy material
and possesses an anion exchange capacity of 0.08 meq/g. I t
hydrolyses in water and ma -- shov: atiion exchs.mge p rope r t i e s in
ac id ic and nonaqueous media. In fac t in concentrated n i t r i c
acid and concentrated sulphuric acid i t d issolves to a very
small ex ten t , i-'urther ref luxing t h i s mater ia l with n i t r i c acid
may prove to be useful and t h i s aspect i s to be s tud ied .
Detailed s tud ies are to be ca r r i ed out on a l l these ion
exchange mate r ia l s synthesized above to make a f u l l use of t i ie i r
ion exchange p o t e n t i a l i t i e s .
148
1 , Qureshi , M. ano ThaLur, J . S .
J . l n o r j . I Juc l . Ghem. L e t t . , 15, 239, 1979.
2 . pekarek , V. aaid Benesova, M.
J . I n o i v , . ITucl. Ghem., 26, 1745, 1964.
5 . pekarok, ^/., Vesely , V. ;uict U l l r i c h , J .
B u l l . 3oc. Ghim. i ' ' raiice., 1844, 1968.
4 . pekarek , V. , Vesely , V. ajid Abbrent , i-I,
J . I n o r y . Wucl. Ghem., 27, U 5 9 , 1965.
5 . Qureshi , H., Rat IJ o r e , U . S . , Thakur, J . 3 . caid
Qureshi , P . 11.
Reac t ive P o l y m e r s . , 1, 101-108, 1985
6 . Akid. R. imo. DarvJent, J . R .
J . Ghem. See . Lal ton Tra j i s . , No .2 , 595, 1985
7 . pekarek , V. and Vese ly , V.
Talaxita Rev. , 19, 219, 1972o
8 . Smit, V . J . R . , Jocobs , J . J . aJid Robb, fu
J . I n o r - . N u c l . Ghem., 12, 104, 1959.
9 . Sxoit, V . J . R . , Qer. P a t . , 1, 210, 1966.
149
10. Ma l l i k , '«J.U., t i r i v a s t a v a , 3oIi. ajid i^um^.r, S.
TaJLaJita., 25, 323, 1976.
1 1 . J a i n , A.K., Singh, R .P . and Agra'V'al, S.
J . I n d . Ghem. S o c , ^/XIX, 106, 1902.
1 2 . I ' la l l ik , VioU., S r i v a c t a v a , o . k . , Razdon, P . and
Kumar, 3,
J .E l ec t roa j i . a l . Ghem., 72, 111, 1976.
1 3 . Horen, G-. and Ghizdatia, L .
Rev. Roum.Chim., 2 1 ( 4 ) , 589, 1976.
H . Ka to , M., I s h i , l i . , Hideo, i-I., i^^obayashi, i-1, and
I S h i , H o
Japan K a k a i . , 115, 4 1 3 , 1976.
1 5 . Quresh i , H., Ra thore , HoS. and ThaJiur, J.3.
T a l a n t a . , 25, 232, 1978.
1 6 . Vogel, A.l .
"A Text Book of Q u a n t i t a t i v e I n o r g a n i c A n a l y s i s "
Longman, London, 4 t h ed . 1978, p . 4 0 9 .
C H A P T E R - V I
150
M Mmd'a AT THiJ CUitllELATlUH Oi?' Kd VALUES \aTlI
BASIC PROPERTIES Oi-' SOi-a; INO£GALaG
ION EXGHAI GEHS
IirriluDUOTlOl^
In o r d e r t o a r r i v e a t a u s e f u l c o r r e l a t i o n oi t h e b a s i c
p r o p e r t i e s such as ion exchmige c a p a c i t y , i o n i c r a d i u s , atomic
number i o n i c charge \ ' i t h t h e Kd v a l u e s of i n o r g a n i c ion
exchangers an e f f o r t has been made to summarise t h e s e p r o p e r t i e s
of some i n o r g a n i c ion exchangers i n t h e form of s u i t a b l e
p l o t s .
Let us c o n s i d e r f i r s t t h e case of meta l ant imonateo as
i n o r g a n i c ion exchange r s . The l o g Kd vs atomic number f o r t en
ant imonate ion exchangers a r e p l o t t e d i n P i g s . 18-27 , t h e
average Kd v a l u e s vs atomic number in P i g . 28 and t h e average
Kd vs atomic number f o r a l k a l i n e e a r t h metal i o n s in P i g . 2 9 .
There a re some genercil c h a r a c t e r i s t i c s t o be n o t e d . Ha has
t h e maximum average l o g Kd f o r t h e an t imonate exchangers vjhich i s
l a r g e r than t h a t of any o t h e r i o n . Thus I tege exchangers can be
used f o r t h e s e p a r a t i o n of Na from K , L i , Rb and Cs . This
has been done by A b e [ ' l , 2 ] . S i m i l a r l y t h e s e exchangers have high
Kd v a l u e s of Ag , Hg and pb , Very low Kd v a l u e s are + 2 r e p o r t e d i o r Hg . I t t h e r e f o r e appea r s t h a t t h e Kd va lues
depend upon t h e i n t e r a c t i o n of t h e coun te r i o n s w i th the anion
151
80 40 60
Atomic Number Figl 8-A plot of log kd vs Atomic number. Exchanger: Ceric
antimonate, Form: H"^form, Nature; Amorphous, Size: 100-200mesh,pH:2-3.
95
152
4.5
•o
en O
Pb*2
• Co*2
Mg+2 Ca -2
Jh*'«
Mn+2
20 80 95 40 60 Atomic Number
Fig. 19 - A plot of log kd vs Atomic number. Exchanger: Chromium antimonate, Form: H"*"form, Nature: Amorphous, pH:3-4.
153
•a
O
40 60
Atomic Number Fig. 2 0 - A plot of log kd vs Atomic number. Exchanger :Titanic
antimonate,Form: H"*"form, Nature.Amorpjious, Size-.100-200mesh,pH:2-3.
154
20 40 60 Atomic Number
80 95
Fig. Z1 - A plot of log kd vs Atomic number. Exchanger: Zirconium antimonate, Form iH"^ form, Nature .-Amorphous Size: 100-200mesh,pH:e-3
155
3 -
• o
O
1 -Mg*2
•Ga*3 /
Ni*2 \ / ^ ,
f \ r / l •Sr^Z
^ ^ M n + 2
/ C a * 2
1 , . J
• Cd+2
A. Pr*3
\ AN<1*3 , Y MSm*3
Ba*2 \ tTb*3 ^
Gd*3| /
Dy*3<V
Ho*-3
1
- ^ P b * 2
« 20 80 40 60
Atomic Number
Fig.ZZ-A plot of log kd vs Atomic number. Exchanger: Iron antimonate,Form: H"*" form, Nature .Amorphous, Size:150-Z50mesh,pH:1.
95
156
20 80 95 40 60
Atomic Number Fig.Z3-A plot of log kd vs Atomic number. Exchanger: Stannic
antimonate,Form: H"*'form, Nature: Amorpiious, Size;50-100mesh,pH:2-3
157
80 95 40 60 Atomic Number
Fig.ZA-Aplot of log kd vs Atomic number. Exchanger '.Niobium antimonate, Form: H" form, Nature: Semi crystalline, pH:1.
158
Atomic Number Fig.Z5-Aplot of log kdvs Atomic number.Exchanger; Antim-
onic acid, Form :H"^ form, Nature :CrystaUine, Size: 100-200 mesh.
159
20 80 40 60 Atomic Number
Fig.Z6-A plot of log kdvs Atomic number. Exchanger: Lead antimonate.For^: H+form, Nature: Amorphous, Size: ZOO mesh, pH:Z.
160
20 40 60
Atomic Number 80 95
Fig.Z7-A plot of log kd vs Atomic number. Exchanger: Lead antimonate,Form: H+form, Nature .Crystalline, pH:Z-3.
161
95 40 60 Atomic Number
Fig.Z8-Aplot of log ave.kd vs Atomic number for metal ions on various antimonate exchangers.
162
3r NIOBIUM ANTIMONATE
Ca* Sf*^
Ba**
en o
5r CHROMIUM ANTIMONATE
Sr*
Mg** • -
10 ZO 30 40 50 60
Atomic Number Fig.Z9-A plot of log kd vs Atomic number for
Alkaline earth metal ions.
163
O
ZIRCONIUM ANTIMONATE
Ca**
STANNIC ANTIMONATE
Mg*
10 20 30 40 50 60
Cont'd. Atomic Number Fig.Z9-Aplot of log kd vs Atomic number for
Alkaline earth metal ions.
164
3r CERIC ANTIMONATE
Ca* - •Ba*
en o — 1
-
Mg** •
1
TITANIUM ANTIMONATE
^^l—-^
. 1 1
_ _ , - ^ B a * *
1 1
2
1
AMORPHOUS LEAD ANTIMONATE
r ca** Sr»*
1 1 1 1 1
Ba** •
' 10 20 30 40 50 60
Cont'd. Atomic Number Fig.Z9-Aplot of log kd vs Atomic number for
Alkaline earth metal ions.
165
o
IRON ANTIMONATE
Sr
Mg** C«**
J L _i I
Sr* Ca*
Ba**(C.A)
10 20 30 40 50 60
Cont'd. Atomic Number Fig.29-A plot of log kd vs Atomic number for
Alkaline earth metal ions.
166
lA A N D I B
J i_ ZO 40 60
I IA ANDI IB
-o ^ 4 (Li >
O
6r
20 40 60 80 I I I A A N D I I I B
Sc*3 Y
J L
IVA AND IVB
ZrO' + 2 HfO • 2
Pb • 2
20 40 60
VAANDVB
90
V0*2
J L 20
3.5
3
40 VIII
60 90 • Co**
-1 I 20 4 0 60 90 10 30 30 40
Cont'd. Atomic Number
Fig.Z9-Aplotof logave.kdvs Atomic number for metal ions in a group.
-o
> Z
O
20
Cont'd.
LANTHANIDES AND ACTINIDES
Ho*'
40 60 Atomic Number
80
167
95
Fig.29 -A plot of log ave.kd vs Atomic number for metal ions in a grt)up.
>yiiM.v<
168
Lue> m a t r i z . I n ordei: t o b r i n ^ a b u u t t h e dej jonuence of L'J -/ol\
on atoi i i ic numb-jj?, p l o t c have been laade I 'or t h e Ka vij_ue!j oi'
+2 +2 +2 +2 Mg , Ca , Sr and Ba on v a r i o u s a n t i i a o n a t e s . I n most
+2 +2
o a s e s i lg shows t h e l o w e s t lid v a l u e vjhere a s Ba sho^.'s t h e
h i g h e s t . A c o m p a r i s o n of t h e Kd v a l u e s on t h e amorphous and
c r y s t a l l i n e l e a d a n t i m o n a t e s i s i n s t r u c t i v e , \ i lh i le t h e
c r y s t a l l i n e m a t e r i a l shows a r e .^ r . l a r t r e n d t h e amor^ihous l e a d
a n t i m o n a t e shows an e r r a t i c b e h a v i o u r .
S i m i l a r t r e n d s a r e n o t i c e d f o r p l o t s of lOtj Ld v s i o n i c
r a d i i ( F i g s . 5 0 - 4 1 ) . Thus a s t h e i o n i c r a d i u s i n c r e a s e s t h e r e
i s a r e g u l a r i n c r e a s e i n Kd v a l u e s . T h i s i s b e c a u s e t h e i o n s
a r e exchanged a s h y d r a t e d i o n s and t h e i o n s w i t h t h e l o w e s t
i o n i c r a d i i have t h e l a r g e s t h y d r a t e d i o n i c r a d e i . The t r a i d
of n i o b i u m a n t i m o n a t e , chromium a n t i m o n a t e , t i t an i ' o i - i a r i t i u ^ n a t e ,
i r o n a n t i u i o n a t e and l e a a a n t i m o n a t e a r e s i i x i i l a r . Once ag.u.n
t h e d i f f e r e n c e bet^;een t h e c r y s t a l l i n e and a u o r p h o u s l e a d
a n t i m o n a t e s i s w o r t h n o t i c i n g .
The p l o t s of i o n exchange c a p a c i t y v s h y d r a t e d i o n i c
r a d i i a r e i n s t r u c t i v e ( P i g . 4 2 ) . The i o n exchcjige c a p a c i t y aeponas
upon t \ /o f a c t o r s :
1. Hydrated ion ic r a d i i
2. u e l e e t i v i t y
As the hydrated ionic radius increases the ion exchange c parity
decreases as the exchau. e now becomes more difficult. Thuj for
169
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 o
Ionic Radius (A) Fig.30-A plot of log kd vs Ionic radius.Chromium antimonate.
170
4.8
4 -
cn o
Rb* ^ C s *
J_ 0.2 0.4 0.6 0.8 10 1.2 1.4 1.6 1.8
0
Ionic Radius (A)
Fig.31 - A plot of log kd vs Ionic radius.Titanium antimonate
171
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 0
Ionic Radius (A) Fig.32-A plot oflogkd vs Ionic radius.Stannic antimonate.
172
0.2 0.4 0.6 0.8 1.0 l.E 1.4 1.6 1.8 0
Ionic Radius (A) Fig.33- A plot of log kd vs Ionic radius.Zirconium antimonate.
Cj'rlfMs'/i
173
en o
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 o
Ionic Radius (A) Fig. 3 4 - A plot of log kd vs Ionic radius.Niobium antimonate.
174
0.2 0.4 0.6 0.8 1.0 12 1.4 1.6 1.8 0
Ionic Radius (A) Fig.35 - A plot of log kd vs Ionic radius.Ceric antimonate
175
0 2 0.4 0 6 0-8 1.0 1.2 1.4 1.6 1.8 0
Ionic Radius (A)
Fig. 3 6 - A plot of log kd vs Ionic radius. Iron antimonate.
176
O
1.2 0
Ionic Radius (A) Fig.37- A plot of log kd vs ionic radius. Lead antimonate(a)
177
4.9 -
O
0.2 0.4 0.6 0.8 1.0 1.Z 1.4 1.6 1.8 o
Ionic Radius (A) Fig.38- A plot of log kd vs Ionic radius.Crystalline antim-
onic acid.
178
O.Z 0.4 0.6 0.8 1.0 \.Z 1.4 1.6 1.8 0
Ionic Radius (A) 0
Fig.39-Aplotof logkd vs Ionic radius (A) .Crystalline lead antimonate.
-o Jit:
>
o
0.2 0.4 0.6 0.8 1.0 1.2 o
Ionic Radius (A)
1.4 1.6 1.8
Fjg-40 -A plot of log ave.kd vs Ionic radius for metal ions on various antimonate exchangers.
180
-o ^ 4 <u >
o *-
6r
IIA ANDllB
5 1 1.5
IIIA ANDIIIB
Sc*3
VA ANOVB
ycr^
Cr*3 4
Bi*'
5
•5 1
IVA ANDIVB
Zrcf*
HfcT^
1.5
*Pb' ,•2
1.5 VIII
Cont'd. Ionic Radius(A)
Fig.40-A plot of log ave.kdvs Ionic radius (A) for metal ions in a group.
)/A^'i{^
181
CJ
^
q
o» 6
00
d
,,«.
d'^S'
vO d
«n d
•^ d
lO
d
CJ d
CO Z I
^
cn o
o
o <
fO
to
"E <\J +-» c
_ l
O
. , 3 <
CO 3
TD
O
o "~" >
T 3
>
cn
< 4 -
o •M _o
o JJ +-» c o O
a. < I
O cn
P>J9A1?601
182
2 -
"O
O
ZIRCONIUM ANTIMONATE
Ba*
Ma**, Sr*
5
4
3
Z
1
CHROMIUM ANTIMONATE
'
Ca*V
- J . . . . 1 1
NIOBIUM
Mg •
ANTIMONATE
Ca^r
1
•Ba**
/sr**
1 1
STANNIC ANTIMONATE
Ca** i""
0.4 0.8 \.Z 1.6 0.4 0.8 1.Z 1.6 0
Ionic Radius(A) Fig.41 -A plot of log kd vs Ionic radius (A) for Alkaline earth
metal ions.
183
3 r CERIC ANTIMONATE
T3
o
3
2
1
IRON/!
-
1
iNTIMONATE
1. .. .1 1
0.4 0.8 1.2 1.6
TITANIUM ANTIMONATE
• B a -
J I
-
-
AMORPHOUS LEAD ANTIMONATE
Mg**»—_£*^!.#—-•^*
1 1 1 1
0.4 0 8 1.2 1.6
Cont'd. Ionic Radius (A)
Fig.41 -A plot of log kd vs Ionic radius (A) for Alkaline earth metal ions.
184
3r
-o 2
O
Cont'd.
Ba**(C.A)
1 - (C A)-COMPLETE ABSORPTION
0.4 0.8 1.2 1.6 0
Ionic Radius(A) Fig.41 -Aplot of logkd vs Ionic radius (A).
Crystalline lead antimonate.
185
2.0 r
1.5
1.0
cr g 0.5
o a. m o a> cr> S 2.0
J C o
c: o
NIOBIUM ANTIMONATE ( Sb/Nb=0.71)
ALKALI METALS _ ALKALINE EARTH METALS
K*
TITANIUM ANTIMONATE (Sb/Ti =1.04)
ALKALI METALS ALKALINE EARTH METALS
Ba**
c.u
15
1.0
0.5
K*
> N a *
-
1 1
\ L I *
1 •
\ca**
e 8 10 Z 4 6 0
Hydrated ionic radius{A) 0
Fig.42- A plot of Hydrated ionic radius (A) vs Ion exchange capacity (meq/g)
186
z.Or
1.5
CT>
cr <U E
>> 4-> O <tJ o. fd o a« en c aJ o X a> c: o
1.0
0 5
2.0
1.5
1.0
05
CERIUM ANTIMONATE(Sb/Ce=0.32)
ALKALI METALS ^ ALKALINE EARTH METALS
J J
Ba*V
Ca*
NICKEL ANJIMONATE (Sb/Ni = 0.77)
ALKALI METALS ALKALINE EARTH METALS
K*Na* Mg**
2 4
Cont'd.
8 4 6 0
Hydrated ionic radius(A) 0
8 10
Fig.4Z-A plot of Hydrated ionic radius (A) vs Ion exchange capacity (meq/g).
187
2.0r
1.5-
s ^ 1.0 cr a> E
4-> O m ex o a> c
><
§ 15
1.0
0.5-
STANNIC ANTIMONATE (Sb/Sn=5.1)
ALKALI METALS _ ALKALINE EARTH METALS
-
-
-
Ba**
Vxa**
1 1
^Mg++
' '
ZIRCONIUM ANTIMONATE (Sb/Zr =1.03)
ALKALI METALS ALKALINE EARTH METALS
Na+
KU
tU*
• MQ
2
Cont'd.
8 4 6 0
Hydrated ionic radius( A) o
8 10
Fig.42-Apiot of Hydrated ionic radius (A) vs Ion exchange capacity (meq/g).
188
C7^
e 2.0
o
CO o
c
o X c o
1.5
1.0
0.5
CRYSTALLINE ANTIMONIC ACID
ALKALI METALS
Na*
8
Cont'd. Hydratedionic radius(A) Fig.42 -A plot of Hydrated ionic radius (A)
vs Ion exchange capacity (meq/g),
189
Z.Or
en c r
J '° •5 0-5 C 3 L
O
<U
cn c
o X a> c o
1.0
0.5
AMORPHOUS LEAD ANTIMONATE (Sb/Pb = 5 )
ALKALI METALS _ ALKALINE EARTH METALS
KV«Na*
Mg*+
CRYSTALLINE LEAD ANTIMONATE (Sb/Pb=2.5)
ALKALI METALS ^ ALKALINE EARTH METALS
K*
^Na+ .
i ^ L i *
Z 4 6
Cont'd.
8 10 Z 4 6 o
Hydrated ionic radiuslA) 0
8 10
Fig.4Z-Aplot of Hydrated ionic radius (A) vs Ion exchange capacity (meq/g ).
190
a l k a l i metals the t rend i s Gs'*'> Rb% K'''> Na"*'> Li"*" . This
t rend i s no t iceab le fo r cerium antimonate, n icke l antimonate,
niobium antimonate, t i t an ium antimonate and to some extent l eaa
antimonate.
The second f a c t o r i s the spec i f i c s e l e c t i v i t y of antimonic
ac id . Antimonic acid i s kiiovm to be hii^hly s e l ec t i ve for Wa
ions . This effect i s apparent in s tannic antimonate, zirconiuji
antimonate and antimonic ac id . Let us now discuss each case
separa te ly , i 'or t i t an ium antimonate the authors s t a t e tha t
"Except for Li"*" aJid Ba"*" the ion exchange capacity i s negl ig ib ly
affected by the s ize ^ d charge of the exchaJiging ion"[3] . This
i s not t rue as the plot of ion exchange capacity vs hydratea
ion ic r a d i i shows (Titanium antimonate in P i g . 4 2 ) . fur ther the
authors s t a t e "As the mixing r a t i o of antimony to t i tanium
increases t-he exchange capacity also i n c r e a s e s . This becomes
maximum at antimony to t i t an ium r a t i o of 4 f 1 " . This has not been
explained by the authors but i s understandable considering that
antimonic acid l o s e s i t s ion exchange capacity for cat ions on
p a r t i a l replace.-aent by metal i o n s . This replacement i s minimum
at the high Sb/Ti r a t i o of 4oO. A plot of the ion exchange
capacity vs hydrated ion ic r a d i i shows tha t the ion exchange
capacity decreases as the hydrated ionic radius i s increaced.
This i s the normal sequence.
Zirconium antimonate synthesized by Tan don and Hathew[4]
shows a higher exchange capacity fo r Na"*" ions than for K^ and
191
Li"^ i o n s as i s t h e case f o r an t imonic a c i d . This i s probaoly
because Sb/Zr r a t i o i s 1 .05. Abe and I t o had reuiarked t h a t
i n t h e z i rconium ant imonate which they had s y n t h e s i z e d normiil
s e l e c t i v i t y Was observed f o r t h e a l k a l i me t a l s [5 ] . They f u r t h e r
showed t h a t i f Sb/H r a t i o i s e^reater than 1, then un reac t ed
an t imonic a c i d i s p r e s e n t in t h e a n t i m o n a t e . This obse:cvation
i s in consonance wi th t h e d a t a of Tandon e t a l . on z i r c o n i u u
a n t i m o n a t e . ^ f u r t h e r conf i rmat ion i s o b t a i n e d from t h e i r da ta on
s t a n n i c a n t i m o n a t e . I4athew and Tandon s y n t h e s i z e d Gt;innic +
ant imonate and de te rmined t h e ion exchange c a p a c i t y f o r L i ,
Na"*" , K"*" , H H | , Rb+ , Gs" , i ig'*' , Ga" ^ and Ba"*" [6] . They
remarked "No r e g u l a r t r e n d i s observed in t h e case of a l k a l i
m e t a l s , however in t h e case of a l k a l i n e e a r t h me ta l s t h e
exchange capac i t y i n c r e a s e s w i th i n c r e a s i n g t h e i o n i c r a d i i " .
This i s no t c o r r e c t . A p l o t of ion exchange capac i ty vs hydr.ated
i o n i c r a d i i ( S t a t m i c an t imonate i n i ' i g . 42) shows t h a t t he ion
exchange c a p a c i t y i s maximum f o r Na i o n s and inf t ic t t h e order of
s e l e c t i v i t y i s t h e same as f o r an t imonic a c i d . Thic Gupp0':ts the
o b s e r v a t i o n s of Abe and I t o . The 3b/Sn r a t i o f o r s t a n n i c ant imo
n a t e i s 5.0 and t h e r e f o r e i t c o n t a i n s a l a r g e amount of ant imonic +4 +
a c i d . The exchange of Sn w i th H i o n s of an t imonic ac id may be r e p r e s e n t e d by t h e equa t ion
2 H2Sb205(0H)2 + Sn"^ = SnSb205(OH)2 (eq .6 )
192
giving a product of the Sb/Sn r a t i o of 1. These observations
are appl icable to cerium antimonate, n icke l antimonate and
niobium antimonate a l s o . All the three have Sb/M r a t i o of l e s s
than 1 and shovj the normal order of preference .
This explanation does not apply to amorphous and
c r y s t a l l i n e lead antimonates. The exchange react ion in t h i s
case "Will be
(H50"^)2 Sb^Og 2H2O + Pb'*"2 r = pb Sb205.2H20 (eq.7)
For complete replacement Sb/pb r a t i o should be 2. Thus if
Sb/Pb r a t i o i s g r ea t e r than 2, then some antimonic acid should
be l e f t unreacted and the mater ia l should shoifJ some s e l e c t i v i t y
fo r Ua i ons . However i t appears t ha t the c ry s t a l s t ruc ture
of lead antimonate i s so r i g i d tha t a f t e r most of the protons 2+ have been blocked out by Pb the mater ia l no longer shows the
s e l e c t i v i t y assoc ia ted with antimonic ac id .
A number of i n t e r e s t i n g f ea tu re s can be seen in the p l o t s
of log ave. Kd vs charge on the exchanging ion (P ig . 43 ) .
Or(III)Sb shows the l a r g e s t Kd values fo r metal ions of 2, 3 and
4 Valencies ana Ge(III)Sb shows the minimum. The Ld adsorjition
curve of the c r y s t a l l i n e lead antimonate i s almost a niircor
image of the curve for amorphous lead antimonate. As a general
193
Charge on the ion—v
Fig.43^ A plot of log ave.kd vs Charge on the ion for various
antimonate exchangers.
194
3.5
3.0
Z.5
5 20 > rtJ
o 1.5
1.0
0.5
-y " /
y
1 1 . j _
(O-CRYSTALLINE.
(A)-AMORPHOUS.
1 1
+1
Cont'd.
*Z +3 +4
Charge on the ion—> + 5
Fig.43 -A plot of log ave.kd vs Charge on the ion for various antimonate exchangers.
195
ru le the Kd values should increase with the charge on the
i on . This i s shown by Zr(IV)Sb and Ti(IV)Sb. However, in
most cases the ave. Kd f i r s t decreases and then increases
as in the case of Gr(I I I )Sb, Sn(IV)Sb andNb(V)Sb. This
may be due to two contradic tory f a c t o r s . (1) Increase in
charge i nc rease s the a t t r a c t i o n fo r the cat ion f o r the
exchanger. (2) Increase in the hydrated radius decreases
the i n i t i a l a t t r a c t i o n of the ca t ions to the ion exchanger.
196
1 . Abe, M.
B u l l . Ghem. Soc. J p n . , 4 2, 2683, 1969.
2 . Abe, H., AchiBad Ghsau, E.A. and Hayashi , K.
Analc Ghem., 52, 524, 1980.
3 . G i l l , J o S . and Tandon, S.H.
J . i l a d i o a J i a l . Ghem., 20, 5 , 1974.
4 . iVIathew, J . and Tendon, S.N.
J . R a d i o a n a l . Ghem., 27, 315, 1975o
5« Abe, W. and I t o , H.
B u l l . Ghem., Soc. J p n . , 4 2, 1013, 1967.
6 . Mathew, J . aJid Tan don, SoN.
Acta . Ghim. (Budapest) . , 92(1) ,1 ,1 977.