1958 - diamond - surface areas of clay minerals as derived from measurements of glycerol retention

8/20/2019 1958 - Diamond - Surface Areas of Clay Minerals as Derived From Measurements of Glycerol Retention

1/14

SURF CE RE S OF CL Y MINER LS S DERIVED FROM

ME SUREMENTS OF GLYCEROL RETENTION

y

SIDNEY DIAMOND AND EARL B. KII~TER

Bureau of Public Roads, Physical Research Division, Washington, D.C.

ABSTRACT

The use of glycerol retention measurements to calculate surface areas of clay minerals is

described. Assuming that the glycerol retained on external surfaces is monomolecular in

thickness, and that both this layer and the monomolecular glycerol layers adsorbed on

internal surfaces of montmorillonite, vermiculite, and halloysite are of the density of liquid

glycerol, it is calculated that each percentage of glycerol retained corresponds to an area of

17.6 square meters per gram on external surfaces and 35.3 on internal surfaces. The corre-

sponding figures for ethylene glycol retention under these conditions are 22.3 and 44.6,

respectively. For nonexpanding clays, surface areas calculated from glycerol retention

values agree well with published figures derived from Brunauer, Emmett, and Teller

(B.E.T.) gas adsorption measurements. For montmorillonites, surface areas agree reason-

ably well with published determinations based on B.E.T. treatment using polar adsorbates.

Values of surface area are also presented for samples of vermiculite and endellite and for

the nonexpanding clay minerals--illi te, kaolinite, halloysite, and allophane.

Calculations of the surface area as a function of particle size for montmorillonites of

hypothetically uniform particle sizes show that montmorillonites dispersed into very thin

flakes must have an appreciable external surface. The ratio of internal to total surface is

shown to furnish an estimate of the thickness of the individual montmorillonite flakes.

Glycerol retention data for a Wyoming bentonite saturated with a number of different

cations are interpreted as indicating particle thicknesses varying from 3 unit cells (about

30A) for Na + saturation to about 20 unit cells for saturation with a number of polyvalent

cations.

INTRODUCTION

The most widely used method for the measurement of surface areas of very

fine materia ls involves the adsorpti on of nitr ogen (or simil ar gases) at low

temperatures. When the adsorption isotherm data obtained are analyzed

according to the theory of multimolecular adsorption developed by Brunauer,

Emmett, and Teller (1938), they yield a value for the volume or weight of a

monomo tec ular layer of the gas on the external surface of the sample. With a

suitabl e value for the cross-sectional area of the gas molecule, this monol aye r

capacit y can be converted to surface area.

A difficulty arises in mea suri ng surface areas of clays containi ng montmor-

illonite, vermiculite, and endellite, since these have, in addi tion to the e xternal

surfaces of the indivi dual particles, a large area of so-called int ern al surfac e

which is not accessible to nitroge n. Recently, however, gas adsor ption meas-

urements on montmorillonite s have been carried out with polar gases, notabl y

water vapor and ammonia, and interpretation of the results according to the

B.E.T. equation has given values for combined i nterna l and external surfaces

334


2/14

SIDNEY DIAMONDAND EARL B KINTER 335

o f t h e s a m e o r d e r o f m a g n i t u d e a s t h e t h e o r e t i c a l v a l u e o f a b o u t 7 6 0 m 2 / g

p r e d i c t e d f r o m d i m e n s i o n s o f t h e l a t t i c e s t r u c t u r e .

A s r e p o r t e d i n a c o n c u r r e n t p a p e r K i n t e r a n d D i a m o n d , 1 9 5 8 ) , a m e t h o d

wa s de ve lope d f o r m e a su r ing g lyc e r o l r e t e n t ion o f c l a ys. G lyc e r o l - t r e a t e d c l a ys

a r e h e a t e d a t 1 1 0 ~ i n th e p r e s e n c e o f f re e g l y c e ro l v a p o r , r a p i d l y l o s in g

e x c es s g l y c e r o l a n d a r r i v i n g a t a w e i g h t e q u i li b r i u m . A t e q u i l i b r i u m , m o n t -

m o r i ll o n i te s , v e r m i c u l i te , a n d e n d e l li t e w e r e f o u n d t o r e t a i n a m o n o m o l e c u l a r

l a ye r o f g lyc e r o l on the i r i n t e r na l su r f a c e s . I t wa s a lso shown tha t t he r e i s a

de f in i t e r e t e n t ion o f g lyc e r o l on the e x te r na l su r f a c e s o f t he se a nd o the r c l a y

m i n e r a l s , p r e s u m a b l y a s a m o n o m o l e c u l a r la y e r . I t i s t h e p u r p o s e o f t h e p re s -

e n t p a p e r t o d e r i v e a p p r o p r i a t e f a c t o r s t o c o n v e r t g l y c e r o l r e t e n t i o n d a t a t o

v a l u es o f s u r f a c e a r ea , t o c o m p a r e c o m p u t e d s u r f a c e a r e a v a l u e s f o r a n u m b e r

o f c l a ys w i th pub l i she d va lue s f o r t he sa me o r s imi l a r c l a ys , a nd to in t e r p r e t

som e o f t he se va lue s in t e r ms o f the d ime ns ion s o f i nd iv id ua l pa r t i c l e s o f

m o n t m o r i l l o n i t e s .

C O N V E R S IO N O F G L Y C E R O L R E T E N T I O N D A T A

T O V A L U E S O F S U R F A C E A R E A

T h e v o l u m e o f a g r a m o f g l y c e r o l a t n o r m a l d e n s i t y 1 . 2 6 g / c m 3 ) i s 0 .7 9 4

c m 3. A s s u m i n g t h a t g l y c e r o l r e t a i n e d o n t h e i n t e r n a l s u r f ac e s o f m o n t m o r i l -

l o n i t e a t e q u i l i b r i u m i s i n t h e f o r m o f a m o n o m o l e c u l a r l a y e r a t t h i s d e n s i t y

a nd w i th a t h i c kne ss o f 4 .5A a s ind ic a t e d by x - r a y d i f f r a c t ion r e su l t s d i s-

c u s s ed b e l o w ) , t h e a r e a o f t h e g l y c e r o l f i lm m a y b e c o m p u t e d a s f o ll o w s :

V o l u m e 0 . 7 94 c m 3

- - = 1765 m 2

Ar e a o f g lyc e r o l l a ye r Th ic kne ss 4 .5 • 10- s c m

p e r g r a m o f g l y c e r o l r e t a in e d . T h u s a g l y c e r o l r e t e n t i o n o f 1 p e r c e n t w o u l d b e

e q u i v a l en t t o a m o n o l a y e r a r e a o f 1 7 . 65 m 2 / g ; h o w e v e r , si n c e th e l a y e r o f g l y .

c e r o l i s be twe e n two ba sa l su r f a c e s o f t he c l a y , t he i n t e r na l c l ay s u r f ac e cov-

e r e d b y t h e m o n o l a y e r i s t w i c e t h e a r e a o f t h e m o n o l a y e r i t s el f, o r 3 5 . 3 m 2 / g .

I f i t i s f u r t h e r a s s u m e d t h a t a m o n o m o l e c u l a r l a y e r o f g l y c e r o l i s s i m i l a r l y

r e t a i n e d o n t h e e x t e r n a l su r f a c e s o f t he c l a y pa r t i c l e s , t he e x t e r n a l s u r a c e

a r e a c ov e r e d f o r e a c h p e r c e n t o f g lyc e r o l r e t a ine d i s 17 .65 m 2. The se c a l c u la-

t i ons c o r r e spo nd to a c r os s - se c t iona l a r e a o f 26 .9A 2 pe r m o l e c u l e of g lyce ro l .

T h e v a l u e s a s s u m e d f o r t h e d e n s i t y a n d t h i c k n e s s o f t h e g l y c e r o l l a y e r a r e

ope n to some que s t ion . Th e de ns i ty a t 20~ i s u se d a bove , whe r e a s the a c tua l

d e t e r m i n a t i o n o f r e t e n t i o n i s m a d e at l l 0 ~ T h e d e n s i t y o f g l y c e r o l a t 1 1 0 ~

c a lc u la t e d f r om the f o r mu la in the I n t e r na t iona l C r i t i c a l Ta b le s i s 1 .20 , a bou t

5 p e r c e n t l es s t h a n t h a t a t 2 0 ~ A s t o t h e t h ic k n e s s o f t h e m o n o l a y e r , x - r a y

d i f f r a c t i o n d a t a w e r e o b t a i n e d i n o u r o w n l a b o r a t o r y o n t h e b a s a l s p a c i n g s o f

s e v e ra l m o n t m o r i l lo n i t e s i n t h r e e c o n d i t i o n s : t h e m o n o l a y e r g l y c e r o l c o m p l e x ,

the two- l a ye r c om ple x , a nd c o l l a pse d by he a t t re a tm e n t . S pa c ings f o r t he

m o n o l a y e r c o m p l e x r a n g e d f r o m 1 3 .8 A t o 1 4 .5 4 A , t h e a v e r a g e b e i n g a b o u t

1 4 . 1 A ; f o r t h e tw o - l a y e r c o m p l e x , s p a c i n g s r a n g e d f r o m 1 7 .7 A t o a b o u t 1 8 .4 A ,

a v e r a g i n g a b o u t 1 8 . 0 A ; a n d f o r c o l l a p s e d m o n t m o r i l l o n i t e s , s p a c i n g s w e r e


3/14

6

SURF CE RE S ND GLYCEROLRETENTION

c lose to 9 .6A in a ll c a se s . Th e r a nge s in the spa c ings o f t he two c om ple xe s

ind ic a t e t ha t sma l l bu t r e a l d i f f e r e nc e s e x i s t be twe e n d i f f e r e n t mon tmor i l l on -

i t es ; s m a l l d i f f e re n c e s w e r e a l so n o t e d f o r t h e s a m e m o n t m o r i l lo n i t e s s a t u r a t e d

w i t h d i f f e r e n t c a t io n s . F r o m t h e s p a c i n g d a t a c i t ed , a v a lu e o f 4 . 5 A w a s t a k e n

a s the th i c kne ss o f t he mono la ye r , no t ing~ howe ve r , t ha t 8 .4A wa s ob ta ine d

f o r t h e t w o - l a y e r c o m p l e x , i n c l o s e a g r e e m e n t w i t h t h e 8 . 3 A v a l u e c i t e d b y

M a c E w a n 1 9 4 8 ) .

T h e t r u e t h ic k n e s s o f a c o r r e s p o n d i n g m o n o l a y e r o f g l y c e r o l i n v e r m i c u l i t e

i s d i f f ic u l t t o d e t e r m i n e . A l t h o u g h x - r a y m e a s u r e m e n t s o f g l y c e ra t e d v e rm i c u -

l i t e a nd ve r mic u l i t e c o l l a pse d by he a t ing ind ic a t e a d i f f e r e nc e in spa c ing o f

a p p r o x i m a t e l y 5 A 1 4 . 2 - 9 . 2 A ) , t h e r e is d o u b t th a t t h is d i f f e re n c e r e p re s e n ts

t h e a c t u a l th i c k n e ss o f th e g l y c e r o l m o n o l a y e r . T h e r e a p p e a r s t o b e n o e ss en -

t i a l d i f f e r e nc e be twe e n the spa c ings o f g lyc e r a t e d a nd g lyc o la t e d ve r mic u l i t e s ,

bo th b e ing a bo u t 14 .1 -14 .3A, in sha r p c on t r a s t t o t he r e a l d i f f e r e nc e s be twe e n

g l y c e r a t e d a n d g ly c o l a t e d m o n t m o r i l l o n i t es . A s W a l k e r 1 9 5 0 ) h a s p o i n t e d

ou t , t h i s spa c ing in ve r mic u l i t e s i s e s se n t i a l ly t he sa me a s t ha t s e t by the

h y d r a t e d i n t e r l a y e r c a t io n M g 2~) p r e v i o u s t o t r e a t m e n t w i t h t h e p o l y a l c o h o l .

A l though th i s spa c ing i s t hus r e t a ine d a f t e r t r e a tme n t w i th the po lya lc oho l , i t

m a y w e l l b e t h a t th e m o n o l a y e r d o e s n o t f u l l y o c c u p y t h e s p a c e. I n v i ew o f

t h is u n c e r t a i n t y , i t is f e lt t h a t t h e m o n o l a y e r t h i c k n es s d e r i v e d f r o m m e a s u r e -

m e n t s o f m o n t m o r i l lo n i t e c o m p l e x e s w o u l d b e a r e a s o n a b l e a p p r o x i m a t i o n f o r

t h e t h i c k n e s s o f t h e c o r r e s p o n d i n g m o n o l a y e r i n v e r m i c u l i t e .

A s d e s c r ib e d i n a c o n c u r r e n t p a p e r K i n t e r a n d D i a m o n d , 1 9 5 8 ) , t h e o r ig i -

na l spa c ing o f 10 .1A f o r a n e nde l l i t e C h a t tooga C o . , G e or g ia ) wa s inc r e a se d

t o 1 1 .2 A u p o n g l y c e r a t io n . T h e th i c k n e ss o f t h e g l y c e r o l m o n o l a y e r w o u l d

t h u s b e 4 .0 A , w h i c h i s i n r e a so n a b l e a g r e e m e n t w i t h t h e 3 . 8 A f i g u r e g i v e n b y

M a c E w a n 1 9 4 8 ) f o r a g l y c e r o l m o n o l a y e r i n e n d e ll it e . T h e c r o s s- s e ct i o n al

a r e a p e r g l y c e r o l m o l e c u l e c o r r e s p o n d i n g t o a 4 . 0 A m o n o l a y e r th i c k n e s s a t

l i q u i d d e n s i t y ) w o u l d b e a b o u t 3 0 A -~, a s c o m p a r e d t o 2 7 A 2 c o m p u t e d f r o m t h e

4 . 5 A th i c k n e ss f o r m o n o l a y e r o f m o n t m o r i l t o n i t e c o m p l e x e s . D e s p i te t h e 1 0

pe r c e n t d i f f e r e nc e , t he l a t t e r f a c to r w i l l be u se d in c a l c u la t ing the su r f a c e a r e a

o f e nde l l i t e f r om g lyc e r o l r e t e n t ion da t a .

C o r r e s p o n d i n g f i g u r e s f o r t h e r e t e n t i o n o f e t h y le n e g ly c o l o n m o n t m o r i l l o n -

i re u n d e r s i m i l a r c i r c u m s t a n c e s c a n b e c o m p u t e d i n t h e sa m e m a n n e r . A s s u m -

ing the de ns i ty a s t ha t o f l i qu id g lyc o l , a nd the th i c kne ss o f t he mo le c u le a s

3 . 9A f r o m x - r a y d i f f r a c t i o n e v i d e n c e ) , t h e re t e n t i o n o f e a c h 0 .0 1 g o f g l y c o l

c o r r e sp ond s to a n a r e a o f 22 .3 m 2 on e x te r na l su r f a c e s a nd tw ic e th i s , o r 4 4 .6

m 2, on in t e r na l su r f a c e s ; t h i s c o r r e spo nds to a c r os s - se c t iona l a r e a o f 23 .0A 2

p e r m o l e cu l e , w h i c h c o n t r a s ts s t r o n g l y w i t h t h e 3 3 A 2 f i g u r e s u g g e s te d b y D y a l

a n d H e n d r i c k s 1 9 5 0 ) f o r e t h y l e n e g l y c o l o n m o n t m o r i l l o n i t e .

Pu bl ished D eterminations of Sur ace Areas

of M ontmoril lonite Clays

D y a l a n d H e n d r i c k s 1 9 5 0 ) c o m p u t e d t h e t h e o r e t i c a l b a s a l- f ac e s u r f a c e

a r e a o f

pure

m o n t m o r i l l o n i t e a s 8 1 0 m - ~ M o o n e y , K e e n a n , a n d W o o d


4/14

SIDNEY DIAMOND AND EARL B KINTER 337

( 19 5 2 ) a n d Q u i r k ( 1 95 5 ) c o m p u t e d v a lu e s o f a b o u t 76 0 m 2 / g . A n u m b e r o f

au tho rs have l i s t ed exper imen ta l va lues o f su r face a rea fo r s evera l mon tmor -

i ll on it e s , de t e rm ined by (1 ) l ow- t em pera tu re adso rp t i on m ethods employ ing

n i t rogen o r o the r nonpo la r gases fo r ex t e rna l su r faces and (2 ) adso rp t i on o f

a m m o n i a o r w a t e r v a p o r f o r t o t a l s u r fa c e . S e v e ra l h a v e r e p o r t e d e t h y l e n e

g l y c o l r e t e n ti o n v a l u es d e t e r m i n e d a c c o r d i n g t o t h e m e t h o d o f D y a l a n d H e n -

d r ic k s ( 1 9 5 0 ) , f r o m w h i c h s u r f a c e a r e a s c a n b e c o m p u t e d b y u s i n g t h e f a c t o r

p r o p o s e d b y D y a l a n d H e n d r i c k s , c o r r e s p o n d i n g t o a n a r e a o f 3 3A 2 per mole-

cu l e , o r t he f ac to r sugges t ed above , co r respond ing t o an a rea o f 23A 2 fo r t he

e thy l ene g lyco l mo lecu l e .

In genera l , t he r epo r t ed va lues o f external s u r f ac e a r e a r a n g e f r o m a b o u t 1 5

to abou t 100 m 2/g (Brooks , 1955; Ze t t l emoyer , You ng , and Chess ick , 1955 ;

Lopez-Gonza lez and De i tz , 1952 ; M ooney , Ke enan , an d W ood , 1952, 1952a ;

Dy a l and He ndr i cks , 1950 ; Ne l son and H endr i cks , 1943) . A num ber o f f ac-

t o r s s e e m i n g l y c o n t r i b u t e to t h e v a r i a t io n , i n c l u d i n g t h e t y p e a n d p u r i t y o f t h e

mo n tm or i l l on i t e , t he s a tu ra t i ng ca t i on , t he o u tgas s ing t emp era tu re , an d i n gen-

e ra l t he p repara to ry t r ea tmen t r ece ived by t he s ample .

The va lues o f

total

su r face a rea genera l l y r epo r t ed fo r measu remen t s wi th

po l a r gases r ange f rom abou t ha l f t o somewhat above t he ca l cu l a t ed t heo re t i -

ca l surface area of 760 to about 800 me/g (Orchis ton , 1954, 1955; Zet t le-

m oye r , Yo ung , and Chess i ck, 1955 ; M or t l and , 1955 ; M ooney , Kee nan , and

W ood , 1952 , 1952a) . Ca t i on sa tu ra t i on appa ren t l y has cons ide rab l e i n f l uence

on the su r face a reas ind i ca t ed . The re i s a d i s c repanc y i n tha t ce r t a in a u tho rs

c a l c u la t e su r f a c e a r e a s a f t e r d o u b l i n g t h a t p o r t i o n o f t h e m o n o l a y e r c a p a c i t y

due t o i n t e rna l su r faces , wh i l e o the r s do no t . In f ac t , t he gen era l va l i d i t y o f

ca l cu l a t i ng t o t a l su r face a reas f rom w ate r vapor adso rp t i on da t a i s open t o

some ques t i on (Qu i rk , 1955) .

Sur]ace Areas o Montmoril lonites Derived

]rom Glycerol Retention Data

In Tab l e 1 a re p resen t ed g lyce ro l r e t en t i on da t a and ca l cu l a t ed su r face

a reas fo r m inus 0 . 2 -mic ron f rac t i ons o f s everal mon tm or i l lon i t e s o f t he A . P . I .

r e fe rence s e r ie s . The p red om inan t ca t i on i n a l l cases i s cons ide red t o be Na §

s ince sod ium metaphospha t e was used i n t he i n i t i a l d i spe r s ion o f a l l s amples .

Ex te rna l su r face a rea was ca lcu l a t ed by mul t i p ly ing t he ex t e rna l g lyce ro l

re t en t i on by the f ac to r 17.65 . The d i f fe rence be tween t o t a l and ex t e rna l g ly -

ce ro l r e t en t i on rep resen t s t he i n t e rna l r e t en t i on , f rom which t he i n t e rna l su r -

face a rea w as ob t a ined b y m ul t i p ly ing by t he f ac to r 35 .3 .

Two o f t he mon tmor i l l on i t e s , H-25 and H-28 , a s i nd i ca t ed b y h igh re t en t i on

va lues a f t e r 600~ t r ea tmen t , were no t i r r eve r s ib ly co l lapsed , and t he average

of t he ex t e rna l r e t en t i on va lues o f t he o the r mo n tmo r i l lon i t e s was used i n ca l-

cu l a t i ng su r face a reas o f t hese two mate r i a l s . Gene ra l ly speak ing , the ex t e rna l

su r face a reas i nd i ca t ed a re r e l a t i ve ly smal l, r ang ing f ro m 16 t o 35 m2/g . In t e r -

n a l s u r fa c e s a re a b o u t 2 0 ti m e s a s g re a t , ra n g i n g f r o m a b o u t 6 0 0 t o m o r e t h a n


5/14

33 8 SURFACE AREAS AND GLYCE ROL RETENTION

T A B L E 1 . - - G L Y C E R O L R E T E N T I O N V A L U E S A N D C O M P U T E D S U R F A C E

A R E A S O F - - 0 . 2 g F R A C T IO N S O F S O M E A . P . I . S ER IE S R E F E R E N C E

M O N T M O R I L L O N IT E S N A * P R E D O M I N A N T C A T I O N )

N o. T ype Sour ce

R e t en t i on , Pe r cen t Sur f ace A r ea , m2 g

E xt e r na l

A f t e r

T o t a l 600~ I n t e r na l E x t e r na l I n t e r na l J o r a l

H ea t i ng )

H -1 9 M ontmo rillonite Polkville, 19.3 1.8 17.5 32 618 650

Miss.

H -2 3 M ontmo rillonite Cham bers, 18.9 0.9 18.0 16 636 652

Ariz.

H -2 4 Montmori l lonite Otay, Calif. 22 2 2.0 20.2 35 71 4 749

H -2 5 Mon tmori llonite Upton, W yo. 18.1 11.01

1 .6 ) 2 1 6 . 5 ) 2 8) 5 8 3 ) 6 1 1 )

H -2 8 M ontmo rillonite Little Rock , 18.4 11.41

Ark. 1 .6) 2 16 .8) 28) 5 9 4 ) 622)

H -3 3a Non tronite Garfield, 14.2 1.4 12.8 25 452 477

Wash.

1 600oC heating insufficient to inhibit retention of glycerol on internal surfaces.

2 Average figure for external retention of mo ntmo rillonites; surface areas com puted using

this figure are enclosed in parentheses.

7 0 0 m 2 / g n e a r t h e m a x i m u m e x p e c te d f o r p u r e m o n t m o r i ll o n i te . T h e m a x i -

m u m t o t a l s u r f a c e a r e a i n d i c a t e d is t h a t f o r t h e H - 2 4 m o n t m o r i l lo n i t e , 7 4 9

m 2 / g . T h e n o n t r o n i t e s a m p l e , H - 3 3 a , h a s t h e s a m e o r d e r o f e x t e r n a l a r e a a s

t h e m o n t m o r i ll o n i te s b u t a s o m e w h a t l o w e r i n te r n a l a r e a , p r o b a b l y d u e l a r g e l y

t o a h i g h c o n t e n t o f i r o n o x i d e i m p u r i ti e s i n th i s v e r y f i n e f r a c t io n , b u t p a r t l y

a l s o t o t h e e f fe c t o f s u b s t it u t i o n o f t h e r e l a t iv e l y h e a v y i r o n i o n f o r t h e m u c h

l ig h t e r m a g n e s i u m i n t h e c r y s t a l l at ti ce . T h i s w o u l d i n c r e a s e t h e w e i g h t o f th e

u n i t ce ll a n d c o r r e s p o n d i n g l y r e d u c e t h e s u r f a c e a r e a p e r g r a m .

I n T a b l e 2 a r e p r e s e n t e d s i m i l a r d a t a f o r a b e n t o n i t e V o l c l a y , A m e r i c a n

C o l l o id C o .) s a t u r a t e d w i t h s e v e ra l d i f fe r e n t c a t i o n s b y t r e a t m e n t w i th i o n -

e x c h a n g e r e si n s. T h e c la y m a t e r i a l p a s s i n g t h e 2 0 0 - m e s h s i ev e ) w a s n o t

f r a c t i o n a t e d o r o t h e r w i s e p u r i f i e d . A c c o r d i n g l y , t h e sa m p l e w a s n o t p a r t i c u -

l a r ly p u r e , x - r a y d i f f r a c t i o n d a t a s h o w i n g t h e p r e s e n c e o f a b o u t 1 0 p e r c e n t

q u a r t z ; i t i s l i k e ly t h a t o t h e r i m p u r i t i e s , s u c h a s v o l c a n i c g l a ss , w e r e a l s o p r e s -

e n t. A s e x p e c t e d , f o r K + a n d N H 4 + s a t u r a t i o n t h e v a l u es o f i n t e r n a l s u r f a c e

a r e a a r e l o w s in c e th e s e c a t i o n s a r e k n o w n t o c o l l a p s e s o m e o f t h e e x p a n d i n g

l a y e rs i r re v e r s ib l y o n d r y i n g t o 1 1 0 ~ N a + s a t u r a t io n g a v e a n u n u s u a l l y h i g h

v a l u e f o r e x t e r n a l s u r f a c e a n d a c o r r e s p o n d i n g l y l o w v a l u e f o r i n t e r n a l s u r -

f a c e ; q u a l i ta t i v e l y t h i s c o u l d h a v e re s u l t e d f r o m a n e x t r e m e d i s p e r s i o n o f t h e

N a + - s a t u r a t e d c l a y i n t o v e r y t h i n p a r t i c l e s , a p o s s i b i l i t y t h a t i s f u r t h e r d e v e l-

o p e d l a te r i n t h e re p o r t . T h e r e l a ti v e l y l o w e r e x t e rn a l s u r f a c e a r e a s a n d h i g h e r

i n t e r n a l s u r f a c e a r e a s o b t a i n e d f o r s a t u r a t i o n w i t h t h e p o l y v a l e n t c a t i o n s a r e

n o t e w o r t h y ; v a l u e s f o r t h e d i v a l e n t c a t i o n s C a 2+ a n d F e 2+ a p p e a r t o b e s i m i la r ,


6/14

SIDNEY DIAMOND AND EARL B. KINTER 339

w hi l e M g 2§ y i e l d s a s om e w ha t h i ghe r va l ue o f i n t e r na l s u r f a c e , s i m i l a r t o t he

va l ue s o b t a i n e d f o r s a t u r a t i on w i t h t he t r i va l e n t c a t i ons F e 3§ a nd A18§

T h e r e l a t i v e o r d e r o f t o t a l s u r f a c e a r e a s o f m o n t m o r i l l o n i t e s s a t u r a t e d w i t h

v a r i o u s c a t i o n s f o u n d f r o m t h i s w o r k i s q u i t e s i m i l a r t o t h a t r e p o r t e d b y

O r c h i s t o n ( 1 9 5 5 ) f o r r e s u lt s o f w a t e r v a p o r s o r p t i o n o n a n A r i z o n a m o n t m o r -

i ll o n it e a n d f o r s u r f a c e a r e a s c a l c u l a te d f r o m B o w e r a n d G s c h w e n d s ( 1 9 5 2 )

d a t a o n g l y c o l r e t e n t io n o f d i ff e r e n t s a t u r a t i o n s o f a W y o m i n g b e n t o n i t e .

T h e r e i s g e n e r a l a g r e e m e n t i n t h e r e l a t i v e o r d e r s , w i t h t h e n o t a b l e e x c e p t i o n

t h a t t h e r a n k i n g o f M g 2+ i s c o n s i d e r a b l y h i g h e r i n t h e s e r ie s d e t e r m i n e d b y

g l yc e r o l r e t e n t i on .

TABLE 2.--SURFACE AREA OF VOLCLAY BENTONITE


7/14

34 SURFACE AREAS AND GLYCEROL RETENTION

d a t a f o r m i n u s 2 -m i c r o n fr a c t i o n s o f t w o A . P . I . k a o l i n it e s H - l , M u r f r e e s b o r o ,

A r k a n s a s , a n d H - 5, B a t h , S o u t h C a r o l i n a ) . V a l u e s re p o r t e d f o r s u r f a c e a r e a s

o f v a r io u s k a o l in i te s b y n i t ro g e n a n d e t h a n e a d s o r p t i o n r a n g e f r o m a b o u t 7 t o

a b o u t 3 0 m 2 / g B r o o k s , 1 9 5 5 ; K e e n a n , M o o n e y , a n d W o o d , 19 5 2 ; D y a l a n d

He ndr i cks , 1950 ; N e l son and H endr i cks , 1943) . S u r face a reas o f kao l i n i t e s

wi th in t h i s r ange were a l so i nd i ca t ed by adso rp t i on o f t he po l a r gases , wa t e r

a n d a m m o n i a O r c h i s to n , 1 9 5 4 ; M o r t la n d , 1 9 5 5 ) .

G l y c e r o l r e t e n t io n o f a m i n u s 2 - m i c ro n f r a c t i o n o f a n E n g l i s h c h i n a c l a y

i n d i c a t e d a su r f a c e a r e a o f 2 5 m 2 / g ; D y a l a n d H e n d r i c k s 1 9 5 0 ) r e p o r t a su r -

face a rea o f 28. 2 m2 /g fo r a s im i l a r size f r ac t i on o f an E ng l i sh ch ina c l ay .

Vermiculite

S ur face a reas were a l so ca l cu l a t ed fo r t he ve rmicu l i t e desc r ibed i n a com-

p a n i o n p a p e r K i n t e r a n d D i a m o n d , 1 9 5 8 ) . G l y c e r o l r e t e n ti o n d a t a o n c o a r s e

f l akes r e t a ined on a 200-mesh s ieve) o f t h i s s eeming ly pu re ve rmicu l i t e i nd i-

c a t e a to t a l s u r f a c e o f 2 75 m 2 / g . W h e n t h e f la k e s w e r e m e c h a n i c a l ly re d u c e d

in s ize t o minu s 2 mic rons , a m uch h ig her va lue o f 685 m 2/g w as ob t a ined ,

neg l ec t i ng i n t he ca l cu l a t i on t he minor po r t i on o f g lyce ro l r e t en t i on on ex t e r -

na l su r faces . The l a t t e r va lue comp ares c lo se ly w i th t hose o f mon tmor i l l on i t e s ,

and i nd i ca t es a v i r t ua l l y comple t e pene t ra t i on o f g lyce ro l i n to t he i n t e r l aye r

spaces , i n con t ras t wi th t he apparen t l y r educed pene t ra t i on o f t he l a rge r

f l akes. A range o f 100 t o 300 m 2/g by wa te r adso rp t i on ) fo r to t a l su r face

a r e a a n d a v a l u e o f 0 .5 m 2 / g b y n it r o g e n a d s o r p t i o n ) f o r e x te r n a l s u r f a c e

a rea have been repo r t ed fo r coa r se commerc i a l ve rmicu l i t e be fo re ex fo l i a t i on

Zon ol i te Co. , 1954) .

HaUoysite

In genera l , t he su r face a reas o f ha l l oys i t e s by gas adso rp t i on a re somewhat

h i g h e r t h a n t h o s e o f k a o l i n i t e s , m o s t p u b l i s h e d v a l u e s b e i n g a b o u t 4 5 m e / g

Brooks , 1955 ; D ya l and He ndr i cks , 1950 ; Ne l son and He ndr i cks , 1943) .

Va lues ca l cu l a t ed f rom g lyce ro l r e t en t i on da t a fo r two un f rac t i ona t ed A. P . I .

r e fe rence ha l l oys i te s H-12b , Bedfo rd , Ind i an a , and H-13 , Eu reka , Utah ) a re

76 and 102 m2/g respec t i ve ly . The Bedfo rd sample i s r epo r t ed as con t a in ing

a b o u t l 0 p e r c e n t a l lo p h a n e M a i n , K e r r , a n d H a m i l to n , 1 9 5 0 ) , w h i c h m a y

e x p l a in t h e re l a ti v e ly h i g h v a l u e f o u n d f o r i t. H o w e v e r , t h o u g h t h e E u r e k a

sample has a s eem ing ly g rea t e r su r face a rea t ha n t he Be dfo rd , t hese au tho rs

d id no t r epo r t i t t o con t a in a l lophane . The d i sc rep ancy i s no t a t t r i bu t ab l e t o

ende l l i t e l aye r s i n t he ha l l oys i t e , s i nce i n de t e rmin ing t he g lyce ro l r e t en t i on

v a l u e t h e s a m p l e w a s p r e d r i e d a t l l 0 ~ a n d a n y e n d e ll it e l a y e r s w o u l d h a v e

been col lapsed .

ndeUite

A to t a l su r face a rea o f 430 m2/g was ob t a ined fo r a s ample o f ende l l i t e

f rom Cha t tooga Co . , Georg i a , f rom g lyce ro l r e t en t i on da t a fo r ma te r i a l p re -


8/14

SIDNEY DIAMOND AND EAR L B KINTER 341

s e r v e d i n t h e n a t u r a l m o i s t s t a t e ; r e t e n t i o n o n a p o r t i o n o f t h i s m a t e r i a l p r e -

d r i e d a t 1 1 0 ~ i n d i c a t e d a n e x t e r n a l s u r f a c e o f o n l y 2 7 m 2 / g . B o t h v a l u e s

a r e b a s e d o n a n a s s u m e d a r e a o f 2 6 . 9 A 2 p e r m o l e c u l e o f g l y c e ro l , as d e r i v e d

f r o m d a t a o n m o n t m o r i l lo n i t e - g l y c e r o l c o m p l e x e s. A s p r e v i o u s l y d i sc u s se d ,

t h e v a l u e s m a y b e a b o u t 1 0 p e r c e n t t o o l o w .

411ophane

A t o t a l s u r f a c e a r e a o f a p p r o x i m a t e l y 2 6 0 m Z / g f o r a s o i l a l l o p h a n e w a s

d e r i v e d f r o m r e t e n t i o n d a t a o n t h e m i n u s 2 - m i c r o n f r a c t i o n o f a n A n d o s o i l

f r o m J a p a n . T h e D . T .A . c u r v e o f th i s m a t e r i a l a n d i ts c o m p l e t e l a ck o f c r y s-

t a l l i n i t y , a s s h o w n b y x - r a y d i f f r a c t i o n , i n d i c a t e t h a t i t m a y b e d e s c r i b e d a s

e s se n t i a l ly pu r e a l l opha ne . Th e su r f a c e a r e a wa s c a l c u l a t e d f r om the g lyc e r o l

r e t e n t i o n d a t a o n th e a s s u m p t i o n t h a t a ll t h e g l y c e ro l w a s r e t a in e d o n e x t e r -

na l su r f a c e s . Th i s su r f a c e - a r e a f i gu r e f o r t he An do so il a l l opha ne is i n goo d

a g r e e m e n t w i t h s u r f a c e a r e a s d e t e r m i n e d b y n i t r o g e n a d s o r p t i o n f o r s o m e

a l l o p h a n e s o i l - c l a y f r a c t i o n s f r o m N e w Z e a l a n d , w h i c h a v e r a g e a b o u t 3 0 0

m 2 / g ( B i r re l l a n d G r a d w e l l, 1 9 5 6 ) .

G L Y C E R O L R E T E N T I O N O F N O N - C L A Y M A T E R I A L S

A n a t t e m p t w a s m a d e t o d e t e r m i n e t h e a p p l i c a b i l it y o f t h e g l y c e r o l r e t e n t i o n

m e t h o d t o t h e m e a s u r e m e n t o f s u r f a c e a r e a s o f v a r i o u s m a t e r i a l s o t h e r t h a n

c l a y m ine r a l s . S a mp le s o f s e ve r a l suc h m a te r i a l s o f know n su r f a c e a r e a ( a s

m e a s u r e d b y n i t r o g e n a d s o r p t i o n ) w e r e k i n d l y s u p p l ie d b y D r . V . R . D e i tz o f

t h e B o n e - C h a r R e s e a r c h P r o j e c t , I n c ., N a t i o n a l B u r e a u o f S t an d a r d s . T h e s e

s a m p l e s i n c l u d e d a s i l i c a m a t e r i a l d e r i v e d f r o m o p e n - h e a r t h f u r n a c e o p e r a -

t i on , a s i l i c a - a lumina c r a c k ing c a t a ly s t , a bone - c ha r ( c he mic a l ly i de n t i c a l t o

h y d r o x y a p a t i t e ) , a n d a p u r e s a m p l e o f a n a t a s e ( T i O 2 ) . N i t r o g e n s u r f ac e ar e a s

r a n g e d f r o m 1 0 m 2 / g f o r t h e a n a ta s e t o a b o u t 5 5 0 m Z / g f o r t h e c r a c k i n g ca ta -

ly s t. Th e r e wa s a de f in i t e e qu i l i b r ium in t he r e t e n t ion o f g lyc e r o l by a l l t he se

m a t e r i a l s e x c e p t t h e a n a t a s e ; b u t w h e n t h e r e t e n t io n v a l u e s w e r e c o n v e r t e d t o

s u r f a c e a r e a b y t h e f a c t o r p r e v i o u s l y d e r i v e d f o r c l a y m i n e r a l s ( 1 7 . 6 5

mZ/g

p e r p e r c e n t r e t e n t io n ) t h e i n d i c a t e d s u r f a c e a r ea s w e r e o n l y a b o u t 5 0 p e r c e n t

o f t h e n i t r o g e n a d s o r p t i o n f i g u r e s .

A l though the r e i s a de f in i t e r e t e n t ion o f g lyc e r o l on the su r f a c e s o f mos t o f

t h e se m a t e r i a l s u n d e r t h e e x p e r i m e n t a l c o n d i t i o n s i n v o l v ed , t h e n a t u r e o f t h e

pa c k ing o f t he mo le c u le s on the i r su r f a c e s i s no t ne c e s sa r i l y t he s a me a s i t i s

on c l a ys . P o r e s ha v ing su r f a c e s a c c e s s ib l e t o n i t r oge n bu t no t t o g lyc e r o l

c ou ld a l so a c c oun t f o r t he l ow va lue s ob ta ine d .

S U R F A C E A R E A S O F M O N T M O R I L L O N I T E I N T E R M S

O F P A R T I C L E D I M E N S I O N S

O n e p o s si b le e x p l a n a t i o n o f t h e r a t h e r p r o n o u n c e d v a r i a t io n i n s u r f a ce - a re a

m e a s u r e m e n t s o f a m o n t m o r i l l o n i t e s a t u r a te d w i t h d i f fe r e n t c a ti o n s i s t h a t t h e


9/14

34 SURFACE AREAS AND GLYCEROL RETENTION

c a t io n s m a y c a u s e d i f f e r e n c e s i n t h e d e g r e e o f d i s p e r s i o n o f t h e m o n t m o r i ll o n -

i r e pa r t i c l e s a nd the e f f e c t ive pa r t i c l e si z e. B r oo ks ( 1955) c onc lude d tha t f o r

s o d i u m W y o m i n g b e n t o n i t e , th e e f f e c t i v e p a r t i c l e si ze i n a n a q u e o u s s u sp e n -

s i o n w a s a p p r e c i a b l y s m a l l e r t h a n t h e p a r t i c le - a g g r e g a t e a c c es s ib l e to n i t r o g e n

a f t e r d r y i n g . M e a s u r e m e n t s i n v o l v i n g i n t e r n a l su r f a c e s m u s t e m p l o y p o l a r

mo le c u le s ; i n a p r e v ious ly d r i e d sa mple , t he e x te n t t o wh ic h the se po la r mo le -

c u le s pe ne t r a t e be twe e n the un i t - c e l l su r f a c e s a nd a l so the e x te n t t o wh ic h the

pe n e t r a t ion d i s r up t s t he pa r t i c l e - a gg r e ga te s a nd a l t e rs t he e f f e c t ive pa r t i c l e s iz e

m a y d e p e n d o n t h e p a r t i c u l a r c a t i o n p r e s e n t.

I t s e e ms r e a sona b le tha t i f sod ium, a d i spe r s ing c a t ion , we r e p r e se n t , t he

d i s r u p t i o n o f p a r t i c le s w o u l d b e g r e a t e r t h a n w i t h a p o l y v a l e n t , f l o c c u l a t in g

c a t ion . Th e g lyc e r o l - r e t e n t ion t e c hn ique spe c i f i c a l ly invo lve s a dd i t io n o f g ly -

c e r o l a n d w a t e r t o a d r i e d c l a y , w i t h o n l y s u c h d i s p e r s io n a s c a n b e a c h i e v e d

b y m o d e r a t e s h a k i n g ; w h i l e t h i s h a s b e e n s h o w n t o r e s u l t i n e s s en t i al l y c o m -

p l e te p e n e t r a t i o n o f t h e g l y c e r o l t h r o u g h o u t t h e i n t e r l a y e r s u r fa c e s , th e e f f e c t

o f t h e t r e a t m e n t o n t h e b r e a d t h a n d t h i c k n e s s o f th e r e s u l t in g m o n t m o r i l l o n i t e

p a r t i c l e s i s l ik e l y t o v a r y w i t h th e n a t u r e o f t h e s a t u r a t i n g c a t i o n .

I f t h i s poss ib i l i t y i s a l l owe d , i t be c ome s o f i n t e r e s t t o a t t e mp t to c a l c u la t e

t h e i n t e r n a l a n d e x t e r n a l s u r f a c e a r e a s o f m o n t m o r i l l o n i t e a s f u n c t i o n s o f

p a r t i c l e d i m e n s i o n s . F o r t h is p u r p o s e , th e f o l l o w i n g d im e n s i o n s m a y b e u s e d

fo r the uni t ce l l o f m on tm or i l lon i te : a ~--- 5 .1A ; b = 8 .8A ; c - -- - 9 .6A. Th e

c ompos i t i on o f t he un i t c e l l i s t a ke n a s

2 [ (All .67) (Mg0.33) Si4 O lo(O H ) 21

wi th 718 a tom ic un i t s , ne g le c t ing the e xc ha ng e a b le c a t ion . F o r s imp l i c i ty , a

m o n t m o r i l l o n i t e p a r t i c le c a n b e c o n s i d e r e d a s a r e c t a n g u l a r s o l id L, M, a n d N

un i t c e ll s t h i c k in the a , b , a nd c d ime n s ions , r e spe c t ive ly . W e a k b ond ing in

the c d i r e c t ion pe r mi t s t he e n t r a nc e o f po la r mo le c u le s a nd thus a l l un i t - c e l l

s u r f a ce s n o r m a l t o th e c d i r e c t io n ( e x c e p t t h e t o p a n d b o t t o m o f t h e p a rt i c le )

a r e i n t e r n a l s u r f a c e s , t h e t o p a n d b o t t o m o f t h e p a rt i c le a n d t h e e d g e a n d

e nd su r f a c e s c ons t i t u t ing the e x te r na l su r f a c e s .

A f u r t h e r s i m p l i f ic a t i o n c an b e m a d e b y a s s u m i n g t h a t t h e p a r t i c l e c o n t a in s

r o u g h l y t h e s a m e n u m b e r o f u n i t c el ls in t h e a a n d t h e b d i r e c t ions , t hus

r e q u i r i n g o n l y t w o p a r a m e t e r s f o r s u r f a c e a r e a c a l c u l a ti o n s : L , t h e w i d t h o f

the pa r t i c l e i n un i t c el ls i n t he a a n d b d i r e c t ions ; a nd N , the he ig h t o f t he

p a r t i c l e i n u n i t c el ls i n t h e c d i r e c t io n . A d i a g r a m m a t i c r e p r e s e n t a t i o n o f a

m o n t m o r i l l o n i t e p a r t i c l e a c c o r d i n g t o th i s c o n c e p t i s p r o v i d e d i n F i g u r e 1 .

T h e e x t e r n a l s u r f a c e a r e a p e r g r a m o f p a rt i c le s o f a g i v e n si ze i s th e p r o d u c t

o f t h e e x t e r n a l s u r f a c e p e r p a r t i c l e a n d t h e n u m b e r o f p a r t ic l e s p e r g r a m . I t

c a n b e s h o w n t h a t e m p l o y i n g th e s e s i m p l i f ic a t io n s t h e e x t e r n a l s u r f a c e a r e a o f

a m o n t m o r i l l o n i t e o f u n i f o r m p a r t i c l e s iz e c a n b e e x p r e s se d a s :

2241 ( N) + 754 ( L )

E x t e r n a l s u r f a c e ( m e / g ) = L N

T h i s e x t e r n a l s u r f a c e c a n b e a p p o r t i o n e d i n t o /ace sur/ace, g i v e n b y 7 5 4 / N


10/14

SIDNEY DIAMOND AND EA RL B. KINTER 34 3

w h i c h i s i n d e p e n d e n t o f p a r t i c l e w i d t h ) , a n d ed ge sur face g i v e n b y 2 2 4 1 / L

w h i c h i s i n d e p e n d e n t o f p a r t i c l e t h i c k n e s s ) .

T h e internal surface o f t h i s h y p o t h e t i c a l m 0 n t m o r i l l o n i t e c a n b e e x p r e s s e d

a s

7 5 4 N - 1 )

I n t e rn a l s u r fa c e m e / g ) - - N

w h i c h i s i n d e p e n d e n t o f p a r ti c l e w i d t h ) .

T h e total surface i s t he sum o f t he in t e r na l a nd e x te r na l su r f a c e s a nd i s

g i v e n b y :

2241

T o t a l s u r f a c e m 2 / g ) = ~ + 7 5 4

Th us the to t a l su r f a c e is i nde pe n de n t o f t he th i c kne ss o f t he pa r t i cl e s . I nde e d ,

f o r w i d e e n o u g h p a r ti c l e s a b o u t 1 0 0 u n i t ce ll s i n w i d t h ) t h e e d g e c o n t r i b u -

t ion be c ome s sma l l , a nd the to t a l su r f a c e a r e a i s e s se n t i a l ly a c ons t a n t . Mon to

m o r i l l o n i t e s c o m p o s e d o f p a r t i c l e s o f l e s s e r w i d t h s h o u l d h a v e p r o g r e s s i v e l y

l a r g e r t o t a l s u r f a c e a re a s a s p r o g r e s s iv e l y g r e a t e r a m o u n t s o f e d g e s u r f a c e a r e

e xpose d .

I f a t t e n t ion i s c on f ine d to pa r t i c l e s o f su f f i c i e n t w id th th a t e dg e su r f a c e doe s

n o t b e c o m e a p p r e c i a b l e a n d p r e s u m a b l y m o s t re a l m o n t m o r i l lo n i t e s a r e m a d e

~ 0 = 5 1 A

A b = 8 . S A

- - i o - ~ C = 9 . 6 A

C

FIGURE 1.--Diagramm atic m od el of a mo ntmorillonite particle. A, Unit cell ou tline.

B, Collapsed particle ex hibiting onIy external surface. C, E xp and ed particle exhibiting

external and internal surface.


11/14

44 SURFACE AREAS ANDG L Y E R O L R E T E N T I O N

u p o f s u c h p a r t i c l e s ) , t h e t o t a l s u r f a c e i s e s s e n t i a l ly a c o n s t a n t . S i n c e t h e

a m o u n t o f i n t e r n a l s u r f a c e d e p e n d s o n p a r t i c l e th i c k n e s s , t h e re l a t iv e p r o p o r -

t i o n o f in t e r n a l t o to t a l s u r f a c e s h o u l d p r o v i d e a n i n d i c a t i o n o f t h e t h i c k n e s s

o f t h e p a r t i c le s . F i g u r e 2 p r e s e n t s t h e c a l c u l a t e d r a t i o o f i n t e r n a l t o t o t a l

s u r f a c e a r e a v s . p a r t i c le t h ic k n e s s f o r v a r i o u s p a r t i c l e w i d th s . I f p a r t ic l e

w i d t h s a b o v e 1 0 0 u n i t c e ll s a r e a ss u m e d , th e n a r r o w b a n d a b o v e L = 1 0 0 c a n

b e u s e d a s a c a l i b r a t i o n c u r v e g i v i n g a n e s t im a t e o f p a r t i c le th i c k n e s s a s a

f u n c t i o n o f t h e i n t e r n a l t o t o t a l s u r f a c e a r e a r a t io .

I 0 0 0 1

6

5 0 o . o s 3

T 4 0 1 0 . 0 4 ~ .

~o 1o.o3 ~

-

zo

1 0 . 0 2

~, 4

]ooo ~

w

0 3 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 0

R A T I O O F C A L C U L A T E D I N T E R N A L TO C A L C U L A T E D T O T A L

SURF CE RE PER GR M

F IG U R E 2 , R a t i o o f c a l c u l a t e d i n t e r n a l t o c a l c u l a t e d t o t a l s u r f a c e a r e a p e r g r a m o f h y p o -

t h e t i c a l m o n t m o r i l lo n i t e p a r t i c l e s as a f u n c t i o n o f p a r t i c le t h i c k n e s s N ) f o r v a r i o u s p a r ti -

c l e w i d t h s L ) .

I t m u s t b e b o r n e i n m i n d t h a t t h e m o d e l e m p l o y e d r e p r e se n ts a m o n t m o r i l -

l o n i te p a r ti c l e a s a r e c t a n g u l a r s o l id w i t h s m o o t h s u r f a c e s a n d i s t h u s a g r o s s

s i m p l i f i c a t i o n ; r e a l m o n t m o r i l l o n i t e p a r t ic l e s a r e o f c o u r s e i r r e g u l a r i n o u t -

l in e , a s s e e n in e l e c tr o n m i c r o g r a p h s , a n d a r e o f v a r y i n g t h ic k n e s s e s a n d o f t e n

c u r le d , c r u m p l e d , o r o t h e r w i s e d i s t o r t e d , i f i n d e e d i n d i v i d u a l p a r t ic l e s c a n b e

o b s e r v e d a t a ll. F u r t h e r m o r e t h e s i m p l e m a t h e m a t i c a l d e r i v a t i o n i s f o r a

m a t e r i a l h a v i n g p a r t ic l e s a ll o f t h e s a m e s iz e ; r e a l m o n t m o r i l lo n i t e s a r e p o l y -

d i s p er s e , a n d t h e s u r f a c e a r e a w o u l d b e a f f e c t e d b y t h e n a t u r e o f th e p a r t i c le

s iz e d i s t r i b u t i o n .

C o n s i d e r a t i o n m u s t a l s o b e g i v e n t o t h e r e d u c t i o n i n i n t e r n a l s u r f a c e c a u s e d

b y p a r t i a l i r r e v e r s i b l e c o l l a p s e o f t h e i n t e r l a y e r s p a c e s a f t e r s a t u r a t i o n w i t h


12/14

SIDNEY DIAMONDAND EARL B KINTER 345

c e r t a in c a t ions no ta b ly K + a nd NH4+) , t he p r e se nc e o f impur i t i e s , a nd o the r

c ompl i c a t ing f a c to r s .

T h e c o m p u t e d r a t i o s o f i n t e r n a l t o t o t a l s u r f a c e a r e a s d e t e r m i n e d b y g l y -

c e r o l r e t e n t i o n f o r t h e v a r i o u s c a t i o n s a t u r a t io n s o f t h e V o l c l a y m o n t m o r i l l o n -

i te T a b l e 2 ) c a n b e c o m p a r e d w i th F i g u r e 2 , e v e n t h o u g h t h e m e a s u r e d t o t a l

su r f a c e a r e a s a r e no t t he s a me f o r t he d i f f e r e n t c a t ion sa tu r a t ions . I f pa r t i c l e

wid th i s a s sume d to be in e xc e ss o f 100 un i t c e i l s , a t h i c kne ss o f 3 to 4 un i t

c e l l s i s i nd ic a t e d f o r t he Na +- sa tu r a t e d mon tmor i l l on i t e , 6 t o 7 un i t c e l l s f o r

the sa tu r a t ion w i th H +, a nd a bo u t 20 u n i t c e i ls f o r s a tu r a t ions w i th the v a r ious

po lyva le n t c a t ions .

S i m i l a r e x p e r i m e n t a l l y d e t e r m i n e d r a t i o s c a n b e c a l cu l a t ed f r o m t h e s u r -

f a c e a r e a da t a f o r t he 0 .2 - mic r on f r a c t ions o f s e ve r a l A .P . I . s e r i e s mon tmor i l -

l on i t e s a s li s t e d in Ta b le 1 . I n a l l t he se sa mple s N a § i s c ons ide r e d to be the

p r e d o m i n a n t c a t i o n , si n c e d i s p e r s io n w a s a c c o m p l i s h e d w i t h s o d i u m m e t a p h o s -

pha te . De sp i t e t h i s f a c t , t he e x te r na l su r f a c e a r e a s r e p o r t e d f o r t he se fine fr a c -

t ions a r e low , the h ighe s t be ing on ly 35 m 2 /g ; a nd the r a t io s o f i n t e r na l t o

to t a l su r f a c e a r e a ll ove r 95 pe r c e n t . Th i s w ou ld ind ic a t e , a c c o r d ing to the

p r e v ious in t e r p r e t a t ion , t ha t t he ind iv idua l pa r t i c l e s we r e 30 o r mor e un i t c e l l s

in th ic kne ss , c on t r a s t in g s t r on g ly w i th the 3 to 4 un i t c e l l t h i c kne ss p r e v io us ly

ind ic a t e d f o r Na +- sa tu r a t e d Vo lc l a y .

S i n c e e x p e r i m e n t a l c o n f i r m a t i o n o f t h e s e d e d u c t i o n s i s c o m p l e t e l y l a c k in g ,

t h e e s t im a t e p r o v i d e d s h o u l d n o t b e c o n s i d e r e d a s d i r e c t e v i d e n c e t h a t t h e p a r -

t i c le t h i c kne ss is a c tua l ly a s i nd ic a t e d . I nde e d , suc h e xpe r im e n ta l c on f i r m a -

t ion i s d i f f i c u l t t o p r oc u r e , s inc e the m on tm or i l l on i t e pa r t i c le s e x i s t ing , f o r

e x a m p l e , in a n e l e c tr o n m i c r o s c o p e p r e p a r a t i o n m a y b e q u i t e d i f f e r e n t in s i z e

f r o m t h e p a r t i c l e s c o m p r i s i n g a g l y c e r o l r e t e n t i o n s p e c i m e n a t e q u i l i b r i u m .

Ev id e nc e e x i s ts t ha t sm a l l va r i a t ion s in d i spe r s ion , d r y in g , g r ind ing , o r o the r

p r e p a r a t o r y t r e a t m e n t s p r o d u c e c o n s i d e r a b l e v a r i a t i o n s i n t h e r e s u l t i n g e x t e r -

na l su r f a c e a r e a s o f mon tmor l lon i t e s , a nd thus in the i r a ppa r e n t pa r t i c l e s i z e s

B r o o k s , 1 9 5 5 ; Z e t tl e m o y e r , Y o u n g , a n d C h e s si ck , 1 9 5 5 ; M o o n e y , K e e n a n ,

a n d W o o d , 1 9 5 2 a ) . T h e p a rt i c le s t h u s o b s e r v e d o r m e a s u r e d b y a n y p a r t ic u -

l a r e x p e r i m e n t a l p r o c e d u r e a r e t h o s e t h a t h a p p e n t o e x i s t a f t e r t h e n e c e s s a r y

sa mple p r e pa r a t ions tha t a r e i nvo lve d .

C O N C L U S I O N S

T h e f o l l o w i n g co n c l u s io n s a r e d r a w n f r o m t h e w o r k d e s c r ib e d i n t h is p a p e r :

1 . G lyc e r o l r e t e n t ion m a y be e mploy e d to p r ov id e a r e l a t ive ly s imp le a nd

r a p i d m e t h o d o f m e a s u r i n g s u r f a c e a re a s o f b o t h e x p a n d i n g a n d n o n e x p a n d -

ing c la ys . A se pa r a t e de t e r m ina t ion o f t he g lyc e r o l r e t a ine d on e x te r na l su r -

f a c e s i s r e qu i r e d f o r c om pu ta t io n o f t he to t a l su r f a c e o f e xpa nd in g c l a ys . S u r -

f a c e a r e a s o f c l a y s c o m p o s e d o f m i x t u r e s o f m o n t m o r i U o n i t e a n d v e r m i c u l i t e

m a y b e d e t e r m i n e d w i t h o u t r e f e r e n c e t o t h e r e l a t iv e a m o u n t s o f e a c h p r e s e n t.

2 . C a lc u la t ions o f su r f a c e a r e a s o f non e xp a nd ing c l a y m ine r a l s f r om g ly -

c e r o l r e t e n t i o n d a t a a r e i n g o o d a g r e e m e n t w i t h p u b l i s h e d v a l ue s f o r t h e s a m e

o r s i m i l a r m a t e r i al s d e r i v e d f r o m g a s - a d s o rp t i o n m e t h o d s .


13/14

3 4 6 S U R F A C E A R E A S A ND G L Y C E R O L R E T E N TIO N

3 . C a l c u l a t i o n s o f e x t e r n a l su r f a c e a r e a s o f m o n t m o r i l l o n i t e c l a y s f r o m

g l y c e r o l - r e t e n t i o n d a t a o f h e a t e d m o n t m o r i l l o n i t e s a r e i n a p p r o x i m a t e a g r e e -

m e n t w i t h r e p o r te d m e a s u r e m e n t s b y

nonpolar

g a s - a d s o r p t i o n m e t h o d s , e s p e -

c i a l l y w h e n t h e v a r i a t i o n s i n e x t e r n a l su r f a c e s p r o d u c e d b y d i f f e r e n c e s i n p r e -

t r e a t m e n t s a r e c o n s i d e r e d .

4 . C a l c u l a t i o n s o f

total

s u r f a c e a r e a s o f m o n t m o r i l l o n i t e c l a y s a r e in r e a -

s o n a b l e a g r e e m e n t w i t h t h o se r e p o r t e d f o r s i m i l a r m a t e r i a l s b y a d s o r p t i o n o f

polar

g a s e s , n o t a b l y N H 3 . T h e v a l u e s ar e s o m e w h a t l o w e r t h a n c e r t a i n p u b -

l i sh e d v a l u e s d e r i v e d f r o m w a t e r - v a p o r d e s o r p t i o n i s o t h e r m s ; h o w e v e r , t h e

c o r r e c t n e s s o f t h e l a t t e r v a l u e s h a s b e e n q u e s t i o n e d .

5 . I t is s u g g e s t e d t h a t th e f a c t o r p r o p o s e d b y D y a l a n d H e n d r i c k s t o c o n -

v e r t e t h y le n e g l y c o l r e t e n t i o n d a t a t o s u r f a c e a r e a i s a b o u t o n e - t h i r d t o o h i g h .

A f a c t o r i s p r o p o s e d t h a t i s c o n s i s t e n t w i t h a l i q u i d l i k e p a c k i n g a n d t h e

o b s e r v e d t h i c k n e ss o f t h e g l y c o l f i l m s b y x - r a y d i f f r a c t i o n m e a s u r e m e n t s .

6 . T h e r e l a t i o n s b e t w e e n t h e i n t e r n a l a n d t h e e x t e r n a l su r f a c e a r e a s a n d

t h e p a r t ic l e t h i c k n e s s a n d w i d t h h a v e b e e n w o r k e d o u t f o r m o n t m o r i l l o n i t e o n

t h e b a s is o f a s i m p l i f i e d m o d e l o f a m o n t m o r i l l o n i t e p a r t i c l e . I t i s s h o w n t h a t

t h e r a t i o o f i n t e r n a l t o t o t a l s u r f a c e m a y p r o v i d e a n e s t i m a t e o f p a r t i c l e

t h i c k n e s s f or a g i v e n m o n t m o r i l l o n i t e .

R E F E R E N C E S

Birre l l , K. S . , and Gradwel l , M. 1956, Ion exch ange phenomena in some soils containing

amorphous mineral consti tuents : J . Soil Sci . (London), v . 7 , p . 130-147.

Bower, C. A., and G schwend, F . B., 1952, Ethy lene glycol re tention of soils as a me asure

of surface ar ea: Soil Sci. Soc. Am er. Proc. , v . 16, p . 342-345.

Brooks, C. S. , 1955, Nitrogen adsorption experiments on several c lay minerals : Soil Sci . ,

v. 79, p. 331-348.

Brunauer, S. , Emm ett, P . H., and T eller, E., 1938, Ad sorptio n of gases in m ultim olecu lar

layers: J . Amer. Chem. Soc., v. 60, p. 309-319.

Dyal, R. S. , and Hendricks , S. B., 1950, Total surface of c lays in polar l iquids as a charac-

teristic index: Soil Sci., v. 69, p. 421-432.

Kee nan, A. G., Mooney, R. W ., and Wood, L. A., 1951, The re la tio n between exchan geable

ions and water adso rption on k aoli nite : J . Phys. Coll . Chem., v . 55, p. 1462-1474.

Kin ter, E. B., and Diamond, S. , 1958, Gra vim etric determ ination of monolayer glycero l

complexes o f c lay minera ls : in Clays and Clay Minera ls , Na t . Acad . Sc i . - -Na t . Res .

Council pub. 5 66, p. 318-333.

Lopez-Gonzalez , J . de D ., and Deitz , V. R., 1952, Surface changes in an orig inal and acti-

vated bentonite : J . Res . Nat. Bur. Standards , v . 48, p . 325-333.

MacEwan, D. M. C., 1948, Complexes of c lays with organ ic com pound s: I . Complex forma-

t ion be tween mon tmori l lon i te and h a l loys i te and ce r ta in o rgan ic l iqu ids : F a rad ay Soe .

Trans., v. 44, p. 368-375.

M ain, M. S., Ke rr, P. F . , and H am ilton, P. K., 1950, Occurrence and micro scopic exami-

na t ion o f re fe rence c lay minera l spec imens : Amer . Pe t ro l . Ins t . P ro jec t 49 , Rep t . 5 ,

Columbia U nivers ity , N. Y., 59 p .

Mooney, R. W., Keenan, A. G., and Wood, L. A., 1952, Adsorption of water vapor by

mo ntm oril lonite I : J . A me r. Chem. Soc. , v . 74, p . 1367-1371.

Mooney, R. W., Keenan, A. G., and Wood, L. A., 1952a, Adsorption of water by montmor-

il lonite II : J . Amer. Ch em . Soc., v . 74, 6 . 1371-1374.

Mortland, M. M., 1955, Adsorption of ammonia by c lays and muck: Soil Sci . , v . 80, p .

11-18.

Nelson, R. A., and Hendricks , S. B., 1943, Specific surface of some clay minerals , soils ,

and soil colloids: Soil Sci., v. 56, p. 285-296.


14/14

S IDNE Y DI AM OND AND E ARL B . KI N T E R 3 4 7

Orch is ton H. D. 1954 Adsorp t ion o f wa te r vapor I I : Clays a t 25~ So i l Sc i . v . 78 p .

463-480.

Or c h i s to n H . D . 1 9 5 5 A d s o r p t i o n of wa t e r v a p o r I I I : Ho m o io n i c m o n tm o r i ll o n i te s a t

25~ Soil SoL v. 79 p . 71-78.

Qui rk J . P . 1955 S ign i f ican ce o f a reas ca lcu la ted f rom wa te r vapor so rp t ion i so the rms by

use of the B.E.T . eq ua tion : Soil Sci . v . 80 p . 423--430.

W alker G. F . 1950 V erm icu l i te -o rgan ic com plexes : Na tu re v . 166 p . 695-697 .

Ze t t lemoy er A. C. Y oung G. J . and Chess ick J . J . 1955 S tud ies o f the su r face chemis -

t r y o f s i l i c a t e m in e r a l s I I I : He a t s o f im m e r s io n o f b e n to n i t e i n wa t e r : J . P h y s . Ch e m .

v. 59 p. 962-966.

Zono l i te Co . 1954 Che mica l and phy s ica l p roper t ie s o f ve rm icu l i te : Zono l i te Co . Ch icago

Il l . 14 p .

1958 - diamond - surface areas of clay minerals as derived from measurements of glycerol retention

Documents