mineralogical and chemical characterization of various bentonite and smectite-rich clay materials

June 2010

Working Reports contain information on work in progress

or pending completion.

The conclusions and viewpoints presented in the report

are those of author(s) and do not necessarily

coincide with those of Posiva.

S i rpa Kumpu la inen

Leena K iv i ranta

B+Tech Oy

Work ing Report 2010 -52

Mineralogical and Chemical Characterization ofVarious Bentonite and Smectite-Rich

Clay MaterialsPart A: Comparison and Development of Mineralogical

Characterization MethodsPart B: Mineralogical and Chemical Characterization

of Clay Materials

MINERALOGICAL AND CHEMICAL CHARACTERIZATION OF VARIOUS BENTONITE AND SMECTITE-RICH CLAY MATERIALS ABSTRACT

Mineralogy is an essential issue in understanding thermo-hydro-mechanical-chemical

(THMC) behavior of bentonite materials. Mineralogy affects, among others, chemical

composition of pore water, susceptibility for erosion, and transport of radionuclides.

Consequently, mineralogy affects the designs of the buffer and backfill components.

The objective of this work was to implement and develop mineralogical and chemical

methods for characterization of reference clays considered for use as buffer and backfill

materials in nuclear waste disposal. In this work, different methods were tested,

compared, developed, and best available techniques selected. An additional aim was to

characterize reference materials that are used in various nuclear waste disposal

supporting studies, e.g., the SKB’s alternative buffer material (ABM) experiment.

Materials studied included three Wyoming-bentonites, two bentonites from Milos, four

bentonites from Kutch district, and two Friedland clays. Minerals were identified using

x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and polarizing

microscopy. Mineralogical composition was estimated using Rietveld-analysis.

Chemical methods were used to support and validate mineralogical interpretation. Total

chemical composition was determined from decomposed samples using spectrometry

(ICP-AES) and combustion (Leco-S, Leco-C). Ferric and ferrous iron species were

distinguished titrimetrically and the amount of soluble sulphate was determined using

ion chromatography. In addition, cation exchange capacity and original exchangeable

cations were determined. Chemical composition of fine (<2µm) fractions and poorly

crystalline Fe-, Al- and Si-phases determined by selective extractions were used in

structural calculations of smectite.

XRD is a basic method for all mineralogical characterization, but it is insensitive for

detecting trace minerals and variations in the structural chemical composition of clay

minerals. Polarizing microscopy proved to be useful in characterization of coarse

fractions with regard to identification of trace minerals, estimation of particle size

distribution, and characterization of crystal morphology, possible alteration of minerals,

as well as mineral assemblages. FTIR not only supported mineralogical observations

from XRD, but it revealed variations in clay structural compositions, and the presence

of mineral impurities in purified clay fractions that were used as the basis of structural

calculations.

The Wyoming-type Na-bentonites under analysis were very similar to one another and

contained approximately 80 wt.% of smectite. All Kutch bentonites were enriched with

ferric iron, were Al-rich, and their kaolin mineral content varied, up to 20 wt.%.

Bentonites from Milos-area were Ca-rich and contained slightly more illite in fine

fraction than bentonites from Wyoming or Kutch areas. Friedland clays consisted

approximately 22 wt.% of smectite and 34 wt.% of illite.

Keywords: clay, bentonite, chemical composition, mineralogical composition

BENTONIITTIEN JA SMEKTIITTI-PITOISTEN SAVIEN KEMIALLINEN JA MINERALOGINEN KARAKTERISOINTI TIIVISTELMÄ

Mineralogialla on tärkeä merkitys puskuri- ja täyteaineiden termo-hydro-mekaanis-

kemiallisen (THMC) käyttäytymisen ymmärtämisessä. Mineralogia vaikuttaa muun

muassa materiaalin huokosveden kemialliseen koostumukseen, eroosioherkkyyteen, ja

radionuklidien kulkeutumiseen. Täten mineralogia vaikuttaa myös puskuri- ja

täyteainekomponenttien suunnitteluun.

Tutkimuksen tarkoituksena oli kehittää ydinjätteen loppusijoituksessa käytettävien

puskuri- ja täyteainesavien mineralogisen ja kemiallisen koostumuksen määrittämiseen

toimivia menetelmiä, sekä määrittää eri tutkimusprojekteissa, kuten ABM-projektissa,

käytettyjen referenssisavien kemiallinen ja mineraloginen koostumus. Tutkimus oli

kaksiosainen. Ensin testattiin, verrattiin ja kehitettiin menetelmiä, ja valittiin parhaat

käytettävissä olevat menetelmät. Toisessa osassa valittuja menetelmiä käytettiin

referenssisavimateriaalien koostumuksen määrittämiseen.

Tutkitut materiaalit sisälsivät kolme Wyoming-bentoniittia, kaksi bentoniittia

Milokselta, neljä bentoniittia Kutchin alueelta, ja kaksi Friedland-savea. Mineraalien

tunnistamiseen käytettiin röntgendiffraktiota (XRD), infrapunaspektroskopiaa (FTIR) ja

polarisaatiomikroskopiaa. Mineralogisen koostumuksen määrittämiseen käytettiin

Rietveld-analyysiä. Alkuaineiden kokonaispitoisuudet määritettiin sulatteesta spektro-

metrillä (ICP-AES) ja polttomenetelmillä (Leco-S, Leco-C). Raudan eri hapetusmuodot

erotettiin titraamalla ja liukoisen sulfaatin määrä ionikromatografialla. Lisäksi määri-

tettiin kationinvaihtokapasiteetti sekä vaihtuvien kationien laatu ja määrä. Hieno-

aineksen (<2µm) kemiallista koostumusta ja heikkouutoilla määritettyjen huonosti

kiteisten Fe-, Al-, ja Si-faasien määrää käytettiin smektiitin rakennelaskuihin.

Mineralogiseen analyysiin käytetyt menetelmät paljastivat materiaaleista eri ominai-

suuksia ja havainnot tukivat hyvin toisiaan. Kemiallista analyysiä käytettiin mine-

ralogisten havaintojen tukena ja määritetyn mineralogisen koostumuksen luotettavuuden

varmistamiseen.

Tutkitut Wyoming-tyyppiset Na-bentoniitit olivat hyvin samankaltaisia ja sisälsivät

noin 80 wt.% smektiittiä. Kutchin-alueelta peräisin olevat bentoniitit olivat kaikki

rikastuneet ferriraudan ja alumiinin suhteen, niiden kaoliniittipitoisuus vaihteli suuresti

ja oli jopa 20 wt.%. Tutkittujen Miloksen alueelta olevien Ca-rikkaiden bentoniittien

illiittipitoisuus oli aavistuksen suurempi kuin Wyoming- ja Kutchin alueelta olevien

bentoniittien. Friedland-savien smektiittipitoisuus oli noin 22 wt.% ja illiittipitoisuus

noin 34 wt.%.

Avainsanat: savi, bentoniitti, kemiallinen koostumus, mineraloginen koostumus

1

TABLE OF CONTENTS ABSTRACT TIIVISTELMÄ

LIST OF ABBREVIATIONS .......................................................................................... 3 Part A: comparison and development of mineralogical characterization methods ........ 5 FOREWORD ............................................................................................................... 5 1 INTRODUCTION ...................................................................................................... 7

1.1 Background ........................................................................................................ 7 1.2 Earlier work ........................................................................................................ 7 1.3 Objectives for research ...................................................................................... 8

2 MATERIAL PREPARATION ..................................................................................... 9

2.1 Homogenization of bulk samples ........................................................................ 9 2.2 Purification and homoionization of clay fraction .................................................. 9

3 METHODS .............................................................................................................. 11

3.1 Identification of minerals .................................................................................. 11 3.1.1 XRD .......................................................................................................... 11 3.1.2 FTIR .......................................................................................................... 14 3.1.3 Optical polarizing microscopy .................................................................... 15 3.1.4 Overall conclusions on mineralogical methods for identification ................ 16

3.2 Exchangeable cations and CEC ....................................................................... 16 3.2.1 Exchangeable cations ............................................................................... 16 3.2.2 Comparison of methods to determine exchangeable cations ..................... 17 3.2.3 CEC .......................................................................................................... 18 3.2.4 Comparison of methods to determine CEC ............................................... 20

3.3 Selective extractions ........................................................................................ 20 3.3.1 Citrate-bicarbonate-dithionite extraction .................................................... 20 3.3.2 Sodium carbonate extraction ..................................................................... 21

3.4 Chemical composition ...................................................................................... 21 3.4.1 Water, carbon and sulphur ........................................................................ 21 3.4.2 Fe2+/Fe3+ -ratio .......................................................................................... 22 3.4.3 Total chemical composition ....................................................................... 23

3.5 Mineralogical composition ................................................................................ 23 3.5.1 Quantification of single mineral phases ..................................................... 23 3.5.2 Calculation of structural formula for smectite ............................................. 24 3.5.3 Rietveld analysis ....................................................................................... 24

4 CONCLUSIONS ..................................................................................................... 27 Part B: Mineralogical and chemical characterization of clay materials ........................ 29 5 MATERIALS ........................................................................................................... 29

5.1 Wyoming, USA ................................................................................................. 29 5.2 Milos, Greece ................................................................................................... 29 5.3 Kutch, Gujarat, India ........................................................................................ 29 5.4 Friedland, Neubrandenburg, Germany ............................................................. 30

2

6 RESULTS ............................................................................................................... 31 6.1 Mineralogy ....................................................................................................... 31

6.1.1 XRD .......................................................................................................... 31 6.1.2 Greene-Kelly ............................................................................................. 36 6.1.3 FTIR .......................................................................................................... 37 6.1.4 Optical polarizing microscopy .................................................................... 41 6.1.5 Other observations .................................................................................... 44 6.1.6 Summary on identification of minerals ....................................................... 44

6.2 Exchangeable cations and CEC ....................................................................... 45 6.3 Chemical composition ...................................................................................... 46

6.3.1 Poorly crystalline Fe, Al and Si .................................................................. 46 6.3.2 Total chemical composition ....................................................................... 46

6.4 Mineralogical composition ................................................................................ 48 6.4.1 The amount of illite .................................................................................... 48 6.4.2 Calculation of structural formula for smectite ............................................. 49 6.4.3 Total mineralogical composition ................................................................ 50

REFERENCES .......................................................................................................... 51 LIST OF APPENDICES ............................................................................................. 55

3

LIST OF ABBREVIATIONS

ABM Alternative buffer material

CBD Citrate-bicarbonate-dithionite extraction

CEC Cation exchange capacity

EC Electric conductivity

EG Ethylene glycol

FTIR Fourier transform infrared spectroscopy

IC Ion chromatography

ICP-AES Inductively coupled plasma atomic emission spectroscopy

PP Polypropene

SC Sodium carbonate extraction

S/C-analyzer Sulphur/Carbon-analyzer

SEM-EDS Scanning electron microscopy – Energy dispersive spectroscopy

TEM Transmission electron microscopy

TEM-EDS Transmission electron microscopy – Energy dispersive spectroscopy

TG/DTA Thermal analysis

XRD X-ray diffraction

XRF X-ray fluorescence spectroscopy

5

PART A: COMPARISON AND DEVELOPMENT OF MINERALOGICAL CHARACTERIZATION METHODS

FOREWORD

The aim of this work is to test, compare and develop methods for mineralogical

characterization of bentonites and smectite-rich clay materials. Characterization of

eleven different clay materials will be done in the following work: “Part B:

Mineralogical and chemical characterization of clay materials” using the methodology

implemented in this work.

7

1 INTRODUCTION

1.1 Background

Bentonite is considered for use as a buffer and backfill material in nuclear waste

repository because it is highly plastic, has adequate chemical and mineralogical

stability, low permeability and beneficial swelling properties. Mineralogy is an essential

issue in understanding the thermo-hydro-mechanical-chemical (THMC) behavior of

bentonite materials. It affects, among others, the composition of pore water,

susceptibility for erosion and transport of radionuclides. Consequently, mineralogy

affects the designs of buffer and backfill components.

Bentonite is a natural product resulting from the alteration of volcanic ash. Complexity

brought on by small particle size of the material and its variability as a natural product

makes mineralogical interpretation often challenging. Difficulties are encountered in the

identification of poorly crystalline clay minerals, mixed-layered clay minerals, hydroxy-

intercalated clay minerals and poorly crystalline accessory minerals, as well as in

quantification. Sample preparation techniques and mineralogical methods used for

characterization can also cause variability in reported mineralogical compositions.

1.2 Earlier work

Carlson (2004) characterized mineralogy of variable bentonites using XRD, FTIR,

TEM, TEM-EDS, CEC, XRF and S/C-analyzer. Comparison of different CEC methods

was done using variable solutes (LiCl, BaCl2, CsCl, buffered NH4-acetate (pH 7) and

Cu2+

-ethylenediamine), solution strengths (0,01 M; 0,1 M) and pH (4, 7). However,

CEC was determined only from bulk samples, and therefore, contained accessory

minerals such as carbonates, which dissolved during extraction and complicated the

interpretation. Further, extractable ions were analyzed, not the adsorbed cation fraction.

Quantification was done based on experimentally defined mineral intensity factors from

XRD-patterns supported by chemical determinations, which is susceptible to errors,

because such quantification method does not take into account natural crystallinity

variations in clay minerals. Quantification accuracy in this study was approximated as

5 %.

In Carlson & Keto (2006), inter-laboratory comparison of different sample preparation

techniques, XRD, FTIR, CEC, exchangeable cation extraction, total chemical

composition and quantitative methods showed inequality in results. Not only the

methods varied but also sample heterogeneity was present. Quantification resulted in

large variation (up to several tens of percentages) in estimated smectite contents

between different laboratories.

Karnland et al. (2006) characterized mineralogical, chemical and physical properties of

variable bentonites and smectite-rich materials. For mineralogical quantification they

compared the results from Rietveld analysis (which were adjusted with chemical

analyses for some parameters) and chemical determinations resulting in an accuracy of

only few percentages.

8

Ahonen et al. (2008) listed tests to assure the quality of bentonite. Smectite content,

CEC, semiquantitative mineral composition, chemistry and water content were included

in mineralogical and chemical quality assurance tests. In the experimental part of their

report, comparison of different methods to determine water content (gravimetric, water

analyzer, TG/DTA) and CEC (BaCl2, buffered NH4-acetate (pH 7), methylene blue)

revealed some differences between the methods, but didn’t give direct answers for the

reasons of these differences.

1.3 Objectives for research

Objectives for work were:

1. To establish and build capacity, resources and develop skills in clay mineralogical

research in Finland, especially on bentonite.

2. To test and improve currently used mineralogical qualification and quantification

methods for bentonites and smectite-rich materials.

3. To test and select mineralogical methods recommended to be used in characterization

procedures for clay materials considered for use in nuclear disposal.

The aim was to improve the mineralogical methodology for more precise determination

of smectite content as well as for mineralogical quantification in general. Recommended

methods to be used in the future were selected after comparison of results from various

methods (this study, the earlier work of Carlson (2004), Carlson & Keto (2006),

Karnland et al. (2006) and Ahonen et al. (2008)) and between various laboratories (e.g.

ABM reference samples tested by different ABM project partners).

9

2 MATERIAL PREPARATION

2.1 Homogenization of bulk samples

Materials were dried in a convection oven in 60 oC, and gently ground mechanically in

agate mortar with pestle. The ground material was sieved through 1 mm mesh size net.

Any material retained on the 1 mm net was ground and sieved again through the 1 mm

net. The grinding and sieving were repeated until all of the material had passed through

the sieve. Above described initial homogenization is essential for gravel-sized materials

such as Asha 505, since visual appearance and therefore also composition of gravel

sized agglomerate particles may vary (Appendix 1).

Homogenized bulk material was used for randomly oriented XRD, CEC, exchangeable

cation extractions and determination of chemical composition.

2.2 Purification and homoionization of clay fraction

Before particle size fractionation, the material was washed free from dissolvable salts.

Ten grams of homogenized bulk material was dropped gradually to 1 L of deionized

water in a glass beaker, which was simultaneously stirred with a magnetic stirrer.

Stirring was continued overnight. Deionized water was produced with Elga Micromeg

MC:DS Cartridge and had an EC < 0,5 µS/cm. Analytical grade NaCl was added to a

concentration of 1 M and the mixing of the suspension was continued with a magnetic

stirrer for at least 2 h. Suspension was left to settle, and the clear supernatant was

removed. Addition of water and NaCl was repeated two times. Thereafter, material was

washed 3-4 times by addition of deionized water and centrifugation (5-15 minutes with

2000-3600 rpm) until supernatant became slightly turbid. Sedimented slurry, except the

coarsest fraction, was transferred into dialysis membranes (regenerated cellulose, 3500

MWCO) that were placed into 5 L acrylic tubes filled with deionized water. Dialysis

water outside the membranes was changed daily until the EC stabilized < 10 µS/cm for

three days. Material was taken out from dialysis membrane and suspended with 1 L of

deionized water in glass beaker. Suspension was left to settle for at least 12 h to remove

particles > 2 µm in diameter. After removal, chloride salt of target exchangeable cation

(Na+, Mg

2+) was added to a concentration of 1 M for monovalent cation salts and 0,5 M

for divalent cation salts and the resulting suspension was mixed with a magnetic stirrer

for at least 2 h. The material was left to settle, supernatant removed and procedure

repeated again two times. Then, material was centrifuge-washed 3-4 times with

deionized water and dialysed. A third round of homoionization, centrifuge-washing and

dialysis steps were done to finalize the purification process. The repeated purification

process described above was done, because our results (Table 2-1) as well as results of

Karnland et al. (2006) showed that cation exchange was not complete after only one

round of washings and dialysis.

Table 2-1 also demonstrates the problems in purification of calciferous clays. Because

carbonates don’t dissolve completely during the washing/homoionisation procedure,

they will continue dissolving during dialysis. In this process divalent cations are

released and they will replace the monovalent cations. In future, the purification process

of carbonate-rich clays could be enhanced with removal of carbonates prior the first

dialysis.

10

Table 2-1. Effect of Na-homoionization and dialysis cycles on saturation of

exchangeable cation sites of Volclay MX-80 measured with NH4Cl-method (section 3.2).

Saturation of exchangeable sites Exchangeable cations (in dry (105oC) weight)

Ca K Mg Na Ca K Mg Na Sum

% % % % eq/kg eq/kg eq/kg eq/kg eq/kg

Initial 21 2 8 69 0,18 0,02 0,07 0,62 0,90

After 1. cycle 10 0 10 80 0,09 0,00 0,09 0,71 0,89

After 2. cycle 1 0 4 95 0,01 0,00 0,03 0,76 0,79

After 3. cycle 1 0 2 97 0,01 0,00 0,01 0,78 0,80

During purification procedure, while stirring bulk materials using magnetic stirrer, some

magnetic particles stuck to the stirrer (Figure 2-1). Intensity of magnetism as well as

colour of magnetic particles varied in different samples.

After purification procedures, clay material was dried at 60 oC, and ground gently in

agate mortar.

Purified and homoionized clay fraction was used for oriented XRD, FTIR, selective

extractions, and determination of chemical composition and CEC. Coarse fraction that

settled to the bottom of beaker during clay fraction separation was used for optical

polarizing microscopy.

Figure 2-1. Magnetic stirring bar showing presence of magnetic minerals in AC200.

11

3 METHODS

3.1 Identification of minerals

To identify minerals present in clay materials various methods must be used.

Identification of all minerals present must be done before any attempt on quantification

of mineralogical composition.

The techniques used were selected to identify crystalline minerals present (e.g. quartz,

cristobalite, tridymite, feldspars, calcite, dolomite, siderite, pyrite, magnetite, goethite)

and to distinguish 1:1 clays (serpentine, kaolin, talc) from 2:1 clays (smectite,

vermiculite, illite, mica) and variable layer charged 2:1 clays (chlorite, sepiolite,

palygorskite). Differentiation between dioctahedral (e.g. montmorillonite, beidellite and

nontronite) and trioctahedral (saponite, hectorite) smectite group minerals was also

done.

3.1.1 XRD

Analysis of bulk samples

Analysis of randomly oriented bulk material was done to identify crystalline minerals

present and to make a distinction between dioctahedral and trioctahedral clay minerals

using positioning of d(060) reflections. Mineralogical quantification (see section 3.5.3)

using Rietveld method is based on XRD patterns of randomly oriented mounts.

Samples were ground in agate mortar with pestle to a particle size < 10 µm.

Approximately 10 mg of ground clay was mixed with acetone on a glass slide.

Alternatively, sample preparation by filling the cavity of an aluminium sample holder

using back-filling technique, was tested. Samples were put into a rotating sample

holder, scanned with Philips X’Pert MPD diffractometer equipped with Cu anode tube

and monochromator, a variable divergence slit, using wavelength of Kα1 = 1,54060; Kα2

= 1,54443; and Kβ = 1,39225; voltage of 40kV and current of 55 mA, from 2 to 70o 2θ

with 0,02o counting steps and 1 s/step counting time at the Geological Survey of

Finland.

Variation and sources of error in sampling (by analysing 3 to 5 samples), in sample

preparation (by analysing the same sample mount and mixing the sample between

preparations) and in analysis (by analysing the same mount with the same instrumental

settings repeatedly) were tested. Error in sampling was tested with all samples, but error

in sample preparation and in analysis only with one sample, namely ABM MX-80.

Multiple sample mounts were prepared and measured from each sample material and

they tended to produce fairly similar XRD patterns. However, confirmation to the

existence of some smaller peaks was gained using this multiple sample analysis

technique as the peaks stood out better from the background in some scans than in the

other. The variability in the intensity and position of the peaks in the XRD patterns of

multiple sample mounts were in similar range as in the XRD patterns measured by

analysing same sample mount in triplicate with the same instrumental settings.

12

Sample mounts prepared from the same sample by mixing the sample between the

measurements tend to become oriented, which was indicated by more intense d(001)

peaks. Thus, the more rapid the sample mounting is and less mixing is involved the

better.

ABM MX-80 mounts prepared by the alternative method by filling the sample holder

cavity with ground powder became slightly oriented. Orientation was due to necessary

pressing of the powder to fix it to the sample mount. Orientation appeared as increased

intensity of the d(001) peaks of montmorillonite and illite/mica at approximately 12 Å

and 10 Å, respectively. In addition, albite and quartz peaks were more intense than in

patterns of sample mounts prepared with the glass slide method, possibly due to grain

size effect resulting from inhomogeneous grinding of the much larger amount of

material needed for this mounting method and due to the tendency of feldspars and

quartz to orientate because of their perfect cleavage.

All samples except ABM Asha contained quartz. Consequently, 5 wt.% of quartz was

added to Asha sample, because quartz peak at 1,542 Å (Levien et al., 1980) was used as

an internal standard to adjust the shift in d(060) line positioning.

The position of d(060) line is for most dioctahedral clay minerals near 1,49-1,50 Å, and

for trioctahedral clay minerals 1,52-1,55 Å. The position of d(060) line for kaolinite is

1,490 Å; illite 1,499 Å and montmorillonite 1,492-1,504 Å (Brindley & Brown 1980).

Conclusions: From tested mounting methods, fast mixing with acetone seemed to

produce less oriented XRD patterns than the filling method. Using triplicate samples

instead of just one gave better result in identification of minor phases. To achieve more

precise peak positioning a standard must be added to some samples (Wong-Ng &

Hubbard 1987).

Analysis of clay fraction

XRD analysis of purified clay fraction was done to identify clay minerals present.

Variable techniques including orientation, saturation, solvation and heating, were used.

Oriented mounts were prepared from purified clay fractions that had been

converted to Mg-forms. Filter-membrane peel-off technique (Drever 1973;

Moore & Reynolds 1989) was used for preparation of the oriented mounts. A

concentrated suspension containing approximately 600 mg of purified clay in 10

mL of deionized water was vacuum filtered onto 0,45 µm pore size cellulose

filter. Sample mounts were dried in air and scanned with XRD from 2 to 35o 2θ

with 0,02o counting steps with counting time of 1s/step.

Ethylene glycol (EG) solvation was used to identify swelling clay minerals, i.e.

smectites. Oriented sample mounts were placed on a platform in a desiccator

containing EG and put into an oven at 60 oC for 20 h. Mounts were scanned

immediately after solvation from 2 to 20o 2θ with 0,02

o counting steps with

counting time of 1s/step.

13

Percentage of illite layers in illite/smectite mixed-layer minerals was estimated

by the composite peaks at 10 o2θ and at ~15-16

o2θ and their peak angle distance

(Δ2θ) according to Moore & Reynolds (1989). The results and the comparison

with other techniques to estimate illite content is reported in section 3.5.1.

Heating oriented mount at 550 oC for 2 h results in disappearance of kaolin

peaks at d-value of 7 Å allowing distinction of kaolin minerals from chlorites.

Oriented mounts were placed in a furnace for 2 h at 550 oC. Mounts were

scanned after heating from 2 to 20o 2θ with 0.02

o counting steps with counting

time of 1s/step.

Conclusions: To identify clay minerals present, clay fraction must be analysed

separately using oriented mounts and different solvation and heating techniques. If

heating is used merely to indicate the presence of kaolin minerals, it is not necessary for

samples not showing 7 Å peak.

Greene-Kelly test

Greene-Kelly test (Greene-Kelly 1953; Lim & Jackson 1986) was used to identify the

charge location in smectite structure, i.e. to differentiate montmorillonite (octahedral

charge > tetrahedral charge) from beidellite, nontronite or saponite (octahedral charge <

tetrahedral charge). The technique is based on saturation of clay with LiCl and heating

to 250 oC, which results into permanent collapse of the montmorillonite basal spacing to

9.5 Å and further, decrease in CEC (Lim & Jackson 1986).

Purified and homoionized clay was dispersed in deionized water, treated three

times with 3 M LiCl solution and thereafter washed three times with 0,01 M

LiCl in 90 % ethanol. Oriented mounts were prepared by smearing a thick paste

of Li-clay on a silica slide. Oriented clay mounts were dried in air and heated at

250 oC overnight. After cooling, the mounts were placed in a desiccator

containing glycerol and heated at 90 oC for 18 h. For comparison, oriented

mount was prepared from Na-exchanged clay (excluding addition of LiCl) and it

was heated and solvated with glycerol similarly. Sample mounts were dried in

air and scanned with XRD from 2 to 15o 2θ with 0,02

o counting steps.

Loss of CEC due to Li uptake was also tested. The bulk sample was dispersed in

3 M LiCl, stirred at least for 2 h with magnetic stirrer, washed with deionized

water and the clay fraction was separated by centrifugation (5 min, 730 rpm).

Correspondingly, the clay fraction was treated once with 3 M LiCl solution and

washed with deionized water until incipient dispersion. The sample was placed

into a porcelain crucible and heated at 250 oC for 24 h. For comparison, Na

exchanged purified clay was heated similarly at 250 oC overnight. The samples

were ground in agate mortar with acetone and dried at 60 oC before CEC

determination with Cu(II)-triethylenetetramine-method (see section 3.2.3).

Conclusions: Li uptake resulted in loss of swelling ability and CEC in some samples.

However, since loss of swelling ability was also complete in some samples that showed

only partial loss in CEC, the CEC measured after lithium saturation and heating cannot

14

directly be attributed to the charge originating from the tetrahedral sheet unless the

sample is comprised of pure smectite (e.g. in Friedland clays also illite and kaolinite

may contribute to the remaining CEC value). FTIR-analysis and structural calculations

support the observations on whether tetrahedrally charged smectites are present or not.

3.1.2 FTIR

Fourier transform infrared spectroscopy (FTIR) was used for the identification of clay

minerals (especially kaolin) and poorly crystalline mineral phases, but also for

identification of possible adsorbed elements or functional groups.

Smectite gives rise on inner-surface OH stretching bands at 3660 & 3630 cm-1

(for

beidellite), 3632 cm-1

(for montmorillonite) or 3564 cm-1

(for nontronite) (Farmer &

Russell 1967). Usually the band for smectites is broad and several unresolved spectral

components contribute to it. The exact position of the band depends on the chemical

composition of the smectite, AlAlOH stretching band is typically at 3620-3630 cm-1

,

AlMgOH stretching band at 3687 cm-1

and AlFe3+

OH stretching band at ~3597 cm-1

(Farmer 1974). Usually the two latter bands are not resolved from AlAlOH band in Al-

rich smectites (see Table 6-3) (Farmer 1974). In kaolin minerals, inner-surface OH

stretching bands are seen at 3697 cm-1

, 3669 cm-1

, 3652 cm-1

and 3620 cm-1

(Farmer

1974).

Structural OH bending vibrations for clay minerals locate at 950-600 cm-1

(see Table 6-

3) (Farmer, 1974). AlAlOH bending band can be assigned to smectite and/or kaolin

minerals at 919-913 cm-1

. AlFe3+

OH bending band for smectite locates at 890-870 cm-1

.

The position of this band is decreasing with increasing Fe content. At 860-840 cm-1

are

AlMgOH bending bands for smectite. Fe3+

Fe3+

OH bands at 850 and 818-815 cm-1

are

indicating the presence of nontronite. The exact position and molar absorptivity of all

above mentioned OH bending bands depends on water content and type of

exchangeable cation (Xu et al. 2000). The band at approximately 920 cm-1

is least

affected by type of exchangeable cation, but most affected by water content.

Beidellite and montmorillonite have similar spectra, but beidellite has characteristic Al-

O out-of-plane and Al-O-Si in-plane bands at 818 cm-1

and 770 cm-1

(Russell 1987).

The same Al-O and Al-O-Si vibrations are also characteristic for illites, but they locate

at 825 cm-1

and 750 cm-1

(Russell 1987).

Effect of purification process on FTIR patterns was studied by performing analyses for

ABM MX-80. Spectra were recorded from bulk material, purified clay (clay fraction

fractionated by washing with distilled water and gravity sedimentation) and from

purified and homoionized clay fraction.

Two different amounts of ground sample material (0.5 and 2 mg) were mixed with 200

mg of KBr powder in vibratory grinder and pressed to 13 mm diameter discs. The two

mixtures were used to distinguish between strong and weak mineral bands. Higher

sample concentrations are better in detecting OH-stretching bands at 3750-3400 cm-1

(Farmer 1974).

15

KBr discs were dried for 20 h at 150 oC in order to remove adsorbed water. Infrared

spectrum was recorded in triplicate using transmission mode in a range from 4000 to

200 cm-1

with Perkin Elmer Spectrum One FTIR spectrometer at the Department of

Geology, University of Helsinki. Resolution of scans was 4 cm-1

.

Although use of two mixing ratios (2 mg and 0.5 mg) is recommended e.g. by Farmer

(1974), the benefit for the mineral identification using different mixing ratios of the

same sample was found not to be significant.

Heating did not affect positioning of bands, nor to the intensity other than those of

water, which was consistent with observations of Carlson (2004), but not with Xu et al.

(2000). Although heating reduced hydroxyl bands created by adsorbed water, OH-

stretching and bending bands of water at approximately 3436 and 1630 cm-1

were still

present in all samples.

Due to the fact that also bulk material consisted mostly of clay materials, the FTIR

spectra of bulk material and clay fractions looked principally the same. However,

absorption bands of clay minerals were more intense in the spectra of clay fraction and

further, some bands and small curves arising from accessory carbonates and silica were

more intense in the spectra of the bulk samples.

Comparison of FTIR spectra of purified and homoionized clay fraction with spectra of

clay fraction just separated by gravitation revealed that intensity of the bands arising

from accessory minerals (carbonates, silica) was only slightly decreased in purified and

homoionized clay fraction. Small changes indicate that despite of the purification

process the clay is not entirely pure from accessory minerals. In the future, a smaller

grain-size fraction (e.g. <1 μm) could be used, because the <2μm fraction often contains

both cristobalite and quartz.

Conclusions: FTIR supports the mineralogical observations made by XRD. It is fast,

cost-effective, and doesn’t require much sample material. FTIR-analysis is useful in

detecting small amounts of accessory minerals and impurities that don’t necessarily

appear in XRD-analysis.

3.1.3 Optical polarizing microscopy

Optical microscopy can reveal the presence of optically isotropic silica glass or

amorphous opal silica, which can’t be identified with XRD. It helps in identifying

coarse-grained accessory minerals and in detecting presence of small amounts of

accessory minerals. Also, particle size distribution, possible mineral transformations,

morphological characteristics etc. can be examined.

Coarse fraction (> 2 µm), which was separated from clay material by gravity

sedimentation, was used for the examinations. Small amount of sample was gently

ground in agate mortar, placed on a glass slide and drop of glycerol (with refractive

index of 1,47) was added. Cover glass was placed on top. Sample mounts were

observed with plane- and cross-polarized light. Among others, colour, pleochroism,

16

birefringence, particle size, morphology, and isotropicity of mineral particles were

examined.

Conclusions: Although amorphous silica was not detected, polarizing light microscopy

proved to be very useful in supporting mineralogical observations made by XRD. For

example, the composition of plagioclase could be determined for some samples.

3.1.4 Overall conclusions on mineralogical methods for identification

X-ray diffraction is a fundamental method for identification of accessory minerals and

clay minerals present in bentonites and other smectite-rich clay materials. However,

XRD has its disadvantages e.g. when minerals are present only as traces their

identification is difficult. Thus, it is beneficial to use XRD in combination with other

methods, as here it was done with FTIR and polarizing microscopy. In addition to

mineral identification by FTIR, it can also reveal something about composition of

minerals, e.g. type of smectite present, which can’t be done with XRD. First glance of

material and first identifications of coarse grained accessory minerals as well as trace

minerals (e.g. as it was done for zircon) can be done with optical microscopy. Optical

microscopy also gave information on other properties, which were not seen with XRD

or FTIR e.g. crystal shape and possible alteration processes.

Still, some elements that were present in chemical analysis (section 3.4) were not

included in the list of identified minerals (see section 6.1.6). For example, sulphates

(e.g. gypsum) and sulphides (e.g. pyrite) were discovered to be present in chemical

analysis, but not identified in mineralogical analyses (with some exceptions).

To conclude, mineralogical characterization should be done using combination of XRD,

FTIR, polarizing microscopy and chemical analysis.

3.2 Exchangeable cations and CEC 3.2.1 Exchangeable cations

Exchangeable cations adsorbed in the interlayers of clay minerals can be extracted and

determined with various methods. Ammonium and barium ions are often used as index

cations in exchangeable cation extractions and CEC determinations (Bain and Smith

1987; Carlson 2004). Selectivity of exchangeable cation on Ba2+

or NH4+ ions differ

from each other and reactivity in variable solutes (water or alcohol) are also different.

Barium cations may react with sulphate ions that are liberated from dissolution of

gypsum or anhydrite, and precipitate as barite, which may give erroneous results. As

many of bentonites contain gypsum, BaCl2-extraction was not tested here. Two different

methods to extract exchangeable cations using ammonium as the index cation were

tested. NH4-acetate- extraction (pH 7) (Bain and Smith 1987; Chapman 1965) was

performed for bulk material and for clay fraction (Na-exchanged <2 m fraction) to

determine the effect of carbonate dissolution on the results and to test whether the

homo-ionization process had been successful. NH4Cl-method (Karnland et al. 2006)

was tested for bulk material because the ethanol solution used in the extraction

17

shouldn’t dissolve carbonates as excessively as the water solution used in NH4-acetate-

extraction.

NH4Cl (in 80 % ethanol)

1 g of ground bulk material was dispersed in approximately 20 mL of 0.5 M NH4Cl in

80% ethanol. Suspension was shaken for 30 minutes, centrifuged at 3600 rpm for 15

min, and supernatant decanted to a volumetric flask. The extraction was repeated two

times with 15 ml of extraction solution to reach the total volume of 50 mL. The extract

was filtered through 0.2 µm pore size filter, ethanol was evaporated and the extract

diluted back to 50 mL with deionized water. The amount of dissolved Ca, Fe, K, Na and

Mg was determined using ICP-AES at Labtium Oy.

The results were adjusted against adsorbed water content (determined gravimetrically at

105 oC), and reported as equivalent charges / kg of dry weight.

NH4-acetate (pH 7)

Buffered 1 M NH4-acetate solution (pH 7) was prepared by adjusting the pH of 1 M

NH4-acetate solution (aq) with acetic acid. 0.5 g of air-dry and ground bulk clay was

dispersed in 50 mL of NH4-acetate solution. The mixture was shaken on a rocking

platform for 2 h and centrifuged at 3600 rpm for 15 min. The supernatant was filtered

through 0.2 µm filter, diluted to 50 mL using volumetric flask and extracted cations

were analysed using ICP-AES at Labtium Oy.

The results were adjusted against adsorbed water content (determined gravimetrically at


3.2.2 Comparison of methods to determine exchangeable cations

The results of NH4Cl and NH4-acetate exchangeable cation extractions are shown in

Table 3-1. Saturation of exchangeable cation sites is listed as percentages in Table 3-2.

Table 3-1. Exchangeable cations (equivalent charges /kg dry weight (105 oC)).

NH4Cl (in 80 % ethanol) NH4-acetate (pH 7)

Ca2+ Fe2+ K+ Mg2+ Na+ Ca2+ Fe2+ K+ Mg2+ Na+

ABM MX-80 bulk 0,15 0,00 0,01 0,06 0,55 0,34 0,00 0,02 0,10 0,51

ABM MX-80 <2µm,

Na-exchanged

- - - - - 0,00 0,00 0,00 0,01 0,73

ABM Asha bulk 0,12 0,00 0,01 0,09 0,67 0,23 0,00 0,01 0,18 0,59

ABM Asha <2µm, Na-exchanged

- - - - - 0,01 0,00 0,00 0,02 0,76

ABM DepCaN bulk 0,26 0,00 0,01 0,22 0,20 0,96 0,00 0,02 0,30 0,20

ABM DepCaN <2µm,

Na-exchanged

- - - - - 0,01 0,00 0,01 0,03 0,81

ABM Friedland bulk 0,01 0,00 0,02 0,04 0,24 0,08 0,00 0,02 0,07 0,23

ABM Friedland <2µm,

Na-exchanged

- - - - - 0,00 0,00 0,02 0,01 0,31

18

Table 3-2. Saturation of exchangeable cation sites as percentages.

NH4Cl (in 80 % ethanol) NH4-acetate (pH 7)

Ca2+ Fe2+ K+ Mg2+ Na+ Ca2+ Fe2+ K+ Mg2+ Na+

ABM MX-80 bulk 20 0 2 7 71 35 0 2 10 53

ABM MX-80 <2µm,

Na-exchanged

- - - - - 0 0 0 2 98

ABM Asha bulk 13 0 1 10 76 23 0 1 18 59

ABM Asha <2µm, Na-exchanged

- - - - - 2 0 0 2 96

ABM DepCaN bulk 38 0 2 31 29 65 0 1 20 14

ABM DepCaN <2µm,

Na-exchanged

- - - - - 1 0 1 3 95

ABM Friedland bulk 4 0 6 13 76 20 0 5 17 58

ABM Friedland <2µm,

Na-exchanged

- - - - - 1 0 5 3 91

As Tables 3-1 and 3-2 show, cation exchange sites are not fully taken by Na even after

three dialysis cycles. The amount of exchangeable Fe varied in different samples, but

was still extremely low. The results of exchangeable cation extractions of NH4Cl and

NH4-acetate methods varied significantly for Ca and Mg, slightly for Na, but not for K.

NH4-acetate method seemed to dissolve Ca- and Mg-carbonates, and should not be used

for analysis of exchangeable cations from bulk materials. The results gained using

NH4Cl method were somewhat similar as results of Karnland et al. (2006) for same type

of materials.

3.2.3 CEC

Cation exchange capacity (CEC) is an important parameter as it gives indication of the

presence and content of clay minerals in the sample. CEC can be determined as a sum

of exchangeable cations (eg. NH4Cl- and NH4-acetate- methods in section 3.2.1) and by

directly displacing the exchangeable cations with some appropriate compound. Among

others, cobalt hexamine trichloride (Ciesielski & Sterckeman 1997), silver thiourea

(Chhabra et al. 1975), methylene blue (Kahr & Madsen 1995), ethylenediamine

complex of Cu(II) (Bergaya & Vayer 1997) and triethylenetetramine and

tetraethylenepentamine complexes of Cu(II) (Meier & Kahr 1999) have been used in

CEC measurements. Many CEC methods are susceptible to sample preparation steps

(size fraction, homoionization, purification, water content), solute, ionic strength,

solid/solution ratio, buffering agents added, pH, and the method of detection (analysis

of adsorbed or dissolved contents using spectroscopy, photometry, or titration). Type of

impurities and exchangeable cations present can have an effect on which method is

most suitable for particular sample. Herein, three commonly used methods; Cu(II)-

triethylenetetramine, ammonium acetate (pH 7) and NH4Cl-methods were compared. In

Cu(II)-triethylenetetramine-method (Ammann et al. 2005; Meier and Kahr 1999), the

adsorbed cation fraction is measured instead of analyzing the extracted cations and

thereby the errors caused by the dissolution of accessory minerals are avoided. Cu(II)-

triethylenetetramine-method was used to measure CEC of both clay fractions and bulk

materials.

Cu(II)-triethylenetetramine

Adsorption of Cu-organic complex onto cation exchange sites is measured in Cu(II)-

triethylenetetramine method (Meier & Kahr 1999; Ammann et al. 2005; Karnland et al.

19

2006). The method may be susceptible to extreme pH changes (between pH 4 and pH

11-12 the molar extinction coefficient of Cu(II)-triethylenetetramine is constant)

(Ammann et al. 2005), and it is not best suited for some materials, such as zeolites

(Meier & Kahr 1999).

0.015 M Cu(II)-triethylenetetramine solution was prepared by dissolving 2.309 g of

triethylenetetramine (purity grade ~95 %) and 2.394 g of anhydrous Cu(II) sulphate

(analytical grade) in deionized water to a volume of 1000 mL. Solution had an end pH

of ~8.4.

200 mg of air–dry and ground bulk sample or clay fraction was dispersed in 25 mL of

deionized water with assistance of ultrasonic bath (45 kHz, 120 W, 10 min). 10 mL of

0.015 M Cu(II)-triethylenetetramine solution was added and allowed to react on a

rocking platform for 15 minutes. The suspension was centrifuged at 3600 rpm for 15

minutes, and the supernatant collected. The water content of initial clay was determined

gravimetrically by drying at 105 oC for 24 h.

The Cu(II)-triethylenetetramine concentration in the supernatant was measured

spectrophotometrically. A calibration curve for the measurements was determined from

a series of dilute Cu(II)-triethylenetetramine solutions (0.015 M; 0.010 M; 0.005 M;

0.0015 M; 0.00015 M). Absorptions were measured at 620 nm (maxima at 577 nm)

using Thermo Scientific Genesys 10S UV-Vis spectrophotometer and deionized water

as a blank solution. 3 mL of the supernatant was pipetted into 10 mm optical glass

cuvette and the absorption of the solution was measured. Cu(II)-triethylenetetramine

concentration was determined by comparing the absorbtion of the supernatant solution

to the calibration curve. CEC was calculated from the difference of Cu(II)-

triethylenetetramine concentrations in initial Cu(II)-triethylenetetramine solution and

sample solution. Because the extinction is shown to be pH dependent at low (< 3.5) and

high pH (> 12) (Ammann et al. 2005), the pH of supernatant was measured after

extraction. All extractions and determinations were done in duplicate and results

reported as mean values. The standard deviations of results varied between 0.00002-

0.01eq/kg.

Results were adjusted against adsorbed water content (determined gravimetrically at


NH4Cl (in 80 % ethanol)

The NH4Cl extraction is described in section 3.2.1. The CEC was calculated as a sum of

exchangeable cations, adjusted against adsorbed water content (determined

gravimetrically at 105 oC), and reported as equivalent charges / kg of dry weight.

NH4-acetate (pH 7)

The NH4-acetate extraction is described in section 3.2.1. The CEC was calculated as a

sum of exchangeable cations, adjusted against adsorbed water content (determined

gravimetrically at 105 oC), and reported as equivalent charges / kg of dry weight.

20

3.2.4 Comparison of methods to determine CEC

CEC determined by Cu(II)-triethylenetetramine-, NH4Cl - and NH4-acetate (pH 7)-

methods were compared (Table 3-3).

Table 3-3. Comparison of CEC-values measured with different methods. Values are

given as charge equivalents/kg and they are adjusted to dry (105 oC) clay content.

Sample Cu(II)-trien NH4-acetate (pH 7) NH4Cl

CEC CEC CEC

ABM MX-80 bulk 0,84 0,96 0,77

ABM MX-80 <2µm, Na-exchanged 0,87 0,75 -

ABM Asha bulk 0,90 1,00 0,90

ABM Asha <2µm, Na-exchanged 0,91 0,79 -

ABM Deponit CaN bulk 0,82 1,48 0,70

ABM Deponit CaN <2µm, Na-exchanged 0,94 0,81 -

ABM Friedland bulk 0,26 0,40 0,31

ABM Friedland <2µm, Na-exchanged 0,41 0,34 -

CEC’s measured with Cu(II)-triethylenetetramine method were in overall a bit smaller

for bulk samples than for purified clay fractions, which is consistent with clay content

difference in bulk sample and purified fraction.

Cation exchange capacities measured by Cu(II)-triethylenetetramine method were

somewhat similar as the values of Karnland et al. (2006). pH measured after extraction

showed no major changes from the initial value of Cu(II)-triethylenetetramine solution

(pH 8.4).

Cation exchange capacities measured with the ammonium acetate method from bulk

samples produced higher values than other methods, which were most likely due to

dissolution of accessory carbonates during extraction.

3.3 Selective extractions

Identification and quantification of some mineral phases, e.g. poorly crystalline iron and

aluminium hydroxides and amorphous silica, is not possible with conventional

mineralogical methods, e.g. XRD in the presence of crystalline mineral phases. Poorly

crystalline mineral phases are small-sized and reactive, meaning that they can dissolve

and precipitate easily affecting the pore water composition, form cementing structures

and alter the physical properties of the material. Selective extraction methods can either

be used for quantification of easily soluble phases, or to purify the material before other

chemical or mineralogical determinations (Smith & Mitchell 1987). Herein, selective

extractions were used for estimation of the amount of poorly crystalline phases in

purified clay fraction in order to support the structural calculations. Although these

methods are very useful in determining the content of poorly crystalline phases in the

sample, they can also lead to a partial dissolution of clay minerals (Smith & Mitchell

1987; Farmer et al. 1977; Mehra & Jackson 1960).

3.3.1 Citrate-bicarbonate-dithionite extraction

Citrate-bicarbonate-dithionite (CBD) extraction (Mehra & Jackson 1960) was used for

quantification of poorly crystalline Fe oxides that can occur as thin layers on clay

21

particles. 0.5 g of dry (105 oC) purified clay was placed in a 50 mL polypropene (PP)

centrifuge tube together with 20 mL of 0.3 M Na-citrate solution and 2.5 mL of 1 M

NaHCO3. The tube was placed in a water bath and heated to 80 oC. Then, one third of

0.5 g of Na2S2O4 was added, the mixture stirred constantly for one minute and then

occasionally for 5 minutes. Addition of sodium dithionite and mixing was repeated

twice until there was no reddish colour visible in the clay. The mixture was allowed to

cool down. Then 5 mL of saturated NaCl solution and 5 mL of acetone was added to

induce flocculation. The mixture was centrifuged at 3600 rpm for 15 min, supernatant

collected, the residue washed with 40 mL of deionized water, recentrifuged, added to

the previous supernatant, filtered through 0,45 µm and diluted to 100 mL with deionized

water in a volumetric flask. Chemical composition (Fe, Al, Mg and Si) of the extract

was studied with ICP-AES at Labtium Oy. The concentrations of Al and Mg were

below their detection limits in most of the samples.

3.3.2 Sodium carbonate extraction

The amount of readily soluble Al and Si in clay materials was studied with 0.5 M

sodium carbonate extraction (SC) (Farmer et al. 1977). 0.100 g of purified clay was

placed in a centrifuge bottle (PP) together with 80 mL of 0.5 M Na2CO3 solution. The

suspension was shaken for 16 h, centrifuged and supernatant collected, filtered through

0,45 µm and diluted to 100 ml with deionized water in a volumetric flask. Chemical

composition (Fe, Al, Mg and Si) of the extract was studied with ICP-AES at Labtium

Oy. The concentrations of Fe and Mg were below their detection limits in most of the

samples.

Conclusions: CBD extraction dissolved minor amounts of Fe, but also some Si, which

may indicate that easily soluble silica was also dissolved or that poorly crystalline Fe

contained also silica. The amount of extracted silica in CBD and sodium carbonate

extraction solutions was of the same magnitude. Due to the fact that concentrations of

Al and Mg in CBD extraction and concentrations of Fe and Mg in SC extraction were

mostly below their detection limits, dissolution of clay minerals in tested weak

extractions was considered to be insignificant.

3.4 Chemical composition

Chemical composition of the material was defined for qualification and quantification

purposes.

3.4.1 Water, carbon and sulphur

Light, easily volatilized or non-fluorescent elements were determined separately using

gravimetric or combustion techniques. Such elements and substances included water,

carbon and sulphur. Furthermore, speciation of water, carbon and sulphur was analyzed.

Water

Adsorbed water, i.e. moisture content, was determined gravimetrically by drying

approximately 10-15 g of sample in a convection oven at 105 oC for 24 h. The loss on

22

ignition (LOI) at 1000 oC was measured at Labtium Oy. It was considered to present the

amount of crystalline water after subtraction of carbon and sulphate contents.

Carbon

The carbon content was determined with combustion (Leco) at Labtium Oy. Carbon

released below 550 oC was considered to be bound to organic matter, and carbon

released at 550-1000 oC to be inorganic (bound to carbonates).

Sulphur

Dissolvable sulphate content was determined by water extractions and determination of

dissolved sulphate from the extract by ion chromatography (IC) at Labtium Oy. Total

sulphur content was determined by combustion at 1200 oC (Leco) at Labtium Oy. The

amount of sulphur other than sulphate was considered to be bound in sulphides.

3.4.2 Fe2+/Fe3+ -ratio

Fe2+

/Fe3+

-ratio was determined from bulk materials and clay fractions (Table 3-4) at

Labtium Oy. Dried (105 oC) and ground material was decomposed with hydrofluoric

acid. The concentration of Fe2+

was determined titrimetrically with 0.05 N K2CrO7

(Saikkonen & Rautiainen 1993). The concentration of Fe3+

was determined by

subtracting ferrous iron concentration from total concentration of Fe, which was

determined using lithium metaborate fusion, nitric acid dissolution and ICP-AES (see

section 3.4.3).

In bulk materials, iron was mostly in its ferric form, except in samples from Friedland

area. In clay fractions, Fe3+

was even more predominant.

Table 3-4. The ratio of Fe2+

and Fe3+

in bulk materials and clay fractions.

Wet chemistry

Bulk <2µm, Na-

exchanged

Wyoming, USA

ABM MX80 0,115 0,063

WyMX80 0,125 0,067

Volclay 0,160 0,086

Milos, Greece

ABM DepCaN 0,047 0,024

AC200 0,093 0,021

Kutch, India

ABM Asha 0,006 0,007

Basic-Starbentonite 0,048 0,002

HLM-Starbentonite 0,081 0,001

Ca-Starbentonite 0,001 0,001

Friedland, Germany

ABM Friedland 0,652 0,150

SH Friedland 0,472 0,148

23

3.4.3 Total chemical composition

The bulk materials and clay fractions were digested using lithium metaborate fusion and

nitric acid dissolution. Concentrations of dissolved elements were determined using

ICP-AES at Labtium Oy. The results were normalized to 100 % after taking into

account LOI, S and C analyses.

Conclusions: Some elements that were discovered to be present in chemical analysis

were not present in minerals identified by mineralogical methods. Hence, chemical

analyses of bulk materials were used to support mineralogical observations and to verify

the mineralogical composition determined by mineralogical methods.

Chemical analyses of clay fractions were used to calculate structural composition of

smectite, which were used further in verifying CEC determinations. Determination of

chemical composition of clay fraction proved to be important also for more reliable

determination of illite content in smectite.

Determination of Fe speciation proved to be important for bulk materials, as iron was

present in some samples partly in ferrous form. In clay fractions, iron was mostly in its

ferric form.

3.5 Mineralogical composition

Only after identifying the mineral phases present, mineralogical composition can be

defined.

3.5.1 Quantification of single mineral phases

Illite content in illite/smectite interlayers

According to Moore & Reynolds (1989), positions of the composite peaks of (001) illite

/ (002) smectite at approximately 9o

2θ and (002) illite / (003) smectite at approximately

16-17o

2θ of glycolated oriented mounts can be used to determine illite content.

Estimations done based on this peak angle difference (oΔ 2θ) are not as susceptible to

e.g. specimen alignment errors than estimations done by using only one of these peaks.

Peak angle difference was used to determine illite content in illite/smectite interlayers of

Wyoming, Kutch and Milos samples. For Friedland clays only 002/003 peak position

was used due to peak interferences at 001/002.

The content of illite was also calculated from total chemical composition of clay

fraction, assuming that all K+ was bound to illite, since no feldspars or other K

+–bearing

minerals were found in XRD analysis of clay fractions. Illite, which had an ideal

structure (a layer charge of 1.5 per O20(OH)4 structural unit) (Brindley & Brown 1980)

and molecular formula K1.5(Si7Al)(Al3.5Mg0.5)O20(OH)4 was used in calculations.

The illite content calculated using the Moore & Reynolds (1989) method gave much

more unreliable illite contents than the chemical composition based illite content (see

section 6.4.1).

24

Poorly crystalline Fe, Al and Si phases

The amount of poorly crystalline Fe, Al, and Si phases in purified clay fractions was

defined based on CBD- and Na2CO3 extractions (sections 3.3.1 and 3.3.2).

Carbonates, sulphates and sulphides

In studied materials, the carbonate was considered to be bound to calcite (CaCO3), the

sulphate to gypsum (CaSO4) and the sulphur to pyrite (FeS2). It should be noted, that

part of the carbonates, can be bound also to dolomite (materials from Milos) or siderite

(materials from Friedland) (see section 6.3.2).

3.5.2 Calculation of structural formula for smectite

Before calculation of structural formula for smectite, the chemical composition of

purified clay fraction was adjusted according to Karnland et al. (2006) by subtracting

still remaining mineral impurities from clay fraction (illite, poorly crystalline Fe, Al,

and Si phases, calcite, gypsum and pyrite), in order to get chemical composition of pure

smectite phase. Molecular formula K1.5(Si7Al)(Al3.5Mg0.5)O20(OH)4 was used for illite.

For samples containing kaolin minerals, also subtraction of kaolinite with ideal formula

of Al4Si4O10(OH)8 was done after defining the kaolin mineral content in Rietveld

analysis. The Al, C, Ca, Fe, K, Mg, S and Si contents were adjusted accordingly.

Calculations were done according to Newman (1987) assuming that structural units

contained 24 anions (O20(OH)4), but that unit cell and density were unknown.

3.5.3 Rietveld analysis

Carlson (2004) quantified mineralogical composition of clay materials using mineral

intensity factors (MIF’s), which are based on intensities of peaks in XRD analysis. This

method is susceptible to e.g. compositional changes of mineral phases and sample

orientation, both which are always present in clays. The accuracy of the MIF method is

also rough, approximately 5 %. More modern method to determine mineralogical

composition is Rietveld refinement, which is based on full XRD pattern fit. Rietveld

approach allows occurrence of changes in structural composition and partial orientation

of mineral phases, which makes it more suitable for analysis of mineralogical

composition of clays than traditional peak intensity based methods. The accuracy of

Rietveld is also better. Karnland et al. (2006) reported an estimated accuracy of ± 5 %

for swelling minerals and ± 1 % for several other minerals depending on mineral

composition and quality of diffractograms. For Rietveld, various programs with variable

capabilities and variable graphical user interfaces have been developed.

Herein, mineralogical composition was determined from bulk XRD patterns (Appendix

2) using a full-profile Rietveld refinement by Siroquant software. First, low angle

intensity aberrations produced by auto-slit geometry were corrected using a program

inbuilt calibration function. Then, background was subtracted. Refinement was done in

several subsequent stages until no major improvement in pattern fit was achieved.

25

Parameters like instrument zero, phase scales, half-widths, unit cell dimensions, and

preferred orientation were refined.

In order to find the precision in analysis, three or sometimes five separate XRD-patterns

(measured from separate samples) were analysed for each studied material with similar

refinement strategies. The precision turned out to be fairly good. For example, the

standard deviations of quantified smectite contents varied between 0,9 % and 5,8 %.

Results of all quantifications are presented in appendix 3.

Minerals that were identified with XRD, FTIR or polarizing microscopy were, in some

cases, present in such a small amounts that they could not be included in quantification.

Further, some minerals that were not identified at first, were added during Rietveld

analysis, to get a better fit for the x-ray pattern.

In order to check the accuracy of Rietveld-analyses, chemical composition of each

material was calculated from the determined mineralogical compositions. The same

method was used by Karnland et al. (2006). In these calculations an ideal chemical

formula was used for each mineral identified with Rietveld analysis. Only for

montmorillonite, the calculated structural formula was used (section 3.5.2). The results

of these calculations are presented in Appendix 3. The chemical compositions

calculated from mineralogical compositions were compared with the measured chemical

compositions and it showed that Rietveld-analysis leads to overestimation of some

minerals and underestimation of some other minerals (see Appendix 3). For example,

minerals that have similar XRD-patterns, such as montmorillonite and illite, lead to

overestimation of illite content in Rietveld analysis. Pyrite and gypsum contents were

often overestimated as well. Such conflicts could be improved by more detailed

mineralogical quantification analysis procedures (i.e. improved knowledge of actual

minerals present, improved Rietveld procedures and more accurate XRD

measurements), and by determining mineralogical composition with combinations of

XRD-based quantification and chemical analyses.

Conclusions: Rietveld-analysis showed to be fast and effective method to quantify

minerals in reference clays. However, it should always be supplemented with

determination of chemical composition to verify the results.

27

4 CONCLUSIONS

Smectite-rich clay materials can be characterized quite well with the mineralogical and

chemical methods selected and tested here, and the use of these methods is continued in

the future studies of bentonite and smectite-rich clay materials. FTIR and optical

microscopy supplemented the interpretation made by XRD, and Rietveld-analysis is a

fast and effective method to quantify minerals in clays. However, Rietveld-analysis

should always be supplemented with determination of chemical composition to verify

the results. Different methods in quantifying illite content gave inconsistent results. To

achieve consistency, illite content should be calculated using combination of Rietveld-

method and chemical analyses, as done by Karnland et al. (2006). More effort should

also be addressed to improving and determining the accuracy of Rietveld

quantifications.

The remaining CEC after Li-treatment and heating in the Greene-Kelly test can’t

directly be correlated to tetrahedrally charged smectite content, since loss of swelling

ability was also complete in some samples that showed only partial loss of CEC. FTIR-

analysis and structural calculations support the observations on whether tetrahedrally

charged smectites are present or not. The Cu(II)-triethylenetetramine method worked

well for analysis of CEC and NH4Cl-extraction in 80 % alcohol for original

exchangeable cations. Determination of Fe speciation proved to be important for bulk

materials as both ferrous and ferric iron states were observed. In clay fractions, iron was

mostly in its ferric form.

Quality of the structural formula calculations for smectite could be improved by

performing chemical analysis and selective extractions for the <1 μm size fraction of the

material, because the <2μm fraction often contains both cristobalite and quartz. The

overall effect of selective extractions (CBD and SC) on the results of structural

calculations was not large, but they are still recommended to be used in order to

improve the accuracy of the calculations. In addition, CBD-extraction gives valuable

data of reactive iron phases, which may cause cementation. The chemical composition

of purified and Na-exchanged clay fractions showed that they still contained small

amounts of Ca and K, as well as carbonates and organic matter. In the future, it could be

taken into account in the calculations, that part of the carbonates can be bound to

dolomite or siderite instead of calcite. Alternatively, carbonates could be removed with

a mild acid pre-treatment. Organic carbon could be removed with some appropriate pre-

treatment as well. Determination of layer charge with the alkylammonium method

rather than just calculation on the basis of chemical composition would further support

the validity of the purification process. Further, the results of structural calculations

could be compared to structural calculation results that are based on chemical

composition from single clay particles analyzed by TEM-EDS.

29

PART B: MINERALOGICAL AND CHEMICAL CHARACTERIZATION OF CLAY MATERIALS

5 MATERIALS Studied reference materials included bentonites and smectite-rich clay materials that are

used in various research projects on nuclear waste disposal. Photos of studied materials

are presented in Appendix 1.

5.1 Wyoming, USA

Bentonites in Wyoming, USA, have been formed in situ as a result of alteration of felsic

volcanic ash in shallow marine environments. Bentonite products from Wyoming, USA

are typically sodium-rich (Slaughter & Earley 1965, Elzea & Murray 1989, Elzea &

Murray 1990, Smellie 2001).

Three different lots of Wyoming-type Na-bentonites were studied:

- Reference MX-80, used in the ABM experiment of SKB. Hereafter, ABM MX-80.

- Reference MX-80, used in a long term (8y) Fe-bentonite interaction test of VTT.

Hereafter, Wyoming MX-80.

- Reference MX-80 produced by Volclay, used in various Posiva projects. Hereafter

Volclay.

5.2 Milos, Greece

Bentonites from Milos, Greece have been formed after hydrothermal alteration of

volcanic rocks of intermediate composition. The dominant montmorillonite interlayer

cation in Milos bentonite is calsium (Christidis et al. 1995, Decher et al. 1996).

Two different lots of bentonites from Milos were studied:

- Reference Deponit CaN, used in the ABM experiment of SKB. Hereafter, ABM

DepCaN.

- Reference AC200, used in self-healing tests of backfill. Hereafter, AC200.

5.3 Kutch, Gujarat, India

Bentonites in Kutch district, India, are typically Na-rich and they are strongly colored

with iron oxides. They have formed mostly through alteration of volcanic ash in saline

water and associated with basaltic rocks (Shah 1997).

Four different lots of bentonites from Kutch region were studied:

- Reference Asha 505, used in the ABM experiment of SKB. Hereafter ABM Asha.

- Reference Basic Starbentonite distributed by Dasico. Hereafter, Basic-Starbentonite.

- Reference Calcium Starbentonite distributed by Dasico. Hereafter, Ca-Starbentonite.

- Reference Starbentonite HLM distributed by Dasico. Hereafter, HLM-Starbentonite.

30

5.4 Friedland, Neubrandenburg, Germany

Friedland clays were formed in shallow marine environments as a result of

sedimentation of volcanic tephra and eroded detrital material, and underwent early

diagenesis. Due to complex formation history, Friedland clays contain among others,

mixed-layered illite and smectite, as well as kaolin (Henning & Kasbohm 1998; Pusch

2001).

Two different lots of bentonites from Friedland were studied:

- Reference Friedland clay, used in ABM experiment of SKB. Hereafter, ABM

Friedland.

- Reference Friedland clay, used in self-healing tests of backfill. Hereafter, SH

Friedland.

31

6 RESULTS

6.1 Mineralogy 6.1.1 XRD

Bulk material

XRD-patterns of bulk samples are presented in Figure 6-1 and in Appendix 2, which

also includes a list of identified minerals.

The position of d(060) line was for Wyoming- and Milos-bentonites at 1,497 Å (Table

6-1) indicating the presence of dioctahedral smectite, such as montmorillonite. The

d(060)-line for Kutch-bentonites was broad or splitted varying from 1,490 to 1,503,

suggesting the presence of kaolin minerals in addition to montmorillonite (Moore &

Reynolds 1989). For Friedland clays the position of d(060)-lines were at 1,502 and at

1,542 Å. Possible presence of trioctahedral clay minerals in Friedland clays can’t be

discounted, due to strong reflection of quartz at the same d-value (1.542 Å).

Clay fraction

All samples from Wyoming, Milos and Kutch showed a strong d(001) reflection

approximately at 14 Å, which shifted fully to 16-17 Å after EG solvation, indicating the

presence of smectite. The d(001) reflection of Friedland clay samples shifted only partly

indicating the presence of mixed-layer smectite-illite. After heating at 550 oC d(001)

line in all samples collapsed approximately to 9,5 Å (Figure 6-1, Table 6-1).

All studied Kutch and Friedland clay samples showed a peak at 7 Å, which disappeared

after heating in 550 oC indicating the presence of kaolin minerals (Figure 6-1) (Moore &

Reynolds 1989). The intensity of the 7 Å kaolin peak varied in Kutch samples, being

strongest in ABM Asha and weakest in Ca-Starbentonite.

Clay fractions of all Wyoming-bentonites showed indications of presence of quartz and

cristobalite impurities. Quartz was found also in SH Friedland clay fraction. In order to

avoid these impurities in the future, a smaller size fraction (e. g. <1µm fraction) could

be used instead of the <2µm fraction.

35

Figure 6-1. X-ray diffraction patterns of randomly oriented bulk samples, oriented clay

fraction, ethylene glycol (EG) solvated and heated (550 oC) mounts from bottom to top.

36

Table 6-1. Position of important lines (in Å) used in identification of illite/smectite (I/S),

and the amount of illite (I) interlayers in I/S calculated using the method of Moore and

Reynolds (1989). The illite contents for Friedland clays are very uncertain, because the

Moore-Reynolds index is difficult to evaluate for Friedland clays.

Fraction Bulk Clay

Treatment Oriented EG 550oC Identified clay

minerals and

impurities Line/

interpretation

d(060) Dioct./

Trioct.

d(001) d(001) d(002) d(003) I % in

I/S

d(001)

Wyoming, USA

ABM MX80 1,497 Dioct. 14,66 16,49 8,41 5,60 0 9,48 I/S, Q, Cr

WyMX80 1,497 Dioct. 14,38 16,68 8,44 5,61 1 9,54 I/S, Q, Cr

Volclay 1,497 Dioct. 13,02 15,38 8,22 5,46 9 9,08 I/S, Q, Cr

Milos, Greece

ABM DepCaN 1,496 Dioct. 14,72 16,58 8,44 5,59 4 9,44 I/S

AC200 1,498 Dioct. 14,16 16,17 8,37 5,53 8 9,58 I/S

Kutch, India

ABM Asha

1,494;

1,503

Dioct. 14,75 16,54 8,36 5,57 2 9,53 I/S, K

Basic-Starbent.

1,490,

1,500

Dioct. 14,31 16,74 8,49 5,56 12 9,52 I/S, K, Cr

HLM-Starbent. 1,498 Dioct. 14,33 16,48 8,42 5,58 8 9,46 I/S, K

Ca-Starbent. 1,503 Dioct. 14,32 16,43 8,42 5,56 7 9,63 I/S, K

Friedland,

Germany

ABM Friedland

1,502;

1,542

Dioct.(+

Trioct.?)

13,99 16,51 9,84 5,51 35 9,66 I/S, K

SH Friedland

1,502;

1,542

Dioct.(+

Trioct.?)

13,58 16,34 9,79 5,20 75 9,87 I/S, K, Q

Abbreviations: I/S=illite/smectite, K=kaolin, Q= quartz; Cr=cristobalite

6.1.2 Greene-Kelly

All clay samples showed the collapse of 16-17 Å montmorillonite peak to

approximately 9.5 Å after Li-saturation, heating at 250 oC and glycerol solvation, except

samples from Kutch region, indicating that they contained at least small amounts of

tetrahedrally charged smectite, presumably beidellite (Figure 6-2) (Moore & Reynolds

1989). Na-exchanged clay swelled after heating and glycerol treatment normally. The 7

Å peak in Kutch and Friedland clay samples is caused by kaolin minerals.

Li fixation in montmorillonite caused ~85 % decrease in CEC for Wyoming bentonites,

~75 % decrease in CEC for Milos bentonites, ~65-50 % decrease in CEC for Kutch

bentonites and ~52 % decrease in CEC for Friedland clays. It is worth to notice that the

magnitude of decrease in CEC was not consistent with the XRD observations. Friedland

clay samples showed Li fixation by montmorillonite in XRD, but less decrease in CEC

than other montmorillonite samples. The loss in CEC was similar for Wyoming, Milos,

and Friedland clay samples as in Karnland et al. (2006). For most Kutch region samples,

the loss in CEC was couple of tens of percentages lower than in the samples of

Karnland et al. (2006). However, the chemical and mineralogical composition of studied

materials might have varied, which was indicated, for example, by variations in kaolin

content of samples in this study and in the study of Karnland et al. (2006). Na-

exchanged clays did not show any decrease in CEC due to heating at 250 oC.

37

Figure 6-2 and Table 6-2. XRD-patterns of Li-exchanged, heated (250 oC) and

glycerol-treated oriented mounts (on left) and loss of CEC after treatment with Li and

heating at 250 oC (on right).

CEC after

(eq/kg)

CEC loss

(%)

Li-ABM MX80 0,14 84

Li-Volclay 0,13 86

Li-WyMX80 0,14 85

Li-ABM Asha 0,43 52

Li-Basic-Starbentonite 0,41 56

Li-HLM-Starbentonite 0,50 49

Li-Ca-Starbentonite 0,35 66

Li-ABM DepCaN 0,22 77

Li-AC200 0,28 73

Li-ABM Friedland 0,21 49

Li-SH Friedland 0,22 54

6.1.3 FTIR

FTIR scan’s of all samples showed patterns typical for clay minerals.

Wyoming- and Milos-bentonites showed strong absorption bands approximately at 3630

cm-1

, and a small curve at 3700 cm-1

suggesting that they contained Al-rich smectites,

mostly montmorillonite (Farmer & Russell 1967; Farmer 1974). Distinct OH-stretching

bands at ~3698 cm-1

and ~3621 cm-1

, and a Si-O-deformation band at ~697 cm-1

were

indicative of kaolin minerals presence in most of the Kutch and both Friedland clay

samples, which masked the possible absorption bands of smectite at 3600 cm-1

region

(Figure 6-3, Table 6-3) (Farmer 1974).

All samples showed small CO3-stretching at approximately 1430 cm-1

indicating the

presence of carbonate impurities (Figure 6-3) (Russell 1987).

Si-O vibration near 1100 cm-1

was present in almost all sample spectra (Farmer &

Russell 1967; Farmer 1974). In Kutch and Friedland clay samples its intensity was

proportional to the intensity of kaolin mineral bands. Si-O stretching at 1033-1048 cm-1

present in all samples was assigned to tetrahedral silica located in clay minerals or

quartz (Figure 6-3, Table 6-3) (Farmer & Russell 1967).

AlAlOH bending band assigned to smectite and/or kaolin minerals at 919-913 cm-1

was

present in all sample spectra (Figure 6-3, Table 6-3) (Farmer, 1974). AlFe3+

OH band at

890-870 cm-1

was present almost in all spectra (Figure 6-3, Table 6-3). The position of

this band is decreasing with increasing Fe content, and appeared at slightly lower

wavenumber in the spectra of Kutch and Friedland clay samples than in spectra of

Wyoming and Milos samples (Table 6-3). Bending due to AlMgOH at 860-840 cm-1

38

was present in all spectra of Wyoming and Milos (Figure 6-3, Table 6-3). In some

Kutch and Friedland clay samples the position of AlMgOH bending was at lower

wavenumber, and could also arise from Al-O vibrations of illite since 750 cm-1

Al-O-Si

band was also present (Farmer 1974; Russell 1987). The 750 cm-1

band could also arise

from perpendicular Si-O vibration of kaolin minerals (Madejová & Komadel 2001). The

Al-O and Al-O-Si vibrations of beidellite at 818 cm-1

and 770 cm-1

or the Fe3+

Fe3+

OH

bands of nontronite at 850 and 818-815 cm-1

were not seen in any of the sample spectra

(Figure 6-3).

In FTIR patterns of Wyoming-bentonites and Friedland clays distinct Si-O stretching

band at ~800 cm-1

resulted from quartz, opal, cristobalite or other polymorphs of SiO2

(Madejová & Komadel 2001). Friedland clays showed also Si-O stretching band at 780

cm-1

indicating the presence of quartz (Figure 6-3, Table 6-3) (Russell 1987).

39

Figure 6-3. FTIR-patterns of clay fractions measured from pressed pellets (2 mg clay to

200 mg KBr) after heating in 150 oC overnight. Materials from Wyoming are marked

with blue, from Milos in green, from Kutch in red, and from Friedland in black colour.

Some peaks (Table 6-3) are indicated with arrows to the spectra (water (H2O),

carbonate (CO3), smectite (S), kaolin mineral (K), illite (I), quartz (Q), polymorphs of

SiO2 (SiO) and Si-O stretching of clays (Si-O-Si).

40

Table

6-3

. T

he

posi

tion o

f F

TIR

abso

rpti

on b

ands

of

studie

d b

ento

nit

es a

nd c

lay

mate

rials

, and b

and a

ssig

nm

ents

(S=

smec

tite

, K

=ka

oli

n

min

erals

, I=

illi

te, Q

=qu

art

z).

Vib

rati

on

OH-stretching

bands

H2O-stretching

H2O-bending

Si-O stretching

OH-bending

OH-bending

band of smectite

or Al-O band of

illite

Si-O stretching

Si-O bending

Sa

mp

le

OH stretching of inner

surface hydroxyl groups

(K)

AlMgOH (S)

AlAlOH (K, S)

AlFe3+

OH (S)

H2O

H2O

Si-O-Si

Tetrahedral Si-O (S,K,Q)

AlAlOH (S,K)

AlFeOH (S)

AlMgOH (S)

AlMgOH (S)

Al-O (I)

Q, free Si-O

Si-O (Q)

Si-O (K),

Al-O-Si (I) Trioktah. Si-O?

Si-O (S, K)

Al-O, Si-O

Al-O-Si

Si-O-Si

Si-O

AB

M M

X-8

0

36

27

34

36

16

33

1

04

7

91

9

88

0

84

8

7

99

6

96

62

4

52

5

46

8

Vo

lcla

y

36

34

34

55

16

24

11

16

10

40

91

6

88

2

84

8

7

99

72

5

69

2

62

3

52

5

46

8

WyM

X-8

0

36

36

34

41

16

24

11

19

10

47

91

8

88

2

84

8

7

99

72

5

69

5

62

2

52

5

46

8

AB

M D

epC

aN

36

36

34

47

16

30

1

04

0

91

7

88

0

84

1

7

95

7

00

62

5

52

5

46

8 4

23

AC

20

0

36

35

34

37

16

31

1

03

5

91

7

87

8

84

3

7

94

6

99

62

3

52

4

46

9 4

23

AB

M A

sha

36

97

3

62

1 3

59

1

34

36

16

30

11

07

10

35

91

4

87

7

79

4

7

52

6

96

62

5

53

2

46

9 4

30

Bas

ic-S

tarb

. 3

69

8

3

62

2

34

46

16

29

11

12

10

35

91

4

87

5

8

34

79

4

7

52

6

92

5

26

46

9 4

23

HL

M-S

tarb

.

36

88

36

22

34

60

16

30

11

12

10

35

91

9

87

8

79

7

6

90

5

24

46

9 4

23

Ca-

Sta

rb.

36

23

34

32

16

29

11

09

10

38

91

7

87

8

8

34

79

7

6

85

62

0

52

2

46

6

AB

M F

ried

. 3

69

9

3

62

1

34

23

16

27

11

09

10

32

91

3

83

3

80

0

78

0

75

5

6

98

5

36

47

1 4

28

SH

Fri

ed.

36

99

3

62

1

34

32

16

26

11

14

10

34

91

3

87

5

8

31

80

0

77

8

75

5

6

97

5

33

47

1 4

27

40

41

6.1.4 Optical polarizing microscopy

Particle size of coarse fraction of Wyoming bentonite was largest and consisted mostly

of quartz and plagioclase (Figure 6-4). The composition of plagioclase was determined

based on extinction angle, and was close to that of albite. Other minerals and mineral

groups identified were carbonates, biotite, hematite, and possibly apatite and zircon. No

opal or glass was detected.

Coarse fractions of Milos samples contained mostly carbonates (Figure 6-4), but also

some quartz, biotite, hematite and opaque minerals. No opal or glass was detected.

The particle size and composition of coarse fraction of Kutch samples varied largely.

Particle size of ABM Asha was clearly smaller than that of Ca-Starbentonite or

Wyoming or Milos samples. Kutch samples contained lot of brownish, red (hematite)

and yellowish (goethite) opaque iron oxide minerals (Figure 6-4). In Ca-Starbentonite

and Basic Starbentonite quartz was observed. In Ca-Starbentonite and in HLM

Starbentonite traces of chlorite was present. No opal or glass was detected.

Coarse fraction of Friedland clays contained quartz and opaque minerals (Figure 6-4).

Yellow-brownish opaque high relief crystals had often a black opaque center. Traces of

other clay minerals (mica/illite, biotite and chlorite) were present. No opal or glass was

detected.

ABM MX-80

Volclay

42

Wyoming MX-80

ABM DepCaN

AC200

ABM Asha

43

Basic-Starbentonite

Ca-Starbentonite

HLM-Starbentonite

ABM Friedland

44

SH Friedland

Figure 6-4. Optical polarizing microscopy pictures of coarse fraction in plane

polarized (right) and crossed polarized light (left).

6.1.5 Other observations

Magnetism

Magnetic minerals in clay materials from Wyoming and Milos stuck tightly to the

stirrer and were black in colour. The amount of magnetic minerals in clays from Kutch

area were higher than in bentonites from Wyoming, but the magnetism of particles

seemed to be weaker (particles didn’t attach so tightly to the stirrer as in samples from

Wyoming and Milos), and the particles were dark brown in colour. Based on their

colour and magnetism, the magnetic particles in Wyoming and Milos samples were

thought to be magnetite (Fe3O4) and in Kutch samples maghemite (γ-Fe2O3). The

amount of magnetic minerals in Friedland clays was very small.

SEM-EDS

Wyoming MX-80 was studied additionally with scanning electron microscopy (SEM)

and energy dispersive spectroscopy (EDS). It contained accessory mineral grains that

were pyrite (FeS2) and apatite based on EDS analysis.

6.1.6 Summary on identification of minerals

The summary on minerals that were identified based on XRD, FTIR, polarizing

microscopy and other techniques is presented in Table 6-4.

Some elements that were present in chemical analysis were not included in the list of

identified minerals. For example, sulphates (e.g. gypsum) and sulphides (e.g. pyrite)

were discovered to be present in chemical analysis, but not identified in mineralogical

analyses (with some exceptions). The reason for that was that they were present only in

traces, their crystallinity (crystal size, crystal order) was poor, or that the techniques

used were not best suited for their detection. The list of minor or trace minerals can

therefore only be considered approximate.

45

Table 6-4. Full list of identified minerals and the techniques used.

Minerals Wyoming, USA Milos, Greece Kutch, India Friedland, Germany

ABM MX80

WyMX80 Volclay ABM

DepCaNAC200

ABM Asha

Basic- Star.

HLM-Star.

Ca-Star.

ABM Friedland

SH Friedland

Montmorillonite x x x x x x x x x x x Other smectite x x x x x Illite/dioct.-mica x x x x x x x m,x Kaolinite x, f x, f x, f x x, f x, fBiotite m m m m Chlorite m m m Calcite m m m,x x m,x x x x x Dolomite x Quartz m,x m,x m,x x m,x m,x x m,x m, x m,x Plagioclase m,x m,x m,x x x x Siderite x Cristobalite x x x x Gypsum x x x x Goethite m, o m m Hematite m m m,x m, o m,x m,x m,x Maghemite o x, o x, o x, o Magnetite x,o x,o x, o o x x x o Anatase x x x x Pyrite o x x Zircon m m m Apatite m, o m

Notices: Identification in x=XRD, f=FTIR, m=optical polarizing microscopy, o=other 6.2 Exchangeable cations and CEC Based on analyses of exchangeable cations, all Wyoming-bentonites, AC-200 from Milos and ABM-Asha and HLM Starbentonite from Kutch were Na-bentonites (Table 6-5). However, they still contained some amount of Ca and Mg in exchangeable sites. Exchangeable cations in samples ABM DepCaN, Basic Starbentonite and Ca-Starbentonite were more clearly mixtures of Na, Ca and Mg. Friedland clays were mostly in Na-form and their CEC was only one third or fourth of that of the bentonites. Table 6-5. Exchangeable cations and CEC of bulk materials measured with NH4Cl- and Cu(II)-triethylenetetramine-methods. Exchangeable cations CEC Saturation of exchangeable sites Exchangeable cations (in dry (105oC) weight) Cu-trien Ca K Mg Na Ca K Mg Na Sum % % % % eq/kg eq/kg eq/kg eq/kg eq/kg eq/kg Wyoming, USA ABM MX80 27 2 9 62 0,25 0,02 0,08 0,57 0,92 0,84 WyMX80 23 2 7 69 0,21 0,02 0,06 0,63 0,92 0,85 Volclay 21 2 8 69 0,18 0,02 0,07 0,62 0,90 0,89 Volclay2 22 2 8 67 0,20 0,02 0,07 0,59 0,88 0,89 Milos, Greece ABM DepCaN 51 2 25 23 0,47 0,02 0,23 0,21 0,92 0,82 AC200 6 2 8 84 0,06 0,02 0,08 0,92 1,09 0,95 Kutch, India ABM Asha 22 0 16 62 0,20 0,00 0,14 0,56 0,90 0,90 Basic-Starbentonite 30 1 19 51 0,29 0,01 0,18 0,49 0,97 0,92 HLM-Starbentonite 13 1 11 76 0,16 0,01 0,13 0,93 1,23 1,00 Ca-Starbentonite 29 1 16 55 0,32 0,01 0,18 0,61 1,12 1,00 Friedland, Germany ABM Friedland 4 6 13 76 0,01 0,02 0,04 0,24 0,31 0,26 SH Friedland 2 5 9 83 0,01 0,03 0,04 0,38 0,46 0,31

46

The sum of cations in NH4Cl-extraction was in general slightly higher than the CEC’s

measured with Cu(II)-triethylenetetramine-method, indicating that a small amount of

soluble accessory minerals may have dissolved during the extraction.

6.3 Chemical composition 6.3.1 Poorly crystalline Fe, Al and Si

The content of citrate-bicarbonate-dithionite (CBD) extractable Fe in clay fraction was

highest for Kutch samples, up to 1.5 wt.%, corresponding to 15 wt.% of all Fe in clay

fraction (Table 6-6). The content of CBD extractable Fe in other clay materials was

lower, 0,1-0,5 wt.%. The content of CBD extractable Si was 0,4-0,6 wt.%, and could

originate from dissolved iron oxides, other poorly crystalline Si phases, but also from

partial dissolution of montmorillonite. The concentrations of Al and Mg in CBD

extractions were below their detection limits (< 10 mg/L), which suggests that

dissolution of montmorillonite was insignificant.

The content of sodium carbonate (SC) extractable Si in clay fraction was highest for

Wyoming bentonites, up to 1,2 wt.%. SC extractable Si in all samples was

approximately 1% of total contents (Table 6-6). SC extractable Al was lower, 0,1-0,3

wt.%. The concentrations of Fe and Mg in SC extractions were below their detection

limits (< 10 mg/L).

Table 6-6. The contents of poorly crystalline Fe, Al and Si phases in clay fraction.

Free iron oxides Free silica and aluminium oxides

Fe2O3 SiO2 SiO2 Al2O3

wt.% CBD/total wt.% CBD/total wt.% SC/total wt.% SC/total

Wyoming, USA

ABM MX80 0,16 0,045 0,50 0,008 0,87 0,013 0,11 0,006

Volclay 0,08 0,021 0,36 0,006 0,93 0,016 0,11 0,005

Volclay2 0,08 0,020 0,36 0,006 0,88 0,015 0,10 0,004

WyMX80 0,08 0,019 0,37 0,006 1,16 0,019 0,14 0,006

Milos, Greece

ABM DepCaN 0,39 0,085 0,64 0,010 0,58 0,009 0,25 0,013

AC200 0,21 0,036 0,42 0,007 0,83 0,015 0,29 0,013

Kutch, India

ABM Asha 1,47 0,149 0,57 0,010 0,46 0,008 0,27 0,012

Basic-Starbentonite 0,83 0,070 0,56 0,011 0,62 0,012 0,25 0,012

Ca-Starbentonite 0,55 0,044 0,61 0,011 0,61 0,011 0,18 0,010

HLM-Starbentonite 1,07 0,073 0,68 0,013 0,75 0,014 0,17 0,009

Friedland, Germany

ABM Friedland 0,50 0,084 0,39 0,007 0,38 0,007 0,17 0,007

SH Friedland 0,26 0,035 0,33 0,006 0,58 0,011 0,09 0,004

6.3.2 Total chemical composition

Total chemical composition of bulk materials are presented in Table 6-7.

Kutch bentonites contained high amount of Fe, up to 10 wt.%. Bulk materials from

Wyoming, Milos and Kutch contained mostly ferric iron, but Friedland clays up to

approximately 36 % of ferrous iron. The probable source of Fe2+

in Friedland clay was

accessory siderite, which was detected in XRD.

47

Titanium content of Kutch bentonites was high, up to 1,7 wt.% (as TiO2). Titanium

oxide mineral (anatase) was detected also in XRD-analysis. Also other clay materials

contained small amounts of Ti.

Chemical analyses showed that Milos bentonites contained significant amount of

carbonates, approximately 8-9 wt.% of CaCO3 (if all CO3 is considered to be bound to

Ca-carbonates), which is consistent with microscopy observations of coarse fraction as

well as with results of XRD analysis. However, some of the carbonates in Milos

bentonites are Mg-carbonates. They were identified with XRD and also the results of

chemical analysis suggest that. Friedland clays contained couple of percentages of

carbonates. According to chemical analysis results, most of carbonates in Friedland

clays are siderite, because the Ca-content of Friedland clays is too low to account for all

the carbonates. Also other samples contained small amounts of carbonates. The amount

of organic impurities (carbon) in all samples was at maximum approximately 0.3 wt.%.

All samples contained small amounts of soluble sulphate, but only in some samples

sulphate-bearing minerals such as gypsum (CaSO4) was detected with mineralogical

methods. The amount of other sulphur than sulphate bound in all samples was low

(below <1 wt.%), and was considered to be bound to sulphides. However, only in

couple of samples sulphide minerals (pyrite) were detected. Milos bentonites and

Friedland clay contained more sulphides than Wyoming and Kutch bentonites.

Table 6-7. Total chemical composition of bulk materials. The results are normalized to

100 %, excluding adsorbed water (H2O).

SiO2 Al2O3 Fe2O3 FeO TiO2 MgO CaO Na2O K2O CO3 Org.

C

SO4 S(oth

er)

LOI H2O

wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.%

Wyoming, USA

ABM MX80 65,37 18,70 3,50 0,36 0,15 2,34 1,29 2,19 0,53 0,79 0,14 0,14 0,20 5,36 9,49

Volclay 64,32 19,00 3,30 0,48 0,15 2,56 1,66 2,03 0,62 0,99 0,15 0,08 0,18 5,70 8,40

WyMX80 64,88 18,92 3,28 0,37 0,15 2,41 1,23 2,05 0,59 0,62 0,13 0,07 0,22 5,90 9,76

Milos, Greece

ABM DepCaN 57,66 16,96 4,71 0,20 0,75 3,26 5,04 0,90 0,98 5,12 0,02 0,35 0,62 8,94 12,79

ABM DepCaN2 57,71 17,02 4,66 0,28 0,75 3,28 5,09 0,89 0,91 4,90 0,01 0,28 0,62 8,78 12,79

AC200 56,38 17,07 5,01 0,42 0,78 3,49 4,73 2,97 0,59 5,60 0,00 0,20 0,39 8,16 9,88

Kutch, India

ABM Asha 51,15 21,23 13,40 0,07 1,20 2,02 0,73 2,02 0,06 0,36 0,02 0,01 0,02 8,11 11,71

Basic-Starbentonite 54,21 17,44 12,63 0,54 1,35 2,78 1,63 1,40 0,14 0,68 0,01 0,24 0,16 7,71 8,81

Ca-Starbentonite 58,24 15,27 11,52 0,01 1,52 3,14 1,67 1,62 0,21 0,32 0,00 0,25 0,17 6,65 12,44

HLM-Starbentonite 55,31 15,48 13,52 0,99 1,66 2,46 1,21 2,45 0,22 0,97 0,00 0,04 0,03 6,67 14,72

Friedland, Germany

ABM Friedland 60,61 17,28 4,46 2,62 0,95 1,93 0,48 1,09 2,94 2,40 0,31 0,53 0,39 7,25 4,01

SH Friedland 60,17 17,41 5,28 2,24 0,93 2,06 0,63 1,19 2,67 2,03 0,27 0,70 0,47 6,95 7,72

Chemical composition of purified and Na-exchanged clay fractions showed that they

still contained small amounts of Ca and K, as well as carbonates and organic matter.

The sulphate and sulphide were nearly removed. In future, pre-treatments to remove

organic carbon and carbonates could be done in order to get material, which doesn’t

contain these substances. In clay fractions of all samples, iron was in ferric form (Table

6-8).

48

Table 6-8. Total chemical composition of purified and homoionized clay fractions. The results are normalized to 100 %, excluding adsorbed water (H2O).

SiO2 Al2O3 Fe2O3 FeO TiO2 MgO CaO Na2O K2O CO3 Org.

C SO4 S(oth

er) LOI H2O

wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.% wt.%Wyoming, USA ABM MX80 65,34 20,20 3,62 0,21 0,14 2,29 0,03 2,73 0,06 0,30 0,10 0,00 0,00 5,39 2,69 Volclay 60,26 22,69 3,94 0,31 0,13 2,88 0,00 2,99 0,07 0,71 0,05 0,01 0,01 6,74 2,00 WyMX80 61,02 22,52 4,04 0,25 0,12 2,70 0,03 2,87 0,07 1,00 0,01 0,01 0,01 6,37 2,04 Milos, Greece ABM DepCaN 62,30 19,83 4,62 0,10 0,85 2,93 0,05 2,73 0,55 0,26 0,04 0,00 0,03 6,00 2,94 AC200 57,29 21,72 5,95 0,11 0,76 3,72 0,11 3,27 0,24 0,32 0,10 0,00 0,01 6,83 5,94 Kutch, India ABM Asha 54,92 22,53 9,87 0,06 0,53 1,79 0,05 2,75 0,14 0,35 0,07 0,00 0,00 7,36 3,72 ABM Asha2 55,07 22,76 9,31 0,10 0,34 1,76 0,03 2,65 0,18 0,81 0,08 0,00 0,00 7,81 3,72 Basic-Starbentonite 52,90 20,79 11,91 0,02 0,97 2,76 0,00 2,82 0,07 0,03 0,11 0,00 0,01 7,77 2,25 Ca-Starbentonite 54,72 18,37 12,47 0,02 1,05 3,27 0,11 3,02 0,07 0,14 0,13 0,00 0,02 6,88 4,48 HLM-Starbentonite 52,96 18,51 14,66 0,01 1,23 2,47 0,00 2,94 0,07 0,11 0,08 0,00 0,01 7,15 4,58 Friedland, Germany ABM Friedland 54,63 23,57 5,91 0,80 0,86 2,31 0,03 1,37 2,92 0,18 0,43 0,01 0,01 7,58 2,00 SH Friedland 51,52 23,99 7,36 0,98 0,77 2,65 0,03 1,48 2,74 2,02 0,12 0,02 0,02 8,45 2,04

6.4 Mineralogical composition 6.4.1 The amount of illite The illite content calculated using the Moore & Reynolds (1989) method based on XRD gave much more unreliable illite contents than the potassium content based illite content (Table 6-9). The illite contents given by Rietveld analysis were also much too high, and were not consistent with the results of chemical analysis. Therefore, the actual illite content should be calculated using combination of Rietveld-method and chemical analyses, as done by Karnland et al. (2006). Table 6-9. Illite content in clay fractions (wt.%) estimated with two different methods and in bulk samples estimated with Rietveld analysis.

Clay fraction Bulk material XRD: Moore

& Reynolds (1989)

Chemical composition

(K+)

Rietveld

Wyoming, USA ABM MX80 0 1 0 WyMX80 1 1 2 Volclay 9 1 2 Milos, Greece ABM DepCaN 4 6 9 AC200 8 3 6 Kutch, India ABM Asha 2 2 13 Basic-Starbentonite 12 1 7 HLM-Starbentonite 8 1 12 Ca-Starbentonite 7 1 3 Friedland, Germany ABM Friedland 35 32 32 SH Friedland 75 30 35

49

6.4.2 Calculation of structural formula for smectite

Structural calculations (Table 6-10) indicated that, in general, Wyoming-bentonites are

beidellitic montmorillonites (octahedral charge > tetrahedral charge) and Kutch-

bentonites montmorillonitic beidellites (octahedral charge < tetrahedral charge).

Table 6-10. Structural composition for purified Na-exchanged smectite components in

various clay materials. The calculated values of the charge and CEC of ABM MX-80

and Dep-CaN are unreliable.

Wyoming, USA Milos, Greece Kutch, India Friedland,

Germany

ABM MX80

WyMX80 Volclay ABM

DepCaN AC200

ABM Asha

Basic-Star.

HLM-Star.

Ca-Star.

ABM Friedland

SH Friedland

Tetrahedral

positions

-Si4+ 8,112 7,700 7,649 8,014 7,466 7,673 7,195 7,276 7,366 7,804 7,140

-Al3+ 0,000 0,300 0,351 0,000 0,534 0,327 0,805 0,724 0,634 0,196 0,860

-Sum 8,000 8,000 8,000 8,000 8,000 8,000 8,000 8,000 8,000 8,000 8,000 Octahedral

positions

-Al3+ 2,991 3,105 3,093 2,909 2,794 2,283 2,379 2,027 2,203 2,222 2,102

-Fe3+ 0,332 0,389 0,379 0,441 0,590 1,170 1,221 1,555 1,273 1,094 1,343

-Fe2+ 0,022 0,026 0,032 0,008 0,012 0,008 0,002 0,000 0,000 0,176 0,203

-Mg2+ 0,433 0,520 0,557 0,574 0,744 0,482 0,600 0,556 0,688 0,591 0,700

-Sum 3,777 4,040 4,061 3,931 4,141 3,944 4,202 4,138 4,163 4,084 4,348

Interlayer

positions

-Ca2+ 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000

-Mg2+ 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000

-K+ 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000 0,000

-Na+ 0,674 0,725 0,757 0,733 0,867 0,986 0,801 0,867 0,832 0,711 0,719

-Sum 0,674 0,725 0,757 0,733 0,867 0,986 0,801 0,867 0,832 0,711 0,719

O 24 24 24 24 24 24 24 24 24 24 24

H 4 4 4 4 4 4 4 4 4 4 4

Unit cell

weight 742 749 750 747 759 774 777 787 778 774

788

Charges

-Tetrahedral

charge 0,449 -0,300 -0,351 0,055 -0,534 -0,327 -0,805 -0,724 -0,634 -0,196 -0,860

-Octahedral

charge -1,123 -0,425 -0,406 -0,788 -0,334 -0,658 0,004 -0,143 -0,198 -0,515 0,141

-Total charge -0,674 -0,725 -0,757 -0,733 -0,867 -0,986 -0,801 -0,867 -0,832 -0,711 -0,719

CEC (smectite)

calculated 0,91 0,97 1,01 0,98 1,14 1,27 1,03 1,10 1,07 0,92 0,91

CEC (clay fraction)

measured

0,87 0,90 0,93 0,94 1,06 0,91 0,93 0,98 1,03 0,41 0,47

Table 6-10 shows that the amount of Si in ABM MX-80 and in ABM DepCaN was

above the value that can actually fit into the structure (8 atoms). This indicates the

presence of accessory quartz, cristobalite or poorly crystalline Si phases (e.g. opal) in

purified clay fractions that were used for chemical analysis, and that structural

calculations are therefore unreliable for these materials. The calculated structural

formulas for smectites are presented in Table 6-11. The occupation of exchangeable

cation sites is adjusted according to measured original exchangeable cation distribution

in bulk materials excluding potassium.

50

Table 6-11. Structural formulas of smectites. Exchangeable cations are adjusted according to original exchangeable cation distribution in bulk material excluding potassium. The calculated structural formula of ABM MX-80 and Dep-CaN are not reliable.

Sample Structural formula of smectite Exchangeable cation sites Octahedral sites Tetrahedral sites Wyoming, USA ABM MX80 Na0,43Ca0,09Mg0,03 Al2,99Fe3+

0,33Fe2+0,02Mg0,43 Si8,00Al0,00 O20(OH)4

WyMX80 Na0,51Ca0,08Mg0,02 Al3,11Fe3+0,39Fe2+

0,03Mg0,52 Si7,70Al0,30 O20(OH)4 Volclay Na0,54Ca0,08Mg0,03 Al3,09Fe3+

0,38Fe2+0,03Mg0,56 Si7,65Al0,35 O20(OH)4

Milos, Greece ABM DepCaN Na0,17Ca0,19Mg0,09 Al2,91Fe3+

0,44Fe2+0,01Mg0,57 Si8,00Al0,00 O20(OH)4

AC200 Na0,75Ca0,03Mg0,03 Al2,79Fe3+0,59Fe2+

0,01Mg0,74 Si7,47Al0,53 O20(OH)4 Kutch, India ABM Asha Na0,61Ca0,11Mg0,08 Al2,28Fe3+

1,17Fe2+0,01Mg0,48 Si7,67Al0,33 O20(OH)4

Basic-Starbentonite Na0,41Ca0,12Mg0,08 Al2,38Fe3+1,22Fe2+

0,00Mg0,60 Si7,20Al0,80 O20(OH)4 HLM-Starbentonite Na0,66Ca0,06Mg0,05 Al2,03Fe3+

1,56Fe2+0,00Mg0,56 Si7,28Al0,72 O20(OH)4

Ca-Starbentonite Na0,46Ca0,12Mg0,07 Al2,20Fe3+1,27Fe2+

0,00Mg0,69 Si7,37Al0,63 O20(OH)4 Friedland, Germany ABM Friedland Na0,58Ca0,02Mg0,05 Al2,22Fe3+

1,09Fe2+0,18Mg0,59 Si7,80Al0,20 O20(OH)4

SH Friedland Na0,63Ca0,01Mg0,03 Al2,10Fe3+1,34Fe2+

0,20Mg0,70 Si7,14Al0,86 O20(OH)4

6.4.3 Total mineralogical composition Total mineralogical composition of eleven studied materials is presented in Table 6-12. Results are average values from Rietveld quantifications of 3-5 XRD-diffractograms. The variation in mineralogical composition results and calculated chemical compositions are presented in Appendix 3. Table 6-12. Mineralogical composition determined with Rietveld –method. The results are mean values from Siroquant-analyses of 3-5 diffractograms.

Minerals Wyoming, USA Milos, Greece Kutch, India Friedland, GermanyABM MX80 WyMX80 Volclay

ABM DepCaN AC200

ABM Asha

Basic-Star.

HLM-Star. Ca-Star.

ABM Friedland

SH Friedland

Smectite 81,3 77,5 79,1 72,1 80,4 67,1 79,4 76,6 83,3 31,8 38,4 Illite 0,5 0,6 0,6 4,6 2,1 1,4 0,6 0,6 0,6 19,6 20,3 Kaolinite 22,7 4,0 5,8 2,2 9,7 8,5 Calcite 0,5 0,7 3,1 7,2 5,8 0,7 1,9 1,1 0,9 Muscovite 5,3 8,3 7,5 4,7 4,7 4,9 3,0 4,8 5,2 4,3 Dolomite 1,1 0,4 Quartz 3,8 4,8 4,4 0,7 0,2 0,8 2,2 2,3 28,5 23,1 Plagioclase 1,5 2,3 1,7 1,5 0,0 1,4 0,5 2,9 0,5 0,5 0,9 Siderite 2,7 1,6 Cristobalite 1,9 0,4 0,5 0,4 0,0 0,3 Tridymite 2,6 1,6 1,9 2,8 1,7 0,0 0,4 0,3 0,2 Gypsum 0,7 1,2 1,3 1,6 1,2 0,9 1,5 1,2 1,6 1,2 2 Goethite 1,0 0,4 3,1 1,8 4,5 1,4 Hematite 0,4 0,1 0,5 0,7 0,3 1,5 0,5 0,6 Maghemite 1,6 1,5 0,4 0,5 Magnetite 1,2 1,4 1,1 1,0 0,8 0,1 Anatase 0,1 0,0 0,2 0,5 0,3 0,7 0,7 0,9 0,9 Pyrite 0,7 0,8 0,6 0,9 1,4 0,7 0,8 Zircon 0,1 0,1

51

REFERENCES

Ahonen L., Korkeakoski P., Tiljander M., Kivikoski H., Laaksonen R. 2008. Quality

assurance of the bentonite material. Posiva WR 2008-33. Posiva Oy, Olkiluoto,

Finland.

Ammann L., Bergaya F., Lagaly G. 2005. Determination of the cation exchange

capacity of clays with copper complexes revisited. Clay Minerals, 40, 441-453.

Bain D.C., Smith B.F.L. 1987. Chemical Analysis, in: Wilson M.J. (Ed.), A Handbook

of Determinative Methods in Clay Mineralogy. Blackie & Son Ltd., London, pp. 248-

274.

Bergaya F., Vayer M. 1997. CEC of clays: Measurement by adsorption of a copper

ethylenediamine complex. Applied Clay Science, 12, 275-280.

Brindley G.W., Brown G. (Eds.) 1980. Crystal structures of clay minerals and their x-

ray identification. Mineralogical Society, Monograph 5. 495p.

Carlson L. 2004. Bentonite mineralogy. Part 1: Methods of investigation – a literature

review. Part 2: Mineralogical research of selected bentonites. Posiva WR 2004-02.

Posiva Oy, Olkiluoto, Finland.

Carlson L., Keto P. (Eds.) 2006. Verification of substitution of bentonites by

montmorillonitic clays. Summary report on Czech montmorillonitic clays. Posiva WR

2006-62. Posiva Oy, Olkiluoto, Finland.

Chapman H.D. 1965. Cation Exchange Capacity, in: Black C.A. (Ed.), Methods of Soil

Analysis. American Society of Agronomy, Madison, Wisconsin, pp. 891-901.

Chhabra R., Pleysier J., Cremers A. 1975. The measurement of the cation exchange

capacity and exchangeable cations in soils: A new method, in: Proceedings of the

International Clay Conference (Mexico), Applied Publishing Ltd. Wilmette, Illinois,

USA, pp. 439-449.

Christidis G., Scott P., Marcopoulos T. 1995. Origin of the bentonite deposits of eastern

Milos, Aegean, Greece: Geological, mineralogical and geochemical evidence. Clays

and Clay Minerals, 43, 63-77.

Ciesielski H., Sterckeman T. 1997. Determination of cation exchange capacity and

exchangeable cations in soils by means of cobalt hexamine trichloride. Effect of

experimental conditions. Agronomie, 17, 1-7.

Decher A., Bechtel A., Echle W., Friedrich G., Hoernes S. 1996. Stable isotope

geochemistry of bentonites from the island of Milos (Greece). Chemical Geology, 129,

101-113.

52

Drever J.I. 1973. The preparation of oriented clay mineral specimen for x-ray

diffraction analysis by a filter-membrane peel technique. American Mineralogist, 58,

553-554.

Elzea J. M., Murray H. H. 1989. Trace element composition of the Cretaceous Clay

Spur bentonite and implications for its alteration history. 9th

Int. Clay Conference,

Strasbourg. Abstract p. 132.

Elzea J. M., Murray H. H. 1990. Variation in the mineralogical, chemical and physical

properties of the Cretaceous Clay Spur bentonite in Wyoming and Montana. Applied

Clay Science, 5, 229-248.

Farmer V.C. (Ed.) 1974. The infrared spectra of minerals. Mineralogical Society,

Monograph 4.

Farmer V.C., Russell J.D. 1967. Infrared absorption spectrometry in clay studies. Clays

and Clay Minerals, 15, 121-142.

Farmer V.C., Smith B.F.L., Tait J.M. 1977. Alteration of allophane and imogolite by

alkaline digestion. Clay Minerals, 12, 195-198.

Greene-Kelly R. 1953. The identification of montmorillonoids in clays. Journal of Soil

Science, 4, 233-237.

Henning K.-H., Kasbohm J. 1998. Mineralbestand und Genese feinkörniger quartärer

und präquartärer Sedimente in NE-Deutschland unter besonderer Berücksichtigung des

“Friedländer Tones”.- Berichte der DTTG, Bd. 6: S. 147–167; Greifswald.

Kahr G., Madsen F.T. 1995. Determination of the cation exchange capacity and the

surface area of bentonite, illite and kaolinite by methylene blue adsorption. Applied

Clay Science, 9, 327-336.

Karnland O., Olsson S., Nilsson U. 2006. Mineralogy and sealing properties of various

bentonites and smectite-rich clay materials. SKB TR-06-30. Swedish Nuclear Fuel and

Waste Management Company (SKB), Stockholm, Sweden.

Lim C.H., Jackson M.L. 1986. Expandable phyllosilicate reactions with lithium on

heating. Clays and Clay Minerals, 34, 346-352.

Levien L., Prewitt C., Weidner D. 1980. Structure and elastic properties of quartz at

pressure. American Mineralogist, 65, 920-930.

Madejová J., Komadel P. 2001. Baseline studies of the clay minerals society source

clays: infrared methods. Clays and Clay Minerals, 49, 410-432.

Mehra O.P., Jackson M.L. 1960. Iron oxide removal from soils and clays by a

dithionite-citrate system buffered with sodium bicarbonate. 7th

National Conference on

Clays and Clay Minerals, 317-327.

53

Meier L.P., Kahr G. 1999. Determination of the cation exchange capacity (CEC) of

clay minerals using the complexes of copper(II) ion with triethylenetetramine and

tetraethylenepentamine. Clays and Clay Minerals, 47, 386-388.

Moore D.M., Reynolds R.C. 1989. X-ray diffraction and the identification and analysis

of clay minerals. Oxford University Press, Inc.

Newman A.C.D. (Ed.) 1987. Chemistry of clays and clay minerals. Mineralogical

Society, Monograph No. 6.

Pusch R. 2001. The Buffer and Backfill Handbook. Part 2: Materials and techniques.

SKB TR-02-12. Swedish Nuclear Fuel and Waste Management Company (SKB),

Stockholm, Sweden.

Russell J.D. 1987. Infrared Methods, in: Wilson M.J. (Ed.), A Handbook of

Determinative Methods in Clay Mineralogy. Blackie & Son Ltd., London, pp. 133-173.

Saikkonen R.J., Rautiainen I.A. 1993. Determination of ferrous iron in rock and

mineral samples by three volumetric methods. Bulletin of the Geological Society of

Finland, 65, 59-63.

Shah N. R. 1997. Indian bentonite – focus on the Kutch region. Industrial Minerals, no.

359, pp 43–47.

Slaughter M., Earley J. W. 1965. Mineralogy and Geological Significance of the

Mowry Bentonites. Wyoming. Geological Society of America, Special Paper 83, 1-116.

Smellie J. 2001. Evidence from the geological record to evaluate the suitability of

bentonite as a buffer material during the long-term underground containment of

radioactive wastes. SKB TR-01-26. Swedish Nuclear Fuel and Waste Management

Company (SKB), Stockholm, Sweden.

Smith B.F.L., Mitchell B.D. 1987. Characterization of poorly ordered minerals by

selective chemical methods, in: Wilson M.J. (Ed.), A Handbook of Determinative

Methods in Clay Mineralogy. Blackie & Son Ltd., London, pp. 275-294.

Wong-Ng W., Hubbard C. R. 1987. Standard Reference Materials For X-Ray

Diffraction Part II. Calibration Using d-Spacing Standards (242).

Xu W., Johnston C.T., Parker P., Agnew F. 2000. Infrared study of water sorption on

Na-, Li-, Ca-, and Mg-exchanged (SWy-1 and SAz-1) montmorillonite. Clays and Clay

Minerals, 48, 120-131.

55

LIST OF APPENDICES

Appendix 1. Photos of clay materials

Appendix 2. X-ray diffraction patterns of randomly oriented bulk materials

Appendix 3. Variations in mineralogical compositions determined using Rietveld

refinement from multiple diffractograms.

57


58


59

Appendix 2: Diffraction patterns of randomly oriented bulk materials (ABM MX-80)

60

Appendix 2: Diffraction patterns of randomly oriented bulk materials (ABM Asha)

61

Appendix 2: Diffraction patterns of randomly oriented bulk materials (ABM DepCaN)

62

Appendix 2: Diffraction patterns of randomly oriented bulk materials (ABM

Friedland)

63

Appendix 2: Diffraction patterns of randomly oriented bulk materials (Wyoming MX-

80)

64

Appendix 2: Diffraction patterns of randomly oriented bulk materials (Volclay)

65

Appendix 2: Diffraction patterns of randomly oriented bulk materials (SH Friedland)

66

Appendix 2: Diffraction patterns of randomly oriented bulk materials (AC200)

67

Appendix 2: Diffraction patterns of randomly oriented bulk materials (Basic-Star.)

68

Appendix 2: Diffraction patterns of randomly oriented bulk materials (HLM-Star.)

69

Appendix 2: Diffraction patterns of randomly oriented bulk materials (Ca-Star.)

71

Appendix 3: Variations in mineralogical compositions determined using Rietveld


Mineralogical composition of Wyoming bentonites. Minerals ABM MX-80 Wyoming MX80 Volclay

1 2 3 4 5 1 2 3 1 2 3

Smectite 87,9 84,0 80,0 78,7 77,7 74,3 75,4 79,2 77,8 77,6 79,2

Illite 0,1 0,1 0,1 0,1 0,1 1,7 3,7 0,1 1,4 3,1 0,1

Biotite 0,3

Muscovite 2,4 4,1 6,4 6,7 7,0 10,9 6,6 7,4 8,0 6,0 8,3

Calcite 0,1 0,1 0,1 0,6 1,4 0,6 1,3 0,1 0,8 1,0 1,3

Quartz 3,5 3,8 3,6 4,2 3,9 4,8 4,8 4,7 4,8 4,3 4,0

Plagioclase 0,1 1,0 1,9 2,1 2,5 2,2 2,5 2,1 1,5 2,1 1,4

Cristobalite 1,9 2,1 2,0 2,0 1,4 0,5 0,7 0,4 0,6 0,4

Tridymite 2,6 3,6 2,9 2,2 1,7 1,2 1,6 2,1 1,9 2,5 1,4

Gypsum 0,5 0,7 0,4 1,1 1,0 1,1 1,3 1,3 1,5 1,2 1,1

Hematite 0,6 0,3 0,3 0,2

Magnetite 0,3 0,4 1,7 1,4 2,0 1,6 1,5 1,2 1,1 0,7 1,5

Anatase 0,0 0,1 0,1 0,0 0,2 0,1 0,1 0,2 0,2

Pyrite 0,7 0,0 0,8 0,9 1,1 0,6 1 0,7 0,4 0,6 0,7

Zircon 0,1 0,1 0,2

Chemical composition of Wyoming bentonites calculated based on mineralogical

compositions and for comparison, the chemical composition analyzed (Anal.). Compounds ABM MX-80 Wyoming MX80 Volclay

1 2 3 4 5 Anal. 1 2 3 Anal. 1 2 3 Anal.

Na2O 1,81 1,84 1,86 1,86 1,89 2,19 1,79 1,85 1,88 2,05 1,87 1,95 1,90 2,03

MgO 2,30 2,19 2,09 2,06 2,03 2,34 2,31 2,40 2,42 2,41 2,58 2,61 2,59 2,56

CaO 1,06 1,12 1,00 1,47 1,86 1,29 1,63 2,09 1,47 1,23 1,87 1,88 2,00 1,66

Fe2O3 4,06 3,65 5,32 4,98 5,68 3,90 5,95 5,80 5,56 3,69 4,82 4,56 5,74 3,83

Al2O3 19,00 19,02 19,25 19,15 19,15 18,70 22,06 21,34 21,37 18,92 21,82 21,62 21,86 19,00

SiO2 66,23 66,57 64,64 64,01 62,41 65,37 59,65 59,75 61,3 64,88 60,17 60,87 59,21 64,32

H2O 0,20 0,33 0,38 0,53 0,53 0,72 0,57 0,61 0,67 0,52 0,60

SO3 1,15 0,39 1,30 1,68 1,93 0,11 1,29 1,12 1,51 0,06 0,37 0,44 0,55 0,73

CO2 0,04 0,05 0,06 0,27 0,60 0,58 0,25 0,56 0,03 0,45 1,19 1,39 1,38 0,07

K2O 0,29 0,49 0,76 0,8 0,84 0,53 1,43 1,93 0,88 0,59 1,08 0,99 0,99 0,62

TiO2 0,00 0,05 0,05 0,04 0,18 0,15 0,13 0,02 0,05 0,15 0,14 0,18 0,22 0,15

ZrO2 0,05 0,04 0,11

72



Mineralogical composition of Milos bentonites and smectite-rich materials. Minerals ABM Deponit CaN AC-200

1 2 3 4 5 1 2 3

Smectite 69,6 65,0 65,4 71,5 68,7 78,0 74,5 77,9

Illite 10,9 10,8 8,8 4,5 8,5 6,6 6,2 4,4

Muscovite 1,5 6,9 5,2 5,7 4,0 4,7 5,1 4,2

Calcite 7,7 6,3 7,4 6,8 7,6 5,4 6,4 5,6

Dolomite 0,3 0,7 1,1 1,8 1,4 0,2 0,5 0,4

Quartz 0,4 0,8 1,2 0,6 0,5 0,2 0,2 0,2

Plagioclase 1,2 1,6 2,1 1,4 1,2 0,1 0,0 0,0

Tridymite 3,0 2,7 2,8 2,8 2,8 1,2 1,1 2,9

Gypsum 1,8 1,7 1,6 1,2 1,6 1,0 1,2 1,4

Goethite 1,2 0,6 1,1 1,4 0,9 0,0 0,7 0,5

Hematite 0,0 0,6 0,6 0,5 0,6 0,7 0,7 0,6

Magnetite 1,6 1,0 0,8 0,6 0,8 0,5 1,5 0,5

Anatase 0,4 0,5 0,6 0,5 0,4 0,2 0,4 0,3

Pyrite 0,6 0,7 1,2 0,8 1,0 1,4 1,6 1,2

Chemical composition of Milos bentonites and smectite-rich materials calculated based

on mineralogical compositions and for comparison, the chemical composition analyzed

(Anal.). Compounds ABM Deponit CaN AC-200

1 2 3 4 5 Anal. 1 2 3 Anal.

Na2O 0,63 0,59 0,59 0,65 0,63 0,90 2,35 2,25 2,35 2,97

MgO 3,32 3,22 3,27 3,57 3,47 3,26 3,56 3,47 3,54 3,49

CaO 6,64 5,95 6,79 6,51 6,88 5,04 3,71 4,38 4,01 4,73

Fe2O3 6,46 5,78 6,46 6,30 6,19 4,93 7,03 8,61 7,26 5,48

Al2O3 17,93 19,3 18,26 18,14 18,03 16,96 21,13 20,35 20,23 17,07

SiO2 54,93 54,77 53,84 54,66 54,16 57,66 53,15 51,00 53,42 56,38

H2O 0,56 0,73 0,68 0,65 0,61 0,90 0,43 0,55 0,52 2,97

SO3 1,63 1,79 2,37 1,67 2,07 0,29 2,30 2,71 2,24 0,17

CO2 3,50 3,07 3,78 3,82 4,00 3,76 2,46 3,05 2,66 4,10

K2O 1,16 1,81 1,41 1,08 1,24 0,98 1,15 1,16 0,89 0,59

TiO2 0,39 0,47 0,58 0,50 0,40 0,75 0,22 0,44 0,30 0,78

73



Mineralogical composition of Kutch bentonites. Minerals ABM Asha Basic Starbent. HLM Starbent. Ca-Starbent.

1 2 3 4 5 1 2 3 1 2 3 1 2 3

Smectite 56,1 53,3 57,0 53,3 56,0 78,4 66,9 73,7 65,8 69 61,9 81,8 79,8 82,4

Illite 16,5 13,2 12,1 12,9 12,1 4,8 8,7 7,5 10,0 13,3 11,5 0,1 3,9 3,9

Kaolinite 20,3 26,4 20,1 25,8 21,0 3,1 5,0 3,9 8,2 2,7 6,4 2,0 2,7 2,0

Muscovite 4,1 6,1 4,5 1,2 3,6 4,2 5,2 5,5 3,6

Calcite 1,1 0,3 0,8 0,8 0,7 1,6 2,3 1,7 1,3 0,5 1,4 1,5 0,5 0,6

Quartz 0,8 0,9 0,7 2,4 2,6 1,5 2,5 2,0 2,4

Plagioclase 1,3 2,3 1,0 1,5 0,8 0,0 1,2 0,4 2,4 2,3 4,1 1,4 0,0 0,0

Cristobalite 0,5 0,2 0,5 0,0 0,1 0,0 0,1 0,4 0,3

Tridymite 0,0 0,0 0,0 0,2 0,0 0,6 0,1 0,6 0,0 0,6 0,2 0,1 0,3 0,2

Gypsum 0,4 0,5 1,2 1,4 0,9 1,1 2,1 1,4 1,0 1,7 1,0 1,5 1,6 1,7

Goethite 1,4 1,2 5,5 1,2 6,2 1,7 2,2 1,6 5,3 0,9 7,4 1,7 1,3 1,3

Hematite 0,5 0,3 0,1 0,7 0,0 1,3 1,6 1,5 0,5 0,9 0,0 0,6 0,6 0,5

Maghemite 1,8 1,7 1,3 1,3 1,7 1,0 2,3 1,1 0,7 0,5 0,0 0,6 0,4 0,4

Anatase 0,5 0,7 0,9 0,8 0,6 1,0 0,4 0,8 1,1 1,2 0,4 1,0 1,0 0,8

Chemical composition of Kutch bentonites calculated based on mineralogical

compositions and for comparison, the chemical composition analyzed (Anal.). Compounds ABM Asha Basic Starbent. HLM Starbent. Ca-Starbent.

1 2 3 4 5 Anal. 1 2 3 Anal. 1 2 3 Anal. 1 2 3 Anal.

Na2O 1,83 1,86 1,83 1,78 1,77 2,02 1,28 1,23 1,25 1,40 2,06 2,14 2,16 2,45 1,65 1,45 1,5 1,62

MgO 2,12 1,92 2,03 1,94 2,00 2,02 3,12 2,78 3,01 2,78 2,54 2,73 2,44 2,46 3,50 3,51 3,62 3,14

CaO 1,30 0,85 1,36 1,41 1,24 0,73 2,57 3,15 2,70 1,63 1,60 1,44 1,63 1,21 2,72 2,16 2,32 1,67

Fe2O3 10,34 9,52 13,29 9,55 14,04 13,48 13,57 14,24 13,26 13,24 16,75 13,56 16,77 14,62 13,43 12,54 12,66 11,53

Al2O3 22,89 24,04 21,59 23,55 21,71 21,23 20,64 21,12 21,02 17,44 18,18 18,43 18,74 15,48 18,14 19,02 18,51 15,27

SiO2 52,60 52,70 50,42 51,9 50,07 51,15 51,19 48,78 50,68 54,21 50,45 53,31 50,01 55,31 53,19 53,74 54,22 58,24

H2O 0,24 0,24 0,80 0,41 0,82 2,02 0,58 0,94 0,67 1,40 0,82 0,61 1,16 2,45 0,71 0,71 0,64 1,62

SO3 0,21 0,25 0,54 0,63 0,43 0,01 0,49 0,99 0,67 0,20 0,49 0,80 0,48 0,03 0,67 0,73 0,78 0,21

CO2 0,49 0,13 0,35 0,36 0,33 0,27 0,69 1,02 0,75 0,50 0,55 0,23 0,60 0,71 0,66 0,22 0,28 0,24

K2O 1,50 1,20 1,10 1,18 1,10 0,06 0,93 1,51 1,21 0,14 1,05 1,63 1,54 0,22 0,62 1,00 0,78 0,21

TiO2 0,46 0,67 0,85 0,81 0,59 1,20 1,03 0,40 0,82 1,35 1,11 1,15 0,4 1,66 1,00 1,02 0,76 1,52

74



Mineralogical composition of Friedland clays. Minerals ABM Friedland SH Friedland

1 2 3 4 5 1 2 3

Smectite 21,1 18,7 17,9 19,3 19,1 26,4 21,0 24,2

Illite 27,9 39,3 31,7 31,2 30,9 29,9 38,7 35,9

Kaolinite 8,8 13,6 8,5 8,8 8,6 8,7 7,9 9

Muscovite 5,8 2,3 6,4 5,7 5,8 5,8 3,8 3,3

Quartz 32,7 19,9 30,1 29,6 30,4 24,3 23,3 21,8

Plagioclase 0,0 1,6 0,0 0,5 0,5 0,1 1,5 1,2

Siderite 2,5 2,4 3,1 2,8 2,9 1,5 1,7 1,7

Gypsum 0,4 2,1 1,3 1,2 0,9 2,4 1,5 2,1

Magnetite 0,0 0,0 0,1 0,1 0,1

Pyrite 0,6 0,2 1,0 0,8 0,8 0,9 0,7 0,7

Chemical composition of Friedland clays calculated based on mineralogical

compositions and for comparison, the chemical composition analyzed (Anal.). Compounds ABM Friedland SH Friedland

1 2 3 4 5 Anal. 1 2 3 Anal.

Na2O 0,50 0,63 0,42 0,52 0,51 1,09 0,70 0,72 0,77 1,19

MgO 1,50 1,71 1,48 1,52 1,51 1,93 1,85 1,86 1,92 2,06

CaO 0,19 0,74 0,45 0,42 0,35 0,48 0,83 0,53 0,73 0,63

Fe2O3 5,00 4,29 5,30 5,11 5,19 7,37 5,93 5,01 5,58 7,77

Al2O3 15,65 18,62 16,43 16,41 16,28 17,28 17,76 18,70 18,46 17,41

SiO2 67,87 61,66 65,39 65,76 66,14 60,61 62,09 62,54 61,50 60,17

H2O 0,35 0,55 0,56 0,50 0,46 0,77 0,49 0,60

SO3 1,02 1,24 1,87 1,56 1,45 0,44 2,30 1,60 1,97 0,59

CO2 0,97 0,91 1,19 1,05 1,09 1,76 0,58 0,63 0,64 1,49

K2O 3,22 3,84 3,64 3,51 3,50 2,94 3,40 3,96 3,66 2,67

mineralogical and chemical characterization of various bentonite and smectite-rich clay materials

Documents