Working
Report
2010-52
Mineralogical and Chemical Characterization of
Various Bentonite and Smectite-Rich
Clay Materials
Part A: Comparison and Development of Mineralogical
Characterization Methods
Part B: Mineralogical and Chemical Characterization
of Clay Materials
Sirpa
Kumpulainen
Leena
Kiviranta
B+Tech Oy
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.
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-mekaaniskemiallisen (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 spektrometrillä (ICP-AES) ja polttomenetelmillä (Leco-S, Leco-C). Raudan eri hapetusmuodot
erotettiin titraamalla ja liukoisen sulfaatin määrä ionikromatografialla. Lisäksi määritettiin kationinvaihtokapasiteetti sekä vaihtuvien kationien laatu ja määrä. Hienoaineksen (<2µm) kemiallista koostumusta ja heikkouutoilla määritettyjen huonosti
kiteisten Fe-, Al-, ja Si-faasien määrää käytettiin smektiitin rakennelaskuihin.
Mineralogiseen analyysiin käytetyt menetelmät paljastivat materiaaleista eri ominaisuuksia ja havainnot tukivat hyvin toisiaan. Kemiallista analyysiä käytettiin mineralogisten 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
4
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.
6
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, hydroxyintercalated 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+, Mg2+) 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).
Initial
After 1. cycle
After 2. cycle
After 3. cycle
Ca
%
21
10
1
1
Saturation of exchangeable sites
K
Mg
Na
%
%
%
2
8
69
0
10
80
0
4
95
0
2
97
Exchangeable cations (in dry (105oC) weight)
Ca
K
Mg
Na
Sum
eq/kg
eq/kg
eq/kg
eq/kg
eq/kg
0,18
0,02
0,07
0,62
0,90
0,09
0,00
0,09
0,71
0,89
0,01
0,00
0,03
0,76
0,79
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 0,02o 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 0.02o 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 0,02o 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 Alrich 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 63) (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 AlO 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, OHstretching 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-acetateextraction.
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
105 oC), and reported as equivalent charges / kg of dry weight.
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)).
ABM MX-80 bulk
ABM MX-80 <2µm,
Na-exchanged
ABM Asha bulk
ABM Asha <2µm, Naexchanged
ABM DepCaN bulk
ABM DepCaN <2µm,
Na-exchanged
ABM Friedland bulk
ABM Friedland <2µm,
Na-exchanged
Ca2+
0,15
-
NH4Cl (in 80 % ethanol)
Fe2+
K+
Mg2+
0,00
0,01
0,06
-
Na+
0,55
-
Ca2+
0,34
0,00
NH4-acetate (pH 7)
Fe2+
K+
Mg2+
0,00
0,02
0,10
0,00
0,00
0,01
Na+
0,51
0,73
0,12
-
0,00
-
0,01
-
0,09
-
0,67
-
0,23
0,01
0,00
0,00
0,01
0,00
0,18
0,02
0,59
0,76
0,26
-
0,00
-
0,01
-
0,22
-
0,20
-
0,96
0,01
0,00
0,00
0,02
0,01
0,30
0,03
0,20
0,81
0,01
-
0,00
-
0,02
-
0,04
-
0,24
-
0,08
0,00
0,00
0,00
0,02
0,02
0,07
0,01
0,23
0,31
18
Table 3-2. Saturation of exchangeable cation sites as percentages.
ABM MX-80 bulk
ABM MX-80 <2µm,
Na-exchanged
ABM Asha bulk
ABM Asha <2µm, Naexchanged
ABM DepCaN bulk
ABM DepCaN <2µm,
Na-exchanged
ABM Friedland bulk
ABM Friedland <2µm,
Na-exchanged
Ca2+
20
-
NH4Cl (in 80 % ethanol)
Fe2+
K+
Mg2+
0
2
7
-
Na+
71
-
Ca2+
35
0
NH4-acetate (pH 7)
Fe2+
K+
Mg2+
0
2
10
0
0
2
Na+
53
98
13
-
0
-
1
-
10
-
76
-
23
2
0
0
1
0
18
2
59
96
38
-
0
-
2
-
31
-
29
-
65
1
0
0
1
1
20
3
14
95
4
-
0
-
6
-
13
-
76
-
20
1
0
0
5
5
17
3
58
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 0.000020.01eq/kg.
Results were adjusted against adsorbed water content (determined gravimetrically at
105 oC), and reported as equivalent charges / kg of dry weight.
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
ABM MX-80 bulk
ABM MX-80 <2µm, Na-exchanged
ABM Asha bulk
ABM Asha <2µm, Na-exchanged
ABM Deponit CaN bulk
ABM Deponit CaN <2µm, Na-exchanged
ABM Friedland bulk
ABM Friedland <2µm, Na-exchanged
Cu(II)-trien
CEC
0,84
0,87
0,90
0,91
0,82
0,94
0,26
0,41
NH4-acetate (pH 7)
CEC
0,96
0,75
1,00
0,79
1,48
0,81
0,40
0,34
NH4Cl
CEC
0,77
0,90
0,70
0,31
-
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, Naexchanged
Wyoming, USA
ABM MX80
WyMX80
Volclay
0,115
0,125
0,160
0,063
0,067
0,086
Milos, Greece
ABM DepCaN
AC200
0,047
0,093
0,024
0,021
Kutch, India
ABM Asha
Basic-Starbentonite
HLM-Starbentonite
Ca-Starbentonite
0,006
0,048
0,081
0,001
0,007
0,002
0,001
0,001
Friedland, Germany
ABM Friedland
SH Friedland
0,652
0,472
0,150
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.
26
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 Rietveldmethod 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. FTIRanalysis 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 pretreatment 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.
28
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.
32
33
34
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
Treatment
Line/
interpretation
Bulk
Clay
EG
d(002)
d(003)
I % in
I/S
550oC
d(001)
Identified clay
minerals and
impurities
0
1
9
9,48
9,54
9,08
I/S, Q, Cr
I/S, Q, Cr
I/S, Q, Cr
5,59
5,53
4
8
9,44
9,58
I/S
I/S
8,36
5,57
2
9,53
I/S, K
16,74
8,49
5,56
12
9,52
I/S, K, Cr
14,33
14,32
16,48
16,43
8,42
8,42
5,58
5,56
8
7
9,46
9,63
I/S, K
I/S, K
13,99
16,51
9,84
5,51
35
9,66
I/S, K
13,58
16,34
9,79
5,20
75
9,87
I/S, K, Q
Oriented
d(001)
d(001)
d(060)
Dioct./
Trioct.
Wyoming, USA
ABM MX80
WyMX80
Volclay
1,497
1,497
1,497
Dioct.
Dioct.
Dioct.
14,66
14,38
13,02
16,49
16,68
15,38
8,41
8,44
8,22
5,60
5,61
5,46
Milos, Greece
ABM DepCaN
AC200
1,496
1,498
Dioct.
Dioct.
14,72
14,16
16,58
16,17
8,44
8,37
1,494;
1,503
1,490,
1,500
1,498
1,503
Dioct.
14,75
16,54
Dioct.
14,31
Dioct.
Dioct.
1,502;
1,542
1,502;
1,542
Dioct.(+
Trioct.?)
Dioct.(+
Trioct.?)
Kutch, India
ABM Asha
Basic-Starbent.
HLM-Starbent.
Ca-Starbent.
Friedland,
Germany
ABM Friedland
SH Friedland
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). Naexchanged 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).
ABM MX-80
Volclay
WyMX-80
ABM DepCaN
AC200
ABM Asha
Basic-Starb.
HLM-Starb.
Ca-Starb.
ABM Fried.
SH Fried.
Sample
3699
3699
H2O-stretching
H2O
1107
1112
1112
1109
1109
1114
1116
1119
H2O-bending
H2O
1633
1624
1624
1630
1631
1630
1629
1630
1629
1627
1626
Si-O stretching
Si-O-Si
3436
3455
3441
3447
3437
3436
3446
3460
3432
3423
3432
Tetrahedral Si-O (S,K,Q)
1047
1040
1047
1040
1035
1035
1035
1035
1038
1032
1034
OH-bending
AlAlOH (S,K)
919
916
918
917
917
914
914
919
917
913
913
AlFeOH (S)
875
880
882
882
880
878
877
875
878
878
AlMgOH (S)
848
848
848
841
843
OH-bending
band of smectite
or Al-O band of
illite
Si-O stretching
AlMgOH (S)
Al-O (I)
834
833
831
834
Si-O-Si
Al-O-Si
Si-O (S, K)
Si-O (K),
Al-O-Si (I)
Trioktah. Si-O?
Si-O (Q)
799
696 624 525 468
799
725 692 623 525 468
799
725 695 622 525 468
795
700 625 525 468 423
794
699 623 524 469 423
794
752
696 625 532 469 430
794
752
692
526 469 423
797
690
524 469 423
797
685 620 522 466
800 780 755
698
536 471 428
800 778 755
697
533 471 427
Q, free Si-O
OH-stretching
bands
OH stretching of inner
surface hydroxyl groups
(K)
3697
3698
AlFe3+OH (S)
AlAlOH (K, S)
AlMgOH (S)
3627
3634
3636
3636
3635
3621 3591
3622
3688 3622
3623
3621
3621
Si-O bending
Al-O, Si-O
Vibration
Si-O
Table 6-3. The position of FTIR absorption bands of studied bentonites and clay materials, and band assignments (S=smectite, K=kaolin
minerals, I=illite, Q=quartz).
40
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
Montmorillonite
Other smectite
Illite/dioct.-mica
Kaolinite
Biotite
Chlorite
Calcite
Dolomite
Quartz
Plagioclase
Siderite
Cristobalite
Gypsum
Goethite
Hematite
Maghemite
Magnetite
Anatase
Pyrite
Zircon
Apatite
Wyoming, USA
ABM
MX80
x
Milos, Greece
WyMX80
Volclay
x
x
ABM
DepCaN
x
x
x
x
m
m
m
m
m,x
m,x
m,x
m,x
m,x
m,x
m,x
x
x
x
x
x
x
x,o
AC200
x
x
Kutch, India
ABM
Asha
x
x
x
x, f
BasicStar.
x
x
HLMStar.
x
x
CaStar.
x
x
x, f
x, f
x
x
m
x
m
x
m,x
x
m,x
m
x
x
x
x
m,x
m,x
x
x
m
m
m,x
x,o
x, o
o
o
m
m, o
m, x
m,x
x
x
x
m, o
m, o
o
x
m
Friedland,
Germany
ABM
SH
Friedland Friedland
x
x
x
x
m,x
x, f
x, f
m
m
x
m
m,x
x, o
x
x
m
m,x
x, o
x
x
x
m,x
x, o
x
x
o
x
m
m
x
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 CaStarbentonite 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 NH4Cland Cu(II)-triethylenetetramine-methods.
Exchangeable cations
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
CEC
Cu-trien
eq/kg
Wyoming, USA
ABM MX80
WyMX80
Volclay
Volclay2
27
23
21
22
2
2
2
2
9
7
8
8
62
69
69
67
0,25
0,21
0,18
0,20
0,02
0,02
0,02
0,02
0,08
0,06
0,07
0,07
0,57
0,63
0,62
0,59
0,92
0,92
0,90
0,88
0,84
0,85
0,89
0,89
Milos, Greece
ABM DepCaN
AC200
51
6
2
2
25
8
23
84
0,47
0,06
0,02
0,02
0,23
0,08
0,21
0,92
0,92
1,09
0,82
0,95
Kutch, India
ABM Asha
Basic-Starbentonite
HLM-Starbentonite
Ca-Starbentonite
22
30
13
29
0
1
1
1
16
19
11
16
62
51
76
55
0,20
0,29
0,16
0,32
0,00
0,01
0,01
0,01
0,14
0,18
0,13
0,18
0,56
0,49
0,93
0,61
0,90
0,97
1,23
1,12
0,90
0,92
1,00
1,00
Friedland, Germany
ABM Friedland
SH Friedland
4
2
6
5
13
9
76
83
0,01
0,01
0,02
0,03
0,04
0,04
0,24
0,38
0,31
0,46
0,26
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
Fe2O3
SiO2
wt.%
CBD/total
wt.%
CBD/total
Free silica and aluminium oxides
SiO2
Al2O3
wt.%
SC/total
wt.%
SC/total
Wyoming, USA
ABM MX80
Volclay
Volclay2
WyMX80
0,16
0,08
0,08
0,08
0,045
0,021
0,020
0,019
0,50
0,36
0,36
0,37
0,008
0,006
0,006
0,006
0,87
0,93
0,88
1,16
0,013
0,016
0,015
0,019
0,11
0,11
0,10
0,14
0,006
0,005
0,004
0,006
Milos, Greece
ABM DepCaN
AC200
0,39
0,21
0,085
0,036
0,64
0,42
0,010
0,007
0,58
0,83
0,009
0,015
0,25
0,29
0,013
0,013
Kutch, India
ABM Asha
Basic-Starbentonite
Ca-Starbentonite
HLM-Starbentonite
1,47
0,83
0,55
1,07
0,149
0,070
0,044
0,073
0,57
0,56
0,61
0,68
0,010
0,011
0,011
0,013
0,46
0,62
0,61
0,75
0,008
0,012
0,011
0,014
0,27
0,25
0,18
0,17
0,012
0,012
0,010
0,009
Friedland, Germany
ABM Friedland
SH Friedland
0,50
0,26
0,084
0,035
0,39
0,33
0,007
0,006
0,38
0,58
0,007
0,011
0,17
0,09
0,007
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
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
Org.
C
wt.%
wt.%
SO4
LOI
H2O
wt.%
S(oth
er)
wt.%
Wyoming, USA
ABM MX80
Volclay
WyMX80
wt.%
wt.%
65,37 18,70
64,32 19,00
64,88 18,92
3,50
3,30
3,28
0,36
0,48
0,37
0,15
0,15
0,15
2,34
2,56
2,41
1,29
1,66
1,23
2,19
2,03
2,05
0,53
0,62
0,59
0,79
0,99
0,62
0,14
0,15
0,13
0,14
0,08
0,07
0,20
0,18
0,22
5,36
5,70
5,90
9,49
8,40
9,76
Milos, Greece
ABM DepCaN
ABM DepCaN2
AC200
57,66 16,96
57,71 17,02
56,38 17,07
4,71
4,66
5,01
0,20
0,28
0,42
0,75
0,75
0,78
3,26
3,28
3,49
5,04
5,09
4,73
0,90
0,89
2,97
0,98
0,91
0,59
5,12
4,90
5,60
0,02
0,01
0,00
0,35
0,28
0,20
0,62
0,62
0,39
8,94
8,78
8,16
12,79
12,79
9,88
Kutch, India
ABM Asha
Basic-Starbentonite
Ca-Starbentonite
HLM-Starbentonite
51,15
54,21
58,24
55,31
21,23
17,44
15,27
15,48
13,40
12,63
11,52
13,52
0,07
0,54
0,01
0,99
1,20
1,35
1,52
1,66
2,02
2,78
3,14
2,46
0,73
1,63
1,67
1,21
2,02
1,40
1,62
2,45
0,06
0,14
0,21
0,22
0,36
0,68
0,32
0,97
0,02
0,01
0,00
0,00
0,01
0,24
0,25
0,04
0,02
0,16
0,17
0,03
8,11
7,71
6,65
6,67
11,71
8,81
12,44
14,72
Friedland, Germany
ABM Friedland
SH Friedland
60,61 17,28
60,17 17,41
4,46
5,28
2,62
2,24
0,95
0,93
1,93
2,06
0,48
0,63
1,09
1,19
2,94
2,67
2,40
2,03
0,31
0,27
0,53
0,70
0,39
0,47
7,25
6,95
4,01
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
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
wt.%
Org.
C
wt.%
Wyoming, USA
ABM MX80
Volclay
WyMX80
65,34 20,20
60,26 22,69
61,02 22,52
3,62
3,94
4,04
0,21
0,31
0,25
0,14
0,13
0,12
2,29
2,88
2,70
0,03
0,00
0,03
2,73
2,99
2,87
0,06
0,07
0,07
0,30
0,71
1,00
0,10
0,05
0,01
0,00
0,01
0,01
0,00
0,01
0,01
5,39
6,74
6,37
2,69
2,00
2,04
Milos, Greece
ABM DepCaN
AC200
62,30 19,83
57,29 21,72
4,62
5,95
0,10
0,11
0,85
0,76
2,93
3,72
0,05
0,11
2,73
3,27
0,55
0,24
0,26
0,32
0,04
0,10
0,00
0,00
0,03
0,01
6,00
6,83
2,94
5,94
Kutch, India
ABM Asha
ABM Asha2
Basic-Starbentonite
Ca-Starbentonite
HLM-Starbentonite
54,92
55,07
52,90
54,72
52,96
22,53 9,87
22,76 9,31
20,79 11,91
18,37 12,47
18,51 14,66
0,06
0,10
0,02
0,02
0,01
0,53
0,34
0,97
1,05
1,23
1,79
1,76
2,76
3,27
2,47
0,05
0,03
0,00
0,11
0,00
2,75
2,65
2,82
3,02
2,94
0,14
0,18
0,07
0,07
0,07
0,35
0,81
0,03
0,14
0,11
0,07
0,08
0,11
0,13
0,08
0,00
0,00
0,00
0,00
0,00
0,00
0,00
0,01
0,02
0,01
7,36
7,81
7,77
6,88
7,15
3,72
3,72
2,25
4,48
4,58
Friedland, Germany
ABM Friedland
SH Friedland
54,63 23,57
51,52 23,99
0,80
0,98
0,86
0,77
2,31
2,65
0,03
0,03
1,37
1,48
2,92
2,74
0,18
2,02
0,43
0,12
0,01
0,02
0,01
0,02
7,58
8,45
2,00
2,04
5,91
7,36
SO4
LOI
H2O
wt.%
S(oth
er)
wt.%
wt.%
wt.%
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
XRD: Moore
Chemical
& Reynolds
composition
(1989)
(K+)
Bulk material
Rietveld
Wyoming, USA
ABM MX80
WyMX80
Volclay
0
1
9
1
1
1
0
2
2
Milos, Greece
ABM DepCaN
AC200
4
8
6
3
9
6
Kutch, India
ABM Asha
Basic-Starbentonite
HLM-Starbentonite
Ca-Starbentonite
2
12
8
7
2
1
1
1
13
7
12
3
Friedland, Germany
ABM Friedland
SH Friedland
35
75
32
30
32
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 Kutchbentonites 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
Tetrahedral
positions
-Si4+
-Al3+
-Sum
Octahedral
positions
-Al3+
-Fe3+
-Fe2+
-Mg2+
-Sum
Interlayer
positions
-Ca2+
-Mg2+
-K+
-Na+
-Sum
O
H
Unit cell
weight
Charges
-Tetrahedral
charge
-Octahedral
charge
-Total charge
CEC (smectite)
calculated
CEC (clay
fraction)
measured
Milos, Greece
Kutch, India
Friedland,
Germany
ABM
SH
Friedland Friedland
ABM
MX80
WyMX80
Volclay
ABM
DepCaN
AC200
ABM
Asha
BasicStar.
HLMStar.
CaStar.
8,112
0,000
8,000
7,700
0,300
8,000
7,649
0,351
8,000
8,014
0,000
8,000
7,466
0,534
8,000
7,673
0,327
8,000
7,195
0,805
8,000
7,276
0,724
8,000
7,366
0,634
8,000
7,804
0,196
8,000
7,140
0,860
8,000
2,991
0,332
0,022
0,433
3,777
3,105
0,389
0,026
0,520
4,040
3,093
0,379
0,032
0,557
4,061
2,909
0,441
0,008
0,574
3,931
2,794
0,590
0,012
0,744
4,141
2,283
1,170
0,008
0,482
3,944
2,379
1,221
0,002
0,600
4,202
2,027
1,555
0,000
0,556
4,138
2,203
1,273
0,000
0,688
4,163
2,222
1,094
0,176
0,591
4,084
2,102
1,343
0,203
0,700
4,348
0,000
0,000
0,000
0,674
0,674
24
4
0,000
0,000
0,000
0,725
0,725
24
4
0,000
0,000
0,000
0,757
0,757
24
4
0,000
0,000
0,000
0,733
0,733
24
4
0,000
0,000
0,000
0,867
0,867
24
4
0,000
0,000
0,000
0,986
0,986
24
4
0,000
0,000
0,000
0,801
0,801
24
4
0,000
0,000
0,000
0,867
0,867
24
4
0,000
0,000
0,000
0,832
0,832
24
4
0,000
0,000
0,000
0,711
0,711
24
4
0,000
0,000
0,000
0,719
0,719
24
4
742
749
750
747
759
774
777
787
778
774
0,449
-0,300
-0,351
0,055
-0,534
-0,327
-0,805
-0,724
-0,634
-0,196
-1,123
-0,425
-0,406
-0,788
-0,334
-0,658
0,004
-0,143
-0,198
-0,515
0,141
-0,674
-0,725
-0,757
-0,733
-0,867
-0,986
-0,801
-0,867
-0,832
-0,711
-0,719
0,91
0,97
1,01
0,98
1,14
1,27
1,03
1,10
1,07
0,92
0,91
0,87
0,90
0,93
0,94
1,06
0,91
0,93
0,98
1,03
0,41
0,47
788
-0,860
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
Exchangeable cation sites
Structural formula of smectite
Octahedral sites
Tetrahedral sites
Wyoming, USA
ABM MX80
WyMX80
Volclay
Na0,43Ca0,09Mg0,03
Na0,51Ca0,08Mg0,02
Na0,54Ca0,08Mg0,03
Al2,99Fe3+0,33Fe2+0,02Mg0,43
Al3,11Fe3+0,39Fe2+0,03Mg0,52
Al3,09Fe3+0,38Fe2+0,03Mg0,56
Si8,00Al0,00
Si7,70Al0,30
Si7,65Al0,35
O20(OH)4
O20(OH)4
O20(OH)4
Milos, Greece
ABM DepCaN
AC200
Na0,17Ca0,19Mg0,09
Na0,75Ca0,03Mg0,03
Al2,91Fe3+0,44Fe2+0,01Mg0,57
Al2,79Fe3+0,59Fe2+0,01Mg0,74
Si8,00Al0,00
Si7,47Al0,53
O20(OH)4
O20(OH)4
Kutch, India
ABM Asha
Basic-Starbentonite
HLM-Starbentonite
Ca-Starbentonite
Na0,61Ca0,11Mg0,08
Na0,41Ca0,12Mg0,08
Na0,66Ca0,06Mg0,05
Na0,46Ca0,12Mg0,07
Al2,28Fe3+1,17Fe2+0,01Mg0,48
Al2,38Fe3+1,22Fe2+0,00Mg0,60
Al2,03Fe3+1,56Fe2+0,00Mg0,56
Al2,20Fe3+1,27Fe2+0,00Mg0,69
Si7,67Al0,33
Si7,20Al0,80
Si7,28Al0,72
Si7,37Al0,63
O20(OH)4
O20(OH)4
O20(OH)4
O20(OH)4
Friedland, Germany
ABM Friedland
SH Friedland
Na0,58Ca0,02Mg0,05
Na0,63Ca0,01Mg0,03
Al2,22Fe3+1,09Fe2+0,18Mg0,59
Al2,10Fe3+1,34Fe2+0,20Mg0,70
Si7,80Al0,20
Si7,14Al0,86
O20(OH)4
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
Smectite
Illite
Kaolinite
Calcite
Muscovite
Dolomite
Quartz
Plagioclase
Siderite
Cristobalite
Tridymite
Gypsum
Goethite
Hematite
Maghemite
Magnetite
Anatase
Pyrite
Zircon
Wyoming, USA
Milos, Greece
ABM
ABM
MX80 WyMX80 Volclay DepCaN AC200
81,3
77,5
79,1
72,1
80,4
0,5
0,6
0,6
4,6
2,1
0,5
5,3
0,7
8,3
3,1
7,5
3,8
1,5
4,8
2,3
4,4
1,7
1,9
2,6
0,7
0,4
1,6
1,2
0,5
1,9
1,3
0,4
0,1
1,4
0,0
0,8
0,1
1,1
0,2
0,6
0,1
1,2
0,1
0,7
7,2
4,7
1,1
0,7
1,5
5,8
4,7
0,4
0,2
0,0
2,8
1,6
1,0
0,5
1,7
1,2
0,4
0,7
1,0
0,5
0,9
0,8
0,3
1,4
ABM
Asha
67,1
1,4
22,7
0,7
Kutch, India
BasicHLMStar.
Star.
79,4
76,6
0,6
0,6
4,0
5,8
1,9
1,1
4,9
3,0
Friedland, Germany
ABM
SH
Ca-Star. Friedland Friedland
83,3
31,8
38,4
0,6
19,6
20,3
2,2
9,7
8,5
0,9
4,8
5,2
4,3
1,4
0,8
0,5
2,2
2,9
2,3
0,5
0,0
0,9
3,1
0,3
1,6
0,4
0,4
1,5
1,8
1,5
1,5
0,0
0,3
1,2
4,5
0,5
0,4
0,3
0,2
1,6
1,4
0,6
0,5
0,7
0,7
0,9
0,9
28,5
0,5
2,7
23,1
0,9
1,6
1,2
2
0,1
0,7
0,8
51
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54
55
LIST OF APPENDICES
Appendix 1.
Appendix 2.
Appendix 3.
Photos of clay materials
X-ray diffraction patterns of randomly oriented bulk materials
Variations in mineralogical compositions determined using Rietveld
refinement from multiple diffractograms.
56
57
Appendix 1. Photos of clay materials
58
Appendix 1. Photos of clay materials
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 MX80)
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.)
70
71
Appendix 3: Variations in mineralogical compositions determined using Rietveld
refinement from multiple diffractograms.
Mineralogical composition of Wyoming bentonites.
Minerals
Smectite
Illite
Biotite
Muscovite
Calcite
Quartz
Plagioclase
Cristobalite
Tridymite
Gypsum
Hematite
Magnetite
Anatase
Pyrite
Zircon
ABM MX-80
3
4
80,0
78,7
0,1
0,1
1
87,9
0,1
2
84,0
0,1
5
77,7
0,1
2,4
0,1
3,5
0,1
1,9
2,6
0,5
4,1
0,1
3,8
1,0
2,1
3,6
0,7
6,4
0,1
3,6
1,9
2,0
2,9
0,4
6,7
0,6
4,2
2,1
2,0
2,2
1,1
7,0
1,4
3,9
2,5
1,4
1,7
1,0
0,3
0,0
0,7
0,4
0,1
0,0
1,7
0,1
0,8
1,4
0,0
0,9
2,0
0,2
1,1
Wyoming MX80
1
2
3
74,3
75,4
79,2
1,7
3,7
0,1
10,9
0,6
4,8
2,2
0,5
1,2
1,1
0,6
1,6
0,1
0,6
6,6
1,3
4,8
2,5
1,6
1,3
0,3
1,5
7,4
0,1
4,7
2,1
0,7
2,1
1,3
0,3
1,2
1
0,1
0,7
0,1
1
77,8
1,4
0,3
8,0
0,8
4,8
1,5
0,4
1,9
1,5
1,1
0,1
0,4
Volclay
2
77,6
3,1
6,0
1,0
4,3
2,1
0,6
2,5
1,2
0,7
0,2
0,6
3
79,2
0,1
8,3
1,3
4,0
1,4
0,4
1,4
1,1
0,2
1,5
0,2
0,7
0,2
Chemical composition of Wyoming bentonites calculated based on mineralogical
compositions and for comparison, the chemical composition analyzed (Anal.).
Compounds
Na2O
MgO
CaO
Fe2O3
Al2O3
SiO2
H2O
SO3
CO2
K2O
TiO2
ZrO2
1
1,81
2,30
1,06
4,06
19,00
66,23
0,20
1,15
0,04
0,29
0,00
2
1,84
2,19
1,12
3,65
19,02
66,57
0,33
0,39
0,05
0,49
0,05
ABM MX-80
3
4
5
1,86
1,86 1,89
2,09
2,06 2,03
1,00
1,47 1,86
5,32
4,98 5,68
19,25 19,15 19,15
64,64 64,01 62,41
0,38
0,53 0,53
1,30
1,68 1,93
0,06
0,27 0,60
0,76
0,8
0,84
0,05
0,04 0,18
Anal.
2,19
2,34
1,29
3,90
18,70
65,37
0,11
0,58
0,53
0,15
Wyoming MX80
1
2
3
Anal.
1,79 1,85 1,88 2,05
2,31 2,40 2,42 2,41
1,63 2,09 1,47 1,23
5,95 5,80 5,56 3,69
22,06 21,34 21,37 18,92
59,65 59,75 61,3 64,88
0,72 0,57 0,61
1,29 1,12 1,51 0,06
0,25 0,56 0,03 0,45
1,43 1,93 0,88 0,59
0,13 0,02 0,05 0,15
0,05 0,04
1
1,87
2,58
1,87
4,82
21,82
60,17
0,67
0,37
1,19
1,08
0,14
Volclay
2
3
1,95 1,90
2,61 2,59
1,88 2,00
4,56 5,74
21,62 21,86
60,87 59,21
0,52 0,60
0,44 0,55
1,39 1,38
0,99 0,99
0,18 0,22
0,11
Anal.
2,03
2,56
1,66
3,83
19,00
64,32
0,73
0,07
0,62
0,15
72
Appendix 3: Variations in mineralogical compositions determined using Rietveld
refinement from multiple diffractograms.
Mineralogical composition of Milos bentonites and smectite-rich materials.
Minerals
Smectite
Illite
Muscovite
Calcite
Dolomite
Quartz
Plagioclase
Tridymite
Gypsum
Goethite
Hematite
Magnetite
Anatase
Pyrite
1
69,6
10,9
1,5
7,7
0,3
0,4
1,2
3,0
1,8
1,2
0,0
1,6
0,4
0,6
ABM Deponit CaN
2
3
4
65,0
65,4
71,5
10,8
8,8
4,5
6,9
5,2
5,7
6,3
7,4
6,8
0,7
1,1
1,8
0,8
1,2
0,6
1,6
2,1
1,4
2,7
2,8
2,8
1,7
1,6
1,2
0,6
1,1
1,4
0,6
0,6
0,5
1,0
0,8
0,6
0,5
0,6
0,5
0,7
1,2
0,8
5
68,7
8,5
4,0
7,6
1,4
0,5
1,2
2,8
1,6
0,9
0,6
0,8
0,4
1,0
1
78,0
6,6
4,7
5,4
0,2
0,2
0,1
1,2
1,0
0,0
0,7
0,5
0,2
1,4
AC-200
2
74,5
6,2
5,1
6,4
0,5
0,2
0,0
1,1
1,2
0,7
0,7
1,5
0,4
1,6
3
77,9
4,4
4,2
5,6
0,4
0,2
0,0
2,9
1,4
0,5
0,6
0,5
0,3
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
Na2O
MgO
CaO
Fe2O3
Al2O3
SiO2
H2O
SO3
CO2
K2O
TiO2
1
0,63
3,32
6,64
6,46
17,93
54,93
0,56
1,63
3,50
1,16
0,39
ABM Deponit CaN
2
3
4
5
0,59
0,59
0,65 0,63
3,22
3,27
3,57 3,47
5,95
6,79
6,51 6,88
5,78
6,46
6,30 6,19
19,3 18,26 18,14 18,03
54,77 53,84 54,66 54,16
0,73
0,68
0,65 0,61
1,79
2,37
1,67 2,07
3,07
3,78
3,82 4,00
1,81
1,41
1,08 1,24
0,47
0,58
0,50 0,40
AC-200
Anal.
1
2
3
Anal.
0,90 2,35 2,25 2,35 2,97
3,26 3,56 3,47 3,54 3,49
5,04 3,71 4,38 4,01 4,73
4,93 7,03 8,61 7,26 5,48
16,96 21,13 20,35 20,23 17,07
57,66 53,15 51,00 53,42 56,38
0,90 0,43 0,55 0,52 2,97
0,29 2,30 2,71 2,24 0,17
3,76 2,46 3,05 2,66 4,10
0,98 1,15 1,16 0,89 0,59
0,75 0,22 0,44 0,30 0,78
73
Appendix 3: Variations in mineralogical compositions determined using Rietveld
refinement from multiple diffractograms.
Mineralogical composition of Kutch bentonites.
Minerals
Smectite
Illite
Kaolinite
Muscovite
Calcite
Quartz
Plagioclase
Cristobalite
Tridymite
Gypsum
Goethite
Hematite
Maghemite
Anatase
1
56,1
16,5
20,3
ABM Asha
2
3
4
53,3 57,0 53,3
13,2 12,1 12,9
26,4 20,1 25,8
5
56,0
12,1
21,0
1,1
0,3
0,8
0,8
0,7
1,3
2,3
1,0
1,5
0,8
0,0
0,4
1,4
0,5
1,8
0,5
0,0
0,5
1,2
0,3
1,7
0,7
0,0
1,2
5,5
0,1
1,3
0,9
0,2
1,4
1,2
0,7
1,3
0,8
0,0
0,9
6,2
0,0
1,7
0,6
Basic Starbent.
1
2
3
78,4 66,9 73,7
4,8
8,7
7,5
3,1
5,0
3,9
4,1
6,1
4,5
1,6
2,3
1,7
0,8
0,9
0,7
0,0
1,2
0,4
0,5
0,2
0,5
0,6
0,1
0,6
1,1
2,1
1,4
1,7
2,2
1,6
1,3
1,6
1,5
1,0
2,3
1,1
1,0
0,4
0,8
HLM Starbent.
1
2
3
65,8
69
61,9
10,0 13,3 11,5
8,2
2,7
6,4
1,2
3,6
4,2
1,3
0,5
1,4
2,4
2,6
1,5
2,4
2,3
4,1
0,0
0,1
0,0
0,0
0,6
0,2
1,0
1,7
1,0
5,3
0,9
7,4
0,5
0,9
0,0
0,7
0,5
0,0
1,1
1,2
0,4
Ca-Starbent.
1
2
3
81,8
79,8
82,4
0,1
3,9
3,9
2,0
2,7
2,0
5,2
5,5
3,6
1,5
0,5
0,6
2,5
2,0
2,4
1,4
0,0
0,0
0,1
0,4
0,3
0,1
0,3
0,2
1,5
1,6
1,7
1,7
1,3
1,3
0,6
0,6
0,5
0,6
0,4
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
Na2O
MgO
CaO
Fe2O3
Al2O3
SiO2
H2O
SO3
CO2
K2O
TiO2
1
1,83
2,12
1,30
10,34
22,89
52,60
0,24
0,21
0,49
1,50
0,46
2
1,86
1,92
0,85
9,52
24,04
52,70
0,24
0,25
0,13
1,20
0,67
ABM Asha
3
4
1,83 1,78
2,03 1,94
1,36 1,41
13,29 9,55
21,59 23,55
50,42 51,9
0,80 0,41
0,54 0,63
0,35 0,36
1,10 1,18
0,85 0,81
5
1,77
2,00
1,24
14,04
21,71
50,07
0,82
0,43
0,33
1,10
0,59
Anal.
2,02
2,02
0,73
13,48
21,23
51,15
2,02
0,01
0,27
0,06
1,20
Basic Starbent.
1
2
3 Anal.
1,28 1,23 1,25 1,40
3,12 2,78 3,01 2,78
2,57 3,15 2,70 1,63
13,57 14,24 13,26 13,24
20,64 21,12 21,02 17,44
51,19 48,78 50,68 54,21
0,58 0,94 0,67 1,40
0,49 0,99 0,67 0,20
0,69 1,02 0,75 0,50
0,93 1,51 1,21 0,14
1,03 0,40 0,82 1,35
HLM Starbent.
1
2
3 Anal.
2,06 2,14 2,16 2,45
2,54 2,73 2,44 2,46
1,60 1,44 1,63 1,21
16,75 13,56 16,77 14,62
18,18 18,43 18,74 15,48
50,45 53,31 50,01 55,31
0,82 0,61 1,16 2,45
0,49 0,80 0,48 0,03
0,55 0,23 0,60 0,71
1,05 1,63 1,54 0,22
1,11 1,15 0,4 1,66
1
1,65
3,50
2,72
13,43
18,14
53,19
0,71
0,67
0,66
0,62
1,00
Ca-Starbent.
2
3 Anal.
1,45 1,5 1,62
3,51 3,62 3,14
2,16 2,32 1,67
12,54 12,66 11,53
19,02 18,51 15,27
53,74 54,22 58,24
0,71 0,64 1,62
0,73 0,78 0,21
0,22 0,28 0,24
1,00 0,78 0,21
1,02 0,76 1,52
74
Appendix 3: Variations in mineralogical compositions determined using Rietveld
refinement from multiple diffractograms.
Mineralogical composition of Friedland clays.
Minerals
Smectite
Illite
Kaolinite
Muscovite
Quartz
Plagioclase
Siderite
Gypsum
Magnetite
Pyrite
1
21,1
27,9
8,8
5,8
32,7
0,0
2,5
0,4
0,0
0,6
ABM Friedland
2
3
4
18,7
17,9
19,3
39,3
31,7
31,2
13,6
8,5
8,8
2,3
6,4
5,7
19,9
30,1
29,6
1,6
0,0
0,5
2,4
3,1
2,8
2,1
1,3
1,2
0,0
0,1
0,1
0,2
1,0
0,8
5
19,1
30,9
8,6
5,8
30,4
0,5
2,9
0,9
0,1
0,8
SH Friedland
1
2
3
26,4
21,0
24,2
29,9
38,7
35,9
8,7
7,9
9
5,8
3,8
3,3
24,3
23,3
21,8
0,1
1,5
1,2
1,5
1,7
1,7
2,4
1,5
2,1
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
Na2O
MgO
CaO
Fe2O3
Al2O3
SiO2
H2O
SO3
CO2
K2O
ABM Friedland
1
2
3
4
0,50 0,63 0,42 0,52
1,50 1,71 1,48 1,52
0,19 0,74 0,45 0,42
5,00 4,29 5,30 5,11
15,65 18,62 16,43 16,41
67,87 61,66 65,39 65,76
0,35 0,55 0,56 0,50
1,02 1,24 1,87 1,56
0,97 0,91 1,19 1,05
3,22 3,84 3,64 3,51
5
Anal.
1
0,51 1,09 0,70
1,51 1,93 1,85
0,35 0,48 0,83
5,19 7,37 5,93
16,28 17,28 17,76
66,14 60,61 62,09
0,46
0,77
1,45 0,44 2,30
1,09 1,76 0,58
3,50 2,94 3,40
SH Friedland
2
3
Anal.
0,72 0,77 1,19
1,86 1,92 2,06
0,53 0,73 0,63
5,01 5,58 7,77
18,70 18,46 17,41
62,54 61,50 60,17
0,49 0,60
1,60 1,97 0,59
0,63 0,64 1,49
3,96 3,66 2,67