mineralogical studies of montmorillonite - vttkyt2014.vtt.fi/boa_workshop_19082014/tiljander.pdf ·...
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Bentonite
- A material consisting predominantly of smectite minerals(most commonly montmorillonite).
• Common accessory minerals:quartz, K-feldspar, plagioclase, pyrite (sulphides), mica, apatite,calcite, zircon, kaolinite, illite and goethite
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Methods used for mineralogical studies ofbentonite
• Methods and instruments at GTK:
1. X-ray diffraction (XRD):until 5/2012: Philips X’Pert MPDsince 6/2013: Bruker D8 Discover A25
2. Scanning electron microscope (SEM)JEOL JSM 5900 LV
3. Electron probe micro-analyzer (EPMA)Cameca SX100
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XRD:Qualitative
mineralcompositon
SEM:Concentrationof the mineral
phases
EPMA:Quantitative
analysisfrom mineral
phases
The aim of the mineralogical research was toimprove mineralogical analysis techniques andknowledge about the bentonite material.
• Bentonite is a difficult material to sample due to it’s swellingproperties
– Within this project we learned to make resonable good samplepreparates for electron opitical methods
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Research made in BOA project
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2011 XRD analyses from samples SWY-2 and Na-dissolution tests*Emmi Myllykylä / VTT
SEM-Feature analyses (and preliminary analysis with EPMA) from samplesmade for TEM (transmission electron microscopy) analyses*Michal Matusewicz / VTT
2012 Developing sampling and analyses methods : SEM-Feature and EPMA*Emmi Myllykylä and Michal Matusewicz / VTTSampling ”15 year test” samples *Joonas Järvinen and Michal Matusewicz / VTT
2013 SEM-Feature analyses from Ca-exhanged samples *Emmi Myllykylä / VTTSEM-Feature and EPMA analyses from ”15 year test” samples*Joonas Järvinen and Michal Matusewicz / VTT
2014 Processing SEM-Feature data and new EPMA analyses from ”15 year test”samples. A manuscipt from the results.*Joonas Järvinen and Michal Matusewicz / VTT
*co-operation with
Samples for scanning electron microscope(SEM) and electron microprobe (EPMA)
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Samples Ca-A and MX-F
Swy-2-P
Swy-2-O
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XRD analyses• Traditional method for clay mineral studies
– Possibility to study swelling properties of clay minerals– Semiquantitative analysis method– Easy method to estimate sample purity– Fast
NameSmectite%
Quartz% others
SWY-2-O 80 15K-feldspar,Calcite
SWY-2-P 95 5 noneSWY-2-P
light 96 4 noneSWY-2-P
dark 99 1 none
MV 25A 80 20 none
SV 25A 98 2 none
VMV 60A 95 5 none
VMV 25A 95 5 none
VSV 25A 95 5 calcite
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SAMPLES:
SWY-2-O: original Na-smectite
SWY-2-Purified (SWY-2-P)Freeze dried and purifiedSWY-2-O –material
Na-montmorillonitedissolution test samples
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15.3
10.0
10.3
12.0
13.3
13.0
18.2
SWY-2-O SWY-2-P12.4
13.7
10.0
10.5
12.2
12.6
18.2
550C
200CKCl
MgCl2 + glyserin
MgCl2oriented
550C
200C
KCl
MgCl2 + glyserin
MgCl2
oriented
SEM analyses from samples prepared for TEM(Thermal Electron Microscopy):Improved sampling method
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MX-F 2011
MX-F 2012
SEM analyses from samples prepared for TEM(Thermal Electron Microscopy)
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Sample 7: MX-80 ( =1.3) 0.1 M NaCl
SEM-feature –analyses
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BSE*-image from sample MX-80 1.3 NaClBack-scattered electron
Fe-oxKfp
PyrKfp
Kfp = K-feldsparPyr = pyriteFe-ox = Fe-oxide
% totalfeatures
% totalarea
Numberof grains
Montmorillonite 49.3 98.1 606Quartz 30.1 0.8 370Pyrite 7.6 0.2 93K-feldspar 7.5 0.4 92Plagioclase 3.7 0.3 46Goethite 0.6 0.1 7Biotite 0.4 <0.1 5Fe-Silik 0.1 <0.1 1Kaolinite 0.1 <0.1 1Illiitti 0.2 <0.1 2Garnet 0.2 <0.1 2Apatite 0.2 <0.1 2Zircon 0.2 <0.1 2
1229
0102030405060708090
100
Mon
tmor
illon
ite
Qua
rtz
Pyrit
e
K-fs
p
Plag
iocl
ase
Goet
hite
Biot
ite
Fe-S
ilik
Kaol
inite
Illiit
ti
Garn
et
Apat
ite
Zirc
on
MX-80 1.3 NaCl% total features % total area
MX-80 samples
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% total features 0.7 W 1.0 W 1.3 W 1.6 W0.7
NaCl1.0
NaCl1.3
NaCl1.6
NaCl
Montmorillonite 92.8 95.5 - 91.3 - 66.8 49.3 94.0K-fsp 2.8 2.0 - 3.9 - 22.2 7.5 2.0Quartz 2.2 0.9 - 2.7 - 5.0 30.1 2.5
Plagioclase 1.5 1.0 - 0.8 - 3.0 3.7 0.5Diopside 0.3 - - - - - - -Calcite 0.2 - - 0.1 - - - -Biotite 0.1 - - 0.1 - 0.1 0.4 0.3Pyrite 0.1 0.5 - 0.9 - 2.5 7.6 0.5
Goethite - - - 0.2 - 0.1 0.6 0.1Kaolinite - - - 0.1 - - 0.1 -
Fe-Silicate - - - 0.03 - - 0.1 -Apatite - - - 0.03 - 0.1 0.2 -
Monazite - - - - 0.1 - -Illiitti - - - - - 0.2 -Garnet - - - - - 0.2 -Zircon - - - - - 0.2 -
% total area 0.7 W 1.0 W 1.3 W 1.6 W0.7
NaCl1.0
NaCl1.3
NaCl1.6
NaCl
Montmorillonite 93.3 98.7 - 95.6 - 96.3 98.07 96.0K-fsp 3.5 0.8 - 2.7 - 3.3 0.40 1.8Quartz 1.0 0.3 - 1.1 - 0.1 0.84 1.7
Plagioclase 0.3 0.2 - 0.3 - 0.2 0.31 0.1Diopside 0.1 - - - - - - -Calcite 0.5 - - 0.1 - - - -Biotite 1.3 - - 0.02 - 0.001 0.04 0.05Pyrite 0.02 0.02 - 0.1 - 0.1 0.20 0.02
Goethite - - - 0.1 - 0.0004 0.13 0.3Kaolinite - - - 0.01 - - 0.001 -
Fe-Silicate - - - 0.004 - - 0.001 -Apatite - - - 0.004 - 0.003 0.001 -
Monazite - - - - - 0.001 - -Illiitti - - - - - - 0.01 -Garnet - - - - - - 0.001 -Zircon - - - - - - 0.002 -
MX-80 MX-80 MX-80 MX-80 MX-80 MX-80
% * 0.7 W 1.0 W 1.6 W1.0
NaCl1.3
NaCl1.6
NaClSiO2 59.6 39.8 44.8 47.5 44.5 48.0 49.3Al2O
3 21.1 13.9 15.6 17.2 16.5 18.1 17.7MgO 3.3 1.6 1.9 1.5 1.7 1.6 2.3Na2O 2.5 0.1 0.6 0.1 0.4 0.4 0.0CaO 0.5 0.6 0.6 0.6 0.7 0.6FeO 2.0 2.0 2.6 2.3 2.2 2.2
H2O+ 4.5H2O- 8.9H2O 13.4 39.6 31.9 29.1 31.7 27.8 26.4Tot. 99.9
* Theoretical composition (w-%) of montmorillonite. Olin et al. 2011. Coupledbehaviour of bentonite buffer. Results of PUSKURI-project. VTT Research Notes2587. 85 p.
EPMA analyses as an average of 3 best the samples.
”15 year test” samples for mineralogical analyses
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*Allard water: groundwater solution typical of granitic terrain(pH=8.2, HCO3= 115.9, CO3=0, Na=53, K=3.9, Mg=4.3, Ca 18, Al= 0.07, Cu=0.01,SiO2=10, Fe=0.1, F=7.8, Cl=59, PO4=0.3, SO4=10 (concentrations in mg/l)Melamed and Pitkänen, 1996 (VTT Research notes 1766)
423
422
421
H2O*
Steel sinter
1
2
3
4
”15 year test” samples
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Aerobic conditionsAnaerobic conditions
Mineralogical changes were observed in samples kept in aerobic conditions.
Major changes have occurred in samples located in the middle of the copper cylinder.Secondary copper mineral phases have been formed.Two different copper minerals, cuprite (Cu2O) and malachite (Cu2(CO3)(OH)2) ), wereobserved in samples B432 and B422.
A432 A422 A412 B432 B422 B412
inner outerinner outer
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Main mineral phase: montmorillonite (Na,Ca)0.3(Al,Mg)2Si4O10(OH)2 ·nH2O (95-99 %)
Major minerals with montmorillonite:K-feldspar KAlSi3O8Plagioclase NaAlSi3O8Quartz SiO2Siderite FeCO3Sulphides * mainly pyrite FeS2Biotite K(Mg,Fe2+)3(Al,Fe3+)Si3O10(OH,F)2
Accessory minerals: Secondary mineral phases:Calcite CaCO3 Cuprite Cu2OBarite BaSO4 MalachiteCu2(CO3)(OH)2Apatite Ca5(PO4)3FIlmenite FeTiO3Zircon ZrSiO4Goethite –Fe3+O(OH)Kaolinite Al2Si2O5(OH)4Sphalerite(Zn,Fe)SIllite K1-1.5Al4(Si7-6.5Al1-1.5O20)(OH)4
Phases of the bentonite
Sulphides*:pure pyrite phases
as well asdifferent variations of
Fe-Cu-S phases
SEM-Feature analyses - results
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Percentage of themeasured area Number of analysed grains
B432 B422 B412 A432 A422 A412 B432 B422 B412 A432 A422 A412Montmorillonite 95.2 98.1 97.1 97.3 97.9 96.9 Montmorillonite 3814 2545 3275 4631 2381 1864Malachite 1.9 1.0 - - - - Malachite 19 32 0 0 0 0K-fsp 0.9 0.2 0.6 0.6 0.7 0.9 K-fsp 392 155 908 610 734 909Siderite 0.8 0.2 0.5 0.6 0.3 0.4 Siderite 265 99 623 463 390 492Plagioclase 0.7 0.2 0.7 0.5 0.4 0.4 Plagioclase 249 124 940 448 470 532Quartz 0.2 0.0 0.1 0.3 0.03 0.1 Quartz 308 90 229 688 170 101Sulphides 0.1 0.1 0.2 0.1 0.1 0.1 Sulphides 64 54 174 132 157 141Biotite 0.1 0.03 0.1 0.1 0.1 0.1 Biotite 12 5 65 12 71 84Cu-min + cuprite 0.03 0.2 0.01 - - - Cu-min + cuprite 49 141 2 0 0 0Goethite - - 0.2 - 0.1 0.2 Goethite 0 0 39 0 25 32Apatite 0.02 <0.01 0.02 0.02 0.01 0.01 Apatite 8 4 29 9 13 18Calcite 0.01 <0.01 0.5 0.5 0.3 0.8 Calcite 9 1 275 198 76 287Ilmenite <0.01 - <0.01 <0.01 0.03 0.01 Ilmenite 2 0 2 1 2 6Barite <0.01 - <0.01 0.2 0.01 <0.01 Barite 1 0 3 1 2 1Zircon <0.01 - <0.01 - 0.01 <0.01 Zircon 1 0 3 0 5 1Kaolinite <0.01 - <0.01 <0.01 <0.01 <0.01 Kaolinite 2 0 1 1 3 5Illite - - 0.01 - <0.01 <0.01 Illite 0 0 9 0 2 1Measured area(sq. mm) 9 15 21 29 25 20 sum total grains 5195 3250 6577 7194 4501 4474
sum accessoryminerals 72 146 363 210 128 351
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•Theoretical composition of themontmorillonite (w-%). Olin et.al. 2011.
Quantitative (EPMA) analysis from clay phase
A=anaerobic conditionsB= aerobic conditions
% * VTT-A VTT-BSiO2 59.6 59.3 56.8Al2O3 21.1 21.6 20.8MgO 3.3 3.3 3.0Na2O 2.5 1.3 1.3CaO - 1.0 0.8FeO - 2.9 3.8
H2O+ 4.5
H2O- 8.9
Tot. H2O 13.4 10.0 12.8Tot. 99.9 99.4 99.4
Mineralogicalchanges wereobserved in sampleskept in aerobicconditions.
Copper also exists inthe lattice of smectite,major compositionswere noticed in thevicinity of copperminerals(malachite*).
Comment CuO (w-%)A412 0.0204A432 n.d.B412 0.3054B412 0.3786B432 0.2766B432 0.1383B432 0.1981B432 0.1899B432 0.3705B432 0.3594B432 * 0.3667B432 * 0.8597B432 * 0.6362B432 * 1.3290
Conclusions of the ”15 year test”
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The general composition of smectite was similar in both test conditions• Major mineralogical changes occur in aerbobic conditions
Easy dissolving minerals have leached out and new mineral phases have born
• Secondary mineral phases (Malachite Cu2(CO3)(OH)2 and Cuprite Cu2O)have born in the inner part of the bentonite cylinder
• Copper was observed as trace element in the clay matrix in anaerobicsamples in the vicinity of Cu-minerals
• Calcite goethite and apatite are rare more common in the outer part of thecylinder
• There are (Fe-Cu-S phases) pyrite in the outer part of the cylinder
• Pure pyrite is clearly more in the inner part of the cylinder in both testenvironments
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Secondary copper minerals in sample B432
Barite grain in sample B432
Barite
Cuprite
Siderite Malachite