Mineralogical studies of montmorillonite - VTTkyt2014.vtt.fi/boa_workshop_19082014/Tiljander.pdf · X-ray diffraction (XRD): until 5/2012 ... since 6/2013: Bruker D8 Discover A25

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1Mia Tiljander, 19.8.2014

Mineralogical studies of montmorillonite

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


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

3Mia Tiljander , 19.8.2014

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


Research made in BOA project


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)

6Mia Tiljander 19.8.2014

Samples Ca-A and MX-F

Swy-2-P

Swy-2-O


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


SAMPLES:

SWY-2-O: original Na-smectite

SWY-2-Purified (SWY-2-P)Freeze dried and purifiedSWY-2-O –material

Na-montmorillonitedissolution test samples


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


MX-F 2011

MX-F 2012

SEM analyses from samples prepared for TEM(Thermal Electron Microscopy)


Sample 7: MX-80 ( =1.3) 0.1 M NaCl

SEM-feature –analyses


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


% 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


*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


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


Stereomicroscope image from sample B432


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


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


•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”


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


Secondary copper minerals in sample B432

Barite grain in sample B432

Barite

Cuprite

Siderite Malachite


Left: pyrite with light bornite rim. Right: small pyrite balls

Goethite and calcite grains in sample A412

Documents

Mineralogical studies of montmorillonite - VTTkyt2014.vtt.fi/boa_workshop_19082014/Tiljander.pdf · X-ray diffraction (XRD): until 5/2012 ... since 6/2013: Bruker D8 Discover A25