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e-mail: sabine.petit@univ- poitiers.fr Pauline ANDRIEUX Sabine PETIT Alain DECARREAU FRE3114 CNRS, HydrASA Université de Poitiers 40, ave. du Recteur Pineau 86022 POITIERS Cedex FRANCE

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Synthesis of Clay Minerals and the Relationship between Formation Processes and Crystal Chemistry. Pauline ANDRIEUX Sabine PETIT Alain DECARREAU FRE3114 CNRS, HydrASA Université de Poitiers 40, ave. du Recteur Pineau 86022 POITIERS Cedex FRANCE. e-mail: [email protected]. - PowerPoint PPT Presentation

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Page 1: e-mail: sabine.petit@univ-poitiers.fr

e-mail: [email protected]

Pauline ANDRIEUX

Sabine PETIT

Alain DECARREAU

FRE3114 CNRS, HydrASAUniversité de Poitiers

40, ave. du Recteur Pineau86022 POITIERS Cedex

FRANCE

Page 2: e-mail: sabine.petit@univ-poitiers.fr

- determine the experimental conditions which led to mineral crystallization (in very simplified systems)

constrain possible conditions of formation for those minerals

- obtain good reference minerals with monitored crystal chemistry

determine their spectroscopic fingerprint

Page 3: e-mail: sabine.petit@univ-poitiers.fr

Beidellite Nontronite

Tetrahedral charge

Montmorillonite

Octahedral charge

Fe3+-Montmorillonite

(Theoretical)

Page 4: e-mail: sabine.petit@univ-poitiers.fr

(Theoretical)

(Si (4-x) Al, Fe3+x) Fe3+

2 O10 (OH)2 M+x

IV VI

Fe3+- nontronite(Si (4-x) Fe3+

x) Fe3+2 O10 (OH)2 M+

x

nontronite(Si (4-x) Alx) (Al, Fe3+ ) 2 O10 (OH)2 M+

xBeidellite

Page 5: e-mail: sabine.petit@univ-poitiers.fr

Ditrigonal cavity

Ditrigonal cavity

Tetrahedral sheet

Octahedral sheet

R(VI), �

OHR(IV)

OTetrahedral sheet

dioctahedral (tv) dioctahedral (cv)

Ditrigonal cavity

Ditrigonal cavity

Tetrahedral sheet

Octahedral sheet

R(VI),

OH

R(IV)

OTetrahedral sheet

Schematic representation of the octahedral sheet

Page 6: e-mail: sabine.petit@univ-poitiers.fr

dioctahedral (tv) dioctahedral (cv)

O H\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

h

OH

R = Al, Fe3+

Page 7: e-mail: sabine.petit@univ-poitiers.fr

dioctahedral (tv) dioctahedral (cv)

OH

R = Al, Fe3+

Fe3+

H+

Al

O

vacancy

Page 8: e-mail: sabine.petit@univ-poitiers.fr

Ferruginous smectite SWa-1

NIR MIROH region+ OH

(Si3.70Al0.30 ) (Al0.57 Fe3+1.33 Mg0.10) O10(OH)2 Na+

0.40

Page 9: e-mail: sabine.petit@univ-poitiers.fr

Ferruginous smectite SWa-1

NIR MIR

2.29

4361

+ Fe3+2OH

12.2

820

Fe3+2OH

Wavelength (µm)

Page 10: e-mail: sabine.petit@univ-poitiers.fr

Ferruginous smectite SWa-1

NIR MIR

AlAl

4563

2.24

4464

+ AlFe3+OH

AlFe3+OH

11.4

875

Wavelength (µm)

Page 11: e-mail: sabine.petit@univ-poitiers.fr

Ferruginous smectite SWa-1

AlAl

4563

AlA

l92

0

2.19

4563

+ Al2OH

456310.87

920

Al2OH

NIR MIR

Wavelength (µm)

Page 12: e-mail: sabine.petit@univ-poitiers.fr

OH

Fundamental vibrationsOH combination

OH

OH overtones (µm)

(cm-1)_

MIRNIRUV VisFar IR

OHOH OHSiO SiO11000 4000 400

0.9 2.5 25

H2OH2OH2OH2OH2O

2WOH >> W2OH

X = 1/2W2OH - WOH = -85.6 cm-1

Petit et al. (2004) Phys. Chem. Minerals, 31, 585-592.

X : anharmonicity constant

Page 13: e-mail: sabine.petit@univ-poitiers.fr

Wavenumber (cm-1)

4600 4350 4100

2.17 2.30 2.44Wavelength (µm)

SWa-1

2.24

4464

2.29

4361

Ref

lect

ance

Reflects different conditions of formation

NIR is most often not self – sufficient but it could help

AlFeOHFe2OH

(Al2OH)

Page 14: e-mail: sabine.petit@univ-poitiers.fr

Requirements:

- minimize the variables of the system

- reproducibility

- homogeneous and definite chemical composition

Use an amorphous gel with the clay stoechiometry

Page 15: e-mail: sabine.petit@univ-poitiers.fr

Basic reaction :

silica source: SiO2Na2O

metal source: salt (chloride, nitrate…)

equilibrated agent: HCl, NaOH, …..

Ex: nontronite

4 SiO2Na2O + 2 FeCl3 + 2 HCl 8 NaCl + H2O + Si4 Fe2 O11

beidellite

4 SiO2Na2O + 2 AlCl3 +2 HCl 8 NaCl + H2O + Si4 Al2 O11

Coprecipitation of gel with the clay stoechiometry

Decarreau (1983) ’s protocol

Page 16: e-mail: sabine.petit@univ-poitiers.fr

The coprecipitate is:

- centrifuged and washed

- dried and crushed (or frieze dried)

The starting material is ready to use.

Page 17: e-mail: sabine.petit@univ-poitiers.fr

Aim:

Reproduce in laboratory clay formation

Clays similar to clays formed at the earth surface are synthesized by hydrothermal treatment at T <= 250°C (at equilibrium water P)

From kaolinite syntheses performed at several temperatures (180-300°C), Rayner [1962] calculated a half-reaction time of 16.104 years at 20°C.

Problem: we cannot use geological times !

The rate constant of an heterogeneous chemical reaction in aqueous phase is given by :

k = A.exp - (E/RT)

Ageing time of clay synthesis can be minimized by an increase of T.

Page 18: e-mail: sabine.petit@univ-poitiers.fr

< 100°C : PFA reactors (copolymer of ethylene tetrafluor)

From 100 to 240°C : reactors with metal bodies and removable Teflon liners

Starting material (300-500 mg)

+distilled water

(30 cc)

(+ HCl or NaOH)

Teflon

Metal

Page 19: e-mail: sabine.petit@univ-poitiers.fr

(Theoretical)

Fe3+- nontronite(Si (4-x) Fe3+

x) Fe3+2 O10 (OH)2 M+

x

nontronite

Page 20: e-mail: sabine.petit@univ-poitiers.fr

Starting from Fe2+:

2 SiO2Na2O + FeCl2 Si2FeNa2O6 + 2 NaCl

after drying the gel, iron is oxidized

pH is adjusted to 12.5 with NaOH

ageing time 4 weeks

T = 75, 90, 100, 125, 150 °C *

*aegirine (Na Fe3+Si2O6 ) is obtained at higher temperatures (Decarreau et al. Eur. J. Mineral. 16, 85-90, 2004)

(Decarreau et al. Clays&Clay Min. 322-337, 2008)

Page 21: e-mail: sabine.petit@univ-poitiers.fr

0 10 20 30 40 50 60 70 80 90

T (°C)

150

125

110

100

90

75gel

001 02-11004 13-20 06-33

15-24-31

Si3.25Fe3+0.75 Fe3+

2 O10(OH)2 Na+0.75

(Decarreau et al. Clays&Clay Min. 322-337, 2008)

Page 22: e-mail: sabine.petit@univ-poitiers.fr

51986975

20

25

30

35

40

45

50

55

60

65

%R

éfle

cta

nce

(O

ffse

t)

4500 5000 5500 6000 6500 7000 7500

Wavenumber (cm-1)

Wavelength (µm)

2.29

1.43

1.92

43732Fe3+2OH

H2O

Fe3+2OH

H2O

fresh gel

starting gel

nontronite

2.414144

?

Page 23: e-mail: sabine.petit@univ-poitiers.fr

100°C

110°C

125°C

150°C

75°C

90°C

60

64

68

72

76

80

5000 6000 7000

Wavenumber (cm-1)

+ Fe3+2OH2 Fe3+

2OH

H2O

H2O

?%

Ref

lect

anc

e (

offs

et)

6982 5204 4373 4144

1.43Wavelength (µm)

1.92 2.29

2.41

1.47

6800

Page 24: e-mail: sabine.petit@univ-poitiers.fr

- Well crystallized nontronite can be synthesized under either oxidizing or partially reducing conditions.

- the range of synthesis pH is narrow (12 to 12.5)- at lower pH hematite or hisingerite are

formed- at higher pH and for temperatures >180°C

aegirine is formed

Thermodynamic equilibrium diagram of aegirine with 2:1 phyllosilicates with the following structural formula: Si (4-x) Fe3+

x Fe3+2 O10 (OH)2 Na+

x

after Decarreau et al. (2004) Eur. J. Mineral., 85-90.

Page 25: e-mail: sabine.petit@univ-poitiers.fr

(Theoretical)

(Si (4-x) Al, Fe3+x) Fe3+

2 O10 (OH)2 M+x

IV VI

Fe3+- nontronite(Si (4-x) Fe3+

x) Fe3+2 O10 (OH)2 M+

x

nontronite(Si (4-x) Alx) (Al, Fe3+ ) 2 O10 (OH)2 M+

xBeidellite

Page 26: e-mail: sabine.petit@univ-poitiers.fr

Starting gel Al/Fe Fe3+/Fe2+ T (°C) pHf result

0.2/1.8 Fe3+ 150°C 10.82 nontronite

170°C 10.81 nontronite

200°C 10.68 nontronite

220°C 10.28 nontronite + zeolite

Fe2+ 150°C 11 nontronite + zeolite

170°C 10.78 nontronite + zeolite

200°C 10.66 nontronite + zeolite

0.4/1.6 Fe3+ 170°C 10.12 hisingerite

200°C 10.23 hisingerite

220°C 10.23 hisingerite

Fe2+ 170°C 11.59 nontronite + zeolite

200°C 11.27 nontronite + zeolite

10.71 nontronite

220°C 10.81 zeolite +nontronite

Page 27: e-mail: sabine.petit@univ-poitiers.fr

1000

2000

3000

4000

5000

6000

3 13 23 33 43 53 63

Position (°2Theta)

Co

un

ts

3 13 23 33 43 53 63

6000

5000

4000

3000

2000

1000Position (°2Theta) Cuk

Cou

nts

15.9 Å4.52 Å

3.64 Å

2.58 Å 1.528 Å

XRD powder pattern

1.919 Å

2.294373

2.224510

1.915224

1.436980

40

45

50

55

60

65

70

75

80

85

90

95

100

% R

efle

cta

nce

4500 5000 5500 6000 6500 7000 7500

Wavenumber (cm-1)

Wavelength (µm)

1.466833

2 Fe3+2OH

H2O

H2O

+ Fe3+2OH

Page 28: e-mail: sabine.petit@univ-poitiers.fr

Starting gel Al/Fe Fe3+/Fe2+ T (°C) pHf result

1/1 Fe2+ 200°C 11.51 nontronite + zeolite

10.39 Al-nontronite

6.73 Fe3+-beidellite

1.8/0.2 Fe3+ 220°C 10.38 beidellite + zeolite

Fe2+ 220°C 9.34 beidellite

7.30 beidellite + zeolite

4.99 kaolinite

7.67 beidellite + kaolinite

Page 29: e-mail: sabine.petit@univ-poitiers.fr

%R

efle

cta

nce

(O

ffse

t)

4500 5000 5500 6000 6500 7000 7500 8000

Wavenumber (cm-1)

Wavelength (µm)

1.8Al0.2Fe

0.2Al1.8Fe

0.4Al1.6Fe

1Al1Fe pHi=6.3, pHf=6.7

2Fe

1Al1Fe pHi=8.4, pHf=10.4

6982

1.43

7100

1.41H2O

5204

1.92

6800

1.47H2O

2 Fe3+2OH

2 Al3+2OH

+ R3+2OH

Page 30: e-mail: sabine.petit@univ-poitiers.fr

1.8Al0.2Fe

0.2Al1.8Fe

0.4Al1.6Fe

1Al1Fe pHi=6.3, pHf=6.7

2Fe

1Al1Fe pHi=8.4, pHf=10.4

4200 4400 4600 4800

Wavenumber (cm-1)

% R

efle

ctan

ce

(O

ffse

t)

4462

Wavelength (µm)

4566

4373

2.29

2.24

2.19 + Fe3+2OH

+ Al2OH

+ AlFe3+OH

Page 31: e-mail: sabine.petit@univ-poitiers.fr

- nontronite can crystallize under partially reducing or oxidizing conditions if available water, Si, Fe and alkaline pH without biology and organic acids

- poorly crystalline nontronite can be obtained for days at low temperature

- however, the pH conditions range is narrow

- the range increases when Al increases (same with Mg)

- pH conditions hardly control crystal-chemistry of synthesized clays

- high T are not convenient for nontronite

- nontronite/zeolite paragenesis may correspond to the same geochemical conditions

What is the «stability » of nontronite (or hingerite) under rather acidic atmosphere ? (no H+ activity ?)

Page 32: e-mail: sabine.petit@univ-poitiers.fr

YESTERDAY topic

(Identification of phyllosilicates)

- poorly crystalline nontronite give the same NIR signal than well crystallized one (width of the OH combination band does not decrease significantly)

- doublet (or triplet) in the 2.2 µm region does not necessarily reflect the presence of several minerals (… and is the mystery of the doublet at 2.2 and 2.28 µm solved? )

- NIR alone is most often not enough to characterize muti-component samples unambiguously