Speciation and role of iron phases in cement to fix heavy metals

Transcription

1 2 nd Mechanisms and modelling of waste/cement interactions international Workshop Speciation and role of iron phases in cement to fix heavy metals J. Rose 1,2, A. Benard 2,3, A. Masion 1,2, P. Chaurand 1,2, I. Moulin 4, J-Y Bottero 1,2 1: CEREGE UMR 6635 CNRS-Univ. Paul Cezanne, Aix en Provence, France 2 : ARDEVIE, Europole Méditerranéen de l Arbois, Aix en Provence, France 3: INERIS Domaine du Petit Arbois, BP 33, Aix en Provence, France 4: LERM, 10, rue Mercoeur, Paris, France rose@cerege.fr October 12-16, 2008 Le Croisic/France

2 Fixation of heavy metals (HM) in cement (OPC) Many OPC mineral phases can fix HM: C-S-H : Pb, Zn, Eu AFm : Cr (III, VI), Ettringite : almost all!!! Other minor phases. (LDH )

3 Leaching of Portland cement (as an example) ph<12.5 ph >12.5 Kamali, 2003 Cement corrosion Non-Altered zone Altered zone Dissolution fronts Dissolution / precipitation ph modification Can fix heavy metals Water (Without carbonate) Adenot, 1992 Gel of Si and Al CSH CSH décalc. Low Ca/Si Ettringite ++ Hydrog. Altered zone CSH Ca/Si Ettringite hydrogarnet CSH Ettringite hydrogarnet MonosulfoAlCa MonosulfoAlCa Portlandite

4 Leaching of Portland cement (as an example (30 days at 35 C in water) What about long term evolution (no ettringite ) Normalized concentration Altered layer Ettringite front Ca norm S Unaltered layer XGT-5000 µ-xrf (HORIBA). (Rh X-ray source, KV voltage, µm spot size distance from solid-water interface (µm)

5 Leaching of Portland cement (as an example) What about long term evolution (no ettringite ) Iron? Iron (III) is highly insoluble. Normalized concentration Fe Altered layer Ettringite front Ca norm S Unaltered layer XGT-5000 µ-xrf (HORIBA). (Rh X-ray source, KV voltage, µm spot size distance from solid-water interface (µm)

6 Iron (oxyhydr-)oxide in natural systems Alteration (hydrolysis): very long term!! Formation of FeOOH/Fe 2 O 3 Transport and fixation of numbers of species during oxidation-precipitation Fe(II) Release of numbers of species during reduction Cycle dissolutionneoformation Associated with redox front and biological activity Fe(III)OOH

7 Natural system: (in oxic zones, near neutral ph) Nutrients Pollutants FeOOH amorphous = ferrihydrite Adsorption and incorporation into the matrix (ferrihydrite) : U, Cr, Co, Ni, Mn, As, Se, Pb, U ) FeOOH / Fe 2 O 3 crystallised (Goethite, hematite ) Adsorption

8 Iron (oxy-hydr-)oxides for waste treatment Highly reactive minerals Many metals and metalloïds can be adsorbed or incorporated They are used as adsorbants (water treatment, physico-chemical processes) Coagulation-Floculation : Raw water sludge Coagulant: iron salt

9 Iron phases in cement?? µ-xrf profiles Normalized concentration Altered surface Ca norm S Fe Pb distance from solid-water interface (µm) After long term leaching : one of the only remaining phase?

10 Iron in Portland cement Anhydrous phase calcium silicates C 3 S, C 2 S 3 CaO.SiO 2 2 CaO.SiO 2 CaSO4 Calcium Aluminates C 3 A 3 CaO.Al 2 O 3 Cement hydration = dissolution + precipitation calcium-ferric aluminate C 4 AF 2 CaO (Al 2 O 3, Fe 2 O 3 ) Hydrated phases C-S-H xcao.sio 2.yH 2 O Ca(OH) 2 C 3 (A,F)H 6 3CaO.(Al 2 O 3,Fe 2 O 3 ).6H 2 O AFm AFt (ettringite) ferric phase ( hydrated phase: FeOOH)?) Möschner et al, GCA, 2008

11 Hydration of C4AF what do we know? calcium ferroaluminates C4AF? +SO4 calcium aluminates C3AF -SO4 Möschner et al GCA 2008: Not starting from C4AF Ettringite AFm Al<=>Fe? C3AH6 + Fe phase?? Teoreanu et al. (1979), Fukuhara et al. (1981), Rogers and Aldrige (1977), and Brown (1987) : amorphous FeOOH phase can exist No molecular scale investigation

12 Iron in other cements: slag, Fe C2F/C4AF FeO Fe3O4

13 Aim of the work To determine the speciation of iron on synthetic system (C4AF ) To determine the speciation of iron on OPC (still ongoing research) To determine the interaction with heavy metals on synthetic system. To determine the speciation on leached OPC?

14 Molecular scale approach: determination of the iron speciation in cement phases 1cm From cm Polarized light microscope XRD 1 mm mm µm 100 µm Mg S Cr SEM-EDX µ-xrf (fragile samples) (synchrotron (small spot size, sensitive)) XAS Micro-XAS (synchrotron) O Si Fe Ca As 2 R(Å) 4 6 Å

15 Structure at the local scale : X-ray Absorption Spectroscopy Element K1S L 1 2S L 2 2p 1/2 H 13.6 (ev). Ar K Ca Ti V Cr Mn Fe μ White line E0 1 s Pré-edge Prépic Edge= XANES EXAFS Backscatterer EC Central Atome central Atom K L 1,2,3 M 1,2,3,4, Energie ( ev) XANES = X-ray Absorption Near-Edge Spectroscopy : REDOX STATE EXAFS = Extended X-ray Absorption Fine-Structure : ATOMIC ENVIRONMENT

16 EXAFS a b μ 0 (k) μ 1 (k) EXAFS curve = Fingerprint of the atomic structure χ(k) = μ(k) μ 1(k) μ 1 (k) μ 0 (k) c d Transformée de Fourier inverse e χ(k) = μ(k) μ 1 (k) μ 1 (k) μ 0 (k)

17 XANES = fingerprint EXAFS = fingerprint Reference spectra : Redox state Symmetry αfe O Hematite 2 3 Fe O Magnetite 3 4 Fe(II) CO3 C2AF C4AF γ-feooh (Lepidocrocite) FeOOH (ferrihydrite) From 0 to 6-10 Å (multiple scattering : high e mean free path) Energy (ev)

18 eeded to see this picture. XANES = fingerprint EXAFS = fingerprint Reference spectra : Redox state Nature, number And distance of neighboring atoms k*χ(k) From 0 to 4-5 Å (single scattering : low mean free path) -1 Siderite Maghemite Magnetite Hematite Akaganeite Gœthite Nontronite (Fe-Si clay) Fe rich clay (smectite) Ferrihydrite Lepidocrocite AFm Ettringite C4AF C2F k(å -1 )

19 EXAFS In a sample : Fe is in C4AF (40%) and Ettringite (60%) Ettringite 0.6 Sample = Ettringite C4AF kχ(k) C4AF -1.2 with XANES The same K(Å -1 ) 10 12

20 Local scale study Procedure : PCA, then linear combination (XANES and EXAFS) EXAFS modelling (XANES : still difficult on heterogeneous sample) With XAS : the fit does not indicate that the mineral exist: it reflects a similar atomic structure XAS does not require long range order.

21 RESULTS : Hydration of C4AF in LW (without sulfate) Hydration liquid/solid ratio of 0.5, 10, 60. C4AF hydrated 48 H C4AF Anhydrous X-ray counts C3AH6 Complete hydration : C3AH6 Rose et al, Waste Management, theta ( ) (Co k α)

22 Hydration of C4AF in LW (without sulfate) Hydration liquid/solid ratio of 10 AFM = C4AF hydrated 24 H C4AF hydrated 48 H C4AF anhydrous 7.7 Å Anhydrous C4AF transition phase 7.5 Å C3AH6 8.2 Å Where is Fe?? theta ( ) (Co k α)

23 EXAFS results at the Fe K edge Comparison with FeOOH, Fe-oxides; carbonates, AFm, Ettringite, C4AF, C2F AFm and Ettringite from Moschner et al GCA, 2008 k*χ(k) Siderite Maghemite Magnetite Hematite Akaganeite Gœthite Nontronite (Fe-Si clay) Fe rich clay (smectite) Ferrihydrite Lepidocrocite AFm Ettringite C4AF C2F k(å -1 )

24 EXAFS results at the Fe K edge 1.2 Ferrihydrite 0.8 Goethite Ettringite k*χ(k) AFm C4AF hydrated 48 h C4AF hydrated 24 h C4AF anhydrous?? Difficulty to fit -0.4 AFm and Ettringite from Moschner et al GCA, 2008 Calculated curve 59 % C4AF 15 % ferrihydrite 19 % Goethite k(å -1 ) ±10-15% 15%

25 EXAFS results at the Fe K edge EXAFS modelling χ(k) = N i=1 N i S 0 2 kr i amplitude phase f i ( θ,k,r i )e 2σ i 2 k 2 i λ(k) e 2R sin( 2kR i +φ i (k)+ 2δ c (k)) N Fe N Fe - -Ca Fe-O = 6 Ca = 8 R O Ca R Fe R Fe - -Ca Fe-O = 2 Å Ca = 3.4 Å

26 EXAFS results at the Fe K edge EXAFS modelling experimental C4AF (48H) calculated k 3 χ(k) k(å -1 ) 48 H Fe - Fe distance : how can we go further?

27 Structural approach Fe-Fe = Fe-Fe = Å Å Fe-Fe = Å Fe-Fe > 3.70Å

28 Structural approach Atomic pair Distance (Å) Number of Fe neighbours Goethite (α-feooh) Fe--Fe Fe--Fe Fe--Fe Ferrihydrite (amorphous- FeOOH) Fe--Fe Fe--Fe Hemathite (α-fe2o3) Fe--Fe Fe--Fe Fe--Fe Fe--Fe C3AH6 AFm Fe-Ca 3.51Å 6 Fe-Ca 3.35 Å 6

29 Hydration of C4AF (in LW) 48 H 24 H.. C4AF + FeOOH FeOOH + hydrogarnet What about Portland cement??

30 Iron in hydrated Portland cement 1.2 Ferrihydrite k*χ(k) Goethite Ettringite AFm C4AF hydrated 48 h hydrated portland cement -0.4 Calculated curve 30 % C4AF 12 % FeOOH 44 % AFm k(å -1 )

31 Iron in hydrated Portland cement AFm Ettringite?? k*χ(k) Ferrihydrite Goethite Ettringite AFm C4AF hydrated 48 h hydrated portland cement -0.4 Calculated curve 30 % C4AF 12 % FeOOH 44 % Ettringite k(å -1 )

32 Iron in hydrated Portland cement k*χ(k) Calculated curve 30 % C4AF 12 % FeOOH 44 % AFm hydrated portland cement surface of leached portland cement Calculated curve 32 % C4AF 36 % FeOOH 20 % AFm k(å -1 )

33 In OPC at the micro scale #3 500µm #2 #1 µ-xrf (Fe) Lucia (SLS) (µ-xanes + µ-exafs) #4 αfe 2 O 3 Hematite Fe 3 O 4 Magnetite #4 #3 #2 Fe(II) CO3 C2AF C4AF #1 γ-feooh (Lepidocrocite) FeOOH (ferrihydrite) Energy (ev) Energy (ev)

34 Summary Hydration of C4AF (-SO 4 ) : FeOO + Fe in hydrogarnet (No Fe and AFm??) In presence of SO4 (CaSO4) : ettringite (Mochner et al, 2008) In OPC : remaining C4AF (local scale) + FeOOH + AFm (??). More amorphous Fe at the surface.

35 What is the role of iron phases in heavy metal fixation Stage 1: C4AF + Heavy metal interactions Stage 2 : on real system

36 C4AF hydrated in presence of metals Fe and lead : isotherms: (L/S ratio (0.5 to 60); with LW, [Pb] initial from 10-3 to mol/l) Everything fixed by the solid Nothing in solution

37 Reactivity between iron phases and metals (pure system) C4AF hydrated in presence of metals Fe and lead : isotherms: (L/S ratio (0.5 to 60); with LW, [Pb] initial from 10-3 to mol/l) Everything fixed by the solid Nothing in solution

38 EXAFS at the Pb L edge Pb radial distribution function EXAFS at the Pb LIII edge (Pb+FeOOH) FDR O Fe 3.3 H 2 O R(Å) R(Å) Experimental Calculated (Bargar et al, 1998) 3.9 k 3 *χ(k) K(Å -1 )

39 C4AF hydrated in presence of metals Fe in presence of Cr 10-4 [Cr] s mol.g C4AF hydrated with Cr(VI) C4AF hydrated with Cr(III) of the [Cr(III)+lime water] solution e [Cr] (mol.l -1 ) e

40 EXAFS at the Cr K edge Atomic pair R() σ() N Residue Cr--Cr/Fe Cr--Ca Cr--Cr/Fe Cr C3A(Cr)H6 (Cr)FeOH

41 C4AF in presence of Cr(VI) X-ray counts Å 7.5 Å 8.2 Å 7.5 Å 9.6 Å C4AF hydrated 24 H C4AF hydrated 48 H Anhydrous C4AF C4AF + Cr(VI) fe/cr=0.15 Anhydrous C4AF C3AH theta ( ) (Co k α)

42 C4AF in presence of Cr(VI) Al-Ca layer Interlayer Al-Ca Layer - Cr(VI)O 2- Interlayer 4 C4AF + Cr(VI) Cr(VI) in solution (100%) Al-Ca Layer Energy (ev) Ca Al AFm Interlayer site

43 And in leached Portland cement? 2.5 Pb A B 2 1.5???? Fe Fe Si

44 Lead and C-S-H 29 Si NMR CSH hydrated in presence of Pb New peak at ppm Q 1 Q 2 Q ' 1 Q 2 '' Q '' ppm -95 Ca FDR 0.5 Experimental Calculated EXAFS at the Pb LIII edge CSH structure Si Pb Si Rose et al, langmuir,, R(Å) ~1 Si at 3,75Å de Pb ~0,8 Ca at 3,58Å de Pb

45 First EXAFS results (noisy) 0.8 First fits with Fe in the second coordination sphere k 2 χ(k) Pb in leached Portlant cement Fe in second coordination sphere Pb in hydrated Portlant cement K(Å -1 )

46 EXAFS results Pb in leached Portlant cement Pb in hydrated Portlant cement FFT More Iron No enough R+Δ(R) (Å)

47 Conclusion Existence of FeOOH amorphous phase after cement hydration Iron phases formed after C4AF hydration strongly incorporate metals (Cr, Pb ) Metal and iron in cement: needs further investigation (µ-xrf at the micron scale in leached zones ) Implications: iron(iii) phases may play a positive role for the long term fixation of metals and metalloids but under oxic conditions (reductive dissolution of iron).

48 Acknowledgment J-L Hazemann and O. Proux (ESRF, FAME beamline) V. Briois (LURE, D44 beamline and SOLEIL Samba) A-M Flank (SLS-Soleil, Lucia beamline) Funding from the European Community through the INERWASTE Craft European program, and the YPREMA company.

49 µ-xrf Ca high S Mg 500µm low 400 µm XGT-5000 X-ray spectro-microscope (HORIBA). (Rh X-ray source, 15 KV voltage, 10 µm spot

50 Reactivity of Iron oxide Fonction de distribution radiale Uranium U-O U-OH U-Fe lead Selenate R(Å) Pb-O Pb-Fe Fonction de distribution radiale R(Å) Fonction de distribution radiale Highly reactive particles (U, Cr, Co, Ni, Mn, As, Se, Pb, U ) Se-O Se-Fe R(Å)

51 Reactivity of iron oxide

52 Structural approach Atomic pair Distance Number C3AH6 Al/Fe-O 1.91Å 6 Fe--Ca 3.51Å 6 AFm Al/Fe-O 1.90Å 6 Al/Fe--Ca 3.35Å 6

53 EXAFS Transformée de Fourier: Probabilité de présence des atomes voisins de l élément X st coordination sphere 2nd coordination sphere F(R) R(A) Central atom

54 FeCl3 Nucleation and growth of FeOOH (in water) = Ferrihydrite?? Edge Double corner Fe24 (16Å) Fe(NO)3 (Bottero et al, 1994, Rose et al, 1997)

55 Modeling Calculation: Translation into a chemical-transport model code (CHESS-HYTEC) Translation of experimental data into thermodynamic data For Pb retention sites (Nonat C-S-H model (Nonat et al, 01, Pointeau,01) SiOH + Ca 2+ + Pb H 2 O 4H + <==> SiOCaPb(OH) 3 log K(25 C) = SiOH + SiOH + SiO 2(aq) + Ca 2+ + Pb 2+ -H 2 O 4H + <==> SiOH-CaSiOPb-SiOH log K(25 C) = Experimental (µ-xrf) Calculated (CHESS-HYTEC) Benard,, Rose et al., in prep