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, 13545 Aix en Provence, France 2 : ARDEVIE, Europole Méditerranéen de l’Arbois, 13545 Aix en Provence, France 3: INERIS Domaine du Petit Arbois, BP 33, 13545 Aix en Provence, France 4: LERM, 10, rue Mercoeur, 75011 Paris, France rose@cerege.fr http://Se3d.cerege.fr http://nano.cerege.fr October 12-16, 2008 Le Croisic/France
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…)
Leaching of Portland cement (as an example) Cement corrosion pH<12.5 Non-Altered zone pH >12.5 Altered zone Dissolution / precipitation pH modification Kamali, 2003 Can fix heavy metals Can fix heavy metals Dissolution fronts Gel of Si and Al CSH CSH CSH CSH décalc. Low Ca/Si Ca/Si Ettringite Ettringite Ettringite ++ Water (Without carbonate) hydrogarnet Hydrog. hydrogarnet MonosulfoAlCa MonosulfoAlCa Portlandite Adenot, 1992 Altered zone
Leaching of Portland cement (as an example ( 30 days…at 35°C in water ) � What about long term evolution (no ettringite…) 2.5 2.5 2.5 Ca norm Ca norm Ca norm S S S XGT-5000 µ-XRF 2 2 2 Normalized concentration Normalized concentration Normalized concentration (HORIBA). (Rh X-ray d d source, 15-50 KV voltage, r r e e e e 1.5 1.5 1.5 r r 100-10 µm spot size y e y e a a t t l l A l l A 1 1 1 Unaltered layer Unaltered layer E E t t t r i n g i t e t r i n g i t e 0.5 0.5 0.5 f r o n t f r o n t 0 0 0 0 0 0 2000 2000 2000 4000 4000 4000 6000 6000 6000 8000 8000 8000 distance from solid-water interface (µm) distance from solid-water interface (µm) distance from solid-water interface (µm)
Leaching of Portland cement (as an example) � What about long term evolution (no ettringite…) � Iron ? Iron (III) is highly insoluble. 2.5 Fe Fe Ca norm S XGT-5000 µ-XRF 2 Normalized concentration (HORIBA). (Rh X-ray source, 15-50 KV voltage, d d r r e e e 1.5 e 100-10 µm spot size r r e y y e a a t t l l A l l A 1 Unaltered layer Unaltered layer Ettringite Ettringite 0.5 front front 0 0 2000 4000 6000 8000 distance from solid-water interface (µm)
Iron (oxyhydr-)oxide in natural systems Alteration (hydrolysis): very long term!! Formation of FeOOH/Fe 2 O 3 Release of Transport and fixation of numbers of numbers of species during species during oxidation-precipitation reduction Fe(II) Cycle dissolution- neoformation Associated with redox front and biological Fe(III)OOH activity
Natural system: (in oxic zones, near neutral pH) Pollutants Pollutants Nutrients Nutrients FeOOH amorphous FeOOH amorphous FeOOH / Fe 2 FeOOH / Fe 2 O O 3 3 crystallised crystallised = ferrihydrite = ferrihydrite (Goethite, hematite… …) ) (Goethite, hematite Adsorption and Adsorption and incorporation into the incorporation into the Adsorption Adsorption matrix (ferrihydrite) : matrix (ferrihydrite) : U, Cr, Co, Ni, Mn, As, Se, Pb, U…)
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
Iron phases in cement?? µ-XRF profiles Altered Altered 2.5 2.5 Ca norm Ca norm surface surface S S Fe Fe 2 2 Normalized concentration Normalized concentration Pb 1.5 1.5 1 1 0.5 0.5 0 0 0 0 2000 2000 4000 4000 6000 6000 8000 8000 distance from solid-water interface (µm) distance from solid-water interface (µm) After long term leaching : one of the only remaining phase? After long term leaching : one of the only remaining phase?
Iron in Portland cement Anhydrous phase calcium Calcium calcium-ferric silicates Aluminates aluminate C 3 S, C 2 S C 3 A C 4 AF 3 CaO.SiO 2 3 CaO.Al 2 O 3 2 CaO (Al 2 O 3 , 2 CaO.SiO 2 Fe 2 O 3 ) Cement hydration = CaSO4 CaSO4 dissolution + precipitation Hydrated phases C-S-H C 3 (A,F)H 6 xCaO.SiO 2 .yH 2 O 3CaO.(Al 2 O 3 ,Fe 2 O 3 ).6H 2 O AFm Mö öschner schner et al, et al, M Ca(OH) 2 AFt (ettringite) GCA, 2008 GCA, 2008 “ferric” phase (‘hydrated phase: FeOOH)?)
Hydration of C4AF what do we know? calcium calcium ferroaluminates aluminates C4AF? C3AF -SO4 +SO4 Mö öschner schner et al et al M Al<=>Fe? Ettringite Ettringite AFm AFm GCA 2008: GCA 2008: Not starting from C4AF Not starting from C4AF C3AH6 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
Iron in other cements: slag,… � Fe � C2F/C4AF � FeO � Fe3O4
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…?
Molecular scale approach: determination of the Molecular scale approach: determination of the iron speciation in cement phases iron speciation in cement phases Polarized light microscope Polarized light microscope 100 µm SEM-EDX XRD… … XRD µ-XRF Mg (fragile samples) (synchrotron 1 mm S (small spot size, sensitive)) 1cm Cr From cm From cm µ µm m mm mm XAS XAS Si O Fe Fe Ca Micro- -XAS XAS Micro Å Å As (synchrotron) (synchrotron) 2 R(Å) 4 6
Structure at the local scale : X-ray Absorption Spectroscopy Element K1S L 1 2S L 2 2p 1/2 H 13.6 (eV) Edge= XANES Backscatterer …. Ar 3205.9 326.3 250.6 EXAFS EXAFS μ K 3608.4 378.6 297.3 White line Ca 4038.5 438.4 349.7 … Ti 4966 560.9 460.2 V 5465 626.7 519.8 Central Atom Atome central Cr 5989 696 583.8 Pré-edge Prépic Mn 6539 769.1 649.9 E E 0 0 7112 Fe 844.6 719.9 E E C C 1 s 1 s M 1,2,3,4,5 68 6 80 00 0 7 70 00 00 0 7 72 20 00 0 74 7 40 00 0 76 7 60 00 0 78 7 80 00 0 80 8 00 00 0 L 1,2,3 Energie ( eV) K XANES = X-ray Absorption Near-Edge Spectroscopy : REDOX STATE EXAFS = Extended X-ray Absorption Fine-Structure : ATOMIC ENVIRONMENT
EXAFS a b μ 1 (k) μ 0 (k) c d EXAFS curve = Fingerprint of χ ( k ) = μ ( k ) − μ 1 ( k ) μ 1 ( k ) − μ 0 ( k ) the atomic structure Transformée de Fourier inverse e χ ( k ) = μ ( k ) − μ 1 ( k ) μ 1 ( k ) − μ 0 ( k )
XANES = fingerprint EXAFS = fingerprint � Reference spectra : α Fe 2 O 3 Hematite � Redox state Fe 3 O 4 Magnetite Fe(II) CO3 � Symmetry C2AF C4AF γ -FeOOH (Lepidocrocite) QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a QuickTime™ and a None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor None decompressor are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. are needed to see this picture. FeOOH (ferrihydrite) From 0 to … … 6 6- -10 10 Å Å From 0 to 7100 7120 7140 7160 7180 (multiple scattering : high e mean free path) (multiple scattering : high e mean free path) Energy (eV)
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