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The Fe II-III oxyhydroxycarbonate fougerite mineral and green rusts in hydromorphic soils

The Fe II-III oxyhydroxycarbonate fougerite mineral and green rusts in hydromorphic soils J.-M. R. Génin et al. Institut Jean Barriol Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564 CNRS- Université Henri Poincaré-Nancy 1,

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The Fe II-III oxyhydroxycarbonate fougerite mineral and green rusts in hydromorphic soils

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  1. The FeII-III oxyhydroxycarbonate fougerite mineral and green rusts in hydromorphic soils J.-M. R. Génin et al. Institut Jean Barriol Laboratoire de Chimie Physique et Microbiologie pour l'Environnement,UMR 7564 CNRS-Université Henri Poincaré-Nancy 1, Département Matériaux et Structures, ESSTIN, 405 rue de Vandoeuvre, F-54600 Villers-lès-Nancy, France. E-Mail:genin@lcpme.cnrs-nancy.fr Green rusts and fougerite in the biogeochemical cycle of iron, A. Herbillon and J.-M. R. Génin Editors, C. R. Geoscience, 338 (2006) 393-498. “Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

  2. Organic matter Humus Total Organic Carbon Exchangeable Mn Exchangeable Fe Nitrate-N Fe(II) of total Fe CaCO3 (wt-%) (mg kg-1) (wt-%) (mg kg-1) (%) (mg kg-1) 0 2 4 6 20 40 60 0 0,2 0,4 0 10 20 0 1 2 0 10 20 0 0 0 0 0 0 Ferric oxyhydroxides 1 1 1 1 1 Depth (m) 2 2 2 2 2 2 fougerite 3 3 3 3 3 3 4 4 4 4 4 4 Vibeke Ernstsen, Geological Survey of Denmark and Greenland Hydromorphic gley soil profile Valley of the Vraine river, 10 km north of Vittel (France) The morphology of hydromorphicgley soils, first described in 1905 by G. N. Vysostskii1, remained a mystery up till recently when Mössbauer spectroscopy has been the determining tool to identify the iron containing compound that lies in a horizon formed under waterlogged conditions in an anaerobic environment, which encourages the reduction of iron compounds by microorganisms and often causes mottling of soil into a patchwork of greenish-blue-grey and rust colors. This finding is of utmost practical importance since there exists a correlation between the concentration of some pollutants and that of FeII ions that are dissolved in the water table. For instance, nitrates disappear where FeII appear in the anaerobic zone by following the water level in equilibrium with a mineral, which has been given the name of fougerite (IMA 2003-05). It occurs to be the FeII-III oxyhydroxycarbonate of formula FeII6(1-x) FeIII6x O12 H2(7-3x) CO3 where the domain of x is limited to [0.33-0.67]. Originally studied for explaining the corrosion of iron-based materials, FeII-III hydroxysalts belong to the family of layered double hydroxides (LDH) and are constituted of layers,[FeII(1-x) FeIIIx (OH)2 ]x+, and interlayers, [(x/n)An-(mx/n)H2O]x-.Here, we shallconsider only the case where the anion is CO32-. • 1G. N. Vysostskii, Gley, Pochvovedeniye, 4 (1905) 291-327. Depth profile analysis of a gleysol in Denmark through the redox zone between 2 and 3 meters deep. From left to right: Concentration of total organic carbon, calcium carbonate, nitrate, exchangeable iron, {[FeII] / [Fetotal]} and exchangeable Mn. Nitrates disappear when FeII appears.

  3. The FeII-III hydroxycarbonate can be prepared by coprecipitation of a mixture of ferrous and ferric salts in the presence of carbonate ions when adding NaOH solution. Mössbauer spectra measured at 78 K demonstrate that the range of composition for x = [FeIII]/[Fetotal] is limited to [1/4, 1/3] since for x > 1/3 there exists two phases , the Green rust at x = 1/3, GR(CO32-), and another phase, a-FeOOH. The spectrum of GR(CO32-) consists of 2 ferrous doublets D1 and D2 with large quadrupole splitting D and one ferric doublet D3 with small splitting. D2 D2 x = 0.25 x = 0.33 D3 x 0.25 D1D2D3 d 1.28 1.28 0.47 D 2.97 2.55 0.43 RA 62 12 26 x 0.33 D1D2D3 d 1.28 1.28 0.47 D 2.97 2.55 0.43 RA 48 18 34 x 0.4 D1+D2D3S1S2 H 490 482 d 1.30 0.50 0.43 0.54 D 2.9 0.47 0 0 RA 52 25 17 6 x 0.5 D1+D2D3S1S2 H 473 453 d 1.29 0.49 0.39 0.53 D 2.87 0.48 0 0 RA 39 19 26 16 Hyperfine parameters H (kOe), d and D (mm s-1), RA(%) D1 Transmittance % D3 D1 Transmittance % 78 K (a) (b) 78 K Velocity (mm s-1) 100 S2 S2 S1 S1 99 x = 0.4 D3 x = 0.5 D3 Transmittance % Transmittance % D’1 D’1 78 K 98 (c) (d) 78 K 97 97 92 96 95 FeII-FeIII ions coprecipitation giving for x > 1/3 a mixture of phases: GR(CO32-) and goethite 87 94 FeII(1-y)FeIIIy(OH)2 (y/2)CO3 with 1/4< y < 1/3 -4 -4 -3 -3 -2 -2 -1 -1 0 0 1 1 2 2 3 3 4 4 82 Velocity (mm s-1) 101 101 99 99 97 97 95 93 95 91 Velocity (mm s-1) 93 89 91 87 -12 -12 -8 -8 -4 -4 0 0 4 4 8 8 12 12 Velocity (mm s-1)

  4. x = 0.33 XRD and Mössbauer spectroscopy allowed us to determine the structure of all FeII-III hydroxysalts green rusts. (b) With synchrotron GR(CO32-) R(-3)ma = 0.317588(2) nm c = 2.27123(3) nm R. Aissa, M. Francois, C. Ruby, F. Fauth, G. Medjahdi, M. Abdelmoula, J.-M. Génin, Formation and crystallographical structure of hydroxysulphate and hydroxycarbonate green rusts synthetised by coprecipitation  • J. Phys. Chem. Solids, 67 (2006)1016-1019. (a) FeII4 FeIII2 (OH)12 CO3 Structure of GR(CO32-) FeII-III hydroxycarbonate at x = (1/3); (a) Three-dimensional view of the stacking of brucite-like layers. OH- ions lie at the apices of the octahedrons surrounding the Fe cations. CO32- ions in interlayers. (b) Projections along the c axis of the CO32- anions for three interlayers constituting a repeat. Génin, J.-M. R.; Aissa, R.; Géhin, A.; Abdelmoula, M.; Benali, O.; Ernstsen, V.; Ona-Nguema, G.; Upadhyay, C.; Ruby, C. Fougerite and FeII-III hydroxicarbonate green rust; ordering, deprotonation and/or cation substitution; structure of hydrotalcite-like compounds and mythic ferrosic hydroxide Fe(OH)(2+x). Solid State Sci., 7 (2005) 545-572.

  5. D2 x = 0.33 Transmittance % x ~ 0.50 D3 Transmittance % D1 H2O2 with H2O2 (b) e 78 K Eh(V) (a) 78 K 0.3 d 0.2 c Velocity (mm s-1) 0.1 D150 % b 0.0 D333 % x = 0.33 Probability density (p) D217 % -0.1 D138 % a D333 % (a) (b) -0.2 100 78 K Probability density (p) D416.5 % x ~ 0.50 0.2 0.4 0.6 0.8 1.0 1.2 1.4 -1 0 1 2 3 D212.5 % Quadrupole splitting D (mm s-1) 78 K {2 × [n(H2O2) / n(Fetotal)] + (1/3)} 99 -1 0 1 2 3 Quadrupole splitting D (mm s-1) x ~ 0.78 Transmittance % x = 1 x ~ 0.63 Transmittance % 98 Transmittance % (e) (d) (c) 78 K 78 K 97 78 K -4 -2 0 2 4 Velocity (mm s-1) D443 % 96 D467 % x ~ 0.78 (d) D431 % D128 % x ~ 0.63 D335 % (e) D1 + D222 % x = 1 Probability density (p) Probability density (p) D333 % D332 % Probability density (p) (c) 95 D29 % 78 K 78 K 78 K 94 -1 0 1 2 3 -1 0 1 2 3 -1 0 1 2 3 -4 -3 -2 -1 0 1 2 3 4 Quadrupole splitting D (mm s-1) Quadrupole splitting D (mm s-1) Quadrupole splitting D (mm s-1) 100 96 -4 -4 -4 -3 -3 -3 -2 -2 -2 -1 -1 -1 0 0 0 1 1 1 2 2 2 3 3 3 4 4 4 92 88 84 Velocity (mm s-1) 100 96 92 100 88 98 84 96 Velocity (mm s-1) 100 94 96 92 88 84 Velocity (mm s-1) The in situ oxidation of green rusts by deprotonationUse a strong oxidant such as H2O2, Dry the green rust and oxide in the air, Violent air oxidation, Oxide in a basic medium… FeII6(1-x) FeIII6x O12 H2(7-3x) CO3 FeII-III oxyhydroxycarbonate 0 < x < 1 “Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

  6. GR(CO32-) x = 0.33 H2O2 x = 0.50 (b) (a) 003 Intensity (arb. unit) Diffraction Angle (2q°) TEM and XRD patterns of the FeII-III oxyhydroxycarbonate due to the in situ deprotonation 0.2 µm 0.2 µm 012 (a) 113 006 018 H2O2 x = 1 Aerial x = 1 015 110 (c) (d) Intensity (arb. unit) Diffraction Angle (2q°) 10 10 20 20 30 30 40 40 0.5 µm 0.5 µm (b) (c) (d)

  7. The oxidation or reduction of GR(CO32-) gives rise to GR(CO32-)* or GR(CO32-)§, i.e. FeII6(1-x) FeIII6x O12 H2(7-3x) CO3 where x [0, 1]; the fougerite mineral is limited to the range [1/3, 2/3]. R = {nOH-/ (nFe(II) + nFe(III))} fougerite Ferroxyhite d’ FeOOH E 3 Pro- & deprotonation ofGR(CO32-) Fe3 O4 D 2.5 GR(CO32-)* Ferric GR Fe(OH)2 B G 2 GR(CO32-) Stoichiometric A 1.67 A: FeII6 O12 H14 CO3 B: FeII4 FeIII2 (OH)12 CO3 C: FeII2 FeIII4 O12 H10 CO3 D: FeIII6 O12 H8 CO3 AD: FeII6(1-x) FeIII6xO12H2(7-3x) CO3 G: Fe(OH)2 H: Fe3 O4 E: Ferroxyhite d’ FeOOH GR(CO32-)§ Ferrous GR 1.5 Voltammograms obtained on an iron disc at 10 mVs−1 in 0.4 M NaHCO3 solution at 25 °C and pH = 9.6. 1 FeII4FeIII2(OH)12CO3 + O2 FeIII6O12H8CO3 + 2 H2O 0.5 Fe(II) Fe(III) Mass balance diagram of iron compounds 0 0.33 0.67 0 0.2 0.4 0.6 0.8 1 xFe(III) = {nFe(III) / (nFe(II) + nFe(III))}

  8. GR* is also obtained by bacterial reduction of ferric oxyhydroxide • Production of Fe(II) and consumption of methanoate during culture of Shewanella putrefaciens in presence of lepidocrocite gFeOOH. The initial amount of FeIII (as lepidocrocite ) and of methanoate were respectively 80 mM and 43 Mm. • (b) X-ray pattern of the solid phase of incubation experiments with S. putrefaciens: mixture of green rust (GR1) and siderite (S) obtained after 15 days of incubation. • (c) Mössbauer spectrum after 6 days of bioreduction. • (c)TEM observations and • (d) optical micrograph of GR crystals obtained by reduction of lepidocrocite by S. putrefaciens; One sees the bacteria that respirate GR*. 80 12 70 (b) (a) Fe(II) (mM) GR1 (003) 60 9 GR1 (006) 50 6 S (104) Intensity (a.u.) GR1 (018) 40 GR1 (015) GR1 (012) Fe(II) S (018) Methanoate 30 3 Abiotic control Methanoate (mM) 20 0 2 q 10 20 30 40 50 60 10 0 D2 (c) 0 6 12 18 24 30 36 Dg Time (days) Transmittance (%) bioreduction D1 D’3 x~ 0.50 78 K Six days (d) -4 -2 0 2 4 Velocity (mm s-1) (e) (A. Zegeye) 20 µm (G. Ona-Nguema) G. Ona-Nguema, M. Abdelmoula, F. Jorand, O. Benali, A. Géhin, J.-C. Block and J.-M. R. Génin, Iron (II,III)hydroxycarbonate green rust formation and stabilization from lepidocrocite bioreduction, Environ. Sci. and Technol. 36 (2002) 16-20 100 98 96 94 92 5 µm

  9. Comparison between field experiments and laboratory assays The similarity between the original spectrum obtained in 19961 (a) and that of the deprotonated oxyhydroxycarbonate2 (b) is striking. More recently, field experiments were done in Fougères using back-scattering miniaturized Mössbauer spectrometer MIMOS3 (c) to follow the value of ratio x with time and depth in situ within the gley soil. (d) The fougerite mineral is able to reduce pollutants within the water table such as nitrates. Dissimilatory iron reducing bacteria regenerate the fougerite active mineral4. (b) Transmittance % x = 0.50 78 K synthetic Fougères -4 -3 -2 -1 0 1 2 3 4 fougerite D1 Velocity (mm s-1) (c) D3 CH2O CH2O FeIII FeII + CO32- NO3- N2, NH4+ +CO32- 293 K D2 1, 2 4, 5 3 (d) (a) -3 -2 -1 0 1 2 3 4 -4 Velocity (mm s-1) 1. J.-M. R Génin., G. Bourrié, F. Trolard, M. Abdelmoula, A. Jaffrezic, Ph. Refait, V. Maître, B. Humbert and A. Herbillon, Thermodynamic equilibria in aqueous suspensions of synthetic and natural Fe(II) - Fe(III) green rusts; occurences of the mineral in hydromorphic soils, Environ. Sci. Technol. 32 (1998) 1058-1068. 2. J.-M. R. Génin, R. Aïssa, A. Géhin, M. Abdelmoula, O. Benali, V. Ernstsen, G. Ona-Nguema,C. Upadhyay and C. Ruby, Fougerite and FeII–III hydroxycarbonate green rust; ordering, deprotonation and/or cation substitution; structure of hydrotalcite-like compounds and mythic ferrosic hydroxide Fe(OH)(2+x), Solid State Sci., 7 (2005) 545-572. 3. D. Rodionov, G. Klingelhöfer, B. Bernhardt, C. Schröder, M. Blumers, S. Kane, F. Trolard, G. Bourrié, and . J.-M. R. Génin, Automated Mössbauer spectroscopy in the field and monitoring of fougerite, Hyperfine Interactions, 167 (2006) 869-873. 4. C. Ruby, C. Upadhyay, A. Géhin, G. Ona-Nguema and J.-M. R. Génin, In situ redox flexibility of FeII-III oxyhydroxycarbonate green rust and fougerite, Environ. Sci. Technol., 40 (2006) 4696-4702. Fougerite : FeII6(1-x)FeIII6xO12H2(7-3x)CO3 100.0 99.5 x~ 0.50 99.0 98.5 98.0 D3 Transmittance % D1 78 K Fougères 4 -4 -2 0 2 Velocity (mm s-1)

  10. Fougerite is the active mineral that is mixed with clay minerals and responsible for the natural reduction of nitrates in gley soils within the water table. 100 100 99 δ Δ H G RA (mm s−1) (mm s−1) (kOe) (mm s−1) (%) Depth 2 m DFeIII (para +clay)0.39 0.65 0.67 55 (para +clay) DFeII (clay) 1.17 2.85 0.41 11.7 S1 (goethite) 0.37 −0.21 474 0.41 10.6 S2 (goethite) 0.38 −0.19 442 0.70 22.5 S1 +S2 (goethite) 33 Depth 2.50 m DFeIII 0.39 0.62 0.72 57.7 (para+clay+foug) DFeII (clay+ foug) 1.18 2.86 0.44 30.4 S (goethite) 0.43 −0.19 468 0.68 11.8 Depth 3 m DFeII (foug) 1.17 2.84 0.37 39 DFeIII (foug) 0.39 0.63 0.55 40.5 DFeII (clay) 0.96 2.71 0.30 9 DFeIII (clay) 0.20 0.48 0.42 11.5 S S1 + S2 DFeII DFeII 99 Transmittance (%) 98 (b) (a) Transmittance (%) DFeIII DFeIII 2.50 m 78 K 2 m 78 K 98 -10 -5 0 5 10 15 97 -15 -10 -5 0 5 10 15 velocity (mm s-1) velocity (mm s-1) Oxidised zone Reduced zone FeIII (d) 100 DFeII(clay) DFeIII(clay) goethite 99 DFeII(foug) Fe+2aq Transmittance (%) Ferricoxyhydroxides (c) DFeIII(foug) 98 fougerite paramagnetic 3 m 78 K FeII 97 clays clays Hyperfine parameters of Mössbauer spectra measured at 78 K of samples extracted in Denmark at different depths of 2 m, 2.50 m, 3 m out of hydric soils from (a) an oxidised zone to (c) a reduced zone. A mixture of fougerite, ferric oxyhydroxides and clay minerals is observed. H: hyperfine field (kOe); δ: isomer shift (mm s−1) with respect to α Fe at room temperature; Δ or ε: quadrupole splitting or shift (mm s−1); Γ : half-width at half maximum (mm s−1); RA: relative abundance (%). -4 -2 0 2 4 velocity (mm s-1) J.-M. R. Génin, R. Aïssa, A. Géhin, M. Abdelmoula, O. Benali, V. Ernstsen, G. Ona-Nguema,C. Upadhyay and C. Ruby, Fougerite and FeII–III hydroxycarbonate green rust; ordering, deprotonation and/or cation substitution; structure of hydrotalcite-like compounds and mythic ferrosic hydroxide Fe(OH)(2+x), Solid State Sci.,7 (2005) 545-572. FeIII FeII

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