Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 3 4 1999 10.5194/hess-3-593-1999 http://www.hydrol-earth-syst-sci.net/3/593/1999/ http://www.hydrol-earth-syst-sci.net/3/593/1999/hess-3-593-1999.html http://www.hydrol-earth-syst-sci.net/3/593/1999/hess-3-593-1999.pdf 593 599 0000-00-00 The reduction of chromate ions by Fe(II) layered hydroxides S. Loyaux-Lawniczak Ph. Refait P. Lecomte J.-J. Ehrhardt J.-M. R. Génin Laboratoire de Chimie Physique pour L'Environment, UMR 7564 CNRS-Univ. H. Poincaré - Nancy 1, 405, rue de Vandoeuvre, F 54600 Villers-lès-Nancy, France Centre National de Recherche sur les Sites et Sols Pollués, 930 Bd Lahure, BP 537, F 59505 Douai cedex. e-mail address for corresponding author: genin@lcpe.cnrs-nancy.fr The reduction of chromate ions by Fe(OH)₂ and the iron (II)-iron (III) hydroxysulphate green rust, GR(SO₄^2-), was studied to evaluate whether such synthetic layered hydroxides and the corresponding natural green rust mineral could be involved in the natural attenuation of contaminated environments. The resulting Cr (III) bearing phases, which would govern the subsequent behaviour of chromium, were clearly characterised. Both compounds proved to be very reactive and oxidised instantaneously while chromate ions were reduced to Cr (III) as evidenced by X-ray photoelectron spectroscopy. Mass balance (ICP-AES) demonstrated that the Fe/Cr ratio inside the solid end product was equal to the initial Fe/Cr ratio. The solid phases, analysed by X-ray diffraction, Raman and Mossbauer spectroscopies were identified as Cr-substituted poorly crystallised iron (III) oxyhydroxides in both cases, more precisely δ-FeOOH when starting with Fe(OH)₂ and ferrihydrite when starting with GR(SO₄^2-).