Adsorption of Au ferrihydrites using Au-LIII edge XAFS spectroscopy

Abstract

Samples of Au(III) adsorbed onto ferrihydrites have been prepared from pure ferrihydrites and various gold(III) chloride solutions and characterized by Au-LIII edge XAFS spectroscopy. On ferrihydrite surfaces, Au is present either as Au(III)Cl2O23- or Au(III)ClO34-, Au(III)O45- square planar complexes with Au-O and Au-Cl distances of 2.00(2) and 2.28(2) Å. These results show that the redox state of Au remains unchanged during adsorption in contrast to the short range environment of Au which is strongly sensitive on the pH and the Cl molality of the solution during adsorption.