Adsorption of Au ferrihydrites using Au-L-III edge XAFS spectroscopy

Samples of Au(III) adsorbed onto ferrihydrites have been prepared from pure ferrihydrites and various gold(III) chloride solutions and characterized b y Au-L-III edge XAFS spectroscopy. On ferrihydrite surfaces, Au;is present either as Au(III)Cl2O23- or ALI(III)ClO34-, Au(III)O-4(5-) square planar co mplexes with Au-O and Au-Cl distances of 2.00(2) and 2.28(2) Angstrom. Thes e results show that the redox state of Au remains unchanged during adsorpti on in contrast to the short range environment of Au which is strongly sensi tive on the pH and the Cl molality of the solution during adsorption.