OXIDATION-KINETICS OF ULTRASMALL COLLOIDAL CHALCOPYRITE (CUFES2) WITH ONE-ELECTRON OXIDANTS

The stopped flow technique has been used to study the oxidation of ultrasmall colloidal chalcopyrite (CuFeS2) particles (diameter 50-90 angstrom) by the one-electron oxidants hexacyanoferrate(III) (Fe(CN)6(3-)) and hexachloroiridate(IV) (IrCl6(2-)) in aqueous solution. The stoichiometry of the initial oxidation step corresponds to the reaction CuFeS2(s) + 5H2O --> Cu(OH)2(s) + Fe(OH)3(s) + 2S0(s) + 5H+ + 5e-. Further oxidation of the elemental sulfur results in the formation of S2O3(2-) and SO4(2-) in solution, as determined by ion chromatography. Time-resolved measurement of both the oxidant and chalcopyrite concentrations has provided a detailed understanding of the mechanism involved in the oxidation of colloidal chalcopyrite.