KINETICS OF THE INTERACTION OF GOLD CHLORIDE SOLUTIONS ON ARSENOPYRITE

The stoichiometry and kinetics of AuCl4- cementation on arsenopyrite w ere studied. For solution potentials of 970-1020 mV (vs. SHE) the over all process is given by: 14/3 AuCl4 + FeAsS + 8H(2)O --> 14/3 Au + Fe3 + + SO42 + AsO43- + 56/3 Cl- + 16H(+) The kinetics are limited by tran sport in an aqueous phase with an activation energy of 20 kJ/mol. Kine tic constants are independent of the initial AuCl4- concentration. The pH and chloride ion concentration have an insignificant effect. The a ddition of thiourea in the ratio [Tio]/[Au[(III)] = 4 inhibited the ce mentation profess instantaneously. An X-ray photoelectron spectroscopy /Electron spectroscopy for chemical analysis (XPS/ESCA) depth profile study of the attacked arsenopyrite surface is included and a possible mechanism for arsenopyrite oxidation is discussed. Binding energies an d quantitative analysis for S, As, Fe and Au are reported. (C) 1998 El sevier Science B.V.