Kinetics of the interaction of gold chloride solutions on arsenopyrite

The stoichiometry and kinetics of AuCl 4 − cementation on arsenopyrite were studied. For solution potentials of 970–1020 mV (vs. SHE) the overall process is given by: 14/3 AuCl − 4 + FeAsS +8 H 2 O →14/3 Au + Fe 3+ + SO 2 4 + AsO 3− 4 + 56/3 Cl − +16 H + The kinetics are limited by transport in an aqueous phase with an activation energy of 20 kJ/mol. Kinetic constants are independent of the initial AuCl 4 − concentration.The pH and chloride ion concentration have an insignificant effect. The addition of thiourea in the ratio [Tio]/[Au[ III ]=4 inhibited the cementation process 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 and quantitative analysis for S, As, Fe and Au are reported.