Abstract
Thiourea, as an environmentally friendly gold lixiviant, has the potential to replace highly toxic cyanide. The effect of foreign ions including Cu2+, Ag+, Pb2+, Zn2+, AsO33− and AsO43− on gold leaching in an acidic thiourea solution was investigated in this paper. Leaching results showed that the foreign ions had an adverse effect on thiourea leaching of gold. The gold dissolution (except low Pb2+ concentrations, i.e., < 20 mg/L) and thiourea stability both were in order of no foreign ions ≈ Zn2+ > Pb2+ > AsO33− > AsO43− > Ag+ > Cu2+. The thiourea dissolution of gold could be improved at low concentrations of Pb2+ (<20 mg/L), although the thiourea consumption was also increased. The thermodynamic analysis and the scanning electron microscope (SEM) and X-ray photon spectroscopy (XPS) analyses suggested that the foreign ions resulted in insignificant changes in the corrosion characteristics of leached gold surface and the quantity and chemical state of surface species. The possible mechanism for the effect of foreign ions on thiourea leaching of gold was proposed that the thiourea consumption in the presence of foreign ions was significantly increased, leading to the marked deterioration of thiourea dissolution of gold.
Published Version
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