Gold cyanidation using hydrogen peroxide

Gold cyanidation, using hydrogen peroxide as an oxidising agent, has been s tudied by performing kinetic experiments, open circuit potential measuremen ts and voltammetry. Small amounts of hydrogen peroxide make the cyanidation rate lower than that in conventional cyanidation, but higher amounts can m ake the cyanidation rate double. At low temperatures, the process is contro lled by a chemical reaction, whereas at higher temperatures, it is controll ed by diffusion with higher rates with respect to conventional gold cyanida tion at atmospheric pressure. As the presence of hydrogen peroxide displace s the mixed potential of cyanidation to more anodic potentials, where oxyge n activity is nil, cyanidation can be performed under conditions of low oxy gen pressure. In these conditions, cyanidation is established at transpassi ve potential regions of gold anodic dissolution and the cyanidation rate is determined by the cyanide concentration. The cyanidation rate can be tripl ed by adding small amounts of thallium (I) ions to cyanidation with hydroge n peroxide. (C) 1999 Elsevier Science B.V. All rights reserved.