Chlorination not only complicates the after-treatment process by dissolving some or most of the sulphides in the treatment of sulphide ores, but also increases the consumption of oxidizing agents such as chlorine gas. In addition, the stability of gold chloride complexes is not high, and when in contact with other reducing agents (sulphides in ores or products of low oxidation states produced during oxidative decomposition), it can be easily redeposited to significantly reduce leaching rate. Therefore, chlorination is relatively suitable for acidic ores with sulphur content less than 0.5%, and generally, pre-treatment and oxidative desulfurization are necessary for gold-bearing sulphides.
Kim Chang Sok, a researcher at the School of Science and Engineering, has proposed a new environmentally-friendly gold chlorination hydrometallurgy process consisting of pressure oxidation pretreatment, chloride leaching and ion exchange resin adsorption of high-sulfur refractory gold concentrate, identified necessary indices through basic research, and provided basic data for the application of environmentally-friendly non-cyanidation of refractory gold concentrate.
The highest gold leaching rate of about 96.54% was obtained when the pressure oxidized residue of refractory gold concentrate was chlorinated at pH=4, sodium hypochlorite concentration of 0.5%, sodium chloride concentration of 75g/L, temperature of 30℃, liquid-solid ratio of 3:1 and time of 120min.
For more information, you can refer to his paper “New Method of Environment-Friendly Chlorination Hydrometallurgy of Refractory Gold Concentrates” in “Proceedings of KUTIC-2025”.