Investigation of the leaching of the platinum group metal concentrate in hydrochloric acid solution by chlorine

Abstract

The dissolution of platinum-group metals (PGMs) requires a high chloride ion concentration in an acidic solution and a suitable oxidant. At Impala Platinum Refinery, the concentrate is leached in a hydrochloric acid solution using chlorine gas as the oxidant. The goal of this leaching step is a total dissolution of the PGMs and gold. The silver precipitates as silver chloride. The efficiency of this stage is crucial for the performance of the precious metals refinery. The aim of this project is to investigate the factors that influence the efficiency of the PGM leaching operation and to model for the results obtained. In order to investigate and evaluate the total dissolution of the PGt;~; in HClICl2 leach system, it is necessary to establish the effective conditions for the dissolution of chlorine gas in hydrochloric acid solution. The results showed that the solubility of chlorine gas increases with an increase in the acid concentration and chlorine gas concentration but decreases as the temperature increases. The HCI solution is almost saturated with chlorine after about 50 minutes. The chlorine mass' msfer coefficient is dependent on the temperature, the stirrer speed, the concentration of the HCI solution and that of the chlorine. [Abbreviated abstract. Open document to view full version]