Studies on gold elution and electrowinning using sodium carbonate media

Laboratory-scale experiments on gold elution and electrolysis in sodium carbonate media were performed. The effect of solution composition, flow rate, and acid washing on the elution of gold from loaded carbons was studied. Both laboratory and plant loaded carbons were evaluated for their elution behaviour. It was found that the percent of gold eluted was greatly influenced by the temperature, acid concentration, and residence time of the acid washing step. The concentration of sodium carbonate affects the elution of the gold. In some cases, a mixture of sodium carbonate and sodium hydroxide was more effective than sodium carbonate alone. The electrolysis behaviour of some plant was studied to ascertain whether problems with anode corrosion, scale formation and poor gold deposition kinetics were associated with the medium properties or the process practice. It was found that the solution composition had to be compatible with both elution and electrowinning to avoid disruption of the gold mill circuit.