Cyanidation of gold ores containing copper, silver, lead, arsenic and antimony

Cyanidation tests on two ore samples from two different gold deposits are reported. The first sample contained 10.5 ppm gold with high arsenic and antimony, while the second sample had a low gold content (2.5 ppm) but a high silver content (160 ppm). The first series of test work focused on determining the optimal conditions for extracting gold from both samples, concluding that for the first sample, the optimum parameters were 4000 mg/L cyanide concentration, pH 11.1 and a 24-hour cyanidation time. For the second sample, the parameters were 2500 mg/L, pH 10.5, and 24 hours. The silver and gold recoveries were 94.91% and 28.2% for the first sample and 92.5% and 93.5% for the second sample, respectively. In the second series of tests, oxidizing agents like H2O2 and air were used to enhance gold extraction kinetics, leading to the conclusion that air injection greatly benefited leaching kinetics. The third series involved acid pretreatment and roasting, which reduced cyanide consumption and increased gold recoveries significantly. Results indicated arsenic, antimony, cadmium, and mercury were considerably reduced in roasted samples.