Arsenic removal strategy in the processing of an arsenopyritic refractory gold ore

Abstract

In the gold mining industry, the exploitation of low-grade refractory deposits generates effluents with high arsenic concentrations. In this study, an additional stage in the processing of an arsenopyritic refractory gold ore was studied. Arsenic extraction in an alkaline pretreatment was evaluated to avoid metalloid release in the subsequent gold thiosulfate leaching stage, without affecting precious metal extraction. Experiments were conducted with different extracting agents (citric acid, sodium bicarbonate, oxalic acid, deionized water); contact time in the alkaline pretreatment stage (6 and 13 days) was also assessed; furthermore, the effect of arsenic extraction time (4 h, 6 days and 12 days), concentration of oxalic acid (0.02, 0.1, 0.5 M) and temperature (25, 70 °C), was studied. The results showed that it is possible to remove arsenic without altering the subsequent release of gold (80%). The best conditions were: 0.1 M oxalic acid for 1 h and at 70 °C. Finally, it was observed that the concentration of As released into the subsequent thiosulfate leach decreases by 97.7% (from 640 to 15 mg/l), thereby conserving its ability to eventually be recycled after gold recovery.