Alkaline Sulfide Pretreatment of an Antimonial Refractory Au-Ag Ore for Improved Cyanidation

This paper presents the alkaline sulfi de pretreatment of an antimonial refractory gold and silver ore. In the ore, gold occurs mainly as gold-silver alloys and as associated with quartz and framboidal pyrite grains, and, to a small extent, as the inclusions within antimonial sulfi des. Silver is present extensively as antimonial sulfi des such as andorite. Alkaline sulfi de pretreatment was shown to allow the decomposition of the antimonial sulfi de minerals (up to 98% Sb removal) and to remarkably improve the amenability of gold (e.g., from <49% up to 83%) and silver (e.g., from <18% up to 90%) to subsequent cyanide leaching. An increase in reagent concentration (1–4 mol/L Na2S or NaOH) and temperature (20–80°C), and a decrease in particle size seem to produce an enhancing effect on metal extraction. These fi ndings suggest that alkaline sulfi de leaching can be suitably used as a chemical pretreatment method prior to the conventional cyanidation for antimonial refractory gold and silver ores. © 2010, Springer. All Rights Reserved.