Extraction of low-grade silver from a refractory Au-Ag ore in cyanidation by pretreatment with reductive alkaline leaching

The occurrence state of the low-grade silver (30.7 ppm) In refractory gold-silver ore from Beiya (Yunnan, China) was characterized. A pretreatment process of reductive leaching by cuprous in ammonia-ammonium sulfate alkaline solution was reported in this paper. Cu metal was employed to reduce cupric to cuprous based on the Cu2 + observed in the ore. The effects of the process parameters on the leaching ratio of Mn and Ag were investigated, including the amounts of ammonia and ammonium and the amount of Cu metal, the liquid-solid ratio and the leaching time. The results showed that silver mainly occurred in the manganese ore as isomorphism. The best result of the cyanidation leaching ratio of silver in this work was 78.96% under the conditions of 0.02 mol/L NH3·H2O, 1.0 mol/L (NH4)2SO4, 4 g of Cu wire, a liquid-solid ratio of 3:1 and a stirring speed of 300 r/min for 4 h. This work developed a comprehensive recovery process for the manganese-silver resource with low-grade silver.