Gold recovery from roasted refractory gold concentrate through cyclic extraction using MnO2-assisted thiocyanate leaching and cementation with zinc powder

Abstract

Cyanidation has long served as the industrial standard in the gold industry, necessitating heightened attention to cyanide management owing to its inherent toxicity. This study developed a novel MnO₂-assisted thiocyanate leaching system as an alternative to cyanide. The sample was generated from a refractory gold concentrate processed by roasting, containing 54.4 g/t gold with iron oxide and quartz as the major mineral phases. Within the framework of the novel system, gold recovery was investigated in terms of gold association, recovery behavior, thermodynamics, and optimization using cyclic extraction protocols. The most suitable leaching conditions were determined as 1.20 mol/L NaSCN, 4.00 mmol/L MnO₂, pH at 1.00, liquid-to-solid ratio of 4 mL/g, and leaching duration of 24 h, resulting in a maximum gold extraction of 94.8%. Subsequent zinc precipitation facilitated a gold recovery of 99.4% from the leachate. Furthermore, the implementation of a cyclic extraction scheme, coupled with reagent addition to offset consumption, yielded a significant thiocyanate dosage reduction by 75% while maintaining gold recovery. This acidic leaching system yields satisfactory gold recovery with minimized reagent consumption, particularly suited for refractory gold ore that has undergone acidic pretreatment.