Sustainable Large-scale Hyper-enrichment of Gold via Ferrous Sulfide-mediated Sulfuric Acid Leaching

Abstract

The engineered transformation of low-gold-grade pyrite into hyper-enriched gold concentrates has critical significance in environmental protection and economic sustainability. Nevertheless, the artificial hyper-enrichment of gold has been challenging to achieve due to the stringent conditions required for mineralization. Herein, this work proposed a conversion of pyrite to ferrous sulfide (FeS) for realizing hyper-enrichment gold concentrates and rapid acid leaching, as well as increasing the added value of Fe and S resources simultaneously. The transition state of Fe_1-xS during FeS formation provides diffusion channel for Au atom transfer and gather. Afterwards, FeS phase is able to dissolve fastly in 30 minutes, inhibiting the formation of S₈ secondary inclusions around gold effectively. Using this method, the gold grade can increase up to 70.70 g/t and the residue yield of the concentrates is reduced to 3.4%. Additionally, high-value Fe- and S- containing products are yielded as green vitriol and sulfur, respectively. Besides, gram-scale concentrates produced by kilogram-scale FeS are evaluated for industrial application, emphasizing process stability and economic sustainability.