Enargite concentrate processing by the combination of mechanochemical, hydrometallurgical and precipitation methods

• Mechanical activation improves the extraction of arsenic from enargite concentrate.
• Solution with As content obtained after leaching was precipitated as Na3AsS4.
• By mechanochemical reduction of Cu2S with Fe, it is possible to get elemental Cu.

This paper investigates the possibility of enargite concentrate treatment using an environmentally friendly route. Enargite Cu3AsS4 contains dangerous arsenic, and this element can be removed by leaching with Na2S in very alkaline environment (pH > 12.5). Arsenic passes into the leach, while the copper sulfide produced represents a raw material suitable for pyrometallurgy. We have shown that more than 80% of the arsenic can be extracted by atmospheric alkaline leaching at 95 °C, when mechanical pretreatment of enargite concentrate in an attritor is applied. The solubilized arsenic can be transformed into solid Na3AsS4. The solid product Cu2S can be further treated with elemental iron by mechanochemical reduction in a planetary mill. The final product forms a Cu/FeS composite from which iron can be separated by leaching with HCl. The proposed two-step process of milling (enhancement of arsenic removal (I) and obtaining of elemental copper (II)) illustrates the principal possibility of transforming minerals into metals.