Fast and Selective Leaching of Pyrrhotite in the Presence of Pentlandite

The projected increase in nickel demand for the energy transition will require greater primary extraction of nickel from sulfidic ore bodies. However, a selective and rapid leaching method to remove the iron sulfide mineral pyrrhotite is needed to upgrade nickel concentrates, minimize potential acid rock drainage of solid residues, and valorize legacy tailings. We demonstrate how VSO 4 or CrCl 2 can quantitatively leach pyrrhotite from nickel sulfide-bearing feedstocks completely within 20 min at 25 °C, while limiting nickel leaching to less than 5%. Across six feedstocks, the residual nickel mass fraction in the solids almost doubles compared to the original feedstock, as pentlandite, pyrite, and copper sulfide minerals remain intact. Process throughput is governed by proton supply rather than kinetics, as raising the concentration of sulfuric acid sustains complete extraction up to mass loadings of 300 g/L. The ambient pressure, temperature, and lack of SO x production suggest that this type of reductive leach method may provide a means of selective pyrrhotite removal from concentrates and tailings, while producing precursors of salable forms of sulfur and iron from pyrrhotite.