Upgrading of a chalcopyrite concentrate by reaction with copper(II) and sulfite – Unexpected formation of Chevreul’s salt, Cu2SO3·CuSO3·2H2O

Recovery of aqueous copper(II) onto a chalcopyrite concentrate was shown to be rapid at 60 °C in the presence of S(IV), in this case sulfite. Surprisingly, rather than partial conversion of chalcopyrite to a copper sulfide such as chalcocite or covellite, copper was removed from solution by precipitation of a mixed-valence copper sulfite, Chevreul’s salt (Cu2SO3·CuSO3·2H2O). This has application as a way to increase the copper grade of chalcopyrite concentrates using the leachate from a Galvanox™ leach of flotation tailings, offering several advantages over similar processes employing an autoclave to effect copper precipitation.