Effect of Na2SO3 on the floatability of chalcopyrite and enargite

[Display omitted] •The effect of Na2SO3 on the floatability of chalcopyrite and enargite was studied.•Na2SO3 treatment depressed the floatability of both minerals in the absence of PAX.•PAX followed by Na2SO3 treatment exhibited a selective depressing effect on chalcopyrite.•Na2SO3 produced SO42− species and reduced the adsorbed PAX on chalcopyrite.•The adsorbed PAX prevents Na2SO3 from forming SO42− on the enargite surface. The effect of sodium sulfite (Na2SO3) on the floatability of chalcopyrite and enargite was investigated in this work. The micro flotation tests of single and mixed minerals were performed under various concentrations of Na2SO3. The micro flotation tests of single minerals showed that Na2SO3 depressed the floatability of both minerals at pH 9 in the absence of potassium amyl xanthate (PAX). Interestingly, the addition of PAX followed by the Na2SO3 treatment selectively improved the recovery of enargite. On the other hand, the recovery of chalcopyrite remained low under a similar condition. The single mineral flotation results indicate that separation of chalcopyrite and enargite might be possible using PAX and Na2SO3 treatment. Indeed, the mixed mineral flotation results were in agreement with the flotation results of single minerals. The mineral surface was analyzed by X-ray photoelectron spectroscopy (XPS) after the treatments to explain the phenomenon. The XPS results show the presence of sulfate species on both mineral surfaces after the Na2SO3 treatment. The adsorbed PAX could prevent the formation of this sulfate species on the enargite surface and rendered the surface hydrophobic. However, the adsorbed PAX could not prevent the formation of sulfate species on the chalcopyrite surface and rendered the surface hydrophilic.