A novel copper depressant for selective flotation of chalcopyrite and molybdenite

•The novel depressant depressed chalcopyrite other than molybdenite.•The depression was mainly due to formation of CuS on chalcopytie surface.•Selective flotation of chalcopyrite and molybdenite was achieved.•This depressant was more economical and environment friendly over Na2S. In this work, the effect of Na2S2O3 and the mixture of Na2S2O3 and Cu2+ on the selective flotation performances of chalcopyrite and molybdenite were investigated through single and mixed mineral flotation tests. The depression mechanisms were studied in detail through Zeta potential, contact angle, XPS and Raman measurement. The results indicated that Na2S2O3 had more powerful depression effect on chalcopyrite than that on molybdenite. The depression could be greatly enhanced with the addition of Cu2+ without losing selectivity. XPS and Raman measurement revealed that Na2S2O3 and Cu2+ chemically adsorbed on chalcopyrite surface, formation of CuS which was responsible for the depression. On the other hand, the surface of molybdenite was slightly affected after the treatment in the mixed solution of Na2S2O3 and Cu2+. This new depressant had the advantage of low cost and environment friendly over conventional depressant, which could be utilized as an alternative depressant for the selective flotation separation of chalcopyrite and molybdenite.