Novel application of depressant sodium mercaptoacetate in flotation separation of chalcopyrite and pyrite

•SMA can effectively separate chalcopyrite and pyrite by flotation at pulp pH 6.5.•SMA can be adsorbed on the surface of pyrite to reduce its hydrophobicity and hinder the adsorption of collector.•Weak adsorption of SMA on its surface does not reduce the hydrophobicity of chalcopyrite surface.