Selective depression of galena in the galena and chalcopyrite system by the Fe(II)-activated persulfate process

The separation of galena (PbS) from chalcopyrite (CuFeS2) requires strong oxidants for the depression of PbS, due to the excellent hydrophobicity of PbS. In this work, an advanced oxidation process, i.e., S2O82-/Fe2+ treatment, was employed to selectively depress PbS. The parameters of the S2O82-/Fe2+ process were determined via flotation tests as follows: pH 3, 1:1 S2O82-/Fe2+ molar ratio, and 10 min reaction time. The S2O82-/Fe2+ treatment selectivity decreased the hydrophobicity of the PbS surface. UV-vis spectroscopy results revealed that SO4 center dot- (major species) and center dot OH radicals were produced in solution by the activation of Fe2+. The SO4 center dot-/center dot OH radicals reacted with the PbS surface, generating the SO42- and PbSO4 species. These species coated the PbS surface, forming a hydrophilic PbS surface and inhibiting the PbS flotation. By contrast, the S2O82-/Fe2+ treatment generated only a minimal amount of SO42- (5.98 % of the total S species) on the CuFeS2 surface. Therefore, the CuFeS2 surface was hydrophobic and CuFeS2 particles could still be floated into the foam phase. This study provides a promising method for the selective depression of PbS in the PbS-CuFeS2 mixture.