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⁻ (major species) and OH radicals were produced in solution by the activation of Fe²⁺. The SO₄⁻/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.