Flotation separation of galena and chalcopyrite by using hydroxyl radicals from an Fe2+/NaClO system as depressants

Abstract

The flotation separation of galena (PbS) and chalcopyrite (CuFeS₂) is not yet fully resolved due to the lack of efficient depressants. This study proposed a new depressant, i.e. an Fe²⁺/NaClO system, as an efficient PbS depressant. The inhibition effect of the Fe²⁺/NaClO system is attributed to the oxidation effect of •OH radicals from the reaction between HClO and Fe²⁺. The recovery of PbS is only 9.48 % and that of CuFeS₂ is 82.33 % under the following conditions: pH 3.5, 4 min reaction time, 10:1 Fe²⁺:NaClO molar ratio and 1 × 10⁻² mol/L NaClO concentration. Contact angle test results suggested that the hydrophobicity of PbS was decreased by conditioning with the Fe²⁺/NaClO system. X-ray photoelectron spectroscopy results showed that the S²⁻ species on the PbS surface was oxidised into SO₄²⁻, and thus, PbSO₄ occurred on the PbS surface. Furthermore, SO₄²⁻ concentration reached 61.67 % of the total S species. Oxidative production coated the PbS surface well, depressing PbS flotation. However, the Fe²⁺/NaClO system barely changed the components of the CuFeS₂ surface. The CuFeS₂ surface still exhibits a high hydrophobic level. Therefore, PbS can be efficiently separated from CuFeS₂ by using the Fe²⁺/NaClO system.