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

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