Effects of different inorganic oxidizers on removal of xanthate pre-adsorbed on chalcopyrite surface: An effective approach for flotation depression using KMnO4

Abstract

Removal of pre-adsorbed xanthate is a crucial step to the further separation of chalcopyrite from other sulfide minerals possessing similar floatability. Traditionally, adding excess sodium sulfide (Na2S) suffers from a series of environmental problems. Herein, to seek more effective alternatives, inorganic oxidizers i.e., KMnO4, H2O2 and Ca(ClO)2 were employed. Comparative effects of inorganic oxidizers and Na2S on removal of sodium butyl xanthate (NaBX) on chalcopyrite surface were investigated. Results showed that the adsorption of NaBX on chalcopyrite surface followed Langmuir isotherm, and the product was Cu(BX)2 at pH 8. Xanthate removal performance of different additives followed: KMnO4 > H2O2 > Ca(ClO)2 > Na2S, and 0.5 mmol/L of KMnO4 could get the same effect as 2.73 mmol/L of Na2S. FT-IR studies revealed that oxidation products of Cu(BX)2 with different oxidizers included dixanthogen (ROCSS)2, perxanthate ROCSSO− and thiocarbonate ROCOS−, while Na2S removed NaBX from the mineral surface via the competitive adsorption which was non-specifical ion exchange. Furthermore, surface analysis confirmed that KMnO4 treatment rendered the mineral surface less hydrophobic owing to the formation of FeOOH and Fe2(SO4)3, and the formed cupric oxide prevented the re-adsorption of xanthate or its reaction product, consequently decreasing the chalcopyrite floatability from 86% to 12%. These findings indicated that KMnO4 might be a promising alternative to Na2S in separation chalcopyrite from molybdenite which are both pre-floated by xanthate.