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

• There was a competitive adsorption of Na 2 S and NaBX on the chalcopyrite surface. • Xanthate removal performance of additive followed: KMnO 4 > H 2 O 2 > Ca(ClO) 2 > Na 2 S. • Formed FeOOH and Fe 2 (SO 4 ) 3 modified chalcopyrite surface to hydrophilic with KMnO 4 . • KMnO 4 could effectively separate xanthate-preadsorbed chalcopyrite from molybdenite . 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 (Na 2 S) suffers from a series of environmental problems. Herein, to seek more effective alternatives, inorganic oxidizers i.e., KMnO 4 , H 2 O 2 and Ca(ClO) 2 were employed. Comparative effects of inorganic oxidizers and Na 2 S 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: KMnO 4 > H 2 O 2 > Ca(ClO) 2 > Na 2 S, and 0.5 mmol/L of KMnO 4 could get the same effect as 2.73 mmol/L of Na 2 S. FT-IR studies revealed that oxidation products of Cu(BX) 2 with different oxidizers included dixanthogen (ROCSS) 2 , perxanthate ROCSSO − and thiocarbonate ROCOS − , while Na 2 S removed NaBX from the mineral surface via the competitive adsorption which was non-specifical ion exchange. Furthermore, surface analysis confirmed that KMnO 4 treatment rendered the mineral surface less hydrophobic owing to the formation of FeOOH and Fe 2 (SO 4 ) 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 KMnO 4 might be a promising alternative to Na 2 S in separation chalcopyrite from molybdenite which are both pre-floated by xanthate.