Separation mechanism of chalcopyrite and pyrite due to H2O2 treatment in low-alkaline seawater flotation system

The effects of H2O2 on the flotation separation of chalcopyrite and pyrite in seawater were investigated. Pyrite was more significantly oxidized by 0.05 vol% H2O2 in seawater at pH 8, as compared to that of chalcopyrite. Under optimized condition, a recovery difference of greater than 70% was obtained for chalcopyrite and pyrite. The contact angle measurements showed that pyrite surface was more hydrophilic as compared to chalcopyrite in the presence of 0.05 vol% H2O2. In addition, the collector of butyl xanthate is more difficult to adsorb on the surface of H2O2-treated pyrite (adsorption dosage reduced from 0.18 to 0.06 mg g(-1)), further decreasing its floatability. The heat released due to xanthate adsorption on chalcopyrite and pyrite decreased from 26.5 mJ to 25.9 mJ and from 23.1 mJ to 15.2 mJ, after H2O2 treatment, respectively, indicating less adsorption of xanthate due to the oxidation treatment, especially for pyrite. The XPS data indicated the dissolution of Fe from the oxidized chalcopyrite surface and the formation of various hydrophobic S species such as S-2(2-), S-n(2-) , S-0 on chalcopyrite surface. In contrast, Fe(II) on pyrite surface was oxidized by H2O2 to form hydrophilic Fe2O3, Fe (OH)(3), FeOOH and Fe-2(SO4)(3) species. Therefore, this study reveals that H2O2 can be used as a high-efficient depressant for pyrite when separating chalcopyrite and pyrite in low-alkali seawater flotation system.