Pyrogallic acid as depressant for flotation separation of pyrite from chalcopyrite under low-alkalinity conditions

Abstract Effective and low-cost flotation separation of chalcopyrite and pyrite has always been a challenge in the minerals processing industry. Traditional depressants in a Cu–Fe sulfide flotation system, such as lime, tend to require a high dosage and have low selectivity. We investigated the effect of pyrogallic acid on the flotation separation of chalcopyrite and pyrite. After treatment with pyrogallic acid under appropriate conditions, pyrite recovery dropped by 65%, while that of chalcopyrite dropped only slightly. Adsorption measurements showed that pyrogallic acid significantly reduced the amount of sodium butyl xanthate adsorption on the pyrite surface. Zeta potential, infrared, and X-ray photoelectron spectroscopy analyses confirmed that pyrogallic acid most likely interacts with pyrite surface via chemisorption with Fe sites, and thereby strengthens the hydrophilicity of the pyrite particles. Localized electrochemical impedance spectroscopy measurements further indicated that pyrogallic acid could significantly adsorb on the pyrite surface. Therefore, Pyrogallic acid could be a promising depressant for pyrite and provide flotation separation of Cu–Fe sulfide ores under low-alkalinity conditions.