Selective Adsorption Mechanism of Ferric Ions on the Surfaces of Chalcopyrite and Pyrite in Flotation

When copper ores containing pyrite are crushed and ground, many unavoidable Fe3+ ions will be produced and enter the flotation process. At present, the adsorption mechanism of Fe3+ on chalcopyrite and pyrite surfaces is not clear. Here, the adsorption behaviors of Fe3+ on the surfaces of chalcopyrite and pyrite were systematically investigated by micro-flotation tests, infrared spectra studies, X-ray photoelectron spectroscopy analysis (XPS), first-principles density functional theory calculations and theoretical analysis of the coordination field. The micro-flotation tests showed that the recovery rate of pyrite reduced with the growth of pH, but the recovery rate of chalcopyrite was basically unchanged. The infrared spectra analysis revealed that the intensities of the characteristic xanthate peaks of the C=S and C-O-C groups in the Fe3+-treated pyrite surface changed more noticeably than those of the xanthate peaks of the Fe3+-treated chalcopyrite. XPS showed that Fe (OH)3 was more easily and spontaneously adsorbed on pyrite than chalcopyrite surfaces. First-principles DFT calculations and electronic structure analysis further showed that pyrite had a stronger adsorption of Fe (OH)3 than chalcopyrite. This work sheds new light on the adsorption mechanism of Fe3+ on the surfaces of chalcopyrite and pyrite during flotation.