Dual Role of Fe2+ in the Galena Flotation and Influence on Selective Separation

Fe ions, as one of the unavoidable metal ions, are present in flotation pulp as ferric and ferrous species, and the effect of ferric species on the flotation behavior of sulfide minerals has been widely discussed in the above literatures. However, the effect of ferrous species has rarely been noticed. In this paper, the effect of ferrous species on the flotation behavior and surface characteristics of galena was investigated by using microflotation, zeta potential measurements, X-ray photoelectron spectrometer (XPS) analysis, and density functional theory (DFT) calculations. Microflotation tests indicated that the flotation recovery of galena with potassium butyl xanthate (KBX) as collector was significantly decreased with the addition of Fe²⁺ in the pulp, and the recovery was further decreased with increasing dosage of Fe²⁺. In addition, the finer the galena particles, the greater the decrease in flotation recovery. Zeta potential analysis illustrated that the isoelectric point (IEP) was shifted from 4.4 to 5.8 due to the adsorption of ferrous hydroxyl complexes on the galena surface and the zeta potential. XPS surface analysis suggested that the surface oxidation of galena was alleviated by the consumption of O₂ in the pulp, which reduced the adsorption of the collector KBX on and the oxidation of xanthates to dixanthogens. Density functional theory (DFT) calculations confirmed that the ferrous hydroxyl complex FeOH⁺ could be adsorbed on the galena surface by interactions between Fe and S atoms.