Improved flotation separation of sulfide minerals by synthesized surfactant based on para-position methyl effect

Abstract

Flotation, as one of the greatest technologies in the 21st century, enables humans to utilize the mineral resources on a large scale. The key to a successful flotation separation is the surfactants with unique selectivity towards different minerals. A flotation surfactant has both chelating side and hydrophobic side. In the past decades, the selectivity of the flotation surfactants has been always attributed to the chelating side. Inspired by an interesting ‘magic methyl effect’ in the field of pharmaceutical chemistry that introducing a methyl group on the hydrophobic side can significantly improve the medicine’s selectivity. In this work, based on an archetype collector sodium benzenesulfinate (SBS) which bears inconspicuous selectivity towards galena and pyrite, a methyl group was introduced to synthesize a novel collector sodium p-toluenesulfinate (SPTS). The flotation tests confirmed that SPTS has much better selectivity than SBS and ethyl xanthate (EX), a commonly used collector for galena flotation against pyrite, which was supported by the results of FTIR, XPS, adsorption capacity and contact angle measurements. DFT calculations revealed that the selectivity of SPTS stems from its desolvation effect and the difference in hydration layers of galena and pyrite. The SPTS can destroy the S···H hydrogen-bonded water molecules via desolvation effect and adsorb on galena surface to make it hydrophobic, but cannot repel the FeO chemically bonded water molecules on pyrite surface. However, the SBS or EX can realize co-adsorption with the water molecules on both minerals with no selectivity. This study provided a new strategy for designing the selective surfactants for successful sulfide minerals flotation.