Effect of oxidation on the flotation behavior of pyrite: Surface oxidation products and collector adsorption mechanisms

This study establishes the oxidation-dependent flotation behavior of pyrite and elucidates how surface-state evolution regulates collector adsorption at the mineral–solution interface. Using a pyrite monomineral from Shandong, China, oxidation treatments were carried out in water and in KMnO4, H2O2, and NaClO solutions, followed by microflotation, contact angle, FTIR, zeta potential, XPS, SEM–EDS, and DFT analyses. Pyrite exhibited favorable flotation with butyl xanthate and ammonium dibutyl dithiophosphate at pH ~6.5 and a collector dosage of 100 g/t. Mild oxidation in water enhanced butyl xanthate flotation, whereas increasing oxidation intensity, through higher oxidant dosage or prolonged treatment time, progressively depressed flotation in all systems. Surface characterization showed that oxidation converted pyrite from a collector-responsive, hydrophobic surface to a less reactive and less hydrophobic one. This transition was associated with depletion of Fe–S active sites, accumulation of oxygen-containing Fe and S species, and a nonmonotonic evolution of elemental sulfur, which promoted hydrophobicity only at intermediate oxidation stages. DFT calculations further revealed that Fe-centered sites dominate collector binding and that oxidation weakens adsorption through active-site depletion and reduced interfacial electronic interaction. These findings provide design-oriented insight into oxidation-mediated interfacial regulation of sulfide mineral flotation.