Microscopic mechanism of the combined collectors BHA and KBX synergistic adsorption on sulfidized malachite surface and its influence on floatability

Considering the heterogeneity of surface sulfidization during the sulfidization flotation process of oxidized copper minerals and the poor economic efficiency of direct flotation using chelating collectors alone, the use of combined collectors is well established in mineral flotation practice. Nevertheless, theoretical studies addressing their application to the flotation of oxidized copper minerals remain limited. In this work, a systematic investigation is conducted into the flotation performance and adsorption characteristics of combined collector potassium butyl xanthate (KBX) and benzohydroxamic acid (BHA) in the sulfidization flotation process of malachite. Micro-flotation experiments indicate that the KBX + BHA markedly improves the flotation recovery of malachite relative to single-collector systems. Adsorption measurements, zeta potential analysis, Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), and contact angle measurements indicate that the combined collectors can form stacked adsorption and intercalated adsorption on the surface of sulfidized malachite, resulting in an increased thickness and density of collector adsorption layer. Additional insights obtained from time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) indicate that BHA is predominantly adsorbed on the malachite surface via chelation between its nitrogen-containing functional groups and active copper sites located in unsulfidized or unstable sulfidized regions. The introduction of KBX promotes the adsorption of BHA and interacts with active copper sites in fully sulfidized regions. Consequently, within the combined collector system, BHA and KBX are able to synergistic adsorb onto the sulfidized malachite surface and forming a compact and stable collector adsorption layer, this interaction enhanced surface hydrophobicity, thereby improving floatability of malachite.