An efficient malachite sulfidation flotation reagent system: CaSx- potassium n-butoxypropyl xanthate

To enhance the enrichment efficiency of copper oxide ores, calcium polysulfide (CaSx) in combination with potassium n-butoxypropyl xanthate (BPX) was applied for the sulfidization flotation of malachite in this study—marking the first reported use of this reagent system for such a purpose. Flotation experiments demonstrated that the CaSx-BPX system exhibited superior selectivity and separation performance for malachite relative to calcite and quartz, outperforming three reference systems: CaSx-Sodium isobutyl xanthate(IBX), Na 2 S-BPX, and Na 2 S-IBX. Under optimized conditions (pH = 7, CaSx dosage of 200 mg/L, and BPX dosage of 100 mg/L), the recovery of malachite, calcite, and quartz were 98.23%, 5.89%, and 2.35%, respectively. Zeta potential analyses showed a negative shift in the surface potential of malachite over the pH range of 7–12 after the addition of CaSx, followed by a further negative shift upon BPX adsorption. The XPS results further indicate that CaSx forms stable Cu(I/II)–S chelates on the malachite surface. Subsequently, the sulfided malachite chemically reacts with BPX to form C–S–Cu(I/II) chemical bonds. Contact angle measurements revealed that malachite undergoes a transition from hydrophilic to hydrophobic upon treatment with CaSx–BPX, whereas calcite and quartz retain their hydrophilic nature. This differential wettability provides a rational explanation for the high flotation selectivity achieved among the three minerals.