Enhancing persulfate activation with combined Fe(Ⅱ) and Cu(Ⅱ) catalysts to generate sulfate radicals for the rapid oxidation of galena

PS/Fe 2+ /Cu 2+ reagents inhibited PbS flotation with 30   s of reaction. • Cu 2+ raised the SO 4 • − yield in the PS/Fe 2+ /Cu 2+ solution. • SO 4 • − oxidized the PbS surface, producing PbO and SO 4 2− . • Cu 2+ raised the Fe 3+ concentration in solution and improved the Fe 2+ /Fe 3+ cycle. Galena (PbS) depression in PbS–chalcopyrite (CuFeS 2 ) mixture via SO 4 • − radicals generated from persulfate (PS)/Fe 2+ typically requires a high PS concentration (0.15   mol/L) and a prolonged reaction time (10   min). This study employed a combined Cu 2+ /Fe 2+ catalyst to enhance SO 4 • − generation at a lower PS concentration. Flotation tests were conducted to determine optimal PbS treatment conditions using the PS/Fe 2+ /Cu 2+ system. The results showed that effective PbS depression was achieved with a PS concentration of 6.5 × 10 −3 mol/L and a reaction time of only 30   s. The synergistic role of Cu 2+ was investigated using surface analyses, including contact angle tests, XPS, Raman and UV-visible spectra. Contact angle measurements revealed that after 30   s of treatment, the PbS surface angle decreased to 38.2°, whereas the CuFeS 2 surface remained hydrophobic. Oxidation products, including PbO and SO 4 2− , formed on the PbS surface. SO 4 • − and •OH both existed in the system to react with the PbS surface, and SO 4 • − was the major radical species as indicated by the radical quenching tests. UV–visible spectrum results implied that Cu 2+ increased the equilibrium Fe 3+ concentration, thereby facilitating the Fe 2+ /Fe 3+ cycle and sustaining PS activation. The rapid oxidation capacity of the PS/Fe 2+ /Cu 2+ system demonstrates strong potential for industrial application. Download: Download high-res image (202KB) Download: Download full-size image