Abstract Using persulfate advanced oxidation process to treat industrial cyanide wastewater, the effects of persulfate concentration, temperature, pH, and reaction time on the removal extent of pollutants were examined, and the process reaction mechanism was studied. X-ray diffraction and electron paramagnetic resonance spectroscopy (EPR) were used to analyze and characterize the precipitates and active free radicals produced during the oxidation process. Studies have shown that the removal extent of total cyanide and free cyanide increases with the increase in persulfate concentration and reaction time and shows a trend of first increasing and then decreasing with the increase in pH. Under room temperature, when the persulfate concentration was 0.0210 mol/L, pH = 10, and the reaction time was 20 min, the removal extents of total cyanide, free cyanide, copper, and zinc in cyanide wastewater were 83.09%, 100%, 90.27%, and 80.47%, respectively. EPR analysis confirmed the existence of SO4•–, •OH, and O2•– active free radicals, with O2•– originated from the dissolved oxygen in the cyanide wastewater. The persulfate oxidation process contained direct persulfate oxidation and active radical oxidation of Cu+ activation persulfate. S2O82– direct oxidation of cyanide accounts for 63.93%, and S2O82– mainly exists in the water phase in the form of SO42–. The indirect oxidation by SO4•–, •OH, and O2•– accounted for 16.44%, 5.34%, and 14.29%, respectively. Persulfate oxidation could effectively treat industrial cyanide wastewater, and this study has important theoretical and practical significance for the gold smelting industry to tap the potential to recover certain metals, increase efficiency, and support the comprehensive utilization of resources.
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