CATALYTIC EFFECT OF METAL IONS ON THE OXIDATION OF THIOCYANATE IONS WITH HYDROGEN PEROXIDE

Thiocyanate (SCN⁻) ions, formed during the cyanidation of gold ores, pose a significant environmental problem when present in mine processing wastewater. In this study, the oxidation of potassium thiocyanate model solutions (10–1000 mg/L) with hydrogen peroxide, in the presence and absence of Cu2+ and Fe2+ ions, was investigated at room temperature. Residual SCN⁻ concentrations were determined by bromatometric titration and UV-spectroscopy. Without a catalyst, H2O2 showed the weakest effect at all concentrations, leaving 6–17% residual SCN⁻ even at the highest applied dose. The addition of Cu2+ and Fe2+ ions markedly accelerated oxidation via Fenton and Fenton-like mechanisms, achieving 95–100% removal efficiency at doses above 500 µL, with Fe2+ generally showing slightly higher catalytic activity than Cu2+. The catalytic effect became more pronounced as the initial concentration decreased: at 10 mg/L, complete (100%) degradation of thiocyanate was achieved in the presence of Fe2+. These findings recommend Fe2+- and Cu2+-catalyzed H2O2-based processes as a promising technological solution for the effective detoxification of thiocyanate-containing wastewater from gold processing plants.