China Nonferrous Metallurgy

Given the difficulty in completely removing cyanide from cyanide tailings and the associated environmental risks during high-temperature smelting, this study investigates cyanide tailings derived from a gold concentrate in Shandong Province and systematically examines cyanide removal behavior as well as the migration and transformation of sulfide minerals under oxidative roasting conditions. By systematically regulating roasting temperature, residence time, oxygen concentration, and gas flow rate, the optimal operating conditions for cyanide removal were identified, and the sulfur fixation behavior and its influence on the cyanide removal process were analyzed. The results indicate that at a roasting temperature of 500°C for 30 min under an air atmosphere with a gas flow rate of 400 mL·min^-1, the total cyanide removal efficiency reached 97. 36%, and the cyanide concentration in the leachate of the roasted product decreased to 0. 187 mg·L^-1, satisfying national discharge standards. The study demonstrates that CaO and MgO generated from the decomposition of carbonate minerals, together with iron oxides formed by sulfide oxidation, can capture SO₂ in situ during roasting, thereby partially fixing sulfur in the form of sulfates, with the sulfur fixation efficiency remaining stably above 60%. Meanwhile, SO₂ released from sulfide oxidation can synergistically enhance the oxidation and decomposition of cyanide in the presence of O₂ under appropriate conditions. Combined XPS characterization and thermodynamic analysis elucidated the mechanism underlying the breakdown of Fe-CN complexes and the complete elimination of cyanide-containing species. Overall, the results confirm that oxidative roasting enables efficient cyanide removal from tailings while significantly reducing sulfur-bearing gaseous emissions, thereby providing both theoretical insight and technical support for the safe utilization and pollution control of cyanide tailings in high-temperature co-smelting systems.