Simultaneous cyanide detoxification and sulfur immobilization in low-sulfur cyanide tailings via sustainable oxidation roasting: process optimization and mechanistic insights.

This study presents a novel, cleaner oxidation roasting technology for the harmless treatment of low-sulfur cyanide tailings, enabling simultaneous cyanide detoxification and sulfur immobilization. Following systematic process optimization, the total cyanide concentration in the roasted products was reduced below the detection limit (<0.04 mg/kg), and the S immobilization rate reached 82.22%. Addition of CaO as a fixation agent further increased the S immobilization rate to 98.78%, effectively minimizing SO2 emissions. The underlying mechanisms of cyanide detoxification and synchronous sulfur immobilization were comprehensively elucidated using TOF-SIMS, XRD, online gas analysis, and TG-DSC-MS. Results showed that the hexacyanoferrate complex K4Fe(CN)6 undergoes two-stage oxidative decomposition: first, oxygen absorption forms KCNO with release of CO, CO2, NO, and NO2; then, KCNO oxidizes to K2CO3 and gaseous products at higher temperatures. Concurrently, sulfur in the tailings is oxidized to SO2 and subsequently converted to stable sulfate through reaction with in-situ generated or externally added CaO. This technology provides an efficient, environmentally benign approach for the comprehensive treatment of cyanide tailings, significantly reducing toxicity and secondary pollution while promoting sustainable management of gold mining wastes.