Experimental Study on the Removal of Copper Cyanide from Simulated Cyanide Leaching Gold Wastewater by Flocculation Flotation

The removal of copper–cyanide complexes from cyanide gold leaching tail water poses a significant challenge, as they are difficult to eliminate and risk causing secondary pollution. This study developed a synergistic flocculation–flotation process using the bio-collector sodium cocoyl glycinate (SCG) and the coagulant polyferric sulfate (PFS) for purification. Simulated wastewater, prepared based on actual gold mine effluent, was treated under optimized conditions of reagent dosage, a solution pH of 6–10, and a flotation time of 1–5 min, achieving high removal efficiencies of 96.48% for copper and 94.68% for total cyanide. Mechanistic studies via FT-IR, Zeta potential, and XPS revealed that Fe3+ from PFS formed Fe-CN complexes with both free and copper-complexed cyanide. Simultaneously, copper ions coordinated with SCG to generate a hydrophobic Fe-CN-Cu-SCG ternary complex, which was subsequently removed by adsorption onto air bubbles via the hydrophobic chains of SCG. This work provides a novel, efficient, and mechanistically clear strategy for the advanced treatment of cyanide-containing tailing water with a gold content of 0.021 mg/L.