High-Arsenic Acidic Wastewater Disposal in Non-Ferrous Smelting: A Critical Review of Fundamentals and Processes

The co-smelting of complex gold concentrates with copper concentrates via the matte capturing process generates substantial high-arsenic acidic wastewater (HAAW) containing H2SO4 50–60 g/L, As 15–30 g/L, and coexisting Cu, Pb, Zn, Cd, F−, and Cl−. This review critically evaluates treatment technologies, focusing on sulfide precipitation—a major method for direct arsenic removal under strong acidity. Lime neutralization, lime-ferric co-precipitation, scorodite, and sulfide precipitation are compared by principles and performance. Sulfide precipitation offers high efficiency, low sludge volume, and simultaneous heavy-metal removal; however, its application suffers from four bottlenecks: inaccurate dosing, low sulfur utilization, poor settleability due to colloidal As2S3, and insufficient residue stability. These are linked to three mechanistic knowledge gaps: thermodynamic equilibrium and competitive precipitation in multi-metal-sulfide-water systems, As2S3 nucleation and growth under supersaturation, and interfacial chemistry and coagulation of colloidal As2S3. These gaps span the entire reaction-nucleation-separation chain. This review bridges engineering and fundamental science, providing a theoretical basis for controllable sulfur release, selective metal recovery, and enhanced residue stability, guiding next-generation HAAW treatment.