The disposal of sulfide-arsenic cake

Abstract

When processing sulfide copper-zinc concentrates at copper smelters, sulfide-arsenic cakes are formed, which are subject to disposal. To solve the global environmental problem of arsenic in the metallurgical and mining industries, it must be reliably concentrated and fixed in technological flows with subsequent waste disposal. The fusion of arsenic cake with elemental sulfur leads to the formation of vitreous sulfides, which are less toxic in comparison with dispersed powdered cake, homogeneous and compact in shape. The fusion product is represented by non-stoichiometric arsenic sulfide, similar in composition to As2S5. The high chemical stability of glassy arsenic sulfides is confirmed by the results of leaching by TCLP method. The fusion products have 100 times lower solubility compared to the initial cake. Achieving the solubility of arsenic in the alloy below the threshold concentration (5 mg/dm3 ) makes it possible to recommend the disposal of arsenic cake by fusing it with elemental sulfur. The fusion products belong to non-hazardous waste and are suitable for long-term storage. The composition and structure of cake fusions with iron powder have been studied. New compounds of variable composition were identified in the fused samples: arsenides and sulfides of iron, arsenic sulfides and arsenopyrites. Studies have shown that the products of fusion with iron have a solubility 10–15 times lower than the arsenic compounds in the initial cake but above the threshold concentration as per TCLP method. Therefore, fusion with iron cannot be recommended for practical use for the disposal of arsenic cakes.