Treatment of copper flash smelter flue dusts for copper and zinc extraction and arsenic stabilization

A flue dust sample of copper from flash smelting furnace has been extensively characterized. The main phases of the dusts are magnetite, cuprospinel, chalcocyanite, zincosite, dolerophanite, and claudetite. As minor phases, tenorite, arsenolite, delafossite and enargite were detected. In the sample studied, particles were mainly spherical and less than 60 μm. The leaching of flue dust sample with water dissolved copper sulfates and zinc sulfates and, partially, arsenic oxides, in an exothermic process. The leaching of the residue after water leaching in several acid media increased the dissolution of copper and arsenic oxides and small amounts of zinc. A preliminary study by hydrocyclone classification was carried out with the objective of to obtain two fractions: a coarse fraction rich in copper and a fine fraction rich in arsenic. However, results obtained in this sample were not very successful. In the stabilization study, the residue obtained after leaching the copper flash smelter flue dust with sulfuric acid was mixed with sludge from a paper factory (co-inertization process). The smaller size fraction (> 12 μm) obtained in the hydrocyclone was also mixed with this sludge. Results obtained derived of the application of a standard leaching test over these residues indicate that they were stabilized. Thus, the resulting mixtures should be dumped without generating major environmental problems.