Clean hydrometallurgical route to recover zinc, silver, lead, copper, cadmium and iron from hazardous jarosite residues produced during zinc hydrometallurgy.

A hydrometallurgical process for treating the hazardous jarosite residue from zinc hydrometallurgy was proposed, for not only detoxifying the residue, but also recovering the contained valuable metal components. The jarosite was initially activated and decomposed by sintering at 650°C for 1h. The sintered residue was leached in 6mol L(-1) aqueous NH(4)Cl solution at 105°C, followed by filtration. The leaching extraction of Zn, Pb, Cu, Cd and Ag are more than 95%. During reduction with Zn powder, more than 93% of Pb, Cu, Ag and Cd can be simultaneously recovered. Then the NH(4)Cl leaching residue were leached again in 30wt% aqueous NaOH solution for 1h at 160°C, and about 94% of As and 73% of Si were removed from the residue. The final residue was almost completely detoxified, and contains about 55wt% Fe, which can be used as an iron concentration.