Treatment of smelting residue for arsenic removal and recovery of copper using pyro–hydrometallurgical process

Abstract

During pyro-metallurgical processing of non-ferrous metals, smelting residues such as smelter slag, flue gas, containing value metals and also harmful substances are inevitably generated as secondary product. For reduction of environmental loading and recovery of the value metals, such materials demand proper treatment options. In this research, some experimental steps were investigated to remove high arsenic (As: 19.5 wt%) and recover copper (Cu: 3.1 wt%) contained in such smelting residues. In the first-stage arsenic and other volatile materials were removed by pyro-metallurgical treatment and in the second-stage the treated residue from pyro-processing was treated in hydrometallurgical processing involving a two-stage leaching operation in H 2SO 4 solution to dissolve the metals followed by solvent extraction using LIX-84I as extractant to recover dissolved Cu in final leached solution. The results showed that over 90% of arsenic in smelting residue was removed by volatilization and recovered as As 2O 3 while copper content increased to 4.2 wt%. In the two-stage leaching process, first up to 90% of arsenic was selectively dissolved in 0.25 mol/L H 2SO 4 solution and second, the solids were further leached in 1.0 mol/L H 2SO 4 solution giving 85% of copper dissolution. Over 90% of copper dissolved into solution was recovered by solvent extraction. Finally over 99% of arsenic dissolved in the first-stage leach solution was co-precipitated with iron dissolved in second-stage leach solution after copper recovery.