Comparison of Leaching of Copper-Nickel Concentrates and Metallurgical Slag with Biogenic Ferric Iron

The leaching of nonferrous metals from copper-nickel sulfide concentrates and copper-nickel slags with ferric sulfate solution obtained by microbial oxidation of ferrous sulfate was studied. The process was carried out at 80 degrees C, pH 1.15, and 9.8 g/L Fe3+. Most nickel was shown to be leached from the slags within 1.5 h. When copper-nickel concentrates were leached for 7 h, the maximum possible concentration of nonferrous metals was not reached. The leaching rates of copper and nickel from slags were close: up to 177 and 141 mg/(L h), respectively. The leaching rates of nonferrous metals from copper-nickel concentrates were significantly lower and ranged from 25 to 39 mg/(L h) for nickel and from 14 to 23 mg/(L h) for copper. The efficiency of leaching of the copper-nickel concentrates was independent of their chemical composition. However, the nickel recovery into the liquid phase was approximately four times higher than the extraction of copper. At the same time, the copper content increased in all leach residues, in comparison with the original concentrates. Slag leaching was characterized by a relatively short duration, high recovery of nonferrous metals into the liquid phase (99%), and their low content in the solids (0.11-0.14%).