Copper Recovery from Chalcopyrite Flotation Concentrate Using Mixed Mesophilic Strains Subjected to Microwave and Ultrasound Irradiation

Abstract

The current study compared the bioleaching ability of a mutated mesophilic mixed culture with that of a non-mutated mesophilic mixed culture and a moderately thermophilic mixed culture. Mutation experiments were carried out using ultrasonic and microwave irradiation on Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, and Acidithiobacillus thiooxidans, mesophilic bacteria used in copper bioleaching. The mutational effects of irradiation were determined by measuring the ferrous iron and elemental sulfur oxidation rates. The mutated strains exhibiting the best oxidation activity were used in bioleaching tests. Bioleaching experiments using the mutated mixed culture were carried out under the same optimized operational conditions as for the non-mutated mesophilic mixed culture. The bioleaching results were compared to copper recovery obtained by the moderately thermophilic mixed culture. The copper recovery achieved by the non-mutated mesophilic mixed culture was 34.2% after 30 days and increased to 39.06 and 37.21% for ultrasonic- and microwave-mutated mesophilic mixed cultures, respectively. The bioleaching rate increased using mutated mesophilic mixed cultures, such that the copper recovery for the ultrasonically mutated mixed culture reached 34.01% after 12 days and for the microwave-irradiated mixed culture reached 33.15% after 15 days. The results of bioleaching experiments using mutated mesophilic mixed cultures under optimized operational conditions showed that the copper recovery attained was 49.12 and 44.36% for mesophilic mixed cultures mutated by ultrasound and microwaves, respectively. These were comparable with the maximum copper recovery obtained by the moderately thermophilic mixed culture which was 49.8%, especially for the ultrasonically mutated mixed culture.