In the present work the effect of alkaline sulfide leaching (ASL) on the extraction of copper and zinc from low-grade copper concentrate containing chalcopyrite, tennantite, sphalerite, and pyrite during batch and continuous bioleaching experiments was studied. It was demonstrated that ASL and further bioleaching may be a promising approach for treatment of copper–zinc concentrates containing tennantite as this approach allows increasing copper extraction degree in comparison to one-stage bioleaching by 1.6–2.3 times. Thus, ASL was shown to be effective for pretreatment of tennantite containing concentrates to improve bioleaching for copper extraction. At the same time, ASL led to decrease in zinc extraction by 1.4–1.5 times. Therefore, the development of combined hydrometallurgical processes including ASL and bioleaching for effective metal leaching requires further studies to avoid negative effect on zinc extraction.
Tank bioleaching of substandard arsenic-bearing sulfide copper–zinc concentrate, containing 1.70, 6.22, and 7.30% of arsenic, copper, and zinc, was performed. The concentrate contained pyrite, chalcopyrite, tennantite, and sphalerite. Bioleaching was performed at 40°C using a mixed culture of acidophilic microorganisms in two modes. In the first mode, pulp density was 10%, while in the second it comprised 15%. Bioleaching made it possible to extract 17 and 70% of copper and zinc in the first mode, and 15 and 72% of copper and zinc in the second mode. The results obtained that bioleaching can be an effective approach to remove zinc from substandard copper-zinc concentrates. At the same time, copper minerals, including arsenic-bearing mineral tennantite, may be comparatively resistant to bioleaching, so requires the development of novel hydrometallurgical approaches for effective processing.
The goal of the present work was to evaluate the possibility to improve bioleaching of Cu-Zn concentrate containing tennantite by means of using alkaline sulfide leaching (ASL). Concentrate contained 18.1% Cu, 6.2% Zn, and 1.7% As. ASL allows removing arsenic by means of destruction tennantite (Cu12As4S13) that results in the formation of dissolved thioarsenite and CuS and CuS2 in solid residues. ASL was performed under the following conditions: 95°C, pulp density 20%, residence time 6 h, NaOH concentration 3.5M, Na2S concentration 1.5M. ASL residue contained 17.8% Cu, 6.4% Zn, and 0.2% As. Bioleaching of the concentrate and ASL solid residue was performed in stirred tank reactor under the following conditions: 40°C, pulp density 10%, residence time 20 d. Cu extraction reached 21 and 37%, while Zn extraction was 38 and 47% during concentrate and ASL residue bioleaching. The results obtained demonstrated that ASL pretreatment of the concentrate containing tennantite led to significant increase in copper extraction. Therefore, two-stage leaching including ASL and bioleaching may be considered as promising approach for processing tennantite-containing products since it allows avoiding emission of toxic gases and providing comparatively high copper and zinc extraction.
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