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A bioleaching study of chalcopyrite concentrate in a stirred-tank bioreactor in the presence of three domesticated or non-domesticated moderately thermophilic bacteria, Acidithiobacillus caldus, Leptospirillum ferriphilum and Sulphobacillus thermosuphidooxidans, is presented. The results indicate that the optimal microbial growth conditions of the bacteria are a temperature of 45 degrees C and an initial pH value of 1.5 and, under these conditions, the microbial growth of the domesticated bacteria and the bioleaching rate are higher than those employing the non-domesticated bacteria. Using the domesticated bacterial strains, the leaching rate of copper reaches 94.00% with a pulp density of 50 g/l and stabilises at ca. 80% when the pulp density reaches 100 g/l. Under the optimal parameters for the stirred reactor of a stirring speed of 350 rpm and an aeration intensity of 500 ml/min, the final concentration of copper ions is 17.36 g/l and the leaching rate of copper is 85.60% for 30 d of chalcopyrite bioleaching., A bioleaching study of chalcopyrite concentrate in a stirred-tank bioreactor in the presence of three domesticated or non-domesticated moderately thermophilic bacteria, Acidithiobacillus caldus, Leptospirillum ferriphilum and Sulphobacillus thermosuphidooxidans, is presented. The results indicate that the optimal microbial growth conditions of the bacteria are a temperature of 45 degrees C and an initial pH value of 1.5 and, under these conditions, the microbial growth of the domesticated bacteria and the bioleaching rate are higher than those employing the non-domesticated bacteria. Using the domesticated bacterial strains, the leaching rate of copper reaches 94.00% with a pulp density of 50 g/l and stabilises at ca. 80% when the pulp density reaches 100 g/l. Under the optimal parameters for the stirred reactor of a stirring speed of 350 rpm and an aeration intensity of 500 ml/min, the final concentration of copper ions is 17.36 g/l and the leaching rate of copper is 85.60% for 30 d of chalcopyrite bioleaching.

Variations in the microbial community structure were investigated during the tank bioleaching of a Pb-Zn-Sn concentrate from Meizhou, Guangdong, China, using three bacterial strains, Acidthiobacillus caldus, Leptospirillum ferriphilum and Sulphobacillus thermosulphidooxidans. Cu extraction of 85.6% was obtained after 30 days. Acidthiobacillus caldus was the dominant population in the initial stage, with an abundance of 73.8%, Sulphobacillus thermosulphidooxidans was dominant from the 18th day to the end of the bioleaching process, while the abundance of Leptospirillum ferriphilum changed only slightly. The total Fe concentration decreased significantly from the 6th to the 14th day, attributed to precipitation, while the solution potential increased sharply from the 1st to the 3rd day, reached a peak of 540 mV, decreased sharply to 390 mV during the 4th day and then steadily increased. The results indicated that the bioleaching process required a higher solution potential within a certain range and an appropriate concentration of ferric ions., Variations in the microbial community structure were investigated during the tank bioleaching of a Pb-Zn-Sn concentrate from Meizhou, Guangdong, China, using three bacterial strains, Acidthiobacillus caldus, Leptospirillum ferriphilum and Sulphobacillus thermosulphidooxidans. Cu extraction of 85.6% was obtained after 30 days. Acidthiobacillus caldus was the dominant population in the initial stage, with an abundance of 73.8%, Sulphobacillus thermosulphidooxidans was dominant from the 18th day to the end of the bioleaching process, while the abundance of Leptospirillum ferriphilum changed only slightly. The total Fe concentration decreased significantly from the 6th to the 14th day, attributed to precipitation, while the solution potential increased sharply from the 1st to the 3rd day, reached a peak of 540 mV, decreased sharply to 390 mV during the 4th day and then steadily increased. The results indicated that the bioleaching process required a higher solution potential within a certain range and an appropriate concentration of ferric ions.

Shaking flask and column leach experiments were carried out on a low- grade ore from Hami, Xinjiang, China, using bacterial cultures of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferrooxidans and At. caldus. Ni, Co and Cu recoveries of 94%, 62% and 70%, respectively, were obtained after 68 days of flask leaching including 18 days of acid pre-leaching and 50 days of bioleaching. Column leaching for 139 days including 19 days of acid pre- leaching and 120 days of bioleaching resulted in Ni, Co and Cu recoveries of 46%, 39% and 13%, respectively, indicating that Ni and Co exhibit the same leaching behaviour. K, Na and Fe(III) ions in the leach solution formed jarosite within the ore bed, with some Ni and Cu ions incorporated in the jarosite precipitates which reduced the overall metal recovery. Mg was preferentially leached from the gangue minerals by the acid, resulting in the formation of a Mg-depleted silicate skeleton, but residue analysis indicated that Mg was re-deposited into the skeleton during bioleaching., Shaking flask and column leach experiments were carried out on a low- grade ore from Hami, Xinjiang, China, using bacterial cultures of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferrooxidans and At. caldus. Ni, Co and Cu recoveries of 94%, 62% and 70%, respectively, were obtained after 68 days of flask leaching including 18 days of acid pre-leaching and 50 days of bioleaching. Column leaching for 139 days including 19 days of acid pre- leaching and 120 days of bioleaching resulted in Ni, Co and Cu recoveries of 46%, 39% and 13%, respectively, indicating that Ni and Co exhibit the same leaching behaviour. K, Na and Fe(III) ions in the leach solution formed jarosite within the ore bed, with some Ni and Cu ions incorporated in the jarosite precipitates which reduced the overall metal recovery. Mg was preferentially leached from the gangue minerals by the acid, resulting in the formation of a Mg-depleted silicate skeleton, but residue analysis indicated that Mg was re-deposited into the skeleton during bioleaching.