Bioleaching of Chalcopyrite with Thermophiles: Temperature-pH-ORP Dependence
The copper extraction yield from thermophilic bioleaching of chalcopyrite depends on temperature, pH, and the oxidation-reduction potential (ORP), as well as the activity of the microbe used.We studied copper extraction yields obtained from chalcopyrite with three thermophiles, Acidianus brierleyi, Sulfolobus metallicus, and Metallosphaera sedula, under various pH and temperature conditions and with different initial amounts of ferric iron. The results indicated that the capacity of each thermophile strain to leach iron as Fe3+ differed, which affected the influence of pH, temperature, ORE and microbial activity level on the yield of copper. Microbial activity can cause ORP to be close to the critical value (450 mV) at which copper extraction at 65℃ can be higher than that at 80℃. An initial pH of 1.5 retards the precipitation of jarosite, allowing temperatures as high as 80℃ to result in copper extraction yields close to 100%. However, if a thermophile with a poor capacity to form Fe3+ is employed, 100% copper extractions can also be obtained at pH 2.5, because ORP is low as result of low amounts of Fe3+ in solution. Optimum temperatures for the growth of thermophiles did not always mean high copper extraction yields. Conversely, high biomass concentrations depending on the capacity of the thermophile swain to leach iron as Fe3+, can result in excess Fe3+ in solution, leading to the precipitation of large amounts of Fe3+ as jarosite. The bioleaching capacity of A. brierleyi was reduced or suppressed when insufficient initial Fe3+ was provided to trigger the leaching reaction, whereas S. metallicus and M. sedula were less sensitive to the initial availability of Fe3+. This result confirmed that a direct enzymatic attack on the mineral surface could initiate the leaching reaction, but later ORP governed the leaching rate of chalcopyrite.
J. Vilcáez K. Suto C. Inoue
Graduate School of Environmental Studies, Tohoku University, Sendal, Japan
国际会议
XXIV International Mineral Processing Congress(第24届国际矿物加工大会)
北京
英文
2779-2788
2008-09-24（万方平台首次上网日期，不代表论文的发表时间）