| 概要 |
In order to tackle the dual challenge of utilizing highly refractory chalcopyrite (CuFeS_2) while saving scarce freshwater resources, this study aimed to systematically understand the individual role ...of chemical lixiviant and bioleaching microorganisms in the complex Fe^3+_-Cu^2+_-SO_4^2−_-Cl^− chalcopyrite leaching system. In general freshwater bioleaching conditions, the Eh level sharply increased, and the “high-E_h-bioleaching” became the major leaching driving force. In this case, the lowest Cu yield was obtained. The chalcopyrite leaching reaction responded differently to different salinity levels. At a low salinity of 0.5% NaCl, chemical Cl^−_-leaching effect resulted in a higher Cu yield than the fresh-water “high-E_h-bioleaching” system. The growth of tested microbes was observed at 0.5% NaCl, but partial deactivation of microbial Fe-oxidation suppressed the E_h level. Under this condition, synergism between the chemical Cl^−_-leaching effect and the “low-E_h-bioleaching” effect was found. At a high salinity of 2% NaCl, on the other hand, no active cell growth was observed, and thus pre-grown cells were used to mimic the presence of Cl^−_-tolerant cells. Chemical Cl^−_-leaching readily proceeded at 2% NaCl at low E_h, but quickly ceased upon the depletion of H^+. The presence of bioleaching cells somewhat slowed down the speed of chemical Cl^−_-leaching, but the acid depletion was alleviated by microbial acid generation. Chemical Cl^−_-leaching, which favors low E_h condition, was the main driving force for chalcopyrite leaching at 2% NaCl. Therefore, the activity of Cl^−_-tolerant S-oxidizer alone, rather than mixed Fe- and S-oxidizing consortium, was shown to play a critical role in maximizing the chalcopyrite dissolution.続きを見る
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