Microbial community structure and redox potential in a copper sulphide bioleaching system with low pH, high ferric concentration and elevated temperature

摘要

Zijinshan copper bioheapleaching-SX-EW plant is well operated in a unique low redox potential leaching system with low pH, high ferric concentration and elevated temperature, in which the copper is leached efficiently and pyrite dissolution is relatively inhibited. This paper demonstrates the effect of low pH, high ferric concentration and elevated temperature on ferrous oxidizing activity in column leaching which simulated the environment of Zijinshan bioheapleaching system. Column bioleaching was performed under different temperatures, ferric concentrations and pH valves by using the raffinate solution from Zijinshan bioheapleaching process. Real-time PCR assays were further used to investigate the microbial community structure attached to the ore surface. Results show that at ambient-temperature with initial total iron concentration of 15 g/L and pH 1. 2, the solution redox potential was quickly increased to 850 mV(vs. SHE) , acidophiles' concentrations was relatively high, and pyrite dissolution was accelerated. When initial iron concentration was increased to 50 -60 g/L, while pH was maintained in the range of 1. 2 to 0. 9, the growth of microorganisms was inhibited and the increase of solution redox potential was delayed. Column tests operated at different temperatures using high ferric concentration and low pH raffinate solution showed that under high leaching temperature (60t!) , the growth of iron oxidizers such as Leptospirillum. sp. and Ferroplasma. sp. were significantly inhibited and solution redox potential varied at low level between 640 -680 mV through the whole leaching process. However, the redox potential started to increase after 60 leaching days reaching a maximum of 800 mV at 301, and it slowly increased to 730 mV at 451. Our findings indicate that ferrousoxidizing microorganisms in Zijinshan bioheapleaching system were inhibited by elevated temperature, high ferric concentration and low pH; required for maintaining low redox potential. In such low redox potential leaching system, copper minerals could be leached out efficiently,and pyrite dissolution was relatively restrained due to the strong relation to redox potential, which met the mineral dissolution kinetics of Zijinshan copper mine.