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Abstract:The catalysis of carbon materials with different specific surface areas (SSA) (2, 400, 800 and 1200 m 2 /g) on complex copper ores bioleaching by moderately mixed thermophiles was investigated. The copper extractions increased with the rise in SSA of carbon materials. A recovery of 98.8% copper in the presence of 1200 m 2 /g activated carbon was achieved, and improved by 30.7% and 76.4% compared with biotic control and chemical leaching. Moreover, the addition of 1200 m 2 /g activated carbon adsorbed large amount of bacteria, accelerated the oxidation rate of ferrous iron and maintained the solution redox potential at relatively low values, and significantly increased the dissolution of primary copper sulfide (62.7%) compared to biotic control (6.0%). Microbial community succession revealed that activated carbon changed the microbial community composition dramatically. The S. thermosulfidooxidans ST strain gained a competitive advantage and dominated the microbial community through the whole bioleaching process. The promoting effect of carbon material with higher SSA on copper extraction was mainly attributed to better galvanic interaction, biofilm formation, direct contact and lower redox potential.

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Acidithiobacillus thiooxidans A01 is widely used in bioleaching processes and commonly thrives in most metal-rich environments. However, interactions between different heavy metals remain obscure. In this study, we elaborated the effect of ferric iron on the growth and gene expression of At. thiooxidans A01 under the stress of nickel. The results showed that 600 mM Ni 2+ completely inhibited the growth and sulfur metabolism of At. thiooxidans A01. However, trace amounts of Fe 3+ (0.5 mM) facilitated the growth of At. thiooxidans A01 in the presence of 600 mM Ni 2+ . With the addition of 5 mM Fe 3+ , the maximum cell density reached 1.84 × 10 8 cell/mL, and pH value was 0.95. In addition, metal resistance-related and sulfur metabolism genes were significantly up regulated with extra ferric iron. Taking the whole process into account, the promoting effect of Fe 3+ addition can be attributed to the following: (1) alleviation of the effects of Ni 2+ toxicity and restoring the growth of At. thiooxidans A01, (2) a choice of multiple pathways to export nickel ion and producing precursor of chelators of heavy metals. This can suggest that microorganisms may widely exhibit metabolic activity in iron-rich environments with heavy metals. Our study will facilitate the technique development for the processing of ore bodies with highly challenging ore compositions.