Microbial Ecology and Solution Chemistry of Interstitial and Flowing Liquid Phases during Bioleaching of Low-grade Sulfide Ore

摘要

Work on aggregate-scale bioleaching columns has strongly suggested that there are significant differences in cell numbers and dynamics between the interstitial (stagnant) and flowing liquid phases within a bioleaching column. To build on this work, a contacting method was used to isolate the interstitial phase and analyse soluble metal concentrations, microbial cell numbers and microbial community structure. Columns were inoculated with a mixed culture. The leaching results showed good agreement with the previous aggregate-scale work. Although there appeared to be no significant benefit of using a mixed culture over a pure culture of Acidithiobacillus ferrooxidans, the material was very low grade chalcopyrite ore so not expected to leach well under mesophile conditions. As with the pure culture work, a significantly higher cell concentration was found in the interstitial liquid compared to the flowing liquid phase. All metal concentrations were significantly higher in the interstitial phase than the flowing liquid phase. For example, copper and iron concentrations were 150 and 10 time greater, respectively. Analysis of the microbial community revealed that community structure differed markedly between the two phases. However, the statistical significance of this difference is uncertain (p = 0.1). Overall, the results further suggest that the leachate of a bioleaching heap is not a realistic proxy for the environmental conditions experienced by the majority of the microbial community; solution chemistry in particular may be vastly different (by up to two orders of magnitude) at the mineral surface than in the bulk flowing solution.