The use of bio-oxidation in the treatment of mine tailings

Abstract

One of the most interesting and potentially important developments relating to the mining industry is the use of bacteria, namely Thiobacillus ferrooxidans, in biohydrometallurgical process to extract metals from ores. These processes are known as bio-oxidation and have been proven to be efficient, cost effective, safe, and environmentally friendly methods of extracting metals from ores and concentrates. Along with declining ore grade, the generation of acid mine drainage and the release of dissolved metals from sulfide-bearing tailings into the environment are serious problems plaguing the mining industry. The latter is due to the presence of the naturally occurring bacteria Thiobacillus ferrooxidans, the same organism used to extract metals from ores. To further examine the bio-oxidation process, aside from literature review, four different reactors were set up to determine whether the bio-oxidation process could be used to treat mine tailings by extracting more metals from them and therefore producing a more environmentally friendly waste product. The importance of adding inoculum to enhance the process was examined as well as the effect of adding a supplementary carbon source. It was found that, after 60 days of operation, the inoculated reactor produced very similar results to that which was not inoculated as well as the sterilized 'control' reactor. It was also found that the acetic acid used as the supplementary carbon source significantly impeded the bio-oxidation process. This work demonstrates that, using bio-oxidation, about 70% of metals can be recovered from the tailings in a short time of 60 days.