Reductive processes in biohydrometallurgy: New opportunities for mineral processing and for metal recovery from waste streams and process waters
This paper describes results from recent experimental work carried out at Bangor University in which the abilities of acidophilic bacteria to catalyze reductive transformations of iron or sulfur have been harnessed to develop new approaches for bioleaching ores, and for remediating mine waters and capturing metals from mine process streams. Three scenarios are highlighted. In the first, effective solubilisation of nickel from an oxidized limonite ore has been demonstrated using the well-known acidophilic autotroph Acidithiobacillus ferrooxidans, grown anaerobically using elemental sulfur as electron donor. The process is one of reductive mineral dissolution, in which the bacteria couple the oxidation of sulfur to the reduction of ferric iron in the mineral goethite ( which contained most of the nickel in the ore) causing its dissolution and release of nickel and ferrous iron, both of which remained in solution in the acidic leach liquors. Concurrent indirect reductive dissolution (by ferrous iron) of the Mn(IV) mineral asbolane caused cobalt and manganese to be released from this mineral, pointing to a more generic application for the reductive dissolution of minerals beyond those containing ferric iron. A 2 L packed-bed reactor containing immobilized Acidiphilium SJH biomass using glycerol as electron donor was set up and shown to be highly efficient at reducing soluble ferric iron present in synthetic feed liquors. Conversion of between 90 and 99. 9％ of iron was obtained with dilution rates of up to 0. 87 h-1 , with ~ 1 g of ferric iron being reduced ( h -1 ) at the highest flow rates. Ferrous iron-generating bioreactors have potential for indirect bioleaching of oxidized ores, or as integral components of mine water remediation systems. Lastly, selective precipitation of copper and zinc from synthetic mine waters containing a variety of soluble metals has been demonstrated in anaerobic bioreactors, operated at pH 2. 2 and above, using novel consortia of acidophilic sulfate-reducing bacteria. These bioreactors have highlighted how more environmentally-benign approaches could be developed to remediate AMD streams, in which pH amelioration is combined with the recovery and recycling of dissolved metals.
iron reduction reductive mineral dissolution metal precipitation sulfate reduction sulfidogenesis
D. Barrie Johnson
School of Biological Sciences, Bangor University, Bangor, UK
国际会议
The 19th International Biohydrometallurgy Symposium(第19届国际生物湿法冶金大会 IBS2011)
长沙
英文
23-29
2011-09-18（万方平台首次上网日期，不代表论文的发表时间）