Geoactive fungi such as Aspergillus niger play a significant role in bioweathering processes and element cycling. These organisms are able to secrete a range of metabolically produced organic acids, such as oxalic acid, into their microenvironment. This enables them to mediate mineral dissolution, leading to metal solubilization and also biomineralization in the form of secondary oxalate biominerals. In this investigation, such biotransformation processes by geoactive fungi were explored as a means of bioprocessing and biorecovery of cobalt – an element identified as being of key industrial and strategic importance. A range of Co-bearing laterite and pyrite ores were investigated, in addition to seafloor ferromanganese nodules, for their susceptibility to fungal biotransformations. Direct examination of fungal-colonized cobalt-containing substrates by light and scanning electron microscopy was used to reveal mineral transformations at the microscale. Bioleaching studies in liquid media revealed differences between the ore substrates, with bioleaching being more effective from laterites: in some cases >90% Co was released. The influence of mineral presence on the range of organic acids produced and the effectiveness of culture filtrates for bioleaching and/or mineral precipitation were also examined. The work contributes to understanding the factors that influence chemoorganotrophic cobalt bioleaching and biomineral precipitation at micro- and nanoscales, with the aim of optimising maximal cobalt biorecovery from solution.
Full conference title:
- MS 2017