Rare Earth Elements (REEs) are an essential component in most modern technologies and play a key role in medical technology, environmental protection, energy efficiency, digital technology and defence. Decrease in global supply and ever increasing demand for REEs provides Australia, and in particular Western Australia, with an opportunity to become a major player in the REE industry. Conventional REE processing methods are complex, costly, use aggressive reagents and they are harsh on the environment. As an alternative to this approach this study investigated the use of phosphate solubilising microorganisms (PSMs) to liberate REEs from REE phosphate minerals. Numerous microbial species are capable of transforming insoluble forms of phosphate to soluble forms and are applied in agricultural settings (Igual et al., 2001). This study applied the use of known PSM’s to the leaching of REEs from a Western Australian monazite ore.
Monazite was added at a 0.5% pulp density to PVK media and REE levels in the leachate analysed by ICP-EOS. Of twenty five known PSB tested the best performer, a Penicillium sp. successfully released bound REEs (Ce, La, Nd and Pr) preferentially over potential ‘contaminants’, thorium and iron, from the sterile monazite into the leachate, at a total concentration of 12.32 mg L-1. These microbial isolates leached REEs from the MWM in quantities significantly greater than was recorded with abiotic dissolution of the ores alone. Indigenous microorganisms present on unsterilized monazite leached the REE’s at very low levels 0.9 mg L-1 however, inoculation of unsterilized monazite with the previously tested phosphate solubilisers, enabled us to increase the levels of REE released into the leachate four fold. A synergistic effect of between indigenous and inoculant microorganisms was demonstrated.