Interactions of phosphate solubilising microorganisms with natural rare-earth phosphate minerals: a study utilizing Western Australian monazite

Abstract

Many microbial species are capable of solubilising insoluble forms of phosphate and are used in agriculture to improve plant growth. In this study, we apply the use of known phosphate solubilising microbes (PSM) to the release of rare-earth elements (REE) from the rare-earth phosphate mineral, monazite. Two sources of monazite were used, a weathered monazite and mineral sand monazite, both from Western Australia. When incubated with PSM, the REE were preferentially released into the leachate. Penicillum sp. released a total concentration of 12.32 mg L rare-earth elements (Ce, La, Nd, and Pr) from the weathered monazite after 192 h with little release of thorium and iron into solution. However, cultivation on the mineral sands monazite resulted in the preferential release of Fe and Th. Analysis of the leachate detected the production of numerous low-molecular weight organic acids. Gluconic acid was produced by all microorganisms; however, other organic acids produced differed between microbes and the monazite source provided. Abiotic leaching with equivalent combinations of organic acids resulted in the lower release of REE implying that other microbial processes are playing a role in solubilisation of the monazite ore. This study demonstrates that microbial solubilisation of monazite is promising; however, the extent of the reaction is highly dependent on the monazite matrix structure and elemental composition.

Secondary lanthanide phosphate mineralisation in weathering profiles of I-, S- and A-type granites

“…Interestingly, regardless of their high insolubility the secondary lanthanide phosphates are removed from the overlying soil while being concentrated in the weathered rock below (Taunton et al , 2000a,b). The dissolution mechanisms remain unknown, but theoretical considerations such as measurements of REE complexation by siderophores (Christenson and Schijf, 2011), organic acids (Goyne, et al ., 2010) and biogenic dissolution of REE/P-bearing minerals (Cervini-Silva et al , 2005; Brisson et al , 2016; Corbett et al , 2017) hint at a potential microbiological role in dissolution.…”

Microbial cooperation improves bioleaching recovery rates

“…It has been shown that mixed acidophilic populations increase recovery rates of copper 12 compared to pure cultures. Our research initially conducted with pure cultures 13 (Figure 1) demonstrated low recovery rates of REEs from a concentrated Western Australian monazite, whereas when bioleaching was performed using nonsterile ore complete with the native population and an introduced PSM (Figure 2), REE leaching rates increased tenfold with some species 14 . These leaching rates were much greater than those recorded with either pure cultures or the native consortia alone.…”

Bioreductive Dissolution as a Pretreatment for Recalcitrant Rare-Earth Phosphate Minerals Associated with Lateritic Ores

“…Although~9% of the cerium and 5% of the lanthanum were leached using A. thiooxidans at pH 0.9, the results again suggest that bioreductive dissolution can improve accessibility to monazite, but further studies including analysis of the residue are needed. Recent studies addressing only monazite dissolution using phosphate-solubilizing bacteria have shown different degrees of success with leaching efficiencies for REE recovery (between 0.1% and 25%), though differences in ores and experimental conditions may explain the varying results [5,25,26].…”