Bioleaching of rare earth elements from monazite sand

Abstract

Three fungal strains were found to be capable of bioleaching rare earth elements from monazite, a rare earth phosphate mineral, utilizing the monazite as a phosphate source and releasing rare earth cations into solution. These organisms include one known phosphate solubilizing fungus, Aspergillus niger ATCC 1015, as well as two newly isolated fungi: an Aspergillus terreus strain ML3-1 and a Paecilomyces spp. strain WE3-F. Although monazite also contains the radioactive element Thorium, bioleaching by these fungi preferentially solubilized rare earth elements over Thorium, leaving the Thorium in the solid residual. Adjustments in growth media composition improved bioleaching performance measured as rare earth release. Cell-free spent medium generated during growth of A. terreus strain ML3-1 and Paecilomyces spp. strain WE3-F in the presence of monazite leached rare earths to concentrations 1.7-3.8 times those of HCl solutions of comparable pH, indicating that compounds exogenously released by these organisms contribute substantially to leaching. Organic acids released by the organisms included acetic, citric, gluconic, itaconic, oxalic, and succinic acids. Abiotic leaching with laboratory prepared solutions of these acids was not as effective as bioleaching or leaching with cell-free spent medium at releasing rare earths from monazite, indicating that compounds other than the identified organic acids contribute to leaching performance.

Effects of Sulfate Reduction on Trichloroethene Dechlorination by Dehalococcoides-Containing Microbial Communities

“…The sulfide concentration was measured at the end of the experiments by the methylene blue method (59). Trace metal concentrations were analyzed on an Agilent Technologies 7700 series ICP-MS (60).…”

Microorganisms meet solid minerals: interactions and biotechnological applications

“…Organic acids produced by filamentous fungi have been demonstrated to be able to leach REEs from ores, such as bauxite reside and monazite sand (Brisson et al 2016;Qu and Lian 2013). Citric acid produced by Penicillium tricolor was shown to have the potential for recovering REEs and radionuclides from bauxite residue by the formation of soluble complexes.…”

“…Aspergillus niger and two newly isolated strains, Aspergillus terreus strain ML3-1 and Paecilomyces spp. strain WE3-F, were found to be able to use monazite as their sole phosphate source and, hence, were able to solubilize phosphate to release REEs (Brisson et al 2016).…”

Integration of microbial and chemical processing for a sustainable metallurgy

“…The microorganisms used can potentially solubilize the phosphates after producing organic acids as main metabolic product to leach the REMs. Brisson et al 44 compared the leaching efficiency of biogenic and commercial organic acids and found a significant difference with less solubilization of radioactive elements like thorium and less phosphate precipitation. The study indicates that direct bioleaching yields higher efficiency of REMs than spent medium bioleaching.…”