Enhanced recovery of rare earth elements from carbonatite ore by biological pretreatment

The increasing demand for rare earth elements (REEs) necessitates the development of more efficient and environmentally friendly leaching methods. This study investigates the use of biological pretreatment to improve metal recovery from REE ore obtained from the Mushgia Khudag deposit. Characterization of the ore revealed a total REE content of 6.99%, with X-ray diffraction analysis identifying calcite and apatite as the dominant minerals, while REEs were primarily found in the forms of monazite and parisite. Experimental results demonstrated that ore pre-treated with a mixed thiobacteria culture (Tmix) achieved a 1.40-fold increase in metal recovery compared to direct acid leaching. Additionally, Bacillus sp. (B. sp.) bacteria improved recovery by 1.07-fold. Monitoring changes in pH, oxidation-reduction potential (ORP), and zeta potential during the pre-treatment process indicated that the bacteria did not directly dissolve the REEs but rather modified the surface charge and mineral structure of the ore, facilitating more efficient acid leaching. The use of Tmix bacteria for pretreatment significantly improved leaching efficiency, reduced acid consumption, and minimized environmental impact.