Abstract
The indispensable role of rare earth elements (REEs) in modern technology devices is creating immense stress to the metallurgical exploitation of low-grade ores. In this context, for an effective extraction of REEs from vein-deposited Korean monazite has been studied using the process integration of microbial activity with the chemical technology. The applied fungi, Aspergillus niger not only attacks to break the phosphate matrix of monazite but also excretes organic acid mixture to form REEs’ complexation. It enables to dissolve more than 73% of phosphorus with simultaneous conversion of REEs’ phosphates into oxalates which was evident by the instrumental analysis. Subsequently, iron was bio-leached before undergoing the sulfuric leaching in the presence of ozone to dissolve cerium as Ce(IV) and other REEs (Y, La, and Eu) in their tri-valent form. More than 90% of REEs’ recovery has been achieved, which were separated by solvation with the organic extractant Cyanex 923 for Ce(IV)-extraction and the oxalate precipitation of other REEs.