Extraction of Ce and Th from Monazite Using REE Tolerant Aspergillus niger

In the present study, bioleaching of monazite, one of oldest and most water-resistant mineral to microbial attack, was tested for its amenability toward extraction of Ce, Th, and U using heterotrophic fungal species, Aspergillus niger. Shake flask experiments were carried out using Bromfield, sucrose, synthetic, and standard media containing 2%(w/v) of monazite for 60 days. Several parameters such as media pH, redox potential, siderophore production, biomass, and metal oxidation were analyzed at different intervals during the process of bioleaching. The maximum concentration of Ce obtained was 0.701, 0.229, 0.132, and 0.052 mg/L in Bromfield, synthetic, sucrose, and standard media(s), respectively. Thorium was identified only in synthetic (0.026 mg/L) and sucrose (0.0175 mg/L) media, whereas uranium was not observed in any of the media attempted. The results were corroborated with analysis by SEM characterization of the head and residues.