Bioleaching of some Rare Earth Elements from Egyptian Monazite using Aspergillus ficuum and Pseudomonas aeruginosa

Aspergillus ficuum and Pseudomonas aeruginosa exhibit good potential in generating varieties of organic acids effective for bioleaching some rare earth elements (REEs) from Egyptian monazite (purity 97 %) and (thorium-uranium) concentrate. Batch experiments are performed to compare the bioleaching efficiencies of the one and 2-step bioleaching processes. The highest percentages of bioleached REEs from monazite and (Th-U) concentrate directly by A. ficuum are found to be 75.4, 63.8 % at a pulp density 0.6, 1.2 % (w/v), respectively, after 9 days of incubation at 30 °C and 63.5, 52.6 % by P. aeruginosa after 8 days of incubation at 35 °C using a shaking incubator at 175 rpm. It is also found that 14.3 and 1.4 g/l of citric and oxalic acid, respectively, are produced by A. ficuum, while 6.3 g/l of 2-ketogluconic acid is produced by P. aeruginosa. The highest percentages of chemical leaching of REEs from 0.6 % monazite using citric acid 14.3 g/l, oxalic acid 1.4 g/l, citric/oxalic acids 15.7 g/l and 2- ketogluconic acid 6.3 g/l after 24 h are 55.7, 26.0, 58.8 and 45.6 %, respectively. This work addresses the area of beneficiation of the used mineral to solubilize REEs through the biotechnological route in Egypt, where the bioleaching method is more effective than the chemical one using organic acids. doi:10.14456/WJST.2014.8