MAISA M. AMIN*, I.E. EL-AASSY*, M.G. EL-FEKY*, A.M. SALLAM**, E.M. EL-SAYED**, AFAF A. NADA***, NAREMAN M. HARPY*^#

*Nuclear Material Authority, Cairo, Egypt
**Physics Department, Biophysics group, Faculty of Science, ”Ain Shams” University, Cairo, Egypt
***Nuclear Physics, Physics Faculty of Woman for Art, Science and Education, ”Ain Shams” University, Cairo, Egypt

The main concern of this study is to test the ability of some fungi isolated from Sinai Peninsula carbonaceous shales to perform microbial leaching of rare earth elements (REEs) from these rocks. Two methods of REEs bioleaching were tested using both direct (active) and indirect (passive) processes. Direct bioleaching process of carbonaceous shale samples was found to be more effective than indirect process for all tested microorganisms. Bioleaching efficiency of REEs using different fungal strains increases with decreasing REEs concentrations when their growth rate decreases. Strains of Aspergillus (A. niger and A. flavus) were found to be the most efficient organisms. The maximum extraction yield of total REEs was 86% at 7 days incubation time, 1% pulp density, and 30 ºC incubation temperature. A. niger and A. flavus exhibit good potential in generating a variety of organic acids (citric and oxalic) effective for REEs solubilization. Citric and oxalic acids contents produced by A. niger was higher than A. flavus interpreting higher REEs bioleaching efficiency of A. niger than A. flavus. From properly prepared pregnant bio-leach liquor, the leached REEs were recovered in the form of REEs oxalate product using classical chemical technique.

Corresponfing author’s e-mail: nareman.harpy@hotmail.com

Full text: PDF