MICROBIAL LEACHING OF SOME VALUABLE ELEMENTS FROM EGYPTIAN PHOSPHATE ROCK

Abstract

Four phosphate rock samples representing different phosphate mineralization modes in Egypt wereselected from Abu Tartur, Nile valley and Red sea areas. Factors affecting the phosphate rock solubilizationand some of the contained valuable elements by Aspergillus niger, Penicillium sp. and Pseudomonasfluorescence, were studied with especial orientation towards the completion of phosphate rock samplessolubilization especially the low grade one. Effect of nitrogen source type on leaching efficiency byAspergillus niger when two nitrogen sources on the phosphate bioleaching efficiency, it is clear thatthe ammonium chloride is more favorable as nitrogen source than sodium nitrate in the bioleaching ofphosphate rocks.When Aspergillus niger was applied under the following conditions: 50 g/l of sucrose asa carbon source, 0.1 N of ammonium chloride as a nitrogen source, 10 days incubation period, 0.5% solid:liquid ratio for P2O5 and 5% for U and REE and - 270 mesh of grain size. The optimum leaching of P2O5,U and REE from phosphate rock samples reached (23.27%, 17.4%, 11.4%, respectively), while at -60 meshthey reached to 16.58%, 28.9%, 30.2% respectively. The optimum conditions for the maximal leachingefficiencies of P2O5, U and REE when applying the Penicillium sp. from the phosphate rock samples were:100 g/l of sucrose as a carbon source for P2O5 and U and 10 g/l for REE, 7,15 and 10 days incubationperiod for P2O5, U and REE, respectively, 0.5% solid: liquid ratio for P2O5 and 5% for U and REE. Finally,the application of phosphate rock samples grinded to -270 mesh of grain size for P2O5 and (-60 to -140)for U and REE. The studied leaching efficiency of P2O5, U and REE gave at -270 mesh 33.66%, 24.3%,15.9% respectively, while at -60 mesh they gave 33.76%, 26.7%, 17.8% and at -140 mesh gave 31.32%,27.9%, 17.6%, respectively.The optimum conditions for the P2O5 leaching efficiency when applying thePseudomonas fluorescence were: 10 g/l of beef extract, 10 days incubation period, 0.5% solid: liquid ratioand -270 mesh of grain size reaching 79.35%. The same behavior was traced for both U and REE leachingefficiencies thus they reached 57.4% and 37.6%, respectively. While the attained results showed that thenon sterilized rock is more favorable and the addition of phosphate rock after the incubation of organism for4 days gave the higher efficiency than the addition of rock at the beginning of experiment.