Bioleaching – Extraction studies of some metal values from the mineralized younger granite of El Missikat – Central Eastern Desert – Egypt

Abstract

The sample under study was collected from El Missikat area. El-Missikat lies in the Eastern Desert of Egypt, 85 km from Qena along the river Nile. El Missikat area was mined for its economic mineral deposits especially for gold and copperbeside radioactive minerals (uranophane, uraninite and pitchblend), sulfide minerals (galena and pyrite), transparent minerals (fluorite, zircon and monazite) as well as Fe and /or Ti-oxide (magnetite, ilmenite, hematite, rutile and sphene). The aim of the present work is to Study the ability of Microorganisms to solubilize some metal values from ElMissikat ore and study the factors affecting the bioleaching process to obtain the best conditions for Solubilization of some economic elements namely; Mo, Th, Fe, Pb and REEs beside extraction of Mo, U and REEs which record high leaching efficiency in the bioleaching process. For this purpose, a technological representative sample of El Missikat younger granite ore material was collected. The chemical analysis of this sample revealed the presence of 0.4% REEs, 0.21% lead, 0.2% uranium and 0.09% molybdenum. The mineralogical analysis of the sample under study revealed that it contains Galena, Quartz, Pyrite, Hematite, and Fluorophlogopite as analyzed by XRD. From the previous experiments, it is possible to conclude that the maximum leaching efficiencies of the studied elements were almost achieved by using A. niger, under the given conditions: adjusting leach liquor's pH to be 6.0 with addition of 100 g/L sucrose at 33°C for 14 days incubation period without shaking. In addition, incubation periods influenced mostly leaching the elements of interest such as molybdenum and rare earth elements from the ore sample. On the other hand, oxalic and citric acids are the main organic acids that solubilize the elements under study where oxalic acid secretion was more by both A. niger and A. flavous. The consumption of organic acids was more in A. Flavous media where the final pH was alkaline (above 7.0) in the meantime the solubilization of the elements was not high due to the precipitation of metal-acid complexes. The extraction of some metal values (U, Mo and REEs) from the actual bioleach liquor was done by applying the previously mentioned optimum leaching conditions upon 140 g of the provided working ore sample. The prepared leach liquor (650 ml) of pH 3.0 was found to assay: 75 ppm Mo, 100 ppm U, 2700 Fe and 180 ppm REEs. Two successive separation techniques were used namely; anion exchange technique for U and Mo extraction by purolite A 400 resin followed bydirect precipitation for REEs separation. Firstly, the prepared bioleach liquor was subjected