Biomineralization of black shale using indeginous microbes

Abstract

The main concern of the present research work was to find a more feasible and economical method to extract metal ions from low grade discarded ores like black shale by Aspergillus niger and Penicillium notatum. Major elements present on the exposed surface of black shale identified by EDX study were iron, silicon, aluminum, copper and oxygen. Black shale ore mainly contained aluminosilicate minerals such as illite, kaolinite and muscovite and sulphide minerals were pyrite, pyrhotite, Ni-sulphide, sphelrite and chalcopyrite. Oxide minerals like quartz, aluminum oxide, wollastonite and dolomite were also detected by XRD. Raw sample mainly composed of (mgL -1 ) Al 8799.00, Fe 3761.00, Cu 39.07, Co 18.26, Zn 31.88 and Ni 8.25. Different agricultural wastes in the presence of sulphuric acid as substrates were evaluated in organic acid production in shaking flasks with and without ultrasonic treatment. Comparatively, A. niger exhibited a good potential in generating varieties of organic acids effective for metal ions solubilization in case of samples treated ultrasonically. Maximum recovery of metals was achieved in samples treated ultrasonically in both cases of microbes. In case of A. niger, maximum solubilization of aluminum (93.12 %), iron (90.12 %) and zinc (89.41 %) was achieved in the optimized medium of molasses containing 5 % level of ore treated ultrasonically whereas copper (94.03 %) was extracted in sample containing optimized mango peel at 5 % level of ore density. Cobalt recovery (93.32 %) was found in medium having 8 % level of seed cake treated ultrasonically whereas in case of P. notatum, maximum recovery of aluminum (69.23 %) was achieved in optimized seed cake media at 3 % level of ore density. Iron (72.35 %) was recovered in media having 8 % level of mango peel. Copper (68.88 %) and Cobalt (86.42 %) recovery was detected in optimized molasses at 5 and 4% ore density respectively whereas zinc (78.70 %) was extracted maximum in medium having optimized mango peel at 5 % level of ore density. Overall, A. niger showed better potential to extract metals from ore compared to P. notatum. Ultrasonic wave treatment not only increases the growth of microbes and organic acid production but metal ions dissolution from the ore matrices indicated that this low grade discarded ore may be the potential source for metals in future panorama.