Microbial Beneficiation of Salem Iron Ore Using Penicillium purpurogenum
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NUMEROUS iron ore mines are operating in India. During the mining process, a large amount of relatively lower grade iron ore containing 55 to 60 pct Fe is generated and stockpiled as a result of lower market and industrial value. Because of the increasing demand of iron and steel, the mining of iron ore also is increasing, and hence, lower grade iron ores are accumulating more heavily. To meet the iron demand, new technologies must be developed to process the lower grade ores. The low-grade iron ores have poor blast furnace operation, low reducibility, and low strength as a result of major impurities like alumina and silica as well as minor impurities like Na, K, S, and P. Before iron extraction, the lower grade ores must be beneficiated to remove the impurities. The amount of alumina and silica in iron ore must be below 2 pct to make the ore suitable for the steel and iron industry. However, each source of iron ore has its own peculiar mineralogical characteristics and requires a specific beneficiation treatment depending on the nature of the gangue present and its association with the ore structure.[1] The advanced physical methods such as froth floatation, gravity separation, reduction roasting, and magnetic separation could be used to beneficiate the iron ore, but all of them are energy and cost intensive. The M. MISHRA, Senior Research Fellow, M. PRADHAN, Project Assistance, L.B. SUKLA, Deputy Director, and B.K. MISHRA, Director, are with the Institute of Minerals and Materials Technology, CSIR, Bhubaneswar, 751013, India. Contact e-mail: mousumi_official@ yahoo.co.in Manuscript submitted July 20, 2009. Article published online October 23, 2010. METALLURGICAL AND MATERIALS TRANSACTIONS B
chemical methods produce a lot of hazardous wastes. So all of the aforementioned methods are not suitable for processing lower grade ores. Biobeneficiation is considered to be an ecofriendly, promising, and revolutionary solution to these problems and is gaining more importance as a result of enforcement of strict antipollution laws.[2] Both chemolithotrophic and heterotrophic microorganisms play an important role in the solubilization of metal ions[3] Heterotrophic bacteria and fungi are known to produce organic acids that can dissolve metals by forming salts or complexes like chelates.[4] These chelates are soluble or insoluble depending on the structure of the ligands as well as the insolubility of the complexes in relation to the Eh and pH of the system. Microbes, basically fungus, are well known for their ability to produce organic acids (oxalic, isocitric, succinic, malic, citric, etc.) and among them, Aspergillus sp. has been studied the most intensively.[5–7] Biosynthesis of oxalic acid from glucose occurs by hydrolysis of oxaloacetate to oxalate and acetate catalyzed by cytosolic oxaloacetase. Citric acid is an intermediate of the tricarboxylic acid cycle. Although the use of different microorganisms in ore leaching is well established, the use of microorganisms in reducing alumina and silica from ore has been attempted in
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