World Environment 2012, 2(6): 110-115 DOI: 10.5923/j.env.20120206.01 Microbial Treatment of Lateritic Ni-ore for Iron Beneficiation and Their Characterization N. Pradhan 1 , R. R. Nayak 2 , D. K. Mishra 1 , E. Priyadarshini 1 , L. B. Sukla 1,* , B. K. Mishra 1 1 Institute of Minerals and Materials Technology, Council of Scientific & Industrial Research (CSIR), Bhubaneswar, 751013, India 2 Indian Institute of Chemical Technology, Council of Scientific & Industrial Research (CSIR), Hyderabad, 500 007, India Abstract This study aims at studying effect of anaerobic dissimilatory iron (III) reducing bacterial consortium on dif- ferent phases of iron present in lateritic nickel ore. Such conversion in lateritic nickel ore are helpful in better recovery of sorbed metal values like Ni and Co by subsequent bioleaching or acid leaching. Here properties of thermally and microbi- ally reduced lateritic nickel ore are compared vis-à-vis original ore. An anaerobic dissimilatory iron (III) reducing bacterial consortium capable of using glucose as carbon source and lateritic nickel ore as terminal electron acceptor was used for microbial reduction of ore under anaerobic condition. Microbial reduction changes the initial light brown colour of the lat- eritic nickel ore to dark brown. The change in colour is due to the conversion of goethite to magnetite, which is confirmed from the XRD pattern. The FTIR spectra and the UV-Visible spectra support the presence both goethite and hematite. The study shows that changes in phases brought about by microbial treatment are different than those by thermal treatment. The carrier mediated exchange interaction between Fe 2+ and Fe 3+ ions in lateritic nickel ore sample treated with IRB consortium is responsible for higher ferromagnetic ordering. The thermal reduction of the same sample showed lowering of ferromag- netic ordering due to the decreasing percentage of Fe 2+ and Fe 3+ ions. Keywords Iron Reducing Bacteria, Lateritic Ore, Goethite, Magnetite, Magnetic Properties 1. Introduction In lateritic nickel ore, nickel is associated with iron phase where as cobalt is associated with manganese phase[1]. Natural Fe(III) oxides are high in surface area and are reac- tive[2]. Fe(III) oxides adsorb a wide range of metal cations and anions by complexation to surface hydroxyl groups[3]. Nickel lateritic ore of Sukinda, Orissa, contains 0.8% Ni and 0.049% Co which makes them the only nickel deposit in India. More focus had been given by IMMT Bhubanes- war on this material for extraction of nickel and cobalt[4-7]. However, thermal activation or thermal reduction of ore is required for better recovery of metal values[8]. Heating of ore resulted in conversion of goethite to hematite, which was responsible for releasing nickel from Fe(II) lattice and resulted in better recovery[7]. This type of reduction is not cost effective in terms of energy consumption and may not be employed for large scale operations. Hence, it is desir- able to have an alternative ecofriendly and low cost method, which makes the subsequent metal extraction more feasible. Ferric iron oxides are widespread in anoxic aqueous en- vironment and have been reported to act aselectron sink during biodegradation of various natural and xenobiotic * Corresponding author: lbsukla@immt.res.in (L.B. Sukla) Published online at http://journal.sapub.org/env Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved compounds[9-11]. Microbial Fe (III) reduction results in the generation of several important Fe(II)-containing minerals in sedimentary environments, including magnetite Fe(II)Fe(III) 2 O 4 , which is a magnetic mineral. Magnetite formation during dissimi- latory Fe(III) reduction is reported for different pure cul- tures of bacteria[12] as well as for Fe(III)-reducing enrich- ment consortium[13]. Microbial dissimilatory Fe(III) reduc- tion plays an important role in the geochemical cycling of iron and organic matter in anoxic ecological system[14]. Iron-reducing microbes generally belong to the genera Shewanella, Geobacter, Geovibrio, Desulfobulbus etc [15-17]. If bacterial reduction method is successful, cost intensive method of ore roasting process can be eliminated. Such ‘dissimilatory’ processes have opened up new and fascinating areas of research with potentially exciting prac- tical applications. Applying a biological approach to address this problem, we investigated the use of naturally occurring iron reducing bacteria for the reduction of lateritic nickel ore (iron phase) in a low cost ecofriendly way. 2. Materials and Methods 2.1. Lateritic Nickel Ore Lateritic Nickel ore was procured from Sukinda mines of Orissa Mining Corporation (OMC), India. The sample was a