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Esther J.,CSIR - Institute of Minerals And Materials Technology | Esther J.,Academy of Council of Scientific and Innovative Research AcSIR | Panda S.,CSIR - Institute of Minerals And Materials Technology | Sukla L.B.,CSIR - Institute of Minerals And Materials Technology | And 7 more authors.
Hydrometallurgy | Year: 2015

The nickeliferous chromite overburden (COB) awaits a suitable technology to extract the obstinate nickel ingrained in its goethite matrix. In the present study, a novel Bio-Reduction Acid Leaching (BRAL) approach has been proposed using dissimilatory iron reducing bacteria (DIRB) which is inherently capable of transforming iron mineral phases via bio-reduction (BR). Mineralogical characterization of the bio-reduced COB using XRD and FTIR confirmed the phase transformation of goethite to hematite and magnetite with exposure of the nickel oxide peaks. Further, morphological characterization using FESEM vividly highlighted the changes of acicular goethite to granular magnetite deposits on the extra polymeric substance (a scaffold for electron transfer) secreted by DIRB consortium over the surface of COB. Further, enhanced nickel extraction was achieved with a reductive acid leaching (AL) approach with 6N sulfuric acid and 2% glucose (reducing agent) at 65 °C for 6 h. A cumulative of 83.6% nickel was achieved through this BRAL approach. The pregnant leach solution (PLS) generated as a result of the AL approach was subjected to a hydrometallurgical route to recover metallic nickel. Solvent extraction (SX) of the PLS was performed using 0.5 M NaD2EHPA as extractant. The pregnant nickel-loaded electrolyte was subjected to electrowinning (EW) to recover metallic nickel of 99.6% purity. The process flow-sheet is believed to provide a suitable eco-friendly, potential method to efficiently extract nickel from low grade nickel laterites to meet the ever growing demands caused by depletion of high grade nickel sulfidic ores. © 2015 Elsevier B.V. Source


Esther J.,CSIR - Institute of Minerals And Materials Technology | Esther J.,Academy of Council of Scientific and Innovative Research AcSIR | Sukla L.B.,CSIR - Institute of Minerals And Materials Technology | Sukla L.B.,Academy of Council of Scientific and Innovative Research AcSIR | And 3 more authors.
Korean Journal of Chemical Engineering | Year: 2014

Advances in applied and industrial microbial biotechnology have opened up many new avenues for application of several microorganisms. A group of certain metal reducers such as the dissimilatory iron reducing microorganisms possess an inherent potential to reduce oxidized metals under strict anaerobic/facultative anaerobic condition, thereby opening possibilities to combat environmental pollution. This unique property has invited researchers towards understanding the metabolic regulatory pathways that enables the microbes to thrive under extreme environmental conditions. Currently, dissimilatory iron reducing bacteria (DIRB) is in the focus of researchers to elucidate the specific mechanisms responsible for microbial metal reduction. The recent advances towards understanding the metabolism of iron reduction in Shewanella and Geobacter, the model DIRB has been covered in this review. It is believed that the metabolic insights into the Fe (III) reduction systems of the model DIRB; Shewanella and Geobacter (as discussed in the review) can be a basis for metabolic engineering to provide improved practical applications. With the advancement of our existing knowledge on the metabolic processes of the model iron reducers, applications ranging from laboratory to field scale practices can be carried out. DIRB has gained immense interest for its application in the field of bioremediation, electrobiosynthesis, and bioelectronics in this decade. It can therefore be anticipated that the forthcoming years will see more applications of microbial iron reducers based on the existing as well as advanced metabolic informations available in open source literature. © 2014, Korean Institute of Chemical Engineers, Seoul, Korea. Source


Esther J.,CSIR - Institute of Minerals And Materials Technology | Esther J.,Academy of Council of Scientific and Innovative Research AcSIR | Panda S.,CSIR - Institute of Minerals And Materials Technology | Behera S.K.,CSIR - Institute of Minerals And Materials Technology | And 6 more authors.
Bioresource Technology | Year: 2013

The effect of an adapted dissimilatory iron reducing bacterial consortium (DIRB) towards bio-reduction of Sukinda chromite overburden (COB) with enhanced recovery of nickel and cobalt is being reported for the first time. The remarkable ability of DIRB to utilize Fe(III) as terminal electron acceptor reducing it to Fe(II) proved beneficial for treatment of COB as compared to previous reports for nickel leaching. XRD studies showed goethite as the major iron-bearing phase in COB. Under facultative anaerobic conditions, goethite was reduced to hematite and magnetite with the exposure of nickel oxide. FESEM studies showed DIRB to be associated with COB through biofilm formation with secondary mineral precipitates of magnetite deposited as tiny globular clusters on the extra polymeric substances. The morphological and mineralogical changes in COB, post DIRB application, yielded a maximum of 68.5% nickel and 80.98% cobalt in 10days using 8M H2SO4. © 2013 Elsevier Ltd. Source

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