Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
STUDIES ON THE BIOREMEDIATION OF CHROMIUM USING A BACTERIAL STRAIN ISOLATED FROM A CHROMITE MINE Divyasree C Prabhakaran, Jean Riotte and S Subramanian Department of Materials Engineering and Indo-French Cell for Water Sciences, Indian Institute of Science, Bangalore 560012, India ABSTRACT The potential of a bacterial strain isolated from water samples collected from a chromite mine in Odisha, India has been assessed for the bioremediation of hexavalent chromium, a toxic environmental pollutant. The isolate was identified as Sphingopyxis sp., a Gram negative bacterium, adopting molecular biological protocols and biochemical characterisation techniques. Detailed investigations on the bio-removal of Cr (VI) were carried out using Sphingopyxis sp. cells and the various parameters affecting the biosorption process were evaluated. About 55 % biosorption of Cr (VI) was obtained using Sphingopyxis sp. bacterial cells and the residual chromium in solution was found to be bio-reduced to the trivalent form, namely Cr (III). Thus, complete bioremediation of Cr (VI) could be achieved using the mine isolate, with contributions from both biosorption and bioreduction mechanisms. The Cr(VI) biosorption isotherm obtained for the isolate was found to follow a typical Langmuirian behaviour and the free energy value of biosorption was determined to be ~-25 kJ/mol, indicative of involvement of chemical binding forces in the bioremediation process. The chromium biosorption kinetics by the isolate followed a pseudo second order reaction. The FTIR spectral studies revealed that carboxyl, hydroxyl, amino and phosphate groups were involved in the biosorption process. X-ray photoelectron spectroscopic studies on the bacterial cells interacted with Cr (VI) confirmed the presence of both Cr (VI) and Cr (III) on the cell surface. The electrokinetic studies revealed that the surface potential of the bacterial cells were less electronegative subsequent to interaction with Cr(VI), compared to the cells alone, which further testified to the binding of positively charged Cr(III) ions, formed by bioreduction of Cr(VI), to the bacterial cell surface. A marginal shift in the iso-electric point obtained for the bacterial cells interacted with Cr (VI), corroborated the involvement of chemical binding forces in the bioremediation process. KEYWORDS Bioremediation, Cr(VI), chromite mine, Sphingopyxis sp., biosorption, bioreduction