Studies on the Bioremediation of Chromium from Aqueous Solutions Using C. paurometabolum

The potential of Corynebacterium paurometabolum , a Gram positive acid fast bacterium, has been investigated as a biosorbent for the remediation of Cr(VI) and Cr(III). A complete bioremediation of Cr(VI) has been achieved at an equilibrium time of 2 h, initial Cr(VI) concentration of 4 mg/L, pH 1 and a biomass loading of 3.1 × 10 10 cells/mL, with equal contributions from biosorption and bioreduction processes, while 55% biosorption has been accomplished at an equilibrium time of 2 h, initial Cr(III) concentration of 4 mg/L, pH 3 and a biomass loading of 3.4 × 10 10 cells/mL with respect to the bioremediation of Cr(III). The biosorption isotherms of Cr(VI) and Cr(III) exhibited a typical Langmuirian behaviour. The Gibbs free energies (∆G) have been determined to be −25.5 and −29.5 kJ/mol respectively for Cr(VI) and Cr(III), suggestive of chemisorption. The desorption studies have indicated only a marginal release of Cr(VI)/Cr(III) into the bulk solution, attesting to the irreversible nature of biosorption. FTIR studies have revealed the involvement of hydroxyl, carboxyl, amino and phosphate groups in the biosorption of Cr(VI)/Cr(III). Electrokinetic and X-ray photoelectron spectroscopic studies have provided evidence in support of the biosorption and bioreduction mechanisms of chromium remediation.