Biological removal of Cr (VI) by bacterial isolates obtained from metal contaminated sites

Abstract

Present study demonstrates the application of indigenous bacteria and pure culture of Azotobacter for removal of Cr (VI) from the aqueous solution and industrial effluent. Minimum inhibitory concentration (MIC) was determined for 3 bacterial isolates (B1, B2, B3) and pure culture of Azotobacter. The effect of various parameters such as effect of initial Cr (VI) concentration, biomass dose, and time were examined to study the biosorption and bioaccumulation separately using live and dead cells, respectively. It was found that bacterial isolate B2 showed maximum Cr (IV) removal capacity (102 mg g −1 biomass, dry weight) at initial Cr (VI) concentration of 150 mg/L. Langmuir and Freundlich isotherm model was applied, which gave a good representation of the experimental equilibrium concentrations for the biosorption of Cr (VI). During bioaccumulation process also live bacterial strain B2 showed maximum bioaccumulation i.e., 106 mg g−1 at initial Cr (VI) concentration of 150 mg/L at pH 4.0. Bioaccumulation process was found to be time dependent since removal of Cr (VI) increased with time and equilibrium state was reached at 72–96 hours. This study demonstrates the potential of indigenous bacterial strains isolated from the contaminated site for evolving eco-friendly treatment for small-scale industrial effluent.