Biosorption of chromium(VI) using Bacillus subtilis SS-1 isolated from soil samples of electroplating industry

Soils around the electroplating industry are often polluted with metals. The aim of the study was to assess Cr(VI) adsorption potential of chromium-resistant bacteria isolated from soil samples collected in and around electroplating industry, Coimbatore, India. A total of six morphologically different chromium-resistant bacteria were isolated from the soil samples and assayed for resistance to Cr(VI). Isolate designated SS-1 exhibited maximum resistance to Cr(VI) (600 mg/l) and subsequently identified as Bacillus subtilis based on the morphology, phenotypic characters, and partial 16S rDNA sequences. Batch experiments were carried out as a function of time, initial Cr(VI) concentration (100 mg/l), pH (2), and biosorbent dose (0.1 g/l). The maximum percentage of Cr(VI) removal was found to be 98.7 %. The experimental data showed a better fit with Langmuir model over Freundlich model throughout the range of initial concentrations. The kinetic models were examined with pseudo-first-order and pseudo-second-order kinetics. Fourier transform infrared spectroscopy studies confirmed the involvement of carboxyl and amide groups in Cr(VI) adsorption. Scanning electron microscopic studies revealed that nature of the bioadsorbent was altered after Cr(VI) adsorption. The results revealed that Cr(VI) was considerably adsorbed onto bacterial biomass, and it could be an economical method for the removal of Cr(VI) from aqueous solution.