KINETICS AND EQUILIBRIUM STUDIES ON THE BIOSORPTION OF HEXAVALENT CHROMIUM FROM AQUEOUS SOLUTIONS USING BACILLUS SUBTILIS BIOMASS

Abstract. Heavy metal contamination of industrial effluents is one of the significant environmental problems due to their toxic nature and accumulation throughout the food chain as non-biodegradable pollutants. In this study, dead Bacillus subtilis biomass was assessed for its efficiency to remove chromium(VI) from aqueous solutions. Optimum pH and temperature for biosorption of Cr(VI) were found to be 2.0 and 30oC, respectively. The biomass has the maximum biosorption capacity of 14.54 mg/g of biomass at 100 ppm initial chromium concentration and 2 g/l biomass loading. The biosorption process followed pseudo first order kinetic model, implying that the initial rate of biosorption is totally independent of the initial concentration. The biosorption of Cr(VI) is well described by Langmuir isotherm, which express the existence of monolayer adsorption under the experimental conditions. The adsorption-desorption experiments performed inferred the reusability of the biomass. X-ray photoelectron spectroscopy studies revealed that chromium bound on to the B. subtilis biomass was in trivalent form