Biosorption and speciation of chromium in aqueous medium using water hyacinth

Abstract

ABSTRACT This study focuses on the speciation of chromium that occurs during biosorption of chromium in an aqueous medium using dried and powdered stems, roots and leaves of water hyacinth (Eichhornia crassipes ) as biosorbents. The effects of physico-chemical parameters like pH and biosorbent dosage on the removal of Cr(VI) and its conversion to Cr(III) were investigated through batch studies. FTIR spectroscopy plots of raw and chromium loaded biomass were compared to explore the functional groups actively involved in biosorption of chromium. Pseudo-second-order kinetic model was found to be applicable to all the parts of water hyacinth. Langmuir isotherm showed better fit for all the parts with maximum removal capacity of 13.05 mg/g, 26.74 mg/g and 39.21 mg/g for stems, roots and leaves, respectively. Structural analysis using SEM showed the presence of large specific surface area on stems, roots and leaves, thus, affirming their suitability for biosorption process. Chemical analysis using EDX confirmed uptake of chromium by all the parts of water hyacinth. The build-up of Cr(III) concentration in the solution as a result of the reduction of Cr(VI) was also studied. Reduction of Cr(VI) to Cr(III) was found to be maximum with water hyacinth leaves at an optimum dosage of 12 g/L at pH 1 within the contact time of 45 min. Overall, the biomass of E. crassipesshowed good potential at low pH for treatment of industrial effluents containing Cr(VI).