Biosorption of Hexavalent Chromium Using Bark of Cassia spectabilis

Biosorption is a relatively new process that has proven very promising in the removal of heavy metal contaminants from aqueous solutions. The biosorption of Cr(VI) from aqueous solution using bark of Cassia spectabilis has been investigated in a batch system. The effect of various parameters such as pH, contact time, adsorbent dosage and initial concentration of Cr(VI) on the biosorption process were studied. The maximum removal of Cr(VI) was observed at pH 1.0. The Study indicated that both biosorption and bioreduction were involved in removal of Cr(VI). The sorption equilibrium exhibited a better fit to the Langmuir isotherm than Freundlich isotherm. The maximum biosorption of Cassia spectabilis bark to remove Cr(VI) was 12.865 mg/g. The dimensionless equilibrium parameter, RL, signifies a favorable adsorption of Cr(VI) on the adsorbent and is found to be 0.441 (0 < RL<1). Pseudo first-order and second order kinetic models were used to evaluate the mechanism of adsorption. Kinetic evaluation of the experimental data showed that the biosorption process follows pseudo- second order kinetic model.Keywords: Hexavalent chromium; Biosorption; Cassia spectabilis bark; Adsorption isotherm; Adsorption kineti