Removal of Cr(VI) From Waste Water By Peanut shell

An Agricultural waste peanut shell has been used for the removal of Cr(VI) from aqueous solution. The effects of different parameters such as contact time, adsorbate concentration, pH of the medium and temperature were investigated and maximum uptake of Cr(VI) was 314.22 mg g-1 at pH 2.0, initial Cr(VI) concentration of 200 mg L- 1, and temperature of 400C. Effect of pH showed that peanut shell was not only removing Cr(VI) from aqueous solution but also reducing toxic Cr(VI) into less toxic Cr(III). The sorption kinetics was tested with first order reversible, pseudo-first order and pseudo second order reaction and it was found that Cr(VI) uptake process followed the pseudo-second order rate expression. Different thermodynamic parameters viz., changes in standard free energy, enthalpy and entropy have also been evaluated and it has been found that the reaction was feasible, spontaneous and endothermic in nature. The Langmuir and Freundlich equations for describing sorption equilibrium were applied and it was found that the process was well described by Langmuir isotherm. Desorption studies was also carried out and found that complete desorption of Cr(VI) took place at pH of 9.5.