Application of natural adsorbent from silver impregnated Arachis hypogaea based thereon in the processes of hexavalent chromium for the purification of water

Different industries generate huge amounts of chromium, both in solid and liquid form which leached out and find their way to the aquifers. Here we report the removal of Cr(VI) by the silver impregnated activated carbon developed from agricultural waste material at pH 3 from drinking water. Result revealed that adsorption of chromium(VI) on silver impregnated groundnut husk carbon was endothermic in nature. Thermodynamic parameters such as the entropy change, enthalpy change and Gibbs free energy change were found to be 1.68 kJ mol(-1) K-1, 0.46 kJ mol(-1) and -4.38 kJ mol(-)1, respectively. The measured adsorption kinetics is well described by a pseudo first-order kinetic model. The effect of flow rate, column depth and initial concentration of chromium(VI) on the removal of chromium by the impregnated adsorb ent is presented. Scanning Electron Microscope (SEM), Electron Dispersive X-ray Analysis (EDX) and FTIR analysis show that the silver is impregnated on the surface. Shifts in the FTIR spectra suggest that dichromate binding occurs with silver and other functional groups and that silver treated groundnut husk carbon removes chromium. The 96h static acute toxicity test was conducted to ensure the safe disposal of the used adsorbent. (C) 2008 Elsevier B.V. All rights reserved.