Removal of Hexavalent Chromium from Aqueous Solutions by Low-Cost Rice Husk-Based Activated Carbon: Kinetic and Thermodynamic Studies

Abstract

The release of heavy metals with several industrial effluents is a major issue of concern for environmental protection due to their toxic and stable nature. Among several newer separation techniques invented for the remediation of such nuisance, adsorption has been able to keep its position on demand. In this work, comparative analysis on process performance of activated carbon (AC) as derived from rice husk with the commercial one has been carried out for the removal of highly hazardous hexavalent chromium (Cr(VI)) from aqueous solution. Effects of operational parameters such as pH of the solution, initial concentration of adsorbate on process efficiency were studied. The percentage removal of Cr (VI) at pH of 2 was found to be up to 97.8% and 91.23% for commercial and rice husk-derived AC, respectively. Adsorption kinetics has been studied through different kinetic models such as pseudo-first-order, pseudo-second-order and intra-particle diffusion models. Pseudo-second-order model agreed well for both the adsorbents. Adsorption isotherm was studied to be best fitted to Langmuir isotherm model. The adsorption was found to be endothermic in nature from thermodynamic view point and equilibrium constant was found to increase with increasing temperature.