Sorption study of chromium sorption from wastewater using cereal by-products

Abstract The present work is aimed at exploring carbon which was prepared by calcination of Cereal By-Product (CBP) and used as adsorbent for the removal of Chromium (VI) from a surface treating industry. The effects of various parameters such as adsorbent dosage, pH, contact time were studied. As the adsorption process is pH dependent, it showed maximum removal efficiency of Cr(VI) in the pH range of 6–8 for an initial chromium concentration of 132 mg/L. Effect of temperature on the equilibrium constant was studied and the thermodynamic parameters like standard Gibb's free energy (Δ G °), standard enthalpy (Δ H °) and standard entropy (Δ S °) were also investigated. The positive values of Δ H 0 and Δ G 0 indicated an endothermic and a non spontaneous thermodynamically adsorption, respectively. Pseudo second-order model was found to best represent the kinetics of Cr(VI) adsorption. Intraparticle diffusion studies show that the mechanism of adsorption was mainly dependent on diffusion. The Langmuir, Freundlich and Temkin isotherm were used to describe the adsorption equilibrium studies of calcinated cereal by-product at 20 °C. Temkin isotherm showed better fit than Freundlich and Langmuir isotherms. It was demonstrated that the removal effectiveness reached nearly 90.37% when using optimal conditions as used for the treatment of wastewaters containing chromium as a low cost alternative compared to commercial activated carbon and other adsorbents reported.