Adsorption, kinetic and equilibrium studies of Cr(VI) by hazelnut shell activated carbon

The adsorption of chromium(VI) from aqueous solutions on to hazelnut shell activated carbon (HSAC) was investigated. The adsorption was carried out by varying parameters such as the agitation time, the initial solution pH, the initial Cr(VI) concentration and the temperature. The experimental data were well fitted by the pseudo-first-order kinetic model allowing the rate constants to be evaluated. The Langmuir isotherm provided the best correlation for the adsorption of Cr(VI) onto the activated carbon. The adsorption of Cr(VI) was pH-dependent. The adsorption capacity as calculated from the Langmuir isotherm was 170 mg/g at an initial pH of 1.0 for a Cr(VI) solution of 1000 mg/l concentration. Thermodynamic parameters were evaluated, indicating that the adsorption was endothermic and involved monolayer adsorption of Cr(VI).