Determination of kinetic and equilibrium parameters of the batch adsorption of Cr(VI) onto waste acorn of Quercus ithaburensis

The efficiency of waste acorn of Quercus ithaburensis (WAQI) as an adsorbent for removing Cr(VI) ions from synthetic wastewater has been studied. Batch adsorption experiments were carried out as a function of pH, adsorbent mass, Cr(VI) ion concentration, agitation rate and temperatures. Maximum metal sorption was found to occur at initial pH 2.0. The adsorption capacity of WAQI was found to be 31.48 mg g−1 for initial Cr(VI) concentration of 400 mg L−1 at 25 °C. Batch adsorption models, based on the assumption of the pseudo first-order, pseudo second-order mechanism and Elovich equation were applied to examine the kinetics of the adsorption. The results showed that kinetic data were followed fitting the pseudo second-order model than the pseudo first-order and Elovich equation.Thermodynamic parameters such as ΔH°, ΔS° and ΔG° were calculated. The adsorption process was found to be endothermic and spontaneous. The results were analyzed by the Langmuir, Freundlich, Dubinin–Radushkevich (D–R), Temkin, Frumkin, Harkins–Jura, and Smith equation using linearized correlation coefficient at different temperature. The characteristic parameters for each isotherm have been determined. Models and the isotherm constant were evaluated depending on temperature. Langmuir and Freundlich equation is found to best represent the equilibrium data for Cr(VI) ions–waste acorn systems.