Abstract: By products of agriculture and forestry were widely applied in environmental protection as the high quality adsorbent due to the high content of lignocellulosic materials,such as cellulose,hemi-cellulose and lignin.In this study,hazelnut shell adsorbent was prepared with hazelnut shell as feedstock and the adsorption mechanism of cations in water was investigated.Methylene blue (MB) cation was used as the object of study,different experimental parameters were evaluated in batch adsorption experiments to determine the optimal adsorption conditions,the isotherm adsorption model and adsorption kinetic model were established,and the thermodynamics of adsorption was discussed.The results demonstrated that the adsorption processes were strongly dependent on pH,initial concentration,contact time and temperature.The maximum removal of MB was observed at an optimum acidic pH of 5.0-7.0.Adsorption equilibrium was reached within 2 h for MB.The experimental data were analyzed using Langmuir isotherm model.It was found that Langmuir model fitted better the equilibrium adsorption data and the adsorption process followed pseudo-second-order reaction kinetics.The thermodynamics of MB adsorption onto hazelnut shell indicated its spontaneous and exothermic nature.

Key words: hazelnut shell, biosorption, methylene blue, kinetics, isothermal adsorption