Adsorption of methylene blue onto activated carbon obtained from ZnCl2-activation of paulownia wood: kinetic and equilibrium studies

In this study, an activated carbon was prepared from paulownia (P. tomentose) wood by chemical activation with ZnCl2. Pore properties including surface area, pore volume, pore size distribution and average pore diameter of the activated carbon were determined by N-2 adsorption at 77 K using the BET, t-plot and density functional theory (DFT) methods. The activated carbon had a BET surface area of 2736 m(2) g(-1) and total pore volume of 1.387 cm(3) g(-1). The use of activated carbon for the removal of methylene blue (MB) from aqueous solutions was investigated in a batch system different pH, initial dye concentrations contact times, temperatures and adsorbent doses. The extent of dye removal decreased with increasing initial MB concentration and increased with increasing contact time, temperature and adsorbent dosage. The equilibrium data were analyzed by the Langmuir and Freundlich isotherm models. The experimental data for the adsorption of MB dye fit the Langmuir isotherm model very well and the maximum monolayer adsorption capacity of the activated carbon was determined as 322.58, 384.61, 370.37 mg g(-1) for 25, 35 and 45 degrees C, respectively. The adsorption kinetics were found to follow a pseudo-second-order kinetic model. The changes in entropy (Delta S degrees) and heat of adsorption (Delta H degrees) for MB adsorption on activated carbon were positive.