Equilibrium isotherms and kinetics modeling of methylene blue adsorption on agricultural wastes-based activated carbons

Agricultural wastes, date stones, have been used as precursor for activated carbon production by chemical activation with zinc chloride. The equilibrium isotherms and kinetics of methylene blue dye adsorption on such carbon were then examined at 30 °C. Equilibrium adsorption data were analyzed by the Langmuir, Freundlich and Sips isotherm models. The results show that the best fit was achieved with the Sips isotherm equation with a maximum adsorption capacity of 398.19 mg/g. Pseudo-first order, pseudo-second order and intraparticle diffusion models were used to analyze the kinetic data obtained at different initial methylene blue concentrations. The adsorption kinetic data were well described by the pseudo-second order model.