Equilibrium and Kinetics of Methylene Blue Sorption on Clay-Carbonate Diatomite

Surface characteristics of the clay-carbonate diatomite and its adsorption properties with respect to methylene blue (MB) were investigated. The equilibrium isotherms were modeled by the Langmuir, Frendlich, and Dubinin–Radushkiewicz equations. The Langmuir model more adequately described the experimental data with a correlation coefficient of 0.9783 and a maximum adsorption capacity of 112.8 mg/g. The partition factor was 0.143, indicating the favorability of the sorption process. The treatment of the experimental kinetic data showed that the pseudo second order model better describes the kinetic curves of the MB sorption. Within the particle diffusion does not control the sorption rate of MB, the main contribution to the rate limitation was made by film diffusion. The activation sorption energy, calculated by the Dubinin-Radushkiewicz model was 17.4 kJ/mol, which testifies the predominance of physical sorption. The results show that this sorbent can be used for the purposes of water purification from organic pollutants.