Pectin gels cross-linked by Ca2+: An efficient material for methylene blue removal

Pectin gels (PG) with high removal efficiency of methylene blue (MB) has been prepared by the most simple and full-blown ionically cross-linking method. Some unconspicuous pores presented on the surface of PG. The PG was employed to remove MB, and the adsorption isotherms, kinetics, and mechanism for the MB on PG was studied. The R-2 value of Langmuir isotherm was higher than that of Freundlich isotherm. The adsorption capability calculated from the Langmuir plot was 354.6 mg/g, and the values of essential characteristics, RL, indicated the favorable adsorption. The Dubinin-Radushkevich isotherm fitted the experimental data better, which illuminated the chemical adsorption of MB dye in the adsorption process. In addition, the value of adsorption energy was 33.865 kJ/mol which was calculated by fitting the experimental data with Dubinin-Radushkevich equation. The adsorption of MB on PG was followed by the pseudo-second-order model and KASRA model, and the adsorption process was controlled by film diffusion. The results indicated that the PG could be used to effectively remove MB from aqueous solutions. (C) 2017 Elsevier B.V. All rights reserved.