Strategically designed porous polysilicate acid/graphene composites with wide pore size for methylene blue removal

Abstract

Polysilicate acid/graphene composites were synthesized in the oil phase using a facile one-pot method. Si-based groups, Cl, and residual oxygenated functional groups effectively reduced the irreversible aggregation process. Stacking sheets with these groups tend to form wide pores. These pores were not formed in the graphene sheets, but they were formed instead by sheet aggregation. Adsorption data indicated that the porosity of the material had more remarkable influence on the adsorption capacity than high surface area. The adsorption kinetics was modeled using first- and second-order rates and the Elovich and Weber–Morris intraparticle diffusion models. The adsorption process follows the second-order rate and Elovich model. The Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models were applied to describe the equilibrium isotherms and determine the isotherm constants. Methylene blue adsorption preferably fits the Langmuir adsorption isotherm model, which suggests a monolayer coverage of adsorbed molecules.