Adsorption isotherms and kinetics of cationic and anionic dyes on three-dimensional reduced graphene oxide macrostructure

We demonstrate adsorption behaviors of acid red 1 (AC1) and methylene blue (MB) dyes on three-dimensional (3D) reduced graphene oxide (rGO) macrostructure. The distinct interactions of two dyes with the active sites result in the different adsorption behaviors and thus, represent the notable disparity in the adsorption capacities and kinetics. The equilibrium data for MB are fitted to Langmuir isotherm model, while Freundlich model is suitable for the equilibrium isotherm of AC1. The adsorption rates of both dyes are found to follow the pseudo-second order kinetics. The 3D rGO macrostructures are more favorable for the adsorption of cationic dyes rather than the anionic dyes due to strong specific interactions. (C) 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.