Adsorption kinetics and thermodynamic parameters of cationic dyes from aqueous solutions by using a new strong cation-exchange resin

Poly(glycidylmethacrylate) was grafted via surface-initiated-atom transfer radical polymerization (SI-ATRP) on a cross-linked acrylate based resin. Epoxy groups of the grafted polymer, were modified into strong cation-exchange groups (i.e., sulfonic groups) in the presence of sodium sulfite. The adsorption of Crystal Violet and Basic Fuchsine on the strong cation-exchange resin was studied under different experimental conditions. The adsorption process for both basic dyes was pH dependent. The maximum adsorption was observed for both dyes between pH 2.0 and 7.0. The maximum adsorption capacity of the cation-exchange resin for CV and BF dyes were found to be 76.8 and 127.0 mg/g, respectively. Adsorption of the dyes on the resin fitted to Langmuir and Temkin isotherm models and followed the pseudo-second-order kinetics. The values of Gibbs free energy of adsorption (ΔG°) were found to be −2.92 and −6.31 kJ/mol at 308 K for CV and BF dyes, respectively. These negative values indicated the spontaneity of the adsorption of the dyes on the resin. Desorption of both dyes was achieved from the resin by using 0.1 M HNO3 and desorption ratio up to 97% was obtained over seven adsorption/desorption cycles.