Simultaneous Removal of Cationic and Anionic Dyes from Binary Solutions Using Carboxymethyl Chitosan Based IPN Type Resin

Abstract

In this study, a novel bead form IPN type resin comprising poly (2-Dimethylaminoethyl) methacrylate and carboxymethyl chitosan networks with a high dye adsorption capacity. The adsorbent was synthesized by a combination of serial reactions, including bead formation, cross-linking, and carboxymethylation of chitosan, then the photo-polymerization of DMAEM inside these beads. To assess the simultaneous basic and acidic dye removal efficacy (Safranine T; ST and Indigo carmine; IC) and characteristics, batch adsorption experiments were carried out. The effects of different parameters such as contact time, adsorbent dosage, initial dye concentration (25–400 ppm), and pH on the adsorption process were investigated. Under optimized conditions (adsorbent dosage, 1.5 g/L; pH, 3; initial concentration 250 ppm (125 ppm ST + 125 ppm IC), temperature, 25 °C), adsorption studies showed that the resin has significant high adsorption capacity (qe = 126 and 130.5 mg/g for ST and IC, respectively). Adsorption isotherm studies showed that Langmuir, Langmuir–Freundlich, Redlich-Peterson, and D-R models fitted the adsorption equilibrium data quite well, while the Freundlich model gave poor fittings. Besides, for all initial dye concentrations in the range of 25–400 ppm in the binary mixture (except 12.5 ppm IC initial concentration), the process is favorable. According to adsorption model calculations, the adsorption takes place with a monolayer coverage, and the main dominant force for the system is weak interactions indicating physical adsorption. Kinetics studies showed that for both dye, the adsorption process could be expressed very well by the PFO model and PSO; however, the PFO model is somewhat better in predicting the experimental qe values.