Synthesis of a hydrogel by grafting of acrylamide-co-sodium methacrylate onto chitosan for effective adsorption of Fuchsin basic dye.

This work was designed to produce effective adsorbent from acrylamide (AAm), sodium methacrylate (SMA), and chitosan (CTS) through free radical grafting polymerization for removing the Fuchsin dye from its solution. The gel fraction and the grafting parameters were studied, and the results showed maximum grafting percentage (1014.3%) and gel fraction (83.5%) when the molar ratio of SMA to AAm was 1: 1 (the best ratio). In addition, incorporation of SMA into the gel structure enhanced the swelling of the gel by 6.63-10.25-fold as compared with the AAm-graft-CTS gel. FT-IR, TGA, DTG, DTA, and SEM were utilized to investigate the gels. Capacity for the adsorption of Fuchsin basic dye via batch process was tested and the impact of SMA, contact time, agitation rate, gel dose, dye concentration, temperature, and pH were studied. The maximum removal % (97.2%) was achieved at the best ratio. Best fitting was found by pseudo-second-order kinetic and Freundlich isotherm. Evaluation of the thermodynamic parameters was done, and it was found that the adsorption process was exothermic in nature and spontaneous and unfavorable at high temperature. The negative value of ∆S (-0.148 KJ K-1 mol-1) indicated the decrease in randomness at the solid-liquid interface.