Preparation and Characterization of Gamma Radiation Assisted Poly-Vinyl Alcohol/Acrylic Acid/Poly-4-Styrene Sulphonic Acid Based Hydrogel: Application for Textile Dye Removal

In this study, poly-vinyl alcohol (PVA), acrylic acid (AAc), and poly-4-styrene sulphonic acid (PSSa) were copolymerized in different compositions using gamma irradiation to form the hydrogel. FTIR study showed that AAc act as a crosslinker for the formation of transparent hydrogel and optimization study affirmed that crosslinking density increased with the increase of AAc content. The swelling study revealed that hydrogel with 30% acrylic acid and 70% PSSa (PAC(30)PS(70)) exhibited the best swelling properties with a maximum diffusion coefficient of 2.94 cm(2)s(-1)and the diffusion of water inside the hydrogel was found to be of Fickian character. Methylene blue was used as a model dye for sorption and the effect of sorbent dosage, contact time, initial dye concentration, pH, and temperature on sorption were observed for the study. The maximum sorption capacity of 131.58 mg/g was observed at normal temperature, neutral pH, and hydrogel dosage of 0.05 grams (g). The sorption of dye data best fitted with pseudo first-order kinetic equation and Boyd kinetic plot indicates that the adsorption process was controlled by film diffusion (external diffusion). The negative values of Delta H (- 18.57 kjmol(-1)) from the thermodynamics study, confirmed that the adsorption process was exothermic and more favorable at lower temperature. The reusability study specified that the sorption capacity gets reduced from 90.96 to 57.45% after four consecutive cycles ensuring that the hydrogel can be effectively utilized as recyclable adsorbents for industrial applications.