Radiation crosslinked swellable ionic gels: equilibrium and kinetic studies of basic dye adsorption

Abstract

High-energy gamma radiation was employed to synthesize acrylic acid (AA)-based simple hydrogel adsorbent for environmental remediation of dye effluent. The adsorbent was tested for the aqueous solutions of two basic dyes, namely, Basic red 29 (BR 29) and Methylene blue (MB). The AA concentration of 20% (w/v) and absorbed dose of 30 kGy were optimized to synthesize AA hydrogel having good strength, and faster uptake kinetics for a wide range of dye concentration (10–5,000 mg/L). Equilibrium adsorption of both the dyes BR 29 and MB were better described by Langmuir adsorption. The equilibrium dye adsorption capacity onto AA hydrogel was found to be very high i.e. 1,123 mg/g (or 3.04 mmol/g) and 220 mg/g (or 0.68 mmol/g) for BR 29 and MB, respectively. The adsorption of BR 29 onto AA hydrogel followed the pseudo-first-order kinetics only in the initial time scale, whereas the adsorption of MB on AA hydrogel followed pseudo-second-order kinetics over the entire range of adsorption process. Desorption studies helped to elucidate the mechanism of dye adsorption and recycling of the spent adsorbent. The overall adsorption–desorption studies of these dyes on simple AA-based hydrogels are quite encouraging for more exploration.