Preparation of thermal/pH-sensitive semi-interpenetrating network hydrogels from quaternary chitosan via an amino-anhydride click reaction for efficient dye removal from aqueous solutions

Novel thermal/pH-sensitive quaternary chitosan-based semi-interpenetrating network hydrogels were facilely fabricated via an amino-anhydride click reaction in aqueous solutions and used for water treatment. First, a series of terpolymers (PNAM) of acrylamide, N-isopropylacrylamide, and maleic anhydride was prepared via free radical copolymerization. Next, PNAM, poly(allylaminehydrochloride), and quaternary chitosan were dissolved in water, rapid gelation was observed after the pH of the solution was adjusted to alkaline. Then, single-factor experiments were applied to optimize the preparation parameters. The hydrogel was found to be thermal/pH sensitive. Finally, choosing Eosin Y as a model dye, the effect of the initial concentration, temperature, contact time, adsorbent dosage, ionic strength, and pH on the adsorption behavior was studied. The adsorption capacity could reach 1799 mg/g under optimized conditions. The adsorption performance of the hydrogels can be well described by the pseudo-second-order kinetic model and the Langmuir model. The thermodynamic study suggests that the adsorption of Eosin Y is a spontaneous, endothermic, and entropy-increasing process. In view of its adsorption performance and facile preparation process, the hydrogel is expected to be used as a promising adsorbent.