Bidirectionally pH-Responsive Zwitterionic Polymer Hydrogels with Switchable Selective Adsorption Capacities for Anionic and Cationic Dyes

Solution pH is an important factor in the adsorptive behavior of ionizable dyes in the chemical and biotechnology industries. In this study, novel pH-responsive zwitterionic hydrogels were prepared by the copolymerization of acrylic acid and methylacryloyloxyethyl trimethylammonium chloride. The results indicated that the hydrogels showed bidirectionally pH-responsive behaviors: the swelling ratio was small in neutral pH value and increased with the increase or decrease of pH values. Meanwhile, the selective adsorption capacities of the hydrogels for anionic or cationic dyes could be controlled by adjusting the pH values. The hydrogels might be applied in many fields, such as adsorption and separation and water treatment.