Cyclodextrin Hydrogels: Rapid Removal of Aromatic Micropollutants and Adsorption Mechanisms

Aromatic micropollutants found in wastewater pose threats to human health, and it is necessary to remove them from wastewater. Cyclodextrin hydrogel is one of the most promising environmentally friendly materials for removing aromatic micro pollutants from wastewater by means of adsorption. In this study, we have synthesized a cyclodextrin hydrogel designed to simultaneously adsorb a cationic dye (methylene blue, MB) and an endocrine disrupting compound, EDC (bisphenol A, BPA) and provide insights into the design of adsorbents for multicomponent wastewater purification. Polymeric dextran-poly(acrylic acid)-beta-cyclodextrin (Dex-PAA-CD) was prepared by the copolymerization of glycidyl methacrylate (GMA), methacrylate-substituted dextran (Dex-MA), acrylic acid, and vinyl-derivatized beta-cyclodextrin (beta-CD-MA). The adsorption of MB and BPA by the Dex-PAA-CD hydrogel presented short equilibrium time. The adsorption of MB and BPA was independent of each other, and their adsorption mechanisms were proved to be electronic interaction and cyclodextrin host-guest interaction, respectively. The maximum adsorption capacities of MB and BPA onto Dex-PAA-CD are determined to be 5.60 and 0.144 mmol/g by the Sips isotherm. The Dex-PAA-CD hydrogel retains a high adsorption capacity even after five adsorption/desorption cycles and demonstrates the feasibility of designing reusable adsorbents to remove multiple pollutants from wastewater.