Cyclodextrin Hydrogels: Rapid Removal of Aromatic Micropollutants and Adsorption Mechanisms

Abstract

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 micropollutants 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)−β-cyclodextrin (Dex–PAA–CD) was prepared by the copolymerization of glycidyl methacrylate (GMA), methacrylate-substituted dextran (Dex-MA), acrylic acid, and vinyl-derivatized β-cyclodextrin (β-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.

Cyclodextrin‐Cross‐Linked Hydrogels for Adsorption and Photodegradation of Cationic Dyes in Aqueous Solution

“…It is known that k A reflects the comprehensive outcomes of the different adsorption performance of outer surfaces (referred to readily accessible contacting sites) and interior surfaces (referred to less accessible binding sites) of adsorbent [21] . Therefore, the CD‐containing hydrogels/adsorbents may possess different adsorption performance towards dye molecules, thus giving quite distinctive kinetics parameters [12,14,17,22,23] …”

“…fabricated a supramolecular hydrogel using vinyl‐terminated β‐CD and adamantane derivatives, which showed rapid self‐recovery ability, high mechanical strength and good cell biocompatibility [16] . Moreover, when vinyl‐containing β‐CD and dextran were copolymerized with acrylic acid in water, a supramolecular hydrogel was constructed with the two polymeric chains, thus showing efficient adsorption of different organic pollutants through the synergistic electrostatic and host‐guest interactions [17] . By utilizing the facile UV‐initiated free‐radical copolymerization with vinyl‐containing monomers, our group also constructed a series of CD‐based supramolecular hydrogels, which could be widely applied as tunable photoluminescent self‐sorting materials [18] and polyrotaxane‐based stretchable supercapacitors [19] …”

Removal of Organic Micropollutants from Water by Macrocycle‐Containing Covalent Polymer Networks

“…[14] Thec avity of b-CD is relatively hydrophobic and it forms host-guest inclusion complexes with avariety of guests via ac ombination of solvatophobic and van der Waals interactions. [15] Because of its recognition features and av ariety of other favorable physicochemical and biological properties, b-CDs and their analogues have been used across aw ide range of supramolecular chemistry-related applications. [16] Recently, b-CD-based polymers have also received considerable attention for their possible role in environmental remediation.…”

“…This is because macrocycle‐based host–guest interactions are often sensitive to changes in the environmental conditions, including pH, light, temperature, pressure, redox conditions, anions, cations, solvent, and so on [9–13] . Common macrocycles that have been incorporated into polymeric networks for water purification include cyclodextrins (CDs), [14–20] calixarenes, [21–26] pillararenes, [27–32] resorcinarenes, [33–37] and imidazolium macrocycles [38–41] . On the other hand, other typical macrocycles, including crown ethers, [42–44] cucurbiturils (CBs), [45–47] and calix[4]pyrroles (C4Ps,) [48–50] have not yet been widely used in this context.…”

Removal of Organic Micropollutants from Water by Macrocycle‐Containing Covalent Polymer Networks

“…[9][10][11][12][13] Thei nclusion of macrocycles is also expected to make regeneration of the polymer materials more facile.T his is because macrocyclebased host-guest interactions are often sensitive to changes in the environmental conditions,including pH, light, temperature,p ressure,r edox conditions,a nions,c ations,s olvent, and so on. [9][10][11][12][13] Common macrocycles that have been incorporated into polymeric networks for water purification include cyclodextrins (CDs), [14][15][16][17][18][19][20] calixarenes, [21][22][23][24][25][26] pillararenes, [27][28][29][30][31][32] resorcinarenes, [33][34][35][36][37] and imidazolium macrocycles. [38][39][40][41] On the other hand, other typical macrocycles,i ncluding crown ethers, [42][43][44] cucurbiturils (CBs), [45][46][47] and calix [4]pyrroles (C4Ps,)…”