Progress of synthetic cyclodextrins-based materials as effective adsorbents of the common water pollutants: Comprehensive review

Recently, cyclodextrin (CD)-based adsorbents have received significant attention for water-pollutant removal owing to their excellent properties, such as rapid adsorption kinetics, easy regeneration, and high mechanical stability. This review systematically covers the current methods for preparing CD-based adsorbents, including crosslinking, immobilization (grafting), self-assembly, molecular imprinting, and ionic imprinting. The characterization of CD-based adsorbents using FTIR, SEM, and BET analysis is also discussed. Furthermore, the use of CD-based adsorbents for the adsorption of specific pollutants, such as heavy metals, dyes, endocrine-disrupting chemicals, pharmaceuticals, and other organic pollutants, is highlighted by introducing the adsorption properties and mechanisms. Compared with native cyclodextrins, modified cyclodextrins facilitate the separation of the adsorbent from the aqueous phase, thus enhancing the application of CD-based adsorbents in practical applications. Most of the reported CD-based adsorbents demonstrate high efficiency for the adsorption of different pollutants. Moreover, the interior hydrophobic cavity of CDs predominantly contributes to capturing organic pollutants, particularly endocrine-disrupting chemicals. The performance of crosslinked and immobilized CD-based adsorbents for the simultaneous removal of mixed pollutants is excellent. Most CD-based adsorbents can be easily regenerated using a suitable desorption eluent. The challenges and limitations associated with CD-based adsorbents are presented, along with possible solutions and developments for highly efficient CD-based adsorbents that can be applied in practical wastewater treatment.