Remediation of water pollution with native cyclodextrins and modified cyclodextrins: A comparative overview and perspectives

Although native and modified cyclodextrins (CDs) are somewhat effective in environmental applications, there is a continued interest in understanding their distinct role in various applications and effectiveness. This review highlights the tremendous efforts that have been made to enhance the efficiency of CDs for challenging environmental applications such as treating multi-pollutant mixtures or elucidating sorption mechanisms. To overcome these limitations, the modification of CDs using cross-linking agents has attracted attention due to their distinctive abilities to interact with a variety of environmental pollutants. The interest in new CD derivatives has resulted in the creation of many novel materials, including cross-linked polymers or hydrogels, effective cross-linkers, CD-based composites, CD-immobilized supports, CD-based membranes, and molecularly impregnated functional materials. Some basic questions concerning the effectiveness of these CD classes still warrant clarification. In this review, we present the first comprehensive outline of environmental remediation strategies using CDs and CD derivatives to accomplish the following objectives: (i) to provide an overview of the diverse environmental applications of CD and its derivatives, (ii) to provide up-to-date and useful information about their synthesis, features, and characterization (iii) and to understand their contribution to the remediation of heavy metals and organic pollutants from a comparative point of view. Finally, modified CDs are shown to be effective, non-toxic, and degradable in comparison with native CD, especially epichlorohydrin cross-linked CD (ECP) gels, which are considered pioneers among CD derivatives.