Environmental applications of water-insoluble β-cyclodextrin-epichlorohydrin polymers

Chemical cross-linking using epichlorohydrin as cross-linking agent is the most straightforward method to produce water-insoluble β-cyclodextrin-based polymers. The numerous OH groups available on cyclodextrin (CD) molecules are active sites capable of forming a number of linkages. Although this cross-linking reaction has been known for 50 years and is well documented, and relatively easy to use for the preparation of CD-based networks, some basic questions concerning the reaction still continue to interest the scientific community. The main objectives of this review are (i) to describe the synthesis and characterization of insoluble CD-epichlorohydrin polymers, (ii) to provide useful information on their most important features, (iii) and to summarize the developments in the use of these materials for environmental purposes. In particular, the description of relevant environmental applications such as sorption-oriented processes, detoxification of wastewater, color removal, and concentration and purification of solutions is included. In this aim, an extensive pool of data from the literature, from 270 papers, reviews, patents and books, has been compiled. The various interactions occurring between pollutants and CD-epichlorohydrin polymer in the sorption processes are presented, and future research trends are discussed.