Cyclodextrin-based Materials for Removing Micropollutants From Wastewater

In recent years, several efforts have been made for developing simple and cost-effective strategies for eliminating multiple organic and inorganic pollutants from wastewater. Pharmaceuticals, dyes and heavy metals expelled from pharmaceutical and textile industries, frequently coexist in wastewater and exhibit different complex properties, which makes the respective individual or simultaneous removal processes a continuous challenge of high, undisputed social and technological interest. The unique properties of cyclodextrins combined with its biocompatible and bioabsorbant character allow for simultaneously removing different pollutants from water by means of sorption/inclusion. Although there is a general consensus that the mechanism of sorption is based on the formation of host-guest supramolecular complexes and that cyclodextrin-based materials are effective complexation agents for targeting environmental pollutants, outperforming the conventional systems, the role of other phenomena, external to the binding sites and involving the polymer network, are still under intense scrutiny and discussion. These are related to contributions from polymer-polymer interaction, including association, surface sorption, hydrophobic interactions, electrostatics, hydrogen bonding, and also ion exchange, chelation and microprecipitation. They are governed by the type of material (e. g. native or modified polymer) and by the experimental conditions (e. g. pH, temperature, molar ratios). This review provides an upto- date discussion on the key advances in developing cyclodextrin-based materials (polymers, hydrogels and nanocomposites) used as sorbents for removing toxic compounds from wastewater. Relevant aspects regarding the benefits, structural variations and preparation procedures of these macromolecular systems, and corresponding supramolecular properties, complexation behavior, adsorption mechanisms and removal performances for different pollutants are also outlined.