Silica Materials Containing Cyclodextrin for Pollutant Removal

This chapter reviews the use of cyclodextrin-silica hybrid systems and cyclodextrin-functionalized silica used as adsorbents or filters for the removal of inorganic and organic pollutants from aqueous solutions in solid-phase extraction and adsorption-oriented processes. Actually, there is a need to develop efficient processes for the synthesis and application of multifunctional silica-based materials for pollutant removal by adsorption or filtration, and for sample purification and concentration using solid-phase extraction. On one hand, of silica-based adsorbents are low-cost, robust inorganic solids having large surface areas, high porosity, and excellent mechanical, physical and chemical properties, and wide possibilities of functionalization due to silanol reactivity. On the other hand, cyclodextrins are natural molecules obtained from the enzymatic degradation of starch. They belong to the family of cage molecules due to their structure which is composed of a hydrophobic cavity that can encapsulate other molecules. Cyclodextrin-functionalized silicas usually display improved access to the binding sites because the moieties are located on the external surface of the material. In cyclodextrin-silica hybrid systems prepared through sol-gel or self-assembly process, cyclodextrin molecules are located within the framework of nanoporous silicas. Here, both high cyclodextrin loadings, robust structures and higher surface area are observed. Cyclodextrin-based silica materials have strong binding affinities for chemical substances such as metal ions, dyes, pesticides, and drugs.