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ABSTRACT:The suspension polymerization of ␤-cyclodextrin (␤-CD) with epichlorohydrin (EP) has been studied using a fractionated factorial design with two levels and six variables (␤-CD:EP molar ratio, NaOH concentration, temperature, stirring speed, delay time before paraffin addition, and ␤-CD concentration). Different variables, such as the amount of ␤-CD in the product, particle size, degree of swelling, and sorption capacity, have been analyzed as the responses for the synthesized polymers. The experimental design approach permitted to select the optimal conditions of synthesis depending on the desired features of the product.

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A cyclodextrin-based polymer was prepared by crosslinking β-cyclodextrin with epichlorohydrin to be assessed as a sorbent material for cresols in packed-bed columns. Both Langmuir and Freundlich isotherms were appropriate to describe the sorption equilibrium in the conditions tested, and the thermodynamic parameters obtained for this process confirmed its exothermic nature with similar enthalpies (between − 6.8 and − 8.3 kJ/mol) for the three isomers. The removal of cresols from water was carried out in nine cycles of sorption–desorption in fixed-column experiments with the cyclodextrin hydrogel, achieving sorption capacities of 6.2, 11.6, and 15.1 mg/g for o-, m-, p-cresol, respectively. These differences in sorption capacities are due to the different chemical structures of cresols, that is, the relative position of the methyl and hydroxyl groups. However, similar sorption rates were observed for each isomer, with a mean value of 0.10 mg-cresol g-CDP–1 min–1 in all cases. The experimental data for the breakthrough and the elution curves have been successfully modeled by two effective two-parameter equations, a dose–response model for the sorption step and a pulse-peak model for the regeneration step. The cyclodextrin polymer matrix has been proven to be an effective a good sorbent material for removing cresols from water, exhibiting remarkable reusability performance and structural stability throughout the successive elution steps carried out with methanol.