Removal of azo dye from aqueous solution by host–guest interaction with β-cyclodextrin

Water pollution is a serious threat to the human beings’ survival and development and a universal problem across community society. In this work, a novel β-cyclodextrin (β-CD) hydrogel was successfully synthesized by polycondensation reaction using epichlorohydrin (EPI) and β-CD under basic condition, and the swelling ratio at room temperature was up to 181%. The adsorption behavior and adsorption mechanism of EPI crosslinked β-CD were evaluated by using acid orange 7 (AO7) as a model dye. We found that the adsorption process obeyed the pseudo-second-order kinetic model, and the maximum adsorption capacity of AO7 was estimated to be 132 mg g–1, which is much higher than the bamboo charcoal, titanium dioxide and so on. Moreover, intraparticle diffusion model indicates that the adsorption process can be divided into three stages: diffusion of the AO7 to β-CD hydrogel surface, intraparticle diffusion, establishment of the adsorption equilibrium, and the host–guest interaction between the hydrophobic naphthyl group and the cavity of β-CD plays the decisive role in the adsorption of AO7 onto β-CD hydrogel.