Preparation of a carboxymethyl β-cyclodextrin polymer and its rapid adsorption performance for basic fuchsin

The presence of dyes in a water system has potential adverse effects on the ecological environment. The conventional cyclodextrin (CD) polymer only has CD cavities as adsorption sites and exhibits slow adsorption for dye removal. In this study, we designed a novel carboxymethyl beta-CD polymer (beta-CDP-COOH). The structural properties of beta-CDP-COOH were characterized as an irregular cross-linked polymer with negative surface charge, and the introduction of carboxymethyl groups greatly enhanced the adsorption ability of the beta-CD polymer to basic fuchsin (BF). The maximum removal efficiency of beta-CDP-COOH (96%) could be achieved within 1 min, whereas that of conventional beta-CD polymer (70%) was achieved after 50 min. The adsorption mechanism revealed that the adsorption behavior of beta-CDP-COOH could be effectively fitted with the pseudo-second-order kinetic model and Langmuir isotherm. Both CD cavities and carboxymethyl groups were effective adsorption sites, so beta-CDP-COOH had an advantage in adsorption capacity over the conventional beta-CD polymer. This study indicated that beta-CDP-COOH is a potential highly efficient adsorbent for the removal of cationic dye contaminants.