Preparing γ-cyclodextrin-immobilized starch and the study of its removal properties to dyestuff from wastewater

Abstract

A novel natural polymeric adsorbing material γ-cyclodextrin immobilized starch (CS- γCD) was prepared by introducing host functional molecule γ-cyclodextrin (γ-CD) into starch, using epichlorohydrin (ECH) as a cross-linking agent and sodium hydroxide as a catalyst, via the aqueous-phase synthesis method. The γ-cyclodextrin content in CS-γCD was up to 8.15% determined by the bromocresol green (BCG) hyperchromic spectrophotometric method. The structures of CS-γCD were characterized by infrared spectrum (FT-IR), 13C-nuclear magnetic resonance spectrum ( 13 C-NMR), scanning electron microscope (SEM), x-ray diffraction (XRD), and gel permeation chromatography (GPC). We investigated the adsorption performances and kinetics of CS-γCD to three different kinds of dyestuff including methylene blue (MB), methyl purple (MP), and congo red (CR). The results showed the adsorbing capacities of CS-γCD to three kinds of dyes had obviously increased compared with native starch and diatomite, and the CS-γCD was also found to have a significant advantage in adsorption of macro-molecule dye such as CR over other adsorbing materials. The adsorption behaviors of CS-γCD on the three dyestuffs could be better described by a Langmuir model (R 2 >0.99), but also had relatively high correlation to Freundlich model. The pseudo second-order model could better describe the adsorption behaviors. The CS-γCD could be enzymolysised, while its degradation rate was much lower than native starch, which indicated that CS-γCD had a relatively higher structural stability and longer service life, these characters could be beneficial for the popularization and application of CS-γCD in fields of wastewater treatment and environment remediation.