Highly efficient selective adsorption of anionic dyes by modified beta-cyclodextrin polymers

摘要

The nitrile groups in the tetrafluoroterephthalonitrile-crosslinked beta-cyclodextrin (beta-CD) were modified by (1) the reaction with the diethanolamine resulting in the hydroxyalkylaminoalkylamide groups or the hydroxyalkylaminoimide groups (2) the reduction of the borane-tetrahydrofuran complex resulting in the amide groups to form two novel beta-CD based polymers (CDPs), namely the CDP-DEA and the CDP-NH2, correspondingly. Furthermore, the dye adsorption abilities of these two CDPs in the aqueous solution were investigated using the anionic dyes including the Congo red (CR) and the orange G (OG). For both the CDP-DEA and the CDP-NH2, the pseudo second-order model fitted well with their adsorption dynamics and their equilibrium adsorption process followed the Langmuir isotherm model. The maximum adsorption capacities of the CDP-DEA for CR at pH=5 and OG at pH=3 were 813 mg/g and 442 mg/g, respectively, while the corresponding values of the CDP-NH2 were 40 mg/g and 446 mg/g, respectively. It was found that the electrostatic attraction played an important role in the anionic dye adsorption of the CDP-DEA and the CDP-NH2. (c) 2020 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.