Preparation of waterborne polyurethane/β-cyclodextrin composite nanosponge by ion condensation method and its application in removing of dyes from wastewater

Currently, polymer nanosponges have received extensive attention. However, developing new synthetic techniques for novel nanosponges remains a challenge. Furthermore, to date, composite nanosponge adsorbents based on waterborne polyurethane(WPU) and β-cyclodextrin(β-CD) have not been reported.Herein, a novel green method, ion condensation method, was developed in this study for the preparation of polymer nanosponge adsorbents for efficient removal of dyes from wastewater. Based on the principle of charge repulsion between nanoparticles to maintain emulsion stability, waterborne polyurethane/β-cyclodextrin composite nanosponges(WPU-x,y) were prepared by coagulating the emulsions synthesized from 2,2-dimethylolpropionic acid, polypropylene glycol and hexamethylene diisocyanate as raw materials in a mixture of hydrochloric acid and anhydrous ethanol. The structure and appearance of WPU-x,y were characterized by attenuated total reflectance Fourier transform infrared spectroscopy,thermal gravimetric analyzer, scanning electron microscope and mercury intrusion porosimetry. The adsorption capacity of WPU-x,y was tested by parameters such as cross-linking degree, β-CD dosage, contact time, initial dye concentration and p H value. The study found that WPU-4,4.62 had the best adsorption effect on methylene blue(MB), the maximum removal rate was 93.42%, and the maximum adsorption capacity was 136.03 mg·g-1. Moreover, the Sips isotherm and pseudo-second-order-model were suitable for MB adsorption. Therefore, this study provides some perspectives for the fabrication of nanosponge adsorbents.