Highly flexible β-cyclodextrin polymer surface-functionalized polyurethane membrane captures organic pollutant phenolphthalein from aqueous media

Abstract

Cyclodextrin polymer materials, as a class of promising adsorbents, have received enormous attention because of their easy complexation with most organic compounds. However, such materials are usually in powder form and not convenient to separate from an aqueous media after adsorption, challenges remain in the development of cyclodextrin polymer adsorbents with both efficient adsorption capacity and flexibility. Here, we design a kind of β-cyclodextrin polymer (PCD) functionalized adsorbent via the polymerization of β-cyclodextrin and hexamethyl diisocyanate accompanied by the casting of the mixed solution of polyurethane (PU) and PCD. The flexible adsorbent (PU/PCD) is composed of PU matrix and PCD dispersed phase, which presents remarkable mechanical properties and can be folded 100 times without breaking. Since the surface enrichment of abundant PCD components in the PU/PCD blends could provide numerous accessible adsorption sites, the maximum adsorption capacity of organic pollutant phenolphthalein (PHP) by PU/PCD could reach 235.85 mg/g, which is superior to many other reported adsorbents containing β-CD. Density functional theory (DFT) is employed to understand the interaction mechanism between β-CD and PHP, demonstrating that the supramolecular complex formed is relatively stable. In addition, PU/PCD exhibits good water stability and reusability, and the removal efficiency remains above 96 % even after 5 consecutive cycles of adsorption-desorption. This work thus provides a new insight into the fabrication of PCD surface-functionalized efficient adsorbent with good flexibility and complex affinity for small organic molecules in aqueous media.