Polydopamine-assisted attachment of β-cyclodextrin on porous electrospun fibers for water purification under highly basic condition

Abstract

Polydopamine (PDA), a mussel-inspired adhesive polymer, has recently been explored as promising adsorbent for water purification. The adsorption ability of PDA for some pollutant species, however, decreases significantly under basic conditions because the electrostatic repulsion between negatively charged pollutants and PDA adsorbents. In this work, porous electrospun polystyrene (PS) fibers are functionalized by coating a thin layer of PDA and subsequently attaching β-cyclodextrin (β-CD) on the surface. With abundant catechol groups, the PDA layer allows facile attachment of β-CD on the fiber surface via multiple hydrogen bonds. The tailored porous morphology of the PS fibers and precisely controlled PDA coating thickness provide the functionalized fibers (β-CD/PDA/PS) large specific surface area. Furthermore, the formation of inclusion complexes and the multiple hydrogen bonds between PDA and the very weak acidic hydroxyl groups on CDs are not significantly disturbed by the high pH environments. These endow the β-CD/PDA/PS fibers much improved ability in adsorption of negatively charged pollutants under highly basic conditions than PDA-functionalized fibers. The β-CD/PDA/PS fibers can effectively remove phenolphthalein from aqueous solutions at pH=10, and also exhibit good stability in ethanol, providing the fibers reusability.