Hyperbranched poly(ether amine)@poly(vinylidene fluoride) (hPEA@PVDF) porous membranes for selective adsorption and molecular filtration of hydrophilic dyes

Abstract

Porous membranes with selective adsorption are of great interest because of their wide application in molecular filtration, industrial separation and water treatment. To adsorb dyes with selectivity and high flux, the unique selective adsorption behavior of amphiphilic hyperbranched poly(ether amine) (hPEA) materials toward guest molecules and the facile preparation of a stable porous structure of poly(vinylidene fluoride) (PVDF) were combined to fabricate novel hPEA@PVDF porous membranes through non-solvent induced phase separation (NIPS). The resulting hPEA@PVDF membranes were further cross-linked through the photo-dimerization of coumarin groups in hPEA, and their morphologies were characterized using a scanning electron microscope (SEM), wide angle X-ray diffractometer (WAXD) and differential scanning calorimeter (DSC). The adsorption behavior of hPEA@PVDF porous membranes toward twelve hydrophilic dyes was investigated in detail. Regardless of their charge states, hPEA@PVDF porous membranes exhibited quick adsorption behavior toward Erythrosin B (ETB), Rose Bengal (RB) and Eosin B (EB) with a high adsorption capacity (Q_eq) around 600 μmol g⁻¹ but very slow adsorption behavior toward Calcein (Cal) and Methylene Blue Trihydrate (MB) with a low adsorption capacity. Based on their unique selective adsorption behavior toward hydrophilic dyes, hPEA@PVDF porous membranes could separate mixtures of dyes in aqueous solution through molecular filtration with a high flux rate. In addition, the hPEA@PVDF porous membranes were easily regenerated and maintained high separation efficiency over five adsorption–washing cycles. hPEA@PVDF membranes showed great advantages of large adsorption capacity, fast separation of dyes, easy regeneration and low cost due to their porous structure and unique selective adsorption behavior toward hydrophilic dyes, and might find great potential in separation and water treatment.