The increasing release of micropollutants into water resources and their adverse effects on aquatic ecosystem and human health have aroused global concerns. [1] Steroid hormones including natural estrone (E1) and estradiol (E2) and synthetic 17β-ethinyl estradiol (EE2) are one such type of micropollutants widely found in wastewater. [2,3] Despite their trace levels (1-100 ng L −1) in water sources, steroid hormones can disrupt the endocrine system of human and other organisms by interfering the synthesis, secretion, transport, binding of natural hormones. [4] The negative health impacts of steroid hormones on animals are well documented, such as feminization in fish, [5] intersexuality in wild roach, [6] and tachycardia in bullfrog tadpoles. [7] In addition, increasing evidence has shown that exposures to steroid hormones causes negative impacts on human health like obesity, diabetes, intellectual disability, and male infertility. [8] Therefore, it is an urgent task to remove steroid hormones from water source for protecting human health and ecosystem. Inadequate removal of steroid hormones by conventional wastewater treatment systems has motivated the development of advanced treatment technologies such as activated carbon adsorption, advanced oxidation processes, and membrane technology for treating such micropollutants. [9] Among them, membrane technology is considered to be a promising strategy for water purification because of its high efficiency, ease of operation, and small footprints. [10] For example, nanofiltration (NF) and reverse osmosis (RO) processes have been used to remove hormones via a combination of mechanisms such as size exclusion, charge repulsion, and adsorption. [11-13] However, the low water permeability of NF and RO membranes requires high operation pressure and frequent membrane cleaning, [14,15] which significantly increases the operation and maintenance of such processes. Hence, development of advanced membranes that are able to reject or capture steroid hormones at higher water permeability is highly desired. Affinity membranes separate molecules based on the specific physical and chemical interactions between ligands and target molecules rather than by sieving mechanisms. [16-19] Combining The occurrence of steroid hormones in water and their serious impact on human and ecosystem demand high performance materials for efficient removal of such micropollutants. Here, an affinity membrane is developed for hormone removal with regenerable binding sites. By using photodynamic disulfides as a linker, UV induced detachment of β-CD ligands from the membrane surface is demonstrated. The macroporous base membrane is first fabricated via a polymerization induced phase separation method using 2-hydroxyethyl methacrylate (HEMA) and ethylene dimethylacrylate (EDMA) monomers. Then the affinity membranes are prepared by immobilizing β-CD ligands to the poly(HEMA-co-EDMA) base membrane through the 2-carboxyethyl disulfide linker. The β-CD functionalized affinity membrane shows a 30% increase of E2 ho...
