Preparation of high-permeance polyester nanofiltration membranes utilizing biobased phloretin derivatives for antibiotic separation

Abstract

Antibiotics in water bodies pose a significant threat to the health of plants, animals, and humans, thereby contributing to severe ecological crises. Polyamide nanofiltration (NF) membranes are extensively employed for the separation and purification of antibiotics but are limited by relatively low permeation fluxes. In this study, three biobased phloretin derivatives—phloretin (Pt), phlorizin (Pz), and naringenin dihydrochalcone (Ng), were selected as water-phase monomers and reacted with trimesoyl chloride to fabricate three novel polyester NF membranes. The results demonstrated that the variations in the molecular structure gradients, including twisted conformation and molecular weight, of the three derivatives significantly influenced the structure and properties of polyester NF membranes. In-depth mechanistic analysis revealed that the diffusion rates (mainly related to molecular weight) of the three derivatives into the oil-phase solution, rather than their reactivity with TMC, governed the interfacial polymerization (IP) process. Consequently, Pt-based polyester NF membranes exhibited relatively dense layers compared to Pz- and Ng-based ones, achieving rejections of 92.4 % and 85.7 % for bacitracin and erythromycin, respectively, while maintaining a permeance of 35.2 L/m² h bar, which was significantly higher than that of conventional polyamide NF membranes. Meanwhile, the relatively loose structure of the Pz- and Ng-based polyester NF membranes made their permeance reach as high as 65.8 L/m²·h·bar and 107.2 L/m² h bar, respectively, while maintaining intermediate separation level for five antibiotic molecules. Furthermore, the three polyester NF membranes demonstrated excellent chlorine resistance, antifouling properties, and good environmental adaptability. The three biobased polyester NF membranes in this study offer a novel approach for the development of high-flux NF membranes for antibiotic separation and other specialized scenarios. The correlation between the molecular structure of the derivatives and the membrane separation performance further deepens the understanding of polyester-based IP theory.