Triethanolamine-based zwitterionic polyester thin-film composite nanofiltration membranes with excellent fouling-resistance for efficient dye and antibiotic separation

Abstract

Water pollution and scarcity caused by small organic compounds (dyes and antibiotics) have attracted considerable attention due to their potential adverse effects on ecological environment and human body. Nanofiltration membranes with high performance, such as high rejection and fouling resistance, are expected to address these challenges. Herein, a new zwitterionic triethanolamine-based (Z-TEOA) monomer is proposed for the fabrication of zwitterionic polyester thin-film composite nanofiltration (ZNF) membranes. Z-TEOA is successfully synthesized via the ring-open reaction between TEOA and 1,3-propane sultone. ZNF membranes are fabricated via the interfacial polymerization under alkaline conditions. All fabricated membranes exhibit enhanced hydrophilicity and permeability due to the introduction of the zwitterionic functionality in the thin film layers. Specifically, the optimum membrane (ZNF1.5-5) shows an ultralow water contact angle (WCA) of 20.2°, high rejections to Congo red (CR, 99.9%), methyl blue (MB, 99.7%), orange G (OG, 95.9%), and tetracycline (TC, 96.7%). The uncompromised MB rejection of the ZNF membrane after a chlorine exposure (10,000 ppm.h) indicates its excellent chlorine resistance. Furthermore, the achieved ultrahigh flux recovery ratio (FRR, 97.8%) for MB demonstrates its outstanding fouling-resistant performance. All results reveal its potential for applications in the treatment of wastewaters from textile and pharmaceutical industries.