Surface modification of nanofiltration membrane using quaternary diethanolamine for efficient antibiotics/salt separation.

Nanofiltration plays a crucial role in antibiotic desalination from high salinity water, but the membranes often have low water permeability and insufficient selectivity between antibiotics and salts. In this study, a Gemini-type quaternary diethanolamine monomer (QTDEA) containing quaternary ammonium and hydroxyl groups was synthesized. This monomer had a hybrid spatial structure combining both rigid and flexible components, allowing it to covalently graft to the acyl chloride groups on the nascent polyamide (PA) film. The resulting modified PA-QTDEA membrane exhibited enhanced hydrophilicity, reduced negative charge, and a looser structure. It demonstrated a high water permeance of 18.2 L m−2 h−1·bar−1 for chlortetracycline hydrochloride (CTC) desalination from a NaCl solution of 10 g L−1, and the NaCl/CTC selectivity was 21.2. This research presents an efficient method for improving the performance of antibiotic desalination through surface modification using the novel QTDEA monomer. [Display omitted] • Novel Gemini-type monomer QTDEA is synthesized and used for the surface modification. • Grafting is achieved by the esterification of –OH in QTDEA with acyl chloride in TMC. • QTDEA with rigid and flexible hybrid structure increases the pore size of PA film. • Quaternary ammonium in QTDEA reduces membrane charge and Donnan exclusion. • Modified membrane improves both water permeability and antibiotics/salt selectivity. [ABSTRACT FROM AUTHOR]