Surface-engineered nanofiltration membranes with quaternary piperazinium electrolyte for enhanced antibiotics/NaCl separation

Nanofiltration offers unique advantages in antibiotic desalination, however, conventional membranes often suffer from low water permeance and limited antibiotics/salt selectivity. To address this, we synthesized a strong electrolyte monomer, AHEP (1,4-bis(2-aminoethyl)-1,4-bis(2-hydroxyethyl)piperazine-1,4-diium bromide), and engineered a high-performance nanofiltration membrane. Featuring dual quaternary ammonium centers and multiple hydroxyl/amine groups, AHEP was covalently anchored onto a PIP-TMC membrane surface via amidation reaction. The resulting PIP-TMC-AHEP membrane achieved 97.5 % Na 2 SO 4 rejection coupled with water permeance of 17.5 L·m −2 ·h −1  bar −1 —representing a 3.7-fold permeance enhancement over the unmodified PIP-TMC counterpart. High antibiotic rejection efficiencies (>92 %) were consistently demonstrated for ciprofloxacin, tetracycline, oxytetracycline, and levofloxacin. Furthermore, the membrane exhibited outstanding separation capability for antibiotic/NaCl mixtures (feed: 100 pm tetracycline and 10,000 ppm NaCl, tetracycline/NaCl selectivity is 45.9) alongside significantly antifouling and antibacterial ability.