Amino acid-based loose polyamide nanofiltration membrane with ultrahigh water permeance for efficient dye/salt separation

Loose nanofiltration (NF) membranes with a considerable water permeance are highly desired for the separation of hazardous dyes and salts from saline textile wastewater. However, further improving the water permeance of loose NF membranes with superior sieving capabilities remains a daunting challenge. Herein, a novel amino acid-based loose polyamide NF membrane was successfully developed via an interfacial polymerization (IP) process between arginine (Arg) and trimesoyl chloride (TMC) on PES substrates. The negatively charged, hydrophilic surface and ultrathin (87 nm) polyamide layer, afforded the membrane with a high separation performance. The optimal Arg/TMC membrane displayed an ultrahigh pure water permeance of 130.4 L m⁻² h⁻¹ bar⁻¹ with high dye rejection (Congo red: 99.6%, Direct Red 23: 99.0%, Reactive Blue 2: 98.5%, Reactive Orange 16: 95.2%), and low salt rejection (3.8% for NaCl and 7.2% for Na₂SO₄). In addition, the Arg/TMC membrane maintained good antifouling properties. L-Glutamine and L-Serine were also utilized as aqueous monomers, confirming the universality of the amino acids for the facile preparation of high-performance loose NF membranes. By choosing amino acids with suitable R groups, it is expected to develop amino acid-based NF membranes for the separation of various dyes.