Polyamide thin films with nanochannel networks synthesized at the liquid-gas interface for water purification

Abstract

An important challenge concerning thin-film composite (TFC) membranes in brine treatment is to increase their water permeance while maintaining salt rejection for desalination performance. Structural control of polyamide (PA) thin films is a key factor in improving the desalination performance. In this study, we employed a Langmuir-Schaefer technique to fabricate PA Langmuir monolayers by interfacial polymerization of m-phenylenediamine and trimesoyl chloride at the liquid-gas interface and deposition on polysulfone supports. This technique allows the fabrication of nanoscale-controlled PA multilayers (2.3 nm per layer) with a nanochanneled structure through repeated deposition. The nanochannels of PA thin-film multilayers were clarified using the neutron reflectivity technique. UV treatment facilitates the maintenance of water-permeable sites in the nanochannels, which increases the water permeance up to 203% without loss of salt rejection performance.