Polyamide nanofilms synthesized by a sequential process of blade coating-spraying-interfacial polymerization toward reverse osmosis

Thin film composite (TFC) membranes composed of polyamide nanofilms and porous substrates have received enhancing attention to desalination for overcoming the nexus of serious scarcity and huge demand for fresh water. Up to now, it is still a big challenge to avoid the complex interference of the porous substrates on the interfacial polymerization of amine and acyl chloride monomers for synthesizing polyamide nanofilms at lower carbon footprint. Herein, we report a sequential process of blade coating–spraying–interfacial polymerization for scalable preparation of polyamide nanofilms that shine in high-performance desalination. Our sequential process consists of 1) blade coating the viscous solution of water/glycerol/m-phenylenediamine (MPD) to form an anti-interference aqueous film, 2) spaying the organic solution of Isopar H/trimesoyl chloride (TMC) under a controlled and economical way onto the water/glycerol/MPD film, and 3) conducting the interfacial polymerization of MPD and TMC at the constructed organic-aqueous interface. The whole process highly reduces the utilization of organic solvents to meet the demands of lower carbon footprint. The synthesized polyamide nanofilms exhibit extremely low roughness and 10 nm thickness in an area larger than 200 cm2, which can be composited with various porous substrates. The as-prepared TFC membranes represent a high desalination performance of water permeance of 1.89 L m−2 h−1 bar−1 with 97.4% NaCl rejection. Our strategy broadens the way to large-scale synthesis of polyamide nanofilms for high-efficiency desalination membranes.