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[Display omitted] • Polyamide nanofilms around 10 nm are facilely synthesized by a scalable process. • A sequential process of coating-spraying-interfacial polymerization is developed. • Organic solvent consumption reduces by 99 % compared with conventional process. • The polyamide nanofilms represent high performance as desalination membranes. 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. [ABSTRACT FROM AUTHOR]

It is deemed as a silver bullet that the mass production of desalination membranes will solve the exacerbated water scarcity, which normally uses polyamide nanofilm as the perm-selective layer through interfacial polymerization. Although there have been significant breakthroughs in laboratory research in recent years, the same good results cannot all be reproduced owing to many differences between pilot tests and mass production, such as the use of organic solvents. Herein, a new perspective is proposed for elucidating the deep reason that viscous isoalkanes are welcomed in the industrial production of desalination membranes. Interfacial polymerization of amine and acyl chloride is dissected from the initial stage including the distribution and enrichment of monomers at the aqueous–organic interface, as well as the diffusion and solvation state of polyamide oligomers. The viscous isoalkanes not only suppress the diffusion of acyl chloride monomer but also provide a better solvation environment for polyamide oligomers. Polyamide nanofilms with reduced thickness and roughness are obtained with an enhanced cross-linking density. The corresponding desalination membranes exhibit improved water permeance (~3 Lm−2h−1bar−1) and rejection to NaCl (~99 %) that surpasses the performance of free-standing polyamide nanofilms recently reported. Our facile strategy will facilitate the transformation of laboratory results into the mass production of customized high-performance desalination membranes. [Display omitted] • Viscous isoalkanes are discussed in detail as solvents in producing desalination membranes. • The viscous isoalkanes are demonstrated to suppress the diffusion of acyl chloride monomer. • The viscous isoalkanes also provide a better solvation environment for polyamide oligomers. • Corresponding polyamide-based membranes exhibit improved desalination performance. [ABSTRACT FROM AUTHOR]

The deepening crisis of freshwater resources has been driving the further development of new types of membrane-based desalination technologies represented by nanofiltration membranes. Solving the existing trade-off limitation on enhancing the water permeance and the rejection of salts is currently one of the most concerned research interests. Here, a facile and scalable approach is proposed to tune the interfacial polymerization by constructing a calcium alginate hydrogel layer on the porous substrates. The evenly coated thin hydrogel layer can not only store amine monomers like the aqueous phase but also suppress the diffusion of amine monomers inside, as well as provide a flat and stable interface to implement the interfacial polymerization. The resultant polyamide nanofilms have a relatively smooth morphology, negatively charged surface, and reduced thickness which facilitate a fast water permeation while maintaining rejection efficiency. As a result, the as-prepared composite membranes show improved water permeance (~30 Lm−2h−1bar−1) and comparable rejection of Na2SO4 (>97%) in practical applications. It is proved to be a feasible approach to manufacturing high-performance nanofiltration membranes with the assist of alginate hydrogel regulating interfacial polymerization. [ABSTRACT FROM AUTHOR]