Demystifying viscous isoalkanes as the organic solvent in interfacial polymerization for manufacturing desalination membranes

Abstract

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.