High-performance polyethyleneimine based reverse osmosis membrane fabricated via spin-coating technology

Conventional thin-film composite (TFC) reverse osmosis (RO) membranes prepared by ultrafast and uncontrolled interfacial polymerization (IP) generally have unsatisfactory permeability and high fouling propensity, which distinctly impedes their development and wide application. Controllable thickness and roughness offer an opportunity to optimize the permeability and fouling resistance of RO membranes. In this work, we propose spin-coating assisted multilayer interfacial polymerization (SMIP) as a promising approach to fabricating high-performance RO membranes using polyethyleneimine (PEI) and 1, 3, 5-benzoyl chloride (TMC). SMIP integrates the high efficiency and uniformity of spin-coating technology, the nano-level and individual properties control of multilayer interfacial polymerization, and the simplicity of the IP process. Combining the strong hydrophilicity with low diffusion efficiency and positive charge of PEI, a thin, intrinsically hydrophilic, smoother and almost electro-neutral polyamide (PA) nanofilm was obtained. The optimal RO membrane with a controlled thickness of the selective layer (≈61 nm) has a water permeance of 3.12 L m−2 h−1 bar−1 and an acceptable NaCl rejection of 97.5%, while the strong hydrophilicity, minimal surface roughness and almost neutral surface charge afford it excellent fouling resistance. SMIP technology not only provides a new approach to preparing highly permeable and low-fouling RO membranes using macromolecular monomers, but also has great application potential in other separation membranes due to its precise control of the selective layer.