Engineering highly permeable thin-film composite nanofiltration membranes by strengthening the diffusion control of amine monomer via deep eutectic solvent

Thin-film composite nanofiltration (TFC NF) membranes play an important role in seawater desalination and wastewater decontamination, while the presence of trade-off effect between permeability and selectivity limits their further application. Tuning amine monomer diffusion has been considered as the key to optimizing the physicochemical structure of polyamide (PA) layer and thus achieving the preparation of highly permeable TFC NF membranes. In this study, deep eutectic solvent (DES) was used as an aqueous-phase additive to enhance the control of piperazine (PIP) diffusion via a novel integrated synergistic mechanism of hydrogen bonding interaction and viscosity modulation during interfacial polymerization (IP) process. Correspondingly, the addition of DES can not only optimize membranes surface properties (hydrophilicity, surface negative charge, roughness) but also reduce the thickness of PA layer from 93 +/- 9 nm to 31 +/- 4 nm. The results showed that the modified membrane maintained a high Na2SO4 rejection (99.3%) and a favorable pure water permeance of 43.3 L center dot m(-2)center dot h(-1)center dot bar(-1), which presented approximately 6-fold higher pure water permeance than that of commercial membranes NF-90. Therefore, this study provides a promising strategy to fabricate highly permeable TFC NF membranes and opens up a new avenue for DES application in water treatment.