Acetone extraction induced piperazine diffusion reaction for regulating thin film composite nanofiltration membrane

The regulation of monomer diffusion in interfacial polymerization played a vital role in manipulating structure and enhancing separation performance of nanofiltration (NF) membrane. The co-solvent strategy has been recognized to be valid and applicable for improving membrane performance. However, the underlying mechanism for its effect on the diffusion progress of amine monomers was still unclear and contradictory. In this study, we found that the added co-solvent (acetone) induced piperazine diffusion flood through interfacial co-solvent extraction effect due to the interfacial enrichment of acetone and innovatively proposed a concept of “acetone extraction effect”. The mechanism and molecular dynamics simulation (MD) were used to systematically explain the effect of diffusion on the morphology and properties of the membranes. The prepared NF membranes exhibited improved separation performance for Calcium (CaCl2, 71.5 ± 0.6 %) and Magnesium (MgCl2, 83.1 ± 0.8 %) ions, which were better than many of the recorded membranes. This study provided a new idea for the co-solvent effect in interfacial polymerization and promising guidance for the preparation of superior NF membranes. [Display omitted] •Innovative concept of acetone extraction effect induced piperazine diffusion reaction.•NF membranes with more uniform, compact and small pore size were prepared.•Improved separation performance for Calcium and Magnesium ions.•MD simulation revealed the mechanism of co-solvent regulating PIP diffusion.