High-Flux Thin Film Composite Membranes Prepared by Interfacial Polymerization With Pyridine or Pyrimidine Structured Diamines as Aqueous Phase Monomers for Efficient Organic Solvent Nanofiltration

Herein, a series of high-flux thin film composite organic solvent nanofiltration (TFC OSN) membranes were prepared using diamine monomers with pyridine or pyrimidine structures (2,6-Diaminopyridine (Pd), 4,6-Diaminopyrimidine (Pm)) alternatively to M-phenylenediamine (MPD) via interfacial polymerization (IP). Compared to MPD, Pd and Pm have a different number of electron-donating N atoms in the six-membered ring skeleton. As nucleophilic reagents, the presence of N atoms affects the chemical composition, structure, and cross-linkage degree of the polyamide active layers formed by their A₂-B₃ type nucleophilic substitution reactions. The results show that the membranes prepared with Pd or Pm have higher permeability to solvent than the membrane prepared with MPD. The solvent flux of the TFC-Pd membrane (19.12 L m⁻² h⁻¹ bar⁻¹) and TFC-Pm membrane (12.35 L m⁻² h⁻¹ bar⁻¹) was 2.30 and 1.49 times that of the TFC membrane (8.32 L m⁻² h⁻¹ bar⁻¹), respectively. Meanwhile, the rejection of EB dye by the TFC-Pd and TFC-Pm membranes was more than 90%. Furthermore, the prepared TFC-Pd and TFC-Pm membranes all showed good organic solvent resistance and long-term operation even after immersion in strong polar N, N-Dimethylformamide at 60°C for 6 days, indicating that the high-flux OSN membranes prepared with Pd or Pm monomers have good long-term stability.