Inorganic salt-conditioning preparation of a copper (II) ions-doped thin film composite membrane with ridge-valley morphology for efficient organic solvent nanofiltration

Herein, a copper (II) ions-doped thin film composite (TFC-Cu) membrane with ridge-valley morphology was prepared by interfacial polymerization (IP) via incorporating copper (II) ions in the aqueous phase. The complexation of copper (II) ions with N atoms on m-phenylenediamine (MPD) affects the diffusion of MPD from the aqueous to the oil phase, leading to instability of the IP process and consequently the formation of ridge-valley morphology on the membrane surface. The ridge-valley morphology increases the contact area between the membrane and the solvent, which lays the foundation for increased solvent permeability. Moreover, the hydrophilicity and permeability of the composite membrane can be modulated by adjusting the content of copper (II) ions in the aqueous phase. The methanol permeation performance of the preferred TFC-Cu100 membrane was 13.27 L m−2 h−1 bar−1, an improvement of 65.46% over the unmodified TFC membrane. Meanwhile, the TFC-Cu100 membrane also showed a high retention level (98.82%) of RDB dye. In addition, the TFC-Cu100 membrane maintained good long-term organic solvent nanofiltration (OSN) performance after 10 days of immersion in N, N-dimethylformamide (DMF) at 80 °C. This work offers attractive prospects for the modification of the IP process using other inorganic salts to optimize the OSN performance of the membrane.