Surface fluorination of polyamide nanofiltration membrane for enhanced antifouling property

• Nanofiltration membranes with low surface free energy were prepared.
• Fluorinated polyamine was synthesized and grafted onto polyamide membrane surface.
• The resultant nanofiltration membranes exhibited superior antifouling property.

A new kind of fluorinated polyamine was successfully synthesized and grafted onto the polyamide membrane surface to fabricate an antifouling nanofiltration membrane with low surface free energy. The surface composition of the fluorinated polyamide nanofiltration membrane was confirmed by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The membrane cross-section morphology was observed by a field emission scanning electron microscopy (FESEM). The presence of perfluoroalkyl groups on the membrane surface significantly lowered the surface free energy from 60.0 to 44.4 mJ/m2. The filtration experiment results indicated that the surface fluorination did not lower the separation performance of the polyamide nanofiltration membrane significantly. The antifouling experiment results demonstrated that the fluorinated polyamide nanofiltration membranes exhibited superior antifouling property, that is, high flux recovery ratio (~98.5%) and low total flux decline ratio (~11%) during protein aqueous solution and humic acid aqueous solution filtration.