Improved performance of polyvinylidene fluoride membrane blended with modified multi-walled carbon nanotubes by electret treatment

In this paper, electret treatment was used to enhance the electrostatic repulsion between the membrane and bovine serum albumin, so as to improve the anti-fouling ability and recycling rate of the membrane. The polarization charge is provided by the dipole orientation of polyvinylidene fluoride (PVDF) materials, and the space charge is composed of the interfacial charge between the filler and the matrix and the bulk charge of the hollow structure of the multi-walled carbon nanotubes. The results showed that after electret treatment, the surface potential of the membrane increased, the PVDF crystal type changed from α to β, and the crystallinity increased. Grafting of N-vinylpyrrolidone onto multi-walled carbon nanotubes (MWCNTs-g-PVP), which contain a large number of hydrophilic groups after modification, reduces the contact angle of the composite film from 86.9° to 62.7°. The pure water flux and flux recovery rate of MWCNTs-g-PVP/PVDF composite membranes after electret treatment was increased from 189.31 L·m⁻²·h⁻¹ and 90% to 233.55 L·m⁻²·h⁻¹ and 94.7%, respectively, and the rejection rate increased about 30%. Through the circulation experiment, it can be seen that the anti-fouling performance and recycling rate of the membrane is improved, which is caused by electrostatic repulsion.