Study on the improvement of PVDF flat ultrafiltration membrane with MWCNTs-OH as the additive and the influence of different MWCNTs-OH scales

Abstract Poly(vinylidene fluoride) (PVDF) ultrafiltration membrane has many advantages that make it widely applicated in water treatment. Still, the PVDF membrane's nature easy to pollute the defects, which makes it a severe threat to the further development of the PVDF membrane, which makes hydrophilic modification necessitated. Here we fabricated the PVDF-based blended matrix nanocomposite membranes using hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) as the additive via low-temperature thermally induced phase separation (L-TIPS) method. Consequently, the addition of MWCNTS-OH significantly improved the pure water flux (from 365.38 L/(m2·h) to 617.24 L/(m2·h)), hydrophilicity, and anti-fouling property of the membrane, and gave PVDF membrane more potent mechanical properties. Besides, the influence of different tube diameters ( 50 nm) of MWCNTS-OH on membrane properties were investigated and obtained the most suitable adding tube diameters of MWCNTS-OH: when the tube diameter of MWCNTs-OH was 10-20 nm; membrane surface roughness decreased from 0.354 μm to 0.071 μm, and the dynamic contact angle was the lowest among the membranes about 77.6°; flux recovery ratio (FRR) values were higher than 92% by adding MWCNTs-OH. Our research for the further development and optimization of PVDF membrane provides a new perspective.