Ultrasonication favors TiO2 nano-particles dispersion in PVDF ultrafiltration membrane to effectively enhance membrane hydrophilicity and anti-fouling capability.

The influence of ultrasonication on membrane performance was investigated by two ultrasonication modes, direct and indirect ultrasonication as pretreatment, and simply improved PVDF-TiO2 membranes' performance was systematically compared. Ultrasound intensity of 100% and ultrasonication time ranged from 1 to 2 h positively affect membrane permeability. Characterization results manifested that membrane structure was eventually optimized with an even nano-TiO2 dispersion by direct ultrasonication. Analysis of surface roughness reflected that PVDF-TiO2 (MS-U2) surface morphological pattern was peak-valley structure that resisted fouling greatly. A good fitting of experimental result and Tansel's simulation illustrated that anti-fouling ability was realized direct ultrasonication modified membrane. PVDF-TiO2 (MS-U2) membrane showing the lowest |τ| reflecting the time required to reach a certain level of the fouling degree was the lowest. Relying upon modified Hermia's model analysis, protein blockage within the membrane pore was one major fouling mechanism; surface blockage degree of PVDF-TiO2 (MS-U2) was relative slight. Fouling mechanism analyzed by two models reflected that PVDF-TiO2 (MS-U2) membrane exhibited a higher anti-protein fouling ability during cross-flow filtration process.