Remarkable Anti-Fouling Performance of TiO2-Modified TFC Membranes with Mussel-Inspired Polydopamine Binding

It has been proven that a versatile bio-glue, polydopamine, can firmly bind TiO2 (titanium dioxide) nanoparticles on thin film composite (TFC) membranes. In this work, the anti-fouling behaviour of this novel polydopamine-TiO2-modified membrane is evaluated, based on the static bovine serum albumin (BSA) surface adhesion of the membranes and the relative flux decline. The results show that the anti-fouling performance of this new membrane is significantly improved in dark conditions when compared with the neat TFC membrane and the membranes only modified by polydopamine or TiO2. When filtrating a 0.5 g·L−1 BSA solution in dark conditions, the flux of the polydopamine-TiO2-modified membrane remains constant, at 95% of its pure water flux after 30 min filtration for 8 h of the experiment. This indicates a significant increase in anti-fouling performance when compared to the 25% flux decline observed for the neat TFC membrane, and to the 15% flux decline of those only modified by polydopamine or TiO2. This remarkable anti-fouling behaviour is attributed to an improved and uniform hydrophilicity, due to the presence of TiO2 and to the regular nanosized papillae structure of the polydopamine-TiO2 coating. Furthermore, since dopamine-modified TiO2 has visible light-induced photocatalytic properties, the membrane’s photocatalytic performance was also tested in light conditions. However an increase of flux and decrease of retention were observed after 24 h of continuous illumination, indicating that light may also affect the top layer of the membrane.