Photo-induced antifouling polyvinylidene fluoride ultrafiltration membrane driven by weak visible light

To enhance the performance of ultrafiltration membranes, a polyvinylidene fluoride (PVDF) blending membrane with photo-induced antifouling performance was fabricated. La 3+ - and Yb 3+ -doped titanium dioxide-reduced graphene oxide (TiO 2 -RGO) composites were initially prepared by adsorption-phase synthesis coupled with solvothermal reduction. The doped TiO 2 -RGO composites were then blended with the PVDF materials. The results showed that adding well-distributed, doped, and hydrophilic TiO 2 -RGO improved the pore structures and surface polarity of the blending membranes, thus improving their permeation and antifouling performance. After addition of doped TiO 2 -RGO with photocatalytic activity, the antifouling performance of the resulting blending membranes increased under weak visible-light irradiation. The agglomerated doped TiO 2 -RGO in the polymeric matrix reduced the hydrophilicity and porosity of the resulting membranes, thereby decreasing their water permeability and antifouling performance. Solvothermal reduction through ethylene glycol also improved the photocatalytic activity of Yb-doped TiO 2 -RGO and enhanced the affinity between doped TiO 2 -RGO and PVDF. These two effects simultaneously increased the water permeability and photo-induced antifouling performance of the blending membranes. The flux recovery rate of the blending membranes containing Yb-doped TiO 2 -RGO treated by ethylene glycol exceeded 69% after illumination. In particular, the flux recovery rate of membranes reached about 96% after illumination coupling with washing.