Durable PVDF photocatalytic membranes with TiO2@PDA incorporated into/onto for dye degradation under visible-light

Abstract

Visible light–driven photocatalytic membranes are a promising, energy-efficient approach for wastewater treatment. In this study, a visible light–responsive TiO2@polydopamine (TiO2@PDA) core–shell was developed for integration into polyvinylidene fluoride (PVDF) membranes. The use of polydopamine enhances the binding of the photocatalyst to the membrane and improves the oxidation resistance of the membrane material. We examined the impact of TiO2@PDA positioning within the membrane using two techniques: mixed-matrix membranes (MMMs) and surface coating. We found that better dispersion of TiO2@PDA in MMMs leads to higher photodegradation performance compared to a surface-coated membrane. At comparable TiO2 loadings (3.5–4.0 %), MMMs degraded 95.1 % of dye, while surface-coated membrane degraded 89.2 %. The M7 membrane (7 % TiO2@PDA in the dope) absorbed and degraded 98.1 % of Reactive Red 239 (RR 239) dye under visible light irradiation for 150 min with filtration, compared to 4.0 % degradation without filtration, highlighting the importance of in-pore photocatalytic activity. The MMMs method achieved robust binding stability between TiO2@PDA and the membrane. Both integration methods demonstrated high reusability, with approximately a 10 % reduction in efficiency after 10 cycles. These results demonstrated the potential of applying a simple method to modify TiO2, solving problems with its low visible light absorption and binding stability and protecting PVDF membranes from photodegradation, thus enhancing the practical applications of photocatalytic membranes.