Effective Decolorization of Rhodamine B by a Ti Foam-Based Photocatalytic Membrane Reactor

In this study, a Ti foam-based photocatalytic membrane reactor (PMR) was constructed for rhodamine B (RhB) wastewater decolorization. Ti foam was chosen as a membrane and visible-light-driven C₃N₄ was chosen as a photocatalyst. The results showed that the decolorization efficiency could be up to 100% with a flow rate of 6.93 mL/min when the PMR was applied in the treatment of a 30 mg/L RhB solution and the concentration of C₃N₄ was 1 g/L. pH played an important role in the decolorization performance of the PMR. Alkalinity was not conducive to the decolorization of RhB in the PMR, which was mainly due to the property that RhB was difficult to dissolve in an alkaline solution. Membrane fouling was mainly caused by a C₃N₄ photocatalyst, while the effect of RhB on membrane fouling was negligible. Membrane fouling could be retarded when the PMR was applied for RhB treatment under visible-light irradiation, which was because of photoinduced hydrophilicity of C₃N₄. The membrane flux could be restored to its initial values after simple ultrasonic cleaning and backwashing. This was due to the large difference between the pore size of Ti foam and the particle size of C₃N₄ and the super hydrophilicity of Ti foam and C₃N₄.