Photocatalytic nanocomposite membranes for high-efficiency degradation of tetracycline under visible light: An imitated core-shell Au-TiO2-based design

Abstract

Herein, Au-TiO2 nanocomposite photocatalysts were initially constructed through a three-step-synthesis strategy including the sodium citrate reduction method, sol-gel method and high-temperature hydrothermal method. After that, Au-TiO2/PVDF photocatalytic nanocomposite membranes with visible light response were synthesized by a phase conversion process, thereinto, the Au-TiO2 nanocomposite and PVDF powder were mixed into casting solutions by physical blending. Various characterization methods, such as SEM, TEM, FTIR, XRD, XPS, WCA and UV-vis DRS, etc., were used to systematically characterize the micromorphology, structural composition, wettability and optical properties of different samples. The UV-vis DRS results showed that the as-prepared nano-Au doping structure effectively enhanced the utilization factor of visible light in the process of photocatalytic degradation. The antifouling results of BSA adsorption experiments showed that 0.3-Au-TiO2/PVDF composite membranes possessed good antifouling performance. By analyzing the regeneration stability experiments, it could be found that the 0.3-Au-TiO2/PVDF composite membranes also exhibited excellent regeneration stability and easy separation and recovery features. The photocatalytic degradation of different membranes under visible light was investigated with tetracycline. The results showed that the photocatalytic degradation rate of 0.3-Au-TiO2/PVDF nanocomposite membranes reached 75% within 120 min. Moreover, the first-order kinetic linear fitting showed that the k value of 0.3-Au-TiO2/PVDF composite membranes was 0.01212 min−1, which was 2.7 times and 2.0 times higher than that of 0.1-Au-TiO2/PVDF and 0.5-Au-TiO2/PVDF composite membranes. That is to say, photocatalytic activity of 0.3-Au-TiO2/PVDF composite membranes were obviously improved.