# Recent Advances and Applications of Semiconductor Photocatalytic Technology
## 6 Application
### Wastewater Treatment
In the photolysis rhodamine B experiments, the prepared flexible TiO\({}_{2}\)/PVDF composites showed a higher photocatalytic efficiency than pure PVDF. In particular, the TiO\({}_{2}\)/PVDF(H10) composite treated for 10 h in the hydrothermal reaction showed the highest photocatalytic activity (as show in Figure 11A). As shown in Figure 11B, the TiO\({}_{2}\)/PVDF(H10) composite still maintains its high photocatalytic efficiency after five photocatalytic experiments. Figure 11: (**A**) Photodegradation profiles of rhodamine B over the samples: Rhodamine B without photocatalyst, PVDF and TiO\({}_{2}\)/PVDF composites hydrothermal treated for 4 h, 6 h, and 10 h. (**B**) The photocatalyst treated for 10 h was used for rhodamine B degradation, and the number of cycles was five times [167]. [PERSON] et al. [353] synthesized Ni-doped BiVO\({}_{4}\) photocatalysts using the microwave hydrothermal method. In the photocatalytic degradation experiments, the Ni-doped BiVO\({}_{4}\) photocatalyst showed better photocatalytic performance than pure BiVO\({}_{4}\). As shown in Figure 12, pure BiVO\({}_{4}\) has a strong absorption in the UV to 510 nm range, while the absorption edge of Ni-doped samples is significantly red-shifted as the Ni dopant concentration increases. In Figure 13, [PERSON] and coworkers evaluated the photocatalytic disinfection activity of BiVO\({}_{4}\) and Ni-doped BiVO\({}_{4}\) by inactivating _Escherichia coli_ in an aqueous buffer solution under different light sources. The results show that pure BiVO\({}_{4}\) and 1 wt% Ni-doped BiVO\({}_{4}\) require only 1 h to inactivate _E. coli_ to 100% under full spectrum sunlight illumination. However, after visible light irradiation for 5 h, the inactivation rate of pure BiVO\({}_{4}\) against _E. coli_ reaches 72%, while the 3 wt% and 1 wt% Ni-doped BiVO\({}_{4}\) against _E. coli_ inactivation rate of is 89% and 92%, respectively. Obviously, 1 wt% Ni-doped BiVO\({}_{4}\) shows higher efficiency, and as the doping amount of Ni increases the inactivation rate of _E. coli_ gradually decreases. [PERSON] et al. [354; 355] developed a simple two-step method to prepare three-dimensional ordered macroporous (3 DOM) gold-loaded TiO\({}_{2}\) photonic crystal photocatalysts. Based on this method, following the procedures shown in Figure 14A, i-TiO\({}_{2}\)-o and i-Au-TiO\({}_{2}\)-o photocatalysts were further generated. Both i-TiO\({}_{2}\)-o and i-Au-TiO\({}_{2}\)-o films prepared by this method exhibit a highly ordered interconnected porous structure, which is advantageous for the adsorption of target contaminants and utilization of solar energy. In the decomposition experiments of benzoic acid (BA), both i-TiO\({}_{2}\)-o and i-Au-TiO\({}_{2}\)-o showed higher decomposition rates than anatase TiO\({}_{2}\). As shown in Figure 14B, under ultraviolet irradiation, the decomposition rate of BA by i-Au-TiO\({}_{2}\)-o is five or more times the decomposition rate of BA by anatase-type TiO\({}_{2}\). Figure 12: UV-Vis diffuse reflectance spectra of BiVO\({}_{4}\) samples with different wt% of Ni ions. Inset is the Kubelka–Munk plot with the corresponding band gap energies [353]. Figure 13: Inactivation of _E. coli_ on: (**A**) Irradiation to full solar spectrum light; (**B**) visible light [353].