Highly-Efficient and Visible Light Photocatalytical Degradation of Organic Pollutants Using TiO2-Loaded on Low-Cost Biomass Husk

A composite composing of TiO₂ nanoparticles load on biomass rice husk (RH) is developed by directly growing TiO₂ nanoparticles on RH. The in-situ growth of the nanocrystals on RH is achieved by a low-cost and one-step homogeneous precipitation. Rapid hydrolysis proceeds at 90 °C by using ammonium fluotitanate and urea to facilitate the selective growth of TiO₂. The method provides an easy access to the TiO₂-RH composite with a strong interaction between TiO₂ nanoparticles and the underlying RH. The structure and composition of TiO₂-RH are characterized by using X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and UV-vis absorption spectroscopy. TiO₂ nanoparticles-RH exhibits a good photocatalytic degradation of methyl orange. The results show that 92% of methyl orange (20 mg L^-1) can be degraded within three hours in visible light. The catalytic activity of the composite is not reduced after 6 cycles, and it still reaches 81% after 6 cycles. The enhanced performance is ascribed to the suitable particle size the good dispersibility. It is expected that the high photocatalytical performance and the cost-effective composite presented here will inspire the development of other high-performance photocatalysts.

GO-TiO2 as a Highly Performant Photocatalyst Maximized by Proper Parameters Selection

The synthesis and characterization of novel graphene oxide coupled to TiO₂ (GO-TiO₂) was carried out in order to better understand the performance of this photocatalyst, when compared to well-known TiO₂ (P25) from Degussa. Thus, its physical-chemical characterization (FTIR, XRD, N₂ isotherms and electrochemical measurements) describes high porosity, suitable charge and high electron mobility, which enhance pollutant degradation. In addition, the importance of the reactor set up was highlighted, testing the effect of both the irradiated area and distance between lamp and bulb solution. Under optimal conditions, the model drug methylthioninium chloride (MC) was degraded and several parameters were assessed, such as the water matrix and the catalyst reutilization, a possibility given the addition of H₂O₂. The results in terms of energy consumption compete with those attained for the treatment of this model pollutant, opening a path for further research.

Effect of Biogenic Silica Behavior in the Incorporation of Mesoporous Anatase TiO2 for Excellent Photocatalytic Mineralization of Sodium Diclofenac

TiO2/SiO2 composites were synthesized via a simple sol gel method by surface reduction of Ti4+ ions to Ti3+ using titanium isopropoxide as a TiO2 precursor and rice husks (RHA) as a SiO2 source. The silica content and calcination temperature of the materials were evaluated. Thermal, crystallographic and physicochemical aspects suggest that biogenic silica (SiO2) can improve the thermal stability of the anatase phase of TiO2, when the SiO2 content reaches 20%. The N2 adsorption-desorption isotherms showed that the SiO2-modified samples have uniform pore diameters and a large specific surface area. The XPS analysis showed the surface reduction of Ti4+ ions to Ti3+ within the TiO2 network via oxygen vacancies after SiO2 introduction, which is beneficial for the photocatalytic reaction. Photocatalytic degradation of sodium diclofenac (SDFC) shows that TiO2/SiO2 composites have better activity compared to commercial P25. Mesoporous TiO2 composite modified with 20 wt% SiO2 showed better photocatalytic mineralization than P25 (83.7% after 2 h instead of 57.3% for P25). The excellent photocatalytic mineralization of the photocatalysts can be attributed to the high anatase crystallinity exhibited by XRD analysis, high specific surface area, surface hydroxyl groups, and the creation of oxygen vacancy, as well as the presence of Ti3+ ions.