Effect of irradiation wavelength on the heterogeneous photocatalytic removal of organic pollutants using TiO2 and ZnO

The efficiency of TiO2 and ZnO was compared during the photocatalytic removal of neonicotinoid pesticides (imidacloprid and thiacloprid) and sulfonamide antibiotics (sulfamethazine and sulfamethoxypyridazine), causing severe environmental and health problems. The differences between LEDs emitting at 365 nm and 398 nm were compared, and removal efficiencies were tested in tap water and biologically treated wastewater matrices. The effect of the most abundant anions, Cland HCO3 on the removal efficiency and •OH formation was also compared. TiO2 was more sensitive to the matrices and the irradiation wavelength. •OH production was higher for TiO2, and 398 nm photons resulted in a higher contribution of •OH. Efficiencies were not reduced by matrix components for ZnO, which is mainly the result of increased •OH-production by Cl- . In the case of TiO2 and 365 nm photons, the formation of CO3 from HCO3 -was assumed. For TiO2, the significant inhibition of matrices could not be explained solely by the effect of anions

Application of high power UV LEDs in heterogeneous photocatalysis

In our work, we designed and built a photochemical reactor with High Power LED light sources, and then tested its operation by heterogeneous photocatalytic decomposition of coumarin. The UV-LEDs emitting at a wavelength of 367(±10) nm were built into a frame with air-cooling elements. A well-controlled electrical power source was used to control and regulate the light output of the LEDs. The photon flux was measured at different electric power inputs, and was found to be linearly dependent on electrical power. Coumarin was used to test the new photoreactor during heterogeneous photocatalysis using TiO2 and ZnO as photocatalysts. At low photon flux the UV-LEDs outperformed a fluorescent mercury-vapor lamp in terms of efficiency and power consumption, but their usage at high electric input is not favorable

Heterogeneous photocatalysis of sulfonamides using TiO2 and ZnO photocatalysts with mercury-vapor and led light sources

Sulfonamides are one of the most often used antibiotics worldwide. The spread of antibioticresistant bacteria and the serious health problems caused by them justify the importance of removing antibiotics and their metabolites from water. Heterogeneous photocatalysis is one of the promising methods for elimination of trace organic pollutants from water. This work aims at the investigation of heterogeneous photocatalytic removal of two sulfonamide antibiotics, sulfamethazine and sulfamethoxypyridazine. Commercially available TiO2 and ZnO were used as photocatalysts, and a mercury vapor lamp (300-400 nm) and UV-LEDs (398 nm) were used as light sources. The efficiency and cost-effectiveness of heterogeneous photocatalysis in the removal of sulfonamides were compared, using TiO2 and ZnO, in suspensions irradiated with mercury vapor lamp and LEDs. The mercury vapor lamp was found to be more effective due to the better utilization of UV light by the photocatalysts. The LED light source was also worse in terms of operating costs, and TiO2 with mercury vapor lamps was the most efficient at removing the total organic carbon content

BiOCl/BiOI composit photocatalysts - investigation of their efficiency using UV and visible led light sources

Due to its unique layered structure, bismuth oxyhalide (BiOX, where X=F, Cl, Br, I) has potential applications as a photocatalytic material in clean energy utilization and environmental purification. In this work, BiOI, BiOCl, and their composites with various BiOI:BiOCl molar ratios were synthesized and characterized for their heterogeneous photocatalytic applications. The methyl orange was used as a model pollutant and UV and visible LED light sources were applied. Adsorption measurements and photocatalytic tests proved that, the BiOI/BiOCl composite, which contains 80% BiOI and 20% BiOCl, showed the best activity. The composite catalyst showed good activity under visible light and was particularly better than pure BiOI and BiOCl under UV radiation. The transformation mechanism of methyl orange is initiated by direct charge transfer processes, via photosensitization