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

Comparison of advanced oxidation processes for the removal of trimethoprim and 5-fluorouracil

Two pharmaceuticals, trimethoprim (TRIM), an antibiotic, and 5-fluorouracil (5-FU), a widely used cytostatic, were applied as target substances to compare the efficiency of various AOPs, such as UV (254 nm), UV/VUV (254/185 nm) photolysis, ozonation, and O3/UV process. Opposite that, there is no significant difference between the molar absorbance of target substances; TRIM transformed very slowly, while 5-FU degradation was fast in 254 nm radiated solutions. The low-intensity 185 nm VUV photons highly increased the transformation and mineralization rate of both components. Ozonation was highly effective for eliminating both compounds. However, the mineralization was limited due to the formation products being resistant to ozone. The O3/UV process primarily increased the mineralization rate, but no significant change in the transformation rates was observed. Comparing the individual methods in terms of energy consumption, the O3, and O3/UV combination was the most effective for both compounds. The effect of biologically treated wastewater as a real matrix significantly reduced the transformation rate in the case of UV/VUV photolysis, while the matrix effect was moderated for O3/UV and negligible or even positive for ozonation

Investigation of the transformation of 5-fluorouracil cytostatics by UV and VUV photolysis

In this work, UV (254 nm), UV/VUV185 nm, and VUV172 nm photolysis of 5-fluorouracil (5- FLU), a cytostatic drug were investigated. For the water treatments three type of lightsources were applied: a low-pressure mercury vapour lamps emitting only 254 nm UV light, an other low-pressure mercury vapour lamps emitting both 254 nm UV and 185 nm VUV light, and a Xe excimer light source emitting 172 nm VUV photons. In parallel, with the transformation of 5-FLU, H2O2 formation was detected and measured. During UV/VUV185 nm photolysis, the formation of H2O2 follows a maximum curve, while in the case of UV photolysis, it shows a saturation curve. Its concentration reached higher value in the case of UV/VUV185 nm than in UV radiation. To enhance the efficiency of the reactors, we used air, O2 and N2 gases and assessed their effect to the photolysis of 5-FLU to see wich parameters are the most suitable for transforming it

Effect of inorganic ions on the vacuum-uv photolysis of water

Vacuum-ultraviolet (VUV) photolysis is based on high-energy radiation ( < 200 nm) where photons are absorbed by water and produce highly reactive species; primarily HO• and H• , and in smaller quantities eaq . VUV photolysis, due to the radicals formed, can efficiently transform and mineralize organic contaminants without any other additives. In this work, the effect of different inorganic ions (Cl– , NO3 ,HCO3 ), present in large amounts in wastewater, was investigated in the case of two different types of VUV light sources. The conventionally used low-pressure mercury-vapor lamp emits both 254 nm UV and 185 nm VUV photons and is widely used in water treatment for disinfection (254 nm) and producing high purity water (254/185 nm). The other applied light source was the Xe excimer lamp, used mainly in the laboratory scale, emits quasi-monochromatic 172 nm VUV light. The effect of inorganic ions during VUV photolysis depends on the radical scavenging capacity, molar absorbance of ions, and the properties of the radicals and radical ions formed from them by VUV or UV photolysis (for UV/VUV185nm), which is well reflected by the results presented

Investigation of UV/S2O8 2- and UV/VUV/ S2O8 2- processes on the degradation of trimethoprim

Several environmental and public health problems are caused by toxic pharmaceuticals with biological activity released into the environment. Conventional biological water treatment methods are generally not effective enough to completely remove pharmaceuticals, especially antibiotics from waters, so advanced oxidation processes should be used as a complementary method. In this study, the removal efficiency of trimethoprim (TRIM) was investigated using UV (254 nm), UV/VUV (254/185 nm) photolysis, and UV/S2O8 2– and UV/VUV/S2O8 2– treatments. Opposite to the relatively high molar absorbance of TRIM at 254 nm, the simple UV photolysis was ineffective for its elimination. Its removal and mineralization were significant in the case of UV/VUV photolysis due to the •OH formation from water via absorption of 185 nm VUV light. The addition of S2O8 2– highly increased the transformation and mineralization rate in both cases due to the formation of SO4 . At the highest concentration of S2O8 2– , both UV and UV/VUV185nm photolysis removed the total TOC content within 45 minutes