A novel approach to interpret quasi-collimated beam results to support design and scale-up of vacuum UV based AOPs

Assessing the Chemical-Free Oxidation of Trace Organic Chemicals by VUV/UV as an Alternative to Conventional UV/H2O2

“…Chloride and nitrate can compete with H 2 O for VUV 185 nm absorbance and then inhibit the oxidation performance. For example, the chloride at 9.3 mg L –1 accounted for more than 55% of the total VUV 185 nm absorbance by the solution . However, chloride and nitrate are also activated by VUV 185 nm to form reactive chloride/nitrogen species, which can contribute to the oxidation performance.…”

“…16,17 However, one major challenge reducing the efficiency of UV-AOPs is the low molar absorption coefficient of most chemical reagents (e.g., H 2 O 2 and persulfate) at typical UV wavelengths. This limits the efficiency of the generation of reactive species, 18 and Kovoor George et al 19 concluded that the useful absorbed UV that can generate reactive species limits the oxidation performance, design, and operation of UV-AOPs. Especially in real water, water matrices can compete with radical sensitizers and absorb around 60− 95% of the UV photons.…”

“…29 On the one hand, VUV can be absorbed by many water constituents, which reduces the efficiency of radical generation during the VUV/UV treatment of real water matrices. 40,41 On the other hand, VUV photolysis of water matrix components, such as chloride and nitrate, can result in the generation of additional reactive species, 19 which may (partly) compensate for the inhibition of VUV absorption by the water matrix. Moreover, due to high absorption by water and constituents, VUV 185 nm decays rapidly along the light path length in water (L p ).…”

“…To meet the above challenges, emerging UV light lamps are extensively investigated for UV-AOPs. − One option was to adjust the emission wavelength of UV lamps to match the absorbance spectra of chemical reagents. For example, the UV lamps emitting at 280–300 nm were tested for chlorine photolysis, and medium-pressure mercury lamps (200–240 and 300–325 nm) or far-UV (222 nm) were studied to activate NO 3 – . , Another approach is the application of vacuum-UV (VUV, <200 nm) that can be absorbed by H 2 O to generate • OH in a chemical-free oxidation process. , In comparison to conventional UV/H 2 O 2 oxidation, VUV can be fully absorbed by H 2 O and significantly reduces the H 2 O 2 requirement. , One of 185 nm (VUV) is emitted by LPUV lamps designed with high-purity quartz as the wall. , These modified LPUV lamps emit dual wavelengths at 185 and 254 nm (VUV/UV), and are already frequently applied for the production of ultrapure water as well as the rapid measurement of total organic carbon …”

“…29,30 In comparison to conventional UV/H 2 O 2 oxidation, VUV can be fully absorbed by H 2 O and significantly reduces the H 2 O 2 requirement. 19,31 One of 185 nm (VUV) is emitted by LPUV lamps designed with high-purity quartz as the wall. 32,33 These modified LPUV lamps emit dual wavelengths at 185 and 254 nm (VUV/UV), and are already frequently applied for the production of ultrapure water 34 as well as the rapid measurement of total organic carbon.…”