Novel vacuum-UV-(VUV) and UV-excimer flow-through photoreactors for waste water treatment and for wavelength-selective photochemistry

摘要

In treatment of waste waters, the efficiency of the vacuum-UV (VUV) oxidation of organic water contaminants in excimer flow-through photoreactors at gamma — 172 nm without addition of supplementary oxidizing agents is demonstrated. The consecutive double irradiation of pure air-saturated water at gamma = 172 nm and A = 222 nm leads to the intrinsic formation of hydrogen peroxide and of ozone by 172-nm-photolysis, which is followed by their UV-photodegradationatl = 222 nm. Therefore, VUV/UV-excimer technology combines the principles of the conventional H_2O_2-UV and O_3-UV processes within an efficient photoreactor. The bleaching of rhodamine B and of naphthol AS dyes is accompanied by TOC-elimination via photomineralization, Chloro-hydrocarbons (VOC) dissolved in water are largely photomineralized by YUV/UV-irradiation. The superiority of this novel technique over the conventional UV-oxidation is evaluated by the TOC-reduction of formaldehyde-containing industrial waste water. In molecular photochemistry, the production of previtamin D_3 was optimized by wavelength-selective double irradiation of 7-dehydrocholesterol with UV-excimer lamps at gamma_1 = 259 nm and at gamma_2 = 342 nm. In conclusion, excimer technology has enormous impact on the development of advanced oxidation processes for water treatment and on industrial molecular photochemistry.