The UV-C radiation mechanism to form HO2• radicals from water

Abstract

The formation of chemically active particles in distilled water via continuous and pulsed light radiation was investigated. The source of the continuous radiation was a DKB-9 UV mercury low pressure lamp (λ = 253.7 nm). Upon UV lamp irradiation of water, hydrogen peroxide was formed in a yield of (1 ± 0.2) 10-7 mol (L s)-1. The pulsed radiation source was the plasma of a spark electric discharge in air with a continuous radiation spectrum and a weak maximum at λ = 220 nm. The radiation affected the water through quartz glass. In this case, nitrous and nitric acids formed in the water, but no accumulation of hydrogen peroxide was detected. The formation of the active products can be explained by the interaction of exited water molecules that formed due to the radiation. The energy threshold for the formation of hydrogen peroxide corresponds to a radiation wavelength of less than 1220 nm. To directly identify HO2• radicals, we studied redox reactions in solutions containing Fe2+, Fe3+ and I- ions at pH values from 0.8 to 8.1. The quantum yield of HO2• radicals in an acidic medium under the action of the mercury lamp radiation was 0.015 ± 0.005.