On the oxidation of gaseous iodine at elevated temperatures

The aim in this study was to examine the oxidation of gaseous inorganic and organic iodine when exposed to gaseous ozone and UV (c-type) radiation. The experiments were conducted with EXSI-CONT (EXperimental Studies on Iodine chemistry - CONTainment) facility. Gaseous iodine was exposed to UV radiation with a radiation wavelength maximum at 185 nm, which is able to generate ozone (O3) from air efficiently. Additional ozone was produced with an ozone generator. The oxygen to nitrogen ratio and the humidity of the carrier gas was varied in the tests as well. The experiments were conducted at 50 °C, 90 °C and 120 °C. The residence time of the gas flow inside the facility was varied from 1.75 s to 7 s. The formation and growth of the iodine containing aerosol particles was characterised online with Scanning Mobility Particle Sizer (SMPS), Electrical Low Pressure Impactor (ELPI), Condensation Particle Counter (CPC) and Tapered Element Oscillating Microbalance (TEOM) devices. During the tests the speciation of gaseous reaction products was measured using Fourier Transform Infra-Red analyser (FTIR). After the tests, the concentration of gaseous and particulate iodine fractions was quantified with Inductively Coupled Plasma Mass Spectrometry (ICPMS). The size, morphology and elemental composition of particles was also analysed using Scanning Electron Microscopy coupled with Energy-Dispersive X-ray spectroscopy (SEM-EDX)