Enhancement of gaseous iodine emission by aqueous ferrous ions during the heterogeneous reaction of gaseous ozone with aqueous iodide

摘要

Gaseous I_2 formation from the heterogeneous reaction of gaseous ozone with aqueous iodide in the presence of aqueous ferrous ion (Fe ~(2+)) was investigated by electron impact ionization mass spectrometry. Emission of gaseous I_2 increased as a function of the aqueous FeCl_2 concentration, and the maximum I_2 formation with Fe~(2+) was about 10 times more than without Fe~(2+). This enhancement can be explained by the OH~-scavenging by Fe~(3+) formed from Fe~(2+) ozonation to produce colloidal Fe(OH)_3. This mechanism was confirmed by measurements of aqueous phase products using a UV-vis spectrometer and an electrospray ionization mass spectrometer. We infer that such a pH-buffering effect may play the key role in general halogen activations.