Aqueous h 2o 2 production from o 3 in glass impingers

Abstract

The aqueous generation of H 2O 2 from bubbling ozonized air through water in glass impingers is investigated. O 3 loss is monitored throughout each experiment. Aqueous H 2O 2 is measured at the end of each experiment. The mole quantities of O 3 lost (ΔO 3) and H 2O 2 formed (ΔH 2O 2) are calculated. There is a stoichiometric relationship between ΔO 3 and ΔH 2O 2 which is independent of bubbling time, solution acidity and initial O 3 concentration but is dependent upon the liquid water content of each impinger. For 10 ml of water in each impinger, the AO 3 to ΔH 2O 2 mole ratio is between 2:1 and 3:1 and for 20 ml is between 1:1 and 1:2. Increasing the solution acidity increases the rates of O 3 loss and H 2O 2 generation. This result contradicts mechanisms in which a O 3 + HO − reaction is used to initiate radical formation and H 2O 2 production. These results are interpreted through a combination of glass surface chemistry and bulk aqueous chemistry. The O 3-H 2O 2 impinger mechanisms involve O 3 adsorption and/or reaction on the impinger surface and its surface products subsequent reaction with water or trace impurities in the water. Experiments using tetrafluorethylene (TFE) impingers in place of glass impingers are conducted to examine the role of surface chemistry. The TFE impingers are found to substantially increase ΔO 3 and ΔH 2O 2 without changing their mole ratio. This is attributed to an enhanced O 3-H 2O surface chemistry or O 3 reaction with unsaturated Teflon linkages or impurities in the Teflon from machining.