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30 Physical and Thermal Technologies <br /> r, <br /> The rate of decomposition was measured as .millseconds, with intermediate <br /> ozonides with a lifetime <2ms, as shown by stopped-flow conductometry. <br /> Since a total HVOC content of.1000µg/L in a flow of 100 gallons per <br /> minute contains only .32 mol/hr, the capacity to effectily reduce HVOC content to <br /> drinking water levels is considerable at a low energy usage. <br /> The mechanism of ozone attack (Figure 1) suggested by Criegee involves <br /> attacking the central double bond. Ozone first forms a 7r complex that collapses <br /> into a zwitterionic a complex. This primary zwitterion closes to the primary <br /> ozonide. The primary ozonide is an unstable trioxide. The primary ozonide <br /> cleaves an 0-0 bond heterolytically. Then'the secondary zwitterion decomposes <br /> into a carbonyl compound and the tertiary zwitterion. In the presence of water, <br /> the compounds decompose to CO, and dilute HCl (Masten, 1986). <br /> 0 <br /> /O—O8 \ <br /> H CI O O O <br /> 03 1 CI 0+ I <br /> C= C\ H—iCI—{ H—"-C—i—CI <br /> I <br /> CI C1 CI Cl C! <br /> r <br /> OH <br /> O ,0 <br /> H—C + HCI rz CI—C—O—OH + C1 C1 <br /> O—OH I HCl <br /> H <br /> +H2O <br /> CO2 + H2O CO2 + 2HC1 <br /> FIGURE 1. Mechanism of attack of TCE by Criegee oxidation (Dowideit <br /> and von Sonntag, 1998; Masten, 1986). <br /> Recent laboratory testing at the Max Planck Institute of Aquatic Chemistry <br /> has confirmed that the Criegee oxidation pathway dominates over competing <br /> mechanisms in aqueous solution (Dowideit and von Sonntag, 1998). Stopped- <br /> flow reactions in aqueous solution showed the olefins (ethene, trichloroethene, <br /> cis-1,2 dichloroethene, trans-1,1 dichloroethene, and vinyl chloride) nearly <br /> exclusively follow the Criegee mechanism and cleave into a carbonyl compound <br /> and a hydroxyhydroperoxide, which in the case of a chlorine substituent rapidly <br /> loses HCl. In the cases of chlorinated olefins, no HCl-releasing intermediate with <br /> a lifetime longer than 1 millisecond was detected. <br /> No organic by-products were found. No newly-formed volatile <br /> organochlorine compounds have been observed in laboratory reactions <br /> (Kusakabe, et al., 1991; Dowideit and von Sonntag, 1998). Field analyses have <br />