MECHANISMS AND KINETICS OF OZONE AND HYDROXYL RADICAL REACTIONS WITH MODEL ALIPHATIC AND OLEFINIC COMPOUNDS (WATER, AQUEOUS PHASE, HYDROGEN PEROXIDE, ULTRAVIOLET RADIATION)

In this study the rate and efficiency of ozonation and related processes for the oxidation of volatile chlorinated organics chemicals were determined. Trichloroethylene (TCE) and 1,1-dichloro-1-propene (DCP) were used as model olefins, while 1,2-dichloroethane (DCE) were employed as model aliphatics. The rate of decomposition of DCE and TCE by ozone and ozone/UV was determined. The direct reactions involving ozone and the indirect reactions involving secondary oxidants (formed from decomposed ozone) were studied using ozone/OH('-), ozone/UV(254 nm), ozone/H(,2)O(,2), and H(,2)O(,2)/UV(254 nm).; Rapid oxidation of DC by the direct reaction with ozone predominated at low pH. A higher pH, where ozone decomposes more rapidly to form OH radicals, TCE and PeCl were oxidized more efficiently. However, increasing the pH resulted in a decrease in the efficiency of DCP oxidation. DCE was only slowly oxidized even at high pH.; Ozone/H(,2)O(,2) at high pH and ozone/UV resulted in the production of OH radicals and hence an increase in the efficiency of oxidation of TCE, DCE and PeCl by ozone. Again a decrease in the efficency of DCP oxidation was observed.; The H(,2)O(,2)/UV(254 mn) treatment oxidized all 4 compounds very slowly. Half-lives of greater than 30 minutes were observed for DCP, TCE, and PeCl when solutions containing 52(mu)M H(,2)O(,2) were irradiated. DCE had a half-life of 110 minutes.; The stoichiometric values ((DELTA)Cl('-)/(DELTA)DCP) were determined in unbuffered solutions. These ratios were found to be independent of the oxidation pathway suggesting that the extent to which the dechlorination reaction occurs did not depend upon the method of oxidation.; In natural waters, DCP was found to degrade after an initial amount of ozone was consumed. Results from solutions of DCP prepared in distilled water were comparable to those prepared in Swiss waters.; The results described are important for the use of ozonation and related processes in water treatment. Contrary to previous expectations, the oxidation of aliphatics by OH radicals is inefficient and would be a costly removal method. Ozone treatment would be efficient only for the oxidation of a single or a mixture of a few olefins.