RATE CONSTANTS FOR REACTION OF HYDROXYL RADICALS WITH SEVERAL DRINKING-WATER CONTAMINANTS

Rate constants for reactions of the hydroxyl radical with 25 potential organic drinking water contaminants, including solvents, haloalkanes, esters, aromatics, and pesticides for example, aldicarb, atrazine, 1,2-dibromo-3-chloropropane, endrin, glyphosate, haloforms, lindane, picloram, etc.), have been measured in water using relative rate methods. A variety of HO.-generating techniques were used, including ozone decomposition, Fenton's reaction, and a convenient new method employing photo-Fenton's s chemistry. In addition, rate constants for 19 other compounds were estimated using structure-activity relationships. The present results are consistent with previous work that demonstrated that HO. is a relatively nonselective radical toward C-H bonds, but is least reactive with aliphatic polyhalogenated compounds. Olefins and aromatics all react at nearly diffusion-controlled rates in water, unlike the case in the gas phase where these compounds react more selectively. The rate constants are useful in estimating HO.-induced oxidation rates of organic compounds in a variety of aqueous systems including atmospheric water droplets, sunlit surface waters, supercritical and near-critical water reactors, and room temperature radical oxidation processes.