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This paper summarizes a portion of a study to identify and evaluate stable reaction intermediates from UV-mediated oxidation processes as they would be applied to typical groundwater contaminants. The complete study investigated three photodegradation processes for their applicability to the removal of BTEX from groundwater. Each involved UV irradiation but in combination with hydrogen peroxide, ozone, or titanium dioxide. Described herein are some typical results of the UV/H2O2 oxidation of toluene using a 20 L reactor equipped with 6 x 75W low pressure mercury lamps. Toluene and H2O2 solutions were prepared in deionized water at pH 5 to 6 to approximate full-scale treatment conditions. Experiments involved the use of real groundwaters, obtained from local contamination sites, and synthetic waters (pure water fortified with individual or mixtures of BTEX compounds). Results of the experiments using synthetic waters facilitated identification of all possible intermediates. A mass balance approach was used to determine the extent of treatment under various conditions, and will ultimately be used to estimate the final toxicity of the treated water. When toluene had been degraded to below regulated limits (between approximately 2 and 5 minutes irradiation time), there were significant quantities of phenols and organic acids still present in solution. Some of the phenols and organic acids that were identified include: formic acid, acetic acid, pyruvic acid, glycolic acid, oxalic acid, o-, m- and p-cresol, 3- and 4-methylcatechol and methylhydroquinone. The organic acids in particular resisted oxidation long after toluene was essentially below its regulatory limit of 1 mg/L. Includes 27 references, table, figures.

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Edition: Vol. - No. Published: 01/01/1999File Size: 1 file , 300 KB