HAZARDOUS WASTE & HAZARDOUS MATERIALS Volume 10, Number 2, 1993 Mary Ann Liebert, Inc., Publishers Short Wavelength Ultraviolet Photolysis of Aqueous Carbon Tetrachloride GREGORY A. LORAINE Department of Environmental Science & Engineering University of North Carolina Chapel Hill, NC 27514 ABSTRACT A dielectric barrier discharge xenon-xenon excimer lamp, which emits with a maximum peak at 172 nm, was used to photolyze carbon tetrachloride (CC14) in air and in water. In air the primary removal mechanism for CC14 was found to be oxidation by atomic oxygen 0(1D) . The 0(1D) radicals were formed by photolysis of 02. Direct photolysis of CC14 and reaction with OH-, from the photodissociation of H20, were found to play minor roles. In aqueous phase photolysis, direct photolysis of CC14 was minimal and reactions with OH' or H' from the photolysis of H20 were found to dominate the removal rate. The energy costs of Vacuum Ultraviolet (VUV) photolysis as a treatment method are estimated for CC14 and chloroform (CHC13) . INTRODUCTION At 68% of the hazardous waste sites with contaminated groundwater in the US, the pump and treat method of groundwater remediation is used [1] . If the groundwater is contaminated with volatile organics, air stripping with or without offgas scrubbing by granular activated carbon is commonly applied. Vacuum Ultraviolet (VUV) photolysis may provide a treatment option for certain organic compounds. Carbon tetrachloride, chloroform, trichlorotrifluoroethane and other halogenated organics are major groundwater contaminants [2] which absorb strongly in the VUV range. Air streams from stripping of water contaminated with these compounds can be treated with UV to degrade these compounds [3][4][5][6]. Because of their ubiquity in the environment and the strong data base available for these compounds from the study of halocarbon photodegradation in the stratosphere, the photolysis of carbon tetrachloride (CCL4) , chloroform (CHC13) , and 1,1,2- trichlorotrifluoroethane (C12FC2F2C1) was investigated. A number of different types of UV lamps have been used for wastewater treatment. The most commonly used sources for UV light are low pressure mercury arc lamps, high pressure mercury arc lamps and xenon flash lamps [7]. The low pressure mercury arc lamp emits a UV spectrum consisting of a few discrete lines. Most of the UV (>90%) 185