~ Pergamon 0045-6535(95)00151-4 Chemosphere, Vol. 31, No. 3, pp. 2873-2885, 1995 Copyright © 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0045-6535/95 $9.50+0.00 APPLICATION OF PHOTOCHEMICAL REACTOR MODELS TO UV I~ADIATION OF TRICHLOROETHYLENE IN WATER F.J.Beitrln', M. Gonddez, F.J. Rivas and J. Jaramiilo Departamento de Ingenieria Quimica y Energrtica. Universidad de Extremadura, 06071 Badajoz, Spain (Received in Germany 2 March 1995; accepted 28 April 1995) ABSTRACT The UV irradiation of trichloroethylene in water was studied. Degradation rates depend on the initial TCE concentration and nature of the water. Volatilization contribute to the disappearance rate of TCE between 5% and 12% when initial TCE concentration are 25 and 100 lagl 1, respectively. In surface waters containing up to 17 mgl~ of TOC conversion of TCE is only 54% compared to 80% reached in ultrapure water (with less than 20 tagt ~ of TOC) in 90 min. Degradation rates of TCE decrease with the increase of TOC content of the water. Quantum yields of TCE at 254 nm have been determined from different photochemical kinetic models. Differences between models are likely due to effects (reflection-refraction phenomena) not accounted for in the kinetic equations. From the PSSE model TCE quantum yield has been found to be 1.712a:0.041 mol.photon -~. ~TRODUCTION Hazardous chemicals such as solvents, pesticides, polynuclear aromatic hydrocarbons, constitute a real threat of surface or groundwater (1, 2). It is also known that a large variety of these priority pollutants can be effectively removed through the use of oxidation methods involving the action of UV radiation and hydroxyl radicals (3, 4). Nowadays, attention is paid to development of chemical or photochemical kinetic models to predict the level of pollutant degradation with these oxidation techniques (5). As far as processes involving UV radiation are concerned these kinetic models require the knowledge of some parameters like quantum yields that can be calculated with the use of photochemical kinetic equations. In this paper we present results of the UV irradiation of a priority pollutant, trichloroethylene TCE, that was taken as model compound to determine its quantum yield. TCE is an unsaturated organochlorine compound used for vapor degreasing of metals, paint and ink formulation (6). TCE has been found in different soil, air and water environments. TCE has been detected and its concentration quantified in surface, drinking and even ground waters (7, 8). Some previous papers have already treated the oxidation of TCE (9 - 11) but they do not focus on the UV photochemical kinetics, or if so, they do not deal with quantum yield determination. Due to the importance of competition from natural substances (12), the UV irradiation of TCE in two surface waters was also measured. 2873