PHOTOINDUCED OXIDATIVE REACTIONS OF DIOXIN AND ITS CHLORINATED DERIVATIVE ON LAPONITE SURFACES

Photochemical reactions of dioxin and its chlorinated derivative on a sodium laponite surface were investigated. Photoirradition of DBO/lapo nite(Ta = 20-degrees-C) initiates chemical degradation of DBO, which i s confirmed by diffuse reflectance spectral studies. Photoirradiation on DBO/laponite (Ta = 20-degrees-C) at -196-degrees-C generates DBO.+; on warming DBO.+ recombines with electrons or electron adducts and ch emiluminescence is observed. Photoirradiation of DBO/laponite (Ta = 32 5-degrees-C) at room temperature produces stable DBO.+; the reaction o f DBO.+ with water and pyridine can be observed in detail. Time-resolv ed diffuse reflectance spectral studies give information on the primar y processes on the surface. End product analysis by HPLC indicates tha t the photoproducts of DBO degradation on laponite are the same at all activation temperatures for the solids. This supports the premise tha t DBO degradation is a radical process in nature, i.e., radical cation s are initially formed through one-electron oxidation, with subsequent reaction of ions with water or bonded hydroxyl groups on the surface. Reaction of DBO.+ with pyridine is shown to be controlled by pyridine diffusion into the inner layer space. Reaction mechanisms of DBO.+ wi th water and pyridine are proposed.