Degradation of propoxur in water using 2,4,6-triphenylpyrylium-Zeolite Y as photocatalyst - Product study and laser flash photolysis

Direct UV photolysis of aerated aqueous solutions of propoxur leads to an a lmost complete disappearance of the starting material and the formation of the photo-Fries rearrangement products. The degree of mineralization estima ted by the difference between the initial and the combined final moles is, however, small. Laser flash photolysis techniques established that the key intermediate in the direct aqueous photolysis is 2-isopropoxyphenoxyl radic al. Photocatalyzed mineralizations using 2,4,6-triphenylpyrylium ion encaps ulated inside the supercages of Zeolite Y under irradiation conditions in w hich propoxur is not directly altered, produces a degree of mineralization comparable to that achieved using TiO2. Formation of minor amounts of 2-iso propoxyphenol, 1,2-dihydroxybenzene and isopropoxy-dihydroxybenzene was obs erved in photocatalyzed degradations. Laser flash photolysis established th at a mechanism involving an initial electron transfer between excited TP+ a nd propoxur is possible. (C) 2000 Elsevier Science B.V. All rights reserved .