A comparative study for the synergistic effect of ozone on the gamma-irradiated and photocatalytic reaction of 4-chlorobenzaldehyde

The synergistic effect of ozone on both, the TiO2-mediated photocatalytic a nd gamma-rays induced degradation of 1 x 10(-3) mol dm(-3) 4-chlorobenzalde hyde (4-ClBzAl) was studied as a function of absorbed energy. The formation of formaldehyde (HCHO), H+ and Cl- ions as well as of carboxylic acid was used to follow the degradation processes. The highest efficiency for the su bstrate degradation was achieved by the simultaneous action of ozone and ph otocatalysis on 4-ClBzAl in aqueous solution. On the other hand, the degrad ation yield of the substrate by ozonation is three times higher compared to the degradation yield observed by gamma-rays in the presence of ozone. Thi s yield is however, higher than that obtained by gamma-radiolysis in the pr esence of air. Benzoic, 4-chlorobenzoic, fumaric, glyoxylic, mucconic, and oxalic acids were formed as common final reaction products in each degradat ion process. (C) 2000 Published by Elsevier Science S.A.