Kinetics of the reaction between ozone and p-hydroxybenzoic acid in a semibatch reactor

The kinetic regime in the ozone and p-hydroxybenzoic acid reaction system a t pH 3 and 7 can be considered a slow reaction, whereas at pH 10 the rapid reaction mainly occurred in the liquid film and developed in the fast absor ption kinetic regime. On the basis of the discussion of kinetic regime and the experimental observations, the kinetic expressions for the p-hydroxyben zoic acid, glyoxal, and dissolved ozone concentration can be developed for both pH 3 and 7 and were verified with the experimental data. The reaction rate constants were also calculated. The agreement between the experimental observations and the model predictions was reasonably good. However, at pH 7, a positive deviation in the decaying glyoxal profile and the overestima tion for the p-hydroxybenzoic acid and dissolved ozone concentration were f ound. The reasons for the discrepancy between the predicted and measured co ncentrations were also discussed.