Kinetics of p-hydroxybenzoic acid photodecomposition and ozonation in a batch reactor

The decomposition of p-hydroxybenzoic acid, an important pollutant present in the wastewaters of the olive oil industry, has been carried out by a dir ect photolysis provided by a polychromatic UV radiation source, and by ozon e. In both processes, the conversions obtained as a function of the operati ng variables (temperature, pH and ozone partial pressure in the ozonation p rocess) are reported. In order to evaluate the radiation flow rate absorbed by the solutions in the photochemical process, the Line Source Spherical E mission Model is used. The application of this model to the experimental re sults provides the determination of the reaction quantum yields which value s ranged between 8.62 and 81.43 l/einstein. In the ozonation process, the f ilm theory allows to establish that the absorption process takes place in t he fast and pseudo-first-order regime and the reaction is overall second-or der, first-order with respect to both reactants, ozone and p-hydroxybenzoic acid. The rate constants are evaluated and vary between 0.18 X 10(5) and 2 9.9 x 10(5) l/mel s depending on the temperature and pH, (C) 2000 Elsevier Science B.V. All rights reserved.