Ozonation and photodegradation kinetics of pollutant acids in wastewaters

The kinetics of the degradation of four phenolic acids by ozonation and polychromatic UV radiation were investigated. The acids: p-hydroxyphenylacetic, homoprotocatechuic (3,4-dihydroxyphenylacetic acid), gentisic (2,5-dihydroxybenzoic acid) and 2,3-dihydroxybenzoic, have been selected because of they constitute major pollutants present in some agro-industrial wastewaters. The p-hydroxyphenylacetic acid was initially ozonated and UV irradiated alone. Its kinetic constants and reaction orders in the ozonation process were deduced by using a model based in the film theory which takes into account the mass transfer with the chemical reaction. The quantum yields in the photodegradation process were evaluated from a simple reaction mechanism with the help of an emission model to determine the radiation flow rate absorbed. Later, in the simultaneous ozonation and UV photodegradation of the mixtures of the four acids, competitive kinetic methods were developed to determine the individual rate constants between ozone and each acid in the ozonation process, and the individual quantum yields for every acid in the photodegradation process.