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 kinctic 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.
On etudie les cinetiques de la degradation de quatre acides phenoliques par ozonisation et radiation polychromatique aux UV. On a choisi les acides p-hydroxyphenylacetique, homoprotocatechnique (acide 3,4-dihydroxyphenylacetique), gentisique (acide 2,5-dihydroxybenzoique) et 2,3-dihydroxybenzoique parce qu'ils constituent les principaux polluants presents dans certaines eaux usees agro-industrielles. L'acide p-hydroxyphenylacetique a ete initialement ozonise et irradiee aux UV seul. Ses constantes cinetiques et ses ordres de reaction dans le procede d'ozonisation ont ete deduites au moyen d'un modele s'appuyant sur la theorie du film qui tient compte du transfert de matiere avec la reaction chimique. Les rendements quantiques du procede de photodegradation ont ete evalues a partir d'un mecanisme de reaction simple allie a un modele d'emission afin de determiner le debit de radiation absorbe. Par la suite, dans I'ozonisation et la photodegradation aux UV simultanees des melanges des quatre acides, on a mis au point des methodes cinetiques concurrentes pour determiner les constantes de vitesse individuelles entre I'ozone et chaque acide dans le procede d'ozonisation ainsi que les rendements quantiques de chacun des acides dans le procede de photodegradation.