Etude comparative de la degradation de quelques molecules aromatiques simples en solution aqueuse par photolyse UV et par photolyse du peroxyde d'hydrogene

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Abstract
The photooxidation of some chloroaromatic and nitroaromatic compounds (chlorobenzenes, nitrobenzenes) in water by UV radiation and UV radiation in the presence of hydrogen peroxide was studied. Diluted aqueous solutions of organic compounds (10‐4 mol l‐1) were irradiated at pH 7.5 and at 16°C in a closed reactor equiped with a low pressure mercury vapor lamp. The results showed that chlorobenzenes are more rapidly photodecomposed than nitroaromatic compounds and the rates of degradation were greatly increased by addition of hydrogen peroxide (10‐3 mol l‐1). The degradation pathway of aromatic compounds in the presence of hydrogen peroxide and UV light leads to the production of hydroxylated derivatives (phenolic compounds) as intermediates and chloride, nitrate and carbon dioxide as oxidation end‐products. The effects of benzene ring substituents (Cl, NO2, OH) on the oxidation rate of aromatic compounds by H2O2/UV and the influence of the UV absorbance of the irradiated solutions at 253.7 nm on the rate of photolysis of H2O2 are also discussed in this paper.