Etude de la degradation des trihalo‐methanes en milieu aqueux dilue par irradiation UV ‐ determination du rendement quantique de photolyse a 253,7 nm1

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Abstract
In this study, the degradation of trihalomethanes (THM) by UV irradiation at 253.7 nm was investigated. Experiments were carried out with dilute aqueous solutions of CHCl3, CHCl2Br, CHBr2Cl and CHBr3 (< I0–6 mol 1‐1) at 20°C and pH = 7.5 and with photochemical reactors equipped with a low‐pressure mercury vapour lamp. Under our experimental conditions (irradiation time ≤ 30 minutes), the results showed that only the brominated THMs were photolysed. The quantum yield values for the photolysis of the three brominated THMS which could be determined from the kinetic results were found to be equal to 0.43 ± 0.01 at 253.7 nm and at 20°C. Moreover, ionic chromatography analysis revealed that organic halogen present in CHCl2 Br, CHBr2 Cl and CHBr3 was completely converted into chloride and bromide ions during irradiation.