Cinétique de phototransformation de polluants organiques émergents en solution aqueuse diluée

Abstract

Les vitesses de phototransformation de quatre hormones (estradiol, éthinylestradiol, progestérone, testostérone) et de deux anti-inflammatoires non stéroïdiens (diclofénac et naproxen) ont été étudiées en milieu aqueux dilué. Les expériences de photolyse ont été réalisées sous irradiation monochromatique (254 nm) et sous irradiation polychromatique (λ > 280 nm). Les résultats expérimentaux ont montré que les rendements quantiques de photodécomposition sont faibles (entre 0,02 et 0,08) à l’exception du diclofénac (de l’ordre de 0,30). L’influence de la concentration en oxygène dissous sur les rendements quantiques de photolyse a aussi été examinée. À partir des résultats obtenus, les rendements d’élimination des composés étudiés dans les conditions de désinfection des eaux par irradiation UV à 254 nm ont été estimés.The photodecomposition of some emerging organic pollutants (4 hormones: estradiol, ethynylestradiol, progesterone, testosterone; and 2 nonsteroidal anti-inflammatory drugs: diclofenac and naproxen) has been investigated in dilute aqueous solution. The photolysis experiments were carried out under monochromatic irradiation (254 nm) and under polychromatic irradiation (λ > 280 nm). The calculated quantum yields of photodecomposition under monochromatic irradiations were low (between 0.02 and 0.08) except for diclofenac for which the value was about 0.30. The influence of oxygen concentration was also examined and the removal yields of these compounds under the conditions used for the UV-disinfection of drinking water at 254 nm were estimated

Photodegradation of naproxen and its photoproducts in aqueous solution at 254 nm: A kinetic investigation

“…This fact is in agreement with Meite's results (Meite et al, 2010) who reported that the value of the quantum yield of naproxen photolysis at 254 nm, estimated by using a simple model of the type Ln½C=½C o ¼ À2:3$ε l $[$F l $I o ðlÞ ¼ Àk app $t, increases at increasing oxygen concentration in the liquid bulk. This observation may explain the discrepancies found in the literature for naproxen quantum yield values reported by different Authors (Meite et al, 2010;Benitez et al, 2009;Pereira et al, 2007a,b).…”

“…The values of quantum yields of direct UV 254 -photolysis for NP 1 and NP 2 species were estimated for the first time in the present paper, whereas the value calculated for F NP (1.297$10 À2 AE 1.23$10 À3 mol E À1 ) is in good agreement with that previously reported (1.5$10 À2 AE 5.0$10 À3 mol E À1 ) by Meite et al (2010). From the comparison of the three parameters F NP , F NP1 and F NP2 it can be assessed that, at the same experimental starting conditions, the photoreactivity at 254 nm follows the order: NP > NP 1 > NP 2 even if the order of molar absorptivities is ε 254…”

“…This observation may explain the discrepancies found in the literature for naproxen quantum yield values reported by different Authors (Meite et al, 2010;Benitez et al, 2009;Pereira et al, 2007a,b).…”

“…Unfortunately due to the severe conditions adopted, the results achieved during this study could not be used to predict the fate of this species during the sterilization procedure for reuse. Kinetic indications on naproxen removal during irradiation at 254 nm were also reported by others (Pereira et al, 2007a,b;Benitez et al, 2009;Meite et al, 2010). The quantum yield and the photoproduct distribution depend in a sensible way on the adopted conditions (aerobic versus anaerobic medium).…”

“…In particular, the quantum yields of direct photolysis (at 254 nm) in water, under aerated media, reported in three previous papers, are not in good agreement: 9.3$10 À3 AE 2.7$10 À4 mol E À1 (Pereira et al, 2007a,b), 49.8$10 À3 mol E À1 (Benitez et al, 2009) and 24.0$10 À3 AE 5.0$10 À3 mol E À1 (Meite et al, 2010). These discrepancies in the quantum yields can be probably attributed to the influence of the concentration of dissolved oxygen as observed by Meite and coauthors who, under controlled operative conditions (pH 5.5e6.0, T ¼ 25 C, photon flux 10 À7 E l À1 s À1 ), estimated the following values of quantum yields: 1.5$10 À2 mol E À1 , 2.40$10 À2 mol E À1 and 5.60$10 À2 mol E À1 for dissolved oxygen concentrations of 0.01 mM, 0.26 mM and 1.3 mM respectively.…”