Kinetic degradation model and estrogenicity changes of EE2 (17alpha-ethinylestradiol) in aqueous solution by UV and...

The photochemical degradation and estrogenicity removal of 17alpha-ethinylestradiol in aqueous solutions was investigated via ultraviolet (UV) photolysis and UV/H(2)O(2) process with a low-pressure UV lamp. The results indicated that the kinetics of both oxidation processes well fitted the pseudo-first-order kinetics. EE(2) can be partially removed by UV radiation alone with kinetic constants increasing from 0.0054 to 0.2753 min(-1) with the UV intensity increase. The EE(2) degradation rate enhanced from 0.0364 to 0.0684 min(-1) when H(2)O(2) was combined with the photolysis process (UV/H(2)O(2)), even though EE(2) was not oxidized when same amounts of H(2)O(2) existed in the aqueous solutions. The kinetic parameters of pseudo-first-order kinetics showed positive correlation to UV intensity and also H(2)O(2) concentration, however negative to the initial EE(2) concentration. A regression model was developed for pseudo-first-order rate constant as a function of the UV intensity, H(2)O(2) concentration and initial EE(2) concentration, which could be used to estimate the EE(2) degradation rate at various operational conditions. The yeast estrogen screen (YES) was employed to evaluate the estrogenicity of photolytic water samples. Results showed that more than 95% of the estrogenicity was removed after 40 min irradiation and the parent compound EE(2) was mainly responsible for the observed estrogenicity.