Kinetic degradation model and estrogenicity changes of EE2 (17α-ethinylestradiol) in aqueous solution by UV and UV/H2O2 technology

The photochemical degradation and estrogenicity removal of 17 alpha-ethinylestradiol in aqueous solutions was investigated via ultraviolet (UV) photolysis and UV/H2O2 process with a low-pressure UV lamp. The results indicated that the kinetics of both oxidation processes well fitted the pseudo-first-order kinetics. EE2 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 EE2 degradation rate enhanced from 0.0364 to 0.0684 min(-1) when H2O2 was combined with the photolysis process (UV/H2O2), even though EE2 was not oxidized when same amounts of H2O2 existed in the aqueous solutions. The kinetic parameters of pseudo-first-order kinetics showed positive correlation to UV intensity and also H2O2 concentration, however negative to the initial EE2 concentration. A regression model was developed for pseudo-firstorder rate constant as a function of the UV intensity, H2O2 concentration and initial EE2 concentration, which could be used to estimate the EE2 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 EE2 was mainly responsible for the observed estrogenicity. (C) 2010 Elsevier B.V. All rights reserved.