Photodegradation of 17β-estradiol in aquatic solution under solar irradiation: Kinetics and influencing water parameters

Photodegradation of the natural steroid 17 beta-estradiol (E2), an endocrine disrupting hormone which is commonly released into aquatic environments, was investigated under simulated sunlight (290-700 nm) using a solar simulator in the presence of several natural water constituents including NO3-, Fe-3(+), HCO3-, humic acid and turbidity. The E2 degradation followed pseudo-first-order kinetics, with the rate constant decreasing slightly with increasing initial constituent concentration while increasing with the square root of solar intensity in the region of 25-100 mW cm(-2). The rate of mineralization based on the total organic carbon (TOC) reduction was always lower than E2 degradation, although the TOC of the solution decreased steadily with irradiation time. In the presence of NO3-, Fe-3(+), and humic acid, the photodegradation rate increased significantly, attributed to photosensitization by the reactive species, while HCO3- slowed down the degradation rate because of OH* scavenging. Turbidity also reduced the photodegradation of E2 by decreasing light transmittance due to attenuation. The solution pH also had a considerable effect on the rate with maximum degradation occurring around a neutral pH of 7. (C) 2011 Elsevier B.V. All rights reserved.