Abstract
UV/H2O2, which is an advanced treatment technology used to reduce multiple contaminants, is effective in potable water treatment. Simultaneous degradation effects and kinetics of three types of coexisting micropollutant estrogens (steroid estrogens, SEs), including estrone (E1), 17β-estradiol (E2) and 17α-ethinyl estradiol (EE2), in deionized water were studied. Experiments were carried out with ultraviolet-C (UVC) radiation, together with hydrogen peroxide (H2O2), in a cylinder photoreactor. The results demonstrated that the degradation processes of all of the estrogens strongly fit first-order kinetics. Single solutions of E1, E2 and EE2 showed higher degradation rates and removal efficiencies under the same reaction conditions compared with those under mixed conditions. Coexisting combinations of estrogens were put into the UV/H2O2 system to estimate their possible competitive influences on each other by examining their removal efficiencies and reaction rate constant, k, values. E1 is predominantly reduced rapidly during the competition, while the presence of other estrogens has negligible impacts on E1; however, the degradation of E2 and EE2 is affected by the competitive background, not in relation to the types but to the existing amounts. In the UV/H2O2 system, photocatalysis of the estrogens can stably produce an intermediate X, with the highest quantity coming from E1, while considerably lower quantities are obtained from E2 and EE2.
Highlights
Estrogens, including estrone (E1), 17β-estradiol (E2), 17α-ethinyl estradiol (EE2) and estriol (E3), occur in natural environments, such as surface water, seawater and soil, and have attracted significant concern due in part to reports linking these compounds to lower sperm counts in adult males, increases in cancer, and strong and powerful endocrine disrupter activity, even at extremely low concentrations [1,2]
Eluents were evaporated to dryness using nitrogen and dissolved in acetonitrile again to a final volume of 1 mL, which was transferred to a vial and analyzed using high performance liquid chromatogram (HPLC)
UVA was found to be efficient in E1 reduction but had no effect on E2, which suggested that the breakdown energy of the chemical bond in E2 is higher than that of E1
Summary
Estrogens (steroid estrogens, SEs), including estrone (E1), 17β-estradiol (E2), 17α-ethinyl estradiol (EE2) and estriol (E3), occur in natural environments, such as surface water, seawater and soil, and have attracted significant concern due in part to reports linking these compounds to lower sperm counts in adult males, increases in cancer, and strong and powerful endocrine disrupter activity, even at extremely low concentrations [1,2]. Estrogens have similar tetracyclic structures, with different chemical groups or spatial arrangements at the C-16 and C-17 positions. They exist in the effluent of municipal facilities and some industrial plants, such as those that breed livestock and those that produce prophylactics. These types of pollution are collected during wastewater treatment and cannot be removed efficiently, resulting in their release into natural systems [3,4]. EE2 degradation processes in the UV/H2O2 system are consistent with the first order kinetic model under different combination conditions, and the reaction rate constant and the half-life show influences of co-existent estrogens on EE2.
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