Oxidative Transformation of 17β-estradiol by MnO2 in Aqueous Solution

17β-Estradiol (E2) is known as a natural endocrine disruptor and often found in municipal sewage. Batch experiments were conducted to assess the oxidative transformation of E2 in aqueous solutions by MnO2 and the probable degradation pathway. The results suggested that E2 could be degraded by MnO2, and the oxidation reaction deviated from pseudo-first-order kinetics due to the accumulation of reaction products in mineral surfaces and a gradual change of the surface site distribution toward less reactive sites. MnO2 dosage had a positive effect on oxidative transformation of E2, and both the initial reaction rate and the adsorption of E2 to oxide surfaces increased as the pH decreased. Two products, estrone and 2-hydroxyestradiol, were detected by gas chromatography coupled with mass spectrometry, and the probable degradation pathway was proposed. Results suggest that E2 can be oxidatively transformed by MnO2, which will provide some new insights into the interaction of estrogens with manganese oxides in natural soils and sediments.