The aqueous degradation of bisphenol A and steroid estrogens by ferrate

The aqueous reactivity of five prominent endocrine disrupting chemicals (EDCs) with potassium ferrate has been studied. The degradation kinetics and reaction pathways for bisphenol A (BPA) have been considered in detail, and the reaction rate constants for 17α-ethynylestradiol (EE2), estrone (E1), β  -estradiol (E2), and estriol (E3) have been determined, from tests carried out in the pH range of 8–12 and at different reactant molar ratios. The rate constants were determined by a kinetic model incorporating the various species equilibria for the EDC compounds and ferrate, using observations of the temporal reduction in EDC and ferrate concentrations. In agreement with other studies, the oxidation of the EDCs was found to be greater for mono-protonated ferrate, HFeO4-, than for non-protonated ferrate, FeO42-. Among the five EDCs, all of which have phenol moieties, the ferrate oxidation of the four steroid estrogens (each incorporating the cyclopentanoperhydrophenanthrene ring) had higher reaction rates than BPA. The by-products of BPA degradation by ferrate were analyzed by liquid chromatography/mass spectrometry–mass spectrometry (LC/MS–MS) and gas chromatography/mass spectrometry–mass spectrometry (GC/MS–MS) and nine specific compounds were identified, including p-isopropylphenol, 4-isopropanolphenol, p-isopropenylphenol, and some dicarboxylic acids, etc. It is concluded that ferrate oxidation could be an effective treatment method for the purification of waters containing these particular EDCs.