Fenton-like oxidation mechanism for simultaneous removal of estriol and ethinyl estradiol by green synthesized Mn3O4 NPs.

• Green synthesis of Mn 3 O 4 NPs was as a new Fenton catalyst. • The removal efficiency was 97.5% for E3 and 96.4% for EE2. • Various radicals were observed in the catalytic system. • A new mechanism was proposed. Manganese tetroxide (Mn 3 O 4) nanomaterials were prepared by green tea extract and applied to catalyze sodium peroxydisulfate (PDS) for the simultaneous degradation of estriol/17a-ethinylestradiol (E3/EE2) with removal efficiencies of 97.5 and 96.4% for E3 and EE2, respectively. XPS also showed that before and after the reaction the divalent manganese content decreased from 50.2 to 34.8%, indicating divalent manganese plays a major role in the catalytic process. EPR quenching and electrochemical studies showed that while initially singlet oxygen (1O 2), sulfate (SO 4 •-), superoxide (O 2 •-) and hydroxyl (•OH) radicals were all generated in the system, thereafter, the oxidation of E3/EE2 mainly depended on 1O 2 and O 2 •-, where O 2 •- intermediates participated in the generation of 1O 2 in the Fenton-like process. LC-MS analysis showed that degradation products of E3/EE2 were mainly produced via hydroxyl and sulfate degradation pathways. Finally, a mechanism of Fenton-like oxidation of E3/EE2 was proposed. [ABSTRACT FROM AUTHOR]