Synergistic multiple active species driven fast estrone oxidation by δ-MnO2 in the existence of methanol.

Endocrine-disrupting chemicals (EDCs) cause serious threats to human health. Five types of MnO2 were synthesized and characterized. They exhibited different removal performances for three EDCs, i.e., estrone (E1), ethynylestradiol (EE2) and bisphenol A (BPA). Only δ-MnO2 can completely remove E1 within 120 min at pH 3.0. Free Mn (III) was determined at the beginning of the reaction and participated in the EDCs removal process. Electron spin resonance (ESR) indicated that δ-MnO2 could produce superoxide anions (·O2-) and singlet oxygen (1O2) in the existence of methanol. The reactive oxygen species (ROS) quenching experiments showed 1O2 have certain contribution to the E1 removal by δ-MnO2. The source of ROS is mainly the lattice oxygen from δ-MnO2, and can be replenished through the layer structure destruction caused by the reaction between Mn(III) and E1. The ROS dependent EDCs removal by δ-MnO2 leads to a deep understanding on this well-known oxidant.