Roles of intrinsic Mn sites and lattice oxygen in mechanochemical debromination and mineralization of decabromodiphenyl ether with manganese dioxide.

Commercial β-MnO with a chemical formula of approximate MnMnO was used for mechanochemical (MC) oxidative degradation of decabromodiphenyl ether (BDE209). The ball milling process initiated the degradation of BDE209 on β-MnO, yielding a nearly complete degradation and debromination of BDE209 within 2 h. The use of β-MnO exhibited much higher MC debromination efficiency than that by using birnessite (δ-MnO, 40.2%), BiO (45.6%), CaO (65.3%), and persulfate (81.9%). It was demonstrated that the oxidative degradation of BDE209 was promoted by the redox half reactions of both Mn→ Mn and Mn→ Mn, but naturally existed Mn centers on the surface of β-MnO functioned as dominant reactive species at the initial stage of the MC degradation (often before the degradation efficiency of BDE209 achieved 50%). Moreover, the surface lattice oxygen of MnO, rather than O, played a key role in the debromination and mineralization of BDE209. The Mn sites on β-MnO not only easily accepted the electron of BDE209, but also promoted the mobility of lattice oxygen from the bulk to the surface for mineralizing BDE209. These results firstly highlighted the importance of Mn availability and oxygen mobility on the reactivity of manganese oxide for the MC oxidative degradation of organic pollutants.