Porous Ɛ-Mno2 Nanoplate as a Catalyst for Peroxymonosulfate Activation Towards Enhanced Degradation of Bisphenol a

A porous Ɛ-MnO 2 nanoplate was successfully synthesized by a facile hydrothermal route. For comparison, several manganese oxides, including Mn 5 O 8 , Mn 2 O 3 and Mn 3 O 4 , were obtained via tuning the calcining temperature. These manganese oxides were characterized and applied for the activation of peroxymonosulfate (PMS) to degrade bisphenol A (BPA). The resulting BPA removal rates followed the rank order: Ɛ-MnO 2 > Mn 5 O 8 > Mn 2 O 3 > Mn 3 O 4 . In the Ɛ-MnO 2 /PMS system, the BPA degradation rate reached 93.2% within 30 min with a mineralization efficiency of 75% within 120 min. In addition, the influence of several coexisting anions, humic acid, initial pH, temperature and peroxide species were investigated. Moreover, electron paramagnetic resonance (EPR) and quench tests confirmed the dominant contribution of HO• to the degradation of BPA. The BPA degradation pathways were identified based on LC–MS analysis. Finally, according to the quench tests and XPS results, we conclude that Mn(II) could be the main active site to initiate PMS activation via single-electron transfer. Then, Mn(III) reacted with another PMS molecule to produce Mn(IV) and HO• , but the transition from Mn(IV) to Mn(II) was not easy and might be the rate-determining step in the overall degradation process.