Biogenic manganese oxide: An efficient peroxymonosulfate activation catalyst for tetracycline and phenol degradation in water

From the view of environment and easy availability, to develop the most efficient manganese oxide for peroxymonosulfate (PMS) activation is of great importance for the degradation of recalcitrant organic pollutants. In this study, biogenic manganese oxide (BioMnOx) exhibited an unprecedented efficiency than the most efficient 3D α-Mn2O3 prepared by chemical method. 100% of phenol degradation at 40 min and 99.4% of tetracycline removal at 60 min were achieved over BioMnOx with PMS, which was 3-fold faster than 3D α-Mn2O3. BioMnOx also has an excellent long-term stability and good performance toward the pollutants degradation at a wide pH range of 3.0–9.0. Most importantly, 1O2 was identified as the primary reactive species in BioMnOx/PMS system based on the trapping experiment and EPR analysis. The PMS activation over BioMnOx should follow a self-decomposition and energy quenching mechanism instead of electron transfer process as confirmed by the XPS analysis. Finally, the degradation pathways of tetracycline and phenol by 1O2 over BioMnOx were proposed according to HPLC and HPLC-MS results, which are greatly different from that by OH oxidation in the literature.