Role variations of MnOx on monoclinic BiVO4 (110)/(040) facets for enhanced Photo-Fenton reactions

Compared with traditional Fenton reaction, peroxymonosulfate based advanced oxidation processes (PMS-AOPs) are more effective to remove the organic pollutants in wastewater in a wider pH range. Herein, selective loading of MnOx on monoclinic BiVO4 (110) or (040) facets were achieved by photo-deposition method with addition of different Mn precursors and electron/hole trapping agents. MnOx has good chemical catalysis activity for PMS activation, which can also enhance photogenerated charge separation, thus leading to enhanced activities than naked BiVO4. The BPA degradation reaction rate constants of MnOx(040)/BiVO4 and MnOx(110)/BiVO4 system are 0.245 min(-1) and 0.116 min(-1), which are 6.45 and 3.05 times larger than that of naked BiVO4, respectively. The roles of MnOx on different facets are different, which will promote OER process on (110) facets and utilize the dissolved O-2 to produce O-2(center dot-) and O-1(2) more effectively on (040) facets. O-1(2) is the dominated reactive oxidation species of MnOx(040)/BiVO4, while SO4 center dot- and center dot OH play more important roles on MnOx(110)/BiVO4, which are proved by quenching experiments and chemical probe identifications, thus mechanism in MnOx/BiVO4-PMS-light system is proposed. The good degradation performance of MnOx(110)/BiVO4 and MnOx(040)/BiVO4 and mechanism theory may promote the application of photocatalysis in PMS based wastewater remediation.

Automated summary

Compared with traditional Fenton reaction, peroxymonosulfate based advanced oxidation processes (PMS-AOPs) are more effective in removing organic pollutants in wastewater over a wider pH range. This study demonstrated that selectively loading MnOx on monoclinic BiVO4 (110) or (040) facets through photo-deposition method improved the catalytic activity and charge separation, resulting in significantly enhanced degradation activities. The mechanism of MnOx/BiVO4-PMS-light system was proposed based on quenching experiments and chemical probe identifications.