Improvement of peroxymonosulfate utilization efficiency for sulfamethazine degradation by photo-electron activating peroxymonosulfate: Performance and mechanism.

Enhancing the utilization efficiency of oxidant is of great importance for advanced oxidation processes (AOPs). Herein, nitrogen-doped titania dioxide/carbon (NTC7) catalyst was fabricated via pyrolyzing NH2-MIL-125 under nitrogen atmosphere at 700 °C. Excitation of NTC7 under visible light can successfully achieve efficient activation of peroxymonosulfate (PMS) (NTC7 + PMS + Vis). Degradation performance and PMS activation mechanism were systematically investigated using sulfamethazine (SMT) as the target pollutant. It was found that the photo-generated electrons excited from NTC7 under visible light played the dominant role in enhancing the productive consumption of PMS. Its utilization increased by 66 % (Δ[PMS]/Δ[SMT] = 7.0) in NTC7 + PMS + Vis process and the degradation rate was 2.14 times higher than that of NTC7 + PMS process. The ketonic CO groups and structural defects were responsible for the generation of 1O2 in dark activation while radicals (•OH, O2•-) were more inclined to be continuously produced in NTC7 + PMS + Vis process. The involved degradation pathways, intermediates, and toxicity assessment have been studied in detail. This work provides an effective approach to enhance the utilization efficiency of oxidant for pollutant degradation by AOPs.

Oxygen Vacancies in Piezoelectric ZnO Twin-Mesocrystal to Improve Peroxymonosulfate Utilization Efficiency via Piezo-Activation for Antibiotic Ornidazole Removal.

Piezoelectric mesocrystals as defective materials have been demonstrated to possess adsorptive and catalytic properties in redox reactions. However, there is still a lack of research on the quantitative relationship between the defect concentration and the piezocatalytic performance in piezoelectric mesocrystals. Herein, twin-hierarchical structure ZnO piezoelectric mesocrystals are taken with different oxygen-vacancies (OVs) concentrations to quantitatively investigate the effect of defect content on the peroxymonosulfate (PMS) piezo-activation in water purification. The ZnO piezoelectric mesocrystal with moderate OVs concentration exhibits a rapid antibiotic ornidazole (ORZ) pollutants degradation rate (0.034 min-1 ) and achieves a high PMS utilization efficiency (0.162) that exceeds the most state-of-the-art catalytic processes, while excessive OVs suppressed the piezocatalytic performance. Through calculations of electron property and reactants affinity, a quantitative relationship between OVs concentration and piezocatalytic properties is established. The ZnO mesocrystal with moderate OVs concentration realized increased electron delocalization, reduced charge transfer barrier, and enhanced reactants affinity, thus accelerating the kinetics of PMS activation. This work provides theoretical guidance for the application of defect engineering in mesocrystal to realize enhanced piezocatalytic performance.

Enhanced utilization efficiency of peroxymonosulfate via water vortex-driven piezo-activation for removing organic contaminants from water.

The efficient activation and utilization of peroxymonosulfate (PMS) in PMS-based advanced oxidation processes is a high-priority target for the removal of organic contaminants. This work introduces a water vortex-driven piezoelectric effect from few-odd-layered MoS2 into the PMS activation to remove benzotriazole (BTR) and other organic contaminants from the water. Approximately 91.1% of BTR can be removed by the MoS2 piezo-activated PMS process with a reaction rate constant of 0.428 min-1, which is 2.09 times faster than the sum of the individual MoS2, water vortex, and piezocatalysis rates. Meanwhile, the PMS utilization efficiency reached 0.0147 in the water vortex-driven piezo-activation system, which is 3.97 times that of the sum from the vortex/PMS and MoS2/PMS systems. These results demonstrate that the presence of MoS2 under a water vortex can trigger a piezoelectric potential and generate abundant free electrons to activate PMS to generate various active species for degradation of organic contaminants.