Insights into the Kinetics, Theoretical Model and Mechanism of Free Radical Synergistic Degradation of Micropollutants in UV/Peroxydisulfate Process

The degradation of acyclovir (ACY) and atenolol (ATL) in the UV/peroxydisulfate (UV/PDS) process has been systematically considered, focusing on the degradation kinetics, theoretical models, and reaction pathways via applying a microfluidic UV reaction system. The removal efficiencies of ACY and ATL were >94.8%, and the apparent degradation rate constants (kobs) were 0.0931 and 0.1938 min−1 at pH 6.0 in the UV/PDS system. The sulfate radical (SO4•−) and hydroxyl radical (•OH) were identified as the major reactive radicals. The pH-dependent reaction rate constants of ACY and ATL with •OH and SO4•− were measured via the competing kinetics. Meanwhile, the contributions of •OH and SO4•− for ACY and ATL degradation were calculated by the radical steady-state hypothesis, and the results revealed that SO4•− occupied a decisive position (>84.5%) for the elimination of ACY and ATL. The contribution of •OH became more significant with the increasing pH, while SO4•− was still dominant. Moreover, ACY and ATL degradation performance were systematically evaluated via the experiments and Kintecus model under different operational parameters (Cl−, Br−, HCO3−, NOM, etc.) in the UV/PDS process. Furthermore, the plausible reaction pathways of ACY and ATL were elucidated based on the Fukui function theory and ultra-performance liquid chromatography-tandem quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) analysis. The UV/PDS process has been demonstrated to be an efficient and potential application for micropollutants mitigation

Insights into the photocatalytic ozonation over Ag2O-ZnO@g-C3N4 composite: Cooperative structure, degradation performance, and synergistic mechanisms

In this work, Ag2O and ZnO modified g-C3N4 (Ag2O-ZnO@CNx) catalysts were fabricated by a simple precipitation-reflux method and employed for visible-light-driven photocatalytic ozonation process towards oxalic acid (OA) degradation. A series of characterizations such as XRD, TEM, XPS, UV-vis DRS, PL, Mott- Schottky were conducted to investigate the impact of loading Ag2O-ZnO on the microstructure and catalytic properties of catalysts. It was noteworthy that the mesoporous and backbone structure did not perceptibly change after doping Ag2O-ZnO to g-C3N4. Moreover, the separation of photogenerated e h+ pairs, the mobility of e transfer, and the photocatalytic ozonation performance were improved with the increase in doping amount of g-C3N4. Amongst, the [email protected] achieved 83.43% of OA removal efficiency and the highest k value (0.0311 min 1), showing an excellent synergistic effect (synergy index η = 10.37) in this coupling system. Moreover, the [email protected] exhibited satisfactory reusability for multiple consecutive cycles (≥5). Through the radical scavenger experiments and ESR spectra, the reactive species including h+, e , O2¿ , 1O2 and ¿OH were verified to play an important role in PhOx system. Accordingly, an empirical kinetic model was established to predict OA concentration with the given operational parameters. The synergistic mechanism of OA degradation in the PhOx system was also proposed. Overall, the results presented a new insight into the application of PhOx process in water treatment