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The environmentally benign Fe2(MoO4)3 plays a crucial role in the transformation of organic contaminants, either through catalytically decomposing oxidants or through directly oxidizing the target pollutants. Because of their dual roles and the complex surface chemical reactions, the mechanism involved in Fe2(MoO4)3-catalyzed PDS activation processes remains obscure. In this study, Fe2(MoO4)3 was prepared via the hydrothermal and calcine method, and photoFenton degradation of methyl orange (MO) was used to evaluate the catalytic performance of Fe2(MoO4)3. Fe2(MoO4)3 catalysts with abundant surface oxygen vacancies were used to construct a synergistic system involving a photocatalyst and PDS activation. The oxygen vacancies and Fe2+/Fe3+ shuttle played key roles in the novel pathways for generation of •O2−, h+, and 1O2 in the UV–Vis + PDS + FMO-6 photoFenton system. This study advances the fundamental understanding of the underlying mechanism involved in the transition metal oxide-catalyzed PDS activation processes. [ABSTRACT FROM AUTHOR]

In order to improve the catalytic activity of cobalt molybdate (CoMoO4), a PDS-activated and UV-vis assisted system was constructed. CoMoO4 was prepared by coprecipitation and calcination, and characterized by XRD, FTIR, Raman, SEM, TEM, XPS, TGA Zeta potential, BET, and UV-Vis DRS. The results showed that the morphology of the CoMoO4 nanolumps consisted of stacked nanosheets. XRD indicated the monoclinic structures with C2/m (C32h, #12) space group, which belong to α-CoMoO4, and both Co2+ and Mo6+ ions occupy distorted octahedral sites. The pH of the isoelectric point (pHIEP) of CMO-8 at pH = 4.88 and the band gap of CoMoO4 was 1.92 eV. The catalytic activity of CoMoO4 was evaluated by photo-Fenton degradation of Congo red (CR). The catalytic performance was affected by calcination temperature, catalyst dosage, PDS dosage, and pH. Under the best conditions (0.8 g/L CMO-8, PDS 1 mL), the degradation efficiency of CR was 96.972%. The excellent catalytic activity of CoMoO4 was attributed to the synergistic effect of photo catalysis and CoMoO4-activated PDS degradation. The capture experiments and the ESR showed that superoxide radical (·O2−), singlet oxygen (1O2), hole (h+), sulfate (SO4−·), and hydroxyl (·OH−) were the main free radicals leading to the degradation of CR. The results can provide valuable information and support for the design and application of high-efficiency transition metal oxide catalysts. [ABSTRACT FROM AUTHOR]