Photocatalytic activation of peroxymonosulfate (PMS) by novel mesoporous Ag/ZnO@NiFeO nanorods, inducing radical-mediated acetaminophen degradation under UVA irradiation.

A new mesoporous Ag/ZnO@NiFeO nanorod was prepared by a facile, low-cost, and environmentally friendly strategy from a bimetallic FeNi-MIL-88 metal organic framework (MOF), as an effective catalyst and peroxymonosulfate (PMS) photo-activator. The structural, morphological, optical, and magnetic properties, as well as the material composition were investigated by XRD, FE-SEM, EDX, HR-TEM, XPS, DRS, PL, EIS, VSM, N adsorption-desorption and ICP-AES analysis. 1.0% w/w loading of Ag nanoparticles on ZnO@NiFeO led to the best catalytic activity for PMS activation under UVA in acetaminophen (ACT) degradation. The maximum degradation efficiency for ACT was 100% within 15 min (at pH = 7.0), with a first-order rate constant of 0.368 min. The calculated quantum yield (1.3 × 10 molecule/photon) of the optimum catalyst was 2.05, and 5.63 times higher than its simple constituents, ZnO@NiFeO and NiFeO, respectively. Among the various inorganic ions, Cl and HCO showed significant inhibition effect in 1.0%w/w Ag/ZnO@NiFeO/PMS/UVA system, due to radical quenching effects. Based on scavenger experiments, HO and SO were the dominant reactive species in photocatalytic process coupled with PMS. Due to presence of the Fe/Fe, and Ni/Ni reaction cycles in the as-made catalyst, the reaction rate of PMS activation was greatly enhanced. Moreover, the formation of a hetero-junction structure with NiFeO and ZnO promoted the charge separation of the photo-generated electron/hole pairs. Finally, the major intermediates produced during the reaction were detected by LC-MS analysis, and a plausible mechanism for the photocatalytic degradation of ACT was proposed and discussed in detail.