Photocatalytic activation of peroxymonosulfate (PMS) by novel mesoporous Ag/ZnO@NiFe2O4 nanorods, inducing radical-mediated acetaminophen degradation under UVA irradiation

A new mesoporous Ag/ZnO@NiFe2O4 nanorod was prepared by a facile, low-cost, and environmentally friendly strategy from a bimetallic Fe2Ni-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-2 adsorption-desorption and ICP-AES analysis. 1.0% w/w loading of Ag nanoparticles on ZnO0.04@NiFe2O4 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(-1). The calculated quantum yield (1.3 x 10(-3) molecule/ photon) of the optimum catalyst was 2.05, and 5.63 times higher than its simple constituents, ZnO0.04@NiFe2O4 and NiFe2O4, respectively. Among the various inorganic ions, Cl- and HCO3- showed significant inhibition effect in 1.0%w/w Ag/ZnO0.04@NiFe2O4/PMS/UVA system, due to radical quenching effects. Based on scavenger experiments, HO center dot and SO4 center dot- were the dominant reactive species in photocatalytic process coupled with PMS. Due to presence of the Fe3+/Fe2+, and Ni2+/Ni3+ 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 NiFe2O4 and ZnO promoted the charge separation of the photogenerated 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. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

A new mesoporous Ag/ZnO@NiFe2O4 nanorod was prepared using a facile, low-cost, and environmentally friendly strategy as an effective catalyst and peroxymonosulfate (PMS) photo-activator for ACT degradation. The catalyst showed high catalytic activity and efficient degradation of ACT due to the formation of a hetero-junction structure with NiFe2O4 and ZnO, as well as the presence of Fe3+/Fe2+ and Ni2+/Ni3+ reaction cycles enhancing the PMS activation rate. The study also proposed a plausible mechanism for the photocatalytic degradation of ACT based on LC-MS analysis of the reaction intermediates.