Boosting catalytic activity of Fe-based perovskite by compositing with Co oxyhydroxide for peroxymonosulfate activation and ofloxacin degradation

Abstract

A novel Fe-based perovskite hybrid catalyst was designed by sol-gel preparation of Ni-substitution of LaFeO₃ containing in-situ growth of metal oxyhydroxide (MeOOH, Me=Mn, Ni, Co). The performances of metal oxyhydroxide-perovskite composites (MeOOH/LaFe_0.5Ni_0.5O₃) for peroxymonosulfate (PMS) activation and ofloxacin (OFL) degradation were investigated. CoOOH/LaFe_0.5Ni_0.5O₃ exhibited the best OFL degradation efficiency of 91.84 % within 15 min. Compared with LaFe_0.5Ni_0.5O₃, the specific surface area (from 21.391 to 100.216 m²·g⁻¹) and pore volume (from 0.080 to 0.226 cm³·g⁻¹) of CoOOH/LaFe_0.5Ni_0.5O₃ increased drastically. Among the structures and properties, substitution of Ni into B-site of LaFeO₃ accelerated the electron transfer and promoted the redox cycle between Fe³⁺/Fe²⁺ and Ni²⁺/Ni⁰. Besides, doping with CoOOH could provide more active sites for the catalyst and more electrons for the activation of PMS to generate reactive species. The higher redox potential of Co ions resulted in good thermodynamic cycling between Co³⁺/Co²⁺, Fe³⁺/Fe²⁺ and Ni²⁺/Ni⁰. Moreover, oxygen vacancies (V_o) on the material surface were involved in the activation of PMS. Quenching experiments and electron paramagnetic resonance (EPR) verified that the catalytic reaction was primarily driven by both ·O₂^- (radical way) and ¹O₂ (non-radical way), with electron transfer process (ETP) also had some effect on OFL degradation. In addition, the conversion of radicals to non-radicals was demonstrated. Finally, the degradation pathway of OFL and the ecotoxicity of the intermediates were proposed. The work provided scientific support and theoretical basis for the development of efficient heterogeneous PMS catalysts.