Effective mineralization of p-nitrophenol by catalytic ozonation using Ce-substituted La_1‒xCe_xFeO₃ catalyst

In this study, cerium-doped lanthanum ferrite perovskite oxides (La_1‒xCe_xFeO₃) with different A-site were synthesized using a sol-gel method and they were used as ozonation catalyst for p-nitrophenol (PNP) mineralization for the first time. Catalytic activity in terms of total organic carbon (TOC) removal followed the order of La_0.8Ce_0.2FeO₃ > La_0.4Ce_0.6FeO₃ > La_0.6Ce_0.4FeO₃ > La_0.2Ce_0.8FeO₃ > LaFeO₃ with 77, 66, 61, 60 and 56% respectively. The synthesized catalysts were characterized by diffraction of X-ray (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) and scanning electronic microscopy (SEM). Moreover, electron spin resonance (ESR) and radicals quenching experiments showed that the active oxygen species in the ozone decomposition process are mainly hydroxyl radical (·OH), and also include superoxide radical (O₂^-) and singlet oxygen (¹O₂). Furthermore, the superior activity of La_0.8Ce_0.2FeO₃ could be attributed to the higher surface area, the richer lattice oxygen, richer surface -OH groups and the facilitated redox Ce³⁺/Ce⁴⁺ and Fe²⁺/Fe³⁺ cycling. In addition, this study provides an insight to use metal-doped perovskite catalysts for catalytic ozonation.