Enhanced activation of peroxymonosulfate by Sr-doped LaFeO₃ perovskite for Orange I degradation in the water

A-site doping of perovskite has been considered to be an effective method to simultaneously boost catalytic performance and limit metal release in heterogeneous catalysis. Herein, various Sr-doped LaFeO₃ perovskites (La_1-xSr_xFeO_3-δ) were synthesized and evaluated as a heterogeneous catalyst to activate peroxymonosulfate (PMS) for the degradation of Orange I (OI) in water. Specifically, La_0.6Sr_0.4FeO_3-δ (LSFO-40) exhibited a remarkable improvement in catalytic activity with a k constant of 0.0411 min⁻¹, which was approximately 3 times higher than that of LaFeO₃ (0.0142 min⁻¹). The superior stability was obtained with less metal leaching after Sr doping. Such enhancement was mainly attributed to the modified surface properties created by Sr doping, such as a rapid transformation of Fe(II)/Fe(III) redox pair, a large number of oxygen vacancies and surface hydroxyl groups, additionally, the strong interaction between PMS and Fe sites and facilitated electron transfer for PMS activation catalyzed by LSFO-40 also stimulated OI degradation. These also promoted the generation of a considerable amount of superoxide radical (O₂^[rad]−) and singlet oxygen (¹O₂), which was tested as the main reactive oxygen species (ROSs). The synergistic effect of iron and oxygen species ensured a continuous ROSs generation and excellent catalytic performance. Finally, neither a wide pH range of 5.0–9.0 or co-existing anions (Cl⁻ and HCO₃⁻) showed a negligible inhibitory effect on OI removal, implying a great potential application of the LSFO-40/PMS system in practical wastewater treatment.