Investigation of catalytic activity and mechanism for RhB degradation by LaMnO3 perovskites prepared via the citric acid method

Abstract

LaMnO₃ nanoparticles were synthesized by the citric acid complex sol–gel method and used to degrade rhodamine B (RhB) in aqueous solution. We found that without adding additional oxidants to the reaction system or light irradiation, LaMnO₃ exhibits an excellent degradation ability of RhB under highly acidic conditions and achieves about 98.0% degradation efficiency. This result showed that LaMnO₃ itself provides an effective oxidative system to degrade RhB. Furthermore, based on the intermediates detected by ultraviolet-visible spectrophotometry (UV-vis) and liquid chromatography mass spectrometry (LC-MS), a reasonable degradation pathway of RhB was proposed, including N-de-ethylation, chromophore cleavage, ring opening and mineralization. LaMnO₃ can maintain the perovskite structure in the reaction system, and abundant vacancies of LaMnO₃ promote the generation of active oxygen species. Furthermore, electron transfer between Mn⁴⁺ and Mn³⁺ in LaMnO₃ is the key to the degradation of organic matter in this reaction system.