A novel LaFeO3 catalyst synthesized from sodium diethylenetriamine pentamethylene phosphonate for degradation of diclofenac through peroxymonosulfate activation: degradation pathways and mechanism study

Abstract

In this paper, some perovskite catalysts LaFeO₃ (LFO) were prepared by using the efficient chelating properties of sodium diethylene triamine pentamethylene phosphonate (DTPMP-2Na) toward metal ions, and the best catalyst LFO-0.1 was selected by using diclofenac sodium as the target pollutant. Then, the influence of different factors (PMS dosage, catalyst dosage, substrate concentration and anion) on the degradation of DCF in a LFO-0.1/PMS system was studied. The catalyst was characterized, and the reaction mechanism of diclofenac (DCF) in the LFO-0.1/PMS system was analyzed. It was concluded that hydroxyl radicals, sulfate radicals and singlet oxygen were produced in the LFO-0.1/PMS system. In the reaction system, singlet oxygen is considered to be the main factor for DCF degradation in this system, and the generation of sulfate radicals is mainly attributed to oxygen vacancies and the electron transfer between Fe³⁺ and Fe²⁺. Through the centrifugal recovery of the catalyst to explore its stability, the conclusion is that LFO-0.1 is a stable catalyst. Finally, 15 kinds of oxidation intermediates and products were identified, and the possible degradation pathways of DCF were analyzed, including decarboxylation, dechlorination, C–N cleavage, hydroxylation, ring-closure and ring-opening.