Enhanced degradation of atrazine by nanoscale LaFe1-xCuxO3-δ perovskite activated peroxymonosulfate: Performance and mechanism

Abstract

Cu-doped LaFeO3 perovskite (LaFe1-xCuxO3-δ, LFCx) synthesized using a sol-gel method was introduced in the heterogeneous activation of peroxymonosulfate (PMS) for atrazine degradation. The obtained LFCx catalysts were characterized by several technologies and the results showed that Cu was incorporated into the perovskites lattice successfully. In addition, the introduction of Cu resulted in the mixed valence state of Fe(III)/Fe(II) and Cu(II)/Cu(I) in perovskite structure. LaFe0.8Cu0.2O3-δ (LFC0.2) exhibited excellent catalytic activity and stability towards the degradation of atrazine. Atrazine (23 μM) was removed completely within 60 min in the presence of 0.5 g/L catalyst and 0.5 mM PMS. The efficient degradation was obtained when the initial pH ranged from 2 to 10. Sulfate radicals (SO4•-) and hydroxyl radicals (HO•) generated during activation process were determined as the main reactive species based on the electron spin resonance (ESR) studies and radical quenching experiments. The enhanced catalytic activity derived from the lower valence state of Fe and Cu as well as the synergetic effect between them. A surface catalyzed-redox cycle between Fe(III)/Fe(II) and Cu(II)/Cu(I), along with surface hydroxyl groups (-OH), were all responsible for the decomposition of PMS. The oxygen vacancies could promote the chemical bonding with PMS and enhance the reactivity of Fe and Cu. The 12 transformation products were determined by LC-MS and the degradation mechanisms were further proposed, which involved five different pathways. The perovskite that possesses bimetallic active sites can be a promising catalyst for PMS activation towards the degradation of persistent organic pollutants with high-efficiency.