Enhanced performance of LaFeO3 perovskite for peroxymonosulfate activation through strontium doping towards 2,4-D degradation

Abstract

ABO3-type perovskite oxides with diverse active metal sites and stable texture structures have attracted much attention in heterogeneous catalysis, including catalysis of peroxymonosulfate (PMS) for wastewater treatment. Here, Sr was introduced into the A-site of LaFeO3 (LFO) perovskite to modify its structure for enhancing the catalytic performance. Specifically, La0.5Sr0.5FeO3 (LSF50) with a lower valence state of Fe and abundant oxygen vacancies exhibited excellent catalytic activity for PMS activation to degrade 2,4-dichlorophenoxyacetic acid (2,4-D), 5.7 times higher than the catalytic activity of LFO. In the presence of 0.6 g/L LSF50 and 1 mM PMS, 2,4-D (10 mg/L) could be completely removed within 60 min. Magnetic LSF50 showed a low level of metal leaching and good reusability for 2,4-D degradation. Moreover, the excellent degradation efficiency was maintained in a large range of initial pH from 5 to 11 as well as in a real water matrix such as surface water. Various reactive oxygen species (ROS) involving sulfate radical (SO4−), hydroxyl radical (HO), and singlet oxygen (1O2) were generated during the catalysis. Based on electron spin resonance (ESR) studies and radical quenching experiments, SO4− played a dominant role in 2,4-D degradation. A coupled PMS activation mechanism for the major free radicals and minor 1O2 was proposed for the rapid degradation of 2,4-D in LSF50/PMS system. The transformation byproducts were identified and the possible degradation pathways were proposed. This study provides a new insight for the development of efficient A-sites-modified perovskite oxide for PMS activation in environmental remediation.