Removal of aqueous metazachlor, tembotrione, tritosulfuron and ethofumesate by heterogeneous monopersulfate decomposition on lanthanum-cobalt perovskites

Abstract

This study reports LaCoO3 perovskite oxide activity in the removal of aqueous herbicides (metazachlor, tembotrione, tritosufuron and ethofumesate) by means of potassium monopersulfate (MPS) decomposition. The influence of initial MPS concentration and catalyst load have been assessed. MPS is instantaneously absorbed onto the perovskite surface where this species decomposes. Thus, MPS breakage leads to the formation of powerful oxidizing radicals which react with herbicides in solution. Tritosulfuron was the most recalcitrant compound towards this technology. Catalyst stability was tested by means of consecutive reuse cycles. No appreciable loss of activity was experienced. Experiments in the presence of tert-butyl alcohol, methanol and carbonate outlined the importance of radicals in herbicides degradation. Finally, synthetized LaCoO3 was characterized. Scanning and transmission electron microscopy showed the presence of nanosized material, mostly spherical shaped, with 15.20 m2 g−1 of BET area. LaCoO3 perovskite structure was corroborated by diverse techniques such as X-ray fluorescence (La:Co atomic ratio of 1:1), X-ray photoelectron spectroscopy (surface Co(III) and La(III)), and X-ray diffraction (rhombohedral LaCoO3 phase).