Lithium cobalt oxide with excellent electron mobility: An efficient activator of peroxymonosulfate for the degradation of sulfamethoxazole

Abstract

Aiming at the problems of sulfamethoxazole (SMX), such as large amount of usage, high degradation difficulty and low removal efficiency of conventional sewage treatment technology, commercial lithium cobalt oxide (LCO) was employed as heterogeneous catalyst to activate peroxymonosulfate (PMS) for SMX degradation in this study. Various characterization methods were applied to investigate the morphology and physicochemical properties of LCO catalysts. Then, complete removal of SMX (2.5 mg/L) was attained within 30 min, the dissolution of cobalt ion was less than 0.1 mg/L, and the removal rate of SMX could still be maintained at 90% after five consecutive cycles, revealing that LCO had outstanding catalytic performance, excellent electron transfer rate, wide operating pH range and good stability. The susceptibility of inorganic anions, diverse water bodies and distinct contaminants to LCO/PMS system was investigated to explore its realistic application. Further exploration demonstrated that the reactive species generated on SMX degradation were sulfate radical (SO₄^•–) and hydroxyl radical (^•OH), in which SO₄^•– performed a leading role. Integrated with XPS analysis, it was proposed that the Co³⁺/Co²⁺ redox companions were the active sites for activating PMS. The possible degradation pathways were put forward by discussing the intermediates of SMX which identified by UPLC-QTOF-MS/MS. In short, this work was conducive to supply a reference for the application of cobalt based doped heterogeneous catalyst in the field of wastewater treatment.