High performance of carbon nanotube-encapsulated CuFe2O4 for peroxonosulfate activation: A process of degradation of sulfamethoxazole in complex matrix water via a singlet oxygen-dominated pathway

The common advanced oxidation process has problems such as short free radical life, low utilization rate, and weak catalyst stability. In this study, CuFe2O4 spinel was encapsulated in carbon nanotubes (CNT) to activate peroxymonosulfate (PMS), and a catalyst CuFe2O4-in-CNT with a closed structure was synthesized. The catalyst exhibits exceptional catalytic performance in the degradation of sulfamethoxazole, effectively degrading 96.10% of sulfamethoxazole (SMX) within a mere 10 min. At the same time, carbon nanotubes provide a relatively ideal nano-enclosed space for the filling of CuFe2O4 nanoparticles. The confinement effect in CuFe2O4-in-CNT/PMS system is reflected in the following three aspects: (i) The catalyst with a closed structure can effectively alleviate the influence of macromolecular organic matter on the catalytic system; (ii) The reactive species (O2 center dot-, SO4 center dot-, HO center dot) accelerated recombination in a confined reaction space and rapidly converted to 1O2 as the major active substance; (iii) Strengthen the way of electron transfer. The interaction of catalysts, oxidants and pollutants is enhanced in a nano-enclosed environment by CuFe2O4-in-CNT/PMS process. In addition, CuFe2O4 nanoparticles were filled in the CNT cavity, which further affected the catalytic performance and stability. The removal rate of SMX by CuFe2O4-in-CNT was 90% after five cycles.