Active and stable CoOx sites promotes peroxymonosulfate activation for sulfamethoxazole degradation through nonradical pathways

Cobalt (Co) single-atom sites are considered as the most efficient active sites in peroxymonosulfate (PMS) based advanced oxidation processes. However, CoO configurations instead of Co-N configurations were scarcely explored. Herein, isolated Co single atoms were successfully implanted onto hydroxyl decorated UiO-66 (Co/UiO-66-220) to generate [Zr6O4(OH)4(BDC)5.35(OH)1.30(OH2)1.30] structure to form {ZrOCoOZr} single-site through coordination strategy. Owing to the strong electron transfer ability of CoOx sites, the Co/UiO-66-220/PMS system displayed outstanding degradation performance and 100 % sulfamethoxazole (SMX) degradation efficiency was achieved within 10 min. Remarkably, the system also displayed excellent degradation performance in the presence of anions and complex actual wastewater. The membrane system was particularly effective, achieving a 90.32 % removal efficiency within 240 min. The nonradical species, singlet oxygen (52.8 %), electron transfer (4.9 %) and high-valent cobalt-oxo species (Co (IV) = O) (23.9 %), were dominated in the degradation process. The generated intermediates are low-toxicity. The results demonstrate the excellent activity of CoOx sites for PMS activation and its practical application potential for remediation of organic contaminants.