Atomic cation-vacancy modulated peroxymonosulfate nonradical oxidation of sulfamethoxazole via high-valent iron-oxo species

The formation of high-valent active species during peroxymonosulfate (PMS) activation has attracted great interest. However, how to rapidly generate high-valent active species during PMS activation process remains ambiguous. Herein, iron vacancy anchored layered double hydroxides activated PMS process were designed to enhance the removal rate of sulfamethoxazole (SMX) by 30.0 times to PMS alone, which even showed much superiority to the homogeneous Fe2+/PMS system. Due to the cooperation of Fe vacancies, PMS favored to be adsorbed on Fe2 sites (adjacent to iron vacancy) and combined with Fe2 sites to form Fe(II)-O-SO3-OH complex. Then, the accepted electrons led to the cleavage of S-O bond in Fe(II)-O-SO3-OH complex, resulting in the spontaneous generation of Fe(IV)=O/Fe(V)=O species. Finally, PMS activation pathways were proposed from radical oxidation to nonradical oxidation via high-valent iron-oxo species. This study provides a new perspective on generation of high-valent iron-oxo species for excellent performance and resistance with real wastewater.