Confined Fe0@CNTs for highly efficient and super stable activation of persulfate in wide pH ranges: Radicals and non-radical co-catalytic mechanism

Efficient catalysis in wide pH ranges with good stability still poses a great challenge in advanced oxidation processes (AOPs). Herein, confined nano-Fe0 in carbon nanotubes cavity (Fe0-in-CNTs) was fabricated as a heterogeneous catalyst for persulfate (PS) activation, fulfilling ultra-efficient degradation of sulfamethazine with the turnover frequency even 10-folds higher than that of most catalysts in literatures. Due to the collective effect of radicals (SO4−, OH and O2−) and non-radical (1O2) at different pH, Fe0-in-CNTs exhibited an excellent catalytic performance in wide pH ranges (2–10) with extremely low leaching iron (0.33% of raw Fe doping content). Moreover, the cycling of surface ≡Fe2+/≡Fe3+ by Fe0 that protected by CNTs cavity greatly improved the performance and reusability of the catalyst. This confinement effect on Fe0-in-CNTs was effective for degradation of multiple pollutants, advantaged over many Fe-based catalysts, and was valid for activation of other oxidants (e.g·H2O2) in AOPs. This study provides a wide pH-independent PS activator via confinement catalysis, exhibiting a promising prospect and a significant breakthrough in AOPs.