Cobalt species immobilized on nitrogen‑doped ordered mesoporous carbon for highly efficient catalytic ozonation of atrazine.

[Display omitted] • Co 3 O 4 loaded on cobalt-nitrogen doped ordered mesoporous carbon (Co 3 O 4 @Co-N-CMK3) was prepared. • Atrazine (ATZ) removal was 99.6% at 15 min with rate constant of 0.354 min−1 in Co 3 O 4 @Co-N-CMK3/O 3. • Co2+ and Co N x were active sites for O 3 decomposition and O 2 /OH generation. • The synergy between Co 3 O 4 and Co-N-CMK3 promoted interface electron transfer. • ATZ degradation pathway and toxicity evaluation of intermediates were proposed. The strategy of coupling transition metal and N-doped carbon catalysts have garnered great attention in catalytic ozonation. To overcome the inferior mass transfer of O 3 , we prepared a hetero-structure catalyst (Co 3 O 4 @Co-N-CMK3), which was composed of Co 3 O 4 nanoparticles (NPs) and cobalt-nitrogen doped ordered mesoporous carbon. Co 3 O 4 @Co-N-CMK3 displayed a uniformly arranged long-range mesoporous channel structure with large surface area (537.24 m2/g). The adsorption efficiency of ATZ (10 μM) was 55% at 15 min in presence of 0.05 g/L catalyst. After aeration of 3.5 mg/L O 3 gas (50 mL min-1), the ATZ removal increased to 99.6% with rate constant of 0.354 min-1 in Co 3 O 4 @Co-N-CMK3/O 3 , 35.4-fold that in ozonation. The turnover frequency (TOF) value of Co 3 O 4 @Co-N-CMK3 reached 7.08 min-1 g-1, which was 2.2-93.2 folds higher than the reported ozonation catalysts. Co 3 O 4 @Co-N-CMK3 displayed the adsorption performance for ATZ and could activate O 3 into O 2 - and OH effectively. The ≡Co2+ and ≡Co-N x were main active sites. The synergy between Co 3 O 4 and Co-N-CMK3 accelerated interface electron transfer, which was conducive to the redox of ≡Co2+/≡Co3+. The degradation pathway and intermediates toxicity were speculated using HPLC-MS measurement and Toxicity Estimation Software Tool simulation. The stability of Co 3 O 4 @Co-N-CMK3 for ATZ removal was certified by five consecutive experiments in catalytic ozonation. Moreover, the Co 3 O 4 @Co-N-CMK3/O 3 process had good applicability to common anions and humic acid, real water and different pollutants. [ABSTRACT FROM AUTHOR]