Correlation of Active Sites to Generated Reactive Species and Degradation Routes of Organics in Peroxymonosulfate Activation by Co-Loaded Carbon

Abstract

Peroxymonosulfate (PMS)-based advanced oxidation processes (PMS-AOPs) as an efficient strategy for organic degradation are highly dependent on catalyst design and structured active sites. However, the identification of the active sites and their relationship with reaction mechanisms for organic degradation are not fully understood for a composite catalyst due to the complex structure. Herein, we developed a family of Co encapsulated in Ndoped carbons (Co-PCN) with tailored types and contents of active sites via manipulated pyrolysis for PMS activation and ciprofloxacin (CIP) degradation, focusing on the correlation of active sites to generated reactive species and degradation routes of organics. The structure−function relationships between the different active sites in Co-PCN catalysts and reactive oxygen species (ROS), as well as bond breaking position of CIP, were revealed through regression analysis and density functional theory calculation. Co−N x , O−CO, CO, graphitic N, and defects in Co-PCN stimulate the generation of 1 O 2 for oxidizing the C−C bond in the piperazine ring of CIP into CO. The substitution of F by OH and hydroxylation of the piperazine ring might be induced by SO 4•− and • OH, whose formation was affected by C−O, Co(0), Co−N x , graphitic N, and defects. The findings provided new insights into reaction mechanisms in PMS-AOP systems and rational design of catalysts for ROS-oriented degradation of pollutants.

Cobalt Single Atoms Anchored on Oxygen‐Doped Tubular Carbon Nitride for Efficient Peroxymonosulfate Activation: Simultaneous Coordination Structure and Morphology Modulation

“…With the structure change from CoÀ N 4 moiety to CoÀ N 3 O 1 moiety, the inhibition of L-histidine increased from 35.28 % to 63.05 %, while the inhibition of TBA decreased from 78.71 % to 6.73 % (Figure 3e). Note that other factors such as the interaction between PMS and L-histidine, [33] PMS self-decomposition, [31] electron transfer [4,34] et al could have an impact on the degradation process. Throughout a series of experiment under different conditions (Figure S17 and S18), we further identified that 1 O 2 were dominant radicals and the origin relied on PMS activation by CoÀ N 3 O 1.…”

“…With the structure change from Co−N 4 moiety to Co−N 3 O 1 moiety, the inhibition of L‐histidine increased from 35.28 % to 63.05 %, while the inhibition of TBA decreased from 78.71 % to 6.73 % (Figure 3e). Note that other factors such as the interaction between PMS and L‐histidine, [33] PMS self‐decomposition, [31] electron transfer [4, 34] et al. could have an impact on the degradation process.…”

“…[30] To further investigate the origins of the catalyst's activity, the potential correlations between the effect factors and catalytic performance of catalysts in these PMS-AOPs were established (Figure 3c). [31] The magnitude and degree of the correlation were represented by the shade of color and the size of circle, respectively. Furthermore, the number of asterisk referred to a significant level.…”

“…Liquid chromatography-mass spectrometry (LC-MS) was performed to identify the degradation intermediates. [31] As displayed in Figure S11, the chromatograms of a 5 mg L À 1 CIP solution at different reaction times were presented. The labeled peaks are corresponding to CIP with m/z = 332 at retention time 10.7 min and major degradation intermediates with m/z = 348 at retention time 4.5 min.…”

“…Liquid chromatography–mass spectrometry (LC‐MS) was performed to identify the degradation intermediates [31] . As displayed in Figure S11, the chromatograms of a 5 mg L −1 CIP solution at different reaction times were presented.…”