Low-temperature molten-salt synthesis of Co3O4 nanoparticles grown on MXene can rapidly remove ornidazole via peroxymonosulfate activation.

We further developed previous work on MXene materials prepared using molten salt methodology. We substituted single, with mixed salts, and reduced the melting point from >724 °C to <360 °C. Cobalt (Co) compounds were simultaneously etched and doped while the MXene material was created using various techniques in which Co compounds occur as Co3O4. The synthesized Co3O4/MXene compound was used as a peroxymonosulfate (PMS) activator that would generate free radicals to degrade antibiotic ornidazole (ONZ). Under optimal conditions, almost 100% of ONZ (30 mg/L) was degraded within 10 min. The Co3O4/MXene + PMS system efficiently degraded ONZ in natural water bodies, and had a broad pH adaptation range (4-11), and strong anion anti-interference. We investigated how the four active substances were generated using radical quenching and electron paramagnetic resonance (EPR) spectroscopy. We identified 12 ONZ intermediates by liquid chromatography-mass spectrometry and propose a plausible degradative mechanism.

Ultrasmall nitrogen-doped Cu0·92Co2·08O4 nanocrystal-decorated cerium dioxide nanoparticles for fast and complete degradation of ranitidine via permonosulfate activation.

A simple and efficient coagulation method was used for the rapid preparation of nitrogen-doped copper-cobalt oxide (N-Cu0.92Co2·08O4) supported on cerium dioxide (CeO2), that is, N-Cu0.92Co2·08O4@CeO2. A low concentration of N-Cu0.92Co2·08O4@CeO2 (0.15 g L-1) was shown to rapidly activate permonosulfate (PMS) (0.15 g L-1) to achieve 100% degradation of ranitidine within 10 min. A 100% degradation of ranitidine enabled by the catalyst was achieved over a wide range of pH (5.5-9.0), which could be completed within 8 min in the presence of anionic H2PO4-. Moreover, the N-Cu0.92Co2·08O4@CeO2 catalyst enabled more than 90% degradation of various typical antibiotics within 30 min, including tetracycline, sulfaixoxazole, and chloramphenicol, with degradation rates of 100%, 93.51%, and 90.01%, respectively. Even after four catalytic cycles, N-Cu0.92Co2·08O4@CeO2 could be regenerated to achieve 100% degradation of ranitidine. Electrochemical analysis demonstrated that the combination of N-Cu0.92Co2·08O4@CeO2 and PMS immediately produced a strong current density, thereby rapidly producing reactive oxygen species (ROS) with high performance for the degradation of the target pollutant. Combined ion quenching and electron paramagnetic resonance analyses indicated that the main ROS was the non-free radical 1O2. Finally, a plausible ranitidine degradation pathway was deduced based on liquid chromatography-mass spectrometry (LC-MS) analysis, wherein the toxic substance N-nitrosodimethylamine was not produced during the degradation process. In short, this study provides a new perspective for preparing ternary metal catalysts for advanced oxidation processes with practical application significance.