Cobalt oxides grown in-situ on carbon nitride nanosheets for efficient peroxymonosulfate activation and organic contaminants degradation: Performance, mechanism, and application study

Heterogeneous peroxymonosulfate (PMS) activation processes are considered promising Fenton-like oxidation technologies, and the design of heterogeneous catalysts is key to enhancing their practical applicability. In this study, a catalyst consisting of cobalt oxides grown in situ on carbon nitride nanosheets (CoO_x-CN) was designed for PMS activation and the degradation of emerging organic contaminants. The CN substrate increased the specific surface area and enhanced the exposure of reactive sites in CoO_x-CN, while the NH₃ released during the calcination of CN reduced cobalt species, promoting the formation of sub-valent CoO crystal planes and oxygen vacancies (O_V). As a result, the CoO_x-CN/PMS system demonstrated efficient tetracycline removal efficiency, reaching 99.4 % within 21 min, with a specific catalytic kinetic constant (K_specific) of 0.016 L·min^-1m⁻². Mechanism studies indicated that the strong electronic interaction between CoO_x-CN and PMS induced the generation of reactive species responsible for the degradation of organic contaminants. Based on theoretical calculations, intermediate identification, and toxicity analysis, a degradation pathway and toxicity evolution for tetracycline were proposed. Additionally, the application of CoO_x-CN in a membrane system and its performance in treating natural water bodies confirmed its potential for real-scale applications. This work provides a reference for the design of Fenton-like catalysts and their application in actual wastewater treatment scenarios.