Nitrogen-Vacancy-Rich Co3O4/Carbon Nitride Activating Peroxymonosulfate for Efficient Micropollutant Degradation: Dominant Role of Superoxide Radicals

Abstract

The widespread use of tetracycline (TC) antibiotics poses significant environmental and health risks due to their persistence and toxicity in aquatic ecosystems. In this study, a heterogeneous catalyst composed of Co₃O₄ supported on graphitic carbon nitride (Co₃O₄/CN) was developed to efficiently activate peroxymonosulfate (PMS) for TC degradation. A series of Co₃O₄/CN composites with different cobalt loadings were synthesized via a straightforward pyrolysis process. The optimized 12%Co₃O₄/CN sample exhibited an enhanced specific surface area, abundant nitrogen vacancies, and improved electron transfer efficiency, achieving 86.6% degradation of TC within 30 min, with 5.4-fold enhancement in reaction rate constant than PMS-only systems. Consistently high degradation efficiencies were also observed for various other micropollutants. Mechanism investigations revealed that O₂·^- radicals played a dominant role in TC degradation, while SO₄·^-, ¹O₂, and ·OH radicals also contributed significantly, all synergistically promoted by the redox cycling of Co²⁺/Co³⁺ species and the presence of nitrogen vacancies. Notably, the catalytic system exhibited broad pH adaptability, excellent reusability, and effective mineralization capacity. Toxicity assessment further indicated a reduced ecotoxicity of TC degradation byproducts. This study thus offers a promising and environmentally sustainable solution for the effective remediation of antibiotic-contaminated wastewater.

Keywords: Catalysis; Co(3)O(4)/CN; Nitrogen vacancy; PMS activation; Tetracycline (TC) degradation.