Promoting oxygen vacancies utility for tetracycline degradation via peroxymonosulfate activation by reduced Mg-doped Co3O4: Kinetics and key role of electron transfer pathway

Cheng Wang; Lian Chang; Xiaodan Zhang; Hongxiang Chai; Yuming Huang

doi:10.1016/j.envres.2024.118892

Promoting oxygen vacancies utility for tetracycline degradation via peroxymonosulfate activation by reduced Mg-doped Co₃O₄: Kinetics and key role of electron transfer pathway

Environ Res. 2024 Apr 9;252(Pt 2):118892. doi: 10.1016/j.envres.2024.118892. Online ahead of print.

Authors

Cheng Wang¹, Lian Chang², Xiaodan Zhang¹, Hongxiang Chai³, Yuming Huang⁴

Affiliations

¹ Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Southwest University, Chongqing, 400715, China.
² Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing University, Chongqing, 400045, China.
³ Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing University, Chongqing, 400045, China. Electronic address: chaihx@cqu.edu.cn.
⁴ Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Southwest University, Chongqing, 400715, China. Electronic address: ymhuang@swu.edu.cn.

PMID: 38599451
DOI: 10.1016/j.envres.2024.118892

Abstract

Developing cobalt-based catalysts with a high abundance of oxygen vacancies (V_o) and exceptional V_o utility efficiency for the prompt removal of stubborn contaminants through peroxymonosulfate (PMS) activation poses a significant challenge. Herein, we reported the synthesis of the reduced Mg-doped Co₃O₄ nanosheets, i.e. Mg-doped Co₃O₄-r, via Mg doping and followed by NaBH₄ reduction, aiming to degrade tetracycline (TC). Various characterization results illustrated that NaBH₄ reduction imparted higher V_o utility efficiency to Mg-doped Co₃O₄-r, along with an ample presence of reduced Co²⁺ species and an increased surface area, thereby substantially elevating PMS activation capability. Notably, Mg-doped Co₃O₄-r achieved more than 97.9% degradation of 20 mg/L TC within 10 min, showing an over 8-fold increase in reaction rate relative to the Mg-doped Co₃O₄ (k_obs: 0.3285 min^-1 vs 0.0399 min^-1). The high removal efficiency of TC was sustained across a broad pH range of 3-11, even in the presence of common anions and humic acid. Radical quenching trials, EPR outcomes, and electrochemical analysis indicated that neither radicals nor ¹O₂ were the primary active species. Instead, electron transfer pathway played a dominant role in TC degradation. The Mg-doped Co₃O₄-r displayed excellent recyclability and versatility. Even after the fifth cycle, it maintained an impressive 83.0% removal of TC. Furthermore, it exhibited rapid degradation capabilities for various pollutants, including levofloxacin, pefloxacin, ciprofloxacin, malachite green, and rhodamine B. The TC degradation pathway was proposed based on LC-MS determination of its degradation intermediates. This study showcases an innovative strategy for the rational design of an efficient cobalt-based activator, leveraging electron transfer pathways through PMS activation to degrade antibiotics effectively.

Keywords: Electron transfer pathway; Oxygen vacancies; Peroxomonosulfate; Subsequent-reduction; Utility efficiency.