Regulating nonradicals generation through peroxymonosulfate activation via localized dipole to enhance wastewater biodegradability.

Abstract

It is still greatly desirable to activate peroxymonosulfate (PMS) forming nonradicals for the removal of electron-rich contaminants in complex water matrices. However, achieving this on heterogeneous metal-based catalysts with uniform electron distribution remains challenging due to the asymmetric structure of PMS molecules (H-O-O-SO₃^-). Here, inspired by the dipole effect, we design a Co-doped ZnO catalyst (ZOC) to break charge symmetry at active sites and enhance nonradicals generation. The high charge density at Co sites facilitates two-electron transfer, promoting O-O and O-H bond cleavage to form high-valent cobalt-oxo (Co^IV=O), while positively polarized Zn sites drive PMS self-decomposition to generate singlet oxygen (¹O₂). As a result, the synergistic system of ¹O₂ and Co^IV = O results in a k-value of 73.93 min⁻¹ M⁻¹ for aniline (AN) degradation, 189.6 times higher than ZnO/PMS (ZO/PMS), and also shows a high selectivity for electron-rich new pollutants. The practicality of this outstanding nonradicals system is confirmed by a significant increase in biochemical oxygen demand/chemical oxygen demand (BOD/COD) of the mixed wastewater to over 0.55 in the air-lifting internal circulating reactor. This study offers a structural regulation for controlling catalytic functionality and provides general guidelines for designing Fenton-like reactors to enhance wastewater biodegradability.