Low-valence Co nanoparticles anchored on biochar as efficient peracetic acid activators: Singlet oxygen-dominated tetracycline degradation and mechanistic insight

A low-valence cobalt nanoparticles supported on biochar (HS-15Co) was synthesized. • Low-valence Co promotes electron transfer to PAA, sustaining the non-radical activation process. • Singlet oxygen ( 1 O 2 ) is the dominant reactive oxygen species in the HS-15Co/PAA system. • The TC degradation pathway and intermediate toxicity were analyzed. • This work offers insights for designing carbon-supported metal catalysts and enhancing PAA-based water purification. Peracetic acid (PAA)-based advanced oxidation processes (AOPs) are promising for antibiotic wastewater remediation, while the role of cobalt valence states in PAA activation remains unclear. Herein, a series of low-valence Co-loaded biochar catalysts (HS-xCo) were synthesized, realizing uniform dispersion of Co nanoparticles and formation of low-valence Co species. The target HS-15Co catalyst exhibited superior catalytic performance, achieving 94.6% tetracycline (TC) degradation, which was 3.0 times that of pristine biochar. Structural characterizations confirmed that low-valence Co(0)/Co(II) nanoparticles were stably anchored on biochar surface without obvious agglomeration. Quenching experiments and electron spin resonance (EPR) verified singlet oxygen ( 1 O 2 ) as the predominant reactive oxygen species (ROS) responsible for TC degradation. Electrochemical measurements and Density functional theory (DFT) calculations corroborated that Co incorporation significantly enhanced PAA adsorption and promoted interfacial electron transfer, thus boosting PAA activation efficiency. Furthermore, three possible TC degradation pathways were proposed based on liquid chromatography-mass spectrometry (LC-MS) analysis, and toxicity prediction demonstrated that most degradation intermediates showed lower toxicity than parent TC. This work provides a low-valence Co/biochar catalyst for efficient PAA activation through 1 O 2 -dominated pathway, offering a feasible strategy for emerging organic pollutant removal in aquatic environment. Download: Download high-res image (164KB) Download: Download full-size image