Mechanical insights into a novel ultra-efficient amorphous-Co3S4 activator of peroxymonosulfate for rapid degradation of acetochlor

Abstract

The herbicide acetochlor (ACT) has newly raised concerns in China’s latest drinking water quality standards. Exceptional removal efficacy of micropollutants by peroxymonosulfate (PMS) activated using amorphous metal-based catalysts have been recently reported. However, the efficiency of amorphous cobalt tetrasulfide (amorphous-Co₃S₄) in activating PMS and its performance in degrading ACT, as well as the underlying mechanisms involved, remain unclear. Herein, we synthesized amorphous-Co₃S₄ via a facile two-step hydrothermal method and firstly employed it as an ultra-efficient PMS activator for rapid degradation of ACT. Completely removal of ACT (10 mg/L) was achieved within 2 min at a low PMS dosing of 0.2 mM, with a notable utilization efficiency of 0.8150 mmol/(g·min). The main mechanism underlying PMS activation involved Co²⁺/Co³⁺ redox cycling, with sulfate and hydroxyl radicals identified as the primary reactive oxidizing species. Moreover, single electron transfer, radical addition, demethylation, and dechlorination reactions were the major pathways for ACT degradation, resulting in the formation of ACT•⁺, ACT(+OH)•, ACT(–CH₃)•, and ACT(−Cl)•. Subsequently, these are subjected to further degradation and ultimately mineralization, yielding intermediates with lower ecotoxicity than ACT itself. This study demonstrates the ultra-efficiency of amorphous-Co₃S₄ on PMS activation and establishes its potential application in environmental engineering practices.