Alkaline earth metal-doped Mn3O4 for peroxymonosulfate activation: A non-radical strategy dominated by 1O2 for tetracycline degradation

CaO/MgO-Mn 3 O 4 catalysts were prepared for the activation of PMS to degrade TC. • Revealing the non-radical degradation pathway dominated by 1 O 2 . • The system demonstrated excellent anti-interference ability and stability. • The surface -OH played a bridging role in the generation of ROSs. • Predicted the biological toxicity of the TC intermediate. In advanced oxidation processes, free radical-mediated mechanisms have garnered considerable research interest for the remediation of emerging contaminants (ECs). However, compared with non-radical pathways, free radical pathways were prone to side reactions and exhibited poorer environmental adaptability. In this study, alkaline earth metal-doped Ca/Mg-Mn 3 O 4 catalysts with different doping ratios were synthesized to activate peroxymonosulfate (PMS) for the degradation of tetracycline (TC). The optimized catalyst, Ca-Mn 3 O 4 -   10%, achieved 86% TC removal within 90 min, with an apparent rate constant of 0.0218 min −1 , which is 3.04 times higher than that of the pristine Mn 3 O 4 /PMS system. Free radical quenching experiments demonstrated that the degradation of TC was predominantly attributed to a non-radical pathway dominated by singlet oxygen. After five consecutive cycles, the Ca-Mn 3 O 4 -   10% catalyst still maintained a degradation efficiency over 82%, showing excellent catalytic stability. Furthermore, the catalyst exhibited strong resistance to common anions, organic substances, changes in solution pH, and various water matrices. Based on the identification of intermediate products, three degradation pathways were proposed. Toxicity assessment using a predictive model indicated that the biological toxicity of most degradation products was significantly reduced. This study offers new insights and theoretical support into the degradation of wastewater containing ECs via a non-radical mechanism. Download: Download high-res image (273KB) Download: Download full-size image