Template-assisted synthesis of CaCO₃-stabilized cobalt silicate nanoflowers for efficient peroxymonosulfate activation with minimized cobalt leaching

Abstract Cobalt-based catalysts demonstrate significant activity in activating peroxymonosulfate (PMS) for the degradation of water pollutants. Nevertheless, their practical application remains constrained due to concerns regarding potential cobalt leaching, associated toxicity risks, and overall stability under operational conditions. A novel CoCa-SBA-600 catalyst was synthesized via a hydrothermal-assisted SBA-15 sacrificial templating strategy, where the zeolite simultaneously served as a silicate precursor and structural scaffold. Comprehensive characterization (XRD, FTIR, SEM, TEM and XPS) confirmed the co-existence of CaCO₃-stabilized cobalt silicate nanoflowers with ultrathin two-dimensional layered morphology. The CaCO₃ incorporation remarkably enhanced PMS activation efficiency while suppressing Co²⁺ leaching (⩽0.51 mg l⁻¹), achieving 99.29% metronidazole (MNZ) degradation within 10 min at 500 mg l⁻¹ catalyst dosage. The system demonstrated exceptional universality, degrading multiple antibiotics (⩾96.97% efficiency within 10 min) across diverse aqueous matrices (tap/lake/river water) and maintained >98% MNZ removal after four cycles, highlighting robust stability. Mechanistic studies verified singlet oxygen (¹O₂) as the dominant reactive species via quenching experiments and EPR analysis, with proposed MNZ degradation pathways aligned with LC-MS data. Notably, seed germination assays confirmed the low biotoxicity of degradation intermediates. The calcium carbonate-mediated stabilization strategy proposed in this study achieves efficient stabilization of cobalt silicate materials. The insights gained not only advance the development of environmentally friendly advanced oxidation processes but also provide a new paradigm for designing long-lasting catalysts for environmental remediation applications.