Bioreduction-assisted synthesis of Co nanoclusters for selective singlet oxygen generation in ciprofloxacin degradation

Singlet oxygen ( 1 O 2 ) is an efficient reactive oxygen species that, due to its relatively long lifetime and broad pH adaptability, has been considered an excellent alternative to free radicals in advanced oxidation processes. However, achieving sustained 1 O 2 generation and its effective degradation of target pollutants remains challenging. In the present study, a facile co-precipitation–calcination–microwave approach was employed, incorporating Biscogniauxia mediterranea metabolites to promote the formation of zero-valent cobalt. Consequently, a highly dispersed cobalt nanocluster catalyst (Co@NC-800-MW) was successfully prepared, which markedly enhanced the catalyst’s electron-transfer efficiency. Density functional theory calculations of adsorption energies indicated that 1 O 2 generation was thermodynamically favored. Electron paramagnetic resonance (EPR) measurements demonstrated that Co@NC-800-MW maintained continuous 1 O 2 production and played a central role in the degradation of ciprofloxacin (CIP), exhibiting high catalytic efficiency over a wide pH range (3.0–9.0). Furthermore, continuous-flow experiments confirmed the catalyst’s stability: after treating 500 mL of actual water sample with 10 mg of Co@NC-800-MW, the CIP removal rate remained at 80 %. In addition, ecotoxicity tests revealed that the treated water exhibited significantly reduced biological toxicity. These findings provide important theoretical support for the application of advanced oxidation technologies in practical water pollution remediation.