Enhanced detoxification of enrofloxacin during confined catalytic ozonation

Ozonation, a widely investigated and applied technology to eliminate organic contaminants from water, is confronted with the unintended generation of toxic transformation products (TPs). In this study, we investigated the confinement effect on the detoxification of ozonation for the first time via comparing the confined catalyst and its non-confined peer, i.e. FeMn nanoparticles in mesopores of zeolite SBA-15 and FeMn on the exterior of zeolite. Material characterization and catalytic kinetics demonstrated that both catalysts shared an identical instinct catalytic behavior, but reactive oxygen species contributed a higher ratio to the oxidation of organics in the confined system than the non-confined peer. It was found that the confined system led to a significantly low toxicity of enrofloxacin TPs measured with the respiratory inhibition of bacteria, the development of zebrafish embryo, and the in silico toxicity endpoints, likely due to the distinct compositions and levels of enrofloxacin TPs discovered with mass spectrometry. Degradation tests further revealed that the confined ozonation effectively reduced the interference of organic matrix. The calculation with molecular dynamics demonstrated that the diffusion retarding effects of mesopores can leverage the oxidation toward small target contaminants over large matrix organics. The superior detoxification and anti-interference capacity of confined ozonation, demonstrated in this study, inspires a promising pathway to tackle the application challenges of catalytic oxidation.