Potential and degradation mechanism of sulfamethoxazole removal by the synergistic effect of micro-nano bubbles and sodium hypochlorite.

In this paper, the potential and mechanistic behavior of micro-nano bubbles (MNBs) synergistic with sodium hypochlorite (NaClO) in the degradation of sulfamethoxazole (SMX) were thoroughly investigated. In the MNBs-NaClO system, the effects of varying environmental factors (NaClO concentration, pH, inorganic anions, surfactants) on the degradation efficiency of SMX were investigated. The degradation products and pathways of SMX were investigated to reveal the degradation mechanism of antibiotics within the MNBs-NaClO system by using density functional theory (DFT) and high-performance liquid chromatography-mass spectrometry (LC-MS). The degradation rate of SMX increased with the increase of NaClO concentration. SMX allowed efficient degradation in a wide pH range. The inorganic anion PO showed a strong inhibitory effect on the degradation of SMX. Surfactants had a consistent inhibitory effect on the degradation progress of SMX. According to the degradation behavior of SMX in the MNBs-NaClO system, three degradation pathways were proposed: nitrosation, S-N bond breaking, chlorine substitution and chlorine oxidation. This study evaluated the removal efficiency of sulfonamide antibiotics by the synergistic MNBs-NaClO technology, revealing unique degradation mechanisms and fate pathways. It provides a critical theoretical basis for precisely predicting their environmental behavior and ecological risks in advanced oxidation systems/aquatic environments.