Novel MBP/Fe2+/PMS process for efficient synergistic degradation of cefixime in water

Cefixime (CFX), a widely used antibiotic, has become a challenge for the treatment of antibiotic pollution in water bodies. In this study, the performance and mechanism of microbubbling plasma (MBP) combined with ferrous ions (Fe²⁺) to activate peroxymonosulfate (PMS) and peroxodisulfate (PDS) in degrading CFX were compared. The effects of the dosages of PMS/PDS and Fe²⁺, plasma discharge voltage, and gas flow rate on the degradation efficiency were investigated systematically. Under optimal conditions, the degradation rate of CFX reached 90.75 %, which was significantly higher than that of MBP alone (a 27.81 % increase) and the MBP/PDS system (a 23.76 % increase), indicating a high degree of synergy among MBP, Fe²⁺, and PMS. The energy efficiency of this system was as high as 1.95 g/kWh. Ultraviolet–visible spectroscopy and total organic carbon analysis indicated that the addition of PMS and Fe²⁺ promoted the degradation and mineralization of CFX. The detection of reactive oxygen and nitrogen species combined with radical scavenging experiments confirmed that singlet oxygen (¹O₂), hydroxyl radicals (·OH) and sulfate radicals (SO₄·⁻) were the most important active species in the degradation process. Based on the results of a liquid-chromatography–mass-spectrometry analysis, three main CFX degradation pathways were identified. In addition, the toxicities of CFX and its degradation intermediates were evaluated using toxicity assessment software. This study provides a new plasma-based method for the degradation of CFX, which has value as a reference for the future treatment of antibiotic-polluted water bodies.