Ultrasound synergistic iron-nitrogen biocarbon activated persulfate to ofloxacin degradation

An iron-nitrogen co-doped cattail carbon (Fe-N@CC) was prepared by chemical modification using potassium ferrate, urea, and biomass of cattail. The specific surface area of Fe-N@CC was 552.13 m2/g, with abundant functional groups on the Fe-N@CC surface. The synergistic manner with physical field strength of ultrasound (US) and chemical modification of Fe-N@CC was applied in the activation of persulphate (PS). The US/Fe-N@CC/PS system achieved the highest degradation efficiency compared to other systems, with 99.72% ofloxacin (OFX) degradation rate within 30 min. The results indicated that the non-radical pathway dominated by singlet oxygen (1O2) played an important role in the US/Fe-N@CC/PS system for OFX degradation. The sp2-hybrid carbon of C-N, pyridinic N, and α-Fe0 as the active site in Fe-N@CC, while effects of US such as strong turbulence, liquid flow contribute to enhanced mass transfer, cavitation effects, and locally higher pressures and temperatures, these synergistic effects promoted electron transfer and production of reactive oxygen species during OFX degradation in US/Fe-N@CC/PS system. The ten intermediates and four degradation pathways of OFX were determined by liquid chromatography-mass spectrometry and density functional theory calculations. The toxicity of most intermediates was lower than that of the parent OFX as determined by the toxicity analysis software in the US/Fe-N@CC/PS system. The new approach to synergistically activating PS by US physical field strength and with chemical modification using Fe-N@CC had provided an efficient method for the treatment of antibiotics.