The behavior of surface acidity on photo-Fenton degradation of ciprofloxacin over sludge derived carbon: Performance and mechanism

[Display omitted] Sludge derived carbon (SC) has been widely used in advanced oxidation processes as an effective and economic catalyst. In this study, we applied surface modified SC for the first time to catalyze the heterogeneous photo-Fenton process with ciprofloxacin, a highly concerned emerging contaminant, as a model substance. H2SO4 was used to acidify the SCs under varying acid dosages, temperatures, and reaction time lengths. The surface acidity of SCs was quantitatively characterized with NH3-TPD. A strong correlation between the surface acidity and the catalytic activity was clearly demonstrated. The highest catalytic activity was obtained with SC whose acidity was 0.149 mmol·g−1 after being modified with 6 mol·L−1 H2SO4 at −20 ℃ for 24 h. In addition, XRD, XRF, BET, XPS, and HRTEM were also used to characterize the obtained SC. ·OH radicals were found to be the main reactive species by EPR. Ten transformation products were identified by GC–MS, based on which three possible reaction pathways were proposed.