Photo-fenton degradation of levofloxacin wastewater by hybrid biochar under circumneutral conditions

Abstract

In this study, the method of zero-valent iron activating persulfate method (ZVI-PS) was employed to dewater sludge, which was then mixed with humic coal (HC) and carbonized to successfully prepare a hybrid biochar catalyst. When applied to treat levofloxacin (LVFO) wastewater in the photo-fenton system, it exhibited excellent performance under circumneutral conditions, effectively addressing the dependence of traditional fenton systems on acidic environments and significantly broadening the pH application range. This study systematically investigated the effects of factors such as catalyst dosage, H₂O₂ dosage, xenon lamp power, and pH on the degradation efficiency of levofloxacin. The results showed that under the conditions of a catalyst dosage of 1 g/L, H₂O₂ dosage of 0.6 mL/L, xenon lamp power of 300 W, and pH 7, the degradation rate of LVFO by the hybrid biochar reached 92.58%, far higher than 55.86% for humic coal. This is primarily attributed to the abundant iron species on the surface of the hybrid biochar, which facilitate iron cycling and thus effectively enhance catalytic activity. Active species quenching experiments revealed that the system degrades LVFO mainly through a non-radical pathway of singlet oxygen (¹O₂), maintaining excellent degradation capacity for LVFO under circumneutral conditions. After 5 cycles of reuse, the iron leaching rate of the catalyst was lower than 0.56%, and it still maintained high catalytic efficiency. A degradation pathway of LVFO was proposed based on three-dimensional fluorescence spectroscopy and detection of intermediate  products.This study provides an efficient, economical, and environmentally friendly solution for treating actual wastewater  containing levofloxacin, demonstrating practical application value.