Safe and efficient degradation of metronidazole using highly dispersed ß-FeOOH on palygorskite as heterogeneous Fenton-like activator of hydrogen peroxide.

In this study, the highly dispersed ß-FeOOH on palygorskite (H-ß-FeOOH/PAL) was prepared and investigated as Fenton catalyst for H2O2 activation towards metronidazole (MTZ). Based on electron spin resonance and probe techniques, hydroxyl radicles (•OH) as main reactive oxygen species was confirmed, and much more •OH were generated over H-ß-FeOOH/PAL than T-ß-FeOOH/PAL using traditional impregnation method. The enhanced Fe(III) to Fe(II) cycle due to the highly dispersed ß-FeOOH leads to the fast degradation of metronidazole over H-ß-FeOOH/PAL. 92.8% of MTZ degradation efficiency was achieved within 180 min by adding 17 mmol/L H2O2 and 40 mg/L of H-ß-FeOOH/PAL at pH 6.0. The bacterial cytotoxicity during MTZ degradation process also decreased with reaction time and achieved zero at 66 min, indicating MTZ was not only efficiently degraded but also safely transformed. Besides, the possible MTZ degradation pathway was further proposed based on the intermediates identified by HPLC-MS.