Carbothermal reduction synthesis of zero-valent iron and its application as a persulfate activator for ciprofloxacin degradation

Abstract

• Novel Fe@BC was synthesized by carbothermal reduction method. • Corn straw based-biochar was used as a carbon source to prepare ZVI. • The synthesis process of ZVI was the conversion of Fe 2 O 3 into Fe 3 O 4 , and then into Fe 0 . • Ciprofloxacin was effectively removed by Fe@BC/PS. In the present research, zero-valent iron (ZVI) was synthesized by carbothermal reduction method and its formation mechanism was studied. The obtained material (Fe@BC) was applied as a persulfate (PS) catalyst for ciprofloxacin degradation. Further, Scanning Electron Microscopy (SEM) of Fe@BC has shown that the crystal shape of Fe 2 O 3 changed with the increase in temperature, and also revealed the spherical morphology of ZVI. X-ray Diffraction (XRD) further verified the process of conversion of Fe 2 O 3 to Fe 3 O 4 and then to ZVI. X-ray Photoelectron Spectroscopy (XPS) revealed that the change of iron valence state during the conversion process and the peak area of Fe 2+ increased with sintering temperature. The effect of experimental parameters including pH, Fe@BC dosage, PS concentration and temperature on ciprofloxacin degradation, were thoroughly investigated. The results illustrated that the Fe@BC has excellent catalytic performance and can remove 90.78% of ciprofloxacin within 120 min. Free radical quenching experiments confirmed that the reaction of ciprofloxacin with ∙ OH and SO 4 ∙ - mainly occurs on the Fe@BC surface. Based on the different experiments, it was proposed that degradation mechanism of ciprofloxacin via Fe@BC includes three aspects. Thus, it was found that carbothermal synthesis of Fe@BC is cost effective and potential technology for ciprofloxacin remediation.