Degradation mechanism of norfloxacin in water using persulfate activated by BC@nZVI/Ni

In this work, biochar-supported nano zero-valent iron/nickel bimetallic composite (BC@nZVI/Ni) was synthesized using liquid phase reduction method and used to activate persulfate (PS) to degrade norfloxacin (NOR) in water. The synthesized BC@nZVI/Ni was characterized using scanning electron microscope (SEM), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The effects of various reaction parameters, such as mass ratio of nZVI/Ni to BC, PS concentration, initial pH value, temperature, humic acid and the inorganic anions on NOR degradation were investigated using the system of nZVI/Ni/PS. The results showed that the system of nZVI/Ni/PS showed the higher degradation efficiency. The quenching experiments and EPA analysis manifested that center dot SO4- was the predominant radical species in acidic and neutral conditions, while center dot OH played an important role in alkaline environment. Matrix-assisted laser desorption-ionization time of flight mass spectrometry (MALDI-TOF MS) analysis illustrated that NOR can be degraded through multiple routes, such as decarboxylation, defluorination and cleavage of piperazine ring in the presence of center dot SO4- and center dot OH. These results demonstrated that nZVI/Ni/PS process was a promising strategy for treating norfloxacin-containing wastewater.