Insights into the mechanism of persulfate activation with nZVI/BC nanocomposite for the degradation of nonylphenol

Nonylphenol (NP) is an endocrine disrupting chemical which is capable of interfering with the hormonal system of various organisms in the environment. In this study, nanoscale zero-valent iron (nZVI) supported on biochar (BC) nanocomposite (nZVI/BC) was synthesized using low-cost rice husk through reduction of ferrous iron with sodium borohydride as a reductant under nitrogen atmosphere. The morphology and structure of nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller studies. The synthesis nZVI/BC nanocomposite is used as an efficient persulfate (PS) activator to generate sulfate radicals (SO4−) for the degradation of NP. The degradation efficiency of NP (20 mg/L) was 96.2% within 120 min using initial dosage of 0.4g/L nZVI/BC3 and concentrations of 5 mM persulfate. The effects of reaction parameters such as initial pH, PS concentration and dosage of nZVI/BC3 nanocomposite were investigated. The presence of oxygen functional groups on the surface of BC and large surface area, nZVI/BC nanocomposite increased generation of SO4− which enhanced NP degradation. The radical scavenger experiments and electron paramagnetic resonance (EPR) studies showed that both SO4− and OH were responsible for degradation of NP. The findings of this study provide new insights into the mechanism of nZVI/BC activating persulfate and its potential applications for the treatment of wastewater.