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 center dot-) 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 center dot- which enhanced NP degradation. The radical scavenger experiments and electron paramagnetic resonance (EPR) studies showed that both SO4 center dot- and (OH)-O-center dot 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. (C) 2016 Published by Elsevier B.V.