In this study, Fe@Fe 2 O 3 core-shell nanowires were first used as a novel Fenton iron reagent. The nanowires were synthesized through the reduction of ferric chloride aqueous solution by sodium borohydride at ambient atmosphere, without protection of inert gases or vacuum. Rhodamine B (RhB) could be efficiently degraded in aqueous media by a novel sonochemical-assisted Fenton (sono-Fenton) system based on these Fe@Fe 2 O 3 core-shell nanowires. The RhB degradation processes were monitored by UV-vis spectroscopy and total organic carbon (TOC) analysis. Fe@Fe 2 O 3 core-shell nanowires showed much higher activity in the sono-Fenton system than other iron reagents such as commercial zerovalent iron powders (Fe 0 ), ferrous ions (Fe 2+ ), and ferric ions (Fe 3+ ). It was found that near 100% decoloration and over 60% TOC removal of RhB (5 mg‚L -1 ) could be achieved in 60 min by this novel sono-Fenton system with 0.018 mol‚L -1 Fe@Fe 2 O 3 coreshell nanowires. This new iron reagents before and after the sono-Fenton reaction were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The characterizations found that the nanowires were transferred to nanotubes/nanoparticles covered with Fe 3 O 4 / Fe 2 O 3 after the sono-Fenton process. A possible mechanism of sono-Fenton degradation of RhB with Fe@Fe 2 O 3 nanowires was proposed on the basis of the experimental results. It involved homogeneous Fenton and heterogeneous Fenton oxidative degradation simultaneously. The high activity of core-shell Fe@Fe 2 O 3 nanowires and the success of their mass production make them attractive for the treatment of organic pollutants in water.

In this study, we developed an efficient and reusable sono-Fenton system with Fe@Fe 2 O 3 core-shell nanowires as the iron reagent. Similar to our previous sono-Fenton system working at pH ) 2, this system could also much more effectively degrade rhodamine B than those with Fe 2+ , Fe 2+ /Fe 2 O 3 , or commercial zerovalent iron particles as the iron reagents at neutral pH. The nature of the Fe@Fe 2 O 3 nanowire Fenton iron reagent was examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). It was found that this novel Fenton iron reagent could be recycled in this sono-Fenton system working at neutral pH. More importantly, the efficiency of this neutral-pH sono-Fenton system with adding 0.001 mol L -1 of Fe 2+ even reached 92% for degrading RhB at neutral pH. This efficiency was close to that of our previous sono-Fenton system working at pH ) 2. We proposed a possible mechanism for the sono-Fenton degradation of RhB over Fe@Fe 2 O 3 core-shell nanowires at neutral pH, which involved an in situ recycling of iron species (Fe 0 f Fe n+ f Fe 2 O 3 ). We believe that this economical and facile sono-Fenton system based on an Fe@Fe 2 O 3 core-shell nanowire iron reagent may be applied to practical wastewater treatment.