Fe@Fe2O3 Core−Shell Nanowires as Iron Reagent. 1. Efficient Degradation of Rhodamine B by a Novel Sono-Fenton Process

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 core−shell 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.