Magnetic separation of metal sulfides/oxides by Fe3O4 at room temperature and atmospheric pressure

The recovery of heterogeneous catalysts can save costs and avoid secondary pollution, but its separation efficiency and recovery cost are limited by conventional separation methods such as precipitation–flocculation, centrifugation and filtration. In this paper, we found that surface-defective metal sulfides/oxides (WS 2 , CuS, ZnS, MoS 2 , CdS, TiO 2 , MoO 2 and ZnO) commonly used in advanced oxidation processes (AOPs) could be magnetically recovered at room temperature and atmospheric pressure by mechanically mixing with Fe 3 O 4 . Zeta potential, Raman, X-ray photoelectron spectroscopy (XPS) and electro-spin resonance (ESR) spectra were measured to explore the mechanism of the magnetic separation phenomenon. The exposed active metal sites on the surface of defective metal sulfides/oxides are beneficial for the formation of chemical bonds, which are combined with electrostatic force to be responsible for the magnetic separation. Moreover, other factors affecting the magnetic separation were also investigated, such as the addition of amount of Fe 3 O 4 , different solvents and particle sizes. Finally, WS 2 was chosen to be applied as a co-catalyst in Fenton reaction, which could be well separated by the magnetic Fe 3 O 4 to achieve the recycle of catalyst in Fenton reaction. Our research provides a general strategy for the recycle of metal sulfides/oxides in the catalytic applications.