A facile one-pot synthesis of monodisperse ring-shaped hollow Fe3O4 nanospheres for waste water treatment

• Ring-shaped hollow Fe3O4 nanospheres were prepared by a facile solvothermal method.
• The mean diameter is 150 nm with narrow size distribution.
• The hollow Fe3O4 exhibits hierarchical porous character with large surface area.
• The product shows high pollutant removal capability and can be regenerated easily.

Monodisperse ring-shaped hollow Fe3O4 nanospheres with an average diameter of 150 nm were synthesized using a facile one-pot solvothermal method with NH4Ac as a precipitation agent without any other additives. The results showed that the as-prepared product was composed of aggregated nanoparticles and possessed open holes on the shell; thus, the nanosphere exhibited a hierarchical porous structure. The surface area of the as-prepared product was significantly enhanced compared with that of the solid sample. Moreover, the nanosphere exhibited excellent magnetic properties with high saturation magnetization. When tested as an adsorbent for organic pollutant in waste water treatment, the as-prepared product exhibited rapid adsorption rate, high adsorption efficiency, and quick magnetic separation with the help of an external magnetic field.