In this work firstly Fe3O4 nanoparticles were synthesized via a sono-chemical method. At the second step magnesium hydroxide shell was synthesized on the magnetite-core under ultrasonic waves. For preparation Fe3O4-MgO the product was calcinated at 400 ºC for 2h. Properties of the product were examined by X-ray diffraction pattern (XRD), scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Vibrating sample magnetometer (VSM) shows nanoparticles exhibit superparamagnetic behavior. The photo-catalytic behavior of Fe3O4- Mg(OH)2 nanocomposite was evaluated using the degradation of a methyl orange (MeO) aqueous solution under ultraviolet (UV) light irradiation. The results show that Fe3O4-Mg(OH)2 nanocomposites have applicable magnetic and photo-catalytic performance
