Recyclable Fe3O4/hydroxyapatite (HAP) composite nanoparticles have been developed as a novel photocatalyst support based on the embedment of magnetic Fe3O4 particles into HAP via homogeneous precipitation method The resultant nanoparticles were characterized by transmission electron microscope (TEM) Fourier transform infrared (FTIR) spectrometer and X-ray diffraction (XRD) These particles are almost spherical in shape and have a unique size of about 25 nm in diameter The Fe3O4/HAP nanoparticles show superior catalytic activity in the process of the diazinon degradation under UV III in adiation The superparamagnetic properties of the Fe3O4/HAP nanoparticles provide a convenient route for separation of the catalyst from the reaction mixture by application of an external permanent magnet The spent catalyst could be recycled without appreciable loss of catalytic activity (C) 2010 Elsevier B V All rights reserved