The aim of this study was to develop synthetic magnetite nanoparticles (nFe3O4) with preferential reactivity for trace elements (TE) for possible environmental applications as adsorbents. The synthetic magnetite materials obtained through the co-precipitation of both Fe 3+ and Fe 2+ ions (Fe 2+ / Fe 3+ = 0.5) were characterized by a set of complementary techniques such as X-ray diffraction, transmission and scanning electron microscopy, Fourier transform infrared and Raman spectroscopy, and BET adsorption method. The resulting nFe3O4 displayed a wide specific surface area (100 m 2 g-1) with particles reaching a size of about 10 nm, smaller than those of the well-crystallized commercial ones (cFe3O4) estimated at 80 nm while showing a BET surface area of 6.8 m² g-1. The adsorption properties of the synthetic nFe304 magnetite nanoparticles were characterized and compared to commercial analogues with the adsorption of both arsenic and copper. The equilibrium adsorption isotherms were properly fitted with Langmuir and Freundlich equation models. The maximum adsorption capacity for the solid phase, qm, obtained for the adsorption of arsenic onto nFe3O4 had an increase of 69.46% comparative to the value obtained for the adsorption of arsenic on cFe3O4. The results suggested that the iron oxide nanoparticles