The present invention relates to a process for the synthesis of iron oxide type magnetic nanoparticles by the reaction of coprecipitation in ionic liquids, comprising dissolving FeCland FeCl, in a 1:2 molar ratio, in 1-butyl-3-methyl imidazole tetrafluoroborate, deoxygenation of the solution with argon and heating the reaction mixture, while magnetically stirring, under argon, gradually from 80°C when the pH is brought to 9-10 with potassium hydroxide, the pH being controlled and maintained for 30 minutes as long as the coprecipitation reaction lasts, thereafter the solution is brought to the room temperature, the formed salts being removed by magnetic separation, the resulting nanoparticles being dispersed into the ionic liquid, followed by adding glycolic acid, the mixture being brought to 80°C while magnetically stirring under argon, when there takes place the magnetite stabilization by the absorption reaction for 1 h at 80°C, thereafter the magnetic nanoparticles are magnetically separated from the ionic liquid, being washed with distilled water and dried in the drying closet at 60°C.
