Millions of tons of hazardous iron oxide residues are produced during the iron purification process of sulphate leaching solutions in nonferrous metals hydrometallurgy industry per year. The generated iron oxide residues, which mainly contain goethite and gypsum precipitates adsorbing the hazardous elements of arsenic, sulfur, zinc, and germanium, pose great threats to the local ecological environment and human health. We proposed a novel method, treatment and recovery of goethite and gypsum by the synthetic magnetic nanoparticles (MNPs) such as á-Fe3O4 and ã-Fe2O3, to treat the residues efficiently and cost-effectively. MNPs served as the magnetic crystal nuclei of the goethite precipitates during the iron purification process, and the goethite and gypsum precipitates formed under this condition can be separated in magnetic field. Subsequently, the magnetic crystal nuclei were cycle used by rod milling and magnetic collecting the obtained goethite precipitates to cut costs. Both the precipitates were digested as the raw materials of iron making and building materials, respectively. Additionally, we found that the separation efficiency of the goethite and gypsum precipitates was much higher when ã-Fe2O3 was used as the crystal nuclei, indicating that the surface of ã-Fe2O3 was more favorable for the formation of goethite particles than á-Fe3O4.