Feasibility study of magnetic separation of sample powders with small difference in their specific gravity, which was ineffective, was carried out by magnetic separation by focusing on the difference in their magnetic properties. An apparatus to separate the ferromagnetic particles from the mixed powder with small difference in its specific gravity was made. To investigate the relation between the sizes of the particles and separation efficiency, systematical examination of the separation ratio was done while changing the sizes of the ferromagnetic and paramagnetic particles. Successful separation of dry powders with small difference in their gravities was achieved in a magnetic field by using this apparatus. With a sample composed of a mixture of Cu-Zn ferrite and Al2O3 with the grain size of 45 μm, the separation efficiency of the Al2O3 was close to 100%. As the size of particles of the mixed powers became smaller, its separation efficiency decreased, which could be attributed to the aggregation/flocculation of each particle.
