Sink-float separators using permanent magnets and water based magnetic fluid

The development of sink-float separators for materials of different densities, which utilize the levitation force of magnetic fluid, have been recently reported. The system usually consists of an electromagnet, separation cell, equipment for recovery of magnetic fluid smeared on the separated products, and controlling system. This paper describes and discusses the construction of sink-float separators using permanent magnets and provides test results for artificial mixtures of nonferrous metals. Ferrite magnet and rare-earth cobalt magnet were used as magnetic field generators in two separators. One for separating aluminum from other nonmagnetic metals, and the other to separate copper, zinc and lead from each other. A series of tests were performed on samples of 6 to 30 mm size, and it was found that the separators operated as expected. The separation of finer metals, however, proved difficult due to the attractive force which acts between nonmagnetic bodies immersed in magnetic fluid in a magnetic field. The chemical process to recover the magnetic fluid from smeared separation products is also proposed.