PhD defence: Magnetic Sedimentation in Aqueous Ferrofluids for Magnetic Density Separation

Separation of mixed materials, such as household waste, is an important step in the processing of such materials. For instance, separation of different types of plastic is essential in the recycling process. An efficient method for separation of waste materials is magnetic density separation. In this technique, materials are brought into a magnetic liquid, which flows over a magnet. Through a combination of gravity on the material and magnetic force on the liquid, each material will float at a height which is specific for the density of that material. In principle, this process can be applied to all nonmagnetic materials, but the heavier the material, the stronger the magnetic field needs to be.

In this research, we investigated the performance and behavior of magnetic liquids in strong magnetic fields. Not only were several magnetic liquids investigated, but we also developed a model with which the behavior of magnetic liquids in strong magnetic fields can be predicted. The main conclusion is that understanding the behavior of magnetic liquids in weak magnetic fields leads to accurate prediction of the behavior in strong magnetic fields.