Improving the separation of plastic waste with magnetic fields

Magnetic density separation has recently been developed by Umincorp. Magnetic density separation uses a ferrofluid that generates a vertical mass density gradient when in the presence of a magnetic field. In other words, as you move from the top of the fluid to the bottom, the apparent mass density of the fluid increases.

When plastic particles are added to this ferrofluid, the various particles move to a height in the fluid where the apparent mass density of the ferrofluid is about the same as the mass density of the plastic particles. Separated plastic can then be reused in higher-value products, and this significantly increases the economic feasibility of recycling. An example of such application can be seen in this video.
The separation process is occurring
inside the magnetic density separator where, at the end of the machine, horizontal plates remove the fluid/particle mixtures at different heights. The different mixtures contain different mass densities of plastic particles and the particles are then separated from the ferrofluid by a centrifuge resulting in plastic particles with a specific mass density range, which can be used as an indicator of the type of plastic in this mass density range.

(More in Innovative Materials volume 6 2021)

‘The article ‘Turbulence and particle behavior in a magnetic density separation application‘ is online>