Particle technology has made enormous progress in recent years and offers ever broader application possibilities. Engineered Nanoparticles (ENPs) are used in many industries, from tire incorporation to medical technology. This leads to increasing production figures, which will hardly decrease in the future. Separation technology has only been able to keep pace with this progress to a limited extent, although it is crucial both for the production and for the recovery of these particles from the environment. The demand for highly specific particle systems with a number of defined properties is growing steadily, but most separation technologies are optimized for a single particle feature only. For example, filtration processes separate by size or classical magnetic separators separate by susceptibility. In order to fractionate a particle mixture according to several particle properties, a series connection of several separation processes is traditionally implemented, which increases costs and product loss. This motivates the search for new techniques that are capable of separating by several particle characteristics simultaneously and can therefore be described as multidimensional.

Within the framework of this research project, a multidimensional separation process is to be developed that specifically targets the particle size range 100 nm - 10 µm. In simplified terms, magnetic particles are to be selectively agglomerated with the non-magnetic particles and then to be separated in a magnetic field. This process is known as magnetic seeded filtration and is dependent on both particle size and surface properties. Especially the selective agglomeration represents the challenge.  In addition to the application in highly specific, multidimensional classification, this process also shows potential in the clarification of diluted suspensions. Consequently, the application of magnetic seeded filtration to the separation of microplastics from wastewater streams is also investigated.

Figure 1: Schematic illustration of the multidimensional magnetic seeded filtration. Black: Magnetic particles. Green / Red: nonmagnetic particles.