Motivation and Background
During the multiple steps of ore processing or recycling, particles can reach the size of a few microns or smaller. Classical separation technologies like froth flotation reach their limits for this ultra-fine particle fraction. Carrier flotation has the potential of separating very small particles by using hydrophobized magnetic microparticles instead of microbubbles.
The preconditions in carrier flotation are an efficient mixing along with a high probability for collision and attachment of carrier and valuable particles. For a deeper understanding of these processes on the microscale, model experiments with fluorescent microspheres as valuable particles are carried out. A collection event, during which a cluster of magnetic nanoparticles is attached to a microsphere, typically consists of three steps:
- Approaching of both particles due to their relative velocity
- Contact of the particle surfaces with attractive particle-particle interaction
- Reorientation of the freshly formed aggregate in the flow field
By applying a magnetic field, large aggregates containing several clusters of magnetic nanoparticles and microspheres are formed. These strongly covered valuable particles can be directed to the desired location in the container and separated. After the magnetic field is removed, the large clusters disaggregate again so that most of the carrier particles can be recovered.
Substeps of a collection event
Controlled movement of covered valuable particles by applying a magnetic field