(208d) Sedimentation Acceleration of Remanent Iron Oxide by Magnetic Flocculation

Sedimentation based separation processes are widely distributed in industrial processes to separate particles from a liquid phase. Since we are stepping into the ?Nanoworld? the demands on effective separation technologies raise rapidly. Classical separation devices can hardly quench these new challenges. As a matter of fact new separation concepts have to be developed. One of these new approaches lies in the application of hybrid separation methods especially in the superposition of magnetic fields for the separation of magnetic particles. The possible product portfolio can be seen in pigment production, nanomagnetics production for electronics and in bio separation. A promising step into that direction demonstrates the magnetic field enhanced cake filtration. As a consequence of this batch process, the development of continuous processes for magnetic field enhanced separation has to be enforced. In sedimentation processes in mass force field the settling behaviour of the particles strongly depends on the physico-chemical properties, concentration and the particle size distribution of the product. To influence the sedimentation of particles a change of especially these parameters is possible. By adjusting the pH for example the interparticle forces, in particular the electrostatic repulsion can be manipulated. For remanently magnetic particles like magnetite also the pre-treatment in an external magnetic field leads to a change of the interparticle interactions. By magnetising the particles apart from van-der-Waals attraction and electrostatic repulsion an additional potential is induced, the magnetic attraction, which easily dominates the other potentials and results in agglomeration in the primary minimum. By sedimentation analysis a wide spectra of parameters like pH, magnetic field strength and concentration have been investigated. The results show a strong increase of sedimentation velocity by magnetic flocculation of the raw suspension. This leads to a raise in throughput due to the acceleration of the sedimentation kinetics by a non-chemical interaction to the physico-chemical properties in the feed stream of the separation apparatus.