Fractionating of finest particles using cross-flow separation with superimposed electric field

Abstract

The dispersion of fine particles in a liquid phase with highly specific physical properties is increasing in significance, since these suspensions are often intermediates for the production of modern coatings, structured reinforced plastic or for printed electronics.Production processes like precipitation or crystallization commonly generate particles with broad particle size distributions. In known separation processes, such as sedimentation, filtration or centrifugation, the particles are either classified according to a certain grain size or sorted by a physical characteristic. However, in many applications in which finely dispersed multicomponent mixtures have to be separated, the usage of a single separating feature is no longer sufficient. This is especially relevant, if in addition to small particle sizes (<10 µm) the respective particle fractions in the mixture possess varying surface or material properties, and at the same time industrially relevant product quantities have to be achieved.In this work, a novel multidimensional fractionation technique based on a cross-flow separation of particles with a superimposed electric field has been presented, and the possibility for the application of the developed method as a classification process has been demonstrated. An experimental setup was constructed and the classification with different separation media were experimentally investigated. The influence of hydrodynamic forces in the laminar boundary layer and the electrophoretic forces on the particle movement was revealed with a CFD approach. The used particle system was analyzed with regard to its particle size distribution, shape and electrophoretic mobility for the application in the multidimensional fractionation.Based on CFD simulations, the flow channels and the size of the filter area were designed and the operating conditions of the process were optimized. The developed technique of particle fractionating due to competing hydrodynamic and electrophoretic forces is a promising method for a continuous, highly specific fractionation of micro- and sub-micron suspensions. It allows not only fractionation with regard to the particle size, but also the chemical composition and the physical properties of the individual particles.