Electrostatic Separation

ELECTROSTATIC SEPARATION is defined as "the selective sorting of solid species by means of utilizing forces acting on charged or polarized bodies in an electric field. Separation is effected by adjusting the electric and coacting forces, such as gravity or centrifugal force, and the different trajectories at some predetermined time. Separations made in air are called Electrostatic Separation. Separations made using a corona discharge device, are called High Tension Separations. Separations made in liquids are termed separation by Dielectrophesis, and if motion is due to polarization effects in nonuniform electric fields. Electrophoresis is when separations are made if motion is due to a free charge on the species in an electric field. There are no industrial applications of mineral concentrations by electrophoresis of dielectrophesis." 1

Electrostatic separation is important in the production of minerals, also in the reclamation of other valuable materials, as well as the cleaning of some food products. When every effort is being made by Process Engineers to make use of all concentrating equipment available for the recovery of critical minerals and reclaimed materials, the subject of applied electrostatic separation is of interest. Refer to Fig.2, for a diagram of how standard electrostatic separators function.

Fig. 2, Typical Electrostatic Separator Diagram
A very simple demonstration of electrostatic separation can be made by taking a handful of salted peanuts, rubbing the skins off, then taking a comb, rubbing it on fur or the coat sleeve until a static charge has been collected on the comb, and passing it over the peanuts and skins. The skins are easily removed from the peanuts. Hulls may be removed from ground coffee in the same manner. Under the influence of an electrostatic charge there is a difference in the susceptibility and behavior of most materials, minerals, salts, and food products. This can be controlled to a great extent by potential, polarity, temperature, and conditioning of the surface of the particles. Oftentimes, by a combination of these factors, the desired separation is closely controlled.

1. J.E. Lawyer, Electrostatic and Magnetic Separation
2. H. Johnson, Applied Electrostatic Separation
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