Application of dielectrophoresis for the separation of minerals

Comminution is an energy intensive process, accounting for approximately 29% of total mining energy ( Tromans, 2008). Better liberation at coarser size ranges (0.5–2 mm) has been identified by the minerals industry as an opportunity for energy conservation. In order to capitalise on future developments in comminution, an effective coarse particle separation method is required for liberated particles which are too coarse for flotation. This paper reviews the application of dielectrophoresis as a potential technique for the removal of coarse liberated gangue, thereby significantly reducing the volume of ore continuing onto fine grinding. Dielectrophoresis is the translational motion of neutral matter caused by polarisation effects in a non-uniform electric field. A simple apparatus has been constructed, in which the deflection of a particle in a non-uniform electrical field is used to quantitatively measure the dielectrophoretic force on quartz and galena particles of various sizes. The results show that the force increases as a function of voltage squared and particle radius cubed. This technique can potentially be used to measure the effective permittivity of single mineral particles and quantify the effect of particle composition on separation.