Evaluation of the potential for using dielectrophoresis to separate minerals

• The application of dielectrophoresis to mineral processing is explored.
• The dielectrophoretic force was measured on quartz and chalcopyrite particles.
• Relationships were found between the force and particle size, shape, and position in the field.
• The test procedure described can be used to measure the permittivity of mineral particles.

The mineral processing industry requires alternative separation techniques to help deal with rising energy costs and decreasing ore grades. Dielectrophoresis is a little known mechanism potentially able to separate mineral particles based on differences in electrical properties. There are many areas of minerals processing that would benefit from the application of dielectrophoresis. These include early removal of gangue, recovery of ultra-fine particles, upgrading of flotation concentrates or simply as a laboratory analysis technique. However, a more thorough understanding of the dielectrophoretic force is required to effectively design a practical separator.The aim of the work described here was to measure the dielectrophoretic force on single particles of chalcopyrite and quartz to determine the effect of particle size, shape and position in an electric field. The force was determined by measuring the deflection of a particle attached to a glass fibre positioned between a pin and plate electrode. The dielectrophoretic force was found to be proportional to particle size cubed and inversely proportional to the distance between the particle and the pin cubed. Particle shape also affects the experienced force, and strategies were investigated to minimise this source of variation. With the effect of these parameters fully characterised, the single particle test cell can be used to determine the permittivity of single particles of various composition.