The mineral processing industry requires alternative separation techniques to help combat rising energy costs and decreasing ore grades. Dielectrophoresis may be one such technology. Dielectrophoresis is the translational motion of neutral matter caused by polarisation effects in a non-uniform electric field (Pohl, 1978). It uses a non-uniform electrical field to separate particles on the basis of their permittivity. In order to determine its viability, the dielectrophoretic force was measured for individual mineral particles.
In order to measure the dielectrophoretic force on mineral particles a simple apparatus was constructed. The deflection of a particle in a non-uniform electrical field was used to quantitatively measure the dielectrophoretic force. The dielectrophoretic force was initially measured on single mineral particles of chalcopyrite, galena and quartz to determine the effect of particle size, position and shape. The variation due to particle size, position and shape was required to validate the relationships predicted by the force equation, and remove possible sources of error from further experiments. 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. The particle shape, specifically the aspect ratio and centre of gravity, also has a large effect on the experienced force.
The response of composite particles to dielectrophoresis was also investigated. The electrical properties of composite materials involve complex relationships between the permittivity, shape and distribution of the individual grains within the materials. The relationship between composition and dielectrophoretic force was measured on single particles from a number of sources. These results were used to populate a model separator that could predict the separation characteristics of the samples.
The insights gained from this model separator helped deduce potential applications of the technology. There are many areas of mineral processing that would benefit from the application of dielectrophoresis. These include: coarse removal of gangue, recovery of ultra-fine particles, upgrading of flotation concentrates, or simply as a laboratory analysis technique.