“Dry Flotation”: A Novel Electrostatic Separation by Modifying Particle Surface with Surfactant and Electrolyte

Electrostatic and/or high tension separation has been used for the separation of rare metal bearing minerals, foods, industrial wastes, and so on. Since the separation is achieved by the difference mainly in surface conductivity of materials, the efficiency in humid circumstances is very low and the applicability is considerably limited. We applied the following two-stages pretreatment technique to the electrostatic separation process, which involves (1)adjustment of surface wettability by adsorbing surfactant on particle surface, and (2)control of the surface conductivity by spraying electrolyte aqueous solution. The addition of this pretreatment technique has been found to create a new selectivity. High separation efficiency was achieved even in humid circumstances and selectivity can also be obtained among non-conductor materials. The selectivity created by this process is very similar to that of flotation. This separation technique could be applied to the processing of many kinds of solid waste materials to be separated.