GB869367A - Separation of solid particles by electrophoretic means - Google Patents

Abstract

869,367. Separating particles from suspensions electrophoretically. AUSTRALIA, COMMONWEALTH OF. July 3, 1957 .[July 9, 1956], No. 21041/57. Class 41. Particles to be separated are suspended in an insulating carrier liquid of high electrical resistivity, and are coated with a charge modifying substance added to the suspension by which the particles move in a desired direction to an electrode when an electric field is applied, which electric field is of a magnitude insufficient to cause ionisation of the carrier liquid. In Fig. 1 particles 1, 2 are suspended or dispersed in a carrier liquid 3 contained in an insulating vessel 4. Electrodes 5, 6 are disposed at a distance greater than that at which ionisation or arcing occur e.g. in the case of carbon tetrachloride and a voltage of 15,000, the electrodes are 1 inch apart. The added coating material imparts a change in the inherent electric charge on the particles which are separated by moving to the electrode of opposite polarity or of different charge value. A removable screen, e.g. a paper sheet or metal surface, may be introduced between the electrodes, and thus become coated with particles of different nature on each side. In a continuous separation process, Fig. 6, mixed coated particles and carrier liquid pass through a pipe 12 into the container 4. Belts 24, 25 are supported on rollers 14, 18 forming electrodes, and a voltage is applied between the fixed electrode 5 and roller 14, and similarly between electrode 6 and roller 18. The particles separate and collect on belts at 7, 8 and are removed by scrapers 22, 23. Particlefree liquid is discharged through a pipe 13 and is re-used. In a further modification, one electrode is formed by a conductive lining to a vessel having an insulated casing, and a tubular member mounted therein comprises the other electrode. The particles to be separated may be mixtures of mineral substances, emulsified particles e.g. paints and pigments, and the charge modifying substance may be a dye, resin, oil, wax or gum. For examples, it is stated that dispersed particles of copper sulphate, " Monolite " (Registered Trade Mark) pigments, cotton fibre and cadmium sulphide in CCl 4 are attracted to the negative electrode, the addition of gum dammar emulsion reverses the inherent charge and the particles move to the positive electrode. The reverse is the case with shellac, calcium carbonate, sulphur, lithium hydroxide and when talc is used as charge modifying material. A mixture of antimony sulphide and calcium fluoride suspended in CCl 4 is thus separated using added beeswax.