GB337738A - Improvements in or relating to processes for the purification of graphites - Google Patents

Abstract

337,738. Rabetrano, E. Nov. 9, 1928, [Convention date]. Wet separating.-Graphite in minerals of low carbon content is separated from silica, silicates, oxides of iron &c. by fractional precipitation in a liquid containing a colloid, the fraction containing the graphite being afterwards subjected to electro-osmotic action in a vessel in which the settlement of all the particles in suspension is retarded either mechanically or by the presence of a colloid or by both methods simultaneously. The mineral, ground and roughly purified by centrifugal action and decantation, is suspended in a liquid, preferably water, to which is added a colloid to increase the viscosity of the liquid, such as dextrine, alumina, saponin, gelatine or potassium silicate. The treatment may be repeated with the precipitated fraction containing the graphite which is then introduced into a vessel 1 through passages 2 and 2a. Perforated plates 3 maintained at different electric potentials are arranged so that the graphite is attracted to the upper plate and impurities to the lower. An agitator 7 to cause the liquid to circulate upwardly and so to delay the precipitation of the particles is located between the plates and a stirrer 8 above the upper plate. The graphite passes out at 4 and impurities are discharged at 5. The precipitation of the particles may also be delayed by centrifugal action or by the addition of a colloid or bv a combination of mechanical and chemical methods. Colloids may also be added to reverse or vary the potentials of the particles.