Patent GB-1352515-A (GB)
Title: Separation of particulate materials
IPC: G02B5/32
Filed: 1970-04-15
Abstract: 1352515 Inorganic particle treatment ENGLISH CLAYS LOVERING POCHIN & CO Ltd 19 April 1971 [15 April 1970 8 Jan 1971] 18067/70 Heading C1A [Also in Divisions B1-B2] In a method of separating fine particles, having a gravitational settling velocity in a fully flocculated aqueous suspension of not more than 1 mm./hr. at 20 C., of a mineral from a mixture of the fine particles of the mineral and other particles, the fine particles are brought into contact with solid bodies having a mean diameter of at least 10 microns so that the fine particles are preferentially adsorbed in the surface of the solid bodies and the solid bodies holding the adsorbed fine mineral particles are separated from the remainder of the particles. In a first embodiment, an aqueous slurry of particles of a first mineral, e.g. kaolin, is deflocculated by the addition of a deflocculating agent, e.g. a condensed phosphate, a soluble salt of a polysilic, polyacrylic or polymethacrylic acid or a water-soluble carboxylic acidvinyl compound copolymer The deflocculated slurry is brought into contact with coarse particles of a second mineral which are coated with a surface-active reagent. The second mineral may be the same as, or different (e.g. talc or calcite) from the first mineral; it may chemically absorb the surface-active reagent or it may have a surface electrical charge opposite to that of the first mineral. The surface-active reagent may be a long chain amine, polyacrylamide or polyacrylate salt. The fine particles of the first mineral are adsorbed on the coated coarse particles of the second mineral and are separated therewith from the other particles by sieving, by sedimentation of by separation in a hydraulic cyclone. The fine particles of the first mineral can then be separated from the coarse particles of the second mineral by agitation in an alkaline solution, e.g. of sodium hydroxide. In a second embodiment, particles of a first mineral, e.g. kaolin, are made into a pulp and deflocculated. Coarse particles of a second mineral are coated with a surface-active reagent and brought into contact with the pulp so that the fine particles of the first mineral are adsorbed by the particles of the second mineral which are then removed from the suspension by frotte flotation In a first flotation process a 20% solids aqueous slurry of particles of the first mineral and coated particles of the second mineral with the fine particles of the first mineral adsorbed thereon is conditioned by agitation. During or before conditioning, there is mixed with the aqueous slurry a deflocculant, e.g. sodium silicate, and alkali, e.g. ammonium hydroxide, to raise the pH of the slurry and a collector for one of the two minerals, e.g. a fatty acid with 8 to 20 C atoms such as oleic or lauric acid. After conditioning, a frotting agent, e.g. pine oil, or a methyl or ethyl ether of a polypropylene glycol, is added to the slurry. The reagentized slurry is then introduced in a frotte flotation cell and subjected to a frotte flotation process yielding a frotte product and a discharge product, one of which consists of the particles of the second mineral with the fine particles of the first mineral adsorbed thereon, and the other of which consists of the other particles of the first mineral. An alternative second flotation process at a low pH is also described. In a third embodiment, the solid bodies on which the fine particles of the mineral to be separated are adsorbed, are in the form of fibres comprising one or more of the following: (a) fibres, e.g. cellulosic fibres having in their natural state, cations disposed along their length; (b) fibres which can absorb a surfaceactive reagent, e.g. a cationic starch, a polyamine or a polyethylimine; or (c) fibrous minerals, e.g. asbestos.