Patent GB-613841-A (GB)
Title: Improvements in or relating to electro-recovery of metals
IPC: C25C5/02
Filed: 1945-11-01
Abstract: 613,841. Making composite plates and metal powder. NATIONAL LEAD CO. Nov. 1, 1945, No. 29039. Convention date, Jan. 13. [Class 83 (ii)] [Also in Group XXXVI] A process for the recovery of a metal in powder or pulverulent form includes electrodeposition of the metal (see Group XXXVI) upon a thin open-work pattern of electricallyconductive material in which the total projected area of the openings constitutes from 15 to 90 per cent of the projected area of the pattern and the openings do not exceed 0.5 in. in width, until the thickness of the deposit exceeds 0.03 in., and then pulverizing the deposit and pattern without prior separation. The pattern preferably consists of a highly perforated sheet or strips of strands or of a screen or gauze, the above area ratio corresponding to from about 2 to about 40 mesh, the preferred range being from 40 to 80 per cent (from 12 to 24 mesh) using wire of diameter 0.05 in. to 0.008 in. in the range 0.10 in. to 0.001 in. and generally of the same metal as that being deposited, or one which will form an alloy therewith, or of a plastic substance coated or impregnated with a conductive material and it may be grooved or crimped. It may also be cylindrical or disc-shaped. The width of the openings should preferably be less than 0.10 in. and the thickness of the deposit may exceed 0.3 in. Gold, silver, copper, manganese, iron, nickel, cobalt, zinc, cadmium, tin and lead may be recovered by this process. Preferably copper is used for the pattern when recovering manganese. The electrodeposition is generally continued until the deposited metal has entirely filled the pattern openings but may be terminated before this occurs. The pattern with the deposit is then broken away from the frame work in which it has been supported, and pulverized. For the recovery of iron a 16-mesh screen composed of iron wire of 0.01 in. diameter is used, weighing about 0.11 lbs. per square foot. Fig. 3 shows a cross-section of the slab 8 obtained, which may weigh more than 200 times as much as the screen 7 embedded in it. When the temperature of electrolysis is kept below 60‹ C. brittle iron is produced and the slab shown is first crushed, e.g. in a jaw crusher, and then pulverized, e.g. in a ball-mill, to a fineness of 100 mesh or less, preferably in a neutral atmosphere, e.g. N 2  or CO 2 . Any portions of the screen (<SP>1</SP>/ 5  or less) not reduced to the proper particle size may be removed by sifting. The screen will constitute 0.33 to 0.5 per cent by weight of the deposited iron. If the screen and deposit are 98 and 99.99 per cent pure iron respectively, the purity of the final powder containing all the screen will be 99.98 per cent. For an extremely pure powder, the screen is made from a non-magnetic substance and the powders separated by a magnetic process. The Specification as open to inspection under Sect. 91 comprises also rolling, forging, melting or the like of the slab, and annealing in the presence of reducing gases. Also, the deposit may be removed from the pattern by melting where the melting points differ widely, e.g. lead from a stainless steel pattern. This subject-matter does not appear in the Specification as accepted.