GB1209975A - Improvements in the electrolytic refining of metals - Google Patents

Abstract

1,209,975. Fused-salt electro-refining of metals. ASSOCIATED LEAD MFRS. Ltd. and W.D. DAVIS. July 2, 1969 [April 10, 1968, No.17302/68. Heading C7B. Electrolytic refining of metals using a fused salt electrolyte is carried out in a cell containing a lower molten metal cathode 13, an upper molten metal anode 19, a flux (electrolyte) impregnated porous diaphragm 16 beneath and in contact with the anode 19, a layer of molten flux (molten electrolyte) between the cathode 14 and the underside of the diaphragm 16, and another layer of molten flux 20 on top of the anode 19 and in contact with the diaphragm 16. The diaphragm may consist of a flexible felt of ceramic fibres. The cell shown comprises a steel casting 10 lined with blocks of ceramic material 12 which are shaped to form a well 13 in which is contained the cathode 14 and electrolyte layer 15, the well being provided with tubes 27 and 32 which provide a syphon arrangement for the withdrawal of the molten metal deposited at and forming the cathode 14, and also form the means by which the cathode is connected to the source of electrical supply. The diaphragm 16 is supported on bars 17 of ceramic material, and may be separated from the blocks 12 by ribs (9) formed on the blocks, in order to permit escape of gases formed during electrolysis, Fig.3 (not shown). Contact between the anode and the electrical supply is provided by graphite anode conductor 23. The cell is also provided with cooling coils 11 and 29, a thermocouple 24, and a graphite baffle plate 26 to protect the diaphragm from direct impact of added anode metal. The method may be used in the refining of metal, e.g. of lead or lead alloys, or the separation of metals, e.g. pure lead can be recovered from alloy containing antimony, bismuth or tin; lead-tin alloy may be recovered from an alloy of lead-tinantimony; impurities such as arsenic, iron, copper, antimony, and bismuth may be recovered from tin; impurities such as lead, cadmium, tin and copper may be separated from zinc, and a zinc-cadmium alloy may be separated into zinc and cadmium. An oxide precipitating metal may be present in the electrolyte, e.g. stannous chloride may be present in the refining of lead to lessen damage to the diaphragm. The electrolyte may comprise molten salts such as sodium chloride, potassium chloride and the chlorides of the metals forming the anode and cathode.