GB1042733A - Electrolytic recovery of alkali metals - Google Patents

Abstract

<PICT:1042733/C6-C7/1> <PICT:1042733/C6-C7/2> <PICT:1042733/C6-C7/3> In recovering alkali metal by cathodic deposition from an electrolyte consisting of a complex compound containing an organoalkali metal-aluminium or -boron complex compound using a cathode resistant to both alkali metal and the electrolyte, the cathode is coated before electrolysis with cadmium or gold to improve its wettability by alkali metal. Typically the coating is applied to a thickness of 1 to 5 m on a substrate of copper. If other metals such as iron, alloy steel, aluminium or nickel are used, they are preferably copper plated if a cadmium coating is to be used. The process is described for recovering sodium from a sodium amalgam anode. The cathode may be of large surface area being formed by a series of connected spaced regularly perforated plates or grids arranged with the apertures in register or staggered. Alternatively the cathode may comprise an apertured plate 10a with pins (Figs. 8 to 10 not shown) or tubular projections 24 extending into them from a plate 10b. Instead of circular apertures, close packed rows of square, hexagonal or equilateral triangle openings may be provided. Collected sodium is removed in a direction parallel to the planes of the plates. For example with a horizontal amalgam anode 20 sodium deposited within the copper grid cathode structure 16 is tapped off by overflow 23. Electrolyte 18 is maintained at a pressure sufficient to prevent the sodium which is more dense falling downwardly out of the cathode, electrolyte passing through pipes extending through the cathode for return via the impeller pipe. The cell, cathode support and feed pipes are of insulating material. If desired the cathode may be provided with an insulating net for assisting retention of the sodium as in Specification 955,252. In another arrangement (Fig. 19 not shown) the electrolyte pressure is provided hydrostatically and electrolyte which passes through the grid portions of the cathode floats atop the sodium. Instead of a sodium amalgam pool the anode may comprise a vertical rotating disc fed with amalgam (Fig. 7 not shown). Impure sodium may be refined by supporting it as anode within one of the net-like electrode structures described above as cathodes. By using a cathode as described as the lower electrode in an electrolyte containing a sodium-aluminium alkoxy triethyl with an aluminium anode above it, sodium is formed at the cathode and alkoxy aluminium diethyl is formed at the anode.