RU2736620C2 - Electrolysis cell for extraction of bismuth from lead alloy in electrolyte of sodium hydroxide - Google Patents

Abstract

FIELD: technological processes; electricity.

SUBSTANCE: invention relates to electrolysis cell and electrolyte for extraction of bismuth from lead alloys in electrolyte of sodium hydroxide. Electrolysis cell comprises an anodic heated bath and a cathode bath with a mixer made up of a double mixer made from an upper and a lower mixers, wherein the upper mixer is arranged at the level of the upper level of the cathode bath and consists of a disc and a cone, installed with a gap between the disc and the base of the cone, wherein cone walls are perforated to draw foam electrolyte through perforation of cone and ejection thereof to wall of anode through gap between disc and cone base, lower mixer is made in form of propeller with inclined blades and arranged to allow immersion to bottom, and cathode bath is installed on tray for collection of slurries. Electrolyte for extraction of bismuth from alloys in electrolyte based on sodium hydroxide in electrolysis cell contains 5-10 % of sodium sulphite.

EFFECT: higher extraction of bismuth metal at anode with extraction of 90 % and possibility of maximum separate oxidation of antimony into sludges with extraction of 80 %.

2 cl, 1 dwg

Description

The invention relates to the refining of heavy non-ferrous metals by electrolysis in molten salts.

Known analogue of the electrolyzer [1], containing an anode bath designed to melt sodium hydroxide. A cathode bath is concentrically installed inside it. The cathode metal and sodium hydroxide electrolyte in the electrolyzer are stirred with a stirrer.

The disadvantage of the analogue is that the mixer does not contribute to the separation of impurities. The stirrer creates only the uniformity of the concentrations of the compounds and impurities formed in the entire volume of the cathode metal and electrolyte.

As a prototype adopted [2. RU 2254389 C1, C22B1 13/06, 20.06.2005] electrolyzer and electrolyte for the extraction of bismuth from lead alloys in sodium hydroxide electrolyte.

The method of refining lead from bismuth is carried out using molten caustic soda as an electrolyte. The electrolyzer contains a boiler with an initial lead-bismuth alloy with a submerged stirrer and is filled with an electrolyte from a caustic soda melt, in which an anode - a steel disk is immersed. From cathode lead, bismuth is accumulated in the electrolyte in the form of a suspension of Na ₃ Bi compounds. When the electrolyte is leached in water, the compound decomposes and a bismuth sponge is obtained. Pure lead remains at the cathode.

The disadvantage of the prototype in the need for an additional operation - the leaching of the electrolyte in water to isolate the bismuth sponge, and there is a loss of alkali. In addition, when processing antimony alloy, an alloy of bismuth with antimony will be obtained.

The technical result is to increase the degree of release of metallic bismuth at the anode with the provision of separate maximum oxidation of antimony into slimes. In the electrolyzer, a double mixer is immersed in the cathode bath 2. The propeller of the lower agitator 4, submerged to the bottom, is equipped with inclined blades, which provide, during rotation, the displacement of the lower metal layers to the surface of separation of the metal with the electrolyte. Unlike the mixer according to the prototype, which provides a uniform concentration of impurities throughout the volume, the proposed lower mixer with inclined blades ensures the rise of the lower layer with increased concentration to the surface layer of the metal of the cathode bath. Since the cathode bath is installed on a pallet, bismuth flowing down the anode wall accumulates in the gap between the anode wall and the pallet wall. Sludge of antimony thiosalts settles on the pallet and accumulates. This separation facilitates the coalescence of the bismuth droplets into a separate phase for unloading. The stirrer at the level of the upper level of the cathode bath 2 consists of a disc 5 and a base of a hollow cone 6, the walls of which are perforated. Since the Na ₃ Bi compound is insoluble in lead, as it is lighter than the metal, the compound accumulates in the form of foam together with unoxidized Na ₃ Sb at the interface between the cathode metal and the electrolyte. In addition to the slow natural diffusion of compounds towards the anode, the overhead jet mixer throws them more intensively towards the anode. Metal having a higher specific gravity than the electrolyte is not entrained through the perforation into the cone cavity.

The electrolyte contains 5-10% sodium sulfite, which oxidizes Sb to strong compounds of sodium oxythiostibnates Na ₃ SbO ₃ and Na ₃ SbS ₃ and converts antimony into sludge. When a direct current passes through a sodium hydroxide solution, sodium is released at the cathode, which binds such impurities as tin, bismuth, antimony dissolved in lead into compounds NaSn, Na ₃ Bi and Na ₃ Sb. The NaSn compound, readily soluble in alkali, accumulates in the electrolyte and, as it accumulates, partially precipitates with the sludge.

Thus, the features characterizing the implementation of the double mixer from the upper and lower mixers, while the lower mixer is made in the form of a propeller with inclined blades and is placed to ensure immersion to the bottom, as well as the placement of the upper mixer at the level of the upper level of the cathode bath, are essential essential features , which lead to an increase in the degree of release of metallic bismuth at the anode, and a separate maximum oxidation of antimony into slimes.

Literature

1. Omelchuk A.A., Zarubitskiy O.G., Opanasyuk V.P., Zakharchenko N.F., Dyakov V.E. Behavior of multicomponent lead-tin alloys at cathodic polarization in sodium hydroxide melt \\ Ukr Khim.zh, 2002, v 68, No. 7-8, p37-43.

2. RF Pat. No. 2254389 - Method for electrochemical refining of lead from bismuth - Chekushin B.C., Baksheev SP., Oleinikova NV; State educational institution of higher professional education "Krasnoyarsk State Academy of Non-Ferrous Metals and Gold" // C22B 13/06; Application: 2003132576 dated 06.11.2003; Op 20.06.2005 Bi No. 17.

Claims (2)

1. An electrolyzer for the extraction of bismuth from lead alloys in an electrolyte based on sodium hydroxide, containing an anode heated bath and a cathode bath with a stirrer placed in it, characterized in that the stirrer is made double of the upper and lower mixers, while the upper mixer is located at the level of the upper the level of the cathode bath and consists of a disc and a cone installed with a gap between the disc and the base of the cone, while the walls of the cone are perforated to draw in the electrolyte foam through the perforation and eject it to the anode wall through the gap between the disc and the base of the cone, the lower mixer is made in the form of a propeller with inclined blades and placed to ensure immersion to the bottom, and the cathode bath is installed on a sludge collection tray. 2. An electrolyte for the extraction of bismuth from lead alloys in an electrolyte based on sodium hydroxide in an electrolytic cell according to claim 1, characterized in that it contains 5-10% sodium sulfite.

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