RU2346067C2 - Method of gallium extraction from wastes of electrolytic refining of aluminium - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention concerns method of gallium extraction from wastes of electrolytic refining of aluminium. Method includes its grinding and leaching by means of alkaline solution. Leaching is implemented at vacuum over surface of solution 100-4000 Pa with atmospheric air inflow till hydrogen concentration less than 4 rev%.

EFFECT: reduction of foam forming at gallium extraction; increasing of safety and controllability of the process.

1 tbl, 5 ex

Description

The invention relates to the field of metallurgy of rare metals, in particular to the production of gallium from waste electrolytic refining of aluminum, such as an anode deposit and a similar spent anode alloy.

The known method (RF Patent No. 2064518 IPC С22 В 58/00, С01G 15/00, application. January 27, 1992, publ. July 27, 1996) extracting gallium from the anode deposit, which involves the processing of the starting material with an alkaline solution at a temperature of 100 ° C and pressure of 1.5-4.5 atm with air supply at a speed of 240-280 l / h. Such a technological technique makes the leaching process extremely explosive, since hydrogen inevitably liberated during dissolution of the aluminum-containing anode deposit in combination with air forms an explosive mixture in a closed volume.

Closest to the claimed technical solution (prototype) is a method for extracting gallium from an anode alloy (Ivanova RV Chemistry and technology of gallium. - M .: Metallurgy, 1973, p. 306-307). The crushed anode alloy is subjected to hydrochemical treatment with a hot solution of sodium hydroxide at normal pressure. The leaching process of the crushed anode alloy is accompanied by rapid evolution of hydrogen and, as a result, abundant foaming, which greatly complicates the process, and in some cases makes it completely uncontrollable. In addition, hydrogenated foam, especially coarse foam, is capable of burning and popping in a large volume.

The aim of the invention is to reduce foaming during the extraction of gallium from metal waste from electrolytic refining of aluminum.

As a result, this provides increased safety and controllability of the leaching process of the anode deposit and the spent anode alloy similar in composition to the method for extracting gallium-containing gallium-containing waste from aluminum electrolytic refining.

The technical result is achieved by the fact that in the method of extracting gallium from waste from the process of aluminum electrolytic refining, including grinding and leaching with an alkaline solution, leaching is carried out by diluting 100-4000 Pa with a suction of atmospheric air to a hydrogen concentration of less than 4 vol%.

The essence of the method is as follows.

The height of the foam layer above the surface of the solution is directly proportional to the rate of hydrogen gas evolution and inversely proportional to the rate of destruction of the foam cells. All other things being equal, excess pressure outside each individual cell stabilizes it and extends its life. The rarefaction outside the cell leads to its expansion and rapid destruction. As a result, the lower the pressure in the reactor for leaching waste aluminum electrolytic refining, the smaller the foam layer above the surface of the solution. If at the same time there is a sufficient air leak in the reactor, then fresh air dilutes hydrogen to a concentration below explosive (less than 4 vol.%). Thus, the process of leaching waste aluminum electrolytic refining under vacuum with a sufficient suction of air becomes adjustable from the point of view of foaming and safe, since it eliminates the possibility of accumulation of explosive mixtures.

The effect of pressure in the reactor for leaching waste aluminum electrolytic refining on the height of the foam layer above the surface of the solution are given in the following examples.

Example 1

Upon receipt of gallium according to the claimed method, the anode precipitate was subjected to grinding by crushing to a particle size of -3 mm The crushed material was leached in a laboratory cell with a stirrer with a sodium hydroxide solution containing 166 g / L Na ₂ O _ku at a temperature of 100 ° C. The leaching of the anode deposit was carried out in a box under a vacuum of 100 Pa with a suction of atmospheric air. The solid phase was introduced in an amount providing a calculated caustic module of 2.0-2.5. The height of the foam above the surface of the solution is about 30 mm. The hydrogen concentration measured above the upper section of the cell using a portable analyzer AVP-02, amounted to 3 vol.%. The process was satisfactorily controlled and was successfully completed. The foam was small-meshed, unstable and non-combustible.

Example 2

Obtaining gallium by the present method was carried out in the same manner as described in example 1, except that the leaching process of the anode deposit was carried out under a vacuum of 2000 Pa. The height of the foam above the surface of the solution is about 15 mm. The hydrogen concentration above the upper section of the cell was 1.5 vol.%. The process was well controlled and was successfully completed. The foam was small-meshed, unstable and non-combustible.

Example 3

Obtaining gallium by the present method was carried out in the same manner as described in example 1, except that the leaching process of the anode deposit was carried out under a vacuum of 4000 Pa. In this case, the height of the foam above the surface of the solution is about 5 mm. The hydrogen concentration above the upper section of the cell was 0.5 vol.%. The process was well controlled and was successfully completed. The foam was small-meshed, unstable and non-combustible.

Example 4

Obtaining gallium according to the prototype was carried out in the same manner as described in example 1, except that the leaching process of the anode deposit was carried out at normal pressure. The hydrogen concentration above the upper section of the cell was 13 vol.%. During leaching, the height of the foam layer exceeded 150 mm and poured over the edge. As a result, 80% of the initial solution volume passed into the foam. Small particles of the anode alloy were floated by foam and carried out of the cell. The foam was coarse-grained, capable of catching fire with cotton on contact with an open flame.

Example 5

Obtaining gallium in violation of the regime factors of the proposed method was carried out in the same manner as described in example 1, except that the leaching process of the anode deposit was carried out under a vacuum of 50 Pa. The height of the foam above the surface of the solution is about 100 mm. The hydrogen concentration above the upper section of the cell was 4 vol.%, Which corresponds to the explosive hazard limit value. Coarse foam, capable of catching fire with cotton on contact with an open flame.

Obviously, the second transcendental value (a vacuum of more than 4000 Pa) will not lead to a decrease in the technical result of the proposed method, however, achieving a high vacuum (vacuum) is expensive, and therefore impractical.

For the convenience of comparing the results, the examples are summarized in the table, from which it follows: the lower the pressure in the reactor for leaching aluminum electrolytic refining wastes, the smaller the foam layer above the solution surface.

Example No. Way Vacuum above the solution surface, Pa The height of the foam layer above the surface of the solution, mm The concentration of hydrogen above the surface of the solution, vol.% one one hundred thirty 3 2 The claimed 2000 fifteen 1,5 3 4000 5 0.5 four According to the prototype 0 More than 150 13 5 To beyond fifty one hundred four

Claims (1)

A method for extracting gallium from aluminum electrolytic refining wastes, including grinding and leaching with an alkaline solution, characterized in that the leaching is carried out by diluting 100-4000 Pa with a suction of atmospheric air to a hydrogen concentration of less than 4 vol.%.