RU2246549C2 - Method for gallium refining - Google Patents

Abstract

FIELD: non-iron metallurgy, in particular gallium refining.

SUBSTANCE: crude gallium is converted to highly volatile gallium(I) oxide Ga₂O by metal heating in presence of gallium(III) oxide Ga₂O₃ at 500-700⁰C in vacuum to provide a slop. Highly volatile gallium(I) oxide Ga₂O is fed into disproportionation zone under the same conditions followed by disproportionation to form metal gallium and gallium(III) oxide Ga₂O₃ at 700-900⁰C Obtained slop is recycled to reuse by addition to starting crude gallium.

EFFECT: purified gallium with decreased content of Sn, Fe, Al, Si, Ni impurities; reduced waste; and low cost process.

4 tbl, 1 ex

Description

The invention relates to methods for refining gallium and can be used in the electronic industry, non-ferrous metallurgy and other industries involved in the processing of gallium-containing raw materials.

A known method of refining gallium (Ivanova RV Chemistry and technology of gallium. M., "Metallurgy", 1973, p. 355), including the conversion of draft gallium into trichloride GаСl ₂ (III), the action of pure chlorine diluted on the metal nitrogen and thoroughly dried with sulfuric acid, followed by distillation of gallium trichloride when heated to a temperature of 145 ° C. The main disadvantage of this method is the use of chlorine as a reagent, a very toxic substance, which leads to the formation of a large amount of waste during the detoxification operation.

The closest in technical essence to the claimed object is a method (Ivanova R.V. Chemistry and gallium technology. M., Metallurgy, 1973, p. 362), which includes treating the blister gallium melt with chlorine to form gallium dichloride GaCl ₂ ( II). Then the dichloride is disproportionated, the resulting gallium trichloride is distilled in the presence of chlorine under a pressure of less than 1.01 · 10 ⁵ Pa at 180-200 ° C and 1.33 · 10 ⁴ Pa at 160-180 ° C. Then, gallium trichloride is dissolved in water and subjected to electrolysis to isolate gallium in the form of a metal.

The main disadvantages of the proposed method are the following:

- a low degree of purification of gallium during distillation, since along with the formation of gallium dichloride followed by disproportionation to gallium trichloride, chlorides of impurity elements are formed having close boiling points to the main component, gallium trichloride GaCl ₃ (III), polluting the resulting gallium (table 1 );

- high toxicity of the technological process, since the processing of rough gallium is carried out by chlorine - a very toxic substance. The distillation distillation residue, which is gallium trichloride GaCl ₃ (III) and chloride elements of impurities, is a very hygroscopic substance, smokes in air, attracts moisture and turns into an aggressive jelly-like mass, interacts with most metals. Upon dissolution of the obtained gallium trichloride GaCl ₃ (III) in water and subsequent electrolysis in the anode space, chlorine (Cl ₂ ) is also formed, which is very toxic and requires additional detoxification operations, which leads to the formation of a large amount of waste;

- the bottom residue after distillation of gallium trichloride requires additional operations to extract gallium from it, which also leads to the formation of additional waste and makes the process expensive.

Table 1 Component Mp, ° C Bp ° C Traction, ° С GaCl ₃ 77.8 201 FeCl ₃ 309 319 * SnCl ₄ -33 113.7 AlCl ₃ - - 179.7 SiCl ₄ -68.8 57 * - already at 100 ° С it noticeably disappears.

The technical result of the invention is to increase the degree of purification of gallium, reduce toxicity, reduce the amount of waste generated and reduce the cost of the process.

The technical result provided by the invention is achieved by the fact that in this method of purification of gallium, including the conversion of draft gallium into a chemical compound and the production of metallic gallium, characterized in that the draft gallium is transferred in the synthesis zone to volatile gallium oxide Ga ₂ O (I) by heating in the presence of gallium oxide Ga ₂ O ₃ (III) in vacuum at a temperature of 500-700 ° C, with the formation of a still bottom, volatile gallium oxide Ga ₂ O (I) is transferred from the synthesis zone to the disproportionation zone under the same conditions and disproportion the volatile gallium oxide Ga ₂ O (I) is positioned at a temperature of 700-900 ° С to obtain metallic gallium and gallium oxide Ga ₂ O ₃ (III), and the resulting still bottom residue is sent for reuse upon addition to the initial rough gallium.

The production of gallium of a higher degree of purity is achieved due to the fact that the conversion of blister gallium into a chemical compound by the reaction 4Ga + Ga ₂ O ₃ → 3Gа ₂ О results in the formation of a volatile gallium oxide compound Ga ₂ O (I), which can be easily removed under conditions of dynamic vacuum from the synthesis zone, and impurities remain in the evaporator reactor. This is possible due to the fact that most of the impurities form oxides, the melting and boiling points of which are much higher than that of gallium oxide Ga ₂ O (I) (table 2).

table 2 Component Mp, ° C Bp ° C Traction, ° С Ga ₂ o - - > 500 FeO 1371 2512 Sno ₂ 1630 - Fe ₃ O ₄ 1583 2623 Fe ₂ O ₃ 1350 - Nio 1957 CuO 1336 SiO ₂ 1720 Al ₂ O ₃ 2053 > 3000

For elements of impurities that may be present in the initial mixture of rough gallium and gallium oxide Ga ₂ O ₃ (III) not in the form of oxides, the boiling points are given in table 3.

Table 3 Component Bp ° C Fe 3000 Sn 2270 Al 2500 Si 2287 Ni 2900 Cu 2595

Table 3 shows that these temperatures are also significantly higher than that of gallium oxide Ga ₂ O (I).

Thus, gallium oxide vapor Ga ₂ O (I), purified from impurities at this stage, passing through a warmer zone with a temperature of 700-900 ° C, is disproportionate, forming gallium of a higher degree of purity and gallium oxide Ga ₂ O ₃ (III ), which is used repeatedly for the preparation of the initial mixture with rough gallium. Comparative data on the degree of purification of gallium in the present method and the prototype method are shown in table 4.

Using the proposed method for the purification of gallium provides, in addition, reducing the toxicity of the process, reducing the amount of waste and the cost of the process.

Reducing the toxicity of the process is achieved by the fact that when transferring blister gallium into an volatile compound, less toxic gallium oxide Ga ₂ O ₃ (III) is used as a reagent, the reaction produces nontoxic oxide Ga ₂ O (I), and the disproportionation is carried out in a nontoxic medium - in a dynamic vacuum.

Reducing the amount of waste generated is achieved by the fact that the bottom residue is sent not for recycling, but for reuse. In the bottom residue (impurity collector), 5-10% by weight of the initial gallium charge remains (taken in excess). This distillation residue is used repeatedly - it is added to the initial loading of gallium. As the accumulation of impurities exceeds the solubility limit of gallium, the latter is sent to the filtration operation, where insoluble impurities are separated.

Cheaper process is achieved by the fact that the main reagent gallium oxide Ga ₂ O ₃ (III) is used repeatedly, the operation of detoxification of waste is excluded.

It was experimentally obtained that the formation of volatile Ga ₂ O (I) oxide at a temperature of less than 500 ° C does not occur. At a temperature of more than 700 ° C in the synthesis zone in the reactor, simultaneously with the formation of volatile oxide Ga ₂ O (I), the reverse process begins - the disproportionation of Ga ₂ O (I) to gallium and gallium oxide Ga ₂ O ₃ (III), which leads to a sharp yield reduction.

The process of disproportionation occurs at a temperature of 700-900 ° C. At a temperature of less than 700 ° C, the process of disproportionation does not occur. It is impractical to increase the temperature of more than 900 ° C, since the likelihood of contamination of disproportionation products with container materials increases and the cost of electricity increases.

An example of a specific implementation of the method.

On the balance weighed 1.1 kg of rough gallium (gallium is taken in excess of 10% by weight) and placed in a graphite container. 0.672 kg of gallium oxide Ga ₂ O ₃ (III) is weighed and placed in the same container. A filled container is placed in the synthesis zone in a quartz reactor, which is heated by a dual-zone resistance furnace and connected to a pumping system consisting of mechanical and diffusion pumps. A special capacitor is placed in the disproportionation zone onto which gallium and gallium oxide Ga ₂ O ₃ (III) are deposited during disproportionation. The vacuum is turned on, and after reaching a residual pressure of 0.1 Pa, a dual-zone furnace is heated. The heating task is set in such a way that the temperature in the synthesis zone is 500 ° C, and in the disproportionation zone - 700 ° C. For 0.5 hours, both zones enter the mode and then are kept under these conditions for 1 hour. After that, tasks are set for the zones of 700 ° C and 900 ° C, respectively, and after the zones reach the mode after 2 hours, they are kept under these conditions for 0.5 hours. Raising the temperature for two hours to a temperature of 700 ° C in the synthesis zone and 900 ° C in the disproportionation zone provides, on the one hand, the completeness of the synthesis and disproportionation reactions, and, on the other hand, the maximum purity of gallium formed after disproportionation, since with such a slow a rise in temperature excludes the possibility of the transfer of impurity elements from the synthesis zone to the disproportionation zone due to their mechanical capture by Ga ₂ O (I) gallium oxide pairs. At the end of the process, the furnace is turned off, cooling is performed for two hours, the vacuum system is turned off. The reactor is filled with an inert gas, nitrogen. After that, a special capacitor with gallium and gallium oxide Ga ₂ O ₃ (III) is removed. Gallium is poured into a fluoroplastic beaker, weighed and analyzed for impurities by chemical spectral and polarographic methods. Ga ₂ About ₃ (III) is collected in a plastic bag, weighed and sent to prepare the initial mixture.

The remaining examples on the boundary limits of the technological modes of the proposed method are presented in table 4.

The table shows that the degree of purification of gallium by the claimed method increases by the following impurities: Sn, Fe, Al, Si, Ni.

Claims (1)

A method for refining gallium, including the conversion of blister gallium into a chemical compound and the production of metallic gallium, characterized in that blister gallium is converted in the synthesis zone to volatile gallium oxide Ga ₂ O (I) by heating in the presence of gallium oxide Ga ₂ O ₃ (III) in vacuum at a temperature of 500-700 ° C with the formation of a still bottom, volatile gallium oxide Ga ₂ O (I) is transferred from the synthesis zone to the disproportionation zone under the same conditions and the volatile gallium oxide Ga ₂ O (I) is disproportioned at a temperature of 700-900 ° C with iem metallic gallium and gallium oxide Ga ₂ O ₃ (III), and the resultant distillation residue is sent to reuse when added to the unfinished gallium source.