JPH0674461B2 - Method for collecting metallic gallium - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for electrolytically collecting gallium from a gallium-containing alkaline solution.

More specifically, it relates to a method mainly composed of pretreatment for electrolysis of a gallium-containing alkaline solution.

2. Description of the Related Art Recently, gallium has been used as a raw material for semiconductors such as gallium-arsenic compounds and gallium-phosphorus compounds, which have been recognized as having excellent performance as semiconductors, and the demand has increased.

However, although gallium is widely distributed in the crust, no specific ore has been found. Therefore, in order to obtain gallium, the present condition is that gallium, which is contained in a small amount in zinc ore, bauxite ore, germanium ore, etc., is recovered as a by-product from the production of zinc, aluminum, germanium, etc., which are the main components. .

For example, bauxite ore used to produce aluminum contains gallium in an amount of about 10 to 100 mg / Kg, which is entrained when extracting the aluminum content with an alkali such as sodium hydroxide, and is used as an alkaline solution of circulating sodium aluminate. It is known that the so-called Bayer solution is concentrated to about 100 to 400 mg / l. The following methods are known as methods for recovering gallium from this liquid.

For example, as described in JP-A-58-49620, JP-A-58-52450, and JP-A-58-9688, gallium is adsorbed using a chelate resin and then eluted with hydrochloric acid, sulfuric acid, etc. Add alkali to make an alkaline solution of gallium,
Method for obtaining gallium by electrolysis of this, Japanese Patent Publication No. 33-4056
As described in Japanese Patent Laid-Open Publication, a liquid containing gallium is electrolyzed by using mercury as a cathode, and gallium is electrodeposited, then dissolved with sodium hydroxide, separated from mercury, and then a cathode such as stainless steel is used again. Electrolysis, US Patent No.
As disclosed in the invention of No. 2582376, there is known a method of obtaining gallium by blowing carbon dioxide gas to precipitate and separate an aluminum content and a gallium content, leaching the gallium content with an alkali, and then electrolyzing in a sodium hydroxide solution.

On the other hand, as a method for recovering gallium from zinc ore, after extracting from zinc ore with sulfuric acid, the gallium content is extracted, purified, and concentrated by repeating neutralization, sulfurization treatment, acid dissolution, and alkali dissolution, and then sodium hydroxide. A method of electrolyzing in a liquid is known.

In the case of carrying out by such a method, since heavy metal ions are contained as an impurity component in the electrolytic solution, for example, in the presence of vanadium, current is consumed due to change in valence from pentavalent to octavalent during electrolysis. As a result, the current efficiency of gallium deposition is significantly reduced, or gallium deposition does not occur.
It is contained in a large amount in the deposited gallium, and there is an adverse effect such as a decrease in the purity of the deposited gallium. In addition, when a metal ion such as lead or copper, which has a potential close to that of gallium or is noble, is present in the electrolytic solution, these are preferentially deposited at the same time as gallium, which lowers the purity of the deposited gallium, causing a problem. is there.

As a method for removing vanadium among heavy metal ions, a method of treating with a reducing agent such as a gallium-based alloy containing aluminum and zinc in a liquid containing vanadium or aluminum, hydrazine and its salts, ferrous sulfate, and sodium sulfide Using a reducing substance such as, for example, direct current, and optionally a reaction containing alkaline earth elements such as calcium-containing by-products in the production of calcium oxide, calcium hydroxide, magnesium hydroxide and / or alumina A method is known in which a solution is treated with an agent and, after this treatment, it is separated as a precipitate (Japanese Patent Publication No. Sho 50-26486).
No. 52-23515, U.S. Pat. No. 3677918).

Problems to be Solved by the Invention However, it is difficult to reduce the vanadium concentration to 20 mg / l or less by vanadium containing 200 mg / l or more by these treatments, and there is a problem such as loss of gallium content. Further, when a metal such as zinc is used, zinc is electrodeposited in the subsequent electrolysis step, leading to a decrease in the purity of metallic gallium.

In view of such circumstances, as a result of intensive studies, the inventors have found a method for efficiently removing heavy metals and obtaining gallium with high yield and high purity, and arrived at the present invention.

Means for Solving the Problems That is, the present invention is a solid solution produced by adding metallic aluminum to an alkaline solution of gallium containing heavy metal ions as impurities to cause a reduction reaction, and then adding a calcium compound. This is a method in which a substance is separated and removed, and then water-soluble sulfide is added to the obtained solution to separate and remove a formed precipitate, and then the obtained solution is electrolyzed to collect metallic gallium.

The alkaline solution of gallium containing heavy metal ions as an impurity used in the present invention, for example, adsorbs gallium from a so-called Bayer solution using a liquid adsorbent or a chelate resin, and elutes it to give an alkaline solution,
The Bayer solution is electrolyzed with mercury as the cathode, and after gallium is electrodeposited, a solution obtained by dissolving with sodium hydroxide, carbon dioxide gas is blown into the Buyer solution to separate and separate the aluminum content and the gallium content, and the alkali A solution obtained by leaching the gallium content with an alkaline solution derived from the Bayer solution, or a gallium-containing solution after the metal is treated with gallium, a gallium alloy, a gallium-containing compound or a gallium-containing mineral with an acid or an alkali. Finally, it is made alkaline and contains heavy metal ions as impurities. Examples of heavy metal ions as impurities include vanadium, uranium, lead, and copper.

Metal aluminum is added to the alkali solution to reduce vanadium or uranium having a high valence to low valence among heavy metal ions as impurities.

Metallic aluminum is used in the form of powder, small particles, or foil. The amount is about 0.1 to 5 g per 1 of the alkaline solution. If 5 g or more of aluminum is used, gallium ions are reduced and metallic gallium is deposited, which is not preferable. If the amount added is less than 0.1 g / l, the impurity ions are not sufficiently reduced, which is not preferable. This reduction reaction is performed at about 50 ° C to 110 ° C.

As the calcium compound, calcium hydroxide, calcium oxide or the like is used, and the amount thereof is the alkali solution 1
It is about 5g to 50g.

This calcium compound is added at about 70 ° C to 110 ° C to solidify low valence ions such as vanadium and uranium as precipitates. Solids are removed by ordinary solid-liquid separation operations such as filtration and centrifugation.

Water-soluble sulfide is added to the separated liquid. Water-soluble sulfides include sodium sulfide, ammonium sulfide, hydrogen sulfide, and the like.

As a result, heavy metal ions such as copper and lead are converted to sulfides to form precipitates. In this case, nickel chloride or the like may be added as a coprecipitant.

The precipitate can be removed by a conventional solid-liquid separation method. The solution thus separated is electrolyzed by adjusting the amount of alkali in some cases. The electrolysis can be carried out by a known method. That is, known electrodes such as zinc, nickel, stainless steel, lead, and carbon can be used for the cathode, and known electrodes such as zinc, nickel, stainless steel, and gallium can be used for the anode. In particular, as the cathode material, one having a large hydrogen overvoltage, which is likely to deposit gallium, is particularly preferable.

The current density varies depending on the type of electrode, liquid temperature, and liquid composition, but 0.01 to 0.5 A / cm ² is preferable in terms of current efficiency and productivity. The gallium concentration in the solution used for electrolysis is 0.5 g / l to 300 g / l, and the alkali concentration is 10 g as Na ₂ O.
/ l to 300 g / l is particularly preferred. If the concentration of gallium or alkali is too low, the gallium will not be electrodeposited or the current efficiency will be poor, and if it is too high, the liquid viscosity will increase and the current efficiency will decrease.

The temperature during electrolysis is above the melting point of metallic gallium 80 ° C
Is preferred. If it is lower than this, it is difficult to continuously take out the electrodeposited metal gallium, and if the temperature is high, the re-dissolution rate of the electrodeposited metal gallium is increased, resulting in a decrease in current efficiency.

EXAMPLES The method of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Examples 1 to 5 vanadium 300 mg / l, lead 50 mg / l, copper 10 mg / l, gallium 80 g / l,
500 ml of a liquid containing 150 g / l of Na ₂ O was added with the amount of metallic aluminum powder shown in Table 1 at 70 ° C., stirred for 30 minutes, and then added with the amount of calcium oxide shown in Table 1 at 95 ° C. for 2 hours. After stirring, solid-liquid separation was performed, and then 0.16 g of sodium sulfide was added to 1
After stirring for 10 hours, the mixture was allowed to stand at room temperature for 10 hours and then passed over with paper. The analytical values of each component in the obtained solution are as shown in Table 1. This solution was electrolyzed at 50 ° C. for 24 hours at a current of 2.5 amps using a nickel plate as an anode and a stainless plate as a cathode. The purity of the deposited gallium was 99.99% or more. The current efficiency at this time is shown in Table 1.

Examples 6 and 7 The same treatment as in Examples 1 and 5 was carried out except that calcium hydroxide was used instead of calcium oxide in Examples 1 and 5, and as a result, gallium having a purity of 99.99% or more was obtained.

Table 2 shows the amounts of the metallic aluminum powder and calcium hydroxide used, the concentrations of vanadium, lead, copper and gallium in the liquid after the treatment, and the current efficiency.

Comparative Examples 1 to 8 The same treatments as in Example 1 were carried out and electrolysis was performed except that the amounts of aluminum, calcium oxide and calcium hydroxide shown in Table 3 were used. The results are shown in Table 3.

Comparative Examples 4 and 5 The same treatment as in Example 1 or 6 was carried out except that the sodium sulfide treatment was not carried out. The results are shown in Table 4.

EFFECTS OF THE INVENTION According to the method of the present invention, when collecting metallic gallium from an alkaline solution of gallium containing heavy metal ions as impurities, the heavy metal can be efficiently removed, and high-purity gallium can be obtained in high yield.

Claims (2)

[Claims] 1. An alkaline solution of gallium containing heavy metal ions as impurities is first added with metallic aluminum to cause a reduction reaction, and then a calcium compound is added to separate and remove a solid product formed, which is then obtained. A method in which water-soluble sulfide is added to the obtained solution to separate and remove the formed precipitate, and then the obtained solution is electrolyzed to collect metallic gallium. 2. The method according to claim 1, wherein the amount of metallic aluminum added is 0.1 g to 5 g per 1 of the alkaline solution.