JPS587698B2 - Golden gallium noseizohouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing metallic gallium from an aqueous alkaline aluminate solution containing gallium.

More specifically, carbon dioxide, carbonic acid, and a selected acidic substance (hereinafter referred to as acidic substance) are added to an aqueous alkaline aluminate solution containing gallium to co-precipitate hydrated gallium oxide and alumina, and the co-precipitated product is The present invention relates to a method for producing metallic gallium economically and in a high yield without roasting the co-precipitated product, by dissolving it in an alkaline aqueous solution and then subjecting it to electrolysis to produce metallic potassium.

} Gallium is widely distributed in grains, but there is no specific ore.

However, since gallium is similar in properties to aluminum, it is eluted together with alumina in the Bayer process, in which alumina is produced by alkaline cooking of bauxite, and is dissolved in the Bayer liquid during recycling. Since it accumulates, metallic gallium is currently produced from this Bayer liquid on an industrial scale.

Generally, the concentration of gallium (hereinafter referred to as Ga) in the Bayer liquid is about 0.1 to 0.3 g/l.

As a method for producing metallic gallium from an alkaline aluminate aqueous solution containing gallium, (1) adding an acidic substance such as carbon dioxide or carbon to an alkaline aluminate aqueous solution containing gallium, and precipitating the aluminum in the liquid as alumina; The ratio of gallium and aluminum in the solution is increased by separation, and then an acidic substance is added to the treatment solution again to co-precipitate hydrated gallium oxide and alumina [most of the co-precipitates have the formula MAlO2.H2C03
(M represents Na or K) Dawsonite.

[U.S. Pat. 582,377 specification)
, (2) Increase the ratio of gallium to aluminum in the solution by adding a water-soluble calcium compound to an alkaline aluminate aqueous solution containing gallium to insolubilize and separate the aluminum content as calcium aluminate, and then add it to the above treatment solution. A method of adding an acidic substance to co-precipitate hydrated gallium oxide and alumina, then dissolving the co-precipitate in an alkaline aqueous solution and subjecting it to electrolytic treatment (U.S. Pat. No. 2,582,376) is publicly known.

However, in either method, when the co-precipitate is dissolved in an alkaline aqueous solution and electrolyzed without roasting,
There is a phenomenon in which electrolytic deposition of gallium is observed in the very early stages, but then no electrolytic deposition occurs.

Conventionally, this cause was thought to be due to organic substances in the co-precipitate, and in order to eliminate this cause, the co-precipitate was roasted to remove the organic substance, then dissolved in an alkaline aqueous solution, and electrolyzed. has been adopted.

However, since co-precipitates are fine particles with a particle size of several microns, they require a complicated and expensive roasting operation, resulting in a significant increase in the unit consumption.

The present inventors have conducted extensive research on a non-roaring method in which the co-precipitate is dissolved in an alkaline aqueous solution without being roasted, and then electrolyzed. It was discovered that when gallium is dissolved in an alkaline aqueous solution and electrolyzed, the main reason for preventing the electrolytic deposition of gallium is the alkali carbonate present in the electrolyte.

The alkali carbonate in this electrolyte is produced by carbonate radicals from dawsonite produced by the acidic substance used to cause co-precipitation of hydrated gallium oxide and alumina, and when the co-precipitate is not roasted. , its generation is inevitable.

However, in the known method of roasting the co-precipitate,
When organic substances are burned or decomposed and removed, the carbonate radicals in dawsonite are released as CO2 gas, so even if the roasted co-precipitate is dissolved in an alkaline aqueous solution, no alkali carbonate will be present in the electrolyte, and no alkali carbonate will be present in the electrolyte. However, in the case of the above-mentioned roasting method, no influence of alkali carbonate was observed.

The purpose of the present invention is to add an acidic substance to an alkaline aluminate aqueous solution containing gallium, co-precipitate hydrated gallium oxide and alumina, dissolve the co-precipitate in an alkaline aqueous solution without roasting, electrolyze it, and produce metals. The object of the present invention is to provide a simple and economical method for producing gallium.

That is, the present invention adds an acidic substance selected from carbon dioxide and carbonic acid to an alkaline aluminate aqueous solution containing gallium, causes hydrated gallium oxide and alumina to co-precipitate, and after dissolving the co-precipitate without roasting. The concentration of alkali carbonate in the alkaline aqueous solution is expressed as a concentration ratio to the saturated concentration (hereinafter, this concentration ratio is referred to as saturation degree): 0.9
In the method for producing metallic gallium by electrolyzing an alkali aluminate aqueous solution containing gallium obtained by dissolving gallium in an aqueous alkali solution in an amount of 5 or more, and then dissolving the non-baked co-deposit, After the degree of saturation of the alkali carbonate in the aqueous alkali aluminate solution containing gallium obtained by dissolving the non-roasted co-precipitate is less than 0.95,
The object of the present invention is to provide a method for producing metal gallium in a high yield, simply, and economically by electrolysis.

The method of the present invention will be described in more detail below.

In carrying out the method of the present invention, the alkali aluminate aqueous solution containing gallium in an amount of about 0.1 g/l or more can be used as the raw material for the alkali aluminate aqueous solution containing gallium.
Anything can be used.

Examples of such an aqueous alkali aluminate solution containing gallium include a Bayer one-step circulating alkali aluminate aqueous solution;
An acidic substance such as carbon dioxide or carbonic acid is added to the boiled circulating aqueous alkali aluminate solution or the untreated or treated liquid, and the aluminum content in the liquid is precipitated and separated mainly as aluminum hydroxide, or slaked lime, raw stone)
Contains a high concentration of gallium after adding water-soluble calcium compounds such as ash and calcium chloride to insolubilize and separate the aluminum content in the liquid as calcium aluminate to increase the ratio of gallium to aluminum in the liquid. An alkaline aluminate aqueous solution or the like can be used.

In carrying out the method of the present invention, first, hydrated gallium oxide and alumina are co-precipitated in the aqueous alkali aluminate solution containing the raw material gallium, and gallium in the solution is precipitated and separated as a co-precipitate. Acidic substances such as carbon dioxide (can be used in gaseous, liquid, or solid form) and carbonic acid are added.

Co-precipitation can generally be carried out at room temperature to 70°C.

Preferably, the co-precipitation is carried out such that the ratio of gallium (as Ca):alumina (as Al203) in the co-precipitate is about 1:35-150.

The co-precipitate mainly consists of dawsonite, and its composition is 0.3-1% by weight of Ga, Al20335 in wet state.
-45% by weight, CO2 20-30% by weight, humic organic matter o. i~0.5% by weight and the balance water.

Separation of co-precipitates from aqueous alkaline aluminate solutions is done by filtration.
This may be carried out by known means such as sedimentation and centrifugation.

The separated co-precipitate can be used as is, or if necessary, add water or water.
After washing with warm water to remove organic substances or dehydrating and drying, it is dissolved in an aqueous alkaline solution.

In carrying out the method of the present invention, the above-obtained co-precipitate is mixed with an alkali aqueous solution, such as caustic soda, in an amount such that the degree of saturation of the alkali carbonate in the alkali aluminate aqueous solution after dissolving the co-precipitate is about 0.95 or more. or dissolved in caustic potash.

Therefore, the reason why the saturation degree of alkali carbonate in the aqueous alkali aluminate solution after dissolving the co-precipitate is set to be about 0.95 or more is that the saturation degree of alkali carbonate is adjusted to less than about 0.95 at this stage. For example, the proportion of co-precipitates dissolved in the alkaline aqueous solution becomes smaller, resulting in a lower gallium concentration in the solution and a lower gallium yield per unit amount of solution.

To explain more specifically, when the gallium concentration in the electrolytic solution is lower than about 2 g/l, the gallium yield per unit liquid volume decreases, so the gallium concentration in the electrolytic solution is usually about 2 g/l.
12. Above, preferably 2.5 to 6 g/l. Ca:C02 in the co-precipitate
Since the weight ratio of 0.3 to 1:20 to 30, if the gallium concentration in the electrolyte is made to be about 2 &/l or more, the saturation level of alkali carbonate in the electrolyte will inevitably decrease. This is because if the degree of saturation is less than 0.95, the yield of gallium will be reduced to 1.2% or more.

The aqueous alkaline solution used for dissolving the co-precipitate is generally about 70971 or more (as M20), preferably about 100 to 600 g/l, because the lower the concentration, the lower the rate of dissolution of the co-precipitate. An alkaline aqueous solution is used.

Dissolution of the co-precipitate is usually carried out at about 70-250°C.

Is the co-precipitate dissolved when carrying out the method of the present invention? The alkali aluminate aqueous solution containing gallium with an alkali carbonate saturation of about 0.95 or more is then adjusted so that the alkali carbonate saturation is less than 0.95, preferably 0.9 or less.

There is no particular lower limit to the degree of saturation of alkali carbonate, and it may be arbitrarily selected in consideration of economic efficiency.

The saturation degree of the alkali carbonate in the alkali aluminate aqueous solution can be adjusted, for example, by adding water, an alkali aqueous solution, etc. to the alkali aluminate aqueous solution, or by cooling the alkali aluminate aqueous solution and separating the precipitated alkali carbonate. Do you heat it or add slaked lime, quicklime, etc. to this alkaline aluminate aqueous solution? Methods such as adding a soluble calcium compound to causticize the alkali carbonate, or appropriately combining these methods can be applied.

The water, aqueous alkali solution, amount of water-soluble calcium compound added, cooling temperature, etc. used to adjust the saturation degree of the alkali carbonate may be appropriately selected so as to maintain the saturation conditions limited above.

Therefore, it is an extremely important factor that the degree of saturation of the alkali carbonate is less than 0.95, and if the degree of saturation of the alkali carbonate is 0.95 or more, electrolytic deposition of gallium will not occur.

The reason for this is that the saturation level of alkali carbonate in the electrolyte is 0.95.
In this case, alkali carbonate is precipitated by electrolysis and covers the electrode surface, thereby preventing damage to the electrolysis of gallium.

Although it is not essential to remove lead, iron, organic substances, etc. from the co-deposit solution before or after adjusting the saturation level of the alkali carbonate, it is desirable to remove lead, iron, organic substances, etc. in order to obtain more preferable results.

After adjusting the saturation of alkali carbonate, that is, the aqueous aluminate aqueous solution containing gallium to be subjected to electrolysis contains about 2 to 6 g/L of gallium, 70 to 400 g/L of Na2O
The saturation of 2C03 is made to be less than 0.95.

In carrying out the method of the present invention, the gallium-containing alkaline aluminate aqueous solution, which has been treated under the electrolytic treatment conditions and has an alkali carbonate saturation of 0.95 or less, is then electrolyzed by a known method.

Electrolysis is generally performed at a temperature above which gallium can be electrodeposited in liquid form, that is, above the melting point of gallium to 100°C, using carbon, nickel, stainless steel, etc. as an anode, nickel, stainless steel, iron, lead, copper, etc. as a cathode. Using a current density of 0.1 to IA/cm2 and a voltage of 4 to 8
It can be carried out under known conditions such as V.

The purity of the metallic gallium thus produced is equal to or higher than that of the metallic gallium obtained by the roasting method, and there is no problem.

According to the method of the present invention described in detail above, metallic gallium can be produced without roasting the co-precipitate, and the process is significantly simplified compared to the known roasting method, making it economical and industrially possible. Its significance is extremely dog-like.

The method of the present invention will be explained below with reference to Examples, but the method of the present invention is not limited thereto.

Example 1 Blow carbon dioxide gas into the decomposition liquid of Bayer 1 step to produce hydroxyl acid? Na 2 O10 9/lk after precipitation of aluminum
An aqueous sodium aluminate solution containing 12,038 g/l, 0.15 g/l, and 10 g/l of humic organic substances was used as a raw material.

Carbon dioxide gas was blown into 2 m2 of the raw material sodium aluminate aqueous solution to precipitate a co-precipitate of hydrated gallium oxide and alumina, and the solid-liquid separation was performed to separate a cake with a solid content concentration of 50% by weight.

Ga in solid content 0. 7% by weight, and 2% by weight of CO2.

55 parts by weight of 550 g/l raw soda were mixed with 100 parts by weight of the cake obtained above, heated to 100°C, dissolved the co-precipitate with stirring, and cooled to 50°C, the temperature during electrolysis.

The gallium concentration in the obtained solution was 3.2 g/l: -N
a20175g/l1Na2CO3120g/l (Na
The saturation concentration of Na2CO3 at a temperature of 20175 g/l is 1209/l.

Therefore, the saturation degree of Na2C03 was 1.0).

Water was added to the solution in which the co-precipitate obtained above was dissolved to prepare an electrolytic solution having the degree of sodium carbonate saturation shown in Table 1.

The thus prepared alkaline aluminate aqueous solution containing gallium was supplied to an electrolytic cell having a nickel anode and a stainless steel plate as a cathode, and was heated at 50°C and at a current density of o. Electrolysis was carried out for 5 hours at 5 A/m and a voltage of 5 .

As a result, the gallium concentration in the solution after electrolysis was as shown in Table 1.

? From Table 1, the saturation degree of alkali carbonate in the electrolyte is 0.

When it is 95 or more, electrolytic deposition of gallium is not observed, but when it is less than 0.95, it is clear that electrolytic deposition of gallium occurs.

Example 2 After blowing carbon dioxide gas into the boiled liquid after boiling down in Bayer 1 step to precipitate aluminum hydroxide, Na20 10
j! /IJ, AA2038 9/L Ga0.17
An aqueous sodium aluminate solution containing 10 g/l of humic organic substances was used as a raw material.

Carbon dioxide gas was blown into 2 m of the raw material sodium aluminate aqueous solution to precipitate a co-precipitate of hydrated gallium oxide and alumina, and the mixture was separated into solid and liquid to separate a cake having a solid concentration of 50% by weight.

The solid content was 0.9% by weight of Ca and 2% by weight of CO2.

70 parts by weight of 550g/13 raw soda was mixed with 100 parts by weight of the cake obtained above, heated to 110°C, and dissolved with stirring to dissolve the co-precipitate.
Cooled to ℃.

The gallium concentration in the obtained solution was 3.79/l, Na
2 0 2 3 0 g/ l1N a2 co37
5g/il1Na 2 02 30 g/L temperature 50
The degree of saturation at °C was 1.0).

The co-precipitate obtained above is dissolved and the N in the solution is added to the solution.
0.5 times (molar ratio) Ca(OH) to a2CO3
2 was added with stirring and a causticizing reaction was carried out for 0.5 hours, followed by solid-liquid separation.

The composition of the obtained filtrate was Ga3. 7 9/l, N
a202 3 5 g/l, Na2CO36 6.5
g/l, and the degree of saturation at 50°C was 0.9.

The gallium-containing alkaline aluminate aqueous solution whose saturation was adjusted in this way was supplied to an electrolytic cell with a nickel anode and a stainless steel plate as a cathode, and was heated at 50°C, a current density of 0.5 A/m2, and a voltage of 5 cm for 5 hours. went.

As a result, the gallium concentration in the solution after electrolysis was 0.22g/
It was l.

For comparison, electrolysis was performed in exactly the same manner as above except that the causticization treatment was not performed, and no electrolytic deposition was observed.

From the above results, it is clear that metallic gallium can be produced by a non-roasting method.

Claims (1)

[Claims] 1 Adding an acidic substance selected from carbon dioxide and carbonic acid to an aqueous alkaline aluminate solution containing gallium to co-precipitate hydrated gallium oxide and alumina, and without roasting the co-precipitate, An alkali aluminate containing gallium obtained by dissolving the alkali aluminate in an amount such that the concentration of alkali carbonate in the aqueous alkali solution is 0.95 or more expressed as a concentration ratio to the saturated concentration, and then dissolving the non-roasted co-precipitate. In a method for producing metallic gallium by electrolyzing an aqueous solution, the concentration of alkali carbonate in an alkali aluminate aqueous solution containing gallium obtained by dissolving the non-roasted co-deposit is expressed as the concentration ratio to the saturated concentration. A method for producing metallic gallium from an alkaline aluminate aqueous solution containing gallium, which comprises electrolyzing the gallium-containing alkali aluminate aqueous solution after the gallium is reduced to less than 0.95.