JPS6134493B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for separating excess acid from an aqueous gallium-containing mineral acid solution and then recovering gallium by electrolysis. Gallium is an extremely important metal as a raw material for electronic materials, but there are no ores containing abundant gallium, and the only industrial manufacturing method is, for example, alkali extraction of alumina from bauxite ore, which contains a small amount of gallium. Methods of separating and recovering from Bayer's solution (sodium aluminate solution) obtained by the process, and methods of recovering in the black ore zinc smelting process are known. These methods are diverse, but with the exception of the direct electrolysis method using Bayer's solution, the general method is to concentrate the gallium component using pretreatment operations such as solvent extraction and precipitation separation for a starting material containing a trace amount of gallium. There is a method of obtaining gallium by removing impurities and electrolyzing the resulting aqueous solution containing a gallium component, often in an alkaline aqueous solution.
Mineral acids are often used in this pretreatment operation, and a large amount of alkali must be added during electrolysis, resulting in a large amount of acid and alkali being wasted, and the coexistence of a large amount of salt causing electrolysis. In addition to the disadvantages that troubles are difficult to avoid, there are many disadvantages such as the increase in the amount of aqueous solution to be treated due to the neutralization operation, which increases the capacity of the equipment and increases equipment costs. There is a strong desire to develop an efficient method that does not have these drawbacks. As a method for recovering gallium from a sodium aluminate solution, for example, there is a method described in JP-A-51-32411. This method involves liquid-liquid extraction of gallium contained in the sodium aluminate solution from the Bayer process using water-insoluble substituted hydroxynoline to remove impurities, and then back extraction. However, since this electrolysis is mostly carried out under alkaline conditions, there are problems as mentioned above. On the other hand, as already mentioned, GaP,
GaAs, GaAs ₁ ―xPx, GaxIn ₁ ―xP, GaxA ₁ ―
The waste generated when processing crystalline materials such as xAs and Gd ₃ Ga ₅ O ₁₂ into electronic material elements is also an extremely valuable resource. The amount of gallium waste is increasing year by year with the development of the electronic industry, and many techniques for recovering gallium from waste have been proposed. Examples of waste containing gallium are: (1) GaP, GaAs, GaAs ₁ -xPx, GaxIn ₁ -xP,
GaxA ₁ - Waste from the production of polycrystalline and single crystals of intermetallic compounds and metal oxides such as xAs, Gd ₃ Ga ₅ O ₁₂ (2) Cutting layer when cutting wafers from polycrystals and single crystals (3) There are acid solutions for mirror-finishing wafers, etc. An example of a method for recovering metallic gallium from waste is the method described in Japanese Patent Publication No. 38661/1983. This method involves dissolving gallium-containing waste, that is, a gallium-containing composition such as an intermetallic compound consisting of gallium and a group Vb element, in an acidic or basic solution in the presence of an oxidizing agent, and then adjusting the pH. After precipitating the gallium component, the precipitate is separated, the separated product is then dissolved in an alkaline solution, and the solution is then electrolyzed to recover gallium. In this case, the precipitate is often formed as a gel, and in this case, it is necessary to maintain the precipitate under heat and ripen it as described in column 4, lines 13 to 20 of the publication. And the separation of precipitates is sedimentation,
It is said that this can be done by known means such as filtration and centrifugation. This process requires a separation step involving a gel that is difficult to handle, so it is difficult to use in terms of equipment.
It also has the disadvantage of being extremely large-scale in terms of workability. In view of the current situation, the present inventors have conducted repeated research on a method for efficiently recovering high-purity gallium at a high yield from a gallium-containing mineral acid aqueous solution.
The invention has been completed. That is, in the present invention, when recovering gallium from an aqueous gallium-containing mineral acid solution, the aqueous gallium-containing mineral acid solution is placed in a diffusion dialysis tank in which a mineral acid aqueous solution is passed through an ion exchange membrane on one side and water is counter-flowed on the other side. From a gallium-containing mineral acid aqueous solution, which is characterized by passing water through it to separate excess acid, adjusting the pH of the obtained dialysate to a range in which gallium can be isolated by electrolysis, and then electrolyzing it. Regarding the recovery method of gallium. In the present invention, as the gallium-containing mineral acid aqueous solution, for example, gallium in a sodium aluminate solution obtained by the Bayer method described in JP-A-51-32411 is extracted with water-insoluble substituted hydroxynoline to remove impurities. Then, a solution obtained by back-extracting this with a strong mineral acid, a solution obtained by dissolving the gallium-containing waste described in Japanese Patent Publication No. 56-38661 in concentrated hydrochloric acid and concentrated nitric acid in the presence of an oxidizing agent, Solutions obtained by dissolving gallium-containing wastes with mineral acids as described in No. 54-117315 and Japanese Patent Application Laid-Open No. 56-9223 can be used. A diffusion dialysis tank is a device that efficiently separates acids and salts by utilizing the difference in diffusion rate between the acids and salts through an ion exchange membrane, and is widely used for purposes such as recovering waste acids. In dialysis operation, stock solution is introduced from the bottom of one chamber vertically isolated by an ion exchange membrane (hereinafter referred to as a diffusion dialysis membrane) to create an upward flow, and water is introduced from the top of the other chamber to flow downward. By this,
The acid concentration of the water gradually increases due to the acid that has diffused and reaches the bottom, where the acid in the undiluted solution is recovered. Next, the present invention will be explained in detail by taking as examples a method for recovering gallium from waste containing gallium and a method for recovering gallium from a sodium aluminate solution using the Bayer method, but the present invention is not limited to these. Needless to say, this is not something that can be done. When recovering gallium-containing waste, the gallium-containing waste is first oxidized and decomposed, but if this waste is, for example, cutting waste, organic matter such as cutting oil is attached to it, and in this case, it is burned or treated with a solvent. These must be removed in advance by washing or the like. Moreover, it is necessary to crush this waste as necessary so that it can be easily oxidized and decomposed. The waste that has been pretreated in this way is first subjected to wet oxidative decomposition. Oxidative decomposition is carried out using oxidizing acids such as hydrochloric acid-nitric acid, hydrofluoric acid-nitric acid, nitric acid-perchloric acid, etc. Next, after removing undissolved matter, the solution is passed through a diffusion dialysis tank at an acid concentration of IN or higher and a gallium concentration of 1 g/ or higher. If the acid concentration is lower than IN, the acid will not be recovered sufficiently. Furthermore, if the gallium concentration does not reach 1 g/g, the current efficiency in the electrolytic solution to be adjusted is lowered than in the dialysate. Generally speaking, the processing speed when passing fluid through a diffusion dialysis tank is
0.2 to 2/hr·m ² is suitable. If it is too fast, the acid and salt will not be separated sufficiently, and if it is too slow, the salt will be lost to the recovered acid side and the efficiency of the device will decrease. The diffusion dialysis tank used in the present invention is a film-like anion exchange membrane with a thickness of 0.10 to 0.20 mm formed by a paste method using a styrene-divinylbenzene membrane, and commercially available NeoSepta AFN and AFA
(Product name manufactured by Tokuyama Soda Co., Ltd.), Selemion DSV, DMV
(trade name manufactured by Asahi Glass Co., Ltd.) etc. are suitable. Regarding the separation of acids and salts in a diffusion dialysis tank, there are large differences depending on the type of acid (hydrochloric acid, nitric acid, phosphoric acid, hydrofluoric acid, etc.) in addition to the processing speed. Almost no phosphoric acid is separated. Therefore, when the oxidized decomposition solution is passed through a diffusion dialysis tank, among the acids, hydrochloric acid, nitric acid, and hydrofluoric acid are recovered with high efficiency.
Oxide acids of group Vb elements are difficult to recover and remain in the dialysate. Next, an alkaline solution is added to the dialysate after recovering the acid, and the alkaline concentration is adjusted to a range where metal gallium is easily deposited by electrolysis. The preferred alkali concentration is 0.5 to 5N; if it is less than 0.5N, it will promote hydrogen generation during electrolysis, and if it exceeds 5N, it will cause insufficient defoaming and insufficient diffusion of the generated gas due to an increase in liquid viscosity, etc. Reduce efficiency. If a precipitate is formed, it can be easily removed by filtration. The electrolysis is a normal aqueous solution electrolysis, and is preferably carried out under the following conditions. That is, a nickel plate is used as the cathode, a platinum plate is used as the anode, liquid metal gallium, etc.
Using a nickel plate, etc., the cathode current density is 0.01 to 0.5A/
cm ² , a bath temperature of 40 to 80°C, and a concentration of gallium metal in the electrolyte of 0.02 to 1.5 mol/are appropriate. These condition ranges are necessary to obtain high current efficiency. Gallium in the liquid exists as gallate ions GaO ₂ and is deposited on the cathode by electrolysis. In this way, highly purified gallium can be efficiently recovered from various types of waste containing gallium. In addition, even if the oxidized decomposition solution was not passed through the diffusion dialysis membrane, but the alkali concentration was adjusted by directly adding alkali, and the precipitate was removed, electrolysis was performed under the same conditions, but no gallium was deposited. In this way, by using diffusion dialysis, the amount of neutralizing alkali that could not be recovered from the acid can be reduced.Furthermore, by adding alkali to the dialysate to adjust the alkali concentration and performing electrolysis, metallic gallium can be recovered, so the neutralizing gel can be removed. generation, filtration,
This has the great effect of eliminating complicated processes such as cleaning. This will be explained in more detail below using Examples and Comparative Examples. Example 1 Gallium/Phosphorus Wafer cuttings (oil-based paste) were fired in an open electric furnace to burn off adhering organic substances such as lubricating oil to obtain 10.0 g of gallium/phosphorous powder. Add 1.0 parts by weight of this powder to oxidizing mixed acid (1.2 parts by weight of conc.HC + 1.0 parts by weight of conc.HNO ₃ )22
Part by weight was added and the liquid was stirred to oxidize and decompose GaP. Next, filter the oxidized decomposition liquid, leaving 0.1g of unresolved residue.
was filtered to obtain a clear filtrate. This filtrate was passed through a diffusion dialysis tank using Selemion DMV manufactured by Asahi Glass Co., Ltd. as a diffusion dialysis membrane at a rate of 1/m ² ·hr, and at the same time, water was placed oppositely through the diffusion dialysis membrane. The acid was diffused to the side and recovered. Table 1 shows the liquid compositions of the filtrate, recovered acid, and dialysate.

[Table] Add 15N caustic soda solution to this dialysate.
A sodium gallate solution with a Na ₂ O concentration of 110 g/gallium concentration of 0.15 mol/was obtained. After separating the precipitate in this solution by filtration, 400 ml of the filtrate was used as an electrolyte, and the platinum plate was used as an anode and the nickel plate was used as a cathode.
When the current was applied at 10A/ ^dm2 for 3 hours, the purity of the cathode was confirmed.
Obtained 4.1 g of 99.99% metallic gallium. Example 2 A lump of gallium arsenide, which is a by-product waste during the production of gallium arsenide single crystals, was crushed and passed through a Tyler standard sieve.
It was made into a powder with a total volume of 170 mesh. 20 parts by weight of conc nitric acid having a specific gravity of 1.38 was added to 1.0 parts by weight of this powder, and the liquid was stirred to oxidize and decompose GaAs. Next, the oxidized decomposition liquid was filtered, and the undissolved residue was separated.
At the ^same time, water was placed oppositely through a diffusion dialysis membrane, and the acid was recovered on the water side. The liquid compositions of the filtrate, recovered acid, and dialysate are shown in Table 2.

[Table] Add 10N caustic soda solution to this dialysate,
Na ₂ O concentration 55g/, gallium concentration 0.15mol/
A sodium gallate solution was obtained. When 400 ml of this solution was used as an electrolytic solution, a nickel plate was used as an anode, and liquid gallium was used as a cathode and current was applied at a cathode current density of 5 A/dm ² for 6 hours, 4.1 g of metallic gallium with a purity of 99.99% was obtained at the cathode. Example 3 The acid solution (regia) used for mirror finishing the gallium phosphorous wafer was filtered, and the filtrate was transferred to a diffusion dialysis tank (as a diffusion dialysis membrane, Selemion manufactured by Asahi Glass Co., Ltd.
DSV was used) at a rate of 0.5/ml/hr, and at the same time, water was placed oppositely through a diffusion dialysis membrane, and the acid was diffused and recovered on the water side. Table 3 shows the liquid compositions of the filtrate, recovered acid, and dialysate.

[Table] Add 15N caustic soda solution to this dialysate.
A sodium gallate solution with a Na ₂ O concentration of 80 g/gallium concentration of 0.03 mol/was obtained. 1000 ml of this solution was used as an electrolyte, and when electricity was applied for 10 hours at a cathode current density of 3 A/dm ² using a platinum plate as an anode and a nickel plate as a cathode, 2 g of metallic gallium with a purity of 99.99% was deposited on the cathode. Comparative Example 1 Gallium phosphorus powder obtained in the same manner as Example 1
1.0 parts by weight of oxidizing mixed acid (conc.HC1.2 parts by weight +
22 parts by weight of conc.HNO ₃ (1.0 parts by weight) were added, the liquid was stirred to oxidize and decompose GaP, and the oxidatively decomposed liquid was then filtered to remove the undissolved residue by filtration to obtain a clear filtrate. A 10N caustic soda solution was added to this filtrate to obtain a sodium gallate solution with a Na ₂ O concentration of 110 g/ and a gallium concentration of 0.15 mol/. After separating the precipitate by filtration,
When 400 ml of the filtrate was used as an electrolytic solution and electrolyzed under the same conditions as in Example 1, gallium did not precipitate at all. Comparative Example 2 Gallium phosphorous powder obtained in the same manner as Example 1
Add 22 parts by weight of oxidizing mixed acid (1.2 parts by weight conc.HC + 1.0 parts by weight concHNO ₃ ) to 1.0 parts by weight, stir the liquid to oxidize and decompose GaP, and then filter the oxidized decomposition liquid to remove undissolved residue. A clear filtrate was obtained by filtration.
When the filtrate was cooled with water and an aqueous solution of IN caustic soda was gradually added to adjust the pH to 6, a large amount of gel-like precipitate was produced. After concentrating the slurry concentration to 10 g/min by decantation, filter press (filter cloth air permeability approx. 20 c.c./cm ² min, filtration pressure 4.0 kg/min)
^cm2 ), the cake with 80% moisture content was 0.2Kg/
m ² ·hr was obtained. The concentration of gallium in the cake is
It was 2.7% by weight. Next, the cake was washed three times by decantation using 4.0 parts by weight of water per 1.0 parts by weight, and dehydrated by the filter press described above. 300 parts by weight of the obtained cake was dissolved in 120 parts by weight of 10N caustic soda aqueous solution to reduce the Na ₂ O concentration.
An aqueous solution of sodium gallate with a gallium concentration of 0.15 mol/100 g was obtained. Purity was obtained by electrolyzing 400ml of this aqueous solution as an electrolyte under the same conditions as in Example 1.
Obtained 3.7g of 99.99% gallium. Example 4 A method for recovering sodium aluminate from the Bayer process will be explained using an example. By the method described in JP-A No. 51-32411,
Aluminate solution containing Ga0.2g/ (NaOH150g/
, A ₂ O ₃ 80g/) and extract liquid (Kelex 100 8
%, n-decanol 8%, versatic acid 4%,
After contacting with serocin (80%) and extracting Ga
After removing impurities such as A and Na using 6.4NHC, Ga was back-extracted using 2NHC. The solution was transferred to a diffusion dialysis tank (Celemion manufactured by Asahi Glass Co., Ltd.) as a diffusion dialysis membrane.
DMV was used) at a rate of 1/m ² hr, and at the same time, water was placed oppositely through a diffusion dialysis membrane, and the acid was diffused and recovered on the water side. Table 4 shows the compositions of the back extract, recovered acid, and dialysate.

[Table] Add 15N caustic soda solution to this dialysate,
A sodium gallate solution with a concentration of 110 g of Na ₂ O and 0.02 mol of gallium was obtained. When 1500 ml of this solution was used as an electrolyte, a nickel plate was used as an anode, and liquid gallium was used as a cathode at a cathode current density of 3 A/dm ² for 10 hours, 2 g of metallic gallium with a purity of 99.99% was deposited on the cathode. As is clear from the above Examples and Comparative Examples, according to the method of the present invention, acid can be recovered, and metallic gallium can be obtained by directly electrolyzing the alkali gallium acid after neutralization. Since gel handling is not required at all in the process, the treatment is carried out quickly without the need for complicated processes, equipment, or operations such as aging of sediment, sedimentation separation, inclined water washing, filter press, etc., and the amount of water used is reduced. This brings about extremely beneficial results in industrial practice, such as the use of a small amount of .

Claims (1)

[Claims] 1. When recovering gallium from a gallium-containing mineral acid aqueous solution, the gallium-containing mineral acid aqueous solution and water are passed through a diffusion dialysis tank through an ion exchange membrane, in which the mineral acid aqueous solution flows in one direction and water flows in the other direction. A method for recovering gallium from a gallium-containing mineral acid aqueous solution, which comprises: separating excess acid, adjusting the pH of the obtained dialysate to a range in which potassium can be isolated by electrolysis, and then electrolyzing the solution. .