JPH0791059B2 - Recovery method of gallium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is widely used as a compound semiconductor in the electronic industry, such as gallium arsenide (hereinafter abbreviated as Ga.As), gallium phosphorus (hereinafter abbreviated as Ga.P), and the like. The present invention relates to a method for separating and recovering Ga from scrap containing Ga generated during the production of the compound of 1.

In the production of Ga.As, Ga.P, etc., generally, a single crystal is produced from a solution of these compounds by a pulling method, the single crystal is cut into a wafer, and the wafer is cut into chips of several mm square. As described above, in the above manufacturing process, a large amount of cutting waste is generated during several cutting steps, and the amorphous portion at the upper end of the crystal is cut during the single crystal refining, or polycrystalline gallium arsenide is formed in the crucible. A considerable amount of scrap is generated because of the remaining compounds such as gallium and phosphorus.

On the other hand, gallium is a rare element whose abundance is small, and no specific ore exists. Therefore, it is required to recover gallium from the scrap and reuse it, and various methods have been known as recovery methods.

[Prior Art] Conventional recovery methods can be roughly classified into a wet method and a dry method.
An example of the wet method is to dissolve gallium / arsenic-containing scrap with an acid or an alkali in the presence of an oxidizing agent, and to dissolve the pH of the solution.
Is adjusted to 2 to 8 to precipitate a hydroxide of gallium, which is separately recovered, dissolved in an alkali, and electrolyzed to recover metal gallium. (Japanese Patent Publication No. 56-3866).
Another example is oxidative decomposition of an intermetallic compound consisting of gallium and a Vb group element of the periodic table of elements with hydrogen peroxide in an alkaline aqueous solution, and then the obtained gallium acid and an alkali salt containing an alkali salt of a Vb group element oxygen acid. This is a method of recovering metallic gallium by electrolyzing an aqueous solution (Japanese Patent Laid-Open No. 50-84410).

The above-mentioned wet methods are basically based on the fact that the scrap containing gallium is dissolved with an acid or an alkali, and impurities are removed by precipitation or the like, followed by electrolytic collection.

Next, as a dry method, in the case of Ga / P, 500 scraps are used.
~ 1000 ℃, in the case of Ga · As, vacuum distillation at a high temperature of 1100 ~ 1150 ℃, sublimate P and As to condense and recover it, while cooling the purified molten Ga and then recovering by washing with acid Has been published (East German Patent No. 159421) and (JP-A-57-57).
No. 101625). However, none of these published methods are free of problems. That is, in the wet method, when dissolved, gases such as phosphine (PH ₃ ) and hydrogen (H ₂ ) are generated, and phosphine is particularly toxic and spontaneously ignited, which is dangerous. Further, in the case of the dry method, there is a problem that the distillation temperature is extremely high and the energy cost increases, and further, the precipitated phosphorus is ignited, which is dangerous.

[Knowledge on Problem Solving] The present inventor has found that chlorides of gallium / arsenic and phosphorus have low melting points and can be melted at a relatively low temperature, and the boiling points of these chlorides are GaCl ₃ 201 ° C. and AsCl ₃ 130. ℃, PCl ₃ 75
℃, PCl ₅ 166 ℃, which is relatively low and has a sufficient temperature difference, try to distill and separate the scrap containing the above gallium into chloride with chlorine gas. The inventors have found that high-purity gallium can be recovered by this method, and completed the present invention.

[Structure of the Invention] The present invention reacts scrap containing Ga with chlorine to obtain Ga
Further, the present invention provides a method for recovering Ga, characterized in that a crude gallium chloride obtained by distillative separation after or at the same time as chlorination is purified by using a part or all of other elements as a chloride.

The present invention is a unique Ga separation and recovery method that should be called a chlorination distillation method that is completely different from the conventional method.

The drawing shows a flow sheet of the separating and collecting method according to the present invention. In the present invention, as a means for melting scrap containing gallium, scrap containing gallium is charged into a melting vessel and chlorination is performed with chlorine gas.

The gallium-containing scrap is preferably crushed and used to enhance contact with chlorine gas. As described above, the gallium-containing scrap used as the raw material is gallium / arsenic,
It is possible to use various kinds of cutting scraps and pieces generated from the manufacturing process of compound semiconductor such as gallium / phosphorus, and various scraps containing metal gallium.

According to the method of the present invention, crude metal gallium containing a large amount of impurities can be treated in the same manner. The reaction in the chlorination step is generally represented by the following formula.

_{Ga + Cl 2 → GaCl 2 GaCl} 2 +1/2 Cl 2 → GaCl 3 As + 3/2 Cl 2 → AsCl 3 P + 3/2 Cl 2 → PCl 3 PCl 3 + Cl 2 → PCl 5 M + x / 2 Cl 2 → MClx M here Indicates a metal other than the above. In this way, gallium produces two types of chlorides, GaCl ₂ and GaCl ₃ , but GaCl ₂ is converted to GaCl ₃ if chlorine gas is supplied in excess, as needed in the subsequent separation and purification process. .

The blowing rate of chlorine gas is not particularly limited, and is appropriately selected from economic factors such as reaction efficiency of chlorine gas and reaction time.

In addition to gallium chloride, the product after the chlorination contains chlorides of impurity metals contained in the raw material for treatment, and thus chlorides of these impurities and gallium chloride are separated by distillation. Most of chlorides in the medium and chlorides such as AsCl ₃ and PCl ₃ formed from impurities in scrap have a boiling point significantly lower than the boiling point of GaCl ₃ of 201 ° C., and thus most of them are separated by distillation. It is also possible to carry out the chlorination and the distillation of the low boiling point chloride at the same time by maintaining the above chlorination reaction at the temperature of the distillation step as shown here.

If the Ga-containing scrap contains phosphorus, part of the phosphorus is PC
l ₅ next, this PCl ₅ covers the PCl ₅ the surface of the scrap in the melting point of below 160 ° C. as high as 160 ° C., the reaction does not proceed, it is to carry out the chlorination at 160 ° C. or higher. More preferably, chlorination is performed while volatilizing PCl ₃ and PCl ₅ .
Further, since PCl ₅ has a high boiling point of 166 ° C. and is close to the boiling point of GaCl ₃ of 201 ° C., which is difficult to separate, it is preferable to reduce the generation of PCl ₅ . The chlorination temperature is 300 to reduce the production of PCl _5.
It is preferable that the temperature is not lower than 0 ° C.

AsCl _3, PCl distillation residue after distillation of low-boiling chlorides, such as _3, the GaCl _2, GaCl ₃ as a main component, other high-boiling chlorides produced from impurities in the scrap, for example AlCl ₃ or CrCl Crude gallium chloride containing ₃ etc. After further purification or immediate reduction, metallic gallium is recovered.

As one of the purification methods, there are methods by distillation and rectification. In the case of this method, chlorine gas is further blown into the crude gallium chloride to convert GaCl ₂ into GaCl ₃ having a lower boiling point (rechlorination), and then GaCl ₃ is distilled and further rectified by an ordinary method. , Purified gallium chloride (GaCl ₃ ) can be obtained by separating and purifying from other impurities.

The crude gallium chloride or purified gallium chloride obtained in the above step is reduced as necessary to obtain metallic gallium. As a reduction method for reducing crude gallium chloride or purified gallium chloride to recover metallic gallium, it is possible to carry out (a) aluminum powder, zinc powder reduction, (b) hydrogen reduction, and (c) electrowinning. it can.

The reactions of these methods are represented by the following equations.

(A) aluminum powder, reduction with zinc dust _{GaCl 3 + Al → Ga + AlCl} 3 2GaCl 3 + 3Zn → 2Ga + 3ZnCl 3 (b) hydrogen reduction _{2GaCl 3 + 3H 2 → 2Ga +} 6HCl GaCl 2 + H 2 → Ga + 2HCl (c) electrowinning Ga ³⁺ + 3e ^- → Ga Ga ²⁺ ＋ 2e ⁻ → Ga aluminum powder, zinc powder reduction unlike the hydrogen reduction method does not include the function of efficiently separating impurities, so the gallium chloride is purified in advance by the above method. Must be used.

Next is electrowinning. There are cases where an acidic solution is used and cases where an alkaline solution is used. When using an acidic solution, to prevent the simultaneous precipitation of impurities and the generation of AsH ₃ ,
It is necessary to purify gallium chloride in advance. When an alkaline solution is used, gallium chloride is neutralized, the formed gallium hydroxide [Ga (OH) ₃ ] precipitate is separated, alkali such as NaOH is added and dissolved, and electrolysis is performed. in this case,
Metallic impurities such as iron are insoluble in the alkaline bath, so they are easily separated. Arsenic, chromium, etc. form insoluble compounds in the alkaline bath and are over-separated. Further, the same method can be used regardless of whether GaCl ₂ is GaCl ₂ or GaCl ₃ . Therefore, according to this method, the crude gallium chloride can be directly treated. Other low boiling point chlorides separated from gallium can be recovered as a high purity chloride through a purification step, and can be recovered as a high purity metal by a reduction step and used as a semiconductor raw material.

[Effect of the present invention] According to the method of the present invention, not only high-purity gallium but also arsenic can be simultaneously separated and recovered from gallium-arsenic scrap, for example.

Since the gallium-containing scrap and the chlorine gas are directly reacted in the method of the present invention, the reaction time is shorter than that in the melting by the wet method.

When gallium-containing scrap contains phosphorus,
The wet method produces phosphine which is highly toxic and spontaneously ignitable, and the dry method produces spontaneous pyrophoric phosphorus, but the method of the present invention does not produce these hazardous substances, Can be done safely.

The method of the present invention has a distillation temperature of about 200 ° C. to 500 ° C., which is much lower than the high temperature distillation of 1150 ° C. which is carried out by the conventional dry method, so that the energy cost is much lower and it can be carried out. It's easy. Moreover, according to the method of the present invention, GaC
By obtaining l ₃ , AsCl ₃ , and PCl ₃ , the high-purity gallium chloride, arsenic chloride, and phosphorus chloride suitable as a semiconductor raw material can be directly obtained in the form of chloride. Further, the obtained crude gallium chloride, purified gallium chloride, purified arsenic chloride, and purified phosphorus chloride can be further reduced to be recovered as 6N-purity metallic gallium, metallic arsenic, and metallic phosphorus.

[Detailed Disclosure of the Invention] 500 g of gallium and arsenic scrap was placed in the four-necked flask of Example 12.
I put it in. It was heated to 60 ° C. Then, Cl ₂ gas was blown into the bath at a rate of 400 ml / min. Since the chlorination reaction of gallium and arsenic is an exothermic reaction, the temperature inside the flask is 70 to 90 ° C.
Becomes Partly volatilized AsCl ₃ was cooled by a cooling tube attached to the Cl ₂ gas outlet of the flask to become liquid and returned to the flask. After further blowing 348 of Cl ₂ gas into the flask, the produced mixed solution of GaCl ₃ and AsCl ₃ was taken out. The produced amount was 1242 g (GaCl ₃ 607 g, AsCl ₃ 605 g).

Next, 500 g of this mixed solution was taken out, put into a 500 ml four-necked flask, and heated by a mantle heater for distillation purification. The distillation tube had a length of 500 mm and an inner diameter of 20 mm and was filled with glass beads.

First, the temperature of the upper part of the distillation tube was set to 130 ° C. to distill AsCl ₃ . The distillate was cooled and vaporized by a cooling tube, taken out as a liquid, and then weighed to analyze the components. After distilling AsCl ₃ , the temperature of the upper part of the distillation tube was set to 200 ° C. to distill GaCl ₃ .
The recovered AsCl ₃ was 222 and the purity was 99.9%. The recovered GaCl ₃ was 239 g and its purity was 99.8%.

Example 2 GaCl ₃ (purity 99.8%) obtained in Example 1 was rectified.
As the distillation tube, a glass tube having a length of 1000 mm and an inner diameter of 50 mm was filled with glass beads and used. The first distillate was rich in AsCl ₃ . After that a rich GaCl ₃ was obtained. The obtained GaCl ₃ was 191 g and had a purity of 99.9999%.

Example 3 500 g of gallium / phosphorus scrap was charged in the four-necked flask of Example 2, and this was heated to about 300 ° C. with a mantle heater.

Cl ₂ was then bubbled into the flask at 500 ml / min. Most of gallium turns into GaCl _{3 and} volatilizes, and most of phosphorus also turns into PCl ₃ and some turns into PCl ₅ , so that the new surface of scrap always reacts with Cl ₂ . Since the reaction is exothermic, the temperature can be maintained with almost no heating. The volatilized chloride is cooled to 120 to 160 ° C., and GaCl ₃ is condensed and recovered. Since PCl ₃ has a boiling point of 75 ° C, it does not condense, and GaCl ₃ can be purified. The gas mainly containing PCl ₃ is further cooled, and PCl ₃
Other low boiling chlorides condense.

After bubbling Cl ₂ gas 120, a chloride rich in gallium (Ga content 149 g, P content 14 g) and a chloride low in gallium (Ga content 3 g, P content 56 g) were obtained.

After dissolving the gallium-rich chloride in 1.5 water, NaO
Adjusted to PH6 with H, gallium hydroxide Ga (OH)
_The precipitate was recovered as No. ₃ . Most of the phosphorus enters the liquid and is removed. After further adding NaOH to gallium hydroxide Ga (OH) ₃ to dissolve gallium, impurities in the liquid were removed by various reagents, and electrolytic collection was performed to recover 146 g of gallium metal. The purity was 99.996%.

Example 4 The gallium-containing scrap (Ga 78
%, Bi 5%, SiO ₂ 15%). After heating the flask to 240 ° C. with a mantle heater, Cl ₂ gas was blown into the flask at a rate of 400 ml / min. The chlorination reaction of gallium and bismuth is an exothermic reaction, so the temperature inside the flask is approximately 250 ° C.
Maintained at. At this temperature, the boiling point of BiCl ₃ stays in the flask because it has a boiling point of 441 ° C., but since the boiling point of GaCl ₃ is 201 ° C., it volatilizes and is condensed and recovered by cooling.

After injecting 250 Cl ₂ gas, G of 99.99% purity in the cooling section
956 g of aCl ₃ was obtained.

[Brief description of drawings]

 The figure is a flow sheet illustrating the method of the present invention.

Claims (1)

[Claims] 1. A method of reacting scrap containing gallium with chlorine to form gallium and some or all of other elements into chloride, and purifying crude gallium chloride that has been distilled off after chlorination or simultaneously with chlorination. Recovery method of gallium.