JPS63291819A - Recovery of gallium - Google Patents

Abstract

PURPOSE:To easily and safely obtain high-purity Ga in a short time at a low energy cost without generating hazardous substance, by chlorinating Ga- containing scarps with Cl2, distilling the reaction product simultaneous to or after the chlorination reaction, purifying the resultant crude GaCl2 and reducing the product. CONSTITUTION:Ga-containing scraps generated e.g. from a production process of a compound semiconductor such as GaAs or GaP are pulverized, as necessary, and made to react with Cl2 gas to chlorinate a part or total of Ga and other elements. Simultaneous to or after the chlorination reaction, the low-boiling chloride (e.g. AsCl3 or PCl3) existing in the raw material as an impurity is separated by distillation to obtain crude GaCl2. The crude GaCl2 is purified by blasting Cl2 gas into the compound to obtain GaCl3 and subjecting the product to distillation and then fractional distillation. The resultant refined GaCl3 is reduced or electrolyzed to recover high-purity Ga.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to gallium arsenide (hereinafter abbreviated as Ga-AS), which is widely used in the electronic industry as a compound semiconductor.

The present invention relates to a method for separating and recovering Ga from scrap containing Ga generated during the production of compounds such as gallium phosphorous (hereinafter abbreviated as Ga*P) and in other cases.

Generally, Ga・As, Ga*P, etc. are manufactured by manufacturing a single crystal from a solution of these compounds by a pulling method, cutting the single crystal into a wafer, and cutting the sea urchin/\ into chips of several mm square. disconnect. In this way, in the above manufacturing process, a large amount of cutting waste is generated when going through several stages of cutting processes, and when refining a single crystal, the irregularly shaped part at the top of the crystal is cut off, and the crucible contains polycrystalline gallium arsenide. A considerable amount of scrap is generated due to the fact that compounds such as gallium and phosphorus remain.

On the other hand, gallium is a rare element that exists in small amounts, and there is no specific ore.Therefore, it is required to recover and reuse gallium from the above-mentioned scrap, and various methods have been known to date. ing.

[Prior art] Conventional recovery methods can generally be divided into wet methods and dry methods.

An example of a wet method is to dissolve gallium-arsenic-containing scrap with acid or alkali in the presence of an oxidizing agent, and to reduce the p.
Adjust H to 2 to 8 to precipitate gallium hydroxide,
This is a method of collecting this in a separate furnace, dissolving it in an alkali, electrolyzing it, and recovering it as metallic gallium. (Tokuko Showa 5B-388
Another example is the oxidative decomposition of an intermetallic compound consisting of gallium and an element of Group VB of the Periodic Table of Elements with hydrogen peroxide in an alkaline aqueous solution, and then the resulting gallium acid and the oxyacid of Group VB element. This is a method of recovering metallic gallium by electrolyzing an alkaline aqueous solution containing an alkali salt (Japanese Unexamined Patent Publication No. 84410/1983). The above wet methods all involve dissolving gallium-containing scrap with acid or alkali. However, the basic method is to perform electrowinning after removing impurities by precipitation etc.

Next, as a dry method, in the case of Ga5P, scrap is
00~1000℃, 1100~11 for Ga@A+
A method has been published in which P and As are sublimated through vacuum distillation at a high temperature of 50°C to recover them, while the purified molten Ga is recovered by cooling and washing with acid (East German Patent No. 159421). ) and (Unexamined Japanese Patent Publication No. 57-1018
No. 25).

However, none of these published methods is without problems; in the wet method, gases such as phosphine (PH3) and hydrogen (H2) are generated during dissolution, and phosphine in particular is highly toxic. , which is dangerous because it spontaneously combusts. In addition, in the case of the dry method, there is a problem that the distillation temperature is extremely high and energy costs are increased, and furthermore, the precipitated phosphorus can ignite, making it dangerous.

[Findings related to problem solving 1 The present inventor found that chlorides of gallium arsenide and phosphorus have low melting points and can be melted at relatively low temperatures, and that the boiling points of these chlorides are 201°C for GaCl3 and 1°C for AsCl3.
30℃, PCl375℃, Pct, 1813℃, which are relatively low and have a sufficient temperature difference, the scrap containing gallium was converted into chloride with chlorine gas and separated by distillation. They tried to do this and found that highly pure gallium could be recovered by this method, leading to the present invention.

[Structure of the invention] The present invention involves reacting scrap containing Ga with chlorine,
The present invention provides a method for recovering G'a, which is characterized by converting some or all of Ga and other elements into chlorides, and purifying crude gallium chloride separated by distillation after chlorination or simultaneously with chlorination.

The present invention is a unique Ga separation and recovery method that can be called a chlorination distillation method, which is completely different from conventional methods.

The drawing shows a flow sheet of the separation and recovery method according to the present invention. In the present invention, as a means for melting scrap containing gallium, the scrap containing gallium is charged into a melting container and chlorinated with chlorine gas. Do the following.

The gallium-containing scrap is preferably used after being crushed in order to increase contact with chlorine gas.
It is possible to use various kinds of cutting chips and fragments generated from the manufacturing process of compound semiconductors such as gallium phosphorus, and various kinds of scraps containing metallic gallium.

According to the method of the present invention, crude metal gallium containing a large amount of impurities can also be treated in the same way.

The reaction in the chlorination step is generally expressed by the following formula.

Ga + 012->GaCl2 GaCl2 + 1/2 C12-→GaCl3As
+ 3/2 012->A3Cl5P + 3/2 0
h→PCI3 Pct3+ C12−÷Pc+5 M + x/ 2 012−→MC1x Here, M represents a metal other than the above. In this way, gallium is GaCl2
Two types of chlorides, GaCl3 and GaCl3, are produced, but if chlorine gas is supplied in excess as required in the subsequent separation and purification process, GaCl2 is converted to GaCl3.

There is no particular restriction on the blowing speed of chlorine gas, and it is appropriately selected based on economic factors such as reaction efficiency and reaction time of chlorine gas.

Since the product after chlorination contains chlorides of impurity metals contained in the treated raw materials in addition to gallium chloride, these impurity chlorides and gallium chloride are first separated by distillation. Chlorides such as AsCl3 and PCl3 generated from chlorides in the medium and impurities in scrap are
Most of these are separated by distillation because they have a boiling point considerably lower than the boiling point of 3. It is also possible to carry out the distillation of substances at the same time.

When Ga-containing scrap contains phosphorus, some of the phosphorus becomes Pct, and this PCI has a melting point of 180'C, which is as high as < IEiO.
It is better to carry out chlorination at 180°C or higher, more preferably PCI3 and PCI5, as the reaction will not proceed.
It is best to carry out chlorination while volatilizing.

In addition, Pct has a high boiling point of 18Ei℃, which is close to the boiling point of GaCl3 of 201℃ and is difficult to separate, so it is preferable to reduce the formation of pat5.In order to reduce the formation of Pct, the chlorination temperature should be set to 300℃ or higher. It is preferable to do so.

After distilling low boiling point chlorides such as AsCl3 and PCl3, the distillation residue is a crude chloride containing GaCl2 and GaCl3 as main components and other high boiling point chlorides generated from impurities in the scrap, such as AlCl3 and CrCl3. It is gallium. Metallic gallium is recovered after further purification or by immediate reduction.

One of the purification methods is a method using distillation and rectification. In this method, first, chlorine gas is further blown into the crude gallium chloride to convert GaCl2 into GaCl3, which has a lower boiling point.
(rechlorination), and then convert GaC13 according to a conventional method.
By distilling and further rectifying, purified gallium chloride (GaC13) can be obtained by separating and purifying it from other impurities.

The crude gallium chloride or purified gallium chloride obtained in the above steps is reduced as necessary to obtain metallic gallium. As reduction methods for recovering metallic gallium by reducing crude gallium chloride or purified gallium chloride, it is possible to implement the following methods: (a) reduction with aluminum powder or zinc powder, (b) hydrogen reduction, and (C) electrowinning. can.

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

(a) Reduced GaCl3 + AI - Ga + AlCl32 (ia
c13 + 3Zn--m-←>2Ga+ 32
nC13(b) Hydrogen reduction 2GaC13+ 3H2-1 → 2Ga + 8HCIG
aC12+ H2-→Ga+ 2HC1 (c) Electrowinning Ga3++ 3e-→Ga Ga" + 2e--La Ga Reduction using aluminum powder or zinc powder is different from the hydrogen reduction method; the reduction method itself requires efficient separation of impurities. Since it does not contain any functionality, gallium chloride must be purified in advance by the above method before use.

Next is electrowinning, which may use an acidic solution or an alkaline solution. When using an acidic solution, it is necessary to purify gallium chloride in advance to prevent simultaneous precipitation of impurities and generation of AsH3. When using an alkaline solution, gallium chloride is neutralized, and the precipitate of gallium hydroxide [Ga(OH)3] produced is separated in a furnace.
Add potassium such as NaOH to dissolve and perform electrowinning. in this case.

Metal impurities such as iron are insoluble in alkaline baths and are therefore easily separated. Arsenic, chromium, etc. are separated by filtration after forming insoluble compounds in an alkaline bath. Also, gallium is GaCl
2 or GaCl3 can be treated in the same manner. Therefore, when using this method, crude gallium chloride can be directly processed. Other low-boiling point chlorides that are separated from gallium can also be recovered as high-purity chlorides through a purification process and then as high-purity metals through a reduction process, which can be used as semiconductor raw materials.

[Effects 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, for example, gallium arsenide scrap at low cost.

Since the method of the present invention directly reacts gallium-containing scrap with chlorine gas, the reaction time is shorter than in wet melting.

In addition, if the gallium-containing scrap contains phosphorus,
The wet method produces highly toxic and pyrophoric phosphine, and the dry method produces pyrophoric phosphorus, but the method of the present invention does not produce these potentially dangerous substances and is easy to work with. 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 carried out in the conventional dry method, and therefore the energy cost is much lower and it is easier to implement. It's easy. Furthermore, according to the method of the present invention, by purifying GaCl3, AsCl3, and Pct3 from crude gallium chloride low-boiling chloride, high-purity gallium chloride, arsenic chloride, and phosphorus chloride, which are suitable as semiconductor raw materials, can be directly converted into chloride. can be obtained in the form of Moreover, by further reducing the obtained crude gallium chloride, purified gallium chloride, purified arsenic chloride, and purified phosphorus chloride, it is possible to recover 8N purity metal gallium, metal arsenic, and metal phosphorus.

[Specific Disclosure of the Invention] Example 1 50 gallium arsenic scraps in 2 40 flasks
I put in 08. This was heated to 60°C and then 40 (l
Since the chlorination reaction of gallium and arsenic, in which C12 gas was blown into the bath at a ratio of sJL/win, is an exothermic reaction,
The temperature inside the flask will be 70-80°C. Partially volatilized AsCl3 was cooled by a cooling pipe attached to the CI2 gas outlet of the flask, became liquid, and returned to the flask.

After further blowing 3481 C12 gas into the flask,
A mixed solution of GaCl3 and AgCl3 produced was taken out.

The amount produced was 1242 g (GaC13807 g, As
Cl3eosg).

Next, extract 500g from this mixture and add 5001/40
It was placed in a flask and heated with a mantle heater to perform distillation purification. The distillation tube had a length of 500 mm, an inner diameter of 20 mm, and was filled with glass beads.

First, the temperature at the top of the distillation tube was set at 130° C. to distill As013. The distillate was cooled and evaporated in a condenser tube, taken out as a liquid, and then weighed and analyzed for components.

After distilling AsCl3, the temperature at the top of the distillation tube was set to 200℃.
℃ and distilled GaCl3 0 recovered A, te
13 weighed 222g and had a purity of 99.9%. Also, the recovered GaCl3 was 238g and its purity was 99.8$
Met.

Example 2 The GaC13 obtained in Example 1 (purity 98.8) was rectified. The distillation tube used was a glass tube with a length of 1000 mm and an inner diameter of 50 μl filled with glass beads. As the first distillate, one rich in AsCl3 was obtained. Then GaCl
A product rich in 3 was obtained. The obtained GaCI 3 is 1
91g, purity 99.9999$ Te Atsuta.

Example 3 500 gallium phosphorus scraps in 2 40 flasks
This was heated to about 300°C using a mantle heater.

Next, C12 was injected into the flask at 500 mA/sin. Most of the gallium became Gacl3 and volatilized, and most of the phosphorus also became pc+3 and some of it also volatilized as PCl5, so there was always a new surface of the scrap. Since the 0 reaction with C12 is an exothermic reaction, the temperature can be maintained with almost no need for heating. The volatilized chloride is cooled to 120 to 180°C, and GaC13 is condensed and recovered. Since the boiling point of pc+3 is 75℃, it does not condense, and G
Purification of aCl3 can be performed. The gas mainly composed of Pct is further cooled, and Pct3 and other low boiling point chlorides are condensed.

After injecting CI2 gas 1201, gallium-rich chloride (Ga content 149 g, P content 14 g) and gallium-poor chloride (Ga content 3 g, P content 58
g) was obtained.

After dissolving gallium-rich chloride in 1.5 fL of water, it was adjusted to P)IS with NaOH, and gallium was precipitated and recovered as gallium hydroxide Ga(OH)3. Most of the phosphorus enters the furnace fluid and is removed. Gallium hydroxide Ga(O
H) After further adding NaOH to 3 and dissolving gallium,
Impurities in the liquid were removed using various reagents, and 148 g of gallium metal was recovered by electrolytic sampling. Purity is 99.99
It was 82.

Example 4 Gallium-containing scrap (Ga
500g of 78L Bi 5L Si0215%)
I entered. After heating the flask to 240℃ with a mantle heater, 400+1! ; Because the chlorination reaction of gallium and bismuth, in which CI2 gas was blown into the flask at a ratio of L/win, is an exothermic reaction, the temperature inside the flask is maintained at approximately 250°C. At this temperature, BiCl3 has a boiling point of 441°C and therefore remains in the flask, while GaCl3 has a boiling point of 201°C.
Therefore, it volatilizes and is condensed and recovered by cooling.

After injecting 2501 CI2 gas, the purity is 99 in the cooling section.
．． 3956 g of 99% GaCl was obtained.

[Brief explanation of drawings]

The figure is a flow sheet illustrating the method of the invention. Patent applicant: Mitsubishi Metals Corporation Agent: Patent Attorney Masahiro Matsui (Outside - 1 person)

Claims (1)

[Claims] 1. Recovery of gallium, which consists of reacting scrap containing gallium with chlorine to convert some or all of gallium and other elements into chlorides, and purifying crude gallium chloride separated by distillation after or simultaneously with chlorination. Method.