JPS63270426A - Method for recovering metallic gallium from gallium-containing material - Google Patents

Abstract

PURPOSE:To recover liquid-metal gallium in high purity, by adding and mixing a binder into a gallium-bearing material containing the fine grains of gallium compounds, by heating and burning the resulting mixture, and by applying vacuum thermal decomposition to the above. CONSTITUTION:A gallium-bearing material containing the fine grains of gallium compounds hitherto treated as waste, such as dross, is used as a raw material. An inorganic and/or organic binder is added and mixed into the above-mentioned raw material to be treated. At this time, alumina hydrosol, clay minerals, etc., are used as the inorganic binder and, as the organic binder, PVA, polyethylene glycol, etc., are used, and it is preferable the additive quantity to at least about 0.001pts.wt. per pts.wt. of the above-mentioned fine grains. The above mixture is preferably dried previously and is compacted, if necessary, into a sheet-like state, etc., and is then subjected to heating and burning at about 300-1,000 deg.C as pretreatment. The resulting burnt material in which the fine grains of gallium compound are bound together and made difficult to scatter is subjected to vacuum thermal decomposition at about 10<-5>-100mm at about 1,000-1,300 deg.C. The resulting liquid-metal gallium is recovered by separating the decomposition residue by filtration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for recovering metallic gallium from gallium-containing materials containing gallium compound fine particles that are by-produced as scrap or waste in semiconductor manufacturing factories and the like.

[Prior art]

When manufacturing wafers of semiconductors such as gallium arsenide and gallium phosphide, there is a cutting process for converting these semiconductor single crystals into perfect cylinders, and a cutting process for cutting the semiconductor cylinders into wafers.

A large amount of cutting waste and cutting waste is generated as fine powder.

Since such cutting and cutting steps are performed while adding cutting oil or cutting water, the generated fine powder is collected while being dispersed in the cutting oil.

Then, by subjecting this dispersion to a sedimentation treatment, a concentrated liquid containing fine powder is recovered. A concentrate containing this fine powder is usually called dross. Such dross is extremely difficult to handle because it contains a large amount and various types of impurities mixed in during the cutting and cutting processes, as well as mineral oil-type or water-soluble cutting oil and cutting aids. In the past, metallic gallium was hardly used as a raw material for recovery and was disposed of. However, in order to compensate for the shortage of gallium resources, there is a strong desire to effectively utilize this as a gallium resource.

〔the purpose〕

An object of the present invention is to provide a novel method for recovering metallic gallium from a gallium-containing material containing gallium compound fine particles such as dross, which has been conventionally treated as waste, as a raw material.

〔composition〕

According to the present invention, in a method for recovering metallic gallium from a gallium-containing material containing fine particles of a gallium compound, an inorganic and/or organic binder is added and mixed to the gallium-containing material, and the mixture is shaped as necessary. After that, it is characterized by comprising a pretreatment step of heating and firing, and a pyrolysis step of vacuum pyrolysis of the fired product in which the gallium compound fine particles obtained in the pretreatment step are bonded to each other to generate liquid metal gallium. A method of recovering metallic gallium from a gallium-containing material is provided.

The gallium-containing material that can be used as the raw material to be treated in the present invention may be in powder or liquid form as long as it contains gallium compound fine particles, such as the above-mentioned dross,
Materials that have not been considered as metal gallium recovery resources can also be used6.Furthermore, dry fine powder of this dross, liquid scrap of gallium compounds, and finely pulverized bulk scrap can also be used. Further, the gallium component in the raw material to be treated is a gallium compound that yields metallic gallium through thermal decomposition, such as gallium arsenide or gallium phosphide.

The inorganic and organic binders used in the present invention are:
It is used to bind gallium compound fine particles to each other and prevent the gallium compound fine particles from scattering during vacuum pyrolysis. Concentrated liquid (sludge) containing fine particles of gallium compounds such as dross.

Even if you try to directly vacuum pyrolyze it, the liquid contained in it will volatilize, causing problems such as contaminating the vacuum system, and it is also undesirable because the dry fine powder will scatter after the liquid has volatilized. . Also. When a concentrated liquid containing fine particles of a gallium compound such as dross is dried and this dried product is subjected to vacuum pyrolysis, it is also undesirable because the fine powder similarly scatters.

By using the above-mentioned inorganic and organic binders.

Such inconveniences are avoided.

In the present invention, first, in the pretreatment step, an inorganic and/or organic binder is mixed with the raw material to be treated,
This mixture is shaped as necessary and then heated and fired to obtain a fired product in which fine particles are bonded to each other. In this case, as the inorganic or organic binder, various conventionally known substances that are conventionally used for bonding fine powder particles to each other can be used. Examples of such inorganic binders include inorganic oxide hydrosyls such as alumina hydrosyl, alumina silica hydrosyl, silica hydrosyl, magnesia hydrosyl, and titania hydrosyl, and their precursors, attapulgite, kaolin, and montmorillonite. , clay minerals such as sepiolite, alkali silicates, alkali aluminates, aluminum salts, cement, lime, etc. In the present invention, gallium, arsenic, phosphorus, etc. can also be used, and furthermore, muddy scrap generated in the wafer polishing process and hydrosil obtained from this muddy scrap can be used. Further, as an organic binder, for example.

In addition to organic polymers such as starch, polyvinyl alcohol, carboxymethyl cellulose, and alginic acid, polyethylene glycol, glycerin, pitch, and graphite can also be used. The amount of the inorganic and/or organic binder (hereinafter also simply referred to as binder) added is at least 0.001 parts by weight, usually 0.01 to 1 part by weight, per 1 part by weight of fine particles (dry basis) in the raw material to be treated. The proportion is 0.2 parts by weight.

A mixture of the raw material to be treated and a binder is heated and baked, but if the raw material to be treated is a muddy substance such as dross, it contains a large amount of water and oil, so this water and oil are removed by drying. It is best to dry it beforehand. This drying is usually carried out at a temperature of 50 to 300°C, preferably 100 to 200°C.
It is carried out at 00°C. Also.

This drying can also be performed under vacuum or an inert gas atmosphere. Furthermore, the mixture of the raw material to be treated and the binder can be subjected to a molding process to form a molded product.

In this case, if the raw material to be processed contains water and oil, such as dross, a binder is added and mixed therein, and then the water and oil are removed by drying, etc., and the material is adjusted to be suitable for molding.
Shape.

If the raw material to be processed is powdery, such as dried dross, or finely pulverized plate-like scrap or block-like scrap, a binder and an appropriate amount of water are added thereto to form the material. The shape of the molded product may be arbitrary, such as a plate, a single sphere, a pellet, or a cylinder, and its dimensions may be such that it does not scatter. Usually, the length of the major axis is 2 to 100
It is about +o+m. The type of binder is appropriately selected in relation to the type of raw material to be treated. For example, when the raw material to be treated is an oily slurry, it is preferable to use an oil-soluble binder such as polyethylene glycol or pitch. In the case of slurry, it is preferable to use water-soluble organic polymers such as starch and alginic acid, and hydrophilic binders such as hydrosil and clay minerals.

When the mixture of the raw material to be treated and the binder is dried as described above or as a molded product, the moisture or liquid content of the dried product is usually 1 to 50% by weight2. Preferably it is 5 to 20% by weight.

The heating and baking in the pretreatment step of the present invention is usually carried out at a temperature of 300 to 1000°C. By this firing, a sintered body in which fine particles are strongly bonded to each other via a binder is obtained. Unlike fine powder, such a sintered body does not cause scattering when it is subjected to vacuum pyrolysis. Note that when an organic binder is used, this binder is thermally decomposed and coked during firing and converted to coke (carbon content), and this coke content acts as a binder for the sintered body. .

In the pretreatment step used in the present invention, the heating drying and heating baking are preferably carried out in an inert gas atmosphere or under reduced pressure conditions because gallium compounds are easily oxidized. Any material can be used as long as it does not react with the compound, and nitrogen gas, argon, etc. are generally used. Further, as the reduced pressure condition, a pressure condition of about 10 −4 to 100 mmHg is usually adopted.

Next, the fired product (sintered product) obtained from the pretreatment process as described above is subjected to vacuum pyrolysis treatment in order to recover gallium metal. This vacuum pyrolysis treatment.

Generally, the residual gas pressure is 10″S~100m+aH
The test is carried out under vacuum conditions of 1,000 to 1,300°C and heating conditions of 1,000 to 1,300°C.

The higher the vacuum and temperature conditions, the higher the decomposition rate of gallium compounds, but the greater the evaporation loss of gallium.

Therefore, normally 10-' to 10'' mmHg, 105
It is carried out under conditions of 0 to 1150°C.

Through this vacuum pyrolysis treatment, the gallium compound contained in the raw material to be treated undergoes thermal decomposition, and the gallium component is converted into liquid gallium metal, and other components, such as arsenic and phosphorus, are converted into gas. It is converted into arsenic and phosphorus. The gaseous arsenic and phosphorus generated by this thermal decomposition can be recovered by bringing them into contact with a cooling surface of 200° C. or lower and precipitating them as solids. On the other hand, the decomposition residue containing liquid metal gallium, binder, impurities, and unreacted substances is subjected to solid-liquid separation treatment such as filtration. Thereby, metal gallium contained in the decomposition residue can be recovered in liquid form.

When filtering decomposition residue, a sieve with a mesh size of 50 mesh or finer is usually used.6 The binder used in the present invention is separated by this solid-liquid separation process, and no contamination with the liquid metal gallium occurs. No.

The purity of the metal gallium thus recovered, excluding indium, is usually 3N (nine) to 5N (nine).

〔effect〕

According to the present invention, metallic gallium can be recovered with high purity from gallium-containing materials that contain fine particles of gallium compounds and have been difficult to effectively utilize as a gallium recovery resource, and this has great industrial significance. .

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weight.

Example 1 Oily muddy scrap of gallium arsenide fine particles containing about 18% oil content (mainly light oil) was distilled in an inert gas atmosphere, and then further heated at about 500°C for 1 hour to remove light content. 3.1% carbon, 44% gallium, 46% arsenic, and other impurities (In, P, SL, Fe
etc.) A powder with an elemental composition of 5% was obtained.

Next, solvent-extracted coal (pitch obtained by solvent extraction of coal under hydrogen pressure) containing 89.4% carbon, 2.7% ash, and 40.4% toluene-insoluble content is added to this powder as an organic binder. Add 5% of the mixture and mix well. Place 500g of the mixture in a quartz reaction tube and heat at 150°C while flowing inert gas.
After being kept at 500° C. for 3 hours, it was further kept at 500° C. for 1 hour and fired. Through this firing, the organic binder was thermally decomposed into coke, and the fine powder was converted into a fired product in which the particles were bonded to each other by coke.

Next, this reaction tube was connected to a vacuum evacuation device equipped with an arsenic precipitation trap (the area from the reaction tube to the trap was heated to approximately 500°C), and the temperature was raised to 1,100°C at a rate of 300°C/Hr. This temperature was maintained for 3 hours to thermally decompose the gallium compound in the fired product. The degree of vacuum on the vacuum side of the arsenic trap during pyrolysis at 1,100°C is 104 to 10-
'mm11g. Next, the obtained vacuum pyrolysis residue was taken out and filtered through a 100-mesh filter cloth to remove 1 to 10 p of each of Si, Fe, Cu, and Ca as impurities.
pm, 150.1 g of metallic gallium containing 1.7 ppm of As and 3.1% of In was obtained in liquid form.

Example 2 500 g of oily mud scrap shown in Example 1 was
While heating to 0° C., inert gas was passed through the solution to reduce the oil content to 1.5%. Next, 75 g of cornstarch and 120 g of water were added to this dried product and thoroughly mixed and kneaded. This mixed wire was compression molded into a cylinder having a diameter of 1011III+ and a height of about 10 mm using a mold. This molded product was dried at 120°C for 5 hours, and then at 500°C for 2 hours in a nitrogen stream.

Then, it was baked at 700°C for 2 hours. The carbon content of the fired product was 5.2%. Next, this calcined product was subjected to vacuum pyrolysis at 1,120°C for 5 hours in the same manner as in Example 1, and the decomposition residue was filtered to obtain metallic gallium 163.
3 g was obtained. Impurities in this metallic gallium include 3.4% In, 0.7ppm+ As, Fa,
Mg and Ca were found in amounts of ~10 ppm each.

Example 3 Aqueous slurry scrap of gallium arsenide fine particles containing about 14% water was used as the raw material to be treated. Elemental analysis of this material after drying it at 500°C for 1 hour revealed 0.3% carbon, 43% gallium, 50% arsenic, and 0.0% impurities such as In and Fe.
It showed 1%.

First, in order to obtain an inorganic binder, a block of sepiolite ore is dry-pulverized using a ball mill.

Coarse particles were separated and removed using a 100 mesh sieve to obtain finely powdered sepiolite.Next, 200 parts of water was added to 100 parts of this sepiolite and thoroughly kneaded to obtain 100 parts of this mixed wire.
After adding 200 parts of the raw material to be treated and sufficiently mixing and kneading, the mixture was extruded into a cylinder having a diameter of about 2 mW. This molded product was dried in the same manner as in Example 2.
It was fired to obtain a fired product with a Ga content of 39%. When 500 g of this calcined product was subjected to vacuum pyrolysis under the same reaction conditions as in Example 2 and the decomposition residue was filtered, 148.3 g of metallic Ga
was recovered. As an impurity in this Ga, As is 0.
3ppm, In, Fe, Cu, Ca is 11-1O
pp approved.

Example 4 100 g of the raw material to be treated shown in Example 3, 20 g of water, and 2 g of white carbon made of fine silica particles with a diameter of 1 to 20 μm were thoroughly mixed, and this mixture was placed in a quartz crucible.
This was further placed in a quartz reaction tube, dried in a nitrogen stream in the same manner as in Example 1, and then fired at 500°C for 1 hour.

Next, this fired product was treated in the same manner as in Example 1, and 1,150
Vacuum pyrolysis was carried out at ℃ for 1 hour. When the resulting thermal decomposition residue was filtered through a 100 mesh filter cloth, 28.0 g of metallic Ga was recovered. This product contains A as an impurity.
s is 10pp+a, In is 78ppm, Fe, Ca
, Mg was observed at 1 to 10 PP+, respectively.

Example 5 The elemental composition of the product dried at 90°C for 3 hours is carbon 0.4
%, Ga46%, As53%, other impurities (SL,
Finely powdered gallium arsenide scrap containing 0.8% (In, Fe, AQ) in total and 90% or more of 20 mesh passes was used as the raw material to be processed. After drying this raw material to be treated at 90°C for 3 hours, 4N was added to 100 parts of this powder.
20 parts of metallic gallium was added and thoroughly mixed using a mixer. The thus obtained mixture was compression molded in the same manner as in Example 2 to a diameter of 10 mm and a height of 10 mm.

This molded product was fired at 500° C. for about 2 hours in a nitrogen stream.

Next, put 100g of this molded product into a quartz crucible and
Vacuum pyrolysis was performed at °C for 3 hours. 100% of thermal decomposition residue
When filtered through a mesh filter cloth, 4L1g of gold RGa was obtained. From this, 31.4 from Ga and As scrap
It is recognized that g of Ga was recovered. As an impurity of Ga, As is 3. lppm, In, Fe, Ca
, Cu were observed in amounts of 1 to 10 ppm, respectively.

Claims (1)

[Claims] (1) In a method for recovering metallic gallium from a gallium-containing material containing gallium compound fine particles, an inorganic and/or organic binder is added and mixed to the gallium-containing material,
After shaping this mixture as necessary, there is a pretreatment process in which the mixture is heated and fired, and the fired product in which the gallium compound fine particles obtained in the pretreatment process are bonded to each other is vacuum pyrolyzed to produce liquid metal gallium. A method for recovering metallic gallium from a gallium-containing material, comprising a decomposition step.