JP2604590B2 - Method for recovering metallic gallium from gallium-containing materials - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for recovering metallic gallium from gallium-containing substances including gallium compound fine particles that are by-produced as scrap or waste in a semiconductor manufacturing plant or the like.

(Prior art)

In the production of semiconductor wafers such as gallium arsenide and gallium phosphide, a large amount of cutting waste and a large amount of chips are generated in a cutting process for turning the semiconductor single crystal into a perfect cylinder and a cutting process for cutting the semiconductor perfect cylinder into a wafer. Cutting chips are generated as fine powder. Such cutting and cutting process,
Since the cutting is performed while pouring the cutting oil or the cutting water, the generated fine powder is collected in a state of being dispersed in the cutting oil. Then, a concentrated liquid containing fine powder is recovered by subjecting the dispersion to sedimentation. The concentrate containing this fine powder,
It is usually called dross. Such a dross
In addition to containing a large amount and many kinds of impurities mixed in the cutting process and the cutting process, it is very difficult to handle because it contains mineral oil type or water soluble type cutting oil and cutting aid. It is hardly used as recovered material and is disposed of. However, in order to compensate for the shortage of gallium resources, there is a strong demand for effective utilization of the gallium resources.

〔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.

〔Constitution〕

According to the present invention, in a method of recovering metallic gallium from a gallium-containing material containing gallium compound fine particles, an inorganic and / or organic binder is added to and mixed with the gallium-containing material, and the mixture is added under an inert gas atmosphere or under vacuum. The gallium-containing material is characterized by recovering the liquid metal gallium by drying and heating to a temperature of 300 to 1000 ° C., and sintering the obtained sintered body by vacuum pyrolysis. A method for recovering metallic gallium is provided.

The gallium-containing material that can be used as the raw material to be treated in the present invention can be used in any form of powder or liquid as long as it contains gallium compound fine particles, and is completely considered as a conventional metal gallium recovery resource, such as the aforementioned dross. Those that did not exist can also be used. In addition, a dry fine powder of the dross, a liquid scrap of the gallium compound, or a finely pulverized lump scrap can also be used. Also,
The gallium component in the raw material to be treated is a gallium compound that gives metallic gallium by thermal decomposition of gallium arsenide, gallium phosphide, or the like.

The inorganic and organic binders used in the present invention are used for bonding gallium compound fine particles to each other to prevent scattering of the gallium compound fine particles during vacuum pyrolysis. Concentrated liquid (mud) containing gallium compound fine particles such as dross may cause inconveniences such as vaporization of the liquid contained therein even if it is intended to be directly pyrolyzed by vacuum, and contaminate the vacuum system. It is not preferable because the dry fine powder is scattered after the volatile matter is volatilized. Also. When a concentrated solution containing gallium compound fine particles such as dross is dried and the dried product is pyrolyzed in a vacuum, the fine powder is similarly scattered, which is not preferable. Such disadvantages are avoided by using the inorganic and organic binders.

In the present invention, first, in a pretreatment step, an inorganic and / or organic binder is formed as a raw material to be treated, and this mixture is molded as necessary, followed by heating and firing to obtain a fired product in which fine particles are mutually bonded. . In this case, as the inorganic or organic binder, various conventionally known substances conventionally used for binding fine powder particles can be used. Examples of such an inorganic binder include inorganic oxide hydrosols such as alumina hydrosol, alumina silica hydrosol, silica hydrosol, magnesia hydrosol, titania hydrosol and precursors thereof, attapulgide, kaolin, montmorillonite. And minerals such as sepiolite, alkali silicate, alkali aluminate, aluminum salts, cement, lime and the like. In the present invention, gallium, arsenic, phosphorus, and the like can be used, and further, mud scrap generated in a wafer polishing step and a hydrosol obtained from the mud scrap can be used. Further, as an organic binder, for example, starch, polyvinyl alcohol,
In addition to organic polymers such as carboxymethyl cellulose and alginic acid, polyethylene glycol, glycerin, pitch, graphite and the like can be used. The amount of the inorganic and / or organic binder (hereinafter, also simply referred to as a binder) is at least 0.001 part by weight, usually 0.0% by weight, per 1 part by weight of fine particles (dry matter basis) in the raw material to be treated.
The ratio is 1 to 0.2 parts by weight.

The mixture of the raw material to be processed and the binder is heated and calcined.If the raw material to be processed is a mud such as dross, it contains a large amount of water and oil, so that the water and oil are removed by drying. It is better to dry in advance. This drying is usually performed at a temperature of 50 to 300 ° C, preferably 100 to 200 ° C. The drying is performed under an inert gas atmosphere or under vacuum. Further, the mixture of the raw material to be treated and the binder can be subjected to a molding step to form a molded product. In this case, if the raw material to be treated contains water or oil such as dross, after adding and mixing a binder thereto,
Moisture and oil are removed by drying or the like, adjusted to one suitable for molding, and molded. When the raw material to be processed is a powdered material such as a dried dross material or a finely pulverized plate scrap or a lump scrap, an appropriate amount of moisture is added to the raw material together with a binder. The shape of the molded product may be any shape such as a plate, a lump, a sphere, a pellet, and a cylinder, and the size may be any size as long as it does not scatter. Usually, the length of the major axis is about 2 to 100 mm. 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 mud, it is preferable to use an oil-soluble binder such as polyethylene glycol or pitch.On the other hand, when an aqueous mud is used, starch or a water-soluble organic polymer such as alginic acid may be used. , Hydrosols, clay minerals, and other hydrophilic binders are preferred.

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 in the dried product is generally 1 to 50% by weight, preferably 5 to 20% by weight. .

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

In the pretreatment step used in the present invention, the heat drying and heat baking are performed in an inert gas atmosphere or under reduced pressure, since the gallium compound is easily oxidized. Any inert gas may be used as long as it does not react with the gallium compound. Generally, nitrogen gas, argon, or the like is used. The decompression condition is usually 10 ^-4 to
A pressure condition of about 100 mmHg is adopted.

Next, the calcined product (sintered product) obtained from the pretreatment step as described above is subjected to a vacuum pyrolysis treatment in order to recover gallium metal. This vacuum pyrolysis process generally comprises
It is carried out under a vacuum condition of residual gas 10 ^{−5 to} 100 mmHg and a heating condition of 1000 to 1300 ° C. The higher the vacuum and temperature conditions, the higher the decomposition rate of the gallium compound, but the greater the loss of gallium evaporation. Therefore, usually, 10 ^-4 ~ 10 ^-1 mmHg, 1050 ~
It is performed under the condition of 1150 ° C.

By this vacuum pyrolysis process, the gallium compound contained in the raw material to be processed undergoes thermal decomposition, and the gallium component is converted to liquid gallium metal, and other components such as arsenic and phosphorus are converted to gaseous form. Is converted to arsenic and phosphorus. The gaseous arsenic and phosphorus generated by the thermal decomposition can be recovered by bringing the gaseous arsenic and phosphorus into contact with a cooling surface at a temperature of 200 ° C. or lower and precipitating them as solids. On the other hand, the decomposition residue containing the liquid metal gallium and the binder, impurities and unreacted substances is subjected to a solid-liquid separation treatment such as filtration.
Thereby, metallic gallium contained in the decomposition residue can be recovered in a liquid state. When filtering the decomposition residue, a sieve having a mesh finer than 50 mesh is usually used. The binder used in the present invention is separated by this solid-liquid separation treatment, and does not mix with the liquid metal gallium. The purity of the metal gallium thus recovered excluding indium is usually 3N (nine) to 5N (nine).

〔effect〕

According to the present invention, gallium compound fine particles are contained, and it is difficult to effectively use it as a gallium recovery resource, but from gallium-containing substances, metallic gallium can be recovered with high purity, and its industrial significance is great. is there.

〔Example〕

Next, the present invention will be described in more detail with reference to examples.
All parts and percentages shown below are based on weight.

Example 1 An oily mud-like scrap of gallium arsenide fine particles containing about 18% of oil (mainly light oil) was distilled in an inert gas atmosphere, and further heated at about 500 ° C. for 1 hour to remove the light fraction. 3.1% carbon, 44% gallium, 46% arsenic,
A powder having an elemental composition of 5% of other impurities (In, P, Si, Fe, etc.) was obtained.

Next, to this powder, 5% of an organic binder containing solvent-extracted coal containing 89.4% carbon, 2.7% ash, and 40.4% toluene-insoluble matter (pitch obtained by solvent extraction under hydrogen pressure of coal) was added and mixed well. 500 g of the resulting product was put into a quartz reaction tube, kept at 150 ° C. for 3 hours while flowing an inert gas, and then further fired at 500 ° C. for 1 hour. By this firing, the organic binder was pyrolyzed to coke, and the fine powder was converted into a fired product in which the particles were joined by coke.

Next, this reaction tube was connected to a vacuum exhaust device equipped with an arsenic precipitation trap (the temperature from the reaction tube to the trap was heated to about 500 ° C), and the temperature was raised to 1,100 ° C at a rate of 300 ° C / Hr. The 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 thermal decomposition at 1,100 ° C was 10 ^-2 to 10 ^-4 mmHg. Next, the obtained vacuum pyrolysis residue was taken out and filtered with a 100-mesh filter cloth.
150 g of metallic gallium containing ~ 10 ppm, 1.7 ppm of As, and 3.1% of In.
1 g was obtained in liquid form.

Example 2 500 g of the oily muddy scrap shown in Example 1 was heated to about 90 ° C. while flowing an inert gas to reduce the oil content to 8%. Next, corn starch (75 g) and water (120 g) were added to the dried product and mixed and kneaded well. This kneaded material was compression-molded into a cylinder having a diameter of 10 mm and a height of about 10 mm using a mold. After drying this molded product at 120 ° C. for 5 hours, it is heated at 500 ° C. in a nitrogen stream.
For 2 hours and then at 700 ° C. for 2 hours. The carbon content of the fired product was 5.2%. Next, the fired product was subjected to vacuum pyrolysis at 1,120 ° C. for 5 hours in the same manner as in Example 1,
By filtering the decomposition residue, metallic gallium 163.
3 g were obtained. In this metallic gallium, the impurity is In.
3.4%, As 0.7 ppm, Fe, Mg, and Ca 1 to 10 ppm each.

Example 3 An aqueous slurry of gallium arsenide fine particles containing about 14% of water was used as a raw material to be treated. This one at 500 ℃
Elemental analysis of the dried material for 0.3 hours revealed that
3%, 50% arsenic, and 0.1% impurities such as In and Fe.

First, in order to obtain an inorganic binder, lump sepiolite ore was dry-pulverized with a ball mill, and coarse particles were separated and removed with a 100-mesh sieve to obtain fine powder-form sepiolite. Next, 200 parts of water was added to 100 parts of this sepiolite and sufficiently kneaded, and 100 parts of the kneaded material and 50 parts of water were further sufficiently mixed and kneaded with 200 parts of the raw material to be treated, and then the diameter was reduced to about 100 parts. It was extruded into a 2 mm cylinder. This molded product was dried and fired in the same manner as in Example 2 to obtain a fired product having a Ga content of 39%. 500 g of this calcined product was pyrolyzed in vacuum under the same reaction conditions as in Example 2, and the decomposition residue was filtered. As a result, 148.3 g of metallic Ga was recovered. As an impurity in Ga, the content of As is 0.
3 ppm, 1-10 ppm of In, Fe, Cu, and Ca were observed.

Example 4 20 g of water and a diameter of 1 to 2 were added to 100 g of the raw material to be treated shown in Example 3.
2 g of white carbon composed of 0 μm silica fine particles were mixed well, and this mixture was placed in a quartz crucible, further placed in a quartz reaction tube, dried in a nitrogen stream in the same manner as in Example 1, and then dried at 500 ° C. for 1 hour. Fired for hours.

Next, the fired product was heated at 1,150 ° C. in the same manner as in Example 1.
For 1 hour under vacuum. The obtained pyrolysis residue is 100
When filtered through a mesh filter cloth, 28.0 g of metallic Ga was recovered. This substance contains 10 ppm of As and 7 ppm of In as impurities.
8 ppm, Fe, Ca, and Mg were found in amounts of 1 to 10 PPm, respectively.

Example 5 After drying at 90 ° C. for 3 hours, the element composition was 0.4 carbon.
%, Ga46%, As53%, and other impurities (Si, In, Fe, A
l) was 0.8% in total, and 90% or more used 20 mesh pass fine pulverized gallium arsenide scrap as a raw material to be treated. After the raw material to be treated was dried at 90 ° C. for 3 hours, 20 parts of 4N metal gallium was added to 100 parts of the powder, and the mixture was sufficiently mixed with a mixer. The mixture thus obtained was compression molded to a diameter of 10 mm and a height of 10 mm in the same manner as in Example 2. This molded product was fired at 500 ° C. for about 2 hours in a nitrogen stream.

Next, 100 g of this molded product was placed in a quartz crucible and vacuum pyrolyzed at 1080 ° C. for 3 hours. Filtration of the pyrolysis residue with a 100 mesh filter cloth gave 48.1 g of metallic Ga. This indicates that 31.4 g of Ga was recovered from the Ga and As scrap. As an impurity of Ga, As is 3.1 ppm, In, F
e, Ca, and Cu were observed in amounts of 1 to 10 ppm, respectively.

Claims (1)

(57) [Claims] 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 to and mixed with the gallium-containing material, and the mixture is mixed under an inert gas atmosphere or under vacuum. Metal from gallium-containing material, characterized in that it is dried and sintered under heating at a temperature of 300 to 1000 ° C., and liquid metal gallium is recovered by vacuum pyrolysis of the obtained sintered body. Gallium recovery method.