JP2001232234A - Method for concentrating gallium compound from precipitate containing gallium compound, abrasive grain, and cutting oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gallium compound concentration method with an improved gallium compound recovery ratio and capable of suppressing generation of industrial wastes. SOLUTION: The method for concentrating a gallium compound from a precipitate containing a gallium compound, an abrasive grain, and a cutting oil comprises a first step of dissolving the cutting oil of the precipitate in a solvent compatible with the cutting oil and having a boiling point lower than the thermal decomposition temperature of the gallium compound and simultaneously dispersing the gallium compound and the abrasive grain of the precipitate in the solvent, a second step of wet classifying the solvent in which the gallium compound and the abrasive grain are dispersed and separating the solvent in which a fine powder containing mainly the gallium compound is dispersed and the solvent in which a coarse powder containing mainly the abrasive grain is dispersed, a third step of separating the solvent from the solvent in which the fine powder is dispersed to obtain the fine powder, and a fourth step of supplementing the abrasive grain in the same quantity as that of the abrasive grain separated as the fine powder after the solvent is removed based on necessity from the solvent in which the coarse powder is dispersed, adjusting the quantity of the cutting oil, and making the gallium compound a slurry for the time of wire saw cutting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for concentrating and recovering gallium from a gallium compound, abrasive grains and cutting oil containing cutting oil generated during the production of a compound semiconductor crystal wafer containing gallium such as gallium phosphide. And a method for concentrating a gallium compound.

[0002]

2. Description of the Related Art In the process of manufacturing a compound semiconductor crystal containing gallium such as gallium phosphide, when cutting a compound semiconductor crystal containing gallium (hereinafter referred to as a gallium compound), a diamond inner peripheral blade cutting device has conventionally been used. Was used. Most of the sediment generated as cutting chips at this time is a cutting powder of a gallium compound, and has been effectively used as a raw material for recovering metallic gallium.

[0003] Recently, in order to reduce the cost by reducing the cutting loss, cutting methods for gallium compounds have been described.
It has been replaced by a wire saw cutting method with less cutting margin. In this wire saw cutting method, cutting oil in which abrasive grains are dispersed (hereinafter referred to as slurry) is used, so that the deposits generated when cutting the wire saw are fine cutting powder (fine powder) and coarser grinding powder. Collected as a mixture containing grains (coarse powder) and cutting oil. In the wire saw cutting, the gallium compound content in the sediment was 10% by weight or less due to the large amount of abrasive grains used, and the gallium concentration was low.

[0004] Therefore, when gallium is to be recovered from the above-mentioned sediment generated at the time of cutting the wire saw, it is necessary to perform a recovery treatment on the sediment having a low concentration of the gallium compound. Conventionally, the above deposits have been disposed of as industrial waste because they are not economically viable.

[0005] However, from the viewpoint of effectively utilizing the gallium resources, which tend to be insufficient, there has been a strong demand for a method of economically recovering gallium from the deposits generated when cutting a wire saw.

Under such technical background, the present applicant has already proposed a method for simply and remarkably concentrating and recovering gallium content from a deposit containing a gallium compound, abrasive grains and cutting oil. (See Japanese Patent Application No. 11-76884).

That is, the method proposed by the applicant is as follows:
A method for concentrating gallium from a precipitate containing a gallium compound, abrasive grains and cutting oil, wherein the cutting oil in the precipitate is mixed with a solvent having a boiling point lower than a thermal decomposition temperature of the gallium compound and being compatible with the cutting oil. Dissolving the gallium compound and abrasive grains in the precipitate and dispersing the abrasive grains, and a fine powder mainly containing a gallium component and an abrasive for removing the abrasive grains from the solvent in which the gallium compound and the abrasive grains are dispersed. A second step of obtaining a solvent in which the fine powder is dispersed by wet classification into coarse powder mainly containing grains,
A third step of separating the solvent from the solvent in which the fine powder is dispersed to obtain fine powder, and heating the obtained fine powder at a temperature lower than the thermal decomposition temperature of the gallium compound to remove the remaining solvent into fine powder; And a fourth step of removing from the substrate.

[0008]

According to the above method, however, in the second step, about 9% of the gallium compound in the precipitate is removed.
Although 0% could be recovered as fine powder, coarse powder mainly composed of abrasive grains still contained about 10% of a gallium compound. However, since the coarse powder is disposed of as industrial waste, it is not recovered, and the recovery rate of the gallium compound is about 90% at the upper limit.

The present invention has been made in view of such problems, and has as its object to further improve the recovery rate of gallium compounds and reduce the amount of industrial waste.

[0010]

That is, the invention according to claim 1 is a method for concentrating gallium from a gallium compound, an abrasive, and a sediment containing cutting oil generated when the gallium compound is cut with a wire saw. In, a first step of dissolving the cutting oil in the precipitate and dispersing the gallium compound and abrasive grains in the precipitate in a solvent compatible with the cutting oil and having a boiling point lower than the thermal decomposition temperature of the gallium compound, Wet classification of the gallium compound and the solvent in which the abrasive grains are dispersed,
The second step of separating the solvent in which the fine powder mainly containing gallium compound is dispersed and the solvent in which the coarse powder mainly containing abrasive grains is dispersed, and the solvent in which the fine powder obtained in the second step is dispersed The third step of obtaining a fine powder by separating the solvent from the, the coarse powder obtained in the second step was removed as a fine powder in the second step after removing the solvent as necessary from the dispersed solvent A fourth step of replenishing abrasive grains equal to or less than the amount of abrasive grains, adjusting the amount of cutting oil for the coarse powder and the replenished abrasive grains, and preparing a slurry for cutting the gallium compound with a wire saw is provided. It is characterized by the following.

According to the method for concentrating gallium compounds according to the first aspect of the present invention, the gallium component separated as coarse powder in the second step can be finally reused by repeatedly using the coarse powder as abrasive grains. Specifically, all can be separated and recovered as fine powder. In addition, since the coarse powder is reused as abrasive grains, the amount of newly used abrasive grains is suppressed, so that the amount of industrial waste finally disposed of can be reduced.

[0012]

Embodiments of the present invention will be described below in detail.

First, the method for concentrating a gallium compound according to the present invention comprises the following first to fourth steps.

(1) First Step In the first step of the method, the cutting oil in the precipitate is dissolved in a solvent compatible with the cutting oil and having a boiling point lower than the thermal decomposition temperature of the gallium compound. Disperse the gallium compound and abrasive grains within.

Here, the gallium compound and abrasive grains in the precipitate are dispersed in the solvent for the following reasons. That is, the abrasive grains at the time of wire saw cutting are usually dispersed in a high concentration in cutting oil, so that the above-mentioned precipitate has a high viscosity, so that the gallium compound and the abrasive grains in the precipitate must be dispersed in a solvent. This is because removal of abrasive grains by wet classification in the second step may be insufficient.

The solvent is not particularly limited as long as it is compatible with the cutting oil and has a boiling point lower than the thermal decomposition temperature of the gallium compound, but cutting oil is preferable (claim 2).

From the viewpoint of the separation efficiency of the wet classification in the second step, a solvent having a lower viscosity than cutting oil, for example, kerosene, is more suitable as the solvent. However, the coarse powder separated in the second step is regenerated as a wire saw cutting slurry in the fourth step. At this time, if a solvent having a lower viscosity than the cutting oil remains, the slurry It is difficult to adjust the viscosity of the mixture to an appropriate value. In this regard, if the solvent is cutting oil, it is not necessary to remove the solvent even if the amount of the solvent needs to be adjusted.

The boiling point of cutting oil or kerosene usually has a temperature range, but the boiling point used when referring to the level of a certain boiling point in the temperature range means "the upper limit of the boiling point" in this specification.

(2) Second Step In the second step, in order to remove the abrasive grains from the solvent in which the gallium compound and the abrasive grains are dispersed, fine powder mainly containing gallium and coarse powder mainly containing abrasive grains are removed. Wet classification is performed to obtain a solvent in which the fine powder is dispersed.

Here, the wet classification includes a natural sedimentation method,
Although a filtration method using a filter having a larger opening diameter than the fine powder can be applied, a method using a liquid cyclone that can be continuously processed and is economical (claim 3) is suitable.
In addition, regarding the setting of the classification point in the hydrocyclone,
The following setting method is exemplified. That is, a part of the precipitate is collected as a sample, and after the collected precipitate is dried, the dried precipitate is treated with an etchant that dissolves a gallium compound, such as aqua regia, Comparison of each particle size distribution of the precipitate before and after the treatment (that is, comparison of the particle size distribution of the precipitate before the treatment containing the gallium compound and the abrasive grains and the particle size distribution of the precipitate after the treatment with the gallium compound removed)
The particle size distribution of the gallium compound contained in the sediment is preferably measured in advance and set to about the maximum particle size of the gallium compound.

(3) Third Step In the third step, the solvent is separated from the solvent in which the fine powder is dispersed to obtain the fine powder mainly containing gallium.

Here, as a means for separating the solvent from the solvent in which the fine powder is dispersed, a natural sedimentation method and a filtration method using a filter having a smaller opening diameter than the fine powder can be applied. Suitable and economical methods using decanter centrifuges are suitable. From a more economic perspective,
The solvent separated by the decanter-type centrifugal separator is preferably reused as the solvent in the first step.

From the fine powder obtained in the third step, the fine powder is dissolved in an acid and then neutralized to convert the gallium content into gallium hydroxide, and then the gallium hydroxide is dissolved in an alkaline solution. The metal gallium can be recovered by electrolysis.

(4) Fourth Step In the fourth step, after removing the solvent as necessary from the solvent in which the coarse powder obtained in the second step is dispersed, the abrasive powder separated as fine powder in the second step is removed. The same amount of abrasive grains as the amount of grains is replenished, and the amount of cutting oil for the coarse powder and the replenished abrasive grains is adjusted to obtain a slurry for cutting the gallium compound with a wire saw.

Here, if necessary, when the solvent added in the first step is a solvent having a low viscosity other than the cutting oil, the solvent is removed from the coarse powder to such an extent that the cutting characteristics are not adversely affected. However, when the solvent is cutting oil, it is not necessary to remove the solvent.

Further, in this step, abrasive particles having the same amount or less as the amount of the separated abrasive particles together with the fine powder are replenished. If the amount of coarse powder is sufficient, it is not always necessary to replenish the new abrasive grains, but it is not necessary that the amount is exactly the same when replenishing the same amount as the amount of abrasive grains separated together with the fine powder. The amount of abrasive grains separated as fine powder may be calculated in advance from the analysis value of solids separated as fine powder by wet classification, and abrasive grains may be supplemented by the calculated value.

When a magnetic material such as a wire piece of a wire saw is contained in the above-mentioned sediment, it is preferable to remove the magnetic material. Specifically, in at least one of the first step, the second step, and the third step, a magnetic substance such as a wire piece contained in the solvent is removed using a magnet (claim 4). By this removal treatment, when obtaining the metal gallium using the fine powder obtained in the third step as a raw material, it is possible to omit a complicated de-Fe treatment for reducing the impurity concentration of the metal gallium.

Further, foreign matter may be mixed in the coarse powder separated in the second step. However, if foreign matter larger than the abrasive particle diameter is mixed in the slurry, the cutting characteristics are adversely affected. Is preferably removed. Specifically, in at least one of the first step, the second step, and the fourth step, the solid content is filtered with a filter (claim 5).

As described above, according to the concentration method of the present invention, since the coarse powder is reused as a slurry, the gallium compound separated as the coarse powder is returned to the concentration step of the gallium compound again to produce industrial waste. It will eventually be collected as fine powder without being disposed of. Further, since only the abrasive grains separated as fine powder are disposed of as industrial waste, the amount of industrial waste can be reduced.

[0030]

Embodiments of the present invention will be specifically described below.

Gallium phosphide single crystal (pyrolysis temperature: 68
(0 ° C.) The deposits generated as cutting chips when 18 pieces were cut with a wire saw were treated as follows. In addition, this deposit is a cutting powder of gallium phosphide, abrasive grains mainly composed of SiC,
And cutting oil (boiling point: 200 to 400 ° C.). The results of analyzing the precipitate are shown in Table 1 below.

[0032]

[Table 1]

Further, a part of the precipitate is collected as a material, and the collected precipitate is dried. The dried precipitate is treated with aqua regia, and the precipitate before and after the aqua regia etching treatment is performed. Is shown in FIG. From the comparison between the particle size distribution before etching containing gallium phosphide and abrasive grains shown in FIG. 1 and the particle size distribution after etching with gallium phosphide removed, the phosphidization contained in the sediment was confirmed. Gallium is 5
It is presumed that the particle size is not more than μm.

First, 56.1 kg of the above-mentioned sediment (gallium compound content: 5122 g) was put into 375 liters of cutting oil, and after stirring and dispersion, a permanent magnet was put in to remove the material adsorbed by the magnet, and the dispersion was dispersed. Obtained.

Next, the obtained dispersion is filtered with a 100 μm filter to remove coarse particles, and then classified using a liquid cyclone at a boundary of 5 μm to obtain an upstream dispersion mainly containing gallium (including fine powder). ) About 355 liters and about 39 liters of a downstream dispersion (including coarse powder) mainly containing abrasive grains were obtained.

About 355 liters of the upstream dispersion containing fine powder obtained by this classification was centrifuged using a decanter-type centrifugal separator under the conditions of a centrifugal acceleration of 3200 G and a residence time of 60 seconds to obtain 12.8 kg (gallium). Compound content 459
5 g) of a solid was obtained. Further, about 39 liters of the downstream dispersion containing the coarse powder was allowed to stand, and the solid content was allowed to settle by itself, and the cutting oil in the supernatant was removed to obtain 45.5 kg (514 g of a gallium compound content).

The results of analyzing the solid content of the upstream dispersion and the solid content of the downstream dispersion are shown in Table 2 below.

[0038]

[Table 2]

Next, after adding 6.78 kg of new abrasive grains having the same weight as the weight of the abrasive grains in the solid content of the upstream dispersion liquid, that is, the weight of the abrasive grains separated as fine powder, the cutting oil was added to the solid content of the downstream dispersion liquid. After the addition, the specific gravity was adjusted, and the slurry was again used as a slurry for wire saw cutting for cutting 18 gallium phosphide single crystals. It should be noted that the cutting characteristics were not different from those when using a slurry prepared from new abrasive grains.

The cut precipitate was allowed to stand, the solid content was allowed to settle, and the cutting oil in the supernatant was removed. The results of the second precipitate analysis are shown in Table 3.

[0041]

[Table 3]

57.1 kg of the above-mentioned precipitate (gallium compound content: 5636 g) was treated in the same manner as in the first treatment of the precipitate, and 13.0 kg (gallium compound content: 5122 g) was obtained.
g) of the upstream dispersion solid content and 45.9 kg (gallium compound content 505 g) of the downstream dispersion solid content were obtained. Table 4 shows the analysis results of the solid content of the upstream dispersion and the solid content of the downstream dispersion.

[0043]

[Table 4]

As can be seen from the comparison of the content of the solid content of the downstream dispersion in Tables 2 and 4, even if the coarse powder is reused as a slurry, the gallium compound is not concentrated in the coarse powder. It can be seen that the gallium compound is ultimately recovered as fine powder by repeated use.

[0045]

As described above, according to the method for concentrating gallium compounds from sediments according to the present invention, the gallium compounds separated as coarse powders by reusing the coarse powder after wet classification as a slurry can be obtained. Eventually, it can be recovered as fine powder. Further, since only the abrasive grains separated as fine powder are disposed of as industrial waste, the amount of industrial waste can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the particle size distribution of a precipitate before and after aqua regia etching.

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Claims (5)

[Claims] In a method of concentrating gallium from a gallium compound generated when a gallium compound is cut by a wire saw, a grit containing abrasive grains and cutting oil, the gallium compound is compatible with cutting oil and thermally decomposes the gallium compound. A first step of dissolving the cutting oil in the precipitate in a solvent having a boiling point lower than the temperature and dispersing the gallium compound and the abrasive grains in the precipitate, and wet classifying the solvent in which the gallium compound and the abrasive grains are dispersed. And the second step of obtaining a solvent in which the fine powder mainly containing the gallium compound is dispersed and the solvent in which the coarse powder mainly containing the abrasive grains is dispersed, the fine powder obtained in the second step is dispersed. The third step of separating the solvent from the solvent to obtain a fine powder, the coarse powder obtained in the second step after removing the solvent as necessary from the dispersed solvent is separated as fine powder in the second step Replenish abrasive particles less than the same amount Gallium compound, abrasive grains and cutting, characterized by comprising a fourth step of adjusting the amount of cutting oil with respect to the coarse powder and the replenished abrasive grains and making the slurry when the gallium compound is cut with a wire saw. A method for concentrating a gallium compound from an oil-containing precipitate. 2. The method according to claim 1, wherein the solvent used in the first step is a cutting oil. 3. The method according to claim 1, wherein the wet classification in the second step is performed using a liquid cyclone.
A method for concentrating a gallium compound from a deposit containing the gallium compound, abrasive grains and cutting oil described in the above. 4. The method according to claim 1, wherein at least one of the first step, the second step and the third step removes a magnetic substance contained in the precipitate using a magnet. A method for concentrating a gallium compound from a precipitate containing the gallium compound, abrasive grains and cutting oil according to any one of the above. 5. The method according to claim 1, further comprising: means for removing foreign matters having a maximum abrasive grain size or more in at least one of the first step, the second step, and the fourth step. A method for concentrating a gallium compound from a deposit containing the gallium compound, abrasive grains and cutting oil described in the above.