JP2002322579A - Method for refining metallic particle and method for refining particle stuck with metallic impurity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evade danger caused by the generation of hydrogen, and plant troubles and the reduction of the quality caused by the flocculation of particles. SOLUTION: Metallic particles 1 whose surfaces have been stuck with impurities are treated with an acidic aqueous solution 2 to remove the impurities from the surfaces of the metallic particles 1. At this time, an inert gas is fed from an inert gas feed pipe 5 into the acidic aqueous solution 2. Hydrogen generated by the reaction of the metallic particles 1 and the acidic aqueous solution 2 is diluted with the inert gas. By the bubbling effect of the inert gas, the flocculation and precipitation of the metallic particles 1 are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying metal particles and a method for purifying particles to which metal impurities are attached, and more particularly to a method for purifying metal particles by removing impurities with an acidic aqueous solution and a method for purifying particles to which metal impurities are attached. It relates to a purification method.

[0002]

2. Description of the Related Art Metallic silicon used in the chemical industry usually has a purity of 99.5% or more. However, ordinary metal silicon for chemical industry contains impurities such as Fe, Al, and Ca in the vicinity of 1,000 ppm, and thus cannot be used as a raw material for solar cells and ceramics that require high purity.

In recent years, from the viewpoint of resource saving, protection of the global environment, disposal regulations, and the like, there is a situation in which it is required to reuse particulate metal waste materials that have been conventionally disposed of.

Accordingly, various methods have been developed for purifying metal particles by removing impurities adhering to the surface. For example, Japanese Patent Application Laid-Open No. 6-107406 discloses a method for purifying metal particles in which Si (silicon) particles as metal particles having impurities adhered to the surface are treated at room temperature with an acidic aqueous solution, and then filtered and washed with water.

[0005] In this refining method, first, metallic silicon is added to 50 μm.
m or less, and impurities segregated or interspersed at the interface and inside of the metal silicon crystal particles are exposed on the surfaces of the Si particles fined by the pulverization. Thereafter, the Si particles obtained by the pulverization are introduced into a 1 to 5% by weight aqueous HF solution to remove impurities exposed on the particle surface at room temperature. A natural oxide film (SiO ₂ ) is formed on the surface of the pulverized Si particles by a reaction with oxygen in the air. In order to remove impurities, the natural oxide film must be removed in advance. However, by treating with the HF aqueous solution, the natural oxide film can be removed.

[0006]

However, when the metal particles are purified by the acidic treatment using the acidic aqueous solution as described above, there are the following problems.

That is, when the metal particles are subjected to the acid treatment, hydrogen is generated as shown in the following formulas (1) and (2), and the reaction heat is generated due to the chemical reaction between the metal particles and the acidic aqueous solution. Therefore, if a large amount of hydrogen is generated and the explosion limit concentration of hydrogen (4%) is exceeded, there is a possibility of explosion. If heat is released and hydrogen is released using a reaction vessel whose opening is open to the atmosphere, the risk of explosion is reduced, but it cannot be said to be a reliable safety measure.

4HF + Si → SiF ₄ + 2H ₂ (1) 2H ₂ O + Si → SiO ₂ + 2H ₂ (2) Further, in an acidic aqueous solution, metal particles aggregate or grow, and the metal particles precipitate accordingly. Then, due to a decrease in the contact interface between the acidic aqueous solution and the metal particles, the effect of removing impurities by the acidic aqueous solution is reduced, which may lead to a reduction in purification efficiency and a reduction in quality.

It is also possible to improve the effect of removing the impurities by the acidic aqueous solution by preventing the aggregation of the metal particles by using a stirring device. However, if the stirring is performed forcibly using a stirrer, the above reaction is activated by the collision or heat generated by the stirring, and the amount of generated hydrogen is extremely increased. Therefore, there is a problem that the danger of explosion is increased.

[0010] Further, such agglomeration and growth of metal particles may cause plant troubles such as blockage of piping.

[0011] These problems in the method for purifying metal particles using an acidic aqueous solution described above can also occur when ceramic particles or resin particles having metal impurities adhered to the surface are treated with an acidic aqueous solution.

The present invention has been made in view of the above circumstances, and a method for purifying metal particles and a method for adhering metal impurities, which can avoid dangers due to hydrogen generation, plant troubles due to particle aggregation, and quality deterioration. It is an object of the present invention to provide a method for purifying particles.

[0013]

According to the present invention, there is provided a method for purifying metal particles, comprising the steps of: treating a metal particle having an impurity attached to its surface with an acidic aqueous solution to remove the impurity from the surface of the metal particle; A method for purifying metal particles to be removed, wherein an inert gas is supplied into the acidic aqueous solution.

In order to solve the above-mentioned problems, the method for purifying particles having metal impurities adhered thereto according to the present invention comprises treating the ceramic particles or resin particles having metal impurities adhered to the surface with an acidic aqueous solution. A method for purifying ceramic particles or resin particles for removing the metal impurities from the surface of the method, wherein an inert gas is supplied into the acidic aqueous solution.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for purifying metal particles of the present invention, the impurities are removed from the surfaces of the metal particles by treating the metal particles having the impurities attached to the surface with an acidic aqueous solution.

The method for treating the metal particles with an acidic aqueous solution is not particularly limited. For example, a treatment method in which metal particles having impurities attached to an acidic aqueous solution accommodated in a reaction vessel can be adopted. If the metal particles to which the impurities are attached are put into an acidic aqueous solution, the surface of the metal particles to which the impurities are attached is dissolved by the acidic aqueous solution (if the impurities themselves are dissolved by the acidic aqueous solution, the impurities themselves are also dissolved. By doing so, the impurities can be removed from the surfaces of the metal particles.

The reaction vessel for accommodating the acidic aqueous solution is preferably prepared from the viewpoint of avoiding corrosion by the acidic aqueous solution.
It is preferable to use one made of synthetic resin rather than one made of metal or glass.

At this time, it is possible to completely open the opening of the reaction vessel containing the acidic aqueous solution to completely open it to the atmosphere. However, since the acidic aqueous solution comes into direct contact with the atmosphere, the gas having a high hydrogen concentration is used. However, there is a high possibility that the gas will come into contact with the air, thereby increasing the risk of explosion. For this reason,
Preferably, the opening of the reaction vessel is closed with a lid or the like to prevent air from entering the reaction vessel. At this time, if the inside of the reaction vessel is completely closed, the pressure of the inside of the reaction vessel becomes high due to the supplied inert gas, which may cause damage to the apparatus and risk of scattering of the internal solution and generated gas. Is preferably provided. Further, it is preferable that this exhaust port is provided in a ceiling portion or a top lid portion of the reaction vessel in order to effectively exhaust hydrogen having a low specific gravity. It is also possible to forcibly evacuate the inside of the sealed reaction vessel by using a separately provided gas absorbing device or the like.

The temperature of the acidic aqueous solution can be appropriately set within a range of about 0 to 40 ° C., and is preferably room temperature from the viewpoint of energy cost reduction. Further, the time for the treatment with the acidic aqueous solution can be appropriately set, and can be about 4 to 24 hours.

When the metal particles are charged into the acidic aqueous solution contained in the reaction vessel, the acidic aqueous solution can be positively stirred by a stirring device, but will be described in Examples described later. As described above, when the stirrer is used, the reaction represented by the above formulas (1) and (2) is promoted, the amount of generated hydrogen and the amount of generated heat are increased, and the amount of oxygen in the air dissolved in the acidic aqueous solution is also increased. Since the amount increases due to the stirring action, the risk of explosion increases. For this reason, it is preferable not to use a stirring device.

The type of the metal particles is not particularly limited as long as the oxidation reaction is not likely to be promoted at room temperature and in the atmosphere. For example, Si particles, Fe (iron) particles, Al (aluminum) particles, Ni (nickel) particles, and Ti (titanium) particles can be employed.

The average particle size of the metal particles is 3 to
It is preferably about 15 μm, particularly preferably about 3 to 7 μm. Average particle size of metal particles is 15μ
If it exceeds m, the sedimentation of the metal particles is remarkable, and if the aggregation proceeds from the deposition, the probability of contact between the surface of the metal particles and the acidic aqueous solution is reduced, so that the effect of removing impurities is extremely reduced. On the other hand, if the average particle size of the metal particles is less than 3 μm, the effect of removing impurities is extremely reduced due to aggregation and cohesive growth in the acidic aqueous solution, or the efficiency of the solid-liquid separation operation after treatment with the acidic aqueous solution is reduced. Problems.

The type of the acidic aqueous solution is not particularly limited as long as it has a property of dissolving at least the surface of the metal particles. For example, 0.5 to 5 mass% HF aqueous solution, 0.5 to 5 mass% HCl aqueous solution, 0.5 to 5 mass%
A 5 mass% H ₂ SO ₄ aqueous solution can be employed.

The method for purifying metal particles of the present invention is most characterized in that an inert gas is supplied into the acidic aqueous solution.

When the metal particles are treated with the acidic aqueous solution, there is a danger of explosion due to heat generation and hydrogen generation as described above.
In particular, when the metal particles are subjected to acidic treatment in a closed reaction vessel in which the opening is closed, the hydrogen concentration in the reaction vessel easily exceeds the explosion limit concentration, and explosion easily occurs.

In this regard, in the present invention, since the metal particles are treated with the acidic aqueous solution while supplying the inert gas into the acidic aqueous solution, the hydrogen concentration in the acidic aqueous solution is reduced by diluting with the inert gas. And the hydrogen concentration in the closed space inside the reaction vessel (when the opening of the reaction vessel is closed and the inside of the reaction vessel is closed) or in the atmosphere around the reaction vessel (when the opening of the reaction vessel is opened) Can be reduced by diluting with the inert gas.
For this reason, it is possible to effectively avoid the danger of explosion due to the generation of hydrogen, and it is possible to improve safety.

Further, a bubbling effect due to the inert gas supplied into the acidic aqueous solution can be expected. That is, due to the bubbling effect of the inert gas, it is possible to effectively suppress the metal particles from aggregating or aggregating and causing the metal particles from settling. For this reason, the contact interface between the acidic aqueous solution and the metal particles is reduced due to the aggregation and precipitation of the metal particles, and the reduction of the impurity removal effect by the acidic aqueous solution can be effectively suppressed. It is possible to suppress a decrease in purification efficiency and a decrease in quality due to aggregation and precipitation.

Further, plant troubles such as clogging of pipes caused by agglomeration and growth of metal particles can be solved.

Here, the supply amount of the inert gas into the acidic aqueous solution is preferably adjusted according to the generation amount of hydrogen. Specifically, hydrogen in a closed space inside the reaction vessel (when the opening of the reaction vessel is closed and the inside of the reaction vessel is closed) or in an atmosphere around the reaction vessel (when the opening of the reaction vessel is opened) It is preferable to adjust the supply amount of the inert gas according to the amount of generated hydrogen so that the concentration is always equal to or lower than the explosion limit concentration (4%). This makes it possible to reliably avoid the danger of explosion due to hydrogen generation.

The amount of hydrogen generated by the chemical reaction between the acidic aqueous solution and the metal particles is highest immediately after the metal particles are put into the acidic aqueous solution, and tends to decrease with time. It is considered that the generation amount of hydrogen decreases with the lapse of time because an oxide film is formed on the surface of the metal particles. For this reason, from the viewpoint of avoiding the danger of explosion due to hydrogen generation, immediately after the metal particles are charged into the acidic aqueous solution, the maximum supply amount of the inert gas is supplied, and thereafter the amount of hydrogen generated It is preferable that the supply amount of the inert gas is gradually reduced in accordance with the gradual decrease of the inert gas.

The type of the inert gas is not particularly limited, and N ₂ , Ar, He or the like can be used.

Next, in the method for purifying particles having metal impurities attached thereto according to the present invention, the ceramic particles or resin particles having metal impurities attached to the surface are treated with an acidic aqueous solution. Thereby, the metal impurities are dissolved and removed from the surfaces of the ceramic particles or the resin particles.

The method for treating ceramic particles or resin particles with an acidic aqueous solution can be basically the same as the above-described method for purifying metal particles.

Types of the above ceramic particles or resin particles
As long as they do not hinder plant operation.
It is not particularly limited. For ceramic particles, for example
Ba SiO_Two(Silica) particles, Al_TwoO_Three(Alumina) grains
Child and TiO_Two(Titania) particles can be adopted,
For resin particles, for example, PE (polyethylene) particles,
Uses PP (polypropylene) particles and epoxy resin particles
can do.

The average particle size of the ceramic particles or the resin particles is preferably about 3 to 15 μm, particularly preferably about 3 to 7 μm. When the average particle size of the ceramic particles or the resin particles exceeds 15 μm, the particles are significantly settled, and the contact with the acidic aqueous solution is reduced by the deposition, so that the effect of removing impurities is extremely reduced. On the other hand, when the average particle size of the ceramic particles or the resin particles is less than 3 μm, the effect of removing impurities is extremely reduced due to aggregation or cohesive growth in the acidic aqueous solution, or the efficiency of the solid-liquid separation operation after treatment with the acidic aqueous solution is reduced. There are problems such as lowering.

The type of the acidic aqueous solution is not particularly limited as long as it has a property of dissolving impurities attached to the surface of the particles. For example, 0.5 to 5 mass% HF
Aqueous solution, 0.5-5 mass% HCl aqueous solution and 0.5%
An H ₂ SO ₄ aqueous solution of ５5 mass% can be employed.

The method for purifying ceramic particles or resin particles of the present invention is most characterized in that an inert gas is supplied into the acidic aqueous solution, as in the method for purifying metal particles of the present invention.

When ceramic particles or resin particles having metal impurities adhered to the surface are treated with an acidic aqueous solution, heat is generated and hydrogen is generated due to a chemical reaction between the metal impurities and the acidic aqueous solution, which is the same as when treating metal particles with an acidic aqueous solution. ,
With explosion hazard. Further, when the ceramic particles or the resin particles are treated with the acidic aqueous solution, there are problems of plant trouble and quality deterioration due to the aggregation of the particles as in the case of the metal particles.

In this respect, in the method for purifying ceramic particles or resin particles of the present invention, the ceramic particles or resin particles having metal impurities adhered to the surface are treated with the acidic aqueous solution while supplying an inert gas into the acidic aqueous solution. Therefore, similarly to the above-described method for purifying metal particles of the present invention, it is possible to effectively avoid the danger of explosion due to the generation of hydrogen, and to improve safety. Further, it is possible to suppress a decrease in purification efficiency and a decrease in quality due to agglomeration and precipitation of ceramic particles or resin particles, and to eliminate a plant trouble such as blockage of a pipe.

Further, the supply amount of the inert gas into the acidic aqueous solution is preferably adjusted according to the amount of hydrogen generated, as in the above-described method for refining metal particles of the present invention.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Example 1 As the metal particles 1, the purity was 9
9.5% or more of chemical industrial grade metallic silicon was pulverized to prepare Si particles having an average particle diameter of 5 to 6 μm, and as the acidic aqueous solution 2, an HF aqueous solution having a concentration of 2 mass% and a normal temperature was prepared.

On the other hand, a synthetic resin reaction vessel (capacity: 2000 liters) 3 with a lid 4 was prepared.

An inert gas supply port 3a is formed through the center of the bottom wall of the reaction vessel 3. The other end of the reaction port 3 is connected to an inert gas supply device (not shown). One end of the inert gas supply pipe 5 is connected. The inert gas supply pipe 5 has a tip curved portion 5a which is bent in a substantially J shape and opens downward.

The lid 4 has an inverted tapered shape (substantially quadrangular pyramid shape) so that generated hydrogen collects at the uppermost portion.
An exhaust port 4a is formed at the uppermost end (the tip of an inverted tapered shape or a substantially quadrangular pyramid shape). And this exhaust port 4a
Is connected to one end of an exhaust pipe 6 whose other end is connected to an exhaust processing system (not shown).

The inert gas supply pipe 5 is provided at the center of the bottom wall of the reaction vessel 3 in order to effectively exert a bubbling effect by the inert gas. The reason why the tip curved portion 5a that opens downward is provided is to prevent the metal particles 1 from entering the inert gas supply pipe 5. The reason why the exhaust port 4a is provided in the lid 4 located at the uppermost part of the reaction vessel 3 is to take into account the exhaust efficiency of hydrogen having a small specific gravity.

Then, 500 kg of the HF aqueous solution 2 was put in the reaction vessel 3 and 100 kg of the metal particles 1 were put in the acidic aqueous solution 2, and then the opening of the reaction vessel 3 was closed by the lid 4. Immediately after that, the inert gas supply device (not shown) is operated, and the inert gas supply pipe 5 is turned on.
, An inert gas was supplied into the HF aqueous solution 2 in the reaction vessel 3.

In this embodiment, N ₂ is used as an inert gas. Further, the supply amount of the inert gas was fixed at 25 m ³ / hr. Note that the supply amount of the inert gas is adjusted so that the hydrogen concentration in the acidic aqueous solution 2 and the reaction vessel 3 becomes equal to or less than the explosion limit concentration (4%) in accordance with the hydrogen generation amount obtained in advance. is there.

After 4 hours from the continuous supply of the inert gas, the suspension after the treatment was transferred to a filter, and the acidic aqueous solution 2 was removed by pressure filtration. Thereafter, the resultant was washed with ion-exchanged water and dried to obtain highly purified Si particles.

(Evaluation) Regarding the obtained Si particles, the adhesion amount of impurities (Fe, Al, Ca) was determined by ICP (Induct).
The measurement was performed using an immediately Coupled Plasma) analyzer. The result is shown by a solid line in FIG. 2 together with the result of the Si particles treated in the same manner after 2 hours from the supply of the inert gas.

For comparison, Comparative Example 1 was processed in the same manner as in Example 1 except that no inert gas was supplied.
2 is also shown by a dotted line in FIG.

As is apparent from FIG. 2, the effect of removing impurities is improved by supplying an inert gas. This is due to the bubbling effect of the inert gas supplied from the inert gas supply pipe 5 into the acidic aqueous solution 2.
Since the aggregation and growth of the metal particles 1 and the precipitation of the metal particles 1 due to the aggregation can be effectively suppressed, the contact interface between the metal particles 1 and the acidic aqueous solution 2 can be reliably secured. Conceivable.

Further, in this embodiment, the gas in the acidic aqueous solution 2 and the reaction vessel 3 is diluted with the inert gas, and the hydrogen concentration in the acidic aqueous solution 2 and the reaction vessel 3 is less than the explosion limit concentration (4%). Since the inert gas is supplied at a supply amount adjusted to be as follows, the danger of explosion due to the generation of hydrogen can be reliably avoided, and safety can be improved.

Further, in the present embodiment, the opening of the reaction vessel 3 is closed by the lid 4 to prevent air from entering the reaction vessel 3, and through the exhaust pipe 6 provided in the lid 4. The gas in the reaction vessel 3 is discharged outside through an exhaust processing system (not shown). For this reason, the possibility that the gas having a high hydrogen concentration comes into contact with air is extremely low, and the danger of explosion due to the generation of hydrogen can be more reliably avoided.

(Evaluation of Hydrogen Generation Amount) In Example 1 described above, the relationship between the time elapsed since the supply of the inert gas and the hydrogen generation amount was examined. The result is shown in FIG.

As is clear from FIG. 3, the amount of hydrogen generated is
Immediately after the metal particles 1 are put into the acidic aqueous solution 2,
It tends to decrease over time. For this reason, from the viewpoint of avoiding the danger of explosion due to hydrogen generation, immediately after the metal particles 1 are charged into the acidic aqueous solution 2, the inert gas is supplied at the highest supply rate into the acidic aqueous solution 2 and then the As the amount of hydrogen generated gradually decreases over time,
The supply amount of the inert gas may be gradually reduced.

In the first embodiment, immediately after the metal particles 1 are charged into the acidic aqueous solution 2, the supply amount of the inert gas is set to 2
The supply amount of the inert gas may be set to 5 m ³ / hr, and then the supply amount of the inert gas may be gradually reduced, and after a lapse of 10 hours, the supply amount of the inert gas may be set to about 5 m ³ / hr.

Further, Comparative Example 1 was treated in the same manner as in Example 1 except that no inert gas was supplied, and Example 1 was repeated except that no inert gas was supplied and a stirrer was used. With respect to Comparative Example 2 which was similarly treated, the amount of generated hydrogen was examined. FIG. 4 shows the result together with the result of the first embodiment.

As is apparent from FIG. 4, in Comparative Example 2 using the stirrer, the amount of hydrogen generated after 10 hours was about three times that of Example 1, and the amount of generated hydrogen was extremely increased.
This indicates that the use of a stirrer increases the risk of explosion, so it is clear that it is better not to use a stirrer.

On the other hand, in Comparative Example 1 in which no inert gas was supplied and no stirrer was used, it was possible to suppress the amount of generated hydrogen. Plant troubles such as blockage of the plant may occur.

Example 2 Fe and A as metal impurities
Prepare ceramic particles (SiO ₂ particles) having an average particle size of 10 μm to which
An acidic aqueous solution (HF aqueous solution) at room temperature at an ass% was prepared.

Then, similarly to the first embodiment, 10 kg of the acidic aqueous solution is put into the reaction vessel 3 and 2 kg of the ceramic particles are put into the acidic aqueous solution, and then the opening of the reaction vessel 3 is closed by the lid 4. did. Immediately thereafter, an inert gas supply device (not shown) was operated, and an inert gas was supplied from the inert gas supply pipe 5 into the acidic aqueous solution in the reaction vessel 3.

In this embodiment, N ₂ is used as an inert gas. In addition, the supply amount of the inert gas was set to 5 m ³ / hr. The supply amount of the inert gas is adjusted so that the hydrogen concentration in the acidic aqueous solution and in the reaction vessel 3 becomes equal to or lower than the explosion limit concentration (4%) in accordance with the hydrogen generation amount obtained in advance. .

After 4 hours since the supply of the inert gas was continued, the treated suspension was transferred to a filter, and the acidic aqueous solution was removed by pressure filtration. Thereafter, the particles were washed with ion-exchanged water and dried to obtain highly purified ceramic particles.

Example 3 Fe and A as Metal Impurities
l, Ca and other resin particles having an average particle diameter of 10 μm (P
E particles) and an acidic aqueous solution (HF aqueous solution) having a concentration of 2 mass% at room temperature.

Then, similarly to the first embodiment, 10 kg of the acidic aqueous solution is put into the reaction vessel 3 and 2 kg of the resin particles are put into the acidic aqueous solution, and then the opening of the reaction vessel 3 is closed by the lid 4. did. Immediately thereafter, an inert gas supply device (not shown) was operated, and an inert gas was supplied from the inert gas supply pipe 5 into the acidic aqueous solution in the reaction vessel 3.

In this embodiment, N ₂ is used as an inert gas. In addition, the supply amount of the inert gas was set to 5 m ³ / hr. The supply amount of the inert gas is adjusted so that the hydrogen concentration in the acidic aqueous solution and in the reaction vessel 3 becomes equal to or lower than the explosion limit concentration (4%) in accordance with the hydrogen generation amount obtained in advance. .

After 4 hours from the continuous supply of the inert gas, the suspension after the treatment was transferred to a filter, and the acidic aqueous solution was removed by pressure filtration. Thereafter, the resin particles were washed with ion-exchanged water and dried to obtain highly purified resin particles.

[0069]

As described in detail above, according to the method for purifying metal particles and the method for purifying particles to which metal impurities are attached according to the present invention, the acid treatment is performed while supplying an inert gas to reduce the generation of hydrogen. It is possible to avoid the dangers involved and plant troubles and quality deterioration due to particle aggregation, thereby improving safety and quality and reducing equipment troubles.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a method for purifying metal particles according to a first embodiment.

FIG. 2 relates to the first embodiment, by supplying an inert gas,
FIG. 9 is a diagram showing that an impurity removing effect is improved.

FIG. 3 is a diagram showing a relationship between an elapsed time and an amount of generated hydrogen according to the first embodiment.

FIG. 4 is a diagram comparing the amount of hydrogen generated in Example 1 in which an inert gas is supplied, Comparative Example 1 in which an inert gas is not supplied, and Comparative Example 2 in which a stirring device is used, according to Example 1; is there.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal particle 2 ... Acidic aqueous solution 3 ... Reaction vessel 5 ... Inert gas supply pipe 6 ... Exhaust pipe

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Claims (2)

[Claims] 1. A method for purifying metal particles, wherein the impurities are removed from the surface of the metal particles by treating the metal particles having the impurities attached to the surface with an acidic aqueous solution, wherein the inert gas is contained in the acidic aqueous solution. And a method for purifying metal particles. 2. A method for purifying ceramic particles or resin particles, wherein the metal impurities are removed from the surface of the ceramic particles or resin particles by treating the ceramic particles or resin particles having metal impurities attached to the surface with an acidic aqueous solution. A method for purifying particles having metal impurities attached thereto, wherein an inert gas is supplied into the acidic aqueous solution.