JP2001059195A - Method for recovering platinum group metal from platinum group metal-containing solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To separate and recover almost whole of platinum group metals included in a catalytic soln. (such as a used catalytic soln. discharged in a catalyzing stage of electrolesss plating treatment) without being recovered practically heretofore, particularly palladium from the soln. by a simple means. SOLUTION: In this method for recovering platinum group metals by electrolytic reduction from a soln. contg. platinum group metals or the compds. thereof in a colloidal state, an electrolysis pretreating agent is added into a catalytic soln. to dissolve the colloidal particles, thus the platinum group metals are made into the ionized state. Then the soln. is subjected to electrolytic reduction, thus the platinum group metals are precipitated and recovered. By the method, almost the whole quantity of the platinum group metals included in the platinum group-contg. soln. can easily be recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for recovering a platinum group metal from a solution containing a platinum group metal or a compound thereof, and more specifically, for example, a method for discharging a platinum group metal in a catalyzing step of electroless plating. A method for recovering palladium from a spent catalyst solution.

[0002]

2. Description of the Related Art Recently, non-conductive materials such as plastics and ceramics have been
It is common practice to plate metals such as copper and nickel and various alloys. For example, metal parts are applied to daily necessities for design reasons, and some automobile parts and electric products are used for the purpose of imparting corrosion resistance and blocking electromagnetic waves.
Such metal plating is generally performed. Further, a similar metal plating technique is used in the manufacture of a printed wiring board and the like. However, in these plating processes, since the object is a non-conductive material such as plastic, normal electroplating cannot be applied immediately. Therefore, in order to impart conductivity in advance to the surface of such a non-conductive material,
Usually, a chemical plating process, that is, an electroless plating process is performed.

[0003] Electroless plating refers to plating performed without applying electric energy to the aqueous solution from the outside. When plating on the surface of a non-conductive material, the principle of plating metal plating on the surface is, for example, reduction of the plating metal salt. If the metal deposition principle is based on reduction, such electroless plating can be performed simply by a reduction reaction. However, the plating metal can be easily and / or strongly applied to the surface to be plated. Given the join,
The use of a catalyst is preferred and is usual. That is, in a typical electroless plating process, a catalyst of a platinum group metal or the like (for example, palladium) serving as a nucleus of a catalytic reaction is applied to the surface of a base material in advance, and then used as a nucleus for the catalytic reaction. And depositing a plating of copper, nickel or the like on the base material. Thereby, metal can be plated on the surface of the non-conductive material.

[0004] Usually, the electroless plating is performed according to the following procedure. That is, first, a degreasing step is performed using an alkaline degreasing liquid containing a surfactant for the purpose of removing oil and dirt attached to the surface of the non-conductive member to be treated and improving the wettability of the material surface. Then
An etching step of roughening the surface of plastic or the like with an etching agent is performed. By this step, the treated surface is roughened, and the adhesion after plating between the metal to be plated and a member such as plastic can be enhanced.

Next, a step of applying a catalyst for a deposition reaction of electroless plating to the surface of the base material, that is, a so-called catalyzing step is performed. The reason that this step is required is that the metal to be electrolessly plated is unlikely to be deposited on materials other than the catalytic substance, and therefore, in order to perform electroless plating on a non-conductive base material, the surface must first be coated. This is because it is necessary to adsorb the catalyst. In this step, in order to perform such catalyst application, a colloidal acidic solution (that is, a catalyst solution) in which tin and palladium are mixed, which is generally called a “catalyzer” or a “catalyst”, is used. ing. In the electroless plating process, after this catalyzing step, if necessary, an activation process for removing the influence of tin is performed, and then the base material is placed in an electroless plating solution containing copper, nickel, or the like. The substrate is immersed and electroless plating is performed on the surface of the substrate.

[0006] The electroless plating treatment is usually carried out in the above-described procedure. In the catalyzing step, particularly, in the catalyzing step, copper is gradually contained in the plating treatment during the plating process. It may be mixed. In such a case, usually, when a certain copper concentration is reached, the catalyst liquid is to be disposed of as a waste liquid. In many cases, the amount of the catalyst metal (for example, palladium) contained in the waste liquid of the catalyst liquid is small. Therefore, conventionally, the catalyst liquid is finally mixed with other waste liquid and then disposed of by an external specialist. They have been disposed of or disposed of in-house wastewater treatment facilities to meet certain environmental standards before being disposed of. Therefore, attempts to separate and recover platinum group metals such as palladium contained in the catalyst solution generated by the electroless plating have been scarcely made.

In the above-mentioned catalyst solution, it is known that a platinum group metal such as palladium forms a colloid and is stably dispersed in the solution, and the colloid particles have a diameter of Smaller than 1 μm, for example 10 to 2
It is known that it is about 0 Å. For this reason, it was difficult to separate and collect by simple filtration, centrifugal sedimentation or the like. Also, the platinum group metal as a colloid liquid is essentially metal particles,
Since it is not in the ionic state, it cannot be recovered electrochemically.

[0008] On the other hand, in recent years, interest in recycling palladium contained in various kinds of waste has been increasing due to a rising price of palladium. In addition, due to the recent growing interest in environmental issues, many companies have put forth the philosophy of environmental recycling, and companies and organizations that emit the above-mentioned catalyst solution should also collect palladium in wastewater. Was desired.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a solution comprising a platinum group metal, typically as colloidal particles, particularly from the aforementioned catalyst solution containing palladium as colloidal particles. It is an object of the present invention to provide a method for separating and recovering almost all of the platinum group metals (particularly palladium) by a simple means.

[0010]

According to the present invention, a platinum group metal is recovered electrochemically, that is, by electrolysis, from a platinum group metal-containing liquid which has been conventionally discarded with little recovery treatment. When the solution is subjected to electrolysis, a pretreatment agent, for example, typically an oxidizing agent, is added to dissolve colloid particles of a platinum group metal that is stably dispersed in the solution to form platinum. It is based on the discovery that the group metal can be in an ionized state, whereby the platinum group metal can be more easily precipitated when the solution is electrolytically reduced.

<Summary> That is, the method for recovering a platinum group metal according to the present invention is a method for recovering a platinum group metal from a solution containing a platinum group metal or a compound thereof in a colloidal state by electrolytic reduction, wherein An electrolytic pretreatment agent is added, and the colloidal particles are dissolved to convert the platinum group metal into an ionized state, and the electrolytic reduction is performed to precipitate and recover the platinum group metal. It is.

<Effect> According to the method of the present invention, a platinum group metal can be easily and efficiently recovered from a liquid containing a platinum group metal or a compound thereof. Further, by the method of the present invention, it is possible to recover a relatively expensive platinum group metal in a catalyst solution, which has hardly been recovered conventionally, and as a result, it is possible to reuse it. Further, according to the method of the present invention, almost all of the platinum group metal contained in the liquid containing the platinum group metal can be easily recovered. The liquid containing a platinum group metal or a compound thereof, which is a target of the present invention, is typically a colloidal solution of a platinum group metal, and the pretreatment agent is an oxidizing agent, specifically, for example, aqueous hydrogen peroxide. However, the fact that such a special form of metal is destroyed in its colloidal state by the action of an electrolytic pretreatment agent such as aqueous hydrogen peroxide, and becomes a more advantageous state for electrolytic reduction treatment. I'm interested. Considering that platinum group metals generally do not dissolve under severe conditions, a small amount of hydrogen peroxide in a colloid solution in which a large amount of water coexists means that a state suitable for electrolytic reduction was realized. It was a surprise.

[0013]

DETAILED DESCRIPTION OF THE INVENTION <Platinum Group Metal-Containing Solution> A solution containing a platinum group metal or a compound thereof to be treated in the method of the present invention (hereinafter referred to as a platinum group metal-containing solution). "May be" means a liquid containing a platinum group metal (particularly in a colloidal state) or a compound thereof obtained in various industrial processes.
This does not exclude organic ones, although aqueous ones are common. Examples of such platinum group metal-containing solutions include:
Examples of the catalyst solution containing platinum group metal colloid particles used (or used) in various catalytic reactions are exemplified.
In the present invention, such a catalyst liquid is preferable. In addition,
In the present invention, the term "catalyst liquid" refers to a catalyst liquid used in a catalytic reaction (that is, a catalyst waste liquid) as described above.
In addition, a catalyst solution before use, a catalyst cleaning solution, and the like are also included.

The platinum group metal-containing solution preferred in the present invention is used in a so-called catalyzing step in performing electroless plating, that is, in a step of seeding an object to be plated with an active nucleus of a catalyst such as a platinum group metal. (Or used) catalyst solution.

Further, the platinum group metal referred to in the present invention includes:
Among the Group VIII elements of the periodic table, palladium Pd, ruthenium Ru, rhodium Rh, osmium Os, iridium Ir, and platinum Pt are exemplified. In the present invention, palladium (Pd) is particularly preferred. Therefore, a preferred embodiment of the present invention relates to a method for recovering palladium from a catalyst solution. As a specific example of the catalyst liquid in a preferred embodiment of the present invention, “sensitizer HS-201
B (or HS-202B) "(manufactured by Hitachi Chemical). This is used to deposit palladium (catalyst) for initiating an electroless copper plating reaction on the surface of the substrate to be plated.

In a preferred embodiment of the present invention, the platinum group metal-containing solution is an acidic solution containing palladium or an acidic solution containing palladium and tin, and more specifically, an acidic catalyst solution containing palladium chloride or palladium chloride and tin. An acidic catalyst solution containing: Usually, palladium or palladium-tin is considered to be present in the liquid in a colloidal state. In this case, it is known that the colloid particles have a diameter of at least less than 1 μm, more specifically, for example, about 10 to 20 Å. However, in this state, it is obviously difficult to separate by filtration with filter paper or the like, or to settle by centrifugation or the like.

The concentration of the platinum group metal in the platinum group metal-containing solution to be treated in the present invention may be any concentration as long as the solution contains at least the platinum group metal. For example, in the case of a catalyst solution in the catalyzing step of the electroless plating process, in terms of the amount of palladium chloride,
Usually, the amount is less than the catalyst liquid control range of 0.1 to 0.5 g / L. In addition, such a platinum group metal-containing solution may be subjected to the method of the present invention after being concentrated or diluted in advance by using various conventional concentration or dilution means, if necessary. Further, the platinum group metal-containing solution to be treated in the present invention is usually an acidic solution, and specifically, usually has a pH lower than 5, for example, about 0 to 3
It is about.

When the platinum group metal-containing solution to be treated in the present invention is a used catalyst solution, various contaminants accompanying use in the pretreatment step of the catalytic reaction are mixed in the catalyst solution. Often. Therefore, the catalyst liquid to be treated in the present invention usually contains various contaminants.
For example, in the catalyst solution used in the catalyzing step of the electroless plating process, with repeated use in this step, impurities such as copper, glass, resin and other plating base components increase, and gradually. The efficiency of the catalysis step may be reduced. In such a case, in order to prevent a decrease in the efficiency of the catalyzing step, the catalyst liquid is often replaced with a new one at the time when the impurities increase to some extent, and the catalyst liquid targeted in the present invention is such a case. It can be a catalyst liquid discharged to.

For example, it is known that when an electroless copper plating process is performed in the manufacture of a printed wiring board or the like, the copper concentration in the catalyst solution increases with use. In such a case, the catalyst solution is usually replaced with a new one when the copper concentration exceeds about 2000 ppm. Therefore, in one preferred embodiment of the present invention, the platinum group metal-containing solution to be treated in the present invention,
A catalyst solution comprising palladium or palladium and tin, which may comprise more than 2000 ppm of copper. In addition, such a liquid is often brownish black.

<Electrolytic Pretreatment Agent> As a pretreatment agent for electrolysis used in the present invention, a platinum group metal (which is considered to be formed in a platinum group metal-containing solution by being added to the platinum group metal-containing solution) Any substance can be used as long as it can break the colloidal state of (particularly palladium) (ie, dissolve the colloidal particles) into an ionized state. An example of such an electrolytic pretreatment agent is an oxidizing agent. In the present invention, two or more of these electrolytic pretreatment agents may be used in combination. An oxidizing agent is preferred as the electrolytic pretreatment agent used in the present invention. Such oxidizing agents include, for example, oxygen, ozone, hydrogen peroxide, peroxide, oxygen acids (nitrite, nitric acid, permanganate, chromic acid,
Chloric acid, hypochlorous acid, perchloric acid, bromic acid) and salts thereof, hot concentrated sulfuric acid, aqua regia (a mixture of nitric acid and hydrochloric acid), and halogen. Preferred as the electrolysis pretreatment agent of the present invention are the above-mentioned oxidizing agents, that is, those substances which oxidize other substances and are themselves reduced. Particularly preferred as the electrolytic pretreatment agent used in the present invention is hydrogen peroxide.

When using the above electrolytic pretreatment agent,
When the electrolysis pretreatment agent is a gas, it can be mixed with another gas if necessary, and then the gas serving as the electrolysis pretreatment agent can be passed through the platinum group metal-containing liquid. For example, when using oxygen, which is a kind of oxidizing agent, as an electrolytic pretreatment agent, utilizing that oxygen is contained in the air,
Air may be aerated through the platinum group metal-containing liquid. Preferred electrolytic pretreatment agents in the present invention are those soluble in the target catalyst solution, specifically, those soluble in water,
Therefore, for example, when hydrogen peroxide is used as an electrolytic pretreatment agent, it is common to add hydrogen peroxide to the catalyst solution in the form of aqueous hydrogen peroxide. Therefore, a particularly preferred electrolytic pretreatment agent used in the present invention is aqueous hydrogen peroxide. In this case, the hydrogen peroxide solution used is, for example, 20 to 60%,
It is desirable that the hydrogen peroxide solution is preferably 30 to 50%, particularly preferably 35%. In the present invention,
As such an electrolytic pretreatment agent, a commercially available product for the purpose of an oxidizing agent or the like is obtained from a supplier, and it is dissolved as it is or as necessary in a solvent such as water.
May be used.

When the electrolytic pretreatment agent, particularly the oxidizing agent, is added to the catalyst solution, the colloid of the platinum group metal present in the acidic solution can be placed in an oxidizing environment, whereby the colloid particles are formed. Dissolves into an ionized state,
it is conceivable that. However, when the electrolysis pretreatment agent in the present invention is an oxidizing agent, the mechanism that the colloidal particles of the platinum group metal are in an ionized state is not essential.
What is essential in the present invention is that the colloidal liquid to be subjected to the electrolytic operation is a state in which the colloidal state has been destroyed, and the state is determined by a change in the color of the colloidal liquid when the pretreatment agent is an oxidizing agent. You can know. That is,
Catalyst solution (especially catalyst solution containing palladium in colloidal state)
The color tone is, by the addition of the electrolytic pretreatment agent as described above,
It is recognized that the color changes from brown-black to yellow-transparent.

In the present invention, the agent for breaking the colloidal state is referred to as an electrolytic pretreatment agent, but this does not mean that the treatment with the treatment agent should be performed before the electrolytic treatment. That is, since the colloidal liquid is subjected to the electrolysis operation in a state where the colloidal state is destroyed, the colloidal state may be destroyed during the electrolysis operation, that is, it may be performed in a so-called `` in situ '' manner. , Is obvious. Therefore, for example, it is possible to immediately start the energization of the colloid liquid and apply the electrolysis conditions, and then add hydrogen peroxide to destroy the colloid state and immediately cause electrolytic reduction. Further, a predetermined amount of the electrolytic pretreatment agent may be added at a time before the electrolysis operation, or the pretreatment agent may be added little by little continuously or intermittently during the electrolysis operation.

<Method of recovering platinum group metal (electrolytic reduction method)>
The following description relates to the procedure of the platinum group metal recovery method of the present invention. A platinum group metal-containing solution to be subjected to the platinum group metal recovery method of the present invention is provided from various production steps and treatment processes. For example, when the solution to be treated is a catalyst solution used in the catalyzing step of the electroless plating treatment, the pH is usually about 0 to 3 and the liquid color is brown-black.

<< Addition of Electrolytic Pretreatment Agent >> An electrolysis pretreatment agent is added to the obtained platinum group metal-containing solution. The addition of the electrolytic pretreatment agent is generally performed before the electrolytic reduction treatment, but it is added at the start of the electrolytic reduction treatment, or it can be further added during the electrolytic reduction treatment as described above. . The electrolytic pretreatment agent is usually added in the form of an aqueous solution, as described above. However, when the electrolytic pretreatment agent is a gas, it may be supplied by aeration. Good. The amount of the electrolytic pretreatment agent to be added is preferably at least such that the colloidal particles of the platinum group metal considered to be present in the catalyst solution to be treated are dissolved and become ionic. As long as the amount of the condition is satisfied, the input amount (or aeration amount) of the electrolytic pretreatment agent is determined by the amount of the solution to be treated, the input form of the electrolytic pretreatment agent or the concentration of the electrolytic pretreatment agent therein, Various changes can be made by the above method. For example, the catalyst solution to be treated (Pd concentration 231 ppm, pH 2.1) is 500
When the electrolytic pretreatment agent is 35% hydrogen peroxide, the amount of the electrolytic pretreatment agent to be used is about 3 ml.

When the electrolytic pretreatment agent is added, the amount of the electrolytic pretreatment agent may be adjusted according to the progress of the state of the liquid to be treated. For example, when the solution to be treated is the catalyst solution used in the catalyzing step of the electroless plating process, the color of the solution is initially brown-black, but the colloid particles expected by the introduction of the electrolytic pretreatment agent are dissolved. When the platinum group metal is brought into an ionic state, it is recognized that the liquid color changes to yellow and transparent. Therefore, the charging amount of the electrolytic pretreatment agent may be adjusted based on such a change in the liquid color.

<< Electrolytic Recovery Operation >> Next, the solution obtained by dissolving the colloidal particles of the platinum group metal in the solution in the ionic state as described above is subjected to an electrolytic reduction operation, and the platinum group metal in the solution is recovered. I do. The recovery operation (electrolytic recovery operation) of the platinum group metal from the catalyst solution by electrolytic reduction is usually carried out by placing the catalyst solution to be treated in a vessel (electrolysis tank) having an anode and a cathode for performing an electrolysis treatment, and supplying an electric current thereto. This is carried out by flowing, depositing the target platinum group metal on the cathode, and recovering it. In this case, as described above, the addition of the electrolytic pretreatment agent may be performed before, after, or during the electrolytic treatment.

In the above-mentioned electrolytic treatment, any material can be used in the present invention as long as it can cause a so-called anodic reaction in which positive charges flow from the electrode toward the solution. Therefore, for example, as an anode material, an anode material such as stainless steel (SUS) can be used in addition to an insoluble anode such as carbon, ferrite, platinum, and platinum-plated titanium.
The anode material used in the present invention can be appropriately selected according to the properties of the solution to be subjected to the electrolytic treatment, the resistance of the material to the solution, the expected anode reaction resistance, or the type of the target metal. it can.

On the other hand, the cathode made of any material can be used as the cathode as long as it can give a negative charge to the metal ions and consequently cause a reaction in which the metal is electrochemically deposited, that is, a cathode reaction. It can be used in the invention. Therefore, in the present invention, for example, platinum-plated titanium, stainless steel, titanium, nickel, platinum,
Materials such as copper and 42 alloy can be used as the cathode. The cathode material used in the present invention is, as in the case of the anode material, the nature of the solution to be subjected to the electrolytic treatment, the resistance of the material to the solution, the resistance in the expected cathode reaction,
Alternatively, it can be appropriately selected according to the type of the target metal or the like. The cathode preferably has a surface area as large as possible so that the target platinum group metal can be easily deposited. Therefore, for example, a cathode filled with particulate matter can be used as the cathode.

In the electrolytic recovery operation of the present invention,
Normally, a current is applied to maintain a current density sufficient to deposit the desired platinum group metal on the cathode surface. That is, the current density applied in the electrolytic recovery operation in the present invention is generally about 2 to 12.5 A / dm.
² , preferably about ^{2 to} 5 A / dm ² , more preferably 2 A / dm ² . Specifically, for example, when the liquid volume is 5
When there is a treated catalyst solution having a target palladium concentration of 231 ppm in 00 ml, the current can be 4 A (constant) and the current density can be about 12.5 A / dm ² (at this time, as an anode material, Platinum-plated titanium and stainless steel as cathode material). In addition, when there is a treated catalyst solution having a liquid volume of 500 ml and a target palladium concentration of 122 ppm (the anode material and the cathode material are the same as described above), the current is 1 A (constant) and the current density is 2 A / dm. It can be on the order of ^two . Also,
By controlling the current density, the amount of Sn deposited can be controlled, and the state of electrodeposition on the cathode can be controlled. Therefore, in the present invention, it is also possible to set the current density in consideration of the amount of Sn deposition and the state of electrodeposition in advance.

In the electrolytic recovery operation of the present invention, the platinum group metal-containing liquid (electrolytic solution) to be subjected to the electrolytic treatment may be stirred during the electrolytic treatment, if necessary, in order to increase the electrolytic treatment efficiency. The liquid may be heated or cooled in order to increase the efficiency of the electrolytic treatment.

When the electrolytic reduction recovery operation is performed as described above, the target platinum group metal can be deposited (electrodeposited) on the cathode surface. The electrolytic reduction operation is usually continued until the platinum group metal of interest is scarcely present in the electrolyte (for example, until the amount is less than 5% of the initial amount), but is not limited thereto. Not something.
For example, a processing liquid 500 m containing 231 ppm of palladium
The current density was 12.5 A using platinum-plated titanium for the anode material and stainless steel for the cathode material.
When performing the electrolytic reduction operation at / dm ² , the operation is performed until palladium in the treated catalyst liquid is almost completely absent.
The required electrolysis time is about 3 hours.

The target platinum group metal is usually electrodeposited on the cathode surface in accordance with the electrolytic operation, so that the cathode is taken out of the electrolytic cell to obtain the electrodeposit.
Can be recovered. In addition, depending on the composition of the treated electrolyte, the nature and form of the cathode material, and the like, the target platinum group metal may be electrodeposited and peel off from the cathode surface with the electrolytic operation. Alternatively, the electrodeposition on the cathode surface may not be sufficient and may float in the liquid as particles. In such cases, in addition to collecting the electrodeposited material on the cathode surface, collect the separated electrodeposits and suspended particles (also referred to as electrodeposited particles in the following). Can also. At this time, the peeled-off electrodeposits and the like can be collected by separating them from the liquid using a filter such as filter paper.

As a result of the above electrolytic recovery operation, the target platinum group metal (particularly palladium) is contained in the liquid after the treatment.
Usually there is little or no presence.
On the other hand, in the collected electrodeposits and / or electrodeposit particles, most or almost all of the platinum group metal (particularly palladium) existing in the liquid before the treatment (for example, in the liquid before the treatment) (At least 95%, preferably at least 99% of the amount of the target platinum group metal).
The obtained electrodeposit is added with aqua regia to dissolve the platinum group metal (particularly palladium), from which the target platinum group metal can be recovered. In addition, the recovered electrodeposit can be separated from the target platinum group metal contained therein by a conventional separation operation such as molten electrolysis, thereby obtaining an isolated product thereof. As described above, according to the present invention, by collecting the formed electrodeposit, almost or almost all of the platinum group metal contained therein can be recovered from the solution before the treatment.

[0035]

The following is a specific description of the present invention by showing examples of the present invention. The present invention is not limited to these.

In the following examples, the concentrations of palladium, copper and tin were determined by the following measuring methods. [Measurement method of palladium concentration] In a 100 ml volumetric flask, about 50 ml of pure water and a hydrochloric acid solution (concentrated hydrochloric acid: water = 1: 2) 1
0 ml are added, followed by 1 ml of hydrogen peroxide. Next, 2 ml of a sample solution containing palladium is added to this solution, and the solution is diluted 50-fold with pure water to obtain a measurement solution. For this measurement solution, the concentration of palladium in the solution is measured using an atomic absorption spectrometer to determine the concentration of palladium in the sample. [Measurement method of copper concentration] A measurement solution containing a sample solution is obtained in the same manner as described above, and the copper concentration in the solution is measured using an atomic absorption spectrometer to determine the copper concentration in the sample. [Measurement Method of Tin Concentration] In the same manner as above, a measurement solution containing a sample solution is obtained, and the tin concentration in the solution is measured using an ICP emission spectrometer to determine the tin concentration in the sample.

According to the method of the present invention, palladium was recovered from the spent catalyst solution as follows. [Example 1] Palladium (Pd) not containing tin (Sn) as a catalyst liquid in the catalyzing step of the electroless plating treatment
An aqueous colloid solution was used. The catalyst solution after this treatment step (hereinafter referred to as catalyst solution A) was collected and used in the following test. In the above catalyst solution A, the Pd concentration was 231 ppm,
The Cu concentration was 37 ppm. 500 parts of this catalyst solution A
3 ml of a 35% aqueous hydrogen peroxide solution was added thereto, and the colloidal state of palladium in the catalyst solution was broken to ionize. During this process, it was observed that the liquid color changed from brown-black to yellow-transparent.

Next, the obtained catalyst solution was subjected to an electrolytic reduction operation for 3 hours under the following electrolysis conditions (a).・Electrolysis conditions (a)・ Liquid temperature Room temperature (31 ° C at the end of electrolysis) ・ Current 4A (constant) ・ Current density 12.5A / dm ²・ Anode material Pt plating Ti ・ Cathode material SUS304 (stainless steel) ・ Agitated

Table 1 below shows the palladium concentration and the copper concentration in the treated catalyst solution and the pH value of the solution during the electrolytic operation. Table 1 also shows the observation results of the liquid color and the like in the course of the electrolytic operation.

Table 1 <Results of Pd recovery test from Pd-containing (Sn-free) catalyst solution> Electrolysis time Cu concentration Pd concentration Liquid pH value Catalytic solution (hour) (ppm) (ppm) and state of cathode in electrolysis process 0 37 231 2.1 Liquid color, transparent yellow 125 143 2.1 Metal electrodeposition on cathode 2 4 21 2.1 The amount of electrodeposition is increasing 3 1 0 2.0 Liquid color, transparent

After completion of the electrolysis operation (after electrolysis for 3 hours), the amount of electrodeposits deposited on the cathode surface was calculated from the difference in cathode weight to be 0.2 g. As can be seen from Table 1, almost no palladium was present in the catalyst solution after the completion of the electrolysis operation. From this, it was found that almost all of the palladium present in the catalyst solution before the operation was electrodeposited as an electrodeposit (content theoretical Pd amount 115 m
g, theoretical Cu content 19 mg). Therefore, it was found that by the operation of Example 1 according to the present invention, almost all of the palladium contained therein could be recovered from the sample catalyst solution.

Example 2 In the catalyzing step of the electroless plating treatment, an aqueous palladium (Pd) colloid solution containing tin (Sn) was used as a catalyst solution. The catalyst solution after this treatment (hereinafter referred to as catalyst solution B) was collected and used in the following test. In the above catalyst solution B, the Pd concentration is 122 p.
The pm and Cu concentrations were 601 ppm. This catalyst liquid B
Is prepared, and 35% hydrogen peroxide solution 3
Then, the colloidal state of palladium in the catalyst solution was broken and ionized. During this process, it was observed that the liquid color changed from brown-black to yellow-transparent.

Next, the obtained catalyst solution was subjected to an electrolytic reduction operation for 3 hours under the following electrolysis conditions (b).・Electrolysis conditions (b)・ Liquid temperature Room temperature (32 ° C at the end of electrolysis) ・ Current 4A (constant) ・ Current density 12.5A / dm ²・ Anode material Pt plating Ti ・ Cathode material SUS304 (stainless steel) ・ Agitated

Table 2 shows the palladium concentration, copper concentration, and pH value of the treated catalyst solution during the electrolytic operation.
It is shown in FIG. Table 2-1 also shows the observation results of the liquid color and the like in the course of the electrolytic operation.

Table 2-1 <Results of Pd recovery test from Pd-Sn-containing catalyst solution (1)> Electrolysis time Cu concentration Pd concentration Liquid pH value Catalytic liquid (hour) (ppm) (ppm) and state of cathode in electrolysis process 0 601 122 0.3 Liquid color, yellow transparent 1 212 52 0.3 Particles without electrodeposition on cathode Floating 2 48.7 4.8 0.3 Particles are increasing 3 6.7 0 0.3 Liquid color, transparent

After completion of the electrolysis operation (after three hours of electrolysis), the total weight of the amount of electrodeposits deposited on the cathode surface and the particles collected in the catalyst solution subjected to the electrolysis operation Was 1.8 g. As can be seen from Table 2-1, almost no palladium was present in the catalyst solution after the completion of the electrolysis operation. From this, it was found that almost all of the palladium present in the catalyst solution before the operation was electrodeposited as an electrodeposit (content theoretical Pd amount 61 m
g, contained theoretical Cu amount 300 mg). Therefore, it was found that almost all of the palladium contained in the sample catalyst solution could be recovered by the operation of Example 2 according to the present invention.

Here, the composition of the particles among those recovered by this electrolysis operation was analyzed by X-ray fluorescence analysis. The results are shown in Table 2-2 below.

[0048]

As can be seen from Table 2-2, in the operation according to Example 2, although palladium could be recovered by the electrolytic operation, it was found that a large amount of tin was deposited at the same time due to the large current density.

Example 3 A test was carried out under the same conditions as in Example 2 for the treatment with the used catalyst solution and the electrolytic pretreatment agent before the electrolytic treatment.

Next, the catalyst solution after the treatment with the electrolytic pretreatment agent was subjected to an electrolytic reduction operation under the following electrolytic conditions (c).
Time went.・Electrolysis conditions (c)・ Liquid temperature Room temperature (25 ° C at the end of electrolysis) ・ Current 1A (constant) ・ Current density 2A / dm ²・ Anode material Pt plating Ti ・ Cathode material SUS304 (stainless steel) ・ Agitated

Table 3 below shows the palladium concentration and copper concentration in the treated catalyst solution and the pH value of the solution during the electrolytic operation. Table 3 also shows the observation results of the liquid color and the like in the course of the electrolytic operation.

Table 3 <Results of Pd recovery test from Pd-Sn containing catalyst solution (2)> Electrolysis time Cu concentration Pd concentration Liquid pH value Catalytic liquid in electrolysis process (hour) (ppm) (ppm) and state of cathode 0 601 122 0.3 Liquid color, transparent yellow 1 346 93 0.3 Electrodeposition on cathode 2 64 24 0.3 3 11 5 0.3 Liquid color, light green (transparent)

After completion of the electrolysis operation (after three hours of electrolysis), the amount of electrodeposits deposited on the cathode surface was calculated from the difference in cathode weight to be 0.4 g. As can be seen from Table 3, almost no palladium was present in the catalyst solution after the completion of the electrolysis operation. From this, it was found that most of the palladium present in the catalyst solution before the operation was electrodeposited as an electrodeposit (content theoretical Pd amount: 61 mg, content theoretical Cu amount: 300 mg). Therefore, it was found that almost all of the palladium contained in the sample catalyst solution could be recovered by the operation of Example 3 according to the present invention.

Example 4 In the catalyzing step of the electroless plating treatment, an aqueous palladium (Pd) colloid solution containing no tin (Sn) was used as a catalyst solution. The catalyst solution after this treatment step (that is, catalyst solution A) was collected and used for the following test. In the above catalyst solution A, the Pd concentration is 231 p
The pm and Cu concentrations were 37 ppm. 500 ml of this catalyst solution A was prepared, and aeration was performed at 1 L / min for about 5 minutes to dissolve and ionize the palladium colloid in the catalyst solution. During this process, it was observed that the liquid color changed from brown-black to yellow-transparent.

Then, the obtained catalyst solution was subjected to an electrolytic reduction operation for 3 hours under the following electrolytic conditions (d).・Electrolysis conditions (d)・ Liquid temperature Room temperature (34 ° C at the end of electrolysis) ・ Current 4A (constant) ・ Current density 12.5A / dm ²・ Anode material Pt plating Ti ・ Cathode material SUS304 (stainless steel) ・ Agitated

Table 4 below shows the palladium concentration, the copper concentration, and the pH value of the treated catalyst solution during the electrolytic operation. Table 4 also shows the observation results of the liquid color and the like in the course of the electrolytic operation.

Table 4 <Results of Pd recovery test from Pd-containing (Sn-free) catalyst solution> Electrolysis time Cu concentration Pd concentration Liquid pH value Catalytic liquid in electrolysis process (hour) (ppm) (ppm) and state of cathode 0 37 231 2.1 Liquid color, transparent yellow 123 156 2.0 Metal electrodeposition on cathode 2 8 41 2.0 The amount of electrodeposition is on the rise 30.0 1.9 Liquid color, colorless and transparent

After completion of the electrolysis operation (after three hours of electrolysis), the amount of electrodeposits deposited on the cathode surface was calculated from the difference in cathode weight to be 0.2 g. As can be seen from Table 4, almost no palladium was present in the catalyst solution after the electrolysis operation. From this, it was found that almost all of the palladium present in the catalyst solution before the operation was electrodeposited as an electrodeposit (content theoretical Pd amount 115 m
g, theoretical Cu content 19 mg). Therefore, it was found that almost all of the palladium contained in the sample catalyst solution could be recovered by the operation of Example 4 according to the present invention.

[0060]

According to the method of the present invention, almost all of the platinum group metal can be easily and efficiently recovered from the liquid containing the platinum group metal or its compound, and further, the catalyst which has been hardly recovered in the past. The fact that a relatively expensive platinum group metal in a liquid can be recovered and reused has already been described in the section of [Summary of the Invention].

Claims (4)

[Claims] 1. A method for recovering a platinum group metal from a solution containing a platinum group metal or a compound thereof in a colloidal state by electrolytic reduction, wherein an electrolytic pretreatment agent is added to the solution to dissolve the colloidal particles. A method for recovering a platinum group metal, comprising subjecting the ionized state of the platinum group metal to electrolytic reduction to precipitate and recover the platinum group metal. 2. The method of claim 1, wherein the platinum group metal is palladium.
The method described in. 3. The method according to claim 1, wherein the electrolytic pretreatment agent is an oxidizing agent. 4. The method according to claim 1, wherein the electrolytic pretreatment agent is a hydrogen peroxide solution.