JP2002326821A - Method for separating and recovering palladium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover palladium from a solution acidified by hydrochloric acid which contains a palladium ion stabilized by a divalent tin ion. SOLUTION: Tin and palladium are recovered as a coprecipitate by mixing the solution acidified by hydrochloric acid which contains palladium and the divalent tin ion together with water. Furthermore, palladium is seized by a metallic ion treating agent after the coprecipitate is dissolved in the solution acidified by hydrochloric acid again and treated by oxidation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for separating, concentrating and recovering palladium from an aqueous hydrochloric acid solution containing palladium. More specifically, valuable palladium metal is industrially separated from a hydrochloric acid aqueous solution containing tin divalent ions together with palladium ions used for palladium nucleus treatment for palladium plating and electroless plating. , Concentration and recovery methods.

[0002]

2. Description of the Related Art Palladium has excellent corrosion resistance, discoloration resistance, low contact resistance and solderability, and is one of the platings often used in the electronics industry. In addition, when plating plastic materials, decorative articles, electronic equipment parts, etc., a palladium nucleus is applied to the base surface using a mixed catalyst solution of palladium and tin to add a catalytic action to the base surface of the article to be plated. A technique has been implemented. From these plating and palladium nucleus providing steps, various palladium-containing waste liquids as well as washing water for washing the plating liquid and the mixed catalyst liquid excessively attached to the plating target article are discharged.

There are two methods for recovering palladium from such palladium-containing water: (1) a method of recovering the palladium by adsorbing it on an adsorbent such as activated carbon, and (2) a method of extracting the palladium from an aqueous solution with a chelating reagent dissolved in an organic solvent. , (3) a method of recovering with an ion-exchange resin, and (4) a method of recovering by precipitation, etc., are known. At present, they cannot be sufficiently recovered and are discharged as they are.

On the other hand, a carrier in which an anthrahydroquinone compound is carried on a porous carrier (hereinafter referred to as “metal ion treating agent”)
The technology for selectively recovering metal ions by using metal ions has been disclosed. However, when the palladium concentration is extremely low as in the above-mentioned washing water, the reducing ability of the metal ion treating agent is reduced by the influence of dissolved oxygen. Since palladium drops first, palladium cannot be sufficiently recovered.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of recovering valuable palladium from a hydrochloric acid aqueous solution containing a divalent ion of tin together with palladium ions. It is an object of the present invention to provide a method for efficiently recovering palladium in a dilute palladium-containing liquid as described above.

[0006]

The present inventors have studied the behavior of tin ions and palladium ions at different pHs in an aqueous hydrochloric acid solution, and found that (1) both divalent tin ions and tetravalent tin ions have pH values When the value is about 1 or more, hydroxide forms and precipitates, but only divalent tin ions specifically incorporate palladium into the precipitate. (2) Tin divalent ions are 7 mole times the palladium ions. If present, palladium ions hardly remain in the solution. (3) Such a co-precipitate is formed even under dilute conditions such as the above-mentioned washing water. (4) This co-precipitate is recovered. As a result, it has been found that palladium can be recovered industrially advantageously, and the present invention has been completed.

That is, the gist of the present invention is to provide a method of (1) recovering a coprecipitate of tin and palladium generated by mixing an aqueous hydrochloric acid solution containing a divalent ion of tin together with palladium ion with water (2). A) a method of recovering a coprecipitate of tin and palladium formed by mixing an aqueous hydrochloric acid solution containing a divalent ion of tin together with palladium ions with at least 10 times the volume of the aqueous hydrochloric acid solution; A method of recovering a coprecipitate of tin and palladium generated by mixing a hydrochloric acid aqueous solution having a pH of less than 1 containing divalent ions of tin together with ions with water so that the pH after mixing becomes 1 or more, or (4) A hydrochloric acid aqueous solution having a pH of 1 or less containing divalent tin ions together with palladium ions is mixed with water, and further mixed. Palladium separation methods from hydrochloric acid aqueous solution using any of the methods of recovering the co-precipitate of tin and palladium to produce by adjusting the pH of the aqueous solution after the 1 or more.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The hydrochloric acid aqueous solution containing tin divalent ions together with palladium ions to be treated in the present invention includes palladium plating solution and palladium chloride and palladium chloride used in an electroless plating palladium nucleus providing step. An aqueous solution containing palladium ion stabilized with divalent ions of tin in a hydrochloric acid aqueous solution, such as a mixed catalyst liquid with tin (hereinafter, also referred to as “palladium-tin catalyst liquid”), may be mentioned.

Here, a palladium ion stabilized with a divalent tin ion refers to a palladium complex ion in which a divalent tin ion coordinates around or a palladium colloid surrounded by a divalent tin ion. It means a state in which it is stably present in an aqueous solution in the form of particles. Furthermore, even in the case of a palladium-containing aqueous solution that is not stabilized by tin divalent ions, such as a palladium-tin catalyst liquid, the treatment can be similarly performed by adjusting to hydrochloric acid conditions and / or adding tin divalent ions. Can be targeted.

The palladium ion stabilized with tin divalent ions is stably present in an aqueous hydrochloric acid solution, but requires strongly acidic conditions, and usually has a pH of less than 1, preferably about 0.2. Although it is a strongly acidic condition, it may be stable at a higher pH depending on the liquid composition. Further, in order for the palladium ion to be stably present in the aqueous hydrochloric acid solution, the content of divalent tin ions in the aqueous hydrochloric acid solution is preferably 7 mol times or more of the palladium ion,
More preferably, it is 14 mole times or more. Tin 2
When the content of the valence ion is 7 mol times or less, it is not preferable because palladium ions remain in the solution.
Therefore, for example, when a divalent ion of tin is oxidized to tetravalent and reduced like a palladium-tin catalyst liquid used for a long period, a divalent tin compound such as stannous chloride is added. Is preferred.

In the present invention, palladium is separated by forming a coprecipitate of tin and palladium from the above hydrochloric acid aqueous solution containing a divalent tin ion together with palladium ions. Specifically, a coprecipitate of tin and palladium is generated by adjusting the pH value of the aqueous hydrochloric acid solution to 1 or more. Normal pH
By making the value larger than 1, divalent tin ions precipitate as hydroxides, but depending on the composition of the solution, two or more tin ions may be required. This pH adjustment may be performed using an alkali metal hydroxide such as sodium hydroxide or an alkali metal carbonate such as sodium carbonate or sodium hydrogen carbonate. In consideration of the danger due to heat generation, it is preferable to carry out by mixing an aqueous hydrochloric acid solution with water.

In the case of mixing an aqueous hydrochloric acid solution and water, (1) a method of mixing approximately 10 times the volume of water with respect to the aqueous hydrochloric acid solution, and (2) mixing so that the pH after mixing becomes 1 or more. And (3) a method of mixing with water and then adjusting the pH of the mixed aqueous solution to 1 or more. In addition, in order to prevent oxidation of coexisting divalent ions of tin, if necessary, use water with a reduced dissolved oxygen amount, or use water under conditions such as to avoid contact with hydrochloric acid aqueous solution and air. You may mix.

At the time of this precipitation, the divalent tin ions selectively precipitate palladium alone and precipitate. Therefore, the palladium can be separated by recovering the co-precipitate of tin and palladium from the aqueous solution. As a method for collecting the coprecipitate, filtration, a hollow fiber filter,
Conventional methods such as centrifugation and spontaneous sedimentation can be employed. In addition,
The upper limit of the pH value is mainly the pH value at which coexisting ions form a precipitate or the p value at which the tin-palladium precipitate causes re-dissolution.
The lower of the H values is the upper limit. For example, when copper ions coexist, the upper limit of the pH value is 4 or less. By operating under these conditions, it is possible to separate coexisting ions other than palladium and tin ions in the aqueous solution.

Since the recovered co-precipitate contains almost no impurities other than tin and palladium, it is a pretreatment method for recovering palladium and tin. If this co-precipitate is dissolved in an acidic hydrochloric acid solution, the palladium is concentrated. Since a liquid can be obtained, this is a method for concentrating palladium. If necessary, after adjusting the composition, it can be reused as a palladium-tin catalyst liquid. As a method for recovering palladium from the recovered coprecipitate of tin and palladium, redissolve in a hydrochloric acid solution, oxidize and oxidize tin ions to tetravalent, and then carry the anthrahydroquinone compound on the porous carrier. And reducing and capturing only palladium with the resulting metal ion treating agent. This method is preferable because only palladium can be selectively and easily recovered.

This metal ion treating agent has an anthrahydroquinone compound supported on a porous carrier, and is reduced and captured on the metal ion treating agent as metal palladium by the reducing action of the anthrahydroquinone compound. Examples of the porous carrier include inorganic porous carriers such as silicon dioxide, carbon-based porous carriers such as activated carbon and activated carbon fiber, and other carbon particles such as activated carbon prepared hydrophobically.
An aqueous emulsion processed product of polytetrafluoroethylene (see JP-A-53-92981), organic synthetic polymer particles such as a styrene-divinylbenzene copolymer used as an organic synthetic adsorbent, or
These molded articles are exemplified. Among them, activated carbon is particularly preferable because it is inexpensive and easily available.

The anthrahydroquinone compound is a compound having a reversible oxidation-reduction ability, and may be any compound that is stably fixed to a porous carrier by adsorption or the like. Specific examples of the anthrahydroquinone compound include, for example, anthrahydroquinone (9,10-dihydroxyanthracene), a hydrogenated compound thereof, a substituted product thereof, and
And water-soluble salts of anthrahydroquinone compounds.

The aqueous solution of the water-soluble salt of the anthrahydroquinone compound includes, for example, a 1,4,4a, 9a-tetrahydroanthraquinone compound obtained by a Diels-Alder reaction between naphthoquinone and a corresponding 1,3-butadiene compound. Of 1,4-dihydro-9, obtained by reacting an aqueous solution of an alkali metal hydroxide in an equivalent amount (2 times mol with respect to the quinone compound)
An aqueous solution of a disodium salt of a 10-dihydroxyanthracene compound may be used.

In order to prepare a metal ion treating agent in which the above-mentioned anthrahydroquinone compound is supported on the above-mentioned porous carrier, (1) the porous carrier is immersed in a solution in which the anthraquinone compound is dissolved in an organic solvent. After impregnation and adsorption,
A method of treating with a reducing agent such as sodium dithionite (sodium hydrosulfite); (2) immersing a porous carrier in an aqueous solution of a water-soluble salt of an anthrahydroquinone compound; And then immobilized by acid washing after adsorption onto a porous carrier. The method (2) has an advantage that the essential reduction treatment in the method (1) is unnecessary.

The amount of the anthrahydroquinone compound supported on the porous carrier varies depending on the type of the anthrahydroquinone compound, the concentration of palladium in the palladium-containing aqueous solution, the type of the solid porous carrier, the particle size, the specific surface area, and the like. For example, when a disodium salt of 1,4-dihydro-9,10-dihydroxyanthracene and granular activated carbon are used, it is preferable to select from 0.3 to 1.0 mol (M) per liter of the carrier. If the loading amount is small,
A large amount of the metal ion treating agent must be used, and if it is too large, the amount that does not act on palladium increases, which is wasteful, and both are not preferred.

Other separation methods include (1) a method of re-dissolving and oxidizing in the same manner as above, increasing the pH of the solution to precipitate and separate only tin as a hydroxide, and (2) a method of re-dissolving in the same manner. A method of oxidizing, if necessary, and adsorbing and separating with an adsorbent such as activated carbon or ion exchange resin. (3) Similarly, after re-dissolving, the oxidizing treatment is stopped when the oxidation-reduction potential of the solution starts to rise. To precipitate only palladium as a metal (Japanese Patent Application No. 10-333281) (4)
Similarly, there is a method of redissolving and electrolytic reduction, etc., which is an effective method as a pretreatment of these recovery methods.

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following description examples without departing from the gist thereof. In Examples, “%” means “% by weight” unless otherwise specified. "Example 1" palladium concentration 240 ppm, copper concentration 30
20 g of a waste solution of a mixed catalyst solution of palladium and tin used for palladium nucleus treatment for through-hole plating of a printed circuit board containing 00 ppm and a tin concentration of 12000 ppm was mixed with degassed water to make 2 kg, resulting in a pH of 2 and a precipitate formed. . The concentration of palladium in the supernatant was measured by ICP emission spectroscopy and found to be below the detection limit (0.1 ppm). The resulting precipitate was separated by suction filtration to separate palladium and tin from the aqueous solution.

Next, the precipitate was redissolved with 250 ml of hydrochloric acid to obtain a palladium-tin solution, and 250 ml of demineralized water was added to make the total amount 500 ml. Air was blown into the palladium-tin solution to perform oxidation treatment. Since the color of the solution changed from dark black to orange by the air oxidation treatment, it was speculated that the complex of tin and palladium was decomposed. The palladium concentration in the oxidized orange liquid is 240 ppm
And the copper concentration was 60 ppm.

An SV (space velocity) 2 (1 / h) was added to 10 ml of the metal ion treating agent filled with 500 ml of this liquid in a column.
r) (20 ml / h), and the palladium concentration in the liquid passed through the column was analyzed to be 0.1 ppm or less. Furthermore, even when 500 ml of the liquid treated in the same manner was passed through the column, palladium did not leak, and it was visually confirmed that palladium metal was captured on the metal ion treating agent.

The metal ion treating agent used in the present invention was prepared as follows.

One liter (487 g) of granular activated carbon was repeatedly subjected to nitrogen replacement under reduced pressure to replace oxygen in the pores of the activated carbon with nitrogen.
Disodium salt of dihydro-9,10-dihydroxyanthracene (hereinafter referred to as DDA) (hereinafter, the disodium salt of DDA is referred to as "DDAN".
The concentration of N is expressed as a concentration converted to anthraquinone. ) Was added, and the mixture was adsorbed under reduced pressure for 2.5 hours. The mixture was suction filtered under a nitrogen atmosphere,
The obtained filter cake was treated with 1 liter of a 10% sulfuric acid solution, and then washed with 1 liter of demineralized water purged with nitrogen. D
The amount of DA carried was 0.73 mol per liter of activated carbon.

[Comparative Example 1] Air was blown into 20 g of a mixed catalyst liquid mixture of palladium and tin used for palladium nucleus treatment for through-hole plating of a printed circuit board similar to that in Example 1 and oxidized, followed by mixing with water. As a result, the pH became 2 and a precipitate was formed. When the palladium concentration in the supernatant was measured by ICP-issued spectroscopy, the palladium concentration was 2.3 ppm, and almost no palladium could be recovered as a precipitate. It was speculated that palladium did not co-precipitate because the oxidation treatment resulted in all divalent tin ions becoming tetravalent.

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Claims (9)

[Claims] 1. A method for recovering a coprecipitate of tin and palladium produced by mixing an aqueous hydrochloric acid solution containing a divalent ion of tin together with palladium ions with water, the method comprising recovering a coprecipitate of tin and palladium from an aqueous hydrochloric acid solution. Separation method. 2. An aqueous hydrochloric acid solution containing a divalent ion of tin together with palladium ions is added to the aqueous hydrochloric acid solution in an amount of 1: 1.
A method for separating palladium from an aqueous hydrochloric acid solution, comprising recovering a coprecipitate of tin and palladium produced by mixing with at least 0 times the volume of water. 3. A p-ion mixture containing a hydrochloric acid aqueous solution having a pH of less than 1 and containing a divalent ion of tin together with palladium ions.
A method for separating palladium from an aqueous hydrochloric acid solution, comprising recovering a coprecipitate of tin and palladium produced by mixing with water so that H becomes 1 or more. 4. A mixture of tin and palladium formed by mixing a hydrochloric acid aqueous solution having a pH of 1 or less containing divalent ions of tin together with palladium ions with water, and further adjusting the pH of the mixed aqueous solution to 1 or more. A method for separating palladium from an aqueous hydrochloric acid solution, comprising recovering a precipitate. 5. The method for separating palladium according to claim 1, wherein the content of divalent ions of tin in the aqueous hydrochloric acid solution is 7 mol times or more with respect to the palladium ions. 6. A method for concentrating palladium, comprising dissolving a coprecipitate of tin and palladium recovered by the method according to claim 1 in a hydrochloric acid solution. 7. A pretreatment for recovering palladium, characterized by dissolving a coprecipitate of tin and palladium recovered by the method according to claim 1 in a hydrochloric acid solution. Method. 8. A solution obtained by dissolving a coprecipitate of tin and palladium recovered by the method according to any one of claims 1 to 5 in an acid solution of hydrochloric acid and further oxidizing the solution to obtain a porous solution of an anthrahydroquinone compound. A method for recovering palladium, which comprises contacting with a metal ion treating agent supported on a carrier. 9. A method for dissolving a coprecipitate of tin and palladium recovered by the method according to any one of claims 1 to 5 in an acidic solution of hydrochloric acid, and further bringing the oxidized solution into contact with an ion exchange resin. A method for recovering palladium, comprising: