JP2001131652A - Method for separating and recovering palladium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently recover palladium without being affected by a coexistent copper ion, etc. SOLUTION: The pH of a hydrochloric acid-acidified solution containing a palladium ion stabilized by a tin (II) ion is increased to precipitate palladium along with tin, the precipitate is redissolved and oxidized, and then the palladium is reduced and collected by a metal ion processing agent prepared by depositing an anthrahydroquinone compound on a porous carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for separating, concentrating and recovering palladium from an aqueous solution containing palladium. More specifically, from a waste solution such as a palladium plating solution or a mixed catalyst solution of palladium and tin used in a process for imparting palladium nuclei in electroless plating, it is possible to industrially separate, concentrate, and recover valuable palladium metal as a resource. About the method.

[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 electronic 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. Various palladium-containing waste liquids are discharged from the steps of plating and palladium nucleation, and depending on the process, waste liquids mixed with various metal ions are discharged, making the waste water treatment more difficult. . For example, a palladium-containing waste liquid mixed with a large amount of copper ions dissolved from a printed board is discharged from a palladium nucleus providing step of through-hole plating of the printed board.

[0003] As a method of recovering palladium from such an aqueous waste liquid containing palladium, (1) a method of adsorbing and recovering it on a porous carrier such as activated carbon, and (2) an aqueous solution using a chelating reagent dissolved in an organic solvent. (3) a method of recovering with an ion exchange resin,
(4) A method of precipitating and recovering has been conventionally known. However, in the case of a waste liquid containing a large amount of tin together with palladium as in the above-mentioned catalyst liquid, or in the case of a waste liquid mixed with various metal ions, it is difficult to efficiently collect only palladium by any of the above methods, and practically It was not a satisfactory method.

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”)
A technique for selectively recovering metal ions by using a catalyst solution has been disclosed. However, in the case of the above-mentioned catalyst solution, an oxidation treatment is required to eliminate the influence of coexisting tin ions. (JP-A-11-229050)

[0005] Even with this method using a metal ion treating agent, in a waste solution in which a large amount of copper ions coexist as discharged from a palladium nucleus providing step of through-hole plating of a printed board, coexistence is achieved by performing an oxidation treatment. Copper ions are oxidized to divalent ions, and the divalent copper ions are reduced by the metal ion treating agent. In other words, the reducing ability of the metal ion treating agent is reduced. The efficiency of trapping the water decreases. Even in the case of metal ions other than copper ions, a waste liquid in which highly oxidized metal ions such as iron trivalent ions coexist, in other words, metal ions that reduce the reducing ability of the metal ion treating agent coexist. With the waste liquid, the trapping efficiency of palladium decreases.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for efficiently recovering palladium in a palladium-containing solution such as the above-mentioned catalyst solution. An object of the present invention is to provide a method for selectively recovering palladium from a coexisting spent catalyst solution. Another object of the present invention is to provide a method for recovering palladium from a palladium-containing liquid other than the above-mentioned catalyst liquid.

[0007]

Means for Solving the Problems The present inventors examined the behavior of a coexisting system of tin chloride and palladium ion at various pH values, and found that stannous (divalent) and stannic (tetravalent) Both form hydroxides and precipitate at a pH value of about 1 or more, but only stannous specifically incorporates palladium into the precipitate, and almost no palladium ion remains in the solution. The present inventors have found that palladium is not incorporated, and even when copper ions and iron ions coexist, these copper ions and iron ions are not incorporated during precipitation, and the present invention has been completed.

That is, the present invention provides (1) a method of precipitating palladium together with tin hydroxide by increasing the pH of a hydrochloric acid solution containing palladium ions stabilized by divalent ions of tin to form a solution of the hydrochloric acid solution. (2) a method of concentrating palladium, characterized by dissolving a precipitate separated from the acidic hydrochloric acid solution in a hydrochloric acid acidic solution; (3) a method of separating palladium from the acidic hydrochloric acid solution Is dissolved in a hydrochloric acid solution and oxidized, and the palladium is recovered by contacting the solution with a metal ion treating agent having an anthrahydroquinone compound supported on a porous carrier. (4) A precipitate separated from the hydrochloric acid solution is treated with hydrochloric acid. A pretreatment method for recovery of palladium, characterized by being dissolved in an acidic solution.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The palladium-containing aqueous solution to be treated in the present invention is a dilute palladium-containing wastewater or a palladium-containing aqueous solution containing various impurities. Specifically, a mixed catalyst solution of palladium chloride and stannous chloride used in the palladium nucleus providing step of electroless plating (hereinafter, referred to as “palladium-
Aqueous solution containing palladium ions stabilized with divalent ions of tin in an aqueous hydrochloric acid solution (also referred to as "tin catalyst liquid").

Here, a palladium ion stabilized by a divalent tin ion is a palladium complex ion in which a divalent tin ion is coordinated, 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.

In the present invention, such a waste solution of the palladium-tin catalyst solution or a washing solution discharged from the plating step is targeted, but more preferably an aqueous solution in which various metal ions are mixed as impurities. For example, a palladium-tin catalyst liquid mixed with copper ions discharged from a palladium nucleus providing step of through-hole plating of a printed circuit board may be used.

Furthermore, even for an aqueous solution containing palladium ions which is not stabilized by divalent tin ions, such as a palladium-tin catalyst solution, adjustment to hydrochloric acid acidic conditions and / or addition of divalent tin ions. Can be similarly processed.

The palladium ion stabilized by the divalent ion of tin is stably present in the aqueous hydrochloric acid solution, but requires strongly acidic conditions, and usually has a pH of 1 or less, preferably about 0.2. Although it is a strongly acidic condition, it may be stable at a higher pH depending on the liquid composition. The amount of tin relative to palladium ions is usually about several mole times,
It is thought that it exists stably at about 5 to 10 mole times.

According to the present invention, the palladium ion-containing water p stabilized by the tin divalent ion is used.
The palladium is separated by precipitating the palladium with the tin hydroxide by increasing H and separating from the aqueous solution. Usually, this pH operation is performed with an alkali. However, an alkali may be added to the aqueous solution, mixed with the alkaline aqueous solution, or palladium-containing water may be added to the alkaline aqueous solution. Alternatively, the pH may be increased simply by dilution. Examples of the alkali include alkali metal hydroxides such as sodium hydroxide, and alkali metal carbonates such as sodium carbonate and sodium hydrogen carbonate.

Normally, when the pH value is set to be higher than 1, divalent ions of tin precipitate as hydroxides, but two or more tin ions may be required depending on the composition of the liquid. Since only palladium is selectively taken in during the generation of the precipitate to precipitate, palladium can be recovered by separating the generated precipitate from the aqueous solution. As a method for separating the precipitate, a usual method such as filtration, centrifugation, spontaneous sedimentation and the like can be employed. The upper limit of the pH value is mainly the lower one of the pH value at which coexisting ions form a precipitate and the pH value at which the tin-palladium precipitate re-dissolves. 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 separated precipitate contains almost no impurities other than tin and palladium, palladium and tin can be easily recovered. By dissolving this precipitate in a hydrochloric acid solution, a concentrated solution of palladium can be obtained, and after adjusting the composition if necessary, it can be reused as a palladium-tin catalyst solution. As a method for separating and recovering tin and palladium, after redissolving in hydrochloric acid acidic solution, oxidizing,
After oxidizing tin ions to tetravalent, a method of reducing and capturing only palladium with a metal ion treating agent in which an anthrahydroquinone compound is supported on a porous carrier may be mentioned. This method is preferable because only palladium can be selectively and easily recovered.

The metal ion treating agent comprises 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 compounds are compounds having a reversible oxidation-reduction ability, and may be any compounds that are stably fixed to the 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 may be, 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 the mol of the quinone compound) or more.
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 carried on the 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 to allow the water-soluble salt of the anthrahydroquinone compound to be porous 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 an ion exchange resin. 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.

[0023]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following description unless it exceeds the gist. In Examples, “%” means “% by weight” unless otherwise specified.

Example 1 Palladium concentration: 120 pp
m, copper concentration 3,000ppm, tin concentration 12,000p
pm containing catalyst waste liquid (palladium-
1 liter (hereinafter referred to as L) of 1% of a 2.7% sodium hydroxide solution (tin catalyst solution) was added dropwise over 1 hour with stirring over a period of 1 hour to pH 2 to form a precipitate. The concentration of palladium in the supernatant was measured by ICP-issued 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. 1 liter of granular activated carbon (48
7 g) was subjected to a nitrogen replacement treatment under reduced pressure to replace oxygen in the pores of the activated carbon with nitrogen, and then to a concentration of 1 g under nitrogen atmosphere.
Disodium salt of 6% of 1,4-dihydro-9,10-dihydroxyanthracene (hereinafter, referred to as DDA) (hereinafter, the disodium salt of DDA is referred to as "DDAN").
The concentration of DDAN is expressed as a concentration converted to anthraquinone. ) Was added, and the mixture was adsorbed under reduced pressure for 2.5 hours. This mixture was subjected to suction filtration under a nitrogen atmosphere, and 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. The amount of DDA carried was 0.73 mol per liter of activated carbon.

Comparative Example 1 The same palladium-tin catalyst solution as in Example 1 was oxidized by blowing air into 1 L of the same. The oxidized solution had a palladium concentration of 120 ppm and a copper concentration of 3,000 ppm. The air oxidation treatment changed the color from dark black to green, which suggests that the complex of tin and palladium was completely decomposed. When this solution was treated with the metal ion treating agent 10m in the same manner as in Example 1, leakage of palladium was observed from the beginning in the solution passed through the column, and almost no palladium could be recovered. As described above, the results of Example 1 and Comparative Example 1 were
It is shown in Table 1.

[0029]

[Table 1]

"Comparative Example 2" Air was blown into 1 L of the same palladium-tin catalyst liquid as in Comparative Example 1 to perform oxidation treatment. The oxidized solution had a palladium concentration of 120 ppm and a copper concentration of 3000 ppm. Next, 1 L of a 2.7% sodium hydroxide solution was added dropwise over 1 hour with stirring to adjust the pH to 2
To produce a precipitate. At this time, the palladium concentration in the supernatant was 60 ppm. If the palladium-tin catalyst solution is air-oxidized and decomposed into palladium ions and tin tetravalent ions, only tin tetravalent precipitates even if the pH is adjusted to 2 by adding alkali, Could not be recovered.

Example 2 Palladium concentration 200 pp
m, aqueous solution of pH 1 containing copper concentration of 1000 ppm 500
Add stannous chloride hydrochloride solution (1200p as tin)
pm) was added. After standing for 3 hours, the color of the solution changed from yellow-green to dark black. Next, a 2% sodium hydroxide solution was added dropwise with stirring to adjust the pH of the aqueous solution to 2,
Deionized water was added to bring the total volume to 2 L. At this time, the concentration of palladium in the supernatant was measured and found to be below the detection limit. The resulting precipitate was filtered by suction, and the resulting precipitate was redissolved in 250 ml of hydrochloric acid, and 250 ml of demineralized water was added to make the total amount 500 ml. Air was blown into this liquid to perform oxidation treatment. The palladium concentration of the oxidized orange liquid is 200
ppm and the copper concentration was 30 ppm. When this liquid was treated with the metal ion treating agent in the same manner as in Example 1, the palladium concentration in the liquid passed through the column was 0.1%.
At ppm or less, palladium did not leak, and it was visually confirmed that palladium metal was captured on the metal ion treating agent.

[0032]

The palladium ion stabilized by tin divalent ions is selectively precipitated together with tin, whereby palladium can be concentrated and separated. Since the separated precipitate does not contain impurities other than tin and palladium, palladium and tin can be recovered by a simple operation of separating tin and palladium. In particular, it is a suitable method as a pretreatment of a method of recovering palladium from a palladium-tin catalyst solution in which copper ions coexist with a metal ion treating agent. In addition, if the precipitate is redissolved by applying this method, it can be reused as a palladium-tin catalyst solution. Furthermore, after re-dissolving the precipitate, if tin is oxidized to tetravalent by an oxidation treatment, only tin precipitates, so that an aqueous palladium solution can be obtained, which can be used as a pretreatment in a palladium recovery method other than the metal ion treating agent.

Claims (4)

[Claims] 1. Increasing the pH of a hydrochloric acid solution containing palladium ions stabilized by divalent ions of tin, thereby precipitating palladium together with tin hydroxide and separating it from the hydrochloric acid solution. Characteristic method of separating palladium. 2. Increasing the pH of a hydrochloric acid solution containing palladium ions stabilized by tin divalent ions, thereby precipitating palladium together with tin hydroxide and separating the palladium from the hydrochloric acid solution. A method for concentrating palladium, comprising dissolving the precipitated precipitate in a hydrochloric acid solution. 3. The method of claim 1, wherein the pH of the hydrochloric acid solution containing palladium ions stabilized by divalent ions of tin is increased to precipitate palladium together with the hydroxide of tin and separate from the hydrochloric acid solution. A method for recovering palladium, comprising dissolving the precipitated precipitate in a hydrochloric acid solution and contacting the oxidized solution with a metal ion treating agent comprising an anthrahydroquinone compound supported on a porous carrier. 4. The method of claim 1, wherein the pH of the acidic hydrochloric acid solution containing palladium ions stabilized by divalent ions of tin is increased to precipitate palladium together with the hydroxide of tin and separate from the acidic hydrochloric acid solution. A pretreatment method for recovering palladium, characterized by dissolving the precipitated precipitate in a hydrochloric acid solution.