WO2002061156A1

WO2002061156A1 - Method for separating, enriching and recovering palladium

Info

Publication number: WO2002061156A1
Application number: PCT/JP2001/000723
Authority: WO
Inventors: Suehide Hirata; Tatsuya Sakurai
Original assignee: Kawasaki Kasei Chemicals Ltd.
Priority date: 2001-02-01
Filing date: 2001-02-01
Publication date: 2002-08-08

Abstract

A method for recovering palladium by reducing and capturing a palladium ion present in water together with a divalent copper ion and the like, using a metal ion treating agent having a porous carrier and an anthrahydroquinone compound carried thereon, wherein (1) the divalent copper ion is first reduced selectively with a divalent tin ion or the like and then the palladium ion is reduced and captured with the metal ion treating agent, or (2) a solution containing a palladium ion stabilized by a divalent tin ion and being acidified with hydrochloric acid is increased in pH, to thereby precipitate palladium together with tin, the resultant precipitate is again dissolved and subjected to an oxidation treatment, and then the palladium ion is reduced and captured with the metal ion treating agent. The method can be utilized for recovering palladium with good efficiency, without being adversely affected by a coexisting divalent copper ion and the like.

Description

Technical field

The present invention relates to a method for separating, concentrating and recovering palladium from a palladium-containing aqueous solution in which a metal ion such as steel ion and iron ion coexists.

In more detail, wastewater such as palladium plating solution mixed with copper ions and iron ions, and mixed catalyst solution of palladium and tin used for the treatment of palladium nuclei for electroless plating is valuable for resources. The present invention relates to a method for industrially separating, concentrating and recovering palladium. Background art

Palladium has excellent corrosion resistance, discoloration resistance, low contact resistance, and excellent solderability, and is one of the most frequently used plating techniques in the electronics industry. In addition, when plating plastic materials, decorative articles, electronic equipment parts, etc., in order to add a catalytic action to the base surface of the article to be plated, a mixed catalyst liquid of rhodium and tin is used. A technique of providing a palladium nucleus on a base surface has been used. Various wastewater containing palladium is discharged from these plating and palladium nucleation processes. In particular, the palladium nucleation process performed for the through-hole plating of the printed circuit board begins with a large amount of copper ion melted from the printed circuit board. Waste liquid contained is discharged.

There are two methods for recovering palladium from such aqueous wastewater containing palladium: (1) a method in which the palladium is recovered by adsorbing it on a porous carrier such as activated carbon; and (2) a method in which the palladium is dissolved from an aqueous solution using a chelating reagent dissolved in an organic solvent. A method of extraction, (3) a method of recovering with an ion-exchange resin, and (4) a method of recovering by precipitation have been known. However, in the case of a waste liquid containing a large amount of tin together with palladium as in the above catalyst solution, In these methods, it was difficult to efficiently recover only palladium, and it was not a practically satisfactory method.

On the other hand, there has been disclosed a technique for selectively recovering metal ions using a carrier in which an anthrohydroquinone compound is supported on a porous carrier (hereinafter referred to as a “metal ion treating agent”). Oxidation treatment is required to eliminate the effect of coexisting suzuon. (Japanese application publication number: Japanese Patent Application Laid-Open No. H11-221290)

However, when copper ions coexist, such as the palladium sulfuric acid catalyst solution discharged from the catalysis process of the through-hole plating on the printed circuit board, steel ions are converted to copper divalent ions by this oxidation treatment. It will be oxidized. Metal ions, such as divalent ions in this steel, are metal ions that are more oxidizable than the anthraquinone compounds corresponding to the oxidized form of the anthrahydroquinone compound on the metal ion treatment agent. It oxidizes a type of anthrahydroquinone compound to an anthraquinone compound. Therefore, the reducing ability of the metal ion treating agent is undesirably reduced. Other examples of such a metal ion include trivalent iron.

In fact, the present inventors attempted to recover palladium by passing a catalyst solution containing copper ions together with palladium through air oxidation through a column filled with the metal ion treating agent described in the above publication. However, the amount of captured palladium was small, and palladium leaked immediately.

An object of the present invention is to coexist with a metal ion having a higher oxidizing property than an anthraquinone compound corresponding to an oxidized form of an anthrahydroquinone compound on a metal ion treating agent such as a divalent ion of copper, or during the treatment. An object of the present invention is to provide a method for selectively separating, concentrating and recovering palladium from a palladium-containing solution such as the above-mentioned catalyst solution for producing a highly oxidizable metal ion. Disclosure of the invention

The present inventors have studied the above problems, and as a result, selectively reduce only divalent ions of copper and trivalent ions of iron coexisting in the catalyst solution after the oxidation treatment. As a result, the method was studied diligently, and as a result, tin divalent ions, preferably stannous chloride, were able to reduce only divalent ions of steel and trivalent ions of iron. In the presence of an excess of divalent ions of tin, for example, stannous chloride, it is found that palladium complex formation at a slow rate precedes and does not immediately reduce palladium. Completed the invention.

That is, the first invention is a method for recovering palladium in an aqueous solution using a metal ion treatment agent in which an anthrohydroquinone compound is supported on a porous carrier, wherein the coexisting metal ion in the aqueous solution is a metal ion When the metal ion is more oxidizable than the anthraquinone compound corresponding to the oxidized form of the anthrahydroquinone compound on the treating agent, the coexisting metal ion is selectively reduced to a lower oxidizable metal ion. This is a method for recovering palladium, which comprises reducing and capturing palladium with a metal ion treating agent. More specifically, a method in which coexisting metal ions are reduced by a reducing agent capable of selectively reducing coexisting metal ions to low-oxidizing metal ions, and palladium is recovered by a metal ion treatment agent It is.

Furthermore, the behavior of tin chloride and palladium ion coexisting systems at various pH values was investigated. The pH values of both stannous (divalent) and stannic (tetravalent) were approximately A hydroxide forms and precipitates at 1 or more, but only stannous specifically incorporates palladium into the precipitate, leaving little palladium ion in the solution, and stannic does not capture palladium In addition, they found that even when copper ion and iron ion coexist, these copper ions and iron ions were not taken up during precipitation, and completed the second invention.

That is, the second invention raises the pH of a hydrochloric acid acidic solution containing palladium ions stabilized by tin divalent ions, thereby precipitating palladium together with tin hydroxide to form the hydrochloric acid. After separating the precipitate from the acidic solution and dissolving the separated precipitate in another hydrochloric acid solution, the oxidized solution is brought into contact with a metal ion treating agent comprising an anthrahydroquinone compound supported on a porous carrier to form palladium. It is a method of collecting. Further, as the invention accompanying the second invention, (1) increasing the pH of hydrochloric acid acidic solution containing palladium stabilized by tin divalent ion to increase tin hydroxide (2) a method of separating palladium, which comprises precipitating palladium together with a substance and separating it from the hydrochloric acid solution, and (2) dissolving the precipitate separated from the hydrochloric acid solution in another hydrochloric acid solution. A palladium concentration method, and (3) a pretreatment method for recovering palladium characterized by dissolving a precipitate separated from the hydrochloric acid solution in another hydrochloric acid solution. BEST MODE FOR CARRYING OUT THE INVENTION

The palladium-containing aqueous solution to be treated in the present invention is a palladium-containing aqueous solution containing a large amount of copper (II) ion and iron (III) ion. More specifically, the acidity of hydrochloric acid, such as a mixed catalyst solution of palladium chloride and stannous chloride used in the step of applying a palladium nucleus for electroless plating (hereinafter also referred to as “palladium-tin tin catalyst”). It is an aqueous solution containing palladium ions stabilized with divalent ions of tin in the aqueous solution, and is an aqueous solution in which copper ions and iron ions are mixed as impurities. For example, a palladium-tin tin catalyst discharged from the process of catalyzing the through-hole plating of the printed substrate may be used.

Here, the palladium ion stabilized with tin divalent ions is defined as a palladium complex ion in which tin divalent ions are coordinated or a palladium colloid particle surrounded by tin divalent ions. It means a state in which it is stably present in an aqueous solution in such a form. In such a catalyst solution, palladium chloride is formed into a colloidal particle having a valency close to 0 or a complex complex by stannous chloride. Therefore, the palladium ion is treated with a metal ion treatment agent. In order to recover palladium, it is necessary to convert palladium into divalent ions by treatment such as oxidation. Specifically, this oxidation is performed by (1) a method of blowing gas such as air or oxygen into the palladium-containing aqueous solution, (2) a method of adding an appropriate oxidizing agent to the palladium-containing aqueous solution, or (3) an external power supply. Or (4) a method in which a substance having an acid reduction potential higher than 0.6 V (vs. NHE) is added to a palladium-containing aqueous solution, or a potential corresponding to this is supplied from an external power supply. Giving method, and the like. These methods can be used alone or in combination of two or more.

Examples of oxidizing agents that can be used when oxidizing a palladium-containing aqueous solution include oxygen-based oxidizing agents such as air, oxygen, and hydrogen peroxide, chlorine-based oxidizing agents such as perchlorate and gaseous chlorine, and trivalent oxidizing agents. Examples include metal compounds such as iron ions. These can be used alone or in combination of a plurality of oxidizing agents.

If these oxidizing agents are added in large amounts, the oxidizing agents remain in the aqueous solution containing palladium after the oxidation treatment, and the oxidizing power of the remaining oxidizing agents reduces the ability of the metal ionizing agent to recover palladium. I don't like it because she is forced to do so. On the other hand, if the amount of the oxidizing agent is reduced to a value close to the equivalent, the oxidation rate is reduced. In addition, the palladium-containing aqueous solution usually generated in the previous process of electroless plating contains much more tin than palladium, and palladium is oxidized after tin is oxidized. Even if the agent is added in a slight excess, the addition to the palladium will be considerably excessive, and the remaining oxidizing agent will greatly reduce the amount of palladium trapped by the metal ion treating agent. . Conversely, even with a small amount of oxidizing agent, palladium ions are not oxidized and cannot be recovered.

In other words, the amount of the oxidizing agent needs to have a fairly strict equivalence relationship. In addition, in the oxidation treatment under such an equivalence relation, the oxidation rate near the end point becomes slow, and it takes a long time, which is not preferable. A preferred method of oxidizing the aqueous solution containing palladium is to use an excessive amount of an oxidizing agent, remove or inactivate the excess oxidizing agent after the treatment, and then perform a recovery operation using a metal ionizing agent. The way to do it.

When an oxygen-containing gas such as air is used as the oxidizing agent, oxygen remaining in the water after the oxidation treatment is reduced to gold because the solubility of oxygen in water is low. Although the performance of the metal ion treating agent is not greatly reduced, it is ideally preferable to replace the remaining oxygen with an inert gas such as nitrogen after the oxidation is completed. When a gas such as air or oxygen is used as the oxidizing agent, it is usually desirable to blow the gas into a palladium-containing aqueous solution in a fine state at room temperature. The blowing speed and time can be set arbitrarily.In the case of air, palladium is usually blown into a 1 L aqueous solution at a speed of 10 to 300 m1 / min for about 40 hours. Can be oxidized. At this time, the progress of the oxidation of palladium can be confirmed from the coloration of the aqueous solution containing palladium. That is, if the brownish aqueous solution with high turbidity changes to a transparent orange color, it means that zero-valent palladium has been oxidized to divalent palladium ions.

By this oxidation treatment, palladium can be recovered, but at the same time, coexisting copper ion and iron ion are oxidized to copper divalent ion and iron trivalent ion, and as a result, the reducing ability of the metal ion treating agent is reduced. I will lower it. Therefore, in the first invention, the copper divalent ion or iron trivalent ion is selectively reduced to copper monovalent ion ゃ iron divalent ion and passed through the metal ion treatment agent. As a method for selective reduction, a reducing agent that can selectively reduce copper divalent ions and iron trivalent ions to steel monovalent ions and iron divalent ions without reducing palladium ions is known. Adopted. For example, stannous chloride, steel metal, iron metal, hydroxylamine hydrochloride, hydrazine and the like are used. In particular, a tin compound is already contained in this liquid, and the rate of reducing palladium is low, which is preferable. Conversely, sodium sulfite has no effect, and it is not preferable because it generates dangers such as gas generation under acidic conditions.

The addition amount of stannous chloride is preferably an electrochemical equivalent to divalent copper ions and trivalent iron ions contained in the aqueous solution. The electrochemical equivalent value in the present invention refers to the stoichiometry of tin from divalent to tetravalent, which is equivalent to a change from divalent to monovalent for copper ions and from trivalent to divalent ions for iron ions. Value. The content of copper ions and iron ions in the aqueous solution varies depending on the process of the discharged catalyst solution. From 100 mg / L to 400 Omg / L, and 100 to 200 mg / L as iron.

In the reduction with stannous chloride, when a small excess amount of stannous chloride is added, tetrachloropalladium in the liquid phase forms a complex red tinted complex ion with tintin, but over time, Go back. These palladiums can be subjected to a reduction treatment using the metal ion treatment agent used in the present invention. On the other hand, when a large excess of stannous chloride is added to the aqueous solution. The tetrachloride complex ion in the liquid phase forms a dark green complex ion with the tin ion, and the dark green complex ion is not reduced by the metal ion treating agent of the present invention. In other words, the amount of stannous chloride added should be much greater than the equivalent value for copper divalent ions and iron trivalent ions contained in the aqueous solution, both economically and practically. Is not preferred, and 1 to 2 times the equivalent value is appropriate.

By adding stannous chloride to the aqueous solution, the oxidation-reduction potential of the aqueous solution changes sharply. However, in the vicinity of the electrochemical equivalent value of divalent copper (iron) and trivalent iron (iron) in the aqueous solution, it is approximately 20%. It is kept between 0 and 300 mV, more preferably between 270 mV and 220 mV. The oxidation-reduction potential in the present invention can be measured with a commercially available ORP meter, but it is appropriate to use a platinum electrode from the choice of electrodes.

Further, as the aqueous solution containing stannous chloride, a catalyst solution before oxidation can be used. When using a catalyst solution before oxidation, measure the contents of stannous chloride, copper chloride, and iron chloride in the catalyst solution in advance, and determine the amount of chlorinated chloride equivalent to one-half mole of the abundance of copper and iron. Separating the amount of tin containing liquid separately, oxidizing the rest, and mixing the unoxidized liquid separated after oxidation to prepare the target liquid without using new reagents I can do it.

In the first invention, the palladium-containing aqueous solution which has been oxidized and reduced by the above method is brought into contact with a metal ion treating agent having an anthrohydroquinone compound supported on a porous carrier. Bivalent palladium by oxidation treatment The palladium oxidized to palladium ions is reduced and captured as palladium metal on the metal ion treatment agent by the reducing action of the antrahydroquinone compounds on the metal ion treatment agent.

Next, the second invention will be described. In the palladium-containing aqueous solution targeted in the present invention, palladium ions are stabilized by divalent tin ions. The palladium ion is stably present in an aqueous hydrochloric acid solution, but requires strongly acidic conditions, and is usually under a strongly acidic condition of a pH value of 1 or less, preferably about 0.2. May be stable at higher pH. The abundance of tin with respect to palladium ion is usually about several mole times, and it seems that it exists stably at about 5 to 10 mole times.

By increasing the pH of the palladium ion-containing water stabilized by such tin divalent ions, palladium can be precipitated together with the tin hydroxide and separated from the aqueous solution. Usually, this pH operation is carried out using an alkaline solution, but alkali may be added to the aqueous solution, mixed with the alkaline 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 metal include alkali metal hydroxides such as sodium hydroxide and carbonates of alkali metal such as sodium carbonate and sodium hydrogen carbonate.

Normally, when the pH value is set to be higher than 1, tin divalent ions precipitate as hydroxides, but depending on the composition of the solution, two or more tin ions may be required. At the time of this precipitation, only palladium is selectively taken in and precipitated, so that palladium can be recovered by separating the produced precipitate from the aqueous solution. As a method for separating the precipitate, a usual method such as filtration, centrifugation, and natural sedimentation can be employed. The upper limit of the pH value is mainly the lower of the pH value at which coexisting ions form a precipitate and the pH value at which tin-palladium precipitates redissolve. For example, when copper ions coexist, the upper limit of the pH value is 4 or less. By operating under these conditions, separation from coexisting ions other than palladium and sulphonate in the aqueous solution can be achieved. Since the separated precipitate contains almost no impurities other than tin and palladium, palladium and tin can be easily recovered, and it is effective as a pretreatment method for various methods of separating and recovering palladium and tin. If the separated precipitate is dissolved in another hydrochloric acid solution, a concentrated palladium solution can be obtained. If necessary, the composition is adjusted. Reusable as a radium-tin tin catalyst solution.

The method for separating and recovering tin and palladium according to the second invention is as follows. The tin-palladium precipitate separated as described above is dissolved again in another hydrochloric acid solution, and then oxidized to convert tin ions to tetravalent. In this method, only palladium is reduced and captured with a metal ionizing agent after oxidation. This method is preferable because only palladium can be selectively and easily recovered.

Examples of the porous carrier used in the metal ion treatment agent of the present invention include inorganic porous carriers such as silicon dioxide, carbon-based porous carriers such as activated carbon and activated carbon fiber, and carbon such as activated carbon prepared to be hydrophobic. Particles, for example, an aqueous emulsion processed product of polytetrafluoroethylene (see JP-A-53-92981), organic synthetic polymer particles, for example, used as an organic synthetic adsorbent Styrene-divinyl pentene copolymer, or a molded article thereof. Among them, activated carbon is particularly preferable because it is inexpensive and easily available.

The anthrahydroquinone compound used in the metal ion treatment agent of the present invention is a compound having a reversible oxidation-reduction ability, and may be any compound that can be stably immobilized on a porous carrier by adsorption or the like. Specific examples of the anthrahydroquinone compound include, for example, anthrahydroquinone (9,10-dihydroxyxanthracene), a hydrogenated compound thereof, a substituted product thereof, and a water-soluble salt of anthrahydroquinone compound. Ο

Examples of aqueous solutions of the water-soluble salts of the anthrohydroquinone compounds include, for example, 1,4,4a, 9a- obtained by Diels-Alder reaction of naphthoquinone with the corresponding 1,3-butadiene compound. Tetrahydr 1,4-Dihydro 9,10-Dihydroxy thiacene dinatrium compound obtained by reacting an aqueous solution of an alkali metal hydroxide in an amount equivalent to (more than twice the molar amount of the quinone compound) an oral anthraquinone compound. An aqueous salt solution is mentioned.

In order to prepare a metal ion treating agent in which the above-mentioned anthrahydroquinone compound is supported on the porous carrier, (1) the porous carrier is immersed in a solution in which the anthraquinone compound is dissolved in an organic solvent. Impregnated and adsorbed, then treated with a reducing agent such as sodium dithionite (sodium hydrosulfite); (2) Anthrahydrid The porous carrier is immersed in an aqueous solution of a water-soluble salt of a hydroquinone compound. A method in which a water-soluble salt of a droquinone compound is adsorbed on a porous carrier and then washed with an acid to fix the salt. The method (2) has an advantage that the essential reduction treatment in the method (1) is not required.

The amount of the anthrahydroquinone compound to be supported on the porous carrier depends on the type of the anthrahydroquinone compound, and the amount of the anthrohydroquinone compound. It depends on the concentration of palladium in the aqueous solution containing radium, the type of solid porous carrier, the particle size, the specific surface area, and the like. For example, dinadium of 1,4-dihydroxy-19,10-dihydroxyxanthracene When a salt and granular activated carbon are used, it is preferable to select from 0.3 to 1.0 mol (M) per 1 L of the carrier. If the supported amount is small, a large amount of the metal ion treating agent must be used, and if the supported amount is too large, the amount that does not act on palladium increases, which is wasteful.

To recover palladium from a palladium-containing aqueous solution that has been oxidized or reduced by the above method or from a solution in which tin-palladium precipitate has been redissolved, the metal ion treating agent prepared as described above is treated with a palladium-containing aqueous solution. A batch-type treatment method in which an amount equivalent to or less than that necessary for reducing palladium is added and stirred, and then the supported substance is filtered off by decantation or filtration can be used. A method is employed in which a column (tower) is filled with the metal ion treating agent and a palladium-containing aqueous solution is passed. The method of passing the liquid through the column is not particularly limited, and may be upward or downward. For example, a normal liquid passing method can be used. 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 ''.

An aqueous solution having the following composition was prepared using palladium chloride, stannic chloride pentahydrate, cupric chloride and 37% hydrochloric acid (all manufactured by Wako Pure Chemical Industries, Ltd.) to obtain a model catalyst solution.

P d: 100mg / L

C u: 1 000mg / L

S n: 20 g / L

H C 1: 3.7%

1.5 g of stannous chloride equivalent to copper was added to the model catalyst solution prepared above. At this time, the oxidation-reduction potential of the aqueous solution changed from 400 mV to 250 mV. This aqueous solution was passed through a glass drum filled with 10 ml of a metal ion treating agent. The water flow velocity was 4 Om 1 Zh, and the space velocity (unit: lZhr, hereafter referred to as SV) was 4. The palladium ion in the treatment solution was measured by an ICP atomic emission method (hereinafter, ICP). Table 1 shows the results. In the table, the amount of the treatment liquid was represented by the ratio of the volume of the treated solution to the volume of the metal ion treating agent packed in the column (hereinafter referred to as BV).

The metal ion treating agent used in the present invention was prepared as follows. 1 L (487 g) of granular activated carbon was repeatedly subjected to nitrogen replacement under reduced pressure to replace the oxygen in the pores of the activated carbon with nitrogen. 0—The disodium salt of dihydroxyxanthracene (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. Add 950 g of an aqueous solution of) and adsorb under reduced pressure for 2.5 hours I let it. This mixture was subjected to suction filtration under a nitrogen atmosphere, and the obtained filter cake was treated with 1 L of a 10% sulfuric acid solution, and then washed with 1 L of demineralized water purged with nitrogen. The amount of DDA carried was 0.73 mol per liter of activated carbon.

"Comparative Example 1"

The model catalyst solution of Example 1 was passed through a glass column filled with a metal ion treating agent without adding stannous chloride. Flow rate is 40 m1 / h

(S V). The palladium ion in the treatment solution was measured in the same manner as in Example 1, and the results are shown in Table 1.

"Comparative Example 2"

To the model catalyst solution of Example 1 was added stannous chloride (6.0 g) in an amount equivalent to a 5-fold excess with respect to copper. At this time, the oxidation-reduction potential of the aqueous solution was from 400 mV to 50 mV. Changed to At this time, the treatment solution, which turned dark green, was passed through a glass column filled with 10 ml of a metal ion treatment agent. The water flow rate was 40 m 1 / h (S V 4). Palladium ions in the treatment liquid were measured in the same manner as in Example 1, and the results are shown in Table 1. The bar in Table 1 means that the measurement was not performed.

table 1

"Example 2"

An aqueous solution having the following composition was prepared using palladium chloride, varnish chloride 'pentahydrate, cupric chloride, and 37% hydrochloric acid (all of which were made by Wako Pure Chemical Industries, Ltd.). A Dell catalyst solution was used.

P d: i 0 0 mg / L

Cu: 300 mg / L

S n: 20 g / L ·

H C 1: 3.7%

To the above model catalyst solution, 6.5 g of stannous chloride equivalent to copper was added. At this time, the oxidation-reduction potential of the aqueous solution changed from 420 mV to 220 mV. This aqueous solution was passed through a glass ram filled with 10 ml of a metal ionizing agent. The water flow rate was 40 m 1 / h (S V 4). The palladium ion in the treatment solution was measured by ICP. Table 2 shows the results. Table 2

"Example 3"

An aqueous solution having the following composition was prepared using palladium chloride, varnish chloride'pentahydrate, cupric chloride and 3796 hydrochloric acid (all manufactured by Wako Pure Chemical Industries, Ltd.), and used as a model catalyst solution.

Pd: 200 mg / L

Cu: 2000 mg / L.

S n: 20 g / L

H C 1: 3.7%

The model catalyst solution and the stannous chloride aqueous solution were column-treated with a metal ion treating agent while continuously mixing so that the oxidation-reduction potential was 25 OmV. The liquid passing speed was 300 ml / h. The palladium ion in the treatment solution was measured by CP, and the results are shown in Table 3. Table 3

"Example 4"

The palladium soot catalyst solution discharged from the step of applying a catalyst for through-hole plating on a printed substrate was air-oxidized to obtain a catalyst solution having the following composition.

Pd: 130 mg / L

Cu: 990 mg / L

S n: 1 2 g / L

H C 1: less than 0.3%

N a C 1: 240 g / L

The catalyst solution before air oxidation was used as the reducing agent, and the catalyst solution after air oxidation was continuously mixed so as to have an oxidation-reduction potential of 27 OmV, and the column treatment was performed with a metal ion treatment agent. The flow rate of the column through the metal ion treatment agent was 30 Om 1 / h. The palladium ion in the treatment solution was measured by ICP, and the results are shown in Table 4. Table 4

"Example 5"

An aqueous solution of stannous chloride was continuously mixed with the same catalyst solution as in Example 4 so that the oxidation-reduction potential became 270 mV, and the mixture was subjected to column treatment with a metal ionizing agent. The column flow rate was 6 L / h. Palladium ions in the treatment solution were measured by ICP, and the results are shown in Table 5. Table 5

"Example 6"

No ,. Catalyst wastewater (palladium sulfur) discharged from the palladium nucleation process of through-hole plating on printed circuit boards containing a radium concentration of 120 mg / L, a copper concentration of 3,000 mg ZL, a tin concentration of 12, and OO Omg / L To 1 L of the catalyst solution, 1 L of a 2.7% sodium hydroxide solution was added dropwise over 1 hour with stirring to adjust the pH to 2, whereby a precipitate was formed. The concentration of palladium in the supernatant was below the detection limit (0.1 mgZL) as measured by ICP-issued spectroscopy. The precipitate formed 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 tin solution, and 250 ml of demineralized water was added to make the total amount 500 ml. Air was blown into this palladium mousse solution to perform oxidation treatment. The color of the solution changed from dark black to orange by the air oxidation treatment, suggesting that the complex of tin and palladium was decomposed. The oxidized orange liquid had a palladium concentration of 240 mg / L and a copper concentration of 6 OmgZL.

This solution was passed at a flow rate of 20 ml / h (SV 2) through a metal ion treatment agent 1 Om 1 filled with 50 Om 1 in a column, and the palladium concentration in the solution passed through the column was analyzed. However, it was below 0.1 mg / L. 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.

"Comparative Example 3"

Air was blown into 1 L of the same palladium-tin catalyst solution as in Example 6 to perform oxidation treatment. The oxidized solution had a palladium concentration of 12 Omg / L and a copper concentration of 3,000 mg / L. The air oxidation treatment changed the color from dark black to green, suggesting that the complex of tin and palladium was completely decomposed. When this solution was treated with the metal ion treating agent 10 m in the same manner as in Example 6, leakage of palladium was observed from the beginning in the solution passed through the column, and almost no palladium could be recovered. Table 6 shows the results of Example 6 and Comparative Example 3 described above. Table 6

Palladium concentration (mgZL)

Processing solution volume (BV) Example 6 Comparative Example 3

1 0 0.1 or less 1.6

20 0.1 or less 1 8

50 0.1 or less 2 1

80 0.1 or less 5 1

100 0.1 or less 6 5 "Comparative Example 4"

Air was blown into 1 L of the same palladium-tin catalyst solution as in Comparative Example 3 to perform an oxidation treatment. The oxidized solution had a palladium concentration of 1.20 mg / L and a copper concentration of 3000 mg / L. Next, 1 L of a 2.7% sodium hydroxide solution was added dropwise over 1 hour with stirring to adjust the pH to 2, and a precipitate was formed. At this time, the palladium concentration in the supernatant was 6 OmgZL. If the palladium-tin tin catalyst solution is air-oxidized and decomposed into palladium ion and tetravalent ion form of tin, only tetravalent tin precipitates even if the pH is adjusted to 2 by adding aluminum chloride. The palladium could not be recovered.

"Example 7"

To 500 ml of an aqueous solution of pH 1 containing 200 mg / L of palladium and 100 mg of copper, 500 ml of a stannous chloride solution (1,200 mg / L as tin) 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, the pH of the aqueous solution was adjusted to 2, and demineralized water was added to make the total volume 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 suction-filtered, and the resulting precipitate was redissolved in 250 ml of hydrochloric acid, and 250 ml of demineralized water was added to bring the total amount to 500 ml. Air was blown into this solution to perform oxidation treatment. The oxidized orange liquid had a palladium concentration of 200 mgZL and a steel concentration of 30 mgZL. When this solution was treated with a metal ion treating agent in the same manner as in Example 6, the concentration of palladium in the solution that passed through the column was 0.1 mg / L or less, no palladium leaked, and metal ion treatment was performed. It was visually confirmed that palladium metal was captured on the agent.

"Example 8"

No ,. Radium concentration 120 mg / L, copper concentration 3,000 mg ZL, tin concentration Degree of catalyst waste water (palladium-tin tin catalyst solution) discharged from the palladium nucleation process of the through-hole mech on the printed circuit board containing 12, OOO mg ZL 50 m 1 into 1,950 m water Upon addition of 1 and stirring, a brownish-grey colored precipitate formed. At this time, the palladium concentration in the supernatant was measured and found to be below the detection limit. The resulting precipitate was filtered by suction, and the obtained precipitate was redissolved in 25 ml of hydrochloric acid, and demineralized water was added to bring the total amount to 50 ml. Air was blown into this liquid to perform oxidation treatment. The oxidized orange liquid had a palladium concentration of 120 mg ZL and a copper concentration of 30 mg / L. When this solution was treated with a metal ion treating agent in the same manner as in Example 6, the concentration of palladium in the solution passed through the column was 0.1 mg / L or less. Then, the palladium metal was captured visually. Industrial applicability

When recovering the palladium in the palladium catalyst solution mixed with copper ion and iron ion using a metal ion treatment agent, (1) selectively remove copper divalent ions and iron trivalent ions after oxidation treatment. (2) Palladium ion stabilized by tin divalent ion is selectively precipitated together with tin by increasing the pH, and this precipitate is separated and redissolved. According to the method of chemical treatment, interference by coexisting divalent ions of copper and trivalent ions of iron can be prevented, and reduction and capture of palladium by the metal ion treatment agent can be performed. Furthermore, since the precipitate separated by the method of separating and separating tin-palladium in (2) does not contain impurities other than tin and palladium, palladium and tin are recovered by a simple separation operation of tin and palladium. it can. In particular, it is a suitable method as a pretreatment of a method of recovering palladium from a palladium sulfuric acid catalyst solution in which copper ions coexist with a metal ion treating agent. Further, by applying this method, the precipitate can be reused as a palladium-tin tin catalyst solution by re-dissolving the precipitate. Furthermore, after redissolving the precipitate, if tin is oxidized to tetravalent by oxidation treatment, only tin precipitates. An aqueous solution of dime can be obtained, which is also effective as a pretreatment for palladium recovery methods other than the metal ion treatment agent.

Claims

The scope of the claims

1. A method for recovering palladium ions in an aqueous solution using a metal ion treating agent in which an anthrohydroquinone compound is supported on a porous carrier, wherein the coexisting metal ions in the aqueous solution are deposited on the metal ion treating agent. When the metal ion is more oxidizable than the anthraquinone compound corresponding to the oxidized form of the anthrahydroquinone compound, the coexisting metal ion is selectively reduced to a lower oxidized metal ion, and then the palladium is treated with a metal ion treating agent. A method for recovering palladium, comprising reducing and trapping palladium.

2. A method for recovering palladium in an aqueous solution using a metal ion treating agent in which an anthrohydroquinone compound is supported on a porous carrier, comprising a co-existing metal ion force of ⁵ 'in the aqueous solution and a metal ion treatment. When the metal ion is more oxidizable than the anthraquinone compound corresponding to the oxidized form of the anthrahydroquinone compound on the agent, the coexisting metal ion can be selectively reduced to a lower oxidizable metal ion. A method for recovering palladium, comprising reducing and capturing palladium with a metal ion treating agent after reduction with an agent.

3. The method according to claim 2, wherein the reducing agent is a divalent ion of tin.

4. The method according to claim 2, wherein the reducing agent is stannous chloride.

5. The method according to any one of claims 1 to 4, wherein the coexisting metal ion is a divalent ion of copper and a trivalent ion of Z or iron.

6. The amount of stannous chloride added is adjusted by utilizing a change in the oxidation-reduction potential and / or color of the aqueous solution caused by the addition of stannous chloride. The method of paragraph 1.

7. By increasing the pH of a hydrochloric acid solution containing palladium stabilized by tin divalent ion, palladium is precipitated together with the tin hydroxide to form a solution from the hydrochloric acid solution. The separation is performed by dissolving the separated precipitate in another acidic hydrochloric acid solution, and contacting the oxidized solution with a metal ion treating agent having an anthrohydroquinone compound supported on a porous carrier. Recovery method of palladium.

8. By increasing the pH of a hydrochloric acid solution containing palladium ions stabilized by divalent tin ions, the palladium is precipitated together with the tin hydroxide and separated from the hydrochloric acid solution. A method for separating palladium, comprising:

9. By increasing the pH of a hydrochloric acid solution containing palladium ions stabilized by tin divalent ion, palladium is precipitated together with the tin hydroxide, and the hydrochloric acid solution is separated from the hydrochloric acid solution. A method for concentrating palladium, comprising separating and separating the separated precipitate in a hydrochloric acid solution.

10. By increasing the pH of the hydrochloric acid solution containing palladium ions stabilized by the divalent ion of tin, palladium is precipitated together with the tin hydroxide, and the palladium is precipitated from the hydrochloric acid solution. A pretreatment method for recovering palladium, comprising separating and separating a separated precipitate in an acidic solution of hydrochloric acid.