JP2017226896A - Separation recovery method of palladium and tin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of easily, selectively and efficiently separating and recovering palladium and tin from acidic aqueous solution containing palladium, tin and compounds thereof.SOLUTION: The invention relates to a method of separating and recovering palladium and tin from an acidic aqueous solution containing palladium, tin and compounds thereof, including following steps (1) to (3). (1) a step of adjusting pH of the acidic aqueous solution containing palladium, tin and compounds thereof to 3 or more. (2) a step of adding alkali and at least one of a reductant and metal scavenger to the solution at pH of 3 or more obtained in the step (1) to adjust pH to 6 to 10 and forming a palladium-containing precipitate and a tin-containing precipitate. (3) a step of performing solid-liquid separation on the palladium-containing precipitate and the tin-containing precipitate obtained in the step (2) and recovering them.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for separating and recovering palladium and tin.

  In the field of the electronics industry, palladium (Pd) is used, for example, to add catalytic action to the base of a non-conductive article to be plated, such as a plastic material. Such a catalyst addition step is generally performed by contacting a strongly acidic mixed catalyst solution containing palladium and tin with an article to be plated, and after the catalyst addition step, the mixed catalyst adhering to the object to be plated. In order to remove the liquid, a washing step with washing water is performed.

  FIG. 1 is a schematic process diagram for explaining an example of the catalyst addition process and the cleaning process. The strongly acidic mixed catalyst solution containing palladium and tin is stored in the catalyst tank 12, and a non-conductive object to be plated (not shown) such as a plastic material is put into the catalyst tank 12 as a catalyst on the underlying surface. Of palladium is added.

  Subsequently, the article to be plated is put into the washing water tank 14 as indicated by an arrow, and the mixed catalyst solution adhering excessively is removed here. It is also possible to provide a plurality of washing water tanks and perform the washing step by sequentially moving articles to be plated to the washing water tank.

  In each of the above steps, the mixed catalyst solution adhering excessively to the plating target article is brought into the washing water tank 14, and the washing water tank 14 exhibits weak acidity. Then, palladium and tin dissolved in the strongly acidic mixed catalyst solution partially colloidal as hydroxides or precipitate as precipitates in the washing water tank 14, and the washing water in the washing water tank 14 is fine. It becomes cloudy.

  Such a colloid or precipitate affects the throwing power in the subsequent plating process, and causes defects such as uneven plating, pinholes, and adhesion of foreign matter. Therefore, how to manage the amount of colloid or precipitate in the washing water tank 14 in the washing water tank 14 is important in stabilizing the quality of the plated product.

  Therefore, conventionally, for example, measures have been taken such as increasing the amount of washing water in the washing water tank 14 or frequently replacing it. However, such measures have been required to be improved in order to reduce the production efficiency due to labor and cost.

  On the other hand, since palladium is a noble metal and is scarce and expensive in terms of resources, it is extremely important to efficiently recover from the washing water as described above from the viewpoint of reuse and stable supply of palladium. Therefore, generally, measures are taken to introduce used flush water into a wastewater treatment facility, co-precipitate with other heavy metals, and recover these metals.

  However, about half of the palladium contained in the washing water is present as ions, and the above-mentioned measures cannot sufficiently separate and recover palladium. In order to improve the recovery rate of palladium, it is necessary to repeatedly perform treatment at a wastewater treatment facility, and there is a problem that the recovery cost increases. In addition, from the viewpoint of global environmental conservation, it is also desired to remove tin from used washing water and reuse the obtained washing water.

  Other palladium separation and recovery methods include, for example, (1) a method using an ion exchange resin; (2) a method using a chelate resin (see, for example, Patent Document 1); and (3) a method using activated carbon (for example, Patent Document). 2).

  However, in each of the above methods, when a large amount of washing water is processed, tin hydroxide in the washing water is deposited in a cake form on the resin or activated carbon, making it difficult to separate and recover palladium. there were. Further, each of the above methods has problems in that the extraction efficiency of palladium is poor and there is room for improvement in workability and economy.

  Furthermore, the concentration of palladium contained in the washing water is as low as several mg / L to several tens mg / L, and in the conventional method, a very small amount of palladium was discarded without being recovered.

JP 2004-83926 A JP 2000-157984 A

  Accordingly, an object of the present invention is to provide a method capable of easily and selectively separating and recovering palladium and tin from an acidic aqueous solution containing a low concentration of palladium and tin and these compounds. .

  As a result of intensive studies, the present inventors obtained a pH of 6 to 10 by adding a specific additive after adjusting the pH of the acidic aqueous solution containing palladium and tin and these compounds to 3 or more. The present inventors have found that the above problems can be solved by solid-liquid separation of the precipitate, and have completed the present invention.

That is, the present invention is as follows.
1. A method for separating and recovering palladium and tin from an acidic aqueous solution containing palladium and tin and these compounds, comprising the following steps (1) to (3).
(1) Step of setting pH of acidic aqueous solution containing palladium and tin and these compounds to 3 or more (2) Alkali, reducing agent and metal scavenger in aqueous solution of pH 3 or higher obtained in step (1) And adding at least one of the above to pH 6 to 10 to form a palladium-containing precipitate and a tin-containing precipitate (3) Solid-liquid separation of the palladium-containing precipitate and the tin-containing precipitate obtained in step (2) And collecting step 2. 2. The method according to 1 above, wherein the palladium concentration of the acidic aqueous solution is 0.01 to 100 mg / L.
3. 3. The method according to 1 or 2 above, wherein the alkali is at least one selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium bicarbonate and sodium carbonate.
4). 4. The method according to any one of 1 to 3, wherein the addition amount of at least one of the reducing agent and the metal scavenger in the step (2) is 0.2 to 50 mol with respect to 1 mol of palladium.
5. 5. The method according to any one of 1 to 4, wherein the reducing agent is at least one selected from a hydrazine compound, sodium borohydride, sodium hydrogen sulfite, potassium hydrogen sulfite, sodium sulfite and potassium sulfite.
6). 6. The method according to any one of 1 to 5, wherein the metal scavenger is at least one selected from an alkali sulfide salt and an alkyldithiocarbamate.
7). 7. The method according to any one of 1 to 6, wherein in step (3), the palladium-containing precipitate and the tin-containing precipitate are subjected to solid-liquid separation by a membrane filtration method.

  In the method for separating and recovering palladium and tin of the present invention, in step (1), the pH of the acidic aqueous solution containing palladium and tin and these compounds is set to 3 or more. In the step (2), an alkali and at least one of a reducing agent and a metal scavenger are added to the aqueous solution having a pH of 3 or more obtained in the step (1) to obtain an aqueous solution having a pH of 6 to 10. By this step (2), palladium ions and tin ions become precipitates and precipitate.

  In step (3), the precipitate obtained in step (2) is recovered by solid-liquid separation. Through these steps, palladium and tin can be easily and selectively separated and efficiently recovered from an acidic aqueous solution containing palladium and tin and these compounds.

  According to the method of the present invention, it is possible to efficiently separate and collect low-concentration palladium present as ions contained in the washing water, which was difficult to separate and collect by the conventional method. Moreover, according to the method of the present invention, the obtained washing water can be reused, which is excellent from the viewpoint of global environmental conservation.

FIG. 1 is a schematic process diagram for explaining an example of a catalyst addition process and a cleaning process. FIGS. 2A to 2D are graphs showing the particle size distribution of precipitates contained in aqueous solutions having various pH values prepared in Examples.

  Hereinafter, each step of the method of the present invention will be described in more detail.

Process (1)
Step (1) in the present invention is a step of adjusting the pH of the acidic aqueous solution containing palladium and tin and these compounds to 3 or more.

  The acidic aqueous solution containing palladium and tin and these compounds is not particularly limited, but in the present invention, the article to be plated is treated with an acidic mixed catalyst solution containing palladium and tin, and the surface of the substrate is catalyzed. The washing water used for removing the mixed catalyst solution adhering excessively to the article to be plated after the addition of is preferable.

  The palladium concentration of the washing water is not particularly limited, but is preferably 0.01 to 100 mg / L, more preferably 0.01 to 50 mg / L, and still more preferably 0.01 to 10 mg / L. L. Moreover, it is preferable that a tin concentration is 1-80 mg / L, More preferably, it is 1-50 mg / L, More preferably, it is 1-10 mg / L.

  In addition, the acidic aqueous solution used by this invention is not restrict | limited to the said form, For example, a mixed catalyst liquid itself may be sufficient, and a palladium concentration can be 50-200 mg / L, for example in this case. Moreover, tin concentration can be 200-1000 mg / L, for example.

  Specific examples of the palladium compound that may be present in the acidic aqueous solution include palladium chloride and palladium sulfate. Specific examples of the tin compound include stannous chloride, stannic chloride, stannous sulfate, and stannic sulfate.

  In step (1), the pH of the acidic aqueous solution containing palladium and tin and these compounds is adjusted to 3 or more, preferably 6 or more. In order to adjust the pH of the acidic aqueous solution to 3 or more, it is preferable to add an alkali. In general, an acidic aqueous solution has a pH of 1 to 2.5. When at least one of a reducing agent and a metal scavenger is directly added to the acidic aqueous solution in the step (2) described later, these reducing agents are used. The metal scavenger is decomposed, and toxic gases such as hydrogen sulfide may be generated depending on the types of the reducing agent and the metal scavenger. In the present invention, it is possible to alleviate such disadvantages by setting the pH of the acidic aqueous solution to 3 or more. The upper limit value of the pH is not particularly limited, but the pH can be easily adjusted in the step (2) described later by setting the pH to 8 or less, preferably 6 or less.

  The alkali used in step (1) is preferably an alkali other than ammonia water. Use of aqueous ammonia is not preferable because an ammine complex of palladium that does not precipitate in an aqueous solution is formed. The alkali used in the step (1) is preferably at least one selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium bicarbonate and sodium carbonate. Moreover, in this invention, what melt | dissolved or disperse | distributed these alkalis to solvents, such as water, as needed can be used.

Process (2)
In the step (2) in the present invention, an alkali and at least one of a reducing agent and a metal scavenger are added to the aqueous solution having a pH of 3 or more obtained in the step (1) to obtain an aqueous solution having a pH of 6 to 10, and containing palladium. It is a step of forming a precipitate and a tin-containing precipitate.

  In step (2), the pH of the aqueous solution obtained in step (1) is adjusted to 6 to 10, preferably 6 to 9. If the pH is less than 6 in step (2), there are palladium and tin remaining as ions, and it is difficult to separate and recover all the palladium ions present in the acidic aqueous solution. Further, when the pH exceeds 10, there is a risk that the re-dissolved palladium ions may permeate the separation membrane, and particles having a small particle size generated by dissolution of a part of the palladium-containing precipitate and the tin-containing precipitate may cause the separation membrane. There is a risk of permeation or clogging of the separation membrane.

  The order of addition of the alkali, the reducing agent and the metal scavenger is not limited, and the alkali and at least one of the reducing agent and the metal scavenger may be added simultaneously, or after the alkali is added, the reducing agent and the metal Alkali may be added after adding at least one of the scavenger, or after adding at least one of the reducing agent and the metal scavenger. From the viewpoint of improving working efficiency, the alkali, the reducing agent and the metal may be added. It is preferable to add at least one of the collecting agents simultaneously. In addition, when adding at least one of the alkali and the reducing agent and the metal scavenger at the same time, the alkali, at least one of the reducing agent and the metal scavenger and the alkali may be prepared and added simultaneously. Alternatively, a solution in which an alkali and at least one of a reducing agent and a metal scavenger are mixed in advance may be added.

  The alkali used in the step (2) is the same as the alkali described above in the step (1).

As the pH rises, tin precipitates as Sn (OH) ₂ , Sn (OH) ₄ , and palladium in the same manner as Pd (OH) ₂ , thereby facilitating separation and recovery of these. Precipitation of tin and palladium can be visually confirmed when the acidic aqueous solution becomes slightly cloudy.

  Examples of the reducing agent include at least one selected from hydrazine compounds, sodium borohydride, sodium hydrogen sulfite, potassium hydrogen sulfite, sodium sulfite, and potassium sulfite. The hydrazine compound is hydrazine or a derivative thereof, such as hydrazine monohydrate, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine sulfate, 3-chlorobenzohydrazide, hydrazine dihydrobromide hydrate, and hydrazine. Examples thereof include hydromonobromide. In the present invention, among these reducing agents, sodium borohydride is preferred because it is easily reduced to palladium metal.

  Examples of the metal scavenger include at least one selected from alkali sulfides and alkyldithiocarbamates. Among them, alkyldithiocarbamates are preferable because they do not generate harmful hydrogen sulfide.

  Examples of the alkali sulfide include sodium sulfide and potassium sulfide. As the alkyldithiocarbamate, an alkyldithiocarbamate having an alkyl group having 1 to 6 carbon atoms is preferable from the viewpoint of water solubility.

  Examples of the alkyl dithiocarbamate having an alkyl group having 1 to 6 carbon atoms include dimethyldithiocarbamate, diethyldithiocarbamate, dipropyldithiocarbamate, dibutyldithiocarbamate, ethylenebisdithiocarbamate, and methyldithiocarbamate. , Ethyl dithiocarbamate, n-propyldithiocarbamate, n-butyldithiocarbamate, ethylmethyldithiocarbamate, n-butylmethyldithiocarbamate, n-butylethyldithiocarbamate, ethyl-n-propyldithiocarbamate And n-hexylmethyldithiocarbamate and the like. Examples of the form of the alkyldithiocarbamate include sodium salt and potassium salt.

  Each addition amount of such a reducing agent and a metal scavenger is preferably 0.2 to 50 mol, more preferably 1 to 50 mol, and still more preferably 10 to 10 mol with respect to 1 mol of palladium. 50 moles. Palladium ions can be efficiently precipitated by setting each addition amount of the reducing agent and the metal scavenger to 10 to 50 mol with respect to 1 mol of palladium.

  With such an additive, the palladium ion becomes a palladium-containing precipitate such as metal palladium, sulfide salt or alkyldithiocarbamate, and is easily separated and recovered.

Process (3)
Step (3) in the present invention is a step of recovering the palladium-containing precipitate and the tin-containing precipitate obtained in the step (2) by solid-liquid separation. Such solid-liquid separation is not particularly limited as long as a known technique is appropriately used. Examples thereof include a membrane filtration method such as atmospheric pressure filtration, reduced pressure filtration and pressure filtration, a method of separating and recovering precipitates by decantation, centrifugation, flotation separation, and the like.

  In this invention, the form which isolate | separates and collects a deposit by a membrane filtration method is preferable. Examples of the material of the filter medium used in the membrane filtration method include paper, glass fiber, polymer, and the like, and these may be mixed into synthetic fiber.

  The thickness of the filter medium is preferably 0.1 to 3 mm, more preferably 0.1 to 1 mm, and still more preferably 0.1 to 0.3 mm. By these membrane filtration methods, palladium and tin can be separated and recovered more easily because the palladium-containing precipitate and the tin-containing precipitate can be collected on the filter medium without passing through the pore diameter of the filter medium.

  The recovered palladium-containing precipitate and tin-containing precipitate are dissolved in an inorganic acid such as hydrochloric acid or aqua regia, and ammonium chloride salt or ammonia is added to produce an ammonium chloride palladium chloride salt. After separation, in hydrogen By reducing, palladium can be recovered as palladium metal.

  Through the above steps (1) to (3), palladium and tin can be easily and selectively separated and efficiently recovered from an acidic aqueous solution containing palladium and tin and these compounds.

  According to the method of the present invention, almost all of palladium and tin can be separated and recovered from the acidic aqueous solution, so that the washing water can be reused. For example, the permeated water permeated by the membrane filtration method can be suitably reused as industrial cleaning water.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not restrict | limited to the following example.

pH change experiment 100 ml of an acidic aqueous solution (stock solution) having a palladium concentration of 1.6 mg / L, a tin concentration of 234 mg / L and a pH of 2.47 was placed in a beaker, and a 2% aqueous sodium hydroxide solution was added thereto. Then, aqueous solutions having various pH values shown in Table 1 were prepared. The pH was measured with HM-31P manufactured by Toa DKK Corporation.

  The temperature of each aqueous solution, the cloudiness state, and the particle size of the precipitate were examined. The results are also shown in Table 1. The ORP (Oxidation-Reduction Potential) means an oxidation-reduction potential, and was measured by RM-30P manufactured by Toa DKK Corporation. In Table 1, “-” indicates that it has not been measured. Moreover, the particle size distribution of the precipitate contained in each aqueous solution is shown to Fig.2 (a)-(d).

  From the results shown in Table 1 and FIGS. 2A to 2D, when the pH of the aqueous solution was increased, white precipitates increased and sedimentation of the precipitates could be confirmed. The precipitate settled in a few minutes and had good sedimentation, and the supernatant was colorless and transparent.

  The precipitate was filtered through an analytical filter paper [No. manufactured by ADVANTEC Toyo Co., Ltd. 5C], the solid-liquid separability was good, and filtration was possible easily. Moreover, although the particle size of the precipitate increases as the pH of the aqueous solution approaches near neutrality, it has been found that the particle size decreases when the pH is shifted to the alkali side beyond neutrality. When the pH of the aqueous solution was 12.5, the aqueous solution became colorless and transparent, and re-dissolution of the precipitate was confirmed.

Examples 1-9 and Comparative Examples 1-5
About Examples 1-9 and Comparative Examples 2-5, the acidic aqueous solution shown in Table 2 was prepared, and the process (1) was performed using the alkali shown in Table 3. Subsequently, the step (2) was performed on the aqueous solution obtained in the step (2) using various alkalis, reducing agents, and metal scavengers shown in Table 4. In Table 4, “-” indicates that no addition was made.

  Subsequently, for the aqueous solution obtained in the step (2), as a step (3), a filter paper for analysis [manufactured by ADVANTEC Toyo Co., Ltd., diameter φ600 mm, model no. 5C]. About the comparative example 1, the acidic aqueous solution shown in Table 2 was prepared, and only filtration by a process (3) was performed.

  The Pd concentration, Pd amount, Pd recovery rate, Sn concentration, Sn amount, and precipitate concentration (SS concentration) of the filtrate after filtration were examined. The results are shown in Table 5.

  As shown in Table 5, in Examples 1-9, the Pd concentration in the filtrate was lower than in Comparative Examples 1-5. In particular, in Examples 2 to 9, the Pd concentration in the permeate was as low as 0.03 mg / L or less, and was excellent in palladium separation and recovery.

  On the other hand, the pH after adding the reducing agent / metal scavenger to the aqueous solution in Comparative Example 1 and Step (2) in which only Step (3) is performed without performing Step (2) is 6 to 10. In Comparative Examples 2 to 5, which were out of the range, palladium permeated the filter paper and was inferior in palladium separation and recovery.

  From this result, after adjusting the pH of the acidic aqueous solution containing palladium and tin and these compounds to 3 or more, alkali and at least one of a reducing agent and a metal scavenger are added to adjust the pH to 6 to 10, and the palladium containing It is found that palladium and tin can be separated, recovered easily and selectively by forming a precipitate and a tin-containing precipitate, and collecting and recovering the palladium-containing precipitate and the tin-containing precipitate by solid-liquid separation. It was.

12 Catalyst tank 14 Flushing water tank

Claims (7)

A method for separating and recovering palladium and tin from an acidic aqueous solution containing palladium and tin and these compounds, comprising the following steps (1) to (3).
(1) Step of setting pH of acidic aqueous solution containing palladium and tin and these compounds to 3 or more (2) Alkali, reducing agent and metal scavenger in aqueous solution of pH 3 or higher obtained in step (1) And adding at least one of the above to pH 6 to 10 to form a palladium-containing precipitate and a tin-containing precipitate (3) Solid-liquid separation of the palladium-containing precipitate and the tin-containing precipitate obtained in step (2) Process to collect   The method of Claim 1 whose palladium concentration of acidic aqueous solution is 0.01-100 mg / L.   The method according to claim 1 or 2, wherein the alkali is at least one selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium bicarbonate and sodium carbonate.   The method according to any one of claims 1 to 3, wherein an addition amount of at least one of the reducing agent and the metal scavenger in the step (2) is 0.2 to 50 mol with respect to 1 mol of palladium. .   The method according to any one of claims 1 to 4, wherein the reducing agent is at least one selected from a hydrazine compound, sodium borohydride, sodium hydrogen sulfite, potassium hydrogen sulfite, sodium sulfite and potassium sulfite.   The method according to any one of claims 1 to 5, wherein the metal scavenger is at least one selected from an alkali sulfide salt and an alkyldithiocarbamate.   The method according to any one of claims 1 to 6, wherein in step (3), the palladium-containing precipitate and the tin-containing precipitate are subjected to solid-liquid separation by a membrane filtration method.