Recycling method and application of palladium in ion palladium waste liquid of circuit board

Abstract

The invention relates to the technical field of waste liquid treatment, in particular to a cyclic utilization method and application of palladium in a circuit board ion palladium waste liquid. Comprising the following steps: S1, separating metal impurities from the palladium waste liquid to obtain feed liquid I; s2, carrying out palladium ion concentration on the feed liquid I to obtain feed liquid II; s3, reducing the feed liquid II to generate a palladium monomer, and collecting palladium powder; and S4, taking palladium powder to react with an oxidizing agent in an acidic medium to obtain a salt solution containing palladium ions. According to the method, an ion exchange resin adsorption separation method and a liquid membrane extraction method are combined, on one hand, the content of metal impurities in the palladium recovery process is reduced, and the recovery purity of the metal palladium is guaranteed; on the other hand, the recovery rate of metal palladium is effectively increased; the purity of the palladium chloride prepared by the method is up to 98% or above, the quality of the synthesized colloidal palladium activating solution is stable, a closed-loop recovery and utilization process mode can be realized, and the application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of waste liquid treatment technology, and in particular to a method and application for the recycling of palladium in ionic palladium waste liquid from circuit boards. Background Technology

[0002] Currently, the palladium activation solutions used in PCB (printed circuit board) manufacturing processes mainly include colloidal palladium and ionic palladium. Colloidal palladium is primarily used in vertical copper plating lines, while ionic palladium is mainly used in newer horizontal copper plating lines. With the maturity of horizontal copper plating technology, the decrease in equipment costs, and the increasing prominence of labor costs and environmental issues, the advantages of horizontal copper plating compared to traditional vertical copper plating technology are becoming increasingly apparent. More and more PCB manufacturers are inclined to use horizontal copper plating for PCB hole metallization.

[0003] In horizontal copper plating processes, the concentration of the matching ionic palladium activation solution is relatively high, generally controlled within the range of 50-200 ppm in practical applications. The first rinse wastewater after circuit board activation contains a large amount of palladium ions. Furthermore, due to the inherent stability of the ionic palladium activation solution, a large amount of palladium waste liquid is generated during actual transportation, storage, and use, resulting in a waste of precious metal resources. To effectively improve the palladium recovery rate from circuit board waste liquid, researchers both domestically and internationally have conducted varying degrees of research on technologies such as electrolysis, ion exchange, and resin adsorption. However, these studies still have certain shortcomings; the palladium recovery rate from ionic palladium waste liquid is not high, and the impurity content is also high. For example, Chinese invention patent CN105132693B discloses a process for recovering palladium from acidic palladium waste liquid after colloidal palladium activation. Through ion column and anion exchange resin technology, the dissolution and enrichment process of palladium is optimized, achieving palladium recovery and resource utilization. However, the elemental palladium ultimately obtained by this technology still requires further processing to prepare colloidal palladium solutions, etc., and cannot be directly used.

[0004] Against this backdrop, it is imperative to provide a method that can effectively recover palladium from ionic palladium waste liquid from circuit boards and achieve recycling. Summary of the Invention

[0005] To address the technical challenges of low palladium recovery rate and high impurity content in existing ionic palladium waste liquid, which prevent closed-loop recycling, this invention proposes a method for recovering and recycling palladium from ionic palladium waste liquid from circuit boards. This method effectively overcomes the aforementioned technical problems and provides a method for recovering palladium from ionic palladium waste liquid. The recovered palladium solution has a palladium purity of over 98%, which can be directly used to prepare colloidal palladium activation solution. This achieves a closed-loop recycling mode and has broad application prospects.

[0006] The first aspect of this invention provides a method for recycling palladium in ion-based palladium waste liquid from circuit boards, comprising:

[0007] S1. Separate metallic impurities from the palladium waste liquid to obtain feed liquid one;

[0008] S2. Concentrate solution one with palladium ions to obtain solution two;

[0009] S3. Reduce the second liquid material to generate palladium monomer and collect palladium powder;

[0010] S4. Palladium powder is reacted with an oxidizing agent in an acidic medium to obtain a salt solution containing palladium ions.

[0011] Optionally, in step S1, a macroporous weakly acidic cation exchange resin is used to separate metal impurities from the palladium waste liquid.

[0012] To improve the effective separation of palladium ions from base metal (such as copper and nickel) impurities, the macroporous weakly acidic cation exchange resin may optionally be CH-90NA ion exchange resin.

[0013] In some embodiments, step S1 specifically includes: loading a macroporous weakly acidic cation exchange resin (e.g., CH-90NA) into an ion exchange column to obtain a cation exchange resin ion column, and then injecting the filtered palladium ion waste liquid into the cation exchange resin for adsorption and separation. The following ion exchange reaction occurs during this process:

[0014] 2R-COONa+Ni 2+ →(R-COO)2Ni+2Na +

[0015] 2R-COONa+Cu 2+ →(R-COO)2Cu+2Na +

[0016] After treatment with cation exchange resin, Ni in the palladium waste liquid 2+ Cu 2+ It is adsorbed onto the resin, and the Na on the resin... + It then enters the water. When the entire resin layer is in contact with Ni 2+ Cu 2+ When the exchange reaches equilibrium, the ion exchange column can be regenerated with a certain concentration of HCl or H2SO4. The following reaction occurs during this process:

[0017] (R-COO)2Ni+H2SO4→2R-COOH+NiSO4

[0018] (R-COO)2Cu+H2SO4→2R-COOH+CuSO4

[0019] At this point, the resin is in the H-form. Further conversion of the resin to the Na-form using NaOH is as follows:

[0020] R-COOH + NaOH → RCOOH + H₂O

[0021] To increase the palladium ion content after concentration, optionally, step S2 uses liquid membrane extraction to concentrate palladium ions in the feed solution.

[0022] In some embodiments, the liquid membrane extraction step of step S2 specifically includes:

[0023] The liquid membrane extraction step in step S2 specifically includes:

[0024] (1) Based on the total volume of the membrane phase, 3-10% extractant, 2-10% surfactant, 1-5% cyclohexane and the remainder sulfonated kerosene are mixed to form the membrane phase. The membrane phase is then mixed with hydrochloric acid aqueous solution and stirred thoroughly to obtain a white emulsion membrane.

[0025] (2) Mix the purified liquid after separation of S1 with the above white emulsion membrane and shake thoroughly to form a W / O / W type multiple emulsion membrane system;

[0026] (3) The obtained W / O / W type multiple emulsion film system was allowed to stand and separate into layers. The upper residual liquid was removed to obtain Pd-enriched film. 2+ The lower emulsion;

[0027] (4) Heat the obtained emulsion in a water bath for 20-60 minutes to break the emulsion. After cooling, remove the upper organic oil phase to obtain palladium-rich liquid II.

[0028] Furthermore, the liquid membrane extraction step in step S2 specifically includes:

[0029] (1) Based on the total volume of the membrane phase, 6% benzoyl acetone extractant, 5% surfactant (e.g., polyamide derivative ENJ3029), 3% cyclohexane and the remainder sulfonated kerosene are mixed in a beaker to form the membrane phase. The membrane phase and hydrochloric acid aqueous solution (internal phase reagent) are mixed in a container at a volume ratio of 1:1 and stirred thoroughly to obtain a white emulsion membrane.

[0030] (2) Mix the purified liquid after separation of S1 with the above white emulsion membrane at a volume ratio of 1:1 and shake thoroughly to form a W / O / W type multiple emulsion membrane system.

[0031] (3) The obtained W / O / W type multiple emulsion film system was allowed to stand and separate into layers. The upper residual liquid was removed to obtain Pd-enriched film. 2+ The lower emulsion;

[0032] (4) Demulsification: The obtained emulsion is placed in a water bath and heated for 20-60 minutes to demulsify. After cooling to room temperature, the upper organic oil phase is removed to obtain the concentrated liquid rich in palladium (liquid two).

[0033] Optionally, in step S3, a reducing agent is used to reduce liquid two. The reducing agent includes one or more of dimethylaminoborane, formaldehyde, sodium hypophosphite, sodium sulfite, and sodium borohydride. Further, the reducing agent is dimethylaminoborane. Even further, the molar ratio of palladium to reducing agent in liquid two is (2-5):1, most preferably 3:1.

[0034] To promote the effective sedimentation and collection of palladium, optionally, step S3 involves reducing the material solution with reducing agent 1 and then diluting it; further, water is added for dilution, and the palladium powder at the bottom is collected.

[0035] To further reduce the impurity content, the collected palladium powder may be dried; further, the drying temperature is 200-300℃ and the drying time is 1-3h; most preferably, it is baked at 250℃ for 2h.

[0036] Optionally, the acidic medium in step S4 is concentrated hydrochloric acid, and the oxidant is one or more of hydrogen peroxide, nitric acid, sodium hypochlorite, and persulfate; further, the oxidant is hydrogen peroxide.

[0037] Optionally, the volume ratio of the concentrated hydrochloric acid to the oxidant is (1-3):(1-3).

[0038] Optionally, the reaction temperature of step S4 is 40-60°C.

[0039] Further optionally, step S4 specifically includes: taking the palladium powder obtained in step S3, adding a mixture of concentrated hydrochloric acid and hydrogen peroxide, stirring and dissolving at 40-60℃ for 0.1-1h, and cooling to room temperature to obtain a clear palladium chloride solution.

[0040] The second aspect of the present invention provides an application of the method for recycling palladium in the ionic palladium waste liquid of circuit boards as described above, which is applied to the preparation of colloidal palladium activation solution.

[0041] In some embodiments, the preparation steps of the colloidal palladium activating solution include:

[0042] The above-mentioned salt solution containing palladium ions was mixed with tin salt and reducing agent II in an acidic medium to prepare a colloidal palladium activated solution.

[0043] Optionally, the tin salt includes one or more combinations of stannous chloride, sodium stannate, tin tartrate, and tin citrate.

[0044] Optionally, the tin salt includes a first tin salt and a second tin salt; the first tin salt and the second tin salt are independently selected from one of stannous chloride, sodium stannate, tin tartrate, and tin citrate; further, the first tin salt is stannous chloride, and the second tin salt is sodium stannate.

[0045] Optionally, the reducing agent two includes one or more combinations of sodium metabisulfite, sodium hypophosphite, and ascorbic acid; further, it may be sodium metabisulfite.

[0046] Optionally, a stabilizer is added to the preparation step of the colloidal palladium activation solution. The stabilizer includes one or more of urea, gelatin, polyethylene glycol, and sodium potassium tartrate; urea is a further option.

[0047] Optionally, the preparation steps of the colloidal palladium activation solution include:

[0048] Preparation of Solution A: Under stirring conditions at 20-40℃, add the above salt solution containing palladium ions to the acid solution, mix thoroughly, add the first tin salt, and stir to dissolve to obtain Solution A;

[0049] Preparation of solution B: Add the first tin salt, reducing agent II, and stabilizer to the acid solution and stir to dissolve. Then add the second tin salt and stir until homogeneous to obtain solution B.

[0050] The prepared solution B is poured into solution A at 30-50℃, diluted, and then kept at 50-70℃ for 2-6 hours to obtain a colloidal palladium activation solution.

[0051] Optionally, the preparation steps of the colloidal palladium activation solution include:

[0052] Preparation of Solution A: Under stirring conditions at 30°C, the above salt solution containing palladium ions is added to the acid solution. After thorough mixing, the first tin salt is added and stirred to dissolve to obtain Solution A.

[0053] Preparation of solution B: Add the first tin salt, reducing agent II, and stabilizer to the acid solution and stir to dissolve. Then add the second tin salt and stir until homogeneous to obtain solution B.

[0054] At 40℃, the prepared solution B was slowly poured into solution A, diluted with water to 1L, and kept at 60℃ for 4h to obtain colloidal palladium activated solution.

[0055] Beneficial effects:

[0056] This invention provides a method and application for the recycling of palladium in ion palladium waste liquid from circuit boards, which has the following advantages:

[0057] (1) This invention obtains a high-yield and high-purity palladium chloride solution by separating metal impurities, concentrating ionic palladium, reducing and purifying waste palladium solution. The obtained palladium chloride solution can be directly applied to a series of processes such as the synthesis of colloidal palladium activation solution, realizing a closed-loop recycling and utilization mode of palladium waste liquid.

[0058] (2) The present invention uses a macroporous weak acid cation exchange resin to selectively adsorb waste palladium solution, which can effectively separate base metal (such as copper, nickel and other) impurities in the waste solution from palladium ions. The palladium in the solution is concentrated by liquid membrane extraction to obtain an aqueous solution rich in palladium, which effectively improves the palladium recovery rate.

[0059] (3) In this invention, dimethylaminoborane is used to reduce the feed solution. The resulting palladium powder is then diluted and baked at high temperature to further purify the palladium powder and reduce the organic impurities in the product. The palladium chloride prepared by this method can be comparable in quality to commercial palladium chloride. High-purity products are obtained with low-cost process methods. The purity of the final recovered palladium chloride is as high as 98% or more, and the quality of the synthesized colloidal palladium activation solution is stable.

[0060] (4) The salt solution containing palladium ions obtained by the recycling method of this invention can be directly used for the synthesis and use of colloidal palladium solution without further purification. The operation method is simple and controllable, highly practical, and has positive social and economic benefits as well as environmental benefits. It is suitable for widespread promotion in the field of waste liquid recycling. Attached Figure Description

[0061] Figure 1 Example 1: Process flow diagram of palladium recycling method and application in ionic palladium waste liquid from circuit boards;

[0062] Figure 2 Comparison of infrared spectral characterization results between the palladium chloride solution prepared in Example 1 and the commercially available palladium chloride solution;

[0063] Figure 2 The red line corresponds to the sample in Example 1, and the green line corresponds to the commercially purchased sample.

[0064] Figure 3 Stability test results of the colloidal palladium activated solution prepared in Example 1 and the colloidal palladium activated solution synthesized from commercially available palladium chloride; Figure 3 The left image corresponds to the colloidal palladium activated solution synthesized from commercially available palladium chloride, and the right image corresponds to Example 1; Figure 4 Example 1: Comparison diagram of colloidal palladium activation solutions prepared in Comparative Examples 1 and 2; Figure 4 From left to right, the figures correspond to Comparative Example 1, Example 1, and Comparative Example 2, respectively. Detailed Implementation

[0065] Note: Unless otherwise specified, the solvent of the solutions involved in this invention is water; all concentrations involved are mass concentrations; the room temperature is 25°C; and all raw materials used are commercially available.

[0066] Example

[0067] Example 1

[0068] This embodiment provides a method for recycling palladium in ion-based palladium waste liquid from circuit boards, including:

[0069] S1. Macroporous weakly acidic cation exchange resin ( CH-90NA (from Dusheng, USA) was packed into an ion exchange column to obtain a cation exchange resin ion column. Then, 5L of the palladium waste liquid filtered through filter paper was injected into the cation exchange resin for adsorption and separation. The waste palladium liquid flowing out from the other end of the ion column was collected to obtain feed liquid one.

[0070] S2. Concentrate feed solution one with palladium ions to obtain feed solution two; the liquid membrane extraction step specifically includes:

[0071] (1) Based on the total volume of the membrane phase, 6% benzoyl acetone extractant, 5% surfactant (polyamide derivative ENJ3029, from EXXON Chemical Company, USA), 3% cyclohexane and the remainder sulfonated kerosene were mixed in a beaker to form the membrane phase. 750 mL of the membrane phase and 750 mL of 0.2 mol / L hydrochloric acid aqueous solution were mixed in a container and stirred thoroughly to obtain a white emulsion membrane.

[0072] (2) Mix 5L of liquid 1 with 5L of white emulsion film and shake thoroughly to form a W / O / W type multi-emulsion film system;

[0073] (3) The obtained W / O / W type multiple emulsion film system was allowed to stand and separate into layers. The upper residual liquid was removed to obtain Pd-enriched film. 2+ The lower emulsion;

[0074] (4) Demulsification: The obtained emulsion is placed in a water bath and heated at 65°C for 40 minutes to demulsify. After cooling to room temperature, the upper organic oil phase is removed to obtain the concentrated solution rich in palladium (solution two).

[0075] S3. At room temperature, the molar ratio of feed solution 2 (palladium-rich solution) and reducing agent 1 (dimethylaminoborane) is 3:1 (calculated as palladium). Reducing agent 1 is added to feed solution 2 for reduction treatment. After reduction treatment, water is added to dilute the solution to a volume of 5L to allow the palladium powder to settle rapidly and wash the palladium powder. The palladium powder is washed twice with water, and the palladium powder at the bottom is collected and baked in a vacuum drying oven at 250℃ for 2 hours to obtain 6.32g of palladium powder; the recovery rate is 91%.

[0076] S4. Weigh 1g of palladium powder recovered in step S3, add 40mL of a mixture of concentrated hydrochloric acid and hydrogen peroxide, stir and dissolve at 50℃ for 0.5h to obtain a clear palladium chloride solution; wherein the concentration of concentrated hydrochloric acid is 36% (the same below), the concentration of hydrogen peroxide is 30%, and the volume ratio of concentrated hydrochloric acid to hydrogen peroxide is 1:1.

[0077] The recovered palladium chloride solution in this embodiment is used to prepare a colloidal palladium activated solution; the preparation steps of the colloidal palladium activated solution include:

[0078] Preparation of Solution A: Mix 100ml of concentrated hydrochloric acid with 300ml of pure water, add the palladium chloride solution (containing 1g of palladium chloride) prepared by the above method under stirring at 30℃, mix thoroughly, add 2.53g of the first tin salt (stannous chloride), stir until completely dissolved, and obtain Solution A;

[0079] Preparation of Solution B: Add 75g of the first tin salt (stannous chloride), 8g of reducing agent II (sodium metabisulfite), and 50g of stabilizer (urea) to 200ml of concentrated hydrochloric acid aqueous solution with a volume concentration of 1:1 and stir to dissolve. Then add 7g of the second tin salt (sodium stannate) and stir to obtain a white emulsion, which is Solution B.

[0080] At 40℃, the prepared solution B was slowly poured into solution A, and pure water was added to dilute it to 1L. The solution was kept at 60℃ for 4 hours to obtain the colloidal palladium activated solution.

[0081] Comparative Example 1

[0082] The specific implementation method is the same as in Example 1, except that the macroporous weakly acidic cation exchange resin (in step S1) is used instead of... CH-90NA (from Dusheng, USA) was replaced with anion exchange resin (model 9335, sourced from Kunshan Hongfutai Environmental Protection Technology Co., Ltd.); palladium powder recovery rate was 82.3%.

[0083] Comparative Example 2

[0084] The specific implementation method is the same as in Example 1, except that the reducing agent (dimethylaminoborane) in step S3 is replaced with a 50% hydrazine hydrate solution; the palladium powder recovery rate is 90%.

[0085] Performance testing

[0086] 1. Infrared characterization

[0087] The palladium chloride solution prepared in Example 1 was characterized by infrared spectroscopy. Simultaneously, a commercially available palladium chloride solution (Leyan brand, 98% purity) was prepared for characterization and comparison. The results are shown below. Figure 2 .from Figure 2As can be seen, the palladium chloride solution prepared by recovering palladium powder in this invention is close to and highly overlaps with the spectrum of commercially available palladium chloride, which verifies that the purity of the palladium chloride solution of this invention is high, reaching more than 98%.

[0088] 2. Stability Characterization

[0089] The commercially available palladium chloride was prepared into a solution and a colloidal palladium solution was synthesized using the same method as in Example 1. The colloidal palladium activation solution obtained in Example 1 and the colloidal palladium solution prepared from commercially available palladium chloride were subjected to stability testing. The testing method was as follows: the tank was opened at a volume ratio of 0.8% (the colloidal palladium activation solution was added to the tank solution at a dosage of 0.8%), and each colloidal palladium activation solution sample was continuously placed for 10 days. After 10 days, the tank solution was taken and the results were observed. Figure 3 .from Figure 3 As can be seen from the results, no decomposition precipitates were found at the bottom of the beakers. The palladium chloride solution recovered in Example 1 and the colloidal palladium activation solution synthesized from commercially available palladium chloride samples showed good stability.

[0090] The colloidal palladium activation solutions obtained in Example 1, Comparative Examples 1 and 2 were prepared as samples at a ratio of 0.1% for comparison (diluted with copper immersion solution). The results are shown in [Figure Number]. Figure 4 .from Figure 4 It can be seen that the color of the activated solutions prepared in Comparative Examples 1 and 2 is significantly lighter than that in Example 1. The test results show that the palladium content in the colloidal palladium activated solutions of Comparative Examples 1 and 2 is low and does not meet the process requirements.

[0091] The detailed descriptions listed in this invention are merely specific descriptions of feasible implementations of the technology, and are not intended to limit the scope of protection of this application. All equivalent implementations or modifications made without departing from the spirit of the technology of this application should be included within the scope of protection of this application.

Claims

1. A method for recycling palladium in ion-based palladium waste liquid from circuit boards, characterized in that, include: S1. Separate metallic impurities from the palladium waste liquid to obtain feed liquid one; S2. Concentrate solution one with palladium ions to obtain solution two; S3. Reduce the second liquid material to generate palladium monomer and collect palladium powder; S4. Palladium powder is reacted with an oxidizing agent in an acidic medium to obtain a salt solution containing palladium ions.

2. The method for recycling palladium in ion-based palladium waste liquid from circuit boards according to claim 1, characterized in that, In step S1, a macroporous weakly acidic cation exchange resin is used to separate metal impurities from the palladium waste liquid.

3. The method for recycling palladium in ion-based palladium waste liquid from circuit boards according to claim 1, characterized in that, Step S2 uses liquid membrane extraction to concentrate palladium ions in the feed solution.

4. The method for recycling palladium in ion palladium waste liquid from circuit boards according to claim 3, characterized in that, The liquid membrane extraction step in step S2 specifically includes: (1) Based on the total volume of the membrane phase, 3-10% extractant, 2-10% surfactant, 1-5% cyclohexane and the remainder sulfonated kerosene are mixed to form the membrane phase. The membrane phase is then mixed with hydrochloric acid aqueous solution and stirred thoroughly to obtain a white emulsion membrane. (2) Mix the first liquid with the above white emulsion film and shake thoroughly to form a W / O / W type multi-emulsion film system; (3) The obtained W / O / W type multiple emulsion film system was allowed to stand and separate into layers. The upper residual liquid was removed to obtain Pd-enriched film. 2+ The lower emulsion; (4) Heat the obtained emulsion in a water bath for 20-60 minutes to break the emulsion. After cooling, remove the upper organic oil phase to obtain palladium-rich liquid II.

5. The method for recycling palladium in ion-based palladium waste liquid from circuit boards according to claim 1, characterized in that, The S3 step uses a reducing agent 1 to reduce the liquid 2. The reducing agent 1 includes one or more of the following: dimethylaminoborane, formaldehyde, sodium hypophosphite, sodium sulfite, and sodium borohydride.

6. The method for recycling palladium in ion-based palladium waste liquid from circuit boards according to claim 5, characterized in that, In step S3, reducing agent 1 is used to reduce liquid 2, followed by dilution and drying.

7. The method for recycling palladium in ion-based palladium waste liquid from circuit boards according to claim 6, characterized in that, The drying temperature is 200-300℃, and the drying time is 1-3 hours.

8. The method for recycling palladium in ion-based palladium waste liquid from circuit boards according to claim 1, characterized in that, The acidic medium in step S4 is concentrated hydrochloric acid, and the oxidant is one or a combination of hydrogen peroxide, nitric acid, sodium hypochlorite, and persulfate; the salt solution containing palladium ions is a palladium chloride solution.

9. An application of the recycling method according to any one of claims 1-8, characterized in that, It is used in the preparation of colloidal palladium activation solution; The preparation steps of the colloidal palladium activation solution include: The above-mentioned salt solution containing palladium ions was mixed with tin salt and reducing agent II in an acidic medium to prepare a colloidal palladium activated solution.

10. An application according to claim 9, characterized in that, The tin salt includes a first tin salt and a second tin salt; the preparation steps of the colloidal palladium activation solution include: Preparation of Solution A: Under stirring conditions at 20-40℃, add the above salt solution containing palladium ions to the acid solution, mix thoroughly, add the first tin salt, and stir to dissolve to obtain Solution A; Preparation of solution B: Add the first tin salt, reducing agent II, and stabilizer to the acid solution and stir to dissolve. Then add the second tin salt and stir until homogeneous to obtain solution B. The prepared solution B is poured into solution A at 30-50℃, diluted, and then kept at 50-70℃ for 2-6 hours to obtain a colloidal palladium activated solution. The first tin salt and the second tin salt are independently selected from one of stannous chloride, sodium stannate, tin tartrate, and tin citrate.

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