A method for selectively recovering platinum from spent nickel-platinum targets

Abstract

The application discloses a method for selectively recovering platinum from waste nickel-platinum target material, and belongs to the technical field of precious metal separation. In the method, different physical forms of the waste nickel-platinum target material are treated by using appropriate pretreatment methods. For planing materials, an acidic dissolving agent is used to selectively dissolve nickel; for block or ingot materials, aqua regia is used to completely dissolve and then reduce and enrich platinum. The platinum-containing material obtained through pretreatment is dissolved by using aqua regia, the pH of the solution is adjusted to 0.2-0.9, a reducing agent is added to perform a reduction reaction, platinum is selectively precipitated as platinum black, and then sponge platinum with a purity of greater than or equal to 99.95% is obtained through calcination. The method realizes targeted treatment of different forms of waste materials, and through accurate pH adjustment and the synergistic effect of a specific reducing agent, efficient and selective reduction of platinum is realized, the residual platinum in the filtrate is less than 0.5 ppm, secondary recovery is not needed, the process is short, safety is high, the product purity is high, and the method is suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of precious metal separation technology, specifically relating to a method for selectively recovering platinum from waste nickel-platinum targets. Background Technology

[0002] Currently, the process for recovering platinum from waste nickel-platinum sputtering targets mainly employs different technical approaches depending on the form of the waste. For fine-grained waste such as planed or shaving materials, the selective dissolution of nickel with dilute hydrochloric acid or dilute sulfuric acid, taking advantage of the difference in metallic activity between nickel and platinum, is a common method for achieving separation. For example, Wu Yuedong et al. (Kunming Institute of Precious Metals, 2022) studied the selective dissolution of nickel-platinum sputtering target chips with sulfuric acid, achieving a nickel dissolution rate of over 99.4% under optimized conditions. However, this method relies on the mechanism of nickel reacting with acid to generate hydrogen gas, and the large amount of hydrogen generated in actual production poses a very high risk of explosion. Patent application CN119120915A also uses dilute sulfuric acid to perform long-term acid leaching of block or sheet nickel-platinum alloys to separate nickel, but this process is also accompanied by the generation of a large amount of hydrogen gas. Furthermore, its subsequent process of replacing platinum with iron powder requires iron powder with a volume of 25 to 30 times the amount of platinum, which not only results in a long process but also introduces a large amount of iron impurities, increasing post-processing steps and environmental burden.

[0003] For large alloy waste in block or ingot shapes, selective dissolution methods are unsuitable because acid solutions have difficulty penetrating the alloy's interior. Typically, the entire alloy must be dissolved before separation. Patent application CN115418481A discloses a method that involves completely dissolving the waste with aqua regia, followed by a multi-step process of ammonium chloride precipitation, alkaline reduction, and metal displacement to recover platinum. This method is lengthy, requiring the sequential use of multiple reagents such as ammonium chloride, hydrazine hydrate, tin, or lead. Furthermore, to recover trace amounts of platinum remaining in the solution, metal displacement takes 48-96 hours, resulting in low processing efficiency. Patent application CN121653374A uses hot nitric acid to dissolve nickel-platinum waste, utilizing the difference in dissolution rates of nickel and platinum by nitric acid to achieve preliminary separation. However, its dissolution effect on blocky materials is limited, and some platinum dissolves into the solution, requiring precipitation and recovery using sodium sulfide at a pH of 1-2. This approach not only introduces new sulfur impurities but also yields platinum sulfide, requiring further processing to obtain metallic platinum, failing to fundamentally simplify the purification process.

[0004] It is evident that existing technologies generally suffer from two shortcomings: firstly, in processing planed materials, it is difficult to balance separation efficiency and operational safety, particularly as the risk of hydrogen explosion remains unresolved; secondly, the processing of lumpy materials is often complex, consumes large amounts of reagents, and lacks a universal process capable of simultaneously, efficiently, and safely processing different forms of waste. Therefore, developing a recovery method that avoids hydrogen generation, ensures operational safety, simplifies the process, efficiently recovers platinum, and can flexibly adapt to different forms of raw materials remains a pressing technical problem to be solved in this field. Summary of the Invention

[0005] The technical problem to be solved by this invention is that existing recycling processes are difficult to universally and effectively handle waste nickel-platinum targets in different forms.

[0006] The purpose of this invention is to provide a recycling method that can flexibly process waste nickel-platinum targets in different forms, aiming to simplify the process flow, improve the recycling efficiency of platinum, and obtain high-purity sponge platinum products, thereby solving the problems of safety hazards when processing planed materials and complex and inefficient processes when processing block materials in the existing technology.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows.

[0008] A method for selectively recovering platinum from waste nickel-platinum targets includes the following steps: S1. Pre-treat the waste nickel-platinum target material to obtain platinum-containing material; S2. Dissolve the platinum-containing material in aqua regia, add hydrochloric acid to remove nitrate, and obtain a platinum-containing solution; S3. Adjust the pH of the platinum-containing solution to 0.2~0.9, add a reducing agent, and carry out a reduction reaction at 60~100℃ to obtain platinum black by solid-liquid separation; wherein, the reducing agent is at least one of hydrazine hydrate, hydrazine hydrochloride, and zinc wire; S4. Calcining platinum black yields sponge platinum.

[0009] In step S1 of the above method, the waste nickel-platinum target material is planed material; The pretreatment specifically includes: mixing waste nickel-platinum target material with an excess of acidic solvent, stirring to selectively dissolve the material, filtering, washing the filter residue, and obtaining the platinum-containing material.

[0010] Furthermore, the acidic solvent is at least one of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution.

[0011] Furthermore, the acidic solvent is a nitric acid solution.

[0012] Furthermore, the concentration of the acidic solvent is 5% to 40%.

[0013] Furthermore, the selective dissolution temperature is 10~50℃.

[0014] In step S1 of the above method, the waste nickel-platinum target material is in block or ingot form; The pretreatment includes: completely dissolving the waste nickel-platinum target block or ingot material in aqua regia, adding hydrochloric acid to remove nitrates, adjusting the pH of the system to 0.2-0.9, adding excess reducing agent to carry out a reduction reaction, then filtering, taking the filter residue for washing, and obtaining the platinum-containing material.

[0015] Furthermore, the reducing agent is at least one of hydrazine hydrate, hydrazine hydrochloride, and zinc wire.

[0016] Furthermore, the reducing agent is hydrazine hydrochloride.

[0017] Furthermore, the reduction reaction is carried out at a temperature of 60~100℃.

[0018] In step S3 of the above method, the pH is adjusted to 0.2~0.9 using sodium hydroxide solution.

[0019] In step S3 of the above method, the reducing agent is added in excess until the reduction reaction is complete and the platinum content in the resulting filtrate is less than 0.5 ppm.

[0020] In step S3 of the above method, the reducing agent is hydrazine hydrochloride.

[0021] In step S4 of the above method, the calcination temperature is 500~800℃ and the calcination time is 1~5h.

[0022] The beneficial effects of this invention are: This invention designs suitable pretreatment processes for different forms of scrap nickel-platinum targets. For planed material, a specific acidic solvent is used to selectively dissolve nickel at a mild temperature, effectively avoiding the generation of hydrogen gas in traditional acid dissolution processes and eliminating the risk of explosion at the source. For block or ingot alloys, platinum-containing materials are obtained by complete dissolution with aqua regia followed by a single reduction, solving the problem of selective dissolution of large alloys. The platinum-containing materials obtained through both pretreatment paths can be processed in the same core purification stage.

[0023] In the core purification stage, this invention precisely controls the pH of the platinum-containing solution to a strongly acidic range of 0.2–0.9. Under these conditions, the redox potential of the hydrazine-based reducing agent falls within the electrochemical selectivity window where platinum is reduced while nickel remains unreduced, achieving efficient one-step separation of platinum. Based on this principle, the platinum reduction yield reaches over 99.9%, and the platinum residue in the post-reaction filtrate is less than 0.5 ppm, avoiding the drawbacks of traditional processes that require repeated treatment due to incomplete separation.

[0024] Compared to traditional ammonium chloride precipitation or metal displacement methods, this process eliminates multiple steps such as hydrolysis and secondary precipitation, significantly shortening the purification cycle. Furthermore, the reducing agent itself contains no metallic impurities, and the oxidation product is nitrogen gas, ensuring that the final sponge platinum product consistently meets the national standard of 99.95% purity. In summary, this invention provides a targeted treatment solution for waste nickel-platinum targets in different forms and achieves efficient platinum recovery in the core purification stage, demonstrating promising industrial application prospects. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process flow for selectively recovering platinum from waste nickel-platinum targets. Detailed Implementation

[0026] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0027] The present invention provides a method for recovering platinum from waste nickel-platinum targets. First, a suitable pretreatment method is selected according to the physical form of the waste to obtain platinum-containing materials. Then, the platinum-containing materials are subjected to uniform deep purification treatment to finally obtain high-purity sponge platinum.

[0028] Step 1: Pre-treat the waste nickel-platinum target material to obtain platinum-containing material.

[0029] In one specific embodiment of the present invention, when the waste nickel-platinum target material is planed material (i.e., material in a fine state), the following pretreatment steps are performed: (1) Selective Dissolution: The waste nickel-platinum target material is mixed with an excess of acidic solvent and stirred continuously at a temperature of 10-50°C to carry out a selective dissolution reaction. The acidic solvent is selected from at least one of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution, with a mass concentration of 5%-40%. This step utilizes the difference in dissolution behavior of nickel and platinum in acidic media: nickel has much greater metallic activity than platinum and is easily dissolved in dilute acid, while platinum is almost insoluble under these conditions. Traditional processes often use dilute hydrochloric acid or dilute sulfuric acid to dissolve nickel, but a large amount of hydrogen gas is generated during the reaction, posing an explosion risk. This invention has found that when nitric acid is used as a solvent, selective dissolution of nickel can be achieved at a mild temperature, while no hydrogen gas is generated during the reaction, significantly improving operational safety. However, if hydrochloric acid or sulfuric acid is used, hydrogen gas will still be generated, failing to achieve the desired safety effect. Therefore, as a preferred solution, this step uses nitric acid solution as the acidic solvent. After the reaction, nickel enters the solution in the form of nickel nitrate, while platinum remains in solid form. (2) Solid-liquid separation and washing: The reaction mixture obtained in S1-1 is filtered to obtain a nickel-containing filtrate and a platinum-containing filter residue. The filtrate can be directly outsourced for processing or further recycled for nickel recovery. Since the waste nickel-platinum target material has high purity, the obtained filtrate has a high nickel content and few impurities, so it can be used for further recycling to prepare nickel nitrate products, realizing the comprehensive utilization of nickel resources. The platinum-containing filter residue is washed multiple times with pure water to remove residual nickel ions and acid. The washed filter residue is the platinum-containing material, which enters the subsequent core purification process.

[0030] In one specific embodiment of the present invention, when the waste nickel-platinum target material is a large block or ingot-shaped alloy, it is impossible to effectively separate the nickel-platinum through selective dissolution. Therefore, a pretreatment method of complete dissolution followed by one-time reduction is adopted: (1) Complete dissolution with aqua regia: The waste nickel-platinum target material in block or ingot form is completely dissolved in aqua regia. During the dissolution process, continuous stirring and heating are carried out to promote the reaction. Aqua regia is made by mixing concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of 3:1. Its strong oxidizing properties can completely convert nickel and platinum into soluble chlorides. After complete dissolution, hydrochloric acid is added and heated to remove nitrate ions from the solution, resulting in a primary platinum-containing solution containing nickel ions and platinum complex ions.

[0031] (2) Primary reduction enrichment: The pH of the above-mentioned primary platinum-containing solution is adjusted to 0.2-0.9, and an excess reducing agent is added. The reduction reaction is carried out at 60-100℃. The reducing agent is selected from at least one of hydrazine hydrate, hydrazine hydrochloride, and zinc wire. Under this strongly acidic condition, the reducing agent can selectively reduce platinum ions in the solution to metallic platinum precipitate, while nickel ions are hardly reduced and remain in the solution. After the reaction, the solution is filtered to obtain crude platinum filter residue. After washing with pure water, the platinum-containing material is obtained and enters the subsequent core purification process. This step achieves the initial separation of platinum and nickel and enriches platinum in the solid phase, reducing the burden on subsequent deep purification.

[0032] Step Two: Core Purification Process. Regardless of the pretreatment method used to obtain the platinum-containing material, the following identical steps are employed for deep purification: (1) Solution preparation: The platinum-containing material is dissolved in aqua regia. After complete dissolution, hydrochloric acid is added and the mixture is heated to remove nitrates, yielding a platinum-containing solution. This step converts the platinum into [PtCl6]. 2- It enters the solution in the form of nickel ions, and may leave behind a small amount of nickel ions and other trace impurities.

[0033] (2) Selective reduction: The pH of the above platinum-containing solution is precisely adjusted to 0.2~0.9, an excess reducing agent is added, and the reduction reaction is carried out at 60~100℃. The reducing agent is selected from at least one of hydrazine hydrate, hydrazine hydrochloride, and zinc wire, preferably hydrazine hydrochloride.

[0034] This step is crucial for the efficient purification of platinum in this invention. Through extensive experimental research, this invention has discovered that within the strongly acidic pH range of 0.2–0.9, the redox potential of hydrazine-based reducing agents falls within a specific "selective window": this potential is sufficient to [PtCl6]... 2- Pt in 4+ It is reduced to metallic platinum, but not enough to reduce Ni. 2+ Platinum is reduced to metallic nickel. When the pH is below 0.2, the solution is too acidic, inhibiting the reducing power of hydrazine-based reducing agents, resulting in slow kinetics, incomplete reduction, and increased platinum residue in the filtrate. When the pH is above 0.9, nickel ions begin to precipitate as nickel hydroxide precipitate. At this point, platinum black and nickel hydroxide precipitates are present in the solution, making it impossible to separate platinum and nickel, affecting the purity of the platinum product. Simultaneously, base metal ions in the solution are prone to hydrolysis, introducing impurities. Therefore, controlling the pH within the range of 0.2–0.9 allows full utilization of electrochemical selectivity differences, achieving efficient one-step separation of platinum with a reduction yield exceeding 99.9%, and platinum residue in the filtrate after the reaction being less than 0.5 ppm.

[0035] Meanwhile, the reaction temperature of 60~100℃ ensures the kinetic rate of the reduction reaction, allowing it to be completed within a few hours, while avoiding the decomposition of the reducing agent or side reactions that may be caused by excessively high temperatures. When hydrazine hydrochloride is used as the reducing agent, its acidic properties are well-compatible with the reaction system, and its oxidation products are only nitrogen gas and water, without introducing any metal impurities. The platinum content in the filtrate after the reaction is usually less than 0.5ppm, eliminating the need for secondary recovery treatment and directly reducing subsequent environmental pressure.

[0036] (3) Solid-liquid separation: The mixture after the reduction reaction is filtered to obtain filtrate and platinum black filter residue. The platinum residue in the filtrate is extremely low (<0.5 ppm), which can be outsourced for processing or further recovered from nickel. The platinum black filter residue is washed multiple times with pure water to remove attached impurity ions.

[0037] (4) Calcination: Transfer the washed platinum black filter residue to a crucible and calcine at 500~800℃ for 1~5 hours. During calcination, the platinum black particles sinter and grow, transforming into metallic sponge platinum. The selection of calcination temperature and time should ensure that the platinum powder is completely transformed into a dense sponge-like structure, while avoiding excessive sintering that could lead to impurity encapsulation. The resulting sponge platinum was tested and found to have a purity that meets the 99.95% standard in GB / T 1419-2015.

[0038] In summary, this invention designs suitable pretreatment methods for different forms of waste nickel-platinum targets, which not only solves the safety hazards in the processing of planed materials but also achieves the initial enrichment of lumpy materials. The unified core purification process, through precise pH control and the synergistic effect of reducing agents, achieves highly efficient and selective reduction of platinum, significantly shortening the purification process, improving recovery efficiency, and ultimately obtaining high-purity sponge platinum products. This method is simple, safe, and environmentally friendly, and has good industrial application value.

[0039] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0040] Example 1 This embodiment uses waste nickel-platinum target material planing material as raw material to recover platinum according to the following steps: S1. Waste nickel-platinum target planing material was mixed with a 34% nitric acid solution and stirred continuously at 25°C to carry out a selective dissolution reaction, allowing nickel to dissolve while platinum remained in the solid phase. The mixture after the reaction was filtered to obtain filtrate and filter residue. The filter residue was washed several times with pure water and then used for further processing. Testing showed that the platinum content in the obtained filtrate was only 0.1 ppm, indicating that platinum was almost not dissolved, and it was further recovered to prepare nickel nitrate product.

[0041] S2. Dissolve the washed filter residue in aqua regia. After complete dissolution, add hydrochloric acid and heat to remove nitrate, obtaining a platinum-containing solution. Adjust the pH of the platinum-containing solution to 0.6 with sodium hydroxide solution, add hydrazine hydrochloride solution, and carry out a reduction reaction at 90°C, causing platinum to precipitate as platinum black. After the reduction reaction is complete, filter to obtain filtrate and filter residue. Wash the filter residue (platinum black) five times with pure water, drain, and set aside. Testing showed that the platinum content in the obtained filtrate was only 0.1 ppm, suitable for direct outsourcing.

[0042] S3. Transfer the platinum black to a crucible, place it in a muffle furnace, and calcine it at 800℃ for 3 hours. The resulting sponge platinum was then removed. The purity of the obtained sponge platinum was tested, and the results are shown in Table 1.

[0043] Table 1 Chemical composition of sponge platinum

[0044] As shown in Table 1, the Pt content of the platinum sponge prepared in this embodiment reaches 99.98%, which is higher than the 99.95% requirement in GB / T 1419-2015. The contents of all impurity elements are lower than the standard limits, and the total impurity element content is 0.0166%, which is better than the standard requirement of 0.05%. The results indicate that the method of this invention can efficiently recover platinum from waste nickel-platinum target planing material and obtain a high-purity platinum sponge product. Example 2 This embodiment uses block and ingot-shaped waste nickel-platinum targets as raw materials to recover platinum according to the following steps: S1. The waste nickel-platinum target block material was completely dissolved in aqua regia. After complete dissolution, hydrochloric acid was added and the mixture was heated to remove nitrates, yielding a platinum-nickel containing solution. The pH of the obtained platinum-nickel containing solution was adjusted to 0.6 with sodium hydroxide solution, and hydrazine hydrochloride solution was added. A reduction reaction was carried out at 90°C to selectively precipitate platinum. After the reaction, the mixture was filtered to obtain filtrate and filter residue (crude platinum). Testing showed that the platinum content in the filtrate was only 0.1 ppm, which is suitable for direct outsourcing.

[0045] S2. Crude platinum was dissolved in aqua regia. After complete dissolution, hydrochloric acid was added and the mixture was heated to remove nitrates, yielding a platinum-containing solution. The pH of the platinum-containing solution was adjusted to 0.6 with sodium hydroxide solution, and hydrazine hydrochloride solution was added. A reduction reaction was carried out at 90°C, causing platinum to precipitate as platinum black. After the reaction was complete, the solution was filtered, yielding a filtrate and a filter residue (platinum black). The filter residue was washed with pure water and used for later processing. Analysis showed that the platinum content in the obtained filtrate was only 0.1 ppm, which was suitable for direct outsourcing.

[0046] S3. Transfer the platinum black to a crucible, place it in a muffle furnace, and calcine it at 800℃ for 3 hours. Remove the crucible to obtain sponge platinum. The purity of the obtained sponge platinum was tested, and the results are shown in Table 2.

[0047] Table 2 Chemical composition of sponge platinum

[0048] As shown in Table 2, the Pt content of the platinum sponge prepared in this embodiment reaches 99.98%, which is higher than the 99.95% requirement in GB / T 1419-2015. The content of each impurity element is lower than the standard limit, and the total impurity element content is 0.0119%, which is better than the standard requirement of 0.05%. The results show that the method of the present invention can efficiently recover platinum from waste nickel-platinum target blocks and obtain high-purity platinum sponge products.

[0049] Comparative Example 1 This comparative example uses block and ingot-shaped waste nickel-platinum targets as raw materials and recovers platinum according to basically the same steps as in Example 2, the only difference being the pH adjustment in step S2: S1. The waste nickel-platinum target block material was completely dissolved in aqua regia. After complete dissolution, hydrochloric acid was added and the mixture was heated to remove nitrate, yielding a platinum-nickel containing solution. The pH of the obtained platinum-nickel containing solution was adjusted to 0.1 with sodium hydroxide solution, and hydrazine hydrochloride solution was added. A reduction reaction was carried out at 90°C to selectively precipitate platinum. After the reaction, the mixture was filtered to obtain filtrate and filter residue (crude platinum). The platinum content in the filtrate was found to be 521 ppm, requiring secondary recovery treatment.

[0050] S2. Crude platinum was dissolved in aqua regia. After complete dissolution, hydrochloric acid was added and the mixture was heated to remove nitrates, yielding a platinum-containing solution. The pH of the platinum-containing solution was adjusted to 0.1 with sodium hydroxide solution, and hydrazine hydrochloride solution was added. A reduction reaction was carried out at 90°C, causing platinum to precipitate as platinum black. After the reaction was complete, the solution was filtered, yielding a filtrate and a filter residue (platinum black). The filter residue was washed with pure water and used for later use. The platinum content in the filtrate was found to be 483 ppm, requiring secondary recovery treatment.

[0051] S3. Transfer the platinum black to a crucible, place it in a muffle furnace, and calcine it at 800℃ for 3 hours. The resulting sponge platinum was then removed. The purity of the obtained sponge platinum was tested, and the results are shown in Table 3.

[0052] Table 3 Chemical composition of sponge platinum

[0053] Table 3 shows that the obtained platinum sponge has a purity of 99.98%, which meets the 99.95% requirement in GB / T 1419-2015. However, because the pH value of the reduction step was lower than the lower limit specified in this invention, the excessive acidity of the solution inhibited the reducing ability of the hydrazine reducing agent, resulting in incomplete platinum reduction. After the first reduction, the platinum residue in the filtrate was as high as 521 ppm, and after the second reduction, the platinum residue in the filtrate was still 483 ppm, indicating a significant loss of platinum in the filtrate, requiring additional recovery treatment. Calculations show that the platinum recovery rate in this comparative example was only 95.3%. The above results indicate that although a qualified product can be obtained when the pH value is below 0.2, the platinum recovery efficiency is significantly reduced, making it impossible to achieve efficient platinum recovery.

[0054] Comparative Example 2 This comparative example uses block and ingot-shaped waste nickel-platinum targets as raw materials and recovers platinum according to basically the same steps as in Example 2, the difference being the pH adjustment in steps S2 and S4: S1. The waste nickel-platinum target material in lumps was completely dissolved in aqua regia. After complete dissolution, hydrochloric acid was added and the mixture was heated to remove nitrate, yielding a platinum-nickel containing solution. The pH of the obtained platinum-nickel containing solution was adjusted to 1.0 with sodium hydroxide solution, and hydrazine hydrochloride solution was added. A reduction reaction was carried out at 90°C. After the reaction was completed, the solution was filtered to obtain filtrate and filter residue (crude platinum). Testing showed that the platinum content in the filtrate was only 0.5 ppm, which could be directly outsourced for processing.

[0055] S2. Crude platinum was dissolved in aqua regia. After complete dissolution, hydrochloric acid was added and the solution was heated to remove nitrate, yielding a platinum-containing solution. The pH of the resulting platinum-nickel-containing solution was adjusted to 1.0 with sodium hydroxide solution. Hydrazine hydrochloride solution was added, and a reduction reaction was carried out at 90°C, causing platinum to precipitate as platinum black. After the reaction was complete, the solution was filtered, yielding a filtrate and a filter residue (platinum black). The filter residue was washed with pure water and used for later processing. The platinum content in the filtrate was measured to be 0.4 ppm, indicating it could be directly outsourced for further processing.

[0056] S3. Transfer the platinum black to a crucible, place it in a muffle furnace, and calcine it at 800℃ for 3 hours. The resulting sponge platinum was then removed. The purity of the obtained sponge platinum was tested, and the results are shown in Table 3.

[0057] Table 4 Chemical composition of sponge platinum

[0058] Table 4 shows that the purity of the obtained platinum sponge was only 94.61%, far below the 99.95% requirement in GB / T 1419-2015. The nickel impurity content was as high as 5.38%, and the total impurity element content reached 5.3904%. The results indicate that when the pH value is higher than the upper limit specified in this invention, although the reduction reaction of platinum is relatively complete (the platinum residue in the filtrate is only 0.5 ppm and 0.4 ppm), under higher pH conditions, some nickel ions undergo hydrolysis, co-precipitation, or co-reduction, mixing into the platinum black and resulting in a serious exceedance of nickel impurities in the final product. This shows that while pH values ​​exceeding the upper limit of 0.9 do not affect the reduction efficiency of platinum, they do disrupt the reduction selectivity, making it impossible to guarantee product purity.

Claims

1. A method for selectively recovering platinum from waste nickel-platinum targets, characterized in that, Includes the following steps: S1. Pre-treat the waste nickel-platinum target material to obtain platinum-containing material; S2. Dissolve the platinum-containing material in aqua regia, add hydrochloric acid to remove nitrate, and obtain a platinum-containing solution; S3. Adjust the pH of the platinum-containing solution to 0.2~0.9, add a reducing agent, and carry out a reduction reaction at 60~100℃ to obtain platinum black by solid-liquid separation; wherein, the reducing agent is at least one of hydrazine hydrate, hydrazine hydrochloride, and zinc wire; S4. Calcining platinum black yields sponge platinum.

2. The method according to claim 1, characterized in that, In step S1: The waste nickel-platinum target material is a planing material; The pretreatment specifically includes: mixing waste nickel-platinum target material with an excess of acidic solvent, stirring to selectively dissolve the material, filtering, washing the filter residue, and obtaining the platinum-containing material.

3. The method according to claim 2, characterized in that, At least one of the following conditions must be met: The acidic solvent is at least one of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution; The concentration of the acidic solvent is 5% to 40%; The selective dissolution temperature is 10~50℃.

4. The method according to claim 3, characterized in that: The acidic solvent is a nitric acid solution.

5. The method according to claim 1, characterized in that, In step S1: The waste nickel-platinum target material is in block or ingot form; The pretreatment includes: completely dissolving the waste nickel-platinum target block or ingot material in aqua regia, adding hydrochloric acid to remove nitrates, adjusting the pH of the system to 0.2-0.9, adding excess reducing agent to carry out a reduction reaction, then filtering, taking the filter residue for washing, and obtaining the platinum-containing material.

6. The method according to claim 5, characterized in that, At least one of the following conditions must be met: The reducing agent is at least one of hydrazine hydrate, hydrazine hydrochloride, and zinc wire; The reduction reaction is carried out at a temperature of 60~100℃.

7. The method according to claim 6, characterized in that: The reducing agent is hydrazine hydrochloride.

8. The method according to claim 1, characterized in that: In step S3, the reducing agent is added in excess until the reduction reaction is complete and the platinum content in the resulting filtrate is less than 0.5 ppm.

9. The method according to claim 1, characterized in that: In step S3, the reducing agent is hydrazine hydrochloride.

10. The method according to claim 1, characterized in that: In step S4, the calcination temperature is 500~800℃ and the calcination time is 1~5h.

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