A pre-treatment method for noble metal loading ICP test

Abstract

The present application relates to the technical field of noble metal detection, and particularly relates to a pre-treatment method for ICP testing of noble metal loading capacity. The method comprises the following steps: step one: the surface of a metal plate loaded with noble metal is covered with alkali liquor; step two: the metal plate covered with alkali liquor is placed in a crucible and subjected to high-temperature roasting, then the metal plate is cooled, and then an oxidizing agent is coated on the surface of the metal plate and the metal plate is subjected to oxidation roasting again; step three: after the metal plate subjected to high-temperature roasting in step two is cooled, a mixed acidic solution is added to the crucible, and the reaction product is dissolved after the crucible is heated; step four: the reaction product is filtered, and the filtrate is fixed in volume and subjected to ICP testing. Through the steps of stripping and then melting, the use amount of strong oxidizing agent and flux is greatly reduced, and the use amount of acid is also reduced, thereby reducing the cost and environmental burden.

Description

Technical Field

[0001] This invention relates to the field of precious metal detection technology, and specifically to a pretreatment method for ICP testing of precious metal loading. Background Technology

[0002] In the electrochemical industry, such as chlor-alkali production, hydrogen production through water electrolysis, and fuel cells, precious metals (such as platinum, iridium, ruthenium, and their oxides) are often used as active coatings loaded onto anode plates made of valve metals such as titanium. Accurately determining the loading of precious metals on the anode plate surface is crucial for evaluating electrode performance, controlling production costs, optimizing coating processes, and recovering precious metals. Inductively coupled plasma atomic emission spectrometry (ICP-OES / MS) is currently the standard method for determining the content of metal elements, but it requires that the precious metals in the solid sample be completely dissolved and transferred to the liquid phase.

[0003] Currently, the main ICP pretreatment methods for such precious metal coated anodes include: Direct acid dissolution: This method typically uses aqua regia, reverse aqua regia, or a mixture of hydrochloric acid and hydrogen peroxide to soak or heat the anode plate for digestion. However, this method has significant drawbacks: for firmly bonded and dense precious metal oxide coatings, the acid solution is difficult to completely penetrate and react, resulting in low dissolution efficiency and lower results; simultaneously, the severe acid corrosion dissolves the titanium matrix, consuming large amounts of acid, and the high concentration of titanium ions may interfere with subsequent ICP testing. High-temperature alkaline fusion: This method mixes the sample with fluxes such as sodium peroxide and sodium hydroxide, and melts it in a high-temperature muffle furnace, converting all components into acid-soluble forms. While this method ensures complete dissolution of the precious metal, it requires sophisticated equipment (platinum or zirconium crucibles are needed to withstand strong alkaline and oxidizing environments), consumes large amounts of auxiliary materials (fluxes), and introduces a large amount of salt, increasing background and dilution errors in subsequent ICP testing. More importantly, this method typically requires destructive pretreatment such as cutting and grinding large anode plates, which increases operational complexity and leads to poor test representativeness and large errors due to small sampling area and uneven coating. Full sample digestion method (post-powdering treatment): To avoid sampling errors, sometimes the entire or most of the anode plate is mechanically (e.g., milling, scraping) to powder the coating along with part of the substrate, and then the powder is acid-dissolved or alkali-fused. While this method increases the sampling area, the pretreatment process is cumbersome and time-consuming, and precious metals may be lost during grinding due to adsorption, splashing, etc., introducing new errors. At the same time, a large amount of titanium matrix powder also poses difficulties for subsequent digestion and testing.

[0004] In summary, existing technologies generally suffer from the following drawbacks: High equipment requirements and high costs: For example, the use of crucibles made of special materials is necessary. High consumption of auxiliary materials and introduction of interference: The extensive use of strong acids, strong oxidants, or fluxes increases the difficulty of subsequent processing and testing errors. Cumbersome and destructive pretreatment: Operations such as cutting and grinding of raw materials are required, which is time-consuming and labor-intensive and damages the integrity of the samples. Insufficient sampling representativeness and large testing errors: Small-area sampling cannot represent the actual unevenness of the entire anode plate coating, leading to reduced data reliability.

[0005] Therefore, there is an urgent need in this field to develop a pretreatment method for ICP testing of precious metal loading that has low equipment requirements, low auxiliary material consumption, simple pretreatment, is non-destructive or low-destructive, and can achieve large-area sampling to reduce errors. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a pretreatment method for ICP testing of precious metal loading.

[0007] A pretreatment method for ICP testing of precious metal loading, such as Figure 1 As shown, it includes the following steps: Step 1: Spread an alkaline solution over the surface of the metal plate loaded with precious metals; Step 2: First, place the metal plate covered with alkaline solution in a crucible and bake it at high temperature. Then, cool the metal plate down and cover the surface of the metal plate with an oxidant and bake it again. Step 3: After cooling down the metal plate that was calcined at high temperature in Step 2, add a mixed acidic solution to the crucible and heat the crucible to dissolve the reaction products. Step 4: Filter the reaction product, and then perform ICP testing on the filtrate after adjusting the volume.

[0008] Furthermore, in step one, the precious metal is iridium and / or ruthenium; the metal sheet includes a titanium plate, titanium mesh, or titanium wire. Specifically, the precious metal can also be other precious metals such as platinum (Pt).

[0009] Furthermore, in step one, the alkaline solution consists of KOH solution and its alkaline mixture, NaOH solution and its alkaline mixture, and the concentration of the alkaline solution is 20-70%.

[0010] Specifically, KOH solution and its alkaline mixtures include KOH solution, KOH and KNO3 mixture, KOH and NaNO3 mixture, or KOH and other alkaline solutions; NaOH solution and its alkaline mixtures include NaOH solution, NaOH and KNO3 mixture, NaOH and NaNO3 mixture, or NaOH and other alkaline solutions.

[0011] Furthermore, in step one, covering the surface of the metal sheet with alkaline solution specifically involves brushing or directly immersing the surface of the metal sheet in an alkaline solution containing a thickener until the surface is completely covered with alkaline solution.

[0012] Specifically, the thickener is hydroxymethyl cellulose, hydroxyethyl cellulose, xanthan gum, or other alkali-resistant thickeners. Further, in step two, the high-temperature calcination temperature is 380-480℃, and the high-temperature calcination time is 5-20 minutes.

[0013] Furthermore, in step two, the oxidant is Na2O2, BaO2, or NaClO3.

[0014] Furthermore, in step two, the oxidative calcination temperature is 700-850℃, and the calcination time is 2-4 hours.

[0015] Specifically, high-temperature firing involves drying the plate after step one and placing it in a corundum crucible, then placing the corundum crucible in a muffle furnace for high-temperature firing for several minutes. Furthermore, in step three, the mixed acidic solution is a mixture of hydrochloric acid and nitric acid, wherein the ratio of hydrochloric acid to nitric acid is (3-10):1.

[0016] Furthermore, in step three, the volume of the mixed acidic solution is 20-50 times the mass of the oxidant, the leaching temperature is 80-100℃, and the reaction time is 1-3 hours.

[0017] Specifically, the solid-liquid separation methods for leaching include centrifugal separation, vacuum filtration, or natural filtration.

[0018] Compared with the prior art, the present invention has the following beneficial effects: Low equipment requirements: The entire process in this application does not require expensive equipment such as platinum crucibles; conventional muffle furnaces and laboratory glassware are sufficient, which lowers the implementation threshold and cost.

[0019] Low auxiliary material consumption: This application greatly reduces the amount of strong oxidants and fluxes used by first stripping and then melting, while also reducing the amount of acid used, thus lowering costs and environmental burden.

[0020] The pretreatment is simple and requires no destructive pretreatment: the raw materials (anode plates) in this application do not require complex cutting, grinding, or powdering processes. Large-sized plates can be directly treated by brushing or soaking in alkaline solution, maintaining the integrity of the sample and simplifying the operation process.

[0021] Large sampling area and small testing error: Since this application does not require damaging the sample, it can directly process large-area plates, so that the sample taken can better represent the precious metal load on the entire plate surface, effectively overcoming the small sampling error caused by uneven coating, and the test results are more representative and accurate.

[0022] Complete dissolution and accurate results: This application ensures that even dense and robust noble metal oxide coatings can be completely dissolved and transferred into the liquid phase through a multi-step synergistic effect of "stripping-activation-leaching", thus guaranteeing the accuracy and reliability of ICP test results.

[0023] In summary, this invention transfers precious metals from the surface of a metal material to a solution through processes such as alkaline coating / immersion, high-temperature roasting and peeling, oxidative roasting activation, and mixed acid leaching, thereby achieving accurate testing of the precious metal loading on the surface of the metal material. This method has no requirements on sample size, low equipment requirements, low reagent consumption, and convenient testing process, effectively realizing the phase transfer of precious metals on the surface of the metal material, which is beneficial to the accurate testing of precious metal loading. Attached Figure Description

[0024] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating the pretreatment method for ICP testing of precious metal loading in this invention. Figure 2 This is a schematic diagram illustrating the specific steps of the pretreatment method for ICP testing of precious metal loading in this invention. Detailed Implementation

[0027] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0028] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] Example 1 This embodiment provides a preprocessing method for ICP testing of precious metal loading, such as... Figure 1 and Figure 2 As shown, it includes the following steps: Step 1: Spread an alkaline solution over the surface of the metal plate loaded with precious metals; Specifically, a titanium plate with a size of 10cm × 10cm loaded with IrO2-RuO2-Ta2O5 was directly immersed in a 20% potassium hydroxide (KOH) solution containing a thickener; Step 2: First, place the metal plate covered with alkaline solution in a crucible and bake it at high temperature. Then, cool the metal plate down and cover the surface of the metal plate with an oxidant and bake it again. Specifically, the plate processed in step one is dried and placed in a corundum crucible. Then, the corundum crucible is placed in a muffle furnace and baked at 480°C for 5 minutes. After the plate is baked at high temperature, it is taken out and cooled down. Then, 5g of sodium peroxide is covered on its surface and placed in a corundum crucible. Finally, the corundum crucible is placed in a muffle furnace and baked at 700°C for 4 hours. Step 3: After cooling down the metal plate that was calcined at high temperature in Step 2, add a mixed acidic solution to the crucible and heat the crucible to dissolve the reaction products. Specifically, after cooling down the board material treated in step two, add 227ml of hydrochloric acid and 23ml of nitric acid and heat at 95℃ for 2 hours to leach it. Step 4: Filter the reaction product, and then perform ICP testing on the filtrate after adjusting the volume.

[0030] Specifically, the leachate from step three is vacuum filtered, and the filtrate is brought to a final volume for ICP testing.

[0031] Example 2 This embodiment provides a preprocessing method for ICP testing of precious metal loading, such as... Figure 1 and Figure 2 As shown, it includes the following steps: Step 1: Spread an alkaline solution over the surface of the metal plate loaded with precious metals; Specifically, a mixed alkaline solution of 35% KOH and 35% KNO3 was applied to the surface of a titanium plate loaded with IrO2-Ta2O5 with a size of 10cm × 10cm. Step 2: First, place the metal plate covered with alkaline solution in a crucible and bake it at high temperature. Then, cool the metal plate down and cover the surface of the metal plate with an oxidant and bake it again. Specifically, the plate processed in step one is dried and placed in a corundum crucible. Then, the corundum crucible is placed in a muffle furnace and baked at 450°C for 10 minutes. After the plate is baked at high temperature, it is taken out and cooled down. Then, 10g of sodium peroxide is covered on its surface and placed in a corundum crucible. Finally, the corundum crucible is placed in a muffle furnace and baked at 850°C for 2 hours. Step 3: After cooling down the metal plate that was calcined at high temperature in Step 2, add a mixed acidic solution to the crucible and heat the crucible to dissolve the reaction products. Specifically, after cooling down the board material treated in step two, add 150ml of hydrochloric acid and 50ml of nitric acid and heat at 80℃ for 3 hours to leach it. Step 4: Filter the reaction product, and then perform ICP testing on the filtrate after adjusting the volume.

[0032] Specifically, the leachate from step three is vacuum filtered, and the filtrate is brought to a final volume for ICP testing.

[0033] Example 3 This embodiment provides a preprocessing method for ICP testing of precious metal loading, such as... Figure 1 and Figure 2 As shown, it includes the following steps: Step 1: Spread an alkaline solution over the surface of the metal plate loaded with precious metals; Specifically, a 50% NaOH alkaline solution was applied to the surface of a 10cm × 10cm titanium plate loaded with RuO2-Ta2O5. Step 2: First, place the metal plate covered with alkaline solution in a crucible and bake it at high temperature. Then, cool the metal plate down and cover the surface of the metal plate with an oxidant and bake it again. Specifically, the plate processed in step one is dried and placed in a corundum crucible. Then, the corundum crucible is placed in a muffle furnace and baked at 400°C for 15 minutes. After the plate is baked at high temperature, it is taken out and cooled down. Then, 10g of sodium peroxide is covered on its surface and placed in a corundum crucible. Finally, the corundum crucible is placed in a muffle furnace and baked at 800°C for 3 hours. Step 3: After cooling down the metal plate that was calcined at high temperature in Step 2, add a mixed acidic solution to the crucible and heat the crucible to dissolve the reaction products. Specifically, after cooling down the board material treated in step two, add 250ml of hydrochloric acid and 50ml of nitric acid and heat at 90℃ for 2 hours to leach it. Step 4: Filter the reaction product, and then perform ICP testing on the filtrate after adjusting the volume.

[0034] Specifically, the leachate from step three is vacuum filtered, and the filtrate is brought to a final volume for ICP testing.

[0035] Example 4 This embodiment provides a preprocessing method for ICP testing of precious metal loading, such as... Figure 1 and Figure 2 As shown, it includes the following steps: Step 1: Spread an alkaline solution over the surface of the metal plate loaded with precious metals; Specifically, a titanium plate with a size of 10cm×10cm loaded with IrO2-RuO2 was immersed in a mixed alkaline solution of 25% NaOH-25% NaNO3; Step 2: First, place the metal plate covered with alkaline solution in a crucible and bake it at high temperature. Then, cool the metal plate down and cover the surface of the metal plate with an oxidant and bake it again. Specifically, the plate processed in step one is dried and placed in a corundum crucible. Then, the corundum crucible is placed in a muffle furnace and baked at 380°C for 20 minutes. After the plate is baked at high temperature, it is taken out and cooled down. Then, 5g of sodium peroxide is covered on its surface and placed in a corundum crucible. Finally, the corundum crucible is placed in a muffle furnace and baked at 750°C for 3 hours. Step 3: After cooling down the metal plate that was calcined at high temperature in Step 2, add a mixed acidic solution to the crucible and heat the crucible to dissolve the reaction products. Specifically, after cooling down the board material treated in step two, add 160ml of hydrochloric acid and 40ml of nitric acid and heat at 100℃ for 1 hour to leach it. Step 4: Filter the reaction product, and then perform ICP testing on the filtrate after adjusting the volume.

[0036] Specifically, the leachate from step three is vacuum filtered, and the filtrate is brought to a final volume for ICP testing.

[0037] Comparative Example 1 A 10cm × 10cm titanium plate loaded with IrO2-RuO2 (the same loading amount as in Example 1) was coated with 25g of potassium hydroxide and 5g of potassium nitrate. The plate was placed in a nickel crucible and then calcined in a muffle furnace at 400℃ for 20min. The pretreated plate was then rinsed with plenty of water until the alkali coating on the surface was completely dissolved. The rinsing liquid was collected and centrifuged to separate the noble metal coating. The coating was then dried, and 5g of sodium peroxide was added and mixed thoroughly. The mixture was then placed in an alumina crucible and calcined in a muffle furnace at 750℃ for 3h. After calcination, the sample was cooled and removed, then 160ml of hydrochloric acid and 40ml of nitric acid were added and leached at 100℃ for 1h. Solid-liquid separation was performed, and the liquid was brought to a final volume for ICP testing. Compared with Example 1, the loading amount obtained after processing the same raw materials was only 70% of that of this invention.

[0038] In summary, comparing the operational procedures of Examples 1-4 with those of the comparative example, it can be seen that Examples 1-4 of the present invention achieve efficient peeling of the coating and substrate with minimal reagent usage during the pretreatment process for ICP testing of precious metal loading through alkaline coating / immersion and subsequent high-temperature calcination. Simultaneously, the subsequent oxidative calcination confines peeling and oxidation to the same interface, avoiding losses during material transfer and facilitating full contact and activation of the coating by the oxidant. The subsequent thorough acid leaching process completely transfers the precious metal to the liquid phase, enabling accurate testing of the precious metal loading. This invention simplifies the pretreatment process for ICP testing of precious metal loading, allowing for unlimited sample size and eliminating the need for pretreatment such as cutting or powdering. Through the synergistic effect of multiple steps—"peeling-activation-leaching"—the phase transformation process is confined to the substrate surface, ensuring thorough leaching without material transfer or loss, and guaranteeing that the precious metal is completely retained in the leaching solution, thus ensuring accurate and reliable subsequent testing.

[0039] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0040] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A pretreatment method for ICP testing of precious metal loading, characterized in that, Includes the following steps: Step 1: Spread an alkaline solution over the surface of the metal plate loaded with precious metals; Step 2: First, place the metal plate covered with alkaline solution in a crucible and bake it at high temperature. Then, cool the metal plate down and cover the surface of the metal plate with an oxidant and bake it again. Step 3: After cooling down the metal plate that was calcined at high temperature in Step 2, add a mixed acidic solution to the crucible and heat the crucible to dissolve the reaction products. Step 4: Filter the reaction product, and then perform ICP testing on the filtrate after adjusting the volume.

2. The pretreatment method for ICP testing of precious metal loading according to claim 1, characterized in that, In step one, the precious metal is iridium and / or ruthenium; the metal sheet includes titanium plate, titanium mesh or titanium wire.

3. The pretreatment method for ICP testing of precious metal loading according to claim 1, characterized in that, In step one, the alkaline solution is composed of KOH solution and its alkaline mixture or NaOH solution and its alkaline mixture, and the concentration of the alkaline solution is 20-70%.

4. The pretreatment method for ICP testing of precious metal loading according to claim 1, characterized in that, In step one, covering the surface of the metal sheet with alkaline solution specifically involves brushing or directly immersing the surface of the metal sheet in an alkaline solution containing a thickener until the surface is completely covered with alkaline solution.

5. The pretreatment method for ICP testing of precious metal loading according to claim 1, characterized in that, In step two, the high-temperature roasting temperature is 380-480℃, and the high-temperature roasting time is 5-20 minutes.

6. The pretreatment method for ICP testing of precious metal loading according to claim 1, characterized in that, In step two, the oxidant is Na2O2, BaO2, or NaClO3.

7. The pretreatment method for ICP testing of precious metal loading according to claim 1, characterized in that, In step two, the oxidative roasting temperature is 700-850℃, and the roasting time is 2-4 hours.

8. The pretreatment method for ICP testing of precious metal loading according to claim 1, characterized in that, In step three, the mixed acidic solution is a mixture of hydrochloric acid and nitric acid, and the ratio of hydrochloric acid to nitric acid is (3-10):

1.

9. The pretreatment method for ICP testing of precious metal loading according to claim 1, characterized in that, In step three, the volume of the mixed acidic solution is 20-50 times the mass of the oxidant, the leaching temperature is 80-100℃, and the reaction time is 1-3 hours.

Images