Finished product platinum replacement and recovery method

Abstract

The invention relates to the technical field of metal recovery, and discloses a finished product platinum replacement recovery method which comprises the following steps: adding a platinum-containing solution into a reaction kettle, adding sodium hypochlorite to carry out oxidation reaction, adding iron powder to carry out platinum replacement, and filtering to obtain replacement slag; aqua regia is added into the replacement slag, so that platinum is completely dissolved; adding ammonium chloride into the dissolving solution to precipitate platinum in the form of ammonium chloroplatinate, filtering, and washing to obtain a precipitate; the precipitate is calcined at the temperature of 590-620 DEG C, a finished product platinum is obtained, the oxidation reaction time is 0.5-2 hours, the replacement reaction time is 1-4 hours, the oxidation reaction adopts a continuous stirring mode, and the stirring speed is controlled to be 100-400 rpm. Through accurate control of oxidation reaction time and temperature, introduction of an auxiliary oxidant, step-by-step addition of ammonium chloride and dynamic atmosphere regulation and control, the recovery rate and purity of platinum are significantly improved, and the problems of excessive oxidation, low precipitation purity, oxidation loss of platinum and the like in the prior art are effectively avoided.

Description

Technical Field

[0001] The invention relates to the technical field of metal recovery, and in particular to a method for recovering finished platinum by replacement. Background Art

[0002] As one of the precious metals, platinum is widely used in automotive catalysts, chemical reaction catalysts, electronic components and other fields. With the increasing demand for platinum, its recovery technology has become an important research direction. The recovery of platinum usually involves multiple steps such as redox reaction, dissolution precipitation and calcination, with the aim of extracting pure platinum from waste. However, there are still many problems to be solved in the existing platinum recovery technology, especially in improving the platinum recovery rate and the purity of finished platinum.

[0003] In the prior art, the core process of platinum recovery mostly adopts traditional methods such as oxidation reaction, replacement reaction, precipitation reaction and calcination. In the oxidation reaction stage, oxidants such as sodium hypochlorite are usually used to oxidize and dissolve platinum from solid waste. However, the time and temperature of these oxidation reactions are generally fixed, which makes it impossible to accurately control the degree of oxidation, thereby affecting the efficiency of platinum ion conversion. In the precipitation stage, ammonium chloride is often added at one time, resulting in low purity of platinum precipitation and easy formation of impurity precipitation. The calcination stage mostly uses a single atmosphere control, and excessively high temperature or inappropriate atmosphere often leads to oxidation or volatilization loss of platinum, affecting the recovery effect and the final purity of platinum. All of the above technologies have certain limitations.

[0004] Although the existing technology has made certain progress in platinum recovery, it still has obvious shortcomings in improving recovery efficiency and product purity. Some recovery technologies have imprecise time and temperature control in the oxidation reaction, which can easily lead to excessive oxidation or insufficient reduction of platinum, affecting the recovery rate. Secondly, the single addition of ammonium chloride cannot effectively avoid excessive complexation of platinum, resulting in low purity of the precipitate. Finally, the use of a single atmosphere during the calcination process does not fully consider the reduction and oxidation reactions of platinum, which can easily lead to volatilization and oxidation losses of platinum.

[0005] To this end, the present invention proposes a finished product platinum replacement recovery method to solve the deficiencies in the prior art. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for replacing and recovering finished platinum, which solves the problems of low platinum recovery efficiency and purity caused by inaccurate oxidation reaction control, unreasonable addition of ammonium chloride and single calcination atmosphere in some recovery technologies in the prior art.

[0007] To achieve the above objectives, the present invention is implemented by the following technical scheme: a finished product platinum replacement recovery method, comprising the following steps: S1. Add a platinum-containing solution with pH = 1 to a reaction kettle. After adding sodium hypochlorite for an oxidation reaction, add iron powder for platinum replacement, and filter to obtain a replacement residue. In this step, sodium hypochlorite acts as an oxidant and can oxidize platinum ions. During this process, the chlorine oxidant in sodium hypochlorite reacts with platinum ions, releasing oxygen and carrying out oxidation. The oxidized platinum is more likely to participate in the subsequent replacement reaction. Iron powder acts as a reducing agent to reduce platinum to metallic platinum. This reaction is an oxidation-reduction reaction, and the reduction degree of platinum directly affects the efficiency of the replacement process.

[0008] S2. Add aqua regia to the replacement residue to completely dissolve platinum. Platinum metal reacts with chloride ions and nitric acid oxidant in aqua regia to form chloroplatinate. Therefore, platinum changes from the solid metal state to the water-soluble chloroplatinate form. This transformation not only enables platinum to be further separated but also provides a basis for subsequent precipitation.

[0009] S3. Add ammonium chloride to the dissolution solution to precipitate platinum in the form of ammonium chloroplatinate, and filter and wash to obtain a precipitate. Ammonium chloride reacts with platinum ions to form ammonium chloroplatinate precipitate. This process occurs within a certain pH value range. When the concentration of platinum ions in the solution is sufficient, ammonium chloroplatinate precipitate begins to precipitate. During this process, platinum ions react with ammonium chloride to form ammonium chloroplatinate, and platinum precipitates in the form of a solid precipitate.

[0010] The precipitate usually has a high purity and large particles, and is easily separated by filtration. The temperature and pH value during the precipitation process are key factors affecting the precipitation efficiency.

[0011] Precipitation at a lower temperature is conducive to the formation of larger platinum particles, which helps improve the filtration effect and reduce the difficulty of subsequent treatment. Slowly cooling the temperature helps improve the crystallinity of the precipitate and reduce the dissolved platinum in the solution.

[0012] S4. Calcinate the precipitate at 590 °C - 620 °C to obtain the finished platinum.

[0013] In this reaction, ammonium chloroplatinate decomposes under high-temperature conditions to generate metallic platinum, hydrogen chloride, and ammonia. During this process, platinum precipitates in metallic form and enters the final finished platinum. Temperature is crucial for the reduction of platinum and the removal of chlorides. If the temperature is too low, platinum cannot be completely reduced, while too high a temperature may lead to the volatilization loss of platinum. Therefore, the calcination process needs to be strictly controlled between 590 °C and 610 °C to ensure the reduction of platinum and avoid the volatilization loss of platinum.

[0014] During the calcination process, a nitrogen or oxygen dilution atmosphere is used to control the reduction environment of the reaction. A nitrogen protective atmosphere is used at the initial stage of the reaction to reduce the oxidation of platinum. When the reaction reaches a certain temperature, it is switched to an oxygen dilution atmosphere to ensure the volatilization of hydrogen chloride and the complete decomposition of platinum chloride.

[0015] Preferably, the oxidation reaction time is 0.5 - 2 hours, the displacement reaction time is 1 - 4 hours. The oxidation reaction adopts a continuous stirring mode, and the stirring speed is controlled at 100 - 400 rpm. Samples are regularly taken during the reaction to detect the platinum ion concentration, so as to adjust the addition rate of sodium hypochlorite or iron powder.

[0016] In this step, sodium hypochlorite acts as an oxidant on platinum ions, oxidizing them to platinum. The rate of the reaction is affected by the concentration of sodium hypochlorite, temperature and reaction time. The optimization of the oxidation reaction time can be adjusted by monitoring the platinum ion concentration to ensure appropriate oxidation degree, thereby improving the displacement efficiency.

[0017] If the oxidation time is too short, the oxidation degree of platinum is insufficient, affecting the subsequent displacement. On the contrary, if the time is too long, it may lead to unnecessary side reactions.

[0018] Preferably, the oxidation reaction temperature is 20 - 50°C, the displacement reaction temperature is 15 - 40°C, the pH value is controlled at 2 - 4. The reaction process adopts a two-zone temperature control system, maintaining a low temperature in the oxidation stage and gradually increasing the temperature in the displacement stage.

[0019] Temperature has a significant impact on the rate of the oxidation reaction. A lower temperature helps the decomposition rate of sodium hypochlorite to be moderate, avoiding the generation of by-products caused by excessive oxidation. A lower temperature of 20 - 30°C can effectively oxidize platinum ions to platinum without excessive decomposition of sodium hypochlorite at too high a temperature. Preferably, hydrogen peroxide is further added as an auxiliary oxidant in the oxidation reaction, and a titration feeding control is adopted. The addition rate of hydrogen peroxide is controlled at 0.2 - 2 mL / min.

[0020] As an oxidant, hydrogen peroxide can provide more oxygen molecules at a lower temperature, thereby enhancing the oxidation ability of sodium hypochlorite. When hydrogen peroxide decomposes, it releases oxygen, further promoting the oxidation of platinum ions to platinum. Its addition can accelerate the oxidation reaction rate and ensure the complete conversion of platinum ions to platinum, thereby enhancing the effect of the displacement reaction.

[0021] Controlling the addition rate of hydrogen peroxide is crucial for the stability of the reaction. Too fast addition may lead to excessive oxidation, while too slow addition may not reach the required oxidation degree. The titration feeding control dynamically adjusts the addition rate of hydrogen peroxide by real-time monitoring of the platinum ion concentration, enabling the reaction to maintain an ideal oxidation level.

[0022] Preferably, the volume ratio of hydrochloric acid to nitric acid in the aqua regia is controlled at 2.5 - 3.5:1, the dissolution reaction temperature is 50 - 100 °C, the dissolution time is 0.5 - 3 hours. Among them, the final pH value of the dissolution solution is controlled at 0.5 - 1.5, and a stepwise acid addition strategy is adopted, that is, 50% - 70% of the volume of aqua regia is added first for preliminary dissolution, and the remaining aqua regia is gradually supplemented after the reaction is stable.

[0023] Aqua regia has strong oxidizing ability and can effectively oxidize platinum metal to platinum and react with chloride ions to form chloroplatinate. The acidity and oxidizing property of aqua regia provide the necessary conditions for the dissolution of platinum.

[0024] The stepwise acid addition strategy can prevent the generation of excessive by-products during the reaction, such as platinum chloride. After initially adding 50% - 70% of aqua regia, the dissolution reaction will be relatively mild. After the reaction tends to be stable, the remaining aqua regia is gradually added to avoid over-oxidation and side reactions.

[0025] Preferably, as a complexing agent, the mass fraction ratio of ammonium chloride is 0.2 - 1:1, and it is added in stages during the dissolution reaction process, that is, 20% - 40% of ammonium chloride is added at the beginning of the aqua regia reaction, and the remaining part is added when the reaction proceeds 40% - 60% to ensure the stability of the platinum complexing process and avoid the formation of insoluble by-products.

[0026] Ammonium chloride plays a role in complexing platinum ions during the dissolution process, enhancing the stability of platinum ions in the solution. Ammonium chloro complex ions form ammonium chloroplatinate with platinum. The formation of this complex enables platinum to dissolve more stably in the aqua regia solution and avoids the precipitation of platinum or the formation of insoluble by-products.

[0027] Preferably, the precipitation reaction temperature is 10 - 30 °C, the precipitation time is 0.5 - 2 hours, the pH value of the precipitation solution is controlled at 4 - 6, and the stirring rate is controlled during the precipitation process.

[0028] The temperature and pH during the precipitation process are the key factors determining the quality of platinum precipitation. A lower temperature helps the uniform precipitation of platinum particles and improves the crystallinity of the particles, reducing the filtration resistance. The pH value is controlled between 4 - 6 to ensure the stable precipitation of platinum in the form of ammonium chloroplatinate.

[0029] A suitable stirring rate helps ensure the uniform distribution of the precipitate in the solution and enhances the precipitation rate. Too fast stirring may result in too small precipitate particles, making it difficult to filter; too slow may result in incomplete precipitation.

[0030] Preferably, ammonium nitrate is added during the precipitation process to improve the platinum precipitation efficiency, and its mass fraction ratio is 0.1 - 1:1. Ammonium nitrate is added in a stepwise manner, that is, it is gradually added after 50% - 80% of ammonium chloride precipitation is completed, and constant stirring is maintained to enhance the precipitation rate.

[0031] Preferably, the calcination time is controlled at 2 to 6 hours, the calcination temperature is controlled at 590°C to 610°C, and a gradual heating mode is adopted during the calcination process, that is, the temperature is maintained at 200 to 300°C for preheating and dehydration for the first 30 to 60 minutes, and then the temperature is increased to the final target temperature at a rate of 5 to 10°C / min, and the constant temperature is maintained.

[0032] During the calcination process, the temperature and heating rate are controlled to ensure complete reduction of platinum and avoid volatilization loss of platinum. The lower temperature in the early stage helps to remove moisture and volatile chlorides, and the subsequent gradual heating can ensure that platinum is completely reduced to a metallic state.

[0033] Preferably, the calcination process is carried out in a diluted atmosphere of nitrogen and oxygen to control the calcination environment, and dynamic atmosphere regulation is adopted. 99.9% nitrogen is used for protection in the first 1 to 2 hours to reduce platinum oxidation, and when the temperature reaches 550 to 650°C, it is switched to a mixed atmosphere with an oxygen content of 10% to 20%.

[0034] During the calcination process, the initial use of nitrogen can prevent oxidation of platinum and protect platinum from the oxidizing effect of oxygen at high temperatures.

[0035] As the temperature increases, the use of a mixed atmosphere containing a small amount of oxygen can promote the removal of volatile by-products such as hydrogen chloride, while maintaining the reduced state of the platinum metal, ensuring that the final platinum product is high in purity and free of impurities.

[0036] The present invention provides a method for replacing and recovering finished platinum. It has the following beneficial effects: 1. The present invention adopts a strategy of precisely controlling the oxidation reaction time and the replacement reaction time to achieve the technical effect of optimizing the conversion efficiency of platinum ions. Different from the conventional fixed time or excessively long reaction time in the prior art, the present invention avoids excessive oxidation or incomplete reduction of platinum by dynamically adjusting the reaction time, thereby solving the problems of low recovery efficiency and large platinum loss.

[0037] 2. The present invention introduces hydrogen peroxide as an auxiliary oxidant in the oxidation process and adopts titration feeding control to achieve the effect of improving the oxidation rate and selectivity. Compared with the traditional method of using only sodium hypochlorite, the hydrogen peroxide-assisted oxidation of the present invention can effectively avoid the formation of by-products, while improving the oxidation efficiency and yield of platinum, and solving the problems of incomplete oxidation or excessive side reactions.

[0038] 3. The present invention adopts a strategy of adding ammonium chloride in steps to control the precipitation process of ammonium chloroplatinate, thereby achieving the effect of improving the purity and recovery rate of platinum precipitation. In the traditional method, the one-time addition of ammonium chloride easily leads to incomplete precipitation or the formation of impurity precipitation, while the present invention ensures that platinum ions fully react with ammonium chloride by adding in steps, thereby avoiding the formation of insoluble by-products.

[0039] 4. The present invention adopts dynamic atmosphere regulation during the calcination process, achieving the effect of improving the reduction efficiency and purity of platinum. Different from the method of using a single protective atmosphere in the prior art, the present invention uses a nitrogen protective atmosphere at the initial stage of calcination and gradually transitions to an oxygen mixed atmosphere, effectively avoiding the oxidation loss of platinum and ensuring the complete reduction of platinum, thereby improving the quality of the finished platinum. Brief Description of the Drawings

[0040] Figure 1 It is a process flow chart of the production process of the present invention. Detailed Embodiments

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0042] Please refer to the attached Figure 1 : Example 1: Oxidation and displacement reaction: Take 1000 mL of platinum-containing liquid, adjust the pH value to 1, add 6.6 g of sodium hypochlorite, and the mass ratio of sodium hypochlorite to platinum is 3:1. Stir and react for 1 hour. During the oxidation reaction, the temperature of the solution is maintained at 25 °C.

[0043] Then add 4.0 g of iron powder, and the mass ratio of iron powder to platinum is 2:1. The displacement reaction continues for 3 hours, the temperature is controlled at 30 °C, and the platinum ion concentration is sampled and detected every 30 minutes. Adjust the addition amount of iron powder according to the measured platinum concentration.

[0044] Dissolution with aqua regia: After filtering the displacement residue, add 25 mL of aqua regia, and the volume ratio of hydrochloric acid to nitric acid in aqua regia is 3:1. The dissolution reaction lasts for 1 hour, the dissolution temperature is maintained at 65 °C, and the pH value of the final dissolution solution is controlled at about 1.0.

[0045] Addition and precipitation of ammonium chloride: Add 3.5 g of ammonium chloride to the dissolution solution, and the mass ratio of ammonium chloride to platinum is 0.5:1 to form ammonium chloroplatinate precipitate. The precipitation reaction is maintained at 25 °C for 1.5 hours, and the pH value is controlled at 4.5. The stirring rate is 150 rpm to ensure uniform precipitation.

[0046] Calcination: After the precipitate is filtered and washed, it is placed in an electric furnace. The calcination temperature is raised from room temperature to 600 °C. This temperature is maintained for 3 hours, and the rate of temperature increase is 5 °C per minute. A nitrogen protective atmosphere is used during the calcination process. 99.9% nitrogen is introduced in the first hour, and then it is switched to a mixed atmosphere with 10% oxygen content. The final finished product is platinum.

[0047] Example 2: Oxidation and displacement reaction: Take 1500 mL of platinum-containing solution, adjust the pH value to 1, add 9 g of sodium hypochlorite. The mass ratio of sodium hypochlorite to platinum is 3:1. The oxidation reaction is carried out for 1 hour, and the reaction temperature is controlled at 28 °C. During this process, the color of the solution gradually fades, indicating that the oxidation reaction is completed.

[0048] Add 5 g of iron powder. The mass ratio of iron powder to platinum is 2:1. The reaction is carried out for 3 hours, and the temperature is maintained at 35 °C. 2 g of iron powder is added during the mid-stage of the reaction to ensure complete displacement of platinum.

[0049] Dissolution in aqua regia: After the residue after displacement is filtered, add 40 mL of aqua regia to it. The volume ratio of hydrochloric acid to nitric acid in aqua regia is 3:1. The reaction temperature is 80 °C, and the reaction time is 2 hours. The pH value of the final dissolution solution is controlled at 1.2.

[0050] Addition of ammonium chloride and precipitation: Add 4.0 g of ammonium chloride to the dissolution solution. The mass ratio of ammonium chloride to platinum is 0.8:1, so that platinum precipitates in the form of ammonium hexachloroplatinate. The precipitation reaction temperature is 20 °C and lasts for 2 hours. The pH value of the precipitation solution is controlled at 5.0. A stirring rate of 180 rpm is used to ensure uniform precipitation of platinum.

[0051] Calcination: After the precipitate is filtered, it is placed in an electric furnace for calcination. The initial temperature is preheated to 200 °C and maintained for 30 minutes. Then the temperature is raised to 620 °C and kept at a constant temperature for 4 hours. The heating rate is 6 °C per minute. A nitrogen protective atmosphere is used during the calcination process, and it is switched to an oxygen-containing atmosphere at the end of the calcination, and the oxygen concentration is controlled at 12%.

[0052] Example 3: Oxidation and displacement reaction: Take 2000 mL of platinum-containing solution, adjust the pH value to 1, add 7.5 g of sodium hypochlorite. The mass ratio of sodium hypochlorite to platinum is 3:1. The oxidation reaction is carried out for 1.5 hours, and the reaction temperature is controlled at 30 °C.

[0053] Add 4.5 g of iron powder. The mass ratio of iron powder to platinum is 2:1. The displacement reaction is carried out for 3 hours, the temperature is set at 32 °C, and the platinum ion concentration is monitored every 30 minutes, and the iron powder addition rate is adjusted in a timely manner.

[0054] Dissolution in aqua regia: After filtering the replacement slag, 35 mL of aqua regia was added. The volume ratio of hydrochloric acid to nitric acid was 3:1. The temperature was maintained at 85 °C, and the reaction time was 1.5 hours. The pH value of the final dissolution solution was 1.0.

[0055] Addition of ammonium chloride and precipitation: 4.5 g of ammonium chloride was added to the dissolution solution. The mass ratio of ammonium chloride to platinum was 1:1, causing platinum to precipitate as ammonium hexachloroplatinate. The precipitation reaction was carried out at 15 °C for 2 hours, with the pH value controlled at 5.5. A stirring rate of 160 rpm was used during the precipitation process.

[0056] Calcination: After the precipitate was filtered and washed, it was placed in an electric furnace for calcination. The calcination time was 3 hours, and the temperature was gradually increased to 610 °C at a heating rate of 5 °C / minute. A nitrogen protection atmosphere was used in the first hour of calcination, and then it was switched to an oxygen-containing atmosphere with an oxygen concentration of 15%.

[0057] Example 4: Oxidation and replacement reaction: 1200 mL of platinum-containing solution was taken, the pH value was adjusted to 1, and 6 g of sodium hypochlorite was added. The mass ratio of sodium hypochlorite to platinum was 3:1. The oxidation reaction was carried out for 1 hour, and the temperature was maintained at 27 °C.

[0058] Subsequently, 3.6 g of iron powder was added. The mass ratio of iron powder to platinum was 2:1. The replacement reaction was carried out for 2.5 hours, the temperature was maintained at 33 °C, and samples were taken regularly to adjust the amount of iron powder added according to the platinum ion concentration.

[0059] Dissolution in aqua regia: After filtering the replacement slag, 30 mL of aqua regia was added. The volume ratio of hydrochloric acid to nitric acid in aqua regia was 3:1. The reaction temperature was set at 75 °C, the reaction lasted for 1 hour, and the pH value was controlled at 1.1.

[0060] Addition of ammonium chloride and precipitation: 3.2 g of ammonium chloride was added to the dissolution solution. The mass ratio of ammonium chloride to platinum was 0.8:1, causing platinum to precipitate in the form of ammonium hexachloroplatinate.

[0061] The precipitation process was carried out at 25 °C for 1.5 hours, with the pH value maintained at 5.0 and the stirring rate of 140 rpm.

[0062] Calcination: After the precipitate was filtered, it was calcined. The temperature was controlled at 600 °C, the calcination time was 2.5 hours, and the calcination process adopted a stepwise heating mode with a heating rate of 4 °C / minute. A nitrogen protection atmosphere was used in the first hour, and when the temperature reached 450 °C, it was switched to a mixed atmosphere with an oxygen content of 12%.

[0063] Example 5: Oxidation and replacement reaction: 1000 mL of platinum-containing solution was taken, the pH value was adjusted to 1, and 5.5 g of sodium hypochlorite was added. The mass ratio of sodium hypochlorite to platinum was 3:1. The oxidation reaction lasted for 1 hour, and the reaction temperature was maintained at 24 °C.

[0064] Subsequently, 3.2 g of iron powder was added. The mass ratio of iron powder to platinum was 2:1, and a displacement reaction was carried out for 3 hours at a temperature controlled at 32 °C. The amount of iron powder added was dynamically adjusted by online measurement of the platinum ion concentration.

[0065] Dissolution with aqua regia: After filtering the displacement residue, 30 mL of aqua regia was added. The volume ratio of hydrochloric acid to nitric acid in aqua regia was 3:1. The dissolution reaction temperature was set at 60 °C, and the reaction time was 1.5 hours. The pH value of the final dissolution solution was 1.2.

[0066] Addition of ammonium chloride and precipitation: 3.8 g of ammonium chloride was added to the dissolution solution. The mass ratio of ammonium chloride to platinum was 1:1, causing platinum to precipitate in the form of ammonium hexachloroplatinate. The precipitation process was carried out at 20 °C for 1 hour, and the pH value was controlled at 4.8. The stirring rate during the precipitation process was 160 rpm to ensure uniform precipitation of platinum.

[0067] Calcination: After filtering the precipitate, it was placed in an electric furnace for calcination. The calcination temperature was gradually raised to 605 °C and maintained at this temperature for 3 hours.

[0068] The heating rate was 6 °C per minute. A nitrogen protection atmosphere was used in the initial 1 hour. After the temperature reached 450 °C, it was switched to a mixed atmosphere with 12% oxygen content to ensure complete reduction of platinum and removal of chlorides.

[0069] Comparative example: Comparative example 1: Oxidation and displacement reaction: 1000 mL of platinum-containing solution was taken, the pH value was adjusted to 1, 6.6 g of sodium hypochlorite was added. The mass ratio of sodium hypochlorite to platinum was 3:1, and the oxidation reaction was carried out for 1 hour at a temperature of 25 °C.

[0070] 5 g of iron powder was added. The mass ratio of iron powder to platinum was 2:1, and the displacement reaction continued for 3 hours at a temperature maintained at 30 °C. The platinum ion concentration was detected every 30 minutes, and the amount of iron powder added was adjusted in a timely manner.

[0071] Dissolution with aqua regia: After filtering the displacement residue, 30 mL of aqua regia was added. The volume ratio of hydrochloric acid to nitric acid was 3:1. The dissolution reaction temperature was 70 °C, the dissolution time was 1.5 hours, and the pH value was controlled at 1.0.

[0072] Addition of ammonium chloride and precipitation: 3.5 g of ammonium chloride was added to the dissolution solution. The mass ratio of ammonium chloride to platinum was 0.8:1. The precipitation reaction was carried out at 20 °C for 1.5 hours, and the pH value was controlled at 5.0.

[0073] Calcination: After the precipitate is filtered, it is placed in an electric furnace for calcination. The temperature is gradually raised to 620 °C and maintained for 3 hours, with a heating rate of 5 °C / minute. During the calcination process, a protective atmosphere of 99.9% nitrogen is used for the first 1 hour, and then the atmosphere is switched to an atmosphere with an oxygen concentration of 10%.

[0074] Comparative Example 2: Oxidation and displacement reaction: Take 1500 mL of platinum-containing solution, adjust the pH value to 1, add 9 g of sodium hypochlorite, and the mass ratio of sodium hypochlorite to platinum is 3:1. The oxidation reaction time is 1 hour and the temperature is 27 °C.

[0075] Subsequently, add 5 g of iron powder, and the mass ratio of iron powder to platinum is 2:1. The reaction time is 3 hours, the temperature is set at 34 °C, and the platinum ion concentration is detected every 30 minutes during the reaction process.

[0076] Dissolution in aqua regia: After the displacement residue is filtered, add 40 mL of aqua regia, and the volume ratio of hydrochloric acid to nitric acid is 3:1. The dissolution temperature is 75 °C, the reaction lasts for 2 hours, and the pH value is controlled at 1.3.

[0077] Addition of ammonium chloride and precipitation: Add 4.0 g of ammonium chloride to the dissolution solution, and the mass ratio of ammonium chloride to platinum is 1:1. The precipitation reaction is carried out at 25 °C for 2 hours, and the pH value is controlled at 5.2.

[0078] Calcination: After the precipitate is filtered, it is calcined. The calcination temperature is raised from room temperature to 610 °C and maintained for 3 hours, with a heating rate of 7 °C / minute.

[0079] During the calcination process, a 99.9% nitrogen atmosphere is used for the first 2 hours, and then it is switched to a mixed atmosphere with an oxygen content of 13%.

[0080] Comparative Example 3: Oxidation and displacement reaction: Take 1800 mL of platinum-containing solution, adjust the pH value to 1, add 8 g of sodium hypochlorite, and the mass ratio of sodium hypochlorite to platinum is 3:1. The oxidation reaction time is 1 hour and the temperature is set at 26 °C.

[0081] Add 5.0 g of iron powder, and the mass ratio of iron powder to platinum is 2:1. The reaction proceeds for 3 hours, the temperature is controlled at 36 °C, and the platinum ion concentration is detected every 30 minutes to control the reaction progress.

[0082] Dissolution in aqua regia: After the displacement residue is filtered, add 30 mL of aqua regia, and the volume ratio of hydrochloric acid to nitric acid is 3:1. The dissolution reaction temperature is 85 °C, the reaction lasts for 1.5 hours, and the final pH value is 1.0.

[0083] Addition of ammonium chloride and precipitation: Add 4.2 g of ammonium chloride to the dissolution solution, and the mass ratio of ammonium chloride to platinum is 1:1. The precipitation process is carried out at 20 °C for 1 hour, and the pH value is controlled at 5.5.

[0084] Calcination: After filtration, the precipitate is placed in an electric furnace for calcination. The temperature is raised from room temperature to 615 °C, the calcination lasts for 3 hours, and the heating rate is 5 °C / minute.

[0085] At the initial stage, a nitrogen protection atmosphere is used. After the temperature reaches 450 °C, it is switched to an atmosphere with an oxygen content of 14%.

[0086] Comparative Example 4: Oxidation and displacement reaction: Take 1000 mL of platinum-containing solution, adjust the pH value to 1, add 6.0 g of sodium hypochlorite, and the mass ratio of sodium hypochlorite to platinum is 3:1. The oxidation reaction proceeds for 1 hour, and the temperature is controlled at 26 °C.

[0087] Add 4.0 g of iron powder, and the mass ratio of iron powder to platinum is 2:1. The reaction time is 2.5 hours, and the temperature is maintained at 33 °C.

[0088] Dissolution with aqua regia: After the displacement residue is filtered, add 30 mL of aqua regia. The volume ratio of hydrochloric acid to nitric acid is 3:1. The dissolution reaction temperature is set at 80 °C, the reaction lasts for 1 hour, and the pH value is adjusted to 1.3.

[0089] Addition and precipitation of ammonium chloride: Add 3.5 g of ammonium chloride to the dissolution solution. The mass ratio of ammonium chloride to platinum is 1:1. The precipitation reaction is carried out at 25 °C, the precipitation time is 2 hours, and the pH value is controlled at 4.7.

[0090] Calcination: After the precipitate is filtered, it is placed in an electric furnace for calcination. The calcination temperature is raised from room temperature to 605 °C, and kept at a constant temperature for 3 hours. The heating rate is 6 °C / minute.

[0091] During the calcination process, a nitrogen protection atmosphere is used in the first 1 hour, and then it is switched to a mixed atmosphere with an oxygen content of 10%.

[0092] Comparative Example 5: Oxidation and displacement reaction: Take 1000 mL of platinum-containing solution, adjust the pH value to 1, add 6.0 g of sodium hypochlorite, and the mass ratio of sodium hypochlorite to platinum is 3:1. The oxidation reaction lasts for 1 hour, and the temperature is 24 °C.

[0093] Add 4.2 g of iron powder, and the mass ratio of iron powder to platinum is 2:1. Carry out the displacement reaction. The reaction time is 3 hours, and the temperature is controlled at 32 °C.

[0094] Dissolution with aqua regia: After the displacement residue is filtered, add 35 mL of aqua regia. The volume ratio of hydrochloric acid to nitric acid is 3:1. The dissolution reaction is carried out at 80 °C, the reaction time is 2 hours, and the pH value is controlled at 1.1.

[0095] Addition of ammonium chloride and precipitation: 3.8 g of ammonium chloride was added to the dissolution solution. The mass ratio of ammonium chloride to platinum was 1:1. The precipitation reaction was carried out at 20 °C for 1 hour, and the pH value was controlled at 5.2.

[0096] Calcination: After the precipitate was filtered, it was calcined. The temperature was raised from room temperature to 610 °C and kept at a constant temperature for 3 hours. The heating rate was 6 °C / minute.

[0097] During the calcination process, a nitrogen protection atmosphere was used in the first hour, and then it was switched to a mixed atmosphere with an oxygen content of 12%.

[0098] Comparative experiment: Experiment 1: Comparative experiment on oxidation reaction time and displacement reaction time This experiment aims to verify the optimization effect of the present invention by comparing the effects of oxidation reaction time and displacement reaction time on the platinum recovery efficiency. In the experiment, the difference between Example 1 and Comparative Example 1 was only in the length of the oxidation reaction time. The experimental steps are as follows: Oxidation and displacement reaction: 1000 mL of platinum-containing solution was taken, and the pH value was adjusted to 1.

[0099] 6.6 g of sodium hypochlorite was added to the solution. The mass ratio of sodium hypochlorite to platinum was 3:1, and it was stirred and oxidized.

[0100] In Example 1, the oxidation reaction lasted for 1 hour; in Comparative Example 1, the oxidation reaction time was extended to 1.5 hours. The reaction temperature was maintained at 25 °C.

[0101] After the oxidation was completed, 5 g of iron powder was added to the solution. The mass ratio of iron powder to platinum was 2:1, and the displacement reaction was carried out for 3 hours at a temperature of 30 °C.

[0102] Samples were taken every 30 minutes to detect the concentration of platinum ions to judge the reaction progress.

[0103] Filtration and dissolution: After the reaction was completed, the iron powder was filtered off to obtain a platinum-containing solution.

[0104] The solution was dissolved after acid treatment. Ammonium chloride was added to precipitate platinum according to the foregoing method.

[0105] Calcination and analysis: After the precipitate was filtered, it was calcined in an electric furnace. The temperature was raised from room temperature to 600 °C and kept at a constant temperature for 3 hours.

[0106] The heating rate was 5 °C / minute, and a nitrogen protection atmosphere was used. Later, it was switched to a mixed atmosphere with an oxygen content of 10%.

[0107] Finally, the recovery rate of platinum was determined by a spectrometer, ICP-OES, and the purity of the finished platinum was analyzed by X-ray diffraction, XRD.

[0108] Experimental data: Effect of oxidation reaction time and displacement reaction time on platinum recovery rate and purity Experimental summary: When the oxidation reaction time is 1 hour, Example 1 shows a relatively high platinum recovery rate and purity, reflecting the effective oxidation degree of platinum during the oxidation process and the optimized control of platinum ion concentration. When the oxidation reaction time is extended to 1.5 hours, as in Comparative Example 1, the oxidation degree is too high and the platinum ion concentration also increases to a certain extent. Although the displacement reaction time is the same, the higher platinum ion concentration leads to a decrease in the efficiency of the displacement reaction, thus affecting the platinum recovery rate and the purity of the finished platinum. This also indicates that during the oxidation process, too long oxidation time not only fails to further improve the oxidation effect, but may also lead to the instability of platinum ion concentration and affect the efficiency of subsequent reactions.

[0109] It should be noted that in the experiment, the platinum recovery rate of Example 1 is generally higher than that of Comparative Example 1, which may be related to the generation of by-products, incomplete oxidation or increased reduction difficulty of platinum caused by too long oxidation reaction time. Too long oxidation time leads to an increase in platinum ion concentration, which hinders the efficiency of the subsequent displacement reaction. This phenomenon is the main reason for the lower platinum recovery rate in Comparative Example 1 of the experiment.

[0110] Experiment 2: Comparative experiment on the dissolution temperature of aqua regia Experiment description: This experiment aims to study the effect of the dissolution temperature of aqua regia on the dissolution efficiency of platinum and the purity of subsequent precipitation. In the experiment, we compared the platinum recovery effects of Example 2 and Comparative Example 2 at different dissolution temperatures. The specific steps are as follows: Oxidation and displacement reaction: Take 1500 mL of platinum-containing solution, adjust the pH value to 1, add 9 g of sodium hypochlorite, and the mass ratio of sodium hypochlorite to platinum is 3:1. Stir and carry out the oxidation reaction. The oxidation time is set to 1 hour, and the reaction temperature is maintained at 27 °C.

[0111] Subsequently, add 5 g of iron powder, and the mass ratio of iron powder to platinum is 2:1, and carry out the displacement reaction. The displacement reaction time is 3 hours, and the temperature is controlled at 34 °C.

[0112] Sample every 30 minutes to detect the platinum ion concentration to judge the reaction progress.

[0113] Dissolution in aqua regia: After the reaction is completed, filter out the iron powder to obtain the displacement residue. Add the displacement residue to aqua regia, and the volume of aqua regia is set to 40 mL, and the volume ratio of hydrochloric acid to nitric acid is 3:1.

[0114] For Example 2, the dissolution temperature is controlled at 75 °C; for Comparative Example 2, the dissolution temperature is controlled at 80 °C. The dissolution time is set to 2 hours, and the pH value of the dissolution solution is controlled at 1.3.

[0115] Ammonium chloride precipitation: After the dissolution solution is cooled, 4.0 g of ammonium chloride is added to the solution. The mass ratio of ammonium chloride to platinum is 1:1, causing platinum to precipitate in the form of ammonium chloroplatinate. The precipitation process is carried out at 25 °C, the precipitation time is 2 hours, and the pH value is controlled at 5.2.

[0116] Calcination and analysis: After the precipitate is filtered, it is calcined in an electric furnace. The temperature is gradually raised to 610 °C and kept at a constant temperature for 3 hours. The heating rate is 6 °C / minute. During the calcination process, a 99.9% nitrogen protective atmosphere is used in the first hour, and then switched to a mixed atmosphere with an oxygen content of 12% in the later stage.

[0117] Finally, the recovery rate of platinum is determined by ICP-OES, and the purity of the finished platinum is analyzed by XRD.

[0118] Experimental data: Effect of aqua regia dissolution temperature on platinum recovery rate and purity Experimental summary: The experimental results show that a higher aqua regia dissolution temperature, 80 °C compared to 75 °C, although accelerating the dissolution rate of platinum, performs poorly in terms of platinum recovery rate and purity. The platinum recovery rate in Comparative Example 2 is significantly lower than that in Example 2, indicating that although the increase in dissolution temperature accelerates the dissolution process, it may also lead to the formation of more by-products or too high a concentration of platinum ions, thereby affecting the efficiency of the subsequent precipitation reaction. This result is consistent with the mechanism analysis. A higher temperature may promote the dissolution of more impurities, thus affecting the selective dissolution and precipitation of platinum.

[0119] During the experiment, the platinum recovery rate in Example 2 is higher and the purity of the finished platinum is also higher, indicating that the fine adjustment of temperature has a non-negligible impact on the dissolution and precipitation processes. By controlling the dissolution temperature at 75 °C, the side effects caused by too high a temperature can be effectively avoided, enabling platinum to be efficiently dissolved in a shorter time without generating more unnecessary by-products due to too high a temperature.

[0120] This phenomenon also suggests the relationship between temperature and chemical reaction equilibrium in the platinum recovery process. Although a higher dissolution temperature increases the concentration of platinum ions, if not effectively controlled, it may lead to unsatisfactory precipitation effects, thereby affecting the final platinum recovery rate and purity. Therefore, in practical applications, an appropriate temperature range should be maintained to obtain the optimal reaction effect and avoid the negative impacts brought by too high a temperature.

[0121] Experiment 3: Comparative experiment of ammonium chloride addition amount Experimental description: This experiment designed a comparative experiment of different ammonium chloride addition amounts to explore the effect of ammonium chloride addition amount on platinum precipitation efficiency and purity. The experiment compared the different ammonium chloride addition strategies in Example 3 and Comparative Example 3 to analyze their effects on platinum recovery. The specific experimental steps are as follows: Oxidation and replacement reaction: Take 1500 mL of platinum-containing solution, adjust the pH value to 1, add 9 g of sodium hypochlorite, the mass ratio of sodium hypochlorite to platinum is 3:1, stir and carry out oxidation reaction, the oxidation time is set to 1 hour, and the temperature is maintained at 27°C.

[0122] Then, 5 g of iron powder was added, with a mass ratio of iron powder to platinum of 2:1, and a replacement reaction was carried out. The replacement reaction time was 3 hours, and the temperature was controlled at 34°C. During the reaction, samples were taken regularly to detect the platinum ion concentration.

[0123] Ammonium chloride precipitation: After the reaction is complete, filter out the iron powder and add aqua regia to dissolve the solution.

[0124] In the dissolving solution, 4.5 g of ammonium chloride was added in Example 3, the mass ratio of ammonium chloride to platinum was 1:1, and it was added twice, 2 g was added for the first time and 2.5 g was added for the second time; 3.5 g of ammonium chloride was added in Comparative Example 3, the mass ratio of ammonium chloride to platinum was 1:1, and it was added all at once.

[0125] The precipitation process was carried out at 25°C for 2 hours, the pH value was controlled at 5.2, and the stirring rate was 160 rpm.

[0126] Calcination and analysis: After filtering, the precipitate was placed in an electric furnace for calcination. The calcination temperature was set to 610°C, the calcination duration was 3 hours, and the heating rate was 5°C / min.

[0127] During the calcination process, a nitrogen protective atmosphere was used for the first hour, and then switched to a mixed atmosphere with an oxygen content of 12%. After the calcination, the recovery rate and purity of platinum were analyzed by ICP-OES.

[0128] Experimental data: Effect of ammonium chloride addition method on platinum recovery and purity Experimental summary: The experimental results show that the stepwise addition of ammonium chloride significantly improves the platinum recovery rate and the purity of the finished platinum. Compared with the comparative example 3 in which the ammonium chloride is added all at once, the recovery rate of the example 3 is significantly improved.

[0129] The stepwise addition of ammonium chloride contributes to the stable formation of ammonium chloroplatinate, reduces the risk of excessive complexation of platinum ions, and thus improves the precipitation efficiency and purity of platinum.

[0130] This result verifies the key role of the addition method of ammonium chloride in platinum recovery and is also consistent with the mechanism analysis of the present invention.

[0131] By adding in steps, the contact between ammonium chloride and platinum ions is more uniform, making it easier for platinum to form a precipitate-complex in the solution.

[0132] On the contrary, adding ammonium chloride all at once may cause some platinum ions to fail to fully participate in the complexation reaction, reducing the precipitation purity.

[0133] Adding ammonium chloride in steps can effectively avoid the problem of incomplete complexation that may be caused by adding all at once, thus making the precipitation of platinum more pure and greatly improving the platinum recovery rate and purity.

[0134] When the concentration of platinum ions in the solution is low, adding in steps can prevent the excessive dissolution of platinum or the formation of by-products, which also coincides with the mild reaction conditions mentioned in the present invention.

[0135] Adding too much ammonium chloride all at once will cause the concentration of platinum in the solution to be too high, which may instead form insoluble by-products and reduce the recovery efficiency.

[0136] Judging from the experimental data, the platinum recovery rate and purity in Example 3 are generally higher than those in Comparative Example 3, and the XRD peaks are sharper, indicating that the platinum crystal structure is more regular and the crystallinity of the precipitate is higher.

[0137] Through this experiment, the optimization effect of adding ammonium chloride in steps on platinum recovery and purity can be further confirmed, which also provides an experimental basis for the technical solution of the present invention and verifies its innovation and practical feasibility.

[0138] Experiment 4: Comparative experiment on calcination temperature Experiment description: This experiment verifies the key role of the calcination temperature in the reduction and purity of the final platinum product by comparing the effects of different calcination temperatures on the platinum recovery rate and purity.

[0139] Example 4 and Comparative Example 4 were designed in the experiment, with a focus on comparing different settings of the calcination temperature. The specific experimental steps are as follows: Oxidation and displacement reaction: Take 1800 mL of platinum-containing solution, adjust the pH value to 1, add 8 g of sodium hypochlorite, and the mass ratio of sodium hypochlorite to platinum is 3:1. Carry out the oxidation reaction for 1 hour at a temperature controlled at 26°C.

[0140] Then add 5.2 g of iron powder, and the mass ratio of iron powder to platinum is 2:1, and carry out the displacement reaction; The reaction time is 3 hours, the temperature is set at 35°C, and the platinum ion concentration is sampled and detected every 30 minutes.

[0141] Ammonium chloride precipitation: After the reaction is completed, the iron powder is filtered off and the solution is dissolved. 4.5 g of ammonium chloride is added, and the mass ratio of ammonium chloride to platinum is 1:1, and the precipitation reaction is carried out.

[0142] In Example 4, ammonium chloride was added in two portions, 2.5 g in the first stage and 2 g in the second stage; in Comparative Example 4, 4.5 g was added all at once.

[0143] The precipitation process was carried out at 25 °C, the precipitation time was 2 hours, the pH value was controlled at 5.2, and the stirring rate was 150 rpm.

[0144] Calcination and analysis: After the precipitate was filtered, it was placed in an electric furnace for calcination; in Example 4, the calcination temperature was set at 610 °C, the calcination duration was 3 hours, and the heating rate was 5 °C / min.

[0145] In Comparative Example 4, the calcination temperature was set at 620 °C and the heating rate was 6 °C / min.

[0146] During the calcination process, in Example 4, a nitrogen protection atmosphere was used in the first 1 hour, and then switched to a mixed atmosphere with an oxygen content of 12%; in Comparative Example 4, a pure nitrogen protection atmosphere was used in the first 2 hours, and the atmosphere was switched to an atmosphere with an oxygen content of 12% when the temperature reached 450 °C.

[0147] Experimental data: Effect of calcination temperature on platinum recovery rate and purity Experimental summary: From the experimental data, the calcination temperature of Example 4 was set at 610 °C, which had better performance in terms of recovery rate and purity compared to 620 °C in Comparative Example 4. Too high a calcination temperature, especially the high temperature of 620 °C, may cause partial volatilization of platinum metal or excessive oxidation of platinum in an oxygen atmosphere, thereby reducing the recovery rate and purity of platinum. This result is consistent with the mechanism analysis. Excessive increase in temperature will cause partial volatilization loss of platinum, affecting the recovery efficiency. Especially at high temperatures, platinum has stronger volatility and the oxidation reaction rate of platinum metal is faster, which makes the platinum lost during the recovery process unable to be effectively recovered.

[0148] On the other hand, the calcination conditions at 610 °C in Example 4 not only ensured the reduction of platinum metal but also avoided excessive oxidation or volatilization loss. Compared with the high temperature in Comparative Example 4, the lower calcination temperature can effectively reduce side reactions and ensure the recovery efficiency and purity of platinum.

[0149] Generally speaking, the volatilization and oxidation loss of platinum metal caused by excessive temperature indicate that the calcination process requires precise control. Excessive calcination temperature will accelerate the volatilization of platinum, while appropriate calcination temperature can effectively maintain the purity and recovery rate of platinum. Therefore, optimizing the calcination temperature is a key step to improve the platinum recovery efficiency and the purity of the finished platinum.

[0150] Experiment 5: Comparative Experiment on Atmosphere Control Experiment Description: This experiment aims to study the effects of different calcination atmospheres on the recovery rate and purity of platinum, especially the role of the mixed atmosphere of nitrogen and oxygen. The main difference between Example 5 and Comparative Example 5 lies in the control of the atmosphere during the calcination process. The specific experimental steps are as follows: Oxidation and Displacement Reaction: Take 1200 mL of platinum-containing solution, adjust the pH value to 1, add 6.0 g of sodium hypochlorite, and the mass ratio of sodium hypochlorite to platinum is 3:1. Carry out the oxidation reaction for 1 hour at a temperature controlled at 24 °C.

[0151] Subsequently, add 4.0 g of iron powder, and the mass ratio of iron powder to platinum is 2:1. Carry out the displacement reaction for 2.5 hours at a temperature set at 32 °C. During the reaction process, the platinum ion concentration is detected every 30 minutes.

[0152] Ammonium Chloride Precipitation: After the displacement reaction is completed, filter out the iron powder and dissolve the solution. Add 3.8 g of ammonium chloride to the dissolved solution, and the mass ratio of ammonium chloride to platinum is 1:1. Carry out the precipitation reaction.

[0153] In Example 5, ammonium chloride is added in two stages. 2 g is added in the first stage and 1.8 g is added in the second stage; while in Comparative Example 5, 3.8 g of ammonium chloride is added at one time.

[0154] The precipitation process is carried out at 25 °C for 2 hours, with the pH value controlled at 4.8 and the stirring rate at 150 rpm.

[0155] Calcination and Analysis: After the precipitate is filtered, it is placed in an electric furnace for calcination. The calcination temperature in Example 5 is set at 600 °C, the calcination time is 3 hours, and the heating rate is 5 °C / minute.

[0156] During the calcination process, a nitrogen protection atmosphere is used in the first hour, and then it is switched to a mixed atmosphere with an oxygen content of 10%.

[0157] In Comparative Example 5, the calcination temperature is set at 610 °C, the heating rate is 6 °C / minute, a 99.9% nitrogen atmosphere is used in the first 2 hours, and it is switched to a mixed atmosphere with an oxygen content of 12% when the temperature reaches 450 °C.

[0158] Experimental Data: Effect of Atmosphere Control on Platinum Recovery Rate and Purity Summary of experiments: From the experimental data, the dynamic regulation of the nitrogen-oxygen mixed atmosphere in Example 5 can significantly improve the platinum recovery rate and the purity of the finished platinum compared with the use of a single atmosphere in Comparative Example 5. The lower oxygen concentration can effectively avoid the oxidation of platinum. Especially when using a nitrogen protection atmosphere at the initial stage of the calcination process, the oxidation loss of platinum is reduced, thereby improving the recovery rate and purity of platinum. This is consistent with the mechanism analysis. The nitrogen protection atmosphere helps platinum not to be oxidized under high-temperature conditions. At the same time, as the temperature rises, switching to an atmosphere with a lower oxygen content helps to promote the reduction reaction of platinum and reduce the generation of by-products.

[0159] On the other hand, the calcination temperature in Comparative Example 5 is relatively high, and the protection time of the nitrogen atmosphere during the calcination process is too long, resulting in the hindrance of the platinum reduction process and partial oxidation of the platinum metal, both the recovery rate and the purity are affected. The too-high calcination temperature and the too-long nitrogen protection atmosphere may lead to incomplete redox reactions of platinum, thereby reducing the final recovery efficiency of platinum.

[0160] Therefore, reasonable atmosphere control is crucial during the calcination process. By optimizing the dynamic switching of nitrogen and oxygen in Example 5, not only is the platinum reduction process ensured to proceed smoothly, but also the oxidation loss of platinum is effectively avoided. This experimental result further verifies the importance of atmosphere control in improving the recovery rate and the purity of the finished platinum during the platinum recovery process.

Claims

1. A method for recycling platinum in finished products, characterized in that, It includes the following steps: Add the platinum-containing solution into the reaction kettle, add sodium hypochlorite for oxidation reaction, add iron powder for platinum replacement, and filter to obtain the replacement residue; Add aqua regia to the replacement residue to completely dissolve platinum; Add ammonium chloride to the solution to precipitate platinum in the form of ammonium chloroplatinate, and filter and wash to obtain the precipitate; Calcine the precipitate at 590°C - 620°C to obtain the finished platinum.

2. The finished product platinum replacement recovery method according to claim 1, wherein The oxidation reaction time is 0.5 - 2 hours, the replacement reaction time is 1 - 4 hours, the oxidation reaction adopts a continuous stirring mode, the stirring speed is controlled at 100 - 400 rpm, and the platinum ion concentration is regularly sampled and detected during the reaction to adjust the addition rate of sodium hypochlorite or iron powder.

3. A finished product platinum replacement and recovery method according to claim 1, characterized in that The oxidation reaction temperature is 20 - 50°C, the replacement reaction temperature is 15 - 40°C, the pH value is controlled at 2 - 4, and the reaction process adopts a two-zone temperature control system, maintaining a low temperature in the oxidation stage and gradually increasing the temperature in the replacement stage.

4. A method for recycling and recovering finished platinum by displacement according to claim 1, characterized in that, In the oxidation reaction, hydrogen peroxide is further added as an auxiliary oxidant, and titration feeding control is adopted, and the addition rate of hydrogen peroxide is controlled at 0.2 - 2 mL / min.

5. A method for recycling platinum from finished products according to claim 1, characterized in that, The volume ratio of hydrochloric acid to nitric acid in the aqua regia is controlled at 2.5 - 3.5:1, the dissolution reaction temperature is 50 - 100°C, the dissolution time is 0.5 - 3 hours. Among them, the final pH value of the solution is controlled at 0.5 - 1.5, and a stepwise acid addition strategy is adopted, that is, first add 50% - 70% volume of aqua regia for preliminary dissolution, and then gradually supplement the remaining aqua regia after the reaction is stable.

6. A method for recycling platinum from finished products according to claim 1, characterized in that The ammonium chloride is used as a complexing agent, and its mass fraction ratio is 0.2 - 1:1, and it is added in stages during the dissolution reaction process, that is, 20% - 40% ammonium chloride is added at the beginning of the aqua regia reaction, and the remaining part is added when the reaction proceeds 40% - 60%.

7. A method for recycling and replacing finished platinum as claimed in claim 1, characterized in that, The precipitation reaction temperature is 10 - 30°C, the precipitation time is 0.5 - 2 hours, the pH value of the precipitation solution is controlled at 4 - 6, and the stirring rate is controlled during the precipitation process.

8. A method for recycling and replacing finished platinum as claimed in claim 1, characterized in that, Ammonium nitrate is added during the precipitation process to improve the platinum precipitation efficiency, and its mass fraction ratio is 0.1 - 1:

1. Ammonium nitrate is added in a stepwise feeding manner, that is, it is gradually added after 50% - 80% of the ammonium chloride precipitation is completed, and the constant stirring is maintained.

9. A finished product platinum replacement and recovery method according to claim 1, characterized in that, The calcination time is controlled at 2 - 6 hours, the calcination temperature is controlled at 590°C - 610°C, and a gradual heating mode is adopted during the calcination process, that is, it is maintained at 200 - 300°C for 30 - 60 minutes for preheating and dehydration, and then heated to the final target temperature at a rate of 5 - 10°C / min and maintained at a constant temperature.

10. A finished product platinum replacement and recovery method according to claim 1, characterized in that, The calcination is carried out in a diluted atmosphere of nitrogen and oxygen to control the calcination environment, and dynamic atmosphere regulation is adopted. It is protected by 99.9% nitrogen in the first 1 - 2 hours, and switched to a mixed atmosphere with an oxygen content of 10% - 20% when the temperature reaches 550 - 650°C.

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