Method for preparing platinum nitrate from platinum-containing waste liquid and application

Abstract

The invention belongs to the technical field of precious metal secondary resource recycling, and discloses a method for preparing platinum nitrate from platinum-containing waste liquid and application, and the method comprises the following steps: (1) converting the platinum-containing waste liquid into a platinum tetrachloride solution; (2) synthesizing potassium chloroplatinate; (3) synthesizing potassium hydroxyplatinite; (4) synthesizing platinum hydroxide; (5) obtaining a platinum hydroxide hydrate; and (6) synthesizing a platinum nitrate solution. Through the steps, platinum is separated from the platinum-containing waste liquid, and the platinum nitrate solution is prepared. According to the method, platinum and aqua regia are not used, the raw materials are wide in source and low in cost, so that the production cost is reduced, meanwhile, pollutant emission is reduced, the steps are simple, operation is convenient, secondary precious metal resources are fully utilized, and the production cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal secondary resource recycling, in particular to a method for preparing platinum nitrate from platinum-containing waste liquid and its application. Background Art

[0002] Platinum nitrate is a chemical substance with the chemical formula Pt(NO3)2 and a molecular weight of 319.094. Platinum nitrate usually exists in the form of orange-brown powder, and the purity usually reaches Pt≥58.0%1. Platinum nitrate is an orange-brown powder at room temperature, easily soluble in water, and the solution is a reddish-brown liquid. It is stable under acidic conditions, but it is very easy to deliquesce in the air. Platinum nitrate is stable under acidic conditions, but it is very easy to hydrolyze in water. When diluting, dilute nitric acid should be prepared first, and then added to platinum nitrate. Distilled water cannot be used directly, otherwise precipitation is very likely to occur.

[0003] Platinum nitrate is mainly used to prepare palladium-containing compounds, heterogeneous catalysts and material surface coatings, and has good market prospects. It is also one of the essential raw materials for catalysts that purify automobile and motorcycle exhaust, and is widely used in automobile exhaust catalytic converters to load platinum coatings. In addition, platinum nitrate solution is an important intermediate for the preparation of other homogeneous catalysts and an indispensable catalyst raw material for industries such as petrochemicals and fine chemicals. Platinum nitrate is mainly used in the preparation of platinum-containing compounds and catalysts, and is widely used.

[0004] At present, the preparation of platinum nitrate mainly involves dissolving metal platinum in aqua regia, heating the solution to keep it boiling, cooling it naturally after the platinum is completely dissolved, adjusting the pH value with glacial acetic acid after filtering to generate hydroxyplatinic acid, and then dissolving it with nitric acid to obtain the platinum nitrate product. However, the preparation of platinum nitrate mainly uses metal platinum, and the raw materials are expensive, which increases the production cost of the enterprise. At the same time, there are defects such as long process flow and many steps. In addition, the reaction of metal platinum and aqua regia will produce a large amount of waste gas, which needs to be specially treated later, and the operation is cumbersome, which brings great inconvenience to production.

[0005] Therefore, a new related preparation method is urgently needed to meet the usage requirements. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method and application of preparing platinum nitrate from platinum-containing waste liquid.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] A method for preparing platinum nitrate from platinum-containing waste liquid comprises the following steps:

[0009] ⑴ Take a platinum-containing waste liquid, the mass concentration of platinum in the platinum-containing waste liquid is not less than 1%, add a 36% mass concentration hydrochloric acid solution and a 30% mass concentration hydrogen peroxide solution to the platinum-containing waste liquid, heat and boil for 1 to 2 hours, add water during the process to keep the total volume of the solution unchanged, and obtain a solution containing platinum tetrachloride;

[0010] (2) heating the obtained platinum tetrachloride solution to 80-90° C., adding potassium chloride powder thereto, stirring to completely dissolve the potassium chloride powder, and generating potassium chloroplatinate crystals, cooling the solution to room temperature, filtering and separating the potassium chloroplatinate crystals, and washing the potassium chloroplatinate 2-3 times with 95% ethanol by volume, and drying the potassium chloroplatinate crystals at 80-90° C.;

[0011] ⑶ Mix the dried potassium chloroplatinate with water 15 to 20 times the mass of the potassium chloroplatinate, add potassium oxalate, and heat together to a slightly boiling state until all the potassium chloroplatinate crystals are dissolved, and continue to heat and cook for 1 to 2 hours. During the process, add water to maintain the total volume of the initial solution to generate a potassium chloroplatinite solution;

[0012] (4) Add 30% to 50% potassium hydroxide solution to the potassium chloroplatinite solution, stir and dissolve until the pH of the solution is greater than 12, heat and boil the solution for 3 to 4 hours, add water during the process to maintain the original volume of the solution, and cool to obtain a potassium hydroxyplatinite solution;

[0013] ⑸ Under stirring, add 50% to 80% acetic acid aqueous solution to the potassium hydroxybenzoate solution until the pH value of the solution is 5 to 6, and a large amount of dark precipitate is generated. The dark precipitate is filtered and separated, and the filter cake is washed with pure water for 3 to 4 times, and the water is drained to obtain platinum hydroxide hydrate;

[0014] (6) Add 3 to 5 times the weight of the platinum hydroxide hydrate obtained in the previous step to a 65% to 68% nitric acid solution, stir and dissolve at 60 to 70° C. for 4 to 5 hours, cool to room temperature, and filter to obtain a finished platinum nitrate solution.

[0015] Furthermore, in step (1), 300 to 400 ml of 36% hydrochloric acid solution and 50 to 100 ml of 30% hydrogen peroxide solution are added to each liter of platinum-containing waste liquid.

[0016] Furthermore, in step (2), 100 to 200 grams of potassium chloride powder is added per liter of platinum tetrachloride solution.

[0017] Furthermore, in step (3), 0.95 to 1.05 g of potassium oxalate monohydrate is added to each gram of dry chloroplatinic acid.

[0018] The application of the method as described above in the preparation of platinum nitrate.

[0019] The advantages and positive effects achieved by the present invention are:

[0020] 1. The method of the present invention does not need to use metal platinum and aqua regia, and the raw materials are widely available and low in cost, thereby reducing production costs. At the same time, pollutant emissions are reduced, the steps are simple, the operation is convenient, and the secondary precious metal resources are fully utilized, saving production costs.

[0021] 2. The method of the present invention has stable quality and high yield of platinum nitrate. The raw material uses platinum-containing waste liquid, utilizes secondary precious metal resources, reduces production costs, and reduces pollutant emissions.

[0022] 3. Due to the blind mining of mineral resources in the international market, mineral resources are reduced, but demand is rising every year, causing the price of precious metals to soar. Therefore, the market for recycling waste precious metal products is relatively active. Therefore, the present invention will also have a wide range of market applications in the future. Take the supply and demand relationship of platinum from 2023 to 2024 as an example. See Table 1. In 2023, the platinum market experienced a historic tension, with an estimated shortage of up to 33 tons. In the case of a global economic contraction in 2024, the gap is expected to be 11 tons. The demand figures from 2023 to 2024 also show the importance of platinum recycling.

[0023] Table 1

[0024] DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the embodiments. The following embodiments are descriptive rather than restrictive, and the protection scope of the present invention cannot be limited by the following embodiments.

[0026] The various experimental operations involved in the specific embodiments are all routine techniques in the art. For parts not specially annotated in this document, ordinary technicians in the art can implement them by referring to various commonly used reference books, scientific and technological literature or related instructions, manuals, etc. before the filing date of this invention.

[0027] A method for preparing platinum nitrate from platinum-containing waste liquid comprises the following steps:

[0028] ⑴ Take a platinum-containing waste liquid, the mass concentration of platinum in the platinum-containing waste liquid is not less than 1%, add a 36% mass concentration hydrochloric acid solution and a 30% mass concentration hydrogen peroxide solution to the platinum-containing waste liquid, heat and boil for 1 to 2 hours, add water during the process to keep the total volume of the solution unchanged, and obtain a solution containing platinum tetrachloride;

[0029] (2) heating the obtained platinum tetrachloride solution to 80-90° C., adding potassium chloride powder thereto, stirring to completely dissolve the potassium chloride powder, and generating potassium chloroplatinate crystals, cooling the solution to room temperature, filtering and separating the potassium chloroplatinate crystals, and washing the potassium chloroplatinate 2-3 times with 95% ethanol by volume, and drying the potassium chloroplatinate crystals at 80-90° C.;

[0030] ⑶ Mix the dried potassium chloroplatinate with water 15 to 20 times the mass of the potassium chloroplatinate, add potassium oxalate, and heat together to a slightly boiling state until all the potassium chloroplatinate crystals are dissolved, and continue to heat and cook for 1 to 2 hours. During the process, add water to maintain the total volume of the initial solution to generate a potassium chloroplatinite solution;

[0031] (4) Add 30% to 50% potassium hydroxide solution to the potassium chloroplatinite solution, stir and dissolve until the pH of the solution is greater than 12, heat and boil the solution for 3 to 4 hours, add water during the process to maintain the original volume of the solution, and cool to obtain a potassium hydroxyplatinite solution;

[0032] ⑸ Under stirring, add 50% to 80% acetic acid aqueous solution to the potassium hydroxybenzoate solution until the pH value of the solution is 5 to 6, and a large amount of dark precipitate is generated. The dark precipitate is filtered and separated, and the filter cake is washed with pure water for 3 to 4 times, and the water is drained to obtain platinum hydroxide hydrate;

[0033] (6) Add 3 to 5 times the weight of the platinum hydroxide hydrate obtained in the previous step to a 65% to 68% nitric acid solution, stir and dissolve at 60 to 70° C. for 4 to 5 hours, cool to room temperature, and filter to obtain a finished platinum nitrate solution.

[0034] Preferably, in step (1), 300-400 ml of 36% hydrochloric acid solution and 50-100 ml of 30% hydrogen peroxide solution are added to each liter of platinum-containing waste liquid.

[0035] Preferably, in step (2), 100 to 200 grams of potassium chloride powder is added per liter of platinum tetrachloride solution.

[0036] Preferably, in step (3), 0.95 to 1.05 g of potassium oxalate monohydrate is added to each gram of dry chloroplatinic acid.

[0037] The application of the method as described above in the preparation of platinum nitrate.

[0038] Specifically, the relevant preparation and detection are as follows:

[0039] Example 1

[0040] A method for preparing platinum nitrate from platinum-containing waste liquid comprises the following steps:

[0041] (1) Add 2 L of platinum-containing waste liquid to a 5 L beaker, then add 600 mL of 36% hydrochloric acid solution and 100 mL of 30% hydrogen peroxide solution, then heat and boil for 1 hour, and add water to keep the solution volume unchanged, to obtain a platinum tetrachloride solution;

[0042] The platinum waste liquid is produced in the process of producing catalysts for the aerospace industry. In the past, the waste liquid was treated as waste liquid and not recycled because the waste liquid content was too low. In recent years, due to the instability of precious metal market resources and prices, the user has adjusted the waste liquid production process and recycled the waste liquid. The relevant indicators of the waste liquid before and after the improvement are shown in Table 2.

[0043] Appendix-2 Related indicators of new and old processes for platinum waste liquid

[0044]

[0045] The above percentages represent mass percentages.

[0046] (2) When the platinum tetrachloride solution is heated to about 85° C., 200 g of potassium chloride powder is added and stirred to completely dissolve the potassium chloride powder to generate potassium chloroplatinate crystal precipitation, the solution is cooled to room temperature, and the potassium chloroplatinate crystals are separated by filtration using a sand core funnel, and the potassium chloroplatinate is washed twice with a 95% volume concentration ethanol solution, and then the chloroplatinic acid crystals are transferred to a 90° C. constant temperature electric drying oven for drying to obtain potassium chloroplatinate;

[0047] (3) 100 g of dried potassium chloroplatinate was placed in a 5 L glass beaker, and 2000 ml of pure water and 100 g of potassium oxalate monohydrate were added, and the mixture was heated to a slight boiling state until all the potassium chloroplatinate crystals were dissolved, and the mixture was boiled for 1 hour. During the process, water was frequently added to keep the volume of the solution constant. At this time, the solution was red, and a potassium chloroplatinite solution was generated;

[0048] (4) adding a 30% potassium hydroxide solution to the potassium chloroplatinite solution, stirring and dissolving the mixture to make the pH value of the solution greater than 12, and then heating and boiling the solution for 3 hours, adding water at any time to maintain the original volume of the solution, cooling the solution until it turns yellow, and obtaining a potassium hydroxyplatinite solution;

[0049] (5) Add 50% acetic acid aqueous solution to the potassium hydroxybenzoate solution under stirring until the pH value of the solution is between 5 and 6. A large amount of dark precipitate is generated, which is filtered with a glass frit funnel, and the filter cake is washed with pure water three times, and the water is drained to obtain platinum hydroxide hydrate;

[0050] (6) Add 600 g of nitric acid with a volume concentration of 65% to 68% to 200 g of the above obtained platinum hydroxide hydrate, stir and dissolve at 60° C. for 4 hours, cool to room temperature, and filter with a glass sand core funnel. The filtrate is the finished platinum nitrate. The platinum content can be adjusted by concentrating or diluting the platinum nitrate solution according to customer requirements.

[0051] Using the same method, for the same batch of platinum waste liquid, potassium hydroxide with a mass concentration of 30% was added to the potassium chloroplatinite solution in step (1) in Example 1, and the mixture was stirred and dissolved to mix evenly, and the pH of the solution was adjusted to 8 (i.e., Example 2) and 10 (i.e., Example 3) to conduct tests with the same other conditions.

[0052] The comparison table of test results is shown in Table 3.

[0053] Table 3

[0054] Example Amount of platinum waste liquid Platinum content of original waste liquid % pH Platinum nitrate quantity G 1 2000ML 11 Greater than 12 59 2 2000ML 11 8 - 3 2000ML 11 10 -

[0055] It can be determined from Table 3 that when the pH value is greater than 12, it is the best solution for recovering platinum nitrate from waste liquid.

[0056] Using the same method, for the same batch of platinum waste liquid, the 30% mass concentration potassium hydroxide solution in step (1) in Example 1 was replaced with a 20% mass concentration potassium hydroxide solution (ie, Example 4) and other conditions were the same.

[0057] The comparison table of test results is shown in Table 4.

[0058] Table 4

[0059] Example Amount of platinum waste liquid Platinum content of original waste liquid % Potassium hydroxide mass concentration % Platinum nitrate quantity G 1 2000ML 11 30 59 2 2000ML 11 20 16

[0060] Adding potassium hydroxide with a mass concentration of 30% as shown in Table 4 is the best solution for recovering platinum nitrate from waste liquid.

[0061] At the same time, by comparing Examples 1 to 4, it can be seen that in the method of the present invention, in step (1), adding potassium hydroxide with a mass concentration of 30% to the potassium chloroplatinite solution, stirring and dissolving and mixing evenly, so that the solution pH is greater than 12, there is a synergistic effect between the potassium hydroxide solution with a mass concentration of 30% in step (1), and the two can significantly synergistically improve the relevant properties of the prepared ammonium chloroplatinate.

[0062] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for preparing platinum nitrate from platinum-containing waste liquid, characterized in that: The steps include: ⑴ Take a platinum-containing waste liquid, the mass concentration of platinum in the platinum-containing waste liquid is not less than 1%, add a 36% mass concentration hydrochloric acid solution and a 30% mass concentration hydrogen peroxide solution to the platinum-containing waste liquid, heat and boil for 1 to 2 hours, add water during the process to keep the total volume of the solution unchanged, and obtain a solution containing platinum tetrachloride; (2) heating the obtained platinum tetrachloride solution to 80-90° C., adding potassium chloride powder thereto, stirring to completely dissolve the potassium chloride powder, and generating potassium chloroplatinate crystals, cooling the solution to room temperature, filtering and separating the potassium chloroplatinate crystals, and washing the potassium chloroplatinate 2-3 times with 95% ethanol by volume, and drying the potassium chloroplatinate crystals at 80-90° C.; ⑶ Mix the dried potassium chloroplatinate with water 15 to 20 times the mass of the potassium chloroplatinate, add potassium oxalate, and heat together to a slightly boiling state until all the potassium chloroplatinate crystals are dissolved, and continue to heat and cook for 1 to 2 hours. During the process, add water to maintain the total volume of the initial solution to generate a potassium chloroplatinite solution; (4) Add 30% to 50% potassium hydroxide solution to the potassium chloroplatinite solution, stir and dissolve until the pH of the solution is greater than 12, heat and boil the solution for 3 to 4 hours, add water during the process to maintain the original volume of the solution, and cool to obtain a potassium hydroxyplatinite solution; ⑸ Under stirring, add 50% to 80% acetic acid aqueous solution to the potassium hydroxybenzoate solution until the pH value of the solution is 5 to 6, to generate a dark precipitate, filter and separate the dark precipitate, wash the filter cake with pure water for 3 to 4 times, and drain the water to obtain platinum hydroxide hydrate; (6) Add 3 to 5 times the weight of the platinum hydroxide hydrate obtained in the previous step to a 65% to 68% nitric acid solution, stir and dissolve at 60 to 70° C. for 4 to 5 hours, cool to room temperature, and filter to obtain a finished platinum nitrate solution.

2. The method according to claim 1, characterized in that: In step (1), 300 to 400 ml of 36% hydrochloric acid solution and 50 to 100 ml of 30% hydrogen peroxide solution are added to each liter of platinum-containing waste liquid.

3. The method according to claim 1, characterized in that: In step (2), 100 to 200 grams of potassium chloride powder are added per liter of platinum tetrachloride solution.

4. The method according to claim 1, characterized in that: In step (3), 0.95 to 1.05 g of potassium oxalate monohydrate is added to each gram of dry chloroplatinic acid.

5. Application of the method as described in any one of claims 1 to 4 in the preparation of platinum nitrate.

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