Method for refining platinum by alkali-soluble potassium chloroplatinate

Abstract

The invention relates to the field of precious metal refining. The invention particularly relates to a method for refining platinum by alkali-soluble potassium chloroplatinate. The invention relates to a method for refining platinum by alkali-soluble potassium chloroplatinate, which sequentially comprises the following steps of: A, adding KCl into a platinum solution, fully stirring, and washing a filter cake with potassium chloride and hydrochloric acid to obtain a K2PtCl6 filter cake; b, dissolving the K2PtCl6 filter cake obtained in the step A by using NaOH, cooling and filtering to obtain an alkali-soluble mother solution; c, adjusting the acidity of the alkali-soluble mother liquor obtained in the step B with hydrochloric acid, adding NH4Cl to precipitate platinum, fully stirring to generate (NH4) 2PtCl6 precipitate, filtering, and washing a filter cake with ammonium chloride to obtain ammonium chloroplatinate precipitate; and D, calcining the ammonium chloroplatinate obtained in the step C to obtain the sponge platinum with the purity of SM-Pt99.95. According to the method, potassium chloroplatinate is subjected to alkali dissolution, impurities are removed, ammonium chloroplatinate is precipitated, no nitrogen oxide tail gas is discharged in the refining process, and green and efficient refining and purification of platinum are achieved.

Description

Technical Field

[0001] The present invention relates to the field of precious metal refining, and specifically to a method for refining platinum by dissolving potassium chloroplatinate with alkali. Background Art

[0002] The commonly used methods for platinum refining are hydrolysis, ammonium chloride repeated precipitation, and molten salt electrolysis. In comparison, the ammonium chloride repeated precipitation method is simple to operate and the easiest to implement, and is still used by most factories today. However, the ammonium chloride repeated precipitation method has a long production cycle, and the calcination of ammonium chloroplatinate and the dissolution of crude sponge platinum with aqua regia produce waste gases including nitrogen oxides, which cause environmental pollution.

[0003] In order to shorten the production cycle of platinum refining and improve the current situation of nitrogen oxide emissions, many researchers have proposed new methods for platinum refining. Representative methods include the ammonium chloroplatinate (IV) reduction method, patent CN102797018A, and patent CN105441693A. The insoluble ammonium chloroplatinate (IV) precipitate is reduced to soluble ammonium chloroplatinate (II) acid, and the refining and purification of platinum is achieved by repeated precipitation-reduction dissolution. Different from the reduction method, patent CN105256148A uses the method of alkali dissolution of ammonium chloroplatinate to achieve the refining and purification of platinum. The above two methods effectively shorten the refining cycle and improve nitrogen oxide emissions. However, improper control of the reduction method can easily cause excessive reduction to produce platinum black, and the direct yield is low. When the ammonium chloroplatinate is dissolved in the alkali dissolution method, the ammonia nitrogen is fixed in the solution, and the removal of ammonia nitrogen is difficult, resulting in a low process success rate. The method of platinum refining still needs to be improved. Summary of the invention

[0004] The purpose of the present invention is to provide a method for refining platinum by alkali dissolving potassium chloroplatinate, wherein potassium chloroplatinate is alkali dissolved, impurities are removed, and ammonium chloroplatinate is reprecipitated, and no nitrogen oxide tail gas is emitted during the refining process, thereby realizing green and efficient refining and purification of platinum. The refining process is shortened, the refining efficiency is improved, the solubility product law is used to effectively shorten the platinum refining cycle, the direct yield of platinum is increased, nitrogen oxide emissions are reduced, the cost of platinum refining auxiliary materials is saved, the deficiency of inability to precipitate platinum after alkali dissolution caused by incomplete removal of ammonia nitrogen is solved, and the problem of nitrogen oxide waste gas emissions caused by traditional refining processes is solved.

[0005] In order to achieve the above object, the technical solution provided by the present invention is: A method for refining platinum by dissolving potassium chloroplatinate in an alkali, comprising the following steps: A. Add KCl to the platinum solution and stir thoroughly until the solution no longer generates yellow precipitate, filter, and wash the filter cake with a solution having a potassium chloride mass concentration of 10% and a hydrochloric acid concentration of 1 mol / L to obtain a K2PtCl6 filter cake; B. dissolving the K2PtCl6 filter cake obtained in step A with NaOH to a pulping concentration of 10 to 300 g / L, heating, keeping at 30 to 120° C. for 0.5 to 2 h, cooling and filtering to obtain an alkali-soluble mother liquor; C. Use hydrochloric acid to adjust the acidity of the alkali-soluble mother solution obtained in step B, slowly pump hydrochloric acid into the alkali-soluble mother solution B, adjust the acidity of the alkali-soluble mother solution to 0.1-3 mol / L, obtain an acid adjustment solution, add NH4Cl to precipitate platinum, stir thoroughly until no precipitation is generated, generate (NH4)2PtCl6 precipitation, filter, and wash the filter cake with a solution of 15% ammonium chloride mass concentration to obtain ammonium chloroplatinate precipitation; D. Calcinate the ammonium chloroplatinate obtained in step C to obtain SM-Pt99.95 purity sponge platinum.

[0006] The platinum solution of step A is obtained by pretreating a platinum-containing raw material, adding aqua regia at a raw material mass: aqua regia volume ratio of 1:3-5, heating and boiling, concentrating the solution, adding hydrochloric acid at a volume ratio of 1:1 multiple times to drive out nitrate until the solution no longer produces small yellow bubbles, cooling and filtering to obtain a platinum solution with a Pt concentration greater than 10g / L; the amount of KCl added is greater than or equal to the mass of platinum in the platinum solution, and the excess is 5% to 50%.

[0007] The NaOH in step B is a NaOH solution with a mass concentration of 1% to 30%.

[0008] In step C, the concentration of hydrochloric acid is 1-6 mol / L, the flow rate of hydrochloric acid is 0.5-10 L / min, the amount of NH4Cl is greater than or equal to the mass of platinum in the acid adjustment solution C, and the excess is 5%-30%. The filtrate is concentrated and industrially deaminated and returned to step A for recycling.

[0009] Beneficial effects of the present invention:

[0010] 1. The use of KCl to precipitate platinum in step A of the present invention is to avoid introducing ammonia nitrogen into the system, reduce the steps of removing ammonia nitrogen after alkali dissolution, shorten the refining process, and improve the refining efficiency. It not only solves the problem of incomplete removal of ammonia nitrogen causing platinum to be unable to precipitate after alkali dissolution, but also solves the problem of nitrogen and oxygen waste gas emissions caused by traditional refining processes.

[0011] 2. The present invention utilizes the solubility product advantage after alkali dissolution, uses ammonium chloride to precipitate platinum, and calcines to obtain sponge platinum, thereby reducing the step of preparing platinum black by reducing K2PtCl6 with hydrazine hydrate, lowering the cost, and effectively improving the platinum refining cycle.

[0012] 3. In step B of the present invention, NaOH is used to dissolve K2PtCl6, so as to avoid using KOH to increase reagent cost and to avoid using other alkali solutions to bring in ammonia nitrogen or impurity elements. The impurity elements form insoluble hydroxides and remain in the slag, and platinum is dissolved in the alkali solution.

[0013] 4. The filtrate in step C of the present invention is concentrated and industrially deaminated, and then returned to step A for recycling, which effectively saves reagent costs. At the same time, a small amount of platinum in the filtrate is also recycled, thereby improving the direct recovery rate of platinum. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION Example 1

[0015] A. 100g of the raw material was added to 3L of aqua regia, heated and boiled, and after the solution was concentrated, 1L of hydrochloric acid was added 3 times each time to remove nitrate until the solution no longer produced small yellow bubbles, and cooled and filtered to obtain 4.5L of platinum solution, containing 497g of platinum; 521.85g of 5% by mass KCl was added to the platinum solution, fully stirred until the solution no longer generated yellow precipitate, filtered, and the filter cake was washed with a solution having a potassium chloride mass concentration of 10% and a hydrochloric acid concentration of 1mol / L to obtain a K2PtCl6 filter cake; B. Prepare 1.66L of 1% NaOH solution to dissolve the K2PtCl6 filter cake obtained in step A, raise the temperature, keep at 30°C for 2h, cool and filter to obtain an alkaline soluble mother liquor; C. Use 1 mol / L hydrochloric acid to adjust the acidity of the alkali-soluble mother liquor obtained in step B, the hydrochloric acid flow rate is 10 L / min, adjust the acidity of the alkali-soluble mother liquor to 3 mol / L, obtain an acid adjustment solution, add 646.1 g NH4Cl to precipitate platinum, stir thoroughly until no precipitation is produced, generate (NH4)2PtCl6 precipitation, filter, wash the filter cake with a solution of 15% ammonium chloride mass concentration, and obtain ammonium chloroplatinate precipitation; the filtrate is concentrated and industrially deaminated, and returned to step A for recycling; D. Calcinate the ammonium chloroplatinate obtained in step C to obtain 490.54 g of sponge platinum with a purity of SM-Pt99.95. The content of other elements is less than 0.0005 g / L and is not listed. The direct yield of platinum in the process is 98.70%.

[0016] The impurities of platinum solution and sponge platinum are listed in Table 1 below.

[0017] element Platinum solution (g / L) GB / T1419-2015SM-Pt 99.95 / % Sponge platinum / % Sn 0.15 ≤0.005 <0.0005 Pd 0.0064 ≤0.01 0.0028 Fe 0.0795 ≤0.005 0.0008 Zn 0.0098 ≤0.005 <0.0005 Si 0.0039 ≤0.005 <0.0005 Na 6.36 -- <0.0005 K 0.0069 -- 0.0011 Example 2

[0018] A. 100g of the raw material was added to 4L of aqua regia, heated and boiled, and after the solution was concentrated, 1L of hydrochloric acid was added 3 times each time to remove nitrate until the solution no longer produced small yellow bubbles, and cooled and filtered to obtain a 6L platinum solution containing 412g of platinum; 535.6g of KCl with a mass percentage of 30% was added to the platinum solution, fully stirred until the solution no longer generated a yellow precipitate, filtered, and the filter cake was washed with a solution having a potassium chloride mass concentration of 10% and a hydrochloric acid concentration of 1mol / L to obtain a K2PtCl6 filter cake; B. Prepare 2.75L of 15% NaOH solution to dissolve the K2PtCl6 filter cake obtained in step A, raise the temperature, keep at 75°C for 1h, cool and filter to obtain an alkaline-soluble mother liquor; C. Use 3 mol / L hydrochloric acid to adjust the acidity of the alkali-soluble mother liquor obtained in step B, the hydrochloric acid flow rate is 5 L / min, adjust the acidity of the alkali-soluble mother liquor to 1.5 mol / L, obtain an acid adjustment solution, add 486.16 g NH4Cl to precipitate platinum, stir thoroughly until no precipitation is produced, generate (NH4)2PtCl6 precipitation, filter, wash the filter cake with a solution of 15% ammonium chloride mass concentration, and obtain ammonium chloroplatinate precipitation; the filtrate is concentrated and industrially deaminated, and returned to step A for recycling; D. Calcinate the ammonium chloroplatinate obtained in step C to obtain 406.03 g of sponge platinum with a purity of SM-Pt99.95. The contents of other elements are less than 0.0005 g / L and are not listed. The direct yield of platinum in the process is 98.55%.

[0019] The impurities of platinum solution and sponge platinum are listed in Table 2 below.

[0020] element Platinum solution (g / L) GB / T1419-2015SM-Pt 99.95 / % Sponge platinum / % Sn 0.4915 ≤0.005 <0.0005 Pd 0.0036 ≤0.01 0.0016 Fe 0.0866 ≤0.005 0.0006 Zn 0.0356 ≤0.005 <0.0005 Si 0.0028 ≤0.005 <0.0005 Na 9.3 -- 0.0006 K 0.02 -- 0.0020 Example 3

[0021] A. 100g of the raw material was added to 5L of aqua regia, heated and boiled, and after the solution was concentrated, 1L of hydrochloric acid was added 3 times each time to remove nitrate until the solution no longer produced small yellow bubbles, and cooled and filtered to obtain 7.5L of platinum solution, containing 326g of platinum; 489g of 50% by mass KCl was added to the platinum solution, fully stirred until the solution no longer generated yellow precipitates, filtered, and the filter cake was washed with a solution having a potassium chloride mass concentration of 10% and a hydrochloric acid concentration of 1mol / L to obtain a K2PtCl6 filter cake; B. Prepare 32.6L of 30% NaOH solution to dissolve the K2PtCl6 filter cake obtained in step A, heat it, keep it at 120°C for 0.5h, cool and filter, and obtain an alkaline-soluble mother liquor; C. Use 6 mol / L hydrochloric acid to adjust the acidity of the alkali-soluble mother liquor obtained in step B, the hydrochloric acid flow rate is 0.5 L / min, adjust the acidity of the alkali-soluble mother liquor to 1 mol / L, obtain an acid adjustment solution, add 342.3 g NH4Cl to precipitate platinum, stir thoroughly until no more precipitation is produced, generate (NH4)2PtCl6 precipitation, filter, wash the filter cake with a solution of 15% ammonium chloride mass concentration, and obtain ammonium chloroplatinate precipitation; the filtrate is concentrated and industrially deaminated, and returned to step A for recycling; D. Calcinate the ammonium chloroplatinate obtained in step C to obtain 320.78 g of sponge platinum with a purity of SM-Pt99.95. The content of other elements is less than 0.0005 g / L and is not listed. The direct yield of platinum in the process is 98.40%.

[0022] The impurities of platinum solution and sponge platinum are listed in Table 3 below.

[0023] element Platinum solution (g / L) GB / T1419-2015SM-Pt 99.95 / % Sponge platinum / % Sn 0.8320 ≤0.005 <0.0005 Pd 0.0008 ≤0.01 <0.0005 Al 1.2062 ≤0.005 <0.0005 Fe 0.0936 ≤0.005 0.0005 Zn 0.0611 ≤0.005 <0.0005 Ni 0.0017 ≤0.005 <0.0005 Na 14.87 -- 0.0008 K 0.0333 -- 0.0029

Claims

1. A method for refining platinum by dissolving potassium chloroplatinate in an alkali, characterized in that: Follow the steps below: A. Add KCl to the platinum solution and stir thoroughly until the solution no longer generates yellow precipitate, filter, and wash the filter cake with a solution having a potassium chloride mass concentration of 10% and a hydrochloric acid concentration of 1 mol / L to obtain a K2PtCl6 filter cake; B. dissolving the K2PtCl6 filter cake obtained in step A with NaOH to a pulping concentration of 10 to 300 g / L, heating, keeping at 30 to 120° C. for 0.5 to 2 h, cooling and filtering to obtain an alkali-soluble mother liquor; C. Use hydrochloric acid to adjust the acidity of the alkali-soluble mother solution obtained in step B, slowly pump hydrochloric acid into the alkali-soluble mother solution B, adjust the acidity of the alkali-soluble mother solution to 0.1-3 mol / L, obtain an acid adjustment solution, add NH4Cl to precipitate platinum, stir thoroughly until no precipitation is generated, generate (NH4)2PtCl6 precipitation, filter, and wash the filter cake with a solution of 15% ammonium chloride mass concentration to obtain ammonium chloroplatinate precipitation; D. Calcinate the ammonium chloroplatinate obtained in step C to obtain SM-Pt99.95 purity sponge platinum.

2. The method for refining platinum by dissolving potassium chloroplatinate in an alkali solution according to claim 1, characterized in that: The platinum solution of step A is obtained by pretreating a platinum-containing raw material, adding aqua regia at a raw material mass: aqua regia volume ratio of 1:3-5, heating and boiling, concentrating the solution, adding hydrochloric acid at a volume ratio of 1:1 multiple times to drive out nitrate until the solution no longer produces small yellow bubbles, cooling and filtering to obtain a platinum solution with a Pt concentration greater than 10g / L; the amount of KCl added is greater than or equal to the mass of platinum in the platinum solution, and the excess is 5% to 50%.

3. The method for refining platinum by dissolving potassium chloroplatinate with alkali according to claim 1 or 2, characterized in that: The NaOH in step B is a NaOH solution with a mass concentration of 1% to 30%.

4. The method for refining platinum by dissolving potassium chloroplatinate with alkali according to claim 1 or 2, characterized in that: In step C, the concentration of hydrochloric acid is 1-6 mol / L, the flow rate of hydrochloric acid is 0.5-10 L / min, the amount of NH4Cl is greater than or equal to the mass of platinum in the acid adjustment solution C, and the excess is 5%-30%. The filtrate is concentrated and industrially deaminated and returned to step A for recycling.

5. The method for refining platinum by dissolving potassium chloroplatinate in an alkali solution according to claim 3, characterized in that: In step C, the concentration of hydrochloric acid is 1-6 mol / L, the flow rate of hydrochloric acid is 0.5-10 L / min, the amount of NH4Cl is greater than or equal to the mass of platinum in the acid adjustment solution C, and the excess is 5%-30%. The filtrate is concentrated and industrially deaminated and returned to step A for recycling.

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