A method for recovering platinum from mother liquor in P salt production

Abstract

The present invention belongs to the technical field of resource recovery. The present invention provides a method for recovering platinum from a mother liquor produced by a P salt, comprising the following steps: subjecting the mother liquor to a deamination reaction under alkaline conditions to obtain a deamination mother liquor; subjecting the deamination mother liquor to an acidification reaction and an oxidation reaction in sequence to obtain an intermediate mother liquor; subjecting the intermediate mother liquor to a primary reduction reaction and a secondary reduction reaction in sequence, calcining to obtain sponge platinum, and completing the recovery. The platinum recovery method provided by the present invention has simple process operation, and the calcination and decomposition process is environmentally friendly and safe; other metal impurities are not introduced, and the oxidation precipitation of dinitrosodiammine platinum is avoided, solving the problem of easy explosion during calcination and decomposition. At the same time, the platinum reduction in the recovery method of the present invention is thorough, the recovery efficiency is high, and a platinum product that meets national standards (platinum purity ≥ 99.95%) can be directly obtained; it is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of resource recovery, and in particular to a method for recovering platinum from a mother liquor produced by a P salt. Background Art

[0002] Usually in the production and preparation process of dinitroso diamine platinum (CAS number is 14286-02-3), the yield of platinum is only 70%~80.3%, a large amount of platinum is present in the production mother liquor in the form of dissolved dinitroso diamine platinum, dichlorotetraamine platinum, chloroplatinic acid, chloroplatinous acid, etc., and a large amount of volatile and explosive substances such as sodium nitrite and ammoniacal liquor are also left in the production mother liquor simultaneously, but there is no special document report on the treatment and recovery method of dinitroso diamine platinum production mother liquor at present. In " Precious Metal Separation and Refining Technology " (written by Yu Jianmin, published by Chemical Industry Press Chemistry and Applied Chemistry Publishing Center, August 2006, the 1st edition) 6.9, it is proposed: "After chlorine is passed into the preheated diamine dinitroso platinum solution, oxidation is carried out to separate out the insoluble Buchner salt [Pt(NH3)2(NO2)2Cl2] precipitation, and this salt is carefully heated and calcined to obtain sponge platinum". Although the steps of converting [Pt(NH3)2(NO2)2] into [Pt(NH3)2(NO2)2Cl2] precipitation are relatively simple, platinum in other forms cannot be converted, and the recovery of platinum is not complete. In addition, the nitrite in the Brühl salt is prone to explosion during calcination, and calcination decomposition produces nitrogen oxides, which poses a safety and environmental hazard. Therefore, it is very important to provide a safe and high recovery method for recovering metallic platinum from production mother liquor. Summary of the invention

[0003] The object of the present invention is to provide a method for recovering platinum from a P salt production mother liquor, comprising the following steps:

[0004] (1) Under alkaline conditions, subjecting the mother liquor to a deamination reaction to obtain a deamination mother liquor;

[0005] (2) subjecting the deamination mother liquor to an acidification reaction and an oxidation reaction in sequence to obtain an intermediate mother liquor;

[0006] (3) The intermediate mother liquor is subjected to a primary reduction reaction and a secondary reduction reaction in sequence, and calcined to obtain sponge platinum, thereby completing recovery.

[0007] Preferably, the pH of the alkaline condition in step (1) is 8 to 12, and the alkaline solution used in the alkaline condition is one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water, and calcium hydroxide solution;

[0008] The mass concentration of the alkaline solution is 10-20%.

[0009] Preferably, the temperature of the deamination reaction in step (1) is 90-120° C., the stirring speed of the deamination reaction is 40-60 r / min, the vacuum degree of the deamination reaction is 0.075-0.095 KPa, and the time of the deamination reaction is 90-180 min.

[0010] Preferably, the pH of the acidification reaction in step (2) is 1 to 3, and the acid solution of the acidification reaction is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid;

[0011] The mass concentration of the acid solution is 10-40%.

[0012] Preferably, the oxidant used in the oxidation reaction in step (2) is one or more of nitric acid, chlorine, hydrogen peroxide, sodium chlorate, and sodium bromate;

[0013] The mass concentration of the oxidant is 15-20%, and the mass ratio of the oxidant to platinum in the mother liquor is 2-10:1.

[0014] Preferably, the pH of the initial reduction reaction in step (3) is 7 to 10;

[0015] The reagent used for adjusting pH in the preliminary reduction reaction is one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water and calcium hydroxide solution, and the mass concentration of the reagent is 10-20%.

[0016] Preferably, the temperature of the preliminary reduction reaction in step (3) is 60-80° C., and the speed of the preliminary reduction reaction is 100-140 r / min;

[0017] The temperature of the secondary reduction reaction is 60-80° C., and the rotation speed of the secondary reduction reaction is 100-140 r / min.

[0018] Preferably, the reducing agents for the primary reduction reaction and the secondary reduction reaction in step (3) are independently one or more of hydrazine hydrochloride, hydrazine hydrate, hydroxylamine hydrochloride, sodium sulfite, sodium borohydride, and potassium borohydride;

[0019] The mass concentration of the reducing agent is 10 to 80%;

[0020] The mass ratio of the amount of the reducing agent added in the preliminary reduction reaction to the mass ratio of the platinum in the mother liquor is 1 to 5:1.

[0021] Preferably, the mass ratio of the amount of reducing agent added in the secondary reduction reaction in step (3) to the mass ratio of platinum in the mother liquor is 1 to 5:1.

[0022] Preferably, the calcination temperature in step (3) is 700-800° C., and the calcination time is 2-4 hours.

[0023] The present invention has at least the following beneficial effects:

[0024] The present invention provides a method for recovering platinum from a mother liquor produced by a P salt, comprising the following steps: subjecting the mother liquor to a deamination reaction under alkaline conditions to obtain a deamination mother liquor; subjecting the deamination mother liquor to an acidification reaction and an oxidation reaction in sequence to obtain an intermediate mother liquor; subjecting the intermediate mother liquor to a primary reduction reaction and a secondary reduction reaction in sequence, calcining to obtain sponge platinum, and completing the recovery. The recovery method of the present invention has simple process operation, and the calcination and decomposition process is environmentally friendly and safe; other metal impurities are not introduced, and the oxidation precipitation of dinitrosodiammine platinum is avoided, solving the problem of easy explosion during calcination and decomposition. At the same time, the platinum reduction in the recovery method of the present invention is thorough, and the recovery efficiency is high, and a platinum product that meets national standards (platinum purity ≥ 99.95%) can be directly obtained; it is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0025] The present invention provides a method for recovering platinum from a P salt production mother liquor, comprising the following steps:

[0026] (1) Under alkaline conditions, subjecting the mother liquor to a deamination reaction to obtain a deamination mother liquor;

[0027] (2) subjecting the deamination mother liquor to an acidification reaction and an oxidation reaction in sequence to obtain an intermediate mother liquor;

[0028] (3) The intermediate mother liquor is subjected to a primary reduction reaction and a secondary reduction reaction in sequence, and calcined to obtain sponge platinum, thereby completing recovery.

[0029] In the present invention, the pH of the alkaline condition in step (1) is preferably 8 to 12, more preferably 9 to 11, and more preferably 9.5 to 10.5; the alkaline solution used in the alkaline condition is preferably one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water, and calcium hydroxide solution;

[0030] The mass concentration of the alkaline solution is preferably 10 to 20%, more preferably 12 to 18%, and even more preferably 14 to 16%.

[0031] In the present invention, the temperature of the deamination reaction in step (1) is preferably 90-120°C, more preferably 95-115°C, and more preferably 100-110°C; the stirring speed of the deamination reaction is preferably 40-60r / min, more preferably 45-55r / min, and more preferably 48-52r / min; the vacuum degree of the deamination reaction is preferably 0.075-0.095KPa, more preferably 0.080-0.090KPa, and more preferably 0.082-0.088KPa; the time of the deamination reaction is preferably 90-180min, more preferably 120-150min, and more preferably 130-140min.

[0032] In the present invention, the phenomenon when the deamination reaction is completed is that the steam and the cotton swab group dipped in hydrochloric acid do not produce white smoke.

[0033] In the present invention, the pH of the acidification reaction in step (2) is preferably 1 to 3, more preferably 1.5 to 2.5, and more preferably 1.8 to 2.2; the acid solution of the acidification reaction is preferably one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid;

[0034] The mass concentration of the acid solution is preferably 10 to 40%, more preferably 15 to 35%, and even more preferably 20 to 30%.

[0035] In the present invention, the temperature of the acidification reaction in step (2) is preferably 90-120°C, more preferably 95-115°C, and more preferably 100-110°C; the rotation speed of the acidification reaction is preferably 40-60r / min, more preferably 45-55r / min, and more preferably 48-52r / min; the vacuum degree of the acidification reaction is preferably 0.075-0.095KPa, more preferably 0.080-0.090KPa, and more preferably 0.082-0.088KPa; the time of the acidification reaction is preferably 30-90min, more preferably 45-75min, and more preferably 55-65min.

[0036] In the present invention, the end phenomenon of the acidification reaction is that no brown gas is generated after adding acid.

[0037] In the present invention, the purpose of adding acid solution is to convert nitrite in the deamination mother liquor into nitrate.

[0038] In the present invention, the oxidant used in the oxidation reaction in step (2) is preferably one or more of nitric acid, chlorine, hydrogen peroxide, sodium chlorate, and sodium bromate;

[0039] The mass concentration of the oxidant is preferably 15-20%, more preferably 16-19%, and more preferably 17-18%; the mass ratio of the oxidant to platinum in the mother liquor is preferably 2-10:1, more preferably 4-8:1, and more preferably 5-7:1.

[0040] In the present invention, the temperature of the oxidation reaction in step (2) is preferably 90-120°C, more preferably 95-115°C, and more preferably 100-110°C; the rotation speed of the oxidation reaction is preferably 40-60r / min, more preferably 45-55r / min, and more preferably 48-52r / min; the vacuum degree of the oxidation reaction is preferably 0.075-0.095KPa, more preferably 0.080-0.090KPa, and more preferably 0.082-0.088KPa; the time of the oxidation reaction is preferably 30-60min, more preferably 35-55min, and more preferably 40-50min.

[0041] In the present invention, the final phenomenon of the oxidation reaction is that the color of the deamination mother liquor changes from yellow-green to yellow.

[0042] In the present invention, the purpose of adding a strong oxidant is to convert nitrite in the deamination mother liquor into nitrate.

[0043] In the present invention, the pH of the preliminary reduction reaction in step (3) is preferably 7 to 10, more preferably 8 to 9, and more preferably 8.2 to 8.8;

[0044] The reagent used for adjusting the pH of the preliminary reduction reaction is preferably one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water, and calcium hydroxide solution; the mass concentration of the reagent is preferably 10-20%, more preferably 12-18%, and more preferably 14-16%.

[0045] In the present invention, the temperature of the preliminary reduction reaction in step (3) is preferably 60-80°C, more preferably 65-75°C, and more preferably 68-72°C; the rotation speed of the preliminary reduction reaction is preferably 100-140r / min, more preferably 110-130r / min, and more preferably 115-125r / min;

[0046] The temperature of the secondary reduction reaction is preferably 60-80°C, more preferably 65-75°C, and more preferably 68-72°C; the rotation speed of the secondary reduction reaction is preferably 100-140r / min, more preferably 110-130r / min, and more preferably 115-125r / min.

[0047] In the present invention, the reducing agents for the primary reduction reaction and the secondary reduction reaction in step (3) are independently preferably one or more of hydrazine hydrochloride, hydrazine hydrate, hydroxylamine hydrochloride, sodium sulfite, sodium borohydride, and potassium borohydride;

[0048] The mass concentration of the reducing agent is preferably 10 to 80%, more preferably 30 to 60%, and more preferably 40 to 50%;

[0049] The mass ratio of the amount of the reducing agent added in the preliminary reduction reaction to the platinum in the mother liquor is preferably 1 to 5:1, more preferably 2 to 4:1, and more preferably 2.5 to 3.5:1.

[0050] In the present invention, the preliminary reduction reaction can further destroy the stability of dinitrosodiammineplatinum while reducing platinum.

[0051] In the present invention, the mass ratio of the amount of reducing agent added in the secondary reduction reaction in step (3) to the platinum in the mother liquor is preferably 1 to 5:1, more preferably 2 to 4:1, and more preferably 2.5 to 3.5:1.

[0052] The solution obtained by the above preparation method is cooled, precipitated and filtered, washed, dried and calcined to obtain sponge platinum.

[0053] In the present invention, the cooling method is natural cooling, and the cooling target temperature is room temperature.

[0054] In the present invention, the sedimentation method is static sedimentation, and the sedimentation time is preferably 18 to 24 hours, more preferably 19 to 23 hours, and more preferably 20 to 21 hours.

[0055] In the present invention, the reagent used for the washing is deionized water, and the number of washing is preferably greater than or equal to 3 times, more preferably greater than or equal to 4 times, and more preferably greater than or equal to 5 times.

[0056] In the present invention, the drying temperature is preferably 100 to 140°C, more preferably 110 to 130°C, and even more preferably 115 to 125°C.

[0057] In the present invention, the calcination temperature in step (3) is preferably 700-800°C, more preferably 720-780°C, more preferably 740-750°C, and the calcination time is preferably 2-4h, more preferably 2.5-3.5h, more preferably 2.8-3.2h.

[0058] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0059] Example 1

[0060] Take 2.00 kg of dinitrosodiammineplatinum production mother liquor (detected to contain 0.3563% platinum), add 15% sodium hydroxide solution to adjust the mother liquor pH to 9, heat to 110°C, and carry out deamination reaction for 130 minutes under the reaction conditions of 40 r / min and 0.08 KPa. Then, 10% hydrochloric acid solution was added to the solution to adjust the pH to 1, and an acidification reaction was carried out for 55 minutes under the conditions of 110°C, 50 r / min, and 0.08 KPa. Subsequently, 35.63 g of a 20% hydrogen peroxide solution was added while maintaining the acidification reaction conditions to carry out an oxidation reaction. After reacting for 35 minutes, an intermediate mother liquor was obtained. A 15% sodium hydroxide solution was added to the intermediate mother liquor to adjust the pH to 8. The temperature was adjusted to 70°C, and 7.13 g of a 10% sodium borohydride solution was added at a stirring speed of 120 r / min to carry out a preliminary reduction reaction until the solution was clear and colorless. Subsequently, the temperature was maintained at 70°C and the stirring speed was maintained at 120 r / min. 7.13 g of a 20% hydrazine hydrate was added to the clear and colorless solution to carry out a secondary reduction reaction until no bubbles were generated and the reaction was complete. The obtained solution was cooled to room temperature, allowed to stand and precipitate for 18 hours, filtered, and the obtained filter residue was washed three times with deionized water to obtain platinum powder. The platinum powder was dried in an oven at 120°C to constant weight. The platinum powder was placed in an evaporating dish and placed in a muffle furnace and calcined at 750°C for 3 hours to obtain 7.0198 g of sponge platinum product with a recovery rate of 98.51%. The filtrate and washing liquid were combined to about 600 mL to detect the platinum content of 0.0053 mg / L. The detection of the platinum product met the SM-Pt99.95% requirement in GB / T1419-2015.

[0061] Example 2

[0062] Take 5.00 kg of dinitrosodiammineplatinum production mother liquor (detected to contain 0.3563% platinum), add 20% sodium hydroxide solution to adjust the mother liquor pH to 8, raise the temperature to 90°C, and carry out deamination reaction at 60 r / min and 0.085 KPa for 120 minutes. Then, 15% hydrochloric acid solution was added to the solution to adjust the pH to 2, and an acidification reaction was carried out for 45 minutes under the conditions of 90°C, 45r / min, and 0.085KPa. Subsequently, 35.63g of 20% nitric acid solution was added for oxidation reaction while maintaining the acidification reaction conditions unchanged. After reacting for 40 minutes, an intermediate mother liquor was obtained, and a 20% sodium hydroxide solution was added to adjust the pH to 8. The temperature was adjusted to 80°C, and 17.82g of 15% sodium sulfite solution was added under stirring at 120r / min for preliminary reduction reaction until the solution was clear and colorless. Subsequently, the temperature was maintained at 80°C and the stirring speed was maintained at 120r / min. 26.72g of 80% hydrazine hydrate was added to the clear and colorless solution for secondary reduction reaction until no bubbles were generated and the reaction was complete. The obtained solution was cooled to room temperature, allowed to stand and precipitate for 18 hours, filtered, and the filter residue was washed with deionized water four times to obtain platinum powder. The platinum powder was dried in an oven at 120°C to constant weight. The platinum powder was placed in an evaporating dish and placed in a muffle furnace and calcined at 750°C for 3 hours to obtain 17.5602 g of sponge platinum product with a recovery rate of 98.57%. The filtrate and washing liquid were combined to about 4L to detect the platinum content of 0.0049 mg / L. The platinum product test met the SM-Pt99.95% requirement in GB / T1419-2015.

[0063] Example 3

[0064] Take 10.00kg of dinitrosodiammineplatinum production mother liquor (detected to contain 0.2976% platinum), add 20% sodium hydroxide solution to adjust the mother liquor pH to 10, raise the temperature to 110°C, and carry out deamination reaction at 40r / min and 0.078KPa for 105min until the steam and the cotton swab group dipped in hydrochloric acid no longer produce white smoke. Then, 36% hydrochloric acid solution was added to the solution to adjust the pH to 1, and an acidification reaction was carried out for 70 minutes under the conditions of 110°C, 50r / min, and 0.078KPa. Subsequently, 100g of a 15% sodium chlorate solution was added while maintaining the acidification reaction conditions to carry out an oxidation reaction. After reacting for 60 minutes, an intermediate mother liquor was obtained, and a 20% sodium hydroxide solution was added to adjust the pH to 8. The temperature was adjusted to 60°C, and 30g of a 10% sodium borohydride solution was added at a stirring speed of 120r / min to carry out a preliminary reduction reaction until the solution was clear and colorless. Subsequently, the temperature was maintained at 60°C and the stirring speed was maintained at 120r / min, and 30g of an 80% hydrazine hydrate was added to the clear and colorless solution to carry out a secondary reduction reaction until no bubbles were generated and the reaction was complete. The obtained solution was cooled to room temperature, allowed to stand and precipitate for 19 hours, filtered, and the obtained filter residue was washed with deionized water four times to obtain platinum powder. The platinum powder was dried in an oven at 120°C to constant weight, and the platinum powder was placed in an evaporating dish and placed in a muffle furnace and calcined at 750°C for 3 hours to obtain 29.3659 g of sponge platinum product with a recovery rate of 98.68%. The filtrate and washing liquid were combined to about 3.5L to detect the platinum content of 0.0024 mg / L. The platinum product test met the SM-Pt99.95% requirement in GB / T1419-2015.

[0065] Example 4

[0066] Take 20.00kg of dinitrosodiammineplatinum production mother liquor (detected to contain 0.2976% platinum), add 15% sodium hydroxide solution to adjust the mother liquor pH to 10, raise the temperature to 100°C, and carry out deamination reaction for 108min under the reaction conditions of 60r / min and 0.083KPa, until the steam and the cotton swab group dipped in hydrochloric acid no longer produce white smoke. Then, 18% hydrochloric acid solution was added to the solution to adjust the pH to 1, and an acidification reaction was carried out for 55 minutes under the conditions of 100°C, 55 r / min, and 0.083 KPa. Subsequently, 300 g of a 15% sodium bromate solution was added while maintaining the acidification reaction conditions to carry out an oxidation reaction. After reacting for 55 minutes, an intermediate mother liquor was obtained, and a 15% sodium hydroxide solution was added to adjust the pH to 8. The temperature was adjusted to 60°C, and 120 g of a 10% sodium borohydride solution was added under stirring at 120 r / min to carry out a preliminary reduction reaction until the solution was clear and colorless. Subsequently, the temperature was maintained at 60°C and the stirring speed was maintained at 120 r / min. 120 g of a 30% hydrazine hydrochloride was added to the clear and colorless solution to carry out a secondary reduction reaction until no bubbles were generated and the reaction was complete. The obtained solution was cooled to room temperature, allowed to settle for 18 hours, filtered, and the filter residue was washed with deionized water for 5 times to obtain platinum powder. The platinum powder was dried in an oven at 120°C to constant weight. The platinum powder was placed in an evaporating dish and calcined in a muffle furnace at 750°C for 3 hours to obtain 58.7411 g of sponge platinum product with a recovery rate of 98.69%. The filtrate and washing liquid were combined to about 7L to detect the platinum content of 0.0031 mg / L. The platinum product test met the SM-Pt99.95% requirement in GB / T1419-2015.

[0067] It can be seen from the above embodiments that the present invention provides a method for recovering platinum from the mother liquor of P salt production, comprising the following steps: under alkaline conditions, subjecting the mother liquor to a deamination reaction to obtain a deamination mother liquor; subjecting the deamination mother liquor to an acidification reaction and an oxidation reaction in sequence to obtain an intermediate mother liquor; subjecting the intermediate mother liquor to a primary reduction reaction and a secondary reduction reaction in sequence, calcining to obtain sponge platinum, and completing the recovery. The recovery method of the present invention has simple process operation, and the calcination and decomposition process is environmentally friendly and safe; no other metal impurities are introduced, and the oxidation precipitation of dinitrosodiammine platinum is avoided, solving the problem of calcination and decomposition being prone to explosion. At the same time, it can be seen from experimental verification that the platinum reduction in the recovery method of the present invention is thorough, the recovery efficiency is high, and a platinum product that meets national standards (platinum purity ≥ 99.95%) can be directly obtained; it is suitable for large-scale industrial production.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for recovering platinum from a P salt production mother liquor, characterized in that: The following steps are involved: (1) Under alkaline conditions, subjecting the mother liquor to a deamination reaction to obtain a deamination mother liquor; (2) subjecting the deamination mother liquor to an acidification reaction and an oxidation reaction in sequence to obtain an intermediate mother liquor; (3) subjecting the intermediate mother liquor to a primary reduction reaction and a secondary reduction reaction in sequence, calcining to obtain sponge platinum, and completing recovery; Wherein, the mother liquor in step (1) is the mother liquor produced by dinitrosodiammineplatinum; The temperature of the deamination reaction in step (1) is 90-120° C., the stirring speed of the deamination reaction is 40-60 r / min, the vacuum degree of the deamination reaction is 0.075-0.095 KPa, and the time of the deamination reaction is 90-180 min.

2. The recycling method according to claim 1, characterized in that: The pH of the alkaline condition in step (1) is 8 to 12, and the alkaline solution used in the alkaline condition is one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water, and calcium hydroxide solution; The mass concentration of the alkaline solution is 10-20%.

3. The recycling method according to claim 1, characterized in that: The pH of the acidification reaction in step (2) is 1 to 3, and the acid solution of the acidification reaction is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; The mass concentration of the acid solution is 10-40%.

4. The recovery method according to claim 1 or 3, characterized in that: The oxidant of the oxidation reaction in step (2) is one or more of nitric acid, chlorine, hydrogen peroxide, sodium chlorate, and sodium bromate; The mass concentration of the oxidant is 15-20%, and the mass ratio of the oxidant to the platinum in the mother liquor of step (1) is 2-10:

1.

5. The recycling method according to claim 1, characterized in that: The pH of the initial reduction reaction in step (3) is 7 to 10; The reagent used for adjusting pH in the preliminary reduction reaction is one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water and calcium hydroxide solution, and the mass concentration of the reagent is 10-20%.

6. The recycling method according to claim 5, characterized in that: The temperature of the preliminary reduction reaction in step (3) is 60-80° C., and the speed of the preliminary reduction reaction is 100-140 r / min; The temperature of the secondary reduction reaction is 60-80° C., and the rotation speed of the secondary reduction reaction is 100-140 r / min.

7. The recovery method according to claim 5 or 6, characterized in that: The reducing agents for the primary reduction reaction and the secondary reduction reaction in step (3) are independently one or more of hydrazine hydrochloride, hydrazine hydrate, hydroxylamine hydrochloride, sodium sulfite, sodium borohydride, and potassium borohydride; The mass concentration of the reducing agent is 10 to 80%; The mass ratio of the amount of the reducing agent added in the preliminary reduction reaction to the mass ratio of the platinum in the mother liquor of step (1) is 1 to 5:

1.

8. The recycling method according to claim 7, characterized in that: The mass ratio of the amount of the reducing agent added in the secondary reduction reaction in step (3) to the mass ratio of the platinum in the mother liquor in step (1) is 1 to 5:

1.

9. The recycling method according to claim 8, characterized in that: The calcination temperature in step (3) is 700-800° C., and the calcination time is 2-4 hours.