Method for post-processing electrolyte and recovering metal platinum in electrolyte

Abstract

The invention relates to the technical field of electrolyte post-treatment, in particular to a method for recovering platinum from platinum-containing electrolyte, platinum is recovered based on synergistic extraction of supercritical CO2 and ionic liquid, and efficient migration and selective enrichment of a Pt complex in two phases are realized by regulating supercritical conditions and composition of the ionic liquid; the technology not only overcomes the toxicity and recovery problems of a traditional organic solvent, but also improves the selective separation capacity of platinum in a complex electrolyte matrix, has the outstanding advantages of being environmentally friendly, adjustable in process, high in extraction efficiency, easy to amplify and implement and the like, and is suitable for popularization and application in the fields of waste catalyst regeneration, waste electrolyte treatment, precious metal recovery and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolyte post-treatment, in particular to a method for electrolyte post-treatment and recovery of metallic platinum in electrolyte. BACKGROUND

[0002] As a precious metal catalyst, platinum is widely used in the field of organic electrochemical synthesis due to its excellent catalytic performance and chemical stability. Studies have shown that during the process of organic electrochemical synthesis experiments, metallic platinum will be corroded and fall off, existing in the electrolyte in the form of ions. Due to the scarcity and high price of platinum resources, recycling has important economic and environmental significance. Traditional recycling methods mainly include pyrometallurgy, wet precipitation, reduction precipitation, and electrodeposition. Although these methods are mature, they have problems such as high energy consumption, low recovery efficiency, poor selectivity, and serious secondary pollution. Especially in low-concentration and high-salt systems such as electrolyte, efficient and selective recovery of platinum still faces technical challenges.

[0003] Supercritical CO2, as a green solvent, has attracted widespread attention in the field of metal extraction due to its low toxicity, easy recovery, and strong controllability. Although its direct solubility for polar metal ions is poor, it can be significantly improved by introducing extraction auxiliaries or combining with other extraction media. For example, Chinese patent CN 119332109 B discloses a method for recovering lithium from lithium-containing coal rocks using supercritical CO2 fluid, which improves the recovery rate and environmental friendliness to some extent. However, this method relies on the introduction of specific ligands, and the process is complex, and there is little research on ionic liquid synergistic systems.

[0004] In view of the shortcomings of the prior art, the present application proposes a method for recovering platinum based on supercritical CO2 and ionic liquid synergistic extraction, which realizes efficient migration and selective enrichment of Pt complex in two phases by adjusting supercritical conditions and ionic liquid composition. This technology not only overcomes the toxicity and recovery problems of traditional organic solvents, but also improves the selective separation ability of platinum in complex electrolyte matrix, with outstanding advantages such as green environmental protection, process adjustability, high extraction efficiency, and easy scaling-up, suitable for application in the fields of waste catalyst regeneration, electrolyte waste treatment, and precious metal recovery. SUMMARY

[0005] To solve the problems of high energy consumption, low recovery efficiency, poor selectivity, and serious secondary pollution in the prior art disclosed in the background art, a method for electrolyte post-treatment and recovery of metallic platinum in electrolyte is proposed, i.e. a method for recovering metallic platinum in electrolyte based on supercritical CO2 and ionic liquid synergistic extraction.

[0006] To achieve the above purpose, the present application provides the following technical solutions: The application provides a method for recycling metal platinum in electrolyte, comprising the following steps: Step A, pre-treating electrolyte to obtain a kettle residue containing metal platinum; Step B, pre-treating the kettle residue containing metal platinum to obtain an extraction feed containing metal platinum; Step C, adding an ionic liquid to form an ionic liquid solution system in a supercritical CO2 fluid extraction device, adding the extraction feed containing metal platinum and an extractant into the ionic liquid solution system for extraction to obtain an extraction mixture; Step D, after the extraction mixture is subjected to a multi-stage separation extraction process, performing a solid-liquid separation operation to separate a mother liquor; Step E, reducing the pressure of the mother liquor to convert the supercritical CO2 fluid into a gaseous state, recovering and separating CO2 to obtain a concentrated mother liquor; Step F, desolubilizing the concentrated mother liquor to recover the extractant, and obtaining a concentrated mother liquor to be purified; Step G, treating the concentrated mother liquor to be purified by using an ultrasonic cavitation technology to recover the ionic liquid and the metal platinum.

[0007] Further, in step A, the electrolyte is an electrolyte for synthesizing dimethyl sebacate by electricity; and the electrolyte comprises, by mass percentage, 35-38% of methanol, 5-10% of water, 5-8% of potassium adipate monester, 35-40% of dimethyl sebacate, 0.1-1% of monomethyl adipate, 3-5% of low-boiling-point impurities, 3-5% of high-boiling-point impurities, and 0.001-0.1% of metal platinum ions.

[0008] Further, in step A, the electrolyte pre-treatment is as follows: heating the electrolyte to 90-100 DEG C to perform normal-pressure distillation to preliminarily remove the low-boiling-point solvent methanol, low-boiling-point impurities and part of water; then starting a vacuum pump to reduce the pressure in the system to -0.09 to -0.1 MPa, and slowly heating to 165-200 DEG C to perform negative-pressure distillation to mainly remove dimethyl sebacate, monomethyl adipate and part of high-boiling-point impurities, and collect a distillation residue; adding 50% by weight of propylene carbonate to the distillation residue, heating to 90-100 DEG C, stirring for 0.5-1 hour, then cooling to 0-10 DEG C to perform crystallization to precipitate potassium adipate monester; performing centrifugal separation on the crystallized distillation residue to remove residual potassium adipate monester, and collecting a centrifugal mother liquor; then starting the vacuum pump again to reduce the pressure in the system to -0.09 to -0.1 MPa, and slowly heating to 180-220 DEG C to perform negative-pressure distillation on the centrifugal mother liquor to mainly remove propylene carbonate and part of high-boiling-point impurities, and obtain the kettle residue containing metal platinum.

[0009] Further, in step B, the pre-treatment of the metal platinum-containing still residue is as follows: the still residue is crushed to less than 25-50 mm using a hammer crusher to obtain a material to be ground; the material to be ground, steel balls and stearic acid are mixed and loaded into a ball mill tank, and argon is filled for ball milling treatment; after the ball milling treatment, ultrasonic dispersion is performed; the ultrasonic dispersion is to use the cavitation effect generated by the ultrasonic wave in the medium to form micro-bubbles in the liquid, and the micro-bubbles generate local high temperature and high pressure and micro-jet flow when collapsing, thereby breaking the particle agglomerates and uniformly dispersing the particles to obtain a metal platinum-containing material to be extracted. The platinum concentration in the metal platinum-containing material to be extracted is 100-1000 ppm, the mass ratio of the steel balls to the material to be ground is 10:1-15:1, and the addition amount of stearic acid is 2%-5% of the mass of the material to be ground. The stearic acid acts as a process control agent to prevent particle agglomeration and reduce friction and wear during the grinding process. The ball milling method is used, and the grinding medium (steel ball) and the material are collided and ground with each other by the rotation of the ball mill, so as to refine the particles and break the agglomerates. During the ball milling process, the particles are repeatedly extruded, sheared and impacted under the action of mechanical force, so as to reduce the particle size and uniformly disperse the particles.

[0010] Further, the ball milling treatment is as follows: first-stage ball milling: the ball milling speed is 300-500 rpm, and the ball milling time is 4-8 hours; second-stage ball milling: nano-silicon dioxide is added, and the ball milling is continued, the ball milling speed is 300-500 rpm, and the ball milling time is 4-8 hours; the mass ratio of stearic acid to nano-silicon dioxide is 0.02-0.1:1, which can effectively improve the dispersibility and surface modification effect of nano-silicon dioxide.

[0011] Further, in step C, the mass ratio of the metal platinum-containing material to be extracted, the ionic liquid and the extractant is 1:0.5-1:0.8-1; the ionic liquid is 1-butyl-3-methyl imidazole tetrafluoroborate, and the extractant is one or more of methanol, ethanol and propanol.

[0012] Further, in step C, the extraction conditions are as follows: the CO2 flow rate is set to 40-50 mL / min, the temperature is controlled to be 40-65℃, the pressure is 20-35 MPa, and the extraction time is 1-5 h. In the ionic solution system, the ionic liquid and the supercritical CO2 are fully mixed to form a stable microemulsion. The microemulsion droplets increase the mass transfer interface area, and the metal platinum ions are more easily extracted.

[0013] Further, in step D, the multi-stage separation extraction process is as follows: a three-stage separator is designed, the pressure gradient is 18-22 MPa, 12-16 MPa and 6-10 MPa, and the temperature is 40-65℃, and step-by-step separation is performed; the solid-liquid separation operation is as follows: a microporous membrane with a pore size of 0.1-0.5 μm is used for filtration to remove large-particle impurities.

[0014] Further, the CO2 separated in step E is returned to the supercritical CO2 fluid extraction device in step C for recycling.

[0015] Further, in step F, the recovery of the extractant includes the following steps: transferring the concentrated mother liquor into a vacuum distillation device, setting the vacuum degree to -0.08 to -0.1 MPa, and controlling the temperature at 50-70℃. After vacuum distillation, the extractant is returned to step C for recycling.

[0016] Further, in step G, ultrasonic cavitation technology is used to assist the regeneration of the ionic liquid. The recovery of the ionic liquid and platinum metal using ultrasonic cavitation technology includes the following steps: transferring the concentrated mother liquor to be purified into an ultrasonic container, inserting the ultrasonic probe 2-3 cm below the liquid surface of the concentrated mother liquor to be purified, setting the ultrasonic frequency to 20-25 kHz, the ultrasonic power to 100-200 W, and the temperature to 60-80℃, and treating for 30-60 minutes. During the ultrasonic treatment, magnetic stirring is assisted to further improve the treatment effect. After the ultrasonic treatment, 3-5 times the weight of distilled water is added to the concentrated mother liquor to be purified, so that the ionic liquid and platinum ions are separated. The ionic liquid has limited solubility in water and will separate from the water, while the platinum ions will dissolve in the water, forming a layered structure. Under the conditions of ultrasonic frequency of 20-40 kHz, ultrasonic power of 100-200 W, and temperature of 60-80℃, the layered structure is further treated for 10-30 minutes, and then static separation is performed. The separated ionic liquid is recycled to step C, and the separated aqueous solution containing platinum metal is first filtered to remove the precipitate. The filtered aqueous solution is then subjected to negative pressure distillation under the conditions of -0.09 to -0.1 MPa and 100-105℃ to remove the solvent and obtain crude platinum metal. The crude platinum metal is dried in an oven at 80℃ for 12-24 hours to obtain the platinum metal.

[0017] Compared with the prior art, the present application has the following advantages: High-efficiency platinum metal recovery: The supercritical CO2 fluid extraction technology combined with ionic liquid can achieve high selectivity extraction of platinum metal. Supercritical CO2 has good solubility and adjustable density, which can effectively dissolve platinum metal, while ionic liquid can further enhance the extraction efficiency. Multi-stage separation process: Through multi-stage separation and extraction process, the concentration of platinum metal can be gradually increased, and the interference of impurities can be reduced, thereby improving the purity of the recovered product.

[0018] High-efficiency recovery of ionic liquid: Ultrasonic cavitation technology is used to treat the concentrated mother liquor, which can utilize the cavitation effect generated by ultrasonic waves to effectively separate the ionic liquid from the platinum metal. The local high temperature and micro-jet generated by ultrasonic cavitation can break the binding force between the ionic liquid and the platinum metal, thereby achieving high-efficiency separation of the two. Ultrasonic cavitation technology is a green and environmentally friendly treatment method that does not require additional chemical reagents, thereby reducing environmental pollution.

[0019] Recovery of extractant: By desolventizing treatment, the extractant can be recovered, not only reducing production cost, but also reducing environmental pollution. The recovered extractant can be used for extraction process again, realizing resource recycling.

[0020] Advantages of supercritical CO2 fluid: Supercritical CO2 is a green solvent, which is non-toxic, odorless and non-polluting. In the extraction process, CO2 can be completely recovered without harmful residues. The density and solubility of supercritical CO2 can be controlled by adjusting temperature and pressure, which makes the extraction process highly flexible, and the extraction conditions can be adjusted according to different metal platinum content and impurities.

[0021] Efficiency and economy of the whole process: The whole process from pretreatment to final recovery is closely linked to form an efficient integrated system. Through multi-stage separation and recovery, the recovery rate of metal platinum and ionic liquid is maximized. By recovering the extractant and supercritical CO2, the consumption of raw materials is reduced, and the production cost is reduced. At the same time, the application of ultrasonic cavitation technology also improves the processing efficiency, further reducing energy consumption and time cost. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The overall flowchart of Example 1 of the present application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] Steel balls, Qingzhou Taihong Special Steel Co., Ltd., particle size 4-10 nm.

[0025] Stearic acid, National Pharmaceutical Group Chemical Reagent Co., Ltd., analytical pure, purity > 99%.

[0026] Nanosilica: Suzhou Yuzhu Nanometer Material Co., Ltd., purity > 99.5%, particle size 1-100 nm, specific surface area: 100-300 m² / g.

[0027] Butyl-3-methylimidazolium tetrafluoroborate ionic liquid, Shanghai Chengjie Chemical Co., Ltd., analytical pure, purity > 99%.

[0028] The low boiling point impurities are the impurities with boiling point within 100℃, and the high boiling point impurities are the impurities with boiling point above 100℃. Example 1

[0029] Take 500 g of the electrolyte of dimethyl sebacate electro-synthesis, and the mass ratio of components is: methanol 37.478%, water 8.941%, potassium adipate mon-ester 7.893%, dimethyl sebacate 36.303%, hexanedioic acid monomethyl ester 0.655%, low boiling point impurities 4.148%, high boiling point impurities 4.502%, and the concentration of platinum ions is 0.08%, and the total is 100%.

[0030] A method for recovering platinum from electrolyte, comprising the following steps: Step A: electrolyte pretreatment The electrolyte is heated to 100℃ for normal pressure distillation to preliminarily remove methanol, part of water and low boiling point impurities; switch to negative pressure distillation, the system pressure is reduced to-0.098 MPa, and the temperature is raised to 180℃ to remove dimethyl sebacate, hexanedioic acid monomethyl ester and high boiling point impurities; 29.95 g (50% of the weight of the residual liquid) of propylene carbonate is added to the residual liquid, and stirred at 95℃ for 1 hour; the temperature is lowered to 5℃, potassium adipate mon-ester crystallizes, and the crystallization is removed by centrifugal separation; the mother liquor is subjected to negative pressure distillation again, the system pressure is reduced to-0.098 MPa, and the temperature is raised to 190℃ to remove propylene carbonate and part of high boiling point impurities, and a residual liquid containing platinum is obtained, and the platinum-containing residual liquid is about 20.8 g.

[0031] Step B: residual liquid pretreatment The residual liquid is crushed to 45 mm by using a hammer crusher to obtain a material to be ground; the material to be ground 20.2 g, steel balls 240 g and stearic acid 0.6 g are loaded into a ball mill tank, and argon is filled for ball milling treatment; the first stage ball milling speed is 350 r / min, and the ball milling time is 8 hours; in the second stage ball milling, 8 g of nano silicon dioxide is added, and the ball milling is continued, the ball milling speed is 400 r / min, and the ball milling time is 6 hours. After the ball milling treatment, ultrasonic dispersion is carried out (20 kHz, 120 W, 60℃, 30 minutes) to obtain a platinum-containing material to be extracted 28.8 g with uniform particle size, and the Pt concentration is 138.89 ppm.

[0032] Step C: supercritical extraction operation Prepare 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid 15.5 g, methanol 23.22 g and platinum-containing material to be extracted 28.8 g, and add them into a supercritical CO2 fluid extraction device; the extraction conditions are: CO2 flow rate 45 mL / min, temperature 60℃, pressure 30 MPa, and extraction time 4 hours; a stable microemulsion is formed in the system to realize the migration extraction of platinum.

[0033] Step D: multi-stage separation and solid-liquid separation The pressure of the three-stage separator was set to 20 MPa, 14 MPa and 8 MPa, respectively, and the temperature was 60℃; the solid-liquid separation was performed using a 0.2μm microporous membrane filter to obtain the mother liquor.

[0034] Step E: CO2 recovery The pressure was reduced to atmospheric pressure to vaporize CO2; gaseous CO2 was recovered by condensation and compression for recycling; and concentrated mother liquor 39.52g was obtained.

[0035] Step F: desolventization treatment The concentrated mother liquor was transferred to a vacuum distillation device; distillation was performed at -0.09 MPa and 60℃ for 2 hours; methanol was recovered, and 15.91g of the purified mother liquor was obtained.

[0036] Step G: ultrasonic cavitation separation and platinum recovery The purified concentrated mother liquor was transferred to an ultrasonic container, the ultrasonic probe was inserted 3cm below the liquid surface of the purified concentrated mother liquor, the ultrasonic frequency was 25 kHz, the ultrasonic power was 150 W, the temperature was 65℃, and ultrasonic treatment was performed for 45 minutes; during the ultrasonic treatment, magnetic stirring was assisted to further improve the treatment effect; after the ultrasonic treatment, 56g of distilled water was added to the purified concentrated mother liquor to separate the ionic liquid from the platinum ions; the ionic liquid had limited solubility in water and would separate into layers, and the platinum ions would dissolve in water to form a separate layer; under the conditions of an ultrasonic frequency of 40 kHz, an ultrasonic power of 150 W and a temperature of 65℃, the mixture was further treated for 30 minutes, then it was allowed to stand and separate; the separated ionic liquid was recovered for recycling in step C; the separated aqueous solution containing platinum metal was first filtered to remove the precipitate, then the filtered aqueous solution was subjected to negative pressure distillation under the conditions of -0.098 MPa and 100℃ to obtain crude platinum metal 0.416g; the crude platinum metal was dried in an oven at 80℃ for 12 hours to obtain platinum metal 0.385g with a yield of 96.3%. Example 2

[0037] 500g of electrolyte for the electro-synthesis of dimethyl sebacate was taken, and the mass ratio of the components was as follows: methanol 37.368%, water 9.573%, potassium monohexanedioate 7.534%, dimethyl sebacate 37.329%, monomethyl adipate 0.367%, low-boiling-point impurities 3.342%, high-boiling-point impurities 4.399%, and platinum ion concentration 0.088%, with a total of 100%.

[0038] A method for recovering platinum metal from electrolyte, comprising the following steps: Step A: electrolyte pretreatment The electrolyte was heated to 100°C for atmospheric distillation to remove methanol, part of the water and low-boiling impurities; switch to negative pressure distillation, the system pressure was reduced to -0.098 MPa, the temperature was raised to 180°C, to remove dimethyl sebacate, monomethyl adipate and high-boiling impurities; 30.37 g (50% by weight of the residual liquid) of propylene carbonate was added to the residual liquid, stirred at 95°C for 1 hour; cooled to 5°C, monomethyl adipate potassium salt crystallized, removed by centrifugal separation; the mother liquor was subjected to negative pressure distillation again, the system pressure was reduced to -0.098 MPa, the temperature was raised to 190°C, to remove propylene carbonate and part of the high-boiling impurities, to obtain a platinum-containing kettle residue, about 23.8 g.

[0039] Step B: Kettle residue pretreatment The kettle residue was crushed using a hammer crusher to 50 mm to obtain a material to be ground; the material to be ground 23.8 g, steel balls 280 g, stearic acid 0.9 g were loaded into a ball mill tank, and argon was filled for ball milling treatment; the first stage ball milling speed was 400 rpm, and the ball milling time was 6 hours; the second stage ball milling: 15 g of nano silicon dioxide was added, and the ball milling was continued, the ball milling speed was 400 rpm, and the ball milling time was 6 hours. After ball milling treatment, ultrasonic dispersion was carried out (20 kHz, 120 W, 60°C, 30 minutes) to obtain a platinum-containing material to be extracted 39.7 g with uniform particle size, and the Pt concentration was 110.83 ppm.

[0040] Step C: Supercritical extraction operation The 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid 28.26 g, methanol 36.73 g and platinum-containing material to be extracted 39.7 g were added into a supercritical CO2 fluid extraction device; the extraction conditions were as follows: CO2 flow rate 45 mL / min, temperature 60°C, pressure 30 MPa, and extraction time 4 hours; a stable microemulsion was formed in the system to realize the migration extraction of platinum.

[0041] Step D: Multistage separation and solid-liquid separation The pressure of the three-stage separator was set to 20 MPa, 14 MPa and 8 MPa respectively, and the temperature was 60°C; the solid-liquid separation was carried out using a 0.2 μm microporous membrane to obtain a mother liquor.

[0042] Step E: CO2 recovery The pressure was reduced to atmospheric pressure to make CO2 gasify; the gaseous CO2 was condensed and compressed for recycling; a concentrated mother liquor 66.43 g was obtained.

[0043] Step F: Desolubilization treatment The concentrated mother liquor was transferred into a reduced pressure distillation device; distillation was carried out at -0.09 MPa and 60°C for 2 hours; methanol was recovered to obtain 28.71 g of a material to be purified.

[0044] Step G: Ultrasonic cavitation separation and platinum recovery The concentrated mother liquor to be purified is transferred to an ultrasonic container, an ultrasonic probe is inserted into the concentrated mother liquor to be purified by 3 cm, the ultrasonic frequency is 25 kHz, the ultrasonic power is 150 W, the temperature is 80℃, and the ultrasonic treatment is performed for 60 minutes. During the ultrasonic treatment, auxiliary magnetic stirring is performed to further improve the treatment effect. After the ultrasonic treatment is completed, 140 g of distilled water is added to the concentrated mother liquor to be purified to separate the ionic liquid from the platinum ions. The ionic liquid has limited solubility in water and will separate from the water, and the platinum ions will dissolve in the water to form a layered structure. Under the conditions of an ultrasonic frequency of 40 kHz, an ultrasonic power of 150 W, and a temperature of 80℃, the layered structure is further treated for 60 minutes, and then static separation is performed. The separated ionic liquid is recovered to step C for recycling, and the separated platinum-containing aqueous solution is filtered to remove the precipitate. The filtered aqueous solution is subjected to negative pressure distillation under the conditions of a pressure of -0.098 MPa and a temperature of 100℃ to obtain 0.469 g of crude platinum. The crude platinum is dried in an oven at 80℃ for 12 hours to obtain 0.421 g of platinum with a yield of 95.68%. Example 3

[0045] Take 2000 g of electrolytic decanedioic acid dimethyl ester electrolyte, the component mass ratio is: methanol 36.516%, water 7.653%, potassium adipate monester 7.817%, decanedioic acid dimethyl ester 38.812%, adipic acid monomethyl ester 0.619%, low boiling point impurities 4.537%, high boiling point impurities 3.951%, and the concentration of platinum ions is 0.095%, and the total is 100%.

[0046] A method for recovering platinum from electrolyte, comprising the following steps: Step A: electrolyte pretreatment The electrolyte is heated to 100℃ for atmospheric distillation to preliminarily remove methanol, part of water and low boiling point impurities; switch to negative pressure distillation, the system pressure is reduced to -0.098 MPa, and the temperature is raised to 195℃; add 124.12 g (50% of the weight of the residual liquid) of propylene carbonate to the residual liquid, stir at 95℃ for 1 hour; cool to 5℃, precipitate potassium adipate monester crystals, and remove the crystals by centrifugation; the mother liquor is subjected to negative pressure distillation again, the system pressure is reduced to -0.098 MPa, and the temperature is raised to 190℃ to remove propylene carbonate, adipic acid monomethyl ester, decanedioic acid dimethyl ester and part of the high boiling point impurities, and about 91.9 g of platinum-containing residue is obtained.

[0047] Step B: residue pretreatment The kettle residue is crushed using a hammer crusher to 50 mm to obtain the material to be ground; the material to be ground 91.9 g, steel balls 1200 g, stearic acid 3.6 g are loaded into a ball mill tank, and argon is filled for ball milling treatment; the first stage ball milling speed is 400 rpm, and the ball milling time is 6 hours; the second stage ball milling: 80 g of nano-silicon dioxide is added, and the ball milling is continued, the ball milling speed is 400 rpm, and the ball milling time is 6 hours. After the ball milling treatment, ultrasonic dispersion is carried out (20 kHz, 120 W, 60°C, 45 minutes) to obtain the metal platinum-containing material to be extracted 175.5 g with a Pt concentration of 108.26 ppm.

[0048] Step C: Supercritical extraction operation The 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid 100 g, methanol 155 g and the metal platinum-containing material to be extracted 175.5 g are added into a supercritical CO2 fluid extraction device; the extraction conditions are as follows: CO2 flow rate 45 mL / min, temperature 60°C, pressure 30 MPa, and extraction time 5 hours; a stable microemulsion is formed in the system to realize the migration extraction of platinum.

[0049] Step D: Multistage separation and solid-liquid separation The pressure of the three-stage separator is set to 22 MPa, 16 MPa and 10 MPa respectively, and the temperature is 65°C; the solid-liquid separation is carried out by using a 0.2 μm microporous membrane to obtain the mother liquor.

[0050] Step E: CO2 recovery The pressure is reduced to normal pressure to make CO2 gasify; the gaseous CO2 is condensed and compressed to be recovered and recycled; and the concentrated mother liquor 258.5 g is obtained.

[0051] Step F: Desolubilization treatment The concentrated mother liquor is transferred into a reduced-pressure distillation device; distillation is carried out at -0.09 MPa and 60°C for 2 hours; methanol is recovered to obtain 103.5 g of the material to be purified.

[0052] Step G: Ultrasonic cavitation separation and platinum recovery The concentrated mother liquor to be purified is transferred into an ultrasonic container, an ultrasonic probe is inserted into the concentrated mother liquor to be purified by 3 cm, the ultrasonic frequency is 25 kHz, the ultrasonic power is 150 W, the temperature is 70 DEG C, and the ultrasonic treatment is performed for 60 minutes. During the ultrasonic treatment, auxiliary magnetic stirring is performed to further improve the treatment effect. After the ultrasonic treatment, 400 g of distilled water is added to the concentrated mother liquor to be purified, so that the ionic liquid is separated from the platinum ions. The ionic liquid has limited solubility in water and can be layered with water. The platinum ions are dissolved in water to form a layered structure. Under the conditions of an ultrasonic frequency of 40 kHz, an ultrasonic power of 150 W, and a temperature of 65 DEG C, the layered structure is continuously treated for 30 minutes, and then static separation is performed. The separated ionic liquid is recycled to step C for reuse. The separated aqueous solution containing platinum metal is first filtered to remove the precipitate. The filtered aqueous solution is subjected to negative pressure distillation under the conditions of a pressure of -0.098 MPa and a temperature of 100 DEG C to obtain a crude platinum product 3.391 g. The crude platinum product is dried in an oven at 80 DEG C for 12 hours to obtain 1.841 g of platinum metal with a yield of 96.89%. Example 4

[0053] Other than example 3, the difference between example 3 and the present example is that the particle size of the residue in the kettle is different after being crushed by a hammer crusher. Specifically, the residue in the kettle is crushed by a hammer crusher to 25 mm to obtain the material to be ground. Example 5

[0054] Other than example 3, the difference between example 3 and the present example is that the amount of stearic acid added is different. Specifically, the material to be ground 91.9 g, steel balls 1200 g, and stearic acid 4.5 g are loaded into a ball mill tank, and argon is filled for ball milling treatment. Example 6

[0055] Other than example 3, the difference between example 3 and the present example is that the amount of nano-silicon dioxide added is different. Specifically, in the second stage of ball milling, 120 g of nano-silicon dioxide is added, and the ball milling speed is 400 rpm for 6 hours. Example 7

[0056] Other than example 3, the difference between example 3 and the present example is that the amount of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid added is different. Specifically, 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid 150 g, methanol 155 g, and platinum-containing material to be extracted 175.5 g are added to a supercritical CO2 fluid extraction device. Example 8

[0057] Other than Example 3, the difference between Example 3 is the type of extractant, as follows: 100 g of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid, 155 g of ethanol and 175.5 g of platinum-containing material to be extracted are added into the supercritical CO2 fluid extraction device; Example 9

[0058] Other than Example 3, the difference between Example 3 is the type of extractant, as follows: 100 g of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid, 155 g of ethanol and 175.5 g of platinum-containing material to be extracted are added into the supercritical CO2 fluid extraction device; Example 10

[0059] Other than Example 3, the difference between Example 3 is the type of extractant, as follows: 100 g of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid, 155 g of ethanol and 175.5 g of platinum-containing material to be extracted are added into the supercritical CO2 fluid extraction device;

[0060] Comparative analysis of Example 3 to Example 9 is shown in Table 1.

[0061] Table 1 Comparative analysis of Example 3 to Example 9

[0062] It should be noted that the relational terms herein such as first and second are used merely to distinguish one entity or action from another entity or action without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles, or apparatuses including a series of elements include not only those elements but also other elements not explicitly listed, or other elements inherent in such processes, methods, articles, or apparatuses.

[0063] It should be noted that the above only illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. For those skilled in the art, without departing from the principle of the present application, a number of improvements and refinements can be made, which fall within the protection scope of the claims of the present application.

Claims

1. A method for recovering metallic platinum from an electrolyte, characterized in that: The following steps are involved: Step A, pre-treating the electrolyte to obtain a metal platinum-containing kettle residue; Step B, pretreating the metal platinum-containing kettle residue to obtain a material to be extracted containing metal platinum; Step C, adding an ionic liquid to a supercritical CO2 fluid extraction device to form an ionic liquid solution system, adding a platinum-containing material to be extracted and an extractant to the ionic liquid solution system for extraction to obtain an extraction mixture; Step D, subjecting the extraction mixture to a multi-stage separation and extraction process, and then performing a solid-liquid separation operation to separate and obtain a mother liquor; Step E: reducing the pressure of the mother liquor to convert the supercritical CO2 fluid into a gaseous state, and recovering and separating the CO2 to obtain a concentrated mother liquor; Step F, desolventizing the concentrated mother liquor and recovering the extractant to obtain a concentrated mother liquor to be purified; Step G: The concentrated mother liquor to be purified is treated by ultrasonic cavitation technology to recover the ionic liquid and metallic platinum.

2. The method for recovering metallic platinum in an electrolyte according to claim 1, wherein: In step A, the electrolyte is an electrosynthesized dimethyl sebacate electrolyte; the electrolyte comprises, by mass percentage, 35-38% methanol, 5-10% water, 5-8% potassium salt of monoadipate, 35-40% dimethyl sebacate, 0.1-1% monomethyl adipate, 3-5% low boiling point impurities, 3-5% high boiling point impurities, and a metal platinum ion concentration of 0.001%-0.1%.

3. The method for recovering metallic platinum in electrolyte according to claim 1, characterized in that: In step A, the electrolyte pretreatment is as follows: the electrolyte is heated to 90-100°C and subjected to atmospheric distillation; then the vacuum pump is started to reduce the pressure in the system to -0.09 to -0.1 MPa, slowly heated to 165-200°C, and subjected to negative pressure distillation to collect the distillation residue; 50% by weight of propylene carbonate is added to the distillation residue, heated to 90-100°C, stirred for 0.5-1 hour, and then cooled to 0-10°C for crystallization; the distillation residue after crystallization is centrifuged and the centrifuge mother liquor is collected; then the vacuum pump is started again to reduce the pressure in the system to -0.09 to -0.1 MPa, slowly heated to 150-200°C, and the centrifuge mother liquor is distilled under negative pressure to obtain a kettle residue containing metallic platinum.

4. The method for recovering metallic platinum in an electrolyte according to claim 1, wherein: In step B, the metal platinum-containing kettle residue is pretreated as follows: using a hammer crusher to crush the kettle residue to less than 25-50 mm to obtain a material to be ground; mixing the material to be ground, steel balls, and stearic acid, loading it into a ball mill, and filling it with argon for ball milling; after ball milling, ultrasonic dispersion is performed to obtain a metal platinum-containing material to be extracted, wherein the platinum concentration in the metal platinum-containing material to be extracted is 1000-10000 ppm, the mass ratio of the steel balls to the material to be ground is 10:1-15:1, and the added mass of stearic acid is 2%-5% of the mass of the material to be ground.

5. The method for recovering metallic platinum in electrolyte according to claim 4, characterized in that: The ball milling treatment comprises the following steps: first stage ball milling: ball milling speed of 300-500 rpm, ball milling time of 4-8 hours; second stage ball milling: adding nano-silicon dioxide, continuing ball milling, ball milling speed of 300-500 rpm, ball milling time of 4-8 hours; the mass ratio of stearic acid to nano-silicon dioxide is 0.02-0.1:

1.

6. The method for recovering metallic platinum in electrolyte according to claim 1, characterized in that: In step C, the mass ratio of the platinum-containing material to be extracted, the ionic liquid, and the extractant is 1:0.5-1:0.8-1; the ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate, and the extractant is one or more of methanol, ethanol, and propanol.

7. The method for recovering metallic platinum in electrolyte according to claim 1, characterized in that: In step C, the extraction conditions are as follows: setting the CO2 flow rate to 40-50 mL / min, controlling the temperature to 40-65°C, the pressure to 20-35 MPa, and the extraction time to 1-5 h.

8. The method for recovering metallic platinum in electrolyte according to claim 1, characterized in that: In step D, the multi-stage separation and extraction process is as follows: a three-stage separator is designed with pressure gradients of 18-22 MPa, 12-16 MPa and 6-10 MPa, and a temperature of 40-65°C for stepwise separation; the solid-liquid separation operation is performed by filtration using a microporous membrane with a pore size of 0.1-0.5 μm.

9. The method for recovering metallic platinum in electrolyte according to claim 1, characterized in that: In step F, the extractant recovery comprises the following steps: transferring the concentrated mother liquor into a vacuum distillation apparatus, setting the vacuum degree to 0.08-0.1 MPa, controlling the temperature at 50-70° C., and returning the extractant obtained after vacuum distillation to step C for recycling.

10. The method for recovering metallic platinum in electrolyte according to claim 1, characterized in that: In step G, ultrasonic cavitation technology is used to recover ionic liquid and metallic platinum, which specifically includes the following steps: transferring the concentrated mother liquor to be purified into an ultrasonic container, inserting the ultrasonic probe 2-3 cm below the liquid surface of the concentrated mother liquor to be purified, the ultrasonic frequency is 20-40 kHz, the ultrasonic power is 100-200 W, the temperature is 60-80°C, and the ultrasonic treatment is carried out for 30-60 minutes. During the ultrasonic treatment, magnetic stirring is assisted; after the ultrasonic treatment is completed, 3-5 times the volume of distilled water is added to the concentrated mother liquor to be purified, and the ultrasonic frequency is 20-40 kHz, the ultrasonic power is 100-200 W, and the temperature is 60-80°C. W, 60-80 ° C conditions, continue to treat for 10-30 minutes, and then stand for liquid separation. The separated ionic liquid is recovered to step C for recycling. The separated platinum metal aqueous solution is first filtered to remove the precipitate, and the filtered aqueous solution is subjected to desolventizing treatment at -0.09 to -0.1 MPa, 100-105 ° C conditions to obtain crude metal platinum, which is then dried in an oven at 80 ° C for 12-24 hours to obtain metal platinum.

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