CN110711502B - High-selectivity separation membrane based on rubidium and separation and enrichment method thereof - Google Patents

High-selectivity separation membrane based on rubidium and separation and enrichment method thereof Download PDF

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CN110711502B
CN110711502B CN201911067698.8A CN201911067698A CN110711502B CN 110711502 B CN110711502 B CN 110711502B CN 201911067698 A CN201911067698 A CN 201911067698A CN 110711502 B CN110711502 B CN 110711502B
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孟晓荣
乔茹楷
李佳文
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Xian University of Architecture and Technology
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Abstract

The invention discloses a high-selectivity separating membrane based on rubidium and a separating and enriching method thereof, wherein the high-selectivity separating membrane based on rubidium is prepared by mixing and dissolving a carrier, a basic polymer, a synergist, an organic solvent and the like into a homogeneous solution and then performing a solvent volatilization method. The separation and enrichment of rubidium is to utilize a high-selectivity membrane extraction device of rubidium to carry out efficient extraction, separation and enrichment of rubidium on mixed feed liquid containing alkali metal ions such as rubidium, lithium, sodium and the like under the acceleration of an external electric field. The separation membrane with high selectivity to rubidium ions provided by the invention has the advantages of simple and convenient membrane preparation method and stable performance; the extraction and the back extraction of the rubidium are synchronous, the separation factor of the rubidium/sodium is high, the mass transfer process is stable, and the continuous operation can be realized. Low energy consumption and no secondary pollution. The method can be used for separating and enriching the low-concentration rubidium in high-sodium and high-lithium background solutions such as brine lithium extraction raffinate or lepidolite lithium extraction raffinate.

Description

High-selectivity separation membrane based on rubidium and separation and enrichment method thereof
Technical Field
The invention belongs to the field of hydrometallurgy and industrial separation of rare and noble metals, and relates to a membrane product with a selective separation effect on noble metal rubidium, and a separation and enrichment technology for rubidium.
Background
The alkali metal rubidium has wide practical application in the fields of new energy, aerospace technology, national defense industry and the like. In China, nearly 1000 million tons of rubidium resources are distributed in liquid resources such as seawater and brine at a low concentration of less than 100mg/L, and only a very small amount of rubidium resources exist in ore resources such as lepidolite, cesium lepidolite and the like. After the rubidium content reaches 1g/L, the rubidium can be mineralized and extracted by a fractional crystallization method, a precipitation method and the like, but the low-concentration rubidium is not suitable for precipitation and mineralization extraction. Rubidium salts have higher solubility and are more difficult than alkali metal ions such as sodium, potassium, and lithium, and thus rubidium is an expensive metal.
The methods of adsorption, extraction, ion exchange and the like are suitable for extracting and separating low-concentration substances. Study on adsorption behavior of Zhao Xu (Zhao Xu, et al.) rubidium and potassium on resin and natural clinoptilolite (J)]Salt science and chemical engineering, 2017,46(3):44-46]Comparing the adsorption performance of cation exchange resin, chelating resin and natural clinoptilolite on rubidium, the D001 cation exchange resin is found to have a faster adsorption rate but a larger acidity (2moL/L HCl) for resolution, and coexists with ion K+、Na+And the like. At present, a phenol extracting agent such as 2, 4-di-tert-butylphenol (t-BAMBP) has excellent extraction performance on rubidium, but the liquid-liquid extraction process is complicated, the addition amount of an organic reagent is large, the extraction conditions are harsh, if extraction conditions with high alkalinity above 1MNaOH are needed, or stripping conditions with high acid (such as pH less than or equal to 1) are needed, the problems of equipment damage, potential safety hazard, environmental pollution and the like caused by the reagent are solved, and the industrial application of the method is limited. Crown ether extractants have specific complexing properties for certain metal ions. Literature [ Liuming, application basic research of extraction method of rubidium and cesium from brine [ D]Tianjin City, Tianjin science university, 2015]Dibenzo-21-crown-7 is synthesized, and the extraction performance of rubidium/cesium is researched by taking sulfonated kerosene as a diluent, and research results show that the extraction rate of rubidium/cesium can reach more than 70 percent, and the extraction rate of potassium is only about 30 percent, but unfortunately, ions in an organic phase cannot be effectively back-extracted under various conditions, and the research also loses the practical application value.
Various liquid membrane separation technologies which synchronously carry out extraction and back extraction can solve some disadvantages of liquid-liquid extraction technologies. The stability of the supported liquid membrane is insufficient, and the industrial application has certain limitation. However, the polymer-contained membranes (PIMs) are a more stable novel liquid membrane separation technology and have the advantages of small using amount of the extracting agent and stable property. Document [ Mohapatra P K, Lakshmi D S, Bhattacharyya A, et al. evaluation of polymer inclusion membranes association yield ethers for selective process ion from nuclear consumption ] [ J]Journal of Hazardous Materials,2009,169(1):472-137Separation performance of Cs, the results show that DTBB18C6 film has the best transport rate for cesium. However, the polymer-contained membrane has a slow mass transfer rate and a large bottleneck in industrial application, and no report about the development of membrane extraction separation related technologies of rubidium exists at present. With the leap development of high and new technology in China, the application field of high and new energy such as rubidium is necessarily wider, and the rubidium resource extraction technology is urgently in need of new development and breakthrough.
Disclosure of Invention
The invention aims to provide a high-selectivity separating membrane based on rubidium and a separating and enriching method thereof. The invention is suitable for extracting, separating and enriching rubidium from lepidolite lithium extraction raffinate, seawater, brine and other ores or liquid resources.
The invention is realized by the following technical scheme.
A separation and enrichment method of a high-selectivity separation membrane based on rubidium comprises the following steps:
(1) preparing a rubidium high-selectivity separation membrane:
mixing and dissolving 2.3-2.9% of base polymer, 0.3-0.5% of synergist, 1.2-3.0% of carrier and 94-95.5% of organic solvent according to the mass ratio, volatilizing to constant weight at room temperature, and curing to form a transparent and soft gel-like liquid film with flat appearance;
(2) constructing a liquid membrane extraction device of rubidium accelerated by external electric field coupling:
fixing and sealing a rubidium high-selectivity separation membrane in a liquid membrane mass transfer device, respectively injecting mixed feed liquid containing rubidium and an analytic phase containing rubidium into liquid pools at two sides of the membrane, respectively arranging a platinum electrode connected with an external direct-current power supply in each of the two liquid pools, externally connecting the platinum electrode in the feed liquid pool with an anode of the direct-current power supply, and connecting the platinum electrode in the analytic phase pool with a cathode of the direct-current power supply;
(3) separating and enriching rubidium from lithium and sodium:
and (3) turning on a direct-current power switch, selecting proper voltage, starting a stirring device, and performing selective extraction, separation and enrichment on rubidium under the electric field enhancement.
Preferably, the base polymer is polyvinyl chloride with a molecular weight of 15-25 ten thousand, polyvinylidene fluoride with a molecular weight of 35-50 ten thousand, or a polyvinylidene fluoride-hexafluoropropylene copolymer with a molecular weight of 10-15 ten thousand.
Preferably, the extraction promoter is dicyclohexyl 18 crown 6 or carbon 18 crown 6 or dibenzo 18 crown 6.
Preferably, the carrier is two Lewis hard bases of trioctylphosphine oxide and tri-n-octylamine.
Preferably, the weak polar aprotic solvent is one or a mixture of two of tetrahydrofuran, dichloroethane or N-methylpyrrolidone.
The dissolving process in the step (1) is to continuously stir the mixture for 12-24 hours to form a homogeneous solution; the curing film-forming method comprises the steps of spreading the homogeneous solution in a flat-bottomed glass container for 1.0-2.0 mm, and covering the flat-bottomed glass container to volatilize at normal pressure and room temperature until the weight is constant.
Preferably, the mixed feed liquid containing rubidium is a nitrate solution containing rubidium, potassium, lithium and sodium and free of chloride ions, and the pH value is kept to be 6-8; the solution environment of the rubidium analysis phase is dilute nitric acid, dilute sulfuric acid or neutral deionized water with the pH value of 6-7.
Preferably, in the step (3), the operating voltage of the external power supply is 50-180V, and the current density is not higher than 0.5A; the synchronous stirring speed in the two pools is the same and is not lower than 300 r/min.
Preferably, in the step (3), when the current density exceeds 0.5A or bubbles generated by electrolysis are serious, the mass transfer is stopped and a new separation membrane is replaced.
Preferably, the permeability coefficient of rubidium in the feed liquid phase is 2.2-6.8 μm/s; relative selectivity S of rubidium to lithium, sodium and potassiumRb/Na、SRb/KAnd SRb/Li9.1 to 14.5, 1.1 to 1.3 and 2.0 respectively.
The high-selectivity separating membrane based on rubidium prepared by the method comprises the following raw materials in percentage by mass:
2.3 to 2.9 percent of basic polymer, 0.3 to 0.5 percent of synergistic extractant, 1.2 to 3.0 percent of carrier and 94 to 95.5 percent of weak polar aprotic solvent.
The invention has the advantages and innovations that the technical scheme is implemented as follows:
1. according to the rubidium high-selectivity separation membrane provided by the invention, Lewis hard alkali substances such as trioctylphosphine oxide or tri-n-octylamine and the like which have higher coordination capacity with alkali metal ions and contain polar nitrogen-oxygen chemical bonds are added. The substance has strong binding capacity with alkali metal cations, so that when rubidium ions are dehydrated from a hydration layer, phosphine-oxygen bonds or nitrogen-oxygen complexes in the membrane can be rapidly captured. Thus, it has a stronger selectivity for rubidium.
2. The high-selectivity rubidium separation membrane product provided by the invention is simple in preparation method and mild in process conditions. The dosage of the carrier and the synergist is less, and the selectivity is strong.
3. The carrier used in the high-selectivity rubidium liquid membrane is strong in self-hydrophobicity and low in water solubility. Therefore, the film product has higher stability in practical application and can be continuously and repeatedly used for a long time. Is a high-tech product with energy conservation and emission reduction.
4. The method for selectively separating rubidium from sodium, lithium, potassium and other ions can be used for separating and enriching low-concentration rubidium in high-sodium and high-lithium background solutions such as brine lithium extraction raffinate or lepidolite lithium extraction raffinate, solves the problem of separation of precious metal rubidium from alkali metal ions such as sodium, lithium, potassium and the like, and has important industrial significance.
5. The extraction and the back extraction of the rubidium are synchronous, the separation factor of the rubidium/sodium is high, and the relative selectivity separation factor S of the rubidium, sodium and potassiumRb/NaAnd SRb/KNot less than 14.5 and 2.98 respectively; the mass transfer process is stable and can be continuously operated, and the operation is simple, the energy consumption is low, and the process amplification is easy.
Detailed Description
The following examples further illustrate the embodiments of the present invention in detail.
The invention relates to a high-selectivity rubidium separation membrane and a separation and enrichment method thereof, which comprises the following steps:
step 1: preparing a rubidium high-selectivity separation membrane:
blending 2.3-2.9% of base polymer, 0.3-0.5% of synergist, 1.2-3.0% of carrier and 94-95.5% of weak polar aprotic solvent according to the mass ratio, completely dissolving and continuously stirring for 12-24 hours to form a homogeneous transparent solution, spreading the mixed solution in a flat-bottom glass container for 1.0-2.0 mm, covering the container to volatilize at the normal pressure room temperature until the weight is constant, and curing to form a film.
Wherein the basic polymer is polyvinyl chloride with the molecular weight of 15-25 ten thousand, or polyvinylidene fluoride with the molecular weight of 35-50 ten thousand, or polyvinylidene fluoride-hexafluoropropylene copolymer with the molecular weight of 10-15 ten thousand, which has low price, acid resistance, alkali resistance and stable property.
The synergist is crown ether with specific cavity size, preferably dicyclohexyl 18 crown 6(DB18C6) or dibenzo carbon 18 crown 6.
The liquid phase carrier contains Lewis base capable of coordinating and complexing with rubidium ions and the like through acid-base coordination, and trioctylphosphine oxide or tri-n-octylamine is preferred.
One or two of tetrahydrofuran, dichloroethane, N-methylpyrrolidone and the like as weak polar aprotic solvents.
Step 2: constructing a liquid membrane extraction device of rubidium accelerated by external electric field coupling:
fixing and sealing a high-selectivity rubidium separation membrane in a liquid membrane mass transfer device, respectively injecting mixed liquor containing rubidium and a resolving phase containing rubidium into liquid pools on two sides of the membrane, wherein the mixed liquor containing rubidium is mixed liquor containing one or more than two nitrates of rubidium, lithium, sodium and the like, the concentration of a single metal ion is 10-50 mg/L, and the most suitable concentration is 30 mg/L. The pH of the feed liquid phase is 6-8 and is kept at neutral or nearly neutral condition. The analysis phase is also dilute nitric acid, dilute sulfuric acid or neutral deionized water with the pH value of 6-7.
Respectively arranging a platinum electrode connected with an external direct current power supply in each of the two liquid pools, connecting the platinum electrode in the material liquid pool with the anode of the external direct current power supply, and connecting the platinum electrode in the analytic phase pool with the cathode of the direct current power supply;
and (3): extracting, separating and enriching rubidium:
and turning on a direct current power switch, wherein the selected voltage range is 50-180V, and preferably 100V. Starting the stirring device, and keeping the diffusion speed of the materials in the solution the same at the same rotating speed of not less than 300 r/min.
During the extraction process, care was taken to observe the system current density, keeping operating below 0.5A. When the current density exceeds 0.5A, or the electrolysis phenomenon of water occurs and bubbles generated at the two electrodes are serious, the mass transfer is stopped and the membrane needs to be replaced by a new membrane.
The concentration of rubidium, potassium and sodium ions in the solution on two sides in the mass transfer process is detected by an inductively coupled plasma emission instrument (ICP-OES) after timing sampling.
Wherein the relative selectivity separation factor is the ratio of the permeability coefficients P of the two metal ions:
SRb/Na＝PRb/PNa；SRb/Li＝PRb/PLi；SRb/K＝PRb/PK
the high-selectivity rubidium separation membrane provided by the invention is a technology for selectively extracting rubidium and separating rubidium from sodium, lithium and potassium under the coupling of an external electric field, and is mainly based on the following 3 important principles:
(1) phosphorus oxygen atoms or nitrogen atoms and the like contained in the molecular structure of the carrier, and Lewis alkali with strong electron supply capacity can be combined with alkali metal cations through acid-base complex and coordination, and the premise condition of rubidium mass transfer through a separation membrane is provided by the invention.
(2) The matching between the crown cavity size of the extraction promoter crown ether substances, such as dicyclohexyl 18 crown 6(DB18C6) or dibenzo 18C6, and the radius of the alkali metal ions is the basis of selective mass transfer.
(3) Utilizes the acting force of an electric field to Rb+、K+、Na+、Li+The destruction of the hydration energy of the extraction system realizes the selective mass transfer of the extraction system to the rubidium through the difference of the radius of the rubidium and the coingregated ion, the radius of the hydration ion and the hydration energy.
The invention is further illustrated by the following specific examples.
Example 1:
mixing 2.80% of PVC, 95.13% of tetrahydrofuran, 0.39% of extraction aid DC18C6 and 1.68% of carrier trioctylphosphine oxide, stirring at room temperature until the mixture is completely dissolved, pouring the mixture into a flat glass culture dish, maintaining the liquid level at 1.0-2.0 mm, coating the mixture with a preservative film, covering the cover, horizontally standing the mixture, and volatilizing the mixture at 30 ℃ to form a semitransparent film. Soaking the mixture in a small amount of water and taking out the mixture,the method comprises the steps of selecting a membrane with the thickness of 150-200 mu m by a screw micrometer with the precision of 0.01mm, fixing the membrane by using a sealing gasket and a screw, installing the membrane in a hollow clamping plate at the center of two liquid pools of a liquid membrane permeation device, and sticking the membrane by using a sealant to ensure that materials in the liquid pools at two sides can only transfer mass through the membrane. The effective mass transfer area of the membrane is 3.14cm2. 100mL of aqueous solutions containing 30mg/L of each of rubidium nitrate, sodium nitrate and potassium nitrate were injected into one side cell, wherein the pH of the solutions was between 7.0. + -. 0.1. The resolved phase was poured into 100mL of neutral deionized water. Connecting the platinum electrode in the feed liquid pool with the positive electrode of a power supply, connecting the platinum electrode in the analysis pool with the negative electrode of the power supply, adjusting the voltage of the direct current power supply to be 50V, and turning on a power switch. The electric stirring is started and the stirring speed is kept 300 r/min. The current density in the mass transfer process is maintained below 0.03A, after 26h of mass transfer is finished, the concentration of rubidium in the feed liquid pool is respectively reduced to 3mg/L, the concentration of sodium ions and potassium ions is respectively reduced to 23mg/L and 3.5mg/L, the concentration of rubidium, sodium and potassium in the analysis pool is respectively 26.3mg/L and 6.5mg/L, and 24.5mg/L, and 90% of rubidium ions are subjected to mass transfer. The permeability coefficient of rubidium is 2.5 μm/S, and the relative selectivity separation factor S of rubidium and sodium and potassiumRb/NaAnd SRb/K14.2 and 1.1 respectively. The concentration of rubidium in the resolving cell was 4.3 times that of sodium.
Example 2:
in example 2, the dc voltage was 100V, which is different only in the operating voltage, compared to example 1. The membrane composition, the conditions of the feed liquid phase and the analysis phase are completely the same, the current density is observed to be maintained below 0.02A in the mass transfer process, after the mass transfer of 28h, the concentration of rubidium in the feed liquid pool is lower than 3mg/L, the concentration of sodium ions and potassium ions are respectively reduced to 21.5mg/L and 4.3mg/L, and 90% of rubidium ions are subjected to mass transfer. The concentration of rubidium, sodium and potassium in the analysis pool is 26.3mg/L, 6.9mg/L and 23.5mg/L respectively. The permeability coefficient of rubidium is 2.2 μm/S, and the relative selectivity separation factor S of rubidium and sodium and potassiumRb/NaAnd SRb/K12.5 and 1.3 respectively. The concentration of rubidium in the resolving cell was 3.8 times that of sodium.
Example 3:
example 3 compared with example 1, the membrane composition was different, and the feed solution contained 30mg/L of lithium ions in addition to 30mg/L of each of rubidium, sodium and potassium. Wherein, the composition of the selective separating membrane of rubidium is changed as follows:
2.3% polyvinylidene fluoride, 94.4% dichloroethane as a weakly polar aprotic solvent, 0.3% co-extractant DC18C6 and 3.0% trioctylphosphine oxide as a carrier. Mixing and dissolving the substances into a homogeneous solution, and standing and defoaming the solution in a flat plate container at room temperature to volatilize the solvent. The operating voltage is still kept at 100V, the conditions of the feed liquid phase and the analysis phase are completely the same, after 22 hours of mass transfer is carried out at the stirring speed of 300 r/min, the concentration of rubidium in the feed liquid pool is reduced to 2.5mg/L, the concentrations of lithium ions, sodium ions and potassium ions are respectively reduced to 13.0mg/L, 20.5mg/L and 4.5mg/L,>90% of the rubidium ions are transferred. The rubidium, lithium, sodium and potassium concentrations in the analytical cell were 27.6mg/L, 15mg/L, 6.8mg/L and 23.5mg/L, respectively. The permeability coefficient of rubidium is 6.8 μm/S, and the relative selectivity separation factor S of rubidium and lithium, sodium and potassiumRb/Li、SRb/NaAnd SRb/KRespectively 2.0, 9.1 and 1.1. The concentration of rubidium in the resolving pool is 1.8 times and 3.8 times of lithium and sodium respectively.
Example 4: in this example, the composition of the selective separation membrane of rubidium was different from that of example 1.
Mixing 2.8% of PVC, 94% of tetrahydrofuran and dichloroethane, 0.5% of a synergistic agent dibenzo carbon 18 crown 6 and 2.7% of carrier tri-n-octylamine, stirring at room temperature until the mixture is completely dissolved, pouring the mixture into a glass culture dish, maintaining the liquid level at 1.0-2.0 mm, coating the mixture with a preservative film, covering the cover, horizontally standing the mixture, and volatilizing the mixture at 30 ℃ to form a semitransparent film. Under the conditions of completely same material liquid and analysis on the same membrane extraction device and the same effective mass transfer area of the membrane, volume, concentration and the like as those of the embodiment 1, the platinum electrode in the material liquid pool is connected with the positive electrode of a power supply, the platinum electrode in the analysis pool is connected with the negative electrode of the power supply, 100V operation voltage is adopted, stirring speed of 300 r/min is carried out, after mass transfer is carried out for 24h, the concentration of rubidium in the material liquid pool is reduced to 2.1mg/L, the permeability coefficient of rubidium is 2.7 mu m/s, the relative selectivity separation factor of rubidium and sodium is 14.5, and the relative selectivity separation factor of rubidium and potassium is 1.3. The concentration of rubidium in the analysis cell is 5.2 times of sodium, and the concentration of rubidium in the analysis cell is 5.2 times of sodium. The current density during the mass transfer is maintained below 0.02A.
Example 5: enrichment of rubidium
Mixing 2.9% of polyvinylidene fluoride-hexafluoropropylene copolymer, 95.5% of N-methyl pyrrolidone, 0.4% of synergist DC18C6 and 1.2% of carrier trioctylphosphine oxide, stirring at room temperature until the mixture is completely dissolved, pouring the mixture into a glass culture dish, maintaining the liquid level at 1.0-2.0 mm, coating the mixture with a preservative film, covering the mixture with the preservative film, horizontally standing the mixture, and volatilizing the mixture at 30 ℃ to form a semitransparent film. The material liquid pool is connected with a liquid storage tank of material liquid through a circulating pump in an up-and-down feeding mode on the same membrane extraction device and under the same effective mass transfer area of the membrane as that of the embodiment 1. The total volume of the liquid in the liquid storage tank and the liquid feeding tank is 1L, and the solution contains 30mg/L of rubidium nitrate and sodium nitrate respectively. The pH value is adjusted to 7.0, and the analysis phase is neutral deionized water. And connecting a platinum electrode in the feed liquid pool with a power supply anode, connecting a platinum electrode in the analysis pool with a power supply cathode, and carrying out mass transfer for 80 hours at an operating voltage of 180V and a stirring speed of 300 r/min to reduce the concentration of rubidium and sodium in the feed liquid pool to 4.2mg/L and 22.71mg/L respectively. The concentration of rubidium in the resolving phase is 91.11mg/L, the rubidium is concentrated and enriched by 3.01 times, the concentration of sodium in the resolving phase is only 15.23mg/L, and the concentration of rubidium in the resolving phase is 5 times of sodium. And the current density of the system is kept below 0.05A in the whole mass transfer process.
Example 6: this example is a high selectivity separation membrane of rubidium of example 1, and four cycles of cyclic mass transfer were performed continuously under the same mass transfer conditions. The permeability coefficient of rubidium in four cycles was 3.2, 3.15, 3.05 μm/s, respectively, which was only 4.6% lower than that in the initial cycle. The rubidium high-selectivity separation membrane product provided by the invention has good stability and continuous mass transfer capability.
The present invention is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts according to the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.

Claims (6)

1. A separation and enrichment method of a high-selectivity separation membrane based on rubidium is characterized by comprising the following steps:
(1) preparing a rubidium high-selectivity separation membrane:
blending and dissolving 2.3-2.9% of base polymer, 0.3-0.5% of synergist, 1.2-3.0% of carrier and 94-95.5% of weak polar aprotic solvent according to the mass ratio to form a homogeneous solution, spreading the homogeneous solution in a flat container, covering the flat container, volatilizing the solution to constant weight at room temperature and normal pressure, and curing the solution to form a membrane to obtain the rubidium high-selectivity separation membrane;
the basic polymer is polyvinyl chloride with the molecular weight of 15-25 ten thousand, polyvinylidene fluoride with the molecular weight of 35-50 ten thousand or a copolymer of polyvinylidene fluoride-hexafluoropropylene with the molecular weight of 10-15 ten thousand;
the synergist is 18 carbon crown 6, dicyclohexyl 18 crown 6 or dibenzo 18 crown 6;
the carrier is trioctylphosphine oxide or tri-n-octylamine;
the weak polar aprotic solvent is one or a mixture of two of tetrahydrofuran, dichloroethane or N-methylpyrrolidone;
(2) constructing a liquid membrane extraction device of rubidium accelerated by external electric field coupling:
fixing and sealing a rubidium high-selectivity separation membrane in a liquid membrane mass transfer device, respectively injecting mixed feed liquid containing rubidium and an analytic phase containing rubidium into liquid pools at two sides of the membrane, respectively arranging a platinum electrode connected with an external direct-current power supply in each of the two liquid pools, externally connecting the platinum electrode in the feed liquid pool with an anode of the direct-current power supply, and connecting the platinum electrode in the analytic phase pool with a cathode of the direct-current power supply;
(3) separating and enriching rubidium from lithium and sodium:
setting voltage, stirring, and performing selective extraction, separation and enrichment of rubidium under the electric field enhancement.
2. The separation and enrichment method for the rubidium-based high-selectivity separation membrane as claimed in claim 1, wherein the dissolving process in the step (1) is to continuously stir the mixture for 12-24 hours to form a homogeneous mixed solution; the curing film-forming process is to spread the homogeneous solution in a flat-bottomed glass container for 1.0-2.0 mm and cover the flat-bottomed glass container to volatilize at normal pressure and room temperature until the weight is constant.
3. The separation and enrichment method of the rubidium-based high-selectivity separation membrane is characterized in that the mixed feed liquid containing rubidium is a nitrate solution of rubidium and lithium or sodium without chloride ions, and the pH value is kept at 6-8; the solution environment of the rubidium analysis phase is dilute nitric acid, dilute sulfuric acid or neutral deionized water with the pH value of 6-7.
4. The separation and enrichment method of the rubidium-based high-selectivity separation membrane as claimed in claim 1, wherein in the step (3), the voltage of a direct current power supply is set to be 50-180V, and the current density is not higher than 0.5A; the synchronous stirring speeds in the two tanks are the same and are not lower than 300 r/m;
when the current density exceeds 0.5A or bubbles generated by electrolysis are serious, the mass transfer is stopped and a new separation membrane is replaced.
5. The separation and enrichment method for the rubidium-based high-selectivity separation membrane as claimed in any one of claims 1 to 4, wherein the permeability coefficient of rubidium is 2.2-6.8 μm/s; relative selectivity S of rubidium to lithium and sodiumRb/NaAnd SRb/Li9.1 to 14.5 and 1.1 to 2.98 respectively.
6. A rubidium-based high selectivity separation membrane prepared by the method of claim 5, which is characterized by comprising the following raw materials in mass ratio:
2.3 to 2.9 percent of basic polymer, 0.3 to 0.5 percent of synergistic extractant, 1.2 to 3.0 percent of carrier and 94 to 95.5 percent of weak polar aprotic solvent.
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