An electrically controlled ion extraction membrane, its preparation method and use

Abstract

The application discloses an electrically controlled ion extraction membrane and a preparation method and application thereof, and the electrically controlled ion extraction membrane comprises a support layer and an electrically active extraction layer, the support layer is composed of an ultrafiltration membrane, the electrically active extraction layer is composed of a porous carbon-based membrane, the support layer and the electrically active extraction layer are subjected to suction filtration and vacuum drying to form an ultrafiltration / porous carbon-based composite membrane, the composite membrane is immersed in an extractant to be adsorbed and saturated, and the electrically controlled ion extraction membrane is formed. The application realizes selective separation of lithium ions in salt lake brine, underground brine or concentrated seawater; the extractant in the pore channel of the electrically controlled ion extraction membrane is insoluble in water, is easy to separate, is stable in property, has strong affinity with lithium ions, can selectively extract lithium ions in brine, and then the lithium ions extracted on the membrane are back-extracted into a back-extraction liquid, so that the lithium ion extraction and back-extraction processes are continuously operated; ion transfer is strengthened by using an electric field, a chemical equilibrium of traditional support liquid membrane extraction is broken, and the separation rate is fast; and the application is easy to industrialize.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrically controlled ion extraction membrane and a preparation method thereof, and a method for extracting lithium ions in salt lake brine, underground brine or concentrated seawater using the prepared electrically controlled ion extraction membrane, and belongs to the technical field of electrically controlled ion membrane separation. BACKGROUND

[0002] New energy vehicles and portable electronic devices powered by lithium ion batteries have developed rapidly, which has led to a continuous increase in global demand for lithium resources. At present, about 80% of the proven lithium resource reserves in China are distributed in salt lakes and underground brines in Qinghai and Tibet. Therefore, efficient development of salt lake lithium resources is of great significance to ensure the healthy development of the lithium battery-related industry. However, salt lakes in China generally have the characteristic of high magnesium-lithium ratio. Since the ionic radii of lithium ions and magnesium ions are similar, it is difficult to separate them. Currently, the technologies for extracting lithium from salt lake brine with high magnesium-lithium ratio include adsorption, extraction, and membrane separation. Among them, the adsorption method has simple process, low cost, and high selectivity, but the adsorption and desorption process is time-consuming, and the desorption process consumes a large amount of water; the solvent extraction method has high selectivity and can be operated continuously, but the equipment is prone to corrosion and there is a problem of contamination of the extractant; the membrane separation method is simple to operate and stable to run, but has low selectivity and is prone to membrane pollution.

[0003] Chinese patent CN102718292A discloses an electrically controlled ion-selective membrane separation process. This method utilizes the electrically controlled ion exchange performance and selective permeability of the membrane electrode in a diaphragm electrode reactor. By applying an oxidation-reduction potential to the double diaphragm electrode alternately, the simultaneous introduction and release of target anions and cations are controlled, and under the action of the external electric field applied by the auxiliary electrode, the separation and recovery of anions and cations in dilute solution are realized. This technology can accelerate the separation rate of target ions based on electric field driving, and realize continuous operation at the same time. However, conventional electrically controlled ion-selective membranes are solid-phase membranes, and ions from the solution need to pass through the liquid / solid interface to enter the membrane, which has a large transfer resistance. In addition, electrically controlled ion-selective membranes are usually prepared by compounding organic polymers and inorganic electroactive materials, and the channel size for ion transfer in the membrane is difficult to accurately control, so the selectivity is poor.

[0004] Supported liquid membrane technology is a new type of ion separation method with high selectivity and simple process. Chinese patent CN109680146A discloses a supported liquid membrane lithium extraction device and a membrane method for extracting lithium from brine. Supported liquid membrane technology has the advantages of high selectivity, simple process and can realize simultaneous extraction and back extraction. However, liquid membrane extraction mainly uses the concentration difference of ions as the driving force. When extracting and separating lithium resources from salt lake brine, underground brine or concentrated seawater, the concentration of lithium ions in the brine is low. Therefore, the supported liquid membrane has the problems of slow rate and low efficiency when extracting and separating lithium ions. Therefore, it is of great significance to develop a new lithium ion separation technology for high magnesium-lithium ratio salt lake brine. SUMMARY

[0005] In order to solve the problems of poor selectivity of electrically controlled ion selective permeable membrane when extracting lithium from salt lake brine, underground brine or concentrated seawater, and slow separation rate of supported liquid membrane technology, the present application couples electrically controlled ion selective permeable membrane with supported liquid membrane, proposes an electrically controlled ion extraction membrane, and by establishing an electrically controlled ion membrane extraction and separation system, proposes a method for extracting lithium from salt lake brine, underground brine or concentrated seawater. This method has the characteristics of high selectivity, fast separation rate, and can realize continuous operation of extraction and back extraction at the same time.

[0006] The present application provides an electrically controlled ion extraction membrane, comprising a support layer and an electrically active extraction layer, the support layer is composed of ultrafiltration membrane, the electrically active extraction layer is composed of porous carbon-based membrane, the support layer and the electrically active extraction layer are made into ultrafiltration / multilayer carbon-based composite membrane after being filtered and vacuum dried, the composite membrane is immersed in an extractant to be adsorbed and saturated, and an electrically controlled ion extraction membrane is formed.

[0007] Further, the material of the ultrafiltration membrane is one of cellulose acetate, cellulose acetate ester, polyethylene, polysulfone or polyamide.

[0008] Further, the extractant is one of carboxymethyl trimethyl bis(trifluoromethyl) sulfonimide, 1-butyl-3-methyl imidazole bis(trifluoromethyl sulfonyl) imine-tetrabutyl phosphate, 2-ethylhexyl hydrogen-2-ethylhexyl phosphate tetrabutyl ammonium, 1-butyl-3-methyl imidazole tetraphenylboric acid-tetrabutyl phosphate or bis(2,4,4-trimethyl pentyl) phosphoric acid tetrabutyl phosphor.

[0009] Further, the porous carbon-based membrane is made of conductive carbon material, binder and dispersant, the conductive carbon material is one of carbon nanotube, graphene, nanocarbon fiber or conductive carbon black; the binder is one of polyvinylidene fluoride, polyacrylic acid, polyvinyl alcohol or carboxymethyl cellulose; the dispersant is one of N,N-dimethylformamide, N-methyl pyrrolidone, ethanol or water.

[0010] The present application provides a preparation method of the above-mentioned electrically controlled ion extraction membrane, comprising the following steps:

[0011] (1) mixing the conductive carbon material, the binder and the dispersant in proportion, uniformly mixing by ball milling, and then preparing a carbon-based film on the surface of the ultrafiltration membrane by vacuum suction filtration to obtain an ultrafiltration / carbon-based composite membrane;

[0012] (2) freeze-drying the ultrafiltration / carbon-based composite membrane to completely volatilize the dispersant between the conductive carbon material and the binder in the ultrafiltration / carbon-based composite membrane, forming a porous carbon-based film with a developed pore structure, and preparing an ultrafiltration / porous carbon-based composite membrane;

[0013] (3) placing the ultrafiltration / porous carbon-based composite membrane into an extractant, filling the extractant into the pores of the porous carbon-based film through adsorption, and adsorbing for 5-24 h, so that the porous carbon-based film combined with the support layer of the ultrafiltration membrane is obtained, that is, the electrically controlled ion extraction membrane.

[0014] Further, the material of the ultrafiltration membrane is one of cellulose acetate, cellulose acetate ester, polyethylene, polysulfone or polyamide;

[0015] Further, the conductive carbon material is one of carbon nanotubes, graphene, nanocarbon fibers or conductive carbon black;

[0016] Further, the binder is one of polyvinylidene fluoride, polyacrylic acid, polyvinyl alcohol or carboxymethyl cellulose;

[0017] Further, the dispersant is one of N,N-dimethylformamide, N-methylpyrrolidone, ethanol or water;

[0018] Further, when the conductive carbon material, the binder and the dispersant are mixed, the mass ratio of the conductive carbon material to the binder is 2:1-1:2, and the mass ratio of the conductive carbon material to the dispersant is 1:3-1:10;

[0019] Further, the temperature of the freeze-drying is -10 ℃-100 ℃, the vacuum degree is 0.03 mbar-0.10 mbar, and the freeze-drying time is 5-24 h.

[0020] Further, the extractant is one of carboxymethyl trimethyl bis(trifluoromethyl) sulfonimide, 1-butyl-3-methyl imidazole bis(trifluoromethyl sulfonyl) imine-tetrabutyl phosphate, 2-ethylhexyl hydrogen-2-ethylhexyl phosphate tetrabutyl ammonium, 1-butyl-3-methyl imidazole tetraphenylboric acid-tetrabutyl phosphate or bis(2,4,4-trimethyl pentyl) phosphate tetrabutyl phosphonium.

[0021] The application also provides an electrically controlled ion membrane extraction separation system using the electrically controlled ion membrane, which is composed of a raw material tank A1, a back extraction tank A2, a raw material liquid chamber B1, a back extraction liquid chamber B2, an electrically controlled ion membrane M1, a raw material tank auxiliary electrode C1, a back extraction tank auxiliary electrode C2, a circuit control system D1, a circuit control system D2, a raw material liquid circulating pump E1, a back extraction liquid circulating pump E2 and related pipeline connections; wherein the raw material liquid chamber B1 and the back extraction liquid chamber B2 are separated by the electrically controlled ion membrane M1.

[0022] Specifically, the bottom of the raw material tank A1 is connected with the raw material liquid chamber B1 through the raw material liquid circulating pump E1, and the top of the raw material liquid chamber B1 is connected with the top of the raw material tank A1 through a pipeline to form a circulating loop; the back extraction tank A2 is connected with the back extraction liquid chamber B2 through the back extraction liquid circulating pump E2, and the top of the back extraction liquid chamber B2 is connected with the top of the back extraction tank A2 through a pipeline to form a circulating loop; the raw material liquid chamber B1 and the back extraction liquid chamber B2 are located on the two sides of the electrically controlled ion membrane M1 respectively, the raw material liquid chamber B1 is provided with the raw material tank auxiliary electrode C1, the back extraction liquid chamber B2 is provided with the back extraction tank auxiliary electrode C2, the raw material tank auxiliary electrode C1 and the back extraction tank auxiliary electrode C2 are connected with the circuit control system D1 at the same time, the tank voltage is applied by the circuit control system D1, and the raw material tank auxiliary electrode C1 and the electrically controlled ion membrane M1 are connected with the circuit control system D2 at the same time, the pulse voltage is applied by the circuit control system D2.

[0023] The application provides a method for extracting lithium by using the electrically controlled ion membrane extraction separation system, and the specific steps are as follows:

[0024] (1) the raw material liquid in the raw material tank A1 is sent into the raw material liquid chamber B1 through a pipeline and the raw material liquid circulating pump E1, and then is returned to the raw material tank A1 through a pipeline;

[0025] (2) the back extraction liquid in the back extraction tank A2 is sent into the back extraction liquid chamber B2 through a pipeline and the back extraction liquid circulating pump E2, and then is returned to the back extraction tank A2 through a pipeline;

[0026] (3) the constant tank voltage is applied between the raw material tank auxiliary electrode C1 and the back extraction tank auxiliary electrode C2 by the circuit control system D1;

[0027] (4) the pulse voltage is applied between the raw material tank auxiliary electrode C1 and the electrically controlled ion membrane M1 by the circuit control system D2;

[0028] (5) the target lithium ion in the raw material liquid chamber B1 enters the electrically controlled ion membrane through an extraction process, and enters the back extraction liquid chamber B2 through a back extraction process, so that the extraction and separation of the lithium ion in the raw material liquid are realized.

[0029] Further, the raw material solution is a lithium-containing brine with high magnesium-lithium ratio, wherein the lithium ion concentration is 10 mg / L ~1000 mg / L, and the mass concentration ratio of magnesium to lithium is 5:1~1500:1.

[0030] Further, the back-extraction solution is one of hydrochloric acid aqueous solution, sulfuric acid aqueous solution or nitric acid aqueous solution, and the concentration is 0.5 mol / L ~6 mol / L.

[0031] Further, the constant cell voltage applied between the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back-extraction tank is 0.5 V~1.5 V.

[0032] Further, the pulse voltage applied between the auxiliary electrode C1 of the raw material tank and the electrically controlled ion extraction membrane M1 is 0.5 V ~1.5 V, and the pulse frequency is 0.0001 Hz~10 Hz.

[0033] Further, the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back-extraction tank are one of metal titanium plate, graphite plate, carbon felt, carbon cloth or carbon paper.

[0034] The extractant in the pore of the electrically controlled ion extraction membrane has low surface tension, is difficult to dissolve in water, is stable in nature, and can stably coexist with the raw material solution and the back-extraction solution. The extractant has strong affinity with lithium ions, can selectively extract lithium ions in the raw material solution, and then the lithium ions extracted on the membrane are back-extracted into the back-extraction solution to realize directional and selective separation of lithium ions. This process is different from the traditional extraction method in which extraction and back-extraction need to be carried out in steps, and the electrically controlled ion membrane extraction process can realize continuous operation of the extraction and back-extraction process. The constant cell voltage applied between the auxiliary electrode of the raw material tank and the auxiliary electrode of the back-extraction tank by the electrically controlled ion membrane extraction system can further strengthen the directional transfer of lithium ions from the raw material solution tank to the back-extraction tank through the electrically controlled ion extraction membrane. At the same time, the pulse voltage applied to the auxiliary electrode of the raw material tank and the electrically controlled ion extraction membrane can regulate the charge load of the conductive carbon material in the electrically controlled ion extraction membrane, and then change the microelectric field of the extractant in the pore of the electrically active extraction layer, accelerate the transfer rate of lithium ions in the extractant through the charge-related force, and improve the extraction and separation efficiency.

[0035] The beneficial effects of the present application are as follows:

[0036] (1) The present application utilizes the electrically controlled ion extraction membrane, and combines the electrically controlled ion membrane extraction separation system, so that the selective separation of lithium ions in the salt lake brine, underground brine or concentrated seawater can be realized; the extractant in the pore channel of the electrically controlled ion extraction membrane is insoluble in water, easy to separate, stable in property and has strong affinity with lithium ions, so that the lithium ions in the brine can be selectively extracted, and then the lithium ions extracted on the membrane are back-extracted into the back-extraction liquid, so that the continuous operation of the lithium ion extraction and back-extraction process is realized; the electrically controlled ion extraction membrane is used to extract lithium from the salt lake brine, underground brine or concentrated seawater, and has the characteristics of high selectivity and fast separation rate;

[0037] (2) The present application adopts the electrically controlled ion membrane extraction method, combines the dual action of tank voltage and pulse voltage, utilizes the electric field to strengthen ion transfer, and breaks the chemical equilibrium of the traditional supported liquid membrane extraction, so that the separation rate is fast.

[0038] (3) The present application has a simple synthesis route, low consumption of extractant, low cost and easy industrialization. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is a structure diagram of the electrically controlled ion membrane extraction system;

[0040] Figure 2 is a scanning electron microscope picture of the ultrafiltration / porous carbon-based composite membrane prepared in Example 1;

[0041] Figure 3 is a scanning electron microscope picture of the electrically controlled ion extraction membrane prepared in Example 1;

[0042] In the figure: A1 is a raw material tank, A2 is a back-extraction tank, B1 is a raw material liquid chamber, B2 is a back-extraction liquid chamber, M1 is an electrically controlled ion extraction membrane, C1 is a raw material tank auxiliary electrode, C2 is a back-extraction tank auxiliary electrode, D1 is a circuit control system applied between the raw material tank auxiliary electrode C1 and the back-extraction tank auxiliary electrode C2, D2 is a circuit control system applied between the raw material tank auxiliary electrode C1 and the electrically controlled ion extraction membrane M1, E1 is a raw material liquid circulating pump, and E2 is a back-extraction liquid circulating pump. DETAILED DESCRIPTION

[0043] The present application will be further described below by examples, but is not limited to the following examples.

[0044] Figure 1This is a structural diagram of an electro-controlled ion-extraction membrane system; it consists of a raw material tank A1, a back-extraction tank A2, a raw material liquid chamber B1, a back-extraction liquid chamber B2, an electro-controlled ion-extraction membrane M1, a raw material tank auxiliary electrode C1, a back-extraction tank auxiliary electrode C2, a circuit control system D1, a circuit control system D2, a raw material liquid circulation pump E1, a back-extraction liquid circulation pump E2, and related pipeline connections; wherein, the raw material liquid chamber B1 and the back-extraction liquid chamber B2 are separated by the electro-controlled ion-extraction membrane. Specifically, the bottom of the raw material tank A1 is connected to the raw material liquid chamber B1 via the raw material liquid circulation pump E1, and the top of the raw material liquid chamber B1 is connected to the top of the raw material tank A1 via a pipeline to form a circulation loop; the back-extraction tank A2 is connected to the back-extraction liquid chamber B2 via the back-extraction liquid circulation pump E2, and the top of the back-extraction liquid chamber B2 is connected to the top of the back-extraction tank A2 via a pipeline to form a circulation loop; the raw material liquid chamber B1 and the back-extraction liquid chamber B2 are located on both sides of the electrically controlled ion extraction membrane M1, respectively; the raw material liquid chamber B1 is equipped with the raw material tank auxiliary electrode C1, and the back-extraction liquid chamber B2 is equipped with... An auxiliary electrode C2 for a back-extraction tank is provided. A circuit control system D1 is applied between the auxiliary electrode C1 for the raw material tank and the auxiliary electrode C2 for the back-extraction tank. Both the auxiliary electrode C1 for the raw material tank and the auxiliary electrode C2 for the back-extraction tank are connected to the circuit control system D1, and the tank voltage is applied by D1. A circuit control system D2 is applied between the auxiliary electrode C1 for the raw material tank and the electro-controlled ion extraction membrane M1. Both the auxiliary electrode C1 for the raw material tank and the electro-controlled ion extraction membrane M1 are connected to the circuit control system D2, and the pulse voltage is applied by D2. Example 1

[0045] (1) 100 mg carbon nanotubes, 100 mg polyvinylidene fluoride and 500 mg N,N-dimethylformamide were mixed and ball-milled at a speed of 800 r / min for 8 h. After the mixture was homogeneous, a carbon-based membrane was prepared on the surface of the cellulose acetate ultrafiltration membrane by vacuum filtration to obtain an ultrafiltration / carbon-based composite membrane.

[0046] (2) The ultrafiltration / carbon-based composite membrane was freeze-dried at -40 ℃ and 0.04 mbar for 20 h to completely volatilize the N,N-dimethylformamide between the carbon nanotubes and polytetrafluoroethylene in the carbon-based membrane, forming a porous carbon-based membrane with a well-developed pore structure composed of carbon nanotubes and polytetrafluoroethylene. The ultrafiltration / porous carbon-based composite membrane was prepared, and its scanning electron microscope image is attached. Figure 2 As shown; from Figure 2 As can be seen, carbon nanotubes are uniformly deposited on the surface of the ultrafiltration membrane and stably bonded together by polytetrafluoroethylene. Through freeze-drying, the carbon nanotubes maintain a good three-dimensional porous structure, which facilitates the adsorption of the extractant.

[0047] (3) The ultrafiltration / porous carbon-based composite membrane was placed in the extractant carboxymethyltrimethylbis(trifluoromethyl)sulfonylimide. Through adsorption, carboxymethyltrimethylbis(trifluoromethyl)sulfonylimide filled the pores in the porous carbon-based membrane. After 12 h, the porous carbon-based membrane after adsorption saturation became the electroactive extraction layer. Combined with the ultrafiltration membrane support layer, an electro-controlled ion extraction membrane was prepared. Its scanning electron microscope image is attached. Figure 3 As shown; from Figure 3 As can be seen, the pore structure between carbon nanotubes is effectively filled by the extractant, exhibiting a dense membrane structure.

[0048] (4) Combined with the appendix Figure 1 As shown, the prepared electro-controlled ion extraction membrane is used as M1, and the graphite plate is used as the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back extraction tank. An electro-controlled ion membrane extraction and separation system is assembled to extract and separate lithium ions in brine. The lithium ion concentration in the brine is 200 mg / L, and the mass concentration ratio of magnesium to lithium is 100:1.

[0049] (5) The raw material liquid brine in the raw material tank A1 is sent into the raw material chamber B1 through the raw material liquid circulation pump E1 via the pipeline, and then returned to the raw material tank A1 through the pipeline;

[0050] (6) The 1.0 mol / L hydrochloric acid aqueous solution of the back-extraction liquid in the back-extraction tank A2 is sent into the back-extraction liquid chamber B2 through the pipeline via the back-extraction liquid circulation pump E2, and then returned to the back-extraction tank A2 through the pipeline;

[0051] (7) A constant cell voltage of 1.2 V is applied between the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back extraction tank through the circuit control system D1;

[0052] (8) A pulse voltage of 0.6V is applied between the auxiliary electrode C1 of the raw material tank and the electro-controlled ion extraction membrane M1 through the circuit control system D2, and the pulse frequency is 0.01 Hz;

[0053] (9) The target lithium ions in the raw material liquid chamber B1 enter the electro-controlled ion extraction membrane through the extraction process, and then enter the back extraction liquid chamber B2 through the back extraction process. After 3 hours of extraction and separation, the lithium ion concentration in the back extraction tank A2 is 180 mg / L, the separation efficiency is 90%, the magnesium ion concentration is 430 mg / L, and the magnesium-lithium mass concentration ratio decreases from 100:1 in the brine to 2.39:1, achieving good separation. Example 2

[0054] (1) Mix 100 mg graphene, 120 mg polyacrylic acid and 300 mg water, and mix by ball milling at a speed of 800 r / min for 8 h. After the mixture is homogeneous, prepare a carbon-based membrane on the surface of the cellulose acetate ultrafiltration membrane by vacuum filtration to obtain an ultrafiltration / carbon-based composite membrane.

[0055] (2) The ultrafiltration / carbon-based composite membrane was freeze-dried at a temperature of -50 °C, a vacuum of 0.05 mbar, and a freeze-drying time of 20 h to completely evaporate the water between graphene and polyacrylic acid in the carbon-based membrane, forming a porous carbon-based membrane with a well-developed pore structure composed of graphene and polyacrylic acid, thus preparing the ultrafiltration / porous carbon-based composite membrane.

[0056] (3) The ultrafiltration / porous carbon-based composite membrane is placed in the extractant 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine-tributyl phosphate. The 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine-tributyl phosphate fills the pores in the porous carbon-based membrane through adsorption. After 12 h, the porous carbon-based membrane after adsorption saturation becomes the electroactive extraction layer. Combined with the ultrafiltration membrane support layer, an electro-controlled ion extraction membrane is prepared.

[0057] (4) Combined with the appendix Figure 1 As shown, the prepared electro-controlled ion extraction membrane is used as M1, and carbon felt is used as the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back extraction tank. An electro-controlled ion membrane extraction and separation system is assembled to extract and separate lithium ions in brine. The lithium ion concentration in the brine is 20 mg / L, and the mass concentration ratio of magnesium to lithium is 200:1.

[0058] (5) The raw material liquid brine in the raw material tank A1 is sent into the raw material chamber B1 through the raw material liquid circulation pump E1 via the pipeline, and then returned to the raw material tank A1 through the pipeline;

[0059] (6) The 3.0 mol / L sulfuric acid aqueous solution in the back-extraction tank A2 is sent into the back-extraction chamber B2 through the pipeline via the back-extraction liquid circulation pump E2, and then returned to the back-extraction tank A2 through the pipeline;

[0060] (7) A constant cell voltage of 1.0 V is applied between the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back extraction tank through the circuit control system D1;

[0061] (8) A pulse voltage of 0.9V is applied between the auxiliary electrode C1 of the raw material tank and the electro-controlled ion extraction membrane M1 through the circuit control system D2, and the pulse frequency is 0.001 Hz;

[0062] (9) The target lithium ions in the raw material liquid chamber B1 enter the electro-controlled ion extraction membrane through the extraction process, and then enter the back extraction liquid chamber B2 through the back extraction process. After 3 hours of extraction and separation, the lithium ion concentration in the back extraction tank A2 is 16.5 mg / L, the separation efficiency is 84%, the magnesium ion concentration is 50.5 mg / L, and the magnesium-lithium ratio drops from 200:1 in the brine to 3.06:1, achieving good separation. Example 3

[0063] (1) Mix 100 mg of carbon nanofibers, 150 mg of polyvinyl alcohol and 500 mg of N-methylpyrrolidone, and mix by ball milling at a speed of 800 r / min for 8 h. After the mixture is homogeneous, prepare a carbon-based membrane on the surface of the polyethylene ultrafiltration membrane by vacuum filtration to obtain an ultrafiltration / carbon-based composite membrane.

[0064] (2) The ultrafiltration / carbon-based composite membrane was freeze-dried at a temperature of -60 ℃, a vacuum of 0.08 mbar, and a freeze-drying time of 20 h to completely volatilize the N-methylpyrrolidone between the carbon nanofibers and polyvinyl alcohol in the carbon-based membrane, forming a porous carbon-based membrane with a well-developed pore structure composed of carbon nanofibers and polyvinyl alcohol, thus preparing the ultrafiltration / porous carbon-based composite membrane.

[0065] (3) The ultrafiltration / porous carbon-based composite membrane is placed in the extractant 2-ethylhexylhydro-2-ethylhexyltetrabutylammonium phosphate. The 2-ethylhexylhydro-2-ethylhexyltetrabutylammonium phosphate fills the pores in the porous carbon-based membrane through adsorption. After 12 h, the porous carbon-based membrane after adsorption saturation becomes the electroactive extraction layer. Combined with the ultrafiltration membrane support layer, an electrocontrolled ion extraction membrane is prepared.

[0066] (4) Combined with the appendix Figure 1 As shown, the prepared electro-controlled ion extraction membrane is used as M1, and the titanium plate is used as the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back extraction tank. An electro-controlled ion membrane extraction and separation system is assembled to extract and separate lithium ions in brine, wherein the lithium ion concentration in the brine is 500 mg / L and the mass concentration ratio of magnesium to lithium is 20:1.

[0067] (5) The raw material liquid brine in the raw material tank A1 is sent into the raw material chamber B1 through the raw material liquid circulation pump E1 via the pipeline, and then returned to the raw material tank A1 through the pipeline;

[0068] (6) The 6.0 mol / L nitric acid aqueous solution of the back-extraction liquid in the back-extraction tank A2 is sent into the back-extraction liquid chamber B2 through the pipeline via the back-extraction liquid circulation pump E2, and then returned to the back-extraction tank A2 through the pipeline;

[0069] (7) A constant cell voltage of 1.5 V is applied between the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back extraction tank through the circuit control system D1;

[0070] (8) A pulse voltage of 1.2V is applied between the auxiliary electrode C1 of the raw material tank and the electro-controlled ion extraction membrane M1 through the circuit control system D2, and the pulse frequency is 1.0 Hz;

[0071] (9) The target lithium ions in the raw material liquid chamber B1 enter the electro-controlled ion extraction membrane through the extraction process, and then enter the back extraction liquid chamber B2 through the back extraction process. After 3 hours of extraction and separation, the lithium ion concentration in the back extraction tank A2 is 455 mg / L, the separation efficiency is 91%, the magnesium ion concentration is 580 mg / L, and the magnesium-lithium ratio drops from 20:1 in the brine to 1.27:1, achieving good separation. Example 4

[0072] (1) Mix 100 mg of conductive carbon black, 80 mg of carboxymethyl cellulose and 800 mg of ethanol, and mix by ball milling at a speed of 800 r / min for 8 h. After the mixture is homogeneous, prepare a carbon-based membrane on the surface of the polysulfone ultrafiltration membrane by vacuum filtration to obtain an ultrafiltration / carbon-based composite membrane.

[0073] (2) The ultrafiltration / carbon-based composite membrane was freeze-dried at a temperature of -90 ℃, a vacuum of 0.05 mbar, and a freeze-drying time of 20 h to completely evaporate the ethanol between the conductive carbon black and carboxymethyl cellulose in the carbon-based membrane, forming a porous carbon-based membrane with a well-developed pore structure composed of conductive carbon black and carboxymethyl cellulose, thus preparing the ultrafiltration / porous carbon-based composite membrane.

[0074] (3) The ultrafiltration / porous carbon-based composite membrane is placed in the extractant 1-butyl-3-methylimidazolium tetraphenylboronic acid-tributyl phosphate. The 1-butyl-3-methylimidazolium tetraphenylboronic acid-tributyl phosphate fills the pores in the porous carbon-based membrane through adsorption. After 12 h, the porous carbon-based membrane after adsorption saturation becomes the electroactive extraction layer. Combined with the ultrafiltration membrane support layer, an electrocontrolled ion extraction membrane is prepared.

[0075] (4) Combined with the appendix Figure 1 As shown, the prepared electro-controlled ion extraction membrane is used as M1, and carbon cloth is used as the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back extraction tank. An electro-controlled ion membrane extraction and separation system is assembled to extract and separate lithium ions in brine. The lithium ion concentration in the brine is 900 mg / L, and the mass concentration ratio of magnesium to lithium is 15:1.

[0076] (5) The raw material liquid brine in the raw material tank A1 is sent into the raw material chamber B1 through the raw material liquid circulation pump E1 via the pipeline, and then returned to the raw material tank A1 through the pipeline;

[0077] (6) The stripping solution 0.5 mol / L hydrochloric acid aqueous solution in the stripping tank A2 is sent into the stripping solution chamber B2 through the pipeline by the stripping solution circulating pump E2, and then returned to the stripping tank A2 through the pipeline;

[0078] (7) A constant tank voltage of 0.8 V is applied between the raw material tank auxiliary electrode C1 and the stripping tank auxiliary electrode C2 by the circuit control system D1;

[0079] (8) A pulse voltage of 0.7 V is applied between the raw material tank auxiliary electrode C1 and the electrically controlled ion extraction membrane M1 by the circuit control system D2, and the pulse frequency is 5.0 Hz;

[0080] (9) The target lithium ions in the raw material liquid chamber B1 enter the electrically controlled ion extraction membrane through the extraction process, and enter the stripping solution chamber B2 through the stripping process. After 3 h of extraction separation, the lithium ion concentration in the stripping tank A2 is 780 mg / L, the separation efficiency is 87%, the magnesium ion concentration is 1050 mg / L, and the magnesium-lithium ratio is reduced from 15:1 in the brine to 1.35:1, achieving good separation. Example 5

[0081] (1) 100 mg of carbon nanotubes, 180 mg of polyvinylidene fluoride, and 900 mg of N,N-dimethylformamide were mixed by ball milling at a speed of 800 r / min for 8 h. After mixing uniformly, a layer of carbon-based membrane was prepared on the surface of the polyamide ultrafiltration membrane by vacuum filtration, obtaining an ultrafiltration / carbon-based composite membrane;

[0082] (2) The ultrafiltration / carbon-based composite membrane was freeze-dried at a temperature of -20 ℃ and a vacuum degree of 0.08 mbar for 20 h to completely volatilize the N,N-dimethylformamide between the carbon nanotubes and the polyvinylidene fluoride in the carbon-based membrane, forming a porous carbon-based membrane composed of carbon nanotubes and polyvinylidene fluoride with developed pore structure, thereby preparing an ultrafiltration / porous carbon-based composite membrane;

[0083] (3) The ultrafiltration / porous carbon-based composite membrane was placed in the extractant tetra-n-butylphosphonium bis(2,4,4-trimethylpentyl) phosphate, and the tetra-n-butylphosphonium bis(2,4,4-trimethylpentyl) phosphate was filled into the pores of the porous carbon-based membrane by adsorption. After 12 h, the porous carbon-based membrane saturated by adsorption was an electroactive extraction layer, which was combined with the support layer of the ultrafiltration membrane to prepare an electrically controlled ion extraction membrane;

[0084] (4) The electrically controlled ion extraction membrane was combined with the electrically controlled ion extraction membrane of the raw material tank auxiliary electrode C1 and the stripping tank auxiliary electrode C2 to form an electrically controlled ion extraction system. Figure 1As shown, the prepared electrically controlled ion extraction membrane is used as M1, carbon paper is used as the raw material tank auxiliary electrode C1 and the stripping tank auxiliary electrode C2, and an electrically controlled ion membrane extraction separation system is assembled to extract and separate lithium ions in the brine, wherein the lithium ion concentration in the brine is 300 mg / L, and the mass concentration ratio of magnesium to lithium is 350:1;

[0085] (5) The raw material liquid brine in the raw material tank A1 is sent to the raw material liquid chamber B1 through the pipeline by the raw material liquid circulating pump E1, and then returned to the raw material tank A1 through the pipeline;

[0086] (6) The stripping liquid 2.0 mol / L sulfuric acid aqueous solution in the stripping tank A2 is sent to the stripping liquid chamber B2 through the pipeline by the stripping liquid circulating pump E2, and then returned to the stripping tank A2 through the pipeline;

[0087] (7) A constant tank voltage of 1.1 V is applied between the raw material tank auxiliary electrode C1 and the stripping tank auxiliary electrode C2 by the circuit control system D1;

[0088] (8) A pulse voltage of 0.85 V is applied between the raw material tank auxiliary electrode C1 and the electrically controlled ion extraction membrane M1 by the circuit control system D2, and the pulse frequency is 0.0005 Hz;

[0089] (9) The target lithium ions in the raw material liquid chamber B1 enter the electrically controlled ion extraction membrane through the extraction process, and enter the stripping liquid chamber B2 through the stripping process. After 3 h of extraction and separation, the lithium ion concentration in the stripping tank A2 is 238 mg / L, the separation efficiency is 79%, the magnesium ion concentration is 750 mg / L, and the magnesium to lithium ratio is reduced from 350:1 in the brine to 3.15:1, achieving good separation.

Claims

1. An electro-controlled ion extraction membrane, characterized in that: The membrane consists of a support layer and an electroactive extraction layer. The support layer is composed of an ultrafiltration membrane, and the electroactive extraction layer is composed of a porous carbon-based membrane. The support layer and the electroactive extraction layer are filtered and vacuum dried to form an ultrafiltration / porous carbon-based composite membrane. The composite membrane is immersed in the extractant and becomes saturated with adsorption to form an electro-controlled ion extraction membrane. The material of the ultrafiltration membrane is one of cellulose acetate, cellulose acetate ester, polyethylene, polysulfone, or polyamide. The extractant is one of carboxymethyltrimethylbis(trifluoromethyl)sulfonylimide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide-tributyl phosphate, 2-ethylhexylhydro-2-ethylhexyl tetrabutylammonium phosphate, 1-butyl-3-methylimidazolium tetraphenylboronic acid-tributyl phosphate or bis(2,4,4-trimethylpentyl)tetrabutylphosphine phosphate; The porous carbon-based membrane is made of conductive carbon material, binder, and dispersant. The conductive carbon material is one of carbon nanotubes, graphene, carbon nanofibers, or conductive carbon black. The binder is one of polyvinylidene fluoride, polyacrylic acid, polyvinyl alcohol, or carboxymethyl cellulose. The dispersant is one of N,N-dimethylformamide, N-methylpyrrolidone, ethanol, or water. The method for preparing the electro-controlled ion extraction membrane includes the following steps: (1) The conductive carbon material, binder and dispersant are mixed in proportion and mixed evenly by ball milling. Then, a carbon-based membrane is prepared on the surface of the ultrafiltration membrane by vacuum filtration to obtain an ultrafiltration / carbon-based composite membrane. (2) The ultrafiltration / carbon-based composite membrane is freeze-dried to completely volatilize the dispersant between the conductive carbon material and the binder in the ultrafiltration / carbon-based composite membrane, forming a porous carbon-based membrane with a well-developed pore structure, and thus an ultrafiltration / porous carbon-based composite membrane is prepared. (3) Place the ultrafiltration / porous carbon-based composite membrane into the extractant. The extractant fills the pores in the porous carbon-based membrane through adsorption. After 5-24 h, the porous carbon-based membrane, after adsorption saturation, combines with the ultrafiltration membrane support layer to obtain the electro-controlled ion extraction membrane.

2. The electro-controlled ion extraction membrane according to claim 1, characterized in that: The ultrafiltration membrane material is one of cellulose acetate, cellulose acetate ester, polyethylene, polysulfone, or polyamide; the conductive carbon material is one of carbon nanotubes, graphene, carbon nanofibers, or conductive carbon black; the binder is one of polyvinylidene fluoride, polyacrylic acid, polyvinyl alcohol, or carboxymethyl cellulose; the dispersant is one of N,N-dimethylformamide, N-methylpyrrolidone, ethanol, or water; and the extractant is one of carboxymethyltrimethylbis(trifluoromethyl)sulfonylimide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide-tributyl phosphate, 2-ethylhexylhydro-2-ethylhexyl tetrabutylammonium phosphate, 1-butyl-3-methylimidazolium tetraphenylboronic acid-tributyl phosphate, or bis(2,4,4-trimethylpentyl)tetrabutylphosphine phosphate.

3. The electro-controlled ion extraction membrane according to claim 1, characterized in that: When conductive carbon material, binder and dispersant are mixed, the mass ratio of conductive carbon material to binder is 2:1 to 1:2, and the mass ratio of conductive carbon material to dispersant is 1:3 to 1:

10.

4. The electro-controlled ion extraction membrane according to claim 1, characterized in that: The freeze-drying temperature is -10 ℃ to -100 ℃, the vacuum degree is 0.03 mbar to 0.10 mbar, and the freeze-drying time is 5-24 h.

5. An electro-controlled ion-extraction membrane extraction and separation system using the electro-controlled ion-extraction membrane assembly as described in claim 1 or 2, characterized in that: The system includes a raw material tank A1, a back-extraction tank A2, a raw material liquid chamber B1, a back-extraction liquid chamber B2, an electro-controlled ion extraction membrane M1, a raw material tank auxiliary electrode C1, a back-extraction tank auxiliary electrode C2, a circuit control system D1, a circuit control system D2, a raw material liquid circulation pump E1, and a back-extraction liquid circulation pump E2. The raw material liquid chamber B1 and the back-extraction liquid chamber B2 are separated by the electro-controlled ion extraction membrane M1. The bottom of the raw material tank A1 is connected to the raw material liquid chamber B1 via the raw material liquid circulation pump E1, and the top of the raw material liquid chamber B1 is connected to the top of the raw material tank A1 via a pipeline to form a circulation loop. The back-extraction tank A2 is connected to the back-extraction liquid chamber via the back-extraction liquid circulation pump E2. Chamber B2 is connected to the top of back-extraction tank A2 via a pipeline to form a circulation loop. The raw material chamber B1 and back-extraction chamber B2 are located on opposite sides of the electrically controlled ion extraction membrane M1. The raw material chamber B1 contains a raw material tank auxiliary electrode C1, and the back-extraction chamber B2 contains a back-extraction tank auxiliary electrode C2. Both the raw material tank auxiliary electrode C1 and the back-extraction tank auxiliary electrode C2 are connected to the circuit control system D1, which applies the tank voltage. The raw material tank auxiliary electrode C1 and the electrically controlled ion extraction membrane M1 are also connected to the circuit control system D2, which applies a pulse voltage.

6. A method for lithium extraction using the electronically controlled ion-extraction membrane extraction and separation system as described in claim 5, characterized in that... Includes the following steps: (1) The raw liquid in the raw material tank A1 is sent into the raw liquid chamber B1 through the pipeline via the raw liquid circulation pump E1, and then returned to the raw material tank A1 through the pipeline; (2) The back-extraction liquid in the back-extraction tank A2 is sent into the back-extraction liquid chamber B2 through the pipeline via the back-extraction liquid circulation pump E2, and then returned to the back-extraction tank A2 through the pipeline; (3) A constant cell voltage is applied between the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back extraction tank through the circuit control system D1; (4) A pulse voltage is applied between the auxiliary electrode C1 of the raw material tank and the electro-controlled ion extraction membrane M1 through the circuit control system D2; (5) The target lithium ions in the raw material liquid chamber B1 enter the electro-controlled ion extraction membrane through the extraction process, and then enter the back extraction liquid chamber B2 through the back extraction process, thereby realizing the extraction and separation of lithium ions in the raw material liquid.

7. The lithium extraction method according to claim 6, characterized in that: The feed solution is a lithium-containing brine with a high magnesium-to-lithium ratio, wherein the lithium ion concentration is 10 mg / L to 1000 mg / L and the magnesium-to-lithium mass concentration ratio is 5:1 to 1500:

1. The back-extraction solution is one of hydrochloric acid aqueous solution, sulfuric acid aqueous solution, or nitric acid aqueous solution, with a concentration of 0.5 mol / L to 6 mol / L.

8. The lithium extraction method according to claim 6, characterized in that: A constant cell voltage of 0.5 V to 1.5 V is applied between the auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back extraction tank; The pulse voltage applied between the auxiliary electrode C1 of the raw material tank and the electro-controlled ion extraction membrane M1 is 0.5 V ~ 1.5 V, and the pulse frequency is 0.0001 Hz ~ 10 Hz; The auxiliary electrode C1 of the raw material tank and the auxiliary electrode C2 of the back-extraction tank are respectively one of a titanium plate, a graphite plate, a carbon felt, a carbon cloth, or a carbon paper.

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