A lithium-magnesium separation device, system and method driven by interfacial photothermal concentration

Abstract

The present invention relates to a lithium-magnesium separation device and method driven by interfacial photothermal concentration. The device includes a brine chamber, a photothermal material, a lithium-magnesium separation membrane, and an extract chamber. The brine chamber is used to hold brine; the photothermal material is used to heat the brine; the lithium-magnesium separation membrane is used to separate lithium ions and magnesium ions; the extract chamber is used to hold the lithium ion extract. The photothermal material absorbs light and converts the light energy into heat energy, and the brine undergoes photothermal evaporation and concentration at the interface of the photothermal material. The lithium-magnesium separation membrane is placed between the brine and the extract, and a concentration difference is formed between the brine and the extract. The lithium-magnesium separation membrane uses the concentration difference as the driving force to permeate lithium ions and intercept magnesium ions. This device or method utilizes the conversion of sunlight into heat, efficiently concentrates the brine through interfacial heating, synchronously separates lithium and magnesium during the concentration process, realizes the full utilization of light energy and the seamless connection between concentration and separation, shortens the time for extracting lithium from salt lakes, and reduces the energy consumption of extracting lithium from salt lakes.

Description

Technical Field

[0001] The present invention relates to a lithium-magnesium separation device, and particularly to a lithium-magnesium separation device, system and method driven by interfacial photothermal concentration. Background Art

[0002] As an energy metal promoting world progress, the demand for lithium has been increasing year by year. Therefore, the development of lithium resources is of great significance. China is a large country with rich lithium resources, ranking second in the world in terms of total lithium reserves. Among them, the lithium resources in salt lake brine account for 79% of China's total lithium reserves, mainly distributed in provinces (autonomous regions) such as Qinghai and Tibet in China. For the Qinghai-Tibet region, the industrial foundation is weak, the ecological environment is fragile, and fresh water resources are scarce. This requires that the method for extracting lithium from salt lakes should be green, environmentally friendly, low in energy consumption and low in water consumption.

[0003] At present, in the Qinghai region of China, the method of sun-drying brine in salt pans is used to prepare old brine. The salt pan spreading method requires the development of salt ponds, which causes great damage to the environment, and China has prohibited the excavation of salt pans. The utilization rate of sunlight in salt pan sun-drying is low, and the water evaporation rate is slow, resulting in a long production cycle of old brine. On the other hand, the main methods for extracting lithium from salt lakes in industrial production are solvent extraction method and adsorption method. The solvent extraction method has good selectivity for lithium, but it is easy to cause environmental pollution; the adsorption method can obtain high-purity lithium carbonate, but the adsorbent is prone to dissolution loss and has a high water consumption. In addition, the current solvent extraction method and adsorption method both face the problems of high energy consumption and environmental pollution. Under the requirements of China's dual-carbon policy, it is of great significance to develop a green and low-energy-consuming method for extracting lithium from salt lakes. Summary of the Invention

[0004] In order to solve the problems of serious environmental pollution and high energy consumption in the existing lithium-magnesium separation methods, the present invention provides a lithium-magnesium separation device and method driven by interfacial photothermal concentration. The device or method uses sunlight to convert into heat, efficiently concentrates brine through interfacial heating, synchronously separates lithium and magnesium during the concentration process, realizes the full utilization of light energy, seamless connection of concentration and separation, shortens the time for extracting lithium from salt lakes, and reduces the energy consumption of extracting lithium from salt lakes.

[0005] On the one hand, the present invention provides a lithium-magnesium separation device driven by interfacial photothermal concentration, which includes a brine chamber, a photothermal material, a lithium-magnesium separation membrane and an extract chamber. The brine chamber is used to hold brine; the photothermal material is used to heat the brine; the lithium-magnesium separation membrane is used to separate lithium ions and magnesium ions; the extract chamber is used to hold the lithium ion extract; the photothermal material absorbs light and converts light energy into heat energy, and the brine undergoes photothermal evaporation concentration at the interface of the photothermal material; the lithium-magnesium separation membrane is placed between the brine and the extract, a concentration difference is formed between the brine and the extract, and the lithium-magnesium separation membrane uses the concentration difference as a driving force to permeate lithium ions and intercept magnesium ions.

[0006] On the other hand, a lithium-magnesium separation method is provided, which includes the following steps

[0007] Concentration: The photothermal material heats the brine to heat and concentrate the brine;

[0008] Lithium-magnesium separation: The brine is subjected to lithium-magnesium separation by a lithium-magnesium separation membrane and an extraction liquid. Lithium ions in the brine pass through the lithium-magnesium separation membrane and enter the extraction liquid, while magnesium ions are retained in the brine;

[0009] The concentration and lithium-magnesium separation are carried out simultaneously, and the concentration and lithium-magnesium separation are carried out in the same brine;

[0010] The photothermal material performs interfacial photothermal evaporation concentration on the brine.

[0011] On the other hand, the present invention provides a system provided with the above lithium-magnesium separation device or adopting the above lithium-magnesium separation method.

[0012] The beneficial effects produced by the present invention include:

[0013] (1) The lithium-magnesium separation device in the present invention uses interfacial evaporation to in-situ evaporate and concentrate the brine from the surface of the interfacial photothermal material, constructing a concentration difference on both sides of the lithium-magnesium separation membrane to promote the ion exchange and lithium-magnesium separation on both sides of the membrane.

[0014] (2) The photothermal material heats up under light, and the heat is transferred to the lithium-magnesium separation membrane. The increase in temperature can significantly improve the flux of the lithium extraction liquid and the lithium-magnesium selectivity.

[0015] (3) By coupling interfacial photothermal evaporation concentration with lithium-magnesium separation, while lithium ions are concentrated, a lithium-magnesium separation process with ultra-low energy consumption is realized, and the entire technological process is green and pollution-free, solving the problems of high energy consumption, environmental damage, and low lithium-magnesium separation ratio in the existing lithium extraction processes, and having extremely high economic value. Description of the Drawings

[0016] Figure 1 Assembly structure diagram of the lithium-magnesium separation device in the present invention;

[0017] Figure 2 Disassembly structure diagram of the lithium-magnesium separation device in the present invention;

[0018] Figure 3 Structure diagram of the lithium-magnesium separation membrane in the present invention;

[0019] Figure 4 Flow chart of the lithium-magnesium separation system;

[0020] Figure 5 Effect data diagram of the lithium-magnesium separation device in Examples 4-6. Detailed Embodiments

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0022] The separation of lithium and magnesium is the core link in extracting lithium from salt lakes. The present invention utilizes the abundant sunlight conditions in the Qinghai-Tibet region to develop a lithium-magnesium separation device and method driven by interfacial photothermal concentration. This device or method has a high selectivity for lithium, and the overall process has the advantage of low energy consumption. The lithium-magnesium separation device is used to separate lithium ions and magnesium ions in salt lake brine. The device includes a brine chamber and an extract chamber. A lithium-magnesium separation membrane and a photothermal material are arranged between the two. The brine chamber is used to place brine and also serves as a photothermal evaporation chamber. The extract chamber is used to place the extract. A concentration difference is formed between the brine and the extract. Driven by the concentration difference, the ions in the brine tend to move towards the extract. The lithium-magnesium separation membrane permeates lithium ions and intercepts magnesium ions, thereby achieving the separation of lithium and magnesium. The photothermal material is placed in the brine chamber. The photothermal material is a light-absorbing and heat-generating material that absorbs sunlight and converts it into heat energy to heat the brine. The photothermal material heats the thin water layer on the photothermal interface to achieve efficient heating. After the water layer is heated by the interface, it is concentrated and separated through the lithium-magnesium separation membrane to achieve the integration of concentration and separation. The concentration difference and the temperature generated by photothermal are the energy sources for the operation of the device, and no other energy consumption is generated.

[0023] The photothermal material is hydrophilic or hydrophobic, preferably hydrophilic. The hydrophilic photothermal material is immersed in the brine and is in full contact with the brine. After the brine wets the photothermal material, there is still a thin layer of flowing water. The thickness of the water layer is in the micron or millimeter range, preferably not more than 5 mm. Under this setting, the brine is concentrated to 1 g / L after passing through the photothermal material. The brine flows through the photothermal material in the brine chamber and is heated and concentrated on the interface. Part of the heat of the photothermal material is used to heat the brine, and part is used to heat the lithium-magnesium separation membrane. After the lithium-magnesium separation membrane is heated and the temperature rises, the polymer expands, the membrane pores become larger, which is beneficial for the passage of lithium ions, the lithium flux increases, the lithium-magnesium separation efficiency and the lithium extraction quality are improved, and the lithium separation is complete. The photothermal material is preferably a black light-absorbing material, more preferably black cotton cloth, black PVA hydrophilic sponge, and black softened wood. It exists in a sheet structure, and its area is equivalent to or not much different from the area of the lithium-magnesium separation membrane. The light-absorbing material and the lithium-magnesium separation membrane are stacked. Specifically, a buffer gasket is arranged between the two. On the one hand, the buffer gasket gives a set spacing between the light-absorbing material and the lithium-magnesium separation membrane. On the other hand, it seals the water layer between the two to prevent water from flowing out between the two. The thickness of the photothermal material is preferably 0.1 cm - 2 cm. This thickness can, on the one hand, ensure sufficient heating when the brine flows through, and on the other hand, ensure that the brine can quickly pass through the light-absorbing material to reach the side of the lithium-magnesium separation membrane.

[0024] The components of the device of the present invention are arranged vertically, from top to bottom are the brine chamber, the photothermal material, the lithium-magnesium separation membrane, and the extraction liquid chamber. The upper end of the brine chamber is open, and the lower end is sealed with the photothermal material, that is, the photothermal material is used as the bottom. The water inlet pipe is installed on the left side, and the water outlet pipe is arranged on the right side. After the brine enters through the water inlet pipe, it is heated by the photothermal material and flows out through the water outlet pipe. The upper opening can introduce sunlight, and the light is incident on the photothermal material through the upper opening and converted into heat. Preferably, the side wall of the brine chamber in the present invention is transparent, and the light can be incident not only through the upper opening but also through the side wall, making the most of sunlight. The extraction liquid chamber is provided with a side wall and a bottom wall, and the upper end is open. The lithium-magnesium separation membrane is arranged on the upper end opening end face. The extraction liquid contacts the upper lithium-magnesium separation membrane, and the opening is connected to the lithium-magnesium separation membrane through a gasket. The brine chamber and the photothermal material are also connected through a gasket. The gasket plays a buffering role on the one hand and a sealing role on the other hand to prevent liquid from flowing out. The photothermal material faces the lithium-magnesium separation membrane and a gasket is arranged between them. The water inlet pipe is arranged on the right side of the extraction liquid chamber, and the water outlet pipe is arranged on the left side. The extraction liquid enters from the left side and flows out from the right side, and its water flow direction is opposite to the brine flow direction. Through the power of the pump, the feed liquid flows parallel to the membrane surface, and the shear force generated when passing through the membrane surface will carry away the retention material particles on the membrane filament surface, so that the pollution layer can be continuously maintained in a relatively thin stage. Under the action of pressure, only a part of the liquid will pass through the membrane and enter the downstream. Here, the flow directions are opposite to make the lithium ion exchange more sufficient, which is beneficial to improving the passing speed of lithium and increasing the flux.

[0025] In the present invention, the lithium-magnesium separation membrane comprises a base membrane and a functional layer disposed on the base membrane. The base membrane is a cation exchange membrane, which includes a first side facing the extraction solution and a second side facing the brine. The functional layer is disposed at least on the first side. The functional layer disposed on the first side is provided with a plurality of polymer layers. The plurality of polymers include a polycationic polymer and a polyanionic polymer. The polycationic polymer and the polyanionic polymer are alternately stacked and distributed. The side adjacent to the base membrane is the polycationic polymer, followed by the polyanionic polymer, and the outermost layer is the polycationic polymer. Since the polycationic polymer is positively charged and the polyanionic polymer is negatively charged, an interfacial electric field is formed between the base membrane and the adjacent polycationic polymer, and between the adjacent polycationic polymer and the polyanionic polymer. The direction of this interfacial electric field is opposite to the movement direction of lithium ions. Magnesium ions that have not been filtered by the base membrane are further removed by the action of the interfacial electric field. Lithium ions, due to their small charge amount and small electrostatic force, can pass through the lithium-magnesium separation membrane. As another setting, a functional layer can also be disposed on the second side. Its structure is still that the polycationic polymer adjacent to the base membrane is followed by the polyanionic polymer, the polycationic polymer, and so on in sequence, and the outermost layer is the polycationic polymer. The interfacial electric field formed on this functional layer is the same as the movement direction of lithium ions, which can accelerate the movement of lithium ions. The polycationic polymer is a substance that can react with epichlorohydrin or undergo an amino-aldol condensation reaction with an aldehyde functional group, including but not limited to polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydimethyldiallylammonium chloride (PDDA), and protein macromolecules containing amino groups, etc.; the polyanionic polymer includes but not limited to one or more of polyacrylic acid (PAA), sodium polyvinyl sulfonate (PES), and sodium polystyrene sulfonate (PSS). Preferably, the polycationic polymer layer and the polyanion chloride polymer layer are assembled on the base membrane in the form of impregnation or deposition to form a membrane stack. After assembling the outermost polymer layer, a crosslinking agent is deposited again to increase the stability of the polymer on the base membrane. The crosslinking agent includes one or two of glutaraldehyde or epichlorohydrin. The specific preparation method of the lithium-magnesium separation membrane includes the following steps:

[0026] First step, prepare a polycationic electrolyte solution A, a polyanionic electrolyte solution B, and a crosslinking agent solution C.

[0027] Second step, using the cation exchange membrane as the base membrane, first deposit the polycationic polymer A on one side of the membrane, then deposit a layer of the polyanionic polymer B, and then deposit a layer of the polycationic polymer A again. This is one cycle. Multiple cycles can be performed, and the number of cycles is between 1 and 10. (Since there are anions on the surface of the cation base membrane, a layer of cationic polymer is first assembled using the attraction of positive and negative charges, then a layer of anion is assembled, and then a layer of cation is assembled. It is necessary to ensure that the outermost layer of the assembled membrane is cationic)

[0028] In the third step, a crosslinking agent solution C is deposited on the same side for measurement. (The role of crosslinking is to fix the polymer. Without crosslinking, the polymer on the surface is likely to fall off during actual lithium-magnesium separation, resulting in performance degradation.)

[0029] In the fourth step, it is washed once with an aqueous hydrochloric acid solution with a pH of 2 and water respectively. (The purpose of washing is to wash away the excessively adsorbed and uncrosslinked polymer.)

[0030] In the fifth step, the prepared membrane is assembled into a membrane stack for lithium-magnesium separation.

[0031] The solvents for preparing solutions A, B, and C can be water or alcohols.

[0032] In the present invention, the lithium-magnesium ratio in the brine is between 1 and 1600, the lithium ion concentration in the brine is 0.05 - 5 g / L, and the flow rate of the extraction liquid is controlled between 10 - 50 ml / min. Under this setting, on the one hand, the separated lithium can be fully carried away in time, and water is not excessively wasted, and the extracted lithium-magnesium ratio reaches more than 100.

[0033] The lithium-magnesium separation method in the present invention adopts the above-mentioned lithium-magnesium separation device, which shortens the time for extracting lithium from the salt lake, reduces the energy consumption of extracting lithium from the salt lake, uses photothermal concentration to realize the concentration of the brine and at the same time realizes lithium-magnesium separation, achieves high selectivity for lithium, and obtains high-quality lithium carbonate.

[0034] The present invention will be introduced in detail below in the form of specific embodiments.

[0035] Example 1

[0036] The lithium-magnesium separation device is as Figure 1 and Figure 2 It includes a brine chamber 1, a photothermal material 2, a first gasket 3, a lithium-magnesium separation membrane 4, a second gasket 5, and an extraction liquid chamber 6 arranged in sequence from top to bottom. A through cavity 103 is provided on the brine chamber 1, which is open at both the upper and lower ends. The photothermal material 2 is provided at the lower opening. An inlet pipe 101 and an outlet pipe 102 are respectively provided on the opposite left and right side walls of the brine chamber 1; the upper end of the extraction liquid chamber 6 is open, and its opening is opposite to the lower opening of the brine chamber 1. A lithium-magnesium separation membrane 4 is provided between them. An inlet pipe 601 and an outlet pipe 602 are respectively provided on the opposite right and left side walls of the extraction liquid chamber 6. The brine flows and works in the brine chamber 1, and the extraction liquid flows and works in the extraction liquid chamber 6.

[0037] The extraction liquid chamber 6 is 10 cm long, 10 cm wide, and 3 cm high. The through cavity 103 is a columnar cavity with a diameter of 5 cm. The first gasket 3 and the second gasket 5 are commercially available silicone gaskets, which are 10 cm long, 10 cm wide, and 0.2 cm thick. There is an opening in the middle of the gasket, with a length of 6 cm and a width of 7 cm. In this embodiment, the brine chamber is 10 cm long, 10 cm wide, and 1 cm high. The middle cavity is a columnar cavity with a diameter of 5 cm.

[0038] In this embodiment, the photothermal material 2 is a black PVA hydrophilic sponge, which is cut to a length of 5.5 cm, a width of 5.5 cm, and a thickness of 1 cm. The structure of the lithium-magnesium separation membrane 4 is as Figure 3 , including a base membrane 401, a first functional layer 402, and a second functional layer 403. The first functional layer 402 and the second functional layer 403 have the same structure. The preparation method of the lithium-magnesium separation membrane is as follows: Select the naphthol N112 membrane as the base membrane, prepare a 0.5 M solution of polydimethyldiallylammonium chloride (PDDA) as solution A, prepare a 0.5 M solution of sodium polystyrene sulfonate (PSS) as solution B, and prepare a 1 M solution of glutaraldehyde as solution C. Spray solution A on one side of the naphthol N112 membrane, then spray solution B, then spray another layer of solution A, then spray solution C, and then soak the obtained membrane in a hydrochloric acid aqueous solution with a pH of 2 and water for 1 minute and then take it out. The prepared lithium-magnesium separation membrane is obtained.

[0039] During operation, brine is introduced into the brine chamber 1 from left to right. The lithium concentration of the brine is 2 g / L, and the magnesium concentration is 2 g / L. The flow rate is controlled to be 0.8 ml / L to control the brine inlet rate, so that the water level height (the thickness of the water layer heated by the photothermal material) in the brine chamber 1 is 3 mm. The sunlight irradiation intensity is 1000 W / m -2 . After reaching a steady state, the evaporation rate of water is 1.9 kg / m 2 / h, and the brine on the photothermal conversion material is concentrated by about 5 times. 1 M sodium chloride is introduced into the extraction liquid chamber 6 at a flow rate of 15 ml / L and introduced from right to left. The measured lithium-magnesium separation ratio is 780, and the lithium flux is 30 g / h / m 2 .

[0040] Example 2

[0041] A lithium-magnesium separation system includes a brine concentration device, a lithium-magnesium separation device, a distillation device, and a precipitation device. The process steps are as Figure 4, the salt lake brine is concentrated by a primary concentration device and a secondary concentration device to form mother liquor, potassium chloride and sodium chloride are precipitated, potassium and sodium ions in the brine are removed, and the formed mother liquor flows into a lithium-magnesium separation device to separate lithium ions and magnesium ions in the brine. The lithium-magnesium separation device is the interface photothermal concentration-driven lithium-magnesium separation device obtained in the embodiment of the present invention. After being processed by the lithium-magnesium separation device, lithium ions enter the lithium extraction solution, and the obtained lithium extraction solution enters a distillation device. The distillation device heats and distills the lithium extraction solution to obtain water vapor and lithium-rich liquid. The water vapor is recycled as the water source of the lithium extraction solution, and the lithium-rich liquid flows into a precipitation device to form lithium carbonate.

[0042] Example 3

[0043] The differences between this example and Example 1 are as follows:

[0044] In this example, the photothermal material 2 is selected as black cotton cloth, which is cut to a length of 5.5 cm, a width of 5.5 cm, and a thickness of 0.4 mm.

[0045] During operation, the flow rate of the brine is controlled at 1.2 ml / L to control the brine inlet speed, so that the water level height in the brine chamber 1 is 5 mm. The sunlight irradiation intensity is 1000 W / m -2 .

[0046] Other conditions are the same.

[0047] After reaching the steady state, the evaporation rate of water is 1.8 kg / m 2 / h, and the brine on the photothermal conversion material is concentrated by about 5 times. 1 M potassium chloride is introduced into the extraction liquid chamber 6 at a flow rate of 10 ml / L, and it is introduced from right to left. The measured lithium-magnesium separation ratio is 385, and the lithium flux is 22 g / h / m 2 .

[0048] Examples 4-6

[0049] The differences from Example 1 are only in the water level height and the extraction liquid flow rate. The specific settings and the corresponding brine concentration multiples, lithium-magnesium separation ratios, and lithium fluxes are shown in Figure 5 .

[0050] Comparative Example 1

[0051] The difference between this example and Example 1 is only that:

[0052] During operation, the flow rate of the brine is controlled at 15 ml / L, so that the water level height in the brine chamber 1 is 1 cm. The sunlight irradiation intensity is 1000 W / m -2 .

[0053] Other conditions are the same.

[0054] After reaching the steady state, the evaporation rate of water is 0.3 kg / m2 / h, the brine on the photothermal conversion material was concentrated by about 1.1 times. 1 M potassium chloride was introduced into the extraction liquid chamber 6 at a flow rate of 15 ml / L, flowing from right to left. The lithium-magnesium separation ratio was measured to be 30, and the lithium flux was 8 g / h / m 2 .

Claims

1. A lithium-magnesium separation device driven by interfacial photothermal concentration, characterized in that: include Brine chamber: used to contain brine; Photothermal materials: used to heat brine; Lithium-magnesium separation membrane: used to separate lithium ions and magnesium ions; Extraction liquid chamber: used for containing lithium ion extraction liquid; The components are, from top to bottom, a brine chamber, a photothermal material, a lithium-magnesium separation membrane, and an extraction liquid chamber. The brine chamber is provided with a cavity that passes through from top to bottom. The photothermal material blocks the lower opening of the cavity, the upper opening of the extraction liquid chamber, and the lithium-magnesium separation membrane blocks the upper opening. A sealing gasket is provided between the photothermal material and the lithium-magnesium separation membrane. The photothermal material absorbs light and converts light energy into heat energy, and the brine is photothermally evaporated and concentrated on the interface of the photothermal material; the heat of the photothermal material is directly or indirectly transferred to the lithium-magnesium separation membrane to heat the lithium-magnesium separation membrane, and the indirect transfer is transfer through a medium; The lithium-magnesium separation membrane is placed between the brine and the extract, and a concentration difference is formed between the brine and the extract. The lithium-magnesium separation membrane uses the concentration difference as a driving force to pass lithium ions and intercept magnesium ions. The lithium-magnesium separation membrane comprises a base membrane and a functional layer arranged on the base membrane; The base membrane is a cation exchange membrane; The functional layer is at least arranged on a first side of the cation exchange membrane, and the first side is a side facing the extract; The functional layer at least comprises a first polymer layer, a second polymer layer and a third polymer layer arranged in sequence from the base film outward, the first polymer layer is a polycationic polymer, the second polymer layer is a polyanionic polymer, and the third polymer is a polycationic polymer; The functional layer on the base film comprises several layers of polycationic polymers and several layers of polyanionic polymers. The polycationic polymers and polyanionic polymers are stacked and staggered, and the outermost layer is a polycationic polymer layer.

2. The lithium-magnesium separation device driven by interfacial photothermal concentration according to claim 1, wherein: The photothermal material is a hydrophilic material, and the thickness of the water layer on the photothermal material is in the millimeter level or micrometer level.

3. The lithium-magnesium separation device driven by interfacial photothermal concentration according to claim 1, wherein: The photothermal material and the lithium-magnesium separation membrane meet one of the following requirements: —The distance between the photothermal material and the lithium-magnesium separation membrane is 0-2 cm; —The photothermal material is a sheet material, and a gasket is arranged between the photothermal material and the lithium-magnesium separation membrane and then clamped and fixed by a fixing piece.

4. The lithium-magnesium separation device driven by interfacial photothermal concentration according to claim 1, wherein: The photothermal material satisfies one or more of the following combinations: —The photothermal material is a sheet material, and the thickness of the photothermal material is 0.1cm-2cm; —The photothermal material is black cotton cloth; —The photothermal material is black PVA hydrophilic sponge; —The photothermal material is blackened softened wood.

5. The lithium-magnesium separation device driven by interfacial photothermal concentration according to claim 1, wherein: The lithium-magnesium separation device satisfies one or more of the following combinations: —The brine chamber comprises a water inlet and a water outlet, and the brine enters from the water inlet and flows through the photothermal material and then flows out from the water outlet; the heated and concentrated brine is separated by ions through a lithium-magnesium separation membrane; The extraction liquid chamber comprises a water inlet and a water outlet, and the extraction liquid enters from the water inlet, flows through the lithium-magnesium separation membrane, and then flows out from the water outlet; —The flow direction of brine is opposite to that of extract.

6. The lithium-magnesium separation device driven by interfacial photothermal concentration according to claim 1, characterized in that: The polycationic polymer is a substance that can react with epichlorohydrin or can undergo amine-aldehyde condensation with aldehyde functional groups, including one or more of polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydimethyldiallylammonium chloride (PDDA) and amino-containing protein macromolecules; The anionic polymer includes one or more of polyacrylic acid (PAA), sodium polyvinyl sulfonate (PES), and sodium polystyrene sulfonate (PSS).

7. The lithium-magnesium separation device driven by interfacial photothermal concentration according to claim 1, characterized in that: The brine or extraction solution satisfies one or more of the following combinations: — The magnesium-lithium ratio in the brine is between 1 and 1600; — The lithium concentration in the brine is between 0.05 and 5 g / L; — The flow rate of the extraction solution is controlled between 10 and 50 ml / min; — The extraction solution is a monovalent ion extraction solution; — The extraction solution is a mixed solution of one or several of hydrochloric acid solution, sodium chloride solution, or potassium chloride solution.

8. A lithium-magnesium separation system provided with the lithium-magnesium separation device according to any one of claims 1 to 7.

9. A method for separating lithium and magnesium, characterized in that: It is carried out by using the lithium-magnesium separation device according to any one of claims 1 to 7; It includes the following steps Concentration: The photothermal material heats the brine to heat and concentrate the brine; Lithium-magnesium separation: The brine is subjected to lithium-magnesium separation through the lithium-magnesium separation membrane and the extraction solution. The lithium ions in the brine pass through the lithium-magnesium separation membrane and enter the extraction solution, while the magnesium ions are retained in the brine; The concentration and lithium-magnesium separation are carried out simultaneously, and the concentration and lithium-magnesium separation are carried out in the same brine; The photothermal material performs interfacial photothermal evaporation concentration on the brine.

Images