An acid-resistant electro-driven film for electro-driven separation and a preparation method and application thereof

Abstract

This invention relates to an acid-resistant electro-driven thin film for electro-driven separation, its preparation method, and its application. The preparation method includes the following steps: (1) Base film activation: The base film is activated sequentially with water, alkaline solution, and acid solution to obtain an activated base film; (2) Interfacial polymerization reaction: The activated base film is sequentially immersed in an aqueous phase solution and an organic phase solution, and then subjected to heat treatment to obtain the acid-resistant electro-driven thin film; The aqueous phase solution includes a polyamine compound; The organic phase solution includes an organic solvent and an organic monomer, The organic monomer includes cyanuric chloride and terephthalic diisocyanate. This invention obtains an acid-resistant electro-driven thin film with excellent conductivity and acid resistance and a reasonable pore structure by combining the base film activation process with the interfacial polymerization reaction of polyamine compounds in the aqueous phase solution and cyanuric chloride and terephthalic diisocyanate in the organic phase solution. This enables efficient separation between ions under acidic and electro-driven conditions.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to an acid-resistant electrically driven thin film for electrically driven separation, its preparation method, and its application. Background Technology

[0002] With the advancement of technology, the industrial demand for high-purity rare earth products is constantly increasing, which places higher demands on the separation and purification technologies of rare earth elements. Traditional wet separation technologies such as chemical precipitation, adsorption, and ion exchange have drawbacks such as high cost, complex processes, and low selectivity, hindering their widespread application and promotion. Compared to the aforementioned traditional wet separation technologies, solvent extraction separation technology (saponification rare earth extraction separation) is currently the most advanced and commonly used method for extracting rare earth elements both domestically and internationally. However, saponification rare earth extraction separation technology consumes large amounts of acids and alkalis, resulting in a large amount of high-salt wastewater (such as high-ammonia nitrogen wastewater), causing significant harm to the ecological environment and severely restricting the sustainable development of my country's rare earth industry.

[0003] Membrane separation technology offers advantages over other traditional separation technologies, including simple processes, low energy consumption, and environmental friendliness, and has enormous application potential. Continuously evolving application demands have also driven the development of membrane technology, leading to the development of different membrane processes for various application areas. Currently, membrane processes capable of separating monovalent and multivalent ions mainly include diffusion dialysis, electrodialysis, and nanofiltration. Diffusion dialysis itself has certain drawbacks; using concentration gradients as the driving force makes it difficult to increase the diffusion rate of hydrogen ions, resulting in low separation efficiency. Commercial cation exchange membranes used in electrodialysis have low selectivity for metal ions and hydrogen ions, failing to achieve effective separation. Traditional nanofiltration relies mainly on pore size sieving and electrostatic repulsion to achieve partial ion separation, but it struggles to simultaneously separate rare earth ions and hydrogen ions and recover concentrated acid. Introducing nanofiltration membranes into traditional electrodialysis membrane stacks to replace cation exchange membranes for electrically driven ion separation can effectively address the shortcomings of the aforementioned membrane processes. However, traditional nanofiltration membranes are prone to hydrolysis under acidic conditions, leading to a significant decline in membrane performance and failing to meet the long-term requirements of rare earth separation processes.

[0004] CN107349804A discloses a method for preparing an acid-resistant nanofiltration membrane. An aqueous solution is prepared using polyethyleneimine, aminated graphene, and an acid-binding agent. The nanofiltration membrane is prepared using cyanuric chloride as the oil phase monomer via interfacial polymerization. The addition of aminated graphene can improve the membrane flux to some extent, but its high price makes industrial application difficult. CN115608176A discloses a method for preparing a positively charged acid-resistant nanofiltration membrane by grafting ANPI onto PEI-TMC, enabling the deposition of metal ions (Cu) in electroplating. 2+ and Ni 2+The high permeability and rejection rate of the membrane, along with the presence of amide bonds in its structure, make it prone to hydrolysis during use. CN113332859A uses a layer-by-layer assembly technique to prepare a polyelectrolyte acid-resistant membrane, but it relies on electrostatic interaction to form the membrane, without considering the control of membrane pore size by the monomer structure or testing the membrane's acid resistance. CN115212728A uses an impregnation method to load an organometallic framework onto a tannic acid-iron membrane to obtain a tannic acid-iron acid-resistant nanofiltration membrane. However, it lacks research on the stability of the organometallic framework under acidic conditions, and its acid resistance needs further improvement. It also has a low rejection rate for high-valence metal ions. CN114515520A uses a reaction between amine monomers such as telage base amines and aldehyde monomers to prepare a membrane with imine bonds, which are unstable under acidic and alkaline conditions.

[0005] In view of the shortcomings of the existing technology, how to prepare a thin film with strong acid resistance and excellent separation effect is an urgent technical problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide an acid-resistant electro-driven thin film for electro-driven separation, its preparation method, and its applications. This invention utilizes an activation process for the base film combined with the interfacial polymerization reaction of polyamine compounds in an aqueous solution with cyanuric chloride and terephthalic diisocyanate in an organic solution. By employing a substrate with high conductivity and materials exhibiting high reactivity and strong acid resistance, and by controlling the pore structure of the film, an acid-resistant electro-driven thin film with excellent conductivity and acid resistance and a reasonable pore structure is obtained. This provides the prerequisite for achieving long-term and efficient separation of different ions under acidic and electro-driven conditions.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing an acid-resistant electrically driven thin film for electrically driven separation, the method comprising the following steps:

[0009] (1) Base membrane activation: The base membrane is activated sequentially with water, alkaline solution and acid solution to obtain the activated base membrane;

[0010] (2) Interfacial polymerization reaction: The activated base film is sequentially immersed in an aqueous solution and an organic solution, and then subjected to heat treatment to obtain the acid-resistant electro-driven film;

[0011] The aqueous solution includes a polyamine compound;

[0012] The organic phase solution includes an organic solvent and an organic monomer, wherein the organic monomer includes cyanuric chloride and terephthalic diisocyanate.

[0013] The present invention provides a method for preparing an acid-resistant electro-driven thin film for electro-driven separation. First, by activating the base film, the pore size of the base film surface and interior can be modified, thereby facilitating subsequent reactions on the base film and promoting the reaction between the activated groups on the base film surface and the amine functional groups of the aqueous monomer, further strengthening the connection between the support layer and the separation layer in the acid-resistant electro-driven thin film, and enhancing the mechanical strength and stability of the acid-resistant electro-driven thin film. Next, the activated base film surface is wetted with an aqueous solution and an organic solution combined with a heat treatment process, allowing the polyamine compounds in the aqueous solution to react with the triamine groups in the organic solution. Interfacial polymerization of cyanuric chloride and terephthalic diisocyanate on the surface of an activated base membrane enables the control of the membrane pore structure and the formation of a separation layer on the surface of the porous support layer of the base membrane. The reaction of cyanuric chloride and terephthalic diisocyanate with a polyamine compound yields a polyamine-urea composite membrane, which improves the film's acid resistance and reactivity, providing a prerequisite for its application under acidic conditions. The pore structure controlled during the interfacial polymerization of the activated base membrane provides a prerequisite for the separation of single ions and high-valence ions. Furthermore, the resulting membrane exhibits good conductivity, enabling its use in electrically driven separation processes. In addition, the triazine ring conjugated structure introduced into the separation layer and the CN bonds generated by the interfacial polymerization further enhance acid stability.

[0014] This invention utilizes an activation process for the base membrane combined with the interfacial polymerization reaction of polyamine compounds in an aqueous solution with cyanuric chloride and terephthalic diisocyanate in an organic solution. By employing a substrate with high conductivity and materials exhibiting high reactivity and acid resistance, an electro-driven thin film with excellent conductivity, acid resistance, and high reactivity can be obtained. Furthermore, the combination of activation and interfacial polymerization allows for the control of the film's pore structure, resulting in a film with a specific pore structure. This enables the retention of rare earth ions and the passage of hydrogen ions, thus providing the prerequisite for long-term and efficient separation of rare earth ions and hydrogen ions under acidic and electro-driven conditions.

[0015] Preferably, the base film in step (1) is made of any one or a combination of at least two of polyacrylonitrile, polycarbonate, polyvinyl chloride, polysulfone, polyethersulfone, sulfonated polysulfone or polyvinylidene chloride, preferably polyacrylonitrile.

[0016] Preferably, the molecular weight cutoff of the base membrane in step (1) is 30-80 kDa, such as 30 kDa, 35 kDa, 40 kDa, 45 kDa, 50 kDa, 55 kDa, 60 kDa, 65 kDa, 70 kDa, 75 kDa or 80 kDa.

[0017] Preferably, the thickness of the base film in step (1) is 0.10-0.20 mm, such as 0.10 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm or 0.20 mm.

[0018] Preferably, the water treatment time in step (1) is 3-15 hours, such as 3 hours, 5 hours, 7 hours, 9 hours, 11 hours, 13 hours or 15 hours.

[0019] Preferably, the treatment time of the alkaline solution in step (1) is 30-180 min, such as 30 min, 40 min, 60 min, 80 min, 100 min, 120 min, 140 min, 160 min or 180 min.

[0020] Preferably, the treatment temperature of the alkaline solution in step (1) is 10-60℃, such as 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃.

[0021] Preferably, the concentration of the alkaline solution in step (1) is 1-5 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L.

[0022] This invention improves the activation effect on the base film by controlling the alkaline treatment time, temperature and concentration during the activation process, and promotes the reaction between the activated groups on the base film surface and the amine functional groups of the aqueous monomer, thereby enhancing the mechanical strength and stability of the obtained acid-resistant electro-driven film.

[0023] Preferably, the treatment time of the acid solution in step (1) is 1-6 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0024] Preferably, the acid solution in step (1) is processed at a temperature of 10-30°C, such as 10°C, 15°C, 20°C, 25°C or 30°C.

[0025] Preferably, the concentration of the acid solution in step (1) is 0.1-2.0 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, or 2.0 mol / L.

[0026] This invention optimizes the activation effect of the base film by controlling the acid treatment time, temperature, and concentration during the activation process, thereby improving the mechanical strength and stability of the obtained acid-resistant electro-driven film.

[0027] Preferably, the activated base film described in step (1) is further washed and dried after activation.

[0028] Preferably, the wetting in step (2) specifically includes: placing the activated base film in an aqueous solution for a first wetting, then taking out the first-wetted base film and placing it in an organic solution for a second wetting.

[0029] Preferably, the first soaking time is 5-60 min, such as 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0030] By controlling the first immersion time, this invention enables the aqueous monomer to better immerse the activated base film, ensuring an effective reaction between the activated base film and the aqueous monomer, thereby promoting the mechanical strength and stability of the obtained acid-resistant electro-driven film.

[0031] Preferably, the temperature of the first immersion is 10-30°C, such as 10°C, 15°C, 20°C, 25°C or 30°C.

[0032] Preferably, the second soaking time is 2-20 min, such as 2 min, 4 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min or 20 min.

[0033] Preferably, the temperature of the second immersion is 10-30°C, such as 10°C, 15°C, 20°C, 25°C or 30°C.

[0034] Preferably, the heat treatment temperature is 50-80℃, such as 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃.

[0035] Preferably, the heat treatment time is 1-20 min, such as 1 min, 2 min, 4 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min or 20 min.

[0036] Preferably, the polyamine compound includes any one or a combination of at least two of diethylenetriamine, tetraethylenepentamine, polyethyleneimine, branched polyethyleneimine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, melamine, piperazine, or 1,4-bis(3-aminopropyl)piperazine.

[0037] Preferably, the aqueous solution in step (2) further includes a surfactant.

[0038] Preferably, the surfactant comprises any one or a combination of at least two of sodium dodecyl sulfate, phospholipids, choline, sodium dodecyl sulfate, or sodium dodecylbenzene sulfonate, with sodium dodecyl sulfate being the most preferred.

[0039] Preferably, the concentration of the polyamine compound in the aqueous solution in step (2) is 0-2.0 wt%, excluding 0, for example 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, or 2.0 wt%.

[0040] Preferably, the concentration of the surfactant in the aqueous solution in step (2) is 0-0.50 wt%, excluding 0, for example 0.01 wt%, 0.05 wt%, 0.10 wt%, 0.15 wt%, 0.20 wt%, 0.25 wt%, 0.30 wt%, 0.35 wt%, 0.40 wt%, 0.45 wt%, or 0.50 wt%.

[0041] Preferably, the organic solvent includes any one or a combination of at least two of n-hexane, cyclohexane, ethyl acetate, or toluene, with n-hexane being the most preferred.

[0042] Preferably, the concentration of cyanuric chloride in the organic phase solution in step (2) is 0-0.20 wt%, excluding 0, for example 0.02 wt%, 0.04 wt%, 0.06 wt%, 0.08 wt%, 0.10 wt%, 0.12 wt%, 0.14 wt%, 0.16 wt%, 0.18 wt%, or 0.20 wt%, etc.

[0043] This invention regulates the concentration of cyanuric chloride in the organic phase solution, thereby controlling the degree of crosslinking of the membrane and influencing the membrane structure obtained by interfacial polymerization. If the concentration of cyanuric chloride is too low, the membrane structure resulting from the interfacial polymerization reaction will change, and it may even fail to effectively block rare earth ions from passing through the acid-resistant electro-driven membrane. If the concentration of cyanuric chloride is too high, it will inhibit the interfacial polymerization reaction between terephthalic diisocyanate and polyamine compounds, thus consuming raw materials and preventing the membrane performance from being effectively improved.

[0044] Preferably, the concentration of terephthalic diisocyanate in the organic phase solution in step (2) is 0-0.20 wt%, excluding 0, for example 0.01 wt%, 0.02 wt%, 0.04 wt%, 0.06 wt%, 0.08 wt%, 0.10 wt%, 0.12 wt%, 0.14 wt%, 0.16 wt%, 0.18 wt%, or 0.20 wt%, etc.

[0045] In a second aspect, the present invention provides an acid-resistant electro-driven thin film for electro-driven separation, wherein the acid-resistant electro-driven thin film is prepared by the preparation method described in the first aspect.

[0046] The acid-resistant electro-driven thin film for electro-driven separation provided by this invention is prepared by a specific preparation method. It has high acid resistance, good conductivity and reactivity, and a reasonable pore structure, and can achieve long-term and efficient separation of rare earth ions and hydrogen ions under acidic and electro-driven conditions.

[0047] Preferably, the acid-resistant electro-driven film comprises a negatively charged porous support layer and a positively charged separation layer.

[0048] Preferably, the positively charged separation layer comprises an interfacial polymerization product of an aqueous solution and an organic solution.

[0049] Preferably, the thickness of the separation layer of the acid-resistant electro-driven thin film is 60-150nm, such as 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm or 150nm.

[0050] Thirdly, the present invention provides an electrically driven separation device, the electrically driven separation device comprising the acid-resistant electrically driven thin film for electrically driven separation described in the second aspect.

[0051] This invention provides an electrically driven separation device that uses a specific acid-resistant electrically driven membrane to replace the cation exchange membrane and perform the main separation function. Under the synergistic effect of electric field driving, electrostatic effect and membrane size sieving effect, it can achieve long-term and efficient separation of rare earth ions and hydrogen ions in rare earth feed solution.

[0052] As a preferred embodiment of the present invention, the electro-driven separation device further includes a first anion exchange membrane and a second anion exchange membrane located on both sides of the acid-resistant electro-driven membrane, an anode plate located on the side of the first anion exchange membrane away from the acid-resistant electro-driven membrane, and a cathode plate located on the side of the second anion exchange membrane away from the acid-resistant electro-driven membrane. A desalination chamber is formed between the acid-resistant electro-driven membrane and the first anion exchange membrane, and a concentration chamber is formed between the acid-resistant electro-driven membrane and the second anion exchange membrane.

[0053] The electrically driven separation device provided by this invention uses a specific acid-resistant electrically driven membrane to replace the cation exchange membrane and undertake the main separation function. It interacts with the first and second anion exchange membranes set on both sides of the membrane. Combined with the anode and cathode plates on both sides of the device, it can achieve long-term and efficient separation of rare earth ions and hydrogen ions in the rare earth feed solution in the desalination chamber under the synergistic effect of electric field drive, electrostatic effect and membrane size sieving effect. At the same time, a higher concentration of acid solution is recovered in the concentration chamber.

[0054] Preferably, the acid-resistant electro-driven film comprises a negatively charged porous support layer and a positively charged separation layer.

[0055] Preferably, the acid-resistant electrically driven film is placed into the desalination chamber through the separation layer.

[0056] Preferably, a first electrode chamber is formed between the first anion exchange membrane and the anode plate.

[0057] Preferably, a second electrode chamber is formed between the second anion exchange membrane and the cathode plate.

[0058] Preferably, the electrically driven separation device further includes an external desalination chamber storage component, a concentration chamber storage component, and an electrode chamber storage component.

[0059] Preferably, the outlet of the desalination chamber storage component is connected to the inlet of the desalination chamber, and the inlet of the desalination chamber storage component is connected to the outlet of the desalination chamber.

[0060] Preferably, the outlet of the concentration chamber storage component is connected to the inlet of the concentration chamber, and the inlet of the concentration chamber storage component is connected to the outlet of the concentration chamber.

[0061] Preferably, the outlet of the electrode chamber storage component is connected to the inlet of the first electrode chamber, the outlet of the first electrode chamber is connected to the inlet of the second electrode chamber, and the outlet of the second electrode chamber is connected to the inlet of the electrode chamber storage component.

[0062] It should be noted that, in the electrically driven separation device provided in this invention, taking the arrangement direction of the first anion exchange membrane, the acid-resistant electrically driven membrane, and the second cation exchange membrane in the electrically driven separation device as the first direction, the acid-resistant electrically driven membrane and the inlet and outlet of the desalination chamber are disposed on the same first partition plate with a thickness. In the first direction, the acid-resistant electrically driven membrane is located on the side of the first partition plate closer to the concentration chamber, and the inlet and outlet of the desalination chamber are located on the side of the first partition plate closer to the desalination chamber. Similarly, the first anion exchange membrane and the inlet and outlet of the first electrode chamber are fixed on the same second partition plate with a thickness. In the first direction, the first anion exchange membrane is located on the side of the first partition plate closer to the concentration chamber. The second partition is located on the side near the desalination chamber. The inlet and outlet of the first electrode chamber are located on the second partition on the side near the first electrode chamber. The second anion exchange membrane and the inlet and outlet of the concentration chamber are fixed on the same third partition with a thickness. In the first direction, the second anion exchange membrane is located on the side of the third partition near the second electrode chamber, and the inlet and outlet of the concentration chamber are located on the side of the third partition near the first electrode chamber. The inlet and outlet of the second electrode chamber are located on a fourth partition between the third partition and the cathode plate. The fourth partition has an opening, so that the area between the third partition and the fourth partition is interconnected with the area between the fourth partition and the cathode plate, and together they serve as the second electrode chamber.

[0063] Preferably, a conveying component is provided between the outlet of the desalination chamber storage component and the inlet of the desalination chamber.

[0064] Preferably, a conveying component is provided between the outlet of the concentration chamber storage component and the inlet of the concentration chamber.

[0065] Preferably, a conveying component is provided between the outlet of the electrode chamber storage component and the inlet of the first electrode chamber.

[0066] The present invention provides a conveying component between the outlet of the storage component and the inlet of each chamber for conveying the liquid stored in the storage component into the chamber.

[0067] Preferably, the electrically driven separation device further includes a power supply system.

[0068] Preferably, the power supply system includes a positive terminal and a negative terminal.

[0069] Preferably, the positive terminal of the power supply system is connected to the anode plate, and the negative terminal of the power supply system is connected to the cathode plate.

[0070] Preferably, the power supply system includes a regulated power supply or a regulated current power supply.

[0071] Fourthly, the present invention provides an electrically driven separation method based on the electrically driven separation device described in the third aspect, the electrically driven separation method comprising:

[0072] Under electrically driven conditions, an acid-resistant electrically driven thin film is used to separate rare earth ions and hydrogen ions in a rare earth feed solution to obtain a rare earth solution.

[0073] The electro-driven separation method provided by this invention employs an electro-driven separation device containing a high-performance acid-resistant electro-driven thin film, which can achieve the separation of small-radius monovalent ions and large-radius high-valent ions under acidic and electro-driven conditions, thereby enabling long-term and efficient separation of rare earth ions and hydrogen ions under acidic conditions.

[0074] As a preferred embodiment of the present invention, the electrically driven separation method specifically includes the following steps:

[0075] Rare earth feed solution is introduced into the desalination chamber, and acid feed solution is introduced into the concentration chamber. A first electrolyte solution and a second electrolyte solution are introduced into the first electrode chamber and the second electrode chamber, respectively. The power supply system is used to energize the cathode plate and the anode plate to separate rare earth ions and hydrogen ions in the rare earth feed solution in the desalination chamber. The hydrogen ions in the desalination chamber reach the concentration chamber through an acid-resistant electrically driven membrane, while the rare earth ions in the desalination chamber are retained in the desalination chamber, resulting in a separated rare earth solution and a concentrated acid solution.

[0076] In the electro-driven separation method provided by this invention, under electro-driven conditions, hydrogen ions inside the rare earth feed solution in the desalination chamber migrate to the concentration chamber through an acid-resistant electro-driven membrane. The porous structure of the acid-resistant electro-driven membrane blocks the passage of rare earth ions, trapping them in the desalination chamber. Under the action of an electric field, anions inside the electrolyte solution in the second electrode chamber enter the concentration chamber through the second anion exchange membrane, while anions in the desalination chamber enter the first electrode chamber through the first anion exchange membrane. Furthermore, in order to achieve charge balance in the entire reaction system, under electro-driven conditions, hydrogen ions in the desalination chamber continuously migrate to the concentration chamber, thereby achieving efficient separation of rare earth ions and hydrogen ions inside the rare earth feed solution in the desalination chamber, resulting in a separated rare earth solution and concentrated acid solution.

[0077] Preferably, the specific process of introducing rare earth liquid into the desalination chamber includes: transferring the rare earth liquid in the desalination chamber storage component to the desalination chamber through a conveying component.

[0078] Preferably, the specific process of introducing acid raw material into the concentration chamber includes: transferring the acid raw material in the concentration chamber storage component to the concentration chamber through a conveying component.

[0079] Preferably, the specific process of introducing the first electrolyte solution and the second electrolyte solution into the first electrode chamber and the second electrode chamber respectively includes: transferring the electrolyte solution in the electrolyte storage component to the first electrode chamber through the conveying component, and then transferring it to the second electrode chamber through the first electrode chamber, thereby introducing the first electrolyte solution and the second electrolyte solution into the first electrode chamber and the second electrode chamber respectively.

[0080] Preferably, the first electrolyte solution and the second electrolyte solution have the same composition.

[0081] Preferably, the rare earth solution comprises a rare earth solution and an acid reagent.

[0082] Preferably, the concentration of rare earth ions in the rare earth feed solution is 5-15 mmol / L, such as 5 mmol / L, 7.5 mmol / L, 10 mmol / L, 12.5 mmol / L or 15 mmol / L.

[0083] Preferably, the concentration of hydrogen ions in the rare earth feed solution is 15-25 mmol / L, such as 15 mmol / L, 17.5 mmol / L, 20 mmol / L, 22.5 mmol / L, or 25 mmol / L.

[0084] Preferably, the concentration of the acidic raw material is 15-25 mmol / L, such as 15 mmol / L, 17.5 mmol / L, 20 mmol / L, 22.5 mmol / L, or 25 mmol / L.

[0085] Preferably, the volume ratio of the rare earth solution to the acid raw material is (0.8-1.1):(0.9-1.2), wherein the rare earth solution is selected from a range of 0.8-1.1, such as 0.8, 0.9, 1 or 1.1; and the acid raw material is selected from a range of 0.9-1.2, such as 0.9, 1, 1.1 or 1.2.

[0086] Preferably, the concentrations of the first electrolyte solution and the second electrolyte solution are independently selected from 0.1-0.5 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L.

[0087] Preferably, the volume ratio of the rare earth feed solution, the first electrolyte solution, and the second electrolyte solution is (0.8-1.1):(0.9-1.2):(0.9-1.2), wherein the rare earth feed solution is selected from a range of 0.8-1.1, for example, 0.8, 0.9, 1, or 1.1; the first electrolyte solution is selected from a range of 0.9-1.2, for example, 0.9, 1, 1.1, or 1.2; and the second electrolyte solution is selected from a range of 0.9-1.2, for example, 0.9, 1, 1.1, or 1.2.

[0088] Preferably, the current density of the energized circuit is 5-15 mA / cm². 2 For example, 5mA / cm 2 6mA / cm 2 7mA / cm 2 8mA / cm 2 9mA / cm 2 10mA / cm 2 11mA / cm 2 12mA / cm 2 13mA / cm 2 14mA / cm 2 Or 15mA / cm 2 wait.

[0089] Preferably, the hydrogen ion permeability in the desalination chamber is above 90%, such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%.

[0090] Preferably, the rare earth ion rejection rate in the desalination chamber is above 90%, such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%.

[0091] Compared with the prior art, the present invention has at least the following beneficial effects:

[0092] (1) This invention utilizes an activation process for the base membrane combined with the interfacial polymerization reaction of polyamine compounds in the aqueous solution with cyanuric chloride and terephthalic diisocyanate in the organic solution. By employing a substrate with good conductivity and highly reactive and acid-resistant materials, an electro-driven thin film with excellent conductivity, acid resistance, and high reactivity can be obtained. Furthermore, the combination of activation and interfacial polymerization allows for the control of the film's pore structure, resulting in a film with a specific pore structure. This enables the retention of rare earth ions and the passage of hydrogen ions, thus providing the prerequisite for long-term and efficient separation of rare earth ions and hydrogen ions under acidic and electro-driven conditions.

[0093] (2) The acid-resistant electro-driven thin film for electro-driven separation provided by the present invention is prepared by a specific preparation method. It has high acid resistance, good conductivity and reactivity, and a reasonable pore structure. It can achieve long-term and efficient separation of rare earth ions and hydrogen ions under acidic conditions and electro-driven conditions.

[0094] (3) The present invention provides an electrically driven separation device that uses a specific acid-resistant electrically driven membrane to replace the cation exchange membrane to undertake the main separation function. Under the synergistic effect of electric field drive, electrostatic effect and membrane size sieving effect, it can achieve long-term and efficient separation of rare earth ions and hydrogen ions in rare earth feed liquid.

[0095] (4) The electro-driven separation method provided by the present invention uses an electro-driven separation device containing an acid-resistant electro-driven thin film with excellent performance. It can separate small-radius monovalent ions and large-radius high-valent ions under acidic and electro-driven conditions, and thus achieve long-term and efficient separation of rare earth ions and hydrogen ions under acidic conditions. Attached Figure Description

[0096] Figure 1 This is a schematic diagram of the structure of the electrically driven separation method provided by the present invention;

[0097] Among them, 1, acid-resistant electrically driven membrane; 2, first anion exchange membrane; 3, second anion exchange membrane; 4, anode plate; 5, cathode plate; 6, desalination chamber; 6-1, desalination chamber inlet; 6-2, desalination chamber outlet; 7, concentration chamber; 7-1, concentration chamber inlet; 7-2, concentration chamber outlet; 8, first electrode chamber; 8-1, first electrode chamber inlet; 8-2, first electrode chamber outlet; 9, second electrode chamber; 9-1, second electrode chamber inlet; 9-2, second electrode chamber outlet; 10, desalination chamber storage component; 10-1, desalination chamber storage component inlet; 10-2, desalination chamber storage component outlet; 11, concentration chamber storage component; 11-1, concentration chamber storage component inlet; 11-2, concentration chamber storage component outlet; 12, electrode chamber storage component; 12-1, electrode chamber storage component inlet; 12-2, electrode chamber storage component outlet; 13, power supply system; 14, material conveying component.

[0098] Figure 2 This is a schematic diagram illustrating the process principle of the electro-driven separation device composed of the acid-resistant electro-driven thin film of the present invention in the electro-driven separation method.

[0099] Figure 3 This is a cross-sectional SEM image of the acid-resistant electro-driven thin film provided in Example 2.

[0100] Where A is the separation layer and B is the support layer. Detailed Implementation

[0101] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0102] The rare earth solution used in the following examples comprises a rare earth sulfate solution, wherein the total concentration of rare earth ions is 10 mmol / L, and the rare earth ions include lanthanum ions, samarium ions, and ytterbium ions, which are representative elements in light rare earth, medium rare earth, and heavy rare earth, respectively. The molar ratio of lanthanum ions, samarium ions, and ytterbium ions in the rare earth solution is 1:1:1, and the concentration of hydrogen ions in the rare earth solution is 20 mmol / L.

[0103] The commercial nanofiltration membrane TS-40 used in the following examples is from TRISEP, Inc., USA.

[0104] Example 1

[0105] This embodiment provides a method for preparing an acid-resistant electrically driven thin film, comprising the following steps:

[0106] S1. Activation of the base membrane: A polyacrylonitrile base membrane with a molecular weight cutoff of 50 kDa was immersed in water for 10 hours. Then, the polyacrylonitrile base membrane was removed from the water and immersed in a sodium hydroxide solution with a concentration of 2 mol / L at a solution temperature of 45℃ for 30 minutes. Then, the polyacrylonitrile base membrane after alkali immersion was removed and placed in hydrochloric acid with a concentration of 0.3 mol / L at 25℃ for 3 hours. The acid-immersed polyacrylonitrile base membrane was then rinsed with deionized water and dried to obtain the activated polyacrylonitrile base membrane.

[0107] S2. Preparation of aqueous solution: Dissolve polyethyleneimine and sodium dodecyl sulfate in deionized water and mix thoroughly. The concentration of polyethyleneimine is 0.5 wt% and the concentration of sodium dodecyl sulfate is 0.10 wt%, thus obtaining an aqueous solution.

[0108] S3. Preparation of organic phase solution: Dissolve cyanuric chloride and terephthalic diisocyanate in n-hexane to obtain an organic phase solution. The concentration of cyanuric chloride in the organic phase solution is 0.07 wt%, and the concentration of terephthalic diisocyanate is 0.01 wt%.

[0109] S4. Interfacial polymerization reaction: The polyacrylonitrile base film activated in step S1 is placed in the aqueous phase solution obtained in step S2 for first immersion at a temperature of 25°C for 10 min. The polyacrylonitrile base film after first immersion is removed, washed with deionized water, and then dried. The polyacrylonitrile base film after first immersion is then placed in the organic phase solution obtained in step S3 for second immersion at a temperature of 25°C for 2 min. The polyacrylonitrile base film after second immersion is washed with n-hexane and then dried. The dried polyacrylonitrile base film is then heat-treated at 60°C for 5 min to obtain an acid-resistant electro-driven film. The obtained acid-resistant electro-driven film includes a negatively charged porous support layer and a positively charged separation layer.

[0110] This embodiment provides an example of using the acid-resistant electrically driven thin film obtained by the above preparation method to assemble an electrically driven separation device. A schematic diagram of the electrically driven separation device is shown below. Figure 1 As shown, the device specifically includes an acid-resistant electrically driven membrane 1 located in the middle region of the electrically driven separation device. A first anion exchange membrane 2 and a second anion exchange membrane 3 are respectively arranged on both sides of the acid-resistant electrically driven membrane 1. An anode plate 4 is arranged on the side of the first anion exchange membrane 2 away from the acid-resistant electrically driven membrane 1, and a cathode plate 5 is arranged on the side of the second anion exchange membrane 3 away from the acid-resistant electrically driven membrane 1. A desalination chamber 6 is formed between the first anion exchange membrane 2 and the acid-resistant electrically driven membrane 1, and a concentration chamber 7 is formed between the second anion exchange membrane 3 and the acid-resistant electrically driven membrane 1. The separation layer in the acid-resistant electrically driven membrane 1 is fixed towards the desalination chamber 6. A first electrode chamber 8 is formed between the first anion exchange membrane 2 and the anode plate 4, and a second electrode chamber 9 is formed between the second anion exchange membrane 3 and the cathode plate 5.

[0111] The electrically driven separation unit also includes a desalination chamber storage component 10, a concentration chamber storage component 11, and an electrode chamber storage component 12. The outlet 10-2 of the desalination chamber storage component is connected to the desalination chamber inlet 6-1 via a pipeline, and the inlet 10-1 of the desalination chamber storage component is connected to the outlet 6-2 of the desalination chamber via a pipeline. The outlet 11-2 of the concentration chamber storage component is connected to the concentration chamber inlet 7-1 via a pipeline, and the inlet 11-1 of the concentration chamber storage component is connected to the outlet 7-2 of the concentration chamber via a pipeline. The outlet 12-2 of the electrode chamber storage component is connected to the inlet 8-1 of the first electrode chamber via a pipeline, and the outlet 8-2 of the first electrode chamber is connected to the inlet 9 of the second electrode chamber via a pipeline. -1 is connected by a pipeline, and the outlet 9-2 of the second electrode chamber is connected to the inlet 12-1 of the electrode chamber storage component by a pipeline; a conveying component 14 is also provided between the outlet 10-2 of the desalination chamber storage component and the inlet 6-1 of the desalination chamber, between the outlet 11-2 of the concentration chamber storage component and the inlet 7-1 of the concentration chamber, and between the outlet 12-2 of the electrode chamber storage component and the inlet 8-1 of the first electrode chamber, to transfer and circulate the solution in each storage component to each chamber. The conveying component 14 is specifically a peristaltic pump.

[0112] The electrically driven separation device also includes a power supply system 13, which is a DC regulated power supply. The positive terminal of the power supply system 13 is connected to the anode plate 4, and the negative terminal of the power supply system 13 is connected to the cathode plate 5.

[0113] Example 2

[0114] The method for preparing the acid-resistant electro-driven thin film provided in this embodiment includes the following steps:

[0115] S1. Activation of the base membrane: A polyacrylonitrile base membrane with a molecular weight cutoff of 50 kDa was immersed in water for 10 hours. Then, the polyacrylonitrile base membrane was removed from the water and immersed in a sodium hydroxide solution with a concentration of 2 mol / L at a solution temperature of 45℃ for 30 minutes. Then, the polyacrylonitrile base membrane after alkali immersion was removed and placed in hydrochloric acid with a concentration of 0.3 mol / L at 25℃ for 3 hours. The acid-immersed polyacrylonitrile base membrane was then rinsed with deionized water and dried to obtain the activated polyacrylonitrile base membrane.

[0116] S2. Preparation of aqueous solution: Dissolve polyethyleneimine and sodium dodecyl sulfate in deionized water and mix thoroughly. The concentration of polyethyleneimine is 0.5 wt% and the concentration of sodium dodecyl sulfate is 0.10 wt%, thus obtaining an aqueous solution.

[0117] S3. Preparation of organic phase solution: Dissolve cyanuric chloride and terephthalic diisocyanate in n-hexane to obtain an organic phase solution. The concentration of cyanuric chloride in the organic phase solution is 0.06 wt%, and the concentration of terephthalic diisocyanate is 0.02 wt%.

[0118] S4. Interfacial polymerization reaction: The polyacrylonitrile base film activated in step S1 is placed in the aqueous phase solution obtained in step S2 for first immersion at a temperature of 25°C for 10 min. The polyacrylonitrile base film after first immersion is removed, washed with deionized water, and then dried. The polyacrylonitrile base film after first immersion is then placed in the organic phase solution obtained in step S3 for second immersion at a temperature of 25°C for 2 min. The polyacrylonitrile base film after second immersion is washed with n-hexane and then dried. The dried polyacrylonitrile base film is then heat-treated at 60°C for 10 min to obtain an acid-resistant electro-driven film. The obtained acid-resistant electro-driven film includes a negatively charged porous support layer and a positively charged separation layer.

[0119] This embodiment provides an acid-resistant electro-driven thin film obtained by the above preparation method for assembling an electro-driven separation device. Except for the change in the acid-resistant electro-driven thin film, the specific structure of the electro-driven separation device is the same as that in Embodiment 1.

[0120] Example 3

[0121] The method for preparing the acid-resistant electro-driven thin film provided in this embodiment includes the following steps:

[0122] S1. Activation of the base membrane: A polyacrylonitrile base membrane with a molecular weight cutoff of 50 kDa was immersed in water for 10 hours. Then, the polyacrylonitrile base membrane was removed from the water and immersed in a sodium hydroxide solution with a concentration of 2 mol / L at a solution temperature of 45℃ for 30 minutes. Then, the polyacrylonitrile base membrane after alkali immersion was removed and placed in hydrochloric acid with a concentration of 2 mol / L at 25℃ for 3 hours. The acid-immersed polyacrylonitrile base membrane was then rinsed with deionized water and dried to obtain the activated polyacrylonitrile base membrane.

[0123] S2. Preparation of aqueous solution: Dissolve polyethyleneimine and sodium dodecyl sulfate in deionized water and mix thoroughly. The concentration of polyethyleneimine is 0.5 wt% and the concentration of sodium dodecyl sulfate is 0.10 wt%, thus obtaining an aqueous solution.

[0124] S3. Preparation of organic phase solution: Dissolve cyanuric chloride and terephthalic diisocyanate in n-hexane to obtain an organic phase solution. The concentration of cyanuric chloride in the organic phase solution is 0.04 wt%, and the concentration of terephthalic diisocyanate is 0.04 wt%.

[0125] S4. Interfacial polymerization reaction: The polyacrylonitrile base film activated in step S1 is placed in the aqueous solution obtained in step S2 for first immersion at a temperature of 25°C for 10 min. The polyacrylonitrile base film after first immersion is removed, washed with deionized water, and then dried. The polyacrylonitrile base film after first immersion is then placed in the organic solution obtained in step S3 for second immersion at a temperature of 25°C for 2 min. The polyacrylonitrile base film after second immersion is washed with n-hexane and then dried. The dried polyacrylonitrile base film is then heat-treated at 60°C for 20 min to obtain an acid-resistant electro-driven film. The obtained acid-resistant electro-driven film includes a negatively charged porous support layer and a positively charged separation layer.

[0126] This embodiment provides an acid-resistant electro-driven thin film obtained by the above preparation method for assembling an electro-driven separation device. Except for the change in the acid-resistant electro-driven thin film, the specific structure of the electro-driven separation device is the same as that in Embodiment 1.

[0127] Example 4

[0128] The only difference between this embodiment and Embodiment 2 is that the preparation method of the acid-resistant electro-driven film provided in this embodiment further includes immersing the prepared acid-resistant electro-driven film in a 15wt% sulfuric acid solution for 20 days, and then fixing it in an electro-driven separation device. All other contents are the same as in Embodiment 2.

[0129] Example 5

[0130] The only difference between this embodiment and Embodiment 2 is that the preparation method of the acid-resistant electro-driven film provided in this embodiment further includes immersing the prepared acid-resistant electro-driven film in a 15wt% sulfuric acid solution for 30 days, and then fixing it in an electro-driven separation device. All other contents are the same as in Embodiment 2.

[0131] Comparative Example 1

[0132] The only difference between this comparative example and Example 2 is that this comparative example directly uses the commercial nanofiltration membrane TS-40 as the electrically driven membrane, which is fixed in the electrically driven separation device. All other contents are the same as in Example 2.

[0133] Comparative Example 2

[0134] The only difference between this comparative example and Example 4 is that the acid-resistant electro-driven membrane is replaced with a commercial nanofiltration membrane TS-40. Specifically, the commercial nanofiltration membrane TS-40 is soaked in a 15wt% sulfuric acid solution for 20 days before being used as the electro-driven membrane and fixed in the electro-driven separation device. All other contents are the same as in Example 4.

[0135] Comparative Example 3

[0136] The only difference between this comparative example and Example 5 is that the acid-resistant electro-driven membrane is replaced with a commercial nanofiltration membrane TS-40. Specifically, the commercial nanofiltration membrane TS-40 is soaked in a 15wt% sulfuric acid solution for 30 days before being used as the electro-driven membrane and fixed in the electro-driven separation device. All other contents are the same as in Example 5.

[0137] Comparative Example 4

[0138] The only difference between this comparative example and Example 1 is that in the preparation method of the acid-resistant electro-driven film provided in this comparative example, terephthalic diisocyanate is omitted from the organic phase solution, and the concentration of cyanuric chloride in the organic phase solution is 0.08 wt%. All other contents are the same as in Example 1.

[0139] Application Example 1

[0140] This application example uses the electrically driven separation device provided in Example 1 to perform an electrically driven separation method, which specifically includes the following steps:

[0141] (I) The rare earth solution in the desalination chamber storage component is transported to the desalination chamber by a peristaltic pump, the sulfuric acid solution with a concentration of 20 mmol / L in the concentration chamber storage component is transferred to the concentration chamber by a peristaltic pump, and the sodium sulfate solution with a concentration of 0.3 mol / L in the electrode chamber storage component is transferred to the first electrode chamber and the second electrode chamber by a peristaltic pump. The volume ratio of the rare earth solution in the desalination chamber, the sulfuric acid solution in the concentration chamber, the sodium sulfate solution in the first electrode chamber and the sodium sulfate solution in the second electrode chamber is 1:1:1:1.

[0142] (II) A DC regulated power supply is used to energize the electrically driven separation device, with a current density of 5.15 mA / cm². 2 The rare earth ions and hydrogen ions in the rare earth feed solution in the desalination chamber are separated. The hydrogen ions in the desalination chamber migrate to the concentrate through an acid-resistant electro-driven membrane, while the rare earth ions in the desalination chamber are retained in the desalination chamber by the acid-resistant electro-driven membrane, resulting in a separated rare earth solution and a concentrated acid solution.

[0143] Application Example 2

[0144] Except for the use of the electrically driven separation device provided in Example 2 for the electrically driven separation method, this application example is the same as application example 1.

[0145] Application Example 3

[0146] Except for the use of the electrically driven separation device provided in Example 3 for the electrically driven separation method, this application example is the same as application example 1.

[0147] Application Example 4

[0148] Except for the use of the electrically driven separation device provided in Example 4 for the electrically driven separation method, this application example is the same as application example 1 in all other respects.

[0149] Application Example 5

[0150] Except for the use of the electrically driven separation device provided in Example 5 for the electrically driven separation method, this application example is the same as application example 1.

[0151] Comparative Application Example 1

[0152] Except for the use of the electric drive separation device provided in Comparative Example 1 for the electric drive separation method, this comparative application example is the same as application example 1 in all other aspects.

[0153] Comparative Application Example 2

[0154] Except for the use of the electric drive separation device provided in Comparative Example 2 for the electric drive separation method, this comparative application example is the same as application example 1.

[0155] Comparative Application Example 3

[0156] Except for the use of the electric drive separation device provided in Comparative Example 3 for the electric drive separation method, this comparative application example is the same as application example 1.

[0157] Comparative Application Example 4

[0158] Except for the use of the electric drive separation device provided in Comparative Example 4 for the electric drive separation method, this comparative application example is the same as application example 1.

[0159] The specific test process and parameter design for detecting the rare earth ion rejection rate, hydrogen ion transmittance, and selective separation coefficient of the acid-resistant electrically driven thin film separation process provided in corresponding use cases 1-5 and comparative application examples 1-4 are as follows:

[0160] (1) Retention rate of rare earth ions: The total concentration of rare earth ions in the desalination chamber was tested by an inductively coupled plasma emitter. The total concentration of rare earth ions in the initial desalination chamber was recorded as A0, and the total concentration of rare earth ions in the desalination chamber after electric drive separation was recorded as A1. The retention rate of rare earth ions was A1 / A0×100%.

[0161] (2) Hydrogen ion transmission rate: The concentration of hydrogen ions in the desalination chamber is measured by pH meter. The initial concentration of hydrogen ions in the desalination chamber is recorded as B0, and the concentration of hydrogen ions in the desalination chamber after electric separation is recorded as B1. The hydrogen ion transmission rate is (B0-B1) / B0×100%.

[0162] (3) Selectivity separation coefficient:

[0163]

[0164] Wherein, A0 and A1 are the initial and final concentrations of rare earth ions in the desalination chamber, respectively;

[0165] B0 and B1 are the initial and final concentrations of hydrogen ions in the desalination chamber, respectively.

[0166] The test results are shown in Table 1.

[0167] Table 1

[0168] Rare earth ion rejection rate (%) Hydrogen ion permeability (%) Selective separation coefficient Application Example 1 99.78 96.37 23686.52 Application Example 2 99.90 93.83 27404.20 Application Example 3 98.91 97.49 3506.99 Application Example 4 99.83 95.10 10063.26 Application Example 5 99.48 96.73 5067.32 Comparative Application Example 1 94.37 96.45 455.49 Comparative Application Example 2 22.79 91.49 - Comparative Application Example 3 15.41 91.09 - Comparative Application Example 4 93.82 94.25 248.80

[0169] The test results show that:

[0170] (1) As can be seen from Application Examples 1 to 5, the present invention, through the activation process of the base membrane combined with the interfacial polymerization reaction of polyamine compounds in the aqueous solution and cyanuric chloride and terephthalic diisocyanate in the organic solution, uses a substrate with good conductivity and materials with high reactivity and strong acid resistance, and regulates the pore structure of the membrane, to obtain an acid-resistant electro-driven membrane with excellent conductivity and acid resistance and a reasonable pore structure. This enables long-term and efficient separation of different ions under acidic and electro-driven conditions. In particular, a comparison between Application Example 2 and Application Examples 4-5 shows that after the acid-resistant electro-driven membrane obtained in Application Example 2 was immersed in 15wt% sulfuric acid solution for 20 days and 30 days respectively in Application Example 4 and Application Example 5, it was fixed in an electro-driven separation device for the separation of rare earth ions and hydrogen ions in rare earth feed solution. The rare earth ion rejection rate and hydrogen ion permeability were still high, further proving the excellent acid resistance stability of the acid-resistant electro-driven membrane provided by the present invention.

[0171] Figure 2 A schematic diagram of the process principle of the electro-driven separation device composed of the acid-resistant electro-driven membrane of the present invention in the electro-driven separation method is given. As shown in the figure, rare earth ions in the rare earth feed solution inside the desalination chamber are trapped in the desalination chamber by the acid-resistant electro-driven membrane, while hydrogen ions in the rare earth feed solution can pass through the acid-resistant electro-driven membrane into the concentration chamber. At the same time, under the action of electrostatic effect, anions in the second electrode chamber reach the concentration chamber through the second anion exchange membrane, and anions in the desalination chamber reach the first electrode chamber through the first anion exchange membrane. In order to achieve charge balance, under the electro-driven condition, hydrogen ions in the desalination chamber will continuously pass through the acid-resistant electro-driven membrane into the concentration chamber, thereby achieving the separation of rare earth ions and hydrogen ions in the rare earth feed solution in the desalination chamber, thus obtaining the separated rare earth solution and concentrated acid solution.

[0172] Figure 3A cross-sectional SEM image of the acid-resistant electro-driven film provided in Example 2 is given. As can be seen from the figure, the acid-resistant electro-driven film obtained in Example 2 has a separation layer A with a relatively dense upper surface and a support layer B located below the separation layer.

[0173] (2) By comparing Application Example 2 with Comparative Application Example 1, it can be seen that, compared with the commercial nanofiltration membrane TS-40, the acid-resistant electrically driven membrane provided by the present invention has a higher rare earth ion rejection rate and hydrogen ion permeability, and a higher selective separation coefficient.

[0174] (3) By comparing Application Example 4 with Comparative Application Example 2, and Application Example 5 with Comparative Application Example 3, it can be seen that compared with the commercial nanofiltration membrane TS-40, which is soaked in a 15wt% sulfuric acid solution and then fixed in an electrically driven separation device for use in an electrically driven separation method, the acid-resistant electrically driven membrane prepared in this invention has a higher rare earth ion rejection rate and a higher hydrogen ion permeability after being fixed in an electrically driven separation device for the electro-driven separation of rare earth feed liquid. This shows that compared with the commercially available nanofiltration membrane, the acid-resistant electrically driven membrane prepared in this invention has superior acid resistance and acid stability, and has significant practical value.

[0175] (4) By comparing Application Example 1 with Comparative Application Example 4, it can be seen that if the preparation method of the acid-resistant electro-driven film of the present invention omits the terephthalic diisocyanate in the organic solution, the rare earth ion rejection rate and hydrogen ion transmittance of the obtained acid-resistant electro-driven film will be worse, and the selective separation coefficient of the film will be significantly reduced.

[0176] In summary, this invention, through an activation process of the base membrane combined with the interfacial polymerization reaction of polyamine compounds in the aqueous solution with cyanuric chloride and terephthalic diisocyanate in the organic solution, utilizes a substrate with good conductivity and highly reactive and acid-resistant materials to obtain an electro-driven thin film with excellent conductivity, acid resistance, and high reactivity. Furthermore, the combination of activation and interfacial polymerization allows for the control of the film's pore structure, resulting in a film with a specific pore structure. This enables the retention of rare earth ions and the passage of hydrogen ions, thereby achieving long-term and efficient separation of rare earth ions and hydrogen ions under acidic and electro-driven conditions.

[0177] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an acid-resistant electrically driven thin film for electrically driven separation, characterized in that, The preparation method includes the following steps: (1) Base membrane activation: The base membrane is activated sequentially with water, alkaline solution and acid solution to obtain the activated base membrane; (2) Interfacial polymerization reaction: The activated base film is sequentially immersed in an aqueous solution and an organic solution, and then subjected to heat treatment to obtain the acid-resistant electro-driven film; The aqueous solution includes a polyamine compound; The organic phase solution includes an organic solvent and an organic monomer, wherein the organic monomer includes cyanuric chloride and terephthalic diisocyanate.

2. The preparation method according to claim 1, characterized in that, The base film in step (1) is made of any one or a combination of at least two of polyacrylonitrile, polycarbonate, polyvinyl chloride, polysulfone, polyethersulfone, sulfonated polysulfone or polyvinylidene chloride, preferably polyacrylonitrile; Preferably, the molecular weight cutoff of the base membrane in step (1) is 30-80 kDa; Preferably, the thickness of the base film in step (1) is 0.10-0.20 mm; Preferably, the water treatment time in step (1) is 3-15 hours; Preferably, the treatment time of the alkaline solution in step (1) is 30-180 min; Preferably, the treatment temperature of the alkaline solution in step (1) is 10-60℃; Preferably, the concentration of the alkaline solution in step (1) is 1-5 mol / L; Preferably, the treatment time of the acid solution in step (1) is 1-6 hours; Preferably, the treatment temperature of the acid solution in step (1) is 10-30℃; Preferably, the concentration of the acid solution in step (1) is 0.1-2.0 mol / L; Preferably, the activated base film described in step (1) is further washed and dried after activation.

3. The preparation method according to claim 1 or 2, characterized in that, The wetting process in step (2) specifically includes: placing the activated base film in an aqueous solution for a first wetting, then taking out the first-wetted base film and placing it in an organic solution for a second wetting; Preferably, the first soaking time is 5-60 minutes; Preferably, the temperature of the first immersion is 10-30°C; Preferably, the second soaking time is 2-20 minutes; Preferably, the temperature of the second immersion is 10-30°C; Preferably, the heat treatment temperature is 50-80℃; Preferably, the heat treatment time is 1-20 minutes.

4. The preparation method according to any one of claims 1-3, characterized in that, The polyamine compound includes any one or a combination of at least two of the following: diethylenetriamine, tetraethylenepentamine, polyethyleneimine, branched polyethyleneimine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, melamine, piperazine, or 1,4-bis(3-aminopropyl)piperazine. Preferably, the aqueous solution in step (2) further includes a surfactant; Preferably, the concentration of the polyamine compound in the aqueous solution in step (2) is 0-2.0 wt%, excluding 0; Preferably, the concentration of the surfactant in the aqueous solution in step (2) is 0-0.50 wt%, excluding 0; Preferably, the organic solvent includes any one or a combination of at least two of n-hexane, cyclohexane, ethyl acetate or toluene, with n-hexane being the most preferred. Preferably, the concentration of cyanuric chloride in the organic phase solution in step (2) is 0-0.20 wt%, and does not include 0; Preferably, the concentration of terephthalic diisocyanate in the organic phase solution in step (2) is 0-0.20 wt%, and does not include 0.

5. An acid-resistant electro-driven thin film for electro-driven separation, characterized in that, The acid-resistant electro-driven thin film is prepared by the preparation method described in any one of claims 1-4.

6. The acid-resistant electro-driven thin film for electro-driven separation according to claim 5, characterized in that, The acid-resistant electro-driven thin film includes a negatively charged porous support layer and a positively charged separation layer; Preferably, the positively charged separation layer comprises an interfacial polymerization product of an aqueous solution and an organic solution.

7. An electrically driven separation device, characterized in that, The electrically driven separation device includes the acid-resistant electrically driven thin film for electrically driven separation as described in claim 5 or 6.

8. The electrically driven separation device according to claim 7, characterized in that, The electro-driven separation device further includes a first anion exchange membrane and a second anion exchange membrane located on both sides of the acid-resistant electro-driven membrane, an anode plate located on the side of the first anion exchange membrane away from the acid-resistant electro-driven membrane, and a cathode plate located on the side of the second anion exchange membrane away from the acid-resistant electro-driven membrane. A desalination chamber is formed between the acid-resistant electro-driven membrane and the first anion exchange membrane, and a concentration chamber is formed between the acid-resistant electro-driven membrane and the second anion exchange membrane. Preferably, the acid-resistant electro-driven film comprises a negatively charged porous support layer and a positively charged separation layer; Preferably, the acid-resistant electrically driven film is placed into the desalination chamber through the separation layer; Preferably, a first electrode chamber is formed between the first anion exchange membrane and the anode plate; Preferably, a second electrode chamber is formed between the second anion exchange membrane and the cathode plate; Preferably, the electrically driven separation device further includes a power supply system; Preferably, the power supply system includes a positive terminal and a negative terminal; Preferably, the positive terminal of the power supply system is connected to the anode plate, and the negative terminal of the power supply system is connected to the cathode plate; Preferably, the power supply system includes a regulated power supply or a regulated current power supply.

9. An electrically driven separation method based on the electrically driven separation device according to claim 7 or 8, characterized in that, The electrically driven separation method includes: Under electrically driven conditions, an acid-resistant electrically driven thin film is used to separate rare earth ions and hydrogen ions in a rare earth feed solution to obtain a rare earth solution.

10. The electrically driven separation method according to claim 9, characterized in that, The electrically driven separation method specifically includes the following steps: Rare earth feed solution is introduced into the desalination chamber, acid feed solution is introduced into the concentration chamber, and a first electrolyte solution and a second electrolyte solution are introduced into the first electrode chamber and the second electrode chamber, respectively. The power supply system is used to energize the cathode plate and the anode plate to separate rare earth ions and hydrogen ions in the rare earth feed solution in the desalination chamber. The hydrogen ions in the desalination chamber reach the concentration chamber through an acid-resistant electrically driven membrane, while the rare earth ions in the desalination chamber are retained in the desalination chamber, resulting in a separated rare earth solution and a concentrated acid solution. Preferably, the rare earth solution comprises a rare earth solution and an acid reagent; Preferably, the concentration of rare earth ions in the rare earth feed solution is 5-15 mmol / L; Preferably, the concentration of hydrogen ions in the rare earth feed solution is 15-25 mmol / L; Preferably, the concentration of the acid feedstock is 15-25 mmol / L; Preferably, the volume ratio of the rare earth slurry to the acid raw material is (0.8-1.1):(0.9-1.2); Preferably, the current density of the energized circuit is 5-15 mA / cm². 2 ; Preferably, the hydrogen ion permeability in the desalination chamber is above 90%; Preferably, the rare earth ion rejection rate in the desalination chamber is above 90%.

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