A binary ionic liquid fiber membrane, a preparation method and application in adsorbing palladium

Abstract

The application provides a binary ionic liquid fiber membrane, a preparation method and application in adsorption of palladium, and belongs to the technical field of adsorption materials, and comprises the following steps: mixing dichloromethane and acetic acid to obtain a first solution; dissolving cellulose acetate, a first ionic liquid and a second ionic liquid in the first solution to obtain a second solution; the first ionic liquid and the second ionic liquid are alkenyl imidazole salts with different length alkyl side chain molecular structures; adding N,N'-methylene bisacrylamide and benzoyl peroxide into the second solution, heating, stirring and warming to obtain a third solution; performing high-pressure electrospinning on the third solution to obtain a binary ionic liquid fiber membrane; or performing irradiation on the second solution after high-pressure electrospinning to obtain a binary ionic liquid fiber membrane. The binary ionic liquid fiber membrane prepared by the application can efficiently and selectively adsorb and recover palladium from a complex acidic solution, and has the advantages of faster adsorption speed, better selectivity and better salt resistance.

Description

Technical Field

[0001] This invention belongs to the field of adsorption material technology, and more specifically, relates to a binary ionic liquid fiber membrane, its preparation method, and its application in adsorbing palladium. Background Technology

[0002] Currently, common techniques for recovering and separating palladium from the liquid phase mainly include chemical precipitation, solvent extraction, ion exchange, and adsorption. However, these methods all have significant limitations in practical applications.

[0003] Chemical precipitation: This method typically involves adding sulfides or reducing agents to precipitate the target metal. While simple to operate, it suffers from poor selectivity, is prone to co-precipitating other metallic impurities, and generates large amounts of sludge containing heavy metals, causing secondary pollution and treatment challenges. Furthermore, it is difficult to achieve high-purity separation and recovery of palladium for solutions with complex compositions.

[0004] Solvent extraction is a relatively mature industrial recovery method that utilizes specific extractants (such as tributyl phosphate and amine extractants) to selectively complex target metal ions in an organic phase. However, this method has a long process, requires the use of large amounts of volatile, flammable, and toxic organic solvents, and poses safety and environmental risks. Furthermore, the back-extraction and organic phase regeneration steps after extraction are complex, resulting in high operating costs.

[0005] Ion exchange method: This method uses ion exchange resins for adsorption and recovery. The drawbacks of this method are that traditional resins have limited adsorption capacity for palladium and rhenium, slow kinetic rates, and insufficient stability in high-acidity or complex matrices. The resin regeneration process consumes large amounts of acid and alkali, generating waste liquid, and the resin is prone to swelling, breakage, or loss of functional groups, resulting in a limited service life.

[0006] Traditional adsorption materials include activated carbon, silica gel, and biochar. While these materials are relatively inexpensive, they generally suffer from poor adsorption selectivity, low adsorption capacity, and weak affinity for target metal ions. To improve performance, complex chemical modifications are usually required, which are cumbersome processes and may introduce new environmental pollution.

[0007] In recent years, ionic liquids, as a novel type of green solvent and functional material, have shown great potential in the field of separation science due to their extremely low vapor pressure, designable molecular structure, good thermal stability, and unique coordination ability with metal ions. Cellulose, the most abundant natural polymer in nature, has advantages such as being renewable, biodegradable, inexpensive, and easy to chemically modify. Combining ionic liquids with cellulose to prepare functional materials is considered a highly promising strategy.

[0008] However, existing palladium adsorption materials still suffer from the following key drawbacks: poor selectivity, low efficiency, and poor stability and regeneration performance.

[0009] In the inventor's previous research, the application of unary ionic liquid fiber membranes in palladium recovery was studied. Based on this research, the inventor further improved the preparation system of ionic liquid fiber membranes in order to further improve the performance of ionic liquid fiber membranes in terms of adsorption rate, selectivity, and salt resistance. Summary of the Invention

[0010] In previous studies, the inventors discovered that the shorter the alkyl side chain of the ionic liquid, the better its hydrophilicity, which is beneficial for mass transfer; the longer the alkyl side chain, the higher its selectivity for palladium. To prepare nanofiber membranes with faster adsorption rates and higher selectivity, this invention utilizes cellulose and two alkenyl imidazole salt ionic liquids with different alkyl side chain molecular structures to prepare a spinning solution, and then uses electrospinning technology to prepare a binary ionic liquid / cellulose nanomembrane adsorption material.

[0011] Therefore, the purpose of this invention is to provide a binary ionic liquid fiber membrane, its preparation method, and its application in palladium adsorption, to overcome the shortcomings of existing palladium recovery technologies, such as poor selectivity, low efficiency, and poor stability and regeneration performance of the adsorbent material. This invention provides a novel functional material with high selective adsorption capacity for palladium. It possesses both excellent mass transfer kinetics and structural stability, enabling rapid adsorption and easy regeneration and desorption. It can synergistically and efficiently recover palladium from complex acidic solutions (such as industrial leachates), and compared with unary ionic liquid fiber membranes, it has advantages such as faster adsorption speed, better selectivity, and better salt tolerance (NaNO3).

[0012] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a binary ionic liquid fiber membrane, comprising the following steps:

[0013] Dichloromethane and acetic acid are mixed to obtain the first solution;

[0014] Cellulose acetate, a first ionic liquid, and a second ionic liquid are dissolved in the first solution to obtain a second solution; the first ionic liquid and the second ionic liquid are alkenyl imidazole salts with alkyl side chain molecular structures of different lengths;

[0015] N,N'-methylenebisacrylamide and benzoyl peroxide are added to the second solution, heated and stirred to obtain a third solution. The third solution is then subjected to high-voltage electrospinning to obtain a binary ionic liquid fiber membrane; or the second solution is subjected to high-voltage electrospinning followed by irradiation to obtain a binary ionic liquid fiber membrane.

[0016] Furthermore, the general chemical structural formulas of the first ionic liquid and the second ionic liquid are represented as: [Vim-C n [X];

[0017] Wherein, Vim represents 1-vinylimidazolium cation; C n [X] represents a straight-chain alkyl group attached to the nitrogen position at the 3rd nitrogen position of the imidazole ring, with n carbon atoms, n = 1, 2, 3, 4, 6, 8, 10; [X] represents an anion, which is any one of bromide ion, chloride ion, tetrafluoroborate ion, and hexafluorophosphate ion.

[0018] Furthermore, the first ionic liquid is 1-vinyl-3-ethylimidazolium bromide, the second ionic liquid is 1-vinyl-3-decylimidazolium bromide, and the molar ratio of the first ionic liquid to the second ionic liquid is 1:9-9:1.

[0019] Furthermore, based on a volume of 10 mL for the first solution, the amount of cellulose acetate added is 1-2 g, and the total amount of the first ionic liquid and the second ionic liquid added is 2.5-6 mmol / L.

[0020] Furthermore, during the preparation of the third solution, the heating temperature is 50-90 °C, the mass ratio of N,N'-methylenebisacrylamide to benzoyl peroxide is 80-120 mg: 5-21 mg, and the stirring time is 8-12 h.

[0021] Furthermore, the high-voltage electrospinning temperature is 10-40 ℃, the humidity is 20%-70%, the voltage is 10 kV-20 kV, and the inner diameter of the spinning needle is 0.6-1.2 mm.

[0022] Furthermore, the volume ratio of the dichloromethane to the acetic acid is 2:1.

[0023] In a second aspect, the present invention provides a binary ionic liquid fiber membrane prepared by any of the preparation methods described above.

[0024] A third aspect of the present invention provides an application of a binary ionic liquid fiber membrane in the adsorption and recovery of palladium.

[0025] Further, the method includes the following steps: placing the binary ionic liquid fiber membrane in a palladium-containing solution, wherein the pH of the palladium-containing solution is 1-5.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] This invention discloses a method for preparing a binary ionic liquid fiber membrane. Two alkenyl imidazole salt ionic liquid monomers with specific metal coordination capabilities and alkyl side chains of different lengths are covalently bonded to a cellulose acetate polymer backbone via in-situ free radical graft copolymerization. The solution is then formed in one step using high-voltage electrospinning to create a high specific surface area nano-binary ionic liquid fiber membrane with a three-dimensional interconnected network structure. The two ionic liquid functional groups with different alkyl side chains are uniformly distributed on and within the fiber surface, serving as adsorption active sites. The nanofiber structure significantly enhances mass transfer efficiency, and the covalent bonding ensures long-term stability of the material during acidic conditions and adsorption-desorption cycles.

[0028] The binary ionic liquid fiber membrane prepared by this invention can achieve rapid adsorption and easy regeneration and desorption, and can efficiently and selectively adsorb and recover palladium from complex acidic solutions (such as complex industrial leachates containing multiple metal ions). Furthermore, compared to unary ionic liquid fiber membranes prepared using only a single type of ionic liquid, the binary ionic liquid fiber membrane of this invention exhibits better performance in terms of adsorption rate, selectivity, and salt tolerance (NaNO3). Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 These are scanning electron microscope images of the binary ionic liquid fiber membranes prepared in Examples 1-5 of this invention;

[0031] Figure 2 The infrared spectra of the binary ionic liquid fiber membranes and CA prepared in Examples 1-5 of this invention are shown.

[0032] Figure 3 The diagram shows the effect of solution pH on the adsorption performance of Pd(II) by the binary ionic liquid fiber membranes prepared in Examples 1-5 of the present invention.

[0033] Figure 4 Comparative graphs of the adsorption kinetics of Pd(II) on the mono-ionic liquid fiber membranes prepared in Comparative Examples 1-4 and the binary ionic liquid fiber membranes prepared in Examples 1-5 are shown.

[0034] Figure 5 The graph shows a comparison of the adsorption capacity of the binary ionic liquid fiber membranes prepared in Examples 1-5 of this invention at contact times of 1 min (a) and 3 min (b).

[0035] Figure 6 The above are isotherm curves of Pd(II) adsorption on the binary ionic liquid fiber membranes prepared in Examples 1-5 of this invention.

[0036] Figure 7 The following graphs illustrate the effect of ionic strength on the adsorption performance of the binary ionic liquid fiber membranes prepared in Examples 1-5 of this invention, provided for the embodiments of the present invention: (a) NaCl, (b) NaNO3;

[0037] Figure 8 A comparative graph showing the effect of ionic strength on the adsorption performance of Pd(II) of the mono-ionic liquid fiber membranes prepared in Comparative Examples 1-4 and the binary ionic liquid fiber membranes prepared in Examples 1-5 when the molar concentration of NaNO3 is 2000 times that of Pd(II) is provided for embodiments of the present invention.

[0038] Figure 9 The diagram shows the effect of coexisting ions on the adsorption performance of Pd(II) on the binary ionic liquid fiber membranes prepared in Examples 1-5 of this invention.

[0039] Figure 10 The adsorption selectivity of the mono-ionic liquid fiber membrane prepared in Comparative Examples 1-4 and the binary ionic liquid fiber membrane prepared in Examples 1-5 of the present invention is compared when the molar ratio of coexisting ion concentration to Pd(II) concentration is 1:1, as provided for embodiments of the present invention.

[0040] Figure 11 The coexisting ions at different concentrations provided in the embodiments of the present invention are CF-IL-C2 / C 10 A comparison of adsorption efficiency when the dosage of -1:9 is 10 mg and 30 mg, respectively;

[0041] Figure 12 The diagram illustrates the repeated adsorption and utilization of palladium in a binary ionic liquid fiber membrane cycling experiment provided in this embodiment of the invention. Detailed Implementation

[0042] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0043] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0044] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of embodiments of the invention, "first" may also be referred to as "second," and similarly, "second" may also be referred to as "first." Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0045] A first aspect of this invention provides a method for preparing a binary ionic liquid fiber membrane, comprising the following steps:

[0046] (1) Dichloromethane and acetic acid are mixed in a certain volume ratio to obtain the first solution;

[0047] (2) Dissolve cellulose acetate, the first ionic liquid, and the second ionic liquid in the first solution to obtain the second solution; the first ionic liquid and the second ionic liquid are alkenyl imidazole salts with alkyl side chain molecular structures of different lengths;

[0048] (3) Add a certain amount of N,N'-methylenebisacrylamide (MBAA) and benzoyl peroxide (BPO) to the second solution, and sonicate to mix the solution evenly. Heat and stir in an oil bath condensation system, and then continue to heat to a certain temperature and continue stirring to obtain the third solution.

[0049] (4) Place the third solution in a syringe, use a stainless steel spinning needle with a suitable inner diameter, and spin under high voltage electrospinning at a suitable humidity, temperature and a certain voltage. After spinning, a binary ionic liquid fiber membrane is obtained.

[0050] In this embodiment of the invention, step (3) is to use a chemical method, namely an in-situ free radical graft copolymerization reaction, to firmly bind two ionic liquid monomers with alkyl side chains of different lengths to the cellulose acetate polymer backbone in a covalent manner.

[0051] In addition, two ionic liquid monomers with alkyl side chains of different lengths can be firmly bonded to the cellulose acetate polymer backbone by radiation: the second solution is directly spun according to the above step (4), and then the spun ionic liquid fiber membrane is irradiated with a radiation source to promote cross-linking polymerization of the ionic liquid and obtain a binary ionic liquid fiber membrane. Specifically, the irradiation source can be γ-rays, electron beam irradiation, photopolymerization (such as ultraviolet light), etc. The irradiation dose of γ-rays and electron beam irradiation is 10-300 kGy.

[0052] In step (1) above, the mixing of dichloromethane and acetic acid is carried out at room temperature (generally 20-35℃) for 3-5 minutes. Specifically, the volume ratio of dichloromethane to acetic acid can be 2:1. In this embodiment of the invention, dichloromethane and acetic acid are mixed to form the first solution. Dichloromethane has a strong dissolving ability and can quickly dissolve rice straw-derived cellulose acetate, while acetic acid evaporates quickly during spinning, which can promote fiber solidification. At the same time, the volume ratio of the two is controlled at 2:1. Under this ratio, the fiber output speed during spinning is moderate, which can balance the two parameters of the evaporation rate of the spinning solution and the degree of fiber solidification, and is less likely to clog the needle.

[0053] In step (2) above, the ionic liquid selected is an alkenyl imidazole salt functionalized ionic liquid monomer with alkyl side chains of different lengths and specific metal coordination ability. This type of ionic liquid containing double bonds can polymerize to form a polyionic liquid, ensuring that the prepared binary ionic liquid fiber membrane remains insoluble in palladium-containing solutions and can exist stably. Specifically, the general chemical structural formulas of the first and second ionic liquids can be represented as: [Vim-C n [X]. Vim represents 1-vinylimidazolium cation; C n [X] represents a straight-chain alkyl group attached to the nitrogen (N) position of the imidazole ring, with n carbon atoms (n = 1, 2, 3, 4, 6, 8, 10); [X] represents anion, commonly bromide (Br⁻), chloride (Cl⁻), tetrafluoroborate (BF4⁻), hexafluorophosphate (PF6⁻), etc. Bromine salts (Br⁻) are commonly used in polymerization reactions due to their solubility and reactivity. Other examples include 1-allyl-3-methylimidazolium chloride, 1-methyl-3-(2-methacryloyloxyethyl)imidazolium bromide, and 1-vinylbenzimidazole bromide.

[0054] Preferably, the first ionic liquid is 1-vinyl-3-ethylimidazolium bromide, and the second ionic liquid is 1-vinyl-3-decylimidazolium bromide, with a molar ratio of 1:9 to 9:1. In this way, the prepared binary ionic liquid fiber membrane can achieve rapid adsorption and easy regeneration and desorption, and can efficiently and selectively adsorb and recover palladium from complex acidic solutions (such as complex industrial leachates containing multiple metal ions).

[0055] Furthermore, taking the volume of the first solution as 10 mL, the amount of cellulose acetate added is 1-2 g, and the total amount of the first and second ionic liquids added is 2.5-6 mmol / L. The preparation of the second solution can be carried out at room temperature. cellulose acetate (CA) is a polymer material; if the amount added is too low, the membrane cannot be spun; if the CA content is too high, the main component of the membrane is CA, which will reduce its adsorption performance for palladium. The ionic liquid in the membrane is the key component for palladium adsorption. When preparing nanofiber membranes using chemical methods, a heating treatment is performed during solution preparation. During the heating process, the ionic liquid polymerizes under the action of an initiator, forming a polymer. If the amount of ionic liquid is too high, the polymer formed by heating is relatively viscous, leading to unsuccessful spinning. Therefore, in the preparation of the second solution in this embodiment of the invention, the appropriate addition ratio of ionic liquid and CA must be controlled to ensure successful spinning and that the final ionic liquid fiber membrane has good palladium adsorption capacity.

[0056] In step (3) above, during the preparation of the third solution, the heating temperature is 50-90 ℃, i.e., the chemical reaction temperature is 50-90 ℃, the mass ratio of N,N'-methylenebisacrylamide to benzoyl peroxide is 80-120 mg: 5-21 mg, and the stirring time is 8-12 h. Under these reaction conditions, benzoyl peroxide, as an initiator, can successfully initiate the polymerization reaction of the ionic liquid; controlling a sufficiently long reaction time can ensure that the polymerization reaction is complete, and all the ionic liquids polymerize to form polyionic liquids.

[0057] In step (4) above, the high-voltage electrospinning temperature is 10-40 ℃, the humidity is 20%-70%, the voltage is 10kV-20 kV, the inner diameter of the spinning needle is 0.6-1.2 mm, and the spinning solution used is 5-20 mL. In this embodiment of the invention, when using two ionic liquids as solvents for cellulose electrospinning, it is necessary to precisely control the temperature, humidity, and voltage because these parameters directly affect the rheological properties of the spinning solution, the stretching behavior of the jet, the evaporation and solidification of the solvent, and the final fiber morphology and diameter.

[0058] The binary ionic liquid fiber membrane prepared in this embodiment of the invention is used for the adsorption and recovery of palladium. Specifically, the adsorption process includes the following steps: placing a certain mass of the binary ionic liquid fiber membrane in a palladium(II)-containing solution, preferably with a pH of 1-5. Adsorption is performed by shaking or stirring at room temperature. The binary ionic liquid fiber membrane material can rapidly and selectively adsorb palladium ions in the solution.

[0059] Desorption and regeneration: The adsorption-saturated binary ionic liquid fiber membrane is placed in an acidic desorption solution containing thiourea (such as a 0.5 mol / L thiourea-hydrochloric acid solution) for desorption treatment. The target metal is efficiently eluted, and the membrane can restore its adsorption performance after simple water washing and drying, enabling multiple cycles of use.

[0060] The following detailed embodiments further illustrate a binary ionic liquid fiber membrane, its preparation method, and its application in palladium adsorption according to the present invention.

[0061] Example 1

[0062] A method for preparing a binary ionic liquid fiber membrane includes the following steps:

[0063] 1) Mix dichloromethane and acetic acid in a volume ratio of 2:1 to obtain solution a;

[0064] 2) 1.33 g of cellulose acetate (CA), 3.27 mmol of 1-vinyl-3-ethylimidazolium bromide ([Vim-C2]Br, 99%), and 1-vinyl-3-decylimidazolium bromide ([Vim-C...)... 10 [Vim-C2]Br (99%) was dissolved in 10 mL of solution a, wherein [Vim-C2]Br and [Vim-C 10 The molar ratio of Br is 1:9. After stirring thoroughly for 4 hours, both are completely dissolved to obtain solution b.

[0065] 3) Add 107.1 mg N,N'-methylenebisacrylamide (MBAA) and 20 mg benzoyl peroxide (BPO) to solution b and mix. Sonicate for 5 minutes to ensure uniform mixing. Heat the mixture to 50 °C and stir for 1 h in an oil bath condenser system. Then heat the mixture to 85 °C and continue stirring for 12 h to obtain solution c.

[0066] 4) Take 10 mL of solution c and place it in a syringe. Using a stainless steel spinning needle with an inner diameter of 0.84 mm, an outer diameter of 1.28 mm, and a total length of 2.5 mm, perform high-voltage electrospinning at a humidity of 30-50%, a temperature of 20-30 ℃, and a voltage of 18 kV. After spinning, dry the material at 60 ℃ for 12 h to obtain the binary IL / CA nanofiber material, denoted as CF-IL-C2 / C. 10 -1:9.

[0067] The SEM image of the binary IL / CA nanofiber material prepared in this embodiment is shown below. Figure 1 Its FTIR spectrum is shown in Figure 2 .

[0068] Example 2

[0069] A method for preparing a binary ionic liquid fiber membrane includes the following steps:

[0070] 1) Mix dichloromethane and acetic acid in a volume ratio of 2:1 to obtain solution a;

[0071] 2) 1.33 g of cellulose acetate (CA), 3.27 mmol of 1-vinyl-3-ethylimidazolium bromide ([Vim-C2]Br, 99%), and 1-vinyl-3-decylimidazolium bromide ([Vim-C...)... 10 [Vim-C2]Br (99%) was dissolved in 10 mL of solution a, wherein [Vim-C2]Br and [Vim-C 10 The molar ratio of Br is 3:7. After stirring thoroughly for 4 hours, both are completely dissolved to obtain solution b.

[0072] 3) Add 107.1 mg N,N'-methylenebisacrylamide (MBAA) and 18.7 mg benzoyl peroxide (BPO) to solution b and mix. Sonicate for 5 minutes to ensure uniform mixing. Heat the mixture to 50 °C and stir for 1 h in an oil bath condenser system. Then heat the mixture to 85 °C and continue stirring for 12 h to obtain solution c.

[0073] 4) Take 10 mL of solution c and place it in a syringe. Using a stainless steel spinning needle with an inner diameter of 0.84 mm, an outer diameter of 1.28 mm, and a total length of 2.5 mm, perform high-voltage electrospinning at a humidity of 30-50%, a temperature of 20-30 ℃, and a voltage of 18 kV. After spinning, dry the material at 60 ℃ for 12 h to obtain the binary IL / CA nanofiber material, denoted as CF-IL-C2 / C. 10 -3:7.

[0074] The SEM image of the binary IL / CA nanofiber material prepared in this embodiment is shown below. Figure 1 Its FTIR spectrum is shown in Figure 2 .

[0075] Example 3

[0076] A method for preparing a binary ionic liquid fiber membrane includes the following steps:

[0077] 1) Mix dichloromethane and acetic acid in a volume ratio of 2:1 to obtain solution a;

[0078] 2) 1.33 g of cellulose acetate (CA), 3.27 mmol of 1-vinyl-3-ethylimidazolium bromide ([Vim-C2]Br, 99%), and 1-vinyl-3-decylimidazolium bromide ([Vim-C...)... 10[Vim-C2]Br (99%) was dissolved in 10 mL of solution a, wherein [Vim-C2]Br and [Vim-C 10 The molar ratio of Br is 1:1. Stir thoroughly for 4 hours to completely dissolve both compounds, resulting in solution b.

[0079] 3) Add 107.1 mg N,N'-methylenebisacrylamide (MBAA) and 17 mg benzoyl peroxide (BPO) to solution b and mix. Sonicate for 5 minutes to ensure uniform mixing. Heat the mixture to 50 °C and stir for 1 h in an oil bath condenser system. Then heat the mixture to 85 °C and continue stirring for 12 h to obtain solution c.

[0080] 4) Take 10 mL of solution c and place it in a syringe. Using a stainless steel spinning needle with an inner diameter of 0.84 mm, an outer diameter of 1.28 mm, and a total length of 2.5 mm, perform high-voltage electrospinning at a humidity of 30-50%, a temperature of 20-30 ℃, and a voltage of 18 kV. After spinning, dry the material at 60 ℃ for 12 h to obtain the binary IL / CA nanofiber material, denoted as CF-IL-C2 / C. 10 -1:1.

[0081] The SEM image of the binary IL / CA nanofiber material prepared in this embodiment is shown below. Figure 1 Its FTIR spectrum is shown in Figure 2 .

[0082] Example 4

[0083] A method for preparing a binary ionic liquid fiber membrane includes the following steps:

[0084] 1) Mix dichloromethane and acetic acid in a volume ratio of 2:1 to obtain solution a;

[0085] 2) Under air conditions, 1.33 g of cellulose acetate (CA), 3.27 mmol of 1-vinyl-3-ethylimidazolium bromide ([Vim-C2]Br, 99%), and 1-vinyl-3-decylimidazolium bromide ([Vim-C2]Br, 99%) were mixed. 10 [Vim-C2]Br (99%) was dissolved in 10 mL of solution a, wherein [Vim-C2]Br and [Vim-C 10 The molar ratio of Br is 7:3. After stirring thoroughly for 4 hours, both are completely dissolved to obtain solution b.

[0086] 3) Add 107.1 mg N,N'-methylenebisacrylamide (MBAA) and 15.5 mg benzoyl peroxide (BPO) to solution b and mix. Sonicate for 5 minutes to ensure uniform mixing. Heat the mixture to 50 °C and stir for 1 h in an oil bath condenser system. Then heat the mixture to 85 °C and continue stirring for 12 h to obtain solution c.

[0087] 4) Take 10 mL of solution c and place it in a syringe. Using a stainless steel spinning needle with an inner diameter of 0.84 mm, an outer diameter of 1.28 mm, and a total length of 2.5 mm, perform high-voltage electrospinning at a humidity of 30-50%, a temperature of 20-30 ℃, and a voltage of 18 kV. After spinning, dry the material at 60 ℃ for 12 h to obtain the binary IL / CA nanofiber material, denoted as CF-IL-C2 / C. 10 -7:3.

[0088] The SEM image of the binary IL / CA nanofiber material prepared in this embodiment is shown below. Figure 1 Its FTIR spectrum is shown in Figure 2 .

[0089] Example 5

[0090] A method for preparing a binary ionic liquid fiber membrane includes the following steps:

[0091] 1) Mix dichloromethane and acetic acid in a volume ratio of 2:1 to obtain solution a;

[0092] 2) Under air conditions, 1.33 g of cellulose acetate (CA), 3.27 mmol of 1-vinyl-3-ethylimidazolium bromide ([Vim-C2]Br, 99%), and 1-vinyl-3-decylimidazolium bromide ([Vim-C2]Br, 99%) were mixed. 10 [Vim-C2]Br (99%) was dissolved in 10 mL of solution a, wherein [Vim-C2]Br and [Vim-C 10 The molar ratio of Br is 9:1. After stirring thoroughly for 4 hours, both are completely dissolved to obtain solution b.

[0093] 3) Add 107.1 mg N,N'-methylenebisacrylamide (MBAA) and 14 mg benzoyl peroxide (BPO) to solution b and mix. Sonicate for 5 minutes to ensure uniform mixing. Heat the mixture to 50 °C and stir for 1 h in an oil bath condenser system. Then heat the mixture to 85 °C and continue stirring for 12 h to obtain solution c.

[0094] 4) Take 10 mL of solution c and place it in a syringe. Using a stainless steel spinning needle with an inner diameter of 0.84 mm, an outer diameter of 1.28 mm, and a total length of 2.5 mm, perform high-voltage electrospinning at a humidity of 30-50%, a temperature of 20-30 ℃, and a voltage of 18 kV. After spinning, dry the material at 60 ℃ for 12 h to obtain the binary IL / CA nanofiber material, denoted as CF-IL-C2 / C. 10 -9:1.

[0095] The SEM image of the binary IL / CA nanofiber material prepared in this embodiment is shown below. Figure 1 Its FTIR spectrum is shown in Figure 2 .

[0096] Example 6

[0097] A method for preparing a binary ionic liquid fiber membrane includes the following steps:

[0098] 1) Mix dichloromethane and acetic acid in a volume ratio of 2:1 to obtain solution a;

[0099] 2) 1.33 g of cellulose acetate (CA), 3.27 mmol of 1-vinyl-3-ethylimidazolium bromide ([Vim-C2]Br, 99%), and 1-vinyl-3-decylimidazolium bromide ([Vim-C...)... 10 [Vim-C2]Br (99%) was dissolved in 10 mL of solution a, wherein [Vim-C2]Br and [Vim-C 10 The molar ratio of Br is 1:9. After stirring thoroughly for 4 hours, both are completely dissolved to obtain solution b.

[0100] 3) Take 10 mL of solution b and place it in a syringe. Use a stainless steel spinning needle with an inner diameter of 0.84 mm, an outer diameter of 1.28 mm, and a total length of 2.5 mm to spin the solution using high voltage electrospinning at a humidity of 30-50%, a temperature of 20-30 ℃, and 18 kV. After spinning, dry the solution at 60 ℃ for 12 h.

[0101] 4) The nanofiber material obtained in 3) was irradiated using electron beam irradiation technology at a dose of 150 kGy. The irradiated material was then labeled as CF-IL-C2 / C. 10 -R-1:9.

[0102] SEM images of the binary IL / CA nanofiber materials prepared in Examples 1-5 of this invention are shown below. Figure 1 FTIR spectra can be found Figure 2 , Figure 1 , 2 The morphology of the synthesized sample and the changes in its chemical structure before and after synthesis are presented. Figure 1 The results showed that the binary IL / CA nanofiber materials had a clear nanofiber structure, and there was no significant difference in fiber diameter among the five materials, with an average fiber diameter of 200-300 nm. Figure 2 Infrared spectral results show that the characteristic peaks of -OH and C=O of CA appear at 1372 cm⁻¹. -1 and 1660 cm -1 The sample exhibited a distinct characteristic peak of ester group C=O stretching vibration at 1735 cm⁻¹. This peak remained even after modification with the imidazole ionic liquid, indicating that the main chain structure was not disrupted. Simultaneously, a significantly enhanced absorption peak appeared in the 1570–1620 cm⁻¹ region, which can be attributed to the C=N and aromatic ring skeletal vibrations of the imidazole ring, indicating the successful introduction of the imidazole structure. The peak shape changed in the 1200–1300 cm⁻¹ region, possibly related to the superposition of C–N stretching vibrations. These results demonstrate that imidazole ionic liquids were successfully modified onto cellulose acetate while maintaining the integrity of the substrate structure.

[0103] Comparative Example 1

[0104] The difference between this and Example 1 is that the ionic liquid added in step 2) is different: only 3.27 mmol of 1-vinyl-3-ethylimidazolium bromide ([Vim-C2]Br, 99%) is added, and the prepared mono-ionic liquid fiber membrane material is designated as CAIL-C2.

[0105] Comparative Example 2

[0106] The difference between this and Example 1 is that the ionic liquid added in step 2) is different: only 3.27 mmol of 1-vinyl-3-butylimidazolium bromide ([Vim-C4]Br, 99%) is added, and the prepared mono-ionic liquid fiber membrane material is designated as CAIL-C4.

[0107] Comparative Example 3

[0108] The difference between this and Example 1 is that the ionic liquid added in step 2) is different: only 3.27 mmol of 1-vinyl-3-octylimidazolium bromide ([Vim-C8]Br, 99%) is added, and the prepared mono-ionic liquid fiber membrane material is designated as CAIL-C8.

[0109] Comparative Example 4

[0110] The difference between this and Example 1 is that the ionic liquid added in step 2) is different: only 3.27 mmol of 1-vinyl-3-decylimidazolium bromide ([Vim-C)) is added. 10The unary ionic liquid fiber membrane material prepared from Br (99%) is designated CAIL-C. 10 .

[0111] The adsorption performance characterization results of the binary IL / CA nanofiber materials prepared in Examples 1-5 of this invention are shown in the figure below. Figure 3-12 The adsorption performance of the binary ionic liquid fiber membrane prepared by irradiation in Example 6 of this invention for palladium is largely the same as that of the binary ionic liquid fiber membrane prepared by chemical method in Example 1, with no significant difference, and will not be described separately.

[0112] The specific procedures for the adsorption performance characterization experiment of this invention are as follows:

[0113] (1) Effect of pH on the adsorption performance of Pd(II) by binary IL / CA nanofibers

[0114] Prepare a 50 mg / L Pd(II) solution using PdCl2, and adjust the pH to 1-5 using 0.1 mol / L HCl and NaOH; weigh 10 mg of CF-IL-C2 / C 10 -1:9、 CF-IL-C2 / C 10 -3:7、 CF-IL-C2 / C 10 -1:1、 CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10 Five portions of each of the -9:1 ratio were placed in 12 mL sample bottles, and the prepared Pd(II) solutions of different pH values ​​were added to the sample bottles. The sample bottles containing the mixture were placed in a constant temperature water bath shaker, and the conditions were set at 160 rpm and 30 ℃ for 24 h. After the reaction was completed, the mixture in the bottle was separated into solid and liquid components. The liquid was filtered through a 0.45 μm polyethersulfone filter, and the filtrate was taken for testing. All experiments in the adsorption performance characterization experiment of this invention were performed in parallel groups. The concentration of the sample before and after adsorption was determined by ICP-OES. The adsorption amount and adsorption efficiency were calculated as shown in formulas (1) and (2):

[0115] (1)

[0116] (2)

[0117] In formulas (1) and (2), C0 (mg / L) represents the initial concentration of Pd(II); C e (mg / L) represents the concentration of Pd(II) in the sample vial at reaction equilibrium; m(mg) represents the concentration of CF-IL-C2 / C added to the sample vial. 10 -1:9、 CF-IL-C2 / C 10-3:7、 CF-IL-C2 / C 10 -1:1、 CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10 -9:1 actual mass; V (mL) represents the volume of liquid added to the sample vial.

[0118] (2) Adsorption kinetics

[0119] Weigh out 10 mg of CF-IL-C2 / C respectively 10 -1:9、 CF-IL-C2 / C 10 -3:7、 CF-IL-C2 / C 10 -1:1、 CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10 Five samples were prepared in a 9:1 ratio and placed in 12 mL sample bottles. 10 mL of Pd(II) solution with an initial concentration of 50 mg / L was added to each bottle. The pH of the solution was adjusted to 2 using 0.1 mol / L HCl. The bottles were then placed in a water bath constant temperature shaker and shaken at 30 ℃ and 160 rpm for five time points between 0 and 16 min. After the sample liquid was removed, it was filtered through a 0.45 μm filter. The concentration of Pd(II) before and after adsorption was then tested using ICP-OES, and the adsorption amount was calculated using formula (1).

[0120] (3) Adsorption isotherm

[0121] Ten Pd(II) solutions with concentrations ranging from 5 to 400 mg / L were prepared. The pH of the solutions was adjusted to 2 using 0.1 mol / L HCl. 10 mg of CF-IL-C2 / C was weighed out for each solution. 10 -1:9、 CF-IL-C2 / C 10 -3:7、 CF-IL-C2 / C 10 -1:1、CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10 Ten portions of each of the 9:1 ratio were added to a 12 mL sample bottle. The above solution was added to the weighed sample bottle and placed in a water bath constant temperature shaking oven. The conditions were set at 30 ℃ and 160 rpm for 24 h. After the reaction was completed, the sample was taken and filtered through a 0.45 μm filter. Then, the concentration of Pd(II) in the sample before and after adsorption was tested by ICP-OES, and the adsorption amount was calculated by formula (1).

[0122] (4) Effect of ionic strength on the adsorption performance of Pd(II) by IL / CA nanofiber materials

[0123] Six 50 mL solutions of NaCl or NaNO3 with different concentrations of Pd(II) (50 mg / L) were prepared using PdCl2 and NaCl or NaNO3 respectively. The pH of the solutions was adjusted to 2 using 0.1 mol / L HCl. The molar ratios of Pd(II) to NaCl or NaNO3 were 1:0 (blank), 1:1, 1:10, 1:100, 1:1000, and 1:2000 respectively. Then, 10 mg of CF-IL-C2 / C... 10 -1:9、CF-IL-C2 / C 10 -3:7、 CF-IL-C2 / C 10 -1:1、 CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10 Six portions of each of -9:1 were added to the above solution and placed in a water bath constant temperature shaking box. The conditions were set at 30 ℃ and 160 rpm for 24 h. After the reaction was completed, the sample was filtered through a 0.45 μm filter. Then, the concentration of Pd(II) before and after adsorption was tested by ICP-OES, and the adsorption efficiency was calculated by formula (2).

[0124] (5) Adsorption selectivity

[0125] To address the complex environment where Pd(II) coexists with multiple metal ions in real-world conditions, six common coexisting ions found in palladium-containing tailings, electronic waste resources, and spent catalysts were selected: Cu(II), Fe(III), Zn(II), Ni(II), Pb(II), and Co(II). These coexisting ions were formulated with Pd(II) to create a seven-component simulated solution. The Pd(II) ion concentration was 50 mg / L, and the molar ratios of Pd(II) with the coexisting ions Cu(II), Fe(III), Zn(II), Ni(II), Pb(II), and Co(II) were 1:0, 1:1, 1:5, 1:10, 1:20, and 1:50, respectively. The solution was adjusted to pH 2 using 0.1 mol / L HCl, and then 10 mg of CF-IL-C2 / C... 10 -1:9、 CF-IL-C2 / C 10 -3:7、 CF-IL-C2 / C 10 -1:1、 CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10Six portions of each of the 9:1 ratio were added to the above solution. The mixture was then placed in a water bath constant temperature shaking chamber and shaken at 30℃ and 160 rpm for 24 h. After the reaction was completed, the sample was filtered through a 0.45 μm filter. The concentration of Pd(II) before and after adsorption was then tested using ICP-OES, and the adsorption efficiency was calculated using formula (2).

[0126] The adsorption performance characterization experimental results of this invention are as follows:

[0127] (1) Effect of pH on the adsorption performance of Pd(II) by binary IL / CA nanofibers

[0128] To investigate the effect of pH on the adsorption performance of binary IL / CA nanofibers, adsorption experiments were conducted at different pH values. The results are as follows: Figure 3 As shown, the adsorption performance of the material for Pd(II) is basically unaffected within the pH range of 2-5. However, with increasing HCl addition, the adsorption performance of the binary IL / CA decreases at pH=1, which is related to the presence of Cl in the solution. - The concentration increases with pH 1; the concentration of C in the solution is related to this. Cl -:C Pd(II) The ratio is extremely high, resulting in a significant competitive adsorption effect. Materials with higher [Vim-C2]Br content show a slight decrease in Pd(II) adsorption efficiency at pH 4-5.

[0129] In addition, from Figure 3 As seen in Example 1, the CF-IL-C2 / C 10 -1:9 contains a small amount of short-chain [Vim-C2]Br, and its adsorption results in palladium are not affected by pH in the pH range of 2-5, compared with CF-IL-C2 / C prepared in Example 5. 10 Compared to the adsorption result of -9:1, this demonstrates that CF-IL-C2 / C 10 -1:9 is applicable over a wide pH range.

[0130] (2) Adsorption kinetics

[0131] For CF-IL-C2 / C 10 -1:9、CF-IL-C2 / C 10 -3:7、CF-IL-C2 / C 10 -1:1、CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10 The adsorption rate of Pd(II) at a ratio of -9:1 was evaluated with contact times of 1, 3, 10, and 15 min. Figure 4(b) shows the adsorption capacity of Pd(II) for the five materials at different contact times. The results show that all five materials can reach adsorption equilibrium within 15 min.

[0132] The adsorption rate of Pd(II) in the materials prepared in Comparative Examples 1-4 was evaluated using the same method, and the results are as follows: Figure 4 As shown in (a). From Figure 4 The adsorption kinetics comparison of (a) and 4(b) shows that the mono-ionic liquid fiber membranes prepared in Comparative Examples 1-4 reach adsorption equilibrium in about 2 h, while the binary ionic liquid fiber membranes prepared in Examples 1-5 can reach adsorption equilibrium within 15 min.

[0133] In addition, CF-IL-C2 / C 10 -1:9、CF-IL-C2 / C 10 -3:7、CF-IL-C2 / C 10 -1:1、CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10 The adsorption capacity of -9:1 at contact times of 1 min and 3 min is compared as follows: Figure 5 (a) Figure 5 As shown in (b). From Figure 5 (a) Figure 5 As seen in (b), with [Vim-C] 10 Increasing the Br content results in a greater adsorption capacity of palladium by the binary ionic liquid fiber membrane at the same adsorption time, indicating faster adsorption kinetics. This suggests that a lower content of short-chain ([Vim-C2]Br) compounds in the binary ionic liquid fiber membrane is beneficial for adsorption.

[0134] (3) Adsorption isotherm

[0135] like Figure 6 As shown, CF-IL-C2 / C 10 -1:9、CF-IL-C2 / C 10 -3:7、CF-IL-C2 / C 10 -1:1、CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10 The adsorption isotherm at 30 °C with a ratio of -9:1 indicates that the adsorption capacity increases rapidly in the initial stage, followed by a slowdown in the rate of increase until equilibrium is reached. This phenomenon is mainly attributed to the presence of a large number of adsorbable sites in the early stages of adsorption, which are gradually occupied until saturation.

[0136] (4) Effect of ionic strength on the adsorption performance of binary IL / CA nanofiber adsorbent material for Pd(II)

[0137] Experimental results of the ionic strength of palladium on the binary IL / CA nanofiber adsorbent material are as follows: Figure 7 As shown in (ab), the figure shows that the adsorption efficiency of the binary IL / CA nanofiber adsorbent material remains basically unaffected even when the molar ratio of Pd(II) to NaCl or NaNO3 is 1:100, or even when the molar ratio of Pd(II) to NaNO3 is 1:2000.

[0138] Furthermore, when the molar concentration of NaNO3 was 2000 times that of Pd(II), the same method was used to investigate the effect of ionic strength on the adsorption performance of Pd(II) in the materials prepared in Comparative Examples 1-4. The comparative results are as follows: Figure 8 As shown in (ab). From Figure 8 As seen in (ab), when the molar ratio of Pd(II) to NaNO3 is 1:2000, the adsorption of Pd(II) by the binary ionic liquid fiber membrane prepared in Examples 1-5 of this invention is not affected by NaNO3, and its adsorption results are better than those of the unary ionic liquid fiber membrane prepared in the comparative example.

[0139] (5) Adsorption selectivity

[0140] To evaluate the adsorption selectivity of ionic liquid-grafted cellulose for Pd(II), the embodiments of the present invention were compared with CF-IL-C2 / C 10 -1:9、CF-IL-C2 / C 10 -3:7、CF-IL-C2 / C 10 -1:1、CF-IL-C2 / C 10 -7:3 and CF-IL-C2 / C 10 A batch adsorption experiment was conducted on a mixture of seven metal ions at a ratio of -9:1. For example... Figure 9 As shown in (ae), these materials exhibit negligible adsorption for competing ions such as Cu(II), Fe(II), Zn(II), Ni(II), Pb(II), and Co(II), while demonstrating a strong affinity for Pd(II). Among them, CF-IL-C2 / C 10 -1:9 exhibits the highest selectivity and is almost unaffected by the coexistence of other cations.

[0141] In addition, from Figure 9 As seen in (ae), [Vim-C2]Br and [Vim-C 10 When the ratio of [Br] varies from 9:1 to 1:9, the content of short-chain [Vim-C2]Br gradually decreases, but the adsorption effect on palladium gradually increases. Furthermore, the binary ionic liquid fiber membrane CF-IL-C2 / C... 10The adsorption selectivity for palladium was best at a ratio of -1:9 (with the lowest proportion of short-chain [Vim-C2]Br), indicating that the presence of a small amount of short-chain [Vim-C2]Br helps to improve the adsorption effect.

[0142] When the molar ratio of coexisting ion concentration to Pd(II) concentration is 1:1, the adsorption selectivity of the unary ionic liquid fiber membrane materials prepared in Comparative Examples 1-4 of this invention for Pd(II) is investigated using the same method. The comparative results are as follows: Figure 10 As shown in (ab), both unary and binary ionic liquid fiber membranes can selectively adsorb Pd(II), but the adsorption efficiency of the binary ionic liquid fiber membranes prepared in Examples 1-5 of this invention for palladium is higher than that of the unary ionic liquid fiber membranes prepared in the comparative examples.

[0143] Figure 11 (ab) shows CF-IL-C2 / C 10 -1:9 adsorption efficiency graphs at dosages of 10 mg and 30 mg, respectively. From Figure 11 (ab) It can be seen that, in coexisting ions of different concentrations, the adsorbent CF-IL-C2 / C 10 When the dosage of the -1:9 ionic liquid fiber membrane was increased from 10 mg to 30 mg, it still exhibited high selectivity for palladium adsorption, while the adsorption efficiency increased simultaneously. In contrast, the mono-ionic liquid fiber membrane prepared in Comparative Examples 1-4, under the same coexisting ionic environment, showed essentially unchanged palladium adsorption efficiency when the dosage was increased from 10 mg to 30 mg. This indicates that the binary ionic liquid fiber membrane prepared in the embodiments of this invention has better application potential.

[0144] The selective adsorption of the binary ionic liquid fiber membrane prepared in this embodiment can be attributed to the following three factors: (1) there is a strong electrostatic interaction between the positively charged quaternary N on the imidazole ring of the ionic liquid and Pd(II); (2) there is a synergistic chelation between the imidazole N and Pd(II). As shown in Table 1, Pd(II) has a high electronegativity and a large covalent index. According to the hard-soft acid-base (HSAB) principle, the nitrogen donor group preferentially coordinates with metal ions with strong covalent and high electronegativity, which explains the excellent affinity of the binary IL / CA for Pd(II); (3) in the long chain ([Vim-C 10 In [Vim-C2]Br), the presence of a small amount of short chains ([Vim-C2]Br) further improves the space utilization on the substrate. Since the short chains occupy a small space, they can make the ionic liquid more densely distributed on the substrate.

[0145]

[0146] The repeated adsorption and utilization of palladium in a binary ionic liquid fiber membrane cycling experiment:

[0147] Weigh out CF-ILC2 / C 10 -9:1 0.01 g was added to 10 mL of an aqueous solution containing 50 mg / L palladium at 30 ℃. After adsorption at pH=2 for 24 h, the supernatant was filtered out using a filter, and the remaining palladium concentration was determined by ICP-OES. The palladium-loaded adsorbent was washed three times with deionized water, and then eluted with a mixture of 0.5 mol / L HCl and thiourea. After each adsorption experiment, the adsorbent was washed three times with deionized water and eluted with a mixture of 0.5 mol / L HCl and thiourea before the next cycle. This cycle was repeated three times.

[0148] Experimental results on the reusability of palladium using binary ionic liquid fiber membranes are as follows: Figure 12 As shown in the figure, after three cycles, the adsorption efficiency of the binary ionic liquid fiber membrane for Pd(II) remained essentially unchanged, indicating that this adsorbent has good recyclability.

[0149] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing a binary ionic liquid fiber membrane, characterized in that, Includes the following steps: Dichloromethane and acetic acid are mixed to obtain the first solution; Cellulose acetate, a first ionic liquid, and a second ionic liquid are dissolved in the first solution to obtain a second solution; the first ionic liquid and the second ionic liquid are alkenyl imidazole salts with alkyl side chain molecular structures of different lengths; N,N'-methylenebisacrylamide and benzoyl peroxide are added to the second solution, heated and stirred to obtain a third solution. The third solution is then subjected to high-voltage electrospinning to obtain a binary ionic liquid fiber membrane; or the second solution is subjected to high-voltage electrospinning followed by irradiation to obtain a binary ionic liquid fiber membrane.

2. The method for preparing a binary ionic liquid fiber membrane as described in claim 1, characterized in that, The general chemical structural formulas of the first ionic liquid and the second ionic liquid are represented as: [Vim-C n [X]; Wherein, Vim represents 1-vinylimidazolium cation; C n [X] represents a straight-chain alkyl group attached to the nitrogen position at the 3rd nitrogen position of the imidazole ring, with n carbon atoms, n = 1, 2, 3, 4, 6, 8, 10; [X] represents an anion, which is any one of bromide ion, chloride ion, tetrafluoroborate ion, and hexafluorophosphate ion.

3. The method for preparing a binary ionic liquid fiber membrane as described in claim 2, characterized in that, The first ionic liquid is 1-vinyl-3-ethylimidazolium bromide, the second ionic liquid is 1-vinyl-3-decylimidazolium bromide, and the molar ratio of the first ionic liquid to the second ionic liquid is 1:9-9:

1.

4. The method for preparing a binary ionic liquid fiber membrane as described in claim 2, characterized in that, With the volume of the first solution being 10 mL, the amount of cellulose acetate added is 1-2 g, and the total amount of the first ionic liquid and the second ionic liquid added is 2.5-6 mmol / L.

5. The method for preparing a binary ionic liquid fiber membrane as described in claim 4, characterized in that, During the preparation of the third solution, the heating temperature is 50-90 °C, the mass ratio of N,N'-methylenebisacrylamide to benzoyl peroxide is 80-120 mg: 5-21 mg, and the stirring time is 8-12 h.

6. The method for preparing a binary ionic liquid fiber membrane as described in claim 1, characterized in that, The high-voltage electrospinning temperature is 10-40 ℃, the humidity is 20%-70%, the voltage is 10 kV-20 kV, and the inner diameter of the spinning needle is 0.6-1.2 mm.

7. The method for preparing a binary ionic liquid fiber membrane according to any one of claims 1-6, characterized in that, The volume ratio of the dichloromethane to the acetic acid is 2:

1.

8. A binary ionic liquid fiber membrane, characterized in that, Prepared using the preparation method described in any one of claims 1-7.

9. The application of a binary ionic liquid fiber membrane as described in claim 8 in the adsorption and recovery of palladium.

10. The application as described in claim 9, characterized in that, Includes the following steps: The binary ionic liquid fiber membrane is placed in a palladium-containing solution with a pH of 1-5.

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