A polychlorinated polymer / graphene oxide composite membrane for ammonia separation and preparation method thereof

Abstract

The invention discloses a polychlorinated polymer / graphene oxide composite membrane for ammonia separation and a preparation method thereof, comprising the following steps: S1, dissolving graphene oxide in solvent I, depositing it on a porous polymer substrate by a vacuum filtration device, and obtaining a graphene oxide composite membrane; S2, dissolving a nitrogen heterocyclic compound containing a carbon-carbon double bond, a cross-linking agent, and an initiator in solvent II, spin-coating on the graphene oxide composite membrane, and then heating for 2 8 hours to obtain a polymer / graphene oxide composite membrane; S3, soaking the polymer / graphene oxide composite membrane in a halogenated hydrocarbon solution to obtain a quaternized polymer / graphene oxide composite membrane; S4, soaking the quaternized graphene oxide polymer composite membrane in a metal chloride solution to obtain a polychlorinated polymer / graphene oxide composite membrane. The composite membrane obtained by the present invention has an efficient ammonia separation effect, and when separating ammonia-containing gas, the ammonia permeability is as high as 3586.3 Barrer, and the ammonia / nitrogen and ammonia / hydrogen selectivities are as high as 674.1 and 214.8, respectively.

Description

Technical Field

[0001] The present invention relates to the technical field of new chemical materials, and in particular to a polychlorinated polymer / graphene oxide composite membrane for ammonia separation and a preparation method thereof. Background Art

[0002] Ammonia (NH3) is an important chemical raw material, with an annual global production of over 200 million tons. NH3 has a wide range of applications, including fertilizer manufacturing, pharmaceutical production, and refrigerant production. In recent years, with the greenhouse effect caused by the use of carbon energy, NH3 has gradually attracted the attention of researchers as a new energy source. NH3 can be pressurized and liquefied at room temperature, has a high energy density, is easy to store and transport, and can be used as a fuel for automobiles and gas turbine power generation. On the other hand, excessive ammonia emissions into the atmosphere can cause serious environmental problems. Emitted NH3 reacts with acidic substances (such as SO x and NO x ) react to form ammonium salts, which form air particles. Therefore, the separation and recovery of ammonia-containing gases is of great significance.

[0003] Currently, technologies for treating ammonia-containing gases primarily include absorption, adsorption, biological treatment, and catalytic oxidation. Absorption is the most commonly used method for treating ammonia-containing gases, and its process flow is relatively simple. However, this method requires a large equipment footprint, consumes high water, steam, and energy, and produces wastewater that can potentially cause secondary pollution. Adsorption utilizes porous materials as adsorbents, adsorbing NH3 onto the surface, thereby separating the NH3. This method offers advantages such as low energy consumption and high NH3 removal rates, but also carries the risks of high cost, potential for secondary pollution, and is only suitable for treating gases with low NH3 concentrations. Common biological treatment methods include biofiltration, biotrickling filtration, and bioabsorption. Biofiltration is relatively mature and widely used, suitable for treating gases with low NH3 concentrations, offering advantages such as high efficiency, large treatment capacity, and no secondary pollution. However, this method requires a large floor space for treating ammonia-containing gases, and the reaction conditions within the tower are difficult to control. Industrially, catalytic oxidation selectively decomposes NH3 into nitrogen (N2) and water (H2O). This method is suitable for treating a variety of ammonia-containing gases and offers high efficiency. However, the catalyst's oxidizing properties must be neither too high nor too low. Excessive oxidizing properties can lead to the formation of byproducts such as nitrogen oxides, resulting in excessive emissions. However, low oxidizing properties reduce reaction activity, making it difficult to meet treatment standards.

[0004] Therefore, developing green ammonia separation technologies with high separation efficiency and low energy consumption is a critical need within the industry. Membrane separation technology, characterized by its environmental friendliness, low energy consumption, and ease of operation, does not involve phase transitions between components. Its application to ammonia-containing waste gas treatment holds great promise. However, existing ammonia separation membranes suffer from low ammonia selectivity and permeation flux. Developing high-performance, low-cost ammonia separation membranes remains a significant technical challenge. Summary of the Invention

[0005] To address the problems of low ammonia selectivity and low ammonia permeation flux in ammonia separation membranes in the prior art, the present invention provides a polychlorinated polymer / graphene oxide composite membrane for ammonia separation and a preparation method thereof. Graphene oxide is loaded on a porous polymer substrate, and a polymer membrane with highly selective adsorption for ammonia is loaded on the graphene oxide to prepare a polymer / graphene oxide composite ammonia-hydrogen separation membrane, which can achieve continuous, rapid, and low-energy separation of ammonia.

[0006] The present invention adopts the following technical solutions:

[0007] A method for preparing a polychlorinated polymer / graphene oxide composite membrane for ammonia separation, characterized by comprising the following steps:

[0008] S1, dissolving graphene oxide (GO) in solvent I and depositing it on a porous polymer substrate through a vacuum filtration device to obtain a graphene oxide composite membrane;

[0009] S2, dissolving a nitrogen heterocyclic compound containing a carbon-carbon double bond, a crosslinking agent, and an initiator in solvent II, spin-coating the mixture on the graphene oxide composite film, and then heating the mixture for 2-8 hours, repeating the process 5-20 times to obtain a polymer / graphene oxide composite film;

[0010] S3, soaking the polymer / graphene oxide composite film in a halogenated hydrocarbon solution, and then drying to obtain a quaternized polymer / graphene oxide composite film;

[0011] S4. Immersing the quaternized graphene oxide polymer composite membrane in a metal chloride solution and then drying it to obtain a polychlorinated polymer / graphene oxide composite membrane.

[0012] In step S1, the mass ratio of graphene oxide to solvent I is 1:(5000-10000).

[0013] In the step S1, the diameter of the graphene oxide sheet is 0.2-0.4 μm.

[0014] In the step S1, the porous polymer substrate is one of a polyethersulfone filter membrane, a nylon filter membrane, a polypropylene filter membrane, and a polytetrafluoroethylene filter membrane with a pore size less than 0.2 μm.

[0015] In the step S1, the solvent I is deionized water.

[0016] In step S2, the nitrogen heterocyclic compound is one of 1-vinylimidazole, 2-methyl-1-vinylimidazole, 3-vinylpyridine, 4-vinylpyridine, and 2-isopropenylpyridine.

[0017] In the step S2, the cross-linking agent is one of N,N′-methylenebisacrylamide, acrylamide, methacrylamide, terephthalic acid, styrene, and β-methylstyrene.

[0018] In the step S2, the initiator is azobisisobutyronitrile or sodium sulfite.

[0019] In step S2, the solvent II is one of deionized water, methanol, ethanol, and dimethyl sulfoxide.

[0020] In step S2, the mass ratio of the nitrogen heterocyclic compound, the crosslinking agent, and the initiator is 1:(0.5-2):(0.2-1), and the mass volume ratio of the nitrogen heterocyclic compound to the solvent II is 1 g:10 ml.

[0021] The heating temperature in step S2 is 60-80°C.

[0022] The halogenated hydrocarbon in the halogenated hydrocarbon solution in step S3 is one of methyl iodide, methyl bromide, and vinyl bromide, and the solvent is one of deionized water, methanol, ethanol, and dimethyl sulfoxide, wherein the volume ratio of the halogenated hydrocarbon to the solvent is 1:(10-15).

[0023] In step S3, the soaking temperature is 40-80° C., and the soaking time is 6-24 h.

[0024] In step S4, the metal chloride in the metal chloride solution is one of CoCl2, CaCl2, MgCl2, ZnCl2, NiCl2, SnCl2, CuCl2, MnCl2, and FeCl2, and the solvent is one of methanol, ethanol, and dimethyl sulfoxide, wherein the molar volume ratio of the metal chloride to the solvent is (1-2) mol:1000 ml.

[0025] In step S4, the soaking temperature is 40-80° C., and the soaking time is 6-24 hours.

[0026] A polychlorinated polymer / graphene oxide composite membrane for ammonia separation prepared according to the preparation method.

[0027] Application of a polychlorinated polymer / graphene oxide composite membrane prepared according to the preparation method in ammonia-hydrogen separation.

[0028] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0029] A. The present invention selects graphene oxide to be loaded on a porous polymer substrate. Graphene oxide has a high specific surface area and a layered structure, which can effectively improve the membrane's permeation flux to ammonia, and it can significantly improve the strength and toughness of the membrane, improving the mechanical properties of the membrane. Nitrogen heterocyclic compounds containing carbon-carbon double bonds undergo free radical polymerization on graphene oxide composite membranes to form highly cross-linked polymer membranes. The thickness of the polymer membrane can be effectively controlled by controlling the concentration of the precursor solution and the number of times the polymer membrane is applied. The polymer / graphene oxide composite membrane is quaternized and treated with metal chlorides to introduce polychlorinated adsorption sites as ammonia selective sites, thereby improving the selectivity for ammonia. By the synergistic effect of graphene oxide and polymer membrane, the high selectivity and high permeation flux of ammonia are simultaneously promoted. According to the preparation method of the present invention, composite membranes are prepared and ammonia separation is carried out by membrane separation, which can achieve continuous, rapid, low-energy separation of ammonia.

[0030] B. The composite membrane obtained by the present invention has a highly efficient ammonia separation effect. When separating ammonia-containing gases, the ammonia permeability is as high as 3586.3 Barrer, and the ammonia / nitrogen and ammonia / hydrogen selectivities are as high as 674.1 and 214.8, respectively.

[0031] C. The raw materials for preparing the composite membrane of the present invention are either commercially available or can be synthesized at low cost, thereby significantly reducing the cost of membrane production and facilitating its large-scale application. DETAILED DESCRIPTION

[0032] The present invention may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concepts of the present invention to those skilled in the art. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention. Example

[0033] This embodiment provides a polychlorinated polymer / graphene oxide composite membrane for ammonia separation, and the preparation method thereof comprises the following steps:

[0034] S1. Weigh 0.05 g of GO powder and mix it with 500 mL of deionized water. Ultrasonicate the mixture for 30 minutes to prepare a uniform and stable GO solution. Deposit 50 mL of the GO solution onto a polyethersulfone filter membrane using a vacuum filtration device. Vacuum dry the mixture at 60°C for 24 hours to prepare a graphene oxide composite membrane.

[0035] S2. Weigh 1-vinylimidazole (0.0531 mol, 5 g), N,N'-methylenebisacrylamide (0.0349 mol, 5 g), and azobisisobutyronitrile (0.0061 mol, 1 g) into 50 mL of methanol and sonicate for 30 minutes to obtain a precursor solution. Place the graphene oxide composite film on a benchtop spin coater, add 1 mL of the precursor solution, spin at 1000 rpm for 30 seconds, and then place in a 60°C oven for 2 hours to allow complete free radical polymerization of the monomers. Repeat this polymerization process five times to obtain a polymer / graphene oxide composite film.

[0036] Weigh 1 mL of iodomethane and mix it with 10 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the polymer / graphene oxide composite membrane in the iodomethane-methanol solution at 40°C for 24 hours. Dry the membrane in a vacuum oven at 80°C for 24 hours to obtain a quaternized polymer / graphene oxide composite membrane.

[0037] CoCl₂ (0.05 mol, 6.49 g) was weighed and mixed with 50 mL of methanol. Ultrasonication was performed for 30 minutes to prepare a homogeneous and stable solution. A quaternized polymer / graphene oxide composite membrane was immersed in the CoCl₂-methanol solution at 40°C for 24 hours and then dried in a vacuum oven at 80°C for 24 hours to obtain a polymer / graphene oxide composite separation membrane, designated Membrane A.

[0038] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeabilities of the three gases were tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that membrane A had a pure ammonia permeability of 3586.3 Barrer, and ammonia / nitrogen and ammonia / hydrogen selectivities of 674.1 and 214.8, respectively.

[0039] This embodiment provides a composite film, the preparation method of which includes the following steps:

[0040] S1. Weigh 0.05 g of GO powder and mix it with 500 mL of deionized water. Ultrasonicate the mixture for 30 minutes to prepare a uniform and stable GO solution. Deposit 50 mL of the GO solution onto a polyethersulfone filter membrane using a vacuum filtration device and vacuum dry it at 60°C for 24 hours to prepare a graphene oxide composite membrane.

[0041] S2. Weigh 1-vinylimidazole (0.0531 mol, 5 g), N,N'-methylenebisacrylamide (0.0349 mol, 5 g), and azobisisobutyronitrile (0.0061 mol, 1 g) into 50 mL of methanol and sonicate for 30 minutes to obtain a precursor solution. Place the graphene oxide composite film on a benchtop spin coater, add 1 mL of the precursor solution, spin at 1000 rpm for 30 seconds, and then place in an oven at 60°C for 2 hours to allow complete free radical polymerization of the monomers. Repeat this polymerization process five times to obtain a polymer / graphene oxide composite film, designated as a 1-vinylimidazole / graphene oxide composite film.

[0042] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeabilities of the three gases were measured, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that the 1-vinylimidazole / graphene oxide composite membrane had a pure ammonia permeability of 790.6 Barrer, and ammonia / nitrogen and ammonia / hydrogen selectivities of 398.5 and 69.3, respectively.

[0043] Combining Example 1 and Comparative Example 1, it can be seen that the composite membrane after quaternization and metal chloride treatment significantly improves the ammonia permeability and ammonia selectivity of the membrane, and the ammonia separation performance is enhanced. Example

[0044] This embodiment provides a polychlorinated polymer / graphene oxide composite membrane for ammonia separation, and the preparation method thereof comprises the following steps:

[0045] S1. Weigh 0.05 g of GO powder and mix it with 500 mL of deionized water. Ultrasonicate for 30 minutes to prepare a uniform and stable GO solution. Deposit 50 mL of the GO solution onto a polyethersulfone filter membrane using a vacuum filtration device and vacuum dry it at 60°C for 24 hours to prepare a graphene oxide composite membrane.

[0046] S2. Weigh 2-methyl-1-vinylimidazole (0.052 mol, 5 g), N,N'-methylenebisacrylamide (0.0175 mol, 2.5 g), and azobisisobutyronitrile (0.0061 mol, 1 g) into 50 mL of methanol and sonicate for 30 minutes to obtain a precursor solution. Place the graphene oxide composite film on a benchtop spin coater, add 1 mL of the precursor solution, spin at 1000 rpm for 30 seconds, and then place in an oven at 60°C for 3 hours to allow complete free radical polymerization of the monomers. Repeat this polymerization process 10 times to obtain a polymer / graphene oxide composite film.

[0047] S3. Weigh 1 mL of iodomethane and mix it with 10 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the polymer / graphene oxide composite film in the iodomethane-methanol solution at 40°C for 24 hours. Dry it in a vacuum oven at 80°C for 24 hours to obtain a quaternized polymer / graphene oxide composite film.

[0048] S4. Weigh 0.05 mol (6.49 g) of CoCl₂ and mix with 50 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Immerse the quaternized polymer / graphene oxide composite membrane in the CoCl₂-methanol solution at 40°C for 24 hours. Dry the membrane in a vacuum oven at 80°C for 24 hours to obtain a polymer / graphene oxide composite separation membrane, designated Membrane B.

[0049] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeabilities of the three gases were tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that membrane B had a pure ammonia permeability of 2534.3 Barrer, and ammonia / nitrogen and ammonia / hydrogen selectivities of 520.2 and 160.7, respectively.

[0050] This embodiment provides a composite film, the preparation method of which includes the following steps:

[0051] S1. Weigh 0.05 g of GO powder and mix it with 500 mL of deionized water. Ultrasonicate the mixture for 30 minutes to prepare a uniform and stable GO solution. Deposit 50 mL of the GO solution onto a polyethersulfone filter membrane using a vacuum filtration device and vacuum dry it at 60°C for 24 hours to prepare a graphene oxide composite membrane.

[0052] S2. Weigh 2-methyl-1-vinylimidazole (0.052 mol, 5 g), N,N'-methylenebisacrylamide (0.0175 mol, 2.5 g), and azobisisobutyronitrile (0.0061 mol, 1 g) into 50 mL of methanol and sonicate for 30 minutes to obtain a precursor solution. Place the graphene oxide composite film on a benchtop spin coater, add 1 mL of the precursor solution, spin at 1000 rpm for 30 seconds, and then place in an oven at 60°C for 3 hours to allow complete free radical polymerization of the monomers. Repeat this polymerization process 10 times to obtain a polymer / graphene oxide composite film.

[0053] S3. Weigh 1 mL of iodomethane and mix it with 10 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the polymer / graphene oxide composite membrane in the iodomethane-methanol solution at 40°C for 24 hours. Dry it in a vacuum oven at 80°C for 24 hours to obtain a quaternized polymer / graphene oxide composite membrane, designated as 2-methyl-1-vinylimidazole / graphene oxide composite membrane.

[0054] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeabilities of the three gases were measured, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that the 2-methyl-1-vinylimidazole / graphene oxide composite membrane had a pure ammonia permeability of 574.5 Barrer, and ammonia / nitrogen and ammonia / hydrogen selectivities of 403.5 and 75.8, respectively.

[0055] Combining Example 2 and Comparative Example 2, it can be seen that the composite membrane after quaternization and metal chloride treatment significantly improves the ammonia permeability and ammonia selectivity of the membrane, and the ammonia separation performance is enhanced. Example

[0056] This embodiment provides a polychlorinated polymer / graphene oxide composite membrane for ammonia separation, and the preparation method thereof comprises the following steps:

[0057] S1. Weigh 0.1 g of GO powder and mix it with 500 mL of deionized water. Ultrasonicate for 30 minutes to prepare a uniform and stable GO solution. Deposit 50 mL of the GO solution onto a polyethersulfone filter membrane using a vacuum filtration device and vacuum dry it at 60°C for 24 hours to prepare a graphene oxide composite membrane.

[0058] S2. Weigh 3-vinylpyridine (0.047 mol, 5 g), acrylamide (0.0704 mol, 7.5 g), and azobisisobutyronitrile (0.0061 mol, 1 g) into 50 mL of methanol and sonicate for 30 minutes to obtain a precursor solution. Place the graphene oxide composite film on a benchtop spin coater, add 1 mL of the precursor solution, spin at 1000 rpm for 30 seconds, and then place in an oven at 60°C for 4 hours to allow complete free radical polymerization of the monomers. Repeat this polymerization process 20 times to obtain a polymer / graphene oxide composite film.

[0059] S3. Weigh 1 mL of iodomethane and mix it with 10 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the polymer / graphene oxide composite membrane in the iodomethane-methanol solution at 50°C for 12 hours. Dry it in a vacuum oven at 80°C for 24 hours to obtain a quaternized polymer / graphene oxide composite membrane.

[0060] S4. Weigh 0.05 mol (6.49 g) of CoCl₂ and mix with 50 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the quaternized polymer / graphene oxide composite membrane in the CoCl₂-methanol solution at 60°C for 12 hours. Dry the membrane in a vacuum oven at 80°C for 24 hours to obtain a polymer / graphene oxide composite separation membrane, designated Membrane C.

[0061] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeabilities of the three gases were tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that membrane C had a pure ammonia permeability of 2668.9 Barrer, and ammonia / nitrogen and ammonia / hydrogen selectivities of 534.5 and 178.8, respectively. Example

[0062] This embodiment provides a polychlorinated polymer / graphene oxide composite membrane for ammonia separation, and the preparation method thereof comprises the following steps:

[0063] S1. Weigh 0.05 g of GO powder and mix it with 500 mL of deionized water. Ultrasonicate the mixture for 30 minutes to prepare a uniform and stable GO solution. Deposit 50 mL of the GO solution onto a polyethersulfone filter membrane using a vacuum filtration device and vacuum dry it at 60°C for 24 hours to prepare a graphene oxide composite membrane.

[0064] S2. Weigh 4-vinylpyridine (0.047 mol, 5 g), methacrylamide (0.0588 mol, 10 g), and azobisisobutyronitrile (0.0305 mol, 5 g) into 50 mL of methanol and sonicate for 30 minutes to obtain a precursor solution. Place the graphene oxide composite film on a benchtop spin coater, add 1 mL of the precursor solution, spin at 1000 rpm for 30 seconds, and then place in an 80°C oven for 6 hours to allow complete free radical polymerization of the monomers. Repeat this polymerization process 15 times to obtain a polymer / graphene oxide composite film.

[0065] S3. Weigh 1 mL of iodomethane and mix it with 10 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the polymer / graphene oxide composite membrane in the iodomethane-methanol solution at 40°C for 24 hours. Dry it in a vacuum oven at 80°C for 24 hours to obtain a quaternized polymer / graphene oxide composite membrane.

[0066] S4. Weigh 0.05 mol (6.49 g) of CoCl₂ and mix with 50 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the quaternized polymer / graphene oxide composite membrane in the CoCl₂-methanol solution at 40°C for 24 hours. Dry the membrane in a vacuum oven at 60°C for 24 hours to obtain a polymer / graphene oxide composite separation membrane, designated as membrane D.

[0067] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeabilities of the three gases were tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that membrane D had a pure ammonia permeability of 1779.6 Barrer, and ammonia / nitrogen and ammonia / hydrogen selectivities of 569.7 and 173.5, respectively. Example

[0068] This embodiment provides a polychlorinated polymer / graphene oxide composite membrane for ammonia separation, and the preparation method thereof comprises the following steps:

[0069] S1. Weigh 0.1 g of GO powder and mix it with 500 mL of deionized water. Ultrasonicate the mixture for 30 minutes to prepare a uniform and stable GO solution. Deposit 50 mL of the GO solution onto a polyethersulfone filter membrane using a vacuum filtration device and vacuum dry it at 60°C for 24 hours to prepare a graphene oxide composite membrane.

[0070] S2. Weigh 2-isopropenylpyridine (0.0335 mol, 5 g), styrene (0.048 mol, 5 g), and azobisisobutyronitrile (0.0122 mol, 2 g) into 50 mL of methanol and sonicate for 30 minutes to obtain a precursor solution. Place the graphene oxide composite film on a benchtop spin coater, add 1 mL of the precursor solution, spin at 1000 rpm for 30 seconds, and then place in an oven at 60°C for 8 hours to allow complete free radical polymerization of the monomers. Repeat this polymerization process five times to obtain a polymer / graphene oxide composite film.

[0071] S3. Weigh 1 mL of iodomethane and mix with 10 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the polymer / graphene oxide composite membrane in the iodomethane-methanol solution at 80°C for 6 hours. Dry the membrane in a vacuum oven at 80°C for 12 hours to obtain a quaternized polymer / graphene oxide composite membrane.

[0072] S4. Weigh 0.1 mol (12.98 g) of CoCl₂ and mix with 50 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Immerse the quaternized polymer / graphene oxide composite membrane in the CoCl₂-methanol solution at 40°C for 24 hours. Dry the membrane in a vacuum oven at 80°C for 24 hours to obtain a polymer / graphene oxide composite separation membrane, designated as Membrane E.

[0073] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeabilities of the three gases were tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that membrane E had a pure ammonia permeability of 1779.6 Barrer, with ammonia / nitrogen and ammonia / hydrogen selectivities of 569.7 and 173.5, respectively. Example

[0074] This embodiment provides a polychlorinated polymer / graphene oxide composite membrane for ammonia separation, and the preparation method thereof comprises the following steps:

[0075] S1. Weigh 0.05 g of GO powder and mix it with 500 mL of deionized water. Ultrasonicate the mixture for 30 minutes to prepare a uniform and stable GO solution. Deposit 50 mL of the GO solution onto a polyethersulfone filter membrane using a vacuum filtration device and vacuum dry it at 60°C for 24 hours to prepare a graphene oxide composite membrane.

[0076] S2. Weigh 1-vinylimidazole (0.0531 mol, 5 g), terephthalic acid (0.0308 mol, 5 g), and azobisisobutyronitrile (0.0183 mol, 3 g) into 50 mL of methanol and sonicate for 30 minutes to obtain a precursor solution. Place the graphene oxide composite film on a benchtop spin coater, add 1 mL of the precursor solution, spin at 1000 rpm for 30 seconds, and then place in a 70°C oven for 5 hours to allow complete free radical polymerization of the monomers. Repeat this polymerization process 10 times to obtain a polymer / graphene oxide composite film.

[0077] S3. Weigh 1 mL of iodomethane and mix it with 15 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the polymer / graphene oxide composite film in the iodomethane-methanol solution at 40°C for 24 hours. Dry it in a vacuum oven at 60°C for 24 hours to obtain a quaternized polymer / graphene oxide composite film.

[0078] S4. Weigh 0.05 mol (6.49 g) of CoCl₂ and mix with 50 mL of methanol. Ultrasonicate for 30 minutes to prepare a uniform and stable solution. Soak the quaternized polymer / graphene oxide composite membrane in the CoCl₂-methanol solution at 80°C for 6 hours. Dry the membrane in a vacuum oven at 80°C for 12 hours to obtain a polymer / graphene oxide composite separation membrane, designated Membrane F.

[0079] A gas separation device was used to separate a mixture of ammonia, nitrogen, and hydrogen. The permeabilities of the three gases were tested, and the ammonia / nitrogen and ammonia / hydrogen selectivities were calculated. The results showed that membrane F had a pure ammonia permeability of 1369.4 barrer, and ammonia / nitrogen and ammonia / hydrogen selectivities of 423.9 and 85.6, respectively. Example

[0080] A composite membrane was prepared by a method similar to that of Example 1, except that the initiator was changed to azobisisobutyronitrile (0.0244 mol, 4 g) and the solvent was changed to ethanol, and similar results were obtained. Example

[0081] A composite membrane was prepared by a method similar to that of Example 2, except that the initiator was changed to azobisisobutyronitrile (0.0305 mol, 5 g), the solvent was changed to deionized water, and the immersion temperature was changed to 50° C. to obtain similar results. Example

[0082] Composite membranes were prepared using a method similar to that of Example 3, except that the porous polymer substrate was replaced with a nylon filter membrane, the immersion temperature was changed to 50° C., and the immersion time was changed to 12 h, and similar results were obtained.

[0083] A composite membrane was prepared using a method similar to that of Example 4, except that the porous polymer substrate was replaced by a polypropylene filter membrane and the solvent was replaced by deionized water, and similar results were obtained.

[0084] A composite membrane was prepared using a method similar to that of Example 6, except that the porous polymer substrate was replaced with a polytetrafluoroethylene filter membrane and the immersion time was changed to 12 h, and similar results were obtained.

[0085] A composite membrane was prepared using a method similar to that of Example 1, except that the porous polymer substrate was replaced with a polytetrafluoroethylene filter membrane, the initiator was changed to sodium sulfite (0.0079 mol, 1 g), and the immersion time was changed to 10 h, obtaining similar results.

[0086] A composite membrane was prepared using a method similar to that of Example 5, except that the porous polymer substrate was replaced by a polypropylene filter membrane, the initiator was changed to azodicarbonamide (0.0119 mol, 1 g), and the immersion temperature was changed to 70°C, obtaining similar results.

[0087] A composite membrane was prepared using a method similar to that of Example 1, except that the halogenated hydrocarbon was replaced by methyl bromide, and similar results were obtained.

[0088] A composite membrane was prepared by a method similar to that of Example 1, except that the halogenated hydrocarbon was replaced by methyl bromide and the metal chloride was replaced by FeCl2 (0.05 mol, 6.3375 g), and similar results were obtained.

[0089] A composite membrane was prepared using a method similar to that of Example 2, except that the halogenated hydrocarbon was replaced by vinyl bromide and the metal chloride was replaced by FeCl2 (0.05 mol, 6.3375 g). Similar results were obtained.

[0090] A composite membrane was prepared using a method similar to that of Example 5, except that the porous polymer substrate was replaced by a polytetrafluoroethylene filter membrane, the halogenated hydrocarbon was replaced by vinyl bromide, and the metal chloride was replaced by FeCl2 (0.05 mol, 6.3375 g). Similar results were obtained.

[0091] A composite membrane was prepared using a method similar to that of Example 3, except that the metal chloride was replaced with MgCl2 (0.05 mol, 4.76 g), and similar results were obtained.

[0092] A composite membrane was prepared using a method similar to that of Example 6, except that the porous polymer substrate was replaced by a polypropylene filter membrane, the initiator was replaced by azodicarbonamide (0.0119 mol, 1 g), and the metal chloride was replaced by MnCl2 (0.05 mol, 6.2920 g). Similar results were obtained.

[0093] A composite membrane was prepared by a method similar to that of Example 1, except that the porous polymer substrate was replaced by a nylon filter membrane, the initiator was replaced by azodicarbonamide (0.0119 mol, 1 g), and the metal chloride was replaced by ZnCl2 (0.05 mol, 6.8143 g). Similar results were obtained.

[0094] The present invention selects graphene oxide to be loaded on a porous polymer substrate. Graphene oxide has a high specific surface area and a layered structure, which can effectively improve the membrane's permeation flux to ammonia, and it can significantly improve the strength and toughness of the membrane, improving the mechanical properties of the membrane. Nitrogen heterocyclic compounds containing carbon-carbon double bonds undergo free radical polymerization on the graphene oxide composite membrane to form a highly cross-linked polymer film. The thickness of the polymer film can be effectively controlled by controlling the concentration of the precursor solution and the number of times of application. The polymer / graphene oxide composite membrane is quaternized and treated with metal chlorides, and polychlorine is introduced as ammonia selective adsorption site to improve the selectivity for ammonia. By the synergistic effect of graphene oxide and polymer membrane, the high selectivity and high permeation flux of ammonia are synchronously promoted. According to the preparation method of the present invention, the composite membrane is prepared and ammonia separation is carried out by membrane separation mode, which can achieve continuous, rapid, low-energy separation of ammonia.

[0095] The raw materials for preparing the composite membrane of the present invention are either commercially available or can be synthesized at low cost, thereby significantly reducing the cost of membrane preparation and facilitating its large-scale application.

[0096] Any matters not described in the present invention are applicable to the prior art.

[0097] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a polychlorinated polymer / graphene oxide composite membrane for ammonia separation, characterized in that: The steps include: S1, dissolving graphene oxide (GO) in solvent I and depositing it on a porous polymer substrate through a vacuum filtration device to obtain a graphene oxide composite membrane; S2, dissolving a nitrogen heterocyclic compound containing a carbon-carbon double bond, a crosslinking agent, and an initiator in solvent II, spin-coating the mixture on the graphene oxide composite film, and then heating the mixture for 2-8 h, repeating the process 5-20 times, to obtain a polymer / graphene oxide composite film; In step S2, the nitrogen heterocyclic compound is one of 1-vinylimidazole, 2-methyl-1-vinylimidazole, 3-vinylpyridine, 4-vinylpyridine, and 2-isopropenylpyridine; The cross-linking agent is one of N,N′-methylenebisacrylamide, acrylamide, methacrylamide, terephthalic acid, styrene, and β-methylstyrene; The initiator is azobisisobutyronitrile or sodium sulfite; The solvent II is one of deionized water, methanol, ethanol, dimethyl sulfoxide S3, soaking the polymer / graphene oxide composite film in a halogenated hydrocarbon solution, and then drying to obtain a quaternized polymer / graphene oxide composite film; In step S3, the halogenated hydrocarbon in the halogenated hydrocarbon solution is one of methyl iodide, methyl bromide, and vinyl bromide, and the solvent is one of deionized water, methanol, ethanol, and dimethyl sulfoxide, wherein the volume ratio of the halogenated hydrocarbon to the solvent is 1:(10-15); S4, soaking the quaternized graphene oxide polymer composite membrane in a metal chloride solution, and then drying it to obtain a polychlorinated polymer / graphene oxide composite membrane; In step S4, the metal chloride in the metal chloride solution is one of CoCl2, CaCl2, MgCl2, ZnCl2, NiCl2, SnCl2, CuCl2, MnCl2, and FeCl2, and the solvent is one of methanol, ethanol, and dimethyl sulfoxide, wherein the molar volume ratio of the metal chloride to the solvent is (1-2) mol:1000 ml.

2. The preparation method according to claim 1, characterized in that In step S1, the mass ratio of graphene oxide to solvent I is 1:(5000-10000).

3. The preparation method according to claim 1, wherein: In step S1, the diameter of the graphene oxide sheet is 0.2-0.4 μm; The porous polymer substrate is one of a polyethersulfone filter membrane, a nylon filter membrane, a polypropylene filter membrane, and a polytetrafluoroethylene filter membrane having a pore size of less than 0.2 μm; The solvent I is deionized water.

4. The preparation method according to claim 1, wherein: In step S2, the mass ratio of the nitrogen heterocyclic compound, the crosslinking agent, and the initiator is 1:(0.5-2):(0.2-1), and the mass volume ratio of the nitrogen heterocyclic compound to the solvent II is 1 g:10 ml.

5. The preparation method according to claim 1, wherein: The heating temperature in step S2 is 60-80°C.

6. The preparation method according to claim 1, wherein: In step S3, the soaking temperature is 40-80° C., and the soaking time is 6-24 h; the drying temperature is 60-80° C., and the drying time is 12-24 h.

7. The preparation method according to claim 1, wherein: In step S4, the soaking temperature is 40-80° C., and the soaking time is 6-24 hours; the drying temperature is 60-80° C., and the drying time is 12-24 hours.

8. A polychlorinated polymer / graphene oxide composite membrane for ammonia separation prepared by the preparation method according to any one of claims 1 to 7.

9. Use of a polychlorinated polymer / graphene oxide composite membrane prepared by the preparation method according to any one of claims 1 to 7 in ammonia-hydrogen separation.