A PPy / PSf / PEG polymer composite membrane and its preparation method and application

Abstract

The present invention relates to the technical field of polymer composite materials, and in particular to a PPy / PSf / PEG polymer composite membrane and a preparation method and application thereof. The preparation method comprises: fixing a polysulfone membrane on stainless steel, and then clamping it on a platinum electrode clamp as a working electrode to construct a three-electrode system; dispersing a pyrrole monomer in deionized water to obtain a first electrolyte, taking the first electrolyte and adding it to a sulfuric acid aqueous solution to mix, and then adding ZrO2-C nanoparticles to obtain a second electrolyte; placing the three-electrode system in the first electrolyte, and conducting a 200 nm ion ion electrolysis reaction at a current density of 0.4 to 0.6 mA / cm 2 The electrolyte was deposited for 0.5 to 1 hour and then placed in the second electrolyte at a current density of 0.1 to 0.4 mA / cm 2 After deposition for 1.5 to 3 hours, the polysulfone membrane treated with electrodeposition is removed, rinsed with deionized water, and dried for the first time to obtain a PPy / PSf composite membrane. The PPy / PSf composite membrane is then completely immersed in a polyethylene glycol aqueous solution for 3 to 5 hours, removed, and dried for the second time to obtain a PPy / PSf / PEG composite membrane. The PPy / PSf / PEG polymer composite membrane prepared by the present invention has high helium flux and selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer composite materials, and in particular to a PPy / PSf / PEG polymer composite film and a preparation method and application thereof. Background Art

[0002] Natural gas is mainly composed of CH4, C2H6, C3H8, C4H 10 It is composed of hydrocarbon gases, small amounts of non-hydrocarbon gases such as CO2 and N2, and trace to minute amounts of rare gases such as helium. The rare gas helium has special physical properties such as inactive chemical properties, low thermal conductivity and electrical resistance, low melting and boiling points, and easy luminescence. Therefore, it has important industrial uses and application value in aerospace, atomic energy, low-temperature superconductivity, deep diving, laser, electronics, medicine, metallurgy, oil and gas exploration and other fields or industries. Natural gas is the most important source of helium for industrial use. At present, the main technology used in natural gas helium extraction is the cryogenic method. However, the use of cryogenic technology alone for helium purification still has problems such as low operational flexibility, high equipment investment, and high energy consumption. It is not competitive in terms of economic benefits. At the same time, it is difficult to remove hydrogen from the raw gas by cryogenic method, and the product concentration is difficult to guarantee.

[0003] In recent years, membrane separation has gradually been applied in the field of helium purification. The membrane separation method uses the difference in permeability of each component in the gas during the dissolution, diffusion, and desorption processes under the pressure difference on both sides of the membrane to achieve the separation effect. The membrane separation method is simple to operate, has low energy consumption, low equipment construction and operation costs, and is highly competitive. Designing helium separation membranes with high helium selectivity and high gas flux is of great significance for achieving the economy of helium extraction from natural gas, reducing dependence on helium imports, and achieving independent production and use of helium. Polymer membranes are made of high molecular polymers. Ordinary polymer membranes are widely used in gas separation due to their light weight, low cost, and simple preparation process. Organic polymers are easy to synthesize, easy to modify, and have good film-forming properties. However, since organic membranes are not resistant to high pressure, have low mechanical strength, and poor acid and alkali resistance and thermal stability, they cannot meet the requirements of industrial applications.

[0004] However, the membrane separation method has very high requirements for helium separation membranes. They must have high flux and separation selectivity coefficient to purify helium in natural gas, and they must also have excellent high temperature resistance and plasticization resistance. Optimizing the membrane manufacturing process and the preparation of high-performance gas separation membranes are hot topics for further research. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a PPy / PSf / PEG polymer composite membrane and its preparation method and application, so as to at least solve the problems of existing helium separation membranes such as low gas flux, small separation selectivity, weak high temperature resistance and plasticization resistance.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] A first aspect of an embodiment of the present invention provides a method for preparing a PPy / PSf / PEG polymer composite membrane, comprising the following steps:

[0008] The cleaned and dried polysulfone membrane was wrapped and fixed on stainless steel with insulating tape, and then clamped on a platinum electrode clamp as the working electrode, with a stainless steel sheet as the counter electrode and a saturated calomel electrode as the reference electrode to construct a three-electrode system.

[0009] Dispersing pyrrole monomer in deionized water and stirring to obtain a first electrolyte, adding the first electrolyte to a sulfuric acid aqueous solution and mixing, then adding ZrO2-C nanoparticles and ultrasonically dispersing to obtain a second electrolyte;

[0010] The three-electrode system is placed in the first electrolyte and the current density is 0.4-0.6 mA / cm 2 The electrolyte was deposited for 0.5 to 1 hour and then placed in the second electrolyte at a current density of 0.1 to 0.4 mA / cm 2 After deposition for 1.5 to 3 h, the polysulfone membrane treated by electrodeposition was removed, washed with deionized water, and dried for the first time to obtain a PPy / PSf composite membrane;

[0011] The PPy / PSf composite membrane was completely immersed in a polyethylene glycol aqueous solution for 3 to 5 hours, taken out, and dried for a second time to obtain a PPy / PSf / PEG composite membrane.

[0012] In some embodiments, the concentration of the pyrrole monomer in the first electrolyte is 0.01 to 0.05 mol / L.

[0013] In some embodiments, the first electrolyte and the sulfuric acid aqueous solution are mixed in a volume ratio of (0.002-0.005):1, and the sulfuric acid concentration in the sulfuric acid aqueous solution is 0.5 mol / L.

[0014] In some embodiments, the concentration of ZrO2-C nanoparticles in the second electrolyte is 0.15-0.5 g / L.

[0015] In some embodiments, the ZrO2-C nanoparticles are prepared as follows:

[0016] Terephthalic acid and ZrCl4 are added to N,N-dimethylformamide, ultrasonically treated for 20 to 30 minutes, glacial acetic acid is added, and ultrasonically treated for another 20 to 30 minutes. The mixture is then transferred to a hydrothermal autoclave and heated at 100 to 120°C for reaction for 20 to 24 hours. The mixture is then centrifuged and precipitated with dimethylformamide and ethanol, and dried to obtain UiO-66. UiO-66 is used as a precursor and thermally decomposed at 750 to 850°C for 2 to 3 hours in a N2 atmosphere to obtain ZrO2-C nanoparticles.

[0017] In some embodiments, the molar ratio of terephthalic acid to ZrCl4 is 1:(1-1.3), and the molar volume ratio of terephthalic acid to dimethylformamide is 1 mmol:(100-200) mL.

[0018] In some embodiments, the concentration of polyethylene glycol in the polyethylene glycol aqueous solution is 2 to 5 wt %.

[0019] In some embodiments, the first drying condition is drying at a temperature of 30-40° C. for 15-24 hours, and the second drying condition is drying in a constant temperature drying oven at a temperature of 50-60° C. and a humidity of 30-40% for 10-15 hours.

[0020] A second aspect of an embodiment of the present invention provides a PPy / PSf / PEG polymer composite membrane, which is prepared using the preparation method described in the first aspect.

[0021] A third aspect of the embodiments of the present invention provides the use of the PPy / PSf / PEG polymer composite membrane of the second aspect in a helium separation membrane.

[0022] The present invention discloses a method for preparing a PPy / PSf / PEG polymer composite membrane. The method uses MOF-derived ZrO2-C nanoparticles to regulate the polysulfone membrane, increase the specific surface area and metal active sites of the polysulfone membrane, and improve helium separation performance. Polypyrrole (PPy) is selected as a conductive polymer, and ZrO2-C nanoparticles are introduced to electropolymerize PPy and deposit it on PSf. This can effectively improve the stability of the membrane, promote the interaction between PSf and PEG, and further facilitate the formation and growth of the PEG solution on the PSf surface.

[0023] The PPy / PSf / PEG polymer composite membrane prepared by the present invention has high helium flux and selectivity. After testing, the helium flux can reach 375GPU, and the He / CH4, He / N2, and He / CO2 selectivities can reach 357, 335, and 379, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the three-electrode system in the present invention;

[0025] Figure 2 This is a graph showing the anti-plasticization performance test results of the polymer composite film prepared in Example 1;

[0026] Figure 3 This is a graph showing the anti-plasticization performance test results of the polymer composite film prepared in Comparative Example 5. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0028] In the specification and claims herein, the terms "first" and "second" are used to distinguish different objects, rather than to describe a specific order of objects. In the description of the embodiments of this application, unless otherwise specified, the meaning of "plurality" refers to two or more. For example, "multiple processing units" refers to two or more processing units, etc., and "multiple components" refers to two or more components, etc.

[0029] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0030] The English definitions in this invention are as follows:

[0031] PPy: polypyrrole; PSf: polysulfone; PEG: polyethylene glycol; SCE: saturated calomel electrode; DMF: N,N-dimethylformamide; Py: pyrrole monomer.

[0032] In order to improve the chemical stability and gas selectivity of the membrane, the present invention proposes a method for preparing a PPy / PSf / PEG polymer composite membrane. The polysulfone membrane is regulated by MOF-derived ZrO2-C nanoparticles, the specific surface area and metal active sites of the polysulfone membrane are increased, and the helium separation performance is improved. Polypyrrole (PPy) is selected as the conductive polymer, and ZrO2-C nanoparticles are introduced to electropolymerize PPy and deposit it on PSf. This can effectively improve the stability of the membrane, promote the interaction between PSf and PEG, and facilitate the formation and growth of PEG solution on the PSf surface.

[0033] The preparation method of the PPy / PSf / PEG polymer composite membrane of the present invention comprises the following steps:

[0034] See Figure 1 ( Figure 1 (where CE stands for counter electrode, RE stands for reference electrode, and WE stands for working electrode) the cleaned and dried polysulfone membrane was wrapped and fixed on stainless steel with insulating tape, and then clamped on a platinum electrode clamp as the working electrode, the stainless steel sheet as the counter electrode, and the saturated calomel electrode as the reference electrode to construct a three-electrode system;

[0035] Dispersing pyrrole monomer in deionized water and stirring to obtain a first electrolyte, adding the first electrolyte to a sulfuric acid aqueous solution and mixing, then adding ZrO2-C nanoparticles and ultrasonically dispersing to obtain a second electrolyte;

[0036] The three-electrode system is placed in the first electrolyte and the current density is 0.4-0.6 mA / cm 2 The electrolyte was deposited for 0.5 to 1 hour and then placed in the second electrolyte at a current density of 0.1 to 0.4 mA / cm 2 After deposition for 1.5 to 3 h, the polysulfone membrane treated by electrodeposition was removed, washed with deionized water, and dried for the first time to obtain a PPy / PSf composite membrane;

[0037] The PPy / PSf composite membrane was completely immersed in a polyethylene glycol aqueous solution for 3 to 5 hours, taken out, and dried for a second time to obtain a PPy / PSf / PEG composite membrane.

[0038] The concentration of pyrrole monomer in the first electrolyte is 0.01 to 0.05 mol / L, and the first electrolyte is mixed with a sulfuric acid aqueous solution at a volume ratio of (0.002 to 0.005):1, wherein the sulfuric acid concentration in the sulfuric acid aqueous solution is 0.5 mol / L. The concentration of ZrO2-C nanoparticles in the second electrolyte is 0.15 to 0.5 g / L.

[0039] The preparation method of ZrO2-C nanoparticles is as follows:

[0040] Terephthalic acid and ZrCl4 are added to N,N-dimethylformamide, ultrasonically treated for 20 to 30 minutes, glacial acetic acid is added, and ultrasonically treated for another 20 to 30 minutes. The mixture is then transferred to a hydrothermal autoclave and heated at 100 to 120°C for reaction for 20 to 24 hours. The mixture is then centrifuged and precipitated with dimethylformamide and ethanol, and dried to obtain UiO-66. UiO-66 is used as a precursor and thermally decomposed at 750 to 850°C for 2 to 3 hours in a N2 atmosphere to obtain ZrO2-C nanoparticles. The molar ratio of terephthalic acid to ZrCl4 is 1:(1-1.3), the molar volume ratio of terephthalic acid to dimethylformamide is 1 mmol:(100-200) mL, the concentration of polyethylene glycol in the polyethylene glycol aqueous solution is 2-5 wt%, the first drying condition is drying at a temperature of 30-40°C for 15-24 hours, and the second drying condition is drying in a constant temperature drying oven at a temperature of 50-60°C and a humidity of 30-40% for 10-15 hours.

[0041] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0042] Example 1

[0043] The preparation method of the PPy / PSf / PEG polymer composite membrane of this embodiment is as follows:

[0044] (1) Construction of a three-electrode system

[0045] Cut the 2cm 2 The PSf membrane was repeatedly rinsed with deionized water and dried. The surface of the stainless steel sheet was polished with sandpaper, then repeatedly rinsed with deionized water and ethanol, and air-dried. The PSf membrane was wrapped around the stainless steel sheet with electrical insulating tape and then clamped to a platinum electrode holder as the working electrode. The stainless steel sheet served as the counter electrode, and a saturated calomel electrode served as the reference electrode to construct a three-electrode system.

[0046] (2) Preparation of ZrO2-C nanoparticles

[0047] 1 mmol of terephthalic acid and 1 mmol of ZrCl4 were dissolved in 150 ml of DMF and sonicated for 20 minutes. 20 ml of glacial acetic acid was added and sonicated for 30 minutes. The mixture was then transferred to a hydrothermal reactor and heated at 100°C for 24 hours. The mixture was then centrifuged and precipitated with DMF and ethanol and dried overnight at 60°C in a vacuum oven to produce UiO-66. Using UiO-66 as a precursor, it was pyrolyzed at 800°C for 2 hours under a nitrogen atmosphere to obtain MOF-derived ZrO2-C nanoparticles.

[0048] (3) Preparation of electrolyte

[0049] Pyrrole monomer was dispersed in deionized water and stirred to obtain a first electrolyte solution with a pyrrole concentration of 0.04 mol / L. 0.14 ml of the first electrolyte solution was added to 50 ml of 0.5 mol / L sulfuric acid solution and magnetically stirred for 30 minutes to completely dissolve it. 0.010 g of ZrO2-C nanoparticles was then weighed and added, and ultrasonicated at room temperature to uniformly disperse them, to obtain a second electrolyte solution.

[0050] (4) Preparation of PPy / PSf composite membrane

[0051] Polypyrrole was deposited on the porous surface of the PSf membrane in two steps by constant current electrochemical method. First, the three-electrode system was placed in the first electrolyte and the current density was 0.5 mA / cm 2 The electrolyte was deposited for 1 h and then placed in the second electrolyte at 0.25 mA / cm 2 The electroplated polysulfone membrane was removed and repeatedly washed with deionized water to remove surface pollutants. After washing, it was dried in an oven at 30°C for 20 hours to obtain a PPy / PSf composite membrane.

[0052] (5) Compound with PEG

[0053] PEG was dissolved in deionized water and stirred at room temperature to dissolve to prepare a polyethylene glycol aqueous solution with a concentration of 4 wt%. The PPy / PSf composite membrane of step (4) was immersed in the 4 wt% polyethylene glycol aqueous solution. After soaking for 3 h, the free solution on the surface of the membrane was removed and the membrane was placed in a constant temperature drying oven at a temperature of 60°C and a humidity of 40% and dried for 10 h to obtain a PPy / PSf / PEG polymer composite membrane.

[0054] Example 2

[0055] The preparation method of the PPy / PSf / PEG polymer composite membrane of this embodiment is as follows:

[0056] (1) Construction of a three-electrode system

[0057] Cut the 2cm 2 The PSf membrane was repeatedly rinsed with deionized water and dried. The surface of the stainless steel sheet was polished with sandpaper, then repeatedly rinsed with deionized water and ethanol, and air-dried. The PSf membrane was wrapped around the stainless steel sheet with electrical insulating tape and then clamped to a platinum electrode holder as the working electrode. The stainless steel sheet served as the counter electrode, and a saturated calomel electrode served as the reference electrode to construct a three-electrode system.

[0058] (2) Preparation of ZrO2-C nanoparticles

[0059] 1 mmol of terephthalic acid and 1.2 mmol of ZrCl4 were dissolved in 150 ml of DMF and sonicated for 25 minutes. 20 ml of glacial acetic acid was added and sonicated for 20 minutes. The mixture was then transferred to a hydrothermal reactor and heated at 110°C for 20 hours. The mixture was then centrifuged with DMF and ethanol and dried overnight at 60°C in a vacuum oven to produce UiO-66. Using UiO-66 as a precursor, the mixture was pyrolyzed at 750°C for 3 hours under a nitrogen atmosphere to obtain MOF-derived ZrO2-C nanoparticles.

[0060] (3) Preparation of electrolyte

[0061] Pyrrole monomer was dispersed in deionized water and stirred to obtain a first electrolyte solution with a pyrrole concentration of 0.01 mol / L. 0.10 ml of the first electrolyte solution was added to 50 ml of 0.5 mol / L sulfuric acid solution and magnetically stirred for 30 minutes to completely dissolve it. 0.0075 g of ZrO2-C nanoparticles was then added and ultrasonicated at room temperature to uniformly disperse them, obtaining a second electrolyte solution.

[0062] (4) Preparation of PPy / PSf composite membrane

[0063] Polypyrrole was deposited on the porous layer of PSf membrane in two steps by constant current electrochemical method. First, the three-electrode system was placed in the first electrolyte and the current density was 0.4 mA / cm 2 The electrolyte was deposited for 0.5 h at 0.1 mA / cm 2 The polysulfone membrane treated with electrodeposition was removed and repeatedly washed with deionized water to remove surface pollutants. After washing, it was dried in an oven at 35°C for 15 hours to obtain a PPy / PSf composite membrane.

[0064] (5) Compound with PEG

[0065] PEG was dissolved in deionized water and stirred at room temperature to dissolve to prepare a 2 wt% polyethylene glycol aqueous solution. The PPy / PSf composite membrane of step (4) was immersed in the 2 wt% polyethylene glycol aqueous solution. After soaking for 4 h, the free solution on the surface of the membrane was removed and the membrane was placed in a constant temperature drying oven at a temperature of 50°C and a humidity of 30% and dried for 14 h to obtain a PPy / PSf / PEG polymer composite membrane.

[0066] Example 3

[0067] The preparation method of the PPy / PSf / PEG polymer composite membrane of this embodiment is as follows:

[0068] (1) Construction of a three-electrode system

[0069] Cut the 2cm2 The PSf membrane was repeatedly rinsed with deionized water and dried. The surface of the stainless steel sheet was polished with sandpaper, then repeatedly rinsed with deionized water and ethanol, and air-dried. The PSf membrane was wrapped around the stainless steel sheet with electrical insulating tape and then clamped to a platinum electrode holder as the working electrode. The stainless steel sheet served as the counter electrode, and a saturated calomel electrode served as the reference electrode to construct a three-electrode system.

[0070] (2) Preparation of ZrO2-C nanoparticles

[0071] 1 mmol of terephthalic acid and 1.3 mmol of ZrCl4 were dissolved in 200 ml of DMF and sonicated for 30 minutes. 20 ml of glacial acetic acid was added and sonicated for 25 minutes. The mixture was then transferred to a hydrothermal reactor and heated at 120°C for 22 hours. The mixture was then centrifuged and precipitated with DMF and ethanol and dried overnight at 60°C in a vacuum oven to produce UiO-66. Using UiO-66 as a precursor, it was pyrolyzed at 850°C for 2 hours under a nitrogen atmosphere to obtain MOF-derived ZrO2-C nanoparticles.

[0072] (3) Preparation of electrolyte

[0073] Pyrrole monomer was dispersed in deionized water and stirred to obtain a first electrolyte solution with a pyrrole concentration of 0.05 mol / L. 0.25 ml of the first electrolyte solution was added to 50 ml of 0.5 mol / L sulfuric acid solution and magnetically stirred for 30 minutes to completely dissolve it. 0.025 g of ZrO2-C nanoparticles was then added and ultrasonicated at room temperature to uniformly disperse them, obtaining a second electrolyte solution.

[0074] (4) Preparation of PPy / PSf composite membrane

[0075] Polypyrrole was deposited on the porous layer of PSf membrane in two steps by constant current electrochemical method. First, the three-electrode system was placed in the first electrolyte and the current density was 0.6 mA / cm 2 The electrolyte was deposited for 1 h at 0.4 mA / cm 2 The polysulfone membrane treated by electrodeposition was removed and repeatedly washed with deionized water to remove surface pollutants. After washing, it was dried in an oven at 40°C for 24 hours to obtain a PPy / PSf composite membrane.

[0076] (5) Compound with PEG

[0077] PEG was dissolved in deionized water and stirred at room temperature to dissolve to prepare a 5 wt% polyethylene glycol aqueous solution. The PPy / PSf composite membrane of step (4) was immersed in the 5 wt% polyethylene glycol aqueous solution. After soaking for 5 h, the free solution on the surface of the membrane was removed and the membrane was placed in a constant temperature drying oven at a temperature of 55° C. and a humidity of 35% and dried for 15 h to obtain a PPy / PSf / PEG polymer composite membrane.

[0078] Comparative Example 1

[0079] This comparative example prepares a PPy / PSf composite film. This comparative example also has the steps of constructing a three-electrode system, preparing ZrO2-C nanoparticles, and preparing an electrolyte, which are the same as those in Example 1, except that:

[0080] Polypyrrole was deposited on the porous surface of the PSf membrane in two steps by constant current electrochemical method. First, the three-electrode system was placed in the second electrolyte and the current density was 0.5 mA / cm 2 The electrolyte was then deposited at 0.25 mA / cm 2 The polysulfone membrane treated with electrodeposition was removed and repeatedly washed with deionized water to remove surface pollutants. After washing, it was dried in an oven at 30°C for 20 hours to obtain a PPy / PSf composite membrane, which was recorded as a PPy / PSf-1-3.5 composite membrane.

[0081] Comparative Example 2

[0082] This comparative example prepares a PPy / PSf composite film. The difference between this comparative example and comparative example 1 is that:

[0083] Polypyrrole was deposited on the porous surface of the PSf membrane in two steps by constant current electrochemical method. First, the three-electrode system was placed in the first electrolyte and the current density was 0.5 mA / cm 2 The electrolyte was then deposited at 0.25 mA / cm 2 The polysulfone membrane treated with electrodeposition was removed and repeatedly washed with deionized water to remove surface pollutants. After washing, it was dried in an oven at 30°C for 20 hours to obtain a PPy / PSf composite membrane, which was recorded as a PPy / PSf-2-3.5 composite membrane.

[0084] Comparative Example 3

[0085] In this comparative example, the ZrO2-C nanoparticles in Example 1 are replaced with carbon nanotubes. Specifically, the preparation method of the PPy / PSf / PEG polymer composite film in this comparative example is as follows:

[0086] (1) Construction of a three-electrode system

[0087] Cut the 2cm 2 The PSf membrane was repeatedly rinsed with deionized water and dried. The surface of the stainless steel sheet was polished with sandpaper, then repeatedly rinsed with deionized water and ethanol, and air-dried. The PSf membrane was wrapped around the stainless steel sheet with electrical insulating tape and then clamped to a platinum electrode holder as the working electrode. The stainless steel sheet served as the counter electrode, and a saturated calomel electrode served as the reference electrode to construct a three-electrode system.

[0088] (2) Preparation of electrolyte

[0089] Pyrrole monomer was dispersed in deionized water and stirred to obtain a first electrolyte solution with a pyrrole concentration of 0.04 mol / L. 0.14 ml of the first electrolyte solution was added to 50 ml of 0.5 mol / L sulfuric acid solution and magnetically stirred for 30 minutes to completely dissolve the solution. 0.010 g of carbon nanotubes was then added and ultrasonicated at room temperature to obtain a third electrolyte solution.

[0090] (3) Preparation of PPy / PSf composite membrane

[0091] Polypyrrole was deposited on the porous surface of the PSf membrane in two steps by constant current electrochemical method. First, the three-electrode system was placed in the first electrolyte and the current density was 0.5 mA / cm 2 The electrolyte was deposited for 1 h at 0.25 mA / cm 2 The electroplated polysulfone membrane was removed and repeatedly washed with deionized water to remove surface pollutants. After washing, it was dried in an oven at 30°C for 20 hours to obtain a PPy / PSf composite membrane.

[0092] (4) Compound with PEG

[0093] PEG was dissolved in deionized water and stirred at room temperature to dissolve to prepare a polyethylene glycol aqueous solution with a concentration of 4 wt%. The PPy / PSf composite membrane of step (3) was immersed in the 4 wt% polyethylene glycol aqueous solution. After soaking for 3 h, the free solution on the surface of the membrane was removed and the membrane was placed in a constant temperature drying oven at a temperature of 60°C and a humidity of 40% and dried for 10 h to obtain a PPy / PSf / PEG polymer composite membrane.

[0094] Comparative Example 4

[0095] In this comparative example, a one-step deposition method was used for 3.5 hours, and no ZrO2-C nanoparticles were added to the electrolyte. Specifically, the preparation method of the PPy / PSf / PEG polymer composite film of this embodiment is as follows:

[0096] (1) Construction of a three-electrode system

[0097] Cut the 2cm 2 The PSf membrane was repeatedly rinsed with deionized water and dried. The surface of the stainless steel sheet was polished with sandpaper, then repeatedly rinsed with deionized water and ethanol, and air-dried. The PSf membrane was wrapped around the stainless steel sheet with electrical insulating tape and then clamped to a platinum electrode holder as the working electrode. The stainless steel sheet served as the counter electrode, and a saturated calomel electrode served as the reference electrode to construct a three-electrode system.

[0098] (2) Preparation of electrolyte

[0099] Pyrrole monomer was dispersed in deionized water and stirred to obtain a first electrolyte solution with a pyrrole concentration of 0.04 mol / L. 0.14 ml of the first electrolyte solution was added to 50 ml of a 0.5 mol / L sulfuric acid solution and magnetically stirred for 30 minutes to completely dissolve the monomer, thereby obtaining a fourth electrolyte solution.

[0100] (3) Preparation of PPy / PSf composite membrane

[0101] Polypyrrole was deposited on the porous surface of the PSf membrane in two steps by constant current electrochemical method. The three-electrode system was placed in the third electrolyte and the current density was 0.5 mA / cm 2 The polysulfone membrane treated by electrodeposition was removed and repeatedly washed with deionized water to remove surface pollutants. After washing, it was dried in an oven at 30°C for 20 hours to obtain a PPy / PSf composite membrane.

[0102] (4) Compound with PEG

[0103] PEG was dissolved in deionized water and stirred at room temperature to dissolve to prepare a polyethylene glycol aqueous solution with a concentration of 4 wt%. The PPy / PSf composite membrane of step (4) was immersed in the 4 wt% polyethylene glycol aqueous solution. After soaking for 3 h, the free solution on the surface of the membrane was removed and the membrane was placed in a constant temperature drying oven at a temperature of 60°C and a humidity of 40% and dried for 10 h to obtain a PPy / PSf / PEG polymer composite membrane.

[0104] Comparative Example 5

[0105] The PEG / PPy / PSf polymer composite membrane was prepared in this comparative example, and the preparation method thereof is as follows:

[0106] (1) Construction of a three-electrode system

[0107] Cut the 2cm 2The PSf membrane was rinsed repeatedly with deionized water. After drying, the PSf membrane was completely immersed in a 4wt% polyethylene glycol aqueous solution. After soaking for 3 hours, the free solution on the membrane surface was removed and the membrane was placed in a constant temperature drying oven at a temperature of 60°C and a humidity of 40% for 10 hours to obtain a PEG / Psf composite membrane. After polishing the surface of the stainless steel sheet with sandpaper, it was repeatedly rinsed with deionized water and ethanol and blown dry for later use. The soaked and dried PEG / Psf composite membrane was wrapped and fixed on the stainless steel with electrical insulating tape and then clamped on a platinum electrode clamp as the working electrode. The stainless steel sheet was used as the counter electrode and a saturated calomel electrode was used as the reference electrode to construct a three-electrode system.

[0108] (2) Preparation of ZrO2-C nanoparticles

[0109] 1 mmol of terephthalic acid and 1 mmol of ZrCl4 were dissolved in 150 ml of DMF and sonicated for 20 minutes. 20 ml of glacial acetic acid was added and sonicated for 30 minutes. The mixture was then transferred to a hydrothermal reactor and heated at 100°C for 24 hours. The mixture was then centrifuged and precipitated with DMF and ethanol and dried overnight at 60°C in a vacuum oven to produce UiO-66. Using UiO-66 as a precursor, it was pyrolyzed at 800°C for 2 hours under a nitrogen atmosphere to obtain MOF-derived ZrO2-C nanoparticles.

[0110] (3) Preparation of electrolyte

[0111] Pyrrole monomer was dispersed in deionized water and stirred to obtain a first electrolyte solution with a pyrrole concentration of 0.04 mol / L. 0.14 ml of the first electrolyte solution was added to 50 ml of 0.5 mol / L sulfuric acid solution and magnetically stirred for 30 minutes to completely dissolve it. 0.010 g of ZrO2-C nanoparticles was then weighed and added, and ultrasonicated at room temperature to uniformly disperse them, to obtain a second electrolyte solution.

[0112] (4) Preparation of PEG / PPy / PSf polymer composite membrane

[0113] Polypyrrole was deposited on the porous layer of the PEG / Psf composite membrane in two steps by constant current electrochemical method. First, the three-electrode system was placed in the first electrolyte and the current density was 0.5 mA / cm 2 The electrolyte was deposited for 1 h and then placed in the second electrolyte at 0.25 mA / cm 2 The PEG / Psf composite membrane treated with electrodeposition was removed and repeatedly washed with deionized water to remove surface pollutants. After washing, it was dried in an oven at 30°C for 20 hours to obtain a PEG / PPy / PSf polymer composite membrane.

[0114] The membranes prepared in Examples 1-3 and Comparative Examples 1-5 were used as test samples and subjected to gas separation performance tests as follows:

[0115] The polymer composite membranes prepared in Examples 1-3 and Comparative Examples 1-5 were cut and packaged in a component. The test pressure was set to 0.4 MPa and the temperature was set to room temperature. The retentate and permeate sides were purged with argon. The test gases included CH4, He, CO2 and N2. The test results are shown in Table 1.

[0116]

[0117] Table 1

[0118] The data in Table 1 show that the PPy / PSf / PEG composite membrane of the present invention has high flux and selectivity, with a helium flux of up to 375 GPU and He / CH4, He / N2, and He / CO2 selectivities of 357, 335, and 379, respectively. Comparing the data of Example 1 with that of Comparative Example 2, it can be seen that the PPy / PSf-2-3.5 composite membrane has a lower helium flux of only 131 GPU and a He / CH4 selectivity of only 135. This indicates that soaking the PPy / PSf-2-3.5 composite membrane in PEG can effectively improve the helium flux and selectivity of the composite membrane. Comparing the data of Comparative Example 1 with that of Comparative Example 2, while Comparative Example 1 used only one electrolyte for two-step electrolysis, Comparative Example 2 used two electrolytes for two-step electrolysis. However, the helium flux and selectivity of Comparative Example 2 were superior to those of Comparative Example 1, further demonstrating that the choice of electrolyte also affects the helium flux and selectivity. Electrodeposition of PPy first, followed by electrodeposition of PPy and ZrO2-C nanoparticles, is beneficial for improving the helium flux and selectivity of the composite membrane. Comparing the data of Example 1 with that of Comparative Example 3, the ZrO2-C nanoparticles of Example 1 were replaced with carbon nanotubes in Comparative Example 3. The helium flux of Comparative Example 3 was similar to that of Example 1, but the helium selectivity was poorer. This indicates that ZrO2-C nanoparticles can effectively improve the selectivity of helium.

[0119] The anti-plasticization performance of the polymer composite films prepared in Example 1 and Comparative Example 5 were tested using the ternary mixed gas He / CO2 / CH4 and He / CO2 / N2 as feed gases. The test results are shown in Figure 2 and Figure 3 .

[0120] Figure 2 This is a graph showing the anti-plasticization performance test results of the polymer composite film prepared in Example 1. Figure 3 This is a graph showing the anti-plasticization performance test results of the polymer composite film prepared in Comparative Example 5. Figure 2 It can be seen that with the increase of feed pressure, the helium selectivity does not decrease significantly. Figure 3Testing of the comparative example's anti-plasticization performance revealed that increasing feed pressure significantly reduced helium selectivity and increased helium flux, indicating that as pressure increased, the polymer chains in the comparative example's membrane structure shifted, resulting in poor anti-plasticization performance. Furthermore, this study further demonstrated that electropolymerizing ZrO2-C nanoparticles and Py solution onto the composite membrane substrate resulted in excellent anti-plasticization performance.

[0121] In summary, the PPy / PSf / PEG polymer composite membrane prepared by the present invention can be used for helium membrane separation and purification.

[0122] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that the technical solutions of the present invention may be modified or replaced with equivalents without departing from the spirit and scope of the technical solutions of the present invention, and such modifications or equivalents shall be encompassed by the claims of the present invention. Any techniques, shapes, and structures not described in detail herein are well known.

Claims

1. A method for preparing a PPy / PSf / PEG polymer composite membrane, characterized in that: The following steps are involved: The cleaned and dried polysulfone membrane was wrapped and fixed on stainless steel with insulating tape, and then clamped on a platinum electrode clamp as the working electrode, with a stainless steel sheet as the counter electrode and a saturated calomel electrode as the reference electrode to construct a three-electrode system. Dispersing pyrrole monomer in deionized water and stirring to obtain a first electrolyte, adding the first electrolyte to a sulfuric acid aqueous solution and mixing, then adding ZrO2-C nanoparticles and ultrasonically dispersing to obtain a second electrolyte; The three-electrode system is placed in the first electrolyte and the current density is 0.4-0.6 mA / cm 2 The electrolyte was deposited for 0.5 to 1 hour and then placed in the second electrolyte at a current density of 0.1 to 0.4 mA / cm 2 After deposition for 1.5 to 3 h, the polysulfone membrane treated by electrodeposition was removed, washed with deionized water, and dried for the first time to obtain a PPy / PSf composite membrane; The PPy / PSf composite membrane was completely immersed in a polyethylene glycol aqueous solution for 3 to 5 hours, taken out, and dried for a second time to obtain a PPy / PSf / PEG composite membrane.

2. The method for preparing a PPy / PSf / PEG polymer composite membrane according to claim 1, wherein The concentration of the pyrrole monomer in the first electrolyte is 0.01 to 0.05 mol / L.

3. The method for preparing a PPy / PSf / PEG polymer composite membrane according to claim 2, wherein: The first electrolyte and the sulfuric acid aqueous solution are mixed in a volume ratio of (0.002-0.005):1, and the sulfuric acid concentration in the sulfuric acid aqueous solution is 0.5 mol / L.

4. The method for preparing a PPy / PSf / PEG polymer composite membrane according to claim 1, wherein The concentration of ZrO2-C nanoparticles in the second electrolyte is 0.15-0.5 g / L.

5. The method for preparing a PPy / PSf / PEG polymer composite membrane according to claim 4, wherein: The preparation method of the ZrO2-C nanoparticles is as follows: Terephthalic acid and ZrCl4 were added to N,N-dimethylformamide, ultrasonically treated for 20 to 30 minutes, glacial acetic acid was added, and ultrasonically treated for another 20 to 30 minutes. The mixture was transferred to a hydrothermal autoclave and heated at 100 to 120°C for 20 to 24 hours. The mixture was then centrifuged and precipitated with N,N-dimethylformamide and ethanol, and dried to obtain UiO-66. Using UiO-66 as a precursor, ZrO2-C nanoparticles were obtained by pyrolysis at 750-850℃ for 2-3h in N2 atmosphere.

6. The method for preparing a PPy / PSf / PEG polymer composite membrane according to claim 5, wherein: The molar ratio of the terephthalic acid to ZrCl4 is 1:(1-1.3), and the molar volume ratio of the terephthalic acid to N,N-dimethylformamide is 1 mmol:(100-200) mL.

7. The method for preparing a PPy / PSf / PEG polymer composite membrane according to claim 1, wherein: The concentration of polyethylene glycol in the polyethylene glycol aqueous solution is 2-5 wt %.

8. The method for preparing a PPy / PSf / PEG polymer composite membrane according to claim 1, wherein: The first drying condition is drying at a temperature of 30-40° C. for 15-24 hours, and the second drying condition is drying in a constant temperature drying oven at a temperature of 50-60° C. and a humidity of 30-40% for 10-15 hours.

9. A PPy / PSf / PEG polymer composite membrane, characterized in that: The polymer composite membrane is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the PPy / PSf / PEG polymer composite membrane according to claim 9 in a helium separation membrane.

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