CN115228307B

CN115228307B - Graphene oxide separation membrane, preparation method and application thereof in ethylene/ethane separation

Info

Publication number: CN115228307B
Application number: CN202210071430.7A
Authority: CN
Inventors: 刘公平; 程龙; 金万勤
Original assignee: Nanjing Tech University
Current assignee: Nanjing Tech University
Priority date: 2022-01-21
Filing date: 2022-01-21
Publication date: 2023-07-07
Anticipated expiration: 2042-01-21
Also published as: CN115228307A

Abstract

The invention relates to a modified graphene oxide separation membrane, a preparation method and application thereof in ethylene/ethane separation, and belongs to the technical field of separation membrane preparation and application. Silver ions are introduced onto a segment of polyelectrolyte by an ion exchange method, and the polyelectrolyte segment loaded with silver ions is introduced between Graphene Oxide (GO) nano sheets by a blending suction filtration method, so that the silver nanocluster@GO laminated film is prepared. Based on the screening effect of GO sub-nano interlayer channels on ethylene/ethane molecules and the reversible pi complexing interaction of silver nanoclusters on ethylene molecules, the preferential permeation of ethylene molecules is promoted, and the high-efficiency separation of ethylene/ethane mixed gas is realized. The prepared silver nanocluster@GO laminated film has excellent performance stability in the testing process of ethylene/ethane mixed gas exceeding 100 hours, and has a good application prospect in the aspect of preparing high-purity ethylene.

Description

Graphene oxide separation membrane, preparation method and application thereof in ethylene/ethane separation

Technical Field

The invention relates to a modified graphene oxide separation membrane, a preparation method and application thereof in ethylene/ethane separation, and belongs to the technical field of separation membrane preparation and application.

Background

Ethylene is one of the most important chemical raw materials in the petrochemical industry and is widely used in the production of downstream products such as polyethylene, polyvinyl chloride and ethanol. At present, ethylene is produced mainly by steam cracking of ethane or naphtha and subsequent purification processes. However, due to the close physical properties and kinetic diameters of ethylene and ethane, achieving efficient separation of the two molecules is very challenging. Compared with the low-temperature rectification and adsorption separation technology, the membrane separation technology has the advantages of low energy consumption, environmental friendliness, convenient operation and the like, thereby showing great potential. The preparation of the high-performance separation membrane material is the core of high-efficiency separation of ethylene/ethane.

Currently, polymeric membranes generally exhibit a tradeoff between permeability and selectivity because the difference in molecular kinetic diameters of ethylene and ethane is very small (only

) The separation efficiency of the polymer membrane is low. Few membrane materials are capable of achieving ethylene/ethane separation due to the lack of efficient sieving channels and functional groups that enhance ethylene affinity. Graphene Oxide (GO) membranes are a novel class of membrane separation materials that exhibit excellent gas separation properties based on ultra-thin thickness and extraordinary mass transfer characteristics, but lower ethylene/ethane separation properties. While metal ions (such as Ag ⁺ ) The incorporation of GO interlayers to enhance the affinity of GO membranes for ethylene is difficult because electrostatic interactions between positively charged metal ions and negatively charged GO nanoplatelets will lead to defects in the membrane structure. In addition, if common metal salts (e.g., agBF ₄ ) Generally, the ionic bond between the metal ion and the anion is stronger, so that the metal ion is more difficult to dissociate and then has complexation with ethylene. Therefore, there is a need to develop new strategies to prepare metal ion modified defect free GO membranes for ethylene/ethane separations and explore methods to enhance silver ion activity.

Disclosure of Invention

The technical problems to be solved in practice of the invention are as follows: the graphene oxide separation membrane in the prior art has the problem of low separation performance in the process of being applied to ethylene/ethane separation; and solves the problems of metal ion agglomeration, nonselective defect caused by electrostatic action between metal ions and GO and the activity of the metal ions as a promotion transfer carrier in the process of introducing the metal ions into the GO membrane.

The technical conception of the invention is as follows: by introducing polyelectrolyte chain segments to anchor metal ions, the integrity of the membrane structure is ensured while the uniform dispersion of metal nanoclusters in the membrane is realized; and the metal cluster introduced by the strategy has higher activity, is easy to generate reversible pi complexation with ethylene, and realizes the high-efficiency separation of ethylene/ethane (figure 1).

The graphene oxide separation membrane comprises a selective separation layer and a support layer, wherein the selective separation layer comprises graphene oxide nano sheets, and nanoclusters formed by silver ions and polyelectrolyte are further contained between the nano sheets.

The polyelectrolyte is selected from sodium polystyrene sulfonate (PSS) or ion exchange resin Nafion.

The supporting layer is made of porous inorganic materials or porous organic materials.

The porous organic material is selected from polyacrylonitrile, polycarbonate, polyethersulfone and the like, and the inorganic material is selected from alpha-alumina, anodic alumina and the like.

The preparation method of the graphene oxide separation membrane comprises the following steps:

step 1, preparing a dispersion liquid of single-layer graphene oxide nano sheets;

step 2, mixing silver salt with polyelectrolyte solution, performing ion exchange reaction, and adding the mixture into the dispersion liquid obtained in the step 1 to obtain film coating liquid;

and 3, applying the coating liquid obtained in the step 2 on the supporting layer to obtain the separation membrane.

In the step 1, the single-layer graphene oxide nano sheet is obtained by dispersing graphene oxide in an aqueous solution, performing ultrasonic treatment, and centrifuging to obtain a supernatant; the concentration of the graphene oxide in the aqueous solution is 0.01-0.5wt%, and the ultrasonic treatment time is 1-10h.

In the step 2, the silver salt is selected from silver nitrate, silver tetrafluoroborate or silver trifluoromethane sulfonate, and the polyelectrolyte is selected from sodium polystyrene sulfonate (PSS) or ion exchange resin Nafion; the ion exchange reaction time is 12-36h, the concentration of the silver salt in the solution is 0.005-0.05wt%, and the concentration of the polyelectrolyte in the solution is 0.0005-0.08wt%.

In the step 3, the coating liquid is applied to the surface of the supporting layer by spin coating or filtration, and further needs to be dried.

The graphene oxide separation membrane is applied to separation of ethylene/ethane mixed gas.

Advantageous effects

According to the preparation method of the modified GO film, through the introduction of polyelectrolyte, on one hand, the sulfonate on the chain segment forms a hydrogen bond effect with the oxygen-containing functional group of the GO nano-sheet, and on the other hand, forms an electrostatic interaction with silver ions, so that the interaction between GO and silver ions is effectively weakened, and possible defects are reduced.

With inorganic salts (e.g. AgBF ₄ ) In a strong ionic bond phase, ag at the anionic site of the polyelectrolyte ⁺ The polymer has weak interaction with polyelectrolyte, thus having stronger activity of generating reversible complexation with ethylene, and helping to promote ethylene to rapidly penetrate through the membrane layer.

Under the anchoring action of polyelectrolyte, the silver ions in the film layer form nano-scale uniform dispersion, which is helpful for forming continuous promotion transmission channels. Meanwhile, the size of an interlayer channel of the GO membrane is precisely regulated to be between the molecular dynamics diameters of ethylene and ethane, and the separation performance is further improved based on the size screening effect. The final produced GO membrane separation performance exceeds the reported upper ethylene/ethane separation performance bound and remains stable for 100h of continuous testing, demonstrating its potential in ethylene purification applications.

Drawings

FIG. 1 is a schematic illustration of the membrane and separation process of the present invention.

FIG. 2 is a process flow of the preparation method.

FIG. 3, (a) is a physical diagram of a 0.5mg/mL GO aqueous solution, which shows a Tadall effect. (b) AFM image of GO nanoplatelets and corresponding height data. (c) A physical view of a silver nanocluster @ GO (agnc @ GO) film, including a top view and a front view of tweezers bending the film. (d-f) cross-sectional SEM images, surface SEM images, and AFM images of agnc@go films. (g-i) AgBF ₄ Cross-sectional SEM images, surface SEM images, and AFM images of the GO film.

FIG. 4, agNC@GO sample, (a) TEM image and (b) High Angle Annular Dark Field (HAADF) image, and corresponding (c) STEM-EDS mapping image of silver and (d) elemental sulfur. (e) TEM image of AgNC@GO membrane section, (f) high power TEM image, STEM-EDS mapping image of silver, sulfur, carbon and oxygen elements. (g) Spherical aberration corrected TEM image of AgNC@GO sample and (h-i) TEM image of two-dimensional (2D) sub-nanochannels.

FIG. 5, (a) AgBF ₄ Spherical aberration corrected TEM image of/GO sample and (b) salient AgBF ₄ TEM image of lattice fringes of nanocrystals.

FIG. 6, (a) AgBF ₄ HAADF image of/GO sample and STEM-EDS mapping image of (b) silver, (c) carbon and (d) oxygen element.

FIG. 7 is AgBF ₄ XPS characterization profiles of/GO membrane and AgNC@GO membrane.

FIG. 8 is AgBF ₄ Ethylene/ethane separation performance comparison of the/GO membrane and the agnc@go membrane.

Detailed Description

The modified GO separation membrane has excellent separation performance on ethylene/ethane mixed gas, and comprises a support material layer and an effective silver nanocluster@GO separation layer loaded on the support layer, wherein the thickness of the separation layer is 50-500nm. The preparation process and the gas separation performance test of the modified GO membrane are detailed as follows:

(1) Preparing GO dispersion liquid: firstly, preparing GO powder raw materials into dispersion liquid, fully stripping the nano-sheets into a single layer through ultrasonic treatment, and obtaining supernatant containing the single-layer GO nano-sheets after centrifugal treatment for the subsequent film forming process. Commercial GO raw materials can be adopted, and the original sheet diameter is 40-50 mu m. The concentration of GO in the dispersion is in the range of 0.01 to 0.5wt% and the time of sonication can be 1 to 10 hours.

(2) Preparation of modified GO membrane: the GO separation layer is required to be prepared on the support layer in this step, and the support material layer used here may be an organic support (e.g. polyacrylonitrile, polycarbonate, polyethersulfone, etc.) or an inorganic support (e.g. α -alumina, anodized alumina, etc.), which should be porous so that filtration of GO suspension and uniform deposition of GO can be performed. Firstly, mixing a metal salt solution with a polyelectrolyte solution, wherein the silver salt can be silver nitrate, silver tetrafluoroborate or silver trifluoromethane sulfonate, the polyelectrolyte can be sodium polystyrene sulfonate (PSS) or ion exchange resin Nafion 117, and the sodium ions in the polyelectrolyte are exchanged into silver ions through an ion exchange process (figure 2), and the time of the ion exchange process can be 12-36h. And then mixing the prepared polyelectrolyte solution loaded by silver ions with GO solution, wherein the transverse dimension of the GO nano-sheet can be 0.5-2 mu m, and preparing the silver nanocluster@GO (AgNC@GO) film on the support body by a vacuum suction filtration method. And after the suction filtration is finished, the membrane layer is taken down and is dried at normal temperature for 24-48 hours. The prepared film is named as AgNC@GO-X, wherein X represents the mass fraction (wt%) of silver nanoclusters in the AgNC@GO film, and the atomic percentage of silver elements in the film can be measured by XPS and converted. And characterizing the microscopic morphology of the membrane and the size of channels between the inner layers of the membrane by SEM and TEM, and finally, carrying out gas separation performance test on the membrane.

(3) Gas separation performance test of modified GO membrane: and placing the prepared graphene oxide film in a film assembly, wherein the upstream of the film assembly is humidified ethylene/ethane mixed gas, and the downstream of the film assembly is humidified purge gas. The mol ratio of ethylene to ethane in the ethylene/ethane mixed gas can be 1:99-50:50, the total flow rate of the mixed gas can be 30-100mL/min, the humidity of upstream and downstream moisture is kept consistent, and the humidity range is 10% -90%; the purge gas may be argon, helium or methane and the purge gas flow rate may be 1-5mL/min. After a certain test time and the graphene oxide film reaches a stable state, the gas at the downstream outlet of the component is connected to a gas chromatograph for gas composition analysis, and the total flow rate of the downstream gas is tested by a soap bubble method, so that the permeation rates of ethylene and ethane are respectively calculated. The stabilization time of the GO membrane can be 3-6 hours, and the detector of the gas chromatograph can be a thermal conductivity detector or a flame ionization detector.

Example 1 at Ag ⁺ /Na ⁺ AgNC@GO film is prepared under the conditions that the molar ratio is 10:1 and the mass ratio of GO/PSS is 1:10

(1) Preparing GO dispersion liquid: the GO material adopted in the patent is commercial GO powder, and the original sheet diameter is 40-50 mu m. 40mg of GO powder is weighed and added to 80mL of deionized water, and the mixture is stirred for 1h by a rotor. Then the GO dispersion liquid is placed in an ultrasonic pulverizer, and ultrasonic is carried out for 3 hours under the power of 100W, so that the nano-sheets are uniformly dispersed and fully peeled in the aqueous solution. Then, carrying out centrifugal treatment on the GO dispersion liquid, and taking supernatant liquid for preparing a GO membrane;

(2) Preparation of modified GO membrane: in the step, polyethersulfone is selected as a support body, and a vacuum filtration method is adopted to prepare a membrane. Firstly, preparing a suction filtration solution, and sequentially adding 56.65mg AgBF ₄ And 6mg PSS was added to 200mL deionized water and rotor stirred for 24h. Then adding the GO dispersion liquid (0.6 mg GO) prepared in the step 1 into the solution, stirring for 1h by a rotor, and preparing the AgNC@GO membrane on the polyether sulfone support by a vacuum filtration method. And after the suction filtration is finished, taking down the membrane layer, and drying for 24 hours at normal temperature.

Comparative example 1 Ag ⁺ /Na ⁺ AgNC@GO film is prepared under the conditions that the molar ratio is 1:1 and the mass ratio of GO/PSS is 1:10

(2) Preparation of modified GO membrane: in the step, polyethersulfone is selected as a support body, and a vacuum filtration method is adopted to prepare a membrane. Firstly, preparing a suction filtration solution, and sequentially adding 5.66mg of AgBF ₄ And 6mg PSS was added to 200mL deionized water and rotor stirred for 24h. Then adding the GO dispersion liquid (0.6 mg GO) prepared in the step 1 into the solution, stirring for 1h by a rotor, and preparing the AgNC@GO membrane on the polyether sulfone support by a vacuum filtration method. And after the suction filtration is finished, taking down the membrane layer, and drying for 24 hours at normal temperature.

Comparative example 2 preparation of pure GO film

GO dispersion was prepared following the procedure in example 1, then a certain amount of dispersion (0.6 mg GO) was added to 200mL deionized water, rotor stirred for 1h, then the solution was poured into a vacuum filtration apparatus to prepare a pure GO membrane on a polyethersulfone support, after the solution was completely pumped out, the membrane layer was removed and dried at room temperature for 24h.

Comparative example 3 preparation of PSS/GO film

GO dispersion was prepared following the procedure in example 1, followed by adding a certain amount of dispersion (0.6 mg GO) and 6mg PSS to 200mL deionized water, rotor stirring for 1h, then pouring the solution into a vacuum filtration apparatus to prepare PSS/GO membrane on polyethersulfone support, after the solution was completely drained, the membrane layer was removed and dried at room temperature for 24h.

Comparative example 4AgBF ₄ Preparation of GO membranes

(2) Preparation of modified GO membrane: in the step, polyethersulfone is selected as a support body, and a vacuum filtration method is adopted to prepare a membrane. Firstly, a suction filtration solution is prepared, 113.3mg of AgBF ₄ Added to 200mL deionized water and rotor stirred for 24h. Then adding the GO dispersion liquid (0.6 mg GO) prepared in the step 1 into the solution, stirring for 1h by a rotor, and preparing AgBF on a polyethersulfone support by a vacuum filtration method ₄ /GO membrane. And after the suction filtration is finished, taking down the membrane layer, and drying for 24 hours at normal temperature.

AgBF ₄ Characterization of/GO and AgNC@GO membranes

The GO solution exhibits the tyndall effect (a of fig. 3) due to light scattering of GO nanoplatelets uniformly dispersed in water. AFM images showed that the GO nanoplatelets were about 1 μm in lateral dimension (b of FIG. 3) and the nanoplatelets were about 1nm thick. The agnc@go membrane prepared in example 1 shows a brown separating layer uniformly distributed on the PES support (c of fig. 3). The curved membrane is able to maintain its structural integrity, indicating the flexibility of the membrane and the good bonding force between the separation layer and the support layer.

As a control, agBF in comparative example 4 ₄ the/GO membrane is prepared by direct mixing of AgBF ₄ And GO solution, and vacuum filtered on PES support. SEM image (d-e of FIG. 3) shows AgBF ₄ The thickness of the/GO film is about 58nm, while AgBF ₄ Agglomerated silver nanoparticles were observed on the surface of the GO film, resulting in a large number of wrinkles and defects. In contrast, the thickness of the AgNC@GO film was slightly increased to 70nm due to the introduction of the PSS chains, and a typical two-dimensional laminate structure (g-h of FIG. 3) was observed from the cross section of the film. More importantly, with AgBF ₄ The AgNC@GO film surface was very smooth (f and i of FIG. 3), with the AgNC@GO film surface roughness (Ra) being small (7.22 nm), while AgBF ₄ The surface roughness of the GO film is 11.73nm, because the introduced PSS can be used as an intermediate layer of positively charged silver nanoclusters and negatively charged GO nano sheets, and the electrostatic repulsive effect is effectively reduced. The above results indicate that the introduction of polyelectrolyte can effectively reduce the interaction between silver nanoclusters and GO nanoplatelets, helping to form highly regular GO stacks.

The uniform and continuous distribution of silver nanoclusters in the two-dimensional sub-nano channels plays an important role in efficiently promoting ethylene transfer. To confirm the distribution of silver nanoclusters, the nanocomposite obtained in the agnc@go film forming solution was characterized by TEM. As shown in a of fig. 4, silver nanoclusters are uniformly distributed on GO nanoplatelets. Its HAADF image and the corresponding STEM-EDS mapping image (b-d of fig. 4) showed that the silver and sulfur elements formed a nanoscale distribution on the GO nanoplatelets, confirming the successful incorporation of silver nanoclusters onto the GO nanoplatelets. In addition, cross-sectional TEM images of the film samples were also obtained to observe the distribution of silver nanoclusters within the film. To clearly observe the membrane stack structure, a thicker (-330 nm) agnc@go membrane layer was prepared on a PES support with a GO deposition of 0.6mg (e of fig. 4). The stack of GO nanoplatelets was observed in the magnified TEM image (f of fig. 4), which is consistent with the SEM image (g of fig. 3). EDS mapping images of selected regions demonstrate a uniform distribution of silver, sulfur, carbon and oxygen elements in the region, which demonstrates a uniform modification of silver nanoclusters and PSS in two-dimensional GO sub-nanochannels. As shown in g of fig. 4, silver nanoclusters having a size of-2-3 nm are attached to a honeycomb structure typical of graphene oxide. H-i of FIG. 4 shows a highly ordered 2D sub-nano-channel structure with an interlayer height of 0.44nm, well between the molecular kinetic diameters of ethylene (0.416 nm) and ethane (0.444 nm), thus enabling efficient sieving of ethylene and ethane.

For AgBF in comparative example 4 ₄ GO membrane, agBF obtained from membrane solution was observed by spherical aberration correction TEM ₄ GO nanocomposite (fig. 5). Silver ions were observed to tend to aggregate and form nanocrystals on the GO nanoplatelets surface with dimensions of about 3-6 nm. The lattice fringes of the nanoclusters were 0.223nm, corresponding to AgBF ₄ The (2 2 0) crystal plane of the phase. The larger size nanocrystals can form strong interactions with the GO nanoplatelets and lead to non-selective defects during the assembly of the GO stack. AgBF ₄ HAADF image of/GO sample and corresponding STEM-EDS mapping pattern (FIG. 6) shows that there are a lot of agglomerated silver nanocrystals (high atomic number versus bright spot area in the figure) in the structure, i.e. a lot of silver nanocrystals are formed in the film and unevenly distributed, which is detrimental to complexation with ethylene.

In addition, agBF was analyzed by X-ray photoelectron spectroscopy (XPS) contrast ₄ Elemental composition of/GO and agnc@go films (a-b of fig. 7). The comparison found that a new peak (287.3 eV) appears in the high resolution C1S spectrum of the agnc@go film corresponding to the C-S bond, further verifying the successful incorporation of PSS in the film. The characteristic peak of the C-O bond in the AgNC@GO film moves from 286.8eV to 286.5eV, which proves that hydrogen bonding exists between the hydroxyl group of the GO nano-sheet and the sulfonate in the PSS chain. The mass fraction of silver nanoclusters in the film and Na in PSS were then determined based on XPS ⁺ Is covered with Ag ⁺ Percentage of exchange. In the preparation process of the AgNC@GO film, agBF ₄ With Na in PSS ⁺ The molar ratio of PSS/GO is optimized. For the AgNC@GO film prepared in comparative example 1, according to the content of residual sodium element in the film, na on the PSS chain segment in the film is calculated ⁺ Is covered with Ag ⁺ 41% exchange and 59% sodium ions still exist on the PSS segment, so complete ion exchange is not achieved under this film forming condition, since at this timeThe calculated loading of silver nanoclusters was 15wt% and the film was designated as agnc@go-15. In the case of the AgNC@GO film of example 1, no residual sodium element was detected in the film layer, indicating Na of PSS in the film ⁺ Is covered with Ag ⁺ The percentage of exchange is 100%, so that complete ion exchange is realized under the film forming condition, and the film forming method is beneficial to maximizing the accelerating and transmitting capacity of the film to ethylene. The silver nanocluster loading in the film was 34wt%, and the film was designated as agnc@go-34.

Ethylene/ethane separation performance test of AgNC@GO membrane

Ethylene/ethane separation performance test was performed on the agnc@go membrane as follows: the separation membranes prepared in the above examples and comparative examples were first placed in a membrane module, and then humidified ethylene/ethane mixed gas (ethylene/ethane molar ratio: 1:99) was supplied to the upstream of the membrane module, with a humidity of 85%, and a flow rate of 60mL/min; a humidified purge gas (argon) was supplied downstream of the membrane module, the purge gas humidity was 85% and the flow rate was 2mL/min. After the GO membrane reaches a stable state for 6 hours, the gas at the downstream outlet of the component is connected into a gas chromatograph for gas composition analysis, the detector of the gas chromatograph is a thermal conductivity detector, and the total flow rate of the downstream gas is tested by a soap bubble method, so that the permeation rate of ethylene and ethane and the separation selectivity of ethylene and ethane are respectively calculated.

The results show that the ethylene permeation rate of the AgNC@GO-15 film prepared in comparative example 1 is 22.3GPU and the ethylene/ethane separation selectivity is 6.3 under the ethylene/ethane mixed gas feed of 1:99; whereas the ethylene permeation rate of the AgNC@GO-34 membrane prepared in example 1 was 46.7GPU, the ethylene/ethane separation selectivity was 12.3, and the separation performance exceeded the upper limit of 2013 ethylene/ethane separation performance. In the continuous test process exceeding 100 hours, the AgNC@GO-34 membrane shows excellent performance stability, and has great potential in practical ethylene separation application. The separation performance of the pure GO membrane and the PSS/GO membrane is respectively tested according to the steps, and the result shows that the ethylene permeation rate of the pure GO membrane in comparative example 2 is 4.0GPU, and the ethylene/ethane separation selectivity is 1.2; the PSS/GO membrane prepared in comparative example 3 had an ethylene permeation rate of 3.7GPU and an ethylene/ethane separation selectivity of 1.2. Therefore, both the pure GO membrane and the PSS/GO membrane without silver ions introduced show extremely low ethylene/ethane separation performance, and the silver ions introduced as a transmission carrier are proved to play a key role in promoting the reversible pi complexation of the transmission carrier and the ethylene and promoting the preferential permeation of the ethylene.

Finally we compare in detail the GO membrane, agBF prepared in comparative example 4 ₄ Separation properties of/GO and AgNC@GO-15 membrane prepared in control example 1 (FIG. 8). As shown, GO membranes do not possess ethylene/ethane separation properties, suggesting that even the presence of small defects in the two-dimensional channels would compromise size sieving performance, especially for ethylene/ethane gas pairs differing in molecular dynamics diameters by only 0.028 nm. AgBF ₄ the/GO membrane also showed lower separation performance, probably due to AgBF ₄ The electrostatic interaction between the nanocrystals and the GO nanoplatelets creates non-selective wrinkling, while the complexing activity of the agglomerated silver nanocrystals with ethylene is low. However, the agnc@go-15 membrane prepared in comparative example 1 exhibited significantly improved ethylene/ethane separation performance after the polyelectrolyte was introduced, with an ethylene permeation rate up to 22.3GPU, and an ethylene/ethane separation selectivity exceeding 6. The AgBF ₄ The silver loading in the/GO membrane was 16wt% and the AgNC@GO-15 membrane had nearly the same silver loading, but exhibited completely different separation properties. The main reason of the phenomenon is that the introduction of the PSS chain segment effectively reduces the generation of nonselective defects in the film, and a compact and regular two-dimensional interlayer channel is formed; at the same time, with inorganic salt AgBF ₄ Compared with the silver ion, the binding force of PSS and silver ion is weaker, so that the formed silver nanocluster has higher activity of generating complexation with ethylene, and the prepared silver nanocluster@GO film has excellent ethylene/ethane separation performance.

Claims

1. The application of the graphene oxide separation membrane in the separation of ethylene/ethane mixed gas is characterized in that the graphene oxide separation membrane comprises a selective separation layer and a support layer, and the selective separation layer comprises graphene oxide nano sheets, and nano clusters formed by silver ions and polyelectrolyte are further contained between the nano sheets;

the polyelectrolyte is selected from sodium polystyrene sulfonate (PSS) or ion exchange resin Nafion;

step 3, applying the coating liquid obtained in the step 2 on a supporting layer to obtain a separation membrane;

in the step 2, the silver salt is selected from silver nitrate, silver tetrafluoroborate or silver trifluoromethane sulfonate;

the ion exchange reaction time is 12-36h, the concentration of silver salt in the solution is 0.005-0.05wt%, and the concentration of polyelectrolyte in the solution is 0.0005-0.08wt%;

in the step 3, the coating liquid is applied to the surface of the supporting layer in a spin coating or filtering mode, and the coating liquid is required to be dried;

in the step 1, the monolayer graphene oxide nano-sheets are obtained by dispersing graphene oxide in an aqueous solution, performing ultrasonic treatment, and centrifuging to obtain a supernatant; the concentration of graphene oxide in the aqueous solution is 0.01-0.5wt%, and the ultrasonic treatment time is 1-10h.

2. The use according to claim 1, wherein the support layer is a porous inorganic material or a porous organic material.

3. The use according to claim 2, wherein the porous organic material is selected from polyacrylonitrile, polycarbonate or polyethersulfone and the porous inorganic material is selected from α -alumina.