Graphene oxide composite membrane, ion exchange membrane including same, and manufacturing method thereof

Abstract

The present invention relates to: a graphene oxide composite membrane having significantly improved hydration control and stability compared to conventional graphene oxide separation membranes that are hydrated in aqueous environments; an ion exchange membrane including same; and a manufacturing method thereof. The composite membrane has the effect of greatly improving the lifespan characteristics of the composite membrane by significantly reducing the structural expansion of a graphene oxide coating layer with respect to moisture and improving the structural stability of the graphene oxide coating layer.

Description

Graphene oxide composite membrane, ion exchange membrane including the same, and method for manufacturing the same

[0001] The present invention relates to a graphene oxide composite membrane having improved stability and lifespan characteristics by being crosslinked with aluminosilicate nanoparticles, which are inorganic nanomaterials, a method for manufacturing the same, and an ion exchange membrane for lithium ion extraction using the same.

[0002] Graphene oxide is a two-dimensional planar nanomaterial that contains oxygen-based functional groups (carboxyl groups, hydroxyl groups, etc.) in a single carbon layer structure. Multi-layered graphene oxide membranes, which are made up of stacked graphene oxides, have recently garnered attention as a next-generation membrane material. This is due to the unique characteristics of graphene oxide, such as its inherent hydrophilicity and the development of layered pores (distance between graphene oxide particles) of approximately 1 nm. Since 2012, they have been applied to sub-nanometer separation processes in various fields, such as oxygen barrier membranes (patent registration number 10166223100000), water treatment membranes (application number 10-2021-0024608), and carbon dioxide separation membranes (application number 10-20210055054).

[0003] In particular, graphene oxide has a high degree of hydrophilicity due to the large number of oxygen-based functional groups distributed on its surface, and is therefore being actively researched and developed for ion separation processes in aquatic environments, such as nanofiltration and reverse osmosis.

[0004] However, a critical issue with graphene oxide membranes is that when exposed to moisture, the interlayer space between graphene oxide particles collapses, causing hydration. The first problem with this hydration phenomenon is that the interlayer space between layered graphene oxide particles expands by approximately 0.5 to 1 nm compared to before hydration (within 1 nm), resulting in a loss of nanofiltration-level functionality for ion separation. Furthermore, if hydration continues, the desorption of graphene oxide occurs, resulting in irreversible loss of the manufactured membrane.

[0005] To address the above issues, hydrophilicity suppression methods have been proposed, including thermal reduction methods that partially remove the oxygen-dependent interactions of graphene oxide (Journal of Membrane Science, 601, 117900, 2020) and chemical reduction methods using reducing agents (Carbon, 117, 293-300, 2017). However, these methods reduce the wetting properties of the membrane and decrease the interlayer distance of the reduced graphene oxide, ultimately reducing material permeability.

[0006] Another solution involves introducing a cross-linking agent between graphene oxide layers to improve stability without sacrificing the wetting properties of graphene oxide (Nature Communications, 10, 1253, 2019). However, this approach poses the problem of clogging the nanopores caused by the cross-linking agent, reducing the membrane's ion-selective permeability.

[0007] The present invention aims to solve the above-mentioned problems and other problems related thereto.

[0008] An exemplary object of the present invention is to provide a graphene oxide composite membrane crosslinked by aluminosilicate nanoparticles that prevents hydration and desorption of graphene oxide in an aqueous environment, while not sacrificing hydrophilicity and not causing clogging of nanopores, characterized in that the graphene oxide layers are crosslinked by aluminosilicate nanoparticles through hydrogen bonding and charge compensation.

[0009] Another exemplary object of the present invention is to provide an ion exchange membrane comprising the above graphene oxide composite membrane.

[0010] Another exemplary object of the present invention is to provide a method for producing a graphene oxide composite membrane, comprising the steps of: preparing a graphene oxide dispersion by ultrasonicating a graphene oxide solution; preparing a mixture by mixing aluminosilicate nanoparticles into the graphene oxide dispersion; and preparing a graphene oxide composite membrane by filtering the mixture under reduced pressure.

[0011] The technical tasks to be achieved by the graphene oxide composite film according to the technical idea of ​​the present invention are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0012] This is explained in detail as follows. Meanwhile, each description and embodiment disclosed in this application can also be applied to each other description and embodiment. In other words, all combinations of the various elements disclosed in this application fall within the scope of this application. Furthermore, the scope of this application is not limited by the specific descriptions described below.

[0013] As one aspect for achieving the above object, the present invention provides a graphene oxide composite film in which a graphene oxide layer is crosslinked by aluminosilicate nanoparticles, and the crosslinking is achieved through hydrogen bonding and charge compensation between the graphene oxide layer and the aluminosilicate nanoparticles.

[0014] In one embodiment, the graphene oxide composite film is characterized by comprising 5.0 wt% to 50.0 wt% of aluminosilicate nanoparticles relative to graphene oxide.

[0015] In one embodiment, the graphene oxide composite film is characterized by comprising 5.0 wt% to 50.0 wt% of aluminosilicate nanoparticles relative to 0.5 mg to 5.0 mg of graphene oxide.

[0016] According to one embodiment, the aluminosilicate nanoparticles are characterized by comprising a composite inorganic material derived from an alumina precursor and a silica precursor.

[0017] According to one embodiment, the composite inorganic material derived from the alumina precursor and the silica precursor comprises at least one alumina precursor selected from the group consisting of aluminum-nitrate, aluminum-chloride, aluminum-tri-secbutoxide, aluminum-sulfate, aluminum-isopropoxide, sodium-aluminate, aluminum-2-methoxyethoxide, and aluminum-2-methoxyethoxyethoxide; And it is characterized in that it is a nanoparticle manufactured by a hydrolysis reaction of at least one silica precursor selected from the group consisting of tetra-ethyl-ortho-silicate, tetra-methyl-ortho-silicate, 3-glycidyloxypropyl-trimethoxysilane, 3-aminopropyl-triethoxysilane, sodium-ortho-silicate, tri-methoxypropysilane, and tri-methoxy-octylsilane.

[0018] As another aspect for achieving the above object, the present invention provides an ion exchange membrane including a graphene oxide composite membrane.

[0019] In another aspect for achieving the above object, the present invention provides a method for producing a graphene oxide composite membrane, comprising the steps of: preparing a graphene oxide dispersion by ultrasonicating a graphene oxide solution; preparing a mixture by mixing aluminosilicate nanoparticles into the graphene oxide dispersion; and preparing a graphene oxide composite membrane by filtering the mixture under reduced pressure.

[0020] According to one embodiment, in the step of preparing the mixed solution, the graphene oxide layer is characterized in that it is crosslinked through hydrogen bonding and charge compensation between the graphene oxide and the aluminosilicate nanoparticles.

[0021] According to one embodiment, the concentration of the graphene oxide solution is characterized by being 0.2 mg / mL to 0.6 mg / mL.

[0022] According to one embodiment, the ultrasonic treatment is characterized in that it is performed by irradiating ultrasonic waves of 30 kHz to 50 kHz at a temperature of 30°C or lower with an ultrasonic intensity of 90 W to 110 W.

[0023] According to one embodiment of the present invention, the graphene oxide composite membrane can determine the interlayer distance of the graphene oxide layer depending on the dosage of the aluminosilicate nanoparticles, which are cross-linking agents, and suppresses the hydration phenomenon of the interlayer distance. As a result, the graphene oxide composite membrane exhibits a stable and high lithium ion permeation rate.

[0024] However, the effects that can be achieved by the graphene oxide composite film according to one embodiment of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

[0025] To facilitate a more thorough understanding of the drawings cited in this specification, a brief description of each drawing is provided.

[0026] Figure 1 is a conceptual diagram of aluminosilicate nanoparticles, which are crosslinking agents used in the invention.

[0027] Figure 2 is a conceptual diagram showing the structure of a layer-by-layer cross-linked graphene oxide composite film.

[0028] Figure 3 is a graph showing an X-ray diffraction pattern (dry, wet state) indicating the degree of hydration in a dry state and a wet state of a graphene oxide composite membrane according to the amount of cross-linking agent injected (a), a result of calculating the interlayer space between graphene oxides (b) according to the X-ray diffraction pattern graph (a), a schematic diagram of the hydration phenomenon of a membrane when a cross-linking agent is not injected (c), and a schematic diagram of the hydration phenomenon of a composite membrane when a cross-linking agent is injected (d).

[0029] Figure 4 is a graph showing the physicochemical properties of a composite membrane (Fourier transform infrared spectroscopy) (a) and zeta potential change (b) according to the amount of crosslinking agent injected.

[0030] Figure 5 shows the results of field emission scanning electron microscopy showing the cross-sections of a graphene oxide membrane (a) without cross-linking agent injection and a graphene oxide composite membrane (b) with cross-linking agent injection.

[0031] Figure 6 shows the results of field emission scanning electron microscopy analysis of the degree of structural degradation before and after the stability evaluation under harsh conditions (ultrasonic grinding, 40 kHz, 15 min) for graphene oxide composite membranes according to the amount of cross-linking agent injected (a, b) and a photograph of the membrane after the evaluation (c). Figure 7 shows the results of tensile strength measurements according to the amount of cross-linking agent injected. Figure 8 shows the results of contact angle measurements for water before (a) and after (b) the injection of cross-linking agent.

[0032] Figure 9 shows the lithium ion permeability over time of a graphene oxide separator according to the amount of cross-linking agent injected (a), a graphene oxide separator without cross-linking agent injected after 24 hours of exposure to an aqueous environment (b), a photograph of a graphene oxide separator injected with 50% cross-linking agent (c), and the selectivity of multivalent ions for lithium ions of the fabricated separator (d).

[0033] The invention disclosed herein is susceptible to numerous modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the technology disclosed herein to specific embodiments, and it should be understood that the technology disclosed herein encompasses all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.

[0034] In describing the invention disclosed herein, detailed descriptions of related known technologies will be omitted if they are deemed to unnecessarily obscure the gist of the invention. Furthermore, numbers (e.g., "first," "second," etc.) used throughout the description of this specification are merely identifiers used to distinguish one component from another.

[0035] In this disclosure, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless specifically stated otherwise.

[0036] The terms "about," "substantially," and the like used in the present disclosure are used in a meaning that is at or close to the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure contents that mention exact or absolute numerical values ​​to aid understanding of the present disclosure.

[0037] In this disclosure, "upper" means furthest from the substrate, and "lower" means closest to the substrate. When a first layer is described as being "disposed" "on" a second layer, the first layer is disposed relatively far from the substrate. Unless it is specified that the first layer "and" the second layer "contact," other layers may be present between the first layer and the second layer.

[0038] In the present disclosure, "ion exchange membrane" is a type of separation membrane, and refers to a synthetic resin membrane that selects cations and anions and allows only one side to pass through. A cation exchange membrane has a negatively charged functional group and can selectively allow cations to pass through, and an anion exchange membrane has a positively charged functional group and can selectively allow anions to pass through.

[0039] In the present disclosure, the term “nano” refers to an object having at least one dimension in the nm range.

[0040] The terms “step of” or “step of” as used in the present disclosure do not mean “step for”.

[0041] In the present disclosure, the term "combination thereof" included in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including one or more selected from the group consisting of the components.

[0042] In addition, each component described below may additionally perform some or all of the functions performed by other components in addition to its own main function, and it goes without saying that some of the main functions performed by each component may be performed exclusively by other components.

[0043] The expressions "first," "second," "first," or "second" used in various embodiments can describe various components, regardless of order and / or importance, and do not limit those components. For example, without departing from the scope of the present invention, the first component could be renamed as the second component, and similarly, the second component could also be renamed as the first component.

[0044] The present invention provides aluminosilicate nanoparticles that form covalent bonds or charge compensation with graphene oxide particles to improve the moisture vulnerability of graphene oxide membranes and the resulting decrease in ion selectivity, and by injecting the aluminosilicate nanoparticles into a graphene oxide solution, cross-linking between graphene oxide layers is achieved, thereby providing a composite membrane having moisture vulnerability and a stable lithium extraction capability from lithium-containing brine.

[0045] The above graphene oxide composite film may be a graphene oxide layer cross-linked by aluminosilicate nanoparticles. Here, cross-linking occurs through hydrogen bonding and charge compensation between the graphene oxide layer and the aluminosilicate nanoparticles. The aluminosilicate nanoparticles, which are cross-linking agents, have abundant hydroxyl groups and positive charges, and thus can be cross-linked with the graphene oxide layer through hydrogen bonding and charge compensation to provide a graphene oxide composite film.

[0046] The present invention provides a graphene oxide composite membrane that maintains a stable structure in an aqueous environment by preparing aluminosilicate nanoparticles, which are inorganic crosslinking agents having a nano-size, and mixing them with a graphene oxide solution to form a stable structure between graphene oxide particles.

[0047] In one embodiment, the graphene oxide composite film may include 5.0 wt% to 50.0 wt% of aluminosilicate nanoparticles relative to graphene oxide.

[0048] In one embodiment, the aluminosilicate nanoparticles may be composed of a composite inorganic material derived from an alumina precursor and a silica precursor.

[0049] Unlike inorganic sols, which are composed of a single composition and thus have limitations in improving physicochemical properties, the aluminosilicate nanoparticles can easily control surface properties such as surface charge and hydrogen bonding by adjusting the ratio of aluminum and silicon, making it easy to manufacture a graphene oxide composite film and controlling the physical properties of the manufactured composite film possible.

[0050] According to one embodiment, the composite inorganic material derived from the alumina precursor and the silica precursor may be prepared by a hydrolysis reaction of the silica precursor and the alumina precursor. Examples of the alumina precursor that may be used include aluminum nitrate, aluminum chloride, aluminum tri-sec-butoxide, aluminum sulfate, aluminum isopropoxide, sodium aluminate, aluminum-2-methoxyethoxide, or aluminum-2-methoxyethoxyethoxide.

[0051] Examples of the silica precursor that can be used include tetra-ethyl-ortho-silicate, tetra-methyl-orthosilicate, 3-glycidyloxypropyltrimethoxysilane, 3-aminopropyl-triethoxysilane, sodium-ortho-silicate, tri-methoxy-propysilane, or tri-methoxyoctylsilane.

[0052] According to one embodiment, the aluminosilicate nanoparticles are a composite inorganic material derived from an alumina precursor and a silica precursor, and may be nanometer-sized particles produced by a hydrolysis reaction of the alumina precursor and the silica precursor. When the aluminosilicate nanoparticles are nanometer-sized particles, a stable structure is formed between graphene oxide particles, thereby providing a graphene oxide composite film that maintains a stable structure in an aqueous environment.

[0053] The size of the above aluminosilicate nanoparticles may preferably be about 1 nm.

[0054] According to one embodiment of the present invention, an ion exchange membrane is provided, which comprises a graphene oxide composite membrane according to the present invention.

[0055] The ion exchange membrane described above is a type of separation membrane and may include a graphene oxide composite membrane according to an embodiment of the present invention. The ion exchange membrane is a synthetic functional membrane and can be widely used in various fields such as seawater concentration and desalination, organic acid purification, and recovery of valuable metals. Preferably, the ion exchange membrane can be used for lithium ion extraction in a saline environment. For example, the composite membrane of the present invention can be applied as an ion separation membrane for lithium extraction in an artificial saline environment containing lithium and magnesium.

[0056] According to one embodiment of the present invention, a method for producing a graphene oxide composite membrane is provided, comprising the steps of: preparing a graphene oxide dispersion by ultrasonicating a graphene oxide solution; preparing a mixture by mixing aluminosilicate nanoparticles into the graphene oxide dispersion; and preparing a graphene oxide composite membrane by filtering the mixture under reduced pressure.

[0057] According to one embodiment, in the step of preparing the graphene oxide dispersion, a high-concentration graphene oxide solution is diluted, and the diluted solution is sonicated to prepare the graphene oxide dispersion. The concentration of the graphene oxide solution may be about 0.2 mg / mL to about 0.6 mg / mL, and preferably 0.4 mg / mL may be used. The sonication may be performed by irradiating ultrasonic waves of 30 kHz to 50 kHz at a temperature of 30°C or lower with an ultrasonic intensity of 90 W to 110 W.

[0058] When the volume of the initial graphene oxide solution (0.4 mg / mL) is varied from 1 mL to 100 mL, the thickness of the final composite membrane produced can be approximately 50 to 500 nm when the same amount of aluminosilicate sol is used.

[0059] According to one embodiment, in the step of preparing the mixture, a graphene oxide dispersion and aluminosilicate nanoparticles are mixed to crosslink the graphene oxide layer with the aluminosilicate nanoparticles. At this time, the aluminosilicate nanoparticles are injected onto the graphene oxide layer in the form of an aluminosilicate sol, and through a depressurizing filtration process described below, as shown in FIG. 2, crosslinking can be achieved through hydrogen bonding and charge compensation between the graphene oxide layer and the aluminosilicate nanoparticles to form a graphene oxide composite film. The aluminosilicate nanoparticles can be mixed in an amount of 5 to 50 wt% based on the weight of the graphene oxide, and 100 to 200 mL of the mixture can be stirred.

[0060] If the graphene oxide solution is not sufficiently diluted in the step of preparing the above graphene oxide dispersion, or if the stirring time is reduced in the step of preparing the above mixture, the aluminosilicate nanoparticles may not be evenly dispersed between the graphene oxide layers, or the cross-linking action may not be sufficient, resulting in the problem of the aluminosilicate sol being filtered in the step of depressurizing filtration.

[0061] According to one embodiment, in the step of manufacturing the graphene oxide composite film, the graphene oxide composite film can be manufactured by subjecting the mixture prepared in the step of manufacturing the mixture to a depressurized filtration method.

[0062] Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are for illustrative purposes only. It will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention. It is also natural that such modifications and variations fall within the scope of the appended claims.

[0063] In the present invention, in order to produce a composite membrane with improved hydration phenomenon and structural stability of a graphene oxide membrane, aluminosilicate nanoparticles are introduced between graphene oxide layers to form interlayer cross-linking of the graphene oxide layers. The aluminosilicate nanoparticles are injected between the graphene oxide layers in the form of aluminosilicate nanoparticles. The aluminosilicate nanoparticles are inorganic nanoparticles having a size of about 1 nm and a structure as shown in Fig. 1, and have hydroxyl groups and positive zeta potential properties. The aluminosilicate sol described above forms cross-linking with the negative zeta potential and abundant oxygen-based functional groups of graphene oxide through charge compensation and covalent bonding, respectively.

[0064] An aluminosilicate sol (AS sol) according to one embodiment of the present invention was prepared by setting the ratio of silica precursor and alumina precursor to 10:1.

[0065]

[0066] <Example 1> Preparation of aluminosilicate sol

[0067] The schematic diagram of the aluminosilicate sol used in the present invention is as shown in Fig. 1. For the specific manufacturing method, 0.313 g of aluminum-tri-sec-butoxide, 2.703 g of 3-glycidoxylpropyltrimethoxysilane, and 0.011 g of potassium chloride are mixed in a beaker, stirred for 5 minutes in an ice bath, and 0.135 g of 0.01 mol / L hydrochloric acid is added to cause a hydrolysis reaction for 15 minutes. After that, the beaker is removed from the ice bath and stirred for 15 minutes, and then 0.765 g of 0.01 mol / L hydrochloric acid is slowly added over 10 minutes and stirred for 25 minutes. After that, potassium chloride is removed from the solution using a syringe filter to produce aluminosilicate nanoparticles.

[0068]

[0069] <Example 2> Preparation of graphene oxide composite membrane

[0070] A 10 mL solution of 0.4 mg / mL graphene oxide is diluted 10-fold or more and stirred at 300 rpm or more. 5 to 50 wt% of aluminosilicate nanoparticles are slowly added to the graphene oxide solution over 10 minutes. The solution is then vigorously stirred for at least 6 hours to ensure that the aluminosilicate sol is evenly dispersed in the graphene oxide. The solution is then filtered under reduced pressure to form a graphene oxide composite membrane (Fig. 2).

[0071]

[0072] <Experimental Example 1> Comparison of physicochemical properties of graphene oxide composite membranes according to crosslinking agent dosage

[0073] The physicochemical properties of graphene oxide composite membranes containing 5%, 25%, and 50% of a cross-linking agent were compared according to the above examples in the graphene oxide separator (comparative example).

[0074] Specifically, the interparticle distance (nanopore) of the graphene oxide composite film according to the cross-linking agent dosage was analyzed through the X-ray diffraction pattern. The interlayer distance of the graphene oxide of the composite film was analyzed through the diffraction occurrence angle of X-ray, which was converted into length units through Bragg's equation. As a result, it was confirmed that as the cross-linking agent dosage increased in the wet state, the peak shifted to lower theta (Fig. 3(a)) and the interlayer distance of the graphene oxide decreased (Fig. 3(b)), indicating that the hydration phenomenon was suppressed (Fig. 3(c), (d)).

[0075] In addition, the physicochemical properties of the composite membrane according to the crosslinking agent dosage were confirmed through Fourier transform infrared spectroscopy and zeta potential changes. Specifically, as the crosslinking agent dosage increased, the hydroxyl group-related bands in the Fourier transform infrared spectroscopy at 3,200 to 3,600 cm -1 We confirmed that the peak in the region decreased (Fig. 4(a)). This confirmed the formation of hydrogen bonds between the cross-linking agent and graphene oxide particles. Furthermore, as the amount of cross-linking agent injected increased, the change in zeta potential decreased (Fig. 4(b)), confirming that the positively charged aluminosilicate sol cross-linking agent cross-links the negatively charged graphene oxide through electrostatic bonding.

[0076] The results of analyzing the cross-sections of a graphene oxide membrane without cross-linking agent injection and a graphene oxide composite membrane (b) injected with a cross-linking agent using field emission scanning electron microscopy are as shown in Fig. 5.

[0077] The degree of structural degradation before and after the harsh condition stability evaluation of the graphene oxide composite membrane according to the amount of cross-linking agent injected was analyzed using a field emission scanning electron microscope, and it was confirmed that the structural stability was maintained even under harsh conditions when the cross-linking agent was injected (Fig. 6).

[0078] In addition, the composite membranes manufactured according to the cross-linking agent injection amount (0, 25, 50%) were cut into 1.5 cm X 2.5 cm, and the tensile strength was measured by applying a force at a loading rate of 10 mm / min. As a result, it was confirmed that the tensile strength was improved when the cross-linking agent was injected at 50% (Fig. 7(a)). That is, it was confirmed that the graphene oxide separator without cross-linking agent injection (Fig. 7(b)) showed lower elasticity as it was confirmed that it cracked when bent severely compared to the composite membrane with 50% cross-linking agent injection (Fig. 7(c)).

[0079]

[0080] <Experimental Example 2> Comparison of water contact angles of graphene oxide composite membranes according to crosslinking agent injection

[0081] The contact angle characteristics for water of a graphene oxide composite membrane mixed with 50% of a cross-linking agent according to the above example were compared with a graphene oxide separator (comparative example).

[0082] Specifically, as a result of dropping 6 ㎕ of distilled water onto the surface of the composite membrane as a test subject, the contact angle was 38.0 degrees before the injection of the cross-linking agent, and increased by about 3.8 degrees to 41.8 degrees after the injection, indicating that the contact angle for water was higher when the cross-linking agent was injected (Fig. 8), but it can be confirmed that the structural swelling phenomenon of the graphene oxide coating layer in response to water was significantly reduced without sacrificing hydrophilicity.

[0083]

[0084] <Experimental Example 3> Ion extraction capacity according to the amount of cross-linking agent injected

[0085] The lithium ion extraction ability and selectivity for multivalent ions in a salt water environment of graphene oxide composite membranes in which 5%, 25%, and 50% of a cross-linking agent were mixed in accordance with the above examples were compared in a comparative example of a graphene oxide separator.

[0086] Specifically, the fabricated membrane was inserted into a two-chambered H-type electrochemical cell, and a current of -200 mV to +200 mV was applied at a rate of 10 mV / s through an Ag / AgCl electrode. The ion permeation rate and selectivity of the graphene oxide composite membrane according to the amount of cross-linking agent injected were evaluated through the slope of the current-voltage curve. The concentrations of lithium ions and magnesium ions used were each 0.01 mol / L.

[0087] As a result, the lithium ion permeation rate of the graphene oxide membrane without cross-linking agent gradually increased over time, whereas the graphene oxide composite membrane injected with cross-linking agent showed stable lithium permeation even after long-term exposure to a saline environment (Fig. 9(a)).

[0088] When a cross-linking agent was not injected, the graphene oxide separator decomposed over time and dispersed in water (Fig. 9(b)), but when a cross-linking agent was injected, it was confirmed that the redispersion of the separator did not occur (Fig. 9(c)).

[0089] Additionally, it was confirmed that the 50% graphene oxide-crosslinker composite membrane exhibited higher multi-valent ion selectivity for lithium ions compared to the separator without crosslinker application (Fig. 9(d)).

[0090] For graphene oxide membranes without crosslinking agent, Ni 2+ , Co 2+ , Mg 2+ , Mn 2+ , and Fe 3+ The selectivity for lithium was 2 to 5 for the composite membrane injected with the cross-linking agent, whereas the selectivity for lithium was 7.7 for nickel, 11.0 for cobalt, 13.4 for magnesium, 19.3 for manganese, and 25.3 for iron, respectively. This is a significantly higher selectivity than the membrane not injected with the cross-linking agent, and it is believed that this is because the expansion of the distance between graphene oxide particles is controlled by the cross-linking agent, greatly limiting the permeation of multivalent ions. In other words, as the amount of cross-linking agent injected increases, the lithium / magnesium selectivity increases, which shows that the ion extraction ability in a salt water environment is improved.

[0091] As a result, the graphene oxide composite membrane according to one embodiment of the present invention has a structure with significantly improved stability in an aqueous environment and exhibits excellent ion extraction ability from salt water, so that it can be applied to a lithium ion extraction ion exchange membrane.

[0092] Above, the technology disclosed in this specification has been described in detail with reference to preferred embodiments, but the technical idea of ​​the present invention is not limited to the above embodiments, and various modifications and changes are possible by a person having ordinary knowledge in the art within the scope of the technical idea of ​​the present invention.

Claims

1. A composite film of graphene oxide, in which a graphene oxide layer is cross-linked by aluminosilicate nanoparticles.

2. In paragraph 1, The above graphene oxide composite film is, A graphene oxide composite film crosslinked through hydrogen bonding and charge compensation between the above graphene oxide layer and the above aluminosilicate nanoparticles.

3. In paragraph 1, A graphene oxide composite film comprising 5.0 wt% to 50.0 wt% of aluminosilicate nanoparticles relative to graphene oxide.

4. In paragraph 1, A graphene oxide composite film, wherein the aluminosilicate nanoparticles comprise a composite inorganic material derived from an alumina precursor and silica spheres.

5. In paragraph 4, The above alumina precursor and the composite inorganic material derived from the silica precursor are, At least one alumina precursor selected from the group consisting of aluminum nitrate, aluminum chloride, aluminum tri-sec-butoxide, aluminum sulfate, aluminum isopropoxide, sodium aluminate, aluminum 2-methoxyethoxide and aluminum 2-methoxyethoxyethoxide; and At least one silica precursor selected from the group consisting of tetra-ethyl-ortho-silicate, tetra-methyl-ortho-silicate, 3-glycidyloxypropyl-trimethoxysilane, 3-aminopropyl-triethoxysilane, sodium ortho-silicate, tri-methoxy-propysilane, and tri-methoxy-octylsilane; A composite film of graphene oxide, which is a nanoparticle manufactured by a hydrolysis reaction.

6. Comprising a graphene oxide composite film according to paragraph 1, Ion exchange membrane.

7. A step of preparing a graphene oxide dispersion by ultrasonic treatment of a graphene oxide solution; A step of preparing a mixture by mixing aluminosilicate nanoparticles into the above graphene oxide dispersion; and A step of manufacturing a graphene oxide composite membrane by filtering the above mixture under reduced pressure; including, Method for manufacturing graphene oxide composite film.

8. In paragraph 7, A method for producing a graphene oxide composite film, wherein, in the step of producing the above-mentioned mixed solution, the graphene oxide layer is crosslinked through hydrogen bonding and charge compensation between the graphene oxide and aluminosilicate nanoparticles.

9. In paragraph 7, A method for producing a graphene oxide composite film, wherein the concentration of the above graphene oxide solution is 0.2 mg / mL to 0.6 mg / mL.

10. In paragraph 7, A method for producing a graphene oxide composite film, wherein the above ultrasonic treatment is performed by irradiating ultrasonic waves of 30 kHz to 50 kHz at a temperature of 30°C or lower with an ultrasonic intensity of 90 W to 110 W.

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