CN114618314B - Metal chelate/graphene oxide composite membrane and preparation method and application thereof - Google Patents

Metal chelate/graphene oxide composite membrane and preparation method and application thereof Download PDF

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CN114618314B
CN114618314B CN202210215063.3A CN202210215063A CN114618314B CN 114618314 B CN114618314 B CN 114618314B CN 202210215063 A CN202210215063 A CN 202210215063A CN 114618314 B CN114618314 B CN 114618314B
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张梦辰
李佩珊
姜龙
李铭杰
刘凌丰
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Abstract

The invention provides a metal chelate/graphene oxide composite membrane and a preparation method and application thereof, belonging to the field of thin film materials. According to the invention, through layer-by-layer spin coating, the polydentate ligand and metal cations have chelation between each layer of graphene oxide film, and a structure that the metal chelate is uniformly and stably inserted between the graphene oxide film layers is formed, so that the physical structure and the chemical environment of the two-dimensional nanochannel of the graphene oxide film are accurately regulated, the prepared orderly-assembled metal chelate/graphene oxide composite film can effectively inhibit swelling, promote the rapid transmission of monovalent ions, and effectively intercept divalent ions. The method is used in the related fields of monovalent/divalent ion screening and the like, and shows high permeability and high selectivity in monovalent and divalent salt solution systems.

Description

Metal chelate/graphene oxide composite membrane and preparation method and application thereof
Technical Field
The invention belongs to the field of thin film materials, and particularly relates to a metal chelate/graphene oxide composite film, and a preparation method and application thereof.
Background
The monovalent/divalent ion selective separation technology plays a key role in industrial applications such as brine refining, salt lake lithium extraction, hard water softening and the like. At present, the traditional separation technology is difficult to distinguish monovalent/divalent ions with very similar size and property, and the selective separation is very difficult in practical application. Therefore, the construction of the limited domain nano-channel with ion selective transmission performance based on the novel membrane material has important significance. The latest research finds that the two-dimensional material represented by graphene oxide has atomic-scale thickness and flexibly regulated physicochemical properties, can be stacked to form a regular interlayer two-dimensional nano-channel through ordered assembly, is used for ion selective transmission, and shows great application potential in the fields of environment, resources, energy and the like. However, the two-dimensional nanochannels of the graphene oxide membrane generally have a swelling phenomenon in an aqueous solution, and the structural stability and the ion sieving property of the graphene oxide membrane are seriously damaged. At present, physical limitation, chemical reduction or covalent crosslinking and other methods are used for inhibiting the swelling of two-dimensional channels of the graphene oxide membrane, but the excessively narrow size of the channels between layers can bring about larger permeation resistance, thereby greatly reducing the separation efficiency of the membrane. The size of a graphene oxide two-dimensional membrane channel can be regulated and controlled by using a metal cation non-covalent crosslinking method, but the intercalated metal cations are easy to lose along with the transfer of fluid, so that the selective performance of the membrane is influenced.
Therefore, an effective graphene composite membrane selectively separating monovalent/divalent ions needs to be developed, the physical structure and chemical environment of a two-dimensional nano channel of the graphene oxide membrane can be accurately regulated and controlled while the structural stability of the graphene oxide membrane is maintained, and the functions of promoting the monovalent ions to be rapidly transmitted and intercepting the divalent ions are achieved, so that the efficient selective screening of the monovalent/divalent ions is realized.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a metal chelate/graphene oxide composite membrane and a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the technical scheme that: a preparation method of a metal chelate/graphene oxide composite membrane comprises the following steps:
(1) Uniformly dispersing graphene oxide in a solvent to obtain a graphene oxide dispersion liquid; dissolving a polydentate ligand in a solvent to obtain a chelating agent; dissolving metal ion salt in water to obtain a metal ion salt solution;
(2) And (2) circularly and rotatably coating the graphene oxide dispersion liquid obtained in the step (1), the chelating agent and the metal ion salt solution on a support layer by layer from bottom to top, forming a film layer, and drying to obtain the metal chelate/graphene oxide composite film.
According to the invention, through layer-by-layer spin coating, a polydentate ligand and metal cations are subjected to chelation between each layer of graphene oxide film, and the formed stable metal chelate is uniformly inserted between the graphene oxide film layers, so that the physical structure and the chemical environment of the two-dimensional nanochannel of the graphene oxide film can be accurately regulated and controlled. The polydentate ligand is used as a cross-linking agent, the fixation of interlayer metal cations is ensured through coordination, pi-pi action and hydrogen bonding, and the rapid transmission of monovalent ions is promoted based on hydration compensation effect. Meanwhile, the metal cations are used as central ions, the two-dimensional layered structure of the graphene oxide membrane is further stabilized through cation-pi action and electrostatic interaction, and the size of the limited two-dimensional nano channel is accurately regulated and controlled based on the steric hindrance effect so as to effectively intercept the permeation of divalent ions. Under the synergistic effect of the two, the membrane has high permeability and high selectivity in a monovalent salt solution system and a multivalent salt solution system. The preparation method is simple and feasible, and the prepared metal chelate/graphene oxide composite membrane has a stable structure and has a good application prospect in related fields such as monovalent/divalent ion separation and the like.
In a preferred embodiment of the present invention, in the step (1), the concentration of the graphene oxide dispersion is 0.05 to 0.2mg/mL; the graphene oxide is a monodisperse graphene oxide nanosheet, the transverse size of the graphene oxide nanosheet is 20-30 microns, the single-layer rate is greater than or equal to 99%, and the oxygen content is 30-40%; the solvent includes water.
The inventor finds that the monodisperse graphene oxide nanosheets have a very high surface-to-volume ratio and can be orderly stacked under the assistance of a solvent to form a regular two-dimensional layered membrane structure. The graphene oxide nanosheet has good dispersibility in a water solvent, is not easy to generate a local agglomeration phenomenon, and is beneficial to the assembly and preparation of the graphene oxide membrane. Too low concentration of the graphene oxide dispersion liquid can result in lower film preparation efficiency, and too high concentration can affect the dispersibility of the graphene oxide nanosheets in the solvent. When the concentration provided by the invention is used, the membrane preparation efficiency is high, and the dispersibility of the graphene oxide nanosheet in the solvent is good.
As a preferred embodiment of the present invention, in the step (1), the graphene oxide is uniformly dispersed in the solvent by stirring and/or ultrasonic treatment; the stirring time is 10-60min; the ultrasonic power is 100-700W, and the ultrasonic time is 5-30min.
The inventor finds that proper stirring and ultrasonic processes are beneficial to helping graphene oxide nanosheets to be uniformly dispersed in a solvent, and excessive ultrasonic power and ultrasonic time can cause the size of the nanosheets to be too small, so that the structure and performance of the graphene oxide film are affected.
As a preferred embodiment of the present invention, in step (1), the polydentate ligand comprises 2,2':6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid and/or ethylenediaminetetraacetic acid; the concentration of the chelating agent is 0.1-1mg/mL.
As a preferred embodiment of the present invention, in the step (1), the polydentate ligand is uniformly dispersed in the solvent by stirring and ultrasonic treatment; the stirring time is 30-120min, the ultrasonic treatment power is 100-700W, and the ultrasonic time is 5-30min.
As a preferred embodiment of the present invention, in the step (1), the solvent of the chelating agent includes water and/or N, N-dimethylamide.
As a more preferred embodiment of the present invention, in the step (1), the solvent of the chelating agent is a mixture of N, N-dimethylamide and water in a mass ratio of 20 to 80 wt%.
The inventor finds that proper stirring and ultrasonic processes ensure that the polydentate ligand is fully contacted with solvent molecules, and the polydentate ligand is favorably dissolved. The concentration chelating agent firmly fixes interlayer metal cations through coordination, pi-pi interaction and hydrogen bonding, and promotes monovalent ion rapid transmission based on hydration compensation effect.
As a preferred embodiment of the present invention, in step (1), the metal ion salt includes: at least one of cobalt salt, zinc salt, cadmium salt, barium salt, copper salt and ferrous salt; the concentration of the metal ion salt solution is 0.005-0.01mol/L.
As a more preferred embodiment of the present invention, in step (1), the metal ion salt comprises: at least one of cobalt chloride, zinc chloride, cadmium chloride, barium chloride, copper sulfate, and ferrous sulfate; the concentration of the metal ion salt solution is 0.005-0.01mol/L.
The inventor finds that the metal ion salt can form cation-pi interaction with the graphene oxide base surface as a central ion, so that the two-dimensional layered structure of the graphene oxide membrane is further stabilized, the size of a nano channel is accurately regulated and controlled based on a steric hindrance effect, and the permeation of divalent ions is effectively intercepted.
As a preferred embodiment of the present invention, in the step (2), the spin-coating conditions are that the rotation speed is 800-2000 rpm, the single spin-coating time of each spin-coating layer is 30-120 seconds, and each spin-coating layer needs to be cleaned by water after being spin-coated; the cycle number of the spin coating is 5-30 times.
The inventor finds that the graphene oxide composite membrane with the continuous and defect-free surface can be prepared under the spin coating condition, the multi-tooth ligand and the metal cations can be chelated between each layer of graphene oxide membrane through the layer-by-layer sequential spin coating, and the formed stable metal chelate is uniformly distributed between the graphene oxide membrane layers so as to accurately regulate and control the physical structure and the chemical environment of the two-dimensional nanochannel.
As a preferred embodiment of the present invention, in the step (2), the support is a porous support; the material of the porous support comprises at least one of polyacrylonitrile, polycarbonate, nylon, mixed cellulose ester and alumina.
The inventors have found that the porous support can provide sufficient mechanical strength to the graphene oxide membrane.
As a preferred embodiment of the present invention, in the step (2), the structure type of the porous support is a sheet type or a flat plate type; the average pore diameter of the porous support is 10-1000nm.
The inventor finds that the pore diameter of the porous support is too small, which brings extra mass transfer resistance and affects the membrane separation efficiency. The porous support body with the pore diameter provided by the invention has a good use effect.
As a preferred embodiment of the invention, in the step (2), the drying temperature is 25-60 ℃, and the drying time is 12-36h.
The inventor finds that residual moisture in the film can be removed in the drying process, the film preparation efficiency is lower due to too low drying temperature, and the film structure is damaged due to partial reduction or removal of oxygen groups in the graphene oxide film due to too high drying temperature.
The invention also provides a metal chelate/graphene oxide composite membrane material prepared by any one of the methods.
The invention also provides application of the metal chelate/graphene oxide composite membrane material prepared by any one of the methods in ion selective separation.
Compared with the prior art, the invention has the beneficial effects that:
(1) The monovalent and divalent salt solution system has high permeability and high selectivity, and achieves the functions of promoting the rapid transmission of monovalent ions and intercepting divalent ions, thereby realizing the efficient selective screening of the monovalent/divalent ions.
(2) The preparation method is simple and easy to implement, and the prepared metal chelate/graphene oxide composite membrane is stable in structure.
Drawings
FIG. 1 is a schematic structural diagram of a 2,2' and 6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid-barium oxide/graphene oxide composite film prepared in example 1 of the present invention.
FIG. 2 is a surface scanning electron microscope image of 2,2' 6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid-zinc/graphene oxide composite film prepared in example 2 of the present invention.
FIG. 3 is a scanning electron microscope cross-sectional view of 2,2' and 6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid-zinc/graphene oxide composite film prepared in example 2 of the present invention.
Detailed Description
To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to specific examples. The experimental methods described in the examples are all conventional methods unless otherwise specified; unless otherwise indicated, all reagents and materials are commercially available.
Example 1
The embodiment of the preparation method of the metal chelate/graphene oxide composite membrane specifically comprises the following steps: (1) Dispersing 20mg of graphene oxide nanosheets in 100mL of water, stirring for 30 minutes, and carrying out ultrasonic treatment at 500W for 5 minutes to obtain a uniform graphene oxide dispersion liquid; dissolving 0.025g of 2,2':6',2 "-terpyridine-4,4 ', 4" -tricarboxylic acid in 100mL of 50wt% N, N-dimethylamide in water, stirring for 30 minutes, and sonicating at 700W for 30 minutes to give 0.25mg/mL of 2,2':6',2 "-terpyridine-4,4', 4" -tricarboxylic acid chelating agent; dissolving 0.25g of barium chloride in 100mL of water to obtain a barium chloride solution with the concentration of 0.01 mol/L;
(2) The graphene oxide dispersion liquid, 2,2', 6',2 '-terpyridine-4,4', 4 '-tricarboxylic acid (CAS: 216018-5-5) chelating agent and barium chloride solution are spin-coated for 30 seconds at the rotating speed of 2000 revolutions per minute, the aluminum oxide sheet type support (the average pore diameter is 1000 nanometers) is sequentially spin-coated for forming a film layer with 15 spin-coating cycles, and the prepared film is placed in a vacuum drying box to be dried for 18 hours at the temperature of 45 ℃ to obtain 2,2', 6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid-barium/graphene oxide composite film.
FIG. 1 is a schematic structural diagram of the 2,2' 6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid-barium oxide/graphene oxide composite film prepared in example 1. As can be seen from fig. 1, not only can interlayer metal cations be immobilized by multiple interactions, but also the membrane can form a nanochannel with appropriate physical confinement and good chemical environment.
The prepared 2,2' 6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid-barium/graphene oxide composite membrane is subjected to a penetration test, and the specific test method comprises the following steps:
the membrane is arranged between the feed side and the permeation side of a self-made U-shaped permeation assembly, the graphene oxide surface faces the feed side, and the effective area of the membrane is 4.15cm 2 (ii) a Adding 100mL of deionized water to the permeation side, adding a potassium chloride or magnesium chloride solution with the equal volume concentration of 0.5mol/L to the feeding side, and placing rotors on both sides of the solution to stir so as to eliminate concentration polarization; the ion concentration of the permeate side was measured every 10 minutes using a conductivity meter for 2 hours; a linear fit of the concentration on the permeate side as a function of time was plotted and the permeation rate of the ions was represented by the slope. According to the calculation formula of the permeation rate:
Figure BDA0003529957750000061
wherein J s (mol m -2 h -1 ) As the ion permeation rate,. DELTA.c/. DELTA.t (mg L) -1 h -1 ) Is the change of ion concentration per unit time on the permeation side, V p (L) volume of solution at the permeate side, A (m) 2 ) Effective area of the membrane, M s (gmol -1 ) Is the molecular weight of potassium chloride or magnesium chloride, and can obtain K + The permeation rate is 0.775mol m -2 h -1 ，Mg 2+ The permeation rate is 0.033mol m -2 h -1 (ii) a According to the selectivity calculation formula:
Figure BDA0003529957750000071
wherein J s1 Represents K + Penetration Rate, J s2 Represents Mg 2+ Penetration rate, available K + /Mg 2+ The selectivity was 23.5.
Example 2
The embodiment of the preparation method of the metal chelate/graphene oxide composite membrane specifically comprises the following steps: (1) Dispersing 5mg of graphene oxide nanosheets in 100mL of water, stirring for 60 minutes, and carrying out 700W ultrasonic treatment for 5 minutes to obtain a uniform graphene oxide dispersion liquid; dissolving 0.01g of 2,2':6',2 "-terpyridine-4,4 ', 4" -tricarboxylic acid in 100mL of aqueous solution containing 20wt% of N, N-dimethylamide, stirring for 120 minutes, and carrying out 700W ultrasonic treatment for 10 minutes to obtain 2,2':6',2 "-terpyridine-4,4', 4" -tricarboxylic acid chelating agent of 0.1 mg/mL; dissolving 0.14g of zinc chloride in 100mL of water to obtain a zinc chloride solution with the concentration of 0.01 mol/L;
(2) The graphene oxide dispersion liquid, 2,2', 6',2 '-terpyridine-4,4', 4 '-tricarboxylic acid chelating agent and zinc chloride solution are subjected to spin coating for 60 seconds at the rotating speed of 1500 rpm, the film layer with 25 spin coating cycles is formed on a polyacrylonitrile flat plate type support (the average pore diameter is 10 nanometers), and the prepared film is placed in a vacuum drying box to be dried for 15 hours at the temperature of 50 ℃ to obtain the 2,2', 6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid-zinc/graphene oxide composite film.
The prepared 2,2' 6', 2' -terpyridyl-4,4',4 "-tricarboxylic acid-zinc/graphene oxide composite membrane was subjected to the permeation test, except that the test membrane was different, the test method was the same as in example 1. K can be obtained by testing + The permeation rate was 0.757mol m -2 h -1 ，Mg 2+ The permeation rate is 0.089mol m -2 h -1 ，K + /Mg 2+ The selectivity was 8.5.
FIG. 2 is a surface scanning electron micrograph of the 2,2' 6',2 "-terpyridine-4,4 ', 4" -tricarboxylic acid-zinc oxide/graphene oxide composite film prepared in example 2. As can be seen from fig. 2, the film surface is uniform and continuous. FIG. 3 is a scanning electron micrograph of a cross section of the 2,2' 6',2 "-terpyridine 4,4', 4" -tricarboxylic acid-zinc/graphene oxide composite film prepared in example 2. As can be seen from fig. 3, the membrane exhibits an orderly stacked regular two-dimensional layered membrane structure.
Example 3
The embodiment of the preparation method of the metal chelate/graphene oxide composite membrane specifically comprises the following steps: (1) Dispersing 1mg of graphene oxide nanosheets in 100mL of water, stirring for 10 minutes, and carrying out 100W ultrasonic treatment for 30 minutes to obtain a uniform graphene oxide dispersion liquid; dissolving 0.1g of 2,2':6',2 "-terpyridine-4,4 ', 4" -tricarboxylic acid in 100mL of an aqueous solution containing 80wt% of N, N-dimethylamide, stirring for 60 minutes, and sonicating at 300W for 20 minutes to obtain 1mg/mL of 2,2':6',2 "-terpyridine-4,4', 4" -tricarboxylic acid chelating agent; dissolving 0.07g of zinc chloride in 100mL of water to obtain a zinc chloride solution with the concentration of 0.005 mol/L;
(2) The graphene oxide dispersion, 2,2', 6',2 '-terpyridine-4,4', 4 '-tricarboxylic acid chelating agent and zinc chloride solution are spin-coated for 120 seconds at the rotation speed of 800 rpm, the film layers with 10 spin-coating cycles are sequentially spin-coated on a nylon flat plate type support (the average pore diameter is 500 nanometers), and the prepared film is placed in a vacuum drying box to be dried for 36 hours at the temperature of 25 ℃ to obtain 2,2', 6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid-zinc/graphene oxide composite film.
The prepared 2,2' 6', 2' -terpyridine-4,4 ', 4' -tricarboxylic acid-zinc/graphene oxide composite membrane is subjected to a penetration test,the test method was the same as in example 1 except that the test film was different. Tested to obtain K + The permeation rate is 0.865mol m -2 h -1 ，Mg 2+ The permeation rate was 0.095mol m -2 h -1 ，K + /Mg 2+ The selectivity was 9.1.
Example 4
The embodiment of the preparation method of the metal chelate/graphene oxide composite membrane specifically comprises the following steps: (1) Dispersing 10mg of graphene oxide nanosheets in 100mL of water, stirring for 20 minutes, and carrying out ultrasonic treatment at 500W for 15 minutes to obtain a uniform graphene oxide dispersion liquid; dissolving 0.025g of ethylenediamine tetraacetic acid in 100mL of aqueous solution, stirring for 30 minutes, and carrying out 100W ultrasonic treatment for 30 minutes to obtain an ethylenediamine tetraacetic acid chelating agent of 0.25 mg/mL; dissolving 0.23g of cadmium chloride in 100mL of water to obtain a cadmium chloride solution with the concentration of 0.01 mol/L;
(2) And spin-coating the graphene oxide dispersion liquid, an ethylene diamine tetraacetic acid (CAS: 60-00-4) chelating agent and a cadmium chloride solution at the rotation speed of 1200 rpm for 90 seconds, sequentially spin-coating the mixture on a mixed cellulose ester flat plate type support (the average pore diameter is 200 nanometers) to form a film layer which is subjected to spin-coating circulation for 20 times, and drying the prepared film in a vacuum drying oven at the temperature of 30 ℃ for 24 hours to obtain the ethylene diamine tetraacetic acid-cadmium/graphene oxide composite film.
The prepared ethylenediaminetetraacetic acid-cadmium/graphene oxide composite membrane was subjected to a permeation test, and the test methods were the same as in example 1 except that the test membranes were different. Tested to obtain K + The permeation rate was 0.447mol m -2 h -1 ，Mg 2+ The permeation rate was 0.022mol m -2 h -1 ，K + /Mg 2+ The selectivity was 20.4.
Comparative example 1
The preparation method of the metal ion salt solution spin-coating graphene oxide composite membrane without the chelating agent specifically comprises the following steps:
(1) Dispersing 20mg of graphene oxide nanosheets in 100mL of water, stirring for 30 minutes, and carrying out ultrasonic treatment at 500W for 5 minutes to obtain a uniform graphene oxide dispersion liquid;
(2) And spin-coating the graphene oxide dispersion liquid at 2000 rpm for 30 seconds, sequentially spin-coating the graphene oxide dispersion liquid on an aluminum oxide sheet type support (with an average pore diameter of 1000 nm) to form a film layer which is subjected to spin-coating for 15 times, and drying the prepared film in a vacuum drying oven at 45 ℃ for 18 hours.
The obtained graphene oxide membrane was subjected to a permeation test, and the test methods were the same as in example 1 except that the test membrane was different. Tested to obtain K + The permeation rate was 0.489mol m -2 h -1 ，Mg 2+ The permeation rate was 0.111mol m -2 h -1 ，K + /Mg 2+ The selectivity was 4.4.
Comparative example 2
The preparation method of the spin-coating graphene oxide composite film without the chelating agent specifically comprises the following steps:
(1) Dispersing 20mg of graphene oxide nanosheets in 100mL of water, stirring for 30 minutes, and carrying out ultrasonic treatment at 500W for 5 minutes to obtain a uniform graphene oxide dispersion liquid; dissolving 0.25g of barium chloride in 100mL of water to obtain a barium chloride solution with the concentration of 0.01 mol/L;
(2) And spin-coating the graphene oxide dispersion liquid and the barium chloride solution at a rotation speed of 2000 rpm for 30 seconds, sequentially spin-coating the graphene oxide dispersion liquid and the barium chloride solution on an aluminum oxide sheet type support (with an average pore diameter of 1000 nanometers) to form a film layer which is subjected to spin-coating circulation for 15 times, and drying the prepared film in a vacuum drying oven at 45 ℃ for 18 hours.
The prepared composite graphene oxide membrane was subjected to a permeation test, and the test methods except for the test membrane were the same as those in example 1. K can be obtained by testing + The permeation rate was 0.383mol m -2 h -1 ，Mg 2+ The permeation rate was 0.068mol m -2 h -1 ，K + /Mg 2+ The selectivity was 5.6.
Comparative example 3
The preparation method of the metal ion salt solution-free spin-coating graphene oxide composite film comprises the following steps:
(1) Dispersing 20mg of graphene oxide nanosheets in 100mL of water, stirring for 30 minutes, and carrying out ultrasonic treatment at 500W for 5 minutes to obtain a uniform graphene oxide dispersion liquid; dissolving 0.025g of 2,2':6',2 "-terpyridine-4,4 ', 4" -tricarboxylic acid in 100mL of 50wt% N, N-dimethylamide in water, stirring for 30 minutes, and sonicating at 700W for 30 minutes to give 0.25mg/mL of 2,2':6',2 "-terpyridine-4,4', 4" -tricarboxylic acid chelating agent;
(2) And spin-coating the graphene oxide dispersion liquid and the chelating agent at the rotating speed of 2000 rpm for 30 seconds, sequentially spin-coating the graphene oxide dispersion liquid and the chelating agent on an aluminum oxide sheet type support (the average pore diameter is 1000 nanometers) to form a film layer which is subjected to spin-coating cycle for 15 times, and drying the prepared film in a vacuum drying oven at 45 ℃ for 18 hours.
The prepared composite graphene oxide membrane was subjected to a permeation test, and the test methods except for the test membrane were the same as those in example 1. Tested to obtain K + The permeation rate is 0.270mol m -2 h -1 ，Mg 2+ The permeation rate was 0.047mol m -2 h -1 ，K + /Mg 2+ The selectivity was 5.8.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims (8)

1. A preparation method of a metal chelate/graphene oxide composite membrane is characterized by comprising the following steps:
(1) Uniformly dispersing graphene oxide in a solvent to obtain a graphene oxide dispersion liquid; dissolving a polydentate ligand in a solvent to obtain a chelating agent; dissolving metal ion salt in water to obtain a metal ion salt solution;
(2) Circularly and rotatably coating the oxidized graphene dispersion liquid obtained in the step (1), a chelating agent and a metal ion salt solution on a support layer by layer from bottom to top, forming a film layer, and drying to obtain the metal chelate/oxidized graphene composite film;
in step (1), the polydentate ligand comprises 2,2':6',2 "-terpyridine-4, 4', 4" -tricarboxylic acid and/or ethylenediaminetetraacetic acid; the concentration of the chelating agent is 0.1-1 mg/mL;
in the step (2), the spin coating conditions are that the rotating speed is 800-2000 rpm, the single spin coating time of each spin coating is 30-120 seconds, and each spin coating needs to be cleaned by water after being spin coated; the cycle number of the spin coating is 5-30 times.
2. The method according to claim 1, wherein in step (1), the concentration of the graphene oxide dispersion is 0.05-0.2mg/mL; the graphene oxide is a monodisperse graphene oxide nanosheet, the transverse size of the graphene oxide nanosheet is 20-30 microns, the single-layer rate is greater than or equal to 99%, and the oxygen content is 30-40%; the solvent includes water.
3. The method according to claim 1, wherein in the step (1), the graphene oxide is uniformly dispersed in the solvent by stirring and/or ultrasonic treatment; the stirring time is 10-60min; the ultrasonic power is 100-700W, and the ultrasonic time is 5-30min.
4. The method according to claim 1, wherein in step (1), the solvent of the chelating agent comprises water and/or N, N-dimethylformamide.
5. The method of claim 1, wherein in step (1), the metal ion salt comprises: at least one of cobalt salt, zinc salt, cadmium salt, barium salt, copper salt and ferrous salt; the concentration of the metal ion salt solution is 0.005-0.01mol/L.
6. The method according to claim 1, wherein in step (2), the support is a porous support; the material of the porous support comprises at least one of polyacrylonitrile, polycarbonate, nylon, mixed cellulose ester and alumina; the structure type of the porous support body is a sheet type or a flat plate type; the average pore diameter of the porous support body is 10-1000nm.
7. The metal chelate/graphene oxide composite membrane material prepared by the method of any one of claims 1 to 6.
8. Use of the metal chelate/graphene oxide composite membrane material prepared by the method according to any one of claims 1 to 6 in ion selective separation.
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