Aminated nanofiber membrane, preparation thereof and application of aminated nanofiber membrane in pretreatment of radioactive waste liquid

Abstract

The invention relates to the technical field of membrane separation, in particular to an aminated nanofiber membrane, preparation thereof and application of the aminated nanofiber membrane in pretreatment of radioactive waste liquid. The preparation method comprises the following steps: firstly, carrying out electrostatic spinning treatment on a nanofiber precursor solution and a chitosan solution by utilizing a coaxial spraying device for electrostatic spinning to obtain a nanofiber membrane with a core-shell structure; then carrying out oxidation pretreatment on the nanofiber membrane with the core-shell structure to obtain a pretreated nanofiber membrane; and finally, placing the pretreated nanofiber membrane in a thiourea solution to carry out functional group grafting modification treatment, and drying to obtain the aminated nanofiber membrane. According to the preparation method, the preparation process flow of the aminated nanofiber membrane is short, the material cost is low, the obtained aminated nanofiber membrane has the dual functions of filtering suspended solids and particles in radioactive waste liquid and adsorbing soluble ions, and the problems that in the nuclear industry, the radioactive waste liquid with complex components is long in treatment process flow, high in cost and the like can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, in particular to an amino nanofiber membrane and its preparation and application in pre-treating radioactive waste liquid. Background Art

[0002] In the nuclear industry, the composition of radioactive waste liquid from nuclear power plants is very complex. It not only contains insoluble substances such as suspended matter and micro-nano particles, but also contains plasma or colloidal chemical components such as Cr, Co, Sr, Cs, Sb, Ag, Li, I, and boric acid (radicals). It is highly harmful and difficult to remove. There is an urgent need to develop efficient and environmentally friendly treatment technologies for radioactive waste liquid.

[0003] At present, in the process of treating radioactive liquid waste, a combination of treatment technologies such as activated carbon, ultrafiltration, nanofiltration, reverse osmosis, and adsorption is often used, forming multiple process steps such as pretreatment, main treatment, fine treatment, and post-treatment. There are problems such as long process flow, complex operation, and high equipment cost. In the current radioactive liquid waste treatment technology, membrane separation technology is widely used and runs through almost the entire process flow. Therefore, the development of new membrane materials, the realization of functional integration design, and the enhancement of separation efficiency are the current focus of technology development.

[0004] In the new membrane separation technology disclosed in recent years, electrostatic spinning, electrospraying and other technologies are mainly used to prepare nanofibers, and the multifunctional application of fiber membranes is realized by combining catalysis, adsorption and other functions. For example: Patent CN117504817A discloses a method for preparing Mg(OH)2 carbon nanofiber membranes, which uses carbon nanofiber membranes as substrates and loads Mg(OH)2 / carbon nanofiber membranes formed by magnesium hydroxide. While improving the mechanical properties of the carbon nanofiber membranes, the electrostatic adsorption of the hydroxyl structure on the surface of Mg(OH)2 and the electronic complexation synergistic effect of the conjugated structure π electrons of the carbon nanofibers can enhance the adsorption effect of heavy metal ions; however, this method requires the use of toxic organic solvents such as DMF, which poses a risk of secondary pollution; Patent CN116440862A discloses an amidoximated MXene porous fiber membrane adsorption material with a "rice paper" structure, which has a simple preparation step, a wide range of applications, and excellent uranium adsorption performance, but the raw materials used in this method are relatively expensive, which increases its application cost. Patent CN116926784A discloses a composite nanofiber membrane based on photothermal enhanced uranium ion selective adsorption-photocatalytic cascade mechanism. The composite nanofiber membrane can introduce photothermal conversion into the conventional adsorption-catalytic process, and utilize the temperature sensitivity of polyamidoximes to uranium-specific adsorption to achieve selective enrichment of uranium; however, this method requires the use of external photothermal effects, and there are many limitations in the actual application process. Patent CN117960134A discloses a preparation method and application of a nanofiber membrane that can simultaneously adsorb multiple types of antibiotics. Electrospinning technology and post-modification methods are used to obtain a nanofiber membrane double-modified with polydopamine and a metal organic framework. The adsorption and extraction efficiency of antibiotics reaches more than 90%, and it can be reused after elution; however, the preparation method is cumbersome and the process flow is long. In addition, the use of elastic fiber membranes with variable pore sizes can realize the automated operation of filtration and backwashing. Patent CN117865284A discloses an elastic fiber membrane used in the treatment of sodium thiocyanate solvent wastewater. The elastic fiber membrane filters the sodium thiocyanate solvent wastewater. The water-insoluble matter of the filtered solvent is significantly reduced (by more than 90%), and the turbidity is significantly reduced, which can meet the standard of normal solvent reuse, reducing the amount of solid waste generated by filtration and improving the overall degree of automation of filtration. However, this type of filter membrane only strengthens the application properties in terms of operational flexibility, and the filtering, adsorption and other functionalities of the fiber membrane material itself are not enhanced.

[0005] In summary, it is still crucial to provide a membrane material that can achieve functional integration and enhance separation effect. Summary of the invention

[0006] In order to solve the above problems, the purpose of the present invention is to provide an aminated nanofiber membrane and its preparation and application in the pretreatment of radioactive waste liquid. In the present invention, the preparation process of the aminated nanofiber membrane is short and the material cost is low. The obtained aminated nanofiber membrane has the dual functions of filtering suspended matter and particles in radioactive waste liquid and adsorbing dissolved ions, which can solve the problems of long process flow and high cost of treating radioactive waste liquid with complex components in the nuclear industry.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] The first object of the present invention is to provide a method for preparing an amination nanofiber membrane, comprising the following steps:

[0009] (S1) electrospinning the nanofiber precursor solution and the chitosan solution using a coaxial jet device for electrospinning to obtain a nanofiber membrane with a core-shell structure;

[0010] Among them, the nanofiber membrane with core-shell structure refers to the nanofiber with chitosan coated on the surface;

[0011] (S2) subjecting the nanofiber membrane prepared in step (S1) to oxidative pretreatment to obtain a pretreated nanofiber membrane;

[0012] (S3) placing the pretreated nanofiber membrane prepared in step (S2) in a thiourea solution for functional group grafting modification, and drying to obtain an aminated nanofiber membrane;

[0013] The amino nanofiber membrane refers to a nanofiber membrane with a core-shell structure in which the outer chitosan is grafted with amino functional groups.

[0014] In one embodiment of the present invention, in step (S1), the nanofiber precursor solution is prepared by mixing N,N-dimethylacetamide and fibers;

[0015] Wherein, the fiber is polyacrylonitrile, and the mass ratio of N,N-dimethylacetamide to polyacrylonitrile is 1-2:1-2;

[0016] The chitosan solution is prepared by mixing chitosan, glutaraldehyde, water and acetic acid, wherein the chitosan solution contains chitosan with a mass fraction of 1-10%, glutaraldehyde with a mass fraction of 1-5% and acetic acid with a mass fraction of 2-4%.

[0017] In one embodiment of the present invention, in step (S1), the electrospinning coaxial injection device adopts a double-layer cylinder design, the inner cylinder is injected with the nanofiber precursor solution, and the outer cylinder is injected with the chitosan solution;

[0018] The propulsion speed of the nanofiber precursor solution injection is 1-10 mL / h, and the propulsion speed of the chitosan solution injection is 1-10 mL / h; the diameter of the needle in the electrospinning coaxial injection device is 0.1-5 mm.

[0019] In one embodiment of the present invention, in step (S1), the positive electrode of the high-voltage power supply of the electrospinning coaxial injection device is connected to the needle head, and the negative electrode is connected to the fiber membrane collecting plate;

[0020] The distance between the needle and the fiber membrane collecting plate (ie, the "receiving distance") is 10 to 30 cm, and the voltage is 10 to 25 kV.

[0021] In one embodiment of the present invention, in step (S2), during the oxidation pretreatment, the temperature is 100 to 250° C. and the time is 1 to 6 hours;

[0022] Among them, the oxidation pretreatment process is the process of converting the polymer fiber obtained by electrospinning into carbon fiber, and its purpose is to increase the mechanical strength and thermal stability of the fiber so that it can be used under high temperature and high strength conditions. Oxidation pretreatment can partially oxidize elements such as hydrogen, oxygen and nitrogen in the polymer fiber to form oxides with a high oxygen content, thereby reducing the amount of gas released during fiber carbonization, reducing the internal stress during fiber carbonization and the thermal shrinkage of the fiber, and improving the carbonization efficiency.

[0023] In one embodiment of the present invention, in step (S3), the thiourea solution is prepared by mixing thiourea, epichlorohydrin and acetone;

[0024] Wherein, in the thiourea solution, the mass fraction of thiourea is 1-4%, and the mass fraction of epichlorohydrin is 1-2%.

[0025] In one embodiment of the present invention, in step (S3), during the functional group grafting modification process, the temperature is 60 to 100° C. and the time is 1 to 6 hours;

[0026] Among them, in the functional group grafting modification process, glutaraldehyde is first used as a cross-linking agent to cross-link the chain structure of the chitosan molecule into a three-dimensional network structure, and then epoxychloroparaffin is used as an initiator to replace the hydrogen atoms of the amino groups on the cross-linked chitosan molecules to form an intermediate product; finally, thiourea is used as an initiator, and the hydrogen atoms of the amino groups on it are used to replace the chlorine atoms on the intermediate product. In this way, the chemical modification of chitosan by thiourea can be achieved. Theoretically, the number of amino groups on the modified chitosan can reach three times that of unmodified chitosan.

[0027] Therefore, this functional group grafting modification process is a grafting reaction, the groups involved on chitosan are amino groups, the groups involved on thiourea are amino groups, and epichlorohydrin all participate in the reaction to form an intermediate product.

[0028]

[0029] In one embodiment of the present invention, in step (S3), during the drying process, the temperature is 60 to 200° C. and the time is 1 to 6 hours.

[0030] Based on the complex characteristics of radioactive waste liquid in the nuclear industry, the present invention provides a method for preparing an amino nanofiber membrane with coupled filtering and adsorption functions; specifically, the amino nanofiber membrane is prepared with natural and green chitosan as the raw material for metal ion adsorption, which replaces the combined pretreatment method of activated carbon and carbon fiber, and plays the metal ion adsorption function while filtering suspended matter, particles and other insoluble substances in radioactive waste liquid. As an effective pretreatment method, it can reduce the downstream processing pressure in the current radioactive waste liquid treatment process, reduce the cost of waste liquid treatment, and improve the filtration efficiency of soluble ions and insoluble substances.

[0031] The second object of the present invention is to provide an amino nanofiber membrane prepared by the above method.

[0032] The third object of the present invention is to provide an application of an amino nanofiber membrane in the pretreatment of radioactive waste liquid.

[0033] The present invention uses a nanofiber precursor solution with a filtering function and a chitosan solution with an adsorption function as a matrix, and utilizes a coaxial injection device for electrospinning to first prepare a nanofiber membrane with a core-shell structure, wherein the inner layer of the nanofiber membrane is a nanofiber core (high-efficiency filtration) and the outer layer is a chitosan shell (deep adsorption of metal ions); and further on the basis of the nanofiber membrane, an amino-rich thiourea solution is prepared by functional group grafting, and epichlorohydrin is used as an initiator to chemically modify the aforementioned nanofiber membrane to increase the number of amino functional groups, thereby finally preparing an amino-containing nanofiber membrane.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention adopts a coaxial jet device for electrospinning to prepare a nanofiber membrane with a core-shell structure, wherein the core is a nanometer-scale fiber and the outside is wrapped with a layer of chitosan material with adsorption function, so that the nanofiber membrane has both filtration and adsorption functions.

[0036] (2) The present invention uses green and safe chitosan as the adsorption raw material. Chitosan is abundant in source and low in cost, and it contains a large number of active functional groups such as amino and hydroxyl groups, so that chitosan has a certain adsorption and coordination effect on metal ions. The present invention further uses thiourea to modify chitosan through functional group grafting to increase the number of amino functional groups and enhance the adsorption capacity for metal ions.

[0037] (3) The amino-modified nanofiber membrane provided by the present invention has a simple preparation process, low material cost, and less secondary pollution. As a pretreatment tool for radioactive waste liquid, it can effectively reduce the pressure and cost of downstream treatment of radioactive waste liquid, and is suitable for large-scale industrial production and promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of the preparation process of an amino-modified nanofiber membrane of the present invention;

[0039] Figure 2 Schematic diagram of the structure of the amino nanofiber membrane in the present invention. DETAILED DESCRIPTION

[0040] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] In the following examples, unless otherwise specified, all reagents used are commercially available reagents, and all detection means and methods used are conventional detection means and methods in the art.

[0042] Example 1

[0043] This embodiment provides a method for preparing an amino nanofiber membrane (eg Figure 1 As shown), specifically including the following steps:

[0044] (S1) dissolving 50 g of polyacrylonitrile in 50 g of N,N-dimethylacetamide to prepare a nanofiber precursor solution;

[0045] Dissolve chitosan, glutaraldehyde and acetic acid in deionized water and mix well to obtain a chitosan solution (in the chitosan solution, the mass fraction of chitosan is 5%, the mass fraction of glutaraldehyde is 2%, and the mass fraction of acetic acid is 2%);

[0046] (S2) injecting the nanofiber precursor solution prepared in step (S1) into the inner cylinder of the coaxial injection device of the electrospinning (the injection speed is 5 mL / h), and injecting the chitosan solution prepared in step (S1) into the outer cylinder (the injection speed is 5 mL / h), the needle diameter of the electrospinning coaxial injection device is 1 mm, the distance between the fiber membrane collecting plate and the needle is 20 cm, the high voltage power supply voltage is 15 kV, and a nanofiber membrane with a core-shell structure having a thickness of 55 μm is prepared (wherein the diameter of the nanofiber is 500-900 μm);

[0047] (S3) subjecting the nanofiber membrane with a core-shell structure prepared in step (S2) to an oxidative pretreatment to prepare a pretreated nanofiber membrane with a thickness of 55 μm;

[0048] Among them, during the oxidation pretreatment process, the temperature is 150°C and the time is 2h;

[0049] (S4) dissolving thiourea and epichlorohydrin in an acetone solution to obtain a thiourea solution (in the thiourea solution, the mass fraction of thiourea is 2%, and the mass fraction of epichlorohydrin is 1%);

[0050] Then the pretreated nanofiber membrane prepared in step (S3) was placed in a thiourea solution for functional group grafting modification (controlling temperature at 80°C for 4 hours), and then dried (controlling temperature at 100°C for 2 hours); an amino-modified nanofiber membrane with a thickness of 60 μm (such as Figure 2 shown).

[0051] Example 2

[0052] This embodiment provides an application of an aminated nanofiber membrane in pre-treating radioactive wastewater.

[0053] The aminated nanofiber membrane used in this embodiment is the aminated nanofiber membrane prepared in Example 1, and its specific application is as follows:

[0054] 1L of waste liquid (containing 1wt% insoluble matter and 100ppm chromium metal ions) was filtered through an amino nanofiber membrane with a thickness of 60μm; during the filtration process, the temperature was room temperature, the pressure was normal pressure, and the flow rate was 0.5m 3 / h.

[0055] The experimental results show that after being treated with the amino nanofiber membrane, the content of insoluble matter in the waste liquid is reduced to 0.02wt%, and the content of chromium metal ions is reduced to 70ppm.

[0056] Example 3

[0057] This embodiment provides a method for preparing an amino nanofiber membrane, which specifically includes the following steps:

[0058] (S1) dissolving 75 g of polyacrylonitrile in 50 g of N,N-dimethylacetamide to prepare a nanofiber precursor solution;

[0059] Dissolve chitosan, glutaraldehyde and acetic acid in deionized water and mix well to obtain a chitosan solution (in the chitosan solution, the mass fraction of chitosan is 10%, the mass fraction of glutaraldehyde is 2%, and the mass fraction of acetic acid is 4%);

[0060] (S2) injecting the nanofiber precursor solution prepared in step (S1) into the inner cylinder of the coaxial injection device for electrospinning (the injection speed is 3 mL / h), and injecting the chitosan solution prepared in step (S1) into the outer cylinder (the injection speed is 3 mL / h), the needle diameter of the electrospinning coaxial injection device is 1 mm, the distance between the fiber membrane collecting plate and the needle is 15 cm, the high voltage power supply voltage is 20 kV, and a nanofiber membrane with a core-shell structure having a thickness of 55 μm is prepared (wherein the diameter of the nanofiber is 500-900 μm);

[0061] (S3) subjecting the nanofiber membrane with a core-shell structure prepared in step (S2) to an oxidative pretreatment to prepare a pretreated nanofiber membrane with a thickness of 55 μm;

[0062] Among them, during the oxidation pretreatment process, the temperature is 150°C and the time is 2h;

[0063] (S4) dissolving thiourea and epichlorohydrin in an acetone solution to obtain a thiourea solution (in the thiourea solution, the mass fraction of thiourea is 2%, and the mass fraction of epichlorohydrin is 1%);

[0064] The pretreated nanofiber membrane prepared in step (S3) was then placed in a thiourea solution for functional group grafting modification (controlling the temperature at 80°C for 4 hours), followed by drying (controlling the temperature at 100°C for 2 hours); an amino-modified nanofiber membrane with a thickness of 55 μm was prepared.

[0065] Example 4

[0066] This embodiment provides an application of an aminated nanofiber membrane in pre-treating radioactive wastewater.

[0067] The aminated nanofiber membrane used in this embodiment is the aminated nanofiber membrane prepared in Example 3, and its specific application is as follows:

[0068] 1L of waste liquid (containing 1wt% insoluble matter and 100ppm chromium metal ions) was filtered through an amino nanofiber membrane with a thickness of 55μm; during the filtration process, the temperature was room temperature, the pressure was normal pressure, and the flow rate was 0.4m 3 / h.

[0069] The experimental results show that after being treated with the amino nanofiber membrane, the content of insoluble matter in the waste liquid is reduced to 0.015wt%, and the content of chromium metal ions is reduced to 60ppm.

[0070] Example 5

[0071] This embodiment provides a method for preparing an amino nanofiber membrane, which specifically includes the following steps:

[0072] (S1) dissolving 75 g of polyacrylonitrile in 50 g of N,N-dimethylacetamide to prepare a nanofiber precursor solution;

[0073] Dissolve chitosan, glutaraldehyde and acetic acid in deionized water and mix well to obtain a chitosan solution (in the chitosan solution, the mass fraction of chitosan is 10%, the mass fraction of glutaraldehyde is 2%, and the mass fraction of acetic acid is 4%);

[0074] (S2) injecting the nanofiber precursor solution prepared in step (S1) into the inner cylinder of the coaxial injection device of the electrospinning method (the injection speed is 3 mL / h), and injecting the chitosan solution prepared in step (S1) into the outer cylinder (the injection speed is 3 mL / h), the needle diameter of the electrospinning coaxial injection device is 1 mm, the distance between the fiber membrane collecting plate and the needle is 15 cm, the high voltage power supply voltage is 20 kV, and a nanofiber membrane with a core-shell structure having a thickness of 60 μm is prepared (wherein the diameter of the nanofiber is 500 to 900 μm);

[0075] (S3) subjecting the nanofiber membrane with a core-shell structure prepared in step (S2) to an oxidative pretreatment to prepare a pretreated nanofiber membrane with a thickness of 60 μm;

[0076] Among them, during the oxidation pretreatment process, the temperature is 150°C and the time is 2h;

[0077] (S4) dissolving thiourea and epichlorohydrin in an acetone solution to obtain a thiourea solution (in the thiourea solution, the mass fraction of thiourea is 4%, and the mass fraction of epichlorohydrin is 2%);

[0078] The pretreated nanofiber membrane prepared in step (S3) is then placed in a thiourea solution for functional group grafting modification (controlling temperature at 120°C for 6 hours), followed by drying (controlling temperature at 120°C for 2 hours); an amino-modified nanofiber membrane with a thickness of 60 μm is prepared.

[0079] Example 6

[0080] This embodiment provides an application of an aminated nanofiber membrane in pre-treating radioactive wastewater.

[0081] The aminated nanofiber membrane used in this embodiment is the aminated nanofiber membrane prepared in Example 5, and its specific application is as follows:

[0082] 1L of waste liquid (containing 1wt% insoluble matter and 100ppm chromium metal ions) was filtered through an amino nanofiber membrane with a thickness of 60μm; during the filtering process, the temperature was room temperature, the pressure was normal pressure, and the flow rate was 0.4m 3 / h.

[0083] The experimental results show that after being treated with the amino nanofiber membrane, the content of insoluble matter in the waste liquid is reduced to 0.01wt%, and the content of chromium metal ions is reduced to 55ppm.

[0084] Comparative Example 1

[0085] This comparative example provides a method for preparing an amino nanofiber membrane, which specifically comprises the following steps:

[0086] (S1) dissolving 75 g of polyacrylonitrile in 50 g of N,N-dimethylacetamide to prepare a nanofiber precursor solution;

[0087] Dissolve chitosan, glutaraldehyde and acetic acid in deionized water and mix well to obtain a chitosan solution (in the chitosan solution, the mass fraction of chitosan is 10%, the mass fraction of glutaraldehyde is 2%, and the mass fraction of acetic acid is 4%);

[0088] (S2) injecting the nanofiber precursor solution and chitosan solution prepared in step (S1) into the inner cylinder of the coaxial injection device for electrospinning, the propulsion speed of the solution injection is 3 mL / h, the needle diameter of the electrospinning coaxial injection device is 1 mm, the distance between the fiber membrane collecting plate and the needle is 15 cm, the high voltage power supply voltage is 20 kV, and a nanofiber membrane with a thickness of 50 μm is prepared (wherein the diameter of the nanofiber is 500 to 900 μm);

[0089] (S3) subjecting the nanofiber membrane prepared in step (S2) to an oxidative pretreatment to prepare a pretreated nanofiber membrane having a thickness of 50 μm;

[0090] Among them, during the oxidation pretreatment process, the temperature is 150°C and the time is 2h;

[0091] (S4) dissolving thiourea and epichlorohydrin in an acetone solution to obtain a thiourea solution (in the thiourea solution, the mass fraction of thiourea is 4%, and the mass fraction of epichlorohydrin is 2%);

[0092] The pretreated nanofiber membrane prepared in step (S3) was then placed in a thiourea solution for functional group grafting modification (controlling temperature at 120°C for 6 hours), followed by drying (controlling temperature at 120°C for 2 hours); an amino-modified nanofiber membrane with a thickness of 55 μm was prepared.

[0093] Comparative Example 2

[0094] This comparative example provides an application of an amino nanofiber membrane in pre-treating radioactive wastewater. (Non-core-shell structure)

[0095] The aminated nanofiber membrane used in this comparative example is the aminated nanofiber membrane prepared in Comparative Example 1, and its specific application is as follows:

[0096] 1L of waste liquid (containing 1wt% insoluble matter and 100ppm chromium metal ions) was filtered through an amino nanofiber membrane with a thickness of 55μm; during the filtration process, the temperature was room temperature, the pressure was normal pressure, and the flow rate was 0.4m 3 / h.

[0097] The experimental results show that after treatment with the amino nanofiber membrane, the content of insoluble matter in the waste liquid is 0.05wt%, and the content of chromium metal ions is 80ppm. Since only part of the chitosan in Example 1 is amino-modified to achieve functional group grafting, the adsorption energy of chromium metal ions is reduced.

[0098] Comparative Example 3

[0099] This comparative example provides a method for preparing a nanofiber membrane with a core-shell structure, which specifically comprises the following steps:

[0100] (S1) dissolving 75 g of polyacrylonitrile in 50 g of N,N-dimethylacetamide to prepare a nanofiber precursor solution;

[0101] Dissolve chitosan, glutaraldehyde and acetic acid in deionized water and mix well to obtain a chitosan solution (in the chitosan solution, the mass fraction of chitosan is 10%, the mass fraction of glutaraldehyde is 2%, and the mass fraction of acetic acid is 4%);

[0102] (S2) The nanofiber precursor solution prepared in step (S1) is injected into the inner cylinder of the coaxial injection device for electrospinning (the injection speed is 3 mL / h), and the chitosan solution prepared in step (S1) is injected into the outer cylinder (the injection speed is 3 mL / h). The diameter of the needle of the electrospinning coaxial injection device is 1 mm, the distance between the fiber membrane collecting plate and the needle is 15 cm, the voltage of the high-voltage power supply is 20 kV, and a nanofiber membrane with a thickness of 55 μm and a core-shell structure is prepared (wherein the diameter of the nanofiber is 500-900 μm).

[0103] Comparative Example 4

[0104] This comparative example provides an application of a nanofiber membrane with a core-shell structure in pre-treating radioactive wastewater.

[0105] (Not amino modified)

[0106] The nanofiber membrane with a core-shell structure used in this comparative example is the nanofiber membrane with a core-shell structure prepared in Comparative Example 3, and its specific application is as follows:

[0107] 1L of waste liquid (containing 1wt% insoluble matter and 100ppm chromium metal ions) was filtered through a 55μm thick nanofiber membrane with a core-shell structure; during the filtration process, the temperature was room temperature, the pressure was normal pressure, and the flow rate was 0.4m 3 / h.

[0108] The experimental results show that after being treated with the nanofiber membrane with a core-shell structure, the content of insoluble matter in the waste liquid is 0.02wt%, and the content of chromium metal ions is 90ppm.

[0109] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the explanation of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing an amino nanofiber membrane, characterized in that: The following steps are involved: (S1) electrospinning the nanofiber precursor solution and the chitosan solution using a coaxial jet device for electrospinning to obtain a nanofiber membrane with chitosan coated on the outer surface of the nanofiber; (S2) subjecting the nanofiber membrane prepared in step (S1) to oxidative pretreatment to obtain a pretreated nanofiber membrane; (S3) placing the pretreated nanofiber membrane prepared in step (S2) in a thiourea solution for functional group grafting modification, and drying to obtain an aminated nanofiber membrane; The amino nanofiber membrane refers to a nanofiber membrane with a core-shell structure in which the outer chitosan layer is grafted with amino functional groups.

2. The method for preparing an aminated nanofiber membrane according to claim 1, characterized in that: In step (S1), a nanofiber precursor solution is prepared by mixing N,N-dimethylacetamide and fibers; Wherein, the fiber is polyacrylonitrile, and the mass ratio of N,N-dimethylacetamide to polyacrylonitrile is 1-2:1-2; The chitosan solution is prepared by mixing chitosan, glutaraldehyde, water and acetic acid, wherein the chitosan solution contains chitosan with a mass fraction of 1-10%, glutaraldehyde with a mass fraction of 1-5% and acetic acid with a mass fraction of 2-4%.

3. The method for preparing an aminated nanofiber membrane according to claim 1, characterized in that: In step (S1), the electrospinning coaxial injection device adopts a double-layer cylinder design, the inner cylinder is injected with the nanofiber precursor solution, and the outer cylinder is injected with the chitosan solution; The propulsion speed of the nanofiber precursor solution injection is 1-10 mL / h, and the propulsion speed of the chitosan solution injection is 1-10 mL / h; the diameter of the needle in the electrospinning coaxial injection device is 0.1-5 mm.

4. The method for preparing an aminated nanofiber membrane according to claim 1, characterized in that: In step (S1), during the electrospinning process, the receiving distance is 10 to 30 cm and the voltage is 10 to 25 kV.

5. The method for preparing an aminated nanofiber membrane according to claim 1, characterized in that: In step (S2), during the oxidation pretreatment, the temperature is 100 to 250° C. and the time is 1 to 6 hours.

6. The method for preparing an aminated nanofiber membrane according to claim 1, characterized in that: In step (S3), the thiourea solution is prepared by mixing thiourea, epichlorohydrin and acetone; Wherein, in the thiourea solution, the mass fraction of thiourea is 1-4%, and the mass fraction of epichlorohydrin is 1-2%.

7. The method for preparing an aminated nanofiber membrane according to claim 1, characterized in that: In step (S3), during the functional group grafting modification process, the temperature is 60 to 100° C. and the time is 1 to 6 hours.

8. The method for preparing an aminated nanofiber membrane according to claim 1, characterized in that: In step (S3), during the drying process, the temperature is 60 to 200° C. and the time is 1 to 6 hours.

9. An amino nanofiber membrane, characterized in that: It is prepared by the method according to any one of claims 1 to 8.

10. Use of the amino nanofiber membrane as claimed in claim 9 in pre-treatment of radioactive waste liquid.

Images