CN114570336B - Metal adsorption fiber membrane and preparation and application thereof - Google Patents

Metal adsorption fiber membrane and preparation and application thereof Download PDF

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CN114570336B
CN114570336B CN202011374347.4A CN202011374347A CN114570336B CN 114570336 B CN114570336 B CN 114570336B CN 202011374347 A CN202011374347 A CN 202011374347A CN 114570336 B CN114570336 B CN 114570336B
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pan
fiber membrane
metal
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CN114570336A (en
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陈仰
蒋兰英
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Central South University
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    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B01D15/08—Selective adsorption, e.g. chromatography
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0093—Chemical modification
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/34—Polyvinylidene fluoride
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    • B01D71/06—Organic material
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B01D71/42—Polymers of nitriles, e.g. polyacrylonitrile
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    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
    • B01J20/28033—Membrane, sheet, cloth, pad, lamellar or mat
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J20/3085—Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/288—Treatment of water, waste water, or sewage by sorption using composite sorbents, e.g. coated, impregnated, multi-layered
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
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    • B01D—SEPARATION
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    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/24—Mechanical properties, e.g. strength
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
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Abstract

The invention belongs to the technical field of heavy metal sewage treatment, and particularly relates to a heavy metal adsorption fiber membrane which is formed by interlacing and weaving PVDF@PAN composite fibers; the PVDF@PAN composite fiber comprises PVDF inner core fiber and a PAN shell layer coated on the PVDF inner core fiber, wherein the outer surface of the PAN shell layer is a functional layer subjected to oximation and/or carboxylation modification treatment. In addition, the invention also provides a preparation method of the fiber membrane. The invention provides PVDF@PAN composite fibers with a brand new structure and a fiber film material obtained by interweaving the fibers. The membrane material disclosed by the invention has excellent metal adsorption performance, and in addition, has excellent mechanical performance and cyclical adsorption stability.

Description

Metal adsorption fiber membrane and preparation and application thereof
Technical Field
The invention relates to the technical field of environmental management, in particular to a fiber membrane material for adsorbing metal ions.
Background
The fiber membrane material has a porous structure with multiple communication channels due to high porosity, and is an ideal adsorption material. The treatment of wastewater containing metal ions by using a fiber membrane is receiving extensive attention from researchers at home and abroad. The active sites of the membrane material are positioned on the surface or the wall of the membrane, so that the contact between the material and metal ions can be greatly increased, the reaction time is shortened, the reaction flow is shortened, and the volume of the reactor is controlled. The methods commonly used to prepare fibrous membranes include: stretching, template synthesis, phase separation, self-assembly and electrospinning, which is the only method that can continuously prepare nanofiber membranes.
At present, the electrostatic spinning preparation of the nanofiber has the advantages of simplicity in operation, adjustable structure, high porosity, large specific surface area and the like, and is widely applied to the fields of water treatment and the like. Among them, amidoxime-based nanofiber membranes have high affinity and selectivity for metal ions, which are particularly prominent in terms of metal adsorption separation, but the problem of poor mechanical strength and durability presents challenges for large-scale applications. A large number of researchers find that with the increase of the surface modification and oximation degree, the phenomena of shrinkage, agglomeration, embrittlement and the like of the fiber inevitably occur, and the chemical modification causes irreversible damage to the material, so that the amidoxime nanofiber prepared at present is difficult to combine the adsorption performance and the mechanical strength.
Aiming at the problems, the prior art provides some solution ideas, mainly comprising: hot pressing, solvent annealing treatment, non-woven fabric support and other methods. The methods have respective defects, such as heating to a temperature above 90 ℃ in hot pressing treatment and hot pressing the fiber membrane, which is wasteful for the current energy to the large environment; the solvent annealing treatment is carried out by generating solvent vapor to treat the fiber membrane, and the solvent vapor definitely causes harm to people and the environment; nonwoven fabrics have good mechanical properties, however, how to attach the fibrous membrane to the surface more firmly is still a breakthrough aspect.
Disclosure of Invention
In order to solve the problem that the adsorption performance and the structural stability of the existing metal adsorption fiber membrane (metal adsorption membrane) are difficult to be compatible, the first aim of the invention is to provide a metal adsorption fiber membrane with a brand new structure, and to provide a fiber membrane material with good metal adsorption performance and mechanical stability.
The second aim of the invention is to provide a preparation method of the metal adsorption fiber membrane, which aims to prepare the fiber membrane material with excellent mechanical property and metal adsorption property.
A third object of the present invention is to provide a use of the metal-adsorbing fiber membrane in metal adsorption.
For a metal adsorption fiber membrane, in order to obtain good metal adsorption performance, the membrane is usually required to be structurally modified, however, functional modification can etch and reconstruct the surface of the fiber structure to a great extent, so that the technical problems of collapse, shrinkage, agglomeration, embrittlement and the like of the fiber structure are easily caused, the structural integrity and mechanical performance of the membrane are seriously affected, the adsorption performance, structural stability and adsorption stability of the membrane are greatly affected, and the following improvement scheme is provided aiming at the technical problems:
a metal adsorption fiber membrane is formed by interlacing and braiding PVDF@PAN composite fibers;
the PVDF@PAN composite fiber comprises PVDF inner core fiber and a PAN shell layer coated on the PVDF inner core fiber, wherein the outer surface of the PAN shell layer is a functional layer subjected to oximation and/or carboxylation modification treatment.
The invention provides PVDF@PAN composite fibers with a brand new structure and a fiber film material obtained by interweaving the fibers. The membrane material disclosed by the invention has excellent metal adsorption performance, and in addition, has excellent mechanical performance and cyclical adsorption stability.
The synergy of the material component characteristics of the fiber and the core-shell (PAN shell) -shell (active layer on the outer surface of PAN) double-shell structure characteristics of the fiber membrane material is the key for improving the metal adsorption performance, the membrane structural stability and the adsorption stability. It has also been found that the PAN is composited on the PVDF surface without gaps between the two, and that the PAN is functionally modified on the outer surface of the PAN, and that the active layer does not extend through the entire PAN layer, thus contributing to improved metal adsorption and mechanical structural stability.
Preferably, the PVDF core fiber has a diameter of 0.36-0.45 μm.
The thickness of the PAN shell layer is 0.24-0.32 mu m.
Preferably, in the outer layer PAN, the ratio of the functional layer (referred to as the volume ratio) is 50% -85%; preferably 70 to 80%.
The invention also provides a preparation method of the metal adsorption fiber membrane, which comprises the following steps:
step (1):
obtaining a PVDF-dissolved solution A and a PAN-dissolved solution B; taking the solution A as core liquid and the solution B as outer layer casting film liquid, and carrying out coaxial electrostatic spinning treatment to obtain a PVDF@PAN base film; the concentration of PVDF in the solution A is 6-12wt%; the concentration of PAN in solution B is 10-14wt%;
the voltage of the electrostatic spinning process is 13KV to 15KV;
step (2):
performing functional modification treatment on the outer surface of the PAN of the PVDF@PAN base film, and then performing freeze drying to obtain the PVDF@PAN base film;
the functionalization is oximation and/or carboxylation.
The invention researches find that in order to successfully construct the fiber membrane with the double-shell structure and improve the structural stability and the adsorption performance of the fiber membrane, the problems of the composite morphology of PVDF and PAN and the activity modification degree of the outer surface of the PAN need to be properly solved. Through researches, the coaxial electrostatic mode means provided by the invention is adopted, and the voltage, the modification treatment mechanism and the freeze drying means in the electrostatic mode process are combined to control, so that synergy can be generated, the contact compactness of a PAN interface and a PVDF interface can be controlled, the modification treatment degree is controlled, and the double-shell structure is maintained, so that the fiber membrane with the double-shell structure and excellent structural stability and metal adsorption performance can be prepared unexpectedly. In addition, the fiber membrane prepared by the preparation method has good appearance and no broken wire chain beads.
According to the invention, PVDF is sprayed out of the core hole by adopting the coaxial electrostatic spinning needle head, and PAN is sprayed out of the outer hole, so that PVDF (polyvinylidene fluoride) @ PAN base film which takes PVDF as an inner core fiber and uniformly coats PAN on the surface of the inner core fiber is obtained, and researches also find that the surface compounding state of PVDF and PAN can be improved further based on the cooperative control of concentration and voltage in the spinning solution, so that the gap formed by interface separation of the PVDF and the PAN is avoided, and the metal adsorption performance of the fiber film is further improved.
According to the method, the base film is prepared by matching materials with the mass in the film casting liquid and adopting a coaxial electrostatic spinning method, and the flexible aminated fiber film with good appearance, high strength and excellent adsorption performance is obtained by combining a freeze drying method.
Preferably, the PVDF has a molecular weight of 15 to 25 ten thousand; preferably, the PVDF is PVDF6020.
Preferably, the solvent in the solution A is a solvent capable of dissolving PVDF, preferably at least one of N, N-dimethylacetamide (DMAc) and N, N-Dimethylformamide (DMF);
research shows that the PAN film casting solution is matched with the PVDF film casting solution, which is beneficial to fibers with complete core-shell structure; however, when the PVDF concentration is too high (e.g., above the upper limit), the viscosity of the casting solution increases, which may affect the electrospinning process and affect the properties of the fiber film.
Preferably, the PVDF content in the solvent a is 10 to 12wt.%. In the present invention, the balance in solution A is solvent.
The preparation mode of the PVDF-containing solution A is as follows: adding PVDF into solvent such as N, N-dimethylacetamide, and mixing at 40-60deg.C.
Preferably, the PAN has a molecular weight of 13-16 ten thousand; more preferably 14 to 15 ten thousand.
Preferably, the solvent in the solution B is a solvent capable of dissolving PAN, preferably at least one of N, N-dimethylacetamide and N, N-dimethylformamide.
Preferably, the PAN-containing solution B is prepared by the following steps: adding PAN into solvent such as N, N-dimethylacetamide, and mixing at 40-60deg.C.
Preferably, the PAN content in the solvent B is 11-13 wt.%; further preferably 11.5 to 12.5wt.%. In the present invention, the balance of the solution B is solvent. It was found that, in the preferred proportions, the strength and the adsorption performance of the fibrous membrane are unexpectedly improved in cooperation with other conditions, and in particular, the strength and the retention of the adsorption performance after the circulation thereof can be further improved.
The invention researches that the accurate control of the voltage is beneficial to the smooth performance of the spinning process, can improve the form of the base film and is beneficial to improving the metal adsorption performance and the structural stability of the obtained fiber film. However, when the voltage is too high, electrostatic stretching is too large, resulting in separation of the inner and outer layers, and when the voltage is too small, the electrostatic force is insufficient to draw the casting solution into fibers.
Preferably, in the electrostatic mode process, the spinning voltage is 13.5-14.5 KV; further preferably 14 to 14.5KV. It was found that at the preferred voltages, the metal adsorption properties and the structural stability of the noteworthy fibrous membranes could be surprisingly further improved.
According to the invention, on the basis of controlling the proportion and voltage of the casting solution, the control of flow speed regulation is further matched, so that the nanofiber membrane with small fiber diameter, large hole volume and complete core-shell morphology can be further prepared.
Preferably, in the electrostatic mode, the distance between the coaxial spinneret and the receiving plate is 14-16cm; further preferably 15cm. The flow rate of PAN is 0.5-1mL/h; preferably 0.5-0.6 mL/h, the flow rate of PVDF is 0.5-1mL/h; preferably 0.5 to 0.6mL/h.
In the preferred test process of the invention, PAN and PVDF casting solution are respectively filled into a syringe, a catheter is used for connecting a coaxial spinning needle, the inner aperture of the needle is 374 mu m, the concentric aperture is 534 mu m, the distance between the needle and a roller is adjusted to be 15cm, 14kv high-voltage static electricity is connected to the needle, the flow rate of the casting solution is controlled to be 0.5-1mL/h, the winding speed of the roller is controlled to be 300-450rn/min, and the base film is obtained after the continuous time is 1-3 h.
In the invention, under the control of the spinning means and the conditions, the surface modification treatment means is further controlled, so that the synergy is further generated, and the prepared fiber film has good metal adsorption performance and structural stability.
Preferably, the step of oximating the surface is:
placing the PVDF@PAN base film into a modified solution a dissolved with hydroxylamine and alkali, and carrying out surface oximation treatment;
preferably, the alkali is at least one of anhydrous sodium carbonate and anhydrous sodium bicarbonate;
in the modified solution a, the molar ratio of hydroxylamine to alkali is 1:1-2.5:1;
preferably, the molar concentration of hydroxylamine in the modifying solution a is 0.4 to 0.6mol/L;
preferably, the temperature of the oximation modification process is 60-80 ℃;
preferably, the time of the oximation modification process is 60-180min; more preferably 110 to 140 minutes.
The carboxylated surface treatment comprises the following steps:
placing the PVDF@PAN base film into a modification solution b dissolved with alkali, and carrying out surface carboxylation treatment;
preferably, the alkali is at least one of sodium hydroxide and potassium hydroxide;
preferably, in the modifying solution b, the molar concentration of the alkali is 1 to 5mol/L;
preferably, the temperature of the oximation modification process is 60-80 ℃;
preferably, the time for the oximation modification process is 30-120min.
In the present invention, the modified material is obtained by washing (washing the modified material with water, for example) after the modification treatment, and freeze-drying.
Preferably, the time of freeze-drying is 4-7 hours.
In the present invention, the molding may be performed under low temperature conditions, for example, at-20 to 5℃before the freeze-drying.
According to a preferred scheme, the method comprises the following steps of: preparing a base film by coaxial electrostatic spinning of PAN casting film liquid and PVDF casting film liquid, and performing amidoxime modification and freeze drying to obtain a flexible amidoxime fiber film; the PAN casting solution comprises 10-14wt% of PAN (preferably 11.5-12.5%), the balance being a polar solvent, and the PVDF casting solution comprises 6-12wt% of PVDF (preferably 10-12%), and the balance being a solvent; the voltage in the spinning process is 13.5KV to 14.5KV.
The amidoxime functional groups have excellent ion exchange capacity and selectivity, and fiber damage caused by the amidoxime functional groups is irreversible. The invention takes PAN as an outer layer and PVDF as an inner layer for the first time, and prepares the core-shell fiber membrane by coaxial electrostatic spinning of the two solutions. The inventor finds that after PVDF is added as an inner layer material, the mechanical strength of the fiber after oximation reaction basically maintains the state before oximation, and the appearance of the fiber is furthest reserved by freeze drying, which has great significance for improving the service performance of the oximation fiber material. Meanwhile, the inventor discovers through a great deal of researches that the flexible aminated fiber membrane with good appearance, high strength and good lead ion adsorption performance can be unexpectedly prepared by matching the membrane casting solution with the membrane forming mode.
The invention also provides application of the metal adsorption fiber membrane, which is used for adsorbing lead metal ions;
preferably, a method for adsorbing lead metal ions (Pb 2+ )。
Advantageous effects
1. The invention provides a metal adsorption fiber membrane with a brand new double-shell structure, and the invention discovers that the performance of the membrane material in metal adsorption can be unexpectedly improved based on the cooperative control of the substances and the structure, for example, the adsorption performance of metal can be improved, the adsorption stability of the metal can be improved, the structural stability of the material can be improved, and the attenuation degree of mechanical properties can be controlled.
2. The invention also provides a preparation method of the metal adsorption fiber membrane, which uses PVDF as core liquid, PAN as external casting film liquid, adopts a coaxial electrostatic mode means, and combines the voltage, the modification treatment mechanism and the combined control of the freeze drying means in the processes of the spinning solution and the electrostatic mode, so that synergy can be generated, the contact compactness of the PAN and the PVDF interface can be controlled, and the modification treatment degree can be controlled, thus the fiber membrane with the double-shell structure and excellent structural stability and metal adsorption performance can be prepared unexpectedly.
3. In the invention, by combining the characteristics of the fiber membrane with the double-shell structure, the amidoxime modification treatment is further preferably adopted, so that the appearance of the flexible nanofiber membrane can be effectively kept, and the amidoxime functional group not only has an excellent chelating effect on metal ions, but also has unique selectivity, and the inventor discovers that the core-shell fiber structure can keep the appearance of the amidoxime fiber, maintain the original strength, improve the service performance of the fiber membrane, and in addition, the flexible amination membrane still has very good metal ion capturing capability and selectivity.
4. The preparation method of the invention has simple operation, good film forming performance, complete core-shell morphology, and the strength of the modified material is not changed to 80 percent before modification, and the composite fiber film has the following properties on Pb 2+ The adsorption capacity of the film reaches 89.3mg/g, the adsorption capacity of 45% of the original film is still maintained after the film is repeatedly used for 5 times, the mechanical strength of the film is unchanged after the film is repeatedly used for a plurality of times, the original appearance is basically maintained, and the film has the prospect of industrial application.
Drawings
FIG. 1 is a TEM image and SEM image of the composite nanofiber membrane prepared in example 2; wherein a is a spinning diagram for preparing a fiber membrane, b is a TEM diagram for preparing the fiber, and c is an SEM diagram; as can be seen from figure a, there is a droplet build up at the tip of the needle, which results in an increase in beading of the fibre surface (as shown in figures b and c) and a decrease in fibre structural strength.
FIG. 2 is a TEM image and SEM image of the composite nanofiber membrane prepared in example 1; wherein a is a spinning diagram for preparing a fiber membrane, b is a TEM diagram for preparing the fiber, and c is an SEM diagram; as can be seen from figure a, the spinning process is uniform and stable, forming a complete core-shell structured fibrous membrane (as shown in figures b and c).
FIG. 3 is a TEM image and SEM image of the composite nanofiber membrane prepared in example 3; wherein a is a spinning diagram for preparing a fiber membrane, b is a TEM diagram for preparing the fiber, and c is an SEM diagram; it can be seen from figure a that two taylor cones are formed near the tip, which means that the inner and outer layers separate to form a single layer structure (as shown in figures b and c, there is a core-shell separation), resulting in a decrease in the strength of the modified fibrous membrane.
FIG. 4 is a graph of the macro morphology of the composite nanofiber membranes prepared in example 1 and comparative example 1; wherein a is a fibrous membrane macro-morphology graph of comparative example 1, it can be seen that the fibrous membrane without the PVDF supporting layer has serious shrinkage after modification; b is a graph of the macroscopic morphology of the fibrous membrane of example 1 and c is a graph of the flexibility of example 1, it being seen that the fibrous membrane with core-shell structure maintains the complete morphology and structural stability.
Detailed Description
PAN: the molecular weight is 13-15 ten thousand.
PVDF: model 6020.
With a coaxial needle, the inside diameter of the bore in the needle was 374 μm and the inside diameter of the outer bore was 534 μm.
Example 1
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 12wt% and 88wt% at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting solution obtained in the step (1) and the step (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 14kv high-voltage static electricity at the needle head, enabling the flow rate of the casting solution to be 0.5mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
(4) Preparation of composite nanofiber membranes
And (3) treating the base film obtained in the step (3) with 100mL of a mixed solution of hydroxylamine hydrochloride and anhydrous sodium carbonate (wherein the molar concentration of the hydroxylamine is 0.5M and the molar ratio of the hydroxylamine to the anhydrous sodium carbonate is 2:1) for 2 hours at 70 ℃ to obtain the amidoxime nanofiber film. Freezing and forming the obtained modified fiber membrane at the temperature of minus 20 ℃, and then freezing and vacuum drying to obtain the modified fiber membrane; the volume ratio of the modified layer is 80%.
(5) Amidoxime fiber membrane for adsorbing Pb in water 2+
Adding the fibrous membrane to lead (Pb) 2+ ) In (2) the solution was subjected to shaking adsorption for 10 hours, the supernatant was collected, the concentration of the solution before and after the adsorption reaction was measured by ICP-OES, and Pb was calculated by the fiber membrane 2+ Is used as the adsorption amount of the catalyst.
The test shows that the mechanical strength of the fiber membrane before modification (referred to as a base membrane) is 3.567MPa, the mechanical strength of the composite fiber membrane after modification (referred to as the composite membrane after modification in the step 4) is 80% before modification, the lead ion adsorption amount in the aqueous solution is 89.3mg/g, and after repeating for 5 times, the lead ion adsorption amount is 40.2mg/g, and the mechanical strength is 79% before modification.
Example 2
The main difference compared to example 1 is that the voltage of the spinning process is adjusted:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 12wt% and 88wt% at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting solution obtained in the step (1) and the step (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 13kv high-voltage static electricity at the needle head, enabling the flow rate of the casting solution to be 0.5mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
(4) Preparation of composite nanofiber membrane (same as in example 1)
And (3) treating the base film obtained in the step (3) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film. The resulting modified fiber film was freeze-molded at-20℃and then dried by freeze vacuum.
(5) Amidoxime fiber membrane for adsorbing Pb in water 2+ (same as in example 1)
Adding the fiber membrane into a lead-containing aqueous solution, oscillating and adsorbing for 10 hours, taking supernatant in the solution, measuring the concentration of the solution before and after the adsorption reaction by ICP-OES, and calculating the adsorption quantity of the fiber membrane to Pb < 2+ >.
The mechanical strength of the fiber film before modification is 3.567MPa (the strength before modification is similar to that of the embodiment 1), the mechanical strength of the composite fiber film after modification is 55% before modification, the lead ion adsorption amount in the aqueous solution is 85.7mg/g, and after repeating for 5 times, the lead ion adsorption amount is 39.6mg/g, and the mechanical strength is 26% before modification. As compared with the examples, the adsorption performance is reduced, and the structural stability and the circulation stability are reduced.
Example 3
The main difference compared to example 1 is that the voltage of the spinning process is adjusted:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 12wt% and 88wt% at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting film solutions obtained in the steps (1) and (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 15kv high-voltage static electricity at the needle head, enabling the flow rate of the casting film solution to be 0.5mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
(4) Preparation of composite nanofiber membrane (same as in example 1)
And (3) treating the base film obtained in the step (3) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film. The resulting modified fiber film was freeze-molded at-20℃and then dried by freeze vacuum.
(5) Amidoxime fiber membrane for adsorbing Pb in water 2+ (same as in example 1)
Adding the fiber membrane into a lead-containing aqueous solution, oscillating and adsorbing for 10 hours, taking supernatant in the solution, measuring the concentration of the solution before and after the adsorption reaction by ICP-OES, and calculating the adsorption quantity of the fiber membrane to Pb < 2+ >.
The mechanical strength of the fiber membrane before modification is 3.61MPa, the mechanical strength of the composite fiber membrane after modification is 16% before modification, the lead ion adsorption amount in the aqueous solution is 36.6mg/g, after repeating for 5 times, the lead ion adsorption amount is 11.7mg/g, and the mechanical strength is 15% before modification. As compared with the examples, the adsorption performance is reduced, and the structural stability and the circulation stability are reduced.
Example 4
The main difference compared with example 1 is that the concentration of PAN membrane solution is controlled, specifically:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 14wt% and 86wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 12wt% and 88wt% at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting film solutions obtained in the steps (1) and (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 14kv high-voltage static electricity at the needle head, enabling the flow rate of the casting film solution to be 0.5mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
(4) Preparation of composite nanofiber membrane (same as in example 1)
And (3) treating the base film obtained in the step (3) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film. The resulting modified fiber film was freeze-molded at-20℃and then dried by freeze vacuum.
(5) Amidoxime fiber membrane for adsorbing Pb in water 2+ (same as in example 1)
Adding the fiber membrane into a lead-containing aqueous solution, oscillating and adsorbing for 10 hours, taking supernatant in the solution, measuring the concentration of the solution before and after the adsorption reaction by ICP-OES, and calculating the adsorption quantity of the fiber membrane to Pb < 2+ >.
The study found that the strength of the base film was similar to that of example 1, but the mechanical strength of the modified composite fiber film was 42% before modification, the lead ion adsorption amount in the aqueous solution was 83.2mg/g, and after repeating 5 times, the lead ion adsorption amount was 40.5mg/g, and the mechanical strength was 21% before modification. As compared with the examples, the adsorption performance is reduced, and the structural stability and the circulation stability are reduced.
Example 5
The main difference compared with example 1 is that the concentration of PAN membrane solution is controlled, specifically:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 10wt% and the weight percentage of 90wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 12wt% and 88wt% at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting film solutions obtained in the steps (1) and (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 14kv high-voltage static electricity at the needle head, enabling the flow rate of the casting film solution to be 0.5mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
(4) Preparation of composite nanofiber membrane (same as in example 1)
And (3) treating the base film obtained in the step (4) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film. The resulting modified fiber film was freeze-molded at-20℃and then dried by freeze vacuum.
(5) Amidoxime fiber membrane for adsorbing Pb in water 2+ (same as in example 1)
Adding the fiber membrane into a lead-containing aqueous solution, oscillating and adsorbing for 10 hours, taking supernatant in the solution, measuring the concentration of the solution before and after the adsorption reaction by ICP-OES, and calculating the adsorption quantity of the fiber membrane to Pb < 2+ >.
The strength of the base film was found to be similar to that of example 1, but the mechanical strength of the modified composite fiber film was 49% before modification, the lead ion adsorption amount in the aqueous solution was 73.5mg/g, and after repeating 5 times, the lead ion adsorption amount was 32.1mg/g, and the mechanical strength was 19% before modification. As compared with the examples, the adsorption performance is reduced, and the structural stability and the circulation stability are reduced.
Example 6
The main difference compared with example 1 is that the concentrations of PAN membrane solution and PVDF membrane solution are controlled, specifically:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 10wt% and 90wt% at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting film solutions obtained in the steps (1) and (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 14kv high-voltage static electricity at the needle head, enabling the flow rate of the casting film solution to be 0.5mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
(4) Preparation of composite nanofiber membrane (same as in example 1)
And (3) treating the base film obtained in the step (3) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film. The resulting modified fiber film was freeze-molded at-20℃and then dried by freeze vacuum.
(5) Amidoxime fiber membrane for adsorbing Pb in water 2+ (same as in example 1)
Adding the fiber membrane into lead-containing water solution, oscillating and adsorbing for 10h, collecting supernatant, measuring concentration before and after adsorption reaction by ICP-OES, and calculating Pb content of the fiber membrane 2+ Is used as the adsorption amount of the catalyst.
The strength of the base film before modification was found to be similar to that of example 1, and the mechanical strength of the composite fiber film after modification was 76% before modification, the lead ion adsorption amount in the aqueous solution was 92.4mg/g, and after repeating 5 times, the lead ion adsorption amount was 50.6mg/g, and the mechanical strength was 75% before modification. The adsorption properties, structural stability and cyclic stability were found to vary little in comparison with the examples.
Example 7
The main difference compared to example 1 is that the voltage of the spinning process is adjusted, specifically:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 12wt% and 88wt% at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting film solutions obtained in the steps (1) and (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 13.5kv high-voltage static electricity at the needle head, and obtaining the base film after the casting film solutions are respectively 0.5mL/h, wherein the winding speed of the roller is 300rn/min and the duration is 2 h.
(4) Preparation of composite nanofiber membrane (same as in example 1)
And (3) treating the base film obtained in the step (3) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film. The resulting modified fiber film was freeze-molded at-20℃and then dried by freeze vacuum.
(5) Amidoxime fiber membrane for adsorbing Pb in water 2+ (same as in example 1)
Adding the fiber membrane into lead-containing water solution, oscillating and adsorbing for 10h, collecting supernatant, measuring concentration before and after adsorption reaction by ICP-OES, and calculating Pb content of the fiber membrane 2+ Is used as the adsorption amount of the catalyst.
The strength of the base film before modification was found to be similar to that of example 1, and the mechanical strength of the composite fiber film after modification was 70% before modification, the lead ion adsorption amount in the aqueous solution was 80.3mg/g, and after repeating 5 times, the lead ion adsorption amount was 44.2mg/g, and the mechanical strength was 58% before modification. As compared with the examples, the adsorption performance, the structural stability and the cyclic stability are not changed greatly, but the strength attenuation after the cyclic treatment is obvious compared with the example 1.
Example 8
The main difference compared to example 1 is that the voltage of the spinning process is adjusted, specifically:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 12wt% and 88wt% at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting film solutions obtained in the steps (1) and (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 14.5kv high-voltage static electricity at the needle head, and obtaining the base film after the casting film solutions are respectively 0.5mL/h, wherein the winding speed of the roller is 300rn/min and the duration is 2 h.
(4) Preparation of composite nanofiber membrane (same as in example 1)
And (3) treating the base film obtained in the step (3) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film. The resulting modified fiber film was freeze-molded at-20℃and then dried by freeze vacuum.
(5) Amidoxime fiber membrane for adsorbing Pb in water 2+ (same as in example 1)
Adding the fiber membrane into lead-containing water solution, oscillating and adsorbing for 10h, collecting supernatant, measuring concentration before and after adsorption reaction by ICP-OES, and calculating Pb content of the fiber membrane 2+ Is used as the adsorption amount of the catalyst.
The strength of the base film before modification was found to be similar to that of example 1, and the mechanical strength of the composite fiber film after modification was 74% before modification, the lead ion adsorption amount in the aqueous solution was 85.6mg/g, and after repeating 5 times, the lead ion adsorption amount was 50.4mg/g, and the mechanical strength was 72% before modification. The adsorption properties, structural stability and cyclic stability were found to vary little in comparison with the examples.
Comparative example 1
The only difference compared to example 1 is that the double shell structure according to the invention (without PVDF as inner support) is not constructed, as follows:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of base film
And (3) filling the casting solution obtained in the step (1) into a 10mL syringe, connecting a 22-gauge needle with a Teflon catheter, adjusting the distance between the needle and a roller to be 15cm, connecting 14kv high-voltage static electricity at the needle, enabling the flow rate of the casting solution to be 0.5mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
(3) Composite nanofiber membrane modification (same as in example 1)
And (3) treating the base film obtained in the step (2) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film.
The modified composite fiber film has serious shrinkage and embrittlement, the mechanical strength of the fiber film can not be measured, and the use value is lost, as shown in fig. 4 a. Experiments show that the oximation modification degree exceeds 35%, PAN without a core-shell structure can shrink and deform, and the oximation modification degree exceeds 80%, and the fiber membrane with the core-shell structure still maintains the complete morphology.
Comparative example 2
The difference from example 1 is that the inner layer support material was modified, specifically as follows:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of PSF solution
The PSF solution is prepared by uniformly mixing 12 weight percent of polysulfone with the molecular weight of 12 ten thousand and 88 weight percent of solvent N, N-dimethylacetamide at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting film solutions obtained in the steps (1) and (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 14kv high-voltage static electricity at the needle head, enabling the flow rate of the casting film solution to be 0.5mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
(4) Preparation of composite nanofiber membrane (same as in example 1)
And (3) treating the base film obtained in the step (3) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film.
(4) Amidoxime fiber membrane for adsorbing Pb in water 2+ (same as in example 1)
Adding the fiber membrane into a lead-containing aqueous solution, oscillating and adsorbing for 10 hours, taking supernatant in the solution, measuring the concentration of the solution before and after the adsorption reaction by ICP-OES, and calculating the adsorption quantity of the fiber membrane to Pb < 2+ >.
The mechanical strength of the modified composite fiber membrane is 62% before modification, the lead ion adsorption capacity in the aqueous solution is 73.8mg/g, and after repeating for 5 times, the lead ion adsorption capacity is 32.5mg/g, and the mechanical strength is 33% before modification. Therefore, by adopting PVDF and matching with the structure and the control of the conditions, the strength and the adsorption performance of the material can be unexpectedly improved, and the strength retention rate after multiple cycles is improved.
Comparative example 3
The difference from example 1 is mainly that the spinning mode was changed, specifically:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 12wt% and 88wt% at normal temperature.
(3) Preparation of spinning solution
Uniformly stirring the casting film liquid obtained in the steps (1) and (2) according to the volume ratio of 1:1 until a homogeneous phase solution is formed
Respectively filling the above-mentioned materials into 10mL syringes, connecting coaxial needle heads with Teflon catheter, regulating distance between needle head and cylinder to 15cm, introducing 14kv high-voltage static electricity into needle head, making flow rate of casting solution be 0.5mL/h, winding up cylinder at 300rn/min, and continuously holding for 2 hr so as to obtain the described base film.
(4) Nanofiber membrane preparation (same as in example 1)
Filling the spinning solution obtained in the step (3) into a 10mL syringe, connecting a 22-gauge needle with a Teflon catheter, adjusting the distance between the needle and a roller to be 15cm, introducing 14kv high-voltage static electricity at the needle, enabling the flow rate of the casting solution to be 1mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
In the subsequent modification experiments, the modification solution cannot infiltrate the base film, and the modification is ineffective; the desired adsorption film cannot be obtained.
Comparative example 4
The difference from example 1 is mainly that the drying system was changed, specifically:
(1) Preparation of PAN solution
The PAN solution is prepared by uniformly mixing polyacrylonitrile with 15 ten thousand molecular weight and solvent N, N-dimethylacetamide with the weight percentage of 12wt% and 88wt% at 60 ℃.
(2) Preparation of PVDF solution
The PVDF solution is prepared by uniformly mixing PVDF with the model of 6020 and solvent N, N-dimethylacetamide according to the weight percentage of 12wt% and 88wt% at normal temperature.
(3) Preparation of base film
And (3) respectively filling the casting film solutions obtained in the steps (1) and (2) into a 10mL syringe, connecting a coaxial needle head with a Teflon catheter, adjusting the distance between the needle head and a roller to be 15cm, connecting 14kv high-voltage static electricity at the needle head, enabling the flow rate of the casting film solution to be 0.5mL/h, enabling the winding speed of the roller to be 300rn/min, and continuing for 2h to obtain the base film.
(4) Preparation of composite nanofiber membrane
And (3) treating the base film obtained in the step (3) with 100mL hydroxylamine hydrochloride and anhydrous sodium carbonate at 70 ℃ for 2 hours to obtain the amidoxime nanofiber film. The resulting modified fibrous membrane was dried at 60 ℃.
(5) Amidoxime fiber membrane for adsorbing Pb in water 2+ (same as in example 1)
Adding the fiber membrane into lead-containing water solution, oscillating and adsorbing for 10h, collecting supernatant, measuring concentration before and after adsorption reaction by ICP-OES, and calculating Pb content of the fiber membrane 2+ Is used as the adsorption amount of the catalyst.
The strength before modification was found to be similar to that of example 1, but the lead ion adsorption amount in the aqueous solution of the modified composite fiber membrane was 51.7mg/g, and after repeating 5 times, the lead ion adsorption amount was 22.5mg/g. The research shows that the adsorption performance has a larger influence.

Claims (21)

1. The metal adsorption fiber membrane is characterized by being formed by interlacing and weaving PVDF@PAN composite fibers;
the PVDF@PAN composite fiber comprises PVDF inner core fiber and a PAN shell layer coated on the PVDF inner core fiber, wherein the outer surface of the PAN shell layer is a functional layer subjected to oximation and/or carboxylation modification treatment;
the metal adsorption fiber membrane is prepared through the following steps:
step (1):
obtaining a PVDF-dissolved solution A and a PAN-dissolved solution B; taking the solution A as core liquid and the solution B as outer layer casting film liquid, and carrying out coaxial electrostatic spinning treatment to obtain a PVDF@PAN base film; the concentration of PVDF in the solution A is 6-12wt%; the concentration of PAN in the solution B is 11.5-12.5wt%;
the voltage of the electrostatic spinning process is 13.5-14.5 KV;
step (2):
performing functional modification treatment on the outer surface of the PAN of the PVDF@PAN base film, and then performing freeze drying to obtain the PVDF@PAN base film;
the functionalization is oximation and/or carboxylation.
2. The metal-adsorbing fiber membrane as set forth in claim 1, wherein the PVDF core fiber has a diameter of 0.36 to 0.45 μm; the thickness of the PAN shell layer is 0.24-0.32 mu m.
3. The metal-adsorbing fiber membrane as set forth in claim 1 or 2, wherein the functional layer has a volume ratio of 50% to 85% in the outer layer PAN.
4. A method for preparing the metal-adsorbing fiber membrane according to any one of claims 1 to 3, comprising the steps of:
step (1):
obtaining a PVDF-dissolved solution A and a PAN-dissolved solution B; taking the solution A as core liquid and the solution B as outer layer casting film liquid, and carrying out coaxial electrostatic spinning treatment to obtain a PVDF@PAN base film; the concentration of PVDF in the solution A is 6-12wt%; the concentration of PAN in the solution B is 11.5-12.5wt%;
the voltage of the electrostatic spinning process is 13.5-14.5 KV;
step (2):
performing functional modification treatment on the outer surface of the PAN of the PVDF@PAN base film, and then performing freeze drying to obtain the PVDF@PAN base film;
the functionalization is oximation and/or carboxylation.
5. The method for preparing a metal-adsorbing fiber membrane according to claim 4, wherein the molecular weight of the PVDF is 15 to 25 ten thousand.
6. The method of claim 5, wherein the PVDF is PVDF6020.
7. The method of claim 4, wherein the solvent in the solution A is a solvent capable of dissolving PVDF.
8. The method for producing a metal-adsorbing fiber membrane according to claim 7, wherein the solvent in the solution A is at least one of N, N-dimethylacetamide and N, N-dimethylformamide.
9. The method for producing a metal-adsorbing fiber membrane according to claim 4, wherein the PVDF content in the solution a is 10 to 12wt.%.
10. The method of producing a metal-adsorbing fiber membrane as set forth in claim 4, wherein the molecular weight of PAN is 13 to 16 ten thousand.
11. The method for producing a metal-adsorbing fiber membrane as set forth in claim 4, wherein the solvent in the solution B is a solvent capable of dissolving PAN.
12. The method for producing a metal-adsorbing fiber membrane as set forth in claim 11, wherein the solvent in the solution B is at least one of N, N-dimethylacetamide and N, N-dimethylformamide.
13. The method for producing a metal-adsorbing fiber membrane as set forth in claim 4, wherein a distance between the coaxial spinneret and the receiving plate used in the electrostatic process is 14-16cm; the flow rate of PAN is 0.5-1mL/h, and the flow rate of PVDF is 0.5-1mL/h.
14. The method for producing a metal-adsorbing fiber membrane as set forth in claim 4, wherein the step of oximating the surface is:
and (3) placing the PVDF@PAN base film into a modified solution a dissolved with hydroxylamine and alkali, and carrying out surface oximation treatment.
15. The method for producing a metal-adsorbing fiber membrane according to claim 14, wherein the alkali is at least one of anhydrous sodium carbonate and anhydrous sodium bicarbonate;
in the modified solution a, the molar ratio of hydroxylamine to alkali is 1:1-2.5:1;
in the modified solution a, the molar concentration of hydroxylamine is 0.4-0.6 mol/L;
the temperature of the oximation modification process is 60-80 ℃;
the oximation modification process is carried out for 60-180min.
16. The method for producing a metal-adsorbing fiber membrane as set forth in claim 4, wherein the step of carboxylated surface treatment is:
and (3) placing the PVDF@PAN base film into a modification solution b dissolved with alkali, and carrying out surface carboxylation treatment.
17. The method for producing a metal-adsorbing fiber membrane as set forth in claim 16, wherein the alkali is at least one of sodium hydroxide and potassium hydroxide;
in the modified solution b, the molar concentration of alkali is 1-5 mol/L.
18. The method of producing a metal-adsorbing fiber membrane as set forth in claim 4, wherein the surface-modified metal-adsorbing fiber membrane is obtained by freeze-drying.
19. The method of producing a metal-adsorbing fiber membrane as set forth in claim 18, wherein the time for freeze-drying is 4 to 7 hours.
20. Use of a metal-adsorbing fiber membrane according to any one of claims 1 to 3 or a metal-adsorbing fiber membrane produced by a production process according to any one of claims 4 to 19 for adsorbing lead metal ions.
21. Use according to claim 20 for adsorbing lead metal ions in aqueous solutions.
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