CN113070049A - Preparation method of amino-enhanced amidoxime-based swelling layer polyacrylonitrile fiber adsorbent - Google Patents

Preparation method of amino-enhanced amidoxime-based swelling layer polyacrylonitrile fiber adsorbent Download PDF

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CN113070049A
CN113070049A CN202110392820.XA CN202110392820A CN113070049A CN 113070049 A CN113070049 A CN 113070049A CN 202110392820 A CN202110392820 A CN 202110392820A CN 113070049 A CN113070049 A CN 113070049A
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fiber
pan
amidoxime
solution
swelling layer
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王君
鞠培海
刘琦
刘婧媛
于静
陈蓉蓉
朱佳慧
孙高辉
李茹民
刘培礼
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Harbin Engineering University
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    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
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    • B01J20/265—Synthetic macromolecular compounds modified or post-treated polymers

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Abstract

A method for constructing an amidoxime group swelling layer with enhanced amino on the surface of polyacrylonitrile fibers is to construct a hydrophilic swelling layer structure on the surface of the polyacrylonitrile fibers. The specific process comprises the following steps: under the ventilation environment, adding PAN fiber into a three-neck bottle filled with ethylenediamine solution, heating in an oil bath, and refluxing to obtain PAN-NH2(ii) a Then using hydroxylamine hydrochloride solution with pH value of 7 to react with PAN-NH2Ammoximation treatment to obtain PAN-NH2-AO. The invention has the advantages that: the introduced hydrophilic group amino can not only enhance the hydrophilicity of the fiber to increase the swelling, but also increase the adsorption performance of the fiber as an adsorption group; the thickness of the amidoxime-based swelling layer enhanced by the amino on the surface of the polyacrylonitrile fiber is effectively controlled by changing the reaction time, the temperature and the concentration of reactants, so that the thickness of the swelling layer is controllable.

Description

Preparation method of amino-enhanced amidoxime-based swelling layer polyacrylonitrile fiber adsorbent
Technical Field
The invention relates to the technical field of uranium extraction from seawater, in particular to a method for constructing an amidoxime swelling layer with enhanced amino on the surface of polyacrylonitrile fiber.
Background
With the development of nuclear power, the demand of uranium increases day by day all over the world, and the reserve of terrestrial uranium ore is limited, so that the development demand of nuclear industry is difficult to meet. 45 hundred million tons of uranium resource storage in the ocean is enough to meet the energy demand of mankind for over ten thousand years, and a new round of competition research of extracting uranium from seawater begins in many countries.
The adsorbent taking polyacrylonitrile as a matrix has made a great deal of research progress in the aspect of extracting uranium from seawater, and has achieved certain achievements in practical application. But the adsorption capacity and the adsorption efficiency of the method still cannot meet the requirement of extracting uranium from seawater in large quantity for industrial production. The amidoxime group series of polymers are the polymers which are generally recognized as having the best U (VI) adsorption performance. Generally, the more amidoxime groups in the material, the better the U (VI) adsorption performance, so that the improvement of the nitrile group conversion rate and the amidoxime density in the adsorbent is an important method for improving the adsorption capacity of the adsorbent. Therefore, researchers research the relation between the thickness of a gel layer formed by amidoximation on the surface of polyacrylonitrile fibers and the uranium adsorption performance, and find that the adsorption capacity is in positive correlation with the thickness of the gel layer. However, when the content of amidoxime groups reaches a certain degree, the morphology and the performance of the fibers can be changed, so that the adsorption performance of the adsorbent cannot be continuously improved, and even the adsorption behavior can be hindered. This is because at a higher degree of amidoximation, the amidoxime groups on the surface of the polyacrylonitrile fiber are gelled. In the amidoximation process, amidoxime groups obtained by the surface reaction of polyacrylonitrile fibers are generally combined with water molecules to form a hydrogel layer, so that the diameter of the fibers is increased, and the mechanical strength is reduced. And a gel layer formed by amidoxime groups is compact, diffusion of uranyl ions is hindered, and the adsorption capacity of uranium is reduced. Therefore, to continue to increase the adsorption performance of amidoxime-modified polyacrylonitrile fibers, the structural properties of the gel layer on the fiber surface must be changed. The problem of diffusion of uranyl ions on the surface of polyacrylonitrile fibers is solved.
In view of the above problems, the present invention provides a method for changing the structural properties of amidoxime gel layers. That is, before amidoximation is performed on the surface of polyacrylonitrile fiber, a strong hydrophilic group is grafted on a polyacrylonitrile molecular chain. The strong hydrophilic group plays two roles on the molecular chain: firstly, the hydrophilicity of the amidoxime gel layer is greatly enhanced, and a large amount of water is absorbed due to strong hydrophilicity, so that a molecular chain on the surface of the fiber swells to form a swelling layer structure. The swelling layer structure enables the space between molecular chains to be large, and uranium can permeate into the swelling layer, so that the adsorption capacity is improved. Secondly, the amino group is also used as a strong coordination group of the uranyl ion and can adsorb the uranyl ion together with the amidoxime group.
Disclosure of Invention
Aiming at the problems of the existing amidoximated polyacrylonitrile fiber under the condition of high amidoximated degree, the invention provides a solution for enhancing an amidoxime swelling layer by using amino. Effectively solves the problem of diffusion of uranyl ions in the hydrogel layer in the high amidoximation process of the polyacrylonitrile fiber.
The specific implementation method is to adopt ethylenediamine as a strong hydrophilic group, and introduce strong hydrophilic amino on the surface of polyacrylonitrile while carrying out amidoximation on the polyacrylonitrile. The amino group can greatly promote the hydrophilicity of amidoximated polyacrylonitrile, so that the molecular chain containing amidoxime groups and amino groups on the fiber surface is swelled, and a swelling layer is formed on the polyacrylonitrile surface. When the polymer molecular chain is swelled, the small molecular substance can penetrate into the swelling layer. Therefore, when the amidoxime swelling layer with the enhanced amino groups swells in an aqueous solution, U (VI) is promoted to diffuse in the swelling layer, the problem of diffusion of uranyl ions under high amidoxime degree is solved, and the adsorption capacity is improved.
The present invention according to the above inventive concept includes the steps of:
the method comprises the following steps: PAN-NH2The preparation of (1): adding a certain amount of deionized water into a beaker, and cooling the beaker in ice bath; adding ethylenediamine into ionized water while stirring; after the addition is finished, continuing ice bath for 1h for cooling; transferring the ethylenediamine solution in the beaker into a volumetric flask, and fixing the volume to a scale mark; preparing 10-30vol% ethylenediamine solution;
step two: the solution preparation process needs to be carried out in a ventilation environment in the whole process, the solution is transferred into a three-mouth bottle, 4g of PAN fiber is weighed and added into the three-mouth bottle, and PAN is completely immersed below the liquid level of the solution; heating the three-necked bottle in oil bath to 70 ℃, and refluxing for 5-24 h;
step three: cooling to room temperature, taking out the fiber, and washing with deionized water and ethanol to be neutral; drying the fiber for 12h to obtain PAN-NH2;
Step four: PAN-NH2-preparation of AO; 11g of hydroxylamine hydrochloride are dissolved in 500ml of deionized water and Na is added2CO3Adjusting the pH value of the solution to 7, and transferring the solution into a three-mouth bottle; 4g PAN-NH2Adding the fiber into a three-mouth bottle, and completely immersing the fiber below the liquid level of the solution;
step five: heating the three-necked bottle to 80 ℃, and refluxing for 2-12 h; cooling to room temperature, taking out the fiber, and washing with deionized water and ethanol for several times; drying the fiber for 12h to obtain PAN-NH2-AO。
Advantageous effects
1. The invention constructs the amidoxime group swelling layer with enhanced amino on the surface of the polyacrylonitrile fiber, and improves the hydrophilicity of the fiber surface. The molecular chain spacing between the swelling layer in the swelling process is increased, uranyl ions permeate into the swelling layer, the collision probability between the uranyl ions and the adsorption groups is increased, and the adsorption capacity is improved. Fig. 1 is a schematic diagram of the swelling process of the swelling layer in adsorption. In example 1, of PANThe water contact angle is 107.92 degrees, the liquid drop is stable on the fiber surface, and the liquid drop still does not soak after 60 s. And PAN-NH2And PAN-NH2The instantaneous contact angles of AO were 113.36 ° and 86.42 °, respectively, and the drop was completely infiltrated inside the fiber after 0.62s and 0.59s, respectively.
2. The thickness of the amidoxime-based swelling layer enhanced by the amino on the surface of the polyacrylonitrile fiber is effectively controlled by changing the reaction time, the temperature and the concentration of reactants, so that the thickness of the swelling layer is controllable. In the swelling ratio test of the adsorbent prepared in example 1, it can be seen that PAN-NH is formed after an amino-enhanced amidoxime swelling layer is formed on the surface of polyacrylonitrile2The swelling ratio of-AO was greatly increased from 5.01% to 20.73%.
3. The introduced hydrophilic group amino can not only enhance the hydrophilicity of the fiber to increase the swelling, but also increase the adsorption performance of the fiber as an adsorption group. By XPS fine spectral analysis, in PAN-NH2The active sites participating in the uranium adsorption process in-AO are amidoxime groups, amino groups and amide bonds.
Drawings
FIG. 1 is a schematic diagram of the process of promoting adsorption by swelling an amidoxime swelling layer with enhanced amino groups
FIG. 2 is a schematic diagram of the preparation process of an amidoxime group swelling layer with enhanced amino group
FIG. 3 PAN (a) and PAN-NH (b) prepared in example 12, (c)PAN-NH2-AO, (d) SEM image and digital photograph of PAN-AO
FIG. 4 adsorption capacities of adsorbents prepared in example 1 at different pH values
FIG. 5 adsorption experiment of the adsorbent prepared in example 1 in a marine environment
FIG. 6 swelling ratio test of the adsorbent prepared in example 2
The specific embodiment is as follows:
example 1
A preparation method of an amino-enhanced amidoxime-based swelling layer polyacrylonitrile fiber adsorbent is shown in a preparation flow chart of figure 2, and specifically comprises the following steps:
the method comprises the following steps: PAN-NH2And (4) preparing. In situ roastingAdding a certain amount of deionized water into the cup, and cooling the beaker in an ice bath. Then 125mL of ethylenediamine is slowly added to, for example, ionized water, with stirring. After the addition is finished, the ice bath is continued for 1h for cooling. The ethylenediamine solution in the beaker was transferred to a 500ml volumetric flask and the volume was made up to 500 ml. Preparing the ethylenediamine solution with the concentration of 10-30 vol%. The solution preparation process needs to be carried out in a fume hood all the way. The above solution was transferred to a three-necked flask, and 4g of PAN fiber was weighed into the three-necked flask and the PAN was completely submerged below the solution level. Heating the three-necked bottle in oil bath to 70 ℃, and carrying out heat preservation and reflux for 12 h. Cooling to room temperature, taking out the fiber, and washing with deionized water and ethanol to be neutral. Drying the fiber in a drying oven for 12h to obtain PAN-NH2。
Step two: PAN-NH2-preparation of AO. 11g of hydroxylamine hydrochloride are dissolved in 500ml of deionized water and Na is added2CO3The solution was adjusted to pH 7 and transferred to a three-necked flask. 4g PAN-NH2 fiber was added to a three-necked flask and completely submerged below the solution level. The three-necked flask was refluxed for 8 hours by cooling due to heating to 80 ℃. Cool to room temperature and take out the fiber and wash several times with deionized water and ethanol. Drying the fiber in a drying oven for 12h to obtain PAN-NH2-AO。
Meanwhile, pure PAN fiber is adopted to carry out the experiment of the second step, and PAN-AO is prepared to be used as a contrast adsorbent.
In this example, the prepared adsorbent was subjected to SEM test to observe changes in its micro-morphology, as shown in FIG. 3. Comparison found, PAN-NH2No significant agglomeration of-AO occurred, but significant agglomeration shrinkage of PAN-AO occurred, which was not favorable for the next adsorption experiment.
The adsorbents were tested for adsorption performance at different pH values as shown in figure 4. The test method is as follows: with NaCO3And HNO3Mixing 100 mg.L-1The pH values of the U (VI) solution are respectively adjusted to 2, 3, 4, 5, 6, 7, 8 and 9. 20mg of the above adsorbent was immersed in 50mL of the above solution, respectively. Oscillating for 12h at normal temperature, measuring the concentration of U (VI) in the solution after adsorption equilibrium in the supernatant, measuring each group of data for three periods, taking an average value, and calculating the adsorption capacity. DiscoveryPAN -NH2-AO has an adsorption capacity greater than PAN-NH2。
The adsorbent prepared in the embodiment is subjected to an adsorption performance test in an actual marine environment for 91 days continuously near the sea area of the great Changshan island in the yellow sea. PAN-NH as shown in FIG. 52The adsorption capacity of-AO in the actual marine environment reaches 0.312mg g-1Is greater than PAN-NH2While pure PAN fibers have little adsorption capacity for U (vi) in marine environments.
Example 2
This example was substantially identical to the process described in example 1, except that in step one, the ethylenediamine concentration was adjusted to 30vol% and the reaction time was adjusted to 24 h.
In this example, the prepared adsorbent was subjected to a swelling ratio test. The test method is as follows: observing the prepared single polyacrylonitrile fiber under an optical microscope and measuring the diameter D of the single polyacrylonitrile fiber1. Then, a proper amount of deionized water is dropped on the glass slide, so that the water slowly infiltrates the observed fibers. After the fibers are fully swelled in water, the diameter D of the same fiber is measured2. The swelling ratio of the adsorbent prepared in this example as shown in fig. 6 reached 25%. If the concentration of the reactant ethylenediamine is increased, the swelling ratio of the fiber is increased, but the mechanical strength of the fiber is deteriorated.
Example 3
This example is substantially identical to the process described in example 1, except that in step two, the reaction time was adjusted to 12 h.
In this example, the prepared adsorbent has a high amidoxime grafting rate. If the reaction time is continuously increased, the polyacrylonitrile fiber will shrink, which affects the adsorption performance.
Example 4
This example is substantially identical to the process described in example 1, except that in step one, the ethylenediamine concentration is adjusted to 10 vol%. And in the second step, the reaction time is adjusted to be 4 h.
In the embodiment, the grafting rates of the ethylenediamine and the amidoxime are low, but the mechanical properties of the fiber can be effectively maintained. Meanwhile, the synergistic adsorption effect of the two functional groups can also keep better adsorption performance.
Example 5
This example is essentially identical to the process described in example 1, except that in step one, the reaction time is adjusted to 90 ℃.
In this example, the swelling ratio is higher by building a thicker swelling layer structure on the fiber surface with higher reaction temperature.
Example 6
This example is substantially identical to the process described in example 1, except that in step two, the solvent was changed to 20% aqueous ethanol.
In this embodiment, the change of the solvent can increase the wettability of the fiber in the solution, so that the reaction is more complete.

Claims (6)

1. A method for constructing an amidoxime group swelling layer with enhanced amino on the surface of polyacrylonitrile fiber,
the method comprises the following steps: PAN-NH2The preparation of (1): adding a certain amount of deionized water into a beaker, and cooling the beaker in ice bath; adding ethylenediamine into ionized water while stirring; after the addition is finished, continuing ice bath for 1h for cooling; transferring the ethylenediamine solution in the beaker into a volumetric flask, and fixing the volume to a scale mark; preparing 10-30vol% ethylenediamine solution;
step two: the solution preparation process needs to be carried out in a ventilation environment in the whole process, the solution is transferred into a three-mouth bottle, 4g of PAN fiber is weighed and added into the three-mouth bottle, and PAN is completely immersed below the liquid level of the solution; heating the three-necked bottle in oil bath to 70 ℃, and refluxing for 5-24 h;
step three: cooling to room temperature, taking out the fiber, and washing with deionized water and ethanol to be neutral; drying the fiber for 12h to obtain PAN-NH2;
Step four: PAN-NH2-preparation of AO; 11g of hydroxylamine hydrochloride are dissolved in 500ml of deionized water and Na is added2CO3Adjusting the pH value of the solution to 7, and transferring the solution into a three-mouth bottle; 4g PAN-NH2Adding the fiber into a three-mouth bottle, and completely immersing the fiber below the liquid level of the solution;
step five: heating the three-necked bottle to 80 ℃, and refluxing for 2-12 h; cooling to room temperature, taking out the fiber, and washing with deionized water and ethanol for several times; drying the fiber for 12h to obtain PAN-NH2-AO。
2. The method for constructing an amidoxime-based swelling layer with enhanced amino group on the surface of polyacrylonitrile fiber according to claim 1, wherein the concentration of ethylenediamine in the first step is adjusted to 30vol%, and the reaction time in the second step is 24 h.
3. The method for constructing an amidoxime-based swelling layer on the surface of polyacrylonitrile fiber according to claim 1, wherein in the second step, the reaction time is adjusted to 12 hours.
4. The method for constructing an amidoxime-based swelling layer with enhanced amino group on the surface of polyacrylonitrile fiber according to claim 1, wherein the concentration of ethylenediamine in the first step is 10%, and the reaction time in the second step is adjusted to 4 hours.
5. The method for constructing an amidoxime-based swelling layer on the surface of polyacrylonitrile fiber according to claim 1, wherein the reaction time in the second step is 90 ℃.
6. The method for constructing an amidoxime-based swelling layer with enhanced amino groups on the surface of polyacrylonitrile fiber according to claim 1, wherein in the second step, the solvent is 20% ethanol aqueous solution.
CN202110392820.XA 2021-04-13 2021-04-13 Preparation method of amino-enhanced amidoxime-based swelling layer polyacrylonitrile fiber adsorbent Pending CN113070049A (en)

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SE9001144D0 (en) * 1989-03-31 1990-03-29 Lagstroem Goeran URANIUM ADSORBENT
CN109289803A (en) * 2018-09-29 2019-02-01 西南科技大学 Polyamines base/amidoxime group modification polyfunctional group ion-exchange fibre method of preparation and use
CN109364891A (en) * 2018-11-14 2019-02-22 上海交通大学 A kind of modified polyacrylonitrile and preparation method thereof handling stibium-containing wastewater
CN110732160A (en) * 2019-11-26 2020-01-31 中国科学院过程工程研究所 method for dynamically adsorbing heavy metals in solution and application thereof
CN113373681A (en) * 2021-05-11 2021-09-10 西南科技大学 Method for treating nuclear fuel element process wastewater by using polyamine functionalized fiber

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Title
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