CN114643046A - Preparation method of amidoxime microgel adsorbent and application of amidoxime microgel adsorbent in rapid uranium extraction - Google Patents

Abstract

The invention belongs to the technical field of adsorption and separation functional materials, and relates to a preparation method of an amidoxime microgel adsorbent and its rapid uranium extraction application. The steps are: firstly using N'N-diethylacrylamide DEA as a backbone monomer to prepare a carboxyl-rich microgel, then using amidation reaction to modify diaminomaleonitrile, and using hydroxylamine hydrochloride to further convert the nitrile group. The reaction becomes an amidoxime group. In the present invention, DEA is used as the skeleton monomer to synthesize a microgel that can swell in an organic solvent, so that the hydrogel material can be modified with amidoxime groups in the organic solvent, and no special amidoxime monomer needs to be synthesized , a greatly simplified material preparation method; due to the use of microgel materials for uranium adsorption, the swelling rate is much higher than that of general hydrogels, so the adsorption rate is greatly improved.

Description

A kind of preparation method of amidoxime microgel adsorbent and its application in rapid uranium extraction

technical field

The invention belongs to the technical field of preparation of functional materials for adsorption and separation, and in particular relates to a preparation method of an amidoxime microgel adsorbent and its application for rapid uranium extraction.

Background technique

Nuclear energy is a mature energy source that can continuously provide electricity on a large scale with extremely high energy density and ultra-low greenhouse gas emissions. Because of the large-scale use of nuclear energy, nuclear leakage accidents caused by accidental factors also occur from time to time. Radioactive elements will not only pollute the marine environment, but also accumulate in marine organisms. After human consumption, it will also cause serious harm to the human body. Uranium is the main nuclear element, so we need a sorbent that can quickly deal with leaked uranium.

Polymer cross-linked network hydrogels have attracted extensive attention in many application fields due to their versatility in composition, ease of preparation, and tunable physical properties. The hydrogel swells in water and retains a large amount of water while maintaining its chemical structure. In recent years, reports on the application of hydrogel materials to the adsorption of metal ions have gradually increased. However, when hydrogel materials are adsorbed, they still have the disadvantage of slow adsorption rate, which needs to be solved urgently. Microgels are hydrogels with a size of 0.5-10 μm, which have the excellent characteristics of hydrogels. At the same time, since the swelling rate of hydrogels is inversely proportional to their size, the swelling and water absorption rate of microgels will be much higher than that of general macroscopic water. gel material. The application of microgel materials to adsorb uranium can greatly improve the adsorption rate.

The amidoxime group matches the size of U(VI) due to its unique steric configuration, and the selective adsorption of U(VI) can be achieved through coordination. Based on this, the ability to selectively adsorb U(VI) can be given to the material by introducing amidoxime groups. When modifying the amidoxime group on the material, it is necessary to use an organic solvent, but common hydrogel materials cannot swell in organic solvents and are in a shrunken state, and the reaction efficiency is greatly reduced. Therefore, it is urgent to develop a hydrogel material that can swell in organic solvents.

In order to avoid the above deficiencies, it is necessary to develop a new type of hydrogel material that can swell in organic solvents for easy modification and has a fast adsorption rate, which can be used for selective uranium extraction.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the purpose of the present invention is to overcome the problems that the hydrogel is not easy to be modified in an organic solvent and the adsorption rate is slow, and provides a preparation method of an amidoxime-based microgel. Amidoxime-functionalized microgel-based adsorbent was prepared with amidoxime group as selective ligand and N'N-diethylacrylamide as microgel backbone monomer.

In order to achieve the above-mentioned technical purpose, the technical scheme adopted in the present invention is as follows:

(1) Preparation of carboxyl functionalized microgel (Microgel-COOH);

Add a certain amount of N'N-diethylacrylamide (DEA), N'N-dimethylbisacrylamide (Bis), acrylic acid (AAc) and sodium dodecyl sulfate (SDS) to a certain volume of In deionized water, the mixed solution is ventilated for a period of time t ₁ , heated to a temperature T ₁ with stirring in a water bath, and then a certain amount of potassium persulfate (KPS) is added to react for a period of time t ₂ . The obtained solution was dialyzed using a dialysis bag with a molecular weight of 300,000, and finally freeze-dried to obtain a product carboxyl microgel.

(2) Preparation of nitrile functionalized microgel (Microgel-CN);

A certain amount of Microgel-COOH, diaminomaleonitrile (DAMN), 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) and N- Hydroxysuccinimide (NHS) was added to a certain volume of ethanol, the temperature was controlled at T ₂ , and the stirring reaction was at time t ₃ . The obtained solution was dialyzed using a dialysis bag with a molecular weight of 300,000, and finally freeze-dried to obtain Microgel-CN.

(3) Preparation of amidoxime functionalized microgel adsorbent (Microgel-AO):

A certain amount of Microgel-CN, sodium hydroxide and hydroxylamine hydrochloride synthesized in step (2) was added to the mixed solution of ethanol water, heated to temperature T ₃ , and stirred for reaction time t ₄ . The reacted solution was dialyzed using a 300,000 dialysis bag, and finally freeze-dried to obtain amidoxime-based microgels.

Preferably, in step (1), the dosage ratio of DEA, Bis, AAc, SDS, deionized water and KPS is: 0.5-2.5g: 0.01-0.08g: 0.05-0.2g: 0.005-0.02g: 50 -120mL; 0.02-0.1g, the reaction temperature T1 is 65-90°C, the reaction time _t1 is _10-60min , and the reaction time _t2 is 2-8h.

Preferably, in step (2), the proportion of the amount of Microgel-COOH, DAMN, EDC, NHS and ethanol synthesized in step (1) is 0.5-2g: 0.1-0.3g: 0.2-0.53g: 0.1 -0.33g: _80-150mL , the reaction temperature T2 is 4-40°C, and the reaction time _t3 is 6-24h.

Preferably, in step (3), the dosage ratio of the mixed solution of Microgel-CN, hydroxylamine hydrochloride, NaOH and ethanol water synthesized in the step (2) is 0.5-2g: 0.5-10g: 0.5-5g: 80- In 150 mL of ethanol-water mixed solution, the volume ratio of ethanol and deionized water is 7:3 to 9:1. _The reaction temperature T3 is 65-80°C, and the reaction time t4 is _2-12h .

The use of the amidoxime microgel adsorbent prepared by the invention for selective adsorption and separation of hexavalent uranium in solution. The specific usage is as follows: at 15-50 ℃, the material is placed in a solution with a uranium concentration of 0.1-200 mg/L and a pH of 4-9, and the adsorption is completed after 1-2880 min.

Beneficial effects of the present invention:

(1) The present invention selects the amidoxime group as the selective functional unit of U (VI), and uses the microgel with a smaller size as the substrate to prepare the amidoxime functionalized microgel-based adsorbent, and realizes the utilization of U (VI). (VI) Rapid specific adsorption.

(2) the present invention obtains the microgel rich in amidoxime groups by further modification through radical precipitation polymerization, because the gel swelling speed is inversely proportional to its particle size, so the microgel adsorbent with smaller particle size , greatly improving the adsorption rate; since the monomer of the microgel backbone is DEA, the synthesized hydrogel can also swell in some organic solvents, which provides convenience for the further modification of amidoxime groups and avoids complex synthesis. Monomer, simplifying material synthesis steps.

Description of drawings

FIG. 1 is SEM images (a, b) and DLS data graph (c) of Microgel-AO in Example 1. FIG.

FIG. 2 is a graph of FI-IR data of Microgel-CN and Microgel-AO in Example 1. FIG.

Figure 3 shows the effect of pH on the uranyl ion adsorption capacity of the amidoxime-based microgel prepared in Example 1.

FIG. 4 is the adsorption kinetics of the Microgel-AO prepared in Example 1 for uranyl ions and its model fitting curve.

5 shows the effect of temperature on the adsorption equilibrium of Microgel-AO prepared in Example 1 on the uranyl ion and its model fitting curve.

Figure 6 shows the adsorption selectivity of the Microgel-AO prepared in Example 1.

Detailed ways

In the specific embodiment of the present invention, the recognition performance evaluation is carried out according to the following method: it is completed by using a static adsorption experiment. The adsorption capacity of 5.0 mg Microgel-AO for U(VI) in the range of pH 4.0-9.0 was tested, the content of U(VI) after adsorption was measured by inductively coupled plasma emission spectrometer, and the optimal adsorption pH was determined according to the results ; Secondly, the effect of adsorption time on the adsorption capacity of Microgel-AO was studied, and the Pseudo first-order model and Pseudo second-order model were used to fit and analyze the data respectively. In order to study the maximum adsorption capacity of Microgel-AO, we used The adsorption equilibrium test was carried out in the range of U(VI) concentration of 10-60 ppm. The Langmuir model and the Freundlich model were used for fitting, and the adsorption capacity was calculated according to the results. Several other substances with the same structure as the uranyl ion were selected as Competing adsorbate, participating in the study of the selective adsorption performance of Microgel-AO.

The present invention will be further described below in conjunction with specific implementation examples.

Example 1:

(1) Preparation of Microgel-COOH;

In a flask, 1.66g DEA, 0.0432g Bis, 0.101g AAc and 0.0115g SDS were added to 100mL deionized water, and after passing N ₂ for 30min, heated to 70°C using magnetic stirring, 0.081g KPS was added, and the reaction was continued for 5h. After the reaction, the reacted solution was dialyzed using a 300,000 dialysis bag, and dialyzed with pure water for 7 days. The water was changed three times a day to remove incompletely reacted monomers, and finally lyophilized to obtain carboxyl microgels.

(2) Preparation of Microgel-CN;

1.5 g of Microgel-COOH obtained in step (1), 0.151 g of DAMN, 0.268 g of EDC and 0.163 g of NHS were added to 100 mL of ethanol. Magnetic stirring was heated to 40 ° C, and the reaction was carried out for 12 h. After the reaction, the reacted solution was dialyzed using a 300,000 dialysis bag, and dialyzed in pure water for 7 days. The water was changed three times a day to remove incompletely reacted monomers, and finally Microgel-CN was obtained by freeze-drying.

(3) Preparation of Microgel-AO:

In a flask, add 1.5 g of Microgel-CN obtained in step (2), 5 g of hydroxylamine hydrochloride and 2.2 g of NaOH to 100 mL of a solution containing 9:1 ethanol and water, and adjust it with 1 M sodium hydroxide solution. pH to 8, heated to 80 degrees with stirring, and reacted for 6h. After the completion of the reaction, the reacted solution was dialyzed using a dialysis bag of 300,000, and dialyzed in pure water for 7 days. gel.

As shown in Figure 1, the microgel synthesized in step (1) is basically spherical and can be monodispersed; from the DLS data map in Figure 1c, it can be seen that the particle size of the material is uniform in the aqueous environment, with a particle size of 735 Between -765nm, the monodispersity coefficient is small, 0.065;

As shown in Figure 2, in the FI-IR data, compared with Microgel-CN, the characteristic peak of the nitrile group disappears around 2230-2240 nm in Microgel-AO, which proves that the nitrile group has basically reacted into an amidoxime group .

In summary, the material has been synthesized successfully.

Example 2:

(1) Preparation of Microgel-COOH;

In a flask, add 0.5g DEA, 0.01g Bis, 0.05g AAc and 0.005g SDS to 100mL deionized water, pass N ₂ for 30min, heat to 70°C with magnetic stirring, add 0.02g KPS, and react for 2h. After the reaction, the reacted solution was dialyzed using a 300,000 dialysis bag, and dialyzed with pure water for 7 days. The water was changed three times a day to remove incompletely reacted monomers, and finally lyophilized to obtain carboxyl microgels.

(2) Preparation of Microgel-CN;

0.5 g of Microgel-COOH obtained in step (1), 0.1 g of DAMN, 0.2 g of EDC and 0.1 g of NHS were added to 100 mL of ethanol. Magnetic stirring was heated to 4 ℃, and the reaction was carried out for 6 h. After the reaction, the reacted solution was dialyzed using a 300,000 dialysis bag, and dialyzed in pure water for 7 days. The water was changed three times a day to remove incompletely reacted monomers, and finally Microgel-CN was obtained by freeze-drying.

(3) Preparation of Microgel-AO:

In a flask, add 0.5 g of Microgel-CN obtained in step (2), 0.5 g of hydroxylamine hydrochloride and 0.5 g of NaOH to 100 mL of solution containing ethanol and water in a ratio of 8:2, using a 1M sodium hydroxide solution Adjust pH to 8, stir and heat to 65 degrees, and react for 2h. After the completion of the reaction, the reacted solution was dialyzed using a 300,000 dialysis bag, and dialyzed in pure water for 7 days. gel.

Example 3:

(1) Preparation of Microgel-COOH;

In a flask, 2.5g DEA, 0.08g Bis, 0.2g AAc and 0.02g SDS were added to 100mL deionized water, and after 30min of N ₂ was used, it was heated to 70°C using magnetic stirring, 0.1g KPS was added, and the reaction was continued for 12h. After the reaction, the reacted solution was dialyzed using a 300,000 dialysis bag, and dialysis was performed in pure water for 7 days. The water was changed three times a day to remove incompletely reacted monomers, and finally Microgel-COOH was obtained by freeze-drying.

(2) Preparation of Microgel-CN;

2 g of Microgel-COOH obtained in step (1), 0.3 g of DAMN, 0.53 g of EDC and 0.33 g of NHS were added to 100 mL of ethanol. Magnetic stirring was heated to 40 ° C, and the reaction was carried out for 24 h. After the reaction, the reacted solution was dialyzed using a 300,000 dialysis bag, and dialyzed in pure water for 7 days. The water was changed three times a day to remove incompletely reacted monomers, and finally Microgel-CN was obtained by freeze-drying.

(3) Preparation of Microgel-AO:

In the flask, 2g of the nitrile-based microgel obtained in step (2), 10g of hydroxylamine hydrochloride and 5g of NaOH were added to a 100mL solution containing ethanol-water in a ratio of 8:2, and adjusted with a 1M sodium hydroxide solution. pH to 8, heated to 90 degrees with stirring, and reacted for 2h. After the reaction, the reacted solution was dialyzed using a 300,000 dialysis bag, and dialyzed in pure water for 7 days. The water was changed three times a day to remove incompletely reacted monomers. Finally, Microgel-AO was obtained by freeze-drying.

Performance Testing:

Ambient pH has a huge impact on the metal ion adsorption behavior; therefore, the effect of Microgel-AO on the adsorption capacity of U(VI) in the pH range of 4.0-9.0 was investigated. As shown in Figure 3, when the pH value is not higher than 6.0, the adsorption capacity of Microgel-AO shows a gradual upward trend with the increase of pH value. When the pH value is higher than 6.0, the adsorption capacity increases with the increase of pH value. reduce.

The adsorption kinetics of Microgel-AO for different concentrations of U(VI) are shown in Fig. 4. It can be seen from the figure that the adsorption capacity of Microgel-AO increased rapidly within the first 5 minutes and reached the maximum adsorption capacity within 10 minutes. The Pseudo first-order model and the Pseudo second-order model were used to fit, calculate and analyze the data respectively.

In order to study the maximum adsorption capacity of Microgel-AO, we carried out adsorption equilibrium experiments in the range of U(VI) concentration of 10-60 mg·L ^-1 , fitted the adsorption data with Langmuir model and Freundlich model, and explored The effect of temperature on adsorption capacity. As shown in Figure 5, the adsorption capacity increases with increasing temperature in the tested temperature range.

The combination of interfering ions and amidoxime groups may have a huge impact on the adsorption capacity of amidoxime-based microgels for U(VI) adsorption. We selected VO ^3- , Co ²⁺ , Ni ⁺ , Zn ²⁺ , Pb ^{2 +} , ^{Ca 2+} , ^{Mg 2+} , K ⁺ and Na ^{+ were} used as competing ^ions for U(VI ^{) .} Adsorption behavior in mixed solutions of ⁺ , Mg ²⁺ , K ⁺ , Na ⁺ and U(VI). As shown in Figure 6, in the presence of numerous interfering ions, Microgel-AO still has the highest adsorption capacity for U(VI), which is much larger than that of VO ^3- , Co ²⁺ , Ni ⁺ , Cu ²⁺ , Zn ²⁺ , The corresponding adsorption capacity of low-concentration metal ions such as Pb ²⁺ .

Explanation: The above embodiments are only used to illustrate the present invention and not to limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above-mentioned various embodiments, those of ordinary skill in the art should It should be understood that the present invention can still be modified or equivalently replaced; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims (9)

1. a preparation method of amidoxime microgel adsorbent, is characterized in that, comprises the steps: (1) Preparation of carboxyl functionalized microgel Microgel-COOH; A certain amount of N'N-diethylacrylamide DEA, N'N-dimethylbisacrylamide Bis, acrylic acid AAc, and sodium dodecyl sulfate SDS were added to a certain volume of deionized water, and the mixed solution was aerated. After a period of time t ₁ , the water bath is stirred and heated to a temperature T ₁ , and then a certain amount of potassium persulfate KPS is added to react for a period of time t ₂ , the obtained solution is dialyzed, and finally freeze-dried to obtain a product carboxyl microgel; (2) Preparation of nitrile functionalized microgel Microgel-CN; A certain amount of Microgel-COOH, diaminomaleonitrile DAMN, 1-ethyl-(3-dimethylaminopropyl) carbodiimide EDC and N-hydroxysuccinimide synthesized in step (1) Amine NHS was added to a certain volume of ethanol, the temperature was controlled at T ₂ , the stirring reaction was at time t ₃ , the obtained solution was dialyzed, and finally freeze-dried to obtain Microgel-CN; (3) Preparation of amidoxime functionalized microgel adsorbent (Microgel-AO): A certain amount of Microgel-CN, sodium hydroxide and hydroxylamine hydrochloride synthesized in step (2) were added to the mixed solution of ethanol water, heated to temperature T ₃ , and stirred for reaction time t ₄ ; dialyze the reacted solution, Finally, freeze-dried to obtain amidoxime-based microgels. 2. preparation method as claimed in claim 1 is characterized in that, in step (1), the consumption ratio of described DEA, Bis, AAc, SDS, deionized water and KPS is: 0.5-2.5g: 0.01-0.08 g: 0.05-0.2 g: 0.005-0.02 g: 50-120 mL; 0.02-0.1 g. 3 . The preparation method according to claim 1 , wherein, in step (1), the reaction temperature T ₁ is 65-90° C., the reaction time t ₁ is 10-60 min, and the reaction time t ₂ is 2-8 h. 4 . 4. preparation method as claimed in claim 1 is characterized in that, in step (2), the consumption ratio of Microgel-COOH, DAMN, EDC, NHS and ethanol is 0.5-2g: 0.1-0.3g: 0.2-0.53g : 0.1-0.33g: 80-150mL. 5 . The preparation method according to claim 1 , wherein, in step (2), the reaction temperature T ₂ is 4-40° C., and the reaction time t ₃ is 6-24 h. 6 . 6. preparation method as claimed in claim 1 is characterized in that, in step (3), the consumption ratio of the mixed solution of Microgel-CN, hydroxylamine hydrochloride, NaOH and ethanol water is 0.5-2g: 0.5-10g: 0.5- 5g: 80-150mL, wherein, in the mixed solution of ethanol and water, the volume ratio of ethanol and deionized water is 7:3 to 9:1. 7 . The preparation method according to claim 1 , wherein, in step (3), the reaction temperature T ₃ is 65-80° C., and the reaction time t ₄ is 2-12 h. 8 . 8 . The preparation method of claim 1 , wherein in steps (1) to (3), dialysis is performed using a dialysis bag with a molecular weight of 300,000. 9 . 9. The use of the amidoxime microgel adsorbent prepared by the method according to any one of claims 1-8 for the selective adsorption and separation of hexavalent uranium in solution.

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