Sodium alginate-polyamidoxime composite hydrogel sphere uranium adsorption material and preparation method thereof

Abstract

The invention discloses a sodium alginate-polyamidoxime composite hydrogel sphere uranium adsorbent and a preparation method thereof, and relates to a uranium adsorption material and a preparation method thereof. The invention aims to solve the problems of insufficient stability, low adsorption capacity and poor selectivity of the existing adsorption material with amidoxime group for extracting uranium. Sodium alginate and hyperbranched polyamide molecules are adopted as the basis, after sodium alginate is subjected to calcium ion forming, a gel structure is reinforced through covalent cross-linking to enhance the stability, a three-dimensional gel network is formed through cross-linking of a hyperbranched structure, polyamidoxime is introduced into the gel network, and through two-time forming of ionic cross-linking and covalent cross-linking, the stability of the hydrogel is improved. The sodium alginate-poly (amidoxime / amide) composite gel ball with a three-dimensional porous structure is constructed. The hydrogel ball adsorption material contains rich amidoxime functional groups, shows excellent adsorption capacity and ion selectivity to uranium, and has excellent mechanical strength. The method is suitable for preparing the hydrogel sphere uranium adsorbent.

Description

Technical Field

[0001] The present invention relates to a sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorption material and a preparation method thereof. Background Art

[0002] Facing the increasing energy consumption in today's society, developing clean energy to replace fossil fuels is an effective way to balance energy demand and environmental crisis. Among them, nuclear energy is widely concerned as a recognized clean energy. Uranium is the main component of nuclear fuel in nuclear energy. Currently, uranium mainly comes from terrestrial mineral resources. However, with the development demand of nuclear energy, the uranium reserves on land have shown a shortage trend and are expected to be exhausted within the next 80 - 120 years. At the same time, the ocean contains rich uranium resources. It is estimated that the ocean contains 4.5 billion tons of uranium, which is 1000 times the uranium reserves on land and can provide energy supply for the nuclear industry for thousands of years. The main existence form of uranium in the ocean is uranyl ions. However, due to the very low concentration of uranium in seawater and the existence of many interfering ions, exploring a selective, efficient and economical extraction method is a necessary condition for obtaining uranium resources in the ocean.

[0003] The existing methods for extracting uranium mainly include membrane separation method, ion exchange method, solvent extraction method, adsorption method, etc. Among them, due to the simple process, low cost, high efficiency and environmental friendliness of the adsorption method, the adsorption method has become an effective and economical method and is thus widely used. The key point of the adsorption method lies in designing efficient and economical adsorption materials.

[0004] Hydrogel materials have attracted much attention due to their unique solid - liquid dual properties and good morphology controllability. Among them, sodium alginate (SA) - based gel sphere materials not only have the general properties of hydrogels, but also the granular macroscopic morphology is more suitable for a variety of adsorption apparatuses and is easy to directly recycle. At the same time, the preparation scheme of sodium alginate (SA) - based gel sphere materials is simple and the raw materials are cheap and easily available, which has good benefits in the development of adsorption materials. Although SA - based gel spheres can be used to remove uranium ions from aqueous solutions, the adsorption based only on carboxyl groups cannot obtain good uranium selectivity. Polyamidoxime (PAO) has excellent performance in uranium recovery from solutions due to its extensive amidoxime functional groups with strong complexing ability and selectivity. However, due to strong intermolecular hydrogen bonds, the molecular chains are prone to agglomeration and the hydrophilicity is reduced, resulting in problems such as insufficient stability and adsorption capacity, which limit its direct application. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of insufficient stability, low adsorption capacity and poor selectivity existing in the existing materials for adsorbing uranium. A sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorption material and a preparation method thereof are proposed.

[0006] The structural formula of the uranium adsorption material of the sodium alginate - polyamidoxime composite hydrogel sphere of the present invention is as follows:

[0007]

[0008] The preparation method of the uranium adsorption material of the sodium alginate - polyamidoxime composite hydrogel sphere of the present invention is carried out according to the following steps:

[0009] I. Prepare a composite gel solution using polyamidoxime, sodium alginate, and hyperbranched polyamide as raw materials:

[0010] Weigh sodium alginate powder and dissolve it in deionized water to obtain a sodium alginate solution; weigh polyamidoxime powder and dissolve it in sodium hydroxide solution to obtain an alkaline polyamidoxime solution; weigh hyperbranched polyamide powder and dissolve it in deionized water to obtain a polyamide solution; add the polyamidoxime solution and the polyamide solution to the sodium alginate solution and carry out mechanical stirring at room temperature, and obtain a composite gel solution after standing;

[0011] The ratio of the mass of the sodium alginate powder to the volume of deionized water is (400 - 700) mg : (8 - 20) mL;

[0012] The ratio of the mass of the polyamidoxime powder to the volume of the sodium hydroxide solution is (0.15 - 1) g : (8 - 20) mL;

[0013] The concentration of the sodium hydroxide solution is 0.4 - 0.7 mol / L;

[0014] The ratio of the mass of the hyperbranched polyamide powder to the volume of deionized water is (0.25 - 2) g : (4.5 - 8) mL;

[0015] The mass ratio of sodium alginate to polyamidoxime is 1 : (0.5 - 1.5); the mass ratio of polyamidoxime to hyperbranched polyamide is 1 : (1.2 - 2.5);

[0016] The mechanical stirring time is 10 - 40 min, and the standing time is 15 - 40 min;

[0017] II. Crosslink the composite gel solution obtained in step I twice to obtain sodium alginate - polyamidoxime composite hydrogel spheres;

[0018] The process of the two - step crosslinking is as follows: Drop the composite gel solution obtained in step I into a calcium ion solution for primary cross - linking and forming, then filter and wash it several times with deionized water to obtain gel spheres; then place the gel spheres in a glutaraldehyde solution for secondary cross - linking and forming, shake during the secondary cross - linking and forming process, then wash the gel spheres several times with deionized water, and finally freeze - dry to obtain the uranium adsorption material of the sodium alginate - polyamidoxime composite hydrogel sphere;

[0019] The time for the first cross-linking and forming is 1 - 5 h, the calcium ion solution is calcium chloride solution with a concentration of 2 - 4 wt.%.

[0020] The time for the second cross-linking and forming is 7 - 12 h, and the mass fraction of the glutaraldehyde solution is 1.5 - 4%.

[0021] The principle and beneficial effects of the present invention are as follows:

[0022] 1. The sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorption material of the present invention contains abundant amino and amidoxime functional groups, shows excellent adsorption capacity for uranium, has high adsorption rate and uranium ion selectivity; it has the highest adsorption capacity at pH = 6, and the removal rate of uranium ions in the uranium solution with a concentration C 0 = 100 ppm and pH = 6 can reach more than 95% (the adsorption capacity can reach more than 475 mg / g).

[0023] 2. Due to the synergistic adsorption effect of amino and amidoxime groups, during the coordination process with uranium ions, additional binding sites and enhanced affinity are provided, thereby improving the adsorption efficiency and capacity for uranium ions, making the equilibrium adsorption capacity of the sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorption material obtained in the present invention more than that of the microporous polymer synthesized from sodium alginate and polyamidoxime as raw materials.

[0024] 3. The present invention uses sodium alginate, polyamidoxime and hyperbranched polyamide as raw materials, cross-linked and woven by Ca 2+ and secondarily cross-linked with glutaraldehyde. Through deep covalent cross-linking reaction, a microporous spherical adsorption material with rich pores is produced. The microporous adsorption material contains abundant amino and amidoxime functional groups, making the amino - amidoxime group bifunctional adsorption material obtained in the present invention show excellent adsorption capacity for uranium, with high adsorption rate and uranium ion selectivity; the adsorption material of the present invention has high selective adsorption for uranium ions in aqueous solutions containing coexisting ions such as K + , Na + , Mg 2+ , Ca 2+ , Ba 2+ , Sr 2+ , Co 2+ , Cu 2+ .

[0025] 4. In the present invention, a composite gel solution was first prepared using sodium alginate, polyamidoxime, and hyperbranched polyamide as raw materials. The composition of the gel solution contains a large number of amino and carboxyl groups, providing a basis for subsequent cross-linking reactions. In addition, the three polymer components in the gel solution contain a large number of amino and carboxyl groups, making the material have good hydrophilicity and being easily involved in the reaction for cross-linking to improve the mechanical properties of the material. The gel solution obtained in the present invention was cross-linked twice. Selecting to cross-link twice, the first cross-linking was based on sodium alginate in the gel solution, and gel beads were formed by cross-linking with calcium ions to form a stable three-dimensional porous structure. The second cross-linking further enhanced the stability of the material through cross-linking with glutaraldehyde.

[0026] 5. In the present invention, after the addition of HA, the SA-PAO / HA gel beads as a whole showed an obvious porous spherical shape and had richer pores under microscopic observation. This is because the multi-branched structure in the hyperbranched polyamide molecules is connected to sodium alginate and polyamidoxime through multi-branched structures during covalent cross-linking, forming disordered multi-branched long chains in three-dimensional space, thereby forming a three-dimensional network-supported gel system, enabling the material to achieve a porous structure during the process of secondary cross-linking and forming. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Infrared spectra of SA-PAO / HA prepared in Example 1, raw materials, and SA-PAO in Example 2;

[0028] Figure 2 Scanning electron micrograph of SA-PAO / HA prepared in Example 1;

[0029] Figure 3 Graph showing the relationship between the uranium adsorption rate of SA-PAO / HA prepared in Example 1 and the solid-liquid ratio (the ratio of the mass of the adsorbent to the volume of the adsorption solution);

[0030] Figure 4 Graph showing the removal rates of different cations by the adsorption material; in the figure, SA-PAO / HA is the adsorption material prepared in Example 1, and SA-PAO is the adsorption material prepared in Example 2;

[0031] Figure 5 Graph showing the relationship between the adsorption amount of SA-PAO / HA for U(VI) and the HA content. DETAILED DESCRIPTION OF THE INVENTION

[0032] The technical solution of the present invention is not limited to the following specific embodiments listed, and also includes any reasonable combination between the specific embodiments.

[0033] Specific Embodiment 1: The structural formula of the uranium adsorption material of the sodium alginate-polyamidoxime composite hydrogel beads in this embodiment is:

[0034]

[0035] This embodiment has the following beneficial effects:

[0036] 1. The sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorption material of this embodiment contains abundant amino and amidoxime functional groups, shows excellent adsorption capacity for uranium, has a high adsorption rate and uranium ion selectivity; it has the highest adsorption capacity at pH = 6, and the removal rate of uranium ions in a uranium solution with a concentration C 0 = 100 ppm and pH = 6 can reach more than 95% (the adsorption capacity can reach more than 475 mg / g).

[0037] 2. Due to the synergistic adsorption effect of amino and amidoxime groups, during the coordination process with uranium ions, additional binding sites and enhanced affinity are provided, thereby improving the adsorption efficiency and capacity for uranium ions, making the equilibrium adsorption capacity of the sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorption material obtained in this embodiment more than that of the microporous polymer synthesized from sodium alginate and polyamidoxime as raw materials.

[0038] 3. This embodiment uses sodium alginate, polyamidoxime and hyperbranched polyamide as raw materials, cross - linked and woven by Ca 2+ and secondarily cross - linked with glutaraldehyde. Through a deep covalent cross - linking reaction, a microporous spherical adsorption material with abundant pores is produced. The microporous adsorption material contains abundant amino and amidoxime functional groups, making the amino - amidoxime group bifunctional adsorption material obtained in this embodiment show excellent adsorption capacity for uranium, having a high adsorption rate and uranium ion selectivity; the adsorption material of this embodiment has high selective adsorption for uranium ions in an aqueous solution containing co - existing ions such as K + , Na + , Mg 2+ , Ca 2+ , Ba 2+ , Sr 2+ , Co 2+ , Cu 2+ .

[0039] 4. In this embodiment, first, a composite gel solution is prepared using sodium alginate, polyamidoxime and hyperbranched polyamide as raw materials; the composition of the gel solution contains a large amount of amino and carboxyl groups, providing a basis for subsequent cross - linking reactions. In addition, the three polymer components in the gel solution contain a large amount of amino and carboxyl groups, making the material have good hydrophilicity and being easily involved in the reaction for cross - linking, improving the mechanical properties of the material; the gel solution obtained in this embodiment is cross - linked twice; choosing to cross - link twice, the first cross - linking takes the sodium alginate in the gel solution as the main body, and forms gel spheres through calcium ion cross - linking to make the material have a stable three - dimensional porous structure, and the second cross - linking further enhances the stability of the material through the cross - linking of glutaraldehyde.

[0040] Specific Embodiment 2: The preparation method of the sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorption material in this embodiment is carried out according to the following steps:

[0041] I. Prepare a composite gel solution using polyamidoxime, sodium alginate, and hyperbranched polyamide as raw materials:

[0042] Weigh sodium alginate powder and dissolve it in deionized water to obtain a sodium alginate solution; weigh polyamidoxime powder and dissolve it in sodium hydroxide solution to obtain an alkaline polyamidoxime solution; weigh hyperbranched polyamide powder and dissolve it in deionized water to obtain a polyamide solution; add the polyamidoxime solution and the polyamide solution to the sodium alginate solution and perform mechanical stirring at room temperature, and obtain a composite gel solution after standing;

[0043] The ratio of the mass of the sodium alginate powder to the volume of deionized water is (400 - 700) mg:(8 - 20) mL;

[0044] The ratio of the mass of the polyamidoxime powder to the volume of the sodium hydroxide solution is (0.15 - 1) g:(8 - 20) mL;

[0045] The concentration of the sodium hydroxide solution is 0.4 - 0.7 mol / L; using a sodium hydroxide solution with strong alkalinity is beneficial to the dissolution of polyamidoxime powder;

[0046] The ratio of the mass of the hyperbranched polyamide powder to the volume of deionized water is (0.25 - 2) g:(4.5 - 8) mL;

[0047] The mass ratio of sodium alginate to polyamidoxime is 1:(0.5 - 1.5); the mass ratio of polyamidoxime to hyperbranched polyamide is 1:(1.2 - 2.5); after using more hyperbranched polyamide, the abundant negatively charged functional groups of hyperbranched polyamide such as amino, imino, acyloxy, etc. can improve the adsorption efficiency and capacity for uranium ions by providing additional binding sites and enhancing affinity, coordinately enhancing the complexation of amidoxime groups with uranium ions, thereby promoting the overall uranium adsorption amount. At the same time, the more branched structure is the key to the formation of the porous structure of the gel sphere.

[0048] The mechanical stirring time is 10 - 40 min, and the standing time is 15 - 40 min; standing after stirring can eliminate bubbles and ensure the uniformity of the gel spheres formed during crosslinking.

[0049] II. Crosslink the composite gel solution obtained in step I twice to obtain sodium alginate - polyamidoxime composite hydrogel spheres;

[0050] The process of the two - stage cross - linking is as follows: Drop the composite gel solution obtained in Step 1 into a calcium ion solution for the first - stage cross - linking and forming, then filter and wash it several times with deionized water to obtain gel beads; then place the gel beads in a glutaraldehyde solution for the second - stage cross - linking and forming. During the second - stage cross - linking and forming process, shake them, and then wash the gel beads several times with deionized water. Finally, freeze - dry to obtain the uranium - adsorbing material of sodium alginate - polyamidoxime composite hydrogel beads;

[0051] The time for the first - stage cross - linking and forming is 1 - 5 h. The calcium ion solution is a calcium chloride solution with a concentration of 2 - 4 wt.%;

[0052] The time for the second - stage cross - linking and forming is 7 - 12 h, and the mass fraction of the glutaraldehyde solution is 1.5 - 4%.

[0053] This embodiment has the following beneficial effects:

[0054] 1. The uranium - adsorbing material of sodium alginate - polyamidoxime composite hydrogel beads in this embodiment contains abundant amino and amidoxime functional groups, shows excellent adsorption ability for uranium, has a high adsorption rate and uranium ion selectivity; it has the highest adsorption capacity at pH = 6, and the removal rate of uranium ions in a uranium solution with a concentration C 0 = 100 ppm and pH = 6 can reach more than 95% (the adsorption capacity can reach more than 475 mg / g).

[0055] 2. Due to the synergistic adsorption effect of amino and amidoxime groups, during the coordination process with uranium ions, it provides additional binding sites and enhanced affinity, thereby improving the adsorption efficiency and capacity for uranium ions, making the equilibrium adsorption capacity of the uranium - adsorbing material of sodium alginate - polyamidoxime composite hydrogel beads obtained in this embodiment more than that of the microporous polymer synthesized from sodium alginate and polyamidoxime as raw materials.

[0056] 3. This embodiment uses sodium alginate, polyamidoxime and hyperbranched polyamide as raw materials, cross - linked and woven by Ca 2+ and undergoes a second - stage cross - linking with glutaraldehyde. Through a deep covalent cross - linking reaction, a microporous spherical adsorbing material with rich pores is produced. The microporous adsorbing material contains abundant amino and amidoxime functional groups, making the amino - amidoxime group bifunctional adsorbing material obtained in this embodiment show excellent adsorption ability for uranium, have a high adsorption rate and uranium ion selectivity; the adsorbing material in this embodiment has high selective adsorption for uranium ions in an aqueous solution containing co - existing ions such as K + , Na + , Mg 2+ , Ca 2+ , Ba 2+ , Sr 2+ , Co 2+ , Cu 2+ .

[0057] 4. In this embodiment, a composite gel solution was first prepared using sodium alginate, polyamidoxime, and hyperbranched polyamide as raw materials. The composition of this gel solution contains a large number of amino and carboxyl groups, providing a basis for subsequent cross-linking reactions. In addition, the three polymer components in the gel solution contain a large number of amino and carboxyl groups, making the material have good hydrophilicity and being easily involved in the reaction for cross-linking, improving the mechanical properties of the material. The gel solution obtained in this embodiment was cross-linked twice. Selecting to cross-link twice, the first cross-linking was based on sodium alginate in the gel solution, and it was cross-linked and formed into gel beads through calcium ions, endowing the material with a stable three-dimensional porous structure. The second cross-linking further enhanced the stability of the material through the cross-linking of glutaraldehyde.

[0058] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 2 is that the ratio of the mass of the sodium alginate powder to the volume of deionized water in Step 1 is 500 mg: 10 mL.

[0059] Specific Embodiment 4: The difference between this embodiment and Specific Embodiment 2 is that the ratio of the mass of the polyamidoxime powder to the volume of the sodium hydroxide solution in Step 1 is 0.5 g: 10 mL.

[0060] Specific Embodiment 5: The difference between this embodiment and Specific Embodiment 2 is that the concentration of the sodium hydroxide solution in Step 1 is 0.5 mol / L.

[0061] Specific Embodiment 6: The difference between this embodiment and Specific Embodiment 2 is that the ratio of the mass of the hyperbranched polyamide powder to the volume of deionized water in Step 1 is 1 g: 5 mL.

[0062] Specific Embodiment 7: The difference between this embodiment and Specific Embodiment 2 is that the mass ratio of sodium alginate to polyamidoxime in Step 1 is 1:1; the mass ratio of polyamidoxime to hyperbranched polyamide is 1:2.

[0063] Specific Embodiment 8: The difference between this embodiment and Specific Embodiment 2 is that the time for the first cross-linking and forming in Step 2 is 2 h, the calcium ion solution is calcium chloride solution, and the concentration is 2.5 wt.%.

[0064] Specific Embodiment 9: The difference between this embodiment and Specific Embodiment 2 is that the time for the second cross-linking and forming in Step 2 is 9 h, and the mass fraction of the glutaraldehyde solution is 2%.

[0065] Specific Embodiment 10: The difference between this embodiment and Specific Embodiment 2 is that the number of times of washing with deionized water in Step 2 is 3 - 5 times.

[0066] Example 1:

[0067] The preparation method of the sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorbent in this embodiment is carried out according to the following steps:

[0068] I. Prepare a composite gel solution using polyamidoxime, sodium alginate, and hyperbranched polyamide as raw materials:

[0069] Weigh 500 mg of sodium alginate (SA) powder and dissolve it in 10 mL of deionized water to obtain a sodium alginate solution; weigh 500 mg of polyamidoxime (PAO) powder and dissolve it in 10 mL of sodium hydroxide solution with a concentration of 0.5 mol / L to obtain an alkaline polyamidoxime solution; weigh 1000 mg of hyperbranched polyamide (HA) powder and dissolve it in 5 mL of deionized water to obtain a polyamide solution; add the polyamidoxime solution and the alkaline polyamide solution to the sodium alginate solution and carry out mechanical stirring at a speed of 500 r·min -1 for 25 min at room temperature, and then let it stand for 40 min to obtain a composite gel solution;

[0070] II. Crosslink the composite gel solution obtained in step I twice to obtain sodium alginate - polyamidoxime composite hydrogel spheres;

[0071] The process of the two - step crosslinking is as follows: Drop the composite gel solution obtained in step I into a calcium chloride solution with a concentration of 2.5 wt.% for primary cross - linking and forming for 2 h, then filter and wash it 3 times with deionized water to obtain gel spheres; then place the gel spheres in a glutaraldehyde solution with a mass fraction of 2% for secondary cross - linking and forming for 9 h. During the secondary cross - linking and forming process, shake it, then wash the gel spheres 3 times with deionized water, and finally freeze - dry to obtain the sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorption material (SA - PAO / HA).

[0072] The structural formula of the sodium alginate - polyamidoxime composite hydrogel sphere uranium adsorption material prepared in this embodiment is:

[0073]

[0074] To better understand the promoting effect of hyperbranched polyamide (HA) on the amidoximated porous adsorbent, and to explore the effects of the proportion of amino and amidoxime contents and the microporous structure, an aminated porous polymer without HA (Example 2) and the SA - PAO / HA material (Example 1) prepared with 1000 mg of HA were used for comparison.

[0075] Example 2:

[0076] I. Prepare a composite gel solution using polyamidoxime, sodium alginate, and hyperbranched polyamide as raw materials:

[0077] Weigh 500 mg of sodium alginate (SA) powder and dissolve it in 10 mL of deionized water to obtain a sodium alginate solution; weigh 500 mg of polyamidoxime (PAO) powder and dissolve it in 10 mL of sodium hydroxide solution with a concentration of 0.5 mol / L to obtain an alkaline polyamidoxime solution; add the alkaline polyamidoxime solution to the sodium alginate solution and carry out mechanical stirring at a speed of 500 r·min -1 for 25 min at room temperature, and let it stand for 40 min to obtain a composite gel solution;

[0078] II. Crosslink the composite gel solution obtained in step I twice to obtain sodium alginate-polyamidoxime composite hydrogel spheres;

[0079] The process of the two crosslinkings is as follows: Drop the composite gel solution obtained in step I into a calcium chloride solution with a concentration of 2.5 wt.% for the first crosslinking and molding for 2 h, then filter and wash it 3 times with deionized water to obtain gel spheres; then place the gel spheres in a glutaraldehyde solution with a mass fraction of 2% for the second crosslinking and molding for 9 h, shake during the second crosslinking and molding process, then wash the gel spheres 3 times with deionized water, and finally freeze-dry to obtain gel spheres (SA-PAO).

[0080] Experiment:

[0081] ①. Conduct a laboratory uranium adsorption experiment: Weigh 0.01 g of SA-PAO / HA prepared in Example 1 and place it in a 250 mL conical flask, then add 50 mL of uranium solution (uranyl nitrate solution, adsorption solution) with pH = 6. After adsorbing for a certain time at 25 °C, separate the adsorbent SA-PAO / HA with a porous filter membrane to obtain the uranium solution after adsorption, then measure the concentrations of U(VI) in the uranyl nitrate solution before and after adsorption by inductively coupled plasma atomic emission spectrometry (ICP-AES), and calculate the adsorption capacity q of SA-PAO / HA for U(VI) according to formula (1) e ;

[0082]

[0083] In formula (1), C 0 is the concentration (mg / L) of the uranium solution before adsorption, C e is the concentration (mg / L) of the uranium solution after adsorption equilibrium, V is the volume (L) of the adsorption solution, and m is the mass (g) of the adsorbent;

[0084] ② Coexisting ion competitive adsorption experiment: First, prepare a coexisting ion solution: Weigh nitrates of potassium ions, sodium ions, calcium ions, magnesium ions, copper ions, strontium ions, cobalt ions, and barium ions with the same amount of substance as uranyl ions on an electronic balance, place them in a 250 mL beaker, add 100 mL of deionized water to dissolve, ultrasonicate for 15 min until completely dissolved, and then transfer to a 1000 mL volumetric flask and make up the volume for standby. Then add it to a centrifuge tube, and then add the adsorbent. Stir at 25 °C, and perform ICP-AES determination on the concentration of uranium in the supernatant after the adsorbent adsorbs, and calculate the removal rate of various ions by the adsorbent using formula (1).

[0085] ③ Adsorption experiment of SA-PAO without adding HA: Weigh 10 mg of the gel beads (SA-PAO) prepared in Example 2 and place them in a 250 ml conical flask, then add 10 mL of uranium solution (uranyl nitrate solution) with pH = 6. After adsorbing for a specific time at 25 °C, separate the adsorbent with a porous filter membrane to obtain the uranium solution after adsorption. Then use ICP-AES to measure the concentration of U(VI) in the uranium solution before and after adsorption, and calculate the adsorption capacity q of the adsorbent for U(VI) according to formula (1). e Measure the concentration of U(VI) in the uranyl nitrate solution before and after adsorption, calculate the adsorption capacity for U(VI) according to formula (1). The adsorption capacity of Example 1 is 475.35 mg / g, and the adsorption capacity of Example 2 is 374.41 mg / g. Example 2 has a lower adsorption capacity compared with Example 1, which fully reflects the porous structure exhibited by the introduction of polyamide in Example 1 and the synergistic effect of amino and amidoxime groups conducive to the improvement of the adsorption capacity.

[0086] Figure 1 is the infrared spectrogram of SA-PAO / HA prepared in Example 1, raw materials, and SA-PAO in Example 2; as Figure 1 known, the characteristic peak appearing at 938 cm -1 can be attributed to the stretching vibration peak of N-O in the amidoxime group, and the characteristic peaks at 1658 cm -1 and 1388 cm -1 indicate the presence of C=N and C-N in the polymer, and the stretching vibration peak of C-O-C belonging to the SA polysaccharide chain at 1030 cm -1 . The C-N absorption peak of tertiary amine appears at 1104 cm -1 , which proves the introduction of HA. This indicates that Example 1 successfully prepared a uranium adsorption material with amino-amidoxime bifunctional groups.

[0087] Figure 2 is the scanning electron micrograph of SA-PAO / HA prepared in Example 1; as Figure 2As shown, the gel beads as a whole show an obvious porous spherical shape and have richer pores under microscopy.

[0088] Figure 3 Figure showing the relationship between the uranium adsorption rate of SA-PAO / HA prepared in Example 1 and the solid-liquid ratio (the ratio of the mass of the adsorbent to the volume of the adsorption solution); Figure 3 It can be seen that as the solid-liquid ratio increases, the removal rate of uranyl ions gradually increases. When the solid-liquid ratio increases to 0.8 g / L, the curve of the removal rate almost tends to be balanced.

[0089] Figure 4 Figure showing the removal rates of the adsorbent for different cations; The competitive adsorption with common cations in seawater shows that the adsorbent still maintains excellent uranium selectivity (the removal rate exceeds 80%) in the presence of various interfering ions.

[0090] Example 3:

[0091] The preparation method of the sodium alginate-polyacrylamidine oxime composite hydrogel bead uranium adsorbent in this example is carried out according to the following steps:

[0092] I. Prepare a composite gel solution using polyacrylamidine oxime, sodium alginate, and hyperbranched polyamide as raw materials:

[0093] Weigh 500 mg of sodium alginate (SA) powder and dissolve it in 10 mL of deionized water to obtain a sodium alginate solution; weigh 500 mg of polyacrylamidine oxime (PAO) powder and dissolve it in 10 mL of sodium hydroxide solution with a concentration of 0.5 mol / L to obtain an alkaline polyacrylamidine oxime solution; weigh 500 mg of hyperbranched polyamide (HA) powder and dissolve it in 5 mL of deionized water to obtain a polyamide solution; add the polyacrylamidine oxime solution and the alkaline polyamide solution to the sodium alginate solution and carry out mechanical stirring at a speed of 500 r·min -1 for 25 min at room temperature, and then let it stand for 40 min to obtain a composite gel solution;

[0094] II. Crosslink the composite gel solution obtained in step I twice to obtain sodium alginate-polyacrylamidine oxime composite hydrogel beads;

[0095] The process of the two crosslinkings is as follows: Drop the composite gel solution obtained in step I into a calcium chloride solution with a concentration of 2.5 wt.% for the first crosslinking and shaping for 2 h, then filter and wash it 3 times with deionized water to obtain gel beads; then place the gel beads in a glutaraldehyde solution with a mass fraction of 2% for the second crosslinking and shaping for 9 h, shake during the second crosslinking and shaping process, then wash the gel beads 3 times with deionized water, and finally freeze-dry to obtain the sodium alginate-polyacrylamidine oxime composite hydrogel bead uranium adsorbent (SA-PAO / HA).

[0096] Weigh 0, 250, 750, 1250, and 1500 mg of hyperbranched polyamide (HA) powder respectively, and dissolve them in 5 mL of deionized water to obtain 5 polyamide solutions. Other processes and parameters are the same as those in Example 3, and uranium adsorption materials with different hyperbranched polyamide (HA) contents are prepared according to the process of Example 3.

[0097] In Example 1 and Example 3, the molecular weight of polyamidoxime used is 100,000 - 200,000;

[0098] Figure 5 It is the relationship diagram between the adsorption amount of U(VI) by SA-PAO / HA and the HA content. As the HA content gradually increases, the increment of the unit uranium adsorption amount of SA-PAO / HA shows a trend of first increasing and then decreasing, but generally the adsorption amount increases and reaches the maximum at 750 mg. This is because the abundant negatively charged functional groups in HA, such as amino groups, imino groups, acyloxy groups, etc., can coordinate the complexation of amidoxime groups with uranium ions, thereby promoting the overall uranium adsorption amount. At the same time, the addition of too much HA dilutes the amidoxime groups excessively, resulting in a decrease in the adsorption effect.

Claims

1. A sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material, characterized in that: The structural formula of sodium alginate-polyamidoximine composite hydrogel sphere uranium adsorption material is:

2. The method for preparing the sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material according to claim 1, characterized in that: The preparation method is carried out according to the following steps:

1. Preparation of composite gel solution using polyamidoxime, sodium alginate and hyperbranched polyamide as raw materials: Weighing sodium alginate powder and dissolving it in deionized water to obtain a sodium alginate solution; weighing polyamidoxime powder and dissolving it in a sodium hydroxide solution to obtain an alkaline polyamidoxime solution; weighing hyperbranched polyamide powder and dissolving it in deionized water to obtain a polyamide solution; adding the polyamidoxime solution and the polyamide solution to the sodium alginate solution and mechanically stirring them at room temperature, and then standing to obtain a composite gel solution; The ratio of the mass of the sodium alginate powder to the volume of deionized water is (400-700) mg: (8-20) mL; The ratio of the mass of the polyamidoxime powder to the volume of the sodium hydroxide solution is (0.15-1) g: (8-20) mL; The concentration of the sodium hydroxide solution is 0.4-0.7 mol / L; The ratio of the mass of the hyperbranched polyamide powder to the volume of deionized water is (0.25-2) g: (4.5-8) mL; The mass ratio of sodium alginate to polyamidoxime is 1:(0.5-1.5); the mass ratio of polyamidoxime to hyperbranched polyamide is 1:(1.2-2.5); The mechanical stirring time is 10-40 minutes, and the standing time is 15-40 minutes; 2. Cross-linking the composite gel solution obtained in step 1 twice to obtain sodium alginate-polyamidoximine composite hydrogel spheres; The process of the double cross-linking is as follows: dropping the composite gel solution obtained in step 1 into a calcium ion solution for primary cross-linking molding, then filtering and washing with deionized water for several times to obtain gel balls; then placing the gel balls in a glutaraldehyde solution for secondary cross-linking molding, shaking during the secondary cross-linking molding process, then washing the gel balls with deionized water for several times, and finally freeze-drying to obtain a sodium alginate-polyamidooxime composite hydrogel ball uranium adsorption material; The time of the primary cross-linking molding is 1-5 hours, and the calcium ion solution is a calcium chloride solution with a concentration of 2-4wt.%; The secondary cross-linking molding time is 7-12 hours, and the mass fraction of the glutaraldehyde solution is 1.5-4%.

3. The method for preparing the sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material according to claim 1, characterized in that: In step 1, the ratio of the mass of the sodium alginate powder to the volume of deionized water is 500 mg:10 mL.

4. The method for preparing the sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material according to claim 1, characterized in that: The ratio of the mass of the polyamidooxime powder in step 1 to the volume of the sodium hydroxide solution is 0.5 g:10 mL.

5. The method for preparing the sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material according to claim 1, characterized in that: The concentration of the sodium hydroxide solution in step 1 is 0.5 mol / L.

6. The method for preparing the sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material according to claim 1, characterized in that: In step 1, the ratio of the mass of the hyperbranched polyamide powder to the volume of deionized water is 1 g:5 mL.

7. The method for preparing the sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material according to claim 1, characterized in that: In step 1, the mass ratio of sodium alginate to polyamidoximine is 1:1; the mass ratio of polyamidoximine to hyperbranched polyamide is 1:

2.

8. The method for preparing the sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material according to claim 1, characterized in that: The time for the primary cross-linking molding in step 2 is 2 hours, and the calcium ion solution is a calcium chloride solution with a concentration of 2.5 wt.%.

9. The method for preparing the sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material according to claim 1, characterized in that: The time for the secondary cross-linking molding in step 2 is 9 hours, and the mass fraction of the glutaraldehyde solution is 2%.

10. The method for preparing the sodium alginate-polyamidoxime composite hydrogel spherical uranium adsorption material according to claim 1, characterized in that: The deionized water washing times in step 2 are 3-5 times.

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