A hydrogel adsorption material and a preparation method and application thereof

Abstract

The application provides a preparation method of a hydrogel adsorption material, comprising the following steps: preparing layered double hydroxides (LDHs); loading zero-dimensional carbon nanomaterial into nanocellulose to obtain solution A; dissolving chitosan in acetic acid to obtain solution B; uniformly mixing solution A, solution B and the LDHs dispersed in ethanol to obtain a pre-polymerization solution; adding a crosslinking agent into the pre-polymerization solution, and heating to fully gelate, and then washing to obtain the hydrogel adsorption material. The preparation method of the hydrogel adsorption material can effectively capture and fix iodine ions, and the prepared hydrogel adsorption material has good cycle stability. The application also provides an application of the hydrogel adsorption material in iodine ion adsorption.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a hydrogel adsorption material loaded with layered double metal hydroxides, a preparation method and an application thereof. Background Art

[0002] With the rapid development of the global economy, humanity's demand for energy is growing. Nuclear energy, with its advantages of not emitting greenhouse gases or other toxic gases, is considered one of the most promising future energy sources. Iodine is the primary fission product of nuclear power plant fuel. Due to its volatility, iodine is a major radionuclide that contaminates the environment early in nuclear explosions and reactor accidents. Excessive iodine intake can also significantly increase the incidence of hypothyroidism, autoimmune thyroid disease, and papillary thyroid cancer.

[0003] In the prior art, the method for removing I - The main methods include surface adsorption, ion exchange, chemical precipitation, solvent extraction, membrane separation, etc. Although there are many methods to remove iodide ions, most of them have low removal efficiency, and some high-efficiency removal methods are accompanied by high costs, which restricts the promotion and application of related methods. Adsorption is an effective way to remove iodide ions, with many advantages such as easy operation, high efficiency and low cost; however, the quality of its effect depends greatly on the performance of the adsorbent itself. Therefore, the development of an efficient adsorbent is the key to ensure the effective implementation of such methods. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a hydrogel adsorption material and a preparation method and application thereof, wherein the hydrogel adsorption material can effectively capture and fix iodine ions and has good cycle performance and stability.

[0005] The first aspect of the present invention is to provide a method for preparing a hydrogel adsorbent material, comprising the following steps:

[0006] A method for preparing a hydrogel adsorption material, characterized in that it comprises the following steps:

[0007] Step S1, preparing layered double hydroxides LDHs;

[0008] Step S2, loading the zero-dimensional carbon nanomaterial into nanocellulose to obtain solution A;

[0009] Step S3, adding the chitosan solution to acetic acid to obtain solution B;

[0010] Step S4, uniformly mixing solution A, solution B and layered double hydroxides (LDHs) dispersed in ethanol to obtain a prepolymer solution;

[0011] Step S5, adding a crosslinking agent to the prepolymer solution, heating to fully gel, and washing to obtain a hydrogel adsorbent material.

[0012] Further, in step S1, the method for preparing the layered double hydroxide LDHs comprises:

[0013] The magnesium salt and the aluminum salt are mixed to prepare a mixed solution, the pH value of the mixed solution is adjusted to 8.0-10.0, stirring is performed, and overnight aging treatment is performed;

[0014] Filtering, washing, and drying are performed to obtain LDH particles.

[0015] Calcination is performed at a rate of 3-5 ℃ / min from room temperature to 480-550 ℃, and the temperature is maintained for 3-6 h to obtain the layered double hydroxide LDHs. Specifically, the rate of temperature increase can be 3 ℃ / min, 4 ℃ / min, or 5 ℃ / min, or other values within the range. The calcination temperature can be 480 ℃, 490 ℃, 500 ℃, 510 ℃, 520 ℃, 530 ℃, 540 ℃, or 550 ℃, or other values within the range.

[0016] Further, the molar ratio of the magnesium salt to the aluminum salt is 3-5:1, the magnesium salt is MgCl2·6H2O, the aluminum salt is AlCl3·6H2O, and the base used to adjust the pH value is a mixed solution of sodium hydroxide and sodium carbonate. Specifically, the molar ratio of the magnesium salt to the aluminum salt can be 3:1, 4:1, or 5:1, or other values within the range.

[0017] Further, in step S2, the method for preparing the solution A comprises:

[0018] The zero-dimensional carbon nanomaterial, EDC, and NHS are introduced into the CN suspension, and mixing is performed under ultrasonic stirring.

[0019] Acetic acid buffer is added, and magnetic stirring is performed at room temperature.

[0020] Further, the zero-dimensional carbon nanomaterial is prepared by using ethylenediamine and citric acid as raw materials, performing hydrothermal reaction at 190 ℃ for 5 h, and performing filtration and dialysis.

[0021] Further, in the solution A, the mass ratio of the zero-dimensional carbon nanomaterial to the nanocellulose is 4-6:50 (such as 4:50, 5:50, or 6:50, or other values within the range), and the mass concentration of the nanocellulose is 0.6-1 wt% (such as 0.6 wt%, 0.8 wt%, or 1 wt%, or other values within the range).

[0022] The mass concentration of chitosan in solution B is 1.5-2.5 wt% (for example, it can be 1.5 wt%, 2 wt% or 2.5 wt%, or other values in the range);

[0023] The mass ratio of the layered double hydroxide to chitosan is 4-6:2 (for example, it can be 4:2, 5:2 or 6:2, or other values in the range);

[0024] The mass ratio of solution A to solution B is 10-20:100 (for example, it can be 10:100, 15:100 or 20:100, or other values in the range).

[0025] The second aspect of the present application is to provide a hydrogel adsorption material prepared by the method of the first aspect.

[0026] The third aspect of the present application is to provide the use of the hydrogel adsorption material of the second aspect in the adsorption of iodine ions.

[0027] Further, in the adsorption of iodine ions, the pH value of the system is 6-8, the temperature is 25-55℃, and the initial concentration of the adsorbate is 120-200 mg / L.

[0028] Compared with the prior art, the hydrogel adsorption material, its preparation method and use provided by the present application have the following beneficial effects:

[0029] Firstly, the hydrogel adsorption material provided by the present application takes layered double metal oxide as the main body, contains positively charged metal ions, can adsorb iodine ions through electrostatic attraction between the positively charged metal ions and iodine ions, and the layered metal oxide is modified by high-temperature calcination to convert the carbonate ions between the layers into carbon dioxide and magnesium-aluminum oxide, thereby providing more exchange adsorption sites; chitosan and nanocellulose are used to build a three-dimensional network structure, which can adsorb iodine ions through electrostatic attraction due to the rich amino groups, and the three-dimensional network structure improves the adsorption space of the material, so that the material has excellent adsorption performance. Through the study on the adsorption behavior of the hydrogel adsorption material of the present application, it is found that the material can effectively capture and immobilize iodine ions, and has good cycle stability.

[0030] Secondly, the hydrogel adsorption material provided by the present application loads zero-dimensional carbon nanomaterials with significant fluorescence performance in nanocellulose, so that the absorbance of iodine solution can be measured by ultraviolet spectrophotometry, the iodine content in the solution can be calculated through the measured absorbance value, and then the adsorption amount of iodine on the adsorbent can be calculated through the mass balance relationship. This method is simple and convenient to measure. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0032] Figure 1 XRD diffraction pattern of the layered double hydroxide in the present application;

[0033] Figure 2 Isotherm adsorption curve of the hydrogel adsorption material in the present application;

[0034] Figure 3 Influence diagram of different pH conditions on adsorption effect;

[0035] Figure 4 Influence diagram of different temperature conditions on adsorption effect;

[0036] Figure 5 Influence diagram of different initial concentrations of adsorbate on adsorption effect. DETAILED DESCRIPTION

[0037] In order to make the person skilled in the art better understand the technical solutions in the embodiments of the present application, and make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be further described.

[0038] The endpoints of the ranges and any values disclosed in this document are not limited to the precise values stated. These ranges and values should be construed as having endpoints that are near the value that is stated. For ranges, the endpoints are included within the range unless specified otherwise. For values, the value is included within the range unless specified otherwise. For example, a range of 1-10 should be construed as including any number from 1 to 10, including the numbers 1 and 10. The same principle applies to the description of combinations.

[0039] Example 1 Preparation of layered double hydroxide LDHs

[0040] A mixed solution was prepared by dissolving 1.22 g of MgCl2·6H2O and 0.36 g of AlCl3·6H2O in 100 mL of deionized water. The pH of the solution was controlled at 10 by introducing a mixture composed of 0.6 M sodium hydroxide and 0.3 M sodium carbonate. Mechanical stirring was maintained at 65°C for 4 hours, followed by an overnight aging process. The resulting LDH was filtered, rinsed with water, and dried at 80°C. The LDH was calcined in a muffle furnace, with the temperature gradually increasing from room temperature to 500°C at a rate of 5°C / min, and maintained for 4 hours, to obtain layered double hydroxide LDHs.

[0041] The carbonate in the intercalated layered double metal hydroxide is converted into carbon dioxide and magnesium aluminum oxide after calcination. Aluminum magnesium oxide has the exchange and adsorption properties with iodide ions, thus providing more exchange sites, thereby improving the adsorption performance of the material. The XRD diffraction pattern of the layered double metal oxide is as follows: Figure 1 shown.

[0042] Example 2 Preparation of hydrogel adsorption material

[0043] A method for preparing a hydrogel adsorption material comprises the following steps:

[0044] Step S1, preparing layered double hydroxides (LDHs) using the process of Example 1;

[0045] Step S2, loading the zero-dimensional carbon nanomaterial into nanocellulose to obtain solution A;

[0046] Specifically, ethylenediamine and citric acid were first hydrothermally reacted at 190°C for 5 hours, followed by filtration and dialysis to prepare zero-dimensional carbon nanomaterials (CDs). The raw material mixture ratio was: 4.035g citric acid, 0.468mL ethylenediamine, and 90ml water. Then, 1.2g of a 0.5wt% CDs solution, 13.0mg EDC, and 50.0mg NHS were introduced into 5.0g of a 1.0wt% CNs suspension, and a homogeneous mixture was obtained by sonication for 1 hour. Acetic acid buffer (2.5mL) with a pH of 3.5 was then introduced into the solution, and the mixture was magnetically stirred at room temperature for 12 hours to obtain Solution A.

[0047] Step S3, adding the chitosan solution to acetic acid to obtain solution B;

[0048] Specifically, 3 g of chitosan was dissolved in 147 g of acetic acid with a concentration of 2 wt % to obtain solution B.

[0049] Step S4, uniformly mixing solution A, solution B and layered double hydroxides (LDHs) dispersed in ethanol to obtain a prepolymer solution;

[0050] Specifically, 0.5 g of layered double hydroxide was dispersed in 4.5 g of ethanol, and then 1.5 g of solution A and 10 g of solution B were added to obtain a prepolymer solution.

[0051] Step S5: Add a crosslinking agent to the prepolymer solution, heat to fully gelate it, and wash to obtain a hydrogel adsorption material. Specifically, glutaraldehyde (1 ml, 0.5 wt%) is used as a crosslinking agent, heated to 30°C, and reacted for 5 hours. The product is then washed in double-distilled water to obtain a hydrogel product.

[0052] The hydrogel product is a cross-linked layered double hydroxide with chitosan and nanocellulose. Chitosan and nanocellulose build a three-dimensional network structure. Due to its rich amino groups, it can adsorb iodide ions through electrostatic attraction, and its three-dimensional network structure increases the adsorption space of the material, thus giving the material excellent adsorption performance. The isothermal adsorption curve of the hydrogel adsorption material is shown in the figure below. Figure 2 shown.

[0053] Example 3 Application of hydrogel adsorption material

[0054] Adsorption experiments were carried out on the hydrogel composite adsorbent under conditions of different pH, temperature, and adsorption concentration to obtain the optimal parameters of the hydrogel adsorption material in iodide ion adsorption.

[0055] Standard curve drawing:

[0056] Prepare a potassium iodide solution with a concentration gradient of 0, 5, 10, 15, 20, and 25 mg / l. Use a UV spectrophotometer to record the absorbance (A) of the iodine solution at the maximum absorption wavelength (226 nm). Plot a standard curve with the iodine solution concentration as the abscissa and the corresponding absorbance as the ordinate. Calculate the iodine content in the solution using the measured absorbance.

[0057] The amount of iodine adsorbed on the adsorbent is then calculated using the mass balance relationship. The calculation formula is as follows:

[0058]

[0059] Among them, C0, C e represent the initial and final concentrations of the iodine solution, V(L) represents the volume of the iodine solution, m(g) represents the initial weight of the adsorbent, and Q e (mg / g) represents the adsorption amount. The Langmuir model simulation results show that I - The maximum adsorption capacity is 231.9 mg / g.

[0060] Parameter optimization experiment:

[0061] 1. Take 200 mg / L iodide ion solution, add a certain amount of hydrogel adsorption material at 50°C, and test the adsorption effect of the hydrogel adsorption material on iodide ions under different pH conditions.

[0062] See also Figure 3 , is the effect of different pH conditions on adsorption effect. Figure 3 It can be seen that when the pH value is in the range of 3-9, the iodide ion adsorption capacity first increases with the increase of pH. When the pH value reaches 6-8, the adsorption capacity reaches the highest value, and then the adsorption capacity decreases. Therefore, the adsorption effect is best when the pH is 6-8.

[0063] 2. Take 200 mg / L iodine ion solution, add a certain amount of hydrogel adsorption material, control the pH value of the solution to be 8, and test the adsorption effect of the hydrogel adsorption material on iodine ions under different temperature conditions.

[0064] Please refer to Figure 4 , which is an influence diagram of different temperature conditions on the adsorption effect. It can be seen from Figure 4 that when the temperature is in the range of 15-55℃, the iodine ion adsorption capacity increases with the increase of temperature. Therefore, the adsorption effect is the best when the temperature is 55℃.

[0065] 3. Take an appropriate amount of iodine solution, test the adsorption effect of different initial concentrations of adsorbate on iodine ions under the conditions of 55℃ and pH value of 8.

[0066] Please refer to Figure 5 , which is an influence diagram of different initial concentrations of adsorbate on the adsorption effect. It can be seen from Figure 5 that when the initial concentration of adsorbate is in the range of 40-200 mg / L, the iodine ion adsorption capacity increases with the increase of the initial concentration of iodine ions. Therefore, the adsorption effect is the best when the adsorbate concentration is 200 mg / L.

[0067] Example 4: Cycle stability test of hydrogel adsorption material

[0068] The hydrogel adsorption material of Example 2 was subjected to adsorption-desorption experiments for 6 consecutive cycles to evaluate its cycle stability. The method is: 200 mg / L iodine ions are adsorbed, and 0.01 mol / L sodium carbonate solution is used for desorption.

[0069] The adsorption capacity of each cycle is as follows:

[0070]

[0071]

[0072] From the above data, it can be seen that after 6 cycles, the adsorption capacity of the hydrogel still maintains 91.7% of the adsorption capacity of the first cycle, which shows that the hydrogel adsorbent of the present application can effectively remove iodine ions, and has stable cycle performance.

[0073] The hydrogel adsorption material of the present application not only can effectively remove iodine ions, but also has the function of measuring the adsorption amount of iodine ions, and is convenient to use.

[0074] The above describes the embodiments of the present application in detail, but the present application is not limited to the described embodiments. Various changes, modifications, replacements and variations of these embodiments made by those skilled in the art without departing from the principles and spirits of the present application still fall within the protection scope of the present application.

Claims

1. A method for preparing a hydrogel adsorption material, characterized in that: The steps include: Step S1, preparing layered double hydroxides (LDHs); Step S2, loading the zero-dimensional carbon nanomaterial into nanocellulose to obtain solution A; Step S3, adding the chitosan solution to acetic acid to obtain solution B; Step S4, uniformly mixing solution A, solution B and layered double hydroxides (LDHs) dispersed in ethanol to obtain a prepolymer solution; Step S5: adding a cross-linking agent to the prepolymer solution, heating it to fully gelate it, and washing it to obtain a hydrogel adsorption material.

2. The method for preparing a hydrogel adsorption material according to claim 1, wherein: In step S1, the method for preparing layered double hydroxides (LDHs) comprises: Mixing magnesium salt and aluminum salt to prepare a mixed solution, adjusting the pH value of the mixed solution to 8.0-10.0, stirring, and aging overnight; Filtering, washing, and drying to obtain LDH particles; Calcination is carried out by gradually increasing the temperature from room temperature to 480-550°C at a rate of 3-5°C / min and keeping the temperature for 3-6 hours to obtain layered double hydroxides LDHs.

3. The method for preparing the hydrogel adsorption material according to claim 2, wherein: The molar ratio of the magnesium salt to the aluminum salt is 3-5:1, the magnesium salt is MgCl2·6H2O, the aluminum salt is AlCl3·6H2O, and the base for adjusting the pH value is a mixed solution of sodium hydroxide and sodium carbonate.

4. The method for preparing a hydrogel adsorption material according to claim 1, wherein: The zero-dimensional carbon nanomaterial is prepared by using ethylenediamine and citric acid as raw materials, performing a hydrothermal reaction at 190° C. for 5 hours, and then filtering and dialysis.

5. The method for preparing the hydrogel adsorption material according to claim 1, wherein: In solution A, the mass ratio of zero-dimensional carbon nanomaterial to nanocellulose is 4-6:50, and the mass concentration of nanocellulose is 0.6-1 wt%; In solution B, the mass concentration of chitosan is 1.5-2.5wt%; The mass ratio of layered double hydroxide to chitosan is 4-6:2; The mass ratio of solution A to solution B is 10-20:

100.

6. A hydrogel adsorption material, characterized in that: Prepared by the method according to any one of claims 1 to 5.

7. Use of the hydrogel adsorption material according to claim 6 in iodide ion adsorption.

8. The use according to claim 7, characterized in that During the iodide ion adsorption process of the hydrogel adsorption material, the system pH value is 6-8, the temperature is 25-55° C., and the initial concentration of the adsorbate is 120-200 mg / L.

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