A gel composite material, its preparation method and use

Abstract

The application belongs to the technical field of gel materials, and particularly relates to a gel composite material, a preparation method and application thereof. The application provides a preparation method of a gel composite material, which comprises the following steps: first mixing reduced graphene oxide, a quaternary phosphonium salt ionic liquid and a solvent to perform liquid phase reaction, so as to obtain a supported reduced graphene oxide; second mixing the supported reduced graphene oxide, sodium alginate and a polyethyleneimine aqueous solution, and then dropping into an inorganic salt solution to perform gel reaction, so as to obtain the gel composite material. The gel composite material obtained by the application has the characteristics of good corrosion resistance, high selectivity and high recycling rate as an adsorbent for uranium extraction from seawater.

Description

Technical Field

[0001] This invention belongs to the field of gel materials technology, specifically relating to a gel composite material, its preparation method, and its application. Background Technology

[0002] Seawater contains over 4 billion tons of uranium resources, equivalent to thousands of times its total land reserves, and its energy reserves could satisfy humanity's energy needs for tens of thousands of years. Therefore, research on uranium extraction from seawater is of great significance.

[0003] The performance requirements for adsorbents used in seawater uranium extraction are as follows: (1) Corrosion resistance: The marine environment is a complex corrosive environment. In a high-salt environment, seawater itself is a strong corrosive medium. In addition, marine microorganisms, attached organisms and their metabolic products all directly or indirectly accelerate the corrosion process. Seawater uranium extraction is different from the usual short-term adsorption in the laboratory. Usually, the adsorbent is placed in seawater for several months, which requires the adsorbent to have excellent salt resistance and corrosion resistance. (2) High selectivity: The chemical composition of natural seawater is relatively complex, mainly including sodium chloride, potassium chloride, magnesium sulfate and dozens of other elements such as iron, lithium, iodine, aluminum, bromine, and strontium. Uranium is only one of these dozens of elements, and its content is extremely low, usually around 3 ppb. (3) Recyclability: Usually, it is a powder material, which is not easy to recycle and has a poor recycling rate. This is the biggest bottleneck problem in the application of seawater uranium extraction.

[0004] Therefore, there is an urgent need for a seawater uranium extraction adsorption material that has good corrosion resistance, high selectivity, and can be recycled. Summary of the Invention

[0005] The purpose of this invention is to provide a gel composite material, its preparation method, and its application. The gel composite material obtained by the method provided by this invention has the characteristics of good corrosion resistance, high selectivity, and high recyclability.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a gel composite material, comprising the following steps:

[0008] Reduced graphene oxide, quaternary phosphate ionic liquid and solvent are first mixed and then reacted in the liquid phase to obtain supported reduced graphene oxide.

[0009] The supported reduced graphene oxide, sodium alginate, and polyethyleneimine aqueous solution were mixed and then added dropwise to an inorganic salt solution to carry out a gel reaction, thereby obtaining the gel composite material.

[0010] Preferably, the quaternary phosphorus ionic liquid includes Cyphos IL101.

[0011] Preferably, the mass ratio of the reduced graphene oxide to the quaternary phosphorus ionic liquid is 1:1;

[0012] The concentration of quaternary phosphate ionic liquid in the first mixture obtained is 0-10%, and is not 0.

[0013] Preferably, the liquid phase reaction is carried out at room temperature for 8 to 12 hours; the gelation reaction is carried out under static conditions.

[0014] Preferably, the mass concentration of the polyethyleneimine aqueous solution is 15 g / L;

[0015] The ratio of the supported reduced graphene oxide, sodium alginate, and polyethyleneimine aqueous solution is 1g:2g:100mL.

[0016] Preferably, the inorganic salt in the inorganic salt solution is calcium chloride;

[0017] The inorganic salt solution has a mass concentration of 3%.

[0018] Preferably, the gelation reaction takes 12 hours and is carried out at a temperature of 30–60°C; the gelation reaction is carried out under static conditions.

[0019] Preferably, after the gelation reaction, the method further includes post-processing the obtained colloid;

[0020] The post-processing includes sequentially performing a first water wash, acid wash, a second water wash, freezing, thawing, filtration, and drying.

[0021] The present invention also provides a gel composite material prepared by the preparation method described in the above technical solution.

[0022] The present invention also provides the application of the gel composite material described above as an adsorbent in seawater uranium extraction.

[0023] This invention provides a method for preparing a gel composite material, comprising the following steps: first, mixing reduced graphene oxide, a quaternary phosphate ionic liquid, and a solvent to conduct a liquid-phase reaction to obtain supported reduced graphene oxide; second, mixing the supported reduced graphene oxide, sodium alginate, and an aqueous solution of polyethyleneimine, and then adding the mixture dropwise to an inorganic salt solution to conduct a gel reaction to obtain the gel composite material. This invention uses reduced graphene oxide supported on a quaternary phosphate ionic liquid as a matrix, and utilizes the esterification reaction of the carboxyl groups of sodium alginate and the amino groups of polyethyleneimine, as well as the crosslinking reaction with metal ions, to construct gel spheres. Ultimately, the gel composite material obtained by this invention serves as an adsorbent for uranium extraction from seawater, exhibiting good corrosion resistance, high selectivity, and high recyclability. Attached Figure Description

[0024] Figure 1 This is a comparison of the adsorption effects of SPGO obtained in Example 1 and SGO obtained in Comparative Example 1 on uranium at different pH values.

[0025] Figure 2 The adsorption kinetics curve of SPGO obtained in Example 1;

[0026] Figure 3 The adsorption isotherm curve of SPGO at 288 K obtained in Example 1;

[0027] Figure 4 The adsorption isotherm curve of SPGO at 298 K obtained in Example 1;

[0028] Figure 5 The adsorption isotherm curve of SPGO at 308 K obtained in Example 1;

[0029] Figure 6 The image shows the adsorption effect of SPGO in simulated seawater experiments obtained in Example 1.

[0030] Figure 7 The figure shows the results of the SPGO recycling experiment obtained in Example 1;

[0031] Figure 8 SEM images of rGO, PGO, and SPGO;

[0032] Figure 9 Infrared spectra of rGO and PGO;

[0033] Figure 10 Infrared spectra of SPGO, SGO, the adsorbed gel material (SPGO-U), and the desorbed gel material (D-SPGO);

[0034] Figure 11 SEM images of the gel material after adsorption (SPGO-U) and the gel material after desorption (D-SPGO);

[0035] Figure 12 EDS diagrams of the gel material (SPGO), the adsorbed gel material (SPGO-U), and the desorbed gel material (D-SPGO);

[0036] Figure 13 XPS plots of the gel material (SPGO) and the post-adsorption gel material (SPGO-U). Detailed Implementation

[0037] This invention provides a method for preparing a gel composite material, comprising the following steps:

[0038] Reduced graphene oxide, quaternary phosphate ionic liquid and solvent are first mixed and then reacted in the liquid phase to obtain supported reduced graphene oxide.

[0039] The supported reduced graphene oxide, sodium alginate, and polyethyleneimine aqueous solution were mixed and then added dropwise to an inorganic salt solution to carry out a gel reaction, thereby obtaining the gel composite material.

[0040] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0041] In this invention, reduced graphene oxide, quaternary phosphate ionic liquid and solvent are first mixed and then reacted in a liquid phase to obtain supported reduced graphene oxide.

[0042] In this invention, the quaternary phosphorus ionic liquid preferably includes Cyphos IL101. In this invention, the solvent is preferably methanol.

[0043] In this invention, the mass ratio of the reduced graphene oxide to the quaternary phosphate ionic liquid is preferably 1:1; the concentration of the quaternary phosphate ionic liquid in the first mixture is preferably 0-10%, and not 0, and more preferably 3-5%.

[0044] Prior to the first mixing, the present invention preferably includes heat treatment of the reduced graphene oxide; the heat treatment process is preferably: heating in an oven at 120°C for 30 minutes. In the present invention, after the reduced graphene oxide has been heat-treated, the first mixing is preferably performed while it is still hot, i.e., no cooling process is performed. In the present invention, by heat-treating the reduced graphene oxide and performing the first mixing while it is still hot, the loading of the quaternary phosphate ionic liquid can be better achieved.

[0045] In this invention, the first mixing process preferably includes: dispersing a quaternary phosphate ionic liquid in a solvent to obtain an ionic liquid dispersion; heating the reduced graphene oxide and then adding the ionic liquid dispersion to the heated reduced graphene oxide while it is still hot.

[0046] In this invention, the temperature of the liquid-phase reaction is 100–130°C, more preferably 110–120°C; the time is preferably 20–50 min, more preferably 30–40 min. In this invention, the liquid-phase reaction is preferably carried out under static conditions.

[0047] Following the liquid-phase reaction, the present invention preferably further includes drying the obtained material; the drying process is preferably carried out at 120°C for 12 hours. In the present invention, quaternary phosphate ionic liquid can be loaded onto reduced graphene oxide through a liquid-phase reaction.

[0048] After obtaining the supported reduced graphene oxide, the present invention mixes the supported reduced graphene oxide, sodium alginate and polyethyleneimine aqueous solution, and then adds them dropwise to an inorganic salt solution to carry out a gel reaction, thereby obtaining the gel composite material.

[0049] In this invention, the preferred mass concentration of the polyethyleneimine aqueous solution is 15 g / L; the preferred ratio of the supported reduced graphene oxide, sodium alginate, and polyethyleneimine aqueous solution is 1 g: 2 g: 100 mL. In this invention, the preferred inorganic salt in the inorganic salt solution is calcium chloride; the preferred mass concentration of the inorganic salt solution is 3%. This invention does not impose a specific limitation on the amount of the inorganic salt solution, as long as complete gelation is ensured. In a specific embodiment of this invention, the preferred amount of the inorganic salt solution is 500 mL.

[0050] In this invention, the second mixing process is preferably as follows: after mixing the supported reduced graphene oxide and sodium alginate, add the mixture to an aqueous solution of polyethyleneimine, and then perform ultrasonic treatment and heating and stirring sequentially. In this invention, the ultrasonic treatment time is preferably 5 minutes; the heating and stirring temperature is preferably 50°C, and the time is preferably 6 hours.

[0051] In this invention, the gelation reaction time is preferably 12 hours, and the temperature is preferably 30–60°C, more preferably 40–50°C. In this invention, the gelation reaction is preferably carried out under static conditions.

[0052] In this invention, after the gelation reaction, it is preferable to further perform post-treatment on the obtained colloid; the post-treatment preferably includes sequentially performing a first water wash, an acid wash, a second water wash, freezing, thawing, filtration, and drying. In this invention, the first water wash is preferably performed three times; the acid wash uses a hydrochloric acid solution with a concentration of 0.05 mol / L; the acid wash process preferably involves immersing the gel in the acid solution; the acid wash time is preferably 2.5 hours; the second water wash is preferably performed using deionized water until neutral; the freezing time is preferably overnight; and the drying temperature is preferably 30°C.

[0053] The present invention also provides a gel composite material prepared by the preparation method described in the above technical solution.

[0054] This invention also provides the application of the gel composite material described in the above-mentioned technical solution in uranium extraction from seawater. This invention does not impose any particular limitation on the specific implementation of the application; any method well-known to those skilled in the art can be used.

[0055] To further illustrate the present invention, a gel composite material, its preparation method, and its application are described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] A Cyphos IL101 dispersion with a concentration of 5 wt% was prepared using methanol as a solvent. Reduced graphene oxide (rGO) was heated in an oven at 120 °C for 30 min, and then the Cyphos IL101 dispersion (with a mass ratio of 1:1 between reduced graphene oxide and Cyphos IL101 and a concentration of 5% Cyphos IL101 in the resulting mixture) was added while still hot. After standing at room temperature for 10 h, the mixture was dried at 120 °C for 12 h to obtain supported reduced graphene oxide (PGO).

[0058] 1 g of PGO and 2 g of sodium alginate (SA) were mixed and then 100 mL of 15 g / L polyethyleneimine was added. After sonication for 5 min, the mixture was stirred in an oil bath at 50 °C for 6 h. The mixture was then added dropwise to 500 mL of 3% CaCl2 aqueous solution. The mixture was allowed to stand at room temperature for 12 h to carry out the gelation reaction. The resulting colloid was washed with water three times, soaked in 0.05 M hydrochloric acid solution for about 2.5 h, washed with deionized water until neutral, frozen overnight, thawed, filtered, and dried at 30 °C to obtain the gel composite material (SPGO).

[0059] Comparative Example 1

[0060] The gel composite material was prepared according to the method of Example 1, except that Cyphos IL101 was not added. The resulting gel composite material is denoted as SGO.

[0061] Performance testing

[0062] Test Example 1

[0063] Adsorption experiment

[0064] To study the adsorption effect of SPGO on uranium, a series of adsorption experiments were designed, and the adsorption rate R of SPGO on uranium (Equation 1), the adsorption capacity qe (Equation 2) were calculated, and the kinetics of SPGO adsorption of uranium were fitted (Equations 3-4), the isothermal adsorption was fitted (Equations 5-6), and the thermodynamics (7-9) were calculated.

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] ΔG 0 =-RTln(K) c (8)

[0073]

[0074] Among them, C0 (mg / L) and C e (mg / L) represent the uranium (VI) concentration in the solution before and after the reaction, respectively; V (L) is the solution volume, and m (g) is the dry weight of SPGO; q e (mg / g) represents the amount of uranium(VI) adsorbed by SPGO at adsorption equilibrium; q t (mg / g) represents the amount of uranium(VI) adsorbed by SPGO at time t (min);

[0075] k1 (g / mg) and k2 (mg / g) are the constants of the pseudo-first-order kinetic and pseudo-second-order kinetic models, respectively;

[0076] q m (mg / g) represents the maximum adsorption capacity, K L (L / mg) and K F ((mg / g)(L / mg)1 / n) is the isothermal adsorption constant, ΔH 0 (kJ / mol), ΔS 0 (J / (mol·K)), ΔG 0 (kJ / mol), R and T(K) are enthalpy change, entropy change, Gibbs free energy, ideal gas constant (8.314 J / mol·K) and Kelvin, respectively.

[0077] 1. Effect of initial pH on adsorption

[0078] Figure 1 This is a comparison of the adsorption effects of SPGO obtained in Example 1 and SGO obtained in Comparative Example 1 on uranium at different pH values.

[0079] like Figure 1As shown, rGO exhibits poor adsorption performance for uranium, but after loading Cyphos IL101, the adsorption capacity of PGO for uranium is significantly improved under the same conditions. However, in the experiment, PGO recovery was difficult, as it easily adhered to the inner wall of the container, causing significant losses. Therefore, PGO was cross-linked with SA and PEI to prepare gel spheres for uranium adsorption, facilitating adsorbent recovery. Simultaneously, experimental results show that SPGO maintains good adsorption performance for uranium under the same conditions, indicating that the method of preparing SPGO by cross-linking PGO with SA and PEI is feasible.

[0080] like Figure 1 As shown, within the initial solution pH range of 5–9, the adsorption capacity of SPGO for uranium begins to increase at pH 5, reaching its maximum at pH 8, where the adsorption rate reaches 99%. Subsequently, the adsorption capacity gradually decreases with increasing pH. This is because the types of uranyl ions in the solution differ under different pH conditions. Between pH 5 and 7.5, [(UO2)] x (OH) y ] z+ Uranium carbonate (SPGO) is the main component of the solution, and when the pH exceeds 7.5, it exists primarily as negatively charged uranyl carbonate. Uranyl carbonate is relatively stable, but its decomposition can be promoted by free hydrogen ions. SPGO contains phosphate, carboxyl, amino, and hydroxyl groups. The P=O group of the phosphate group has a strong coordination effect with uranium, and according to the hard / soft acid / base theory, uranyl cations preferentially bind to the harder phosphate group and the softer carboxyl group. Furthermore, the presence of amino and hydroxyl groups promotes the adsorption of uranium by P=O. Therefore, the adsorption capacity of SPGO for uranium gradually increases from pH 5. However, when the pH exceeds 7, the adsorption capacity decreases with increasing uranyl carbonate content. In nature, seawater has a pH of approximately 8, therefore SPGO can be used for uranium extraction from seawater.

[0081] Simultaneously, due to the negative charge of the carboxyl group, it electrostatically adsorbs positively charged uranyl ions and electrostatically repels negatively charged uranyl ions. Therefore, the adsorption capacity of SGO without phosphate groups for uranium gradually decreases from pH 5. Furthermore, experiments showed that when the initial pH of the solution exceeds 7, SGO cannot maintain its form and completely dissolves. However, after adding Cyphos IL101, SPGO can still maintain its form in solutions with pH values ​​above 7. This is because Cyphos IL101 has high thermal stability and electrochemical properties.

[0082] 2. Adsorption kinetics

[0083] Adsorption kinetics can determine the solute absorption rate and the residence time required to complete the adsorption reaction. Figure 2The effect of adsorption time on the adsorption of uranium (VI) by SPGO was investigated. At 298 K, 0.020 g of SPGO adsorbed 90.0 mL of uranium solution with pH 8 and concentrations of 4.6 and 10.5 mg / L, respectively. Figure 2 As shown, adsorption reached equilibrium at approximately 600 min. Relevant kinetic parameters are shown in Table 1. The results indicate that the adsorption kinetics of SPGO for U(VI) at both concentrations conform to a pseudo-second-order model, suggesting that the adsorption of U(VI) by SPGO is chemisorption.

[0084] Comparing the effects of time on the adsorption of uranium by SGO and SPGO, it was found that the adsorption rates of the two were basically the same within 0-1 h, while SGO adsorption was faster from 1 to 4 h. Both reached adsorption equilibrium around 10 h. However, SPGO adsorbed significantly more uranium than SGO. This may be because SPGO contains phosphate groups, which have a strong coordination effect with uranium.

[0085] Table 1 Adsorption Kinetics

[0086]

[0087] 3. Adsorption isotherm

[0088] Figure 3 The adsorption isotherm curve of SPGO at 288 K obtained in Example 1; Figure 4 The adsorption isotherm curve of SPGO at 298 K obtained in Example 1; Figure 5 The adsorption isotherm curve of SPGO at 308 K obtained in Example 1;

[0089] like Figures 3-5 As shown in Table 2, the adsorption capacity of SPGO for uranium increases with increasing temperature. Furthermore, the Langmuir model better matches the adsorption curve of SPGO for uranium; therefore, the adsorption of uranium by SPGO is a homogeneous monolayer adsorption primarily based on the Langmuir model. In conclusion, at 308 K and pH 8, the theoretical maximum adsorption capacity of SPGO for uranium is 188.296 mg / g.

[0090] Table 2 Adsorption isotherms

[0091]

[0092] 3. Adsorption thermodynamics

[0093] Thermodynamic parameters are shown in Table 3. The adsorption amount decreases with increasing temperature (Table 2), ΔH 0 >0 indicates that the adsorption of uranium by SPGO is an endothermic reaction. ΔS 0 A value greater than 0 indicates an increase in the randomness and disorder of the solid-liquid surface during adsorption. ΔG 0<0, which means that the adsorption process of uranium by SPGO is spontaneous and thermodynamically feasible. In summary, the adsorption process of U(VI) by SPGO is a spontaneous endothermic process, which is consistent with the adsorption isotherm.

[0094] Table 3 Adsorption Thermodynamics

[0095]

[0096] Test Example 2

[0097] Simulated seawater experiment and natural seawater experiment

[0098] To investigate the adsorption selectivity of SPGO for uranium in seawater, simulated seawater containing Na, Mg, Ca, U, V, Zn, Ni, Cu, and Fe was prepared for adsorption experiments. At 298 K, 0.020 g of SGO and SPGO were used to adsorb 90 mL of simulated seawater, respectively, and the reaction was allowed to proceed for 12 h. The concentrations of each element in the solution after adsorption were measured, and K0 was calculated. d Value (Formula 10).

[0099] The adsorption effect of SPGO on uranium in real seawater was also studied. Natural seawater from the Yellow Sea near Weihai, Shandong Province was collected, filtered through a 0.22 μm membrane to remove microorganisms, and then 0.020 g of SPGO was used to adsorb 100 mL of natural seawater at 298 K, with adsorption repeated 10 times. SGO was used as a control in a comparative experiment.

[0100]

[0101] To investigate whether Cyphos IL101 increases material selectivity, a multi-element mixed solution containing uranium was prepared. Experimental results showed that ( Figure 6 ), SGO without Cyphos IL101 loading for uranium K d The value is significantly higher than that of other ions, which is due to the K value of SGO relative to vanadium. d The K+ value was 7.7 times higher, indicating that SGO has good selectivity for uranium. This may be due to the presence of the carboxyl group, which promotes the dissociation of the uranyl tricarbonate complex, making it easier for SGO to bind to uranyl ions. After loading Cyphos IL101, the K+ value of SGO for uranium was significantly increased. d The value increased significantly, approximately equal to the K value of SGO for uranium. d The value is twice that of SPGO, which is also the K value of vanadium. d The value is 15.6 times higher. This indicates that loading Cyphos IL101 can improve the material's selectivity for uranium, especially for UV. After loading Cyphos IL101, phosphate groups are generated in SPGO. The P=O of the phosphate group can synergistically adsorb uranium with hydroxyl and amino groups, which promotes the selective adsorption of uranium by SPGO.

[0102] The adsorption results from natural seawater show that both SPGO and SGO have a certain adsorption effect on uranium in natural seawater. However, the adsorption capacity of SPGO for uranium (4 μg / g) is significantly higher than that of SGO (3 μg / g), while the adsorption capacity for vanadium (1.5 μg / g) is lower than that of SGO (2 μg / g), which is consistent with the results of the selectivity experiment. This indicates that SPGO loaded with Cyphos IL101 has high selectivity for uranium.

[0103] Test Example 3

[0104] Recycling Experiment

[0105] Material recycling can reduce costs, therefore, the recycling performance of SPGO needs to be tested. At 313 K, SPGO adsorbed with 5 mg / L uranium was desorbed using hydrochloric acid at pH 1.5, and the desorption rate was calculated using Equation 11. The desorbed SPGO was washed three times with deionized water, air-dried, and then subjected to adsorption again. The adsorption-desorption cycle was performed five times, and the adsorption and desorption rates were measured in each cycle.

[0106]

[0107] Among them, C D (mg / L) represents the uranium concentration in the eluent, V D (mL) represents the volume of the elution buffer.

[0108] The adsorbed sample was desorbed at 313K using HCl at pH 1.5. The test results are as follows: Figure 7 As shown, by Figure 7 It can be seen that after four adsorption-desorption cycles, the adsorption rate of SPGO for 5 mg / L uranium decreased slightly, from 96.5% to about 95.8%, and further decreased to 93.5% in the fifth cycle. Meanwhile, the desorption rate gradually increased from about 90% in the first cycle to 93% over the five cycles. This indicates that SPGO has good recycling performance.

[0109] Test Example 4

[0110] Adsorption mechanism

[0111] To further investigate the adsorption mechanism of uranium by SPGO, SPGO before and after uranium adsorption, as well as after desorption, was characterized after natural air drying. The surface structure, microstructure, and elemental composition of SPGO were analyzed using scanning electron microscopy. The molecular structure and surface functional groups of SPGO were determined by FT-IR using the direct tablet method. The surface elemental valence states of SPGO were determined by XPS. The average pore size and porosity of the material were determined using specific surface area (BET).

[0112] Figure 8SEM images of rGO, PGO, and SPGO are provided, where a represents rGO, b represents PGO, and c represents SPGO; from Figure 8 As can be seen, rGO exhibits a distinct layered structure; after loading Cyphos IL101, PGO still maintains its layered structure; while after crosslinking PEI and SA to generate SPGO, a less obvious layered structure can be observed on the surface, indicating that PGO was successfully crosslinked. Simultaneously, fine pores are generated on the SPGO surface, providing channels for the passage of uranyl ions.

[0113] BET results showed that the specific surface area of ​​PGO loaded with Cyphos IL101 was 2.74 m². 2 / g, with an average pore size of 3.15nm; while SPGO has a specific surface area of ​​2.07m². 2 / g, with an average pore size of 5.77nm, showing a significant increase in pore size, which may be due to the addition of sodium alginate.

[0114] Figure 9 Infrared spectra of rGO and PGO. Figure 10 Infrared spectra of SPGO, SGO, the adsorbed gel material (SPGO-U), and the desorbed gel material (D-SPGO);

[0115] from Figures 9-10 It can be seen that rGO is at 1728cm -1 The peak at [value] is caused by C=O, but its intensity is weak, which may be due to the reduction of carboxyl groups on the surface of graphene oxide after reduction. Meanwhile, rGO loaded with Cyphos IL101 shows peaks at 2956.1, 2925.6, and 2854.9 cm⁻¹. -1 A distinct peak appeared at this point, caused by the stretching of CH3 and aliphatic CH. The values ​​at 1463.5 and 1110.5 cm... -1 The peak at 718.7 cm is caused by PC stretching. -1 The deformation (out-of-plane) of CH and PC at this point is due to the presence of these defects. This indicates that rGO was successfully loaded with Cyphos IL101. However, after PGO crosslinks with SA and PEI, the crosslinking effect at 3000-3500 cm⁻¹ is due to the amino-rich nature of PEI. -1 The stretching vibration peaks of OH and NH at 2956.1 cm⁻¹ are broadened. -1 The peaks disappear, at 2925.6 and 2854.9 cm. -1 The peak intensity decreases at 1728.9 cm⁻¹. -1 The C=O peak at 1598.6 cm⁻¹ is significantly enhanced, along with those at 1404.9 cm⁻¹. -1 The presence of both asymmetric and symmetric stretching vibrations of the -COO group indicates successful SA crosslinking. The 1463.5 cm⁻¹... -1The PC stretching vibration disappeared at 1241.8cm, but it persisted at 1241.8cm. -1 A peak of P=O appears at 1030.4 cm⁻¹, and at 1030.4 cm⁻¹... -1 A peak of PO(R) group appears at 718 cm⁻¹. -1 The weakening of the CH and PC peaks nearby indicates that phosphate groups were generated on the SPGO surface after PGO containing Cyphos IL101 crosslinking. (668.5 cm⁻¹) -1 The crosslinking at the NH stretching vibration indicates that PGO has successfully crosslinked with SA and PEI. In summary, the SPGO surface contains functional groups such as phosphate, carboxyl, hydroxyl, and amino groups.

[0116] After uranium adsorption, a distinct O=U=O peak (921.4 cm⁻¹) appeared in the infrared spectrum of SPGO-U. -1 This indicates that SPGO successfully adsorbed uranium, consistent with the results of XPS, SEM-Mapping, and SEM-EDS. Comparing the infrared spectra before and after SPGO adsorption, it was found that after adsorption, the uranium concentration at 1728.9 cm⁻¹... -1 The C=O peak weakens at 1598.6 cm⁻¹. -1 The increased intensity of the -COO- peak indicates that the carboxyl group participated in the reaction. At 1241.8 cm⁻¹... -1 The peak at P=O disappears at 1030.4 cm⁻¹. -1 The weakening of the PO peak at 668.5 cm⁻¹ indicates that the phosphate groups participated in the reaction during uranium adsorption. -1 The weakening of the NH peak indicates that the amino group also participates in the reaction. This is consistent with the results of XPS and EDS. After desorption, comparing the infrared spectrum of SPGO, D-SPGO showed an O=U=O peak, which is due to incomplete resolution. The peaks at 1598.6 and 1404.9 cm⁻¹ are also observed. -1 The asymmetric and symmetric stretching vibration peaks of -COO at 1241 cm⁻¹ shifted and their intensity decreased. -1 The intensity of the P=O peak at the point decreases due to the participation of both in the reaction. All characteristic peaks of SPGO are still present in the infrared spectrum of D-SPGO, indicating that the properties of SPGO have not changed significantly after multiple adsorption cycles, and therefore it can be recycled.

[0117] Figure 11 SEM images of the adsorbed gel material (SPGO-U) and the desorbed gel material (D-SPGO), where a is SPGO-U and b is D-SPGO. Figure 11As can be seen from the SEM images, after adsorption, the surface pores of SPGO-U disappear, the layered structure disappears, and the material surface exhibits wrinkling. However, after five adsorption-desorption cycles, the surface of D-SPGO becomes smoother, and no layered structure or pores are observed. Therefore, the adsorption effect of SPGO on uranium decreases after multiple adsorption-desorption cycles.

[0118] Figure 12 EDS images of the gel material (SPGO), the gel material after adsorption (SPGO-U), and the gel material after desorption (D-SPGO) are shown, where (a) is SPGO, (b) is SPGO-U, and (c) is D-SPGO. It can be seen that uranium was detected in the adsorbed SPGO, indicating that SPGO does indeed adsorb uranium. Due to incomplete desorption, uranium was still detected in D-SPGO. In the SEM-Mapping image, phosphorus (P) is uniformly distributed, indicating that P-containing groups are uniformly dispersed in SPGO. Simultaneously, after adsorption, uranium (U) is uniformly dispersed on the SPGO surface, indicating that U reacted with phosphate groups.

[0119] Figure 13 XPS spectra of the gel material (SPGO) and the post-adsorption gel material (SPGO-U) are shown, with spectra representing C1s, O1s, N1s, U 4f, and P 2p, respectively. In the overall spectrum, SPGO-U exhibits a distinct U 4f peak, while the U 4f spectrum shows 4f peaks at 381.86 eV and 379.90 eV, and at 392.61 eV and 390.84 eV, respectively. 7 / 2 U 4f 5 / 2 The presence of peaks indicates that SPGO successfully adsorbed uranium. The C1s spectrum of SPGO includes a -CN peak at 286.26 eV, an NC=O peak at 287.71 eV, a C=O peak at 288.77 eV, and a peak at 283.50 eV, which may represent a metallic carbon compound. After adsorption, the C=O peak shifts, likely due to the involvement of the carboxyl group in the reaction, while the -CN peak shifts to 286.05 eV due to the involvement of the amino group. In the O1s spectrum of SPGO, there is a P=O peak at 531.23 eV, a PO peak at 533.01 eV, a C-OH peak at 532.18 eV, and an OCO peak at 533.88 eV. This indicates that SPGO generates phosphate groups after cross-linking. After adsorption, the C-OH peak shifted, the P=O peak shifted to 531.56 eV, and the PO peak shifted to 532.86 eV. Simultaneously, a new peak at 530.63 eV represents the O1s binding energy of the phosphate group, indicating that the phosphate and hydroxyl groups participated in the adsorption of uranium. In the N1s spectrum of SPGO, the peaks at 401.34 eV and 399.65 eV represent the NH4+ and NH4+ binding energies, respectively. 3+The peaks for -NH2 and -NH2 were observed. After uranium adsorption, no N was detected in the XPS spectrum of SPGO-U, indicating that the amino group participated in the reaction during adsorption. A P 2p peak appeared at 132.24 eV in SPGO, indicating that rGO successfully loaded Cyphos IL101, and that PGO successfully crosslinked with SA and PEI. After adsorption, the P 2p peak narrowed and shifted to 132.58 eV, indicating that the phosphate group participated in the reaction.

[0120] Infrared spectroscopy and XPS characterization results show that the SPGO surface contains a large number of carboxyl, hydroxyl, amino, and phosphate groups. Studies indicate that the binding mechanism between carboxyl groups and uranyl ions is mainly monodentate and bidentate ligands, while phosphate, hydroxyl, and amino groups form stable complexes with uranyl ions. Therefore, SPGO exhibits good adsorption performance for uranium. Uranyl carbonate has a relatively stable structure and low adsorption affinity, while carboxyl groups can promote its decomposition through free hydrogen ions. Simultaneously, P=O has a strong coordination effect with uranium, and the synergistic effect of amino and hydroxyl groups with phosphate groups further promotes the adsorption of uranium by SPGO, thus SPGO exhibits high selectivity for uranium. In summary, loading Cyphos IL101 can improve the selective adsorption performance of the material for uranium.

[0121] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a gel composite material, characterized in that, Includes the following steps: Reduced graphene oxide, quaternary phosphate ionic liquid and solvent are first mixed and then reacted in the liquid phase to obtain supported reduced graphene oxide. The first mixing process includes: dispersing the quaternary phosphate ionic liquid in a solvent to obtain an ionic liquid dispersion; After heating the reduced graphene oxide, the ionic liquid dispersion was added to the heated reduced graphene oxide while it was still hot. The heating process was as follows: heating in an oven at 120°C for 30 minutes; the liquid phase reaction was carried out at room temperature for 8-12 hours; the liquid phase reaction was carried out under static conditions; the mass ratio of the reduced graphene oxide to the quaternary phosphate ionic liquid was 1:

1. The supported reduced graphene oxide, sodium alginate, and polyethyleneimine aqueous solution were mixed and then added dropwise to an inorganic salt solution to carry out a gel reaction, thereby obtaining the gel composite material; the mass concentration of the polyethyleneimine aqueous solution was 15 g / L; the ratio of the amount of the supported reduced graphene oxide, sodium alginate, and polyethyleneimine aqueous solution was 1 g: 2 g: 100 mL; the inorganic salt in the inorganic salt solution was calcium chloride.

2. The preparation method according to claim 1, characterized in that, The concentration of quaternary phosphate ionic liquid in the first mixture obtained is 0~10%, and is not 0.

3. The preparation method according to claim 1, characterized in that, The inorganic salt solution has a mass concentration of 3%.

4. The preparation method according to claim 1, characterized in that, The gelation reaction was carried out over a period of 12 hours at a temperature of 30-60°C, and was conducted under static conditions.

5. The preparation method according to claim 1, characterized in that, The gel reaction process also includes post-processing of the resulting colloid. The post-processing includes sequentially performing a first water wash, acid wash, a second water wash, freezing, thawing, filtration, and drying.

6. The gel composite material prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the gel composite material according to claim 6 as an adsorbent in seawater uranium extraction.

Images