A polyamidoxime-loaded biochar sphere adsorbent material for efficient uranium extraction and its preparation method

Abstract

The present invention discloses a preparation method of a polyamidoxime-loaded biochar sphere adsorbent material for efficient uranium extraction, which includes weighing 0.5 g of polyamidoxime powder and completely dissolving it in a sodium hydroxide solution to obtain an alkaline polyamidoxime solution; then adding 100 μL of glutaraldehyde and 0.1 g of biochar spheres to the alkaline polyamidoxime solution, and shaking it on a shaker at a speed of 150 rpm for 6 h, taking out the biochar spheres and drying them at 60 °C to obtain the polyamidoxime-loaded biochar sphere adsorbent. The method of the present invention uses high-temperature carbonization to obtain biochar spheres, and then uses a chemical cross-linking reaction to load polyamidoxime to obtain the present adsorbent. This method is simple to operate, low in cost, green and pollution-free. Moreover, the polyamidoxime-loaded biochar sphere adsorbent material prepared by this method has high porosity and high hydrophilicity, and the uranium adsorption rate in natural seawater is as high as 0.27 mg / g / d.

Description

Technical Field

[0001] The present invention relates to the field of functional materials, and particularly to a loaded polyamidoxime biochar sphere adsorbent material for efficient uranium extraction and a preparation method thereof. Background Art

[0002] Uranium is the main raw material for promoting the development of nuclear power, and a large supply of uranium is an important factor in the development of nuclear power. However, uranium ores on the earth cannot provide sustainable energy for nuclear energy, while the deep sea contains rich uranium, and its reserves are approximately 1000 times that of land uranium. At present, extracting uranium from seawater faces many difficulties and challenges, including extremely low uranium concentration in seawater, coexistence of competitive ions, and marine biofouling.

[0003] Existing seawater uranium extraction technologies mainly include solvent extraction method, ion exchange method, adsorption method, etc. Among them, the adsorption method is considered to have the most promising application prospects. Its basic principle is to transfer uranyl ions from the aqueous phase to the active sites of the adsorption functional material, and through interaction, uranium is separated from seawater and enriched on the adsorption functional material. Among them, polyamidoxime-based adsorbents, as a typical polymer material, have received great attention in extracting uranium from seawater in the past 40 years due to their good binding ability with uranyl ions in seawater. By typically grafting or crosslinking with other carrier materials with specific functions, the uranium adsorption performance of polyamidoxime-based adsorbents has been greatly improved. However, the application of polyamidoxime-based adsorbents is still hindered by insufficient uranium adsorption capacity, slow adsorption rate, and high manufacturing cost. Therefore, it is necessary to develop a loaded polyamidoxime biochar sphere adsorbent material for efficient uranium extraction and a preparation method thereof. Summary of the Invention

[0004] In view of this, the present invention provides a loaded polyamidoxime biochar sphere adsorbent material for efficient uranium extraction, which solves the problem that the existing amidoxime-based adsorbent material has low uranium adsorption efficiency due to the insufficient exposure of the functional groups of the amidoxime group.

[0005] The present invention adopts a preparation method of a loaded polyamidoxime biochar sphere adsorbent material for efficient uranium extraction, including the following steps: weighing 0.5 g of polyamidoxime powder and completely dissolving it in a sodium hydroxide solution to obtain an alkaline polyamidoxime solution; then adding 100 μL of glutaraldehyde and 0.1 g of biochar spheres to the alkaline polyamidoxime solution, and shaking it on a shaker at a speed of 150 rpm for 6 h, taking out the biochar spheres and drying them at 60 °C to obtain a loaded polyamidoxime biochar sphere adsorbent.

[0006] Preferably, the biochar spheres are prepared by the following method: adding the exponentially growing Penicillium chrysogenum culture medium to the potato dextrose medium at a volume ratio of 1%, then culturing with shaking at 180 rpm at 27 °C for 3 days, then washing with deionized water and freeze-drying to obtain Penicillium chrysogenum mycelial spheres, and then carbonizing the mycelial spheres in an argon atmosphere at a heating rate of 5 °C / min to 600 °C for 2 h.

[0007] Preferably, the volume of the sodium hydroxide solution is 10 mL and the concentration is 0.3 mol / L.

[0008] Preferably, the polyamidoxime powder is prepared by the following method: weighing 5.6 g of hydroxylamine hydrochloride and completely dissolving it in 100 mL of N,N-methylenefomamide, then adding 4.12 g of sodium carbonate and 1.6 g of sodium hydroxide to make the solution reach neutrality, and then stirring and mixing at 45 °C for 1 h. Then weigh 4 g of polyacrylonitrile and add it to the mixed solution, and stir at 65 °C for 24 h to obtain a polyacrylonitrile mixed solution; then completely dissolve 2.8 g of hydroxylamine hydrochloride in 30 mL of N,N-methylenefomamide, add 0.8 g of sodium carbonate and 2.06 g of sodium hydroxide to adjust the pH of the solution to neutrality and stir for 10 min, then add this solution to the previously prepared polyacrylonitrile mixed solution, and react at 65 °C for 24 h. Collect the supernatant and centrifuge at 10000 rpm for 10 min. Slowly drip the collected supernatant into anhydrous ethanol to obtain a white flocculent precipitate, and then wash it several times with anhydrous ethanol, and filter and dry to obtain the polyamidoxime powder.

[0009] On the other hand, the present invention provides a polyamidoxime-loaded biochar sphere adsorbent material for highly efficient uranium extraction, wherein the loading amount of polyamidoxime is 22.87%.

[0010] By using the preparation method of the polyamidoxime-loaded biochar sphere adsorbent material provided by the present invention, biochar spheres are obtained by high-temperature carbonization, and then polyamidoxime is loaded by chemical cross-linking reaction to obtain the present adsorbent. Substantially, the molecular chains of polyamidoxime self-crosslink and interpenetrate with the carbonized mycelia, so as to be firmly loaded on the surface of the carbonized mycelial spheres. This method is simple in operation, low in cost, green and pollution-free. Moreover, the polyamidoxime-loaded biochar sphere adsorbent material prepared by this method has a high porosity, the pore size rate is 90.94%, the average pore size is 13.5 μm, and it has high hydrophilicity. Therefore, it has high seawater permeability, which can further promote the exposure of the amidoximation functional groups in the material and uranium adsorption. In the simulated seawater containing 16 ppm of uranium, the biochar sphere adsorbent reaches the adsorption equilibrium within 10 h, the adsorption capacity for uranium is 211.35 mg / g, and the uranium adsorption rate in natural seawater is as high as 0.27 mg / g / d. Description of the Drawings

[0011] Figure 1Schematic diagram of the preparation process of a polyamidoxime-loaded biochar sphere adsorbent material for efficient uranium extraction in Example 1;

[0012] Figure 2 Infrared spectra of biochar spheres (BS) and polyamidoxime-loaded biochar sphere adsorbents (PAO-BS) in Example 1;

[0013] Figure 3 Thermogravimetric curves of biochar spheres (BS), polyamidoxime (PAO), and polyamidoxime-loaded biochar sphere adsorbents (PAO-BS) in Example 1;

[0014] Figure 4 Scanning electron micrographs of biochar spheres (left) and polyamidoxime-loaded biochar sphere adsorbents (right) in Example 1;

[0015] Figure 5 Schematic diagram of the pore size distribution of the polyamidoxime-loaded biochar sphere adsorbent in Example 1;

[0016] Figure 6 Contact angle test results of the polyamidoxime-loaded biochar sphere adsorbent in Example 1;

[0017] Figure 7 Kinetic curves of uranium adsorption by the polyamidoxime-loaded biochar sphere material in simulated seawater doped with uranium at different concentrations in Example 1;

[0018] Figure 8 Adsorption test results of uranyl ions and other competitive metal ions by the polyamidoxime-loaded biochar sphere material in Example 1 after 10 days of interaction with circulating natural seawater;

[0019] Figure 9 Uranium adsorption rates of the polyamidoxime-loaded biochar sphere material in Example 1 and other existing polyamidoxime-based adsorbents in natural seawater. Specific Embodiments

[0020] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0021] Penicillium chrysogenum fungi were purchased from Ningbo Test Biotechnology Co., Ltd., hydroxylamine hydrochloride and polyacrylonitrile were purchased from Shanghai Merck Biochemical Technology Co., Ltd., N,N-methylformamide was purchased from Beijing Huawei Ruike Chemical Co., Ltd., and potato dextrose agar medium was purchased from Guangdong Huankai Microbial Co., Ltd.

[0022] Example 1: Refer to Figure 1 , a preparation method of a polyamidoxime-loaded biochar sphere adsorbent material for efficient uranium extraction, comprising the following steps:

[0023] Preparation of polyamidoxime:

[0024] First, weigh 5.6 g of hydroxylamine hydrochloride and completely dissolve it in 100 mL of N,N - methyleneformamide. Then add 4.12 g of sodium carbonate and 1.6 g of sodium hydroxide to make the solution reach a neutral pH level. After that, stir the mixed solution at 45 °C for 1 h. Then weigh 4 g of polyacrylonitrile and add it to the mixed solution, and stir at 65 °C for 24 h to obtain a polyacrylonitrile mixed solution; completely dissolve 2.8 g of hydroxylamine hydrochloride in 30 mL of N,N - methyleneformamide, add 0.8 g of sodium carbonate and 2.06 g of sodium hydroxide to adjust the pH of the solution to neutral. After stirring for 10 min, add this solution to the previously prepared polyacrylonitrile mixed solution, and react at 65 °C for 24 h. Collect the supernatant and centrifuge it at 10000 rpm for 10 min. Slowly drop the collected supernatant into absolute ethanol to obtain a white flocculent precipitate, and then wash it several times with absolute ethanol, and filter and dry it to obtain polyamidoxime powder.

[0025] Preparation of biochar spheres:

[0026] Add the exponentially growing Penicillium chrysogenum liquid to the newly prepared potato dextrose medium according to a volume ratio of 1%, then shake - culture at 27 °C and 180 rpm for 3 days. After that, wash it with deionized water and freeze - dry to obtain white mycelial spheres with a particle size of 1.5 - 2.5 mm. Then heat the mycelial spheres to 600 °C at a rate of 5 °C / min in an argon atmosphere and carbonize for 2 h to obtain biochar spheres (BS).

[0027] Preparation of polyamidoxime - loaded biochar spheres:

[0028] Weigh 0.5 g of polyamidoxime powder and completely dissolve it in 10 mL of sodium hydroxide solution with a concentration of 0.3 mol / L to obtain a polyamidoxime solution; then add 100 μL of glutaraldehyde and 0.1 g of biochar spheres to the polyamidoxime solution, and shake it on a shaker at a speed of 150 rpm for 6 h. Then filter it using a filter screen, take out the reacted biochar spheres and dry them at a temperature of 60 °C to obtain a polyamidoxime - loaded biochar sphere adsorbent (PAO - BS).

[0029] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the ratio of the biochar spheres to the polyamidoxime powder used in step S103 is different. As shown in the results of Table 1, when the mass ratio of polyamidoxime to biochar spheres is 5:1, the uranium - extraction performance of the prepared adsorbent is the best.

[0030] Table 1

[0031]

[0032] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that in step S103, the biochar spheres were immersed in an alkaline polyamidoxime solution, then placed in a vacuum drying oven and evacuated overnight. PAO was uniformly loaded onto the surface of the biochar spheres by vacuum pressurization, and then the excess PAO solution was drained. The biochar spheres loaded with PAO were placed in a freeze dryer for drying. The dried biochar spheres loaded with PAO were subjected to an adsorption experiment, but it was found during the experiment that the loaded PAO fell off, indicating that the biochar spheres loaded with polyamidoxime by vacuum impregnation were unstable.

[0033] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that in step S103, polyamidoxime powder was adhered to the biochar spheres using polydopamine as an adhesive. Dopamine hydrochloride was dissolved in a Tris-HCl buffer solution with a pH of 8.5, and at the same time, the biochar spheres were added. Polydopamine was deposited on the surface of the biochar spheres, the excess liquid was drained, and the biochar spheres deposited with polydopamine were placed in a freeze dryer for drying. The dried biochar spheres were immersed in an alkaline PAO solution, and it was found that the solution turned black and the deposited polydopamine fell off. This indicates that this method also cannot stably load PAO onto the biochar spheres to prevent it from falling off.

[0034] Example 2: The structural characterization and performance testing of the adsorbent material of the biochar spheres loaded with polyamidoxime prepared in Example 1 were carried out.

[0035] (1) The biochar spheres (BS) and the biochar spheres loaded with polyamidoxime (PAO-BS) were characterized using a Fourier transform infrared spectrometer (FT-IR). The results are as Figure 2 shown. Compared with the biochar spheres, the peak characteristics of the amidoxime group were observed in the biochar spheres loaded with polyamidoxime, corresponding to the stretching vibrations of C=N at 1644 cm -1 and N-O at 932 cm -1 respectively, indicating that PAO had been successfully loaded onto the BS. Further, the PAO content of PAO-BS was determined by TG analysis. As Figure 3 the results show: The weight loss observed at temperatures above 100 °C was related to the release of water absorbed by the BS. When the temperature was raised to 600 °C, the mass of the BS remained basically unchanged. However, PAO showed weight loss in the temperature ranges of room temperature to 160, 160 - 350, and 350 - 600 °C respectively. When the temperature reached 600 °C, the residual mass was 42.11%. For PAO-BS, within the first 160 °C, the removal of bound water led to a 13.62% mass loss. In addition, the decomposition of the amidoxime group and the PAO main chain also caused mass losses at 160 - 350 and 350 - 600 °C respectively. Therefore, based on the mass loss observed between 160 - 600 °C, the weight of PAO incorporated into PAO-BS was calculated to be 22.87%.

[0036] (2) The biochar spheres (BS) and the biochar spheres loaded with polyamidoxime (PAO-BS) were tested using a scanning electron microscope (SEM). As shown in the SEM images Figure 4 , the surface of the biochar spheres is relatively smooth with larger pores, while the surface of the biochar spheres loaded with polyamidoxime is relatively rough and the pores decrease after loading polyamidoxime. Further, according to the mercury intrusion test results as shown in Figure 5 , it shows that the pore size rate of the biochar spheres loaded with polyamidoxime is 90.94%. The average pore size is 13.5 μm, and its special structure with high porosity is more conducive to the adsorption of uranyl ions.

[0037] (3) As shown in the contact angle measurement results in Figure 6 , after the biochar loaded with polyamidoxime contacts with water droplets for 0.15 s, the contact angle reaches 0°, indicating that the biochar material loaded with polyamidoxime has excellent hydrophilicity.

[0038] (4) The kinetic test of the biochar spheres loaded with polyamidoxime in Example 1 for the adsorption of uranium in simulated seawater with different concentrations of doped uranium. As shown in the adsorption kinetic analysis diagram in Figure 7 , in the simulated seawater containing 16 ppm uranium, the biochar sphere adsorbent reaches the adsorption equilibrium within 10 h, and the adsorption capacity for uranium is 211.35 mg / g. This indicates that the high porosity and excellent hydrophilicity of the biochar spheres loaded with polyamidoxime provide a channel for the entry of uranyl ions, and also shows that this adsorbent material has the characteristics of efficient adsorption of uranyl ions and its structure is stable, and the loaded polyamidoxime does not fall off during the immersion process in simulated seawater.

[0039] (5) The adsorption ability of the biochar spheres loaded with polyamidoxime in Example 1 for uranium and other competitive metal ions after interacting with circulating natural seawater for 10 days. As shown in the results in Figure 8 , it shows that the biochar sphere material loaded with polyamidoxime has good selectivity for uranyl ions, and the adsorption ability of other interfering ions is less than half of that of uranium.

[0040] (6) The uranium extraction rate test of the biochar spheres loaded with polyamidoxime in Example 1 in natural seawater. After filtering natural seawater for 10 days, the uranium extraction performance of PAO-BS reaches 2.70 mg / g, and the average extraction rate is 0.27 mg / g / d. Compared with a series of other existing amidoxime-based uranium adsorbents (Table 2 and Figure 9 ), PAO-BS achieves a rapid uranium recovery rate from natural seawater, proving that PAO-BS has excellent performance and rapid recovery rate as a uranium adsorbent.

[0041] Table 2 Comparison of uranium adsorption rates between the present invention and existing amidoxime-based uranium adsorbents

[0042]

[0043] In summary, by adopting the preparation method of the supported polyamidoxime biochar sphere adsorbent material provided by the present invention, biochar spheres are obtained through high-temperature carbonization, and then polyamidoxime is supported through a chemical cross-linking reaction to obtain the present adsorbent. This method is simple to operate, low in cost, green and pollution-free. Moreover, the supported polyamidoxime biochar sphere adsorbent material prepared by this method has a high porosity (pore size ratio is 90.94%, average pore size is 13.5 μm) and hydrophilicity, so it has high seawater permeability, which further promotes the utilization of amidoxime functional groups in the material and speeds up the uranium adsorption rate (0.27 mg / g / d).

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A preparation method of a polyamidoxime-loaded biochar sphere adsorbent material for efficient uranium extraction, characterized in that, It includes the following steps: Weigh 0.5 g of polyamidoxime powder and completely dissolve it in sodium hydroxide solution to obtain an alkaline polyamidoxime solution; Then, add 100 μL of glutaraldehyde and 0.1 g of biochar spheres to the alkaline polyamidoxime solution, and shake it on a shaker at a speed of 150 rpm for 6 h. Take out the biochar spheres and dry them at 60 °C to obtain a biochar sphere adsorbent loaded with polyamidoxime. The biochar spheres are prepared by the following method: Add the exponentially growing Penicillium chrysogenum culture medium to the potato dextrose medium according to a volume ratio of 1%, then shake and culture at 27 °C at 180 rpm for 3 days. Then wash with deionized water and freeze-dry to obtain Penicillium chrysogenum mycelial spheres. Then heat the mycelial spheres to 600 °C at a rate of 5 °C / min in an argon atmosphere and carbonize for 2 h.

2. The preparation method of a supported polyamidoxime biochar sphere adsorbent material for efficient uranium extraction according to claim 1, characterized in that, The volume of the sodium hydroxide solution is 10 mL and the concentration is 0.3 mol / L.

3. The preparation method of an adsorbent material of a polyamidoxime-loaded biochar sphere for efficient uranium extraction according to claim 1, characterized in that, The polyamidoxime powder is prepared by the following method: Weigh 5.6 g of hydroxylamine hydrochloride and completely dissolve it in 100 mL of N,N-methylenebisformamide. Then add 4.12 g of sodium carbonate and 1.6 g of sodium hydroxide to make the solution neutral, and then stir and mix at 45 °C for 1 h. Then weigh 4 g of polyacrylonitrile and add it to the mixed solution, and stir at 65 °C for 24 h to obtain a polyacrylonitrile mixed solution; Then completely dissolve 2.8 g of hydroxylamine hydrochloride in 30 mL of N,N-methylenebisformamide, add 0.8 g of sodium carbonate and 2.06 g of sodium hydroxide to adjust the pH of the solution to neutral, stir for 10 min, then add this solution to the previously prepared polyacrylonitrile mixed solution, and react at 65 °C for 24 h. Collect the supernatant and centrifuge at 10000 rpm for 10 min. Slowly drip the collected supernatant into anhydrous ethanol to obtain a white flocculent precipitate, then wash it several times with anhydrous ethanol, and filter and dry to obtain polyamidoxime powder.

4. A biochar sphere adsorbent material loaded with polyamidoxime for highly efficient uranium extraction prepared by the method according to claim 1.

Images