Temperature-sensitive amidoxime-modified bacterial cellulose hydrogel, its preparation method and application

Abstract

The present application provides a kind of temperature-sensitive amidoxime modified bacterial cellulose hydrogel and its preparation method, it is related to novel adsorbent material technical field.The present application is prepared by gradient temperature method after the amidoxime modification of bacterial cellulose and certain proportion of temperature-sensitive monomer N-isopropyl acrylamide, initiator 2,2'-azo (2-methylpropylimid) dihydrochloride and crosslinking agent N,N-methylene bisacrylamide to obtain hydrogel.Among them, the amidoxime modification of bacterial cellulose improves the uranium adsorption capacity and the selectivity to uranium, and after the preparation of hydrogel, the addition of temperature-sensitive monomer also speeds up the adsorption rate of hydrogel to uranium.The preparation method is simple and fast, and the cost is low;The modified hydrogel material has good temperature sensitivity, high adsorption efficiency, high selectivity and can be reused repeatedly.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new adsorption materials, in particular to a preparation method of a temperature-sensitive amine oxime modified bacterial cellulose hydrogel for uranium adsorption. BACKGROUND

[0002] With the rapid growth of global population and the rapid development of industrialization, the demand for energy is also accelerating. Due to the depletion of traditional fossil fuels (coal, oil, natural gas, etc.), the world is facing a huge energy crisis. At the same time, major environmental problems such as air quality and climate warming also put higher requirements on alternative energy. Nuclear energy, as a kind of efficient and clean energy, helps to solve the shortage of fossil fuels and the impact on climate and environment, and uranium, as a basic resource of nuclear energy, has attracted great attention. At present, the methods for extracting uranium at home and abroad mainly include evaporation concentration, chemical precipitation, ion exchange, adsorption separation, biological treatment and other methods. Adsorption method has attracted more and more attention in recent years due to its simple operation, rich materials, mature technology and wide application range.

[0003] After decades of development, the adsorption materials for uranium mainly include inorganic adsorption materials, synthetic polymer adsorption materials and nano adsorption materials. Inorganic adsorption materials (such as lead compounds, manganese dioxide, basic zinc carbonate, etc.) have the advantages of fast adsorption rate, simple preparation and easy elution. Organic adsorbents include phosphonic acid series, amine series, macrocyclic compound series and amine oxime compound series materials. The bonding electrons on the C=N double bond of amine oxime group undergo chelation reaction with the lone pair electrons on O in C=N-O, and show strong complexing ability and high selectivity, and become the best material for extracting uranium. However, due to the poor hydrophilicity and low adsorption kinetics efficiency of single amine oxime group adsorption material, the adsorption rate of uraniumyl ion is not satisfactory. To further improve the adsorption rate of amine oxime group adsorption material, introducing bacterial cellulose and amine oxime group to produce synergistic adsorption is undoubtedly an effective and feasible way.

[0004] Bacterial cellulose (BC) is fermented by bacteria such as acetic acid bacteria, has high specific surface area, high water absorption and other characteristics, is easy to interact with other substances in water phase, and the main functional group of BC is -OH, which has a certain adsorption effect on metal ions. However, due to the poor selectivity of UO2 2+ , and the existence of strong hydrogen bond system in BC, its adsorption performance is poor. Therefore, it is necessary to modify the bacterial cellulose with high specific surface area with amine oxime to improve its adsorption selectivity and adsorption capacity for uranium.

[0005] Therefore, how to provide a kind of high adsorption rate, high selectivity, amidoxime modified bacterial cellulose hydrogel is the technical problem to be solved by the skilled in the art. SUMMARY

[0006] Therefore, the present application provides a kind of preparation method of temperature-sensitive amidoxime modified bacterial cellulose hydrogel, solve the problem of low uranium adsorption capacity and low adsorption efficiency of the existing similar materials.

[0007] It should be noted that the adsorption material of amidoxime group is because it is UO2 2+ High selectivity and adsorption capacity, is the most ideal uranium extraction adsorption material, amidoxime modification is carried out to bacterial cellulose, so that the material has the high specific surface area of bacterial cellulose and the selectivity and adsorption capacity of UO2 2+ Selectivity and adsorption capacity, realize the high efficiency, high selectivity and high adsorption capacity of UO2 2+ Adsorption.

[0008] Temperature-sensitive hydrogel is a kind of intelligent hydrogel that can produce morphological change when affected by external temperature change, generally crosslinked by high molecular chain, and has three-dimensional network structure. Because there are a large number of hydrophilic and hydrophobic groups on the chain, when the environmental temperature of the gel changes, the change of the strength of the action of the two groups will cause the swelling or shrinkage of the gel. Because small molecules in solution can freely diffuse and permeate in the network structure of hydrogel, therefore, hydrogel is often used to adsorb small molecular substances, such as heavy metal ions, from aqueous solution.

[0009] Further, the present application prepares temperature-sensitive amidoxime group bacterial cellulose hydrogel by amidoxime modification of bacterial cellulose and polymerization of N-isopropyl acrylamide, which is used for adsorption and separation of uranium ions in liquid.

[0010] Specifically, the present application combines N-isopropyl acrylamide with high temperature sensitivity and amidoxime bacterial cellulose with high selectivity and high adsorption capacity into temperature-sensitive hydrogel. When the environmental temperature of the gel increases, the change of the strength of the action of the hydrophilic and hydrophobic groups will cause the shrinkage of the gel structure, thereby accelerating the adsorption rate.

[0011] In order to achieve the above purpose, the present application provides the following technical scheme:

[0012] The first technical purpose of the present application is to provide a kind of preparation method of temperature-sensitive amidoxime modified bacterial cellulose hydrogel, and the method specifically includes the following steps:

[0013] (1) Synthesis of cyanoethyl bacterial cellulose: under the condition of alkali, the activated hydroxyl group in bacterial cellulose reacts with C=C double bond in acrylonitrile to generate Michael addition reaction.

[0014] The 1.44g dry weight of bacterial cellulose gel is broken by a pulverizer and dispersed in 160 mL of NaOH solution (1 mol / L) and activated for 7 hours at room temperature, then 80 mL of acrylonitrile is added dropwise under stirring and reacted for 12 hours at room temperature, the obtained product is centrifuged and washed with ultrapure water for 3 times, and the supernatant is removed, to obtain cyanoethyl bacterial cellulose;

[0015] (2) Synthesis of amidoxime group cellulose (BCAO): nucleophilic addition reaction of cyanoethyl and hydroxylamine.

[0016] A mixed solution of 200 mL of hydroxylamine hydrochloride (NH2OH•HCl) and sodium hydroxide (NaOH) [n(NH2OH•HCl):n(NaOH)]=1:1] is prepared and added into a round-bottom flask, and the cyanoethyl bacterial cellulose is added into the mixed solution, and after stirring at 50℃ for 12 hours, the obtained product is centrifuged and washed with ultrapure water for 3 times, and the supernatant is removed, to obtain the amidoxime group bacterial cellulose (BCAO);

[0017] (3) 0.5g of BCAO is dispersed in 100 mL of 0.5% NaOH solution, 2.5g of temperature-sensitive monomer N-isopropyl acrylamide, 4.5g of initiator 2,2'-azobis(2-methylpropylimide) dihydrochloride (AIBA) and 0.31g of crosslinking agent N,N-methylenebisacrylamide (BIS) are added, and after reaction at 30℃ for 3 hours, at 40℃ for 1 hour, at 50℃ for 1 hour, at 60℃ for 1 hour and at 70℃ for 3 hours, the obtained product is washed with deionized water for 3 times, to obtain the temperature-sensitive amidoxime modified bacterial cellulose hydrogel (BCOU).

[0018] The second technical purpose of the present application is to provide the temperature-sensitive amidoxime modified bacterial cellulose hydrogel prepared by the above method.

[0019] The third technical purpose of the present application is to provide the application of the temperature-sensitive amidoxime modified bacterial cellulose hydrogel prepared by the above method in uranium adsorption.

[0020] It should be noted that the present application is used for uranium separation and extraction, the bacterial cellulose is modified by amidoxime and combined with the temperature-sensitive monomer N-isopropyl acrylamide, so that the uranium adsorption capacity and adsorption rate of the bacterial cellulose are enhanced.

[0021] According to the above technical solution, compared with the prior art, the temperature-sensitive amidoxime modified bacterial cellulose hydrogel, the preparation method and the application thereof provided by the present application have the following excellent effects:

[0022] 1) The present application adopts the amido-hydroxyl bacterial cellulose as the matrix, combines with the temperature-sensitive monomer, and prepares the temperature-sensitive hydrogel through the gradient temperature method, the preparation method is simple, the cost is low, and the hydrogel has good application prospect in the uranium extraction in seawater.

[0023] 2) The present application uses N-isopropyl acrylamide as the temperature-sensitive monomer, synthesizes the amido-hydroxyl bacterial cellulose hydrogel (BCOU), the N-isopropyl acrylamide is cooperatively adsorbed with the amido-hydroxyl group, the operation is simple, and the prepared hydrogel has good temperature sensitivity and can be quickly adsorbed at high temperature.

[0024] 3) The present application modifies the bacterial cellulose through the amido-hydroxyl group, the amido-hydroxyl group can form strong chelation with heavy metal ions, changes the defect that the adsorption performance of the bacterial cellulose is poor, and increases the coordination and adsorption efficiency.

[0025] 4) The experimental results show that the amido-hydroxyl modified bacterial cellulose hydrogel of the present application has the quick and efficient uranium adsorption-desorption capacity at high temperature, and can be repeatedly used, so that the hydrogel has good application prospect in the uranium extraction in seawater. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiment or the prior art description will be briefly introduced below, and obviously, the drawings in the following description can also be obtained by the person skilled in the art without any creative labor on the premise of the provided drawings.

[0027] Figure 1 (a) is a preparation flowchart of BCOU, (b) is an action mechanism diagram of BCOU and UO2 2+ .

[0028] Figure 2 is a structure diagram of BCOU and an action structure diagram of BCOU and UO2 2+ .

[0029] Figure 3 (a)-(e) are DSC diagrams of BCOU-1 to BCOU-5, Figure 3 (f) is a phase change temperature diagram of BCOU under the optimal conditions of the present application.

[0030] Figure 4 (a) is an infrared spectrum diagram of BC and BCAO, Figure 4 (b) is an infrared spectrum diagram of BCAO, NIPAM and BCOU.

[0031] Figure 5SEM images of (a) BCOU surface, (b) BCOU cross-section, (c) BCOU (with uranium) surface, (d) BCOU (with uranium) cross-section.

[0032] Figure 6 (a) are XPS spectra of BCOU before and after adsorbing uranium, (b) are U4f XPS spectra of BCOU before and after adsorbing uranium.

[0033] Figure 7 are graphs of the effects of different temperatures (a), times (b), pH (c), uranium concentrations (d) on the adsorption capacity of BCOU.

[0034] Figure 8 is a selective adsorption graph of BCOU in 1.0 mg / g mixed metal ion solution.

[0035] Figure 9 is a graph of five adsorption-desorption cycles of BCOU at 25℃ and 55℃. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the embodiments of the present application and the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0037] The embodiments of the present application disclose a preparation method of a temperature-sensitive amine oxime modified bacterial cellulose hydrogel.

[0038] In order to better understand the present application, the following embodiments are further specifically described below, but it should not be understood as limiting the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content are also regarded as falling within the protection scope of the present application.

[0039] The technical solutions of the present application will be further described below with reference to specific embodiments.

[0040] Embodiment 1

[0041] The preparation method of the temperature-sensitive amine oxime modified bacterial cellulose hydrogel comprises the following steps:

[0042] (1) 1.44 g of dry bacterial cellulose was broken by a grinder and dispersed in 160 mL of NaOH solution (1 mol / L) and activated at room temperature for 7 h, then 80 mL of acrylonitrile was added dropwise under stirring, and reacted at room temperature for 12 h, then the product was washed by centrifugation with ultrapure water for 3 times, and the supernatant was removed, to obtain cyanoethyl bacterial cellulose.

[0043] (2) A mixed solution of 200 mL of 0.5 mol / L hydroxylamine hydrochloride (NH2OH•HCl) and sodium hydroxide (NaOH) [n(NH2OH•HCl):n(NaOH)]=1:1] was prepared and added to a round-bottom flask, and the cyanoethyl bacterial cellulose was added to the mixed solution, and after stirring at 50°C for 12 h, the product was washed by centrifugation with ultrapure water for 3 times, and the supernatant was removed, to obtain amidoxime group cellulose (BCAO).

[0044] (3) 0.5 g of dry BCAO was dispersed in 100 mL of 0.5% NaOH solution, 2.5 g of temperature-sensitive monomer N-isopropyl acrylamide, 4.5 g of initiator 2,2'-azobis(2-methylpropylimide) dihydrochloride (AIBA), and 0.31 g of crosslinking agent N,N-methylenebisacrylamide (BIS) were added, and reacted at 30°C for 3 h, at 40°C for 1 h, at 50°C for 1 h, at 60°C for 1 h, and at 70°C for 3 h, and then washed with deionized water for 3 times to obtain a temperature-sensitive polyamidoxime hydrogel (BCOU).

[0045] Example 2

[0046] The preparation method of the temperature-sensitive bacterial cellulose amidoxime hydrogel comprises the following steps:

[0047] (1) 1.44 g of dry bacterial cellulose was broken by a grinder and dispersed in 160 mL of NaOH solution (1 mol / L) and activated at room temperature for 10 h, then 80 mL of acrylonitrile was added dropwise under stirring, and reacted at room temperature for 12 h, then the product was washed by centrifugation with ultrapure water for 3 times, and the supernatant was removed, to obtain cyanoethyl bacterial cellulose.

[0048] (2) A mixed solution of 200 mL of 1 mol / L hydroxylamine hydrochloride (NH2OH•HCl) and sodium hydroxide (NaOH) [n(NH2OH•HCl):n(NaOH)]=1:1] was prepared and added to a round-bottom flask, and the cyanoethyl bacterial cellulose was added to the mixed solution, and after stirring at 50°C for 18 h, the product was washed by centrifugation with ultrapure water for 3 times, and the supernatant was removed, to obtain amidoxime group cellulose (BCAO).

[0049] (3) 0.5 g of BCAO was dispersed in 100 mL of 0.5% NaOH solution, 2.5 g of temperature-sensitive monomer N-isopropyl acrylamide, 5.0 g of initiator 2,2'-azobis(2-methylpropylimide) dihydrochloride (AIBA), and 0.31 g of crosslinking agent N,N-methylenebisacrylamide (BIS) were added, and the reaction was carried out at 30°C for 3 hours, at 40°C for 1 hour, at 50°C for 1 hour, at 60°C for 1 hour, and at 70°C for 3 hours, and then the temperature-sensitive polyamidoxime hydrogel (BCOU) was obtained by washing with deionized water three times.

[0050] Example 3

[0051] The method for preparing the temperature-sensitive bacterial cellulose amidoxime hydrogel comprises the following steps:

[0052] (1) 1.44 g of bacterial cellulose with a dry weight was crushed by a crusher and then dispersed in 160 mL of NaOH solution (1 mol / L) and activated at room temperature for 7 hours, and then 80 mL of acrylonitrile was added dropwise under stirring, and the reaction was carried out at room temperature for 12 hours, and then the product was centrifugally washed with ultrapure water three times, and the supernatant was removed, and thus cyanoethyl bacterial cellulose was obtained.

[0053] (2) A mixed solution of 200 mL of 1 mol / L hydroxylamine hydrochloride (NH2OH•HCl) and sodium hydroxide (NaOH) [n(NH2OH•HCl):n(NaOH)]=1:1] was prepared and added to a round-bottom flask, and the cyanoethyl bacterial cellulose was added to the mixed solution, and the reaction was carried out under stirring at 50°C for 12 hours, and then the product was centrifugally washed with ultrapure water three times, and the supernatant was removed, and thus amidoxime-based cellulose (BCAO) was obtained.

[0054] (3) 0.5 g of BCAO was dispersed in 100 mL of 0.5% NaOH solution, 2.5 g of temperature-sensitive monomer N-isopropyl acrylamide, 5.0 g of initiator 2,2'-azobis(2-methylpropylimide) dihydrochloride (AIBA), and 0.31 g of crosslinking agent N,N-methylenebisacrylamide (BIS) were added, and the reaction was carried out at 30°C for 3 hours, at 40°C for 1 hour, at 50°C for 1 hour, at 60°C for 1 hour, and at 70°C for 3 hours, and then the temperature-sensitive polyamidoxime hydrogel (BCOU) was obtained by washing with deionized water three times.

[0055] In order to further illustrate the superiority of the present patent technology compared with the prior art, the inventors also conducted the following tests, and the specific content is as follows:

[0056] Experiment 1: for illustrating the temperature sensitivity of BCOU:

[0057] The temperature sensitivity of BCOU material (wet weight: approximately 25 mg) was tested using a differential scanning calorimeter (DSC). The instrument parameters were set as follows: N2 protection (flow rate: 50 mL / min), initial temperature of 10 °C, heating to 90 °C at a rate of 10 K / min and then cooling to 10 °C. An aluminum crucible with dimensions of φ6.7*4 mm was used for the sample cell.

[0058] For BCOU, by Figure 3 As shown in (a)-(c), when the amount of NIPAM is 2.0 g and 3.0 g, the endothermic and exothermic peaks become less obvious, and the phase transition temperature of the gel increases, which is not conducive to practical applications. Therefore, it can be concluded that the amount of NIPAM is better at 2.5 g.

[0059] Regarding AIBA usage, a comparison Figure 3 As shown in (b), (d) and (e), when the amount of AIBA is 4.0g and 5.0g, the endothermic curve becomes more complex and the number of endothermic peaks is not obvious, which is not conducive to the subsequent exploration of adsorption conditions. Therefore, the amount of AIBA is better when it is 4.5g.

[0060] Experiment 2: Used to illustrate the structure of BCOU:

[0061] Fourier transform infrared spectroscopy was used to analyze the infrared spectra of BCAO, NIPAM, and freeze-dried BCOU using the KBr pellet method. Field emission scanning electron microscopy was used to analyze the surface and cross-section microstructure of freeze-dried BCOU and BCOU (containing uranium). X-ray spectroscopy was used to analyze the freeze-dried BCOU and BCOU (containing uranium).

[0062] Figure 4 (a) shows the infrared spectra of BC and BCAO, with the spectral density at 2256 cm⁻¹. -1 The spikes at 1657 and 908.4 cm⁻¹ originate from the stretching vibrations of -C≡N. -1 The absorption bands appearing at [value] are attributed to the stretching vibrations of -C=N and -N-OH, respectively, indicating that BC has been grafted with a methylamine oxime group. Furthermore, the stretching vibration of -OH in the spectrum [value] is [value] at 3367 cm⁻¹. -1 The nearby spectral band shifted to 3416 cm. -1 The presence of -NH2 groups in BCAO nearby indicates successful BCAO polymerization. Figure 4 (b) In the infrared spectrum, the -NH stretching vibration peak of NIPAM is located at 3441 cm⁻¹. -l and 2972 ​​cm -l The extensional vibration of -CH, the bending vibration of -NH and the extensional vibration of CN are superimposed at 1547 cm. -l An absorption peak appeared, indicating that NIPAM had been successfully polymerized with BCAO.

[0063] like Figure 5 In the SEM images, the hydrogel exhibits a relatively large, uniform microporous structure before uranium absorption. Figure 5 (a, b)) After adsorption, the interior no longer has a large number of pores, and the pores are significantly reduced in size. Figure 4 (c, d)). This indicates that the thermosensitive monomer NIPAM was successfully polymerized with BCAO, and also demonstrates that the microstructure of the gel can be significantly modulated by changing the temperature.

[0064] like Figure 6 XPS spectra showed that the specific biphasic peaks (392.5 eV, 381.6 eV) in the uranium-adsorbed hydrogel and the uranium-containing hydrogel compared to the original BCOU hydrogel indicated that uranyl ions had been adsorbed in the hydrogel.

[0065] Experiment 3: To illustrate the adsorption properties of BCOU

[0066] UO2 2+ Concentration was determined using the arsene III ultraviolet spectrophotometric method, with the detection wavelength set at 652 nm. The standard curve was prepared as follows: UO2 concentrations of 20, 40, 60, 80, and 100 μg / mL were prepared respectively. 2+ Take 1 mL of each solution and add it to a 10 mL volumetric flask. Then, add 0.5 mL of 0.1 mol / L hydrochloric acid, 1 mL of 0.05 mol / L Na₂EDTA solution, and 1 mL of 500 mg / L azoarsine III solution sequentially. Dilute to the mark with ultrapure water to prepare standard solutions with concentration gradients of 2 μg / mL, 4 μg / mL, 6 μg / mL, 8 μg / mL, and 10 μg / mL. Calculate the uranium concentration using a linear regression equation derived from the standard curve.

[0067] Determination of optimal adsorption temperature: 10 mg of thermosensitive hydrogel was placed in 80 mL of 50 μg / mL UO2 at pH 4.52. 2+ In the solution, the adsorption was carried out at different temperatures (45℃, 50℃, 55℃, 60℃, 65℃, 70℃) for 1 h in a constant temperature water bath shaker, followed by filtration. The residual UO2 in the filtrate was measured. 2+ The concentration was determined, and the optimal adsorption temperature was found to be 55℃. Figure 7 (a)).

[0068] Determination of optimal adsorption time: 10 mg of thermosensitive hydrogel was placed in 80 mL of 50 μg / mL UO2 solution with pH = 4.52. 2+The solution was placed in a constant temperature water bath shaker at 55℃ for adsorption at 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 120 min, and 180 min, respectively, and then filtered. The residual UO2 in the filtrate was measured. 2+ The optimal adsorption time was determined to be 80 min based on the concentration. Figure 7 (b)).

[0069] Determination of optimal adsorption pH: 10 mg of thermosensitive hydrogel was placed in 80 mL of 50 μg / mL UO2. 2+ In the solution, the pH was adjusted to 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, and 7.0. The solutions were then placed in a constant-temperature water bath shaker at 55℃ for 90 min for adsorption, followed by filtration. The remaining UO2 in the filtrate was measured. 2+ The optimal adsorption pH was determined to be 4.5 (concentration). Figure 7 c)).

[0070] Determination of optimal adsorption concentration: 10 mg of thermosensitive hydrogel was placed in 80 mL of solutions containing 0.10 mg / mL, 0.20 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1.0 mg / mL, 1.1 mg / mL, and 1.2 mg / mL L / O2, respectively. 2+ In the solution, the pH was adjusted to 4.5, and the solution was placed in a constant temperature water bath shaker at 55℃ for 80 min for adsorption. After filtration, the residual UO2 in the filtrate was measured. 2+ To determine the optimal adsorption concentration ( ) Figure 7 (d)).

[0071] The uranium adsorption content of the adsorbent is obtained according to the following formula (1):

[0072] (1)

[0073] Where Q is the adsorption amount, C0 is the original concentration of the uranium solution, and C t The concentration of the filtrate after uranium adsorption, where V is the volume of the uranium solution.

[0074] Experiment 4: To illustrate the cyclic adsorption performance of BCOU at room temperature (25℃) and high temperature (55℃).

[0075] Two groups of 10 mg thermosensitive hydrogels were placed in 80 mL of 1.0 mg / mL UO2 solution. 2+In solution, the pH of the solution was adjusted to 4.5, and then placed in a constant temperature water bath shaker at room temperature and 55°C respectively for 90 min adsorption and then filtered. The concentration of the residual UO2 2+ in the filtrate was measured. After adsorbing uranium, the hydrogel membrane was immersed in 200 mL of eluent (1 mol / L Na2CO3 and 0.1 mol / L H2O2) for 60 min of stirring. After the elution was completed, the hydrogel was taken out of the eluent and immersed in pure water, and the water was changed several times. Finally, the hydrogel was immersed in a solution containing uranium for the next cycle. The adsorption-elution process was repeated five times.

[0076] It can be seen from Figure 9 that the initial adsorption capacity of BCOU at 55°C is 580.89 mg / g, and the initial adsorption capacity of BCOU at 25°C is 343.54 mg / g. After 5 adsorption-desorption cycles, the uranium adsorption capacity of BCOU-55°C is 485.89 mg / g, which is 83.65% of the initial uranium adsorption capacity; the uranium adsorption capacity of BCOU-25°C is 286.43 mg / g, which is 83.38% of the initial uranium adsorption capacity. The desorption rate of BCOU-25°C and BCOU-55°C can reach more than 88%; the adsorption capacity of BCOU-25°C after 5 cycles is only 49.31% of that of BCOU-55°C. After 5 cycles, the adsorption capacity and desorption rate of BCOU decrease, but still remain at a high level. The results show that the hydrogel has fast and efficient uranium adsorption-desorption capacity and the material has better adsorption effect at high temperature, and can be repeatedly used.

[0077] Experiment 5: to illustrate the selective adsorption performance of BCOU

[0078] BCOU (dry weight 10 mg) was taken into 80 mL of 1.0 mg / mL mixed metal ion solution (Cu 2+ , Mg 2 + , Ca 2+ , Pb 2+ , Cd 2+ , Na + , K + , Zn 2+ , UO2 2+ ) with pH 4.5, and adsorbed at 55°C for 90 min. Each metal ion was measured by ICP-Mass, and the adsorption results of different ions were calculated by analyzing the concentrations before and after adsorption, as shown in Figure 8 , which shows that the adsorption capacity of the hydrogel for uranium is much higher than that for any other metal ion, indicating that the hydrogel of the application has good selectivity for uranium.

[0079] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a temperature-sensitive amidoxime-modified bacterial cellulose hydrogel, characterized by, The method specifically comprises the following steps: (1) crushing the bacterial cellulose gel and dispersing it in a NaOH solution, activating at room temperature, then adding acrylonitrile dropwise under stirring, reacting at room temperature, and washing the obtained product with ultra-pure water by centrifugation three times to remove the supernatant, thereby obtaining cyanoethyl bacterial cellulose; (2) preparing a mixed solution of hydroxylamine hydrochloride NH2OH•HCl and sodium hydroxide NaOH, adding it into a round-bottom flask, adding cyanoethyl bacterial cellulose into the mixed solution for reaction, washing the obtained product with ultra-pure water by centrifugation three times to remove the supernatant, thereby obtaining amidoxime group modified bacterial cellulose BCAO; (3) dispersing the BCAO in a NaOH solution, adding a temperature-sensitive monomer N-isopropyl acrylamide, an initiator 2,2'-azobis(2-methylpropylimide) dihydrochloride AIBA, and a crosslinking agent N,N'-methylenebisacrylamide BIS, washing with deionized water three times after reaction, thereby obtaining the temperature-sensitive amidoxime modified bacterial cellulose hydrogel BCOU.

2. The method for preparing a temperature-sensitive, amidoxime-modified bacterial cellulose hydrogel according to claim 1, characterized by, In the step (1), the activation time of the bacterial cellulose is 7-10 h, and the volume / mass ratio of the added acrylonitrile to the bacterial cellulose is 60-80 mL:1.44 g.

3. The method for preparing a temperature-sensitive, amidoxime-modified bacterial cellulose hydrogel according to claim 2, characterized in that, In the step (1), the volume of the NaOH solution is 150-170 mL, and the concentration is 0.8-1.0 mol / L, and the reaction is carried out at room temperature for 12 h.

4. The method for preparing a temperature-sensitive, amidoxime-modified bacterial cellulose hydrogel according to claim 1, characterized by, In the step (2), the molar ratio of the prepared mixed solution of hydroxylamine hydrochloride NH2OH•HCl and sodium hydroxide NaOH is 1:1, the stirring reaction time is 12 h, and the stirring reaction temperature is 50°C.

5. The method for preparing the thermosensitive amine oxime-modified bacterial cellulose hydrogel according to claim 1, characterized in that, In the step (3), the volume of the NaOH solution is 100 mL, and the mass fraction is 0.5-0.8%; the mass ratio of the BCAO to the N-isopropyl acrylamide is 1:5-1:7, and the mass ratio of the BCAO to the 2,2'-azobis(2-methylpropylimide) dihydrochloride is 1:8-1:10; the reaction conditions are 30°C for 3 h, 40°C for 1 h, 50°C for 1 h, 60°C for 1 h, and 70°C for 3 h.

6. A temperature-sensitive amidoxime-modified bacterial cellulose hydrogel prepared by the method of claim 1, wherein the bacterial cellulose hydrogel is characterized by, The hydrogel is a temperature-sensitive thermal shrinkage and cold expansion hydrogel material for uranium extraction.

7. The temperature-sensitive amidoxime modified bacterial cellulose hydrogel prepared by the method of claim 1 or the temperature-sensitive amidoxime modified bacterial cellulose hydrogel of claim 6 in uranium adsorption.

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