A method for selectively separating uranium and radium

Abstract

This invention discloses a method for selectively separating uranium and radium, belonging to the field of solid waste treatment technology. The method utilizes modified rapeseed straw hydrothermal carbon (HTC-AA-Na). The hydrothermal carbon preparation method includes placing pretreated rapeseed straw in an aqueous acrylic acid solution for carbonization to obtain hydrothermal carbon HTC-AA rich in carboxyl functional groups; then, HTC-AA is placed in a NaOH solution and stirred, and the H groups in the carboxyl groups are removed through cation exchange. + Replaced with Na + HTC-AA-Na was obtained. When NaNO3 was added to a mixed solution containing uranium and radium, HTC-AA-Na selectively adsorbed uranium while hardly adsorbing radium; when EDTA-2Na was added to the same solution, HTC-AA-Na selectively adsorbed radium while hardly adsorbing uranium, thus achieving selective separation of uranium and radium. This invention provides a green and sustainable technical path for the harmless treatment of uranium tailings.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, and in particular to a method for selectively separating uranium and radium. Background Technology

[0002] The large amounts of tailings generated during uranium mining and smelting are one of the largest sources of radioactive waste from the nuclear industry. Uranium tailings are rich in uranium (U). 238 U), radium ( 226 Long-lived naturally occurring radioactive nuclides such as Ra, 226 Ra is 238 The decay products of U, when both are in radioactive equilibrium, are approximately 1.0g per 3.0t uranium ore containing uranium metal. 226 Ra.

[0003] If efficient separation and recovery from uranium tailings can be achieved... 226 Ra, extract 226 Ra can be used in the preparation of medical isotopes, neutron source preparation and other industrial applications, which can significantly improve the comprehensive utilization rate of uranium resources and generate considerable economic benefits.

[0004] The key to efficient radium separation from uranium tailings lies in achieving effective separation of uranium and radium. Uranium mainly exists as hexavalent uranyl ions (UO2). 2+ Radium exists in the form of divalent cations (Ra), exhibiting strong migration ability and chemical reactivity; while radium, as a key daughter product in the uranium decay chain, mainly exists as divalent cations (Ra). 2+ Uranium exists in the form of uranium, and its chemical properties are similar to those of alkaline earth metals such as barium and calcium. In actual processing, uranium and radium often coexist in tailings leachate. Their chemical behaviors are similar under complex conditions such as acidity, ionic strength, and coexisting ions, making selective separation extremely difficult.

[0005] Rapeseed straw, generated after harvest, has long been treated as waste, resulting in low resource utilization. Rapeseed straw is rich in cellulose, hemicellulose, and lignin, and its surface contains numerous active functional groups such as hydroxyl and carboxyl groups, giving it potential as a biomass adsorbent. However, unmodified rapeseed straw has limited adsorption capacity and poor selectivity for radionuclides, making it difficult to directly use for the selective separation of uranium and radium in uranium tailings.

[0006] Therefore, developing a method for efficiently and selectively separating uranium and radium from uranium tailings using waste rapeseed straw as raw material is of great practical significance and application value for achieving the harmless treatment and resource utilization of uranium tailings as well as the high-value utilization of agricultural waste. Summary of the Invention

[0007] The purpose of this invention is to provide a method for selectively separating uranium and radium, which uses waste rapeseed straw as raw material to prepare modified hydrothermal carbon HTC-AA-Na, thereby achieving selective separation of uranium and radium in uranium tailings, while taking into account both solid waste treatment and resource utilization.

[0008] To achieve the above objectives, the present invention provides a method for selectively separating uranium and radium, using modified rapeseed straw hydrothermal carbon, comprising: 0.05-0.3 g / L of modified rapeseed straw hydrothermal carbon and 0-0.6 M NaNO3 were added to a mixed solution containing uranium and radium. The modified rapeseed straw hydrothermal carbon selectively adsorbed uranium in the mixed solution. When 0.05-0.3 g / L of modified rapeseed straw hydrothermal carbon and 1-10 mM EDTA-2Na are added to a mixed solution containing uranium and radium, the modified rapeseed straw hydrothermal carbon does not adsorb uranium.

[0009] Preferably, the NaNO3 concentration is 0.6M.

[0010] A preferred method for preparing modified rapeseed straw hydrothermal carbon includes the following steps: S1: The pretreated rapeseed straw was placed in an acrylic acid aqueous solution and carbonized in a hydrothermal reactor to obtain HTC-AA, a hydrothermal carbon material rich in carboxyl functional groups. S2: The HTC-AA obtained in S1 was placed in NaOH solution and stirred. The H group in the carboxyl group was removed through cation exchange. + Replaced with Na + The modified hydrothermal carbon material HTC-AA-Na was obtained.

[0011] Preferably, in S1, the rapeseed straw pretreatment method is to cut it into pieces with a particle size of less than 0.5 cm.

[0012] The concentration of the acrylic acid aqueous solution is 2.5-5wt%, and the mass-volume ratio of rapeseed straw to acrylic acid aqueous solution is 0.5-1.5g:25-35mL.

[0013] Preferably, in S1, the carbonization reaction temperature is 160-200℃, the reaction time is 6-12h, and the temperature is allowed to drop naturally after the reaction is completed.

[0014] Preferably, in S2, the concentration of NaOH solution is 0.6-1.2M.

[0015] The mass-to-volume ratio of HTC-AA to NaOH solution is 50-150g: 60-100mL.

[0016] Preferably, in S2, the stirring speed is 800-1200 rpm and the stirring time is 0.5-1.5 h.

[0017] Therefore, the method for selectively separating uranium and radium of the present invention has the following beneficial effects: (1) This invention uses waste rapeseed straw as raw material to prepare high-performance adsorbent. Not only are the raw materials widely available and inexpensive, but the preparation process is also simple and environmentally friendly. This technology has the dual advantages of reducing agricultural solid waste and utilizing resources, and has significant economic benefits and prospects for promotion and application.

[0018] (2) This invention can recover uranium for nuclear fuel recycling and extract radium for high value-added applications, realizing the transformation of radioactive nuclides in uranium tailings into valuable resources and significantly improving the comprehensive utilization level of uranium resources.

[0019] (3) This invention provides a green and sustainable technical path for the harmless treatment of uranium tailings.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The image shows the characterization of the HTC-AA-Na material prepared in Example 1 of this invention, where (a) is a flowchart of the preparation of HTC-AA-Na material, (b) is an image of waste rapeseed straw, (c) is a SEM image of HTC-AA-Na material, and (d) is an XRD pattern of HTC-AA-Na material. Figure 2 The HTC-AA-Na material of this invention adsorbs U(VI) and Ba at different dosages. 2+ The performance graphs are shown, where (a) is the removal rate graph and (b) is the removal efficiency graph. Figure 3 The HTC-AA-Na material of this invention adsorbs U(VI) and Ba at different NaNO3 concentrations. 2+ The performance graphs are shown, where (a) is the removal rate graph and (b) is the separation factor graph for uranium and barium. Figure 4 The HTC-AA-Na material of this invention adsorbs U(VI) and Ba at different EDTA-2Na concentrations. 2+ The performance graphs are shown, where (a) is the removal rate graph and (b) is the separation factor graph for barium and uranium. Figure 5The HTC-AA-Na material of this invention adsorbs NaNO3 at different concentrations. 238 U and 226 The performance graphs of Ra are shown, where (a) is the removal rate graph and (b) is the separation factor graph of uranium and radium. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] To make the objectives, technical solutions, and advantages of this application clearer, more thorough, and more complete, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The following detailed descriptions are all illustrations of embodiments, intended to provide further detailed explanation of the present invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0025] The instruments, equipment, reagents, and materials used in the examples were all obtained commercially.

[0026] Example 1 A method for preparing modified hydrothermal carbon HTC-AA-Na using waste rapeseed straw, the process is as follows: Figure 1 As shown in (a), the steps include: S1. Take 1.0g of waste rapeseed straw, cut it into pieces with scissors to a particle size of less than 0.5cm, place it in a 50mL hydrothermal reactor, add 30mL of ultrapure water and 3mL of acrylic acid, seal it, and place it in a forced-air drying oven for hydrothermal reaction at 190℃ for 8h. After the reaction is completed, allow it to cool naturally to room temperature, filter the solid product in the reactor, wash it three times with water and twice with ethanol, and dry it in a vacuum drying oven at 60℃ for 2h to obtain a hydrothermal carbon material rich in carboxyl functional groups, denoted as HTC-AA.

[0027] S2. Weigh 100g of HTC-AA and add it to 80mL of 0.1M NaOH solution. Stir at 1000rpm for 1h on a magnetic stirrer. After the reaction is complete, filter and collect the solid. Wash it with water 3 times and ethanol 2 times in sequence. Dry it in a vacuum drying oven at 60℃ for 2h to obtain the modified hydrothermal carbon material, denoted as HTC-AA-Na.

[0028] Figure 1 The middle (b) shows a picture of the rapeseed straw used in the experiment, and the inset shows a picture of HTC-AA-Na. It can be seen that HTC-AA-Na prepared from rapeseed straw is yellow granular.

[0029] HTC-AA-Na was characterized using SEM and XRD, and the results are as follows: Figure 1 As shown in (c)-(d). From Figure 1As shown in (c), HTC-AA-Na exhibits a wrinkled, sheet-like structure; from Figure 1 As shown in (d), its XRD pattern shows characteristic diffraction peaks belonging to graphite (PDF#89-8490) and cellulose (PDF#50-2241).

[0030] The above results indicate that the rapeseed straw successfully underwent a carbonization reaction, providing sufficient active sites for the separation of uranium and radium.

[0031] Test Example 1 because 226 Ra emits alpha and gamma rays during its decay process, causing significant radiation damage to the human body. Initially, barium (Ba), which has similar chemical properties to radium (Ra), was used in simulation experiments. After obtaining optimized conditions, further real-world experiments were conducted. 226 Thermal experimental separation study of Ra.

[0032] ①The effect of HTC-AA-Na material dosage on uranium and barium adsorption performance: S1. Weigh a certain mass of UO2(NO3)2·6H2O and Ba(NO3)2 solid, dissolve them in ultrapure water, and prepare a mixed solution with a uranium and barium concentration of 10 mg / L.

[0033] S2. Take three 60 mL portions of the above mixed solution and add 0.1 g / L, 0.2 g / L, and 0.3 g / L of HTC-AA-Na material, respectively. Take samples at preset time points, 3 mL each time, filter quickly through a syringe filter, and collect the filtrate for analysis.

[0034] S3. The concentrations of uranium and barium in the filtrate were determined using inductively coupled plasma atomic emission spectrometry, and the removal efficiency η (%) of HTC-AA-Na for uranium and barium at different dosages was calculated according to the following formula.

[0035] ; in, The initial uranium or barium concentration (mg / L) The concentration of uranium or barium at equilibrium (mg / L).

[0036] The results are as follows Figure 2 As shown, HTC-AA-Na exhibits excellent adsorption performance for both uranium and barium. With increasing HTC-AA-Na dosage, its removal efficiency for uranium and barium gradually increases. When the dosage reaches 0.3 g / L, the removal efficiencies for uranium and barium reach 99.6% and 99.1%, respectively, approaching 100%.

[0037] ②The effect of NaNO3 concentration on the adsorption performance of HTC-AA-Na for uranium and barium: S1. Prepare a mixed solution with uranium and barium concentrations of 10 mg / L each.

[0038] S2. Take four 60 mL portions of the above mixed solution and add different doses of NaNO3 to each portion to adjust the NaNO3 concentration in the mixed solution to 0.1 M, 0.2 M, 0.4 M, and 0.6 M. Take samples at preset time points, 3 mL each time, filter quickly through a syringe filter, and collect the filtrate for analysis.

[0039] S3. The concentrations of uranium and barium in the filtrate were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the removal efficiency η (%) and partition coefficient of HTC-AA-Na for uranium and barium at different NaNO3 concentrations were calculated according to the following formulas. ) and separation factor ( ).

[0040] ; ; Where V is the solution volume (mL) and m is the HTC-AA-Na dosage (mg). denoted as the partition coefficient of uranium (mL / g). The partition coefficient for barium (mL / g).

[0041] Removal efficiency test results are as follows Figure 3 As shown in (a), when no NaNO3 was added, the removal efficiencies of HTC-AA-Na for uranium and barium reached 99.6% and 99.1%, respectively. As the NaNO3 concentration gradually increased from 0 to 0.6 M, the adsorption performance of HTC-AA-Na for uranium remained basically unchanged, while the adsorption performance for barium almost dropped to 0.

[0042] The results of the separation factor determination for barium and uranium are as follows: Figure 3 As shown in (b), when the NaNO3 concentration is 0, the separation factor of uranium and barium ( The value was 2.1; however, when the NaNO3 concentration increased to 0.6 M, Reached 5126.9; after conversion, It increased by 2441.3 times.

[0043] The above results indicate that NaNO3 enables HTC-AA-Na to achieve highly selective separation that adsorbs only uranium without adsorbing barium.

[0044] ③ The effect of EDTA-2Na concentration on the adsorption performance of HTC-AA-Na for uranium and barium: S1. Prepare a mixed solution with uranium and barium concentrations of 10 mg / L each.

[0045] S2. Take three 60 mL portions of the above mixed solution and add different doses of EDTA-2Na to each portion to adjust the EDTA-2Na concentration in the mixed solution to 1 mM, 3 mM, and 6 mM. Take samples at preset time points, 3 mL each time, filter quickly through a syringe filter, and collect the filtrate for testing.

[0046] S3. The concentrations of uranium and barium in the filtrate were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the partition coefficients of HTC-AA-Na on uranium and barium at different EDTA-2Na concentrations were calculated. K d ) and separation factor ( SF Ba / U ).

[0047] Removal efficiency test results are as follows Figure 4 As shown in Figure (a), without the addition of EDTA-2Na, the removal efficiencies of HTC-AA-Na for uranium and barium reached 99.6% and 99.1%, respectively. When the concentration of EDTA-2Na was 1 mM, HTC-AA-Na showed almost no adsorption of uranium, while the removal rate of barium decreased to 34.1%. When the concentration of EDTA-2Na increased to 3 mM, HTC-AA-Na still did not adsorb uranium, but the removal rate of barium rebounded to 51.4%. Further increasing the concentration of EDTA-2Na led to a decrease in the removal rate of barium by HTC-AA-Na. Therefore, 3 mM EDTA-2Na is the optimal concentration for the separation of uranium and barium.

[0048] The results of the separation factor determination for barium and uranium are as follows: Figure 4 As shown in (b), when the concentration of EDTA-2Na is 3 mM, the separation factor of barium and uranium ( SF Ba / U It reached a maximum value of 69.7.

[0049] The above results demonstrate that adding NaNO3 is far more effective than adding EDTA-2Na in achieving the separation of uranium and barium in HTC-AA-Na, therefore subsequent... 226 The Ra thermal experiment was conducted with the addition of NaNO3.

[0050] Test Example 2 238 U and 226 Real-world thermal experiments investigating Ra separation: S1. The uranium concentration is prepared to be 10 mg / L, and the radium activity concentration is 12440 Bq / L (~3.4 × 10⁻⁶). -4 A mixed solution of (mg / L) yields a U / Ra mass ratio of approximately 2.94 × 10⁻⁶ mg / L. 5 It is relatively close to the U / Ra mass ratio in uranium tailings.

[0051] S2. Take three 60 mL portions of the above mixed solution and add different doses of NaNO3 to each portion to adjust the NaNO3 concentration in the mixed solution to 0.2 M, 0.4 M, and 0.6 M. Take samples at preset time points, 3 mL each time, filter quickly through a syringe filter, and collect the filtrate for analysis.

[0052] S3. The concentration of uranium in the filtrate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the activity of radium in the filtrate was determined using a liquid scintillation analyzer. The removal efficiency η (%) and partition coefficient of HTC-AA-Na for uranium and radium at different NaNO3 concentrations were calculated. ) and separation factor ( ).

[0053] The removal rate measurement results are as follows Figure 5 As shown in Figure (a), when no NaNO3 was added, the removal efficiencies of HTC-AA-Na for uranium and radium reached 99.5% and 99.3%, respectively. When the NaNO3 concentration increased from 0 to 0.6 M, the adsorption performance of HTC-AA-Na for uranium remained almost unchanged, but the removal rate of radium decreased from 99.3% to 2%.

[0054] The separation factor diagram of uranium and radium is shown below. Figure 5 As shown in (b), when the NaNO3 concentration is 0, the separation factor of uranium and radium ( The value was 1.7; however, when the NaNO3 concentration increased to 0.6 M, Reached 5487.3; after conversion, This represents an increase of 3227.8 times. The above results indicate that NaNO3 enables HTC-AA-Na to achieve highly selective separation by adsorbing only uranium without adsorbing radium.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for selectively separating uranium and radium, characterized in that, The application of modified rapeseed straw hydrothermal carbon includes: 0.05-0.3 g / L of modified rapeseed straw hydrothermal carbon and 0.1-0.6 M NaNO3 were added to a mixed solution containing uranium and radium. The modified rapeseed straw hydrothermal carbon selectively adsorbed uranium in the mixed solution. Alternatively, 0.05-0.3 g / L of modified rapeseed straw hydrothermal carbon and 1-6 mM EDTA-2Na can be added to a mixed solution containing uranium and radium. The modified rapeseed straw hydrothermal carbon selectively adsorbs radium in the mixed solution. The modified rapeseed straw hydrothermal carbon is obtained by hydrothermal carbonization of rapeseed straw in an acrylic acid solution, followed by modification with NaOH, and includes the following steps: S1: The pretreated rapeseed straw was placed in an acrylic acid aqueous solution and carbonized in a hydrothermal reactor to obtain HTC-AA, a hydrothermal carbon material rich in carboxyl functional groups. S2: The HTC-AA obtained in S1 was placed in NaOH solution and stirred. The H group in the carboxyl group was removed through cation exchange. + Replaced with Na + Modified hydrothermal carbon from rapeseed straw, HTC-AA-Na, was obtained.

2. The method for selectively separating uranium and radium according to claim 1, characterized in that: The NaNO3 concentration is 0.6M.

3. The method for selectively separating uranium and radium according to claim 1, characterized in that: In S1, the rapeseed straw pretreatment method is to cut it into particles smaller than 0.5 cm; the concentration of acrylic acid aqueous solution is 2.5-5 wt%, and the mass-volume ratio of rapeseed straw to acrylic acid aqueous solution is 0.5-1.5 g: 25-35 mL; the carbonization reaction temperature is 160-200℃, the reaction time is 6-12 h, and the reaction is allowed to cool naturally after completion.

4. The method for selectively separating uranium and radium according to claim 1, characterized in that: In S2, the concentration of NaOH solution is 0.6-1.2M; the mass-to-volume ratio of HTC-AA to NaOH solution is 50-150g:60-100mL; the stirring speed is 800-1200rpm, and the stirring time is 0.5-1.5h.

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