Ce2s3@fe composite material, and preparation method and application thereof

Abstract

The application discloses a Ce2S3@Fe composite material and a preparation method and application thereof, and belongs to the technical field of radioactive wastewater treatment, and the preparation of the Ce2S3@Fe composite material comprises the following steps: under the protection of inert gas, cerium sulfide is added into a ferric iron solution, and then a sodium borohydride solution is slowly added dropwise, so that the ferric iron is reduced to zero-valent iron by using the reducing property of the sodium borohydride solution and is uniformly loaded on the surface of the cerium sulfide, thereby forming the Ce2S3@Fe composite material; and the prepared Ce2S3@Fe composite material is applied to purification of uranium-containing wastewater. 2+ The application adopts the above Ce2S3@Fe composite material, the preparation method and the application thereof, and has the advantages of convenient operation, low cost, environmental friendliness, fast reduction rate, long UO2 stabilization time, all-weather operation, simultaneous consideration of radioactive wastewater treatment and uranium resource recovery.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of radioactive wastewater treatment, and in particular to a Ce2S3@Fe composite material and a preparation method and application thereof. BACKGROUND

[0002] At present, mainstream technologies for treating uranium-containing wastewater include adsorption, precipitation, extraction and reduction methods. Among the above methods, the reduction method is particularly concerned because it can reduce free UO2 2+ to UO2, which is a nuclear fuel for a power reactor. Zero-valent iron (Fe) is widely used in uranium pollution remediation due to its wide source, low price, strong reduction capacity and environmental friendliness. However, zero-valent iron particles are prone to aggregation, and a passivation layer is easily formed on the surface of the particles, which hinders the migration of electrons in the core to the surface, resulting in a significant reduction in the reactivity of the particles. In addition, Fe 3+ dissolved from the passivation layer (mainly composed of Fe2O3) on the surface of the zero-valent iron particles will further oxidize the reduction product UO2 2+ to UO2 , resulting in the resolubilization of uranium and affecting the long-term treatment effect. SUMMARY

[0003] The purpose of the application is to provide a Ce2S3@Fe composite material and a preparation method and application thereof, which are convenient to operate, low in cost, environmentally friendly, fast in UO2 2+ reduction rate, long in UO2 stability time, capable of all-weather operation, and capable of simultaneously considering radioactive wastewater treatment and uranium resource recovery.

[0004] To achieve the above purpose, the application provides a preparation method of a Ce2S3@Fe composite material, which comprises the following steps:

[0005] S1, preparing an Fe 3+ solution, bubbling inert gas into the Fe 3+ solution to remove dissolved oxygen in the solution;

[0006] S2, adding Ce2S3 to the solution of S1 and stirring to make Fe 3+ uniformly adsorbed on the surface of Ce2S3, and then adding a NaBH4 solution dropwise to reduce Fe 3+ in situ to Fe and uniformly load the Fe on the surface of Ce2S3;

[0007] S3, performing solid-liquid separation, washing and drying on the product obtained in S2 to obtain a Ce2S3@Fe composite material.

[0008] Preferably, in S1, the volume of the Fe 3+ solution is 40-80 mL, the concentration is 1-5 mM, the inert gas is one of nitrogen and argon, and the flow rate is 50-200 mL / min.

[0009] Preferably, in S2, the dosage of Ce2S3 is 0.1-0.5 g / L, and the stirring time is 6-12 h.

[0010] Preferably, in S2, the volume of NaBH4 solution is 2-8 mL, and the concentration is 0.2-2 mM.

[0011] Preferably, in S3, the solid-liquid separation is one of suction filtration and centrifugation, and the washing mode is water washing 3-5 times and alcohol washing 2-3 times.

[0012] Preferably, in S3, the drying mode is vacuum drying, the drying temperature is 50-80℃, and the drying time is 2-6 h.

[0013] The application further provides a Ce2S3@Fe composite material prepared by the above method.

[0014] The application further provides an application of the Ce2S3@Fe composite material, which is applied to purify uranium-containing wastewater.

[0015] Preferably, the application comprises the following steps: under normal temperature and pressure, the Ce2S3@Fe composite material is added into the uranium-containing wastewater, and Fe is used to reduce UO2 2+ , and Ce2S3 is used to reduce Fe 3+ , so that UO2 2+ in the uranium-containing wastewater is quickly removed.

[0016] Preferably, the concentration of the uranium-containing wastewater is 0.1-500 ppm, the pH is 2-10, the dosage of the Ce2S3@Fe composite material is 0.1-0.5 g / L, and the reduction time of UO2 2+ is 30-120 min.

[0017] Therefore, the Ce2S3@Fe composite material, the preparation method and the application thereof have the following beneficial effects:

[0018] (1) The reduction of UO2 2+ by the Ce2S3@Fe composite material is carried out under normal temperature and pressure, without input of photoelectric energy, without sacrifice agent / electrolyte, without influence of weather, and without limitation of site, which has the advantages of convenient operation, low cost, environmental friendliness, etc.

[0019] (2) The Ce2S3@Fe composite material is built-in magnetic, can be quickly and low-energy separated by an external magnetic field, completely solves the industry bottleneck of difficult recycling and easy secondary pollution of traditional nanomaterials, greatly reduces the secondary environmental risk, and lays a foundation for the recycling of nanomaterials.

[0020] (3) The present application aims to directly reduce UO2 2+ in uranium-containing wastewater into power reactor nuclear fuel UO2, and simultaneously achieve the dual goals of radioactive wastewater purification and uranium resource recycling. In addition, this technology fundamentally eliminates the problem of U(VI) concentration rebound in the application of traditional iron-based materials.

[0021] The technical solutions of the present application will be further described in detail below with the aid of drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a characterization diagram of the Ce2S3@Fe composite material prepared in Example 1 of the present application, wherein Figure 1 (a) in FIG. is a SEM characterization diagram of the Ce2S3@Fe composite material, Figure 1 (b) in FIG. is a XRD characterization diagram of the Ce2S3@Fe composite material, Figure 1 (c) in FIG. is a VSM characterization diagram of the Ce2S3@Fe composite material, Figure 1 (d) in FIG. is an EPR characterization diagram of the Ce2S3@Fe composite material;

[0023] Figure 2 is a performance comparison diagram of different reaction systems of the present application for U(VI) reduction;

[0024] Figure 3 is a performance diagram of the Ce2S3@Fe composite material of the present application for reducing U(VI) under different pH conditions and a result diagram of the maximum adsorption capacity of the Ce2S3@Fe composite material for uranium, wherein Figure 3 (a) in FIG. is a performance diagram of the Ce2S3@Fe composite material for reducing U(VI) under different pH conditions, Figure 3 (b) in FIG. is a result diagram of the maximum adsorption capacity of the Ce2S3@Fe composite material for uranium;

[0025] Figure 4 is a performance diagram of the Ce2S3@Fe composite material of the present application for removing U(VI) in different real water bodies and a diagram of the influence of interfering ions on the performance of the Ce2S3@Fe composite material for reducing U(VI), wherein Figure 4 (a) in FIG. is a diagram of the influence of interfering ions on the performance of the Ce2S3@Fe composite material for reducing U(VI), Figure 4 (b) in FIG. is a performance diagram of the Ce2S3@Fe composite material for removing U(VI) in different real water bodies;

[0026] Figure 5 is a column experimental device and performance diagram of the Ce2S3@Fe composite material of the present application for purifying uranium-containing wastewater, wherein Figure 5(a) shows the column experimental setup for purifying uranium-containing wastewater using Ce2S3@Fe composite materials. Figure 5 (b) in the figure shows the breakthrough curve of the Ce2S3@Fe composite material. Figure 5 (c) in the figure represents the desorption curve of the Ce2S3@Fe composite material. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0029] Example 1

[0030] This invention provides a Ce2S3@Fe composite material, the preparation method of which is as follows:

[0031] Add 60 mL of ultrapure water to a 100 mL beaker, then add 242 mg of FeCl3·6H2O. Next, purge the solution with nitrogen gas (100 mL / min) to remove dissolved oxygen. Then add 100 mg of Ce2S3 and stir for 10 hours to allow the FeCl3 to evaporate. 3+ Uniformly adsorbed onto the Ce2S3 surface; 5 mL of 0.5 mol / L NaBH4 aqueous solution was added to the reaction system dropwise, and the reaction was allowed to proceed for 0.5 h. After the reaction was completed, the mixture was filtered, washed, and then subjected to 60°C. o The Ce2S3@Fe composite material was obtained by drying at C for 3 hours, wherein the washing consisted of washing with water 3 times and washing with alcohol 2 times.

[0032] The obtained Ce2S3@Fe composite material was characterized by SEM, XRD, VSM, and EPR. The results are as follows: Figure 1 As shown, by Figure 1 As can be seen in (a) of the image: the SEM image shows that fine iron nanoparticles are uniformly attached to the Ce2S3 surface, and that... Figure 1 The XRD pattern in (b) shows characteristic diffraction peaks belonging to the Ce2S3 phase (PDF#27-0104) and the Fe phase (PDF#06-0696), indicating that the present invention has successfully prepared Ce2S3@Fe composite material.

[0033] Figure 1 The VSM curve in (c) demonstrates that the Ce2S3@Fe composite material exhibits significant superparamagnetism at room temperature, with a saturation magnetization of approximately 50 emu / g, which ensures rapid magnetic separation and recycling of the material after use. Figure 1The EPR data of (d) in the above table shows that the Ce2S3@Fe composite material has abundant sulfur vacancies (g = 2.004), which provides abundant attachment sites for the adsorption of UO2 2+ .

[0034] The performance of the Ce2S3@Fe composite material prepared in Example 1 was explored.

[0035] I. Performance exploration of Ce2S3@Fe composite material for reducing uranium, the specific operation is as follows:

[0036] Step 1: A certain amount of UO2(NO3)2·6H2O solid was dissolved in ultrapure water to prepare uranium-containing wastewater with a concentration of 20 mg / L.

[0037] Step 2: Take 4 portions of 200 mL of uranium-containing wastewater from step 1, and add 0.1 g / L of Ce2S3@Fe composite material, Ce2S3+Fe, Fe, and Ce2S3 into the uranium-containing wastewater, respectively. Sample at the set time gradient, 4 mL each time, then filter rapidly with a needle filter, and save the liquid sample for testing.

[0038] Step 3: The residual U(VI) concentration in the filtrate of step 2 was determined by inductively coupled plasma atomic emission spectrometry, and the concentration change of U(VI) at each time point in different systems was calculated.

[0039] The results are shown in Figure 2 , and it can be seen that: Figure 2 Fe alone can reduce U(VI), but there is a rebound phenomenon of U(VI) concentration, which has the risk of secondary release; Ce2S3 alone can also reduce U(VI), but the reduction performance is not very ideal; simple mechanical mixing of Ce2S3 and Fe (Ce2S3+Fe) can also improve the reduction performance of U(VI); but the Ce2S3@Fe composite material obtained by closely combining Ce2S3 and Fe has much higher reduction performance of U(VI) than the mechanical mixing of Ce2S3 and Fe, and there is no U(VI) rebound phenomenon in a period of up to 7200 min.

[0040] The above results fully prove that the prepared Ce2S3@Fe composite material is not a simple physical mixture between Ce2S3 and Fe, but a unique and closely combined composite structure. This structure is conducive to electron transfer and reactant enrichment, thereby synergistically improving the reduction rate of U(VI) and the long-term stability of UO2.

[0041] II. Influence exploration of pH on the reduction performance of Ce2S3@Fe composite material for U(VI), including the following steps:

[0042] Step 1: Prepare 60 mL of uranium-containing wastewater with an initial uranium concentration of 20 ppm and a pH gradient of 2, 3, 4, 6, 8, and 10, respectively.

[0043] Step 2: Add 0.1 g / L of Ce2S3@Fe composite material to the uranium-containing wastewater from Step 1, then sample at 0 min and 120 min, with 4 mL each time, and quickly filter with a needle filter to preserve the liquid sample for testing.

[0044] Step 3: Use an inductively coupled plasma atomic emission spectrometer to determine the residual U(VI) concentration in the filtrate and calculate the removal rate of U(VI) under different pH conditions.

[0045] The results are shown in (a) of Figure 3 It can be seen that the Ce2S3@Fe composite material exhibits good U(VI) removal ability in a wide pH range (pH 3–pH10), especially under weakly acidic conditions, with the fastest reaction rate and complete removal of U(VI) within 40 min. The removal efficiency decreases under strong acidic and strong alkaline conditions. The main reason for the pH dependence is that excessive H + will compete with U(VI) for active sites on the material surface and inhibit the reduction reaction. In alkaline conditions, OH - will undergo hydrolysis with UO2 2+ to form negatively charged uranyl hydroxyl complexes, forming a hydration layer that covers the active sites and hinders electron transfer, resulting in reduced reaction activity. In the near-neutral to weakly acidic range, the material surface charge state and UO2 2+ form are more conducive to adsorption and electron transfer, thus exhibiting optimal removal performance.

[0046] III. Investigation of the maximum adsorption capacity of Ce2S3@Fe composite material for U(VI), including the following steps:

[0047] Step 1: Prepare 60 mL of uranium-containing wastewater with a concentration gradient of 0.1 mg / L, 1 mg / L, 10 mg / L, 20 mg / L, 50 mg / L, 100 mg / L, 200 mg / L, and 500 mg / L.

[0048] Step 2: Add 0.1 g / L of Ce2S3@Fe composite material to the uranium-containing wastewater from Step 1, then sample at 0 min and 120 min, with 4 mL each time, and quickly filter with a needle filter to preserve the liquid sample for testing.

[0049] Step 3: Use an inductively coupled plasma atomic emission spectrometer to determine the U(VI) concentration C e(mg / L), and calculate the equilibrium adsorption capacity Q of the material at each initial concentration according to the following formula. m (mg / g).

[0050] ;

[0051] in, The initial uranium concentration (mg / L) The volume of the solution is (L). The dosage (g) of Ce2S3@Fe composite material.

[0052] The results are as follows Figure 3 As shown in (b), it can be seen that the equilibrium adsorption capacity (Q) of the Ce2S3@Fe composite material is... m The adsorption capacity increases rapidly with increasing initial U(VI) concentration (C0). A significant increase in adsorption capacity occurs when the concentration reaches 10-20 ppm; however, the adsorption capacity gradually approaches saturation after reaching 100 ppm. The maximum adsorption capacity (Q) of the Ce2S3@Fe composite material is shown below. m The adsorption capacity was 738.2 mg / g, indicating that the Ce2S3@Fe composite material has an extremely high loading capacity for uranium. This ultra-high adsorption capacity proves that there are a large number of active sites on the surface of the Ce2S3@Fe composite material that can bind to U(VI), suggesting that this material has great development potential and application value in the fields of radioactive wastewater treatment and uranium resource recovery, and is a highly competitive candidate material.

[0053] IV. Investigation into the influence of interfering ions on the reduction performance of U(VI) in Ce2S3@Fe composite materials, including the following steps:

[0054] Step 1: Prepare a solution with a uranium concentration of 20 ppm, then add Cl... - SO4 2- NO3 - HCO3 - Na + K + Ca 2 + Mg 2+ The resulting uranium-containing wastewater contained interfering ions, with a concentration of 10 mM for all ions.

[0055] Step 2: Add 0.1 g / L of Ce2S3@Fe composite material to the uranium-containing wastewater from Step 1, and then take samples at 0 min and 120 min respectively, 4 mL each time. Filter the samples quickly with a syringe filter and preserve the liquid samples for testing.

[0056] Step 3: The concentration of residual U(VI) in the filtrate was determined by inductively coupled plasma atomic emission spectrometer, and the removal rate of U(VI) under different interference ions was calculated.

[0057] The results are shown in (a) of Figure 4 It can be seen that under the condition of no interference ions, the removal efficiency of Ce2S3@Fe composite material for U(VI) is close to 100%. In the presence of various interference ions, Ce2S3@Fe composite material shows good resistance. Compared with HCO3 - has a certain degree of inhibition on the removal efficiency of U(VI). This is mainly due to HCO3 - is easy to form soluble carbonato-uranyl complex with UO2 2+ , reducing the probability of UO2 2+ contacting the active sites of the material.

[0058] The exploration proves that Ce2S3@Fe composite material can still maintain high and stable removal performance for U(VI) in complex water containing common anions and cations, showing excellent ion interference resistance and application prospect in actual environment.

[0059] Five, the removal performance of Ce2S3@Fe composite material for U(VI) in different actual water bodies includes the following steps:

[0060] Step 1: Five kinds of actual water samples were collected, including ultrapure water (UP Water), tap water (Tap Water from Nanhua University), lake water (Lake Water from Hengyang Pinghu Park), river water (River Water from Xiangjiang River), and seawater (SeaWater from Bohai Sea), and then five kinds of actual uranium-containing wastewater with an initial uranium concentration of 20 ppm were prepared.

[0061] Step 2: 0.1 g / L of Ce2S3@Fe composite material was added to the actual uranium-containing wastewater of step 1, and then samples were taken at 0 min and 120 min, respectively, each time taking 4 mL, and rapidly filtering with a needle filter to obtain liquid samples for testing.

[0062] Step 3: The concentration of residual U(VI) in the filtrate was determined by inductively coupled plasma atomic emission spectrometer, and the removal rate of U(VI) in different real water samples was calculated.

[0063] The results are shown in (a) of Figure 4As shown in (b) of FIG. 1, it can be seen that in the single-component ultrapure water, the removal efficiency of Ce2S3@Fe composite material on U(VI) is close to 100%, and the performance is optimal; in the tap water, the removal efficiency of U(VI) still remains at a very high level (~98%); in the more complex natural water body (lake water, river water), the removal rate of U(VI) by the Ce2S3@Fe composite material still exceeds 90%; in the seawater with extremely high ionic strength and the most complex composition, the removal efficiency of U(VI) by the Ce2S3@Fe composite material decreases, but still remains above 85%. This shows that the material is not only suitable for laboratory ideal conditions, but also has great application potential for treating actual wastewater and coping with extremely complex environments (such as nuclear power plant coastal discharge outlets and contaminated seawater).

[0064] Six, column experiment of Ce2S3@Fe composite material purifying uranium-containing wastewater, including the following steps:

[0065] Step 1: 100 mg of Ce2S3@Fe composite material is filled into an adsorption column with a specification of Ф×h=10 mm×100 mm.

[0066] Step 2: 2000 mL of uranium-containing wastewater with an initial uranium concentration of 100 ppm is prepared.

[0067] Step 3: In the downward flow mode, first, 1 mL / min of ultrapure water is passed into the adsorption column to remove bubbles in the adsorption column, and then the uranium-containing wastewater of step 2 is passed into the adsorption column at a flow rate of 1 mL / min, and every 8 mL of effluent is collected as a sample, and then the residual U(VI) concentration in the effluent is determined by inductively coupled plasma atomic emission spectrometer.

[0068] Step 4: After the adsorption column of step 3 is saturated, first, 36 mL of ultrapure water is passed into the adsorption column at a flow rate of 1 mL / min to remove the residual feed solution and other impurity ions in the adsorption column, and then 0.5 M HNO3 is passed into the adsorption column at a flow rate of 1 mL / min for uranium desorption, and every 4 mL of desorption solution is collected as a sample, and then the U(VI) concentration in the desorption solution is determined by inductively coupled plasma atomic emission spectrometer. The above operation is carried out by using the device shown in (a) of FIG. 1. Figure 5

[0069] The results are shown in FIG. 1. Figure 5 Figure 5 ​​As shown in (b), when the volume of uranium-containing wastewater introduced into the adsorption column is small, the U(VI) concentration in the effluent is essentially zero, indicating that at this stage, the U(VI) in the uranium-containing wastewater is completely adsorbed by the Ce2S3@Fe composite adsorption column. When the volume of the effluent exceeds 744 mL, the U(VI) concentration in the effluent begins to be detected, indicating that the Ce2S3@Fe composite adsorption column begins to penetrate. When the volume of the effluent reaches 1016 mL, the U(VI) concentration in the influent is equal to that in the effluent, indicating that the Ce2S3@Fe composite adsorption column is completely saturated. Calculations show that the adsorption capacity of the Ce2S3@Fe composite adsorption column for uranium is 744 mg / g, which is similar to the maximum adsorption capacity of 738.2 mg / g in the batch experiment. Figure 3 (b) is basically the same. During the desorption stage, 24 mL of desorption solution is sufficient to completely desorb 92.2% of the uranium in the adsorption column, and the maximum concentration of uranium in the desorption solution reaches 9928.5 ppm. Figure 5 (c)). The above results demonstrate that Ce2S3@Fe composite materials can enrich and concentrate dispersed uranium and are easily desorbed and separated, showing great potential for large-scale industrial applications.

[0070] Therefore, the present invention employs the above-mentioned Ce2S3@Fe composite material, its preparation method, and its application, which is convenient to operate, low in cost, environmentally friendly, and UO2-free. 2+ It has a fast reduction rate, long UO2 stabilization time, can operate around the clock, and can simultaneously handle radioactive wastewater treatment and uranium resource recovery.

[0071] 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 preparing Ce2S3@Fe composite material, characterized in that: Includes the following steps: S1, Preparation of Fe 3+ Solution, to Fe 3+ An inert gas is bubbled into the solution to expel dissolved oxygen. S2. Add Ce2S3 to the solution of S1, stir, and let Fe... 3+ Fe was uniformly adsorbed onto the Ce₂S₃ surface, and then NaBH₄ solution was added dropwise to remove Fe. 3+ It is reduced to Fe in situ and uniformly loaded onto the Ce2S3 surface; S3. The product obtained in S2 is subjected to solid-liquid separation, washing, and drying to obtain Ce2S3@Fe composite material.

2. The method for preparing a Ce2S3@Fe composite material according to claim 1, characterized in that: In S1, Fe 3+ The solution volume is 40-80 mL, the concentration is 1-5 mM, the inert gas is either nitrogen or argon, and the flow rate is 50-200 mL / min.

3. The method for preparing a Ce2S3@Fe composite material according to claim 1, characterized in that: In S2, the dosage of Ce2S3 is 0.1-0.5 g / L, and the stirring time is 6-12 h.

4. The method for preparing a Ce2S3@Fe composite material according to claim 1, characterized in that: In S2, the volume of the NaBH4 solution is 2-8 mL, and the concentration is 0.2-2 mM.

5. The method for preparing a Ce2S3@Fe composite material according to claim 1, characterized in that: In S3, solid-liquid separation is one of vacuum filtration and centrifugation, and the washing method is 3-5 times with water and 2-3 times with alcohol.

6. The method for preparing a Ce2S3@Fe composite material according to claim 1, characterized in that: In S3, the drying method is vacuum drying, the drying temperature is 50-80℃, and the drying time is 2-6 hours.

7. A Ce2S3@Fe composite material, characterized in that: The Ce2S3@Fe composite material was prepared using the preparation method described in any one of claims 1-6.

8. An application of a Ce2S3@Fe composite material, characterized in that: The Ce2S3@Fe composite material described in claim 7 is applied to the purification of uranium-containing wastewater.

9. The application of the Ce2S3@Fe composite material according to claim 8, characterized in that: The application includes the following steps: At room temperature and pressure, Ce2S3@Fe composite material was added to uranium-containing wastewater to reduce UO2 using Fe. 2+ and Ce2S3 reduction of Fe 3 + UO2 in uranium-containing wastewater 2+ Quick removal.

10. The application of the Ce2S3@Fe composite material according to claim 9, characterized in that: The concentration of uranium-containing wastewater is 0.1-500 ppm, the pH is 2-10, the dosage of Ce2S3@Fe composite material is 0.1-0.5 g / L, and UO2... 2+ The reduction time is 30-120 minutes.

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