Ce2S3-coated Fe composite material as well as preparation method and application thereof

Abstract

The invention discloses a Ce2S3-coated Fe composite material and a preparation method and application thereof, and belongs to the technical field of radioactive wastewater treatment.The preparation method of the Ce2S3-coated Fe composite material comprises the following steps that under the protection of inert gas, cerium sulfide is added into a ferric iron solution, then a sodium borohydride solution is slowly dropwise added, stirring is carried out, and the Ce2S3-coated Fe composite material is obtained; and ferric iron is reduced into zero-valent iron by utilizing the reducibility of the cerium sulfide, and the zero-valent iron is uniformly loaded on the surface of the cerium sulfide to form the Ce2S3-coated Fe composite material, and the prepared Ce2S3-coated Fe composite material is applied to purification of uranium-containing wastewater. According to the Ce2S3-coated Fe composite material and the preparation method and application thereof, operation is convenient, the cost is low, environment friendliness is achieved, the UO2 < 2 + > reduction rate is high, the UO2 stabilization time is long, all-weather operation can be achieved, and radioactive wastewater treatment and uranium resource recovery can be both considered.

Description

Technical Field

[0001] This invention relates to the field of radioactive wastewater treatment technology, and in particular to a Ce2S3@Fe composite material, its preparation method, and its application. Background Technology

[0002] Currently, the mainstream technologies for treating uranium-containing wastewater include adsorption, precipitation, extraction, and reduction. Among these methods, reduction stands out because it can remove free UO2. 2+ The direct reduction of zero-valent iron (Fe) to uranium (UO2) in power reactors has attracted significant attention. Zero-valent iron is widely used in uranium contamination remediation due to its abundant sources, low price, strong reducing power, and environmental friendliness. However, zero-valent iron particles are prone to agglomeration, and a passivation layer easily forms on their surface, hindering the migration of electrons from the core to the surface and significantly reducing its reactivity. Furthermore, Fe originating from the passivation layer on the surface of zero-valent iron (mainly composed of Fe2O3)... 3+ The dissolution process will then re-oxidize the reduction product UO2 back to UO2. 2+ This leads to the re-dissolution of uranium, affecting the long-term treatment effect. Summary of the Invention

[0003] The purpose of this invention is to provide a Ce2S3@Fe composite material, its preparation method, and its applications, which are 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.

[0004] To achieve the above objectives, the present invention provides a method for preparing Ce2S3@Fe composite materials, comprising 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.

[0005] Preferably, 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.

[0006] Preferably, in S2, the dosage of Ce2S3 is 0.1-0.5 g / L, and the stirring time is 6-12 h.

[0007] Preferably, in S2, the volume of the NaBH4 solution is 2-8 mL and the concentration is 0.2-2 mM.

[0008] Preferably, in S3, the solid-liquid separation is one of vacuum filtration and centrifugation, and the washing method is washing with water 3-5 times and washing with alcohol 2-3 times.

[0009] Preferably, in S3, the drying method is vacuum drying, the drying temperature is 50-80℃, and the drying time is 2-6h.

[0010] The present invention also provides a Ce2S3@Fe composite material, which is prepared by the above-described method for preparing a Ce2S3@Fe composite material.

[0011] This invention also provides an application of Ce2S3@Fe composite material, which is used to purify uranium-containing wastewater.

[0012] Preferably, the application includes the following steps: adding Ce2S3@Fe composite material to uranium-containing wastewater at room temperature and pressure, and using Fe to reduce UO2. 2+ and Ce2S3 reduction of Fe 3+ UO2 in uranium-containing wastewater 2+ Quick removal.

[0013] Preferably, 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 the UO2 content is... 2+ The reduction time is 30-120 minutes.

[0014] Therefore, the present invention, employing the above-mentioned Ce2S3@Fe composite material, its preparation method, and its application, has the following beneficial effects: (1) The effect of Ce2S3@Fe composite material on UO2 2+ The reduction is carried out under natural conditions of normal temperature and pressure, without the need for photoelectric energy input, sacrificial agent / electrolyte, unaffected by weather, and without site restrictions. It has the advantages of convenient operation, low cost, and environmental friendliness. (2) The Ce2S3@Fe composite material has built-in magnetism, which can achieve rapid and low-energy solid-liquid separation by applying an external magnetic field. This completely solves the industry bottleneck of traditional nanomaterials being difficult to recycle and easy to cause secondary pollution, greatly reduces the secondary environmental risk, and lays the foundation for the recycling of nanomaterials. (3) The present invention aims to remove UO2 from uranium-containing wastewater. 2+It directly reduces to UO2, the nuclear fuel for power reactors, simultaneously achieving the dual goals of radioactive wastewater purification and uranium resource recycling. Furthermore, this technology fundamentally eliminates the U(VI) concentration rebound problem present in traditional iron-based material applications.

[0015] 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

[0016] Figure 1 This is a characterization diagram of the Ce2S3@Fe composite material prepared in Example 1 of this invention, wherein... Figure 1 Image (a) in the image is a SEM image of the Ce2S3@Fe composite material. Figure 1 (b) in the figure is the XRD characterization diagram of the Ce2S3@Fe composite material. Figure 1 (c) in the figure is the VSM characterization diagram of Ce2S3@Fe composite material. Figure 1 (d) in the figure is the EPR characterization diagram of Ce2S3@Fe composite material; Figure 2 This is a comparison chart of the performance of different reaction systems of the present invention in reducing U(VI); Figure 3 These are graphs showing the performance of the Ce2S3@Fe composite material in reducing U(VI) under different pH conditions and the results of investigating the maximum adsorption capacity of the Ce2S3@Fe composite material for uranium. Figure 3 (a) shows the performance of Ce2S3@Fe composite material in reducing U(VI) under different pH conditions. Figure 3 Figure (b) shows the results of the investigation on the maximum adsorption capacity of Ce2S3@Fe composite material for uranium; Figure 4 This invention presents the effect of interfering ions on the U(VI) reduction performance of Ce2S3@Fe composite material and the performance of Ce2S3@Fe composite material in removing U(VI) in different real water bodies. Figure 4 (a) shows the effect of interfering ions on the reduction performance of U(VI) in Ce2S3@Fe composite materials. Figure 4 (b) in the figure shows the performance of Ce2S3@Fe composite material in removing U(VI) in different real water bodies; Figure 5 This invention relates to a column experimental apparatus and performance diagram for purifying uranium-containing wastewater using Ce2S3@Fe composite materials. 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

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] 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.

[0019] Example 1 This invention provides a Ce2S3@Fe composite material, the preparation method of which is as follows: 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 water treatment. 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.

[0020] 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, by 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.

[0021] 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 1 EPR data from (d) show that the Ce2S3@Fe composite material has abundant sulfur vacancies (g=2.004), which provides a basis for UO2. 2+ The adsorption provides abundant attachment sites.

[0022] The properties of the Ce2S3@Fe composite material prepared in Example 1 were investigated.

[0023] I. Investigation into the performance of Ce2S3@Fe composite material in reducing uranium, the specific operation is as follows: Step 1: Dissolve a certain weight of UO2(NO3)2·6H2O solid in ultrapure water to prepare uranium-containing wastewater with a concentration of 20 mg / L.

[0024] Step 2: Take 200 mL of each of the uranium-containing wastewater samples from Step 1, and add 0.1 g / L Ce2S3@Fe composite material, Ce2S3+Fe, Fe, and Ce2S3 to the uranium-containing wastewater respectively. Take samples at the set time gradient, 4 mL each time, and then quickly filter them with a syringe filter. Save the liquid samples for testing.

[0025] Step 3: The concentration of residual U(VI) in the filtrate from Step 2 was determined using inductively coupled plasma atomic emission spectrometry, and the changes in U(VI) concentration at different time points under different systems were calculated.

[0026] The results are as follows Figure 2 As shown, by Figure 2 It can be seen that Fe alone can reduce U(VI), but there will be a rebound in U(VI) concentration, posing a risk of secondary release; Ce2S3 alone can also reduce U(VI), but the reduction performance is not ideal; simple mechanical mixing of Ce2S3 and Fe (Ce2S3+Fe) can also improve the reduction performance of U(VI); however, the Ce2S3@Fe composite material obtained by tightly combining Ce2S3 and Fe has a much higher reduction performance of U(VI) than the mechanical mixing of Ce2S3 and Fe, and no U(VI) rebound phenomenon was observed during the long period of 7200 min.

[0027] The above results fully demonstrate that the prepared Ce2S3@Fe composite material does not consist of a simple physical mixture of Ce2S3 and Fe, but rather forms a unique, tightly bound composite structure. This structure facilitates electron transfer and reactant enrichment, thereby synergistically enhancing the reduction rate of U(VI) and the long-term stability of UO2.

[0028] II. Investigation of the effect of pH on the reduction performance of U(VI) in Ce2S3@Fe composite materials, including the following steps: Step 1: Prepare 60 mL of uranium-containing wastewater with an initial uranium concentration of 20 ppm and pH gradients of 2, 3, 4, 6, 8, and 10 respectively.

[0029] 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.

[0030] Step 3: The concentration of residual U(VI) in the filtrate was determined by inductively coupled plasma atomic emission spectrometry, and the removal rate of U(VI) under different pH conditions was calculated.

[0031] The results are as follows Figure 3 As shown in (a), the Ce2S3@Fe composite material exhibits good U(VI) removal capacity over a wide pH range (pH 3–pH 10), with the fastest reaction rate under weakly acidic conditions, achieving complete U(VI) removal within 40 min. Under strongly acidic and strongly alkaline conditions, the removal efficiency decreases. The main reason for this pH dependence is that under strong acidity, excess H+... + It competes with U(VI) for active sites on the material surface and inhibits the reduction reaction. Under alkaline conditions, OH... - Will with UO2 2+ Hydrolysis occurs, generating negatively charged uranyl hydroxyl complexes, forming a hydration layer that covers the active sites and hinders electron transfer, leading to decreased reactivity. In the near-neutral to weakly acidic range, the surface charge state of the material is related to UO2. 2+ Its morphology is more conducive to adsorption and electron transfer, thus exhibiting optimal removal performance.

[0032] III. Investigation of the maximum adsorption capacity of Ce2S3@Fe composite material for U(VI), including the following steps: Step 1: Prepare 60 mL of each of the following concentration gradients for uranium-containing wastewater: 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.

[0033] Step 2: Add 0.1 g / L of Ce2S3@Fe composite material to the uranium-containing wastewater from Step 1. Take samples at 0 min and 120 min, 4 mL each time. Filter the samples quickly with a syringe filter and preserve the liquid samples for testing.

[0034] Step 3: Determine the U(VI) concentration C in the filtrate at equilibrium using inductively coupled plasma atomic emission spectrometry. 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).

[0035] ; in, The initial uranium concentration (mg / L) The volume of the solution is (L). The dosage (g) of Ce2S3@Fe composite material.

[0036] 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.

[0037] IV. Investigation into the influence of interfering ions on the reduction performance of U(VI) in Ce2S3@Fe composite materials, including the following steps: 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.

[0038] 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.

[0039] Step 3: The concentration of residual U(VI) in the filtrate was determined by inductively coupled plasma atomic emission spectrometry, and the removal rate of U(VI) under different interfering ion conditions was calculated.

[0040] The results are as follows Figure 4 As shown in (a), it can be seen that under conditions without interfering ions, the Ce2S3@Fe composite material achieves a near 100% removal efficiency for U(VI). The Ce2S3@Fe composite material exhibits good tolerance in the presence of various interfering ions. In contrast, HCO3... - It inhibits the removal efficiency of U(VI) to some extent. This is mainly attributed to HCO3. - Easy and UO2 2+The formation of soluble uranyl carbonate complexes reduces UO2. 2+ The probability of contact with the active sites of the material.

[0041] The study demonstrated that the Ce2S3@Fe composite material can still maintain efficient and stable removal performance of U(VI) in complex water bodies containing common anions and cations, showing excellent resistance to ion interference and promising application prospects in real-world environments.

[0042] V. Investigation of the removal performance of Ce2S3@Fe composite material for U(VI) in different actual water bodies, including the following steps: Step 1: Collect five actual water samples, including ultrapure water (UP Water), tap water (from Nanhua University), lake water (from Hengyang Pinghu Park), river water (from Xiangjiang River), and seawater (from Bohai Sea), and then prepare five spiked actual uranium-containing wastewater samples with an initial uranium concentration of 20 ppm.

[0043] Step 2: Add 0.1 g / L of Ce2S3@Fe composite material to the actual uranium-containing wastewater from Step 1. Then, take samples at 0 min and 120 min, 4 mL each time, and quickly filter the samples using a syringe filter to obtain liquid samples for testing.

[0044] Step 3: The concentration of residual U(VI) in the filtrate was determined by inductively coupled plasma atomic emission spectrometry, and the removal rate of U(VI) in different real water samples was calculated.

[0045] The results are as follows Figure 4 As shown in (b), it can be seen that in ultrapure water with a single composition, the Ce2S3@Fe composite material achieves a near 100% removal efficiency for U(VI), exhibiting optimal performance. In tap water, the removal efficiency for U(VI) remains at an extremely high level (~98%). In natural water bodies with more complex compositions (lake water, river water), the removal rate of U(VI) by the Ce2S3@Fe composite material still exceeds 90%. In seawater with extremely high ionic strength and the most complex composition, although the removal efficiency of U(VI) by the Ce2S3@Fe composite material decreases somewhat, it still remains above 85%. This indicates that this material is not only suitable for ideal laboratory conditions but also possesses great application potential for treating actual wastewater and dealing with extremely complex environments (such as coastal discharge outlets of nuclear power plants and contaminated seawater).

[0046] VI. Column experiment investigation on the purification of uranium-containing wastewater using Ce2S3@Fe composite material, including the following steps: Step 1: Take 100 mg of Ce2S3@Fe composite material and fill it into an adsorption column with dimensions Ф×h=10 mm×100 mm.

[0047] Step 2: Prepare 2000 mL of uranium-containing wastewater with an initial uranium concentration of 100 ppm.

[0048] Step 3: Adopt the bottom-up flow mode. First, pass ultrapure water at 1 mL / min to remove air bubbles in the adsorption column. Then, pass the uranium-containing wastewater from Step 2 into the adsorption column at a flow rate of 1 mL / min. Collect one sample every 8 mL of effluent. Then, use inductively coupled plasma atomic emission spectrometry to determine the residual U(VI) concentration in the effluent.

[0049] Step 4: After the adsorption column in Step 3 is saturated, first, 36 mL of ultrapure water is bubbled into the adsorption column at a flow rate of 1 mL / min to remove residual feed solution and other impurity ions. Then, 0.5 M HNO3 is bubbled into the adsorption column at a flow rate of 1 mL / min for uranium desorption. A sample of 4 mL of desorption solution is collected, and the U(VI) concentration in the desorption solution is determined using inductively coupled plasma atomic emission spectrometry. The above operations employ... Figure 5 The apparatus shown in (a) is used for investigation.

[0050] The results are as follows Figure 5 As shown, by 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.

[0051] 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.

[0052] 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 a 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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