A method for removing U(VI) from uranium-containing wastewater

Abstract

The present invention relates to the technical field of radioactive wastewater treatment, and provides a method for removing U(VI) from uranium-containing wastewater. The method provided by the present invention comprises the following steps: mixing mesoporous silicon and hydrogen peroxide with uranium-containing wastewater for reaction, and removing U(VI) from the uranium-containing wastewater; the pH value of the uranium-containing wastewater is 3-7. The present invention uses mesoporous silicon as an adsorbent to adsorb U(VI) in uranium-containing wastewater, and at the same time utilizes hydrogen peroxide to react with the adsorbed U(VI) to generate water strontium uranium ore precipitation fixed on the surface of the mesoporous silicon, thereby achieving efficient removal of U(VI). The method provided by the present invention has the advantages of simple operation, low cost and no secondary pollution. The results of the embodiment show that the method provided by the present invention has a good removal effect on uranium-containing wastewater with a concentration range of 0.1-50 mg / L, and the removal rate can reach more than 96%.

Description

Technical Field

[0001] The invention relates to the technical field of radioactive wastewater treatment, and in particular to a method for removing U(VI) from uranium-containing wastewater. Background Art

[0002] Uranium is the main nuclear fuel for nuclear energy production and is currently mainly obtained through uranium mining and smelting. At present, the intensity of uranium mining and smelting is continuously increasing, and a large amount of low-concentration uranium-containing wastewater is inevitably produced during the uranium mining and smelting process. Uranium has both chemical toxicity and radiotoxicity, and its half-life is as long as 4.468×10 9 a. If it is not treated promptly and effectively, its toxicity will exist for a long time and continue to spread, thus posing a serious threat to the ecological environment and human health.

[0003] At present, the common method for removing uranium from water is adsorption, which has the advantages of low cost, convenient operation and good repeatability. However, this method has problems such as limited adsorption capacity, low removal rate and selectivity that needs to be strengthened. In recent years, the method of photocatalytic reduction separation and removal of uranium has gradually become a research hotspot due to its simple operation, high efficiency and environmental friendliness. However, most of the systems for photocatalytic removal of uranium that have been reported require harsh conditions such as inert gas atmosphere and ultraviolet light irradiation, and require the addition of organic matter as a sacrificial agent, which is inconvenient to operate. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for removing U(VI) from uranium-containing wastewater. The present invention realizes efficient removal of U(VI) from uranium-containing wastewater through the combined action of hydrogen peroxide and mesoporous silicon. The method provided by the present invention is green, environmentally friendly and easy to operate.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for removing U(VI) from uranium-containing wastewater, comprising the following steps:

[0007] Mesoporous silicon and hydrogen peroxide are mixed with uranium-containing wastewater to react, thereby removing U(VI) from the uranium-containing wastewater;

[0008] The pH value of the uranium-containing wastewater is 3-7.

[0009] Preferably, the pore size of the mesoporous silica is 2.2 to 54.5 nm, and the pore volume is 0.021 to 0.975 cm 3 / g, specific surface area is 2.57~532.16m 2 / g, and the particle size distribution is 350~580nm.

[0010] Preferably, the method for preparing mesoporous silicon comprises the following steps:

[0011] The ethyl orthosilicate, octadecyltrimethoxysilane, ammonia water and ethanol aqueous solution are mixed for co-condensation reaction to obtain silica microspheres;

[0012] The silicon dioxide microspheres are calcined to obtain the mesoporous silicon.

[0013] Preferably, the mass fraction of the hydrogen peroxide is 30% to 40%; the amount of hydrogen peroxide added is based on controlling the concentration of hydrogen peroxide in the uranium-containing wastewater to 6.528 to 65.28 mmol / L.

[0014] Preferably, the U(VI) concentration in the uranium-containing wastewater is 0.1 to 50 mg / L.

[0015] Preferably, the volume ratio of the mass of the mesoporous silicon to the uranium-containing wastewater is 0.1 to 2 g / L.

[0016] Preferably, the reaction temperature is room temperature and the reaction time is 0.5 to 18 hours.

[0017] Preferably, the uranium-containing wastewater is uranium tailings pond seepage water.

[0018] The present invention provides a method for removing U(VI) from uranium-containing wastewater, comprising the following steps: mixing mesoporous silicon and hydrogen peroxide with uranium-containing wastewater for reaction, and removing U(VI) from the uranium-containing wastewater; the pH value of the uranium-containing wastewater is 3-7. The present invention uses mesoporous silicon as an adsorbent to adsorb U(VI) in uranium-containing wastewater, and at the same time utilizes hydrogen peroxide to react with the adsorbed U(VI) to generate water strontium uranium ore precipitation fixed on the surface of the mesoporous silicon, thereby achieving efficient removal of U(VI). The method provided by the present invention does not require a catalyst, harsh conditions such as an inert gas atmosphere and ultraviolet light irradiation, and does not require a sacrificial agent. The method provided by the present invention is simple to operate, low in cost, does not generate secondary pollution, and can still ensure a good removal effect. The results of the embodiment show that the removal rate of the method provided by the present invention for uranium-containing wastewater with a concentration range of 0.1-50 mg / L is as high as more than 96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a transmission electron microscope image of the mesoporous silicon prepared in Example;

[0020] Figure 2 is the BET diagram of the mesoporous silicon prepared in Example;

[0021] Figure 3 is a pore size distribution diagram of the mesoporous silicon prepared in Example;

[0022] Figure 4 is the FT-IR image of the mesoporous silicon prepared in Example and its treatment of uranium-containing wastewater;

[0023] Figure 5 is an XPS graph of the mesoporous silicon prepared in Example and its treatment of uranium-containing wastewater;

[0024] Figure 6 is the XRD pattern of the mesoporous silicon prepared in Example and its XRD pattern after treating uranium-containing wastewater;

[0025] Figure 7 1 is a diagram showing the effect of removing uranium in Examples 1 to 5 under different pH conditions of uranium-containing wastewater;

[0026] Figure 8 It is a diagram showing the effect of removing uranium in Example 1 and Examples 6 to 8 under different concentrations of hydrogen peroxide in uranium-containing wastewater;

[0027] Fig. 9 It is a diagram showing the effect of removing uranium in Example 1 and Examples 9 to 12 under different U(VI) concentration conditions in uranium-containing wastewater. DETAILED DESCRIPTION

[0028] The present invention provides a method for removing U(VI) from uranium-containing wastewater, which is characterized by comprising the following steps:

[0029] Mesoporous silicon and hydrogen peroxide are mixed with uranium-containing wastewater to react, thereby removing U(VI) from the uranium-containing wastewater;

[0030] The pH value of the uranium-containing wastewater is 3-7.

[0031] In the present invention, unless otherwise specified, all substances are commercially available products well known to those skilled in the art.

[0032] Mesoporous silicon and hydrogen peroxide are mixed with uranium-containing wastewater for reaction to remove U(VI) in the uranium-containing wastewater. In the present invention, the pH value of the uranium-containing wastewater is preferably 5 to 7, more preferably 5±0.05; the solution used to adjust the pH value of the uranium-containing wastewater is preferably a NaOH solution or a HCl solution; the amount of hydrogen peroxide added is preferably based on controlling the concentration of hydrogen peroxide in the uranium-containing wastewater to 6.528 to 65.28 mmol / L, more preferably 32.64 to 65.28 mmol / L, and further preferably 32.64 mmol / L; the U(VI) concentration in the uranium-containing wastewater is preferably 0.1 to 50 mg / L, more preferably 1 to 50 mg / L; the uranium-containing wastewater is preferably uranium tailings pond percolation water.

[0033] In the present invention, the pore size of the mesoporous silica is preferably 2.2 to 54.5 nm, more preferably 2.2 to 10.5 nm, and the pore volume is preferably 0.021 to 0.975 cm 3 / g, more preferably 0.625 to 0.679 cm 3 / g, and the specific surface area is preferably 2.57 to 532.16 m 2 / g, more preferably 350.21 to 419.93 m 2 / g, and the particle size distribution is preferably 350 to 580 nm, more preferably 450 to 550 nm.

[0034] In the present invention, the mesoporous silicon can be commercially available or prepared by itself. When prepared by itself, the preparation method of the mesoporous silicon preferably includes the following steps: mixing tetraethyl orthosilicate, octadecyltrimethoxysilane, ammonia water and ethanol aqueous solution for co-condensation reaction to obtain silica microspheres; calcining the silica microspheres to obtain the mesoporous silicon. In the present invention, the volume ratio of the tetraethyl orthosilicate to octadecyltrimethoxysilane is preferably 6:3-4, more preferably 6:3; the volume ratio of the ammonia water, ethanol and water is preferably 3.4:75-80:10-15, more preferably 3.4:75:10; the volume ratio of the tetraethyl orthosilicate to water is preferably 6:10-12, more preferably 6:10; the mass fraction of the ammonia water is preferably 32%; the ethanol is preferably commercially available anhydrous ethanol; the present invention has no special requirements for the mixing method, and it only needs to be mixed evenly. In this embodiment, it is preferred to first dissolve the ammonia water in the ethanol aqueous solution, then mix the tetraethyl orthosilicate and octadecyltrimethoxysilane, and mix the resulting mixed solution The method comprises the following steps: adding the mixture dropwise into an ethanol aqueous solution dissolved with ammonia water; the dropping rate is preferably 2 mL / min; the temperature of the co-condensation reaction is preferably room temperature; after the dropwise addition is completed, the obtained reaction solution is preferably allowed to stand, filtered and dried for the first time in sequence to obtain silica microspheres; the standing time is preferably 3 h; the temperature of the first drying is preferably 70°C; the time of the first drying is preferably 12 h; the temperature of the calcination is preferably 550°C; the time of the calcination is preferably 6 h; after the calcination, the obtained product is preferably acid-washed and dried for the second time in sequence, the acid-washing reagent is preferably a hydrochloric acid solution, the temperature of the second drying is preferably 70°C; the time of the second drying is preferably 12 h.

[0035] In the present invention, the volume ratio of the mass of the mesoporous silicon to the uranium-containing wastewater is preferably 0.1-2 g / L, more preferably 2 g / L; the mass fraction of the hydrogen peroxide is preferably 30-40%, more preferably 30%.

[0036] In the present invention, there is no special requirement for the mixing method, as long as the mixture is mixed evenly; the reaction temperature is preferably room temperature, and the reaction time is preferably 0.5 to 18 hours, more preferably 12 to 18 hours; in an embodiment of the present invention, the reaction is preferably carried out in an air bath shaker, and the rotation speed of the air bath shaker is preferably 180 rpm.

[0037] After the reaction is completed, the reaction liquid is preferably filtered first to filter out the mesoporous silicon adsorbed with the strontium uranium ore precipitate, and the remaining liquid is the treated wastewater with low uranium content.

[0038] In order to further illustrate the present invention, the method for removing U(VI) from uranium-containing wastewater provided by the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0039] The mesoporous silica used in the present invention is prepared by the following method: 6 mL of tetraethyl orthosilicate and 3 mL of octadecyltrimethoxysilane are mixed uniformly under magnetic stirring, and then added to 3.4 mL of ethanol-water (V 2 ) containing 32% ammonia water at a drop rate of 2 mL / min. 乙醇 =75mL, V 水 =10mL) solution, stirring was stopped after the addition was completed, the reaction solution was allowed to stand for 3h, and then filtered to obtain silica microspheres, the silica microspheres were placed in a 70°C oven and dried for 12h, transferred to a muffle furnace, and kept at a constant temperature of 550°C for 6h, and naturally cooled to room temperature, and the obtained product was neutralized with a 1mol / L hydrochloric acid solution, and finally the obtained product was placed in a 70°C oven and dried for 12h to obtain the mesoporous silicon. Figure 1 TEM image of mesoporous silicon. Figure 1 It can be seen that the mesoporous silica is spherical and has a particle size of about 500 nm. Figure 2 and Figure 3 They are the BET diagram and pore size distribution diagram of mesoporous silica, respectively. Figure 2 and Figure 3 It can be seen that the pore volume of mesoporous silica is 0.679 cm 3 / g, specific surface area is 419.93m 2 / g, and the average pore size is 6.46nm.

[0040] Example 1

[0041] Add 150 mL of uranium-containing wastewater with a L(VI) concentration of 20 mg / L into a 250 mL conical flask, adjust the pH value of the uranium-containing wastewater to 5±0.05 with 0.1 mol / L NaOH / HCl solution, then add 0.3 g of mesoporous silica and 0.5 mL of 30% hydrogen peroxide, place the conical flask in a constant temperature air bath shaker at 25°C and a rotation speed of 180 rpm, and react for 12 hours before the reaction is completed.

[0042] Detection of uranium concentration in uranium-containing wastewater: Before and after the reaction, take 2 mL of solution with a syringe and filter it with a 0.22 μm filter membrane, and determine the uranium concentration in the sample by ICP-MS.

[0043] Figure 4The FT-IR image of mesoporous silicon and its treatment of uranium-containing wastewater shows that at 800 cm -1 and 1068cm -1 The characteristic absorption peak of Si-O appeared at 956cm -1 A characteristic absorption peak belonging to O=U=O appeared at , indicating that uranium was successfully fixed on the mesoporous silicon surface. Figure 5 This is an XPS graph of mesoporous silicon and its treatment of uranium-containing wastewater. It can be seen that after treatment using the method provided by the present invention, a characteristic signal peak belonging to U (VI) appears on the surface of the mesoporous silicon, further indicating that uranium is fixed on the surface of the mesoporous silicon. Figure 6 2 is the XRD diagram of mesoporous silicon and the XRD diagram of the mesoporous silicon after treating uranium-containing wastewater. It can be seen that after the treatment by the method provided by the present invention, the uranium product generated on the surface of the mesoporous silicon is strontium uranium ore ((UO2)O2·2H2O).

[0044] Embodiments 2 to 5

[0045] The method of Example 1 was used to remove U(VI) from uranium-containing wastewater. Other conditions were the same as those of Example 1, except that:

[0046] The pH values ​​of uranium-containing wastewater were adjusted to 3, 4, 6 and 7 respectively.

[0047] Calculate uranium removal rate: Removal rate = (uranium-containing wastewater concentration C o - Uranium-containing wastewater concentration after the reaction is completed C t ) / C o × 100%. The U(VI) removal rates of Examples 1 to 5 were measured and the results were as follows: Figure 7 As shown. Figure 7 It can be seen that when the pH values ​​are 3, 4, 5, 6 and 7, the removal rates of U(VI) are 3.95%, 98.97%, 99.50%, 99.49% and 72.37%, respectively. Therefore, when the pH value of uranium-containing wastewater is 5, the removal effect is best.

[0048] Embodiment 6-8

[0049] The method of Example 1 was used to remove U(VI) from uranium-containing wastewater. Other conditions were the same as those of Example 1, except that:

[0050] The volumes of hydrogen peroxide added were 0.1 mL, 0.2 mL and 1.0 mL respectively. The removal rates of U(VI) in Example 1 and Examples 6 to 8 were measured. The results are as follows: Figure 8 As shown. Figure 8It can be seen that when the concentrations of hydrogen peroxide in the uranium-containing wastewater are 6.528 mmol / L (Example 6), 13.06 mmol / L (Example 7), 32.64 mmol / L (Example 1) and 65.28 mmol / L (Example 8), the removal rates of U(VI) are 91.5%, 95.38%, 99.50% and 99.45%, respectively. Therefore, when the concentration of hydrogen peroxide in the uranium-containing wastewater is 32.64 mmol / L, the removal effect is optimal.

[0051] Examples 9-12

[0052] The method of Example 1 was used to remove U(VI) from uranium-containing wastewater. Other conditions were the same as those of Example 1, except that:

[0053] The concentrations of U(VI) in the uranium-containing wastewater were 1 mg / L, 5 mg / L, 10 mg / L and 50 mg / L respectively. The removal rates of U(VI) in Example 1 and Examples 9-12 were measured, and the results were as follows: Fig. 9 As shown. Fig. 9 It can be seen that when the U(VI) concentration in the uranium-containing wastewater is 1 mg / L (Example 9), 5 mg / L (Example 10), 10 mg / L (Example 11), 20 mg / L (Example 1) and 50 mg / L (Example 12), the removal rates of U(VI) are 98.7%, 96.7%, 97.07%, 99.5% and 98.6%, respectively. Therefore, the method provided by the present invention has a good removal effect on uranium-containing wastewater with a U(VI) concentration in the range of 1 to 50 mg / L.

[0054] Embodiment 13

[0055] The method of Example 1 was used to remove U(VI) from uranium-containing wastewater. Other conditions were the same as those of Example 1, except that:

[0056] The uranium-containing wastewater is the percolation water of a uranium tailings pond in southern my country. The U(VI) concentration in the uranium-containing wastewater is 180.4μg / L, the pH value is 6.02, and the step of adjusting the pH value is omitted. The U(VI) concentration in the treated wastewater is measured, and the results show that the U(VI) concentration after treatment is 4.9μg / L. From the above results, it can be seen that the method provided by the present invention greatly reduces the U(VI) concentration in the percolation water of the uranium tailings pond, and the U(VI) content in the treated wastewater reaches the drinking water standard specified by the World Health Organization (WHO). Therefore, the method provided by the present invention can efficiently treat low-concentration uranium-containing wastewater generated in actual production.

[0057] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for removing U(VI) from uranium-containing wastewater, characterized in that: The following steps are involved: Mesoporous silicon and hydrogen peroxide are mixed with uranium-containing wastewater to react, thereby removing U(VI) from the uranium-containing wastewater; The pH value of the uranium-containing wastewater is 3 to 7; The preparation method of mesoporous silicon comprises the following steps: The ethyl orthosilicate, octadecyltrimethoxysilane, ammonia water and ethanol aqueous solution are mixed for co-condensation reaction to obtain silica microspheres; calcining the silicon dioxide microspheres to obtain the mesoporous silicon; The amount of hydrogen peroxide added is based on controlling the concentration of hydrogen peroxide in the uranium-containing wastewater to 32.64-65.28 mmol / L.

2. The method according to claim 1, characterized in that The pore size of the mesoporous silica is 2.2 to 54.5 nm, and the pore volume is 0.021 to 0.975 cm 3 / g, specific surface area is 2.57~532.16m 2 / g, and the particle size distribution is 350~580nm.

3. The method according to claim 1, characterized in that The mass fraction of the hydrogen peroxide is 30% to 40%.

4. The method according to claim 1, characterized in that: The U(VI) concentration in the uranium-containing wastewater is 0.1-50 mg / L.

5. The method according to claim 1 or 4, characterized in that: The volume ratio of the mass of the mesoporous silicon to the uranium-containing wastewater is 0.1-2 g / L.

6. The method according to claim 1 or 3, characterized in that: The reaction temperature is room temperature and the reaction time is 0.5 to 18 hours.

7. The method according to claim 1 or 4, characterized in that: The uranium-containing wastewater is the seepage water from the uranium tailings pond.

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