A method for treating uranium-containing laundry waste water from a nuclear fuel element plant with aminated pva fibers

Abstract

The application provides a method for treating uranium-containing laundry wastewater of a nuclear fuel element factory by using aminated PVA fiber. The fiber takes polyvinyl alcohol fiber as a base material, and amino groups are grafted onto the base material by using an epoxy activation method and a hydrothermal method to prepare a new aminated PVA fiber (numbered XKXW-X). The preparation method is simple, the aminated PVA fiber has stable performance, good hydrophilicity, high adsorption capacity and can be reused, and the adsorption capacity of uranium under the optimized conditions is as high as 395.4 mg / g. The XKXW-X prepared by the application has good selectivity (K d ≥ 1.55*10 5 mL g ‑1 ) for uranium, and the uranium removal rate can reach 98.4% when the real nuclear fuel element factory uranium-containing laundry wastewater is treated. Therefore, the XKXW-X has good application prospect in treating the uranium-containing laundry wastewater of the nuclear fuel element factory.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of radioactive wastewater treatment, and particularly relates to a synthesis method of amino-functionalized PVA fiber, and deep purification of uranium-containing laundry wastewater from a nuclear fuel element plant and efficient extraction of uranium. BACKGROUND

[0002] The nuclear power industry is in a rapid development stage, and the demand for uranium resources is increasing. In the front end of the nuclear fuel cycle, a type of low-concentration uranium-containing laundry wastewater will be generated in the production process of nuclear fuel elements. This type of wastewater contains dispersants, acid and alkali regulators, fabric brighteners, fragrances, enzyme preparations and other surfactants, with a COD of 1-200 mg / L, and also contains shoe cover-borne ground suspended solids and particulate matter and other pollutants. Compared with conventional uranium-containing process wastewater, the water quality is more complex, and specific pretreatment methods or more resistant and highly selective purification materials need to be developed. Currently, there are two treatment processes for this type of uranium-containing laundry wastewater: one is the traditional ammonium salt precipitation-silica gel adsorption, and the surfactants will cause silica gel poisoning; the other is the emerging membrane treatment method, which is treated by microfiltration-nanofiltration-reverse osmosis in three stages, and the uranium concentration in the effluent is less than 50 ppb. However, due to the presence of a large amount of suspended solids and particulate matter in the uranium-containing laundry wastewater, the membrane material is prone to clogging, and the membrane material is expensive, the reverse osmosis pressure is high, and the cleaning is difficult, which often causes downtime for repair. Therefore, it is necessary to develop a new material for efficient extraction of U(VI) from laundry wastewater generated in the production process of nuclear fuel elements. Functionalized fibers, as a type of coordination polymer, are metal ion adsorption and separation materials containing special functional groups, which can be used in the fields of metal ion absorption and enrichment, radiochemical separation, radioactive wastewater treatment, etc. They are better than many adsorbents, and compared with the commonly used polyacrylonitrile base material, polyvinyl alcohol fibers have better acid and alkali resistance, hydrophilicity, etc. In addition, polyvinyl alcohol fibers have good weather resistance and sunlight resistance, high mechanical strength, and good thermal stability. The hydroxyl groups in the matrix can react with various reagents. Thus, different functional groups can be grafted to facilitate fiber grafting modification. Amino groups can form complexes with metal ions, and amino-based adsorbents have a large adsorption capacity and good selectivity for uranium.

[0003] The XKXW-X described in the present application uses polyvinyl alcohol fiber as the base material, introduces amino functional groups through a simple epoxy activation and amination reaction, has a simple grafting method, stable performance, good hydrophilicity, and high adsorption capacity, and has good selectivity for uranium. Currently, there is no report on the application of this type of fiber in the field of uranium-containing laundry wastewater from a nuclear fuel element plant. Therefore, XKXW-X has practical application value for solving the scarcity of resources and potential environmental problems. SUMMARY

[0004] The application aims to provide a method for treating uranium-containing laundry wastewater in a nuclear fuel element factory by using aminated PVA fiber.

[0005] The application uses polyvinyl alcohol fiber as a base material, first performs epoxy activation treatment on the polyvinyl alcohol fiber, then grafts amino groups onto the fiber after epoxy activation through a hydrothermal reaction to synthesize XKXW-X. The aminated PVA fiber is used to efficiently extract uranium from uranium-containing laundry wastewater by using the chelation performance of amino groups and metal ions.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows.

[0007] (1) Epoxy activation: take a proper amount of polyvinyl alcohol fiber and add it to a beaker containing a mixed solution of epichlorohydrin (10.0-20.0 mL), dimethyl sulfoxide (10.0-15.0 mL), and NaOH (5.0-6.0 mol / L), seal the beaker, and place it in a water bath constant temperature oscillator at 70-90℃ for 4-5h. Wash the activated fiber with deionized water until it is neutral, and dry it at 60-80℃.

[0008] (2) Base modification: according to the mass ratio of the fiber after epoxy activation to the aminating agent of 1:9.8-49, add the fiber after epoxy activation to a mixed solution of the aminating agent and the swelling agent in a volume ratio of 1.0-5.0:1, use a high-pressure reaction kettle to perform a hydrothermal reaction at 105-135℃ for 3-4h, then wash it with deionized water at 40-60℃ until it is neutral, and dry it at 60-80℃ to obtain aminated PVA fiber (numbered XKXW-X).

[0009] To efficiently remove uranium from uranium-containing laundry wastewater in a nuclear fuel element factory, the following measures can be taken:

[0010] (1) Appropriately increase the dosage of XKXW-X to improve the removal efficiency of uranium-containing laundry wastewater;

[0011] (2) Within a certain range, increasing the adsorption temperature and prolonging the adsorption time are both conducive to improving the removal rate of uranium in uranium-containing laundry wastewater by XKXW-X.

[0012] The application provides a method for treating uranium-containing laundry wastewater in a nuclear fuel element factory by using aminated PVA fiber, which has the following advantages compared with the prior art:

[0013] (1) XKXW-X compared to the original fiber hydrophilicity significantly enhanced, the adsorption capacity of target ions significantly increased; in addition, in the presence of U, Mg, Al, Cr, Fe, Ca, Ba, Si, Ni, K, Sr and other elements in the uranium-containing laundry wastewater, XKXW-X has strong selectivity for uranium adsorption, distribution coefficient can reach 1.55*10 5 mL g -1 , uranium removal rate (≥98.4%);

[0014] (2) XKXW-X in the pH 5-9 conditions of uranium removal rate (≥90%), can be applied to most of the uranium-containing laundry wastewater;

[0015] (3) environmentally friendly, no secondary pollution, suitable for efficient treatment and resource recycling of uranium-containing laundry wastewater, good cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the present application, the drawings used in the prior art description will be briefly introduced as follows.

[0017] Figure 1 pH on the effect of XKXW-X removal of uranium in wastewater;

[0018] Figure 2 a is the effect of XKXW-X on the adsorption capacity of uranium at different temperatures and initial concentrations.b and c are the simulated Langmuir, Freundlich and other adsorption isotherm models, and the R 2 The value of R

[0019] Figure 3 The efficiency of 6 XKXW-X adsorption / desorption cycles.

[0020] Figure 4 The distribution coefficient of XKXW-X for each element in the uranium-containing laundry wastewater of the nuclear fuel element plant and the removal rate of each element. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with the embodiments of the present application.

[0022] Example 1

[0023] 50.0 mL of uranium solution with a concentration of 50 mg / L was added to 10 groups of conical flasks, respectively, and 1.0 mol / L HCl and Na2CO3 solution was used to adjust the pH value from 2 to 11, and 0.02 g of XKXW-X was added. After 24 h of action, filtration was performed for solid-liquid separation, and the supernatant was obtained. The concentration of uranium in the supernatant was tested by ICP-OES, and according to the adsorption equilibrium formula, it was calculated that the adsorption capacity of XKXW-X for uranium was the largest at pH = 6.0, reaching 112.95 mg / g.

[0024] Example 2

[0025] 0.02 g of XKXW-X was taken, respectively, and 50 mL of uranium solution with an initial concentration of 5, 10, 20, 50, 75, 100, 125, 150, 200 mg / L was added, and 1.0 mol / L HCl and Na2CO3 solution was used to adjust the pH value to 6 at 35, 40, 45°C. After 24 h of reaction, the results were as shown in Table a. Figure 2 The Langmuir model and the Freundlich model were used for simulation, and b and c were obtained, respectively. Figure 2 Figure 2 The results showed that the adsorption of the fiber conformed to the Langmuir adsorption isotherm, and the maximum adsorption capacity of XKXW-X for uranium was 395.4 mg / g.

[0026] Example 3

[0027] 50 mL of uranium solution with a concentration of 50 mg / L was taken in a conical flask, 1.0 mol / L HCl and Na2CO3 solution was used to adjust the pH value to 6.0, and 0.02 g of XKXW-X was added. After 24 h of action, filtration was performed, and the supernatant 1 was obtained. The XKXW-X after adsorbing uranium was added to 50 mL of 0.10 mol / L sodium carbonate solution, and after standing for 2-3 h, filtration was performed, and the supernatant 2 was obtained. The concentration of uranium in the supernatant 1 and the supernatant 2 was tested by ICP-OES, and the adsorption rate and the removal rate of XKXW-X for uranium were calculated according to the adsorption equilibrium formula. The above experiment was repeated for 6 times to explore the recycling performance of XKXW-X. After 6 times of repeated recycling, the adsorption and desorption performance was stable. It was shown that XKXW-X had good recycling performance.

[0028] Example 4

[0029] In order to verify the actual application effect of XKXW-X, XKXW-X was used to treat the real uranium-containing laundry waste liquid of a nuclear fuel element factory, and the waste liquid included U, Mg, Al, Cr, Fe, Ca, Ba, Si, Ni, K, Sr and other elements. 0.02 g of XKXW-X was taken, and 50 mL of uranium-containing laundry waste liquid was added. After 24 h of reaction at 25°C, the results were as shown in Table a.​Figure 4 The removal rate and distribution coefficient Kd of XKXW-X to uranium are shown in the figure. XKXW-X has a high removal rate and a high distribution coefficient Kd to uranium d 98.4% and 1.55×10 5 mL g -1 , which shows good selective adsorption and good application prospect.

Claims

1. A method for treating uranium-containing laundry effluent from a plant for processing nuclear fuel elements with aminoated PVA fibers, characterized in that, The specific steps are as follows: (1) epoxy activation: a certain amount of polyvinyl alcohol fiber is added to a beaker containing a mixed solution of 10.0-20.0 mL of epichlorohydrin, 10.0-15.0 mL of dimethyl sulfoxide and 5.0-6.0 mol / L NaOH, and then sealed and placed in a water bath constant temperature oscillator at 70-90°C for 4-5 h; the epoxy-activated fiber is washed with deionized water until neutral, and dried at 60-80°C to obtain the epoxy-activated fiber; (2) amination modification: the epoxy-activated fiber is added to a mixed solution of amine reagent and swelling agent, and then subjected to hydrothermal reaction in a high-pressure reaction kettle at 105-135°C for 3-4 h, and then washed with deionized water at 40-60°C until neutral and dried to obtain the aminated PVA fiber.

2. A process for the treatment of laundry effluent containing uranium from a plant for the production of fuel elements for nuclear reactors with aminated PVA fibres according to claim 1, characterized by the fact that, The aminated PVA fiber can efficiently adsorb uranium in laundry wastewater containing uranium, surfactants, anions and cations, and has good selectivity for uranium.

3. A process for the treatment of laundry effluent containing uranium from a plant for the production of fuel elements for nuclear reactors with aminated PVA fibres according to claim 2, characterized by the fact that, The surfactant includes dispersant, fabric brightener, the anion includes NO3 - , Cl - , the cation includes Mg 2+ , Ca 2+ , Pb 2+ , Sr 2+ .

4. The method of claim 1, wherein the method is characterized by, The aminated PVA fiber after adsorption is desorbed with 0.01-0.1 mol / L Na2CO3, HCl, HNO3, H2SO4 solution, so that the adsorbent can be recycled.

5. The method for treating laundry waste water containing uranium in a plant for processing nuclear fuel elements with aminated PVA fibers according to claim 1, characterized by the fact that, The aminated PVA fiber can be made into a fiber cloth or gauze.

6. The method of treating uranium-containing laundry waste water from a nuclear fuel element plant according to claim 1, wherein The pH of the laundry wastewater containing uranium in the nuclear fuel element plant is 6-9.

7. A process for treatment of laundry effluent containing uranium from a plant for processing nuclear fuel elements with aminated PVA fibers according to claim 1, characterized by that, The laundry wastewater containing uranium in the nuclear fuel element plant contains surfactants, nitrate, ammonium nitrogen, COD is 1-200 mg / L, and uranium concentration is 1-20 mg / L.

Images