A process for the recovery of uranium from sodium calcine having uranium adsorbed thereon

Abstract

The present application relates to the technical field of uranium waste treatment, and particularly relates to a method for recovering uranium from sodium lime adsorbed with uranium. The method for recovering uranium from sodium lime adsorbed with uranium comprises the following steps: S1, adding a nitric acid solution to the sodium lime adsorbed with uranium to perform uranium elution, and obtaining a uranyl nitrate solution; S2, separating the eluted sodium lime from the uranyl nitrate solution; and S3, adjusting the pH value of the uranyl nitrate solution, so that the uranium is recovered in the form of sodium diuranate precipitate. The present application is simple in operation, high in uranium recovery rate, and can recycle the uranium in a recyclable form while reducing the solid waste treatment cost.

Description

Technical Field

[0001] This invention relates to the field of uranium waste treatment technology, and more particularly to a method for recovering uranium from soda lime that has adsorbed uranium. Background Technology

[0002] During the separation of uranium hexafluoride (UF6) samples from the 2S cylinder, some UF6 residue remains in the separation system. Sodium lime is used to adsorb this residue. However, the combination of residual liquid UF6 with the solid adsorbent sodium lime in the UF6 separation system produces radioactive solids with a uranium content of 20%–30%, increasing the cost of radioactive waste disposal and causing some degree of pollution to the storage environment. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for recovering uranium from uranium-adsorbed soda lime, which is simple to operate, has a high uranium recovery rate, and recovers uranium in a recyclable form while reducing the cost of solid waste treatment.

[0004] This invention provides a method for recovering uranium from soda lime that has adsorbed uranium, comprising:

[0005] Step S1: Add nitric acid solution to soda lime containing uranium to perform uranium desorption, and obtain uranyl nitrate solution;

[0006] Step S2: Separate the analyzed soda lime from the uranyl nitrate solution;

[0007] Step S3: Adjust the pH of the uranyl nitrate solution so that uranyl ions in the solution are recovered as sodium diuranate precipitate.

[0008] Preferably, the concentration of the nitric acid solution is 4–16 mol / L.

[0009] Preferably, the concentration of the nitric acid solution is 8 mol / L.

[0010] Preferably, the mass-to-volume ratio of the uranium-adsorbed soda lime to the nitric acid solution is 1 g: 4-10 mL.

[0011] Preferably, in step S3, sodium hydroxide is used to adjust the pH value of the uranyl nitrate solution.

[0012] Preferably, in step S3, the pH of the uranyl nitrate solution is adjusted to 13.

[0013] Compared with the prior art, the method for recovering uranium from soda lime adsorbed with uranium of the present invention has the following beneficial effects:

[0014] 1) The method of using nitric acid solution for analysis and alkaline solution for precipitation is feasible and has the characteristics of simple operation. The entire analysis and recovery process only includes three steps: analysis, separation and precipitation.

[0015] 2) It has the characteristic of high recovery rate. The recovery rate of uranium in soda lime is between 86.2% and 96.9%.

[0016] 3) It has the characteristics of low cost of desorption and recovery. The reagents used for the desorption and recovery of uranium in soda lime are common, inexpensive and readily available.

[0017] 4) Low waste generation is beneficial to environmental protection. After treatment, the generation of uranium-containing solid waste is greatly reduced, as are the costs of solid waste recycling, transportation, storage, and management, thus reducing environmental pollution. Detailed Implementation

[0018] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0019] Embodiments of the present invention disclose a method for recovering uranium from soda lime adsorbed with uranium, comprising:

[0020] Step S1: Add nitric acid solution to soda lime containing uranium to perform uranium desorption, and obtain uranyl nitrate solution;

[0021] Step S2: Separate the dissolved soda lime from the uranyl nitrate solution;

[0022] Step S3: Adjust the pH of the uranyl nitrate solution so that uranyl ions in the solution are recovered as sodium diuranate precipitate.

[0023] This invention primarily uses nitric acid to desorb uranium adsorbed in soda lime, and recovers the uranium by precipitating the resulting uranyl nitrate as sodium diuranate. This reduces solid waste treatment costs and recovers uranium in a recyclable form.

[0024] When using nitric acid solution for uranium desorption, the concentration of the nitric acid solution has a significant impact on the desorption effect. If the acid concentration is too low, uranium is difficult to desorb quickly from soda lime; if the acid concentration is too high, the reaction is too violent, the temperature is difficult to control, and the operation is highly dangerous. Therefore, it is necessary to strictly control the concentration of the nitric acid solution.

[0025] The concentration of the nitric acid solution is preferably 4–16 mol / L, more preferably 4–16 mol / L, and most preferably 8 mol / L.

[0026] The mass-to-volume ratio of the uranium-adsorbed soda lime to the nitric acid solution is 1 g: 4-10 mL.

[0027] The uranium-containing solution and uranium-removing solid waste generated after analysis are separated into solid and liquid components. The solid waste is then cleaned and deregulated after being monitored for dosage. The uranium-containing solution is then further processed.

[0028] To avoid introducing impurities, the pH of the uranyl nitrate solution is adjusted to 13 with sodium hydroxide, so that the uranyl ions in the uranium-containing solution react completely with the sodium hydroxide, and the uranyl ions in the solution can be completely precipitated, so that the uranium can be recovered in the form of sodium diuranate precipitate.

[0029] To further understand the present invention, the method for recovering uranium from uranium-adsorbed soda lime provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0030] Examples 1-3

[0031] 1) Desorption of uranium adsorbed in soda lime

[0032] Following the quartering sampling method, 50g of soda lime adsorbed with uranium hexafluoride was weighed, and an 8mol / L nitric acid solution was prepared as the eluent. 400mL of the eluent solution was added to the soda lime, and the mixture was stirred at room temperature for 4 hours.

[0033] Table 1. Effects of different concentrations of nitric acid on the desorption of uranium from soda lime.

[0034]

[0035] Based on the experimental data in Table 1, when the acid concentration is 4 mol / L, the acid concentration is too low and uranium cannot be fully desorbed from the soda lime within two hours. When the acid concentration is 16 mol / L, the concentration of uranium desorbed is similar to that when the acid concentration is 8 mol / L, but the reaction is more vigorous and exothermic, which is not conducive to controlling the reaction temperature when there is a large amount of material, and there is a certain degree of danger in operation. Therefore, 8 mol / L was chosen as the acid concentration for desorbing uranium adsorbed in soda lime.

[0036] 2) Solid-liquid separation

[0037] The uranium-containing solution and uranium-removing solid waste generated after analysis are separated into solid and liquid components. The solid waste is then cleaned and deregulated after being monitored for dosage. The uranium-containing solution is then further processed.

[0038] 3) Uranium recovery

[0039] The pH of the uranium-containing solution is adjusted to 13, allowing the uranyl ions in the solution to react completely with sodium hydroxide, thus completely precipitating the uranyl ions and recovering the uranium as sodium diuranate precipitate.

[0040] 4) Uranium recovery experiment in soda lime

[0041] 500g of soda lime was used to fully adsorb 49.75g of uranium. The "quartering method" was selected for sampling. After several mixing and reduction, 400mL of 8mol / L nitric acid solution was added to the 50g soda lime sample. The mixture was stirred at room temperature for 4h. The solution was filtered and diluted to 1000mL with distilled water. The uranium concentration in the solution was measured. Six parallel determinations were performed. The measurement results are shown in Table 2.

[0042] Table 1 Results of the analytical recovery rate determination

[0043]

[0044] Based on the experimental data in Table 2, the uranium recovery rate can reach over 90% using the selected analytical technique.

[0045] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recovering uranium from soda lime adsorbed with uranium, characterized in that, include: Step S1: Add nitric acid solution to uranium-adsorbed soda lime to perform uranyl nitrate desorption, and obtain uranyl nitrate solution; the concentration of the nitric acid solution is 4~16 mol / L; the mass-to-volume ratio of uranium-adsorbed soda lime to nitric acid solution is 1g:4~10mL; Step S2: Separate the dissolved soda lime from the uranyl nitrate solution; Step S3: Adjust the pH of the uranyl nitrate solution so that uranyl ions in the solution are recovered as sodium diuranate precipitate.

2. The method for recovering uranium from soda lime adsorbed with uranium according to claim 1, characterized in that, The concentration of the nitric acid solution is 8 mol / L.

3. The method for recovering uranium from soda lime adsorbed with uranium according to claim 1, characterized in that, In step S3, sodium hydroxide is used to adjust the pH value of the uranyl nitrate solution.

4. The method for recovering uranium from soda lime adsorbed with uranium according to claim 3, characterized in that, In step S3, the pH of the uranyl nitrate solution is adjusted to 13.

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