CN108611490A - The method extracted the extractant of strontium from high activity liquid waste and extract strontium - Google Patents

Abstract

The invention provides an extractant for extracting strontium from high-level radioactive waste liquid and a method for extracting strontium. The structure of the extractant is: Wherein, both R ₁ and R ₂ represent an alkyl group, R ₁ has 6-8 carbon atoms, and R ₂ has 10-12 carbon atoms. The method for extracting strontium from high-level waste liquid by using the above-mentioned extractant comprises the following steps: (1) preparing extractant-kerosene solution as an extraction system; (2) adding oxalic acid and HEDTA to high-level waste liquid, and adjusting the high-level The acidity of the waste liquid; (3) using the extraction system to extract strontium from the high-level waste liquid.

Description

Extraction agent for extracting strontium from high-level radioactive waste liquid and method for extracting strontium

technical field

The invention belongs to the field of nuclear fuel reprocessing, and in particular relates to an extraction agent for extracting strontium from high-level radioactive waste liquid and a method for extracting strontium.

Background technique

There are more than 60 kinds of elements in the spent fuel, U and Pu can be extracted through the Purex process, and the rest of the elements mainly enter the high-level waste liquid. High-level waste liquid contains a certain amount of Sr-90, and it is of great significance to separate Sr-90. On the one hand, Sr-90 can be used as a raw material for the production of isotope batteries; on the other hand, extracting Sr-90 can reduce high-level waste Nuclides with high heat release in the liquid, thereby effectively reducing the volume of the glass solidified body.

There are many methods for extracting strontium in high-level radioactive waste, including precipitation, ion exchange, membrane separation, chromatography and extraction. Among them, the extraction method has good selectivity, high product yield and purification effect, and is suitable for continuous operation, and the key to the extraction method lies in the selection of the extractant.

Extraction agents for strontium extraction mainly include four types: biscarbaboryl cobalt chloride, phosphate esters, crown ethers and amide pod ethers. Among these four types of extractants, dicarbaboryl chlorides and cobalt have strong extraction ability for most "hard acids" such as Cs, An, Ln, etc., but their selectivity is poor. Phosphate esters can only be extracted at low acidity, and the selectivity is poor. It is necessary to add a variety of aqueous phase complexing agents to prevent the extraction of Fe, Zr and other elements. The selectivity of crown ethers is better, but the synthesis is more difficult, and the solubility in alkanes is poor. Among the amide pod ether extractants, currently reported mainly are N,N,N',N'-tetraoctyl amide pod ether and tetrabutyl amide pod ether, N,N,N',N'-tetraoctyl The extraction capacity of amide pod ether is low, and the content of N,N,N',N'-tetraoctylamide pod ether extractable elements (Zr, Sr, etc.) Occurs, phase modifiers such as TBP and monoamide need to be added, which leads to a complex extraction system and a decrease in the distribution ratio of extracted strontium; tetrabutylamide pod ether has strong extraction ability, but it is more prone to three phases, so 50% N-dodecane-isooctanol is used as a diluent. Due to the high solubility of isooctyl alcohol in water and complex radiolysis products, it is still difficult to apply it to the treatment of high-level radioactive waste. Based on the above-mentioned shortcomings of various strontium extractants, in order to improve the effect of extracting strontium from high-level radioactive waste liquid and improve the comprehensive performance of strontium extractants, it is necessary to develop a new strontium extractant and a method for extracting strontium.

Contents of the invention

In order to solve the current low comprehensive performance of the extractant for extracting strontium from high-level radioactive waste liquid, and each extractant has obvious performance shortcomings, the present invention provides an extraction method for extracting strontium from high-level radioactive waste liquid Agent and method for extracting strontium.

The structure of the extractant is:

Wherein, both R ₁ and R ₂ represent an alkyl group, R ₁ has 6-8 carbon atoms, and R ₂ has 10-12 carbon atoms.

A method for extracting strontium from high-level radioactive waste liquid by using the above-mentioned extractant, comprising the following steps:

(1) preparation of extractant-kerosene solution as extraction system;

(2) Add oxalic acid and HEDTA to the high-level waste liquid, and adjust the acidity of the high-level waste liquid;

(3) Using the extraction system to extract strontium from high-level waste liquid.

According to one embodiment, the concentration of the extractant in the extraction system is 0.18-0.22 mol/L.

According to one embodiment, the kerosene may be replaced by n-dodecane.

According to one embodiment, the concentration of the oxalic acid is 0.2-0.3 mol/L.

According to one embodiment, the concentration of the HEDTA is 0.04-0.06 mol/L.

According to one embodiment, the adjusting the acidity of the high level waste liquid is adjusted to 2.5-3.5mol/L.

The extractant of the present invention belongs to asymmetric amide pod ether compounds, has excellent comprehensive extraction performance, and has excellent solubility in alkane solvents such as kerosene, does not appear three phases in the extraction process, and does not need to add a phase modifier. Strontium has strong extraction ability and good selectivity. The method for extracting strontium of the invention can effectively extract strontium from high-level radioactive waste liquid.

Detailed ways

The technical solutions of the present invention will be further specifically described below through examples. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It may be evident, however, that one or more embodiments may be practiced without these specific details.

The extractant of the present invention belongs to the asymmetric amide pod ether compound, and the selection of the number of R1 carbon atoms is beneficial to ensure the extraction capacity. The choice of R2 carbon number is beneficial to control the viscosity of the extraction system, the phase separation is faster in the extraction process, and at the same time avoid three phases in the extraction process.

According to the extraction performance research of the extractant of the present invention to strontium, it can be known that: one, the distribution ratio of the extraction of strontium by the same concentration extractant is consistent with the change law of acidity, all of which increase first and then decrease with the increase of acidity, and the maximum distribution ratio corresponds to The concentration of nitric acid in the extraction system is 3mol/L; secondly, when the acidity is the same, the distribution ratio of the extracted strontium increases significantly with the increase of the concentration of the extractant. After testing and screening, when the concentration of the extractant is 0.18-0.22mol/L, the extraction distribution is larger and the phase separation is faster.

The extraction performance of the extraction agent of the present invention to the key split elements is as shown in Table 1, as can be seen from Table 1: when no aqueous phase complexing agent is added, the distribution of Zr and Pd extracted by the extraction agent is relatively high; after adding oxalic acid, the distribution of Zr is relatively high; ratio decreased significantly; after adding HEDTA, the distribution ratio of Pd decreased significantly.

After testing and screening, using oxalic acid with a concentration of 0.2-0.3mol/L and HEDTA with a concentration of 0.04-0.06mol/L as the aqueous phase complexing agent can effectively prevent the extraction of metal ions such as Zr and Pd.

Table 1 Extraction agent of the present invention to the extraction performance of key split elements

According to an example, the present invention extracts the extractant of strontium from the high-level radioactive waste liquid (the C atom number of R ₁ is 8, and the C atom number of R ₂ is 12), and its structure is:

According to an example, using the extractant of the present invention to extract strontium from a certain high-level radioactive waste liquid, the main steps are as follows:

(1) Extractant-kerosene solution is prepared as an extraction system; the concentration of the extractant in the extraction system can be 0.2mol/L; the kerosene can be replaced by n-dodecane. Before extracting strontium, use DIAMEX process or amide pod ether process to extract actinides and lanthanides in high-level radioactive waste liquid.

(2) Add oxalic acid and HEDTA in the high-level waste liquid, and adjust the acidity of the high-level waste liquid; the concentration of the oxalic acid can be 0.2mol/L; the concentration of the HEDTA can be 0.05mol/L; the adjustment The acidity of high level waste liquid can be adjusted to 3mol/L.

(3) Using the extraction system to extract strontium from high-level waste liquid.

In the extraction system of this example, the distribution ratio of each element is shown in Table 2. It can be seen from Table 2 that the distribution ratio of Sr is greater than 10, that is, under the condition of a ratio of 1:1, the single-stage extraction rate can reach 90%; the distribution ratio of other elements is less than 0.2, that is, strontium and other split elements The separation factor is greater than 50. The above data show that the extraction system can effectively extract strontium from high-level radioactive waste liquid, and the product has a high purity.

Using the extractant of the present invention to carry out multiple groups of parallel tests, when the number _of C atoms in R1 is _6-8 , and the number of C atoms in R2 varies within the range of 10-12, good extraction effects have been achieved.

The distribution ratio of each element in the extraction system of table 2

It is found by comparative test research that other two asymmetric amide pod ether compounds similar to the extractant structure of the present invention can not effectively extract strontium from high-level radioactive waste liquid, and these two compounds are as follows:

The solubility of compound 1 in n-dodecane is less than 0.1mol/L, which is difficult to meet the extraction requirements; although the solubility of compound 2 in n-dodecane is greater than 0.1mol/L, when it contacts with water or nitric acid, serious Emulsification, does not meet the extraction requirements. And the extraction agent of the present invention has good dissolvability in n-dodecane, and the limiting acidity of the water phase of its extraction nitric acid is big, and is greater than 10mol/L, does not appear three-phase in the extraction process, does not need to add phase modifier, extracts Sr, The limiting concentration of Zr in the organic phase can also better meet the extraction requirements.

Although some embodiments according to the present general inventive concept have been shown and described, those of ordinary skill in the art should understand that changes can be made to these embodiments without departing from the principles and spirit of the present general inventive concept , the scope of the present invention is defined by the claims and their equivalents.

Claims (7)

1. an extractant for extracting strontium from high-level radioactive waste liquid, characterized in that the structure of the extractant is: Wherein, both R ₁ and R ₂ represent an alkyl group, R ₁ has 6-8 carbon atoms, and R ₂ has 10-12 carbon atoms. 2. A method of extracting strontium from high-level radioactive waste liquid using an extractant as claimed in claim 1, characterized in that the method may further comprise the steps: (1) preparation of extractant-kerosene solution as extraction system; (2) Add oxalic acid and HEDTA to the high-level waste liquid, and adjust the acidity of the high-level waste liquid; (3) Using the extraction system to extract strontium from high-level waste liquid. 3. The method according to claim 2, characterized in that: the concentration of the extractant in the extraction system is 0.18-0.22mol/L. 4. The method according to claim 2, characterized in that: the kerosene is replaced by n-dodecane. 5. The method according to claim 2, characterized in that: the concentration of the oxalic acid is 0.2-0.3mol/L. 6. The method according to claim 2, characterized in that: the concentration of the HEDTA is 0.04-0.06mol/L. 7. The method according to claim 2, characterized in that: said adjusting the acidity of the high-level waste liquid is adjusted to 2.5-3.5mol/L.