JPH0486599A - Method and material for removing strontium and/or antimony - Google Patents

Abstract

PURPOSE:To enable the removal of strontium Sr and/or antimony Sb efficiently by treating a high basic concentration solution by a removing material containing manganese dioxide (MnO2). CONSTITUTION:A removing material containing MnO2 is worked in a form of powder, particle, fiber or the like and a quantity of use thereof is determined according to the concentrations of Sr and Sb in a solution. pH of a solution to be treated is appropriately above about 5 in an NaNO3 system when iodine is contained and preferably above about 7 viewed from performance of an adsorbent. The pH is not limited specifically in an Na2 SO4 system and a phosphate system but preferably above about 7. There is no limit specifically when phosphoric acid is produced. For example, a raw liquid 5 is supplied with a raw material pump 2 from a tank 5 to a column 3 packed with about 1g of a particulate spinel type MnO2 as adsorbent 4 with a mesh of about 100 or less and 200 or more and the solution treated leaving a line 6 is analyzed about 420 min. later and no Sr was detected.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for removing strontium and/or antimony from a solution containing strontium or antimony, particularly a solution (waste liquid) at a high salt concentration, and a removal material used therein. Regarding.

In the present invention, a solution (waste liquid) refers to a solution using water, a hydrophilic solvent, or a mixture thereof as a solvent.

(Prior Art) An example of conventional technology for removing strontium and antimony is wastewater treatment in the nuclear field.

In other words, radioactive low-level concentrated waste liquid generated from nuclear facilities such as nuclear fuel reprocessing plants and nuclear power plants contains 20
0-400g/R sodium nitrate and about 0-200g
/ρ sodium carbonate, 5 to 50 g/β salts such as sodium nitrite (hereinafter collectively referred to as NaNO3), approximately 25% sodium sulfate, and approximately 12% sodium borate salts ( These are hereinafter collectively referred to as Na and SO4 systems), and under high salt concentration conditions, radioactive cation nuclides such as Sr and Cs are included.

In addition, waste solvent (TBP) from the solvent extraction process of U and Pu
) Libutyl phosphoric acid) + n-dodecane, etc.) A liquid phase oxidation method has been proposed as one of the methods for treating oxidized waste liquid (such as 150 g/g of phosphoric acid, etc.) in which this solvent is liquid phase oxidized. (hereinafter collectively referred to as phosphoric acid) contains radioactive cation nuclides such as antimony.

As a treatment method for such a solution, NaNO2, Na2
In NaNOx systems containing Cox and the like, in addition to Sr and the like, ions such as Ca and Mg are present at 200 ppm or more in the solution, so attempts have been made to adsorb and remove Sr using an inorganic adsorbent.

On the other hand, when producing phosphoric acid as a product from these solutions, if the raw materials contain impurities, the product will have many impurities and problems will occur, but for example, distillation can be used to obtain a purer product. Sometimes, problems such as a decrease in the yield of the product occur.

(Problems to be Solved by the Invention) In other words, the above-mentioned conventional technology in the field of nuclear energy has the following problems to be solved.

1) When adsorbing Sr in a solution in the above NaNOx system, the presence of Ca and Mg lowers the adsorption ability and significantly increases the amount of adsorbent used.

2) In order to coprecipitate sb in a phosphoric acid system, it is necessary to maintain the pH at about 7 and take a long coprecipitation time.
Weak against fluctuations in H value.

3) Furthermore, when producing the above-mentioned phosphoric acid, there are the above-mentioned problems.

The present invention aims to solve the problems of the above-mentioned prior art, and aims to provide a method and a removal material for efficiently removing strontium and/or antimony from a solution.

(Means for Solving the Problems) The present inventors have conducted various studies in order to overcome the above-mentioned problems, and as a result, the present inventors have found that the purpose can be achieved by using manganese dioxide as a treatment material under specified conditions. Based on this finding, the present invention has been completed.

That is, the present invention provides (1) a method characterized in that a solution with a high salt concentration is treated with manganese dioxide to remove strontium and/or antimony, and (2) a method containing manganese dioxide that removes strontium and/or antimony. The object of the present invention is to provide a removal material characterized by the following.

The present invention is applied to solutions with high salt concentrations in terms of removal efficiency, and is applied to solutions with a concentration close to saturation, that is, 50% or more of the saturation concentration, preferably 80% or more, particularly preferably 90% or more of the saturation concentration.
Suitable for 0% or higher solutions.

Gun dioxide outperforms other treatments in removing high concentrations.

In the present invention, N a given as an example in the nuclear field
NO! If the system contains iodine, the pH of the solution to be treated is
is preferably 5 or more, and preferably 7 or more in view of the performance of the adsorbent. For Na2SO4 and phosphoric acid systems, the pH is not particularly limited, but is preferably 7 or higher. Moreover, when producing phosphoric acid, there are no particular restrictions.

The manganese diaate used in the present invention is an oxide represented by the formula M n Oz, and among these, those having a spinel crystal structure are particularly preferred.

In the present invention, the removal material can be processed into any desired shape such as powder, granules, or fibers.

The dose is not particularly limited (it can be appropriately determined depending on the concentrations of strontium and antimony in the solution).

Further, the removal material of the present invention can be reused by regenerating it with nitric acid, caustic soda, etc. The present invention is a batch type,
Both semi-patch and continuous methods can be used.

(Effects of the Invention) As described above, when the removal method and removal material according to the present invention are used, 1) In one example in the field of nuclear power, in addition to efficiently removing Sr and Sb, Not only can each solution in the system be treated individually, but also when they are mixed, they can be treated all at once, so the number of liquid types to be managed can be reduced.

2) In addition, when producing phosphoric acid directly, it is easy to purify the phosphoric acid as a product, and even if distillation is required, impurities are removed, so there is less residue in the pot. , the product yield will be higher.

(Example) Next, the present invention will be explained in more detail based on examples.

Example 1 400 g/42 N a N Oz 50 as stock solution
g/ρ N a 2 COz 50 g/I2
An aqueous solution containing 5:300:300 ppm of NaNO2; Sr; Ca: Mg ions and having a pH of 7 was treated with the apparatus shown in FIG.

That is, a column 3 (inner diameter 8 mm, wall thickness 700 mm) filled with 1 g of granular spinel type manganese dioxide of 100 mesh below 200 mesh as adsorbent 4 was transferred from stock solution tank 1 to stock solution 5 using stock solution transport pump 2 at a rate of 0.3 ml/min.
mm).

After 420 minutes, the Sr ion concentration of the treated liquid coming out of line 6 was reduced to 1. It was analyzed using C and P methods, but it was not detected.

Example 2 A treatment test was conducted in the same manner as in Example 1 except that 5 ppm of sb was added to the stock solution of Example 1.

After 250 minutes, the Sr and Sb of the liquid to be treated coming out from line 6 was reduced to 1. As a result of analysis using the C, P, method, these were not detected.

Example 3.4, Comparative Examples 1 to 7 Batch tests of various adsorbents were conducted using the same liquid composition as in Example 2. The adsorbent has a particle size of 100 mesh below 200 mesh, and 0.1 g of the adsorbent is heated at 30°C for 2 days at 10 rpm.
I immersed it in the solution of m. The results are shown in Table 1.

It can be seen from Table 1 that manganese dioxide, especially spinel type, exhibits an extremely high distribution coefficient.

Example 5 A treatment test was conducted in the same manner as in Example 2 except that Ca and Mg ions were removed. The results were similar to Example 2.

Example 6 Approximately 5000 ppm of phosphate ion was added to the stock solution of Example 1.
was added and the same operation as in Example 1 was performed.

Even after 420 minutes, no Sr was detected in the treated liquid coming out of line 6.

Example 7 The stock solution of Example 1 was added to 250 g/ρ sodium sulfate, 12
The same operation as in Example 1 was performed except that 0 g/DI sodium borate was used. The results were equally good.

Example 8 The anion in the stock solution of Example 1 was replaced with 200 g/9 phosphoric acid, and the other cations were carried out under the same conditions. The results were almost the same as in Example 1.

Example 9 The same procedure as in Example 8 was carried out by adding 5 ppm of sb.

The results were almost the same as in Example 8.

[Brief explanation of drawings]

FIG. 1 shows an example of a flow sheet used to carry out the method of the present invention.

Claims (2)

[Claims] (1) A method characterized by treating a solution with a high salt concentration with manganese dioxide to remove strontium and/or antimony. (2) A removal material containing manganese dioxide that removes strontium and/or antimony.