JPS6055448B2 - How to recover uranium from seawater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently recovering uranium from seawater.

Seawater contains about 3 ppb of uranium in the form of uranyl carbonate, and extensive research is being conducted to recover and obtain this uranium.

The method for recovering uranium from seawater is to pass the seawater through a layer of adsorbent that can adsorb uranium and adsorb the uranium.
The adsorbed uranium is eluted from the adsorbent using an eluent,
The uranium in the eluent is further concentrated to obtain solid uranium.

As one such method, for example, uranium in seawater is adsorbed on a titanic acid-based adsorbent, and the adsorbed uranium is eluted from the adsorbent with an aqueous ammonium carbonate solution.
A method has been proposed in which a uranium aqueous solution with a concentration of approximately ppm is formed, ammonium carbonate in the aqueous solution is removed, and then the solution is concentrated to obtain solid uranium.

However, to remove the ammonium carbonate used in this method from an aqueous solution, steam is passed through the aqueous solution to remove CO2 and NH in the form of steam distillation. Not only does the energy consumption required for heated steam for the decomposition be extremely large, but also the ammonia, a component of the cracked gas that is recycled for the preparation of the eluent, is present in the adsorbent. It has the disadvantage that it remains in the water and contaminates seawater. Also,
Using aqueous sodium carbonate solution to elute uranium from the adsorbent,
A method has also been proposed in which uranium and soda carbonate are separated by subjecting an eluent containing about 1 to 10 ppm of uranium to electrolytic dialysis using an ion exchange membrane, but this method also consumes a large amount of electricity, so it is not an industrially advantageous method. isn't it.

In view of these circumstances, the inventor of the present invention has conducted extensive research on an effective method for recovering uranium from seawater, and as a result, the present inventor has discovered that a mineral salt aqueous solution containing uranium is brought into contact with a specific chelate resin. It was discovered that uranium and uranium can be easily separated, leading to the present invention.

That is, the present invention adsorbs uranium in seawater onto an adsorbent containing titanic acid, elutes it with an aqueous solution containing carbonate or hydrogen carbonate, and uses the uranium-containing eluent with a strongly basic anion exchange resin. After adsorbing uranium, the uranium is eluted with a mineral salt-containing aqueous solution, and in the obtained uranium-containing mineral salt aqueous solution, some or all of the hydrogen atoms of the amino groups are replaced with methylene phosphonic acid groups. The present invention provides a method for recovering uranium from seawater, which comprises contacting with a phenolic chelate resin having a primary or secondary alkylamino group in the phenol nucleus to elute adsorbed uranium. .

Uranium in seawater is first adsorbed and collected by various adsorbents, but in the method of the present invention, a titanic acid-containing adsorbent containing titanic acid as an adsorbent component is used.

Any titanic acid-containing adsorbent may be used as long as it is an adsorbent containing titanic acid, and such an adsorbent can be prepared by a conventionally known method (for example, Kokka Shi 7A1486
(1971), Seawater Magazine? 102C79), seawater magazine? 16
C81), seawater magazine? 156C81), Seawater Magazine 35162
C81)). Adsorption of uranium onto an adsorbent can be easily achieved by bringing seawater into contact with the adsorbent using either the commonly used column method or batch method.

The contact temperature is suitably 5°C to 50°C, for example. Next, the uranium adsorbed on the adsorbent is eluted with an aqueous solution containing carbonate or hydrogen carbonate, but an aqueous solution containing both salts can also be used. The concentration of the aqueous solution containing such a carbonate or hydrogen carbonate is preferably, for example, 0.1 to 3N, particularly 0.5 to 1N. Further, examples of carbonates include sodium carbonate, potassium carbonate, ammonium carbonate, and the like, and examples of hydrogen carbonates include sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate, and the like. jThese can be used alone or in combination. The appropriate temperature of the eluent is, for example, 15°C to 80'C. The uranium concentration of the uranium-containing liquid thus obtained is usually 1 to 20 ppm. The uranium-containing liquid containing the carbonate or hydrogen carbonate 4 thus obtained is then brought into contact with a strongly basic anion exchange resin to adsorb uranium, and is separated from salts.

The contact method may be either a column method or a batch method. In addition, the contact temperature is, for example, 5°C.
~50°C is suitable. As a result, the carbonate or hydrogen carbonate aqueous solution and uranium can be separated, and the separated carbonate or hydrogen carbonate aqueous solution can be used again as the eluent. Next, the uranium adsorbed on the strongly basic anion exchange resin is eluted by contacting with an aqueous solution containing a mineral salt having a concentration of, for example, 0.5 to 2N.

Examples of such mineral acid salts include, but are not limited to, sodium chloride, potassium chloride, ammonium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, and the like. In addition, the strong basic ion exchange resin used at this time may be a strong basic ion exchange resin that is generally commercially available, such as Diaion SA-10A (manufactured by Mitsubishi Chemical Corporation), Amperlite IRA-400 (Rohm Examples include, but are not limited to, Dowex 1 (manufactured by Dow Chemical Company) (manufactured by Andhaas Company). The eluate thus obtained is a relatively concentrated uranium solution containing usually about 5 to 50 ppm of uranium. In the method of the present invention, a uranium-containing mineral salt aqueous solution obtained as described above is mixed with a primary or secondary alkyl group in which some or all of the hydrogen atoms of the amino group are substituted with methylene phosphonic acid groups. Uranium is adsorbed onto the resin by contacting it with a phosphorus-containing phenol chelate resin that has an amino group in the phenol nucleus, and is eluted to obtain a highly concentrated uranium solution.

The phosphorus-containing phenol chelate resin used in the method of the present invention can be produced, for example, by the following method. That is, a phenol derivative containing a primary or secondary alkylamino group is reacted with formaldehyde and phosphorous acid in the presence of a mineral acid, and some or all of the protons of the amino group are replaced with methylenephosphonic acid, After that, it can be produced by reacting phenols and aldehydes to form a gel. Examples of the phenol derivative containing a primary or secondary alkylamino group used in this case include tyrosine, ammonia aresol, amine salicylate, etc., and examples of the mineral acid include hydrochloric acid, sulfuric acid, etc. I can do it. Examples of phenols include phenol and resorcinol, and examples of aldehydes include formaldehyde and acetaldehyde. Further, the shape of the phosphorus-containing phenol chelate resin used in the present invention is preferably granular, but it may be in any shape such as fibrous or plate-like. Contact between such a specific phosphorus-containing phenol-based chelate resin and the uranium-containing mineral salt aqueous solution can be carried out by a column method,
Any batch method can be adopted, and
A suitable contact temperature is 5°C to 50°C.

In this way, uranium can be adsorbed onto the chelate resin, and the mineral salt aqueous solution and uranium can be separated, and this mineral salt aqueous solution can be used again as the eluent.

Next, the uranium adsorbed on the phosphorus-containing phenol chelate resin can be easily eluted by contacting with an aqueous solution containing, for example, 0.3 to 2N carbonate and/or hydrogen carbonate. The contact method may be either a column method or a batch method. Further, a suitable contact temperature is 5°C to 50°C. The uranium concentration of the eluent thus obtained is 2,000 to 20,000 ppm, resulting in a very highly concentrated uranium solution. The highly concentrated uranium-containing solution thus obtained can be efficiently obtained as solid uranium by applying a known technique such as a precipitation method.

The present invention achieves extremely efficient adsorption and elution treatment of uranium in seawater adsorbed using a titanic acid-containing adsorbent using a combination of a strongly basic anion exchange resin and a phosphorus-containing phenol chelate resin as adsorbents. This method often proposes a method for recovering uranium from seawater, and the eluent or eluent aqueous solution that elutes the adsorbed uranium is completely recycled in the combined treatment of the present invention and is effectively utilized virtually completely within the system. Therefore, the method of the present invention has no risk of environmental pollution or wasteful energy consumption, compared to various conventional methods of recovering uranium from seawater.
It is industrially desirable because it can recover uranium from seawater very effectively.

Hereinafter, the features of the present invention will be explained in more detail with reference to Examples and Reference Examples. Reference example 1 Polyacrylamide with a polymerization degree of 500 to 1 million and 80%
5% polyacrylic acid hydrazide (hereinafter abbreviated as PAH) obtained by reacting with an aqueous hydrazine solution was added to 200 g of activated carbon impregnated with titanic acid, mixed for about 15 minutes, and heated to 65°C.
It was dried at a temperature of 30% to a moisture content of 30%.

This lump was crushed using a mortar and then sieved to produce a granular adsorbent containing titanic acid. Reference Example 2 1 mole of tyrosine and 2 moles of phosphorous acid are dissolved in a 20% aqueous hydrochloric acid solution, heated to reflux while stirring, and 3 moles of phosphorous acid are dissolved in the solution.
6 mol of 7% formalin aqueous solution was added dropwise over an hour.

After the dropwise addition was completed, the mixture was further stirred and refluxed for 1 hour. Then, after cooling to room temperature, hydric soda was added and PHL
It was made alkaline to 1. Add 1.5 mol of resorcin and 5 mol of 37% formalin to this solution, and while stirring,
Further n-paraffin was added. Next, while stirring, the mixture was heated at 60°C for 1 hour, then at 80°C for 1 hour, at 90°C.
After successively heating for 1 hour, the contents began to solidify into granules. After that, transfer the contents to an autoclave and heat at 120℃.
The gelation was completed by reacting at a temperature of 5 hours. The thus obtained granular resin was isolated by filtration, air-dried, washed with water, and then immersed in a 1N H2S04 solution to convert the resin from Na type to H type. This was filtered to obtain bead-shaped phosphorus-containing phenol chelate resin. Example 1 Adsorbent 2.5e containing titanic acid obtained in Reference Example 1 was
It was packed into a 50 m 11 ψ x 20 - column, and 60 d of seawater (uranium concentration 3 ppb) was passed through it at a temperature of 25°C.

The liquid passing rate at that time was S. V. (Space velocity) 1001
/・It was Hr. After that, 0.5 sodium hydrogen carbonate - 0.5 N sodium hydrogen carbonate aqueous solution 2 was added to this column.
5e to S. V. A liquid was passed through the resin at a rate of 3 l/hr at a temperature of 60'C to elute the uranium adsorbed on the resin. The uranium concentration of this eluent was 3.5 ppm (this solution was classified as Solution A). Next, strongly basic ion exchange resin SA-10A (manufactured by Mitsubishi Kasei Corporation) 1.5e was packed in a column of 100 mnψ x 50 h, and solution A 25' was passed through the column at a temperature of 25°C. The liquid passing rate at that time was S. V. It was 5l/hr. (The liquid that comes out of the column after passing through the column is called liquid B.) Thereafter, a 6% aqueous sodium chloride solution 10e is added to the column using S.I. V. 2l/hr
When the uranium adsorbed on the resin was eluted by passing the liquid through the resin at a temperature of 25°C, 41 ml of a 6% sodium chloride aqueous solution containing 18 ppm of U (this liquid is referred to as liquid C) and 2.5 ppm of U were obtained.
6% sodium chloride 6e containing M (this liquid is referred to as C″ liquid) was obtained.

Next, phosphorus-containing phenol chelate resin 1 obtained in Reference Example 2
0cc to 10TfrI&φ×(a)? packed in a column of
The C liquid 41 was subjected to S.I. V. The solution was passed through at 3 l/hrl at 25°C.

(The liquid that comes out of the column after passing through the column is called liquid D.) Then, 70 cc of a 1N aqueous sodium hydrogen carbonate solution is added to the S. V.
A liquid was passed through the resin at a rate of 2 liters per hour at a temperature of 25° C. to elute the uranium adsorbed on the resin. The uranium concentration of this eluent is 5000
The uranium was very high in ppm, and by neutralizing it with HCl and adding aqueous ammonia, it was possible to recover uranium as a solid substance as ammonium deuterate (yellow cake). On the other hand, titanate-type adsorbent 2 that desorbed uranium
．． 60 d of seawater was passed through 5' again.

The liquid passing rate at that time was S. V. The lOOl/Hrl temperature was 25°C. After that, the above B liquid 25e was added to SN. 3
A liquid was passed through the resin at a l/Hrl temperature of 25° C. to elute the uranium adsorbed on the resin. The uranium concentration of this eluent is 3.4 pp
It was m. (This liquid will be referred to as liquid E.) Next, use the strongly basic ion exchange resin SA-1 from which uranium was eluted in the above experiment.
Add liquid E to A 25e8sN. The liquid was passed through at a temperature of 51/Hrl and 25°C.

Thereafter, a mixture of Solution D 4e<5C'' and Solution 6' was passed through the strongly basic ion exchange resin SA-1C)A that had adsorbed uranium. Through this elution operation, a saline solution 41 containing 22 ppm of U was mixed. (This solution is referred to as Solution F.) Next, the phosphorus-containing phenol chelate resin Solution F 4e from which uranium had been eluted in the experiment described above was passed through the reactor at an SV of 2 l/Hrl temperature of 25°C.

After that, 70 cc of 1N sodium hydrogen carbonate aqueous solution was added to S.I.
V. The uranium adsorbed on the resin was eluted by passing 2 l/hr at a temperature of 25°C. The uranium concentration of this eluent is 5000
It was possible to recover uranium as a solid content at a high yield of ppm using the precipitation method. Comparative Example 1 10 cc of each of commercially available chelate resins Diaion CR-10 (manufactured by Mitsubishi Kasei Corporation), Uniselect 8UR-50 (manufactured by Unitika Corporation), and Dowex A-1 (manufactured by Dow Chemical Corporation) was added to 1071117! The C liquid 4e obtained in Example 1 was packed in a column of ψ×50 wgg and S. V. 5l/h
r, the solution was passed through the solution at a temperature of 25°C, but the adsorption efficiency of uranium in solution A to the above resin was very poor, and even if it was desorbed in the same way as in the case of phosphorus-containing phenol chelate resin, the uranium concentration in the eluent remained low. It was 500 ppm or less.

Claims (1)

[Claims] 1. Adsorb uranium in seawater onto an adsorbent containing titanic acid, elute it with an aqueous solution containing carbonate or hydrogen carbonate, and contact the uranium-containing eluate with a strongly basic anion exchange resin to remove uranium. After adsorbing uranium, uranium is eluted with an aqueous solution containing a mineral salt, and the obtained aqueous solution of a uranium-containing mineral salt is converted into a primary uranium in which some or all of the hydrogen atoms of the amino groups are substituted with methylene phosphonic acid groups. Alternatively, a method for recovering uranium from seawater, which comprises contacting with a phenolic chelate resin having a secondary alkylamino group in the phenol nucleus to elute adsorbed uranium.