JPS6349734B2 - - Google Patents

Description

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

Seawater contains about 3 ppb of uranium.
As a method for obtaining uranium from seawater, research has been conducted on a method in which uranium is adsorbed by passing seawater through a uranium adsorbent, then the adsorbed uranium is eluted, and finally solid uranium is obtained from the eluate. has been done. For example, uranium in seawater is adsorbed onto a titanate-based adsorbent, and the adsorbed uranium is eluted with ammonium carbonate to create an aqueous solution containing uranium at a concentration close to 10 ppm. From this, the ammonium carbonate is removed and a uranium aqueous solution is created. A method has been proposed to obtain solid uranium and further solidify it to recover solid uranium. In this method, ammonium carbonate is passed through steam and converted into CO ₂ and NH ₃ in the form of steam distillation.
However, the gas is recovered and recycled.
Ammonia may remain on the adsorbent and contaminate seawater,
It has drawbacks such as high energy consumption in steam thermal decomposition.

A method has also been proposed in which uranium and soda carbonate are separated by using a sodium carbonate solution to elute uranium from an adsorbent and subjecting this eluent to electrolytic dialysis using an ion exchange membrane. However, it consumes a lot of power and is not an advantageous method in terms of cost.

On the other hand, as a uranium adsorbent other than titanic acid,
It is known that amidoxime type chelate resins are effective uranium adsorbents (for example, Japanese Patent Publication No. 32834/1983). In the case of this resin, it is effective to elute the adsorbed uranium with an aqueous mineral acid solution, and the uranium concentration of the mineral acid eluent is said to be about 1 to 20 ppm. However, due to the low uranium concentration, solvent extraction methods and precipitation methods cannot be used effectively, and no effective method has been found to further concentrate the uranium in this uranium-containing mineral acid aqueous solution and ultimately obtain solid uranium. This is the actual situation.

Therefore, in view of these actual circumstances, the present inventor conducted extensive research on a method for recovering uranium from seawater, and as a result, the inventors of the present invention have developed a method of adsorbing uranium in seawater onto an adsorbent, and then contacting a uranium-containing liquid obtained by adsorbing uranium with a specific chelate resin. They discovered that uranium in seawater can be efficiently recovered, and arrived at the present invention.

That is, the present invention adsorbs uranium in seawater onto an adsorbent, elutes the adsorbed uranium with an aqueous mineral acid solution to obtain a uranium-containing liquid, and introduces the obtained uranium-containing liquid as a chelate-forming group into a phenol nucleus. contact with a phenolic chelate resin (hereinafter referred to as phosphorus-containing phenolic chelate resin) having a group in which some or all of the hydrogen atoms of the primary and/or secondary alkylamino groups have been substituted with methylene phosphonic acid groups. This is a method for recovering uranium from seawater.

In the present invention, in order to recover uranium from seawater, it is first necessary to obtain a uranium-containing liquid. For this purpose, for example, seawater and adsorbent are brought into contact, and either a column method or a batch method can be used as the contact method. Moreover, as a contact temperature, 5 degreeC - 50 degreeC is suitable. Next, the uranium adsorbed on the adsorbent is eluted with an aqueous mineral acid solution, and the concentration of the aqueous mineral acid solution at this time is preferably, for example, 0.1 to 3N, particularly 0.2 to 1N. In addition, as mineral acids, for example,
Examples include hydrochloric acid, sulfuric acid, and nitric acid, and these can be used alone or in combination. The uranium concentration of the uranium-containing liquid obtained in this way is 1 to
It is 20ppm.

Next, in the present invention, the uranium-containing liquid obtained above is brought into contact with the phosphophenol-containing chelate resin, and the contacting method may be either a column method or a batch method. Moreover, as a contact temperature, 5 degreeC - 50 degreeC is suitable. Thereby, the mineral acid aqueous solution and uranium can be separated, and the separated mineral acid aqueous solution can be used again as the eluent. Next, the uranium adsorbed on the phosphorus-containing phenol chelate resin is eluted. For this purpose, it may be brought into contact with, for example, a 5-20N mineral acid aqueous solution or a 0.5-2N carbonate-containing aqueous solution. Examples of mineral acids at this time include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.
Examples of carbonates include sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium carbonate, and ammonium hydrogen carbonate. The uranium temperature of the eluent thus obtained is 100 to 2000 ppm, resulting in a very highly concentrated uranium solution.

The thus obtained high-concentration uranium-containing solution can be subjected to known techniques such as a solvent extraction method or a precipitation method, and solid uranium can be efficiently obtained using this method.

Examples of the adsorbent used in the present invention include commercially available amidoxime type chelate resins and carboxylic acid type weakly acidic ion exchange resins, and chelate resins having amidoxime groups are particularly preferred. Further, the resin matrix is preferably porous, and the shape of the resin is preferably granular, but any shape such as fibrous or plate-like may be used.

A patent application was previously filed for the phosphophenol-containing chelate resin used in the present invention (Japanese Patent Application No. 36358/1983).
It is a resin and can be manufactured, 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 to replace some or all of the protons of the amino group with methylenephosphonic acid, After that, it can be produced by reacting phenols and aldehydes to form a gel. Examples of phenol derivatives containing a primary or secondary alkylamino group used at that time include tyrosine, ammonia aresol, salicylamine, etc., and mineral acids such as:
Preferred examples of hydrochloric acid, sulfuric acid, and phenols include phenol and resorcinol, and of aldehydes, formaldehyde and acetaldehyde. Further, the shape of the phosphophenol-containing chelate resin used in the present invention is preferably granular, but it may be in any shape such as fibrous or plate-like.

Since the uranium solution obtained by the present invention has a very high uranium concentration, solvent extraction methods and precipitation methods, which were previously inapplicable, can be effectively used, thereby reducing wasted energy consumption. It is possible to efficiently recover uranium from seawater without having to do anything.

Next, the present invention will be specifically explained with reference to Examples.

Reference Example 1 1 mole of tyrosine and 2 moles of phosphorous were dissolved in a 20% aqueous hydrochloric acid solution and heated to reflux with stirring. In this state, 37% formalin aqueous solution 6
ml was added dropwise over an hour and continued stirring while refluxing for an additional hour. Then, after cooling to room temperature, caustic soda was added to make the mixture alkaline to pH 11. To this liquid, 1.5 mol of resorcin and 5 mol of 37% formalin were added, and further, n-paraffin was added with stirring. Then, while stirring, the temperature was increased to 60°C.
After heating for 1 hour at 90°C, 1 hour at 80°C, and 1 hour at 90°C, the contents began to solidify into particles. Thereafter, the contents were transferred to an autoclave and reacted at 120°C for 5 hours to complete gelation. The obtained granular resin was isolated by filtration, air-dried, washed with water, and then immersed in a 1NH ₂ SO ₄ solution to convert the resin from Na type to H type. Thereafter, this resin was filtered to obtain bead-shaped phosphophenol-containing chelate resin.

Example 1 Amidoxime type chelate resin Duolite CS
346 (diamond, made by Shamrock) 250c.c.
It was packed into a 50 mmφ x 1000 mm column, and 4000 ml of seawater (uranium concentration was 3 ppb) was passed through it at 25°C. The liquid passing rate at that time was SV (space velocity) 50 1/hr. After that, add 0.5N sulfuric acid aqueous solution to this column.
2.5 was passed through the resin at SV3 1/hr at 25°C to elute the uranium adsorbed on the resin. The uranium concentration in this eluent was 2.8 ppm. (This liquid is referred to as liquid A.) Next, 3 c.c. of the resin obtained in Reference Example 1 was packed into a 10 mmφ x 50 mm column, and 2.5 of the liquid A was added to the column at SV5 1/hr.
The solution was passed at 25°C. (The liquid that comes out of the column after passing through the column is called liquid B.) After that, add 25 c.c. of 5M phosphoric acid solution to SV2 1/
hr was passed through the resin at 25°C to elute the uranium adsorbed on the resin. The uranium concentration in this eluent is 180ppm
and was very high, making it possible to apply the solvent extraction method.

On the other hand, 4,000 ml of seawater was again passed through the 250 c.c. of amidoxime-type chelate resin from which uranium had been desorbed.
At that time, the liquid flow rate was SV50 1/hr, and the temperature was:
It was 25℃. After that, add the above B solution, 2.5,
The uranium adsorbed on the resin was eluted by passing SV3 1/hr at 25°C.

The uranium concentration in this eluent was 2.7 ppm.

Comparative Example 1 Diaion CR, a commercially available chelate resin
−10 (manufactured by Mitsubishi Kasei Corporation), Uniselect UR-50
(manufactured by Unitika) and Dowex A-1 (manufactured by Dow Chemical) were each packed into a 10 mmφ x 50 mm column, and 2.5 of the A solution obtained in Example 1 was added.
Although the SV5hr ^-1 liquid was passed through the resin at a temperature of 25°C, almost no uranium in liquid A was adsorbed by the resin.

Furthermore, when 2.5 of Solution A was passed through the amidoxime type chelate resin of Example 1 at an SV of 5 hr ^-1 and a temperature of 25° C., almost no uranium in Solution A was adsorbed by the resin.

Claims (1)

[Claims] 1. Adsorb uranium in seawater onto an adsorbent, elute the adsorbed uranium with an aqueous mineral acid solution to obtain a uranium-containing solution, and use the obtained uranium-containing solution as a chelate-forming group to form phenol nuclei. Uranium from seawater is brought into contact with a phenolic chelate resin having a group in which some or all of the hydrogen atoms of the introduced primary and/or secondary alkylamino groups are substituted with methylene phosphonic acid groups. Collection method. 2. The recovery method according to claim 1, wherein the adsorbent is a chelate resin having an amidoxime group.