JPS5948941B2 - Uranium collection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for collecting uranium from dilute aqueous uranium solutions using an ion exchanger.

Collecting uranium from low-grade ores can increase the amount of uranium currently available by several to several tens of times, and is extremely useful for securing energy resources.

Conventionally, extraction methods using solvents and ion exchange methods using ion exchangers have been used in the uranium refining process to collect uranium from aqueous uranium solutions leached from uranium ore. The uranium concentration of the aqueous solution is relatively high, about 0.2 g or more.

However, in general, the uranium concentration of the leachate obtained by treating uranium ore with an eluent such as sulfuric acid depends on the grade of the ore.
Especially low-grade ores such as uranium content 0. The uranium concentration of the leachate obtained from ore with a grade of about 10% is several tens of pl]T
1, which is extremely low.

Moreover, this type of leachate has a high ratio of competing ions such as iron, aluminum, and sulfate radicals to uranium, and conventional methods cannot be directly applied to the collection of uranium from dilute aqueous uranium solutions.

In particular, in order to collect uranium from such a dilute aqueous uranium solution by the conventional ion exchange method using an ion exchange resin,
For example, there was the following problem.

(b) A large amount of leachate must be treated to collect a unit amount of uranium.

(b) As long as conventional ion exchangers (strongly basic anion exchange resins are recommended) are used, the amount of uranium adsorbed per unit used is low and the rate of uranium adsorption is low, resulting in faster processing. is difficult.

Therefore, an object of the present invention is to provide a method that can efficiently collect uranium from an aqueous uranium solution, particularly a dilute aqueous uranium solution with a uranium concentration of several ppb to several hundred ppm.

Another object of the present invention is to provide a method capable of collecting uranium from a dilute aqueous uranium solution as a highly concentrated uranium solution.

The inventors have discovered that the above objects may be advantageously achieved by using a fibrous ion exchanger containing specific ion exchange groups.

The present invention is characterized in that a fibrous ion exchanger containing a quaternary ammonium group and/or a pyridyl group as an ion exchange group and having a fiber diameter of 100 μm or less is used in the form of granules in which the fibers are entangled and bonded to each other. , a method of collecting uranium from a dilute aqueous uranium solution using an ion exchanger.

According to the present invention, uranium is adsorbed onto a fibrous ion exchanger quickly and with a high adsorption rate from a large amount of dilute uranium aqueous solution,
By efficiently eluting the adsorbed uranium, uranium can be collected as a highly concentrated uranium solution.

The ion exchanger used in the present invention is made by interlacing and bonding fine fibrous ion exchangers having a fiber diameter of 100 μm or less, and has a granular shape.

Generally, the smaller the fiber diameter, the higher the adsorption rate in the treatment liquid, but if the fiber diameter is too small, the strength and liquid permeability will decrease.

The fiber diameter is therefore preferably from 1 to 100 microns, especially from 5 to 70 microns, and within this range mixtures of fibrous ion exchangers having different fiber diameters may be used.

In the present invention, the fiber diameter is expressed as the square root of the product of the maximum diameter and the minimum diameter when the cross section of the fiber is not circular, and is measured in a dry state.

Generally, the fiber length of the fibrous ion exchanger is preferably 1 to 15 mm.

The fibrous ion exchanger having the above-mentioned morphological properties contains a quaternary ammonium group, a quaternized pyridyl group, or both groups as ion exchange groups.

The more these ion exchange groups there are, the better the uranium adsorption rate is, and it is preferable that the ion exchanger contains at least 2.0 milliequivalents of ion exchange groups per 1 g (dry weight) of the ion exchanger.

Examples of the fibers used as the basis of the ion exchanger include polyvinyl chloride fibers, polyolefin fibers, preferably polyethylene fibers, and cellulose fibers, preferably cellulose acetate fibers.

The ion exchange group can be formed by a conventional method, such as by reacting a haloalkyl group with a tertiary amine such as trimethylamine, dimethylethanolamine, triethylamine, etc., or by reacting a haloalkyl compound such as methyl bromide with a tertiary amino group. Particularly effective are quaternized ammonium groups formed by this method, as well as quaternized pyridyl groups formed by reacting a haloalkyl compound with a pyridyl group.

The fibrous ion exchanger is preferably produced, for example, by the method described below.

(a) A monomer solution prepared by adding a polymerization initiator to styrene or vinylbenzyl chloride and divinylbenzene is applied to polyvinyl chloride fibers, polyethylene fibers or cellulose acetate fibers, and polymerized while being absorbed into the fibers. A method of introducing an ammonium group, or (
b) 2-vinylpyridine, 4-vinylpyridine and 2-
A monomer solution prepared by adding a polymerization initiator to at least one kind of methyl-5-vinylpyridine and divinylbenzene,
A method in which the material is polymerized while being absorbed into cellulose acetate fibers or polyvinyl chloride fibers.

The ion exchanger used in the present invention has a larger specific surface area than ion exchange resins conventionally used in ion exchange methods, and has a fine fibrous structure with most of the surface exposed to the outside, so it can absorb adsorption. In addition to being extremely fast, it has good buoyancy in water, making it possible to adsorb and collect uranium in a short period of time.

In this case, the difference in adsorption rate with conventional ion exchange resins is extremely large; for example, in pile water with a uranium concentration of 50 ppb (18
, 2), when using the fibrous ion exchanger of the present invention, the residual uranium concentration reaches a level of 1 ppb or less in about 3 to 4 hours, but when using a conventional ion exchange resin, the concentration of residual uranium is the same. It takes several days to reach the standard.

In the present invention, the fibrous ion exchanger is used in the form of granules interlaced and bonded together.

In this case, it is important that the structure of the granules is such that the voids formed between the fibers communicate in random directions.

This allows the voids between the fibers to become sufficient passageways for the treatment liquid to allow the surfaces of most of the fibers making up the granules to function as exposed surfaces, thus allowing adsorption and desorption (elution).
The advantageous properties of the fibrous ion exchanger itself, which allow the process to be carried out in a short period of time, can be maintained.

The voids in the granules are significantly larger than those in conventional ion exchange resins.

When manufacturing granules, as mentioned above, in order to utilize the surface of the fibrous ion exchanger that makes up the granules as effectively as possible, it is necessary to use adhesives or fillers that cover the surface. should be avoided.

If this point is kept in mind, granules can be produced by any method.

For example, the following method is particularly preferred.

Using a fibrous ion exchanger containing a thermoadhesive component, this aggregate is heated and adhered in a mutually entangled state at the contact points of the fibers, and then granulated by cutting, crushing, etc., or ion exchanger is used. A monomer solution containing a polymerization initiator and at least one of 2-vinylpyridine, 4-vinylpyridine, and 2-methyl-5-vinylpyridine and divinylbenzene is impregnated and adsorbed onto the fiber aggregate that forms the basis of the exchanger. The polymer is then polymerized while being absorbed into the fibers, and it is made into granules by cutting, crushing, etc., and if necessary, some or all of the basic fibers are removed (the remaining polymer retains its fibrous form). ).

The granules may be, for example, spherical, granular, rod-like, plate-like, crushed pieces, or other shapes.

The particle size of the granules is generally 12 to obtain favorable liquid permeability.
0 to 3 mesh, and 80 in terms of liquid permeability and adsorption.
~5 mesh (all ASTM standard sieves) is preferred.

Although the fibrous ion exchanger granules can be used by being dispersed in an aqueous uranium solution, it is particularly preferable to use them in the form of a packed bed packed in a column or the like.

By using it as a packed bed, it is possible to increase the amount of liquid passed per unit time, that is, to speed up the processing, and it is also possible to perform elution easily, so uranium can be extracted from a high-concentration uranium solution using a small amount of eluent. can be obtained as

Furthermore, by making the fibrous ion exchanger into granules, the amount that can be packed into a unit volume (packing density) is increased, and clogging due to minute solids becomes less likely to occur.
Operations such as backwashing, which are practically essential in column methods, can be easily performed.

According to the present invention, uranium can be efficiently collected from any aqueous solution containing uranium, and particularly excellent effects are exhibited when collecting uranium from a dilute aqueous uranium solution.

Examples of the uranium aqueous solution to which the method of the present invention is applied include the following.

Acidic leaching liquid obtained by treating uranium ore with a mineral acid such as sulfuric acid; alkaline leaching liquid obtained by treating uranium ore with an alkaline substance such as soda carbonate, ammonium carbonate, etc.; various kinds of uranium-containing wastewater, as well as natural waters containing uranium, such as river water containing trace amounts of uranium, underground water from uranium mines, etc.

When the ion exchange group of the ion exchanger used is a quaternary ammonium group, it is hardly affected by the pH (hydrogen ion concentration) of the uranium aqueous solution being treated, but in the case of a quaternized pyridyl group, It is preferable to process under acidic conditions of 3 or less.

As eluents for desorbing uranium adsorbed on ion exchangers, eluents used for ordinary ion exchangers,
For example, nitric acid, sulfuric acid, ammonium nitrate, sodium nitrate, sodium chloride, ammonium carbonate, sodium carbonate, etc. can be used alone or in a mixture of two or more.

These different eluents may also be used sequentially.

In the elution operation, it is preferable that a uranium-adsorbing ion exchanger is packed in a preferably elongated container such as a column, and an eluent is passed through the packed bed.

Elution can also be carried out continuously in countercurrent, such as by continuously supplying the uranium-adsorbing ion exchanger from one side of the elongated container and continuously supplying and contacting the eluent from the other side.

Owing to the above-described structure of the ion exchanger used, uranium can be easily eluted, so that only a small amount of eluent is required, and therefore uranium can be obtained in the form of a highly concentrated uranium solution.

Example 1 (a) Production of granular ion exchanger: Low-density polyethylene (Yukalon manufactured by Mitsubishi Yuka, ηsp/.

-0,8) 20 parts, methylene chloride 80 parts and Nonipol 200 (nonionic surfactant manufactured by Sanyo Chemical Co., Ltd.) 0.1
Place the sample in an autoclave and raise the temperature while stirring to prepare a homogeneous solution.

When the solution temperature at the time of discharge is set to 200° C. and the solution is discharged through an orifice at the bottom of the autoclave, a fibrous aggregate containing a small amount of flakes is obtained.

This material was mixed with water as a dispersion liquid, and was heated to 0.2
% slurry, poured onto a 120 mesh screen with a diameter of 20 cm, and dehydrated and dried to a thickness of 3.5 mm.
45 g of cardboard-like material is obtained.

This cardboard-like material was evenly impregnated with 60 g of a monomer mixture consisting of 100 parts of vinylbenzyl chloride (ortho-rose mixture), 5 parts of styrene, 20 parts of divinylbenzene, and 0.3 parts of azobisisobutyronitrile. Upon immersion for 12 hours in a hot water bath at 0.degree. C., the monomer mixture is polymerized while being absorbed within the polyethylene filament.

In this way, the terpolymer is formed within the polyethylene fibers to form an aggregate of fibers with a thickness of 5. Omm plate-like object 1
03g is obtained.

When this plate-like material is observed under a microscope, there is almost no change except that the fiber surface is slightly thicker than before polymerization.
Although sufficient voids are maintained between the fibers, the fibers adhere to each other at their contact points, giving the overall shape a rigid plate shape.

This plate-like material was crushed into granules of 80 to 13 meshes (ASTM standard), immersed in a 30% trimethylamine aqueous solution at 40°C for 2 days and nights, and then washed with water to remove quaternary ammonium groups as ion exchange groups. A granular ion exchanger is obtained.

The shape of this granular ion exchanger is the same as the shape before introduction of the ion exchange group, except that the particle size has increased slightly, and the diameter is 5.
No change in shape was observed even if a cm column was filled with water as a medium, air was fed from below, and the contents were stirred for 24 hours.

The neutral salt decomposition ability of this granular ion exchanger is 1g dry weight.
2.8 milliequivalents per unit.

(b) Collection of uranium: 150 cc of the granular ion exchanger thus obtained was packed into a column with an inner diameter of 20 mm, and for comparison, a conventional strongly basic anion exchange resin (Diaion PA manufactured by Mitsubishi Chemical Industries, Ltd.) was used.
-320) was similarly packed into the column.

As the uranium aqueous solution, leached liquid (uranium concentration 1200 p
Dilute uranium aqueous solution σ'H, 2,65, uranium concentration 32.5 pp obtained by diluting p, PHI, I) with water
) was supplied to the gong ram at a rate of Sv (space velocity) of 50 and passed through the packed bed, and the relationship between the amount of treated liquid and the uranium concentration in the treated liquid was investigated.

In the case of a conventional column using a strong basic anion exchange resin, when the amount of treated liquid passed through it exceeds 401, approximately 1 ppm of Ura A leakage is observed, and gradually increases until the amount of treated liquid reaches 901.
At the time of (opIIn, 4ppm at 1001, 1101
Therefore, the flow of liquid with a concentration of 6 ppf Tl was stopped.

On the other hand, in the case of the column using the granular ion exchanger according to the method of the present invention, the flow of the liquid was stopped due to leakage of 11 ppm of uranium only when the treated liquid amount reached 901, but
Up to No. 91, the leakage of uranium was 0.3 ppm or less and excellent adsorption performance was maintained.

Therefore, in the case of the method of the present invention using a granular ion exchanger, although the overall adsorption capacity is almost the same as that of conventional ion exchange resins, the amount of leakage up to the breakthrough point is extremely low and exceeds a certain level. On the other hand, when leakage is a problem, it has the advantage of being able to process large quantities.

Next, the 32.5 ppm diluted uranium aqueous solution 401 was passed through a column to adsorb uranium on the granular ion exchanger and the conventional strong basic anion exchange resin, respectively.
IM-ammony nitrate 10 in two columns packed with 0cc
．． An eluent consisting of LM-nitric acid was passed at a rate of SU (space velocity) of 8 to elute the uranium.

The results of sampling the effluent every 100 cc in each case are shown in the following table.

As is clear from this result, in the case of the method of the present invention, the second
~ About 97% of the adsorbed uranium is eluted from a total of 400 cc of effluent of the fifth fraction, whereas in the case of conventional strongly basic anion exchange resins, only about 93% of the adsorbed uranium is eluted even from 1000 cc of total effluent. It wasn't done.

Due to such a difference in eluability, the method of the present invention provides a high concentration ratio and a high elution rate.

Example 2 (a) Production of granular ion exchanger: Polyvinyl chloride fibers with a single fiber fineness of 3.0 tenier were
Vinylbenzyl chloride (ortho-para mixture) 10
0 parts, 3.0 parts of divinylbenzene (purity 55% by weight), and 0.0 parts of azobisisobutyronitrile as a polymerization initiator.
Add a monomer mixture of 8 parts to 1.9 parts by weight of fiber.
The monomer mixture is absorbed into the fibers by applying 5 times the amount and then immersing it in warm water at 75°C.

The water temperature is maintained at 75° C. for 12 hours to form vinylbenzyl chloride-divinylbenzene copolymer within the fibers.

Next, this fiber was cut into lengths of 11 mm, immersed in a 30% by weight trimethylamine aqueous solution at 35°C for 2 days and nights, and the reaction solution was removed by washing with water, resulting in a fibrous material containing quaternary ammonium groups as ion exchange groups. A strongly basic anion exchanger is obtained.

This fibrous anion exchanger has a neutral salt resolution capacity of 245 milliequivalents and an acid neutralization capacity of 265 milliequivalents per gram of dry weight in CI form, and the fiber diameter in the dry state is 55 microns.

This fiber aggregate with a thermal adhesive component was heated to adhere to each other in a mutually entangled state at the contact points of the fibers, and then crushed to form granules of 80 to 30 meshes.

(b) Collection of uranium 5.399 g (dry weight) of the above granular fibrous anion exchanger was collected in underground water (pH 7.9, uranium concentration 42 ppb).
When 901 was placed in a stainless steel container and stirred at room temperature, the uranium concentration was 0.5p after 24 hours.
98.8% of the uranium in the mine water was adsorbed.

In contrast, conventional strongly basic anion exchange resins containing quaternary ammonium groups (Diaion PA manufactured by Mitsubishi Chemical Industries, Ltd.
-320, particle size 297-1190μ, porous),
In a test conducted under the same conditions, the uranium concentration in underground water after 24 hours was 22 ppb (uranium adsorption rate 47.6%).
), 8 ppb even after 72 hours (uranium adsorption rate 81
%)Met.

The fibrous ion exchanger adsorbed with uranium was
Packed into a 4 mm column, IM-ammonium nitrate 10
．． Using IM-nitric acid as the eluent, 99.8% of the adsorbed uranium was
% was eluted.

Claims (1)

[Scope of Claims] 1. A fibrous ion exchanger containing a quaternary ammonium group and/or a pyridyl group as an ion exchange group and having a fiber diameter of 100 μm or less is used in the form of granules in which the fibers are entangled and bonded to each other. A method of collecting uranium from a dilute aqueous uranium solution using an ion exchanger. 2. The method according to claim 1, characterized in that a dilute aqueous uranium solution is passed through the packed bed of granular material of the fibrous ion exchanger.