JPH028969B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for capturing uranyl ions using a membrane. More specifically, the present invention relates to a method for capturing uranyl ions contained in an aqueous solution such as seawater, in which uranyl ions are directly obtained as a concentrated solution through a membrane without desorption. An object of the present invention is to efficiently capture uranyl ions without using much energy.

In recent years, attempts have been made in many fields to recover uranyl ions from aqueous solutions containing uranyl ions, such as seawater and dam drainage. In today's so-called oil crisis, uranyl ions are attracting attention as a source of nuclear energy, and developed countries are competing to research ways to recover uranyl ions from seawater, which is said to be inexhaustible.

Conventionally, methods for capturing uranyl ions in seawater include filling columns with adsorbents made of titanic acid, polymers having macrocyclic hexaketones as functional groups, macrocyclic hexacarboxylic acids, etc., or using these adsorbents. A method is known in which uranyl ions are adsorbed onto an adsorbent by bringing a film into contact with seawater, and then desorbing the uranyl ions with an acid. However, according to these methods, the adsorption rate of uranyl ions is slow, and even with the best adsorbents, contact with seawater for several months is still required, and the saturated adsorption rate per unit weight (g) of adsorbent is low. The amount is only a few mg. For adsorption, on the one hand, the particle size of the adsorbent is required to be small in order to facilitate contact with a large amount of seawater, but on the other hand, in order to suppress loss into seawater, the particle size is required to be small. A large size is desirable, but in practice it is difficult to suppress the loss of the adsorbent and capture an amount of uranyl ions that is commensurate with the cost of labor. moreover,
After adsorption, a process is required to desorb the small amount of uranyl ions adsorbed on a large amount of adsorbent and regenerate the adsorbent, and the problem is that the adsorbent suffers large chemical and mechanical losses during this process. In addition, there are many disadvantages such as the time required to reach desorption equilibrium, the processing cost for increasing the amount of adsorption, and the effort required for desorption. Due to these difficulties, there has not yet been an example of a practical adsorption/desorption system for uranyl ions from seawater.

As a result of various studies in view of the above points, the present inventor has completed a method for directly obtaining uranyl ions contained in aqueous solutions such as seawater as a concentrated solution through a membrane without desorption. .

That is, the present invention provides a polymer membrane, a liquid membrane, or a filter-fixed bilayer membrane having the function of adsorbing uranyl ions between an aqueous solution such as seawater containing uranyl ions and an aqueous solution containing a metal salt of carbonic acid or bicarbonate. This is a method for capturing uranyl ions using a membrane, which is characterized by transporting and concentrating uranyl ions in an aqueous solution such as seawater into an aqueous solution containing the metal salt of carbonate or bicarbonate.

Examples of the metal salt of carbonate or bicarbonate used in the present invention include those known as desorbents such as sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate.

The membranes capable of adsorbing uranyl ions used in the present invention include polymer membranes, liquid membranes, or fixed filters containing hexaketone, hexacarboxylic acid, amidoxime, dithiocarbamate, etc., which are known as uranyl ion adsorbents to date. Bilayer membranes can be mentioned.

In order to obtain the above-mentioned polymer membrane, it may be formed into a membrane using a known polymer synthesis method having the above-mentioned functional groups or reaction to the polymer.

To obtain a polymer film containing hexaketone, a copolymer of styrene and a monomer having two vinyl or isopropenyl groups, such as divinylbenzene, tetraethylene glycol, or dimethacrylic acid ester, is mixed with chloromethyl chloride in the presence of zinc chloride. The chloromethylstyrene unit obtained by reacting with methyl ether may be reacted with hexaketone using a base such as potassium carbonate or sodium hydride in a solvent such as dimethylformamide or dimethyl sulfoxide.

To obtain a polymer film containing hexacarboxylic acid,
Obtain chloromethylstyrene units in the same manner as above,
This is converted into aminomethylstyrene units by the Gabriel synthesis method. Chloroform is added to hexacarboxylic acid, 3 to 6 equivalents of triethylamine are added, then 1 to 2 equivalents of ethyl chlorocarbonate are added, and then the above polymer containing aminomethylstyrene units is added.

To obtain a polymer film containing amidoxime, at least one monomer having a nitrile group such as acrylonitrile or methacrylonitrile and at least one polymerizable monomer having two vinyl groups or isopropenyl groups in the molecule are used. Copolymerize with monomer and treat the resulting membrane with NH ₂ OH and then with caustic soda. Examples of the polymerizable monomer having two vinyl or isopropenyl groups in the molecule include divinylbenzene, tetraethylene glycol dimethacrylate, triethylene glycol diacrylate, and butadiene.

To obtain a polymer film containing dithiocarbamate, a polyamine is reacted with carbon disulfide in the presence of an alkali such as aqueous ammonia, sodium hydroxide, potassium hydroxide, etc., in a solvent such as water, methanol, or ethanol. Examples of polyamines include polyethyleneimine, condensation polymers of tetraethylenepentamine and 3-carboxyglutaric acid and 3,4-dicarboxyadipic acid, and poly(N-methylaminomethylstyrene).

In addition, the above-mentioned hexaketone, hexacarboxylic acid,
Polymer membranes containing amidoxime and dithiocarbamate can also be used in the form of membrane components in the form of salts with hydrophobic quaternary ammonium cations such as trioctylmethylammonium and stearyltrimethylammonium. In the case where these salts are allowed to coexist, these quaternary ammonium cations and salts such as chloride and bromide may be brought into contact with a polymer membrane supporting a uranyl ion adsorbent, either as they are or dissolved in an appropriate organic solvent. Alternatively, the uranyl ion adsorbent may be retained in the form of a salt in a polymer membrane containing quaternary ammonium groups. As the polymer membrane containing quaternary ammonium groups, polyethyleneimine made stearylated, laurylated, and insoluble in water can be used. As a uranyl ion adsorbent, hexaketone (1, 3, 9,
11, 17, 19-hexaoxocyclotetracosane)
and its long-chain alkyl derivatives, 1, 3, 9, 11,
17,19-hexaoxo-2-n-lauryl-cyclotetracosane, or hexacarboxylic acid (1,
1,10,10,19,19-hexacarboxycycloheptacosane) and its long chain alkyl derivatives, 1-stearylaminocarbonyl-1,10,10,19,19
-Pentacarboxycycloheptacosane, 1,10
-bis(laurylaminocarbonyl)-1, 10,
19, 19-tetracarboxycycloheptacosane,
Amidoxime dodecanoate, tetraethylenepentamine-1,4,7,10,13-pentapropionic acid amidoxime piperazine-N,N'-dithiocarbamic acid diammonium salt, N,N'-dimethylethylenediamine-N,N'-dithiocarbamine Acid dipotassium acid, 1,13-dityltetraethylenepentamine-1,4,7,10,13-pentadithiocarbamic acid pentaammonium salt, etc. can be used.

The thickness of the polymer membrane described above varies depending on the type of monomer or polymer used to form the membrane, the place of use, etc., but 0.1 mm to 0.5 mm is usually sufficient.

As a liquid film, hexaketone (1, 3, 9,
11, 17, 19-hexaoxocyclotetracosane)
and its long-chain alkyl derivatives, 1, 3, 9, 11,
17,19-hexaoxo-2-n-lauryl-cyclotetracosane, also hexacarboxylic acid (1,
1,10,10,19,19-hexacarboxycycloheptacosane) and its long chain alkyl derivatives, 1-stearylaminocarbonyl-1,10,10,19,19
-Pentacarboxycycloheptacosane, 1,10
-bis(laurylaminocarbonyl)-1, 10,
19, 19-tetracarboxycycloheptacosane,
Amidoxime dodecanoate, tetraethylenepentamine-1,4,7,10,13-pentapropionic acid amidoxime piperazine-N-N'-dithiocarbamic acid diammonium salt, N,N'-dimethylethylenediamine-N,N'-dithiocarbamine Acid dipotassium salt, 1,13-dimethyl-tetraethylenepentamine-1,4,7,10,13-pentadithiocarbamic acid pentaammonium salt, etc. as is, or hydrophobic 4, such as trioctylmethylammonium, stearyltrimethylammonium, etc. xylene, hexachlorobutadiene, polybutadiene,
Dissolve in water-insoluble liquid such as liquid paraffin,
A multiphase liquid film formed by adding an oil-soluble surfactant such as sorbitan monooleate or sorbitan monostearate can be used.

For the filter-fixed bilayer membrane, an adsorbent such as hexaketone (1, 3, 9, 11, 17, 19-hexaoxocyclotetracosane) used in the liquid membrane is added to the porous polymer membrane. As in the case of , as is or in the form of a salt with a hydrophobic quaternary ammonium cation such as trioctylmethylammonium or stearyltrimethylammonium,
A functional membrane obtained by dissolving it in a volatile low-boiling solvent such as chloroform, methylene chloride, or ether and impregnating it into a membrane filter such as a tetrafluoroethylene resin membrane, cellulose acetate membrane, or nitrocellulose membrane can be used.

Next, the effects of the present invention will be explained.

The uranium direct enrichment capture system using the membrane of the present invention differs from conventional adsorption methods in that the uranyl ions adsorbed on the membrane are continuously and automatically transported using carbonate or bicarbonate ions. Or, it is characterized by concentration into an aqueous phase containing bicarbonate ions. This makes it possible to maintain a high concentration at all times without blocking the uranyl ion adsorption sites within the membrane, so that a large amount of uranyl ions can be captured per unit volume or unit weight of the membrane.

Furthermore, since the uranyl ions obtained by the present invention are already concentrated in the aqueous phase containing carbonate or bicarbonate ions, there is no need to take out the membrane and subject it to a desorption process. It is only necessary to replace the membrane material as appropriate, which not only eliminates the labor and expense of the desorption process, but also avoids mechanical and chemical loss of the membrane material caused by the desorption process.

The present invention will be explained below based on examples.

Example 1 A nitrile rubber (sulfur vulcanized) formed into a film (thickness 0.1 mm) of an acrylonitrile-butadiene copolymer latex having a nitrile content of 35% is mixed with 15% hydroxylamine in methanol at 80°C for 50 minutes. After reacting for an hour, it was immersed in 1N NaOH solution at room temperature overnight.

This membrane is held by a support frame, and the uranium concentration is
When placed between seawater to which uranyl acetate was added to give a concentration of 5.2 ppm (undiluted solution) and a 5% NaHCO ₃ aqueous solution (receiving solution), 2.2 mg-U was transferred from the stock solution to the receiving solution after one day of contact. /g- Transport and concentration of uranyl ions in the membrane was observed.

Example 2 Acrylonitrile membrane filter (manufactured by Daicel, OUY-M, thickness 0.1 mm) was
Heated in a methanol solution of NH ₂ OH at 80° C. for 6 hours. Hold the obtained membrane with a support frame and
8.1ppm uranyl acetate enriched seawater (undiluted solution) and 5%
When transporting uranyl ions between NaHCO ₃ aqueous solution (receiving liquid), uranyl ions were transported in 2 days.
A result of 6.8 mg-U/cm ² -membrane was obtained.

Example 3 32 mg of hexacarboxylic acid in 5 ml of chloroform
(0.05 mmol) and 30 mg (0.3 mmol) of triethylamine were added to this solution.
0.5 ml of a chloroform solution containing mg (0.09 mmol) was added, and 10 minutes later, 24 mg (0.09 mmol) of stearylamine was added and stirred at room temperature for 30 minutes. 1N hydrochloric acid 5
ml was added and extracted with ether (10 ml, 3 times). The ether extracts were combined and washed three times with 15 ml of 5% aqueous sodium bicarbonate solution to remove unreacted hexacarboxylic acid. After esterification, the reaction product was analyzed by thin-layer chromatography to reveal mono-hexacarboxylic acid,
It was found to be a mixture of di- and tristearylamides. IR 1670, 1530, 1260 cm ^-1 Dissolve the above hexacarboxylic acid amide mixture in 10 ml of chloroform, and aqueous layer I (uranyl ion
When the water layer (0.01N NaHCO 3 ) was placed between the water layer (0.01N NaHCO ₃ ) and transported, the uranyl ion concentration in the water layer changed as follows: 2 days later 5 days later Water layer 0.5ppm 0 Water layer 4.7ppm 6.0ppm However, the uranyl ions in the water layer were transported through the chloroform layer and completely transferred to the water layer after 8 days.

Example 4 3 ml (0.045 mol) of acrylonitrile was added dropwise to 5.6 g (0.03 mol) of laurylamine, and after the exothermic reaction had subsided, the reaction was carried out at 60°C for 3 hours. After distilling off excess acrylonitrile under reduced pressure, it was added to a methanol solution of 1.3 g (0.04 mol) of hydroxylamine.
80ml and heated at 80°C for 3 hours. Methanol was distilled off to obtain a solid.

IR: 2900, 2840, 1665, 1590, 1450, 1370cm
^-1 Dissolve 20mg of 4-azahexadecanoic acid amidoxime in 2ml of chloroform and add Fluoropore (manufactured by Sumitomo Electric, FPO45, pore size 0.45μ, size 13mm)
Soaked for 30 minutes and air-dried for 10 minutes. After repeating immersion and air drying 5 times, the membrane was held on a support frame,
8.1ppm uranyl acetate enriched seawater as stock solution, 5%
When NaHCO ₃ aqueous solution was used as a receiving liquid and brought into contact, a transport/concentration amount of 4.4 mg-U/cm ³ -membrane was obtained after 2 days of contact.

Example 5 30 mg (0.3 mmol) of triethylamine and 104 mg (0.3 mmol) of stearyltrimethylammonium chloride were added to 32 mg (0.05 mmol) of hexacarboxylic acid and dissolved in 5 ml of chloroform. saturation
After washing twice with 0.5 ml of NaHCO ₃ aqueous solution, fixation on the fluoropores was performed according to Example 4.

8.1ppm uranium-enriched seawater as a stock solution at 5%
Membrane transport was performed using NaHCO ₃ solution as a receiving liquid, and a result of 4.4 mg-U/cm ³ -membrane was obtained after one day.

Example 6 8 mg (0.02 mmol) of hexaketone was dissolved in 2 ml of chloroform and immobilized on the fluoropore according to Example 4.

6.0ppm uranium enriched seawater as stock solution with 5% Na ₂ CO ₃
Membrane transport was performed using the solution as a receiving liquid, and after one day, a result of 2.8 mg-U/cm ³ -membrane was obtained.

Claims (1)

[Claims] 1. A polymer membrane with the function of adsorbing uranyl ions between an aqueous solution such as seawater containing uranyl ions and an aqueous solution containing a metal salt of carbonic acid or bicarbonate,
uranyl ion production using a membrane characterized by interposing a liquid membrane or a filter-fixed bilayer membrane to transport and concentrate uranyl ions in an aqueous solution such as seawater into the aqueous solution containing the metal salt of carbonic acid or bicarbonate. Capture method.