JPS58205543A - Uranium adsorbent and its production - Google Patents

Abstract

PURPOSE:To form an adsorbent having excellent adsorption and desorption efficiency for uranium, mechanical strength and durability in an optional shape by allowing an uranium adsorptive layer contg. an amidoxime group to exist locally on the surface of the adsorbent by a radiation graft polymn. method. CONSTITUTION:Ionizing radiations are beforehand irradiated to a base material consisting of an org. or inorg. or their composite material of an optional shape; thereafter, the base material is brought into contact with 1 or >=2 kinds of polymers contg. a nitrile group and polymerizable monomers which can convert the nitrile group to amidoxime when said polymers are caused to react with hydroxylamine (e.g., acrylonitrile, vinylidene cyanide) or the ionizing radiations are irradiated to said base material while the material is held in contact with said polymerizable monomers, to produce the graft polymer grafted with said polymerizable monomers only on the surface or surface layer of the base material. The graft polymer is caused to react with hydroxylamine to convert the nitrile group in the graft chain to an amidoxime group.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention proposes the use of a combination of various substrates and a monomer having a functional group that can be converted into an amidoxime group, and a method of contacting them, to remove trace amounts of uranium dissolved in a water bath solution. The present invention relates to a uranium adsorbent in which a uranium adsorption layer is localized on the surface or surface layer of the adsorbent, and a method for manufacturing the same.

In addition to electrodialysis and reverse osmosis membrane methods using ion exchange membranes and semipermeable membranes, ion exchange resins, chelate resins, flocculants, etc. are used to purify and reuse industrial wastewater, or to recover useful substances. Separation methods based on adsorption and coagulation have been applied. In particular, for the selective separation and recovery of heavy metals present in trace amounts in water bath liquids, compounds that form a total complex with the target heavy metal ion species are useful.

All prior art related to the present invention will be described.

It is well known that the resin Amidosim has excellent uranium adsorption ability as an adsorbent for uranium present in seawater, as described in, for example, JP-A-53-126088. The resin described in JP-A No. 53-126088 (C) is obtained by reacting a polymer having a nitrile group with hydroxylamine, and a polymer containing acrylonitrile as its main component is mainly used. In addition, in order to improve the mechanical strength, swelling resistance, and durability of the resin as an adsorbent, a polymer having a nitrile group and divinylbenzene etc. Copolymers with polyfunctional monomers such as Shape according to Amakawa, even particle-like, fibrous, etc.
It is difficult to obtain resins in various shapes such as a web or a film. Furthermore, in order to improve the adsorption performance, it is necessary to increase the concentration of amidoxime groups, but in resins obtained by polymerization or copolymerization of nitrile group-containing monomers such as acrylonitrile, regardless of their shape, The distribution of nitrile groups in the resin is uniform, so that the amidoxime groups are distributed all the way to the center of the resin. Adsorption/desorption of m-quality substances onto solid-phase adsorbents occurs from the surface layer of the adsorbent, and progresses as the solution gradually diffuses into the interior over time, so the adsorption capacity of the amidoxime groups distributed in the center of the resin increases. In order to effectively utilize the adsorption/desorption time, it is necessary to lengthen the adsorption/desorption time, which results in a decrease in productivity. Furthermore, since the amidoxime group is hydrophilic, if the amidoxime group is distributed all the way to the center of the resin, the entire resin will swell, resulting in extremely low mechanical strength, which is insufficient for repeated use of adsorption and desorption. It is difficult to obtain a durable adsorbent.

In the course of research on the modification of various materials by radiation graft polymerization, the present inventors discovered that C and C were combined in an appropriate manner with respect to the graft polymerization base material, monomer properties, and grafting conditions. It has been found that the amount of grafted strands can be controlled arbitrarily.

The present invention is based on this knowledge, and improves uranium adsorption/desorption efficiency, mechanical strength, and durability by localizing a layer with adsorption ability on the surface or surface layer of an adsorbent using a radiation graft polymerization method. It is an excellent adsorbent and can be provided in any shape.

Hereinafter, the entire configuration of the present invention will be explained in detail.

According to the present invention, a uranium adsorbent in which a uranium adsorption layer having an amidoxime group is grafted only on the surface or surface layer of a substrate made of an organic type, an inorganic type, or a composite material thereof in an arbitrary shape, and is The layer thickness ratio of the adsorption layer is 1:
A uranium adsorbent having a ratio of 10 to 10:10 is provided.

Furthermore, according to the present invention, a substrate made of an organic type, an inorganic type, or a composite material thereof in an arbitrary shape is irradiated with ionizing radiation in advance, and then a polymer containing a nitrile group is reacted with hydroxylamine. One or two polymerizable monomers capable of converting the nitrile group into amidoxime
A graft polymer in which the polymerizable monomer is grafted only to the surface or surface layer of the substrate by irradiating ionizing radiation while bringing the polymerizable monomer into contact with a seed or more or by contacting the substrate with the polymerizable monomer. After the combined production, the uranium adsorption layer with amidoxime groups is localized on the surface or surface layer of the substrate by converting the nitrile groups in the graft chains to amidoxime groups by reacting the graft polymer with hydroxylamine. A method of manufacturing a uranium adsorbent is provided.

The present invention'fc! In carrying out the application, as the base material of the adsorbent, various M organic or inorganic solid compounds that can be grafted with the following monomer #:-Neela by the action of radiation can be used, but considering the purpose of the present invention, In particular, it is advisable to select a base material with excellent mechanical strength, seawater resistance, and chemical resistance. For example, in the organic system, there are various polymeric materials, such as polyolefins, rhodan polyolefins, polyesters, etc.
Examples include polyethers, and examples of inorganic base materials include:
There are silica, alumina, activated carbon, etc. Moreover, as for the shape of the base material, it is preferable to choose the shape that is most suitable for the adsorption/desorption method, but graft polymerization can also be performed on base materials of any shape described below. Therefore, granular, spherical, membrane-like, tubular, fibrous, and all these processed plate-like,
Although it is possible to obtain adsorbents in all shapes such as net-like and mat-like, it is possible to obtain adsorbents with better adsorption/desorption efficiency (C). Basically preferred.

Polymerizable monomers which contain nitrile groups and which can be converted into amidoxime groups by reacting the polymer with total hydroxylamine used in the present invention include, for example, acrylonitrino, vinylidene cyanide, crotonitrile, meg To Krylonitorino, Talorua? IJ lonitrile, 2
-Nanoethyl acrylate, 2-nor/ethyl methacrylate, etc. can be used alone or in combination of two or more.

In the present invention, the radiation source used to graft-polymerize the above-mentioned nitrile group-containing monomer by irradiating the base material with total ionizing radiation includes α-rays, β-rays, γ-rays, accelerated electron beams, X-rays, etc. However, gamma rays or accelerated electron paddles are preferred from the viewpoint of industrial ease. In addition, the graft polymerization method includes a method in which a polymerizable monomer is brought into contact with a base material that has been irradiated with ionizing radiation in advance to impart grafting activity (pre-irradiation method), or a method in which the base material and the polymerizable monomer are grafted together. A method (simultaneous irradiation method) of grafting the monomers by irradiating them with ionizing radiation in contact with each other can be used. It is preferable to select it appropriately depending on the gender and the like.

In the present invention, the most important point is that the part to be grafted is limited to the surface or surface layer of the base material.
Only by soiling does it become possible to obtain a uranium adsorbent in which the uranium adsorption layer is localized on the surface or surface layer, which is the object of the present invention.

Therefore, in order to graft a monomer only to the surface or surface layer of the base material, depending on the characteristics of the base material and the monomer,
It is necessary to select these combinations or grafting conditions, which can be achieved by the following embodiments. That is, when grafting a monomer onto a base material, (1) the base material is brought into contact with the monomer or its solution in gaseous form; or (2) A base material that does not swell in the monomer or its solution, such as Teflon or an inorganic base material, is completely rehydrated, and this is carried out by immersing it in the monomer or its solution. Or (2) The purpose can be achieved by using a monomer or a solution thereof in which the graft chain becomes a precipitation system when the monomer is grafted. The irradiation dose, grafting temperature, time, monomer concentration, etc. depend on the characteristics of the base material and monomer used, i.e., the difficulty of generating graft active sites by irradiation with ionizing radiation, their stability, and the monomer concentration. It is preferable that the ratio of the thickness of the uranium adsorbed layer and the non-adsorbed layer of the finally obtained adsorbent be in the range of 1:10-, =LO:10, which is appropriately determined depending on the polymerizability of the polymer. .

The conversion of the nitrile group in the graft chain into an amidoxime group in the present invention can be carried out by a known method using hydroxylamine. That is, the graft polymer obtained by the above method is immersed in a bath solution of total hydroxylamine salt,
The reaction temperature is 40 to 80°C and the reaction time is 4 to 10 hours. As the solvent, water, dimethyl sulfoxide, alcohols, tetrahydrofuran, etc. may be used alone or as a mixture of 2.4 liters or 1 ton. For hydroxylamide, hydrochloride, sulfate, acetate, etc. are used, and the concentration ranges from 1 to
10%, preferably 3 to 6''.

The adsorption performance of the adsorbent of the present invention for uranium varies depending on the size of the base material, the type of monomer, the shape of the base material, the thickness of the graft layer (adsorption layer), etc., but the most efficient concentration of amidoxime groups As for 3~8 meq/ji'
-Guf7to chain.

The entire history of the present invention will be specifically explained below using examples, but these are not intended to limit the scope of the present invention.

Example 1. As a comparative example, a fiber of 40 μm in wire diameter of tetrafluorinated ethylene-ethylene copolymer (77σ) was heated with an electron accelerator (voltage 15 MeV,
Irradiation was performed at 30 Mrad in a nitrogen atmosphere using a current of 1 mA)k. The irradiated fibers were immersed in acrylonitrile in which nitrogen gas had been bubbled in advance to bring the dissolved oxygen concentration below Q, 1p7WrL, and reacted at 25"C for 3 hours to obtain fibers with a grafting rate of 48%. Next, the grafted fibers were immersed in a 3% water-methanol (1:1 weight ratio) mixture of hydroxylamine hydrochloride neutralized with potassium hydroxide, and reacted at 80"C for 6 hours to form ζ anions. Replacement capacity 4.8meq/? of adsorbent was obtained.

A part of this adsorbent was added to a 0.02N sulfuric acid aqueous solution for 3 hours.
After soaking at 0°C for 24 hours, the characteristic X-ray intensity of copper at the fracture surface of the fiber was determined using an X-ray microarray analyzer (XMA).
In other words, the amidoxime group was localized in the surface layer of the fiber, and C was shown to have no amidoxime group in the center.

On the other hand, when this adsorbent 0.12 was immersed in 50 ml of seawater with a uranium concentration of 51 μ/l adjusted by adding uranyl nitrate and shaken at 30°C for 1 hour, the amount of uranium adsorbed was 48 μf10. ty=adsorbent, and the uranium adsorption efficiency was 96%.

Comparative Example For comparison, an adsorbent obtained by the same procedure as above except that polyvinyl chloride fibers with a wire diameter of 40 μmφ was used had a graft ratio of 45%; anion exchange capacity, 3.
5 meq/t; Uranium adsorption amount, 25μt; 10,
1 as one adsorbent; the adsorption efficiency was 50%, and the amidoxime groups were uniformly distributed (see Figure 2).

40 irradiated with 10 M rad in the same manner as in Example 1.
Polyvinyl chloride fibers of μmφ are placed in the upper chamber of a glass reactor divided into two upper and lower chambers by a perforated plate, and the lower chamber has a dissolved oxygen concentration of 0. Acrylonitrile at a concentration of 1 ppm or less was injected, and the fibers were allowed to react at 30''C for 5 hours in a state where they came into simulated contact with a gas blow-up tube.The grafting rate at this time was 70%.

After treating the graft polymer of Example 1 in the same method as in Example 1, uranium was completely adsorbed in the same manner, resulting in an anion exchange capacity of 5 meq/t; uranium adsorption amount.

48μP10. I P-adsorbent; uranium adsorption efficiency, 96
%, obtained. Further, the graft layer was found to have a thickness of about 3 μm from the surface by XMA foot measurements.

Example & An adsorbent was obtained in the same manner as in Example 1, using polypropylene non-woven stone as the base material and an Ac IJ o nitrile solution to which IQwt% of water was added as the monomer solution. The grafting rate was 45%, the anion exchange capacity was 4.5,
The rrLeq/l niger raft layer was 5 μm thick from the fiber surface.

Uranium was adsorbed using the same method as in Example 1, and the amount of adsorption was 4T and 5μf70.1, respectively. - Adsorbent: Uranium adsorption efficiency was 95%.

Example A spherical silica gel for chromatogram packing material with a diameter of 10 μm was placed in the upper chamber of a glass container consisting of two upper and lower chambers partitioned by a part of the filter of a Tun G-4 glass filter, and the dissolved oxygen concentration was 0. After injecting acrylonitrile to lppm or less and shielding it with a royal gold lead block,
0 gamma rays were irradiated at a dose rate of I x 10'rad/hr for 3 hours at room temperature to obtain a graft polymer with a graft ratio of 15%. Next, amide quinomization was performed in the same manner as in Example 1, and 0.1 ft" of the obtained adsorbent was taken and made into a diameter of 11 m.
Fill a zφ glass column with seawater whose concentration was adjusted with uranyl nitrate (uranium concentration 1'n9/l) 5 (J
rrIlf was allowed to flow down for 1 hour. After this treatment, the amount of uranium adsorbed by the adsorbent is 48.3μ? 10,1?
- adsorbent, the efficiency of which was 96.5%.

Examples & In Example 1, R fibers of cinafluoropropylene (i diameter 4 Q ILmφ
), irradiation, graft reaction, post-treatment, etc. were performed in exactly the same manner except that methacrylonitrile was used as the cyan group-containing monomer and the grafting (immersion) temperature was 40°C. The grafting rate was 23%, and the graft layer was approximately 8 μm thick from the surface of the rock fibers. As a result of the uranium adsorption test conducted in the same manner as in Example 1, the amount of uranium adsorbed was 48μ/10.
The IP-adsorbent had a uranium adsorption efficiency of 96%.

[Brief explanation of drawings]

FIG. 1 is an X-ray intensity distribution photograph showing a uranium adsorption layer of a uranium adsorbent manufactured according to one embodiment of the present invention. FIG. 2 is an X-ray intensity distribution photograph showing a uranium adsorption layer of a uranium adsorbent manufactured by a method other than the present invention for comparison. Patent applicant: Japan Atomic Energy Research Institute 3, ■■■ 1゜1. −１■ ■■■;: X;, ゛, ■ ■・

Claims (1)

[Scope of Claims] A uranium adsorbent in which a uranium adsorption layer having an amidoxime group is grafted only on the surface or surface layer of an organic, inorganic, or composite base material of any shape. The layer thickness ratio of the uranium adsorption layer and the non-adsorption layer is 1 = 10 to 1
A uranium adsorbent characterized by being 0:LO. B. A polymer containing a nitrile group is prepared by irradiating a substrate made of an organic type, an inorganic type, or a composite material thereof in any shape with ionizing radiation in advance, and then reacting the nitrile group with the total hydroxylamine of the polymer. The base material is brought into contact with one or more polymerizable monomers capable of converting the group into amidoxime, or by irradiating the base material with ionizing radiation while bringing the base material into contact with the polymerizable monomer. An amidoxime group consisting of producing a graft polymer in which the polymerizable monomer is grafted only on the surface or surface layer, and then converting the graft polymer into a nitrile-based amidoxime group in the graft chain by reacting the graft polymer with hydroxylamine. A method for producing an L-penetrating material in which a uranium adsorption layer having a uranium adsorption layer is localized on the surface or surface layer of the base material. (a) The method according to claim 2, wherein the contact between the base material and the polymerizable monomer is performed by bringing the base material into contact with the polymerizable monomer or its solution in a gaseous state. The contact between the substrate and the polymerizable monomer is carried out by immersing the substrate, which does not swell in the polymerizable monomer or its solution, in line 5C (!).
The method described in section. & The method of claim 2, wherein the polymerizable monomer is selected from the group consisting of acrylonitrile, vinylidene cyanide, crotonitrile, methacrylaterile, chloroacrylonitrile, 2-cyanoethyl acrylate, and 2-cyanoethyl methacrylate. . 3. The method according to claim 2, wherein the ratio of the layer thicknesses of the uranium adsorbed layer and the non-adsorbed layer containing G amidoxime foundation is in the range of 1=10 to 10:10. 7 The concentration of amidoxime groups is 3-8 mgq/f-
The method according to claim 2, which is a graft chain.