JPH032011B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing a spherical fiber adsorbent. More specifically, the present invention provides an amidoxime-type fiber adsorbent that has a high adsorption rate and capacity for uranium, and is spherical and easy to separate, which can be suitably used for recovering uranium from dilute solutions such as seawater. It relates to a simple manufacturing method. BACKGROUND ART In recent years, due to oil shocks and the depletion of petroleum resources, the energy structure has been diversified from the conventional reliance on petroleum, and the use of nuclear energy has become particularly important. For this reason, uranium, which exists in large quantities in seawater, has attracted attention as an energy source. In seawater, there is approximately
Uranium is contained at a concentration of approximately 3 ppb, and in order to recover it, an adsorbent with excellent adsorption capacity and selectivity is required. In addition, the adsorbent must be resistant to seawater, easy to handle and regenerate, and available at low cost in large quantities, making recovery equipment economical. By the way, polymer compounds having an amidoxime group have excellent uranium adsorption ability (U.S. Pat. No. 3,088,798), can selectively adsorb uranium in seawater (Japanese Patent Publication No. 54-32834), and can be easily and inexpensively adsorbed. Because it is readily available, research is being actively conducted to put it into practical use for uranium adsorption. In order to recover uranium from a dilute solution such as seawater using such an adsorbent, the shape of the adsorbent is generally considered to be granular or cloth-like. In the case of granular adsorbents, a fixed bed method or a fluidized bed method is usually used, and in particular, various fluidized bed methods have been studied so far for the recovery of uranium from seawater. However, these fixed bed systems and fluidized bed systems have the disadvantage that they require a large amount of equipment and the cost of recovering uranium is high. On the other hand, in the case of cloth-like adsorbents, methods such as a streamer method and a multilayer parallel plate method have been proposed, but these methods have the drawbacks of a small amount of adsorbent per volume and a large occupied area, making them impractical. In the case of the spherical adsorbent of the present invention, as shown in FIG. 1 of the attached drawings, a bag-shaped fishing net 1 is filled with adsorbent and attached to a floating body 2, or as shown in FIG. As shown, it is possible to use a method such as filling a fish cage-like fishing net 3 with adsorbent and attaching it to the floating body 2, and it is not necessary to use a fixed bed method or a fluidized bed method that requires a large amount of equipment cost, so it is not practical. advantageous to Regarding the spheroidization of fibers, a method has been devised in which organic fibers are dispersed in a liquid and the dispersion is stirred to obtain a fiber mass (Japanese Patent Application Laid-Open No. 180229/1983). Problems to be Solved by the Invention In view of the above-mentioned circumstances, the object of the present invention is to obtain a spherical material that has a high adsorption rate and adsorption capacity for uranium and can be suitably used for recovering uranium from dilute solutions such as seawater. An object of the present invention is to provide a method for efficiently producing an amidoxime type fiber adsorbent that can uniformly adsorb uranium to its interior. Means for Solving the Problems As a result of extensive research, the present inventors found that acrylic fibers of a predetermined shape were stirred and heated in a methanol solution containing hydroxylamine.
By simultaneously converting the fibers into amidoximes and spheroidizing them, the above objective can be achieved, and furthermore, by subjecting the obtained spherical adsorbents to a specific surface treatment, they can be made to have excellent durability. Based on these findings, we have completed the present invention. That is, the present invention involves adding acrylic fibers with a fiber length of 5 to 30 mm and a fiber diameter of 3 d or more to a methanol solution containing hydroxylamine, heating the fibers while stirring, and simultaneously converting the fibers into amidoxime and forming them into a spherical shape. A method for producing an amidoxime-type spherical fiber adsorbent characterized by It is something to do. The acrylic fibers used in the method of the present invention have a fiber length of 5 to 30 mm and a fiber diameter of 3D or more, but in particular, a fiber length of 5 to 10 mm and a fiber diameter of 10 to 10 mm.
A range of 15d is preferred. If the shape of the acrylic fiber deviates from the above range, it will be difficult to obtain the desired spherical adsorbent. On the other hand, the content of hydroxylamine in the solvent solution is usually selected in the range of 1 to 5% by weight, and the ratio of acrylic fiber to hydroxylamine is selected in the range of 1:1 to 1:2 by weight. . As the solvent, methanol, methanol-water, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), etc. are used. The amidoxime formation of the acrylic fibers is usually carried out under normal pressure while heating and refluxing, and the reaction time is about 1 to 10 hours. In the present invention, the acrylic fiber is formed into a spherical shape while being converted into an amidoxim, and as the amidoximization and spheroidization proceed simultaneously,
A spherical adsorbent having a fast forming speed and excellent strength when treated with an alkali is efficiently formed.
The sphere diameter is preferably in the range of 5 to 40 mm. This spherical diameter depends on conditions such as the shape of the fibers, the shape and stirring speed of the agitator, and the shape and size of the container. Therefore, in order to obtain a spherical fiber adsorbent having a desired spherical diameter, the above-mentioned conditions must be met. need to be selected appropriately. The spherical fiber adsorbent obtained in this way may be used as a uranium adsorbent after being immersed in an alkaline aqueous solution for about 1 to 48 hours and treated with alkali, but defibration causes a decrease in adsorption performance. In order to prevent this, it is desirable to treat the surface with a hydrophilic binder. As this hydrophilic binder, for example, polyacrylic acid hydrazide, polyacrylonitrile, polyacrylamide, etc. are used. When using polyacrylic acid hydrazide, after soaking the spherical fiber adsorbent in an aqueous polyacrylic acid hydrazide solution for several minutes,
The polyacrylic acid hydrazide adhering to the surface of the adsorbent is insolubilized by drying or immersing it in epichlorohydrin. This kind of surface-treated spherical fiber adsorbent is
The adsorption performance does not deteriorate due to defibration during use, resulting in excellent durability. This material is treated with alkali by immersing it in an alkaline aqueous solution for about 1 to 48 hours in the same manner as described above, and then used as a uranium adsorbent. 1 and 2 are explanatory diagrams showing an example of how the adsorbent obtained by the method of the present invention is used. In FIG. 1, a bag-shaped fishing net 1 is filled with the adsorbent, and floating bodies 2,
Fig. 2 shows a method in which the floating body 2' is attached to a fishing net 1' and held in the expanded state using a weight 3.A fish cage-like enclosure surrounded on all sides by a fishing net 1' is filled with adsorbent material, and a floating body 2'...
This shows the cage method for establishing fish in the sea. The spherical fibrous adsorbent obtained by the method of the present invention can be placed and used underwater using equipment with an extremely simple structure, but in the same way as conventional granular adsorbents, A fixed bed method or a fluidized bed method may be used. The spherical fiber adsorbent obtained by the method of the present invention can uniformly adsorb uranium to its interior, and the adsorbed uranium can be easily desorbed by acid treatment, making it possible to recycle and reuse the adsorbent. be. Effects of the Invention According to the method of the present invention, it is possible to efficiently produce a spherical amidoxime type fiber adsorbent that has a high adsorption rate and adsorption capacity for uranium and is suitable for recovering uranium from dilute solutions such as seawater. Since the obtained adsorbent is spherical, it is extremely simple to recover uranium from dilute solutions without the need to use a fixed bed method or fluidized bed method, which requires a large amount of equipment, unlike granular adsorbents. Uranium can be economically advantageously recovered from dilute solutions. Examples Next, the present invention will be explained in more detail with reference to Examples. Example 1 5 g of acrylic fiber with a fiber diameter of 15 d and a fiber length of 10 mm and 200 ml of hydroxylamine 1M methanol solution were
Pour into a 300ml three-necked round-bottom separable flask.
Using a stirrer rod with a blade length of 6 cm, the mixture was refluxed for 8 hours while stirring at a rotational speed of 200 rpm to obtain a spherical fiber adsorbent with a diameter of 1 to 1.5 cm. Next, this adsorbent was dissolved in a 4% by weight aqueous sodium hydroxide solution.
After being immersed for a period of time and treated with alkali, it was used for uranium adsorption experiments. The spherical fiber adsorbent obtained in this way is filled in a column, filtered seawater is passed through the column, the adsorbent is taken out at predetermined intervals, the surface part of the adsorbent is loosened, and the fibers on the surface part are removed. The adsorbed uranium was separated into the inner fibers and was desorbed with 1N hydrochloric acid, and the amount of uranium adsorbed in each was measured. For comparison, we also loosened spherical fibers and packed them into a column in a layer to conduct a uranium adsorption experiment. These results are shown in Table 1. As can be seen from this table, it is clear that uranium is adsorbed to the inside of the spherical adsorbent.

[Table] Example 2 A spherical fiber adsorbent was prepared by stirring the same basic fibers as in Example 1 in a methanol solution at room temperature for 8 hours using the apparatus of Example 1, and converting the resulting spherical bodies into amidoximes for an additional 8 hours. The spherical fibers were made into spherical bodies, and the spherical fiber adsorbents were obtained by spheroidizing the same basic fibers as in Example 1 into amidoxime treatment for 8 hours in a room temperature methanol solution in the same manner as in Example 1.
When the spherical fiber adsorbent obtained by the method of simultaneous amidoxime formation and spheroidization is made into a spheroid, the time required for each spheroidization, the defibration rate when an alkali treatment is performed for 8 hours, and the seawater Table 2 shows the amount of uranium adsorbed in the six days since. Compared to the method according to the present invention for obtaining spheroids, the method of performing spheroidization and amidoximation separately to obtain spheroids requires a long time for the formation of spheroids, and during alkali treatment, High defibration rate. Furthermore, the spherical bodies obtained by the method according to the present application are
It has a higher adsorption ability for seawater uranium than spherical bodies and spherical bodies.

[Table] Example 3 The spherical fiber adsorbent prepared in Example 1 was mixed with polyacrylic acid hydrazide (molecular weight 300,000, hydrazide conversion rate
45%) aqueous solution for 10 minutes, and then vacuum-dried to insolubilize the polyacrylic acid hydrazide adhering to the adsorbent surface. This kind of spherical fiber adsorbent not treated with polyacrylic acid hydrazide was defibrated after 24 hours of alkali treatment, but the spherical fiber adsorbent treated with polyacrylic acid hydrazide was not defibrated even after 24 to 48 hours of alkali treatment. It was not delicate. Furthermore, even after long-term adsorption experiments, no fibers were observed to come off or break. Uranium adsorption properties were measured for spherical fiber adsorbents that were not PAH-treated and treated with alkali for 16 hours (not defibrated) and PAH-treated spherical fiber adsorbents that were treated with alkali for 24 hours. The results are shown in Table 3. As can be seen from this table, the spherical fiber adsorbent treated with polyacrylic acid hydrazide has a higher uranium adsorption rate than that without such treatment.

【table】 [Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams showing examples of different methods for recovering uranium from seawater using the spherical fiber adsorbent obtained by the present invention. In the figure, numeral 1 is a bag-shaped fishing net, 2 is a floating body,
1' is a fishing net for enclosure.

Claims (1)

[Claims] 1. Acrylic fibers with a fiber length of 5 to 30 mm and a fiber diameter of 3 d or more are added to a methanol solution containing hydroxylamine, and heated while stirring to convert the fibers into amidoxime and simultaneously form them into a spherical shape. A method for producing an amidoxime type spherical fiber adsorbent, characterized by: 2. Add acrylic fibers with a fiber length of 5 to 30 mm and a fiber diameter of 3D or more to a methanol solution containing hydroxylamine, heat while stirring to convert the fibers into amidoxime, and simultaneously shape them into a sphere,
A method for producing an amidoxime type spherical fiber adsorbent, which comprises subsequently surface-treating the spherical molded body with a hydrophilic binder.