JPS6051379B2 - Manufacturing method of magnetic adsorbent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a magnetic adsorbent, and particularly to a method for producing a magnetic adsorbent that has excellent adsorption performance when collecting uranium from seawater and is easy to recover.

Adsorption is said to be the most feasible method for extracting uranium from seawater.

The adsorption method is a method for extracting uranium by bringing seawater into contact with an adsorbent, and there are two methods: a fixed bed method and a slurry method. Slurry systems have many advantages over fixed bed systems. That is, according to this method, since the particle size of the adsorbent is small and the adsorption speed is high, (a) the amount of adsorbent and/or desorbent used can be reduced, (b) the device can be made smaller, and (c) ) The amount of seawater to be treated can be increased, and (d) there is no need to worry about the floating matter in the seawater clogging the adsorption bed and increasing the pressure drop, unlike in the case of the fixed bed method. However, the biggest drawback of this slurry method is that the recovery rate of the adsorbent adsorbing uranium from seawater is low.

Recovery of adsorbent using the slurry method is usually carried out by sedimentation separation method in large-scale platforms such as seawater uranium extraction. In this case, the recovery rate of the adsorbent is approximately 70%
The remaining 30% is said to flow into seawater, which not only significantly reduces the recovery rate of uranium but also causes marine pollution. An object of the present invention is to eliminate such drawbacks and provide a method for producing a magnetic adsorbent that has excellent adsorption performance and is easy to recover.

The present invention has the following configuration to achieve the above object.

That is, in the method for producing a magnetic adsorbent of the present invention, a mixed solution of titanium sulfate, ferrous salt, and urea is heated to about 85 to 10
The reaction is characterized by being carried out at a temperature within the range of 0° C. and a final pH within the range of about 5.5 to 9.3. From the above viewpoint, the inventors of the present invention have conducted various studies on ways to effectively recover the adsorbent that has adsorbed uranium in seawater. In this case, the present invention was achieved by discovering that a hydrous titanium oxide-iron oxide adsorbent prepared using titanium sulfate can adsorb a large amount of uranium and has excellent magnetic separation performance (magnetic susceptibility). be.

Fine powder of hydrous titanium oxide (TiO2.NH2O) is said to have the largest adsorption amount of uranium, and various titanium compounds have been proposed as raw materials for its production.

In producing a hydrous titanium oxide adsorbent, the uranium adsorption activity is thought to be promoted by the anions contained in the raw material compound, which generate surface hydroxyl groups, which are active sites for uranium adsorption, during precipitation. In the present invention, it has been confirmed that the extremely excellent effects described above are exhibited by using sulfate ions as anions. In the present invention,
In order to make the adsorbent magnetic, iron hydroxide is uniformly precipitated using ferrous salt and urea decomposition method.

As is well known, in the urea decomposition method, urea is added to an aqueous solution containing metal ions, and the temperature is usually about 85°C or higher (urea decomposition temperature).
This is a method in which urea is decomposed by heating to a temperature of 100°C, and a homogeneous precipitate of metal hydroxide is gradually formed using the generated ammonia. The ferrous salt used to impart magnetism is
Although the influence of the type on the adsorption amount and magnetic susceptibility is small,
It was found that the urea decomposition method showed a higher magnetic susceptibility than the normal neutralization method. This is because iron oxide is produced by air oxidation as the heating temperature rises, and γ, which is a magnetic substance, is produced.
This is thought to be due to the progress of the formation of -Fe2O3 and especially the crystallization to Fe3O4 (magnetite), and this was confirmed by X-ray diffraction. In the present invention,
Add urea to a mixed solution of titanium sulfate and ferrous salt and add about 85~
Heat to a temperature in the range of 100'C to bring the final pH of the solution to about 5.5-9.3 to produce a uniform precipitate.

In this case, if the heating temperature is below about 85°C, urea will not be decomposed, while if the heating temperature is above about 100°C, the adsorption power of the resulting adsorbent will decrease. Further, unless the pH is about 5.5 or higher, precipitation will not occur smoothly. Considering the amount of raw materials used and the time required for production, these conditions are: pH 6 or higher, temperature 9.
It is desirable to set the temperature to about 0°C. Furthermore, in the present invention, in order to increase the amount of uranium adsorbed by the magnetic adsorbent, the higher the titanium content, the better; however, in order to increase the magnetic susceptibility, the lower the titanium content is.

Therefore, in order to obtain a magnetic adsorbent with a large amount of adsorption and a high magnetic susceptibility, the composition ratio is an important factor.
In the present invention, titanium sulfate and ferrous salt are used in a ratio such that the molar ratio of titanium sulfate to ferrous salt (hereinafter referred to as Ti/Fe) is within the range of about 0.5 to 6. ,
Excellent adsorption performance and magnetic separation performance can be obtained, and outside this range, either performance will deteriorate. Although ferrous sulfate is preferred as the ferrous salt in the present invention, other ferrous salts such as ferrous chloride can also be effectively used. In carrying out the present invention, a predetermined amount of titanium sulfate and ferrous salt are mixed, and an amount (not particularly limited) sufficient to react with the titanium sulfate and ferrous salt and decompose to a predetermined pH value is added to the solution. of urea is added, and the resulting mixed solution is reacted by heating at a predetermined temperature and a predetermined final pH in an air atmosphere, and then allowed to cool. After cooling to room temperature, wash the precipitate with water using a decanting method, centrifuge, and dry for several days (room temperature).
By post-pulverizing, a powdered magnetic adsorbent can be obtained. Next, the present invention and its effects will be explained by examples, but the present invention is not limited thereto.

Example 1 Ti/Fe was set to 1.0, and 150 y of urea was added to a mixed solution of 200 ml of a titanium sulfate aqueous solution with a concentration of 6 mol/f and 200 ml of a ferrous sulfate aqueous solution with a concentration of 0.6 mol/f, This mixed solution was heated to 90°C under an air atmosphere.

When the final pH of the solution reached 6.0, heating was stopped and the solution was allowed to cool. After cooling, the precipitate was washed with water using a decanting method. Next, the precipitate was centrifuged, dried at room temperature for about 10 days, and ground in an agate mortar to a particle size of about 20 to 40 μm. Using this powder as a sample, the adsorption amount of uranium and magnetic separation performance (capture rate) were investigated using the following method.

The amount of uranium adsorbed was 10 ppb in sample 3 of uranium-enriched seawater.
After adding 0 mg and stirring for 5 hours, uranium in the liquid was determined by spectrophotometry using Arsenazo (a reagent for uranium analysis), and calculated from the difference in concentration before and after adsorption. Moreover, the magnetic separation performance was determined by the following method. That is, seawater 3' containing approximately 300 mg of sample was placed in a high gradient magnetic separator (HighG
radiantMagrleticSeparatOr
, HGMS), while passing through the HGMS,
The sample is captured by the filter section (magnetized nickel wire mesh). The capture rate of the sample was determined by analyzing titanium in the liquid before and after passing through the HGMS. The capture conditions in this case are: external magnetic field: 25,000e1, void ratio of wire mesh: 0.9s, thickness of wire mesh: 0.
5T1, and the flow rate was 0.37TL/sec. Example 2 Example 1 except that ferrous chloride was used as the ferrous salt
conducted a similar experiment.

Examples 3 and 4 An experiment similar to Example 1 was conducted except that the final pH of the solution was 5.5 and 9.0, respectively.

Examples 5 and 6 The same experiment as in Example 1 was conducted except that the heating temperature of the solution was 85° C. and 100° C., respectively.

Example 7 Ti/Fe was set to 0.5, and 200 mt of a titanium sulfate aqueous solution with a concentration of 0.3 mol/f and 200 ml of a ferrous sulfate aqueous solution with a concentration of 0.6 mol/f were mixed.
An experiment similar to Example 1 was conducted.

Example 8. Example except that F'+'Tj/Fe was 2.0, and 200 mt of a titanium sulfate aqueous solution with a concentration of 0.6 mol/f and 200 ml of a ferrous sulfate aqueous solution with a concentration of 0.3 mol/f were mixed. An experiment similar to 1 was conducted.

Example 9 Example 1 except that T1/Fe was 6.0 and 200 ml of a titanium sulfate aqueous solution with a concentration of 0.6 mol/e and 200 ml of a ferrous sulfate aqueous solution with a concentration of 0.1 mol/l were mixed.
conducted a similar experiment.

Comparative Example 1 An experiment similar to Example 1 was conducted except that titanium tetrachloride was used instead of titanium sulfate.

Comparative Example 2 Example 1 except that Ti/Fe was 0.3 and 200 ml of a titanium sulfate aqueous solution with a concentration of 0.18 mol/f and 200 ml of a ferrous sulfate aqueous solution with a concentration of 0.6 mol/f were mixed. conducted a similar experiment.

Comparative Example 3 Example 1 except that Ti/Fe was 8.0 and 200 mt of titanium sulfate aqueous solution with a concentration of 0.48 mol/l and 200 ml of ferrous sulfate aqueous solution with a concentration of 0.06 mol/e were mixed.
conducted a similar experiment.

As mentioned above, the main raw materials in Examples 1 to 9 and Comparative Examples 1 to 3,
The production conditions and performance test results of each magnetic adsorbent obtained are summarized in the table below.

As is clear from the table, the magnetic adsorbents according to the present invention shown in Examples 1 to 9 have a large amount of uranium adsorbed and excellent magnetic separation performance.

As described above, according to the present invention, it is possible to provide a magnetic adsorbent that has excellent uranium adsorption performance, good magnetic separation performance, and can be easily recovered from seawater.

Claims (1)

[Claims] 1. A mixed solution consisting of titanium sulfate, ferrous salt, and urea is heated at a temperature in the range of about 85 to 100°C and about 5.5 to 9.5°C.
A method for producing a magnetic adsorbent, characterized in that the reaction is carried out at a final pH within the range of 3. 2. The method for producing a magnetic adsorbent according to claim 1, wherein titanium sulfate and ferrous salt are mixed in a molar ratio of about 0.5 to 6.