JPS6053160B2 - How to extract uranium from seawater - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for adsorbing and collecting uranium in seawater,
More specifically, the present invention relates to a method for collecting uranium in seawater, which is characterized in that an adsorbent that has come into contact with seawater is recovered using a magnetic separation method.

Approximately 100 million tons of uranium is dissolved in seawater.

The uranium concentration in seawater is extremely low, approximately 3.3 μg/e, and it is necessary to bring a huge amount of seawater into contact with the adsorbent. The methods of bringing seawater and adsorbent into contact can be roughly divided into three types. The first method is to pack the adsorbent in a fixed bed and pass seawater through it, the second method is to place a sheet etc. carrying the adsorbent in seawater and bring it into contact with it, and the third method is to make the adsorbent into a fine slurry. This method involves contacting with seawater. In the first method, a fine particulate adsorbent cannot be used because the pressure loss becomes large, and therefore relatively large particles are used, so the amount of adsorption is not very large. There is also a strong possibility that the adsorption bed will become clogged with sand or other solid matter in the seawater. The second method has problems with contact with seawater, requiring the adsorbent to be immersed in seawater for a long period of time, and the amount of adsorption cannot be said to be large compared to other methods. On the other hand, since the third method uses an adsorbent with a fine particle size, the amount of adsorption per gram of adsorbent is also larger compared to the other two methods. In the conventional method, after contact with seawater, the adsorbent is recovered using a sedimentation tank. However, this method requires a long time for settling and requires a very large settling tank. Moreover, the recovery rate of the adsorbent is 10
It is difficult to reduce the amount of uranium to 0%, and there is a risk that the amount of uranium extracted will decrease and there will be marine pollution. An object of the present invention is to provide an apparatus and method for bringing a magnetic uranium adsorbent into contact with seawater, then efficiently recovering the adsorbent by a magnetic separation method, and desorbing uranium from the adsorbent. .

In order to efficiently recover uranium using the slurry method, (1) the adhesive must have a large amount of uranium adsorbed;

Also, the adsorption speed is fast. (2) The adsorbent can be efficiently recovered. etc. is desired. Regarding (1), it has been reported that in hydrous titanium oxide adsorbents, the amount of uranium adsorbed per gram is proportional to the apparent outer surface area of the particles.
(Sugano et al.; Journal of the Atomic Energy Society of Japan VOl.l2, No.ll
97O) Therefore, the finer the particles, the greater the amount of uranium adsorbed per g adsorbent. However, from the viewpoint of (2), there are many problems in reducing the particle size. The particle size for which adsorbents can be efficiently sedimented and recovered using conventional sedimentation methods is limited to 100 μm. Another option is to collect the particles using a centrifuge, but the amount of seawater that must be processed is enormous, making it difficult to put this into practice. On the other hand, when magnetic separation is used, the particle size of the adsorbent can be further reduced, and the amount of uranium adsorbed can therefore be significantly increased. Furthermore, the magnetic separation method has no problems in treating large amounts of seawater. In the magnetic separation method, the capture limit size of magnetic particles is determined by the balance between the attractive force of the magnetic field acting on the magnetic particles and the forces such as fluid pressure and gravity that try to remove the particles. In the case of a hydrous titanium oxide/iron composite adsorbent in which magnetite is mixed at 1/1, the particle size is 1p in the KOlm-MarstOn type large gradient magnetic separator (HGMS), as shown in Figure 1.
It is possible to capture up to m. (Uchiyama, Applied Physics Vol. 45
sNO. 2. 1976) By reducing the particle size of the adsorbent from 100 pm to 1 pm, the amount of uranium adsorbed per 1 g of adsorbent can be dramatically increased to 10 μm.

Moreover, the uranium adsorbed on the adsorbent can be eluted with a desorption solution such as ammonium carbonate solution, and the adsorbent can be reused.

To summarize the present invention, (1) after bringing a magnetic adsorbent into contact with seawater, the adsorbent adsorbing uranium is separated and recovered from the seawater by magnetic separation;
A seawater uranium extraction method characterized by eluting uranium in one or more stages.

(2) To separate and recover the magnetic adsorbent using magnetic separation, the adsorbent is captured in the filter using a magnetic separation filter, and then the desorption liquid is sent into the magnetic separation filter to elute the uranium in the adsorbent. Characteristic uranium desorption method.

(3) After uranium desorption, the adsorbent is washed with water, the magnetic field of the magnetic filter is turned off, and the adsorbent captured by the filter is backwashed and desorbed for reuse.

is obtained.

Examples of the present invention will be described in detail below.

FIG. 2 is a flow sheet outlining the invention. Seawater is introduced into the stirring tank 1 from the seawater inlet 3. On the other hand, the magnetic adsorbent is supplied into the seawater from the adsorbent inlet 4 and mixed by the stirrer 2. After the adsorbent adsorbs uranium in seawater, valves 6 and 7 are opened to send the seawater containing the adsorbent to the magnetic separator 5, where it is absorbed into the filter 17 by the large gradient magnetic field generated in the magnetic separation filter 17. Capture magnetic adsorbent. Next, close valves 6 and 7, open valves 8 and 9,
The uranium adsorbed on the adsorbent is eluted through a uranium desorption fluid, such as a few percent ammonium carbonate solution. In order to reduce the amount of desorption liquid as much as possible and increase the uranium concentration in the desorption liquid, the desorption liquid may be passed through the magnetic filter several times by connecting the desorption liquid inlet 13 and the desorption liquid outlet 14. Finally, the high concentration 5 uranium solution is taken out from the desorption liquid outlet 14. After desorbing uranium from the adsorbent, close grooves 8 and 9,
Open the valves 10 and 11 and let the backwash water pass through the backwash liquid inlet 15. At this time, by turning off the magnetic field of the magnetic separation filter 14, the adsorbent captured in the magnetic separation filter 14 is easily desorbed from the magnetic separation filter 14 by backwash water and passes through the adsorbent introduction pipe 16. Then, it is fed back into the seawater. In Figure 3, two magnetic separators are installed in parallel to continuously adsorb and desorb uranium. FIG. 4 shows that uranium is desorbed from the adsorbent that has adsorbed uranium captured by the magnetic separator 118, and at the same time, the magnetic field of the magnetic separation filter is cut to remove the adsorbent from the magnetic separation filter. is recovered using a magnetic separator ■.

If necessary, the uranium concentration in the desorption solution can be increased by passing the desorption solution through the magnetic separator (2) twice.
Note that since the desorption from the adsorbent from the magnetic separator 1 is completed in a very short time, it is possible to semi-continuously recover the adsorbent in seawater using the magnetic separator 1. Figure 5 is suitable for adsorbents with relatively large particle sizes; in the case of particles with a particle size of 100 pm or more and a ferromagnetic material such as magnetite, it is possible to collect them even in a small magnetic field, so drums using permanent magnets are mainly used. type magnetic separator is applied. Seawater containing adsorbent is supplied from the top of the drum-type magnetic separator 20. The magnetic adsorbent moves on the rotating drum by a permanent magnet 21 provided inside the rotating drum 22, is separated from the seawater, and forms a desorption layer 23.
sent to. Here, the uranium is eluted and extracted from the adsorbent. On the other hand, the adsorbent is used for reconsumption. Figure 6 is applicable to the recovery of adsorbents with a wide range of particle sizes.
The adsorbent with a relatively large particle size is allowed to settle in the sedimentation tank 24, and the adsorbent with a small particle size that does not settle is recovered by large gradient magnetic separation, thereby reducing the load on the magnetic separator.

The adsorbent deposited at the bottom of the sedimentation tank 24 is removed by a slurry pump 25.
and treated with a desorption layer 2-3. By applying a magnetic separation method to the collection of adsorbent, the present invention can significantly reduce the particle size of the adsorbent compared to conventional methods, thereby dramatically increasing the amount of uranium adsorbed per gram of adsorbent. This increase is obvious and is very effective for extracting uranium from seawater and from low-concentration uranium solutions.

[Brief explanation of the drawing]

Figure 1 is a diagram of the relationship between particle size captured by magnetic separation and induced magnetization, Figure 2 is a basic diagram of a seawater uranium extraction device,
Figure 3 shows the case in which uranium is adsorbed and desorbed continuously.
Figure 4 shows the case where uranium in the adsorbent and the adsorbent are desorbed from the magnetic separation filter at the same time, Figure 5 shows the case where adsorbent with relatively large particle size is recovered, and Figure 6 shows the case of sedimentation. A system diagram of the system is shown in which the adsorbent is recovered using a combination of magnetic separation and magnetic separation. 1... Stirring tank, 2... Stirrer, 3...
...Seawater inlet, 4...Adsorbent inlet, 5.
...Magnetic separator, 6●◆●●Valve 19710...
●Valve 2, 8111 Valve 3, 9... Male valve 10... Valve 5, 11... Valve 6, 12... Seawater outlet, 13... ... Desorption liquid inlet, 14 ... Desorption liquid outlet, 15 ...
Backwash liquid inlet) port, 16... Adsorbent inlet pipe, 17.
...Magnetic separation filter, 18...Magnetic separator 1, 19...Magnetic separator ■, 20...
...Drum type magnetic separator, 21...Permanent magnet, 2
2... Rotating drum, 23... Desorption layer,
24... Sedimentation tank, 25... Slurry pump.

Claims (1)

[Scope of Claims] 1. Seawater characterized in that when extracting uranium from seawater, a magnetic adsorbent is brought into contact with seawater, and then a magnetic separator is used to capture the adsorbent and extract uranium. How to extract middle uranium. 2. A method for extracting uranium according to claim 1, characterized in that a uranium desorption liquid is brought into contact with a magnetic adsorbent while the adsorbent remains in a magnetic separator. 3 In claim 1, magnetic separators for adsorbent recovery are installed in parallel, and while the first magnetic separator is recovering adsorbent from seawater, the adsorption in the second magnetic separator is A method for collecting uranium from seawater, which is characterized by desorbing uranium adsorbed by a reagent. 4. In claim 1, the adsorbent adsorbing uranium captured in the first magnetic separator is backwashed with a uranium desorption liquid to desorb the adsorbent from the magnetic separator,
A method for collecting uranium, characterized in that the adsorbent is then captured by a second magnetic separator and the uranium is eluted with a uranium desorption solution. 5. When collecting uranium from seawater using an adsorbent, after the magnetic adsorbent comes into contact with seawater, the seawater containing the adsorbent is led to a sedimentation tank, and the adsorbent with large particles is collected from the bottom of the sedimentation tank. A method for collecting uranium in seawater, which is characterized by introducing seawater containing adsorbent with small particles into a magnetic separator from the upper part of a sedimentation tank, and recovering the adsorbent with the magnetic separator.