Rare earth extraction method, rare earth extraction system, and rare earth manufacturing method

Abstract

To provide a rare earth extraction method, a rare earth extraction system, and a rare earth manufacturing method capable of reducing a burden of transporting materials used in rare earth extraction and expanding uses of extraction residues.SOLUTION: A rare earth extraction method is performed by a rare earth extraction system 101, and includes electrolysis step S225 in which an acidic liquid 17 is obtained by electrolysis of an electrolyte 49, which is pure water, and extraction step S211 in which rare earth components contained in rare earth-containing mud 15 raised from a seabed 103 to the ocean surface is extracted using the acidic liquid 17 obtained in the electrolysis step S225.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a rare earth extraction method, a rare earth extraction system, and a rare earth production method. [Background technology]

[0002] Rare earths are found in large quantities, for example, on the seabed of the central Pacific Ocean, far from the mainland, and such remote ocean areas can be rare earth mining sites. A conventional technique for refining rare earths involves treating rare earth-containing mud extracted from the seabed with an acid such as dilute hydrochloric acid to extract the rare earth components contained in the mud (see, for example, Patent Document 1 below). Since the extraction residue remaining after this extraction process is acidic, Patent Document 1 discloses that the extraction residue is neutralized by adding an alkaline material such as sodium hydroxide, quicklime, or slaked lime, and the neutralized product is used as a material for civil engineering materials such as concrete. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-131262 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when such extraction processes are carried out at mining sites, materials used in the process, such as acidic solutions, must be transported from the mainland to remote ocean areas, resulting in a significant transportation burden. Furthermore, because acids such as dilute hydrochloric acid are used to extract rare earths, the extraction residue contains electrolytes such as Cl. Because such electrolytes can cause deterioration of concrete and mortar, even if the neutralized product of this extraction residue were used as a civil engineering resource, it is not necessarily possible to obtain civil engineering materials of the required quality, and the uses for the extraction residue have sometimes been limited.

[0005] Therefore, an object of the present invention is to provide a rare earth extraction method, a rare earth extraction system, and a rare earth production method that can reduce the burden of transporting materials used in rare earth extraction and expand the uses of extraction residue. [Means for solving the problem]

[0006] The gist of the present invention lies in the following [1] to

[12] .

[0007] [1] A rare earth extraction method comprising: an electrolysis step of obtaining an acidic solution by electrolyzing pure water; and an extraction step of extracting rare earth components contained in rare earth-containing mud that has been brought up from the seabed to the ocean surface using the acidic solution obtained in the electrolysis step.

[0008] [2] The rare earth extraction method according to [1], further comprising a power generation step of generating a portion of the electrical energy used in the electrolysis step by utilizing the hydrogen gas and oxygen gas generated in the electrolysis step.

[0009] [3] The rare earth extraction method according to [1] or [2], wherein in the electrolysis step, electricity generated by a solar cell is used as at least a part of the energy for the electrolysis.

[0010] [4] The rare earth extraction method according to any one of [1] to [3], further comprising a classification step, prior to the extraction step, of classifying the mud brought up from the seabed to the ocean surface and obtaining the classified mud on the larger particle side as the rare earth-containing mud to be used in the extraction step.

[0011] [5] The rare earth extraction method according to [4], wherein the classification is performed using a hydrocyclone device or a decanter-type centrifuge in the classification step.

[0012] [6] The rare earth extraction method according to [4], further comprising a waste material removal step of separating and removing waste materials including amphitheat from the large-grain mud classified in the classification step, prior to the extraction step.

[0013] [7] The rare earth extraction method according to any one of [4] to [6], further comprising a classification residue treatment step of mixing a solidification material with the small particle classification residue generated in the classification step to solidify and modify it.

[0014] [8] The rare earth extraction method according to any one of [1] to [7], further comprising an extraction residue treatment step of neutralizing and modifying the extraction residue generated in the extraction step with the alkaline solution generated in the electrolysis step.

[0015] [9] The rare earth extraction method according to [8], further comprising a neutralization residue treatment step of mixing a solidification material with the neutralization residue treated in the extraction residue treatment step to solidify and modify the neutralization residue.

[0016]

[10] The rare earth extraction method according to [9], further comprising a neutralization residue dehydration step of dehydrating the neutralization residue prior to the neutralization residue treatment step, wherein the water component separated and removed from the neutralization residue in the neutralization residue dehydration step is used as part of the water to be electrolyzed in the electrolysis step.

[0017]

[11] A rare earth extraction system comprising: an electrolysis unit that obtains an acidic solution by electrolysis of pure water; and an extraction unit that extracts rare earth components contained in rare earth-containing mud that has been brought up from the seabed to the ocean surface using the acidic solution obtained in the electrolysis unit.

[0018]

[12] A method for producing rare earths, comprising: an electrolysis step of obtaining an acidic solution by electrolyzing pure water; and an extraction step of extracting rare earth components contained in rare earth-containing mud that has been brought up from the seabed to the ocean surface, using the acidic solution obtained in the electrolysis step. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a rare earth extraction method, a rare earth extraction system, and a rare earth production method that can reduce the burden of transporting materials used in rare earth extraction and expand the uses of extraction residue. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram showing a rare earth mining site where a rare earth extraction method and a rare earth extraction system according to an embodiment of the present invention are used. [Figure 2] FIG. 1 is a flow chart showing a rare earth extraction method according to an embodiment of the present invention. [Figure 3] FIG. 1 is a flow chart showing a rare earth extraction method according to an embodiment of the present invention. [Figure 4] FIG. 1 is a flow chart showing a rare earth extraction method according to an embodiment of the present invention, and in particular, a flow chart showing a process for obtaining an acidic solution and an alkaline solution. [Figure 5] FIG. 1 shows an electrolysis apparatus. [Figure 6] FIG. 2 is a diagram illustrating a power supply device. [Figure 7] 1 is a block diagram showing a rare earth extraction system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of a rare earth extraction method, a rare earth extraction system, and a rare earth production method according to the present invention will be described in detail with reference to the drawings. The rare earth extraction method performed by a rare earth extraction system 101 (FIG. 1) of this embodiment is a method for extracting rare earth components from seabed mud 1 that has been hauled up to the surface from the seabed 103 (FIG. 1) at a rare earth mining site. Rare earths refer to a total of 17 elements, including 15 lanthanoids (lanthanum (La) to lutetium (Lu)) and scandium (Sc) and yttrium (Y), which belong to Group 3 of the periodic table.

[0022] Seabed mud 1 is lifted up from the seabed 103 at a rare earth mining site to the ocean surface, for example, by the method shown in FIG. 1. That is, as shown in FIG. 1, a mud lifting pipe 107 is installed extending from a ship 105 to the seabed 103. A compressed air pipe 109 is connected to the lower end of the mud lifting pipe 107, and compressed air is sent to the lower end of the mud lifting pipe 107 from the ship 105. The high-pressure air supplied from the compressed air pipe 109 causes the seabed mud 1 to be sucked in together with seawater from the lower opening of the mud lifting pipe 107. An upward flow of a mixture of compressed air bubbles, seawater, and seabed mud 1 is then generated inside the mud lifting pipe 107. This flow of the mixture causes the seabed mud 1 to be lifted up onto the ship 105 together with the air bubbles and seawater. An underwater backhoe 111 is placed on the seabed 103 near the lower end of the mud lifting pipe 107, and the seabed mud 1 sucked into the mud lifting pipe 107 is loosened and collected by the underwater backhoe 111.

[0023] The rare earth extraction system 101 may be installed on a ship 105, as in the example shown in Figure 1. Alternatively, the rare earth extraction system 101 may be installed on land near the rare earth mining site. Alternatively, some of the components of the rare earth extraction system 101 may be installed on the ship 105, and other components may be installed on nearby land. In other words, each component of the rare earth extraction system 101 may be appropriately located near the rare earth mining site, including on the ship 105.

[0024] When the rare earth extraction system 101 is installed on a ship 105, the salvaged seabed mud 1 is introduced into the rare earth extraction system 101 on the ship 105. When the rare earth extraction system 101 is installed on nearby land, the salvaged seabed mud 1 is transported to the land by the ship 105 or another transport vessel 113 and introduced into the rare earth extraction system 101. The seabed mud 1 is then processed in the rare earth extraction system 101, and ultimately the rare earths 25 (FIG. 2) contained in the seabed mud 1 are obtained.

[0025] The rare earth extraction method executed by the rare earth extraction system 101 will be described with reference to Figures 2 to 4. Figures 2 to 4 show a flow diagram of the rare earth extraction method divided into three diagrams due to drawing size restrictions. Arrow A shown in the flow diagram of Figure 2 continues to A in Figure 3, and similarly, arrow B shown in the flow diagram of Figure 4 continues to B in Figure 2, and arrow C shown in the flow diagram of Figure 4 continues to C in Figure 3. In particular, Figure 4 shows the process for obtaining acidic solution 17 and alkaline solution 33 in this rare earth extraction method.

[0026] As shown in Figure 2, first, a classification step S201 is carried out to classify the seabed mud 1 that has been brought up to sea. In the classification step S201, the seabed mud 1 is separated into large-particle mud 5 having a predetermined particle size or more, and classification residue 3, which is small-particle mud having a particle size less than the predetermined particle size. The predetermined particle size is, for example, 20 µm. A known solid-liquid separator can be used as the classifier 301 (Figure 7) used for the classification process in the classification step S201, such as a hydrocyclone device or a decanter-type centrifuge.

[0027] Next, in the unwanted matter removal step S205, unwanted matter 13 including amphitheatre is separated and removed from the large-grain mud 5 obtained in the classification step S201. As a method for separation and removal in this unwanted matter removal step S205, for example, a microbubble flotation method can be suitably adopted, and as the separator 305 (FIG. 7) used for this, a microbubble flotation device or the like can be adopted.

[0028] Thereafter, the water component 21 is removed from the large-grain mud 5 after the removal of the unwanted materials by dehydration treatment S207. As the dehydration device 307 (FIG. 7) used in the dehydration treatment S207, a known dehydration device such as a decanter or a filter press can be used. As described above, by removing the unwanted materials 13 and the water component 21 from the seabed mud 1, a rare-earth-containing mud 15 containing rare earths is obtained. The water component 21 can be discharged into the sea after undergoing any necessary water treatment. Because the majority of the water component 21 is seawater, the water treatment burden for discharging this water component 21 into the sea can be kept relatively low.

[0029] Meanwhile, the classification residue 3 generated in the above-mentioned classification step S201 is subjected to a dehydration treatment S203 to remove the water component 11. The dehydration treatment S203 may be performed in the same manner as the above-mentioned dehydration treatment S207. The water component 11 may be discharged into the sea after undergoing the necessary water treatment. As the majority of the water component 11 is seawater, the water treatment burden for discharging this water component 11 into the sea can be kept relatively light.

[0030] The dehydrated classified residue 9 is modified in a classified residue processing step S209. In the classified residue processing step S209, the classified residue 9 is mixed with a solidification material 7 and solidified. Examples of the solidification material 7 that can be used include alkaline solidification materials such as cement and lime, and magnesium oxide (MgO). The classified residue 9 solidified with the solidification material 7 is effectively utilized as civil engineering materials 19, such as bricks, blocks, backfill material, or modifier material. This civil engineering material 19 is used, for example, in civil engineering projects such as island development near rare earth mining sites.

[0031] Since the rare earth-containing mud 15 described above contains the target rare earths, the rare earth components contained in the rare earth-containing mud 15 are extracted in the extraction step S211. In the extraction step S211, an acidic liquid 17 is mixed with the rare earth-containing mud 15. The origin of this acidic liquid 17 will be described later. The rare earth-containing mud 15 dissolves in the acidic liquid 17, and the rare earths contained in the rare earth-containing mud 15 are extracted into the liquid phase. This solution containing the rare earths is obtained as a rare earth component-containing liquid 23. Thereafter, in the purification step S213, the rare earth component-containing liquid 23 is treated in a predetermined purification process to obtain rare earths 25. As the purification process in the purification step S213, a known rare earth purification process for purifying rare earths from a rare earth component-containing liquid is adopted.

[0032] After the rare earth component-containing liquid 23 is collected in the extraction step S211, an extraction residue 27 remains. The extraction residue 27 is subjected to a dehydration treatment S215 to remove the water component 29. The dehydration treatment S215 may be performed in the same manner as the above-mentioned dehydration treatment S207. The water component 29 generated here is used as part of the electrolyte 49 (FIG. 4) described below. In this case, the water component 29 may be subjected to a purification treatment before being added to the electrolyte 49.

[0033] The extraction residue 31 after the dehydration treatment S215 is acidic due to the influence of the acidic solution 17, and is therefore modified in the extraction residue treatment step S217 as shown in FIG. 3. That is, in the extraction residue treatment step S217, an alkaline solution 33 is added to the extraction residue 31 after dehydration, and the extraction residue 31 is neutralized. The origin of this alkaline solution 33 will be described later. The neutralization residue 35 neutralized in the extraction residue treatment step S217 is subjected to a dehydration treatment in the neutralization residue dehydration step S219, and the water component 37 is removed. The neutralization residue dehydration step S219 may be performed in a manner similar to the dehydration treatment S207 described above. The water component 37 generated here is used as part of the electrolyte 49 (FIG. 4), which will be described later. In this case, the water component 37 may be subjected to a purification treatment before being added to the electrolyte 49.

[0034] The neutralization residue 39 after dehydration in the neutralization residue dehydration step S219 is modified in the neutralization residue treatment step S221. That is, in the neutralization residue treatment step S221, the neutralization residue 39 is mixed with a solidification material 41 and solidified. As with the solidification material 7 described above, the solidification material 41 may be, for example, an alkaline solidification material such as cement or lime, or MgO (magnesium oxide). The neutralization residue 39 solidified by the solidification material 41 is then effectively utilized as civil engineering materials 43, such as bricks, blocks, backfill material, or modifier. This civil engineering material 43 is used, for example, in civil engineering works such as island development work carried out near rare earth mining sites.

[0035] The process for producing civil engineering materials 43 from the neutralization residue 35 (neutralization residue dehydration step S219 and neutralization residue treatment step S221) may be common to the process for producing civil engineering materials 19 from the classification residue 3 (dehydration step S203 and classification residue treatment step S209: FIG. 2). That is, the classification residue 3 (FIG. 2) generated in the classification step S201 and the neutralization residue 35 (FIG. 3) generated in the extraction residue treatment step S217 may be mixed and processed together. Specifically, this mixture is dehydrated using a method similar to the dehydration step S203 or the neutralization residue dehydration step S219, and the dehydrated product is treated using a method similar to the classification residue treatment step S209 or the neutralization residue treatment step S221 to produce civil engineering materials. In this way, civil engineering materials are produced from materials with a wide particle size distribution, which are a mixture of classified residue 3 with a relatively small particle size and neutralized residue 35 with a relatively large particle size, and therefore civil engineering materials of higher quality are obtained compared to civil engineering materials 19 and 43.

[0036] As described above, the rare earth production method of this embodiment includes a rare earth extraction method executed by the rare earth extraction system 101. The rare earth production method of this embodiment further includes the above-mentioned purification step S213, in which rare earths 25 are purified from the rare earth component-containing liquid 23, as described above.

[0037] Next, the process for producing the aforementioned acidic solution 17 (FIG. 2) and alkaline solution 33 (FIG. 3) will be described with reference to FIGS. 4 and 5. FIG. 5 is a diagram showing an electrolysis apparatus 325 used in the process shown in FIG. 4. In this process, the acidic solution 17 and alkaline solution 33 are obtained by electrolyzing pure water. Note that the term "pure water" used here does not only refer to pure water in the strict sense, but also includes water containing a small amount of electrolyte added to ensure the electrical conductivity required for practical use. Specific examples of the process for producing the acidic solution 17 and alkaline solution 33 will be described below.

[0038] The electrolysis device 325 shown in FIG. 5 includes an electrolytic cell 71 in which an electrolytic solution 49 is stored. The electrolytic solution 49 is pure water containing a small amount of electrolyte 47 (FIG. 4) added to ensure practical electrical conductivity. The raw water for the electrolytic solution 49 is produced by purifying seawater 45 (FIG. 4) from a rare earth mining site through a water purification process S222. The water purification process S222 may be performed by known methods such as reverse osmosis or distillation. Alternatively, the raw water for the electrolytic solution 49 may be purified freshwater available on land near the rare earth mining site. The electrolyte 47 contained in the electrolytic solution 49 does not contain Cl (chlorine) or I (iodine), and examples of such electrolytes include KOH, NaOH, H2SO4, and HNO3.

[0039] The electrolytic cell 71 includes an anode 73 and a cathode 75 immersed in the electrolytic solution 49, and a partition wall 79 that divides the interior of the electrolytic cell 71 into two sections, one between the anode 73 and the other between the cathode 75. The anode 73 and the cathode 75 are made of a chemically inert material and may be, for example, a graphite electrode. The partition wall 79 is a plate or membrane that allows ions in the electrolytic solution 49 to pass through, and may be, for example, a biscuit plate.

[0040] Furthermore, the electrolyzer 325 includes a power supply unit 77 that serves as an energy source for electrolysis. The power supply unit 77 includes a solar panel 323 that generates solar power and a power generation device 327, which will be described later, and applies a potential difference between the anode 73 and the cathode 75.

[0041] Using such an electrolyzer 325, the electrolysis step S225 is performed as shown in Fig. 4. That is, the electrolyte 49 is electrolyzed by electric energy 51 from the power supply unit 77 (Fig. 5). The chemical reactions occurring at the anode 73 and the cathode 75 are as follows. Anode 73: H2O(l) → 1 / 2O2(g) + 2H + + 2e - …(1) Cathode 75: 2H2O(l) + 2e - → H2(g) + 2OH - …(2)

[0042] As shown in the above formulas (1) and (2), in the electrolysis step S225, water in the electrolytic solution 49 is decomposed into oxygen gas 53 generated at the anode 73 and hydrogen gas 55 generated at the cathode 75. Also, as shown in the above formulas (1) and (2), hydrogen ions (H + ) is generated at the cathode 75, and hydroxide ions (OH - Therefore, in the space 83 on the anode 73 side in the electrolytic cell 71 divided into two by the partition wall 79, hydrogen ions (H + ) increases, and hydroxide ions (OH - ) increases.

[0043] Therefore, by extracting the electrolytic solution 49 from the anode-side space 83 of the electrolytic cell 71, an acidic solution 17 containing a large amount of hydrogen ions (i.e., a low pH) can be obtained. For example, an acidic solution 17 with a pH of about 0.5 can be obtained here. Similarly, by extracting the electrolytic solution 49 from the cathode-side space 85 of the electrolytic cell 71, an alkaline solution 33 containing a large amount of hydroxide ions (i.e., a high pH) can be obtained. For example, an alkaline solution 33 with a maximum pH of about 13.5 can be obtained here. The acidic solution 17 obtained as described above is then used in the extraction step S211 described above, as shown in FIG. 2. The alkaline solution 33 obtained as described above is then used in the extraction residue treatment step S217 described above, as shown in FIG. 3.

[0044] Next, a description will be given of the power supply unit 77. The solar panel 323 of the power supply unit 77 includes a solar cell. The solar panel 323 generates electric energy 51 by performing solar power generation S223 using sunlight on site, as shown in FIG.

[0045] The power generation device 327 of the power supply unit 77 performs the power generation step S227 (FIG. 4) by utilizing the oxygen gas 53 and hydrogen gas 55 generated in the electrolysis step S225 described above. For this reason, in the electrolysis step S225 described above, the generated oxygen gas 53 and hydrogen gas 55 are each recovered from the electrolysis device 325.

[0046] As shown schematically in Fig. 6, the power generation device 327 includes an electrolytic cell 91 in which an electrolytic solution 89 is stored, and a cathode 93 and an anode 95 immersed in the electrolytic solution 89. The cathode 93 and the anode 95 are electrically connected via an external circuit 98 outside the electrolytic solution 89. The electrolytic solution 89 is water to which a small amount of electrolyte has been added to ensure electrical conductivity. A porous material 97 such as cloth is provided on the surfaces of the cathode 93 and the anode 95 to supply gas evenly to the electrode surfaces.

[0047] In such a power generation device 327, oxygen gas 53 recovered from the electrolyzer 325 is supplied to the cathode 93, and hydrogen gas 55 is supplied to the anode 95. Then, the following chemical reaction occurs at the cathode 93 and the anode 95, causing a current to flow in the external circuit 98. By extracting the current from this external circuit 98, electrical energy 51 is obtained. Cathode 93: O2(g) + 2H + (aq) + 2e - → H2O(l) …(3) Anode 95: H2(g) + 2OH - (aq) → 2H2O(l) + 2e - …(4)

[0048] 6, as long as the power generation device 327 can generate electrical energy 51 by utilizing the oxygen gas 53 and hydrogen gas 55 generated in the electrolysis step S225. For example, the power generation device 327 may be a fuel cell. Furthermore, the power generation device 327 may be a device that ultimately generates electrical energy 51 by, for example, generating thermal energy or mechanical energy through a combustion reaction between the oxygen gas 53 and the hydrogen gas 55.

[0049] In the power supply unit 77 described above, multiple electrolytic cells 71 may be connected in series to one solar panel 323. Theoretically, electrolysis is possible if there is a potential difference of more than 1.3 V between the anode 73 and cathode 75 of one electrolytic cell 71. Therefore, the number of electrolytic cells 71 to be connected can be set according to the operating voltage of the solar panel 323 so that this potential difference can be satisfied. Furthermore, the presence of the power generation device 327 makes it possible to reduce the performance requirements of the solar panel 323. Furthermore, if the solar panel 323 can generate sufficient electrical energy 51, the power generation device 327 may be omitted.

[0050] Theoretically, when an acidic solution 17 with a pH of 0.5 is to be produced, the hydrogen ion concentration of this acidic solution 17 is about 0.316 mol / L, so 1 m 3 To produce this acid solution 17, 0.316 mol × 96485 kC = 30489.26 kC is required. If the voltage applied to one electrolytic cell 71 is 2 V, this theoretically corresponds to 16.94 kWh.

[0051] The power supply unit 77 may further include a power supply device other than the solar panel 323 and the power generation device 327. When the rare earth extraction system 101 is installed on the ship 105, another power supply device, generator, or battery mounted on the ship 105 may be used as the other power supply device. Use of such a power supply device enables a stable supply of electric energy 51. The power supply unit 77 may also include other types of power generation devices that generate electricity from energy sources present on-site (at or near the rare earth mining site), such as wind power generation devices or wave power generation devices, instead of or in addition to the solar panel 323.

[0052] Next, a rare earth extraction system 101 for carrying out the above-described rare earth extraction method will be described with reference to Fig. 7. As shown in Fig. 7, the rare earth extraction system 101 includes a classification device 301, a dehydration device 307, a separation device 305, a mixer 309, an extraction device 311, a neutralization reaction device 317, a water purification device 322, and an electrolysis device 325.

[0053] The classifier 301 is a device that performs the classification step S201 described above. For example, a hydrocyclone device or a decanter-type centrifuge is used as the classifier 301. The dehydrator 307 is a device that performs the dehydration treatments S203, S207, and S215 and the neutralization residue dehydration step S219 described above. For example, a decanter device or a filter press device is used as the dehydrator 307. The separator 305 is a device that performs the unnecessary matter removal step S205 described above. For example, a microbubble flotation device is used as the separator 305.

[0054] The mixer 309 is an apparatus that performs the above-mentioned classification residue processing step S209 and neutralization residue processing step S221. For example, the mixer 309 has a mixing container (not shown) into which the classification residue 3, neutralization residue 39, and solidification materials 7 and 41 are charged, and a stirring unit (not shown) that stirs the mixture.

[0055] The extraction apparatus 311 is an apparatus that performs the extraction step S211 described above. For example, the extraction apparatus 311 includes a reaction vessel (not shown) into which the rare earth-containing mud 15 and the acidic liquid 17 are introduced, an agitation unit (not shown) that agitates the mixture, and a solid-liquid separation unit (not shown) that separates the rare earth component-containing liquid 23 from the extraction residue 27.

[0056] The neutralization reaction apparatus 317 is an apparatus that performs the extraction residue treatment step S217. For example, the neutralization reaction apparatus 317 has a reaction vessel (not shown) into which the dehydrated extraction residue 31 and the alkaline solution 33 are charged, and a stirring unit (not shown) that stirs the mixture.

[0057] The water purifier 322 is a device that performs the above-mentioned water purification process S222. For example, the water purifier 322 may be a reverse osmosis membrane device, a distillation device, or any other known pure water production device.

[0058] Electrolyzer 325 is an apparatus that performs the electrolysis step S225 described above. As described with reference to Figures 5 and 6, electrolyzer 325 includes electrolytic cell 71 and power supply unit 77, which includes solar panel 323 and power generation device 327. Power supply unit 77 may include another type of power generation device that generates power from an on-site energy source, such as a wind power generation device or a wave power generation device, instead of or in addition to solar panel 323. If such a power generation device that generates power from an on-site energy source (such as solar panel 323, wind power generation device, or wave power generation device) can generate sufficient electrical energy 51, power generation device 327 may be omitted.

[0059] Note that a known rare earth refining system for refining rare earths from a rare earth component-containing liquid is adopted as the rare earth refining system 313 that performs the refining step S213. The rare earth refining system 313 may be installed on the ship 105 in parallel with the rare earth extraction system 101. Alternatively, the rare earth refining system 313 may be installed on land near the rare earth mining site. The rare earth refining system 313 obtains rare earths 25 by treating the rare earth component-containing liquid 23 with a predetermined refining process.

[0060] A rare earth production system 100 that implements the rare earth production method of this embodiment includes a rare earth extraction system 101 and a rare earth refining system 313. The components of the rare earth production system 100, including on a ship 105, may be appropriately arranged near a rare earth mining site.

[0061] The effects of the rare earth extraction method, rare earth production method, and rare earth extraction system 101 of this embodiment described above will be described.

[0062] In the rare earth extraction method performed by the rare earth extraction system 101 of this embodiment, the acidic solution 17 required in the extraction step S211 is obtained by electrolysis in the electrolysis step S225. Therefore, if water for preparing the electrolyte solution 49 is obtained near the rare earth mining site, the acidic solution 17 can be produced using this water as a material. This eliminates the need to transport the acidic solution 17 from the mainland to a remote rare earth mining site, reducing the burden of transporting materials.

[0063] The rare earth extraction method of this embodiment also includes an extraction residue treatment step S217 in which the extraction residue 31 generated in the extraction step S211 is neutralized and modified with an alkaline solution 33 generated in the electrolysis step S225. That is, the alkaline solution 33 required in the extraction residue treatment step S217 is also obtained by electrolysis in the electrolysis step S225. Therefore, there is no need to transport the alkaline solution 33 from the mainland to a remote rare earth mining site, further reducing the burden of transporting materials.

[0064] That is, the materials supplied from outside to this rare earth extraction system 101 are mainly a small amount of electrolyte 47 for preparing electrolytic solution 49, solidifying materials 7 and 41, etc., and there is no need to supply from outside the acidic solution 17 or alkaline solution 33, which are required in large quantities. Therefore, there is no need to transport large amounts of acidic solution 17 or alkaline solution 33 from the mainland to remote rare earth mining sites, reducing the burden of transporting materials.

[0065] Furthermore, the electrolyte solution 49 in the electrolysis step S225 is pure water containing a small amount of electrolyte 47 added to ensure practically necessary electrical conductivity. Therefore, the electrolyte contained in the acidic solution 17 is theoretically only a small amount derived from the electrolyte 47, and as a result, the electrolyte contained in the extraction residue 27 is also small. In other words, compared to when common hydrochloric acid or sulfuric acid is used as the acidic solution 17, the electrolyte contained in the extraction residue 27 can be said to be extremely small. In this way, the electrolyte content in the generated extraction residue 27 is kept low, which broadens the range of uses for this extraction residue 27 and allows for an increase in the amount of extraction residue 27 that can be effectively utilized.

[0066] While the above-mentioned electrolytes can be a factor in the deterioration of concrete and mortar, the extraction residue 27 contains a small amount of electrolytes, and therefore the extraction residue 27 can be used as a raw material for relatively high-quality civil engineering materials 43 with fewer factors that can cause deterioration. That is, by subjecting the extraction residue 27 to the extraction residue treatment step S217 and the neutralization residue treatment step S221, etc., a high-quality civil engineering material 43 with fewer neutralized salts that can cause deterioration can be obtained.

[0067] The alkaline solution 33 used in the extraction residue treatment step S217 is also obtained by electrolysis in the electrolysis step S225. Therefore, the electrolyte contained in the alkaline solution 33 is theoretically only a small amount derived from the electrolyte 47. This also reduces the content of neutralized salts in the civil engineering material 43.

[0068] Among electrolytes, Cl (chlorine) and I (iodine) are particularly likely to be major degradation factors for concrete and mortar, and therefore, an electrolyte 47 that does not contain Cl or I is adopted as the electrolyte 47 added to the electrolytic solution 49. Therefore, the extraction residue 27 can be a raw material for relatively high-quality civil engineering materials 43 that contain fewer major degradation factors such as Cl and I. That is, by subjecting this extraction residue 27 to the extraction residue treatment step S217 and the neutralization residue treatment step S221, etc., a high-quality civil engineering material 43 that contains fewer Cl and I salts that can be particularly likely to be degradation factors can be obtained.

[0069] The use of the neutralization residue 39 is not limited to the material for the civil engineering materials 43. That is, since the acidic solution 17 and the alkaline solution 33 are obtained by electrolysis of pure water, as described above, the amount of neutralized salt generated in these neutralization reactions is small, and therefore the amount of neutralized salt contained in the neutralization residue 39 is small. Therefore, the range of uses for the neutralization residue 39 is widened, and much of the neutralization residue 39 can be effectively utilized.

[0070] In the rare earth extraction method of this embodiment, a portion of the electrical energy 51 used in the electrolysis step S225 is generated in the power generation step S227, which utilizes the hydrogen gas 55 and oxygen gas 53 generated in the electrolysis step S225. This configuration makes it possible to effectively utilize the hydrogen gas 55 and oxygen gas 53, thereby reducing the amount of energy that needs to be supplied from outside to the electrolysis device 325. This in turn reduces the amount of energy that needs to be transported from the mainland to remote rare earth mining sites, further reducing the burden of transporting materials.

[0071] Furthermore, in the electrolysis step S225, power obtained from a power generation device (e.g., solar panel 323, wind power generation device, wave power generation device, etc.) that generates power from an energy source present on-site (at or near the rare earth mining site) is used as at least a portion of the electrical energy 51. For example, in the example shown in FIG. 4, power generated by the solar cell of the solar panel 323 is used as at least a portion of the electrical energy 51 in the electrolysis step S225. With this configuration, a portion of the electrical energy 51 can be generated from an energy source present on-site (e.g., solar light, wind power, wave power, etc.). Therefore, the amount of energy that needs to be supplied from an external source to the electrolysis device 325 can be reduced, which in turn reduces the amount of energy sources that need to be transported from the mainland to the remote rare earth mining site, further reducing the burden of transporting materials.

[0072] In the rare earth extraction method of this embodiment, the seabed mud 1 is classified in a classification step S201 prior to the extraction step S211, and the classified large-particle mud 5 is introduced into the extraction step S211. Since rare earths are contained in relatively large amounts in the large-particle mud of the seabed mud 1, by classifying the seabed mud 1 in advance and proceeding only with the large-particle mud 5 to the extraction step S211, the feasibility of this rare earth mining business can be improved.

[0073] Furthermore, after the undesired matter 13 containing amphitheatrein is separated and removed from the large-grain mud 5 classified in the classification step S201 in the undesired matter removal step S205, the treated mud is introduced into the extraction step S211. Because this type of undesired matter 13 containing amphitheatrein reacts with acid, if the process proceeds to the extraction step S211 without separating and removing the undesired matter 13, a larger amount of acidic solution 17 is required to react with the undesired matter 13. In contrast, in the rare earth extraction method of this embodiment, the undesired matter removal step S205 is performed before the extraction step S211, thereby reducing the amount of acidic solution 17 required. This ultimately reduces the amount of materials that need to be transported from the mainland to remote rare earth mining sites, further easing the burden of transporting materials.

[0074] The rare earth extraction method of this embodiment includes a classification residue processing step S209 in which the classification residue 3 generated in the classification step S201 is mixed with a solidification material 7 to solidify and modify the residue. The rare earth extraction method of this embodiment also includes a neutralization residue processing step S221 in which the neutralization residue 39, which has been treated in the extraction residue processing step S217, is mixed with a solidification material 41 to solidify and modify the residue. The classification residue processing step S209 and the neutralization residue processing step S221 allow the residues to be effectively utilized as civil engineering materials 19, 43, thereby reducing the burden of residue disposal. Furthermore, if these civil engineering materials 19, 43 are used in civil engineering work, such as island development work, carried out near a rare earth mining site, the amount of materials transported from the mainland to the civil engineering work site is reduced, thereby easing the burden of material transportation.

[0075] Furthermore, the rare earth extraction method of this embodiment includes a neutralization residue dehydration step S219 in which the neutralization residue 35 is dehydrated prior to the neutralization residue treatment step S211. The water component 37 generated by this dehydration treatment is used as part of the electrolyte solution 49 in the electrolysis step S225. Similarly, the water component 29 generated by the dehydration treatment S215 of the extraction residue 27 is also used as part of the electrolyte solution 49 in the electrolysis step S225. By reusing the water components 29 and 37, which contain relatively little seawater components, as material for the electrolyte solution 49, the consumption of the electrolyte solution 49 and the electrolyte 47 can be reduced.

[0076] (Reference form) Although the effect of expanding the range of uses for extraction residue 27 as described above is reduced, electrolyte 49 does not necessarily have to be pure water. For example, even in the following case, it is not necessary to transport large amounts of acidic solution 17 or alkaline solution 33 from the mainland to a remote rare earth mining site, and the burden of transporting materials is reduced.

[0077] For example, the electrolytic solution 49 may be a sodium hydroxide aqueous solution. Even in this case, oxygen gas and hydrogen gas are generated at the anode 73 and the cathode 75 of the electrolyzer 325, so the power generation device 327 can be used as part of the power supply unit 77. Alternatively, for example, the electrolytic solution 49 may be a hydrochloric acid aqueous solution. In this case, chlorine gas rather than oxygen gas is generated from the anode 73, and hydrogen gas is generated from the cathode 75. In this case, the power generation device 327 cannot be used as part of the power supply unit 77, but this is not a problem as long as the required performance of the power supply unit 77 is satisfied by the solar panel 323 alone.

[0078] The electrolyte 49 may also be seawater. Alternatively, the electrolyte 49 may be freshwater. The above-mentioned freshwater may be freshwater obtained, for example, from land near a rare earth mining site. In these cases, the water purification process S222 can be omitted, making it easier to prepare the electrolyte 49. Furthermore, when the electrolyte 49 is freshwater, it contains less Cl and other elements than seawater. Therefore, the extraction residue 27 can be used as a relatively high-quality civil engineering material 43 with fewer major degradation factors such as Cl. In this case, the neutralized salt in the neutralization residue 39 also contains little Cl. Therefore, the range of uses for the neutralization residue 39 is wider, and much of the neutralization residue 39 can be effectively utilized.

[0079] The present invention can be implemented in various forms, including the above-described embodiment, with various modifications and improvements based on the knowledge of those skilled in the art. It is also possible to configure modified examples by utilizing the technical matters described in the above-described embodiment. The configurations of the respective embodiments may be used in appropriate combination. [Explanation of symbols]

[0080] 3...Classification residue, 5...Large grain mud, 7, 41...Solidification material, 13...Unwanted matter, 15...Rare earth-containing mud, 17...Acidic liquid, 23...Rare earth-containing liquid (rare earth component), 27...Extraction residue, 33...Alkaline liquid, 35...Neutralization residue, 49...Electrolyzed water (pure water), 53...Oxygen gas, 55...Hydrogen gas, 101...Rare earth extraction system, 311...Extraction device (extraction section), 323...Solar panel (solar cell), 325...Electrolyzer (electrolysis section), S201...Classification process, S205...Unwanted matter removal process, S209...Classification residue treatment process, S211...Extraction process, S217...Extraction residue treatment process, S219...Neutralization residue dehydration process, S221...Neutralization residue treatment process, S225...Electrolysis process, S227...Power generation process.

Claims

1. an electrolysis step of obtaining an acidic solution by electrolysis of pure water; an extraction step of extracting rare earth components contained in the rare earth-containing mud lifted up from the seabed to the ocean surface using the acidic solution obtained in the electrolysis step; A rare earth extraction method comprising:

2. 2. The rare earth extraction method according to claim 1, further comprising a power generation step of generating a portion of the electrical energy used in the electrolysis step by utilizing the hydrogen gas and oxygen gas generated in the electrolysis step.

3. 2. The rare earth extraction method according to claim 1, wherein in the electrolysis step, electricity generated by a solar cell is used as at least a part of the energy for the electrolysis.

4. 2. The rare earth extraction method according to claim 1, further comprising a classification step, prior to the extraction step, of classifying the mud brought up from the seabed to the ocean surface and obtaining the classified mud with larger particles as the rare earth-containing mud to be used in the extraction step.

5. 5. The rare earth extraction method according to claim 4, wherein the classification step is performed using a hydrocyclone device or a decanter-type centrifuge.

6. 5. The rare earth extraction method according to claim 4, further comprising, prior to the extraction step, a waste material removal step of separating and removing waste materials containing aphidite from the large grain mud classified in the classification step.

7. 7. The rare earth extraction method according to claim 6, further comprising a classification residue treatment step of mixing a solidification material with the small particle classification residue generated in the classification step to solidify and modify it.

8. 2. The rare earth extraction method according to claim 1, further comprising an extraction residue treatment step of neutralizing and modifying the extraction residue generated in the extraction step with the alkaline solution generated in the electrolysis step.

9. 9. The rare earth extraction method according to claim 8, further comprising a neutralization residue treatment step of mixing a solidification material with the neutralization residue treated in the extraction residue treatment step to solidify and modify the neutralization residue.

10. The method further includes a neutralization residue dehydration step of dehydrating the neutralization residue before the neutralization residue treatment step, 10. The rare earth extraction method according to claim 9, wherein the water component separated and removed from the neutralization residue in the neutralization residue dehydration step is used as part of the water to be electrolyzed in the electrolysis step.

11. an electrolysis unit for obtaining an acidic solution by electrolysis of pure water; an extraction unit that extracts rare earth components contained in the rare earth-containing mud that has been brought up from the seabed to the ocean surface using the acidic solution obtained in the electrolysis unit; A rare earth extraction system comprising:

12. an electrolysis step of obtaining an acidic solution by electrolysis of pure water; an extraction step of extracting rare earth components contained in the rare earth-containing mud lifted up from the seabed to the ocean surface using the acidic solution obtained in the electrolysis step; A method for producing rare earths comprising:

Images