Lithium recovery method and lithium recovery system

Abstract

To produce lithium with reduced energy consumption, cost, and environmental burden.SOLUTION: A lithium recovery method for recovering lithium from a lithium-containing medium comprises: cultivating a salt-tolerant plant or a salt-resistant plant using the medium; and recovering the lithium concentrated in the body of the salt-tolerant plant or the salt-resistant plant, or the lithium discharged from the plant body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a lithium recovery method and system. [Background technology]

[0002] Demand for lithium has been increasing in recent years, and this trend is expected to continue. For example, lithium-ion batteries are used as the primary power source for electric vehicles. The widespread use of electric vehicles is being promoted to reduce greenhouse gas emissions, and demand is expected to continue to increase. However, lithium has problems, such as unstable supply and environmental impacts such as water and soil contamination during its production process (see, for example, Non-Patent Document 1). Known sources of lithium resources are broadly divided into hydrospheres, such as continental salt lakes, brines, and seawater, and geospheres, such as lithium deposits. Two known lithium production methods are the concentration of "salt lake brines" from the hydrosphere and the purification of minerals such as "spodumene ore (spodumene pyroxene)" from the geosphere (see, for example, Non-Patent Document 2). These production processes require a lot of energy and cost, and consume large amounts of water. Therefore, expanding lithium production raises concerns about water shortages for agricultural and domestic use, for example. Furthermore, since by-products such as sodium sulfate are generated during the lithium refining process, there is a problem that wastewater generated during lithium refining pollutes water and soil. Therefore, there has been a demand for lithium production technology that can reduce the environmental burden described above while suppressing energy consumption. Furthermore, as a problem related to the environmental burden of lithium, there has been an environmental problem caused by waste generated from used lithium-ion batteries as a pollution source (see, for example, Non-Patent Document 3).

[0003] In addition to the lithium resource sources already described, lithium is known to be contained in soil, mainly in clay minerals, at a concentration of about 7-200 ppm (see, for example, Non-Patent Document 4), and it is also known that Japanese soil contains 10-100 ppm of lithium (see, for example, Non-Patent Document 5).

[0004] Conventional methods for recovering metals from soil include the use of plants known as hyperaccumulators, which accumulate specific metals at high concentrations (see, for example, Non-Patent Documents 6-9 and Patent Documents 1-6). More specifically, phytoremediation utilizes the metal accumulation capabilities of plants, such as hyperaccumulators, to purify contaminated soil. Phytomining also utilizes plants to recover trace amounts of rare metals present in soil. Phytoremediation is a low-cost, low-environmental impact environmental remediation technique that uses plant absorption, accumulation, metabolism, and decomposition to remove contaminants from soil and other environments (see, for example, Non-Patent Documents 10-12). The target substances are organic pollutants such as heavy metals and dioxins, which are sources of contamination. Phytomining primarily targets high-value-added precious metals and rare metals. It involves adsorbing and accumulating the target metal ions within plants from soil and other environments, then recovering the plants and extracting and refining the target metals. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-45875 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-92172 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-159181 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-75821 [Patent Document 5] Japanese Patent Application Laid-Open No. 2004-275051 [Patent Document 6] Japanese Patent Application Laid-Open No. 2002-336837 [Non-patent literature]

[0006] [Non-Patent Document 1] Japan Research Institute Research Focus “Lithium production issues affecting the global shift to EVs”, No. 2022-012 [Non-patent document 2] Shunzo Ishihara, "Granite Petrology and Pegmatite Resource Theory for Lithium," Geological News No. 670, pp. 27-45, June 2010 [Non-patent document 3] Wojciech Mrozik et al., "Environmental impacts, pollution sources and pathway of spent lithium-ion batterise", Energy Environ. Sci., 2021. [Non-patent document 4] Cannon, HL et al., "Lithium in Unconsolidated Sediments and Plants of the Basin and Range Province, Southern California and Nevada" 1975(No.918); United States Government Printing Office: Washington, DC, USA [Non-Patent Document 5] Mitsutsune Ohta et al., "Soil Geochemical Map of Japan", Geochemistry Vol. 57, pp. 247-278, 2023 [Non-patent document 6] Barbara Leitenmaier et al., "Compartmentation and complexity of metals in hyperaccumulator plants", Front. Plant Sci., 4, 374, 2013. [Non-Patent Document 7] Roger D. Reeves et al., "A global database for plants that hyperaccumulate metal and metalloid trace elements", New Phytol., 218, 407-411, 2017. [Non-patent document 8] Mitch M. Lasat, "Phytoextraction of Toxic Metals: A Review of Biological Mechanisms", J. Environ. Qual., 31, 109-120, 2002. [Non-Patent Document 9] Laurence Kavanagh et al., "Induced Plant Accumulation of Lithium", Geosciences, 2018, 8, 56. [Non-Patent Document 10] An Yan et al., "Phytoremediation: A Promising Approach for Revegetation of Heavy Metal-Polluted Land", Front. Plant Sci., 11, 359, 2020. [Non-Patent Document 11] Mitsutake Yoshida et al., "Current Status and Issues of Phytoremediation", Taisei Corporation Technology Center Report, No. 38, 06, 2005. [Non-Patent Document 12] Wang Xiaoqian et al., "Phytoremediation of Contaminated Soil," Bulletin of the Saitama Prefectural International Center for Environmental Science, No. 3, 114-123, 2004. Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, lithium purification technology that can reduce energy consumption and costs while further mitigating the environmental impact compared to conventional methods for producing lithium from lithium resource sources has been desired, but such technology has not been fully explored. While technology for recovering specific metals from soil using hyperaccumulator plants is considered to be a technology that can at least reduce the environmental impact, no technology for recovering lithium has been known. For example, Non-Patent Document 9 shows that lithium accumulation in plants of the Brassicaceae family can be induced by using chelating agents such as ethylenediaminetetraacetic acid (EDTA) and ethylenediamine-N,N'-disuccinic acid (EDDS). However, the feasibility of recovering lithium has not been fully explored. [Means for solving the problem]

[0008] The present disclosure can be realized in the following forms. (1) According to one embodiment of the present disclosure, there is provided a method for recovering lithium from a medium containing lithium, comprising cultivating a halophyte or a salt-tolerant plant in the medium, and recovering lithium concentrated inside the plant body of the halophyte or the salt-tolerant plant or lithium excreted from the plant body. According to this embodiment of the lithium recovery method, lithium can be recovered from the medium by a very simple method in which a halophyte or a salt-tolerant plant is cultivated in a medium containing lithium, and lithium concentrated inside the plant or lithium excreted from the plant is recovered. Therefore, lithium can be produced while reducing energy consumption, costs, and environmental impact. (2) In the lithium recovery method of the above aspect, the plant may have salt glands, and lithium excreted from the salt glands may be recovered. With this configuration, the plant can continue to grow without being damaged, and steps such as recovery, dissolution, and extraction of the plant can be eliminated, thereby enabling highly efficient and sustainable recovery of lithium while significantly reducing energy consumption, costs, and environmental impact. (3) In the lithium recovery method of the above aspect, the lithium discharged from the salt glands to the surface of the plant may be recovered using a suction device. With this configuration, the simple method of using a suction device makes it possible to recover a large amount of lithium at once while suppressing the inclusion of impurities, thereby improving recovery efficiency. (4) In the lithium recovery method of the above aspect, the lithium excreted from the salt glands to the surface of the plant may be recovered by washing the surface of the plant with a washing solution. With this configuration, lithium can be recovered by the simple method of washing the surface of the plant. (5) In the lithium recovery method of the above aspect, lithium may be recovered from the plant having bicellular salt glands or multicellular salt glands. With this configuration, the operation of recovering lithium from the surface of the plant can be easily performed. (6) In the lithium recovery method of the above aspect, Rhodes grass may be used as the halophyte or salt-tolerant plant. With this configuration, lithium can be recovered more efficiently and easily. (7) In the lithium recovery method of the above embodiment, the medium may be soil containing 1 ppm or more and 1000 ppm or less of lithium. With this configuration, lithium can be recovered from a lithium source that has been difficult to use in the past. (8) In the lithium recovery method of the above aspect, the medium may be an aqueous solution containing 1 ppm or more and 1000 ppm or less of lithium. With this configuration, lithium can be recovered from a lithium source that has been difficult to use in the past. (9) According to another aspect of the present disclosure, there is provided a lithium recovery system for recovering lithium from a medium containing lithium, the lithium recovery system including: a cultivation unit including a halophyte or halotolerant plant and an aqueous medium that is an aqueous solution for cultivation, the cultivation unit cultivating the halophyte or halotolerant plant using the aqueous medium; and an aqueous medium supply unit supplying the cultivation unit with a lithium-containing liquid from which lithium is to be recovered as the aqueous medium. According to this lithium recovery system, halophytes or halotolerant plants are cultivated in the cultivation unit using an aqueous medium that is a lithium-containing solution supplied from the aqueous medium supply unit. This makes it possible to recover lithium concentrated inside the halophytes or halotolerant plants and lithium discharged from the plants, thereby recovering lithium from the aqueous medium while reducing energy consumption, costs, and environmental impact. (10) In the lithium recovery system of the above aspect, the cultivation unit may perform hydroponic cultivation of the halophyte or salt-tolerant plant using the aqueous medium. With this configuration, lithium can be recovered by a simple method of hydroponic cultivation of the halophyte or salt-tolerant plant. (11) In the lithium recovery system of the above aspect, the lithium-containing liquid may be a lithium-containing waste liquid generated in a lithium production process or a lithium recycling process. With such a configuration, the utilization efficiency of lithium can be improved. The present disclosure can be realized in various forms other than those described above, such as a method for recycling lithium, a method for recycling lithium-ion batteries, a method for purifying lithium-contaminated soil, a method for purifying lithium-containing wastewater, and a method for improving lithium production efficiency. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flowchart showing a lithium recovery method. [Figure 2] FIG. 1 is an explanatory diagram schematically illustrating an example of a lithium recovery system. [Figure 3]An explanatory diagram showing the cultivation conditions and measurement results for Rhodes grass. [Figure 4] An explanatory diagram showing the cultivation conditions and measurement results for plants other than Rhodes grass. [Figure 5] FIG. 1 is an explanatory diagram schematically illustrating the configuration of a hydroponic cultivation device. [Figure 6] FIG. 1 is an explanatory diagram showing a schematic diagram of soil cultivation. [Figure 7] An explanatory diagram showing an optical microscope image of a cross section of the sixth leaf of Rhodes grass. [Figure 8] An explanatory diagram showing a secondary electron image of a cross section of the sixth leaf of Rhodes grass. [Figure 9] An explanatory diagram showing a photograph of hydroponically grown Rhodes grass 24 days after sowing. [Figure 10] FIG. 1 is an explanatory diagram showing the relationship between the dry weight of Rhodes grass and the LiCl concentration. [Figure 11] An explanatory diagram showing an optical photograph of the abaxial side of a leaf after the addition of 2 mM LiCl. [Figure 12] FIG. 10 is an explanatory diagram showing the relationship between the amount of discharged salt and the amount of discharged Li and the LiCl concentration. [Figure 13] FIG. 10 is a graph showing the relationship between the discharged salt Li concentration, the aboveground Li concentration, and the added LiCl concentration. [Figure 14] An explanatory diagram showing a photograph of Rhodes grass grown in Li-added soil after 35 days. [Figure 15] FIG. 1 is an explanatory diagram showing the measurement results of the dry weight of the aboveground parts and the amount of Li released after soil cultivation. [Figure 16] This figure shows a photograph of a filter when salt is collected from leaves using the vacuum method. [Figure 17] An explanatory diagram showing a photograph of Nipponbare grown hydroponically 24 days after sowing. [Figure 18] FIG. 1 is an explanatory diagram showing the relationship between the dry weight of Nipponbare and the LiCl concentration. [Figure 19] FIG. 1 is an explanatory diagram showing a photograph of an ice plant grown in soil. [Figure 20] An explanatory diagram showing a photograph of soil-grown okahijiki. DETAILED DESCRIPTION OF THE INVENTION

[0010] A. Lithium recovery method: FIG. 1 is a flowchart showing a lithium recovery method according to an embodiment of the present disclosure. When carrying out the lithium recovery method of this embodiment, first, a halophyte or halotolerant plant and a medium containing lithium are prepared (step T100). Hereinafter, "halophyte" and "halotolerant plant" will be collectively referred to as "halotolerant plant, etc.", and a "medium containing lithium" will be referred to as "Li-containing medium." Furthermore, lithium can exist in various forms, such as lithium ions and lithium salts, but in the following description, these forms may be referred to as "lithium" without distinction.

[0011] Here, "halophytes" refers to plants (especially seed plants) that can tolerate relatively high salt concentrations, while "salt-tolerant plants" refer to plants that are resistant to growth inhibition up to a certain salt concentration. Plants are classified into three types based on their growth response to salt, particularly NaCl: "salt-sensitive plants," "salt-tolerant plants," and "halophytes." Most plants belong to the "salt-sensitive" category and rapidly experience a decrease in growth or growth impairment in response to salt stress. "Salt-tolerant plants" can tolerate and maintain growth up to a certain level of salt stress, but beyond that, changes such as a decrease in growth, damage to leaf and stem morphology, and yellowing of the plant body are observed. "Halophytes" generally have the property of increasing growth under salt stress levels that would reduce the growth of "salt-sensitive" or "salt-tolerant" plants, and some species can survive and continue to grow under salt stress up to the salt concentration of seawater (approximately 3% NaCl). For example, the halophyte Salicornia glomerata achieves high tolerance to salt stress by accumulating excess salt in a part of the plant body, causing the tissues in that part, except for the vascular sheath, to wither and die.

[0012] At least some of these "salt-tolerant plants" possess organs called "salt glands." Salt glands are found in a variety of dicotyledonous and monocotyledonous plant species, and have been reported in over 50 species across 14 families (Front. Plant Sci. 8 1-20, 2017). The structure of salt glands varies by species, but they can be broadly classified into three types: saccular-hair salt glands, multicellular salt glands, and bicellular salt glands (Jpn. J. Crop Sci., 90, 235-246, 2021).

[0013] Saccular hair-type salt glands, also known as bladder cells, are found in plants of the Amaranthaceae family, such as Chenopodium album and quinoa, and in plants of the Aizoaceae family, such as ice plants. Bladder cells are approximately 1,000 times larger than normal cells and accumulate high concentrations of salt within the cells. Multicellular salt glands are found in 11 other dicotyledonous families, including the mangrove tree Avicennia marina. Bicellular salt glands are found in grasses. Almost all grasses, except for those in the Pooideae subfamily, are known to have bicellular hairs in the epidermis of their aboveground parts. In particular, some in the Chloridoideae subfamily have been shown to function as salt glands, actively excreting salt (Front. Plant Sci. 8 1-20, 2017).

[0014] The lithium recovery method of this embodiment, as described below, involves cultivating a salt-tolerant plant or the like in a Li-containing medium and recovering lithium from the plant or the like in a Li-containing medium. The various salt-tolerant plants described above can be used as the salt-tolerant plant or the like for this purpose. Using a salt-tolerant plant or the like belonging to the Amaranthaceae family, which has a "saccular-hair-type salt gland," enables efficient recovery of lithium concentrated in bladder cells. Furthermore, using a salt-tolerant plant or the like, such as mangrove marina, which has a "multicellular salt gland," or a salt-tolerant plant or the like belonging to the Poaceae subfamily, such as Rhodes grass (Chloris gayana Kunth), which has a "bicellular salt gland," allows relatively high concentrations of lithium-containing salts to be continuously secreted from the salt glands. The secreted salts can then be recovered. This allows for highly efficient and sustainable lithium recovery while continuing to grow the plant without harming it and significantly reducing energy consumption, costs, and environmental impact.

[0015] In general, classifications such as "halophytes" and "halotolerant plants" are often evaluated based on their tolerance to sodium (Na) using NaCl or the like. It is particularly important that the "halotolerant plants, etc." used in the lithium recovery method of this embodiment have high tolerance to lithium (Li). From this perspective, Rhodes grass is particularly preferable as the "halotolerant plants, etc." This is because, although "halophytes" have higher tolerance to sodium (Na) than "halotolerant plants," Rhodes grass, which is a "halotolerant plant," has the property of being more tolerant to lithium (Li) than the "halophytes" ice plant and seaweed, as will be described later.

[0016] As described above, the "salt-tolerant plants, etc." used in this embodiment may be those that have "saccular hair-type salt glands" and store lithium within their bodies, or those that have "multicellular salt glands" or "bicellular salt glands" and secrete lithium from the salt glands. The "salt-tolerant plants, etc." used in this embodiment are preferably plants that can grow while storing a certain amount of lithium (Li) within their bodies when cultivated in a Li-containing medium (Li-accumulating plants).

[0017] The "Li-containing medium" prepared together with the "salt-tolerant plants, etc." in step T100 of FIG. 1 is a medium containing the lithium to be recovered. The "Li-containing medium" is a medium used to cultivate the "salt-tolerant plants, etc." as described below, and can be water or soil. The "Li-containing medium" may be, for example, soil containing 1 ppm or more and 1000 ppm or less of lithium, or an aqueous solution containing 1 ppm or more and 1000 ppm or less of lithium. The lithium concentration in the "Li-containing medium" may be adjusted as appropriate depending on the level of lithium tolerance of the "salt-tolerant plants, etc." (including the extent to which the lithium concentration affects the growth rate) and the extent to which the lithium concentration affects the lithium accumulation and lithium secretion capabilities of the "salt-tolerant plants, etc."

[0018] Such a "Li-containing medium" may be, for example, a lithium-containing waste liquid generated during lithium production by other lithium production methods. As in the case of producing lithium from hydrosphere lithium resources described above, lithium recovery from a lithium-containing liquid can be performed relatively easily by chemical methods or methods using adsorbents. However, it has been difficult to recover lithium from a lithium-containing liquid with a sufficiently high efficiency. Specifically, recovering more than 90% of lithium from hydrosphere lithium resources has been difficult from a cost perspective. Thus, after lithium recovery from hydrosphere lithium resources using a conventional method, a lithium-containing waste liquid containing a relatively low concentration of lithium can be used as a "Li-containing medium." This can improve lithium production efficiency while suppressing cost increases, for example. Furthermore, using such a lithium-containing waste liquid moderately reduces the lithium concentration in the "Li-containing medium," facilitating lithium recovery from a medium with a lithium concentration suitable for cultivating "salt-tolerant plants, etc."

[0019] The "Li-containing medium" can also be lithium-containing wastewater generated during the lithium recycling process from lithium-containing devices. For example, the lithium-ion battery recycling process involves dissolving metals through acid treatment followed by extraction to recover the metals. However, the efficiency of such metal recovery is known to be lower than that of other metal elements, e.g., 91-99% for nickel (Ni), 95-99% for cobalt (Co), and 94-99% for manganese (Mn), while the efficiency for lithium (Li) is only 80-90% (Carbon Energy, 2, 6-43, 2020). As a result, a large amount of wastewater containing unrecovered lithium ions is discharged. Using such lithium-containing wastewater as the "Li-containing medium" can increase the lithium recycling efficiency. Furthermore, reducing the lithium concentration in the wastewater can reduce pollution of the wastewater receiving area.

[0020] Furthermore, the "Li-containing medium" may be a mineral with a relatively low lithium concentration, which has not previously been mined among the aforementioned geospheric lithium resources, or soil containing such a mineral. Generally, when mining lithium, minerals with a higher lithium concentration are prioritized, while minerals with a lower lithium concentration are postponed for recovery. Furthermore, minerals with a lower lithium concentration tend to have a lower recovery efficiency relative to the cost. By using minerals with a relatively low lithium concentration, such as those described above, as the "Li-containing medium," it becomes easier to recover lithium, which has previously been difficult to recover. Furthermore, by using minerals with a relatively low lithium concentration, such as those described above, it becomes easier to recover lithium from a medium with a lithium concentration suitable for the cultivation of "salt-tolerant plants, etc." Furthermore, if there is already soil contaminated with lithium due to the aforementioned lithium production or lithium recycling, such lithium-contaminated soil may be used as the "Li-containing medium."

[0021] Returning to FIG. 1 , after the "salt-tolerant plants, etc." and the "Li-containing medium" are prepared in step T100, the "salt-tolerant plants, etc." are then cultivated using the "Li-containing medium" (step T110). When the "Li-containing medium" is soil, the "salt-tolerant plants, etc." can be cultivated by planting them directly in such soil. In this case, for example, the "salt-tolerant plants, etc." may be planted in a cultivation container containing the "Li-containing medium," or the "salt-tolerant plants, etc." may be planted in land containing lithium-contaminated soil as the "Li-containing medium." Alternatively, the "salt-tolerant plants, etc." may be cultivated by mixing soil with a lower lithium concentration with the soil serving as the "Li-containing medium" to adjust the lithium concentration in the soil. Furthermore, when using plants that have already been planted in land with a relatively low lithium concentration (for example, grasses such as Rhodes grass planted in a pasture) as the "salt-tolerant plants, etc.", the "Li-containing medium" may be mixed (plowed) into the soil (pasture, etc.) in which such "salt-tolerant plants, etc." are planted.

[0022] Generally, clay and humus in soil are negatively charged, so cations, including lithium ions, are adsorbed (base exchanged) and retained in the soil. Therefore, when cultivating salt-tolerant plants in soil containing a Li-containing medium as described above, chelating agents such as ethylenediaminetetraacetic acid (EDTA) or ethylenediamine-N,N'-disuccinic acid (EDDS) can be added to the soil to dissolve the adsorbed lithium and facilitate its absorption by the salt-tolerant plants. When using a chelating agent, EDDS is preferred because of its biodegradability. Alternatively, organic acids such as oxalic acid and citric acid can be added to the soil to dissolve lithium and facilitate its absorption by the salt-tolerant plants. Alternatively, or in addition to adding organic acids to the soil, plants that release organic acids from their roots can be planted together with the salt-tolerant plants. Various plants, such as legumes and grasses (including Rhodes grass), are known to secrete organic acids from their roots.

[0023] When the "Li-containing medium" is an aqueous medium such as the lithium-containing waste liquid described above, in step T110, the "salt-tolerant plants, etc." can be hydroponically cultivated using such an aqueous medium, or by diluting the aqueous medium as necessary. Here, "hydroponics" includes both a method using a solid medium such as hydroballs, rock wool, or coco peat instead of soil (hydroculture), and a method of cultivating plants using only a culture solution as a medium without using a solid medium. Furthermore, when cultivating "salt-tolerant plants, etc." using soil, the "Li-containing medium," which is an aqueous medium, may be used as water to supply to the soil.

[0024] FIG. 2 is an explanatory diagram schematically illustrating an example of a lithium recovery system. The lithium recovery system 10 shown in FIG. 2 is an apparatus for cultivating salt-tolerant plants 20 and recovering lithium from the plants 20. The system includes a cultivation unit 30 and an aqueous medium supply unit 40. The cultivation unit 30 includes the salt-tolerant plants 20 and an aqueous medium 32, which is an aqueous solution for cultivation, and is used to cultivate the plants 20 using the aqueous medium 32. The cultivation unit 30 includes a container 34 for storing the aqueous medium 32, which can be distributed, and a substrate 36, which is disposed above the container 34 and serves as a substrate for planting the plants 20, and is made of a sponge or the like. The aqueous medium 32 is a lithium-containing liquid from which lithium is recovered. It is not particularly limited as long as it is a liquid capable of growing the plants 20. For example, the aqueous medium 32 may be the lithium-containing waste liquid described above. As shown in FIG. 2, the aqueous medium 32 contains dissolved and ionized lithium. The container 34 is provided with an inlet channel 33 through which the lithium-containing liquid used as the aqueous medium 32 flows into the container 34, and an outlet channel 34 through which the aqueous medium 32 flows out of the container 34. The aqueous medium supply unit 40 is a device that supplies the lithium-containing liquid from which lithium is to be recovered as the aqueous medium 32 to the cultivation unit 30, and is connected to the inlet channel 33. The configuration of the aqueous medium supply unit 40 is not particularly limited as long as it can supply the lithium-containing liquid, but it can be configured, for example, to include a tank that stores lithium-containing waste liquid and a pump that pumps the lithium-containing waste liquid from the tank to the inlet channel 33. Note that, as an example, the lithium recovery system 10 in FIG. 2 is provided with the cultivation unit 30 that performs hydroponic cultivation. However, a cultivation unit that performs soil cultivation may be provided instead of or in addition to the cultivation unit 30 that performs hydroponic cultivation.

[0025] In step T110, the salt-tolerant plants are cultivated using the Li-containing medium, and lithium in the Li-containing medium is absorbed by the salt-tolerant plants through their roots. If the salt-tolerant plants have, for example, saccular hair-type salt glands, the lithium absorbed by the salt-tolerant plants from the Li-containing medium is concentrated and stored in the salt glands inside the plant. If the salt-tolerant plants have, for example, multicellular salt glands or bicellular salt glands, the lithium absorbed by the salt-tolerant plants from the Li-containing medium is excreted from the salt glands on the surface of the plant. Figure 2 shows the excretion of lithium-containing salt 22 from the surface of the salt-tolerant plants 20.

[0026] After lithium has been concentrated and stored inside the salt-tolerant plant through cultivation in step T110, or after lithium-containing salts have been excreted from the plant, such lithium is recovered from the plant (step T120). When lithium has been stored inside the "salt-tolerant plant, etc.", lithium can be recovered from the "salt-tolerant plant, etc." by, for example, drying the plant and then adding an acid such as sulfuric acid or nitric acid to turn the plant into a solution.

[0027] Furthermore, when lithium-containing salts are excreted from the surface of the "salt-tolerant plants, etc.", lithium can be recovered, for example, by sucking the excreted lithium-containing salts using a suction device. In this case, efficient recovery can be achieved, for example, by attaching a filter to cover the suction port of the suction device and capturing the sucked lithium-containing salts with the filter. Alternatively, when lithium-containing salts are excreted from the surface of the "salt-tolerant plants, etc.", lithium can be recovered by washing the surface of the plant with a cleaning solution such as water, dissolving the lithium-containing salts in the cleaning solution, and evaporating the water from the resulting cleaning solution. In particular, the method using the suction device described above is desirable because it is an extremely simple method with few steps, enables large-scale recovery processing at one time while suppressing the introduction of impurities, and easily increases recovery efficiency. When the "salt-tolerant plants, etc." have "multicellular salt glands" or "bicellular salt glands" and lithium-containing salts are excreted from the plant, the excretion of such lithium-containing salts is continuous. Therefore, in the lithium recovery system 10, lithium can be continuously recovered by, for example, periodically recovering lithium by washing the plant body or using a suction machine while appropriately supplying the lithium-containing liquid. Furthermore, steps such as recovering and dissolving the plant body can be eliminated for lithium recovery.

[0028] According to the lithium recovery method configured as described above, lithium can be recovered from the Li-containing medium by a very simple method of cultivating a "salt-tolerant plant, etc." using a "Li-containing medium" and recovering lithium from the plant body or the surface of the "salt-tolerant plant, etc." In other words, by cultivating the "salt-tolerant plant, etc.", the lithium in the "Li-containing medium" is absorbed by the "salt-tolerant plant, etc.", making it possible to recover lithium from the plant body or the surface of the plant body. Therefore, this method can be a new lithium production method that can recover lithium while significantly reducing the environmental load associated with lithium recovery and reducing the amount of energy and cost required for lithium recovery compared to conventional methods using hydrosphere or geosphere lithium resource sources. [Example]

[0029] <Experimental Method> As shown in Figure 1, salt-tolerant plants were cultivated in Li-containing media (lithium-containing aqueous solution and lithium-containing soil) and lithium was recovered from the plants. The "halophytic plants" were the Catambora cultivar of Rhodes grass (Chloris gayana Kunth), a species of the Chloridoideae subfamily of the Poaceae family that possesses bicellular salt glands. The "halophytic plants" included the ice plant (Mesembryanthemum crystallinum), which possesses sac-like hair-like salt glands, and the Japanese oak (Salsola komarovii), which is thought to lack salt glands. Furthermore, the "Nipponbare" (Oryza sativa L.), a member of the Poaceae family, was used as an example of a plant that does not belong to the "halophytic plants" category. The plants were grown hydroponically, in soil, or both. Hydroponic cultivation is believed to eliminate the effect of lithium ion adsorption by soil.

[0030] Figures 3 and 4 are explanatory diagrams summarizing the conditions for cultivating plants and the measurement results for the cultivated plants. Figure 3 is an explanatory diagram for Rhodes grass, and Figure 4 is an explanatory diagram for plants other than Rhodes grass. Below, the cultivation method, lithium recovery method, and analysis method will be explained in order.

[0031] [Hydroponic cultivation of Rhodes grass] Rhodes grass seeds were soaked in 70% ethanol, washed with sterile water, then sterilized in a 3% aqueous solution of sodium hypochlorite, and then washed with sterile water. The sterilized seeds were sown on 1 / 2 MS (Murashige and Skoog) medium (pH 5.7, MES 0.5 g / L, agar 8 g / L) and incubated at 25°C under 12 hours of light (150 μmol m -2 ·s -1The seeds were grown in an incubator set at 12 hours dark and 12 hours dark. Three days after sowing, the germinated seeds were transplanted into a sponge soaked in 1 / 2 MS medium solution (pH 5.7, MES 0.5 g / L). Six days after sowing, the sponge was placed in a hydroponic container filled with 1 / 2 MS medium solution, and hydroponic cultivation began.

[0032] 5 is an explanatory diagram showing a schematic configuration of a hydroponic cultivation apparatus 130 in which a sponge 136 into which germinated Rhodes grass has been transplanted is installed. The hydroponic cultivation apparatus 130 includes a container 134 in which an aqueous medium 132 is stored, a sponge 136 that is placed above the container 134 and serves as a substrate into which germinated Rhodes grass 120 has been transplanted, and an evaporation prevention film 137 that is placed above the sponge 136 to cover the opening of the container 134. As described above, the aqueous medium 132 at the start of hydroponic cultivation is a 1 / 2 MS medium solution.

[0033] After hydroponic cultivation began, LiCl was added to the culture solution (aqueous medium 132). LiCl addition was performed by replacing the aqueous medium 132 with the ½ MS medium solution containing added LiCl 10 days after sowing, when the fifth leaf began to emerge. The LiCl concentrations of the ½ MS medium solution were 0 mM (control), 0.1 mM, 0.2 mM, 0.4 mM, 0.6 mM, 0.8 mM, 1 mM, 2 mM, 4 mM, 6 mM, 8 mM, and 10 mM (1 mM Li = 6.94 ppm Li) (Samples 1 to 12 shown in Figure 3). The LiCl concentration of the ½ MS medium solution (aqueous medium 132) is also referred to as the "added LiCl concentration." One week after LiCl addition, the aboveground parts of the Rhodes grass 120 were washed with pure water to remove salt excreted from the salt glands. Thereafter, the plants were again cultivated for one week using a 1 / 2 MS aqueous solution with added LiCl as the aqueous medium 132 (24 days after sowing), and then the discharged salts were recovered by the washing method described below.

[0034] [Growing Rhodes grass in soil] Rhodes grass is grown in soil using petalite (LiAlSiO 10The experiment was carried out using soil containing lithium (Li concentration: 22664 ppm) to examine whether the discharged salts contained lithium. Specifically, petalite was added to a soil mixture of river sand and potting soil in a 1:1 (vol%) ratio, and the lithium concentration of the soil was adjusted to 22 ppm or 220 ppm to prepare two types of petalite-added soil (samples No. 13 and 14 shown in Figure 3). Rhodes grass was sown in 120 mL pots containing each of these soils, and the pots were then placed in containers containing 1 / 2 MS medium solution.

[0035] FIG. 6 is an explanatory diagram showing a schematic view of soil cultivation. The soil cultivation device 230 includes a pot 238 containing soil and having a plant 220 planted in the soil, and a container 234 in which the pot 238 is placed and an aqueous medium 232 is arranged around the pot 238. As described above, Rhodes grass was used as the plant 220, the pot 238 was provided with petalite-added soil, and a 1 / 2 MS medium solution was used as the aqueous medium 232. The cultivation was carried out at 25°C under light conditions for 12 hours (150 μmol m -2 ·s -1 Rhodes grass was grown in an incubator set at 12 hours of darkness. Thirty-five days after sowing, the excreted salts were collected using the washing method described below.

[0036] [Recovery of discharged salt by washing method] The above-ground parts of Rhodes grass 120 were washed with pure water, and the salt discharged from the Rhodes grass was recovered by evaporating the water in which the salt had dissolved.

[0037] [Recovery of discharged salt using vacuum method] In addition to the washing method described above, a vacuum method was also used to recover salt discharged from Rhodes grass. Specifically, a filter was attached to the aspirator so as to cover the suction port, and salt discharged onto the surface of the aboveground part of the Rhodes grass was directly sucked in by the aspirator and collected on the filter.

[0038] [Nihonbare Hydroponic Cultivation] Nipponbare was hydroponically grown under the same conditions as Rhodes grass. The LiCl concentrations of the 1 / 2 MS medium solution used as the aqueous medium 132 were 0 mM (control), 0.2 mM, 1 mM, 2 mM, and 10 mM (samples 15 to 19 shown in Figure 4).

[0039] [Cultivation of ice plant and okahijiki in Li-added soil] Ice plant and okahijiki, known as halophytes, were cultivated in soil supplemented with lithium to confirm their lithium tolerance. Soil cultivation was carried out using an apparatus with the same configuration as the soil cultivation apparatus 230 in Figure 6. First, five seeds of each of ice plant and okahijiki were sown in pots 238 filled with soil to which no lithium had been added, and then the pots 238 were placed in containers 234 containing an aqueous 1 / 2 MS medium solution as the aqueous medium 232. The pots were then cultivated at 20°C under light conditions for 12 hours (150 μmol m -2 ·s -1 The plants were grown in an incubator set at 12 hours dark and 1 week dark. One week after sowing, the plants were thinned to one per pot, and from 28 days after sowing, they were cultivated for 40 days in a 1 / 2 MS medium solution (pH 5.7, MES 0.5 g / L) containing 1 mM LiCl. LiCl was added by transferring the pot 238 to a container 234 containing an aqueous medium 232 containing a 1 / 2 MS medium solution (pH 5.7, MES 0.5 g / L) containing 1 mM LiCl. The ice plant 28 days after sowing before the addition of LiCl was designated Sample No. 20, the ice plant cultivated for 40 days after the addition of LiCl was designated Sample No. 21, the okahijiki 28 days after sowing before the addition of LiCl was designated Sample No. 22, and the okahijiki 40 days after the addition of LiCl was designated Sample No. 23 (see Figure 4).

[0040] [Measurement of excreted salt amount] The weight of salt obtained by evaporating the washing solution from the Rhodes grass to dryness was measured as the amount of salt excreted from the Rhodes grass. Rhodes grass was washed on a plant-by-plant basis, and the amount of salt per plant was measured for each sample. The measurement results are shown as "amount of salt excreted (mg / plant)" in Figure 3 and Figure 12, which will be described later.

[0041] [Measurement of the amount of discharged lithium and calculation of the lithium concentration in the discharged salt] The amount of lithium released from the Rhodes grass was measured using ion chromatography (IC). Specifically, the washings from the Rhodes grass were evaporated to dryness, and the lithium ions contained in the resulting salt were quantitatively analyzed using IC. The Rhodes grass was washed individually, and the amount of released lithium per plant was measured for each sample. The measurement results are shown as "Li released (μg / plant)" in Figure 3 and Figures 12 and 15(B) described below. The lithium concentration in the released salt (Li concentration in the released salt) was calculated by calculating the ratio of the "Li released (μg / plant)" to the "salt released (mg / plant)." The calculation results are shown as "Li concentration in the released salt (%)" in Figure 3 and Figure 13 described below.

[0042] [Measurement of plant dry weight] The plant body of each sample was divided into the above-ground part and the root part, dried, and the weight of each was measured. Dry weight measurements were performed on a plant-by-plant basis. The measurement results for the above-ground part are shown as "above-ground dry weight (mg / plant)" in Figures 3 and 4, and in Figures 10, 15(A), and 18 described below. The measurement results for the root part are shown as "root dry weight (mg / plant)" in Figures 10 and 18 described below.

[0043] [Measurement of lithium amount in plant body and calculation of lithium concentration] For samples 1, 3, 7, 8, 12, and 15–23, 0.1 g of dried plant aerial parts was added to 10 mL of 50% sulfuric acid, followed by 10 mL of 30% nitric acid. The mixture was heated to 300°C to extract the ions. The lithium content in the extract was then quantitatively analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The amount of lithium per plant was calculated from the measured values, and the percentage of the dry weight of the aerial parts (mg / plant) was calculated. For Rhodes grass (samples 1, 3, 7, 8, and 12), measurements were performed on plants whose surfaces had been washed 24 days after sowing. The calculated results are shown as “aerial Li concentration (%)” in Figures 3 and 4 and Figure 13 (described below).

[0044] [Optical microscope observation] Cross-sectional tissue observation of Rhodes grass leaves was performed using an optical microscope. A section 20–30 cm from the base of the sixth leaf of Rhodes grass plants grown in a lithium-free solution 24 days after sowing was sampled, immersed in a surfactant (Triton X-100, 0.5%), and fixed in 5% agarose. Then, slices were cut into 100 μm-thick sections using a microslicer, stained with toluidine blue (0.05%), and tissue observation was performed.

[0045] [SEM observation] Rhodes grass was observed using a scanning electron microscope (SEM). The sample for observing the shape of the salt glands was prepared in an ionic liquid (ethyl (2-hydroxyethyl) dimethylammonium methanesulfonate; CH 19 NO4S) was diluted with ethanol and dropped onto the sample surface, and the sample was observed at a 30° tilt in a low vacuum atmosphere of 50 Pa.

[0046] <Experimental Results> [Structure of the salt gland] The surfaces of above-ground plant parts, such as leaves and stems, are characterized by protruding structures formed by modified epidermal cells, collectively known as trichomes. Trichomes in the grass family are classified into three types: macrohairs, which are long; prickles, which are shorter than macrohairs and have a broad base and a sharp tip; and microhairs, which are tiny, densely packed bicellular trichomes. Functionally, trichomes are classified as secretory and non-secretory. Both macrohairs and prickles are non-secretory and are thought to function primarily as physical defenses against animal and insect herbivory. On the other hand, microhairs are considered secretory because they have been confirmed to secrete small amounts of polysaccharides, proteins, minerals, and other substances in a wide range of plant subfamilies, including rice and maize. Although the role of trichomes in many plant species remains unclear, it has been shown that in some salt-tolerant species of the Polytrichomeae subfamily, they function as salt glands that actively excrete inorganic salts (Jpn. J. Crop Sci., 90, 235-246, 2021).

[0047] Figures 7 and 8 are explanatory diagrams showing images of a cross-section of the sixth leaf of Rhodes grass 24 days after sowing, grown in a culture medium without adding lithium. Figure 7 is an optical microscope image, where Figure 7(A) shows the salt gland on the adaxial side, Figure 7(B) shows the salt gland on the abaxial side, and Figure 7(C) shows an enlarged view of the salt gland. In the figures, arrows indicate the salt gland. Figure 8 is a secondary electron image, where Figure 8(A) shows the secondary electron image on the abaxial side, and Figure 8(B) shows the secondary electron image of the salt gland. In the figures, arrows indicate the salt gland. The salt glands on the adaxial side of the leaf were located on the small veins (Fig. 7(A)), whereas those on the abaxial side were located between the veins (Fig. 7(B)). This distribution was consistent with the literature (Takao Oi et al., "MORPHOLOGY AND ULTRASTRUCTURE OF THE SALT GLANDS ON THE LEAF SURFACE OF RHODES GRASS (CHLORIS GAYANA KUNTH)", Int. J. Plant Sci., 173, 454-463, 2012). Furthermore, the large hairs were located on the same vein as the salt glands, whereas the sting hairs were located on a different vein (Fig. 8(A)). As shown in Fig. 7(C), the salt glands of Rhodes grass are bicellular, consisting of a basal cell and a cap cell. It is believed that ions transported from the basal cell are excreted from the tip of the cap cell. In the backscattered electron image of the salt gland shown in Figure 8(B), excreted salt was confirmed at the tip of the apical cell.

[0048] [Effect of Li addition on the growth of Rhodes grass] Figure 9 is an explanatory photograph showing Rhodes grass grown hydroponically 24 days after sowing. The LiCl concentrations in the aqueous medium 132 used for hydroponic cultivation are 0 mM (control) in Figure 9(A), 2 mM in Figure 9(B), 4 mM in Figure 9(C), 6 mM in Figure 9(D), 8 mM in Figure 9(E), and 10 mM in Figure 9(F). The photographs show hydroponic cultivation in a container with an upper diameter of 13 cm.

[0049] Fig. 10 is an explanatory diagram showing the relationship between the dry weight per plant of the above-ground parts and roots of Rhodes grass grown hydroponically 24 days after sowing and the concentration of LiCl added to the aqueous medium 132. As shown in Fig. 10, the addition of LiCl at 2 mM or less did not have a clear effect on the growth of Rhodes grass, whereas when the added LiCl concentration exceeded 2 mM, the growth of the above-ground parts and roots decreased almost in proportion to the added amount.

[0050] [Lithium excretion from salt glands] Figure 11 is an explanatory diagram showing an optical photograph of the abaxial side of a leaf after two weeks of hydroponic cultivation in an aqueous medium to which 2 mM LiCl had been added. In the figure, the arrow indicates crystals that formed when the exudate excreted from the salt glands dried. Figure 12 is an explanatory diagram showing the relationship between the amount of salt and Li excreted over the following week from a single Rhodes grass plant (the above-ground parts of which had been washed with pure water to remove salt) grown hydroponically 17 days after sowing and the concentration of added LiCl.

[0051] As shown in Figure 12, when the added LiCl concentration was 0.4 mM or less, the amount of salt excreted did not change significantly with changes in the added LiCl concentration. However, when the added LiCl concentration was 0.4 mM or more, the amount of salt excreted decreased with increasing added LiCl concentration. On the other hand, the amount of excreted Li was highest when the added LiCl concentration was 2 mM and decreased with increasing added LiCl concentration. As described above, it was confirmed that lithium is contained in the excreted salt when Rhodes grass is grown in a Li-containing aqueous solution.

[0052] [Analysis of Li concentration in aboveground parts and excreted salts] Figure 13 shows the relationship between the lithium concentration in the excreted salt (excreted salt Li concentration) and the added LiCl concentration for the week following the rinsing of the aboveground parts of hydroponically grown Rhodes grass with pure water 17 days after sowing, and also the relationship between the aboveground Li concentration and the added LiCl concentration 24 days after sowing. As shown in Figure 13, the aboveground Li concentration did not increase significantly with increasing added LiCl concentration. In contrast, the excreted salt Li concentration tended to increase with increasing added LiCl concentration above 1 mM. For example, at an added LiCl concentration of 2 mM, the excreted salt Li concentration (0.94%) was approximately 27 times higher than the aboveground Li concentration (0.04%). For example, while phytomining requires the cutting and burning of the aboveground parts of plants, the recovery of lithium excreted from salt glands of Rhodes grass and other plants may be more efficient by periodically collecting only the excreted salt.

[0053] [Li release from Rhodes grass grown in Li-added soil] Figure 14 is an explanatory diagram showing photographs of Rhodes grass grown in petalite-added soil 35 days after sowing. Figure 14(A) shows the results of cultivation in petalite-added soil with a Li concentration of 22 ppm, and Figure 14(B) shows the results of cultivation in petalite-added soil with a Li concentration of 220 ppm. Figure 15 is an explanatory diagram showing the measurement results of the dry weight of the aboveground parts (Figure 15(A)) and the amount of Li released (Figure 15(B)) of Rhodes grass grown in petalite-added soil 35 days after sowing.

[0054] As shown in Figure 15, it was confirmed that lithium was excreted from the salt glands of Rhodes grass grown in petalite-added soil (Li-added soil) regardless of the amount of petalite added, at Li concentrations of 22 ppm and 220 ppm. This indicates that it is possible to recover lithium from soil by cultivating Rhodes grass in soil containing lithium and recovering lithium from the salt excreted by the salt glands.

[0055] [Recovery of discharged salt using vacuum method] Figure 16 is an explanatory photograph showing the filter attached to the vacuum cleaner when salt was collected from the surface of Rhodes grass leaves by the vacuum method. As shown in Figure 16, the collection of discharged salt was observed, confirming that the discharged salt can be collected by the vacuum method.

[0056] [Results of hydroponic cultivation of rice cultivar Nipponbare] Figure 17 is an explanatory diagram showing the state of Nipponbare grown hydroponically 24 days after sowing. The LiCl concentration in the culture solution, which is the aqueous medium 132, is 0 mM (control) in Figure 17(A), 2 mM in Figure 17(B), and 10 mM in Figure 13(C). Here, the state of hydroponic cultivation using a container with an upper diameter of 13 cm is shown.

[0057] Figure 18 shows the relationship between the dry weight of the shoots and roots per plant of Nipponbare (shown in Figure 17 ), i.e., Nipponbare grown hydroponically 24 days after sowing, and the LiCl concentration in the culture solution used for hydroponic cultivation. Comparing the results for Nipponbare (shown in Figure 18 ) with the results for Rhodes grass (shown in Figure 10 ), both shoot and root dry weights were nearly identical at 0 mM LiCl. However, at 2 mM LiCl, Rhodes grass exhibited shoot and root dry weights nearly identical to those at 0 mM LiCl, whereas Nipponbare exhibited shoot and root dry weights that were approximately half of those at 0 mM LiCl. Thus, Rhodes grass exhibited higher lithium tolerance than Nipponbare, a grass species, at 2 mM LiCl.

[0058] [Results of soil cultivation of ice plant and okahijiki] As shown in Figure 4, when the halophytes ice plant and okahijiki were cultivated in soil, the addition of LiCl to the soil significantly increased the Li concentration in the aboveground shoots, confirming that lithium had accumulated within the plant bodies (comparison between samples No. 20 and 21, and between samples No. 22 and 23). In other words, the halophytes ice plant and okahijiki are known to accumulate sodium within their bodies and exhibit high sodium tolerance, but it was also confirmed that they can accumulate lithium, which is an alkali metal like sodium, within their bodies. Therefore, it is thought that lithium in the soil used for cultivation can be recovered by extracting lithium from the plant bodies.

[0059] Fig. 19 is an explanatory diagram showing a photograph of soil-grown ice plant, and Fig. 20 is an explanatory diagram showing a photograph of soil-grown okahijiki. Fig. 19(A) and Fig. 20(A) show the results when LiCl was not added to the soil (samples No. 20 and 22), and Fig. 19(B) and Fig. 20(B) show the results when LiCl was added to the soil using a 1 mM LiCl solution and the plants were cultivated for 40 days (samples No. 21 and 23).

[0060] As shown in Figure 19(B), the addition of LiCl to the soil caused most of the leaves of the ice plant to wither and die, and as shown in Figure 20(B), the addition of LiCl to the soil also caused the leaves of the hijiki to turn yellow and show poor growth. Furthermore, as shown in Figure 4, the addition of LiCl to the soil significantly reduced the dry weight of the aboveground parts of both the ice plant and the hijiki, and growth was inhibited (comparison between samples No. 20 and 21, and between samples No. 22 and 23). Both the ice plant and the hijiki are halophytes, known to be able to grow in soil containing high concentrations of sodium ions. They are more sodium-tolerant than the salt-tolerant plant Rhodes grass, but Rhodes grass tended to be more tolerant to lithium ions.

[0061] The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0062] The present disclosure can also be realized in the following forms. [Application example 1] A method for recovering lithium from a medium containing lithium, comprising the steps of: Cultivating a halophyte or salt-tolerant plant using the medium; The lithium concentrated inside the plant body of the halophyte or salt-tolerant plant or the lithium excreted from the plant body is recovered. Lithium recovery methods. [Application example 2] The lithium recovery method according to Application Example 1, The plant comprises a salt gland, Recovering lithium excreted from the salt gland Lithium recovery methods. [Application example 3] The lithium recovery method according to Application Example 2, The lithium excreted from the salt glands to the surface of the plant body is collected using a suction device. Lithium recovery methods. [Application example 4] The lithium recovery method according to Application Example 2, The surface of the plant body is washed with a washing solution to recover lithium excreted from the salt glands onto the surface of the plant body. Lithium recovery methods. [Application example 5] The lithium recovery method according to any one of Application Examples 2 to 4, Lithium is recovered from the plant body having bicellular salt glands or multicellular salt glands as the salt glands. Lithium recovery methods. [Application Example 6] The lithium recovery method according to any one of Application Examples 1 to 5, Rhodes grass is used as the halophyte or salt-tolerant plant. Lithium recovery methods. [Application Example 7] The lithium recovery method according to any one of Application Examples 1 to 6, As the medium, soil containing lithium of 1 ppm or more and 1000 ppm or less is used. Lithium recovery methods. [Application Example 8] The lithium recovery method according to any one of Application Examples 1 to 6, As the medium, an aqueous solution containing lithium of 1 ppm or more and 1000 ppm or less is used. Lithium recovery methods. [Application Example 9] A lithium recovery system for recovering lithium from a medium containing lithium, comprising: a cultivation section including a halophyte or a salt-tolerant plant and an aqueous medium that is an aqueous solution for cultivation, and cultivating the halophyte or the salt-tolerant plant using the aqueous medium; an aqueous medium supply unit that supplies a lithium-containing liquid from which lithium is to be recovered as the aqueous medium to the cultivation unit; Equipped with Lithium recovery system. [Application Example 10] The lithium recovery system according to Application Example 9, The cultivation section performs hydroponic cultivation of the halophyte or salt-tolerant plant using the aqueous medium. Lithium recovery system. [Application Example 11] The lithium recovery system according to Application Example 9 or 10, The lithium-containing liquid is a lithium-containing waste liquid generated in a lithium production process or a lithium recycling process. Lithium recovery system. [Explanation of symbols]

[0063] 10...Lithium recovery system 20...Salt-tolerant plants, etc. 22...Lithium-containing salt 30…Cultivation Department 32,132,232…aqueous medium 33...Inflow channel 34,134…Container part 34...Outflow channel 36...Base material 40...Aqueous medium supply section 120...Rose Glass 130...Hydroponic cultivation device 136...Sponge 137...Evaporation prevention film 220...plant 230...Soil cultivation device 234...Container 238...Pot

Claims

1. A method for recovering lithium from a medium containing lithium, comprising the steps of: Cultivating a halophyte or salt-tolerant plant using the medium; The lithium concentrated inside the plant body of the halophyte or salt-tolerant plant or the lithium excreted from the plant body is recovered. Lithium recovery methods.

2. 2. The lithium recovery method according to claim 1, The plant comprises a salt gland, Recovering lithium excreted from the salt gland Lithium recovery methods.

3. The lithium recovery method according to claim 2, The lithium excreted from the salt glands to the surface of the plant body is collected using a suction device. Lithium recovery methods.

4. The lithium recovery method according to claim 2, The surface of the plant body is washed with a washing solution to recover lithium excreted from the salt glands onto the surface of the plant body. Lithium recovery methods.

5. The lithium recovery method according to claim 2, Lithium is recovered from the plant body having bicellular salt glands or multicellular salt glands as the salt glands. Lithium recovery methods.

6. The lithium recovery method according to claim 5, Rhodes grass is used as the halophyte or salt-tolerant plant. Lithium recovery methods.

7. 2. The lithium recovery method according to claim 1, As the medium, soil containing 1 ppm or more and 1000 ppm or less of lithium is used. Lithium recovery methods.

8. 2. The lithium recovery method according to claim 1, As the medium, an aqueous solution containing 1 ppm or more and 1000 ppm or less of lithium is used. Lithium recovery methods.

9. A lithium recovery system for recovering lithium from a medium containing lithium, comprising: a cultivation section including a halophyte or a salt-tolerant plant and an aqueous medium that is an aqueous solution for cultivation, and cultivating the halophyte or the salt-tolerant plant using the aqueous medium; an aqueous medium supply unit that supplies a lithium-containing liquid from which lithium is to be recovered as the aqueous medium to the cultivation unit; Equipped with Lithium recovery system.

10. 10. The lithium recovery system of claim 9, The cultivation section performs hydroponic cultivation of the halophyte or salt-tolerant plant using the aqueous medium. Lithium recovery system.

11. 10. The lithium recovery system of claim 9, The lithium-containing liquid is a lithium-containing waste liquid generated in a lithium production process or a lithium recycling process. Lithium recovery system.

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