Method for extracting scattered metal gallium in soil by utilizing ferns

Abstract

The invention relates to a method for extracting scattered metal gallium in soil by utilizing pteridophyte, and belongs to the technical field of plant mining. The invention provides application of pteridophyte in extraction of metal gallium in soil. According to the method, gallium-enriched plants are screened out according to the enrichment amount of gallium metal by the fern leaves of different types, and then gallium is extracted from the plants by utilizing the screened plants, so that gallium metal recycling is realized. Therefore, gallium in the soil can be enriched and extracted by using the gallium-enriched pteridophyte.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plant mining, and particularly relates to a method for extracting scattered metal gallium in soil by using ferns. BACKGROUND

[0002] Gallium (Ga) is a scattered metal, and its compounds are widely used in the fields of semiconductors, photoelectric materials and solar cells, and belongs to important metal resources. Gallium is a key metal supporting the development of clean energy technology. With the rapid development of new material industries represented by light-emitting diodes (LEDs) and copper-indium-gallium-selenium (CIGS) thin-film solar cells, gallium has attracted worldwide attention. As a key metal mineral, the content of gallium in the earth's crust is only 0.0015%. Gallium rarely exists in the form of independent mineral in nature, and the main reason is that elemental gallium is easily oxidized to Ga2O3 in a humid environment, so that gallium-rich minerals are extremely rare. Gallium is usually associated with bauxite, sphalerite and coal and other minerals. At present, the global gallium production and geological reserves are in a decoupling state, and the main reason is that more than 90% of the primary gallium in the world is recovered as a by-product in the process of producing alumina by Bayer method, and a small amount is extracted from smelting zinc slag, iron slag or phosphorus slag.

[0003] In recent decades, the vigorous development of high-tech industries inevitably leads to the release of gallium in the form of gallium arsenide into the environment in mining, extraction, refinement and manufacturing activities. The pollution of arsenic gallium in soil poses a health risk to humans through the food chain, so how to scientifically and sustainably utilize gallium metal resources is a major problem to be solved at present.

[0004] Botanical mining technology utilizes hyperaccumulating plants and harvests their above-ground parts to recover gallium resources, providing an economical and effective solution for gallium resource recovery. Gallium is present in almost all plants, but at very low concentrations, ranging from 0.05 to 5 ppm. Patent CN119530567A discloses a method for recovering gallium from lime precipitates in alumina mother liquor. This method effectively recovers gallium from gallium-containing lime precipitates, addressing the issue of high gallium content and improving gallium recovery rates. However, it still does not eliminate the dependence on alumina (bauxite) for gallium resource recovery, and the process carries significant environmental risks. Patent CN111451260A discloses a method for phytomining rare earth elements using pokeweed. This method involves planting pokeweed on rare earth-contaminated soil to remediate the contaminated soil, restore vegetation, enrich rare earth elements in the soil through pokeweed, and harvest the top part of pokeweed to recover rare earth elements. However, this patent only explores the ability of pokeweed to enrich rare earth elements and its ability to complete the resource recovery of rare earth elements through phytomining. It is unclear whether the phytomining technology can be applied to other plants and whether it can complete the resource recovery of other metal elements under the premise of environmental friendliness and sustainability.

[0005] Therefore, given the current high demand for gallium and the contradiction between the high dependence of gallium recycling on alumina and the inevitable environmental pollution it causes, seeking an economical, effective, and environmentally friendly approach to gallium metal resource utilization is a key technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for extracting rare metal gallium from soil using ferns.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides the application of ferns in the extraction of metallic gallium from soil.

[0009] This invention screens gallium-accumulating plants by analyzing the gallium enrichment levels in the leaves of different fern species, and then utilizes these selected plants for phytogammation, thus realizing the resource utilization of gallium. Therefore, gallium-accumulating ferns can be used to enrich and extract gallium from soil.

[0010] As a preferred embodiment of the first aspect, the fern is any one of the following: Selaginellaceae, Pteris vittata, Pteris simonii, Pteris spp., and Pteris sinensis.

[0011] As a preferred embodiment of the first aspect, the leaf gallium content of Selaginella kraussiana A.Braun is 111.93-165.60 mg / kg; the leaf gallium content of Vandenboschia griffithii (Miq.) Copel is 40.32-53.48 mg / kg; the leaf gallium content of Hypodematium sinense Ching is 1623.45-1885.32 mg / kg; and the leaf gallium content of Huperzia chinense (Milne ex Druce) Chun is 67.22-68.06 mg / kg.

[0012] The ferns with gallium enrichment function are screened in the application, which include Selaginella kraussiana A.Braun, Vandenboschia griffithii (Miq.) Copel, Hypodematium sinense Ching and Huperzia chinense (Milne ex Druce) Chun, and it is found that the leaf gallium content of the ferns is high. The leaf gallium content of Selaginella kraussiana A.Braun is 111.93-165.60 mg / kg, the leaf gallium content of Vandenboschia griffithii (Miq.) Copel is 40.32-53.48 mg / kg, the leaf gallium content of Hypodematium sinense Ching is 1623.45-1885.32 mg / kg, and the leaf gallium content of Huperzia chinense (Milne ex Druce) Chun is 67.22-68.06 mg / kg. The leaf Ga of the ferns is greater than or equal to 50 mg / kg, and it can be seen that the ferns have excellent gallium enrichment capacity. Therefore, the ferns have good application prospect as gallium-rich mining plants.

[0013] Selaginella kraussiana A.Braun is a soil-borne plant of Selaginella genus of Selaginellaceae. The plant is creeping, and has no horizontal underground stem; root supports grow discontinuously along the creeping stem and branches, grow from the upper part of the bifurcation of the stem and branches, and are nearly hairless; the main stem is regularly pinnately branched, has joints, is straw-colored, and the stem is nearly quadrangular or has grooves; all the leaves are alternately arranged, the surface is smooth, the edge is not entire, and there is no white edge; the sporophyll is compact, is quadrangular, and is terminal or lateral. Because the sporophyll is obviously smaller than that of Selaginella uncinata, it is named as "Selaginella kraussiana". Selaginella kraussiana is often found in shady and humid rocks or in stream forest. It is originally from Africa, and is also cultivated in Europe and America.

[0014] Pteris terminalis Wall. Ex J. Agardh is a plant of Pteridaceae and Pteris. Rhizome is short and erect or oblique, woody, thick, apex covered with dark brown scales. Leaves are clustered; petiole is dark brown, upward is straw color, slightly shiny, hard, thick, glabrous; leaf blade is broadly triangular, bilobed; lateral lobes are 5-10 pairs, the largest pair at base, with short petiolules. Rhachis is straw color, with shallow longitudinal grooves on upper surface. It grows in sparse forest or shrub at altitude of 600-2700 meters. It is native to tropical and subtropical humid forest, and likes warm and humid environment. Direct sunlight and dry soil can cause its leaf blade to fade from green to pale yellow. It is distributed in Japan (Honshu, Shikoku, Kyushu), Philippines, Hawaiian Islands, Fiji Islands, Malaysia, Laos, Vietnam, India, Nepal and China

[0015] Hypodematium crenatum (Forssk.) Kuhn is a plant of Hypodematium crenatum (Forssk.) Kuhn. Plant height is 20-50 cm. Rhizome is thick, horizontal, covered with scales with leaf petiole base. Leaves are nearly born, petiole is 10-25 cm long, straw color, upper part covered with grayish white pubescence; leaf blade is 20-30 cm long, ovate pentagonal, trilobed; 8-12 pairs of lobes, the largest pair at base is 10-20 cm long, 5-10 cm wide at base, triangular long oval, heart-shaped at base, with short petiolules, bilobed; 6-10 pairs of small lobes, the largest one at base is 2-5 cm wide at base, ovate triangular, nearly round at base, lower part extends downward with narrow wing, bilobed, last small lobe is long oval, base and small rhachis are synsedimentary, bilobed, lobe is long oval, entire or slightly wavy; veins are obvious, lateral veins are bilobed, single; leaf is herbaceous, yellow green after drying, both sides covered with grayish white pubescence with leaf axis and each bilobed axis; lower surface of rhachis occasionally has red brown linear needle-shaped narrow scales. Sporangia are round, dorsally located in middle of lateral veins, 1-3 per lobe; indusium is large, kidney-shaped, light gray, membranous, densely covered with pubescence on back, persistent. Spores are round kidney-shaped, with dense folds on periclathrum, forming obvious curved stripes, surface is smooth. It is widely distributed in Asian subtropical regions and Africa. It grows in dry limestone cracks at altitude of 50-1800 meters.

[0016] Diplopterygium chinense (Rosenstock) De Vol is a perennial evergreen fern of the family of Diplopteridaceae and the genus of Diplopterygium. The plant is about 3 meters high; rhizome is transverse and densely covered with brown scales; petiole is dark brown, 5-6 mm thick, densely covered with reddish-brown scales, and the latter is smooth. Leaf blade is huge, bipinnate, pinnate, and small pinnate is alternate, pinnately deeply lobed, slightly oblique, lanceolate, and bladeless at base; leaf is papery, midrib is flat on top, lateral veins are convex on both sides, densely covered with star-shaped soft hair along the midrib, lateral veins and edges, and rachis is brownish; sporangium is round, located between the midrib and the edge of the leaf, slightly close to the midrib, and attached to the upper side of the basal vein. D. chinense is distributed in Yunnan, Guizhou, Sichuan and other provinces. It also grows in Vietnam, and grows in the forest, shrub and sunny grass slope at an altitude of 300-1400 m. It prefers warm and humid environment and shade, and is suitable for growing in loose and fertile, organic-rich and acidic soil.

[0017] In a second aspect, the application provides a method for extracting metal gallium from soil by using ferns, which comprises planting ferns on soil, harvesting the aboveground parts of the ferns after the ferns grow for 90 days, and realizing the mining of metal gallium by the ferns.

[0018] The application realizes the mining of gallium by planting ferns which can enrich gallium on soil, harvesting the aboveground parts of the ferns which enrich gallium after the plants grow, and realizing the mining of gallium by the plants.

[0019] As a preferred embodiment of the second aspect, the ferns are any one of Cibotium barometz, Pteris cretica, Diphellia pinnata and D. chinense.

[0020] The gallium-enriched ferns screened by the application include C. barometz, P. cretica, D. pinnata and D. chinense, and it is found that the gallium content of the leaf blades of these ferns is high. Research shows that the gallium content in the ash of C. barometz harvested per mu is 3318.2 g, the gallium content in the ash of P. cretica harvested per mu is 1657.8 g, the gallium content in the ash of D. pinnata harvested per mu is 1991.7 g, and the gallium content in the ash of D. chinense harvested per mu is 2094.9 g.

[0021] As a preferred embodiment of the second aspect, the pH value of the soil for planting C. barometz, P. cretica, D. pinnata and D. chinense is 4-6, and the soil is red soil.

[0022] Since the pteridophytes, which like shady, humid and warm environment, are widely distributed in China, especially in the tropics and subtropics, and the pH of the soil in China gradually decreases from north to south, the soil type in the tropics and subtropics is mainly red soil. Therefore, the pteridophytes rich in gallium in the application are planted in the environment of red soil with pH value of 4-6, which is more conducive to the growth of the pteridophytes.

[0023] As a preferred embodiment of the second aspect, the Selaginellaceae small green cloud, the Pteridaceae stream edge Pteridium, the Plagiogyriaceae Plagiogyria are planted in the tropical monsoon climate zone, and the Lycopodiaceae Chinese Lycopodium is planted in the subtropical monsoon climate zone.

[0024] It is found through research that the Selaginellaceae small green cloud, the Pteridaceae stream edge Pteridium and the Plagiogyriaceae Plagiogyria are more conducive to the growth and gallium enrichment in the tropical monsoon climate zone, and the Lycopodiaceae Chinese Lycopodium is more conducive to the growth and gallium enrichment in the subtropical monsoon climate zone. Therefore, the Selaginellaceae small green cloud, the Pteridaceae stream edge Pteridium and the Plagiogyriaceae Plagiogyria are planted in the tropical monsoon climate zone, and the Lycopodiaceae Chinese Lycopodium is planted in the subtropical monsoon climate zone, which is more conducive to the gallium-rich collection of different pteridophytes.

[0025] As a preferred embodiment of the second aspect, the method further comprises drying the above-ground part of the pteridophyte.

[0026] As a preferred embodiment of the second aspect, the method further comprises ashing the dried above-ground part of the pteridophyte.

[0027] As a preferred embodiment of the second aspect, the ashing temperature is 500-550 DEG C.

[0028] As a preferred embodiment of the second aspect, the ash content of the Selaginellaceae small green cloud after ashing is 1678.93-2483.95 g, the ash content of the Pteridaceae stream edge Pteridium after ashing is 604.88-802.18 g, the ash content of the Plagiogyriaceae Plagiogyria after ashing is 1623.45-1885.32 g, and the ash content of the Lycopodiaceae Chinese Lycopodium after ashing is 1008.39-1020.93 g.

[0029] Compared with the prior art, the application has the following beneficial effects:

[0030] The application is based on the plant mining technology, and first proposes the mining technology of gallium element by using pteridophytes, realizes the gallium resource by harvesting the above-ground part of the pteridophytes, and provides an economic and effective and environment-friendly solution for solving the gallium metal resource.

[0031] Although soil is the gallium reservoir, it is difficult to exploit and utilize gallium in soil by traditional technology. The method can obtain several times of gallium concentration in soil by plant enrichment and leaf ashing, and the obtained gallium biomine composition is simpler, more conducive to obtain, separate and purify. By this method, not only can it be decoupled from the by-product recovery in the traditional gallium resource method of aluminum oxide process, but also can solve the environmental problems in the gallium production process. Using ferns to carry out plant mining of gallium elements can realize gallium resource by harvesting ferns, and provide an economic and effective and environment-friendly solution to solve gallium metal resource. The method has the characteristics of scientificity, wide application range, reasonable method, low cost, and strong pertinence and universality. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The screening results of ferns for gallium enrichment are shown in the schematic diagram.

[0033] Figure 2 The results of using Hainan ferns to collect Ga are shown in the schematic diagram.

[0034] Figure 3 The results of using Jiangxi ferns to collect Ga are shown in the schematic diagram. DETAILED DESCRIPTION

[0035] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in combination with specific examples.

[0036] Example 1: Screening of gallium-rich plants

[0037] This embodiment selected ferns with strong gallium accumulation capabilities from a wide range of ferns, including *Dryopteris emeraldii*, *Pteris vittata*, *Dryopteris heterophyllus*, *Pteris vittata*, *Pteris thunbergii*, *Pteris thunbergii*, *Pteris hominis*, *Pteris terrestris ... Back-back fern, Beijing iron-horn fern, flat-feathered maidenhair fern, broad-scaled hairy fern, drooping lycophyte, selaginella, Jiangnan star fern, Chinese selaginella, curved-axis sea ferns, stream-hole bowl fern, thin-leaved selaginella, hairy-leaved axial vein fern, rare feathered hairy fern, red-capped hairy fern, cold fern, entire-margined maidenhair fern, whip-leaved maidenhair fern, hairy fern, star-haired fern, fan-leaved maidenhair fern, narrow-topped hairy fern, black fern, rhomboid compound-leaved ear fern, narrow-winged iron-horn fern, viviparous dog-ridge, lateral short-gut fern, dimorphic selaginella, charming hairy fern, single-leaved crescent fern, extended-feathered ovoid fern, cycad fern, thread-feathered maidenhair fern, creeping selaginella, large scutellaria, sparse-leaved hoof-shaped fern, black hairy fern, scutellaria, Yue Li Bai, golden star fern, long-leaved nephrolepis, stream-side maidenhair fern, swollen-foot fern, Chinese Li Bai, small green cloud. For each target fern species, healthy, intact leaves were harvested from plants with similar growth conditions, following the principle of "3-4 parallel samples per species"; corresponding rhizosphere soil samples were collected simultaneously. Habitat and stress performance were recorded during sampling to ensure that the selected fern species possess the tolerance and scale potential required for subsequent phytomining.

[0038] The collected samples were brought back to the laboratory for processing. For the obtained plant samples, they were first washed, then dried in an oven at 60°C and weighed. The plant samples were then ground and crushed. If they could not be fully ground and crushed manually, a ball mill was used for crushing.

[0039] Plant sample digestion: Check that the inside of the digestion tube is clean. If the element to be detected is trace, to avoid contamination, weigh a certain amount of plant sample (≈100mg), ensuring the sample weight added to each tube is as consistent as possible, and record the mass of the added sample. Add 8mL of concentrated nitric acid to the digestion tube containing the sample, cap, and incubate overnight. Digest to 1mL using a graphite furnace digester, add 1mL of H2O2, and continue digesting to 1mL. Transfer the sample from each digestion tube to a 15mL centrifuge tube.

[0040] The sample dilution was quantified using a gravimetric method: the digestion tube was rinsed three times with 2% dilute nitric acid to ensure that all samples were washed out, and then poured into a 15 mL centrifuge tube. The mass of the centrifuge tube was recorded. The solution was then filtered through a 0.45 μm filter membrane and stored for later analysis.

[0041] The concentration of Ga in the plant leaf extraction solution was determined using an inductively coupled plasma optical emission spectrometer (ICP-OES), and the calculation formula is as follows:

[0042]

[0043] wherein the density of 2% dilute nitric acid is equivalent to water.

[0044] The screening results are shown in Table 1. Figure 1 As shown in Table 1, the gallium enrichment abilities of Chinese Leptodermum of Leptodermum family, small Cuiyun of Selaginellaceae, Xibian Pteris of Pteridaceae and Tumorous Foot Fern of Lepisoraceae are stronger, all of which are more than 50 mg / kg (average value). Therefore, Chinese Leptodermum of Leptodermum family, small Cuiyun of Selaginellaceae, Xibian Pteris of Pteridaceae and Tumorous Foot Fern of Lepisoraceae are selected for subsequent experiments.

[0045] Example 2 Utilizing small Cuiyun of Selaginellaceae, Xibian Pteris of Pteridaceae and Tumorous Foot Fern of Lepisoraceae to collect Ga in soil

[0046] Small Cuiyun of Selaginellaceae, Xibian Pteris of Pteridaceae and Tumorous Foot Fern of Lepisoraceae were planted in a tropical monsoon climate zone, the average annual temperature of which is 24℃, the average annual precipitation of which is 2000mm, the soil type of which is red soil, the soil pH of which is 4.55-5.54, which is acidic, and the soil Ga content of which is measured to be 151.60 mg / kg. The specific operation is as follows:

[0047] 1. Small Cuiyun of Selaginellaceae, Xibian Pteris of Pteridaceae and Tumorous Foot Fern of Lepisoraceae were planted in the forest understory near Songtao Reservoir in Danzhou City, Hainan Province in mid-July, with a planting density of 4500 plants per mu, and Pteris multifida was used as a comparison. At the time of planting, spore propagation was used, the soil needed to be loose and well-drained, the soil needed to be kept moist on a daily basis, and thin liquid fertilizer was applied regularly, and dead and yellow leaves were pruned in a timely manner.

[0048] 2. After 90 days, the aboveground parts of small Cuiyun of Selaginellaceae, Xibian Pteris of Pteridaceae, Tumorous Foot Fern of Lepisoraceae and Pteris multifida were harvested, dried in an oven and then fully ashed in a muffle furnace at 550℃.

[0049] 3. Ga content was determined:

[0050] Determination method:

[0051] The collected samples were taken back to the laboratory for processing. For the obtained plant samples, they were first washed, then dried in an oven at 60℃, and then placed in a muffle furnace, which was heated from room temperature to 600℃ at a rate of 10℃ / min and maintained for 2h to obtain plant ash.

[0052] Plant sample digestion: check if the inside of the digestion tube is clean. If the detected element is trace, in order to avoid contamination, weigh a certain amount of ash (about 100 mg), and add the same amount of sample to each tube. Record the weight of the added sample. Add 8 mL of concentrated nitric acid to the digestion tube with the sample, cover it overnight. Digest in the graphite furnace instrument until 1 mL. Continue to digest until 1 mL after adding 1 mL of H2O2. Transfer the sample in the digestion tube to a 15 mL centrifuge tube.

[0053] Quantify the sample dilution using the mass method: rinse the digestion tube with 2% dilute nitric acid three times to ensure that all samples are washed out and poured into a 15 mL centrifuge tube. Finally, record the mass of the centrifuge tube. Filter the solution with a 0.45 μm filter membrane and store it for testing.

[0054] Determine the Ga concentration in the plant ash extraction solution using inductively coupled plasma optical emission spectrometer (ICP-OES). The calculation formula is as follows:

[0055]

[0056] The density of 2% dilute nitric acid is equivalent to water.

[0057] Determination results:

[0058] The results are shown in Figure 2 The ash Ga content of Selaginellaceae Xiaocuiyun, Pteridaceae Xibianfengyou, and Lobariaceae Zunfu is >800 mg / kg. Xibianfengyou, Zunfu, and Xiaocuiyun can recover about 1657.8 g, 1991.7 g, and 3318.2 g of Ga per mu, respectively. Pteridium aquilinum can only recover about 116.0 g of Ga per mu. The recovery calculation formula is as follows:

[0059] Recovery (g) = weight of plant ash per mu x Ga concentration in ash

[0060] Example 3: Collection of Ga from soil using Chinese Lobaria of Lobariaceae

[0061] Chinese Lobaria of Lobariaceae is planted in a subtropical monsoon climate area with an average annual temperature of 19°C and an average annual precipitation of 1774 mm. The soil type is red soil, the soil pH is 4.42-5.57, and it is acidic. The Ga content of the soil is 124.67 mg / kg. The specific operation is as follows:

[0062] 1. Plant Chinese Lobaria of Lobariaceae in the farmland of Baishuizhai in Dingnan County, Ganzhou City, Jiangxi Province in mid-July, with a planting density of 4500 plants per mu. Use Dryopteris erythrosora as a control. When planting, use spore propagation, and the soil should be loose and well-drained. Keep the soil moist on a daily basis, apply thin liquid fertilizer regularly, and prune the yellow leaves in a timely manner.

[0063] 2, 90 days after harvest of the above-ground parts of Cibotium barometz and Drynaria fortunei, dry them in an oven and then ash them in a muffle furnace at 550℃.

[0064] 3, Ga content determination:

[0065] Determination method:

[0066] Sample collection: The collected samples were taken back to the laboratory for processing. For the obtained plant samples, they were first washed, then dried in an oven at 60℃, weighed, and then ground and crushed. If manual grinding and crushing were not sufficient, a ball mill was used for crushing.

[0067] Plant sample digestion: Check whether the inside of the digestion tube is clean. If the detected element is trace, in order to avoid contamination before and after, weigh a certain amount of plant sample (≈100mg). The weight of the sample added to each tube should be as consistent as possible, and the mass of the added sample should be recorded. Add 8mL of concentrated nitric acid to the digestion tube with the sample, cover it overnight. Digest on a graphite furnace digester to 1mL, and then continue to digest to 1mL after adding 1mL of H2O2. Transfer the sample in the digestion tube to a 15mL centrifuge tube one by one.

[0068] Quantitative dilution of the sample using the mass method: rinse the digestion tube with 2% dilute nitric acid three times to ensure that all samples are washed out and poured into a 15mL centrifuge tube. Finally, record the mass of the centrifuge tube, and filter the solution with a 0.45μm filter membrane and store it for testing.

[0069] Determine the Ga concentration in the plant ash solution using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0070] Determination results:

[0071] The results are shown in Table 1. Figure 3 The ash Ga content of Cibotium barometz is >1000mg / kg, and about 2094.9g of Ga can be recovered per mu. Drynaria fortunei can only recover about 203.5g of Ga per mu.

[0072] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and do not limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. Use of a fern in extracting metal gallium from soil.

2. Use according to claim 1, wherein The fern is any one of Selaginella uncinata, Pteris cretica, Cyathea togoi, and Sinopteridium chinense.

3. The use according to claim 1, wherein The leaf blade of the Selaginella uncinata contains 111.93-165.60 mg / kg of gallium; the leaf blade of the Pteris cretica contains 40.32-53.48 mg / kg of gallium; the leaf blade of the Cyathea togoi contains 108.23-125.69 mg / kg of gallium; and the leaf blade of the Sinopteridium chinense contains 67.22-68.06 mg / kg of gallium.

4. A method for extracting metal gallium from soil using a fern, characterized by, The method comprises planting the fern on soil, harvesting the aboveground part of the fern after the fern has grown for 90 days, and thereby realizing the mining of metal gallium by the fern.

5. The method of claim 4, wherein, The fern is any one of Selaginella uncinata, Pteris cretica, Cyathea togoi, and Sinopteridium chinense.

6. The method of claim 5, wherein, The method further comprises drying the aboveground part of the fern.

7. The method of claim 6, wherein, The method further comprises ashing the dried aboveground part of the fern.

8. The method of claim 7, wherein, The ashing temperature is 500-550 ℃.

9. The method of claim 8, wherein, The ashed Selaginella uncinata contains 1678.93-2483.95 g of ash; the ashed Pteris cretica contains 604.88-802.18 g of ash; the ashed Cyathea togoi contains 1623.45-1885.32 g of ash; and the ashed Sinopteridium chinense contains 1008.39-1020.93 g of ash.

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