How to make and use soil conditioners

Abstract

To provide a method and an apparatus for obtaining aluminum-reduced soil and minerals that, when acidified, causes little aluminum elution from the soil and minerals, which has an adverse effect on plants and animals. [Solution] The method for preparing aluminum-reduced soil and minerals of the present invention involves extracting aluminum from soil and mineral samples by contacting the samples with an extractant R consisting of gluconolactone. The aluminum extraction device comprises an extraction chamber filled with an aluminum-containing sample and an extraction liquid supply mechanism for supplying an extraction liquid consisting of an acidic aqueous solution of gluconolactone into the extraction chamber. The method for preparing plant growing soil involves extracting aluminum from the sample with the extractant, then adding an organic acid such as phosphate or citric acid to the resulting aluminum-reduced sample to detoxify the aluminum ions and replenish magnesium, potassium, and calcium.

Description

[Technical Field]

[0001] The present invention relates to an aluminum extraction method and an aluminum extraction apparatus for producing aluminum-reduced soil and minerals using an aluminum extractant, and a method for utilizing aluminum-reduced soil and minerals. [Background technology]

[0002] Generally, aluminum contained in soil and minerals is liberated as aluminum ions when the soil pH drops below 5.6. Aluminum ions not only inhibit root formation and root elongation in plants, but also bind to phosphate, a fertilizer component, making it unavailable to plants. Roots are important organs that absorb water and inorganic salts, and inhibiting their elongation not only results in poor plant growth but also reduces tolerance to high temperatures and drought. Furthermore, if liberated aluminum ions flow into ponds or rivers, they can have a detrimental effect on living organisms, particularly fish, and can be fatally toxic. Therefore, measures are being taken to prevent soil and mineral acidification. Specifically, alkaline lime (calcium oxide, calcium hydroxide, calcium carbonate) is added to soil and minerals to prevent a drop in their pH.

[0003] However, the effectiveness of preventing aluminum ion leaching by adjusting the pH of soil and minerals as described above is significantly lost due to acidification caused by acid rain, etc. Furthermore, excessive application of lime to prevent acidification can cause problems such as damage due to excess calcium, reducing crop yields.

[0004] In addition, by using minerals that do not contain aluminum as soil, the effects of aluminum ions can be eliminated.

[0005] However, even the minerals mentioned above contain aluminum ions as impurities. For example, quartz is a transparent silicon dioxide crystal, but red or cloudy quartz contains aluminum. Refining the minerals to remove the aluminum is extremely expensive, making them unsuitable for use in general plant cultivation soil.

[0006] On the other hand, aluminum can also be extracted from clay minerals contained in soil using a chelating agent such as glycol ether diamine tetraacetic acid (EGTA) (see, for example, Patent Document 1).

[0007] However, such chelating agents are highly biotoxic and therefore impose a large environmental load on cultivated land, lake shores, riverbeds, etc. Furthermore, wastewater containing such chelating agents also imposes a large environmental load. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-160801 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in light of the above circumstances, and its object is to provide a method for extracting aluminum from soil and mineral samples that does not require the use of compounds, equipment, or methods that have a large environmental impact, an extraction apparatus used therein, and a method for preparing and using aluminum-reduced soil and mineral samples. [Means for solving the problem]

[0010] The aluminum extraction method of the present invention is characterized by extracting aluminum from soil and mineral samples by contacting the samples with an extracting solution consisting of an aqueous solution of gluconolactone / gluconic acid. Note that gluconolactone and gluconic acid are essentially the same compound, and both exist in equilibrium at a weakly acidic pH.

[0011] In the aluminum extraction method of the present invention, the extraction liquid preferably has a pH of less than 7.

[0012] In the aluminum extraction method of the present invention, the extraction liquid preferably has a gluconolactone concentration of 10 mM or more.

[0013] In the aluminum extraction method of the present invention, the temperature of the extraction liquid with which the soil and mineral sample are brought into contact is preferably 2°C or higher.

[0014] In the aluminum extraction method of the present invention, the extraction liquid may contain a polyaminoacetic acid-based chelating agent and an organic acid.

[0015] The aluminum extraction device of the present invention is characterized by comprising an extraction chamber into which an aluminum-containing soil or mineral sample is filled, and an extraction liquid supply mechanism for supplying an extraction liquid comprising an acidic aqueous solution of gluconolactone into the extraction chamber.

[0016] The method of use of the present invention is characterized by extracting aluminum, detoxifying the aluminum ions by adding organic acids such as phosphate, malic acid, citric acid, and succinic acid, and then neutralizing and adding minerals to create soil and mineral samples for plant cultivation. [Effects of the Invention]

[0017] According to the aluminum extraction method of the present invention, aluminum contained in soil and mineral samples can be extracted by contacting the soil and mineral samples with an extractant consisting of an aqueous solution of gluconolactone. Gluconolactone is a highly biologically safe substance found in honey and used as a food additive. It is also present in the metabolic pathways of living organisms and is biodegradable, posing a low environmental burden. Furthermore, it is readily available and can be used by many people around the world. Therefore, because the aluminum extraction method of the present invention does not use a strong alkaline or strong acid solution, there is little risk of adverse effects on bacteria in the soil, even when reusing soil and mineral samples after aluminum extraction.

[0018] According to the aluminum extraction device of the present invention, the above-mentioned aluminum extraction method can be carried out simply and easily.

[0019] According to the method for preparing soil for plant cultivation of the present invention, harmless insoluble aluminum phosphate can be produced by contacting the soil with an extracting solution consisting of an aqueous solution of gluconolactone and then reacting the extracted aluminum with phosphate. Furthermore, adding magnesium lime or other additives neutralizes the pH and supplies metal ions such as potassium, magnesium, and calcium to replace the extracted aluminum, thereby neutralizing the charge. This eliminates the effects of aluminum and makes soil for plant cultivation extremely easy.

[0020] According to the aluminum extraction method of the present invention, an aluminum solution can be obtained by contacting soil or mineral samples with an extractant consisting of an aqueous solution of gluconolactone. This aluminum solution inhibits the root formation and elongation of most plants, suppressing plant growth. Furthermore, inhibiting root elongation shortens the roots, making the plants easier to uproot. As a result, plant removal can be easily performed. [Brief explanation of the drawings]

[0021] [Figure 1]FIG. 1 is a block diagram showing an example of a scheme for the aluminum extraction method of the present invention. [Figure 2] 1 is a cross-sectional view showing an outline of the configuration of an example of an aluminum extraction apparatus of the present invention. [Figure 3] 1 is a graph showing the results of Experimental Example 1. [Figure 4] 10 is a graph showing the results of Experimental Example 2. [Figure 5] 10 is a graph showing the results of Experimental Example 3. [Figure 6] 10 is a graph showing the results of Experimental Example 4. [Figure 7] 10 is a graph showing the results of Experimental Example 5. [Figure 8] 10 is a graph showing the results of Experimental Example 6. [Figure 9] 10 is a graph showing the results of Experimental Example 7. [Figure 10] 10 is a graph showing the results of Experimental Example 8. [Figure 11] 10 is a graph showing the results of Experimental Example 9. [Figure 12-1] 10 is a photograph showing the results of Experimental Example 10. [Figure 12-2] 10 is a photograph showing the results of Experimental Example 10. [Figure 12-3] 10 is a graph showing the results of Experimental Example 10. [Figure 13-1] 10 is a photograph showing the results of Experimental Example 11. [Figure 13-2] 10 is a photograph showing the results of Experimental Example 11. [Figure 13-3] 10 is a graph showing the results of Experimental Example 11. [Figure 14] 10 is a photograph showing the results of Experimental Example 12. [Figure 15] 10 is a photograph showing the results of Experimental Example 13. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be described below through embodiments of the present invention, but the following embodiments do not limit the invention as claimed, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0023] [Aluminum extraction method] The aluminum extraction method of the present invention is a method for extracting aluminum contained in soil and mineral samples by contacting the soil and mineral samples with an extracting liquid consisting of an aqueous solution of gluconolactone or powder.

[0024] [Aluminum-containing sample] The soil and mineral samples or raw materials that can be used are not particularly limited as long as they are solids that contain aluminum. The target sample for aluminum extraction is a solid raw material, such as minerals containing aluminum oxide (Al2O3), such as corundum and bauxite, orthoclase (KAlSi3O8) and (XAl2O3) m (SiO2) n [wherein X represents a metal atom such as Fe, Mn, Cu, etc.], and clay minerals containing these can be used. In particular, as shown in the results of the experimental examples described below, the aluminum extraction method of the present invention can be effectively applied to aluminum silicate-containing minerals, which are highly crystallized minerals from which aluminum could not previously be separated and extracted without the use of strong acids or various chelating agents. In addition, if the solid raw material is an amorphous mineral that has not yet crystallized, or a mineral that contains compounds such as a metal compound bonded to organic matter or a metal carbonate, it can be easily extracted using a chelating agent such as gluconolactone, ethylenediaminetetraacetic acid (EDTA), or glycoletherdiaminetetraacetic acid (EGTA), and an organic acid.

[0025] As the soil and mineral sample, soil itself containing the above minerals may be used. Soil collected from the ground or commercially available can be used as is or after necessary pretreatment.

[0026] [Extraction liquid] The extraction solution used for extraction is an aqueous solution of gluconolactone obtained by dissolving gluconic acid or a gluconate in an aqueous medium, and the gluconolactone contained in this aqueous solution is produced by equilibration with gluconic acid. Gluconic acid is a substance present in the metabolic pathway of living organisms and is biodegradable and highly safe for living organisms, so the aluminum extraction method of the present invention can extract aluminum with extremely high safety.

[0027] Examples of aqueous media that can be used include sodium acetate buffer, glycine-HCl buffer, phosphate buffer, citrate buffer (citric acid + sodium citrate), citrate phosphate buffer (citric acid + sodium phosphate), borate buffer, tartrate buffer, and Tris buffer.

[0028] The extraction liquid is preferably acidic, more preferably at pH 5.6 or less, and particularly preferably at pH 2.0 to 3.0. If the pH of the extraction solution is neutral or alkaline, gluconolactone will be ring-opened to form gluconic acid through equilibration, making it impossible to extract aluminum with gluconolactone efficiently. An extraction solution with a pH of 5.6 or less can effectively extract aluminum with gluconolactone, and an extraction solution with a pH of 3.0 or less can extract aluminum with even higher efficiency. Furthermore, a pH of 2.0 or higher ensures safety for the human body during extraction.

[0029] The concentration of gluconolactone in the extraction solution is preferably 10 mM or more, and although this varies depending on the pH and temperature of the extraction solution, it is more preferably 1,000 to 2,000 mM. By setting the gluconolactone concentration to 10 mM or more, aluminum can be effectively extracted by gluconolactone. Gluconolactone reaches a saturated concentration at approximately 2,000 mM.

[0030] The temperature at which the soil or mineral sample is contacted with the extraction liquid may be 2°C or higher, preferably 40°C or higher, and may further be 60°C or higher. The higher the contact temperature between the aluminum-containing sample and the extraction liquid, the more efficiently aluminum can be extracted.

[0031] [Combined use with polyaminoacetic acid chelating agents] The extraction solution may contain a polyaminoacetic acid chelating agent as another chelating agent. By using gluconolactone and a polyaminoacetic acid chelating agent in combination, aluminum can be extracted more efficiently. As the polyaminoacetic acid-based chelating agent, glycol ether diamine tetraacetic acid (EGTA), ethylene diamine tetraacetic acid (EDTA), or the like can be used.

[0032] The concentration of the polyaminoacetic acid chelating agent in the extraction solution is preferably 50 to 250 mM, more preferably 150 to 250 mM. By using a polyaminoacetic acid chelating agent with a concentration in the above range, aluminum can be extracted with high efficiency while minimizing the environmental impact of the polyaminoacetic acid chelating agent.

[0033] [Combined use with organic acids] The extraction solution may contain other organic acids such as malic acid, acetic acid, citric acid, and oxalic acid. By using gluconolactone in combination with an organic acid, aluminum can be extracted more efficiently. As the organic acid, malic acid, acetic acid, citric acid, succinic acid, natural amorphous organic acid mixtures such as fulvic acid, humic acid, and mixtures thereof can be used.

[0034] The concentration of the organic acid in the extraction solution is preferably 10 to 250 mM, more preferably 10 to 50 mM. By keeping the concentration of the organic acid within this range, aluminum can be extracted with high efficiency while minimizing the effect of pH decrease caused by the extractant.

[0035] Specifically, as shown in Figure 1, the aluminum extraction method of the present invention involves first contacting soil and mineral samples with a solution or powder of extractant prepared to the desired concentration and pH conditions. The aluminum-containing wastewater is then drained away. If the powder is in contact with the soil, the soil is drained away with water. This yields crude aluminum-reduced soil.

[0036] According to the aluminum extraction method of the present invention, aluminum contained in soil and mineral samples can be extracted by contacting the soil and mineral samples with an extractant consisting of an aqueous solution of gluconolactone, i.e., by operating under mild conditions at room temperature. Furthermore, gluconolactone is a substance present in the metabolic pathways of living organisms, is biodegradable, highly biologically safe, and is readily available, thereby minimizing environmental impact and contributing to environmental protection. As a result, the aluminum extraction method of the present invention does not use a strong alkaline or strong acid solution, and therefore, even when the soil and mineral samples after aluminum extraction are reused, there is little risk of adverse effects on bacteria in the soil, and they can be used, for example, as soil for cultivation.

[0037] In the aluminum extraction method of the present invention, as shown in the results of the experimental examples described below, the higher the acidity of the extraction solution, the more aluminum is extracted, which suggests that the extraction of aluminum is not due to the chelate effect. This is because an extraction solution containing gluconolactone is in chemical equilibrium with gluconic acid and gluconolactone formed by an intramolecular bond of said gluconic acid, and as the extraction solution becomes more acidic, the amount of gluconic acid with a carboxyl group that contributes to the chelate effect decreases and the amount of gluconolactone in which the carboxyl group is ring-closed increases.

[0038] [Aluminum Extraction Device] The aluminum extraction apparatus of the present invention is an apparatus used to carry out the aluminum extraction method described above. FIG. 2 is a cross-sectional view showing the outline of the configuration of an example of an aluminum extraction apparatus of the present invention. This aluminum extraction apparatus 10 is equipped with a flow pipe 11 having a vertically extending straight extraction chamber 12 formed therein, which is filled with soil or aluminum-containing solid material sample S. An inlet 14 is opened at the upper end of this flow pipe 11 for introducing an extraction liquid R consisting of an extractant containing acidic gluconolactone, and an outlet 15 is opened at the lower end of the flow pipe 11 for discharging an aluminum-containing liquid M obtained by contacting the soil and mineral sample S with the extraction liquid R. A filtering member (not shown), such as a filter, is provided at the outlet 15 to allow the liquid aluminum-containing solution M to pass through but not the solid soil and mineral sample S. The inlet 14 is connected to, for example, a tank (not shown) for storing the extraction liquid R via an inlet channel 14A, and the inlet channel 14A is further provided with a flow rate adjusting means (not shown) for adjusting the supply rate of the extraction liquid R supplied to the extraction chamber 12. These components constitute an extraction liquid supply mechanism for supplying the extraction liquid R to the extraction chamber 12. In FIG. 1, 15A is an outlet path for discharging the aluminum solution M.

[0039] The flow pipe 11, the inlet channel 14A, and the outlet channel 15A are made of a material that is durable against the extraction liquid R, for example.

[0040] The aluminum extraction device 10 is preferably provided with a temperature adjusting means for adjusting the temperature inside the extraction chamber 12 and a pressure adjusting means for adjusting the pressure inside the extraction chamber 12.

[0041] According to the aluminum detection device of the present invention, the above-mentioned aluminum extraction method can be carried out easily.

[0042] [Method of washing soil after aluminum extraction] After aluminum extraction, aluminum ions still remain on the soil surface. Some of the extracted aluminum ions can be washed away by running water over the soil. Phosphate can also be used to create aluminum phosphate, which can be insoluble in water and detoxified. Furthermore, organic acids such as citric acid, malic acid, succinic acid, and oxalic acid, as well as mixtures thereof, can be used to chelate aluminum ions and detoxify them.

[0043] [Methods for using soil and mineral samples after aluminum extraction] The aluminum-reduced soil or mineral samples prepared by this invention have little elution of aluminum ions, which are harmful to aquatic organisms due to a decrease in pH caused by acid rain, etc., and can be used as foundation soil or embankment stones for lakes and aquaculture ponds.

[0044] [Method for preparing soil for plant cultivation after aluminum extraction] The pH of soil from which aluminum has been extracted using an extractant is low, making it unsuitable for general plant cultivation. To use the soil as plant cultivation soil, the soil from which aluminum has been extracted according to the present invention is neutralized and mineralized. Neutralization can be achieved by adding hydroxides, carbonates, ammonia, calcium oxide, magnesium oxide, etc. Furthermore, since the aluminum extraction results in a deficiency of cations, these are replenished by adding metal ions such as potassium, magnesium, and calcium. Through these processes, soil and mineral samples suitable for plant cultivation can be obtained.

[0045] [Method of using the extract after aluminum extraction] The aluminum ions extracted from soil and mineral samples by the extractant inhibit root growth and root elongation, and can be used as an aid in suppressing the growth and removal of weeds. The extractant can be sprayed directly onto the target area, or a solution containing aluminum ions extracted from soil and mineral samples by the extractant can be sprayed.

[0046] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications can be made.

[0047] Below, an example of an experiment conducted to confirm the effects of the present invention will be described.

[0048] <Experimental Example 1: Concentration Dependence> Aluminum was extracted by contacting soil with extraction solutions containing various concentrations of sodium gluconate under the following specific conditions: [Mineral samples] Type: Ground soil Sample size: 1g [Extraction liquid] pH 5.0 Sodium gluconate concentration: (0-200mM) Buffer solution: 50 mM potassium acetate buffer (pH 5.0) ·Dropped amount: 1mL Contact Condition ·Temperature: 25℃ Duration: 1 hour The results are shown in the graph in FIG.

[0049] As is clear from the graph in FIG. 3, the amount of aluminum extracted increases as the sodium gluconate concentration, i.e., the gluconolactone concentration, increases.

[0050] <Experimental Example 2: Concentration Dependence and Temperature Dependence> Aluminum was extracted by contacting the soil sample with the extraction solution containing various concentrations of sodium gluconate at various temperatures under the following specific conditions: [Soil sample] Type: Ground soil Sample size: 0.1g [Extraction liquid] pH 3.8 Sodium gluconate concentration: (0~200mM) Buffer solution: 25 mM sodium acetate buffer (pH 3.8) ·Dropped amount: 0.2mL Contact Condition ·Temperature: 25℃, 40℃, 55℃ Duration: 20 hours The results are shown in the graph in FIG.

[0051] As is clear from the graph in Figure 4, the higher the temperature, the greater the amount of aluminum extracted.

[0052] <Experimental Example 3: pH Dependence of Aluminum Extraction from Terrestrial Soil> Aluminum was extracted from terrestrial soil by contacting the extraction solution with each pH under the following specific conditions: [Soil sample] Type: Dry terrestrial soil Sample size: 0.01g [Extraction liquid] pH 3.8 to pH 5.6 Sodium gluconate concentration: 10mM Buffer solutions: 25 mM HCl / KCl buffer solution (pH 2), 25 mM sodium citrate buffer solution (pH 3), 25 mM sodium acetate buffer solution (pH 4, pH 5), 25 mM sodium phosphate buffer solution (pH 6, pH 7) ·Dropped amount: 1.8mL Contact Condition ·Temperature: 25℃ Duration: 30 minutes The results are shown in Figure 5 (△). ● indicates the results of a control experiment carried out in the same manner except that buffer solutions of various pH values ​​were used as the extraction solution.

[0053] As is clear from the graph in Figure 5, aluminum can be extracted when the pH is below 7. Furthermore, the amount of aluminum extracted increases as the pH decreases. At pH 4 or below, the amount of aluminum extracted remains unchanged.

[0054] <Experimental Example 4: Extraction of aluminum from horticultural soil> [Soil sample] Type: Red clay, Kanuma clay (commercially available) Sample size: 1g [Extraction liquid] Sodium gluconate concentration: 50mM Buffer solution: 50 mM sodium acetate buffer (pH 5) ·Dropped amount: 1.0mL Contact Condition ·Temperature: 25℃ Duration: 3 hours The results are shown in Figure 6. In Figure 6, the error bars indicate the standard deviation of three tests.

[0055] From the graph in FIG. 6, it was confirmed that aluminum could be extracted from commercially available garden soils, red soil and Kanuma soil, using the gluconolactone solution of the present invention.

[0056] <Experimental Example 5: Aluminum extraction when extractant powder is sprayed on soil> [Soil sample] Type: Ground soil Sample size: 0.5g [Extractant] Sodium gluconate: 0.5g Extract with 0.5mL of water after a certain time Contact Condition ·Temperature: 25℃ The results are shown in Figure 7. In Figure 7, the error bars indicate the standard deviation of three tests.

[0057] As is clear from the graph in Figure 7, aluminum can be extracted by spraying water after spraying sodium gluconate. The longer the contact time, the more aluminum can be extracted.

[0058] <Experimental Example 6: Removal of extracted aluminum ions using potassium phosphate> [Soil sample] Type: Ground soil Sample size: 1g [Extractant] 50 mM sodium gluconate (100 mM sodium acetate buffer, pH 5.0) [Contact conditions: Aluminum extraction] ·Temperature: 25℃ Duration: 1 hour [Contact conditions: removal of aluminum ions] Remover: 1mM potassium dihydrogen phosphate solution ·Temperature: 25℃ Duration: 10 minutes The results are shown in Figure 8.

[0059] As is clear from the graph in Figure 8, the extracted aluminum ions can be removed by adding phosphate.

[0060] <Experimental Example 7: Removal of extracted aluminum ions with citric acid> [Soil sample] Type: Ground soil Sample size: 1g [Extractant] 50 mM sodium gluconate (100 mM sodium acetate buffer, pH 5.0) [Contact conditions: Aluminum extraction] ·Temperature: 25℃ Duration: 1 hour [Contact conditions: removal of aluminum ions] Remover: 1mM citric acid solution ·Temperature: 25℃ Duration: 10 minutes The results are shown in Figure 9. In Figure 9, the error bars indicate the standard deviation of three tests.

[0061] As is clear from the graph in Figure 9, the extracted aluminum ions can be removed by adding phosphate, which causes the aluminum ions to react with phosphoric acid to produce insoluble aluminum phosphate.

[0062] <Experimental Example 8: Extraction of aluminum from each extraction material> (8-1) Extraction solution B: Gluconolactone Aluminum was extracted by contacting dried soil and mineral samples with extraction solution B. Specifically, 200 μL of extraction solution B (25 mM glycine-HCl buffer (pH 3.0) containing 100 mM sodium gluconate) at pH 3.0 was added dropwise to 100 mg of dried soil, and the mixture was left at 25°C for 1 hour, then centrifuged, and the aluminum concentration in the supernatant was measured. The results are shown in bar graph B of Figure 10. (8-2) Extraction solution C: EGTA The aluminum concentration was measured in the same manner, except that extraction solution C was used instead of extraction solution B. The results are shown in bar graph C in Figure 10. Extraction solution C was prepared by adding EGTA to a 25 mM glycine-HCl buffer solution (pH 3.0) to give a concentration of 100 mM EGTA (pH 3.0). (8-3) Extraction solution D: Gluconolactone + EGTA The aluminum concentration was measured in the same manner, except that extraction solution D was used instead of extraction solution B. The results are shown in bar graph D in Figure 10. Extraction solution D was prepared by adding sodium gluconate and EGTA to a 25 mM glycine-HCl buffer solution (pH 3.0) so that the concentrations of each were 100 mM. (8-4) Buffer: Control The aluminum concentration was measured in the same manner, except that extraction solution A was used instead of extraction solution B. The results are shown in bar graph A of Figure 10. Extraction solution A is a 25 mM glycine-HCl buffer solution (pH 3.0) that does not contain sodium gluconate or EGTA. In Figure 10, the error bars indicate the standard deviation of triplicate tests.

[0063] As is clear from bar graph B in Figure 10, when an acidic extraction solution containing only gluconolactone is used, aluminum can be extracted more efficiently at room temperature than when an extraction solution containing only EGTA is used (bar graph C). Furthermore, by using gluconolactone and EGTA in combination (bar graph D), aluminum can be extracted more efficiently than when an acidic extraction solution containing only gluconolactone is used (bar graph B). Moreover, the effect of using gluconolactone and EGTA in combination was not simply an additive effect of the effect when an extraction solution containing only gluconolactone and the effect when an extraction solution containing only EGTA were used, but a greater synergistic effect was obtained.

[0064] Furthermore, visual observation of the supernatants after extraction with the above extraction solutions A to D revealed that the supernatant obtained from extraction solution B, which contained only sodium gluconate, was clear, while the supernatant obtained from extraction solution C, which contained only EGTA, and the supernatant obtained from extraction solution D, which used a combination of gluconolactone and EGTA, were earth-colored. This is presumably because a large amount of organic matter contained in the soil, which is an aluminum-containing sample, was also extracted at the same time. When aluminum extraction is performed in an environment where environmental considerations are not necessary, such as in a factory, the combined use of EGTA and gluconolactone can improve aluminum extraction efficiency.

[0065] <Experimental Example 10: Concentration dependency when used in combination with malic acid> The aluminum-containing sample was contacted with an extracting solution containing gluconolactone and malic acid, an organic acid, adjusted to various concentrations, to extract aluminum. The specific conditions were as follows: [Aluminum-containing sample] Type: Commercially available red clay Sample size: 0.5g [Extraction liquid] pH 5.0 Sodium gluconate concentration: 100mM Malic acid concentration: (0, 50, 100, 200mM) Buffer solution: 100 mM sodium acetate buffer (pH 5.0) ·Dropped amount: 1.0mL Contact Condition ·Temperature: 25℃ Duration: 6 hours The results are shown in the graph of FIG.

[0066] As is clear from the graph in Figure 11, when the concentration of malic acid coexisting with gluconolactone is 50-100 mM, the amount of aluminum extracted increases. At 200 mM malic acid, the amount of extracted aluminum ions decreased compared to the control without added malic acid. Malic acid is known to have a chelating effect, albeit a small one. It is thought that the high concentration of malic acid chelated some of the extracted aluminum ions, resulting in a decrease in the measured aluminum ion value.

[0067] <Experimental Example 11: Cultivation experiment of soybeans in soil adjusted for cultivation after aluminum extraction> [Soil sample] Soil sample preparation: A planter was used to avoid external influences such as root-cutting insects. 10 L of commercially available plant cultivation soil was placed in the planter, and aluminum was extracted with 2 L of 50 mM gluconolactone and 2 mM potassium phosphate (50 mM potassium acetate (pH 5.0)). 50 g was then mixed in per square meter of soil. This was then left for three days, and this was designated as reduced-aluminum soil (A). Soil treated in the same way without the addition of gluconolactone served as the control (B). Cultivated species: soybean (very early edamame (Sakata Seed)) The results are shown in Figures 12-1, 12-2, and 12-3.

[0068] As shown in Figure 12-1, after 42 days, soybeans planted in the reduced-aluminum soil (A) grew better than those planted in the untreated control soil (B). As shown in Figures 12-2 and 12-3, soybeans grown in the reduced-aluminum soil (A) produced approximately 1.3 times the number of pods and 1.6 times the number of seeds compared to those grown in the control soil (B). It was clear that using the reduced-aluminum soil prepared according to the present invention improved plant growth and increased crop yields. Meanwhile, roots in the reduced-aluminum soil also grew better than those in the control soil, but comparisons were not possible because it was not possible to remove the soil or to uproot the plants from the soil.

[0069] <Experimental Example 12: Wheat cultivation experiment in soil adjusted for cultivation after aluminum extraction> [Soil sample] Soil sample preparation: A planter was used to avoid external influences such as root-cutting insects. 10 L of commercially available plant cultivation soil was placed in the planter, and aluminum was extracted with 2 L of 50 mM gluconolactone and 2 mM potassium phosphate (50 mM potassium acetate (pH 5.0)). 50 g was then mixed in per square meter of soil. This was then left for three days, and this was designated as reduced-aluminum soil (A). Soil treated in the same way without the addition of gluconolactone served as the control (B). Cultivated species: Wheat (Yumeasahi) Cultivation method: Wheat was soaked in water for three days and the germination of wheat was confirmed. Each soil was placed in a planter, and four germinated grains were planted in each of four locations. When the wheat had about four leaves, it was trampled once. Cultivation period: 220 days The results are shown in Figures 13-1, 13-2, and 13-3.

[0070] As shown in Figure 14-1, wheat planted in aluminum-extracted soil (A) grew better than wheat planted in untreated control soil (B) at 36 days of cultivation. Furthermore, as shown in Figure 14-2, the yield of wheat planted in aluminum-extracted soil (A) was 130.0 g, approximately 1.3 times higher than the yield of wheat planted in untreated control soil (B), which was 101.7 g. As shown in Figure 14-3, at harvest, wheat planted in aluminum-extracted soil (A) had a maximum root length of 25-40 cm, longer than the approximately 15-20 cm of wheat planted in untreated control soil (B), indicating a reduced inhibitory effect of aluminum on root elongation (the bar in the figure indicates 10 cm). This demonstrates that soil from which aluminum was removed by the present invention results in good root growth and plant growth.

[0071] Experimental Example 13: Effect of aluminum released by the present invention on the growth of oats [Soil sample] Soil: 10 L of commercially available soil for plant cultivation was used. 500 mL of 50 mM gluconolactone (50 mM potassium acetate (pH 5.0)) was added to the left side of the planter. Then, 50 g of dolomitic lime was spread on each square meter of soil. The planter was then left to stand for one day. ·Cultivated species: oats Cultivation period: 40 days The results are shown in Figure 14.

[0072] As shown in Figure 14, the growth of oats planted in soil near the area where gluconic acid was added was suppressed compared to the control soil without the addition of gluconic acid. This indicates that when only gluconic acid is added, the free aluminum suppresses plant growth.

[0073] <Experimental Example 14: Extraction of aluminum from minerals> Aluminum was extracted by contacting the mineral with a gluconolactone solution under the following specific conditions: [Mineral samples] Type: Small chunks of aluminum-containing minerals (topaz, rhyolite, lapis lazuli, prehnite, feldspar, sodalite, blue-and-white, spodumene, zoisite, obsidian) crushed to a diameter of approximately 4-6 mm Sample size: 0.25-1.16g [Extraction liquid] pH 5.0 Gluconolactone concentration: (50mM) Buffer solution: 50 mM sodium acetate buffer (pH 5.0) ·Dropped amount: 1mL Contact Condition ·Temperature: 25℃ Duration: 20 hours The results are shown in the graph of FIG.

[0074] As shown in Figure 15, aluminum can be extracted from various minerals containing aluminum using an aluminum extractant containing gluconolactone. Aluminum was particularly well extracted from sodalite and blue-green sapphire, which belong to the silicate minerals of the sodalite group. [Industrial Applicability]

[0075] By using the aluminum-reduced soil or aluminum-containing sample prepared by this invention as foundation soil or bank protection stones for lakes, aquaculture ponds, and recreational fishing ponds, the amount of aluminum leached by acid rain, which is harmful to aquatic organisms, can be reduced.

[0076] The present invention creates aluminum-reduced soil and minerals for plant cultivation by liberating aluminum from soil, inactivating it with phosphate ions and a chelating agent, and then coordinating metals useful to plants, such as calcium, potassium, and magnesium, to the aluminum-depleted areas. It is known that when soil pH drops due to, for example, acid rain, the aluminum in the soil is liberated as aluminum ions, which inhibits plant growth. Soybeans, wheat, and other crops grew better in soil treated with the present invention than in untreated soil. Therefore, the present invention can be effectively used in agricultural and horticultural applications.

[0077] The aluminum extraction method of the present invention can liberate aluminum from soil. Aluminum ions bind to phosphate ions, a nutrient necessary for plants in the soil, making them unavailable to plants. They also have effects such as inhibiting plant root growth. These effects are known to inhibit plant growth. In the present invention, free aluminum ions are inactivated with phosphate ions. However, without inactivation, the free aluminum ions inhibit plant growth. Therefore, the gluconic acid solution used in the present invention can be effectively used as a herbicide. [Explanation of symbols]

[0078] 10. Aluminum Extraction Equipment 11 Flow pipe 12 Extraction chamber 14 Inlet 14A Inflow channel 15 Outlet 15A Outflow channel M Aluminum-containing solution R Extraction liquid S Aluminum-containing sample

Claims

1. An aluminum extraction method comprising contacting soil and mineral samples with an extractant comprising gluconolactone to extract aluminum contained in the soil and mineral samples.

2. 2. The method for extracting aluminum according to claim 1, wherein the extractant is an aqueous solution, and the extraction liquid has a pH of less than 7.

3. 3. The aluminum extraction method according to claim 1, wherein the extractant is an aqueous solution and the concentration of gluconolactone is 10 mM or more.

4. 4. The method for extracting aluminum according to claim 1, wherein the temperature of the extractant with which the soil and mineral samples are brought into contact is 2° C. or higher.

5. 5. The aluminum extraction method according to claim 1, wherein the extractant contains a polyaminoacetic acid-based chelating agent, malic acid, citric acid, acetic acid, and phosphate.

6. A method for preparing soil for plant cultivation, comprising the steps of: extracting aluminum according to any one of claims 1 to 5; neutralizing the soil; and replenishing useful metal ions.

7. A method for inhibiting plant growth, comprising carrying out the aluminum extraction procedure according to any one of claims 1 to 5 from soil and mineral samples, and utilizing the toxicity of aluminum ions.

8. 1. An aluminum extraction apparatus comprising: an extraction chamber in which a soil or mineral sample is filled; and an extraction liquid supply mechanism for supplying an extraction liquid comprising an aqueous solution of the extractant into the extraction chamber.

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