Method for soil reclamation, restoration and improvement of a limestone mine area

Abstract

The application discloses a method for lime rock mine area soil reclamation, repair and improvement, which comprises the following steps: mixing citric acid, tartaric acid and water to obtain a first leaching agent; mixing rhamnolipid, quaternary ammonium salt modified chitosan microspheres and water to obtain a second leaching agent; mixing soluble starch, water, biochar powder, microbial inoculum, humic acid, algal powder and potassium dihydrogen phosphate, then adding the mixture into a mixed solution prepared by mixing liquid paraffin and span 80, and adding epichlorohydrin to react to obtain slow-release starch microspheres; and mixing the slow-release starch microspheres and water to obtain a soil improvement agent; ploughing the surface soil of the lime rock mine area, and sequentially using the first leaching agent, the second leaching agent and water for leaching treatment; and spraying the soil improvement agent into the surface soil. The application can effectively improve the acid-base property of the lime rock mine area soil, improve the soil fertility, and reduce the metal such as iron, copper and manganese and the toxic and harmful substances such as sulfate in the soil.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation technology in limestone mining areas, specifically relating to a method for soil reclamation, remediation, and improvement in limestone mining areas. Background Technology

[0002] The mineral composition of limestone is mainly calcite, accompanied by dolomite, magnesite, and other carbonate minerals. Some limestone deposits also contain alumina, organic matter such as coal and bitumen, as well as sulfates such as gypsum and anhydrite. As a major raw material for lime and cement production, limestone mining has increased with the continuous growth of construction projects. Much of this mining is done through open-pit mining, which has severely damaged the ecological environment of limestone mining areas. Extensive mining activities have destroyed the surface soil structure, stripping away topsoil and exposing surface rocks. Weathering and rainwater runoff then cause significant nutrient loss from the soil, leading to soil alkalization and decreased fertility. Furthermore, metals such as iron, copper, and manganese in the soil are easily exposed and flow into groundwater, causing pollution. Currently, the main method for remediating limestone mining areas is to cover the soil with topsoil. However, this requires a large amount of topsoil, and the resulting soil layer has low nutrient content and poor stability, making it unsuitable for rapid planting. Therefore, it is still necessary to research and develop a convenient, fast, and effective method for soil reclamation, restoration, and improvement, taking into account the characteristics of soil in limestone mining areas, in order to reduce environmental pollution and damage in limestone mining areas and create a good mining environment. Summary of the Invention

[0003] To address the aforementioned shortcomings, this invention discloses a method for soil reclamation, restoration, and improvement in limestone mining areas. This method can effectively improve the acidity and alkalinity of soil in limestone mining areas, enhance soil fertility, and reduce the levels of metals such as iron, copper, and manganese, as well as toxic and harmful substances such as sulfates in the soil.

[0004] This invention is achieved using the following technical solution:

[0005] A method for soil reclamation, restoration, and improvement in limestone mining areas includes the following steps:

[0006] (1) A first leaching agent is obtained by mixing citric acid, tartaric acid and water, wherein the weight ratio of citric acid, tartaric acid and water is (2-3):(0.5-1):100; a second leaching agent is obtained by mixing rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water, wherein the weight ratio of rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water is (1-3):(3-8):100; a mixture A is obtained by mixing soluble starch and water in a mass ratio of 1:(8-10); a mixture B is obtained by mixing biochar powder, microbial agent, humic acid, algae powder, potassium dihydrogen phosphate and water in a mass ratio of (10-15):(3-5):(1-3):(5-8):(0.3-0.5):100; then the mixture A and the mixture B are mixed in a volume ratio of 1:( Mix the liquid paraffin (1-1.2) in a ratio and stir at 50-60℃ for 10-20 min to obtain mixture C. At the same time, take liquid paraffin and add Span80 under stirring to obtain mixture D. The volume ratio of liquid paraffin to Span80 is 100:(2.5-10). Heat mixture D to 50-60℃ and slowly add mixture C under stirring. Then add epichlorohydrin and react for 3-5 h. The volume ratio of mixture C to mixture D is 1:10 and the volume ratio of epichlorohydrin to mixture C is 1:20. Cool and let stand to remove the oil phase and centrifuge to obtain precipitate E. Wash precipitate E with isopropanol and dry to obtain slow-release starch microspheres. Then mix slow-release starch microspheres and water in a mass ratio of (3-5):100 to obtain soil conditioner.

[0007] (2) The topsoil of the limestone mining area is tilled, and then a spray pipe is installed on the topsoil to spray the soil with a leaching agent for leaching treatment. A leaching liquid recovery pipe is installed in the topsoil layer to recover the leaching liquid after leaching treatment. The leaching treatment is first performed with the first leaching liquid obtained in step (1) for 12-24 hours, with a liquid-to-solid ratio of (5-10) mL:1g. Then, the second leaching liquid obtained in step (1) is used for 3-5 days, with a liquid-to-solid ratio of (10-20) mL:1g. Then, water is used for leaching for 1-2 days. Then, the leaching liquid recovery pipe is stopped or removed. The soil conditioner obtained in step (1) is then sprayed into the topsoil at a rate of 300-400 mL / m. 2 Herbaceous plants should be planted 8–12 hours after the soil conditioner has been sprayed.

[0008] Further, the preparation method of the quaternary ammonium salt modified chitosan microspheres in step (1) is to mix epoxy quaternary ammonium salt and water in a mass ratio of 1:(4-5) to obtain a mixture F, add chitosan to a 0.1% hydrochloric acid solution, the mass ratio of chitosan to hydrochloric acid solution is (1.5-3.5):200, then heat to 50-60℃ under stirring and slowly add the mixture F, then continue to stir the reaction at 50-60℃ for 36-48h, then add solid sodium hydroxide to adjust the pH to 12, let stand to obtain precipitate G, filter and wash precipitate G with ethanol, then dissolve precipitate G in a 1% acetic acid solution to obtain an aqueous solution. The mass ratio of the precipitate to the acetic acid solution is (0.5-2):100. Liquid paraffin is taken and mixed with Span80 under stirring to obtain an oil phase solution. The volume ratio of the liquid paraffin to Span80 is 100:(2.5-10). Then, the aqueous phase solution is slowly added to the oil phase solution and stirred, and reacted at 45-55℃ for 1-2 hours. Then, glutaraldehyde is added and the reaction continues for 3-5 hours. After natural cooling to room temperature, the oil phase solution is removed and centrifuged to obtain precipitate H. The precipitate H is then washed with isopropanol and dried to obtain quaternary ammonium salt modified chitosan microspheres. The volume ratio of the aqueous phase solution to the oil phase solution is 1:10, and the volume ratio of the glutaraldehyde to the aqueous phase solution is 1:20.

[0009] Furthermore, the microbial agent mentioned in step (1) includes one or more combinations of Bacillus licheniformis, Bacillus pumilus, Bacillus subtilis, and Bacillus cereus.

[0010] Furthermore, the biochar powder mentioned in step (1) is obtained by pyrolyzing and carbonizing a mixture of straw, weeds, and sawdust in a heating furnace, followed by crushing and passing it through a 200-mesh sieve. Using straw, weeds, and sawdust to prepare biochar powder can achieve effective utilization of waste resources. Moreover, biochar powder can adsorb microorganisms, providing a suitable environment for their reproduction, thereby effectively improving the effect of soil conditioners.

[0011] Furthermore, the algae powder mentioned in step (1) is one or a combination of spirulina powder and chlorella powder. Using spirulina powder and chlorella powder can provide nutrients for microorganisms and the soil, and regulate the organic matter content of the soil.

[0012] Furthermore, in step (2), the topsoil of the limestone mining area is tilled to a depth of 30-50cm.

[0013] Compared with existing technologies, this technical solution has the following advantages:

[0014] This invention first uses a first leaching agent, prepared by mixing citric acid, tartaric acid, and water, to leach the topsoil of a limestone mining area. On one hand, the soil in limestone mining areas is alkaline, and the first leaching agent can effectively adjust the soil pH. On the other hand, the synergistic effect of citric acid and tartaric acid in the first leaching agent can form complexes with heavy metals in the soil, which are then removed through leaching, reducing the heavy metal content in the soil. Next, this invention uses a second leaching agent, prepared by rhamnolipids, quaternary ammonium salt-modified chitosan microspheres, and water, to treat the soil. The quaternary ammonium salt-modified chitosan microspheres are obtained by grafting chitosan with epoxy quaternary ammonium salt and then cross-linking it. These microspheres can effectively adsorb heavy metals and harmful substances (such as sulfates and asphalt) in the soil, thereby achieving harmless treatment of the soil. Simultaneously, the added rhamnolipids can promote… The invention improves the adsorption effect of quaternary ammonium salt modified chitosan microspheres by dispersing them. Then, the soil is treated by water rinsing to further reduce the content of harmful substances in the soil. Finally, a soil conditioner is sprayed. This soil conditioner is a slow-release microsphere that continuously releases the conditioner into the soil. It is made by using soluble starch as a coating layer, then encapsulating a conditioner made of biochar powder, microbial agents, humic acid, algae powder, potassium dihydrogen phosphate, and water. The microspheres prepared using soluble starch also have good hygroscopic properties, which can help retain water in the soil. Simultaneously, the use of biochar powder, microbial agents, humic acid, algae powder, and potassium dihydrogen phosphate in this invention can effectively improve the soil environment and increase the nutrient content of the soil, thereby benefiting plant cultivation. Implementation

[0015] The present invention is further illustrated by the following examples, but these are not intended to limit the invention. Specific experimental conditions and methods not specified in the following examples are generally conventional methods well known to those skilled in the art.

[0016] Example 1: A method for soil reclamation, restoration, and improvement in limestone mining areas, comprising the following steps:

[0017] (1) Citric acid, tartaric acid and water are mixed to obtain the first leaching agent, wherein the weight ratio of citric acid, tartaric acid and water is 2.8:0.8:100; rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water are mixed to obtain the second leaching agent, wherein the weight ratio of rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water is 2.5:6:100; soluble starch and water are mixed in a mass ratio of 1:9 to obtain mixture A; biochar powder, microbial agent, humic acid, algae powder, potassium dihydrogen phosphate and water are mixed in a mass ratio of 14:4:2.5:7:0.4:100 to obtain mixture B; then mixture A and mixture B are mixed in a volume ratio of 1:1.1. Mixture C was obtained by stirring at 58°C for 15 minutes. Simultaneously, liquid paraffin was taken and mixed with Span 80 under stirring to obtain mixture D. The volume ratio of liquid paraffin to Span 80 was 100:8. Mixture D was heated to 58°C, and mixture C was slowly added under stirring. Then epichlorohydrin was added and reacted for 4 hours. The volume ratio of mixture C to mixture D was 1:10, and the volume ratio of epichlorohydrin to mixture C was 1:20. After cooling and settling to remove the oil phase, the precipitate E was obtained by centrifugation. After washing precipitate E with isopropanol and drying, slow-release starch microspheres were obtained. The slow-release starch microspheres and water were then mixed at a mass ratio of 4.5:100 to obtain a soil conditioner.

[0018] The preparation method of the quaternary ammonium salt modified chitosan microspheres is as follows: Epoxy quaternary ammonium salt and water are mixed in a mass ratio of 1:4.8 to obtain mixture F. Chitosan is added to a 0.1% hydrochloric acid solution (mass ratio of chitosan to hydrochloric acid solution is 3:200). The mixture is then heated to 58°C under stirring, and mixture F is slowly added. The reaction is continued at 56°C for 40 hours with stirring. Solid sodium hydroxide is then added to adjust the pH to 12. After standing, precipitate G is obtained. After filtration, precipitate G is washed with ethanol. Then, precipitate G is dissolved in a 1% acetic acid solution to obtain an aqueous solution. The precipitate and acetic acid... The mass ratio of the acid solution is 1.5:100. Liquid paraffin is taken and mixed with Span80 under stirring to obtain an oil phase solution. The volume ratio of the liquid paraffin to Span80 is 100:8. Then, the aqueous phase solution is slowly added to the oil phase solution and stirred. The reaction is carried out at 50°C for 1.5 hours. Then, glutaraldehyde is added and the reaction is continued for 4 hours. After natural cooling to room temperature, the oil phase solution is removed and centrifuged to obtain precipitate H. The precipitate H is washed with isopropanol and dried to obtain quaternary ammonium salt modified chitosan microspheres. The volume ratio of the aqueous phase solution to the oil phase solution is 1:10, and the volume ratio of the glutaraldehyde to the aqueous phase solution is 1:20.

[0019] The microbial agent is a mixture of Bacillus licheniformis, Bacillus pumilus, Bacillus subtilis, and Bacillus cereus; the biochar powder is obtained by pyrolyzing and carbonizing a mixture of straw, weeds, and sawdust in a heating furnace, followed by crushing and passing it through a 200-mesh sieve; the algae powder is a mixture of Spirulina powder and Chlorella powder.

[0020] (2) The topsoil of the limestone mining area is tilled to a depth of 45cm. Then, a spray pipe is installed on the topsoil to spray the soil with a leaching agent for leaching treatment. A leaching liquid recovery pipe is installed in the topsoil layer to recover the leaching liquid after leaching treatment. The leaching treatment is first treated with the first leaching liquid obtained in step (1) for 20 hours with a liquid-to-solid ratio of 8mL:1g. Then, the second leaching liquid obtained in step (1) is used for 4 days with a liquid-to-solid ratio of 18mL:1g. Then, water is used for leaching for 2 days. Then, the leaching liquid recovery pipe is stopped or removed. Finally, the soil conditioner obtained in step (1) is sprayed into the topsoil at a rate of 380mL / m. 2 Herbaceous plants should be planted 10 hours after the soil conditioner is sprayed.

[0021] In a limestone mining area in Hezhou, Guangxi, experimental areas were divided and treated according to the method described in this embodiment. Cosmos seeds were then sprayed. After 3 months, the survival rate of the cosmos was 95% and the vegetation coverage reached 52%.

[0022] Example 2: A method for soil reclamation, restoration, and improvement in limestone mining areas, comprising the following steps:

[0023] (1) Citric acid, tartaric acid and water are mixed to obtain the first leaching agent, wherein the weight ratio of citric acid, tartaric acid and water is 2:0.5:100; rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water are mixed to obtain the second leaching agent, wherein the weight ratio of rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water is 1:3:100; soluble starch and water are mixed in a mass ratio of 1:8 to obtain mixture A; biochar powder, microbial agent, humic acid, algae powder, potassium dihydrogen phosphate and water are mixed in a mass ratio of 10:3:1:5:0.3:100 to obtain mixture B; then mixture A and mixture B are mixed in a volume ratio of 1:1 and heated to 50°C. Mixture C was obtained by stirring at ℃ for 10 min. Simultaneously, liquid paraffin was taken and Span 80 was added under stirring to obtain mixture D. The volume ratio of liquid paraffin to Span 80 was 100:2.5. Mixture D was heated to 50℃, and mixture C was slowly added under stirring. Then epichlorohydrin was added and reacted for 3 h. The volume ratio of mixture C to mixture D was 1:10, and the volume ratio of epichlorohydrin to mixture C was 1:20. After cooling and standing to remove the oil phase, the precipitate E was obtained by centrifugation. After washing precipitate E with isopropanol and drying, slow-release starch microspheres were obtained. The slow-release starch microspheres and water were then mixed at a mass ratio of 3:100 to obtain a soil conditioner.

[0024] The preparation method of the quaternary ammonium salt modified chitosan microspheres is as follows: Epoxy quaternary ammonium salt and water are mixed in a mass ratio of 1:4 to obtain mixture F. Chitosan is added to a 0.1% hydrochloric acid solution, with a mass ratio of chitosan to hydrochloric acid solution of 1.5:200. Then, under stirring, the mixture is heated to 50°C and mixed with mixture F is slowly added. The reaction is continued at 50°C for 48 hours. Solid sodium hydroxide is then added to adjust the pH to 12. After standing, precipitate G is obtained. After filtration, precipitate G is washed with ethanol. Then, precipitate G is dissolved in a 1% acetic acid solution to obtain an aqueous solution. The precipitate and acetic acid... The mass ratio of the acid solution is 0.5:100. Liquid paraffin is taken and mixed with Span80 under stirring to obtain an oil phase solution. The volume ratio of the liquid paraffin to Span80 is 100:2.5. Then, the aqueous phase solution is slowly added to the oil phase solution and stirred. The reaction is carried out at 45°C for 1 hour. Then, glutaraldehyde is added and the reaction is continued for 3 hours. After natural cooling to room temperature, the oil phase solution is removed and centrifuged to obtain precipitate H. The precipitate H is washed with isopropanol and dried to obtain quaternary ammonium salt modified chitosan microspheres. The volume ratio of the aqueous phase solution to the oil phase solution is 1:10, and the volume ratio of the glutaraldehyde to the aqueous phase solution is 1:20.

[0025] The microbial agent is a mixture of Bacillus licheniformis, Bacillus pumilus, and Bacillus subtilis; the biochar powder is obtained by pyrolyzing and carbonizing a mixture of straw, weeds, and sawdust in a heating furnace, followed by crushing and passing it through a 200-mesh sieve; the algae powder is spirulina powder.

[0026] (2) The topsoil of the limestone mining area is tilled to a depth of 30cm. Then, a spray pipe is installed on the topsoil to spray the soil with a leaching agent for leaching treatment. A leaching liquid recovery pipe is installed in the topsoil layer to recover the leaching liquid after leaching treatment. The leaching treatment is first treated with the first leaching liquid obtained in step (1) for 12 hours with a liquid-to-solid ratio of 5mL:1g. Then, the second leaching liquid obtained in step (1) is used for 3 days with a liquid-to-solid ratio of 10mL:1g. Then, water is used for leaching for 1 day. Then, the leaching liquid recovery pipe is stopped or removed. Finally, the soil conditioner obtained in step (1) is sprayed into the topsoil at a rate of 300mL / m. 2 Herbaceous plants should be planted 8 hours after the soil conditioner has been sprayed.

[0027] In a limestone mining area in Hezhou, Guangxi, experimental areas were divided and treated according to the method described in this embodiment. Cosmos seeds were then sprayed. After 3 months, the survival rate of the cosmos was 94%, and the vegetation coverage reached 50%.

[0028] Example 3: A method for soil reclamation, restoration, and improvement in limestone mining areas, comprising the following steps:

[0029] (1) A first leaching agent is obtained by mixing citric acid, tartaric acid and water, wherein the weight ratio of citric acid, tartaric acid and water is 2.2:0.6:100; a second leaching agent is obtained by mixing rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water, wherein the weight ratio of rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water is 1.5:4:100; soluble starch and water are mixed in a mass ratio of 1:8.5 to obtain mixture A; biochar powder, microbial agent, humic acid, algae powder, potassium dihydrogen phosphate and water are mixed in a mass ratio of 12:3.5:1.5:6:0.4:100 to obtain mixture B; then mixture A and mixture B are mixed in a volume ratio of 1:1.05. Mixing and stirring at 52°C for 15 min yields mixture C. Simultaneously, liquid paraffin is added to Span 80 under stirring to obtain mixture D. The volume ratio of liquid paraffin to Span 80 is 100:4. Mixture D is heated to 52°C, and mixture C is slowly added under stirring. Then, epichlorohydrin is added and reacted for 4 h. The volume ratio of mixture C to mixture D is 1:10, and the volume ratio of epichlorohydrin to mixture C is 1:20. After cooling and settling to remove the oil phase, the mixture is centrifuged to obtain precipitate E. Precipitate E is washed with isopropanol and dried to obtain slow-release starch microspheres. The slow-release starch microspheres and water are then mixed at a mass ratio of 3.5:100 to obtain a soil conditioner.

[0030] The preparation method of the quaternary ammonium salt modified chitosan microspheres is as follows: Epoxy quaternary ammonium salt and water are mixed in a mass ratio of 1:4.2 to obtain a mixture F. Chitosan is added to a 0.1% hydrochloric acid solution, with a mass ratio of chitosan to hydrochloric acid solution of 2:200. The mixture is then heated to 52°C under stirring, and mixture F is slowly added. The reaction is continued at 54°C for 36–48 hours with stirring. Solid sodium hydroxide is then added to adjust the pH to 12. After standing, precipitate G is obtained. After filtration, precipitate G is washed with ethanol. Then, precipitate G is dissolved in a 1% acetic acid solution to obtain an aqueous solution. The mass ratio of liquid paraffin to acetic acid solution is 1:100. Liquid paraffin is mixed with Span80 under stirring to obtain an oil phase solution. The volume ratio of liquid paraffin to Span80 is 100:5. Then, aqueous solution is slowly added to the oil phase solution and stirred. The mixture is reacted at 48°C for 1.5 hours. Glutaraldehyde is then added and the reaction continues for 4 hours. The mixture is then naturally cooled to room temperature. After removing the oil phase solution, the mixture is centrifuged to obtain precipitate H. The precipitate H is then washed with isopropanol and dried to obtain quaternary ammonium salt modified chitosan microspheres. The volume ratio of the aqueous phase solution to the oil phase solution is 1:10, and the volume ratio of glutaraldehyde to the aqueous phase solution is 1:20.

[0031] The microbial inoculant is a mixture of Bacillus pumilus and Bacillus subtilis; the biochar powder is obtained by pyrolyzing and carbonizing a mixture of straw, weeds and sawdust in a heating furnace, followed by crushing and passing it through a 200-mesh sieve; the algae powder is a mixture of Spirulina powder and Chlorella powder.

[0032] (2) The topsoil of the limestone mining area is tilled to a depth of 35cm. Then, a spray pipe is installed on the topsoil to spray the soil with a leaching agent for leaching treatment. A leaching liquid recovery pipe is installed in the topsoil layer to recover the leaching liquid after leaching treatment. The leaching treatment is first treated with the first leaching liquid obtained in step (1) for 18 hours with a liquid-to-solid ratio of 6mL:1g. Then, the second leaching liquid obtained in step (1) is used for 3.5 days with a liquid-to-solid ratio of 12mL:1g. Then, water is used for leaching for 1 day. Then, the leaching liquid recovery pipe is stopped or removed. Finally, the soil conditioner obtained in step (1) is sprayed into the topsoil at a rate of 320mL / m. 2 Herbaceous plants should be planted 10 hours after the soil conditioner is sprayed.

[0033] In a limestone mining area in Hezhou, Guangxi, experimental areas were divided and treated according to the method described in this embodiment. Cosmos seeds were then sprayed. After 3 months, the survival rate of the cosmos was 98%, and the vegetation coverage reached 55%.

[0034] Example 4: A method for soil reclamation, restoration, and improvement in limestone mining areas, comprising the following steps:

[0035] (1) Citric acid, tartaric acid and water are mixed to obtain the first leaching agent, wherein the weight ratio of citric acid, tartaric acid and water is 3:1:100; rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water are mixed to obtain the second leaching agent, wherein the weight ratio of rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water is 3:8:100; soluble starch and water are mixed in a mass ratio of 1:10 to obtain mixture A; biochar powder, microbial agent, humic acid, algae powder, potassium dihydrogen phosphate and water are mixed in a mass ratio of 15:5:3:8:0.5:100 to obtain mixture B; then mixture A and mixture B are mixed in a volume ratio of 1:1.2 and 6 Mixture C was obtained by stirring at 0℃ for 20 min. Simultaneously, liquid paraffin was taken and Span80 was added under stirring to obtain mixture D. The volume ratio of liquid paraffin to Span80 was 100:10. Mixture D was heated to 60℃, and mixture C was slowly added under stirring. Then epichlorohydrin was added and reacted for 5 h. The volume ratio of mixture C to mixture D was 1:10, and the volume ratio of epichlorohydrin to mixture C was 1:20. After cooling and standing to remove the oil phase, the precipitate E was obtained by centrifugation. After washing precipitate E with isopropanol and drying, slow-release starch microspheres were obtained. The slow-release starch microspheres and water were then mixed at a mass ratio of 5:100 to obtain a soil conditioner.

[0036] The preparation method of the quaternary ammonium salt modified chitosan microspheres is as follows: Epoxy quaternary ammonium salt and water are mixed in a mass ratio of 1:5 to obtain mixture F. Chitosan is added to a 0.1% hydrochloric acid solution, with a mass ratio of chitosan to hydrochloric acid solution of 3.5:200. Then, under stirring, the mixture is heated to 60°C and mixed solution F is slowly added. The reaction is continued at 60°C for 36 hours. Solid sodium hydroxide is then added to adjust the pH to 12. After standing, precipitate G is obtained. After filtration, precipitate G is washed with ethanol. Then, precipitate G is dissolved in a 1% acetic acid solution to obtain an aqueous solution. The precipitate and... The mass ratio of acetic acid solution is 2:100. Liquid paraffin is taken and Span80 is added under stirring to obtain an oil phase solution. The volume ratio of liquid paraffin to Span80 is 100:10. Then, the aqueous phase solution is slowly added to the oil phase solution and stirred. The reaction is carried out at 55°C for 2 hours. Then, glutaraldehyde is added and the reaction is continued for 5 hours. After natural cooling to room temperature, the oil phase solution is removed and centrifuged to obtain precipitate H. The precipitate H is washed with isopropanol and dried to obtain quaternary ammonium salt modified chitosan microspheres. The volume ratio of the aqueous phase solution to the oil phase solution is 1:10, and the volume ratio of glutaraldehyde to the aqueous phase solution is 1:20.

[0037] The microbial inoculant is a mixture of Bacillus pumilus, Bacillus subtilis, and Bacillus cereus; the biochar powder is obtained by pyrolyzing and carbonizing a mixture of straw, weeds, and sawdust in a heating furnace, followed by crushing and passing it through a 200-mesh sieve; the algae powder is Chlorella powder.

[0038] (2) The topsoil of the limestone mining area is tilled to a depth of 50cm. Then, a spray pipe is installed on the topsoil to spray the soil with a leaching agent for leaching treatment. A leaching liquid recovery pipe is installed in the topsoil layer to recover the leaching liquid after leaching treatment. The leaching treatment is first treated with the first leaching liquid obtained in step (1) for 24 hours with a liquid-to-solid ratio of 10mL:1g. Then, the second leaching liquid obtained in step (1) is used for 5 days with a liquid-to-solid ratio of 20mL:1g. Then, water is used for leaching for 2 days. Then, the leaching liquid recovery pipe is stopped or removed. Finally, the soil conditioner obtained in step (1) is sprayed into the topsoil at a rate of 400mL / m. 2 Herbaceous plants should be planted 12 hours after the soil conditioner is sprayed.

[0039] In a limestone mining area in Hezhou, Guangxi, experimental areas were divided and treated according to the method described in this embodiment. Cosmos seeds were then sprayed. After 3 months, the survival rate of the cosmos was 94%, and the vegetation coverage reached 51%.

[0040] Comparative Example 1: The method for soil reclamation, restoration, and improvement in limestone mining areas described in this comparative example differs from the method described in Example 1 only in that tartaric acid is not added to the first leaching agent in step (1). Experimental areas were divided in a limestone mining area in Hezhou, Guangxi, and treated according to the method described in this example. Cosmos seeds were then sprayed. After 3 months, the survival rate of the Cosmos was 90%, and the vegetation coverage reached 43%.

[0041] Comparative Example 2: The method for soil reclamation, restoration, and improvement in limestone mining areas described in this comparative example differs from the method described in Example 1 only in that, in step (1), chitosan is used instead of quaternary ammonium salt-modified chitosan microspheres and rhamnose glycolipids to prepare the second leaching agent. Experimental areas were divided in a limestone mining area in Hezhou, Guangxi, and treated according to the method described in this example. Cosmos seeds were then sprayed. After 3 months, the survival rate of the cosmos was 68%, and the vegetation coverage reached 32%.

[0042] Comparative Example 3: The method for soil reclamation, restoration, and improvement in limestone mining areas described in this comparative example differs from the method described in Example 1 only in that, in step (1), soluble starch is not used to prepare slow-release microspheres; instead, biochar powder, microbial agents, humic acid, algae powder, potassium dihydrogen phosphate, and water are directly mixed to prepare a soil conditioner. In a limestone mining area in Hezhou, Guangxi, experimental areas were divided, and the method described in this example was followed. Cosmos seeds were then sprayed. After 3 months, the survival rate of the Cosmos was 79%, and the vegetation coverage reached 39%.

[0043] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for soil reclamation, restoration, and improvement in limestone mining areas, characterized in that: Includes the following steps: (1) A first leaching agent is obtained by mixing citric acid, tartaric acid and water, wherein the weight ratio of citric acid, tartaric acid and water is (2-3):(0.5-1):100; a second leaching agent is obtained by mixing rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water, wherein the weight ratio of rhamnolipin, quaternary ammonium salt modified chitosan microspheres and water is (1-3):(3-8):100; a mixture A is obtained by mixing soluble starch and water in a mass ratio of 1:(8-10); a mixture B is obtained by mixing biochar powder, microbial agent, humic acid, algae powder, potassium dihydrogen phosphate and water in a mass ratio of (10-15):(3-5):(1-3):(5-8):(0.3-0.5):100; then the mixture A and the mixture B are mixed in a volume ratio of 1:( Mix the liquid paraffin (1-1.2) in a ratio and stir at 50-60℃ for 10-20 min to obtain mixture C. At the same time, take liquid paraffin and add Span80 under stirring to obtain mixture D. The volume ratio of liquid paraffin to Span80 is 100:(2.5-10). Heat mixture D to 50-60℃ and slowly add mixture C under stirring. Then add epichlorohydrin and react for 3-5 h. The volume ratio of mixture C to mixture D is 1:10 and the volume ratio of epichlorohydrin to mixture C is 1:

20. Cool and let stand to remove the oil phase and centrifuge to obtain precipitate E. Wash precipitate E with isopropanol and dry to obtain slow-release starch microspheres. Then mix slow-release starch microspheres and water in a mass ratio of (3-5):100 to obtain soil conditioner. (2) The topsoil of the limestone mining area is tilled, and then a spray pipe is installed on the topsoil to spray the soil with a leaching agent for leaching treatment. A leaching liquid recovery pipe is installed in the topsoil layer to recover the leaching liquid after leaching treatment. The leaching treatment is first performed with the first leaching liquid obtained in step (1) for 12-24 hours, with a liquid-to-solid ratio of (5-10) mL:1g. Then, the second leaching liquid obtained in step (1) is used for 3-5 days, with a liquid-to-solid ratio of (10-20) mL:1g. Then, water is used for leaching for 1-2 days. Then, the leaching liquid recovery pipe is stopped or removed. The soil conditioner obtained in step (1) is then sprayed into the topsoil at a rate of 300-400 mL / m. 2 Herbaceous plants should be planted 8–12 hours after the soil conditioner has been sprayed.

2. The method for soil reclamation, restoration, and improvement in limestone mining areas according to claim 1, characterized in that: The preparation method of the quaternary ammonium salt modified chitosan microspheres in step (1) is as follows: epoxide quaternary ammonium salt and water are mixed in a mass ratio of 1:(4-5) to obtain a mixture F. Chitosan is added to a 0.1% hydrochloric acid solution, and the mass ratio of chitosan to hydrochloric acid solution is (1.5-3.5):

200. Then, under stirring, the mixture F is slowly added after heating to 50-60℃. The mixture is then stirred and reacted at 50-60℃ for 36-48 hours. Solid sodium hydroxide is then added to adjust the pH to 12. After standing, precipitate G is obtained. After filtration, precipitate G is washed with ethanol. Then, precipitate G is dissolved in a 1% acetic acid solution to obtain an aqueous solution. The mass ratio of the precipitate to the acetic acid solution is (0.5-2):

100. Liquid paraffin is taken and Span80 is added under stirring to obtain an oil phase solution. The volume ratio of the liquid paraffin to Span80 is 100:(2.5-10). Then, the aqueous phase solution is slowly added to the oil phase solution and stirred. The reaction is carried out at 45-55℃ for 1-2 hours. Then, glutaraldehyde is added and the reaction is continued for 3-5 hours. After natural cooling to room temperature, the oil phase solution is removed and centrifuged to obtain precipitate H. The precipitate H is washed with isopropanol and dried to obtain quaternary ammonium salt modified chitosan microspheres. The volume ratio of the aqueous phase solution to the oil phase solution is 1:10, and the volume ratio of the glutaraldehyde to the aqueous phase solution is 1:

20.

3. The method for soil reclamation, restoration, and improvement in limestone mining areas according to claim 1, characterized in that: The microbial agent mentioned in step (1) includes one or more combinations of Bacillus licheniformis, Bacillus pumilus, Bacillus subtilis and Bacillus cereus.

4. The method for soil reclamation, restoration, and improvement in limestone mining areas according to claim 1, characterized in that: The biochar powder mentioned in step (1) is obtained by pyrolyzing and carbonizing a mixture of straw, weeds and sawdust in a heating furnace, and then crushing it through a 200-mesh sieve.

5. The method for soil reclamation, restoration, and improvement in limestone mining areas according to claim 1, characterized in that: The algae powder mentioned in step (1) is one or a combination of spirulina powder and chlorella powder.

6. The method for soil reclamation, restoration, and improvement in limestone mining areas according to claim 1, characterized in that: In step (2), the topsoil of the limestone mining area is tilled to a depth of 30-50cm.