Soil reconstruction method based on organic matter enrichment and application

Abstract

The invention discloses a soil reconstruction method based on organic matter enrichment and application, and relates to the technical field of soil remediation. The invention discloses a soil reconstruction method based on organic matter enrichment. The soil reconstruction method comprises the following steps: adding a soil remediation agent into soil; the preparation method of the soil remediation agent comprises the following steps: drying, crushing, soaking and filtering the yellow tobacco straws, and taking filtrate as yellow tobacco straw leachate; crushing the camellia oleifera shells to obtain camellia oleifera shell powder; and mixing the yellow tobacco straw leachate, the camellia oleifera shell powder and the modified biochar to obtain the soil conditioner. The prepared soil remediation agent is applied to tailing soil obtained after ionic rare earth ore mining, and rapid remediation and reconstruction of the soil are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a soil reconstruction method based on organic matter enrichment and its application. Background Art

[0002] Rare earth is a general term for 15 lanthanide elements, scandium (21st element) and yttrium (39th element) (a total of 17 elements) in the periodic table of chemical elements. Rare earth is called "industrial vitamin" and "the mother of new materials". It is widely used in aerospace, electronics, medical and health industries and is an important strategic mineral resource. The mining process of ion-adsorbing rare earth ores mainly includes three different technologies: in-situ leaching, heap leaching and in-situ leaching. In-situ leaching has been widely used in the mining industry because it has the advantages of less workload, lower labor intensity and lower cost compared to other technologies. However, the use of in-situ leaching technology requires the excavation of shallow trenches, injection wells and collection trenches, and the injection of ammonium sulfate solution. During the excavation of the injection holes in the ore body, 1 / 3 of the preparation and topsoil are still disturbed. The long-term, high-concentration injection of the leaching agent ammonium sulfate solution into the ore body forms rare earth sulfate and ammonium hydroxide in the soil, which are then precipitated with oxalic acid or ammonium carbonate to become rare earth oxalate or ammonium carbonate. The high concentration is harmful to the surrounding soil plants, damaging the vegetation roots and losing the water-fixing and soil-retaining function. In addition, the remaining tailings contain a lot of heavy metals, which enter the surface and groundwater with soil erosion, leading to water resource pollution.

[0003] The treatment and restoration of rare earth mines and surrounding contaminated farmland soil is an urgent problem to be solved to ensure the safety of agricultural products and human health. It is also an environmental problem that must be faced and solved for the sustainable development and utilization of rare earth resources, and is of great significance to the development of regional agricultural economy. The restoration technology for mine ecology is mainly divided into: physical method, chemical method and biological method. The physical method has the advantage of not causing secondary pollution to the environment, but has the disadvantages of small application scope and incomplete restoration; the biological method has the advantages of low cost and no secondary pollution, but has the disadvantages of limited application scope and long restoration time; the chemical method is to repair by adding modifiers, eluents, etc. to change the form of heavy metals, which has the advantage of high efficiency. However, the existing soil conditioners are added to the tailings soil of ionic rare earth mines. Due to the acidic soil, they have poor adsorption and deposition effects on heavy metals and slow soil restoration. Summary of the invention

[0004] The purpose of the present invention is to provide a soil reconstruction method and application based on organic matter enrichment to solve the following technical problems:

[0005] Existing soil conditioners are added to acidic soils, resulting in poor adsorption and deposition effects on heavy metal ions in the soil and unsatisfactory soil remediation effects.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A soil reconstruction method based on organic matter enrichment includes the following steps: the soil reconstruction method includes adding a soil remediation agent to the soil;

[0008] The preparation method of the soil remediation agent comprises the following steps:

[0009] S1: drying, crushing, soaking and filtering yellow tobacco straw, and taking the filtrate as yellow tobacco straw extract;

[0010] S2: Mix yellow tobacco straw extract, tea oil shell powder, and modified biochar to obtain a soil conditioner; the soil conditioner includes 10-50g tea oil shell powder, 10-50mL yellow tobacco straw extract, and 2-10g modified biochar;

[0011] The method for preparing modified biochar comprises the following steps:

[0012] A1: Add phytic acid and deionized water into a reactor and disperse them evenly, add epoxidized biochar, control the temperature at 60-70°C, keep the reaction warm for 3-6 hours, wash with water, and dry to prepare phosphorylated biochar;

[0013] A2: Add phosphorylated biochar, distilled water and melamine into a reactor and disperse them evenly. Control the temperature to 80-90°C, keep the reaction warm for 3-6 hours, centrifuge, wash with ethanol and dry to obtain amination biochar.

[0014] A3: Add the organic magnetic particles, anhydrous ethanol and amino biochar into the reactor and disperse them evenly. Control the temperature at 75-85°C, keep the temperature under stirring for 12-18 hours, wash with anhydrous ethanol, wash with water, and freeze-dry to obtain modified biochar.

[0015] As a further solution of the present invention: the phytic acid and deionized water in A1 are added to the reactor and dispersed evenly, and the epoxidized biochar is added in a ratio of 1-2 g: 10 mL: 1 g.

[0016] As a further solution of the present invention: the addition ratio of phosphorylated biochar, distilled water and melamine in A2 is 10g:100-300mL:1-3g.

[0017] As a further solution of the present invention: the addition ratio of the organic magnetic particles, anhydrous ethanol and amino biochar in A3 is 0.5-3g:100-200mL:10g.

[0018] As a further embodiment of the present invention: the preparation method of epoxidized biochar comprises the following steps:

[0019] B1: Dry, sinter, crush and sieve the remaining solids from the preparation of yellow tobacco straw extract to obtain biochar particles;

[0020] B2: Add biochar particles, methanol solution and sodium hydroxide solution into a reactor, control the temperature at 40-50°C, keep warm and stir for 4-8 hours, wash with water and dry to obtain pretreated biochar particles;

[0021] B3: Add pretreated biochar particles, γ-glycidyloxypropyltrimethoxysilane and toluene into a reactor, stir at room temperature for 1-3 hours, and dry to obtain epoxidized biochar.

[0022] As a further solution of the present invention: the specific steps of drying and sintering in B1 are: placing in an oven at 60-80°C, drying for 1-3h, placing in a muffle furnace under a nitrogen environment at 500-600°C, sintering for 0.5-5h (heating rate 10°C / min); the particle size of the biochar particles is 1-5mm.

[0023] As a further solution of the present invention: the methanol solution in B2 is 20-40wt% methanol aqueous solution, and the sodium hydroxide solution is 20-25wt% sodium hydroxide aqueous solution; the addition ratio of biochar particles, methanol solution, and sodium hydroxide solution is 10g:30-60mL:200-300mL.

[0024] As a further solution of the present invention: the addition ratio of the pretreated biochar particles, γ-glycidyloxypropyltrimethoxysilane, and toluene in B3 is 1 g: 0.1-0.5 mL: 20-100 mL.

[0025] As a further solution of the present invention: the preparation method of the organic magnetic particles comprises the following steps: adding ferroferric oxide particles, toluene and octadecyltriethoxysilane into a reaction kettle and dispersing them evenly, reacting them in a sealed autoclave at 120-150° C. for 3-6 hours, washing with ethanol and drying to obtain the organic magnetic particles.

[0026] As a further embodiment of the present invention, the addition ratio of ferrosoferric oxide particles, toluene and octadecyltriethoxysilane is 1 g: 50-100 mL: 0.1-0.5 mL.

[0027] As a further solution of the present invention: the preparation method of the ferroferric oxide particles comprises the following steps: in a nitrogen atmosphere, ferric chloride hexahydrate, sodium acetate and ethanol are added to a reaction kettle and dispersed evenly, the temperature is controlled at 150-160° C., the reaction is kept warm for 1-3 hours, the reaction is carried out in a sealed autoclave at 200-250° C. for 9-12 hours, and the ferroferric oxide particles are washed with ethanol and dried to obtain ferroferric oxide particles.

[0028] As a further solution of the present invention: the specific preparation method of the yellow tobacco straw extract is: the yellow tobacco straw is dried and crushed into 3-10 mm yellow tobacco straw particles; the yellow tobacco straw particles are placed in water at room temperature and soaked for 2-4 days, and the filtrate is filtered to obtain the yellow tobacco straw extract.

[0029] The above-mentioned soil reconstruction method based on organic matter enrichment is applied to repair tailings soil after ionic rare earth mining.

[0030] As a further solution of the present invention: 10-100 g of soil remediation agent is added per kilogram of tailings soil.

[0031] Beneficial effects of the present invention:

[0032] (1) The present application uses yellow tobacco straw particles as raw materials and obtains yellow tobacco straw leaching liquid through water immersion treatment. The yellow tobacco straw leaching liquid prepared in the present application is mixed with tea husk powder and modified biochar to obtain a soil remediation agent. The yellow tobacco straw leaching liquid prepared in the present application contains sugars, lignin and inorganic salt ions, wherein lignin and pentosan molecules are adsorbed on the surface of the modified biochar, so that the surface of the modified biochar has the same charge. Due to the repulsion of like charges, it tends to be dispersed. The rich inorganic salt ions in the leaching liquid are added to the soil to effectively regulate the inorganic salt ion content in the soil; and the surfactants such as sugars and lignin in the yellow tobacco straw leaching liquid increase the double layer potential of the material, increase the surface tension, increase the stability of the soil remediation agent in acidic soil, and effectively improve the remediation effect of the soil remediation agent on tailings soil.

[0033] (2) The present application utilizes the solids remaining from the preparation of yellow tobacco straw leachate for drying and sintering to obtain biochar; the surface area of ​​the biochar prepared in the present application enables it to have more oxygen-containing functional groups such as hydroxyl, carbonyl, ether bond, amide, etc., and the π electrons provided by the aromatic structure of the biochar form a cation-π effect, adsorb inorganic pollutants in the soil, and precipitate with heavy metal ions; the biochar prepared in the present application includes an aromatic structure with strong oxidation ability and a carbon-oxygen structure and a fat structure that are easily degraded. The biochar prepared in the present application has the advantages of alkaline pH, large specific surface area, high porosity, and large ion exchange capacity. After being applied to the soil, it can improve soil fertility, improve soil physical and chemical properties, and achieve the fixation of nitrogen and phosphorus in the soil.

[0034] The present application uses sodium hydroxide solution to treat biochar particles, grafts hydroxyl groups on the surface, and uses γ-glycidyloxypropyltrimethoxysilane for epoxidation treatment to obtain epoxidized biochar; the present application further reacts the epoxy groups on the surface of the epoxidized biochar with the phosphate groups in phytic acid, grafts phosphate groups on the surface of the biochar, and uses the phosphate groups to react with melamine to graft amino groups on the surface of the biochar to obtain amination biochar; finally, the present application uses amination biochar as a matrix, deposits organic magnetic particles on the surface of amination biochar, and obtains modified biochar; the present application organically modifies the biochar, the negative charge and alkaline functional groups of the material are increased, and cations are effectively adsorbed. The modified biochar prepared by the present application adsorbs, deposits, and solidifies the remaining rare earth ions in the soil. Rare earths can enhance the photosynthesis of crops, promote the growth of crop roots, improve the ability of crops to resist pests and diseases and adversity, and further achieve soil remediation. The soil remediation agent prepared by the present application not only has good adsorption and water holding properties, but also plays a positive role in maintaining soil nutrients and has a good effect on the fixation of pollutants. DETAILED DESCRIPTION

[0035] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1 The method for preparing epoxidized biochar comprises the following steps:

[0037] B1: The remaining solids from the preparation of yellow tobacco straw extract were placed in an oven at 80°C and dried for 1 hour, then placed in a muffle furnace in a nitrogen environment and heated to 500°C at a rate of 10°C / min, sintered for 1 hour, and crushed and sieved to obtain biochar particles with a particle size of 1 mm;

[0038] B2: 10 g of biochar particles, 30 mL of 37 wt% methanol solution, and 200 mL of 20 wt% sodium hydroxide solution were added into a reactor, the temperature was controlled at 40°C, the mixture was stirred for 4 h, washed with water, and dried to obtain pretreated biochar particles;

[0039] B3: 1 g of pretreated biochar particles, 0.5 mL of γ-glycidyloxypropyltrimethoxysilane, and 20 mL of toluene were added into a reactor, stirred at room temperature for 3 h, and dried to obtain epoxidized biochar.

[0040] Example 2 The method for preparing the organized magnetic particles comprises the following steps:

[0041] C1: In a nitrogen atmosphere, 4.05 g of ferric chloride hexahydrate, 7.2 g of sodium acetate, and 50 mL of ethanol were added to a reactor and dispersed evenly. The temperature was controlled at 150°C and the reaction was kept warm for 3 h. The reaction was then carried out in a sealed autoclave at 200°C for 9 h. The particles were washed with ethanol and dried to obtain ferrosoferric oxide particles.

[0042] C2: 1 g of ferroferric oxide particles, 50 mL of toluene, and 0.5 mL of octadecyltriethoxysilane were added into a reaction kettle and dispersed evenly. The mixture was reacted at 120° C. for 6 h in a sealed autoclave. The particles were washed with ethanol and dried to obtain organic magnetic particles.

[0043] Example 3 The method for preparing modified biochar comprises the following steps:

[0044] A1: 10 g of phytic acid and 100 mL of deionized water were added to a reactor and dispersed evenly, 10 g of the epoxidized biochar prepared in Example 1 was added, the temperature was controlled at 60° C., the reaction was kept warm for 3 h, and the biochar was washed with water and dried to prepare phosphorylated biochar;

[0045] A2: 10 g of phosphorylated biochar, 100 mL of distilled water, and 1 g of melamine were added to a reactor and dispersed evenly. The temperature was controlled at 80 °C and the reaction was kept warm for 3 h. The reaction was then centrifuged, washed with ethanol, and dried to obtain amino-treated biochar.

[0046] A3: 0.5 g of the organic magnetic particles prepared in Example 2, 100 mL of anhydrous ethanol, and 10 g of amino-modified biochar were added into a reactor and dispersed evenly. The temperature was controlled at 75°C and kept warm for 12 h under stirring. The biochar was washed with anhydrous ethanol, washed with water, and freeze-dried to obtain modified biochar.

[0047] Example 4 The method for preparing modified biochar comprises the following steps:

[0048] A1: 15 g of phytic acid and 100 mL of deionized water were added to a reactor and dispersed evenly, 10 g of the epoxidized biochar prepared in Example 1 was added, the temperature was controlled at 65° C., the reaction was kept warm for 3 h, and the biochar was washed with water and dried to prepare phosphorylated biochar;

[0049] A2: 10 g of phosphorylated biochar, 200 mL of distilled water, and 2 g of melamine were added to a reactor and dispersed evenly. The temperature was controlled at 85 °C and the reaction was kept warm for 3 h. The reaction was then centrifuged, washed with ethanol, and dried to obtain amino-treated biochar.

[0050] A3: 1.5 g of the organic magnetic particles prepared in Example 2, 150 mL of anhydrous ethanol, and 10 g of amino-modified biochar were added into a reactor and dispersed evenly. The temperature was controlled at 80°C and kept warm for 15 h under stirring. The biochar was washed with anhydrous ethanol, washed with water, and freeze-dried to obtain modified biochar.

[0051] Example 5 The method for preparing modified biochar comprises the following steps:

[0052] A1: 20 g of phytic acid and 100 mL of deionized water were added to a reactor and dispersed evenly, 10 g of the epoxidized biochar prepared in Example 1 was added, the temperature was controlled at 70° C., the reaction was kept warm for 6 h, and the biochar was washed with water and dried to prepare phosphorylated biochar;

[0053] A2: 10 g of phosphorylated biochar, 300 mL of distilled water, and 3 g of melamine were added to a reactor and dispersed evenly. The temperature was controlled at 90 °C and the reaction was kept warm for 6 h. The reaction was then centrifuged, washed with ethanol, and dried to obtain amino-treated biochar.

[0054] A3: 3 g of the organic magnetic particles prepared in Example 2, 200 mL of anhydrous ethanol, and 10 g of amino-modified biochar were added into a reactor and dispersed evenly. The temperature was controlled at 85°C and kept warm for 18 h under stirring. The biochar was washed with anhydrous ethanol, washed with water, and freeze-dried to obtain modified biochar.

[0055] Example 6 A soil reconstruction method based on organic matter enrichment comprises the following steps:

[0056] S1: The yellow tobacco straw is dried and crushed into yellow tobacco straw particles of 5 mm, and the yellow tobacco straw particles are soaked in water at room temperature for 2 days, and the filtrate is filtered to obtain the yellow tobacco straw extract;

[0057] S2: Mix 50 mL of yellow tobacco straw extract, 50 g of camellia oleifera shell powder with a particle size of 1 mm, and 5 g of modified biochar prepared in Example 3 to obtain a soil conditioner;

[0058] S3: Add 10g of soil remediation agent to every kilogram of tailings soil after ionic rare earth mining.

[0059] Example 7 A soil reconstruction method based on organic matter enrichment comprises the following steps:

[0060] S1: The yellow tobacco straw is dried and crushed into yellow tobacco straw particles of 5 mm, and the yellow tobacco straw particles are soaked in water at room temperature for 2 days, and the filtrate is filtered to obtain the yellow tobacco straw extract;

[0061] S2: Mix 50 mL of yellow tobacco straw extract, 50 g of camellia oleifera shell powder with a particle size of 1 mm, and 5 g of modified biochar prepared in Example 4 to obtain a soil conditioner;

[0062] S3: Add 10g of soil remediation agent to every kilogram of tailings soil after ionic rare earth mining.

[0063] Example 8 A soil reconstruction method based on organic matter enrichment comprises the following steps:

[0064] S1: The yellow tobacco straw is dried and crushed into yellow tobacco straw particles of 5 mm, and the yellow tobacco straw particles are soaked in water at room temperature for 2 days, and the filtrate is filtered to obtain the yellow tobacco straw extract;

[0065] S2: Mix 50 mL of yellow tobacco straw extract, 50 g of camellia oleifera shell powder with a particle size of 1 mm, and 5 g of modified biochar prepared in Example 5 to obtain a soil conditioner;

[0066] S3: Add 10g of soil remediation agent to every kilogram of tailings soil after ionic rare earth mining.

[0067] Comparative Example 1 The preparation method of epoxidized biochar comprises the following steps:

[0068] B1: The remaining solids from the preparation of yellow tobacco straw extract were placed in an oven at 80°C and dried for 1 hour, then placed in a muffle furnace in a nitrogen environment and heated to 500°C at a rate of 10°C / min, sintered for 1 hour, and crushed and sieved to obtain biochar particles with a particle size of 1 mm;

[0069] B2: 1 g of pretreated biochar particles, 0.5 mL of γ-glycidyloxypropyltrimethoxysilane, and 20 mL of toluene were added into a reactor, stirred at room temperature for 3 h, and dried to obtain epoxidized biochar.

[0070] Comparative Example 2 The preparation method of magnetic particles comprises the following steps:

[0071] In a nitrogen atmosphere, 4.05 g of ferric chloride hexahydrate, 7.2 g of sodium acetate, and 50 mL of ethanol were added to a reaction kettle and dispersed evenly. The temperature was controlled at 150°C and the reaction was kept warm for 3 h. The reaction was carried out in a sealed autoclave at 200°C for 9 h. The magnetic particles were washed with ethanol and dried to obtain magnetic particles.

[0072] Comparative Example 3 The preparation method of modified biochar comprises the following steps:

[0073] A1: 15 g of phytic acid and 100 mL of deionized water were added to a reactor and dispersed evenly, 10 g of the epoxidized biochar prepared in Comparative Example 1 was added, the temperature was controlled at 65°C, the reaction was kept warm for 3 h, washed with water, and dried to prepare phosphorylated biochar;

[0074] A2: 10 g of phosphorylated biochar, 200 mL of distilled water, and 2 g of melamine were added to a reactor and dispersed evenly. The temperature was controlled at 85 °C and the reaction was kept warm for 3 h. The reaction was then centrifuged, washed with ethanol, and dried to obtain amino-treated biochar.

[0075] A3: 1.5 g of the organic magnetic particles prepared in Example 1, 150 mL of anhydrous ethanol, and 10 g of amino-modified biochar were added into a reactor and dispersed evenly. The temperature was controlled at 80° C. and kept warm for 15 h under stirring. The biochar was washed with anhydrous ethanol, washed with water, and freeze-dried to obtain modified biochar.

[0076] Comparative Example 4 The preparation method of modified biochar comprises the following steps:

[0077] A1: 15 g of phytic acid and 100 mL of deionized water were added to a reactor and dispersed evenly, 10 g of the epoxidized biochar prepared in Comparative Example 1 was added, the temperature was controlled at 65°C, the reaction was kept warm for 3 h, washed with water, and dried to prepare phosphorylated biochar;

[0078] A2: 1.5 g of the organic magnetic particles prepared in Example 1, 150 mL of anhydrous ethanol, and 10 g of phosphorylated biochar were added into a reactor and dispersed evenly. The temperature was controlled at 80° C. and kept warm for 15 h under stirring. The biochar was washed with anhydrous ethanol, washed with water, and freeze-dried to obtain modified biochar.

[0079] Comparative Example 5 The preparation method of modified biochar comprises the following steps:

[0080] A1: 15 g of phytic acid and 100 mL of deionized water were added to a reactor and dispersed evenly, 10 g of the epoxidized biochar prepared in Comparative Example 1 was added, the temperature was controlled at 65°C, the reaction was kept warm for 3 h, washed with water, and dried to prepare phosphorylated biochar;

[0081] A2: 10 g of phosphorylated biochar, 200 mL of distilled water, and 2 g of melamine were added to a reactor and dispersed evenly. The temperature was controlled at 85 °C and the reaction was kept warm for 3 h. The reaction was then centrifuged, washed with ethanol, and dried to obtain amino-treated biochar.

[0082] A3: Add 1.5 g of the magnetic particles prepared in Comparative Example 2, 150 mL of anhydrous ethanol, and 10 g of amino-modified biochar into a reactor and disperse them evenly. Control the temperature to 80°C, keep the mixture warm for 15 h under stirring, wash with anhydrous ethanol, wash with water, and freeze-dry to obtain modified biochar.

[0083] Comparative Example 6 The preparation method of modified biochar comprises the following steps:

[0084] A1: 10 g of the epoxidized biochar prepared in Example 1, 200 mL of distilled water, and 2 g of melamine were added to a reactor and dispersed evenly. The temperature was controlled at 85° C. and the reaction was kept warm for 3 h. The reaction was centrifuged, washed with ethanol, and dried to obtain the amination biochar.

[0085] A2: 1.5 g of the organic magnetic particles prepared in Example 1, 150 mL of anhydrous ethanol, and 10 g of amino-modified biochar were added into a reactor and dispersed evenly. The temperature was controlled at 80° C. and kept warm for 15 h under stirring. The biochar was washed with anhydrous ethanol, washed with water, and freeze-dried to obtain modified biochar.

[0086] Comparative Example 7 Compared with Example 7, Example 7 only replaces the modified biochar prepared in Example 4 added in Example 7 with an equal amount of the modified biochar prepared in Comparative Example 3, and the other components and preparation methods are exactly the same as those in Example 7.

[0087] Comparative Example 8 Compared with Example 7, Example 8 only replaces an equal amount of the modified biochar prepared in Example 4 added in Example 7 with the modified biochar prepared in Comparative Example 4, and the remaining components and preparation method are exactly the same as those in Example 7.

[0088] Comparative Example 9 Compared with Example 7, Example 9 only replaces an equal amount of the modified biochar prepared in Example 4 added in Example 7 with the modified biochar prepared in Comparative Example 5, and the remaining components and preparation method are exactly the same as those in Example 7.

[0089] Comparative Example 10 Compared with Example 7, Example 10 only replaces an equal amount of the modified biochar prepared in Example 4 added in Example 7 with the modified biochar prepared in Comparative Example 6, and the remaining components and preparation method are exactly the same as those in Example 7.

[0090] Comparative Example 11 Compared with Example 7, Example 11 only replaces the yellow tobacco straw extract added in Example 7 with an equal amount of deionized water, and the other components and preparation method are completely consistent with Example 7.

[0091] Comparative Example 12 Compared with Example 7, Example 12 only replaces the tea oil shell powder with a particle size of 1 mm added in Example 7 with an equal amount of peanut shell powder with a particle size of 1 mm, and the remaining components and preparation method are exactly the same as those in Example 7.

[0092] Performance Testing

[0093] Soil testing

[0094] (1) Soil sample preparation: Soil from the cultivated layer of a rare earth mining area is collected and placed in a cool, dry and ventilated place for drying. After drying, the soil is placed in a ziplock bag and placed in a cool and ventilated place;

[0095] (2) The physical and chemical properties of the sampled soil and the reconstructed soil were tested using the methods described in the Soil Agricultural Chemical Analysis Methods:

[0096] ① Soil pH: The carbon dioxide distilled water extraction method was used. The specific steps were as follows: 10 g of soil sample passed through a 20-mesh sieve and 50 mL of distilled water were mixed evenly, allowed to stand for 30 minutes, and then measured using a pH meter. The test results are shown in Table 1.

[0097] ② Soil organic matter content: Potassium dichromate volumetric method is used. The specific steps are as follows: add 0.1g (accurate to 0.0001g) of soil sample passed through a 100-mesh sieve, 5mL of 0.8mol / L potassium dichromate, and 5mL of concentrated sulfuric acid solution into a digestion tube and place it on a digestion instrument. Set the temperature to 230℃ and heat until the solution is slightly boiling for 5 minutes. After cooling, wash the digested solution into a triangular flask with pure water, keeping the volume of the solution in the triangular flask at 60-70mL. Add 3 drops of o-phenanthroline indicator and titrate with 0.2mol / L ferrous sulfate solution. The solution changes color from orange-yellow to blue-green to brick red. Record the titration volume and calculate the organic matter content in the soil according to the following formula:

[0098]

[0099] In the formula, c-0.8mol / L potassium dichromate solution concentration, mol / L; 5-the volume of potassium dichromate solution added, mL; V0-the volume of ferrous sulfate solution used to titrate the blank solution, mL; V-the volume of ferrous sulfate solution used to titrate the sample, mL; 3-the molar mass of 1 / 4 carbon atom, g / mol; 10 -3 -mL to L conversion coefficient; 1.1-oxidation correction coefficient; m-soil sample mass, g; k-coefficient of air-dried soil replaced by oven-dried soil; 1.724-average conversion coefficient of soil organic carbon replaced by soil organic matter; the test results are shown in Table 1;

[0100] ③ Total nitrogen content in soil: Alkaline hydrolysis diffusion method is used. The specific steps are as follows: add 1g (accurate to 0.0001g) of soil sample passed through a 60-mesh sieve, selenium powder and potassium sulfate mixed accelerator into a narrow-necked funnel, shake well and add 5mL of concentrated sulfuric acid, digest at 280℃ for 40min, and adjust the volume to 50mL after digestion, which is the test solution. Pipette 5mL of the test solution and place it in the outer chamber of the diffusion dish, 3mL of boric acid mixed indicator in the inner chamber, apply alkaline glue on the edge of the diffusion dish, cover with frosted glass, rotate several times to make it completely bonded, unscrew a slit and add 5mL of 0.4mol / L NaOH solution to the outer chamber, rotate the cover tightly, fix it with a rubber band and place it in a 40℃ constant temperature box for reaction. Take it out after 24h and titrate it with 0.01mol / L sulfuric acid solution. Stop titration when the solution changes from blue to slightly red, record the titration volume, and calculate the total nitrogen content in the soil according to the following formula:

[0101]

[0102] Wherein, c-0.01mol / L sulfuric acid standard solution concentration, mol / L; V0-volume of sulfuric acid solution used for titration of blank solution, mL; V-volume of sulfuric acid solution used for titration of sample, mL; 0.014-grams of 1mg equivalent nitrogen; m-mass of soil sample, g; 50-volume of test solution, mL; 5-volume of test solution involved in reaction, mL; 1000-unit conversion coefficient; the test results are shown in Table 1;

[0103] ④ Soil alkaline nitrogen content: The alkaline diffusion method is used. The specific steps are as follows: place 2g (accurate to 0.0001g) of soil sample that has passed a 60-mesh sieve in the outer chamber of the diffusion dish, shake it slightly to flatten the soil sample, add 2mL of boric acid mixed indicator to the inner chamber, apply alkaline glue on the edge of the diffusion dish, cover it with frosted glass, rotate it several times to make it completely bonded around the circle, turn the glass cover to leave a slit, add 10mL of 1mol / L sodium hydroxide solution to the outer chamber, rotate the cover tightly, fix it with a rubber band, and place it in a 40℃ constant temperature box for reaction. After 24 hours, take it out and titrate it with 0.01mol / L sulfuric acid solution. Stop the titration when the solution changes from blue to slightly red, record the titration volume, and calculate the alkaline nitrogen content in the soil according to the following formula:

[0104]

[0105] Wherein, c-0.005mol / L sulfuric acid standard solution concentration, mol / L; V0-volume of sulfuric acid solution used for titration of blank solution, mL; V-volume of sulfuric acid solution used for titration of sample, mL; 14-molar mass of nitrogen atom, g / mol; m-mass of soil sample, g; 1000-unit conversion coefficient; the test results are shown in Table 1;

[0106] ⑤ Total phosphorus content in soil: The sodium hydroxide melting-molybdenum antimony colorimetric method is used. The specific steps are as follows: 0.25g (accurate to 0.0001g) of soil sample passed through a 100-mesh sieve is placed at the bottom of a nickel crucible, and 2g of sodium hydroxide is spread on it. The crucible is placed in a muffle furnace and the temperature is raised to 400℃. The power is suspended for 15min, and then the temperature is raised to 720℃ and maintained for 15min. Take it out and cool it. Add 10mL of pure water and heat it on a hot plate (80℃). After stirring and dissolving, pour it into a 50mL volumetric flask, wash the crucible with water, make up the volume, filter, transfer 5mL of the filtrate to a 50mL colorimetric tube, dilute it to 3 / 5 with water, add 3 drops of dinitrophenol indicator, adjust it to slightly yellow with 100g / L sodium carbonate solution, add 5mL of molybdenum antimony color developer, shake well, add water to make up the volume, and place it at room temperature of 15℃ for 30min. Finally, use a 700nm, 1cm light path cuvette and blank solution to zero on the spectrophotometer, measure the absorbance, and draw a phosphorus standard curve (P content and absorbance) to calculate the total phosphorus content by absorbance:

[0107]

[0108] In the formula, ρ is the mass concentration of phosphorus found on the standard curve, mg / g; m is the mass of the soil sample, g; V1 is the volume of the sample after melting, mL; V2 is the volume of the sample during color development, mL; V3 is the volume of the molten sample, mL; 10 -3 -The coefficient of converting mg / L to kg; 100 / (100-H)-The coefficient of converting air-dried soil sample to oven-dried soil; H-The percentage of moisture content in air-dried soil; The test results are shown in Table 1;

[0109] ⑥ Available phosphorus content in soil: Use hydrochloric acid-sulfuric acid-molybdenum-antimony colorimetric method, the specific steps are: shake 5g (accurate to 0.0001g) of soil sample through 100 mesh sieve, 0.05mol / L HCl+0.025mol / L (1 / 2H2SO4) extractant for 5min, filter, take 1mL of filtrate and add it to 25mL colorimetric tube, add 24mL ascorbic acid-sulfuric acid-ammonium molybdate colorimetric solution, shake well, let it stand for 30min, use 700nm, 1cm light path colorimetric dish on the spectrophotometer, blank solution to zero, and measure absorbance. By drawing the phosphorus standard curve (P content and absorbance), calculate the available phosphorus content by absorbance:

[0110]

[0111] In the formula, ρ is the mass concentration of phosphorus found on the standard curve, mg / g; m is the mass of the soil sample, g; 25 is the volume of the extractant, mL; 25 is the volume of the fixed volume during color development, mL; the test results are shown in Table 1;

[0112] ⑦ Total potassium content in soil: Sodium hydroxide melting-flame photometry is used. The specific steps are as follows: 0.25g (accurate to 0.0001g) of soil sample that has passed through a 100-mesh sieve is placed at the bottom of a nickel crucible, and 2g of sodium hydroxide is spread on it. The crucible is placed in a muffle furnace and heated. When the temperature rises to 450°C, keep it for 15 minutes. Take it out and cool it. Add 10mL of pure water and heat it on a hot plate (80°C) to dissolve and pour it into a 50mL volumetric flask. Wash the crucible with 0.2mol / L H2SO4, and pour the washing liquid into the volumetric flask. Control the volume to 40mL, add 5 drops of 50vt% HCl, 5mL 25vt% H2SO4, add water to make up the volume, and filter it to obtain the test solution. Pipette 5mL of the test solution into a 50mL volumetric flask, add water to make up the volume, measure it on a flame photometer, and record the galvanometer reading. Calculate the total potassium content by drawing a potassium standard curve (K content and galvanometer reading):

[0113]

[0114] Where, ρ-mass concentration of potassium found on the standard curve, mg / g; m-mass of soil sample, g; m-volume of extractant, mL; V-volume of the test solution, mL; η-multiple fractions; 10 6 -ug is converted to g; the test results are shown in Table 1;

[0115] ⑧ Soil available potassium content: nitric acid extraction-flame photometry, the specific steps are: 2.5g (accurate to 0.0001g) of soil sample passed through a 100-mesh sieve is placed in a test tube, added to a 2mol / L nitric acid solution and shaken for 30min, filtered, and the filtrate is measured with a flame photometer. By drawing a potassium standard curve (K content and galvanometer reading), the available content is calculated:

[0116]

[0117] Where, V-volume of added extract, mL; m-mass of soil sample, g; the test results are shown in Table 1;

[0118] Table 1: Statistical table of physical and chemical properties of soil samples after treatment

[0119]

[0120]

[0121] As can be seen from Table 1, the soil remediation agent prepared in the present application is added to the ionic rare earth mine tailings soil, which effectively regulates the content of substances such as organic matter and inorganic salts in the soil and repairs the soil performance.

[0122] (3) Adsorption and desorption performance of rare earth ions: 0.1 g of the modified biochar prepared in Examples 3-5 and Comparative Examples 3-6 was added to 100 mL of 100 mg / L La(III) solution, the pH was adjusted to 4, and the experimental temperature was 30° C. for 12 h. After adsorption equilibrium, the remaining La(III) concentration in the solution was calculated by ultraviolet spectrophotometry; the modified biochar after adsorption was separated from the solution and eluted with deionized water for 30 min, and the La(III) concentration in the eluate was calculated by ultraviolet spectrophotometry; the test results are shown in Table 2;

[0123] Table 2: Statistical table of performance test data of modified biochar of Examples 3-5 and Comparative Examples 3-6

[0124]

[0125] It can be seen from Table 2 that the modified biochar prepared in the present application has a good adsorption and fixation effect on rare earth ions in the soil; the modified activated carbon prepared in the present application is added to the soil remediation agent to adjust the ionic rare earth mine tailings soil, effectively adsorb and fix the rare earth ions in the soil, and further improve the soil improvement effect.

[0126] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A soil reconstruction method based on organic matter enrichment, characterized in that: The soil reconstruction method comprises the following steps: the soil reconstructing method comprises adding a soil remediation agent to the soil; The preparation method of the soil remediation agent comprises the following steps: S1: drying, crushing, soaking and filtering yellow tobacco straw, and taking the filtrate as yellow tobacco straw extract; S2: Mix yellow tobacco straw extract, tea oil shell powder, and modified biochar to obtain a soil conditioner; the soil conditioner includes 10-50g tea oil shell powder, 10-50mL yellow tobacco straw extract, and 2-10g modified biochar; The preparation method of the modified biochar comprises the following steps: A1: Add phytic acid and deionized water into a reactor and disperse them evenly, add epoxidized biochar, control the temperature at 60-70°C, keep the reaction warm for 3-6 hours, wash with water, and dry to prepare phosphorylated biochar; A2: Add phosphorylated biochar, distilled water and melamine into a reactor and disperse them evenly. Control the temperature to 80-90°C, keep the reaction warm for 3-6 hours, centrifuge, wash with ethanol and dry to obtain amination biochar. A3: Add the organic magnetic particles, anhydrous ethanol and amino biochar into the reactor and disperse them evenly. Control the temperature at 75-85°C, keep the temperature under stirring for 12-18 hours, wash with anhydrous ethanol, wash with water, and freeze-dry to obtain modified biochar.

2. A soil reconstruction method based on organic matter enrichment according to claim 1, characterized in that: The phytic acid and deionized water in A1 were added to the reactor and dispersed evenly, and the epoxidized biochar was added in a ratio of 1-2 g: 10 mL: 1 g.

3. A soil reconstruction method based on organic matter enrichment according to claim 1, characterized in that: The addition ratio of phosphorylated biochar, distilled water, and melamine in A2 was 10 g: 100-300 mL: 1-3 g.

4. The soil reconstruction method based on organic matter enrichment according to claim 1, characterized in that: The addition ratio of the organic magnetic particles, anhydrous ethanol, and amino biochar in A3 is 0.5-3g:100-200mL:10g.

5. The soil reconstruction method based on organic matter enrichment according to claim 1, characterized in that: The preparation method of the epoxidized biochar comprises the following steps: B1: Dry, sinter, crush and sieve the remaining solids from the preparation of yellow tobacco straw extract to obtain biochar particles; B2: Add biochar particles, methanol solution and sodium hydroxide solution into a reactor, control the temperature at 40-50°C, keep warm and stir for 4-8 hours, wash with water and dry to obtain pretreated biochar particles; B3: Add pretreated biochar particles, γ-glycidyloxypropyltrimethoxysilane and toluene into a reactor, stir at room temperature for 1-3 hours, and dry to obtain epoxidized biochar.

6. A soil reconstruction method based on organic matter enrichment according to claim 5, characterized in that: The methanol solution in B2 is 20-40wt% methanol aqueous solution, and the sodium hydroxide solution is 20-25wt% sodium hydroxide aqueous solution; the addition ratio of biochar particles, methanol solution, and sodium hydroxide solution is 10g:30-60mL:200-300mL.

7. The soil reconstruction method based on organic matter enrichment according to claim 5, characterized in that: The addition ratio of pretreated biochar particles, γ-glycidyloxypropyltrimethoxysilane, and toluene in B3 is 1 g: 0.1-0.5 mL: 20-100 mL.

8. The soil reconstruction method based on organic matter enrichment according to claim 1, characterized in that: The preparation method of the organic magnetic particles comprises the following steps: adding ferroferric oxide particles, toluene and octadecyltriethoxysilane into a reaction kettle and dispersing them uniformly, reacting them at 120-150° C. for 3-6 hours in a sealed autoclave, washing with ethanol and drying to obtain the organic magnetic particles.

9. The soil reconstruction method based on organic matter enrichment according to any one of claims 1 to 8 is applied to repair tailings soil after ionic rare earth mining.

10. The use according to claim 9, characterized in that: Add 10-100g soil remediation agent per kilogram of tailings soil.

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