A soil reconstruction method and application based on organic matter enrichment

Abstract

The present invention discloses a soil reconstruction method and application based on organic matter enrichment, which relates to the technical field of soil remediation. The present invention discloses a soil reconstruction method based on organic matter enrichment, comprising the following steps: adding a soil remediation agent to the soil; the preparation method of the soil remediation agent comprises the following steps: drying, pulverizing, soaking, and filtering yellow tobacco straws, and taking the filtrate as the yellow tobacco straw leachate; pulverizing oil-tea camellia husks to obtain oil-tea camellia husk powder; mixing the yellow tobacco straw leachate, the oil-tea camellia husk powder, and modified biochar to obtain a soil conditioner. The soil remediation agent prepared in this application is applied to the tailing soil after the mining of ionic rare earth ores to achieve the rapid repair and reconstruction of the soil.

Description

Technical Field

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

[0002] Rare earth is the general term for 15 elements in the lanthanide series of the periodic table of chemical elements and the 21st element scandium and the 39th element yttrium (a total of 17 elements). Rare earth is known as the "industrial vitamin" and the "mother of new materials", and is widely used in industries such as aerospace, electronics, and medical and health, and is an important strategic mineral resource. The mining processes of ion-adsorption rare earth ores mainly include three different technologies: in-situ leaching, heap leaching, and in-situ leaching. Among them, 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 with other technologies. However, the use of the in-situ leaching process requires the excavation of shallow grooves, injection wells, and liquid collection ditches, and the perfusion of ammonium sulfate solution. One-third of the preparation and topsoil of the ore body injection holes are still disturbed. The long-term and high-concentration injection of the leaching agent ammonium sulfate solution into the ore body forms rare earth sulfate and ammonium hydroxide in the soil on the one hand, and then becomes rare earth oxalate or rare earth ammonium carbonate after precipitation with oxalic acid or ammonium bicarbonate. The high concentration is harmful to the surrounding soil plants, the roots of the vegetation are damaged, and the function of fixing water and protecting soil is lost. Moreover, the remaining tailings still contain a lot of heavy metals, which enter the surface and groundwater with soil erosion, resulting in water resource pollution.

[0003] The treatment and remediation of polluted farmland soil in rare earth mines and their surrounding areas are urgent problems to be solved to ensure the safety of agricultural products and human health, and are also environmental problems that must be faced and solved in the sustainable development and utilization of rare earth resources, which is of great significance to the regional agricultural economic development. The restoration technologies for mine ecology are 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 range and incomplete remediation; the biological method has the advantages of low cost and no secondary pollution, but has the disadvantages of limited application range and long remediation time; the chemical method is to repair by adding modifiers, leaching solutions, etc. to change the forms of heavy metals, and has the advantage of high efficiency. However, when the existing soil modifiers are added to the tailing soil of ion-type rare earth mines, due to the acidic soil, the adsorption and deposition effect on heavy metals is poor, and the soil remediation speed is slow. 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, and solve the following technical problems:

[0005] When the existing soil modifiers are added to acidic soil, the adsorption and deposition effect on heavy metal ions in the soil is poor, and the soil remediation effect is not ideal.

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

[0007] A soil reconstruction method based on organic matter enrichment, comprising 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 includes the following steps:

[0009] S1: Dry, crush, soak, and filter the yellow tobacco straw, and take the filtrate as the yellow tobacco straw leachate;

[0010] S2: Mix the yellow tobacco straw leachate, camellia oleifera fruit shell powder, and modified biochar to obtain a soil conditioner; The soil conditioner includes 10 - 50 g of camellia oleifera fruit shell powder, 10 - 50 mL of yellow tobacco straw leachate, and 2 - 10 g of modified biochar;

[0011] The preparation method of the modified biochar includes the following steps:

[0012] A1: Add inositol hexaphosphate and deionized water to a reaction kettle and disperse evenly, add epoxidized biochar, control the temperature at 60 - 70 °C, keep the temperature for reaction for 3 - 6 h, wash with water and dry to prepare phosphorylated biochar;

[0013] A2: Add phosphorylated biochar, distilled water, and melamine to a reaction kettle and disperse evenly, control the temperature at 80 - 90 °C, keep the temperature for reaction for 3 - 6 h, centrifuge, wash with ethanol, and dry to obtain amino-functionalized biochar;

[0014] A3: Add organic magnetic particles, absolute ethanol, and amino-functionalized biochar to a reaction kettle and disperse evenly, control the temperature at 75 - 85 °C, keep the temperature for reaction for 12 - 18 h under stirring conditions, wash with absolute ethanol, wash with water, and freeze-dry to obtain modified biochar.

[0015] As a further scheme of the present invention: In A1, the addition ratio of inositol hexaphosphate, deionized water added to the reaction kettle and dispersed evenly, and epoxidized biochar added is 1 - 2 g: 10 mL: 1 g.

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

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

[0018] As a further scheme of the present invention: The preparation method of epoxidized biochar includes the following steps:

[0019] B1: Dry, sinter, crush, and sieve the filter residue solid remaining after preparing the yellow tobacco straw leachate to obtain biochar particles;

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

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

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

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

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

[0025] As a further scheme of the present invention: The preparation method of the organic magnetic particles includes the following steps: Add magnetic iron oxide particles, toluene, and octadecyltriethoxysilane into a reaction kettle and disperse evenly, react in a sealed autoclave at 120 - 150 °C for 3 - 6 h, wash with ethanol and dry to obtain organic magnetic particles.

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

[0027] As a further scheme of the present invention: The preparation method of the magnetic iron oxide particles includes the following steps: In a nitrogen atmosphere, add ferric chloride hexahydrate, sodium acetate, and ethanol into a reaction kettle and disperse evenly, control the temperature at 150 - 160 °C, keep warm and react for 1 - 3 h, react in a sealed autoclave at 200 - 250 °C for 9 - 12 h, wash with ethanol and dry to obtain magnetic iron oxide particles.

[0028] As a further solution of the present invention: The specific preparation method of the yellow tobacco straw leachate is as follows: The yellow tobacco straw is dried and crushed into yellow tobacco straw particles with a size of 3 - 10 mm; the yellow tobacco straw particles are placed in water and soaked at room temperature for 2 - 4 days, and the filtrate is taken by filtration, which is the yellow tobacco straw leachate.

[0029] The above soil reconstruction method based on organic matter enrichment is applied to the restoration of tailing soil after the mining of ionic rare earth ores.

[0030] As a further solution of the present invention: 10 - 100 g of soil repair agent is added to each kilogram of tailing soil.

[0031] The beneficial effects of the present invention:

[0032] (1) In this application, yellow tobacco straw particles are used as raw materials and treated by water immersion to obtain yellow tobacco straw leachate. The yellow tobacco straw leachate prepared in this application, together with camellia fruit shell powder and modified biochar, is mixed to obtain a soil repair agent. The yellow tobacco straw leachate prepared in this application contains sugars, lignin, and inorganic salt ions. Among them, lignin and pentosan molecules are adsorbed on the surface of the modified biochar, making the surface of the modified biochar have the same charge. Due to the repulsion of like charges, it tends to be in a dispersed state. The abundant inorganic salt ions in the leachate are added to the soil to effectively adjust the content of inorganic salt ions in the soil; moreover, the surfactants such as sugars and lignin in the yellow tobacco straw leachate increase the double - layer potential and surface tension of the material, increasing the stability of the soil repair agent in acidic soil and effectively improving the repair effect of the soil repair agent on tailing soil.

[0033] (2) In this application, the solid remaining after preparing the yellow tobacco straw leachate is dried and sintered to obtain biochar; the surface area of the biochar prepared in this application enables it to have more oxygen - containing functional groups such as hydroxyl, carbonyl, ether bond, and amide. The π - electrons provided by the aromatic structure of the biochar form cation - π interaction to adsorb inorganic pollutants in the soil and precipitate with heavy metal ions; the biochar prepared in this application structurally includes an aromatic structure with strong oxidation ability, and a carbon - oxygen structure and a fatty structure that are easily degraded. The biochar prepared in this application has the advantages of being alkaline in pH, large specific surface area, high porosity, and large ion exchange capacity. After being applied to the soil, it improves soil fertility, improves soil physical and chemical properties, and realizes the fixation of nitrogen and phosphorus in the soil.

[0034] This application uses a sodium hydroxide solution to treat biochar particles, graft hydroxyl groups on their surfaces, and perform epoxidation treatment with γ-glycidoxypropyltrimethoxysilane to obtain epoxidized biochar; then, the epoxy groups on the surface of the epoxidized biochar in this application react with the phosphate groups in phytic acid to graft phosphate groups on the biochar surface, and react with melamine using the phosphate groups to graft amino groups on the biochar surface to obtain amino-functionalized biochar; finally, this application uses the amino-functionalized biochar as a matrix and deposits organically modified magnetic particles on the surface of the amino-functionalized biochar to obtain modified biochar; this application performs organic modification on biochar, and the material has an increased negative charge and basic functional groups, effectively adsorbing cations. The modified biochar prepared in this application adsorbs, deposits, and solidifies the remaining rare earth ions in the soil. Rare earth 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 in this application not only has good adsorption performance and water retention performance, but also plays a positive role in maintaining soil nutrients, and has a good effect on the fixation of pollutants. Detailed implementation manners

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] The preparation method of epoxidized biochar in Example 1 includes the following steps:

[0037] B1: Place the filter residue remaining after preparing the leachate of yellow tobacco straw in an oven at 80 °C and dry for 1 h. Place it in a muffle furnace and heat it to 500 °C at a heating rate of 10 °C / min in a nitrogen environment, sinter for 1 h, and crush and sieve to obtain biochar particles with a particle size of 1 mm.

[0038] B2: Add 10 g of biochar particles, 30 mL of 37 wt% methanol solution, and 200 mL of 20 wt% sodium hydroxide solution to a reaction kettle, control the temperature at 40 °C, keep stirring for 4 h, wash with water and dry to obtain pretreated biochar particles.

[0039] B3: Add 1 g of pretreated biochar particles, 0.5 mL of γ-glycidoxypropyltrimethoxysilane, and 20 mL of toluene to a reaction kettle, stir at room temperature for 3 h, and dry to obtain epoxidized biochar.

[0040] The preparation method of organically modified magnetic particles in Example 2 includes 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 reaction kettle and dispersed evenly. The temperature was controlled at 150 °C, and the reaction was carried out for 3 h while maintaining the temperature. Then, the reaction was carried out at 200 °C in a sealed autoclave for 9 h. After washing with ethanol and drying, iron oxide particles were obtained.

[0042] C2: 1 g of iron oxide particles, 50 mL of toluene, and 0.5 mL of octadecyltriethoxysilane were added to a reaction kettle and dispersed evenly. The reaction was carried out at 120 °C in a sealed autoclave for 6 h. After washing with ethanol and drying, organically modified magnetic particles were obtained.

[0043] The preparation method of the modified biochar in Example 3 includes the following steps:

[0044] A1: 10 g of phytic acid and 100 mL of deionized water were added to a reaction kettle and dispersed evenly. 10 g of the epoxidized biochar prepared in Example 1 was added. The temperature was controlled at 60 °C, and the reaction was carried out for 3 h while maintaining the temperature. After washing with water and drying, phosphorylated biochar was prepared.

[0045] A2: 10 g of phosphorylated biochar, 100 mL of distilled water, and 1 g of melamine were added to a reaction kettle and dispersed evenly. The temperature was controlled at 80 °C, and the reaction was carried out for 3 h while maintaining the temperature. After centrifugation, washing with ethanol, and drying, amino-functionalized biochar was obtained.

[0046] A3: 0.5 g of the organically modified magnetic particles prepared in Example 2, 100 mL of absolute ethanol, and 10 g of amino-functionalized biochar were added to a reaction kettle and dispersed evenly. The temperature was controlled at 75 °C, and the reaction was carried out for 12 h under stirring conditions while maintaining the temperature. After washing with absolute ethanol, washing with water, and freeze-drying, modified biochar was obtained.

[0047] The preparation method of the modified biochar in Example 4 includes the following steps:

[0048] A1: 15 g of phytic acid and 100 mL of deionized water were added to a reaction kettle and dispersed evenly. 10 g of the epoxidized biochar prepared in Example 1 was added. The temperature was controlled at 65 °C, and the reaction was carried out for 3 h while maintaining the temperature. After washing with water and drying, phosphorylated biochar was prepared.

[0049] A2: 10 g of phosphorylated biochar, 200 mL of distilled water, and 2 g of melamine were added to a reaction kettle and dispersed evenly. The temperature was controlled at 85 °C, and the reaction was carried out for 3 h while maintaining the temperature. After centrifugation, washing with ethanol, and drying, amino-functionalized biochar was obtained.

[0050] A3: 1.5 g of the organically modified magnetic particles prepared in Example 2, 150 mL of absolute ethanol, and 10 g of amino-functionalized biochar were added to a reaction kettle and dispersed evenly. The temperature was controlled at 80 °C, and the reaction was carried out for 15 h under stirring conditions while maintaining the temperature. After washing with absolute ethanol, washing with water, and freeze-drying, modified biochar was obtained.

[0051] Example 5 The preparation method of the modified biochar includes the following steps:

[0052] A1: Add 20 g of inositol hexaphosphate and 100 mL of deionized water into a reaction kettle, disperse evenly, add 10 g of the epoxidized biochar prepared in Example 1, control the temperature at 70 °C, keep the temperature for reaction for 6 h, wash with water and dry to obtain phosphorylated biochar;

[0053] A2: Add 10 g of phosphorylated biochar, 300 mL of distilled water, and 3 g of melamine into a reaction kettle, disperse evenly, control the temperature at 90 °C, keep the temperature for reaction for 6 h, centrifuge, wash with ethanol, and dry to obtain amino-functionalized biochar;

[0054] A3: Add 3 g of the organic magnetic particles prepared in Example 2, 200 mL of absolute ethanol, and 10 g of amino-functionalized biochar into a reaction kettle, disperse evenly, control the temperature at 85 °C, keep the temperature for reaction for 18 h under stirring conditions, wash with absolute ethanol, wash with water, and freeze-dry to obtain the modified biochar.

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

[0056] S1: Dry the yellow tobacco straw and crush it into yellow tobacco straw particles with a size of 5 mm. Place the yellow tobacco straw particles in water and soak them at room temperature for 2 days. Filter to obtain the filtrate, which is the yellow tobacco straw leaching solution;

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

[0058] S3: Add 10 g of the soil conditioner to each kilogram of the tailing soil after ion-type rare earth ore mining.

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

[0060] S1: Dry the yellow tobacco straw and crush it into yellow tobacco straw particles with a size of 5 mm. Place the yellow tobacco straw particles in water and soak them at room temperature for 2 days. Filter to obtain the filtrate, which is the yellow tobacco straw leaching solution;

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

[0062] S3: Add 10 g of the soil conditioner to each kilogram of the tailing soil after ion-type rare earth ore mining.

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

[0064] S1: After drying and crushing the yellow tobacco straws into yellow tobacco straw particles with a size of 5 mm, soak the yellow tobacco straw particles in water at room temperature for 2 days, filter to obtain the filtrate, which is the yellow tobacco straw leachate;

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

[0066] S3: Add 10 g of the soil repair agent to each kilogram of the tailing soil after ion-type rare earth ore mining.

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

[0068] B1: Place the remaining filter residue solid after preparing the yellow tobacco straw leachate in an oven at 80 °C and dry for 1 h. Place it in a muffle furnace and heat it up to 500 °C at a heating rate of 10 °C / min in a nitrogen environment, sinter for 1 h, and crush and sieve to obtain biochar particles with a particle size of 1 mm;

[0069] B2: Add 1 g of the pretreated biochar particles, 0.5 mL of γ-glycidoxypropyltrimethoxysilane, and 20 mL of toluene to a reaction kettle, stir at room temperature for 3 h, and dry to obtain epoxidized biochar.

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

[0071] In a nitrogen atmosphere, add 4.05 g of ferric chloride hexahydrate, 7.2 g of sodium acetate, and 50 mL of ethanol to a reaction kettle and disperse evenly. Control the temperature at 150 °C, keep the temperature for 3 h, react at 200 °C in a sealed autoclave for 9 h, wash with ethanol and dry to obtain magnetic particles.

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

[0073] A1: Add 15 g of inositol hexaphosphate and 100 mL of deionized water to a reaction kettle and disperse evenly. Add 10 g of the epoxidized biochar prepared in Comparative Example 1, control the temperature at 65 °C, keep the temperature for 3 h, wash with water and dry to prepare phosphorylated biochar;

[0074] A2: Add 10 g of phosphorylated biochar, 200 mL of distilled water, and 2 g of melamine to a reaction kettle and disperse evenly. Control the temperature at 85 °C, keep the temperature for 3 h, centrifuge, wash with ethanol and dry to obtain amino-functionalized biochar;

[0075] A3: Add 1.5 g of the organically modified magnetic particles prepared in Example 1, 150 mL of absolute ethanol, and 10 g of amino-functionalized biochar to a reaction kettle and disperse evenly. Control the temperature at 80 °C, keep the temperature for 15 h under stirring conditions, wash with absolute ethanol, wash with water, and freeze-dry to obtain modified biochar.

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

[0077] A1: Add 15 g of inositol hexaphosphate and 100 mL of deionized water into a reaction kettle, disperse evenly, add 10 g of the epoxidized biochar prepared in Comparative Example 1, control the temperature at 65 °C, keep the temperature for reaction for 3 h, wash with water and dry to obtain phosphorylated biochar;

[0078] A2: Add 1.5 g of the organic magnetic particles prepared in Example 1, 150 mL of absolute ethanol and 10 g of phosphorylated biochar into a reaction kettle, disperse evenly, control the temperature at 80 °C, keep the temperature for 15 h under stirring conditions, wash with absolute ethanol, wash with water and freeze-dry to obtain modified biochar.

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

[0080] A1: Add 15 g of inositol hexaphosphate and 100 mL of deionized water into a reaction kettle, disperse evenly, add 10 g of the epoxidized biochar prepared in Comparative Example 1, control the temperature at 65 °C, keep the temperature for reaction for 3 h, wash with water and dry to obtain phosphorylated biochar;

[0081] A2: Add 10 g of phosphorylated biochar, 200 mL of distilled water and 2 g of melamine into a reaction kettle, disperse evenly, control the temperature at 85 °C, keep the temperature for reaction for 3 h, centrifuge, wash with ethanol and dry to obtain amino-functionalized biochar;

[0082] A3: Add 1.5 g of the magnetic particles prepared in Comparative Example 2, 150 mL of absolute ethanol and 10 g of amino-functionalized biochar into a reaction kettle, disperse evenly, control the temperature at 80 °C, keep the temperature for 15 h under stirring conditions, wash with absolute ethanol, wash with water and freeze-dry to obtain modified biochar.

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

[0084] A1: Add 10 g of the epoxidized biochar prepared in Example 1, 200 mL of distilled water and 2 g of melamine into a reaction kettle, disperse evenly, control the temperature at 85 °C, keep the temperature for reaction for 3 h, centrifuge, wash with ethanol and dry to obtain amino-functionalized biochar;

[0085] A2: Add 1.5 g of the organic magnetic particles prepared in Example 1, 150 mL of absolute ethanol and 10 g of amino-functionalized biochar into a reaction kettle, disperse evenly, control the temperature at 80 °C, keep the temperature for 15 h under stirring conditions, wash with absolute ethanol, wash with water and freeze-dry to obtain modified biochar.

[0086] Comparative Example 7 Compared with Example 7, only the modified biochar prepared in Example 4 added in Example 7 was replaced with the modified biochar prepared in Comparative Example 3 in equal amount, and the remaining components and preparation method were exactly the same as those in Example 7.

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

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

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

[0090] Comparative Example 11 Compared with Example 7, only the leachate of yellow tobacco straw added in Example 7 was replaced with deionized water in equal amount, and the remaining components and preparation method were exactly the same as those in Example 7.

[0091] Comparative Example 12 Compared with Example 7, only the camellia fruit shell powder with a particle size of 1 mm added in Example 7 was replaced with peanut shell powder with a particle size of 1 mm in equal amount, and the remaining components and preparation method were exactly the same as those in Example 7.

[0092] Performance Detection

[0093] Soil Determination

[0094] (1) Preparation of soil samples: The cultivated layer soil in a certain rare earth mining area was collected, and the collected soil was placed in a cool, dry and ventilated place for drying. After drying, it was put into a self-sealing bag and placed in a cool and ventilated place.

[0095] (2) The physical and chemical properties of the sampled soil and the soil after soil reconstruction were detected by the method described in "Methods for Agricultural Chemical Analysis of Soils":

[0096] ① Soil pH: The carbon dioxide distilled water extraction method was used. The specific steps were as follows: 10 g of soil samples passed through a 20-mesh sieve and 50 mL of distilled water were mixed evenly and left standing for 30 min, and then measured with a pH meter; the detection results are shown in Table 1.

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

[0098]

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

[0100] ③ Total nitrogen content in soil: The alkali-hydrolysis diffusion method was used. The specific steps are as follows: Add 1 g (accurate to 0.0001 g) of soil sample passed through a 60-mesh sieve, selenium powder and potassium sulfate mixed accelerator into a narrow-necked funnel, shake well, add 5 mL of concentrated sulfuric acid, digest at 280 °C for 40 min, and after digestion, make up the volume to 50 mL to obtain the test solution. Pipette 5 mL of the test solution into the outer chamber of a diffusion dish and 3 mL of boric acid mixed indicator into the inner chamber. Apply alkaline glue solution around the edge of the diffusion dish, cover it with a ground glass, rotate it several times to make it completely adhere, unscrew a slit and add 5 mL of 0.4 mol / L NaOH solution to the outer chamber, rotate and cover it tightly, fix it with a rubber band, and place it in a 40 °C constant temperature oven for reaction. After 24 h, take it out and titrate with 0.01 mol / 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] where c is the concentration of the 0.01 mol / L sulfuric acid standard solution, in mol / L; V0 is the volume of the sulfuric acid solution used for titrating the blank solution, in mL; V is the volume of the sulfuric acid solution used for titrating the sample, in mL; 0.014 is the number of grams of 1 mg equivalent nitrogen; m is the mass of the soil sample, in g; 50 is the volume of the test solution after volume fixation, in mL; 5 is the volume of the test solution participating in the reaction, in mL; 1000 is the unit conversion factor; the test results are shown in Table 1;

[0103] ④ Soil available nitrogen content: The alkaline hydrolysis diffusion method is adopted. The specific steps are as follows: Place 2 g (accurate to 0.0001 g) of soil sample passed through a 60-mesh sieve in the outer chamber of the diffusion dish, gently shake to level the soil sample, add 2 mL of boric acid mixed indicator to the inner chamber, apply alkaline adhesive solution to the edge of the diffusion dish, cover with a ground glass, rotate several times to make it completely adhered around, turn the glass cover to expose a narrow slit, add 10 mL of 1 mol / L sodium hydroxide solution to the outer chamber, rotate and cover tightly, fix with a rubber band and place in a 40 °C constant temperature oven for reaction. After 24 h, take it out and titrate with 0.01 mol / L sulfuric acid solution. Stop titration when the solution changes from blue to slightly red, record the titration volume, and calculate the available nitrogen content in the soil according to the following formula:

[0104]

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

[0106] ⑤ Soil total phosphorus content: The sodium hydroxide melting - molybdenum antimony anti - colorimetric method is adopted. The specific steps are as follows: Place 0.25 g (accurate to 0.0001 g) of soil sample passed through a 100 - mesh sieve at the bottom of a nickel crucible, spread 2 g of sodium hydroxide on it, put the crucible into a muffle furnace, raise the temperature to 400 °C, pause the power supply for 15 min, then raise the temperature to 720 °C and keep it for 15 min. Take it out and cool, add 10 mL of pure water and heat on a hot plate (80 °C), stir and dissolve, then pour it into a 50 - mL volumetric flask, wash the crucible with water, make up the volume, filter, transfer 5 mL of the filtrate to a 50 - mL colorimetric tube, dilute it with water to 3 / 5, add 3 drops of dinitrophenol indicator, adjust to slightly yellow with 100 g / L sodium carbonate solution, add 5 mL of molybdenum antimony anti - color reagent, shake well, add water to make up the volume, and place it at room temperature of 15 °C for 30 min. Finally, zero with a blank solution using a 700 - nm, 1 - cm optical path cuvette on a spectrophotometer, measure the absorbance, calculate the total phosphorus content by drawing a phosphorus standard curve (P content vs. absorbance) and through the absorbance:

[0107]

[0108] where ρ is the mass concentration of phosphorus obtained from the standard curve, mg / g; m is the mass of the soil sample, g; V1 is the volume of the sample after melting and constant volume, mL; V2 is the volume of constant volume during color development, mL; V3 is the volume of the molten sample taken, mL; 10 -3 is the coefficient for converting mg / L to kg; 100 / (100 - H) is the coefficient for converting air-dried soil sample to oven-dried soil; H is the percentage of water content in the air-dried soil; the test results are shown in Table 1;

[0109] ⑥ Soil available phosphorus content: The hydrochloric acid-sulfuric acid-molybdenum antimony anti-colorimetric method is used. The specific steps are as follows: Weigh 5 g (accurate to 0.0001 g) of soil sample passed through a 100-mesh sieve, add 0.05 mol / L HCl + 0.025 mol / L (1 / 2H2SO4) extractant, shake for 5 min, filter, take 1 mL of the filtrate and add it to a 25-mL colorimetric tube, add 24 mL of ascorbic acid-sulfuric acid-ammonium molybdate color-developing solution, shake well, let stand for 30 min, use a 700-nm, 1-cm light path cuvette on a spectrophotometer, zero with the blank solution, and measure the absorbance. By plotting the phosphorus standard curve (P content vs. absorbance), calculate the available phosphorus content from the absorbance:

[0110]

[0111] where ρ is the mass concentration of phosphorus obtained from 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 constant volume during color development, mL; the test results are shown in Table 1;

[0112] ⑦ Soil total potassium content: The sodium hydroxide melting-flame photometry method is used. The specific steps are as follows: Place 0.25 g (accurate to 0.0001 g) of soil sample passed through a 100-mesh sieve at the bottom of a nickel crucible, spread 2 g of sodium hydroxide on it, put the crucible into a muffle furnace and heat. When the temperature rises to 450 °C, keep it for 15 min. Take it out and cool, add 10 mL of pure water, heat (80 °C) on a hot plate to dissolve, pour it into a 50-mL volumetric flask, wash the crucible with 0.2 mol / L H2SO4, pour the washing liquid into the volumetric flask together, control the volume to 40 mL, add 5 drops of 50 vt% HCl and 5 mL of 25 vt% H2SO4, add water to constant volume, and filter to obtain the test solution. Take 5 mL of the test solution into a 50-mL volumetric flask, add water to constant volume, measure on a flame photometer, and record the galvanometer reading. By plotting the potassium standard curve (K content vs. galvanometer reading), calculate the total potassium content:

[0113]

[0114] Where ρ is the mass concentration of potassium obtained from the standard curve, in mg / g; m is the mass of the soil sample, in g; m is the volume of the leaching agent, in mL; V is the constant volume of the test solution, in mL; η is the aliquot multiple; 10 6 -the coefficient for converting μg to g; the test results are shown in Table 1;

[0115] ⑧ Available potassium content in soil: The nitric acid extraction-flame photometry method was used. The specific steps were as follows: Place 2.5 g (accurate to 0.0001 g) of soil sample passed through a 100-mesh sieve into a test tube, add 2 mol / L nitric acid solution, shake for 30 min, filter, take the filtrate and measure it with a flame photometer. By plotting the potassium standard curve (K content vs. galvanometer reading), calculate the available content:

[0116]

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

[0118] Table 1: Statistical table of physical and chemical properties data of the treated soil samples

[0119]

[0120]

[0121] As can be seen from Table 1, the soil conditioner prepared in this application is added to the ionic rare earth ore tailing soil, effectively regulating the contents of organic matter and inorganic salts in the soil and repairing the soil properties.

[0122] (3) Adsorption and desorption properties of rare earth ions: Add 0.1 g of the modified biochar prepared in Examples 3-5 and Comparative Examples 3-6 to 100 mL of 100 mg / L La(Ⅲ) solution, adjust the pH to 4, and let it stand at 30 °C for 12 h. After adsorption equilibrium, use ultraviolet spectrophotometry to calculate the remaining La(Ⅲ) concentration in the solution; Separate the adsorbed modified biochar from the solution and elute it with deionized water for 30 min, and use ultraviolet spectrophotometry to calculate the La(Ⅲ) concentration in the eluate; The test results are shown in Table 2;

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

[0124]

[0125] As can be seen from Table 2, the modified biochar prepared in this application has good adsorption and fixation effects on rare earth ions in the soil; Adding the modified activated carbon prepared in this application to the soil conditioner to adjust the ionic rare earth ore tailing soil can effectively adsorb and fix rare earth ions in the soil, further improving the soil improvement effect.

[0126] The above has described in detail an embodiment of the present invention. However, the above content is only a preferred embodiment of the present invention and should not be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for reconstructing ionic rare earth tailings soil, characterized in that: The steps include: the reconstruction method includes 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 to 75-85°C, keep the temperature for 12-18 hours under stirring, wash with anhydrous ethanol, wash with water, and freeze-dry to obtain modified biochar. 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; 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.

2. The method for reconstructing ionic rare earth tailings soil 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. The method for reconstructing ionic rare earth tailings soil 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 method for reconstructing ionic rare earth tailings soil 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 method for reconstructing ionic rare earth tailings soil according to claim 1, characterized in that: The methanol solution in B2 is a 20-40wt% methanol aqueous solution, and the sodium hydroxide solution is a 20-25wt% sodium hydroxide aqueous solution; the addition ratio of biochar particles, methanol solution, and sodium hydroxide solution is 10g:30-60mL:200-300mL.

6. The method for reconstructing ionic rare earth tailings soil according to claim 1, 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.

7. The method for reconstructing ionic rare earth tailings soil according to claim 1, characterized in that: Add 10-100g soil remediation agent per kilogram of tailings soil.

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