A remediation modifier for contaminated soil and a method for preparing the same

Abstract

This invention relates to the field of soil remediation and improvement technology, specifically disclosing a soil remediation and improvement agent for contaminated soil and its preparation method. The remediation and improvement agent comprises the following raw materials in parts by weight: modified remediation masterbatch, hydroxyapatite, sodium bentonite, mineral-derived potassium humate, and polyaspartic acid. The preparation method includes: firstly, using lignin to disperse and fix an iron source on biochar and zeolite to obtain a modified carrier; then, using a colloid formed from sodium alginate and silane, adhering modified lithium titanate and modified bismuth tungstate to the carrier surface, and then applying a low-temperature compound bacterial agent to obtain the modified remediation masterbatch; finally, mixing the masterbatch with other raw materials and granulating. The improver prepared by this invention utilizes the synergistic effect of multiple materials to simultaneously adsorb heavy metals and degrade organic pollutants, and the process is controllable, making it suitable for agricultural applications.

Description

Technical Field

[0001] This invention relates to the field of soil remediation and improvement technology, and more specifically, to a remediation and improvement agent for contaminated soil and its preparation method. Background Technology

[0002] With the development of industrialization and modern agriculture, soils face a severe challenge from complex pollution by heavy metals (such as cadmium and lead) and organic pollutants (such as pesticides and polycyclic aromatic hydrocarbons). This complex pollution has a toxicity amplification effect, and there are complex interactions between pollutants, which not only leads to the degradation of soil ecological functions but also seriously threatens food safety and human health.

[0003] Currently, applying remediation amendments is the primary method for treating contaminated soil. Common materials include biochar, clay minerals, photocatalysts, and microbial agents. However, existing amendment products and preparation technologies still have the following significant drawbacks: 1. Existing materials such as bismuth tungstate and lithium titanate have narrow photoresponse ranges, fast photogenerated carrier recombination rates, and low degradation efficiency; moreover, their preparation processes mostly rely on high-temperature autoclaves or expensive organic solvents, resulting in high costs and making it difficult to meet the needs of large-scale, low-cost agricultural applications.

[0004] 2. In the preparation of composite materials, strong mechanical shearing or ball milling processes are commonly used, which severely damages the original rich pore structure of carriers such as biochar and zeolite, resulting in a significant decrease in specific surface area and a large reduction in adsorption sites and microbial habitat space.

[0005] 3. In existing technologies, the bond between photocatalytic particles and the support relies mainly on physical stacking or van der Waals forces, resulting in weak interfacial adhesion. Under complex soil environments and water erosion conditions, the active components are easily detached from the support surface, leading to unsustainable remediation effects.

[0006] 4. The strong oxidizing free radicals generated by photocatalysis can damage and kill coexisting functional bacteria while degrading pollutants; in addition, the high temperature environment of traditional granulation process leads to low survival rate of bacterial agents and difficulty in colonization, making it difficult to exert the long-term effect of bioremediation.

[0007] 5. Existing products mostly rely on single physical adsorption or chemical degradation. Once the adsorption material reaches saturation, it is prone to desorption, causing secondary pollution. Single degradation materials are also difficult to fix heavy metals, and cannot effectively address complex organic-inorganic composite pollution.

[0008] Therefore, there is an urgent need to develop a soil conditioner with a mild preparation process that can completely preserve the pore structure and microbial activity of the material, and has a highly efficient photocatalytic-adsorption-microbial synergistic remediation function.

[0009] Based on the above statements, this invention proposes a soil remediation agent and its preparation method. Summary of the Invention

[0010] To address the problems of existing soil remediation materials, such as difficulty in treating complex pollution, easy loss of photocatalytic activity, and easy occurrence of soil compaction and microbial death, this invention provides a soil remediation modifier and its preparation method.

[0011] In a first aspect, the present invention provides a soil remediation and amendment agent for contaminated soil, employing the following technical solution: A soil remediation agent comprising the following raw materials in parts by weight: 65-85 parts modified remediation masterbatch, 10-15 parts hydroxyapatite, 5-10 parts sodium bentonite, 5-8 parts mineral-derived potassium humate, and 0.5-1 parts polyaspartic acid.

[0012] Preferably, the modified repair masterbatch is made by mixing composite powder, premix, and composite bacterial powder.

[0013] Preferably, the composite powder is made by mixing modified lithium titanate and modified bismuth tungstate.

[0014] Preferably, the method for preparing the modified lithium titanate includes the following steps: A1. Dissolve titanium sulfate and ammonium dihydrogen phosphate in water, add lithium carbonate and glucose, stir well to obtain a sol; A2. After drying the sol, calcination is carried out. After calcination, the sol is cooled to room temperature and ground to obtain modified lithium titanate.

[0015] By adopting the above technical solution, a phosphorus source is introduced for high-temperature solid-phase phosphating, and Ti-OP polar chemical bonds are constructed on the surface of lithium titanate crystals. Due to the difference in electronegativity of phosphorus atoms, this surface bonding layer not only forms a permanent surface dipole moment, promoting the separation of photogenerated charges, but also significantly enhances the electrostatic adsorption capacity of the material surface for cationic heavy metals (such as Cd²⁺ and Pb²⁺).

[0016] Preferably, in step A1, the mass ratio of titanium sulfate, lithium carbonate, glucose, ammonium dihydrogen phosphate and water is 4-6:0.8-1.2:1-2:0.4-0.6:40-50.

[0017] Preferably, the stirring in step A1 refers to stirring for 18-24 hours at a temperature of 80-90℃ and a rotation speed of 300-500 r / min.

[0018] Preferably, the drying in step A2 refers to drying in a forced-air drying oven at 80-100℃ until constant weight.

[0019] Preferably, in step A2, calcination refers to heating to 700-800℃ at a heating rate of 3-5℃ / min and holding at that temperature for 3-4 hours.

[0020] Preferably, the grinding in step A2 refers to: using a planetary ball mill, ball milling at a speed of 300-400 r / min for 50-60 min, and passing through a 200-300 mesh sieve.

[0021] Preferably, the method for preparing the modified bismuth tungstate includes the following steps: B1. Dissolve bismuth nitrate and sodium tungstate in water, add sodium fluoride, stir well, and adjust the pH of the system to 3-4 using glacial acetic acid to obtain an acidic precursor solution. B2. Place the acidic precursor solution in a reaction vessel, stir and react. After the reaction is complete, centrifuge, wash and dry to obtain modified bismuth tungstate.

[0022] By adopting the above technical solution, the surface energy of the crystal plane is selectively reduced by utilizing the strong chemical adsorption between F⁻ ions and Bi atoms, inhibiting the stacking of crystals along the c-axis and inducing their growth into a two-dimensional nanosheet structure. This structure can shorten the distance that photogenerated carriers migrate to the surface and expose more highly active reaction sites, significantly improving the photocatalytic redox capability.

[0023] Preferably, in step B1, the mass ratio of bismuth nitrate, sodium tungstate, sodium fluoride, and water is 2.8-3.2:0.9-1.1:0.1-0.2:60-70.

[0024] Preferably, the stirring in step B1 refers to stirring for 40-50 minutes at room temperature and a rotation speed of 300-500 r / min.

[0025] Preferably, the stirring reaction in step B2 refers to stirring for 20-24 hours at a temperature of 160-180℃ and a rotation speed of 50-100 r / min.

[0026] Preferably, in step B2, the centrifugation, washing, and drying process refers to: centrifuging for 10-15 minutes at a power of 1.5-2.5 kW and a rotation speed of 6000-7000 r / min, washing the solid 2-3 times each with dilute sodium hydroxide solution and water, and then drying it in a vacuum drying oven at 80-90℃ for 8-10 hours.

[0027] Preferably, the method for preparing the composite powder includes the following steps: Modified lithium titanate, modified bismuth tungstate, and anhydrous ethanol were mixed, ultrasonically dispersed, and then the anhydrous ethanol was removed by rotary evaporation. The mixture was then ground to obtain a composite powder.

[0028] By adopting the above technical solution, using anhydrous ethanol as a dispersion medium, the agglomeration barrier between nanoparticles is broken under the action of shock waves and microjets generated by high-frequency ultrasonic cavitation effect, so that modified lithium titanate is uniformly dispersed and anchored on the surface of two-dimensional nanosheets of modified bismuth tungstate; then, through rotary evaporation, the surface tension is used to induce the two to form a tight surface-to-surface contact or point-to-surface contact during the slow evaporation of the solvent, thus constructing a stable Z-shaped heterojunction structure.

[0029] Preferably, the mass ratio of the modified lithium titanate, the modified bismuth tungstate, and the anhydrous ethanol is 1-2:1-2:10-15.

[0030] Preferably, the ultrasonic dispersion refers to ultrasonic dispersion for 30-45 minutes under the conditions of temperature 30-40℃, power 300-500W, and frequency 35-45KHz.

[0031] Preferably, the temperature of the rotary evaporation is 50-60°C.

[0032] Preferably, the grinding refers to: placing the material in a planetary ball mill and grinding for 10-20 minutes under the conditions of motor power 1.2-2.2kW, rotation speed 300-500r / min, and ball-to-material mass ratio 3-5:1.

[0033] Preferably, the method for preparing the premix includes the following steps: C1. Dissolve citric acid and ferric chloride hexahydrate in water, add sodium lignosulfonate, and stir until completely dissolved to obtain an activated solution; C2. After drying the dry distilled biochar and natural zeolite powder, put them into a mixer and mix them evenly to obtain a dry mixture; C3. Add the activating liquid to the dry mixture while stirring, continue stirring until uniform, transfer to an oven for heating, and obtain the premix.

[0034] By adopting the above technical solution, the amphiphilic characteristics of lignin are utilized to achieve high dispersion and immobilization of iron source on biochar surface while retaining the hydrophilic pores of the material. At the same time, by utilizing the electron transport capability of lignin, an electron transport channel is constructed between biochar and iron source, accelerating the electron flow of redox reaction and significantly improving the oxidative degradation activity of soil organic pollutants.

[0035] Preferably, in step C1, the mass ratio of sodium lignosulfonate, citric acid, ferric chloride hexahydrate, and water is 3-5:3-5:1.8-2.2:40-50.

[0036] Preferably, the stirring in step C1 refers to stirring for 30-40 minutes at 60-70℃ and a rotation speed of 300-500 r / min.

[0037] Preferably, in step C2, the mass ratio of dry distilled biochar to natural zeolite powder is 5-6:3-4.

[0038] Preferably, the drying in step C2 refers to drying in a vacuum drying oven at a temperature of 100-110℃ for 3-4 hours.

[0039] Preferably, the mixing in step C2 refers to mixing for 5-10 minutes at room temperature and a rotation speed of 800-1000 r / min.

[0040] Preferably, the mass ratio of dry mix to activation liquid in step C3 is 100:5-8.

[0041] Preferably, in step C3, the stirring speed is 200-300 r / min, and the stirring time is 10-15 min.

[0042] Preferably, the conditions for adding the activating solution in step C3 are as follows: the solution is added to the dry mixture through the mixing machine's inlet at a drip rate of 10-20 mL / min.

[0043] Preferably, the heating in step C3 refers to heating in an oven at a temperature of 100-110℃ for 1-2 hours.

[0044] Preferably, the compound microbial powder includes the following preparation steps: Under sterile conditions, Bacillus megaterium powder, Bacillus jellyoid powder, and Bacillus subtilis powder were placed in a V-type mixer and mixed evenly to obtain a compound bacterial powder.

[0045] Preferably, the mass ratio of Bacillus megaterium, Bacillus jellyoidus, and Bacillus subtilis is 3-5:2-4:2-4.

[0046] Preferably, the mixing refers to mixing at a rotation speed of 15-20 r / min for 10-15 min.

[0047] Preferably, the preparation method of the modified repair masterbatch includes the following steps: D1. Mix the composite powder and sodium alginate aqueous solution, add γ-glycidyl etheroxypropyltrimethoxysilane, stir evenly to obtain composite adhesive solution; D2. Place the premixed material in a rotary mixer, add the composite adhesive while stirring, continue stirring until uniform, add calcium chloride aqueous solution for curing, and dry to obtain the repair carrier; D3. Place the repair carrier in a mixer, add the compound bacterial powder, mix evenly, and obtain the modified repair master powder.

[0048] By adopting the above technical solution, the silane coupling agent is hydrolyzed in situ in the sodium alginate aqueous system to generate active silanol groups, which form chemical adsorption with the modified composite powder and carrier surface groups. After calcium chloride crosslinking and heat treatment, calcium alginate forms an ion-coordinated gel network, while the silanols undergo dehydration condensation to form Si-OC and Si-OM covalent bonds, thereby constructing an organic-inorganic double interpenetrating network structure with porous characteristics on the carrier surface, realizing the stable immobilization of photocatalytic materials. At the same time, the electrostatic attraction between the positive potential of the gel coating layer surface and the negative charge of the microbial cell wall is used to achieve the directional adsorption and loading of composite bacterial powder, and the steric hindrance effect of the gel layer reduces the direct impact of photogenerated carriers on microbial activity.

[0049] Preferably, in step D1, the mass ratio of the composite powder, sodium alginate aqueous solution, and γ-glycidoxypropyltrimethoxysilane is 10-15:100:0.1-0.2.

[0050] Preferably, the mass fraction of sodium alginate aqueous solution in step D1 is 1.5-2.0%.

[0051] Preferably, the term "stirring evenly" in step D1 refers to stirring for 20-30 minutes at room temperature and a rotation speed of 800-1200 r / min.

[0052] Preferably, in step D2, the mass ratio of the premix, the composite adhesive, and the calcium chloride aqueous solution is 100:15-20:5-8.

[0053] Preferably, the mass fraction of the calcium chloride aqueous solution in step D2 is 3-5%.

[0054] Preferably, in step D2, the stirring speed of the composite adhesive solution is 25-35 r / min, and the stirring time is 10-15 min.

[0055] Preferably, in step D2, drying refers to drying under hot air conditions at a temperature of 60-80℃ until the moisture content is less than 10%.

[0056] Preferably, the mass ratio of the repair carrier to the compound bacterial powder in step D3 is 100:3-5.

[0057] Preferably, the term "uniform mixing" in step D3 refers to mixing for 10-15 minutes at room temperature and a rotation speed of 15-20 r / min.

[0058] Secondly, the present invention provides a method for preparing a soil remediation and amendment agent for contaminated soil, employing the following technical solution: A method for preparing a soil remediation and amendment agent for contaminated soil includes the following preparation steps: S1. Mix potassium humate, polyaspartic acid and water, and stir until completely dissolved to obtain a mixed solution; S2. Place the modified repair masterbatch, hydroxyapatite and sodium bentonite in a high-speed mixer and mix them evenly to obtain a mixture. S3. Add the mixed solution to the mixture while stirring, control the feeding speed, and stir while pouring. After the feeding is completed, continue to stir evenly, transfer to a disc granulator to obtain wet granules with a particle size of 2-4mm, and then dry them in a low-temperature air dryer to obtain the repair and improvement agent.

[0059] Preferably, the stirring in step S1 refers to stirring for 20-30 minutes at a temperature of 40-50℃ and a rotation speed of 300-400 r / min.

[0060] Preferably, the mixing in step S2 refers to mixing for 10-15 minutes at room temperature and a rotation speed of 1000-1200 r / min.

[0061] Preferably, in step S3, the stirring speed is 300-400 r / min, the feeding rate is 5-10 L / min, and the stirring time is 15-20 min.

[0062] Preferably, in step S3, the disc tilt angle of the disc granulator is 45°-55°, and the disc rotation speed is 10-15 r / min.

[0063] Preferably, in step S3, drying refers to: inlet air temperature of 35-45℃ and drying time of 40-50min.

[0064] In summary, the present invention has the following beneficial effects: 1. This invention integrates physical adsorption, chemical degradation, and biological metabolism functions through modified remediation masterbatch. The carrier (biochar, zeolite) and additive (hydroxyapatite) first enrich and fix heavy metals (such as Cd, Pb) and organic pollutants in the soil. Subsequently, the loaded photocatalytic material generates oxidative active species under natural light, degrading organic pollutants into harmless small molecules. At the same time, the composite microorganisms further mineralize stubborn organic matter, effectively solving the problems of low efficiency and easy desorption of single remediation technologies, and realizing efficient remediation of soils contaminated with heavy metals and organic compounds.

[0065] 2. This invention utilizes an organic-inorganic dual gel network structure to effectively separate the internal microorganisms from the external photocatalyst in space. This structure not only avoids direct oxidative damage to the microbial cell walls caused by photogenerated holes, but also provides the microorganisms with a microenvironment that can retain moisture and nutrients, enabling them to maintain high-activity colonization even under harsh conditions such as soil drought or strong ultraviolet radiation, thereby extending the action period of the repair agent.

[0066] 3. The mineral-derived potassium humate and polyaspartic acid (PASP) introduced in the formulation of this invention are high-quality plant growth regulators and fertilizer synergists, which can stimulate crop root growth and improve the crop's absorption and utilization of nitrogen, phosphorus and potassium. At the same time, the compound use of sodium bentonite, dry distilled biochar and natural zeolite powder significantly improves the soil's aggregate structure and enhances the soil's water retention, fertilizer retention capacity and permeability.

[0067] 4. The main raw materials of this invention, such as biochar and sodium lignosulfonate, are derived from agricultural waste or papermaking by-products, realizing the resource utilization of waste. The modified lithium titanate and bismuth tungstate prepared are chemically stable, non-toxic and harmless environmentally friendly materials that will not cause secondary pollution to the soil during use, and have good economic and ecological benefits. Detailed Implementation

[0068] The present invention will be further described in detail below with reference to the embodiments.

[0069] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0070] The key raw materials used in this invention are sourced from the following sources: Titanium sulfate: CAS No.: 13693-11-3, provided by Shanghai Zhanyun Chemical Co., Ltd.; Lithium carbonate: CAS No.: 554-13-2, Model: JC-0035, provided by Zhengzhou Juepai Chemical Products Co., Ltd. Glucose: CAS No.: 50-99-7, provided by Suzhou Zhuowei Chemical Co., Ltd.; Ammonium dihydrogen phosphate: CAS No.: 7722-76-1, provided by Shanghai Aladdin Biochemical Technology Co., Ltd.; Lithium titanate: CAS No.: 12031-82-2, provided by Shanghai Maclean Biochemical Technology Co., Ltd. Bismuth tungstate: CAS No.: 13595-87-4, provided by Shanghai Maclean Biochemical Technology Co., Ltd. γ-glycidoxypropyltrimethoxysilane: CAS No.: 2530-83-8, provided by Shanghai Xinyu Biotechnology Co., Ltd.; Bismuth nitrate: CAS No.: 10361-44-1, provided by Shanghai Maclean Biochemical Technology Co., Ltd. Sodium tungstate: CAS No.: 13472-45-2, provided by Shanghai Maclean Biochemical Technology Co., Ltd. Sodium fluoride: CAS No.: 7681-49-4, provided by Shanghai Aladdin Biochemical Technology Co., Ltd. Sodium alginate: CAS No.: 9005-38-3, provided by Wuhan Jiyesheng Chemical Co., Ltd.; Sodium lignosulfonate: CAS No.: 8061-51-6, provided by Shanghai Maclean Biochemical Technology Co., Ltd. Citric acid: CAS No.: 77-92-9, provided by Shanghai Aladdin Biochemical Technology Co., Ltd. Ferric chloride hexahydrate: CAS No.: 10025-77-1, provided by Shanghai Aladdin Biochemical Technology Co., Ltd.; Dry distillation biochar: Brand: Zhongxin Lantian, Dry distillation temperature: 800℃, provided by Henan Zhongxin Lantian Environmental Protection Equipment Co., Ltd. Natural zeolite powder: Brand: Malin, Density: 1.9g / cm³, supplied by Lingshou County Malin Mineral Products Processing Plant; Bacillus megaterium: Brand: Haizhou, CAS No.: 1405-87-4, Colony Count: 20 billion / g, provided by Shandong Haizhou Bioengineering Co., Ltd. Bacillus gelatinosa: Brand: RUICHENBIO, Model: RCJZYB1000, Colony Count: 100 billion / g, provided by Weifang Ruichen Biotechnology Co., Ltd. Bacillus subtilis: Brand: RUICHENBIO, Model: RCKC1000, Colony Count: 100 billion / g, provided by Weifang Ruichen Biotechnology Co., Ltd. Hydroxyapatite: Brand: Huatai Biotechnology, CAS No.: 1306-06-5, provided by Xi'an Huatai Health Industry Co., Ltd. Sodium-based bentonite: Brand: Mingqi, CAS No.: 1302-78-9, provided by Jinan Mingqi Chemical Co., Ltd. Potassium humate from mineral sources: Brand: Jinyuecheng, provided by Shandong Jinyuecheng Chemical Co., Ltd.; Polyaspartic acid: CAS No.: 35608-40-6, provided by Henan Lanchao Chemical Products Co., Ltd.

[0071] Examples 1-3 provide a soil remediation agent for contaminated soil and its preparation method.

[0072] Example 1 The preparation method of modified lithium titanate includes the following steps: A1. Control the mass ratio of titanium sulfate, lithium carbonate, glucose, ammonium dihydrogen phosphate and water to 4:0.8:1:0.4:40. Dissolve titanium sulfate and ammonium dihydrogen phosphate in water, add lithium carbonate and glucose, and stir for 24 hours at 80℃ and 300r / min to obtain a sol. A2. The sol was dried in an 80°C oven to constant weight, and then calcined at 700°C for 4 hours at a heating rate of 3°C / min. After calcination, it was cooled to room temperature and then ball-milled for 60 minutes at 300 r / min using a planetary ball mill. The sol was then passed through a 200-mesh sieve to obtain modified lithium titanate. The preparation method of modified bismuth tungstate includes the following steps: B1. Control the mass ratio of bismuth nitrate, sodium tungstate, sodium fluoride and water to 2.8:0.9:0.1:60. Dissolve bismuth nitrate and sodium tungstate in water, add sodium fluoride, and stir for 50 min at room temperature and 300 r / min. Adjust the pH of the system to 3 using glacial acetic acid to obtain an acidic precursor solution. B2. The acidic precursor solution was placed in a reaction vessel and stirred for 24 hours at 160℃ and 50 r / min. After the reaction was completed, it was centrifuged for 15 minutes at 1.5 kW and 6000 r / min. The solid was washed twice with dilute sodium hydroxide solution and water, and then dried in a vacuum drying oven at 80℃ for 10 hours to obtain modified bismuth tungstate. The preparation method of composite powder includes the following steps: The mass ratio of modified lithium titanate, modified bismuth tungstate, and anhydrous ethanol was controlled at 1:1:10. The modified lithium titanate, modified bismuth tungstate, and anhydrous ethanol were mixed and ultrasonically dispersed for 45 min at 30℃, 300W, and 35KHz. The anhydrous ethanol was removed by rotary evaporation at 50℃. The mixture was then placed in a planetary ball mill and ball-milled for 20 min at 1.2kW motor, 300r / min rotation speed, and a ball-to-material mass ratio of 3:1 to obtain the composite powder. The preparation method of the premix includes the following steps: C1. Control the mass ratio of sodium lignosulfonate, citric acid, ferric chloride hexahydrate and water to 3:3:1.8:40. Dissolve citric acid and ferric chloride hexahydrate in water, add sodium lignosulfonate, and stir for 40 minutes at 60℃ and 300 r / min until completely dissolved to obtain an activated solution. C2. Control the mass ratio of dry distilled biochar and natural zeolite powder to 5:3. Dry the dry distilled biochar and natural zeolite powder in a vacuum drying oven at 100℃ for 4 hours, then put them into a mixer and mix for 10 minutes at room temperature and a speed of 800r / min to obtain a dry mixture. C3. Control the mass ratio of dry mixture and activation liquid to 100:5. Add the activation liquid to the dry mixture through the liquid inlet of the mixer at a drop rate of 10 mL / min at a speed of 200 r / min. Continue stirring for 15 min, transfer to an oven, and heat at 100℃ for 2 h to obtain the premix. The compound microbial powder includes the following preparation steps: The mass ratio of Bacillus megaterium, Bacillus colloidis, and Bacillus subtilis was controlled at 3:2:2. Under aseptic conditions, the powders of Bacillus megaterium, Bacillus colloidis, and Bacillus subtilis were placed in a V-type mixer and mixed for 15 minutes at a speed of 15 r / min to obtain a composite bacterial powder. The preparation method of modified repair masterbatch includes the following steps: D1. Control the mass ratio of composite powder, sodium alginate aqueous solution and γ-glycidoxypropyltrimethoxysilane to be 10:100:0.1. Mix the composite powder and sodium alginate aqueous solution with a mass fraction of 1.5%, add γ-glycidoxypropyltrimethoxysilane, and stir for 30 min at room temperature and 800 r / min to obtain composite adhesive solution. D2. Control the mass ratio of premix, composite adhesive and calcium chloride aqueous solution to 100:15:5. Place the premix in a rotary mixer, add the composite adhesive at room temperature and 25 r / min, continue stirring for 15 min, add 3% calcium chloride aqueous solution at a rate of 10 mL / min, and dry under hot air at 60℃ until the moisture content is less than 10% to obtain the repair carrier. D3. Control the mass ratio of the repair carrier and the compound microbial powder to 100:3. Place the repair carrier in a mixer, add the compound microbial powder, and mix for 15 minutes at room temperature and a rotation speed of 15 r / min to obtain the modified repair master powder. A soil remediation and amendment agent for contaminated soil comprises the following raw materials in parts by weight: 65 parts modified remediation masterbatch, 10 parts hydroxyapatite, 5 parts sodium bentonite, 8 parts mineral-derived potassium humate, and 0.5 parts polyaspartic acid. A method for preparing a soil remediation and amendment agent for contaminated soil includes the following preparation steps: S1. Mix potassium humate, polyaspartic acid and water (the amount of water is twice the total mass of potassium humate and polyaspartic acid), and stir for 30 minutes at 40℃ and 300r / min until completely dissolved to obtain a mixed solution. S2. The modified repair masterbatch, hydroxyapatite and sodium bentonite are placed in a high-speed mixer and mixed for 15 minutes at room temperature and a speed of 1000 r / min to obtain a mixture. S3. Add the mixed solution to the mixture at a speed of 300 r / min, control the feeding rate at 5 L / min, and stir while adding. After the feeding is completed, continue stirring for 20 min, then transfer to a disc granulator, set the disc tilt angle to 45° and the disc speed to 10 r / min to obtain wet granules with a particle size of 2 mm. Then dry them for 50 min at an air inlet temperature of 35°C in a low-temperature air dryer to obtain the repair and improvement agent.

[0073] Example 2 The preparation method of modified lithium titanate includes the following steps: A1. Control the mass ratio of titanium sulfate, lithium carbonate, glucose, ammonium dihydrogen phosphate and water to 5:1:1.5:0.5:45. Dissolve titanium sulfate and ammonium dihydrogen phosphate in water, add lithium carbonate and glucose, and stir for 21 hours at 85℃ and 400 r / min to obtain a sol. A2. The sol was dried in a 90℃ forced-air drying oven to constant weight, and then calcined at 750℃ for 3.5h at a heating rate of 4℃ / min. After calcination, it was cooled to room temperature and then ball-milled for 55min at 350r / min using a planetary ball mill and passed through a 250-mesh sieve to obtain modified lithium titanate. The preparation method of modified bismuth tungstate includes the following steps: B1. Control the mass ratio of bismuth nitrate, sodium tungstate, sodium fluoride and water to 3:1:0.15:65. Dissolve bismuth nitrate and sodium tungstate in water, add sodium fluoride, and stir for 45 min at room temperature and 400 r / min. Adjust the pH of the system to 3.5 with glacial acetic acid to obtain an acidic precursor solution. B2. The acidic precursor solution was placed in a reaction vessel and stirred for 22 hours at 170°C and 80 r / min. After the reaction was completed, it was centrifuged for 12.5 minutes at 2 kW and 6500 r / min. The solid was washed three times each with dilute sodium hydroxide solution and water and then dried in a vacuum drying oven at 85°C for 9 hours to obtain modified bismuth tungstate. The preparation method of composite powder includes the following steps: The mass ratio of modified lithium titanate, modified bismuth tungstate, and anhydrous ethanol was controlled at 1.5:1.5:12.5. The modified lithium titanate, modified bismuth tungstate, and anhydrous ethanol were mixed and ultrasonically dispersed for 40 min at 35℃, 400W, and 40KHz. The anhydrous ethanol was removed by rotary evaporation at 55℃. The mixture was then placed in a planetary ball mill and ball-milled for 15 min at 2kW motor, 400r / min rotation speed, and a ball-to-material mass ratio of 4:1 to obtain the composite powder. The preparation method of the premix includes the following steps: C1. Control the mass ratio of sodium lignosulfonate, citric acid, ferric chloride hexahydrate and water to 4:4:2:45. Dissolve citric acid and ferric chloride hexahydrate in water, add sodium lignosulfonate, and stir for 35 minutes at 65℃ and 400 r / min until completely dissolved to obtain an activated solution. C2. Control the mass ratio of dry distilled biochar to natural zeolite powder to be 5.5:3.5. Dry the dry distilled biochar and natural zeolite powder in a vacuum drying oven at 105℃ for 3.5h, then put them into a mixer and mix for 8min at room temperature and 900r / min to obtain a dry mixture. C3. Control the mass ratio of dry mixture to activation liquid to be 100:6.5. Add the activation liquid to the dry mixture through the liquid inlet of the mixer at a drop rate of 15 mL / min at a speed of 250 r / min. Continue stirring for 12.5 min, transfer to an oven, and heat at 105℃ for 1.5 h to obtain the premix. The compound microbial powder includes the following preparation steps: The mass ratio of Bacillus megaterium, Bacillus colloidis, and Bacillus subtilis was controlled at 4:3:3. Under aseptic conditions, the powders of Bacillus megaterium, Bacillus colloidis, and Bacillus subtilis were placed in a V-type mixer and mixed for 12.5 min at a speed of 18 r / min to obtain the composite bacterial powder. The preparation method of modified repair masterbatch includes the following steps: D1. Control the mass ratio of composite powder, sodium alginate aqueous solution and γ-glycidoxypropyltrimethoxysilane to be 12.5:100:0.15. Mix the composite powder and sodium alginate aqueous solution with a mass fraction of 1.7%, add γ-glycidoxypropyltrimethoxysilane, and stir for 25 min at room temperature and 1000 r / min to obtain composite adhesive solution. D2. Control the mass ratio of premix, composite adhesive and calcium chloride aqueous solution to 100:17.5:6.5. Place the premix in a rotary mixer, add the composite adhesive at room temperature and 30 r / min, continue stirring for 12.5 min, add 4% calcium chloride aqueous solution at a rate of 15 mL / min, and dry under hot air at 70℃ until the moisture content is less than 10% to obtain the repair carrier. D3. Control the mass ratio of the remediation carrier and the compound microbial powder to 100:4. Place the remediation carrier in a mixer, add the compound microbial powder, and mix for 12.5 min at room temperature and a rotation speed of 18 r / min to obtain the modified remediation master powder. A soil remediation and amendment agent for contaminated soil comprises the following raw materials in parts by weight: 72 parts modified remediation masterbatch, 12.5 parts hydroxyapatite, 7.5 parts sodium bentonite, 6.5 parts mineral-derived potassium humate, and 0.75 parts polyaspartic acid. A method for preparing a soil remediation and amendment agent for contaminated soil includes the following preparation steps: S1. Mix potassium humate, polyaspartic acid and water (the amount of water is twice the total mass of potassium humate and polyaspartic acid), and stir for 25 minutes at 45℃ and 350 r / min until completely dissolved to obtain a mixed solution. S2. The modified repair masterbatch, hydroxyapatite and sodium bentonite are placed in a high-speed mixer and mixed for 12.5 min at room temperature and a speed of 1100 r / min to obtain a mixture. S3. Add the mixed solution to the mixture at a speed of 350 r / min, control the feeding rate at 8 L / min, and stir while adding. After the feeding is completed, continue stirring for 7.5 min, transfer to a disc granulator, set the disc tilt angle to 50° and the disc speed to 13 r / min to obtain wet granules with a particle size of 3 mm, and then dry them for 45 min at an inlet air temperature of 40°C in a low-temperature air dryer to obtain the repair and improvement agent.

[0074] Example 3 The preparation method of modified lithium titanate includes the following steps: A1. Control the mass ratio of titanium sulfate, lithium carbonate, glucose, ammonium dihydrogen phosphate and water to 6:1.2:2:0.6:50. Dissolve titanium sulfate and ammonium dihydrogen phosphate in water, add lithium carbonate and glucose, and stir for 18 hours at 90℃ and 500 r / min to obtain a sol. A2. The sol was dried in a 100℃ forced-air drying oven to constant weight, and then calcined at 800℃ for 3 hours at a heating rate of 5℃ / min. After calcination, it was cooled to room temperature and then ball-milled for 50 minutes at 400 r / min using a planetary ball mill. The sol was then passed through a 300-mesh sieve to obtain modified lithium titanate. The preparation method of modified bismuth tungstate includes the following steps: B1. Control the mass ratio of bismuth nitrate, sodium tungstate, sodium fluoride and water to 3.2:1.1:0.2:70. Dissolve bismuth nitrate and sodium tungstate in water, add sodium fluoride, and stir for 40 min at room temperature and 500 r / min. Adjust the pH of the system to 4 with glacial acetic acid to obtain an acidic precursor solution. B2. The acidic precursor solution was placed in a reaction vessel and stirred for 20 hours at 180°C and 100 r / min. After the reaction was completed, the mixture was centrifuged for 10 minutes at 2.5 kW and 7000 r / min. The solid was washed three times each with dilute sodium hydroxide solution and water and then dried in a vacuum drying oven at 90°C for 8 hours to obtain modified bismuth tungstate. The preparation method of composite powder includes the following steps: The mass ratio of modified lithium titanate, modified bismuth tungstate, and anhydrous ethanol was controlled at 2:2:15. The modified lithium titanate, modified bismuth tungstate, and anhydrous ethanol were mixed and ultrasonically dispersed for 30 min at 40℃, 500W, and 45KHz. The anhydrous ethanol was removed by rotary evaporation at 60℃. The mixture was then placed in a planetary ball mill and ball-milled for 10 min at 2.2kW, 500r / min, and a ball-to-material mass ratio of 5:1 to obtain the composite powder. The preparation method of the premix includes the following steps: C1. Control the mass ratio of sodium lignosulfonate, citric acid, ferric chloride hexahydrate and water to 5:5:2.2:50. Dissolve citric acid and ferric chloride hexahydrate in water, add sodium lignosulfonate, and stir for 30 minutes at 70℃ and 500 r / min until completely dissolved to obtain an activated solution. C2. Control the mass ratio of dry distilled biochar and natural zeolite powder to 6:4. Dry the dry distilled biochar and natural zeolite powder in a vacuum drying oven at 110℃ for 3 hours, then put them into a mixer and mix for 5 minutes at room temperature and a speed of 1000r / min to obtain a dry mixture. C3. Control the mass ratio of dry mixture and activation liquid to 100:8. Add the activation liquid to the dry mixture through the liquid inlet of the mixer at a drop rate of 20 mL / min at a speed of 300 r / min. Continue stirring for 10 min, transfer to an oven, and heat at 110℃ for 1 h to obtain the premix. The compound microbial powder includes the following preparation steps: The mass ratio of Bacillus megaterium, Bacillus colloidis, and Bacillus subtilis was controlled at 5:4:4. Under aseptic conditions, the powders of Bacillus megaterium, Bacillus colloidis, and Bacillus subtilis were placed in a V-type mixer and mixed for 10 minutes at a speed of 20 r / min to obtain a composite bacterial powder. The preparation method of modified repair masterbatch includes the following steps: D1. Control the mass ratio of composite powder, sodium alginate aqueous solution and γ-glycidoxypropyltrimethoxysilane to be 15:100:0.2. Mix the composite powder and sodium alginate aqueous solution with a mass fraction of 2.0%, add γ-glycidoxypropyltrimethoxysilane, and stir for 20 min at room temperature and a speed of 1200 r / min to obtain composite adhesive solution. D2. Control the mass ratio of premix, composite adhesive and calcium chloride aqueous solution to 100:20:8. Place the premix in a rotary mixer, add the composite adhesive at room temperature and 35 r / min, continue stirring for 10 min, add 5% calcium chloride aqueous solution at a rate of 20 mL / min, and dry under hot air at 80℃ until the moisture content is less than 10% to obtain the repair carrier. D3. Control the mass ratio of the repair carrier and the compound microbial powder to 100:5. Place the repair carrier in a mixer, add the compound microbial powder, and mix for 10 minutes at room temperature and a rotation speed of 20 r / min to obtain the modified repair master powder. A soil remediation and amendment agent for contaminated soil comprises the following raw materials in parts by weight: 85 parts modified remediation masterbatch, 15 parts hydroxyapatite, 10 parts sodium bentonite, 5 parts mineral-derived potassium humate, and 1 part polyaspartic acid. A method for preparing a soil remediation and amendment agent for contaminated soil includes the following preparation steps: S1. Mix potassium humate, polyaspartic acid and water (the amount of water is twice the total mass of potassium humate and polyaspartic acid), and stir for 20 minutes at 50℃ and 400r / min until completely dissolved to obtain a mixed solution. S2. The modified repair masterbatch, hydroxyapatite and sodium bentonite are placed in a high-speed mixer and mixed for 10 minutes at room temperature and a speed of 1200 r / min to obtain a mixture. S3. Add the mixed solution to the mixture at a speed of 400 r / min, control the feeding rate at 10 L / min, and stir while adding. After the feeding is completed, continue stirring for 15 min, transfer to a disc granulator, set the disc tilt angle to 55° and the disc speed to 15 r / min to obtain wet granules with a particle size of 4 mm, and then dry them for 40 min at an air inlet temperature of 45°C in a low-temperature air dryer to obtain the repair and improvement agent.

[0075] To verify the overall performance of the repair and improvement agents in Examples 1-3 of this invention, the inventors set up Comparative Examples 1-6, as follows: Comparative Example 1 The difference between this comparative example and Example 1 is that, in the preparation of the composite powder, the modified lithium titanate was replaced by commercially available lithium titanate in equal mass, while the remaining steps and raw materials were the same as in Example 1. The preparation method of composite powder includes the following steps: The mass ratio of lithium titanate, modified bismuth tungstate, and anhydrous ethanol was controlled at 1:1:10. The lithium titanate, modified bismuth tungstate, and anhydrous ethanol were mixed and ultrasonically dispersed for 45 min at 30℃, 300W, and 35KHz. The anhydrous ethanol was removed by rotary evaporation at 50℃. The mixture was then placed in a planetary ball mill and ball-milled for 20 min at 1.2kW motor, 300r / min rotation speed, and a ball-to-material mass ratio of 3:1 to obtain the composite powder.

[0076] Comparative Example 2 The difference between this comparative example and Example 1 is that, in the preparation of the composite powder, the modified bismuth tungstate is replaced by commercially available bismuth tungstate, while the remaining steps and raw materials are the same as in Example 1. The preparation method of composite powder includes the following steps: The mass ratio of modified lithium titanate, bismuth tungstate, and anhydrous ethanol was controlled at 1:1:10. The modified lithium titanate, bismuth tungstate, and anhydrous ethanol were mixed and ultrasonically dispersed for 45 min at 30℃, 300W, and 35KHz. The anhydrous ethanol was removed by rotary evaporation at 50℃. The mixture was then placed in a planetary ball mill and ball-milled for 20 min at 1.2kW motor, 300r / min rotation speed, and a ball-to-material mass ratio of 3:1 to obtain the composite powder.

[0077] Comparative Example 3 The difference between this comparative example and Example 1 is that no composite powder is prepared. In step D1, the modified lithium titanate, modified bismuth tungstate and sodium alginate aqueous solution are directly mixed. The remaining steps and raw materials are the same as in Example 1. D1. The mass ratio of modified lithium titanate, modified bismuth tungstate, sodium alginate aqueous solution and γ-glycidoxypropyltrimethoxysilane was controlled at 5:5:100:0.1. Modified lithium titanate, modified bismuth tungstate and sodium alginate aqueous solution with a mass fraction of 1.5% were mixed, and γ-glycidoxypropyltrimethoxysilane was added. The mixture was stirred for 30 min at room temperature and 800 r / min to obtain the composite adhesive.

[0078] Comparative Example 4 The difference between this comparative example and Example 1 is that γ-glycidoxypropyltrimethoxysilane was not added in step D1, while the remaining steps and raw materials were the same as in Example 1. D1. Control the mass ratio of composite powder to sodium alginate aqueous solution to 10:100. Mix the composite powder and sodium alginate aqueous solution with a mass fraction of 1.5% and stir for 30 minutes at room temperature and a speed of 800 r / min to obtain composite adhesive solution.

[0079] Comparative Example 5 The difference between this comparative example and Example 1 is that, in preparing the modified repair masterbatch, the composite bacterial powder is mixed with the composite powder and premix first, while the remaining steps and raw materials are the same as in Example 1. The preparation method of modified repair masterbatch includes the following steps: D1. Control the mass ratio of premix, compound powder and compound microbial powder to 100:1.5:3. Put the premix, compound powder and compound microbial powder into the mixer and mix for 15 minutes at room temperature and a speed of 15 r / min to obtain the mixed dry material. D2. Control the mass ratio of sodium alginate aqueous solution and γ-glycidoxypropyltrimethoxysilane to be 100:0.1. Add γ-glycidoxypropyltrimethoxysilane to sodium alginate aqueous solution with a mass fraction of 1.5% and stir for 30 min at room temperature and a speed of 800 r / min to obtain pure gel solution. D3. Control the mass ratio of the mixed dry material, pure adhesive solution, and calcium chloride aqueous solution to 100:15:5. The mixed dry materials were placed in a rotary mixer, and pure adhesive liquid was added at room temperature and a speed of 25 r / min. The mixture was stirred for 15 min, and a 3% calcium chloride aqueous solution was added at a rate of 10 mL / min. Finally, the mixture was dried at 60℃ until the moisture content was less than 10% to obtain the modified repair master powder.

[0080] Comparative Example 6 The difference between this comparative example and Example 1 is that sodium lignosulfonate and citric acid are not used when preparing the premix. Ferric chloride hexahydrate is dissolved in 0.1 mol / L dilute hydrochloric acid to prepare ferric chloride impregnation solution. The remaining steps and raw materials are the same as in Example 1. The preparation method of the premix includes the following steps: C1. Control the mass ratio of ferric chloride hexahydrate and dilute hydrochloric acid to 1.8:40, dissolve ferric chloride hexahydrate in 0.1 mol / L dilute hydrochloric acid to obtain ferric chloride impregnation solution; C2. Control the mass ratio of dry distilled biochar and natural zeolite powder to 5:3. Dry the dry distilled biochar and natural zeolite powder in a vacuum drying oven at 100℃ for 4 hours, then put them into a mixer and mix for 10 minutes at room temperature and a speed of 800r / min to obtain a dry mixture. C3. Control the mass ratio of dry mixture and ferric chloride impregnation solution to 100:5. Add ferric chloride impregnation solution to dry mixture through the liquid inlet of the mixer at a drop rate of 10 mL / min at a speed of 200 r / min. Continue stirring for 15 min, transfer to an oven, and heat at 100℃ for 2 h to obtain premix.

[0081] Performance testing 1. Preparation of test soil Topsoil from a contaminated farmland was collected, air-dried, and sieved. A solution of cadmium (Cd) and chlorpyrifos pesticide were added to the soil. The total cadmium content of the contaminated soil was 2.5 mg / kg, the chlorpyrifos content was 10.0 mg / kg, the pH value was 6.2, and the organic matter content was 15.5 g / kg.

[0082] 2. Experimental grouping and treatment Take the above-mentioned contaminated soil and place it into plastic basins, with each basin containing 2.0 kg of soil. Add the remediation and amendment prepared in Examples 1-3 and Comparative Examples 1-6 at 2% of the soil mass, mix well, and set up a blank control group (CK, without any amendment added). Maintain the soil moisture content at 60% of field capacity and incubate for 45 days under simulated natural light conditions (12h light / 12h darkness, light intensity about 100mW / cm²) at room temperature (25±2℃).

[0083] 3. Detection indicators and methods (1) Soil available cadmium (DTPA-Cd) removal rate Available cadmium in the soil was extracted using the DTPA extraction method, and the content was determined using a graphite furnace atomic absorption spectrophotometer (AAS). The calculation formula was: Removal rate = (Content in CK group - Content in treatment group) / Content in CK group × 100%.

[0084] (2) Degradation rate of chlorpyrifos The residual chlorpyrifos in the soil was extracted by ultrasonic extraction and determined by gas chromatography (GC). The degradation rate was calculated as follows: Degradation rate = (initial content - content after 45 days) / initial content × 100%.

[0085] (3) Soil dehydrogenase activity (DHA) The TTC (triphenyltetrazolium chloride) colorimetric method was used for determination, and the unit is μgTPF / g·h.

[0086] (4) TCLP leaching concentration (heavy metal stability) The long-term safety of the reaction remediation was tested in accordance with the standard HJ / T300-2007 "Leaching Toxicity of Solid Waste - Acetic Acid Buffer Solution Method".

[0087] The performance test results and experimental results are shown in Table 1 below.

[0088] Table 1: Performance Test Results As shown in Table 1 above, the remediation and amendment agents prepared in Examples 1-3 of this invention exhibit excellent comprehensive performance in terms of soil heavy metal passivation rate, organic pesticide degradation rate, soil microecological activity, and long-term stability, which are significantly better than those in Comparative Examples 1-6.

[0089] As can be seen from the data shown in Example 1 and Comparative Example 1, Comparative Example 1 uses commercially available ordinary lithium titanate, which has not undergone mechanical and chemical activation and in-situ reduction by biomass carbon source. The crystal lattice lacks sufficient Ti³⁺ defects and oxygen vacancies, resulting in weak visible light response and poor electron capture ability. The heavy metal removal rate and pesticide degradation rate are both lower than those in Example 1.

[0090] As can be seen from the data shown in Example 1 and Comparative Example 2: Comparative Example 2 uses commercially available ordinary bismuth tungstate, which has not been doped with fluorine ions or microstructure controlled. The crystal lattice lacks oxygen vacancy defects and abundant mesoporous structures, resulting in low photogenerated carrier separation efficiency and insufficient reactive sites, thus reducing the degradation efficiency of organic pollutants.

[0091] As shown by the data from Example 1 and Comparative Example 3, the modified lithium titanate and bismuth tungstate in Comparative Example 3 only physically stacked together and failed to build a tight Z-shaped heterojunction interface electric field, which led to rapid in-situ recombination of photogenerated electron-hole pairs and a significant reduction in the mineralization efficiency of organic pesticides.

[0092] Data from Example 1 and Comparative Example 4 show that Comparative Example 4 lacks the chemical bond of γ-glycidoxypropyltrimethoxysilane, and the gel film and composite powder are only connected by physical adsorption. Under the soil leaching environment, the active components are easily detached and lost, resulting in an increase in TCLP leaching concentration and a deterioration in long-term remediation performance.

[0093] Data from Example 1 and Comparative Example 5 show that in Comparative Example 5, the composite bacterial powder was mixed with the composite powder and premix, and the active free radicals generated by the photocatalytic material directly contacted the functional microorganisms, resulting in a decrease in soil dehydrogenase activity.

[0094] Data from Example 1 and Comparative Example 6 show that Comparative Example 6 lacks the complexing and dispersing effect of sodium lignosulfonate and citric acid. During the drying process, iron ions are prone to agglomerate to form large oxide particles and block the pores of biochar, resulting in a decrease in specific surface area and a decline in the physical adsorption and chemical complexation ability for the heavy metal cadmium.

[0095] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A soil remediation and amendment agent for contaminated soil, characterized in that, The raw materials include the following parts by weight: 65-85 parts modified repair masterbatch, 10-15 parts hydroxyapatite, 5-10 parts sodium bentonite, 5-8 parts mineral-derived potassium humate, and 0.5-1 parts polyaspartic acid. The modified repair masterbatch is made by mixing composite powder, premix, and composite bacterial powder; the composite powder is made by mixing modified lithium titanate and modified bismuth tungstate.

2. The soil remediation and amendment agent according to claim 1, characterized in that, The preparation method of the modified lithium titanate includes the following steps: A1. Dissolve titanium sulfate and ammonium dihydrogen phosphate in water, add lithium carbonate and glucose, stir well to obtain a sol; A2. After drying the sol, calcination is carried out. After calcination, the sol is cooled to room temperature and ground to obtain modified lithium titanate.

3. The soil remediation and amendment agent according to claim 1, characterized in that, The preparation method of the modified bismuth tungstate includes the following steps: B1. Dissolve bismuth nitrate and sodium tungstate in water, add sodium fluoride, stir well, and adjust the pH of the system to 3-4 using glacial acetic acid to obtain an acidic precursor solution. B2. Place the acidic precursor solution in a reaction vessel, stir and react. After the reaction is complete, centrifuge, wash and dry to obtain modified bismuth tungstate.

4. The soil remediation and amendment agent according to claim 1, characterized in that, The method for preparing the composite powder includes the following steps: Modified lithium titanate, modified bismuth tungstate, and anhydrous ethanol were mixed, ultrasonically dispersed, and then the ethanol was removed by rotary evaporation. The mixture was then ground to obtain a composite powder.

5. The soil remediation and amendment agent according to claim 4, characterized in that, The mass ratio of the modified lithium titanate, modified bismuth tungstate, and anhydrous ethanol is 1-2:1-2:10-15.

6. The soil remediation and amendment agent according to claim 1, characterized in that, The preparation method of the premix includes the following steps: C1. Dissolve citric acid and ferric chloride hexahydrate in water, add sodium lignosulfonate, and stir until completely dissolved to obtain an activated solution; C2. After drying the dry distilled biochar and natural zeolite powder, put them into a mixer and mix them evenly to obtain a dry mixture; C3. Add the activating liquid to the dry mixture while stirring, continue stirring until uniform, transfer to an oven for heating, and obtain the premix.

7. The soil remediation and amendment agent according to claim 1, characterized in that, The compound microbial powder includes the following preparation steps: Under sterile conditions, Bacillus megaterium powder, Bacillus jellyoid powder, and Bacillus subtilis powder were placed in a V-type mixer and mixed evenly to obtain a compound bacterial powder.

8. The soil remediation and amendment agent according to claim 7, characterized in that, The mass ratio of Bacillus megaterium, Bacillus jellyoidus, and Bacillus subtilis is 3-5:2-4:2-4.

9. The soil remediation and amendment agent according to claim 1, characterized in that, The preparation method of the modified repair masterbatch includes the following steps: D1. Mix the composite powder and sodium alginate aqueous solution, add γ-glycidyl etheroxypropyltrimethoxysilane, stir evenly to obtain composite adhesive solution; D2. Place the premixed material in a rotary mixer, add the composite adhesive while stirring, continue stirring until uniform, add calcium chloride aqueous solution for curing, and dry to obtain the repair carrier; D3. Place the repair carrier in a mixer, add the compound bacterial powder, mix evenly, and obtain the modified repair master powder.

10. A method for preparing a soil remediation and amendment agent according to any one of claims 1-9, characterized in that, The preparation steps include the following: S1. Mix potassium humate, polyaspartic acid and water, and stir until completely dissolved to obtain a mixed solution; S2. Place the modified repair masterbatch, hydroxyapatite and sodium bentonite in a high-speed mixer and mix them evenly to obtain a mixture. S3. Add the mixed solution to the mixture while stirring, control the feeding speed, and stir while pouring. After the feeding is completed, continue to stir evenly, transfer to a disc granulator to obtain wet granules with a particle size of 2-4mm, and then dry them in a low-temperature air dryer to obtain the repair and improvement agent.

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