An improved agent for treating cadmium contaminated soil and a preparation method thereof

Abstract

The application discloses an improver for treating cadmium contaminated soil and a preparation method thereof, and belongs to the technical field of heavy metal contaminated soil treatment. The improver comprises the following raw materials: iron oxide, tri-potassium phosphate, biochar, corn sugar residue, xanthan gum, sodium citrate, vitamin E, arbutin, bilirubin and sodium bicarbonate. The improver is applied to cadmium contaminated soil, cadmium ions in the soil can be adsorbed and precipitated to form cadmium precipitates, the toxicity of the cadmium ions is reduced, earthworms ingest the cadmium precipitates into the body and fix them, so that the cadmium content in the soil is reduced. The improver can also promote the absorption, ingestion and digestion of cadmium ions by earthworms, maintain the normal physiological activities of the earthworms, reduce the toxic effect of cadmium on the earthworms, and make the earthworms better treat cadmium contaminated soil. The preparation method of the improver is simple, good in effect and friendly to the environment.

Description

Technical Field

[0001] This invention relates to the field of heavy metal contaminated soil remediation technology, and in particular to a soil conditioner for remediating cadmium contaminated soil and its preparation method. Background Technology

[0002] Cadmium is a soft, silvery-white rare metal and a dangerous environmental pollutant. It not only leads to reduced crop yields and quality, but also has a strong toxic effect on animals and humans. When the environment is contaminated with cadmium, it can accumulate in organisms and enter the human body through the food chain, causing chronic poisoning. The Minamata disease and Itai-itai disease incidents in Japan were caused by consumers consuming foods contaminated with mercury and cadmium for a long time.

[0003] Currently, the main methods for remediating cadmium-contaminated soil are physical, chemical, and biological remediation. Physical remediation, the traditional approach, includes methods such as soil replacement, electrochemical methods, leaching, and thermal treatment. While highly efficient and thorough, physical remediation is complex, costly, and can easily lead to a decline in soil fertility. Chemical remediation involves introducing soil conditioners and inhibitors into the contaminated soil to increase soil organic matter, cation exchange capacity, and clay content, altering the soil's physicochemical properties. This causes cadmium to undergo oxidation, reduction, precipitation, adsorption, inhibition, and antagonism, reducing its bioavailability. Chemical remediation offers moderate effectiveness and cost and is simple to operate; however, inappropriate raw material selection can easily cause secondary pollution. Bioremediation is a new method that uses biotechnology to remediate contaminated soil, utilizing biological agents to reduce and purify cadmium in the soil or decrease its toxicity. Earthworms, as typical large soil animals, maintain soil ecological stability by altering the bacterial and fungal communities in the soil, improving soil organic matter composition and nutrient cycling. Earthworms are most prone to accumulating cadmium and arsenic in the soil, making them important in the remediation of cadmium-contaminated soil. They generally absorb cadmium through two pathways: one is through skin absorption of available cadmium from the soil, and the other is through a series of physiological activities such as feeding and digestion. However, earthworms have a certain tolerance and accumulation capacity for the heavy metal cadmium during cadmium pollution remediation. When earthworms absorb and accumulate too much cadmium, they will suffer from cadmium toxicity, causing cell membrane damage, affecting their normal physiological activities, and resulting in low remediation efficiency. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a soil conditioner for treating cadmium-contaminated soil and its preparation method. The conditioner reduces the toxicity of cadmium ions in the soil, thereby reducing the toxicity of cadmium to earthworms and enhancing the earthworms' ability to absorb and accumulate cadmium, thus solving the problem of low treatment efficiency.

[0005] The present invention solves the above-mentioned technical problems through the following technical means:

[0006] An amendment for remediating cadmium-contaminated soil, the amendment comprising the following raw materials in parts by weight:

[0007] 2-3 parts iron oxide, 2-3 parts tripotassium phosphate, 20-30 parts biochar, 10-15 parts corn sugar residue, 15-20 parts xanthan gum, 15-20 parts sodium citrate, 15-20 parts vitamin E, 10-15 parts arbutin, 5-10 parts bilirubin, 0.5-1 part sodium bicarbonate.

[0008] This invention also discloses a method for preparing a soil conditioner for remediating cadmium-contaminated soil, the method of which is as follows:

[0009] (1) Vitamin E was added to ethanol and stirred to dissolve, resulting in mixture A;

[0010] (2) Add sodium bicarbonate to water and mix, then heat in a water bath. After cooling to room temperature, add bilirubin and mix evenly. Then add arbutin and sodium citrate and put into a mixer and stir evenly to obtain mixture B.

[0011] (3) Add water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and put them into a homogenizer for homogenization. After homogenization, add corn sugar residue, iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the improver.

[0012] Furthermore, in step (1), the mass ratio of vitamin E to ethanol is 1:2.

[0013] Furthermore, the conditions for water bath heating in step (2) are: temperature 40-60℃, time 10-15min.

[0014] Furthermore, in step (2), the stirring speed is 600-800 r / min and the stirring time is 5-10 min.

[0015] Furthermore, the homogenization conditions in step (3) are: homogenization pressure 15-20 MPa, homogenization time 10-15 min.

[0016] Furthermore, the application rate of the modifier is 0.3-1.5 kg / m³. 2 .

[0017] Furthermore, the soil needs to be tilled before applying the soil amendment, as detailed below:

[0018] Till the soil to a depth of 30-50cm, then spray water onto the tilled soil to fully wet the surface. Apply a soil conditioner, and then till the soil a second time to allow the conditioner to be incorporated into the soil.

[0019] Earthworms are the most common omnivorous terrestrial annelids in soil. They can absorb cadmium ions from the soil through their skin and can also reduce the cadmium ion content in the soil through physiological activities such as feeding and digestion, thus remediating cadmium-contaminated soil. The soil conditioner prepared in this invention is applied to cadmium-contaminated soil after tilling, and then tilled again to allow the conditioner to penetrate the soil. The iron oxide in the conditioner can adsorb and precipitate cadmium ions in the soil, reducing cadmium ion toxicity. Tripotassium phosphate can combine with cadmium ions to form stable precipitates, fixing them and reducing cadmium ion toxicity. Earthworms ingest these fixed cadmium precipitates during feeding, thus fixing the cadmium ions in their bodies and reducing the cadmium ion content in the soil. However, iron oxide and tripotassium phosphate are easily lost after being applied to the soil, reducing the amount of cadmium ions fixed. Therefore, biochar and xanthan gum are added to increase the soil's adsorption capacity, thereby increasing the soil's adsorption capacity for iron oxide and tripotassium phosphate, inhibiting their loss, and increasing the amount of cadmium ions fixed by iron oxide and tripotassium phosphate. This increases the amount of cadmium precipitates in earthworms, thus better reducing the cadmium ion content in the soil. However, excessive cadmium intake by earthworms can still cause cadmium poisoning, leading to the production of large amounts of reactive oxygen species (ROS) in their bodies. This ROS can exceed safe levels, triggering lipid peroxidation, damaging earthworm cell membranes, affecting normal physiological activities, and even causing earthworm death, thus reducing remediation efficiency. Therefore, arbutin, bilirubin, corn residue, sodium citrate, and vitamin E are added to the soil conditioner. Arbutin can increase the activity of superoxide dismutase in earthworms, clearing excess ROS and reducing the degree of damage to earthworm cell membranes. Bilirubin can further clear ROS produced in earthworms, maintaining normal physiological activities. Corn residue, sodium citrate, and vitamin E can promote earthworm growth, reproduction, and life activities, thereby improving soil remediation effectiveness and solving the problem of earthworm poisoning, cell membrane damage, and death caused by excessive cadmium intake. As long as earthworms are carrying out their life activities, they can continuously remediate cadmium-contaminated soil, improving remediation efficiency.

[0020] Beneficial effects:

[0021] 1. This invention discloses a soil conditioner for treating cadmium-contaminated soil and its preparation method. The conditioner can adsorb and fix cadmium ions in cadmium-contaminated soil into cadmium precipitates, thereby reducing their toxicity. Earthworms ingest these cadmium precipitates during feeding and fix them in their bodies, thereby reducing the cadmium ion content in the soil and effectively treating cadmium-contaminated soil.

[0022] 2. This invention discloses a soil conditioner for cadmium-contaminated soil and its preparation method. The biochar and xanthan gum added to the conditioner can increase the soil's adsorption capacity for iron oxide and tripotassium phosphate, inhibit their loss, thereby increasing the amount of cadmium fixed by iron oxide and tripotassium phosphate and improving the treatment efficiency.

[0023] 3. This invention discloses a soil conditioner for treating cadmium-contaminated soil and its preparation method. The prepared conditioner can help earthworms remove excess reactive oxygen species produced in their bodies, maintain the normal life activities of earthworms, reduce the toxic effects of cadmium ions on earthworms, and improve the soil treatment effect of earthworms.

[0024] 4. This invention discloses a soil conditioner for treating cadmium-contaminated soil and its preparation method. The conditioner can promote the growth, reproduction, and life activities of earthworms, thereby promoting the treatment of cadmium-contaminated soil by earthworms.

[0025] 5. This invention discloses a soil conditioner for treating cadmium-contaminated soil and its preparation method. The preparation method of the conditioner is simple, environmentally friendly, and effective, and can effectively treat cadmium-contaminated soil. Detailed Implementation

[0026] The present invention will be described in detail below with reference to specific embodiments:

[0027] Example 1: Preparation of Modifier

[0028] Weigh out 25g iron oxide, 25g tripotassium phosphate, 250g biochar, 120g corn residue, 170g xanthan gum, 170g sodium citrate, 170g vitamin E, 120g arbutin, 70g bilirubin, and 7g sodium bicarbonate.

[0029] Preparation method:

[0030] (1) Add vitamin E to 850g of ethanol and stir to dissolve to obtain mixture A;

[0031] (2) Add sodium bicarbonate to 3.5 kg of water and mix. Heat in a water bath at 50°C for 12 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then add arbutin and sodium citrate and put into a mixer and stir at 700 r / min for 7 min to obtain mixture B.

[0032] (3) Add 1.7 kg of water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and place in a homogenizer to homogenize at 17 MPa pressure for 12 min. After homogenization, add corn sugar residue, iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the modifier.

[0033] Example 2: Preparation of Modifier II

[0034] Weigh out 20g iron oxide, 20g tripotassium phosphate, 200g biochar, 100g corn residue, 150g xanthan gum, 150g sodium citrate, 150g vitamin E, 100g arbutin, 50g bilirubin, and 5g sodium bicarbonate.

[0035] Preparation method:

[0036] (1) Add vitamin E to 750g of ethanol and stir to dissolve to obtain mixture A;

[0037] (2) Add sodium bicarbonate to 2.5 kg of water and mix. Heat in a water bath at 40°C for 10 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then add arbutin and sodium citrate and put into a mixer and stir at 600 r / min for 5 min to obtain mixture B.

[0038] (3) Add 1.5 kg of water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and place in a homogenizer to homogenize at 15 MPa pressure for 10 min. After homogenization, add corn sugar residue, iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the modifier.

[0039] Example 3: Preparation of Modifier

[0040] Weigh out 30g iron oxide, 30g tripotassium phosphate, 300g biochar, 150g corn residue, 200g xanthan gum, 200g sodium citrate, 200g vitamin E, 150g arbutin, 100g bilirubin, and 10g sodium bicarbonate.

[0041] Preparation method:

[0042] (1) Vitamin E was added to 1 kg of ethanol and stirred to dissolve, resulting in mixture A;

[0043] (2) Add sodium bicarbonate to 5 kg of water and mix. Heat in a water bath at 60°C for 15 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then add arbutin and sodium citrate and put into a mixer and stir at 800 r / min for 10 min to obtain mixture B.

[0044] (3) Add 2kg of water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and place in a homogenizer to homogenize at 20MPa pressure for 15min. After homogenization, add corn sugar residue, iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the modifier.

[0045] Comparative Example 1: Preparation of Modifier

[0046] In contrast to Example 1, the only difference is that iron oxide was not added during the preparation of the modifier in Comparative Example 1.

[0047] Weigh out 25g tripotassium phosphate, 250g biochar, 120g corn residue, 170g xanthan gum, 170g sodium citrate, 170g vitamin E, 120g arbutin, 70g bilirubin, and 7g sodium bicarbonate.

[0048] Preparation method:

[0049] (1) Add vitamin E to 850g of ethanol and stir to dissolve to obtain mixture A;

[0050] (2) Add sodium bicarbonate to 3.5 kg of water and mix. Heat in a water bath at 50°C for 12 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then add arbutin and sodium citrate and put into a mixer and stir at 700 r / min for 7 min to obtain mixture B.

[0051] (3) Add 1.7 kg of water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and place in a homogenizer to homogenize at 17 MPa pressure for 12 min. After homogenization, add corn sugar residue, tripotassium phosphate and biochar and mix evenly to obtain the modifier.

[0052] Comparative Example 2: Preparation of Modifier

[0053] In contrast to Example 1, the only difference is that tripotassium phosphate was not added during the preparation of the modifier in Comparative Example 2.

[0054] Weigh out 25g iron oxide, 250g biochar, 120g corn residue, 170g xanthan gum, 170g sodium citrate, 170g vitamin E, 120g arbutin, 70g bilirubin, and 7g sodium bicarbonate.

[0055] Preparation method:

[0056] (1) Add vitamin E to 850g of ethanol and stir to dissolve to obtain mixture A;

[0057] (2) Add sodium bicarbonate to 3.5 kg of water and mix. Heat in a water bath at 50°C for 12 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then add arbutin and sodium citrate and put into a mixer and stir at 700 r / min for 7 min to obtain mixture B.

[0058] (3) Add 1.7 kg of water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and place in a homogenizer to homogenize at 17 MPa pressure for 12 min. After homogenization, add corn sugar residue, iron oxide and biochar and mix evenly to obtain the improver.

[0059] Comparative Example 3: Preparation of Modifier

[0060] In contrast to Example 1, the only difference is that no biochar and xanthan gum were added during the preparation of the modifier in Comparative Example 3.

[0061] Weigh out 25g of iron oxide, 25g of tripotassium phosphate, 120g of corn residue, 170g of sodium citrate, 170g of vitamin E, 120g of arbutin, 70g of bilirubin, and 7g of sodium bicarbonate.

[0062] Preparation method:

[0063] (1) Add vitamin E to 850g of ethanol and stir to dissolve to obtain mixture A;

[0064] (2) Add sodium bicarbonate to 3.5 kg of water and mix. Heat in a water bath at 50°C for 12 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then add arbutin and sodium citrate and put into a mixer and stir at 700 r / min for 7 min to obtain mixture B.

[0065] (3) Add mixture A and mixture B to 1.7 kg of water and then homogenize in a homogenizer at 17 MPa pressure for 12 min. After homogenization, add corn sugar residue, iron oxide and tripotassium phosphate and mix evenly to obtain the improver.

[0066] Comparative Example 4: Preparation of Modifier

[0067] Compared with Example 1, the only difference is that corn residue was not added during the preparation of the improver in Comparative Example 4.

[0068] Weigh out 25g iron oxide, 25g tripotassium phosphate, 250g biochar, 170g xanthan gum, 170g sodium citrate, 170g vitamin E, 120g arbutin, 70g bilirubin, and 7g sodium bicarbonate.

[0069] Preparation method:

[0070] (1) Add vitamin E to 850g of ethanol and stir to dissolve to obtain mixture A;

[0071] (2) Add sodium bicarbonate to 3.5 kg of water and mix. Heat in a water bath at 50°C for 12 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then add arbutin and sodium citrate and put into a mixer and stir at 700 r / min for 7 min to obtain mixture B.

[0072] (3) Add 1.7 kg of water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and place in a homogenizer to homogenize at 17 MPa pressure for 12 min. After homogenization, add iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the modifier.

[0073] Comparative Example 5: Preparation of Modifier

[0074] In contrast to Example 1, the only difference is that sodium citrate was not added during the preparation of the modifier in Comparative Example 5.

[0075] Weigh out 25g iron oxide, 25g tripotassium phosphate, 250g biochar, 120g corn residue, 170g xanthan gum, 170g vitamin E, 120g arbutin, 70g bilirubin, and 7g sodium bicarbonate.

[0076] Preparation method:

[0077] (1) Add vitamin E to 850g of ethanol and stir to dissolve to obtain mixture A;

[0078] (2) Add sodium bicarbonate to 3.5 kg of water and mix. Heat in a water bath at 50°C for 12 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then add arbutin and put it into a mixer and stir at 700 r / min for 7 min to obtain mixture B.

[0079] (3) Add 1.7 kg of water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and place in a homogenizer to homogenize at 17 MPa pressure for 12 min. After homogenization, add corn sugar residue, iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the modifier.

[0080] Comparative Example 6: Preparation of Modifier

[0081] A comparative example was formed with Example 1, the only difference being that in Comparative Example 6, vitamin E was not added during the preparation of the improver to prepare mixture A.

[0082] Weigh out 25g iron oxide, 25g tripotassium phosphate, 250g biochar, 120g corn residue, 170g xanthan gum, 170g sodium citrate, 120g arbutin, 70g bilirubin, and 7g sodium bicarbonate.

[0083] Preparation method:

[0084] (2) Add sodium bicarbonate to 3.5 kg of water and mix. Heat in a water bath at 50°C for 12 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then add arbutin and sodium citrate and put into a mixer and stir at 700 r / min for 7 min to obtain mixture B.

[0085] (3) Add 1.7 kg of water to xanthan gum and stir to mix evenly. Then add mixture B and place it in a homogenizer to homogenize at 17 MPa pressure for 12 min. After homogenization, add corn sugar residue, iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the modifier.

[0086] Comparative Example 7: Preparation of Modifier

[0087] A comparative example was formed with Example 1, the only difference being that arbutin was not added during the preparation of the modifier in Comparative Example 7.

[0088] Weigh out 25g iron oxide, 25g tripotassium phosphate, 250g biochar, 120g corn residue, 170g xanthan gum, 170g sodium citrate, 170g vitamin E, 70g bilirubin, and 7g sodium bicarbonate.

[0089] Preparation method:

[0090] (1) Add vitamin E to 850g of ethanol and stir to dissolve to obtain mixture A;

[0091] (2) Add sodium bicarbonate to 3.5 kg of water and mix. Heat in a water bath at 50°C for 12 min. After cooling to room temperature, add bilirubin and stir until well mixed. Then put it into a mixer and stir at 700 r / min for 7 min to obtain mixture B.

[0092] (3) Add 1.7 kg of water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and place in a homogenizer to homogenize at 17 MPa pressure for 12 min. After homogenization, add corn sugar residue, iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the modifier.

[0093] Comparative Example 8: Preparation of Modifier

[0094] In contrast to Example 1, the only difference is that no bilirubin was added during the preparation of the modifier in Comparative Example 8.

[0095] Weigh out 25g iron oxide, 25g tripotassium phosphate, 250g biochar, 120g corn residue, 170g xanthan gum, 170g sodium citrate, 170g vitamin E, 120g arbutin, and 7g sodium bicarbonate.

[0096] Preparation method:

[0097] (1) Add vitamin E to 850g of ethanol and stir to dissolve to obtain mixture A;

[0098] (2) Add sodium bicarbonate to 3.5 kg of water and mix. Heat in a water bath at 50°C for 12 min. After cooling to room temperature, add arbutin and sodium citrate and then put into a mixer and stir at 700 r / min for 7 min to obtain mixture B.

[0099] (3) Add 1.7 kg of water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and place in a homogenizer to homogenize at 17 MPa pressure for 12 min. After homogenization, add corn sugar residue, iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the modifier.

[0100] Experiment: Determination of the effect of the modifier

[0101] 1. For comparison, soil amendment experiments were conducted on cadmium-contaminated soil prepared in Example 1 and Comparative Examples 1-8. The experiments were carried out in farmland near an industrial park in Chongqing. A separate area of ​​900 m² was designated as the experimental zone. 2 .

[0102] 2. Before the experiment, the soil in the experimental area was tilled to a thickness of approximately 40 cm. The initial cadmium ion content in the soil was then measured to be approximately 1.03 mg / kg. Water was sprayed onto the soil to fully wet the surface. The soil was then evenly divided into 10 small areas, corresponding to Example 1, Comparative Examples 1-8, and the blank control (the blank control group had the soil amendment replaced with water). Each small area was 9 m². 2 Then, evenly sprinkle 2 kg of earthworms into each area, and then follow the formula of 1 kg / m². 2 The amounts of the amendments from Example 1, Comparative Examples 1-8, and the blank control group were sprayed onto the corresponding soils. The cadmium content in each soil was measured after 5 months and 9 months, respectively. The data are shown in Table 1, with units of mg / kg.

[0103] Table 1

[0104] Example 1 0.56 0.14 Comparative Example 1 0.72 0.35 Comparative Example 2 0.69 0.31 Comparative Example 3 0.67 0.29 Comparative Example 4 0.62 0.27 Comparative Example 5 0.65 0.25 Comparative Example 6 0.63 0.23 Comparative Example 7 0.72 0.32 Comparative Example 8 0.73 0.36 Blank control 0.91 0.63

[0105] Based on the data analysis in Table 1, we can conclude that:

[0106] (1) After adding earthworms to cadmium-contaminated soil and applying soil conditioner, the cadmium ion content in the soil was significantly reduced. Among them, Example 1 showed the best effect. After 5 months of treatment, the cadmium ion content in the soil decreased by 0.47 mg / kg, and after 9 months, the decrease was 0.89 mg / kg. Compared with Example 1, Comparative Examples 1-2 showed a smaller reduction in cadmium content in the soil. This is because iron oxide and tripotassium phosphate were not added in Comparative Examples 1-2, resulting in a lower degree of cadmium ion fixation and a lower earthworm intake, which led to a smaller reduction in cadmium content in the soil.

[0107] (2) Compared with Example 1, the cadmium content in soil of Comparative Example 3 decreased less. This is because biochar and xanthan gum were not added in Comparative Example 3, which reduced the soil’s adsorption capacity for iron oxide and tripotassium phosphate, resulting in a lower degree of cadmium fixation and a lower earthworm intake, thus reducing the cadmium ion content in soil.

[0108] (3) Compared with Example 1, the cadmium content in soil of Comparative Examples 4-6 was reduced to a smaller extent. This is because corn sugar residue, sodium citrate and vitamin E were not added to Comparative Examples 4-6, which reduced the growth and reproduction effects on earthworms and reduced the amount of cadmium ions absorbed and accumulated by earthworms.

[0109] (4) Compared with Example 1, the reduction in cadmium content in soil was smaller in Comparative Examples 7-8. This is because arbutin and bilirubin were not added to Comparative Examples 7-8, respectively, which failed to remove excess reactive oxygen species in earthworms. As a result, when earthworms ingested excessive cadmium ions, their cell membranes were damaged, earthworms died, their normal physiological activities were affected, and the treatment efficiency was reduced.

[0110] (5) In the blank control group, when the modifier was replaced with water, the earthworms did not have the synergistic effect of the promoter when treating cadmium-contaminated soil, which greatly reduced the efficiency of earthworms in treating cadmium-contaminated soil. This shows that when the modifier prepared in this invention is applied to cadmium-contaminated soil, the modifier can adsorb and fix cadmium ions to form cadmium precipitates. Earthworms can effectively reduce the cadmium content in the soil by ingesting the cadmium precipitates and fixing them. The modifier enhances the earthworms' treatment of cadmium-contaminated soil and improves the treatment efficiency by reducing the toxicity of cadmium ions in the soil.

[0111] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A soil conditioner for remediating cadmium-contaminated soil, characterized in that, The modifier comprises the following raw materials in parts by weight: 2-3 parts iron oxide, 2-3 parts tripotassium phosphate, 20-30 parts biochar, 10-15 parts corn sugar residue, 15-20 parts xanthan gum, 15-20 parts sodium citrate, 15-20 parts vitamin E, 10-15 parts arbutin, 5-10 parts bilirubin, 0.5-1 part sodium bicarbonate.

2. A method for preparing a soil conditioner for remediating cadmium-contaminated soil, characterized in that, The method for preparing the modifier is as follows: (1) Vitamin E was added to ethanol and stirred to dissolve, resulting in mixture A; (2) Add sodium bicarbonate to water and mix, then heat in a water bath. After cooling to room temperature, add bilirubin and mix evenly. Then add arbutin and sodium citrate and put into a mixer and stir evenly to obtain mixture B. (3) Add water to xanthan gum and stir to mix evenly. Then add mixture A and mixture B and put them into a homogenizer for homogenization. After homogenization, add corn sugar residue, iron oxide, tripotassium phosphate and biochar and mix evenly to obtain the improver.

3. The method for preparing a soil conditioner for remediating cadmium-contaminated soil according to claim 2, characterized in that, In step (1), the mass ratio of vitamin E to ethanol is 1:

2.

4. The method for preparing a soil conditioner for remediating cadmium-contaminated soil according to claim 3, characterized in that, The conditions for water bath heating in step (2) are: temperature 40-60℃, time 10-15min.

5. A method for preparing a soil conditioner for remediating cadmium-contaminated soil according to claim 4, characterized in that, In step (2), the stirring speed is 600-800 r / min and the stirring time is 5-10 min.

6. A method for preparing a soil conditioner for remediating cadmium-contaminated soil according to claim 5, characterized in that, The homogenization conditions in step (3) are: homogenization pressure 15-20 MPa, homogenization time 10-15 min.

7. A method for preparing a soil conditioner for remediating cadmium-contaminated soil according to claim 6, characterized in that, The application rate of the modifier is 0.3-1.5 kg / m³. 2 .

8. A method for preparing a soil conditioner for remediating cadmium-contaminated soil according to claim 7, characterized in that, The soil needs to be tilled before applying the soil amendment, as detailed below: Till the soil to a depth of 30-60cm, then spray water onto the tilled soil to wet the surface. Apply a soil conditioner, and then till the soil a second time to allow the conditioner to be incorporated into the soil.