Passivator and preparation method thereof, and safe utilization method of cadmium-polluted soil based on combination of mulberry and passivator
By preparing passivating agents and combining Cd low-cumulative mulberry varieties, a technical system for low-cumulative mulberry planting + passivating agents to jointly regulate Cd contaminated soil was constructed, which solved the problem of soil control and achieved safe use of soil and the safety of mulberry products.
Patent Information
- Application Number
- CN202510110685.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-23
- Publication Date
- 2025-04-29
AI Technical Summary
The existing technology is difficult to effectively control medium and highly heavy metal contaminated soil, especially in terms of economic and time costs. At the same time, the low-cumulative mulberry varieties lack the ability to absorb and enrich heavy metals, which cannot meet the safety needs of mulberry products.
Using the passivator preparation method, biochar is prepared by heating the straw powder in an oxygen-limiting environment, and KMnO4-YMC regulator is prepared by reacting with the KMnO4 solution. Combined with the Cd low-accumulative mulberry varieties, a technical system for low-accumulative mulberry planting + passivator to jointly regulate Cd contaminated soil.
The safe utilization of moderate to severe Cd contaminated soil is achieved, the Cd content in mulberry leaves is reduced, the soil pH value is increased, the concentration of soluble Cd is reduced, the amount of Cd absorbed by mulberry trees is reduced, and the safety requirements of mulberry products are met.
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Figure CN119899670A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of safe utilization of heavy metal soil, and specifically relates to a passivator and a preparation method thereof, and a method for safely utilizing cadmium-contaminated soil based on the combination of mulberry trees and the passivator. Background Art
[0003] Using existing soil heavy metal pollution control technology to remove and repair large areas of medium- and high-level heavy metal contaminated soil is unbearable in terms of the economic cost of physical removal and the time cost of biological restoration such as plants. In view of the stringent requirements of food safety, the "production and repair" model of using modifiers and edible crops is suitable for the safe use and repair of low-level contaminated soils, but not for medium- and high-level heavy metal contaminated soils in mining areas. From the perspective of medium- and high-level heavy metal contaminated soil control strategies, safe use and repair based on economic crops that do not directly / indirectly enter the food chain and have economic value has become a new development direction.
[0004] As one of the main economic crops, mulberry trees have a wide range of adaptability to natural environmental factors such as air, soil, temperature, light, and water, and have a well-developed root system and large biomass. In addition to being used as silkworm feed, they are widely used as ecological forest tree species in sand control, desertification control, and soil and water conservation. In recent years, its potential for safe utilization and restoration of heavy metal soil pollution has also been gradually explored. However, there are significant differences in the absorption and enrichment of heavy metals among different varieties. And because the heavy metal content in medium and highly heavy metal-contaminated soils is relatively high, simply planting low-accumulation mulberry varieties cannot meet the needs of mulberry product safety. Therefore, this patent uses potted experiments to screen out Cd low-accumulation mulberry varieties, develops passivation-type soil regulators, and constructs a low-accumulation mulberry planting + passivation agent combined regulation Cd-contaminated soil safe utilization technology system, which has good application and development prospects. Summary of the invention
[0005] In view of the above-mentioned defects existing in the prior art, the present invention aims to provide a highly efficient soil Cd passivator without secondary environmental pollution, and to provide a technical method for the safe utilization of mulberry trees by using an exogenous regulator in moderately and severely Cd-contaminated soil.
[0006] In order to achieve the above object, the present invention adopts the following technical solutions:
[0007] A method for preparing a passivating agent comprises the following steps:
[0008] (1) air-drying the straw for 3 to 5 days under natural conditions, drying in an oven at 65 to 70° C., crushing the dried material in a grinder, and then sieving to obtain straw powder;
[0009] (2) placing the straw powder in an atmosphere furnace, and providing an oxygen-limited environment by connecting high-purity nitrogen; setting the furnace to a heating rate of 5°C / min, maintaining at 500-550°C, and then naturally cooling to room temperature; and then passing the obtained straw biochar through a sieve;
[0010] (3) Weigh 50 g of straw biochar, wash it repeatedly with deionized water, boil it to remove dust and impurities on the surface, and then put it in an oven at 100-105°C to dry for 5-6 hours, take it out and place it in a desiccator for later use; weigh the washed straw biochar, add KMnO4 solution, mix it thoroughly with a glass rod, and then put it in a stirrer and stir it at 60-70°C; after stirring, wash it with deionized water and anhydrous ethanol respectively, and mark it with KMnO4 modification after washing; put it in an oven to dry to constant weight, and cool it to room temperature to obtain a passivating agent.
[0011] Furthermore, the straw is one or more of corn straw and rice straw.
[0012] Furthermore, in step (1), the sieving is through a 100-mesh sieve; and the drying time is more than 24 hours.
[0013] Furthermore, in step (2), the sieving is through a 100-mesh sieve; and the time of maintaining at 500-550° C. is 5 hours.
[0014] Furthermore, in step (3), the boiling time is 2 hours.
[0015] Furthermore, in step (3), the KMnO4 solution is 0.1 mol / L; the weighing of the washed straw biochar and the addition of the KMnO4 solution are specifically as follows: weighing 10.0074 g of the washed straw biochar and adding 50 ml of 0.1 mol / L KMnO4 solution.
[0016] Furthermore, in step (3), the stirring time is more than 6 hours; and the drying temperature is 60°C.
[0017] A method for safely utilizing cadmium-contaminated soil based on the combination of mulberry trees and a passivating agent comprises the following steps:
[0018] (1) When turning the soil before transplanting mulberry seedlings, mix the regulator with fertilizer and spread it into the soil. Turn it into the soil as the land is cultivated. Sprinkle it three times in a row, with a dosage of 200 kg / mu of soil each time.
[0019] (2) Soaking mulberry seeds in 45°C warm water, cooling naturally, soaking for another 12 hours, and placing them in wet sand to germinate in an environment with a relative humidity of 80%; sowing them when the seed coat breaks and the seeds are white; digging furrows with a row spacing of 30 cm and a furrow depth of 1-2 cm, sowing 1 kg per square meter, covering with soil, and germinating after 10 days. When the seedlings are 3-4 cm tall, thinning is performed, and when the seedlings are 15-20 cm tall, strong seedlings are selected and transplanted to soil contaminated with Cd;
[0020] (3) After the mulberry trees grow, mulberry leaves are harvested regularly and used to produce feed, thereby achieving safe utilization of contaminated soil.
[0021] Compared with the prior art, the advantages of the present invention are:
[0022] 1. Realize the safe utilization of soils with moderate or severe Cd pollution;
[0023] 2. Select mulberry tree varieties with low Cd accumulation to reduce the Cd content in mulberry leaves;
[0024] 3. KMnO4-YMC regulator is added into the contaminated soil after tillage to make the soil mix more evenly;
[0025] 4. Adding KMnO4-YMC increases the soil pH, thereby gradually reducing the concentration of soluble Cd in the soil and reducing the amount of Cd absorbed by mulberry trees;
[0026] 5. KMnO4-YMC regulator has a larger specific surface area and pore volume, which improves the adsorption capacity of exchangeable Cd in the soil. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 The distribution of Cd content in mulberry leaves of different varieties without the treatment of the regulator in Example 4;
[0028] Figure 2 This is the soil pH distribution diagram under the treatment of different regulators in Example 4;
[0029] Figure 3 The distribution diagram of soil available Cd content under different control agents in Example 4;
[0030] Figure 4 This is the distribution diagram of Cd content in mulberry leaves under the treatment of different regulators in Example 4. DETAILED DESCRIPTION
[0031] The present invention will be further described in detail below in conjunction with specific embodiments, but the embodiments of the present invention are not limited thereto. For process parameters not particularly noted, conventional techniques may be used.
[0032] Example 1
[0033] 1) Corn straw (YM) was collected from the farmland of Shuitang Village, Pingshan Town, Hezhang County, Bijie City, Guizhou Province. YM was air-dried under natural conditions for 5 days and dried in an oven at 65°C for 24 hours. The dried material was crushed in a grinder and then passed through a 100-mesh sieve. YM was tightly packed into a ceramic crucible and then placed in an atmosphere furnace, which provided an oxygen-limited environment by connecting high-purity nitrogen. The furnace was set to a heating rate of 5°C / min, maintained at a stable temperature of 550°C for 5 hours, and then naturally cooled to room temperature. The obtained YM biochar (YMC) was then passed through a 100-mesh sieve.
[0034] 2) Weigh 50g of YMC in a 500ml beaker, wash it repeatedly with deionized water for 3 times, boil it for 2h, remove the dust and impurities on the surface, put it in an oven at 105℃ to dry for 6h, take it out and place it in a desiccator for use. Weigh 15.8003g of KMnO4 solid in a 1000ml volumetric flask, dilute to the scale line and shake well, label it (0.1mol / L KMnO4) for use. Weigh 10.0074g of YMC in a 250ml beaker, add 50ml of 0.1mol / L KMnO4 solution, mix it thoroughly with a glass rod, put it in a stirrer and stir it below 60℃ for 6h. After stirring, wash it with deionized water and anhydrous ethanol for 3 times respectively, and mark it as KMnO4 modified after washing. Put it in an oven at 60℃ to dry for 12h, cool it to room temperature, mark it as KMnO4-YMC, and seal it for use.
[0035] 3) When turning the soil before transplanting mulberry seedlings, mix the KMnO4-YMC regulator with fertilizer and sprinkle it into the soil, then turn it into the soil along with the tillage, sprinkle it three times in a row, and each time the dosage is 200kg / mu of soil. (2. Apply once, the dosage is 100kg / mu of soil; 3. Apply once, the dosage is 300kg / mu of soil;)
[0036] 4) Soak the seeds of Yuesang 69851 mulberry tree in 45℃ warm water, cool naturally, soak for another 12h, place in wet sand, and maintain a relative humidity of 80% for germination; sow when the seed coat breaks and turns white. When sowing, dig furrows with a row spacing of 30cm and a furrow depth of 1-2cm. Sow 1kg per square meter and cover with soil. After about 10 days, seedlings will emerge. Thin out when the seedlings are 3-4cm tall. When the seedlings are 15-20cm tall, select strong seedlings and transplant them to soil contaminated by Cd;
[0037] 5) After the mulberry trees grow, mulberry leaves are harvested regularly and used to produce feed, thereby achieving safe utilization of contaminated soil.
[0038] Example 2
[0039] 1) Corn straw (YM) was collected from the farmland of Shuitang Village, Pingshan Town, Hezhang County, Bijie City, Guizhou Province. YM was air-dried under natural conditions for 5 days and dried in an oven at 65°C for 24 hours. The dried material was crushed in a grinder and then passed through a 100-mesh sieve. YM was tightly packed into a ceramic crucible and then placed in an atmosphere furnace, which provided an oxygen-limited environment by connecting high-purity nitrogen. The furnace was set to a heating rate of 5°C / min, maintained at a stable temperature of 550°C for 5 hours, and then naturally cooled to room temperature. The obtained YM biochar (YMC) was then passed through a 100-mesh sieve.
[0040] 3) When turning the soil before transplanting mulberry seedlings, mix the YMC regulator with fertilizer and spread it into the soil, turn it into the soil along with the tillage, and spread it three times in a row, with each time spreading the dosage of 200kg / mu of soil. (2. Apply once, the dosage is 100kg / mu of soil; 3. Apply once, the dosage is 300kg / mu of soil;)
[0041] 4) Soak the seeds of Yuesang 69851 mulberry tree in 45℃ warm water, cool naturally, soak for another 12h, place in wet sand, and maintain a relative humidity of 80% for germination; sow when the seed coat breaks and turns white. When sowing, dig furrows with a row spacing of 30cm and a furrow depth of 1-2cm. Sow 10kg per square meter and cover with soil. After about 10 days, the seedlings will emerge and the seedlings will be thinned out when they are 3-4cm tall. When the seedlings are 15-20cm tall, select strong seedlings and transplant them to soil contaminated by Cd;
[0042] 5) After the mulberry trees grow, harvest the mulberry leaves regularly.
[0043] Example 3
[0044] 1) Rice straw (SD) was collected from the farmland of Xiaojing Township, Xiuwen County, Guiyang City, Guizhou Province. The SD was air-dried under natural conditions for 5 days and dried in an oven at 65°C for 24 hours. The dried material was crushed in a grinder and then passed through a 100-mesh sieve. The SD was tightly packed into a ceramic crucible and then placed in an atmosphere furnace, which provided an oxygen-limited environment by connecting high-purity nitrogen. The furnace was set to a heating rate of 5°C / min, maintained at a stable temperature of 550°C for 5 hours, and then naturally cooled to room temperature. The obtained SD biochar (SDC) was then passed through a 100-mesh sieve.
[0045] 3) When turning the soil before transplanting mulberry seedlings, mix the SDC regulator with fertilizer and spread it into the soil, turn it into the soil along with the tillage, and spread it three times in a row, with each time spreading the dosage of 200kg / mu of soil. (2. Apply once, the dosage is 100kg / mu of soil; 3. Apply once, the dosage is 300kg / mu of soil)
[0046] 4) Soak the seeds of Yuesang 69851 mulberry tree in 45℃ warm water, cool naturally, soak for another 12h, place in wet sand, and maintain a relative humidity of 80% for germination; sow when the seed coat breaks and turns white. When sowing, dig furrows with a row spacing of 30cm and a furrow depth of 1-2cm. Sow 10kg per square meter and cover with soil. After about 10 days, the seedlings will emerge and the seedlings will be thinned out when they are 3-4cm tall. When the seedlings are 15-20cm tall, select strong seedlings and transplant them to soil contaminated by Cd;
[0047] 5) After the mulberry trees grow, harvest the mulberry leaves regularly.
[0048] Example 4
[0049] Table 1 Mulberry germplasm resource information
[0050]
[0051]
[0052] The information of mulberry germplasm resources is shown in Table 1. The distribution of Cd content in leaves of different varieties of mulberry trees without the action of exogenous regulators was analyzed by pot experiments. Figure 1 The results showed that Yuesang 69851 had the lowest leaf Cd content in moderately and severely Cd-contaminated soils, and Yuesang 69851 low-accumulation mulberry species was selected as the carrier of exogenous regulator-assisted mulberry safe utilization technology in moderately and severely Cd-contaminated soils.
[0053] Soil pH distribution under different regulator treatments Figure 2 ; Figure 2 CK: control group; KMnO4-YMC-100: KMnO4 modified corn straw biochar, added at 100 kg / mu; KMnO4-YMC-300: KMnO4 modified corn straw biochar, added at 300 kg / mu; KMnO4-YMC-600: KMnO4 modified corn straw biochar, added at 600 kg / mu; YMC-100: corn straw biochar, added The amount of corn straw biochar was 100kg / mu; YMC-300: corn straw biochar, the amount of addition was 300kg / mu; YMC-600: corn straw biochar, the amount of addition was 600kg / mu; SDC-100: rice straw biochar, the amount of addition was 100kg / mu; SDC-300: rice straw biochar, the amount of addition was 300kg / mu; SDC-600: rice straw biochar, the amount of addition was 600kg / mu. After adding corn straw biochar (YMC) and KMnO4-modified corn straw biochar (KMnO4-YMC), the soil pH increased significantly compared with the control group (CK), thereby gradually reducing the concentration of soluble Cd in the soil, as shown in Figure 2. Figure 3 ; Figure 3CK: control group; KMnO4-YMC-100: KMnO4 modified corn straw biochar, added at 100 kg / mu; KMnO4-YMC-300: KMnO4 modified corn straw biochar, added at 300 kg / mu; KMnO4-YMC-600: KMnO4 modified corn straw biochar, added at 600 kg / mu; YMC-100: corn straw biochar, added The amount of Cd absorbed by mulberry trees is reduced by 100 kg / mu; YMC-300: corn straw biochar, the amount of addition is 300 kg / mu; YMC-600: corn straw biochar, the amount of addition is 600 kg / mu; SDC-100: rice straw biochar, the amount of addition is 100 kg / mu; SDC-300: rice straw biochar, the amount of addition is 300 kg / mu; SDC-600: rice straw biochar, the amount of addition is 600 kg / mu. Figure 4 ) to achieve safe use.
[0054] Example 5: Distribution of Cd content in leaves of different varieties of mulberry leaves without regulator treatment
[0055] The test soil was collected from the traditional zinc smelting pollution area of Magu Town, Hezhang County, Guizhou Province. The physical and chemical properties and Cd content of the test soil are shown in Table 2. First, the collected test soil was spread out and air-dried naturally. After air-drying, debris and plant roots were picked out of the soil. After being sieved with a stainless steel sieve and fully mixed, it was potted for mulberry sowing. A total of 20 mulberry species were selected (see Table 1), and 3 replicates were set for each soil, totaling 180 pots. 2.5 kg of soil samples numbered HZ-H, HZ-M, and HZ-L were weighed and placed in pots with trays, and equal numbers of mulberry seeds (100 seeds) were sown. After sowing, regular weeding, fertilization, watering and other maintenance were carried out. After 14 weeks of growth, the mulberry leaves were harvested, the leaf samples were digested by drenching, and the Cd content was determined by ICP-MS. The distribution of Cd content in mulberry leaves of different varieties without regulator treatment is shown in Figure 1 The results showed that Yuesang 69851 had the lowest leaf Cd content in moderately and severely Cd-contaminated soils, and Yuesang 69851 low-accumulation mulberry species was selected as the carrier of exogenous regulator-assisted mulberry safe utilization technology in moderately and severely Cd-contaminated soils.
[0056] Table 2 Physical and chemical properties and Cd content of tested soil samples
[0057] Soil name pH (no unit) Eh(mv) SOM(g / kg) CEC (cmoL / kg) Alkaline nitrogen (mg / kg) Cd(mg / kg) HZ-L 8.39 -72.1 38.1 11.7 104 2.78 HZ-M 7.85 -42.2 49.1 14.3 173 6.66 HZ-H 7.65 -31.1 63.8 6.61 28.3 144
[0058] Example 6: Soil available Cd content, mulberry leaf Cd content distribution and influence on soil pH after treatment with different regulators
[0059] CK: control group, no treatment; KMnO4-YMC-100: KMnO4 modified corn straw biochar, the addition amount is 100kg / mu; KMnO4-YMC-300: KMnO4 modified corn straw biochar, the addition amount is 300kg / mu; KMnO4-YMC-600: KMnO4 modified corn straw biochar, the addition amount is 600kg / mu; YMC-100: corn straw biochar, the addition amount is 100kg / mu; YMC-300: corn straw biochar, the addition amount is 300kg / mu; YMC-600: corn straw biochar, added at 600kg / mu; SDC-100: rice straw biochar, added at 100kg / mu; SDC-300: rice straw biochar, added at 300kg / mu; SDC-600: rice straw biochar, added at 600kg / mu, etc. 10 groups of treatments, each with 3 replicates, maintaining soil moisture, after stabilization for 60 days, collect part of the treated soil, air dry naturally, grind through a 200 mesh sieve, and dry in an oven at 65℃. Weigh 1.000g of the sample in a 50mL polyethylene centrifuge tube, add 40mL of 0.11mol / L acetic acid (HOAc), and shake at 22℃±5℃ for 16h. Then, centrifuge at 3000g for 20min. Separate the supernatant into a 100mL clean volumetric flask. Afterwards, repeat the above washing twice with 20mL ultrapure water (but only shake for 15min), combine the washing solution with the extract, and make up to the scale, filter into a 10mL centrifuge tube with a needle filter membrane, store at 4°C, and determine the effective Cd content by I CP-MS. Weigh 5g of dried soil sample, place in a 50ml polyethylene centrifuge tube, add 12.5ml of deionized water cooled to room temperature, seal and shake for 10min, let stand for 30min, and measure the pH of the solution with a pH meter. Select strong seedlings and transfer them to the Cd-contaminated soil stabilized by the above 10 groups of different treatments, and harvest after 12 weeks of growth. Rinse the harvested mulberry leaves repeatedly with tap water and then rinse with deionized water 3 times. Absorb the surface moisture with absorbent paper, dry in an oven at 60°C, and crush to 60 mesh. Determine the Cd content in the mulberry leaves. The results are shown in the table below. Figure 4 . Figure 4CK: control group; KMnO4-YMC-100: KMnO4 modified corn straw biochar, added at 100 kg / mu; KMnO4-YMC-300: KMnO4 modified corn straw biochar, added at 300 kg / mu; KMnO4-YMC-600: KMnO4 modified corn straw biochar, added at 600 kg / mu; YMC-100: corn straw biochar, added The amount is 100kg / mu; YMC-300: corn straw biochar, the addition amount is 300kg / mu; YMC-600: corn straw biochar, the addition amount is 600kg / mu; SDC-100: rice straw biochar, the addition amount is 100kg / mu; SDC-300: rice straw biochar, the addition amount is 300kg / mu; SDC-600: rice straw biochar, the addition amount is 600kg / mu.
[0060] The distribution of soil pH, soil available Cd content and mulberry leaf Cd content under different treatments are shown in Figure 2. Figure 2 , 3 and 4. The results showed that the soil pH increased significantly after adding corn straw biochar (YMC) and KMnO4-modified corn straw biochar (KMnO4-YMC) compared with the control group (CK), which gradually reduced the concentration of soluble Cd in the soil. This in turn reduced the amount of Cd absorbed by mulberry leaves (see Figure 4 ), among which KMnO4 modified corn straw biochar was added at a dosage of 600 kg / mu, and the Cd content of mulberry leaves was less than 1 mg / kg, meeting the Cd content limit requirements in the feed hygiene standard GB13078-2017.
[0061] The above embodiments are provided for a better understanding of the present invention, but are not limited to the best implementation mode and do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the present invention with the features of other prior arts shall fall within the protection scope of the present invention.
Claims
1. A method for preparing a passivating agent, characterized in that: The steps include: (1) air-drying the straw under natural conditions for 3 to 5 days at 65 to 70° C., crushing the dried material, and then sieving to obtain straw powder; (2) placing the straw powder in an atmosphere furnace, which is connected to a high-purity nitrogen atmosphere to provide an oxygen-limited environment; maintaining the temperature at 500-550° C., then naturally cooling to room temperature, and then passing the obtained straw biochar through a sieve; (3) Weigh the straw biochar, wash it repeatedly with deionized water, boil it to remove the dust and impurities on the surface, dry it at 100-105°C for 5-6 hours, take it out and place it in a dryer for use; weigh the washed straw biochar, add the KMnO4 solution, mix it thoroughly and stir it at 60-70°C; after stirring, wash it with deionized water and anhydrous ethanol respectively, mark it with KMnO4 modification after washing; dry it to constant weight, and cool it to room temperature to obtain the passivation agent.
2. The method for preparing a passivating agent according to claim 1, characterized in that: The straw is one or more of corn straw and rice straw.
3. The method for preparing a passivating agent according to claim 1, characterized in that: In step (1), the sieving is through a 100-mesh sieve; and the drying time is more than 24 hours.
4. The method for preparing a passivating agent according to claim 1, characterized in that: In step (2), the sieving is through a 100-mesh sieve; the time of maintaining at 500-550° C. is 5 hours, and the adding rate is 5° C. / min.
5. The method for preparing a passivating agent according to claim 1, characterized in that: In step (3), the boiling time is 2 hours.
6. The method for preparing a passivating agent according to claim 1, characterized in that: In step (3), the KMnO4 solution is 0.1 mol / L; the weighing of the washed straw biochar and the addition of the KMnO4 solution are specifically as follows: weighing 10.0074 g of the washed straw biochar and adding 50 ml of 0.1 mol / L KMnO4 solution.
7. The method for preparing a passivating agent according to claim 1, characterized in that: In step (3), the stirring time is more than 6 hours; and the drying temperature is 60°C.
8. A passivating agent prepared by the preparation method according to any one of claims 1 to 7.
9. A method for safely utilizing cadmium-contaminated soil based on the combination of mulberry trees and the passivator according to claim 8, characterized in that: The steps include: (1) When turning the soil before transplanting mulberry seedlings, mix the regulator with fertilizer and spread it into the soil. Turn it into the soil as the land is cultivated. Sprinkle it three times in a row, with a dosage of 200 kg / mu of soil each time. (2) Soaking mulberry seeds in warm water, cooling naturally, soaking again, and placing in wet sand for germination; sowing when the seed coat breaks and turns white; digging furrows at a row spacing of 30 cm and a furrow depth of 1-2 cm, sowing 1 kg per square meter, covering with soil, and germinating after 10 days. When the seedlings are 3-4 cm tall, thinning is performed, and when the seedlings are 15-20 cm tall, strong seedlings are selected and transplanted to soil contaminated with Cd; (3) After the mulberry trees grow, mulberry leaves are harvested regularly and used to produce feed, thereby achieving safe utilization of contaminated soil.