Method for improving phytoremediation of heavy metal cadmium / lead contaminated soil by using beta-cyclodextrin

Abstract

The invention provides a method for improving phytoremediation of heavy metal cadmium / lead contaminated soil by using beta-cyclodextrin, and belongs to the technical field of heavy metal contaminated soil remediation. The method comprises the following steps: applying beta-cyclodextrin into the heavy metal cadmium / lead polluted soil, carrying out soil flooding treatment, and planting cadmium / lead tolerant and enriched plants; the application amount of the beta-cyclodextrin is 5-25 g / m < 2 >. According to the method, the enrichment capacity of plants to cadmium / lead is remarkably improved through beta-cyclodextrin, and test data shows that after beta-cyclodextrin is applied, the cadmium content of the roots, stems and leaves of amaranthus hypochondriacus is remarkably improved compared with that of a blank group, the repair period is greatly shortened, and the defect that traditional plant repair efficiency is low is overcome. The method has the advantages of being green, safe, easy to operate, quick in effect taking and high in practicability.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal contaminated soil remediation technology, and in particular relates to a method for using β-cyclodextrin to enhance the remediation of cadmium / lead contaminated soil by plants. Background Technology

[0002] In today's society, industrialization is progressing at an unprecedented pace, and the use of chemicals in agricultural production is also increasing daily. However, the negative impacts of this process cannot be ignored, with soil heavy metal pollution gradually evolving into a serious global environmental problem. Heavy metals such as cadmium and lead are highly toxic, easily migrate, and have strong bioaccumulation properties, making them important pollutants that threaten the stability of ecosystems. For example, cadmium affects a series of physiological processes in plants, including photosynthesis, respiration, nucleic acid metabolism, and root cell division; through biomagnification in the food chain, cadmium not only damages the kidneys in humans but also causes bone diseases.

[0003] Faced with the thorny problem of cadmium and lead contaminated soil, existing remediation technologies, while numerous, all have unavoidable limitations. Physical remediation methods, such as topsoil replacement and soil replacement, can directly remove pollutants from the soil, but often require enormous engineering work, are costly, and may even cause secondary pollution, resulting in further damage to the surrounding environment. Chemical leaching, a chemical remediation method, can rapidly reduce cadmium levels in the soil in the short term, but inevitably damages the original soil structure and disrupts the soil's internal ecological balance. Bioremediation methods, such as phytoremediation, while environmentally friendly, have a long remediation cycle, low efficiency, and stringent requirements on soil environmental conditions.

[0004] It is precisely under such predicaments that the search for a cadmium-contaminated soil remediation technology that is efficient, economical, environmentally friendly, and easy to operate has become a major issue that urgently needs to be addressed in the field of environmental protection. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for improving the remediation of cadmium / lead contaminated soil by plants using β-cyclodextrin, which has the advantages of being green and safe, simple to operate, fast-acting, and highly practical.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for enhancing phytoremediation of cadmium / lead contaminated soil using β-cyclodextrin involves applying β-cyclodextrin to the cadmium / lead contaminated soil, subjecting the soil to flooding, and then planting cadmium / lead tolerant and accumulating plants. The application rate of β-cyclodextrin is 5-25 g / m². 2 .

[0007] Preferably, impurities in the contaminated soil are removed before the β-cyclodextrin is applied; the impurities include stones and gravel.

[0008] Preferably, the β-cyclodextrin is mixed with water at a volume ratio of 1:20-40 and then sprayed.

[0009] Preferably, after applying the β-cyclodextrin, the contaminated soil is deeply tilled to a depth of 20-30 cm to mix the β-cyclodextrin with the contaminated soil.

[0010] Preferably, the soil flooding treatment lasts for 2-3 days.

[0011] More preferably, after the soil flooding treatment, the surface soil moisture content is maintained at 60%-90% for 5-15 days.

[0012] Preferably, the cadmium / lead tolerant and accumulating plants are selected from one or more of black nightshade, amaranth, and rapeseed.

[0013] More preferably, after the cadmium / lead tolerant and enriching plant has completed its growth period, the above-ground parts are collected and subjected to harmless treatment.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for enhancing phytoremediation of soil contaminated with heavy metals cadmium / lead using β-cyclodextrin. β-cyclodextrin is a natural oligosaccharide derivative with no risk of secondary pollution. The phytoremediation process does not damage the soil structure and can maintain the soil ecological balance, thus solving the problems of secondary pollution from physical remediation and soil structure damage from chemical remediation.

[0015] This invention significantly enhances the cadmium / lead accumulation capacity of plants by applying β-cyclodextrin. Experimental data show that after β-cyclodextrin application, the cadmium content in the roots, stems, and leaves of amaranth seeds was significantly higher than in the control group, greatly shortening the remediation cycle and overcoming the low efficiency of traditional phytoremediation methods. This invention is applicable to cadmium / lead contaminated soils with varying degrees of pollution, from moderate (2 mg / kg) to severe (5 mg / kg). The application rate of β-cyclodextrin and the combination of plant species can be adjusted according to the pollution situation to adapt to various soil environments. Attached Figure Description

[0016] Figure 1 The growth of amaranth in cadmium-contaminated soil in Experiment Example 1 is shown in the experimental group (left) and the control group (right). Figure 2 The image shows the growth of amaranth in cadmium-contaminated soil in Experiment Example 2, specifically in the experimental group (left) and the control group (right). Detailed Implementation

[0017] This invention provides a method for enhancing the remediation of cadmium / lead contaminated soil using β-cyclodextrin. The method involves applying β-cyclodextrin to the cadmium / lead contaminated soil, subjecting the soil to flooding, and then planting cadmium / lead tolerant and accumulating plants. The application rate of β-cyclodextrin is 5-25 g / m². 2 Cyclodextrin is a conical, cyclic oligosaccharide composed of 7-8 glucose units linked by 1,4-glycosidic bonds. The molecule has a three-dimensional cyclic structure containing a nonpolar cavity. The outer end of the cavity is composed of primary hydroxyl groups, exhibiting hydrophilicity and readily forming hydrogen bonds for association between molecules. The cavity contains hydrophobic regions due to the shielding effect of CH bonds. The hydrophilic and hydrophobic properties of cyclodextrin can effectively improve the migration capacity of heavy metal ions in soil, thereby enhancing the absorption efficiency of heavy metal ions by plant roots.

[0018] In this invention, it is preferable to remove impurities from the contaminated soil before applying β-cyclodextrin, and more preferably, the impurities include stones and gravel.

[0019] In this invention, it is preferred to mix β-cyclodextrin with water at a volume ratio of 1:20-40 and then spray, and more preferably to mix at a volume ratio of 1:30 and then spray.

[0020] In this invention, it is preferable to apply β-cyclodextrin followed by deep tilling of the contaminated soil to a depth of 20-30 cm, more preferably 25 cm, to mix the β-cyclodextrin with the contaminated soil, thereby facilitating the reaction between the β-cyclodextrin and the heavy metals cadmium / lead. This invention does not specifically limit the method of deep tilling; as one possible implementation, tilling equipment or machinery can be used to deeply till the cadmium-contaminated soil.

[0021] In this invention, it is preferable that the soil flooding treatment lasts for 2-3 days, and more preferably, after the soil flooding treatment, the surface soil moisture content is maintained at 60%-90% for 5-15 days. Soil flooding treatment can enhance the dispersibility of β-cyclodextrin in contaminated soil, promote its contact reaction with heavy metal ions, and create a humid environment suitable for plant growth; maintaining a surface soil moisture content of 60%-90% thereafter can continuously ensure the activity of β-cyclodextrin and the absorption efficiency of plant roots.

[0022] In this invention, the preferred cadmium / lead tolerant and accumulating plants are selected from one or more of black nightshade, amaranth, and rapeseed. More preferably, after the cadmium / lead tolerant and accumulating plants have completed their growing season, the aboveground parts are collected and subjected to harmless treatment. The cadmium / lead tolerant and accumulating plants can absorb heavy metal ions fixed by β-cyclodextrin through their roots and transport them to the aboveground parts for accumulation. Finally, by harvesting the aboveground parts of the plants and subjecting them to harmless treatment, heavy metals are removed from the soil.

[0023] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0024] Example 1 A method for enhancing phytoremediation of cadmium / lead contaminated soil using β-cyclodextrin, comprising the following steps: (1) Remove stones and gravel from the contaminated soil before applying β-cyclodextrin; (2) According to 15g / m 2 The application rate is determined by mixing β-cyclodextrin with water at a volume ratio of 1:30 and spraying the mixture, followed by deep tilling of the contaminated soil to a depth of 25 cm. (3) After applying β-cyclodextrin, irrigate with water and maintain the water level for 3 days; after the water level is lifted, continue to control the surface soil moisture content to 75% and maintain it for 10 days. (4) Sow amaranth seeds. After the growing season, collect the above-ground parts and carry out harmless treatment.

[0025] Example 2 A method for enhancing phytoremediation of cadmium / lead contaminated soil using β-cyclodextrin, comprising the following steps: (1) Remove stones and gravel from the contaminated soil before applying β-cyclodextrin; (2) According to 5 / m 2 The application rate is determined by mixing β-cyclodextrin with water at a volume ratio of 1:20 and spraying the mixture, followed by deep tilling of the contaminated soil to a depth of 20 cm. (3) After applying β-cyclodextrin, irrigate with water and maintain the water level for 2 days; after the water level is restored, continue to control the surface soil moisture content to 60% and maintain it for 15 days. (4) Sow the black nightshade seeds. After the growing season, collect the above-ground parts and carry out harmless treatment.

[0026] Example 3 A method for enhancing phytoremediation of cadmium / lead contaminated soil using β-cyclodextrin, comprising the following steps: (1) Remove stones and gravel from the contaminated soil before applying β-cyclodextrin; (2) According to 25g / m 2 The application rate is as follows: mix β-cyclodextrin with water at a volume ratio of 1:40 and spray, and then deeply till the contaminated soil to a depth of 30cm. (3) After applying β-cyclodextrin, irrigate with water and maintain the water level for 3 days; after the water level is restored, continue to control the surface soil moisture content to 90% and maintain it for 5 days. (4) Sow seeds of amaranth and rapeseed (1:1). After the growing season, collect the above-ground parts and carry out harmless treatment.

[0027] Experimental Example 1 β-Cyclodextrin enhances the efficacy of phytoremediation of cadmium-contaminated soil. (1) Prepare cadmium-contaminated soil, crush and sieve it until the soil particle size is less than 2 mm, and remove impurities such as stones and gravel; (2) Prepare a cadmium solution, impregnate and equilibrate the prepared cadmium-contaminated soil, and adjust the average cadmium pollution content of the soil to 5 mg / kg; (3) Set up an experimental group and a blank group. The experimental group was given β-cyclodextrin at a ratio of 25g:1000g soil and mixed evenly. The blank group was not treated. (4) Cultivate amaranth seeds, which have a cadmium enrichment effect, and transplant them into the soil after they have grown into seedlings (with consistent initial cadmium content). Water them regularly and pour the leached liquid back into the soil to reduce cadmium loss. (5) When the amaranth seeds mature, take the roots, stems and leaves and test their cadmium content. The results are shown in Table 1.

[0028] Table 1. Cadmium content in amaranth roots, stems, and leaves under different treatments.

[0029] According to Table 1 and Figure 1 It can be seen that, compared with the blank group without β-cyclodextrin, more cadmium was detected in the roots, stems and leaves of amaranth in the experimental group with β-cyclodextrin. This indicates that the beneficial effect of applying 25g of β-cyclodextrin per kilogram of heavily polluted soil is to enhance the migration ability of heavy metal cadmium ions and promote the enrichment of soil cadmium by amaranth.

[0030] Experimental Example 2 Similar to Experiment 1, the difference was that the average cadmium pollution content in the soil was controlled at 2 mg / kg, and the results are shown in Table 2.

[0031] Table 2. Cadmium content in amaranth roots, stems, and leaves under different treatments.

[0032] According to Table 2 and Figure 2 It can be seen that, compared with the blank group without β-cyclodextrin, more cadmium was detected in the roots, stems and leaves of amaranth in the experimental group with β-cyclodextrin. This indicates that the beneficial effect of applying 25g of β-cyclodextrin per kilogram of moderately polluted soil is to enhance the migration ability of heavy metal cadmium ions and promote the enrichment of soil cadmium by amaranth.

[0033] Experimental Example 3 The effect of β-cyclodextrin on the remediation of cadmium-contaminated soil. (1) Prepare cadmium-contaminated soil, crush and screen it until the soil particle size is less than 2 mm, and remove impurities such as stones and gravel; (2) Prepare a cadmium solution, impregnate and equilibrate the prepared cadmium-contaminated soil, and adjust the average cadmium pollution content of the soil to 2 mg / kg; (3) Set up an experimental group and a control group. The experimental group was given β-cyclodextrin at a ratio of 25g:1000g soil and mixed evenly. The control group was given β-cyclodextrin at a ratio of 15g:1000g soil and mixed evenly. (4) Cultivate amaranth seeds, which have a cadmium enrichment effect, and transplant them into the soil after they have grown into seedlings (with consistent initial cadmium content). Water them regularly and pour the leached liquid back into the soil to reduce cadmium loss. (5) When the amaranth seeds mature, take its roots, stems and leaves and test their cadmium content. The results are shown in Table 3.

[0034] Table 3. Cadmium content in amaranth roots, stems, and leaves under different treatments.

[0035] As shown in Table 3, compared to the control group treated with β-cyclodextrin at a ratio of 15g:1000g, the experimental group treated with β-cyclodextrin at a ratio of 25g:1000g showed higher levels of cadmium in all three major organs (grain, root, stem, and leaf). This indicates that applying 25g of β-cyclodextrin per kilogram of moderately contaminated soil is more beneficial than applying 15g of β-cyclodextrin. In practical applications, the application rate should be 5-25g / m³. 2 The application of β-cyclodextrin can effectively improve the remediation efficiency of phytoremediation of soil contaminated with heavy metals cadmium / lead.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for enhancing phytoremediation of cadmium / lead contaminated soil using β-cyclodextrin, characterized in that, β-Cyclodextrin was applied to cadmium / lead contaminated soil, followed by soil flooding treatment, and then cadmium / lead tolerant and accumulating plants were planted; the application rate of β-cyclodextrin was 5-25 g / m². 2 .

2. The method according to claim 1, characterized in that, Before applying the β-cyclodextrin, impurities in the contaminated soil are removed; the impurities include stones and gravel.

3. The method according to claim 1, characterized in that, The β-cyclodextrin is mixed with water at a volume ratio of 1:20-40 and then sprayed.

4. The method according to claim 1, characterized in that, After applying the β-cyclodextrin, the contaminated soil is deeply tilled to a depth of 20-30 cm to mix the β-cyclodextrin with the contaminated soil.

5. The method according to claim 1, characterized in that, The soil flooding treatment lasted for 2-3 days.

6. The method according to claim 1 or 5, characterized in that, After the soil flooding treatment, the surface soil moisture content should be maintained at 60%-90% for 5-15 days.

7. The method according to claim 1, characterized in that, The cadmium / lead tolerant and enriching plants are selected from one or more of black nightshade, amaranth, and rapeseed.

8. The method according to claim 1 or 7, characterized in that, After the cadmium / lead tolerant and enriching plants have completed their growth period, the above-ground parts will be collected and subjected to harmless treatment.

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