A method for repairing cadmium-zinc composite contaminated soil by using an amendment and woody plants

Abstract

The present invention relates to the technical field of cadmium-zinc composite contaminated soil remediation, and discloses a method for remediating cadmium-zinc composite contaminated soil by using an improver in collaboration with woody plants, comprising: preparing and using rice straw biochar functionalized with polyaspartic acid or / and attapulgite functionalized with branched carboxyl functional monomer M-Carboxylation as a soil improver for cadmium-zinc composite contaminated soil; and 2 The soil conditioner is fully mixed into the top 20-40 cm of weakly alkaline soil heavily contaminated with cadmium and zinc compounds at a ratio of 0.05; woody oak seedlings are planted, and weeding and pest control is performed regularly. The present invention uses the conditioner to chelate cadmium and zinc ions in the soil, promoting the transport of cadmium and zinc from the roots to the aboveground parts of the oak tree, increasing the accumulation of cadmium and zinc in the woody oak tree, and significantly improving the oak tree's efficiency in remediating cadmium and zinc compound-contaminated soil.

Description

Technical Field

[0001] The invention relates to the technical field of cadmium-zinc composite contaminated soil remediation, and specifically to a method for remediating cadmium-zinc composite contaminated soil by using an improver in collaboration with woody plants. Background Art

[0002] Most heavy metal elements are located in the transition zone of the periodic table and generally have multiple valence states. Therefore, they are highly chemically active and can participate in a variety of reactions and processes in the environment, easily causing irreversible damage to the environment. Cadmium (Cd) pollution is the most serious of all heavy metal pollution. However, in nature, heavy metals are often associated or combined. For example, cadmium (Cd) and zinc (Zn) have similar geochemical and environmental characteristics. Because zinc ore typically contains 0.1%-0.5% cadmium (Cd), the mining process and subsequent extraction release of zinc (Zn) into the environment are often accompanied by cadmium (Cd) pollution.

[0003] Amendment-phytoremediation technology involves adding soil amendments to the soil to adjust its nutrients and physical and chemical conditions, thereby altering the plant's absorption of metals. It is considered a promising technology for remediating contaminated soils. While plants typically exhibit symptoms of toxicity when absorbing non-essential metal elements, hyperaccumulators can absorb several or even hundreds of times the amount that ordinary plants can absorb. However, extracting heavy metals from hyperaccumulators requires that the metals be activated—that is, converted into a form that can be absorbed and utilized by plants.

[0004] The study found that attapulgite is a 2:1 type layered chain crystalline hydrated magnesium aluminum salt mineral existing in nature, and its structural formula is (Mg, Al, Fe)5Si8O 20 (OH)2(H2O)4·4H2O, the crystals are rod-shaped, fibrous, with pores running through the layers, and the surface is concave and convex. It has a large specific surface area, high thermal stability, and exhibits good adsorption and ion exchange properties. However, the purity of natural attapulgite is low and its adsorption capacity is very limited.

[0005] Biochar is a highly aromatic, insoluble solid material produced through the anoxic thermal polymerization of waste biomass. It possesses advantages such as large surface area, numerous pores, and excellent adsorption properties. Biochar adsorbs heavy metals primarily through physical adsorption, electrostatic interactions, ion exchange, and surface complexation, with ion exchange and surface complexation playing a dominant role. However, biochar is significantly deficient in its ability to chelate and activate heavy metals and convert them into forms that can be absorbed and utilized by plants.

[0006] In addition to herbaceous plants with hyperaccumulation capacity for heavy metals, an increasing number of woody plants, such as willow, poplar and oak, also show outstanding potential for phytoremediation of heavy metal contaminated soils due to their high accumulation capacity or tolerance to heavy metals, as well as high biomass production and low labor costs.

[0007] Research has found that using chelating agents in conjunction with phytoremediation can address the low efficiency of heavy metal extraction by plants, significantly enhancing the application value of phytoremediation. However, most current chelating agents suffer from difficulties with degradation or low chelating power. Polyaspartic acid is a fully biodegradable, environmentally friendly polyamino acid with carboxyl side chains. Summary of the Invention

[0008] In order to overcome the shortcomings of biochar in its ability to chelate and activate cadmium and zinc in soil, and to overcome the limited ability of attapulgite in adsorbing cadmium and zinc in soil, the present invention provides a method for repairing cadmium-zinc composite contaminated soil by using an amendment in collaboration with woody plants. The method uses rice straw biochar functionalized with polyaspartic acid or / and attapulgite functionalized with branched carboxyl functional monomer M-Carboxylation as an amendment for cadmium-zinc composite contaminated soil. The amendment has the function of fixing and passivating cadmium and zinc in soil, and also has the effect of chelating cadmium and zinc in soil. By cooperating with the woody plant oak, the amendment promotes the enrichment of cadmium and zinc from soil to plants, thereby significantly improving the efficiency of repairing cadmium-zinc composite contaminated soil.

[0009] A method for repairing cadmium-zinc composite contaminated soil using an amendment in conjunction with woody plants comprises the following steps:

[0010] Step 1: preparing rice straw biochar functionalized with polyaspartic acid and attapulgite functionalized with branched carboxyl functional monomer M-carboxylation, and using the rice straw biochar functionalized with polyaspartic acid and / or the attapulgite functionalized with branched carboxyl functional monomer M-carboxylation as a soil conditioner for cadmium-zinc composite contaminated soil;

[0011] Step 2: According to 10-35t / hm 2 The soil conditioner prepared in step 1 is fully mixed into the topsoil 20-40 cm of the weakly alkaline cadmium-zinc composite heavily contaminated soil;

[0012] Step 3: Planting oak seedlings, and regularly weeding and pest control;

[0013] The soil conditions are: Cd>29mg / kg, Zn>1100mg / kg, pH=7.6;

[0014] The woody plant is an oak tree, specifically including white oak and nata oak, preferably nata oak;

[0015] The addition ratio of the soil conditioner is preferably 22.5t / hm 2 ;

[0016] The soil conditioner is preferably fully mixed into the top 30 cm of soil;

[0017] The preparation method of rice straw biochar functionalized with polyaspartic acid is as follows: first, rice straw biochar is prepared from rice straw, then the rice straw biochar is modified to obtain chloropropyl functionalized rice straw biochar, and finally, polyaspartic acid and the chloropropyl functionalized rice straw biochar are grafted and composited through a nucleophilic substitution reaction. The specific preparation steps are as follows:

[0018] Step 1-1: clean the rice straw with deionized water, cut it into small pieces, dry it to constant weight, and then place it in a muffle furnace for oxygen-limited cracking and carbonization to obtain rice straw biochar;

[0019] Step 1-2, deionized water, anhydrous ethanol, and 3-chloropropyltrimethoxysilane are sequentially added to the rice straw biochar, stirred for reaction, and NH3·H2O is added to adjust the pH to alkaline. After the reaction, the biochar is washed with deionized water and anhydrous ethanol until neutral, and dried to constant weight to obtain chloropropyl functionalized rice straw biochar;

[0020] Steps 1-3: adding polyaspartic acid to deionized water, adding chloropropyl functionalized rice straw biochar to the above solution, first ultrasonically dispersing, then stirring, condensing and refluxing the reaction, then washing the product with deionized water and anhydrous ethanol, and drying to constant weight to obtain polyaspartic acid functionalized rice straw biochar;

[0021] Wherein, the relative molecular weight of polyaspartic acid is 3000-6000 and the solid content is 40%, preferably the relative molecular weight of polyaspartic acid is 4000;

[0022] The preparation method of the attapulgite functionalized with a branched carboxyl functional monomer M-Carboxylation is as follows: first, the attapulgite is activated, then the activated attapulgite is modified to obtain aminopropyl functionalized attapulgite, and finally the branched carboxyl functional monomer M-Carboxylation and the aminopropyl functionalized attapulgite are grafted and composited through an amidation reaction. The specific preparation steps are as follows:

[0023] Step 2-1, dispersing attapulgite in deionized water, stirring continuously, standing to remove upper suspended impurities, then adding deionized water and hydrogen peroxide to the above solution, stirring continuously, and centrifuging to obtain purified attapulgite, adding hydrochloric acid and deionized water to the purified attapulgite, ultrasonically dispersing, and stirring continuously, washing with deionized and anhydrous ethanol until neutral, and drying to constant weight to obtain activated attapulgite;

[0024] Step 2-2, adding the activated attapulgite to toluene, ultrasonically dispersing, heating the mixed solution under nitrogen protection, adding 3-aminopropyltrimethoxysilane, stirring to react, then filtering, purifying with anhydrous ethanol, and drying to constant weight to obtain aminopropyl functionalized attapulgite;

[0025] Step 2-3, under the protection of nitrogen, adding dichloromethane and a branched carboxyl functional monomer M-Carboxylation to the reactor, adding thionyl chloride dropwise at constant pressure, and then adding aminopropyl functionalized attapulgite, reacting at room temperature, filtering, washing with dichloromethane and deionized water in sequence, and drying to constant weight to obtain a branched carboxyl functional monomer M-Carboxylation functionalized attapulgite;

[0026] The preparation method of the branched carboxyl functional monomer M-Carboxylation is:

[0027] Step 3-1, using pentaerythritol and 5-hexynoic acid as raw materials, carrying out an esterification reaction under the catalysis of p-toluenesulfonic acid to prepare an alkynyl functional monomer M-alkynyl;

[0028] In step 3-2, a thiol-alkyne click reaction is used to initiate a thiol-alkyne addition reaction between one equivalent of an alkyne functional monomer M-alkynyl and eight equivalents of thioglycolic acid under the action of ultraviolet light, thereby preparing a branched carboxyl functional monomer M-Carboxylation.

[0029] Compared with the prior art, the present invention has the following beneficial technical effects:

[0030] The present invention first designs and synthesizes two soil improvers: rice straw biochar functionalized with polyaspartic acid and attapulgite functionalized with branched carboxyl functional monomer M-Carboxylation. Specifically,

[0031] The rice straw biochar, which has a fixation and passivation effect on cadmium and zinc in the soil, and polyaspartic acid, which has a chelation effect on cadmium and zinc in the soil, are compounded through a chemical bonding method (nucleophilic substitution reaction). Its porous structure and rich functional groups can effectively improve soil structure, balance soil pH, improve the rhizosphere environment of oak trees, and promote tree growth. Secondly, the composite material coordinates and combines with soluble cadmium and zinc in the soil through carboxyl functional groups, reducing the toxicity of cadmium and zinc and converting cadmium and zinc into an effective form that can be absorbed and utilized by oak trees. Thirdly, the composite material fixes a portion of cadmium and zinc through adsorption and passivation, promoting the stability of cadmium and zinc in the soil, thereby reducing the toxic effects of cadmium and zinc on oak trees. It also has the significant advantage of being completely biodegradable.

[0032] The attapulgite soil, which has a certain adsorption effect on cadmium and zinc in the soil, and the branched carboxyl functional monomer M-Carboxylation, which has a chelating effect on cadmium and zinc in the soil, are compounded through a chemical bonding method (amidation reaction). Its rough structure and active hydroxyl functional groups can also effectively improve soil structure and balance soil pH. On the one hand, the carboxyl functional groups and sulfur functional groups coordinate with cadmium and zinc in the soil, converting the soluble cadmium and zinc in the soil into a chelated state, reducing the toxicity of cadmium and zinc in the soil and promoting the conversion of cadmium and zinc into an effective form that can be absorbed and utilized by oak trees. On the other hand, it fixes a portion of cadmium and zinc through adsorption, passivation, and reduces the content of soluble cadmium and zinc in the rhizosphere soil.

[0033] By using amendments to chelate cadmium and zinc ions in the soil, the tree growth environment is improved, the vitality and metabolic activity of the tree roots are promoted, the tree roots' absorption of available cadmium and zinc in the soil and the oak tree's ability to transport them from the roots to the aboveground parts are enhanced, and the accumulation of cadmium and zinc in the two woody plants, white oak and natal oak, is increased, achieving the beneficial technical effect of improving the efficiency of the woody plant oak in remediating cadmium and zinc complex contaminated soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the chemical structure of rice straw biochar modified with chloropropyl functionalization;

[0035] Figure 2 and Figure 3 Two molecular configurations of rice straw biochar functionalized with polyaspartic acid;

[0036] Among them, R1 represents rice straw biochar;

[0037] Figure 4 is the chemical structural formula of attapulgite modified with aminopropyl functional group;

[0038] Figure 5 is the chemical structural formula of the alkynyl functional monomer M-alkynyl;

[0039] Figure 6 is the chemical structure of the branched carboxyl functional monomer M-Carboxylation;

[0040] Figure 7 The molecular structure of attapulgite modified by branched carboxyl functional monomer M-Carboxylation;

[0041] Among them, R2 represents attapulgite;

[0042] Figure 8 is a bar graph of cadmium concentrations in various parts of the oak tree in Examples 5, 6, and 7;

[0043] Figure 9 is a bar graph of zinc concentrations in various parts of the oak tree in Examples 5, 6, and 7;

[0044] Figure 10 The bar graphs are of the cadmium and zinc accumulation amounts of individual oak trees in Examples 5, 6, and 7;

[0045] Figure 11 This is a bar graph of the bioaccumulation coefficients of cadmium and zinc in various parts of the oak tree in Examples 5, 6 and 7. DETAILED DESCRIPTION Example 1:

[0046] Preparation of rice straw biochar functionalized with polyaspartic acid as modifier I:

[0047] Preparation of rice straw biochar: Rice straw was cleaned with deionized water, cut into 2 cm long segments, and dried at 60°C to constant weight. The segments were then placed in a muffle furnace for oxygen-limited pyrolysis. The temperature was raised to 500°C at a heating rate of 10°C / min, and the pyrolysis and carbonization were maintained at 500°C for 5 h. The segments were then cooled to room temperature and ground through a 0.25 mm sieve to obtain rice straw biochar.

[0048] Preparation of chloropropyl functionalized rice straw biochar: Take 1 part by weight of rice straw biochar, add 1.2 parts by weight of deionized water, 30 parts by weight of anhydrous ethanol, and 0.85 parts by weight of 3-chloropropyltrimethoxysilane to the rice straw biochar in sequence, first stir and react for 6 hours, then add NH3·H2O to adjust the pH to 9.5, and then continue to react for 24 hours. Finally, use deionized water and anhydrous ethanol to wash to neutrality, and dry at 60°C to constant weight to obtain chloropropyl functionalized rice straw biochar, whose structure is as follows: Figure 1 As shown;

[0049] Preparation of rice straw biochar functionalized with polyaspartic acid: 5 parts by weight of polyaspartic acid (relative molecular weight 4000, solid content 40%) was added to 95 parts by weight of deionized water, 1 part by weight of chloropropyl functionalized rice straw biochar was added to the above solution, ultrasonically dispersed for 10 minutes, stirred and condensed under reflux at 80°C for 6 hours, and then washed three times with deionized and anhydrous ethanol, and dried at 60°C to constant weight to obtain rice straw biochar functionalized with polyaspartic acid, whose molecular configuration is as follows: Figure 2 and Figure 3 shown. Example 2:

[0050] Modifier II - Preparation of attapulgite functionalized with branched carboxyl functional monomer M-Carboxylation:

[0051] Preparation of activated attapulgite: 1 part by weight of attapulgite was dispersed in 15 parts by weight of deionized water, stirred continuously for 2 hours, and allowed to stand for 2 hours to remove the upper suspended impurities. Then, 15 parts by weight of deionized water and 10 parts by weight of hydrogen peroxide (concentration 30%) were added to the above solution, stirred continuously for 5 hours, and centrifuged to obtain purified attapulgite. 1.5 parts by weight of hydrochloric acid (concentration 37.5%) and 13.8 parts by weight of deionized water were added to the purified attapulgite, ultrasonically dispersed for 0.5 hours, and stirred continuously at 80°C for 5 hours. The mixture was washed with deionized and anhydrous ethanol until neutral, and dried to constant weight at 70°C to obtain activated attapulgite.

[0052] Preparation of aminopropyl functionalized attapulgite: 1 part by weight of activated attapulgite was added to 50 parts by weight of toluene, ultrasonically dispersed for 15 minutes, and under the protection of nitrogen (60 mL / min), the mixed solution was heated to 110°C, 2 parts by weight of 3-aminopropyltrimethoxysilane was added, and stirred at 110°C for 12 hours, then filtered, purified with anhydrous ethanol, and dried at 70°C to constant weight to obtain aminopropyl functionalized attapulgite, whose structure is as follows: Figure 4 As shown;

[0053] Preparation of alkynyl functional monomer M-alkynyl: 1.36 parts by weight of pentaerythritol, 4.93 parts by weight of 5-hexynoic acid, 0.07 parts by weight of p-toluenesulfonic acid, and 2.2 parts by weight of cyclohexane water-carrying agent are added to a reactor equipped with a temperature control device, a water separation device, a nitrogen protection device, and a mechanical stirring device. The mechanical stirring, nitrogen protection, and water separation devices are turned on, and the temperature is raised to 140° C. The reaction is carried out at 140° C. for 5 hours. The product is washed with water and distilled under reduced pressure to obtain the alkynyl functional monomer M-alkynyl, whose chemical structure is as follows: Figure 5 As shown;

[0054] Preparation of branched carboxyl functional monomer M-Carboxylation: 5.12 parts by weight of functional monomer M-alkynyl, 7.36 parts by weight of thioglycolic acid, and 100 parts by weight of chloroform were added to the reactor, and after ultrasonic vibration, 0.25 parts by weight of 651 photoinitiator was added. The reactor was vacuumed and filled with nitrogen for 3 cycles and then sealed. The reactor was exposed to ultraviolet light (365 nm, 10 mW / cm 2 ) The reaction was carried out at room temperature for 2 hours. After the reaction was completed, the product was diluted with dichloromethane, precipitated with anhydrous ether, and filtered to obtain a branched carboxyl functional monomer M-Carboxylation, whose chemical structure is as follows Figure 6 As shown;

[0055] Preparation of attapulgite functionalized with branched carboxyl functional monomer M-Carboxylation: Under the protection of nitrogen (60 mL / min), 100 parts by weight of dichloromethane and 5 parts by weight of branched carboxyl functional monomer M-Carboxylation were added to the reactor, 20 parts by weight of thionyl chloride were added dropwise at constant pressure, and then 1 part by weight of aminopropyl functionalized attapulgite was added. The mixture was reacted at room temperature for 2 h, filtered, washed with dichloromethane and deionized water in turn, and dried at 50°C to constant weight to obtain attapulgite functionalized with branched carboxyl functional monomer M-Carboxylation, whose molecular configuration is as follows: Figure 7 shown. Example 3:

[0056] The measurement methods used for each measurement item index in the present invention are as follows:

[0057] (1) Determine the soil pH (potential determination method), as well as the concentrations of calcium, magnesium, and phosphorus in the soil according to the Soil Agrochemical Analysis;

[0058] (2) Determine the cation exchange capacity of soil by extraction-spectrophotometry with hexaamminecobalt trichloride (HJ889-2017).

[0059] (3) Determine the total concentration of cadmium and zinc in soil according to the “Determination of 12 Metal Elements in Soil and Sediment by Aqua Regia Extraction-Inductively Coupled Plasma Mass Spectrometry” (HJ 803-2016);

[0060] (4) Determine the available cadmium and zinc concentrations in soil according to the “Determination of 8 Available Elements in Soil by Diethylenetriaminepentaacetic Acid Extraction-Inductively Coupled Plasma Optical Emission Spectrometry” (HJ 804-2016);

[0061] (5) Determination of cadmium, zinc, calcium, magnesium, phosphorus, potassium, and sulfur in plants: 0.1 g of sample was digested with 5 mL of nitric acid and 1 mL of hydrogen peroxide and determined by ICP-MS; plant standard sample: GBW07603 (GSV-2) shrub branch and leaf component analysis standard material;

[0062] (6) The process parameters of plant heavy metal hyperaccumulation include: the concentration of heavy metals in plants, the bioaccumulation coefficient of heavy metals in plants, and the accumulation of heavy metals in plants (the ultimate indicator for judging the remediation effect);

[0063] Among them, the bioaccumulation coefficient (BCF) of a plant for a certain heavy metal element is an indicator of the ability of a specific part of a plant to absorb and accumulate heavy metals. Its formula is:

[0064] BCF PR =C PR / C S (1)

[0065] Among them, C PR Indicates the concentration of heavy metals in plant roots, C S Indicates the total concentration of heavy metals in soil;

[0066] BCF PO =C PO / C S (2)

[0067] C PO =(C PS ×M DWOPS +C PL ×M DWOPL ) / (M DWOPS +M DWOPL )(3)

[0068] Among them, C PO represents the average concentration of heavy metals in the aboveground parts of plants, C PS Indicates the concentration of heavy metals in plant stems, C PL Represents the concentration of heavy metals in plant leaves, M DWOPL Indicates the stem weight of the plant, M DWOPL Indicates the leaf dry weight of the plant. Example 4:

[0069] Test soil conditions: slightly alkaline soil (pH = 7.6) heavily contaminated with Cd (> 29 mg / kg) and Zn (> 1100 mg / kg);

[0070] Test plants: The woody plants are oaks, including Quercus alba and Quercus nata. Example 5:

[0071] Without adding any amendments, white oak and nata oak seedlings were planted in the test soil of Example 4, weeding and pest control were carried out regularly, and no additional fertilizer was applied. The cadmium and zinc contents in the planted white oak and nata oak were measured for three consecutive years to observe the remediation effects of white oak and nata oak on the cadmium-zinc composite contaminated soil. The data were measured according to the method in Example 3. The specific results are shown in Tables 1-1 to 1-7 below.

[0072] Table 1-1 Soil properties for oak tree planting (no amendments added to the soil)

[0073]

[0074] Table 1-1 Soil properties for oak tree planting (no amendments added to the soil)

[0075]

[0076] Table 1-2 Growth of oak trees planted in soil without any amendments

[0077] (The indicators for each measurement item are the average values of all oak trees planted)

[0078]

[0079] Table 1-3 Cadmium and zinc concentrations in various parts of oak trees planted in soil without any amendments

[0080]

[0081] Table 1-3 Cadmium and zinc concentrations in various parts of oak trees planted in soil without any amendments

[0082]

[0083] Table 1-4 Concentration of mineral elements in various parts of oak trees planted in soil without any amendments

[0084]

[0085] Table 1-4: Mineral element concentrations in various parts of oak trees planted in soil without any amendments

[0086]

[0087] Table 1-4: Mineral element concentrations in various parts of oak trees planted in soil without any amendments

[0088]

[0089] Table 1-5 Accumulation of cadmium and zinc in oak trees grown in soil without any amendments

[0090]

[0091] Table 1-6 Bioaccumulation coefficients of cadmium and zinc in the roots of oak trees planted in soil without any amendments

[0092]

[0093] Table 1-7 Bioaccumulation coefficients of cadmium and zinc in the aboveground parts of oak trees planted in soil without any amendments

[0094]

[0095] Table 1-7 Bioaccumulation coefficients of cadmium and zinc in the aboveground parts of oak trees planted in soil without any amendments

[0096] Example 6:

[0097] Add improver Ⅰ, according to 22.5t / hm 2 The polyaspartic acid functionalized modified rice straw biochar prepared in Example 1 was fully mixed into the topsoil (30 cm) of the test soil in Example 4, and white oak and nata oak seedlings were planted respectively. Weeding and insect control were carried out regularly without applying additional fertilizer. The cadmium and zinc contents in the planted white oak and nata oak were measured for three consecutive years to observe the effect of modifier I on the effectiveness of woody plants white oak and nata oak in repairing cadmium-zinc composite contaminated soil. The data were measured according to the method in Example 3, and the specific results are shown in the following Tables 2-1 to 2-7.

[0098] Table 2-1 Soil properties for oak planting (soil amendment Ⅰ added)

[0099]

[0100] Table 2-1 Soil Properties for Oak Planting (Soil Amendment Ⅰ Added)

[0101]

[0102] Table 2-2 Growth of oak trees planted in soil with amendment Ⅰ

[0103] (The indicators for each measurement item are the average values of all oak trees planted)

[0104]

[0105] Table 2-3 Cadmium and zinc concentrations in various parts of oak trees planted in soil with amendment Ⅰ

[0106]

[0107] Table 2-3 Cadmium and zinc concentrations in various parts of oak trees planted in soil with amendment Ⅰ

[0108]

[0109] Table 2-4 Mineral element concentrations in various parts of oak trees planted in soil with amendment Ⅰ

[0110]

[0111] Table 2-4: Mineral element concentrations in various parts of oak trees planted in soil with amendment Ⅰ

[0112]

[0113] Table 2-4: Mineral element concentrations in various parts of oak trees planted in soil with amendment Ⅰ

[0114]

[0115] Table 2-5 Accumulation of cadmium and zinc in oak trees planted in soil with amendment Ⅰ

[0116]

[0117] Table 2-6 Bioaccumulation coefficients of cadmium and zinc in the roots of oak trees planted in soil with amendment Ⅰ

[0118]

[0119] Table 2-7 Bioaccumulation coefficients of cadmium and zinc in the aboveground parts of oak trees planted in soil with amendment Ⅰ

[0120]

[0121] Table 2-7 Bioaccumulation coefficients of cadmium and zinc in the aboveground parts of oak trees planted in soil with amendment Ⅰ

[0122] Example 7

[0123] Add improver Ⅰ and improver Ⅱ at the same time, according to 22.5t / hm 2The rice straw biochar functionalized with polyaspartic acid prepared in Example 1 and the attapulgite functionalized with branched carboxyl functional monomer M-Carboxylation prepared in Example 2 were evenly compounded in a weight ratio of 1:1, and the mixture was fully mixed into the surface soil (30 cm) of the test soil in Example 4. White oak and nata oak seedlings were planted respectively, and weeding and insect control were carried out regularly without applying additional fertilizer. The cadmium and zinc contents in the planted white oak and nata oak were measured for three consecutive years, and the effects of the compounding of modifier I and modifier II on the effectiveness of the woody plants white oak and nata oak in repairing cadmium-zinc composite contaminated soil were observed. The data were measured according to the method in Example 3, and the specific results are shown in Tables 3-1 to 3-7 below.

[0124] Table 3-1 Soil properties for oak planting (both amendments I and II added to the soil)

[0125]

[0126] Table 3-1 Soil properties for oak planting (both amendments I and II added to the soil)

[0127]

[0128] Table 3-2 Growth of oak trees planted in soils with both amendments I and II

[0129] (The indicators for each measurement item are the average values of all oak trees planted)

[0130]

[0131] Table 3-3 Cadmium and zinc concentrations in various parts of oak trees planted in soils with both amendments I and II added

[0132]

[0133] Table 3-3 Cadmium and zinc concentrations in various parts of oak trees planted in soils with both amendments I and II added

[0134]

[0135] Table 3-4 Concentration of mineral elements in various parts of oak trees planted in soils with both amendments I and II added

[0136]

[0137] Table 3-4: Mineral element concentrations in various parts of oak trees planted in soils with both amendments I and II added

[0138]

[0139] Table 3-4: Mineral element concentrations in various parts of oak trees planted in soils with both amendments I and II added

[0140]

[0141] Table 3-5 Accumulation of cadmium and zinc in oak trees planted in soils with both amendments Ⅰ and Ⅱ

[0142]

[0143] Table 3-6 Bioaccumulation coefficients of cadmium and zinc in the roots of oak trees planted in soils with both amendments I and II

[0144]

[0145] Table 3-7 Bioaccumulation coefficients of cadmium and zinc in the aboveground parts of oak trees planted in soils with both amendments I and II

[0146]

[0147] Table 3-7 Bioaccumulation coefficients of cadmium and zinc in the aboveground parts of oak trees planted in soils with both amendments I and II

[0148] Example 8:

[0149] According to the data in Table 1-3, Table 2-3, Table 3-3, we can get Figure 8 、 Figure 9 ;

[0150] According to the data in Table 1-5, Table 2-5, Table 3-5, we can get Figure 10 ;

[0151] According to the data in Table 1-6, Table 1-7, Table 2-6, Table 2-7, Table 3-6, Table 3-7, the Figure 11 . Example 9:

[0152] According to Table 1-2, Table 2-2, and Table 3-2, whether it is the effect of improver I alone or the effect of improver I and improver II in combination, both modes of action can significantly improve the growth of white oak and nata oak.

[0153] according to Figure 10It can be seen that whether it is the effect of Amendment I alone or the combined effect of Amendment I and Amendment II, both modes of action can significantly increase the accumulation of cadmium and zinc in the two woody plants, Quercus alba and Quercus nata, that is, they improve the remediation efficiency of Quercus alba and Quercus nata on cadmium and zinc co-contaminated soil. Combining Tables 1-5, 2-5, and 3-5, it can be found that Amendment I alone has a greater promotion effect on the remediation effect of Quercus alba, and the combined effect of Amendment I and Amendment II can better improve the accumulation efficiency of Quercus nata on cadmium and zinc.

[0154] According to Table 1-1, Table 2-1, and Table 3-1, the total cadmium concentration and total zinc concentration in the soil fluctuated with the continuous growth of the oak trees, but the effective cadmium concentration and effective zinc concentration in the soil showed a downward trend with the continuous growth of the oak trees. Figure 10 It can be inferred that whether it is the action of Modifier I alone or the action of Modifier I and Modifier II in combination, both modes of action have a passivation effect that reduces the effective content of cadmium and zinc, and at the same time have an activation effect that increases the effective content of cadmium and zinc.

[0155] according to Figure 8 、 Figure 9 、 Figure 11 Furthermore, according to Tables 1-6, 1-7, 2-6, 2-7, 3-6, and 3-7, it can be found that the cadmium accumulation efficiency of each part of Quercus nata is significantly better than that of each part of Quercus alba. The zinc accumulation efficiency of the roots of the oak tree is significantly better than that of its stems and leaves as the growth time of the planted oak trees continues to accumulate.

[0156] According to Tables 1-4, 2-4 and 3-4, whether it is the action of improver I alone or the combined action of improver I and improver II, both modes of action have a certain promoting effect on the absorption of mineral elements in various parts of oak trees.

Claims

1. A method for repairing cadmium-zinc composite contaminated soil by using an amendment in conjunction with woody plants, characterized in that: The steps include: Step 1: preparing rice straw biochar functionalized with polyaspartic acid and attapulgite functionalized with branched carboxyl functional monomer M-carboxylation, and using the rice straw biochar functionalized with polyaspartic acid and / or the attapulgite functionalized with branched carboxyl functional monomer M-carboxylation as a soil conditioner for cadmium-zinc composite contaminated soil; The preparation method of the branched carboxyl functional monomer M-Carboxylation is: Pentaerythritol and 5-hexynoic acid were used as raw materials, and an esterification reaction was carried out under the catalysis of p-toluenesulfonic acid to prepare the alkyne functional monomer M-alkynyl. Using the thiol-alkyne click reaction, a photoinitiator initiates a thiol-alkyne addition reaction between one equivalent of alkyne functional monomer M-alkynyl and eight equivalents of thioglycolic acid under ultraviolet light to prepare a branched carboxyl functional monomer M-Carboxylation. Step 2: According to 10-35t / hm 2 The soil conditioner prepared in step 1 is fully mixed into the topsoil 20-40 cm of the weakly alkaline cadmium-zinc composite heavily contaminated soil; Step three: Plant oak seedlings and regularly weed and control insects.

2. The method for repairing cadmium-zinc composite contaminated soil by using an amendment in collaboration with woody plants according to claim 1, characterized in that: The preparation method of the polyaspartic acid functionalized rice straw biochar is as follows: first, rice straw is used to prepare rice straw biochar, then the rice straw biochar is modified to obtain chloropropyl functionalized rice straw biochar, and finally, polyaspartic acid and the chloropropyl functionalized rice straw biochar are grafted and composited through a nucleophilic substitution reaction.

3. The method for repairing cadmium-zinc composite contaminated soil by using an amendment in conjunction with woody plants according to claim 2, characterized in that: The relative molecular weight of the polyaspartic acid is 3000-6000.

4. The method for repairing cadmium-zinc composite contaminated soil by using an amendment in conjunction with woody plants according to claim 1, characterized in that: The preparation method of the attapulgite functionalized and modified by the branched carboxyl functional monomer M-Carboxylation is as follows: first, the attapulgite is activated, then the activated attapulgite is modified to obtain aminopropyl functionalized attapulgite, and finally, the branched carboxyl functional monomer M-Carboxylation and the aminopropyl functionalized attapulgite are grafted and composited through an amidation reaction.

5. The method for repairing cadmium-zinc composite contaminated soil by using an amendment in conjunction with woody plants according to claim 1, characterized in that: The woody plant oaks include white oak and nata oak.

6. The method for repairing cadmium-zinc composite contaminated soil by using an amendment in conjunction with woody plants according to claim 1, characterized in that: The woody plant oak is Quercus nata.

7. The method for repairing cadmium-zinc composite contaminated soil by using an amendment in conjunction with woody plants according to any one of claims 1 to 6, characterized in that: The addition ratio of the soil conditioner is 22.5t / hm 2 .

8. The method for repairing cadmium-zinc composite contaminated soil by using an amendment in conjunction with woody plants according to any one of claims 1 to 6, characterized in that: The soil conditioner was thoroughly mixed into the top 30 cm of soil.

9. The method for repairing cadmium-zinc composite contaminated soil by using an amendment in conjunction with woody plants according to any one of claims 1 to 6, characterized in that: The soil conditions are: Cd>29 mg / kg, Zn>1100 mg / kg, pH=7.4-7.7.

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