A remediation agent for heavy metal contaminated soil and a preparation method thereof

Abstract

The application relates to the technical field of soil pollution treatment, in particular to a remediation agent for heavy metal contaminated soil and a preparation method thereof, which comprises modified pH adjuster, rice straw, amidoxy ester, livestock and poultry manure, montmorillonite, arbuscular mycorrhizal fungus powder and klebsiella aerogens powder. 2+ Mn 4+ is oxidized into Mn 2+ by O2, the competition absorption of Cd 2+ and Mn 2+ is relieved, the selective absorption and transportation of arbuscular mycorrhizal fungi to Cd 2+ in pokeweed root systems are promoted. When the concentration of Cd 4+ is reduced, the metabolic activity of klebsiella aerogens is active, arbuscular mycorrhizal fungi provide carbon source for the klebsiella aerogens to breed massively, the modified pH adjuster gradually releases the sulfur in the inner layer, generates sulfuric acid after oxidation, creates acidic soil conditions, the klebsiella aerogens secretes citric acid to reduce Mn 2+ into Mn 2+ , so as to promote the absorption of Mn 2+ by pokeweed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil pollution remediation, and particularly relates to a remediation agent for heavy metal contaminated soil and a preparation method thereof. BACKGROUND

[0002] Soil is the basis for human survival. In recent years, with the rapid development of industrialization, soil pollution problems have become increasingly serious. In the soil of mineral resource development areas, due to problems such as mining waste, tailings, smelting slag, etc., the content of heavy metals in the soil is seriously over-standard. The content of heavy metals such as manganese and cadmium in the soil of manganese mining areas is extremely high. The soil polluted by manganese is acidic, which can cause manganese poisoning of plants, resulting in the inability of plants near the manganese mining area to grow. High concentrations of cadmium have strong migration in acidic soil and enter the food chain through farmland near the manganese mining area. The accumulation of high concentrations of cadmium in the human body can cause various diseases and harm human health.

[0003] American pokeweed is widely studied for phytoremediation of heavy metal contaminated soil due to its high absorption and accumulation of cadmium and manganese. It has a large biomass, grows rapidly, is a perennial herbaceous plant, and can remove heavy metals in the soil by repeatedly harvesting stems and leaves. However, when American pokeweed absorbs Cd 2+ and Mn 2+ , Cd 2+ and Mn 2+ are both divalent cations, which compete for the same transport protein (such as the ZIP family) on the root cell membrane of American pokeweed. High Mn 2+ environment inhibits the absorption of Cd 2+ , and vice versa, which leads to mutual inhibition between high concentrations of Cd 2+ and Mn 2+ , reducing the remediation rate of American pokeweed. And when both are excessive, they interfere with the metabolism of essential elements such as calcium and iron, causing leaf yellowing and root browning, resulting in reduced biomass of American pokeweed, reduced remediation rate, the need for continuous replanting, and increased remediation cost. SUMMARY

[0004] (1) Technical problem to be solved

[0005] The purpose of the present application is to provide a remediation agent for heavy metal contaminated soil and a preparation method thereof, which can alleviate the problem of mutual inhibition of high concentrations of manganese and cadmium when American pokeweed is planted in manganese mining areas, and significantly improve the remediation rate of American pokeweed in large areas of soil pollution in manganese mining areas.

[0006] (2) Technical solution

[0007] To achieve the above object, in one aspect, the application provides a remediation agent for heavy metal contaminated soil, comprising the following raw materials in parts by mass: modified pH regulator 30-50 parts, rice straw 5-10 parts, livestock and poultry manure 1-5 parts, montmorillonite 3-6 parts, amine brilliant ester 1-5 parts, arbuscular mycorrhizal fungi powder 10-15 parts, and gas-producing Klebsiella powder 10-15 parts.

[0008] Further, the preparation method of the modified pH regulator comprises the following steps:

[0009] S11. Screen the sulfur particles, select uniform particles with a particle size of 0.5-1 mm, repeat rinsing with 5% H2SO4 for 2-3 times, slightly etch the surface of the sulfur particles, rinse with deionized water, and dry at 60°C for 2 hours to remove water;

[0010] S12. Dissolve PLA in acetone, stir uniformly, and prepare a 15% w / v PLA solution;

[0011] S13. Use a sulfurization bed coater to spray the PLA solution onto the surface of the sulfur particles at 40-50°C, repeat spraying 2-3 times, form a PLA layer with a thickness of 100-150 μm, and obtain a first mixture;

[0012] S14. Dry the first mixture in a vacuum drying oven at 40°C for 12 hours to ensure complete curing of the PLA layer;

[0013] S15. Grind CaCO3 to 100-150 μm, dry at 60°C to remove water, and the water content is <1%;

[0014] S16. Place the first mixture in a rotary drum coater, spray PVA adhesive, uniformly sprinkle CaCO3 onto the surface of the first mixture, repeat spraying PVA and sprinkling CaCO3 until a lime outer layer with a thickness of 400-450 μm is formed, obtain a second mixture, and the rotation speed is controlled at 20-30 rpm;

[0015] S17. Dry the second mixture at 30-40°C for 6-8 hours to ensure complete curing of the PVA adhesive, and obtain the modified pH regulator.

[0016] Further, in the preparation method of the modified pH regulator, the mass ratio of sulfur, PLA, and CaCO3 is 1-1.5:0.3-0.5:3-5.

[0017] Further, the livestock and poultry manure is prepared by flatly laying chicken manure in a closed compost container, sprinkling lime on the surface, adding EM bacteria, adding corn straw, and performing fermentation composting treatment at 30-35°C.

[0018] Further, the preparation method of the arbuscular mycorrhizal fungus powder comprises the following steps:

[0019] S21. inoculate the arbuscular mycorrhizal fungus into a PDA culture medium plate, and place it in a temperature of 24-28℃ for activation culture for 3-5 days;

[0020] S22. re-inoculate the activated culture strain into a liquid culture medium, and perform liquid culture under the condition of a constant temperature of 24-28℃ and a rotation speed of 150-200 r / min for 1-2 days to obtain a liquid culture seed liquid;

[0021] S23. mix the liquid culture seed liquid and a solid culture medium according to an inoculation amount of 6% by weight of the solid culture medium, perform fermentation in a fermentation tray under a temperature of 24-28℃ and a relative humidity of 75-80% until the surface of the solid culture medium is full of spores, and then perform low-temperature drying under a temperature of 25-30℃, crushing to obtain the arbuscular mycorrhizal fungus powder.

[0022] Further, the PDA culture medium comprises the following components: potato 20 parts, glucose 2 parts, agar 1.5 parts, and distilled water 100 parts.

[0023] Further, the liquid culture medium comprises the following components: starch 20 parts, glucose 2 parts, peptone 0.8 parts, KH2PO4 0.2 parts, and distilled water 100 parts.

[0024] Further, the solid culture medium comprises the following components: starch 20 parts, peptone 2 parts, agar 1.5 parts, corn flour 0.8 parts, and KH2PO4 0.2 parts.

[0025] Further, the Klebsiella aerogens is prepared into a Klebsiella aerogens powder according to the preparation method of the arbuscular mycorrhizal fungus powder.

[0026] On the other hand, based on the same inventive concept, the present application further provides a preparation method of a remediation agent for heavy metal contaminated soil, which is applied to the remediation agent for heavy metal contaminated soil and comprises the following steps:

[0027] S31. prepare a modified pH regulator;

[0028] S32. prepare arbuscular mycorrhizal fungus powder and Klebsiella aerogens powder;

[0029] S33. weigh each raw material according to a proportion, perform drying treatment, and fully mix the dried raw materials to obtain the remediation agent for heavy metal contaminated soil;

[0030] S34. evenly spread the prepared remediation agent on the surface layer of soil, and the application amount is 2 kg / ㎡;

[0031] S35. The repair agent is mixed with the surface layer of 20-30 cm soil using a rotary cultivator. The soil to which the repair agent is applied is tilled once a day. After 5-10 days, when the soil is stable, the pokeweed seedlings are planted in the soil and post-maintenance is performed.

[0032] S36. The pokeweed stems and leaves are repeatedly harvested and subjected to ashing and recycling.

[0033] The mechanism of action of the above raw material components is as follows:

[0034] The modified pH regulator is a multi-layer composite structure, the outermost layer of which is lime, which is a good heavy metal fixative. By increasing the alkalinity of the soil, it promotes the formation of hydroxides of Mn 2+ , Cd 2+ , achieving the purpose of adsorbing and fixing heavy metals. The lime used here is CaCO3, which has a slow but lasting effect. In the acid soil of a manganese mine, H + ions are consumed to generate neutral water and carbon dioxide, thereby reducing the acidity. After the acid in the soil is neutralized, the residual CaCO3 continues to hydrolyze to generate OH-ions to maintain the alkaline environment of the soil and provide a certain buffering capacity. Under the alkaline conditions provided by CaCO3, the active Mn 2+ in the soil and the Mn 2+ fixed by arbuscular mycorrhizal fungi are oxidized to Mn 4+ by O2, alleviating the mutual inhibition of Mn 2+ and Cd 2+ , promoting the selective absorption and transport of Cd 2+ by arbuscular mycorrhizal fungi to the roots of pokeweed, and enhancing the absorption of Cd 2+ by pokeweed. As the outer layer of the modified pH regulator dissolves and CaCO3 is fully utilized, the PLA slow-release layer is exposed, and the sulfur in the innermost layer of the pH regulator is slowly released and oxidized to sulfuric acid by soil microorganisms, creating acidic soil conditions. The citric acid secreted by Klebsiella aerogenes reduces Mn 4+ to Mn 2+ in the acidic soil, so that Mn 2+ is absorbed by pokeweed.

[0035] The hyphae of arbuscular mycorrhizal fungi directly or chelate the Mn 2+ in the soil through cell wall components such as chitin and glucose, reducing its mobility and isolating part of the Mn 2+ in the fungal vacuoles, reducing direct toxicity to plants. The organic acids secreted by arbuscular mycorrhizal fungi reduce the rhizosphere pH, promote the conversion of cadmium from insoluble to soluble state, and enhance the absorption of Cd 2+In addition to absorption, arbuscular mycorrhizal fungi expand the absorption range of the root system through their hyphal networks, increasing the contact area of ​​the plant with heavy metals, thereby enhancing the ability of American pokeweed roots to accumulate heavy metals. At the same time, the hyphal network of arbuscular mycorrhizal fungi can provide a carbon source for Klebsiella pneumoniae, promoting the growth and reproduction of Klebsiella pneumoniae.

[0036] Klebsiella pneumoniae is in a dormant state at high cadmium concentrations, but Cd is passively bound to its cell surface. 2+ This shows a preference for Cd 2+ High adsorption capacity of Cd. 2+ As the concentration decreases, *Klebsiella pneumoniae* becomes metabolically active, secreting citric acid that binds to Mn2+ associated with globulin. 2+ This forms a soluble complex, competitively dissociating manganese from its fixed state. Furthermore, in acidic soil created by sulfur released from the inner layer of the modified pH adjuster, citric acid secreted by *Klebsiella pneumoniae* will bind Mn... 4+ Reduce to Mn 2+ This prompted American pokeweed to target Mn 2+ Absorption.

[0037] Rice straw is a natural plant fiber. When crushed to 5-8 cm and mixed into the soil, the humus produced after the decomposition of rice straw acts as a soil binder, promoting soil aggregate formation, enhancing soil permeability, aiding oxygen diffusion, and promoting Mn production under alkaline conditions. 2+ Oxidized by O2 to Mn 4+ This alleviated the impact of American pokeweed on Mn. 2+ and Cd 2+ Competition for absorption increased the absorption efficiency of American pokeweed.

[0038] DA-6 is a highly efficient, broad-spectrum plant growth regulator. It is chemically stable, does not easily decompose at room temperature, and is non-toxic and residue-free, making it widely used in agricultural production. DA-6 can increase the content of chlorophyll, protein, and nucleic acid in plants, enhance photosynthetic efficiency, promote carbon and nitrogen metabolism, regulate the balance of endogenous hormones, thereby promoting cell division, root development, and stem and leaf growth. It can also enhance plant stress resistance, delay senescence, and improve yield and quality.

[0039] Livestock and poultry manure is made by spreading chicken manure evenly in a sealed composting container, adding rice straw, and fermenting and composting it at 30-35℃. It is rich in nitrogen, phosphorus, potassium, organic matter, and beneficial microorganisms, which can improve the physical and chemical properties of the soil, thereby enhancing the disease resistance and growth vitality of crops. Furthermore, the increased organic matter content enhances ion exchange capacity; therefore, livestock and poultry manure acts as a pH-stabilizing buffer, mitigating the impact of modified pH adjusters on soil acidity and alkalinity, and preventing the soil from becoming excessively acidic or alkaline.

[0040] Montmorillonite is a clay mineral with high cation exchange capacity and layered structure, which releases calcium, magnesium and other basic cations under acidic conditions, neutralizes H + ; under alkaline conditions, OH - is adsorbed, H + is released, thereby slowing down the pH change and preventing the fluctuation from affecting soil health.

[0041] (2) Beneficial effects

[0042] Compared with the prior art, the beneficial effects of the present application are:

[0043] 1. The modified pH regulator and arbuscular mycorrhizal fungi play a synergistic effect, which fixes Mn 2+ , and then uses the alkaline conditions created by the outermost CaCO3 of the modified pH regulator to promote the oxidation of Mn 2+ to Mn 4+ , while Cd 2+ is activated by arbuscular mycorrhizal fungi, which relieves the competitive absorption of Mn 2+ and Cd 2+ , and promotes the absorption of Cd 2+ by Phytolacca americana.

[0044] 2. The modified pH regulator and Klebsiella aerogens play a synergistic effect, and after the action of the outermost CaCO3 of the modified pH regulator is completed, the PLA layer is exposed, which gradually decomposes in the soil and releases the inner sulfur, which is oxidized to sulfuric acid under the action of microorganisms, creating acidic soil conditions. Klebsiella aerogens is metabolically active at low cadmium concentrations, and the excreted citric acid reduces Mn 4+ to Mn 2+ in acidic soil, promoting the absorption of Mn 2+ by Phytolacca americana.

[0045] 3. Compared with the traditional single remediation technology, the present application uses a combination of fixing agent-microorganism-plant technologies, which takes the advantages of each other and can more effectively remove heavy metals in the soil. Phytolacca americana preferentially absorbs Cd 2+ in the soil under the action of the remediation agent, when the concentration of Cd 2+ decreases, Mn 4+ is reduced to Mn 2+ , and Mn 2+ is absorbed by Phytolacca americana, which relieves the mutual inhibition of Cd 2+ and Mn 2+ , and improves the absorption of Cd 2+ and Mn 2+ by Phytolacca americana. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1SEM image of modified pH regulator for Example 1 of the present application;

[0047] Figure 2 American pokeweed map for applying repair agent to Example 1 of the present application;

[0048] Figure 3 American pokeweed map for Example 3 of the present application without applying repair agent. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0050] The test equipment and preparations of the following described embodiments are as follows:

[0051] Electronic balance (Germany Sartorius), electric heating air constant temperature dryer (Shanghai Fuma Experimental Equipment), screening machine (Henan Meilong Machinery), pH meter (Shanghai Precision Scientific Instruments), fluidized bed coating machine (Cailong Machinery Technology), vacuum drying oven (Shanghai Jeteng), drum coating machine (Donglong Machinery), scanning electron microscope (Germany Zeiss), agate mortar (Shanghai Jetu Electronic Technology), microwave digestion instrument (Shanghai Xinyi), inductively coupled plasma emission spectrometer (Thermo Fisher); arbuscular mycorrhizal fungi and Klebsiella aerogens were purchased from Beijing Bomingjiye Science and Technology Instrument Technology Co., Ltd., livestock and poultry manure was purchased from Botou Hongtai Intelligent Technology Co., Ltd., rice straw was purchased from Xindeng Agricultural Products, chemical drugs and reagents were purchased from Sigma-Aldrich Company.

[0052] Example 1

[0053] The present embodiment discloses a repair agent for heavy metal contaminated soil, which comprises the following raw materials in parts by mass: modified pH regulator 30 parts, rice straw 5 parts, livestock and poultry manure 1 part, montmorillonite 3 parts, amine ester 1 part, arbuscular mycorrhizal fungus powder 10 parts, and Klebsiella aerogens powder 10 parts.

[0054] It should be noted that in the contaminated soil of the manganese mine area, Cd 2+ and Mn 2+ are both divalent cations, which will compete for the same transport protein (such as ZIP family) on the root cell membrane of American pokeweed, high Mn 2+ environment inhibits the absorption of Cd 2+ , and vice versa, which leads to high concentrations of Cd 2+ and Mn 2+The interaction between these substances reduces the remediation rate of American pokeweed. Furthermore, excessive amounts of both can interfere with the metabolism of essential elements such as calcium and iron, leading to leaf yellowing, root browning, and a decrease in American pokeweed biomass. This further reduces the remediation rate, necessitating continuous replanting and increasing remediation costs. Therefore, it is crucial to use a remediation agent to condition the soil before planting American pokeweed. The modified pH adjuster and arbuscular mycorrhizal fungi in the remediation agent can not only adsorb and fix manganese and cadmium in the soil, but the outermost CaCO3 layer of the modified pH adjuster also creates alkaline conditions (pH = 7.5–8) in the soil. Rice straw enhances soil aeration, facilitates O2 diffusion, and promotes the growth of manganese and cadmium. 2+ It is oxidized to Mn by O2 under alkaline conditions. 4+ The organic acids secreted by arbuscular mycorrhizal fungi lower the rhizosphere pH, promote the conversion of cadmium from an insoluble to a soluble state, and enhance the Cd concentration. 2+ The activity of Mn was thus alleviated. 2+ and Cd 2+ The mutual inhibition effect, and the low concentration of Mn 2+ Promote the export of Cd from American pokeweed 2+ Absorption. Klebsiella pneumoniae is in a dormant state under high cadmium concentrations, and its cell surface passively binds cadmium, exhibiting a high adsorption capacity for cadmium. When Cd... 2+ As the concentration of [acid / sulfur] gradually decreases, *Klebsiella pneumoniae* begins to metabolize more actively. After the outermost layer of CaCO3 in the modified pH adjuster is fully reacted, the PLA layer is exposed. This PLA layer gradually decomposes in the soil, releasing the innermost layer of sulfur. Under the action of microorganisms, this sulfur is oxidized to sulfuric acid, creating acidic soil conditions (pH = 5.5–6). The citric acid secreted by the metabolically active *Klebsiella pneumoniae* then converts Mn [acid / sulfur] into sulfuric acid under these acidic conditions. 4+ Reduce to Mn 2+ At this time, the low concentration of Cd 2+ Under these conditions, promote the absorption of Mn by American merchants 2+ The absorption of carbon by arbuscular mycorrhizal fungi is also facilitated. Simultaneously, the mycelial network of arbuscular mycorrhizal fungi can provide a carbon source for Klebsiella pneumoniae, promoting its growth and reproduction.

[0055] Meanwhile, modified pH adjusters, arbuscular mycorrhizal fungi, and Klebsiella pneumoniae reduce Cd in the soil by immobilizing, adsorbing, and complexing heavy metals. 2+ and Mn 2+ Its mobility improves the soil environment and avoids high concentrations of Cd. 2+ and Mn 2+ It is toxic to American pokeweed, affecting its growth and reproduction.

[0056] The preparation method of the modified pH adjuster includes the following steps:

[0057] S11. Screen the sulfur particles, select the uniform particles with a particle size of 0.5-1 mm, repeat the rinsing with 5% H2SO4 for 2-3 times, slightly corrode the surface of the sulfur particles, rinse with deionized water, and dry at 60°C for 2 hours to remove water;

[0058] S12. Dissolve PLA in acetone, stir uniformly, and prepare a 15% w / v PLA solution;

[0059] S13. Use a fluidized bed coater to spray the PLA solution onto the surface of the sulfur particles at 40-50°C, repeat the spraying for 2-3 times, form a PLA layer with a thickness of 100-150 μm, and obtain a first mixture;

[0060] S14. Dry the first mixture in a vacuum drying oven at 40°C for 12 hours to ensure complete curing of the PLA layer;

[0061] S15. Grind CaCO3 to 100-150 μm, dry at 60°C to remove water, and the water content is <1%;

[0062] S16. Put the first mixture into a drum coater, spray PVA adhesive, uniformly sprinkle CaCO3 on the surface of the first mixture, repeat the spraying of PVA and the sprinkling of CaCO3 until a lime outer layer with a thickness of 400-450 μm is formed, obtain a second mixture, and the rotation speed is controlled at 20-30 rpm;

[0063] S17. Dry the second mixture at 30-40°C for 6-8 hours to ensure complete curing of the PVA adhesive, and obtain a modified pH regulator.

[0064] It should be noted that the modified pH regulator is a multi-layer composite structure, the outermost layer is CaCO3, which gradually dissolves in 0-3 months, and the soil pH rises to 7.5-8. After the complete action of CaCO3, the PLA layer is exposed, which gradually degrades in 3-5 months to release the innermost sulfur, which is oxidized to sulfuric acid under the action of microorganisms, and the pH gradually decreases to 5.5-6. The gradual degradation process of PLA provides a buffering effect for the change of soil acidity and alkalinity, preventing the pH from changing too much in a short time to affect the health of the soil. The modified pH regulator prepared by the method has clear layers and controllable slow release.

[0065] Use a scanning electron microscope (SEM) to observe the cross section of the modified pH regulator as shown in Figure 1 It can be seen that the PLA layer and the lime layer are complete without cracks and peeling.

[0066] In the preparation method of the modified pH regulator, the mass ratio of sulfur, PLA, and CaCO3 is 1:0.3:3.

[0067] The livestock and poultry manure is prepared by fermenting and composting chicken manure in a closed compost container, spreading lime on the surface, adding EM bacteria and corn stalks, and fermenting at 30-35 DEG C.

[0068] The preparation method of the arbuscular mycorrhizal fungus powder comprises the following steps:

[0069] S21. The arbuscular mycorrhizal fungus is inoculated onto a PDA culture medium plate and activated and cultured at a temperature of 24-28 DEG C for 3-5 days;

[0070] S22. The activated and cultured strain is further inoculated into a liquid culture medium, and liquid culture is carried out at a constant temperature of 24-28 DEG C and a rotation speed of 150-200 r / min for 1-2 days to obtain a liquid culture seed liquid;

[0071] S23. The liquid culture seed liquid and the solid culture medium are mixed according to a inoculation amount of 6% by weight of the solid culture medium, fermentation is carried out in a fermentation tray at 24-28 DEG C and a relative humidity of 75-80%, until the surface of the solid culture medium is covered with spores, fermentation is completed, low-temperature drying is carried out at 25-30 DEG C, and crushing is carried out to obtain the arbuscular mycorrhizal fungus powder.

[0072] The PDA culture medium comprises the following components: 20 parts of potatoes, 2 parts of glucose, 1.5 parts of agar and 100 parts of distilled water.

[0073] The liquid culture medium comprises the following components: 20 parts of starch, 2 parts of glucose, 0.8 parts of peptone, 0.2 parts of KH2PO4 and 100 parts of distilled water.

[0074] The solid culture medium comprises the following components: 20 parts of starch, 2 parts of peptone, 1.5 parts of agar, 0.8 parts of corn flour and 0.2 parts of KH2PO4.

[0075] The Klebsiella aerogens powder is prepared according to the preparation method of the arbuscular mycorrhizal fungus powder.

[0076] A preparation method of a remediation agent for heavy metal contaminated soil comprises the following steps:

[0077] S31. A modified pH regulator is prepared;

[0078] S32. An arbuscular mycorrhizal fungus powder and a Klebsiella aerogens powder are prepared;

[0079] S33. The raw materials are weighed according to a proportion, dried, and fully mixed to obtain the remediation agent for heavy metal contaminated soil;

[0080] S34. The prepared remediation agent is uniformly spread on the surface layer of the soil at an application amount of 2 kg / m2;

[0081] S35. Mix the repair agent with the surface layer 20-30 cm of soil with a rotary cultivator, and turn over the soil with the repair agent once a day, and after 5-10 days, when the soil is stable, plant the pokeweed seedlings in the soil and carry out later maintenance;

[0082] S36. Repeat the harvesting of the pokeweed stems and leaves, and carry out ashing and recycling.

[0083] Example 2

[0084] The embodiment discloses a repair agent for heavy metal contaminated soil, which comprises the following raw materials in parts by mass: modified pH regulator 35 parts, rice straw 7 parts, livestock and poultry manure 2 parts, montmorillonite 4 parts, amaranth 2 parts, arbuscular mycorrhizal fungus powder 12 parts, and gas-producing Klebsiella powder 12 parts.

[0085] The preparation method of the modified pH regulator, the arbuscular mycorrhizal fungus powder and the gas-producing Klebsiella powder of the embodiment is consistent with that in Example 1. The preparation method of the repair agent for heavy metal contaminated soil of the embodiment is consistent with that in Example 1.

[0086] Example 3

[0087] The embodiment discloses a repair agent for heavy metal contaminated soil, which comprises the following raw materials in parts by mass: modified pH regulator 45 parts, rice straw 9 parts, livestock and poultry manure 4 parts, montmorillonite 5 parts, amaranth 4 parts, arbuscular mycorrhizal fungus powder 13 parts, and gas-producing Klebsiella powder 13 parts.

[0088] The preparation method of the modified pH regulator, the arbuscular mycorrhizal fungus powder and the gas-producing Klebsiella powder of the embodiment is consistent with that in Example 1. The preparation method of the repair agent for heavy metal contaminated soil of the embodiment is consistent with that in Example 1.

[0089] Example 4

[0090] The embodiment discloses a repair agent for heavy metal contaminated soil, which comprises the following raw materials in parts by mass: modified pH regulator 50 parts, rice straw 10 parts, livestock and poultry manure 5 parts, montmorillonite 6 parts, amaranth 5 parts, arbuscular mycorrhizal fungus powder 15 parts, and gas-producing Klebsiella powder 15 parts.

[0091] The preparation method of the modified pH regulator, the arbuscular mycorrhizal fungus powder and the gas-producing Klebsiella powder of the embodiment is consistent with that in Example 1. The preparation method of the repair agent for heavy metal contaminated soil of the embodiment is consistent with that in Example 1.

[0092] Example 5

[0093] The embodiment differs from Example 1 in that in the preparation method of the modified pH regulator, the mass ratio of sulfur, PLA and CaCO3 is 1.5:0.5:5.

[0094] The embodiment discloses a remediation agent for heavy metal contaminated soil, which mainly comprises the following raw materials in parts by mass: modified pH regulator 30 parts, rice straw 5 parts, livestock and poultry manure 1 part, montmorillonite 3 parts, amaranth 1 part, arbuscular mycorrhizal fungus powder 10 parts and gas-producing Klebsiella powder 10 parts.

[0095] The preparation method of the modified pH regulator, the arbuscular mycorrhizal fungus powder and the gas-producing Klebsiella powder of the embodiment is consistent with that of embodiment 1. The preparation method of the remediation agent for heavy metal contaminated soil of the embodiment is consistent with that of embodiment 1.

[0096] Embodiment 6

[0097] The embodiment differs from embodiment 1 in that the modified pH regulator does not contain CaCO3.

[0098] The embodiment discloses a remediation agent for heavy metal contaminated soil, which mainly comprises the following raw materials in parts by mass: modified pH regulator 30 parts, rice straw 5 parts, livestock and poultry manure 1 part, montmorillonite 3 parts, amaranth 1 part, arbuscular mycorrhizal fungus powder 10 parts and gas-producing Klebsiella powder 10 parts.

[0099] The preparation method of the modified pH regulator comprises the following steps:

[0100] S11. The sulfur particles are sieved, and uniform particles with a particle size of 0.5-1 mm are selected. The sulfur particles are repeatedly washed with 5% H2SO4 for 2-3 times to slightly corrode the surface of the sulfur particles, and then washed with deionized water and dried at 60°C for 2 hours to remove water;

[0101] S12. PLA is dissolved in acetone and stirred uniformly to prepare a 15% w / v PLA solution;

[0102] S13. The PLA solution is atomized and sprayed onto the surface of the sulfur particles at 40-50°C using a sulfurization bed coating machine, and the spraying is repeated for 2-3 times to form a PLA layer with a thickness of 100-150 μm, thereby obtaining a first mixture;

[0103] S14. The first mixture is dried in a vacuum drying box at 40°C for 12 hours to ensure that the PLA layer is completely cured, thereby obtaining the modified pH regulator.

[0104] In the preparation method of the modified pH regulator, the mass ratio of sulfur to PLA is 1:0.3.

[0105] The preparation method of the arbuscular mycorrhizal fungus powder and the gas-producing Klebsiella powder of the embodiment is consistent with that of embodiment 1. The preparation method of the remediation agent for heavy metal contaminated soil of the embodiment is consistent with that of embodiment 1.

[0106] Embodiment 7

[0107] The difference between this embodiment and embodiment 1 is that the modified pH regulator does not contain PLA.

[0108] This embodiment discloses a remediation agent for heavy metal contaminated soil, which mainly comprises the following raw materials in parts by mass: modified pH regulator 30 parts, rice straw 5 parts, livestock and poultry manure 1 part, montmorillonite 3 parts, amine oxides 1 part, arbuscular mycorrhizal fungus powder 10 parts, and gas-producing Klebsiella powder 10 parts.

[0109] The preparation method of the modified pH regulator comprises the following steps:

[0110] S11. Screen the sulfur particles, select uniform particles with a particle size of 0.5-1 mm, repeat rinsing with 5% H2SO4 for 2-3 times, slightly etch the surface of the sulfur particles, rinse with deionized water, and dry at 60°C for 2 hours to remove water;

[0111] S12. Grind CaCO3 to 100-150 μm, dry at 60°C to remove water, and the water content is <1%;

[0112] S13. Put the sulfur into a drum coater, spray PVA adhesive, uniformly sprinkle CaCO3 on the surface of the sulfur, repeat spraying PVA and sprinkling CaCO3 until a lime outer layer with a thickness of 400-450 μm is formed, to obtain a first mixture, and the rotation speed is controlled at 20-30 rpm;

[0113] S14. Dry the first mixture at 30-40°C for 6-8 hours to ensure complete curing of the PVA adhesive, to obtain the modified pH regulator.

[0114] In the preparation method of the modified pH regulator, the mass ratio of sulfur to CaCO3 is 1:3.

[0115] The preparation method of the arbuscular mycorrhizal fungus powder and the gas-producing Klebsiella powder of this embodiment is consistent with that of embodiment 1. The preparation method of the remediation agent for heavy metal contaminated soil of this embodiment is consistent with that of embodiment 1.

[0116] Embodiment 8

[0117] The difference between this embodiment and embodiment 1 is that the modified pH regulator does not contain sulfur.

[0118] This embodiment discloses a remediation agent for heavy metal contaminated soil, which mainly comprises the following raw materials in parts by mass: modified pH regulator 30 parts, rice straw 5 parts, livestock and poultry manure 1 part, montmorillonite 3 parts, amine oxides 1 part, arbuscular mycorrhizal fungus powder 10 parts, and gas-producing Klebsiella powder 10 parts.

[0119] The preparation method of the modified pH regulator comprises the following steps:

[0120] S11. Grind CaCO3 to 100-150 μm, dry at 60°C to remove moisture, moisture <1%;

[0121] S12. Put PLA particles into a drum coater, spray PVA binder, evenly sprinkle CaCO3 on the surface of PLA, repeat spraying PVA and sprinkling CaCO3 until a lime outer layer with a thickness of 400-450 μm is formed, to obtain a first mixture, the rotation speed is controlled at 20-30 rpm;

[0122] S13. Dry the first mixture at 30-40°C for 6-8 hours to ensure complete curing of the PVA binder, to obtain a modified pH regulator.

[0123] In the preparation method of the modified pH regulator, the mass ratio of PLA to CaCO3 is 0.3:3.

[0124] The preparation method of the arbuscular mycorrhizal fungus powder and the preparation method of the Klebsiella aerogens powder in this embodiment are consistent with those in Embodiment 1. The preparation method of the remediation agent for heavy metal contaminated soil in this embodiment is consistent with that in Embodiment 1.

[0125] Control group 1

[0126] The difference between this embodiment and Embodiment 1 is that the modified pH regulator is not contained.

[0127] The remediation agent for heavy metal contaminated soil disclosed in this embodiment comprises the following raw materials in parts by mass: rice straw 5 parts, livestock and poultry manure 1 part, montmorillonite 3 parts, amine oxides 1 part, arbuscular mycorrhizal fungus powder 10 parts, and Klebsiella aerogens powder 10 parts.

[0128] The preparation method of the arbuscular mycorrhizal fungus powder and the preparation method of the Klebsiella aerogens powder in this embodiment are consistent with those in Embodiment 1. The preparation method of the remediation agent for heavy metal contaminated soil in this embodiment is consistent with that in Embodiment 1.

[0129] Control group 2

[0130] The difference between this embodiment and Embodiment 1 is that the arbuscular mycorrhizal fungus powder and the Klebsiella aerogens powder are not contained.

[0131] The remediation agent for heavy metal contaminated soil disclosed in this embodiment comprises the following raw materials in parts by mass: modified pH regulator 33 parts, rice straw 6 parts, livestock and poultry manure 2 parts, montmorillonite 4 parts, and amine oxides 2 parts.

[0132] The preparation method of the modified pH regulator in this embodiment is consistent with that in Embodiment 1. The preparation method of the remediation agent for heavy metal contaminated soil in this embodiment is consistent with that in Embodiment 1.

[0133] Control group 3

[0134] This example is a blank control group, without adding the repair agent.

[0135] This example is a preparation method of a repair agent for heavy metal contaminated soil, consistent with example 1.

[0136] Test verification: In the Jiangxi Ganzhou Nankang manganese mine area, dig a good planting pit, the specification of the planting pit is: 200-250 cm long, 150-200 cm wide, 20-30 cm deep; The spacing between each planting pit is 5-6 meters. The prepared repair agent is evenly applied on the surface of the soil in each planting pit, the application amount is 2 kg / ㎡, and the repair agent is mixed with the surface layer 20-30 cm soil by rotary tiller, the soil with the repair agent is turned over once a day, after 5-10 days, 25 Phytolacca americana seedlings are planted in the soil, the survival number of Phytolacca americana is checked every month, and the survival rate is calculated.

[0137] The concentration of Cd 2+ and Mn 2+ absorbed by Phytolacca americana is calculated: after Phytolacca americana matures, the stems and leaves are harvested every other month, the stems and leaves are soaked in 0.2% dilute nitric acid for 6 hours in a clean space, then the stems and leaves are continuously washed with ultrapure water to remove surface impurities, placed in an oven at 60°C and dried to constant weight, crushed with a marbled mortar, sieved through a 60-100 mesh sieve, and 0.5g of sieved sample is weighed into a digestion tube, 6mL of concentrated nitric acid and 2mL of hydrogen peroxide are added, and the temperature is raised to 180°C according to the microwave digestion instrument program, then cooled and diluted to 50mL, and the concentration of Cd 2+ and Mn 2+ is detected by inductively coupled plasma optical emission spectrometer (ICP-OES).

[0138] Table 1 Survival rate of Phytolacca americana in example group and control group

[0139] Group January February March April May June Example 1 88％ 72％ 72％ 64％ 64％ 64％ Example 2 80％ 76％ 76％ 76％ 76％ 76％ Example 3 100％ 96％ 96％ 96％ 96％ 96％ Example 4 96％ 92％ 92％ 92％ 88％ 88％ Example 5 76％ 68％ 68％ 68％ 68％ 68％ Example 6 28％ 28％ 20％ 16％ 16％ 12％ Example 7 64％ 60％ 60％ 52％ 52％ 52％ Example 8 48％ 40％ 40％ 32％ 32％ 32％ Control 1 36％ 28％ 20％ 20％ 20％ 16％ Control 2 60％ 52％ 36％ 36％ 36％ 36％ Control 3 20％ 12％ 12％ 8％ 8％ 8％

[0140] Table 2 Cd 2+ and Mn 2+ content in stems and leaves of Phytolacca americana in example group and control group

[0141]

[0142]

[0143]

[0144] The survival of Phytolacca americana in the example group and the control group is shown in Table 1. As can be seen from the data in Table 1, the survival rate of Phytolacca americana in the control group 3 without adding the repair agent is significantly lower than that in example 1, and the survival rate of Phytolacca americana in the control group 2 is significantly lower than that in example 2. Figure 2As can be seen, the American pokeweed in Example 1 with the addition of the repair agent has lush branches and leaves, and the leaves are emerald green, while Figure 3 The leaves of the American pokeweed in the control group 3 without the addition of the repair agent are yellow and dry, and the branches and leaves are sparse. In comparison with the control group 1, the survival rate of the American pokeweed in Example 1 with the modified pH regulator is obviously increased, indicating that the modified pH regulator plays an important role in improving the soil environment for the growth of the American pokeweed. In comparison with Example 1, the survival rates of the American pokeweed in Example 5 are different, which may be related to the different mass ratios of the main components of the modified pH regulator, i.e., sulfur, PLA and CaCO3. By optimizing the ratios of these components, the role of the modified pH regulator in the survival of the American pokeweed can be further played. In Example 1, 2, 3 and 4, the survival rates of the American pokeweed in different examples are different, which may be related to the different ratios of the components in the modified pH regulator, the arbuscular mycorrhizal fungus powder and the Klebsiella aerogens powder in each example. By optimizing the ratios of these components, the role of the repair agent for the heavy metal contaminated soil in the survival of the American pokeweed can be further played.

[0145] The contents of Cd 2+ and Mn 2+ in the stems and leaves of the American pokeweed in the example groups and the control group are shown in Table 2. As can be seen from the data in Table 2, the concentrations of Cd 2+ and Mn 2+ in the stems and leaves of the American pokeweed in the control group 3 without the addition of the repair agent are obviously lower than those in the other groups with the addition of the repair agent, indicating that the mutual inhibition of Cd 2+ and Mn 2+ is obvious, while the inhibition is reduced after the application of the repair agent, and the absorption rate of the American pokeweed to Cd 2+ and Mn 2+ is increased. In comparison with the control group 1, the concentrations of Cd 2+ and Mn 2+ in the stems and leaves of the American pokeweed in Example 1 with the modified pH regulator are obviously higher, indicating that the modified pH regulator plays an important role therein. The concentration of Cd 2+ in the stems and leaves of the American pokeweed in Example 1 first increases and then decreases, while the concentration of Mn 2+ continuously increases, and the concentration of Cd 2+ is higher than that of Mn 2+ in the early stage. In Example 6 without CaCO3 compared with Example 1, the concentrations of Cd 2+ and Mn 2+ in the stems and leaves of the American pokeweed are both gently increased, and tend to be stable after reaching a certain concentration, and the concentration of Mn 2+ is higher than that of Cd 2+ , which indicates that the CaCO3 in the modified pH regulator creates an alkaline condition to promote the oxidation of Mn 2+ into Mn 4+ , and relieves the inhibition of Cd 2+and Mn 2+ The inhibition of Cd 2+ In Example 8 without sulfur, the concentration of Cd 2+ and Mn 2+ in the stems and leaves of pokeweed is gently rising, and tends to be stable after a certain concentration, and the concentration of Cd 2+ is higher than that of Mn 2+ , which shows that sulfur in the modified pH regulator promotes the reduction of Mn 4+ to Mn 2+ , and promotes the absorption of Mn 2+ by pokeweed. In Example 1 compared with Example 5, the concentrations of Cd 2+ and Mn 2+ are different, which may be related to the different mass ratios of sulfur, PLA and CaCO3 in the modified pH regulator. The absorption of Cd 2+ and Mn 2+ by pokeweed can be further improved by optimizing the adjustment of the proportion. In Example Groups 1, 2, 3 and 4, the concentrations of Cd 2+ and Mn 2+ in Example 3 are the highest, which may be related to the specific formula proportion in the example, indicating that the absorption of Cd 2+ and Mn 2+ by pokeweed can be further improved by optimizing the adjustment of the formula proportion.

[0146] Through the above limited experiments, the remediation agent for heavy metal contaminated soil of the present application indeed has the effect of alleviating the mutual inhibition of Cd 2+ and Mn 2+ , and improving the absorption of Cd 2+ and Mn 2+ by pokeweed. By adding the modified pH regulator, the outermost CaCO3 first plays a role, creating an alkaline soil condition, Mn 2+ is oxidized to Mn 4+ by O2, and the organic acid secreted by arbuscular mycorrhizal fungi reduces the rhizosphere pH, promotes the transformation of cadmium from a difficult-to-dissolve state to a soluble state, activates Cd 2+ , and slows down the mutual inhibition of high concentrations of Mn 2+ and Cd 2+ , at this time, low concentration of Mn 2+ promotes the absorption of Cd 2+ by pokeweed. When Cd 2+When the concentration decreases, K. oxytoca becomes active in metabolism, the outermost CaCO3 of the modified pH regulator is fully used, and the PLA layer is exposed and gradually degraded in the soil to release the innermost sulfur, which is oxidized to sulfuric acid under the action of microorganisms to create acidic conditions in the soil. Citric acid secreted by K. oxytoca will reduce Mn 4+ to Mn 2+ at this time, low concentration of Cd 2+ promotes the absorption of Mn 2+ by P. heterophylla. At the same time, the modified pH regulator, arbuscular mycorrhizal fungi and K. oxytoca can reduce the migration of manganese and cadmium in the soil by fixing, adsorbing and complexing heavy metals, improve the soil environment, and avoid the poisoning of P. heterophylla.

[0147] Finally, it should be noted that although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or make equivalent replacements for part of the technical features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A remediation agent for heavy metal contaminated soil, characterized by, Mn 2+ 、Cd 2+ mutual inhibition, improve the absorption of Mn 2+ 、Cd 2+ of phytolacca americana, including the following raw materials by mass fraction: modified pH regulator 30~50 parts, rice straw 5~10 parts, livestock manure 1~5 parts, montmorillonite 3~6 parts, amine fresh ester 1~5 parts, arbuscular mycorrhizal fungi powder 10~15 parts, klebsiella aerogenes powder 10~15 parts; The preparation method of the modified pH regulator comprises the following steps: S11. Screen the sulfur particles, select uniform particles with a particle size of 0.5-1 mm, repeat the rinsing with 5% H2SO4 for 2-3 times, slightly corrode the surface of the sulfur particles, rinse with deionized water, and dry at 60°C for 2 hours to remove water; S12. Dissolve PLA in acetone, stir uniformly, and prepare a 15% w / v PLA solution; S13. Use a fluidized bed coater to spray the PLA solution onto the surface of the sulfur particles at 40-50°C, repeat the spraying for 2-3 times, form a PLA layer with a thickness of 100-150 μm, and obtain a first mixture; S14. Dry the first mixture in a vacuum drying box at 40°C for 12 hours to ensure complete curing of the PLA layer; S15. Grind CaCO3 to 100-150 μm, dry at 60°C to remove water, and the water content is less than 1%; S16. Put the first mixture into a rotary drum coater, spray PVA adhesive, uniformly sprinkle CaCO3 to adhere to the surface of the first mixture, repeat the spraying of PVA and the sprinkling of CaCO3 until a lime outer layer with a thickness of 400-450 μm is formed, obtain a second mixture, and the rotation speed is controlled at 20-30 rpm; S17. Dry the second mixture at 30-40°C for 6-8 hours to ensure complete curing of the PVA adhesive, and obtain the modified pH regulator; In the preparation method of the modified pH regulator, the mass ratio of sulfur, PLA, and CaCO3 is 1-1.5:0.3-0.5:3-5.

2. The remediation agent for heavy metal contaminated soil according to claim 1, characterized by, The livestock and poultry manure is prepared by flatly laying chicken manure in a closed compost container, sprinkling lime on the surface, adding EM bacteria, adding corn stalks, and performing fermentation composting treatment at 30-35°C.

3. The remediation agent for heavy metal contaminated soil according to claim 1, characterized by, The preparation method of the arbuscular mycorrhizal fungus powder comprises the following steps: S21. Inoculate the arbuscular mycorrhizal fungus into a PDA culture medium plate, and place it in a temperature of 24-28°C for 3-5 days of activation culture; S22. Transfer the activated culture to a liquid culture medium, and perform liquid culture at a constant temperature of 24-28°C and a rotation speed of 150-200 r / min for 1-2 days to obtain a liquid culture seed solution; S23. Mix the liquid culture seed solution and the solid culture medium according to a inoculation amount of 6% by weight of the solid culture medium, perform fermentation in a fermentation tray at 24-28°C and a relative humidity of 75-80% until the surface of the solid culture medium is covered with spores, and then perform low-temperature drying at 25-30°C, crushing, and obtaining the arbuscular mycorrhizal fungus powder.

4. The remediating agent for heavy metal contaminated soil according to claim 3, characterized by, The PDA culture medium comprises the following components: 20 parts of potato, 2 parts of glucose, 1.5 parts of agar, and 100 parts of distilled water.

5. The remediating agent for heavy metal contaminated soil according to claim 3, characterized by, The liquid culture medium comprises the following components: 20 parts of starch, 2 parts of glucose, 0.8 parts of peptone, 0.2 parts of KH2PO4, and 100 parts of distilled water.

6. The remediating agent for heavy metal contaminated soil according to claim 3, wherein The solid culture medium comprises the following components: 20 parts of starch, 2 parts of peptone, 1.5 parts of agar, 0.8 parts of corn flour, and 0.2 parts of KH2PO4.

7. The remediating agent for heavy metal contaminated soil according to claim 1, characterized by, The preparation method of the arbuscular mycorrhizal fungus powder is used to prepare the Klebsiella aerogens powder.

8. A method for preparing a remediation agent for heavy metal contaminated soil, which is applied to the preparation of the remediation agent for heavy metal contaminated soil according to any one of claims 1 to 7, characterized by, The method comprises the following steps: S31. Preparing a modified pH regulator; S32. Preparing arbuscular mycorrhizal fungi powder and Klebsiella aerogens powder; S33. Weighing each raw material according to a proportion, carrying out drying treatment, and fully mixing the dried raw materials to obtain a remediation agent for heavy metal contaminated soil; S34. Spraying the prepared remediation agent on the surface layer of soil at a spraying amount of 2 kg / m2; S35. Mixing the remediation agent with the soil in the surface layer of 20-30 cm by using a rotary cultivator, turning over the soil with the remediation agent once a day, and after 5-10 days, planting pokeweed seedlings in the soil and carrying out later maintenance after the soil is stabilized; S36. Repeatedly harvesting the stems and leaves of the pokeweed and carrying out ashing recovery treatment.

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