Composition for repairing heavy metal contaminated soil as well as preparation method and application of composition

Abstract

The invention relates to the technical field of contaminated soil remediation, in particular to a heavy metal contaminated soil remediation composition and a preparation method and application thereof. The heavy metal contaminated soil remediation composition is composed of a microbial agent for heavy metal treatment and a Fe3O4 (at) TiO2 (at) C material, and the microbial agent for heavy metal treatment is loaded on the Fe3O4 (at) TiO2 (at) C material. According to the composition, physical remediation, chemical remediation and biological remediation can be conducted at the same time, Fe3O4 and C are adopted to generate a physical adsorption effect on heavy metal ions, so that the heavy metal ions are enriched on the composition, Fe3O4 and TiO2 and C are adopted to conduct chemical photocatalytic degradation on the heavy metal ions, then microorganisms are adopted to conduct conversion on the heavy metal ions, and therefore the heavy metal ions can be effectively degraded. Efficient treatment of soil heavy metal ions is achieved through the composition.

Description

Technical Field

[0001] The present invention relates to the technical field of contaminated soil treatment, and in particular to a composition for repairing heavy metal contaminated soil, and a preparation method and application thereof. Background Art

[0002] Heavy metals refer to those with a density greater than 4.5 g / cm 3 Metals, heavy metals in environmental pollution, mainly refer to mercury, arsenic, lead, chromium, cadmium, etc. Soil pollution has become one of the important global environmental problems. Due to mining, metal smelting, and agricultural application of industrial wastewater and sludge, a large number of toxic and harmful heavy metal elements enter the soil system. They stay in the soil for a long time and are difficult to degrade, hidden and irreversible. They not only lead to soil degradation, reduced crop yield and quality, but also may affect people's health through the food chain.

[0003] At present, the methods used for heavy metal pollution control include physical remediation, chemical remediation and biological remediation. For biological remediation, the basic principle of its remediation is to use the unique ability of organisms to decompose toxic and harmful substances to achieve the purpose of removing pollutants in the soil; its advantages are that it does not destroy soil organic matter, does not make major disturbances to the soil structure, and has low cost; its disadvantages are that the remediation cycle is long and it is usually not suitable for the remediation of highly contaminated soil. For physical remediation, it is a technology that removes or separates pollutants from the soil through various physical processes; its advantages are high remediation efficiency and fast speed, and its disadvantages are often high costs. For chemical remediation, it is a technology that adds chemical substances to the soil, removes pollutants in the soil or reduces the biological effectiveness or toxicity of pollutants in the soil through chemical reactions such as oxidation-reduction, chelation or precipitation of heavy metals and organic matter; its advantages are high remediation efficiency and relatively fast speed; its disadvantages are that it is easy to destroy the soil structure and easily produce secondary pollution due to the addition of chemical agents; it can be seen that physical, chemical and biological remediation methods all have their own advantages and disadvantages.

[0004] Existing technologies often consider using physical remediation, chemical remediation or biological remediation to treat heavy metal soil pollution, and the functions of the materials disclosed in the existing technologies are relatively single. These reasons all lead to poor remediation capabilities for heavy metal contaminated soil. Summary of the invention

[0005] In view of the shortcomings of the above-mentioned prior art, the present invention provides a composition for repairing heavy metal contaminated soil, a preparation method and application thereof; the composition for repairing heavy metal contaminated soil of the present invention can simultaneously perform physical repair, chemical repair and biological repair, and adopts Fe 3 O 4 and C produce physical adsorption on heavy metal ions, so that heavy metal ions are enriched in the composition for remediation of heavy metal contaminated soil.3 O 4 @TiO 2 @C Chemical photocatalytic degradation of heavy metal ions is carried out, and then microorganisms are used to transform the heavy metal ions, and the composite material is used to achieve efficient treatment of heavy metal ions in the soil.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A composition for remediation of heavy metal contaminated soil, comprising a microbial agent for heavy metal treatment and Fe 3 O 4 @TiO 2 @C material composition, microbial agents for heavy metal treatment are loaded on Fe 3 O 4 @TiO 2 @C materials, Fe 3 O 4 @TiO 2 @C material has a large specific surface area, which allows the microbial agent to be stably loaded on Fe 3 O 4 @TiO 2 @C The surface and pores of the material;

[0008] Fe 3 O 4 @TiO 2 @C material is composed of polyacrylonitrile, organic porogen, nano-TiO 2 and nano-Fe 3 O 4 After blending, it is first electrospun and then calcined at high temperature.

[0009] Preferably, Fe 3 O 4 @TiO 2 @C material was prepared according to the following steps:

[0010] Polyacrylonitrile and an organic porogen are co-dispersed in N, N'-dimethylformamide to obtain a precursor; polyacrylonitrile is a carbon raw material, and polyacrylonitrile is currently the most widely used material for preparing carbon fibers. The organic porogen volatilizes during the carbonization process of polyacrylonitrile, so that the obtained carbon material forms an internal porous structure. At this time, a porous carbon material is obtained after calcining the polyacrylonitrile. The porous structure of the porous carbon material is convenient for loading microbial agents; and the mass ratio of polyacrylonitrile to N, N'-dimethylformamide is 10-15:100; the mass ratio of methyl methacrylate to polyacrylonitrile is 40-80:100;

[0011] Nano-TiO 2 and nano-Fe 3 O4 Mixed with the precursor to obtain spinning solution; nano-TiO 2 It is an important type of inorganic semiconductor material, which is non-toxic and has good photochemical stability. Therefore, TiO 2 Photocatalytic degradation; however, TiO 2 The large bandgap (E = 3.2 eV) makes it impossible to effectively utilize solar energy, resulting in low photocatalytic efficiency. In addition, the recycling problem is difficult and easily causes secondary pollution. Based on this, the present invention uses nano-TiO 2 and nano-Fe 3 O 4 Mixed together in the precursor, nano-Fe 3 O 4 On the one hand, it is convenient to adsorb soil heavy metal ions, and on the other hand, it is convenient to recover the entire composition. 2 and nano-Fe 3 O 4 After being combined with porous carbon materials, trace amounts of Fe 3+ Can reduce TiO 2 The bandgap width expands the absorption wavelength range and improves the photocatalytic performance.

[0012] The spinning solution is electrospun to obtain spinning fibers, and the spinning fibers are crushed and calcined to obtain Fe 3 O 4 @TiO 2 @C material, the purpose of electrospinning is to convert nano-TiO 2 、Nano-Fe 3 O 4 Fixed in the precursor, and then crushed to obtain small-sized materials. At this time, nano-TiO 2 、Nano-Fe 3 O 4 Stable combination with porous carbon materials;

[0013] The electrospinning conditions are as follows: using an electrospinning needle with an inner diameter of 0.27-1.15 mm, advancing at a voltage of 13-22 kV, a receiving distance of 13-22 cm, and an electrospinning propulsion speed of 0.5-2 mL / h;

[0014] The microbial agent used for heavy metal treatment is loaded on Fe 3 O 4 @TiO 2 @C material, a composition for remediation of heavy metal contaminated soil was obtained, Fe 3 O 4 @TiO 2The porous structure of @C material is suitable for the attachment of microbial agents. At this time, the composition for remediation of heavy metal contaminated soil is used to treat the heavy metals in the soil.

[0015] Preferably, the microbial agent consists of bacterial powder and bioactive substances, the bioactive substances consist of sugars and amino acids, and the mass ratio of bacterial powder, sugars and amino acids is 60-80:20-40:20-30, sugars are carbon sources selected from glucose, fructose, lactose or maltose, amino acids are nitrogen sources, and bioactive substances provide the bacterial powder with the nutrients required for growth.

[0016] Preferably, the bacterial powder is composed of Pseudomonas sp, Acidithiobacillus sp and Geobacter metallireducens. The bacterial powder transforms heavy metals, improves the processing capacity, and improves the soil structure. The mass ratio of the three is 1-3:2-3:2-4. Of course, all bacterial agents that can be used for the remediation of heavy metal contaminated soil can be used in this application, and are not limited to the several types disclosed in this application.

[0017] Preferably, the loading method is: Fe 3 O 4 @TiO 2 @C material is added to the immobilization medium, then sterilized, and then 5-10% by mass of microbial agent is added and fixed at room temperature for 12-24 hours;

[0018] Among them, Fe 3 O 4 @TiO 2 @C The mass ratio of material to immobilization medium is 1-1.5:100.

[0019] Preferably, nano-TiO 2 、Nano-Fe 3 O 4 The mass ratio of polyacrylonitrile to polyacrylonitrile is 0.8-1.2:1:100.

[0020] Preferably, the organic porogen is selected from methyl methacrylate, and the added methyl methacrylate volatilizes during the carbonization process, so that the carbon material forms an internal porous structure.

[0021] Preferably, the calcination conditions are: in an inert atmosphere, first heating to 180-250° C. and then keeping the temperature for 1-3 hours, and then calcining at 500-800° C. for 1-4 hours. During the calcination process, polyacrylonitrile is decomposed to obtain a carbon material.

[0022] The present invention also protects a composition for repairing heavy metal contaminated soil obtained by the above preparation method, wherein the composition for repairing heavy metal contaminated soil uses a porous carbon material as a carrier, and nano-Fe 3 O 4 and nano-TiO 2 It is stably attached to the porous carbon material, and then the microorganisms are adsorbed on the surface of the porous carbon material.

[0023] The present invention also protects the use of the composition for repairing heavy metal contaminated soil in preparing heavy metal contaminated soil repair materials, wherein the heavy metal ions in the heavy metal contaminated soil are Cd 2+ Cr 4+ 、As 3+ , Pb 4+ , Hg 2+ or Zn 2+ .

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention provides a composition for remediating heavy metal contaminated soil, which comprises a microbial agent for heavy metal treatment and Fe 3 O 4 @TiO 2 @C material composition, Fe 3 O 4 @TiO 2 @C material uses carbon as a carrier, and carbon realizes Fe 3 O 4 、TiO 2 Carbon materials can accept photogenerated electrons due to their strong electron storage capacity and the characteristics of metal conduction band, and carbon nanomaterials coated with TiO 2 After that, due to carbon and TiO 2 The Fermi level difference between the TiO 2 The photocatalytic efficiency of Fe 3 O 4 Trace amounts of Fe 3+ Can reduce TiO 2 The bandgap width expands the absorption wavelength range and improves the photocatalytic performance.

[0026] 2. The toxicity of heavy metals to humans is often closely related to their existence state. Generally speaking, different metal forms have different toxic effects. Microorganisms cannot degrade and destroy heavy metals, but they can fix, move or transform heavy metals in the soil, change their environmental chemical formation in the soil, promote the detoxification of toxic and harmful substances or reduce their toxicity, thereby achieving the purpose of bioremediation. Therefore, in the present invention, Fe 3 O 4 @TiO 2 @C material was loaded with Pseudomonas sp, Acidithiobacillus sp and Geobactermetallireducens;

[0027] Pseudomonas sp and Geobacter metallireducens combine with surrounding heavy metal ions through microbial cells to form precipitates, thereby reducing the concentration of free heavy metal ions in the soil. At the same time, they transform heavy metal ions into non-toxic or low-toxic forms through oxidation / reduction reactions to complete the repair process.

[0028] Acidithiobacillus sp. can adsorb trivalent arsenic in the soil onto the surface of iron oxides. Tetravalent chromium is reduced to trivalent and adsorbed onto the surface of iron oxides. Tetravalent molybdenum, tetravalent and hexavalent selenium, and hexavalent uranium undergo redox reactions with iron compounds. Soil organic matter stimulates sulfur bacteria to decompose sulfates. The products react with heavy metals in the soil to form sulfides. The sulfides are adsorbed onto the surface of iron oxides, increasing their stability. Mercury ions generate sulfide precipitates through a series of reactions and are adsorbed onto the surface of iron oxides, increasing their stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the Fe of Example 1 3 O 4 @TiO 2 @SEM image of C material;

[0030] Figure 2 is the Fe of Example 1 3 O 4 @TiO 2 UV-visible absorption diagram of @C material. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0032] Nano-TiO 2 It is an important type of inorganic semiconductor material. Due to its non-toxicity and good photochemical stability, it is widely used in photocatalysis, dye-sensitized photovoltaic cells and photocatalytic water splitting to produce hydrogen. 2 TiO has high light utilization rate and high surface activity, making it an ideal photocatalytic material. 2 In terms of photocatalytic applications, there are still problems such as low photocatalytic efficiency and difficult recycling. In view of the above technical problems, the present invention adopts Fe 3 O 4 and TiO 2 Composite with carbon materials, Fe 3 O 4 It has an adsorption effect on heavy metals and is easy to recycle. It can also enhance the quality of nano-TiO 2 The photocatalytic performance of nano-TiO 2 There are technical defects.

[0033] The Pseudomonas sp in the present application was purchased from Shanghai Lianmai Bioengineering Co., Ltd., Acidithiobacillus sp was purchased from Shanghai Guyan Industrial Co., Ltd., and Geobacter metallireducens was purchased from Ningbo Mingzhou Biotechnology Co., Ltd.

[0034] The immobilization culture medium of the present invention is composed of: 10g sucrose, 6g beef extract, 1000mL distilled water, and the pH is adjusted to 7.0-7.5.

[0035] The technical solution of the present invention is further explained below with examples, which are as follows:

[0036] Example 1

[0037] A method for preparing a composition for remediating heavy metal contaminated soil comprises the following steps:

[0038] S1, dispersing polyacrylonitrile and organic porogen methyl methacrylate in N, N-dimethylformamide to obtain a precursor;

[0039] The mass ratio of polyacrylonitrile to N, N'-dimethylformamide is 13:100; the mass ratio of methyl methacrylate to polyacrylonitrile is 60:100;

[0040] S2, nano-TiO 2 and nano-Fe 3 O 4 Mixing them together in a precursor to obtain a spinning solution;

[0041] Nano-TiO 2 、Nano-Fe 3 O 4 The mass ratio of polyacrylonitrile is 1:1:100;

[0042] S3, electrospinning the spinning solution to obtain spinning fibers, drying the spinning fibers, cutting them into millimeter lengths, and calcining them in sequence to obtain Fe 3 O 4 @TiO 2 @C material;

[0043] The electrospinning conditions were as follows: using an electrospinning needle with an inner diameter of 1.0 mm, advancing at a voltage of 20 kV, a receiving distance of 20 cm, and an electrospinning propulsion speed of 1.5 mL / h;

[0044] The calcination conditions are: in an inert atmosphere, first raise the temperature to 200°C, then keep it at that temperature for 2h, and then calcine at 600°C for 3h;

[0045] S4. Loading the microbial agent for heavy metal treatment on Fe 3 O 4 @TiO 2 @C material, a composition for remediation of heavy metal contaminated soil is obtained;

[0046] The microbial agent is composed of bacterial powder and biologically active substances, the biologically active substances are composed of sugar and amino acids, and the mass ratio of bacterial powder, sugar and amino acids is 70:30:25; the bacterial powder is composed of Pseudomonas sp, Acidithiobacillus sp and Geobacter metallireducens, and the mass ratio of the three is 2:2.5:3;

[0047] The load method is:

[0048] Fe 3 O 4 @TiO 2 @C material was added to the immobilization medium, then sterilized, and then 8% by mass of microbial agent was added and fixed at room temperature for 18 hours;

[0049] Among them, Fe 3 O 4 @TiO 2 @C The mass ratio of material to immobilization medium is 1.2:100.

[0050] Example 2

[0051] A method for preparing a composition for remediating heavy metal contaminated soil comprises the following steps:

[0052] S1, dispersing polyacrylonitrile and organic porogen methyl methacrylate in N, N-dimethylformamide to obtain a precursor;

[0053] The mass ratio of polyacrylonitrile to N, N'-dimethylformamide is 10:100; the mass ratio of methyl methacrylate to polyacrylonitrile is 40:100;

[0054] S2, nano-TiO 2 and nano-Fe 3 O 4 Mixing them together in a precursor to obtain a spinning solution;

[0055] Nano-TiO 2 、Nano-Fe 3 O 4 The mass ratio of polyacrylonitrile is 0.8:1:100;

[0056] S3, electrospinning the spinning solution to obtain spinning fibers, drying the spinning fibers, cutting them into millimeter lengths, and calcining them in sequence to obtain Fe 3 O 4 @TiO 2 @C material;

[0057] The electrospinning conditions were as follows: using an electrospinning needle with an inner diameter of 0.27 mm, advancing at a voltage of 22 kV, a receiving distance of 13 cm, and an electrospinning propulsion speed of 0.5 mL / h;

[0058] The calcination conditions are as follows: in an inert atmosphere, first raise the temperature to 250°C and then keep it at that temperature for 1 hour, and then calcine at 500°C for 4 hours;

[0059] S4. Loading the microbial agent for heavy metal treatment on Fe 3 O 4 @TiO 2 @C material, a composition for remediation of heavy metal contaminated soil is obtained;

[0060] The microbial agent is composed of bacterial powder and biologically active substances, the biologically active substances are composed of sugar and amino acids, and the mass ratio of bacterial powder, sugar and amino acids is 60:20:20; the bacterial powder is composed of Pseudomonas sp, Acidithiobacillus sp and Geobacter metallireducens; the mass ratio of the three is 1:2:4;

[0061] The loading method is: Fe 3 O 4 @TiO 2 @C material was added to the immobilization medium, then sterilized, and then 5% by mass of microbial agent was added and fixed at room temperature for 12 hours;

[0062] Among them, Fe 3 O 4 @TiO 2 @C The mass ratio of material to immobilization medium is 1:100.

[0063] Example 3

[0064] A method for preparing a composition for remediating heavy metal contaminated soil comprises the following steps:

[0065] S1, dispersing polyacrylonitrile and organic porogen methyl methacrylate in N, N-dimethylformamide to obtain a precursor;

[0066] The mass ratio of polyacrylonitrile to N, N'-dimethylformamide is 15:100; the mass ratio of methyl methacrylate to polyacrylonitrile is 70:100;

[0067] S2, nano-TiO 2 and nano-Fe 3 O 4 Mixing them together in a precursor to obtain a spinning solution;

[0068] Nano-TiO 2 、Nano-Fe 3 O 4 The mass ratio of polyacrylonitrile is 1.1:1:100;

[0069] S3, electrospinning the spinning solution to obtain spinning fibers, drying the spinning fibers, cutting them into millimeter lengths, and calcining them in sequence to obtain Fe 3 O 4 @TiO 2 @C material;

[0070] The electrospinning conditions were as follows: using an electrospinning needle with an inner diameter of 1.0 mm, advancing at a voltage of 13 kV, a receiving distance of 22 cm, and an electrospinning propulsion speed of 1.5 mL / h;

[0071] The calcination conditions are as follows: in an inert atmosphere, first raise the temperature to 180°C and then keep it at that temperature for 2 hours, and then calcine at 800°C for 1 hour;

[0072] S4. Loading the microbial agent for heavy metal treatment on Fe 3 O 4 @TiO 2 @C material, a composition for remediation of heavy metal contaminated soil is obtained;

[0073] The microbial agent is composed of bacterial powder and biologically active substances, the biologically active substances are composed of sugar and amino acids, and the mass ratio of bacterial powder, sugar and amino acids is 70:40:25; the bacterial powder is composed of Pseudomonas sp, Acidithiobacillus sp and Geobacter metallireducens; the mass ratio of the three is 2:3:4;

[0074] The loading method is: Fe 3 O 4 @TiO 2 @C material was added to the immobilization medium, then sterilized, and then 8% by mass of microbial agent was added and fixed at room temperature for 18 hours;

[0075] Among them, Fe 3 O 4 @TiO 2 @C The mass ratio of material to immobilization medium is 1.5:100.

[0076] Example 4

[0077] A method for preparing a composition for remediating heavy metal contaminated soil comprises the following steps:

[0078] S1, dispersing polyacrylonitrile and organic porogen methyl methacrylate in N, N-dimethylformamide to obtain a precursor;

[0079] The mass ratio of polyacrylonitrile to N, N'-dimethylformamide is 13:100; the mass ratio of methyl methacrylate to polyacrylonitrile is 80:100;

[0080] S2, nano-TiO 2 and nano-Fe 3 O 4 Mixing them together in a precursor to obtain a spinning solution;

[0081] Nano-TiO 2 、Nano-Fe 3 O 4 The mass ratio of polyacrylonitrile is 1.2:1:100;

[0082] S3, electrospinning the spinning solution to obtain spinning fibers, drying the spinning fibers, cutting them into millimeter lengths, and calcining them in sequence to obtain Fe 3 O 4 @TiO 2 @C material;

[0083] The electrospinning conditions were as follows: using an electrospinning needle with an inner diameter of 1.15 mm, advancing at a voltage of 18 kV, a receiving distance of 20 cm, and an electrospinning propulsion speed of 2 mL / h;

[0084] The calcination conditions are as follows: in an inert atmosphere, first raise the temperature to 160°C and then keep it at that temperature for 3 hours, and then calcine at 700°C for 2.5 hours;

[0085] S4. Loading the microbial agent for heavy metal treatment on Fe 3 O 4 @TiO 2 @C material, a composition for remediation of heavy metal contaminated soil is obtained;

[0086] The microbial agent is composed of bacterial powder and biologically active substances, the biologically active substances are composed of sugar and amino acids, and the mass ratio of bacterial powder, sugar and amino acids is 80:40:30; the bacterial powder is composed of Pseudomonas sp, Acidithiobacillus sp and Geobacter metallireducens; the mass ratio of the three is 3:3:4;

[0087] The loading method is: Fe 3 O 4 @TiO 2 @C material was added to the immobilization medium, then sterilized, and then 10% by mass of microbial agent was added and fixed at room temperature for 24 hours;

[0088] Among them, Fe 3 O 4 @TiO 2 @C The mass ratio of material to immobilization medium is 1.5:100.

[0089] Examples 1-4 of the present invention all prepared compositions for the remediation of heavy metal contaminated soil for heavy metal ion treatment in soil. The composition for the remediation of heavy metal contaminated soil prepared in Example 1 is used as an example for research. The specific research methods and results are as follows:

[0090] (1)Fe 3 O 4 @TiO 2 @C Material structure confirmation:

[0091] Figure 1 is the Fe of Example 1 3 O 4 @TiO 2 @C material scanning electron microscope image, the results show that Fe 3 O 4 @TiO 2 @CThe material has good morphology and a porous structure, which facilitates the attachment of microorganisms.

[0092] Figure 2 is the Fe of Example 1 3 O 4 @TiO 2 @C UV-visible absorption diagram of the material, the results show that pure TiO 2 It has strong light absorption only in the ultraviolet region, while Fe 3 O 4 @TiO 2 @C material exhibits strong light absorption in the visible light range, so Fe 3 O 4 @TiO 2 @C materials and TiO 2 Compared with the conventional nanostructured carbon nanotubes, the light absorption and photocatalytic activity were enhanced.

[0093] (2) Remediation of heavy metal soil pollution:

[0094] The composition of Example 1 of the present invention was used to repair heavy metal contaminated soil, and the repaired soil was arsenic contaminated soil. The specific operations studied during the repair process are as follows:

[0095] Biomass determination method: Select the windmill grass growing well in the tailings area as the experimental object, dig up the grass with roots and soil, and select 10 plants with similar plant height as parallel samples; separate the windmill grass from its rhizosphere soil, then air-dry the soil sample in a cool and dry place, remove the stones, grind it through a 0.2mm sieve and dry it for later use; after washing and drying the windmill grass, measure its plant height and fresh weight, and then dry it at 60℃ to constant weight, measure the dry weight of the roots and aboveground parts of the windmill grass, and then crush the roots and aboveground parts of the plants respectively, and store the crushed samples separately;

[0096] Arsenic concentration determination method: Add soil samples and windmill grass into polytetrafluoroethylene digestion tubes respectively, then moisten them with water, add 16mL nitric acid and 4mL perchloric acid, cover the lid and shake well, place it for 24 hours, place it in a digester and heat it for 1 hour, remove the lid and continue heating, and control the heating temperature below 200°C until gray-white residue remains in the tube. Remove and cool it, dissolve the residue with 50% nitric acid solution by volume, transfer it to a 50mL colorimetric tube, wash it with ultrapure water, and finally make up to volume with ultrapure water. Use an atomic fluorescence spectrophotometer to determine the arsenic concentration in soil samples and windmill grass. All detection treatments were repeated 3 times and the results were averaged.

[0097] The method for remediating arsenic-contaminated soil with a composition is as follows: 1.5 kg of uncontaminated soil is added to a flower pot, and then 1 mg mL -1 Arsenic standard solution, so that the concentration of arsenic in the potting soil is 5 mg kg -1 , planted 10 selected windmill grasses, and then sowed 50 mg of the composition of Example 1 on the soil surface, first let the windmill grass seedlings grow for 7 days, then watered once every two days to maintain 60% of the water holding capacity, added nutrient solution once after 10 days, and after 60 days, removed the whole windmill grass, washed it, and then used 5mmol·L -1 The roots were soaked in calcium nitrate solution for 15 minutes, washed with deionized water, withered and dried, and the biomass, plant height and arsenic concentration of the windmill grass were determined, and the arsenic concentration in the soil was also determined; 10 windmill grasses without the composition were used as the control group, and the plant height of the control group was similar to that of the experimental group, recorded as CK.

[0098] Table 1 Biomass results before and after the experiment

[0099]

[0100] The results of the determination of the biomass of the windmill grass before and after the experiment are shown in Table 1. After the soil was treated with the composition, the plant height and fresh weight of the windmill grass increased, proving that the treatment of arsenic-contaminated soil with the composition can effectively promote the growth of windmill grass. The reason is that the metabolic activity of microorganisms and the arsenic treatment have improved the physical and chemical properties of the soil to a certain extent, thereby promoting plant growth.

[0101] Table 2 Results of arsenic concentration in windmill grass and soil

[0102]

[0103]

[0104] The results of arsenic concentration determination in windmill grass and soil are shown in Table 2. It can be seen from Table 2 that after the composition is spread on the soil and the windmill grass is cultivated for a period of time, the arsenic concentrations in the windmill grass and soil are greatly improved. This is because the composition improves the physical and chemical properties of the soil to a certain extent, promotes the absorption and accumulation of heavy metals in the soil and windmill grass by the composition, and achieves the purpose of quickly repairing arsenic-contaminated soil.

[0105] The following is a study on the growth-promoting effect on the crop corn:

[0106] The experimental site is located in Halahai Town, Nong'an County, which is 60km from Changchun City and is located on the western edge of the northeastern uplift zone of the Songliao Plain depression. The county has a flat terrain and the cultivated land area is mainly chernozem. The experiment set up two treatments and three replications, with an area of ​​10m per plot. 2 Treatment 1 was conventional fertilizer treatment; Treatment 2 was combination + conventional fertilizer; corn variety was Xianyu 335, density was 60,000 / hm 2 , the total amount of conventional fertilizer is NP 2 O 5 -K 2 O 270-90-90kg / hm 2 ; Base fertilizer NP 2 O 5 -K 2 O is 90-90-90kg / hm 2 ; Top dressing was applied to both treatments at the jointing stage, and the yield measurement data analysis is shown in Table 3.

[0107] Table 3 Plot corn yield data table

[0108]

[0109] There was a significant difference in corn yield between the combination + conventional fertilizer and the chemical fertilizer treatment. The yield of the test plot of the combination + chemical fertilizer treatment was 9.74kg / 5m 2 , calculated by area, is 19481.74kg / hectare; the yield of conventional fertilizer in the yield test area is 6.18kg / 5m 2 , calculated based on area, it is 12355.36 kg / hectare.

[0110] Table 4 Effects of different annual combinations + conventional fertilizer treatments on corn yield composition and yield

[0111]

[0112] Table 5 Effects of conventional fertilizer treatments on corn yield composition and yield in different years

[0113]

[0114] From the 2022-2023 corn yield composition table in Table 4-5, it can be seen that the 2022 combination + conventional fertilizer yield per mu is 799.93kg / 667m 2 , conventional fertilizer treatment yield 772.35kg / 667m 2 The combination of chemical fertilizers + conventional fertilizers increased by 3.5% compared with conventional fertilizers. In 2023, the corn yield of the combination of chemical fertilizers + conventional fertilizers was 826.42 kg / 667 m 2 ; Conventional fertilizer treatment 781.9kg / 667m 2 ; The combination + conventional fertilizer treatment increased by 5.6% compared with the conventional fertilizer treatment;

[0115] In 2022-2023, the average yield per mu of the combination + conventional fertilizer treatment was 813.18 kg, and the yield increase rate was 3.3%; while the average yield per mu of the conventional fertilizer treatment for two years was 777.17 kg, and the yield increase rate was 1.2%; because the combination + conventional fertilizer fertilizer is more stable and has better repeatability, there is no difference in the same treatment for two years.

[0116] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A composition for remediating heavy metal contaminated soil, characterized in that: It is composed of a microbial agent for heavy metal treatment and a Fe3O4@TiO2@C material, wherein the microbial agent for heavy metal treatment is loaded on the Fe3O4@TiO2@C material; The Fe3O4@TiO2@C material is prepared by blending polyacrylonitrile, organic porogen, nano-TiO2 and nano-Fe3O4, first by electrospinning and then by high-temperature calcination.

2. A composition for remediating heavy metal contaminated soil according to claim 1, characterized in that: Fe3O4@TiO2@C material was prepared according to the following steps: Dispersing polyacrylonitrile and an organic porogen in N,N-dimethylformamide to obtain a precursor; Mixing nano-TiO2 and nano-Fe3O4 into a precursor to obtain a spinning solution; The spinning solution is subjected to electrostatic spinning, crushing and calcination to obtain Fe3O4@TiO2@C material.

3. A composition for remediating heavy metal contaminated soil according to claim 2, characterized in that: The mass ratio of nano-TiO2, nano-Fe3O4 and polyacrylonitrile is 0.8-1.2:1:

100.

4. The composition for remediating heavy metal contaminated soil according to claim 2, characterized in that: The organic porogen is selected from methyl methacrylate.

5. The composition for remediating heavy metal contaminated soil according to claim 2, characterized in that: The calcination conditions are: in an inert atmosphere, first raise the temperature to 180-250°C and then keep it at that temperature for 1-3 hours, and then calcine at 500-800°C for 1-4 hours.

6. The composition for remediating heavy metal contaminated soil according to claim 1, characterized in that: The microbial agent consists of bacterial powder and bioactive substances, the bioactive substances consist of sugar and amino acids, and the mass ratio of bacterial powder, sugar and amino acids is 60-80:20-40:20-30.

7. The composition for remediating heavy metal contaminated soil according to claim 6, characterized in that: The bacterial powder is composed of Pseudomonas sp, Acidithiobacillus sp and Geobacter metallireducens.

8. A method for preparing the composition for remediation of heavy metal contaminated soil according to claim 1, characterized in that: The steps include: The Fe3O4@TiO2@C material is added to the immobilization medium, and then sterilized, and then 5-10% by mass of microbial agent is added, and fixed at room temperature for 12-24 hours; Among them, the mass ratio of Fe3O4@TiO2@C material to immobilization culture medium is 1-1.5:

100.

9. Use of the composition for remediation of heavy metal contaminated soil according to claim 1 in preparing heavy metal contaminated soil remediation materials.

10. The use according to claim 9, characterized in that: The heavy metal ion in heavy metal contaminated soil is Cd 2+ Cr 4+ 、As 3+ , Pb 4+ , Hg 2+ or Zn 2+ .

Images