An ecological restoration soil preparation method

Abstract

The present invention relates to the technical field of the regeneration of polluted soil, and particularly relates to an ecological restoration soil preparation method. This method is to mix activated sludge, corn straw, microbial inoculum fermentation broth, modified palygorskite, bentonite, and calcium carbonate to obtain a soil remediation agent, apply the soil remediation agent to the soil, rototill and mix evenly, and after watering thoroughly, plant a plant community on it after 1 to 2 weeks. This soil remediation method uses activated sludge and microbial inoculum to increase soil microbial activity, corn straw to improve water retention and air permeability, modified palygorskite and bentonite to improve soil structure, and calcium carbonate to supply calcium, so as to achieve the sustainable utilization of the soil.

Description

Technical Field

[0001] The present invention relates to the technical field of the regeneration of polluted soil, and particularly to an ecological restoration soil cultivation method. Background Art

[0002] The ecological restoration soil cultivation method is a comprehensive environmental pollution treatment technology aimed at restoring the health and ecological functions of the soil through natural and artificial means, including the following: Progressive ecological restoration, removing toxic pollutants in the soil, clearing solid waste, and improving the soil to enhance its productivity; Taking artificial measures to restore the ecosystem to a certain reference state; Relying on the self-restoring ability of the ecosystem to develop in a healthy direction. Soil bioremediation technology, using plants and their symbiotic microorganisms to extract, transfer, absorb, decompose, transform or immobilize pollutants in the soil; Improving the physical and chemical properties of the soil directly or indirectly through soil animals to increase soil fertility; Using indigenous microorganisms or artificially domesticated microorganisms to reduce the activity of harmful pollutants or degrade them into harmless substances through metabolic actions. Soil improvement, using modifiers such as lime, organic fertilizers, and biochar to optimize the assembly of rhizosphere microbial communities and enhance the disease resistance and antioxidant capacity of the soil. Physical / chemical remediation technology, fixing pollutants in the soil to prevent their migration; Using chemical solvents to dissolve and extract pollutants from the soil; Degrading pollutants through chemical reactions; Using electric fields to drive the migration of pollutants and conduct treatment. Combined remediation technology, combining microbial / animal-plant combined remediation technology, chemical / physicochemical-biological combined remediation technology, and physical-chemical combined remediation technology to remediate the soil of mixed pollution sites. Thermodynamic remediation technology, using heat conduction or thermal radiation to achieve the remediation of polluted soil. Phytoremediation, directly or indirectly absorbing, volatilizing, separating, and degrading pollutants by planting selected plants and their rhizosphere microorganisms. Bioremediation, using microorganisms, especially indigenous bacteria, foreign bacteria, and genetically engineered bacteria, to transform and degrade pollutants through their metabolic actions. A win-win model of ecological restoration and livelihood improvement, when carrying out soil remediation, combining with the development of green industries to maximize the benefits of ecological restoration and benefit the people. The selection and application of these methods need to be comprehensively considered according to specific soil conditions, pollutant types, and expected remediation goals.

[0003] CN107384418A provides a soil-fixing ecological restoration agent and a preparation method thereof. The soil-fixing ecological restoration agent is obtained by crushing and refining crop waste rich in plant fiber tissue, wetting, fermenting, drying, and then adding a certain proportion of fine sand, aluminum sulfate, sodium silicate, expanded perlite, and activated sludge, and then screening. On the one hand, the soil-fixing ecological restoration agent in the invention enhances the pulling force and cementing effect between soil clumps and particles, achieving the technical effect of fixing and restoring the soil and preventing soil erosion and migration; on the other hand, effective technical means are adopted to avoid the side effects of soil hardening and compaction that the soil-fixing ecological restoration agent may cause. The soil-fixing ecological restoration agent has the characteristics of being green and environmentally friendly, having a wide range of raw material sources, low cost, simple preparation process, convenient use, and no side effects.

[0004] CN110238191B discloses a net-laying ecological restoration method for pesticide organic-polluted soil, which can improve the singularity of traditional microbial ecological restoration. Using a variety of microbial agents as raw materials, relying on the synergistic symbiosis and common metabolism among microorganisms, it significantly enhances the efficacy of microbial agents in restoring the soil ecosystem and degrading pesticide organic pollutants, especially for the restoration of soil pollution caused by pesticide organic matter is very obvious; at the same time, nutrient agents and active humic acid have the functions of improving the soil, improving the living environment of beneficial microorganisms and promoting their growth and reproduction, thereby improving the efficacy of microbial agents, shortening the time required for soil restoration, and supplemented by a special net-laying device, the microbial agents can be purposefully guided to every corner of the soil to be restored, promoting their penetration and restoration effects in the soil, and planting resistant plants such as water hyacinth on pesticide organic-polluted soil has a better improvement effect on pesticide organic pollution.

[0005] Microbial degradation has become an effective means for treating various organic pollutants due to its high efficiency, cost-effectiveness, and safety. In recent years, the use of microbial degradation technology to treat organic and inorganic residual pollution in soil has received increasing attention. However, microbial degradation has certain limitations: a single microorganism can often only degrade specific types of pollutants, and in addition, the degradation rate is slow, and the restoration effect of a single microbial agent is not ideal. Currently, the restoration method of microbial agents mostly adopts the method of turning the soil and spraying, and this method has some deficiencies: first, it requires a large amount of manpower and material resources; second, after spraying, the microorganisms need time to spread and penetrate by themselves, this process lacks pertinence, and the penetration ability is limited; moreover, heavy metals are highly toxic and difficult to be decomposed by microorganisms. These factors limit the efficiency and effect of microbial agents in soil restoration. Summary of the Invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide an ecological restoration soil cultivation method.

[0007] Generally speaking, there are mainly five occurrence forms of heavy metals in soil, including residual state, organic state, iron / manganese state, carbonate form and ionic form. Microbial remediation adsorbs, precipitates and redox heavy metals in soil through the metabolic process of microorganisms. By changing the occurrence state of heavy metals, their bioavailability and migration ability are decreased. However, heavy metals are difficult to be decomposed, so it is difficult to decompose heavy metals in soil only by microorganisms. Due to its unique chemical composition and structure, palygorskite has a large specific surface area and cation exchange capacity, and can stably adsorb heavy metal ions. However, a large amount of mineral impurities in natural palygorskite will affect the adsorption property, so modification treatment is needed.

[0008] The present invention provides a modified palygorskite. First, impurities in pores are removed by acid treatment to increase the specific surface area, and then palygorskite is modified with trimethoxy(2-pyridin-4-yl)silane to graft pyridine groups on its surface. Since the pyridine groups form stable coordination bonds with heavy metal ions through their nitrogen atoms, and possible π-π stacking or hydrogen bond interactions, they show adsorption properties for heavy metal ions. Therefore, the modified palygorskite has stronger ability to remove heavy metals.

[0009] Bacillus subtilis, as a common plant growth-promoting rhizobacterium (PGPR), can play a key role in conferring plant tolerance to biotic and abiotic stresses through induced systemic resistance (ISR), biofilm formation and lipopeptide production. As part of bioremediation technology, Bacillus subtilis can purify metal-contaminated soil and act as an effective denitrifying agent in agroecosystems, while improving the carbon sequestration process when applied at regulated concentrations.

[0010] Azotobacter beijerinckii can efficiently remediate acidified soil, and as a biological agent, it has the advantages of being non-toxic and pollution-free. Azotobacter beijerinckii converts atmospheric nitrogen into ammonia nitrogen available to plants, effectively increasing the nitrogen content in soil, thereby improving soil fertility and promoting plant growth. The symbiotic relationship formed by Azotobacter beijerinckii and plant roots not only enhances the stress resistance of plants, but also attracts other beneficial microorganisms, increasing the biodiversity of soil. In addition, the activities of Azotobacter beijerinckii improve the physical structure of soil, increase the porosity and aeration of soil, and contribute to the decomposition of organic matter and nutrient cycling.

[0011] Bacillus licheniformis preparations have a positive effect on environmental remediation. Especially when preparing microecological preparations with viable bacteria at the industrial fermentation scale, the spore count is one of the important quality indicators. Yeasts such as Candida utilis can participate in the decomposition and cycling of organic matter through their biotransformation, promote the increase of soil nutrients, contribute to the improvement of soil structure and plant growth. Through their biochemical actions, these microorganisms can not only improve the fertility and structure of the soil, but also reduce soil pollution, promote the healthy growth of plants, and play a positive role in ecological soil remediation.

[0012] To achieve the above object, the present invention provides a method for cultivating soil for ecological remediation, comprising the following steps, by weight:

[0013] Mix 20 - 30 parts of activated sludge, 20 - 30 parts of corn straw, 40 - 60 parts of microbial inoculant fermentation broth, 10 - 25 parts of modified palygorskite, 5 - 10 parts of bentonite, and 4 - 10 parts of calcium carbonate to obtain a soil remediation agent. Apply the soil remediation agent to the soil, rototill and mix evenly, water thoroughly, and then plant a plant community on it after 1 - 2 weeks.

[0014] Further, the microbial inoculant fermentation broth includes Bacillus subtilis, Azotobacter beijerinckii, Bacillus licheniformis, and Candida utilis.

[0015] Further, the mass ratio of Bacillus subtilis, Azotobacter beijerinckii, Bacillus licheniformis, and Candida utilis in the microbial inoculant fermentation broth is 2 - 5:3 - 4:1 - 3:1 - 3.

[0016] Further, the microbial inoculant fermentation broth is obtained by mixing each strain in proportion and fermenting at 28 - 32 °C for 12 - 15 days in a culture medium.

[0017] Further, 100 - 200 kg of the soil remediation agent is applied per mu of soil.

[0018] The preparation method of the modified palygorskite includes the following steps:

[0019] X1. Add palygorskite to a 9 wt% hydrochloric acid solution, heat in a water bath, oscillate for 2 - 4 h, then filter, dry, and pulverize to obtain activated palygorskite;

[0020] X2. Add the activated palygorskite to water, stir evenly to obtain a gel, then add trimethoxy(2 - pyridin - 4 - ethyl)silane, shear at high speed for 10 - 30 min, then filter, wash the residue with ethanol, dry, and pulverize to obtain the product.

[0021] Further, the solid - liquid ratio of palygorskite to hydrochloric acid is 1:2 g / mL.

[0022] Further, the heating temperature range is 50~60°C.

[0023] Further, the mass ratio of the activated palygorskite to trimethoxy(2-pyridin-4-ylethyl)silane is 1:0.5~2.

[0024] Further, the rotation speed of the high-speed shearing is 13000~15000 rpm.

[0025] Preferably, the preparation method of the modified palygorskite includes the following steps:

[0026] X1. Add palygorskite to a 9wt% hydrochloric acid solution with a solid-liquid ratio of 1:2 g / mL, heat it in a water bath to 50~60°C, oscillate for 2~4 h, then filter, dry, and pulverize to obtain activated palygorskite;

[0027] X2. Add the activated palygorskite to water, stir evenly to obtain a gel, then add trimethoxy(2-pyridin-4-ylethyl)silane. The mass ratio of the activated palygorskite to trimethoxy(2-pyridin-4-ylethyl)silane is 1:0.5~2. After high-speed shearing at 13000~15000 rpm for 10~30 min, filter. The residue is washed with ethanol, dried, and pulverized to obtain the product.

[0028] Advantages of the present invention:

[0029] 1. Compared with the prior art, the present invention provides a modified palygorskite. First, impurities in the pores are removed by acid treatment to increase the specific surface area. Then, trimethoxy(2-pyridin-4-ylethyl)silane is used to modify palygorskite, and pyridine groups are grafted on its surface. Since the pyridine groups form stable coordination bonds with heavy metal ions through their nitrogen atoms, and possible π-π stacking or hydrogen bond interactions, the modified palygorskite shows adsorption properties towards heavy metal ions. Therefore, the modified palygorskite has stronger ability to remove heavy metals.

[0030] 2. This soil remediation method uses activated sludge and microbial agents to increase soil microbial activity, corn straw to improve water retention and aeration, modified palygorskite and bentonite to improve soil structure, and calcium carbonate to supplement calcium. By comprehensively applying these components and through reasonable water management and plant cultivation, contaminated soil can be effectively restored, its fertility and biodiversity can be enhanced, and sustainable utilization of the soil can be achieved. Specific embodiments

[0031] Trimethoxy(2-pyridin-4-ylethyl)silane, CAS No.: 73324-70-6.

[0032] Bacillus subtilis CGMCC 1.821, Azotobacter beijerinckii CGMCC 1.9044, Bacillus licheniformis CGMCC 1.10314, and Candida utilis CGMCC 2.3047 are all commercially available and are all from the China General Microbiological Culture Collection Center.

[0033] Activated sludge, with VSS / TSS of organic content greater than 0.7 ± 0.1, effective sludge granularity greater than 75%, sedimentation rate: 50 - 150 m / h, particle diameter 0.5 - 2 mm, water content 90%, Jiangxi Shu'erli Environmental Protection Technology Co., Ltd.

[0034] Composition of the culture medium: In 1 L of the culture medium, there are 10.0 g of peptone, 3.0 g of beef extract, 20.0 g of glucose, 5.0 g of sodium chloride, 1.5 g of magnesium sulfate, 3.0 g of dipotassium hydrogen phosphate, 15.0 g of agar, and pH = 7.0 ± 0.2.

[0035] Example 1

[0036] An ecological restoration soil preparation method includes the following steps, by weight:

[0037] Mix 25 parts of activated sludge, 20 parts of corn straw, 50 parts of microbial inoculant fermentation broth, 15 parts of modified palygorskite, 8 parts of bentonite, and 6 parts of calcium carbonate to obtain a soil repair agent. The microbial inoculant fermentation broth is obtained by mixing Bacillus subtilis, Azotobacter beijerinckii, Bacillus licheniformis, and Candida utilis in a mass ratio of 4:3:3:2, fermenting at 30 °C, and culturing in the culture medium for 12 d. Apply 150 kg of the soil repair agent per mu to the soil. After rotary tilling and mixing evenly, water thoroughly and then plant a plant community on it after 2 weeks.

[0038] The preparation method of the modified palygorskite includes the following steps, by weight:

[0039] X1. Add 20 parts of palygorskite to 40 parts of 9 wt% hydrochloric acid solution, heat in a water bath to 60 °C, oscillate for 3 h, then filter, dry, and crush to obtain activated palygorskite;

[0040] X2. Add 15 parts of activated palygorskite to 250 parts of water, stir evenly to obtain a gel, then add 15 parts of trimethoxy(2 - pyridin - 4 - ethyl)silane, shear at 14000 rpm for 20 min, then filter. The residue is washed with ethanol, dried, and crushed to obtain the product.

[0041] Example 2

[0042] It is basically the same as Example 1, and the only difference is that the weight part of trimethoxy(2 - pyridin - 4 - ethyl)silane is 10 parts.

[0043] Example 3

[0044] It is basically the same as Example 1, and the only difference is that the weight portion of trimethoxy(2-pyridin-4-yl-ethyl)silane is 20 portions.

[0045] Example 4

[0046] It is basically the same as Example 1, and the only difference is that the weight portion of trimethoxy(2-pyridin-4-yl-ethyl)silane is 30 portions.

[0047] Control Example 1

[0048] An ecological restoration soil cultivation method includes the following steps, by weight portion:

[0049] Mix 25 portions of activated sludge, 20 portions of corn straw, 50 portions of microbial inoculum fermentation broth, 15 portions of palygorskite, 8 portions of bentonite, and 6 portions of calcium carbonate to obtain a soil repair agent. The microbial inoculum fermentation broth is obtained by mixing Bacillus subtilis, Azotobacter beijerinckii, Bacillus licheniformis, and Candida utilis according to a mass ratio of 4:3:3:2, fermenting at 30°C, and culturing in a medium for 12 d. Apply 150 kg of the soil repair agent per mu to the soil, mix well by rotary tillage, water thoroughly, and then plant a plant community on it after 2 weeks.

[0050] Control Example 2

[0051] An ecological restoration soil cultivation method includes the following steps, by weight portion:

[0052] Mix 25 portions of activated sludge, 20 portions of corn straw, 50 portions of microbial inoculum fermentation broth, 15 portions of modified palygorskite, 8 portions of bentonite, and 6 portions of calcium carbonate to obtain a soil repair agent. The microbial inoculum fermentation broth is obtained by mixing Bacillus subtilis, Azotobacter beijerinckii, Bacillus licheniformis, and Candida utilis according to a mass ratio of 4:3:3:2, fermenting at 30°C, and culturing in a medium for 12 d. Apply 150 kg of the soil repair agent per mu to the soil, mix well by rotary tillage, water thoroughly, and then plant a plant community on it after 2 weeks.

[0053] The preparation method of the modified palygorskite includes the following steps, by weight portion:

[0054] Add 20 portions of palygorskite to 40 portions of 9 wt% hydrochloric acid solution, heat in a water bath to 60°C, oscillate for 3 h, then filter, dry, and pulverize to obtain it.

[0055] Control Example 3

[0056] An ecological restoration soil cultivation method includes the following steps, by weight portion:

[0057] Mix 25 parts of activated sludge, 20 parts of corn straw, 50 parts of microbial inoculant fermentation broth, 15 parts of modified palygorskite, 8 parts of bentonite, and 6 parts of calcium carbonate to obtain a soil conditioner. The microbial inoculant fermentation broth is obtained by mixing Bacillus subtilis, Azotobacter beijerinckii, Bacillus licheniformis, and Candida utilis in a mass ratio of 4:3:3:2, fermenting at 30°C, and culturing in a medium for 12 days. Apply 150 kg of the soil conditioner per mu to the soil. After rotary tilling and mixing evenly, water thoroughly, and then plant a plant community on it after 2 weeks.

[0058] The preparation method of the modified palygorskite includes the following steps, in parts by weight:

[0059] X1. Add 20 parts of palygorskite to 40 parts of 9wt% hydrochloric acid solution, heat in a water bath to 60°C, oscillate for 3 h, then filter, dry, and pulverize to obtain activated palygorskite;

[0060] X2. Add 15 parts of activated palygorskite to 250 parts of water, stir evenly to obtain a gel, then add 15 parts of propyltrimethoxysilane, shear at 14000 rpm for 20 min, then filter. Wash the residue with ethanol, dry, and pulverize to obtain the product.

[0061] Test Example 1

[0062] Select a piece of land with soil acidification and pollution as the soil restoration test site, and adopt the soil cultivation method in the present invention for ecological restoration. Divide the soil restoration test site into 7 plots according to the area, labeled as test plots 1-7, and ensure that test plots 1-7 are isolated from each other. Before the restoration, detect and record various soil indicators, and take the average value by multi-point testing. Similarly, check and record after ecological restoration. The specific data are shown in Table 1.

[0063] Table 1 Test results of various indicators for ecological restoration of acidified and polluted soil

[0064]

[0065] Activated sludge and microbial inoculum fermentation broth introduce a rich microbial community into the soil, promoting the decomposition of organic matter and nutrient cycling. Corn straw, as a source of organic matter, improves the water retention and aeration of the soil, while releasing nutrients. Modified palygorskite and bentonite jointly improve the soil structure and enhance its water retention and cation exchange capacity. Calcium carbonate is used to provide calcium elements. After applying at a rate of 150 kg per mu and rotary tilling and mixing evenly, combined with appropriate water management, and then planting a plant community, the plant roots can improve the soil structure, increase the soil porosity, and enhance the soil aeration and water retention. The growth and death of the roots can also promote the increase of soil organic matter. A diverse plant community can increase soil biodiversity and help maintain and enhance the functions and services of the soil ecosystem. Plants absorb nutrients from the soil through their roots, convert them into organic matter through photosynthesis, and return them to the soil after death, promoting nutrient cycling. Therefore, the method for ecological restoration of soil of the present invention can effectively improve the quality of contaminated soil, realize the reuse of soil, and thus improve various indicators of acidified soil.

[0066] Test Example 2

[0067] Select a piece of land contaminated with heavy metals as the soil remediation test site, and adopt the soil cultivation method in the present invention for ecological restoration. Divide the soil remediation test site into 7 plots according to the area, marked as test plots No. 1 - 7, and ensure that the test plots No. 1 - 7 are isolated from each other. Detect the content of heavy metals (lead, cadmium, mercury, arsenic, chromium) in the soil, record it as the initial value, and then detect the content of heavy metals (lead, cadmium, mercury, arsenic, chromium) in the soil again after restoration by the cultivation method of the present invention. Take the average value by taking multiple-point tests. The specific data are shown in Table 2.

[0068] Table 2 Test Results of Various Indicators for Ecological Restoration of Heavy Metal-Contaminated Soil

[0069]

[0070] From the test results of heavy metal content, it can be seen that the cultivation method of the present invention has a good remediation effect on heavy metal-contaminated soil. Compared with Control Example 1, in Control Example 1, palygorskite was not activated and modified, and a large amount of mineral impurities in natural palygorskite would affect the adsorption performance, so the adsorption effect was inferior to that of the Example. In Control Example 2, palygorskite was acid-treated to remove impurities in the pores and increase the specific surface area, so the adsorption performance was improved compared with Control Example 1. In the Example, after acid-treating palygorskite, trimethoxy(2-pyridin-4-yl)silane was further used to modify palygorskite, and pyridine groups were grafted on its surface. Since the pyridine groups form stable coordination bonds with heavy metal ions through their nitrogen atoms, and possible π-π stacking or hydrogen bonding effects, they show adsorption properties for heavy metal ions. Therefore, the modified palygorskite has stronger ability to remove heavy metals. In Control Example 3, propyltrimethoxysilane was used to modify palygorskite, without pyridine groups, so the effect of enhancing adsorption was inferior to that of Example 1. In Examples 1 to 4, the mass ratios of palygorskite to trimethoxy(2-pyridin-4-yl)silane were different, resulting in different adsorption performances. This may be because when the amount of trimethoxy(2-pyridin-4-yl)silane was small, the permanent negative charges on the surface of palygorskite could not be well balanced, and when the amount of trimethoxy(2-pyridin-4-yl)silane was too large, it would instead affect the porosity of palygorskite. Therefore, the addition amount in Example 1 was the best.

[0071] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A method for preparing soil for ecological restoration, characterized in that: The method comprises the following steps, in parts by weight: A soil remediation agent is prepared by mixing 20-30 parts of activated sludge, 20-30 parts of corn stalks, 40-60 parts of microbial fermentation liquid, 10-25 parts of modified palygorskite, 5-10 parts of bentonite, and 4-10 parts of calcium carbonate. The soil remediation agent is applied to the soil, rotary tilled and mixed, and then planted on the soil after 1-2 weeks of watering. The preparation method of the modified palygorskite comprises the following steps: X1. Add palygorskite to a 9wt% hydrochloric acid solution at a solid-liquid ratio of 1:2 g / mL, heat in a water bath to 50-60°C, shake for 2-4 hours, filter, dry, and crush to obtain activated palygorskite; X2. Add activated palygorskite into water, stir evenly to obtain a gel, then add trimethoxy(2-pyridine-4-ethyl)silane, the mass ratio of activated palygorskite to trimethoxy(2-pyridine-4-ethyl)silane is 1:0.5~2, high-speed shearing at 13000~15000rpm for 10~30min, then filter, wash the residue with ethanol, dry and crush to obtain the product.

2. The method for preparing soil for ecological restoration according to claim 1, characterized in that: The microbial inoculant fermentation liquid comprises Bacillus subtilis, Azotobacter beijerinckii, Bacillus licheniformis and Candida utilis.

3. The method for cultivating ecological restoration soil according to claim 2, characterized in that: The mass ratio of Bacillus subtilis, Azotobacter beijerinckii, Bacillus licheniformis and Candida utilis in the microbial inoculant fermentation liquid is 2-5:3-4:1-3:1-3.

4. The method for cultivating soil for ecological restoration according to claim 2, characterized in that: The microbial agent fermentation liquid is obtained by mixing various strains in proportion, fermenting at 28-32° C., and culturing in a culture medium for 12-15 days.

5. The method for cultivating soil for ecological restoration according to claim 1, characterized in that: The soil remediation agent is applied at 100-200 kg per mu of soil.

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