In-situ passivation remediation method for heavy metals in farmland soil

Abstract

The application provides an in-situ passivation remediation method for heavy metals in farmland soil, and belongs to the field of heavy metal passivation in soil. The in-situ passivation remediation method for heavy metals in farmland soil is composed of the following steps: premixing, primary fermentation and secondary fermentation. The premixing is to uniformly mix pig manure, chicken manure, a composite passivation agent, a microbial inoculum and farmland soil, to adjust the C / N ratio and the water content of the mixture, to obtain a premix, and then to perform primary fermentation and secondary fermentation in an aerobic environment. The in-situ passivation remediation method for heavy metals in farmland soil can effectively combine the passivation agent with the compost fermentation, avoid the adverse effects of the fermentation components on the passivation agent during the composting process, improve the adaptability to different soil characteristics, realize stable and efficient treatment of different characteristic soils, further improve the in-situ passivation remediation effect on heavy metals in farmland soil, and effectively avoid the situation that the heavy metals in the soil are released again after the soil heavy metals are passivated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of soil heavy metal passivation, in particular to an in-situ passivation remediation method for farmland soil heavy metals. BACKGROUND

[0002] Currently, heavy metals in the soil will accumulate over time, not only affecting the normal growth of crops, but also eventually enriching in the human body through food chains and other pathways, endangering human health. "Source control" is a measure to prevent and control soil heavy metal pollution. However, due to the different types and degrees of industrial development in different regions, the physicochemical properties of the soil in different regions will show obvious spatial heterogeneity; at the same time, different heavy metal elements in farmland soil will change dynamically with time and accumulation, which comprehensively leads to the fact that the existing passivation remediation methods for farmland soil heavy metals cannot effectively adapt to the soil characteristics of different regions, and thus cannot achieve stable and efficient treatment of different characteristics of soil in different regions.

[0003] "Polluted soil remediation" is also an important measure to prevent and control soil heavy metal pollution. The in-situ passivation technology for soil heavy metals is to add passivation components to soil containing heavy metals, and at the same time, to fix the heavy metals in the soil by a certain passivation method, or to convert the high-valence heavy metals with strong activity into low-valence and residual state with low pollution through precipitation / co-precipitation, chemical adsorption, ion exchange, organic complexation, oxidation and reduction, and thus to achieve the passivation remediation of heavy metal soil.

[0004] Among them, the commonly used in-situ passivation method for soil heavy metals mainly includes inorganic method, organic method and inorganic-organic method. The inorganic method is to use inorganic passivation agent for in-situ passivation remediation of farmland soil heavy metals, which has the characteristics of simple operation and is suitable for large-area soil remediation. However, the inorganic passivation agent required is large in amount, the treatment effect of different characteristics of soil in different regions is unstable, and it may also cause secondary pollution to the soil. In addition, the fixed soil heavy metals may also be released again to pollute the soil.

[0005] The organic method is to use compost to fix heavy metals in the soil through adsorption complexation, precipitation and oxidation reduction while degrading organic pollutants in the soil by microbial aerobic fermentation. Compared with other soil heavy metal passivation methods, compost fermentation has the advantages of easy access to raw materials (livestock and poultry manure, etc.), not only fixing heavy metals, but also providing nutrients for soil and improving soil physical and chemical properties. Using poultry manure compost to passivate and remediate heavy metal contaminated soil has the dual significance of agricultural pollution reuse and ecological remediation. However, in the process of composting farmland soil heavy metals, there is still a problem of unstable fermentation treatment effect of different characteristics of soil in different regions, and the fermentation treatment effect needs to be further improved.

[0006] Further, in the inorganic-organic method, the method of combining inorganic passivator with compost can avoid the defects of single method to a certain extent, but in the treatment of different characteristics of soil in different areas, the inorganic passivator cannot effectively cooperate with the composting process, and the fermentation components generated in the composting process also affect the effect of the inorganic passivator, and the passivation and repair effect of the heavy metals in the farmland soil needs to be further improved. SUMMARY

[0007] In order to solve the technical problems in the prior art, the present application provides an in-situ passivation and repair method for heavy metals in farmland soil, which can realize effective cooperation of passivation agent and compost fermentation, avoid the adverse effects of fermentation components on passivation agent during composting process, improve the adaptability to different soil characteristics, realize stable and efficient treatment of different characteristics of soil, further improve the in-situ passivation and repair effect of heavy metals in farmland soil, and effectively avoid the release of soil heavy metals after passivation.

[0008] To solve the above technical problems, the technical solutions adopted by the present application are as follows:

[0009] An in-situ passivation and repair method for heavy metals in farmland soil, comprising the following steps: premixing, primary fermentation and secondary fermentation.

[0010] The premixing method is to mix pig manure, chicken manure, composite passivation agent, microbial inoculum and farmland soil uniformly, adjust the C / N ratio and moisture content of the mixture to obtain a premix;

[0011] The premix is subjected to primary fermentation and secondary fermentation in an aerobic environment to complete the in-situ passivation and repair method for heavy metals in farmland soil;

[0012] The composite passivation agent is composed of the following steps: primary compounding, secondary compounding and modification.

[0013] The primary compounding method is to uniformly grind zeolite powder, mesoporous activated carbon and ZSM-5 molecular sieve, and then treat the mixture with a treatment solution to obtain a primary compound;

[0014] The treatment solution is an ethanol solution containing dissolved vinyltri(β-methoxyethoxy)silane;

[0015] The secondary compounding method is to put zirconium chloride and iron chloride into N,N-dimethylformamide (DMF) and disperse uniformly to obtain a first dispersion liquid; put terephthalic acid and acetic acid into N,N-dimethylformamide (DMF) and disperse uniformly to obtain a second dispersion liquid; mix the first dispersion liquid, the second dispersion liquid and the primary compound, and then react at 120-130℃ in a sealed environment to obtain a secondary compound.

[0016] The modification method is that the secondary composite is modified by thiol to prepare the composite passivator.

[0017] Further, in the premix, the microbial agent is a combination of Bacillus subtilis, Bacillus laterosporus and Candida utilis; the weight ratio of Bacillus subtilis, Bacillus laterosporus and Candida utilis is 5-6:5-6:2-2.5.

[0018] Preferably, in the premix, the C / N ratio of the mixed material is adjusted to 23-25:1, and the water content of the mixed material is controlled to 50-55wt%;

[0019] The weight ratio of pig manure, chicken manure, composite passivator, microbial agent and farmland soil is 18-20:18-20:5-6:0.4-0.5:400-420.

[0020] Preferably, in the primary compounding, the zeolite powder, the mesoporous activated carbon and the ZSM-5 molecular sieve are uniformly ball milled, then sprayed into a treatment solution, continuously ball milled, vacuum dried to prepare the primary composite;

[0021] In the treatment solution, the concentration of vinyl tris(β-methoxyethoxy)silane is 4-4.5wt%;

[0022] The weight ratio of the zeolite powder, the mesoporous activated carbon, the ZSM-5 molecular sieve and the treatment solution is 10-12:7-8:3-3.5:2-3.

[0023] Preferably, in the secondary compounding, the first dispersion liquid, the second dispersion liquid and the primary composite are kept at 120-130℃ for 22-24h;

[0024] In the first dispersion liquid, the weight ratio of zirconium chloride, iron chloride and N,N-dimethylformamide is 0.5-0.6:0.1-0.15:20-22;

[0025] In the second dispersion liquid, the weight ratio of terephthalic acid, acetic acid and N,N-dimethylformamide is 0.4-0.5:2-2.5:20-22;

[0026] The weight ratio of the first dispersion liquid, the second dispersion liquid and the primary composite is 1:1:0.16-0.18.

[0027] Further, the modification method is that the secondary composite is put into a modification solution, uniformly dispersed, then heated to 60-65℃ under stirring, after keeping at the temperature and stirring, the solid is separated out; the solid is kept at room temperature for 3-4h in a vacuum environment, then vacuum dried to prepare the composite passivator;

[0028] The modification liquid is a cysteine solution with a concentration of 0.6-0.7 mol / L.

[0029] Further, the one-time fermentation method is as follows: the premix is stacked and formed, and one-time fermentation is carried out in an aerobic environment; the center temperature of the compost is monitored in real time during the one-time fermentation; when the center temperature of the compost reaches 65-70 DEG C, the compost is turned over after 70-75 h of continuous fermentation; the compost is turned over again every 48-50 h after turning over, and the compost is turned over for 3-4 times; the composite reinforcing agent is added during the next turning over, the compost is uniformly turned over, and the one-time fermentation is completed.

[0030] The adding amount of the composite reinforcing agent is 2.5-3% of the dry weight of the farmland soil.

[0031] Further, the preparation method of the composite reinforcing agent is as follows: the secondary composite in the preparation of the composite passivation agent is put into the reinforcing liquid, stirring is carried out until the temperature reaches 45-55 DEG C, the solid is separated after heat preservation and stirring, vacuum drying is carried out, and the composite reinforcing agent is prepared.

[0032] The reinforcing liquid is a deionized water solution in which plantago extract, green tea extract and oregano extract are dispersed.

[0033] Preferably, in the reinforcing liquid, the content of the plantago extract is 2-2.5 wt%, the content of the green tea extract is 2-2.5 wt%, and the content of the oregano extract is 1-1.2 wt%.

[0034] Further, the secondary fermentation method is as follows: after the one-time fermentation is completed, the turning over is stopped, and secondary fermentation is carried out in an aerobic environment; the center temperature of the compost is monitored in real time during the secondary fermentation; when the center temperature of the compost is lower than 42 DEG C, the secondary fermentation is stopped after 4-5 days of standing, and the in-situ passivation and repair of the heavy metals in the farmland soil are completed.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] (1) The in-situ passivation repair method for heavy metals in farmland soil of the present application, by mixing the heavy metal contaminated farmland soil with livestock and poultry manure, composite passivation agent and microbial inoculant in the premixing step to obtain a premix; in the preparation of the composite passivation agent, the zeolite powder, mesoporous activated carbon and ZSM-5 molecular sieve are modified by ball milling with vinyltri(β-methoxyethoxy)silane to obtain a primary composite; the primary composite is then compounded with Zr / Fe metal organic framework to obtain a secondary composite; the secondary composite is then modified with mercapto to prepare the composite passivation agent; then, in the presence of the composite passivation agent, a primary fermentation is carried out to passivate and compost the heavy metals in the farmland soil; then, before the primary fermentation is completed, the composite intensifier is mixed by turning the pile, the secondary composite in the composite intensifier passivates the heavy metals in the farmland soil, and at the same time, the plant active ingredients (plantain extract, green tea extract, oregano extract) reduce the heavy metals in the farmland soil, and a secondary fermentation is carried out; the passivation agent and the composting fermentation can be effectively matched to avoid the adverse effects of the fermentation components on the passivation agent during composting, improve the adaptability to different soil characteristics, realize stable and efficient treatment of different soil characteristics, further improve the in-situ passivation repair effect of the heavy metals in the farmland soil, and effectively avoid the release of the heavy metals in the soil after passivation.

[0037] (2) The in-situ passivation repair method for heavy metals in farmland soil of the present application, after in-situ passivation repair of the farmland soil with heavy metal leaching concentration of Pb 297.313 mg / L, Cd 1.466 mg / L, Zn 262.527 mg / L and Cu 497.139 mg / L, the heavy metal leaching concentration can be reduced to Pb 3.955 mg / L, Cd 0.037 mg / L, Zn 15.064 mg / L and Cu 3.443 mg / L; the passivation rate of heavy metal Pb can reach 98.7%, the passivation rate of heavy metal Cd can reach 97.5%, the passivation rate of heavy metal Zn can reach 94.3%, and the passivation rate of heavy metal Cu can reach 99.3%.

[0038] (3) The in-situ passivation repair method for heavy metals in farmland soil of the present application can achieve good in-situ passivation repair effect, effectively cooperate the passivation agent with the compost fermentation, avoid the adverse effect of the fermentation components on the passivation agent in the compost process, improve the adaptability to different soil characteristics, and realize stable and efficient treatment of different characteristic soils.

[0039] (4) The in-situ passivation repair method for heavy metals in farmland soil of the present application can effectively avoid the release of contaminated soil after the passivation of soil heavy metals; the obtained fermentation product is treated with simulated acid rain solution for 20 times, and the leaching concentration of heavy metals is Pb 4.054 mg / L, Cd 0.038 mg / L, Zn 15.387 mg / L, and Cu 3.510 mg / L; compared with the initial leaching concentration of the fermentation product, the change rate of the leaching concentration of each heavy metal is not greater than 2.7%. DETAILED DESCRIPTION

[0040] In order to have a clearer understanding of the technical features, objects and effects of the present application, the specific embodiments of the present application will be described.

[0041] Example 1

[0042] The present embodiment provides an in-situ passivation repair method for heavy metals in farmland soil. According to the relevant provisions of the national standard GB5085.3-2007 "Hazardous Waste Identification Standard Leaching Toxicity Identification", it is determined that the leaching concentration of each heavy metal in the farmland soil targeted by the present embodiment is: Pb 297.313 mg / L, Cd 1.466 mg / L, Zn 262.527 mg / L, and Cu 497.139 mg / L.

[0043] The in-situ passivation repair method for heavy metals in farmland soil of the present embodiment comprises the following steps:

[0044] 1. Pre-mixing

[0045] The pig manure, chicken manure, composite passivation agent, microbial inoculant and farmland soil contaminated by heavy metals are mixed uniformly, then the sawdust is used to adjust the C / N ratio of the mixture to 23:1, and the moisture content of the mixture is controlled to 50wt%, to obtain a pre-mixture.

[0046] The weight ratio of pig manure, chicken manure, composite passivation agent, microbial agent, and farmland soil is 18:18:5:0.4:400.

[0047] The microbial agent is a composition of Bacillus subtilis, Brevibacillus laterosporus, and Candida utilis. The weight ratio of Bacillus subtilis, Brevibacillus laterosporus, and Candida utilis is 5:5:2.

[0048] Each strain in the microbial agent can be purchased through a commercial channel. The Latin name of Bacillus subtilis is Bacillus subtilis, and the effective bacterial concentration is ≥150 billion cfu / g. The Latin name of Brevibacillus laterosporus is Brevibacillus laterosporus, and the effective bacterial concentration is ≥100 billion cfu / g. The Latin name of Candida utilis is Candida utilis, and the effective bacterial concentration is ≥80 billion cfu / g.

[0049] The composite passivation agent is prepared by the following steps:

[0050] 1) Primary compounding

[0051] The zeolite powder, mesoporous activated carbon, ZSM-5 molecular sieve, and deionized water are put into a ball mill, the ball-to-material ratio is controlled to be 10:1, the ball milling speed is 150 rpm, after ball milling for 5 min, the treatment solution is sprayed, and after continuing ball milling for 10 min, a ball milling mixture is obtained; the ball milling mixture is washed with deionized water, and then transferred into a vacuum drying box, dried at 80°C for 10 h in a vacuum degree of 800 Pa, to prepare a primary compound.

[0052] The treatment solution is an ethanol solution in which vinyltri(β-methoxyethoxy)silane is dissolved; in the treatment solution, the concentration of vinyltri(β-methoxyethoxy)silane is 4 wt%; and the volume concentration of the ethanol solution is 55%.

[0053] The weight ratio of the zeolite powder, mesoporous activated carbon, ZSM-5 molecular sieve, deionized water, and treatment solution is 10:7:3:9:2.

[0054] 2) Secondary compounding

[0055] The zirconium chloride and the ferric chloride are put into N,N-dimethylformamide DMF and uniformly dispersed by ultrasonic to prepare a first dispersion liquid; the terephthalic acid and the acetic acid are put into N,N-dimethylformamide DMF and uniformly dispersed by ultrasonic to prepare a second dispersion liquid; the first dispersion liquid, the second dispersion liquid and a primary compound are transferred into a high-pressure reaction kettle, the high-pressure reaction kettle is sealed, the whole high-pressure reaction kettle is transferred into a thermostat, and the reaction is carried out at 120℃ for 22 hours, and then the solid is separated after natural cooling to room temperature; the solid is sequentially washed by DMF and ethanol, and then placed in a vacuum drying box, dried at 70℃ for 8 hours in a vacuum degree of 0.08 MPa to prepare a secondary compound.

[0056] In the first dispersion liquid, the weight ratio of the zirconium chloride, the ferric chloride and the N,N-dimethylformamide is 0.5:0.1:20.

[0057] In the second dispersion liquid, the weight ratio of the terephthalic acid, the acetic acid and the N,N-dimethylformamide is 0.4:2:20.

[0058] The weight ratio of the first dispersion liquid, the second dispersion liquid and the primary compound is 1:1:0.16.

[0059] 3) Modification

[0060] The secondary compound is put into 5 times the volume of a modification liquid, uniformly dispersed by ultrasonic, and then heated to 60℃ at a heating rate of 0.2℃ / min under stirring, and the solid is separated after incubation and stirring for 2 hours, and then transferred into a vacuum drying box, and dried at 60℃ to constant weight after being placed at room temperature for 3 hours in a vacuum degree of 0.05 MPa, and then crushed to prepare a composite passivator.

[0061] In the modification liquid, the concentration of the cysteine solution is 0.6 mol / L.

[0062] 2, Primary fermentation

[0063] The premix is formed into a pile, and the oxygen volume content in the environment is controlled to be 15% by forced ventilation to perform primary fermentation; the center temperature of the compost is monitored in real time during the primary fermentation, and the compost is turned over after the center temperature of the compost reaches 65℃ and continues to ferment for 70 hours; the compost is turned over again every 48 hours after turning over, and the compost is turned over for a total of 3 times, and the composite reinforcing agent is added during the next turning over, the compost is uniformly turned over, and the primary fermentation is completed.

[0064] In the composite reinforcing agent, the addition amount is 2.5% of the dry weight of the farmland soil.

[0065] The preparation method of the composite reinforcing agent is as follows: the secondary composite prepared in the preparation of the composite passivator is put into 8 times the volume of the reinforcing liquid, stirred and heated to 45 DEG C, and after 10 hours of incubation and stirring, the solid is separated, transferred into a vacuum drying oven, dried at 70 DEG C to constant weight under a vacuum degree of 0.02 MPa, and ground to obtain the composite reinforcing agent.

[0066] The reinforcing liquid is a deionized water solution in which plantain extract, green tea extract and oregano extract are dispersed. The content of the plantain extract in the reinforcing liquid is 2 wt%, the content of the green tea extract is 2 wt%, and the content of the oregano extract is 1 wt%. The plantain extract, the green tea extract and the oregano extract in the reinforcing liquid can be obtained by commercial channels.

[0067] 3, secondary fermentation

[0068] After the primary fermentation is completed, the turning is stopped, and the secondary fermentation is performed by forced aeration to control the oxygen volume content in the environment to be 15%. The center temperature of the compost is monitored in real time during the secondary fermentation, and when the center temperature of the compost is lower than 42 DEG C, the secondary fermentation is stopped after 4 days of standing to obtain the fermentation product, and the in-situ passivation remediation of the heavy metals in the farmland soil is completed.

[0069] It is determined that the leaching concentration of each heavy metal in the fermentation product obtained after the in-situ passivation remediation of the heavy metals in the farmland soil by the method of the embodiment is: Pb 4.802 mg / L, Cd 0.043 mg / L, Zn 17.417 mg / L, and Cu 3.570 mg / L.

[0070] It is calculated that the passivation rate of the heavy metal Pb in the in-situ passivation remediation method of the heavy metals in the farmland soil in the embodiment is 98.4%, the passivation rate of the heavy metal Cd is 97.1%, the passivation rate of the heavy metal Zn is 93.4%, and the passivation rate of the heavy metal Cu is 99.3%.

[0071] Embodiment 2

[0072] The embodiment provides an in-situ passivation remediation method of heavy metals in farmland soil. According to the relevant provisions of the national standard GB5085.3-2007 "Hazardous waste identification standard: leaching toxicity identification", it is determined that the leaching concentration of each heavy metal in the farmland soil targeted by the embodiment is: Pb 297.313 mg / L, Cd 1.466 mg / L, Zn 262.527 mg / L, and Cu 497.139 mg / L.

[0073] The in-situ passivation remediation method of heavy metals in farmland soil provided in the embodiment is composed of the following steps:

[0074] 1, premixing

[0075] The pig manure, chicken manure, composite passivation agent, microbial inoculant and the farmland soil polluted by heavy metals are mixed uniformly, then the sawdust is used to adjust the C / N ratio of the mixture to 24:1, and the water content of the mixture is controlled to 52wt%, to obtain a premix.

[0076] The weight ratio of the pig manure, chicken manure, composite passivation agent, microbial inoculant and farmland soil is 19:19:5.5:0.45:410.

[0077] The microbial inoculant is a composition of Bacillus subtilis, Brevibacillus laterosporus and Candida utilis. The weight ratio of Bacillus subtilis, Brevibacillus laterosporus and Candida utilis is 5.5:5.5:2.3.

[0078] Each strain in the microbial inoculant can be purchased through the market. The Latin name of Bacillus subtilis is Bacillus subtilis, and the effective bacterial concentration is ≥1.5 billion cfu / g; the Latin name of Brevibacillus laterosporus is Brevibacillus laterosporus, and the effective bacterial concentration is ≥1 billion cfu / g; the Latin name of Candida utilis is Candida utilis, and the effective bacterial concentration is ≥0.8 billion cfu / g.

[0079] The composite passivation agent is prepared by the following steps:

[0080] 1) Primary compounding

[0081] The zeolite powder, mesoporous activated carbon, ZSM-5 molecular sieve and deionized water are put into a ball mill, the ball-to-material ratio is controlled to be 11:1, the ball milling speed is 180 rpm, after ball milling for 7 min, a treatment solution is sprayed, and after continuing ball milling for 15 min, a ball milling mixture is obtained; the ball milling mixture is washed with deionized water, and then transferred into a vacuum drying box, dried at 85°C for 11h in a vacuum degree of 850Pa, to prepare a primary compound.

[0082] The treatment solution is an ethanol solution in which vinyltri(β-methoxyethoxy)silane is dissolved; in the treatment solution, the concentration of vinyltri(β-methoxyethoxy)silane is 4.2wt%; the volume concentration of the ethanol solution is 58%.

[0083] The weight ratio of the zeolite powder, mesoporous activated carbon, ZSM-5 molecular sieve, deionized water and treatment solution is 11:7.5:3.2:9.5:2.5.

[0084] 2) Secondary compounding

[0085] The zirconium chloride, iron chloride are put into N,N-dimethylformamide DMF, and uniformly dispersed by ultrasonic to prepare a first dispersion liquid; the terephthalic acid, acetic acid are put into N,N-dimethylformamide DMF, and uniformly dispersed by ultrasonic to prepare a second dispersion liquid; the first dispersion liquid, the second dispersion liquid, and a primary compound are transferred into a high-pressure reaction kettle, and after the high-pressure reaction kettle is sealed, the whole high-pressure reaction kettle is transferred into a thermostat, and after being kept at a temperature of 125℃ for 23h, the solid is separated out after natural cooling to room temperature; the solid is sequentially washed by DMF and ethanol, and then placed in a vacuum drying box, and dried at 75℃ for 9h under a vacuum degree of 0.085MPa to prepare a secondary compound.

[0086] In the first dispersion liquid, the weight ratio of zirconium chloride, iron chloride, and N,N-dimethylformamide is 0.55:0.13:21.

[0087] In the second dispersion liquid, the weight ratio of terephthalic acid, acetic acid, and N,N-dimethylformamide is 0.45:2.2:21.

[0088] The weight ratio of the first dispersion liquid, the second dispersion liquid, and the primary compound is 1:1:0.17.

[0089] 3) Modification

[0090] The secondary compound is put into 5.5 times the volume of a modification liquid, and uniformly dispersed by ultrasonic, and then under stirring, heated to 62℃ at a heating rate of 0.25℃ / min, and after being kept at the temperature for 2.5h, the solid is separated out, and then transferred into a vacuum drying box, and kept at room temperature for 3.5h under a vacuum degree of 0.055MPa, and then dried at 65℃ until the weight is constant, and then crushed to prepare a composite passivator.

[0091] In the formula, the modification liquid is a cysteine solution with a concentration of 0.65mol / L.

[0092] 2, Primary fermentation

[0093] The premix is formed into a pile, and subjected to primary fermentation by forced ventilation to control the oxygen volume content in the environment to be 15.5%; the center temperature of the compost is monitored in real time during the primary fermentation, and after the center temperature of the compost reaches 68℃, the compost is further fermented for 72h, and then turned over; the compost is turned over again every 49h after turning over, and the compost is turned over a total of 4 times, and then the composite reinforcing agent is added during the next turning over, and the compost is uniformly turned over to complete the primary fermentation.

[0094] In the formula, the addition amount of the composite reinforcing agent is 2.8% of the dry weight of the farmland soil.

[0095] The preparation method of the composite reinforcing agent is as follows: the secondary composite prepared in the preparation of the composite passivator is put into 9 times the volume of the reinforcing liquid, stirred and heated to 50 DEG C, and after 11 hours of heat preservation and stirring, the solid is separated, transferred into a vacuum drying oven, dried to constant weight at 75 DEG C under a vacuum degree of 0.025 MPa, and crushed to obtain the composite reinforcing agent.

[0096] The reinforcing liquid is a deionized water solution in which plantain extract, green tea extract and oregano extract are dispersed. The content of the plantain extract in the reinforcing liquid is 2.2 wt%, the content of the green tea extract is 2.3 wt%, and the content of the oregano extract is 1.1 wt%. The plantain extract, the green tea extract and the oregano extract in the reinforcing liquid can be obtained by commercial channels.

[0097] 3, secondary fermentation

[0098] After the primary fermentation is completed, the turning is stopped, forced ventilation is adopted to control the oxygen volume content in the environment to be 15.5%, and secondary fermentation is carried out. The center temperature of the compost is monitored in real time during the secondary fermentation, and when the center temperature of the compost is lower than 42 DEG C, the secondary fermentation is stopped after 4.5 days of standing, the fermentation product is obtained, and the in-situ passivation remediation of the heavy metals in the farmland soil is completed.

[0099] It is determined that the leaching concentration of each heavy metal in the fermentation product obtained after the in-situ passivation remediation of the heavy metals in the farmland soil by the method of the embodiment is: Pb 3.955 mg / L, Cd 0.037 mg / L, Zn 15.064 mg / L, and Cu 3.443 mg / L.

[0100] It is calculated that the passivation rate of the heavy metal Pb in the in-situ passivation remediation method of the heavy metals in the farmland soil in the embodiment is 98.7%, the passivation rate of the heavy metal Cd is 97.5%, the passivation rate of the heavy metal Zn is 94.3%, and the passivation rate of the heavy metal Cu is 99.3%.

[0101] Embodiment 3

[0102] The embodiment provides an in-situ passivation remediation method of heavy metals in farmland soil. According to the relevant provisions of the national standard GB5085.3-2007 "Hazardous waste identification standard Leaching toxicity identification", it is determined that the leaching concentration of each heavy metal in the farmland soil targeted by the embodiment is: Pb 297.313 mg / L, Cd 1.466 mg / L, Zn 262.527 mg / L, and Cu 497.139 mg / L.

[0103] The in-situ passivation remediation method of heavy metals in farmland soil provided by the embodiment is composed of the following steps:

[0104] 1, premixing

[0105] The pig manure, chicken manure, composite passivation agent, microbial inoculant and farmland soil contaminated by heavy metals are mixed uniformly, then the sawdust is used to adjust the C / N ratio of the mixture to 25:1, and the water content of the mixture is controlled to 55wt%, to obtain a premix.

[0106] The weight ratio of the pig manure, chicken manure, composite passivation agent, microbial inoculant and farmland soil is 20:20:6:0.5:420.

[0107] The microbial inoculant is a composition of Bacillus subtilis, Brevibacillus laterosporus and Candida utilis. The weight ratio of Bacillus subtilis, Brevibacillus laterosporus and Candida utilis is 6:6:2.5.

[0108] Each strain in the microbial inoculant can be purchased through the market. The Latin name of Bacillus subtilis is Bacillus subtilis, and the effective bacterial concentration is ≥1.5 billion cfu / g; the Latin name of Brevibacillus laterosporus is Brevibacillus laterosporus, and the effective bacterial concentration is ≥10 billion cfu / g; the Latin name of Candida utilis is Candida utilis, and the effective bacterial concentration is ≥8 billion cfu / g.

[0109] The composite passivation agent is prepared by the following steps:

[0110] 1) Primary compounding

[0111] The zeolite powder, mesoporous activated carbon, ZSM-5 molecular sieve and deionized water are put into a ball mill, the ball-to-material ratio is controlled to be 12:1, the ball milling speed is 200 rpm, after ball milling for 10 min, a treatment solution is sprayed, and after continuing ball milling for 20 min, a ball milling mixture is obtained; the ball milling mixture is washed with deionized water, and then transferred into a vacuum drying oven, dried at 90℃ for 12h in a vacuum degree of 900Pa, to prepare a primary compound.

[0112] The treatment solution is an ethanol solution in which vinyltri(β-methoxyethoxy)silane is dissolved; in the treatment solution, the concentration of vinyltri(β-methoxyethoxy)silane is 4.5wt%; the volume concentration of the ethanol solution is 60%.

[0113] The weight ratio of the zeolite powder, mesoporous activated carbon, ZSM-5 molecular sieve, deionized water and treatment solution is 12:8:3.5:10:3.

[0114] 2) Secondary compounding

[0115] The zirconium chloride and the ferric chloride are put into N,N-dimethylformamide DMF and uniformly dispersed by ultrasonic to prepare a first dispersion liquid; the terephthalic acid and the acetic acid are put into N,N-dimethylformamide DMF and uniformly dispersed by ultrasonic to prepare a second dispersion liquid; the first dispersion liquid, the second dispersion liquid and a primary compound are transferred into a high-pressure reaction kettle, the high-pressure reaction kettle is sealed, the whole high-pressure reaction kettle is transferred into a thermostat, and the reaction is carried out at 130 DEG C for 24 hours; then, the solid is separated after natural cooling to room temperature; the solid is sequentially washed by DMF and ethanol, and then placed in a vacuum drying box, dried at 80 DEG C for 10 hours in a vacuum degree of 0.09 MPa, and a secondary compound is prepared.

[0116] The weight ratio of the zirconium chloride, the ferric chloride and N,N-dimethylformamide in the first dispersion liquid is 0.6:0.15:22.

[0117] The weight ratio of the terephthalic acid, the acetic acid and N,N-dimethylformamide in the second dispersion liquid is 0.5:2.5:22.

[0118] The weight ratio of the first dispersion liquid, the second dispersion liquid and the primary compound is 1:1:0.18.

[0119] 3) Modification

[0120] The secondary compound is put into 6 times the volume of a modification liquid, uniformly dispersed by ultrasonic, heated to 65 DEG C at a heating rate of 0.3 DEG C / min under stirring, and then the solid is separated after stirring for 3 hours; the solid is transferred into a vacuum drying box, placed at room temperature for 4 hours in a vacuum degree of 0.06 MPa, and then dried at 70 DEG C until constant weight; the compound passivation agent is prepared after crushing.

[0121] The modification liquid is a cysteine solution with a concentration of 0.7 mol / L.

[0122] 2, Primary fermentation

[0123] The premix is formed into a pile, and the primary fermentation is carried out by forced ventilation to control the oxygen volume content in the environment to be 16%; the compost center temperature is monitored in real time during the primary fermentation, and the compost center temperature is kept at 70 DEG C; the compost is turned over after 75 hours of continuous fermentation; the compost is turned over again every 50 hours, and the compost is turned over a total of 4 times; the composite reinforcing agent is added during the next turning over, the compost is uniformly turned over, and the primary fermentation is completed.

[0124] The addition amount of the composite reinforcing agent is 3% of the dry weight of the farmland soil.

[0125] The preparation method of the composite reinforcing agent is as follows: the secondary composite prepared in the preparation of the composite passivator is put into 10 times the volume of the reinforcing liquid, stirred and heated to 55°C, and then kept stirring for 12 hours. After that, the solid is separated and transferred into a vacuum drying oven, dried at 80°C under a vacuum degree of 0.03 MPa until the weight is constant, and then crushed to obtain the composite reinforcing agent.

[0126] The reinforcing liquid is a deionized water solution in which the plantago extract, the green tea extract and the oregano extract are dispersed. The content of the plantago extract in the reinforcing liquid is 2.5 wt%, the content of the green tea extract is 2.5 wt%, and the content of the oregano extract is 1.2 wt%. The plantago extract, the green tea extract and the oregano extract in the reinforcing liquid can be purchased through the market.

[0127] 3, secondary fermentation

[0128] After the primary fermentation is completed, the turning is stopped, and the secondary fermentation is carried out by forced aeration to control the oxygen volume content in the environment to be 16%. During the secondary fermentation, the center temperature of the compost is monitored in real time. When the center temperature of the compost is lower than 42°C, the secondary fermentation is stopped after 5 days of standing, and the fermentation product is obtained, and the in-situ passivation remediation of the heavy metals in the farmland soil is completed.

[0129] It is determined that, after the in-situ passivation remediation of the heavy metals in the farmland soil is carried out by the method of the embodiment, the leaching concentration of each heavy metal in the obtained fermentation product is: Pb 4.258 mg / L, Cd 0.040 mg / L, Zn 15.936 mg / L, and Cu 3.501 mg / L.

[0130] It is calculated that, in the in-situ passivation remediation method of the heavy metals in the farmland soil in the embodiment, the passivation rate of the heavy metal Pb is 98.6%, the passivation rate of the heavy metal Cd is 97.3%, the passivation rate of the heavy metal Zn is 93.9%, and the passivation rate of the heavy metal Cu is 99.3%.

[0131] Embodiment 4

[0132] The in-situ passivation remediation method of the heavy metals in the farmland soil in the embodiment is the same as that in Embodiment 2, and the difference is that the content of the heavy metals in the farmland soil is different. According to the relevant provisions of the national standard GB5085.3-2007 "Hazardous Waste Identification Standard Leaching Toxicity Identification", it is determined that the leaching concentration of each heavy metal in the farmland soil in the embodiment is: Pb 368.434 mg / L, Zn 436.825 mg / L, Cr 114.406 mg / L, and As 10.711 mg / L.

[0133] The leaching concentration of each heavy metal in the fermentation product obtained after in-situ passivation repair of the heavy metals in the farmland soil by the method of the embodiment is: Pb 4.917 mg / L, Zn 27.291 mg / L, Cr 4.228 mg / L, and As 0.028 mg / L.

[0134] It is calculated that the in-situ passivation repair method of the heavy metals in the farmland soil in the embodiment has a passivation rate of 98.7% for the heavy metal Pb, a passivation rate of 93.8% for the heavy metal Zn, a passivation rate of 96.3% for the heavy metal Cr, and a passivation rate of 99.7% for the heavy metal As.

[0135] Example 5

[0136] The in-situ passivation repair method of the heavy metals in the farmland soil of the embodiment is the same as that of Example 2, and the difference lies in that the heavy metal content in the farmland soil is different. According to the relevant provisions of the national standard GB5085.3-2007 Identification Standard for Hazardous Waste Identification of Leaching Toxicity, it is determined that the leaching concentration of each heavy metal in the farmland soil of the embodiment is: Pb 301.605 mg / L, Mn 584.961 mg / L, Hg 3.314 mg / L, and Cr 148.768 mg / L.

[0137] The leaching concentration of each heavy metal in the fermentation product obtained after in-situ passivation repair of the heavy metals in the farmland soil by the method of the embodiment is: Pb 4.095 mg / L, Mn 24.286 mg / L, Hg 0.031 mg / L, and Cr 5.309 mg / L.

[0138] It is calculated that the in-situ passivation repair method of the heavy metals in the farmland soil in the embodiment has a passivation rate of 98.6% for the heavy metal Pb, a passivation rate of 95.8% for the heavy metal Mn, a passivation rate of 99.1% for the heavy metal Hg, and a passivation rate of 96.4% for the heavy metal Cr.

[0139] Comparative Example 1

[0140] The technical solution of Example 2 is adopted, and the same heavy metal content farmland soil is treated, and the difference lies in that: 1) the preparation of the composite passivation agent omits the secondary compounding and modification steps, and the primary compound is replaced by the composite passivation agent; 2) the plantain extract, green tea extract, and oregano extract are replaced by the composite reinforcing agent and used in the first fermentation; wherein the total amount of the plantain extract, green tea extract, and oregano extract is 0.05% of the dry weight of the farmland soil; and the weight ratio of the plantain extract, green tea extract, and oregano extract is 2.2:2.3:1.1.

[0141] The leaching concentration of each heavy metal in the fermentation product obtained after in-situ passivation repair of the heavy metals in the farmland soil by the method of the embodiment is: Pb 29.137 mg / L, Cd 0.150 mg / L, Zn 41.742 mg / L, and Cu 39.274 mg / L.

[0142] The passivation rate of the in-situ passivation repair method of the heavy metals in the farmland soil in the embodiment is 90.2% for Pb, 89.8% for Cd, 84.1% for Zn, and 92.1% for Cu.

[0143] Comparative Example 2

[0144] The technical solution of Example 2 is adopted, and the farmland soil with the same heavy metal content is treated, with the difference being that: 1) in the preparation of the composite passivation agent, the first compounding step is omitted, and zeolite powder is used to replace the first compound for the second compounding step; 2) the addition of the composite intensifier is omitted.

[0145] The leaching concentration of each heavy metal in the fermentation product obtained after in-situ passivation repair of the heavy metals in the farmland soil by the method of the embodiment is: Pb 29.137 mg / L, Cd 0.150 mg / L, Zn 41.742 mg / L, and Cu 39.274 mg / L.

[0146] The passivation rate of the in-situ passivation repair method of the heavy metals in the farmland soil in the embodiment is 90.2% for Pb, 89.8% for Cd, 84.1% for Zn, and 92.1% for Cu.

[0147] Further, the fermentation products obtained in Example 2, Comparative Example 1, and Comparative Example 2 are respectively placed in a constant temperature environment of 25°C, and a simulated acid rain solution (the pH of the simulated acid rain solution is 5.0, the acid component in the simulated acid rain solution is sulfuric acid and nitric acid, and the weight ratio of sulfuric acid to nitric acid is 10:1) is uniformly sprayed on the fermentation products, the spraying amount of the simulated acid rain solution being 60% of the dry weight of the fermentation products; after the simulated acid rain solution is sprayed, the fermentation products are left to stand for 6 hours and then dried at 65°C; after the above process is repeated for 20 times, the leaching concentration of each heavy metal in the fermentation product is determined. At the same time, the change rate of the leaching concentration of each heavy metal in the fermentation product after treatment with the simulated acid rain solution is calculated compared with the initial leaching concentration of each heavy metal in the fermentation product.

[0148] The specific results are shown in the following table:

[0149]

[0150] It can be seen that the in-situ passivation repair method for heavy metals in farmland soil of the present application, by mixing the farmland soil contaminated by heavy metals with livestock and poultry manure, composite passivation agent and microbial inoculum in the premixing step to obtain a premix; in the preparation of the composite passivation agent, zeolite powder, mesoporous activated carbon and ZSM-5 molecular sieve are modified by ball milling with vinyltri(β-methoxyethoxy)silane to obtain a primary composite; the primary composite is then compounded with Zr / Fe metal organic framework to obtain a secondary composite; the secondary composite is then modified with mercapto to prepare the composite passivation agent; then, in the presence of the composite passivation agent, a primary fermentation is carried out to passivate and compost the heavy metals in the farmland soil; then, before the primary fermentation is completed, the composite intensifier is mixed into the compost by turning the pile, the secondary composite in the composite intensifier passivates the heavy metals in the farmland soil, and at the same time, the plant active ingredients (plantain extract, green tea extract, oregano extract) reduce the heavy metals in the farmland soil, and a secondary fermentation is carried out; the passivation agent and the compost fermentation can be effectively matched to avoid the adverse effects of the fermentation components on the passivation agent during composting, improve the adaptability to different soil characteristics, realize stable and efficient treatment of different characteristic soils, further improve the in-situ passivation repair effect of the heavy metals in the farmland soil, and effectively avoid the release of the heavy metals in the soil after passivation.

[0151] Unless otherwise stated, the percentages used in the present application are mass percentages.

[0152] Finally, it should be noted that: the above only describes the preferred embodiments of the present application and is not intended to limit the present application, 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 described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for in-situ passivation remediation of heavy metals in farmland soil, characterized in that, It consists of the following steps: premixing, primary fermentation, and secondary fermentation; The premixing method involves mixing pig manure, chicken manure, compound passivating agent, microbial agent and farmland soil evenly, adjusting the C / N ratio and moisture content of the mixture to obtain a premix. The premixed material undergoes primary and secondary fermentation in an aerobic environment to complete the in-situ passivation remediation method for heavy metals in farmland soil. The composite passivating agent is prepared by the following steps: primary composite, secondary composite, and modification; The method of primary composite is to ball-mill zeolite powder, mesoporous activated carbon, and ZSM-5 molecular sieve evenly, and then treat them with a treatment solution to obtain a primary composite. The treatment solution is an ethanol solution containing vinyltris(β-methoxyethoxy)silane; The secondary composite method is as follows: zirconium chloride and ferric chloride are added to N,N-dimethylformamide and dispersed evenly to obtain a first dispersion; terephthalic acid and acetic acid are added to N,N-dimethylformamide and dispersed evenly to obtain a second dispersion; the first dispersion, the second dispersion, and the primary composite are mixed and reacted in a closed environment at 120-130℃ to obtain the secondary composite. In the secondary compounding process, the reaction time of the first dispersion, the second dispersion, and the primary composite at 120-130℃ is 22-24 hours; in the first dispersion, the weight ratio of zirconium chloride, ferric chloride, and N,N-dimethylformamide is 0.5-0.6:0.1-0.15:20-22; in the second dispersion, the weight ratio of terephthalic acid, acetic acid, and N,N-dimethylformamide is 0.4-0.5:2-2.5:20-22; and the weight ratio of the first dispersion, the second dispersion, and the primary composite is 1:1:0.16-0.

18. The modification method involves modifying the secondary complex with thiol groups to obtain a composite passivating agent. The method of primary fermentation is as follows: the premix is ​​piled into shape and fermented in an aerobic environment; the temperature of the compost center is monitored in real time during the primary fermentation process; when the temperature of the compost center reaches 65-70℃, fermentation continues for 70-75 hours, and then the pile is turned; after turning, the pile is turned again every 48-50 hours, for a total of 3-4 times; when turning the pile for the next time, a compound fortifying agent is added, and the pile is turned evenly to complete the primary fermentation. The amount of the composite reinforcing agent added is 2.5-3% of the dry weight of the farmland soil; The preparation method of the composite reinforcing agent is as follows: the secondary complex in the preparation of the composite passivating agent is added to the reinforcing liquid, stirred and heated to 45-55℃, kept warm and stirred, the solid is separated, and vacuum dried to obtain the composite reinforcing agent; the reinforcing liquid is a deionized aqueous solution containing plantain extract, green tea extract and oregano extract.

2. The in-situ passivation remediation method for heavy metals in farmland soil according to claim 1, characterized in that, In the premix, the microbial agent is a composition of Bacillus subtilis, Bacillus laterosporus, and Candida utilis; the weight ratio of Bacillus subtilis, Bacillus laterosporus, and Candida utilis is 5-6:5-6:2-2.

5.

3. The in-situ passivation remediation method for heavy metals in farmland soil according to claim 1, characterized in that, In the premixing process, the C / N ratio of the mixture is adjusted to 23-25:1, and the moisture content of the mixture is controlled to be 50-55 wt%. The weight ratio of pig manure, chicken manure, compound passivating agent, microbial agent, and farmland soil is 18-20:18-20:5-6:0.4-0.5:400-420.

4. The in-situ passivation remediation method for heavy metals in farmland soil according to claim 1, characterized in that, In the first compounding process, zeolite powder, mesoporous activated carbon, and ZSM-5 molecular sieve are ball-milled until uniform, then sprayed into a treatment solution, ball-milled again, and vacuum dried to obtain the first compound. The concentration of vinyltris(β-methoxyethoxy)silane in the treatment solution is 4-4.5 wt%. The weight ratio of zeolite powder, mesoporous activated carbon, ZSM-5 molecular sieve, and treatment liquid is 10-12:7-8:3-3.5:2-3.

5. The in-situ passivation remediation method for heavy metals in farmland soil according to claim 1, characterized in that, The modification method is as follows: the secondary composite is added to the modification liquid, dispersed evenly, and then heated to 60-65°C under stirring. After stirring and maintaining the temperature, the solid is separated. The solid is then placed in a vacuum environment and allowed to stand at room temperature for 3-4 hours before being vacuum dried to obtain the composite passivating agent. The modified solution is a cysteine ​​solution with a concentration of 0.6-0.7 mol / L.

6. The in-situ passivation remediation method for heavy metals in farmland soil according to claim 1, characterized in that, The strengthening liquid contains 2-2.5 wt% plantain extract, 2-2.5 wt% green tea extract, and 1-1.2 wt% oregano extract.

7. The in-situ passivation remediation method for heavy metals in farmland soil according to claim 1, characterized in that, The secondary fermentation method is as follows: after the primary fermentation is completed, the turning of the compost pile is stopped, and secondary fermentation is carried out in an aerobic environment; during the secondary fermentation process, the temperature of the compost center is monitored in real time. When the temperature of the compost center is lower than 42℃, the compost is left to stand for 4-5 days, and the secondary fermentation is stopped to complete the in-situ passivation and remediation of heavy metals in farmland soil.

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