Heavy metal contaminated soil passivation remediation conditioner and application thereof

Abstract

The application discloses a heavy metal contaminated soil passivation remediation conditioner and application thereof, and belongs to the technical field of soil remediation. The conditioner takes pomelo peel activated carbon as a carrier, loads ammonium phosphomolybdate nanoclusters after constructing a porous structure through phosphoric acid activation, realizes stable anchoring of active components by constructing a polycaprolactone crosslinking network through click chemistry, and enhances material dispersibility by combining with amphoteric ion functionalization modification process. When applied, the conditioner is compounded and applied with potassium feldspar powder, calcium magnesium phosphate fertilizer, microbial inoculum and other components to form a multilevel adsorption-chelation system, realizes sustained fixation of heavy metals through the synergistic effect of ion exchange, coordination chelation and electrostatic adsorption, and simultaneously improves soil microecology. The prepared conditioner has three-dimensional crosslinking network structure stability and amphoteric ion hydration dispersibility, can significantly improve heavy metal passivation efficiency, has slow-release effect and anti-scouring performance, and realizes synergistic effect of soil remediation and fertility improvement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soil remediation, and particularly relates to a heavy metal contaminated soil passivation remediation conditioner and application thereof. BACKGROUND

[0002] Under the background of accelerating global industrialization and urbanization, China's arable land resources are facing severe challenges. According to the statistics of the agricultural department, the proportion of high-quality arable land is less than 1 / 3, about 13 million hectares of arable land has decreased in productivity due to soil degradation problems such as acidification and salinization, and another 4 million hectares of arable land is in a state of fallow due to heavy metal pollution. This double pressure has seriously restricted the construction of food security system and sustainable development of agriculture. For different types of soil degradation and pollution problems, the academic community generally believes that building a multifunctional soil remediation system is the key to improving the quality of arable land. Among them, soil conditioner developed on the basis of biomass resources has become an important research direction in the field of soil remediation due to its environmental friendliness and resource recycling characteristics.

[0003] Soil conditioner can improve soil quality by improving soil physical, chemical and biological properties. In terms of physical properties, conditioner can significantly improve soil three-phase ratio, enhance water infiltration rate and water holding capacity by regulating pore structure, reducing bulk density and promoting the formation of aggregate structure. Studies have shown that appropriate pore distribution can improve soil aeration porosity, which is directly related to root respiration and nutrient absorption efficiency. In terms of chemical properties, conditioner can adjust soil pH value, promote the formation of organic-inorganic complex and improve soil fertility by proton exchange and coordination. In terms of biological properties, conditioner can increase the number of microorganisms, promote the transformation of organic matter, nutrient cycle and biological remediation, increase soil enzyme activity, and accelerate the transformation of heavy metals and the degradation of organic pollutants.

[0004] The Chinese invention patent with application number CN201710700630.3 discloses a heavy metal contaminated soil conditioner prepared by chelating humic acid, 1,3,5-triazine-2,4,6-trisulfide, nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer, including humic acid salt, 1,3,5-triazine-2,4,6-trisulfide, nitrogen, diaphosphorus pentoxide and potassium oxide, etc. However, the invention only mixes the components simply, without establishing chemical bonding between the components. Mechanical mixing leads to phase separation of the material in the soil solution, resulting in uneven distribution of active components. SUMMARY

[0005] In view of the above, in order to overcome the defects of the prior art, the poly-caprolactone cross-linking network is constructed by click chemistry, the ammonium phosphomolybdate is stably anchored in the pore structure of the biochar, the dispersion stability of the material in the soil is enhanced by the hydration effect of the phosphocholine group, and the dynamic passivation barrier is formed by the synergistic effect of multiple components, so that the continuous fixation of heavy metals and the soil micro-ecological remediation are realized.

[0006] In order to achieve the above purpose, the following technical scheme is adopted: on the one hand, the present application provides a heavy metal contaminated soil passivation and remediation conditioner, which is prepared by the following steps:

[0007] S1, the pomelo peel is crushed to a particle size of 1-3mm, and is carbonized at 10℃ / min to 500-520℃ under nitrogen atmosphere for 3h, then is immersed in a 20% mass concentration phosphoric acid solution, and is activated in a 80℃ constant temperature water bath for 4h, and after washing to neutral, is dried in a 105℃ oven for 12-18h, to obtain pomelo peel activated carbon;

[0008] S2, the pomelo peel activated carbon obtained in step S1 is immersed in a first mixed solution composed of 0.2mol / L ammonium molybdate and 0.1mol / L sodium dihydrogen phosphate, the pH is adjusted to 4.5, and is stirred at 80℃ for 8h, after the reaction, is centrifuged at 3000rpm for 10min, is washed with deionized water for 3 times, and is vacuum dried at 80℃ for 6h, to obtain activated pomelo peel activated carbon loaded with ammonium phosphomolybdate on the surface;

[0009] S3, the caprolactone monomer is opened ring polymerized at 120℃ under nitrogen protection for 24h to generate hydroxyl-terminated poly-caprolactone, the hydroxyl-terminated poly-caprolactone is reacted with sodium azide in DMF at 60℃ for 24h to generate double-end azido group-terminated poly-caprolactone, the double-end azido group-terminated poly-caprolactone is stirred with the activated pomelo peel activated carbon obtained in step S2 and a silane coupling agent in toluene at 60℃ for 12-18h, after centrifugation, is separated and dried at 60-80℃ for 12-24h, to obtain cross-linked modified activated carbon;

[0010] S4, the cross-linked modified activated carbon obtained in step S3 and NO2A-butynyl-di-tert-butyl ester are added to a 30% mass fraction DMF solution, and then are added to a second mixed solution composed of 0.1mol / L copper sulfate and 0.2mol / L ascorbic acid, and are stirred at 40℃ for 16h, are filtered, washed and dried, to obtain a functionalized activated carbon composite material;

[0011] S5, the product obtained in step S4 is added to a dichloromethane solution containing 5% trifluoroacetic acid, and reacted at room temperature for 3h to remove the tert-butyl ester protecting group, and after centrifugation, washed to neutral, and after drying, the deprotection product is obtained, and the deprotection product is dispersed with 2-methacryloyloxyethyl phosphocholine in a phosphate buffer solution at pH 6.8, ultrasonic treatment is carried out at a power of 200W and a frequency of 40kHz for 30-60min, and then freeze-dried at-50℃ for 48h to obtain the conditioning agent product.

[0012] Further, the feeding ratio of the pomelo peel to the phosphoric acid solution in step S1 is 1g:3-6mL.

[0013] Further, the feeding ratio of the pomelo peel activated carbon to the first mixed solution in step S2 is 1g:8-12mL.

[0014] Further, the molar ratio of stannous iso-octoate to caprolactone monomer in step S3 is 1:80-120.

[0015] Further, the molecular weight range of the hydroxyl-terminated poly-caprolactone in step S3 is 5000-20000Da, and the feeding ratio of the hydroxyl-terminated poly-caprolactone, sodium azide and DMF is 1g:0.004-0.02g:20-40mL.

[0016] Further, the feeding ratio of the activated pomelo peel activated carbon, silane coupling agent and toluene in step S3 is 1g:0.1-0.3g:10-20mL, and the silane coupling agent is one or more of KH-550, KH-560 and KH-570.

[0017] Further, the feeding ratio of the cross-linked modified activated carbon, NO2A-butynyl-di-tert-butyl ester, DMF solution, and the second mixed solution in step S4 is 1g:0.3-0.7g:15-25mL:20-40mL.

[0018] Further, the feeding ratio of the functionalized activated carbon composite material to the dichloromethane solution of trifluoroacetic acid in step S5 is 1g:30-70mL, and the feeding ratio of the deprotection product, 2-methacryloyloxyethyl phosphocholine and phosphate buffer in step S5 is 1g:1-3g:20-40mL.

[0019] In another aspect, the present application also provides an application of a heavy metal contaminated soil passivation repair conditioning agent: 20-30 parts by weight of the conditioning agent is uniformly mixed with 5-10 parts by weight of potassium feldspar powder, 10-15 parts by weight of calcium magnesium phosphate fertilizer, 15-25 parts by weight of agricultural lime, 20-30 parts by weight of humic acid, and 0.5-2 parts by weight of microbial agent, and the passivation repair is carried out on the heavy metal contaminated soil at a use amount of 3000kg / ha.

[0020] Further, the microbial agent includes Bacillus amyloliquefaciens, Bacillus subtilis, Aspergillus niger, Pseudomonas aeruginosa and Streptomyces microflavus, the viable count of the Bacillus amyloliquefaciens is greater than or equal to 1*10^8 CFU / g, the viable count of the Bacillus subtilis is greater than or equal to 5*10^7 CFU / g, the viable count of the Aspergillus niger is greater than or equal to 2*10^7 CFU / g, the viable count of the Pseudomonas aeruginosa is greater than or equal to 2*10^7 CFU / g, and the viable count of the Streptomyces microflavus is greater than or equal to 1*10^8 CFU / g.

[0021] The beneficial effects of the present application are:

[0022] (1) The conditioner prepared by the present application can passivate and repair heavy metals in the soil, improve the soil microenvironment, and improve biodiversity. Through the composite loading of naringen activated carbon and ammonium phosphomolybdate, combined with the cross-linked network structure of polycaprolactone and the zwitterionic functionalization of phosphocholine, a multi-level adsorption and chelation system is formed. Ammonium phosphomolybdate fixes heavy metals through ion exchange, triazacyclononane groups form stable coordination structures with heavy metals, and phosphocholine groups further adsorb heavy metal ions through electrostatic interaction. The conditioner is used as a fertilizer in combination with potassium feldspar powder, calcium magnesium phosphate, agricultural lime, humic acid, and microbial agents, which can increase soil permeability and improve soil fertility.

[0023] (2) The activated carbon is prepared from naringen biomass, and a high specific surface area porous structure is formed by phosphoric acid activation, realizing resource utilization and uniformly loading ammonium phosphomolybdate. The selectivity of activated carbon for heavy metals is significantly improved. The polyoxometalate structure of ammonium phosphomolybdate remains stable under acidic conditions, and the molybdenum oxygen tetrahedron specifically coordinates with heavy metal ions. Through the click reaction of the double-azide groups of polycaprolactone with the alkyne groups, a three-dimensional cross-linked network is constructed on the surface of the activated carbon, which not only enhances the mechanical strength of the material, but also prevents the loss of active components. Polycaprolactone is a biodegradable polymer material, and its slow degradation characteristics give the conditioner a slow release effect.

[0024] (3) The triazacyclononane group of NO2A-butynyl-di-tert-butyl ester serves as the core structure of the macrocyclic ligand. This group can catalyze the cycloaddition reaction of the butynyl group with the double-azide groups of polycaprolactone, forming a stable triazole ring cross-linked network. On the one hand, this improves the overall chelation strength, and on the other hand, it significantly improves the mechanical strength and anti-erosion performance of the material. The triazacyclononane group also has strong chelation, and through metal coordination, the triazacyclononane group can act as a Lewis acid catalyst to promote the precipitation reaction of heavy metal ions and acid radicals.

[0025] (4) The carboxylic acid group exposed after the removal of the tert-butyl ester protecting group in NO2A-butynyl-di-tert-butyl ester is introduced with 2-methacryloyloxyethylphosphocholine by covalent, hydrogen bond, etc. binding mode. The 2-methacryloyloxyethylphosphocholine has zwitterionic characteristics, and the phosphocholine group thereon forms a dense hydration layer through hydration, significantly reducing the surface tension of soil particles, so that the conditioner rapidly absorbs water and expands in the soil to form a hydrophilic channel, promoting the penetration of water and nutrients, reducing the risk of runoff and heavy metal loss with water and soil, and reducing the van der Waals force between conditioner particles to prevent the formation of aggregates. The component is decomposed and releases phosphate by the action of phosphatase produced by microorganisms, and dissolves heavy metals by secreting organic acids through the synergistic action of microbial agents and humic acid, cooperates with the phosphorus source in calcium magnesium phosphate fertilizer, and realizes long-term fixation of heavy metals. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The preparation flowchart of the heavy metal contaminated soil passivation and remediation conditioner according to the present application is shown in the following.

[0027] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, and are used to explain the present application together with the embodiments of the present application, and do not constitute a limitation on the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, and all other embodiments obtained by those skilled in the art without creative labor on the basis of the embodiments in the present application shall fall within the scope of protection of the present application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as familiar to one skilled in the art. In addition, any method and material similar or equivalent to those described can be used in the present application. The preferred implementation methods and materials described herein are only used for demonstration, but cannot limit the content of the present application.

[0030] In the following examples, the experimental methods are all conventional methods unless otherwise specified. The test materials used in the following examples are all purchased from commercial channels unless otherwise specified. The preparation flowchart of the conditioner in the following examples is shown in the following. Figure 1 .

[0031] Among them, Bacillus amyloliquefaciens, strain number CICC 10035, is purchased from Beijing Biological Preservation Center.

[0032] Bacillus subtilis, strain number CICC 25064, is purchased from Beijing Biological Preservation Center.

[0033] Aspergillus niger, strain number CICC 2243, purchased from Beijing Biological Preservation Center.

[0034] Pseudomonas aeruginosa, strain number CICC 10204, purchased from Beijing Biological Preservation Center.

[0035] Streptomyces microflavus, strain number CICC 11006, purchased from Beijing Biological Preservation Center.

[0036] Example 1: A heavy metal contaminated soil passivation remediation conditioner and its application, the conditioner is prepared by the following steps:

[0037] S1, 1 g of pomelo peel is crushed to a particle size of 1 mm, carbonized at 10 ℃ / min to 500 ℃ for 3 h under a nitrogen atmosphere, then immersed in 3 mL of a 20% mass concentration phosphoric acid solution, activated at 80 ℃ constant temperature water bath for 4 h, washed to neutral, and dried in an oven at 105 ℃ for 12 h to obtain pomelo peel activated carbon;

[0038] S2, 1 g of the pomelo peel activated carbon obtained in step S1 is immersed in 8 mL of a first mixed solution composed of 0.2 mol / L ammonium molybdate and 0.1 mol / L sodium dihydrogen phosphate, the pH is adjusted to 4.5, and 80 ℃ constant temperature stirring reaction is carried out for 8 h, after the reaction is completed, centrifugation is carried out at 3000 rpm for 10 min, washed with deionized water for 3 times, and vacuum dried at 80 ℃ for 6 h to obtain activated pomelo peel activated carbon loaded with ammonium phosphomolybdate on the surface;

[0039] S3, according to the molar ratio of stannous isooctoate to caprolactone monomer is 1:80, caprolactone monomer is opened ring polymerized at 120 ℃ for 24 h under nitrogen protection, hydroxyl-terminated poly-caprolactone with a molecular weight range of 5000-20000 Da is generated, 1 g of hydroxyl-terminated poly-caprolactone is reacted with 0.004 g of sodium azide in 20 mL of DMF at 60 ℃ for 24 h to generate double-end azido group-terminated poly-caprolactone, the double-end azido group-terminated poly-caprolactone is stirred with 1 g of the activated pomelo peel activated carbon obtained in step S2 and 0.1 g of silane coupling agent KH-550 in 10 mL of toluene at 60 ℃ for 12 h, after centrifugation, separation and drying at 60 ℃ for 12 h, cross-linked modified activated carbon is obtained;

[0040] S4, 1 g of the cross-linked modified activated carbon obtained in step S3 is added to 15 mL of a 30% mass fraction DMF solution, then added to 20 mL of a second mixed solution composed of 0.1 mol / L copper sulfate and 0.2 mol / L ascorbic acid, stirred at 40 ℃ for 16 h, filtered, washed, and dried to obtain a functionalized activated carbon composite material;

[0041] S5, 1 g of the product obtained in step S4 is added to 30 mL of a dichloromethane solution containing 5% trifluoroacetic acid, and the tert-butyl ester protecting group is removed by reaction at room temperature for 3 h, and after centrifugation, it is washed to neutral, and after drying, the deprotected product is obtained, 1 g of the deprotected product is dispersed with 1 g of 2-methacryloyloxyethyl phosphocholine in 20 mL of a phosphate buffer at pH 6.8, and ultrasonic treatment is carried out at a power of 200 W and a frequency of 40 kHz for 30 min, and then freeze-drying is carried out at -50℃ for 48 h to obtain the finished conditioning agent.

[0042] The application is: 20 parts of the conditioning agent are uniformly mixed with 5 parts of potassium feldspar powder, 10 parts of calcium magnesium phosphate fertilizer, 15 parts of agricultural lime, 20 parts of humic acid, and 0.5 parts of microbial agent, and the application amount is 3000 kg / ha for the passivation repair of heavy metal contaminated soil.

[0043] The microbial agent comprises Bacillus amyloliquefaciens, Bacillus subtilis, Aspergillus niger, Pseudomonas aeruginosa, and Streptomyces microflavus, the viable count of the Bacillus amyloliquefaciens is ≥1×10^8 CFU / g, the viable count of the Bacillus subtilis is ≥5×10^7 CFU / g, the viable count of the Aspergillus niger is ≥2×10^7 CFU / g, the viable count of the Pseudomonas aeruginosa is ≥2×10^7 CFU / g, and the viable count of the Streptomyces microflavus is ≥1×10^8 CFU / g.

[0044] Embodiment 2: A heavy metal contaminated soil passivation repair conditioning agent and its application, the conditioning agent is prepared by the following steps:

[0045] S1, 1 g of pomelo peel is crushed to a particle size of 3 mm, and is carbonized at 10℃ / min to 520℃ under a nitrogen atmosphere for 3 h, and then is immersed in 6 mL of a 20% phosphoric acid solution, and is activated at 80℃ in a constant temperature water bath for 4 h, and after washing to neutral, is dried in an oven at 105℃ for 18 h to obtain pomelo activated carbon;

[0046] S2, 1 g of the pomelo activated carbon obtained in step S1 is immersed in 12 mL of a first mixed solution composed of 0.2 mol / L ammonium molybdate and 0.1 mol / L sodium dihydrogen phosphate, the pH is adjusted to 4.5, and 80℃ constant temperature stirring reaction is carried out for 8 h, after the reaction is completed, centrifugation is carried out at 3000 rpm for 10 min, and then it is washed with deionized water for 3 times, and vacuum drying is carried out at 80℃ for 6 h to obtain pomelo activated carbon loaded with ammonium phosphomolybdate on the surface;

[0047] S3, under the protection of nitrogen, the caprolactone monomer was ring-opening polymerized at 120℃ for 24h with stannous octoate as catalyst according to the molar ratio of 1:120, hydroxyl-terminated polycaprolactone with molecular weight range of 5000-20000Da was generated, 1g of the hydroxyl-terminated polycaprolactone was reacted with 0.02g of sodium azide in 40mL of DMF at 60℃ for 24h, to generate azido-terminated polycaprolactone, the azido-terminated polycaprolactone was stirred with 1g of the activated pomelo peel activated carbon obtained in step S2, 0.3g of silane coupling agent composed of KH-550 and KH-560 according to the mass ratio of 1:1 in 20mL of toluene at 60℃ for 18h, after centrifugation, the product was separated and dried at 80℃ for 24h to obtain the cross-linked modified activated carbon;

[0048] S4, 1g of the cross-linked modified activated carbon obtained in step S3 was added to 25mL of 30% mass fraction of DMF solution, followed by being added to 40mL of a second mixed solution composed of 0.1mol / L copper sulfate and 0.2mol / L ascorbic acid, stirring at 40℃ for 16h, filtering, washing, and drying to obtain the functionalized activated carbon composite material;

[0049] S5, 1g of the product obtained in step S4 was added to 70mL of dichloromethane solution containing 5% trifluoroacetic acid, and the tert-butyl ester protecting group was removed by reaction at room temperature for 3h, and the product was washed to neutral after centrifugation, and the deprotection product was obtained after drying, 1g of the deprotection product was dispersed with 3g of 2-methacryloyloxyethyl phosphorylcholine in 40mL of phosphate buffer with pH 6.8, and ultrasonic treatment was carried out at a power of 200W and a frequency of 40kHz for 60min, followed by freeze-drying at-50℃ for 48h to obtain the finished conditioning agent.

[0050] The application is: 30 parts of the conditioning agent are uniformly mixed with 10 parts of potassium feldspar powder, 15 parts of calcium magnesium phosphate fertilizer, 25 parts of agricultural lime, 30 parts of humic acid, and 2 parts of microbial agent, and the application amount is 3000kg / ha for the passivation and repair of heavy metal contaminated soil.

[0051] The microbial agent comprises the same components and viable bacterial counts as in Example 1.

[0052] Example 3: A heavy metal contaminated soil passivation and repair conditioning agent and its application, the conditioning agent is prepared by the following steps:

[0053] S1, 1g of pomelo peel powder was crushed to a particle size of 2mm, and carbonized at 10℃ / min to 510℃ for 3h under a nitrogen atmosphere, then immersed in 4mL of 20% mass concentration phosphoric acid solution, and activated at 80℃ constant temperature water bath for 4h, washed to neutral, and dried in an oven at 105℃ for 15h to obtain pomelo peel activated carbon;

[0054] S2, 1 g of the pomelo peel activated carbon obtained in step S1 was immersed in 10 mL of a first mixed solution composed of 0.2 mol / L ammonium molybdate and 0.1 mol / L sodium dihydrogen phosphate, the pH was adjusted to 4.5, and constant temperature stirring reaction was carried out at 80°C for 8 h. After the reaction, centrifugation was carried out at 3000 rpm for 10 min, washing was carried out with deionized water for 3 times, and vacuum drying was carried out at 80°C for 6 h to obtain activated pomelo peel activated carbon loaded with ammonium phosphomolybdate on the surface;

[0055] S3, under the protection of nitrogen, caprolactone monomers were ring-opening polymerized at 120°C for 24 h with stannous isooctoate as a catalyst at a molar ratio of stannous isooctoate to caprolactone monomers of 1:100 to generate hydroxyl-terminated poly caprolactone with a molecular weight range of 5000-20000 Da. 1 g of the hydroxyl-terminated poly caprolactone was reacted with 0.012 g of sodium azide in 30 mL of DMF at 60°C for 24 h to generate double-end azido group-terminated poly caprolactone. The double-end azido group-terminated poly caprolactone was stirred with 1 g of the activated pomelo peel activated carbon obtained in step S2 and 0.2 g of a silane coupling agent composed of KH-560 and KH-570 at a mass ratio of 1:1 in 15 mL of toluene at 60°C for 15 h. After centrifugation, drying was carried out at 70°C for 18 h to obtain cross-linked modified activated carbon;

[0056] S4, 1 g of the cross-linked modified activated carbon obtained in step S3 was added to 20 mL of a 30% mass fraction DMF solution, and then added to 30 mL of a second mixed solution composed of 0.1 mol / L copper sulfate and 0.2 mol / L ascorbic acid. Stirring reaction was carried out at 40°C for 16 h. After filtration, washing and drying, a functionalized activated carbon composite material was obtained;

[0057] S5, 1 g of the product obtained in step S4 was added to 50 mL of a dichloromethane solution containing 5% trifluoroacetic acid, and reaction was carried out at room temperature for 3 h to remove the tert-butyl ester protecting group. After centrifugation and washing to neutral, the deprotected product was obtained after drying. 1 g of the deprotected product was dispersed with 2 g of 2-methacryloyloxyethyl phosphorylcholine in 30 mL of a phosphate buffer with a pH of 6.8. Ultrasonic treatment was carried out at a power of 200 W and a frequency of 40 kHz for 45 min. Subsequently, freeze-drying was carried out at -50°C for 48 h to obtain a finished conditioning agent.

[0058] The application is: 25 parts of the conditioning agent are uniformly mixed with 7 parts of potassium feldspar powder, 12 parts of calcium magnesium phosphate fertilizer, 20 parts of agricultural lime, 25 parts of humic acid, and 1 part of microbial agent, and the application amount is 3000 kg / ha for the passivation repair of heavy metal contaminated soil.

[0059] The microbial agent comprises the same components and viable bacterial counts as in Example 1.

[0060] Comparative Example 1: This comparative example omits the ammonium phosphomolybdate loading step (i.e. step S2), and directly obtains the activated pomelo peel activated carbon in step S3, and the rest is the same as Example 3.

[0061] Comparative Example 2: This comparative example omits the polycaprolactone crosslinking network construction step (i.e. steps S3-S4), and directly mixes the ammonium phosphomolybdate loaded activated carbon with choline phosphate, and the rest is the same as Example 3.

[0062] Comparative Example 3: This comparative example does not react the deprotected product with 2-methacryloyloxyethyl choline phosphate after preparation, and the rest is the same as Example 3.

[0063] Result analysis: The conditioners prepared in Examples 1-3 and Comparative Examples 1-3 are used for passivation repair of soil, and then the physicochemical properties are tested, and the test results are shown in Table 1.

[0064] Soil passivation repair process is:

[0065] (1) Take heavy metal contaminated farmland soil, remove surface debris, till to a depth of 20 cm, break the soil block to a particle size of <5 mm, mix uniformly, and then divide into test areas, each area is 50m x 50m;

[0066] (2) According to the corresponding weight ratio, mix with potassium feldspar powder, calcium magnesium phosphate fertilizer, agricultural lime, humic acid, and microbial agent, and apply the mixed material to the soil surface at a rate of 3000 kg / ha, and then use a rotary tiller to till twice, to a depth of 20 cm, to mix the material with the surface soil thoroughly;

[0067] (3) Immediately after application, water is applied to maintain soil moisture content at 60%-70% of field water holding capacity, and maintain at room temperature for 30 days, avoiding rainwater erosion during this period.

[0068] According to the "Determination of Soil pH Value by Potentiometric Method", the initial and 3-month treated soil pH values are determined by glass electrode potentiometric method.

[0069] According to the "Determination of Metal Element Content in Soil and Sediment by Microwave Digestion", the initial and 3-month treated soil As, Pb, and Cd contents are determined by inductively coupled plasma mass spectrometry.

[0070] According to the "Potassium dichromate oxidation-external heating method" in NY / T 1121.6-2006, the initial and 3-month treated soil organic matter content is determined.

[0071] According to the "Fumigation extraction method" in GB / T 39228-2020, the initial and 3-month treated soil microbial quantity is determined.

[0072] The activity of catalase (CAT) in the soil before and after treatment for 3 months was determined by ultraviolet spectrophotometry, and the change in absorbance at 240 nm was used to represent the activity of CAT; the activity of superoxide dismutase (POD) in the soil before and after treatment for 3 months was determined by guaiacol colorimetry, and the change in absorbance at 470 nm was used to calculate the activity of POD.

[0073] The contents of As, Pb and Cd in crops were determined according to GB 5009.268-2016, the sown crops were wheat, the variety was Yangmai 20, the sowing amount was 150 kg / ha, the row spacing was 20 cm, the sowing depth was 3-5 cm, the conventional field management was adopted, the growth period was 120 days, after the wheat matured, the aboveground parts were collected, washed with deionized water for 3 times, dried in an oven at 80 ℃ until constant weight, subjected to microwave digestion, and then the contents of As, Pb and Cd in the digestion solution were determined by inductively coupled plasma mass spectrometry.

[0074] Table 1: Test results of the heavy metal contaminated soil passivation repair performance of the conditioners prepared in Examples 1-3 and Comparative Examples 1-3

[0075]

[0076]

[0077] As can be seen from the test results in Table 1, the pH values of the soil after treatment in Examples 1-3 were significantly improved, the contents of As, Pb and Cd after 3 months were reduced to 13.2-15.7 mg / kg, 54.7-60.3 mg / kg and 0.9-1.2 mg / kg, respectively, and the removal rates were 63.2%-82.8%, while the removal rates of the comparative examples were only 32.8%-53.4%, and the removal ability of heavy metals was significantly lower than that of the examples. In addition, the organic matter content of the soil in each example was increased by 50.4%-57.0%, the microbial quantity was increased by 290.6%-375.0%, the activities of CAT and POD were increased by 171%-263% compared with the initial values, and all of them were significantly better than those of the comparative examples. The wheat planted in the soil after passivation treatment had lower contents of As, Pb and Cd in the crops than the comparative examples. Therefore, it is proved that the conditioner disclosed in the present application has a significant effect on the passivation repair of heavy metal contaminated soil.

[0078] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

[0079] The above describes the present application and its embodiments, which are not limited, and the drawings only show one of the embodiments of the present application, and the actual application is not limited thereto. In general, if a person skilled in the art is inspired by it, without departing from the purpose of the present application, without creative design, similar ways and embodiments of the technical solution should belong to the protection scope of the present application.

Claims

1. A heavy metal contaminated soil passivation remediation conditioner characterized by: Preparation by the following steps: S1, the pomelo peel is crushed to a particle size of 1-3 mm, carbonized at 10 ℃ / min to 500-520 ℃ for 3 h under a nitrogen atmosphere, then immersed in a 20% mass concentration phosphoric acid solution, activated in a 80 ℃ constant temperature water bath for 4 h, washed to neutral, and dried in an oven at 105 ℃ for 12-18 h to obtain pomelo peel activated carbon; S2, the pomelo peel activated carbon obtained in step S1 is immersed in a first mixed solution composed of 0.2 mol / L ammonium molybdate and 0.1 mol / L sodium dihydrogen phosphate, the pH is adjusted to 4.5, and stirred at 80 ℃ for 8 h, then centrifuged at 3000 rpm for 10 min, washed with deionized water for 3 times, and vacuum dried at 80 ℃ for 6 h to obtain activated pomelo peel activated carbon loaded with ammonium phosphomolybdate on the surface; S3, stannous isooctoate is used as a catalyst, and caprolactone monomers are ring-opening polymerized at 120 ℃ under nitrogen protection for 24 h to generate hydroxyl-terminated poly-caprolactone, the hydroxyl-terminated poly-caprolactone is reacted with sodium azide in DMF at 60 ℃ for 24 h to generate double-azido group-terminated poly-caprolactone, the double-azido group-terminated poly-caprolactone is stirred with the activated pomelo peel activated carbon obtained in step S2 and a silane coupling agent in toluene at 60 ℃ for 12-18 h, then separated by centrifugation and dried at 60-80 ℃ for 12-24 h to obtain cross-linked modified activated carbon; S4, the cross-linked modified activated carbon obtained in step S3 is added to a 30% mass fraction DMF solution, then added to a second mixed solution composed of 0.1 mol / L copper sulfate and 0.2 mol / L ascorbic acid, and stirred at 40 ℃ for 16 h, then filtered, washed, and dried to obtain a functional activated carbon composite material; S5, the product obtained in step S4 is added to a dichloromethane solution containing 5% trifluoroacetic acid, and reacted at room temperature for 3 h to remove the tert-butyl ester protecting group, then washed to neutral after centrifugation, and dried to obtain a deprotection product, the deprotection product is dispersed with 2-methacryloyloxyethyl phosphocholine in a phosphate buffer solution at pH 6.8, ultrasonically treated at a power of 200 W and a frequency of 40 kHz for 30-60 min, and then freeze-dried at-50 ℃ for 48 h to obtain a finished conditioning agent.

2. The heavy metal contaminated soil passivation remediation conditioner according to claim 1, characterized in that: The feeding ratio of pomelo peel to phosphoric acid solution in step S1 is 1 g:3-6 mL.

3. The heavy metal contaminated soil passivation remediation conditioner of claim 1, wherein: The feeding ratio of pomelo peel activated carbon to the first mixed solution in step S2 is 1 g:8-12 mL.

4. The heavy metal contaminated soil passivation remediation conditioner of claim 1, wherein: The feeding molar ratio of stannous isooctoate to caprolactone monomers in step S3 is 1:80-120.

5. The heavy metal contaminated soil passivation remediation conditioner of claim 1, wherein: The molecular weight of the hydroxyl-terminated poly-caprolactone in step S3 ranges from 5000 to 20000 Da, and the feeding ratio of the hydroxyl-terminated poly-caprolactone, sodium azide, and DMF is 1 g:0.004-0.02 g:20-40 mL.

6. The heavy metal contaminated soil passivation remediation conditioner of claim 1, wherein: The feeding ratio of the activated pomelo peel activated carbon, the silane coupling agent, and toluene in step S3 is 1 g:0.1-0.3 g:10-20 mL, and the silane coupling agent is one or more of KH-550, KH-560, and KH-570.

7. The heavy metal contaminated soil passivation remediation conditioner of claim 1, wherein: The feeding ratio of the cross-linking modified activated carbon, NO2A-butynyl-di-tert-butyl, DMF solution and the second mixed solution in the step S4 is 1g: 0.3-0.7g: 15-25mL: 20-40mL.

8. The heavy metal contaminated soil passivation remediation conditioner of claim 1, wherein: The feeding ratio of the functionalized activated carbon composite material and the dichloromethane solution of trifluoroacetic acid in the step S5 is 1g: 30-70mL, and the feeding ratio of the deprotection product, 2-methacryloyloxyethyl phosphorylcholine and phosphate buffer in the step S5 is 1g: 1-3g: 20-40mL.

9. Use of a heavy metal-contaminated soil passivation remediation conditioner according to any one of claims 1-8, characterized in that: 20-30 parts of the conditioning agent, 5-10 parts of potassium feldspar powder, 10-15 parts of calcium magnesium phosphate, 15-25 parts of agricultural lime, 20-30 parts of humic acid and 0.5-2 parts of the microbial agent are uniformly mixed according to the weight, and the heavy metal contaminated soil is passivated and repaired according to the application amount of 3000kg / ha.

10. Use according to claim 9, characterized in that: The microbial agent comprises Bacillus amyloliquefaciens, Bacillus subtilis, Aspergillus niger, Pseudomonas aeruginosa and Streptomyces microflavus, the viable bacterial count of the Bacillus amyloliquefaciens is greater than or equal to 1*10^8 CFU / g, the viable bacterial count of the Bacillus subtilis is greater than or equal to 5*10^7 CFU / g, the viable bacterial count of the Aspergillus niger is greater than or equal to 2*10^7 CFU / g, the viable bacterial count of the Pseudomonas aeruginosa is greater than or equal to 2*10^7 CFU / g, and the viable bacterial count of the Streptomyces microflavus is greater than or equal to 1*10^8 CFU / g.

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