An ecological activation remediation material for heavy metal contaminated soil and a preparation method thereof

Abstract

The present application belongs to the technical field of contaminated soil remediation, and relates to an ecological activation remediation material for heavy metal contaminated soil and a preparation method thereof, comprising: obtaining biochar by anaerobic pyrolysis, crushing and sieving of corn stalks; obtaining modified biochar wet material by dispersing the biochar in a modified solution, mixing, stirring and heating; obtaining a bacterial suspension by inoculating Burkholderia into LB liquid medium, oscillation culture, centrifugation and resuspending the bacterial body with a protective agent solution; obtaining a spore suspension by inoculating Phanerochaete chrysosporium into a potato glucose agar plate and static culture; obtaining a mixed suspension by mixing the modified biochar wet material, the bacterial suspension and the spore suspension with a sodium alginate solution, and obtaining gel microspheres by dropping the mixed suspension into a calcium chloride solution and taking out and drying. The ecological activation remediation material prepared by the present application can efficiently fix heavy metals, enhance the survival time and long-acting effect of microorganisms in the soil, and promote the recovery of the ecological function of the soil.

Description

Technical Field

[0001] This invention belongs to the field of contaminated soil remediation technology, and relates to an ecologically activated remediation material for heavy metal contaminated soil and its preparation method. Background Technology

[0002] Mining, metal smelting, and chemical production activities result in large amounts of heavy metals entering the soil, seriously threatening ecosystem security and agricultural product quality. While existing soil remediation technologies have made some progress in addressing this problem, they generally have significant limitations. Physical remediation methods, although fast-acting, are costly and severely damage soil structure, making large-scale application difficult. Chemical remediation technologies reduce the activity of heavy metals by adding solidifying or stabilizing agents, but may introduce new chemical substances, posing a risk of secondary pollution.

[0003] Bioremediation technologies, including phytoremediation and microbial remediation, have attracted attention due to their environmentally friendly characteristics. Phytoremediation utilizes hyperaccumulating plants to absorb heavy metals, but it has a long remediation cycle, low efficiency, and is limited by soil conditions and climate factors. Microbial remediation relies on the transformation of heavy metals by specific bacterial species, but microbial activity is easily affected by environmental factors, resulting in unstable remediation effects.

[0004] In recent years, novel remediation materials such as modified biochar and mineral-based materials have become research hotspots. Biochar has a porous structure and abundant surface functional groups, which can effectively adsorb heavy metals. However, ordinary biochar has limited selective adsorption capacity for specific heavy metals and may affect soil nutrient balance.

[0005] Therefore, it is urgent to develop an activation and remediation material that can efficiently fix heavy metals and promote the restoration of soil ecological functions. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an ecological activation and remediation material for heavy metal contaminated soil and its preparation method. The ecological activation and remediation material prepared by this invention can effectively fix heavy metals, while enhancing the survival time and long-term effect of microorganisms in the soil, and promoting the restoration of soil ecological function.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil, the preparation method comprising:

[0009] (I) After crushing the corn stalks, anaerobic pyrolysis was carried out, cooled to room temperature, crushed and sieved to obtain biochar; citric acid, ferrous sulfate heptahydrate and deionized water were mixed to obtain a modified solution, the biochar was dispersed in the modified solution, mixed, stirred and heated, and then separated by suction filtration and washing to obtain modified biochar wet material;

[0010] (II) Burkholderia was inoculated into LB liquid medium, shaken and cultured, then centrifuged, and the bacterial cells were collected. The bacterial cells were resuspended in a protective solution containing trehalose and glycerol to obtain a bacterial suspension. Phanerochaete chrysospora was inoculated into potato dextrose agar plates, and cultured statically until the spores matured. Then, the spores were washed and filtered to obtain a spore suspension.

[0011] (III) The modified biochar wet material, the bacterial suspension and the spore suspension are mixed to obtain a bacterial-char mixture. The bacterial-char mixture is mixed with sodium alginate solution to obtain a mixed suspension. The mixed suspension is dripped into calcium chloride solution using a syringe to obtain gel microspheres. The microspheres are then removed and dried to obtain the ecological activation and restoration material.

[0012] This invention first prepares ferrous citrate-grafted biochar, providing efficient adsorption and complexation sites for heavy metal ions. Then, *Burkholderia burgdorferi* and *Procambarus chrysospora* are loaded onto modified activated carbon; their synergistic effect improves the soil environment and transforms heavy metal ions. Finally, the modified biochar is encapsulated using sodium alginate-calcium chloride gelation to form gel microspheres, achieving the fixation and protection of microorganisms. The ecological activation and remediation material prepared by this invention not only efficiently fixes heavy metals but also enhances the survival time of microorganisms in the soil, promoting the restoration of soil ecological functions.

[0013] First, this invention prepares biochar using agricultural waste corn stalks as raw material. The biochar is modified by citric acid and ferrous sulfate heptahydrate. After the reaction of citric acid and ferrous ions, a ferrous citrate complex is formed, which is grafted onto the surface and pores of the biochar under heating conditions. This grafting modification not only utilizes the huge specific surface area and adsorption performance of the biochar itself, but also introduces a ferrous citrate complex rich in carboxyl functional groups, which significantly enhances the complexing and adsorption capacity of the biochar for various heavy metal ions, providing an ideal porous carrier for subsequent microbial loading.

[0014] Subsequently, this invention uses modified biochar as a porous carrier, loading Burkholderia and Phanerochaete chrysosporium onto its surface and within its pores, effectively solving the technical problems of difficulty in maintaining bacterial activity and easy loss. Burkholderia is a bacterium with strong tolerance to heavy metals, capable of directly converting heavy metal ions through biosorption, intracellular accumulation, and redox reactions. Phanerochaete chrysosporium is a white-rot fungus that secretes abundant extracellular enzymes and organic acids, among other metabolites. These metabolites not only complex and dissolve heavy metals, but its well-developed hyphal network can also penetrate the soil, improving soil structure and providing an ideal soil environment for bacterial migration and colonization. The two work synergistically: Phanerochaete chrysosporium improves the soil environment, making it more suitable for Burkholderia migration and colonization, while Burkholderia converts heavy metal ions.

[0015] Finally, encapsulation is achieved through an ionogel reaction between sodium alginate and calcium chloride. The microorganisms and modified biochar are fixed inside the gel microspheres through a gel network. This not only protects the survival environment of the microorganisms and inhibits the damage of the soil environment to the microorganisms, but also controls the slow release of the microorganisms and their metabolites, preventing the microorganisms and biochar from decomposing and being lost too quickly in the soil. At the same time, the outer gel layer allows water, nutrients and heavy metal ions to diffuse in, maintaining the survival environment of the internal microorganisms, thereby ensuring the durability of the remediation effect.

[0016] As a preferred technical solution of the present invention, in step (I), the heating rate of the anaerobic pyrolysis is 5~10℃ / min, for example, it can be 5.0℃ / min, 5.5℃ / min, 6.0℃ / min, 6.5℃ / min, 7.0℃ / min, 7.5℃ / min, 8.0℃ / min, 8.5℃ / min, 9.0℃ / min, 9.5℃ / min or 10.0℃ / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] In some optional instances, the temperature of the anaerobic pyrolysis is 450~500℃, for example, it can be 450℃, 455℃, 460℃, 465℃, 470℃, 475℃, 480℃, 485℃, 490℃, 495℃ or 500℃, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0018] In some optional instances, the holding time for the anaerobic pyrolysis is 1.5 to 2.5 hours, for example, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, or 2.5 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0019] In some optional instances, the sieve mesh size is 60 to 100 mesh, for example, 60 mesh, 65 mesh, 70 mesh, 75 mesh, 80 mesh, 85 mesh, 90 mesh, 95 mesh or 100 mesh, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0020] As a preferred technical solution of the present invention, in step (I), the concentration of citric acid in the modified solution is 0.8~1.2 mol / L, for example, it can be 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1.0 mol / L, 1.05 mol / L, 1.1 mol / L, 1.15 mol / L or 1.2 mol / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Citric acid molecules are rich in carboxyl functional groups. When they form complexes with ferrous ions and are grafted onto biochar, the density of carboxyl functional groups on the biochar surface is greatly increased. These carboxyl functional groups have a strong specific complexing ability for heavy metal cations, and can firmly adsorb them into the pores of biochar through surface coordination. In addition, the ferrous ions in the complex have reducing properties, which can reduce hexavalent chromium Cr(VI) in the soil to trivalent chromium Cr(III), which is less toxic and less mobile.

[0022] This invention specifically limits the concentration of citric acid in the modified solution to 0.8~1.2 mol / L. Within this range, sufficient and stable ferrous citrate complexes are formed, thereby achieving effective grafting on the surface and within the pores of biochar. When the concentration of citric acid is too low, it cannot coordinate with sufficient ferrous ions to form a sufficient number of complexes, resulting in insufficient density of carboxyl functional groups grafted onto the biochar, affecting its complexation ability for heavy metal ions. When the concentration of citric acid is too high, the excessive acid concentration will erode the pore structure of the biochar, affecting its specific surface area and structural strength; in addition, excessive free citric acid will remain in the pores of the biochar, affecting the activity of subsequently loaded microorganisms.

[0023] In some alternative examples, the concentration of ferrous sulfate heptahydrate in the modified solution is 0.05 to 0.15 mol / L, for example, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, or 0.15 mol / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0024] This invention specifically limits the concentration of ferrous sulfate heptahydrate in the modified solution to 0.05~0.15 mol / L. When the concentration of ferrous sulfate heptahydrate is too low, it cannot combine with sufficient citric acid to form a sufficient number of complexes, resulting in a low density of ferrous ions grafted onto the biochar, which affects the modified biochar's chemical complexation ability and reducing power for heavy metal ions. When the concentration of ferrous sulfate heptahydrate is too high, during the heating process, excess Fe... 2+ It will be oxidized to Fe 3+ This process generates ferric hydroxide precipitate, which clogs the pores of biochar, reducing its specific surface area and adsorption capacity.

[0025] In some alternative examples, the solid-liquid ratio of the biochar to the modified solution is 1 g:(8~12) mL, for example, it can be 1 g:8.0 mL, 1 g:8.5 mL, 1 g:9.0 mL, 1 g:9.5 mL, 1 g:10.0 mL, 1 g:10.5 mL, 1 g:11.0 mL, 1 g:11.5 mL or 1 g:12.0 mL, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0026] In some optional instances, the mixing and heating temperature is 80~90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0027] In some optional instances, the mixing and heating time is 3 to 5 hours, for example, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, or 5.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] Citric acid reacts with ferrous sulfate heptahydrate in aqueous solution via a complexation reaction. Citric acid is a tribasic organic acid containing three carboxyl groups and one hydroxyl group, which are excellent ligands. Ferrous sulfate heptahydrate dissociates into Fe upon dissolution in water. 2+ Under stirring and heating conditions, the anion coordinates with the ferrous ion to form a water-soluble ferrous citrate complex. This complexation reaction not only stabilizes Fe... 2+ To prevent premature oxidation, it is essential to ensure that the modified biochar is grafted with reducing Fe. 2+ rather than Fe 3+ .

[0029] By immersing biochar in a modified solution and heating and stirring, ferrous citrate complexes were loaded onto the biochar. On one hand, the porous structure of the biochar allows for the adsorption of the ferrous citrate complexes; on the other hand, under heating conditions, the carboxyl groups on the complex undergo esterification with the hydroxyl groups on the biochar surface. Simultaneously, the iron ions in the complex can coordinate and exchange with the biochar surface, thus grafting the complexes onto the biochar. A robust loading of the complexes onto the biochar is achieved through a combination of physical adsorption and chemical bonding.

[0030] The porous structure of biochar itself provides a huge specific surface area and adsorption capacity, enabling the adsorption of large amounts of heavy metal ions. The complexes supported within the biochar pores introduce a large number of carboxyl functional groups. These carboxyl functional groups have a strong complexing ability for heavy metal cations, capturing and immobilizing these heavy metal ions adsorbed into the biochar pores. Simultaneously, the Fe in the complexes... 2+ It has reducing properties and can reduce highly toxic hexavalent chromium Cr(VI) in soil to trivalent chromium Cr(III), which is less toxic and has poorer migration.

[0031] As a preferred technical solution of the present invention, in step (II), the temperature of the oscillation culture is 30~35℃, for example, it can be 30℃, 30.5℃, 31℃, 31.5℃, 32℃, 32.5℃, 33℃, 33.5℃, 34℃, 34.5℃ or 35℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] In some optional instances, the oscillation speed of the oscillation culture is 150 to 200 rpm, for example, 150 rpm, 155 rpm, 160 rpm, 165 rpm, 170 rpm, 175 rpm, 180 rpm, 185 rpm, 190 rpm, 195 rpm or 200 rpm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] In some optional instances, the oscillatory culture is carried out to the late logarithmic growth stage.

[0034] In some alternative instances, the centrifugation temperature is 1 to 5°C, for example, it can be 1.0°C, 1.5°C, 2.0°C, 2.5°C, 3.0°C, 3.5°C, 4.0°C, 4.5°C or 5.0°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional instances, the centrifugation speed is 6000~8000 rpm, for example, it can be 6000 rpm, 6200 rpm, 6400 rpm, 6600 rpm, 6800 rpm, 7000 rpm, 7200 rpm, 7400 rpm, 7600 rpm, 7800 rpm or 8000 rpm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0036] In some optional instances, the centrifugation time is 5 to 10 minutes, for example, 5.0 minutes, 5.5 minutes, 6.0 minutes, 6.5 minutes, 7.0 minutes, 7.5 minutes, 8.0 minutes, 8.5 minutes, 9.0 minutes, 9.5 minutes, or 10.0 minutes, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0037] As a preferred technical solution of the present invention, in step (II), the mass fraction of trehalose in the protective agent solution is 5~10wt%, for example, it can be 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 9.5wt% or 10.0wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] In some optional instances, the mass fraction of glycerol in the protective agent solution is 10 to 20 wt%, for example, it may be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0039] After collecting the bacterial cells by centrifugation, the cells aggregated at the bottom of the centrifuge tube as a precipitate. At this point, a preservative solution containing trehalose and glycerol was added, and the tube was vortexed to redisperse the cells, resulting in a homogeneous bacterial suspension. The use of a preservative solution containing trehalose and glycerol for resuspending the cells aims to maintain their viability and physiological activity.

[0040] As a preferred technical solution of the present invention, in step (II), the temperature of static incubation is 25~30℃, for example, it can be 25℃, 25.5℃, 26℃, 26.5℃, 27℃, 27.5℃, 28℃, 28.5℃, 29℃, 29.5℃ or 30℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] In some optional instances, the static incubation period is 5 to 7 days.

[0042] In some optional instances, the eluent used for elution is an aqueous solution of Tween-80 with a mass fraction of 0.01 to 0.1 wt%, such as 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, or 0.1 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0043] A 0.01–0.1 wt% Tween-80 aqueous solution was used as the eluent to wash and dissolve fungal spores attached to the surface of the culture medium, thereby transferring mature spores from the plate to the solution. Because fungal spores are hydrophobic, they easily aggregate and attach to hydrophilic agar surfaces, making them difficult to elute with pure water alone. This invention uses a low-concentration Tween-80 aqueous solution to enhance the wetting properties of the hydrophobic spores, making them easier to detach from the plate surface and dissolve in the eluent.

[0044] As a preferred technical solution of the present invention, in step (III), the mixing ratio of the modified biochar wet material, the bacterial suspension and the spore suspension is 1g:(1~2)mL:(1~2)mL, for example, it can be 1g:1mL:1mL, 1g:1.1mL:1.1mL, 1g:1.2mL:1.2mL, 1g:1.3mL:1.3mL, 1g:1.4mL:1.4mL, 1g:1.5mL:1.5mL, 1g:1.6mL:1.6mL, 1g:1.7mL:1.7mL, 1g:1.8mL:1.8mL, 1g:1.9mL:1.9mL or 1g:2mL:2mL, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] The biochar prepared in this invention is simultaneously loaded with Burkholderia buergerianum and P. chrysosporium spp., which can exert a synergistic effect in the remediation of contaminated soil. Burkholderia buergerianum exhibits heavy metal resistance and can directly convert heavy metal ions through biosorption and redox mechanisms. P. chrysosporium spp., as a white-rot fungus, secretes abundant extracellular enzymes and organic acids; these metabolites can complex and dissolve heavy metals. Furthermore, the network structure of the fungal hyphae can extend in the soil, not only adsorbing heavy metals itself but also improving the soil microenvironment, which is conducive to bacterial colonization and migration.

[0046] In some optional examples, the sodium alginate solution has a mass fraction of 2 to 4 wt%, for example, 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt%, 3.0 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt%, or 4.0 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0047] In some optional instances, the volume ratio of the bacterial char mixture to the sodium alginate solution is 1:(1~2), for example, it can be 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.0, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0048] This invention specifically limits the volume ratio of the bacterial charcoal mixture to the sodium alginate solution to 1:(1~2). When the proportion of sodium alginate solution is too low, the resulting gel network is looser, which facilitates the diffusion of water, oxygen, nutrients, and heavy metal ions. However, the mechanical strength will decrease significantly, making it prone to breakage during use. This causes the internal microorganisms to be prematurely exposed to the harsh soil environment, failing to achieve the goal of long-term slow-release remediation. When the proportion of sodium alginate solution is too high, the resulting gel network structure is too dense, severely hindering the diffusion of water, oxygen, nutrients, and heavy metal ions. This is detrimental to the growth and metabolism of internal microorganisms and also affects the adsorption of heavy metal ions.

[0049] As a preferred technical solution of the present invention, in step (III), the mass fraction of the calcium chloride solution is 2~5wt%, for example, it can be 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt% or 5.0wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] In some alternative examples, the orifice of the syringe is 1 to 1.5 mm, for example, it can be 1.0 mm, 1.05 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm or 1.5 mm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0051] In some optional instances, after the mixed suspension is dropped into the calcium chloride solution to form gel particles, it is further soaked in the calcium chloride solution for 20 to 40 minutes, for example, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes or 40 minutes, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0052] This invention uses sodium alginate and calcium chloride for gelation. The purpose is to immobilize the loaded biochar prepared in previous steps and encapsulate the free bacterial and spore suspensions within the gel network, preventing them from being washed away or lost after application to the soil. Furthermore, the gel microspheres provide a relatively stable growth environment for the internal microorganisms, enhancing their survival rate in harsh soil conditions. Simultaneously, the porous structure of the gel network allows the diffusion of small molecules such as water, nutrients, oxygen, and heavy metal ions, ensuring normal metabolism of the internal microorganisms while controlling the release rate of the microorganisms and their metabolites, thus achieving long-term remediation.

[0053] In some optional examples, the drying temperature of the gel microspheres is 30~40°C, for example, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C or 40°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0054] Secondly, the present invention provides an ecologically activated remediation material for heavy metal contaminated soil prepared by the preparation method described in the first aspect.

[0055] As a preferred technical solution of the present invention, the ecological activation and restoration material includes a load core and a gel embedding layer;

[0056] The loading core includes modified biochar and Burkholderia and Protozoa chrysospora loaded inside the modified biochar, wherein the modified biochar is ferrous citrate complex grafted biochar.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0058] This invention first prepares ferrous citrate-grafted biochar, providing efficient adsorption and complexation sites for heavy metal ions. Then, *Burkholderia burgdorferi* and *Procambarus chrysospora* are loaded onto modified activated carbon; their synergistic effect improves the soil environment and transforms heavy metal ions. Finally, the modified biochar is encapsulated using sodium alginate-calcium chloride gelation to form gel microspheres, achieving the fixation and protection of microorganisms. The ecological activation and remediation material prepared by this invention not only efficiently fixes heavy metals but also enhances the survival time of microorganisms in the soil, promoting the restoration of soil ecological functions. Attached Figure Description

[0059] Figure 1 The following is a flow chart of the preparation process of the ecological activation and restoration materials provided in Examples 1-5 of this invention;

[0060] Figure 2 The infrared spectra of the biochar and modified biochar prepared in Example 1 of this invention are shown. Detailed Implementation

[0061] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0062] Example 1

[0063] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0064] (1) The corn stalks were crushed into straw powder with an average particle size of 2 mm. Under a nitrogen atmosphere, the straw powder was heated to 450°C at a heating rate of 5°C / min and kept at the temperature for 2.5 h to complete the anaerobic pyrolysis. After cooling to room temperature, the powder was crushed and passed through a 60-mesh sieve to obtain biochar.

[0065] Citric acid, ferrous sulfate heptahydrate, and deionized water were mixed to obtain a modified solution with a concentration of 0.8 mol / L for citric acid and 0.05 mol / L for ferrous sulfate heptahydrate. Biochar was dispersed in the modified solution at a solid-liquid ratio of 1 g:8 mL. The mixture was stirred and heated at 80 °C for 5 h. After filtration, separation, and washing, the modified biochar wet material was obtained.

[0066] (2) Add Burkholderia lyophilized powder (CICC 10561) to a small amount of sterilized LB liquid medium, gently pipette to completely dissolve the powder, and prepare a concentrated bacterial suspension. Place the concentrated bacterial suspension in a constant temperature shaker and culture at 30℃ and 200 rpm for 24 h to obtain activated seed culture. In a clean bench, use a sterile pipette to inject the seed culture into LB liquid medium. The inoculation volume of the seed culture is 3% of the volume of LB liquid medium. Culture at 30℃ and 150 rpm until the late logarithmic growth stage (measured by OD). 600 To monitor bacterial growth density, when OD 600 When the value reaches 1.0 and is in the logarithmic growth phase, stop the culture. Then, centrifuge at 1℃ and 6000rpm for 10min, collect the cells, and resuspend the cells in a protective solution containing 5wt% trehalose and 10wt% glycerol to obtain a bacterial suspension.

[0067] Place the mycelial cake of *Phanerochaete chrysosporium* (CICC 40299) on a potato dextrose agar plate with the mycelial side facing up, press gently to ensure close contact between the mycelial cake and the culture medium, cover the plate, invert it and place it in a constant temperature incubator, and incubate it at 25°C for 7 days. Then, wash it with 0.01 wt% Tween-80 aqueous solution, filter it to obtain the spore suspension.

[0068] (3) The modified biochar wet material, bacterial suspension and spore suspension are mixed in a ratio of 1g:1mL:1mL to obtain a bacterial char mixture. The bacterial char mixture is then mixed with a sodium alginate solution with a mass fraction of 2wt% in a volume ratio of 1:1 to obtain a mixed suspension.

[0069] Using a syringe with a 1 mm aperture, the mixed suspension was dripped into a 2 wt% calcium chloride solution. After dripping, gel particles were formed. The mixture was then soaked in the calcium chloride solution for 40 min to obtain gel microspheres. The gel microspheres were filtered out and dried at 30 °C to obtain the ecological activation and restoration material.

[0070] Figure 2 The infrared spectra of the biochar and modified biochar prepared in Example 1 of this invention are shown. As can be seen from the figures, ferrous citrate complexes were successfully loaded onto the surface of the biochar through modification with a citric acid / ferrous sulfate solution. Specifically, at 3500 cm⁻¹... -1 The broad absorption peak at 1700 cm⁻¹ is attributed to the OH stretching vibration, originating from the carboxyl and hydroxyl groups introduced by citric acid; -1 The significantly enhanced absorption peak at 1600 cm⁻¹ is attributed to the C=O stretching vibration, which is due to the esterification reaction between the carboxyl group of the ferrous citrate complex and the hydroxyl group on the biochar surface, indicating that the ferrous citrate complex was successfully grafted onto the biochar surface;-1 and 1400cm -1 The changes in the absorption peaks nearby are attributed to the symmetric and asymmetric stretching vibrations of -COO⁻ in the newly formed ferrous citrate complex; in the range of 500–900 cm⁻¹ -1 The new absorption peaks appearing within the range are attributed to the Fe-O vibration. Therefore, ferrous citrate complexes were grafted onto the surface of biochar after modification with citric acid / ferrous sulfate.

[0071] Example 2

[0072] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0073] (1) The corn stalks were crushed into straw powder with an average particle size of 2 mm. Under a nitrogen atmosphere, the straw powder was heated to 460°C at a heating rate of 6°C / min and kept at the temperature for 2.2 h to complete the anaerobic pyrolysis. After cooling to room temperature, the powder was crushed and passed through a 70-mesh sieve to obtain biochar.

[0074] Citric acid, ferrous sulfate heptahydrate, and deionized water were mixed to obtain a modified solution with a concentration of 0.9 mol / L for citric acid and 0.08 mol / L for ferrous sulfate heptahydrate. Biochar was dispersed in the modified solution at a solid-liquid ratio of 1 g: 9 mL. The mixture was stirred and heated at 82 °C for 4.5 h. After filtration, separation, and washing, the modified biochar wet material was obtained.

[0075] (2) Add Burkholderia lyophilized powder to a small amount of sterilized LB liquid medium, gently pipette to completely dissolve the powder, and prepare a concentrated bacterial suspension. Place the concentrated bacterial suspension in a constant temperature shaker and culture at 30℃ and 200 rpm for 24 h to obtain activated seed culture. In a clean bench, use a sterile pipette to draw up the seed culture and inject it into LB liquid medium. The inoculation volume of the seed culture is 3% of the volume of LB liquid medium. Culture at 31℃ and 160 rpm until the late logarithmic growth stage (by measuring OD). 600 To monitor bacterial growth density, when OD 600 When the value reaches 1.0 and is in the logarithmic growth phase, stop the culture. Then, centrifuge at 2℃ and 6500rpm for 8min, collect the cells, and resuspend the cells in a protective solution containing 6wt% trehalose and 12wt% glycerol to obtain a bacterial suspension.

[0076] Place the mycelium of *Phanerochaete chrysophagus* on a potato dextrose agar plate with the mycelium side facing up, press gently to ensure close contact between the mycelium and the culture medium, cover the plate, invert it and place it in a constant temperature incubator, and incubate it at 26°C for 6 days. Then, wash it with 0.03wt% Tween-80 aqueous solution, filter it to obtain the spore suspension.

[0077] (3) The modified biochar wet material, bacterial suspension and spore suspension were mixed in a ratio of 1g:1.2mL:1.2mL to obtain a bacterial char mixture. The bacterial char mixture was then mixed with a sodium alginate solution with a mass fraction of 2.5wt% in a volume ratio of 1:1.2 to obtain a mixed suspension.

[0078] Using a syringe with a 1.2 mm aperture, the mixed suspension was dripped into a 3 wt% calcium chloride solution. After dripping, gel particles were formed. The mixture was then soaked in the calcium chloride solution for 35 minutes to obtain gel microspheres. The gel microspheres were filtered out and dried at 32°C to obtain the ecological activation and restoration material.

[0079] Example 3

[0080] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0081] (1) The corn stalks were crushed into straw powder with an average particle size of 2 mm. Under a nitrogen atmosphere, the straw powder was heated to 470°C at a heating rate of 7°C / min and kept at the temperature for 2 h to complete the anaerobic pyrolysis. After cooling to room temperature, the powder was crushed and passed through an 80-mesh sieve to obtain biochar.

[0082] Citric acid, ferrous sulfate heptahydrate, and deionized water were mixed to obtain a modified solution with a concentration of 1 mol / L for citric acid and 0.1 mol / L for ferrous sulfate heptahydrate. Biochar was dispersed in the modified solution at a solid-liquid ratio of 1 g:10 mL. The mixture was stirred and heated at 85 °C for 4 h. After filtration, separation, and washing, the modified biochar wet material was obtained.

[0083] (2) Add Burkholderia lyophilized powder to a small amount of sterilized LB liquid medium, gently pipette to completely dissolve the powder, and prepare a concentrated bacterial suspension. Place the concentrated bacterial suspension in a constant temperature shaker and culture at 30℃ and 200 rpm for 24 h to obtain activated seed culture. In a clean bench, use a sterile pipette to draw up the seed culture and inject it into LB liquid medium. The inoculation volume of the seed culture is 3% of the volume of LB liquid medium. Culture at 32℃ and 170 rpm until the late logarithmic growth stage (by measuring OD). 600 To monitor bacterial growth density, when OD600 When the value reaches 1.0 and is in the logarithmic growth phase, stop the culture. Then, centrifuge at 3℃ and 7000rpm for 7min, collect the cells, and resuspend the cells in a protective solution containing 7wt% trehalose and 15wt% glycerol to obtain a bacterial suspension.

[0084] Place the mycelium of *Phanerochaete chrysophagus* on a potato dextrose agar plate with the mycelium side facing up, press gently to ensure close contact between the mycelium and the culture medium, cover the plate, invert it and place it in a constant temperature incubator, and incubate at 27°C for 6 days. Then, wash with 0.05wt% Tween-80 aqueous solution, filter and obtain the spore suspension.

[0085] (3) The modified biochar wet material, bacterial suspension and spore suspension are mixed in a ratio of 1g:1.5mL:1.5mL to obtain a bacterial char mixture. The bacterial char mixture is then mixed with a sodium alginate solution with a mass fraction of 3wt% in a volume ratio of 1:1.5 to obtain a mixed suspension.

[0086] Using a syringe with a 1.3 mm aperture, the mixed suspension was dripped into a 3 wt% calcium chloride solution. After dripping, gel particles were formed. The mixture was then soaked in the calcium chloride solution for 30 minutes to obtain gel microspheres. The gel microspheres were filtered out and dried at 35°C to obtain the ecological activation and restoration material.

[0087] Example 4

[0088] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0089] (1) The corn stalks were crushed into stalk powder with an average particle size of 2 mm. Under a nitrogen atmosphere, the stalk powder was heated to 480°C at a heating rate of 8°C / min and kept at that temperature for 1.8 h to complete the anaerobic pyrolysis. After cooling to room temperature, the powder was crushed and passed through a 90-mesh sieve to obtain biochar.

[0090] Citric acid, ferrous sulfate heptahydrate, and deionized water were mixed to obtain a modified solution with a concentration of 1.1 mol / L for citric acid and 0.12 mol / L for ferrous sulfate heptahydrate. Biochar was dispersed in the modified solution at a solid-liquid ratio of 1 g:11 mL. The mixture was stirred and heated at 88 °C for 3.5 h. After filtration, separation, and washing, the modified biochar wet material was obtained.

[0091] (2) Add Burkholderia lyophilized powder to a small amount of sterilized LB liquid medium, gently pipette to completely dissolve the powder, and prepare a concentrated bacterial suspension. Place the concentrated bacterial suspension in a constant temperature shaker and culture at 30℃ and 200 rpm for 24 h to obtain activated seed culture. In a clean bench, use a sterile pipette to draw up the seed culture and inject it into LB liquid medium. The inoculation volume of the seed culture is 3% of the volume of LB liquid medium. Culture at 33℃ and 180 rpm until the late logarithmic growth stage (by measuring OD). 600 To monitor bacterial growth density, when OD 600 When the value reaches 1.0 and is in the logarithmic growth phase, stop the culture. Then, centrifuge at 4℃ and 7500rpm for 6min, collect the cells, and resuspend the cells in a protective solution containing 8wt% trehalose and 18wt% glycerol to obtain a bacterial suspension.

[0092] Place the mycelium of *Phanerochaete chrysophagus* on a potato dextrose agar plate with the mycelium side facing up, press gently to ensure close contact between the mycelium and the culture medium, cover the plate, invert it and place it in a constant temperature incubator, and incubate it at 28°C for 5 days. Then, wash it with 0.08 wt% Tween-80 aqueous solution, filter it to obtain the spore suspension.

[0093] (3) The modified biochar wet material, bacterial suspension and spore suspension were mixed in a ratio of 1g:1.8mL:1.8mL to obtain a bacterial char mixture. The bacterial char mixture was then mixed with a sodium alginate solution with a mass fraction of 3.5wt% in a volume ratio of 1:1.8 to obtain a mixed suspension.

[0094] Using a syringe with a 1.4 mm aperture, the mixed suspension was dripped into a 4 wt% calcium chloride solution. After dripping, gel particles were formed. The mixture was then soaked in the calcium chloride solution for 25 minutes to obtain gel microspheres. The gel microspheres were filtered out and dried at 38°C to obtain the ecological activation and restoration material.

[0095] Example 5

[0096] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil, such as... Figure 1 As shown, the preparation method specifically includes the following steps:

[0097] (1) The corn stalks were crushed into stalk powder with an average particle size of 2 mm. Under a nitrogen atmosphere, the stalk powder was heated to 500 °C at a heating rate of 10 °C / min and kept at the temperature for 1.5 h to complete the anaerobic pyrolysis. After cooling to room temperature, the powder was crushed and passed through a 100-mesh sieve to obtain biochar.

[0098] Citric acid, ferrous sulfate heptahydrate, and deionized water were mixed to obtain a modified solution with a concentration of 1.2 mol / L for citric acid and 0.15 mol / L for ferrous sulfate heptahydrate. Biochar was dispersed in the modified solution at a solid-liquid ratio of 1 g:12 mL. The mixture was stirred and heated at 90 °C for 3 h. After filtration, separation, and washing, the modified biochar wet material was obtained.

[0099] (2) Add Burkholderia lyophilized powder to a small amount of sterilized LB liquid medium, gently pipette to completely dissolve the powder, and prepare a concentrated bacterial suspension. Place the concentrated bacterial suspension in a constant temperature shaker and culture at 30℃ and 200 rpm for 24 h to obtain activated seed culture. In a clean bench, use a sterile pipette to draw up the seed culture and inject it into the LB liquid medium. The inoculation volume of the seed culture is 3% of the volume of the LB liquid medium. Culture at 35℃ and 200 rpm until the late logarithmic growth stage (by measuring OD). 600 To monitor bacterial growth density, when OD 600 When the value reaches 1.0 and is in the logarithmic growth phase, stop the culture. Then, centrifuge at 5℃ and 8000rpm for 5min, collect the cells, and resuspend the cells in a protective solution containing 10wt% trehalose and 20wt% glycerol to obtain a bacterial suspension.

[0100] Place the mycelium of *Phanerochaete chrysophagus* on a potato dextrose agar plate with the mycelium side facing up, press gently to ensure close contact between the mycelium and the culture medium, cover the plate, invert it and place it in a constant temperature incubator, and incubate at 30°C for 5 days. Then, wash with 0.1 wt% Tween-80 aqueous solution, filter to obtain spore suspension.

[0101] (3) The modified biochar wet material, bacterial suspension and spore suspension are mixed in a ratio of 1g:2mL:2mL to obtain a bacterial char mixture. The bacterial char mixture is then mixed with a sodium alginate solution with a mass fraction of 4wt% in a volume ratio of 1:2 to obtain a mixed suspension.

[0102] Using a syringe with a 1.5 mm aperture, the mixed suspension was dripped into a 5 wt% calcium chloride solution. After dripping, gel particles were formed. The mixture was then soaked in the calcium chloride solution for 20 minutes to obtain gel microspheres. The gel microspheres were filtered out and dried at 40°C to obtain the ecological activation and restoration material.

[0103] Example 6

[0104] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil. The difference from Embodiment 1 is that in step (1), the concentration of citric acid in the modified solution is adjusted to 0.5 mol / L. Other operation steps and process parameters are exactly the same as in Embodiment 1.

[0105] Example 7

[0106] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil. The difference from Embodiment 1 is that in step (1), the concentration of citric acid in the modified solution is adjusted to 1.5 mol / L. Other operation steps and process parameters are exactly the same as in Embodiment 1.

[0107] Example 8

[0108] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil. The difference from Embodiment 1 is that in step (1), the concentration of ferrous sulfate heptahydrate in the modified solution is adjusted to 0.01 mol / L. Other operation steps and process parameters are exactly the same as in Embodiment 1.

[0109] Example 9

[0110] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil. The difference from Embodiment 1 is that in step (1), the concentration of ferrous sulfate heptahydrate in the modified solution is adjusted to 0.2 mol / L. Other operating steps and process parameters are exactly the same as in Embodiment 1.

[0111] Example 10

[0112] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil. The difference from Embodiment 1 is that in step (3), the volume ratio of the bacterial char mixture to the sodium alginate solution is adjusted to 1:0.5. Other operating steps and process parameters are exactly the same as in Embodiment 1.

[0113] Example 11

[0114] This embodiment provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil. The difference from Embodiment 1 is that in step (3), the volume ratio of the bacterial char mixture to the sodium alginate solution is adjusted to 1:3. Other operating steps and process parameters are exactly the same as in Embodiment 1.

[0115] Comparative Example 1

[0116] This comparative example provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil. The difference from Example 1 is that in step (1), the modification treatment of biochar is omitted, and the biochar after anaerobic pyrolysis is directly used as a porous carrier. Other operation steps and process parameters are exactly the same as in Example 1.

[0117] Comparative Example 2

[0118] This comparative example provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil. The difference from Example 1 is that in step (3), the bacterial suspension is omitted, and the modified biochar wet material and spore suspension are mixed at a ratio of 1g:1mL. That is, only Protozoa chrysospora is loaded on the modified biochar, and Burkholderia is not loaded. Other operation steps and process parameters are exactly the same as in Example 1.

[0119] Comparative Example 3

[0120] This comparative example provides a method for preparing an ecologically activated remediation material for heavy metal contaminated soil. The difference from Example 1 is that in step (3), the spore suspension is omitted, and the modified biochar wet material and bacterial suspension are mixed at a ratio of 1g:1mL. That is, Burkholderia is loaded only on the modified biochar, and Proteobacterium chrysosporium is not loaded. Other operation steps and process parameters are exactly the same as in Example 1.

[0121] Application examples

[0122] The ecological activation and remediation material prepared in the example was spread on the surface of the contaminated soil and mechanically tilled to a depth of 20-30 cm. Water was applied as needed to maintain a certain level of soil moisture in order to activate the microorganisms in the material and promote their growth and metabolism.

[0123] The heavy metal ion saturation adsorption capacity, heavy metal removal rate, leaching toxicity, and soil respiration intensity after remediation of the ecologically activated remediation materials prepared in Examples 1-11 and Comparative Examples 1-3 were tested. The specific test steps included:

[0124] (1) Saturated adsorption capacity of heavy metal ions

[0125] Formulating the target heavy metal (Cd) 2+ and Pb 2+ The standard stock solution (1000 mg / L, source solution is Cd(NO3)2·4H2O or Pb(NO3)2) was diluted with deionized water to prepare initial solutions of different concentrations (50 mg / L, 100 mg / L, 200 mg / L, 500 mg / L, 800 mg / L and 1000 mg / L). The pH of all initial solutions was adjusted to 5.0±0.1 with dilute HNO3 or NaOH solution.

[0126] Add 50 mg of the ecological activation and remediation material to a conical flask. Add 50 mL of initial solution of different concentrations (solid-liquid ratio 1:1000) to each flask. Seal the flasks and place them in a constant temperature shaker at 25 ± 1 °C and 150 rpm for 24 h. Immediately after shaking, filter the solution through a 0.45 μm microporous membrane. Determine the residual concentration of heavy metal ions in the filtrate using inductively coupled plasma mass spectrometry (ICP-MS). Calculate the equilibrium adsorption capacity of heavy metal ions for different initial solutions using the following formula:

[0127]

[0128] Among them: Q e To determine the equilibrium adsorption capacity (mg / g), C0 represents the initial concentration of heavy metal ions in the solution (mg / L). e V represents the residual concentration of heavy metal ions in the filtrate (mg / L), V represents the initial solution volume (L), and m represents the sample mass (g).

[0129] The saturated adsorption capacity Q was fitted using the Langmuir model. max :

[0130]

[0131] Among them, K L is the Langmuir constant (L / mg).

[0132] (2) Heavy metal removal rate

[0133] Take clean soil (pH=6.5±0.5, organic matter content 2.5%), crush it and pass it through a 2mm sieve, add Pb(NO3)2 solution and Cd(NO3)2 solution to adjust the Pb content in the soil. 2+ Concentration up to 800±50 mg / kg, Cd 2+ The concentration was increased to 50±5 mg / kg, and the heavy metals were aged for 30 days (25℃) to induce aging.

[0134] The ecologically activated remediation material prepared in the examples was added at 5 wt% of the soil mass and mixed thoroughly. The soil moisture content was adjusted to 50% of field capacity with deionized water and incubated in a constant temperature incubator (25±1℃, protected from light). On the 7th day, soil samples were taken from a depth of 10 cm. After freeze-drying, the soil samples were ground through a 100-mesh sieve and digested using the EPA 3052 method (HCl-HNO3-HF microwave digestion). The Pb content in the soil was determined by ICP-MS. 2+ Concentration and Cd 2+ Concentration, the heavy metal removal rate is calculated using the following formula:

[0135]

[0136] Where C0 is the initial concentration of heavy metal ions in the soil, C t The concentration of heavy metal ions in the soil after 7 days of treatment.

[0137] (3) Leaching toxicity

[0138] Take clean soil (pH=6.5±0.5, organic matter content 2.5%), crush it and pass it through a 2mm sieve, add Pb(NO3)2 solution and Cd(NO3)2 solution to adjust the Pb content in the soil. 2+ Concentration up to 800±50 mg / kg, Cd 2+ The concentration was increased to 50±5 mg / kg, and the heavy metals were aged for 30 days (25℃) to induce aging.

[0139] The ecological activation and restoration material prepared in the example was added at 5 wt% of the soil mass and mixed evenly. The soil moisture content was adjusted to 50% of the field capacity with deionized water and kept in a constant temperature incubator (25±1℃, protected from light). On the 7th day, a soil sample was taken from a depth of 10 cm.

[0140] Dissolve 5.7 mL of glacial acetic acid in 500 mL of deionized water, add 64.3 mL of NaOH solution (concentration of 1 mol / L), bring the volume to 1 L, and adjust the pH to 2.88 ± 0.05 to obtain the extractant.

[0141] Take 5.0g of the remediated soil sample and place it in a centrifuge tube. Add 100mL of extraction solvent at a solid-liquid ratio of 1:20. Place the tube on a vortex mixer and shake continuously at a speed of 30±2rpm for 18h. After shaking, let it stand for 10min. Filter the solution under vacuum using a 0.45μm microporous membrane and collect the filtrate. After acidifying the filtrate with 5wt% dilute nitric acid, determine the concentrations of lead (Pb) and cadmium (Cd) in the filtrate using inductively coupled plasma mass spectrometry.

[0142] (4) Soil respiration intensity

[0143] Take clean soil (pH=6.5±0.5, organic matter content 2.5%), crush it and pass it through a 2mm sieve, add Pb(NO3)2 solution and Cd(NO3)2 solution to adjust the Pb content in the soil. 2+ Concentration up to 800±50 mg / kg, Cd 2+ The concentration was increased to 50±5 mg / kg, and the heavy metals were aged for 30 days (25℃) to induce aging.

[0144] Add the ecological activation and restoration material at 5wt% of the soil mass and mix it evenly. Adjust the soil moisture content to 50% of the field capacity with deionized water. Cultivate in a constant temperature incubator (25±1℃, away from light). Take a soil sample from a depth of 10cm on the 7th day.

[0145] Weigh out 20.0g of the treated soil sample (equivalent to dry soil), pass it through a 2mm sieve, and adjust the soil moisture content to 50% of field capacity. Spread the sample evenly at the bottom of a wide-mouthed bottle. Suspend a small cup containing 10mL of 0.1mol / L NaOH solution inside the bottle. Quickly seal the bottle cap, ensuring good airtightness. Place the bottle in a constant temperature incubator at 25℃ for 24 hours. After incubation, remove the small cup containing NaOH solution and add 5mL of 1mol / L BaCl2 solution to completely precipitate the absorbed CO2 as BaCO3. Then add 2 drops of phenolphthalein indicator; the solution will turn pink. Titrate with 0.05mol / L standard hydrochloric acid solution until the red color disappears, and record the volume of hydrochloric acid solution consumed. A blank control group without soil was also prepared, and the same procedure was followed, recording the volume of hydrochloric acid solution consumed. Three replicate experiments were conducted for each soil sample. Soil respiration intensity was expressed as the amount of carbon dioxide released per kg of dry soil per hour (mg / (kg dry soil·h)).

[0146] The test results are shown in Table 1.

[0147] Table 1

[0148] <![CDATA[Pb 2+ Saturated adsorption capacity (mg / g) <![CDATA[Cd 2+ Saturated adsorption capacity (mg / g) <![CDATA[Pb 2+ Removal rate (%) <![CDATA[Cd 2+ Removal rate (%) TCLP-Pb leaching concentration (mg / L) TCLP-Cd leaching concentration (mg / L) Soil respiration rate (mg / (kg dry soil·h)) Example 1 293.7 326.2 96.8 97.3 1.22 0.88 1.17 Example 2 297.4 329.6 97.1 97.6 1.18 0.84 1.19 Example 3 290.9 323.8 96.5 97 1.26 0.92 1.15 Example 4 295.1 327.9 96.9 97.4 1.2 0.86 1.18 Example 5 299.8 331.3 97.3 97.8 1.15 0.81 1.21 Example 6 261.3 292.7 92.4 93.1 2.67 2.11 1.06 Example 7 253.9 285.4 91.7 92.5 2.95 2.38 1.03 Example 8 266.8 299.5 93.2 93.8 2.44 1.89 1.08 Example 9 258.6 288.2 92 92.7 2.82 2.25 1.04 Example 10 270.4 304.1 93.8 94.3 2.21 1.68 1.12 Example 11 247.5 278.8 90.6 91.4 3.28 2.64 0.97 Comparative Example 1 117.6 138.4 78.2 79.6 8.53 6.95 0.68 Comparative Example 2 229.1 257.9 88.9 89.7 4.06 3.32 0.94 Comparative Example 3 214.7 242.3 87.4 88.3 4.61 3.77 0.95 Blank example — — — — — — 0.43

[0149] The test data from Examples 1, 6, and 7 show that citric acid, as an organic acid, mainly functions by complexing with iron ions and loading them onto the pores and surface of biochar, thereby increasing the density of carboxyl functional groups on the material surface. In Example 6, the concentration of citric acid was too low, and in Example 7, the concentration was too high, both of which reduced the adsorption capacity and the fixation effect on heavy metal ions, and also inhibited the microbial activity of the soil to some extent.

[0150] The test data from Examples 1, 8, and 9 show that the concentration of ferrous sulfate heptahydrate directly affects the Fe content in the material. 2+ The load, an appropriate amount of Fe 2+ The loading can cause co-precipitation of heavy metals. In Example 6, the concentration of ferrous sulfate heptahydrate was too low, which reduced the fixation effect on heavy metal ions; in Example 7, the concentration of ferrous sulfate heptahydrate was too high, which easily oxidized to form ferric hydroxide precipitate, clogging the pores of biochar and affecting the adsorption capacity of the material.

[0151] The test data from Examples 1, 10, and 11 show that the amount of sodium alginate solution directly affects the encapsulation and fixation effect on microorganisms. In Example 10, the amount of sodium alginate solution was too low, resulting in an insufficiently strong gel network structure that could not protect the bacteria, leading to bacterial loss. In Example 11, the amount of sodium alginate solution was too high, resulting in an overly dense gel structure that hindered the diffusion of nutrients and heavy metal ions, which was detrimental to the growth and metabolism of internal microorganisms and also affected the adsorption of heavy metal ions.

[0152] As can be seen from the test data of Example 1 and Comparative Example 1, Comparative Example 1 completely omits biochar modification. The unmodified original biochar has a small specific surface area, insufficient number of surface carboxyl functional groups, poor chemical adsorption and complexation ability for heavy metals, and its surface properties are not conducive to the effective colonization of microorganisms.

[0153] The test data from Example 1, Comparative Example 2 and Comparative Example 3 show that Comparative Example 2 and Comparative Example 3 were loaded with only a single microbial species. The two microorganisms can play a synergistic role in soil remediation. Loading with only a single microbial species will significantly affect the remediation effect of the material.

[0154] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an ecologically activated remediation material for heavy metal contaminated soil, characterized in that, The preparation method includes: (I) After crushing the corn stalks, anaerobic pyrolysis was carried out, cooled to room temperature, crushed and sieved to obtain biochar; citric acid, ferrous sulfate heptahydrate and deionized water were mixed to obtain a modified solution, the biochar was dispersed in the modified solution, mixed, stirred and heated, and then separated by suction filtration and washing to obtain modified biochar wet material; (II) Burkholderia was inoculated into LB liquid medium, shaken and cultured, then centrifuged, and the bacterial cells were collected. The bacterial cells were resuspended in a protective solution containing trehalose and glycerol to obtain a bacterial suspension. Phanerochaete chrysospora was inoculated into potato dextrose agar plates, and cultured statically until the spores matured. Then, the spores were washed and filtered to obtain a spore suspension. (III) The modified biochar wet material, the bacterial suspension and the spore suspension are mixed to obtain a bacterial-char mixture. The bacterial-char mixture is mixed with sodium alginate solution to obtain a mixed suspension. The mixed suspension is dripped into calcium chloride solution using a syringe to obtain gel microspheres. The microspheres are then removed and dried to obtain the ecological activation and restoration material.

2. The preparation method according to claim 1, characterized in that, In step (I), the heating rate of the anaerobic pyrolysis is 5~10℃ / min; The temperature of the anaerobic pyrolysis is 450~500℃; The holding time for the anaerobic pyrolysis is 1.5~2.5h; The sieve mesh size is 60-100 mesh.

3. The preparation method according to claim 1, characterized in that, In step (I), the concentration of citric acid in the modified solution is 0.8~1.2 mol / L; The concentration of ferrous sulfate heptahydrate in the modified solution is 0.05~0.15 mol / L; The solid-liquid ratio of the biochar to the modified solution is 1 g:(8~12) mL; The mixing and heating temperature is 80~90℃; The mixing and heating time is 3-5 hours.

4. The preparation method according to claim 1, characterized in that, In step (II), the temperature for the oscillation culture is 30~35℃; The oscillation speed during the oscillation culture is 150~200 rpm; The oscillating culture was carried out to the late logarithmic growth stage; The centrifugation temperature is 1~5℃; The centrifuge speed is 6000~8000 rpm; The centrifugation time is 5-10 minutes.

5. The preparation method according to claim 1, characterized in that, In step (II), the mass fraction of trehalose in the protective agent solution is 5-10 wt%. The mass fraction of glycerol in the protective agent solution is 10-20 wt%.

6. The preparation method according to claim 1, characterized in that, In step (II), the temperature for static incubation is 25~30℃; The static incubation period is 5-7 days; The elution solution used is a Tween-80 aqueous solution with a mass fraction of 0.01~0.1wt%.

7. The preparation method according to claim 1, characterized in that, In step (III), the mixing ratio of the modified biochar wet material, the bacterial suspension and the spore suspension is 1g:(1~2)mL:(1~2)mL; The sodium alginate solution has a mass fraction of 2-4 wt%. The volume ratio of the bacterial char mixture to the sodium alginate solution is 1:(1~2).

8. The preparation method according to claim 1, characterized in that, In step (III), the mass fraction of the calcium chloride solution is 2-5 wt%. The syringe has an orifice diameter of 1~1.5mm; After the mixed suspension is dropped into the calcium chloride solution, gel particles are formed, and the particles are soaked in the calcium chloride solution for 20-40 minutes. The drying temperature of the gel microspheres is 30~40℃.

9. An ecologically activated remediation material for heavy metal contaminated soil prepared by the preparation method according to any one of claims 1 to 8.

10. The ecological activation and remediation material for heavy metal contaminated soil according to claim 9, characterized in that, The ecological activation and restoration material includes a load core and a gel embedding layer; The loading core includes modified biochar and Burkholderia and Protozoa chrysospora loaded inside the modified biochar, wherein the modified biochar is ferrous citrate complex grafted biochar.

Images