Composite material for promoting release of soil solidified long-chain perfluorinated compound and preparation method thereof

Abstract

The invention relates to the technical field of soil remediation, and discloses a composite material for promoting long-chain perfluorinated compounds solidified in soil to be released to a water body and a preparation method of the composite material. The composite material is prepared from the following raw materials: microorganisms, a porous carrier, natural gel, an iron source and a nitrogen source, wherein the microorganisms comprise iron reducing bacteria and surfactant producing bacteria. According to the composite material provided by the invention, through the combined action of the porous carrier, the gel and the nitrogen source, it is ensured that enough functional bacteria can survive in a harsh soil environment and efficiently exert preset functions; through the synergistic effect of the iron reducing bacteria and the surfactant producing bacteria, synchronous solution immobilization and solubilization are realized, and the release efficiency on long-chain perfluorinated compounds is far higher than that of single strain or chemical surfactant treatment; and by using the biodegradable natural gel and the natural surfactant generated by microorganisms, the problem of secondary pollution caused by residues of a chemical surfactant or a repairing agent is avoided.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, and in particular to a composite material that promotes the release of long-chain perfluorinated compounds solidified in soil into water bodies and its preparation method. Background Technology

[0002] Per- and polyfluoroalkyl substances (PFASs) are a class of emerging pollutants with high persistence and bioaccumulation, and their potential risks to the ecological environment and human health have become a global concern. Industrial emissions, wastewater effluent, and fire-fighting wastewater are the main point or non-point sources of PFASs in the environment. These PFASs enter rivers and other water bodies through surface runoff or direct discharge. As river water flows, overflows, or infiltrates, the PFASs in the aquatic phase come into contact with soil sediments in the riverbed, banks, and surrounding flooded areas. Among them, long-chain perfluoroalkyl substances such as chloropolyfluoroether sulfonic acid (Cl-PFESA / F53B), perfluorononanoic acid (PFNA), and hexafluoropropylene oxide tetrameric carboxylic acid (HFPO-TeA) have strong hydrophobicity and readily adsorb onto soil particles after entering the environment. Through complex interactions with minerals and organic matter in the soil (such as electrostatic adsorption, ligand exchange, and hydrophobic partitioning), they gradually age and solidify, forming non-retrievable substances (NERs). This portion of PFAS, which is embedded and immobilized by minerals, is difficult to detect using conventional extraction techniques, constituting a long-term, hidden source of pollution. It may be released again when environmental conditions change (such as fluctuations in pH and redox potential), posing a continuous threat to groundwater and surrounding water bodies.

[0003] Currently, remediation technologies for PFAS-contaminated soil mainly include adsorption and immobilization, chemical leaching, and microbial degradation. However, these technologies have significant limitations and technical shortcomings when dealing with aged and solidified PFAS, especially those in non-extractable states encapsulated by minerals. CN 103624077 A discloses a novel soil remediation agent and its application in the remediation of polybrominated diphenyl ether (PFAS) contaminated soil. This technology immobilizes pollutants by adding adsorbent materials, reducing their bioavailability. However, this is a "transfer" rather than "elimination" strategy, and does not truly reduce the total amount of PFASs in the soil. The immobilized pollutants still pose a long-term environmental risk of future reactivation. In addition, existing adsorbent immobilization materials are mostly broad-spectrum, with deficiencies in adsorption specificity, target selectivity, immobilization stability, and soil mixing efficiency. CN 112280560 A discloses a composite leaching agent and a method for leaching organic pollutants from soil. This technology uses the chemical surfactant sodium dodecyl sulfate to solubilize and elute pollutants. However, chemical surfactants are difficult to effectively desorb or break the bonds between PFASs and minerals, resulting in low release efficiency for non-extractable PFASs embedded in minerals. Furthermore, the introduction of large amounts of chemical surfactants (sodium dodecyl sulfate, Tween 80, etc.) may itself cause secondary pollution, damaging soil structure and native microbial communities, resulting in poor environmental friendliness. CN 119120029 A discloses an activator-based method for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites using negative pressure infiltration. This method requires complex pretreatment of the soil with specific treatment equipment, is costly, and does not specifically address contaminants in mineral-encapsulated forms.

[0004] In contrast, the theory of utilizing functional microorganisms has shown potential. However, the soil environment is complex and highly competitive, and exogenously introduced engineered bacteria face bottlenecks such as low survival rate, difficulty in colonization, and unstable functional expression. Existing microbial remediation schemes often simply add bacterial agents to the soil without effective protection and proliferation promotion measures for functional bacteria, resulting in poor remediation effects and poor repeatability. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one object of the present invention is to provide a composite material.

[0006] A second objective of this invention is to provide a method for preparing this composite material.

[0007] The third objective of this invention is to provide applications for this composite material.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides a composite material comprising the following raw materials: microorganisms, a porous carrier, a natural gel, an iron source, and a nitrogen source; wherein the microorganisms include iron-reducing bacteria and surfactant-producing bacteria.

[0009] In some embodiments of the present invention, the iron-reducing bacteria include Shewanella sp.、 Acidithiobacillus sp.、 Sulfobacillus sp.、 Acidimicrobium At least one of the sp.

[0010] In some preferred embodiments of the present invention, the iron-reducing bacteria include Shewanella sp. C31、 Acidithiobacillus ferrooxidans (Thiobacillus ferrooxidans) Sulfo bacillus acidophilus (Thiobacillus acidophilus) Acidimicrobium ferrooxidans At least one of (ferrous oxidase microspirilla); wherein, the Shewanella sp. C31 was purchased from the Guangdong Provincial Center for Microbial Culture Collection, with accession number GDMCC No: 62214.

[0011] In some embodiments of the present invention, the surfactant-producing bacteria include Bacillus sp.、 Pseudomonas sp.、 Candida sp.、 Acinetobacter At least one of the sp.

[0012] In some preferred embodiments of the present invention, the surfactant-producing bacteria include Bacillus subtilis (Bacillus subtilis) Pseudomonas aeruginosa (Pseudomonas aeruginosa) Candida bombicola (Bumblebee Candida albicans) Bacillus amyloliquefaciens (Bacillus amyloliquefaciens) Acinetobacter calcoaceticus At least one of (Acinetobacter calciacetate); wherein, the Bacillus subtilis Purchased from China General Microbiological Culture Collection Center, catalog number CGMCC 1.3358.

[0013] In some embodiments of the present invention, the porous carrier includes at least one of volcanic rock, fly ash, ceramsite, vermiculite, montmorillonite, and coal gangue.

[0014] In some preferred embodiments of the present invention, the porous carrier is volcanic rock.

[0015] In some embodiments of the present invention, the natural gel comprises a sodium alginate solution.

[0016] In some embodiments of the present invention, the iron source includes at least one of ferric nitrate, ferric sulfate, ferric chloride, and ferric perchlorate.

[0017] In some preferred embodiments of the present invention, the iron source is ferric nitrate.

[0018] In some embodiments of the present invention, the nitrogen source includes at least one of ferric nitrate, potassium nitrate, sodium nitrate, and calcium nitrate.

[0019] In some preferred embodiments of the present invention, the nitrogen source is ferric nitrate.

[0020] A second aspect of the present invention provides a method for preparing the composite material described in the first aspect of the present invention, comprising the following steps: S1. Iron-reducing bacteria and surfactant-producing bacteria are cultured separately to form bacterial solutions, which are then applied to the surface of a porous carrier to obtain a porous material loaded with microorganisms. S2. The porous material loaded with microorganisms is mixed with natural gel to obtain a primary complex; S3. Dissolve the iron source and nitrogen source in water to form a composite ionic solution, and add the primary composite material dropwise into the composite ionic solution to obtain the composite material.

[0021] In some embodiments of the present invention, the culture conditions for the microorganisms include: a temperature of 25-30°C and a shaking speed of 200-250 rpm.

[0022] In some preferred embodiments of the present invention, the culture conditions for the microorganisms include: a temperature of 25-28°C and a shaking speed of 210-230 rpm.

[0023] In some embodiments of the present invention, the OD of the iron-reducing bacterial solution and the surfactant-producing bacterial solution is... 600 The liquid-to-solid ratios of the iron-reducing bacteria solution, the surfactant-producing bacteria solution, and the porous carrier are selected from 0.8 to 1.2, respectively.

[0024] In some preferred embodiments of the present invention, the OD of the iron-reducing bacterial solution and the surfactant-producing bacterial solution... 600 The liquid-to-solid ratios of the iron-reducing bacteria solution, the surfactant-producing bacteria solution, and the porous carrier are respectively selected from 0.9-1.1; the liquid-to-solid ratios of the iron-reducing bacteria solution, the surfactant-producing bacteria solution, and the porous carrier are respectively selected from (9-11) mL: 100g.

[0025] In some embodiments of the present invention, the ratio of the loading of iron-reducing bacteria to surfactant-producing bacteria in the porous material loaded with microorganisms is 1:(0.8-1.2).

[0026] In some preferred embodiments of the present invention, the ratio of the loading of iron-reducing bacteria to surfactant-producing bacteria in the porous material loaded with microorganisms is 1:(0.9-1.1).

[0027] In some embodiments of the present invention, the concentration of the natural gel is 0.8wt%-1.2wt%; the solid-liquid ratio of the microbial-loaded porous material to the natural gel is 1g:(1.5-2.5)mL.

[0028] In some preferred embodiments of the present invention, the concentration of the natural gel is 0.9wt%-1.1wt%; the solid-liquid ratio of the microbial-loaded porous material to the natural gel is 1g:(1.8-2.2)mL.

[0029] In some embodiments of the present invention, the Fe contained in the composite ionic solution 3+ The molar ratio of the amount of NO3 to the mass of the natural gel contained in the primary complex is (0.02-0.04) mol: 1 g; the NO3- contained in the composite ionic solution - The ratio of the number of moles of the substance to the mass of the natural gel contained in the primary complex is (0.06-0.09) mol: 1g.

[0030] In some preferred embodiments of the present invention, the Fe contained in the composite ionic solution 3+ The molar ratio of the amount of NO3 to the mass of the natural gel contained in the primary complex is (0.02-0.03) mol: 1 g; the NO3 contained in the composite ionic solution - The ratio of the number of moles of the substance to the mass of the natural gel contained in the primary complex is (0.07-0.08) mol: 1g.

[0031] A third aspect of the invention provides the application of the composite material described in the first aspect of the invention in promoting the release of long-chain perfluorinated compounds solidified in soil into water bodies.

[0032] In some embodiments of the present invention, the long-chain perfluorinated compound includes at least one of chloropolyfluoroether sulfonic acid (Cl-PFESA / F53B), perfluorononanoic acid (PFNA), and hexafluoropropylene oxide tetramer carboxylic acid (HFPO-TeA).

[0033] In some embodiments of the present invention, the content of the long-chain perfluorinated compound in the soil is 30-100 ng / g soil.

[0034] In some preferred embodiments of the present invention, the content of the long-chain perfluorinated compound in the soil is 40-60 ng / g soil.

[0035] In some embodiments of the present invention, the amount of the composite material used is (1-5) g / g soil.

[0036] In some preferred embodiments of the present invention, the amount of the composite material is (2-4) g / g soil.

[0037] The basic principles of this invention are explained as follows: The composite material provided by this invention uses iron-reducing bacteria, surfactant-producing bacteria, porous carriers, natural gels, iron sources, and nitrogen sources as raw materials, wherein: Porous carriers can provide a huge specific surface area and rich pore structure. These pores provide attachment points and physical protection for exogenously added functional microorganisms (iron-reducing bacteria and surfactant-producing bacteria), preventing the bacteria from being directly washed away or exposed to harsh soil environments, and providing a place for functional microorganisms to colonize and reproduce in the soil.

[0038] Natural gel (sodium alginate solution) has a certain viscosity and adhesiveness. When mixed with porous materials loaded with microorganisms, due to the large specific surface area and rich pore structure of the porous materials, the viscous natural gel will spontaneously wet, penetrate and adhere to the surface and internal pores of the porous materials under the action of capillary action and surface tension, and uniformly coat the outer surface of the porous material particles to form a primary complex. At this time, the natural gel has not yet gelled and is still in a flowable state. The gel network can provide physical protection for functional microorganisms, thereby significantly improving the survival rate of functional bacteria. In addition, the natural gel can also be slowly degraded and utilized by microorganisms, providing initial carbon sources and energy for functional bacteria, creating conditions for functional bacteria to adapt to the soil environment. The primary complex was added dropwise to a Fe-containing solution. 3+ Upon entering the complex ionic solution, a vigorous cross-linking reaction is immediately triggered at the interface between the two phases, Fe 3+ Ionic crosslinking occurs between sodium alginate and the carboxyl groups on the alginate chain, forming a stable "egg-box" structure, transforming the liquid sodium alginate into a solid gel. This step is crucial for forming the composite material structure; furthermore, Fe... 3+As the terminal electron acceptor in the respiration of iron-reducing bacteria, in order to obtain energy, iron-reducing bacteria actively and efficiently reduce insoluble Fe(III) (the main form of iron oxides in soil) to soluble Fe(II). This process dissolves iron oxide minerals, thereby destroying their encapsulation structure of PFASs and releasing the solidified, non-extractable PFASs. Surfactant-producing bacteria co-loaded with porous materials can secrete biosurfactants (such as lipopeptides). These surfactant molecules have hydrophilic heads and hydrophobic tails, which can adsorb onto the surface of hydrophobic long-chain PFASs, significantly reducing the surface tension of water, increasing the solubility of PFASs in water, and making it easier for them to desorb from soil particles and enter water bodies. The NO3 contained in the composite ionic solution... - As an essential nitrogen source for microorganisms to synthesize proteins, nucleic acids and other life substances, it provides good nutritional conditions for the rapid growth and metabolism of surfactant-producing bacteria, enabling them to synthesize and secrete large amounts of biosurfactants. Through the synergistic effect of the two functional bacteria, a "de-fixation-solubilization" synergistic amplification effect is formed, which greatly improves the release efficiency of PFASs.

[0039] Through the synergistic effect of the above components, the problem of survival and functional expression of functional bacteria in soil is solved, and the chain reaction of "mineral decomposition-pollutant desorption-pollutant solubilization" is catalyzed in a targeted manner, ultimately releasing the solidified long-chain PFASs from the soil phase to the aqueous phase.

[0040] Compared with the prior art, the beneficial effects of the present invention are: The composite material provided by this invention, through the combined action of a porous carrier, gel, and nitrogen source, ensures that a sufficient number of functional bacteria can survive in harsh soil environments and efficiently perform their preset functions, overcoming the bottleneck problems faced by engineered bacteria after entering the soil, such as low survival rate, difficulty in colonization, and unstable functional expression. Through the synergistic effect of iron-reducing bacteria and surfactant-producing bacteria, descaling and solubilization are carried out simultaneously, and its release efficiency for long-chain perfluorinated compounds is much higher than that of single bacterial species or chemical surfactant treatment. The use of biodegradable natural gel and natural surfactants produced by microorganisms avoids the secondary pollution problems caused by chemical surfactants or remediation agent residues, and causes minimal damage to the native soil microbial community and structure. The raw materials required for the preparation of the composite material are readily available, low in cost, and the preparation process is simple, requiring no complex and expensive equipment, making it easy to promote and apply on a large scale. Attached Figure Description

[0041] Figure 1 Here is a cryo-electron microscopy image of the composite material prepared in Example 1; Figure 2 This refers to the situation in Experiment Example 1 where the composite material promotes the release of chloropolyfluoroether sulfonic acid solidified in the soil into the water. Figure 3 In Experiment 1, different composite materials were added to the soil. Shewanella The abundance variation of sp.; Figure 4 In Experiment 1, different composite materials were added to the soil. Bacillus The abundance variation of sp.; Figure 5 This refers to the situation in Experiment Example 2 where the composite material facilitates the release of perfluorononanoic acid solidified in the soil into the water. Figure 6 This refers to the situation in Experiment Example 3 where the composite material facilitates the release of hexafluoropropylene oxide tetramer carboxylic acid, which is solidified in the soil, into the water. Figure 7 This is a schematic diagram illustrating the preparation process and mechanism of action of the composite material in Example 1. Detailed Implementation

[0042] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0043] Iron-reducing bacteria used in the examples Shewanella sp. C31 was purchased from the Guangdong Provincial Microbial Culture Collection Center, accession number GDMCC No: 62214; surfactant-producing bacteria. Bacillus subtilis Purchased from China General Microbiological Culture Collection Center, catalog number CGMCC 1.3358.

[0044] Example 1 This embodiment prepares a composite material using the following steps: S11, will Shewanella sp. C31 strain was cultured in LB medium at 28°C and 220 rpm until OD200. 600 The culture was terminated when the concentration of iron-reducing bacteria reached 1.0. The LB medium was centrifuged and the bacterial cells were resuspended in an equal volume of deionized water to obtain the iron-reducing bacterial solution. S12, will Bacillus subtilis Incubate in LB medium at 28°C and 220 rpm until OD reaches 100%. 600 The culture was terminated when the concentration reached 1.0. The LB medium was centrifuged and the bacterial cells were resuspended in an equal volume of deionized water to obtain a surfactant-producing bacterial solution. S13. Take 10 mL of iron-reducing bacteria solution and surfactant-producing bacteria solution respectively and apply them to the surface of 100 g volcanic rock. Mix them evenly to obtain a porous material loaded with microorganisms. S21. Take 5g of porous material loaded with microorganisms, mix it with 10mL of 1wt% sodium alginate solution, stir evenly, and obtain the primary complex. S31. Add the primary composite to a 50 mL syringe syringe and drip it into 50 mL of 0.05 mol / L ferric nitrate solution at a uniform rate to obtain the composite material.

[0045] Figure 1 Here are cryo-electron microscopy images of the composite material prepared in Example 1, wherein, Figure 1 (a) in the figure represents the overall structure of the composite material. Figure 1 In the diagram, (b) and (c) represent the microstructure of the composite material. Figure 1 As shown in (a), the iron alginate gel forms a continuous three-dimensional network structure, with the volcanic rock completely encapsulated within this gel network. The two are tightly bonded, forming a complete whole, rather than a simple mixture, indicating successful composite material preparation. The porous carrier does not detach from the gel, providing a foundation for strain protection, carbon source provision, and structural stability. Figure 1 As shown in (b), surfactant-producing bacteria are located inside the gel network and at the interface between the gel and the porous carrier. They can move, grow, and metabolize within the porous network of the gel. The network pores of the gel ensure the diffusion of nutrients and metabolites while preventing bacterial loss. Figure 1 As shown in (c), iron-reducing bacteria are distributed around the gel and porous carrier and have good activity.

[0046] Example 2 This embodiment prepares a composite material using the following steps: S11, will Shewanella sp. C31 strain was cultured in LB medium at 28°C and 220 rpm until OD200. 600 The culture was terminated when the concentration of iron-reducing bacteria reached 1.0. The LB medium was centrifuged and the bacterial cells were resuspended in an equal volume of deionized water to obtain the iron-reducing bacterial solution. S12, will Bacillus subtilis Incubate in LB medium at 28°C and 220 rpm until OD reaches 100%. 600 The culture was terminated when the concentration reached 1.0. The LB medium was centrifuged and the bacterial cells were resuspended in an equal volume of deionized water to obtain a surfactant-producing bacterial solution. S13. Take 10 mL of iron-reducing bacteria solution and surfactant-producing bacteria solution respectively and apply them to the surface of 100 g vermiculite. Mix them evenly to obtain a porous material loaded with microorganisms. S21. Take 5g of porous material loaded with microorganisms, mix it with 10mL of 1wt% sodium alginate solution, stir evenly, and obtain the primary complex. S31. The primary composite is added to a 50 mL syringe syringe and then dripped at a uniform rate into a 50 mL mixed solution of ferric chloride and potassium nitrate to obtain the composite material, wherein the Fe in the mixed solution is... 3+ The molar ratio of the amount of NO3 to the mass of sodium alginate in the primary complex is 0.025 mol: 1 g. - The ratio of the number of moles of sodium alginate to the mass of sodium alginate contained in the primary complex is 0.075 mol: 1 g.

[0047] Example 3 This embodiment prepares a composite material using the following steps: S11, will Shewanella sp. C31 strain was cultured in LB medium at 28°C and 220 rpm until OD200. 600 The culture was terminated when the concentration of iron-reducing bacteria reached 1.0. The LB medium was centrifuged and the bacterial cells were resuspended in an equal volume of deionized water to obtain the iron-reducing bacterial solution. S12, will Bacillus subtilis Incubate in LB medium at 28°C and 220 rpm until OD reaches 100%. 600 The culture was terminated when the concentration reached 1.0. The LB medium was centrifuged and the bacterial cells were resuspended in an equal volume of deionized water to obtain a surfactant-producing bacterial solution. S13. Take 10 mL of iron-reducing bacteria solution and surfactant-producing bacteria solution respectively and apply them to the surface of 100 g of coal gangue. Mix them evenly to obtain a porous material loaded with microorganisms. S21. Take 5g of porous material loaded with microorganisms, mix it with 10mL of 1wt% sodium alginate solution, stir evenly, and obtain the primary complex. S31. The primary composite was added to a 50 mL syringe syringe and then dripped at a uniform rate into a 50 mL mixed solution of ferric sulfate and sodium nitrate to obtain the composite material, wherein the Fe in the mixed solution... 3+ The molar ratio of the amount of NO3 to the mass of sodium alginate in the primary complex is 0.025 mol: 1 g. - The ratio of the number of moles of sodium alginate to the mass of sodium alginate contained in the primary complex is 0.075 mol: 1 g.

[0048] Comparative Example 1 This comparative example prepares a composite material, and the steps are as follows: Mix 5g of volcanic rock with 10mL of 1wt% sodium alginate solution, stir well, and then add the mixture at a constant rate to 50mL of 0.05mol / L ferric nitrate solution to obtain the composite material.

[0049] Comparative Example 2 This comparative example prepares a composite material, and the steps are as follows: S11, will Shewanella sp. C31 strain was cultured in LB medium at 28°C and 220 rpm until OD200. 600 The culture was terminated when the concentration of iron-reducing bacteria reached 1.0. The LB medium was centrifuged and the bacterial cells were resuspended in an equal volume of deionized water to obtain the iron-reducing bacterial solution. S12, will Bacillus subtilis Incubate in LB medium at 28°C and 220 rpm until OD reaches 100%. 600 The culture was terminated when the concentration reached 1.0. The LB medium was centrifuged and the bacterial cells were resuspended in an equal volume of deionized water to obtain a surfactant-producing bacterial solution. S13. Take 10 mL of iron-reducing bacteria solution and surfactant-producing bacteria solution respectively and apply them to the surface of 100 g volcanic rock. Mix them evenly to obtain the composite material.

[0050] Experimental Example 1 Add 10 mL of 0.05 mg / L chlorinated polyfluoroether sulfonic acid aqueous solution to 10 g of soil, cover with breathable sealing film and let stand, then slowly evaporate in a dry environment at 30℃. After the solution is evaporated to dryness, aged chlorinated polyfluoroether sulfonic acid contaminated soil is obtained. 3g of the composite materials prepared in Examples 1, 1, and 2 were mixed with 10g of chloropolyfluoroether sulfonic acid contaminated soil, and 50mL of deionized water was added to each mixture. These treatment groups were labeled Group A (Example 1), Group B (Comparative Example 1), and Group C (Comparative Example 2), respectively. Group D, without the composite material, served as the control. All groups were incubated on a shaker (28℃, 220rpm). Supernatants were collected on days 3, 9, and 16, and the content of chloropolyfluoroether sulfonic acid in the supernatant and the concentration of chloropolyfluoroether sulfonic acid in the soil were measured. Shewanella sp. and Bacillus Abundance of sp. (expressed as ASV number).

[0051] The content of chloropolyfluoroether sulfonic acid in the supernatant was measured by liquid chromatography-tandem mass spectrometry (LC-MS).

[0052] Table 1 below shows the content of chloropolyfluoroether sulfonic acid in the supernatant at different time points in Experiment Example 1. Figure 2 To illustrate how the composite material in Experiment Example 1 facilitated the release of chloropolyfluoroether sulfonic acid solidified in the soil into the water, see Table 1 and... Figure 2 It can be seen that, at different treatment times, the amount of fixed polyfluoroethylene sulfonic acid released into the water in group A using the composite material prepared in Example 1 was higher than that in the other groups, and continued to increase over time, proving that the composite material prepared in Example 1 can effectively promote the release of polyfluoroethylene sulfonic acid fixed in the soil into the water, with a long-lasting effect.

[0053] Table 1. Content of chloropolyfluoroether sulfonic acid in the supernatant at different time points in Experiment Example 1

[0054] Table 2 below shows the soil concentrations at different time points in Experiment 1. Shewanella sp. abundance, down Figure 3 In Experiment 1, different composite materials were added to the soil. Shewanella The abundance variations of sp. are shown in Table 2 and Figure 3 It can be seen that in group A, where the composite material prepared in Example 1 was added, the soil contained... Shewanella The abundance of sp. increased steadily during flooding, while in group C, where the composite material prepared in Comparative Example 2 was added, the abundance of sp. in the soil was significantly lower. Shewanella The abundance of *Sp.* gradually decreased during flooding. In groups B and D, where no additional microorganisms were introduced, the abundance of *Sp.* in the soil was significantly lower. Shewanella The consistently low abundance of sp. indicates that the composite material and gel network provided by this invention can provide better physical protection for functional microorganisms, thereby significantly improving the survival rate of functional bacteria.

[0055] Table 2 Soil at different time points in Experiment Example 1 Shewanella abundance of sp. (ASV number)

[0056] Table 3 below shows the soil concentrations at different time points in Experiment Example 1. Bacillus sp. abundance, down Figure 4 In Experiment 1, different composite materials were added to the soil. Bacillus The abundance variations of sp. are shown in Table 3 and Figure 4 It can be seen that in group A, where the composite material prepared in Example 1 was added, the soil contained... Bacillus The abundance of sp. decreased slightly during flooding, but remained stable overall. In contrast, in group C, where the composite material prepared in Comparative Example 2 was added, the abundance of sp. in the soil... Bacillus The abundance of *sp.* continued to decrease during flooding, while in groups B and D, the abundance in the soil increased because no additional microorganisms were introduced. Bacillus The abundance of sp. remains low, further demonstrating that the composite material and gel network provided by this invention can provide better physical protection for functional microorganisms, overcoming the bottleneck problems such as low survival rate, difficulty in colonization, and unstable functional expression faced by engineered bacteria after entering the soil.

[0057] Table 3 Soil at different time points in Experiment Example 1 Bacillus abundance of sp. (ASV number)

[0058] Experimental Example 2 Add 10 mL of 0.05 mg / L perfluorononanoic acid aqueous solution to 10 g of soil, cover with breathable sealing film and let stand, then slowly evaporate in a dry environment at 30℃. After the solution evaporates to dryness, aged perfluorononanoic acid contaminated soil is obtained. 3g of the composite materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 were mixed with 10g of perfluorononanoic acid contaminated soil, and 50mL of deionized water was added to each. The above treatment groups were labeled as Group A (Example 1), Group B (Comparative Example 1), and Group C (Comparative Example 2), respectively, with Group D, which did not add composite materials, as the control. All groups were placed in a shaker for incubation (28℃, 220rpm), and the supernatant was collected on the 3rd, 9th, and 16th days, respectively, and the content of perfluorononanoic acid in the supernatant was measured (test method is the same as in Example 1).

[0059] Table 4 below shows the content of perfluorononanoic acid in the supernatant at different time points in Experiment Example 2. Figure 5 To illustrate how the composite material in Experiment Example 2 facilitated the release of perfluorononanoic acid (PFNO) solidified in the soil into the water, see Table 4 and... Figure 5 It can be seen that, at different treatment times, the amount of fixed perfluorononanoic acid released into the water in group A using the composite material prepared in Example 1 was higher than that in the other groups, and continued to increase over time, proving that the composite material prepared in Example 1 can effectively promote the release of perfluorononanoic acid fixed in the soil into the water, with a long-lasting effect.

[0060] Table 4. Content of perfluorononanoic acid in the supernatant at different time points in Experiment Example 2

[0061] Experimental Example 3 Add 10 mL of 0.05 mg / L hexafluoropropylene oxide tetramer carboxylic acid aqueous solution to 10 g of soil, cover with a breathable sealing film and let stand, then slowly evaporate in a dry environment at 30℃. After the solution is evaporated to dryness, aged hexafluoropropylene oxide tetramer carboxylic acid contaminated soil is obtained. 3g of the composite materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 were mixed with 10g of soil contaminated with hexafluoropropylene oxide tetramer carboxylic acid, and 50mL of deionized water was added to each. The above treatment groups were labeled as Group A (Example 1), Group B (Comparative Example 1), and Group C (Comparative Example 2), respectively, with Group D, which did not add composite materials, as the control. All groups were placed in a shaker for incubation (28℃, 220rpm), and the supernatant was collected on the 3rd, 9th, and 16th days, respectively, and the content of hexafluoropropylene oxide tetramer carboxylic acid in the supernatant was measured (test method is the same as in Example 1).

[0062] Table 5 below shows the content of hexafluoropropylene oxide tetramer carboxylic acid in the supernatant at different time points in Experiment Example 3. Figure 6To illustrate how the composite material in Experiment 3 facilitated the release of hexafluoropropylene oxide tetramer carboxylic acid, which was solidified in the soil, into the water, see Table 5 and... Figure 6 It can be seen that, at different treatment times, the amount of hexafluoropropylene oxide tetramer carboxylic acid released into the water in group A of the composite material prepared in Example 1 was higher than that in the other groups, and continued to increase over time. This proves that the composite material prepared in Example 1 can effectively promote the release of perfluorononanoic acid solidified in the soil into the water, and the effect is long-lasting.

[0063] Table 5. Content of hexafluoropropylene oxide tetramer carboxylic acid in the supernatant at different time points in Experiment Example 3

[0064] Based on the above analysis, it can be seen that the composite material provided by this invention has a strong dissolution-promoting effect on long-chain perfluoroalkyl substances such as chloropolyfluoroether sulfonic acid, perfluorononanoic acid, and hexafluoropropylene oxide tetramer carboxylic acid fixed in soil. Figure 7 This is a schematic diagram illustrating the preparation process and mechanism of action of the composite material in Example 1. Figure 7 It is known that this composite material uses volcanic rock as a porous carrier, loads iron-reducing bacteria and surfactant-producing bacteria, utilizes sodium alginate gel to provide carbon source and physical protection, and uses ferric iron and nitrate as electron acceptors and nitrogen source to promote the functional expression of the strain. The iron-reducing bacteria reduce iron minerals and release embedded long-chain perfluoroalkyl substances, while the surfactant-producing bacteria secrete biosurfactants to enhance the water solubility of long-chain perfluoroalkyl substances. Based on the synergistic effect of each component, the efficient and targeted release of long-chain perfluoro compounds fixed in the soil is achieved.

Claims

1. A composite material, characterized in that, The preparation materials include the following: microorganisms, porous carriers, natural gels, iron sources, and nitrogen sources; wherein the microorganisms include iron-reducing bacteria and surfactant-producing bacteria.

2. The composite material according to claim 1, characterized in that, The iron-reducing bacteria include Shewanella sp.、 Acidithiobacillus sp.、 Sulfobacillus sp.、 Acidimicrobium At least one of the sp.

3. The composite material according to claim 1, characterized in that, The surfactant-producing bacteria include Bacillus sp.、 Pseudomonas sp.、 Candida sp.、 Acinetobacter At least one of the sp.

4. The composite material according to claim 1, characterized in that, The porous carrier includes at least one of volcanic rock, fly ash, ceramsite, vermiculite, montmorillonite, and coal gangue. And / or, the natural gel comprises a sodium alginate solution; And / or, the iron source includes at least one of ferric nitrate, ferric sulfate, ferric chloride, and ferric perchlorate; And / or, the nitrogen source includes at least one of ferric nitrate, potassium nitrate, sodium nitrate, and calcium nitrate.

5. The method for preparing the composite material according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Iron-reducing bacteria and surfactant-producing bacteria are cultured separately to form bacterial solutions, which are then applied to the surface of a porous carrier to obtain a porous material loaded with microorganisms. S2. The porous material loaded with microorganisms is mixed with natural gel to obtain a primary complex; S3. Dissolve the iron source and nitrogen source in water to form a composite ionic solution, and add the primary composite material dropwise into the composite ionic solution to obtain the composite material.

6. The preparation method according to claim 5, characterized in that, The iron-reducing bacteria solution and the surfactant produce the OD of the bacterial solution. 600 The liquid-to-solid ratios of the iron-reducing bacteria solution, the surfactant-producing bacteria solution, and the porous carrier are selected from 0.8 to 1.2, respectively.

7. The preparation method according to claim 5, characterized in that, The concentration of the natural gel is 0.8wt%-1.2wt%; the solid-liquid ratio of the porous material loaded with microorganisms to the natural gel is 1g:(1.5-2.5)mL.

8. The preparation method according to claim 5, characterized in that, The Fe contained in the composite ionic solution 3+ The molar ratio of the amount of NO3 to the mass of the natural gel contained in the primary complex is (0.02-0.04) mol: 1 g; the NO3- contained in the composite ionic solution - The ratio of the number of moles of the substance to the mass of the natural gel contained in the primary complex is (0.06-0.09) mol: 1g.

9. The use of the composite material according to any one of claims 1-4 in promoting the release of long-chain perfluorinated compounds solidified in soil into water.

10. The application according to claim 9, characterized in that, The long-chain perfluorinated compound includes at least one of chloropolyfluoroether sulfonic acid, perfluorononanoic acid, and hexafluoropropylene oxide tetramer carboxylic acid. And / or, the content of the long-chain perfluorinated compound in the soil is 30-100 ng / g soil; And / or, the amount of the composite material used is (1-5) g / g soil.

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