Method for degrading organic pollutants by using natural iron-containing minerals and river and lake bottom muds

Abstract

The application discloses a method for degrading organic pollutants by using natural iron-containing minerals and river and lake bottom mud, and the method is to construct a joint repair system of the natural iron-containing minerals and the river and lake bottom mud to degrade the organic pollutants. The method can realize biological-chemical coupling enhanced degradation of the organic pollutants by constructing a joint repair system integrating bioremediation represented by indigenous microorganisms in the river and lake bottom mud and iron-reducing chemical remediation represented by the iron-containing minerals, and has the advantages of simple process, convenient operation, low cost, good treatment effect, good degradation effect, environmental friendliness and the like, and is a novel microbial remediation method which can be widely used for removing the organic pollutants, has a wide application prospect in the field of environmental remediation, and has high use value and good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of organic pollution bioremediation technology, and relates to a method for degrading organic pollutants, specifically a method for synergistically degrading organic pollutants using natural iron-containing minerals and river and lake sediments. Background Technology

[0002] Microbial remediation technology has attracted significant attention for its environmental friendliness, low risk of secondary pollution, and high safety, making it a promising approach to degrading organic pollutants. However, microorganisms are susceptible to various environmental factors such as temperature, pH, and dissolved oxygen, resulting in a slow degradation process, long biological treatment cycles, and low degradation efficiency. This hinders the practical application of microbial remediation technology. Therefore, enhancing the level of microbial remediation and regulating its efficacy are crucial issues that must be addressed to promote its widespread application in degrading organic pollutants.

[0003] Methods to enhance microbial remediation levels and regulate bioremediation efficiency mainly include the addition of surfactants, the addition of nutrients, chemical oxidation techniques, and the application of organic waste and compost. However, the addition of surfactants can easily cause secondary pollution, and there are relatively few green and biodegradable biosurfactants available, whose safety needs to be assessed. The addition of nutrients can maintain optimal conditions for microbial growth, but it requires continuous addition, which is costly and is mainly used for the bioremediation of environments contaminated by petroleum hydrocarbons. Chemical oxidation techniques have problems such as incomplete remediation, easy generation of secondary pollution, high reagent costs, easy damage to soil physicochemical properties, and impact on soil microbial communities. The application of organic waste and compost requires high time and mechanical costs.

[0004] To address the aforementioned issues, existing technologies primarily employ microbial domestication treatment to enhance microbial activity and tolerance, thereby improving their degradation efficiency for organic pollutants. However, this domestication process requires the addition of large amounts of nutrients, increasing treatment costs. More importantly, the long domestication period hinders the rapid degradation of organic pollutants by current microbial remediation technologies. Therefore, developing a simple, convenient, low-cost, effective, and environmentally friendly method for utilizing microorganisms to degrade organic pollutants is crucial for the effective removal of such pollutants. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for the synergistic degradation of organic pollutants by utilizing natural iron-containing minerals and river and lake sediments. This method is simple, easy to operate, low in cost, has good treatment and degradation effects, and is environmentally friendly.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for synergistically degrading organic pollutants using natural iron-containing minerals and river and lake sediments, wherein the method constructs a joint remediation system using natural iron-containing minerals and river and lake sediments to synergistically degrade organic pollutants.

[0008] In a further improvement to the above method, the concentration of Fe(II) available to microorganisms in the combined remediation system, calculated by wet weight of river and lake sediment, is 40 mg / kg to 360 mg / kg.

[0009] A further improvement to the above method is that the microbial urease activity in the combined remediation system is 1.5 μg NH4. + / g / h~9ug NH4 + / g / h, the dehydrogenase activity is 0.5μg TF / g / h~12.5μg TF / g / h.

[0010] A further improvement to the above method, which uses a combined remediation system constructed from natural iron-containing minerals and river / lake sediments to synergistically degrade organic pollutants, includes the following steps:

[0011] S1. Mix natural iron-containing minerals, river and lake sediments, and organic pollutants to obtain a sediment mixture;

[0012] S2. Cultivate the sediment mixture obtained in step S1 to complete the synergistic degradation of organic pollutants.

[0013] The above method is further improved by adding the following treatment to step S1: adjusting the soil-to-water ratio of the bottom mud mixture to 1:2 to 6.

[0014] In a further improvement to the above method, in step S1, the content of natural iron-containing minerals in the sediment mixture is 0.5% to 2% of the dry weight of the river and lake sediment.

[0015] In a further improvement to the above method, in step S1, the particle size of the natural iron-bearing mineral is 120 mesh to 200 mesh; the natural iron-bearing mineral is the iron-poor mineral Swy-3 and / or the iron-rich mineral NAu-2.

[0016] In a further improvement to the above method, in step S1, the initial concentration of organic pollutants in the sediment mixture is 5 mg / kg to 20 mg / kg based on the dry weight of the river and lake sediment.

[0017] In a further improvement to the above method, in step S1, the organic pollutant is a chlorophenolic organic pollutant; the chlorophenolic organic pollutant is 2,4-dichlorophenol.

[0018] In a further improvement to the above method, in step S2, the culture is carried out at a temperature of 25℃ to 37℃; and the culture time is 60 days to 90 days.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] (1) This invention provides a method for the synergistic degradation of organic pollutants using natural iron-bearing minerals and river / lake sediments. Specifically, the natural iron-bearing minerals act as electron shuttles, mediating interspecific electron transfer among microorganisms to regulate the growth and metabolism of the microbial community. Simultaneously, the iron minerals continuously dissolve in the anoxic environment of shallow sediments, undergoing valence state changes to generate active Fe(II) species, which synergistically reduce organic pollutants. This effectively enhances the reduction and transformation capacity of indigenous microorganisms in the sediment for organic pollutants, significantly reducing their toxicity. Therefore, this invention utilizes natural iron-bearing minerals and river / lake sediments to construct a synergistic remediation system, eliminating the need for microbial domestication. Furthermore, the natural iron-bearing minerals and river / lake sediments used are widely distributed in nature, providing abundant and readily available raw materials, which helps reduce treatment costs. Furthermore, this invention utilizes a co-remediation system constructed from natural iron-containing minerals and river / lake sediments to synergistically degrade organic pollutants. The raw materials involved are solely natural iron-containing minerals, sediments, and deionized water. It eliminates the need for an anaerobic environment or additional nutrients. The overlying aquatic environment in the cultivation system isolates the system from atmospheric oxygen, effectively simulating the anoxic environment of shallow river / lake wetland sediments. This simulated environment more closely resembles the actual conditions of river / lake wetlands, achieving effective reduction of organic pollutants by natural iron-containing minerals coupled with river / lake sediment microorganisms under anoxic conditions. Therefore, this invention, employing a method for the synergistic degradation of organic pollutants using natural iron-containing minerals and river / lake sediments, integrates bioremediation (represented by indigenous microorganisms from river / lake sediments) and iron-reduction chemical remediation (represented by iron-containing minerals). This co-remediation system achieves enhanced bio-chemical coupling degradation of organic pollutants, offering advantages such as simple process, convenient operation, low cost, high treatment and degradation effects, and environmental friendliness. It is a novel microbial remediation method widely applicable to the removal of organic pollutants, with broad application prospects in environmental remediation and high practical value.

[0021] (2) In the method of this invention, by optimizing the concentration of microbial available Fe(II) in the co-remediation system, specifically by setting the concentration of microbial available Fe(II) in the river and lake sediment wet weight to 40 mg / kg to 360 mg / kg, the electron transfer of the system is further enhanced, promoting the effective degradation of organic pollutants. This is because if the concentration of microbial available Fe(II) is too low, it will be detrimental to electron transfer in the co-remediation system, and the degradation process of organic pollutants will be slow. However, due to the limitations of the system's redox conditions and the limited content of added iron minerals, the concentration of microbial available Fe(II) basically increases with the extension of the cultivation time and will accumulate to a certain limit, continuously participating in the redox of organic pollutants. In addition, the interaction between microorganisms and iron-containing minerals in the method of this invention has obvious advantages. This is because some autotrophic chemoenergetic microorganisms in the sediment environment can utilize the iron on the surface of minerals to accelerate the oxidation and dissolution of minerals, and can also reduce passivation by dissolving some precipitates, accelerate electron transfer, and further reduce organic pollutants. Furthermore, in environments without microbial participation, Fe(II) in iron-containing minerals is highly susceptible to oxidative passivation. The resulting Fe(III) iron oxides cover the mineral surface, hindering electron transfer and causing the reaction to cease, which is detrimental to the reduction of organic pollutants. Therefore, adding iron-containing minerals to this combined system can optimize the concentration of Fe(II) available to microorganisms, thereby further enhancing electron transfer and promoting the degradation of organic pollutants. This method is simple to operate, convenient to treat, and truly effective.

[0022] (3) In the method of the present invention, by adjusting the soil-water ratio of the bottom sediment mixture to 1:2 to 6, the water covering the bottom sediment can be kept in a stable state and less affected by the outside world. This creates a stable environment for the growth and reproduction of bottom sediment microorganisms and the reduction of iron minerals, which is conducive to the rapid enrichment and proliferation of microorganisms on the bottom sediment surface. This further couples the action of iron minerals on the reduction and degradation of organic pollutants. This is because if the soil-water ratio is set too low in the joint remediation system, it means that the water covering the bottom sediment is very shallow. When the external environmental conditions change, such as wind and waves, dissolved oxygen fluctuations, etc., the shallow environment where the bottom sediment is located is easily affected. If the soil-water ratio is set too high, it means that the water covering the bottom sediment is very deep, which does not conform to the actual environment of the shallow bottom sediment in rivers, lakes and wetlands.

[0023] (4) In the method of this invention, by optimizing the content of natural iron-containing minerals in the sediment mixture to 0.5% to 2% of the dry weight of the river and lake sediment, the interaction between natural iron-containing minerals and microorganisms in the river and lake sediment can be enhanced, thereby significantly promoting the degradation of organic pollutants. The group with added iron-rich mineral NAu-2 showed the most significant effect, with a degradation rate of 90% on day 60 and virtually no 2,4-DCP residues on day 90, while the group without added natural minerals had approximately 20% 2,4-DCP residues. This is because natural iron-containing minerals can interact with microorganisms in the river and lake sediment on both temporal and spatial scales, forming a mutually beneficial relationship. On the one hand, iron-containing minerals provide energy, nutrients, and electron acceptors required for the growth and metabolism of microorganisms, thereby regulating the growth and metabolism of the microbial community and affecting the morphological distribution and bioavailability of pollutants in the river and lake sediment, thus synergistically degrading organic pollutants. On the other hand, the growth and metabolism of microorganisms also affect the dissolution and precipitation of iron-containing minerals, thereby changing the surface properties of the minerals and the activity of microorganisms, significantly affecting the environmental degradation behavior of organic pollutants in the river and lake sediment.

[0024] (5) In the method of the present invention, the microbial urease activity in the co-remediation system was optimized to 1.5 μg NH4. + / g / h~9ug NH4 + The dehydrogenase activity ranges from 0.5 μg TF / g / h to 12.5 μg TF / g / h. Optimizing microbial urease activity can alleviate the toxic effects of 2,4-DCP pollution on microorganisms, promote organic nitrogen mineralization in the sediment environment, and facilitate nutrient cycling in the sediment. In this invention, the synergistic effect of natural iron-containing minerals and river / lake sediment stabilizes free urease in the co-remediation system, enhances the self-purification capacity of river / lake sediment, and prevents the sediment from turning black and smelly. Optimized microbial dehydrogenase activity promotes microbial activity and organic matter accumulation, which is beneficial for the degradation, transformation, and microbial metabolism of organic pollutants in the sediment. In this invention, the synergistic effect of natural iron-containing minerals and river / lake sediment stimulates energy consumption, leading to higher dehydrogenase activity to counteract the adverse effects of organic pollutants and promote their migration and transformation.

[0025] (6) In the method of the present invention, when a joint remediation system is constructed using natural iron-containing minerals and river and lake sediments to synergistically degrade 2,4-dichlorophenol, the input of 2,4-dichlorophenol pollution stimulates the bacterial community response in the river and lake sediments. By stimulating the river and lake sediments to produce dechlorinating bacteria to cope with the environmental toxicity of 2,4-dichlorophenol stress, at the same time, the addition of iron-containing minerals can effectively stimulate the growth and reproduction of Firmicutes. Firmicutes can participate in the anaerobic dechlorination process of organochlorides and use them for proliferation. Firmicutes can also form endospores that resist various environmental stresses (such as nutrient deficiency and pollutant toxicity). Therefore, the method of synergistic degradation of organic pollutants using natural iron-containing minerals and river and lake sediments in the present invention has a better degradation effect on chlorophenol organic pollutants. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0027] Figure 1 This is a graph showing the detection results of dissolved oxygen content in the water covering the river and lake bottom sediment in Example 1 of the present invention.

[0028] Figure 2 This is a graph showing the trend of pH value changes in river and lake sediments in Example 1 of the present invention.

[0029] Figure 3 This is a comparison chart showing the degradation effects of different remediation systems on 2,4-dichlorophenol in Example 1 of the present invention.

[0030] Figure 4 This is a comparison chart showing the changes in urease (UA) activity in different repair systems in Example 1 of the present invention.

[0031] Figure 5 This is a comparison chart showing the changes in dehydrogenase (DHA) activity in different repair systems in Example 1 of the present invention.

[0032] Figure 6 This is a comparison chart showing the changes in the concentration of microbial available Fe(II) in different remediation systems in Example 1 of the present invention.

[0033] Figure 7 This is a comparison diagram of the microbial colony composition in different repair systems in Example 1 of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0035] In the following examples, unless otherwise specified, the raw materials and instruments used are commercially available, the processes used are conventional processes, the equipment used is conventional equipment, and the data obtained are the average values ​​of more than three repeated experiments.

[0036] Example 1:

[0037] A method for synergistically degrading organic pollutants using natural iron-containing minerals and river / lake sediments, specifically employing a co-remediation system constructed from natural iron-containing minerals and river / lake sediments to synergistically degrade 2,4-dichlorophenol (2,4-DCP), includes the following steps:

[0038] (1) Preparation of natural iron-bearing minerals: The natural iron-bearing minerals used in the experimental system include the iron-poor mineral Swy-3 and the iron-rich mineral NAu-2, both of which were purchased from the American Clay Mineral Association. The natural iron-bearing minerals need to be crushed, ground and sieved. Fine mineral particles that pass through a 200-mesh sieve are selected to obtain natural iron-bearing mineral nanoparticles.

[0039] (2) Establishment of the joint remediation system: Weigh 1g of natural iron-containing mineral nanoparticles, 100g of river and lake sediment, and 2,4-dichlorophenol (2,4-DCP) and mix them evenly. The content of 2,4-DCP in the river and lake sediment is 20mg / kg by dry weight, and the mass percentage of natural iron-containing minerals is 1%. A sediment sample containing natural iron-containing minerals is obtained. 500mL of deionized water is slowly added to the above sediment sample containing natural iron-containing minerals. The sediment is gently and slowly stirred. After the air bubbles in the sediment are expelled, a sediment mixture is obtained.

[0040] (3) The sediment mixture was placed in a 25°C incubator for 90 days to complete the synergistic degradation of 2,4-dichlorophenol.

[0041] In this embodiment, four groups of samples were set up: A, B, C, and D. Each group of samples had three parallel samples. A was natural river sediment without any treatment, which was the blank group and was numbered Blank. B was river sediment with only 2,4-DCP added, which was the control group and was numbered Polluted. C was river sediment with 2,4-DCP and the iron-poor mineral Swy-3 added and was numbered Swy-3addition. D was river sediment with 2,4-DCP and the iron-rich mineral NAu-2 added and was numbered NAu-2addition.

[0042] In this embodiment, during the cultivation process, samples were taken on days 0, 5, 15, 30, 45, and 90 to measure the dissolved oxygen concentration in the supernatant and the pH of the sediment.

[0043] Figure 1 This is a graph showing the detection results of dissolved oxygen content in the overlying water of river and lake sediments in Example 1 of the present invention. Figure 1It can be seen that the dissolved oxygen content in the system was low and showed a downward trend throughout the entire culture period, indicating that the system was basically in a hypoxic state. In particular, the downward trend was very obvious in the group with added iron-rich clay mineral NAu-2, which shows that the addition of iron-containing minerals can stimulate microbial respiration and consume oxygen.

[0044] The pH changes in the sediment of the combined remediation system in Example 1, such as Figure 2 As shown. Figure 2 This is a graph showing the trend of pH value changes in river and lake sediments in Embodiment 1 of the present invention. Figure 2 It is evident that the pH of each sample system remained stable between 7 and 8 throughout the entire degradation cycle, ensuring the normal growth, reproduction, and metabolism of microorganisms.

[0045] In this embodiment, during the culture process, samples were taken on days 0, 5, 15, 30, 45, and 90 to determine the concentration of residual 2,4-DCP.

[0046] The determination method for 2,4-DCP is as follows: Weigh an appropriate amount of sample, add a certain amount of methanol, place in a constant temperature shaking incubator, mix slowly at 150 rpm for 20 min, sonicate, then add methanol for extraction, repeat the sonic extraction process 3 times, centrifuge, and pour off the supernatant. Concentrate all the extracted solution by nitrogen blowing in a water bath at 45℃ and a nitrogen blowing rate of 6 mL / min. After the sample is nearly dry, make up to volume with methanol. After complete dissolution, filter through a 0.22 μm filter membrane, and take 1 mL of the solution to be filtered into a brown liquid chromatography bottle for analysis.

[0047] Figure 3 This is a comparison chart showing the degradation effects of different remediation systems on 2,4-dichlorophenol in Example 1 of the present invention. Figure 3 It was found that 2,4-DCP exhibited the fastest reduction rate in the NAu-2 iron-rich mineral addition group, reaching a reduction rate of 90% by day 60 and being virtually undetectable by day 90. After 90 days of natural incubation (without mineral addition), the residual amount of 2,4-DCP in the sediment was approximately 20%, indicating that the microbial pathway played a dominant role in the reduction of 2,4-DCP in the sediment. The addition of both Swy-3 iron-poor and NAu-2 iron-rich clay minerals promoted reduction, with NAu-2 iron-rich minerals promoting the greatest reduction. This is because the structural iron in NAu-2 undergoes reduction transformation under anaerobic conditions, and iron-reducing bacteria and methanogens in the sediment drive iron reduction, exhibiting active redox properties that mediate the attenuation of 2,4-DCP. This demonstrates that the addition of natural iron-containing mineral nanoparticles can promote the degradation efficiency of 2,4-DCP, thus applying natural iron-containing mineral nanoparticles to the remediation of 2,4-DCP-contaminated sediment is feasible.

[0048] In this embodiment, samples were taken on days 5, 15, 30, 60, and 90 of culture to determine the concentrations of urease, dehydrogenase, and microbial available Fe(II).

[0049] (1) Extraction and detection of urease: Urease activity is detected by the production of NH4 through the urease-mediated hydrolysis of urea within a certain reaction time. + The amount of NH4 was measured. + The concentration was quantified using the indophenol blue colorimetric method. 1 g of sediment was weighed, 0.5 mL of toluene was added, followed by 2.5 mL of 10% urea solution and 5 mL of citrate buffer (pH 6.7). The mixture was thoroughly mixed and incubated at 37°C for 24 h. After centrifugation at 500 rpm for 5 min, the mixture was filtered. 1 mL of the supernatant was collected, and 1 mL of deionized water was added. Then, 0.4 mL of 1.35 M sodium phenolate solution and 0.3 mL of sodium hypochlorite solution (active chlorine content 0.9%) were added. After standing for 20 min, 2.3 mL of deionized water was added to bring the volume to 5 mL, and the absorbance at approximately 630 nm was measured. Another 1 g of sediment was used as a control, with ultrapure water instead of urea solution, and the same procedure was performed.

[0050] Urease is an important extracellular enzyme that promotes the mineralization of organic nitrogen in the environment and is widely used to analyze nutrient cycling and microbial nutrient requirements in sediment. Urease assay results are as follows: Figure 4 As shown. Figure 4 This is a comparison chart showing the changes in urease (UA) activity in different repair systems in Example 1 of the present invention. Figure 4 It was found that the sediment uncontaminated with 2,4-DCP had higher urease activity than the contaminated sediment, indicating that 2,4-DCP inhibited urease activity in the sediment. This is because the toxic effect of 2,4-DCP on microorganisms inhibited the production of urease by active microorganisms. There was no significant difference in urease activity between the 2,4-DCP contaminated sediment and the 2,4-DCP contaminated sediment. Comparing the groups with added Swy-3 iron-poor / NAu-2 iron-rich clay minerals, it was found that the urease activity of the group with added NAu-2 iron-rich clay minerals was generally higher than that of the Swy-3 iron-poor mineral group, indicating that the addition of NAu-2 iron-rich clay minerals had a good stabilizing effect on the free urease released by active microorganisms.

[0051] (2) Dehydrogenase detection: The reduction reaction was performed using 2,3,5-triphenyltetrazolium chloride (TTC) as the hydrogen acceptor, and the concentration of the generated red 2,3,5-triphenylformazan (TF) was quantified by colorimetry. 2g of sediment was weighed, 2mL of 1% TTC solution was added, followed by 2mL of Tris-HCl. The mixture was incubated in a dark room at 37℃ for 15 hours. The reaction was terminated by adding 1mL of formaldehyde, followed by extraction with 4mL of acetone. After balancing and centrifugation, the DHA activity was measured within 30 minutes using a UV spectrophotometer at 485nm. Another 1.5g of sediment was used as a control, but without the addition of TTC (using ultrapure water instead of TTC solution).

[0052] Dehydrogenases play a crucial role in the degradation, transformation, and microbial metabolism of organic pollutants in the environment and are widely used to study changes in microbial oxidative activity in contaminated sites. Dehydrogenase assay results are as follows: Figure 5 As shown. Figure 5 This is a comparison chart showing the changes in dehydrogenase (DHA) activity in different repair systems in Example 1 of the present invention. Figure 5 It was found that in the early stage of cultivation (0–45 days), the activity of dehydrogenases in 2,4-DCP contaminated sediment was significantly higher than that in uncontaminated sediment, with the most significant increase on day 30. This is because the microorganisms stimulated energy consumption in response to the adverse effects of organic pollutants, leading to higher dehydrogenase activity. In the later stage of cultivation (60–90 days), the activity of dehydrogenases in uncontaminated sediment was significantly higher than that in contaminated sediment, with the most significant increase on day 90. This indicates both microbial activity and the abundance of organic matter, and the addition of NAu-2 iron-rich clay minerals can promote both microbial activity and organic matter accumulation.

[0053] (3) Extraction and detection of microbial available iron: 0.5M HCl was used as the extraction solvent, and the iron concentration after shaking extraction was used as the parameters for extractable iron and microbial available iron. The specific operation steps were as follows: 2g of sample was placed in a 25ml centrifuge tube, 20ml of 0.5mol / L HCl was added, the sediment was shaken well, and the sample was extracted at 30℃ in the dark for 24h. Subsequently, the sample was centrifuged at 4000rpm for 10min, and the Fe(II) content was determined after filtration of the supernatant.

[0054] The iron concentration extracted with 0.5M HCl was used to characterize the changes in the amount of iron available to microorganisms in the remediation system. The results are as follows: Figure 6 As shown. Figure 6 This is a comparison chart showing the changes in the concentration of microbially available Fe(II) in different remediation systems in Example 1 of the present invention. Figure 6It can be seen that comparing the Fe(II) content of uncontaminated and contaminated sediments reveals that the Fe(II) content in the contaminated sediment is significantly higher than that in the uncontaminated group. This indicates that the introduced chlorophenol can stimulate microorganisms in the sediment to drive iron reduction. The Fe(II) content in different settings showed a trend of first increasing and then decreasing with the cultivation time. In the early stage of cultivation, Fe(II) produced by microbial reduction rapidly accumulated and participated in the reduction and conversion of chlorophenol. In the later stage of cultivation, the Fe(II) produced by the system was continuously consumed, showing a decreasing trend. For the group with added Nau-2 iron-rich minerals, its Fe(II) content first increased and then decreased, but reached a peak on day 90. This is because by day 60, the chlorophenol in the cultivation system was basically converted, and the generated Fe(II) was no longer used for reduction and conversion, thus accumulating. Compared with other settings, due to the addition of iron-rich minerals, the Fe(II) redox activity was more active, and the structural Fe(II) in Nau-2 could participate in the reduction and conversion of organic pollutants. Meanwhile, from Figure 6 The results show that, in the joint remediation system constructed by natural iron-containing minerals and river and lake sediments in this invention, the concentration of microbial available Fe(II) in the river and lake sediments, based on the wet weight, is 40 mg / kg to 360 mg / kg.

[0055] Depend on Figure 4-6 The results show that the combined remediation system constructed by the present invention using natural iron-containing minerals and river and lake sediments includes a microbial remediation process represented by urease (UA) and dehydrogenase (DHA) and a chemical remediation process represented by microbial available Fe(II). The synergistic effect of the two processes constitutes a bio-chemical combined remediation, which can achieve efficient degradation of organic pollutants.

[0056] In this embodiment, sediment samples were collected on days 5, 15, 30, 45, 60, and 90, respectively. DNA was extracted and PCR amplified, the products were further purified, libraries were constructed, and sequencing was performed to obtain information on the composition of the microbial community in the system.

[0057] Figure 7 This is a comparison diagram of the microbial colony composition in different remediation systems in Example 1 of the present invention. For example... Figure 7As shown, the bacterial abundance at the phylum level changes with culture time in different groups of samples. Group A represents uncontaminated sediment, Group B represents 2,4-DCP contaminated sediment, Group C represents contaminated sediment with added iron-poor clay mineral Swy-3, and Group D represents contaminated sediment with added iron-rich clay mineral NAu-2. Firmicutes, Proteobacteria, Bacteroidetes, and Acidobacteria are the dominant bacterial species in the sediment, accounting for 55%–98% of the total bacteria. High levels of Firmicutes and Proteobacteria (>50%) were observed in most groups. Comparing groups A and B, C, and D, it was found that the abundance of Firmicutes in the sediment samples with added 2,4-DCP was significantly higher than that in the sediment samples without added 2,4-DCP, which was most significant in the early stage of contamination (day 5). Under the action of microorganisms, the abundance of 2,4-DCP in the sediment decreased continuously with the extension of the culture time, and the difference in the abundance of Firmicutes among the groups gradually narrowed. It can be seen that Firmicutes can participate in the anaerobic dechlorination process of organochlorides and use them for proliferation. Furthermore, Firmicutes can form endospores that resist various environmental stresses (such as nutrient deficiency and pollutant toxicity). This indicates that the input of 2,4-DCP stimulated the bacterial community response in the sediment, stimulating the sediment to produce dechlorination bacteria to cope with the environmental toxicity of 2,4-DCP stress. Comparing the abundance of Firmicutes in groups B and C, it was found that only on day 5 of cultivation was the abundance of Firmicutes in group C higher than in group B. Subsequently, the abundance of Firmicutes in group C gradually decreased compared to group B, and the difference became increasingly significant. This is because iron-poor minerals in the sediment can promote the reduction of 2,4-DCP in the initial stage of addition. The concentration of 2,4-DCP in group B was consistently slightly higher than that in group C. Therefore, the Firmicutes produced by group B were consistently higher than those in group C to counteract the toxic effects of 2,4-DCP. In addition, comparing groups C and D, it was found that the addition of iron-containing minerals can effectively stimulate the growth and reproduction of Firmicutes, with the largest abundance difference observed on day 90. As for Proteobacteria, their abundance increased with the extension of cultivation time. In the later stages, the reduction rate of 2,4-DCP in all groups reached approximately 90%, with less residual 2,4-DCP. Therefore, the bacterial community structure and abundance in sediment samples with and without added 2,4-DCP tended to be similar, and the differences gradually decreased.

[0058] In summary, the above results indicate that this invention utilizes natural iron-containing minerals and river / lake sediments to synergistically degrade organic pollutants. By constructing a combined remediation system integrating bioremediation represented by indigenous microorganisms from river / lake sediments and iron-reducing chemical remediation represented by iron-containing minerals, it can achieve enhanced bio-chemical coupling degradation of organic pollutants. This method has advantages such as simple process, convenient operation, low cost, good treatment effect, good degradation effect, and environmental friendliness. It is a novel microbial remediation method that can be widely used to remove organic pollutants, and has broad application prospects in the field of environmental remediation. It also has high application value and promising application prospects.

[0059] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for the synergistic degradation of organic pollutants using natural iron-containing minerals and river / lake sediment, characterized in that, The method involves constructing a combined remediation system using natural iron-containing minerals and river / lake sediments to synergistically degrade organic pollutants, including the following steps: S1. Mix natural iron-bearing minerals, river and lake sediments, and organic pollutants, and adjust the soil-to-water ratio of the sediment mixture to 1:2-6 to obtain a sediment mixture; the content of natural iron-bearing minerals in the sediment mixture is 0.5%-2% of the dry weight of the river and lake sediments; the natural iron-bearing minerals are the iron-poor mineral Swy-3 and / or the iron-rich mineral NAu-2. S2. Cultivate the sediment mixture obtained in step S1 to complete the synergistic degradation of organic pollutants; The concentration of microbial available Fe(II) in the combined remediation system, based on the wet weight of river and lake sediment, ranges from 40 mg / kg to 360 mg / kg; the microbial urease activity in the combined remediation system is 1.5 ug NH4. + / g / h~9 ug NH4 + / g / h, the dehydrogenase activity is 0.5μg TF / g / h~12.5 μg TF / g / h.

2. The method according to claim 1, characterized in that, In step S1, the particle size of the natural iron-bearing mineral is 120 mesh to 200 mesh.

3. The method according to claim 2, characterized in that, In step S1, the initial concentration of organic pollutants in the sediment mixture is 5 mg / kg to 20 mg / kg based on the dry weight of the river and lake sediment.

4. The method according to claim 3, characterized in that, In step S1, the organic pollutant is a chlorophenolic organic pollutant; the chlorophenolic organic pollutant is 2,4-dichlorophenol.

5. The method according to claim 1, characterized in that, In step S2, the culture is carried out at a temperature of 25℃ to 37℃; the culture time is 60 days to 90 days.

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