Composite pollutant degradation method based on synergistic effect of microorganisms and functional materials

Abstract

A composite pollutant degradation method based on a synergistic effect of microorganisms and a functional material belongs to the technical field of environmental pollution control and ecological remediation, and comprises the following steps: introducing zero-valent iron, sodium percarbonate and biochar into a domesticated microbial flora to construct a microorganism and functional material composite treatment system; the synergistic degradation treatment on the OTC and Cr (VI) composite pollutants is realized. Compared with a single microbial system, the composite system has the advantages that the degradation rates of OTC and Cr (VI) are respectively improved by about 10% and 20% when the initial concentration of pollutants is 3 mg / L; and when the pollutant concentration is 6 mg / L, the degradation efficiencies on OTC and Cr (VI) are respectively improved by about 5% and 10%. The system has the advantages of high degradation efficiency, high reaction rate, good system stability and the like. The used materials are wide in source and low in cost, and the in-situ remediation method has good environmental friendliness and engineering popularization prospects and is suitable for in-situ remediation of large-scale combined pollution sites.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental pollution control and ecological restoration, and relates to a method for degrading complex pollutants based on the synergistic effect of microorganisms and functional materials. Specifically, the present invention utilizes the synergistic effect of soil microbial flora and functional materials to achieve the efficient degradation of typical complex pollutants such as oxytetracycline (OTC) and hexavalent chromium (Cr(VI)), and its application in the remediation of contaminated sites. Background Art

[0002] Complex pollution refers to the simultaneous presence of multiple pollutants in the same environmental medium, which interact with each other to affect the atmosphere, water, soil, organisms, and human health, resulting in complex cumulative, synergistic, and even antagonistic impacts. Antibiotic and heavy metal pollution is one of the most prominent and difficult types of complex pollution to control in the current environmental field, and its synergistic toxic effects significantly increase the difficulty of treatment.

[0003] Oxytetracycline (OTC), a tetracycline antibiotic widely used in livestock and poultry farming and medical treatment, often enters farmland environments through animal feces. Soil surrounding farms is found to contain significantly elevated levels of OTC. Its presence in water bodies not only inhibits the growth of beneficial microorganisms and disrupts ecological balance, but can also spread resistance genes, impacting biosafety. More seriously, OTC can accumulate in the human body through the food chain, posing a potential threat to public health. Existing antibiotic removal processes are plagued by complex processes, unstable operations, and high costs, limiting their widespread practical application. Meanwhile, hexavalent chromium (Cr(VI)), a typical heavy metal pollutant primarily derived from industrial emissions such as metallurgy, electroplating, and leather production, is highly toxic, non-biodegradable, and carcinogenic. It can penetrate cell membranes, causing DNA damage and potentially inducing cancer. Chromium residues in water bodies are highly mobile and have a long self-purification cycle, posing a long-term cumulative risk in the environment and the human body.

[0004] Studies have shown that the coexistence of OTC and Cr(VI) produces a combined inhibitory effect on microbial metabolism, making conventional bioremediation ineffective. Traditional physical methods are prone to saturation and have poor selectivity. Chemical oxidation, while highly efficient, produces numerous byproducts, is costly, and carries the risk of secondary contamination. Single microbial remediation technologies have poor tolerance to pollutant toxicity and lack degradation stability. Therefore, there is an urgent need to develop a novel, integrated, high-efficiency, stable, and environmentally friendly composite pollution remediation system.

[0005] Zero-valent iron (ZVI) has been widely used in the field of heavy metal remediation due to its excellent reducing properties and high specific surface area. Sodium percarbonate (SPC), as an environmentally friendly oxidant, can slowly release H2O2 in water, inducing a Fenton-like reaction, thereby efficiently degrading organic pollutants. If used in conjunction with a microbial system, it can significantly improve the pollutant removal rate and shorten the remediation cycle. In addition, in order to improve the activity and stability of microorganisms in the polluted system, introducing biochar as an electron buffer medium and microbial carrier is an effective strategy. Biochar has a porous structure, a high specific surface area and good biocompatibility. It can not only adsorb pollutants and enhance their contact probability with microorganisms, but also provide a stable attachment and growth environment for the bacterial community, significantly improving the degradation efficiency.

[0006] In summary, constructing a multi-component synergistic system of "microorganisms-redox agents-carriers" has become an important development direction in current research on complex pollution control. Summary of the Invention

[0007] The present invention aims to develop a method for degrading complex pollutants based on the synergistic effects of microorganisms and functional materials. This method first constructs a multi-component synergistic degradation system consisting of microorganisms, zero-valent iron (ZVI), sodium percarbonate (SPC), and biochar (BC). This system is then applied to effectively remove typical complex pollutants in the environment—antibiotics (such as oxytetracycline, OTC) and heavy metals (such as hexavalent chromium, Cr(VI)). This system overcomes the low efficiency and system instability of existing single remediation technologies, offering the combined advantages of high efficiency, low energy consumption, environmental friendliness, and safety.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for degrading complex pollutants based on the synergistic effect of microorganisms and functional materials. Specifically, zero-valent iron (ZVI), sodium percarbonate (SPC) and biochar (BC) are introduced into a domesticated microbial flora to construct a composite treatment system of microorganisms and functional materials to achieve synergistic degradation of complex pollutants such as oxytetracycline (OTC) and hexavalent chromium (Cr(VI)).

[0010] As a preferred technical solution of the present invention, the zero-valent iron (ZVI) has a concentration of 0.1 g / L in the composite treatment system, is spherical or granular, and has a particle size of less than 100 μm. It is used to provide electrons to reduce hexavalent chromium (Cr(VI)) and serves as an attachment and transfer carrier for microorganisms.

[0011] As a preferred technical solution of the present invention, the concentration of sodium percarbonate (SPC) in the composite treatment system is 2.5 mM, which can slowly release H2O2 in water, induce a Fenton-like reaction to produce hydroxyl radicals, and accelerate the decomposition of oxytetracycline (OTC).

[0012] As a preferred technical solution of the present invention, the biochar (BC) has a concentration of 0.1 g / L in the composite treatment system. It is produced by pyrolysis of agricultural waste (such as rice husks and corn cobs) at 500-700°C and has a particle size of 100-200 μm. It is used to adsorb pollutants, stabilize microbial structure and enhance electron transfer.

[0013] As a preferred technical solution of the present invention, the method for obtaining and acclimating the microbial flora is:

[0014] (1) Collection and activation of bacterial strains: Collect soil near the roots of trees, weigh 5 g of sample, and place it in 250 mL of sterile water to prepare a soil suspension; stir it evenly under sterile conditions and let it settle for 10 min, then take 1 mL of the supernatant and inoculate it into sterilized LB medium, place it in a 30 °C constant temperature box and let it sit for 48 h to complete the bacterial activation;

[0015] (2) Bacterial expansion: inoculate the activated bacterial solution into fresh LB medium at a 1% inoculum volume and culture in a shaker at 30°C and 150 rpm; measure the OD value at a wavelength of 600 nm daily to observe the growth status of the microorganisms; when the OD value drops significantly, replace the medium with fresh one and continue culturing until the bacterial colony enters a stable logarithmic growth phase;

[0016] (3) Microbial acclimation: The bacterial population was acclimated by adding composite pollutants in a concentration gradient of 1 mg / L, 3 mg / L, 5 mg / L, and 7 mg / L in sequence. The specific operation was as follows: inoculate a new culture medium with a 1% inoculum under sterile conditions, add an appropriate amount of 100 mg / L pollutant stock solution after culturing for 24 hours to make the actual pollutant concentration 1 mg / L, continue culturing and measure the OD value every day, and after the OD value drops significantly, inoculate a new culture medium with a 1% inoculum again, and increase the pollutant concentration to 3 mg / L. Repeat the acclimation steps until the bacterial population adapts to the target concentration environment of 7 mg / L.

[0017] As a preferred technical solution of the present invention, zero-valent iron (ZVI), sodium percarbonate (SPC) and biochar (BC) are introduced into the domesticated microbial flora to construct a microbial and functional material composite treatment system. The specific steps are as follows:

[0018] 0.1 g / L ZVI, 2.5 mM SPC and 0.1 g / L BC were added to the acclimated microbial culture system to construct a composite degradation system. Composite pollutants were added and the initial concentration of pollutants was set at 3 mg / L or 6 mg / L to carry out pollutant removal experiments.

[0019] The present invention introduces zero-valent iron, sodium percarbonate, and biochar into a microbial culture medium to construct a composite system that achieves synergistic degradation of OTC and Cr(VI). Compared with existing technologies, the present invention has the following advantages:

[0020] 1. Significantly Improved Degradation Efficiency: At a pollutant concentration of 3 mg / L, the pure microbial system achieved degradation rates of 71.65% for OTC and 56.07% for Cr(VI), respectively; while the synergistic system achieved rates of 81.02% and 81.36%, respectively. This represents an approximately 10% increase in OTC removal and a more than 25% increase in Cr(VI). At 6 mg / L, the pure microbial system achieved degradation rates of 82.69% for OTC and 71.72% for Cr(VI), respectively; while the synergistic system achieved rates of 87.65% and 92.26%, respectively, demonstrating a stable and highly effective synergistic effect.

[0021] 2. Enhanced system stability: Biochar has a slow-release and protective effect on ZVI and SPC, effectively delaying the passivation of ZVI and reducing the decomposition rate of SPC. At the same time, BC acts as a microbial carrier and electron buffer, enhancing bacterial activity and the electron transfer capacity of the reaction system, extending the microbial activity period by more than 20%.

[0022] 3. Environmentally Friendly: This invention integrates physical, chemical, and biological degradation pathways, offering advantages such as low toxicity, reproducibility, and zero secondary pollution. By building an intelligent remediation system centered on adsorption-biological synergy, it enhances the greenness of pollution control and meets the needs of ecological safety management.

[0023] 4. Broad Application Prospects: The inexpensive materials and simple process offer excellent potential for industrialization and engineering expansion. Suitable for complex pollution scenarios such as aquaculture soil, metallurgical wastewater, sludge treatment, constructed wetlands, and biofilters, the method has strong practical value and potential for expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a curve showing the change in oxytetracycline (OTC) concentration over time in the treatment of complex pollutants by a single microbial system when the initial concentration of the pollutants is 3 mg / L.

[0025] Figure 2 This is a graph showing the change in hexavalent chromium (Cr(VI)) concentration over time in a single microbial system treating complex pollutants when the initial concentration of the pollutants is 3 mg / L.

[0026] Figure 3 This is a graph showing the change in oxytetracycline (OTC) concentration over time in the treatment of complex pollutants by the synergistic system of microorganisms and materials when the initial concentration of the pollutants is 3 mg / L.

[0027] Figure 4This is a graph showing the change in hexavalent chromium (Cr(VI)) concentration over time in the treatment of complex pollutants by the synergistic system of microorganisms and materials when the initial concentration of the pollutants is 3 mg / L.

[0028] Figure 5 This is a curve showing the change of oxytetracycline (OTC) concentration over time in the treatment of complex pollutants by a single microbial system when the initial concentration of the pollutants is 6 mg / L.

[0029] Figure 6 This is a graph showing the change in hexavalent chromium (Cr(VI)) concentration over time in a single microbial system treating complex pollutants when the initial concentration of the pollutants is 6 mg / L.

[0030] Figure 7 This is a graph showing the change in oxytetracycline (OTC) concentration over time in the treatment of complex pollutants by the synergistic system of microorganisms and materials when the initial concentration of the pollutants is 6 mg / L.

[0031] Figure 8 This is a graph showing the change in hexavalent chromium (Cr(VI)) concentration over time in the treatment of complex pollutants by the synergistic system of microorganisms and materials when the initial concentration of the pollutants is 6 mg / L.

[0032] Figure 9 This is the 16S rRNA distribution diagram of microbial flora in LB culture medium without adding pollutants.

[0033] Figure 10 The 16S rRNA distribution of microbial flora in LB culture medium under Cr(VI) contamination conditions.

[0034] Figure 11 The 16S rRNA distribution of microbial flora in LB culture medium under OTC contamination conditions. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with embodiments and drawings.

[0036] Example 1: Degradation experiment of 3 mg / L composite pollutants by a single microorganism

[0037] (1) Soil was collected near the roots of the landscape trees on the south side of Building 34 of Hefei University. 5 g of soil sample (without grass roots) was added to 250 mL of sterile water, mixed thoroughly under sterile conditions, and allowed to stand for 10 min.

[0038] (2) Pipette 1 mL of the supernatant and inoculate into sterile LB medium.

[0039] (3) Place the above culture medium in a 30°C constant temperature incubator for 48 h for activation.

[0040] (4) Transfer the activated bacterial solution to new LB medium at a 1% inoculum volume and culture at 30°C and 150 rpm. Measure OD600 daily. When the culture stabilizes in the logarithmic growth phase, replace the medium and continue culturing.

[0041] (5) The above culture solution was inoculated into new LB medium (100 mL) at a 1% inoculum volume, and 1 mL of pre-prepared composite pollutant at a concentration of 0.1 mg / mL was added to control the composite pollutant concentration in the treatment system to 1 mg / L (OTC and Cr(VI) concentrations were both 1 mg / L). Then, the culture was continued and the OD value was measured daily. After the OD value dropped significantly, the new culture medium was inoculated again at a 1% inoculum volume, and the pollutant concentration was increased to 3 mg / L (1 mL of pre-prepared composite pollutant at a concentration of 0.3 mg / mL was added). The acclimation steps were repeated until the bacterial colony adapted to the target concentration environment of 7 mg / L.

[0042] (6) The acclimated bacterial colony was selected and transferred into a new culture medium at a 1% inoculum size. After culturing for 1 day, 3 mg / L of the combined pollutant (OTC + Cr(VI)) (1 mL of a pre-prepared 0.3 mg / mL combined pollutant) was added and a 58-day degradation experiment was conducted.

[0043] (7) All cultures used in the experiment were LB medium. Samples were collected on days 3, 8, 13, 18, 23, 28, 38, 48, and 58 to determine the pollutant removal rate. OTC was determined by high-performance liquid chromatography (HPLC), and Cr(VI) was determined by diphenylcarbazide colorimetry. Each sample was measured three times. The samples were centrifuged at 8000 rpm for 10 min, and the supernatant was filtered through a 0.22 μm filter membrane for testing.

[0044] like Figure 1 and Figure 2 As shown in the figure, the final degradation rates of OTC and Cr(VI) in this system were 71.65% and 56.07%, respectively.

[0045] Example 2: Degradation experiment of 3 mg / L pollutants by the synergistic system of materials and microorganisms

[0046] Steps (1) to (5): Same as in Example 1.

[0047] Step (6) The acclimated bacterial community was inoculated into a new LB medium (100 mL) at a 1% inoculum size. After culturing for 24 h, 10 mg ZVI (0.1 g / L), 0.25 mmol SPC, and 10 mg biochar were added, respectively. 3 mg / L of the composite pollutant (OTC + Cr(VI)) (1 mL of a pre-prepared composite pollutant with a concentration of 0.3 mg / mL) was also added, and a 58-day synergistic degradation experiment was carried out.

[0048] Step (7): Same as Example 1.

[0049] like Figure 3 and Figure 4 As shown in the figure, the final degradation rates of OTC and Cr(VI) by the synergistic system were 81.02% and 81.36%, respectively.

[0050] Example 3: Degradation experiment of 6 mg / L composite pollutants by a single microorganism

[0051] Steps (1) to (5): Same as in Example 1.

[0052] Step (6) The acclimated bacterial colony was inoculated into a new LB medium at a 1% inoculum size. After culturing for 24 h, 6 mg / L of the composite pollutant (OTC + Cr(VI)) (1 mL of a pre-prepared composite pollutant with a concentration of 0.6 mg / mL) was added and a 58-day degradation experiment was carried out.

[0053] Step (7): Same as Example 1.

[0054] like Figure 5 and Figure 6 As shown in the figure, the final degradation rates of OTC and Cr(VI) in this system were 82.69% and 71.72%, respectively.

[0055] Example 4: Degradation experiment of 6 mg / L pollutant by synergistic system of materials and microorganisms

[0056] Steps (1) to (5): Same as in Example 1.

[0057] Step (6) The acclimated bacterial community was inoculated into a new LB medium at a 1% inoculum size. After culturing for 24 h, 10 mg ZVI (0.1 g / L), 0.25 mmol SPC, and 10 mg biochar were added, respectively. 6 mg / L of the composite pollutant (OTC + Cr(VI)) (1 mL of a pre-prepared composite pollutant with a concentration of 0.6 mg / mL) was also added, and a 58-day synergistic degradation experiment was carried out.

[0058] Step (7): Same as Example 1.

[0059] like Figure 7 and Figure 8 As shown in the figure, the final degradation rates of OTC and Cr(VI) by the synergistic system were 87.65% and 92.26%, respectively.

[0060] Examples 1-4 verify that the composite treatment system of microorganisms and functional materials constructed by the present invention exhibits excellent pollutant removal performance at different pollutant concentrations, especially in the presence of high concentrations of Cr(VI), which still has a high degradation efficiency, significantly better than a single microorganism system, demonstrating the reliability and wide applicability of its synergistic mechanism.

[0061] Figure 9 This is the 16S rRNA distribution diagram of microbial flora in LB culture medium without adding pollutants. Figure 10 The 16S rRNA distribution of microbial flora in LB culture medium under Cr(VI) contamination conditions. Figure 11 The 16S rRNA distribution of microbial flora in LB culture medium under OTC contamination conditions. Figure 9 、 10 , 11 It can be seen that the introduction of pollutants Cr (VI) and OTC significantly affected the structure and composition of the microbial community in LB culture medium. Figure 9 ) compared with Cr(VI) stress ( Figure 10 ) were newly added to the Actinobacteriota (Actinobacteria), revealing that heavy metal pollution may have induced the enrichment of metal-resistant microorganisms. Figure 11 ), we observed increases in potentially resistant or metabolically active microorganisms such as Ralstonia, Pseudomonas, and Acetobacteraceae, potentially related to their tolerance or degradation of antibiotics. Overall, pollutant stress induces clear selective responses and structural succession trends in microbial communities, with increased community complexity and diversity, demonstrating a certain degree of environmental adaptability and restoration potential.

[0062] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for degrading complex pollutants based on the synergistic effect of microorganisms and functional materials, characterized in that: Zero-valent iron (ZVI), sodium percarbonate (SPC) and biochar (BC) were introduced into the domesticated microbial flora to construct a composite treatment system of microorganisms and functional materials to achieve the synergistic degradation of the combined pollutants of oxytetracycline (OTC) and hexavalent chromium (Cr(VI)).

2. The method for degrading composite pollutants according to claim 1, wherein: The zero-valent iron (ZVI) has a concentration of 0.1 g / L in the composite treatment system and is in spherical or granular form with a particle size of less than 100 μm. It is used to provide electrons to reduce hexavalent chromium (Cr(VI)) and serves as an attachment and transfer carrier for microorganisms.

3. The method for degrading composite pollutants according to claim 1, wherein: The sodium percarbonate (SPC) has a concentration of 2.5 mM in the composite treatment system, can slowly release H2O2 in water, induce a Fenton-like reaction to generate hydroxyl radicals, and accelerate the decomposition of oxytetracycline (OTC).

4. The method for degrading composite pollutants according to claim 1, wherein: The biochar (BC) has a concentration of 0.1 g / L in the composite treatment system. It is produced by pyrolysis of agricultural waste at 500-700°C and has a particle size of 100-200 μm. It is used to adsorb pollutants, stabilize microbial structure and enhance electron transfer.

5. The method for degrading composite pollutants according to claim 1, wherein: The method for obtaining and domesticating the microbial flora is as follows: (1) Collection and activation of bacterial strains: Collect soil near the roots of trees, weigh 5 g of sample, and place it in 250 mL of sterile water to prepare a soil suspension; stir it evenly under sterile conditions and let it settle for 10 min, then take 1 mL of the supernatant and inoculate it into sterilized LB medium, place it in a 30 °C constant temperature box and let it sit for 48 h to complete the bacterial activation; (2) Bacterial expansion: inoculate the activated bacterial solution into fresh LB medium at a 1% inoculum volume and culture in a shaker at 30°C and 150 rpm; measure the OD value at a wavelength of 600 nm daily to observe the growth status of the microorganisms; replace the medium with fresh one when the OD value drops significantly, and continue to culture until the bacterial colony enters a stable logarithmic growth phase; (3) Microbial acclimation: The bacterial population was acclimated by adding composite pollutants in a concentration gradient of 1 mg / L, 3 mg / L, 5 mg / L, and 7 mg / L in sequence. The specific operation was as follows: inoculate a new culture medium with a 1% inoculum under sterile conditions, add an appropriate amount of 100 mg / L pollutant stock solution after culturing for 24 hours to make the actual pollutant concentration 1 mg / L, continue culturing and measure the OD value every day, and after the OD value drops significantly, inoculate a new culture medium with a 1% inoculum again, and increase the pollutant concentration to 3 mg / L. Repeat the acclimation steps until the bacterial population adapts to the target concentration environment of 7 mg / L.

6. The method for degrading composite pollutants according to claim 5, wherein: Zero-valent iron (ZVI), sodium percarbonate (SPC) and biochar (BC) were introduced into the domesticated microbial flora to construct a composite treatment system of microorganisms and functional materials. The specific steps are as follows: 0.1 g / L ZVI, 2.5 mM SPC and 0.1 g / L BC were added to the acclimated microbial culture system to construct a composite degradation system. Composite pollutants were added and the initial concentration of pollutants was set at 3 mg / L or 6 mg / L to carry out pollutant removal experiments.

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