A composite nanofiber membrane for immobilized microorganism treatment of diesel contaminated water and a preparation method thereof

Abstract

This invention discloses a composite nanofiber membrane for immobilizing microorganisms to remediate diesel-contaminated water and its preparation method. Specifically, the composite nanofiber membrane is a thermoplastic polyurethane / nanohydroxyapatite composite nanofiber membrane, which not only possesses excellent biocompatibility and mechanical strength but is also non-toxic and harmless, offering considerable cost-effectiveness. Upon introduction into diesel-contaminated water, the composite nanofiber membrane first rapidly adsorbs diesel at the water / oil interface, preventing further diffusion and toxic effects on the aquatic environment. Subsequently, due to the additional adsorption sites provided by the nanoparticles on the membrane, a large number of free bacteria are adsorbed onto the membrane, enhancing the metabolic activity of bacterial cells and their resistance to the toxicity of stubborn compounds, while also strengthening the affinity between hydrophobic compounds and cells, thereby increasing the degradation rate of diesel hydrocarbons by microbial cells. This invention improves the remediation effect of diesel wastewater while expanding the application of composite nanofiber membranes in the field of water pollution treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of materials, and particularly relates to a composite nanofiber membrane for immobilized microbial remediation of diesel-contaminated water and a preparation method thereof. BACKGROUND

[0002] Petroleum is one of the most important resources in modern industry. There is always a risk of spillage as long as petroleum is exploited, transported, stored and used. Oil waste is considered to be a serious persistent harmful pollutant because it can cause extensive damage to ecosystems, including pollution of sediments and water. These accidents bring great harm to the economy, the environment and even human health, and there is an urgent need for efficient mitigation measures to remediate petroleum hydrocarbon-contaminated water. However, due to the low solubility, non-polarity and hydrophobicity of petroleum hydrocarbons, the remediation of petroleum hydrocarbon-contaminated environments is still challenging. The commonly used treatment method, such as the application of chemical dispersants, can potentially be toxic to water bodies, which brings controversy to its use. Therefore, the existing treatment strategies have limited remediation effect on oil-contaminated water and are prone to cause secondary damage to the water environment. In order to more effectively remediate oil-contaminated water, an immobilized bacterial remediation carrier material with environmental friendliness and sustainable remediation is expected to become an effective strategy for water environment treatment.

[0003] Compared with free cells, the immobilization of microorganisms improves the survival rate, metabolic activity and resistance to the toxic effects of recalcitrant compounds of bacteria. Immobilization of microorganisms on appropriate carriers can be utilized in many processes and makes bacteria easy to recover and reuse. Many studies are currently focused on carriers to which microorganisms can adhere, such as polyurethane foam (PUF); polycaprolactone (PCL) sponge, etc. They have known adsorption capacity for bacterial cells and hydrophobic compounds, but the shortcomings are that their loading rate and treatment efficiency need to be further improved due to the limitations of the structure. For example, inorganic materials such as magnetic nanoparticles; modified bamboo charcoal, etc. These products have effectiveness, but one of the disadvantages is non-biodegradability or difficulty in recovery. Therefore, there is an urgent need for a carrier material that is biocompatible, non-dissolving, non-toxic to immobilized cells and the environment, easy to obtain, easy to recover, etc. In addition, the scaffold also needs to be composed of highly interconnected macro- and micro-porous networks to facilitate cell migration and nutrient distribution. In order to meet the above conditions, an immobilized material that has both high adsorption capacity and improves the affinity of microbial cells and hydrophobic substrates is a promising choice.

[0004] Among the different methods of producing porous structure biopolymers, electrospinning technology is one of the most studied methods because of its adaptability, simplicity and availability for large-scale production, all factors contribute to cost-effectiveness. Using electrospinning technology can produce fibers of different diameters from nanometers to microns. Compared with other porous structures, electrospinning nanofiber membranes have higher specific surface area and greater porosity. Therefore, electrospinning membranes are widely used in oil spill repair, removal of toxic metal ions from wastewater, and biomedical fields. The good biocompatibility of TPU nanofiber membranes can make the microorganisms effectively fixed, the excellent mechanical strength and corrosion resistance make it better adapt to the external bad environment, and the non-toxic and harmless have more cost-effective. Hydroxyapatite is a typical environmentally friendly functional material, which has good biocompatibility and high adsorption capacity, high stability, and has been widely concerned in the fields of soil remediation and wastewater treatment. Therefore, introducing it into the TPU fiber membrane can improve the biological activity and biocompatibility of the composite material, and make the bacterial cells better adhere to the scaffold. However, there is a lack of research on the use of electrospinning technology to prepare thermoplastic polyurethane (TPU) / nano-hydroxyapatite modified nanofiber membranes as carriers to remove oil. Only the high adsorption property is enough to show its potential, and it has great research prospect in the field of treating oil hydrocarbon contaminated water. SUMMARY

[0005] Based on this, the application provides a composite nanofiber membrane containing hydroxyapatite. First of all, the composite nanofiber membrane has excellent mechanical, corrosion-resistant and biocompatibility, which can adapt to various external bad environment and successfully repair the contaminated water; Secondly, the non-toxic and harmless nature will not cause secondary damage to the environment during the repair process; Finally, the introduced nano-hydroxyapatite has environmental friendliness and high adsorption, which greatly increases the adsorption sites on the membrane, improves the immobilized microbial effect, increases the affinity of cells and hydrophobic substrates, so as to achieve the purpose of improving the degradation efficiency of diesel oil in contaminated water. Therefore, the application combines electrospinning, microbial immobilization and bioremediation three technologies, which realizes efficient repair of diesel contaminated water and expands the application of fiber membrane in water treatment field.

[0006] To achieve the above object, the application adopts the following technical scheme:

[0007] A composite nanofiber membrane for immobilized microbial repair of diesel contaminated water, the preparation method comprises the following steps:

[0008] (1) Add needle-shaped nano-hydroxyapatite to the solvent system composed of N,N-dimethylformamide and acetone, perform first ultrasonic, then add polyester thermoplastic polyurethane, stir uniformly, perform second ultrasonic, and stand to defoam, to obtain uniform spinning solution S3;

[0009] (2) electrospinning the spinning solution S3 to obtain thermoplastic polyurethane / nano-hydroxyapatite composite nanofiber membrane (TPU / nHA composite nanofiber membrane);

[0010] (3) drying the TPU / nHA composite nanofiber membrane to obtain a composite nanofiber membrane for immobilizing microorganisms to repair diesel-contaminated water.

[0011] Further, in step (1), the solvent system is composed of N,N-dimethylformamide and acetone at a volume ratio of 3:1, the ratio of the needle-shaped nano-hydroxyapatite to the solvent system is 0.5-1.5:100 w / v, the first ultrasonic treatment time is 10-30 min, the stirring is at a speed of 120 r / min, a temperature of 30°C, and a time of 5-10 h, the second ultrasonic treatment time is 10-30 min, and the standing time is 5-15 min.

[0012] Further, in step (2), the spinning voltage is controlled to be 10-20 kv, and the spinning distance is 10-20 cm; further, in step (3), the drying post-treatment is drying in a vacuum oven (-0.085 MPa) at 65°C for 5-10 d to volatilize all solvents.

[0013] The composite nanofiber membrane prepared by the above method for immobilizing microorganisms to treat diesel-contaminated water has broad application prospects in the field of water treatment:

[0014] (1) The composite nanofiber membrane can adsorb hydrophobic substrates. When it is put into contaminated water, it can quickly adsorb diesel in the floating state at the water / oil interface.

[0015] (2) The composite nanofiber membrane serves as a bacterial cell immobilization carrier. The introduced nanoparticles increase the adsorption sites on the membrane, improving the effect of immobilized microorganisms.

[0016] (3) The composite nanofiber membrane improves the affinity of microorganisms to hydrophobic substrates.

[0017] (4) The composite nanofiber membrane is environmentally friendly, corrosion-resistant, biocompatible, easy to recycle, non-toxic to cells and the environment, can provide sustainable repair, and has cost-effectiveness.

[0018] The composite nanofiber membrane manufactured by the application not only has excellent biocompatibility, excellent mechanical strength and corrosion resistance, but also is non-toxic and harmless, recyclable and has considerable cost-effectiveness. It can adapt to various adverse environments, has stable composition and structure, can be repaired for a long time and can be recycled and reused, thereby saving resources and reducing costs to a considerable extent. After being put into a polluted environment, the composite nanofiber membrane can play its oleophilic and hydrophobic properties, quickly adsorb floating oil in the water environment, inhibit the continuous diffusion of leaked oil hydrocarbons, and reduce the hydrocarbons in the water environment, thereby providing a relatively favorable metabolic environment for microorganisms. In addition, the super strong adsorption force of the composite nanofiber membrane can quickly adsorb free bacterial cells on the membrane to form a dense biofilm, which not only can resist the adverse environment outside and reduce the dispersion of bacterial cells in the repair process, but also is conducive to promoting the migration and nutrition distribution of the cells. Finally, the affinity between the bacterial cells and the hydrophobic oil hydrocarbon pollutants is enhanced, and the efficiency of treating the oil hydrocarbon pollutants is improved. Therefore, the composite nanofiber membrane for immobilized microbial repair of diesel oil contaminated water can become a new and efficient biological carrier material for repairing contaminated water. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Transmission electron microscope picture of acicular nano-hydroxyapatite (nHA) used in the application; the scale in A is 2 μm, and the scale in B is 1 μm.

[0020] Figure 2 Scanning electron microscope pictures of the nanofiber membranes prepared in Examples 1-6; wherein, A is a scanning electron microscope picture of the nanofiber membrane prepared in Example 1, B is a scanning electron microscope picture of the nanofiber membrane prepared in Example 2, C is a scanning electron microscope picture of the nanofiber membrane prepared in Example 3, D is a scanning electron microscope picture of the nanofiber membrane prepared in Example 4, E is a scanning electron microscope picture of the nanofiber membrane prepared in Example 5, and F is a scanning electron microscope picture of the nanofiber membrane prepared in Example 6; the scale in A-E is 30 μm, and the scale in F is 20 μm.

[0021] Figure 3 Scanning electron microscope pictures of the composite nanofiber membranes prepared in Examples 7-9; wherein, A is a scanning electron microscope picture of the composite nanofiber membrane (TPU / 0.5HA) prepared in Example 7, B is a scanning electron microscope picture of the composite nanofiber membrane (TPU / 1HA) prepared in Example 8, and C is a scanning electron microscope picture of the composite nanofiber membrane (TPU / 1.5HA) prepared in Example 9; the scale is 20 μm.

[0022] Figure 4The images show the effects of immobilizing microorganisms on the nanofiber membranes or composite nanofiber membranes prepared in Examples 6-9. In the images, A-D represent the loading conditions on the fiber membrane (TPU) of Example 6, the fiber membrane (TPU / 0.5HA) of Example 7, the fiber membrane (TPU / 1HA) of Example 8, and the fiber membrane (TPU / 1.5HA) of Example 9, respectively, and a-d represent their corresponding magnified views. The scale bar in A-D is 30 μm, and the scale bar in a-d is 5 μm.

[0023] Figure 5 The images show the XRD patterns, hydrophobicity, mechanical properties, and characterization of the immobilized microorganisms' performance in remediating diesel-contaminated water for the nanofiber membranes or composite nanofiber membranes prepared in Examples 6-9; where A is the XRD pattern, B is the water contact angle diagram, C is the stretching curve, and D is the characterization of the immobilized microorganisms' performance in remediating contaminated water.

[0024] Figure 6 The images shown are scanning electron microscope (SEM) images of the nanofiber membranes prepared in Example 6 and Comparative Examples 1-2; wherein, A is an SEM image of the nanofiber membrane prepared in Comparative Example 1, B is an SEM image of the nanofiber membrane prepared in Example 6, and C is an SEM image of the nanofiber membrane prepared in Comparative Example 2; the scale bar is 10 μm. Detailed Implementation

[0025] In this invention, the thermoplastic polyurethane (TPU) can be prepared by methods known in the art or obtained commercially. Specifically, the thermoplastic polyurethane used in the embodiments of this invention is a polyester-type thermoplastic polyurethane, purchased from Taiwan Jih Sheng Chemical Co., Ltd., product number BTE-75A, with a weight-average molecular weight of 80,000.

[0026] In this invention, the nano-hydroxyapatite (nHA) can be prepared by methods known in the art or obtained commercially. Specifically, the nano-hydroxyapatite used in the embodiments of this invention is needle-shaped, 90-100 nm long and 15-25 nm wide, and was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with product number H106378-25g. Figure 1 The images shown are transmission electron microscope images of the nano-hydroxyapatite used in the embodiments of the present invention. The results show that nHA is prone to aggregation, but its needle-like structure and size of less than 100 nm can still be seen from the images.

[0027] In this invention, the MSM culture medium formula is as follows: Na₂HPO₄·2H₂O 3.5g; KH₂PO₄ 1.0g, (NH₄)₂SO₄ 0.5g, MgCl₂·6H₂O 0.1g, CaCl₂ 0.046g, Trace Element Solution SL-4 1.0mL, deionized water 1000mL; pH = 7.25. The Trace Element Solution SL-4 formula is as follows: ethylenediaminetetraacetic acid (EDTA) 0.500g, FeSO₄·7H₂O 0.200g, Trace Element Solution SL-6 100mL, deionized water 900mL. The formula for Trace Element Solution SL-6 is as follows: ZnSO4·7H2O 0.100g; MnCl2·4H2O 0.030g, H3BO3 0.300g, CoCl2·6H2O 0.200g, CuCl2·2H2O 0.010g, NiCl2·6H2O 0.020g, Na2MoO4·2H2O 0.030g, and deionized water 1000mL; pH=3.4.

[0028] The composite nanofiber membrane for immobilizing microorganisms to remediate diesel-contaminated water, as described in this invention, is prepared by the following steps:

[0029] (1) Add needle-shaped nano-hydroxyapatite to a solvent system composed of N,N-dimethylformamide and acetone, perform the first ultrasonic treatment, then add polyester thermoplastic polyurethane, stir evenly, perform the second ultrasonic treatment, let stand to defoam, and obtain a uniform spinning solution S3.

[0030] (2) Electrospinning solution S3 was spun to obtain TPU / nHA composite nanofiber membrane.

[0031] (3) The TPU / nHA composite nanofiber membrane was dried and then treated to obtain a composite nanofiber membrane for immobilized microorganisms to remediate diesel polluted water.

[0032] In step (1), the volume ratio of N,N-dimethylformamide and acetone in the solvent system is 3:1, the ratio of needle-like nano-hydroxyapatite to the solvent system is 0.5-1.5:100W / V, the first ultrasonic treatment is ultrasonic treatment at 25℃, 40KHz, and 650W for 10-30min (preferably 20-30min), the stirring is stirring at 120r / min and 30℃ for 5-10h (preferably 6-8h), the second ultrasonic treatment is ultrasonic treatment at 25℃, 40KHz, and 650W for 10-30min (preferably 10-15min), the standing defoaming is standing at 25℃ for 5-15min (preferably 10-15min) to defoam, and the spinning solution S3 contains 22% W / V of polyester thermoplastic polyurethane.

[0033] In step (2), the spinning process conditions are: spinning voltage 10-20kV (preferably 17-20kV), spinning distance 10-20cm (preferably 15-20cm), ambient temperature 25±5℃, and humidity 40-45%.

[0034] In step (3), the drying post-treatment is to dry in a vacuum oven at -0.085 MPa and 65°C for 5 to 10 days (preferably 7 to 10 days) to evaporate all the solvent.

[0035] This invention optimizes the TPU mass concentration during the electrospinning of TPU nanofiber membranes, maximizing the optimization of the membrane's microstructure and resulting in better mechanical and biocompatibility. This, in turn, maximizes the membrane's ability to immobilize microbial cells and its efficiency in remediating polluted water. In the process of nHA blending and modifying TPU nanofiber membranes, the excellent adsorption and biocompatibility of nHA exposes numerous adsorption sites on the fiber surface, enabling the membrane to more effectively immobilize free cells in the environment. Based on the optimized nHA mass concentration, the combined effect of nHA and the fiber membrane is maximized, improving the immobilization and remediation performance of the composite membrane.

[0036] To further understand the present invention, the following embodiments illustrate a composite nanofiber membrane for immobilized microorganisms to remediate diesel-contaminated water and its preparation method. The scope of protection of the present invention is not limited by the following embodiments.

[0037] Example 1

[0038] A nanofiber membrane for immobilizing microorganisms to remediate diesel-contaminated water is prepared by the following steps:

[0039] (1) N,N-dimethylformamide and acetone are mixed evenly at a volume ratio of 3:1 to obtain a solvent system. Then, polyester thermoplastic polyurethane is added to the solvent system and stirred for 8 hours at a speed of 120 r / min and a temperature of 30℃ to obtain a uniform and transparent spinning solution S1. The spinning solution S1 contains 12% W / V polyester thermoplastic polyurethane.

[0040] (2) The spinning solution S1 was ultrasonically treated for 15 min at 25℃, 40KHz and 650W, then allowed to stand at 25℃ for 10 min to defoam, and then naturally cooled to room temperature to obtain the spinning solution S2 for later use.

[0041] (3) Electrospinning solution S2 was spun using electrospinning method, and the spinning voltage was controlled at 18kV, the spinning distance at 15cm, the ambient temperature at 30℃ and the humidity at 45% to obtain thermoplastic polyurethane nanofiber membrane (TPU nanofiber membrane).

[0042] (4) The TPU nanofiber membrane was placed in a vacuum oven and dried at -0.085 MPa and 65°C for 7 days to evaporate all the solvent. It was then naturally cooled to room temperature to obtain a nanofiber membrane for immobilizing microorganisms to remediate diesel polluted water.

[0043] Example 2

[0044] The preparation of nanofiber membranes for immobilized microorganisms to remediate diesel-contaminated water follows the same steps as in Example 1, except that the spinning solution S1 contains 14% W / V polyester thermoplastic polyurethane.

[0045] Example 3

[0046] The preparation of nanofiber membranes for immobilized microorganisms to remediate diesel-contaminated water follows the same steps as in Example 1, except that the spinning solution S1 contains 16% W / V polyester thermoplastic polyurethane.

[0047] Example 4

[0048] The preparation of nanofiber membranes for immobilized microorganisms to remediate diesel-contaminated water follows the same steps as in Example 1, except that the spinning solution S1 contains 18% W / V polyester thermoplastic polyurethane.

[0049] Example 5

[0050] The preparation of nanofiber membranes for immobilized microorganisms to remediate diesel-contaminated water follows the same steps as in Example 1, except that the spinning solution S1 contains 20% W / V polyester thermoplastic polyurethane.

[0051] Example 6

[0052] The preparation of nanofiber membranes for immobilized microorganisms to remediate diesel-contaminated water follows the same steps as in Example 1, except that the spinning solution S1 contains 22% W / V polyester thermoplastic polyurethane.

[0053] Figure 2 Scanning electron microscope (SEM) images of the nanofiber membranes prepared in Examples 1-6 for immobilizing microorganisms to remediate diesel-contaminated water are shown. The images reveal that the nanofiber membrane exhibits the best microstructure and most uniform fiber morphology when the spinning solution S1 contains 22% polyester thermoplastic polyurethane. When the spinning solution S1 contains 12%, 14%, or 16% polyester thermoplastic polyurethane, a large number of beads are present in the nanofiber membranes. Although the number of beads is significantly reduced when the spinning solution S1 contains 18% or 20% polyester thermoplastic polyurethane, it is clear that the nanofiber membrane with 22% polyester thermoplastic polyurethane in the spinning solution S1 exhibits the optimal fiber morphology.

[0054] Example 7

[0055] The following steps were taken to prepare a composite nanofiber membrane for immobilized microorganisms to remediate diesel-contaminated water:

[0056] (1) N,N-dimethylformamide and acetone were mixed evenly at a volume ratio of 3:1 to obtain a solvent system. Then, needle-shaped nano-hydroxyapatite was added to the solvent system. The ratio of needle-shaped nano-hydroxyapatite to the solvent system was 0.5:100W / V. The mixture was ultrasonically treated for 25 minutes at 25°C, 40KHz, and 650W. Then, polyester thermoplastic polyurethane was added and stirred for 8 hours at a speed of 120r / min and a temperature of 30°C. The mixture was then ultrasonically treated for 15 minutes at 25°C, 40KHz, and 650W. The mixture was then allowed to stand at 25°C for 10 minutes to defoam and naturally cooled to room temperature to obtain a uniform spinning solution S3. The mass concentration of polyester thermoplastic polyurethane in the spinning solution S3 was 22%.

[0057] (2) Electrospinning solution S3 was spun by electrospinning, and the spinning voltage was controlled at 18kV, the spinning distance at 15cm, the ambient temperature at 30℃ and the humidity at 45% to obtain a thermoplastic polyurethane / nanohydroxyapatite composite nanofiber membrane (TPU / nHA composite nanofiber membrane).

[0058] (3) The TPU / nHA composite nanofiber membrane was placed in a vacuum oven and dried at -0.085MPa and 65℃ for 7 days to evaporate all the solvent. It was then naturally cooled to room temperature to obtain a composite nanofiber membrane for immobilized microorganisms to remediate diesel polluted water.

[0059] Example 8

[0060] The preparation of a composite nanofiber membrane for immobilized microorganisms to remediate diesel-contaminated water follows the same steps as in Example 7, except that the ratio of needle-shaped nano-hydroxyapatite to the solvent system is 1:100 W / V.

[0061] Example 9

[0062] The preparation of a composite nanofiber membrane for immobilized microorganisms to remediate diesel-contaminated water follows the same steps as in Example 7, except that the ratio of needle-shaped nano-hydroxyapatite to the solvent system is 1.5:100W / V.

[0063] Figure 3 Scanning electron microscope images of the composite nanofiber membranes prepared in Examples 7-9 for immobilizing microorganisms to remediate diesel-contaminated water. Figure 3 A is an electron microscope image of the composite nanofiber membrane prepared in Example 7, which shows that there are fewer nHA particles introduced on the fiber surface. Figure 3 B is an electron microscope image of the composite nanofiber membrane prepared in Example 8, which shows that there are many nHA particles bound to its surface. Figure 3 C is an electron micrograph of the composite nanofiber membrane prepared in Example 9, showing that its surface has the most nHA particles.

[0064] The nanofiber membranes or composite nanofiber membranes prepared in Examples 6-9, each measuring 1 cm × 1 cm, for immobilizing microorganisms to remediate diesel-contaminated water were placed in 20 mL of inorganic salt culture medium, and 1 mL of OD was added to each medium. 600 A 0.2 g / L Bacillus cereus LY-1 bacterial suspension was used, with filtered and sterilized diesel oil added as the sole carbon source at a final concentration of 0.3% w / v. The mixture was cultured for 3 days in a rotary shaker (100 rpm) at 40 ± 1 °C to obtain immobilized fibrous membranes. The immobilized fibrous membranes were removed from the inorganic salt culture medium, rinsed three times with physiological saline to remove impurities, then soaked in 4% glutaraldehyde solution and fixed at 4 °C for 30 min. They were then rinsed three times with sterile physiological saline, and subsequently frozen at -20 °C for 24 h. After freezing, the immobilized fibrous membranes were freeze-dried in a freeze dryer (-65 °C, 20 Pa vacuum) for 24 h. Finally, the samples were sputter-coated with gold and observed using SEM. Results are as follows: Figure 4 As shown, compared with the nanofiber membrane prepared in Example 6, the composite nanofiber membranes prepared in Examples 7 to 9 exhibited better immobilization effects; among them, the composite nanofiber membrane prepared in Example 9 formed a dense biofilm on its surface, exhibiting the best immobilization effect.

[0065] Figure 5 A to Figure 5C shows the XRD pattern, water contact angle diagram, and tensile property diagram of the nanofiber membranes or composite nanofiber membranes prepared in Examples 6-9. The XRD results show that nHA particles were successfully introduced into the composite nanofiber membrane. The water contact angle diagram shows that with the increase of nHA content in spinning solution S3, the hydrophilicity of the membrane increases, thereby improving the membrane's biocompatibility; although the corresponding oleophilicity decreases slightly, it is not significant, and therefore it still has a considerable oil absorption effect. The tensile property diagram shows that the increase of nHA content in spinning solution S3 reduces the mechanical properties of the membrane, but the mechanical properties of the composite nanofiber membrane with a needle-like nano-hydroxyapatite:solvent ratio of 1.5:100 W / V are still sufficiently excellent and can meet various environmental requirements.

[0066] The nanofiber membranes or composite nanofiber membranes prepared in Examples 6-9, each measuring 1 cm × 1 cm, for immobilizing microorganisms to remediate diesel-contaminated water were placed in 20 mL of inorganic salt culture medium, and 1 mL of OD was added to each medium. 600 A 0.2 g / L Bacillus cereus LY-1 bacterial suspension was used, with filtered sterilized diesel oil added as the sole carbon source at a final concentration of 0.3% w / v. The suspension was incubated for 3 days in a rotary shaker (100 rpm) at 40 ± 1 °C. A planktonic cell control was used with only bacterial suspension and no fibrous membrane, while a sterile control was used with neither bacterial suspension nor fibrous membrane. Hydrocarbons and their derivatives were extracted from the culture medium after 3 days of degradation using high-resolution GC-FID analysis. The extraction process and sample preparation were as follows: extraction was performed at room temperature using petroleum ether (60-90 g) as the extraction solvent. All measurements were performed on an Agilent 7890B equipped with a split / splitless SSL injector and FID detector. The GC section was heated to 40 °C for 3 min, then heated to 275 °C at a rate of 12 °C / min and held for 8 min. 1 μL of sample was injected at 300 °C splitlessly. The chromatographic column was an Agilent 19091J-413 HP-5, 30m × 320μm × 0.25μm. Nitrogen carrier gas was maintained at a constant flow rate of 1.5 ml / min. The remediation performance was characterized by... (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 5 D) As can be seen, compared with the repair effect of free cells, the treatment groups of microorganisms immobilized by nanofiber membranes and microorganisms immobilized by composite nanofiber membranes showed a better diesel degradation rate. The diesel degradation rate of microorganisms immobilized by nanofiber membranes prepared in Example 6 was 4.33 percentage points higher than that of free cells. With the increase of nHA content, the diesel degradation rate of microorganisms immobilized by composite nanofiber membranes gradually increased. Among them, the diesel degradation rate of microorganisms immobilized by composite nanofiber membranes prepared in Example 9 was 20.64 percentage points higher than that of free cells.

[0067] Comparative Example 1

[0068] The preparation of nanofiber membranes for immobilized microorganisms to remediate diesel-contaminated water follows the same steps as in Example 6, except that the spinning voltage is controlled at 10 kV and the spinning distance is 15 cm when spinning the spinning solution S2.

[0069] Comparative Example 2

[0070] The preparation of nanofiber membranes for immobilized microorganisms to remediate diesel-contaminated water follows the same steps as in Example 6, except that the spinning solution S2 is controlled by a spinning voltage of 18 kV and a spinning distance of 10 cm.

[0071] The microstructure of the nanofiber membranes prepared in Example 6 and Comparative Examples 1-2 was observed. Figure 6 It is evident that, under the same conditions, reducing the spinning voltage and decreasing the spinning distance are both detrimental to the morphology of the fiber membrane. The nanofiber membrane prepared in Comparative Example 1 has uneven fiber thickness and the presence of beads. Although the nanofiber membrane prepared in Comparative Example 2 has no beads, the fiber diameter is too large and there is adhesion. The nanofiber membrane prepared in Example 6 has uniform fiber thickness and better fiber morphology.

[0072] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. The application of a composite nanofiber membrane for immobilizing microorganisms to treat diesel-contaminated water in the remediation of diesel-contaminated water, characterized in that: The method for preparing the composite nanofiber membrane includes the following steps: (1) Add nano-hydroxyapatite to a solvent system composed of N,N-dimethylformamide and acetone, sonicate for 10-30 min, then add thermoplastic polyurethane, stir at 120 r / min and 30℃ for 5-10 h, sonicate again for 10-30 min, and then let stand for 5-15 min to defoam, to obtain a uniform spinning solution S3; (2) Electrospinning solution S3 was spun to obtain thermoplastic polyurethane / nanohydroxyapatite composite nanofiber membrane. (3) The thermoplastic polyurethane / nanohydroxyapatite composite nanofiber membrane was dried and then treated to obtain a composite nanofiber membrane for immobilizing microorganisms to treat diesel polluted water.

2. The application according to claim 1, characterized in that: In step (1), the solvent system is composed of N,N-dimethylformamide and acetone in a volume ratio of 3:

1.

3. The application according to claim 1, characterized in that: In step (1), the ratio of nano-hydroxyapatite powder to solvent system is 0.5~1.5:100 W / V.

4. The application according to claim 3, characterized in that: In step (1), the ratio of nano-hydroxyapatite powder to solvent system is 1.5:100 W / V.

5. The application according to claim 1, characterized in that: In step (1), the mass fraction of thermoplastic polyurethane in the spinning solution S3 is 8%~22%.

6. The application according to claim 5, characterized in that: In step (1), the mass fraction of thermoplastic polyurethane in the spinning solution S3 is 22%.

7. The application according to claim 1, characterized in that: In step (2), the spinning process conditions are: spinning voltage 10~20kv, spinning distance 10~20cm.

8. The application according to claim 1, characterized in that: In step (3), the post-drying process conditions are: drying in a vacuum oven at -0.085MPa and 65℃ for 5~10 days.

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