Method for photocatalytic degradation of terramycin by using modified carrier biofilm

Abstract

The application discloses a method for photocatalytic degradation of terramycin by using a modified carrier biofilm, and the method is used for photocatalytic and synergic biodegradation treatment of terramycin by using the modified carrier biofilm, wherein the modified carrier biofilm comprises a porous carrier and nano-Fe3O4, the nano-Fe3O4 is fixed on the porous carrier to form a porous carrier with fixed nano-Fe3O4, and a biofilm is grown on the surface and inside of the porous carrier with fixed nano-Fe3O4. In the application, the photocatalytic and synergic biodegradation treatment of terramycin by using the modified carrier biofilm can couple the photocatalytic effect and the biodegradation effect to degrade terramycin, can efficiently and completely convert terramycin into non-toxic or low-toxic products, has the advantages of simple process, convenient operation, high treatment efficiency, high removal efficiency, high mineralization rate and the like, and is a new process capable of rapidly degrading terramycin, and has a very important promoting effect on effectively removing terramycin in the environment.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and microbial pollutant removal, and relates to a method for degrading oxytetracycline, specifically a method for photocatalytic degradation of oxytetracycline using a modified carrier biofilm. Background Technology

[0002] Oxytetracycline, as a broad-spectrum antibiotic, has been widely produced and used. Notably, its polyaromatic ring structure allows it to persist in the environment for extended periods. Currently, oxytetracycline levels ranging from ppb to ppm have been detected in soil, water, and even food. Therefore, effectively removing oxytetracycline from the environment to reduce its harm to the ecological environment and human health is a pressing technical problem that needs to be solved.

[0003] Among numerous water treatment technologies, biological treatment processes have attracted much attention due to their advantages of low cost and environmental friendliness. However, due to their relatively slow reaction kinetics, biological treatment processes are not very effective in treating recalcitrant compounds (such as oxytetracycline). This is because the biodegradation of oxytetracycline by microorganisms is highly limited, easily affected by environmental factors, and faces intense competition with native microorganisms, which hinders the rapid and thorough degradation of organic matter. Therefore, the degradation rate remains low and the degradation effect is unstable. Meanwhile, to address these issues, researchers have proposed immobilized microbial technology. By immobilizing microorganisms in a limited space, the tolerance of microorganisms to the toxicity of target substances is improved, thereby increasing the removal rate of target pollutants. However, existing methods for using immobilized microorganisms to degrade antibiotics still have the following drawbacks: the carrier material is easily decomposed, resulting in poor stability of the immobilized microorganisms, making reuse difficult or ineffective; the specific surface area of ​​the carrier material is small, resulting in limited space for microbial growth and reproduction, making large-scale reproduction difficult, thus the degradation efficiency and removal effect on oxytetracycline remain poor; and the microbial species are limited, requiring domestication to improve their tolerance to oxytetracycline, making large-scale utilization difficult. Furthermore, oxidation / reduction processes (AO / RPs), such as photocatalysis, can rapidly and non-selectively destroy pollutants. However, in practical applications, it is difficult to achieve complete mineralization of oxytetracycline under low-cost conditions, and incomplete reaction products after photocatalysis may still retain toxicity. Therefore, it is essential to overcome these shortcomings and deficiencies to obtain a method that can rapidly and completely convert oxytetracycline into low-toxicity or non-toxic products. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for photocatalytic degradation of oxytetracycline using a modified carrier biofilm that is simple in process, convenient in operation, has high processing efficiency, high removal efficiency and high mineralization rate.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A method for photocatalytic degradation of oxytetracycline using a modified carrier biofilm, wherein the modified carrier biofilm is used to perform photocatalytic synergistic biodegradation of oxytetracycline; the modified carrier biofilm includes a porous carrier and nano-ferric oxide, wherein the nano-ferric oxide is immobilized in the porous carrier to form a porous carrier with immobilized nano-ferric oxide; and a biofilm grows on the surface and inside of the porous carrier with immobilized nano-ferric oxide.

[0007] A further improvement to the above method is the preparation method of the modified carrier biofilm, which includes the following steps:

[0008] S1. Preparation of porous carriers immobilized with nano-ferric oxide;

[0009] S2. The porous carrier with nano-iron oxide fixed is immersed in activated sludge to obtain a porous carrier loaded with activated sludge.

[0010] S3. Microorganisms in a porous carrier loaded with activated sludge are cultured to form a biofilm on the surface and inside the porous carrier, thus obtaining a modified carrier biofilm.

[0011] A further improvement to the above method, in step S1, the preparation method of the porous carrier with immobilized nano-ferric oxide includes the following steps:

[0012] (1) Mix nano-iron oxide, porous carrier and solvent, and sonicate to obtain a suspension;

[0013] (2) The suspension is heated to remove the solvent and a porous carrier with nano-iron oxide is obtained.

[0014] In a further improvement to the above method, in step (1), the mass ratio of the nano-iron oxide to the porous carrier is 0.5 to 1:1; the particle size of the nano-iron oxide is 20 nm; the porous carrier is polyurethane sponge and / or polyvinyl chloride sponge; the solvent is anhydrous ethanol; and the ultrasonic time is 20 min to 30 min.

[0015] The above method is further improved in step (2), wherein the heating is first carried out in a water bath at 60°C until the volume of the direct suspension is reduced to less than one-fifth of the total volume, and then transferred to an oven at 60°C for drying until the solvent is completely evaporated; the heating in the water bath is stirred once every hour for 30 seconds each time; the heating in the oven is stirred once every 0.5 hours for 30 seconds each time; after the solvent is completely removed, the following treatment is also included: the porous carrier with nano-iron oxide fixed is ultrasonicated for 1 min to 3 min, washed with water 3 times, and dried.

[0016] In a further improvement to the above method, in step S2, the soaking is carried out in darkness; the soaking process also includes stirring the activated sludge at a speed of 120 r / min; the temperature of the activated sludge is controlled at 25°C during the soaking process; the soaking time is 24 h; and the activated sludge comes from the secondary sedimentation tank of a wastewater treatment plant.

[0017] In a further improvement to the above method, step S3, during the cultivation of microorganisms in the porous carrier loaded with activated sludge, further includes adding nutrients to the cultivation system, such that the nutrient-added cultivation system contains the following components: 330 mg / L sodium acetate, 29 mg / L NH4Cl, 8 mg / L Na2HPO4·2H2O, and 4 mg / L NaH2PO4; during the cultivation of microorganisms in the porous carrier loaded with activated sludge, nutrients are added every 48 hours.

[0018] In a further improvement to the above method, the cultivation process of microorganisms in the porous carrier loaded with activated sludge is carried out under dark conditions; the cultivation process of microorganisms in the porous carrier loaded with activated sludge also includes stirring the cultivation system at a speed of 120 r / min; the temperature of the cultivation system is controlled at 25°C during the cultivation process of microorganisms in the porous carrier loaded with activated sludge; and the cultivation time is 5 to 7 days during the cultivation process of microorganisms in the porous carrier loaded with activated sludge.

[0019] The above method is further improved by using a modified carrier biofilm to perform photocatalytic synergistic biodegradation of oxytetracycline in wastewater, including the following steps: mixing the modified carrier biofilm with oxytetracycline wastewater, first culturing the microorganisms in the modified carrier biofilm under light conditions, and then culturing the microorganisms in the modified carrier biofilm under dark conditions to complete the degradation of oxytetracycline in the wastewater.

[0020] In a further improvement to the above method, the ratio of the dry weight of the modified carrier biofilm to the volume of the oxytetracycline wastewater is 0.03g to 0.1g: 200mL.

[0021] The above method is further improved by adding nutrients to the wastewater during the cultivation of microorganisms in the modified carrier biofilm, so that the wastewater contains the following components after the addition of nutrients: 330 mg / L sodium acetate, 29 mg / L NH4Cl, 8 mg / L Na2HPO4·2H2O and 4 mg / L NaH2PO4; the nutrient solution is added every 48 hours during the cultivation of microorganisms in the modified carrier biofilm.

[0022] In a further improvement to the above method, the culture time of the microorganisms in the modified carrier biofilm under light conditions is 6h to 12h; the culture time of the microorganisms in the modified carrier biofilm under dark conditions is 60h to 66h; the culture process of the microorganisms in the modified carrier biofilm also includes stirring the wastewater at a speed of 120r / min; the temperature of the wastewater is controlled at 25℃ during the culture process of the microorganisms in the modified carrier biofilm; and the initial concentration of oxytetracycline in the oxytetracycline wastewater is ≤10mg / L.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] (1) To address the shortcomings of existing immobilized microorganisms, such as poor structural stability and low biological activity, which makes it difficult to quickly and thoroughly convert oxytetracycline into non-toxic or low-toxic products, this invention creatively proposes a method for photocatalytic degradation of oxytetracycline using a modified carrier biofilm. The modified carrier biofilm comprises a porous carrier and nano-ferric oxide (Fe3O4). The nano-ferric oxide is immobilized within the porous carrier to form a porous carrier with immobilized nano-ferric oxide. A biofilm grows on the surface and inside the porous carrier with immobilized nano-ferric oxide, making it a novel biofilm material with good structural stability and strong biological activity. Therefore, using this modified carrier biofilm for photocatalytic synergistic biodegradation of oxytetracycline allows for the coupled degradation of oxytetracycline through the photocatalytic and biodegradation effects of the modified carrier biofilm, efficiently and thoroughly converting oxytetracycline into non-toxic or low-toxic products. Specifically, the nano-ferric oxide immobilized on the surface of the porous carrier acts as a photocatalyst, enabling photocatalysis... The biofilm growing on and within the porous carrier can degrade oxytetracycline. It can also utilize oxytetracycline as a carbon source and convert it into low-toxicity or non-toxic metabolites through growth and metabolism. More importantly, nano-ferric oxide can promote the growth and reproduction of microorganisms within the biofilm. Therefore, under the mutual promotion of nano-ferric oxide and the biofilm, oxytetracycline can be rapidly and thoroughly degraded and converted into non-toxic or low-toxic products. Furthermore, the biofilm on the surface of the porous carrier can cover the nano-ferric oxide, thus reducing or preventing the nano-ferric oxide from detaching from the carrier, which is beneficial for improving photocatalytic stability. Moreover, the biofilm growing inside the porous carrier is better protected from the toxic effects of toxic substances and oxidants, thus also improving biodegradation activity. Therefore, when using modified carrier biofilms for photocatalytic degradation of oxytetracycline, the advantages of photocatalysis and microbial technology can be better combined, achieving highly efficient degradation of oxytetracycline. Furthermore, the photocatalytic performance of nano-Fe3O4 used in the modified carrier biofilm of this invention is suitable, causing relatively little damage to microorganisms. Nano-Fe3O4 also exhibits high biocompatibility, preventing additional environmental pollution. In addition, the modified carrier biofilm used in this invention demonstrates strong stability, maintaining a high level of removal efficiency for oxytetracycline even after multiple cycles. This invention's method for photocatalytic degradation of oxytetracycline using a modified carrier biofilm offers advantages such as simple process, convenient operation, high treatment efficiency, high removal efficiency, and high mineralization rate. It represents a novel process for the rapid degradation of oxytetracycline and plays a crucial role in effectively removing oxytetracycline from the environment.

[0025] (2) In this invention, when preparing the modified carrier biofilm, nano-ferric oxide is first fixed onto a porous carrier. The porous structure of the porous carrier firmly fixes the nano-ferric oxide material, thereby forming a porous carrier with a large specific surface area, many active sites, and good structural stability. This porous carrier with nano-ferric oxide can then be used as a site for the enrichment and growth of microorganisms. Microorganisms in activated sludge are cultured, and during the culture process, nano-ferric oxide promotes the growth of microorganisms, thus forming a biofilm on the surface of the porous carrier with a microbial structure similar to the original activated sludge. It also enhances the stability of the microbial community, making the biofilm exhibit superior biological activity. More importantly, the coating effect of the biofilm effectively prevents the nano-ferric oxide from detaching from the porous carrier, thus further enhancing the structural stability of the modified carrier biofilm. The modified carrier biofilm prepared by this invention has advantages such as good structural stability and strong biological activity. It is a novel biofilm material with excellent performance and can be widely used to degrade organic pollutants in the environment. It has high use value and good application prospects. Meanwhile, the preparation method of this invention also has the advantages of simple process, convenient operation and low preparation cost, which are suitable for large-scale preparation and easy for industrial application. It is of great significance for promoting the widespread application of modified carrier biofilms in the field of environmental remediation.

[0026] (3) In this invention, when using modified carrier biofilm to photocatalytically and synergistically biodegrade oxytetracycline in wastewater, the modified carrier biofilm is mixed with oxytetracycline wastewater. The microorganisms in the modified carrier biofilm are first cultured under light conditions, and then cultured under dark conditions. By optimizing the culture method of microorganisms, the photocatalytic and biodegradation effects of the modified carrier biofilm can be utilized more effectively, which is more conducive to the efficient and thorough removal of oxytetracycline from wastewater. Attached Figure Description

[0027] 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.

[0028] Figure 1 This is a scanning electron microscope image of the porous carrier with immobilized nano-Fe3O4 prepared in Example 1 of the present invention.

[0029] Figure 2 This is a comparison chart of the dry weight of the original carrier biofilm and the modified carrier biofilm in Example 1 of the present invention.

[0030] Figure 3 This is a diagram showing the phylum-level microbial community analysis of the activated sludge used in Example 1 of the present invention.

[0031] Figure 4 This is a diagram showing the phylum-level microbial community analysis of the original carrier biofilm in Example 1 of the present invention.

[0032] Figure 5 This is a diagram showing the phylum-level microbial community analysis of the modified carrier biofilm in Example 1 of the present invention.

[0033] Figure 6 This is a diagram showing the removal effect of the modified carrier biofilm on oxytetracycline in Example 1 of the present invention.

[0034] Figure 7 This is a diagram showing the mineralization effect of the modified carrier biofilm on oxytetracycline in Example 1 of the present invention.

[0035] Figure 8 This is a diagram showing the effect of the modified carrier biofilm on the cyclic removal of oxytetracycline in Example 1 of the present invention. Detailed Implementation

[0036] 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. All materials and instruments used in the following embodiments are commercially available.

[0037] Example 1

[0038] A method for photocatalytic degradation of oxytetracycline using a modified carrier biomembrane, specifically involving the photocatalytic synergistic biodegradation of oxytetracycline using a modified carrier biomembrane, comprising the following steps:

[0039] Eight modified carrier biofilms prepared in Example 1 were mixed with 200 mL of wastewater containing oxytetracycline and nutrients, resulting in a mixture with concentrations of oxytetracycline (10 mg / L), NH4Cl (29 mg / L), Na2HPO4·2H2O (8 mg / L), and NaH2PO4 (4 mg / L). The microorganisms in the modified carrier biofilms were first cultured under light for 10 h to utilize the photocatalytic interaction between the microorganisms and the photocatalytic process for synergistic biodegradation of oxytetracycline in the wastewater. The mixture was then transferred to darkness for another 62 h of culture to further biodegrade the oxytetracycline in the wastewater. During the culture process, the rotation speed was controlled at 120 r / min and the temperature at 25 °C to complete the degradation of oxytetracycline in the wastewater. This example is designated as the ICPB group.

[0040] In this embodiment, the method for preparing the modified carrier biomembrane includes the following steps:

[0041] S1. Preparation of porous supports immobilized with nano-ferric oxide:

[0042] (1) Preparation of primitive biofilm carriers

[0043] Commercially available PVC porous sponge was cut into uniform cubes of 10mm×10mm×10mm, washed three times with ultrapure water, and then thoroughly dried in an oven to obtain a porous carrier.

[0044] (2) Immobilization of nano Fe3O4

[0045] At a weight ratio of 1:1, commercially available nano-Fe3O4 and a porous support were placed in a 250 mL beaker. 100 mL of anhydrous ethanol was added to the beaker, and the mixture was sonicated for 30 min to obtain a homogeneous suspension. Subsequently, the suspension was heated in a water bath, and stirred with a glass rod once every hour for 30 s each time, until the volume of the suspension decreased to 20 mL. The suspension was then transferred to an oven, and stirred with a glass rod once every 0.5 hours for 30 s each time, until the liquid was completely evaporated. The solid material was sonicated for 3 min, washed three times with ultrapure water, and dried again in an oven to obtain a porous support with nano-Fe3O4 fixed in place.

[0046] Figure 1 This is a scanning electron microscope (SEM) image of the porous carrier with immobilized nano-ferric oxide prepared in Example 1 of this invention. Figure 1 It is known that in the porous carrier with immobilized nano-Fe3O4 prepared by the present invention, nano-Fe3O4 can be uniformly and fixedly distributed on the surface of the carrier.

[0047] S2. Under dark conditions, the porous carrier with nano-iron oxide fixed is immersed in activated sludge (the activated sludge comes from the secondary sedimentation tank of a sewage treatment plant in Changsha City) for 24 hours. During the immersion process, the activated sludge is stirred at a speed of 120 r / min and the temperature of the activated sludge is controlled at 25℃, so that the activated sludge fills into the interior of the porous carrier, and a porous carrier loaded with activated sludge is obtained.

[0048] S3. A porous carrier loaded with activated sludge is mixed with nutrients, and the microorganisms are cultured in the dark for 6 days at a rotation speed of 120 r / min and a temperature of 25℃. A biofilm forms on the surface and inside the porous carrier, resulting in a modified carrier biofilm. In this step, after adding nutrients, the culture system contains the following components: 330 mg / L sodium acetate, 29 mg / L NH4Cl, 8 mg / L Na2HPO4·2H2O, and 4 mg / L NaH2PO4. New nutrients are added every 48 hours during the culture process.

[0049] The modified carrier biofilm prepared in this embodiment includes a porous carrier and nano-iron oxide. The nano-iron oxide is fixed in the porous carrier to form a porous carrier with fixed nano-iron oxide. A biofilm grows on the surface and inside of the porous carrier with fixed nano-iron oxide. The porous carrier is a PVC porous sponge and the nano-iron oxide has a particle size of 20 nm.

[0050] Take the modified carrier biomembrane prepared in Example 1 of this invention and the original carrier biomembrane (prepared in basically the same way as the modified carrier biomembrane, the only difference being that the original carrier biomembrane did not have nano-iron oxide fixed), dry them, and record their final mass. The difference between the two masses is the dry weight of the biomembrane, and the specific value is as follows: Figure 2 As shown.

[0051] Figure 2 This is a comparison chart of the dry weight of the original carrier biofilm and the modified carrier biofilm in Example 1 of the present invention. Figure 2 It can be seen that, compared with the original carrier biofilm, the dry weight of the modified carrier biofilm prepared by the present invention is increased by 21%, which indicates that the introduction of nano-ferric oxide in the present invention will have a positive impact on the degradation of microorganisms.

[0052] Microbial community analysis was performed on the modified carrier biofilm prepared in Example 1 of this invention and the original carrier biofilm (prepared using essentially the same method as the modified carrier biofilm, the only difference being that the original carrier biofilm did not have nano-iron oxide immobilized).

[0053] Ten cultured modified carrier biofilms and ten original carrier biofilms were placed in 50 mL centrifuge tubes. 50 mM PBS buffer (pH 7) was added, and the tubes were sonicated in a water bath for 3 minutes to detach the biofilms from the carriers. The suspensions were then centrifuged at 10,000 rpm for 10 minutes, and the microbial community composition of the precipitate and the original sludge was analyzed. Specific analytical results are as follows: Figure 3 , Figure 4 and Figure 5 As shown.

[0054] Figure 3 This is a diagram showing the phylum-level microbial community analysis of the activated sludge used in Example 1 of the present invention.

[0055] Figure 4 This is a diagram showing the phylum-level microbial community analysis of the original carrier biofilm in Example 1 of the present invention.

[0056] Figure 5 This is a diagram showing the phylum-level microbial community analysis of the modified carrier biofilm in Example 1 of the present invention.

[0057] Depend on Figure 3 , Figure 4 and Figure 5The comparison shows that the phylum-level microbial community structure of the modified carrier biofilm is more similar to that of the original activated sludge, indicating that fewer microorganisms were limited in growth due to environmental changes during the cultivation process.

[0058] As a performance comparison, a control group was also set up in this embodiment.

[0059] Control group 1: The photocatalysis group was the only photocatalytic reaction group. Eight modified carriers (porous carriers with nano-iron oxide) were used to replace the modified carrier biofilm and placed in the degradation system for reaction. The specific reaction conditions were the same as those of the ICPB group.

[0060] Control group 2: The biological (B) group only had microbial activity. The original carrier biofilm (the preparation method of which is basically the same as that of the modified carrier biofilm, the only difference being that the original carrier biofilm did not fix nano-iron oxide) was used to treat oxytetracycline wastewater in place of the modified carrier biofilm of the present invention. Other conditions were the same as those of the ICPB group.

[0061] Control group 3: The adsorption group was an adsorption group in which 8 modified carriers (porous carriers with nano-iron oxide) were used to replace the modified carrier biofilm and cultured in the dark. Other conditions were the same as those of the ICPB group.

[0062] During the culture process, samples were taken and analyzed to determine the concentration and removal efficiency of oxytetracycline. Specifically:

[0063] Samples for HPLC analysis were filtered through a 0.22 μm aqueous membrane and analyzed using an Agilent 1260 HPLC system with an Agilent EC-C18 column (4.6 x 150 mm, 4 μm). The detection wavelength was 352 nm, the injection volume was 25 μL, the flow rate was 1 mL / min, and the column temperature was 30 °C. A flow ratio of 0.1% formic acid in ultrapure water and 0.1% formic acid in acetonitrile (80:20) was used. The removal rate (R%) of oxytetracycline was calculated using the following formula:

[0064] R% = C 样品 / C 标准 ×100%

[0065] The change in the concentration of oxytetracycline in the degradation system over time, such as Figure 6 As shown.

[0066] Figure 6 This image shows the removal effect of the modified carrier biofilm on oxytetracycline in Example 1 of the present invention. Figure 6It can be seen that after 72 hours of reaction, both the experimental group and the control group have a certain removal effect on oxytetracycline. ICPB can remove oxytetracycline quickly, and the removal rate is higher than that of the control group. After 10 hours of light reaction, the removal rate of oxytetracycline by the modified carrier biofilm of this invention reaches about 80%. After 72 hours of reaction, the removal rate of oxytetracycline can reach 94.3%.

[0067] Furthermore, if the modified carrier biofilm is directly cultured under dark conditions, the biodegradation removal rate of oxytetracycline reaches over 80% after 48 hours of culture, and 85.7% after 72 hours. This comparison shows that culturing the modified carrier biofilm under light conditions is more conducive to the efficient removal of oxytetracycline from the system. Specifically, after culturing under light for 6-12 hours, the photocatalytic synergistic biodegradation effect is basically stable. However, if culturing under light continues thereafter, it does not significantly improve the removal efficiency of oxytetracycline. Moreover, if culturing under light continues, the nano-iron oxide coated with biofilm is difficult to achieve photocatalytic degradation using light. Furthermore, the biofilm surrounding the nano-iron oxide is also easily affected by the adverse effects of photocatalysis. As a result, it is not only difficult to utilize the photocatalytic effect of nano-iron oxide to degrade oxytetracycline, but it is also easy to reduce the activity of the biofilm, ultimately hindering the improvement of the degradation efficiency of oxytetracycline. Therefore, in this invention, by first culturing under light for 6-12 hours and then transferring the culture system to dark conditions, it is more conducive to achieving efficient removal of oxytetracycline.

[0068] The mineralization effect of oxytetracycline was analyzed at the beginning and end of the reaction. Specifically:

[0069] Total Organic Carbon (TOC) Analysis: TOC samples were filtered through a 0.45 μm aqueous membrane and measured using a TOC analyzer (Shimadzu). The detection method was performed according to the manufacturer's instructions. The final TOC removal rate in the degradation system is as follows: Figure 7 As shown.

[0070] Figure 7 This image shows the mineralization effect of the modified carrier biofilm on oxytetracycline in Example 1 of this invention. Figure 7 It can be seen that the TOC removal rate of the ICPB group was significantly higher than that of other control groups, with a TOC removal rate of 41.19% in the ICPB group and only 8.56% in the photocatalysis group.

[0071] Combination Figure 6 and Figure 7 The results show that the method of photocatalytic degradation of oxytetracycline using modified carrier biofilm can rapidly and efficiently remove oxytetracycline from the aquatic environment and improve the mineralization level of oxytetracycline degradation.

[0072] To investigate the reusability of the photocatalytic support, we conducted three batches of cyclic experiments, each lasting 72 hours. At the start of each cycle, the degradation solution was replaced with 10 mg / L OTC degradation solution. The removal rate was evaluated using HPLC. The results of the cyclic experiments are shown below. Figure 8 As shown.

[0073] Figure 8 This is a diagram illustrating the cyclic removal effect of oxytetracycline by the modified carrier biofilm in Example 1 of this invention. Figure 8 It can be seen that after three cycles, the degradation effects of both the ICPB and PC groups decreased to some extent, with the PC group showing a more significant decrease. After three cycles, the degradation rate of oxytetracycline in the PC group was only 56.37%, while the degradation rate of oxytetracycline in the ICPB group could still reach 90.35%. Although there was a certain degree of decrease, the degradation effect remained stable at a high level. Based on the experimental results, we believe that the decrease in the degradation effect of the PC group is related to the shedding of the photocatalyst nmFe3O4. Due to the biofilm coverage and growth, the ICPB group experienced less photocatalyst shedding. Although some biofilm detached due to free radical attack and OTC toxicity, the remaining biofilm could still grow well, completing a tight coupling with photocatalysis to degrade oxytetracycline.

[0074] In summary, the results of this invention demonstrate that the photocatalytic synergistic biodegradation of oxytetracycline using a modified carrier biofilm can couple the photocatalytic and biodegradation effects of the modified carrier biofilm to degrade oxytetracycline, efficiently and thoroughly converting it into non-toxic or low-toxic products. This method has advantages such as simple process, convenient operation, high treatment efficiency, high removal efficiency, and high mineralization rate. It is a novel process for rapidly degrading oxytetracycline and plays a very important role in effectively removing oxytetracycline from the environment.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for photocatalytic degradation of oxytetracycline using a modified carrier biomembrane, characterized in that, The method utilizes a modified carrier biofilm for photocatalytic synergistic biodegradation of oxytetracycline, comprising the following steps: mixing the modified carrier biofilm with oxytetracycline wastewater; culturing the microorganisms in the modified carrier biofilm under light conditions for 6-12 hours, and then culturing them under dark conditions for 60-66 hours to complete the degradation of oxytetracycline in the wastewater; the modified carrier biofilm comprises a porous carrier and nano-ferric oxide, wherein the nano-ferric oxide is immobilized in the porous carrier to form a porous carrier with immobilized nano-ferric oxide; a biofilm grows on the surface and inside of the porous carrier with immobilized nano-ferric oxide; the mass ratio of nano-ferric oxide to porous carrier is 0.5-1:1; the particle size of the nano-ferric oxide is 20 nm; the porous carrier is polyurethane sponge and / or polyvinyl chloride sponge.

2. The method according to claim 1, characterized in that, The method for preparing the modified carrier biomembrane includes the following steps: S1. Preparation of porous carriers immobilized with nano-ferric oxide; S2. The porous carrier with nano-iron oxide fixed is immersed in activated sludge to obtain a porous carrier loaded with activated sludge. S3. Microorganisms in a porous carrier loaded with activated sludge are cultured to form a biofilm on the surface and inside the porous carrier, thus obtaining a modified carrier biofilm.

3. The method according to claim 2, characterized in that, In step S1, the preparation method of the porous carrier with immobilized nano-ferric oxide includes the following steps: (1) Mix nano-iron oxide, porous carrier and solvent, and sonicate to obtain a suspension; (2) The suspension is heated to remove the solvent and a porous carrier with nano-iron oxide is obtained.

4. The method according to claim 3, characterized in that, In step (1), the solvent is anhydrous ethanol; the ultrasound time is 20 min to 30 min. In step (2), the heating is first carried out in a water bath at 60°C until the volume of the suspension is reduced to less than one-fifth of the total volume, and then transferred to an oven at 60°C for drying until the solvent is completely evaporated; during the heating process in the water bath, the mixture is stirred once every hour for 30 seconds each time; during the heating process in the oven, the mixture is stirred once every 0.5 hours for 30 seconds each time; after the solvent is completely removed, the following treatment is also included: the porous carrier with nano-iron oxide is ultrasonicated for 1 min to 3 min, washed with water 3 times, and dried.

5. The method according to claim 4, characterized in that, In step S2, the soaking is carried out in the dark; the soaking process also includes stirring the activated sludge at a speed of 120 r / min; the temperature of the activated sludge is controlled at 25°C during the soaking process; the soaking time is 24 h; the activated sludge comes from the secondary sedimentation tank of the sewage treatment plant.

6. The method according to claim 5, characterized in that, In step S3, the cultivation of microorganisms in the porous carrier loaded with activated sludge further includes adding nutrients to the culture system, such that the culture system contains the following components: 330 mg / L sodium acetate, 29 mg / L NH4Cl, 8 mg / L Na2HPO4•2H2O, and 4 mg / L NaH2PO4; the nutrients are added every 48 hours during the cultivation of microorganisms in the porous carrier loaded with activated sludge; the cultivation of microorganisms in the porous carrier loaded with activated sludge is carried out in the dark; the cultivation of microorganisms in the porous carrier loaded with activated sludge also includes stirring the culture system at a speed of 120 r / min; the temperature of the culture system is controlled at 25°C during the cultivation of microorganisms in the porous carrier loaded with activated sludge; and the cultivation time is 5 to 7 days.

7. The method according to any one of claims 1 to 6, characterized in that, The dry weight ratio of the modified carrier biofilm to the volume of oxytetracycline wastewater is 0.03g~0.1g∶200mL.

8. The method according to claim 7, characterized in that, The cultivation process of microorganisms in the modified carrier biofilm also includes stirring the wastewater at a speed of 120 r / min; the temperature of the wastewater is controlled at 25℃ during the cultivation process of microorganisms in the modified carrier biofilm; and the initial concentration of oxytetracycline in the oxytetracycline wastewater is ≤10 mg / L.

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