Method for preparing sulfate-reducing bacteria modified nano zero-valent iron and method for using same

Abstract

The application discloses a preparation method and use method of sulfate-reducing bacteria modified nano zero-valent iron, and particularly relates to the field of water environment pollution remediation, and comprises the preparation method of sulfate-reducing bacteria modified nano zero-valent iron, a sulfate-reducing bacteria modified nano zero-valent iron and a method for removing sulfamethoxazole (SMX) in water by the sulfate-reducing bacteria modified nano zero-valent iron. The preparation method of the sulfate-reducing bacteria modified nano zero-valent iron is more green and environmentally friendly than the physical and chemical sulfur modification nZVI preparation method, has no energy, ball milling waste or chemical reagent waste residue, and the process raw material source is stable; the prepared sulfate-reducing bacteria modified nano zero-valent iron material (SRB-nZVI) can more efficiently and quickly remove SMX than nZVI or SRB bacterial solution alone; compared with nZVI alone, the SRB-nZVI material can obviously improve the removal rate and removal rate within 7h for removing SMX, the removal rate within 7h can reach 75%, and the final removal rate can reach more than 93%.

Description

Technical Field

[0001] This invention relates to the field of water pollution remediation technology, and more specifically, to a method for preparing and using sulfate-reducing bacteria-modified nano-zero-valent iron. Background Technology

[0002] The overuse and abuse of antibiotics have caused numerous environmental problems, posing a significant threat to ecological security and public health. Sulfamethoxazole (SMX), a typical sulfonamide antibiotic, is widely used worldwide and exhibits significant biotoxicity, environmental persistence, and bioaccumulation, which can cause major harm to human health and environmental ecosystems.

[0003] Currently, commonly used methods for degrading antibiotics include adsorption, biodegradation, and advanced oxidation processes (AOPs). Among them, the Fenton oxidation method has attracted widespread attention because it can rapidly and efficiently degrade antibiotics. This is because the hydroxyl radicals (·OH) generated by the reaction have extremely strong oxidizing properties and can rapidly and efficiently oxidize organic pollutants.

[0004] Due to their high reactivity, small particle size, and abundant surface reaction sites, nZVI particles have been widely used to remove antibiotics from water. Although nZVI particles have proven to be very promising for antibiotic removal, their tendency to aggregate still limits their widespread application. To address these issues, nZVI is typically modified, including surface modification, loading modification, and bimetallic modification. Among these, surface sulfidation modification has been proven effective in removing antibiotics. Currently, research on the preparation of S-nZVI via chemical or mechanochemical sulfidation methods has received considerable attention; however, the potential and mechanism of using sulfate-reducing bacteria (SRB) for SRB-nZVI preparation remain to be further explored. The coupling of nZVI with functional anaerobic bacteria is considered one of the most promising methods for water remediation using sulfur-modified zero-valent iron (S-ZVI) materials. First, the corrosion of nZVI can lower the redox potential (ORP), creating a suitable reducing environment for the growth of anaerobic bacteria. Second, the hydrogen produced by nZVI corrosion can provide electrons to autotrophic bacteria, improving pollutant removal efficiency. Third, the integrated treatment system of nZVI and bacteria can completely degrade pollutants into non-toxic or harmless substances.

[0005] Based on the above analysis, the nZVI sulfurization modification method using functional anaerobic bacteria coupled with nZVI has high research prospects. Summary of the Invention

[0006] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method for preparing sulfate-reducing bacteria-modified nano-zero-valent iron and its application method for removing the antibiotic sulfamethoxazole (SMX) from water. This method achieves a removal rate of 75% for 2 mg / L SMX within 420 min, with a final removal rate exceeding 93%.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing sulfate-reducing bacteria-modified nano-zero-valent iron, the specific preparation steps of which are as follows:

[0008] Step S1: Prepare sulfate-reducing bacteria (SRB) culture medium and store it in an anaerobic bottle. After sealing with butyl rubber stoppers and aluminum caps, autoclave the medium. Inoculate the culture medium with SRB bacteria and then place it in an incubator for cultivation.

[0009] Step S2: Nano-zero valent iron (nZVI) with a particle size of 50 nm is autoclaved in an anaerobic bottle;

[0010] Step S3: Mix SRB bacterial solution and nZVI in a sterile environment to obtain sulfate-reducing bacteria modified nano-zero-valent iron material (SRB-nZVI).

[0011] In a preferred embodiment, the SRB culture medium in step S1 is prepared by the following method:

[0012] Prepared using SRB medium formulation, pH adjusted to 7 with H3PO4, and sealed with a butyl rubber stopper and aluminum cap after passing N2-CO2 mixed gas through for 10 min.

[0013] The N2-CO2 mixed gas ratio is 8:2; the sulfate-reducing bacteria (SRB) culture includes, but is not limited to: pure Desulfovibrio vulgaris Hildenborough (DvH) bacteria and mixed SRB cultured from Pearl River sediment (M-SRB);

[0014] The high-pressure sterilization in step S1 is performed by the following method:

[0015] Sterilize using an autoclave at 120℃ for 30 minutes;

[0016] The inoculation and culture in step S1 are performed by the following method:

[0017] Highly active bacterial solution was obtained by inoculating 4% SRB bacterial solution into the culture medium with a syringe and then incubating it in a 36℃ incubator for 24-36 hours.

[0018] In a preferred embodiment, in step S2:

[0019] nZVI placed in an anaerobic flask:

[0020] Based on the molar mass of sulfur in the culture medium, nZVI with S / Fe = 0.1, 0.3, and 0.5 was weighed and placed in a completely dry anaerobic bottle (the S / Fe of nZVI weighed based on the molar mass of sulfur in the culture medium includes, but is not limited to, 0.1, 0.3, and 0.5). The completely dry anaerobic bottle needs to be dried in an oven at 60°C for more than 30 minutes. After passing N2-CO2 mixed gas through the bottle for 10 minutes, it is sealed with a butyl rubber stopper and an aluminum cap.

[0021] Autoclaving is performed using the following methods:

[0022] Sterilize using an autoclave at 120℃ for 30 minutes.

[0023] In a preferred embodiment, in step S3

[0024] The SRB bacterial solution and nZVI were mixed by the following method: in a sterile environment (clean bench), a blood collection needle was used to connect the SRB bacterial solution and the nZVI anaerobic bottle, and N2-CO2 mixed gas was introduced into the SRB to transfer the SRB bacterial solution into the nZVI anaerobic bottle.

[0025] nZVI corroded the culture medium liquid, generating H2 and Fe. 2+ Fe 3+ and OH - Plasma, in which Fe ions combine with S ions generated by SRB reduction to form sulfur-iron compounds, completes the process of modifying nano-zero valent iron (nZVI) by sulfate-reducing bacteria (SRB).

[0026] The present invention also includes a sulfate-reducing bacteria-modified nano-zero valent iron, which is prepared by a method for preparing sulfate-reducing bacteria-modified nano-zero valent iron.

[0027] The present invention also includes a method for removing sulfamethoxazole from water by modifying nano-zero valent iron with sulfate-reducing bacteria, wherein sulfamethoxazole (SMX) is injected into SRB-nZVI and the reaction is carried out at room temperature.

[0028] In a preferred embodiment, the initial concentration obtained after the injection of SMX is 2-10 mg / L, and the reaction temperature is 25℃-36℃.

[0029] The above process, based on the ability of nZVI itself to remove SMX, involves modifying nano-zero valent iron (nZVI) with sulfate-reducing bacteria (SRB) to obtain SRB-nZVI material. SRB can break some bonds of SMX while modifying nZVI, thus promoting the degradation of SMX.

[0030] The technical effects and advantages of this invention are as follows:

[0031] 1. The present invention uses sulfate-reducing bacteria modified nano-zero-valent iron material (SRB-nZVI) to remove SMX more efficiently and quickly than nZVI or SRB bacterial solution alone. Compared with nZVI alone, SRB-nZVI material significantly improves the removal rate and removal speed of SMX within 7 hours. The SMX removal rate of SRB-nZVI material can reach 75% within 7 hours, and the final removal rate can reach more than 93%.

[0032] 2. The process of preparing sulfate-reducing bacteria modified nano-zero-valent iron material (SRB-nZVI) by the present invention is simpler than the preparation methods of physical and chemical sulfur-modified nZVI, and is also green and environmentally friendly, with no energy, ball milling waste or chemical reagent waste remaining, and the source of raw materials for the process is stable. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the preparation process of the sulfate-reducing bacteria-modified nano-zero-valent iron material (SRB-nZVI) of this invention.

[0034] Figure 2 The image shows the XRD pattern of the sulfate-reducing bacteria-modified nano-zero-valent iron material (SRB-nZVI) after the SMX removal reaction.

[0035] Figure 3 This is a SEM image of the DvH-modified nano-zero-valent iron material (D-nZVI) of this invention after SMX removal.

[0036] Figure 4 This is an LC-MS image of the sulfate-reducing bacteria-modified nano-zero-valent iron material (SRB-nZVI) of the present invention after reaction with SMX.

[0037] Figure 5 This is a diagram showing the decomposition pathway for SMX removal in the sulfate-reducing bacteria-modified nano-zero-valent iron material (SRB-nZVI) of this invention.

[0038] Figure 6 This is a comparison of the SMX removal effect of sulfate-reducing bacteria modified nano-zero-valent iron material (SRB-nZVI) under different S / Fe ratios within 420 min. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1:

[0041] This embodiment provides a method for removing sulfamethoxazole (SMX) from water using pure bacteria modified with nano-zero valent iron (nZVI), comprising the following steps:

[0042] (1) As follows Figure 1 As shown, sulfate-reducing bacteria (SRB) culture medium was prepared, pH was adjusted to 7, and N2-CO2 mixed gas was introduced into the culture medium in the anaerobic bottle for 10 min. After sealing with butyl rubber stopper and aluminum cap, the culture medium was autoclaved at 120℃ for 30 min. After sterilization, DvH pure bacterial solution was inoculated into the culture medium and placed in an incubator for 24-36 h to obtain highly active bacterial solution.

[0043] (2) Based on the molar mass of sulfur in the culture medium, weigh 50 nm nano-zero valent iron (nZVI) with S / Fe = 0.1, 0.3 and 0.5 respectively and place them in a completely dry 150 ml anaerobic bottle. After passing N2-CO2 mixed gas through the bottle for 10 min, seal it with butyl rubber stopper and aluminum cap.

[0044] (3) In a clean bench, a blood collection needle is used to connect the DvH bacterial solution and the nZVI anaerobic bottle, and N2-CO2 mixed gas is introduced into the DvH to transfer the DvH bacterial solution into the nZVI anaerobic bottle. After the two are mixed, the bacterial agent sulfate-reducing bacteria modified nano zero-valent iron material (D-nZVI) is obtained.

[0045] (4) Prepare a 0.1 g / L standard SMX solution. Add 1 ml of standard SMX solution to the D-nZVI prepared in step (3) with S / Fe = 0.1, 0.3, and 0.5 respectively, so that the SMX concentration in the reaction system is 2 mg / L. Store the reaction system in a 36°C incubator in the dark and take samples regularly.

[0046] In this embodiment, the SO4 in the sulfate-reducing bacteria (SRB) culture medium in step (1) 2- The concentration of Na2SO4 was 1.48 g / L.

[0047] In this embodiment, the anaerobic bottle containing culture medium in step (1) is a 150ml anaerobic bottle with 50ml of culture medium added;

[0048] In this embodiment, the inoculation ratio in step (1) is 2 ml of pure DvH bacterial solution in 50 ml of culture medium;

[0049] In this embodiment, the temperature of the incubator in step (1) is set to 36°C;

[0050] In this embodiment, the masses of nZVI with S / Fe = 0.1, 0.3, and 0.5 in step (2) are 0.29 g, 0.097 g, and 0.058 g, respectively;

[0051] Example 2:

[0052] This embodiment provides a method for removing sulfamethoxazole (SMX) from water by using SRB mixed bacteria (M-SRB) modified nano-zero valent iron (nZVI) cultured in Pearl River sediment, comprising the following steps:

[0053] (1) Prepare the culture medium and sterilize the same as in step (1) of Example 1 above. Inoculate 2 ml of Pearl River sediment culture SRB mixed bacteria (M-SRB) in 50 ml of culture medium and then place it in a 36℃ incubator for 24-36 h to obtain a highly active bacterial solution.

[0054] (2) Same as step (2) in Example 1 above, aseptic nZVI weighing and preparation method;

[0055] (3) In a clean bench, a blood collection needle is used to connect the DvH bacterial solution and the nZVI anaerobic bottle, and N2-CO2 mixed gas is introduced into the SRB to transfer the DvH bacterial solution into the nZVI anaerobic bottle. After the two are mixed, the bacterial agent sulfate-reducing bacteria modified nano zero-valent iron material (M-nZVI) is obtained.

[0056] (4) Prepare a 0.1 g / L standard SMX solution. Add 1 ml of standard SMX solution to the M-nZVI prepared in step (3) with S / Fe = 0.1, 0.3, and 0.5 respectively, so that the SMX concentration in the reaction system is 2 mg / L. Store the reaction system in a 36°C incubator in the dark and take samples regularly.

[0057] In this embodiment, the SO4 in the sulfate-reducing bacteria (SRB) culture medium in step (1) 2- The concentration of Na2SO4 was 1.48 g / L.

[0058] In this embodiment, the anaerobic bottle containing culture medium in step (1) is a 150ml anaerobic bottle with 50ml of culture medium added;

[0059] In this embodiment, the inoculation ratio in step (1) is 2 ml of M-SRB mixed bacterial solution in 50 ml of culture medium;

[0060] In this embodiment, the temperature of the incubator in step (1) is set to 36°C;

[0061] In this embodiment, the masses of nZVI with S / Fe = 0.1, 0.3, and 0.5 in step (2) are 0.29 g, 0.097 g, and 0.058 g, respectively;

[0062] Comparative Example

[0063] (1) Prepare the culture medium and sterilize it in the same way as step (1) in Example 1 above;

[0064] (2) Same as step (2) in Example 1 above, aseptic nZVI weighing and preparation method;

[0065] (3) Use a blood collection needle to connect the sterile culture medium and the nZVI anaerobic bottle in a clean bench, and introduce N2-CO2 mixed gas into the sterile culture medium to transfer the sterile culture medium into the nZVI anaerobic bottle. After the two are mixed, unmodified nano zero-valent iron material (nZVI) is obtained.

[0066] Example 3

[0067] Characterization of materials used in the removal of sulfamethoxazole (SMX) from water by pure bacteria of Desulfovibrio vulgaris Hildenborough (DvH) and mixed bacteria of SRB cultured in Pearl River sediment (M-SRB) modified with nano-zero valent iron (D-nZVI, M-nZVI):

[0068] as follows Figure 2 The XRD patterns of the sulfate-reducing bacteria-modified nano-zero-valent iron material (SRB-nZVI) before and after the SMX removal reaction are shown in the 5°-90° diffraction angles. The XRD patterns of D-nZVI and M-nZVI materials show additional FeS peaks, which indicates that the coupling modification of DvH and M-SRB with nZVI was successful. The surface modification of the composite material is loaded with sulfur-iron compounds, which increases the reactivity and electronic selectivity of nZVI.

[0069] The XRD pattern of nZVI material shows numerous diffraction peaks for iron oxides and iron sulfides, indicating that nZVI can react with H2O in the culture medium to generate Fe under the absence of biological influence. 2+ Fe 3+ Plasma is used to oxidize and degrade pollutants via the Fenton reaction; additional iron sulfide compound peaks appeared in D-nZVI and M-nZVI materials, indicating that in the DvH and M-SRB coupled with nZVI systems, Fe... 2+ / Fe 3+ The coupling system exhibits richer binding of ions with sulfur, promoting the sulfurization modification of nZVI; in the growth system of sulfate-reducing bacteria, the microorganisms absorb SO42- from sulfur. 2- It gains electrons and converts SO42- 2- After reduction, the iron ions generated by the addition of nZVI to the system are readily reduced to S. 2-The reaction produces FeS, which exists in solution. The generated FeS is soluble in solvent, can be loaded onto the nZVI surface, and can also be degraded with the aid of SMX.

[0070] as follows Figure 3 The SEM image of the D-nZVI material shows that nZVI particles were successfully coated on the surface of DvH bacteria, forming a new system of bacteria-nZVI particles-surface sulfur-modified compounds, and thus obtaining successfully modified D-nZVI material.

[0071] Example 4

[0072] Removal pathways of D-nZVI and M-nZVI for SMX in water

[0073] as follows Figure 4 The mass spectra of SMX intermediates removed from water by D-nZVI and M-nZVI show that small molecule fragments of SMX appeared in the system, proving that after D-nZVI and M-nZVI materials act on SMX, the CS bond and NS bond are broken, and the relative abundance of SMX in the system is very low. D-nZVI and M-nZVI can successfully remove SMX.

[0074] as follows Figure 5 The decomposition pathway diagram of SMX removal by sulfate-reducing bacteria-modified nano-zero-valent iron material (SRB-nZVI) shows that the main difference between the two degradation pathways lies in the incomplete breaking of the CS bond. The other part of the effect of biomodification of nZVI coupled with SMX removal is manifested in the breaking of the NO bond in the isobufoazole ring, which degrades the isobufoazole ring into smaller molecular products, thus promoting the complete removal of SMX in the aquatic environment.

[0075] Example 5

[0076] The Removal Effect of D-nZVI and M-nZVI on SMX in Water

[0077] like Figure 6 The comparison of the SMX removal effects of sulfate-reducing bacteria-modified nano-zero-valent iron material (SRB-nZVI) under different S / Fe ratios is shown in the figure. Under the coupling of DvH and M-SRB with nZVI, within 420 min, the degradation rate of SMX by the D-nZVI system was higher than that of the nZVI system under different S / Fe conditions, indicating that the presence of DvH can indeed promote the degradation of SMX by nZVI. However, the degradation rate and degradation speed of M-nZVI were higher than those of the nZVI system within 420 min when S / Fe = 0.5, indicating that for mixed-bacterial M-SRB-modified nZVI, there exists a suitable S / Fe ratio that promotes the degradation of SMX by the M-nZVI material.

[0078] like Figure 6 As shown, the degradation rate of SMX by the D-nZVI system was nearly 75% within 420 min, while the degradation rate of SMX by the M-nZVI system was 51%. The main reason is that the D-nZVI and M-nZVI systems used different bacterial strains. The D-nZVI system used pure DvH bacteria, while the M-nZVI system used a mixed culture of SRB cultured from Pearl River sediment. During the sediment acclimation process, only SRB in the M-SRB mixed culture could be guaranteed to be dominant. Furthermore, the sulfate reduction efficiency of the SRB strain obtained through M-SRB mixed culture acclimation was unknown, resulting in a lower sulfate reduction efficiency than that of pure DvH bacteria during the short-term reaction with SMX. Therefore, the degradation rate and degradation speed of SMX by the M-nZVI system were slightly lower than those of the D-nZVI system within 420 min.

[0079] This embodiment demonstrates the existence of a sulfate-reducing bacteria-modified nano-zero-valent iron material that exhibits a higher degradation rate and degradation speed for SMX in water. This material is obtained by sulfurizing nZVI with pure sulfate-reducing bacteria DvH.

[0080] This invention utilizes sulfate-reducing bacteria (SRB) and sterilized nano-zero-valent iron (nZVI) to modify and obtain bio-sulfur-modified nano-zero-valent iron material (SRB-nZVI), thereby achieving the removal of sulfamethoxazole (SMX) from water. This method is simpler and more environmentally friendly in preparation, has a shorter treatment cycle, and better treatment effect. The sulfate-reducing bacteria modified nano-zero-valent iron (SRB-nZVI) system can effectively remove SMX from water, with both removal rate and removal efficiency higher than before nZVI modification, and the final removal rate can reach over 93%.

[0081] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0082] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0083] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for removing sulfamethoxazole from water using sulfate-reducing bacteria-modified nano-zero-valent iron, characterized in that: Sulfamethoxazole was injected into sulfate-reducing bacteria-modified nano-zero-valent iron, and the reaction was carried out at room temperature. The specific preparation steps of the sulfate-reducing bacteria-modified nano-zero-valent iron are as follows: Step S1: Prepare sulfate-reducing bacteria culture medium and store it in an anaerobic bottle. After sealing with butyl rubber stoppers and aluminum caps, autoclave the medium. Inoculate the culture medium with SRB bacteria and then place it in an incubator for cultivation. Step S2: Sterilize 50nm nano-zero valent iron in an anaerobic bottle by autoclaving; Step S3: Mix SRB bacterial solution and nZVI in a sterile environment to obtain sulfate-reducing bacteria modified nano-zero-valent iron material.

2. The method for removing sulfamethoxazole from water according to claim 1, characterized in that: The SRB culture medium in step S1 is prepared by the following method: Prepared using SRB medium formulation, pH adjusted to 7 with H3PO4, and sealed with a butyl rubber stopper and aluminum cap after passing N2-CO2 mixed gas through for 10 min. The high-pressure sterilization in step S1 is performed by the following method: Sterilize using an autoclave at 120℃ for 30 minutes; The inoculation and culture in step S1 are performed by the following method: After adding 4% SRB bacterial solution to the culture medium using a syringe, the culture was placed in a 36℃ incubator for 24-36 hours to obtain a highly active bacterial solution.

3. The method for removing sulfamethoxazole from water according to claim 1, characterized in that: In step S2: nZVI placed in an anaerobic flask: Based on the molar mass of sulfur in the culture medium, nZVI with S / Fe = 0.1, 0.3, and 0.5 were weighed and placed in completely dry anaerobic bottles. After passing N2-CO2 mixed gas through the bottles for 10 min, they were sealed with butyl rubber stoppers and aluminum caps. Autoclaving is performed using the following methods: Sterilize using an autoclave at 120℃ for 30 minutes.

4. The method for removing sulfamethoxazole from water according to claim 1, characterized in that: In step S3: The SRB bacterial solution and nZVI were mixed by the following method: in a sterile environment, a blood collection needle was used to connect the SRB bacterial solution and the nZVI anaerobic bottle, and N2-CO2 mixed gas was introduced into the SRB to transfer the SRB bacterial solution into the nZVI anaerobic bottle.

Images