Preparation method and use method of sulfate reducing bacteria modified nanoscale zero-valent iron

Abstract

The invention discloses a preparation method and a use method of sulfate reducing bacteria modified nanoscale zero-valent iron, and particularly relates to the field of water environment pollution remediation. Comprising a preparation method of the sulfate reducing bacteria modified nanoscale zero-valent iron, and a method for removing sulfamethoxazole (SMX) in a water body by using the sulfate reducing bacteria modified nanoscale zero-valent iron and the sulfate reducing bacteria modified nanoscale zero-valent iron. Compared with physical and chemical sulfur modified nZVI preparation methods, the preparation method disclosed by the invention is more environment-friendly and free of energy, ball-milling wastes or chemical agent wastes are remained, and the raw material source of the process is stable; the SRB-nZVI modified nano zero-valent iron material (SRB-nZVI) has the advantages that SMX can be more efficiently and quickly removed by the aid of the prepared SRB-nZVI modified nano zero-valent iron material as compared with single action of nZVI or SRB (sulfate reducing bacteria) liquid, the SRB-nZVI modified nano zero-valent iron material has the advantages that the SRB-nZVI modified nano zero-valent iron material can be obviously improved in removal rate and removal rate in 7 h as compared with single removal of SMX by the nZVI, the removal rate in 7 h can reach 75%, and the final removal rate can reach 93% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of water environment pollution remediation, and more specifically, to a preparation method and a use method of sulfate-reducing bacteria-modified nano zero-valent iron. Background Art

[0002] The misuse and overuse of antibiotics have caused considerable environmental problems and posed a major threat to ecological security and public health. Sulfamethoxazole (SMX) is a typical sulfonamide antibiotic that is widely used worldwide and has significant biological toxicity, environmental persistence and bioaccumulation, which can cause significant harm to human health and environmental ecosystems.

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

[0004] nZVI particles have been widely used to eliminate antibiotics in water due to their high reactivity, small particle size and abundant surface reaction sites. Although nZVI particles have been shown to have great prospects for removing antibiotics, their disadvantages such as easy agglomeration still limit the widespread application of nZVI. In order to solve the above problems, nZVI is usually modified, including surface modification, loading modification and bimetallic modification. Among them, surface sulfidation modification has been proven to effectively remove antibiotics. At present, the research on the preparation of S-nZVI by chemical or mechanochemical sulfidation has received much attention, but the potential and mechanism of preparing SRB-nZVI by sulfate-reducing bacteria (SRB) need to be further explored. The coupling method of nZVI with functional anaerobic bacteria is considered to be one of the most promising methods for sulfur-modified zero-valent iron (S-ZVI) materials to remediate water bodies. First, the corrosion of nZVI can reduce the redox potential (ORP) and create a suitable reducing environment for the growth of anaerobic bacteria. Secondly, the hydrogen produced by the corrosion of nZVI can provide electrons to autotrophic bacteria, improving the removal efficiency of pollutants. 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] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present invention provide a method for preparing sulfate-reducing bacteria-modified nano zero-valent iron and a method for using the same, and a method for removing the antibiotic sulfamethoxazole (SMX) from water. The method can achieve a removal rate of 75% for 2 mg / L SMX within 420 minutes, and a final removal rate of more than 93%.

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

[0008] Step S1: preparing a sulfate-reducing bacteria (SRB) culture medium and storing it in an anaerobic bottle, sealing it with a butyl rubber stopper and an aluminum cap, and then sterilizing it by high pressure. The culture medium is inoculated with SRB bacteria and then placed in an incubator for culture;

[0009] Step S2: sterilizing nano-zero-valent iron (nZVI) with a particle size of 50 nm in an anaerobic bottle by high pressure;

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

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

[0012] It was prepared using the SRB medium formula, and the pH was adjusted to 7 using H3PO4, and N2-CO2 mixed gas was passed through for 10 minutes, and then sealed with a butyl rubber stopper and an aluminum cap;

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

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

[0015] Use an autoclave to sterilize at 120°C for 30 minutes;

[0016] In step S1, the inoculation culture is performed by the following method:

[0017] 4% SRB bacterial solution was injected into the culture medium with a syringe and then placed in a 36°C incubator for 24-36 hours to obtain a highly active bacterial solution.

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

[0019] nZVI placed in anaerobic bottles:

[0020] Based on the sulfur molar mass in the culture medium, nZVI with S / Fe=0.1, 0.3, and 0.5 is weighed and placed in a completely dry anaerobic bottle (the S / Fe of nZVI weighed based on the sulfur molar mass in the culture medium includes but is not limited to: 0.1, 0.3, and 0.5), and the completely dry anaerobic bottle needs to be dried in an oven at 60° C. for more than 30 min, and a N2-CO2 mixed gas is passed into the bottle for 10 min, and then a butyl rubber stopper and an aluminum cap are used to seal the bottle;

[0021] Autoclave sterilization is performed by:

[0022] Use an autoclave to sterilize at 120°C for 30 min.

[0023] In a preferred embodiment, in step S3

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

[0025] After nZVI was connected to the culture medium liquid, it corroded and generated H2 and Fe 2+ , Fe 3+ and OH - Plasma, in which Fe ions combine with S ions produced by SRB reduction to form ferrosulfide compounds, completing the process of sulfate-reducing bacteria (SRB) modified nano zero-valent iron (nZVI).

[0026] The present invention also includes sulfate-reducing bacteria-modified nanometer zero-valent iron, which is prepared by the preparation method of sulfate-reducing bacteria-modified nanometer zero-valent iron.

[0027] The present invention also includes a method for removing sulfamethoxazole in water by using sulfate-reducing bacteria-modified nano zero-valent iron, wherein sulfamethoxazole (SMX) is injected into SRB-nZVI and reacted 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°C-36°C;

[0029] In the above process, on the basis that nZVI itself can remove SMX, the SRB-nZVI material is obtained by modifying nano zero-valent iron (nZVI) with sulfate-reducing bacteria (SRB). SRB can break certain bonds of SMX while modifying nZVI, thereby promoting the degradation of SMX.

[0030] Technical effects and advantages of the present invention:

[0031] 1. The nanometer zero-valent iron material (SRB-nZVI) modified by the prepared bacterial agent sulfate-reducing bacteria of the present invention can remove SMX more efficiently and quickly than nZVI or SRB bacterial solution acting alone. The removal rate and removal rate of SMX within 7 hours of SRB-nZVI material are significantly improved compared with nZVI alone. The removal rate of SMX by SRB-nZVI material can reach 75% within 7 hours, and the final removal rate can reach more than 93%;

[0032] 2. The process for preparing the sulfate-reducing bacteria-modified nano zero-valent iron material (SRB-nZVI) of the present invention is simpler than the preparation methods of physical and chemical sulfur-modified nZVI. It is also green and environmentally friendly, has no energy, ball milling waste or chemical waste residue, and has a stable source of process raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flow chart for preparing the sulfate-reducing bacteria-modified nano zero-valent iron material (SRB-nZVI).

[0034] Figure 2 This is the XRD diagram of the sulfate-reducing bacteria-modified nano zero-valent iron material (SRB-nZVI) after SMX removal reaction.

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

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

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

[0038] Figure 6 This is a comparison chart of the SMX removal effect of the sulfate-reducing bacteria-modified nano zero-valent iron material (SRB-nZVI) under different S / Fe within 420 minutes of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Embodiment 1:

[0041] This embodiment provides a method for removing sulfamethoxazole (SMX) in water by using pure bacteria Desulfovibrio vulgaris Hildenborough (DvH) modified nano zero-valent iron (nZVI), comprising the following steps:

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

[0043] (2) Based on the sulfur molar mass in the culture medium, nano-zero-valent iron (nZVI) with a particle size of 50 nm was weighed and placed in a completely dry 150 ml anaerobic bottle with S / Fe = 0.1, 0.3, and 0.5. A N2-CO2 mixed gas was introduced into the bottle for 10 min and then sealed with a butyl rubber stopper and an aluminum cap.

[0044] (3) Using a blood collection needle in a clean bench to connect the DvH bacterial solution and the nZVI anaerobic bottle, and introducing a N2-CO2 mixed gas 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 0.1 g / L standard SMX solution, and 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 away from light, and take samples at regular intervals;

[0046] In this embodiment, the SO4 2- The content is Na2SO4 concentration 1.48g / L;

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

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

[0049] In this embodiment, the incubator temperature 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] Embodiment 2:

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

[0053] (1) The culture medium and sterilization method were prepared in the same manner as in step (1) of Example 1 above. 2 ml of the mixed SRB cultured in the Pearl River sediment (M-SRB) solution was inoculated into 50 ml of the culture medium and then placed in a 36° C. incubator for 24-36 h to obtain a highly active bacterial solution.

[0054] (2) The same method as step (2) of Example 1 above for weighing and preparing sterile nZVI;

[0055] (3) Using a blood collection needle in a clean bench to connect the DvH bacterial solution and the nZVI anaerobic bottle, and introducing a N2-CO2 mixed gas 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 0.1 g / L standard SMX solution, and 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 away from light, and take samples at regular intervals;

[0057] In this embodiment, the SO4 2- The content is Na2SO4 concentration 1.48g / L;

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

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

[0060] In this embodiment, the incubator temperature 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) The culture medium and sterilization method are the same as step (1) in Example 1 above;

[0064] (2) The same method as step (2) of Example 1 above for weighing and preparing sterile nZVI;

[0065] (3) Using a blood collection needle in a clean bench to connect the sterile culture medium and the nZVI anaerobic bottle, and introducing N2-CO2 mixed gas into the sterile culture medium to transfer the sterile culture medium into the nZVI anaerobic bottle, and after mixing the two, obtaining unmodified nano zero-valent iron material (nZVI);

[0066] Example 3

[0067] Material characterization of the process of removing sulfamethoxazole (SMX) from water by pure Desulfovibrio vulgaris Hildenborough (DvH) bacteria and mixed SRB bacteria (M-SRB) cultured in the Pearl River sediment 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 at diffraction angles of 5°-90° show that there are additional FeS peaks in the XRD spectra of D-nZVI and M-nZVI materials, which can indicate that the coupling modification of DvH and M-SRB with nZVI is successful, and the surface modification of the composite material loads sulfide iron compounds, which increases the reactivity and electron selectivity of nZVI.

[0069] There are many diffraction peaks of iron oxides and ferrous sulfides in the XRD spectrum of nZVI materials, which proves that nZVI can generate Fe by reacting with H2O in the culture medium without biological influence. 2+ , Fe 3+ plasma, and the pollutants were oxidized and degraded by Fenton reaction; and additional sulfide iron compound peaks appeared in D-nZVI and M-nZVI materials, indicating that in the system of DvH and M-SRB coupled with nZVI, Fe 2+ / Fe 3+ The combination of ions and sulfur elements is richer, and the coupling system promotes the sulfidation modification of nZVI; in the growth system of sulfate-reducing bacteria, microorganisms from SO4 2- and SO4 2- After nZVI is added to the system, the generated iron ions are easily reduced to S 2-The reaction generates FeS, which exists in the solution. The generated FeS can be dissolved in the solvent, loaded on the surface of nZVI, or assisted in degradation after adding SMX.

[0070] as follows Figure 3 As shown in the SEM image of the D-nZVI material, the nZVI particles were successfully coated on the surface of the DvH bacterial cells, forming a new system of bacteria-nZVI particles-surface sulfur-modified compounds, and the successfully modified D-nZVI material was obtained;

[0071] Example 4

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

[0073] as follows Figure 4 The mass spectra of the intermediate products of SMX in water removed by D-nZVI and M-nZVI show that small molecular fragments of SMX appear in the system, proving that after D-nZVI and M-nZVI 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 As shown in the decomposition pathway diagram of SMX removal by sulfate-reducing bacteria-modified nano zero-valent iron material (SRB-nZVI), the difference between the two degradation pathways is mainly the incomplete cleavage of the CS bond. The effect of another part of biological modification of nZVI and coupling with SMX is reflected in the cleavage of the NO bond of the isopentazole ring, which can degrade the isopentazole ring into smaller molecular products, promoting the complete removal of SMX in the water environment;

[0075] Example 5

[0076] Removal effect of D-nZVI and M-nZVI on SMX in water

[0077] like Figure 6 The comparison of the SMX removal effect of sulfate-reducing bacteria modified nano zero-valent iron materials (SRB-nZVI) under different S / Fe conditions shows that, under the coupling of DvH and M-SRB with nZVI, within 420 minutes, the degradation rate of SMX by the D-nZVI system under different S / Fe conditions was higher than that of the nZVI system, indicating that the presence of DvH can indeed promote the degradation of SMX by nZVI. The degradation rate and degradation rate of M-nZVI at S / Fe = 0.5 within 420 minutes were higher than those of the nZVI system, indicating that for nZVI modified by mixed bacteria M-SRB, there is a suitable S / Fe that promotes the degradation of SMX by the M-nZVI material;

[0078] like Figure 6 As shown, within 420 minutes, the degradation rate of SMX by the D-nZVI system was nearly 75%, and the degradation rate of SMX by the M-nZVI system was 51%. The main reason is that the bacterial species in the D-nZVI system and the M-nZVI system are different. The bacterial species in the D-nZVI system are pure DvH bacteria, and the bacterial species in the M-nZVI system are mixed SRB bacteria cultured in the Pearl River sediment. In the process of acclimating the sediment, only SRB in the M-SRB mixed bacteria can be guaranteed to be in a dominant position. At the same time, the sulfate reduction efficiency of the SRB strains obtained by acclimating the M-SRB mixed bacteria is unknown, resulting in a lower sulfate reduction efficiency than that of the DvH pure bacteria in the short-term reaction with SMX. Therefore, within 420 minutes, the degradation rate and degradation rate of SMX by the M-nZVI system are slightly lower than those of the D-nZVI system.

[0079] This embodiment proves that there is a material of nano-zero-valent iron modified by sulfate-reducing bacteria, which has a higher degradation rate and degradation rate for the degradation of SMX in water. The material is obtained by sulfidation modification of nZVI by pure sulfate-reducing bacteria DvH.

[0080] The present invention utilizes sulfate-reducing bacteria (SRB) and sterilized nano zero-valent iron (nZVI) to obtain a biosulfur-modified nano zero-valent iron material (SRB-nZVI) for mixed modification, thereby achieving the removal of sulfamethoxazole (SMX) in water. The preparation process of the method is simpler and more environmentally friendly, the treatment cycle is short, and the treatment effect is good. The sulfate-reducing bacteria-modified nano zero-valent iron (SRB-nZVI) system can effectively remove SMX in water, and the removal rate and removal efficiency are both higher than those before nZVI modification, and the final removal rate can reach more than 93%.

[0081] Finally, a few points should be explained: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, which may refer to mechanical connection or electrical connection, or internal communication between two components, or direct connection. "upper", "lower", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may change;

[0082] Secondly: In the drawings of the embodiments disclosed in the present invention, only the structures related to the embodiments disclosed in the present invention are involved, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other;

[0083] Finally: 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 in the protection scope of the present invention.

Claims

1. A method for preparing sulfate-reducing bacteria-modified nano zero-valent iron, characterized in that: The specific preparation steps are as follows: Step S1: prepare a sulfate-reducing bacteria culture medium and store it in an anaerobic bottle, seal it with a butyl rubber stopper and an aluminum cap, and then sterilize it by high pressure. The culture medium is inoculated with SRB bacteria and then placed in an incubator for cultivation; Step S2: sterilizing nano-zero-valent iron with a particle size of 50 nm in an anaerobic bottle under high pressure; Step S3: In a sterile environment, the SRB bacterial solution and nZVI are mixed to obtain the sulfate-reducing bacteria-modified nano zero-valent iron material.

2. The method for preparing sulfate-reducing bacteria-modified nano zero-valent iron according to claim 1, characterized in that: The SRB culture medium in step S1 is prepared by the following method: It was prepared using the SRB medium formula, and the pH was adjusted to 7 using H3PO4, and N2-CO2 mixed gas was passed through for 10 minutes, and then sealed with a butyl rubber stopper and an aluminum cap; The high pressure sterilization in step S1 is carried out by the following method: Use an autoclave to sterilize at 120°C for 30 minutes; In step S1, the inoculation culture is performed by the following method: 4% SRB bacterial solution was injected into the culture medium with a syringe and then placed in a 36°C incubator for 24-36 hours to obtain a highly active bacterial solution.

3. The method for preparing sulfate-reducing bacteria-modified nano zero-valent iron according to claim 1, characterized in that: In step S2: nZVI placed in anaerobic bottles: Based on the sulfur molar mass in the culture medium, nZVI with S / Fe=0.1, 0.3, and 0.5 were weighed and placed in a completely dry anaerobic bottle. The bottle was filled with N2-CO2 mixed gas for 10 minutes and then sealed with a butyl rubber stopper and an aluminum cap. Autoclave sterilization is performed by: Use an autoclave to sterilize at 120°C for 30 min.

4. The method for preparing sulfate-reducing bacteria-modified nano zero-valent iron 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 a N2-CO2 mixed gas was introduced into the SRB to transfer the SRB bacterial solution into the nZVI anaerobic bottle.

5. A sulfate-reducing bacteria-modified nano zero-valent iron, characterized in that: The invention is prepared by the method for preparing nano zero-valent iron modified by sulfate-reducing bacteria as described in any one of claims 1 to 4.

6. A method for removing sulfamethoxazole from water using the sulfate-reducing bacteria-modified nano zero-valent iron according to claim 5, characterized in that: Sulfamethoxazole was injected into SRB-nZVI, and the reaction was carried out at room temperature.

7. The method for removing sulfamethoxazole from water by using sulfate-reducing bacteria-modified nano-zero-valent iron according to claim 6, characterized in that: The initial concentration obtained after injecting SMX is 2-10 mg / L, and the reaction temperature is 25°C-36°C.

Images