Preparation method and application of zero-valent iron composite material based on biological sulfidation and sulfur-nitrogen co-modification

Abstract

The application relates to a preparation method of a sulfur and nitrogen co-modified zero-valent iron composite material based on biological sulfuration, specifically as follows: an anaerobic sterilization is performed on a sulfate-reducing bacteria culture medium to obtain sterilized culture solution; the sterilized culture solution and nitrogen-modified zero-valent iron are mixed, and then sulfate-reducing bacteria are inoculated to perform microbial sulfuration culture in an anaerobic environment to obtain a microbial composite material; and the microbial composite material is centrifuged, washed and dried in ethanol in an inert gas atmosphere to obtain the sulfur and nitrogen co-modified zero-valent iron composite material. The sulfate-reducing bacteria and the nitrogen-modified zero-valent iron are jointly cultured in the culture medium, and finally the sulfur and nitrogen co-modified zero-valent iron is obtained, the preparation process is simple and efficient, the cost is low, the environment is friendly, and the sulfur and nitrogen co-modified zero-valent iron can be widely applied to the preparation of the sulfur and nitrogen co-modified zero-valent iron.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for preparing and applying a sulfur and nitrogen co-modified zero-valent iron composite material based on biosulfurization. Background Technology

[0002] With the acceleration of industrialization and urbanization, the pollution situation of chlorinated hydrocarbons in groundwater is becoming increasingly serious. Groundwater in many places is polluted to varying degrees, and the scope of pollution is constantly expanding. Therefore, the prevention and control of chlorinated hydrocarbon pollution in groundwater of contaminated sites is urgent.

[0003] Since groundwater always contains various anions and sulfate-reducing bacteria, adding biofriendly iron-based materials to the groundwater for biosulfation to generate FeS can be considered, promoting the degradation of chlorinated hydrocarbons in the groundwater. Zero-valent iron (ZVI) has attracted widespread attention due to its advantages such as large specific surface area, high reactivity, few intermediate products, and environmental friendliness. However, ZVI is prone to aggregation and passivation, leading to reduced mobility and reactivity, thus limiting the large-scale application of ZVI technology. Iron nitride, on the other hand, with its high corrosion resistance and catalytic performance, can significantly improve the reactivity and selectivity of ZVI technology; therefore, zero-valent iron nitride shows promising application prospects in groundwater bioremediation. Summary of the Invention

[0004] To address the problem of the difficulty in biodegrading chlorinated olefins in groundwater, this invention provides a simple, pollution-free, and highly stable method for preparing and applying a sulfur- and nitrogen-modified zero-valent iron composite material based on biosulfurization. The specific technical solution is as follows:

[0005] A method for preparing a sulfur and nitrogen co-modified zero-valent iron composite material based on bio-sulfurization, the method specifically comprising:

[0006] The sulfate-reducing bacteria culture medium was anaerobically sterilized to obtain a sterile culture solution. The sterile culture solution was mixed with nitrogen-modified zero-valent iron and inoculated with sulfate-reducing bacteria. Microbial sulfurization culture was carried out in an anaerobic environment to obtain a microbial composite material. The microbial composite material was centrifuged, washed and dried in ethanol under an inert gas atmosphere to obtain a sulfur and nitrogen co-modified zero-valent iron composite material.

[0007] Further, the sulfate-reducing bacteria culture medium comprises the following components: KH2PO4: 0.5±0.05 g / L, NH4Cl: 1±0.05 g / L, CaCl2: 0.08±0.005 g / L, MgSO4·7H2O: 1.1±0.1 g / L, sodium DL-lactic acid: 2±0.1 g / L, sodium thioglycolate: 0.1±0.01 g / L, yeast extract: 1±0.05 g / L, and vitamin C: 0.1±0.005 g / L.

[0008] Furthermore, the ratio of the sterilized culture medium to the nitrogen-modified zero-valent iron is such that the ratio of the amount of sulfate in the sterilized culture medium to the amount of nitrogen-modified zero-valent iron is 0.03-0.2:1.

[0009] Furthermore, the OD of the sulfate-reducing bacteria in the sterile culture medium... 600 The concentration is 0.01-0.1.

[0010] Furthermore, the conditions for the microbial sulfurization culture are: temperature 28-30℃, static culture, and culture time of 6-7 days.

[0011] Furthermore, the inert gas atmosphere is an argon atmosphere.

[0012] Application of the sulfur and nitrogen co-modified zero-valent iron composite material prepared by the above method in the remediation of groundwater containing chlorinated organic pollutants.

[0013] Furthermore, the chlorinated organic pollutant is at least one of trichloroethylene and chloroform.

[0014] This invention involves co-culturing sulfate-reducing bacteria and nitrogen-modified iron in a culture medium to obtain sulfur- and nitrogen-modified zero-valent iron. The preparation process is simple, efficient, low-cost, and environmentally friendly, and can be widely used in the preparation of sulfur- and nitrogen-modified zero-valent iron. Attached Figure Description

[0015] Figure 1 The X-ray diffraction (XRD) spectrum of the iron-based material prepared in this invention;

[0016] Figure 2 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the S2p layer of the iron-based material prepared in this invention.

[0017] Figure 3 This is a degradation diagram of the culture medium with S / Fe = 0.05 during the preparation of iron-based materials in this invention; where: (A) represents SO42-. 2- The degradation diagram, (B) is S 2- The generated diagram, (C) is Fe 2+ The generated graph;

[0018] Figure 4 This is a degradation diagram of the culture medium with S / Fe = 0.1 during the preparation of iron-based materials in this invention; where: (A) represents SO42-. 2- The degradation diagram, (B) is S 2- The generated diagram, (C) is Fe 2+ The generated graph;

[0019] Figure 5The diagram shows the degradation effect of the iron-based material prepared in this invention during the degradation of trichloroethylene; where: SN-ZVI represents the sulfur-nitrogen-modified zero-valent iron material prepared in Example 1, and N-ZVI represents the nitrogen-modified zero-valent iron material prepared in Comparative Example 1;

[0020] Figure 6 The diagram shows the degradation effect of the iron-based material prepared in this invention during the degradation of chloroform; where: SN-ZVI represents the sulfur-nitrogen-modified zero-valent iron material prepared in Example 1, and N-ZVI represents the nitrogen-modified zero-valent iron material prepared in Comparative Example 1;

[0021] Figure 7 The diagram shows the degradation effect of the iron-based material prepared in this invention during the degradation of trichloroethylene; where: SN-ZVI represents the sulfur-nitrogen-modified zero-valent iron material prepared in Example 2, and N-ZVI represents the nitrogen-modified zero-valent iron material prepared in Comparative Example 2;

[0022] Figure 8 The diagram shows the degradation effect of the iron-based material prepared in this invention during the degradation of chloroform; where: SN-ZVI represents the sulfur-nitrogen-modified zero-valent iron material prepared in Example 2, and N-ZVI represents the nitrogen-modified zero-valent iron material prepared in Comparative Example 2. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings to provide a better understanding of the technical solution.

[0024] Example 1: Preparation of zero-valent iron co-modified with sulfur and nitrogen

[0025] Under anaerobic conditions, the culture medium was aliquoted into 100 mL serum bottles, each containing 55 mL of 1.1 g / L SO42-. 2- The culture medium was autoclaved at 121℃ for 15 min, cooled to room temperature, and placed in a glove box. 0.3 g of nitrogen-modified zero-valent iron was placed in the sterilized culture medium, and 5 mL of centrifuged and resuspended bacterial solution was added. After culturing for 6 days, the medium was washed with ethanol in an inert gas atmosphere and dried in a glove box to obtain sulfur and nitrogen co-modified zero-valent iron material SN-ZVI ([S / Fe]=0.05) with a sulfur to iron molar ratio of 0.05.

[0026] Example 2: Preparation of zero-valent iron co-modified with sulfur and nitrogen

[0027] Under anaerobic conditions, the culture medium was aliquoted into 100 mL serum bottles, each containing 55 mL of 2.2 g / L SO42-. 2-The culture medium was autoclaved at 121℃ for 15 min, cooled to room temperature, and placed in a glove box. 0.3 g of nitrogen-modified zero-valent iron was placed in the sterilized culture medium, and 5 mL of centrifuged and resuspended bacterial solution was added. After culturing for 6 days, the mixture was washed with ethanol in an inert gas atmosphere and dried in a glove box. This yielded SN-ZVI ([S / Fe] = 0.1), a sulfur-nitrogen co-modified zero-valent iron material with a sulfur-to-iron molar ratio of 0.1.

[0028] Comparative Example 1: Preparation of nitrogen-modified zero-valent iron

[0029] Under anaerobic conditions, the culture medium was aliquoted into 100 mL serum bottles, each containing 55 mL of 1.1 g / L SO42-. 2- The culture medium was autoclaved at 121℃ for 15 min, cooled to room temperature, and placed in a glove box. 0.3 g of nitrogen-modified zero-valent iron was placed in the sterilized culture medium and cultured for 6 days. After 6 days, the medium was washed with ethanol in an inert gas atmosphere and dried in a glove box to obtain nitrogen-modified zero-valent iron material (N-ZVI, [S / Fe]=0.05).

[0030] Comparative Example 2: Preparation of Nitrogen-Modified Zero-Valence Iron

[0031] Under anaerobic conditions, the culture medium was aliquoted into 100 mL serum bottles, each containing 55 mL of 2.2 g / L SO42-. 2- The culture medium was autoclaved at 121℃ for 15 min, cooled to room temperature, and placed in a glove box. 0.3 g of nitrogen-modified zero-valent iron was placed in the sterilized culture medium and cultured for 6 days. After culturing, the medium was washed with ethanol in an inert gas atmosphere and dried in a glove box to obtain nitrogen-modified zero-valent iron material (N-ZVI, [S / Fe]=0.1).

[0032] The materials obtained in Examples 1-2 and Comparative Examples 1-2 were washed with anaerobic ethanol, dried in a glove box for 72 hours, ground, and collected in sample bottles for later use.

[0033] The XRD patterns of the samples prepared in Example 1 and Comparative Example 1 are shown below. Figure 1 As shown, the SN-ZVI particles prepared in Example 1 contain FeS and Fe3N on their surface, indicating that ferrous sulfide was successfully generated during the biosulfidation process. The N-ZVI particles prepared in Comparative Example 1 still retain some Fe3N on their surface, indicating that the biosulfidation process does not result in the complete loss of ferric nitride.

[0034] Further analysis of the elemental distribution of the materials was conducted. XPS was used to study the elemental distribution in the SN-ZVI prepared in Example 1 and the N-ZVI prepared in Example 1. Figure 2 As shown, S exists on the surface of the SN-ZVI prepared in Example 1.2- With S n 2- This indicates the presence of polysulfides within the material.

[0035] Monitoring of the biosulfurization process of SN-ZVI revealed that, regardless of whether S / Fe = 0.05 or S / Fe = 0.1, the SO4 content in the system... 2- It is consumed, and its consumption rate is similar to that of a reaction system with only bacteria added, S 2- The amount of SO4 generated 2- The consumption is basically conserved during the reaction process, Fe 2+ The small amount of [acid] produced indicates that polysulfides are generated during the reaction. Figure 3 , Figure 4 ).

[0036] Application Example 1: The effect of sulfur and nitrogen co-modified zero-valent iron on the removal of trichloroethylene from groundwater

[0037] Add 26 mL of buffer solution to each of the two 52 mL serum bottles, then add 0.26 g of SN-ZVI prepared in Example 1 and 0.26 g of N-ZVI prepared in Comparative Example 1, respectively. Add 19 μL of 17.9 g / L TCE solution to each bottle to make the initial concentration 100 μM. Finally, place the serum bottles in a 25 °C constant temperature incubator and place them on a rotating incubator with a rotation speed of n = 30 rpm for continuous and thorough mixing reaction.

[0038] At the designed sampling time point, 100 μL of headspace gas from the serum vial was drawn using a syringe and injected into the GC-FID. The TCE concentration in the serum vial at that sampling time point was measured. The experimental results are as follows: Figure 5 As shown in the figure, linear fitting revealed that the degradation rate of SN-ZVI with a [S / Fe] ratio of 0.05 was 1.94 times that of N-ZVI. This indicates that sulfur and nitrogen co-modification of zero-valent iron can significantly improve the removal efficiency of TCE.

[0039] Application Example 2: The effect of sulfur and nitrogen co-modified zero-valent iron on the removal of chloroform from groundwater

[0040] Add 26 mL of buffer solution to each of the two 52 mL serum bottles, then add 0.26 g of SN-ZVI prepared in Example 1 and 0.26 g of N-ZVI prepared in Comparative Example 1, respectively. Add 21 μL of 14.85 g / L CF solution to each bottle to make the initial concentration 100 μM. Finally, place the serum bottles in a 25 °C constant temperature incubator and place them on a rotating incubator with a rotation speed of n = 30 rpm for continuous and thorough mixing reaction.

[0041] At the designed sampling time point, 100 μL of headspace gas from the serum vial was drawn using a syringe and injected into the GC-FID. The CF concentration in the serum vial at that sampling time point was measured. The experimental results are as follows: Figure 6 As shown in the figure, linear fitting revealed that the degradation rate of SN-ZVI with a [S / Fe] ratio of 0.05 was 5.26 times that of N-ZVI. This indicates that sulfur and nitrogen co-modification of zero-valent iron can significantly improve the removal efficiency of CF.

[0042] Application Example 3: The effect of sulfur and nitrogen co-modified zero-valent iron on the removal of trichloroethylene from groundwater

[0043] Add 26 mL of buffer solution to each of the two 52 mL serum bottles, then add 0.26 g of SN-ZVI prepared in Example 2 and 0.26 g of N-ZVI prepared in Comparative Example 2, respectively. Add 19 μL of 17.9 g / L TCE solution to each bottle to make the initial concentration 100 μM. Finally, place the serum bottles in a 25 °C constant temperature incubator and place them on a rotating incubator with a rotation speed of n = 30 rpm for continuous and thorough mixing reaction.

[0044] At the designed sampling time point, 100 μL of headspace gas from the serum vial was drawn using a syringe and injected into the GC-FID. The TCE concentration in the serum vial at that sampling time point was measured. The experimental results are as follows: Figure 7 As shown in the figure, linear fitting revealed that the degradation rate of SN-ZVI with a [S / Fe] ratio of 0.1 was 2.6 times that of N-ZVI. This indicates that sulfur and nitrogen co-modification of zero-valent iron can significantly improve the removal efficiency of TCE.

[0045] Application Example 4: The effect of sulfur and nitrogen co-modified zero-valent iron on the removal of chloroform from groundwater

[0046] Add 26 mL of buffer solution to each of the two 52 mL serum bottles, then add 0.26 g of SN-ZVI prepared in Example 2 and 0.26 g of N-ZVI prepared in Comparative Example 2, respectively. Add 21 μL of 14.85 g / L CF solution to each bottle to make the initial concentration 100 μM. Finally, place the serum bottles in a 25 °C constant temperature incubator and place them on a rotating incubator with a rotation speed of n = 30 rpm for continuous and thorough mixing reaction.

[0047] At the designed sampling time point, 100 μL of headspace gas from the serum vial was drawn using a syringe and injected into the GC-FID. The CF concentration in the serum vial at that sampling time point was measured. The experimental results are as follows: Figure 8 As shown in the figure, linear fitting revealed that the degradation rate of SN-ZVI with a [S / Fe] ratio of 0.1 was 4.9 times that of N-ZVI. This indicates that sulfur and nitrogen co-modification of zero-valent iron can significantly improve the removal efficiency of CF.

Claims

1. A method for preparing a sulfur and nitrogen co-modified zero-valent iron composite material based on bio-sulfurization, characterized in that... The method is as follows: Sulfate-reducing bacteria culture medium was anaerobically sterilized to obtain a sterile culture solution. The sterile culture solution was mixed with nitrogen-modified zero-valent iron and inoculated with sulfate-reducing bacteria. Microbial sulfurization culture was carried out in an anaerobic environment to obtain a microbial composite material. The ratio of the sterile culture solution to nitrogen-modified zero-valent iron was such that the amount of sulfate in the sterile culture solution was 0.03-0.2:

1. Under an inert gas atmosphere, the microbial composite material was centrifuged, washed, and dried in ethanol to obtain a sulfur and nitrogen co-modified zero-valent iron composite material. The surface of the obtained composite material contained FeS and Fe3N.

2. The preparation method of a sulfur and nitrogen co-modified zero-valent iron composite material based on bio-sulfurization as described in claim 1, characterized in that... The sulfate-reducing bacteria culture medium comprises the following components: KH₂PO₄: 0.5±0.05 g / L, NH₄Cl: 1±0.05 g / L, CaCl₂: 0.08±0.005 g / L, MgSO₄·7H₂O: 1.1±0.1 g / L, sodium DL-lactic acid: 2±0.1 g / L, sodium thioglycolate: 0.1±0.01 g / L, yeast extract: 1±0.05 g / L, and vitamin C: 0.1±0.005 g / L.

3. The preparation method of a sulfur and nitrogen co-modified zero-valent iron composite material based on bio-sulfurization as described in claim 1, characterized in that... The sulfate-reducing bacteria in sterile culture medium OD 600 The concentration is 0.01-0.

1.

4. The preparation method of a sulfur and nitrogen co-modified zero-valent iron composite material based on bio-sulfurization as described in claim 1, characterized in that... The conditions for the microbial sulfurization culture are: temperature 28-30℃, static culture, and culture time of 6-7 days.

5. The method for preparing a sulfur and nitrogen co-modified zero-valent iron composite material based on bio-sulfurization as described in claim 1, characterized in that... The inert gas atmosphere is an argon atmosphere.

6. The application of the sulfur and nitrogen co-modified zero-valent iron composite material prepared by any one of the preparation methods described in claims 1-5 in the remediation of groundwater containing chlorinated organic pollutants.

7. The application as described in claim 6, characterized in that, The chlorinated organic pollutant is at least one of trichloroethylene and trichloromethane.

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