A biological preparation method for zero-valent iron sulfide and its application

Abstract

The present invention discloses a biological preparation method of zero-valent iron sulfide and its application. The beneficial effects of the present invention are as follows: the preparation method of the present invention uses Geobacter sulfurreducens to prepare zero-valent iron sulfide. Geobacter sulfurreducens can reduce and remove the oxide on the surface of zero-valent iron on the one hand, and can accelerate the reaction of elemental sulfur and zero-valent iron on the other hand, so that the preparation method of the present invention has the advantages of fast reaction speed, high reaction efficiency, mild reaction conditions, and no energy consumption; in addition, the preparation method of the present invention uses elemental sulfur and zero-valent iron as reaction raw materials, the raw materials are rich in source, cheap and easy to obtain, low in cost, no pollution to the environment, and no need to consume a lot of energy, which is suitable for large-scale industrial production. In addition, the content of sulfur coated on the surface of zero-valent iron sulfide prepared by the preparation method of the present invention is high, the removal rate of Cr(VI) is high, and the removal speed is fast.

Description

Technical Field

[0001] The invention belongs to the field of material preparation, and specifically relates to a biological preparation method of zero-valent iron sulfide and application thereof. Background Art

[0002] Zero-valent iron is a powerful reducing agent with active chemical properties, low cost and low environmental toxicity. It is widely used to degrade and remove pollutants such as halogenated organic matter and heavy metals in the environment. Although it has many advantages, it also has the disadvantage of poor electron selectivity, that is, electrons tend to transfer to water molecules rather than pollutants, which greatly reduces its ability to remove pollutants in practical water treatment applications. In order to improve the application potential of zero-valent iron in water environments, sulfide modification has become a research hotspot in recent years. Sulfided zero-valent iron is a modified material with sulfide doped on the surface of zero-valent iron. The hydrophobic and semiconductor properties of sulfide can significantly improve the electron selectivity of zero-valent iron and increase the degradation and removal rate of pollutants, thereby greatly improving the life of zero-valent iron in water treatment and its pollutant treatment capacity.

[0003] At present, the preparation methods of zero-valent iron sulfide are mainly divided into two directions, chemical method and mechanical method. Among them, the chemical method mainly uses chemical reagents such as sodium sulfide and morpholineethanesulfonic acid to react with the ferrous ions released by zero-valent iron in water to generate ferrous sulfide, or to promote the reaction of elemental sulfur with zero-valent iron to produce zero-valent iron sulfide. However, the chemical reagents used in the chemical method are not easy to store and transport, are harmful to organisms, or are expensive, which is not conducive to large-scale application. The mechanical method prepares zero-valent iron sulfide by mixing and grinding elemental sulfur powder and zero-valent iron in a planetary ball mill. This method has high requirements for equipment and consumes a lot of energy, increasing production costs. Summary of the invention

[0004] In order to overcome the problems existing in the prior art, one of the objectives of the present invention is to provide a biological preparation method of zero-valent iron sulfide.

[0005] A second object of the present invention is to provide a biological preparation method of zero-valent iron sulfide for use in the field of pollutant removal.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides a biological preparation method for zero-valent iron sulfide, comprising the following steps: mixing elemental sulfur, zero-valent iron and Geobacter sulfur-reducing to obtain the product.

[0008] In the present invention, Geobacter sulfurreducens can reduce the iron oxide on the surface of zero-valent iron and has an extracellular electron transfer function. In the reaction, the oxide layer on the surface of zero-valent iron will be reduced and dissolved by Geobacter sulfurreducens, so that the zero-valent iron contacts with elemental sulfur and undergoes a surface electrochemical reaction, thereby generating ferrous sulfide wrapped on the surface of the zero-valent iron. In addition, in the reaction between zero-valent iron and elemental sulfur, Geobacter sulfurreducens will also accelerate the electron transfer between the two, thereby accelerating this reaction, and ultimately achieving efficient preparation of zero-valent iron sulfide.

[0009] Preferably, the mixing reaction step is carried out under anaerobic conditions. The presence of oxygen will inhibit the activity of Geobacter sulfurreducens, thereby reducing the reaction rate. In addition, oxygen will also cause oxides to form on the surface of zero-valent iron, thereby isolating the contact between elemental sulfur and zero-valent iron, further reducing the reaction rate and reaction possibility of the two.

[0010] Preferably, the temperature of the mixed reaction is 20-40°C; more preferably, the temperature of the mixed reaction is 30-35°C.

[0011] Preferably, the mixing reaction time is 1-4 h; further preferably, the mixing reaction time is 1-2 h; further preferably, the mixing reaction time is 1 to 1.5 h.

[0012] Preferably, the molar ratio of the elemental sulfur to zero-valent iron is (0-1):1, and the elemental sulfur is not 0; further preferably, the molar ratio of the elemental sulfur to zero-valent iron is (0.01-1):1; further preferably, the molar ratio of the elemental sulfur to zero-valent iron is (0.05-0.2):1.

[0013] Preferably, in the mixing reaction step, the concentration of zero-valent iron is 0.01 to 0.4 g / mL; further preferably, in the mixing reaction step, the concentration of zero-valent iron is 0.1 to 0.2 g / mL.

[0014] Preferably, the Geobacter sulfurreducens is a strain in logarithmic growth phase.

[0015] Preferably, in the mixing reaction step, the OD of the bacterial solution of Geobacter sulfurreducens is 600 The value is 0.1~0.7.

[0016] Preferably, the preparation method further comprises a purification step after the mixing reaction step; the purification step comprises: taking out the product zero-valent iron sulfide with a magnet, washing it and freeze-drying it.

[0017] The second aspect of the present invention provides the application of the biological preparation method of zero-valent iron sulfide provided by the first aspect of the present invention in the field of pollutant removal.

[0018] Preferably, the pollutants include organic pollutants and inorganic pollutants.

[0019] Preferably, the organic pollutants include at least one of halogenated hydrocarbons, nitroaromatic hydrocarbons, dyes, drugs, and flame retardants.

[0020] Preferably, the inorganic pollutants include Cu 2+ 、Ni 2+ 、Zn 2+ 、Cd 2+ 、As 3+ Cr 6+ , Pb 2+ , Mn 2+ , U 6+ , 99 Tc, Se 6+ , Sb 3+ 、NO 3- At least one of .

[0021] The beneficial effects of the present invention are as follows: the preparation method of the present invention uses Geobacter sulfurreducens to prepare sulfide zero-valent iron. Geobacter sulfurreducens can reduce and remove the oxide on the surface of zero-valent iron on the one hand, and can accelerate the reaction of elemental sulfur and zero-valent iron on the other hand, so that the preparation method of the present invention has the advantages of fast reaction speed, high reaction efficiency, mild reaction conditions, and no energy consumption; in addition, the preparation method of the present invention uses elemental sulfur and zero-valent iron as reaction raw materials, the raw materials are abundant in source, cheap and easy to obtain, low in cost, no pollution to the environment, and no need to consume a lot of energy, which is suitable for large-scale industrial production. In addition, the content of sulfur coated on the surface of the sulfide zero-valent iron prepared by the preparation method of the present invention is high, the removal rate of Cr(VI) is high, and the removal speed is fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a test chart of the vulcanization efficiency when prepared by the preparation method in Example 1 and Comparative Example 1.

[0023] Figure 2 These are SEM and EDS test images of the sulfided zero-valent iron prepared in Example 1 and Comparative Example 1 and the original zero-valent iron.

[0024] Figure 3 The electrochemical corrosion performance test diagram of the sulfided zero-valent iron prepared in Example 1 and Comparative Example 1 and the original zero-valent iron.

[0025] Figure 4 The particle size distribution test diagram of the sulfided zero-valent iron prepared in Example 1 and Comparative Example 1 and the original zero-valent iron.

[0026] Figure 5The specific surface area and porosity test diagram of the sulfided zero-valent iron in Example 1 and Comparative Example 1 and the original zero-valent iron.

[0027] Figure 6 The test graph shows the Cr(VI) removal rate of the sulfided zero-valent iron prepared in Example 1 and Comparative Example 1 and the original zero-valent iron. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

[0029] In Example 1 of the present invention, the Geobacter sulfurreducens in the logarithmic growth phase refers to OD 600 Bacterial solution when the value is 0.5.

[0030] In Comparative Example 1 of the present invention, the sulfate-reducing bacteria in the logarithmic growth phase refer to OD 600 Bacterial solution when the value is 0.5.

[0031] Example 1

[0032] This example provides a biological preparation method for zero-valent iron sulfide, and the preparation steps are as follows:

[0033] Under anaerobic and room temperature conditions, the purchased Geobacter sulfurreducens was cultured in the culture medium shown in Table 1 until the Geobacter sulfurreducens was in the logarithmic growth phase. The formula of the inorganic salt composition in Table 1 is shown in Table 2, the formula of the trace element composition in Table 1 is shown in Table 3, and the formula of the vitamin composition in Table 1 is shown in Table 4. 400 mg of zero-valent iron powder (400 mesh, 98%), a certain amount of sublimated sulfur powder (S / Fe substance ratio of 0.1) and 1.8 mL of Geobacter sulfurreducens were placed in a 2 mL centrifuge tube, and the centrifuge tube was placed on a rolling mixer with a rotation speed of 80 rpm for reaction for 2 hours. The material in the mixed solution was taken out with a magnet, and then washed with deionized water and freeze-dried to obtain dry sulfide zero-valent iron.

[0034] Table 1 Culture medium formula used for Geobacter sulfurreducens

[0035]

[0036]

[0037] Table 2 Formula of inorganic salt composition

[0038] Components concentration <![CDATA[KH 2 PO 4 (≥99.5%, Zhiyuan, Tianjin)]]> 42g / L <![CDATA[K 2 HPO 4 (≥99.0%, Zhiyuan, Tianjin)]]> 22g / L <![CDATA[NH 4 Cl(≥99.5%, Damao, Tianjin)]]> 20g / L KCl (≥99.8%, Damao, Tianjin) 38g / L NaCl (≥99.5%, Zhiyuan, Tianjin) 36g / L

[0039] Table 3 Formula of trace element composition

[0040] Components concentration Sodium nitrilotriacetate 1.5g / L <![CDATA[MnCl 2 ·4H 2 O(≥99.0%, Zhiyuan, Tianjin)]]> 0.1g / L <![CDATA[FeSO 4 7H 2 O(≥99.0%, Zhiyuan, Tianjin)]]> 0.3g / L <![CDATA[CoCl 2 6H 2 O(≥99.0%, Damao, Tianjin)]]> 0.17g / L <![CDATA[ZnSO 4 7H 2 O(≥99.5%, Zhiyuan, Tianjin)]]> 0.2g / L <![CDATA[CuCl 2 ·2H 2 O(≥99.8%,McLean)]]> 0.03g / L <![CDATA[AlK(SO 4 ) 2 12H 2 O(≥99.0%,Aladdin)]]> 0.005g / L <![CDATA[H 3 BO 3 (≥99.5%, Zhiyuan, Tianjin)]]> 0.005g / L <![CDATA[Na 2 MnO 4 ·2H 2 O(≥99.5%, Damao, Tianjin)]]> 0.09g / L <![CDATA[NiSO 4 6H 2 O(≥98.5%, Zhiyuan, Tianjin)]]> 0.11g / L <![CDATA[Na 2 WO 4 ·2H 2 O(≥99.5%, Aladdin)]]> 0.02g / L

[0041] Table 4 Formula of vitamin composition

[0042]

[0043]

[0044] Comparative Example 1

[0045] This example provides a biological preparation method for zero-valent iron sulfide, and the preparation steps are as follows:

[0046] Under anaerobic and room temperature conditions, the purchased sulfate-reducing bacteria (Desulfovibrio vulgaris Hildenborough) were cultured in the culture medium shown in Table 5 until the sulfate-reducing bacteria were in the logarithmic growth phase. 400 mg of zero-valent iron powder (400 mesh, 98%), a certain amount of sodium sulfate (the molar ratio of S / Fe was 0.1) and 1.8 mL of sulfate-reducing bacteria (Desulfovibrio vulgaris Hildenborough) were placed in a 2 mL centrifuge tube, and the centrifuge tube was placed on a rolling mixer at a speed of 80 rpm for 2 hours. The material in the mixed solution was removed with a magnet, and then washed with deionized water and freeze-dried to obtain dry sulfide zero-valent iron.

[0047] Table 5 Medium formula used for sulfate-reducing bacteria

[0048]

[0049]

[0050] Performance Testing:

[0051] (1) Vulcanization speed

[0052] The sulfurization efficiency during the preparation process was tested. The zero-valent iron sulfide particles prepared in Example 1 and Comparative Example 1 were digested with acid (the volume ratio of nitric acid to hydrochloric acid was 1:3) and then the S content of the zero-valent iron sulfide particles was measured using ICP-OES. The formula was then calculated: sulfurization efficiency = S content of the particles / total amount of S added*100%. The specific test results are as follows: Figure 1 As shown by Figure 1It can be seen that within 2 hours, the sulfurization efficiency of the preparation method in Example 1 has reached 98%, while the sulfurization efficiency of the preparation method in Comparative Example 1 is only 7%, indicating that compared with sulfate-reducing bacteria, the sulfurization speed of the present invention using Geobacter sulfurreducens has been greatly improved, further indicating that the preparation method of the present invention has the effects of fast reaction rate and short time consumption.

[0053] (2) SEM and EDS testing

[0054] The sulfide zero-valent iron and the original zero-valent iron prepared in Example 1 and Comparative Example 1 were analyzed by SEM and EDS respectively. The specific test results are as follows: Figure 2 As shown, Figure 2 (A1) is a SEM test image of the sulfided zero-valent iron obtained in Example 1; Figure 2 (B1) is a SEM test image of the sulfided zero-valent iron prepared in Comparative Example 1; Figure 2 (C1) is the SEM test image of the original zero-valent iron; Figure 2 (A2) is the EDS test graph of the sulfide zero-valent iron prepared in Example 1; Figure 2 (B2) is an EDS test graph of the sulfided zero-valent iron prepared in Comparative Example 1; Figure 2 (C2) is the original EDS test image of zero-valent iron; Figure 2 It can be seen that compared with the original zero-valent iron, the surface loading of S element on the zero-valent iron sulfide prepared in Comparative Example 1 and Example 1 is significantly increased. The surface loading of S element on the zero-valent iron sulfide prepared in Example 1 is large, while the surface loading of S element on the zero-valent iron sulfide prepared in Comparative Example 1 is relatively small, indicating that the surface loading of sulfur on the zero-valent iron sulfide prepared by the preparation method of the present invention is rich. Since the surface of the zero-valent iron sulfide prepared in Example 1 is covered by Geobacter sulfurreducens, the O content in its SEM image is very high, and it is impossible to see Figure 2 (A1) shows the S content, but from its EDS spectrum, Figure 2 (A2) It can be seen that the S content on the surface of zero-valent iron sulfide is very high.

[0055] (3) Electrochemical corrosion performance test

[0056] The sulfide zero-valent iron prepared in Example 1 and Comparative Example 1 and the original zero-valent iron were subjected to electrochemical corrosion tests. The specific test method is as follows: 10 mg of the sulfide zero-valent iron powder sample was weighed and dispersed in 1 mL of ultrapure water, and then 150 μL of 5% Nafion solution was added, and ultrasonicated for 5 minutes to form a uniform suspension. Then 5 μL of the suspension was dripped on the glassy carbon working electrode, dried at room temperature, and used as the working electrode (φ=2 mm) for testing. The test electrolyte was Na 2 SO 4 Solution (Na 2 SO4 The concentration is 0.50mmol / L, the pH is adjusted to 7.0), the auxiliary electrode is a platinum coil, the reference electrode is an Ag / AgCl electrode, the open circuit potential is scanned for 30min, and then the Tafel curve is measured. The scanning range is open circuit potential ±200mV, and the scanning rate is 1mV / s. The Tafel curve measured according to the above test method is as follows Figure 3 As shown in the figure, the measured corrosion potentials are: original zero-valent iron (-0.45V)>sulfurized zero-valent iron of comparative example 1 (-0.59V)>sulfurized zero-valent iron of example 1 (-0.67V). It can be seen that compared with the original zero-valent iron and the sulfided zero-valent iron prepared in comparative example 1, the corrosion potential of the sulfided zero-valent iron prepared in example 1 is greatly reduced, indicating that its ability to transmit electrons is improved, which is beneficial to the removal of pollutants.

[0057] (4) Particle size, specific surface area and porosity testing

[0058] The particle size, BET specific surface area and porosity of the sulfided zero-valent iron and the original zero-valent iron prepared in Example 1 and Comparative Example 1 were tested respectively. The particle size test results are as follows: Figure 4 The specific surface area and porosity test results are shown in Figure 5 The test results of average particle size, BET specific surface area and porosity are summarized in Table 6 below.

[0059] Table 6 Average particle size, BET specific surface area and porosity test results

[0060] Original zero-valent iron Comparative Example 1 Example 1 Average particle size (μm) 38.3 36.6 16.7 <![CDATA[BET specific surface area (m 2 / g)]]> 0.4250 1.4966 3.3617 <![CDATA[Porosity (cm 3 / g)]]> 0.000463 0.003857 0.009901

[0061] It can be seen from Table 6 that compared with the original zero-valent iron, the particle size of the zero-valent iron sulfide prepared in Example 1 is significantly reduced, and the porosity and specific surface area are increased, which gives the zero-valent iron sulfide material a larger reaction area and stronger adsorption capacity.

[0062] (5) Cr(VI) removal effect test

[0063] In an oxygen-free, room temperature environment, 50 mg of the original zero-valent iron, the sulfide zero-valent iron prepared in Example 1 and Comparative Example 1 were placed in 100 mL of K 2 Cr 2 O 7 The serum bottle of the solution was placed on a rolling mixer at a speed of 80 rpm for 1 hour, and then the Cr(VI) content in the mixed solution was tested and its removal rate was calculated. The calculation formula was: removal rate = C / C0*100%, C is the Cr(VI) content in the mixed solution after 1 hour of reaction, C0 is the Cr(VI) content in the mixed solution at 0 hours of reaction. The Cr(VI) removal rate test results measured according to the above test results are as follows: Figure 6 As shown. Figure 6 It can be seen that the zero-valent iron sulfide prepared by the preparation method of the present invention removed 99% of Cr(VI) within 1 hour, while the original zero-valent iron and the zero-valent iron sulfide prepared in Comparative Example 1 only removed 7% and 60% of Cr(VI) in the same time, which shows that the preparation method of the present invention can significantly improve the ability of the prepared zero-valent iron sulfide material to remove pollutants.

[0064] In summary, the preparation method of the present invention uses Geobacter sulfurreducens to prepare zero-valent iron sulfide. Geobacter sulfurreducens can reduce and remove the oxides on the surface of zero-valent iron on the one hand, and accelerate the reaction of elemental sulfur and zero-valent iron on the other hand, so that the preparation method of the present invention has the advantages of fast reaction speed, high reaction efficiency, mild reaction conditions, and no energy consumption. The zero-valent iron sulfide prepared by the preparation method of the present invention in the same time has a high content of sulfur coated on the surface, a high removal rate of Cr(VI), and a fast removal speed.

[0065] In addition, the preparation method of the present invention also has the potential for in-situ repair of polluted environments, because Geobacter sulfurreducens is a bacterium widely present in anaerobic environments such as groundwater and sediments. We can utilize the naturally existing Geobacter sulfurreducens in the polluted environment, and by adding elemental sulfur, zero-valent iron and nutrients required for bacterial growth, etc., with the help of the naturally existing Geobacter sulfurreducens, elemental sulfur and zero-valent iron are reacted in situ to generate sulfide zero-valent iron with strong performance of removing various pollutants in the environment, thereby realizing in-situ environmental governance, further improving the efficiency of environmental governance, and reducing governance costs.

[0066] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A biological preparation method of zero-valent iron sulfide, characterized in that: The following steps are involved: The mixture is prepared by reacting elemental sulfur, zero-valent iron and Geobacter sulphuroreducens; in the mixed reaction step, the bacterial solution OD of Geobacter sulphuroreducens 600 The value is 0.1~0.7; The mixing reaction time is 1 to 4 hours.

2. The biological preparation method of zero-valent iron sulfide according to claim 1, characterized in that: The mixing reaction step is carried out under anaerobic conditions.

3. The biological preparation method of zero-valent iron sulfide according to claim 1, characterized in that: The temperature of the mixed reaction is 20-40°C.

4. The biological preparation method of zero-valent iron sulfide according to claim 1, characterized in that: The molar ratio of the elemental sulfur to the zero-valent iron is (0-1):1, and the elemental sulfur is not zero.

5. The biological preparation method of zero-valent iron sulfide according to claim 1, characterized in that: In the mixing reaction step, the concentration of zero-valent iron is 0.01-0.4 g / mL.

6. The biological preparation method of zero-valent iron sulfide according to claim 1, characterized in that: The Geobacter sulfurreducens is a strain in the logarithmic growth phase.

7. The biological preparation method of zero-valent iron sulfide according to claim 1, characterized in that: The preparation method further comprises a purification step after the mixing reaction step; the purification step comprises: taking out the product zero-valent iron sulfide by using a magnet, washing it and freeze-drying it.

8. Use of the biological preparation method of zero-valent iron sulfide according to any one of claims 1 to 7 in the field of pollutant removal.

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