Method for synergistically degrading trichloroethylene by zero-valent iron and microorganisms

Abstract

The application discloses a method for degrading trichloroethylene by zero-valent iron and microorganisms, and realizes degradation of trichloroethylene by indirect contact between zero-valent iron and microorganisms, and the steps are as follows: 1) obtaining microbial bacteria suspension after subculturing anaerobic dechlorination microorganisms; 2) obtaining nano zero-valent iron or sulfidized nano zero-valent iron by reducing or modifying water-soluble Fe-containing salt by using a reducing agent; 3) placing the zero-valent iron into a special device, then putting the zero-valent iron into the microbial bacteria suspension, injecting trichloroethylene stock solution and high-purity hydrogen, and placing the special device in a water bath shaker to realize degradation of trichloroethylene. The special device is used to realize indirect contact between zero-valent iron and anaerobic dechlorination microorganisms, so that the contact toxicity of zero-valent iron to the dechlorination microorganisms is avoided, and the promoting effect of zero-valent iron on the dechlorination microorganisms in hydrogen production and ORP improvement is maximized, thereby improving the indirect rate in groundwater microbial remediation and the problem of accumulation of toxic intermediate products.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemistry, and particularly relates to a method for degrading trichloroethylene by zero-valent iron and microorganisms. BACKGROUND

[0002] Trichloroethylene is an important chemical raw material, mainly used as an organic solvent, dry cleaning agent, metal degreasing solvent, fire extinguishing agent, etc. Due to the large amount of use, trichloroethylene has become one of the most common pollutants in groundwater, causing long-term impact on the ecological system, affecting the liver and kidney function, nervous system, immune system and endocrine system of human body. Therefore, it is urgent to develop a practical remediation technology to solve the environmental and health problems caused by trichloroethylene pollution.

[0003] For trichloroethylene contaminated groundwater or soil, the commonly used remediation technologies include physical technology (gas phase extraction technology, multi-phase extraction technology, etc.) and chemical technology (in-situ chemical oxidation technology, permeable reactive barrier technology, etc.). However, the remediation of trichloroethylene pollution by physical or chemical means has the defects of high remediation cost, complex equipment and process, certain applicable parameters, possible change of the basic properties and ecological functions of groundwater, etc. The biological remediation, especially the microbial remediation technology, has become a research hotspot for the remediation of trichloroethylene pollution due to its safety, green and economic advantages.

[0004] In aerobic environments, trichloroethylene is difficult to be utilized or degraded by microorganisms; while in anaerobic environments, trichloroethylene can undergo anaerobic dechlorination process, and trichloroethylene is gradually dechlorinated into 1,1-dichloroethylene (DCE), cis-1,2-dichloroethylene (cis-DCE), trans-1,2-dichloroethylene (trans-DCE), vinyl chloride (VC) and nontoxic ethylene. Among numerous dechlorination microbial remediation technologies, in-situ remediation using organohalide-respiring bacteria (OHRB) is an effective solution to remove persistent organohalide pollutants. OHRB (organohalide-respiring bacteria) saves energy by utilizing H2 or organic compounds as electron donors and organohalides as electron acceptors, and different respiratory electron transfer models exist in different lineages of organohalide-respiring bacteria. At present, KB-1, SDC-9 and other microbial agents developed based on Dehalococcoides as the core strain have many application examples of remediating groundwater organochlorine pollution, and have ideal degradation effect on chlorinated alkenes and chlorinated alkanes. As a typical OHRB, Dehalococcoides not only can dechlorinate aliphatic chlorinated hydrocarbons, but also can dechlorinate aromatic chlorinated hydrocarbons, and it is the only known dechlorinating bacteria that can completely degrade TCE (trichloroethylene) into ethylene. It is usually disc-shaped, colorless, non-spore-forming and strict anaerobic bacteria with inactive cells, including many species. Strain 195 among them can metabolize various persistent organic pollutants in the presence of mixed cultures or other electron acceptors, such as polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and polybrominated diphenyl ethers. Previous studies have shown that mixed cultures containing ethene-producing Dehalococcoides 195 are more effective in removing halogenated compounds than pure cultures, and they have important application value in in-situ remediation of groundwater contaminated by organochlorine. However, in the field environment with complex stratigraphy and often without characteristics, the degradation and transformation of trichloroethylene is still a challenging task. For example, physical attenuation processes such as dilution, dispersion and adsorption may dominate the distribution of its concentration, and biodegradation products such as c-DCE, t-DCE and VC during TCE reduction will produce co-contamination, which will lead to more serious groundwater pollution due to the accumulation of these toxic substances.

[0005] In recent years, the method of coupling ZVI with functional anaerobic bacteria has been developed. In theory, the synergistic effect of ZVI and its modification technology and dechlorination microorganisms can effectively remove organic chlorine pollutants. First, the corrosion of ZVI can reduce the oxidation-reduction potential (ORP) and create a suitable reducing environment for the growth of anaerobic bacteria, preventing the accumulation of harmful metabolites. Second, the hydrogen produced by the corrosion of ZVI can provide electrons for bacteria such as dehalogenating bacteria and hydrogen-loving bacteria, improving the removal efficiency of pollutants. Third, microorganisms generally have a lag phase in the initial stage, during which microorganisms cannot quickly degrade target pollutants. During this lag phase of bacteria, chemical reduction of ZVI may compensate for the degradation of pollutants in this stage. The coupling of ZVI and functional anaerobic bacteria is expected to completely degrade pollutants into non-toxic or harmless substances. Combining the two, theoretically, can eliminate the shortcomings of the two single treatment methods. However, in practical applications, the related dechlorination microorganisms may enrich in groundwater contaminated by chlorinated hydrocarbons, and the use of ZVI may affect the growth and metabolism of indigenous dechlorination microorganisms. In particular, the direct contact of zero-valent iron with dechlorination microorganisms and the release of compounds and reaction intermediates during the degradation process may have toxic effects on dechlorination bacteria, which may affect the growth and activity of dechlorination microorganisms. In the presence of zero-valent iron, changes in oxidation-reduction potential may lead to competition between dechlorination microorganisms and other chemicals. Moreover, there may be active oxygen species in groundwater, which may affect the activity of dechlorination microorganisms. In addition, the presence of zero-valent iron may change the concentration of nutrients such as ammonia nitrogen, nitrate, and phosphate in water and the pH of the water, further affecting the growth and activity of dechlorination microorganisms.

[0006] In order to improve the defects of the large accumulation of intermediate toxic products and the toxic effects on microorganisms in the process of microbial dechlorination, the present application provides a method for synergistically degrading trichloroethylene by indirect contact between zero-valent iron and microorganisms. SUMMARY

[0007] In view of the problem in the prior art that direct contact between zero-valent iron and microorganisms easily leads to the accumulation of more difficult-to-decompose toxic substances, the purpose of the present application is to provide a method for synergistically degrading trichloroethylene by zero-valent iron and microorganisms, which reduces the accumulation of toxic substances.

[0008] The present application is realized by the following technical solutions:

[0009] A method for synergistically degrading trichloroethylene by zero-valent iron and microorganisms, which realizes the degradation of trichloroethylene by indirect contact between zero-valent iron and microorganisms, and specifically comprises the following steps:

[0010] 1) Cultivation of microorganisms: stably cultivate anaerobic dechlorination microorganisms in an anaerobic culture medium, and prepare a microbial suspension after subculture;

[0011] 2) Preparation of zero-valent iron: using liquid phase reduction method, the nano zero-valent iron is prepared by reducing the water-soluble salt containing Fe with a reducing agent, or the nano zero-valent iron is modified by using a modifier to prepare sulfidized nano zero-valent iron;

[0012] 3) The nano zero-valent iron or sulfidized nano zero-valent iron prepared in step 2) is placed in a specially designed device, and then the specially designed device is put into the microbial bacteria suspension prepared in step 1), and then trichloroethylene stock solution and high-purity hydrogen gas are injected, and the reaction is carried out in a water bath shaker to achieve the degradation of trichloroethylene.

[0013] Further, the anaerobic medium in step 1) contains 0.1% trace element solution, 0.1% Se / W solution, 1% salt solution, 0.01% vitamin solution, 0.025% resazurin, and Tris-ethanesulfonic acid, L-cysteine hydrochloride, sodium acetate, Na2S·9H2O and other buffers and reducing agents, and the anaerobic water is made up to 1L.

[0014] Further, the anaerobic microorganism in step 1) is ethylene-producing Dehalococcoides sp. 195.

[0015] Further, the reducing agent in step 2) is sodium borohydride, and the concentration is 2.1g / L; the water-soluble salt containing Fe is ferrous sulfate, and contains crystal water; and the modifier is sodium sulfide, and the concentration is 8g / L.

[0016] Further, the time of the reduction reaction in step 2) is 20-30min.

[0017] Further, the specially designed device in step 3) includes an outer tube and an inner tube which are inserted and arranged, the outer tube and the inner tube are both columnar tubes with one end open and the other end closed, and the open end of the inner tube is sealed by a filter membrane and then inserted into the bottom of the outer tube.

[0018] Further, the size of the inner diameter of the outer tube matches the size of the outer diameter of the inner tube, the inner tube and the outer tube are both polytetrafluoroethylene plastic tubes, and the filter membrane is a polyether sulfone filter membrane with a pore size of 0.22μm. Further, in step 3), the dosage of nano zero-valent iron or sulfidized nano zero-valent iron is 0.006g-0.06g, the dosage of trichloroethylene stock solution is 60μl, and the dosage of high-purity hydrogen gas is 5ml. In the preparation process of sulfidized nano zero-valent iron, it is washed with anaerobic water and methanol for three times respectively.

[0019] Further, the concentration of high-purity hydrogen gas in step 3) is 99.99%.

[0020] Further, the degradation reaction conditions in step 3) are 30±1℃ and 100rpm, and the reaction time is one week.

[0021] The present application realizes indirect contact between zero-valent iron and anaerobic dechlorination microorganisms by using a special device, avoids the contact toxicity of zero-valent iron to dechlorination microorganisms, and maximizes the promotion of zero-valent iron to dechlorination microorganisms in terms of hydrogen production and ORP improvement, thereby improving the indirect rate in groundwater microbial remediation and the accumulation of toxic intermediates. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 TEM images of the sulfidized nano zero-valent iron prepared in Example 1 and the nano zero-valent iron prepared in Example 2 (wherein, Figure A is nano zero-valent iron, and B is sulfidized nano zero-valent iron);

[0023] Figure 2 SEM images of the sulfidized nano zero-valent iron prepared in Example 1 and the nano zero-valent iron prepared in Example 2 (wherein, Figure A is nano zero-valent iron, and B is sulfidized nano zero-valent iron);

[0024] Figure 3 Bacterial bio-transmission electron microscope images in the direct contact system of the sulfidized nano zero-valent iron prepared in Example 1 and the nano zero-valent iron prepared in Example 2 with Dehalococcoides ethenogenes 195, respectively (wherein, Figures A and B are Dehalococcoides ethenogenes 195 mixed with nano zero-valent iron, and Figures C and D are Dehalococcoides ethenogenes 195 mixed with sulfidized nano zero-valent iron);

[0025] Figure 4 Structure schematic diagram of the special device of the present application;

[0026] Figure 5 TCE degradation and its products in the direct contact and indirect contact reaction processes of the sulfidized nano zero-valent iron prepared in Example 1 with Dehalococcoides ethenogenes 195 (wherein, Figure A is 1 g / L of the direct contact reaction of sulfidized nano zero-valent iron, Figure B is 1 g / L of the non-contact reaction of sulfidized nano zero-valent iron, and Figure C is a pure bacterial system);

[0027] Figure 6 TCE degradation and its products in the direct contact and indirect contact reaction processes of the nano zero-valent iron prepared in Example 2 with Dehalococcoides ethenogenes 195 (wherein, Figure A is 1 g / L of the direct contact reaction of nano zero-valent iron, Figure B is 1 g / L of the non-contact reaction of nano zero-valent iron, and Figure C is a pure bacterial system);

[0028] Figure 7 TCE degradation and its products in the direct reaction system of the sulfidized nano zero-valent iron and the nano zero-valent iron in Example 3 with TCE in an anaerobic culture medium (wherein, Figure A is 0.1 g / L of nano zero-valent iron, Figure B is 0.1 g / L of sulfidized nano zero-valent iron, Figure C is 1 g / L of nano zero-valent iron, and Figure D is 1 g / L of sulfidized nano zero-valent iron). DETAILED DESCRIPTION

[0029] The technical solutions of the present application are further described below in combination with the drawings and specific embodiments of the present application.

[0030] The main raw materials involved in the following examples, such as ferrous sulfate, sodium hydroxide, sodium borohydride, etc., are all from Aladdin (Shanghai, China), and all reagents are analytical pure. Nanoscale zero-valent iron can be obtained by purchasing commercially available products or prepared according to existing literature.

[0031] The preparation method of sulfidized nanoscale zero-valent iron involved in the following examples is as follows:

[0032] Take 350 mL of ultrapure water solution and 150 mL of methanol into a 1000 mL three-necked flask, set the rotation speed of mechanical stirring to 550 rpm, and aerate for 30 min under the condition of nitrogen flow; add 10 g of FeSO4·7H2O into the three-necked flask, and the solution in the flask is light green; then add 5 mL of NaOH solution (5 mol / L) at a speed of 1 drop / s, and the solution gradually turns dark green; then add 25 mL of NaBH4 solution (2.1 mol / L) at a speed of 2 drops / s using a peristaltic pump, and continue to stir for 30 min after the solution turns black; slowly add 14.4 mL of Na2S stock solution (8 g·L -1 Take 350 mL of ultrapure water solution and 150 mL of methanol into a 1000 mL three-necked flask, set the rotation speed of mechanical stirring to 550 rpm, and aerate for 30 min under the condition of nitrogen flow; add 10 g of FeSO4·7H2O into the three-necked flask, and the solution in the flask is light green; then add 5 mL of NaOH solution (5 mol / L) at a speed of 1 drop / s, and the solution gradually turns dark green; then add 25 mL of NaBH4 solution (2.1 mol / L) at a speed of 2 drops / s using a peristaltic pump, and continue to stir for 30 min after the solution turns black; slowly add 14.4 mL of Na2S stock solution (8 g·L

[0033] After placing the aeration head above the liquid surface, stop stirring, and let the suspension stand under anaerobic conditions for 30 min; discard the supernatant, pour the S-nZVI suspension in the flask into a polytetrafluoroethylene centrifuge tube, and centrifuge at 3500 rpm for 5 min; discard the supernatant in the centrifuge tube after centrifugation, and add the S-nZVI suspension in the flask again for centrifugation to completely centrifuge the suspension in the flask; wash the obtained S-nZVI with anaerobic water and methanol for three times, and then transfer it into a quartz boat for drying in a tube furnace (heat to 105°C at a rate of 3°C / min, maintain for 4 h, and then cool to room temperature); after the tube furnace cools to room temperature, close the instrument, open the air duct, and age the S-nZVI material for 12 h; then transfer it into a glove box, grind it with a mortar, and store it for use in experiments.

[0034] Preparation of trichloroethylene stock solution: prepared in the laboratory by mixing 0.877 mL of methanol and 0.123 mL of TCE stock solution, with a concentration of 179 g / L and a dosage of 60 μl.

[0035] Example 1

[0036] A method for non-contact and synergistic degradation of trichloroethylene by sulfidized nanoscale zero-valent iron and microorganisms, comprising the following steps:

[0037] 1) The ethene-producing Dehalococcoides sp. 195 was pre-enriched in 120 ml serum bottles for one month;

[0038] 2) S-nZVI was prepared in advance according to the steps as needed for the experiment;

[0039] 3) 1 g / L direct contact reaction and indirect contact reaction S-nZVI experimental systems were set up respectively.

[0040] In an anaerobic glove box, 0.06 g of S-nZVI was added to the pre-enriched ethene-producing Dehalococcoides sp. 195 bacterial solution as a direct reaction system, and then an equal amount of S-nZVI was placed in a specially designed device, separated by a 0.22 μm polyether sulfone filter membrane, and added to the same bacterial solution as an indirect contact reaction system, and the gap was resealed with a gasket. Then 60 μL of TCE stock solution (179 g·L -1 ) was injected into the serum bottle, so that the initial concentration of TCE in the reaction system was 179 mg·L -1 , and finally 5 mL of hydrogen gas was injected into all the systems as an electron donor. The serum bottles were placed in a water bath shaker at 30±1℃, 100 rpm, and the reaction time was one week. Every 24 h, 100 μL of headspace was taken and the concentration of TCE and its products was determined by GC-FID.

[0041] At the same time, a blank control was set up: a pure bacterial system without adding any material, and the rest of the conditions were the same as above.

[0042] Example 2

[0043] A method for indirect contact between nano zero-valent iron and microorganisms to synergistically degrade trichloroethylene,

[0044] comprising the following steps:

[0045] 1) The ethene-producing Dehalococcoides sp. 195 was pre-enriched in 120 ml serum bottles for one month;

[0046] 2) nZVI was prepared in advance as needed for the experiment;

[0047] 3) 1 g / L direct contact reaction and indirect contact reaction nZVI experimental systems were set up respectively: in an anaerobic glove box, 0.06 g of nZVI was added to the pre-enriched ethene-producing Dehalococcoides sp. 195 bacterial solution as a direct reaction system, and then an equal amount of nZVI was placed in a specially designed device, separated by a 0.22 μm polyether sulfone filter membrane, and added to the same bacterial solution as a non-contact reaction system, and the gap was resealed with a gasket. Then 60 μL of TCE stock solution (179 g·L -1 ) was injected into the serum bottle, so that the initial concentration of TCE in the reaction system was 179 mg·L-1 Finally, 5 mL of hydrogen gas was injected into all systems as electron donor by using a 5 mL syringe. The serum bottles were placed in a water bath shaker at 30±1℃, 100 rpm, and the reaction time was one week. The headspace of 100 μL was taken every 24 h, and the concentration of TCE and its products were determined by using GC-FID.

[0048] Meanwhile, a blank control was set up, i.e. pure bacteria system without adding any material, and the rest of the conditions were the same as above.

[0049] The above nano zero-valent iron material was prepared by the following method:

[0050] 350 mL of ultrapure water solution and 150 mL of methanol were placed in a 1000 mL three-necked flask, 10 g of FeSO4·7H2O solid was first added, and after dissolution, 5 mL of 5M NaOH solution was added dropwise at a flow rate of 1 drop / s, and after the solution turned dark green, 25 mL of 2.1M NaBH4 solution was added dropwise at a flow rate of 2 drops / s for reduction reaction, the time was 30 min, the whole process was carried out under anaerobic conditions, mechanical stirring was used, and finally the nano zero-valent iron solution was obtained. After being magnetically absorbed and dried, a solid nano zero-valent iron with zero-valent iron content of more than 85% was obtained, which was ground in a glove box and used for characterization and experiment.

[0051] The TEM images of the sulfidized nano zero-valent iron prepared in Example 1 and the nano zero-valent iron prepared in Example 2 are shown in Figure 1 , and the SEM images are shown in Figure 2 .

[0052] The bacterial bio-transmission electron microscope images of the sulfidized nano zero-valent iron prepared in Example 1 and the nano zero-valent iron prepared in Example 2 in the direct contact system with Dehalococcoides ethenogenes 195 are shown in Figure 3 .

[0053] The TCE degradation and its products in the direct contact and indirect contact reaction processes of the sulfidized nano zero-valent iron prepared in Example 1 with Dehalococcoides ethenogenes 195 are shown in Figure 5 .

[0054] The TCE degradation and its products in the direct contact and indirect contact reaction processes of the nano zero-valent iron prepared in Example 2 with Dehalococcoides ethenogenes 195 are shown in Figure 6 .

[0055] The special device needed to be used in the above-mentioned indirect contact reaction system is shown in Figure 4As shown, including the plug-in setting outer tube and inner tube, outer tube and inner tube are both one end open one end closed cylindrical tube, inner tube open end through the filter membrane sealed after the end inserted into the bottom of the outer tube, in use, the zero-valent iron is placed into the inner tube, and then the opening end is sealed through the filter membrane, and then the inner tube opening tube is inserted into the bottom of the outer tube. Since the outer diameter of the inner tube matches the inner diameter of the outer tube, the fixed connection between the inner tube and the outer tube in the natural state can be realized, and only a certain external force can realize the separation of the inner tube and the outer tube.

[0056] Example 3

[0057] A method for degrading TCE by directly adding nZVI and S-nZVI in an anaerobic culture medium:

[0058] 26 mL of sterilized anaerobic mineral salt medium solution was added to a 52 mL serum bottle containing 0.0026 g and 0.026 g of two kinds of zero-valent iron materials (material concentration 0.1 g·L -1 and material concentration 1 g·L -1 ), 26 μL of vitamin solution was added, and the opening was sealed with a polytetrafluoroethylene butyl septum. After ultrasonic treatment for 15 min, 30 μL of TCE stock solution (179 g·L -1 ) was injected into the serum bottle. The serum bottle was placed in a rotary incubator and reacted at 30±1℃, 80 rpm. Every 24 h, 100 μL of headspace was taken, and the concentration of TCE and its products was determined by GC-FID, and the hydrogen concentration in the bottle was determined by GC-TCD. The results are shown in Figure 7 .

[0059] Example 3 and Example 1 and Example 2 used the same material and bacteria solution.

[0060] Result analysis:

[0061] Figures 1-2 TEM and SEM images of sulfurized nano zero-valent iron prepared in Example 1 and nano zero-valent iron prepared in Example 2, respectively. From the TEM images of the two materials in Figure 1 , it can be seen that both materials are easy to aggregate, nZVI particles are aggregated into dendritic aggregates, the particle size of the two is similar, and nZVI and S-nZVI particles have core-shell structure, and the outer surface of S-nZVI exists flocculation compared with nZVI. From Figure 2 , it can be seen that nZVI and S-nZVI particles are spherical particles, and agglomeration can be observed in the images of nZVI and S-nZVI particles, and the agglomeration in the image of nZVI particles is more obvious.

[0062] From Figure 3It can be found that in the system with nZVI, the fine nZVI particles surround and adhere to the cell membrane of Dhc 195; while in the system with S-nZVI, the S-nZVI particles are dispersedly distributed with Dhc 195. This may be related to the charge of the microorganism and the surface of nZVI and S-nZVI, and the zeta potential of Dhc 195 is usually negative, while it has been reported that the zeta potential of S-nZVI is more negative than that of nZVI. The nZVI and S-nZVI particles may destroy the growth of Dhc 195 and affect its degradation of TCE by contacting with the cell membrane, but the contact toxicity of S-nZVI to Dhc 195 is lighter than that of nZVI.

[0063] Figure 5 and Figure 6 The TCE degradation and its products chart during the reaction process of S-nZVI and nZVI materials mixed with / without Dhc 195 can be seen from the figure, and it can be seen that whether S-nZVI or nZVI, the degradation rate of TCE decreases when the material directly contacts with the microorganism, and the activity of Dhc 195 degrading TCE is obviously inhibited, and the inhibition of Dhc 195 degrading TCE by the material after sulfuration is reduced, which may be related to the existence of sulfur layer on the surface of nZVI after sulfuration. In addition, it can be found that with the increase of the culture time of Dhc 195, the inhibition of nZVI and S-nZVI on the activity of Dhc 195 degrading TCE gradually increases, and the accumulation of VC and other toxic products gradually increases.

[0064] Table 1 makes zero-order kinetic fitting to the degradation rate of Dhc 195, which more directly shows the difference in the degradation rate of Dhc 195 under the addition of different concentrations and different types of nZVI. In the first period and the second period of Dhc 195 culture, the addition of 1g·L -1 nZVI and S-nZVI directly shows the obvious inhibition to Dhc 195 degrading TCE in the initial stage. These results show that the addition of nZVI and S-nZVI can significantly affect the degradation activity of Dhc 195 to TCE.

[0065] Table 1

[0066]

[0067] Under the condition of indirect contact reaction between the material and Dhc 195, the addition of 1g·L -1 nZVI and 1g·L -1The degradation rate of TCE in the S-nZVI system was not inhibited compared with the pure Dhc195 degradation system, but was promoted, and VC did not accumulate with time, but showed a downward trend. By observing the TCE degradation reaction kinetics constant of the indirect contact system, it can be seen that in the first cycle, the TCE degradation efficiency of the two material addition systems was about 1.71 and 1.40 times that of the pure Dhc195 degradation system, and in the second cycle, it was about 1.44 and 1.46 times, indicating that the addition of nZVI and S-nZVI in the non-contact system promoted the degradation of Dhc195 to TCE, and also showed that the inhibition of nZVI and S-nZVI to Dhc195 degradation of TCE was caused by direct contact, and nZVI and S-nZVI further damaged Dhc195 cells after contacting the bacteria, and also affected the expression of related dechlorination genes and protein synthesis in Dhc195.

[0068] Figure 7 The TCE degradation reaction kinetics diagram of the two materials in the anaerobic medium system, where the results measured on the 6th day are the reaction end point. In the anaerobic medium, 0.1 g·L -1 nZVI, 1 g·L -1 nZVI, 0.1 g·L -1 S-nZVI and 1 g·L -1 The S-nZVI system cannot effectively degrade TCE, with a degradation rate of <7%. 0.1 g·L -1 The degradation rate of TCE at the reaction end point of the nZVI addition system was 0.9%. 1 g·L -1 The degradation rate of TCE at the reaction end point of the nZVI addition system was 4.4%. 0.1 g·L -1 The degradation rate of TCE at the reaction end point of the S-nZVI addition system was 0.9%. 1 g·L -1 The degradation rate of TCE at the reaction end point of the S-nZVI addition system was 6.2%. The above cases all show that the addition of materials alone has little effect on the degradation of TCE in the medium.

Claims

1. A method for synergistically degrading trichloroethylene by zero-valent iron and microorganisms, characterized in that The method realizes degradation of trichloroethylene by indirect contact between zero-valent iron and microorganisms, and comprises the following steps: 1) Culturing of microorganisms: anaerobic dechlorination microorganisms are stably cultured in an anaerobic culture medium, and a microbial suspension is prepared after subculture; 2) Preparation of zero-valent iron: nano zero-valent iron is prepared by reducing Fe-containing water-soluble salt with a reducing agent, or sulfurized nano zero-valent iron is prepared by modifying nano zero-valent iron with a modifier; the reducing agent is sodium borohydride, and the concentration is 2.1 g / L; the Fe-containing water-soluble salt is ferrous sulfate and contains crystal water; the modifier is sodium sulfide, and the concentration is 8 g / L; 3) The nano zero-valent iron or sulfurized nano zero-valent iron prepared in step 2) is placed in a special device, and then the special device is put into the microbial suspension prepared in step 1), and then trichloroethylene stock solution and high-purity hydrogen are injected, and the reaction is carried out in a water bath shaker to realize degradation of trichloroethylene; The special device comprises an outer tube and an inner tube which are inserted, both of which are columnar tubes with one end open and the other end closed, the open end of the inner tube is sealed by a filter membrane and then inserted into the bottom of the outer tube, the inner diameter of the outer tube matches the outer diameter of the inner tube, both the inner tube and the outer tube are polytetrafluoroethylene plastic tubes, and the filter membrane is a polyether sulfone filter membrane with a pore size of 0.22 μm.

2. The method for synergistically degrading trichloroethylene by zero-valent iron and microorganisms according to claim 1, characterized in that The anaerobic culture medium in step 1) contains 0.1% trace element solution, 0.1% Se / W solution, 1% salt solution, 0.01% vitamin solution and 0.025% resazurin, and the anaerobic water is diluted to 1 L.

3. The method for the synergistic degradation of trichloroethylene by zero-valent iron and microorganisms as described in claim 1, characterized in that... The anaerobic microorganism in step 1) is ethylene-producing Dehalococcoides sp.

195.

4. The method for the synergistic degradation of trichloroethylene by zero-valent iron and microorganisms as described in claim 1, characterized in that... The reduction reaction time in step 2) is 20-30 min.

5. The method of claim 1, wherein the zero-valent iron and microorganisms are used in combination to degrade trichloroethylene. The nano zero-valent iron or sulfurized nano zero-valent iron in step 3) is added in an amount of 0.006 g-0.06 g, the trichloroethylene stock solution is added in an amount of 60 μl, and the high-purity hydrogen is added in an amount of 5 ml.

6. The method of claim 1, wherein the zero-valent iron and microorganisms synergistically degrade trichloroethylene. The concentration of high-purity hydrogen in step 3) is 99.99%.

7. The method of claim 1, wherein the zero-valent iron and the microorganisms are used in combination to degrade trichloroethylene. The degradation reaction conditions in step 3) are 30±1℃ and 100 rpm, and the reaction time is one week.

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