Experimental device for removing trichloroethylene by reinforcing in-situ biological sulfurized zero-valent iron

Abstract

The invention provides an experimental device for enhancing removal of trichloroethylene by in-situ biological sulfurized zero-valent iron. The experimental device comprises a sample injection bag, a peristaltic pump, a seepage column and a post-treatment column, a stainless steel dispensing needle head is inserted into the sample injection bag, the outer end of the dispensing needle head is connected with a Luer internal rotary joint, and the Luer internal rotary joint is connected with a first polytetrafluoroethylene hard tube through a first hose; the right end of the peristaltic pump is connected with the sample injection bag; the upper end of the seepage column is connected with the post-treatment column; the lower end is connected with the peristaltic pump; openings are formed in the side wall of 30 cm in the middle of the seepage column every 5 cm, and the openings are connected through three-way connectors; the middle of the seepage column is divided into six layers to be filled with quartz sand, domestication bacterium liquid is evenly injected into the surface of each layer of quartz sand, and xanthan gum modified zero-valent iron slurry is injected into the seepage column from the side face and the bottom of the seepage column in a multi-point circulation mode. According to the technical scheme, the system error of trichloroethylene removal by the experimental device is reduced, the true degradation phase of a filling medium to trichloroethylene is reduced, the problems of pre-vulcanization and experimental dechlorination separation are solved, the in-situ biological vulcanization and dechlorination effects are improved, and the remediation target of'simultaneous vulcanization and dechlorination 'is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of in-situ groundwater remediation, and in particular to an experimental device for enhancing in-situ biosulfurization of zero-valent iron to remove trichloroethylene. Background Art

[0002] Trichloroethylene (TCE), widely used in industrial applications such as dry cleaning and degreasing, can be released into the ground due to improper manufacturing processes, misuse, and unsafe disposal. It is one of the most common organic contaminants in groundwater. An analysis of 791 groundwater samples nationwide between 2008 and 2010 revealed a detection rate of 3.79% for TCE in my country's groundwater, making it one of the most prominent halogenated hydrocarbon contaminants. Zero-valent iron (ZVI) has been chosen as a suitable in situ groundwater remediation medium due to its high reducibility, low cost, and minimal environmental impact. However, practical applications have limited remediation effectiveness due to issues such as precipitation, aging, and poor target selectivity. Sulfurization modification has been shown to effectively enhance the removal of chlorinated hydrocarbons, particularly TCE, using ZVI. Currently, the sulfurization modification of ZVI is mainly carried out through two methods: liquid-phase synthesis and mechanical ball milling, which respectively deposit ferrous sulfide (FeSx) on the ZVI surface or uniformly distribute it throughout the ZVI particles. However, artificial pre-sulfurization of ZVI increases costs, and the byproducts produced by the liquid-phase synthesis method pose environmental risks. This forces us to seek a greener, more economical, and more efficient sulfurization method.

[0003] In fact, the sulfate concentration in many chlorinated hydrocarbon contaminated sites far exceeds the Class III standard limit for groundwater, and there are abundant sulfate reducing bacteria (SRB), which creates conditions for in situ biosulfurization of oxidized iron minerals or ZVI. When the sulfate content in groundwater is sufficient, organic matter can stimulate the growth of SRB. The respiration of SRB causes the naturally occurring Fe (III) oxide / hydroxide minerals in the sediment to generate reduced pyrite minerals (FeS and FeS2), which promote the reductive dechlorination of chlorinated olefins. In recent years, studies have used SRB to reduce SO4 2- The biogenic sulfide (S 2- 、S - 、Sn 2- ) was used as a new sulfur source for ZVI sulfurization modification to pre-synthesize biosulfurized ZVI. The obtained material showed good trichloroethylene removal performance in subsequent degradation experiments, including a trichloroethylene removal rate and selective reduction ability similar to those of chemically sulfurized ZVI.

[0004] Patent application publication number CN 117658339 A discloses a method for synergistically degrading trichloroethylene (TCE) using zero-valent iron (ZVI) and microorganisms, and patent CN 116002872 B discloses a method for regulating the in-situ self-sulfidation of ZVI and groundwater remediation, both demonstrating the promising remediation performance of biosulfided ZVI. However, both methods pre-biosulfided ZVI prior to dechlorination experiments. This results in a temporal and spatial separation between the pre-biosulfidation of ZVI and the subsequent dechlorination experiments, failing to reflect the impact of actual groundwater environmental conditions on the in-situ biosulfidation process. This hinders the determination of the remediation effectiveness of the biosulfided ZVI system under realistic conditions. Furthermore, during in-situ remediation at actual sites, material mobility significantly impacts the long-term remediation performance of biosulfided ZVI. Excessively low mobility can prevent the material from effectively covering the contaminated plume in the groundwater, preventing effective dechlorination. Furthermore, our preliminary experimental research has revealed that the materials used in the indoor simulation device for TCE-contaminated groundwater remediation experiments significantly interfere with TCE removal. Therefore, it is very necessary to improve the existing experimental equipment and methods, that is, to develop an experimental equipment for enhanced in situ biosulfurization of zero-valent iron to remove trichloroethylene. Summary of the Invention

[0005] In order to make up for the shortcomings of the existing technology, the present invention provides an experimental device for enhanced in-situ biological sulfidation of zero-valent iron to remove trichloroethylene. The invention reduces the systematic error of the experimental device in the removal of trichloroethylene, restores the truth of the degradation of trichloroethylene by the filling medium, solves the problem of separation between pre-sulfidation and experimental dechlorination, improves the in-situ biological sulfidation dechlorination effect, and achieves the remediation goal of "sulfiding and dechlorinating at the same time".

[0006] An experimental device for enhanced in-situ biosulfurization of zero-valent iron to remove trichloroethylene, comprising a sampling bag, a peristaltic pump, a percolation column, and a post-treatment column; A stainless steel dispensing needle is inserted into the sample bag, the outer end of the dispensing needle is connected to a Luer internal rotary joint, and the Luer internal rotary joint is connected to a first polytetrafluoroethylene rigid tube through a first hose; The peristaltic pump uses Viton fluororubber pump tubes to connect the left and right ends, the right end is the first Viton fluororubber pump tube, and the left end is the second Viton fluororubber pump tube. The other ends of the first Viton fluororubber pump tube and the second Viton fluororubber pump tube are respectively connected to the first soft-hard tube conversion joint and the second soft-hard tube conversion joint. The first Viton fluororubber pump tube is connected to the other end of the first polytetrafluoroethylene hard tube through the first soft-hard tube conversion joint, and the second Viton fluororubber pump tube is connected to the second polytetrafluoroethylene hard tube through the second soft-hard tube conversion joint. The seepage column was a 36 cm long glass cylinder with an upper and lower screw cap attached to each end. The upper cap was connected to a first T-joint, which was connected to a post-treatment column filled with activated carbon via a second hose. The lower cap was connected to the other end of a second tetrafluoroethylene rigid tube via a third hose and a combination device. The bottom and top of the column were evenly packed with 3 cm glass beads. The central 30 cm of the column had openings every 5 cm, each connected by a second T-joint. The central 30 cm of the column was filled with quartz sand in six equal layers. 10 mL of acclimated bacterial solution was evenly injected into each layer of sand using a syringe. A xanthan gum-modified zero-valent iron slurry was then circulated into the column from multiple points on the sides and bottom. N2 was continuously purged during the filling process.

[0007] As a preferred solution, the sampling bottle is a round-bottom vertical biological sterile water sample collection bag with a silicone stopper.

[0008] As a preferred solution, a sealing film is used to seal the connection between the Luer internal rotary connector, the first hose and the first polytetrafluoroethylene rigid tube.

[0009] As a preferred solution, the upper screw cap and the lower screw cap are made of polytetrafluoroethylene.

[0010] As a preferred solution, the first soft-hard tube conversion joint and the second soft-hard tube conversion joint are both equipped with an inverted cone joint, which is arranged at the hard interface end of the first soft-hard tube conversion joint and the second soft-hard tube conversion joint.

[0011] As a preferred solution, the combined device includes an external rotating joint, a third three-way joint and an internal rotating joint. The left and right ends of the third three-way joint are respectively connected to the external rotating joint and the internal rotating joint. The external rotating joint is connected to the lower rotating cover through a third hose, and the internal rotating joint is connected to the second polytetrafluoroethylene rigid tube.

[0012] As a preferred solution, the acclimation method of the bacterial solution is as follows: 10 g of the in situ aqueous medium is added to a 500 mL serum bottle, which is filled with simulated groundwater with a dissolved oxygen concentration of less than 0.5 mg / L, and 2 mL / L of sodium lactate is added as a carbon source; the culture is carried out in a shaker at 25°C and 120 rpm, and the SO4 content in the sample is measured regularly. 2- Concentration, the solution was observed to become noticeably black with a pungent odor, indicating successful microbial acclimation. In addition, the simulated groundwater was replaced weekly to maintain microbial activity and ensure its use in subsequent experiments.

[0013] As a preferred embodiment, the preparation method of xanthan gum modified zero-valent iron slurry is as follows: 1 L of ultrapure water and xanthan gum are added to a conical flask, and N2 is introduced into the flask to ensure that the dissolved oxygen concentration in the water is less than 0.5 mg / L; while keeping the bottle mouth sealed, use a mechanical stirrer to stir at high speed for 1 hour until the xanthan gum is evenly dispersed; then, 10 g of micron zero-valent iron (mZVI) is added, and the sealed stirring is continued for 1 hour to ensure that the zero-valent iron is evenly dispersed and modified, thereby obtaining a uniformly dispersed xanthan gum modified zero-valent iron slurry.

[0014] As a preferred solution, the injection bottle is filled with simulated groundwater containing trichloroethylene, and flows from bottom to top into the seepage column at a flow rate of 96.00 μL / min, equivalent to a groundwater flow rate of 11.01 cm / d, to carry out a simulation experiment on in-situ removal of trichloroethylene from groundwater.

[0015] Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art: (1) The present invention solves the problem of temporal and spatial separation between the preliminary biosulfidation of zero-valent iron and the subsequent dechlorination experiment, confirms the possibility of in situ biosulfidation of zero-valent iron in groundwater, and reduces the economic cost of sulfidation technology.

[0016] (2) The round-bottomed vertical biological sterile water sample collection bag with a silicone stopper, the polytetrafluoroethylene rigid tube, the Viton fluororubber pump tube, and the glass seepage column used in the present invention can reduce the device's adsorption of the pollutant trichloroethylene and reduce the impact of the experimental device on the experimental results.

[0017] (3) The detailed connection methods of the experimental device of the present invention can solve the problem of air and water leakage at the interface caused by inconsistent inner diameters of the pipelines.

[0018] (4) The experimental device and method of the present invention for simulating in situ biological sulfidation of zero-valent iron can achieve long-term and stable removal of trichloroethylene from groundwater.

[0019] (5) The device of the present invention has simple operation steps, strong practicality and low cost, which is convenient for the laboratory to simulate the in-situ treatment technology of groundwater pollution in actual sites.

[0020] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which: Figure 1 Schematic diagram of the indoor experimental device of the present invention; Figure 2is a structural diagram of the combined device of the present invention; Figure 3 The distribution of mZVI in different systems in Application Example 2; Figure 4 This is the SEM image of the original 2 μm mZVI sample of Application Example 2; Figure 5 The SEM images of mZVI samples with different layers after reaction with different systems in Application Example 2; Figure 6 XRD images of mZVI samples with different layers after reactions in different systems in Application Example 2; Figure 7 This is a characteristic diagram of the change of trichloroethylene content in the effluent of different systems over time in Application Example 2. DETAILED DESCRIPTION

[0022] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0023] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0024] The following combination Figures 1 to 7 The experimental device for enhanced in-situ biosulfurization of zero-valent iron to remove trichloroethylene according to an embodiment of the present invention is described in detail.

[0025] like Figure 1 、 Figure 2 As shown, the present invention proposes an experimental device for enhancing the removal of trichloroethylene by in-situ biosulfurization of zero-valent iron, comprising a sampling bag 1, a peristaltic pump 2, a seepage column 3, and a post-treatment column 4; A stainless steel dispensing needle 1.1 is inserted into the sampling bag 1. The outer end of the dispensing needle 1.1 is connected to a Luer connector 1.2. The Luer connector 1.2 is connected to a first polytetrafluoroethylene rigid tube 1.4 via a first flexible tube 1.3. Sealing film is wrapped around the connection between the Luer connector 1.2, the first flexible tube 1.3, and the first polytetrafluoroethylene rigid tube 1.4. The sampling bottle 1 is a round-bottomed, vertical biological sterile water sample collection bag with a silicone stopper.

[0026] The peristaltic pump 2 uses Viton fluororubber pump tubes to connect the left and right ends, the right end is the first Viton fluororubber pump tube 2.1, and the left end is the second Viton fluororubber pump tube 2.2. The other ends of the first Viton fluororubber pump tube 2.1 and the second Viton fluororubber pump tube 2.2 are respectively connected to the first soft and hard tube conversion joint 2.3 and the second soft and hard tube conversion joint 2.4. The first Viton fluororubber pump tube 2.1 is connected to the other end of the first polytetrafluoroethylene hard tube 1.4 through the first soft and hard tube conversion joint 2.3, and the second Viton fluororubber pump tube 2.2 is connected to the second polytetrafluoroethylene hard tube 2.5 through the second soft and hard tube conversion joint 2.4; the first soft and hard tube conversion joint 2.3 and the second soft and hard tube conversion joint 2.4 are both equipped with an inverted cone joint, which is arranged at the hard interface end of the first soft and hard tube conversion joint 2.3 and the second soft and hard tube conversion joint 2.4.

[0027] The seepage column 3 is a glass cylinder with a total length of 36 cm. The upper and lower ends of the seepage column 3 are connected to an upper screw cap 3.1 and a lower screw cap 3.2 respectively; the upper screw cap 3.1 is connected to a first three-way joint 3.4, which is connected to a post-treatment column 4 filled with activated carbon through a second hose 3.5; the lower screw cap 3.2 is connected to the other end of the second polytetrafluoroethylene rigid tube 2.5 through a third hose 3.7 and a combination device 3.3; the bottom and top of the seepage column 3 are evenly filled with 3 cm glass beads, and the middle 30 cm side wall is filled with 5 cm glass beads every other 3 cm. The outer swivel joint 3.8 is connected to the lower screw cap 3.2 via a third hose 3.7, and the inner swivel joint 3.10 is connected to the second polytetrafluoroethylene rigid tube 2.5.

[0028] The middle 30 cm of seepage column 3 was filled with quartz sand in six evenly spaced layers. 10 mL of the acclimated bacterial solution was evenly injected onto the surface of each layer using a syringe. A xanthan gum-modified zero-valent iron slurry was then circulated into the column from multiple points along the sides and bottom. During the filling process, nitrogen was continuously introduced to maintain an anaerobic environment.

[0029] The culture medium was acclimated as follows: 10 g of in situ aqueous medium was added to a 500 mL serum bottle, filled with simulated groundwater with a dissolved oxygen concentration of less than 0.5 mg / L (Table 1), and 2 mL / L of sodium lactate was added as a carbon source; the culture was carried out in a shaker at 25°C and 120 rpm, and the SO4 content in the sample was measured regularly. 2- Concentration, the solution was observed to become noticeably black with a pungent odor, indicating successful microbial acclimation. In addition, the simulated groundwater was replaced weekly to maintain microbial activity and ensure its use in subsequent experiments.

[0030] Table 1 Composition of simulated groundwater The preparation method of xanthan gum-modified zero-valent iron slurry is as follows: 1 L of ultrapure water and xanthan gum are added to a conical flask, and nitrogen is introduced into the flask to ensure that the dissolved oxygen concentration in the water is less than 0.5 mg / L; while keeping the bottle mouth sealed, use a mechanical stirrer to stir at high speed for 1 hour until the xanthan gum is completely dissolved; then, 10 g of micron zero-valent iron is added, and the sealed stirring is continued for 1 hour to ensure that the zero-valent iron is evenly dispersed and modified, thereby obtaining a uniformly dispersed xanthan gum-modified zero-valent iron slurry.

[0031] In-situ removal of trichloroethylene from groundwater: Simulated groundwater containing 10 mg / L trichloroethylene was continuously introduced into the above-mentioned simulation column from bottom to top at a flow rate of 96.00 µL / min, equivalent to a groundwater flow rate of 11.01 cm / d, and injected into the seepage column.

[0032] Application Example 1: The effects of trichloroethylene adsorption on indoor experimental simulations were investigated using the independently improved experimental device described above. A control group consisted of a conventional (soft silicone) tube and a PVC seepage column, while an experimental group consisted of a modified experimental device constructed of a rigid polytetrafluoroethylene tube and a glass seepage column. The seepage column in each device was filled with quartz sand treated with hydrochloric acid soaking and ultrapure water rinsing. Simulated groundwater containing trichloroethylene was continuously introduced into the simulated column from bottom to top at a flow rate of 96.00 µL / min, equivalent to a groundwater flow rate of 11.01 cm / day. All other experimental procedures remained the same. The initial trichloroethylene concentration was C0, the concentration at the seepage column inlet was C1, and the concentration at the seepage column outlet was C2. The adsorption rates of trichloroethylene by the water inlet pipes and the adsorption capacity Q of trichloroethylene by the simulated reaction columns in the two experimental devices obtained using the present invention are shown in Table 2.

[0033] Table 2 shows that the rigid PTFE tube in the experimental group exhibited a lower adsorption rate for trichloroethylene compared to the soft silicone tube in the control group. Furthermore, the glass seepage column in the experimental group exhibited a lower adsorption rate for trichloroethylene compared to the PVC seepage column in the control group. Therefore, the use of rigid PTFE tubes and glass seepage columns in the experimental setup is essential.

[0034] Table 2 Adsorption rate data of trichloroethylene by two experimental devices Application Example 2: The experimental setup and in situ biosulfurization system construction method described above were used to simulate the in situ remediation of trichloroethylene-contaminated groundwater. First, the culture medium described in Table 1 was prepared for microbial acclimation, and 10 mL of the acclimated microbial culture was evenly injected into each layer of quartz sand. A control group of non-xanthan gum-modified mZVI (BS2) with a particle size of 2 µm was injected into the seepage column using a manual syringe through a side opening. A control group of 3 g of xanthan gum-modified mZVI (XG-BS2) with a particle size of 2 µm was used. A 2 L xanthan gum-modified zero-valent iron slurry was injected into the seepage column using a multi-point circulation method. Simulated groundwater containing 10 mg / L trichloroethylene was continuously introduced into the seepage column from bottom to top at a flow rate of 96.00 µL / min, equivalent to a groundwater flow rate of 11.01 cm / d. All other experimental procedures remained the same.

[0035] The distribution of mZVI in the BS2 and XG-BS2 groups obtained in the present invention is as follows: Figure 3 As shown in the figure, due to the lack of xanthan gum modification, the mZVI in BS2 was unevenly distributed within the column, primarily concentrated near the injection port. In contrast, the mZVI in the XG-BS2 group, due to the enhanced suspension stability and mobility of the modified group, was more evenly distributed within the percolation column.

[0036] The SEM image of the original 2 μm mZVI sample used in this experiment is as follows: Figure 4 As shown; SEM images of different layers of mZVI samples after reaction of BS2 and XG-BS2 groups obtained in the present invention, as shown Figure 5 As shown, BS2-U is the upper layer of BS2 group, BS2-M is the middle layer of BS2 group, and BS2-B is the lower layer of BS2 group. Similarly, XG-BS2-U, XG-BS2-M, and XG-BS2-B have the same meaning. Figure 4 and Figure 5 It can be seen that a clear flaky structure is formed on the surface of the iron particles of the BS2 and XG-BS2 groups, indicating that biosulfurization has occurred on the surface of these particles, forming a uniform iron sulfide deposition layer. The XRD images of the mZVI samples of different layers after the reaction of the BS2 and XG-BS2 groups obtained by the present invention are as follows: Figure 6 After the reaction, it was observed that ferrous sulfide (FeS; 205 cm -1 ), lepidocrocite (γ-FeOOH; 252 cm -1 ), pyrite (FeS2; 377 cm -1 ), which once again proved the realization of in situ biosulfurization of zero-valent iron.

[0037] The trichloroethylene content in the effluent of the BS2 and XG-BS2 systems obtained in the present invention changes with time, as shown in FIG. Figure 7As shown in the figure, during the initial run of the seepage column (days 0–15), TCE concentrations in all groups decreased over time. The BS2 group experienced a rapid decrease, reaching its lowest concentration on day 8, with a C / C0 ratio of approximately 0.0. The effluent TCE concentration began to gradually increase around day 14. The XG-BS2 group's TCE concentration reached its lowest concentration on day 10, with a C / C0 ratio of approximately 0.2. The effluent TCE concentration began to gradually increase around day 40. This demonstrates that this method can extend the reaction life of the system and successfully achieve the goal of "transforming sulfidation into dechlorination."

[0038] In the description of the present invention, the term "plurality" refers to two or more than two. Unless otherwise expressly defined, the orientations or positional relationships indicated by the terms "upper" and "lower" are based on the orientations or positional relationships shown in the accompanying drawings. They are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. The terms "connect," "install," and "fix" should be understood in a broad sense. For example, "connection" can mean a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] Throughout this specification, terms such as "one embodiment," "some embodiments," and "specific embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0040] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An experimental device for enhanced in-situ biosulfurization of zero-valent iron to remove trichloroethylene, characterized in that: It includes a sample injection bag (1), a peristaltic pump (2), a percolation column (3), and a post-treatment column (4); A stainless steel dispensing needle (1.1) is inserted into the sample injection bag (1), the outer end of the dispensing needle (1.1) is connected to a Luer internal rotary joint (1.2), and the Luer internal rotary joint (1.2) is connected to a first polytetrafluoroethylene hard tube (1.4) through a first hose (1.3); The peristaltic pump (2) uses a Viton fluororubber pump tube to connect the left and right ends, the right end is a first Viton fluororubber pump tube (2.1), and the left end is a second Viton fluororubber pump tube (2.2), the other ends of the first Viton fluororubber pump tube (2.1) and the second Viton fluororubber pump tube (2.2) are respectively connected to a first soft-hard tube conversion joint (2.3) and a second soft-hard tube conversion joint (2.4), the first Viton fluororubber pump tube (2.1) is connected to the other end of the first polytetrafluoroethylene hard tube (1.4) through the first soft-hard tube conversion joint (2.3), and the second Viton fluororubber pump tube (2.2) is connected to the second polytetrafluoroethylene hard tube (2.5) through the second soft-hard tube conversion joint (2.4); The seepage column (3) is a glass cylinder with a total length of 36 cm. The upper and lower ends of the seepage column (3) are respectively connected to an upper screw cap (3.1) and a lower screw cap (3.2); the upper screw cap (3.1) is connected to a first three-way joint (3.4), and the first three-way joint (3.4) is connected to a post-treatment column (4) whose filling medium is activated carbon through a second hose (3.5); the lower screw cap (3.2) is connected to the other end of the second polytetrafluoroethylene hard tube (2.5) through a third hose (3.7) and a combination device (3.3); the bottom and top of the seepage column (3) are evenly filled with 3 cm glass beads, and the middle 30 cm side wall is opened every 5 cm and is connected by the second three-way joint (3.6); the middle 30 cm of the seepage column (3) is connected to the second three-way joint (3.6). The quartz sand was evenly divided into 6 layers with a diameter of 1 cm. 10 mL of the acclimated bacterial solution was evenly injected into the surface of each layer of quartz sand using a syringe. The xanthan gum-modified zero-valent iron slurry was circulated and injected into the seepage column (3) from multiple points on the side and bottom of (3). During the filling process, N2 was continuously introduced to maintain an anaerobic environment.

2. The experimental device for enhancing in-situ biosulfurization of zero-valent iron to remove trichloroethylene according to claim 1 is characterized in that The sampling bottle (1) is a round-bottom vertical biological sterile water sample collection bag with a silicone stopper.

3. The experimental device for enhancing in-situ biosulfurization of zero-valent iron to remove trichloroethylene according to claim 1 is characterized in that The upper screw cap (3.1) and the lower screw cap (3.2) are made of polytetrafluoroethylene.

4. The experimental device for enhancing in-situ biosulfurization of zero-valent iron to remove trichloroethylene according to claim 1, characterized in that The first soft-hard tube conversion joint (2.3) and the second soft-hard tube conversion joint (2.4) both have built-in inverted cone joints, and the inverted cone joints are arranged at the hard interface ends of the first soft-hard tube conversion joint (2.3) and the second soft-hard tube conversion joint (2.4).

5. The experimental device for enhancing in-situ biosulfurization of zero-valent iron to remove trichloroethylene according to claim 1 is characterized in that The combined device (3.3) includes an external rotary joint (3.8), a third three-way joint (3.9) and an internal rotary joint (3.10), the left and right ends of the third three-way joint (3.9) are respectively connected to the external rotary joint (3.8) and the internal rotary joint (3.10), the external rotary joint (3.8) is connected to the lower rotary cover (3.2) through a third hose (3.7), and the internal rotary joint (3.10) is connected to the second polytetrafluoroethylene hard tube (2.5).

6. The experimental device for enhancing in-situ biosulfurization of zero-valent iron to remove trichloroethylene according to claim 1, characterized in that The bacterial culture was acclimated as follows: 10 g of the in situ aqueous medium was added to a 500 mL serum bottle, which was filled with simulated groundwater (Table 1) with a dissolved oxygen concentration lower than 0.5 mg / L, and 2 mL / L of sodium lactate was added as a carbon source; the culture was carried out in a shaker at 25°C and 120 rpm, and the SO4 content in the sample was measured regularly. 2- concentration, the solution was observed to become obviously black with a pungent odor, indicating that the microorganisms were successfully acclimated.

7. The experimental device for enhancing in-situ biosulfurization of zero-valent iron to remove trichloroethylene according to claim 1, characterized in that The preparation method of the xanthan gum modified zero-valent iron slurry is as follows: 1 L of ultrapure water and xanthan gum are added to a conical flask, and N2 is introduced into the flask to ensure that the dissolved oxygen concentration in the water is lower than 0.5 mg / L; while keeping the bottle mouth sealed, use a mechanical stirrer to stir at high speed for 1 hour until the xanthan gum is completely dissolved; then, 10 g of micron zero-valent iron is added, and the sealed stirring is continued for 1 hour to obtain the xanthan gum modified zero-valent iron slurry.

8. The experimental device for enhancing in-situ biosulfurization of zero-valent iron to remove trichloroethylene according to claim 2, characterized in that The injection bottle (1) is filled with simulated groundwater containing trichloroethylene, and flows into the seepage column from bottom to top at a flow rate of 96.00 μL / min, which is equivalent to a groundwater flow rate of 11.01 cm / d, to carry out a simulation experiment on in-situ removal of trichloroethylene from groundwater.

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