Composite titanium electrode, preparation method thereof and method for removing polycyclic aromatic hydrocarbon in soil

Abstract

The invention discloses a composite titanium electrode and a preparation method thereof, the composite titanium electrode comprises a titanium mesh base material and a coating arranged on the titanium mesh base material, and the coating comprises an iron-based MOF carbon material and polytetrafluoroethylene. The preparation method of the composite titanium electrode comprises the following steps: a, adding an iron-based MOF carbon material and an adhesive into a solvent, and mixing and dispersing to obtain a black colloidal mixture; and b, smearing the colloidal mixture on a titanium mesh, carrying out tabletting treatment, washing and drying to obtain the composite titanium electrode. The prepared electrode material has an excellent catalytic effect while playing an electrode role, the removal rate of polycyclic aromatic hydrocarbon in low-permeability soil is greatly increased, meanwhile, disturbance to the pH of the soil is reduced, and the electrode material is suitable for remediation of the low-permeability soil.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation, and specifically relates to a composite titanium electrode and a preparation method thereof, and in particular, also relates to a method for removing polycyclic aromatic hydrocarbons in soil. Background Art

[0002] Most PAHs are hydrophobic and lipophilic, making them difficult to degrade. The accumulation of PAHs in soil / sediment is a major factor in the transfer of pollution to soil, groundwater, plants, and even food. Soil is the primary transit point and reservoir for PAHs, containing over 90% of PAHs in the environment. Low-molecular-weight PAHs with two or three benzene rings are more easily degraded due to their relatively high solubility and volatility. Natural degradation becomes more difficult as the number of hydrocarbon rings increases. Benzo[a]pyrene (BaP) is one of the five-ring high-ring aromatic hydrocarbons. PAHs are carcinogenic to mammals, particularly humans. Many PAHs have been shown to be carcinogenic, with benzo[a]pyrene (BaP) being a particularly potent carcinogen.

[0003] Low permeability soil refers to soil composed mainly of silt and clay, with small pores and a permeability coefficient of less than 10. -5 cm / s soil. Low permeability soil has a series of unique characteristics such as small particle size, large specific surface area, high porosity, poor pore connectivity, and large capillary resistance at multiphase interfaces, all of which affect its seepage characteristics. Most contaminated soils at remediation sites contain low permeability layers. These low permeability layers are mainly composed of silt and clay with small pores. Most organic pollutants are concentrated in these low permeability zones, posing a threat to groundwater supply and ecosystem security. When low permeability strata are not fully remediated, residual pollutants will contaminate adjacent aquifers through back diffusion. Traditional remediation technologies, such as multiphase extraction and in situ chemical oxidation / reduction, are not suitable for low permeability sites because these methods rely on fluid flow to remove pollutants, while the low permeability of the soil limits the contact and desorption of pollutants. Phytoremediation or natural attenuation cannot meet the requirements of certain remediation time periods due to the long remediation time. Therefore, there is an urgent need to research and improve soil remediation. Summary of the Invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems: electrokinetic remediation can enhance the mobility of pollutants and remediation reagents in low-permeability sites through ionization, electroosmosis, electrophoresis, etc. At present, some studies have adopted a combination of electrokinetic remediation and advanced oxidation to repair soil, but in related technologies, there are still problems such as the nano zero-valent iron added during the repair process has poor stability and easy agglomeration due to its small particle size and magnetism, which affects the activity and mobility of the reaction, resulting in less than ideal repair effects, and the electrokinetic remediation treatment causes the pH of the repaired soil to change, thereby causing soil compaction, which makes the compacted soil hard, lacks oxygen, and destroys the structure, affecting subsequent land use. Therefore, it is necessary to conduct in-depth research on electrokinetic soil remediation technology.

[0005] The present invention aims to at least partially address one of the technical problems in the related art. To this end, embodiments of the present invention provide a composite titanium electrode and a method for preparing the same. The prepared electrode material not only functions as an electrode but also exhibits an excellent catalytic effect, significantly improving the removal rate of polycyclic aromatic hydrocarbons in low-permeability soils while minimizing soil pH disturbances, making it suitable for the remediation of low-permeability soils.

[0006] The composite titanium electrode of the embodiment of the present invention includes a titanium mesh substrate and a coating provided on the titanium mesh substrate, wherein the coating includes an iron-based MOF carbon material and polytetrafluoroethylene.

[0007] Advantages and technical effects brought by the composite titanium electrode of the embodiment of the present invention: The composite titanium electrode of the embodiment of the present invention has an iron-based MOF carbon coating arranged on the titanium mesh, so that the electrode material has excellent catalytic activity for oxidants. In the electrokinetic remediation of soil, it can effectively improve the removal rate of polycyclic aromatic hydrocarbons, avoiding the problems of agglomeration and poor catalytic stability caused by the use of nano zero-valent iron in the existing technology, and at the same time improving the pH of the soil and reducing the occurrence of soil acidification / alkalinization problems, and has broad application prospects.

[0008] In some embodiments, in the composite titanium electrode, the mass percentage of the iron-based MOF carbon material is 15-70%.

[0009] In some embodiments, the iron content of the iron-based MOF carbon material is 1%-5% by weight.

[0010] The present invention also provides a method for preparing a composite titanium electrode, comprising the following steps:

[0011] a. Adding the iron-based MOF carbon material and the binder to the solvent, mixing and dispersing them to obtain a black colloidal mixture;

[0012] b. The colloidal mixture is applied to a titanium mesh, pressed into a sheet, and washed and dried to obtain a composite titanium electrode.

[0013] Advantages and technical effects brought by the preparation method of the composite titanium electrode of the embodiment of the present invention: 1. The method of the embodiment of the present invention coats the iron-based MOF carbon material and polytetrafluoroethylene emulsion on the titanium mesh and presses it into an electrode material, so that the prepared electrode material can not only play the role of an electrode, but also has stable and excellent catalytic performance for oxidants. In the electric remediation treatment of the soil, it can greatly improve the removal rate of polycyclic aromatic hydrocarbons in the soil, reduce the disturbance of the soil pH, and improve the soil acidification / alkalinization problem; 2. The method of the embodiment of the present invention has a simple preparation method, and the raw materials are easily available. It can be used for the remediation of low-permeability soils and has broad prospects.

[0014] In some embodiments, in step a, the preparation method of the iron-based MOF carbon material includes: dissolving ferric chloride and 2-aminoterephthalic acid in N,N-dimethylformamide, adding sodium hydroxide solution, heating to react, separating, washing, and drying to obtain a solid iron-based MOF; pyrolyzing the iron-based MOF to obtain an iron-based MOF carbon material.

[0015] In some embodiments, the molar ratio of ferric chloride to 2-aminoterephthalic acid is (1-2):1; the temperature of the heating reaction is 90-150°C, and the reaction time is 8-15h; the temperature of the pyrolysis treatment is 600-900°C, and the pyrolysis treatment time is 1-3h.

[0016] In some embodiments, in step a, the solvent comprises at least one of ethanol, N,N-dimethylformamide, and N-methylpyrrolidone.

[0017] In some embodiments, in step a, the binder includes at least one of polytetrafluoroethylene emulsion or polyvinylidene fluoride. Preferably, the mass ratio of the iron-based MOF carbon material to the binder is (1-6):4.

[0018] The present invention also provides an application of a composite titanium electrode for electrokinetic remediation of polycyclic aromatic hydrocarbons (PAHs) in soil. The composite titanium electrode of the present invention, when used as an electrode material, exhibits excellent catalytic activity toward oxidants, enabling effective electrokinetic remediation of PAHs in soil.

[0019] The present invention also provides a method for removing polycyclic aromatic hydrocarbons in soil, comprising the following steps:

[0020] S1. Placing the soil to be remediated in an electric remediation device, wherein an anode chamber and a cathode chamber are provided at both ends of the electric remediation device, a soil chamber is provided in the middle, a polytetrafluoroethylene membrane is provided between the soil chamber and the anode chamber and / or cathode chamber, and at least one of the electrode chambers of the anode chamber and the cathode chamber uses a composite titanium electrode according to an embodiment of the present invention or a composite titanium electrode prepared by the method according to an embodiment of the present invention as an electrode;

[0021] S2. Add ultrapure water to the two electrode chambers, add a non-ionic surfactant and an oxidant to the anode chamber, and apply voltage to perform electric repair treatment.

[0022] In the method for removing polycyclic aromatic hydrocarbons in soil of the embodiment of the present invention, soil leaching technology, advanced catalytic oxidation technology and electrokinetic remediation technology are used in combination, and non-ionic surfactants are used to increase the apparent solubility of hydrophobic organic pollutants, effectively increase the mobility of pollutants in the soil, greatly improve the removal rate of polycyclic aromatic hydrocarbons, and reduce the disturbance to soil pH.

[0023] In some embodiments, in step S1, the composite titanium electrode is disposed in the anode chamber as an anode, the mass percentage of the iron-based MOF carbon material in the composite titanium electrode is 15-70%, and the cathode chamber uses a graphite electrode as a cathode.

[0024] In some embodiments, in step S1, the composite titanium electrode is disposed in a cathode chamber as a cathode, the mass percentage of the iron-based MOF carbon material in the composite titanium electrode is 15-70%, and the anode chamber uses a graphite electrode as an anode.

[0025] In some embodiments, in step S1, the permeability coefficient of the soil to be repaired is less than 10 -5 cm / s.

[0026] In some embodiments, in step S2, the nonionic surfactant comprises at least one of Tween 80, Brij35, or Triton X-100. Preferably, the volume concentration of the nonionic surfactant in the anode solution in the anode chamber is 5-15%.

[0027] In some embodiments, in step S2, the oxidant includes at least one of sodium persulfate, potassium persulfate, or calcium persulfate. Preferably, the concentration of the oxidant in the anode liquid in the anode chamber is 100-300 g / L.

[0028] In some embodiments, in step S2, the voltage gradient is 0.8-1.8 V / cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1is a schematic diagram of the process for preparing the iron-based MOF carbon material in Example 1;

[0030] Figure 2 is a schematic diagram of the electric repair device used in Example 1;

[0031] Figure 3 1. It is a diagram showing the BaP removal effect of the composite titanium electrode of each embodiment and comparative example in the electrokinetic oxidation remediation soil;

[0032] Figure 4 Graph showing the pH of soil after electrokinetic oxidation and soil remediation using composite titanium electrodes of various embodiments and comparative examples;

[0033] Figure 5 is a curve diagram of current changes during the electric repair cycle of each embodiment and comparative example;

[0034] Figure 6 It is a curve diagram of the change of electroosmotic flow during the electric repair cycle of each embodiment and comparative example. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0036] The composite titanium electrode of the embodiment of the present invention includes a titanium mesh substrate and a coating provided on the titanium mesh substrate, wherein the coating includes an iron-based MOF carbon material and polytetrafluoroethylene.

[0037] The composite titanium electrode of the embodiment of the present invention has an iron-based MOF carbon coating arranged on the titanium mesh, so that the electrode material has excellent catalytic activity for oxidants. In the electrokinetic remediation of soil, it can effectively improve the removal rate of polycyclic aromatic hydrocarbons, avoid the problems of agglomeration and poor catalytic stability caused by the use of nano zero-valent iron in the existing technology, and at the same time improve the pH of the soil and reduce the occurrence of soil acidification / alkalinization problems, and has broad application prospects.

[0038] In some embodiments, the iron-based MOF carbon material in the composite titanium electrode comprises 15-70% by weight, and the iron content in the iron-based MOF carbon material is 1-5% by weight. In the embodiments of the present invention, the iron-based MOF carbon material content and the iron content in the electrode are further optimized to further enhance the removal of pollutants from the soil.

[0039] The present invention also provides a method for preparing a composite titanium electrode, comprising the following steps:

[0040] a. Adding an iron-based MOF carbon material and a binder to a solvent, mixing and dispersing them to obtain a black colloidal mixture, preferably, the binder includes at least one of polytetrafluoroethylene emulsion or polyvinylidene fluoride, and the solvent includes at least one of ethanol, N,N-dimethylformamide, and N-methylpyrrolidone; the mass ratio of the iron-based MOF carbon material to the binder is (1-6):4.

[0041] b. The colloidal mixture is applied to a titanium mesh, pressed into a sheet, and washed and dried to obtain a composite titanium electrode.

[0042] The preparation method of the composite titanium electrode in the embodiment of the present invention is to coat the iron-based MOF carbon material and polytetrafluoroethylene emulsion on a titanium mesh and press it into an electrode material, so that the prepared electrode material can not only play the role of an electrode, but also has stable and excellent catalytic performance for oxidants. In the electric remediation treatment of soil, it can greatly improve the removal rate of polycyclic aromatic hydrocarbons in the soil, reduce the disturbance of soil pH, and improve the soil acidification / alkalinization problem; the method of the embodiment of the present invention has a simple preparation method, and the raw materials are easily available. It can be used for the remediation of low-permeability soil and has broad prospects.

[0043] like Figure 1 As shown, in some embodiments, in step a, the preparation method of the iron-based MOF carbon material includes: dissolving ferric chloride and 2-aminoterephthalic acid in N,N-dimethylformamide, adding sodium hydroxide solution, heating to react, separating, washing, and drying to obtain a solid iron-based MOF; and pyrolyzing the iron-based MOF to obtain the iron-based MOF carbon material. Preferably, the molar ratio of ferric chloride to 2-aminoterephthalic acid is (1-2):1; the temperature of the heating reaction is 90-150°C, and the reaction time is 8-15 hours; the temperature of the pyrolysis treatment is 600-900°C, and the pyrolysis treatment time is 1-3 hours. In the embodiment of the present invention, the iron-based MOF carbon material is prepared by the preferred method, which is conducive to further improving the catalytic activity and stability of the composite titanium electrode to the oxidant.

[0044] The present invention also provides an application of a composite titanium electrode for electrokinetic remediation of polycyclic aromatic hydrocarbons (PAHs) in soil. The composite titanium electrode of the present invention, when used as an electrode material, exhibits excellent catalytic activity toward oxidants, enabling effective electrokinetic remediation of PAHs in soil.

[0045] The present invention also provides a method for removing polycyclic aromatic hydrocarbons in soil, comprising the following steps:

[0046] S1. Placing the soil to be remediated in an electric remediation device, wherein an anode chamber and a cathode chamber are provided at both ends of the electric remediation device, a soil chamber is provided in the middle, a polytetrafluoroethylene membrane is provided between the soil chamber and the anode chamber and / or cathode chamber, and at least one of the electrode chambers of the anode chamber and the cathode chamber uses a composite titanium electrode according to an embodiment of the present invention or a composite titanium electrode prepared by the method according to an embodiment of the present invention as an electrode;

[0047] S2. Add ultrapure water to the two electrode chambers, add a non-ionic surfactant and an oxidant to the anode chamber, and apply voltage to perform electric repair treatment.

[0048] In the method for removing polycyclic aromatic hydrocarbons in soil of the embodiment of the present invention, soil leaching technology, advanced catalytic oxidation technology and electrokinetic remediation technology are used in combination, and non-ionic surfactants are used to increase the apparent solubility of hydrophobic organic pollutants, effectively increase the mobility of pollutants in the soil, greatly improve the removal rate of polycyclic aromatic hydrocarbons, and reduce the disturbance to soil pH.

[0049] In some embodiments, in step S1, the composite titanium electrode is arranged in the anode chamber as an anode, the mass percentage of the iron-based MOF carbon material in the composite titanium electrode is 15-70%, preferably 15-40%, and the cathode chamber uses a graphite electrode as the cathode; the composite titanium electrode is arranged in the cathode chamber as a cathode, the mass percentage of the iron-based MOF carbon material in the composite titanium electrode is 15-70%, preferably 45-70%, and the anode chamber uses a graphite electrode as the anode. In the embodiment of the present invention, the composite titanium electrode can be used as both an anode and a cathode. When used in different electrode chambers, the removal effect of polycyclic aromatic hydrocarbons in the soil is further improved by optimizing the content of the iron-based MOF carbon material in the composite titanium electrode.

[0050] In some embodiments, in step S1, the permeability coefficient of the soil to be repaired is less than 10 -5 The method of the embodiment of the present invention can improve the mobility of pollutants in soil and can be applied to the removal of organic pollutants in low-permeability soil.

[0051] In some embodiments, in step S2, the nonionic surfactant comprises at least one of Tween 80, Brij 35, or Triton X-100, preferably at a volume concentration of 5-15% in the anolyte within the anode chamber; the oxidant comprises at least one of sodium persulfate, potassium persulfate, or calcium persulfate, preferably at a concentration of 100-300 g / L in the anolyte within the anode chamber; and the voltage gradient is 0.8-1.8 V / cm. In embodiments of the present invention, the use of the preferred nonionic surfactant facilitates the dissolution of organic pollutants in the soil, further improving pollutant mobility and thereby enhancing pollutant removal efficiency.

[0052] The present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0053] 1. Preparation of composite titanium electrode

[0054] Example 1

[0055] 1. Preparation of iron-based MOF carbon materials

[0056] Ferric chloride hexahydrate (FeCl3.6H2O) and 2-aminoterephthalic acid (NH2-BDC) in a molar ratio of 1:1 are dissolved in N,N-dimethylformamide (DMF); sodium hydroxide solution is then slowly added dropwise to the solution, magnetically stirred for 30 minutes, and then transferred to a reactor with a Teflon lining; the reactor is placed in an oven and maintained at a temperature of 100°C for 12 hours; after cooling, the MOF is centrifuged from the mixed liquid, first washed three times with an organic solvent DMF, and then washed three times with ethanol. After washing, the obtained solid is vacuum dried at 70°C for 12 hours. The obtained solid is the iron-based MOF, which is ground with an agate mortar and set aside; the iron-based MOF is pyrolyzed at 700°C in a tube furnace, and the obtained solid is ground into powder with an agate mortar to obtain an iron-based MOF carbon material, wherein the mass content of iron in the iron-based MOF carbon material is 4.5%.

[0057] 2. Preparation of composite titanium electrode

[0058] The iron-based MOF carbon material and polytetrafluoroethylene (PTFE) (mass ratio of 1:4) emulsion were added to 20 mL of anhydrous ethanol, rapidly stirred at room temperature for 24 hours, and then ultrasonically treated in a 60°C water bath to obtain a black colloidal mixture. The colloidal mixture was evenly spread on a cleaned titanium mesh and pressed using a tablet press. The above steps were repeated many times to obtain a titanium electrode covered with multilayer PFTE-MOF carbon material. The pressed electrode was immersed in ultrapure water to remove residual ethanol and placed in a 60°C oven to dry to obtain a composite titanium electrode.

[0059] In the composite titanium electrode prepared in this embodiment, the mass percentage of the iron-based MOF carbon material is 20%.

[0060] Example 2

[0061] The method is the same as that of Example 1, except that the mass percentage of the iron-based MOF carbon material in the prepared composite titanium electrode is 60%.

[0062] 2. Electric remediation to remove polycyclic aromatic hydrocarbons in soil

[0063] Example 3

[0064] use Figure 2 The electric remediation device shown is used to remediate contaminated soil.

[0065] The main body of the experimental device consists of three parts: the soil chamber 5 in the middle (15cm(l)×8cm(w)×10cm(h)) and the anode chamber 7 and cathode chamber 3 (5cm(l)×8cm(w)×10cm(h)) arranged at both ends of the device. The anode 6 in the anode chamber 7 is the composite titanium electrode prepared in Example 1, and the cathode 4 in the cathode chamber 3 is a graphite electrode. A polytetrafluoroethylene (PTFE) membrane with a pore size of 5μm is set between the soil chamber 5 and the anode chamber 7 / cathode chamber 3 to prevent soil particles from entering the anode chamber 7 and cathode chamber 3. The anode chamber 7 and the cathode chamber 3 are respectively connected to the liquid storage bottle 9, and the electrolyte is circulated by a peristaltic pump 10, and the flow rate is set to 11.0mL / min. The electric repair device adopts a DC regulated power supply 1, and a voltage and ammeter 2 is used to monitor the current change. An overflow channel is set between the anode chamber 7 and the cathode chamber 3 and the liquid storage bottle 9.

[0066] The total mass of the contaminated soil is about 1.5 kg (the permeability coefficient of the contaminated soil is 3.79×10 -6 The soil chamber 5 was loaded with benzo[a]pyrene (BaP) at a concentration of 6 mg / kg (cm / s) in contaminated soil. The soil surface was roughened before each layer to prevent stratification. Ultrapure water was placed in the anode chamber 7 and the cathode chamber 3 for 24 hours to saturate the soil. The nonionic surfactant Tween 80 was then added to the anode chamber 7, resulting in a 10% volume fraction of Tween 80 in the anode chamber's anolyte. The oxidant sodium persulfate (Na2S2O8) was also added to the anode chamber's anolyte to a PS concentration of 200 g / L. The electrolyte used in the anode chamber 7 and cathode chamber 3 was 0.01 M NaNO3. Every 12 hours, the pH of the liquid in the two reservoir bottles 9 connected to the anode and cathode chambers was adjusted to neutral using 2 mol / L NaOH and H2SO4. The voltage gradient was set to 1.0 V / cm.

[0067] The experimental period was 10 days. After the experiment, the soil column was divided into 5 parts according to the distance from the anode. The BaP concentration and pH in each part of the soil were measured to judge the effect of the repair. The results are shown in Figure 3 and Figure 4 .

[0068] Example 4

[0069] The method is the same as that of Example 3, except that the anode 6 in the anode chamber 7 is the composite titanium electrode prepared in Example 2.

[0070] Example 5

[0071] The method is the same as that of Example 3, except that the cathode 4 in the cathode chamber 3 is the composite titanium electrode prepared in Example 1, and the anode 6 in the anode chamber 7 is a graphite electrode.

[0072] Example 6

[0073] The method is the same as that of Example 3, except that the cathode 4 in the cathode chamber 3 is the composite titanium electrode prepared in Example 2, and the anode 6 in the anode chamber 7 is a graphite electrode.

[0074] Comparative Example 1

[0075] The method is the same as that of Example 3, except that the anode 6 in the anode chamber 7 is a titanium mesh.

[0076] The electrode settings and test results used in the methods for removing polycyclic aromatic hydrocarbons in soil in Examples 3-6 and Comparative Example 1 are shown in Tables 1 and Figure 3-6 .

[0077] Table 1

[0078]

[0079] Through Table 1 and Figure 3It can be seen that the use of composite titanium electrodes composited with iron-based MOF carbon materials in Examples 3-6 of the present invention effectively improves the removal rate of BaP in the soil. In each embodiment and comparative example, although a high concentration of Tween 80 can increase the dissolution rate of BaP, it will also clog the soil pores, and Tween 80 can be oxidized by PS. In Example 3, the content of iron-based MOF carbon material in the composite titanium electrode used at the anode is relatively low, at 20%. The efficient catalytic degradation reaction will consume a large amount of Tween 80, reducing the clogging of soil pores by Tween 80. Therefore, in Example 3, the BaP removal rate at each point in the soil chamber is significantly improved. In Example 4, when the content of iron-based MOF carbon material in the composite titanium electrode used as the anode is as high as 60%, although the iron-based MOF carbon material and PS can quickly undergo catalytic degradation reactions in the anode chamber to generate free radicals, the increase in the content of MOF carbon material in the composite titanium electrode at the anode will lead to a decrease in electroosmosis, as shown in FIG. Figure 6 In Example 4, due to the extremely low electroosmotic flow generated by the electrokinetic remediation, only some oxidants and free radicals were able to migrate in the soil chamber, thus limiting the further improvement of the BaP removal rate. In Examples 5 and 6, when a composite titanium electrode containing an iron-based MOF carbon material was used at the cathode, PS and the MOF carbon material were not in direct contact at the beginning. As the electrokinetic remediation process progressed, PS in the anode chamber migrated toward the cathode, and the activating ions in the iron-based MOF carbon material in the composite titanium electrode at the cathode diffused toward the anode. As the content of the iron-based MOF carbon material in the electrode increased, the active sites that could catalyze PS increased, promoting the degradation of BaP. Example 6 showed a higher BaP removal rate.

[0080] Through Table 1 and Figure 4 It can be seen that the methods of Examples 3-6 all showed better control effects on the pH of the soil after repair compared with Comparative Example 1. In Examples 3 and 4, when a composite titanium electrode containing an iron-based MOF carbon material was used at the anode, the iron-based MOF carbon material in the anode was in direct contact with PS, effectively catalyzing the degradation of Tween 80. In particular, in the repair method of Example 4, the iron-based MOF carbon material content in the anode was relatively high, resulting in a decrease in current and electroosmotic flow. Figure 5 and Figure 6 , effectively reducing the severity of the hydrolysis reaction, and the OH generated at the cathode - The amount of is small, resulting in a significant reduction in the ion content in the system, so the pH of the soil after repair is maintained at a low level as a whole. In Examples 5 and 6, when a composite titanium electrode containing an iron-based MOF carbon material is used at the cathode, Fe ions can consume the hydroxide ions (OH-) produced by hydrolysis in the cathode chamber, avoiding the diffusion of OH- to the anode, and effectively reducing the disturbance of soil pH during the repair process.

[0081] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0082] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A composite titanium electrode, characterized in that: The invention comprises a titanium mesh substrate and a coating layer arranged on the titanium mesh substrate, wherein the coating layer comprises an iron-based MOF carbon material and polytetrafluoroethylene.

2. The composite titanium electrode according to claim 1, characterized in that: In the composite titanium electrode, the mass percentage of the iron-based MOF carbon material is 15-70%; And / or, the mass content of iron in the iron-based MOF carbon material is 1%-5%.

3. A method for preparing the composite titanium electrode according to claim 1 or 2, characterized in that: The steps include: a. Adding the iron-based MOF carbon material and the binder to the solvent, mixing and dispersing them to obtain a black colloidal mixture; b. The colloidal mixture is applied to a titanium mesh, pressed into a sheet, and washed and dried to obtain a composite titanium electrode.

4. The method for preparing a composite titanium electrode according to claim 3, wherein: In step a, the preparation method of the iron-based MOF carbon material includes: dissolving ferric chloride and 2-aminoterephthalic acid in N,N-dimethylformamide, adding sodium hydroxide solution, heating for reaction, separating, washing, and drying to obtain a solid iron-based MOF; and pyrolyzing the iron-based MOF to obtain the iron-based MOF carbon material.

5. The method for preparing a composite titanium electrode according to claim 4, characterized in that: The molar ratio of the ferric chloride to 2-aminoterephthalic acid is (1-2):1; And / or, the heating reaction temperature is 90-150° C., and the reaction time is 8-15 hours; And / or, the temperature of the pyrolysis treatment is 600-900° C., and the time of the pyrolysis treatment is 1-3 hours.

6. The method for preparing a composite titanium electrode according to claim 3, characterized in that: In step a, the solvent includes at least one of ethanol, N,N-dimethylformamide, and N-methylpyrrolidone; and / or the adhesive includes at least one of polytetrafluoroethylene emulsion or polyvinylidene fluoride. Preferably, the mass ratio of the iron-based MOF carbon material to the adhesive is (1-6):

4.

7. Use of the composite titanium electrode according to claim 1 or 2 or the composite titanium electrode prepared by the method according to any one of claims 3 to 6 in electrokinetic remediation to remove polycyclic aromatic hydrocarbons in soil.

8. A method for removing polycyclic aromatic hydrocarbons in soil, characterized in that: The steps include: S1. Placing the soil to be remediated in an electric remediation device, wherein an anode chamber and a cathode chamber are provided at both ends of the electric remediation device, a soil chamber is provided in the middle, a polytetrafluoroethylene membrane is provided between the soil chamber and the anode chamber and / or cathode chamber, and at least one of the electrode chambers of the anode chamber and the cathode chamber adopts the composite titanium electrode according to claim 1 or 2 or the composite titanium electrode prepared by the method according to any one of claims 3-6 as an electrode; S2. Add ultrapure water to the two electrode chambers, add a non-ionic surfactant and an oxidant to the anode chamber, and apply voltage to perform electric repair treatment.

9. The method for removing polycyclic aromatic hydrocarbons in soil according to claim 8, characterized in that: In step S1, the composite titanium electrode is set in the anode chamber as an anode, the mass percentage of the iron-based MOF carbon material in the composite titanium electrode is 15-70%, and the cathode chamber uses a graphite electrode as a cathode; And / or, the composite titanium electrode is arranged in the cathode chamber as a cathode, the mass percentage of the iron-based MOF carbon material in the composite titanium electrode is 15-70%, and the anode chamber adopts a graphite electrode as an anode; And / or, the permeability coefficient of the soil to be repaired is less than 10 -5 cm / s.

10. The method for removing polycyclic aromatic hydrocarbons in soil according to claim 8, characterized in that: In step S2, the nonionic surfactant comprises at least one of Tween 80, Brij 35 or Triton X-100, and preferably, the volume concentration of the nonionic surfactant in the anolyte in the anode chamber is 5-15%; and / or, the oxidant comprises at least one of sodium persulfate, potassium persulfate or calcium persulfate, and preferably, the concentration of the oxidant in the anolyte in the anode chamber is 100-300 g / L; And / or, the voltage gradient is 0.8-1.8 V / cm.

Images