Electrochemical method for synergistically and efficiently degrading pesticide gamma-HCH in water through modified lead dioxide-graphite felt electrode

Abstract

The invention discloses an electrochemical method for synergistically and efficiently degrading pesticide gamma-HCH in water through a modified lead dioxide-graphite felt electrode, and belongs to the field of water treatment through an electrochemical method. The method comprises the following steps: firstly, preparing a modified lead dioxide electrode, constructing an electrolytic reaction system by cooperating with a graphite felt electrode, and performing electrochemical degradation on the pesticide gamma-HCH in water by combining electrolyte. The method is simple and convenient to operate, practical and efficient, has high degradation efficiency and environmental friendliness, realizes degradation of the pesticide gamma-HCH in water in an extremely short time based on direct electron transfer and an indirect oxidation path through the action of leading a cathode and assisting an anode, and keeps a high removal rate in a pH range of 3-11.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, in particular to an electrochemical method for efficiently degrading the pesticide γ-HCH in water by using a modified lead dioxide-graphite felt electrode. Background Art

[0002] Pesticides are essential inputs in agricultural production, designed to increase agricultural yields and ensure their quality. However, in practice, pesticide utilization is extremely low: only approximately 0.1% of pesticides are effectively applied to vegetation, while the remainder enters the atmosphere, water bodies, and soil. Studies have shown that concentrations of various pesticides and their transformation products frequently exceed acute toxicity thresholds or chronic safety limits for aquatic organisms in freshwater ecosystems, including groundwater, rivers, and lakes. This suggests that pesticide pollution is a major stressor of the global freshwater ecosystem crisis, continuously threatening the integrity of freshwater ecosystems and negatively impacting ecosystem function. The organochlorine pesticide hexachlorocyclohexane (HCH) is a prime example. HCH was one of the most commonly used pesticides for agricultural pest control in the mid-20th century. Initially used as technical HCHs (t-HCHs), HCHs were introduced as lindane (Y-HCH) in the late 1970s. Due to its high bioaccumulation and toxicity, its production, sale, and use are prohibited. However, due to its environmental persistence, it can still be detected nationwide. Therefore, finding a method to effectively degrade γ-HCH in water bodies is an urgent problem to be solved.

[0003] In recent years, while membrane separation, material adsorption, and biodegradation processes have shown promising results for treating pesticides in water, they do not achieve efficient degradation of pollutants and are prone to secondary pollution. Electrochemical oxidation is an advanced oxidation technology characterized by operational safety, high automation, wide applicability, ease of operation, high organic pollutant degradation efficiency, and good environmental compatibility. It can be used for the efficient degradation of pesticides in water. In electrochemical oxidation technology, electrode materials are key factors influencing pollutant degradation and mineralization efficiency. Lead dioxide (PbO2) electrodes have high oxygen evolution potential, good conductivity, and low cost. However, pure PbO2 electrodes suffer from issues such as easy exfoliation of the active layer, insufficient catalytic activity, and limited service life. Therefore, we propose an electrochemical method for the efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide an electrochemical method for the efficient degradation of the pesticide γ-HCH in water by using modified lead dioxide-graphite felt electrodes. The method constructs an electrochemical degradation system by synergistically constructing electrodes, can rapidly degrade the pesticide γ-HCH and maintain a high removal rate in a wide pH range, which can effectively solve the problems in the background technology.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solution: an electrochemical method for synergistically and efficiently degrading the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode, comprising the following steps;

[0006] S1 Preparation of modified lead dioxide electrode:

[0007] Preparation of titanium dioxide nanotube substrate: The titanium substrate was etched with oxalic acid solution to obtain a titanium plate, which was then oxidized in ethylene glycol solution at a constant potential of 30V for 1 hour. After secondary oxidation and heat treatment at 500°C, the electrode precursor Ti / TiO2-RNTs with a titanium dioxide nanotube crystal structure was formed;

[0008] Preparation of SnO2-Sb interlayer: The prepared electrode precursor Ti / TiO2-RNTs was placed in a polytetrafluoroethylene-lined stainless steel autoclave filled with 15 mL of 0.1MSnCl4·5H2O and 10 mM SbCl3 ethanol solution and heated at 180°C for 12 h. The SnO2-Sb interlayer was then prepared by calcining at 500°C for 2 h after being cleaned with water and ethanol.

[0009] Preparation of TiO2-RNTs / SnO2-Sb / PbO2-La electrodes: PbO2 coating and La were co-deposited onto the electrode precursor Ti / TiO2-RNTs by electrodeposition. The first electrodeposition was carried out at room temperature at 10 mA / cm 2 The current density was 10 mA / cm2 in a mixed solution of 50 mL 0.1 M PbO and 3.5 M NaOH for 90 min and then the sample was charged at 10 mA / cm2 in an oil bath at 60 °C. 2 The TiO2-RNTs / SnO2-Sb / PbO2-La electrode was obtained by deposition in 100 mL of a mixed solution of 0.5 M Pb(NO3)2, 50 mM NaF, 5 mM La(NO3)3 and 0.1 M HNO3 for 30 min and washing with deionized water.

[0010] S2 Preparation of graphite felt electrodes: The graphite felt was cut into 20 mm × 20 mm pieces, and then ultrasonically treated with deionized water, acetone, ethanol, and deionized water solution, and then dried in an oven to obtain a graphite felt electrode;

[0011] S3 constructed an electrochemical system: a TiO2-RNTs / SnO2-Sb / PbO2-La electrode was used as the anode, a graphite felt electrode was used as the cathode, and the electrode spacing was 10 mm, placed in a single-chamber electrolytic cell with an effective volume of 100 mL;

[0012] S4 Degradation of γ-HCH by electrochemical system based on S3: 100 mL of aqueous solution containing 1 mg / L γ-HCH and 0.1 M Na2SO4 electrolyte was prepared, and then the solution was transferred to the single-chamber electrolytic cell described in S3, and 20 mA / cm 2 The reaction proceeds at a constant current density to complete the degradation of γ-HCH in water.

[0013] Furthermore, in step S1, when preparing the titanium dioxide nanotube substrate, the titanium substrate needs to be etched with 10% oxalic acid solution at 95° C. for 2 hours. The size of the titanium substrate is 20 mm×20 mm×1 mm, and the titanium substrate needs to be polished with coarse sandpaper before etching.

[0014] Furthermore, in step S1, when preparing the titanium dioxide nanotube substrate, the oxidation process uses the titanium plate as the anode and the graphite plate as the cathode, and the electrode spacing is 2 cm.

[0015] Furthermore, in step S1, when preparing the titanium dioxide nanotube substrate, the ethanol solution needs to contain 0.5 wt% NH4F and 4 vol% H2O.

[0016] Furthermore, in step S1, when preparing the titanium dioxide nanotube substrate, the first oxidation time is 1 hour, and the titanium plate after the first oxidation is ultrasonically treated in water for 15 minutes and then subjected to the same second oxidation step.

[0017] Furthermore, in step S1, when preparing the titanium dioxide nanotube substrate, the heating rate during heat treatment is 5° C. / min, and the heat treatment time is 2 h.

[0018] Furthermore, in the preparation of the TiO2-RNTs / SnO2-Sb / PbO2-La electrode in step S1, the target electrode precursor Ti / TiO2-RNTs was used as the anode and the polished titanium plate was used as the cathode in both electrode deposition processes, with an electrode spacing of 2 cm.

[0019] Furthermore, the temperature of the oven during the oven drying process in step S2 is 60°C.

[0020] Furthermore, the content of the single-chamber electrolytic cell in step S3 is 100 mL.

[0021] Furthermore, during the reaction in step S4, a magnetic stirrer is used for stirring, the speed of the magnetic stirrer is set to 500 rpm, the reaction temperature is set to 25±2° C., and the reaction time is 15 minutes.

[0022] Compared with the prior art, the present invention has the following advantages: the electrochemical method of the modified lead dioxide-graphite felt electrode for synergistic and efficient degradation of the pesticide γ-HCH in water has the following advantages:

[0023] By introducing TiO2 nanotubes and SnO2-Sb intermediate layer structure and doping lanthanum (La) element to modify the lead dioxide electrode, an electrochemical degradation system was constructed in conjunction with the graphite felt electrode. 2 After 15 minutes of electrolysis at low temperature, the removal rate of 1 mg / L γ-HCH reached 96.0%. This method is simple to operate, practical and efficient, and has both high degradation efficiency and environmental friendliness. It achieves the degradation of γ-HCH in water in a very short time through the cathode-dominant and anode-assisted effects, based on direct electron transfer and indirect oxidation pathways, and maintains a high removal rate in the pH range of 3-11, breaking through the dependence of traditional electrochemical technology on strong acidic media. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a comparison chart of the degradation effects of γ-HCH by the electrochemical system constructed by the five electrode pairs in Example 1 of the present invention;

[0025] Figure 2 2 is a comparison diagram of the degradation effects of γ-HCH in the anode chamber and cathode chamber of a dual-chamber electrolytic cell in Example 2 of the present invention;

[0026] Figure 3 This is a comparison chart of the degradation effects of γ-HCH under different current density conditions in Example 3 of the present invention;

[0027] Figure 4 This is a comparison chart of the degradation effects of γ-HCH under different pH conditions in Example 4 of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] See also Figure 1-4 , the present invention provides a technical solution: an electrochemical method for synergistically and efficiently degrading the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode, comprising the following steps;

[0030] S1 Preparation of modified lead dioxide electrode:

[0031] Preparation of titanium dioxide nanotube substrate: The titanium substrate is etched with oxalic acid solution to obtain a titanium plate, which is oxidized in ethylene glycol solution at a constant potential of 30V for 1 hour, and then subjected to secondary oxidation and heat treatment at 500°C to form an electrode precursor Ti / TiO2-RNTs with a titanium dioxide nanotube crystal structure. The etching of the titanium substrate requires 10% oxalic acid solution at 95°C for 2 hours. The size of the titanium substrate is 20mm×20mm×1mm. The titanium substrate needs to be polished with coarse sandpaper before etching. The oxidation process uses the titanium plate as the anode and the graphite plate as the cathode. The electrode spacing is 2cm. The ethanol solution needs to contain 0.5wt% NH4F and 4vol% H2O. The first oxidation time is 1 hour. After the first oxidation, the titanium plate is ultrasonically treated in water for 15 minutes and then subjected to the same second oxidation steps. The heating rate during heat treatment is 5°C / minute, and the heat treatment time is 2 hours.

[0032] Preparation of SnO2-Sb interlayer: The prepared electrode precursor Ti / TiO2-RNTs was placed in a polytetrafluoroethylene-lined stainless steel autoclave filled with 15 mL of 0.1MSnCl4·5H2O and 10 mM SbCl3 ethanol solution and heated at 180°C for 12 h. The SnO2-Sb interlayer was then prepared by calcining at 500°C for 2 h after being cleaned with water and ethanol.

[0033] Preparation of TiO2-RNTs / SnO2-Sb / PbO2-La electrodes: PbO2 coating and La were co-deposited onto the electrode precursor Ti / TiO2-RNTs by electrodeposition. The first electrodeposition was carried out at room temperature at 10 mA / cm 2 The current density was 10 mA / cm2 in a mixed solution of 50 mL 0.1 M PbO and 3.5 M NaOH for 90 min and then the sample was charged at 10 mA / cm2 in an oil bath at 60 °C. 2 The TiO2-RNTs / SnO2-Sb / PbO2-La electrodes were obtained after washing with deionized water. In both electrodeposition processes, the target electrode precursor Ti / TiO2-RNTs was used as the anode and the polished titanium plate was used as the cathode. The electrode spacing was 2 cm.

[0034] S2 Preparation of graphite felt electrodes: The graphite felt was cut into 20 mm × 20 mm pieces, and then ultrasonically treated with deionized water, acetone, ethanol, and deionized water solution, and then dried in an oven at 60°C to obtain a graphite felt electrode;

[0035] S3 constructed an electrochemical system: a TiO2-RNTs / SnO2-Sb / PbO2-La electrode was used as the anode, a graphite felt electrode was used as the cathode, and the electrode spacing was 10 mm, placed in a single-chamber electrolytic cell with an effective volume of 100 mL;

[0036] S4 Degradation of γ-HCH by electrochemical system based on S3: 100 mL of aqueous solution containing 1 mg / L γ-HCH and 0.1 M Na2SO4 electrolyte was prepared, and then the solution was transferred to the single-chamber electrolytic cell described in S3, and 20 mA / cm 2 The reaction was carried out at a constant current density of , and the degradation of γ-HCH in the water was completed. A magnetic stirrer was used for stirring during the reaction. The speed of the magnetic stirrer was set to 500 rpm, the reaction temperature was set to 25±2°C, and the reaction time was 15 minutes.

[0037] The present invention provides the following embodiments:

[0038] Example 1: Effect of electrodes on γ-HCH degradation

[0039] In order to verify the high efficiency of the electrochemical system composed of a composite anode (TiO2-RNTs / SnO2-Sb / PbO2-La) and a graphite felt cathode in degrading γ-HCH, the degradation experiment of γ-HCH by the electrochemical system constructed with different electrode groups was carried out. The operation steps are as follows:

[0040] (1) Five 100 mL aqueous solutions containing 1 mg / L γ-HCH and 0.1 M Na2SO4 electrolyte were prepared without adjusting the pH of the solution (original pH = 6.3);

[0041] (2) Constructing an electrochemical system with five electrode pairs:

[0042] Group 1, commercial PbO2 anode + graphite felt (GF) cathode;

[0043] Group 2, TiO2-RNTs / SnO2-Sb / PbO2-La anode + GF cathode;

[0044] Group 3, TiO2-RNTs / SnO2-Sb / PbO2-La anode + graphite plate (GP) cathode;

[0045] Group 4, TiO2-RNTs / SnO2-Sb / PbO2-La anode + titanium plate (TP) cathode;

[0046] Group 5, TiO2-RNTs / SnO2-Sb / PbO2-La anode + stainless steel (SSP) cathode.

[0047] (3) Apply 20mA / cm 2The degradation experiment was carried out at a constant current density of , the distance between the anode and cathode electrodes in the system was 10 mm, the speed of the magnetic stirrer was 500 rpm, and the temperature was 25±2°C;

[0048] (4) After electrolysis for 0, 1, 3, 5, 10, and 15 minutes, 1 mL of water sample was taken into a 10 mL centrifuge tube and 3 mL of n-hexane (chromatographic grade) was added. The sample was vortexed for 1 hour and then centrifuged for 10 minutes (3000 rpm). The upper n-hexane layer was collected and analyzed by gas chromatography-electron capture detector (GC-ECD) to determine the concentration of γ-HCH in the solution.

[0049] Figure 1 The figure is a comparison of the degradation effects of γ-HCH by the electrochemical system constructed by the five electrode pairs in this embodiment. Figure 1 It can be seen that the degradation rate constant k of group 2 for γ-HCH is 0.28493min -1 Higher than Group 1 (0.22906min -1 ), and the second group reached the equilibrium point faster than the first group. After 15 minutes of electrolysis, the removal rate of γ-HCH reached 96.0%, indicating that the catalytic performance of the modified anode TiO2-RNTs / SnO2-Sb / PbO2-La was improved to a certain extent. The degradation rate constant of γ-HCH in the second group was 9.74 times that of the third, fourth and fifth groups (k = 0.02925min). -1 ), 7.06 times (k=0.04038min -1 ), 11.97 times (k=0.02381min -1 ), indicating that when graphite felt with high specific surface area is used as cathode, the removal rate of γ-HCH is increased by more than 50% compared with other cathode materials, confirming that the electrochemical degradation system constructed by TiO2-RNTs / SnO2-Sb / PbO2-La anode and graphite felt cathode can efficiently degrade γ-HCH.

[0050] Example 2: Determining the role of anode / cathode in the degradation of γ-HCH

[0051] In order to clarify the role of anode / cathode in the electrochemical system of TiO2-RNTs / SnO2-Sb / PbO2-La anode and graphite felt cathode on the degradation of γ-HCH, a double-chamber electrochemical degradation experiment was carried out. The operation steps are as follows:

[0052] (1) A cation exchange membrane was used to separate the anode chamber and the cathode chamber, and 50 mL of an aqueous solution containing 1 mg / L γ-HCH and 0.1 M Na2SO4 electrolyte (pH = 6.3) was added to each of the anode chamber and the cathode chamber;

[0053] (2) The TiO2-RNTs / SnO2-Sb / PbO2-La described in Example 1 was used as the anode (in the anode chamber) and the graphite felt was used as the cathode (in the cathode chamber). The electrode spacing was 50 mm and the current density was 20 mA / cm 2 , the speed of the magnetic stirrer was 500 rpm, and the temperature was 25 ± 2 °C;

[0054] (3) After electrolysis for 0, 3, 5, 10, and 15 minutes, 1 mL of the solution from each chamber was taken into a 10 mL centrifuge tube and 3 mL of n-hexane (chromatographic grade) was added. After vortexing for 1 hour, the tube was centrifuged for 10 minutes (3000 rpm) and the upper n-hexane layer was taken for GC-ECD analysis to determine the concentration of γ-HCH in the solution.

[0055] Figure 2 The figure is a comparison of the degradation effects of γ-HCH in the anode chamber and cathode chamber in the double-chamber electrolytic cell in this embodiment. Figure 2 It can be seen that after 15 minutes of electrolysis, the removal rate of γ-HCH in the cathode chamber is 95.5%, the removal rate of γ-HCH in the anode chamber is 43.1%, and the degradation rate constant of γ-HCH in the cathode chamber (k = 0.20301min -1 ) is the anode chamber (k=0.03595min -1 ) is 5.65 times that of the cathode, indicating that the degradation of γ-HCH mainly occurs at the cathode. This may be because γ-HCH obtains electrons from the cathode and is reduced and degraded in conjunction with the active oxygen species (such as ·OH, O2 ·– 、 1 O2, etc.) is more efficient than the direct oxidation degradation by the anode and the active oxygen species (such as OH, SO4 ·– Efficiency of indirect degradation (e.g., etc.).

[0056] Example 3: Effect of current density on γ-HCH degradation efficiency

[0057] In order to verify the removal efficiency of γ-HCH at different current densities by the electrochemical degradation system constructed by TiO2-RNTs / SnO2-Sb / PbO2-La anode and graphite felt cathode and determine the optimal operating parameters, the operation steps are as follows:

[0058] (1) The TiO2-RNTs / SnO2-Sb / PbO2-La anode and graphite felt cathode described in Example 1 were used, with the electrode spacing fixed at 10 mm, placed in 100 mL of γ-HCH4 aqueous solution (initial concentration 1 mg / L, pH = 6.3, 0.1 M Na2SO4 electrolyte), the magnetic stirrer speed was 500 rpm, and the temperature was 25 ± 2 ° C;

[0059] (2) Set 5 groups of current density: 0mA / cm 2, 5mA / cm 2 , 10mA / cm 2 , 20mA / cm 2 , 40mA / cm 2 ;

[0060] (3) The concentration of γ-HCH in the solution was determined using the method of step (4) in Example 1.

[0061] Figure 3 This is a comparison chart of the degradation effects of γ-HCH under different current density conditions in this embodiment. Figure 3 It can be seen that at 5mA / cm 2 , 10mA / cm 2 , 20mA / cm 2 , 40mA / cm 2 Under different current densities, the removal rates of γ-HCH after 15 minutes of reaction were 69.5%, 94.2%, 96.0% and 86.6% respectively. When no current was applied, γ-HCH was not degraded in the system. The above results show that when 20 mA / cm 2 The current density of γ-HCH has the best degradation effect.

[0062] Example 4: pH adaptability verification

[0063] In order to investigate the stability of the electrochemical degradation system constructed by TiO2-RNTs / SnO2-Sb / PbO2-La anode and graphite felt cathode for γ-HCH degradation in a wide pH range, five reaction experiments with different pH solutions were set up. The operation steps are as follows:

[0064] (1) A TiO2-RNTs / SnO2-Sb / PbO2-La anode and a graphite felt cathode were used, the electrode spacing was fixed at 10 mm, and the current density was set to 20 mA / cm3 as described in Example 3. 2 ;

[0065] (2) Five 100 mL aqueous solutions containing 1 mg / L γ-HCH and 0.1 M Na2SO4 electrolyte were prepared. For four of these solutions, the initial pH was adjusted to 3.0, 5.0, 9.0, and 11.0 using 0.1 M H2SO4 and 0.1 M NaOH. The magnetic stirrer was operated at 500 rpm and the temperature was maintained at 25 ± 2°C.

[0066] (3) The concentration of γ-HCH in the solution was determined using the method of step (4) in Example 1.

[0067] Figure 4 This is a comparison chart of the degradation effects of γ-HCH under different pH conditions in this embodiment. Figure 4It can be seen that under the conditions of pH = 3, 5, 6.3, 9, and 11, the removal rates of γ-HCH after 15 minutes of reaction were 81.8%, 94.2%, 96.0%, 83.5%, and 79.9%, respectively, indicating that the electrochemical degradation system constructed by TiO2-RNTs / SnO2-Sb / PbO2-La anode and graphite felt cathode can degrade γ-HCH in a wide pH range, and the removal rate reaches more than 79%. When the pH is 6.3, the effect is the best, with a removal rate of 96%.

[0068] Advantages of the present invention: As shown in Examples 1-4, the present invention achieves the following by constructing an electrochemical degradation system using a modified lead dioxide electrode in conjunction with a graphite felt cathode:

[0069] (1) Highly efficient degradation of γ-HCH, with a γ-HCH removal rate of 96.0% after 15 minutes of electrolysis;

[0070] (2) The anode and cathode synergistically degrade γ-HCH, with the cathode being dominant and the anode assisting;

[0071] (3) The system achieves a γ-HCH removal rate of over 79% in the pH range of 3-11, breaking through the dependence of traditional electrochemical technology on strong acidic media;

[0072] (4) Provide technical support for the efficient degradation of other pesticides in water bodies.

[0073] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An electrochemical method for the efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode, characterized by: The following steps are included: S1 Preparation of modified lead dioxide electrode: Preparation of titanium dioxide nanotube substrate: The titanium substrate was etched with oxalic acid solution to obtain a titanium plate, which was then oxidized in ethylene glycol solution at a constant potential of 30V for 1 hour. After secondary oxidation and heat treatment at 500°C, the electrode precursor Ti / TiO2-RNTs with a titanium dioxide nanotube crystal structure was formed; Preparation of SnO2-Sb interlayer: The prepared electrode precursor Ti / TiO2-RNTs was placed in a polytetrafluoroethylene-lined stainless steel autoclave filled with 15 mL of 0.1MSnCl4·5H2O and 10 mM SbCl3 ethanol solution and heated at 180°C for 12 h. It was then washed with water and ethanol and calcined at 500°C for 2 h to prepare the SnO2-Sb interlayer; Preparation of TiO2-RNTs / SnO2-Sb / PbO2-La electrodes: PbO2 coating and La were co-deposited onto the electrode precursor Ti / TiO2-RNTs by electrodeposition. The first electrodeposition was carried out at room temperature at 10 mA / cm 2 The current density was 10 mA / cm2 in a mixed solution of 50 mL 0.1 M PbO and 3.5 M NaOH for 90 min and then the sample was charged at 10 mA / cm2 in an oil bath at 60 °C. 2 The current density was 100 mL of a mixed solution of 0.5 MPa(NO3)2, 50 mM NaF, 5 mM La(NO3)3 and 0.1 M HNO3 for 30 min, and the TiO2-RNTs / SnO2-Sb / PbO2-La electrode was obtained after washing with deionized water; S2 Preparation of graphite felt electrodes: The graphite felt was cut into 20 mm × 20 mm pieces, and then ultrasonically treated with deionized water, acetone, ethanol, and deionized water solution, and then dried in an oven to obtain a graphite felt electrode; S3 constructed an electrochemical system: a TiO2-RNTs / SnO2-Sb / PbO2-La electrode was used as the anode, a graphite felt electrode was used as the cathode, and the electrode spacing was 10 mm, placed in a single-chamber electrolytic cell with an effective volume of 100 mL; S4 Degradation of γ-HCH by electrochemical system based on S3: 100 mL of aqueous solution containing 1 mg / L γ-HCH and 0.1 M Na2SO4 electrolyte was prepared, and then the solution was transferred to the single-chamber electrolytic cell described in S3, and 20 mA / cm 2 The reaction proceeds at a constant current density to complete the degradation of γ-HCH in water.

2. The electrochemical method for the synergistic and efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: In step S1, when preparing the titanium dioxide nanotube substrate, the titanium substrate needs to be etched with 10% oxalic acid solution at 95° C. for 2 hours. The size of the titanium substrate is 20 mm×20 mm×1 mm. The titanium substrate needs to be polished with coarse sandpaper before etching.

3. The electrochemical method for the synergistic and efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: In step S1, when preparing the titanium dioxide nanotube substrate, the titanium plate is used as the anode and the graphite plate is used as the cathode during the oxidation process, and the electrode spacing is 2 cm.

4. The electrochemical method for the synergistic and efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: In step S1, when preparing the titanium dioxide nanotube substrate, the ethanol solution needs to contain 0.5 wt% NH4F and 4 vol% H2O.

5. The electrochemical method for the efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: In step S1, when preparing the titanium dioxide nanotube substrate, the first oxidation time is 1 hour. After the first oxidation, the titanium plate is ultrasonically treated in water for 15 minutes and then subjected to the second oxidation with the same steps.

6. The electrochemical method for the synergistic and efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: In step S1, when preparing the titanium dioxide nanotube substrate, the heating rate during heat treatment is 5° C. / min and the heat treatment time is 2 h.

7. The electrochemical method for the synergistic and efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: In the preparation of the TiO2-RNTs / SnO2-Sb / PbO2-La electrode in step S1, the target electrode precursor Ti / TiO2-RNTs was used as the anode in both electrodeposition processes, and the polished titanium plate was used as the cathode, with an electrode spacing of 2 cm.

8. The electrochemical method for the synergistic and efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: The temperature of the oven during the oven drying process in step S2 is 60°C.

9. The electrochemical method for the efficient degradation of the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: The content of the single-chamber electrolytic cell in step S3 is 100 mL.

10. The electrochemical method for synergistically and efficiently degrading the pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: During the reaction in step S4, a magnetic stirrer was used for stirring. The speed of the magnetic stirrer was set to 500 rpm, the reaction temperature was set to 25±2° C., and the reaction time was 15 minutes.

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