An electrochemical method for synergistically and efficiently degrading pesticide gamma-hch in water by using modified lead dioxide-graphite felt electrode

Abstract

The application discloses an electrochemical method for degrading pesticide gamma-HCH in water by using a modified lead dioxide-graphite felt electrode, and belongs to the field of water treatment by using an electrochemical method. The application first prepares a modified lead dioxide electrode, constructs an electrolysis reaction system by cooperating with a graphite felt electrode, and combines an electrolyte to electrochemically degrade pesticide gamma-HCH in water. The method is simple, practical and efficient, has high degradation efficiency and environmental friendliness, and is capable of degrading pesticide gamma-HCH in water in a very short time through cathode leading and anode assisting, based on direct electron transfer and indirect oxidation path, and maintaining a high removal rate in a pH range of 3-11.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of water treatment, in particular to an electrochemical method for synergistically and efficiently degrading pesticide gamma-HCH in water by using a modified lead dioxide-graphite felt electrode. BACKGROUND

[0002] Pesticides are important inputs in the process of agricultural production, aiming to improve the yield of agricultural products and ensure the quality of agricultural products. However, in the actual application process, the utilization rate of pesticides is very low, only about 0.1% of the pesticides can effectively act on the vegetation, and the remaining pesticides enter the atmospheric, water and soil environmental media. Studies have shown that in global groundwater, rivers and lakes and other freshwater ecosystems, the detection concentration of various pesticides and their transformation products frequently exceeds the acute toxicological threshold or chronic safety limit of aquatic organisms, indicating that pesticide pollution is a major stress source of global freshwater ecosystem crisis, which continuously threatens the integrity of the freshwater ecosystem, thereby causing negative effects on the ecosystem function. Among them, the organochlorine pesticide hexachlorocyclohexane (hexachlorocyclohexane, HCH) is typical. Hexachlorocyclohexane is one of the most commonly used pesticides for controlling agricultural pests in the mid-20th century. At the beginning, hexachlorocyclohexane was used in the form of industrial hexachlorocyclohexane (t-HCHs), and after the late 1970s, it was used in the form of lindane (Y-HCH). Due to its high biological accumulation and high toxicity, it has been banned from production, sale and use, but due to its environmental persistence, it can still be detected at present. Therefore, it is an urgent problem to find an effective method for degrading gamma-HCH in water.

[0003] In recent years, although membrane separation, material adsorption and biodegradation processes have good effects on the treatment of pesticides in water, they cannot achieve efficient degradation of pollutants, and are prone to cause secondary pollution and other problems. Electrochemical oxidation is a kind of advanced oxidation technology with good safety, high automation, wide application range, good operation convenience, high efficiency of organic pollutant degradation and good environmental compatibility, which can be used for efficient degradation of pesticides in water. In the electrochemical oxidation technology, the electrode material is a key factor affecting the degradation and mineralization efficiency of pollutants. The lead dioxide (PbO2) electrode has the characteristics of high oxygen evolution potential, good conductivity and low cost. However, the pure PbO2 electrode has problems such as easy peeling of the active layer, insufficient catalytic activity and limited service life. Therefore, we propose an electrochemical method for synergistically and efficiently degrading pesticide gamma-HCH in water by using a modified lead dioxide-graphite felt electrode. SUMMARY

[0004] The technical problem solved by the present application is to overcome the existing defects and provide an electrochemical method for synergistically and efficiently degrading pesticide gamma-HCH in water by using a modified lead dioxide-graphite felt electrode, which can quickly degrade pesticide gamma-HCH and maintain a high removal rate in a wide pH range, thereby effectively solving the problems in the background art.

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

[0006] S1: preparing a modified lead dioxide electrode:

[0007] Preparation of TiO2 nanotube substrate: a titanium substrate is etched by an oxalic acid solution to obtain a titanium plate, which is then oxidized at a constant potential of 30V for 1 hour in an ethylene glycol solution, and then subjected to secondary oxidation and heat treatment at 500 DEG C to form an electrode precursor Ti / TiO2-RNTs with a TiO2 nanotube crystal structure;

[0008] Preparation of SnO2-Sb intermediate layer: the prepared electrode precursor Ti / TiO2-RNTs is placed in a polytetrafluoroethylene-lined stainless steel autoclave containing 15 mL of 0.1M SnCl4·5H2O and 10 mM SbCl3 ethanol solution, heated at 180 DEG C for 12 hours, then washed with water and ethanol, and then calcined at 500 DEG C for 2 hours to form a SnO2-Sb intermediate layer;

[0009] Preparation of TiO2-RNTs / SnO2-Sb / PbO2-La electrode: PbO2 coating and La are co-deposited on the electrode precursor Ti / TiO2-RNTs by electrodeposition, the first electrodeposition is carried out at room temperature with a current density of 10 mA / cm 2 for 90 minutes in a mixed solution of 50 mL of 0.1M PbO and 3.5M NaOH, and then at 60 DEG C oil bath with a current density of 10 mA / cm 2 for 30 minutes in a mixed solution of 100 mL of 0.5M Pb(NO3)2, 50 mM NaF, 5 mM La(NO3)3 and 0.1M HNO3, and then washed with deionized water to obtain a TiO2-RNTs / SnO2-Sb / PbO2-La electrode;

[0010] S2: preparing a graphite felt electrode: the graphite felt is cut into 20mm x 20mm, then treated by ultrasonic treatment with deionized water, acetone, ethanol and deionized water, and then dried in an oven to obtain a graphite felt electrode;

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

[0012] S4 Degradation of γ-HCH based on the electrochemical system constructed in S3: prepare 100 mL of aqueous solution containing 1 mg / L of γ-HCH and 0.1 M Na2SO4 electrolyte, then transfer the solution to the single-chamber electrolytic cell described in S3, apply a constant current density of 20 mA / cm 2 to complete the degradation of γ-HCH in the water body.

[0013] Further, 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 2h, and the size of the titanium substrate is 20mm×20mm×1mm. Before etching, the titanium substrate needs to be polished with coarse sandpaper.

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

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

[0016] Further, in step S1, when preparing the titanium dioxide nanotube substrate, the first oxidation time is 1h, and after the first oxidation of the titanium plate is completed, the titanium plate is ultrasonically treated in water for 15 minutes before the second oxidation is performed.

[0017] Further, 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 2h.

[0018] Further, in step S1, when preparing the TiO2-RNTs / SnO2-Sb / PbO2-La electrode, both times of electrodeposition process use the target electrode precursor Ti / TiO2-RNTs as the anode and a polished smooth titanium plate as the cathode, with an electrode spacing of 2 cm.

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

[0020] Further, in step S3, the single-chamber electrolytic cell contains 100 mL.

[0021] Further, in step S4, a magnetic stirrer is used for stirring during the reaction, the rotation 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 modified lead dioxide-graphite felt electrode synergistic high-efficiency electrochemical method for degrading pesticide gamma-HCH in water has the following advantages:

[0023] By introducing TiO2 nanotube and SnO2-Sb intermediate layer structure and modifying the lead dioxide electrode by doping lanthanum (La) element, an electrochemical degradation system is constructed in cooperation with a graphite felt electrode, and the electrolyte is combined to apply a current density of 20 mA / cm 2 After 15 minutes of electrolysis, the removal rate of 1 mg / L gamma-HCH reaches 96.0%; the method is simple, practical and efficient, has high degradation efficiency and environmental friendliness, is a cathode-dominated anode-assisted method based on direct electron transfer and indirect oxidation path, and realizes the degradation of gamma-HCH in water in a very short time, and maintains a high removal rate in the pH range of 3-11, breaking through the dependence of traditional electrochemical technology on strong acidic medium. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a comparison chart of the degradation effect of the electrochemical system constructed by the five groups of electrodes on gamma-HCH in the embodiment 1 of the present application;

[0025] Figure 2 is a comparison chart of the degradation effect of gamma-HCH in the anode chamber and the cathode chamber of the double-chamber electrolytic cell in the embodiment 2 of the present application;

[0026] Figure 3 is a comparison chart of the degradation effect of gamma-HCH under different current densities in the embodiment 3 of the present application;

[0027] Figure 4 is a comparison chart of the degradation effect of gamma-HCH under different pH conditions in the embodiment 4 of the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] Please refer to Figures 1-4 The present application provides a technical solution: a modified lead dioxide-graphite felt electrode synergistic high-efficiency electrochemical method for degrading pesticide gamma-HCH in water, comprising the following steps:

[0030] S1: preparing a modified lead dioxide electrode:

[0031] Preparation of TiO2-RNTs / SnO2-Sb / PbO2-La electrode: PbO2 coating and La were co-deposited on the electrode precursor Ti / TiO2-RNTs by electrodeposition, the first electrodeposition was carried out at room temperature for 90 min in 50 mL of 0.1 M PbO and 3.5 M NaOH mixed solution at a current density of 10 mA / cm2, then in 100 mL of 0.5 M Pb(NO3)2, 50 mM NaF, 5 mM La(NO3)3 and 0.1 M HNO3 mixed solution at a current density of 10 mA / cm2 for 30 min in a 60 °C oil bath, and the TiO2-RNTs / SnO2-Sb / PbO2-La electrode was obtained after deionized water cleaning, the target electrode precursor Ti / TiO2-RNTs was used as anode, and the polished smooth titanium plate was used as cathode, and the electrode distance was 2 cm;

[0032] Preparation of SnO2-Sb intermediate layer: the prepared electrode precursor Ti / TiO2-RNTs was placed in a polytetrafluoroethylene-lined stainless steel autoclave containing 15 mL of 0.1 M SnCl4·5H2O and 10 mM SbCl3 ethanol solution, heated at 180 °C for 12 h, then washed with water and ethanol, and calcined at 500 °C for 2 h to prepare SnO2-Sb intermediate layer;

[0033] Preparation of TiO2-RNTs / SnO2-Sb / PbO2-La electrode: PbO2 coating and La were co-deposited on the electrode precursor Ti / TiO2-RNTs by electrodeposition, the first electrodeposition was carried out at room temperature for 90 min in 50 mL of 0.1 M PbO and 3.5 M NaOH mixed solution at a current density of 10 mA / cm2, then in 100 mL of 0.5 M Pb(NO3)2, 50 mM NaF, 5 mM La(NO3)3 and 0.1 M HNO3 mixed solution at a current density of 10 mA / cm2 for 30 min in a 60 °C oil bath, and the TiO2-RNTs / SnO2-Sb / PbO2-La electrode was obtained after deionized water cleaning, the target electrode precursor Ti / TiO2-RNTs was used as anode, and the polished smooth titanium plate was used as cathode, and the electrode distance was 2 cm; 2 2 Preparation of TiO2-RNTs / SnO2-Sb / PbO2-La electrode: PbO2 coating and La were co-deposited on the electrode precursor Ti / TiO2-RNTs by electrodeposition, the first electrodeposition was carried out at room temperature for 90 min in 50 mL of 0.1 M PbO and 3.5 M NaOH mixed solution at a current density of 10 mA / cm2, then in 100 mL of 0.5 M Pb(NO3)2, 50 mM NaF, 5 mM La(NO3)3 and 0.1 M HNO3 mixed solution at a current density of 10 mA / cm2 for 30 min in a 60 °C oil bath, and the TiO2-RNTs / SnO2-Sb / PbO2-La electrode was obtained after deionized water cleaning, the target electrode precursor Ti / TiO2-RNTs was used as anode, and the polished smooth titanium plate was used as cathode, and the electrode distance was 2 cm;

[0034] S2 Preparation of graphite felt electrode: the graphite felt was cut into 20 mm × 20 mm, then treated by ultrasonic in deionized water, acetone, ethanol and deionized water, and dried in an oven to obtain the graphite felt electrode, and the temperature of the oven was 60 °C during the drying process;

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

[0036] S4 describes the electrochemical system constructed based on S3 for the degradation of γ-HCH: 100 mL of an aqueous solution containing 1 mg / L γ-HCH and 0.1 M Na₂SO₄ electrolyte was prepared. This solution was then transferred entirely to the single-chamber electrolytic cell described in S3, and an application of 20 mA / cm² was performed. 2 The reaction was carried out at a constant current density to complete the degradation of γ-HCH in the water. 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℃, 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] 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, experiments were conducted on the degradation of γ-HCH using electrochemical systems constructed with different electrode combinations. The operation steps are as follows:

[0040] (1) Prepare 5 groups of 100mL aqueous solutions containing 1mg / L γ-HCH and 0.1M Na2SO4 electrolyte, without adjusting the pH of the solution (original pH = 6.3);

[0041] (2) Construct an electrochemical system with 5 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 20 mA / cm 2Degradation experiments were conducted using a constant current density. The distance between the anode and cathode electrodes in the system was 10 mm, the magnetic stirrer was rotated at 500 rpm, and the temperature was 25 ± 2 ℃.

[0048] (4) After electrolysis for 0, 1, 3, 5, 10 and 15 minutes, take 1 mL of water sample into a 10 mL centrifuge tube and add 3 mL of n-hexane (chromatographic grade). Vortex for 1 hour and centrifuge for 10 minutes (3000 rpm). Take the upper n-hexane layer and analyze it with gas chromatography-electron capture detector (GC-ECD) to determine the concentration of γ-HCH in the solution.

[0049] Figure 1 This is a comparison diagram of the degradation effects of the electrochemical systems constructed with the five electrode pairs in this embodiment on γ-HCH. Figure 1 It can be seen that the degradation rate constant k of γ-HCH in group 2 is 0.28493 min. -1 Higher than Group 1 (0.22906 min) -1 The second group reached the equilibrium point faster than the first group, achieving a γ-HCH removal rate of 96.0% after 15 minutes of electrolysis, indicating a certain improvement in the catalytic performance of the modified anode TiO2-RNTs / SnO2-Sb / PbO2-La. The degradation rate constant of γ-HCH in the second group was 9.74 times that of the third, fourth, and fifth groups (k = 0.02925 min). -1 ), 7.06 times (k = 0.04038min) -1 ), 11.97 times (k = 0.02381 min) -1 The results show that graphite felt with high specific surface area increases the removal rate of γ-HCH 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 roles of anode / cathode in the γ-HCH degradation process

[0051] To elucidate the role of the anode / cathode in the degradation of γ-HCH in the TiO2-RNTs / SnO2-Sb / PbO2-La anode-coordinated graphite felt cathode electrochemical system, a two-chamber electrochemical degradation experiment was conducted. The procedure is 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 respectively.

[0053] (2) Using the TiO2-RNTs / SnO2-Sb / PbO2-La described in Example 1 as the anode (located in the anode chamber) and graphite felt as the cathode (located in the cathode chamber), the electrode spacing is 50 mm and the current density is 20 mA / cm². 2 The magnetic stirrer rotates at 500 rpm and the temperature is 25±2℃;

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

[0055] Figure 2 This is a comparison of the degradation effects of γ-HCH in the anode and cathode chambers of the two-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 was 95.5%, and the removal rate of γ-HCH in the anode chamber was 43.1%. The degradation rate constant of γ-HCH in the cathode chamber (k = 0.20301 min) is... -1 ) is the anode chamber (k = 0.03595 min) -1 The γ-HCH degradation rate was 5.65 times higher than that of γ-HCH, indicating that the degradation mainly occurred at the cathode. This may be because γ-HCH gains electrons from the cathode and is reduced and degraded, in conjunction with the reactive oxygen species (such as ·OH and O2) generated in the cathode chamber. ·– , 1 Indirect degradation (such as O2) is more efficient than direct anodic oxidation degradation, which is accompanied by reactive oxygen species (such as ·OH, SO42-) generated by the anode. ·– The efficiency of indirect degradation (etc.).

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

[0057] To verify the removal efficiency of γ-HCH by the electrochemical degradation system constructed with TiO2-RNTs / SnO2-Sb / PbO2-La anode and graphite felt cathode at different current densities and to determine the optimal operating parameters, the following steps were taken:

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

[0059] (2) Set 5 sets of current densities: 0 mA / cm 25mA / cm 2 10mA / cm 2 20mA / cm 2 40mA / cm 2 ;

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

[0061] Figure 3 This is a comparison graph showing the degradation effect of γ-HCH under different current densities in this embodiment. Figure 3 It can be seen that at 5mA / cm 2 10mA / cm 2 20mA / cm 2 40mA / cm 2 At the specified current densities, the removal rates of γ-HCH after 15 minutes of reaction were 69.5%, 94.2%, 96.0%, and 86.6%, respectively. Furthermore, γ-HCH did not degrade in the system without applied current. These results indicate that applying a current of 20 mA / cm² significantly reduces the degradation rate of γ-HCH. 2 The optimal current density has the best effect on the degradation of γ-HCH.

[0062] Example 4: pH adaptability verification

[0063] To investigate the stability of the electrochemical degradation system constructed with TiO2-RNTs / SnO2-Sb / PbO2-La anode and graphite felt cathode over a wide pH range for γ-HCH degradation, five groups of reaction experiments were conducted with solutions at different pH values. The procedures are as follows:

[0064] (1) A TiO2-RNTs / SnO2-Sb / PbO2-La anode and a graphite felt cathode were used, with the electrode spacing fixed at 10 mm and the current density set to 20 mA / cm² as described in Example 3. 2 ;

[0065] (2) Prepare 5 groups of 100 mL aqueous solutions containing 1 mg / L γ-HCH and 0.1 M Na2SO4 electrolyte. The initial pH of the solution in 4 groups was adjusted to 3.0, 5.0, 9.0 and 11.0 with 0.1 M H2SO4 and 0.1 M NaOH. The magnetic stirrer was set to 500 rpm and the temperature was 25 ± 2℃.

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

[0067] Figure 4 This is a comparison graph showing the degradation effect of γ-HCH under different pH conditions in this embodiment. Figure 4It can be seen that under pH conditions of 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. This indicates that the electrochemical degradation system constructed by TiO2-RNTs / SnO2-Sb / PbO2-La anode and graphite felt cathode can degrade γ-HCH over a wide pH range, with a removal rate of over 79%. The effect was best at pH 6.3, with a removal rate of 96%.

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

[0069] (1) It efficiently degrades γ-HCH, and the removal rate of γ-HCH reaches 96.0% after 15 minutes of electrolysis;

[0070] (2) The anolyte and cathode synergistically degrade γ-HCH, with the cathode playing a dominant role and the anode playing an auxiliary role;

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

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

[0073] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An electrochemical method for the synergistic and efficient degradation of pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode, characterized in that: Includes the following steps; S1 Preparation of modified lead dioxide electrodes: Preparation of titanium dioxide nanotube substrate: Titanium substrate was etched with oxalic acid solution to obtain 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℃, electrode precursors Ti / TiO2-RNTs with titanium dioxide nanotube crystal structure were formed. Preparation of SnO2-Sb interlayer: The prepared electrode precursor Ti / TiO2-RNTs were placed in a polytetrafluoroethylene-lined stainless steel autoclave containing 15 mL of 0.1 M SnCl4·5H2O and 10 mM SbCl3 ethanol solution and heated at 180 °C for 12 h. After cleaning with water and ethanol, the SnO2-Sb interlayer was prepared by calcination at 500 °C for 2 h. Preparation of Ti / TiO2-RNTs / SnO2-Sb / PbO2-La electrode: PbO2 coating and La were co-deposited onto Ti / TiO2-RNTs / SnO2-Sb by electrodeposition. The first electrodeposition was performed at room temperature at 10 mA / cm. 2 The current density was deposited in a mixed solution of 50 mL of 0.1 M PbO and 3.5 M NaOH for 90 minutes, followed by deposition in an oil bath at 60 °C at 10 mA / cm². 2 The current density was deposited in a mixed solution of 100 mL of 0.5 M Pb(NO3)2, 50 mM NaF, 5 mM La(NO3)3 and 0.1 M HNO3 for 30 minutes, and then washed with deionized water to obtain Ti / TiO2-RNTs / SnO2-Sb / PbO2-La electrode; S2 Preparation of graphite felt electrode: The graphite felt is cut into 20mm×20mm pieces, and then subjected to ultrasonic treatment with deionized water, acetone, ethanol and deionized water solution, and dried in an oven to obtain the graphite felt electrode. S3 Electrochemical system construction: Ti / TiO2-RNTs / SnO2-Sb / PbO2-La electrode as anode, graphite felt electrode as cathode, electrode spacing 10mm, placed in a single-chamber electrolytic cell with an effective volume of 100mL; S4 describes the electrochemical system constructed based on S3 for the degradation of γ-HCH: 100 mL of an aqueous solution containing 1 mg / L γ-HCH and 0.1 M Na₂SO₄ electrolyte was prepared. This solution was then transferred entirely to the single-chamber electrolytic cell described in S3, and an application of 20 mA / cm² was performed. 2 The reaction proceeds at a constant current density to complete the degradation of γ-HCH in the water.

2. The electrochemical method for the synergistic and efficient degradation of 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 at 95°C for 2 hours using a 10% oxalic acid solution. The size of the titanium substrate is 20mm×20mm×1mm. Before etching, the titanium substrate needs to be polished with coarse sandpaper.

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

4. The electrochemical method for the synergistic and efficient degradation of 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 ethylene glycol solution needs to contain 0.5 wt% NH4F and 4 vol% H2O.

5. The electrochemical method for the synergistic and efficient degradation of 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 is completed, the titanium plate is ultrasonically treated in water for 15 minutes and then subjected to the same second oxidation process.

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

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

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

9. The electrochemical method for the synergistic and efficient degradation of 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 the synergistic and efficient degradation of pesticide γ-HCH in water using a modified lead dioxide-graphite felt electrode according to claim 1, characterized in that: 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℃, and the reaction time was 15 minutes.

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