A reduced graphene oxide modified nickel foam electrode for electro-fenton method, a preparation method and application thereof

Abstract

The application belongs to the technical field of wastewater treatment, and particularly relates to a reduced graphene oxide modified foam nickel electrode for an electro-Fenton method, a preparation method and application, and the preparation method of the reduced graphene oxide modified foam nickel electrode for the electro-Fenton method, characterized by comprising the following steps: S1: pretreating a foam nickel sheet, ultrasonic cleaning, and obtaining the pretreated foam nickel sheet; S2: configuring an oxidized graphene solution, performing hydrothermal reaction on the foam nickel sheet obtained in S1 and the oxidized graphene solution, cleaning, freeze-drying, and obtaining the reduced graphene oxide modified foam nickel electrode. The preparation method of the reduced graphene oxide modified foam nickel electrode for the electro-Fenton method has the effect of improving the electro-Fenton efficiency, thereby promoting the degradation of oil and gas field wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a reduced graphene oxide modified foam nickel electrode for the electro-Fenton method, its preparation method, and its application. Background Technology

[0002] Petroleum industry wastewater contains a large amount of persistent organic pollutants (POPs). Due to the potential seepage of this wastewater, it may have adverse effects on groundwater, river water, and even animals, plants, and humans. Economical and effective treatment methods are needed. Due to the recalcitrant nature of organic pollutants in petroleum industry wastewater, conventional treatment methods such as physical and biological methods are insufficient to effectively remove them. Advanced oxidation methods (AOCs) within chemical treatment can effectively remove recalcitrant organic pollutants. However, conventional AOCs, such as the persulfate process and the traditional Fenton process, require additional oxidant input and significant energy and resource support, and the treatment steps are relatively cumbersome. Therefore, there is an urgent need for low-cost, high-efficiency, and environmentally friendly wastewater treatment methods and devices. The electro-Fenton process is a novel, high-efficiency, and environmentally friendly advanced oxidation treatment technology. However, the development and preparation of high-efficiency electro-Fenton cathodes is a key challenge in electro-Fenton technology, hindering its widespread adoption and application. Meanwhile, in the advanced oxidation wastewater treatment process based on the electro-Fenton process, there are often problems such as slow Fe(III) / Fe(II) circulation, which reduces the efficiency of electro-Fenton oxidation. Therefore, there is an urgent need for a method to prepare a reduced graphene oxide modified foam nickel electrode for the electro-Fenton method. Summary of the Invention

[0003] To address the problems of existing technologies, this invention provides a method for preparing a reduced graphene oxide-modified nickel foam electrode for the electro-Fenton method.

[0004] A method for preparing a reduced graphene oxide-modified nickel foam electrode using the electro-Fenton method includes the following steps:

[0005] S1: First, pre-treat the nickel foam and cut it into a nickel foam sheet. Then, immerse the nickel foam sheet in HCl solution, pure ethanol solution and ultrapure water in sequence, and sonicate it to clean the oxide layer and organic / inorganic impurities on the surface to obtain the pre-treated nickel foam sheet.

[0006] S2: Prepare a solution of graphene oxide, and then put the cleaned nickel foam sheet and graphene oxide from S1 into a polytetrafluoroethylene hydrothermal reactor for hydrothermal reaction. After natural cooling, simply wash the cooled nickel foam sheet loaded with reduced graphene oxide with ultrapure water and then freeze dry it in a freeze dryer to obtain the final reduced graphene oxide modified nickel foam electrode.

[0007] Furthermore, the pretreatment described in S1 involves immersing the nickel foam sheet sequentially in an HCl solution, a pure ethanol solution, and ultrapure water.

[0008] Furthermore, the ultrasound time described in S1 is 15 minutes.

[0009] Furthermore, the hydrothermal reaction time described in S2 is 10–15 h, and the hydrothermal temperature is 170 °C–200 °C.

[0010] Furthermore, the freezing temperature described in S2 is -60°C, and the freeze-drying time is 24 hours.

[0011] Furthermore, the reactor in the hydrothermal reaction of S2 is made of polytetrafluoroethylene.

[0012] A reduced graphene oxide-modified nickel foam electrode for use in the electro-Fenton method.

[0013] An application of a reduced graphene oxide-modified nickel foam electrode using the electro-Fenton method, wherein the reduced graphene oxide-modified nickel foam electrode is used in electrode preparation.

[0014] Technical effect

[0015] (1) The reduced graphene oxide modified nickel foam electrode for the electro-Fenton method provided by the present invention, as the cathode, has oxygen-containing structures such as defective carbon sites and carboxyl groups on the surface of the reduced graphene oxide that are conducive to dissolved oxygen adsorption and electron transfer. This can promote the adsorption of dissolved oxygen and the transfer of electrons from the applied electric field to oxygen, which is conducive to the two-electron redox reaction to reduce O2 to H2O2. The high specific surface area of ​​porous nickel foam provides sites for Fe(III) to accept electrons for reduction at the cathode.

[0016] (2) The reduced graphene oxide-modified nickel foam electrode for the electro-Fenton method provided by this invention generates superoxide radical intermediates during the two-electron redox reaction at the cathode, which can react with Fe(III) to produce Fe(II), thereby improving the Fe(III) reduction capacity. Under the effects of efficient H2O2 generation and rapid Fe(III) reduction, the efficiency of the electro-Fenton reaction is significantly improved, and the degradation efficiency of oil and gas field wastewater is greatly enhanced. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] In the picture:

[0019] Figure 1 This is a pollutant degradation curve of the ACA simulated wastewater treated in Example 1 of the present invention.

[0020] Figure 2 This is a graph showing the H2O2 production yield detected in Example 1 of the present invention.

[0021] Figure 3 This is a graph showing the Fe(II) production yield detected in Example 1 of the present invention.

[0022] Figure 4 This is a graph showing the Fe(II) production yield detected in Example 1 of the present invention. Detailed Implementation

[0023] The following will refer to Embodiment 1 of the present invention and the appendix. Figures 1-3 The technical solutions of the present invention have been clearly and completely described. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] A method for preparing a reduced graphene oxide-modified nickel foam electrode using the electro-Fenton method includes the following steps:

[0026] S1: First, cut a 3cm×3cm×2mm foam nickel sheet with a pore size of 110ppi and a purity of >98%. Immerse the foam nickel sheet in 1.2mmol / L HCl solution, pure ethanol solution and ultrapure water in sequence and sonicate for 15 minutes each to clean the oxide layer and organic / inorganic impurities on the surface.

[0027] S2; Next, prepare a 2 g / L uniform graphene oxide solution, and then put the cleaned nickel foam sheet from S1 and the 2 g / L graphene oxide solution into a polytetrafluoroethylene hydrothermal reactor. The reaction is carried out at 180°C for 12 hours. After natural cooling, a nickel foam sheet loaded with reduced graphene oxide is obtained. The cooled nickel foam sheet loaded with reduced graphene oxide is simply washed with ultrapure water and then placed in a freeze dryer at -60°C for 24 hours to obtain the final reduced graphene oxide modified nickel foam electrode.

[0028] Then, a reduced graphene oxide-modified nickel foam electrode was used as the cathode for the degradation treatment of oil and gas field wastewater. First, soluble inorganic electrolytes and soluble Fe(III) salts (ferric sulfate, ferric nitrate) were added to the oil and gas field wastewater to obtain solution A. A magnetic stirrer was placed at the bottom of the beaker storing solution A to provide dissolved oxygen and promote solute mass transfer. Magnetic stirring was then performed, and an external electric field was used to electrocatalytically degrade solution A. The cathode was a reduced graphene oxide-modified nickel foam electrode, and the anode was a boron-doped diamond (BDD) anode; both electrodes were identical in size and shape. The anode and cathode were fixed by an electrocatalytic degradation device, which consisted of a power supply, a reactor, and auxiliary stirring equipment. Two electrode ports and a sampling port were located at the top of the reactor. Two electrode clamps were inserted into the two electrode ports, and the cathode and anode were fixed in parallel. The two electrode clamps and the power supply were connected by wires. Both the cathode and anode were square thin sheet layers. The auxiliary stirring equipment included a polytetrafluoroethylene (PTFE) magnetic stirrer placed at the bottom of the reactor and an external magnetic stirrer for placing the reactor.

[0029] Combination Figure 1 It can be seen that, in terms of microstructure, the reduced graphene oxide film is flat and uniformly attached to the nickel foam skeleton in the form of nanolayers, and the graphene oxide loading per square centimeter of nickel foam is 0.03 to 0.05 g.

[0030] Oil and gas field wastewater was simulated using 1-adamantane carboxylic acid (ACA), a common toxic and recalcitrant organic pollutant in oil and gas field wastewater. In the simulated ACA wastewater, the solute was ACA and the solvent was water. Anhydrous Na₂SO₄ electrolyte and Fe₂(SO₄)₃ were added to the simulated ACA wastewater, and a mixed solution containing ACA, Na₂SO₄, and Fe₂(SO₄)₃ was used as the wastewater to be degraded. The wastewater was degraded and treated in a reactor within a certain reaction time.

[0031] In the simulated ACA wastewater, the ACA concentration was 10–40 mg / L; the pH was 3–4; the Na₂SO₄ concentration was 20–50 mmol / L; the Fe(III) concentration in Fe₂(SO₄)₃ was 30–150 μmol / L; and the current density during electrocatalytic degradation was 5–20 mA / cm⁻¹. 2 The stirring speed of the agitator is 700-2500 rpm;

[0032] The cathode used a reduced graphene oxide-modified nickel foam electrode, and the anode used a boron-doped diamond (BDD) electrode. ACA-simulated wastewater, as described above, was added to the reactor. The ACA concentration in the simulated wastewater was 18 mg / L, the Na₂SO₄ concentration was 20 mmol / L, the Fe(III) concentration was 90 μmol / L, and the solution volume was 150 mL. A magnetic stirrer was turned on and the stirring speed was controlled at 1500 rpm. An external DC power supply was connected, and the current density was controlled at 11.1 mA / cm². -2 Samples were taken at various time points within the 20-minute reaction time to detect the ACA concentration, and the degradation efficiency of ACA at each sampling time point was calculated. Figure 2 The results show that the concentration of the simulated wastewater in the ACA reaction decreased rapidly within 20 minutes, achieving a wastewater degradation rate of 99.4% by the end of the 20-minute reaction. These results demonstrate that the cathode-enhanced electro-Fenton process for treating oil and gas field wastewater exhibits highly efficient capabilities in degrading and removing organic pollutants from oil and gas field wastewater.

[0033] The amount of H2O2 generated in the cathode-enhanced electro-Fenton method for oil and gas field wastewater degradation treatment, as described in this invention, was determined using potassium titanate spectrophotometry, a commonly used H2O2 detection method. Three experimental groups were set up, each with different experimental conditions, to compare the H2O2 generation capacity among the groups. In this embodiment, Na2SO4 electrolyte solution was used instead of ACA to simulate wastewater, and the solution pH was controlled at 3, the Na2SO4 concentration at 20 mmol / L, and the solution volume at 150 mL. Graphite plate / nickel foam / reduced graphene oxide-modified nickel foam were used as cathodes, and boron-doped diamond (BDD) was used as the anode. The stirring speed was controlled at 1500 rpm. The power supply was turned on, and the power density was controlled at 11.1 mA / cm². -2 The reaction was carried out for 20 minutes, and samples were taken from the reactor at various time points during the reaction time to detect the H2O2 concentration. The H2O2 concentration generated at each time point was calculated. Figure 3 It was found that within a 20-minute reaction time, the graphite plate cathode group and the nickel foam cathode group accumulated H2O2 levels of 125.0 mmol / L and 192.1 mmol / L, respectively, while the reduced graphene oxide-modified nickel foam cathode group accumulated H2O2 levels of 775.6 mmol / L, significantly higher than the graphite plate cathode group and the nickel foam cathode group. This demonstrates that the reduced graphene oxide-modified nickel foam cathode has excellent H2O2 generation capability.

[0034] The amount of Fe(II) generated in the cathode-enhanced electro-Fenton method for oil and gas field wastewater degradation treatment, as described in this invention, was determined using the o-phenanthroline spectrophotometric method, a commonly used method for Fe(II) content detection. Three experimental groups were set up, each with different experimental conditions, to compare the Fe(II) generation capacity among the groups. In this embodiment, a mixed solution containing Na₂SO₄ electrolyte and Fe₂(SO₄)₃ was used instead of ACA simulated wastewater, and the solution pH was controlled at 3, Na₂SO₄ concentration at 20 mmol / L, Fe(III) concentration at 90 μmol / L, and solution volume at 150 mL. Graphite plate / nickel foam / reduced graphene oxide modified nickel foam were used as cathodes, and boron-doped diamond (BDD) was used as anode. The stirring speed was controlled at 1500 rpm. The power supply was turned on, and the power density was controlled at 11.1 mA / cm². -2 The reaction time was 1 minute, and samples were taken from the reactor at various time points during the reaction time to detect the Fe(II) concentration. The changes in Fe(II) concentration at each time point were calculated, and combined with... Figure 4 It can be seen that within the first minute of the reaction, the graphite plate cathode group and the nickel foam cathode group achieved Fe(II) concentrations of 3.6 μmol / L and 25.9 μmol / L, respectively, with conversion rates of 4% and 28.8%. In contrast, the reduced graphene oxide modified nickel foam cathode group achieved a Fe(II) concentration of 35.1 μmol / L, with a conversion rate of 39%, which is significantly higher than that of the graphite plate cathode group and the nickel foam cathode group. This demonstrates that the reduced graphene oxide modified nickel foam electrode has a rapid and efficient Fe(III) reduction capability.

[0035] This invention provides a method for preparing a reduced graphene oxide-modified nickel foam electrode for the electro-Fenton method. The core of this method is the preparation of the reduced graphene oxide-modified nickel foam electrode, which achieves the reduction of graphene oxide and its excellent self-assembly coating on the nickel foam surface through a high-temperature hydrothermal process. This simultaneously promotes the electrode's excellent electrochemical performance and the generation of catalytic sites conducive to H2O2 formation. Freeze-drying improves the surface hydrophobicity of the electrode and the smooth coating effect of the reduced graphene oxide film. When used as a cathode, the prepared reduced graphene oxide-modified nickel foam electrode can adsorb dissolved oxygen, accept a single electron to generate a superoxide radical intermediate, and subsequently accept a single electron to generate H2O2. Furthermore, the large specific surface area of ​​the nickel foam matrix provides numerous sites for the reduction of Fe(III), and the generated superoxide radicals can also react with Fe(III) to promote the Fe(III) / Fe(II) cycle, thereby improving the electro-Fenton efficiency and promoting the degradation of oil and gas field wastewater.

Claims

1. A method for preparing a reduced graphene oxide-modified nickel foam electrode for the electro-Fenton method, characterized in that, Includes the following steps: S1: Pre-treat the nickel foam sheet by ultrasonic cleaning for 15 minutes to obtain the pre-treated nickel foam sheet; S2: Prepare a graphene oxide solution, and carry out a hydrothermal reaction between the nickel foam sheet obtained in S1 and the graphene oxide solution at 170℃~200℃ for 10~15h. After cleaning, freeze-dry at -60℃ for 24h to obtain a reduced graphene oxide modified nickel foam electrode.

2. The method for preparing a reduced graphene oxide-modified nickel foam electrode for the electro-Fenton method according to claim 1, characterized in that, The pretreatment described in S1 involves immersing the nickel foam sheet sequentially in an HCl solution, a pure ethanol solution, and ultrapure water.

3. The method for preparing a reduced graphene oxide-modified nickel foam electrode for the electro-Fenton method according to claim 1, characterized in that, The reactor in the hydrothermal reaction of S2 is made of polytetrafluoroethylene.

4. A reduced graphene oxide modified nickel foam electrode for use in the electro-Fenton method, obtained by the preparation method according to any one of claims 1 to 3.

5. The application of the reduced graphene oxide-modified nickel foam electrode according to claim 4 in the electro-Fenton method, characterized in that, The reduced graphene oxide-modified nickel foam electrode is used in electrode preparation.

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