Preparation method and application of heterogeneous e-fenton cathode material

Abstract

The application discloses a preparation method of a heterogeneous E-Fenton cathode material and application thereof, and uses foamed nickel (NF) and graphite oxide (GO) as raw materials to obtain a graphene-loaded NF (GA-NF) electric Fenton cathode material through steps of acid pickling, electrophoretic deposition, hydrothermal reduction and vacuum drying, so that an efficient E-Fenton process can be realized under a wide pH condition without adding Fe ions and without producing secondary pollution. The heterogeneous E-Fenton cathode material prepared by the method has the advantages of high reaction activity, good treatment effect and the like, and does not need to add Fe ions and hydrogen peroxide, and no iron sludge is produced in the reaction.

Description

Technical Field

[0001] This invention relates to a method for preparing an electrode material, specifically to a method for preparing a heterogeneous E-Fenton cathode material and its application. Background Technology

[0002] Fenton oxidation removes organic matter based on added H2O2 and the catalyst Fe. 2+ The generated hydroxyl radicals (·OH) with strong oxidizing power can degrade and even mineralize organic pollutants. However, H2O2, with its strong corrosive and oxidizing properties, poses serious safety issues during transportation and storage, leading to higher processing costs and operational risks for Fenton oxidation in removing organic matter. In recent years, to further develop Fenton oxidation, electro-Fenton (E-Fenton) technology has emerged. The basic principle of E-Fenton technology is that O2 is reduced to H2O2 at the cathode and reacts with Fe... 2+ The reaction generates ·OH, a highly oxidizing compound, thereby achieving the oxidative degradation of pollutants. In E-Fenton technology, the ·OH generation mechanism involves the generation of Fe through electrodes. 2+ The oxygen reacts with H₂O₂ to form ·OH. In E-Fenton technology, the generation of ·OH is a crucial step, determining the technology's efficiency in degrading organic matter. Specifically, water molecules are oxidized at the anode, producing a small amount of ·OH, while simultaneously, in an acidic medium, the cathode reduces oxygen to hydrogen peroxide (H₂O₂). These reaction processes involve H₂O₂ and Fe produced by electrochemical methods. 2+ As a continuous source of Fenton's reagent, it improves the efficiency of ·OH formation. Traditional Fenton reactions also use H₂O₂ as a chain propagation medium, via Fe... 3+ / Fe 2+ The conversion of OH to continuously generate ·OH is achieved through electrochemical reactions, but E-Fenton technology realizes this process through electrochemical reactions, which improves the efficiency and controllability of the reaction.

[0003] In E-Fenton technology, the mechanism of action of ·OH is primarily through the degradation of organic matter via strong oxidation. ·OH possesses extremely strong oxidizing power, with a redox potential as high as 2.8V, second only to fluorine, enabling it to effectively degrade most organic pollutants. In the Fenton oxidation process, H₂O₂ reacts with Fe... 2+In the presence of ·OH, ·OH is generated, triggering a series of chain reactions. These reactions include not only the direct oxidation of ·OH but may also involve the generation of other reactive oxygen species, all working together to degrade organic matter. A key characteristic of this chain reaction is that once started, it can continue until the reactants are completely degraded or the reaction conditions change. Therefore, E-Fenton technology achieves efficient degradation of organic matter by continuously generating ·OH, ultimately converting it into harmless small molecules such as H2O and CO2, thereby purifying water. E-Fenton requires the addition of homogeneous Fe to the solution. 2+ However, under neutral and alkaline conditions, the produced Fe 3+ Inevitably, iron sludge precipitates form, making it difficult for the H2O2 generated on the cathode material surface to react with Fe in the solution. 2+ The catalytic reaction that forms ·OH makes the E-Fenton oxidation method unsuitable for wastewater treatment over a wide pH range (typically the most suitable pH is ≈3).

[0004] Therefore, developing a heterogeneous E-Fenton cathode material with a wide pH range, especially suitable for near-neutral or alkaline conditions, and capable of efficiently generating ·OH in situ on the electrode surface, would be beneficial for the promotion and application of E-Fenton technology for wastewater treatment. Summary of the Invention

[0005] Studies have shown that heterogeneous Fenton processes can avoid the limitations of homogeneous Fenton processes when Fenton catalysts are dispersed on a matrix in the form of iron-containing nanoparticles. To overcome the limitations of homogeneous Fenton technology, heterogeneous Fenton technology has been extensively studied, and there is a greater demand for developing and utilizing recyclable and highly stable solid-phase catalysts for heterogeneous E-Fenton materials. Different porous solid supports, including activated carbon, zeolite, and biochar, and various synthesis methods, such as precipitation, sol-gel, wet impregnation, and adsorption, have been used to synthesize effective heterogeneous catalysts in EF systems. However, due to the limitations of heterogeneous catalysts, such as low conductivity, high synthesis cost, strong aggregation, and difficulty in agglomerating suspended particles, their application in practical engineering applications may not be easy. In recent years, catalyst particles attached to highly porous electrodes have increased the volume ratio of electrode surface to electrolyte, overcoming the limitations of mass transport and improving the performance of EF in removing pollutants at neutral and near-neutral pH values. In heterogeneous EF processes, H2O2 can be generated via selective oxygen reduction (ORR), which involves two types of reaction pathways: (i) with 2e - The reduction-dominant reaction and (ii) 4e as a competing reaction - Reduction. The catalytic efficiency of heterogeneous iron-based catalysts for the decomposition of H₂O₂ into ·OH depends on the number of exposed active sites in the catalyst and the Fe content.3+ To Fe 2+ The conversion rate, determined by the generation and catalytic effect of H2O2, determines the performance of the cathode and even the entire system. Therefore, the cathode plays a crucial role in in-situ heterogeneous electrofocusing systems. The heterogeneous E-Fenton method has significant advantages such as expanding the working pH, preventing iron ion leaching, improving catalyst stability, and reusability.

[0006] Furthermore, when E-Fenton cathode materials are used for wastewater treatment, the metal surface is highly susceptible to corrosion. Graphene loading on its surface can achieve corrosion protection. Among various surface protection technologies, electrophoretic deposition (EPD) is advantageous for preparing ideal, uniform coatings. Due to its low cost and ease of control, EPD is widely used to deposit composite coatings on conductive substrates, significantly improving the material's wear resistance and service life. As an emerging two-dimensional structure, graphene and graphene oxide exist in the form of sp2 carbon hybrid networks, attracting widespread attention due to their excellent chemical inactivity, superior strength, enhanced resistance to corrosive environments, easy shearing, and good lubrication properties. In various practical applications such as energy storage, field emission devices, and solar cells, there is a high demand for graphene with controllable properties.

[0007] Taking all the above considerations into account, this study aims to prepare graphene-supported nickel foam E-Fenton cathodes using electrophoretic deposition technology to solve the problems of existing E-Fenton reactions, such as the need for external addition of H2O2, the need for external addition of Fe ions, the generation of iron sludge under neutral and alkaline conditions affecting reaction efficiency and causing secondary pollution, narrow pH range, and easy corrosion of iron cathode materials when in contact with air.

[0008] This invention addresses the shortcomings of existing technologies by providing a method for preparing heterogeneous E-Fenton cathode materials and their applications. The method uses nickel foam (NF) and graphite oxide (GO) as raw materials, and obtains graphene-supported NF (GA-NF) E-Fenton cathode materials through steps such as acid washing, electrophoretic deposition, hydrothermal reduction, and vacuum drying. This method enables a highly efficient E-Fenton process under wide pH conditions without the addition of Fe ions, and does not generate secondary pollution. The specific process is as follows:

[0009] This invention first discloses a method for preparing a heterogeneous E-Fenton cathode material, comprising:

[0010] (1) Soak the nickel foam sheet in acetone solution for ultrasonic treatment, then immerse it in 10% H2SO4 solution for acid washing; finally, clean it with deionized water by ultrasonication and vacuum dry it to obtain pretreated nickel foam sheet for use.

[0011] (2) Use deionized water as the dispersion medium for graphite oxide to prepare a graphite oxide suspension for later use.

[0012] (3) The pretreated nickel foam sheet is used as the cathode, and parallel platinum sheets of equal area are placed on both sides of the cathode. The cathode electrophoretic deposition is carried out with constant voltage DC power supply to prepare nickel foam sheet loaded with graphite oxide.

[0013] (4) Transfer the nickel foam sheet loaded with graphite oxide to a polytetrafluoroethylene reactor containing 100 ml of ethylene glycol solution. After high-temperature reduction, it is repeatedly washed with deionized water to obtain a heterogeneous E-Fenton cathode material.

[0014] Further, the size of the nickel foam sheet in step (1) is 10mm×20mm×2mm; the ultrasonic treatment time in the acetone solution is 20min; and the pickling time in the H2SO4 solution is 5min.

[0015] Furthermore, the ultrasonic cleaning with deionized water in step (1) is performed 3 times, with each cleaning session lasting 10 minutes.

[0016] Furthermore, the concentration of the graphite oxide suspension in step (2) is 0.2 mg / ml.

[0017] Furthermore, the size of the platinum sheet in step (3) is 10mm×20mm×1mm.

[0018] Furthermore, the constant voltage in step (3) is 140V and the deposition time is 15min.

[0019] Furthermore, the high-temperature reduction temperature in step (4) is 140°C, and the reduction time is 14h.

[0020] The present invention also discloses a heterogeneous E-Fenton cathode material prepared according to any of the above-described preparation methods.

[0021] The present invention also discloses an application of the above-described heterogeneous E-Fenton cathode material in the treatment of recalcitrant polymeric organic pollutants.

[0022] Furthermore, the application includes:

[0023] In the application of treating recalcitrant high molecular weight organic pollutants, heterogeneous E-Fenton cathode material is used as the cathode, oxygen or air is introduced near the cathode, and an inert electrode is used as the anode. The target of treatment is wastewater or soil containing organic pollutants. An electrolyte solution with a pH of 3 to 8 is added, and organic pollutants are treated by direct current electrolysis.

[0024] Furthermore, the electrolyte solution is a sodium salt or potassium salt electrolyte solution.

[0025] Furthermore, the electrolyte solution is one or more of sodium sulfate, sodium acetate, or sodium nitrate.

[0026] Furthermore, the electrolyte solution is one or more of potassium sulfate, potassium acetate, or potassium nitrate.

[0027] Furthermore, the recalcitrant high molecular weight organic pollutants include, but are not limited to: phenol, norfloxacin, sodium dodecylbenzenesulfonate, and p-nitrophenol.

[0028] Furthermore, the oxygen or air is introduced at a rate of 0.1 to 3.0 L / min; the voltage for DC electrolysis is 2 to 8 V.

[0029] The beneficial effects of this invention are as follows:

[0030] (1) GO was successfully loaded onto NF by electric field driving, and then graphene-loaded NF cathode material that can be used for E-Fenton technology to treat organic wastewater was prepared by hydrothermal reduction.

[0031] (2) The loading of graphene can achieve a certain anti-corrosion effect and improve the degradation performance of nickel foam.

[0032] (3) GO-loaded nickel foam, as the cathode material of the E-Fenton treatment system, has a good degradation effect. Attached Figure Description

[0033] Figure 1 SEM image of nickel foam before graphene loading;

[0034] Figure 2 SEM image of graphene-supported nickel foam;

[0035] Figure 3 This is a combined SEM / mapping image of graphene-supported nickel foam.

[0036] Figure 4 The image shows a mapping diagram of nickel foam supported on graphene, where a represents the distribution of nickel and b represents the distribution of carbon.

[0037] Figure 5 The curves show the RhB removal rates before and after loading the nickel foam Fenton cathode. Detailed Implementation

[0038] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0039] Example 1

[0040] A method for preparing a heterogeneous E-Fenton cathode material includes:

[0041] (1) Place the NF sheet (10mm×20mm×2mm) in acetone solution and sonicate for 20min; then immerse it in 10% H2SO4 solution and acid wash for 5min to slightly corrode it, so that the cracks and porous structure on the NF surface and the hydroxyl groups on the surface are more conducive to the subsequent GO adhesion, and to a certain extent reduce the interfacial resistance between the electrode and the electrolyte, promote the rapid and stable transfer of charge, and thus achieve a tighter load; finally, sonicate clean it three times with deionized water for 10min each time; vacuum dry to obtain pretreated foamed nickel sheet for later use.

[0042] (2) Use deionized water as the dispersion medium for GO and prepare a 0.2 mg / ml GO suspension for later use;

[0043] (3) The pretreated nickel foam sheet was used as the cathode, and parallel platinum sheets (10mm×20mm×1mm) of equal area were placed on both sides of the cathode. The cathode electrophoretic deposition was carried out with a constant voltage of 140V DC power supply for 15min to prepare NF loaded with GO.

[0044] (4) The NF loaded with GO was transferred to a polytetrafluoroethylene reactor containing 100 ml of ethylene glycol solution and reduced at 140 °C for 14 h. After washing with deionized water several times, the heterogeneous E-Fenton cathode material was obtained.

[0045] The SEM image of nickel foam before graphene loading is shown below. Figure 1 As shown, the unmodified nickel foam exhibits a network structure and a relatively smooth surface. The SEM image of the graphene-loaded nickel foam is shown below. Figure 2 As shown, the surface of the nickel foam is fully loaded with sheet-like graphene sheets after graphene modification, forming a good protective film and increasing the surface area of ​​the nickel foam. Figure 3 The image shows a combined SEM / mapping image of graphene-loaded nickel foam, indicating that graphene is uniformly loaded onto the surface of the mesh-like nickel foam, and the loading was successful. Figure 4 This is a mapping image of graphene loaded with nickel foam. The carbon elements are evenly distributed in the image. Figure 2 It can be seen that graphene oxide is hydrothermally reduced to graphene sheets and uniformly loaded on the surface of nickel foam to form a protective film, while increasing the conductivity and surface area of ​​nickel foam. Figure 5 The figure shows the RhB removal rate curves before and after loading the nickel foam electro-Fenton cathode. It can be seen from the figure that the RhB removal rate of the nickel foam cathode before graphene loading was less than 80% after 30 minutes, while the RhB removal rate of the nickel foam electro-Fenton cathode after graphene modification reached 100% after 30 minutes, and the removal effect was greatly increased.

[0046] Experimental Example 1

[0047] The organic dye RhB was removed using the cathode material prepared in Example 1.

[0048] Degradation conditions for RhB:

[0049] 8V voltage, electrode spacing 2cm, electrolyte 0.35mol / LNa2SO4, treatment time 30min, cathode GA-NF (10mm*20mm*2mm), anode Pt sheet (10mm*20mm*1mm), RhB 10mg / L.

[0050] The removal rate was 100% after 30 minutes. Figure 5 The curve is GA-NF-1.

[0051] Experimental Example 2

[0052] RhB removal rate experiment before nickel foam loading

[0053] Degradation conditions for RhB:

[0054] 8V voltage, electrode spacing 2cm, electrolyte 0.35mol / LNa2SO4, treatment time 30min, cathode NF (10mm*20mm*2mm), anode Pt sheet (10mm*20mm*1mm), RhB 10mg / L.

[0055] The removal rate was less than 80% after 30 minutes. Figure 5 The curve NF in the middle.

[0056] In summary, the heterogeneous E-Fenton cathode material prepared using the method of this invention overcomes the pH limitation of traditional E-Fenton cathodes, achieving a removal rate of over 99% for organic dyes (RhB) within 30 minutes under neutral conditions (see details). Figure 5 It has advantages such as high reactivity and good treatment effect, and does not require the addition of Fe ions and hydrogen peroxide, and no iron sludge is generated during the reaction.

[0057] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. These include, but are not limited to, the following:

[0058] 1. By using foam ceramics or other conductive materials as a load, and loading GO in the same way, its performance can be improved.

[0059] 2. Using pharmaceuticals containing elements such as iron, cobalt, and nickel instead of graphene for loading may also improve its performance.

Claims

1. A preparation method of heterogeneous E-Fenton cathode material, comprising: (1) ultrasonic treatment of a foamed nickel sheet in an acetone solution for 20 min, then acid washing in a 10% H2SO4 solution for 5 min; finally ultrasonic cleaning with deionized water for 3 times, each time for 10 min, and vacuum drying to obtain a pretreated foamed nickel sheet for standby; (2) using deionized water as a dispersion medium of graphite oxide to prepare a graphite oxide suspension for standby; (3) using the pretreated foamed nickel sheet as a cathode, and setting parallel platinum sheets with equal area on both sides of the cathode, and performing cathodic electrophoretic deposition at a constant voltage of 140 V for 15 min with a direct current power supply to prepare a foamed nickel sheet loaded with graphite oxide; (4) transferring the foamed nickel sheet loaded with graphite oxide into a polytetrafluoroethylene reactor with a volume of 100 ml containing a glycol solution, reducing at 140℃ for 14 h, and then repeatedly cleaning with deionized water to obtain a heterogeneous E-Fenton cathode material.

2. The preparation method according to claim 1, wherein: the size of the foamed nickel sheet in step (1) is 10 mm x 20 mm x 2 mm.

3. The preparation method according to claim 1, wherein: the concentration of the graphite oxide suspension in step (2) is 0.2 mg / ml.

4. The preparation method according to claim 1, wherein: the size of the platinum sheet in step (3) is 10 mm x 20 mm x 1 mm.

5. A heterogeneous E-Fenton cathode material prepared by the preparation method according to any one of claims 1-4.

6. Use of the heterogeneous E-Fenton cathode material according to claim 5 in treating refractory high-molecular organic pollutants.

7. The use according to claim 6, comprising: in the use of the heterogeneous E-Fenton cathode material in treating refractory high-molecular organic pollutants, using the heterogeneous E-Fenton cathode material as a cathode, passing 0.1-3.0 L / min of oxygen or air near the cathode, using an inert electrode as an anode, treating sewage or soil containing organic pollutants as a treatment object, adding an electrolyte solution with a pH of 3-8, and treating the organic pollutants by direct current electrolysis at 2-8 V.

8. The use according to claim 7, wherein: the refractory high-molecular organic pollutants include phenol, norfloxacin, sodium dodecyl benzene sulfonate, or p-nitrophenol.

Images