Pine needle coke-based gas diffusion electro-fenton cathode and preparation method thereof

Abstract

The application discloses a needle coke-based gas diffusion cathode and a preparation method thereof, and the preparation method comprises the following steps: step one, taking high-conductivity needle coke powder, and performing alkali modification treatment on the needle coke powder to obtain modified needle coke; performing iron salt impregnation calcination treatment on the alkali modified needle coke to obtain iron-loaded needle coke; step two, mixing the modified needle coke and the iron-loaded needle coke with anhydrous ethanol and polytetrafluoroethylene respectively, and pressing the mixture into a gas diffusion layer and an iron-loaded needle coke catalytic layer, and then pressing the gas diffusion layer and the iron-loaded needle coke catalytic layer on both sides of a titanium mesh by using a hydraulic press to obtain a needle coke-based gas diffusion electro-Fenton cathode precursor; and step three, calcining the electrode precursor in a muffle furnace to improve the stability of the electrode precursor, and obtaining a needle coke-based gas diffusion electro-Fenton cathode. The gas diffusion electrode prepared by combining the high-conductivity and stable needle coke and PTFE can form a three-phase system on the surface of the electrode, so that the oxygen can be better contacted with the surface of the electrode, the generation efficiency of H2O2 is improved, and then the treatment effect of the electro-Fenton system on the organic matter is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electrochemical water treatment, and particularly relates to a needle coke-based gas diffusion electro-Fenton cathode and a preparation method thereof. BACKGROUND

[0002] The electro-Fenton technology is a method for degrading organic pollutants in water by using electric energy to catalyze the generation of hydrogen peroxide or ferrous ions and the occurrence of a Fenton reaction to generate hydroxyl radicals with strong oxidizing properties on the basis of the traditional Fenton technology. The electro-Fenton technology is generally divided into the following types according to the source of the Fenton reagent: (1) electro-Fenton H2O2 method (EF-H2O2): Fe 2+ is externally added, and oxygen is introduced into the cathode to generate H2O2 through a reduction reaction; (2) sacrificial anode electro-Fenton, also known as electro-Fenton-iron oxidation method (EF-Feox): the Fenton reagent H2O2 is externally added, and Fe 2+ is oxidized to generate Fe 3+ by losing electrons through a sacrificial iron anode; (3) iron reduction electro-Fenton (EF-Fere): the reagent H2O2 is externally added, and Fe 3+ is reduced to Fe 2+ at the cathode; and the Fenton reagent generates ·OH through a Fenton reaction in the electrolytic cell; and (4) iron reduction-electro-Fenton-H2O2 method (EF-H2O2-Fere): the reagent Fe 3+ is externally added, and Fe 3+ is reduced to Fe 2+ at the cathode, and oxygen is introduced into the cathode to generate H2O2 through a reduction reaction.

[0003] The electro-Fenton technology has many advantages such as simple equipment, efficient and rapid reaction, and complete reaction. However, the disadvantages of the technology are also obvious: the catalytic efficiency of the cathode material is low, the mass transfer of oxygen at the three-phase interface is difficult, which leads to a low yield of hydrogen peroxide, thereby restricting the generation of hydroxyl radicals, and the pH value needs to be adjusted before and after the reaction when treating most wastewater, and a large amount of iron sludge is inevitably produced through side reactions.

[0004] At present, the main methods for solving the above problems are as follows: finding a suitable cathode material to improve the electro-catalytic performance of the electro-Fenton technology; adding a metal catalyst to make the Fenton reaction occur under heterogeneous conditions, improve the recycling of iron ions, and broaden the pH value of the reaction; and improving the reaction device of the electro-Fenton technology.

[0005] In patent No. CN112591857A, a metal and Aza-CMP are loaded on plant straw activated carbon powder to obtain an activated carbon composite material, the activated carbon composite material is wrapped with a titanium mesh to form an electro-Fenton gas diffusion electrode, and the chemical adsorption of oxygen atoms by the Aza-CMP improves the rate of the reduction of oxygen into hydrogen peroxide. SUMMARY

[0006] The application provides a needle coke-based gas diffusion electro-Fenton electrode capable of efficiently generating H2O2 without an external iron source and having good electrocatalytic performance.

[0007] To solve the above problems, the technical scheme adopted by the application is as follows:

[0008] A needle coke-based gas diffusion electro-Fenton cathode and a preparation method thereof, the cathode is composed of an iron-loaded catalytic layer, a titanium mesh and a modified needle coke gas diffusion layer; the catalytic layer is prepared from iron-loaded needle coke, which increases the current utilization rate and realizes the recycling of iron ions; the air diffusion layer is prepared by mixing a hydrophobic binder and modified needle coke, and the polytetrafluoroethylene increases the hydrophobicity of the air layer, reduces the mass transfer resistance of oxygen, improves the oxygen transfer efficiency, and further improves the generation rate of hydrogen peroxide. The titanium mesh not only plays a supporting role to improve the stability of the electrode, but also contributes to the improvement of the electrode performance due to its excellent conductivity. The electrode has good electrocatalytic performance, can effectively reduce the mass transfer resistance of oxygen, and can convert the traditional liquid-phase transfer of oxygen into solid-liquid-gas three-phase mass transfer to produce hydrogen peroxide quickly and efficiently, and the recycling of iron ions in the reaction reduces the generation of iron sludge.

[0009] To achieve the above purpose, the application mainly adopts the following technical scheme:

[0010] A preparation method of a needle coke-based gas diffusion electro-Fenton cathode, comprising the following steps:

[0011] (1) grinding and screening block needle coke to obtain needle coke powder;

[0012] (2) alkali-modifying the needle coke powder with sodium hydroxide to obtain alkali-modified needle coke;

[0013] (3) impregnating and calcining the alkali-modified needle coke in a certain proportion of ferrous sulfate solution to obtain iron-loaded needle coke;

[0014] (4) mixing and pressing the iron-loaded needle coke, anhydrous ethanol and a binder to form a layer, and pressing the layer on the titanium mesh with a hydraulic press; mixing and pressing the alkali-modified needle coke, anhydrous ethanol and a binder to form another layer, and pressing the layer on the other side of the titanium mesh with a hydraulic press and calcining the layer in a muffle furnace to improve the stability of the layer to obtain the needle coke-based gas diffusion electro-Fenton cathode.

[0015] The specific method of grinding and screening is as follows: grinding the block needle coke in a ball mill, and screening the ground needle coke into powder with a 150-200 mesh screen to obtain the powder needle coke.

[0016] The alkali modification treatment, which specifically comprises the following steps: adding needle coke powder into a 0.2-0.5 mol / L sodium hydroxide solution, and stirring at a speed of 100-200 r / min for 2-3 hours under a six-union stirrer, and then drying after filtration to obtain the alkali modified needle coke.

[0017] The iron-loaded needle coke, which specifically comprises the following steps: adding powder needle coke into a 2%-6% ferrous sulfate solution, and stirring at a speed of 150-220 r / min for 3-6 hours under a six-union stirrer, and then drying after filtration, and calcining at a temperature of 200-400 ℃ in a muffle furnace for 3-5 hours to obtain the iron-loaded needle coke.

[0018] The needle coke-based gas diffusion electro-Fenton cathode, which specifically comprises the following steps: mixing the iron-loaded needle coke with a certain amount of anhydrous ethanol and a binder, pressing into a rectangular sheet after evaporation of the ethanol, and pressing onto a titanium mesh using a hydraulic press.

[0019] The needle coke-based gas diffusion electro-Fenton cathode, which specifically comprises the following steps: mixing the modified needle coke with a certain amount of anhydrous ethanol and a binder, pressing into a rectangular sheet after evaporation of the ethanol, and pressing onto the other side of the titanium mesh using a hydraulic press to obtain a needle coke-based gas diffusion electro-Fenton cathode precursor.

[0020] The needle coke-based gas diffusion electro-Fenton cathode, which specifically comprises the following steps: calcining the cathode precursor in a muffle furnace at a temperature of 350-500 ℃ for 3-6 hours to obtain the needle coke-based gas diffusion electro-Fenton cathode.

[0021] Optionally, the hydrophobic binder used in the present application is polytetrafluoroethylene.

[0022] Advantages of the present application:

[0023] (1) The needle coke used in the present application has the characteristics of abundant reserves, large specific surface area, good electrical conductivity and easy graphitization, and is a potential electro-Fenton cathode material;

[0024] (2) In the present application, iron salt is loaded onto the cathode material, and Fe 2+ As a reaction catalyst, it does not need to be added extra, can effectively remove pollutants and does not produce iron sludge;

[0025] (3) The needle coke-based gas diffusion electro-Fenton cathode can form a thin liquid film on the surface of the catalytic layer, and after contacting with the gas, a gas-liquid-solid three-phase interface is formed, which can strengthen the mass transfer of oxygen, improve the H2O2 yield, and improve the utilization efficiency of the electrode;

[0026] (4) The needle coke-based gas diffusion electro-Fenton cathode can produce H2O2 by directly activating oxygen under acidic conditions, and can strengthen the catalytic performance of the system;

[0027] (5) The titanium mesh used in the application serves as the framework of the needle coke-based gas diffusion electro-Fenton cathode, has good electrical conductivity, corrosion resistance and stability, can withstand the pressure in the preparation process of the needle coke-based gas diffusion electro-Fenton cathode, and makes the electrode not deformed;

[0028] (6) The needle coke-based gas diffusion electro-Fenton cathode is a kind of excellent and green electro-Fenton reaction cathode, and the experiment can provide a solid theoretical basis and experimental basis for the application of the electro-Fenton cathode in practice. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the specific forms of the application and the performance in water treatment, the following will briefly describe each part in the specific implementation scheme with the aid of the drawings;

[0030] Figure 1 The prepared form of the needle coke-based gas diffusion electro-Fenton cathode;

[0031] Figure 2 SEM characterization figures of the needle coke before and after loading and after water treatment; DETAILED DESCRIPTION

[0032] The application will be further described and illustrated in combination with the specific implementation scheme.

[0033] 1. Example 1

[0034] 2. The needle coke powder is added into a 0.3 mol / L sodium hydroxide solution and stirred at a speed of 180 r / min for 2 hours under a six-union stirrer, and then filtered and dried to obtain the alkali-modified needle coke. The powder needle coke is added into a 4% ferrous sulfate solution and stirred at a speed of 200 r / min for 4 hours under a six-union stirrer, and then filtered, dried and calcined in a muffle furnace at a temperature of 200℃ for 3 hours to obtain the iron-loaded needle coke. The iron-loaded needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the evaporation of the ethanol, and pressed onto the titanium mesh by using a hydraulic machine. The modified needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the evaporation of the ethanol, and pressed onto the other side of the titanium mesh by using a hydraulic machine to obtain the needle coke and the gas diffusion electro-Fenton cathode precursor. The electrode precursor is placed in a muffle furnace and calcined at a temperature of 450℃ for 5 hours to obtain the needle coke-based gas diffusion electro-Fenton cathode.

[0035] 3. Example 2

[0036] 4. The needle coke powder is added into 0.3 mol / L sodium hydroxide solution and placed under the six-union stirrer to stir at 180 r / min for 2 hours, and then filtered and dried to obtain the alkali-modified needle coke. The powder needle coke is added into 4% ferrous sulfate solution and placed under the six-union stirrer to stir at 200 r / min for 4 hours, and then filtered and dried, and calcined in a muffle furnace at 250°C for 3 hours to obtain the iron-loaded needle coke. The iron-loaded needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the ethanol is evaporated, and pressed on the titanium mesh using a hydraulic machine. The modified needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the ethanol is evaporated, and pressed on the other side of the titanium mesh using a hydraulic machine to obtain the needle coke and gas diffusion electro-Fenton cathode precursor. The electrode precursor is placed in a muffle furnace and calcined at 450°C for 5 hours to obtain the needle coke-based gas diffusion electro-Fenton cathode.

[0037] 5. Example 3

[0038] 6. The needle coke powder is added into 0.3 mol / L sodium hydroxide solution and placed under the six-union stirrer to stir at 180 r / min for 2 hours, and then filtered and dried to obtain the alkali-modified needle coke. The powder needle coke is added into 4% ferrous sulfate solution and placed under the six-union stirrer to stir at 200 r / min for 4 hours, and then filtered and dried, and calcined in a muffle furnace at 300°C for 3 hours to obtain the iron-loaded needle coke. The iron-loaded needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the ethanol is evaporated, and pressed on the titanium mesh using a hydraulic machine. The modified needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the ethanol is evaporated, and pressed on the other side of the titanium mesh using a hydraulic machine to obtain the needle coke and gas diffusion electro-Fenton cathode precursor. The electrode precursor is placed in a muffle furnace and calcined at 450°C for 5 hours to obtain the needle coke-based gas diffusion electro-Fenton cathode.

[0039] 7. Example 4

[0040] 8. The needle coke powder is added into 0.3 mol / L sodium hydroxide solution and placed under a six-union stirrer to stir at a speed of 180 r / min for 2 hours, and then filtered and dried to obtain alkali-modified needle coke; the powder needle coke is added into 4% ferrous sulfate solution and placed under a six-union stirrer to stir at a speed of 200 r / min for 4 hours, and then filtered and dried, and calcined in a muffle furnace at a temperature of 350℃ for 3 hours to obtain iron-loaded needle coke. The iron-loaded needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the ethanol is evaporated, and then pressed on a titanium mesh using a hydraulic press. The modified needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the ethanol is evaporated, and then pressed on the other side of the titanium mesh using a hydraulic press to obtain a needle coke and gas diffusion electro-Fenton cathode precursor. The electrode precursor is placed in a muffle furnace and calcined at a temperature of 450℃ for 5 hours to obtain a needle coke-based gas diffusion electro-Fenton cathode.

[0041] 9. Example 5

[0042] 10. The needle coke powder is added into 0.3 mol / L sodium hydroxide solution and placed under a six-union stirrer to stir at a speed of 180 r / min for 2 hours, and then filtered and dried to obtain alkali-modified needle coke; the powder needle coke is added into 4% ferrous sulfate solution and placed under a six-union stirrer to stir at a speed of 200 r / min for 4 hours, and then filtered and dried, and calcined in a muffle furnace at a temperature of 400℃ for 3 hours to obtain iron-loaded needle coke. The iron-loaded needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the ethanol is evaporated, and then pressed on a titanium mesh using a hydraulic press. The modified needle coke is mixed with a certain amount of anhydrous ethanol and polytetrafluoroethylene, and then pressed into a rectangular sheet after the ethanol is evaporated, and then pressed on the other side of the titanium mesh using a hydraulic press to obtain a needle coke and gas diffusion electro-Fenton cathode precursor. The electrode precursor is placed in a muffle furnace and calcined at a temperature of 450℃ for 5 hours to obtain a needle coke-based gas diffusion electro-Fenton cathode.

[0043] 11. Example 6

[0044] 12. The coking wastewater is treated using the electrodes prepared in the above examples, respectively, the experimental setup is that the applied voltage is 10V, the initial pH of the solution is 3, the distance between the electrodes is 1cm, and the reaction time is 6 hours, and the COD removal rate reaches 98%.

[0045] 13. It should be finally pointed out that the above examples are only used to illustrate the technical solutions of the present application, but not to limit the same; although the present application has been described in detail with reference to the foregoing examples, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing examples can still be modified, or some technical features thereof can be replaced equivalently; and such modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a needle coke-based gas diffusion electro-Fenton cathode, characterized by: The cathode has a metal luster on the surface, high stability and is not easy to fall off; the cathode is composed of an iron-loaded needle coke catalytic layer, a titanium mesh and a modified needle coke gas diffusion layer; the preparation method comprises the following steps: (1) grinding and screening block needle coke to obtain needle coke powder; (2) alkali-modifying the needle coke powder obtained in the step (1) by sodium hydroxide to obtain alkali-modified needle coke; (3) impregnating the alkali-modified needle coke obtained in the step (2) into an iron salt solution with a certain proportion, and then calcining to obtain iron-loaded needle coke; (4) mixing the iron-loaded needle coke obtained in the step (3) with anhydrous ethanol and polytetrafluoroethylene, and then pressing into an iron-loaded needle coke catalytic layer, and pressing the iron-loaded needle coke catalytic layer onto the titanium mesh by using a hydraulic machine; mixing the alkali-modified needle coke obtained in the step (2) with anhydrous ethanol and polytetrafluoroethylene, and then pressing into a modified needle coke gas diffusion layer, and pressing the modified needle coke gas diffusion layer onto the other side of the titanium mesh by using a hydraulic machine, to obtain a needle coke-based gas diffusion electro-Fenton cathode precursor; and (5) calcining the cathode precursor obtained in the step (4) in a muffle furnace to improve the stability, and obtaining a needle coke-based gas diffusion electro-Fenton cathode.

2. The preparation method of the needle coke-based gas diffusion electro-Fenton cathode according to claim 1, characterized in that, The specific method of the step (1) is that the block needle coke is put into a ball mill for grinding, and the powder is screened by using a 150-200 mesh screen to obtain the needle coke powder.

3. The preparation method of a needle coke-based gas diffusion electro-Fenton cathode according to claim 1, characterized in that, The specific method of the step (2) is that the needle coke powder obtained in the step (1) is added into a 0.2-0.5 mol / L sodium hydroxide solution, and is stirred at a speed of 100-200 r / min for 2-3 hours under a six-union stirrer, and then is extracted and dried to obtain the alkali-modified needle coke.

4. The preparation method of a needle coke-based gas diffusion electro-Fenton cathode according to claim 1, characterized in that, The specific method of the step (3) is that the alkali-modified needle coke is added into a 2%-6% iron salt solution, and is stirred at a speed of 150-220 r / min for 3-6 hours under a six-union stirrer, and then is extracted and dried, and is calcined in a muffle furnace at a temperature of 200-400 ℃ for 3-5 hours to obtain the iron-loaded needle coke.

5. The preparation method of a needle coke-based gas diffusion electro-Fenton cathode according to claim 1, characterized in that, The specific method of the step (4) comprises the following steps: the iron-loaded needle coke obtained in the step (3) and polytetrafluoroethylene are mixed with a certain amount of anhydrous ethanol, and then are pressed into a rectangular sheet after the ethanol is evaporated, to obtain the iron-loaded needle coke catalytic layer, and the iron-loaded needle coke catalytic layer is pressed onto the titanium mesh by using a hydraulic machine; wherein the mass ratio of the iron-loaded needle coke to the polytetrafluoroethylene is (3-6):

1.

6. The preparation method of a needle coke-based gas diffusion electro-Fenton cathode according to claim 1, characterized in that, The specific method of the step (4) comprises the following steps: the alkali-modified needle coke obtained in the step (2) and polytetrafluoroethylene are mixed with a certain amount of anhydrous ethanol, and then are pressed into a rectangular sheet after the ethanol is evaporated, to obtain the modified needle coke gas diffusion layer, and the modified needle coke gas diffusion layer is pressed onto the other side of the titanium mesh by using a hydraulic machine, to obtain the needle coke-based gas diffusion electro-Fenton cathode precursor; wherein the mass ratio of the alkali-modified needle coke to the polytetrafluoroethylene is 1:(2-5).

7. The preparation method of a needle coke-based gas diffusion electro-Fenton cathode according to claim 1, characterized in that, The specific method of the step (5) is that the cathode precursor obtained in the step (4) is put into a muffle furnace and is calcined at a temperature of 350-500 ℃ for 3-6 hours, to obtain the needle coke-based gas diffusion electro-Fenton cathode.

8. A needle coke-based gas diffusion electro-Fenton cathode, characterized by, The preparation method is prepared by using any one of the preparation methods in claims 1-7.

Images