Electro-Fenton bifunctional cathode material and preparation method thereof

Abstract

The invention discloses an electro-Fenton bifunctional cathode material and a preparation method thereof.The preparation method comprises the following steps that an iron-carbon material is combined on a conductive substrate sheet, a metal organic carbon framework grows on the iron-carbon material layer in situ, then high-temperature oxygen-free calcination is conducted, and an organic metal framework derived carbon material is obtained; and forming a substrate sheet-iron carbon material-metal organic framework derived carbon material three-layer structure. The structure is applied to an electro-Fenton reaction system, the conductivity is good, the iron-carbon synergistic effect promotes electron transfer, iron circulation is facilitated, and iron mud is reduced; the metal organic framework derived carbon material has a rich pore structure and a large specific surface area, and can efficiently reduce O2 and improve the H2O2 generation reaction rate.

Description

Technical Field

[0001] The present invention relates to the fields of environment and electrode material preparation, and in particular to an electro-Fenton dual-function cathode material and a preparation method thereof. Background Art

[0002] Electro-Fenton technology is developed from electrochemical oxidation technology (AO, AO-H2O2). It is a combination of EAOPs and Fenton technology. It is a new and efficient wastewater treatment technology that can effectively treat wastewater with complex components. Compared with traditional Fenton technology, H2O2 can be generated in situ in the electro-Fenton system, which greatly reduces the risk of harm during transportation, storage and use. 2+ Can continuously pass through Fe 3+ Electrons are generated at the cathode interface (E0 = 0.77 V (vs. SHE)), producing more ·OH, which can further efficiently degrade organic matter. However, the traditional electro-Fenton process has problems such as low H2O2 production and poor Fe recycling capacity.

[0003] In the electro-Fenton system, the generation of H2O2 and the formation of Fe 3+ However, the traditional single cathode single potential method cannot simultaneously achieve the best H2O2 generation and iron reduction. 3+ The favorable cathode required for the reduction of Fe 3+ The cathode potential required for reduction is lower than the cathode potential required for H2O2 generation. For example, Patent Document 1 discloses a method for preparing an electro-Fenton gas diffusion electrode (GDE), in which a large amount of O2 reaches the interior of the electrode, achieving efficient generation of H2O2, but its Fe 3+ The reduction rate is very low and iron sludge is easily formed. Patent Document 2 discloses a metal organic framework derived iron carbon catalyst suitable for heterogeneous electro-Fenton and its preparation method. The iron and carbon in the catalyst synergistically promote electron transfer and can achieve Fe 3+ / Fe 2+ However, H2O2 cannot be produced and the catalyst is not loaded on the electrode sheet, making it difficult to efficiently recycle.

[0004] Patent document 1: Application number: 202011431679.1, application name: An electro-Fenton gas diffusion electrode and its preparation method.

[0005] Patent document 2: Application number: 201911402200.9, application name: A metal-organic framework-derived iron-carbon catalyst suitable for heterogeneous electro-Fenton and its preparation method. Summary of the Invention

[0006] In the existing electrochemical catalytic process, the H2O2 production of the electro-Fenton system is low and the Fe 3+ / Fe 2+ In order to solve the problems of poor recycling capacity, the present invention provides an electro-Fenton dual-function cathode material, and uses it for electro-Fenton catalytic degradation of pollutants;

[0007] At the same time, the present invention also provides a method for preparing the electrode material.

[0008] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0009] An electro-Fenton bifunctional cathode material, the bifunctional cathode material comprising:

[0010] A substrate sheet having electrical conductivity;

[0011] a first layer of iron-carbon material and a second layer of metal-organic framework-derived carbon material bonded to a substrate;

[0012] The iron-carbon atomic ratio of the iron-carbon material is 1:(1-10);

[0013] The loading amount of iron-carbon material on the substrate is 0.01-0.1 g / cm 2 ;

[0014] The loading amount of metal organic framework-derived carbon materials is 0.01-0.1 g / cm 2

[0015] The iron-carbon material is synthesized from iron clusters and terephthalic acid ligands, with a loading thickness of 10 to 50 μm and a specific surface area of ​​about 200 to 1000 m 2 / g, and has abundant unsaturated iron coordination sites. Iron mainly exists in the form of Fe(Ⅲ) with a content of 5-30%.

[0016] The metal organic framework derived carbon material is synthesized from zinc clusters and dimethylimidazole ligands and then calcined at high temperature. The loading thickness is 10-50 μm and the specific surface area is about 600-1000 m 2 / g, with abundant pore sizes and channels.

[0017] Furthermore, the base sheet includes one or more of a stainless steel sheet, a titanium sheet, a copper sheet and carbon paper.

[0018] A method for preparing an electro-Fenton dual-function cathode material comprises the following steps:

[0019] a) mixing deionized water, sodium nitrate, and at least one iron salt to form a solution A; wherein the sodium nitrate has the function of improving electrical conductivity and providing hydroxide ions;

[0020] b) performing an electrodeposition treatment on the substrate using solution A as an electrolyte and a conductive substrate as a cathode;

[0021] c) placing the substrate treated in step b) in an N,N-dimethylformamide solution containing terephthalic acid for hydrothermal treatment;

[0022] d) vacuum drying the substrate processed in step c);

[0023] e) placing the substrate treated in step d) in a solution B formed by mixing anhydrous methanol, dimethylimidazole, polyvinylpyrrolidone, and at least one zinc salt, and stirring for 10 to 30 minutes;

[0024] f) vacuum drying the substrate treated in step e);

[0025] g) performing high-temperature calcination on the substrate processed in step f).

[0026] Wherein, in step c), before the hydrothermal treatment, the substrate needs to be placed in an N,N-dimethylformamide solution containing terephthalic acid and stirred for 10 to 30 minutes;

[0027] Furthermore, in a), the deionized water is aerated with nitrogen (generally for 30 to 60 minutes) to remove dissolved oxygen; and the molar concentration ratio of the iron salt to the sodium nitrate is 1:(1 to 5).

[0028] Furthermore, in b), the current density of the electrodeposition is 1 to 100 mA / cm 2 , time is 1 to 30 minutes; preferably, the current density of the electrodeposition is 5 to 15 mA / cm 2 , the time is 3 to 8 minutes.

[0029] Furthermore, in c), the hydrothermal reaction temperature is 100-120° C., and the time is 12-48 hours; preferably, the hydrothermal reaction temperature is 110° C., and the time is 24-36 hours;

[0030] The molar ratio of terephthalic acid to Fe electrodeposited in b) is 1:2; the concentration of terephthalic acid in N,N-dimethylformamide is approximately 0.01 to 0.05 mol / L;

[0031] Furthermore, in d), the vacuum drying temperature is 60-80°C.

[0032] Furthermore, in e), the molar concentration ratio of zinc salt to dimethylimidazole is 1:(1-5)

[0033] Furthermore, in f), the vacuum drying temperature is 60-80°C.

[0034] Furthermore, in g), the high temperature calcination temperature is 500-900° C., the time is 4-8 hours, and the heating rate is 3-5° C. per minute.

[0035] The electro-Fenton bifunctional cathode material prepared by any of the above methods is used to carry out electro-Fenton treatment of sewage.

[0036] Furthermore, the pollutants treated by electro-Fenton include one or more of methylene blue, rhodamine B, sulfamethazine, sulfadiazine, and tetracycline.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The dual-functional composite material provided by the present invention comprises an iron-carbon material (iron-based material) directly grown in situ on a conductive substrate material. When applied to an electro-Fenton reaction system, the composite material has good electrical conductivity, high catalytic activity, and stable performance. The composite material can be continuously recycled without requiring specific recovery and regeneration steps, and produces very little iron sludge. The carbon material is grown on the iron-carbon material by high-temperature calcination, has a large specific surface area and a rich pore structure, good electrical conductivity, and good catalytic performance. The composite material can stably and efficiently generate hydrogen peroxide to produce OH for pollutant degradation.

[0039] (2) Compared with the traditional method of using a binder to fix the iron-based metal organic framework material to the electrode sheet (base sheet), in fact, the study found that the addition of organic matter such as a binder will affect the conductive properties of the cathode; the preparation method of the electro-Fenton dual-function cathode material provided by the present invention adopts a constant current method to deposit a layer of iron catalyst on the surface of the cathode electrode sheet to obtain a preliminary modified cathode material; the deposited iron is used as an iron source, and is fully contacted with an N,N-dimethylformamide solution dissolved with terephthalic acid, and hydrothermal treatment is performed to obtain a modified cathode with an iron-based metal organic framework material in situ grown on the surface, which can not only avoid the influence of the binder on the conductive properties of the electrode sheet; unexpectedly, the iron-based metal organic framework material grows in situ on the surface of the electrode sheet, which can realize the efficient recycling of the electrode sheet during the use of electro-Fenton, and is not prone to the problem of iron leaching;

[0040] Subsequently, the modified electrode sheet with an iron-based metal-organic framework material in situ grown on the surface is further loaded with a zinc-based metal-organic framework. After high-temperature treatment, the zinc-based metal-organic framework is carbonized into a derivative carbon framework, which greatly improves the cathode conductivity and can produce a two-electron reduction reaction with O2 to efficiently generate H2O2, achieving efficient production of OH.

[0041] Finally, the bifunctional electrode sheet prepared by the in-situ growth method in the present invention has high catalytic activity, simple operation and low cost. On the one hand, it promotes iron circulation and reduces the amount of iron sludge generated. On the other hand, it efficiently produces hydrogen peroxide and has good application prospects.

[0042] (3) The dual-function cathode provided by the present invention is used in the electro-Fenton reaction and is easy to recycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a scanning electron microscope image of the bifunctional cathode obtained in Example 1 of the present invention.

[0044] Figure 2 This is the XRD pattern of the dual-function cathode obtained in Example 1 of the present invention.

[0045] Figure 3 This is the FTIR graph of the dual-function cathode obtained in Example 1 of the present invention.

[0046] Figure 4 This is a graph showing the relationship between the removal rate of sulfadiazine during electro-Fenton degradation of the dual-function cathode obtained in Example 2 of the present invention and the electrode sheets A and B in the comparative example over time. DETAILED DESCRIPTION

[0047] It should be noted that the terms such as "upper", "lower", "left", "right", and "middle" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0048] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0049] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0050] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement, or value. One skilled in the art can readily determine the degree of flexibility for a particular variable.

[0051] As used herein, the term "at least one of" is intended to be synonymous with "one or more of." For example, "at least one of A, B, and C" explicitly includes only A, only B, only C, and combinations of each thereof.

[0052] Concentration, amount and other numerical data can be presented in range format in this article.Should be understood that such range format is only used for convenience and brevity, and should be flexibly interpreted as not only including the numerical value clearly described as range limit, but also including all independent numerical values ​​or subranges encompassed within the scope, just as each numerical value and subrange are clearly described.For example, the numerical range of about 1 to about 4.5 should be interpreted as not only including the limit value of 1 to about 4.5 clearly described, but also including independent numerals (such as 2,3,4) and subranges (such as 1 to 3,2 to 4 etc.).The same principle is applicable to the scope of only narrating a numerical value, such as "less than about 4.5", which should be interpreted as including all above-mentioned values ​​and scopes.In addition, no matter how the breadth of described scope or feature is, this explanation should be applicable.

[0053] Any steps recited in any method or process claims may be performed in any order and are not limited to the order presented in the claims.

[0054] The present invention will be further described below with reference to specific embodiments.

[0055] Example 1

[0056] This embodiment provides an electro-Fenton dual-function cathode material. The electro-Fenton dual-function cathode material comprises a substrate sheet. The substrate sheet is carbon paper;

[0057] The first layer of iron-carbon material and the second layer of carbon material are combined on the substrate; the preparation method of the electro-Fenton dual-function cathode material has an iron-carbon atomic ratio of 1:2;

[0058] Preparation method of electro-Fenton dual-function cathode material The loading amount of iron-carbon material on the substrate is 0.02g / cm 2 ;

[0059] Preparation method of electro-Fenton dual-function cathode material The loading amount of carbon material on iron-carbon material is 0.04g / cm 2

[0060] Preparation method of electro-Fenton bifunctional cathode material The iron-carbon material is synthesized from iron clusters and terephthalic acid ligands, with a loading thickness of 20 μm and a specific surface area of ​​about 385.5 m 2 / g, and has abundant unsaturated iron coordination sites. Iron mainly exists in the form of Fe(Ⅲ) with a content of 27%.

[0061] Preparation method of electro-Fenton dual-function cathode material The carbon material is synthesized from zinc clusters and dimethylimidazole ligands and then calcined at high temperature. The loading thickness is 15 μm and the specific surface area is about 800 m 2 / g, with abundant pore sizes and channels.

[0062] Example 2

[0063] This example provides a detailed preparation method for the electro-Fenton dual-function cathode material in Example 1. The specific steps are as follows:

[0064] a) Take 100ml of deionized water and aerate with high-purity nitrogen for 30 minutes. Weigh 2.78g of ferrous sulfate heptahydrate and 0.85g of sodium nitrate and dissolve them in the aqueous solution. Stir evenly. (The iron salt used in the preparation of the electro-Fenton bifunctional cathode material can also be ferrous chloride tetrahydrate.)

[0065] b) With platinum as anode and stainless steel as cathode, the 2 After electroplating for 5 minutes at a current density of 100 nm, the electrode was rinsed clean and dried in an oven at 60° C. for 2 hours to obtain a preliminarily modified electrode sheet.

[0066] c) Weigh 0.05 mg of terephthalic acid and dissolve it in 15 ml of N,N-dimethylformamide solution. Stir evenly and pour into a stainless steel reactor lined with polytetrafluoroethylene. Place the preliminarily modified electrode sheet and conduct a hydrothermal reaction at 110°C for 24 hours.

[0067] d) The product of the hydrothermal reaction was washed twice with deionized water, anhydrous ethanol, and N,N-dimethylformamide solution, respectively, and then dried in a vacuum drying oven at 60° C. for 10 hours.

[0068] e) Place the dried modified cathode in 20 ml of anhydrous methanol. Add 20 mg of polyvinylpyrrolidone to the suspension, then stir magnetically for 12 hours. Dissolve 0.4 g of zinc nitrate hexahydrate in the mixture and stir for another 12 hours. Finally, add 10 ml of anhydrous methanol containing 0.5 g of dimethylimidazole and stir continuously for 2 hours. (Zinc salts can also be selected from zinc chloride or zinc sulfate in the preparation method of electro-Fenton bifunctional cathode materials.)

[0069] f) Take out the modified electrode sheet, rinse it clean, and dry it in a vacuum oven at 60°C for 12 hours.

[0070] g) After drying, the product was transferred to a tube furnace and heated to 900° C. at a heating rate of 5° C. per minute, calcined under an argon atmosphere for 4 hours, and cooled to room temperature to obtain a modified cathode.

[0071] Example 3

[0072] The electrode sheet prepared in Example 2 was used as the cathode and the platinum sheet was used as the anode. The cathode and anode were both 1 cm in area. 2 square.

[0073] Take 100 ml of 25 mg / L sulfadiazine solution, add 1.42 g of anhydrous sodium sulfate, stir until completely dissolved, adjust pH to 3, apply oxygen aeration at 0.5 L per minute, and apply a constant current of 5 mA.

[0074] The relationship curve of sulfadiazine removal rate over time is as follows Figure 3 As shown, it can be seen that the electrode sheet obtained in Example 2 of the present invention removes 100% of sulfadiazine within 120 minutes through the electro-Fenton reaction. Compared with the unmodified electrode, the removal effect is improved by about 60%. The iron catalytic activity is high, and it is an efficient electro-Fenton modified cathode material.

[0075] Comparative Example 1

[0076] This comparative example provides the following two electrode materials:

[0077] Electrode A

[0078] The preparation method of the electrode material is basically the same as that of Example 2, except that, before step c) the hydrothermal treatment, the stirring operation between the substrate and the N,N-dimethylformamide solution containing terephthalic acid is not performed.

[0079] Electrode B

[0080] The method for preparing the electrode material is basically the same as that in Example 2, except that the high-temperature, oxygen-free pyrolysis treatment in step g) is not performed.

[0081] The prepared electrode sheets A and B were subjected to electro-Fenton oxidation treatment according to the method in Example 3. The relationship curve of sulfadiazine removal rate over time is shown in FIG. Figure 4 As shown, within 120 minutes, the bifunctional electrode in Example 2 had a 100% removal effect on sulfadiazine, while the removal rates of electrode sheet A and electrode sheet B were only 18% and 40%, respectively. The results showed that the bifunctional cathode material in Example 2 had good conductivity and high catalytic performance. The electrode sheet A, which lacked stirring, failed to fully generate the material and had a poor removal effect on sulfadiazine. The uncalcined electrode B had poor conductivity, low current utilization efficiency, and poor catalytic effect.

Claims

1. A method for preparing an electro-Fenton dual-function cathode material, characterized in that: The following steps are involved: a) mixing deionized water, sodium nitrate, and at least one iron salt to form a solution A; b) performing an electrodeposition treatment on the substrate using solution A as an electrolyte and a conductive substrate as a cathode; c) placing the substrate treated in step b) in an N,N-dimethylformamide solution containing terephthalic acid for hydrothermal treatment; d) performing vacuum drying on the substrate sheet processed in step c); e) placing the substrate treated in step d) in a solution B formed by mixing anhydrous methanol, dimethylimidazole, polyvinylpyrrolidone and at least one zinc salt and stirring for 10 to 30 minutes; f) vacuum drying the substrate treated in step e); g) performing a high-temperature calcination treatment on the substrate sheet processed in step f); Wherein, in step c), before the hydrothermal treatment, the substrate needs to be placed in an N,N-dimethylformamide solution containing terephthalic acid and stirred for 10 to 30 minutes.

2. The method for preparing the electro-Fenton dual-function cathode material according to claim 1, wherein: In the above a), the molar concentration ratio of the iron salt to the sodium nitrate is 1:(1-5).

3. The method for preparing the electro-Fenton dual-function cathode material according to claim 1, wherein: In b), the current density of the electrodeposition is 1 to 100 mA / cm 2 , the time is 1 to 30 minutes.

4. The method for preparing the electro-Fenton dual-function cathode material according to claim 1, wherein: In the above process c), the hydrothermal reaction temperature is 100-120° C. and the reaction time is 12-48 hours.

5. The method for preparing the electro-Fenton dual-function cathode material according to claim 1, wherein: In the above step d), the vacuum drying temperature is 60-80°C.

6. The method for preparing the electro-Fenton dual-function cathode material according to claim 1, wherein: In the above-mentioned e), the molar concentration ratio of zinc salt to dimethylimidazole is 1:(1-5).

7. The method for preparing the electro-Fenton dual-function cathode material according to claim 1, wherein: In said f), the vacuum drying temperature is 60-80° C.; in said g), the high-temperature calcination temperature is 500-900° C., the time is 4-8 hours, and the heating rate is 3-5° C. per minute.

8. An application of a composite magnetic material prepared by the method according to any one of claims 1 to 7, characterized in that: Used as an electro-cathode to carry out electro-Fenton degradation of organic pollutants in water.

9. An electro-Fenton dual-function cathode material, characterized in that The bifunctional cathode material includes: The substrate sheet is conductive; a first layer of iron-carbon material and a second layer of metal-organic framework-derived carbon material bonded to a substrate; The iron-carbon atomic ratio of the iron-carbon material is 1:(1-10); The loading amount of iron-carbon material on the substrate is 0.01-0.1 g / cm 2 ; The loading amount of metal organic framework-derived carbon materials is 0.01-0.1 g / cm 2 The iron-carbon material is synthesized from iron clusters and terephthalic acid ligands, with a loading thickness of 10 to 50 μm and a specific surface area of ​​about 200 to 1000 m 2 / g, iron exists in the form of Fe(Ⅲ), with a content of 5-30%; The metal organic framework derived carbon material is synthesized from zinc clusters and dimethylimidazole ligands and then calcined at high temperature. The loading thickness is 10-50 μm and the specific surface area is about 600-1000 m 2 / g.

10. The electro-Fenton bifunctional cathode material according to claim 9, characterized in that The base sheet includes one or more of a stainless steel sheet, a titanium sheet, a copper sheet and carbon paper.

Images