Preparation and application of a copper-aluminum layered bimetallic oxide-modified graphite felt electrode for heterogeneous electro-Fenton system

Abstract

The invention discloses the preparation and application of a modified graphite felt electrode loaded with copper-aluminum layered bimetallic oxide for use in a heterogeneous electro-Fenton system, and belongs to the technical field of electrochemical water treatment. The present invention uses heat-treated graphite felt as a matrix, disperses copper-aluminum bimetallic hydroxides on the surface of the heat-treated graphite felt by a hydrothermal method, and calcines at a high temperature under the condition of strong and continuous nitrogen gas flow, so as to obtain a modified graphite felt electrode with Cu2O and CuO as the main active components. Compared with the original graphite felt and the heat-treated graphite felt, when the modified graphite felt electrode loaded with copper-aluminum bimetallic oxide is used as the cathode material, the degradation efficiency of the heterogeneous electro-Fenton system for sulfamethoxazole wastewater is greatly improved, and the cathode has a low ion leaching rate, strong stability, and good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical water treatment, and relates to the preparation and application of a copper-aluminum layered bimetallic oxide-modified graphite felt electrode for a heterogeneous electro-Fenton system, which is mainly used for electrochemical oxidation and degradation of organic pollutants in water. Background Art

[0002] In recent years, electrochemical advanced oxidation process (EAOP) has attracted more and more attention from scholars because it can effectively remove organic pollutants in water. As a reliable and environmentally friendly water treatment technology, Fenton process is the most widely used EAOP. Its principle is to generate hydroxyl radicals (·OH) with strong oxidizing properties to attack organic pollutants and oxidize and decompose them.

[0003] Traditional Fenton technology shows good potential in removing refractory organic wastewater, but it has disadvantages such as the production of iron sludge, low catalyst utilization, and narrow pH range, which limit its practical application and promotion. Therefore, heterogeneous electro-Fenton technology came into being. The selection of cathode materials is crucial to the catalytic ability of heterogeneous electro-Fenton technology. Graphite felt (GF) is often used as a cathode material because of its large specific surface area, strong conductivity, and good chemical stability.

[0004] Layered bimetallic oxides (LDO) have the advantages of simple synthesis method, low ion leaching rate, high thermal stability, large specific surface area, etc. In addition, LDO can also form electrodes with high catalytic activity by coupling with electrode materials, so it is an ideal choice for heterogeneous catalysts.

[0005] The present invention utilizes the advantages of large specific surface area, strong conductivity and good chemical stability of graphite felt, and batch modifies it by adopting a cheap and easy-to-operate heat treatment method, and couples the heat-treated graphite felt with LDO. The electrode prepared by this method provides a feasibility reference for the removal of organic pollutants by heterogeneous electro-Fenton system, and therefore has important significance. Summary of the invention

[0006] The purpose of the present invention is to prepare a copper-aluminum layered bimetallic oxide-modified graphite felt electrode for a heterogeneous electro-Fenton system, which can effectively improve the degradation efficiency of organic pollutants in water, has good electrode stability, and can be reused many times.

[0007] The specific preparation method of the electrode is as follows:

[0008] (1) Immerse the graphite felt in anhydrous ethanol and perform ultrasonic treatment for 30 minutes to remove oil stains and other organic impurities on the surface; then immerse the graphite felt in deionized water and perform ultrasonic treatment for 5 minutes, and perform this operation multiple times to wash away the anhydrous ethanol and other inorganic impurities remaining on the graphite felt; finally, place the graphite felt in an oven to dry for later use;

[0009] (2) placing the graphite felt obtained in step (1) in a high-temperature atmosphere furnace, continuously introducing a certain flow rate of oxygen, heating to 500° C. at 5° C. / min, and treating for 2 h to obtain heat-treated graphite felt HGF;

[0010] (3) Pour copper nitrate trihydrate, aluminum nitrate nonahydrate (aluminum nitrate nonahydrate: copper nitrate trihydrate = 1:0-3 (molar ratio)) and urea into an autoclave with a 100 mL polytetrafluoroethylene liner, place the autoclave in an oven at 110°C for 12 h, and after the autoclave is heated and cooled to room temperature, open the autoclave to obtain HGF loaded with copper-aluminum double hydroxide, rinse it repeatedly with deionized water until it is clean, place it in an oven at 80°C to dry, and set aside.

[0011] (4) The HGF loaded with copper-aluminum bimetallic hydroxide obtained in step (3) is placed in a muffle furnace, a certain flow of nitrogen is introduced as a protective gas, the temperature is increased to 500° C. at 5° C. / min, and calcined for 2 h to finally obtain a graphite felt electrode modified with copper-aluminum bimetallic oxide.

[0012] Every 10cm 2 The total amount of graphite felt corresponds to 9 mmol of metal salt, 12 mmol of urea, and 60 mL of deionized water.

[0013] The copper-aluminum bimetallic oxide-modified graphite felt electrode prepared by the above invention is used as the cathode in a heterogeneous electro-Fenton system to remove sulfamethoxazole in water. The obtained cathode material is recycled for at least 8 times.

[0014] The copper oxide in the obtained copper-aluminum layered bimetallic oxide exists in the form of cupric oxide and cuprous oxide crystal structures.

[0015] Compared with the prior art, the present invention has the following excellent effects:

[0016] 1. The operation process of the present invention is simple and easy to implement.

[0017] 2. The base graphite felt used in the present invention is inexpensive and has good electrocatalytic performance, and can effectively degrade organic pollutants in water.

[0018] 3. The copper-aluminum bimetallic oxide-modified graphite felt electrode prepared by the present invention has excellent catalytic performance, the removal rate of organic pollutants can reach 100%, and the ion leaching amount is very small, the stability is strong, and it can be recycled for many times. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the XRD pattern of the electrode prepared in Example 1.

[0020] Figure 2 The figure is a diagram showing the degradation effects of sulfamethoxazole wastewater in Example 1 of the present invention and Comparative Examples 1 and 2.

[0021] Figure 3 This is a diagram showing the degradation effect of sulfamethoxazole wastewater in Example 2 of the present invention.

[0022] Figure 4 This is a diagram showing the degradation effect of sulfamethoxazole wastewater in Example 3 of the present invention.

[0023] Figure 5 This is a diagram showing the degradation effect of sulfamethoxazole wastewater after the electrode prepared in Example 1 was recycled 8 times. DETAILED DESCRIPTION

[0024] The following is a description with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to the following embodiments.

[0025] Example 1

[0026] (1) Cut the graphite felt into a shape of 2×5 cm, put it into a beaker, pour a certain volume of anhydrous ethanol solution into the beaker, immerse the graphite felt, and ultrasonically treat it for 30 minutes to remove oil and other organic impurities on the surface; then immerse the graphite felt in deionized water and ultrasonically treat it for 5 minutes. This operation is repeated several times to wash away the anhydrous ethanol and other inorganic impurities remaining on the graphite felt; finally, place the graphite felt in an oven to dry for later use.

[0027] (2) placing the graphite felt obtained in step (1) in a high-temperature atmosphere furnace, continuously introducing a certain flow rate of oxygen, raising the temperature to 500° C. at a rate of 5° C. / min, and treating for 2 h to obtain heat-modified graphite felt HGF.

[0028] (3) A total of 9 mmol of copper nitrate trihydrate and aluminum nitrate nonahydrate (aluminum nitrate nonahydrate: copper nitrate trihydrate = 1:1 (molar ratio)) and 12 mmol of urea were poured into 60 mL of deionized water, and the mixture was transferred together with the HGF obtained in step (2) into an autoclave with a 100 mL polytetrafluoroethylene liner. The autoclave was placed in an oven at 110° C. for 12 h. After the autoclave was heated and cooled to room temperature, the autoclave was opened to obtain HGF loaded with copper-aluminum double hydroxide, which was repeatedly rinsed with deionized water until clean, placed in an oven at 80° C. to dry, and set aside.

[0029] (4) placing the electrode obtained in step (3) in a muffle furnace, introducing a certain flow of nitrogen as a protective gas, heating to 500° C. at 5° C. / min, and calcining for 2 h to finally obtain a graphite felt electrode modified with a copper-aluminum bimetallic oxide.

[0030] (5) The copper-aluminum bimetallic oxide modified graphite felt electrode prepared above was used as cathode, platinum sheet as anode, 0.05M sodium sulfate as electrolyte, pH = 5.7, I = 100mA, and 200mL of 10mg / L sulfamethoxazole wastewater was degraded. At 60min, the degradation efficiency of sulfamethoxazole wastewater reached 100%, as shown in FIG. Figure 2 As shown in curve c.

[0031] Example 2

[0032] The specific preparation process is the same as Example 1, but in step (3), the ratio of aluminum nitrate nonahydrate to copper nitrate trihydrate is changed to 1:0, 1:0.5, 1:1, 1:2, and 1:3, respectively. The electrode prepared above is used as the cathode, the platinum sheet is used as the anode, 0.05M sodium sulfate is used as the electrolyte, pH = 5.7, I = 100mA, and 200mL of 10mg / L sulfamethoxazole wastewater is degraded. Figure 3 As shown in the curve, when the ratio of aluminum nitrate nonahydrate to copper nitrate trihydrate is 1:1 and the reaction time is 60 minutes, the removal rate of sulfamethoxazole wastewater is optimal, reaching 100%.

[0033] Example 3

[0034] The specific preparation process is the same as Example 1, but in step (4), the calcination temperature is changed to 300°C, 400°C, 500°C, and 600°C in sequence. The electrode prepared above is used as the cathode, the platinum sheet is used as the anode, 0.05M sodium sulfate is used as the electrolyte, pH=5.7, I=100mA, and 200mL of 10mg / L sulfamethoxazole wastewater is degraded. Figure 4 As shown in the curve, when the calcination temperature is 500℃ and the reaction time is 60min, the removal rate of sulfamethoxazole wastewater is 100%.

[0035] Comparative Example 1

[0036] (1) Cut the graphite felt into a shape of 2×5 cm, put it into a beaker, pour a certain volume of anhydrous ethanol solution into the beaker, immerse the graphite felt, and ultrasonically treat it for 30 minutes to remove oil and other organic impurities on the surface; then immerse the graphite felt in deionized water and ultrasonically treat it for 5 minutes. This operation is repeated several times to wash away the anhydrous ethanol and other inorganic impurities remaining on the graphite felt; finally, place the graphite felt in an oven to dry for later use.

[0037] The electrode prepared as above was used as cathode, platinum sheet as anode, 0.05 M sodium sulfate as electrolyte, pH = 5.7, I = 100 mA, and 200 mL of sulfamethoxazole wastewater with a concentration of 10 mg / L was degraded.

[0038] That is, the difference between Comparative Example 1 and Example 1 is that only the graphite felt is cleaned and treated. At 120 min, the degradation efficiency of sulfamethoxazole wastewater is 44.1%. Figure 2 As shown in curve a.

[0039] Comparative Example 2

[0040] The specific preparation process is based on the preparation process of comparative example 1, the cleaned graphite felt is placed in a muffle furnace, and the temperature is raised to 500°C at 5°C / min under a certain flow of oxygen, and treated for 2h to obtain heat-treated modified graphite felt HGF.

[0041] The electrode prepared above was used as cathode, platinum sheet as anode, 0.05M sodium sulfate as electrolyte, pH = 5.7, I = 100mA, and 200mL of 10mg / L sulfamethoxazole wastewater was degraded. At 120min, the removal rate of sulfamethoxazole wastewater reached 84.4%. Figure 2 As shown in curve b.

[0042] The copper-aluminum bimetallic oxide-modified graphite felt electrode prepared in the above Example 1 was characterized by XRD.

[0043] like Figure 1 As shown, the main active components of the copper-aluminum bimetallic oxide modified graphite felt electrode are Cu2O and CuO. The co-existence of CuO / Cu2O promotes the degradation of organic pollutants. However, the characteristic diffraction peak of Al2O3 does not appear in the XRD characterization of the copper-aluminum bimetallic oxide modified graphite felt electrode, because Al2O3 exists in an amorphous form and cannot be detected by XRD characterization.

[0044] The stability of the copper-aluminum bimetallic oxide-modified graphite felt electrode prepared in Example 1 in a heterogeneous electro-Fenton system was determined through cyclic experiments. It can be concluded that the copper-aluminum bimetallic oxide-modified graphite felt electrode has good stability. After repeated use for 8 times, the SMX removal rate can still reach 94.4% at 60 minutes.

Claims

1. An application of a copper-aluminum layered bimetallic oxide-modified graphite felt electrode for a heterogeneous electro-Fenton system. The preparation of the copper-aluminum layered bimetallic oxide-modified graphite felt electrode comprises the following steps: (1) Immerse the graphite felt in anhydrous ethanol and treat it with ultrasound for 30 min to remove oil and other organic impurities on the surface; Then, the graphite felt is immersed in deionized water and ultrasonically treated for 5 min. This operation is repeated several times to wash away the anhydrous ethanol and other inorganic impurities remaining on the graphite felt. Finally, the graphite felt is placed in an oven to dry for later use. (2) placing the graphite felt obtained in step (1) in a high-temperature atmosphere furnace, continuously introducing a certain flow rate of oxygen, raising the temperature to 500° C. at a rate of 5° C. / min, and treating for 2 h to obtain heat-treated graphite felt HGF; (3) Pour copper nitrate trihydrate, aluminum nitrate nonahydrate and urea into an autoclave with a 100 mL polytetrafluoroethylene liner, place the autoclave in a 110°C oven for 12 h, and after the autoclave is heated and cooled to room temperature, open the autoclave to obtain HGF loaded with copper-aluminum double hydroxide, rinse it repeatedly with deionized water until it is clean, and place it in an 80°C oven to dry for later use; (4) placing the electrode obtained in step (3) in a muffle furnace, introducing a certain flow of nitrogen as a protective gas, heating to 300°C-700°C at 5°C / min, and calcining for 2h to finally obtain a graphite felt electrode modified with copper-aluminum bimetallic oxide; Every 10 cm 2 The total amount corresponding to graphite felt is 9 mmol of metal salt, 12 mmol of urea, and 60 mL of deionized water; Aluminum nitrate nonahydrate: copper nitrate trihydrate = 1:0-3 (molar ratio); Used as cathode in heterogeneous electro-Fenton system to remove sulfamethoxazole from water; The obtained cathode material can be recycled for at least 8 times.

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