Electrode material for assisting in degradation of organic pollutants and method for degrading organic pollutants

Abstract

The present application discloses an electrode material for assisting in the degradation of organic pollutants and a method for degrading organic pollutants. The electrode material has an iron matrix with a lithium ferrite oxide layer coated on the surface. Among them, the chemical formula of lithium ferrite is LiFe5O8 (LFO). In the present invention, the degradation of organic pollutants is assisted by using this electrode material. This electrode material can not only directly electrolyze and degrade organic pollutants in wastewater, but also electrochemically activate persulfate as the anode and cathode respectively to assist in the degradation of organic pollutants in wastewater. When electrochemically activating persulfate as the anode and cathode to degrade organic pollutants, there is an obvious synergistic effect, which can efficiently degrade organic pollutants. At the same time, this electrode material is inexpensive, has high stability and strong cycle performance, will not cause secondary pollution, and has good practical application prospects.

Description

Technical Field

[0001] This application relates to the technical field of water treatment, and particularly to an electrode material for assisting in the degradation of organic pollutants and a method for degrading organic pollutants. Background Art

[0002] At present, various antibiotics (including sulfamethoxazole, tetracycline, and ciprofloxacin) have been detected in environmental water bodies. These antibiotics not only have a negative impact on the environment but also pose a serious threat to human health. Therefore, the treatment of wastewater containing antibiotic drugs is of great significance.

[0003] The electrochemical activation of persulfate to degrade refractory organic pollutants such as antibiotics has attracted much attention due to its high efficiency and environmental friendliness. Currently, the electroactivation of persulfate includes anodic activation and cathodic activation. At present, the most commonly used anodes include boron-doped diamond anodes, carbon material anodes, dimensionally stable anodes, and iron electrodes. The cathodes are mainly carbon material cathodes. Persulfate can be activated on the electrodes to generate reactive species such as sulfate radicals, hydroxyl radicals, singlet oxygen, and activated persulfate. These reactive species have strong oxidation ability and can efficiently degrade organic pollutants. Although the above materials show high potential in the electroactivation of persulfate to degrade organic pollutants, the high cost, complex preparation process of boron-doped diamond anodes and dimensionally stable anodes, and the low stability of carbon material electrodes and iron electrodes limit their applications.

[0004] Based on the problems of high cost and low stability of the above materials, we propose an electrode material for assisting in the degradation of organic pollutants. The electrode material uses inexpensive and easily available iron as the matrix, and grows a LiFe5O8 oxide layer in-situ on the iron surface. This electrode material can not only be used as an anode to directly electrolyze wastewater to degrade organic pollutants but also be used as an anode and a cathode respectively to electrochemically activate persulfate to efficiently degrade organic pollutants in wastewater. This electrode material is expected to solve the problems of high cost and low stability of other electrode materials, but there is no relevant report yet. Summary of the Invention

[0005] In view of this, this application provides an electrode material for assisting in the degradation of organic pollutants and a method for degrading organic pollutants, which can improve the degradation effect of organic pollutants in organic wastewater.

[0006] <Creation Process>

[0007] It has been generally recognized by those skilled in the art that in the related art, electro-activated persulfate includes anodic activation and cathodic activation. Currently, the most commonly used anodes include boron-doped diamond anodes, carbon material anodes, dimensionally stable anodes, and iron electrodes. The cathodes are mainly carbon material cathodes. Persulfate can be activated on the electrodes to generate reactive species such as sulfate radicals, hydroxyl radicals, singlet oxygen, and activated persulfate. These reactive species have strong oxidation capabilities and can efficiently degrade organic pollutants. Although the above materials show high potential in the degradation of organic pollutants by electro-activated persulfate, the high costs, complex preparation processes of boron-doped diamond anodes and dimensionally stable anodes, and the low stability of carbon material electrodes and iron electrodes limit their applications.

[0008] Based on the above problems, the present inventors proposed an electrode material for assisting in the degradation of organic pollutants. This electrode material can be used as an anode to directly electrolyze wastewater, and degrade the organic pollutants in the wastewater through direct electron transfer reactions and hydroxyl radicals generated by electrolyzing water. At the same time, adding persulfate during the process of electrolyzing wastewater as an anode can promote the degradation of organic pollutants. The added persulfate can promote the generation of hydroxyl radicals and form activated persulfate on the electrode surface, thereby promoting the degradation of organic pollutants. In addition, this electrode material can be used as a cathode to activate persulfate, and persulfate is reduced to sulfate radicals at the cathode, and the organic pollutants are efficiently degraded through sulfate radicals.

[0009] If this electrode material is used as an anode to directly electrolyze and degrade organic pollutants in wastewater, the involved reaction equations are as follows:

[0010] M-R-e - →M-Intermediate-e - →CO2+H2O

[0011] H2O→·OH+H +

[0012] ·OH+R→Products

[0013] Among them, M is the electrode material and R is the organic pollutant.

[0014] If this electrode material is used as an anode to electro-activate persulfate to degrade organic pollutants in wastewater, the involved reaction equations are as follows:

[0015] M-R-e - →M-Intermediate-e - →CO2+H2O

[0016] M+PDS / PMS→M(PDS* / PMS*)

[0017] R + M(PDS* / PMS*) → Products

[0018] H2O → ·OH + H +

[0019] ·OH + R → Products

[0020] If this electrode material is used as the cathode to electroactivate persulfate for degrading organic pollutants in wastewater, the reactions occurring in the electrolytic cell are as follows:

[0021]

[0022]

[0023] Based on the above technical concept, the present invention was created.

[0024] <Electrode Material>

[0025] This electrode material has an iron matrix with a lithium ferrite oxide layer coated on its surface; among them, the chemical formula of lithium ferrite is expressed as LiFe5O8 (denoted as LFO).

[0026] Regarding the preparation process of this electrode material, it has been mastered by relevant technical personnel. Weigh 500 g of anhydrous Li2CO3 - Na2CO3 - K2CO3 (molar ratio: 43.5:31.5:25.0), mix them evenly and place them in an Al2O3 crucible, and then place the Al2O3 crucible in a graphite crucible. First, dry the molten salt electrolyte in an air atmosphere at 300 °C for 12 h, then replace the furnace atmosphere with Ar and maintain a certain positive pressure effect (120 mL / min), raise the temperature to 800 °C and keep it for 30 min to melt the carbonate, and finally cool it to 650 °C for standby. Bundle the Fe sheet electrode (10 mm × 10 mm × 0.5 mm) and the nickel sheet (10 mm × 10 mm) on the molybdenum wire current collector as the anode and cathode respectively, insert the Ag / Ag2SO4 reference electrode, the cathode, and the anode into the molten salt electrolyte, and carry out constant potential polarization of the Fe electrode at 0.5 V (vs Ag / Ag2SO4) for 60 min to prepare the Fe@LFO electrode. Wash the residual salt on the electrode surface with ultrapure water and dry it in a vacuum at 60 °C for 12 h for standby.

[0027] <Method for Degrading Organic Pollutants>

[0028] The types of organic pollutants involved in the degradation of organic pollutants in organic wastewater in this application include but are not limited to sulfamethoxazole.

[0029] The method for degrading organic pollutants in organic wastewater of the present application electrolyzes the organic wastewater containing organic pollutants with the electrode material as described above as the working electrode, and the electrolysis is carried out under the condition of adding sodium sulfate and persulfate.

[0030] Suitable but non-limiting specific examples, the counter electrode for electrolysis is platinum, or other types.

[0031] Suitable but non-limiting specific examples, the electrolysis is carried out at room temperature.

[0032] Suitable but non-limiting specific examples, the persulfate is persulfate or monopersulfate.

[0033] Suitable but non-limiting specific examples, the pH value of the organic wastewater is adjusted to 3 - 11.

[0034] Suitable but non-limiting specific examples, the concentration of persulfate is 0.5 - 5 mmol L -1 。

[0035] Suitable but non-limiting specific examples, the current density is 1 - 10 mA cm -2 。

[0036] The present application has the following beneficial effects:

[0037] 1. The electrode material can degrade organic pollutants in wastewater through multiple ways such as anodic electrolysis, anodic activation of persulfate, and cathodic activation of persulfate.

[0038] 2. The electrode material is inexpensive, has high stability and strong cycling performance, and will not cause secondary pollution, having good practical application prospects. Description of the Drawings

[0039] The following, in combination with the drawings, through a detailed description of the specific embodiments of the present application, will make the technical solutions and other beneficial effects of the present application obvious.

[0040] Figure 1 It is a comparative diagram of the effects of degrading sulfamethoxazole in different systems in Example 1, Comparative Example 1, and Comparative Example 2 of the present application.

[0041] Figure 2 It is the cycling performance of electrochemically activated persulfate for degrading sulfamethoxazole in Example 2 of the present application.

[0042] Figure 3 It is the stability performance of electrochemically activated persulfate for degrading sulfamethoxazole in Example 3 and Comparative Example 3 of the present application. Specific Embodiments

[0043] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0044] In the description of the present application, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0045] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. To simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present application. In addition, the present application may repeat reference numerals and / or reference letters in different examples. This repetition is for the purpose of simplification and clarity and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0046] Taking antibiotic wastewater as a typical organic wastewater below, antibiotics not only have a negative impact on the environment but also cause serious harm to human health. However, it is difficult to degrade antibiotics using traditional sewage treatment methods. Therefore, the treatment of wastewater containing antibiotic drugs is of great significance. Sulfamethoxazole is selected as the target pollutant in the embodiment.

[0047] Example 1

[0048] Prepare a 5 μM concentration of sulfamethoxazole solution. Take 30 mL of the sulfamethoxazole solution into a 100 mL electrolytic cell, using the Fe@LFO electrode as the working electrode and the platinum electrode as the counter electrode. Add 50 mM of sodium sulfate as the supporting electrolyte to the electrolytic cell, and then add 2.5 mM of persulfate. Adjust the current density to 5 mA cm -2 , and use a magnetic stirrer to fully stir the solution at room temperature. Take 0.5 mL of the sample at regular intervals for analysis.

[0049] Comparative Example 1

[0050] Prepare a sulfamethoxazole solution with a concentration of 5 μM. Take 30 mL of the sulfamethoxazole solution into a 100 mL electrolytic cell, add 50 mM of sodium sulfate to the electrolytic cell, and then add 2.5 mM of persulfate. At room temperature, use a magnetic stirrer to fully stir the solution, and take 0.5 mL of the sample for analysis at certain intervals.

[0051] Comparative Example 2

[0052] Prepare a sulfamethoxazole solution with a concentration of 5 μM. Take 30 mL of the sulfamethoxazole solution into a 100 mL electrolytic cell, use the Fe@LFO electrode as the working electrode and the platinum electrode as the counter electrode. Add 50 mM of sodium sulfate to the electrolytic cell as the supporting electrolyte, and adjust the current density to 5 mA cm -2 , and use a magnetic stirrer to fully stir the solution at room temperature. Take 0.5 mL of the sample for analysis at certain intervals.

[0053] Record the changes in the concentration of sulfamethoxazole in the sulfamethoxazole solution in Example 1 and Comparative Examples 1 and 2, and draw the removal rate-time curve. The results are as Figure 1 shown.

[0054] From Figure 1 it can be seen that for the oxidation by persulfate alone, the removal rate of sulfamethoxazole is only 11.2%. When using the Fe@LFO electrode for electrolysis, the removal rate of sulfamethoxazole increases to 80.3%. When persulfate is added during the electrolysis process, the removal rate of SMX further increases to 94.8%.

[0055] Example 2

[0056] Prepare a sulfamethoxazole solution with a concentration of 5 μM. Take 30 mL of the sulfamethoxazole solution into a 100 mL electrolytic cell, use the Fe@LFO electrode as the working electrode and the platinum electrode as the counter electrode. Add 50 mM of sodium sulfate to the electrolytic cell as the supporting electrolyte, and then add 5 mM of persulfate. Adjust the current density to 10 mA cm -2 , and use a magnetic stirrer to fully stir the solution at room temperature. Take 0.5 mL of the sample for analysis at certain intervals. Repeat the experiment 8 times with the same electrode. The results are as Figure 2 shown.

[0057] From Figure 2 it can be seen that the removal rate of sulfamethoxazole almost remains at 100% after 6 cycles and still maintains a removal rate of 93% after 8 cycles, which indicates the good stability of the Fe@LFO electrode.

[0058] Example 3

[0059] Prepare a sulfamethoxazole solution with a concentration of 5 μM. Take 30 mL of the sulfamethoxazole solution into a 100 mL electrolytic cell, using the Fe@LFO electrode as the working electrode and the platinum electrode as the counter electrode. Add 50 mM of sodium sulfate as the supporting electrolyte to the electrolytic cell, and then add 2.5 mM of persulfate. Adjust the current density to 5 mA cm -2 , and use a magnetic stirrer to fully stir the solution at room temperature. After 1 h, take 10 mL of the solution to detect the iron ion concentration.

[0060] Comparative Example 3

[0061] Prepare a sulfamethoxazole solution with a concentration of 5 μM. Take 30 mL of the sulfamethoxazole solution into a 100 mL electrolytic cell, using an iron electrode as the working electrode and the platinum electrode as the counter electrode. Add 50 mM of sodium sulfate as the supporting electrolyte to the electrolytic cell, and then add 2.5 mM of persulfate. Adjust the current density to 5 mA cm -2 , and use a magnetic stirrer to fully stir the solution at room temperature. After 1 h, take 10 mL of the solution to detect the iron ion concentration.

[0062] The optical photos after the experiments in Example 3 and Comparative Example 3 are as Figure 3 shown, and the corresponding iron ion concentrations are shown in Table 1.

[0063] Table 1

[0064]

[0065] Figure 3 and Table 1 show that when electrolyzing for 60 min at a current density of 5 mA cm -2 , the concentration of iron ions dissolved from the Fe@LFO electrode is 0.018 mg / L, while the concentration of iron ions dissolved from the iron electrode as the control sample is as high as 450.2 mg / L. The Fe@LFO electrode material has extremely high stability.

[0066] As described above, it is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application.

Claims

1. A method for degrading organic pollutants in organic wastewater, characterized in that Using the electrode material as the working electrode, electrolyze the organic wastewater containing organic pollutants. The electrolysis is carried out under the conditions of adding sodium sulfate and persulfate. The electrode material has an iron matrix and a lithium ferrite oxide layer coated on the surface. Among them, the chemical formula of lithium ferrite is expressed as LiFe5O8. This electrode material can degrade the organic pollutants in the wastewater through multiple ways such as anodic electrolysis, anodic activation of persulfate, and cathodic activation of persulfate.

2. The method according to claim 1, wherein The electrolysis is carried out at room temperature.

3. The method according to claim 1, characterized in that, The persulfate is persulfate or monopersulfate.

4. The method according to claim 1, wherein The pH value of the organic wastewater is adjusted to 3 - 11.

5. The method according to claim 1, wherein The persulfate concentration is 0.5 - 5 mmol L -1 .

6. The method according to claim 1, characterized in that, The current density of the electrolysis is 1-10 mA cm -2 .

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