An electrochemical cathode for activating persulfate to degrade organic matter in water, preparation method and application thereof

Abstract

The present invention discloses an electrochemical cathode for activating persulfate to degrade organic matter in water, a preparation method, and its application, relating to the field of electrochemical catalytic oxidation water treatment technology. The electrochemical cathode preparation method of the present invention comprises the following steps: pre-treating nickel foam (NF) with hydrochloric acid, ultrasound, and acetone, placing the pre-treated nickel foam in a mixed solution of potassium permanganate and polyethylene glycol 400 in a reactor for hydrothermal reaction, washing and drying the pre-treated nickel foam after the reaction to obtain a Ni / Ni(OH)2 cathode, then placing the Ni / Ni(OH)2 cathode and a glucose solution in a reactor for another hydrothermal reaction, washing and drying the electrode alternately with deionized water and anhydrous ethanol, and finally carbonizing the electrode in a tube furnace under a nitrogen atmosphere to obtain the Ni / NiO@C cathode. The Ni / NiO@C cathode prepared by the present invention has good stability, excellent electrochemical performance, and can efficiently activate persulfate. A single flow of ofloxacin through the cathode can achieve an efficient removal rate of 80.4%. It also has the characteristics of low nickel ion leaching and does not cause secondary pollution.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical catalytic oxidation water treatment, and in particular to an electrochemical cathode for activating persulfate to degrade organic matter in water, a preparation method and application thereof. Background Art

[0002] Medical wastewater contains large amounts of antibiotics, drugs used to treat various bacterial infections in humans and animals. Based on their antibacterial properties and effectiveness, they can be divided into five major categories: quinolones, sulfonamides, tetracyclines, β-lactams, macrolides, and aminoglycosides. Ofloxacin is a representative quinolone antibiotic.

[0003] Due to their inherent stability, antibiotics such as ofloxacin are difficult to photolyze in aqueous environments and biodegrade in sediments, posing a significant potential threat to our environment. Advanced oxidation technologies (ADOs) offer rapid reaction rates and strong oxidative capacity. The free radicals generated by the oxidants in the reaction system can cleave the chemical bonds of large organic molecules into smaller organic molecules or mineralize them into inorganic compounds such as CO2 and H2O. Persulfate-based ADOs are considered one of the most promising technologies for treating antibiotics in wastewater due to their high degradation capacity for pollutants. Persulfate, with its peroxide bond, is similar in structure to hydrogen peroxide and must be activated to produce highly oxidizing reactive oxygen species to degrade organic pollutants such as antibiotics. Therefore, current development of persulfate-based ADOs focuses on the selection and improvement of persulfate activation methods. Common physical activation methods such as ultraviolet irradiation, heating, and ultrasound are effective for persulfate activation but require additional energy input. Transition metal oxides can also effectively activate persulfate, but their cyclic stability and catalytic performance require further improvement. Therefore, the development of efficient and stable persulfate activation methods remains a crucial research topic.

[0004] Electrochemical activation of persulfate is an environmentally friendly method, but currently there are still problems with electrochemical activation of persulfate, such as low activation efficiency and secondary pollution caused by metal ion leaching from the electrode. Therefore, developing an efficient cathode that effectively reduces metal ion leaching is a very important research direction. Summary of the Invention

[0005] To address the deficiencies in the prior art, the present invention provides an electrochemical cathode for activating persulfate to degrade organic matter in water, a preparation method, and applications thereof. The cathode prepared by this preparation method has good stability, excellent electrochemical performance, can efficiently activate persulfate, and has the characteristics of low cathode metal ion leaching, thereby preventing secondary pollution.

[0006] Specifically, the present invention provides a method for preparing an electrochemical cathode for activating persulfate to degrade organic matter in water, characterized in that it comprises the following preparation steps:

[0007] S1: pre-treating nickel foam;

[0008] S2: The pretreated nickel foam is subjected to a hydrothermal reaction in the presence of a strong oxidant and a surfactant to synthesize a Ni / Ni(OH)2 cathode;

[0009] S3: The Ni / Ni(OH)2 cathode is further subjected to a hydrothermal synthesis reaction in the presence of glucose. After the reaction is completed, Ni / Ni(OH)2@C6H 12 O6 cathode;

[0010] S4: Ni / Ni(OH)2@C6H 12 The O6 cathode is carbonized under an inert gas atmosphere to obtain an electrochemical cathode for activating persulfate to degrade organic matter in water.

[0011] In some specific embodiments of the present invention, the strong oxidant in S2 is potassium permanganate, and the surfactant is polyethylene glycol 400.

[0012] In some specific embodiments of the present invention, the specific processing steps of S1-S4 are as follows:

[0013] S1: The nickel foam is subjected to hydrochloric acid ultrasound and acetone soaking, and then washed with deionized water and anhydrous ethanol, and then dried in an oven to obtain the pretreated nickel foam;

[0014] S2: placing the nickel foam after S1 pretreatment in a mixed aqueous solution of potassium permanganate and polyethylene glycol 400, and then performing a hydrothermal reaction in a reactor. After the reaction, the obtained cathode is washed and dried to obtain a Ni / Ni(OH)2 cathode;

[0015] S3: The Ni / Ni(OH)2 cathode prepared in S2 was placed in a glucose solution and subjected to hydrothermal reaction in a reactor. After the reaction, the electrode was washed alternately with deionized water and anhydrous ethanol, and then dried to obtain Ni / Ni(OH)2@C6H 12 O6 cathode;

[0016] S4: Ni / Ni(OH)2@C6H prepared in S3 12 The O6 cathode was placed in a tube furnace and carbonized under a nitrogen atmosphere to obtain an electrochemical cathode for activating persulfate to degrade organic matter in water.

[0017] In some specific embodiments of the present invention, the hydrochloric acid concentration in step S1 is 0.5-2 mol / L, the ultrasonication time is 10-20 min, and the acetone immersion time is 10-20 min.

[0018] In some specific embodiments of the present invention, the preparation process of the mixed aqueous solution of potassium permanganate and polyethylene glycol 400 in step S2 is as follows: first, a potassium permanganate aqueous solution with a concentration of 0.5-3.0 g / L is prepared, stirred, and then polyethylene glycol 400 is added, and stirring is continued to mix uniformly; the volume ratio of polyethylene glycol 400 to water is V 高锰酸钾 :V 聚乙二醇400 =(0.75-10):1.

[0019] In some specific embodiments of the present invention, the temperature of the hydrothermal reaction in step S2 is 150-170° C., and the reaction time is 10-14 h.

[0020] In some specific embodiments of the present invention, the temperature of the hydrothermal reaction in step S3 is 160-180° C., the reaction time is 6-10 h, and the concentration of the glucose solution is 5-25 g / L.

[0021] In some specific embodiments of the present invention, the washing in step S3 is performed by alternating washing with deionized water and anhydrous ethanol for three times, and the drying is performed in an oven at 40-80°C.

[0022] In some specific embodiments of the present invention, the carbonization step in step S4 is as follows: Ni / Ni(OH)2@C6H prepared in step S3 is 12 Place the O6 cathode in a tube furnace under a nitrogen atmosphere, then heat the temperature to 450-550°C at a heating rate of 1-10°C / min; maintain the temperature at 450-550°C for 3-5 hours; after heating, reduce the temperature to room temperature at a cooling rate of 1-10°C / min.

[0023] The present invention also provides an electrochemical cathode based on activated persulfate for degrading organic matter in water, the cathode comprising a substrate and a NiO@C material in situ grown on the surface of the substrate; the cathode is prepared by any of the above-mentioned methods for preparing an electrochemical cathode for activating persulfate for degrading organic matter in water.

[0024] The present invention also provides a cathode prepared by any of the above methods for preparing an electrochemical cathode for activating persulfate to degrade organic matter in water, or the use of the above electrochemical cathode for activating persulfate to degrade organic matter in water in activating persulfate to degrade organic matter in water.

[0025] In some specific embodiments of the present invention, the organic matter is an antibiotic.

[0026] In some specific embodiments of the present invention, the antibiotic is ofloxacin.

[0027] The present invention also provides a penetrating electro-activated persulfate reaction device, comprising an insulating shell, a Ni / NiO@C cathode, a carbon felt anode and an electrode separator. The Ni / NiO@C cathode is an electrochemical cathode prepared by any of the above-mentioned methods for preparing an electrochemical cathode for activating persulfate to degrade organic matter in water, or the above-mentioned electrochemical cathode for activating persulfate to degrade organic matter in water.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The electrode with in-situ growth of NiO on nickel foam has better stability than the electrode with NiO loaded on the surface of nickel foam. NiO is more firmly attached to the electrode surface and has stronger impact resistance.

[0030] 2. Compared with Ni / Ni(OH)2, Ni / NiO@C obtained by C doping has smaller electrochemical impedance and lower nickel ion leaching, and the electrode electrochemical performance is better.

[0031] 3. The Ni / NiO@C cathode prepared in the present invention has the characteristics of strong persulfate activation ability, good stability and low energy consumption, and can achieve efficient removal of antibiotics in water.

[0032] 4. The Ni / NiO@C cathode prepared in the present invention is applied to the persulfate advanced oxidation treatment of antibiotic wastewater. As a penetrating cathode, the overflow operation mode can greatly improve the mass transfer efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Attachment Figure 1 This is a scanning electron microscope image of the Ni / NiO@C cathode provided in Example 1 of the present invention;

[0034] Attachment Figure 2 is an X-ray diffraction pattern of the Ni / NiO@C cathode provided in Example 1 of the present invention;

[0035] Attachment Figure 3 The penetrating electro-activated persulfate reaction device provided in Example 1 of the present invention;

[0036] Attachment Figure 4 This is a comparison chart of cyclic voltammetry tests of the Ni / NiO@C cathode and the Ni / Ni(OH)2 cathode provided in Example 1 of the present invention;

[0037] Attachment Figure 5 This is a comparison diagram of the electrochemical impedance of the Ni / NiO@C cathode and the Ni / Ni(OH)2 cathode provided in Example 1 of the present invention;

[0038] Attachment Figure 6 This is a comparison chart of nickel ion leaching of the Ni / NiO@C cathode, Ni / Ni(OH)2, and Ni / NiO cathodes provided in Example 1 of the present invention;

[0039] Attachment Figure 7 is the ofloxacin removal rate of the Ni / NiO@C cathode provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the application equally.

[0041] Example 1: Preparation of an electrochemical cathode for activating persulfate to degrade organic matter in water

[0042] The cathode is prepared according to the following method, which comprises the following steps:

[0043] (1) A 2*2.5*0.1 cm nickel foam was placed in 1 mol / L hydrochloric acid and ultrasonicated for 10 min, then soaked in acetone and ultrasonicated for 10 min, then washed alternately with deionized water and anhydrous ethanol three times, and then dried in a 60°C oven to complete the pretreatment of the nickel foam.

[0044] (2) Dissolve 0.0525 g of potassium permanganate in 50 ml of deionized water and stir with a magnetic stirrer for 5 min until the solution turns purple. Add 20 ml of polyethylene glycol 400 and continue stirring until the solution turns brown-red to prepare a mixed solution of the above components.

[0045] (3) The pretreated nickel foam and the mixed solution are transferred together into a polytetrafluoroethylene-lined high-pressure reactor, and the reactor is placed in an oven, heated to 160°C and maintained for 12 hours. After the reaction is cooled to room temperature, the nickel foam is washed alternately with deionized water and anhydrous ethanol three times, and then dried in an oven at 60°C for 6 hours to obtain a Ni / Ni(OH)2 cathode.

[0046] (4) 0.9458 g of anhydrous glucose was dissolved in 70 ml of deionized water, and the Ni / Ni(OH)2 cathode and the glucose solution were transferred together into a polytetrafluoroethylene-lined autoclave. The autoclave was then placed in an oven and heated to 170°C for 8 h. After the reaction cooled to room temperature, the Ni / Ni(OH)2 cathode was washed alternately with deionized water and anhydrous ethanol three times, and then dried in an oven at 60°C for 6 h to obtain Ni / Ni(OH)2@C6H12 O6 cathode.

[0047] (5) Ni / Ni(OH)2@C6H 12 The O6 cathode was placed on a porcelain boat and placed in a tube furnace under a nitrogen atmosphere. The temperature was raised from room temperature to 500°C, during which the temperature was increased by 5°C per minute, then maintained at 500°C for 4 hours, and finally cooled by 5°C to room temperature for 1 minute to obtain a Ni / NiO@C cathode.

[0048] The method for preparing an electrochemical cathode for degrading organic matter in water with activated persulfate has high preparation efficiency and low preparation cost.

[0049] Example 2: Characterization of the Ni / NiO@C cathode prepared in Example 1

[0050] The Ni / NiO@C cathode prepared in Example 1 was analyzed and tested using a scanning electron microscope and an X-ray diffractometer. The test results were as follows: Figure 1 and Figure 2 shown.

[0051] like Figure 1 As shown, it can be clearly observed that the coral-shaped NiO@C grows tightly on the nickel foam, which has a large specific surface area, thereby increasing the electrochemical active sites on the surface of the material.

[0052] Depend on Figure 2 It can be seen that the diffraction peaks of Ni / NiO@C correspond one-to-one with the standard cards of NiO and NF, and no other miscellaneous peaks appear, which proves the successful preparation of the Ni / NiO@C cathode.

[0053] Example 3: Cyclic voltammetry and electrochemical impedance spectroscopy of a penetrating electroactivated persulfate reaction device and a cathode

[0054] This embodiment provides a penetrating electro-activated persulfate reaction device, such as Figure 3 The example includes an insulating housing, a carbon fiber anode, an electrode separator, and a Ni / NiO@C cathode. The anode is selected from a carbon cloth anode, a carbon mesh anode, and a carbon fiber felt anode. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) tests were performed on the Ni / NiO@C cathode, Ni / Ni(OH)2 cathode, and nickel foam (NF) using an electrochemical workstation. The Ni / NiO@C cathode, Ni / Ni(OH)2 cathode, and nickel foam (NF) used in this example are all final products, intermediate products, and raw materials in Example 1.

[0055] like Figure 4As shown in the figure, cyclic voltammetry scans were performed on Ni / NiO@C cathode, Ni / Ni(OH)2 cathode and NF in the voltage range of -2-2V. It can be seen from the figure that Ni / NiO@C cathode has the widest electrochemical stable potential window, which indicates that carbon doping greatly increases the electroactive surface area of ​​the electrode surface and improves the electrochemical performance of the electrode.

[0056] like Figure 5 As shown in the figure, electrochemical impedance spectroscopy (EEI) tests were performed on Ni / NiO@C cathode, Ni / Ni(OH)2 cathode and NF respectively. It was found that the Ni / NiO@C cathode had the lowest electrochemical impedance compared with NF and Ni / Ni(OH)2 cathode. This is because the specific surface area of ​​the coral spherical NiO after carbon doping is greatly increased, thereby increasing the electrochemical active sites on the electrode surface, thereby improving the charge transfer performance and reducing the mass transfer resistivity.

[0057] Example 4: Application of electrochemical cathodes activated by persulfate to degrade organic matter in water for the removal of antibiotics from wastewater

[0058] To investigate nickel ion leaching during the process of removing antibiotics with electrode-activated persulfate, samples were collected from the reaction solutions of antibiotic removal using different electrodes (the Ni / NiO@C cathode, Ni / Ni(OH)2 cathode, and Ni / NiO cathode used in this example were the final product and intermediate product in Example 1), and the nickel ion concentration in the solutions was measured by inductively coupled plasma-mass spectrometry (ICP-MS).

[0059] like Figure 6 The test results show that compared with the Ni / Ni(OH)2 cathode and the Ni / NiO cathode, the Ni / NiO@C cathode has the lowest nickel ion leaching, which is far less than the national standard for nickel ion concentration in water (0.5 mg / L). The lower nickel ion leaching greatly reduces the secondary pollution of heavy metals in antibiotic removal.

[0060] Example 5: Testing the effectiveness of electrochemical cathode removal of antibiotics from wastewater by activating persulfate to degrade organic matter in water

[0061] This example applies the electrochemical cathode prepared in Example 1 for the degradation of organic matter in water by activated persulfate to remove antibiotics from wastewater, and tests the removal effect. In order to investigate the removal efficiency of ofloxacin antibiotics, a penetrating reactor was constructed with Ni / NiO@C as cathode and carbon felt as anode. Figure 7 As shown in the figure, a removal experiment of ofloxacin wastewater was carried out.

[0062] 10 mg / L ofloxacin and 1 mmol / L peroxymonosulfate were pumped into the permeation reactor at a flow rate of 0.5 ml / min via a peristaltic pump and syringe pump, respectively. Simultaneously, a 2 V bias was applied to the Ni / NiO@C cathode and carbon felt anode. A single flow of ofloxacin through the reactor instantly achieved 80.4% efficient removal of ofloxacin. The Ni / NiO@C cathode coupled with the liquid permeation flow significantly enhanced mass transfer efficiency and significantly improved ofloxacin removal efficiency. Following these experimental procedures, the Ni / NiO@C cathode was used in a cyclical removal experiment of ofloxacin. After four cycles, the Ni / NiO@C cathode maintained a removal efficiency of over 76%, demonstrating its continued ability to effectively activate peroxymonosulfate and achieve efficient ofloxacin removal.

[0063] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, the above-mentioned features may have similar functions to (but not limited to) those disclosed in this application.

Claims

1. A method for preparing an electrochemical cathode for activating persulfate to degrade organic matter in water, characterized in that: The method comprises the following preparation steps: S1: pre-treating nickel foam; S2: synthesizing a Ni / Ni(OH)2 cathode by hydrothermal reaction of the pretreated nickel foam in the presence of a strong oxidant and a surfactant, wherein the strong oxidant is potassium permanganate and the surfactant is polyethylene glycol 400; S3: The Ni / Ni(OH)2 cathode is further subjected to a hydrothermal synthesis reaction in the presence of glucose. After the reaction is completed, Ni / Ni(OH)2@C6H 12 O6 cathode; S4: Ni / Ni(OH)2@C6H 12 The O6 cathode is carbonized under an inert gas atmosphere to obtain an electrochemical cathode for activating persulfate to degrade organic matter in water.

2. The method for preparing an electrochemical cathode for degrading organic matter in water by activating persulfate as claimed in claim 1, characterized in that: The specific processing steps of S1-S4 are as follows: S1: The nickel foam is subjected to hydrochloric acid ultrasound and acetone soaking, and then washed with deionized water and anhydrous ethanol, and then dried in an oven to obtain the pretreated nickel foam; S2: placing the nickel foam after S1 pretreatment in a mixed aqueous solution of potassium permanganate and polyethylene glycol 400, and then performing a hydrothermal reaction in a reactor. After the reaction, the obtained cathode is washed and dried to obtain a Ni / Ni(OH)2 cathode; S3: The Ni / Ni(OH)2 cathode prepared in S2 was placed in a glucose solution and subjected to hydrothermal reaction in a reactor. After the reaction, the electrode was washed alternately with deionized water and anhydrous ethanol, and then dried to obtain Ni / Ni(OH)2@C6H 12 O6 cathode; S4: Ni / Ni(OH)2@C6H prepared in S3 12 The O6 cathode was placed in a tube furnace and carbonized under a nitrogen atmosphere to obtain an electrochemical cathode for activating persulfate to degrade organic matter in water.

3. The method for preparing an electrochemical cathode for activating persulfate to degrade organic matter in water as claimed in claim 2, characterized in that: In step S1, the concentration of hydrochloric acid is 0.5-2 mol / L, the ultrasonic time is 10-20 min, and the acetone soaking time is 10-20 min.

4. The method for preparing an electrochemical cathode for degrading organic matter in water with activated persulfate according to claim 2, wherein: The preparation process of the mixed aqueous solution of potassium permanganate and polyethylene glycol 400 in step S2 is as follows: first prepare a potassium permanganate aqueous solution with a concentration of 0.5-3.0 g / L, stir, then add polyethylene glycol 400, continue stirring, and mix evenly; the volume ratio of polyethylene glycol 400 to potassium permanganate aqueous solution is V 高锰酸钾 :V 聚乙二醇400 =(0.75-10):

1.

5. The method for preparing an electrochemical cathode for activating persulfate to degrade organic matter in water as claimed in claim 2, characterized in that: The temperature of the hydrothermal reaction in step S2 is 150-170° C., and the reaction time is 10-14 h.

6. The method for preparing an electrochemical cathode for degrading organic matter in water with activated persulfate according to claim 2, wherein: The temperature of the hydrothermal reaction in step S3 is 160-180° C., the reaction time is 6-10 h, and the concentration of the glucose solution is 5-25 g / L.

7. The method for preparing an electrochemical cathode for degrading organic matter in water with activated persulfate according to any one of claims 1 to 6, characterized in that: The specific carbonization steps in step S4 are: 12 Place the O6 cathode in a tube furnace under a nitrogen atmosphere, then heat the temperature to 450-550°C at a heating rate of 1-10°C / min; maintain the temperature at 450-550°C for 3-5 hours; after heating, reduce the temperature to room temperature at a cooling rate of 1-10°C / min.

8. An electrochemical cathode for activating persulfate to degrade organic matter in water, characterized in that: The cathode comprises a substrate and a NiO@C material in situ grown on the surface of the substrate; the cathode is prepared by the preparation method of an electrochemical cathode for activating persulfate to degrade organic matter in water according to any one of claims 1 to 7.

9. Use of the electrochemical cathode prepared by the preparation method of the electrochemical cathode for activating persulfate degradation of organic matter in water according to any one of claims 1 to 7 or the electrochemical cathode for activating persulfate degradation of organic matter in water according to claim 8 in activating persulfate degradation of organic matter in water.

10. A penetrating electro-activated persulfate reaction device comprising an insulating housing, a Ni / NiO@C cathode, a carbon felt anode, and an electrode separator, wherein the Ni / NiO@C cathode is an electrochemical cathode prepared by the method for preparing an electrochemical cathode for activating persulfate to degrade organic matter in water according to any one of claims 1 to 7, or the electrochemical cathode for activating persulfate to degrade organic matter in water according to claim 8.

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