A core-shell structure c@co / nf electrode material, a preparation method and application thereof, and an ec-c@co / nf-pms system

Abstract

The application belongs to the technical field of sewage treatment, and relates to a core-shell structure C@Co / NF electrode material and a preparation method and application thereof, and an EC-C@Co / NF-PMS system. The electrode material takes foamed nickel as a three-dimensional conductive substrate, and a core-shell structure of carbon-embedded cobalt element is uniformly and densely grown in situ on the surface of the foamed nickel. Four elements of C, O, Ni and Co are uniformly distributed in the C@Co / NF electrode material, wherein the atomic percentage content of carbon is the highest and exceeds 50%, Co element is mainly Co 0 , Co 3+ and Co 2+ two mixed valence states are introduced, Ni element is mainly Ni 2+ , and the metal nickel Ni 0 of the substrate itself is reserved. The electrode material has high conductivity, high catalytic activity (excellent degradation capacity), strong stability, good economy and environmental friendliness, can efficiently electroactivate PMS and deeply degrade organic pollutants such as SMX in water.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and relates to preparation of an electrode material for sewage treatment, in particular to a core-shell structure carbon-embedded cobalt (C@Co / NF) electrode material grown in-situ on a foamed nickel (NF) and a preparation method thereof and application of the electrode material in degradation of organic pollutants in sewage. BACKGROUND

[0002] The residues of antibiotic pollutants in water bodies pose a serious threat to the ecological environment and human health. As a widely used antibiotic, sulfamethoxazole (SMX) is frequently detected in environmental water bodies. Traditional treatment methods such as adsorption and biodegradation have problems such as low efficiency, easy secondary pollution and incomplete degradation.

[0003] At present, the advanced oxidation technology (SR-AOPs) based on persulfate is widely studied due to its strong oxidation ability, and the core of the technology is to activate PMS (permonosulfate) / PDS (perdisulfate) to generate sulfate radicals (SO4 •⁻ ). Traditional activation methods include heat, ultraviolet light, carbon materials, transition metal ions and their oxides, but have problems such as high energy consumption and secondary pollution. For example, homogeneous transition metal ions (such as Co 2+ ) have high catalytic efficiency, but are easy to dissolve out to cause secondary pollution and are difficult to recover. The electrocatalytic activation method has become a new direction due to its strong controllability and environmental friendliness. Traditional electrode materials (such as Ti / PbO2) have defects such as high energy consumption (>1.5V), low current efficiency (<50%), high metal active component dissolution rate (>10%) and poor stability when activating persulfate, resulting in low SMX degradation efficiency (<70%) and high operating cost.

[0004] Metal-organic framework (MOF) pyrolytic derived carbon-based materials (such as zeolitic imidazolate framework-67 / foam nickel composite material, ZIF-67 / NF) are used in the field of electrocatalysis due to high specific surface area and adjustable electronic structure, but there are still the following problems: (1) precursor limitation: the conventional ZIF-67 (dodecahedron) is easy to generate CoO@C oxide core after pyrolysis, and the metal cobalt active site is wrapped by the oxidation layer, which has poor conductivity and insufficient active sites, and low electronic transmission efficiency. (2) Poor structural stability: powder catalysts need to be coated with adhesives (such as polyvinylidene fluoride, PVDF), which leads to active site masking and increased charge transmission resistance. (3) Single application scenario: existing researches focus on the energy field (such as lithium battery negative electrode, oxygen evolution reaction OER catalysis), and there is no report on the use of PMS system for degradation of antibiotics. Although recent studies have attempted to use ZIF (zeolitic imidazolate framework) derived materials for pollutant degradation (such as cobalt-nitrogen co-doped carbon nanofiber Co-N / CNF degrades florfenicol), but it adopts electrospinning composite process, which is complicated and difficult to control the uniformity of the core-shell structure; at the same time, the cobalt in the material exists in the form of Co 2+ / Co 3+ oxide, which has insufficient conductivity, resulting in limited PMS activation efficiency (SMX degradation rate <70%). In addition, existing researches explore the loading of metal oxides (such as Co3O4) or carbon materials on substrates (such as foam nickel NF) as electrocatalytic anodes for activating PMS, but they generally have one or more of the following problems: (1) catalytic activity needs to be improved: the activation efficiency of many electrode materials for PMS is insufficient to achieve rapid degradation of pollutants, and the required overpotential is high. (2) Insufficient stability: during long-term electrochemical processes, especially in complex actual water environments, active components (such as cobalt) are prone to leaching or loss (for example, >5%), which leads to a decrease in catalytic activity and may cause secondary pollution. (3) Poor adhesion between substrate and catalytic layer: the active catalytic layer and the conductive substrate (such as NF) are not firmly combined, and are prone to peeling off under long-term operation or water scouring, affecting the electrode life. (4) Preparation cost and economy: although electrode materials relying on noble metals (such as Ir, Ru) may have better performance, the high cost limits their large-scale practical application. (5) Toxicity concerns: if the metal leaching amount is high during the catalytic process, its biological toxicity may have a negative impact on the environment, and the environmental friendliness needs to be improved.

[0005] In summary, there is an urgent need to develop an electrode material with high conductivity, high catalytic activity, excellent stability (low metal leaching), good economy and environmental friendliness for efficient electro-activated PMS and deep degradation of SMX and other organic pollutants in water. SUMMARY

[0006] In view of the defects and deficiencies of the prior art, the purpose of the present application is to provide a core-shell structure C@Co / NF electrode material with high conductivity, high catalytic activity (excellent degradation ability), strong stability, good economy and environmental friendliness, which can efficiently electroactivate PMS and deeply degrade SMX and other organic pollutants in water.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] A core-shell structure C@Co / NF electrode material, the electrode material takes foamed nickel as a three-dimensional conductive substrate, and the core-shell structure of carbon-embedded cobalt element is uniformly and densely grown in situ on the surface of the foamed nickel, and C, O, Ni and Co four elements are uniformly distributed in the C@Co / NF electrode material, wherein the atomic percentage content of carbon is the highest, more than 50%, Co element is mainly Co 0 , and Co 3+ , 2+ Two mixed valence states, Ni element is mainly Ni 2+ , while retaining the metal nickel Ni 0 of the substrate itself.

[0009] The present application also provides a preparation method of a core-shell structure C@Co / NF electrode material, which comprises the following steps:

[0010] Step 1. Foamed nickel pretreatment:

[0011] The original foamed nickel purchased is cut into appropriate size, and is ultrasonically treated with 1.0 M hydrochloric acid solution, deionized water and anhydrous ethanol respectively, and finally is cleaned with deionized water and then dried in a blast drying oven for standby;

[0012] Step 2. Preparation of ZIF-L / NF:

[0013] 2-Methylimidazole and Co(NO3)2·6H2O are respectively dissolved in beakers containing deionized water, and the two solutions are continuously stirred until completely dissolved; then, the dissolved Co(NO3)2·6H2O solution is poured into the dissolved 2-methylimidazole solution, the pretreated foamed nickel is fixed and suspended in the mixed solution; then, the beaker is placed in a blast drying oven and left to grow in situ at room temperature, and finally washed with deionized water repeatedly for three times until the solution becomes clear, and dried in a blast drying oven to obtain a ZIF-L / NF precursor, i.e. a cobalt-based zeolitic imidazolate framework-leaf structure / foamed nickel composite material;

[0014] Step 3. Preparation of C@Co / NF:

[0015] The ZIF-L / NF precursor prepared in step 2 is cut into a suitable size, then placed in the center of the crucible, and then placed in a tube furnace, N2 is passed to isolate the air in the furnace, then the temperature is raised to 500-600 DEG C in 30 min, the heating time is 100-150 min, and the C@Co / NF electrode material, i.e. a carbon-encapsulated cobalt-core-shell structure / foam nickel composite material, is obtained after being taken out when the temperature is reduced to room temperature.

[0016] As a preferred embodiment of the present application, the mass ratio of 2-methylimidazole to Co(NO3)2.6H2O in step 2 is 2-3:1, the pretreated foam nickel is fixed with a paper clip, and in-situ growth is carried out at room temperature for 10-16 h, and the temperature is controlled to be 40-60 DEG C during drying in the air drying oven, and the drying time is 4-8 h.

[0017] As a preferred embodiment of the present application, after N2 is passed in step 3, the temperature is raised to 600 DEG C in 30 min, and the heating time is 120 min.

[0018] As a further preferred embodiment of the present application, the amount of 2-methylimidazole used in step 2 is 1300 mg, the amount of Co(NO3)2.6H2O used is 582 mg, in-situ growth is carried out at room temperature for 12 h, and the temperature is controlled to be 60 DEG C during drying in the air drying oven, and the drying time is 6 h.

[0019] The core-shell structure C@Co / NF electrode material provided by the present application has good activation capacity for persulfate, and therefore can be used as a persulfate activator in activating persulfate, which is persulfate or peroxodisulfate.

[0020] In the degradation experiment of sulfamethoxazole, the core-shell structure C@Co / NF electrode material provided by the present application can achieve a removal rate of 97.35% in 15 min in a persulfate synergistic system, and therefore can be used in the degradation of organic pollutants in wastewater.

[0021] The present application also provides an EC-C@Co / NF-PMS system for electrocatalytic degradation of organic pollutants in wastewater, wherein the core-shell structure C@Co / NF electrode material is used as the anode of an electrolytic cell, a carbon rod electrode is used as the cathode of the electrolytic cell, the anode and the cathode are connected to an electrochemical workstation, the electrolytic cell contains wastewater to be degraded, persulfate and current are added to the wastewater for degradation, and the persulfate is persulfate or peroxodisulfate.

[0022] As a preferred embodiment of the present application, the organic pollutants in the wastewater are dyes and / or antibiotics.

[0023] As a further preferred embodiment of the present application, the dye is rhodamine B or methylene blue, and the antibiotic is sulfamethoxazole, tetracycline hydrochloride or oxytetracycline hydrochloride.

[0024] Advantages and benefits of the present application:

[0025] (1) The C@Co / NF material provided by the present application has a synergistic effect among the metal cobalt core (Co 0 ), the carbon shell and the NF substrate, which collectively improves the electrocatalytic performance thereof; wherein the NF substrate provides a three-dimensional conductive network, promotes electron transmission, and enables the electrode to have a self-supporting characteristic without the need for a binder; the carbon shell can effectively prevent the agglomeration and elution of cobalt nanoparticles, and improve the stability (low metal elution); in addition, the carbon shell is doped with nitrogen, which can itself adjust the electronic structure of the carbon layer, provide more active sites, and enhance the activation ability of PMS.

[0026] (2) In the preparation of the precursor of the present application, the ZIF-L(Co) precursor is grown in situ at room temperature, and the two-dimensional leaf structure of ZIF-L(Co) is used to replace the conventional ZIF-67 (three-dimensional rhombus), which utilizes the high specific surface area and directional growth characteristics to achieve uniform coverage (coverage > 90%) on the NF surface; then pyrolysis is performed in a reducing atmosphere (N2) to generate a metal cobalt core (non-oxide), and the in-situ grown ZIF-L(Co) is modified into a compact and dense carbon layer structure with a core-shell structure, thereby forming a unique structure of nitrogen-doped carbon shell-coated metal cobalt nanoparticles (C@Co) on the NF surface, completely avoiding the problem of insufficient conductivity caused by the use of a binder.

[0027] (3) In the present application, the ZIF-L(Co) is grown in situ on the NF and pyrolyzed, so that the finally formed C@Co is firmly combined with the NF substrate and is not easily detached, ensuring long-term stability (in five consecutive runs, 90% of SMX can be removed within 30 min), and the toxicity of the material can be significantly reduced after pyrolysis, greatly reducing the ecological environmental risk.

[0028] (4) The present application first uses C@Co / NF as an electrocatalytic anode to activate persulfate for the degradation of SMX, and has a degradation rate of 95% for SMX under the conditions of an electric current density of 0.5 mA / cm 2 , a PMS concentration of 0.54 mM, and a SMX concentration of 10 mg / L within 6 min, and a TOC removal rate of 68.2% within 30 min, which has the advantages of fast degradation speed, good degradation effect, degradation of most SMX into non-toxic and harmless small molecular substances, safety and environmental protection, etc.

[0029] (5) The EC-C@Co / NF-PMS system provided by the application has almost no toxicity and extremely low environmental hazards, and almost no toxic hazards to the environment.

[0030] (6) The power consumption of the EC-C@Co / NF-PMS system provided by the application is 0.0042 KWh / m 3 , which is at a very low level. The results show that the EC-C@Co / NF-PMS system has higher efficiency and lower energy consumption in treating SMX, and is more economical and practical.

[0031] (7) The EC-C@Co / NF-PMS system provided by the application has good degradation effect on common water pollutants such as dye organic matter and antibiotics. 99.83% of Rhodamine B (RhB) can be removed within 4 minutes, 95.10% of methylene blue (MBT) can be removed within 10 minutes, 96.45% of oxytetracycline hydrochloride (OTC) can be removed within 15 minutes, and 99.08% of tetracycline hydrochloride (TC) can be removed within 30 minutes. Therefore, it has universal applicability in pollutant removal.

[0032] (8) The EC-C@Co / NF-PMS system provided by the application not only has good performance in treating fixed-phase SMX, but also has great potential in treating flow-phase SMX. The performance activity is maintained at more than 70% after 24 cycles, which provides a new solution for efficiently degrading organic pollutants in flow-phase water.

[0033] (9) The process for preparing the electrode material is simple and has low cost. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a synthesis diagram of the core-shell structure C@Co / NF material in the application; wherein a is a synthesis process diagram; b is a diagram showing that the NF is vertically suspended on a beaker;

[0035] Figure 2 is a comparison diagram of the C@Co / NF prepared in the application and ZIF-L / NF precursor and NF;

[0036] Figure 3Figure is a morphology characterization map of the application; wherein, (a) is a main synthesis route of C@Co / NF; (b1) is an SEM image of NF; (b2) is an SEM image of ZIF-L (Co) / NF; (c1-c2) are SEM images of C@Co / NF at 100 μm and 50 μm; (d1) is a TEM image of C@Co powder; (d2) is an HR-TEM image of C@Co powder; (e) is an EDS mapping image of C@Co / NF;

[0037] Figure 4 Figure is an EDS spectrum of each element of the C@Co / NF material of the application;

[0038] Figure 5 Figure is a structure characterization map of the application; wherein, (a) is XRD of NF, ZIF-L (Co) / NF and C@Co / NF; (b) is XRD of ZIF-L (Co) powder and C@Co powder; (c) is an XPS total spectrum of C@Co / NF; (d) is C element XPS of C@Co / NF; (e) is O element XPS of C@Co / NF; (f) is Co element XPS of C@Co / NF; (g) is Ni element XPS of C@Co / NF;

[0039] Figure 6 Figure is a degradation performance comparison map of the application; wherein, (a) and (b) are degradation performance and first-order kinetic constant of SMX in different systems, respectively; experimental conditions: pH = 6.5±0.2, [C@Co / NF] = 2×2 cm 2 , EC = 0.5 mA / cm 2 , [PMS] = 0.54 mM, [SMX] = 10 mg / L, V = 120 mL, [Na2SO4] = 50 mM, stirring rate = 150 rpm.

[0040] Figure 7 Figure is a comparison map of mineralization rate of SMX in 30 min by EC-C@Co / NF and EC-C@Co / NF-PMS synergistic systems of the application; experimental conditions: pH = 6.5±0.2, [C@Co / NF] = 2×2 cm 2 , EC = 0.5 mA / cm 2 , [SMX] = 10 mg / L, [PMS] = 0.54 mM, V = 120 mL, [Na2SO4] = 50 mM, stirring rate = 150 rpm.

[0041] Figure 8It is the SEM comparison chart of ZIF-L / NF before and after circulation of EC-ZIF-L / NF-PMS system; wherein, (a1) and (a2) are before ZIF-L / NF circulation; (b1) and (b2) are after ZIF-L / NF circulation;

[0042] Figure 9 It is the COD influence of EC-C@Co / NF-PMS system on SMX solution; wherein, (a) is the COD content before and after SMX reaction; (b) is the COD removal rate after 30 min reaction; experimental conditions: pH = 6.5±0.2, [C@Co / NF] = 2×2 cm 2 , EC = 0.5 mA / cm 2 , [SMX] = 10 mg / L, [PMS] = 0.54 mM, V = 120 mL, [Na2SO4] = 50 mM, Stirring speed = 150 rpm;

[0043] Figure 10 It is the stability evaluation of C@Co / NF; wherein, (a) is the degradation SMX cycle stability research; (b) is the XRD before and after C@Co / NF circulation; (c) is the XRD before and after C@Co (Power) circulation; (d) is the XPS total spectrum before and after C@Co / NF circulation; (e) is the Ni element XPS spectrum before and after C@Co / NF circulation; (f) is the Co element XPS spectrum before and after C@Co / NF circulation; (g) is the C element XPS spectrum before and after C@Co / NF circulation; (h) is the SEM before C@Co / NF circulation; (i) is the SEM after C@Co / NF circulation; (j) is the EDS mapping image after C@Co / NF circulation;

[0044] Figure 11 It is the growth state image of NIH-3T3 cells under different concentrations of C@Co (Powder) and ZIF-L (Powder); wherein, (a) is the growth state image under C@Co (Powder); (b) is the growth state image under ZIF-L (Powder);

[0045] Figure 12 It is the CCK-8 dyeing experiment; wherein, (a) is the survival rate of NIH-3T3 cells after being cultured with different concentrations of C@Co (Powder) and ZIF-L (Powder) for 2 h; (b) is the survival rate of NIH-3T3 cells after being cultured with different systems of SMX degradation solution at different time for 2 h;

[0046] Figure 13Fluorescent images of NIH-3T3 live / dead cell staining under the effect of different concentrations of C@Co (Powder) and ZIF-L (Powder);

[0047] Figure 14 Fluorescent images of NIH-3T3 live / dead cell staining in EC-ZIF-L / NF-PMS and EC-C@Co / NF-PMS systems for SMX degradation solution;

[0048] Figure 15 Evaluation of practical application of EC-C@Co / NF-PMS system of the present application; (a) is a comparison of consumed electric energy in EC-C@Co / NF-PMS system and different electrocatalytic degradation SMX systems reported previously; (b) is a performance graph of SMX degradation in continuous flow for 240 min; (c) is a waterfall graph of peak area change of SMX characteristic peak in liquid chromatogram within 240 min; (d) is a schematic diagram of EC-C@Co / NF-PMS system for degrading continuous flow SMX; (e) is a performance graph of EC-C@Co / NF-PMS system for degrading different water pollutants; experimental conditions: pH = 6.5 ± 0.2, [C@Co / NF] = 2 × 2 cm 2 , EC = 0.5 mA / cm 2 , pump A (10 mg / L SMX + 50 mM Na2SO4), pump B (0.54 mM PMS + 50 mM Na2SO4), total flow rate: 12 mL / min, V = 120 mL. DETAILED DESCRIPTION

[0049] The present application is further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the technical solutions described in the present application, but the present application is not limited thereto.

[0050] 1. Instruments and materials

[0051] In the present application, the reagents used in high performance liquid chromatography (HPLC) are chromatographic grade, and other chemical reagents are analytical grade. Foam nickel (NF) is purchased from Kunshan Shangte New Material Co., Ltd.; high-purity graphite carbon rod is purchased from Tianjin Zhongnuo Carbon Co., Ltd.; 2-methylimidazole (C4H6N2, 98%), cobalt nitrate hexahydrate (Co(NO3)2•6H2O, 98%), sulfamethoxazole (SMX, C 10 H 11 N3O3S, 98%) are purchased from Anhui Zesheng Technology Co., Ltd.; sodium sulfate (Na2SO4, AR, 99%), rhodamine B (RhB, C 28 H 31 ClN2O3, AR), methylene blue (MBT, C16 H 18 ClN3S, ≥98%), tetracycline (TC, C 22 H 24 N2O8), oxytetracycline hydrochloride (OTC, C2H 24 N2O9.HCl, 95%), phosphoric acid (H3PO4, AR, ≥85 wt%) were purchased from Shanghai Macklin Biochemical Technology Co., Ltd.; original foam nickel (NF, 99.99%) was purchased from Kunshan Shangte New Material Co., Ltd.; hydrochloric acid (HC1, AR) was purchased from Chengdu Kolon Chemicals Co., Ltd.; anhydrous ethanol (CH3CH2OH, ≥99.7 Wt%) was purchased from Tianjin Tianle Chemical Reagent Co., Ltd.; peroxymonosulfate (KHSO5(≥42%)•0.5KHSO4•0.5K2SO4) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Calcein / PI Cell Viability and Cytotoxicity Assay Kit (C2015M) was purchased from Shanghai Biyun Tian Biotechnology Co., Ltd.; nitric acid (HNO3, AR) was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.; 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and 2,2,6,6-tetramethylpiperidine (TEMP) were purchased from Merck Biosciences Co., Ltd. in Germany; high-purity graphite carbon rods were purchased from Tianjin Zhongnuo Carbon Co., Ltd.

[0052] X-ray diffraction (XRD) on D-MAX2500 (Rigaku, Japan) using Cu Ka radiation to determine crystal structure; scanning electron microscope (SEM, Hitachi, 8100) and energy dispersive X-ray spectroscopy (EDX, AZtec Live UltimMax 100) were used to observe morphology and element distribution; transmission electron microscope (TEM, Hitachi, HT-7800) and high-resolution transmission electron microscope (HR-TEM, Thermo Fisher, TG-G20) were used to observe the microstructure and morphology of the materials; X-ray photoelectron spectroscopy (XPS, Rigaku, AXIS ULTRA DLD) was used to verify the elemental composition of the materials; electrochemical workstation (Chenhua, CHI600E) was used for electrochemical experiments and electrochemical tests; liquid chromatography-mass spectrometry (LC-MS, Agilent, 1290 II-6460) was used to detect intermediates in the degradation solution; multifunctional microplate reader (TECAN, SPARK30086376) was used to detect the level of cell activity; inverted biological microscope (Leica, DM IL LED Fluo, 11521265, 11521274) was used to observe and take pictures of cell growth; peristaltic pump (Rongbai, BT100-2J, YZ1515) was used to realize the flow state of the solution; digestion instrument (HACH, LTG082.03.40003, 14040C0126) was used for pretreatment of the COD sample to be tested; spectrophotometer (Yire, 071114050012) was used to detect the absorbance of the COD sample to be tested; TOC analyzer (Elementar, 38.00-5500, Inbetrieb-vario-TOC-D) was used to detect the total organic carbon content in the solution; UV-Vis spectrophotometer (Pian, TU-1810) and high-performance liquid chromatograph (Dongxi, LC-5510) were used to detect the degradation degree of pollutants in the solution.

[0053] 2. Method and results

[0054] 2.1. Preparation of C@Co / NF:

[0055] 2.1.1 Pretreatment of NF

[0056] The purchased original NF was cut into the size of 2 x 3.5 cm 2 , and then treated with 1.0 M hydrochloric acid solution for 5 min, deionized water for 5 min, and anhydrous ethanol for 5 min, respectively, and finally washed with deionized water for 3 times, and then dried in a blast drying oven at 60 ℃ for 6 h for standby.

[0057] Preparation of ZIF-L (Co) in-situ growth tool:

[0058] The paperclip was made into the shape of a "clothes hanger" with pliers, and the NF (2x3.5 cm 2 ) was fixed with a paperclip in the center of the top, and the NF with the paperclip was put into the "clothes hanger", and the height of the paperclip was adjusted with pliers to ensure that the NF could be suspended vertically in the center of the 50 mL beaker. See Figure 1 (b).

[0059] 2.1.2. Preparation of ZIF-L(Co) / NF

[0060] 1300 mg of 2-methylimidazole (2-Melm) and 582 mg of Co(NO3)2·6H2O were dissolved in a 50 mL beaker containing 25 mL of deionized water, respectively, and the two solutions were continuously stirred for 5 min until completely dissolved. Then, the dissolved Co(NO3)2·6H2O red solution was slowly poured into the dissolved colorless 2-methylimidazole solution without turbulence, and the mixed solution quickly changed to light purple. After the mixed solution was left still for 20 s, the NF (2x3.5 cm 2 ) after pretreatment was fixed with a paperclip and slowly suspended in the mixed solution. Then, the above beaker was placed in a drying oven at room temperature and left in situ for 12 h. Finally, it was washed repeatedly with deionized water three times until the solution became clear, and dried at 60°C in a drying oven for 6 h to obtain the ZIF-L(Co) / NF precursor, i.e. cobalt-based zeolitic imidazolate framework-leaf structure / foam nickel composite material.

[0061] 2.1.3. Preparation of C@Co / NF

[0062] The prepared (2x3.5 cm 2 ) ZIF-L(Co) / NF precursor was cut to a size of (2x2 cm 2 ), then placed in the center of a rectangular crucible, and then placed in a tube furnace. First, N2 was passed for 30 min to isolate the air in the furnace, then the temperature was raised to 600°C for 30 min, and the heating time was 120 min (2 hours of holding). After cooling to room temperature, C@Co / NF electrode material was obtained, i.e. carbon-encapsulated cobalt core-shell structure / foam nickel composite material. Figure 1 (a) is a schematic diagram of the specific synthesis process of C@Co / NF, Figure 2 is a picture of the successful synthesis of ZIF-L / NF and C@Co / NF, where NF is gray, ZIF-L / NF is light purple, and C@Co / NF is black. The material is uniformly and densely grown in situ on the NF.

[0063] 2.2. Characterization and testing:

[0064] 2.2.1. Morphological characterization of C@Co / NF

[0065] As Figure 3 (a) shows that ZIF-L(Co) / NF precursor was successfully prepared on NF by room temperature deposition method, and then C@Co / NF was obtained by calcining ZIF-L(Co) / NF at 600℃ under N2 atmosphere in a tube furnace. The morphology of NF, ZIF-L(Co) / NF and C@Co / NF materials was characterized by scanning electron microscopy (SEM), from Figure 3 (b1) can be seen that the surface of the original NF is relatively smooth, and there is no material on its surface. From Figure 3 (b2) can be seen that after ZIF-L(Co) grows on NF, the smooth surface of NF is stacked with a piece of regular leaf-shaped ZIF-L(Co). From Figure 3 (c1) and (c2) can be seen that after calcination at 600℃ under N2 atmosphere, ZIF-L(Co) leaf shape is pyrolyzed to form a layer of dense carbon material, which is guessed to be the modification of ZIF-L itself to carbon-embedded cobalt elemental core-shell structure at high temperature.

[0066] 2.2.2. Morphology and structure characterization

[0067] In order to further verify the structure of C@Co / NF, C@Co powder scraped from C@Co / NF was tested by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), and the results are shown in Figure 3 (d1) and (d2) show that C@Co material presents a core-shell structure similar to carbon layer coated. The results of high-resolution transmission electron microscopy (HRTEM) test are shown in Figure 3 (d2), two different lattice fringes can be clearly observed, the edge of the black area corresponds to the (002) crystal plane of graphitized carbon PDF#75-1621, and the lattice fringe spacing is 0.338 nm. The black area corresponds to the (111) crystal plane of PDF#89-7093, and the lattice fringe spacing is 0.202 nm. In addition, from Figure 3 (e), it can be seen that four elements (C, O, Ni, Co) exist on C@Co / NF material and are evenly distributed. The EDS spectrum of each element of C@Co / NF material is shown in Figure 4 , in which the atomic percentage of carbon is as high as 64.2%, indicating that C@Co / NF is mostly composed of C.

[0068] In order to further determine the structure of the material, the XRD of NF, ZIF-L(Co) / NF, C@Co / NF, ZIF-L(Co) powder and C@Co powder was tested, as shown in Figure 5 (a-b), from Figure 5(a)It can be seen that NF, ZIF-L (Co) / NF, C@Co / NF have three diffraction peaks at 2θ = 45.10°, 52.44° and 76.82°, which belong to the (111), (200), (220) crystal faces of metal Ni (PDF # 170-0989). Due to the high characteristic peak of Ni, the characteristic peaks of ZIF-L (Co)-MOF, C@Co are covered. In order to further verify the structure of the material, the ZIF-L (Co) powder scraped from ZIF-L (Co) / NF, C@Co powder scraped from C@Co / NF is tested by XRD, and the results are as shown in Figure 5 (b)It can be seen that the ZIF-L(Co) powder has diffraction peaks at 2θ =7.2°, 10.3°, 10.9°, 12.7°, 15.0°, 17.0°, 18.0°, 22.0°, 23.0°, 29.0° and the like, which are highly matched with the ZIF-L (Co) simulated standard card, proving the synthesis of ZIF-L(Co) / NF material. In addition, the C@Co powder has three diffraction peaks at 2θ = 44.28°, 51.34° and 76.7°, which belong to the (111), (200), (220) crystal faces of metal Co (PDF # 15-0806), and the diffraction peak near 2θ = 26.02° belongs to the (002) crystal face of graphitized carbon (PDF # 75-1621). Combined with the previous transmission electron microscopy and high-resolution transmission electron microscopy test results, it is proved that the C@Co / NF material is a core-shell structure of carbon-embedded cobalt element.

[0069] In addition, the present application adopts X-ray photoelectron spectroscopy (XPS) technology to study the fine chemical properties of each element in C@Co / NF. As shown in Figure 5 (c), the XPS full spectrum shows that C@Co / NF is mainly composed of Ni, Co, O, C four elements, respectively located at 854.08 eV, 780.08 eV, 529.08 eV, 285.08 eV, and the Co 2p high-resolution XPS spectrum constructed based on C@Co / NF is as shown in Figure 5 (f), which is mainly composed of seven characteristic peaks, wherein Co 0 located at 778.9 eV, the characteristic peaks near 781.0 and 795.0 eV belong to Co 3+ 2p 3 / 2 and Co 3+ 2p 1 / 2 , the characteristic peaks near 785.8 eV and 796.5 eV belong to Co 2 + 2p 3 / 2 and Co 2+ 2p 1 / 2, satellite peaks of Co are located at 784.5 eV and 798.2 eV. The Ni element XPS spectrum of C@Co / NF is shown in Fig. 8 (g), the peaks at 855.8 eV and 874.0 eV are attributed to Ni Figure 5 2p 2+ 2p 2 / 3 and Ni 2+ 2p 1 / 2 , two shake-up peaks (861.3 eV) and (879.8 eV) are attributed to the satellite peaks of Ni 2p 3 / 2 and Ni 2p 1 / 2 , the peaks of Ni 0 2p 3 / 2 and Ni 0 2p 1 / 2 are located at 853.9 eV and 871.5 eV, respectively, which should be the result of NF itself substrate. XPS analysis shows that Co exists on the surface of C@Co / NF, and Co is mainly in the form of Co 0 . By introducing mixed valence Co and Ni elements, the valence change of PMS occurs in the activation process, realizing the efficient catalytic activation of PMS. The O 1s and C 1s spectra of C@Co / NF are shown in Figs. 8 (d) and (e), Figure 5 (d) and Figure 5 (e), respectively, Figure 5 (d) the characteristic peaks near 529.5 eV and 531.1 eV correspond to lattice oxygen and water adsorption, respectively; Figure 5 (e) the characteristic peaks near 284.7 eV and 288.1 eV correspond to sp 2 hybrid C-C and C-O groups, respectively.

[0070] 2.2.3. Electrocatalytic activation of persulfate for the degradation of sulfamethoxazole

[0071] The degradation experiment of SMX was carried out in a 150 mL cylindrical electrolytic cell, and the volume of the reaction solution was 120 mL. Before the degradation experiment, the carbon rod electrode and C@Co / NF (2×2 cm 2 ) were connected to the electrochemical workstation (Shanghai Chenhua CHI600E) as cathode and anode, respectively, and the two electrodes were placed horizontally with a distance of 3 cm, and the effective area of the anode electrode was 3.6 cm 2, saturated calomel electrode as the reference electrode, respectively, with a 2 cm interval between the cathode and anode, 50 mM of Na2SO4 as electrolyte in advance in the magnetic stirrer 150 rpm speed under the solution dissolved. PMS and current were added to SMX solution to start degradation experiment, according to the set time interval syringe sampling 1 mL, each sample was filtered with 0.22 um water filter head, and then added to the liquid phase sample bottle containing 100 uL methanol, and then immediately quantitatively determined the SMX concentration on high performance liquid chromatography (Beijing east analysis LC5510) (detection wavelength was 270 nm, the mixture of acetonitrile: acetic acid (0.1%) was 60%:40% as mobile phase, the total flow rate was 1.0 mL / min, the test temperature was 35℃, and the sample amount was 10 uL). Equation 1 was used to calculate the degradation rate, and equation 2 was used to calculate the pseudo-first-order kinetics for modeling. In the cycle experiment, after each cycle, the electrode was washed with deionized water for 3 times, and then dried in a forced air drying oven at 60℃ for 6 h before the next cycle experiment.

[0072] 2.2.4. Analysis method

[0073] Pollutant removal rate calculation formula (equation 1): degradation rate (%) = [1- (C t / C0)] × 100%;

[0074] Pseudo-first-order kinetics calculation formula (equation 2): ln(C t / C0) = -K obs t;

[0075] Electric energy consumption calculation formula (equation 3): EE / O = (P × t × 1000) / [V × 60 × lg(C0 / C t )];

[0076] The electric energy (EE / O) of each stage is an effective parameter for evaluating the energy consumption of electrochemical process, which is defined as: the kilowatt-hour (kWh) of electric energy required to reduce the initial pollutant concentration by one order of magnitude in 1 cubic meter of wastewater. In the above formula, C t represents the pollutant concentration (mg / L) at this moment, C0 represents the initial pollutant concentration (mg / L), K obs represents the pseudo-first-order kinetics constant, t represents the reaction time (min), and P and V are the total current power (KW) and the reaction system volume (L), respectively.

[0077] In this embodiment, the content of chemical oxygen demand (COD) in the measurement solution was measured by the traditional K2CrO7 oxidation method (HJ / T 399-2007). The absorbance of the sample at 620 nm was measured by a spectrophotometer, and then the COD standard curve was substituted: CCOD (mg / L) = 2.485 x 10 -4 X + 0.109, the concentration thereof was calculated.

[0078] 2.2.5. Performance evaluation

[0079] In order to verify the excellent degradation performance of the synergistic effect under the EC-C@Co / NF-PMS system, the degradation experiments of SMX under different systems were compared, as shown in Figure 6 (a). At the same time, the first kinetic model was fitted by using formula 2, and the degradation rate constant was fitted, as shown in Figure 6 (b). The results showed that in the single PMS system, the removal rate reached 15.56% within 15 min, and only 19.19% within 30 min, which was due to the weak oxidation ability of PMS itself, and the degradation of SMX could be almost ignored. In the single C@Co / NF system, the removal rate reached 18.68% within 15 min, and only 22.15% within 30 min, which indicated that the adsorption capacity of C@Co / NF material for SMX was poor. However, in the C@Co / NF-PMS synergistic system, the removal rate reached 97.35% within 15 min, which indicated that the C@Co / NF electrode material had good activation ability for PMS. In the EC (electrochemistry)-C@Co / NF system, the removal rate reached 42.92% within 30 min, which was 20.77% higher than that in the single C@Co / NF system, indicating that the anode current played a certain role in the degradation of SMX. In the EC-C@Co / NF-PMS system, the degradation rate was more than 90% within 6 min, and SMX was almost completely removed within 10 min, which was 51.47% higher than that in the C@Co / NF-PMS system, indicating that the addition of current generated more SO4 •- and OH•, etc. Strong oxidizing free radicals, resulting in a significant improvement in performance, compared with the EC-NF-PMS synergistic system, which can only reach 67.42% within 30 min, the former obviously has very good performance, in summary, the addition of current has a certain promoting effect on the degradation of SMX. At the same time, the performance of EC-ZIF-L / NF-PMS system was also tested, which can be seen that it has a slightly slower reaction rate than EC-C@Co / NF-PMS system, and the reason for the good performance of the former comes from the collapse of MOF, which will cause ecological environmental risk, while the latter has very low environmental risk while stabilizing the catalysis. The EC-C@Co / NF-PMS synergistic system has a relatively high pseudo-first-order kinetic reaction rate constant compared with other control systems.

[0080] The application also compares the previously reported PS / PMS degradation SMX system, which illustrates its excellent degradation performance from another aspect, see Table 1.

[0081] Table 1 Comparison of degradation performance of different activated persulfate salt systems for SMX

[0082] System PMS consumption SMX concentration Removal rate Time (min) EC-C@Fe / NF(II) 0.65 mM 25 mg / L 100% 30 EC-CC 1.00 mM 10 μM 80% 30 Fe 0 @Fe3O4-MC]]> 0.80 mM 0.04 mM 100% 120 EC-BDD 1.00 mM 5 μM 84.67% 30 Zn-N@C 0.50 mM 25 μM 95.7％ 20 CoFe / ZSM-5 0.6 g / L 10 mg / L 93% 60 EC-C@Co / NF (the application) 0.54 mM 10 mg / L 95% 6

[0083] As can be seen from Table 1, the degradation speed is fast, the degradation effect is good, under the experimental conditions of low PMS consumption and high concentration of SMX, the application exhibits excellent removal effect, which is beneficial to greatly reduce the application cost and environmental hazards while removing SMX.

[0084] In addition, the mineralization rate of the EC-C@Co / NF, EC-C@Co / NF-PMS synergistic system for 10 mg / L SMX within 30 min is also determined, and the results are shown in Figure 7 As can be seen from Figure 7 It can be seen that the mineralization rate of the EC-C@Co / NF-PMS synergistic system for 10 mg / L SMX within 30 min is 68.2%, which is obviously better than that of EC-C@Co / NF, which shows that the system can degrade most of the SMX into non-toxic and harmless small molecular substances (CO2 and H2O), which is more conducive to environmental protection. At the same time, the total organic carbon of the EC-ZIF-L / NF-PMS system is also determined, and it can be found that the total organic carbon content of the solution is doubled after 30 min of reaction, which may be due to the leaching of the catalyst on the ZIF-L / NF in the solution, which shows that the MOF itself has electrocatalytic degradation and instability, and the results are shown in Figure 8 .

[0085] In order to further study the reaction degree of SMX and its intermediate products, the potassium dichromate oxidation method (HJ / T399-2007) is also used to determine and calculate the COD of the EC-C@Co / NF-PMS system for SMX solution, and the COD removal rate for SMX within 30 min is 76.88% (see Figure 9 ), which shows that a large amount of SMX and by-products are destroyed, and the oxidation effect on the reduced organic matter in water is large.

[0086] 2.2.6. Stability evaluation

[0087] The reusability of C@Co / NF is evaluated. As shown in Figure 10 (a), the EC-C@Co / NF-PMS system can remove 90% of SMX within 30 min in five consecutive runs, showing good cycle stability. The SEM image after catalysis can be seen in Figure 8), ZIF-L has almost completely fallen off NF, which fully illustrates the instability of ZIF-L / NF. In addition, the present application also tests the XRD, SEM and EDS-Mapping of C@Co / NF before and after use, and the results are as follows Figure 10 (b), (h)-(j) shown. After catalysis and the corresponding peaks on the catalyst without using one-to-one correspondence. Before and after using SEM no obvious change and EDS-Mapping after using show that the distribution of each element is uniform after catalysis. In addition, the XPS of C@Co / NF before and after catalysis is also determined, and the Survey and C 1s of C@Co / NF before and after using do not change significantly, as shown in Figure 10 (d)-(g). Because C@Co / NF in the catalytic process in solution contact caused O ads increased. From Figure 10 (d)-(g) can be seen that the proportion of some valence metal in Co 2p and Mn 2p spectrum has changed, which is due to the effect of metal activated PMS catalytic process. In combination with the above tests, the above results show that C@Co / NF has the structural stability required for catalytic reaction.

[0088] 2.2.7. Cell toxicity experiment method

[0089] First, prepare the culture medium containing 1% penicillin-streptomycin solution (HyClone) and 10% calf serum and 89% liquid medium (DMEM), then add NIH3T3 cells (purchased from Beijing Huakeway Cell Biotechnology) to the culture medium and culture in an incubator at 37°C. The cell culture medium is updated every 1 day, and when the NIH3T3 cells enter the logarithmic growth phase, the NIH3T3 cells (5×104 cell / mL) are added to the 96-well plate containing DMEM (100 μL) and cultured for 24 h, with 2 repeats per well. After culturing and adhering, the supernatant is discarded, and 100 μL of catalyst solution or reaction solution (Blank, 0 min, 10 min, 30 min) with concentrations of 100 μg / mL, 200 μg / mL, 500 μg / mL and 1000 μg / mL is added to each well. During the culture period, the live / dead cells are stained by Calcein / PI, and the cell growth condition is recorded by an inverted biological microscope. After 24 h of co-culture, 10 μL of CCK-8 solution is added to each well, and after 4 h of incubation, the absorbance at 450 nm is measured using a microplate reader.

[0090] WST-8 in CCK-8 reagent is reduced to yellow formazan product by dehydrogenase in cell mitochondria, which is proportional to the number of cells, and its absorbance is measured at 450 nm wavelength by enzyme-labeled instrument, which can reflect the number of cells. Through CCK-8 detection, the cytotoxicity of different concentrations of catalyst C@Co (100 μg / mL, 200 μg / mL, 500 μg / mL and 1000 μg / mL) and reaction solution (Blank, 0 min, 10 min, 30 min) on NIH3T3 cells was detected.

[0091] 2.2.8. Toxicity evaluation

[0092] In order to further explore the toxicity level of the SMX solution after degradation and the material itself on the environment, the toxicity was evaluated by three ways of NIH-3T3 cell compatibility experiment (see Figure 11 ), cell counting kit-8 (CCK-8) experiment ( Figure 12 ) and live / dead / cell fluorescence staining experiment ( Figure 13 ). Figure 11 For the image of the growth of NIH-3T3 cells and the growth state image under different concentrations of C@Co (Powder) and ZIF-L (Powder) materials, it can be seen that the initial growth condition of the cells is adherent growth, and as the concentration of the material increases from 100 μg / mL to 1000 μg / mL, due to the toxicity of the material, part of the cells gradually die, showing a floating condition, and no longer adherent growth. From Figure 11 , it can be seen that as the concentration of the material increases, the number of cells showing apoptosis under the growth of NIH-3T3 cells in ZIF-L (Powder) is much larger than that in C@Co (Powder), which shows that the toxicity of the modified C@Co (Powder) is much lower than that of ZIF-L (Powder). In order to more intuitively show the toxicity, the present application observes the toxicity level of the two materials by live / dead cell staining fluorescence image (see Figure 13). Using Calcein, PI, Calcein+PI dyes to specifically stain live cells (green), dead cells (red) and live (dead) cells, respectively, it can be seen that as the concentration of ZIF-L (Powder) and C@Co (Powder) increases, the number of red fluorescence gradually increases, which indicates that the number of dead cells gradually increases. However, the number of cells killed by C@Co (Powder) is much lower than that killed by ZIF-L (Powder), which shows that the toxicity of C@Co (Powder) is much lower than that of ZIF-L (Powder). C@Co (Powder) can only cause individual cell death at a concentration of 100 ug / L, and the catalyst concentration in the EC-C@Co / NF-PMS system is much lower than 100 ug / L, so it is almost harmless to the environment.

[0093] In order to quantitatively illustrate the toxicity level, the present application also carries out CCK-8 staining experiment, and quantitatively detects the number of live cells after co-culturing live cells at different ZIF-L (Powder) and C@Co (Powder) concentrations, and the results are shown in Figure 12 (a). It can be seen that compared with ZIF-L (Powder), the modified C@Co (Powder) has a very high cell survival rate, which shows that the latter has very low toxicity and almost no harm to the environment.

[0094] In addition to exploring the toxicity level of the material itself, the present application also studies the toxicity level of the degradation solution of SMX at different times of the EC-ZIF-L / NF-PMS and EC-C@Co / NF-PMS systems. The live (dead) cell staining cell image is shown in Figure 14It can be seen that the Blank group (50 mM Na2SO4 aqueous solution) causes a small number of cell death, which may be due to the high salt concentration, causing cells to dehydrate and die by osmosis. A large number of NIH-3T3 cells in the 0 min group (10 mg / L SMX solution) died, indicating that the initial concentration of the SMX solution has high toxicity. It can be seen that as the degradation time is prolonged, the EC-ZIF-L / NF-PMS and EC-C@Co / NF-PMS systems 30 min groups have lower cell death fluorescence points than the 10 min groups, indicating that the toxicity gradually decreases. However, the EC-ZIF-L / NF-PMS system 30 min group still causes a large number of cell death, and there is no significant reduction in the number of dead cell fluorescence points compared with the 10 min group and almost similar to the Blank group, indicating that it still has high toxicity. In contrast, the EC-C@Co / NF-PMS system 10 min group has a significant reduction in the number of dead cell fluorescence points compared with the Blank group, and almost no dead cell fluorescence points exist in the 30 min group, indicating that the solution has almost no toxicity and is lower than the Blank group. This may be because the EC-C@Co / NF-PMS system removes SMX while also consuming part of Na2SO4, resulting in a decrease in salt concentration and a decrease in cell damage.

[0095] To quantitatively illustrate the solution toxicity level, the CCK-8 method was used to determine the number of viable cells after 2 h of co-culture of each type of solution, as shown in Figure 12 (b), it can be seen that the EC-C@Co / NF-PMS system has a higher cell survival rate than the EC-ZIF-L / NF-PMS system after degradation, and the 30 min group has a cell survival rate of about 90% (higher than the Blank group). The above results fully demonstrate that the solution after degradation of the EC-C@Co / NF-PMS system is almost non-toxic and has extremely low environmental hazards; also indirectly demonstrate the success of the C@Co / NF modification.

[0096] 2.2.9. Potential application evaluation

[0097] To further verify the feasibility of the EC-C@Co / NF-PMS system in practical application, the present application compares the electrical energy consumed by the system with some previously reported electrocatalytic degradation of SMX. Equation 3 is used to calculate the electrical energy consumption, and the results are shown in Figure 15 (a), the electrical energy consumption of the EC-C@Co / NF-PMS system is 0.0042 KWh / m 3 , which is at a very low level. This result shows that the EC-C@Co / NF-PMS system has high efficiency in treating SMX while still having low energy consumption.

[0098] Considering that there are various different kinds of pollutants in natural environment wastewater, in order to further verify the degradation effect of the EC-C@Co / NF-PMS system on different kinds of pollutants, two common dyes (Rhodamine B (RhB) and methylene blue (MBT)) and two antibiotics (tetracycline hydrochloride (TC) and oxytetracycline hydrochloride (OTC)) were subjected to fixed phase degradation experiments, as shown in Figure 15 (e) Within 4 min, 99.83% of Rhodamine B (RhB) can be removed, and within 10 min, 95.10% of methylene blue (MBT) can be removed, indicating that this system can efficiently degrade dye organic matter. However, within 15 min, 96.45% of oxytetracycline hydrochloride (OTC) can be removed, and within 30 min, 99.08% of tetracycline hydrochloride (TC) can be removed. The difference in degradation efficiency for different antibiotics reflects the difference in structure and activity of the pollutants, which also indirectly indicates that the main active species 1 O2 plays a great role in the catalytic process. In general, the EC-C@Co / NF-PMS system also shows excellent effect on common water pollutants, indicating that it also has good universal applicability in pollutant removal.

[0099] In order to further simulate the actual wastewater treatment scene, the present application independently designs a set of electrocatalytic EC-C@Co / NF-PMS system for degrading continuous flow SMX device, as shown in Figure 15 (d) The electrolyte aqueous solution containing 10 mg / L SMX + 50 mM Na2SO4 is used as the water source A of the A pump, and the electrolyte aqueous solution containing 0.54 mM PMS + 50 mM Na2SO4 is used as the water source B of the B pump. The two water inlets of the liquid inlet pipeline are respectively inserted into the water source A and the water source B, and the water outlet is connected with the water inlet joint at the bottom of the cylindrical electrolytic cell. The electrolyte aqueous solutions of the water source A and the water source B are transported into the electrolytic cell by controlling the A pump and the B pump. The electrolytic cell is arranged on the operation table, and the volume of the reaction solution is 120 mL. The carbon rod electrode and the C@Co / NF (2×2 cm 2 ) are respectively connected to the electrochemical workstation as the cathode and the anode with a horizontal distance of 3 cm between the two electrodes. The effective area of the anode electrode is 3.6 cm 2, the saturated calomel electrode is used as the reference electrode, and is placed at a distance of 2 cm from the cathode and the anode; a water outlet joint is arranged at the upper end of the electrolytic cell, and is communicated with the liquid collecting tank through a liquid outlet pipeline; the flow rates of the two pumps are controlled to be the same, and the total flow rate is 12 mL / min; 10 min is just enough to fill the mixed solution to the water outlet joint and not to overflow outward, at this time, the current is started to be input, the SMX is treated by the EC-C@Co / NF-PMS system, and when the solution overflows outward from the water outlet joint, the time is recorded, and then water is taken from the water outlet joint every 10 min to further detect the SMX content. Figure 15 (b) is 240 min continuous degradation of SMX in a flowing state, and the results show that the EC-C@Co / NF-PMS system can remove more than 70% of SMX within 10 min, and with the continuous increase of the number of continuous treatments, more than 70% of the removal rate can still be maintained within 240 min, Figure 15 (c) is a schematic diagram of the change of the SMX liquid chromatogram peak area. The above results show that the EC-C@Co / NF-PMS system not only has good performance in the treatment of fixed-phase SMX, but also has great potential in the treatment of flowing-phase SMX.

[0100] The above application of specific examples is used to illustrate the present application, and is only used to help understand the present application, and does not limit the present application. According to the idea of the present application, those skilled in the art can make several simple deductions, deformations or substitutions. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A core-shell structure C@Co / NF electrode material, characterized in that, The electrode material takes foam nickel as a three-dimensional conductive substrate, and a uniform and dense core-shell structure of carbon-embedded cobalt is in-situ grown on the surface of the foam nickel. C, O, Ni and Co elements are uniformly distributed in the C@Co / NF electrode material, in which the atomic percentage of carbon is the highest, exceeding 50%, Co element is mainly Co 0 , Co 3+ and Co 2+ two mixed valence states are introduced, Ni element is mainly Ni 2+ , and the metal nickel Ni 0 of the substrate itself is reserved.

2. A preparation method of a core-shell structure C@Co / NF electrode material, characterized in that, The method comprises the following steps: Step 1. Pretreatment of foamed nickel: The original foamed nickel purchased is cut into appropriate size, and is treated with 1.0 M hydrochloric acid solution, deionized water and anhydrous ethanol respectively by ultrasonic, and finally is cleaned with deionized water, and then is dried in a blast drying oven for standby; Step 2. Preparation of ZIF-L / NF: 2-methylimidazole and Co(NO3)2·6H2O are respectively dissolved in beakers containing deionized water, and the two solutions are continuously stirred until completely dissolved; then, the dissolved Co(NO3)2·6H2O solution is poured into the dissolved 2-methylimidazole solution, the pretreated foamed nickel is fixed and suspended in the mixed solution; after that, the beaker is placed in a blast drying oven for static in-situ growth at room temperature, and finally is washed with deionized water repeatedly for three times until the solution becomes clear, and is dried in a blast drying oven to obtain a ZIF-L / NF precursor, i.e. a cobalt-based zeolitic imidazolate framework-leaf structure / foamed nickel composite material; Step 3. Preparation of C@Co / NF: The ZIF-L / NF precursor prepared in step 2 is cut into appropriate size, and then is placed in the center of a crucible, and is placed in a tube furnace, N2 is passed to isolate the air in the furnace, and then the temperature is raised to 500-600℃ for 30 min, and the heating time is 100-150 min, and after the temperature is lowered to room temperature, the C@Co / NF electrode material, i.e. a carbon-encapsulated cobalt-core-shell structure / foamed nickel composite material, is obtained.

3. The method for preparing a core-shell structured C@Co / NF electrode material according to claim 2, characterized in that, In step 2, the mass ratio of 2-methylimidazole to Co(NO3)2·6H2O is 2-3:1, the pretreated foamed nickel is fixed with a paper clip, and the static in-situ growth is carried out at room temperature for 10-16 h, and the temperature is controlled to be 40-60℃ during drying in a blast drying oven, and the drying time is 4-8 h.

4. The method for preparing a core-shell structured C@Co / NF electrode material according to claim 2, characterized in that, In step 3, after N2 is passed, the temperature is raised to 600℃ for 30 min, and the heating time is 120 min.

5. The method for preparing a core-shell structured C@Co / NF electrode material according to claim 3, characterized in that, In step 2, the amount of 2-methylimidazole is 1300 mg, the amount of Co(NO3)2·6H2O is 582 mg, the static in-situ growth is carried out at room temperature for 12 h, and the temperature is controlled to be 60℃ during drying in a blast drying oven, and the drying time is 6 h.

6. The C@Co / NF electrode material prepared by the method of any one of claims 2 to 5 is applied as a persulfate activator in activating persulfate, and the persulfate is peroxymonosulfate or peroxodisulfate.

7. The C@Co / NF electrode material prepared by the method of any one of claims 2 to 5 is applied in degrading organic pollutants in wastewater.

8. An EC-C@Co / NF-PMS system for electrocatalytic degradation of organic pollutants in wastewater, characterized in that, The system takes the C@Co / NF electrode material prepared by the method of any one of claims 2 to 5 as the anode of an electrolytic cell, takes a carbon rod electrode as the cathode of the electrolytic cell, connects the anode and the cathode to an electrochemical workstation, stores wastewater to be degraded in the electrolytic cell, and adds persulfate and current into the wastewater to carry out degradation, and the persulfate is peroxymonosulfate.

9. The EC-C@Co / NF-PMS system for electrocatalytic degradation of organic pollutants in wastewater according to claim 8, characterized in that, The organic pollutants in the wastewater are dyes and / or antibiotics.

10. The EC-C@Co / NF-PMS system for electrocatalytic degradation of organic pollutants in wastewater according to claim 9, characterized in that, The dyes are rhodamine B or methylene blue, and the antibiotics are sulfamethoxazole, tetracycline hydrochloride or oxytetracycline hydrochloride.

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