Electrochemical method for activation of persulfate by an alloy carbon cathode non-radical pathway

Abstract

This invention provides an electrochemical method for activating persulfate via a non-radical pathway using an alloy carbon cathode, belonging to the field of water treatment technology. This invention synthesizes cobalt-nickel alloy carbon nanotube materials through a simple thermal polymerization method. Using carbon nanotubes as a substrate, the prepared alloy carbon nanotube material exhibits high electrochemical activity and a large specific surface area, providing abundant reactive sites. By adjusting the ratio of cobalt to nickel in the material, efficient non-radical activation of persulfate (PMS) can be achieved on the electrode surface, generating two types of non-radicals: singlet oxygen (…). 1 O2) and surface-complexed PMS active species (PMS*). Furthermore, two different PMS activation pathways were applied to remove electron-rich organic pollutants from complex water bodies.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to an electrochemical method for activating persulfate via a non-radical pathway using an alloy carbon cathode. Background Technology

[0002] Faced with increasingly severe environmental pollution and water security challenges, persulfate-based advanced oxidation processes (PMS-AOPs) have demonstrated superior performance in removing recalcitrant organic matter from water bodies. The OO bonds in PMS are easily activated and broken, generating highly reactive free radicals with strong oxidizing capabilities, such as hydroxyl radicals (HO). · ) and sulfate radicals (SO4) ·- However, these free radicals are often consumed by coexisting aquatic matrix components, such as inorganic ions and natural organic matter, producing more toxic secondary pollutants, which limits their practical application in complex aquatic matrices.

[0003] Recently, non-radical oxidation pathways, such as singlet oxygen ( 1 O2, electron transfer process (ETP), and high-valent metals have been identified as important reaction mechanisms in the persulfate activation process. Generally, non-radical systems have moderate oxidizing power compared to highly oxidizing radical systems, leading to insufficient mineralization of organic pollutants. However, in practical water treatment, non-radical oxidation has some technical advantages over radical oxidation:

[0004] (i) Non-radical systems exhibit high selectivity for electron-rich organic matter and bacteria; (ii) Non-radical systems maintain their excellent efficiency in complex aqueous matrices over a wide pH range, with ETP-based oxidation processes showing greater selectivity for organic pollutants as they are unaffected by radical lifetime and migration distance; (iii) Even at high concentrations of halide ions, non-radical systems do not produce toxic halogenated byproducts (e.g., ClO3). - BrO3 - IO3 - (iv) Non-radical pathways have high peroxide utilization efficiency, low stoichiometry between consumed persulfate and target pollutants, can significantly reduce chemical input, and are more economical than conventional AOPs; (v) The redox potential of non-radical pathways can be modulated by controlling the structure / composition (e.g., heteroatoms and defects) and physicochemical properties (e.g., conductivity and zeta potential) of the catalyst.

[0005] Carbon materials are generally considered to induce non-radical activation of PMS, in which carbon nanotubes (CNTs) are formed by sp... 2 Conjugated carbon (CNTs) is composed of a curved, extended, and complete hexagonal network with a relatively low content of defects and functional groups. Therefore, CNTs provide an ideal platform for exploring non-radical pathways to activate PMS in carbon materials. Furthermore, due to the abundant meso / micropores and large specific surface area of ​​CNT materials, the CNT-based PMS-AOP system can enrich degradation intermediates of carbon surface micropollutants through electron transfer pathways (ETP) and continuous coupling reactions, significantly reducing dissolved organic carbon (DOC) and toxicity.

[0006] However, existing PMS activation technologies have low selectivity for non-free pathways. Therefore, this invention uses cobalt-nickel alloy carbon nanotubes to electrochemically activate persulfate, which can significantly improve the selectivity of non-free pathways and generate the desired non-free radical species to achieve efficient removal of pollutants from water. Summary of the Invention

[0007] To address the aforementioned problems in the existing technology, this invention provides an electrochemical method for activating persulfate via a non-radical pathway using an alloy carbon cathode.

[0008] The technical solution of the present invention is as follows:

[0009] An electrochemical method for activating persulfate via a non-radical pathway using an alloy carbon cathode includes the following steps:

[0010] A three-electrode system is used, with Co1Ni3CNT and / or Co3Ni1CNT carbon nanotubes as the cathode and a platinum sheet as the anode, so that the pollutants or organic matter to be degraded can be degraded in a persulfate electrolyte solution.

[0011] Furthermore, the pollutants or organic matter to be degraded include, but are not limited to, sulfadiazine, phenol, bisphenol A, and trichlorophenol.

[0012] Furthermore, the persulfate includes, but is not limited to, permonosulfate (PMS) and perdisulfate (PDS).

[0013] Preferably, the concentration of the pollutant or organic matter to be degraded is 10-500 ppm, and the constant current density of the three-electrode system is 20-50 mA·cm. -2 The pH range of the persulfate electrolyte solution is 2-5, and the degradation temperature is 20-25℃.

[0014] Furthermore, the preparation method of the Co1Ni3CNT and Co3Ni1CNT includes the following steps:

[0015] S1: Weigh melamine, Co source and Ni source in molar ratio. For Co1Ni3CNT, Co source: Ni source = 1:1-4; for Co3Ni1CNT, Co source: Ni source = 1-4:1.

[0016] S2: After mixing the three materials evenly and grinding them thoroughly, after drying, grind them again and mix them evenly. Put them into a porcelain boat and place them in a tube furnace. Heat them to 300-600℃ in flowing nitrogen for 2-3 hours to obtain a brownish-yellow solid.

[0017] S3: The brownish-brown solid obtained in step S2 is ground three times and then placed into a porcelain boat, placed in a tube furnace, and calcined in flowing nitrogen. The furnace is then cooled to obtain a black, fluffy solid.

[0018] S4: The black, bulky solid obtained in step S3 is treated with HCl solution at room temperature, then washed with deionized water and filtered, and finally dried to obtain a black sample, named Co1Ni3CNT or Co3Ni1CNT.

[0019] Preferably, in step S1, the Co source is cobalt nitrate hexahydrate; the Ni source is nickel nitrate hexahydrate.

[0020] Preferably, in step S1, the molar ratio of melamine to the sum of the Co source and the Ni source is 6-10:1.

[0021] More preferably, in step S1, the molar ratio of melamine to the sum of the Co source and the Ni source is 8:1.

[0022] Preferably, in step S2, the drying is performed in an oven at a temperature of 120-130°C for 5-7 hours; the nitrogen flow rate is 30-50 mL / min; and the heating rate is 5-10°C / min.

[0023] Preferably, in step S3, the flow rate of nitrogen is 30-50 mL / min; the calcination is carried out by heating to 600-800℃ at a rate of 5-10℃ / min, and the calcination time is 3-5 h.

[0024] Furthermore, in steps S2 and S3, the ceramic boat is covered and is relatively sealed.

[0025] Preferably, in step S4, the concentration of the HCl solution is 6-7M, and the mass used is 5-10 times that of the black bulky solid; the room temperature treatment time is 24-48h; the temperature of the deionized water washing is 70-100℃; the number of filtrations is 4-6 times; and the drying is performed in an oven at a temperature of 120-130℃ for 5-7h.

[0026] Furthermore, step S4 yields a powdered product, which, when used as a cathode, is uniformly sprayed onto the prepared carbon paper surface using an ultrasonic spraying machine.

[0027] Preferably, for Co1Ni3CNT, the optimal molar ratio of Co source to Ni source is 1:2; for Co3Ni1CNT, the optimal molar ratio of Co source to Ni source is 2:1.

[0028] Furthermore, when the cobalt and nickel sources are in a 1:1 ratio, the product obtained is Co2Ni2CNT, where the ratio of cobalt to nickel is 1:1. Co2Ni2CNT can also activate persulfate via a non-radical pathway, but the activation efficiency is lower than that of Co1Ni3CNT and Co3Ni1CNT.

[0029] The beneficial technical effects of this invention are as follows:

[0030] 1. This invention synthesizes cobalt-nickel alloy carbon nanotube materials via a simple thermal polymerization method. Using carbon nanotubes as a substrate, the prepared alloy carbon nanotube materials exhibit high electrochemical activity and a large specific surface area, providing abundant reactive sites. By adjusting the ratio of cobalt to nickel in the material, efficient non-radical activation of polyoxymethylene (PMS) can be achieved on the electrode surface, generating two types of non-radicals: singlet oxygen (…). 1 O2) and surface-complexed PMS active species (PMS*). Furthermore, two different PMS activation pathways were applied to remove electron-rich organic pollutants from complex water bodies.

[0031] 2. Due to the curved and hollow carbon framework structure of CNTs, they can encapsulate nanoparticles of different sizes, including alloy materials. This leads to more severe twisting of the highly curved CNT substrate to release strain. Utilizing the stress interaction between CNTs and nanoparticles, the adsorption energy and OO bond length of PMS at the active center can be modulated, thereby controlling the electron transfer process between PMS and the active center. This invention utilizes the different interactions between cobalt-nickel alloys and carbon nanotubes, resulting in different electron transfers and thus activation of persulfate; simultaneously, by utilizing the different stress interactions between different nanoparticles and the CNT substrate, PMS is activated through different non-radical pathways, generating different non-radical active species for the removal of electron-rich organic pollutants in water.

[0032] 3. This invention obtains two materials, Co1Ni3CNT and Co3Ni1CNT, by optimizing the mass ratio of melamine and cobalt nitrate hexahydrate + nickel nitrate hexahydrate. Compared with CoCNT and NiCNT alone, Co and Ni co-doping can improve the metal's recycling capacity and reduce metal dissolution. Simultaneously, by adjusting the Co and Ni ratio, alloy carbon nanotubes of different particle sizes can be obtained. The stress interaction between the alloy and carbon nanotubes in different directions can be used in the non-radical activation process of PMS to generate different non-radical species for removing electron-rich organic pollutants from water.

[0033] 4. Compared with traditional methods for degrading electron-rich organic pollutants, such as adsorption, membrane separation, biological treatment, and photocatalysis, the alloy carbon nanotube electrode material of this invention can achieve a highly efficient PMS non-radical activation process, improve the utilization rate of PMS, and generate a large number of active species to degrade electron-rich organic pollutants. It features low energy consumption and simple operation.

[0034] 5. The alloy carbon nanotube electrode material prepared by this invention not only has a good ability to activate PMS through non-radical pathways, but also exhibits strong interference tolerance and stability in the degradation process of electron-rich organic pollutants against complex water matrix backgrounds. It can selectively remove electron-rich pollutants from water bodies and avoid secondary pollution. Attached Figure Description

[0035] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 EPR spectra of PMS* and singlet oxygen generated by electrochemical activation of PMS by Co1Ni3CNT and Co3Ni1CNT.

[0037] Figure 2 A schematic diagram illustrating the efficiency of Co1Ni3CNT and Co3Ni1CNT in degrading sulfadiazine.

[0038] Figure 3 A schematic diagram illustrating the efficiency of Co1Ni3CNT and Co3Ni1CNT in degrading sulfadiazine in the presence of 0-50 ppm of natural organic matter. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0040] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0041] Example 1:

[0042] The specific preparation method of Co1Ni3CNT and Co3Ni1CNT alloy carbon nanotube electrode materials in this embodiment is as follows:

[0043] (1) Weigh out appropriate amounts of melamine, cobalt chloride hexahydrate and nickel chloride hexahydrate, wherein the ratio of melamine to cobalt chloride hexahydrate and nickel chloride hexahydrate is 8:1. For Co1Ni3CNT, the ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate is 1:2; for Co3Ni1CNT, the ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate is 2:1.

[0044] (2) After mixing the three materials evenly, grind them thoroughly in a mortar. After grinding, place the resulting mixed solid in an oven and dry it at 130°C for 6 hours. Grind the obtained solid a second time in a mortar until it is evenly mixed, then put it into a porcelain boat (with a lid, relatively sealed) and place it in a tube furnace. Pyrolyze it at 500°C for 2 hours in flowing nitrogen (40 ml / min) at a rate of 5°C / min. Then cool it to room temperature to obtain a brownish-yellow solid.

[0045] (3) The brownish-brown solid was ground in a mortar and pestle and then placed in a porcelain boat (with a lid, relatively sealed) and placed in a tube furnace. The temperature was raised to 700°C for 3 hours in flowing nitrogen (40 mL / min) at a rate of 5°C / min. After that, it was cooled to room temperature to obtain a black, fluffy solid.

[0046] (4) After treating the black powder with 8 times the mass of 6M HCl solution at room temperature for 30h, centrifuge it, wash the resulting black solid with 80℃ deionized water, filter it 5 times, and finally dry it in an oven at 130℃ for 6h to obtain samples Co1Ni3CNT and Co3Ni1CNT.

[0047] Detection Example 1:

[0048] Co1Ni3CNT and Co3Ni1CNT black powders were uniformly sprayed onto the prepared carbon paper surface using an ultrasonic sprayer to serve as cathodes, with a sprayed catalyst thickness of 1 mm. Using a platinum sheet as the anode, the active species generated during the cathode activation of PMS were investigated. EPR and the trapping agents DMPO and TEMP were used to capture the signals of the active species.

[0049] The two prepared electrode materials, Co1Ni3CNT and Co3Ni1CNT, were immersed in 0.01M PMS solution, respectively, with the power supply set to 25 mA·cm. -2 A constant current density was applied, and the EPR signal was measured after five minutes of energization. The results are as follows: Figure 1 As shown. From Figure 1 As can be seen, the characteristic peak of DMPOX was detected on the Co1Ni3CNT electrode, indicating that the interaction between Co1Ni3CNT and PMS produces an oxidizing active species that can oxidize DMPO to DMPOX. This active species is surface-bound PMS*. Meanwhile, PMS* was not detected on the Co3Ni1CNT electrode.

[0050] Simultaneously, TEMP- was detected on the Co3Ni1CNT electrode. 1 The O2 triplet signal was observed, while no characteristic peak of singlet oxygen was detected on the Co1Ni3CNT electrode. Therefore, the EPR results demonstrate that the electrochemical activation pathways of PMS differ depending on the atomic ratio of the cobalt-nickel alloy carbon nanotube materials. Furthermore, no free radical generation (HO) was detected in either material during PMS activation. · Or SO4 ·– This indicates that both alloy materials can activate PMS through a non-radical pathway.

[0051] Application Example 1:

[0052] The Co1Ni3CNT and Co3Ni1CNT cathode materials from Example 1 were applied to the electrocatalytic reaction system to evaluate the ability of these cathode materials to degrade sulfadiazine in situ on the surface.

[0053] The electrocatalytic degradation experiment was conducted in a 50 mL cuboid quartz glass cell using a three-electrode system. The working electrodes were the Co1Ni3CNT and Co3Ni1CNT electrodes prepared above, with a working area of ​​10.0 cm². 2 The reference electrode was a saturated calomel electrode, and the counter electrode was a platinum sheet electrode. The three-electrode system was placed in parallel in the reaction apparatus, with an electrode spacing of 2 cm.

[0054] A simulated wastewater solution containing sulfadiazine, phenol, bisphenol A, trichlorophenol, and other pollutants with an initial concentration of 10 ppm was used, and 0.01 M PMS and PDS were added to it. A 0.1 mol L... -1 Adjust the pH of the solution with H2SO4 or NaOH. Finally, set the DC power supply to 25 mA·cm⁻¹. -2 A constant current density was used to initiate the degradation reaction. Samples were taken every 5 minutes, with a degradation time of 30 minutes, a reaction temperature of 25°C, and a pH range of 2-5.

[0055] Immediately after sample removal, the reaction was quenched with a quencher (a mixed solution of 0.1M Na₂SO₃, 0.1M KH₂PO₄, 0.1M KI, and 0.05M KOH), followed by filtration through a 0.22 μm filter membrane for subsequent concentration determination. Results are as follows... Figure 2 As shown in Tables 1 and 2.

[0056] Table 1. Effects of Co1Ni3CNT and Co3Ni1CNT on the electrochemical activation of PMS for the degradation of different pollutants.

[0057]

[0058]

[0059] Table 2. The effect of Co1Ni3CNT and Co3Ni1CNT on the electrochemical activation of PDS in degrading different pollutants.

[0060] <![CDATA[Co3Ni1CNT]]> 95.7％ 90.2％ 89.8％ 85.7％ <![CDATA[Co1Ni3CNT]]> 93.3％ 86.6％ 83.2％ 81.5％

[0061] from Figure 2 As shown in Tables 1 and 2, after 30 minutes of degradation, the degradation rates of sulfadiazine by Co1Ni3CNT and Co3Ni1CNT electrochemically activated PMS were 99.8% and 98.7%, respectively; the degradation rates of phenol were 94.7% and 95.2%, respectively; the degradation rates of bisphenol A were 92.2% and 93.4%, respectively; and the degradation rates of trichlorophenol were 89.4% and 90.5%, respectively. The degradation rates of sulfadiazine by Co1Ni3CNT and Co3Ni1CNT electrochemically activated PDS were 93.3% and 95.7%, respectively; the degradation rates of phenol were 86.6% and 90.2%, respectively; the degradation rates of bisphenol A were 83.2% and 89.8%, respectively; and the degradation rates of trichlorophenol were 81.5% and 85.7%, respectively. These results indicate that the electrochemical method of activating persulfate via a non-radical pathway using alloy carbon cathodes can efficiently degrade electron-rich pollutants in water.

[0062] Test Example 2:

[0063] This test case evaluates the impact of naturally occurring organic matter (NOM) in water on Co1Ni3CNT and Co3Ni1CNT as electrochemical cathode materials during the degradation of electron-rich pollutants.

[0064] The electrocatalytic degradation experiment was conducted in a 50 mL cuboid quartz glass cell using a three-electrode system. The working electrodes were the Co1Ni3CNT and Co3Ni1CNT electrodes prepared above, with a working area of ​​10.0 cm². 2 The reference electrode was a saturated calomel electrode, and the counter electrode was a platinum sheet electrode. The three-electrode system was placed in parallel in the reaction apparatus, with an electrode spacing of 2 cm.

[0065] A sulfadiazine solution with an initial concentration of 10 ppm was used as simulated wastewater, to which 0.01 M PMS and 0-50 ppm of natural organic matter (a mixture of humic acid, fulvic acid, and oligosaccharides) were added. A 0.1 mol L⁻¹ solution was used. -1 Adjust the pH of the solution with H2SO4 or NaOH. Finally, set the DC power supply to 30 mA·cm⁻¹. -2 A constant current density was used to initiate the degradation reaction. Samples were taken every 5 minutes, the degradation time was 30 minutes, the reaction temperature was 20℃, and the pH range was 2-5.

[0066] Immediately after sample removal, the reaction was quenched with a quencher (a mixed solution of 0.1 M Na₂SO₃, 0.1 M KH₂PO₄, 0.1 M KI, and 0.05 M KOH), followed by filtration through a 0.22 μm filter membrane for subsequent concentration determination. Results are as follows... Figure 3 As shown, consistent with expectations, as the NOM concentration gradually increased until it reached 50 ppm, both the Co1Ni3CNT / E (PMS) and Co3Ni1CNT / E (PMS) systems maintained high removal efficiencies for sulfadiazine (98.7% and 97.2%, respectively). This indicates that Co... x Ni y The electrocatalytic system of CNT non-radical activated PMS is not easily affected by NOM in practical water treatment applications and can selectively remove electron-rich pollutants in water.

[0067] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, and for those of ordinary skill in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. Therefore, the present invention is not limited to the specific details without departing from the general concept defined by the claims and their equivalents.

Claims

1. The application of an alloy carbon cathode in the non-radical pathway for the activation of persulfate degradation of pollutants, wherein the alloy carbon cathode is a Co1Ni3CNT and / or Co3Ni1CNT carbon nanotube material, characterized in that, Includes the following steps: A three-electrode system was used, with Co1Ni3CNT and / or Co3Ni1CNT carbon nanotubes as the cathode and a platinum sheet as the anode, so that the pollutants to be degraded could be degraded in a persulfate electrolyte solution. For Co1Ni3CNT, the molar ratio of Co source to Ni source is 1:2; for Co3Ni1CNT, the molar ratio of Co source to Ni source is 2:

1. Different interactions between cobalt-nickel alloys and carbon nanotubes lead to different electron transfers, which in turn activate persulfate. At the same time, different stress interactions between different nanoparticles and CNT substrates are used to regulate the activation of PMS through different non-radical pathways, thereby generating different non-radical active species for the removal of electron-rich organic pollutants in water. The different non-free radicals mentioned are two types: singlet oxygen. 1 O2 and surface-complexed PMS active species PMS*; among which Co3Ni1CNT carbon nanotubes generate singlet oxygen. 1 O2 and Co1Ni3CNT carbon nanotube materials generate active species PMS*; and neither material generates free radicals HO when activating PMS. · Or SO4 ·- ; The pollutants to be degraded include sulfadiazine, phenol, bisphenol A, and trichlorophenol; the water containing the pollutants to be degraded contains natural organic matter, which is a mixture of humic acid, fulvic acid, and oligosaccharides. The concentration of the pollutant to be degraded is 10-500 ppm, and the constant current density of the three-electrode system is 20-50 mA·cm. -2 The pH range of the persulfate electrolyte solution is 2-5, and the degradation temperature is 20-25℃.

2. The application according to claim 1, characterized in that, The preparation method of Co1Ni3CNT and Co3Ni1CNT includes the following steps: S1: Weigh melamine, Co source, and Ni source by molar ratio; S2: After mixing the three materials evenly and grinding them thoroughly, after drying, grind them again and mix them evenly. Put them into a porcelain boat and place them in a tube furnace. Heat them to 300-600℃ in flowing nitrogen for 2-3 hours to obtain a brownish-yellow solid. S3: The brownish-brown solid obtained in step S2 is ground three times and then placed into a porcelain boat. The boat is placed in a tube furnace and calcined in flowing nitrogen. The furnace is then cooled to obtain a black, fluffy solid. S4: The black, bulky solid obtained in step S3 is treated with HCl solution at room temperature, then washed with deionized water and filtered, and finally dried to obtain a black sample, named Co1Ni3CNT or Co3Ni1CNT.

3. The application according to claim 2, characterized in that, In step S1, the Co source is cobalt nitrate hexahydrate; the Ni source is nickel nitrate hexahydrate.

4. The application according to claim 2, characterized in that, In step S1, the molar ratio of melamine to the sum of the Co source and the Ni source is 8:

1.

5. The application according to claim 2, characterized in that, In step S2, the drying is performed in an oven at a temperature of 120-130℃ for 5-7 hours; the nitrogen flow rate is 30-50 mL / min; and the heating rate is 5-10℃ / min.

6. The application according to claim 2, characterized in that, In step S3, the flow rate of nitrogen is 30-50 mL / min; the calcination is carried out by heating to 600-800℃ at a rate of 5-10℃ / min for 3-5 hours.

7. The application according to claim 2, characterized in that, In step S4, the concentration of the HCl solution is 6-7M, and the mass used is 5-10 times that of the black bulky solid; the room temperature treatment time is 24-48h; the temperature of the deionized water washing is 70-100℃; the number of filtrations is 4-6 times; and the drying is carried out in an oven at a temperature of 120-130℃ for 5-7h.

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