Preparation method and application of Fe-Ni-C ternary three-dimensional electrode

Abstract

The application discloses a preparation method of Fe-Ni-C ternary three-dimensional electrode and application thereof, and first, a three-dimensional electro-Fenton technology is used to treat landfill leachate membrane concentrated solution, a Fe-Ni-C ternary electrode is introduced to construct a three-dimensional electro-Fenton system, anode oxidation and in-situ Fenton reaction are utilized to remove refractory organic pollutants in the concentrated solution, then, an electrochemical reduction technology is used to treat three-dimensional electro-Fenton effluent, NO3 ‑ -N based nitrogen pollutants are reduced by cathode reduction, and the landfill leachate membrane concentrated solution is treated by a two-stage combined treatment process of three-dimensional electro-Fenton and electrochemical reduction, so that efficient treatment of organic matters and nitrogen pollutants in the membrane concentrated solution is realized.

Description

Technical Field

[0001] This invention relates to the field of landfill leachate treatment technology, specifically to a method for preparing a Fe-Ni-C ternary three-dimensional electrode and its application. Background Technology

[0002] Landfill leachate is a high-concentration, highly polluting organic wastewater that seeps from landfill layers during the landfill process due to the combined effects of water generated from the biodegradation of the landfill itself, infiltration of external precipitation (rainwater, snowmelt, etc.), and water retention within the landfill itself. "Biological treatment-membrane deep treatment," with reverse osmosis (RO) and nanofiltration (NF) technologies at its core, is currently the mainstream technology in the field of landfill leachate treatment. However, as a physical separation process, membrane treatment causes recalcitrant organic matter to accumulate and enrich on the membrane's retention side, producing a secondary byproduct, landfill leachate membrane concentrate, which is even more difficult to treat. Landfill leachate membrane concentrate has a complex composition, contains high concentrations of recalcitrant organic pollutants, has high color and total nitrogen content, poor biodegradability, and presents significant technical challenges and high treatment costs, making it a current challenge in environmental governance.

[0003] Three-dimensional electro-Fenton technology is a highly efficient advanced oxidation water treatment technology. It improves the removal efficiency of organic pollutants by introducing particle electrodes (such as activated carbon or metal oxide-supported catalysts) into a three-dimensional reaction system within the traditional two-dimensional electro-Fenton system. When treating membrane concentrate, the three-dimensional electro-Fenton system directly degrades organic pollutants in the concentrate through oxidation at the anode surface; simultaneously, oxygen supplied by the cathode and the polarized three-dimensional electrode, combined with an aeration device, reacts with H+ in the water. + H2O2 is generated, while the Fe sites carried by the three-dimensional electrodes used in existing technologies can release Fe in situ. 2+ The three-dimensional electro-Fenton technology catalyzes the Fenton reaction of H₂O₂ to generate free radicals, primarily ·OH, that degrade organic matter. While the three-dimensional electro-Fenton technology exhibits high efficiency in degrading organic matter, existing technologies are less effective against nitrate nitrogen (NO₃⁻). - The removal effect of iron ions (-N) is limited, and the three-dimensional electrode has problems such as excessive iron ion leaching and low effective utilization rate. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a method for preparing a Fe-Ni-C ternary three-dimensional electrode and its application, so as to achieve effective treatment of organic matter and nitrogen pollutants in membrane concentrate, thereby solving the problems of limited removal effect of three-dimensional electro-Fenton technology on nitrogen pollutants, excessive iron ion leaching, and low effective utilization rate of the three-dimensional electrode used in the prior art.

[0005] Firstly, in order to solve the above-mentioned technical problems, the present invention provides a method for preparing a Fe-Ni-C ternary three-dimensional electrode, the specific steps of which are as follows:

[0006] Step 1: Mix biochar, conductive carbon black, and polytetrafluoroethylene evenly to obtain an electrode slurry;

[0007] Step 2: Immerse the Fe-Ni foam in the electrode slurry prepared in step 1, so that the electrode slurry uniformly covers the Fe-Ni foam, and then dry it;

[0008] Step 3: Place the product processed in Step 2 in an inert atmosphere and calcine it at 600℃-800℃ for 1h-3h. After cooling, the Fe-Ni-C ternary three-dimensional electrode is obtained.

[0009] Preferably, the biochar is prepared by calcining bamboo.

[0010] Preferably, the mass ratio of polytetrafluoroethylene: conductive carbon black: biochar is (8-10):(0.5-1):1.

[0011] Preferably, the average pore size of the Fe-Ni foam is 0.7 mm to 1 mm.

[0012] Secondly, the present invention provides an application of a Fe-Ni-C ternary three-dimensional electrode. The Fe-Ni-C ternary three-dimensional electrode prepared by the above preparation method is used to treat landfill leachate concentrate to remove organic matter from the concentrate.

[0013] Preferably, the Fe-Ni-C ternary three-dimensional electrode is installed in a device for combined three-dimensional electro-Fenton-electrochemical reduction treatment of landfill leachate membrane concentrate; wherein, the device includes an electrolytic cell, which is divided into a three-dimensional electro-Fenton reaction zone and an electrochemical reduction reaction zone by a middle partition; the three-dimensional electro-Fenton reaction zone and the electrochemical reduction reaction zone are fluidly connected by a water pump;

[0014] A first cathode electrode and a first anode electrode are provided in the three-dimensional electro-Fenton reaction zone. The first anode electrode is connected to the anode of the first DC power supply, and the first cathode electrode is connected to the cathode of the first DC power supply. The Fe-Ni-C ternary three-dimensional electrode is placed in the three-dimensional electro-Fenton reaction zone without contacting the first cathode electrode or the first anode electrode. The first anode electrode is a titanium-iridium-ruthenium coated electrode plate, and the first cathode electrode is one of nickel foam or activated carbon fiber felt.

[0015] A second cathode electrode and a second anode electrode are provided in the electrochemical reduction reaction zone. The second anode electrode is connected to the anode of the second DC power supply, and the second cathode electrode is connected to the cathode of the second DC power supply. The second anode electrode is a titanium-iridium-ruthenium coated electrode plate, and the second cathode electrode is copper foam.

[0016] Preferably, a water pump pumps the supernatant in the three-dimensional electro-Fenton reaction zone to the electrochemical reduction reaction zone; a porous baffle is also provided in the three-dimensional electro-Fenton reaction zone, the porous baffle being located below the first cathode electrode and the first anode electrode; an aeration device is also provided in the three-dimensional electro-Fenton reaction zone, the aeration device being located above the porous baffle and close to the cathode electrode; a sludge discharge hole is provided below the porous baffle, and a water outlet is provided at the bottom of the electrochemical reduction reaction zone.

[0017] Thirdly, the present invention also provides a method for treating landfill leachate concentrate, which uses the apparatus described above and processes the landfill leachate concentrate through the following steps:

[0018] S1: The membrane concentrate is delivered to the three-dimensional electro-Fenton reaction zone of the device. The pH of the membrane concentrate is adjusted to 3-4. The first DC power supply and aeration device are turned on. The plate spacing between the first cathode electrode and the first anode electrode is controlled to be 2 cm, and the electrolysis current density is 20-25 mA / cm². 2 The dosage of the Fe-Ni-C ternary three-dimensional electrode is 10–15 g / L, and the aeration intensity is 0.05 m. 3 / m 3 Electrolysis is carried out for 3-5 hours, during which organic pollutants are effectively degraded through anodic oxidation and Fenton reaction in the three-dimensional electro-Fenton reaction zone.

[0019] S2: After the electrolysis reaction in S1 is completed, turn off the first DC power supply and the aeration device, adjust the pH value of the water in the three-dimensional electro-Fenton reaction zone to 9-10, produce iron sludge, let it stand for at least 30 minutes to settle, and then separate the sludge and water.

[0020] S3: The supernatant after S2 treatment is pumped to the electrochemical reduction reaction zone. The pH of the supernatant is adjusted to 6.5-7.5. The second DC power supply is turned on to carry out the electrolysis reaction. The distance between the second cathode electrode and the second anode electrode is controlled at 2 cm, and the current density is 20-25 mA / cm². 2 In the electrochemical reduction reaction zone, the supernatant is denitrified. Electrolysis is completed after 3-5 hours, and the treated water is discharged through the outlet.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention unexpectedly yielded a highly efficient and stable three-dimensional electrode. The composite structure of the Fe-Ni alloy and the carbon matrix forms a three-dimensional conductive network, which significantly enhances the catalytic activity of the three-dimensional electrode. Utilizing the synergistic effect between Fe and Ni, Fe promotes electron transfer and releases Fe in situ. 2+Ni can increase the generation of H2O2, thereby accelerating the generation of hydroxyl radicals in the electro-Fenton reaction, enabling it to degrade organic matter more efficiently; at the same time, the biochar coating reduces the leaching of Fe / Ni ions through physical isolation, extending the life of the three-dimensional electrode.

[0023] 2. This invention discovers that the three-dimensional porous structure (pore size 0.7mm-1mm) of Fe-Ni foam provides a large specific surface area, promoting contact between reactants and active sites; the porous nature of biochar further enhances adsorption capacity, synergistically achieving the enrichment and degradation of pollutants through electrochemical reactions; moreover, the calcination process promotes the formation of a stable interface between carbon and Fe-Ni, embedding ultra-dispersed Fe-Ni nanoparticles to form a micro-electrolysis cell group under electric field polarization, extending the reaction area from the electrode surface to the entire three-dimensional space; on the other hand, the carbon layer acts as an electron transport network, promoting the in-situ generation of H2O2 at the cathode, and reacting with Fe... 2+ The Fenton reaction is continuously triggered, and no additional Fenton reagent is required during this process.

[0024] 3. This invention also combines three-dimensional electro-Fenton and electrochemical reduction design, and achieves the simultaneous removal of organic matter and nitrogen pollutants through stepwise treatment of degrading organic matter under acidic conditions, separating iron sludge through alkaline precipitation, and reducing nitrate under neutral conditions. At the same time, the iron sludge can be recycled to avoid secondary pollution. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the device for treating landfill leachate membrane concentrate using a three-dimensional electro-Fenton-electrochemical reduction combination method as described in this invention.

[0026] Figure 2 The images show the three-dimensional fluorescence spectra of the landfill leachate membrane concentrate before and after treatment according to the present invention; wherein, a is the original membrane concentrate, b is the effluent from the three-dimensional electro-Fenton reaction zone, and c is the effluent from the electrochemical reduction reaction zone.

[0027] Figure 3 The images show the GC-MS total ion current chromatograms of the landfill leachate membrane concentrate before and after treatment according to the present invention; where a is the original membrane concentrate, b is the effluent from the three-dimensional electro-Fenton reaction zone, and c is the effluent from the electrochemical reduction reaction zone.

[0028] In the diagram: 1. Three-dimensional electro-Fenton reaction zone, 101. First DC power supply, 102. First anode electrode, 103. First cathode electrode, 104. Fe-Ni-C ternary three-dimensional electrode, 105. Porous partition, 106. Aeration pump, 107. Rotor flow meter, 108. Aeration disc, 109. Sludge discharge hole, 2. Electrochemical reduction reaction zone 2, 201. Second DC power supply, 202. Second anode electrode, 203. Second cathode electrode, 204. Water pump, 205. Detailed Implementation

[0029] This invention will describe the technical solutions of the embodiments of the invention clearly and completely. Obviously, the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on this invention are within the scope of protection of this invention.

[0030] Unless otherwise specified in the specific circumstances, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within that range, but are not limited to the specific values ​​listed when the range is defined.

[0031] I. A method for preparing a Fe-Ni-C ternary three-dimensional electrode

[0032] Step 1: Mix biochar, conductive carbon black, and polytetrafluoroethylene evenly to obtain an electrode slurry;

[0033] Step 2: Immerse the Fe-Ni foam in the electrode slurry prepared in step 1, so that the electrode slurry uniformly covers the Fe-Ni foam, and then dry it;

[0034] Step 3: Place the product processed in Step 2 in an inert atmosphere and calcine it at 600℃-800℃ for 1h-3h. After cooling, the Fe-Ni-C ternary three-dimensional electrode is obtained.

[0035] This invention identifies bottlenecks in traditional landfill leachate treatment. Traditional electro-Fenton electrodes exhibit high iron dissolution rates, leading to the loss of active components and secondary pollution (iron sludge). Furthermore, the leachate membrane concentrate has a complex composition (high COD, high salt, and nitrogenous pollutants), making it difficult for a single process to simultaneously remove organic matter and nitrate nitrogen. Additionally, it is challenging to balance the conductivity, catalytic activity, and structural stability of a three-dimensional electrode. Based on these findings, this invention conceives and prepares a novel three-dimensional electrode. For this purpose, a Fe-Ni foam substrate is selected, utilizing bimetallic synergistic catalysis. The electrode is coated with a composite slurry of bamboo biochar and conductive carbon black, optimizing the raw material dosage to balance bonding strength and conductivity. High-temperature calcination graphitizes the biochar, enhancing conductivity and simultaneously forming a carbon layer encapsulating the metal particles to inhibit iron dissolution. Finally, a combination of electro-Fenton (acidic degradation of organic matter) and electrochemical reduction (neutral denitrification) is used, with phased control to avoid reaction interference, achieving the treatment of complex membrane concentrates.

[0036] Therefore, this invention discovers that the prepared Fe-Ni-C ternary three-dimensional electrode exhibits excellent electrochemical performance, enhancing mass transfer and reaction efficiency. The foamed Fe-Ni substrate provides a large specific surface area and hierarchical porous structure, significantly improving the mass transfer rate of reactants. Bamboo biochar and conductive carbon black are calcined in a high-temperature inert atmosphere to form a carbon coating layer. On one hand, the Fe-Ni-C ternary three-dimensional electrode, under electric field polarization, constitutes a micro-electrolysis cell group, extending the reaction area from the electrode surface to the entire three-dimensional space. On the other hand, the carbon layer acts as an electron transport network, promoting the in-situ generation of H2O2 (O2 + 2H+) at the cathode. + +2e - →H2O2), and react with Fe 2+ The continuous triggering of the Fenton reaction (·OH radical mineralization of organic matter) provides a sufficient supply of H2O2, eliminating the need for any Fenton reagent during membrane concentrate treatment. The Fenton reaction continues normally and continuously. Biochar also plays a synergistic catalytic role. After high-temperature pyrolysis, the specific surface area of ​​bamboo-derived biochar significantly increases. Its microporous structure enriches pollutants through molecular sieve effects, while mesopores / macropores accelerate ion diffusion. Simultaneously, oxygen-containing functional groups (such as carboxyl and carbonyl groups) on the biochar surface induce pseudocapacitive behavior, enhancing the charge transfer capacity at the electrode interface. Ultimately, strong oxidation effectively disrupts the chemical structure of the large molecular weight organic matter in the recalcitrant membrane concentrate, breaking it down into smaller molecular weight organic compounds. This overall reduction in the molecular weight of organic matter is more conducive to subsequent electrochemical reduction treatment, making it easier to degrade pollutants in the water and achieving the harmless treatment of the membrane concentrate.

[0037] In some embodiments of the present invention, the biochar is prepared by calcining bamboo as raw material and then carbonizing it.

[0038] In some embodiments of the present invention, the mass ratio of polytetrafluoroethylene (PTFE): conductive carbon black: biochar is (8-10):(0.5-1):1. PTFE acts as a binder; a ratio that is too low (below the stated range) will result in insufficient bonding strength, causing the carbon material to easily detach from the Fe-Ni foam. A ratio that is too high (exceeding the stated range) will reduce porosity, clog the pores of the Fe-Ni foam, significantly reduce the effective specific surface area of ​​the electrode, and hinder the contact between contaminants and active sites. Conductive carbon black is used to connect the biochar particles and the Fe-Ni foam, reducing contact resistance and overall electrode resistance. A ratio that is too low (below the stated range) will increase the internal resistance of the electrode, while a ratio that is too high (exceeding the stated range) will encroach on the space of the biochar, weakening the overall reactivity of the electrode.

[0039] In some embodiments of the present invention, the average pore size of the Fe-Ni foam is 0.7 mm to 1 mm. If the pore size of the Fe-Ni foam is too small, it is easily blocked by the electrode slurry, significantly reducing the effective specific surface area of ​​the electrode. If the pore size is too large, it will reduce the mechanical strength and structural stability of the prepared Fe-Ni-C electrode material.

[0040] II. Application of a Fe-Ni-C ternary three-dimensional electrode

[0041] In this invention, the Fe-Ni-C ternary three-dimensional electrode prepared by the above preparation method is used to treat landfill leachate concentrate to remove organic matter from the concentrate.

[0042] Specifically, the Fe-Ni-C ternary three-dimensional electrode is installed in a device for the combined three-dimensional electro-Fenton and electrochemical reduction treatment of landfill leachate membrane concentrate. This device includes an electrolytic cell, which is divided by a central partition into two independent regions: a three-dimensional electro-Fenton reaction zone 1 and an electrochemical reduction reaction zone 2. The three-dimensional electro-Fenton reaction zone 1 and the electrochemical reduction reaction zone 2 are fluidly connected via a water pump 204. The water pump draws the supernatant from the three-dimensional electro-Fenton reaction zone to the electrochemical reduction reaction zone for further processing.

[0043] A first cathode electrode 103 and a first anode electrode 102 are provided in the three-dimensional electro-Fenton reaction zone 1. The first anode electrode 102 is connected to the anode of the first DC power supply 101, and the first cathode electrode 103 is connected to the cathode of the first DC power supply 101. The Fe-Ni-C ternary three-dimensional electrode 104 is placed in the three-dimensional electro-Fenton reaction zone, ensuring that it does not contact the first cathode electrode 103 or the first anode electrode 102. The first anode electrode 102 is a titanium-iridium-ruthenium coated electrode plate, and the first cathode electrode 103 is one of nickel foam or activated carbon fiber felt.

[0044] A second cathode electrode 203 and a second anode electrode 202 are provided in the electrochemical reduction reaction zone 2. The second anode electrode 202 is connected to the anode of the second DC power supply 201, and the second cathode electrode 203 is connected to the cathode of the second DC power supply 201. The second anode electrode 202 is a titanium-iridium-ruthenium coated electrode plate, and the second cathode electrode 203 is copper foam.

[0045] Preferably, a water pump pumps the supernatant in the three-dimensional electro-Fenton reaction zone to the electrochemical reduction reaction zone. A porous partition 105 is also provided within the three-dimensional electro-Fenton reaction zone 1. The porous partition 105 is located below the first cathode electrode 103 and the first anode electrode 102, and its periphery is fixedly connected to the inner wall of the three-dimensional electro-Fenton reaction zone. The porous partition acts as a physical barrier, separating the sedimentation zone from the electrolysis reaction zone, allowing the iron sludge to settle at the bottom without touching the electrode plates. An aeration device is also provided within the three-dimensional electro-Fenton reaction zone. This aeration device is located above the porous partition and close to the first cathode electrode 103. The aeration device includes an aeration pump 106, a rotor flow meter 107, and an aeration disc 108. The aeration disc 108 is laid above the porous partition 105 and close to the first cathode electrode 102. The aeration device continuously provides sufficient oxygen to the first cathode electrode. A sludge discharge hole 109 is provided below the porous baffle 105, through which the iron sludge generated during the treatment process can be discharged, facilitating the recycling of the iron sludge. A water outlet 205 is provided at the bottom of the electrochemical reduction reaction zone 2, through which the treated water flows out of the electrochemical reduction reaction zone 2.

[0046] III. A method for treating landfill leachate concentrate

[0047] This invention uses the apparatus described above to treat landfill leachate concentrate through the following steps:

[0048] S1: The membrane concentrate is delivered to the three-dimensional electro-Fenton reaction zone of the device. The pH of the membrane concentrate is adjusted to 3-4. The first DC power supply and aeration device are turned on. The plate spacing between the first cathode electrode and the first anode electrode is controlled to be 2 cm, and the electrolysis current density is 20-25 mA / cm². 2 The dosage of the Fe-Ni-C ternary three-dimensional electrode is 10–15 g / L, and the aeration intensity is 0.05 m. 3 / m 3 Electrolysis is carried out for 3-5 hours, during which organic pollutants are effectively degraded through anodic oxidation and Fenton reaction in the three-dimensional electro-Fenton reaction zone.

[0049] S2: After the electrolysis reaction in S1 is completed, turn off the first DC power supply and the aeration device, adjust the pH value of the water in the three-dimensional electro-Fenton reaction zone to 9-10, produce iron sludge, let it stand for at least 30 minutes to settle, and then separate the sludge and water.

[0050] S3: The supernatant after S2 treatment is pumped to the electrochemical reduction reaction zone. The pH of the supernatant is adjusted to 6.5-7.5. The second DC power supply is turned on to carry out the electrolysis reaction. The distance between the second cathode electrode and the second anode electrode is controlled at 2 cm, and the current density is 20-25 mA / cm². 2In the electrochemical reduction reaction zone, the supernatant is denitrified. Electrolysis is completed after 3-5 hours, and the treated water is discharged through the outlet.

[0051] This invention combines the prepared Fe-Ni-C ternary three-dimensional electrode with a processing device. After treating the membrane concentrate, it was unexpectedly discovered that the carbon coating layer protects the Fe-Ni active sites, enabling the ternary three-dimensional electrode to maintain high catalytic activity in a relatively wide pH environment (acidic pH 3-4). Simultaneously, after the Fenton reaction, alkali adjustment treatment allows for the separation and recovery of the generated iron sludge, reducing solid waste treatment costs. The pyrolytic carbon layer significantly inhibits Fe ion leaching, thereby extending the service life of the ternary three-dimensional electrode and giving it long-lasting performance. Furthermore, no additional Fenton reagent is required during the treatment process because the core of the electro-Fenton reaction is the reduction of dissolved oxygen (O2) at the cathode to generate H2O2 (O2 + 2H+). + +2e - →H2O2), this process requires a continuous supply of H2O2 reagent and Fe. 2+ Ferrous salts (commonly ferrous sulfate). In this invention, the three-dimensional electro-Fenton reaction zone employs a Fe-Ni-C ternary three-dimensional electrode. The large pore size (0.7mm-1mm) and carbon coating layer (biochar + conductive carbon black) of the Fe-Ni foam significantly increase the specific surface area and active sites, enhancing O2 adsorption and electron transfer efficiency, enabling efficient and continuous in-situ synthesis of H2O2. Furthermore, the aeration device is placed near the cathode motor, providing a continuous O2 source and maintaining the H2O2 generation rate. Simultaneously, in this invention, Fe... 2+ Exhibiting a stable self-circulation and slow-release mechanism, the Fe-Ni-C ternary three-dimensional electrode exhibits heterogeneous catalysis. The carbon coating layer formed by high-temperature calcination (600-800℃) embeds Fe-Ni nanoparticles, and under electric field polarization, the surface Fe... 0 / Fe 2+ The active sites directly catalyze the decomposition of H2O2 into ·OH(Fe) 2+ +H₂O₂→Fe 3+ +·OH+OH - The first cathode electrode simultaneously reduces and regenerates Fe. 2+ (Fe 3+ +e - →Fe 2+This forms a closed-loop iron cycle; the carbon coating layer acts as a physical barrier to control Fe ion leaching and prevent catalyst loss. Ultimately, through the design of the ternary three-dimensional electrode in this invention, the oxygen-containing functional groups (carboxyl and carbonyl groups) in the carbon layer enhance interfacial charge transfer, enabling it to maintain high activity within a pH range of 3-4. Furthermore, it can recover iron sludge by adjusting the pH to 9-10 after the Fenton reaction to precipitate Fe(OH)3, while maintaining structural stability in an alkaline environment due to carbon protection. Simultaneously, this invention combines back-end electrochemical reduction technology. The front-end three-dimensional electro-Fenton system utilizes anodic oxidation and in-situ Fenton reaction to remove recalcitrant organic pollutants from the concentrate, while the back-end electrochemical reduction technology utilizes cathodic reduction to remove NO3. - Nitrogen pollutants, mainly nitrogen-containing pollutants, are treated using a two-stage combined treatment process of three-dimensional electro-Fenton combined with electrochemical reduction to treat landfill leachate membrane concentrate, ultimately achieving efficient treatment of organic matter and nitrogen pollutants in the membrane concentrate.

[0052] IV. Examples and Comparative Examples

[0053] 1. Preparation of Fe-Ni-C ternary three-dimensional electrode

[0054] Example 1

[0055] Step 1: The biochar is sorted, dried, pulverized, and passed through a 100-mesh sieve to obtain biochar powder for later use. Then, the biochar is mixed evenly with conductive carbon black and polytetrafluoroethylene (PTFE) to obtain an electrode slurry. The mass ratio of biochar to conductive carbon black to PTFE is 10:1:1.

[0056] Step 2: Immerse the Fe-Ni foam in the electrode slurry prepared in step 1, so that the electrode slurry evenly covers the Fe-Ni foam, and then put it in an electric oven to dry at 105°C for 1 hour.

[0057] Step 3: Place the product treated in Step 2 in an inert atmosphere N2, heat it to 600℃ at a heating rate of 5℃ / min, calcine for 2h, and then cool to obtain the Fe-Ni-C ternary three-dimensional electrode.

[0058] Step 4: Taking the leachate membrane concentrate from a landfill as the treatment target, the water quality properties of the membrane concentrate are: pH = 7.4-8.3, COD = 721.71 mg / L. The membrane concentrate is pumped from the collection tank into the three-dimensional electro-Fenton reaction zone (1). Acid is added to adjust the pH of the membrane concentrate to 4. The DC power supply and aeration device are turned on, the distance between the anode and cathode plates is controlled to be 2 cm, and the electrolysis current density is controlled to be 20 mA / cm². 2 The Fe-Ni-C three-dimensional electrode dosage was 10 g / L, and the aeration intensity was 0.05 m. 3 / m 3Electrolysis was carried out for 5 hours. After electrolysis, the power supply and aeration device were turned off. Alkali was added to adjust the water quality to 10 to produce iron sludge. The mixture was allowed to stand for 30 minutes to settle. Then, the sludge and water were separated. After treatment, the COD of the supernatant was reduced to 120.85 mg / L.

[0059] Example 2

[0060] An improvement upon Example 1 was made, except that the mass ratio of biochar to conductive carbon black and polytetrafluoroethylene was 8:1:1. All other steps were identical to Example 1. The COD of the treated landfill leachate membrane concentrate decreased to 151.24 mg / L.

[0061] Example 3

[0062] An improvement upon Example 1 was made, except that the mass ratio of biochar to conductive carbon black and polytetrafluoroethylene was 10:0.5:1. All other steps were identical to Example 1. The COD of the treated landfill leachate membrane concentrate decreased to 144.71 mg / L.

[0063] Example 4

[0064] An improvement upon Example 1 was made, except that the calcination temperature was 700°C. All other steps were identical to Example 1. The COD of the treated landfill leachate membrane concentrate decreased to 167.29 mg / L.

[0065] Example 5

[0066] An improvement upon Example 1 was made, except that the calcination temperature was 800°C. All other steps were identical to Example 1. The COD of the treated landfill leachate membrane concentrate decreased to 173.80 mg / L.

[0067] 2. Leachate concentrate from a landfill

[0068] The leachate concentrate from a landfill was used as the treatment target. The water quality properties of the concentrate were: pH = 7.4–8.3, COD = 721.71 mg / L, TN = 239.76 mg / L, NH4+ + -N = 6.64 mg / L, NO3 - -N = 186.05 mg / L.

[0069] Example 6

[0070] Taking Example 1 as an example, wastewater is first pumped from the collection tank into the three-dimensional electro-Fenton reaction zone (1). Acid is added to adjust the pH of the membrane concentrate to 4. The DC power supply and aeration device are turned on, the distance between the anode and cathode plates is controlled to 2 cm, and the electrolysis current density is controlled to 24.93 mA / cm². 2The Fe-Ni-C three-dimensional electrode dosage was 13.20 g / L, and the aeration intensity was 0.05 m³ / L. 3 / m 3 Electrolysis was carried out for 3 hours. After electrolysis, the power supply and aeration device were turned off. Alkali was added to adjust the water quality to 10, producing iron sludge. The mixture was allowed to stand for 30 minutes to settle, followed by sludge-water separation. After treatment, the COD of the supernatant decreased to 154.5 mg / L, TN decreased to 201.79 mg / L, and NH4+ decreased. + -N decreased to 0.2 mg / L, NO3 - -N decreased to 166.54 mg / L.

[0071] The supernatant after mud-water separation was then pumped into the electrochemical reduction reaction zone (2). The pH of the water was adjusted to 7, and the DC power supply was turned on to carry out the electrolysis reaction. The distance between the anode and cathode plates was controlled to be 2 cm, and the current density was 22.10 mA / cm². 2 After electrolysis for 3 hours, the power was turned off, and the water was then discharged through the outlet. The effluent COD decreased to 91.02 mg / L, TN decreased to 27.42 mg / L, and NH4... + -N is 0.4 mg / L, NO3 - -N decreased to 22.49 mg / L, and the effluent COD and NH4... + Both -N and TN meet the emission limits in Table 2 of the "Standard for Pollution Control of Municipal Solid Waste Landfills" (GB 16889-2024).

[0072] Example 7

[0073] The method was adjusted based on Example 6, with the following differences: the electrolysis time in the three-dimensional electro-Fenton reaction zone was set to 5 hours, and the electrolysis time in the electrochemical reduction reaction zone was also set to 5 hours. All other steps were identical to Example 6. Specifically, after treatment in the three-dimensional electro-Fenton reaction zone, the COD of the supernatant decreased to 105.67 mg / L, TN decreased to 161.89 mg / L, and NH4+ decreased... + -N decreased to 0.92 mg / L, NO3 - -N decreased to 159.17 mg / L. After further treatment in the electrochemical reduction reaction zone, the final effluent COD decreased to 37.98 mg / L, TN decreased to 22.44 mg / L, and NH4+ decreased... + -N is 0.32 mg / L, NO3 - -N decreased to 6.51 mg / L, and the effluent COD and NH4... + Both -N and TN meet the emission limits in Table 2 of the "Standard for Pollution Control of Municipal Solid Waste Landfills" (GB 16889-2024).

[0074] Comparative Example 1

[0075] The leachate concentrate from a landfill was used as the treatment target. The water quality of the concentrate was: pH = 7.4-8.3, COD = 721.71 mg / L. Using foamed Fe-Ni as a three-dimensional electrode, the concentrate was pumped from the collection tank into the three-dimensional electro-Fenton reaction zone (1). Acid was added to adjust the pH of the concentrate to 4. The DC power supply and aeration device were turned on, the distance between the anode and cathode plates was controlled to 2 cm, and the electrolysis current density was controlled to 20 mA / cm². 2 The dosage of the Fe-Ni three-dimensional electrode foam was 10 g / L, and the aeration intensity was 0.05 m. 3 / m 3 Electrolysis was carried out for 5 hours. After electrolysis, the power supply and aeration device were turned off. Alkali was added to adjust the water quality to 10 to produce iron sludge. The mixture was allowed to stand for 30 minutes to settle. Then, the sludge and water were separated. After treatment, the COD of the supernatant was reduced to 239.46 mg / L.

[0076] Comparative Example 2

[0077] An improvement was made to Comparative Example 1, the difference being the use of foamed Fe as a three-dimensional electrode. All other steps were identical to Comparative Example 1. The COD of the treated landfill leachate membrane concentrate decreased to 257.09 mg / L.

[0078] Comparative Example 3

[0079] An improvement upon Comparative Example 1 was made, the difference being the use of biochar as the three-dimensional electrode. All other steps were identical to Comparative Example 1. The COD of the treated landfill leachate membrane concentrate decreased to 349.63 mg / L.

[0080] Further analysis was conducted on Example 6. Figure 2 The images show the three-dimensional fluorescence spectra of the membrane concentrate (a), the three-dimensional electro-Fenton effluent (b), and the electrochemically reduced effluent (c). Three-dimensional fluorescence spectroscopy analysis technology, through the combination of excitation and emission wavelengths, can identify the characteristic fluorescence signals of different organic compounds in water, thereby achieving refined analysis of the types and concentrations of organic pollutants. Based on the similarity of pollutant types, similar organic pollutants can be divided into five two-dimensional fluorescence regions (I, II, III, IV, V) according to specific fluorescence peaks. Region I represents protein-like organic compounds such as tyrosine, Region II represents protein-like organic compounds such as tryptophan, Region III represents fulvic acid-like organic compounds, Region IV represents soluble microbial metabolic byproducts, and Region V represents humic acid-like organic compounds. Figure 2 It can be seen that the organic matter in the initial membrane concentrate is mainly humic acid and fulvic acid. After the membrane concentrate is treated by the three-dimensional electro-Fenton system, the content of humic substances is greatly reduced. After the electrochemical reduction system, the content of organic matter is further reduced, indicating that the combined process can effectively remove the recalcitrant organic matter in the membrane concentrate.

[0081] Figure 3 The images show the GC-MS total ion chromatograms of the membrane concentrate (a), the three-dimensional electro-Fenton effluent (b), and the electrochemically reduced effluent (c). Figure 3 As can be seen, the organic composition of the initial membrane concentrate is very complex. After three-dimensional electro-Fenton electrolysis, the overall abundance of organic matter in the water sample decreased, and the peak heights of the characteristic substances were significantly reduced. This indicates that the three-dimensional electro-Fenton technology effectively destroyed the chemical structure of recalcitrant macromolecular organic matter through strong oxidation, decomposing it into smaller molecular weight organic matter, thereby achieving an overall reduction in the molecular weight of organic matter. After electrochemical reduction treatment, the peak areas of various organic substances were further reduced, and most organic pollutants were effectively degraded. This demonstrates that the three-dimensional electro-Fenton combined electrochemical reduction process can effectively remove pollutants from the membrane concentrate, achieving the harmless treatment of the membrane concentrate.

[0082] The Fe ions leached from the concentrated solutions after treatment in Example 1 and Comparative Example 1 were measured. The Fe ions in the foam Fe-Ni reaction system after the reaction were determined. 2+ Fe 3+ The total Fe ion concentrations were 48.87 mg / L, 29.83 mg / L, and 78.70 mg / L, respectively. The Fe in the Fe-Ni-C reaction system... 2+ Fe 3+ The total Fe ion concentrations were 14.55 mg / L, 25.74 mg / L, and 40.29 mg / L, respectively. The Fe leaching from the foam Fe-Ni mixture... 2+ Fe 3+ The total Fe ion concentrations were 3.36 times, 1.16 times, and 1.95 times that of Fe-Ni-C leaching at 600℃, respectively, demonstrating that Fe-Ni-C can generate Fe in situ at 600℃. 2+ At the same time, it can alleviate the leaching of Fe ions, avoid excessive waste of Fe ions, and reduce the generation of iron sludge.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a Fe-Ni-C ternary three-dimensional electrode, characterized in that, The specific steps are as follows: Step 1: Mix biochar, conductive carbon black, and polytetrafluoroethylene evenly to obtain an electrode slurry; Step 2: Immerse the Fe-Ni foam in the electrode slurry prepared in step 1, so that the electrode slurry uniformly covers the Fe-Ni foam, and then dry it; Step 3: Place the product treated in Step 2 in an inert atmosphere and calcine it at 600 ℃-800 ℃ for 1 h-3 h. After cooling, the Fe-Ni-C ternary three-dimensional electrode is obtained.

2. The preparation method according to claim 1, characterized in that, The biochar is prepared by calcining bamboo.

3. The preparation method according to claim 1, wherein the mass ratio of polytetrafluoroethylene: conductive carbon black: biochar is (8-10):(0.5-1):

1.

4. The preparation method according to claim 1, characterized in that, The average pore size of the Fe-Ni foam is 0.7 mm-1 mm.

5. An application of a Fe-Ni-C ternary three-dimensional electrode, characterized in that, The Fe-Ni-C ternary three-dimensional electrode prepared by the preparation method according to any one of claims 1-4 is used to treat landfill leachate concentrate to remove organic matter from the concentrate.

6. The application according to claim 5, characterized in that, The Fe-Ni-C ternary three-dimensional electrode is installed in a device for the combined treatment of landfill leachate membrane concentrate by three-dimensional electro-Fenton-electrochemical reduction; wherein, the device includes an electrolytic cell, which is divided into a three-dimensional electro-Fenton reaction zone (1) and an electrochemical reduction reaction zone (2) by a middle partition; the three-dimensional electro-Fenton reaction zone and the electrochemical reduction reaction zone are fluidly connected by a water pump (204); A first cathode electrode (103) and a first anode electrode (102) are provided in the three-dimensional electro-Fenton reaction zone. The first anode electrode (102) is connected to the anode of the first DC power supply (101), and the first cathode electrode (103) is connected to the cathode of the first DC power supply (101). A Fe-Ni-C ternary three-dimensional electrode (104) is placed in the three-dimensional electro-Fenton reaction zone without contacting the first cathode electrode (103) and the first anode electrode (102). The first anode electrode is a titanium-iridium-ruthenium coated electrode plate, and the first cathode electrode is one of nickel foam or activated carbon fiber felt. A second cathode electrode (203) and a second anode electrode (202) are provided in the electrochemical reduction reaction zone. The second anode electrode (202) is connected to the anode of the second DC power supply (201), and the second cathode electrode (203) is connected to the cathode of the second DC power supply (201). The second anode electrode is a titanium-iridium-ruthenium coated electrode plate, and the second cathode electrode is copper foam.

7. The application according to claim 6, characterized in that, A water pump pumps the supernatant in the three-dimensional electro-Fenton reaction zone to the electrochemical reduction reaction zone; a porous partition (105) is also provided in the three-dimensional electro-Fenton reaction zone, which is located below the first cathode electrode (103) and the first anode electrode (102); an aeration device is also provided in the three-dimensional electro-Fenton reaction zone, which is located above the porous partition and close to the first cathode electrode; a sludge discharge hole (109) is provided below the porous partition, and a water outlet (205) is provided at the bottom of the electrochemical reduction reaction zone.

8. A method for treating landfill leachate concentrate, characterized in that, Using the apparatus described in any one of claims 6-7, landfill leachate concentrate is treated through the following steps: S1: The membrane concentrate is delivered to the three-dimensional electro-Fenton reaction zone of the device. The pH of the membrane concentrate is adjusted to 3-4. The first DC power supply and aeration device are turned on. The plate spacing between the first cathode electrode and the first anode electrode is controlled to be 2 cm, and the electrolysis current density is 20-25 mA / cm². 2 The Fe-Ni-C ternary three-dimensional electrode is added at a dosage of 10~15 g / L, and the aeration intensity is 0.05 m³ / m³·h. Electrolysis reaction is carried out for 3-5 hours. Organic pollutants are effectively degraded through anodic oxidation and Fenton reaction in the three-dimensional electro-Fenton reaction zone. S2: After the electrolysis reaction in S1 is completed, turn off the first DC power supply and the aeration device, adjust the pH value of the water in the three-dimensional electro-Fenton reaction zone to 9-10, produce iron sludge, let it stand for at least 30 minutes to settle, and then separate the sludge and water. S3: The supernatant after S2 treatment is pumped to the electrochemical reduction reaction zone. The pH of the supernatant is adjusted to 6.5-7.5, and the second DC power supply is turned on to carry out the electrolysis reaction. The distance between the second cathode electrode and the second anode electrode is controlled at 2 cm, and the current density is 20-25 mA / cm². 2 In the electrochemical reduction reaction zone, the supernatant is denitrified. Electrolysis is completed after 3-5 hours, and the treated water is discharged through the outlet.

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