Wastewater treatment process and system based on combination of electro-catalysis and electro-deionization

Abstract

The application discloses a wastewater treatment process and system based on combination of electro-catalysis and electro-deionization, and the process comprises the following steps: S1, inputting first wastewater into a cathode treatment chamber and inputting second wastewater into an anode treatment chamber; S2, applying voltage to make the cathode treatment chamber and the anode treatment chamber carry out electrodialysis, and at the same time, reduction reaction is synchronously carried out in the cathode treatment chamber and oxidation reaction is synchronously carried out in the anode treatment chamber; S3, making part of effluent water of the cathode treatment chamber enter a cathode concentrated water chamber after passing through a first anion exchange membrane, and then enter a fresh water chamber after passing through a first cation exchange membrane; making part of effluent water of the anode treatment chamber enter an anode concentrated water chamber after passing through a second cation exchange membrane, and then enter the fresh water chamber after passing through a second anion exchange membrane; S4, water in the fresh water chamber is finally discharged as qualified wastewater after passing through anion and cation exchange resin. The application integrates three kinds of processes into one, and can make effluent water quality stable to reach the standard of water reuse.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a wastewater treatment process and system based on a combination of electrocatalysis and electrodeionization. Background Technology

[0002] Nitrate wastewater and recalcitrant organic wastewater are widespread. Traditional biological denitrification processes, commonly used for nitrate wastewater, are costly and have long biological growth cycles, resulting in substantial sludge disposal expenses. Ion exchange, reverse osmosis, and electrodialysis processes primarily aim at separation and concentration, generating large quantities of expensive secondary concentrated wastewater. Catalytic hydrogenation can achieve highly efficient nitrate removal, but the continuous introduction of hydrogen gas not only complicates operation but also poses an explosion risk.

[0003] Wastewater containing recalcitrant organic matter, such as dyeing and printing wastewater, is extremely difficult to treat. Currently, the most promising processes are advanced oxidation methods, including Fenton oxidation, photocatalysis, and ozonation. Fenton oxidation produces iron sludge, increasing secondary treatment costs. Photocatalysis requires ultraviolet light for energy and has a long treatment cycle. Ozonation leads to high costs and produces difficult-to-treat byproducts.

[0004] Electrocatalysis has been extensively studied for treating various recalcitrant organic or inorganic ions, but its effectiveness is significantly limited by concentration. Although some electrode materials exhibit high conversion rates, the reaction proceeds rapidly at high reactant concentrations, but slows down and increases side reactions as reactant concentrations decrease. Therefore, many pollutants are difficult to meet wastewater reuse or discharge standards in standalone electrocatalytic systems.

[0005] Electrodeionization is currently used in pure water production, but its main principle lies only in the concentration of pollutants, not in their transformation and removal. Therefore, electrocatalysis and electrodeionization can be combined to meet emission standards while simultaneously transforming pollutants. By changing the electrode materials of the anode and cathode, specific pollutants in different water qualities can be treated accordingly, without affecting the quality of the effluent due to side reactions caused by impurity ions.

[0006] Conventional electrocatalysis can perform separate oxidation or reduction reactions based on the properties of specific pollutants. With alternating membranes, it can be designed so that the anode and cathode correspond to different types of water and carry out oxidation-reduction reactions simultaneously. However, the preparation of reliable electrode materials and the design of related processes are among the obstacles that restrict the application of traditional solutions.

[0007] Therefore, it is now necessary to improve existing technologies to provide more reliable solutions. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a wastewater treatment process and system based on the combination of electrocatalysis and electrodeionization, which addresses the shortcomings of the prior art.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a wastewater treatment process based on a combination of electrocatalysis and electrodeionization, which is used to simultaneously treat a first wastewater containing nitrates and a second wastewater containing organic pollutants. The process includes the following steps:

[0010] S1. Input the first wastewater into the cathode treatment chamber and the second wastewater into the anode treatment chamber. Insert the anode electrode into the anode treatment chamber and the Cu-Pd modified cathode electrode into the cathode treatment chamber.

[0011] S2. Apply voltage to the Cu-Pd modified cathode electrode and anode electrode so that while electrodialysis is carried out in the cathode treatment chamber and the anode treatment chamber, a reduction reaction is carried out simultaneously in the cathode treatment chamber and an oxidation reaction is carried out simultaneously in the anode treatment chamber.

[0012] S3. A portion of the effluent from the cathode treatment chamber passes through the first anion exchange membrane and enters the cathode concentrate chamber, then passes through the first cation exchange membrane and enters the desalination chamber. The remaining effluent from the cathode treatment chamber overflows directly into the desalination chamber. A portion of the effluent from the anode treatment chamber passes through the second cation exchange membrane and enters the anode concentrate chamber, then passes through the second anion exchange membrane and enters the desalination chamber. The remaining effluent from the anode treatment chamber overflows directly into the desalination chamber.

[0013] S4. The water in the freshwater chamber is discharged as qualified wastewater after passing through the anion and cation exchange resins.

[0014] Preferably, the Cu-Pd modified cathode electrode is prepared by the following method:

[0015] 1) Reduced carbon dots are modified in situ on the surface of stainless steel mesh using a hydrothermal method to obtain an electrode substrate;

[0016] 2) Cu was deposited on the surface of the electrode substrate using electrodeposition to obtain a Cu-modified electrode;

[0017] 3) Pd was deposited on the surface of the Cu-modified electrode using the electrodeposition method to obtain the Cu-Pd modified cathode electrode.

[0018] Preferably, step 1) specifically includes:

[0019] 1-1) Pretreatment of stainless steel mesh;

[0020] Cut 20-200 mesh stainless steel mesh into pieces measuring 2.5-10cm x 2.5-10cm with a thickness of 0.5-2cm. First, soak the pieces in acetone for 0.5-2 hours. After removing them, rinse the surface with deionized water. Then, soak them in 5-20% hydrochloric acid and ultrasonically clean them for 15-60 minutes. After removing them, rinse the surface with deionized water. Finally, soak them in deionized water and ultrasonically clean them for 5-30 minutes. Dry the surface of the stainless steel mesh with inert gas.

[0021] 1-2) Place the stainless steel mesh, which has been pretreated in step 1), into the reactor and support it with a bracket, leaving a gap between the stainless steel mesh and the bottom of the reactor.

[0022] 1-3) Add 66-224g of lutein, 73.5-294g of salicylic acid, 42.5-170g of polyethylene glycol, and 11.5-46g of ethylenediamine to 250-1000mL of ethanol and sonicate for 30-90min. Add the resulting dispersion to a reaction vessel and react at 160-205℃ for 6-24h. After the reaction is completed, cool to room temperature, remove the stainless steel mesh, rinse with ethanol and deionized water in sequence, and vacuum dry at 70-90℃ for 3-12h to obtain the electrode substrate.

[0023] Preferably, step 2) specifically includes:

[0024] The electrode substrate obtained in step 1) is inserted into an acidic copper sulfate solution with a concentration of 0.25-1M and a pH of 1-3. Nano-zero copper is deposited on the surface of the electrode substrate using an electrodeposition method. The deposition reaction takes 5-30 minutes. The electrode substrate is then removed and cleaned with ethanol to obtain a Cu-modified electrode.

[0025] Preferably, step 3) specifically includes:

[0026] The Cu-modified electrode prepared in step 2) is inserted into a palladium sulfate solution with a concentration of 0.25-1M and a pH of 1-3. Nanoparticles of zero-valent palladium are deposited on the surface of the Cu-modified electrode using an electrodeposition method. The deposition reaction takes 5-30 minutes. The Cu-modified electrode is then removed, cleaned with ethanol, and dried under vacuum to obtain a Cu-Pd modified cathode electrode.

[0027] Preferably, in the electrodeposition process of steps 2) and 3), the electrode substrate and Cu modified electrode are used as working electrodes, the platinum sheet electrode is used as counter electrode, and the saturated calomel electrode is used as reference electrode. The electrode spacing between the working electrode and the counter electrode is 1.5-6 cm, the stirring rate of the solution during deposition is 400-1500 rpm, and the cathode potential is controlled to be -1V to -4V.

[0028] Preferably, the anode electrode is a BDD electrode.

[0029] The present invention also provides a wastewater treatment system based on electrocatalysis and electrodeionization combined. The system uses the process described above to treat wastewater. The system includes: a freshwater chamber located in the middle, a cathode treatment chamber and a cathode concentrate chamber connected sequentially along a first direction to the middle, and an anode treatment chamber and an anode concentrate chamber connected sequentially along a second direction to the middle, wherein the first direction and the second direction are opposite directions.

[0030] Cu-Pd modified cathode electrode and anode electrode are respectively inserted into the cathode treatment chamber and the anode treatment chamber;

[0031] The cathode treatment chamber and the cathode concentrate chamber are connected by a first anion exchange membrane, and the cathode concentrate chamber and the desalination chamber are connected by a first cation exchange membrane.

[0032] The anode treatment chamber and the anode concentrate chamber are connected by a second cation exchange membrane, and the anode concentrate chamber and the desalination chamber are connected by a second anion exchange membrane.

[0033] The freshwater chamber is filled with anion and cation exchange resins, and an outlet is provided at the bottom of the freshwater chamber.

[0034] Preferably, the tops of both the cathode concentrate chamber and the anode concentrate chamber are sealed by inclined cover plates. Both inclined cover plates are inclined downwards from both sides towards the middle, thereby forming a cathode overflow channel above the cathode concentrate chamber and an anode overflow channel above the anode concentrate chamber. The outer side of the cathode overflow channel is connected to the cathode overflow port at the top of the cathode treatment chamber, and the outer side of the anode overflow channel is connected to the anode overflow port at the top of the anode treatment chamber.

[0035] Preferably, water inlets are provided at the bottom outer side of both the cathode treatment chamber and the bottom outer side of both the anode treatment chamber, and drain pipes are provided at the bottom of both the cathode concentrate chamber and the anode concentrate chamber.

[0036] The bottom of the freshwater chamber is provided with a porous support plate above the water outlet, and the anion and cation exchange resin is disposed above the porous support plate.

[0037] The beneficial effects of this invention are:

[0038] This invention provides a wastewater treatment system and process based on a combination of electrocatalysis and electrodeionization. This invention can simultaneously treat two typical wastewaters from different industries, such as nitrate-containing wastewater and wastewater containing organic pollutants. Nitrate wastewater undergoes a reduction reaction at the cathode, reducing it to nitrogen gas, while recalcitrant organic wastewater undergoes an oxidation reaction at the anode, oxidizing it into substances such as carbon dioxide and water. Furthermore, this invention can simultaneously concentrate anions and cations through electrodialysis for easy recovery. Finally, the wastewater treated by electroreduction and electrodialysis is discharged after removing residual substances through ion exchange resin.

[0039] This invention integrates three processes into one, which can stabilize the effluent quality to meet the standards for reclaimed water reuse. Furthermore, the combined construction of electrocatalysis and electrodialysis can reduce the replacement and use of membranes, and the shared reaction chamber can reduce the cost of the external voltage required for the reaction.

[0040] In the self-made Cu-Pd modified cathode electrode of this invention, reducing carbon dots are pre-modified in situ on a stainless steel mesh electrode substrate. Firstly, this creates a dense, raised surface on the electrode substrate, increasing the surface area. The nano-Cu and Pd loaded onto these carbon dots significantly improves the loading amount and uniformity of Cu and Pd, increasing the number of reducing active sites. Secondly, these carbon dots use lutein and salicylic acid as carbon sources, and incorporate polyethylene glycol and ethylenediamine. These carbon dots effectively inherit the reducing properties of lutein and exhibit strong reducing ability under current, capturing NO3 through Cu. - Subsequently, under the action of Pd and carbon dots, NO3 can be efficiently removed. - The carbon dots are reduced to N2, and in this process, Pd can synergistically enhance the reducing ability of the carbon dots. In addition, the carbon dots have abundant carboxyl, hydroxyl and amino groups on their surface. During the deposition of Cu and Pd, Cu and Pd can be loaded onto the carbon dots in large quantities and uniformly through the coordination, complexation and electrostatic adsorption of copper and palladium ions by these functional groups, thereby improving the loading amount and loading uniformity. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the wastewater treatment system based on the combination of electrocatalysis and electrodeionization of the present invention.

[0042] Figure 2 This is a schematic diagram of the wastewater treatment process based on the combination of electrocatalysis and electrodeionization of the present invention;

[0043] Figure 3 The effluent quality and removal rate of related pollutants under different operating times in Embodiment 1 of the present invention;

[0044] Figure 4The effluent quality and removal rate of related pollutants under different operating times in Embodiment 2 of the present invention;

[0045] Figure 5 The effluent quality and removal rate of related pollutants in Comparative Example 1 of the present invention are shown at different operating times.

[0046] Explanation of reference numerals in the attached figures:

[0047] 1—Cathode treatment chamber; 2—Cu-Pd modified cathode electrode; 3—Cathode concentrate chamber; 4—First anion exchange membrane; 5—First cation exchange membrane; 6—Desalinated water chamber; 7—Anode concentrate chamber; 8—Second anion exchange membrane; 9—Second cation exchange membrane; 10—Anode treatment chamber; 11—BDD electrode; 12—Anion and cation exchange resin; 13—Porous support plate; 14—Outlet; 15—Inclined cover plate; 16—Cathode overflow channel; 17—Cathode overflow port; 18—Anode overflow channel; 19—Anode overflow port; 20—Inlet; 21—Drain pipe; 22—Conductive connection; 23—Wastewater pump. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0049] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0050] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0051] Reference Figure 1-2 The present invention provides a wastewater treatment system based on electrocatalysis and electrodeionization combined, and the treatment process of the system. The system includes: a freshwater chamber 6 located in the middle, a cathode treatment chamber 1 and a cathode concentrate chamber 3 connected sequentially along a first direction towards the middle, and an anode treatment chamber 10 and an anode concentrate chamber 7 connected sequentially along a second direction towards the middle, wherein the first direction and the second direction are opposite directions.

[0052] Cu-Pd modified cathode electrode 2 and anode electrode are respectively inserted in cathode treatment chamber 1 and anode treatment chamber 10;

[0053] The cathode treatment chamber 1 and the cathode concentrate chamber 3 are connected by a first anion exchange membrane 4, and the cathode concentrate chamber 3 and the desalination chamber 6 are connected by a first cation exchange membrane 5.

[0054] The anode treatment chamber 10 and the anode concentrate chamber 7 are connected by a second cation exchange membrane 9, and the anode concentrate chamber 7 and the desalination chamber 6 are connected by a second anion exchange membrane 8.

[0055] The freshwater chamber 6 is filled with anion and cation exchange resins 12, and an outlet 14 is provided at the bottom of the freshwater chamber 6.

[0056] In a preferred embodiment, the tops of both the cathode concentrate chamber 3 and the anode concentrate chamber 7 are sealed by inclined cover plates 15. Both inclined cover plates 15 are inclined downward from both sides toward the middle, thereby forming a cathode overflow channel 16 above the cathode concentrate chamber 3 and an anode overflow channel 18 above the anode concentrate chamber 7. The outer side of the cathode overflow channel 16 is connected to the cathode overflow port 17 at the top of the cathode treatment chamber 1, and the outer side of the anode overflow channel 18 is connected to the anode overflow port 19 at the top of the anode treatment chamber 10.

[0057] In a preferred embodiment, an inlet 20 is provided at the bottom outer side of the cathode treatment chamber 1 and the bottom outer side of the anode treatment chamber 10, and an outlet pipe 21 is provided at the bottom of the cathode concentrate chamber 3 and the anode concentrate chamber 7.

[0058] A porous support plate 13 is provided at the bottom of the freshwater chamber 6 above the outlet 14, and the anion and cation exchange resins 12 are provided above the porous support plate 13.

[0059] In a preferred embodiment, each chamber in the system is formed inside the device housing, which may be made of polymethyl methacrylate.

[0060] This invention also provides a wastewater treatment process based on a combination of electrocatalysis and electrodeionization. This process uses the aforementioned system to simultaneously treat a first wastewater containing nitrates and a second wastewater containing organic pollutants. The process includes the following steps:

[0061] S1. Input the first wastewater into the cathode treatment chamber 1 and the second wastewater into the anode treatment chamber 10. Insert the anode electrode into the anode treatment chamber 10 and the Cu-Pd modified cathode electrode 2 into the cathode treatment chamber 1.

[0062] S2. Apply voltage to Cu-Pd modified cathode electrode 2 and anode electrode so that while the cathode treatment chamber 1 and anode treatment chamber 10 are undergoing electrodialysis, a reduction reaction is simultaneously carried out in the cathode treatment chamber 1 and an oxidation reaction is simultaneously carried out in the anode treatment chamber 10.

[0063] S3. A portion of the effluent from the cathode treatment chamber 1 passes through the first anion exchange membrane 4 and enters the cathode concentrate chamber 3, then passes through the first cation exchange membrane 5 and enters the desalination chamber 6. The remaining effluent from the cathode treatment chamber 1 overflows directly into the desalination chamber 6. A portion of the effluent from the anode treatment chamber 10 passes through the second cation exchange membrane 9 and enters the anode concentrate chamber 7, then passes through the second anion exchange membrane 8 and enters the desalination chamber 6. The remaining effluent from the anode treatment chamber 10 overflows directly into the desalination chamber 6.

[0064] S4, the water in the freshwater chamber 6 is discharged as qualified wastewater after passing through the anion and cation exchange resin 12.

[0065] This invention integrates three wastewater treatment processes into one unit, enabling the simultaneous treatment of two different types of wastewater. Specifically, the three wastewater treatment processes include an electrocatalytic section, an electrodialysis section (electrodeionization), and an ion exchange section. Its main working principle is as follows:

[0066] After the first wastewater containing nitrates enters the cathode treatment chamber 1, under the action of the Cu-Pd modified cathode electrode 2, NO3 is firstly removed through electrocatalysis. - The remaining anions are reduced to N2. Secondly, the remaining anions move towards the positive electrode through electrodialysis and enter the cathode concentrate chamber 3 after passing through the first anion exchange membrane 4 to achieve concentration. The first cation exchange membrane 5 can prevent the anions in the cathode concentrate chamber 3 from entering the desalination chamber 6.

[0067] Similarly, after the second wastewater containing organic pollutants enters the anode treatment chamber 10 on the opposite side, under the action of the BDD electrode 11, firstly, the organic matter is oxidized into CO2 and H2O through electrocatalysis. Secondly, the remaining cationic pollutants move towards the negative electrode through electrodialysis and enter the anode concentrate chamber 7 after passing through the second cation exchange membrane 9 to achieve concentration. The second anion exchange membrane 8 can prevent the cations in the anode concentrate chamber 7 from entering the desalination chamber 6.

[0068] The main effluent from the cathode treatment chamber 1 and the anode treatment chamber 10 is directly discharged into the freshwater chamber 6 via overflow. The water in the freshwater chamber 6 is discharged as qualified wastewater after the anion and cation exchange resin 12 removes anions and cations. The concentrated water in the cathode concentrate chamber 3 and the anode concentrate chamber 7 is periodically discharged through the drain pipe 21.

[0069] This invention can simultaneously treat two typical wastewaters from different industries. For example, the cathode performs a reduction reaction on nitrate wastewater, reducing it to nitrogen gas, while the anode performs an oxidation reaction on recalcitrant organic wastewater, oxidizing it into substances such as carbon dioxide and water. Simultaneously, it can concentrate anions and cations through electrodialysis for easy recovery. Finally, the wastewater treated by electroreduction and electrodialysis is discharged after removing residual substances through ion exchange resin. By integrating these three processes, the effluent quality can be stabilized to meet the standards for reclaimed water reuse. Furthermore, the combined electrocatalysis and electrodialysis system reduces membrane replacement and usage, and the shared reaction chamber reduces the cost of the external voltage required for the reaction.

[0070] In a preferred embodiment, the Cu-Pd modified cathode electrode 2 is prepared by the following method:

[0071] 1) Hydrothermal method for in-situ modification of reduced carbon dots on the surface of stainless steel mesh to obtain electrode substrate:

[0072] 1-1) Pretreatment of stainless steel mesh;

[0073] Cut 20-200 mesh stainless steel mesh into pieces measuring 2.5-10cm x 2.5-10cm with a thickness of 0.5-2cm. First, soak the pieces in acetone for 0.5-2 hours. After removing them, rinse the surface with deionized water. Then, soak them in 5-20% hydrochloric acid and ultrasonically clean them for 15-60 minutes. After removing them, rinse the surface with deionized water. Finally, soak them in deionized water and ultrasonically clean them for 5-30 minutes. Dry the surface of the stainless steel mesh with inert gas.

[0074] 1-2) Place the stainless steel mesh, which has been pretreated in step 1), into the reactor and support it with a bracket, leaving a gap between the stainless steel mesh and the bottom of the reactor.

[0075] 1-3) Add 66-224g of lutein, 73.5-294g of salicylic acid, 42.5-170g of polyethylene glycol, and 11.5-46g of ethylenediamine to 250-1000mL of ethanol and sonicate for 30-90min. Add the resulting dispersion to a reaction vessel and react at 160-205℃ for 6-24h. After the reaction is completed, cool to room temperature, remove the stainless steel mesh, rinse with ethanol and deionized water in sequence, and vacuum dry at 70-90℃ for 3-12h to obtain the electrode substrate.

[0076] 2) Cu was deposited on the surface of the electrode substrate using electrodeposition to obtain a Cu-modified electrode:

[0077] The electrode substrate obtained in step 1) is inserted into an acidic copper sulfate solution with a concentration of 0.25-1M and a pH of 1-3. Nano-zero copper is deposited on the surface of the electrode substrate using an electrodeposition method. The deposition reaction takes 5-30 minutes. The electrode substrate is then removed and cleaned with ethanol to obtain a Cu-modified electrode.

[0078] 3) Pd was deposited on the surface of the Cu-modified electrode using electrodeposition to obtain Cu-Pd modified cathode electrode 2:

[0079] The Cu-modified electrode prepared in step 2) was inserted into a palladium sulfate solution with a concentration of 0.25-1M and a pH of 1-3. Nanoparticles of zero-valent palladium were deposited on the surface of the Cu-modified electrode using an electrodeposition method. The deposition reaction was carried out for 5-30 minutes. The Cu-modified electrode was then removed, cleaned with ethanol, and dried under vacuum to obtain Cu-Pd modified cathode electrode 2.

[0080] In the electrodeposition process of steps 2) and 3), the electrode substrate and Cu modified electrode are used as working electrodes, the platinum sheet electrode is used as counter electrode, and the saturated calomel electrode is used as reference electrode. The electrode spacing between the working electrode and the counter electrode is 1.5-6 cm. The stirring rate of the solution during deposition is 400-1500 rpm, and the cathode potential is controlled from -1V to -4V.

[0081] The cathode electrode is used to remove NO3 while simultaneously performing electrodialysis. - To reduce NO3 to N2, this invention uses a Cu-Pd modified electrode substrate as the cathode electrode, and nano-zero-valent Cu reduces NO3 to N2. - It exhibits good selectivity (Wang Changhong, Liu Zhengyang, Li Changming, et al. Research progress on electrocatalytic nitrate reduction of copper-based materials [J]. Science Bulletin, 2021, 66(34):4411-4424.), while nano-zero-valent Pd can promote NO3 - Ultimately, it is reduced to N2 (Dong Yi, Zhang Lihao, Zhu Zongqiang, et al. Electrocatalytic efficient reduction of nitrate in water using Cu / Pd modified Ni foam cathode: High nitrate removal efficiency and N2-selectivity. Sep Purif Technol 241, 116743.), reducing its reduction to NH4. +The probability of NO3 being released from the cathode electrode depends on the loading amount of nano-zero-valent Cu and Pd, their surface area, and the overall reduced form of the electrode. - The ability to reduce to N2 has a significant impact. In this invention, reducing carbon dots are pre-modified in situ on a stainless steel mesh electrode substrate. Firstly, this creates a dense, raised surface on the electrode substrate, increasing the surface area. The loading of nano-Cu and Pd onto these carbon dots greatly improves the loading amount and uniformity of Cu and Pd, increasing the number of reducing active sites. Secondly, these carbon dots use lutein and salicylic acid as carbon sources, and incorporate polyethylene glycol and ethylenediamine. These carbon dots effectively inherit the reducing properties of lutein and exhibit strong reducing ability under current, capturing NO3 through Cu. - Subsequently, under the action of Pd and carbon dots, NO3 can be efficiently removed. - The carbon dots are reduced to N2, and in this process, Pd can synergistically enhance the reducing ability of the carbon dots. In addition, the carbon dots have abundant carboxyl, hydroxyl and amino groups on their surface. During the deposition of Cu and Pd, Cu and Pd can be loaded onto the carbon dots in large quantities and uniformly through the coordination, complexation and electrostatic adsorption of copper and palladium ions by these functional groups, thereby improving the loading amount and loading uniformity.

[0082] In this invention, stainless steel mesh is used as the base support material. The mesh structure facilitates the in-situ grafting of a large number of carbon dots on the surface during the hydrothermal reaction. After being treated with hydrochloric acid, the stainless steel mesh can be activated on the surface, making it easier for carbon dots to adhere. Moreover, stainless steel mesh is low in cost and conducive to industrial application.

[0083] In a preferred embodiment, the anode electrode is a BDD electrode 11 (boron-doped diamond electrode).

[0084] In some embodiments, the wastewater treated by the present invention has the following characteristics:

[0085] NO3 in the first wastewater - -N concentration is 100–300 mg / L, SO4 2- The concentration is 5-10 g / L; the COD concentration in the second wastewater is 500-1000 mg / L. For the above wastewater, some process parameters in this invention are as follows: the voltage applied to the anode electrode and the Cu-Pd modified cathode electrode 2 is 25-35V; the influent flow rate of the cathode treatment chamber 1 is 0.25-1 L / h; and the influent flow rate of the anode treatment chamber 10 is 0.05-0.2 L / h.

[0086] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0087] Example 1

[0088] Reference Figure 1 A wastewater treatment system based on electrocatalysis and electrodeionization combined. The system includes: a freshwater chamber 6 located in the middle, a cathode treatment chamber 1 and a cathode concentrate chamber 3 connected sequentially along a first direction towards the middle, and an anode treatment chamber 10 and an anode concentrate chamber 7 connected sequentially along a second direction towards the middle, wherein the first direction and the second direction are opposite directions.

[0089] Cu-Pd modified cathode electrode 2 and anode electrode are respectively inserted in cathode treatment chamber 1 and anode treatment chamber 10; cathode treatment chamber 1 and cathode concentrate chamber 3 are connected by a first anion exchange membrane 4, and cathode concentrate chamber 3 and desalination chamber 6 are connected by a first cation exchange membrane 5; anode treatment chamber 10 and anode concentrate chamber 7 are connected by a second cation exchange membrane 9, and anode concentrate chamber 7 and desalination chamber 6 are connected by a second anion exchange membrane 8; desalination chamber 6 is filled with anion and cation exchange resin 12, and a water outlet 14 is provided at the bottom of desalination chamber 6.

[0090] The tops of both the cathode concentrate chamber 3 and the anode concentrate chamber 7 are sealed by inclined cover plates 15. Both inclined cover plates 15 are inclined downward from both sides towards the middle, thereby forming a cathode overflow channel 16 above the cathode concentrate chamber 3 and an anode overflow channel 18 above the anode concentrate chamber 7. The outer side of the cathode overflow channel 16 is connected to the cathode overflow port 17 at the top of the cathode treatment chamber 1 (formed through the gap between the first anion exchange membrane 4 and the top of the cathode treatment chamber 1), and the outer side of the anode overflow channel 18 is connected to the anode overflow port 19 at the top of the anode treatment chamber 10 (formed through the gap between the first anion exchange membrane 4 and the top of the anode treatment chamber 10).

[0091] The cathode treatment chamber 1 and the anode treatment chamber 10 are both provided with inlets 20 at their outer bottoms, and the cathode concentrate chamber 3 and the anode concentrate chamber 7 are both provided with drain pipes 21 at their bottoms. The bottom of the desalination chamber 6 is provided with a porous support plate 13 above the outlet 14, and the anion and cation exchange resins 12 are provided above the porous support plate 13.

[0092] Both the upper ends of the Cu-Pd modified cathode electrode 2 and the anode electrode are connected to conductive connection parts 22 for connecting to an external power source.

[0093] Reference Figure 2 A wastewater treatment process employing the above-described system, used to simultaneously treat a first wastewater containing nitrates and a second wastewater containing organic pollutants, the process comprising the following steps:

[0094] S1. Wastewater pump 23 is used to input the first wastewater into the cathode treatment chamber 1 through the inlet 20 and the second wastewater into the anode treatment chamber 10 through the inlet 20. An anode electrode is inserted into the anode treatment chamber 10 and a Cu-Pd modified cathode electrode 2 is inserted into the cathode treatment chamber 1.

[0095] S2. Apply voltage to Cu-Pd modified cathode electrode 2 and anode electrode so that while the cathode treatment chamber 1 and anode treatment chamber 10 are undergoing electrodialysis, a reduction reaction is simultaneously carried out in the cathode treatment chamber 1 and an oxidation reaction is simultaneously carried out in the anode treatment chamber 10.

[0096] S3. A portion of the effluent from the cathode treatment chamber 1 passes through the first anion exchange membrane 4 and enters the cathode concentrate chamber 3, then passes through the first cation exchange membrane 5 and enters the desalination chamber 6. The remaining effluent from the cathode treatment chamber 1 overflows directly into the desalination chamber 6. A portion of the effluent from the anode treatment chamber 10 passes through the second cation exchange membrane 9 and enters the anode concentrate chamber 7, then passes through the second anion exchange membrane 8 and enters the desalination chamber 6. The remaining effluent from the anode treatment chamber 10 overflows directly into the desalination chamber 6.

[0097] S4. The water in the freshwater chamber 6 passes through the anion and cation exchange resin 12 and is finally discharged from the outlet 14 as qualified wastewater.

[0098] In this embodiment, the Cu-Pd modified cathode electrode 2 is prepared by the following method:

[0099] 1) Hydrothermal method for in-situ modification of reduced carbon dots on the surface of stainless steel mesh to obtain electrode substrate:

[0100] 1-1) Pretreatment of stainless steel mesh;

[0101] Cut 50-mesh stainless steel mesh into 5cm x 5cm pieces with a thickness of 1cm. First, soak them in acetone for 1 hour, then rinse the surface with deionized water. Next, soak them in 10% hydrochloric acid and ultrasonically clean them for 30 minutes. After that, rinse the surface with deionized water. Finally, put them in deionized water and ultrasonically clean them for 10 minutes. Then, dry the surface of the stainless steel mesh with inert gas.

[0102] 1-2) Place the stainless steel mesh, which has been pretreated in step 1), into the reactor and support it with a bracket, leaving a gap between the stainless steel mesh and the bottom of the reactor.

[0103] 1-3) Add 112g lutein, 147g salicylic acid, 85g polyethylene glycol and 23g ethylenediamine to 500mL ethanol and sonicate for 60min. Add the resulting dispersion to the reaction vessel and react at 180℃ for 12h. After the reaction is completed, cool to room temperature, remove the stainless steel mesh, rinse with ethanol and deionized water in sequence, and vacuum dry at 80℃ for 6h to obtain the electrode substrate.

[0104] 2) Cu was deposited on the surface of the electrode substrate using electrodeposition to obtain a Cu-modified electrode:

[0105] The electrode substrate obtained in step 1) was inserted into an acidic copper sulfate solution with a concentration of 0.5M and a pH of 2. Nano-zero copper was deposited on the surface of the electrode substrate using an electrodeposition method. The deposition reaction was carried out for 10 minutes. The electrode substrate was then removed and cleaned with ethanol to obtain a Cu-modified electrode.

[0106] 3) Pd was deposited on the surface of the Cu-modified electrode using electrodeposition to obtain Cu-Pd modified cathode electrode 2:

[0107] The Cu-modified electrode prepared in step 2) was inserted into a palladium sulfate solution with a concentration of 0.5M and a pH of 2. Nanoparticles of zero-valent palladium were deposited on the surface of the Cu-modified electrode using an electrodeposition method. After the deposition reaction was carried out for 10 min, the Cu-modified electrode was removed, cleaned with ethanol, and dried under vacuum to obtain Cu-Pd modified cathode electrode 2.

[0108] In the electrodeposition process of steps 2) and 3), the electrode substrate and Cu modified electrode are used as working electrodes, a 5cm×5cm platinum sheet electrode is used as counter electrode, and a saturated calomel electrode is used as reference electrode. The electrode spacing between the working electrode and the counter electrode is 3cm. The stirring rate of the solution during deposition is 800rpm, and the cathode potential is controlled at -2V.

[0109] In this embodiment, the amount of copper deposited on the prepared Cu-Pd modified cathode electrode 2 is 0.089 g / cm³. 2 The amount of palladium deposited was 0.104 g / cm³. 2 .

[0110] In this embodiment, the influent water quality is:

[0111] NO3 in the first wastewater - -N concentration is 200 mg / L, SO4 2- The concentration is 5 g / L; the COD concentration in the second wastewater is 700 mg / L. For the above wastewater, the main process parameters in this invention are: the voltage applied to the anode electrode and the Cu-Pd modified cathode electrode 2 is 30 V; the influent flow rate to the cathode treatment chamber 1 is 0.5 L / h; and the influent flow rate to the anode treatment chamber 10 is 0.1 L / h.

[0112] The effluent quality after treatment using the process described in this example is as follows:

[0113] Continuous operation resulted in stable NO3 levels in the effluent. - -N concentration is below 8 mg / L, SO4 2- The concentration was below 11 mg / L, while the color of the dyeing and printing wastewater had been removed and the COD concentration was less than 42 mg / L.

[0114] Reference Figure 3 , represents the effluent quality and removal rate of related pollutants at different operating times in this example.

[0115] Example 2

[0116] This embodiment is basically the same as Embodiment 1, except for the main process parameters, as follows.

[0117] The main process parameters in this embodiment are: the voltage applied to the anode electrode and the Cu-Pd modified cathode electrode 2 is 30V, the inlet flow rate of the cathode treatment chamber 1 is 0.6L / h, and the inlet flow rate of the anode treatment chamber 10 is 0.08L / h.

[0118] The effluent quality after treatment using the process described in this example is as follows:

[0119] Continuous operation resulted in stable NO3 levels in the effluent. - -N concentration is below 10 mg / L, SO4 2- The concentration of COD in the dyeing and printing wastewater is less than 21 mg / L, while the color has been removed and the COD concentration is less than 29 mg / L.

[0120] Reference Figure 4 , represents the effluent quality and removal rate of related pollutants at different operating times in this example.

[0121] The processing results from Examples 1 and 2 show that it is effective against NO3. - It has good treatment effects on both nitrogen and COD, and the effluent can meet the industry's standards for recycled water, which has great industrial application value.

[0122] Comparative Example 1

[0123] This example is basically the same as Example 1, except for the main process parameters, as follows.

[0124] The main process parameters in this example are: the voltage applied to the anode electrode and Cu-Pd modified cathode electrode 2 is 20V, the inlet flow rate of cathode treatment chamber 1 is 0.5L / h, and the inlet flow rate of anode treatment chamber 10 is 0.1L / h;

[0125] The quality of the influent is:

[0126] NO3 in the first wastewater - -N concentration is 200 mg / L, SO4 2- The concentration was 5 g / L; the COD concentration in the second wastewater was 700 mg / L.

[0127] The effluent quality after treatment using the process described in this example is as follows:

[0128] Continuous operation resulted in stable NO3 levels in the effluent. --N concentration is below 14 mg / L, SO4 2- The concentration of COD in the dyeing and printing wastewater is less than 23 mg / L, while the color has been removed and the COD concentration is less than 88 mg / L.

[0129] Reference Figure 5 , represents the effluent quality and removal rate of related pollutants at different operating times in this example.

[0130] A comparison with Example 1 shows that in this example, the COD removal effect is poor due to the applied voltage being too low.

[0131] Comparative Example 2

[0132] This example is basically the same as Example 1, except that a different Cu-Pd modified cathode electrode 2 is used. The preparation method of the Cu-Pd modified cathode electrode 2 in this example includes the following steps:

[0133] 1) Pre-treat the stainless steel mesh to obtain the electrode substrate;

[0134] A 50-mesh stainless steel mesh was cut into 5cm x 5cm blocks with a thickness of 1cm. The blocks were first soaked in acetone for 1 hour, then rinsed with deionized water. The blocks were then soaked in 10% hydrochloric acid and ultrasonically cleaned for 30 minutes. The blocks were then rinsed with deionized water. Finally, the blocks were placed in deionized water and ultrasonically cleaned for 10 minutes. The surface of the stainless steel mesh was dried with inert gas to obtain the electrode substrate.

[0135] 2) Cu was deposited on the surface of the electrode substrate using electrodeposition to obtain a Cu-modified electrode:

[0136] The electrode substrate obtained in step 1) was inserted into an acidic copper sulfate solution with a concentration of 0.5M and a pH of 2. Nano-zero copper was deposited on the surface of the electrode substrate using an electrodeposition method. The deposition reaction was carried out for 10 minutes. The electrode substrate was then removed and cleaned with ethanol to obtain a Cu-modified electrode.

[0137] 3) Pd was deposited on the surface of the Cu-modified electrode using electrodeposition to obtain Cu-Pd modified cathode electrode 2:

[0138] The Cu-modified electrode prepared in step 2) was inserted into a palladium sulfate solution with a concentration of 0.5M and a pH of 2. Nanoparticles of zero-valent palladium were deposited on the surface of the Cu-modified electrode using an electrodeposition method. After the deposition reaction was carried out for 10 min, the Cu-modified electrode was removed, cleaned with ethanol, and dried under vacuum to obtain Cu-Pd modified cathode electrode 2.

[0139] In the electrodeposition process of steps 2) and 3), the electrode substrate and Cu modified electrode are used as working electrodes, a 5cm×5cm platinum sheet electrode is used as counter electrode, and a saturated calomel electrode is used as reference electrode. The electrode spacing between the working electrode and the counter electrode is 3cm. The stirring rate of the solution during deposition is 800rpm, and the cathode potential is controlled at -2V.

[0140] In this example, the amount of copper deposited on the prepared Cu-Pd modified cathode electrode 2 is 0.056 g / cm³. 2 The amount of palladium deposited was 0.064 g / cm³. 2 .

[0141] The quality of the influent is:

[0142] NO3 in the first wastewater - -N concentration is 200 mg / L, SO4 2- The concentration was 5 g / L; the COD concentration in the second wastewater was 700 mg / L.

[0143] The effluent quality after treatment using the process described in this example is as follows:

[0144] Continuous operation resulted in stable NO3 levels in the effluent. - -N concentration below 27 mg / L, SO4 2- The concentration of COD in the dyeing and printing wastewater is less than 30 mg / L, while the color has been removed and the COD concentration is less than 43 mg / L.

[0145] A comparison with Example 1 shows that, due to the lack of carbon dot modification on the stainless steel mesh substrate, the amount of deposited copper and palladium is significantly reduced, resulting in a decrease in NO3 deposition. - The ability to remove -N is significantly reduced.

[0146] 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, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A wastewater treatment process based on the combination of electrocatalysis and electrodeionization, characterized in that, The process is used for simultaneously treating the first wastewater containing nitrate and the second wastewater containing organic pollutants, and the process comprises the following steps: S1, inputting the first wastewater into a cathode treatment chamber and the second wastewater into an anode treatment chamber, inserting an anode electrode into the anode treatment chamber and a Cu-Pd modified cathode electrode into the cathode treatment chamber; S2, applying a voltage to the Cu-Pd modified cathode electrode and the anode electrode, so that the cathode treatment chamber and the anode treatment chamber perform electrodialysis, and a reduction reaction is synchronously performed in the cathode treatment chamber and an oxidation reaction is synchronously performed in the anode treatment chamber; S3, making part of the effluent of the cathode treatment chamber enter a cathode concentrated water chamber after passing through a first anion exchange membrane and then enter a dilute water chamber after passing through a first cation exchange membrane, and the remaining effluent of the cathode treatment chamber directly overflows into the dilute water chamber; making part of the effluent of the anode treatment chamber enter an anode concentrated water chamber after passing through a second cation exchange membrane and then enter the dilute water chamber after passing through a second anion exchange membrane, and the remaining effluent of the anode treatment chamber directly overflows into the dilute water chamber; S4, the water in the dilute water chamber is finally discharged as qualified wastewater after passing through anion and cation exchange resins; The Cu-Pd modified cathode electrode is prepared by the following method: 1) hydrothermal method is used to modify reduced carbon dots on the surface of a stainless steel mesh in situ to obtain an electrode substrate; 2) an electrodeposition method is used to deposit Cu on the surface of the electrode substrate to obtain a Cu modified electrode; 3) an electrodeposition method is used to deposit Pd on the surface of the Cu modified electrode to obtain a Cu-Pd modified cathode electrode; Step 1) specifically comprises: 1-1) pretreatment of the stainless steel mesh; The 20-200 mesh stainless steel mesh is cut into a block with a size of 2.5-10 cm x 2.5-10 cm and a thickness of 0.5-2 cm, first soaked in acetone for 0.5-2 h, then washed with deionized water, then soaked in hydrochloric acid with a mass fraction of 5-20%, ultrasonic cleaning for 15-60 min, then washed with deionized water, and finally ultrasonic cleaning for 5-30 min in deionized water, and the surface of the stainless steel mesh is dried with inert gas; 1-2) the pretreated stainless steel mesh is placed in a reaction kettle and supported and fixed by a support, leaving a gap between the stainless steel mesh and the bottom surface of the reaction kettle; 1-3) 66-224 g of lutein, 73.5-294 g of salicylic acid, 42.5-170 g of polyethylene glycol, and 11.5-46 g of ethylenediamine are added to 250-1000 mL of ethanol, ultrasonic dispersion is performed for 30-90 min, the obtained dispersion liquid is added to the reaction kettle, and reaction is performed at 160-205 ℃ for 6-24 h. After the reaction is completed, the reaction kettle is cooled to room temperature, the stainless steel mesh is taken out, washed with ethanol and deionized water, and vacuum dried at 70-90 ℃ for 3-12 h to obtain the electrode substrate.

2. The wastewater treatment process based on the combination of electrocatalysis and electrodeionization according to claim 1, characterized in that, Step 2) specifically comprises: The electrode substrate obtained in step 1) is inserted into an acidic copper sulfate solution with a concentration of 0.25-1 M and a pH value of 1-3, and an electrodeposition method is used to deposit nano zero-valent copper on the surface of the electrode substrate, and the deposition reaction is performed for 5-30 min. The electrode substrate is taken out and washed with ethanol to obtain a Cu modified electrode.

3. The wastewater treatment process based on the combination of electrocatalysis and electrodeionization according to claim 2, characterized in that, Step 3) specifically comprises: The Cu-modified electrode prepared in step 2) is inserted into a palladium sulfate solution with a concentration of 0.25-1 M and a pH value of 1-3, and nanometer zero-valent palladium is deposited on the surface of the Cu-modified electrode by using an electrodeposition method, the deposition reaction is performed for 5-30 min, the Cu-modified electrode is taken out, cleaned with ethanol, and vacuum dried to obtain a Cu-Pd modified cathode electrode.

4. The wastewater treatment process based on the combination of electrocatalysis and electrodeionization according to claim 3, characterized in that, In the electrodeposition process of steps 2) and 3), the electrode substrate and the Cu-modified electrode are used as the working electrode in turn, a platinum electrode is used as the counter electrode, a saturated calomel electrode is used as the reference electrode, the electrode spacing between the working electrode and the counter electrode is 1.5-6 cm, the stirring rate of the solution during deposition is 400-1500 rpm, and the cathode potential is controlled to be-1 V to-4 V.

5. The wastewater treatment process based on the combination of electrocatalysis and electrodeionization according to claim 1, characterized in that, The anode electrode is a BDD electrode.

6. A wastewater treatment system based on the combination of electrocatalysis and electrodeionization, characterized in that, The system adopts the process according to any one of claims 1-5 for wastewater treatment, and the system comprises a freshwater chamber in the middle, a cathode treatment chamber and a cathode concentrated water chamber which are sequentially and communicatively arranged towards the middle along a first direction, and an anode treatment chamber and an anode concentrated water chamber which are sequentially and communicatively arranged towards the middle along a second direction, wherein the first direction and the second direction are opposite directions; The Cu-Pd modified cathode electrode and the anode electrode are respectively inserted into the cathode treatment chamber and the anode treatment chamber; The cathode treatment chamber and the cathode concentrated water chamber are communicated through a first anion exchange membrane, and the cathode concentrated water chamber and the freshwater chamber are communicated through a first cation exchange membrane; The anode treatment chamber and the anode concentrated water chamber are communicated through a second cation exchange membrane, and the anode concentrated water chamber and the freshwater chamber are communicated through a second anion exchange membrane; The freshwater chamber is filled with anion-cation exchange resin, and a water outlet is arranged at the bottom of the freshwater chamber.

7. The wastewater treatment system based on the combination of electrocatalysis and electrodeionization according to claim 6, characterized in that, The top of each of the cathode concentrated water chamber and the anode concentrated water chamber is sealed by an inclined cover plate, both of the inclined cover plates are inclined downward from the two sides to the middle direction, so as to form a cathode overflow channel above the cathode concentrated water chamber and an anode overflow channel above the anode concentrated water chamber, the outer side of the cathode overflow channel is communicated to a cathode overflow port at the top of the cathode treatment chamber, and the outer side of the anode overflow channel is communicated to an anode overflow port at the top of the anode treatment chamber.

8. The wastewater treatment system based on the combination of electrocatalysis and electrodeionization according to claim 7, characterized in that, The outer side bottom of the cathode treatment chamber and the outer side bottom of the anode treatment chamber are both provided with a water inlet, and the bottom of each of the cathode concentrated water chamber and the anode concentrated water chamber is provided with an emptying pipe; The bottom of the freshwater chamber is provided with a porous support plate above the water outlet, and the anion-cation exchange resin is arranged above the porous support plate.

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