A method for multi-stage treatment of copper-containing wastewater driven by graphene oxide-assisted electric field.

Abstract

This invention discloses a method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field-driven process. The method utilizes a graphene oxide-assisted N / O / S multi-coordinated copper ion-imprinted cation exchange membrane as the selective separation interface, employs a membrane arrangement of graphene oxide-assisted copper ion-imprinted cation exchange membrane—anion exchange membrane—cation exchange membrane, and utilizes an electric field for migration and release, with endogenous carbonate as the circulating crystallization medium in a continuous treatment system. This system can synergistically achieve the decomposition and transformation of complexed copper, and the treatment of Cu... 2+ Selective migration and enrichment, polarity reversal release, and in-situ crystallization recovery form "complex copper transformation-Cu". 2+ A closed-loop treatment pathway of "selective enrichment at the membrane interface – reverse release – internal carbonate recycling and crystallization recovery" is employed. This technology can reduce the consumption of external precipitants, lower the post-treatment pressure of copper-containing concentrate, and increase the value of copper resource recovery, providing strong support for the in-depth treatment and resource utilization of wastewater containing complexed copper.

Description

Technical Field

[0001] This invention relates to the field of copper-containing wastewater pollution treatment technology, and in particular to a method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving. Background Technology

[0002] With the rapid development of industries such as photovoltaics, electroplating, electronics manufacturing, and metal surface treatment, the discharge of copper-containing wastewater generated during these processes is gradually increasing. Currently, advanced oxidation, electrochemical separation, and membrane separation technologies are being used for copper-containing wastewater treatment. However, membrane capacitive deionization technology still suffers from insufficient copper ion selectivity in treating complex copper-containing wastewater. Ordinary cation exchange membranes primarily rely on charge repulsion and general cation migration for separation, making it difficult to effectively distinguish Cu ions. 2+ with Na + Ca 2+ Mg 2+ Zn 2+ Coexisting cations; meanwhile, traditional regeneration processes typically only yield copper-containing concentrates, with copper still existing in a free state. Further chemical precipitation or concentration is required, failing to fully realize the direct conversion of copper from pollutant to recyclable solid resources. Furthermore, the carbonate / bicarbonate formed during the reaction and the system's alkalinity are underutilized, often treated as background salts or byproducts. Subsequent copper recovery still relies on external precipitants such as alkali, carbonates, or sulfides, leading to increased reagent consumption, larger sludge volumes, fluctuations in product purity, and higher post-treatment costs. Based on free Cu... 2+ The issues of multi-stage treatment and utilization, effective identification and enrichment, and reuse of alkalinity in the treatment system require the design of targeted solutions. Summary of the Invention

[0003] This invention provides a method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving, to solve the problems of multi-stage treatment of copper-containing wastewater and free Cu. 2+ Effective identification and enrichment, reuse of alkalinity in the treatment system, and free Cu 2+ Technical issues such as effective recycling.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving includes the following steps: S1. Sodium percarbonate and ozone are added to the wastewater pretreatment tank for copper-containing wastewater to create an active oxidation environment, which gradually converts the complexed copper in the wastewater into free Cu. 2+ Meanwhile, the generated carbonate components are retained and used as the reaction medium for subsequent internal circulation crystallization recovery; S2, Free Cu 2+As water flows into the multi-coordinate ion treatment system, the anion exchange membrane is centrally located in the system, with cation exchange membranes and multi-stage treatment membranes on both sides. Among them, the multi-stage treatment membrane is denoted as GO-N / O / S-Cu-IIP-CEM, which uses a cation exchange membrane as the base membrane and constructs a graphene oxide hydrophilic mass transfer layer and a copper ion imprinted functional layer containing N / O / S multi-coordination sites on the surface or near the surface. S3, Free Cu 2+ After entering, it is separated into a concentrated ion region and a dilute ion region by an anion exchange membrane. The concentrated ion region is the cation exchange membrane region located at the positive electrode. Cu 2+ At the positive electrode, it is driven by the electric field to desorb and thus accumulate; S4, the desalination region is the area where the GO-N / O / S-Cu-IIP-CEM is located at the negative electrode. Under the action of the electric field, the fixed negative charge groups of the base film selectively conduct cations and inhibit the entry of anions through the Donnan repulsion effect. Cu 2+ Under the influence of the hydrophilic mass transfer layer channels, it rapidly enters the membrane interface and selectively complexes with the N / O / S coordination recognition sites in the imprinted functional layer. Simultaneously, the imprinted holes in the functional layer also coordinate with Cu through coordination. 2+ Perform selective identification and enrichment; S5, Cu in the depleted ion region 2+ The copper-containing wastewater in the GO-N / O / S-Cu-IIP-CEM region is recognized, captured, and adsorbed. Anions are attracted by the positive electrode electric field and migrate to the concentrated ion region. Consequently, the copper-containing wastewater in the desalination region is treated into freshwater or low-salinity water, and the GO-N / O / S-Cu-IIP-CEM enriches Cu. 2+ Then it enters the regeneration and recycling stage, thus completing the treatment of copper-containing wastewater pollution.

[0005] Furthermore, the sodium percarbonate in the pretreatment tank of S1 is designated as SPC. The carbonate / bicarbonate released by the dissolution of SPC and the alkalinity of the system are retained in the treatment liquid as the endogenous reaction medium for the solidification and recovery of copper. The treated liquid is connected to a gas-liquid mixer via a water pump. This gas-liquid mixer is also connected to an ozone generator. After the treated liquid and ozone are mixed in the gas-liquid mixer, they enter the pretreatment tank for Cu treatment. 2+ Solid-state recycling.

[0006] Furthermore, in S2, the multi-coordinate ion treatment system includes a first end cap, a first electrode assembly, a cation exchange membrane, a first flow channel spacer, an anion exchange membrane, a second flow channel spacer, a multi-stage treatment membrane, a second electrode assembly, and a second end cap, arranged sequentially; wherein the first electrode assembly is a positive electrode and the second electrode assembly is a negative electrode.

[0007] Furthermore, both the first electrode assembly and the second electrode assembly include a graphite plate and have a layer of activated carbon fiber cloth attached to the surface of the graphite plate. The first flow channel spacer and the second flow channel are used to form independent fluid channels and ensure that the solution is uniformly distributed inside the membrane module. The fluid channels are used to achieve Cu 2+ Under the influence of an electric field, it migrates and accumulates at the GO-N / O / S-Cu-IIP-CEM interface.

[0008] Furthermore, the preparation steps of GO-N / O / S-Cu-IIP-CEM in S2 are as follows: S21. The base film is pretreated by sequentially placing it in deionized water, acid solution and salt solution; then the pretreated base film is placed in dopamine hydrochloride solution to allow dopamine to self-polymerize on the film surface to form a polydopamine adhesion layer. S22. Immerse the base membrane treated in S21 into a graphene oxide dispersion to load graphene oxide onto the membrane surface or near the surface layer; after loading is completed, a graphene oxide modified cation exchange membrane is obtained, denoted as GO-CEM. S23. The GO-CEM is immersed in a mixed solution containing N / O / S multi-coordination functional components for functionalization treatment, so that N / O / S multi-coordination sites of amino, carboxyl, hydroxyl and thiol groups are introduced into the membrane surface at the same time; after the reaction is completed, the GO-N / O / S functionalized cation exchange membrane is obtained, which is denoted as GO-N / O / S-CEM. S24. Place GO-N / O / S-CEM in Cu 2+ Coordination reactions occur in the template solution; amino, carboxyl, hydroxyl, and thiol groups on the membrane surface and outer layer, as well as oxygen-containing functional groups of graphene oxide, react with Cu. 2+ Coordination complexation occurs, forming Cu 2+ -N / O / S multi-coordination composite structure; S25. The membrane that has completed coordination in S24 is placed in a glutaraldehyde solution for cross-linking reaction. After cross-linking is completed, Cu is obtained. 2+ Load-type GO-N / O / S-Cu-IIP-CEM.

[0009] Furthermore, the GO-N / O / S-Cu-IIP-CEM surface or surface layer has a Cu content. 2+ The constructed imprints identify holes and N / O / S multicoordination sites of amino, carboxyl, hydroxyl, and / or thiol groups; under the action of an applied low-voltage electric field, Cu is formed through oxidation transformation. 2+ Directed migration towards the functional membrane interface and electrode region, GO-N / O / S-Cu-IIP-CEM combines cation exchange conduction, hydrophilic mass transfer of graphene oxide, and copper ion imprinting recognition, enabling it to migrate towards Na+.+ Mg 2+ Zn 2+ Cu preferentially identifies, captures, and enriches itself in the presence of multiple coexisting cations. 2+ This allows for the selective migration efficiency of copper ions and the enrichment of the membrane interface.

[0010] Furthermore, copper-containing wastewater is rich in Cl- ions. - Cl - Driven by the electric field, they migrate towards the concentrated ion region at the positive electrode, while the anion exchange membrane allows Cl in the dilute ion region to migrate. - The Cu atoms migrate and accumulate; thus, the desorbed Cu atoms accumulate in the concentrated ion region. 2+ and migration of Cl - This creates a high-concentration ion region.

[0011] Furthermore, the first end cap and the first end cap are used to encapsulate and form a multi-coordinate ion treatment system. Both the first end cap and the first end cap have water inlet channels at their bottoms, which are used to allow water to enter the S1-treated system containing free Cu. 2+ Wastewater; the inlet channel is provided with no less than two at the first end sealing plate; The first end cap is located at the positive electrode, and a concentrated water outlet is provided at the top of the first end cap; the concentrated water outlet is used to discharge the wastewater with high concentration of ions after S3 treatment; The second end cap is located at the negative electrode, and a freshwater outlet is located at the top of the first end cap. The freshwater outlet is used to discharge freshwater or low-salinity water after S5 treatment. The freshwater outlet is connected to the outlet pool, which is also equipped with a conductivity meter, a multimeter, and a data acquisition system. The conductivity meter is used to monitor the conductivity of the product water in real time, the multimeter is used to record the operating current signal, and the relevant data is recorded and analyzed through the data acquisition system.

[0012] Furthermore, after the copper-containing wastewater in S5 is treated by GO-N / O / S-Cu-IIP-CEM, it enters the regeneration and recovery stage. By switching the electrode polarities of the first and second electrode components to change the direction of ion migration, the Cu enriched on the electrode surface and at the GO-N / O / S-Cu-IIP-CEM interface is further enhanced. 2+ Released into the regeneration crystallization channel, resulting in the release of a high concentration of Cu. 2+ With CO3 2- / HCO3 - and OH - Synchronous contact in localized areas creates a high ion product and a localized supersaturated environment, inducing the formation of solid copper crystals of basic copper carbonate; the generated crystals are then recovered through sedimentation, filtration, or other solid-liquid separation methods.

[0013] Furthermore, copper-containing wastewater includes copper-containing wastewater from photovoltaic manufacturing, electroplating, electronic cleaning, chemical processing, or other polluted wastewater containing complexed copper, free copper, and various coexisting salt ions.

[0014] The beneficial effects of this invention are reflected in: 1) This invention constructs a continuous processing system using a graphene oxide-assisted N / O / S multi-coordinated copper ion-imprinted cation exchange membrane as the selective separation interface, employing a membrane arrangement of graphene oxide-assisted copper ion-imprinted cation exchange membrane—anion exchange membrane—cation exchange membrane, driven by an electric field for migration and release, and using endogenous carbonate as the circulating crystallization medium. This system can synergistically achieve the complexation and decomposition transformation of complexed copper, Cu... 2+ Selective migration and enrichment, polarity reversal release, and in-situ crystallization recovery form a "complex copper-Cu" structure. 2+ A closed-loop treatment pathway of "selective enrichment at the membrane interface - reverse release - internal circulation crystallization and recovery of carbonate" is employed. This technology can reduce the consumption of external precipitants, lower the post-treatment pressure of copper-containing concentrate, and improve the resource recovery value of copper. It provides strong support for the in-depth treatment and resource utilization of complexed copper-containing wastewater in industries such as photovoltaics, electroplating, electronic manufacturing, circuit boards, and metal surface treatment.

[0015] 2) This invention uses a graphene oxide-assisted copper ion-imprinted cation exchange membrane as the core functional membrane. This membrane contains a layer of material that interacts with Cu ions. 2+ Imprint recognition sites that match spatial configuration and coordination environment can enhance Cu in complex water bodies. 2+ Its selective recognition and directional migration capabilities reduce Na + Mg 2+ Zn 2+ The coexisting cations compete with and interfere with the copper migration and enrichment process; furthermore, the sheet-like structure of graphene oxide can form hydrophilic mass transfer channels on or near the membrane surface, and its oxygen-containing functional groups such as hydroxyl, carboxyl, and epoxy groups can participate in the functionalization construction of the membrane interface, improving the Cu... 2+ This improves the contact efficiency with imprinted sites and enhances the structural stability of the copper ion imprinted functional layer during electric field driving, liquid flow scouring, and periodic regeneration processes.

[0016] Furthermore, by introducing coordination components containing amino, carboxyl, hydroxyl, and / or thiol groups into GO-N / O / S-Cu-IIP-CEM, Cu 2+ Ions can form multi-site cooperative coordination structures such as N / O / S; the recognition holes formed after template removal not only have size matching but also coordination environment matching, thereby improving the membrane's resistance to Cu. 2+ Selectivity and adaptability to complex water conditions.

[0017] 3) The CO3 generated during the percarbonate oxidation process of this invention2- / HCO3 - Alkalinity is no longer discharged as ineffective background salt, but instead participates in the solid-state conversion of copper as an internal circulating reaction medium. This design reduces the amount of precipitating agents such as external alkali, carbonates, or sulfides, lowering operating costs and the risk of secondary pollution. Furthermore, traditional MCDI or membrane separation processes typically only yield copper-containing concentrates, requiring subsequent independent precipitation or solid-liquid separation. This invention releases Cu enriched within the membrane through polarity switching. 2+ This allows it to come into contact with the carbonate-rich internal circulating liquid in the recovery area, creating a locally supersaturated environment that induces the formation of solid copper crystal products such as basic copper carbonate and copper carbonate, thereby increasing the value of copper resource recovery.

[0018] This invention can be used to treat wastewater containing copper complexes such as Cu(II)-EDTA, copper citrate, ammonia-copper complex, and copper aminocarboxylate. Through a continuous coupled process of complex structure transformation, membrane interface selective recognition, and internal circulation crystallization recovery, the stable removal and recovery of copper under complex water quality conditions can be improved. This invention utilizes an electric field to drive Cu... 2+ Migration, enrichment, and release are carried out under mild operating conditions; at the same time, in-situ crystallization of copper ions is achieved through endogenous carbonate circulation, reducing the need for external chemical treatment of copper-containing concentrates, which helps to reduce overall treatment costs and subsequent disposal pressure.

[0019] 4) The graphene oxide-assisted copper ion imprinted cation exchange membrane of the present invention can be used cyclically during adsorption enrichment and polarity reversal release. The internal circulating liquid can be diverted, reused and replenished within the system. The device structure is compatible with existing MCDI modular components and has good prospects for continuous operation, modular integration and engineering application.

[0020] Therefore, this application effectively solves the problem of multi-stage treatment of copper-containing wastewater and the removal of free Cu. 2+ Effective identification and enrichment, reuse of alkalinity in the treatment system, and free Cu 2+ Technical problems such as effective recycling are addressed. Other features and advantages of the invention will be set forth in the following description and will be apparent in part from the description, or may be learned by practicing the invention; the main objects and other advantages of the invention may be realized and obtained by means of the methods particularly pointed out in the description. Attached Figure Description

[0021] Figure 1 This is a diagram of an experimental setup for a multi-stage treatment method of copper-containing wastewater driven by an electric field assisted by graphene oxide. Figure 2 This is a schematic diagram of the structure of a multi-coordinate ion treatment system; Figure 3 This is a partial structural breakdown diagram of a multi-coordinate ion treatment system; Figure 4 It is the contact angle of the cation exchange membrane before modification; Figure 5 It is the contact angle of the modified GO-N / O / S-Cu-IIP-CEM; Figure 6 This is a comparison of SEM analysis results between the cation exchange membrane and the GO-N / O / S-Cu-IIP-CEM. Figure 7 This is a graph showing the changes in copper removal from copper-containing photovoltaic wastewater. Figure 8 It is the effect of GO-N / O / S-Cu-IIP-CEM on Cu under multi-ion coexistence conditions. 2+ Selective adsorption capacity diagram.

[0022] Figure reference numerals: 1-Wastewater pretreatment tank, 2-Ozone generator, 3-Gas-liquid mixer, 4-Water pump, 5-Multi-coordination ion treatment system, 51-First end sealing plate, 52-First electrode assembly, 53-Cation exchange membrane, 54-First flow channel spacer, 55-Anion exchange membrane, 56-Second flow channel spacer, 57-Multi-stage treatment membrane, 58-Second electrode assembly, 59-Second end sealing plate, 6-Effluent tank, 7-Conductivity meter, 8-Multimeter, 9-Inlet water channel, 10-Concentrated water outlet water channel, 11-Desalinated water outlet water channel. Detailed Implementation

[0023] The technical solutions of the present invention will be described in detail below through embodiments. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solutions of the present invention, and should not be construed as limiting the technical solutions of the present invention. Example

[0024] The experiment used actual copper-containing wastewater discharged by a photovoltaic company as the treatment object. Copper in the wastewater mainly existed in complexed and partially free states, with an initial total copper concentration of approximately 150 mg / L. The wastewater was then treated in the experimental apparatus.

[0025] Combination Figures 1 to 8 As shown, the method for multi-stage treatment of copper-containing wastewater driven by an electric field assisted by graphene oxide is further illustrated. The specific steps are as follows: S1. Sodium percarbonate and ozone are added to wastewater pretreatment tank 1 to create an active oxidation environment, which weakens or destroys the coordination bonds of Cu-N and Cu-O, causing the complexed copper in the wastewater to gradually transform into free Cu. 2+ Meanwhile, the generated carbonate components are retained and used as the reaction medium for subsequent internal circulation crystallization recovery.

[0026] In this process, the sodium percarbonate in the pretreatment tank S1 is designated as SPC. The carbonate / bicarbonate released by the dissolution of SPC and the alkalinity of the system are retained in the treatment liquid as the internal reaction medium for the solid-state recovery of copper. The treatment liquid is connected to the gas-liquid mixer 3 via a water pump 4. The gas-liquid mixer 3 is also connected to the ozone generator 2. After the treatment liquid and ozone are mixed by the gas-liquid mixer 3, they enter the pretreatment tank for Cu recovery. 2+ Solid-state recycling.

[0027] S2, Free Cu 2+ As water flows into the multi-coordinate ion treatment system 5, the anion exchange membrane 55 is centrally located in the multi-coordinate ion treatment system 5, with cation exchange membranes 53 and multi-stage treatment membranes 57 located on both sides respectively.

[0028] For the multi-coordination ion treatment system 5 in S2, the multi-coordination ion treatment system 5 includes a first end sealing plate 51, a first electrode assembly 52, a cation exchange membrane 53, a first flow channel spacer layer 54, an anion exchange membrane 55, a second flow channel spacer layer 56, a multi-stage treatment membrane 57, a second electrode assembly 58, and a second end sealing plate 59 arranged sequentially; wherein the first electrode assembly 52 is a positive electrode and the second electrode assembly 58 is a negative electrode.

[0029] In this embodiment, the multi-stage treatment membrane 57 is a graphene oxide-assisted copper ion imprinted cation exchange membrane, denoted as GO-N / O / S-Cu-IIP-CEM. It uses the cation exchange membrane 53 as the base membrane and constructs a graphene oxide hydrophilic mass transfer layer and a copper ion imprinted functional layer containing N / O / S multi-coordination sites on its surface or near the surface.

[0030] In this embodiment, both the first electrode assembly 52 and the second electrode assembly 58 include graphite plates with a layer of activated carbon fiber cloth attached to the surface of the graphite plates. The graphite electrodes are 25cm × 8cm in size and 0.5cm thick, and are respectively disposed on both sides inside the device. Each graphite electrode has a layer of activated carbon fiber cloth 522 with a size of 25cm × 7cm attached to its surface. Due to its large specific surface area and good conductivity, it can serve as the main electrode material for charge collection and conduction, thereby improving the stability of the device's electrical signal output. The dimensions of the first electrode assembly 52, cation exchange membrane 53, first flow channel spacer layer 54, anion exchange membrane 55, and second flow channel spacer layer 56 are all adapted to the electrode assembly.

[0031] The first flow channel spacer layer 54 and the second flow channel spacer layer 56 are polyester mesh spacers with a mesh size of 80-150 mesh. Their overall dimensions are set according to the effective reaction area to form independent fluid channels and ensure uniform solution distribution within the membrane module. These fluid channels are used to achieve Cu... 2+Under the influence of an electric field, it migrates and accumulates at the GO-N / O / S-Cu-IIP-CEM interface.

[0032] The preparation steps of GO-N / O / S-Cu-IIP-CEM in S2 are as follows: S21. Base film pretreatment, surface activation and adhesion layer construction: The base film is cut to a size that matches the first electrode assembly 52 or the second electrode assembly 58, and then pretreated sequentially in deionized water, acid solution, and salt solution. The pretreated base film is then placed in a 1-3 g / L dopamine hydrochloride solution using a Tris-HCl buffer system with a pH of 8.0-8.8 and reacted at 20-35°C for 4-24 h to allow dopamine to self-polymerize on the film surface to form a polydopamine adhesion layer. This step is used to improve the adhesion stability of subsequent graphene oxide and N / O / S multi-coordination imprinted functional layers on the film surface.

[0033] S22, Graphene oxide hydrophilic mass transfer layer loading: A graphene oxide dispersion with a concentration of 0.05–1.0 g / L was prepared and ultrasonically dispersed for 30–120 min to form a uniform and stable dispersion system. The base membrane treated in S1 was immersed in the graphene oxide dispersion and reacted with shaking at room temperature for 2–12 h to load graphene oxide onto the membrane surface or near the surface layer. After loading, the unstable graphene oxide was gently rinsed with deionized water to remove it, resulting in a graphene oxide-modified cation exchange membrane, denoted as GO-CEM. The purpose of this step is to construct hydrophilic sheet mass transfer channels and provide oxygen-containing functional groups and supporting interfaces for the subsequent N / O / S multi-coordinated copper ion imprinted layer.

[0034] S23, N / O / S multi-coordination function single unit load: GO-CEM was functionalized by immersing it in a mixed solution containing N / O / S multi-coordination functional components; polyethyleneimine was prepared as an aqueous solution of 0.5–3.0 wt%, and carboxymethyl chitosan was prepared as a solution of 0.5–2.0 wt%; at the same time, 0.01–1.0 wt% of L-cysteine ​​or other thiol-containing functional components were added to introduce N / O / S multi-coordination sites of amino, carboxyl, hydroxyl and thiol groups onto the membrane surface; the reaction conditions were room temperature shaking for 4–12 h.

[0035] Polyethyleneimine, carboxymethyl chitosan, and L-cysteine ​​are fixed on graphene oxide and the membrane surface through hydrogen bonding, electrostatic adsorption, and amidation to form an N / O / S multi-coordination functional layer. After the reaction is completed, a GO-N / O / S functionalized cation exchange membrane is obtained, denoted as GO-N / O / S-CEM.

[0036] S24, copper ion template coordination: Place GO-N / O / S-CEM in Cu 2+ Coordination reaction occurs in template solution; Cu 2+ The solution was a 10–30 mmol / L CuCl2 solution, pH adjusted to 4.5–5.5, reaction time 6–24 h, and reaction temperature 20–35 °C. In this process, amino, carboxyl, hydroxyl, and mercapto groups on the membrane surface and in the outer layer, as well as the oxygen-containing functional groups of graphene oxide, reacted with Cu... 2+ Coordination complexation occurs, forming Cu 2+ -N / O / S multi-coordination complex structure; this step causes functional groups to surround Cu 2+ The ions arrange themselves spatially to facilitate the subsequent formation of Cu. 2+ The imprint recognition site is based on matching radius, hydration structure, charge density, and coordination configuration.

[0037] S25, Cross-linked fixed imprint structure: Remove the coordinated membrane and gently rinse the unbonded Cu on the membrane surface with deionized water. 2+ The mixture was then placed in a 0.5–2.5 wt% glutaraldehyde solution for a cross-linking reaction for 2–8 h at room temperature or 30–40 °C. Glutaraldehyde reacted with the amino groups in polyethyleneimine, chitosan, or carboxymethyl chitosan to form a cross-linked network, thereby fixing the spatial configuration and arrangement of the N / O / S coordinating groups. The glutaraldehyde concentration was 0.5–2.0 wt%, and the cross-linking time was 3–6 h. After cross-linking, Cu was obtained. 2+ Load-type GO-N / O / S-Cu-IIP-CEM.

[0038] In addition, the cross-linked Cu 2+ The supported membrane was eluted in 0.1–1.0 mol / L hydrochloric acid solution for 6–24 h; the eluent was replaced every 2–4 h during elution until the Cu in the eluent was reduced. 2+ The concentration tends to stabilize or approach the blank value. The eluted GO-N / O / S-Cu-IIP-CEM is repeatedly rinsed with deionized water until the pH of the washing solution is close to neutral. Then, the membrane is immersed in a 0.01–0.1 mol / L NaCl solution for 6–12 hours to convert the membrane into a stable ionic form suitable for the operation of the multi-coordinate ion treatment system. Finally, the membrane is stored in deionized water or a low-concentration NaCl solution to prevent drying and shrinkage or cracking of the functional layer. For long-term storage, it should be sealed and stored at 4°C.

[0039] S3, Free Cu 2+After entering, it is separated into a concentrated ion region and a dilute ion region by the anion exchange membrane 55. The concentrated ion region is the cation exchange membrane region located at the positive electrode. Cu 2+ The wastewater is desorbed and enriched at the positive electrode by the electric field, and then discharged from this point for further treatment.

[0040] In addition, copper-containing wastewater is rich in Cl- ions. - Cl - Driven by the electric field, the ions migrate towards the concentrated ion region at the positive electrode, while the anion exchange membrane 55 allows Cl in the dilute ion region to migrate. - The Cu atoms migrate and accumulate; thus, the desorbed Cu atoms accumulate in the concentrated ion region. 2+ and migration of Cl - This creates a high-concentration ion region.

[0041] S4, the desalination region is the area where the GO-N / O / S-Cu-IIP-CEM is located at the negative electrode. Under the action of the electric field, the fixed negative charge groups of the base film selectively conduct cations and inhibit the entry of anions through the Donnan repulsion effect.

[0042] In this embodiment, Cu 2+ Under the influence of the hydrophilic mass transfer layer channels, it rapidly enters the membrane interface and selectively complexes with the N / O / S coordination recognition sites in the imprinted functional layer. Simultaneously, the imprinted holes in the functional layer also coordinate with Cu through coordination. 2+ Perform selective identification and enrichment.

[0043] In this embodiment, the surface or outer layer of GO-N / O / S-Cu-IIP-CEM has a Cu content. 2+ The constructed imprints identify holes and N / O / S multicoordination sites of amino, carboxyl, hydroxyl, and / or thiol groups; under the action of an applied low-voltage electric field, Cu is formed through oxidation transformation. 2+ Directed migration towards the functional membrane interface and electrode region, GO-N / O / S-Cu-IIP-CEM combines cation exchange conduction, hydrophilic mass transfer of graphene oxide, and copper ion imprinting recognition, enabling it to migrate towards Na+. + Mg 2+ Zn 2+ Cu preferentially identifies, captures, and enriches itself in the presence of multiple coexisting cations. 2+ This allows for the selective migration efficiency of copper ions and the enrichment of the membrane interface.

[0044] S5, Cu in the depleted ion region 2+The copper-containing wastewater in the GO-N / O / S-Cu-IIP-CEM region is recognized, captured, and adsorbed. Anions are attracted by the positive electrode electric field and migrate to the concentrated ion region. Consequently, the copper-containing wastewater in the desalination region is treated into freshwater or low-salinity water, and the GO-N / O / S-Cu-IIP-CEM enriches Cu. 2+ Then it enters the regeneration and recycling stage, thus completing the treatment of copper-containing wastewater pollution.

[0045] In application, the first end sealing plate 51 and the first end sealing plate 52 are used to encapsulate and form the multi-coordinate ion treatment system 5. Both the first end sealing plate 51 and the first end sealing plate 52 have a water inlet channel 9 at their bottoms, which is used to allow water to enter the S1-treated system containing free Cu. 2+ Wastewater; two inlet channels 9 are provided on the first end sealing plate 51.

[0046] The first end sealing plate 51 is located at the positive electrode, and a concentrated water outlet channel 10 is provided at the top of the first end sealing plate 51. The concentrated water outlet channel 10 is used to discharge the wastewater with high concentration of ions after S3 treatment. The second end sealing plate 59 is located at the negative electrode, and a fresh water outlet channel 11 is provided at the top of the first end sealing plate 51. The fresh water outlet channel 11 is used to discharge the fresh water or low saline water after S5 treatment. The fresh water outlet channel 11 is connected to the effluent tank 6. The effluent tank 6 is also equipped with a conductivity meter 7, a multimeter 8, and a data acquisition system. The conductivity meter 7 is used to monitor the conductivity of the product water in real time, the multimeter 8 is used to record the operating current signal, and the relevant data is recorded and analyzed through the data acquisition system.

[0047] Furthermore, after the copper-containing wastewater in S5 is treated by GO-N / O / S-Cu-IIP-CEM, it enters the regeneration and recycling stage. By switching the polarity of the first electrode assembly 52 and the second electrode assembly 58, the ion migration direction is changed, allowing the Cu enriched on the electrode surface and the GO-N / O / S-Cu-IIP-CEM interface to be regenerated. 2+ Released into the regeneration crystallization channel, resulting in the release of a high concentration of Cu. 2+ With CO3 2- / HCO3 - and OH - Synchronous contact in localized areas creates a high ion product and a localized supersaturated environment, inducing the formation of solid copper crystals of basic copper carbonate; the generated crystals are then recovered through sedimentation, filtration, or other solid-liquid separation methods.

[0048] Through wettability testing, combined with Figure 4 and Figure 5 As shown, the unmodified cation exchange membrane 53 exhibits a relatively large surface contact angle of 139.2° under the test conditions, indicating poor aqueous wettability and limited ability of the aqueous solution to spread on the membrane surface. This is unfavorable for the absorption of Cu from copper-containing wastewater. 2+Rapid approach and mass transfer to the membrane interface. After modification, the contact angle of the resulting GO-N / O / S-Cu-IIP-CEM surface decreased to 87.8°, below 90°, indicating a significant enhancement in the hydrophilicity of the membrane surface. This is because the phenolic hydroxyl and amino groups in the polydopamine layer, as well as the numerous amino sites in polyethyleneimine, improve the surface polarity and aqueous compatibility of the membrane; simultaneously, Cu... 2+ The coordination, cross-linking, and elution processes create imprinted cavities with copper ion recognition capabilities on or near the membrane surface, thereby enhancing the Cu... 2+ Accessibility to the membrane interface. The above structure is beneficial for reducing mass transfer resistance at the membrane surface and promoting Cu... 2+ It migrates and binds to imprint recognition sites, thereby improving the selective transport, interfacial enrichment, and subsequent release efficiency of copper ions under electric field-driven conditions.

[0049] Scanning electron microscopy (SEM) analysis: The surface morphology of the unmodified pristine cation exchange membrane 53 and the GO-N / O / S-Cu-IIP-CEM was observed using scanning electron microscopy. For example... Figure 6 As shown, (a) is the original cation exchange membrane 53, and the results show that the surface of the cation exchange membrane 53 has a relatively regular open pore structure; (b) is a GO-N / O / S-Cu-IIP-CEM, which has been loaded with functional monomers and Cu 2+ After coordination and crosslinking treatment, the membrane surface is covered by a uniform and continuous polymer functional layer, and the original pore boundaries are weakened, indicating that the imprinted polymer layer has been successfully constructed. 2+ After elution, no obvious cracks, collapses, or flaking were observed on the GO-N / O / S-Cu-IIP-CEM surface, and a uniformly distributed nanoscale pore structure was observed. These pores can be attributed to specific recognition sites formed after template ion removal, indicating that the GO-N / O / S-Cu-IIP-CEM is suitable for Cu preparation. 2+ Structural basis of selective adsorption and transport.

[0050] During the experiment, three parallel experiments were conducted under optimized conditions: O3 concentration of 0.3 mM, SPC concentration of 14 mM, electrode spacing of 3 mm, and influent flow rate of 1.0 mL / min, to verify the operational stability of the system. Figure 7 As shown, after 120 minutes of pretreatment in the wastewater pond, the copper concentration in the water decreased from approximately 150 mg / L to approximately 31.5 mg / L, indicating that the system can effectively weaken the complexed copper structure and promote copper speciation. During operation, Cu... 2+Driven by a low-voltage electric field, copper migrates towards the GO-N / O / S-Cu-IIP-CEM and electrode interface, where it is preferentially enriched. After 80 minutes of continuous system operation, up to a total time of 200 minutes, the effluent copper concentration drops below 0.29 mg / L, which is lower than the ICP-OES detection limit, indicating a copper removal rate close to 100%. Furthermore, the effluent copper concentration is significantly lower than the total copper emission limit of 0.5 mg / L in the "Electroplating Pollutant Discharge Standard" GB21900-2008.

[0051] like Figure 8 As shown, experimental results indicate that in Na + Ca 2+ Mg 2+ Zn 2+ Under conditions of coexisting ions, GO-N / O / S-Cu-IIP-CEM for Cu 2+ Exhibiting excellent selective adsorption capacity, Cu 2+ The adsorption capacity was significantly higher than that of other competing ions. This significant improvement stemmed from a triple synergistic mechanism: 1) the charge sieving and ion exchange effects of the cation exchange membrane 53; 2) the complexation effect of the N / O / S multi-coordination copper ion-imprinted cation exchange membrane surface assisted by graphene oxide, which has N, O, and S multi-coordination sites; 3) Cu 2+ The selective effect of imprinted pores. The combined effect of these three factors enables the membrane to preferentially capture Cu in complex ionic environments. 2+ The interference from coexisting ions is significantly reduced. Compared with traditional cation exchange membranes, GO-N / O / S-Cu-IIP-CEM exhibits stronger anti-competitive adsorption capacity and selective stability, making it more suitable for complex copper-containing wastewater containing Cu. 2+ Selective separation, enrichment and recovery.

[0052] This invention is applicable to the treatment of copper-containing wastewater in photovoltaic, electroplating, and chemical industries, achieving efficient purification and copper metal recovery. It is suitable for treating low-concentration copper-containing wastewater, copper-containing cleaning solutions, copper-containing regenerated solutions, and bypass treatment of industrial circulating water. Unlike traditional treatment methods that only aim to meet discharge standards, this technology transforms copper from a free state into a stable solid crystalline product, making it suitable for engineering scenarios that require both pollution control and copper resource recovery.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for multi-stage treatment of copper-containing wastewater driven by a graphene oxide-assisted electric field, characterized in that, The specific steps are as follows: S1, adding sodium percarbonate and ozone into the wastewater pretreatment tank for treating copper-containing wastewater to form an active oxidation environment, so that the complexed copper in the wastewater is gradually converted into free Cu 2+ ; at the same time, the generated carbonate component is retained and serves as a source of reaction medium for subsequent internal circulation crystallization recovery; S2, Free Cu 2+ As water flows into the multi-coordinate ion treatment system, the anion exchange membrane is centrally located in the system, with cation exchange membranes and multi-stage treatment membranes on both sides. Among them, the multi-stage treatment membrane is denoted as GO-N / O / S-Cu-IIP-CEM, which uses a cation exchange membrane as the base membrane and constructs a graphene oxide hydrophilic mass transfer layer and a copper ion imprinted functional layer containing N / O / S multi-coordination sites on the surface or near the surface. S3, Free Cu 2+ After entering, it is separated into a concentrated ion region and a dilute ion region by an anion exchange membrane. The concentrated ion region is the cation exchange membrane region located at the positive electrode. Cu 2+ At the positive electrode, it is driven by the electric field to desorb and thus accumulate; S4, the desalination region is the area where the GO-N / O / S-Cu-IIP-CEM is located at the negative electrode. Under the action of the electric field, the fixed negative charge groups of the base film selectively conduct cations and inhibit the entry of anions through the Donnan repulsion effect. Cu 2+ Under the influence of the hydrophilic mass transfer layer channels, it rapidly enters the membrane interface and selectively complexes with the N / O / S coordination recognition sites in the imprinted functional layer. Simultaneously, the imprinted holes in the functional layer also coordinate with Cu through coordination. 2+ Perform selective identification and enrichment; S5, Cu in the dewy ion region 2+ The copper-containing wastewater in the GO-N / O / S-Cu-IIP-CEM region is recognized, captured, and adsorbed. Anions are attracted by the positive electrode electric field and migrate to the concentrated ion region. Consequently, the copper-containing wastewater in the desalination region is treated into freshwater or low-salinity water, and the GO-N / O / S-Cu-IIP-CEM enriches Cu. 2+ Then it enters the regeneration and recycling stage, thus completing the treatment of copper-containing wastewater pollution.

2. The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving as described in claim 1, characterized in that, The sodium percarbonate in the pretreatment tank of S1 is referred to as SPC. The carbonate / bicarbonate and system alkalinity released by the dissolution of SPC are retained in the treatment liquid as the endogenous reaction medium for the solidification and recovery of copper. The treated liquid is connected to a gas-liquid mixer via a water pump. This gas-liquid mixer is also connected to an ozone generator. After the treated liquid and ozone are mixed in the gas-liquid mixer, they enter the pretreatment tank for Cu treatment. 2+ Solid-state recycling.

3. The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving as described in claim 1, characterized in that, In S2, the multi-coordinate ion treatment system includes a first end cap, a first electrode assembly, a cation exchange membrane, a first flow channel spacer, an anion exchange membrane, a second flow channel spacer, a multi-stage treatment membrane, a second electrode assembly, and a second end cap, arranged sequentially; wherein the first electrode assembly is a positive electrode and the second electrode assembly is a negative electrode.

4. The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving as described in claim 3, characterized in that, Both the first electrode assembly and the second electrode assembly contain graphite plates and have a layer of activated carbon fiber cloth attached to the surface of the graphite plates. The first flow channel spacer and the second flow channel are used to form independent fluid channels and ensure that the solution is uniformly distributed inside the membrane module. The fluid channels are used to achieve Cu 2+ Under the influence of an electric field, it migrates and accumulates at the GO-N / O / S-Cu-IIP-CEM interface.

5. The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving as described in claim 3, characterized in that, The preparation steps of GO-N / O / S-Cu-IIP-CEM in S2 are as follows: S21. The base film is pretreated by sequentially placing it in deionized water, acid solution and salt solution; then the pretreated base film is placed in dopamine hydrochloride solution to allow dopamine to self-polymerize on the film surface to form a polydopamine adhesion layer. S22. Immerse the base membrane treated in S21 into a graphene oxide dispersion to load graphene oxide onto the membrane surface or near the surface layer; after loading is completed, a graphene oxide modified cation exchange membrane is obtained, denoted as GO-CEM. S23. The GO-CEM is immersed in a mixed solution containing N / O / S multi-coordination functional components for functionalization treatment, so that N / O / S multi-coordination sites of amino, carboxyl, hydroxyl and thiol groups are introduced into the membrane surface at the same time; after the reaction is completed, the GO-N / O / S functionalized cation exchange membrane is obtained, which is denoted as GO-N / O / S-CEM. S24. Place GO-N / O / S-CEM in Cu 2+ Coordination reactions occur in the template solution; amino, carboxyl, hydroxyl, and thiol groups on the membrane surface and outer layer, as well as oxygen-containing functional groups of graphene oxide, react with Cu. 2+ Coordination complexation occurs, forming Cu 2+ -N / O / S multi-coordination composite structure; S25. The membrane that has completed coordination in S24 is placed in a glutaraldehyde solution for cross-linking reaction. After cross-linking is completed, Cu is obtained. 2+ Load-type GO-N / O / S-Cu-IIP-CEM.

6. The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving as described in claim 5, characterized in that, GO-N / O / S-Cu-IIP-CEM surface or surface layer has Cu 2+ The constructed imprints identify holes and N / O / S multicoordination sites of amino, carboxyl, hydroxyl, and / or thiol groups; under the action of an applied low-voltage electric field, Cu is formed through oxidation transformation. 2+ Directed migration towards the functional membrane interface and electrode region, GO-N / O / S-Cu-IIP-CEM combines cation exchange conduction, hydrophilic mass transfer of graphene oxide, and copper ion imprinting recognition, enabling it to migrate towards Na+. + Mg 2+ Zn 2+ Cu preferentially identifies, captures, and enriches itself in the presence of multiple coexisting cations. 2+ This allows for the selective migration efficiency of copper ions and the enrichment of the membrane interface.

7. The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving as described in claim 5, characterized in that, The copper-containing wastewater is rich in Cl- ions. - Cl - Driven by the electric field, they migrate towards the concentrated ion region at the positive electrode, while the anion exchange membrane allows Cl in the dilute ion region to migrate. - Accumulation through migration; This resulted in the enrichment of desorbed Cu in the concentrated ion region. 2+ and migration of Cl - This creates a high-concentration ion region.

8. The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving as described in claim 5, characterized in that, The first end cap and the first end cap are used to encapsulate and form a multi-coordinate ion treatment system. Both the first end cap and the first end cap have water inlet channels at their bottoms for the water to enter the system containing free Cu after S1 treatment. 2+ Wastewater; the inlet channel is provided with no less than two at the first end sealing plate; The first end cap is located at the positive electrode, and a concentrated water outlet is provided at the top of the first end cap; the concentrated water outlet is used to discharge the wastewater with high concentration of ions after S3 treatment; The second end cap is located at the negative electrode, and a freshwater outlet is located at the top of the first end cap. The freshwater outlet is used to discharge freshwater or low-salinity water after S5 treatment. The freshwater outlet is connected to the outlet pool, which is also equipped with a conductivity meter, a multimeter, and a data acquisition system. The conductivity meter is used to monitor the conductivity of the product water in real time, the multimeter is used to record the operating current signal, and the relevant data is recorded and analyzed through the data acquisition system.

9. The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving as described in claim 8, characterized in that, After the copper-containing wastewater in S5 is treated by GO-N / O / S-Cu-IIP-CEM, it enters the regeneration and recovery stage. By switching the electrode polarities of the first and second electrode components, the ion migration direction is changed, allowing the Cu enriched on the electrode surface and at the GO-N / O / S-Cu-IIP-CEM interface to be regenerated. 2+ Released into the regeneration crystallization channel, resulting in the release of a high concentration of Cu. 2+ With CO3 2- / HCO3 - and OH - Synchronous contact in localized areas creates a high ion product and a localized supersaturated environment, inducing the formation of solid copper crystals of basic copper carbonate; the generated crystals are then recovered through sedimentation, filtration, or other solid-liquid separation methods.

10. The method for multi-stage treatment of copper-containing wastewater based on graphene oxide-assisted electric field driving as described in claim 1, characterized in that, Copper-containing wastewater includes copper-containing wastewater from photovoltaic manufacturing, electroplating, electronic cleaning, chemical processing, or other polluted wastewater containing complexed copper, free copper, and various coexisting salt ions.

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