An electrodialysis system and its usage method

Abstract

This invention provides an electrodialysis system and its usage method, including a control unit and a multi-stage series electrodialysis device. The electrodialysis device is internally equipped with modified ion exchange membranes and modified ion exchange resins, representing an innovation at the material level that improves anti-fouling performance and extends service life from the source. Furthermore, the system is equipped with an ion exchange resin regeneration unit, enabling efficient resin regeneration without chemical reagents. The multi-stage series operation mode of this system involves the first few stages operating in a counter-current manner with progressively decreasing treatment voltage, while the final stage employs a cross-flow mode with some concentrate returned to the preceding stages, thereby stabilizing the feed water quality and mitigating membrane scaling and fouling. The control unit integrates multi-sensor data to adjust operating parameters in real time and features differential pressure-triggered backwashing and periodic chemical cleaning functions, achieving adaptive, efficient, and long-term stable operation of the system.

Description

Technical Field

[0001] This invention belongs to the field of electrodialysis technology, specifically relating to an electrodialysis system and its usage method. Background Technology

[0002] Electrodialysis (ED) is a membrane separation technology that utilizes ion exchange membranes to achieve selective ion migration under a direct current electric field. It is widely used in brackish water desalination, industrial wastewater treatment, and other fields. However, traditional electrodialysis technology still faces the following core problems:

[0003] Firstly, during long-term operation, pollutants accumulate on the membrane surface, leading to fouling and scaling. This results in a decrease in ion migration efficiency.

[0004] Furthermore, the desalination rate of membrane modules is difficult to improve further due to limitations in membrane performance and operating conditions. Moreover, frequent use of acid and alkali reagents to regenerate the resin increases operating costs and generates secondary pollution.

[0005] Therefore, there is an urgent need to develop an efficient, pollution-resistant, and low-cost electrodialysis system and its control method to overcome the limitations of traditional technologies. Summary of the Invention

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An electrodialysis system includes: multiple electrodialysis devices arranged in series, each electrodialysis device comprising: an ion exchange membrane assembly, an ion exchange resin, an anode electrode plate, a cathode electrode plate, and an ion exchange resin regeneration unit; wherein the ion exchange membrane assembly includes a modified cation exchange membrane and a modified anion exchange membrane, the modified cation exchange membrane and the modified anion exchange membrane being alternately arranged between the anode electrode plate and the cathode electrode plate, and multiple alternately arranged concentrate chambers and desalination chambers being formed between adjacent modified cation exchange membranes and modified anion exchange membranes; the inlet of the next-stage electrodialysis device is connected to the outlet of the desalination chamber of the previous-stage electrodialysis device; the modified cation exchange membrane includes a cation-based membrane and a composite coating disposed on the surface of the cation-based membrane, the composite coating being a copolymer of pyrrole and ethyl silicate with a nanoscale protrusion structure, and... The copolymer is incorporating sulfonic acid groups; the modified anion exchange membrane comprises an anion-based membrane and a modified coating disposed on the surface of the anion-based membrane, the modified coating being a three-dimensional network layer formed by crosslinking polyethyleneimine and dopamine; the ion exchange resin fills the desalination chamber, the ion exchange resin comprising modified cation exchange resin and modified anion exchange resin, the modified cation exchange resin being a cation exchange resin matrix loaded with iron oxide; the modified anion exchange resin being an anion exchange resin matrix grafted with quaternary ammonium groups; the exchange resin regeneration unit comprises a titanium-based ruthenium-iridium anode and a titanium-based ruthenium-iridium cathode, the titanium-based ruthenium-iridium anode and the titanium-based ruthenium-iridium cathode being disposed on both sides of the desalination chamber, after the titanium-based ruthenium-iridium anode and the titanium-based ruthenium-iridium cathode are energized, driving the ions adsorbed by the ion exchange resin to migrate directionally and desorb, restoring the adsorption capacity of the ion exchange resin.

[0008] In some embodiments, the electrodialysis system further includes a concentrate circulation pipeline, one end of which is connected to the outlet of the concentrate chamber of the last stage of the electrodialysis device, and the other end of which is connected to the inlet of each stage of the electrodialysis device upstream of the last stage of the electrodialysis device.

[0009] In some embodiments, in the last stage of the electrodialysis apparatus, the liquid flow in the desalination chamber and the concentrate chamber flows at a set angle to the surface of the ion exchange membrane assembly; in each stage of the electrodialysis apparatus upstream of the last stage, the liquid flow direction in the desalination chamber and the concentrate chamber is opposite.

[0010] In some embodiments, the electrodialysis system includes at least four electrodialysis devices, which are arranged in the following order: a primary electrodialysis device, a secondary electrodialysis device, a tertiary electrodialysis device, and a quaternary electrodialysis device.

[0011] In some embodiments, the operating voltages in the primary electrodialysis device, the secondary electrodialysis device, and the tertiary electrodialysis device are 12 V, 10 V, and 8 V, respectively.

[0012] In some embodiments, the electrodialysis system further includes: a controller, a voltage sensor, a current sensor, and multiple water quality detectors; the voltage sensor is used to collect the voltage value within the electrodialysis device in real time; the current sensor is used to collect the current value within the electrodialysis device in real time; the water quality detectors are used to monitor the influent and product water quality of the electrodialysis device in real time, and the multiple water quality detectors include at least one of a total dissolved solids detector, a chemical oxygen demand detector, and a pH detector; the electrodialysis device further includes a power supply, the positive and negative terminals of which are connected to an anode electrode plate and a cathode electrode plate, respectively; the controller is controlled and connected to the power supply, the voltage sensor, the current sensor, and the water quality detectors, and the controller adjusts the output value of the power supply according to the detection data of the voltage sensor, the current sensor, and the water quality detectors.

[0013] In some embodiments, the electrodialysis system further includes a differential pressure detector and a backwashing assembly, wherein the differential pressure detector is used to detect the pressure difference across the ion exchange membrane assembly;

[0014] The backwashing assembly includes a backwash water pipe, a backwash pump, and multiple flushing nozzles. One end of the backwash water pipe is connected to the flushing nozzle, and the opening of the flushing nozzle faces the ion exchange membrane assembly. The backwash pump is mounted on the backwash water pipe to provide power for transporting the backwash water. The differential pressure detector is connected to the backwash pump. When the differential pressure detected by the differential pressure detector reaches or exceeds a set value, it sends a start signal to the backwash pump, which then drives the backwash water to flow through the flushing nozzles to backwash the ion exchange membrane assembly.

[0015] In some embodiments, the backwash water is a citric acid solution or a sodium hydroxide solution.

[0016] The present invention also provides a method for using the above-mentioned electrodialysis system, comprising the following steps: feeding raw water to be treated into multiple electrodialysis devices connected in series for stepwise desalination, with the last electrodialysis device producing product water; after the electrodialysis device has been running for a set time, isolating the desalination chamber, starting the ion exchange resin regeneration unit, and electrochemically regenerating the ion exchange resin in the desalination chamber, so that the ions desorbed from the ion exchange resin migrate to the concentrate chamber, thereby restoring the adsorption capacity of the ion exchange resin.

[0017] In some embodiments, the electrodialysis system further includes a concentrate circulation pipeline, one end of which is connected to the outlet of the concentrate chamber of the last stage electrodialysis device, and the other end of which is connected to the inlet of each stage of the electrodialysis device upstream of the last stage. The method of using the electrodialysis system further includes: returning a portion of the concentrate produced by the last stage electrodialysis device to each stage of the upstream electrodialysis device.

[0018] Compared with the prior art, the electrodialysis system and its usage method provided by the present invention have the following beneficial effects:

[0019] 1. The electrodialysis device provided by this invention achieves a simultaneous improvement in separation efficiency and durability through the synergistic design of modified ion exchange membranes and modified ion exchange resins. Specifically, the modified cation exchange membrane improves separation efficiency and durability. Permeability, improved by modified anion exchange membrane The improved permeability and enhanced hydrophilicity reduce the risk of contamination from organic matter and colloids. In addition, the modified cation exchange resin loaded with iron oxide can catalytically decompose organic matter through the Fenton reaction, while the modified anion exchange resin enhances the adsorption and binding of weakly dissociated substances by grafting quaternary ammonium groups. These material-level innovations endow the system with anti-pollution performance from the source and extend its service life.

[0020] 2. The electrodialysis device provided by this invention also uses a titanium-based ruthenium-iridium electrode to power the modified ion exchange resin, generating electricity through water electrolysis. and It can quickly replace the ions adsorbed by the exchange resin, restoring the exchange capacity of the exchange resin to more than 95% of its initial state. This design eliminates the use of traditional chemical regeneration agents. On the one hand, it eliminates the need for frequent resin replacement, significantly reducing operation and maintenance costs; on the other hand, it avoids the hazardous waste discharge problems caused by chemical agents, which is in line with the needs of green development.

[0021] 3. The electrodialysis system provided by this invention employs a stepped purification process to achieve deep treatment of raw water: four electrodialysis units are connected in series to form a treatment chain of "coarse desalination - fine desalination - terminal purification." The freshwater from the previous stage is directly used as the feed water for the next stage, causing the salinity of the water to decrease step by step, ultimately producing water that fully meets the requirements for high-purity water. The first three stages use countercurrent operation to maintain a stable concentration gradient, while the fourth-stage electrodialysis unit uses a cross-flow mode to create membrane shear scouring, significantly reducing the risk of contaminant adhesion and further ensuring treatment stability. Simultaneously, a portion of the concentrated water from the fourth-stage electrodialysis unit is returned to the first three stages of the electrodialysis unit; after mixing with the raw water, it can buffer calcium... 2+ Mg 2+ Fluctuations in the concentration of easily scale-forming ions make the influent water quality more stable, reducing scaling and fouling of the membrane module;

[0022] 4. The electrodialysis system provided by this invention has a closed-loop intelligent control function. By integrating data from multiple sensors such as voltage, current, TDS, COD, and pH through the controller, it analyzes and automatically adjusts the power output and operating parameters in real time (such as triggering the regeneration of modified ion exchange resin and cleaning of membrane modules). This enables the system to adapt and optimize its operation under different water quality conditions, ensuring stable treatment results and improving the overall energy efficiency ratio. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the electrodialysis device provided by the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of the multi-stage electrodialysis device provided by the present invention.

[0025] Explanation of icon numbers:

[0026] 100—Electrodialysis device; 101—Shell; 102—Inlet; 103—Anode electrode plate; 104—Cathode electrode plate; 105—Ion exchange membrane assembly; 106—Modified cation exchange membrane; 107—Modified anion exchange membrane; 108—Concentrate chamber outlet; 109—Desalinate chamber outlet; 110—Concentrate circulation pipeline;

[0027] 111—First-stage electrodialysis unit; 112—Second-stage electrodialysis unit; 113—Third-stage electrodialysis unit; 114—Fourth-stage electrodialysis unit;

[0028] 200—Controller; 300—DC power supply. Detailed Implementation

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0030] To keep the drawings concise, each figure only schematically shows the parts relevant to the invention, and these do not represent the actual structure of the product. Furthermore, to facilitate understanding, in some figures, only one of components with the same structure or function is schematically depicted, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one."

[0031] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0032] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Furthermore, in the description of this invention, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0034] This invention provides an electrodialysis system, such as Figure 1 As shown, the system includes multiple electrodialysis devices 100 and a control unit. Each electrodialysis device 100 includes: a housing 101, and an anode electrode plate 103, a cathode electrode plate 104, an ion exchange membrane assembly 105, ion exchange resin, and an ion exchange resin regeneration unit disposed inside the housing 101.

[0035] The ion exchange membrane assembly 105 includes a modified cation exchange membrane 106 and a modified anion exchange membrane 107, and the ion exchange resin includes a modified cation exchange resin and a modified anion exchange resin.

[0036] The anode electrode plate 103, the cathode electrode plate 104, the modified cation exchange membrane 106, and the modified anion exchange membrane 107 are arranged in parallel to each other.

[0037] Between the anode electrode plate 103 and the cathode electrode plate 104, modified cation exchange membranes 106 and modified anion exchange membranes 107 are arranged alternately. Multiple concentrate chambers and desalination chambers are formed between adjacent modified cation exchange membranes 106 and modified anion exchange membranes 107. The concentrate chambers and desalination chambers are arranged alternately, wherein the desalination chamber has a desalination outlet pipe and the concentrate chamber has a concentrate outlet pipe.

[0038] An electrode water chamber is provided between the anode electrode plate 103 and the adjacent modified cation exchange membrane 106 (or modified anion exchange membrane 107), and between the cathode electrode plate 104 and the adjacent modified anion exchange membrane 107 (or modified cation exchange membrane 106).

[0039] The modified cation exchange membrane described above is a cation-based membrane and a composite coating on the surface of the cation-based membrane. The composite coating is formed by the copolymerization reaction of pyrrole and ethyl silicate, resulting in a nanoscale protrusion structure on the surface of the cation-based membrane, and sulfonic acid groups (-SO3H) are introduced into the copolymer of pyrrole and ethyl silicate.

[0040] The modification process of the cationic membrane is as follows: First, the cationic membrane is cut into the required size and then soaked in acidic solution, deionized water, and alcohol solution in sequence, followed by ultrasonic cleaning to remove surface impurities and contaminants, thereby activating the ion exchange groups on the membrane surface.

[0041] Pyrrole and ethyl silicate were dissolved in anhydrous ethanol at a specific molar ratio, and an initiator and catalyst were added. The cationic membrane was immersed in the prepared solution. Under specific temperature and pH conditions, pyrrole and ethyl silicate polymerized on the membrane surface to form a nanoscale protrusion structure with a roughness of Ra = 0.8 μm.

[0042] After the reaction is complete, the membrane is removed and thoroughly washed with deionized water to remove any unreacted residues. Then, sulfonic acid groups are introduced onto the formed nanostructure using a sulfonating agent (such as concentrated sulfuric acid, fuming sulfuric acid, or chlorosulfonic acid), ultimately yielding a modified cation exchange membrane. The modified cation exchange membrane contains Na... + The penetration rate increased by 0.36%, and the mechanical strength increased by 40%.

[0043] The modified anion exchange membrane 107 described above is a modified coating disposed on the surface of the anion base membrane. The modified coating is a three-dimensional network cross-linked layer formed by polyethyleneimine and dopamine on the surface of the anion base membrane.

[0044] The modification process of the anion-based membrane is as follows: similar to that of the cationic membrane, it is first cleaned and activated. The anion-based membrane is then immersed in a prepared dopamine solution. Under weakly alkaline conditions, dopamine undergoes an oxidative self-polymerization reaction to form a polydopamine film. Subsequently, the anion-based membrane is immersed in a polyethyleneimine (PEI) solution. On the membrane surface, polyethyleneimine and dopamine form a three-dimensional network structure through covalent bonding.

[0045] Modified anion exchange membrane 107 The permeability increased by 12.57%, while the membrane surface contact angle was significantly reduced from 70° of conventional membranes to 35°. The super-hydrophilic surface makes it difficult for pollutants to adhere, fundamentally reducing the frequency of pollution and chemical cleaning, and protecting the membrane material.

[0046] The aforementioned modified cation exchange resin and modified anion exchange resin were placed in a freshwater chamber. The modified cation exchange resin was a cation exchange resin matrix loaded with iron oxides. The iron oxide particles were nanoscale in size, with a particle size of 10–20 nm. The iron oxides included iron oxide (Fe₂O₃), ferrous oxide (FeO), and magnetite (Fe₃O₄). The modified cation exchange resin loaded with iron oxides could catalytically decompose organic matter through the Fenton reaction, actively reducing biofouling sources on the membrane surface.

[0047] The preparation process of the modified cation exchange resin is as follows: the cation exchange resin matrix is ​​repeatedly washed with deionized water, and then treated several times alternately with acidic and alkaline solutions to clean the pores and activate the surface. The treated cation exchange resin matrix is ​​then immersed in an iron salt solution (such as...). or Driven by concentration gradient, Ions diffuse and adsorb into the pores of the resin, undergoing ion exchange with the groups within the resin. The cation exchange resin matrix, now containing adsorbed iron ions, is then transferred to a precipitant solution (such as sodium hydroxide). or ammonia Under alkaline conditions, it enters the resin pores. Ions undergo hydrolysis to form water-insoluble iron oxides (such as...). , Or hydrated iron oxide).

[0048] The modified anion exchange resin is grafted with quaternary ammonium groups (-N). + The modified anion exchange resin matrix is ​​(CH3)3. The quaternary ammonium groups enhance the adsorption capacity for weakly dissociated substances, increasing the silicon removal rate to 99.2%. The preparation process of the modified anion exchange resin is as follows:

[0049] The activated anion exchange resin matrix was immersed in a solution containing oxidants, reducing agents, and functional monomers, forming free radicals on the membrane surface. Subsequently, monomers containing tertiary amine groups were grafted, as tertiary amines have high reactivity, low steric hindrance, and are easily quaternized. The treated matrix was then immersed in a solution containing dimethylaminoethyl methacrylate (DMAEMA) and a redox initiator, successfully grafting poly(dimethylaminoethyl methacrylate) chains onto the surface of the anion exchange resin matrix. At this point, the resin surface was rich in tertiary amine groups. The PDMAEMA-grafted anion exchange resin matrix was then immersed in an alcoholic solution of iodomethane. The nitrogen atom on the tertiary amine group nucleophilically reacted with the methyl carbon of the iodomethane, undergoing a nucleophilic substitution reaction to form a quaternary ammonium salt. After the reaction was complete, residual reagents and byproducts were washed away. The modified anion exchange resin was finally obtained.

[0050] The ion exchange resin regeneration unit includes at least two titanium-based ruthenium-iridium electrodes, namely a titanium-based ruthenium-iridium anode and a titanium-based ruthenium-iridium cathode. The titanium-based ruthenium-iridium electrodes have titanium as a substrate, covered with an electroactive layer of a mixture of ruthenium dioxide and titanium dioxide. The two titanium-based ruthenium-iridium electrodes are respectively positioned on opposite sides of the freshwater chamber. The electric field strength is controlled by a pulsed power supply to regenerate the modified cation exchange resin and the modified anion exchange resin. The regeneration principle utilizes the electric field generated by the titanium-based ruthenium-iridium electrodes to force ions (such as...) in the water... , , , (etc.) Pass through the ion exchange resin, moving directionally towards the titanium-based ruthenium-iridium anode and cathode, respectively, and are ultimately concentrated and discharged. Specifically:

[0051] Electrolysis of water occurs on the surface of the titanium-based ruthenium-iridium anode: ,produce .

[0052] Adsorbed on the modified cation exchange resin , Isocations, generated at the anode in a titanium-based ruthenium-iridium electrode Driven by an electric field, it moves towards the cathode; as it flows through the cation exchange resin, the high concentration of... With resin Ion exchange occurs, and the ions are displaced. Under the influence of a subsequent electric field, it continues to migrate towards the cathode and enters the concentrate chamber, thus regenerating the cation exchange resin.

[0053] Electrolysis of water occurs on the surface of the titanium-based ruthenium-iridium anode: ,produce .

[0054] Adsorbed on the modified anion exchange resin , Anions generated at the cathode in a titanium-based ruthenium-iridium electrode Driven by an electric field, it moves towards the anode. When it flows through the anion exchange resin, the high concentration of... and Ion exchange occurs, and the ions are displaced. Under the influence of the electric field, it continues to migrate towards the anode and enters the concentrate chamber, where the anion exchange resin regains its exchange capacity.

[0055] In some implementations, such as Figure 2As shown, the electrodialysis system includes at least four electrodialysis units 100, which are connected in series and defined sequentially as a primary electrodialysis unit 111, a secondary electrodialysis unit 112, a tertiary electrodialysis unit 113, and a quaternary electrodialysis unit 114. The freshwater outlet 109 of the primary electrodialysis unit 111 is connected to the inlet 102 of the secondary electrodialysis unit 112. Subsequent electrodialysis units 100 are thus connected in series, meaning the effluent from the freshwater chamber of the previous unit 100 is directly used as the feed water for the next unit 100. This step-by-step treatment mode achieves staged purification.

[0056] The electrodialysis system also includes a concentrate circulation pipeline 110. One end of the concentrate circulation pipeline 110 is connected to the concentrate chamber of the four-stage electrodialysis unit 114, and the other end is connected to the inlet 102 of the first-stage electrodialysis unit 111, the second-stage electrodialysis unit 112, and the third-stage electrodialysis unit 113, respectively. This allows a portion of the concentrate produced by the fourth-stage electrodialysis unit 114 to flow back into the first three stages of the electrodialysis unit 100. This returned concentrate is desalinated water, and its pH, hardness, and alkalinity may have changed (for example, pH changes during desalination). Mixing it with the raw water can improve the quality of the raw water (especially scaling ions such as...). , , The concentration of the membrane plays a buffering and homogenizing role, making the water quality entering the first three stages more stable and reducing the scaling and fouling pressure on the membrane module.

[0057] In addition, the concentrate recirculation design can bring the liquid carrying some salt that should have been discharged from the system back to the front-end treatment stage. The remaining salt will have the opportunity to be migrated to the concentrate chamber for separation again, which improves the overall salt removal efficiency of the system.

[0058] Each of the inlet pipes 102 of the electrodialysis unit 100 is equipped with a filter valve and a flow meter, which can filter impurities and monitor the flow rate of the input water to be treated in real time, ensuring the stability of the water quality and the controllability of the flow rate.

[0059] Furthermore, to address the water quality requirements and separation objectives at different treatment stages, the primary electrodialysis unit 111, secondary electrodialysis unit 112, and tertiary electrodialysis unit 113 employ a counter-current operation mode, where freshwater and concentrate flow in opposite directions within adjacent membrane channels. The quaternary electrodialysis unit 114 utilizes a cross-flow operation mode, where the liquid flow direction forms a certain angle (e.g., 30°~60°) with the surfaces of the modified cation exchange membrane 106 and the modified anion exchange membrane 107. This creates a continuous shearing and scouring effect as the liquid flows across the membrane surfaces. This scouring force disrupts the adhesion balance of contaminants on the membrane surface, promptly carrying colloidal particles, organic matter, and salt scale microcrystals that are about to deposit into the concentrate side for discharge, significantly reducing the risk of irreversible fouling of the membrane modules.

[0060] Furthermore, to achieve optimal energy efficiency and desalination performance, the electrodialysis system employs a voltage-gradient drive strategy, setting sequentially decreasing operating voltages for the primary electrodialysis unit 111, the secondary electrodialysis unit 112, and the tertiary electrodialysis unit 113, specifically 12 V, 10 V, and 8 V, respectively. This voltage gradient design, in conjunction with the aforementioned counter-current series hydraulic structure, ensures that each membrane stack operates under an electric field strength matching the salt concentration of its feed water. This effectively reduces ineffective electrolysis and energy consumption while guaranteeing efficient ion migration, thereby improving the overall desalination efficiency of the system.

[0061] In some embodiments, the control unit includes a controller 200, and voltage sensors, current sensors, and multiple water quality detectors respectively connected to the controller 200. These components work together to achieve precise monitoring and dynamic adjustment of the electrodialysis system's operating status. Specifically, the voltage sensor is used to collect various voltage parameters in the electrodialysis device 100 in real time, including but not limited to: the total voltage between the electrode plates at both ends of a single electrodialysis device 100, the inter-electrode voltage between the anode plate and the adjacent solution, the inter-electrode voltage between the cathode plate and the solution, etc. The voltage sensor converts the collected voltage signals into digital signals that can be recognized by the controller 200, providing a basis for subsequent voltage adjustment.

[0062] The current sensor is used to monitor the real-time current value flowing through the entire electrodialysis device 100 (including the cathode electrode plate 104, the anode electrode plate 103, the modified cation exchange membrane 106, the modified anion exchange membrane 107, and the solution flowing in between). By continuously tracking the stability and trend of the current, the operating indicators such as the degree of membrane fouling and ion migration efficiency can be determined. For example, when the current suddenly drops, it may indicate that the membrane fouling has caused an increase in the circuit resistance, and a control command or cleaning command needs to be triggered in time.

[0063] Water quality detectors are used to monitor the quality of influent and effluent in real time, including but not limited to:

[0064] Total Dissolved Solids (TDS) detector, which detects the concentration of dissolved salts in water in real time;

[0065] Chemical Oxygen Demand (COD) detectors monitor the load of organic pollutants in water;

[0066] A pH detector is used to measure the acidity or alkalinity of water.

[0067] The driving core of the electrodialysis device 100 is a DC power supply 300. The positive terminal of the DC power supply 300 is firmly connected to the anode electrode plate 103, and the negative terminal is connected to the cathode electrode plate 104. When the DC power supply 300 is turned on, a uniform and stable electric field is established between the alternating modified cation exchange membrane 106 and modified anion exchange membrane 107, providing driving force for ion migration.

[0068] The controller 200 receives real-time monitoring data from voltage sensors, current sensors, and water quality detectors. Based on its built-in algorithm model and processing objectives, it performs comprehensive analysis to generate precise adjustment commands for the DC power supply 300. The specific control logic is as follows: The controller 200 first integrates voltage data from the voltage sensor and real-time current data from the current sensor. Combined with water quality parameters such as TDS, COD, and pH, it determines the current operating status. If the TDS value is higher than the target threshold, indicating insufficient desalination efficiency, the controller 200 will increase the current by increasing the output voltage of the DC power supply 300 to accelerate ion migration. If an abnormally high current and drastic pH fluctuations are detected, there may be a risk of membrane damage. The controller 200 will immediately reduce or cut off the power output. When the water quality parameters reach the preset standards, the controller 200 will adjust the power output to a stable state, achieving energy-saving operation.

[0069] For example, the present invention provides a formula for the controller 200 to adjust the current based on the monitoring data of the influent TDS and COD, as shown below:

[0070]

[0071] Where J0 is the reference current density of the DC power supply (15mA / cm²). 2 );

[0072] β is the TDS adjustment coefficient (0.2~0.6);

[0073] γ is the COD adjustment coefficient (0.1~0.4).

[0074] C in and COD in The TDS and COD values ​​of the influent;

[0075] C ref and COD ref The reference values ​​are 1000 mg / L and 50 mg / L, respectively.

[0076] The electrodialysis system achieves stable, efficient, and adaptive operation of the electrodialysis device 100 under complex water quality conditions through a closed-loop linkage of sensor monitoring, intelligent judgment, and real-time control.

[0077] In some embodiments, the electrodialysis system is further provided with a differential pressure detector and a backwashing assembly, wherein the differential pressure detector is used to detect the pressure difference across the modified cation exchange membrane 106 (and the modified anion exchange membrane 107), and when the pressure difference reaches or exceeds a set value (e.g., 0.25 MPa), it is determined that the modified cation exchange membrane 106 has been significantly contaminated or blocked.

[0078] The backwash assembly includes a backwash water pipe, a backwash pump, and multiple flush nozzles. The backwash pump is located on the backwash water pipe and provides power for conveying the backwash water.

[0079] One end of the backwash water pipe is connected to the flushing nozzle, and the opening of the flushing nozzle faces the modified cation exchange membrane 106 (and the modified anion exchange membrane 107).

[0080] When the modified cation exchange membrane 106 becomes significantly fouled or clogged, the electrodialysis system automatically initiates a backwashing procedure. Close the inlet valve of the electrodialysis system, turn on the backwash pump, and perform a backwash for 8 minutes at 3 times the design flow rate. Drain the flushing water and restore the electrodialysis system to normal operation.

[0081] Backwashing can promptly remove contaminants and filter cake from the membrane surface, restore flux, and prevent further deterioration of contamination.

[0082] The differential pressure detector and backwash pump are connected to the controller 200. The controller 200 monitors the differential pressure across the membrane in real time via the differential pressure detector. When the differential pressure reaches the preset trigger threshold, the controller 200 automatically sends a start command to the backwash pump according to its built-in program logic, thereby executing the flushing process to restore filtration efficiency. In addition, the membrane flushing assembly can also be periodically chemically cleaned. After the electrodialysis system has run continuously for 30 days, alternating acid-base cleaning is performed: citric acid (pH=2.5) is used to primarily remove inorganic scale, while sodium hydroxide (pH=12.5) is used to primarily remove organic contaminants and biological slime. Alternating acid-base cleaning can remove stubborn contaminants that backwashing cannot remove, achieving deep cleaning and restoring the performance of the membrane assembly and ion exchange resin.

[0083] Based on the above-described electrodialysis system, the present invention also provides a method for using the above-described electrodialysis system, the steps of which include:

[0084] Before starting the electrodialysis system, check that all pipes, valves, and pumps are tightly connected and leak-free. Confirm that the voltage sensor, current sensor, TDS, pH, COD, and differential pressure detectors are all properly connected to the controller 200 and have been calibrated.

[0085] The raw water to be treated enters the primary, secondary, and tertiary electrodialysis units 113 sequentially. The effluent from each stage becomes the feed water for the next stage, and the salinity decreases progressively. All three electrodialysis units 113 operate in countercurrent mode.

[0086] Controller 200 regulates the application of 12V to the primary electrodialysis unit 111. This is because the influent salinity is highest at this stage, requiring the strongest electric field to drive ion migration. The secondary electrodialysis unit 112 applies 10V. As the influent salinity decreases, the voltage is appropriately reduced to save energy. The tertiary electrodialysis unit 113 applies 8V. With the influent salinity further reduced, an even lower voltage is sufficient to meet the separation requirements.

[0087] The low-salinity freshwater after the first three stages of treatment enters the fourth-stage electrodialysis unit 114 for final desalination, producing the final high-purity product water. A portion of the high-concentration concentrate produced by the fourth-stage electrodialysis unit 114 is discharged, while the remainder is recycled back to the inlet 102 of the first, second, and third-stage electrodialysis units 113 via the concentrate circulation pipeline 110, mixing with the raw water. The recycled liquid acts as a dilution and buffer, reducing fluctuations in water quality entering the first three stages and significantly lowering the risk of scaling on the membrane surface.

[0088] In some implementations, after the electrodialysis system has been running for a certain period of time, the modified ion exchange resin in the desalination chamber needs to be regenerated. First, the desalination process is paused, and the desalination chamber is isolated. The controller 200 starts the power supply, providing power to the titanium-based ruthenium-iridium electrodes on both sides of the desalination chamber. The regeneration process is described in the section on the regeneration unit of the exchange resin described above, and will not be repeated here. The displaced ions migrate to the concentrate chamber under the drive of the electric field and are discharged with the concentrate. After regeneration is complete, the normal desalination process of the electrodialysis system is resumed.

[0089] In some implementations, when the differential pressure detector detects that the differential pressure across the membrane reaches or exceeds a preset threshold, the electrodialysis system triggers automatic backwashing. The controller 200 automatically closes the inlet valve, starts the backwashing pump, and flushes the membrane surface for 10 minutes to effectively remove contaminants from the membrane surface.

[0090] Furthermore, after 30 days of continuous operation of the electrodialysis system, or when the backwashing effect significantly decreases, the electrodialysis system triggers chemical cleaning, performing alternating acid and alkali cleaning on the electrodialysis unit 100 to deeply restore the performance of the membrane and resin, ensuring long-term efficient operation of the system.

[0091] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electrodialysis system, characterized in that, include: Multiple electrodialysis devices are connected in series. Each electrodialysis device includes: an ion exchange membrane assembly, an ion exchange resin, an anode electrode plate, a cathode electrode plate, and an exchange resin regeneration unit. The ion exchange membrane assembly includes a modified cation exchange membrane and a modified anion exchange membrane. The modified cation exchange membrane and the modified anion exchange membrane are alternately arranged between the anode electrode plate and the cathode electrode plate. Multiple alternating concentrate chambers and desalination chambers are formed between adjacent modified cation exchange membranes and modified anion exchange membranes. The inlet of the next-stage electrodialysis device is connected to the outlet of the desalination chamber of the previous-stage electrodialysis device. The modified cation exchange membrane includes a cation base membrane and a composite coating disposed on the surface of the cation base membrane. The composite coating is a copolymer of pyrrole and ethyl silicate with a nanoscale protrusion structure, and sulfonic acid groups are introduced onto the copolymer. The modified anion exchange membrane includes an anion base membrane and a modified coating disposed on the surface of the anion base membrane. The modified coating is a three-dimensional network layer formed by crosslinking polyethyleneimine and dopamine. The ion exchange resin fills the freshwater chamber. The ion exchange resin includes a modified cation exchange resin and a modified anion exchange resin. The modified cation exchange resin is a cation exchange resin matrix supported on iron oxides. The modified anion exchange resin is an anion exchange resin matrix grafted with quaternary ammonium groups. The ion exchange resin regeneration unit includes a titanium-based ruthenium-iridium anode and a titanium-based ruthenium-iridium cathode, which are respectively disposed on both sides of the freshwater chamber. When the titanium-based ruthenium-iridium anode and the titanium-based ruthenium-iridium cathode are energized, they drive the ions adsorbed by the ion exchange resin to migrate in a directional manner and desorb, thereby restoring the adsorption capacity of the ion exchange resin.

2. The electrodialysis system according to claim 1, characterized in that, The electrodialysis system also includes a concentrate circulation pipeline, one end of which is connected to the outlet of the concentrate chamber of the last stage electrodialysis device, and the other end of which is connected to the inlet of each stage of the electrodialysis device upstream of the last stage electrodialysis device.

3. The electrodialysis system according to claim 2, characterized in that, In the final stage of the electrodialysis device, the liquid flow in the desalination chamber and the concentrate chamber flows at a set angle to the surface of the ion exchange membrane assembly. In each stage of the electrodialysis device upstream of the last stage, the flow direction of the desalination chamber and the concentrate chamber is opposite.

4. The electrodialysis system according to any one of claims 1-3, characterized in that, The electrodialysis system includes at least four electrodialysis devices, which are arranged in the following order: primary electrodialysis device, secondary electrodialysis device, tertiary electrodialysis device, and quaternary electrodialysis device.

5. The electrodialysis system according to claim 4, characterized in that, The operating voltages in the primary electrodialysis device, the secondary electrodialysis device, and the tertiary electrodialysis device are 12 V, 10 V, and 8 V, respectively.

6. The electrodialysis system according to claim 1, characterized in that, The electrodialysis system also includes: a controller, a voltage sensor, a current sensor, and multiple water quality detectors; The voltage sensor is used to collect the voltage value inside the electrodialysis device in real time; The current sensor is used to collect the current value in the electrodialysis device in real time. The water quality detector is used to monitor the influent water quality and product water quality of the electrodialysis device in real time. The plurality of water quality detectors include at least one of a total dissolved solids detector, a chemical oxygen demand detector and a pH detector. The electrodialysis device also includes a power source, the positive and negative terminals of which are connected to the anode electrode plate and the cathode electrode plate, respectively. The controller is connected to the power supply, the voltage sensor, the current sensor, and the water quality detector respectively. The controller adjusts the output value of the power supply according to the detection data of the voltage sensor, the current sensor, and the water quality detector.

7. The electrodialysis system according to claim 1 or 6, characterized in that, The electrodialysis system also includes a differential pressure detector and a backwashing assembly, wherein the differential pressure detector is used to detect the pressure difference across the ion exchange membrane assembly; The backwashing assembly includes a backwashing water pipe, a backwashing pump, and multiple flushing nozzles. One end of the backwashing water pipe is connected to the flushing nozzle, and the opening of the flushing nozzle faces the ion exchange membrane assembly. The backwash pump is installed on the backwash water pipe to provide power for transporting backwash water; The differential pressure detector is connected to the backwash pump control. When the differential pressure detected by the differential pressure detector reaches or exceeds the set value, it sends a start signal to the backwash pump, which drives the backwash water to flow through the flushing nozzle to backwash the ion exchange membrane assembly.

8. The electrodialysis system according to claim 7, characterized in that, The backwash water is a citric acid solution or a sodium hydroxide solution.

9. A method of using the electrodialysis system as described in any one of claims 1-8, characterized in that the steps include... include: The raw water to be treated is sequentially fed into multiple electrodialysis devices connected in series for desalination, with the final electrodialysis device producing product water. After the electrodialysis device has been running for a set time, the desalination chamber is isolated, and the ion exchange resin regeneration unit is started to electrochemically regenerate the ion exchange resin in the desalination chamber. Ions desorbed from the ion exchange resin migrate to the concentrate chamber, and the adsorption capacity of the ion exchange resin is restored.

10. The method of using the electrodialysis system according to claim 9, characterized in that, The electrodialysis system also includes a concentrate circulation pipeline, one end of which is connected to the outlet of the concentrate chamber of the last stage of the electrodialysis device, and the other end of which is connected to the inlet of each stage of the electrodialysis device upstream of the last stage of the electrodialysis device. The method of using the electrodialysis system further includes: returning a portion of the concentrated water produced by the last stage of the electrodialysis unit to the upstream stages of the electrodialysis unit.

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