Multi-channel membrane module system for wastewater treatment and resource circulation using redox-based electrodialysis

Abstract

The present invention relates to a multi-channel membrane module system for wastewater treatment and resource circulation using redox-based electrodialysis. Through a redox-mediated bipolar membrane electrodialysis (RBED) in which a redox flow desalination process is combined with a bipolar membrane electrodialysis (BPED), the present invention allows for operation at low potentials by a redox reaction having a low operating potential, in lieu of water decomposition of conventional electrodialysis, thereby offering superior energy efficiency. The multi-channel membrane module system employing the redox-mediated electrodialysis enables highly efficient desalination and resource circulation from waste solutions generated during secondary battery production and metal recovery processes, and energy used for the desalination and resource circulation can be recovered, thereby providing high energy efficiency and price competitiveness.

Description

Multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis

[0001] The present invention relates to a multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, and more particularly, to a multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, which combines a redox flow desalination process with a bipolar electrodialysis process (Bipolar membrane electrodialysis, BPED), and thus operates at a low potential through a redox reaction with a low operating potential instead of the water decomposition of conventional electrodialysis, thereby having excellent energy efficiency and enabling high-efficiency desalination and resource recycling of Na2SO4 waste solution generated in a secondary battery manufacturing process and a metal recovery process, and wherein the energy used for the desalination and resource recycling is recoverable.

[0002] Lithium-ion batteries are used as portable batteries for IT devices such as smartphones and laptops, as well as as a major energy source for electric vehicles (EVs) due to their high output and high energy characteristics. In particular, the demand for lithium-ion batteries is rapidly increasing due to the rapid increase in demand for eco-friendly technologies such as electric vehicles (EVs) and energy storage systems (ESS).

[0003] Wet processes are commonly used to recover valuable metals from spent lithium-ion batteries. These involve leaching the lithium battery cathode active material with sulfuric acid, followed by alkaline precipitation or solvent extraction to recover elements like cobalt. This recovery process inevitably generates highly saline wastewater containing valuable metals. During the wastewater treatment process, this salt-laden wastewater is discharged into the water system, impacting the environment and ecosystem.

[0004] Current waste lithium battery recycling effluent treatment technology is being developed to separate / recover Na2SO4 waste solution through distillation, evaporation, crystallization, and membrane separation.

[0005] However, conventional treatment technologies have problems such as low recovery rates, high energy consumption, and large amounts of gas generation.

[0006] Patent Document 1 discloses a wastewater treatment method using an electrodialysis device composed of an anion exchange membrane and a cation exchange membrane, and Patent Document 2 describes producing a high-concentration alkali hydroxide from a neutral salt at a high current efficiency through electrodialysis using a bipolar membrane and a cation exchange membrane.

[0007] In addition, Patent Document 3 discloses a system for treating wastewater generated in a recycling process for recovering valuable metals from lithium-ion waste batteries, in which strong acids and strong alkalis are recovered from wastewater generated in a recycling process for lithium-ion waste batteries, and treated water discharged from the system is reused as process water within the system, thereby enabling the final wastewater to be treated without discharge. In this case, an electrodialysis process using a bipolar membrane is used.

[0008] Figure 19 shows the cell structure in which a typical bipolar membrane electrodialysis (BPED) process is performed, in which hydrogen ions (H) generated by water decomposition in the bipolar membrane placed in the center + ) and hydroxide ions (OH -) can be selectively passed through adjacent cation or anion exchange membranes and recovered as sulfuric acid (H2SO4) and caustic soda (NaOH).

[0009] However, the above electrochemical treatment technology has the disadvantage of requiring a long process time for high treatment capacity because most processes are performed on a small scale, and a large amount of wastewater is discharged, causing a large environmental burden.

[0010] In addition, the general electrodialysis process-based system has the disadvantages of high energy consumption and the formation of various by-products near the electrodes because it uses high voltage.

[0011] Therefore, although electrochemical processes can treat wastewater without utilizing high pressure at low temperatures, there are still ongoing technical and industrial demands for high energy costs and low treatment capacity.

[0012] In addition, during scale-up for commercialization, the technical difficulties of securing economic feasibility and channel stacking due to expensive bipolar and ion exchange membrane stacking have been pointed out.

[0013] Accordingly, the present invention has been developed as a technology for recycling cellulose that can be operated energy-efficiently at low voltage through a redox reaction of redox substances by using a redox-mediated bipolar electrodialysis (RBED) process that combines a redox flow desalination process with a conventional bipolar electrodialysis (BPED) process, and has completed the present invention by confirming the possibility of scale-up for commercialization by stacking inexpensive porous carbon electrodes of redox reaction channels instead of stacking expensive bipolar membranes and ion exchange membranes to increase the processing capacity.

[0014] (Patent Document 1) Republic of Korea Patent No. 1328279 (announced on November 14, 2013)

[0015] (Patent Document 2) Japanese Patent Laid-Open No. 1993-070984 (published on March 23, 1993)

[0016] (Patent Document 3) Republic of Korea Patent No. 2601857 (announced on November 16, 2023)

[0017] The purpose of the present invention is to provide a multi-channel membrane module system using redox-based electrodialysis for wastewater treatment and resource recycling generated during a secondary battery manufacturing process and a metal recovery process.

[0018] In order to achieve the above object, the present invention provides a multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, which is a cell structure in which a redox reaction channel is arranged adjacent to a positive electrode and the redox reaction channel is driven by an electrochemical reaction of a redox substance, and at least one bipolar membrane, an anion exchange membrane, and a cation exchange membrane are spaced apart from each other inside the cell structure to be sectioned into at least one influent channel and one concentration channel, and when a voltage is applied, wastewater generated in a secondary battery manufacturing process or a metal recovery process that has flowed into the influent channel is ion-separated, and each of the separated ions combines with ions generated from water decomposition in the bipolar membrane and is concentrated in the concentration channel.

[0019] By separating and removing the waste water, Na2SO4, which is generated during the secondary battery manufacturing process and metal recovery process that flows into the above inflow channel, and concentrating and recovering NaOH and H2SO4 in the above concentration channel, energy consumption is low, the ion separation speed is very fast, and recycling and selective separation / concentration / recovery of acids and bases are possible by utilizing a redox reaction and an ion separation membrane.

[0020] A preferred first embodiment of the multi-channel membrane module system of the present invention provides a multi-channel membrane module system for wastewater treatment and resource circulation, in which bipolar membranes are respectively arranged on both sides of the inside of a redox reaction channel arranged adjacent to the two electrodes, and an anion exchange membrane and a cation exchange membrane are sequentially spaced apart from one of the bipolar membranes and separated into sections, thereby forming five channels consisting of two redox reaction channels, two concentration channels, and one influent channel.

[0021] In a second preferred embodiment of the multi-channel membrane module system of the present invention, a cation exchange membrane is disposed on each of the inner sides of a redox reaction channel disposed adjacent to the two electrodes, and an anion exchange membrane and a bipolar membrane are spaced apart from each other between one cation exchange membrane and the other corresponding cation exchange membrane, thereby providing a multi-channel membrane module system for wastewater treatment and resource circulation formed of five channels consisting of two redox reaction channels, two concentration channels, and one influent channel.

[0022] In the above multi-channel membrane module system, one of the cation exchange membranes is a monovalent selective cation exchange membrane.

[0023] A third preferred embodiment of the multi-channel membrane module system of the present invention provides a multi-channel membrane module system for wastewater treatment and resource circulation, in which a single bipolar membrane is arranged at the center of a cell, and anion exchange membranes and cation exchange membranes are alternately arranged left and right from the central bipolar membrane, thereby forming six channels consisting of two redox reaction channels, two concentration channels, and two influent channels.

[0024] Furthermore, in order to increase the capacity of wastewater treatment, the present invention can be manufactured as a stacked module in which at least two or more cell structures can be stacked when the cell structure is a single unit, and porous carbon electrodes are stacked in multiple layers between the redox reaction channels arranged with each electrode, thereby minimizing the use of ion exchange membranes and reducing the cost of system production while enabling large-capacity treatment.

[0025] In addition, the present invention provides an energy recycling system including a resource recovery module composed of a multi-channel membrane module for wastewater treatment and resource circulation using the redox-based electrodialysis described above, and an energy recovery module composed of a redox reaction channel through which a redox substance flows, wherein the resource recovery module and the energy recovery module are connected to each other by the redox reaction channel and flow, and when voltage is applied to the resource recovery module, a charging process is performed, and electric energy input during the charging process generates a potential difference in the module to be stored as chemical energy, and is recovered through a discharge process in the energy recovery module.

[0026] The above resource recovery module and the above energy recovery module are connected to a redox reaction channel made of a redox substance using the same redox pair.

[0027] The multi-channel membrane module system using redox-based electrodialysis of the present invention is an energy-efficient process that can treat wastewater with lower energy consumption than existing processes by a redox-based bipolar membrane electrodialysis process performed at low temperature and pressure, and is an environmentally friendly process that generates very little wastewater because it can treat and recycle Na2SO4 wastewater generated in the secondary battery manufacturing process and metal recovery process without a large amount of compounds.

[0028] In particular, the multi-channel membrane module system using the redox-based electrodialysis of the present invention can selectively separate ions by utilizing a redox reaction and an ion separation membrane, and the ion concentration rate and speed are improved by more than twice compared to the existing process.

[0029] Therefore, energy consumption is low, ion separation speed is very fast, and recycling and selective separation / concentration / recovery of acids and bases are possible by utilizing a bipolar membrane.

[0030] In addition, since it is possible to recover high-purity acids and bases with a purity of 90% or more produced in the Na2SO4 waste liquid treatment process, it is possible to recycle acids and bases, thereby increasing the added value of waste lithium battery black powder, and since it can be used as a raw material in the black powder wet treatment process, it can create a new market for waste lithium battery resource utilization.

[0031] Furthermore, the present invention enables a large-capacity module by laminating porous carbon electrodes that are easy to perform redox reactions instead of laminating expensive bipolar membranes and ion exchange membranes, thereby minimizing the use of ion exchange membranes, simplifying the process and reducing system manufacturing costs, enabling scale-up for commercialization.

[0032] Figure 1 is a first embodiment of a multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention.

[0033] Figure 2 shows the average current density value according to the multi-channel membrane module system of the first embodiment.

[0034] Figure 3 shows the removal rate of the multi-channel membrane module system according to the first embodiment.

[0035] Figure 4 shows the pH change values ​​confirmed in each concentration channel at the beginning of operation and after 2 hours of operation of the multi-channel membrane module system of the first embodiment.

[0036] Figure 5 is a second embodiment of a multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention.

[0037] Figure 6 shows the average current density value according to the multi-channel membrane module system of the second embodiment.

[0038] Figure 7 shows the removal rate of the multi-channel membrane module system according to the second embodiment.

[0039] Figure 8 shows the pH change values ​​confirmed in each concentration channel at the beginning of operation and after 2 hours of operation of the multi-channel membrane module system of the second embodiment.

[0040] Figure 9 is a schematic diagram of a multi-channel membrane module system in which a monovalent selective cation exchange membrane is employed in a multi-channel membrane module for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention.

[0041] Figure 10 is a third embodiment of a multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention.

[0042] Figure 11 shows the average current density value according to the multi-channel membrane module system of the third embodiment.

[0043] Figure 12 shows the removal rate of the multi-channel membrane module system according to the third embodiment.

[0044] Figure 13 shows the pH change values ​​confirmed in each concentration channel at the beginning of operation and after 2 hours of operation of the multi-channel membrane module system of the third embodiment.

[0045] Figure 14 is a schematic diagram of the electrode stacking method of a stacked module of a multi-channel membrane for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention.

[0046] Figures 15 and 17 are real-life examples of multi-channel membrane modules using redox-based electrodialysis, including the stacked modules of Figure 14.

[0047] Figure 18 is a schematic diagram of an energy recycling system using a multi-channel membrane module for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention.

[0048] Figure 19 illustrates the cell structure in which a typical bipolar membrane electrodialysis (BPED) process is performed.

[0049] Hereinafter, the present invention will be described in detail.

[0050] The present invention provides a multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, which is a cell structure in which redox reaction channels are arranged adjacent to positive electrodes and the redox reaction channels are connected and driven by an electrochemical reaction of a redox substance, and at least one bipolar membrane, an anion exchange membrane, and a cation exchange membrane are spaced apart from each other inside the cell structure to be sectioned into at least one inflow channel and one concentration channel, and when voltage is applied, wastewater generated in a secondary battery manufacturing process or a metal recovery process that has flowed into the inflow channel is ion-separated, and each of the separated ions combines with ions generated from water decomposition in the bipolar membrane and is concentrated in the concentration channel.

[0051] The present invention is implemented through a redox-mediated bipolar membrane electrodialysis (RBED) process that combines a redox flow desalination process with a bipolar electrodialysis (BPED) process, and its main components are composed of a multi-channel, an ion exchange membrane, and a bipolar membrane.

[0052] The above bipolar electrodialysis (BPED) process is a desalination electrodialysis process consisting of a positive / negative ion exchange membrane that decomposes water to produce hydrogen ions (H + ) and hydroxide ions (OH - ) is a process that introduces a bipolar membrane (BM) that can produce H . The bipolar membrane is a new type of membrane that combines positive / negative ion exchange membranes and promotes water decomposition reaction by catalytic reaction under an electric field. + Wow OH - It has the function of generating .

[0053] At this time, the bipolar membrane used in the present invention can be a commercially available or known membrane, and is generally manufactured by bonding polymer cation / anion membranes, and the gap between the cation / anion exchange membranes (transition layer) where water decomposition occurs is about 4 to 5 nm.

[0054] The redox-based bipolar electrodialysis process (RBED) of the present invention is a water splitting reaction (minimum operating potential, V) performed on the electrode surface in a conventional bipolar membrane electrodialysis process (BPED). cell = 1.23 V), the oxidation / reduction reaction of the redox substance on the electrode surface (maximum operating potential, V cell = 1.23 V) enables continuous separation and removal of dissolved ions.

[0055] Therefore, through the multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention, the waste water of sodium hydroxide (Na2SO4) generated in the secondary battery manufacturing process and metal recovery process that flows into the influent channel is separated and removed, and hydrogen ions (H) generated from water decomposition in the bipolar membrane are removed. + ) and hydride ions (OH - ) is utilized to concentrate sulfuric acid (H2SO4) and caustic soda (NaOH) in the above-mentioned concentration channel, thereby providing a process capable of recovering resources simultaneously with an energy-efficient desalination process.

[0056] That is, the present invention is a high-efficiency and high-performance process that utilizes a redox reaction and an ion separation membrane, consumes little energy, has a very fast ion separation speed, and utilizes a bipolar membrane to enable recycling and selective separation / concentration / recovery of acids and bases.

[0057] Furthermore, in the embodiment of the present invention, although Na2SO4 is specifically described as an example of wastewater, it is not limited thereto, and ionic substances present in wastewater are used as H using a bipolar membrane. + , OH -It can be concentrated and recovered as a specific substance through production.

[0058] For example, it can be applied to remove, concentrate, and recover various substances based on acids and bases, such as recovery of LiOH from lithium wastewater, recovery of ammonia from ammonium wastewater, capture of CO2 dissolved in seawater, removal and concentration of boron in seawater, production of HCl and NaOH from seawater (NaCl), removal of heavy metals during smelting processes, and recovery of organic acids from industrial and food wastewater.

[0059] In the multi-channel membrane module system using the above redox-based electrodialysis, the redox material can be used without any special restrictions as long as it is a material in which a redox reaction occurs reversibly using the same redox pair, and an example thereof is I3. - / I - , [Fe(CN)6] 3- / [Fe(CN)6] 4- , Zn 2+ / Zn, MVCl2 / MV, etc. can be utilized. In the embodiment of the present invention, Na4Fe(CN)6 is used as a preferred example, but is not limited thereto.

[0060] The above Na4Fe(CN)6 redox substance undergoes a reversible redox reaction as shown in the following reaction scheme 1.

[0061] Reaction Scheme 1

[0062] Fe(CN)6 3- + e - ↔ Fe(CN)6 4-

[0063] The redox reactants of the above redox couple accelerate ion separation while reacting at the electrode.

[0064] In addition, the separated cations and anions can selectively pass through a cation exchange membrane, and the anions can selectively pass through an anion exchange membrane.

[0065] The above cation exchange membrane and anion exchange membrane are microporous insulating separators and may be ion exchange (conductive) membranes. The cation exchange membrane and the anion exchange membrane are installed for electrophysical separation, and the microporous insulating separator can only allow ion movement, while the ion exchange (conductive) membrane can selectively move only cations or anions.

[0066] The ion exchange membrane and electrode used in the present invention may be any of those that have been used in conventional batteries, accumulators, etc., and a general expert in the relevant technical field can select and use them appropriately according to the purpose and conditions of use.

[0067] A preferred first embodiment of the multi-channel membrane module system of the present invention provides a multi-channel membrane module system for wastewater treatment and resource circulation, which comprises a bipolar membrane disposed on each of the inner sides of a redox reaction channel disposed adjacent to the two electrodes, an anion exchange membrane and a cation exchange membrane disposed spaced apart from one of the bipolar membranes, and formed into five channels consisting of two redox reaction channels, two concentration channels, and one influent channel.

[0068] Figure 1 illustrates a first embodiment of a multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention.

[0069] Specifically, it is composed of two bipolar membranes and one anion / cation exchange membrane, and represents a five-channel module consisting of two redox channels (channels 1 and 5 from the left), two concentration channels (channels 2 and 4), and one influent channel (channel 3).

[0070] At this time, the cation exchange membrane arranged on one side of the inflow channel and the anion exchange membrane arranged on the other side of the inflow channel induce separation of specific ions and prevent contamination of the inflow channel and the concentration channel.

[0071] When voltage is applied to the above system, the Na2SO4 waste solution flowing into the inflow channel is Na + and SO4 2- Na2SO4 is removed by separating into ions, and the separated Na + and SO4 2- Ions move into the concentration channels on both sides, and in the bipolar membrane in contact with the redox channel, H is released through a water splitting reaction. + Wow OH - is released and SO4 is released from each concentration channel. 2- and Na + By combining with H2SO4 and NaOH, they are concentrated respectively.

[0072] The multi-channel membrane module system using redox-based electrodialysis of the present invention is configured to induce water decomposition even at low voltages using a bipolar membrane to generate acids and bases, thereby providing a sodium hydroxide (Na2SO4) recycling module that can be operated energy-efficiently at low voltages.

[0073] Figure 2 and Figure 4 show the experimental results for removal of nitrate and recovery of sulfuric acid and caustic soda according to the multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, which is the first embodiment.

[0074] From the results of FIGS. 2 and 3, it can be seen that an average current density of 0.6 mA / cm2 flowed in the multi-channel membrane module system of the first embodiment, and a 6% removal rate of nitrate was achieved for 2 hours.

[0075] In addition, Fig. 4 shows the pH change values ​​confirmed in each concentration channel at the beginning and 2 hours after operation of the multi-channel membrane module system of the first embodiment. In the H2SO4 concentration channel, the initial pH changed from 7.0 to 5.4 after 2 hours. This result is because the H in the bipolar membrane + occurs, and SO4 is transferred from the inflow channel to the concentration channel. 2-It can be confirmed that H2SO4 was generated as it moved. On the other hand, in the NaOH concentration channel, the initial pH changed from 7.0 to 11.0 after 2 hours of operation of the multi-channel membrane module system, and OH in the bipolar membrane - occurs and Na flows from the inflow channel to the concentration channel. + indicates that NaOH has been produced by moving.

[0076] FIG. 5 illustrates a second embodiment of a multi-channel membrane module system for wastewater treatment and resource circulation using redox-based electrodialysis of the present invention, in which cation exchange membranes are respectively arranged on both sides of the inside of redox reaction channels arranged adjacent to the two electrodes, and anion exchange membranes and bipolar membranes are spaced apart from one cation exchange membrane to another corresponding cation exchange membrane, thereby providing a multi-channel membrane module system for wastewater treatment and resource circulation formed of five channels consisting of two redox reaction channels, two concentration channels, and one influent channel.

[0077] Figures 6 and 8 show the performance results of the second embodiment of the multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention. Through Figures 6 and 7, an average current density of 0.5 mA / ㎠ flowed, and a 7% removal rate of nitrate was confirmed for 2 hours.

[0078] Also, in Fig. 8, the pH change values ​​confirmed in each concentration channel at the beginning and 2 hours after operation of the multi-channel membrane module system are shown. In the H2SO4 concentration channel, the initial pH changed from 7.0 to 2.7 after 2 hours. This result is because the H in the bipolar membrane + occurs, and SO4 is transferred from the inflow channel to the concentration channel. 2- As it moves, we can see that H2SO4 is generated.

[0079] On the other hand, in the NaOH concentration channel, the initial pH changed from 7.0 to 11.4 after 2 hours of operation of the multi-channel membrane module system, and OH in the bipolar membrane - occurs and Na flows from the inflow channel to the concentration channel. + indicates that NaOH has been produced by moving.

[0080] These results confirm that high efficiency is achieved with the lowest system resistance because only one bipolar membrane is used in the multi-channel membrane module system and it consists of five channels.

[0081] In addition, in the multi-channel membrane module system of the present invention, a cell structure in which cation exchange membranes are arranged on both inner sides of the redox reaction channel and anion exchange membranes and bipolar membranes are sequentially spaced apart from one of the cation exchange membranes is Fe(CN)6 3- / Fe(CN)6 4- It is possible to prevent the problem of redox substances having a negative charge, such as , being adsorbed on the anion exchange membrane side of an anion exchange membrane and a bipolar membrane. Since the surface of a cation exchange membrane is bonded with a fixed functional group having a negative charge, redox substances having a negative charge are not adsorbed, and therefore, it is advantageous in that a stable desalination process can be performed for a long period of time.

[0082] The multi-channel membrane module system using redox-based electrodialysis of the present invention is configured to induce water decomposition even at low voltages using a bipolar membrane to generate acids and bases, thereby providing a sodium hydroxide (Na2SO4) recycling module that can be operated energy-efficiently at low voltages.

[0083] Since only one bipolar membrane is used and a high efficiency of a cell structure consisting of five channels is achieved, when the cell structure is a single unit, the removal rate of the ion-exchange membrane can be further improved by stacking at least two units, more preferably 2 to 10 units.

[0084] Figure 9 shows a schematic diagram of a multi-channel membrane module system in which a monovalent selective cation exchange membrane is employed in a multi-channel membrane module for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention.

[0085] A monovalent selective cation exchange membrane is placed between the redox reaction channel and the influent channel so that when monovalent cations and polyvalent cations are present in the influent, only monovalent cations can be selectively passed, and the passage of polyvalent ions is inhibited, thereby preventing scale formation by hardness substances among polyvalent ions.

[0086] Specifically, the multi-channel membrane module system using the monovalent selective cation exchange membrane of FIG. 9 is a five-channel module system separated using one bipolar membrane, one anion exchange membrane, one cation exchange membrane, and one monovalent selective cation exchange membrane.

[0087] At this time, the substances flowing into the inflow channel are magnesium ions (Mg) in addition to Na2SO4. 2+ ) and calcium ions (Ca 2+ ) are introduced, the monovalent cation (Na) is introduced through the monovalent selective cation exchange membrane. + ) moves into the redox reaction channel, and divalent cations can prevent scale formation on the electrode by restricting movement between channels, and can remove nitrates without pretreatment.

[0088] In addition, as a third preferred embodiment, a multi-channel membrane module system for wastewater treatment and resource circulation is provided, in which a single bipolar membrane is arranged in the center of a cell, and anion exchange membranes and cation exchange membranes are alternately arranged left and right from the central bipolar membrane, thereby forming six channels consisting of two redox reaction channels, two concentration channels, and two influent channels.

[0089] Specifically, FIG. 10 is a second embodiment of a multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention, which is a 6-channel module system separated using one bipolar membrane and two anion / cation exchange membranes each.

[0090] The mechanism by which H2SO4 and NaOH are produced in each concentration channel is the same, but by using only one bipolar membrane in the middle, two redox channels (channels 1 and 6 from the left), two concentration channels (channels 3 and 4), and two influent channels (channels 2 and 5) are formed.

[0091] Through the above module system, Na2SO4 is removed from two influent channels, and H2SO4 and NaOH are concentrated in two concentration channels, respectively.

[0092] Figures 11 and 13 show the experimental results for removal of nitrate and recovery of sulfuric acid and caustic soda according to the multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis of the third embodiment.

[0093] From the results of FIGS. 11 and 12, it can be seen that an average current density of 0.4 mA / cm2 flowed in the multi-channel membrane module system of the third embodiment, and a 5% removal rate of nitrate was confirmed for 2 hours.

[0094] In addition, the pH change values ​​confirmed in each concentration channel at the beginning of operation and after 2 hours of operation of the multi-channel membrane module system of the third embodiment of Fig. 13 were as follows: in the H2SO4 concentration channel, the initial pH changed from 7.0 to 3.1 after 2 hours, and in the NaOH concentration channel, the initial pH changed from 7.0 to 11.0 after 2 hours of operation of the multi-channel membrane module system. At this time, the H2SO4 and NaOH production mechanisms in each concentration channel are the same as in the system of the first embodiment.

[0095] From the above, the multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention has high energy efficiency because it is driven at a low potential through a redox reaction with a low operating potential instead of water decomposition of conventional electrodialysis, thereby enabling high-efficiency desalination and resource recycling, and thereby realizing an energy saving effect of more than 50% compared to the conventional electrodialysis process.

[0096] In particular, desalination and resource recycling are possible by utilizing the energy storage principle of the redox material used, and the energy used for the desalination and resource recycling can be recovered.

[0097] Therefore, the above energy recovery process is a feature of the redox flow method of the present invention due to the electrochemical reaction of redox material, and thus can be said to be a feature not introduced in conventional water recycling processes.

[0098] Furthermore, the present invention, in order to increase the capacity of wastewater treatment, manufactures the redox reaction channel as a stacked module in which multiple layers of porous carbon electrodes are laminated between each electrode, thereby minimizing the use of ion exchange membranes and reducing the cost of system production, thereby enabling large-capacity treatment.

[0099] Fig. 14 is a schematic diagram of the electrode stacking method of a stacked module of a multi-channel membrane for wastewater treatment and resource recycling using redox-based electrodialysis of the present invention, and Figs. 15 to 17 present a real-life example of a multi-channel membrane module using redox-based electrodialysis including the stacked module.

[0100] The above electrode stack structure can increase processing capacity and enhance ion separation efficiency by stacking inexpensive porous carbon electrodes of redox reaction channels instead of stacking expensive bipolar membranes and ion exchange membranes. Therefore, the electrode stacking method of the stacked module of the multi-channel membrane can remove Na2SO4 and recover high-purity acids and bases with an acid and base purity of 90% or more.

[0101] Therefore, through the electrode stacking method of the stacked module of the multi-channel membrane presented in Fig. 14, an economical and convenient stacking system can be constructed through the strategy of the electrode stacking method during scale-up.

[0102] In addition, the multi-channel membrane module system using redox-based electrodialysis of the present invention utilizes porous carbon electrodes that are highly price competitive compared to electrodialysis processes that utilize expensive metal and metal oxide electrodes in the past due to mild electrochemical reaction conditions of redox substances, thereby minimizing the use of ion exchange membranes through scale-up through electrode stacking in process design, thereby reducing process capital costs and operating costs by about 40% or more.

[0103] FIG. 18 is a schematic diagram of an energy recycling system using a multi-channel membrane module for wastewater treatment and resource circulation using redox-based electrodialysis of the present invention, and is a structure in which two modules including a resource recovery module (module 1) composed of the multi-channel membrane module for wastewater treatment and resource circulation using redox-based electrodialysis and an energy recovery module (module 2) composed of a redox reaction channel through which a redox substance flows are connected via a redox substance.

[0104] Specifically, the resource recovery module (module 1) in Fig. 18 is a resource recovery module comprised of a multi-channel membrane module for wastewater treatment and resource circulation using the redox-based electrodialysis described above. It is a module that separates and removes nitrates from the influent and concentrates acids and bases to recover resources. At this time, it is comprised of an influent channel, a concentration channel, and a redox reaction channel.

[0105] In Fig. 18, the energy recovery module (module 2) is a module that converts and recovers the electrical energy input into chemical energy when electricity is applied (charged) to the resource recovery module (module 1), and is composed only of a redox reaction channel through which a redox substance flows.

[0106] That is, an electric current collector and an electrode are attached to the redox reaction channels of the resource recovery module (module 1) and the energy recovery module (module 2) to induce a redox reaction of a redox substance, and at this time, the redox pair of each redox reaction channel generates a potential difference in the cell through a different redox reaction.

[0107] The operating principle of the system illustrated in Fig. 18 will be explained. When voltage is applied to the resource recovery module (module 1), a charging process begins, causing positive ions in the influent to move toward the cathode and negative ions to move toward the anode. The electrical energy input during the charging process can be stored as chemical energy by generating a potential difference through a redox reaction of a redox substance, and is recovered again through a discharging process in the energy recovery module (module 2). That is, when a potential difference is generated in the module through the charging process, a reverse redox reaction occurs during the discharging process, and at this time, energy is produced through spontaneous electron transfer.

[0108] Although the present invention has been described in detail above only with respect to the described specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and it is natural that such modifications and variations fall within the scope of the appended claims.

Claims

1. A cell structure in which a redox reaction channel is arranged adjacent to both electrodes and the redox reaction channel is connected and driven by an electrochemical reaction of a redox substance. At least one bipolar membrane, anion exchange membrane and cation exchange membrane are spaced apart from each other inside the above cell structure to separate the section into at least one inflow channel and one concentration channel, When voltage is applied, wastewater generated in the secondary battery manufacturing process or metal recovery process that flows into the inflow channel is ion-separated, A multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, in which each of the separated ions is combined with ions generated from water decomposition in a bipolar membrane and concentrated in a concentration channel.

2. A multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, characterized in that the wastewater generated in the secondary battery manufacturing process or metal recovery process that flows into the inflow channel in the first paragraph is sodium hydroxide (Na2SO4).

3. A multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, characterized in that caustic soda (NaOH) and sulfuric acid (H2SO4) are concentrated in the concentration channel in the first paragraph.

4. In the first paragraph, the multi-channel membrane module system A bipolar membrane is arranged on each side of the inside of the redox reaction channel adjacent to the above two electrodes, and an anion exchange membrane and a cation exchange membrane are sequentially spaced apart from one of the bipolar membranes to form a section separation. A multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, characterized by being formed of five channels consisting of two redox reaction channels, two concentration channels, and one influent channel.

5. In the first paragraph, the multi-channel membrane module system On both sides of the inner side of the redox reaction channel placed adjacent to the above two electrodes Cation exchange membranes are respectively arranged, and anion exchange membranes and bipolar membranes are spaced apart from each other corresponding to one cation exchange membrane, thereby separating the sections. A multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, characterized by being formed of five channels consisting of two redox reaction channels, two concentration channels, and one influent channel.

6. In the first paragraph, the multi-channel membrane module system A single bipolar membrane is placed in the center of the cell, and anion exchange membranes and cation exchange membranes are placed spaced apart from the central bipolar membrane in the left and right directions, A multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, characterized by being formed of six channels consisting of two redox reaction channels, two concentration channels, and two influent channels.

7. A multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, characterized in that when the cell structure is a single unit in the first paragraph, at least two or more cell structures are stacked and arranged.

8. A multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, characterized in that any one of the cation exchange membranes in paragraph 5 is a monovalent selective cation exchange membrane.

9. A multi-channel membrane module system for wastewater treatment and resource recycling using redox-based electrodialysis, characterized in that the redox reaction channel in the first paragraph is a stacked module in which porous carbon electrodes are laminated in multiple layers between each electrode.

10. A resource recovery module comprising a multi-channel membrane module for wastewater treatment and resource recycling using redox-based electrodialysis according to any one of the preceding clauses. An energy recovery module comprising a redox reaction channel through which a redox substance flows, The above resource recovery module and the above energy recovery module are connected to the redox reaction channel and are movable, When voltage is applied to the above resource recovery module, a charging process is performed, and the electric energy input during the charging process generates a potential difference in the module and is stored as chemical energy. An energy recycling system that recovers energy through a discharge process in the above energy recovery module.

11. An energy recycling system according to claim 10, characterized in that the resource recovery module and the energy recovery module are connected by a redox reaction channel made of a redox material using the same redox pair.

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