Resource recovery and zero emission treatment system for wastewater generated in preparation process of positive electrode material precursor for secondary battery

Abstract

Disclosed is a system for treating wastewater containing heavy metals and high concentrations of ammonia generated in the preparation of a precursor for a positive electrode material for a secondary battery. According to one aspect of the present invention, there is provided a zero-emission treatment system for wastewater generated in the preparation of a precursor for a positive electrode material for a secondary battery, which includes an ammonia stripping section that removes ammonia components from wastewater generated in the preparation of a precursor, an ion exchange section that removes metal ions, a chemical recovery section that recovers acid and base solutions, and a reclaimed water production section that produces wastewater in which the acid and base solutions have been recovered as reclaimed water used in the zero-emission treatment system.

Description

Technical Field

[0001] This invention relates to a wastewater treatment system for treating wastewater generated during the preparation of cathode material precursors for lithium-ion secondary batteries, thereby achieving resource recovery and zero discharge of the generated wastewater. Background Technology

[0002] The content described in this section is merely background information for this embodiment and does not constitute prior art.

[0003] Lithium-ion rechargeable batteries, due to their high power and high energy characteristics, are used not only as portable batteries in IT devices such as smartphones and laptops, but also as the primary energy source for electric vehicles (EVs). In particular, the demand for lithium-ion batteries is increasing dramatically due to the surge in demand for environmentally friendly technologies such as electric vehicles (EVs) and energy storage systems (ESS).

[0004] Cathode material is one of the core raw materials for lithium-ion rechargeable batteries, accounting for a significant portion of their production cost. It is the active material that embodies the positive electrode characteristics of the battery and is a crucial raw material determining the battery's capacity and voltage.

[0005] This cathode material is made by mixing precursors and raw materials such as lithium and then sintering them. The precursor is an intermediate raw material for the cathode material, which is made by processing minerals such as nickel, cobalt, manganese, and aluminum.

[0006] The most common method for preparing precursors is coprecipitation, which separates the target substance by coprecipitating two or more ions in an aqueous or non-aqueous solution. This coprecipitation method has the advantages of easy operation and control of reaction conditions. However, it suffers from drawbacks such as the long precipitation time and the generation of wastewater containing large amounts of reagents and various metal ions. In particular, the wastewater generated during the preparation of cathode material precursors via coprecipitation is considered one of the most detrimental industrial wastewaters to the environmental ecosystem.

[0007] On the other hand, methods for treating wastewater generated during the preparation of cathode material precursors include precipitation, coagulation, adsorption, or the use of strong acids to remove total nitrogen from the wastewater. However, these wastewater treatment methods result in resource loss because the useful resources contained in the wastewater are discarded. Therefore, there is an urgent need for an environmentally friendly treatment solution that can effectively treat the heavy metals and ammonia components contained in the wastewater, and also recover and reuse the substances that have not been recycled and discharged. Summary of the Invention

[0008] (The problem that the invention aims to solve)

[0009] One objective of an embodiment of the present invention is to provide a wastewater treatment system that recovers resources containing acids and alkalis from wastewater generated during the preparation of precursors for positive electrode materials for secondary batteries, and reuses the treated water discharged from the system as process water within the system, thereby enabling zero-discharge treatment of the final waste liquid and thus eliminating environmental pollution at the source.

[0010] In addition, one objective of an embodiment of the present invention is to provide an environmentally friendly water treatment system that can recover chemicals from ammonia, heavy metals and high-concentration salt components contained in wastewater generated during the preparation of precursors for positive electrode materials for secondary batteries, and reuse them as materials required for the precursor preparation process, thereby saving precursor production costs.

[0011] (The measures taken to solve the problem)

[0012] One aspect of the present invention relates to a zero-discharge treatment system for wastewater generated during the preparation of precursors for positive electrode materials for secondary batteries. This system treats wastewater containing heavy metals and high concentrations of ammonia generated during the preparation of precursors for positive electrode materials for secondary batteries. The zero-discharge treatment system comprises: an ammonia stripping unit that degasses ammonia from the wastewater generated during the precursor preparation process; an ion exchange unit that receives the wastewater after the removal of the ammonia and removes metal ions from the wastewater; a chemical recovery unit that recovers acid and alkaline solutions from the wastewater where the ammonia and metal ions have been removed; and a reclaimed water production unit that filters the wastewater from which the recovered acid and alkaline solutions have been recovered to produce reclaimed water for use in the system.

[0013] One aspect of the zero-emission treatment system further includes a chemical concentration unit that concentrates the acid and alkali solutions recovered by the chemical recovery unit and resupplys them to the precursor preparation process.

[0014] The zero-emission treatment system according to one aspect of the present invention further includes a separation membrane filtration unit that receives wastewater flowing in after treatment in the ion exchange unit, removes organic matter and particulate matter, and then discharges the wastewater to the chemical recovery unit.

[0015] In one aspect of the invention, the aforementioned chemical recovery unit includes a bipolar membrane electrodialysis device to receive the incoming wastewater and recover acid and alkali solutions.

[0016] In one aspect of the invention, in the above-described bipolar membrane electrodialysis apparatus, multiple unit stacks are connected in series to receive the incoming wastewater and perform desalination treatment by multi-stage recovery of acid and alkali solutions.

[0017] In one aspect of the invention, the aforementioned unit stack includes a plurality of anion exchange membranes, cation exchange membranes, and bipolar membranes located between a positive electrode and a negative electrode. These membranes are arranged in a repeating order of anion exchange membrane, cation exchange membrane, and bipolar membrane, with spacers disposed between adjacent membranes.

[0018] In one aspect of the invention, the bipolar membrane electrodialysis apparatus receives the final treated water produced and supplied in the reclaimed water production unit as an electrode solution in order to recover acid and alkali solutions from the wastewater.

[0019] In one aspect of the invention, the bipolar membrane electrodialysis device receives electricity supplied from a solar or wind power generation system and uses it as a power source applied to the positive and negative electrodes.

[0020] In one aspect of the present invention, the pH value of the wastewater generated during the precursor preparation process flowing into the ammonia stripping section is 10 or higher.

[0021] The zero-emission treatment system according to one aspect of the present invention further includes an activated carbon adsorption unit that receives concentrated water containing unfiltered residual pollutants flowing in from the aforementioned reclaimed water production unit, removes organic matter from the concentrated water, and recycles the discharged concentrated water after the removal of organic matter back to the aforementioned chemical recovery unit and into a flow channel supplying wastewater to the aforementioned plurality of unit cells.

[0022] In one aspect of the invention, the ion exchange unit includes a cation exchange resin, and the wastewater flowing into the ion exchange unit contains one or more elements selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al).

[0023] In one aspect of the invention, the aforementioned reclaimed water production unit is a reverse osmosis (RO) membrane device.

[0024] One aspect of the present invention relates to a zero-discharge treatment method for wastewater generated during the preparation of precursors for positive electrode materials for secondary batteries. This method treats wastewater containing heavy metals and high concentrations of ammonia generated during the preparation of precursors for positive electrode materials for secondary batteries. The zero-discharge treatment method includes: a step of removing ammonia from the wastewater generated during the precursor preparation process; a step of removing metal ions from the wastewater where the ammonia has been removed; a step of removing organic matter and particulate matter from the wastewater where the metal ions have been removed; a step of recovering sulfuric acid and sodium hydroxide from the wastewater where the organic matter and particulate matter have been removed; and a step of further removing residual salt from the desalinated wastewater where the sulfuric acid and sodium hydroxide have been recovered to produce reclaimed water.

[0025] In one aspect of the invention, the produced reclaimed water is supplied to a step of recovering sulfuric acid and sodium hydroxide for reuse.

[0026] In one aspect of the invention, in the step of removing ammonia, the wastewater is stripped with air or steam to remove ammonia.

[0027] In one aspect of the invention, in the step of recovering sulfuric acid and sodium hydroxide, wastewater is recovered as sulfuric acid and sodium hydroxide by a bipolar membrane electrodialysis device.

[0028] (The effect of the invention)

[0029] As explained above, according to one aspect of the present invention, wastewater generated during the preparation of precursors for cathode materials is treated so that the chemicals contained in the wastewater can be recovered and reused in the precursor preparation process, thereby enabling resource reuse and reducing the environmental damage caused by waste discharged into the ecosystem, and having advantages such as saving precursor production costs.

[0030] Furthermore, chemicals are recovered from wastewater generated during precursor preparation, and the discharged wastewater is treated as reclaimed water using a reverse osmosis membrane process. This allows for complete recycling of the reclaimed water, achieving zero-discharge treatment within the system, enabling its reuse as process water within the system, including the chemical recovery process. Additionally, the salts contained in the concentrated water from the reverse osmosis membrane process are reintroduced into the chemical recovery process, offering advantages such as improved chemical recovery rates while consistently ensuring the power efficiency of the bipolar membrane electrodialysis unit used for chemical recovery. Attached Figure Description

[0031] Figure 1 This is a process diagram illustrating the resource recovery and zero-discharge treatment system for wastewater generated during the preparation of a positive electrode material precursor for secondary batteries according to an embodiment of the present invention.

[0032] Figure 2 This is a diagram illustrating the configuration of a chemical recovery unit according to an embodiment of the present invention.

[0033] Figure 3 This is a diagram illustrating the unit stack structure of a bipolar membrane electrodialysis apparatus for chemical recovery according to an embodiment of the present invention.

[0034] Figure 4 This is a diagram illustrating the structure of a chemical concentration section according to an embodiment of the present invention.

[0035] Figure 5 This is a flowchart illustrating a zero-discharge treatment method for wastewater generated during the preparation of a cathode material precursor for secondary batteries, according to an embodiment of the present invention. Detailed Implementation

[0036] This invention is capable of various modifications and embodiments, and therefore specific embodiments are illustrated and described in detail in the accompanying drawings. However, this is not intended to limit the invention to the specific implementations, but rather to encompass all modifications, equivalents, or substitutions included within the spirit and scope of the invention. Similar reference numerals have been used for similar constituent elements in the description of the drawings.

[0037] The terms "first," "second," "A," "B," etc., can be used to describe multiple constituent elements, but the constituent elements described above are not limited to the terms used above. The terms used above are only for the purpose of distinguishing one constituent element from other constituent elements. For example, without departing from the scope of the invention, a first constituent element can be named a second constituent element, and similarly, a second constituent element can be named a first constituent element. The term "and / or" includes a combination of multiple related and described items or one item from multiple related and described items.

[0038] When referring to a constituent element being "connected" or "in contact" with another constituent element, although it may be directly connected or in contact with that other constituent element, it should be understood that there may also be other constituent elements between them. Conversely, when referring to a constituent element being "directly connected" or "directly in contact" with another constituent element, it should be understood that there are no other constituent elements between them.

[0039] The terminology used in this application is for illustrative purposes only and is not intended to limit the scope of the invention. A single expression includes multiple expressions unless there is a clear difference in meaning between them. In this application, terms such as "comprising" or "having" should be understood as not precluding the presence or additional possibilities of features, numbers, steps, actions, constituent elements, components, or combinations thereof described in the specification.

[0040] Unless otherwise defined, all terms used herein, including technical or scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art.

[0041] Terms as defined in commonly used dictionaries should be interpreted as having the meaning consistent with the meaning of the relevant technical text, and should not be ideally or excessively interpreted as having a formal meaning unless explicitly defined in this application.

[0042] Furthermore, the various components, processes, steps, or methods included in the embodiments of the present invention can be shared to the extent that they are not technically contradictory.

[0043] Figure 1This is a diagram illustrating a resource recovery and zero-discharge treatment system for wastewater generated during the preparation of a precursor for a secondary battery cathode material, according to an embodiment of the present invention.

[0044] like Figure 1 As shown, an embodiment of the present invention relates to a resource recovery and zero-discharge treatment system 100 (hereinafter referred to as "System 100") for wastewater generated during the preparation of precursors for positive electrode materials for secondary batteries. The system includes a precursor wastewater inflow section 110, an ammonia-stripping section 120, an ion exchange section 130, a separation membrane filtration section 140, a chemical recovery section 150, a chemical concentration section 160, a reclaimed water production section 170, and an activated carbon adsorption section 180.

[0045] The precursor wastewater inlet 110 receives the wastewater generated during the preparation of the precursor for the secondary battery cathode material and supplies the wastewater to the ammonia stripping section 120 in the later stage.

[0046] Lithium-ion secondary batteries consist of four main raw materials: positive electrode material, negative electrode material, separator membrane, and electrolyte. The positive electrode material provides lithium ions. Precursors, as intermediate raw materials for the positive electrode material, are typically prepared via a co-precipitation method. This involves adding a metal salt of the metal used in the positive electrode material and an alkali to water as a solvent to precipitate the metal hydroxide, thus preparing the precursor. In this method, the performance of the precursor can be determined by factors such as the concentration of the metal salt and alkali, the concentration of ammonia, the pH value, and the reaction conditions.

[0047] Therefore, the wastewater generated during precursor preparation contains tens to hundreds of ppm of heavy metals such as nickel (Ni), manganese (Mn), and cobalt (Co). Furthermore, due to the use of ammonia and sodium hydroxide (NaOH), the wastewater is highly alkaline and contains large amounts of inorganic salts and high concentrations of ammonium ions. Among these, ammonia and inorganic salts are examples of substances that can be recovered from System 100 and reused in the precursor preparation process.

[0048] As an example, the wastewater flowing into the precursor preparation process of the cathode material in the system 100 of the present invention contains 50 to 100 mg / L of COD (Chemical Oxygen Demand), 150,000 to 200,000 mg / L of Total Dissolved Solids (TDS), and 8,000 to 12,000 mg / L of ammonium ions (NH4+). + ), 100,000 to 120,000 mg / L of sulfate (SO4) 2- ) and other metal ions.

[0049] In this regard, the inflow wastewater received from the precursor wastewater inflow section 110 is supplied to the ammonia stripping section 120 as a first step, thereby removing the ammonia component from the wastewater.

[0050] The ammonia stripping unit 120 receives wastewater generated during the precursor preparation process supplied from the wastewater inlet unit 110, removes the ammonia component contained in the wastewater, and then discharges it to the ion exchange unit 130.

[0051] The ammonia stripping unit 120 removes ammonia from wastewater by stripping it with air. As shown in the following chemical formula 1, the ammonia component exists in water in an equilibrium state.

[0052] [Chemical Formula 1]

[0053]

[0054] Ammonia is converted into NH4+ based on the pH value of the wastewater. + It exists in the presence of NH3, and the equilibrium pH is 9.25. The higher the pH, the more it exists as NH3. The method of degassing ammonia with air after raising the pH to above 10 is called ammonia stripping.

[0055] As mentioned earlier, ammonia and sodium hydroxide are used in the preparation of the precursor for the cathode material, resulting in wastewater with a pH value typically above 10 (pH level of 10-13). Therefore, the ammonia stripping section 120 of the present invention can degas ammonia without artificially raising the pH value for ammonia degassing, and can adjust the pH value of the wastewater after ammonia removal by the ammonia stripping section 120 to a level of 9-11.

[0056] Furthermore, the ammonia stripping unit 120 of the present invention can employ either air stripping using air or steam stripping using steam as a medium. Compared to degassing methods that utilize air at room temperature, utilizing steam during the ammonia stripping process has advantages such as the ability to further improve the ammonia removal rate.

[0057] As mentioned earlier, the wastewater generated during the precursor preparation process flows into the ammonia stripping section 120 and undergoes a degassing process. At this time, the ammonium ions (NH4+) flowing into the wastewater... + The concentration of ) was at levels ranging from 8,000 to 12,000 mg / L.

[0058] When ammonium ions flow into the downstream chemical recovery unit 150, they may flow into the alkali pipeline and be discharged as ammonia gas, which reduces the power efficiency of the chemical recovery unit 150. To address this, in the system 100 of the present invention, a pretreatment step is introduced into the chemical recovery unit 150, which uses the ammonia stripping unit 120 as a main process, to remove high concentrations of ammonium ions. The wastewater from the ammonia stripping unit 120 is treated to contain ammonium ions at a level of 20 to 100 mg / L before being discharged into the ion exchange unit 130.

[0059] On the other hand, the ammonia separated by degassing in the ammonia stripping section 120 is recovered in the form of ammonia water, and the recovered ammonia water is reused as a raw material in the precursor preparation process. In particular, in the case of the ammonia stripping section 120 using steam as a medium, it is advantageous to condense the recovered steam and recover it in the form of ammonia water.

[0060] The ion exchange unit 130 receives the wastewater supplied after the ammonium ions have been removed once in the ammonia stripping unit 120 and separates the heavy metal components from the wastewater. Afterwards, the treated water, from which the heavy metal components have been removed, is discharged to the membrane filtration unit 140.

[0061] As mentioned above, the wastewater generated during the precursor preparation process contains at least one of the following metals: nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), iron (Fe), and / or magnesium (Mg).

[0062] If these metal ions flow into the chemical recovery section 150, they will form metal crystals, thereby reducing the efficiency of the ion exchange membranes 313 and 315 in the chemical recovery section 150.

[0063] Therefore, in the system 100 of the present invention, an ion exchange unit 130 is further introduced as a secondary pretreatment step of the chemical recovery unit 150, thereby removing metal ions from the wastewater. The ion exchange unit 130 contains ion exchange resin for removing these metal ions, and in particular, it can be formed into a packed tower filled with cation exchange resin.

[0064] The wastewater flowing into the ion exchange unit 130 contains metal ions such as nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), iron (Fe) and / or magnesium (Mg) at a level of 50 to 100 mg / L. The metal ions present in the wastewater can be 100% removed by the ion exchange unit 130.

[0065] In addition, some of the metal ions removed in the ion exchange section 130 can be recovered from the ion exchange resin according to their concentration and recycled as raw materials for the precursor preparation process.

[0066] The separation membrane filtration unit 140 receives the wastewater supplied after the secondary removal of metal ions in the ion exchange unit 130, and after removing some of the organic matter and particulate matter in the wastewater, discharges the wastewater to the chemical recovery unit 150.

[0067] As mentioned above, the wastewater generated during the precursor preparation process contains some organic matter and particulate matter, which can lead to a decrease in the treatment efficiency in the chemical recovery unit 150. Therefore, it is necessary to reduce the organic matter and particulate matter in the wastewater.

[0068] As an example, the separation membrane filtration unit 140 of the present invention can be a UF separation membrane process. When the pretreated water, which has been pretreated by ammonia stripping and ion exchange, passes through the separation membrane filtration unit 140 including the UF separation membrane, particulate matter and a portion of organic matter are removed by membrane filtration, and then discharged to the chemical recovery unit 150.

[0069] The chemical recovery unit 150 receives the wastewater supplied after the removal of organic matter and particulate matter in the separation membrane filtration unit 140, and discharges the wastewater to the chemical concentration unit 160 after recovering the acid (H2SO4) and alkali (NaOH). Furthermore, the desalinated water, from which the acid and alkali have been removed, is discharged to the reclaimed water production unit 170.

[0070] The wastewater flowing into the chemical recovery unit 150 typically contains 8 to 15 wt% Na2SO4. In order to recover deionized water, acids, and alkalis from this wastewater, the chemical recovery unit 150 can be equipped with a bipolar membrane electrodialysis (BPED) device.

[0071] Bipolar membrane electrodialysis devices use ion exchange membranes and only electrical energy to separate or concentrate chemical substances, thus avoiding the generation of byproducts from process operation and having the advantage of being able to treat large amounts of wastewater with low energy consumption.

[0072] To utilize the bipolar membrane electrodialysis unit as the chemical recovery section 150, the system 100 incorporates an ammonia stripping section 120, an ion exchange section 130, and a separation membrane filtration section 140 upstream of the chemical recovery section 150 to remove ammonia, metal ions, and organic matter from the wastewater generated during precursor preparation. The wastewater, having undergone the aforementioned pretreatment process, flows into the chemical recovery section 150 at a level sufficient for high treatment efficiency and stable chemical recovery in the bipolar membrane electrodialysis unit.

[0073] As an example, the influent water quality of the wastewater generated during the precursor preparation process, after undergoing a series of pretreatment processes in the system 100 of the present invention—namely, passing through the ammonia stripping unit 120, the ion exchange unit 130, and the separation membrane filtration unit 140—is shown in Table 1. Most of the organic matter, ammonia, and heavy metals contained in the wastewater generated during the precursor preparation process are removed in the upstream section of the chemical recovery unit 150. As a result, the decrease in treatment efficiency and the generation of byproducts in the chemical recovery unit 150 can be minimized.

[0074] [Table 1]

[0075]

[0076] The chemical recovery unit 150 requires electrode solutions for separating and recovering acids and alkalis from the incoming wastewater. In system 100, the final effluent treated in the reclaimed water production unit 170 is recovered and used as the electrode solution.

[0077] In addition, the chemical recovery unit 150 can receive wastewater flowing in from the separation membrane filtration unit 140 as brine, and can also receive concentrated brine supplied from the activated carbon adsorption unit 180 as a salt solution for the bipolar membrane electrodialysis device.

[0078] The chemical recovery unit 150 performs an electrodialysis process to recover acids and bases in the form of sulfuric acid (H2SO4) and sodium hydroxide (NaOH) from wastewater, respectively. As an example, if 8-15 wt% of Na2SO4 flows into the chemical recovery unit 150, 4-7 wt% of H2SO4 and 3-6 wt% of NaOH can be recovered. The recovered chemicals can then be fed into the chemical concentration unit 160 and adjusted to acid and base concentrations suitable for use in precursor preparation processes.

[0079] The treated water discharged from the chemical recovery unit 150 is discharged to the reclaimed water production unit 170 with a TDS concentration of 13,000 to 15,000 mg / L, as acids and alkalis are recovered.

[0080] The specific composition of the chemical recycling unit 150 will be discussed later. Figure 2 and Figure 3 And will be explained in detail.

[0081] The chemical concentration unit 160 receives acids and bases recovered and supplied in the chemical recovery unit 150, and performs a concentration process to adjust the concentration to a level suitable for reuse in the precursor preparation process. The concentrated acids and bases are then supplied to the precursor preparation process.

[0082] For the sake of reaction efficiency, the precursor preparation process typically uses acid (H2SO4) and base (NaOH) at concentrations of 20% to 50%. Therefore, it is necessary to concentrate the acid and base recovered from the chemical recovery unit 150.

[0083] The system 100 of the present invention can use an evaporator to concentrate acids and bases by heating water to evaporate them.

[0084] Steam is supplied to the various recovered chemicals to evaporate the water contained in the recovered chemicals. The evaporated water is discharged as condensate. The chemicals, which are concentrated to the target concentration (20~50wt%) through evaporation and concentration, are recycled to the precursor preparation process for reuse.

[0085] In addition, the condensate discharged during the evaporation and concentration process is fed into the pipeline of the treated water of the reclaimed water production unit 170 as the electrode liquid of the chemical recovery unit 150 and reused as the electrode liquid of the chemical recovery unit 150.

[0086] The specific composition of the chemical concentration section 160 will be described later. Figure 4 And will be explained in detail.

[0087] The reclaimed water production unit 170 receives wastewater that has been desalinated in the chemical recovery unit 150 and separates and concentrates residual pollutants from the wastewater. The treated water, from which pollutants have been removed in the reclaimed water production unit 170, is supplied as electrode solution to the chemical recovery unit 150, while the residual pollutants separated and concentrated from the wastewater are discharged to the activated carbon adsorption unit 180.

[0088] The reclaimed water production unit 170 further removes residual pollutants from the wastewater that has passed through the chemical recovery unit 150, enabling the system 100 to achieve zero-discharge treatment.

[0089] Wastewater flowing from the chemical recovery unit 150 to the reclaimed water production unit 170 contains TDS in the range of 13,000 to 15,000 mg / L.

[0090] Therefore, the reclaimed water production unit 170 may use a reverse osmosis membrane (RO) to further remove solids from wastewater, but it is not limited to any process that can separate dissolved solids from wastewater.

[0091] As an example, in the case where the reclaimed water production unit 170 consists of an RO process, the RO process operates at a recovery rate of 70 to 90%, and it is preferable to use a membrane made of polyamide material with a salt removal rate of 99.7%.

[0092] The reclaimed water production unit 170, which consists of an RO process, receives and filters the desalinated wastewater flowing in from the chemical recovery unit 150. The TDS content of the treated water after the RO process is less than 1,500 mg / L, more preferably less than 1,000 mg / L, so that it is discharged in a state where most of the salt has been removed. The treated water is recycled to the chemical recovery unit 150 for use as electrode solution (clean water) in the chemical recovery unit 150.

[0093] [Table 2]

[0094]

[0095] Table 2 shows the water quality of the wastewater generated during the preparation of the treated precursor according to an embodiment of the present invention and the treated water discharged from the reclaimed water production unit 170. Table 2 confirms that the treated water produced by the reclaimed water production unit 170 is in a state where most organic matter, heavy metals, and ammonia have been removed, and is therefore sufficient to be recycled as electrode solution in the chemical recovery unit 150 or reused as water for other processes.

[0096] On the other hand, the concentrated water that fails to pass through the RO separation membrane contains TDS in the range of 50,000 to 70,000 mg / L. This concentrated water is discharged to the activated carbon adsorption section 180 for further treatment.

[0097] The activated carbon adsorption unit 180 receives concentrated water containing residual pollutants that has been separated and concentrated in the reclaimed water production unit 170, and adsorbs and removes organic matter from the concentrated water. The concentrated water is then recycled to the chemical recovery unit 150 to be used as brine in the chemical recovery unit 150.

[0098] The concentrated water discharged from the reclaimed water production unit 170 still contains residual salt components that were not recovered in the chemical recovery unit 150. The system 100 of the present invention can recover all chemicals from the salt components contained in the wastewater generated during the precursor preparation process. At the same time, in order to maintain the process efficiency within the chemical recovery unit 150, the concentrated water from the reclaimed water production unit 170 is reprocessed and supplied as brine to the chemical recovery unit 150.

[0099] At this time, the concentrated water discharged from the reclaimed water production unit 170 contains not only residual salt components, but also concentrated organic matter. Therefore, the activated carbon adsorption unit 180 can adsorb and remove the organic matter from the concentrated water.

[0100] The concentrated brine, after organic matter has been removed by the activated carbon adsorption section 180, flows back into the chemical recovery section 150 for use as brine in the chemical recovery section 150. Meanwhile, the concentrated brine discharged from the activated carbon adsorption section 180 flows into the brine piping within the bipolar membrane electrodialysis unit of the chemical recovery section 150, and then flows back to a location further down in the multiple stacks included in the bipolar membrane electrodialysis unit. The wastewater flowing into the chemical recovery section 150 undergoes a desalination process, resulting in a gradual decrease in the salt concentration of the solution, which can lead to side reactions due to overcurrent in the later stages of the electrodialysis unit. Therefore, to compensate for this, the concentrated brine discharged from the activated carbon adsorption section 180 preferably flows back to a location further down in the multiple stacks of the electrodialysis unit.

[0101] The system 100 of the present invention recycles all the final treated water discharged from the reclaimed water production unit 170 to the chemical recovery unit 150 for reuse. In addition, the condensate discharged from the chemical concentration unit 160 and the concentrated brine discharged from the activated carbon adsorption unit 180 are also recycled into the system 100 for reuse or reprocessing. As a result, zero-discharge treatment of wastewater generated during precursor preparation can be achieved in the system 100 of the present invention.

[0102] Figure 2 and Figure 3 This is a diagram illustrating the specific configuration of a chemical recovery unit 150 according to an embodiment of the present invention.

[0103] Figure 2 This is a diagram showing the configuration of the bipolar membrane electrodialysis apparatus, which is the chemical recovery unit 150 of the present invention.

[0104] Reference Figure 2 The chemical recovery unit 150 of the present invention is composed of a bipolar membrane electrodialysis device and includes a unit stack 210, an acid solution recovery tank 230 and an alkali solution recovery tank 250.

[0105] The bipolar membrane electrodialysis apparatus of the present invention includes at least one unit stack 210, wherein the unit stack 210 is configured in series and / or in parallel to receive wastewater flowing in from the separation membrane filtration section 140 and sequentially recover acid and alkali.

[0106] When multiple unit stacks 210 are connected in series, the chemical recovery unit 150 ensures sufficient residence time within itself, thereby enabling the recovery of most of the salt components contained in the wastewater generated during precursor preparation. Furthermore, when multiple unit stacks 210 are connected in parallel, the chemical recovery unit 150 can perform chemical recovery on a larger volume of wastewater.

[0107] As an example, refer to Figure 2The chemical recovery unit 150 includes multiple (n) unit stacks 210 connected in series, capable of performing the recovery of acid and alkali solutions from wastewater, i.e. from salt solutions, n times.

[0108] Unit stack 210 receives incoming wastewater (brine) and performs desalination, separating it into acid solution, alkaline solution, and diluted brine for discharge. A unit stack 210 includes a brine (wastewater) supply channel and two electrode liquid supply channels, an acid solution discharge channel, an alkaline solution discharge channel, and a diluted brine discharge channel.

[0109] In the system 100 of the present invention, the electrodialysis apparatus includes at least one unit stack 210, which may be configured as a stack of 100 to 200 unit cells. The number of unit stacks 210 included in the chemical recovery unit 150 and the number of unit cells stacked within each unit stack 210 may vary depending on the processing capacity of the system 100 and the salt concentration of the incoming wastewater. The detailed configuration of the unit stack 210 is as follows: Figure 3 As shown.

[0110] Figure 3 This is a diagram illustrating the unit stack structure of a bipolar membrane electrodialysis apparatus according to an embodiment of the present invention.

[0111] Reference Figure 3 The unit stack 210 includes a positive electrode 311, an anion exchange membrane 313, a cation exchange membrane 315, a bipolar membrane 317, a negative electrode 319, a brine (wastewater) supply section 330, a first electrode liquid inflow section 340, a second electrode liquid inflow section 350, an acid solution discharge section 360, an alkaline solution discharge section 370, and a diluted brine discharge section 380.

[0112] As described above, the unit stack 210 is formed by stacking multiple units. Each unit includes a brine channel, an acid solution channel, and an alkali channel, each separated by a cation exchange membrane, a bipolar membrane, and an anion exchange membrane. The unit stack 210 can be constructed by repeatedly stacking multiple unit units. Accordingly, anion exchange membrane 313, cation exchange membrane 315, and bipolar membrane 317 are sequentially and repeatedly arranged between the positive electrode 311 and the negative electrode 319 within the unit stack 210. Furthermore, spacers (not shown) are disposed between the internal ion exchange membranes and bipolar membranes, thereby forming channels between the membranes.

[0113] Electrodialysis is a process that uses an ion-exchange membrane and an electric field created by a DC power supply to its ends to separate ionic substances. If salt (MX) flows in, cations (M) will separate under the potential gradient. + The anions (X) move towards the reduction electrode side through the cation exchange membrane 315. -It moves toward the oxidation electrode side through the anion exchange membrane 313, thereby performing desalination.

[0114] In addition, the bipolar membrane 317 is a combination of anion exchange layer and cation exchange layer. When the cation exchange layer of the bipolar membrane 317 is arranged facing the negative electrode 319 and the anion exchange layer is arranged facing the positive electrode 311, water molecules are decomposed into hydrogen ions and hydroxide ions.

[0115] Wastewater (brine) discharged from the separation membrane filtration section 140 is supplied to the brine supply section 330 of the unit stack 210 and moves along the flow channel formed between the anion exchange membrane 313 and the cation exchange membrane 315. The diluted brine that has been desalinated in the unit stack 210 is discharged through the diluted brine discharge section 380.

[0116] On the other hand, as mentioned above, bipolar membrane electrodialysis devices require the addition of electrode liquid, i.e., water, for the desalination of waste liquid. In this invention, the electrode liquid is supplied from the treated water discharged from the reclaimed water production unit 170.

[0117] The electrode solution supplied to the unit stack 210 is supplied to the first electrode solution inlet 340 and the second electrode solution inlet 350. The supplied electrode solution moves along the flow channels between the bipolar membrane 317 and the anion exchange membrane 313, between the bipolar membrane 317 and the cation exchange membrane 315, between the positive electrode 311 and the ion exchange membrane, and between the negative electrode 319 and the ion exchange membrane, and recovers acid and alkali. The acid solution recovered in the unit stack 210 is discharged through the acid solution discharge section 360, and the alkali solution is discharged through the alkali solution discharge section 370.

[0118] Refer again Figure 2 In the case where the chemical recovery unit 150 includes multiple (n) unit stacks 210 arranged in series, the acid solution discharge channel of the (n-2)th unit stack 210 is connected to any one of the electrode liquid supply channels of the (n-1)th unit stack 210, and the alkali solution discharge channel of the (n-2)th unit stack 210 is connected to the other electrode liquid supply channel of the (n-1)th unit stack 210. Additionally, the diluted brine discharge channel of the (n-2)th unit stack 210 is connected to the brine (wastewater) supply channel of the (n-1)th unit stack 210.

[0119] At this time, clean water supplied from the reclaimed water production unit 170 is supplied to the chemical recovery unit 150 through the two electrode liquid supply channels of the first unit stack 210 (1). Subsequently, acid and alkali are recovered simultaneously as they pass through multiple unit stacks 210, thus moving along the electrode liquid supply channels in the form of acid solutions and alkali solutions. As a result, the acid solutions and alkali solutions discharged through the acid solution discharge channel and alkali solution discharge channel of the nth unit stack 210 (n) are finally discharged and collected in the acid solution recovery tank 230 and alkali solution recovery tank 250, respectively.

[0120] In summary, clean water (electrode solution) and wastewater (salt water) are supplied to the upstream unit stack 210 of the multiple unit stacks 210 in the chemical recovery section 150. When voltage is applied to the electrodialysis unit, sulfuric acid (H2SO4) and sodium hydroxide (NaOH) are recovered from the supplied wastewater. After this process, the sulfuric acid discharged from the downstream unit stack 210 is collected in the acid solution recovery tank 230, and the sodium hydroxide is collected in the alkali solution recovery tank 250.

[0121] In addition, the diluted brine discharged from the first unit stack 210 (1) is desalinated and flows into the second unit stack 210 (2) as brine and is desalinated again. As a result, in the nth unit stack 210 (n), the wastewater flowing in from the separation membrane filter section 140 is subjected to the nth desalination process of recovering acid and alkali.

[0122] On the other hand, the ion transfer process in electrodialysis is a result of ion concentration polarization occurring in the ion exchange membrane through convection-diffusion. At this point, the concentration distribution near the ion exchange membrane is linear, with ion transfer caused by electrophoresis and diffusion reaching equilibrium; the higher the applied voltage, the greater the concentration gradient.

[0123] The concentration gradient or the ion transport (current) it causes will not increase indefinitely; it reaches its maximum value at the point where the concentration at the interface between the ion exchange membrane and the solution is zero. This is called the limiting current value caused by the diffusion limit. Since the most salt ions can be removed at the voltage that produces this limiting current, the limiting current value is usually set as the optimal value for the process in desalination systems using electrodialysis.

[0124] Since the limiting current varies depending on the type and concentration of the solution, it can be determined experimentally, and the system's effectiveness can be maximized by operating the electrodialysis device within the range that does not exceed the limiting current.

[0125] The chemical recovery unit 150 of the present invention operates the electrodialysis apparatus in a constant current manner, that is, in a manner that supplies a certain current regardless of the change in solution concentration inside the unit stack 210, so as to control all reactions of electrodialysis.

[0126] However, the chemical recovery unit 150 of the present invention comprises multiple unit stacks 210 of the electrodialysis apparatus arranged in series to desalinate wastewater. In this case, the wastewater passes through multiple unit stacks 210 and is continuously desalinated. If a certain stage of the unit stacks 210 is reached, the ion concentration in the wastewater decreases, resulting in a sharp drop in current.

[0127] If the concentration of the brine flowing into the unit stack 210 decreases and exceeds the limiting current, side reactions such as hydrolysis, salt precipitation, and membrane fouling will occur. In this invention, the demineralized water discharged from the chemical recovery unit 150 is discharged as concentrated water through the reclaimed water treatment unit 170. This concentrated water is then passed through the activated carbon adsorption unit 180 to remove organic matter. The concentrated brine, from which organic matter has been removed, flows back into the chemical recovery unit 150, thereby effectively preventing overcurrent phenomena.

[0128] Reference Figure 2 The concentrated brine discharged from the activated carbon adsorption section 180 flows into the brine (wastewater) supply channel of the multiple unit stacks 210. In this case, in terms of the location where the concentrated brine flows into the channel, it is preferable to flow into the brine (wastewater) supply channel located after the middle section of the unit stack 210 from the most upstream unit stack 210 of the n unit stacks 210, that is, after the n / 2th unit stack 210 (n / 2).

[0129] The rate at which the concentrated brine discharged from the activated carbon adsorption unit 180 flows back into the chemical recovery unit 150 is set to ensure that the salt concentration of the concentrated brine does not exceed the initial salt concentration, i.e., the salt concentration of the wastewater flowing in from the separation membrane filtration unit 140.

[0130] The acid solution recovery tank 230 and the alkali solution recovery tank 250 temporarily store the sulfuric acid and sodium hydroxide recovered from the unit stack 210 of the bipolar membrane electrodialysis unit until they are supplied to the chemical concentration section 160.

[0131] The chemical recovery unit 150 of the present invention uses a bipolar membrane electrodialysis device, which enables the recovery of only acids and bases without generating other byproducts, thus achieving a low-pollution and pollution-free treatment method.

[0132] On the other hand, the chemical recovery unit 150 of the present invention can receive electricity generated and supplied by a renewable energy-based power generation system to drive the bipolar membrane electrodialysis apparatus. As an example, the bipolar membrane electrodialysis apparatus of the present invention can receive all or part of the power supplied from a power generation system that generates electricity using renewable energy sources such as solar or wind power as a power source applied to the positive electrode 311 and negative electrode 319 provided in each unit stack 210 for driving.

[0133] Figure 4 This is a diagram illustrating the structure of a chemical concentration section 160 according to an embodiment of the present invention.

[0134] The chemical concentration section 160 concentrates acid and alkali solutions recovered by evaporation concentration methods to the concentrations of acid and alkali required in the precursor preparation process.

[0135] Reference Figure 4 The chemical concentration section 160 includes an evaporator 410 and a heat recovery unit 420.

[0136] Evaporators 410a and 410b receive recovered acid and alkali solutions from the chemical recovery unit 150 and externally flowing steam, raising the temperature to a range of 120-150°C to evaporate water and concentrate the chemicals. The concentrated chemicals are then fed into the precursor preparation process for reuse. Waste steam discharged during evaporation is recovered for energy recovery and reused within the process. Additionally, the water from which energy is recovered is discharged as condensate, which is recycled and used as the electrode solution in the chemical recovery unit 150.

[0137] At this point, either the acid or alkaline evaporator 410b may further include a heat recovery device 420 upstream, which can receive waste steam discharged from and supplied from another chemical evaporator 410a to preheat the chemicals concentrated in either evaporator 410b.

[0138] As an example, heat recovery device 420 is configured upstream of the evaporator 410b of the alkaline solution. Heat recovery device 420 receives the alkaline solution flowing in from the alkaline solution recovery tank 250, and receives waste steam discharged and supplied from the evaporator 410a of the acid solution and waste steam discharged and supplied from the evaporator 410b of the alkaline solution to preheat the alkaline solution.

[0139] In this way, the waste steam generated in the evaporator 410 of the acid or alkaline solution can be reused for preheating another chemical, thereby saving up to 30-50% of the steam consumed in the chemical concentration section 160. As equipment for reusing steam, a mechanical vapor recompressor (MVR, not shown) or a thermal vapor recompressor (TVR, not shown) can be used.

[0140] The system 100 of the present invention is specifically implemented by configuring a series of unit processes as pretreatment in the process of treating wastewater generated during the preparation of precursors for cathode materials, thereby enabling the effective recovery of chemicals, thereby enabling resource reuse, reducing environmental degradation caused by waste discharged into the ecosystem, and having advantages such as saving precursor production costs.

[0141] In addition, the final treated water discharged from the system 100 and the concentrated water discharged from the unit process are recycled as brine for the chemical recovery unit, which enables the chemical recovery unit to operate stably and recovers all chemicals contained in the wastewater. Therefore, it has the advantage of being able to treat the wastewater generated in the precursor preparation process with zero discharge.

[0142] Figure 5 This is a flowchart illustrating a zero-discharge treatment method for wastewater generated during the preparation of a cathode material precursor for secondary batteries, according to an embodiment of the present invention.

[0143] Remove ammonia from the wastewater generated during the preparation of cathode material precursors (S510).

[0144] The wastewater generated during the preparation of cathode material precursors contains a high concentration of ammonium ions. To address this, the incoming wastewater is stripped with air to remove the ammonia. The ammonia removed from the wastewater is then recovered as ammonia water and reused in the precursor preparation process.

[0145] Removal of cationic metal components from wastewater in which ammonia has been removed (S520).

[0146] Wastewater after ammonia removal is passed through an ion exchange resin to remove metal ions. Wastewater generated during precursor preparation contains various metal ions, which are removed using a cation exchange resin. The metal components removed by the ion exchange resin can be recovered based on their concentration and reused as raw materials in the precursor preparation process.

[0147] For wastewater that has already had ammonia and metal ions removed, remove organic matter and particulate matter (S530).

[0148] To remove organic matter and particulate matter from wastewater, membrane filtration 140 can be used, especially ultrafiltration (UF). Wastewater with organic matter and some particulate matter removed by membrane filtration is discharged to the chemical recovery unit 150.

[0149] Recover chemicals from wastewater in which organic matter and particulate matter have been removed (S540).

[0150] The chemical recovery unit 150 receives wastewater that has undergone a series of pretreatment processes to remove ammonia, metal ions, organic matter, and particulate matter, and uses a bipolar membrane electrodialysis unit to recover acids and alkalis from the high-salinity wastewater. At this point, the incoming wastewater can undergo multi-stage desalination treatment through multiple bipolar membrane electrodialysis units connected in series in the unit stacks 210.

[0151] The recovered chemicals are discharged to the chemical concentration section 160 for reuse in the precursor preparation process, and the desalination wastewater is discharged to the reclaimed water production section 170.

[0152] Treating desalinated wastewater to produce reclaimed water and concentrating recovered chemicals (S550).

[0153] The reclaimed water production section 170 uses a reverse osmosis (RO) membrane separation process to remove residual salts and organic matter from the desalination wastewater. The treated water from the RO membrane is supplied to the chemical recovery section 150 to be used as the electrode solution for a bipolar membrane electrodialysis unit. The unfiltered concentrated water from the reclaimed water production section 170 is further treated in the activated carbon adsorption section 180 to remove organic matter, and is discharged as concentrated brine. This brine is then returned to the wastewater supply channel to replenish the salt concentration in the chemical recovery section 150.

[0154] In addition, the chemicals recovered in the chemical recovery step are concentrated by evaporating water with steam in order to adjust the concentration to a level that can be used in the precursor preparation process, and the chemicals are then reintroduced into the precursor preparation process.

[0155] Although Figure 5 The process is described as being executed sequentially, but this is merely an illustrative representation of the technical concept of one embodiment of the invention. In other words, those skilled in the art can modify the order of the processes described in the various figures without departing from the essential characteristics of one embodiment of the invention, or execute one or more processes in parallel, thereby making various modifications and variations to suit the application. Figure 5 It is not limited to chronological order.

[0156] The above description is merely illustrative of the technical concept of this embodiment. Those skilled in the art can make various modifications and variations without departing from the essential characteristics of this embodiment. Therefore, this embodiment is intended to illustrate the technical concept of this embodiment, and not to limit the technical concept of this embodiment. The scope of the technical concept of this embodiment is not limited by these embodiments. The protection scope of this embodiment should be interpreted by the appended claims, and all technical concepts falling within the equivalent scope should be interpreted as being included within the scope of the claims of this embodiment.

[0157] Cross-reference to related applications

[0158] If this patent application claims priority to U.S. Patent Application No. 10-2023-0153201, filed November 8, 2023 in Korea, all of which shall be incorporated herein by reference. Furthermore, if this patent application claims priority to any country outside the United States for the same reasons described above, all of which shall be incorporated herein by reference.

Claims

1. A zero-discharge treatment system for wastewater generated during the preparation of precursors for cathode materials used in secondary batteries, comprising: The ammonia stripping section removes ammonia from the wastewater generated during the precursor preparation process. The ion exchange unit receives the wastewater after the ammonia components have been removed and removes metal ions from the wastewater. The chemical recovery department recovers acid and alkaline solutions from the wastewater where the ammonia and metal ions have been removed. as well as The reclaimed water production department filters the wastewater from which the aforementioned acid and alkali solutions have been recovered, producing reclaimed water for use in the aforementioned system.

2. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 1, wherein, The aforementioned zero-emission treatment system further includes a chemical concentration unit. The aforementioned chemical concentration unit concentrates the acid and alkali solutions recovered by the aforementioned chemical recovery unit and resupplys them to the precursor preparation process.

3. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 1, wherein, The aforementioned zero-emission treatment system further includes a separation membrane filtration unit, which receives the wastewater flowing in after treatment in the aforementioned ion exchange unit, removes organic matter and particulate matter, and then discharges the wastewater to the aforementioned chemical recovery unit.

4. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 1, wherein, The aforementioned chemical recovery unit includes a bipolar membrane electrodialysis unit to receive the incoming wastewater and recover acid and alkali solutions.

5. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 4, wherein, In the above-mentioned bipolar membrane electrodialysis device, multiple unit stacks are connected in series to receive the incoming wastewater and perform desalination treatment by recovering acid and alkali solutions in multiple stages.

6. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 5, wherein, The aforementioned unit stack includes multiple anion exchange membranes, cation exchange membranes, and bipolar membranes located between the positive and negative electrodes. These multiple membranes are arranged in a repeating sequence of anion exchange membrane, cation exchange membrane, and bipolar membrane. Spacers are arranged between adjacent membranes.

7. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 5, wherein, The aforementioned bipolar membrane electrodialysis device receives the final treated water produced and supplied in the aforementioned reclaimed water production unit in order to recover acid and alkali solutions from the aforementioned wastewater, and uses it as electrode solution.

8. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 5, wherein, The aforementioned bipolar membrane electrodialysis device receives electricity from a solar or wind power generation system and uses it as a power source applied to the positive and negative electrodes.

9. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 1, wherein, The pH value of the wastewater generated during the precursor preparation process flowing into the ammonia stripping section is above 10.

10. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 5, wherein, The aforementioned zero-emission treatment system further includes an activated carbon adsorption unit. The activated carbon adsorption unit receives concentrated water containing unfiltered residual pollutants flowing from the reclaimed water production unit, and removes organic matter from the concentrated water. The concentrated water discharged after the removal of organic matter is recycled back to the aforementioned chemical recovery unit and flows into the wastewater supply channel that supplies the aforementioned multiple unit stacks.

11. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 1, wherein, The aforementioned ion exchange section includes a cation exchange resin. The wastewater flowing into the aforementioned ion exchange unit contains one or more elements selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al).

12. The zero-discharge treatment system for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 1, wherein, The aforementioned reclaimed water production unit is a reverse osmosis (RO) membrane unit.

13. A zero-discharge treatment method for wastewater generated during the preparation of precursors for positive electrode materials used in secondary batteries, comprising treating wastewater containing heavy metals and high concentrations of ammonia generated during the preparation of precursors for positive electrode materials used in secondary batteries, characterized in that the zero-discharge treatment method includes: The step of removing ammonia from wastewater generated during precursor preparation; The step of removing metal ions from wastewater from which the above-mentioned ammonia components have been removed; The steps for removing organic matter and particulate matter from wastewater that has already had the aforementioned metal ions removed; The steps of recovering sulfuric acid and sodium hydroxide from wastewater from which the above-mentioned organic matter and particulate matter have been removed; and The step involves further removing residual salts from the desalinated wastewater, which has already been treated by recovering sulfuric acid and sodium hydroxide, to produce reclaimed water.

14. The zero-discharge treatment method for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 13, wherein, The produced reclaimed water is supplied to the process of recovering sulfuric acid and sodium hydroxide for reuse.

15. The zero-discharge treatment method for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 13, wherein, In the ammonia removal step, the wastewater is stripped with air or steam to remove ammonia.

16. The zero-discharge treatment method for wastewater generated during the preparation of the precursor for the positive electrode material of a secondary battery according to claim 13, characterized in that, In the step of recovering sulfuric acid and sodium hydroxide, the wastewater is recovered into sulfuric acid and sodium hydroxide by a bipolar membrane electrodialysis unit.

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