CN114853245A - Ternary precursor wastewater treatment method and system - Google Patents
Ternary precursor wastewater treatment method and system Download PDFInfo
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- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
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Abstract
The invention discloses a ternary precursor wastewater treatment method, which comprises mother liquor and washing liquor generated in a ternary precursor preparation process, wherein the treatment method comprises a weight removal step, the weight removal step comprises the steps of combining the mother liquor and the concentrated solution of the washing liquor, carrying out first evaporation crystallization, controlling the pH of the combined wastewater to be 2.5-4.5, and carrying out solid-liquid separation to obtain a first evaporation crystallization precipitate and a first evaporation crystallization mother liquor, wherein the first evaporation crystallization precipitate contains heavy metal precipitate. By adopting the ternary precursor wastewater treatment method, the heavy metals in the wastewater can be removed in a self-precipitation manner without adding a large amount of alkali, so that the production cost can be effectively reduced. The invention also discloses a ternary precursor wastewater treatment system for realizing the ternary precursor wastewater treatment method.
Description
Technical Field
The invention relates to the technical field of wastewater treatment, in particular to a lithium battery ternary precursor wastewater treatment method and system.
Background
At present, a precursor material of a ternary positive electrode of a lithium battery is mainly prepared by taking Ni salt, Co salt and Mn salt as raw materials, a coprecipitation method is usually adopted for preparing the ternary precursor material, heavy metal ion salt is prepared into solution according to requirements, heavy metal precipitate is formed under an alkaline condition, and then the ternary precursor material is subjected to centrifugation, washing, slurrying, drying and other steps to obtain a qualified ternary precursor product. The washing liquid contains sodium sulfate, free ammonia and a small amount of metal impurities such as Ni, Co, Mn and the like, and the concentrated solution obtained after concentration treatment is usually merged into the mother solution for treatment.
In the prior art, the conventional process for treating the wastewater is to make metal ions such as nickel, cobalt, manganese and the like form precipitates by using methods such as dosing, alkali regulation and the like, and then remove heavy metal ions in the ternary precursor wastewater through resin secondary adsorption. For example, CN114230084A and CN112299638A both disclose methods for treating ternary precursor wastewater, which both utilize heavy metal ions to form nickel-cobalt-manganese hydroxide precipitate under alkaline conditions for removal. Since the precipitate of hydroxide is usually at a pH above 10, a large amount of alkali is required, otherwise the precipitation reaction of heavy metals cannot be completely carried out, and the addition of a large amount of alkali increases energy consumption and treatment cost.
Disclosure of Invention
The invention aims to solve the problem that the prior art needs to add a large amount of alkali to remove heavy metal ions in ternary precursor wastewater, so that the wastewater treatment cost is increased. The invention provides a novel ternary precursor wastewater treatment method and system, which can remove heavy metals in wastewater in a self-precipitation manner without adding a large amount of alkali, and can effectively reduce the production cost.
Specifically, the invention discloses a ternary precursor wastewater treatment method, wherein the ternary precursor wastewater comprises mother liquor and washing liquor generated in a ternary precursor preparation process. The treatment method comprises a weight removal step, wherein the weight removal step comprises the steps of combining the mother liquor and the concentrated solution of the washing liquor, carrying out primary evaporative crystallization, controlling the pH of the combined wastewater to be 2.5-4.5, and carrying out solid-liquid separation to obtain a primary evaporative crystallization precipitate and a primary evaporative crystallization mother liquor, wherein the primary evaporative crystallization precipitate contains heavy metal precipitate.
The ternary precursor wastewater treated by the method mainly contains ammonium sulfate, oxalate and heavy metal ions mainly comprising Mn ions and Ni ions, and the content of Co ions is usually greatly lower than the content of Mn ions and Ni ions in the wastewater.
In the process of removing the heavy metal ions in the ternary precursor wastewater, the mother liquor is concentrated only by evaporation crystallization, so that the heavy metal ions in the wastewater are separated out in the form of oxalate precipitation, and a primary evaporation crystallization precipitate is formed and removed, so that the content of the heavy metal ions in the primary evaporation crystallization mother liquor is greatly reduced compared with that in the ternary precursor wastewater. Compared with the prior art, the weight removal process has lower process cost because a large amount of alkali is not required to be added. The heavy metal precipitate mainly comprising manganese oxalate and nickel oxalate is removed in the step of removing heavy metal.
If the pH values of the mother liquor and the concentrated solution of the washing liquid are high, ammonia in the wastewater can volatilize in the form of ammonia gas in the evaporation crystallization process, so that the pH values of the mother liquor and the concentrated solution of the washing liquid need to be controlled to be 2.5-4.5, and the reduction of the yield of ammonium sulfate caused by the volatilization of the ammonia in the wastewater is avoided.
Further, the ternary precursor wastewater treatment method also comprises a refining step and a salt preparation step, wherein the refining step comprises the steps of removing residual heavy metal ions in the primary evaporation crystallization mother liquor through resin, and removing residual oxalate in the primary evaporation crystallization mother liquor through adding lime;
and the salt preparation step comprises the steps of carrying out secondary evaporative crystallization on the refined primary evaporative crystallization mother liquor to obtain crystalline salt, and carrying out centrifugal drying on the crystalline salt to obtain the refined ammonium sulfate.
It is difficult to completely remove the heavy metal ions in the wastewater only by performing the primary evaporative crystallization operation in the de-heavy step, and a part of the heavy metal ions also remain in the primary evaporative crystallization mother liquor, and at this time, the residual heavy metal ions need to be adsorbed by a special de-heavy resin to be completely removed. However, it is difficult to completely remove oxalate contained in a large amount in the mother liquor only by precipitation of heavy metals, and it is necessary to further add lime to remove the excess oxalate by formation of calcium oxalate precipitate.
The refined mother liquor hardly contains impurity metal ions and oxalate ions, the refined ammonium sulfate can be obtained by carrying out secondary evaporation and crystallization on the refined mother liquor, and the refined ammonium sulfate after separation and drying can be directly used as a fertilizer product.
Further, the ternary precursor wastewater treatment method further comprises a re-dissolving step after the re-dissolving step, wherein the once evaporative crystallization precipitate is cleaned by using re-dissolving water and then filtered, and the filtrate is combined with the once evaporative crystallization mother liquor and then is refined.
Generally, the concentration multiple of the first evaporative crystallization is controlled to be 3-6 times, so that the primary evaporative crystallization precipitate precipitated in the process does not contain ammonium sulfate and only contains heavy metal precipitate, after solid-liquid separation, the primary evaporative crystallization precipitate is directly removed, and then the primary evaporative crystallization mother liquor is refined. However, in some cases, the concentration multiple and the process of the first evaporative crystallization step are difficult to control, so that the obtained primary evaporative crystallization precipitate contains ammonium sulfate, at this time, the primary evaporative crystallization precipitate needs to be redissolved, so that the ammonium sulfate therein can be dissolved in redissolved water, insoluble heavy metal precipitate is removed after solid-liquid separation, and the filtrate is merged into primary evaporative crystallization mother liquor so that the ammonium sulfate therein can enter a refining step, thereby avoiding resource waste.
Furthermore, the mass ratio of the re-dissolved water to the primary evaporative crystallization precipitate can be controlled to be within 2 times, so that excessive filtrate is prevented from entering the subsequent evaporative crystallization process, and the energy consumption is favorably controlled.
Further, in the ternary precursor wastewater treatment method, in the step of removing the heavy component, the temperature of the first evaporative crystallization is controlled to be 98-110 ℃, and in the step of preparing the salt, the temperature of the second evaporative crystallization is controlled to be 98-110 ℃.
The evaporation temperature is a conventional process parameter, the temperature range is controlled within 98-110 ℃, so that the liquid can be continuously evaporated, the energy consumption is wasted due to overhigh temperature, the evaporation rate is slowed down due to overlow temperature, and the processing capacity is reduced.
Furthermore, the weight removal ratio of the weight removal step in the ternary precursor wastewater treatment method is more than 85%. That is, compared with the original wastewater, more than 85% of heavy metal ions in the original wastewater can be removed by forming heavy metal precipitate after the pretreatment and the heavy metal removal steps.
Furthermore, Ni in the mother liquor of the purified primary evaporative crystallization is less than 0.05mg/L, Co is less than 0.05mg/L, and Mn is less than 0.05 mg/L. The residual heavy metal ions in the primary evaporation crystallization mother liquor can be thoroughly removed through the special heavy metal removal resin.
In the present application, the terms "heavy metal ion removal resin", "adsorption resin" and the like refer to a chelating resin having a specific functional group capable of forming a complex with heavy metal ions in a solution so that the heavy metal ions in the solution are deeply removed.
Further, the refined ammonium sulfate can at least meet the GB/T535-2020 II standard. The refined ammonium sulfate obtained by the salt preparation step can be directly used as a fertilizer, and can reach the standard of fertilizer-grade ammonium sulfate (GB/T535-.
Further, the ternary precursor wastewater treatment method also comprises a pretreatment step, wherein the pretreatment step comprises a mother solution pretreatment step and a washing solution pretreatment step,
the mother liquor pretreatment step comprises a step of adjusting the pH of the mother liquor to precipitate a part of heavy metal ions in the mother liquor and a filtration step;
the washing liquid pretreatment step includes a step of adjusting the pH of the washing liquid to precipitate a part of heavy metal ions therein, a filtration step, an adsorption step, and a concentration step to obtain a concentrated solution of the washing liquid.
The initial wastewater, including mother liquor and washing liquor, is acidic, wherein the pH of the mother liquor is generally below 3, and the pH of the washing liquor is generally 3-6. Respectively adding ammonia water into the efficient mother liquor sedimentation tank and the efficient washing liquor sedimentation tank, adjusting the pH of the wastewater to 6.5-10 by using the ammonia water, and enabling heavy metal ions such as nickel, cobalt, manganese and the like to form hydroxide sediment so as to remove part of the heavy metal ions in the wastewater in advance.
In the invention, the mother liquor and the washing liquor generated in the preparation process of the ternary precursor are separately treated, and the washing liquor needs to be concentrated by a reverse osmosis membrane and then merged into the mother liquor for subsequent evaporation crystallization steps due to the low content of various substances. The wash liquor is concentrated by a reverse osmosis membrane according to the prior art to increase the salt concentration therein. For example, the concentration (mass fraction) of ammonium sulfate in the mother liquor can be 8-9%, while the concentration of ammonium sulfate in the washing solution is usually 1-2%, and after multi-stage reverse osmosis, the concentration of ammonium sulfate in the washing solution can also reach 8-9%.
In a second aspect of the invention, a ternary precursor wastewater treatment system for realizing the ternary precursor wastewater treatment method comprises a mother liquor pretreatment system, a washing liquor pretreatment system and a primary evaporative crystallization system, wherein,
the washing liquid pretreatment system comprises a membrane concentration system, wherein the membrane concentration system at least comprises two stages of reverse osmosis units and is used for performing reverse osmosis on the washing liquid to obtain concentrated liquid of the washing liquid;
and a feed inlet of the primary evaporative crystallization system is respectively connected with a discharge outlet of the mother liquor pretreatment system and a discharge outlet of the washing liquor pretreatment system, and is used for carrying out primary evaporative crystallization after the concentrated solution of the washing liquor is merged into the mother liquor so as to obtain a primary evaporative crystallization precipitate and a primary evaporative crystallization mother liquor. As described above, in the primary evaporative crystallization process of the present invention, the pH of the combined waste water is controlled to be 2.5 to 4.5. Because ammonia water is added in the process of pretreating the mother liquor and the washing liquor to precipitate part of heavy metal ions in the mother liquor and the washing liquor, the wastewater is subjected to a pH adjusting step before entering a primary evaporative crystallization system.
Further, the ternary precursor wastewater treatment system also comprises a refining system and a secondary evaporation crystallization system, wherein,
and a feed inlet of the refining system is connected with a discharge outlet of the primary evaporative crystallization system and is used for removing residual heavy metal ions in the primary evaporative crystallization mother liquor through adsorption resin and removing oxalate in the mother liquor through lime. In the embodiment of the present invention, the heavy metal adsorption resin used is required to be used in the range of pH 5 to 7, and therefore, the wastewater is required to be subjected to a pH adjustment step before entering the purification system.
And a feed inlet of the secondary evaporative crystallization system is connected with a discharge outlet of the refining system and is used for carrying out secondary evaporative crystallization on the refined primary evaporative crystallization mother liquor so as to obtain refined ammonium sulfate.
Furthermore, the ternary precursor wastewater treatment system also comprises a re-dissolving impurity removal system, wherein a feed inlet of the re-dissolving impurity removal system is connected with another discharge outlet of the primary evaporative crystallization system, and a discharge outlet of the re-dissolving impurity removal system is connected with the refining system and is used for re-dissolving the primary evaporative crystallization precipitate so that ammonium sulfate contained in the primary evaporative crystallization precipitate can be re-dissolved and enters the refining system.
Further, the ternary precursor wastewater treatment system also comprises a pure water preparation system, wherein a feed inlet of the pure water preparation system is connected with the membrane concentration system, and the reverse osmosis produced water is further purified to obtain pure water.
In the invention, because the reverse osmosis membrane has low removal rate of ammonium ions, the concentration of ammonium in the reverse osmosis produced water exceeds the water quality requirement of reuse water, and the content of ammonium in the produced water needs to be further reduced through reverse osmosis of pure water.
Drawings
FIG. 1 shows a flow diagram of a ternary precursor wastewater treatment system in an embodiment of the invention.
Reference numerals:
1-mother liquor adjusting tank; 2-a high-efficiency mother liquor sedimentation tank; 3-mother liquor sand filtration and ultrafiltration tank; 4-a washing liquid adjusting tank; 5-washing liquid high-efficiency sedimentation tank; 6-washing liquid sand filtration and ultrafiltration tank; 7-a washing liquid adsorption tank; 8, a first reverse osmosis unit; 9-reverse osmosis unit II; evaporating the raw water pool by 10-ammonium sulfate; 11-ammonium sulfate evaporation crystallization pool; 12-a redissolution impurity removal system; 13-a refining unit; 14-ammonium sulfate recrystallization tank; 15-mixed salt and mixed salt treatment system; 16-a water producing pool of the reverse osmosis unit; 17-pure water reverse osmosis unit.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure. While the invention will be described in conjunction with the preferred embodiments, it is not intended that features of the invention be limited to these embodiments. On the contrary, the invention is described in connection with the embodiments for the purpose of covering alternatives or modifications that may be extended based on the claims of the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be practiced without these particulars. Moreover, some of the specific details have been left out of the description in order to avoid obscuring or obscuring the focus of the present invention. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
It should be noted that in this specification, like reference numerals and letters refer to like items in the following drawings, and thus, once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings.
The terms "first," "second," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
In the description of the present embodiment, it should be further noted that, unless explicitly stated or limited otherwise, the terms "disposed," "connected," and "connected" are to be interpreted broadly, e.g., as a fixed connection, a detachable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present embodiment can be understood in specific cases by those of ordinary skill in the art.
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
According to one embodiment of the invention, the mother liquor is 70m as shown in FIG. 1 3 The flow of the ammonium sulfate/h enters a mother liquor pretreatment system, the concentration of the ammonium sulfate in the mother liquor is 9%, the concentration of the oxalate is 5405mg/L, the concentration of Mn is 715.47mg/L, the concentration of Ni is 527.19mg/L, the concentration of Co is 171.9mg/L, and the pH value is 3.5-4.5. The mother liquor pretreatment system comprises a mother liquor adjusting tank 1, a mother liquor high-efficiency sedimentation tank 2 and a mother liquor sand filtration and ultrafiltration tank 3 which are sequentially connected. The mother liquor contains heavy metal impurities such as higher nickel, manganese, cobalt and the like, ammonia mother liquor is added into the efficient mother liquor sedimentation tank 2, suspended matters are removed through sand filtration and ultrafiltration, water enters a primary evaporative crystallization system, and the pH of the mother liquor is adjusted to about 8 by using ammonia water, so that heavy metal ions in the mother liquor are primarily precipitated and removed.
In a system with high concentration of ammonium sulfate, nickel, manganese and cobalt form stable complexes with ammonium ions, and the formation of corresponding hydroxide precipitates and a large amount of precipitation of nickel, manganese and cobalt cannot be guaranteed only by adjusting the pH value to 8. In addition, the mother liquor contains oxalate with high concentration, although manganese oxalate and nickel oxalate are insoluble in water, the manganese oxalate and nickel oxalate in the solution exist in a complex state with ammonium ions, and the manganese oxalate and nickel oxalate cannot be precipitated just by adjusting the pH value. This portion of the heavy metal ions present in the mother liquor in the complexed state needs to be subjected to a subsequent treatment step in order to be completely removed.
Washing liquid with a volume of 200m 3 And the flow of the ammonium sulfate enters a washing liquid pretreatment system at a flow rate of/h, the concentration of ammonium sulfate in the washing liquid is 1%, the concentration of Mn is 74.11mg/L, the concentration of Ni is 5.4mg/L, the concentration of Co is 1.8mg/L, the pH value is 5.5-6.5, and the amount of oxalate is below the detection limit. The washing liquid pretreatment system comprises a washing liquid adjusting tank 4, a washing liquid high-efficiency sedimentation tank 5, a washing liquid sand filtration and ultrafiltration tank 6, a washing liquid adsorption tank 7 and a reverse osmosis system which are connected in sequence. The washing liquid has large water amount and low ammonium sulfate concentration, and is obtained by removing suspended matters in the washing liquid through pretreatment steps such as a high-efficiency sedimentation tank, sand filtration, ultrafiltration and the like, removing metal ions such as nickel, cobalt, manganese and the like through an absorption resin in a washing liquid absorption tank 7, and then gradually concentrating the washing liquid in a reverse osmosis systemA concentrate of the washing liquid (also called reverse osmosis concentrate) and reverse osmosis produced water. In this embodiment, the reverse osmosis system includes two stages of reverse osmosis units, i.e., a first reverse osmosis unit 8 and a second reverse osmosis unit 9, which are reverse osmosis membranes. The concentration of the ammonium sulfate in the finally obtained reverse osmosis concentrated water is about 9 percent, and the ammonium sulfate and the pretreated mother liquor enter a primary evaporation crystallization system together.
And the reverse osmosis produced water enters a pure water preparation system. Because the reverse osmosis membrane has a low removal rate of ammonium ions, the concentration of ammonium in the reverse osmosis produced water exceeds the water quality requirement of reuse water, and the ammonium in the produced water needs to be further reduced through the pure water reverse osmosis unit 17.
And (3) carrying out primary evaporative crystallization on the mixed solution of the mother solution and the washing solution concentrated solution in a primary evaporative crystallization system, wherein the temperature of the primary evaporative crystallization is controlled to be 100 ℃, and the pH value of the mixed solution is 3. In the present embodiment, the primary evaporative crystallization system includes a raw ammonium sulfate evaporative water tank 10 and an ammonium sulfate evaporative crystallization tank 11. The first evaporation crystallization operation is performed in order to remove heavy metal ions from the wastewater by evaporating the solvent to increase the concentration of heavy metal ions and oxalate in the mother liquor, thereby helping to form nickel-cobalt-manganese oxalate precipitate. Along with the continuous process of the evaporation process, primary evaporation crystallization precipitate and primary evaporation crystallization mother liquor are obtained in the ammonium sulfate evaporation crystallization tank 11, and the primary evaporation mother liquor enters a refining system. And the condensed water generated in the evaporation crystallization process enters a pure water preparation system.
In this example, the precipitate from the first evaporative crystallization contains manganese oxalate, nickel oxalate and a small amount of ammonium sulfate. Because the obtained primary evaporation crystallization precipitate contains ammonium sulfate, the ammonium sulfate contained in the primary evaporation crystallization precipitate needs to be redissolved through redissolving and washing salt. The specific process comprises the following steps: and (3) enabling the primary evaporative crystallization precipitate to enter a re-dissolving impurity removal system, wherein the mass ratio of re-dissolving water to the primary evaporative crystallization precipitate is 2: 1. and then carrying out mud-water separation, wherein a large amount of metal precipitates in industrial production are subjected to mud-water separation through a plate-and-frame filter press, and a laboratory adopts a filtering device for filtering. In this example, the filtrate and the precipitate were separated by a plate and frame filter press, the insoluble matter thus filtered was a heavy metal precipitate, which was subjected to an external treatment, and the filtrate was fed to a purification system. In this embodiment, the re-dissolved water is system reuse water, and may be produced water in any section of the reverse osmosis process.
Of course, in other embodiments of the present invention, the composition of the precipitate from the first evaporative crystallization can be controlled by controlling the evaporation rate of the liquid during the first evaporative crystallization, so that the precipitate does not contain ammonium sulfate and only the oxalate of nickel, cobalt and manganese is precipitated. In this way, the precipitate only needs to be removed directly after the first evaporative crystallization operation, without having to go through a re-elution of the salt.
And refining and impurity removal are carried out on the primary evaporation crystallization mother liquor in a refining system. In the present embodiment, the refining system includes the refining unit 13, and the refining unit 13 includes a heavy metal adsorption resin. Before the primary evaporation crystallization mother liquor passes through the heavy metal adsorption resin, the pH value is adjusted to about 6 so as to ensure that the heavy metal adsorption resin has a good adsorption effect on the residual heavy metal ions in the mother liquor. And adding a proper amount of lime into the mother liquor to remove residual oxalate in the mother liquor. After the resin and the calcium oxalate precipitate are removed, the refined primary evaporative crystallization mother liquor enters a secondary evaporative crystallization system. Ni in the refined primary evaporative crystallization mother liquor is less than 0.05mg/L, Co is less than 0.05mg/L, Mn is less than 0.05mg/L, the removal rate of oxalate in the mother liquor reaches more than 80%, and the residual oxalate can be recycled in the system.
And (3) carrying out secondary evaporative crystallization on the refined primary evaporative mother liquor in a secondary evaporative crystallization system, and finishing in an ammonium sulfate recrystallization tank 14. The temperature of the second evaporation crystallization is controlled to be 100 ℃. As the evaporation process continues, crystalline salt is continuously obtained in the secondary evaporation crystallization system. And (4) centrifuging the crystallized salt, and drying by a fluidized bed to obtain the dried crystallized salt, namely the refined ammonium sulfate. The refined ammonium sulfate obtained in the embodiment meets the standard of GB/T535-2020 ammonium sulfate for fertilizer grade II.
While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing is a more detailed description of the invention, taken in conjunction with the specific embodiments thereof, and that no limitation of the invention is intended thereby. Various changes in form and detail, including simple deductions or substitutions, may be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (12)
1. The ternary precursor wastewater treatment method is characterized by comprising a de-weighting step, wherein the de-weighting step comprises combining a mother liquor and a concentrated solution of a washing solution and then carrying out primary evaporative crystallization, controlling the pH of the combined wastewater to be 2.5-4.5, carrying out solid-liquid separation to obtain a primary evaporative crystallization precipitate and a primary evaporative crystallization mother liquor, and the primary evaporative crystallization precipitate contains heavy metal precipitate.
2. The method for treating ternary precursor wastewater according to claim 1, further comprising a refining step and a salt-making step, wherein,
the refining step comprises the steps of enabling the primary evaporative crystallization mother liquor to pass through resin to remove residual heavy metal ions, and then adding lime to remove residual oxalate;
and the salt preparation step comprises the steps of carrying out secondary evaporative crystallization on the refined primary evaporative crystallization mother liquor to obtain crystalline salt, and carrying out centrifugal drying on the crystalline salt to obtain the refined ammonium sulfate.
3. The method for treating ternary precursor wastewater according to claim 2, further comprising a re-dissolving step after the de-re-dissolving step, wherein the primary evaporative crystallization precipitate is washed with re-dissolving water and then filtered, and the refining step is performed after the filtrate is incorporated into the primary evaporative crystallization mother liquor.
4. The ternary precursor wastewater treatment method according to claim 2 or 3, wherein in the de-emphasis step, the temperature of the first evaporative crystallization is controlled to be 98 to 110 ℃, and in the salt production step, the temperature of the second evaporative crystallization is controlled to be 98 to 110 ℃.
5. The method of treating ternary precursor wastewater according to claim 1, wherein the weight removal ratio of said weight removal step is 85% or more.
6. The method for treating ternary precursor wastewater according to claim 2, wherein Ni in the refined primary evaporative crystallization mother liquor is less than 0.05mg/L, Co is less than 0.05mg/L, and Mn is less than 0.05 mg/L.
7. The ternary precursor wastewater treatment method as claimed in claim 2 or 3, wherein the refined ammonium sulfate at least meets GB/T535-2020 II standard.
8. The ternary precursor wastewater treatment process of claim 1 wherein a pretreatment step comprising a mother liquor pretreatment step and a wash liquor pretreatment step is performed prior to said de-weighting step, wherein,
the mother liquor pretreatment step comprises a step of adjusting the pH of the mother liquor to precipitate a part of heavy metal ions therein and a filtration step;
the washing liquid pretreatment step comprises a step of adjusting the pH of the washing liquid to precipitate a part of heavy metal ions therein, a filtration step, an adsorption step and a concentration step to obtain a concentrated solution of the washing liquid.
9. A ternary precursor wastewater treatment system for implementing the ternary precursor wastewater treatment method according to any one of claims 1 to 8, comprising a mother liquor pretreatment system, a washing liquor pretreatment system, and a primary evaporative crystallization system, wherein,
the washing liquor pretreatment system comprises a membrane concentration system, wherein the membrane concentration system at least comprises two stages of reverse osmosis units and is used for performing reverse osmosis on the washing liquor to obtain a concentrated solution of the washing liquor;
the feed inlet of the primary evaporative crystallization system is respectively connected with the discharge outlet of the mother liquor pretreatment system and the discharge outlet of the washing liquor pretreatment system, and is used for merging the concentrated solution of the washing liquor into the mother liquor and then carrying out the primary evaporative crystallization to obtain the primary evaporative crystallization precipitate and the primary evaporative crystallization mother liquor.
10. The ternary precursor wastewater treatment system of claim 9, further comprising a polishing system and a secondary evaporative crystallization system, wherein,
the feed inlet of the refining system is connected with the discharge outlet of the primary evaporative crystallization system and is used for removing heavy metal ions and oxalate radicals remaining in the primary evaporative crystallization mother liquor;
and the feed inlet of the secondary evaporative crystallization system is connected with the discharge outlet of the refining system and is used for carrying out secondary evaporative crystallization on the refined primary evaporative crystallization mother liquor so as to obtain refined ammonium sulfate.
11. The ternary precursor wastewater treatment system according to claim 10, further comprising a re-dissolution impurity removal system, wherein a feed inlet of the re-dissolution impurity removal system is connected with another discharge outlet of the primary evaporative crystallization system, and a discharge outlet of the re-dissolution impurity removal system is connected with the refining system, and is used for re-dissolving the primary evaporative crystallization precipitate so that ammonium sulfate contained in the primary evaporative crystallization precipitate can be re-dissolved into the refining system.
12. The ternary precursor wastewater treatment system of claim 9, further comprising a pure water system having a feed inlet connected to the membrane concentration system for further purifying the reverse osmosis product water to pure water.
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