CN117800546A - Method for recycling wastewater - Google Patents
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- CN117800546A CN117800546A CN202410127376.2A CN202410127376A CN117800546A CN 117800546 A CN117800546 A CN 117800546A CN 202410127376 A CN202410127376 A CN 202410127376A CN 117800546 A CN117800546 A CN 117800546A
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- 238000011282 treatment Methods 0.000 claims abstract description 114
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- 239000002253 acid Substances 0.000 claims abstract description 47
- 238000000926 separation method Methods 0.000 claims abstract description 27
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- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 231
- 235000006408 oxalic acid Nutrition 0.000 claims description 77
- 239000012528 membrane Substances 0.000 claims description 59
- -1 hydrogen ions Chemical class 0.000 claims description 49
- 239000012141 concentrate Substances 0.000 claims description 22
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 17
- 150000001768 cations Chemical class 0.000 claims description 17
- 229910001415 sodium ion Inorganic materials 0.000 claims description 14
- 238000000909 electrodialysis Methods 0.000 claims description 11
- 238000001704 evaporation Methods 0.000 claims description 11
- 239000001257 hydrogen Substances 0.000 claims description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 11
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 9
- 150000003839 salts Chemical class 0.000 claims description 8
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- 230000001105 regulatory effect Effects 0.000 claims description 3
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- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 16
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- 238000004519 manufacturing process Methods 0.000 description 8
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- 239000000126 substance Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 6
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Abstract
The application provides a recycling treatment method of wastewater, which comprises the following steps: a first nanofiltration step of subjecting wastewater containing monovalent anions and polyvalent anions to a first nanofiltration treatment to obtain first nanofiltration produced water containing monovalent anions and the remaining anions; a first reverse osmosis process, wherein the first nanofiltration produced water is subjected to first reverse osmosis treatment, and is separated to obtain first reverse osmosis concentrated water; a second nanofiltration step of performing a second nanofiltration treatment on the first reverse osmosis concentrated water to obtain a second nanofiltration product water containing monovalent anions; and an ion exchange procedure, wherein the second nanofiltration water is subjected to ion exchange treatment, and the first solution containing acid and the second solution containing alkali are respectively obtained through separation. The recycling treatment method provided by the embodiment of the application can effectively separate and recycle the acid in the wastewater so as to realize recycling of the wastewater.
Description
Technical Field
The application relates to the technical field of wastewater treatment, in particular to a recycling treatment method of wastewater.
Background
The industrial wastewater contains a large amount of various ions, and if the ions can be recycled, the raw material consumption in the industrial production process can be reduced, and the production cost can be reduced. Because of the large ion species in the wastewater, various separation methods are often adopted to treat the wastewater in stages during the treatment of the wastewater, so that various components in the wastewater are separated and recovered step by step.
At present, common wastewater separation methods comprise extraction, neutralization, evaporation and the like. However, these methods are generally used for separating a specific substance, but it is difficult to separate ions in various valence states contained in wastewater, and thus the recycling of wastewater is limited.
Disclosure of Invention
The application provides a recycling treatment method of wastewater, which can effectively separate and recycle acid in the wastewater to realize recycling utilization of the wastewater.
The embodiment of the application provides a recycling treatment method of wastewater, which comprises the following steps: a first nanofiltration step of subjecting wastewater containing monovalent anions and polyvalent anions to a first nanofiltration treatment to separate the monovalent anions and at least part of the polyvalent anions in the wastewater to obtain a first nanofiltration product water containing the monovalent anions and the remaining part of the polyvalent anions; a first reverse osmosis process, wherein the first nanofiltration product water is subjected to first reverse osmosis treatment, and is separated to obtain first reverse osmosis concentrated water, and the concentration of monovalent anions in the first reverse osmosis concentrated water is higher than that in the first nanofiltration product water; a second nanofiltration step of performing a second nanofiltration treatment on the first reverse osmosis concentrated water to separate monovalent anions from the remaining multivalent anions in the first reverse osmosis concentrated water, thereby obtaining a second nanofiltration product water containing the monovalent anions; and an ion exchange process, wherein the second nanofiltration water is subjected to ion exchange treatment so that monovalent anions and hydrogen ions are combined to form acid and cations and hydroxyl ions are combined to form alkali, and the acid-containing first solution and the alkali-containing second solution are respectively obtained through separation.
According to the recycling treatment method provided by the embodiment of the application, after the wastewater is subjected to the first nanofiltration treatment, high-valence ions can be intercepted by utilizing the nanofiltration and the property of penetrating low-valence ions is utilized, so that monovalent anions mainly enter first nanofiltration produced water, and multivalent anions are intercepted, and therefore separation of the monovalent anions and the multivalent anions in the wastewater is realized. And then carrying out first reverse osmosis treatment on the first nanofiltration produced water obtained by nanofiltration separation, and obtaining concentrated water by utilizing the high-pressure side and the produced water performance of the low-pressure side of reverse osmosis so as to obtain first reverse osmosis concentrated water with higher monovalent anion concentration. And then, after the first reverse osmosis concentrated water is subjected to second nanofiltration treatment, monovalent anions mainly enter second nanofiltration produced water, and multivalent anions are trapped, so that the separation of the monovalent anions and the multivalent anions in the first reverse osmosis concentrated water is realized. The second nanofiltration product water is then subjected to an ion exchange treatment such that monovalent anions and cations are combined with hydrogen ions and hydroxide ions, respectively, to obtain a first solution comprising an acid and a second solution comprising a base.
Therefore, according to the recycling treatment method provided by the embodiment of the application, weak acid anions and multivalent strong acid radical anions in the wastewater can be effectively separated by recycling the wastewater, and weak acid anions and cations in the wastewater are recovered to obtain the corresponding first solution containing acid and the corresponding second solution containing alkali, so that recycling utilization of the wastewater is realized.
In some embodiments of the present application, before the first nanofiltration process, the recycling process method further comprises: and an acid regulating procedure, namely adding acid into the wastewater to regulate the pH value of the wastewater to be in the range of 2.5-3.
In some embodiments of the present application, the acid comprises sulfuric acid.
In some embodiments of the present application, the first nanofiltration process comprises:
a primary nanofiltration step of subjecting wastewater containing monovalent anions and polyvalent anions to primary nanofiltration treatment to separate the monovalent anions and at least part of the polyvalent anions in the wastewater, thereby obtaining primary nanofiltration concentrate containing at least part of the polyvalent anions and part of the monovalent anions and primary nanofiltration product containing the remaining part of the monovalent anions and the remaining part of the polyvalent anions;
a secondary nanofiltration step of performing secondary nanofiltration treatment on the primary nanofiltration concentrated water to separate at least part of multivalent anions and part of monovalent anions in the primary nanofiltration concentrated water, thereby obtaining secondary nanofiltration concentrated water containing the at least part of multivalent anions and secondary nanofiltration product water containing part of monovalent anions; the second-stage nanofiltration concentrated water forms first nanofiltration concentrated water, and the first-stage nanofiltration produced water and the second-stage nanofiltration produced water are mixed to form the first nanofiltration produced water.
In some embodiments of the present application, the primary nanofiltration treatment has a molecular weight cut-off of 150Da to 300Da.
In some embodiments of the present application, the volume ratio of the primary nanofiltration product water to the wastewater is 50% -55% in the primary nanofiltration process.
In some embodiments of the present application, the molecular weight cut-off of the secondary nanofiltration treatment is 150Da to 300Da.
In some embodiments of the present application, the volume ratio of the secondary nanofiltration product water to the primary nanofiltration concentrate water in the secondary nanofiltration process is 55% -60%.
In some embodiments of the present application, in the first stage nanofiltration process, the first reverse osmosis produced water obtained by the first reverse osmosis treatment is mixed with the wastewater to perform the first stage nanofiltration process, and/or in the second stage nanofiltration process, the first reverse osmosis produced water obtained by the first reverse osmosis treatment is mixed with the first stage nanofiltration concentrate to perform the second stage nanofiltration process.
In some embodiments of the present application, the pH of the first reverse osmosis produced water is 2-3.
In some embodiments of the present application, in the first reverse osmosis treatment, the volume ratio of the first reverse osmosis produced water to the first nanofiltration produced water is 80% -90%.
In some embodiments of the present application, in the first nanofiltration step, the first nanofiltration step is performed by mixing the wastewater with the second nanofiltration concentrate obtained by the second nanofiltration treatment.
In some embodiments of the present application, the second nanofiltration treatment has a molecular weight cut-off of 150Da to 300Da.
In some embodiments of the present application, in the second nanofiltration process, the second nanofiltration product water to the first reverse osmosis concentrate water volume ratio is 83% -87%.
In some embodiments of the present application, the ion exchange process comprises: and (3) treating the second nanofiltration produced water by adopting a bipolar membrane electrodialysis method so that monovalent anions and hydrogen ions are combined to form acid and cations and hydroxide ions are combined to form alkali, and separating to obtain a first solution containing the acid and a second solution containing the alkali.
In some embodiments of the present application, the acid concentration in the first solution is from 0.24mol/L to 0.28mol/L.
In some embodiments of the present application, the concentration of the base in the second solution is 1.6mol/L to 2mol/L.
In some embodiments of the present application, after the ion exchange process, the recycling process further comprises: and a second reverse osmosis process, wherein the first solution is subjected to second reverse osmosis treatment, and second reverse osmosis concentrated water is obtained through separation, and the acid concentration in the second reverse osmosis concentrated water is higher than the acid concentration in the first solution.
In some embodiments of the present application, in the first nanofiltration step, the first nanofiltration step is performed by mixing the wastewater with the second reverse osmosis produced water obtained by the second reverse osmosis treatment.
In some embodiments of the present application, the acid concentration of the second reverse osmosis concentrate is 0.4mol/L to 0.45mol/L.
In some embodiments of the present application, in the second reverse osmosis treatment, the volume ratio of the second reverse osmosis concentrated water to the first solution is 40% -50%.
In some embodiments of the present application, the recycling method further includes: and an evaporation step of evaporating the first nanofiltration concentrated water to obtain a salt containing multivalent anions and cations.
In some embodiments of the present application, the wastewater comprises sodium ion battery wastewater.
In some embodiments of the present application, the wastewater contains monovalent anions including hydrogen oxalate ions.
In some embodiments of the present application, the wastewater contains multivalent anions including sulfate ions.
In some embodiments of the present application, the cations contained in the wastewater include sodium ions.
In some embodiments of the present application, the first solution comprises an oxalic acid solution.
In some embodiments of the present application, the oxalic acid recovery rate in the wastewater is greater than or equal to 69%.
In some embodiments of the present application, the second solution comprises a sodium hydroxide solution.
In some embodiments of the present application, the salt comprises sodium sulfate.
In some embodiments of the present application, the recovery of sodium sulfate in the wastewater is greater than or equal to 99.5%.
Additional aspects and advantages of the application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the application.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for recycling wastewater provided in some embodiments of the present application;
FIG. 2 is a flow chart of a method for recycling wastewater provided in some embodiments of the present application;
FIG. 3 is a flow chart of a method for recycling wastewater provided in some embodiments of the present application;
fig. 4 is a schematic diagram of the operation of the bipolar membrane electrodialysis system of example 1 of the present application.
Detailed Description
The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.
All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.
All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.
All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.
Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.
The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).
Referring to fig. 1, the present application provides a method for recycling wastewater, which includes:
s100, performing first nanofiltration treatment on the wastewater containing the monovalent anions and the multivalent anions to separate the monovalent anions and at least part of the multivalent anions in the wastewater, thereby obtaining first nanofiltration product water containing the monovalent anions and the rest of the multivalent anions.
S200, performing first reverse osmosis treatment on the first nanofiltration product water, and separating to obtain first reverse osmosis concentrated water, wherein the concentration of monovalent anions and cations in the first reverse osmosis concentrated water is higher than that in the first nanofiltration product water.
S300, a second nanofiltration process, namely performing second nanofiltration treatment on the first reverse osmosis concentrated water to separate monovalent anions from the rest multivalent anions in the first reverse osmosis concentrated water, so as to obtain second nanofiltration product water containing the monovalent anions.
S400, performing ion exchange treatment on the second nanofiltration water so as to combine monovalent anions with hydrogen ions to form acid and cations with hydroxyl ions to form alkali, and separating to obtain a first solution containing acid and a second solution containing alkali.
According to the recycling treatment method provided by the embodiment of the application, after the wastewater is subjected to the first nanofiltration treatment, high-valence ions can be intercepted by utilizing the nanofiltration and the property of penetrating low-valence ions is utilized, so that monovalent anions mainly enter first nanofiltration produced water, and multivalent anions are intercepted, and therefore separation of the monovalent anions and the multivalent anions in the wastewater is realized. And then carrying out first reverse osmosis treatment on the first nanofiltration produced water obtained by nanofiltration separation, and obtaining concentrated water by utilizing the high-pressure side and the produced water performance of the low-pressure side of reverse osmosis so as to obtain first reverse osmosis concentrated water with higher monovalent anion concentration. And then, after the first reverse osmosis concentrated water is subjected to second nanofiltration treatment, monovalent anions mainly enter second nanofiltration produced water, and multivalent anions are trapped, so that the separation of the monovalent anions and the multivalent anions in the first reverse osmosis concentrated water is realized. The second nanofiltration product water is then subjected to an ion exchange treatment such that monovalent anions and cations are combined with hydrogen ions and hydroxide ions, respectively, to obtain a first solution comprising an acid and a second solution comprising a base. Wherein multivalent anions refer to anions having a valence in excess of monovalent, such as divalent anions, trivalent anions, and the like.
The first nanofiltration treatment and the second nanofiltration treatment may be, for example, separation treatments of wastewater by nanofiltration membranes. The nanofiltration membrane is a filtration membrane with a pore diameter between that of ultrafiltration and reverse osmosis, high-valence ions are more easily trapped, and low-valence ions can permeate, so that ions in different valence states can be separated. Illustratively, the first nanofiltration process and the second nanofiltration process may employ disc tube nanofiltration, roll nanofiltration or other nanofiltration means.
Illustratively, the first reverse osmosis treatment is primarily a separation treatment of wastewater by a reverse osmosis membrane. The reverse osmosis membrane is characterized in that a solvent is reverse osmosis against a natural osmosis direction by applying pressure to feed liquid on one side of the membrane, so that permeate solvent, i.e. permeate liquid, is obtained on the low-pressure side of the membrane, and concentrate liquid is obtained on the high-pressure side of the membrane.
Therefore, according to the recycling treatment method provided by the embodiment of the application, weak acid anions and multivalent anions in the wastewater can be effectively separated by recycling the wastewater, and weak acid anions and cations in the wastewater are recovered to obtain the corresponding first solution containing acid and the corresponding second solution containing alkali, so that recycling of the wastewater is realized.
In some embodiments, the wastewater comprises sodium ion battery wastewater. In some embodiments, the wastewater contains monovalent anions that include hydrogen oxalate ions. In some embodiments, the wastewater contains multivalent anions including sulfate ions. In some embodiments, the cations contained in the wastewater include sodium ions. In some embodiments, the first solution comprises an oxalic acid solution. In some embodiments, the second solution comprises a sodium hydroxide solution. The waste water may be, for example, oxalic acid (H 2 C 2 O 4 ) Sodium ion battery waste water produced in the process of preparing sodium ion battery as solvent contains a large amount of oxalic acid, and oxalic acid mainly adopts oxalate (C 2 O 4 2- ) And hydrogen oxalate (HC) 2 O 4 - ) In the form of a gel. In addition, the waste water contains sulfate ions (SO 4 2- ) And sodium ionSon (Na) + )。
According to the recycling treatment method provided by the embodiment of the application, the pH value of the wastewater is controlled within the range of 2.5-3, so that oxalic acid in the wastewater mainly takes HC as a main component 2 O 4 - Is present. At this time, monovalent HC is produced by subjecting the wastewater to a first nanofiltration treatment 2 O 4 - Into the first nanofiltration product water, while the higher valence ions in the wastewater, such as divalent SO 4 2- Is trapped, thereby realizing the separation of oxalic acid and high-valence ions in the wastewater. Then the first nanofiltration product water is subjected to a first reverse osmosis treatment to obtain HC 2 O 4 - And the first reverse osmosis concentrated water with higher concentration. Then the first reverse osmosis concentrated water is subjected to a second nanofiltration treatment to further separate HC 2 O 4 - And high valence ions; then the second nanofiltration product water is subjected to ion exchange treatment, so that anions in the second nanofiltration product water, namely HC 2 O 4 - Conversion to H 2 C 2 O 4 The cation in the second nanofiltration product water is Na + Converted into sodium hydroxide (NaOH).
According to the recycling treatment method provided by the embodiment of the application, the oxalic acid solution and the sodium hydroxide solution can be effectively separated and recovered by recycling the wastewater. And as oxalic acid in the wastewater is separated, COD in the wastewater is reduced, which is beneficial to meeting the environmental protection requirement of wastewater discharge. Wherein COD (Chemical Oxygen Demand) refers to the amount of reducing substances to be oxidized in a water sample measured chemically, and the amount of oxygen equivalent of substances (typically organic substances) which can be oxidized by a strong oxidizing agent in wastewater, so COD is typically used to represent the total amount of organic substances in wastewater.
To more clearly demonstrate the advantages of the recycling treatment method of the present application, the following examples are specifically described with respect to examples in which the monovalent anions contained in the wastewater include hydrogen oxalate ions, the divalent weak acid anions include oxalate ions, the polyvalent anions include sulfate ions, and the cations include sodium ions.
In some embodiments, prior to the first nanofiltration process, the recycling process further comprises: and an acid adjusting step, namely adding acid into the wastewater to adjust the pH value of the wastewater to be within the range of 2.5-3. The oxalate and hydrogen oxalate are converted to each other in solution due to hydrolysis of oxalic acid. The pH value of the wastewater is controlled within the range of 2.5-3, so that the oxalic acid mainly exists in the form of monovalent hydrogen oxalate, and then the monovalent hydrogen oxalate can be separated from multivalent ions such as sulfate radical by nanofiltration, thereby being beneficial to improving the recovery rate of the oxalic acid.
In some embodiments, the acid comprises sulfuric acid. The sulfuric acid is selected to effectively regulate the pH value of the wastewater, and the introduced sulfate radical can be separated from the hydrogen oxalate in the nanofiltration stage, so that the introduction of impurities can be avoided.
In order to improve the separation effect of hydrogen oxalate ions and sulfate ions during nanofiltration, multiple nanofiltration treatments can be performed in stages in the first nanofiltration process.
Referring to fig. 2, in some embodiments, the first nanofiltration process includes:
s110, a primary nanofiltration step, namely carrying out primary nanofiltration treatment on wastewater containing monovalent anions and multivalent anions so as to separate the monovalent anions and at least part of the multivalent anions in the wastewater, thereby obtaining primary nanofiltration concentrated water containing at least part of the multivalent anions and part of the monovalent anions and primary nanofiltration product water containing the rest part of the monovalent anions and the rest part of the multivalent anions;
S120, performing secondary nanofiltration on the primary nanofiltration concentrated water to separate monovalent anions from multivalent anions in the primary nanofiltration concentrated water, thereby obtaining secondary nanofiltration concentrated water containing multivalent anions and secondary nanofiltration product water containing partial monovalent anions; wherein, the second nanofiltration concentrated water forms the first nanofiltration concentrated water, and the first nanofiltration product water and the second nanofiltration product water are mixed to form the first nanofiltration product water.
Through carrying out continuous first-stage nanofiltration treatment and second-stage nanofiltration treatment, the hydrogen oxalate ions and sulfate ions in the first-stage nanofiltration concentrated water can be further separated by utilizing the second-stage nanofiltration treatment, so that the sulfate ion content of the first nanofiltration product water is reduced, and the oxalic acid purity and oxalic acid recovery rate of the finally prepared oxalic acid solution are improved.
To enhance the separation of impurities by the nanofiltration process, in some embodiments, the first order nanofiltration treatment has a molecular weight cut-off of 150Da to 300Da. In some embodiments, the molecular weight cut-off of the secondary nanofiltration treatment is 150Da to 300Da. Wherein, the molecular weight cut-off refers to the molecular weight cut-off of the nanofiltration membrane. Under the proper molecular weight cut-off, the method can ensure that the hydrogen oxalate ions smoothly permeate the nanofiltration membrane, can cut-off and remove organic matters, heavy metals and high-valence salts in the wastewater so as to be beneficial to improving the oxalic acid purity of oxalic acid solution, and can also avoid the problems of macromolecular substance scaling and pollution blocking at the reverse osmosis membrane in the subsequent reverse osmosis process.
Because a small amount of sulfate radical enters nanofiltration water and a certain amount of hydrogen oxalate enters nanofiltration concentrated water during nanofiltration treatment, the ratio of the nanofiltration water to the nanofiltration concentrated water can influence the oxalic acid purity and the oxalic acid recovery rate of an oxalic acid solution. Therefore, it is necessary to control the recovery rate during the nanofiltration process.
In some embodiments, in the primary nanofiltration process, the volume ratio of primary nanofiltration produced water to wastewater is 50% -55%. In some embodiments, in the secondary nanofiltration process, the volume ratio of secondary nanofiltration product water to primary nanofiltration concentrate water is 55% -60%. The volume ratio of the primary nanofiltration produced water and the wastewater is controlled within the above range, so that the recovery rate of oxalic acid can be improved, and the separation of hydrogen oxalate ions and sulfate ions in the secondary nanofiltration treatment and the reduction of the treatment cost can be facilitated. The volume ratio of the secondary nanofiltration produced water to the primary nanofiltration concentrated water is controlled within the range, so that the oxalic acid recovery rate can be improved, and simultaneously, the hydrogen oxalate ions and sulfate ions can be effectively separated, so that the purity of an oxalic acid solution can be improved.
In order to increase the utilization rate of the wastewater, in some embodiments, in the first nanofiltration process, the first reverse osmosis produced water obtained by the first reverse osmosis treatment is mixed with the wastewater to perform the first nanofiltration process. In some embodiments, in the secondary nanofiltration process, the first reverse osmosis produced water obtained by the first reverse osmosis treatment is mixed with the first nanofiltration concentrate water to perform the secondary nanofiltration process.
The first reverse osmosis produced water obtained by the first reverse osmosis treatment also contains a small amount of hydrogen oxalate ions, and the first reverse osmosis produced water is reused in the first nanofiltration process and the second nanofiltration process, so that the hydrogen oxalate ions in the first reverse osmosis produced water are separated and recovered, and the oxalic acid recovery rate is improved.
In some embodiments, the pH of the first reverse osmosis produced water is 2-3. When the pH value is 2-3 and oxalic acid mainly exists in the form of hydrogen oxalate ions, the first reverse osmosis produced water is reused in the primary nanofiltration process and the secondary nanofiltration process, and the effective separation of the hydrogen oxalate ions and sulfate ions can be realized.
In some embodiments, in the first reverse osmosis treatment, the volume ratio of the first reverse osmosis produced water to the first nanofiltration produced water is 80% -90%. The concentration of hydrogen oxalate ions in the first reverse osmosis concentrated water can be increased by controlling the volume ratio of the first reverse osmosis produced water to the first nanofiltration produced water within the above range.
In addition, the second nanofiltration concentrated water obtained by the second nanofiltration treatment also contains hydrogen oxalate ions, so the second nanofiltration concentrated water can be subjected to the circulation treatment.
In some embodiments, in the first nanofiltration step, the second nanofiltration concentrate from the second nanofiltration process is mixed with the wastewater for the first nanofiltration step. Thus, the recovery rate of oxalic acid can be further improved by recovering the hydrogen oxalate ions contained in the second nanofiltration concentrate.
In some embodiments, the second nanofiltration process has a molecular weight cut-off of 150Da to 300Da, wherein the molecular weight cut-off refers to the molecular weight cut-off of the nanofiltration membrane. At the moment, the method can ensure that the hydrogen oxalate ions smoothly permeate the nanofiltration membrane, and can also intercept and remove organic matters, heavy metals and high-valence salts in the wastewater so as to be beneficial to improving the oxalic acid purity of the oxalic acid solution.
In some embodiments, in the second nanofiltration process, the volume ratio of the second nanofiltration product water to the first reverse osmosis concentrate water is 83% -87%. At the moment, the loss of hydrogen oxalate ions can be reduced as much as possible, so that the oxalic acid recovery rate is improved, the quality of sulfate ions in the oxalic acid solution can be reduced, and the purity of the oxalic acid solution is improved.
In some embodiments, the ion exchange process comprises: and (3) treating the second nanofiltration produced water by adopting a bipolar membrane electrodialysis method so that monovalent anions and hydrogen ions are combined to form acid and cations and hydroxide ions are combined to form alkali, and separating to obtain a first solution containing the acid and a second solution containing the alkali.
The bipolar membrane electrodialysis method is a method of combining bipolar membranes with other anion-cation exchange membranes into a bipolar membrane electrodialysis system, thereby performing ion exchange. Bipolar membranes are ion exchange composite membranes, which are typically composed of a cation exchange layer (N-type membrane), an interfacial hydrophilic layer (catalytic layer), and an anion exchange layer (P-type membrane). Under the action of a direct current electric field, the bipolar membrane can dissociate water to obtain hydrogen ions and hydroxyl ions on two sides of the membrane respectively. Thus, hydrogen ions and hydroxyl ions can be introduced into the second nanofiltration produced water by using the bipolar membrane electrodialysis method without introducing new components, so that the hydrogen oxalate ions and sodium ions are converted into corresponding oxalic acid solution and sodium hydroxide solution.
After ion exchange treatment, the first solution is oxalic acid solution, and the second solution is sodium hydroxide solution. And, after the process treatment of the previous embodiment, the concentrations of oxalic acid solution and sodium hydroxide solution can reach the preferred level.
In some embodiments, the oxalic acid concentration of the oxalic acid solution is 0.24mol/L to 0.28mol/L. In some embodiments, the sodium hydroxide solution has a sodium hydroxide concentration of 1.6mol/L to 2mol/L.
Referring to fig. 3, in some embodiments, after the ion exchange process, the recycling method further includes:
s500, performing second reverse osmosis treatment on the first solution, and separating to obtain second reverse osmosis concentrated water, wherein the acid concentration in the second reverse osmosis concentrated water is higher than that in the first solution.
Illustratively, the second reverse osmosis treatment may be a separation treatment of wastewater by a reverse osmosis membrane.
Through carrying out second reverse osmosis treatment on the oxalic acid solution, the properties of concentrated water is obtained by utilizing the high-pressure side and water production is obtained by utilizing the low-pressure side of reverse osmosis, so that second reverse osmosis concentrated water with higher concentration of oxalic acid ions, namely oxalic acid product, is obtained. Therefore, after the oxalic acid solution is further treated through the second reverse osmosis process, the oxalic acid product which can be directly applied to industrialization is obtained.
In order to increase the utilization rate of the wastewater, in some embodiments, in the first nanofiltration process, the second reverse osmosis produced water obtained by the second reverse osmosis treatment is mixed with the wastewater to perform the first nanofiltration process. Illustratively, the second reverse osmosis produced water can be mixed with the first nanofiltration concentrated water to perform a second nanofiltration process, so as to separate and recover the hydrogen oxalate ions in the first reverse osmosis produced water, which is beneficial to improving the oxalic acid recovery rate.
In some embodiments, the acid concentration of the second reverse osmosis concentrated water is 0.4mol/L-0.45mol/L, namely the concentration of the obtained oxalic acid is 0.4mol/L-0.45mol/L, and the oxalic acid product with higher concentration of the oxalic acid hydrogen ions is favorable for direct industrial application.
In some embodiments, the recovery rate of the second reverse osmosis treatment is 40% to 50%, wherein the recovery rate of the second reverse osmosis treatment is the volume ratio of the second reverse osmosis produced water to the first solution. By controlling the recovery rate of the second reverse osmosis treatment within the above-described suitable range, second reverse osmosis concentrated water having a higher concentration of oxadiazon ions can be obtained.
After the treatment of the second reverse osmosis process, the separation and recovery of most oxalic acid in the wastewater can be realized, and the recycling of the wastewater is facilitated. In some embodiments, the oxalic acid recovery rate in the wastewater is greater than or equal to 69%.
In addition to recovering oxalic acid and sodium hydroxide, in some embodiments, the recycling process further comprises: and an evaporation step of evaporating the first nanofiltration concentrated water to obtain a salt containing polyvalent anions and cations.
Because the first nanofiltration concentrated water mainly contains sulfate ions and sodium ions, the salt obtained after the first nanofiltration concentrated water is subjected to evaporation treatment is mainly sodium sulfate, and most of the sulfate ions and sodium ions in the wastewater can be separated and recovered through an evaporation procedure. In some embodiments, the recovery of sodium sulfate in the wastewater is greater than or equal to 99.5%. Therefore, oxalic acid, sulfate ions and sodium ions in the wastewater can be separated and recovered by the recycling treatment method provided by the embodiment of the application, and byproducts such as sodium hydroxide, sodium sulfate and the like are obtained.
The following examples more particularly describe the disclosure of the present application, which are intended as illustrative only, since numerous modifications and variations within the scope of the disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the examples below are by mass, and all reagents and materials used in the examples are commercially available or are obtained synthetically according to conventional methods, as well as the instruments used in the examples.
Example 1
The embodiment provides a recycling treatment method of wastewater, which comprises the following steps:
acid regulating procedure, pumping sodium ion battery waste water into water inlet tank, adopting concentrated sulfuric acid to make pH value be 2.75 so as to make oxalic acid in the waste water mainly adopt HC 2 O 4 - Is present.
A first-stage nanofiltration step of treating wastewater according to a volume of 100m 3 After the flow of/d and the produced water of the first reverse osmosis part and the concentrated water of the second nanofiltration device are mixed, the mixed water is pumped into the first nanofiltration device through a feed pump to carry out first nanofiltration treatment, and the separation of wastewater on the surface of the nanofiltration membrane is realized through automatic control of equipment. Wherein the nanofiltration membrane is 8040 modified nanofiltration membrane, the nanofiltration membrane is A-3012 membrane of Xiamen Jiarong technology Co., ltd, the volume ratio of the first-stage nanofiltration water yield to the wastewater is 53%, the first-stage nanofiltration water yield is firstly in an intermediate tank, and the water yield is 159m 3 And/d, collecting the mixture into a mixed water producing tank. The first-stage nanofiltration concentrated water is discharged to a mixing tank, and the external drainage is 141m 3 D, mixing the first-stage nanofiltration concentrated water with the second-stage reverse osmosis water with pH of 2-3 in a mixing tank, and obtaining the second-stage reverse osmosis waterThe water yield was 24.16m 3 /d。
A secondary nanofiltration step of adding 324.30m to the liquid in the mixing tank 3 And (3) pumping the flow of/d into a secondary nanofiltration device to perform secondary nanofiltration treatment, and realizing the separation of wastewater on the surface of the nanofiltration membrane by automatic control of equipment. Wherein the nanofiltration membrane is an 8040 modified nanofiltration membrane, and the nanofiltration membrane model is an A-3012 membrane of Xiamen Jiakong technology Co. The volume ratio of the secondary nanofiltration water yield to the primary nanofiltration concentrated water is 57 percent, the secondary nanofiltration water yield is firstly carried out in a middle tank, and the water yield is 184.85m 3 And/d, collecting the mixture into a mixed water producing tank. The second-stage nanofiltration concentrated water is discharged to an evaporation tank for evaporating and recovering sodium sulfate, and the external drainage is 139.45m 3 /d。
A first reverse osmosis process, wherein the first nanofiltration water production and the second nanofiltration water production are summarized into a mixed water production tank, and the first reverse osmosis process is carried out according to 343.85m 3 And/d, pumping the flow into a first reverse osmosis device, and realizing the separation of nanofiltration product water on the surface of the reverse osmosis membrane through automatic control of equipment. Wherein the reverse osmosis membrane is an 8040 acid-resistant reverse osmosis membrane, and the first reverse osmosis produced water and the first nanofiltration produced water are 86%. The water yield of the first reverse osmosis water is 293.99m 3 And/d, wherein one part of the first reverse osmosis produced water is recycled for performing the first-stage nanofiltration process, and the other part of the first reverse osmosis produced water is recycled for performing the second-stage nanofiltration process. The reverse osmosis concentrated water is discharged to a reverse osmosis concentrated water tank, and the external water discharge is 49.86m 3 /d。
A second nanofiltration step of concentrating the liquid in the reverse osmosis water tank according to 49.86m 3 And (3) pumping the flow of the/d into a second nanofiltration device for second nanofiltration treatment, and realizing the separation of the wastewater on the surface of the nanofiltration membrane by automatic control of equipment. Wherein the nanofiltration membrane is an 8040 modified nanofiltration membrane, and the nanofiltration membrane model is an A-3012 membrane of Xiamen Jiakong technology Co. The volume ratio of the second nanofiltration water yield to the first reverse osmosis concentrated water is 85%, the second nanofiltration water yield enters a nanofiltration water yield tank, and the water yield is 42.38m 3 And/d. The second nanofiltration concentrated water is recycled for the first nanofiltration process, and the water quantity is 7.84m 3 /d。
An ion exchange procedure, the liquid in the nanofiltration water production tank is processed according to 42.38m 3 The flow of/d is pumped into a bipolar membrane electrodialysis system for ion exchange treatment, whichThe working principle of the bipolar membrane electrodialysis system is shown in figure 4, and a blue bipolar membrane is adopted as the bipolar membrane, and the model is Y-ABC-6-IV/perfluorinated sulfonic acid polar membrane/PP polytetrafluoroethylene separator. After the sodium hydrogen oxalate solution enters the bipolar membrane, oxalic acid is generated in a salt chamber under the action of current in a bipolar membrane electrodialysis system, and part of water (3.50 m 3 /d) and sodium hydroxide is formed. The ion concentration change in the ion exchange process is shown in Table 1, oxalic acid solution with concentration of 0.26mol/L and sodium hydroxide solution with concentration of 2mol/L are obtained after the ion exchange treatment, and the yield of the oxalic acid solution is 40.26m 3 The yield of sodium hydroxide solution was 5.62m 3 /d。
A second reverse osmosis step of subjecting the oxalic acid solution to a process of 40.26m 3 And (3) pumping the flow rate of/d into a second reverse osmosis device to perform second reverse osmosis treatment, and realizing separation of oxalic acid solution on the surface of the reverse osmosis membrane through automatic control of equipment. Wherein the reverse osmosis membrane is an 8040 acid-resistant reverse osmosis membrane, and the volume ratio of the second reverse osmosis concentrated water to the first solution is 40%. The second reverse osmosis produced water is recycled for the secondary nanofiltration process, and the water quantity is 16.10m 3 And d, discharging the second reverse osmosis concentrated water to a product tank, wherein the external water discharge amount is 24.16m 3 And/d, the second reverse osmosis concentrated water is oxalic acid product with the concentration of 0.4 mol/L.
The process operating parameters for example 1 are shown in table 2.
Example 2
Example 2 differs from example 1 in that: the volume ratio of the primary nanofiltration water produced by the primary nanofiltration to the wastewater in the primary nanofiltration process is 50 percent.
Example 3
Example 3 differs from example 1 in that: the volume ratio of the secondary nanofiltration product water to the primary nanofiltration concentrated water is 55 percent.
Example 4
Example 4 differs from example 1 in that: the volume ratio of the first reverse osmosis water production to the first nanofiltration water production is 80%.
Example 5
Example 5 differs from example 1 in that: the volume ratio of the second nanofiltration produced water to the first reverse osmosis concentrated water is 83%.
Comparative example 1
The difference from example 1 is that the waste water is treated by a neutralization method, specifically, calcium carbonate is added into the waste water to neutralize oxalic acid in the waste water, calcium oxalate precipitate is generated, then the calcium oxalate precipitate is filtered to separate oxalic acid in the waste water, the waste water is further evaporated to obtain a sodium sulfate byproduct, and the calcium oxalate is treated outside the solid waste.
Comparative example 2
Oxalic acid wastewater secondary nanofiltration dialysis recycling and calcium precipitation method
The difference from example 1 is that the second nanofiltration process is removed, calcium carbonate is added into the concentrated water of the first nanofiltration process to remove oxalic acid in sodium sulfate, the waste water is evaporated again to obtain qualified sodium sulfate byproducts, the calcium oxalate is disposed outside the solid waste, and the second reverse osmosis concentrated water is recovered to obtain oxalic acid products.
Comparative example 3
The difference from example 1 is that: and mixing the second nanofiltration product water and the second nanofiltration product water in the second nanofiltration process into the bipolar membrane.
Table 1, ion exchange data (over time) for the bipolar membrane electrodialysis system of example 1
Table 2, working procedure operation parameters of example 1
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Wherein, the retention rate of nanofiltration=1-produced water concentration/inlet water concentration; rejection rate of reverse osmosis = 1-concentration of reverse osmosis produced water/concentration of influent water; ion exchange retention = 1-concentration of substance in the first solution/concentration of substance in the feed water;
TABLE 3 Table 3
Note that: oxalic acid recovery = (second reverse osmosis concentrate amount of water x oxalic acid molar concentration in concentrate)/(wastewater amount x oxalic acid molar concentration in wastewater), wherein the content of sodium sulfate in oxalic acid solution is required to be less than 900mg/L; sodium sulfate recovery = (second-stage nanofiltration concentrate amount of sulfate concentration in concentrate)/(amount of wastewater concentration in wastewater).
Referring to Table 1, it can be seen from example 1 that the conversion rate of oxalic acid can reach more than 98% over time, so that most of oxalic acid in wastewater can be recovered. Moreover, the conversion rate of 96% can be achieved within 30min, and the conversion efficiency is high. According to tables 2 and 3, oxalic acid in wastewater can be effectively recovered, the obtained oxalic acid solution is low in impurity content (sodium sulfate is the main impurity), and the recovery rate of sodium sulfate is also high, so that the recycling of wastewater is realized.
TABLE 4 Table 4
Note that: daily operating costs refer to the cost of operating the plant, and the products of resource recovery include oxalic acid, sodium hydroxide and sodium sulfate, and integrated operating cost = total operating cost-value of resource recovery.
According to Table 4, comparing example 1 with comparative example 1 and comparative example 2, the addition of calcium carbonate to neutralize oxalic acid in wastewater in comparative example 1 and comparative example 2, the obtained calcium oxalate precipitate was difficult to directly use and Ca-containing product was produced 2+ The high-salt wastewater with the impurities, increases the wastewater treatment cost, and various valuable resources are not fully utilized. While the method in example 1Oxalic acid solution and byproducts can be directly obtained after wastewater treatment, and the products can be directly applied, so that wastewater treatment cost is reduced.
According to the recycling treatment method provided by the embodiment of the application, oxalic acid, sulfate ions and sodium ions in wastewater can be separated and recovered by controlling parameters of nanofiltration, reverse osmosis and ion exchange stages, and oxalic acid products, sodium sulfate and sodium hydroxide byproducts are obtained. Wherein, the recovery rate of sodium sulfate can reach 99.5%, and the recovery rate of oxalic acid can reach more than 69%. And after oxalic acid in the wastewater is separated and recovered, the content of organic matters in the wastewater is reduced, and the wastewater treatment environment-friendly requirement is met.
The technical features described above may be arbitrarily combined. Although not all possible combinations of features are described, any combination of features should be considered to be covered by the description provided that such combinations are not inconsistent.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.
Claims (10)
1. The recycling treatment method of the wastewater is characterized by comprising the following steps of:
a first nanofiltration step of subjecting wastewater containing monovalent anions and polyvalent anions to a first nanofiltration treatment to separate the monovalent anions and at least part of the polyvalent anions in the wastewater to obtain a first nanofiltration product water containing the monovalent anions and the remaining part of the polyvalent anions;
a first reverse osmosis process, wherein the first nanofiltration product water is subjected to first reverse osmosis treatment, and is separated to obtain first reverse osmosis concentrated water, and the concentration of monovalent anions in the first reverse osmosis concentrated water is higher than that in the first nanofiltration product water;
a second nanofiltration step of performing a second nanofiltration treatment on the first reverse osmosis concentrated water to separate monovalent anions from the remaining multivalent anions in the first reverse osmosis concentrated water, thereby obtaining a second nanofiltration product water containing the monovalent anions;
and an ion exchange process, wherein the second nanofiltration water is subjected to ion exchange treatment so that monovalent anions and hydrogen ions are combined to form acid and cations and hydroxyl ions are combined to form alkali, and the acid-containing first solution and the alkali-containing second solution are respectively obtained through separation.
2. The recycling method according to claim 1, further comprising, before the first nanofiltration step:
an acid regulating procedure, namely adding acid into the wastewater to regulate the pH value of the wastewater to be within the range of 2.5-3;
optionally, the acid comprises sulfuric acid.
3. The recycling method according to claim 1, wherein the first nanofiltration step comprises:
a primary nanofiltration step of subjecting wastewater containing monovalent anions and polyvalent anions to primary nanofiltration treatment to separate the monovalent anions and at least part of the polyvalent anions in the wastewater, thereby obtaining primary nanofiltration concentrate containing at least part of the polyvalent anions and part of the monovalent anions and primary nanofiltration product containing the remaining part of the monovalent anions and the remaining part of the polyvalent anions;
a second nanofiltration step of performing a second nanofiltration treatment on the first nanofiltration concentrate to separate monovalent anions and multivalent anions from the first nanofiltration concentrate, thereby obtaining a second nanofiltration concentrate containing multivalent anions and a second nanofiltration product containing the portion of monovalent anions;
the second-stage nanofiltration concentrated water forms first nanofiltration concentrated water, and the first-stage nanofiltration produced water and the second-stage nanofiltration produced water are mixed to form the first nanofiltration produced water.
4. The recycling treatment method according to claim 3, wherein the molecular weight cut-off of the primary nanofiltration treatment is 150Da to 300Da;
optionally, in the primary nanofiltration treatment, the volume ratio of the primary nanofiltration produced water to the wastewater is 50% -55%;
optionally, the molecular weight cut-off of the secondary nanofiltration treatment is 150Da to 300Da;
optionally, in the secondary nanofiltration treatment, the volume ratio of the secondary nanofiltration product water to the primary nanofiltration concentrate water is 55% -60%.
5. A recycling treatment method according to claim 3, wherein in the primary nanofiltration step, the primary nanofiltration step is performed by mixing the wastewater with the first reverse osmosis produced water obtained by the first reverse osmosis treatment, and/or in the secondary nanofiltration step, the secondary nanofiltration step is performed by mixing the primary nanofiltration concentrated water with the first reverse osmosis produced water obtained by the first reverse osmosis treatment;
optionally, the pH value of the first reverse osmosis produced water is 2-3;
optionally, in the first reverse osmosis treatment, the volume ratio of the first reverse osmosis produced water to the first nanofiltration produced water is 80% -90%.
6. The recycling treatment method according to claim 3, wherein in the first nanofiltration step, the first nanofiltration step is performed by mixing the wastewater with the second nanofiltration concentrate obtained by the second nanofiltration treatment;
Optionally, the molecular weight cut-off of the second nanofiltration treatment is 150Da to 300Da;
optionally, in the second nanofiltration treatment, the volume ratio of the second nanofiltration produced water to the first reverse osmosis concentrated water is 83% -87%.
7. The recycling method according to claim 1, wherein the ion exchange process comprises: treating the second nanofiltration produced water by adopting a bipolar membrane electrodialysis method so as to enable monovalent anions and hydrogen ions to be combined to form acid and cations and hydroxyl ions to be combined to form alkali, and separating to obtain a first solution containing the acid and a second solution containing the alkali respectively;
optionally, the acid concentration in the first solution is 0.24mol/L to 0.28mol/L;
optionally, the alkali concentration in the second solution is 1.6mol/L to 2mol/L.
8. The recycling method according to claim 1, further comprising, after the ion exchange process:
a second reverse osmosis process, wherein the first solution is subjected to second reverse osmosis treatment, and second reverse osmosis concentrated water is obtained through separation, and the acid concentration in the second reverse osmosis concentrated water is higher than that in the first solution;
Optionally, in the first nanofiltration step, mixing the second reverse osmosis produced water obtained by the second reverse osmosis treatment with the wastewater to perform the first nanofiltration step;
optionally, the acid concentration of the second reverse osmosis concentrated water is 0.4mol/L to 0.45mol/L;
optionally, in the second reverse osmosis treatment, the volume ratio of the second reverse osmosis concentrated water to the first solution is 40% -50%.
9. The recycling process according to any one of claims 1 to 8, further comprising:
and an evaporation step of evaporating the first nanofiltration concentrated water to obtain a salt containing multivalent anions.
10. The recycling process according to claim 9, wherein the wastewater comprises sodium ion battery wastewater;
optionally, the monovalent anions contained in the wastewater comprise hydrogen oxalate ions;
optionally, the wastewater contains multivalent anions including sulfate ions;
optionally, the first solution comprises an oxalic acid solution.
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