CN115818858A - LiFSI wastewater treatment method - Google Patents

Abstract

The application relates to a treatment method of LiFSI wastewater. A method for treating LiFSI wastewater, comprising the following steps: adsorption: adsorbing LiFSI wastewater with a resin to obtain a resin adsorbing LiFSI; analyzing: washing the resin adsorbing LiFSI with lye to obtain a LiFSI analysis solution; concentrating: heating and concentrating the LiFSI analysis solution to obtain a lithium-containing concentrated solution; neutralization: add acid to the lithium-containing concentrated solution to obtain a neutralized solution; sink lithium: add carbonate and/or carbon dioxide to the neutralized solution to react , resulting in carbonate precipitation. This application solves the problem that FSI ^‑ cannot be decomposed in large quantities in the existing wastewater treatment process, and at the same time fully recovers lithium resources, which is more environmentally friendly and has high economic benefits.

Description

A kind of treatment method of LiFSI wastewater

technical field

The present application relates to the field of wastewater treatment, in particular to a treatment method for LiFSI wastewater.

Background technique

As an important metal element, lithium is a promising new energy and strategic resource, widely used in electronics, metallurgy, medicine, glass, ceramics, batteries, new energy and other industries. In recent years, with the rapid development of the new energy industry, the demand for lithium has increased sharply.

As a new lithium battery electrolyte, LiFSI (lithium bisfluorosulfonyl imide) has the advantages of high stability, excellent low temperature performance, and good hydrolysis stability. It is gradually replacing LiPF ₆ (lithium hexafluorophosphate). With the LiFSI production process It is becoming more and more mature and the cost is constantly decreasing. In recent years, there are not many new, rebuilt and expanded LiFSI manufacturers, and the output is also increasing rapidly. In addition, the amount of recycling and dismantling of used lithium batteries is also increasing. Regardless of whether a large amount of LiFSI-containing wastewater (LiFSI content is 1,000-20,000ppm) is produced during the production process (cleaning of LiFSI filter residues, production equipment, and packaging barrels) or LiFSI-containing wastewater generated from the recycling and dismantling of waste lithium batteries, if not properly LiFSI is extracted and recovered. The existing sewage treatment process cannot decompose ^FSI- in LiFSI, resulting in FSI- remaining in the water, and ^FSI- (difluorosulfonylimide acid ion) remaining in the water seriously affects the water quality of LAS (anionic surface active agent, the national first-class water quality requirement is less than 0.5ppm), and wastes a large amount of lithium resources simultaneously.

For this reason, the present invention is proposed.

Contents of the invention

The main purpose of the present invention is to provide a treatment method for LiFSI wastewater, which solves the problem that ^FSI- cannot be decomposed in large quantities in the existing wastewater treatment process, and at the same time fully recovers lithium resources, is more environmentally friendly and has high economic benefits.

In order to achieve the above objectives, the present invention provides the following technical solutions.

A treatment method for LiFSI wastewater, comprising the following steps:

Adsorption: Adsorb LiFSI wastewater with resin to obtain resin that adsorbs LiFSI;

Analysis: wash the resin adsorbing LiFSI with lye to obtain a LiFSI analysis solution;

Concentration: heating and concentrating the LiFSI analysis solution to obtain a lithium-containing concentrated solution;

Neutralization: adding acid to the lithium-containing concentrated solution to obtain a neutralized solution;

Lithium sinking: add carbonate and/or carbon dioxide to the neutralization solution to react to obtain carbonate precipitation.

In the above method of the present invention, the LiFSI in the waste water is firstly enriched by means of adsorption and analysis, and then the lye in it is heated to react with the LiFSI, thereby decomposing the FSI ^- into FSO ^3- , SO ₄ ^2- and F ^- , This fundamentally solves the problem of high FSI ^- content in wastewater; finally, after neutralization, lithium sinking agents such as carbonate and carbon dioxide are added to convert lithium ions into lithium carbonate precipitation, thereby recovering lithium in wastewater.

It can be seen that the treatment method of the present invention not only fundamentally removes FSI ^- , but also recovers metal lithium, which improves the economic benefits of wastewater treatment.

Tested and tested, using the treatment method of the present invention, the FSI ^- decomposition rate reaches at least 99.6%, and the lithium recovery rate reaches at least 93%.

The operating conditions and raw material types in the five main steps of the above treatment method can be further optimized to increase the decomposition rate, improve the lithium recovery rate, shorten the reaction time or reduce the cost, etc., such as listed below.

In some embodiments, the alkaline solution is an inorganic strong alkaline solution, preferably at least one or more combinations of sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, and aluminum hydroxide aqueous solution .

On the one hand, strong inorganic bases will not introduce exogenous impurities or impurities that are not easy to remove, and on the other hand, they have strong alkalinity, which can quickly resolve and decompose FSI ^- .

In some embodiments, the lye is at least one of potassium hydroxide solution or sodium hydroxide solution. Due to the different ionic strengths of different salt ions, there are differences in the chemical balance of the decomposition reaction and lithium precipitation reaction. Similar to potassium hydroxide solution or sodium hydroxide solution, it is more conducive to the decomposition reaction and lithium precipitation reaction to be carried out quickly and fully. Therefore, hydrogen is preferred. Potassium oxide solution or sodium hydroxide solution, and potassium hydroxide is more preferred.

In some embodiments, the concentration of the lye is 3%-10%. Considering comprehensive factors such as reaction rate and cost, preferred lye concentration of 3%～10%, such as 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% etc., more preferably The range includes 5% to 8% and so on.

In some embodiments, the temperature of the heating concentration is 80-100°C, preferably 95-100°C. When heated to 80-100°C, the FSI ^- decomposition rate will basically reach the highest level, and other by-products will not be produced at the same time, and the more preferred temperature range is 95-100°C.

In some embodiments, the heating and concentration equipment is one or more of double-effect evaporators, triple-effect evaporators, falling-film evaporators, thin-film evaporators, and distillation towers used in series or in parallel.

These evaporators all have the advantages of high evaporation efficiency and fast heat exchange rate, and the heating and concentration process used in the present invention can simultaneously increase the reaction rate and reduce energy consumption.

In some embodiments, the resin is a neutral resin or a weakly basic resin, preferably PD201 resin.

Neutral resins or weakly basic resins have a higher adsorption coefficient for LiFSI in LiFSI wastewater, among which PD201 resin is preferred.

In some embodiments, the LiFSI content in the LiFSI wastewater is reduced to below 0.2 ppm after the adsorption.

When the LiFSI content is adsorbed to below 0.2ppm, on the one hand, the ^FSI in the resin effluent has met the national standard requirements, and on the other hand, it can ensure that LiFSI is almost completely enriched.

In some embodiments, the neutralization ends with a pH value of 6.5-7.0.

When the neutralization reaches pH=6.5-7.0, lithium carbonate precipitation can be rapidly formed after adding the lithium sinking agent. In the actual treatment process, the end point pH value cannot be completely controlled to a constant specific value, usually a little fluctuation range is allowed, such as 6.5~6.8, 6.8~7.0, etc., even for the treatment of a large amount of wastewater, the end point pH value can be allowed to be 6.5 ~7.0 fluctuates in a wide range.

In some embodiments, the acid added for neutralization is one or more combinations of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, oxalic acid, acetic acid, hypochlorous acid, and formic acid.

Similar to lye, the type of acid added during neutralization should take into account multiple factors such as no or less impurities and fast reaction rate. Sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, oxalic acid, acetic acid, hypochlorous acid, and formic acid can all meet the requirements. Among the above requirements, sulfuric acid is preferred. In addition, these acids may be added in solution or by passing an acid gas during treatment.

In some embodiments, the carbonate is at least one of sodium carbonate and potassium carbonate.

Both of these salts can react with lithium ions to rapidly form lithium carbonate precipitates. The amount of carbonate added is usually determined according to the lithium content in the solution, and it is properly added in excess.

In some embodiments, in the step of sinking lithium, it is also filtered after the reaction, and the filter equipment is preferably a plate and frame filter, a bag filter, a candle filter, a scraper centrifuge, a horizontal centrifuge, One or a combination of pull belt centrifuges, siphon centrifuges, and pusher centrifuges.

Filter out the precipitate, and the effluent can be treated as industrial water or other sewage. Plate and frame filters, bag filters, candle filters, scraper centrifuges, horizontal centrifuges, belt centrifuges, siphon centrifuges, and pusher centrifuges can be used for large flow sewage treatment.

In summary, compared with the prior art, the present invention at least achieves the following technical effects:

(1) Fundamentally removed the FSI in the waste water by decomposition reaction- ^;

(2) Metal lithium in the waste water is reclaimed, and the economic benefit of sewage treatment is improved;

(3) Only common safe and non-toxic chemical reagents such as inorganic alkali, inorganic acid and carbonate are used in the treatment process, which improves the safety of sewage treatment and reduces the cost of raw materials;

(4) The operating conditions in each step are optimized to provide prerequisites for further improving the efficiency and economic benefits of wastewater treatment.

The above description is only an overview of the technical solution of the present application. In order to better understand the technical means of the present application, it can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and understandable , the following specifically cites the specific implementation manner of the present application.

Detailed ways

Embodiments of the technical solutions of the present application will be described in detail below. The following examples are only used to illustrate the technical solution of the present application more clearly, and therefore are only examples, rather than limiting the protection scope of the present application.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the application; the terms used herein are only for the purpose of describing specific embodiments, and are not intended to Limiting the application; the terms "comprising" and "having" and any variations thereof in the description and claims of the application and the above description are intended to cover a non-exclusive inclusion.

In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and should not be understood as indicating or implying relative importance or implicitly indicating the number, specificity, or specificity of the indicated technical features. Sequence or primary-secondary relationship. In the description of the embodiments of the present application, "plurality" means two or more, unless otherwise specifically defined.

Reference herein to an "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The occurrences of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is understood explicitly and implicitly by those skilled in the art that the embodiments described herein can be combined with other embodiments.

In the description of the embodiment of the present application, the term "and/or" is only a kind of association relationship describing associated objects, which means that there may be three kinds of relationships, such as A and/or B, which may mean: A exists alone, and A exists at the same time and B, there are three cases of B alone. In addition, the character "/" in this article generally indicates that the contextual objects are an "or" relationship.

In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), similarly, "multiple groups" refers to more than two groups (including two), and "multiple pieces" refers to More than two pieces (including two pieces).

In the description of the embodiments of this application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection" and "fixation" should be interpreted in a broad sense, for example, it can be a fixed connection or a fixed connection. Disassembled connection, or integration; it can also be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediary, and it can be the internal communication of two components or the interaction relationship between two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the embodiments of the present application according to specific situations.

As mentioned in the background technology, the existing LiFSI wastewater treatment method has the problem that the ^FSI- content is not up to the standard, etc. Therefore, the present invention provides a treatment method with safety and high economic benefits. The method mainly involves five key steps of adsorption, analysis, concentration, neutralization, and lithium precipitation in sequence. This paper lists some examples to illustrate the treatment effect of the present invention, as follows (it should be noted that lithium precipitation in the present invention After a certain previous condition changes, the content of ions involved in the lithium sinking reaction may be different. In order to ensure that the lithium sinking agent is excessive, the dosage of the lithium sinking agent is also different).

Example 1

Take ^4.5m3 of PD201 resin and fill it into the resin column, and enter 2500ppm (referring to the content of LiFSI, the same description below) LiFSI wastewater from the top of the resin column at a flow rate of ^3m3 /h, and discharge it from the bottom and circulate it back to the original water pool. Sampling to detect the LiFSI content of the bottom effluent and online monitoring LAS≤0.2ppm. When the LiFSI content is less than 0.2ppm, the water is discharged; The air is used to dry the water in the resin column, and the treatment is repeated until the LiFSI content of the bottom effluent is ≤0.2ppm.

Pass into the resin column a potassium hydroxide solution with a mass fraction of 5%, and soak for 2 hours. After 2 hours, continue to pump the lye into the resin column at a flow rate of 2m ³ /h and release the lye from the bottom with a flow rate of 2m ³ /h. Continue to feed the lye for 2 hours, then stop the lye, and dry the lye in the resin column to obtain about 6m ³ of lye with a Li ⁺ content of 1-2%. At this time, the next LiFSI adsorption can be carried out after the resin column is desorbed.

When the lye is concentrated to 50% of the volume of the original lye at 92-95°C, stop the concentration, filter and transfer to the neutralization tank for stirring, slowly add hydrochloric acid with a mass fraction of 3% for neutralization, and adjust the pH value to 6.5 After ~7, add deionized water and adjust the Li ⁺ concentration in the solution to 2%; pump ^5m3 of a solution with a 2% Li ⁺ concentration to the alkalization kettle, then pour 760kg of sodium carbonate and stir together for 3~4h, Obtain lithium carbonate turbid solution, finally lithium carbonate turbid solution is carried out centrifugal dehydration through scraper centrifuge to obtain 548kg lithium carbonate powder. The lithium carbonate content in the lithium carbonate powder is 90.2%, the water content is 8.3%, and the impurity content is 1.5%.

Example 2

The main difference from Example 1 is that the lye is replaced by sodium hydroxide, and correspondingly, there is a difference in the amount of sodium carbonate added during lithium precipitation, as follows.

Take ^4.5m3 of PD201 resin and fill it into the resin column, enter 2500ppm LiFSI wastewater from the top of the resin column at a flow rate of ^3m3 /h, discharge from the bottom and circulate back to the original water pool, take samples to detect the LiFSI content of the bottom effluent and online monitoring LAS less than 0.2ppm, when the LiFSI content is less than 0.2ppm, drain the water; when the LiFSI content in the bottom effluent is greater than 0.2ppm or when the online monitoring LAS is greater than 0.2ppm, stop the water intake, use air to dry the water in the resin column, repeat Treatment until the bottom effluent LiFSI content ≤ 0.2ppm.

Pass into the resin column a sodium hydroxide solution with a mass fraction of 5%, and soak for 2 hours. After 2 hours, continue to pump in the lye at a flow rate of 2m ³ /h and release the lye from the bottom at a flow rate of 2m ³ /h. Continue to feed the lye for 2 hours, then stop the lye, and dry the lye in the resin column to get about 6m3 Li ⁺ content of 1-2% lye. At this time, the next LiFSI adsorption can be carried out after the resin column is desorbed.

When the lye is concentrated to 50% of the volume of the original lye at 92-95°C, stop the concentration, filter and transfer to the neutralization tank for stirring, slowly add hydrochloric acid with a mass fraction of 3% for neutralization, and adjust the pH value to 6.5 After ~7, add deionized water and adjust the Li ⁺ concentration in the solution to 2%; pump ^5m3 of a solution with a 2% Li ⁺ concentration to the alkalization kettle, then pour 760kg of sodium carbonate and stir together for 3~4h, Obtain lithium carbonate turbid liquid, carry out centrifugal dehydration through scraper centrifuge to obtain 603kg lithium carbonate powder at last lithium carbonate turbid liquid, lithium carbonate content is 78.7%, water content 10.5%, impurity content 10.8%.

Example 3

The main difference from Example 1 is that the acid added during neutralization is replaced by sulfuric acid, and correspondingly, the amount of sodium carbonate added during lithium precipitation is different, as follows.

Take ^4.5m3 of PD201 resin and fill it into the resin column, enter 2500ppm LiFSI wastewater from the top of the resin column at a flow rate of ^3m3 /h, discharge from the bottom and circulate back to the original water pool, take samples to detect the LiFSI content of the bottom effluent and online monitoring LAS less than 0.2ppm, when the LiFSI content is less than 0.2ppm, drain the water; when the LiFSI content in the bottom effluent is greater than 0.2ppm or when the online monitoring LAS is greater than 0.2ppm, stop the water intake, use air to dry the water in the resin column, repeat Treatment until the bottom effluent LiFSI content ≤ 0.2ppm.

Pass into the resin column a potassium hydroxide solution with a mass fraction of 5%, and soak for 2 hours. After 2 hours, continue to pump the lye into the resin column at a flow rate of 2m ³ /h and release the lye from the bottom with a flow rate of 2m ³ /h. Continue to feed the lye for 2 hours, then stop the lye, and dry the lye in the resin column to obtain about 6m3 Li ⁺ content of 1-2% lye. At this time, the next LiFSI adsorption can be carried out after the resin column is desorbed, and the treatment can be repeated. Until the bottom effluent LiFSI content ≤ 0.2ppm.

When the lye is concentrated to 50% of the volume of the original lye at 92-95°C, stop the concentration, filter and transport to the neutralization tank for stirring, slowly add sulfuric acid with a mass fraction of 4% for neutralization, and adjust the pH value to 6.5 After ~7, add deionized water and adjust the Li ⁺ concentration in the solution to 2%; pump ^5m3 of a solution with a 2% Li ⁺ concentration to the alkalization kettle, then pour 760kg of sodium carbonate and stir together for 3~4h, Obtain lithium carbonate turbid liquid, carry out centrifugation and dehydration with lithium carbonate turbid liquid at last through scraper centrifuge to obtain 551kg lithium carbonate powder, lithium carbonate content is 91.2%, water content 6.7%, impurity content 2.1%, repeat processing, until the LiFSI content of effluent at the bottom ≤0.2ppm.

Example 4

The main difference from Example 1 is that the concentration of lye is increased to 10%, and correspondingly, there is a difference in the amount of sodium carbonate added during lithium precipitation, as follows.

Take ^4.5m3 of PD201 resin and fill it into the resin column, enter 2500ppm LiFSI wastewater from the top of the resin column at a flow rate of ^3m3 /h, discharge from the bottom and circulate back to the original water pool, take samples to detect the LiFSI content of the bottom effluent and online monitoring LAS less than 0.2ppm, when the LiFSI content is less than 0.2ppm, drain the water; when the LiFSI content in the bottom effluent is greater than 0.2ppm or when the online monitoring LAS is greater than 0.2ppm, stop the water intake, use air to dry the water in the resin column, repeat Treatment until the bottom effluent LiFSI content ≤ 0.2ppm.

Pass into the resin column a potassium hydroxide solution with a mass fraction of 10%, and soak for 2 hours. After 2 hours, continue to pump the lye into the resin column at a flow rate of 2m ³ /h and release the lye from the bottom with a flow rate of 2m ³ /h. Continue to feed the lye for 2 hours, then stop the lye, and dry the lye in the resin column to obtain about 6m ³ of lye with a Li ⁺ content of 1-2%. At this time, the next LiFSI adsorption can be carried out after the resin column is desorbed.

When the lye is concentrated to 50% of the volume of the original lye at 92-95°C, stop the concentration, filter and transfer to the neutralization tank for stirring, slowly add hydrochloric acid with a mass fraction of 3% for neutralization, and adjust the pH value to 6.5 After ~7, add deionized water and adjust the Li ⁺ concentration to 1% in the solution; pump 5m into the solution that adjusts the 1%Li ⁺ concentration to the alkalization kettle, then pour into 380kg sodium carbonate and stir together for 3～4h to obtain Lithium carbonate turbid liquid, finally the lithium carbonate turbid liquid is centrifuged and dehydrated through a scraper centrifuge to obtain 270kg lithium carbonate powder, lithium carbonate content is 85.3%, water content 7.8%, impurity content 6.9%.

Example 5

The main difference from Example 1 is that the lithium sinking agent is replaced by carbon dioxide, as follows.

Take ^4.5m3 of PD201 resin and fill it into the resin column, enter 2500ppm LiFSI wastewater from the top of the resin column at a flow rate of ^3m3 /h, discharge from the bottom and circulate back to the original water pool, take samples to detect the LiFSI content of the bottom effluent and online monitoring LAS less than 0.2ppm, when the LiFSI content is less than 0.2ppm, drain the water; when the LiFSI content in the bottom effluent is greater than 0.2ppm or when the online monitoring LAS is greater than 0.2ppm, stop the water intake, use air to dry the water in the resin column, repeat Treatment until the bottom effluent LiFSI content ≤ 0.2ppm.

Pass into the resin column a potassium hydroxide solution with a mass fraction of 5%, and soak for 2 hours. After 2 hours, continue to pump the lye into the resin column at a flow rate of 2m ³ /h and release the lye from the bottom with a flow rate of 2m ³ /h. Continue to feed the lye for 2 hours, then stop the lye, and dry the lye in the resin column to obtain about 6m ³ of lye with a Li ⁺ content of 1-2%. At this time, the next LiFSI adsorption can be carried out after the resin column is desorbed.

When the lye is concentrated to 50% of the volume of the original lye at 92-95°C, stop the concentration, filter and transfer to the neutralization tank for stirring, slowly add hydrochloric acid with a mass fraction of 3% for neutralization, and adjust the pH value to 6.5 After ~7, add deionized water and adjust the Li ⁺ concentration in the solution to 2%; pump 5m ³ solution adjusted to 2% Li + concentration to the alkalization kettle, and then slowly introduce 350kg of carbon dioxide into the kettle, after the feeding is completed Continue for 2 hours to obtain a lithium carbonate turbid solution, and finally carry out centrifugation and dehydration of the lithium carbonate turbid solution through a scraper centrifuge to obtain 606 kg of lithium carbonate powder, the lithium carbonate content is 85.8%, the water content is 13.8%, and the impurity content is 0.4%.

Example 6

The difference from Example 1 is only that lye-potassium hydroxide is replaced by magnesium hydroxide, and all the other operations and conditions remain unchanged.

This embodiment gets 545kg lithium carbonate powder. The lithium carbonate content in the lithium carbonate powder is 86.3%, the water content is 8.5%, and the impurity content is 5.2%.

Example 7-10

The difference from Example 1 is only that the concentration of potassium hydroxide solution is different, which are respectively 2%, 3%, 8%, and 12%, and all the other operations and conditions remain unchanged. As a result, it is found that the analysis effect of Example 7-8 with reduced concentration is poor, causing the resin to reach saturation soon when it is repeatedly used, so the total time of analysis is prolonged; while the analysis effect of Example 9-10 with increased concentration is better, and it can be easily Fast resolution is complete, and the adsorption capacity of the resin increases when it is used repeatedly. In addition, since all the examples quantify the concentration of lithium ions to 2% when depositing lithium, there is no significant difference in the amount of lithium carbonate obtained and the impurity content.

Examples 11-14

The difference from Example 1 is only the temperature during heating and concentration, which are controlled at 70-73°C, 80-85°C, 97-100°C, and 105-110°C respectively, and the rest of the operations and conditions remain unchanged. As a result, it is found that the FSI ^- decomposition effect becomes worse in the embodiment 11-12 that the temperature decreases, resulting in an increase in the amount of acid used when neutralizing; and the decomposition effect of the embodiment 13-14 that the temperature rises is better, and the amount of acid used in the neutralization reduce. In addition, since all the examples quantify the concentration of lithium ions to 2% when depositing lithium, there is no significant difference in the amount of lithium carbonate obtained and the impurity content.

Example 15

The only difference from Example 1 is the type of resin used for adsorption, which is as follows.

Take 4.5m ³ of LX-363 resin and fill it into the resin column, and enter 2500ppm (referring to the content of LiFSI, the same description below) LiFSI wastewater from the top of the resin column at a flow rate of 3m ³ /h, and discharge it from the bottom and circulate it back to the raw water In the pool, take samples to detect the LiFSI content of the bottom effluent and online monitoring LAS≤0.2ppm. When the LiFSI content is less than 0.2ppm, drain the water; when the LiFSI content of the bottom effluent is greater than 0.2ppm or the online monitoring LAS is greater than 0.2ppm, stop water inflow , use air to dry the water in the resin column, and repeat the treatment until the LiFSI content of the bottom effluent is ≤0.2ppm.

Pass into the resin column a potassium hydroxide solution with a mass fraction of 5%, and soak for 2 hours. After 2 hours, continue to pump the lye into the resin column at a flow rate of 2m ³ /h and release the lye from the bottom with a flow rate of 2m ³ /h. Continue to feed the lye for 2 hours, then stop the lye, and dry the lye in the resin column to obtain about 6m ³ of lye with a Li ⁺ content of 0.02-0.05%. At this time, the next LiFSI adsorption can be carried out after the resin column is desorbed.

Concentrate the lye at 92-95°C until the Li ⁺ concentration is 2.3%-2.5%; stop the concentration, filter and transport to the neutralization tank for stirring, slowly add hydrochloric acid with a mass fraction of 3% for neutralization, and adjust the pH value to After 6.5~7, use deionized water to adjust Li ⁺ to 2%; pump 5m ³ of the solution adjusted to 2% Li ⁺ concentration into the alkalization kettle, then pour 760kg of sodium carbonate and stir together for 3~4h to obtain a cloudy solution of lithium carbonate , and finally carry out centrifugation and dehydration with lithium carbonate turbid liquid through scraper centrifuge to obtain 548kg lithium carbonate powder. The lithium carbonate content in the lithium carbonate powder is 65.2%, the water content is 12.3%, and the impurity content is 22.5%.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit it; although the application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present application. All of them should be covered by the scope of the claims and description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims (12)

1. a treatment method of LiFSI waste water, is characterized in that, comprises the following steps: Adsorption: Adsorb LiFSI wastewater with resin to obtain resin that adsorbs LiFSI; Analysis: wash the resin adsorbing LiFSI with lye to obtain a LiFSI analysis solution; Concentration: heating and concentrating the LiFSI analysis solution to obtain a lithium-containing concentrated solution; Neutralization: adding acid to the lithium-containing concentrated solution to obtain a neutralized solution; Lithium sinking: add carbonate and/or carbon dioxide to the neutralization solution to react to obtain carbonate precipitation. 2. the treatment method of LiFSI waste water according to claim 1 is characterized in that, described lye is inorganic strong alkali solution, preferred sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, At least one or more combinations in aluminum hydroxide aqueous solution. 3. the treatment method of LiFSI waste water according to claim 2 is characterized in that, described lye is at least one in potassium hydroxide solution or sodium hydroxide solution. 4. The method for treating LiFSI wastewater according to any one of claims 1-3, characterized in that the concentration of the lye is 3% to 10%. 5. The treatment method of LiFSI wastewater according to claim 1, characterized in that, the temperature of the heating and concentration is 80-100°C, preferably 95-100°C. 6. according to the treatment method of the LiFSI waste water described in claim 1 or 5, it is characterized in that, the equipment of described heating concentration is double effect evaporator, triple effect evaporator, falling film evaporator, thin film evaporator, distillation tower One or several devices are used in series or in parallel. 7. The treatment method of LiFSI wastewater according to claim 1, characterized in that, the resin is neutral resin or weakly basic resin, preferably PD201 resin. 8. The method for treating LiFSI wastewater according to claim 1 or 7, characterized in that, after the adsorption, the LiFSI content in the LiFSI wastewater reaches below 0.2ppm. 9 . The method for treating LiFSI wastewater according to claim 1 , characterized in that, the pH value at the end of neutralization reaches 6.5-7.0. 10. according to the treatment method of claim 1 or 9 described LiFSI wastewater, it is characterized in that, the acid added in the neutralization is one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, oxalic acid, acetic acid, hypochlorous acid, formic acid or multiple combinations. 11. the treatment method of LiFSI waste water according to claim 1 is characterized in that, described carbonate is at least one in sodium carbonate and potassium carbonate. 12. The treatment method of LiFSI waste water according to claim 1, is characterized in that, in described sinking lithium step, also through filtering after reaction, the preferred plate and frame filter of described filter equipment, bag filter, candle One or a combination of type filter, scraper centrifuge, horizontal centrifuge, belt centrifuge, siphon centrifuge, pusher centrifuge.