Treatment method for removing EDTA (Ethylene Diamine Tetraacetic Acid)-Ca in high-salt and high-chlorine lithium-containing mother liquor

Abstract

The invention provides a treatment method for removing EDTA-Ca in a high-salt and high-chlorine lithium-containing mother solution, and belongs to the technical field of lithium salt preparation. The treatment method sequentially comprises the following steps: S100, adjusting the pH value of the lithium-containing mother liquor to be treated to be acidic, and stirring to react for a period of time; s200, after stirring reaction, standing for a period of time, filtering to remove precipitate, and collecting filtrate; s300, adjusting the pH value of the filtrate to be alkaline, adding an oxidizing agent, and stirring to react for a period of time; and S400, heating for a period of time after stirring reaction, filtering to remove precipitate, and collecting filtrate to obtain treated lithium-containing mother liquor. The treatment method can effectively break complexation of EDTA-Ca in the high-salt and high-chlorine lithium-containing mother liquor, effectively remove calcium ions and reduce the EDTA content and solution complexation ability, and has the advantages of less lithium ion loss, low cost, simple and safe process and less impurity introduction.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium salt preparation, and particularly relates to a treatment method of EDTA-Ca in a high-salt high-chlorine lithium-containing mother liquor. BACKGROUND

[0002] In the process of preparing lithium salt from spodumene, lithium sulfate completion liquor is obtained through roasting, acidification, slurry preparation leaching, purification and evaporation concentration. The lithium sulfate completion liquor is used as raw material for lithium carbonate or lithium hydroxide production. For lithium carbonate production, lithium sulfate reacts with sodium carbonate to obtain lithium carbonate product and lithium precipitation mother liquor. After neutralization with sulfuric acid and evaporation crystallization, anhydrous sodium sulfate and sodium precipitation mother liquor are obtained. The lithium sulfate completion liquor contains calcium ions, which will produce calcium carbonate precipitate if directly used for lithium precipitation, resulting in increased impurity content of lithium carbonate product. The existing technology in the industry is to add EDTA during lithium precipitation to form EDTA-Ca, which can reduce the influence of calcium ions in the solution through solid-liquid separation. Therefore, EDTA-Ca will exist in large quantities in the sodium precipitation mother liquor after neutralization and concentration. The sodium precipitation mother liquor contains a high content of lithium and needs to be recycled and utilized. Therefore, the sodium precipitation mother liquor is continuously circulated in the system, thereby enriching a large amount of impurities such as EDTA and EDTA complex, chlorine, etc. The enrichment of impurities will affect the product quality, resulting in a decrease in product quality and causing huge losses to the production enterprises.

[0003] Currently, the commonly used methods for removing EDTA from water bodies mainly include chemical oxidation method, biological degradation method, ion exchange method, membrane separation method, etc.

[0004] Among them, the chemical oxidation method is to use a strong oxidizing agent to oxidize and decompose the organic structure part in the EDTA molecule, so that it is converted into small molecular organic acid or inorganic ion, etc. which is relatively easy to handle. However, the oxidizing agent used usually has a high cost, and some secondary pollutants may be generated during the reaction process, which is troublesome for subsequent treatment. At the same time, when this method is used to treat high-salt high-chlorine lithium-containing mother liquor, chloride ions will consume a part of active groups, reducing the oxidation efficiency of the target organic matter and increasing the amount of oxidizing agent used.

[0005] The biological degradation method is to decompose EDTA by means of microbial metabolism. The degradation process is relatively slow, and the treatment effect is not ideal for high-concentration and difficult-to-degrade EDTA wastewater. Moreover, the growth and metabolism of microorganisms have strict requirements on environmental conditions (such as temperature, pH value, dissolved oxygen, etc.).

[0006] The ion exchange method utilizes ion exchange resin to carry out ion exchange reaction with metal ion complex containing EDTA in water, so that EDTA is freed, and then the freed EDTA is further treated by other methods. The selectivity and exchange capacity of the ion exchange resin are limited, the resin is easily contaminated during use, affecting the exchange performance, and the regeneration process increases the treatment cost.

[0007] The membrane separation method separates the solution containing EDTA through a semi-permeable membrane. The membrane has a high rejection rate for multivalent ions and relatively large organic matters (such as EDTA). However, the cost of the membrane is high, and the membrane is often contaminated during operation, resulting in a decrease in membrane flux, an increase in operation cost and maintenance workload.

[0008] Therefore, the existing methods for removing EDTA from water cannot simultaneously consider the removal efficiency and economy for treating the high-salt high-chlorine lithium-containing mother liquor containing EDTA-Ca, and thus it is necessary to study a new method for removing EDTA-Ca from the high-salt high-chlorine lithium-containing mother liquor. SUMMARY

[0009] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for removing EDTA-Ca from a high-salt high-chlorine lithium-containing mother liquor, which can effectively break the complexation of EDTA-Ca complex in the solution, effectively remove calcium ions, reduce the content and complexing ability of EDTA, have less loss of lithium ions, have low treatment cost, and have simple and safe process and less introduction of impurities.

[0010] The technical solution adopted by the present application is as follows:

[0011] A method for removing EDTA-Ca from a high-salt high-chlorine lithium-containing mother liquor, comprising the following steps performed in sequence:

[0012] S100, adjusting the pH of the lithium-containing mother liquor to be treated to be acidic, and stirring for a period of time;

[0013] S200, after stirring, standing for a period of time, filtering to remove the precipitate, and collecting the filtrate;

[0014] S300, adjusting the pH of the filtrate to be alkaline, adding an oxidizing agent, and stirring for a period of time;

[0015] S400, after stirring, heating for a period of time, filtering to remove the precipitate, collecting the filtrate, and obtaining the lithium-containing mother liquor after treatment.

[0016] In an embodiment of the present application, the lithium-containing mother liquor to be treated is a sodium-precipitating mother liquor in a lithium carbonate production system from spodumene, wherein the concentration of chloride ions in the sodium-precipitating mother liquor is greater than or equal to 33 g / L, the COD value is 10-15 g / L, the concentration of sodium ions is greater than or equal to 85 g / L, and the concentration of sulfate ions is greater than or equal to 230 g / L.

[0017] In an embodiment of the present application, in step S100, sulfuric acid is used to adjust the pH of the lithium-containing mother liquor to be treated to 0.5-3, and the reaction is stirred for 2-6 hours.

[0018] In an embodiment of the present application, in step S200, the filtration is performed after the standing treatment for 5-20 hours.

[0019] In an embodiment of the present application, in step S100, the pH of the lithium-containing mother liquor to be treated is adjusted to 1-2, and the reaction is stirred for 3-4 hours.

[0020] In step S200, the standing treatment is performed for 14-18 hours.

[0021] In an embodiment of the present application, the oxidizing agent is one or more of potassium permanganate, hydrogen peroxide, and sodium hypochlorite; and the mass ratio of the amount of the oxidizing agent added to the total calcium content in the lithium-containing mother liquor to be treated is 4-12:1.

[0022] In an embodiment of the present application, in step S300, the pH of the filtrate is adjusted to 8-11, and the reaction is stirred for 0.5-4 hours.

[0023] In an embodiment of the present application, the oxidizing agent is potassium permanganate, and the mass ratio of the amount of the potassium permanganate added to the total calcium content in the lithium-containing mother liquor to be treated is 6-9:1.

[0024] In an embodiment of the present application, in step S400, after the stirring reaction, the temperature is heated to 50-150 DEG C, and the heat preservation treatment is performed for 10-120 minutes.

[0025] In an embodiment of the present application, in step S400, after the stirring reaction, the temperature is heated to 90-100 DEG C, and the heat preservation treatment is performed for 30-60 minutes.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The method for removing EDTA-Ca from high-salt high-chlorine lithium-containing mother liquor provided by the application first adjusts the pH of the lithium-containing mother liquor to be treated to be acidic, then fully stirs and reacts the solution, effectively breaks the complexation of most EDTA-Ca, and fully separates the broken complexation EDTA and Ca; after standing and treatment, the solution is filtered, which is conducive to the solution reaching equilibrium, so that most of the EDTA and Ca form precipitates respectively, while the lithium in the lithium-containing mother liquor dissolves in the solution and is not filtered out with the EDTA and Ca precipitates, which can effectively reduce the amount of lithium carried out of the precipitates during filtration; then the pH of the filtrate is adjusted to be alkaline, and an oxidizing agent is added to oxidize the remaining EDTA-Ca in the solution and break the complexation to form precipitates; the adjustment to alkalinity and the addition of the oxidizing agent can effectively avoid the oxidation and release of chlorine gas from the chlorine ions in the solution, making the process safer; after the addition of the oxidizing agent, heating treatment is performed, and then the precipitates are removed by filtration, which converts the excess oxidizing agent into precipitates or gas and removes the gas, reduces the introduction of impurities, and ensures the product quality.

[0028] The treatment method can be applied to remove EDTA-Ca complexes from high-salt high-chlorine lithium-containing mother liquor, and is particularly suitable for the treatment of sodium precipitation mother liquor in a lithium spodumene ore production lithium carbonate system, can effectively break the complexation of EDTA-Ca complexes, remove calcium ions, reduce the concentration of calcium ions (the removal rate of total calcium content / concentration is more than 96%, even more than 98%), reduce the EDTA content and the complexing ability of the solution (the complexing ability can be reduced by 97.9%), can well control the introduction of impurities and well avoid the loss of lithium ions (the loss rate of lithium ions is less than 5%), the treatment process is simple, safe, and low in cost, and is suitable for large-scale industrial production; when applied to a lithium spodumene ore production lithium carbonate system, it can provide strong guarantee for obtaining battery-grade lithium carbonate products. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0030] Figure 1 The flowchart of the method for removing EDTA-Ca from high-salt high-chlorine lithium-containing mother liquor. DETAILED DESCRIPTION

[0031] In the following, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and the description are considered to be exemplary in nature rather than limiting.

[0032] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0033] The embodiments of the present application provide a treatment method of EDTA-Ca in high-salt high-chlorine lithium-containing mother liquor, which comprises the following steps performed in sequence:

[0034] S100, adding acid to the lithium-containing mother liquor to be treated to adjust the pH of the solution to be acidic, stirring for a period of time, and breaking the EDTA-Ca complex in the solution.

[0035] Preferably, sulfuric acid is used for pH adjustment, the pH of the solution is adjusted to 0.5-3, and the stirring reaction is performed for 2-6 h. More preferably, the pH of the solution is adjusted to 1-2, and the stirring reaction time is controlled to be 3-4 h. Most of the EDTA-Ca complex can be broken, and the broken EDTA and Ca are separated from each other to form a precipitate.

[0036] S200, after the stirring reaction in step S100, standing for a period of time, and after standing, filtering out the precipitate and collecting the filtrate.

[0037] The standing time is controlled to be 5-20 h, and more preferably, the standing time is controlled to be 14-18 h. The solution can reach a dissolution equilibrium, most of the EDTA and Ca form a precipitate respectively, and the lithium in the lithium-containing mother liquor dissolves in the solution and is not filtered out with the EDTA and Ca, which can effectively reduce the amount of lithium carried out of the precipitate during filtration.

[0038] S300, adjusting the pH of the filtrate to be alkaline, then adding an oxidizing agent, and stirring for a period of time.

[0039] In this step S300, after the filtrate is adjusted to be alkaline, the oxidizing agent is added for treatment, which can effectively avoid the oxidation of chloride ions in the solution to release chlorine gas, and makes the process operation more safe and controllable.

[0040] Preferably, the pH of the filtrate is adjusted to 8-11, and the stirring reaction is performed for 0.5-4 h.

[0041] The oxidizing agent is selected from one or a combination of multiple kinds of potassium permanganate, hydrogen peroxide, and sodium hypochlorite. The mass ratio of the added amount of the oxidizing agent to the total calcium content in the lithium-containing mother liquor to be treated is controlled to be 4-12:1, and preferably, the mass ratio of the added amount of the oxidizing agent to the total calcium content in the lithium-containing mother liquor to be treated is controlled to be 6-9:1.

[0042] The remaining EDTA-Ca complex can be effectively oxidized and broken to form a precipitate.

[0043] More preferably, the pH of the filtrate is adjusted to 8-9. Potassium permanganate is selected as the oxidizing agent, and the mass ratio of the amount of potassium permanganate added to the total calcium content in the lithium-containing mother liquor to be treated is controlled to be in the range of 6-9:1. The stirring reaction time is controlled to be in the range of 0.5-3 h.

[0044] The method can ensure effective oxidation to break the excess EDTA-Ca complex and reduce the use of oxidizing agent. Potassium permanganate has strong oxidizing properties, and its raw material is solid, which is easy to store. The use of potassium permanganate has good and safe oxidation effect.

[0045] S400, after the stirring reaction in step S300, the solution is heated for a period of time, and after the heating treatment, the solution is filtered to remove the precipitate, and the filtrate is collected, thereby completing the removal of EDTA-Ca in the high-salt and high-chlorine lithium-containing mother liquor and obtaining the treated lithium-containing mother liquor.

[0046] Preferably, after the stirring reaction, the solution is heated to 50-150°C and incubated for 10-120 min, and then filtered. More preferably, the heating temperature is controlled to be 90-100°C, and the incubation time is controlled to be 30-60 min. By heating and controlling the heating temperature and time, the excess oxidizing agent can be effectively converted into a precipitate or gas, thereby being separated from the solution and reducing the introduction of impurities.

[0047] Optionally, the lithium-containing mother liquor to be treated is a sodium-precipitating mother liquor in a lithium spodumene ore production lithium carbonate system. Further, the treatment method can treat a sodium-precipitating mother liquor having a chloride ion concentration of ≥33 g / L, a COD value of 10-15 g / L, a sodium ion concentration of ≥85 g / L, and a sulfate ion concentration of ≥230 g / L. Further, the sodium-precipitating mother liquor also has a potassium ion concentration of ≥17 g / L and a boron ion concentration of ≥7.5 g / L. That is, the treatment method can be applied to remove EDTA-Ca complex in a high-salt and high-chlorine lithium-containing mother liquor, and is particularly suitable for treating a sodium-precipitating mother liquor in a lithium spodumene ore production lithium carbonate system. The treatment method can effectively break the complex of EDTA-Ca complex, remove calcium ions, reduce the concentration of calcium ions (the removal rate of total calcium content is ≥96%, and even ≥98%), and reduce the content and complexing ability of EDTA. The treatment method can well control the introduction of impurities and avoid the loss of lithium ions (the loss rate of lithium ions is ≤5%), and has the advantages of simple process, safety, low cost, and suitability for large-scale industrial production.

[0048] The treatment of the sodium-precipitating mother liquor in the lithium spodumene ore production lithium carbonate system by the above method can provide a favorable guarantee for obtaining a battery-grade lithium carbonate product.

[0049] Example 1

[0050] A treatment method for removing EDTA-Ca in a high-salt and high-chlorine lithium-containing mother liquor, comprising the following steps:

[0051] (1) Take 3L of the lithium-containing mother liquor to be treated (i.e., the high-salt high-chlorine lithium-containing mother liquor to be treated) in a beaker, adjust the pH of the solution to 1 with concentrated sulfuric acid, and stir for about 4h.

[0052] The total calcium concentration of the lithium-containing mother liquor to be treated is 1.1g / L, the COD concentration is 14.97g / L, and the lithium ion concentration is 9.75g / L.

[0053] (2) After stirring and reaction, the precipitate is treated by standing for 14h and then by filtration to remove the precipitate.

[0054] (3) Adjust the pH of the filtrate to 9 by adding sodium hydroxide, then add 24g of potassium permanganate, and stir for about 4h.

[0055] (4) Heat the solution after adding potassium permanganate and stirring to about 60℃ and maintain for 120min, then filter to remove the precipitate, and complete the treatment of the high-salt high-chlorine lithium-containing mother liquor to obtain the treated lithium-containing mother liquor.

[0056] The total calcium concentration of the treated lithium-containing mother liquor is 0.0074g / L, the COD concentration is 7.485g / L, and the lithium ion concentration is 9.29g / L. The removal rate of total calcium content / concentration of the treated lithium-containing mother liquor obtained after the treatment of the lithium-containing mother liquor to be treated is about 99.32%, the EDTA removal rate is 50%, and the lithium ion loss rate is 4.72%.

[0057] The treated lithium-containing mother liquor of Example 1 is tested for complexing ability.

[0058] Take 500mL of the treated lithium-containing mother liquor of Example 1, add 50mL of calcium chloride solution (calcium chloride concentration is 60g / L), stir uniformly, then add 20mL of sodium carbonate solution (sodium carbonate concentration is 400g / L), stir for 4h, filter, remove the precipitate, and collect the filtrate.

[0059] The total calcium concentration in the filtrate is 0.023g / L, and the total calcium concentration in the lithium-containing mother liquor to be treated before treatment is 1.1g / L. Therefore, the complexing ability of the treated lithium-containing mother liquor is reduced by 97.9%.

[0060] Example 2

[0061] A method for removing EDTA-Ca from a high-salt high-chlorine lithium-containing mother liquor, comprising the following steps:

[0062] (1) Take 3L of the lithium-containing mother liquor to be treated (i.e., the high-salt high-chlorine lithium-containing mother liquor to be treated) in a beaker, adjust the pH of the solution to 2 with concentrated sulfuric acid, and stir for about 2h.

[0063] The total calcium concentration of the lithium-containing mother liquor to be treated is 0.96 g / L, the COD concentration is 14.07 g / L, and the lithium ion concentration is 11.8 g / L.

[0064] (2) After stirring and reaction, the solution is left to stand for 18 h, then suction filtration is performed, the filtrate is collected, and the precipitate is removed.

[0065] (3) Sodium hydroxide is added to adjust the pH of the filtrate to 8, then 25 g of potassium permanganate is added, and stirring and reaction are performed for about 2 h.

[0066] (4) The solution after adding potassium permanganate and stirring and reaction is heated to about 80°C and kept for 30 min, then filtration is performed, the filtrate is collected, and the precipitate is removed, thereby completing the treatment of the high-salt high-chlorine lithium-containing mother liquor and obtaining a treated lithium-containing mother liquor.

[0067] The total calcium concentration of the lithium-containing mother liquor to be treated is 0.96 g / L, the COD concentration is 14.07 g / L, and the lithium ion concentration is 11.8 g / L.

[0068] Example 3

[0069] A method for removing EDTA-Ca from a high-salt high-chlorine lithium-containing mother liquor, comprising the following steps:

[0070] (1) 2 L of a lithium-containing mother liquor to be treated (i.e., a high-salt high-chlorine lithium-containing mother liquor to be treated) is taken in a beaker, concentrated sulfuric acid is used to adjust the pH of the solution to 2, and stirring and reaction are performed for about 2 h.

[0071] The total calcium concentration of the lithium-containing mother liquor to be treated is 1.2 g / L, the COD concentration is 12.87 g / L, and the lithium ion concentration is 15.12 g / L.

[0072] (2) After stirring and reaction, the solution is left to stand for 18 h, then suction filtration is performed, the filtrate is collected, and the precipitate is removed.

[0073] (3) Sodium hydroxide is added to adjust the pH of the filtrate to 11, then 10 g of potassium permanganate is added, and stirring and reaction are performed for about 4 h.

[0074] (4) The solution after adding potassium permanganate and stirring and reaction is heated to about 100°C and kept for 100 min, then filtration is performed, the filtrate is collected, and the precipitate is removed, thereby completing the treatment of the high-salt high-chlorine lithium-containing mother liquor and obtaining a treated lithium-containing mother liquor.

[0075] The total calcium concentration in the treated lithium-containing mother liquor is 0.041 g / L, the COD concentration is 7.934 g / L, and the lithium ion concentration is 14.47 g / L. That is, the removal rate of the total calcium content / concentration of the treated lithium-containing mother liquor obtained after the above treatment of the lithium-containing mother liquor to be treated is about 96.58%, the EDTA removal rate is 38.35%, and the lithium ion loss rate is 4.30%.

[0076] Comparative Example 1

[0077] A treatment method of EDTA-Ca in a high-salt high-chlorine lithium-containing mother liquor, comprising the following steps:

[0078] (1) Take 3 L of lithium-containing mother liquor to be treated (i.e. high-salt high-chlorine lithium-containing mother liquor to be treated) in a beaker, adjust the pH of the solution to 2 with concentrated sulfuric acid, and stir for about 2 h.

[0079] The total calcium concentration in the treated lithium-containing mother liquor is 0.041 g / L, the COD concentration is 7.934 g / L, and the lithium ion concentration is 14.47 g / L. That is, the removal rate of the total calcium content / concentration of the treated lithium-containing mother liquor obtained after the above treatment of the lithium-containing mother liquor to be treated is about 96.58%, the EDTA removal rate is 38.35%, and the lithium ion loss rate is 4.30%.

[0080] (2) After stirring, do not stand, directly filter, collect the filtrate, and remove the precipitate.

[0081] (3) Adjust the pH of the filtrate to 8 by adding sodium hydroxide, then add 25 g of potassium permanganate, and stir for about 2 h.

[0082] (4) Heat the solution after adding potassium permanganate and stirring to about 80℃, keep for 30 min, then filter, collect the filtrate, and remove the precipitate, to complete the treatment of the high-salt high-chlorine lithium-containing mother liquor, and obtain a treated lithium-containing mother liquor.

[0083] The total calcium concentration in the treated lithium-containing mother liquor is 0.041 g / L, the COD concentration is 7.934 g / L, and the lithium ion concentration is 14.47 g / L. That is, the removal rate of the total calcium content / concentration of the treated lithium-containing mother liquor obtained after the above treatment of the lithium-containing mother liquor to be treated is about 96.58%, the EDTA removal rate is 38.35%, and the lithium ion loss rate is 4.30%.

[0084] Table 1 is the substance concentration and treatment efficiency of the lithium-containing mother liquor before and after treatment in Examples 1-3

[0085]

[0086] In summary, according to Examples 1-3, Comparative Example 1 and Table 1, the treatment method of the present application can effectively break the complexation of EDTA-Ca complex in the lithium-containing mother liquor to be treated, effectively remove calcium ions, reduce the concentration of calcium ions in the solution (the total calcium content removal rate is more than 96%, even more than 98%), reduce the EDTA content and complexing ability; can well avoid the loss of lithium ions (the loss rate of lithium ions is less than 5%), the treatment process is simple, safe and low in cost, and is suitable for large-scale industrial production.

Claims

1. A method for removing EDTA-Ca from high-salt, high-chloride, lithium-containing mother liquor, characterized in that: The process includes the following steps: S100, adjusting the pH of the lithium-containing mother liquor to be treated to acidic, and stirring the reaction for a period of time; S200, stirring the reaction and then allowing it to stand for a period of time, filtering to remove the precipitate, and collecting the filtrate; S300, adjusting the pH of the filtrate to alkaline, adding an oxidant, and stirring the reaction for a period of time; S400, stirring the reaction and then heating for a period of time, filtering to remove the precipitate, collecting the filtrate, and obtaining a treated lithium-containing mother liquor.

2. The method for removing EDTA-Ca from high-salt and high-chlorine lithium-containing mother liquor according to claim 1, wherein: The lithium-containing mother liquor to be treated is the sodium precipitation mother liquor in the lithium carbonate production system of spodumene ore, wherein the chloride ion concentration in the sodium precipitation mother liquor is ≥33 g / L, the COD value is 10-15 g / L, the sodium ion concentration is ≥85 g / L, and the sulfate ion concentration is ≥230 g / L.

3. The method for treating EDTA-Ca in a high-salt, high-chlorine lithium-containing mother liquor according to claim 1 or 2, wherein: In step S100, sulfuric acid is used to adjust the pH of the lithium-containing mother liquor to be treated to 0.5-3, and the reaction is stirred for 2-6 hours.

4. The method for removing EDTA-Ca from high-salt and high-chloride lithium-containing mother liquor according to claim 3, wherein: In step S200, the mixture is allowed to stand for 5 to 20 hours before being filtered.

5. The method for removing EDTA-Ca from high-salt and high-chloride lithium-containing mother liquor according to claim 4, wherein: In step S100, the pH of the lithium-containing mother solution to be treated is adjusted to 1-2, and the reaction is stirred for 3-4 hours; In step S200, the process is left to stand for 14 to 18 hours.

6. The method for removing EDTA-Ca from high-salt, high-chloride lithium-containing mother liquor according to claim 4 or 5, wherein: The oxidant is one or more of potassium permanganate, hydrogen peroxide, and sodium hypochlorite; the mass ratio of the added amount of the oxidant to the total calcium content in the lithium-containing mother liquor to be treated is 4-12:

1.

7. The method for removing EDTA-Ca from high-salt and high-chloride lithium-containing mother liquor according to claim 6, wherein: In step S300 , the pH of the filtrate is adjusted to 8-11, and the reaction is stirred for 0.5-4 hours.

8. The method for removing EDTA-Ca from high-salt, high-chloride, lithium-containing mother liquor according to claim 7, wherein: The oxidant is potassium permanganate, and the mass ratio of the added amount of potassium permanganate to the total calcium content in the lithium-containing mother liquor to be treated is 6-9:

1.

9. The method for removing EDTA-Ca from high-salt, high-chloride lithium-containing mother liquor according to claim 7 or 8, wherein: In step S400, the mixture is stirred for reaction and then heated to 50-150°C and kept warm for 10-120 minutes.

10. The method for removing EDTA-Ca from high-salt, high-chloride, lithium-containing mother liquor according to claim 9, wherein: In step S400, the mixture is stirred for reaction and then heated to 90-100°C and kept warm for 30-60 minutes.

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