Method for treating high-salt high-concentration organic wastewater containing lithium and preparing lithium carbonate

Abstract

The application discloses a method for treating lithium-containing high-salt high-concentration organic wastewater and preparing lithium carbonate, which comprises the following steps: S1, adjusting the pH value of the lithium-containing high-salt high-concentration organic wastewater to above 12, stirring uniformly, filtering, and obtaining solution A; S2, sending the solution A into an electro-catalytic oxidation equipment to electrolyze, reducing the COD value of the solution to below 200 mg / L, and obtaining solution B; S3, aerating, and obtaining slurry; S4, centrifugal filtering, and obtaining filtrate and crude lithium carbonate; S5, slurry washing, and obtaining slurry washing liquid and solid after slurry washing; S6, sending the filtrate obtained in the step S4 and the slurry washing liquid obtained in the step S5 into an evaporation concentration system to concentrate, and obtaining fresh water and concentrated water; and S7, drying the solid after slurry washing obtained in the step S5, and obtaining lithium carbonate products. While the organic pollutants are efficiently removed by electro-catalytic oxidation, the lithium carbonate is precipitated by using the carbon dioxide generated by mineralized organic matters, the method is efficient and fast in removing the organic matters, and the lithium in the wastewater is recycled as resources.

Description

Technical Field

[0001] This invention belongs to the field of environmental wastewater treatment and resource utilization, specifically relating to a method for treating lithium-containing, high-salt, and high-concentration organic wastewater and producing lithium carbonate. Background Technology

[0002] The extraction of lithium salts, the production of lithium batteries, the disposal of lithium batteries, and pharmaceutical production all generate significant amounts of high-salt, high-concentration organic wastewater containing lithium. This not only pollutes the environment but also leads to a serious waste of lithium resources. The development of technologies for treating this high-salt, high-concentration organic wastewater can alleviate the environmental pressure on enterprises and yield significant economic, environmental, and social benefits. Currently, large-scale treatment of this wastewater still faces challenges such as low treatment efficiency and high operating costs, and many key technical problems remain to be solved. Various methods exist for treating this wastewater, including biochemical degradation, evaporation, electrolysis, ion exchange, and membrane methods. While these methods have achieved some success, the high operating and investment costs, as well as equipment corrosion and scaling, hinder the widespread application of these technologies. Solving this problem is a pressing task in this field.

[0003] CN106976893A discloses a method for preparing lithium carbonate from lithium-containing wastewater, belonging to the field of chemical and industrial wastewater treatment technology. Its features include: (1) adjusting the pH of the lithium-containing wastewater to 7-8 using sodium hydroxide solution; (2) rapidly reducing the pressure inside the container, concentrating the wastewater to 10%-20% of the original wastewater volume, and then filtering; (3) adding 0.65 molar amounts of anhydrous sodium carbonate according to the lithium content in the wastewater, and heating to 90-95℃ for reaction; (4) filtering while hot after the reaction, rinsing with a small amount of hot water, and drying to obtain industrial-grade crude lithium carbonate. However, it does not remove organic pollutants, and the purity of the prepared lithium carbonate is not high.

[0004] CN115536047A discloses a method for preparing lithium carbonate from lithium-containing wastewater, comprising the following steps: S1 step: spray roasting step, in which lithium-containing wastewater is spray roasted to obtain lithium-containing precipitate, the roasting temperature being 450-900℃; S2 step: water leaching step, in which water is mixed with lithium-containing precipitate and filtered to obtain a first lithium-enriched solution; S3 step: deep impurity removal step, in which phosphate is added to the first lithium-enriched solution for reaction, and filtered to obtain a second lithium-enriched solution; S4 step: carbonate is added to the second lithium-enriched solution for reaction, and filtered to obtain lithium carbonate. However, this method has high energy consumption, and the gas produced after roasting can easily cause secondary pollution.

[0005] CN115417549B discloses a comprehensive treatment process for high-salt organic wastewater, belonging to the field of petrochemical, chemical, pharmaceutical, and dyeing wastewater treatment technology. The comprehensive treatment process includes concentration, adsorption filtration, concentration crystallization, filtration, and secondary crystallization. In the adsorption filtration step, the concentrated liquid is transferred to a reaction vessel pre-filled with resin for adsorption treatment. After adsorption, solid-liquid separation is performed to obtain the adsorbed liquid, and the resin is then regenerated. However, this process is complex, and the adsorbed organic matter becomes hazardous waste, requiring further treatment. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for treating lithium-containing high-salt and high-concentration organic wastewater and producing lithium carbonate, which can extract lithium carbonate from lithium-containing high-salt and high-concentration organic wastewater while treating it.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows:

[0008] A method for treating high-salt, high-concentration organic wastewater containing lithium and for producing lithium carbonate includes the following steps:

[0009] S1, adjust the pH of the lithium-containing, high-salt, high-concentration organic wastewater to above 12, stir evenly, filter, remove insoluble substances such as mud and sludge from the solution, and obtain solution A;

[0010] S2, Solution A is fed into an electrocatalytic oxidation device (commercially available equipment) for electrolysis to reduce the COD value in the solution to below 200 mg / L, resulting in solution B;

[0011] During the electrolysis process, organic matter in wastewater is mineralized into carbon dioxide, thus removing organic matter from the wastewater and reducing the COD value of the wastewater.

[0012] S3, send solution B into the buffer tank, and pass the carbon dioxide generated in step S2 into the bottom of the buffer tank for aeration; to obtain slurry;

[0013] In step S3, the alkaline condition of the solution itself is used to absorb carbon dioxide, providing carbonate ions for the precipitation of lithium carbonate, and on the other hand, solving the carbon dioxide emission problem in the entire process.

[0014] S4. The slurry obtained after aeration in step S3 is centrifuged and filtered to obtain filtrate and crude lithium carbonate. If the lithium concentration in the filtrate is ≥0.15t%, it is returned to step S2. If the lithium concentration in the filtrate is <0.15%, the filtrate is entered into the evaporation and concentration system for evaporation. The lithium concentration is concentrated to above 0.15% and then returned to S3 for lithium precipitation.

[0015] S5, the crude lithium carbonate obtained in step S4 is washed with slurry to obtain washing solution and washed solid.

[0016] S6. The filtrate obtained in step S4 and the washing liquid obtained in step S5 are sent to the evaporation and concentration system for concentration to obtain fresh water and concentrated water. The fresh water is reused in production, and the concentrated water is returned to the electrocatalytic oxidation equipment in step S2.

[0017] S7. Dry the solid obtained from step S5 after washing to obtain lithium carbonate product.

[0018] Furthermore, in step S1, the lithium content in the high-salt, high-concentration organic wastewater is ≥0.03wt%, the salt content is ≥5wt%, and the COD is ≥5000mg / L.

[0019] Furthermore, in step S1, sodium hydroxide solution is used to adjust the pH value of the high-salt, high-concentration organic wastewater containing lithium. Preferably, the mass concentration of the sodium hydroxide solution is 20%-40%, more preferably 30%. Adjusting the pH value serves two purposes: firstly, it removes calcium, magnesium, iron, and other heavy metals; secondly, it provides alkaline conditions for subsequent lithium precipitation.

[0020] Furthermore, in step S2, during the electrolysis process, the high-frequency vibration device is turned on, with a vibration frequency of 10KHz~50KHZ, and the vibration time is consistent with the electrolysis time.

[0021] Furthermore, in step S2, the wastewater flow rate during electrolysis is 2m. 3 / h~15m 3 / h, current density is 50~1000mA / cm2, electrolysis time is 15min~4h.

[0022] Furthermore, in step S5, the crude lithium carbonate is washed with pure water to remove impurities such as sodium carbonate, potassium carbonate, and sodium chloride. More preferably, the washing process involves stirring at 300-400 rad / min for at least 30 minutes at 80-100°C.

[0023] Furthermore, in step S7, the product is baked at 80℃-120℃ for 2-4 hours.

[0024] This invention can efficiently remove organic pollutants from wastewater without producing other harmful substances. It also utilizes the carbon dioxide produced by oxidizing organic matter to produce lithium carbonate products. The wastewater is eventually evaporated into fresh water (fresh water COD < 20 mg / L) which can be reused in production.

[0025] The present invention has the following main advantages:

[0026] (1) This invention provides a method for treating lithium-containing high-salt and high-concentration organic wastewater. While efficiently removing organic pollutants by electrocatalytic oxidation, lithium carbonate is precipitated by carbon dioxide generated from mineralizing organic matter. This method efficiently and quickly removes organic matter while recovering lithium from the wastewater.

[0027] (2) This invention recycles and utilizes carbon in lithium-containing high-salt and high-concentration organic wastewater, and absorbs carbon dioxide generated from the mineralization of organic matter in the wastewater to prepare lithium carbonate, which significantly reduces the carbon emissions of enterprises.

[0028] (3) The present invention directly produces lithium carbonate from lithium-containing high-salt and high-concentration organic wastewater. The process is short, the equipment is simple, the operation is convenient, and the operating cost is low.

[0029] This invention has a wide range of applications and can be applied to most lithium-containing, high-salt, and high-concentration organic wastewater. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below.

[0031] Unless otherwise stated, all percentages mentioned in this specification refer to percentages by mass. Example

[0032] The component analysis of the lithium-containing, high-salt, and high-concentration organic wastewater used as the raw material in this embodiment is shown in Table 1.

[0033] Table 1. Component analysis of lithium-containing organic wastewater from Anhui Province

[0034]

[0035] The method for treating lithium-containing, high-salt, and high-concentration organic wastewater and producing lithium carbonate in this embodiment includes the following steps:

[0036] S1, take 5L of lithium-containing organic wastewater from Anhui, add 200g of sodium hydroxide solution with a mass concentration of 30%, adjust the pH value to 14, stir at 300 rad / min for 30min, filter, and obtain solution A;

[0037] S2, Solution A was fed into the World BDD electrode as an electrocatalytic oxidation device for electrolytic oxidation. The flow rate was set to 15 m3 / h, the current density was 15 mA / cm2, the high frequency vibration device was adjusted to 40 kHz, the vibration was performed for 2 h, and the electrolysis was performed for 2 h to obtain Solution B, with COD reduced to 181 mg / L.

[0038] S3, send solution B into the buffer tank, and pass the carbon dioxide generated in step S2 into the bottom of the buffer tank for aeration to obtain slurry.

[0039] S4. The slurry obtained after aeration in step S3 is centrifuged and filtered to obtain filtrate and crude lithium carbonate. If the lithium concentration in the filtrate is greater than 0.15%, the process returns to step S2. If the lithium concentration in the filtrate is less than 0.15%, the filtrate enters the evaporation system for concentration.

[0040] S5. The crude lithium carbonate obtained in step S4 is washed with 2 times the amount of pure water at 95°C and stirred at 300 rad / min for 30 min to remove impurities such as sodium carbonate and potassium carbonate from the crude lithium carbonate, and to obtain washing solution and wet lithium carbonate.

[0041] S6, the filtrate obtained in step S4 and the slurry obtained in step S5 are sent to the evaporation and concentration system for concentration to obtain fresh water and concentrated water. The fresh water is reused in production, and the concentrated water is returned to the electrocatalytic oxidation equipment in step S2. The fresh water is reused.

[0042] S7. The solid lithium carbonate obtained after washing in step S5 is dried at 80°C for 4 hours to obtain 599.93g of lithium carbonate product with a lithium carbonate content of 99.6wt%.

[0043] In this embodiment, the COD removal rate reached 99.90%, and the lithium recovery rate in the wastewater reached 95.6%.

[0044] Example 2

[0045] The component analysis of the lithium-containing, high-salt, and high-concentration organic wastewater used as the raw material in this embodiment is shown in Table 2.

[0046] Table 2. Component Analysis of Lithium-Containing Organic Wastewater from Anhui Province

[0047]

[0048] The method for treating lithium-containing, high-salt, and high-concentration organic wastewater and producing lithium carbonate in this embodiment includes the following steps:

[0049] S1, Take 5L of lithium-containing organic wastewater from Anhui, add 130g of 30% sodium hydroxide solution, adjust the pH to 13.7, stir at 300 rad / min for 30min, filter, and obtain solution A;

[0050] S2, Solution A is fed into a World BDD electrode as an electrocatalytic oxidation device for electrolytic oxidation, with a current density of 25 mA / cm², electrolysis for 3 hours, and a flow rate of 8 m / s². 3 / h, the high-frequency vibration device was adjusted to 30KHz and vibrated for 3h to obtain solution B with a COD of 116mg / L;

[0051] S3, send solution B into the buffer tank, and pass the carbon dioxide generated in step S2 into the bottom of the buffer tank for aeration; to obtain slurry;

[0052] S4. The slurry obtained after aeration in step S3 is centrifuged and filtered to obtain filtrate and crude lithium carbonate. If the lithium concentration in the filtrate is ≥0.15t%, it is returned to step S2. If the lithium concentration in the filtrate is <0.15%, the filtrate is entered into the evaporation and concentration system for concentration.

[0053] S5, the crude lithium carbonate obtained in step S4 is washed with 0.4 times its volume of pure water at 75°C and stirred at 300 rad / min for 30 min. This removes impurities such as sodium carbonate and potassium carbonate, yielding a washing solution and wet lithium carbonate.

[0054] S6. The filtrate obtained in step S4 and the washing liquid obtained in step S5 are sent to the evaporation and concentration system for concentration to obtain fresh water and concentrated water. The fresh water is reused in production, and the concentrated water is returned to the electrocatalytic oxidation equipment in step S2.

[0055] S7. The solid obtained after washing in step S5 is dried at 80°C for 4 hours to obtain 628.30g of lithium carbonate product with a lithium carbonate content of 95.8wt%.

[0056] In this embodiment, the COD removal rate reached 99.94%, and the lithium recovery rate in the wastewater reached 96.3%.

[0057] Example 3

[0058] The component analysis of the lithium-containing, high-salt, and high-concentration organic wastewater used as the raw material in this embodiment is shown in Table 3.

[0059] Table 3. Component Analysis of Lithium-Containing Organic Wastewater from Jiangxi Province

[0060]

[0061] The method for treating lithium-containing, high-salt, and high-concentration organic wastewater and producing lithium carbonate in this embodiment includes the following steps:

[0062] S1, Take 5L of lithium-containing organic wastewater from Jiangxi, add 56g of 30% sodium hydroxide solution, adjust the pH to 14, stir at 300 rad / min for 30min, filter, and obtain solution A;

[0063] S2, Solution A is fed into a World BDD electrode as an electrocatalytic oxidation device for electrolytic oxidation, with a current density of 30 mA, an oxidation time of 3 h, and a flow rate of 4 m / s. 3 / h, the high-frequency vibration device was adjusted to 20KHz and vibrated for 3h to obtain solution B with a COD of 153mg / L;

[0064] S3, send solution B into the buffer tank, and pass the carbon dioxide generated in step S2 into the bottom of the buffer tank for aeration; to obtain slurry;

[0065] S4. The slurry obtained after aeration in step S3 is centrifuged and filtered to obtain filtrate and crude lithium carbonate. If the lithium concentration in the filtrate is ≥0.15t%, it is returned to step S2. If the lithium concentration in the filtrate is <0.15%, the filtrate is entered into the evaporation and concentration system for concentration.

[0066] S5, the crude lithium carbonate obtained in step S4 is washed to obtain washing solution and wet lithium carbonate after washing.

[0067] Crude lithium carbonate was washed with 1 part pure water at 80°C and stirred at 400 rad / min for 30 min.

[0068] S6. The filtrate obtained in step S4 and the washing liquid obtained in step S5 are sent to the evaporation and concentration system for concentration to obtain fresh water and concentrated water. The fresh water is reused in production, and the concentrated water is returned to the electrocatalytic oxidation equipment in step S2.

[0069] S7. The solid obtained after washing in step S5 is dried at 80°C for 4 hours to obtain 25.77g of lithium carbonate product with a lithium carbonate content of 99.1wt%.

[0070] The process achieved a COD removal rate of 97.28% and a lithium recovery rate of 94.6% in the wastewater.

[0071] Example 4

[0072] The component analysis of the lithium-containing, high-salt, and high-concentration organic wastewater used as the raw material in this embodiment is shown in Table 4.

[0073] Table 4. Component Analysis of Lithium-Containing Organic Wastewater from Jiangxi Province

[0074]

[0075] The method for treating lithium-containing, high-salt, and high-concentration organic wastewater and producing lithium carbonate in this embodiment includes the following steps:

[0076] S1, take 5L of lithium-containing organic wastewater from Jiangxi, add 82g of 30% sodium hydroxide solution, adjust the pH to 14, stir at 300 rad / min for 30min, filter to remove insoluble matter such as mud from the solution, and obtain solution A;

[0077] S2, Solution A is fed into a World BDD electrode as an electrocatalytic oxidation device for electrolytic oxidation, with a current density of 58 mA / cm², an oxidation time of 4 h, and a flow rate of 8 m / s². 3 / h, the high-frequency vibration device was adjusted to 45KHz, and the vibration time was 4h to obtain solution B with a COD of 110mg / L;

[0078] S3, send solution B into the buffer tank, and pass the carbon dioxide generated in step S2 into the bottom of the buffer tank for aeration; to obtain slurry;

[0079] S4. The slurry obtained after aeration in step S3 is centrifuged and filtered to obtain filtrate and crude lithium carbonate. If the lithium concentration in the filtrate is ≥0.15t%, it is returned to the electrocatalytic oxidation equipment in step S2 for processing. If the lithium concentration in the filtrate is <0.15%, the filtrate is entered into the evaporation and concentration system for concentration.

[0080] S5, the crude lithium carbonate obtained in step S4 is washed to obtain washing solution and wet lithium carbonate after washing.

[0081] Crude lithium carbonate was washed with 1.5 times its volume of pure water at 95°C with stirring at 400 rad / min for 30 min.

[0082] S6. The filtrate obtained in step S4 and the washing liquid obtained in step S5 are sent to the evaporation and concentration system for concentration to obtain fresh water and concentrated water. The fresh water is reused in production, and the concentrated water is returned to the electrocatalytic oxidation equipment in step S2.

[0083] S7. The solid obtained after washing in step S5 is dried at 80°C for 4 hours to obtain 25.59g of lithium carbonate product with a lithium carbonate content of 99.3wt%.

[0084] In this embodiment, the COD removal rate reached 98.05%, and the lithium recovery rate in the wastewater reached 97.1%.

[0085] Example 5

[0086] The component analysis of the lithium-containing, high-salt, and high-concentration organic wastewater used as the raw material in this embodiment is shown in Table 5.

[0087] Table 5. Component analysis of lithium-containing organic wastewater from Gansu Province

[0088]

[0089] The method for treating lithium-containing, high-salt, and high-concentration organic wastewater and producing lithium carbonate in this embodiment includes the following steps:

[0090] S1, Take 5L of lithium-containing organic wastewater from Gansu, add 240g of 30% sodium hydroxide solution, adjust the pH to 14, stir at 300 rad / min for 30min, filter, and obtain solution A;

[0091] S2, solution A is fed into a World BDD electrode as an electrocatalytic oxidation device for electrolytic oxidation, with a current density of 60 mA / cm², an oxidation time of 4 h, and a flow rate of 6.5 m / s². 3 / h, the high-frequency vibration device was adjusted to 35KHz, and the vibration time was 4h to obtain solution B with a COD of 163mg / L;

[0092] S3, send solution B into the buffer tank, and pass the carbon dioxide generated in step S2 into the bottom of the buffer tank for aeration; to obtain slurry;

[0093] S4. The slurry obtained after aeration in step S3 is centrifuged and filtered to obtain filtrate and crude lithium carbonate. If the lithium concentration in the filtrate is ≥0.15wt%, it is returned to step S2. If the lithium concentration in the filtrate is <0.15%, the filtrate is entered into the evaporation and concentration system for concentration.

[0094] S5, the crude lithium carbonate obtained in step S4 is washed to obtain washing solution and wet lithium carbonate after washing.

[0095] Crude lithium carbonate was washed with 1.7 times its volume of pure water at 95°C with stirring at 400 rad / min for 30 min.

[0096] S6. The filtrate obtained in step S4 and the washing liquid obtained in step S5 are sent to the evaporation and concentration system for concentration to obtain fresh water and concentrated water. The fresh water is reused in production, and the concentrated water is returned to the electrocatalytic oxidation equipment in step S2.

[0097] S7. The solid obtained after washing in step S5 is dried at 80°C for 4 hours to obtain 73.30g of lithium carbonate product with a lithium carbonate content of 97.3t.

[0098] In this embodiment, the COD removal rate reached 98.31%, and the lithium recovery rate in the wastewater reached 91.1%.

[0099] Example 6

[0100] The component analysis of the lithium-containing, high-salt, and high-concentration organic wastewater used as the raw material in this embodiment is shown in Table 6.

[0101] Table 6. Component Analysis of Lithium-Containing Organic Wastewater from Gansu Province

[0102]

[0103] The method for treating lithium-containing, high-salt, and high-concentration organic wastewater and producing lithium carbonate in this embodiment includes the following steps:

[0104] S1, take 5L of lithium-containing organic wastewater from Gansu, add 56g of sodium hydroxide solution with a mass concentration of 30%, adjust the pH value to 14, stir at 300 rad / min for 30min, filter to remove insoluble matter such as mud from the solution, and obtain solution A;

[0105] S2, Solution A is fed into the Wolde BDD electrode as an electrocatalytic oxidation device for electrolytic oxidation, with a current density of 73 mA / cm2, an electro-oxidation time of 4 h, and a flow rate of 4 m / s². 3 / h, the high-frequency vibration device was adjusted to 20KHz, and the vibration time was 4h to obtain solution B with a COD of 126mg / L;

[0106] S3, send solution B into the buffer tank, and pass the carbon dioxide generated in step S2 into the bottom of the buffer tank for aeration; to obtain slurry;

[0107] S4. The slurry obtained after aeration in step S3 is centrifuged and filtered to obtain filtrate and crude lithium carbonate. If the lithium concentration in the filtrate is ≥0.15wt%, it is returned to step S2. If the lithium concentration in the filtrate is <0.15%, the filtrate is entered into the evaporation and concentration system for concentration.

[0108] S5, the crude lithium carbonate obtained in step S4 is washed to obtain washing solution and wet lithium carbonate after washing.

[0109] Crude lithium carbonate was washed with twice the amount of pure water at 95°C and stirred at 300 rad / min for 30 min.

[0110] S6. The filtrate obtained in step S4 and the washing liquid obtained in step S5 are sent to the evaporation and concentration system for concentration to obtain fresh water and concentrated water. The fresh water is reused in production, and the concentrated water is returned to the electrocatalytic oxidation equipment in step S2.

[0111] S7. The solid obtained after washing in step S5 is dried at 80°C for 4 hours to obtain 73.45g of lithium carbonate product with a lithium carbonate content of 98.6wt%.

[0112] In this embodiment, the COD removal rate reached 98.70%, and the lithium recovery rate in the wastewater reached 92.5%.

Claims

1. A method for treating high-salt, high-concentration organic wastewater containing lithium and for producing lithium carbonate, characterized in that, Includes the following steps: S1, adjust the pH value of the lithium-containing high-salt and high-concentration organic wastewater to above 12, stir evenly, filter, remove insoluble matter in the solution, and obtain solution A; S2, Solution A is fed into an electrocatalytic oxidation device for electrolysis to reduce the COD value of the solution to below 200 mg / L, thus obtaining Solution B; S3, send solution B into the buffer tank, and pass the carbon dioxide generated in step S2 into the bottom of the buffer tank for aeration; to obtain slurry; S4. The slurry obtained after aeration in step S3 is centrifuged and filtered to obtain filtrate and crude lithium carbonate. If the lithium concentration in the filtrate is ≥0.15t%, it is returned to step S2. If the lithium concentration in the filtrate is <0.15%, the filtrate is entered into the evaporation and concentration system for evaporation. The lithium concentration is concentrated to above 0.15% and then returned to S3 for lithium precipitation. S5, the crude lithium carbonate obtained in step S4 is washed with slurry to obtain washing solution and washed solid. S6. The filtrate obtained in step S4 and the washing liquid obtained in step S5 are sent to the evaporation and concentration system for concentration to obtain fresh water and concentrated water. The fresh water is reused in production, and the concentrated water is returned to the electrocatalytic oxidation equipment in step S2. S7. Dry the solid obtained from step S5 after washing to obtain lithium carbonate product.

2. The method for treating lithium-containing, high-salt, high-concentration organic wastewater and producing lithium carbonate according to claim 1, characterized in that, In step S1, the lithium content in the high-salt, high-concentration organic wastewater is ≥0.03wt%, and the salt content is ≥5wt%.

3. The method for treating lithium-containing, high-salt, high-concentration organic wastewater and producing lithium carbonate according to claim 1 or 2, characterized in that, In step S1, COD ≥ 5000 mg / L.

4. The method for treating lithium-containing, high-salt, high-concentration organic wastewater and producing lithium carbonate according to claim 1 or 2, characterized in that, In step S1, sodium hydroxide solution is used to adjust the pH value of the lithium-containing, high-salt, and high-concentration organic wastewater.

5. The method for treating lithium-containing, high-salt, high-concentration organic wastewater and producing lithium carbonate according to claim 4, characterized in that, The mass concentration of sodium hydroxide solution is 20%-40%.

6. The method for treating lithium-containing, high-salt, high-concentration organic wastewater and producing lithium carbonate according to claim 1 or 2, characterized in that, In step S2, the high-frequency vibration device is turned on during the electrolysis process. The vibration frequency is 10KHz~50KHZ, and the vibration time is the same as the electrolysis time.

7. The method for treating lithium-containing, high-salt, high-concentration organic wastewater and producing lithium carbonate according to claim 1 or 2, characterized in that, In step S2, the wastewater flow rate is 2m during electrolysis. 3 / h~15m 3 / h, current density is 50~1000mA / cm2, electrolysis time is 15min~4h.

8. The method for treating lithium-containing, high-salt, high-concentration organic wastewater and producing lithium carbonate according to claim 1 or 2, characterized in that, In step S5, the crude lithium carbonate is washed with pure water.

9. The method for treating lithium-containing, high-salt, high-concentration organic wastewater and producing lithium carbonate according to claim 1 or 2, characterized in that, In step S5, the slurry is washed at 80℃~100℃ and a speed of 300~400rad / min for more than 30 minutes.

10. The method for treating lithium-containing, high-salt, high-concentration organic wastewater and producing lithium carbonate according to claim 1 or 2, characterized in that, In step S7, bake at 80℃-120℃ for 2-4 hours.

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