A method for recycling NMP in lithium battery waste liquid by in-situ deposition method of inorganic salt

Abstract

The application discloses a method for recycling NMP in lithium battery waste liquid by using in-situ deposition method of inorganic salt, and comprises the following steps: S1, injecting the waste liquid into a treatment pool; S2, adding a soluble X salt aqueous solution with a certain mass fraction into the waste liquid treatment pool and stirring uniformly; S3, adding a soluble Y salt or strong alkali aqueous solution with a certain mass fraction into the above solution while stirring, and then stirring uniformly and standing; S4, performing suction filtration, wherein the filtrate is an NMP aqueous solution, and the precipitate comprises carbon powder, noble metal, a small amount of NMP, inorganic salt and other solid substances; and S5, performing vacuum rectification on the NMP aqueous solution under nitrogen protection, and controlling the vacuum degree to be 0.09-0.1 MPa, the temperature to be 150-170 DEG C, and the rectification time to be 1-3 h, so that the NMP is separated out. The application does not need extremely high energy consumption, and does not need to use a high-cost flocculant, but can achieve the recycling target by using the precipitation and complexation reaction mechanism between cheap and easily obtained inorganic salts, and is suitable for the preliminary recycling of NMP in industrial production.

Description

Technical Field

[0001] This invention relates to the field of lithium battery waste liquid recycling technology, and in particular to a method for recovering NMP from lithium battery waste liquid using an in-situ inorganic salt deposition method. Background Technology

[0002] With the rapid development of information technology and manufacturing, portable electronic products and various household appliances have permeated our daily lives. As living standards improve, people are placing higher demands on the electronic devices they use. Lithium-ion batteries, due to their high energy density, long cycle life, low self-discharge rate, small size, and light weight, have been rapidly adopted in electronic products such as telephones, personal computers, and cameras, as well as electric vehicles. The production of lithium-ion batteries has been increasing by double digits annually. Therefore, the recycling and reuse of lithium battery electrode waste liquid has become an urgent problem to be solved.

[0003] The main components of lithium battery electrode waste liquid are N-methylpyrrolidone (NMP), nano-sized carbon powder particles, colloidal substances, solvents, inorganic salts, and water. The main purpose of this patent is to fully recover NMP, or N-methylpyrrolidone. NMP has the molecular formula C5H9NO and is a colorless, transparent liquid with a molecular weight of 99, a relative density of 1.0260, a melting point of -24.4℃, a boiling point of 203℃, and a flash point of 95℃. It exhibits good stability and high selectivity, and has a slight irritant effect on human skin. Although this solvent has some environmental pollution, its low toxicity and biodegradability mean that effective recycling methods can significantly reduce its environmental impact. NMP solvent is one of the important raw materials for manufacturing lithium batteries, ensuring their proper functioning. Effective recycling of NMP solvent is of great significance for environmental protection and is an inevitable choice for achieving both economic and environmental benefits.

[0004] Therefore, based on the inventor's extensive experience in design, development, and practical manufacturing in the relevant industry, the inventor has researched and improved the existing structure and its shortcomings. The invention provides a method that does not require extremely high energy consumption or the use of high-cost flocculants. It utilizes the precipitation and complexation reaction mechanisms between inexpensive and readily available inorganic salts to achieve the recovery target. This method is suitable for the preliminary recovery of N-methylpyrrolidone in industrial production and the recovery of NMP from lithium battery waste liquid in related impurity removal work, with the aim of achieving a more practical purpose. Summary of the Invention

[0005] To address the problems mentioned in the background section, this invention provides a method that does not require extremely high energy consumption or the use of expensive flocculants. It utilizes the precipitation and complexation reaction mechanisms between inexpensive and readily available inorganic salts to carry flocculent matter to the sediment, thereby achieving solid-liquid separation. After further filtration and other operations, a relatively clear NMP solution can be obtained, achieving a better recovery effect.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for recovering NMP from lithium battery waste liquid using in-situ inorganic salt deposition includes the following steps:

[0008] S1. Inject the waste liquid into the treatment tank;

[0009] S2. Add a certain mass fraction of soluble X salt aqueous solution to the waste liquid treatment tank and stir evenly;

[0010] S3. While stirring the above solution, add a certain mass fraction of soluble Y salt or strong alkali aqueous solution, stir evenly, and then let stand.

[0011] S4. Filter by suction. The filtrate is an aqueous solution of NMP. The precipitate includes solid substances such as carbon powder, precious metals, a small amount of NMP, and inorganic salts.

[0012] S5. Under nitrogen protection, perform vacuum distillation on the NMP aqueous solution, controlling the vacuum degree to be 0.09-0.1MPa, the temperature to be 150-170℃, and the distillation time to be 1-3h to separate NMP.

[0013] Preferably, the soluble X salt in S2 is Ba. 2+ Salt, Ca 2+ One of the salts; the soluble Y salt in S3 is SO4. 2- Salt, CO3 2- A type of salt.

[0014] Preferably, the soluble X salt in S2 is Al. 3+ Salt, Mg 2+ One of the salts; the aqueous solution in S3 is one of the strong bases NaOH and KOH.

[0015] Preferably, the soluble X salt in S2 is Zn. 2+ Salt, Fe 2+ Salt, Fe 3+ Salt, Cu 2+ One of the salts; the aqueous solution in S3 is NaOH, KOH, or CO3. 2- A type of salt.

[0016] Preferably, the mass fraction of the soluble X salt aqueous solution is in the range of 10%-50%; the mass fraction of the soluble Y salt or strong alkali aqueous solution is in the range of 10%-50%.

[0017] Preferably, the settling time in S3 is 24h-48h.

[0018] This invention employs a nitrogen-protected, reduced-pressure distillation method to separate NMP, avoiding the influence of air, lowering the boiling points of each substance during distillation, achieving highly efficient separation, and improving the recovery rate and purity of NMP. Experimental results show that the method provided by this invention can obtain NMP with a purity of over 99% and a recovery rate of over 90%.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. This invention utilizes an inorganic salt in-situ deposition method to recover NMP from lithium battery waste liquid. The inorganic salt in-situ deposition method involves preparing an aqueous solution of two soluble salts or strong bases that can generate sparingly soluble salts in a certain mass ratio, and then adding them sequentially to the lithium battery electrode waste liquid to be treated. This achieves the effect of adsorbing and depositing solid impurities in the waste liquid, thereby recovering N-methylpyrrolidone (i.e., NMP).

[0021] 2. This invention utilizes two inorganic salt solutions to generate a solid sparingly soluble salt, which is then used to adsorb and precipitate impurities in lithium electrode waste liquid. The resulting mixed solution is then filtered to achieve solid-liquid separation. The filtrate is an aqueous solution of NMP, and the filter residue is a solid containing precious metals, carbon powder, etc. This method can recover NMP without heating or consuming energy, does not require traditional organic reagents, and facilitates the recovery of precious metals. This method uses simple materials, is economical and environmentally friendly, and is suitable for industrial production.

[0022] 3. This invention has low energy consumption and can achieve the effect of NMP recovery without external power supply;

[0023] 4. This invention is low in cost and does not require expensive flocculants. It utilizes the precipitation and complexation reaction mechanisms between inexpensive and readily available inorganic salts to carry flocculent matter out for deposition, thereby achieving solid-liquid separation.

[0024] 5. The present invention has a high recovery rate. According to experimental data, the recovery rate of NMP aqueous solution can reach 90%, which has high social use value and application prospects. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the method of the present invention; Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] Treatment of battery waste liquid using Na2CO3 solution and CaCl2 solution

[0030] 200 mL of waste liquid was poured into a 250 mL beaker, followed by a 10% (w / w) Na₂CO₃ solution. After stirring until homogeneous, a 13% (w / w) CaCl₂ solution was slowly poured in while stirring. The mixture was allowed to stand for 24 hours to separate into layers. Filtering was then performed to obtain a residue and a filtrate. The residue consisted of solid substances such as carbon powder, precious metals, NMP, and inorganic salts. The filtrate was an NMP aqueous solution (220 mL). NMP was obtained by vacuum distillation under nitrogen protection at 150 °C and a vacuum of 0.09 MPa for 1 hour. The calculated NMP recovery rate was 91.5%.

[0031] Example 2

[0032] Treatment of battery waste liquid using NH4Cl solution and AgNO3 solution

[0033] 100 mL of waste liquid was poured into a 200 mL beaker, followed by a 19.2% (w / w) NH4Cl solution. After stirring until homogeneous, a 28.2% (w / w) AgNO3 solution was slowly poured in while stirring. The mixture was allowed to stand for 30 hours to separate into layers. Filtering was then performed to obtain a residue and a filtrate. The residue consisted of solid substances such as carbon powder, precious metals, NMP, and inorganic salts. The filtrate was an NMP aqueous solution (105 mL). NMP was obtained by vacuum distillation under nitrogen protection at 155 °C and a vacuum of 0.095 MPa for 1.5 hours. The calculated NMP recovery rate was 91.2%.

[0034] Example 3

[0035] Treatment of battery waste liquid using KOH solution and Al2(SO4)3·18H2O solution

[0036] 100 mL of waste liquid was poured into a 200 mL medium beaker, followed by a 36% KOH solution. After stirring until homogeneous, a 13.3% Al2(SO4)3·18H2O solution was slowly poured in while stirring. The solution was allowed to stand for 35 h to separate into layers. Filtering was then performed to obtain a filter residue and a filtrate. The filter residue consisted of solid substances such as carbon powder, precious metals, NMP, and inorganic salts. The filtrate was an NMP aqueous solution with a volume of 110 mL. NMP was obtained by vacuum distillation under nitrogen protection at a controlled temperature of 158 °C and a vacuum degree of 0.093 MPa for 1.2 h. The calculated recovery rate of NMP was 90.6%.

[0037] Example 4

[0038] Treatment of battery waste liquid using Cu(CH3COO)2 solution and Na2CO3 solution

[0039] 100 mL of waste liquid was poured into a 200 mL medium beaker, followed by a 35.2% Cu(CH3COO)2 solution. After stirring until homogeneous, a 19.4% Na2CO3 solution was slowly poured in while stirring. The mixture was allowed to stand for 45 hours to separate into layers. Filtering was then performed to obtain a residue and a filtrate. The residue consisted of solid substances such as carbon powder, precious metals, NMP, and inorganic salts. The filtrate was an NMP aqueous solution (105 mL). NMP was obtained by vacuum distillation under nitrogen protection at 160 °C and a vacuum of 0.096 MPa for 2 hours. The calculated NMP recovery rate was 91.8%.

[0040] Example 5

[0041] Treatment of battery waste liquid using ZnCl2 solution and KOH solution

[0042] 100 mL of waste liquid was poured into a 200 mL medium beaker, followed by a 12.7% KOH solution. After stirring until homogeneous, a 50% ZnCl2 solution was slowly poured in while stirring. The mixture was allowed to stand for 35 hours to separate into layers. Filtering was then performed to obtain a residue and a filtrate. The residue consisted of solid substances such as carbon powder, precious metals, NMP, and inorganic salts. The filtrate was an NMP aqueous solution (110 mL). NMP was obtained by vacuum distillation under nitrogen protection at 165 °C and a vacuum of 0.098 MPa for 2.5 hours. The calculated NMP recovery rate was 91.3%.

[0043] Example 6

[0044] Treatment of battery waste liquid using KOH solution and Fe2(SO4)3 solution

[0045] 100 mL of waste liquid was poured into a 200 mL medium beaker, followed by a 16.5% KOH solution. After stirring until homogeneous, a 21.8% Fe2(SO4)3 solution was slowly poured in while stirring. The mixture was allowed to stand for 48 hours to separate into layers. Filtering was then performed to obtain a residue and a filtrate. The residue consisted of solid substances such as carbon powder, precious metals, NMP, and inorganic salts. The filtrate was an NMP aqueous solution (100 mL). NMP was obtained by vacuum distillation under nitrogen protection at 170°C and a vacuum of 0.1 MPa for 3 hours. The calculated NMP recovery rate was 90.8%.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for recovering NMP from lithium battery waste liquid using in-situ inorganic salt deposition, characterized in that, Includes the following steps: S1. Inject the waste liquid into the treatment tank; S2. Add a certain mass fraction of soluble X salt aqueous solution to the treatment tank and stir until homogeneous; S3. While stirring the above solution, add a certain mass fraction of soluble Y salt or strong alkali aqueous solution, stir evenly, and then let stand. S4. Filter by suction. The filtrate is an aqueous solution of NMP. The precipitate includes carbon powder, precious metals, a small amount of NMP, and inorganic salt solids. S5. Under nitrogen protection, the NMP aqueous solution in S4 is subjected to vacuum distillation to separate NMP. Soluble salt X reacts with soluble salt Y or a strong base to form a solid, insoluble salt; The mass fraction of the soluble X salt aqueous solution ranges from 10% to 50%; the mass fraction of the soluble Y salt or strong alkali aqueous solution ranges from 10% to 50%. The settling time in S3 is 24h-48h; In the S5 process, the vacuum degree is controlled at 0.09-0.1 MPa, the temperature at 150-170℃, and the distillation time at 1-3 hours.

2. The method for recovering NMP from lithium battery waste liquid using in-situ inorganic salt deposition according to claim 1, characterized in that, The soluble salt X in S2 is Ba. 2+ Salt, Ca 2+ One of the salts; the soluble Y salt in S3 is SO4. 2- Salt, CO3 2- A type of salt.

3. The method for recovering NMP from lithium battery waste liquid using in-situ inorganic salt deposition according to claim 1, characterized in that, The soluble salt X in S2 is Al 3+ Salt, Mg 2+ One of the salts; the aqueous solution in S3 is one of the strong bases NaOH and KOH.

4. The method for recovering NMP from lithium battery waste liquid using in-situ inorganic salt deposition according to claim 1, characterized in that, The soluble salt X in S2 is Zn. 2+ Salt, Fe 2+ Salt, Fe 3+ Salt, Cu 2+ One of the salts; the aqueous solution in S3 is NaOH, KOH, or CO3. 2- A type of salt.

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