A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid

Abstract

The present invention discloses a method for extracting and recovering cobalt-containing choline chloride ethylene glycol deep eutectic solvent electrolytic waste liquid, and relates to the field of waste resource recovery. Steps are as follows: 1) water and extractant are added to cobalt-containing electrolytic waste liquid, and oil phase pH is adjusted after stirring. After sufficient reaction, cobalt-containing organic extract and aqueous deep eutectic solvent are separated and obtained; 2) dilute sulfuric acid is added to the cobalt-containing organic extract obtained in step 1), aqueous phase pH is adjusted and back-extracted, and then aqueous phase and organic phase are separated, and aqueous phase is distilled under reduced pressure to obtain cobalt sulfate solid; Organic phase returns to step 1) and is reused as extractant; 3) by step 1) The aqueous deep eutectic solvent obtained is passed through reduced pressure distillation, and the choline chloride ethylene glycol deep eutectic solvent of regeneration is obtained. The recovery method of the present invention has a high recovery rate for cobalt and choline chloride ethylene glycol deep eutectic solvent, and process is simple, environmentally friendly, and has a large application prospect.

Description

Technical Field

[0001] This invention relates to the field of waste resource recycling, specifically to a method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid. Background Art

[0002] Eutectic solvents are homogeneous liquids formed by mixing hydrogen bond acceptors and hydrogen bond donors in a specific molar ratio. Compared with traditional organic reagents, eutectic solvents have a series of outstanding advantages, such as ease of synthesis, low cost, low toxicity, good solubility, and wide liquid range temperature. These unique properties have made eutectic solvents widely used in the field of electrodeposition. Among a range of eutectic solvents, choline chloride-ethylene glycol eutectic solvent is usually prepared by mixing choline chloride and ethylene glycol in a 1:2 molar ratio. It has excellent solvent properties and metal processing capabilities and is widely used in the electrodeposition preparation of various cobalt-containing new materials. However, the choline chloride-ethylene glycol electrolyte currently used is for single use and is not reused, and the resulting electrolytic waste liquid is rich in valuable cobalt. In addition, compared with water-based solvents, choline chloride-ethylene glycol has a high production cost, is easily soluble in soil, and has poor biodegradability. Direct discharge of cobalt-containing choline chloride-ethylene glycol electrolytic waste liquid not only causes environmental pollution and harms human health, but also wastes valuable cobalt resources and increases process costs. If these cobalt-containing electrolytic waste liquids are effectively recycled, it will be of great significance for achieving efficient resource utilization of cobalt, reducing process costs, and mitigating environmental problems.

[0003] In methods for recovering cobalt-containing electrolytic waste, patent 202310968882.X uses water as a cobalt coordinating agent and oxalic acid as a precipitant to achieve cobalt recovery. However, under acidic conditions, a small amount of cobalt oxalate precipitate will be converted into soluble oxalate compounds, and excess oxalic acid cannot be completely removed by vacuum distillation, resulting in residual cobalt and oxalic acid in the regenerated choline chloride-ethylene glycol electrolyte. Therefore, this recovery method suffers from the problem of low purity in the regenerated choline chloride-ethylene glycol electrolyte. Based on this, the present invention provides a new method for recovering cobalt and regenerating the eutectic solvent of choline chloride-ethylene glycol from cobalt-containing electrolytic waste to overcome the defects in the prior art. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid. This invention uses water as a solvent diluent and a cobalt coordinating agent to reduce the viscosity of the system and control the cobalt coordination form. A mixture of Cyanex 272 and sulfonated kerosene is used as the cobalt extractant to completely separate cobalt from the choline chloride-ethylene glycol electrolyte, and this extractant is reusable. Furthermore, the recovery method of this invention has the advantages of simple process, environmental friendliness, high purity of the regenerated choline chloride-ethylene glycol electrolyte, and stable performance, and has great potential for widespread application.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention discloses a method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid, comprising the following steps:

[0007] 1) Add water and extractant to cobalt-containing electrolytic waste liquid, stir evenly, adjust the pH of the oil phase to 4-8, and after full reaction, separate cobalt-containing organic extract and water-containing eutectic solvent.

[0008] 2) Add dilute sulfuric acid to the cobalt-containing organic extract obtained in step 1) to adjust the pH of the aqueous phase to acidic and perform back-extraction. Then separate the aqueous phase and the organic phase. The aqueous phase is distilled under reduced pressure to obtain cobalt sulfate solid. The organic phase is returned to step 1) as an extractant for reuse.

[0009] 3) The aqueous eutectic solvent obtained in step 1) is subjected to vacuum distillation to obtain the regenerated choline chloride-ethylene glycol eutectic solvent.

[0010] Steps 2) and 3) are not in any particular order.

[0011] Beneficial effects: To ensure complete separation of choline chloride-ethylene glycol and cobalt in the electrolytic waste liquid, this invention uses water as a diluent to reduce the viscosity of the system, facilitating phase separation. Water can also act as a cobalt coordinating agent, regulating the coordination form of cobalt to [CoCl4]. 2- The complex anion is transformed into [CoCl2(H2O)4]. 0 Molecules and [CoCl(H2O)5] + Cations, thus weakening [CoCl4]. 2- The interaction forces between anions promote efficient cobalt extraction. By adjusting the pH of the upper organic phase, some -P-OH groups in the organic extractant Cyanex 272 are converted to -PO groups. -The presence of the [PO-Co] group enhances the coordination ability of Cyanex 272 for cobalt, leading to complete separation of cobalt from choline chloride-ethylene glycol. Therefore, the high extraction efficiency of cobalt is mainly attributed to the hydrophobic effect of Cyanex 272 and the stronger interaction between the -PO and -Co groups compared to [CoCl2(H2O)4]. 0 Molecules and [CoCl(H2O)5] + The interaction forces between cobalt and ethanol are also considered. Furthermore, adding sulfuric acid solution to the cobalt-containing organic phase can break the interaction forces between -PO and Co, restoring -PO-Co to -P-OH, which is beneficial for the recycling of Cyanex 272 and the back-extraction of cobalt. In addition, utilizing the boiling point difference between choline chloride-ethylene glycol and water, water in the filtrate can be further removed by vacuum distillation to obtain a very pure eutectic solvent of choline chloride-ethylene glycol, thereby achieving efficient regeneration of cobalt and the eutectic solvent of choline chloride-ethylene glycol.

[0012] Preferably, the water in step 1) accounts for 0 to 50 wt.% of the total mass of the cobalt-containing electrolytic waste liquid and water.

[0013] Preferably, the extractant is a mixture of Cyanex 272 and sulfonated kerosene; the volume ratio of Cyanex 272 to sulfonated kerosene is 1:9.

[0014] Preferably, the pH adjuster in step 1) is a 5 mol / L NaOH aqueous solution.

[0015] Preferably, the reaction is carried out under stirring conditions; wherein the stirring speed is 300 rpm, the time is 5 to 30 min, and the temperature is room temperature.

[0016] Preferably, in step 2), after adding dilute sulfuric acid, the molar ratio of sulfuric acid to Co(II) in the system is 0.8 to 2.5; and the concentration of the dilute sulfuric acid is 0.2 to 0.6 mol / L.

[0017] Preferably, in step 2), the pH of the aqueous phase is adjusted to 1-4, and the pH adjuster is a 5 mol / L solution of HCl and Na2CO3.

[0018] Preferably, the back-extraction in step 2) is carried out under stirring conditions; wherein the stirring speed is 300 rpm, the temperature is 25-40°C, and the time is 5-30 min.

[0019] Preferably, the vacuum distillation in step 2) is carried out at a temperature of 40–80°C for 2–6 hours and at a pressure of 0.05–0.07 MPa.

[0020] Preferably, the organic phase described in step 2) is returned to step 1) for reuse as an extractant 15 times.

[0021] Preferably, the vacuum distillation in step 3) is carried out under stirring conditions; wherein the stirring speed is 300 rpm, the temperature is 70-100℃, the time is 1-4 h, and the pressure is 0.05-0.07 MPa.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] This invention uses water as a diluent and a cobalt coordinating agent, which reduces the viscosity of the system and regulates the coordination form of cobalt. By adjusting the pH of the upper organic phase, a mixture of Cyanex 272 and sulfonated kerosene is used as the cobalt extractant to completely extract cobalt from the choline chloride-ethylene glycol electrolyte. The cobalt is then converted to cobalt sulfate via back-extraction, and efficient cobalt recovery is achieved through vacuum distillation, with a recovery rate as high as 99.39%. Back-extraction of the cobalt-containing organic phase using sulfuric acid aqueous solution allows for the recycling of the extractant. Vacuum distillation removes water from the aqueous choline chloride-ethylene glycol eutectic solvent, achieving efficient regeneration of the solvent with a recovery rate of up to 98.63%. Furthermore, this recovery process is green and pollution-free, simple to operate, quick, and has low production costs. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0025] Figure 1 This is a flowchart of the recycling process in Example 1;

[0026] Figure 2 The image shows the XRD pattern of the cobalt sulfate solid obtained in Example 1.

[0027] Figure 3 Here are SEM images of the cobalt sulfate solid obtained in Example 1 at different magnifications;

[0028] Figure 4 The effect of water addition as a single variable on cobalt extraction rate;

[0029] Figure 5 The effect of extractant dosage as a single variable on cobalt extraction rate;

[0030] Figure 6 The effect of extraction pH on cobalt extraction rate as a single variable;

[0031] Figure 7 The effect of sulfuric acid aqueous solution dosage as a single variable on cobalt back-extraction rate;

[0032] Figure 8The effect of distillation temperature on cobalt recovery as a single variable;

[0033] Figure 9 The effect of distillation time on cobalt recovery as a single variable;

[0034] Figure 10 The effect of distillation temperature as a single variable on the recovery rate of choline chloride-ethylene glycol solution;

[0035] Figure 11 Effect of distillation time as a single variable on the recovery rate of choline chloride-ethylene glycol solution

[0036] Figure 12 The change in cobalt extraction rate after 15 cycles of extractant under the conditions of Example 9;

[0037] Figure 13 The change in cobalt recovery rate after 15 cycles of extractant under the conditions of Example 9;

[0038] Figure 14 The change in the recovery rate of the choline chloride-ethylene glycol solution after 15 cycles of extractant under the conditions of Example 9; DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0041] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0042] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] The cobalt-containing electrolytic waste liquid used in the embodiments of the present invention is the waste liquid obtained after electrolyzing cobalt with choline chloride-ethylene glycol at a molar ratio of 1:2, wherein the cobalt concentration is 97.6 mmol / L.

[0045] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0046] Except for cobalt-containing electrolytic waste liquid, all other raw materials used in the following embodiments of the present invention are commercially available.

[0047] Example 1

[0048] A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid includes the following steps:

[0049] 1) At room temperature, 10.47 g of water was added to 20 g (17.92 ml) of cobalt-containing electrolytic waste liquid, and then 13.43 ml of extractant (Cyanex 272 and sulfonated kerosene in a volume ratio of 1:9, the same below) was added. The final pH of the oil phase was adjusted to 6.5 with 5 mol / L NaOH aqueous solution. The mixture was stirred at 300 rpm for 15 min at 25 °C to extract cobalt to the upper oil phase. The two phases were then separated to obtain an upper cobalt-containing organic extract and a lower aqueous eutectic solvent. The cobalt extraction rate was 99.9%.

[0050] 2) After phase separation, 11.66 ml of 0.3 mol / L sulfuric acid aqueous solution was added to the cobalt-containing organic extract. The solution separated into layers. The pH of the aqueous phase was adjusted to 2.5 using 5 mol / L HCl and Na₂CO₃ solution. The mixture was stirred at 300 rpm for 10 min at 25 °C until fully reacted. Co(II) was back-extracted into the aqueous phase. The upper and lower layers were separated, and the organic extract could be recycled in step 1). The cobalt-enriched aqueous phase was then distilled at 80 °C and 0.07 MPa for 3 h, washed, and dried to obtain solid cobalt sulfate. The cobalt recovery rate was 96.72%.

[0051] The recycling process flow diagram of this embodiment is as follows: Figure 1As shown in the figure, the recovery process of this invention is simple and can also realize the recycling of the extractant. It has the advantages of being green and pollution-free, simple to operate, short in time, and low in production cost. The XRD pattern of the cobalt sulfate powder obtained in this embodiment is shown in the figure. Figure 2 As shown in the figure, the cobalt sulfate is a monohydrate. Compared with the cobalt sulfate standard card, no impurity peaks appeared, indicating that the recovery method of the present invention can recover pure cobalt sulfate solid. SEM images of the cobalt sulfate solid obtained in this embodiment at different magnifications are shown below. Figure 3 As shown, where, Figure 3 In the image, 'a' represents the SEM image at a magnification of 10000x. Figure 3 In the middle b, it is a SEM image at a magnification of 100,000. As can be seen from the figure, the crystal formed by cobalt sulfate monohydrate has a flat polyhedral structure and a relatively uniform crystal shape. Because the distillation temperature is high, it is conducive to agglomeration, so it stacks and forms clumps during the crystallization process.

[0052] 3) The eutectic solvent enriched phase from step 1) was placed in a vacuum distillation apparatus and distilled for 2.5 h at 100 °C, 0.07 MPa, and 300 rpm. The choline chloride-ethylene glycol recovery rate was 96.07%, and the water content was 2.96%.

[0053] Example 2

[0054] A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid includes the following steps:

[0055] 1) At room temperature, 19.61 g of water was added to 20 g (17.92 ml) of cobalt-containing electrolytic waste liquid, followed by 14.92 ml of extractant. The final pH of the oil phase was adjusted to 8 with 5 mol / L NaOH aqueous solution. The mixture was stirred at 300 rpm for 15 min at 25 °C to extract cobalt to the upper oil phase. The two phases were then separated to obtain an upper cobalt-containing organic extract and a lower aqueous eutectic solvent. The cobalt extraction rate was 99.9%.

[0056] 2) After phase separation, 14.57 ml of 0.3 mol / L sulfuric acid aqueous solution was added to the cobalt-containing organic extract. The solution separated into layers. The pH of the aqueous phase was adjusted to 2 using 5 mol / L HCl and Na₂CO₃ solution. The mixture was stirred at 300 rpm for 15 min at 25 °C until fully reacted. Co(II) was back-extracted into the aqueous phase. The upper and lower layers were separated, and the organic extract could be recycled in step 1). The cobalt-enriched aqueous phase was then distilled at 70 °C and 0.06 MPa for 6 h, washed, and dried to obtain solid cobalt sulfate. The cobalt recovery rate was 96.13%.

[0057] 3) The eutectic solvent enriched phase from step 1) was placed in a vacuum distillation apparatus and distilled for 2.5 h at 95 °C, 0.07 MPa, and 300 rpm. The choline chloride-ethylene glycol recovery rate was 95.83%, and the water content was 3.37%.

[0058] Example 3

[0059] A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid includes the following steps:

[0060] 1) At room temperature, 10.47 g of water was added to 20 g (17.92 ml) of cobalt-containing electrolytic waste liquid, and then 11.94 ml of extractant was added. The final pH of the oil phase was adjusted to 4 with 5 mol / L NaOH aqueous solution. The mixture was stirred at 300 rpm for 20 min at 25 °C to extract cobalt to the upper oil phase. The two phases were then separated to obtain an upper cobalt-containing organic extract and a lower aqueous eutectic solvent. The cobalt extraction rate was 71.37%.

[0061] 2) After phase separation, 5.83 ml of 0.3 mol / L sulfuric acid aqueous solution was added to the cobalt-containing organic extract. The solution separated into layers. The pH of the aqueous phase was adjusted to 2 using 5 mol / L HCl and Na₂CO₃ solution. The mixture was stirred at 300 rpm for 10 min at 25 °C until fully reacted. Co(II) was back-extracted into the aqueous phase. The upper and lower layers were separated, and the organic extract could be recycled in step 1). The cobalt-enriched aqueous phase was then distilled at 80 °C and 0.07 MPa for 2 h, washed, and dried to obtain solid cobalt sulfate. The cobalt recovery rate was 68.12%.

[0062] 3) The eutectic solvent enriched phase from step 1) was placed in a vacuum distillation apparatus and distilled for 2 hours at 90°C, 0.06 MPa, and 300 rpm. The choline chloride-ethylene glycol recovery rate was 94%, and the water content was 4.05%.

[0063] Example 4

[0064] A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid includes the following steps:

[0065] 1) At room temperature, 6.41 g of water was added to 20 g (17.92 ml) of cobalt-containing electrolytic waste liquid, and then 14.92 ml of extractant was added. The final pH of the oil phase was adjusted to 6 with 5 mol / L NaOH aqueous solution. The mixture was stirred at 300 rpm for 10 min at 25 °C to extract cobalt to the upper oil phase. The two phases were then separated to obtain an upper cobalt-containing organic extract and a lower aqueous eutectic solvent. The cobalt extraction rate was 99.8%.

[0066] 2) After phase separation, 6.56 ml of 0.4 mol / L sulfuric acid aqueous solution was added to the cobalt-containing organic extract. The solution separated into layers. The pH of the aqueous phase was adjusted to 3 using 5 mol / L HCl and Na₂CO₃ solution. The mixture was stirred at 300 rpm for 30 min at 25 °C until fully reacted. Co(II) was back-extracted into the aqueous phase. The upper and lower layers were separated, and the organic extract could be recycled in step 1). The cobalt-enriched aqueous phase was then distilled at 60 °C and 0.06 MPa for 2 h, washed, and dried to obtain solid cobalt sulfate. The cobalt recovery rate was 85.14%.

[0067] 3) The eutectic solvent enriched phase from step 1) was placed in a vacuum distillation apparatus and distilled for 3 hours at 80°C, 0.05 MPa, and 300 rpm. The choline chloride-ethylene glycol recovery rate was 93.73%, and the water content was 4.32%.

[0068] Example 5

[0069] A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid includes the following steps:

[0070] 1) At room temperature, 3.30 g of water was added to 20 g (17.92 ml) of cobalt-containing electrolytic waste liquid, and then 10.44 ml of extractant was added. The final pH of the oil phase was adjusted to 6.5 with 5 mol / L NaOH aqueous solution. The mixture was stirred at 300 rpm for 5 min at 25 °C to extract cobalt to the upper oil phase. The two phases were then separated to obtain an upper cobalt-containing organic extract and a lower aqueous eutectic solvent. The cobalt extraction rate was 52.37%.

[0071] 2) After phase separation, 7 ml of 0.2 mol / L sulfuric acid aqueous solution was added to the cobalt-containing organic extract. The solution separated into layers. The pH of the aqueous phase was adjusted to 1 using 5 mol / L HCl and Na₂CO₃ solution. The mixture was stirred at 300 rpm for 25 min at 40 °C until fully reacted. Co(II) was back-extracted into the aqueous phase. The upper and lower layers were separated, and the organic extract could be recycled in step 1). The cobalt-enriched aqueous phase was then distilled at 70 °C and 0.05 MPa for 2 h, washed, and dried to obtain solid cobalt sulfate. The cobalt recovery rate was 33.74%.

[0072] 3) The eutectic solvent enriched phase from step 1) was placed in a vacuum distillation apparatus and distilled for 4 hours at 95°C, 0.05 MPa, and 300 rpm. The recovery rate of choline chloride-ethylene glycol was 92.611%, and the water content was 4.57%.

[0073] Example 6

[0074] A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid includes the following steps:

[0075] 1) At room temperature, 20 g (17.92 ml) of cobalt-containing electrolytic waste liquid was taken, and 13.43 ml of extractant was added. The pH of the oil phase endpoint was adjusted to 4 with 5 mol / L NaOH aqueous solution. The mixture was stirred at 300 rpm for 30 min at 25 °C to extract cobalt to the upper oil phase. The two phases were then separated to obtain an upper cobalt-containing organic extract and a lower aqueous eutectic solvent. The cobalt extraction rate was 38.94%.

[0076] 2) After phase separation, 2.33 ml of 0.6 mol / L sulfuric acid aqueous solution was added to the cobalt-containing organic extract. The solution separated into layers. The pH of the aqueous phase was adjusted to 4 using 5 mol / L HCl and Na₂CO₃ solution. The mixture was stirred at 300 rpm for 25 min at 35 °C until fully reacted. Co(II) was back-extracted into the aqueous phase. The upper and lower layers were separated, and the organic extract could be recycled in step 1). The cobalt-enriched aqueous phase was then distilled at 70 °C and 0.07 MPa for 4 h, washed, and dried to obtain solid cobalt sulfate. The cobalt recovery rate was 36.21%.

[0077] 3) The eutectic solvent enriched phase from step 1) was placed in a vacuum distillation apparatus and distilled for 2 hours at 70°C, 0.07 MPa, and 300 rpm. The choline chloride-ethylene glycol recovery rate was 95.61%, and the water content was 0.62%.

[0078] Example 7

[0079] A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid includes the following steps:

[0080] 1) At room temperature, 20 g (17.92 ml) of cobalt-containing electrolytic waste liquid was taken, and 14.92 ml of extractant was added. The pH of the oil phase endpoint was adjusted to 8 with 5 mol / L NaOH aqueous solution. The mixture was stirred at 300 rpm for 30 min at 25 °C to extract cobalt to the upper oil phase. The two phases were then separated to obtain an upper cobalt-containing organic extract and a lower aqueous eutectic solvent. The cobalt extraction rate was 99.9%.

[0081] 2) After phase separation, 3.5 ml of 0.5 mol / L sulfuric acid aqueous solution was added to the cobalt-containing organic extract. The solution separated into layers. The pH of the aqueous phase was adjusted to 2.5 using 5 mol / L HCl and Na₂CO₃ solution. The mixture was stirred at 300 rpm for 5 min at 30 °C until fully reacted. Co(II) was back-extracted into the aqueous phase. The upper and lower layers were separated, and the organic extract could be recycled in step 1). The cobalt-enriched aqueous phase was then distilled at 40 °C and 0.07 MPa for 4 h, washed, and dried to obtain solid cobalt sulfate. The cobalt recovery rate was 67.36%.

[0082] 3) The eutectic solvent enriched phase from step 1) was placed in a vacuum distillation apparatus and distilled for 1 hour at 100°C, 0.07 MPa, and 300 rpm. The choline chloride-ethylene glycol recovery rate was 95.89%, and the water content was 0.74%.

[0083] Example 8

[0084] A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid includes the following steps:

[0085] 1) At room temperature, 26.18 g of water was added to 50 g (44.79 ml) of cobalt-containing electrolytic waste liquid, and then 29.85 ml of extractant was added. The final pH of the oil phase was adjusted to 6 with 5 mol / L NaOH aqueous solution. The mixture was stirred at 300 rpm for 15 min at 25 °C to extract cobalt to the upper oil phase. The two phases were then separated to obtain an upper cobalt-containing organic extract and a lower aqueous eutectic solvent. The cobalt extraction rate was 99.8%.

[0086] 2) After phase separation, 8.74 ml of 0.4 mol / L sulfuric acid aqueous solution was added to the cobalt-containing organic extract. The solution separated into layers. The pH of the aqueous phase was adjusted to 2.5 using 5 mol / L HCl and Na₂CO₃ solution. The mixture was stirred at 300 rpm for 15 min at 30 °C until fully reacted. Co(II) was back-extracted into the aqueous phase. The upper and lower layers were separated, and the organic extract could be recycled in step 1). The cobalt-enriched aqueous phase was then distilled at 75 °C and 0.07 MPa for 5 h, washed, and dried to obtain solid cobalt sulfate. The cobalt recovery rate was 99.12%.

[0087] 3) The eutectic solvent enriched phase from step 1) was placed in a vacuum distillation apparatus and distilled for 2.5 h at 90 °C, 0.07 MPa, and 300 rpm. The choline chloride-ethylene glycol recovery rate was 97.95%, and the water content was 2.30%.

[0088] Example 9

[0089] A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid includes the following steps:

[0090] 1) At room temperature, 26.18 g of water was added to 50 g (44.79 ml) of cobalt-containing electrolytic waste liquid, and then 33.57 ml of extractant was added. The final pH of the oil phase was adjusted to 6.5 with 5 mol / L NaOH aqueous solution. The mixture was stirred at 300 rpm for 15 min at 25 °C to extract cobalt to the upper oil phase. The two phases were then separated to obtain an upper cobalt-containing organic extract and a lower aqueous eutectic solvent. The cobalt extraction rate was 99.9%.

[0091] 2) After phase separation, 14.57 ml of 0.3 mol / L sulfuric acid aqueous solution was added to the cobalt-containing organic extract. The solution separated into layers. The pH of the aqueous phase was adjusted to 2 using 5 mol / L HCl and Na₂CO₃ solution. The mixture was stirred at 300 rpm for 15 min at 25 °C until fully reacted. Co(II) was back-extracted into the aqueous phase. The upper and lower layers were separated, and the organic extract could be recycled in step 1). The cobalt-enriched aqueous phase was then distilled at 80 °C and 0.07 MPa for 3 h, washed, and dried to obtain solid cobalt sulfate. The cobalt recovery rate was 99.39%.

[0092] 3) The eutectic solvent enriched phase from step 1) was placed in a vacuum distillation apparatus and distilled for 2.5 h at 100 °C, 0.07 MPa, and 300 rpm. The choline chloride-ethylene glycol recovery rate was 98.63%, and the water content was 2.24%.

[0093] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0094] A certain mass (concentration of 97.6 mmol / L) of cobalt-containing electrolytic waste liquid was extracted with C272 to recover cobalt. The volume ratio of extractant C272 to sulfonated kerosene was 1:9. The pH was adjusted with 5 mol / L NaOH solution, and the extraction was carried out at 25℃ and 300 rpm for a certain period of time with stirring. The specific data are as follows:

[0095] Table 1. Cobalt Recovery from C272 Extraction

[0096]

[0097]

[0098] The cobalt-containing organic extract was back-extracted using a sulfuric acid solution of a certain concentration. The pH was adjusted with 5 mol / L HCl and Na2CO3 solution. The back-extraction was carried out at a certain temperature and with stirring at 300 rpm for a certain time to obtain a cobalt-enriched aqueous phase. This phase was then washed and dried under specific temperature, pressure, and time conditions to obtain cobalt sulfate solid. Specific data are as follows:

[0099] Table 2. Back-extraction of cobalt using sulfuric acid solution

[0100]

[0101] The eutectic solvent was placed in a vacuum distillation apparatus for solvent regeneration under certain conditions. Specific data are as follows:

[0102] Table 3. Recovery of choline chloride-ethylene glycol solution by vacuum distillation

[0103]

[0104]

[0105] This invention also conducted single-factor variable experiments on the effects of water addition, extractant dosage, extraction pH, and sulfuric acid aqueous solution dosage on the cobalt back-extraction rate. Figure 4 The effect of water addition as a single variable on cobalt extraction rate; Figure 5 The effect of extractant dosage as a single variable on cobalt extraction rate; Figure 6 The effect of extraction pH on cobalt extraction rate as a single variable; Figure 7 The effect of sulfuric acid aqueous solution dosage as a single variable on cobalt back-extraction rate.

[0106] This invention also conducted single-factor variable experiments on the effects of distillation time and distillation temperature on cobalt recovery. Figure 8 The effect of distillation temperature on cobalt recovery as a single variable; Figure 9 The effect of distillation time on cobalt recovery is a single variable. Figure 10 The effect of distillation temperature as a single variable on the recovery rate of choline chloride-ethylene glycol solution; Figure 11 The effect of distillation time as a single variable on the recovery rate of choline chloride-ethylene glycol solution.

[0107] In this embodiment of the invention, under the conditions of Example 9, the extraction cycle is repeated 15 times. Figure 12 The change in cobalt extraction rate after 15 cycles of extractant under the conditions of Example 9; Figure 13 The change in cobalt recovery rate after 15 cycles of extractant under the conditions of Example 9; Figure 14 The change in the recovery rate of the choline chloride-ethylene glycol solution after 15 cycles of extractant under the conditions of Example 9 is shown.

[0108] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid, characterized in that, The following steps are involved: 1) Add water and extractant to cobalt-containing electrolytic waste liquid, stir evenly, adjust the pH of the oil phase to 4-8, and after full reaction, separate cobalt-containing organic extract and water-containing eutectic solvent. 2) Dilute sulfuric acid was added to the cobalt-containing organic extract obtained in step 1), and then the pH of the aqueous phase was adjusted to acidic and back-extracted. The aqueous phase and organic phase were then separated. The aqueous phase was distilled under reduced pressure to obtain cobalt sulfate solid. The organic phase was returned to step 1) as an extractant for reuse. 3) The aqueous eutectic solvent obtained in step 1) is subjected to vacuum distillation to obtain the regenerated choline chloride-ethylene glycol eutectic solvent. Steps 2) and 3) are not in any particular order; The extractant is a mixture of Cyanex 272 and sulfonated kerosene; the volume ratio of Cyanex 272 to sulfonated kerosene is 1:

9. In step 1), the pH adjuster is a 5 mol / L NaOH aqueous solution; the reaction is carried out under stirring conditions; wherein, the stirring speed is 300 rpm, the time is 5 to 30 min, and the temperature is room temperature; In step 2), after adding dilute sulfuric acid, the molar ratio of sulfuric acid to Co(II) in the system is 0.8–2.5; the concentration of the dilute sulfuric acid is 0.2–0.6 mol / L. In step 2), the pH of the aqueous phase is adjusted to 1-4, and the pH adjuster is a 5 mol / L solution of HCl and Na2CO3. The organic phase described in step 2) is returned to step 1) and reused as an extractant 15 times.

2. The method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid according to claim 1, characterized in that, In step 1), the water accounts for 0–50 wt.% of the total mass of the cobalt-containing electrolytic waste liquid and water.

3. The method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid according to claim 1, characterized in that, The back-extraction described in step 2) is carried out under stirring conditions; wherein the stirring speed is 300 rpm, the temperature is 25-40℃, and the time is 5-30 min.

4. The method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid according to claim 1, characterized in that, The vacuum distillation described in step 2) is carried out at a temperature of 40–80°C, for a time of 2–6 hours, and at a pressure of 0.05–0.07 MPa.

5. The method for extracting and recovering cobalt-containing choline chloride-ethylene glycol eutectic solvent electrolytic waste liquid according to claim 1, characterized in that, The vacuum distillation described in step 3) is carried out under stirring conditions; wherein the stirring speed is 300 rpm, the temperature is 70-100℃, the time is 1-4 h, and the pressure is 0.05-0.07 MPa.

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