Oleic acid-regulated synthesis of hydroxyapatite nanowires and application method thereof in ternary lithium battery valuable metal recovery

Abstract

This invention discloses an oleic acid-controlled synthesis of hydroxyapatite nanowires and its application in the recovery of valuable metals from ternary lithium batteries. The hydroxyapatite nanowires are prepared using a solvothermal method with oleic acid as a crystal growth guide agent, exhibiting a one-dimensional nanowire structure, high specific surface area, and abundant surface functional groups. When used to recover valuable metals from ternary lithium battery leachates, the hydroxyapatite nanowires rapidly reach adsorption equilibrium within 4 minutes at room temperature and selectively adsorb nickel ions (Ni...). 2+ ) and cobalt ions (Co 2+ ), while also targeting lithium ions (Li + The adsorption rate of the adsorbent is extremely low (<5%), thus achieving efficient separation of nickel, cobalt, and lithium. After elution with dilute acid, the recovery rate of nickel and cobalt ions can reach over 90%, and the adsorbent can be recycled more than 5 times without significant performance degradation. This invention features a simple process, low cost, and environmental friendliness, providing a new material and method for the efficient and selective recovery of valuable metals from ternary lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of waste lithium-ion battery resource utilization technology, and in particular to an oleic acid-controlled synthesis of hydroxyapatite nanowires and its application in the recycling of valuable metals from ternary lithium batteries. Background Technology

[0002] With the rapid development of electric vehicles and portable electronic devices, the production and consumption of lithium-ion batteries, especially high-energy-density ternary lithium batteries (NCM / NCA), have surged. This has led to the problem of disposing of a large number of retired batteries. Ternary lithium battery cathode materials contain abundant valuable metals such as nickel (Ni), cobalt (Co), and manganese (Mn), as well as lithium (Li), all of which are strategic resources with extremely high recycling value. However, if improperly disposed of, heavy metal ions from waste batteries can leach into the environment, causing serious pollution. Therefore, developing efficient and green technologies for recycling valuable metals from ternary lithium batteries is crucial for achieving resource recycling, ensuring supply chain security, and protecting the environment.

[0003] Currently, methods for recovering metals from leachate of spent batteries mainly include chemical precipitation, solvent extraction, and ion exchange and adsorption. Chemical precipitation is simple to operate but has poor selectivity, easily introduces new impurity ions, and generates large amounts of heavy metal-containing sludge when processing complex battery leachate, causing secondary pollution. Solvent extraction, while offering high selectivity, is complex, requires large amounts of flammable and toxic organic solvents, poses operational safety risks and potential environmental hazards, and is costly. Ion exchange and adsorption is considered a potentially environmentally friendly technology, but its core lies in developing high-performance adsorbents. Hydroxyapatite (Ca...) 10 (PO4)6(OH)2) is a biocompatible material because of the Ca in its crystal structure. 2+ Hydroxyapatite can undergo ion exchange with various divalent heavy metal ions and its surface is rich in hydroxyl and phosphate groups that can complex with metal ions. It has been studied for the treatment of heavy metal pollution in water. However, hydroxyapatite prepared by conventional methods is mostly micron-sized or randomly shaped particles, which have problems such as small specific surface area, limited adsorption active sites, and slow adsorption rate. It usually takes several hours to reach adsorption equilibrium, which is difficult to meet the efficiency requirements of industrial recycling processes.

[0004] In summary, there is an urgent need in this field to develop a novel adsorption material and method that can: (1) adsorb Ni in the leaching solution of ternary lithium batteries 2+ Co 2+ It has high adsorption capacity and fast adsorption kinetics to adapt to continuous industrial operation; (2) for Ni 2+ Co 2+It has high selectivity and can achieve Li + (3) It is environmentally friendly, has a simple preparation process, low cost and is recyclable.

[0005] Therefore, developing an adsorption material that simultaneously satisfies rapid adsorption kinetics, high selectivity, and environmental friendliness has become crucial for overcoming the technological bottlenecks in the recovery of valuable metals from ternary lithium batteries. Based on this, this invention, through material structure innovation, designs an oleic acid-controlled synthesis of hydroxyapatite nanowires, effectively solving the aforementioned technical challenges. Summary of the Invention

[0006] In view of the problems of slow adsorption rate, poor selectivity and difficulty in achieving efficient separation of nickel, cobalt and lithium in the recovery of valuable metals from ternary lithium batteries by existing adsorption materials as described in the background art, this invention aims to provide an oleic acid-controlled synthesis of hydroxyapatite nanowires and its application method in the recovery of valuable metals from ternary lithium batteries. This application method has the advantages of being fast, efficient, highly selective and environmentally friendly.

[0007] To achieve the above objectives, the present invention provides a technical solution: hydroxyapatite nanowires synthesized under oleic acid control, wherein the hydroxyapatite nanowires are prepared by a solvothermal method using oleic acid as a crystal growth guide agent; the prepared hydroxyapatite nanowires have a one-dimensional nanowire structure with an average diameter of 20-60 nm and a specific surface area of ​​15-25 m². 2 / g; and hydroxyapatite nanowires can be obtained from Ni-containing... 2+ Co 2+ and Li + Selective adsorption of Ni in mixed solutions 2+ and Co 2+ .

[0008] Preferably, the solvothermal preparation process specifically includes the following steps: (1) Mix oleic acid with an alcohol solvent to form a homogeneous oleic acid-alcohol mixture; (2) Provide calcium salt solution (such as CaCl2 solution) and phosphate solution (such as NaH2PO4 solution) and control the calcium-phosphorus molar ratio to be 1.6-1.7:1; (3) Add the calcium salt solution provided in step (2) to the oleic acid-alcohol mixture in step (1), stir and mix well, and then add the phosphate solution to obtain a mixed solution system; (4) Add an alkaline solution (such as NaOH solution) to the mixed solution system obtained in step (3) to adjust the pH value of the mixed solution system to 10.5-12.0; (5) Transfer the mixed solution system after adjusting the pH value in step (4) to a high-pressure reactor and carry out a solvothermal reaction at 160-200℃ for 18-28 hours; (6) After the reaction was completed, the product was separated, washed (in turn with distilled water and anhydrous ethanol) and dried (vacuum dried at 60°C) to obtain hydroxyapatite nanowires.

[0009] Preferably, the alcohol solvent in step (1) is one or a mixture of two of methanol and ethanol.

[0010] Preferably, the temperature of the solvothermal reaction in the high-pressure reactor in step (4) is 180-195℃.

[0011] This invention also discloses a method for the application of hydroxyapatite nanowires synthesized according to the above-described oleic acid-controlled synthesis in the recovery of valuable metals from ternary lithium batteries. The application method specifically includes the following steps:

[0012] a) Provides an acid-treated ternary lithium battery leachate with a pH of 4.0-8.0, wherein the leachate contains Ni. 2+ Co 2+ and Li + ;

[0013] b) Add hydroxyapatite nanowires to the leachate from step a), and stir at room temperature to carry out the adsorption reaction, so that Ni 2+ and Co 2+ Selectively adsorbed, while Li + Retained in solution (i.e., hydroxyapatite nanowires preferentially and rapidly adsorb Ni) 2+ and Co 2+ , and Li + They are then largely retained in the solution, thus achieving separation.

[0014] c) Perform solid-liquid separation on the solution after the adsorption reaction in step b) to obtain Ni-loaded solution. 2+ and Co 2+ Hydroxyapatite nanowires and Li-rich + The solution;

[0015] d) Apply dilute acid solution to the Ni-loaded sample obtained in step c). 2+ and Co 2+ The hydroxyapatite nanowires were eluted to achieve Ni 2+ and Co 2+ Recycling.

[0016] Preferably, in step b), the adsorption reaction time is 0.5-10 minutes, and the adsorption reaction reaches equilibrium within 4 minutes; wherein the amount of hydroxyapatite nanowires added in the adsorption reaction is 0.5-4 g / L.

[0017] Preferably, the adsorption process of nickel and cobalt ions by hydroxyapatite nanowires conforms to the pseudo-second-order kinetic model and the Langmuir monolayer adsorption model.

[0018] Preferably, the dilute acid solution in step d) is 0.05-0.2 mol / L hydrochloric acid, nitric acid or sulfuric acid.

[0019] Preferably, in step d), the elution recovery rate of nickel ions and cobalt ions is not less than 90%.

[0020] Furthermore, the eluted hydroxyapatite nanowires can be recycled after regeneration, and after 5 cycles, the adsorption rate for nickel and cobalt ions is no less than 80%.

[0021] Beneficial effects of this invention:

[0022] (1) Material innovation and excellent performance: By introducing oleic acid as a crystal growth guide, hydroxyapatite with a one-dimensional nanowire structure was successfully prepared. This structure provides a huge specific surface area and abundant surface active sites, which is the structural basis for its rapid adsorption kinetics and high adsorption capacity.

[0023] (2) Extremely fast adsorption rate: Due to the one-dimensional structure and abundant surface functional groups of the nanowires, their adsorption rate for Ni is extremely fast. 2+ The adsorption can reach equilibrium within 4 minutes, far exceeding the several hours required by traditional adsorbents, greatly improving the treatment efficiency and meeting the needs of continuous industrial operation.

[0024] (3) Excellent selectivity and good separation effect: The hydroxyapatite nanowires prepared in this invention have good Ni 2+ and Co 2+ He showed extremely high affinity, and towards Li + The adsorption rate is extremely low (<5%), which enables efficient separation of nickel, cobalt and lithium in one-step adsorption, laying a solid foundation for the subsequent recovery of high-purity lithium products.

[0025] (4) The mechanism is clear and the effect is stable: Experiments show that the adsorption process conforms to the pseudo-second-order kinetic model and the Langmuir monolayer adsorption model, indicating that it is a homogeneous surface adsorption process dominated by chemical adsorption, which explains the intrinsic reasons for its high speed and high selectivity.

[0026] (5) Environmentally friendly and economical: The adsorbent can be easily eluted and regenerated with dilute acid (such as 0.1 M HCl). After being recycled 5 times, the adsorption rate for nickel and cobalt ions can still be maintained at over 80%, and the elution recovery rate of nickel and cobalt ions can reach over 90%. The entire process is mild, requires no complex equipment, does not generate secondary pollution, is low in cost, and has broad prospects for large-scale application. Attached Figure Description

[0027] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0028] Figure 1 This is a scanning electron microscope (SEM) image of the hydroxyapatite nanowires prepared in this invention; the image shows that they are uniformly distributed one-dimensional nanostructures; this structure provides abundant surface active sites, which is beneficial for the rapid adsorption of nickel ions;

[0029] Figure 2 The graph shows the change in nickel ion removal rate under different pH conditions. The results in the graph indicate that the nickel ion removal rate is relatively high in the pH range of 4 to 8. When the pH is too low, the adsorption effect decreases significantly, indicating that the acidity of the solution has a significant impact on the adsorption performance.

[0030] Figure 3 The figure shows the nickel ion adsorption kinetics curve and the fitting results of its pseudo-second-order kinetic model; the solid line in the figure represents the experimental data, the dashed line represents the fitting curve, and the correlation coefficient R is shown. 2 =0.999, indicating that the adsorption process conforms to the pseudo-second-order kinetic model, the adsorption rate is fast, and equilibrium can be reached within 4 minutes;

[0031] Figure 4 The figure shows the adsorption isotherm of nickel ions and the fitting curve of the Langmuir model. The results in the figure show that the adsorption conforms to the Langmuir monolayer model and the maximum adsorption capacity is 11.8 mg / g, indicating that the hydroxyapatite nanowires have uniform surface adsorption characteristics for nickel ions.

[0032] Figure 5 The graph shows the adsorption effect of different ions; the experiment in the graph shows that the adsorbent has a high adsorption capacity for Ni. 2+ Co 2+ It exhibits high selectivity, enabling efficient recovery during the adsorption process while maintaining the target concentration of Li. + The separation effect. Detailed Implementation

[0033] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1: Preparation of hydroxyapatite nanowires and testing of their basic adsorption properties

[0035] 1. Preparation of hydroxyapatite nanowires

[0036] (1) At room temperature, add 10.5 mL of oleic acid to 10 mL of anhydrous ethanol and stir magnetically until completely mixed to form a uniform and transparent oleic acid-ethanol mixture;

[0037] (2) Prepare 50 mL of 0.1 mol / L CaCl2 solution (weighing 0.555 g CaCl2·2H2O) and 50 mL of 0.06 mol / L NaH2PO4 solution (weighing 0.414 g NaH2PO4·2H2O), respectively. At this time, the Ca / P molar ratio is 1.67.

[0038] (3) Slowly add CaCl2 solution to the oleic acid-ethanol mixture in step (1) and stir magnetically for 30 minutes.

[0039] (4) Then, slowly add NaH2PO4 solution to the mixture in step (3), stir evenly to obtain a mixed solution system, slowly add 4 mol / L NaOH solution to the mixed solution system, and adjust the pH value of the mixed solution system to 11.0~11.5;

[0040] (5) Transfer the pH-adjusted mixed solution system to a 100 mL polytetrafluoroethylene-lined stainless steel reactor, place it in an oven, and react at 185°C for 24 hours.

[0041] (6) After the reaction is complete, allow the mixture to cool naturally to room temperature, and then centrifuge at 6000 rpm for 5 minutes to separate the solid product;

[0042] (7) Wash three times each with distilled water and anhydrous ethanol, 30 mL each time, to remove residual oleic acid and impurities;

[0043] (8) The washed solid product was placed in a vacuum drying oven at 60°C and dried for 12 hours. After grinding, white hydroxyapatite nanowire powder was obtained.

[0044] 2. Material characterization and performance testing

[0045] The "Materials Characterization" section includes: (e.g.) Figure 1 As shown, scanning electron microscopy (SEM) characterization revealed that the prepared product is a uniform one-dimensional nanowire structure with an average diameter of approximately 40 nm and a length ranging from several micrometers. Its specific surface area, determined by the BET method, is approximately 18 m². 2 / g.

[0046] "Performance Testing" section: Preparation of Ni-containing... 2+ Co 2+ Li + A mixed solution with a concentration of 50 mg / L was used to simulate the leachate of a ternary lithium battery, and the pH was adjusted to 7.0 with NaOH solution.

[0047] Take 50 mL of the above simulated leachate, add 0.1 g of the hydroxyapatite nanowires prepared in this invention (addition amount is 2 g / L), and stir magnetically for 4 minutes at room temperature to carry out the adsorption reaction;

[0048] After adsorption was complete, centrifugation was performed, and the concentration of each ion in the supernatant was determined using inductively coupled plasma spectroscopy (ICP).

[0049] Result: Ni 2+ The removal rate was 85%, Co 2+ The removal rate was 87%, Li + The retention rate was as high as 98%. This result demonstrates the excellent selective adsorption performance of the material of the present invention.

[0050] Example 2: Adsorption kinetics and cycle stability experiment

[0051] 1. Adsorption kinetics

[0052] The operating steps are the same as in the "Performance Test" section of Example 1, but samples were taken at different time points (1, 2, 4, 6, 8, 10, 15 min) to detect Ni in the solution. 2+ concentration.

[0053] Results: Adsorption reached equilibrium within 4 minutes, and its effect on Ni... 2+ The adsorption process is in high agreement with the pseudo-second-order kinetic model (fit coefficient R). 2 > 0.999), confirming that it is a rapid chemisorption process.

[0054] 2. Elution and Cycling Experiments

[0055] The hydroxyapatite nanowires that had been adsorbed in Example 1 were collected and placed in a 0.1 mol / L dilute hydrochloric acid solution, and eluted by magnetic stirring for 10 minutes.

[0056] After elution, the nanowires were centrifuged, washed with distilled water until neutral, and then vacuum dried at 60°C for reuse.

[0057] Results: Initial elution, Ni 2+ The recovery rate reached 93%. The regenerated nanowires were reused in adsorption-elution cycle experiments. After 5 cycles, their resistance to Ni... 2+ The adsorption rate remained above 82%, demonstrating the material's excellent regeneration performance and stability.

[0058] Example 3: Effect of pH value on adsorption performance

[0059] Prepare multiple 50 mL samples of simulated leachate (Ni 2+ Co 2+ Li + Each (50 mg / L) was used to adjust the pH to 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, and 9.0 respectively using HCl or NaOH solution.

[0060] At each pH condition, 0.1 g of hydroxyapatite nanowires (dosage amount of 2 g / L) were added, stirred at room temperature for 4 minutes, and then centrifuged for determination.

[0061] Result: When pH < 4.0, due to H + Competition is fierce and the material structure may be corroded by acid, Ni 2+ The removal rate is less than 50%. The adsorption effect is optimal within the pH range of 5.0 to 8.0. (Ni) 2+ The removal rate remained stable above 80%, peaking at pH 7.0 (85%). When pH > 8.0, some metal ions began to form hydroxide precipitates, interfering with adsorption evaluation. This experiment determined the optimal adsorption pH range for the method of this invention to be 5.0 ~ 8.0.

[0062] Example 4: Optimization of Adsorbent Dosage

[0063] Multiple 50 mL aliquots of simulated leachate (pH=7.0) were taken, and different masses of hydroxyapatite nanowires were added to each, resulting in dosages of 1, 2, 4, and 6 g / L. The adsorption was measured after 4 minutes.

[0064] Results: When the dosage increased from 1 g / L to 4 g / L, Ni 2+ The removal rate significantly increased from 72% to 96%. Increasing the dosage to 6 g / L slightly improved the removal rate to 98%, but reduced economic benefits. Therefore, considering both efficiency and cost, a dosage of 2-4 g / L is preferred.

[0065] Comparative Example 1: Hydroxyapatite prepared without oleic acid

[0066] Except for the absence of oleic acid, the preparation steps were exactly the same as in Example 1. The resulting product, characterized by SEM, consisted mainly of short rod-shaped and granular aggregates, with a specific surface area of ​​only 8 m². 2 / g.

[0067] The tests were conducted under the same adsorption conditions (pH=7.0, dosage 2 g / L, adsorption time 4 min).

[0068] Result: Its effect on Ni 2+ The removal rate was only 45%, and the adsorption equilibrium time was extended to over 30 minutes. This comparison strongly demonstrates that oleic acid, as a crystal growth guiding agent, is crucial for the formation of high-performance one-dimensional nanowire structures, which are key to achieving rapid and efficient adsorption.

[0069] In summary, this invention has successfully obtained hydroxyapatite with a one-dimensional nanowire structure through a specific preparation method. This material exhibits outstanding advantages such as fast adsorption rate, high selectivity, and easy regeneration and recycling when used to recycle valuable metals from ternary lithium batteries.

[0070] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0071] The above description is only a preferred embodiment of the present invention. Any technical solution that achieves the purpose of the present invention by essentially the same means is within the protection scope of the present invention.

Claims

1. A hydroxyapatite nanowire synthesized under oleic acid control, characterized in that: The hydroxyapatite nanowires were prepared by a solvothermal method using oleic acid as a crystal growth guide agent. The prepared hydroxyapatite nanowires have a one-dimensional nanowire structure with an average diameter of 20-60 nm and a specific surface area of ​​15-25 m². 2 / g; and hydroxyapatite nanowires can be obtained from Ni-containing... 2+ Co 2+ and Li + Selective adsorption of Ni in mixed solutions 2+ and Co 2+ .

2. The oleic acid-controlled hydroxyapatite nanowires according to claim 1, characterized in that: The solvothermal preparation process specifically includes the following steps: (1) Mix oleic acid with an alcohol solvent to form a homogeneous oleic acid-alcohol mixture; (2) Provide calcium salt solution and phosphate solution, and control the calcium-to-phosphorus molar ratio to be 1.6-1.7:1; (3) Add the calcium salt solution provided in step (2) to the oleic acid-alcohol mixture in step (1), stir and mix well, and then add the phosphate solution to obtain a mixed solution system; (4) Add alkali solution to the mixed solution system obtained in step (3) and adjust the pH value of the mixed solution system to 10.5-12.0; (5) Transfer the mixed solution system after adjusting the pH value in step (4) to a high-pressure reactor and carry out a solvothermal reaction at 160-200℃ for 18-28 hours; (6) After the reaction is completed, the product is separated, washed and dried to obtain hydroxyapatite nanowires. The washing is carried out by washing with distilled water and anhydrous ethanol in sequence; the drying is carried out by vacuum drying at 60°C.

3. The oleic acid-controlled hydroxyapatite nanowires according to claim 1, characterized in that: The alcohol solvent in step (1) is one or a mixture of two of methanol and ethanol.

4. The oleic acid-controlled hydroxyapatite nanowires according to claim 1, characterized in that: In step (4), the temperature of the solvothermal reaction in the high-pressure reactor is 180-195℃.

5. A method for applying oleic acid-controlled synthesized hydroxyapatite nanowires according to any one of claims 1-4 in the recovery of valuable metals from ternary lithium batteries, characterized in that: The application method specifically includes the following steps: A ternary lithium battery leachate with a pH of 4.0-8.0, which has undergone acid leaching treatment, is provided, the leachate containing Ni. 2+ Co 2+ and Li + ; Hydroxyapatite nanowires were added to the leachate from step a), and the mixture was stirred at room temperature to carry out an adsorption reaction, allowing Ni... 2+ and Co 2+ Selectively adsorbed, while Li + Retained in solution; The solution after the adsorption reaction in step b) is subjected to solid-liquid separation to obtain a solution loaded with Ni. 2+ and Co 2+ Hydroxyapatite nanowires and Li-rich + The solution; The Ni-loaded solution obtained in step c) was treated with dilute acid solution. 2+ and Co 2+ The hydroxyapatite nanowires were eluted to achieve Ni 2+ and Co 2+ Recycling.

6. The application method according to claim 5, characterized in that: In step b), the adsorption reaction takes 0.5-10 minutes and reaches equilibrium within 4 minutes; the amount of hydroxyapatite nanowires added in the adsorption reaction is 0.5-4 g / L.

7. The application method according to claim 5, characterized in that: The adsorption process of nickel and cobalt ions by hydroxyapatite nanowires conforms to the pseudo-second-order kinetic model and the Langmuir monolayer adsorption model.

8. The application method according to claim 5, characterized in that: The dilute acid solution in step d) is 0.05-0.2 mol / L hydrochloric acid, nitric acid or sulfuric acid.

9. The application method according to claim 5, characterized in that: In step d), the elution recovery rate of nickel ions and cobalt ions is not less than 90%.

10. The application method according to claim 9, characterized in that: The eluted hydroxyapatite nanowires can be recycled after regeneration, and after 5 cycles, the adsorption rate of nickel and cobalt ions is no less than 80%.

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