Preparation method and application of a zinc potassium ferrocyanide / carbon cloth composite electrode material

Abstract

This invention provides a method for preparing a zinc potassium ferricyanide / carbon cloth composite electrode material and its application, relating to the field of electrochemical technology. The method for preparing the zinc potassium ferricyanide / carbon cloth composite electrode material includes the following steps: S1, hydrophilic treatment of carbon cloth to obtain hydrophilic carbon cloth; S2, using the hydrophilic carbon cloth as the working electrode, and using a zinc salt solution as the electrodeposition precursor solution, electrochemically depositing elemental zinc on the surface of the hydrophilic carbon cloth under constant current conditions; S3, after the reaction, removing the carbon cloth, washing it with deionized water, and vacuum drying to obtain an elemental zinc / carbon cloth composite material; S4, placing the elemental zinc / carbon cloth composite material in a potassium ferricyanide aqueous solution, performing a constant-temperature hydrothermal reaction, followed by washing with deionized water and vacuum drying to obtain the zinc potassium ferricyanide / carbon cloth composite electrode material. This zinc potassium ferricyanide / carbon cloth composite electrode material enables rapid, efficient, and selective recovery of cobalt from the leachate of waste lithium cobalt oxide batteries.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to a method for preparing and applying a zinc ferrocyanide potassium / carbon cloth composite electrode material. Background Technology

[0002] Since the first commercial application of lithium-ion batteries in the 1990s, the lithium battery industry has developed rapidly, gradually replacing other rechargeable batteries such as zinc-manganese batteries and lead-acid batteries, becoming the mainstream battery in today's new energy and portable electronic devices. It possesses excellent physicochemical properties such as light weight, long cycle life, and high energy density per unit weight. Lithium cobalt oxide batteries are the most commonly used cathode material in laptops, mobile phones, and digital cameras. However, with the increasingly shorter iteration cycles of electronic products in the information age, a large number of outdated electronic products have become electronic waste and have not been properly recycled. It is reported that by 2025, the total amount of global electronic waste is expected to reach 65.3 million tons, including 464,000 tons of waste lithium batteries. Considering the growing market demand for important industrial raw materials such as lithium, cobalt, and nickel, and the human health problems caused by pollution from waste lithium batteries, recovering high-value metals from waste lithium batteries is crucial from both economic and environmental perspectives.

[0003] Cobalt recovery from waste lithium batteries typically begins with a pretreatment process involving physical separation of metal parts, including mechanical, mechanochemical, and thermal dissolution methods. Subsequently, traditional metal recovery technologies can be categorized into physical calcination and chemical purification. Chemical purification processes include acid leaching and chemical precipitation. Inorganic and organic acids, along with reducing agents (such as hydrogen peroxide), are used to dissolve electrode material powder and leach the metal, which is then directly recovered via chemical precipitation. Physical calcination involves high-temperature treatments for melting and reducing metal parts. However, these technologies utilize large quantities of chemical reagents, consume significant energy, and release acidic wastewater and toxic gases, causing secondary pollution. Therefore, there is an urgent need to find an economical and environmentally friendly alternative method for cobalt recovery.

[0004] Electrochemical adsorption, also known as capacitive deionization, is an advanced technology for removing salt ions from water, first proposed in the 1990s. This technology replaces traditional ion separation techniques such as adsorption, chemical precipitation, ion exchange, and membrane separation. Target ions can be adsorbed during electrode charging or released from the electrode material into the bulk solution through short-circuiting or voltage reversal. With the rapid development of capacitive deionization technology, target ions have expanded from the initial alkali metal ions (potassium, calcium, sodium, magnesium) to some heavy metals (chromium, cadmium, lead, mercury) and rare metals (lithium, cesium, beryllium, titanium). Traditional carbon-based materials, such as activated carbon, graphene, and carbon aerogels, are chosen as conventional capacitive deionization electrode materials due to their good conductivity and large specific surface area. However, due to the mechanism of ion storage in the electrical double layer at the interface, carbon materials exhibit poor selectivity and low removal rates, limiting their application in complex conditions. Therefore, designing novel electrode materials with high selectivity and excellent adsorption / desorption cycle performance is currently a key focus of capacitive deionization technology research.

[0005] Compared to traditional carbon-based materials that rely on an electrobilayer mechanism for ion adsorption, Faraday systems using redox-active materials as electrodes offer advantages such as high ion selectivity and specific capacity, making them promising electrode materials for environmental remediation. Transition metal ferricyanides, also known as Prussian blue and its derivatives, are typical redox-active materials, typically possessing a face-centered cubic lattice structure and open framework, which facilitates the rapid insertion and extraction of cations in aqueous solutions. Potassium zinc ferricyanide, as one of the most chemically stable and least toxic Prussian blue-like materials, has been widely used in the field of aqueous rechargeable batteries. Given the limited reports on the application of potassium zinc ferricyanide in cobalt recovery, and its high cation adsorption capacity, utilizing potassium zinc ferricyanide to recover cobalt from waste lithium cobalt oxide batteries is of significant importance. Summary of the Invention

[0006] Based on the technical problems existing in the background technology, the present invention proposes a preparation method and application of a zinc potassium ferrocyanide / carbon cloth composite electrode material.

[0007] The present invention proposes a method for preparing a zinc potassium ferrocyanide / carbon cloth composite electrode material, comprising the following steps:

[0008] S1. Hydrophilic treatment is applied to the carbon cloth to obtain hydrophilic carbon cloth;

[0009] S2. Using hydrophilic carbon cloth as the working electrode and zinc salt solution as the electrodeposition precursor solution, elemental zinc is electrochemically deposited on the surface of hydrophilic carbon cloth under constant current conditions.

[0010] S3. After the reaction is complete, the carbon cloth is taken out, washed with deionized water and vacuum dried to obtain elemental zinc / carbon cloth composite material;

[0011] S4. The elemental zinc / carbon cloth composite material is placed in an aqueous solution of potassium ferricyanide, and after a constant temperature hydrothermal reaction, it is washed with deionized water and vacuum dried to obtain the potassium ferricyanide / carbon cloth composite electrode material.

[0012] Preferably, in S1, the hydrophilic treatment includes: immersing carbon cloth in a 1-5 mol / L nitric acid solution in a polytetrafluoroethylene reactor, heating at 60-120°C for 6-8 hours, cooling to room temperature, washing with deionized water until neutral, and then storing in deionized water.

[0013] Preferably, in S2, the zinc salt solution is selected from one or more of zinc sulfate solution, zinc chloride solution, and zinc nitrate solution.

[0014] More preferably, in S2, the method for preparing the zinc salt solution includes the following steps: dissolving zinc salt, anhydrous sodium sulfate and boric acid in water and mixing them evenly to obtain a zinc salt solution.

[0015] More preferably, in S2, the mass ratio of zinc salt, anhydrous sodium sulfate, boric acid, and water is (3-10):(3-10):(1-5):50.

[0016] Preferably, in step S2, the constant current used for electrochemical deposition is -100 to -20 mA·cm⁻¹. -2 The duration is 500-1000 seconds.

[0017] Preferably, in step S3, the vacuum drying temperature is 40–80°C and the time is 6–18 hours.

[0018] Preferably, in step S4, the method for preparing the potassium ferricyanide aqueous solution includes the following steps: dissolving potassium ferricyanide in water to obtain a potassium ferricyanide solution.

[0019] More preferably, in S4, the mass ratio of potassium ferricyanide to water is (5-20):50.

[0020] Preferably, in S4, the temperature of the constant-temperature hydrothermal reaction is 60–100°C, and the time is 5–11 hours.

[0021] Preferably, in step S4, the vacuum drying temperature is 40–80°C and the time is 6–18 hours.

[0022] This invention also proposes the application of the zinc potassium ferrocyanide / carbon cloth composite electrode material prepared by the above preparation method in the electrochemical recycling of cobalt elements from waste lithium cobalt oxide batteries.

[0023] Preferably, in the electrochemical recovery of cobalt from waste lithium cobalt oxide batteries, the zinc ferricyanide potassium / carbon cloth composite electrode material prepared by the above method is used as the working electrode, the hydrophilic carbon cloth as the counter electrode, and the silver / silver chloride electrode as the reference electrode.

[0024] Preferably, before the electrochemical recovery experiment of cobalt element from waste lithium cobalt oxide batteries, the zinc potassium ferrocyanide / carbon cloth composite electrode material is placed in a 1 mg / L potassium nitrate solution and pretreated with an oxidation potential of +1.5V (vs. Ag / AgCl) for 30 min to remove potassium ions from the zinc potassium ferrocyanide / carbon cloth composite electrode material.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention provides a method for preparing a zinc-potassium ferricyanide / carbon cloth composite electrode material. The method combines electrochemical deposition of elemental zinc with a hydrothermal reaction of potassium ferricyanide to create a self-supporting electrode with a carbon cloth substrate and loaded with cubic zinc-potassium ferricyanide blocks. This electrode is suitable for the recovery of cobalt from waste lithium cobalt oxide batteries. The open-framework structure and specific selective pseudocapacitive behavior of the zinc-potassium ferricyanide prepared by this invention result in a zinc-potassium ferricyanide / carbon cloth composite electrode material with highly efficient electrochemical adsorption capacity and selectivity for cobalt ions. This characteristic enables the separation of cobalt and lithium ions, and allows for the recovery of important industrial raw materials such as lithium carbonate and cobalt hydroxide through chemical precipitation. This method for preparing and applying a zinc-potassium ferricyanide / carbon cloth composite electrode material not only solves the material loss problem of zinc-potassium ferricyanide materials during use but also improves the mechanical properties and cycle stability of the composite electrode material, and achieves rapid, efficient, and selective recovery of cobalt from the leachate of waste lithium cobalt oxide batteries. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope image of the zinc potassium ferrocyanide / carbon cloth composite electrode material prepared in the embodiments of the present invention.

[0028] Figure 2 Scanning electron microscope (SEM) images of the hydrophilic carbon cloth electrode material (a) prepared in Comparative Example 1 and the elemental zinc / carbon cloth composite material (b) prepared in Comparative Example 2.

[0029] Figure 3 The X-ray diffraction patterns are those of the electrode materials prepared in Examples 1, 1, and 2 of this invention.

[0030] Figure 4 The zinc ferricyanide potassium / carbon cloth composite electrode material prepared for the embodiments of the present invention is subjected to 50mM Co 2+ Cyclic voltammetry curves in solution.

[0031] Figure 5Co of the electrode materials prepared for the embodiments and comparative examples of the present invention 2+ Schematic diagram of electroadsorption kinetics.

[0032] Figure 6 The Co content of the zinc potassium ferrocyanide / carbon cloth composite electrode material in Example 1 of this invention is... 2+ Schematic diagram of the adsorption / desorption cycle performance. Detailed Implementation

[0033] The technical solution of the present invention will be described in detail through specific embodiments.

[0034] In the following examples and comparative examples, the specific information regarding the raw materials used is as follows:

[0035] Carbon cloth: Manufacturer: Shanghai Hesen Electric Co., Ltd.

[0036] Unless otherwise specified, all materials and reagents used in the following examples and comparative examples are commercially available.

[0037] Example 1

[0038] A method for preparing a zinc potassium ferrocyanide / carbon cloth composite electrode material includes the following steps:

[0039] S1. Soak a 2cm (length) × 2cm (width) piece of carbon cloth in a polytetrafluoroethylene reactor containing 50mL of 3mol / L nitric acid solution and heat at 100℃ for 6h. After cooling to room temperature, remove it, wash it with deionized water until neutral, and then store it in deionized water.

[0040] S2. Dissolve 5g of zinc sulfate heptahydrate, 5g of anhydrous sodium sulfate, and 1.6g of boric acid in 50mL of deionized water to obtain a zinc sulfate solution. Use hydrophilic carbon cloth as the working electrode and the zinc sulfate solution as the electrodeposition precursor solution. The constant current used for electrochemical deposition is -50mA·cm. -2 The time is 600 seconds;

[0041] S3. After the reaction is complete, the carbon cloth is taken out, washed with deionized water, and vacuum dried at 60°C for 12 hours to obtain the elemental zinc / carbon cloth composite material.

[0042] S4. Dissolve 10 mg of potassium ferricyanide in 50 mL of deionized water to obtain a potassium ferricyanide aqueous solution. Place the elemental zinc / carbon cloth composite material in the potassium ferricyanide aqueous solution and perform a hydrothermal reaction at 60°C for 7 h. After washing with deionized water and vacuum drying at 60°C for 12 h, the potassium ferricyanide / carbon cloth composite electrode material is obtained. The composite material is KZHCF / CC-1.

[0043] Example 2

[0044] A method for preparing a zinc potassium ferrocyanide / carbon cloth composite electrode material includes the following steps:

[0045] S1. Soak a 2cm (length) × 2cm (width) piece of carbon cloth in a polytetrafluoroethylene reactor containing 50mL of 3mol / L nitric acid solution and heat at 100℃ for 6h. After cooling to room temperature, remove it, wash it with deionized water until neutral, and then store it in deionized water.

[0046] S2. Dissolve 5g of zinc sulfate heptahydrate, 5g of anhydrous sodium sulfate, and 1.6g of boric acid in 50mL of deionized water to obtain a zinc sulfate solution. Use hydrophilic carbon cloth as the working electrode and the zinc sulfate solution as the electrodeposition precursor solution. The constant current used for electrochemical deposition is -50mA·cm. -2 The time is 800 seconds;

[0047] S3. After the reaction is complete, the carbon cloth is taken out, washed with deionized water, and vacuum dried at 60°C for 12 hours to obtain the elemental zinc / carbon cloth composite material.

[0048] S4. Dissolve 10 mg of potassium ferricyanide in 50 mL of deionized water to obtain a potassium ferricyanide aqueous solution. Place the elemental zinc / carbon cloth composite material in the potassium ferricyanide aqueous solution and perform a hydrothermal reaction at 60°C for 7 h. After washing with deionized water and vacuum drying at 60°C for 12 h, the potassium ferricyanide / carbon cloth composite electrode material is obtained. The composite material is KZHCF / CC-2.

[0049] Example 3

[0050] A method for preparing a zinc potassium ferrocyanide / carbon cloth composite electrode material includes the following steps:

[0051] S1. Soak a 2cm (length) × 2cm (width) piece of carbon cloth in a polytetrafluoroethylene reactor containing 50mL of 3mol / L nitric acid solution and heat at 100℃ for 6h. After cooling to room temperature, remove it, wash it with deionized water until neutral, and then store it in deionized water.

[0052] S2. Dissolve 5g of zinc sulfate heptahydrate, 5g of anhydrous sodium sulfate, and 1.6g of boric acid in 50mL of deionized water to obtain a zinc sulfate solution. Use hydrophilic carbon cloth as the working electrode and the zinc sulfate solution as the electrodeposition precursor solution. The constant current used for electrochemical deposition is -50mA·cm. -2 The time is 1000s;

[0053] S3. After the reaction is complete, the carbon cloth is taken out, washed with deionized water, and vacuum dried at 60°C for 12 hours to obtain the elemental zinc / carbon cloth composite material.

[0054] S4. Dissolve 10 mg of potassium ferricyanide in 50 mL of deionized water to obtain a potassium ferricyanide aqueous solution. Place the elemental zinc / carbon cloth composite material in the potassium ferricyanide aqueous solution and perform a hydrothermal reaction at 60°C for 7 h. After washing with deionized water and vacuum drying at 60°C for 12 h, the potassium ferricyanide / carbon cloth composite electrode material is obtained. The composite material is KZHCF / CC-3.

[0055] Comparative Example 1

[0056] A method for preparing a hydrophilic carbon cloth electrode material includes the following steps:

[0057] S1. Soak a 2cm (length) × 2cm (width) piece of carbon cloth in a polytetrafluoroethylene reactor containing 50mL of 3mol / L nitric acid solution and heat at 100℃ for 6h.

[0058] S2. After the reaction is complete, the carbon cloth is taken out, washed with deionized water until neutral, and then vacuum dried at 60°C for 12 hours to obtain the hydrophilic carbon cloth electrode material CC.

[0059] Comparative Example 2

[0060] A method for preparing a single-element zinc / carbon cloth composite electrode material includes the following steps:

[0061] S1. Soak a 2cm (length) × 2cm (width) piece of carbon cloth in a polytetrafluoroethylene reactor containing 50mL of 3mol / L nitric acid solution and heat at 100℃ for 6h. After cooling to room temperature, remove it, wash it with deionized water until neutral, and then store it in deionized water.

[0062] S2. Dissolve 5g of zinc sulfate heptahydrate, 5g of anhydrous sodium sulfate, and 1.6g of boric acid in 50mL of deionized water to obtain a zinc sulfate solution. Use hydrophilic carbon cloth as the working electrode and the zinc sulfate solution as the electrodeposition precursor solution. The constant current used for electrochemical deposition is -50mA·cm. -2 The time is 600 seconds;

[0063] S3. After the reaction is complete, the carbon cloth is removed, washed with deionized water, and vacuum dried at 60°C for 12 hours to obtain the elemental zinc / carbon cloth composite electrode material Zn / CC.

[0064] An application of a zinc ferricyanide potassium / carbon cloth composite electrode material: for the recovery of cobalt from waste lithium cobalt oxide batteries. Specifically, the process involves: first, completely discharging the lithium cobalt oxide batteries from waste laptops in a 5% sodium chloride solution; then, manually disassembling them in a vacuum glove box to obtain the electrode material; subsequently, crushing and sieving to obtain lithium cobalt oxide powder. The ion leaching process is carried out in a 100mL beaker, preparing a 50mL mixed solution containing 2.5mol / L hydrochloric acid and 0.6% (v / v) hydrogen peroxide, and adding 2.5g of lithium cobalt oxide powder to it, stirring at room temperature for 48h. Using a zinc ferricyanide potassium / carbon cloth composite electrode, carbon cloth of the same area, and a silver / silver chloride electrode as the working electrode, counter electrode, and reference electrode, a Co leaching process is performed in a three-electrode system. 2+ Electroadsorption kinetics performance testing. The lithium cobalt oxide leaching solution was diluted 1000 times with deionized water to obtain a mixed metal ion solution containing cobalt and lithium ions. 50 mL of this mixed solution was taken, and the pH was adjusted to 9.0 using 0.1 mol / L ammonia. Before conducting the cobalt ion adsorption experiment, the zinc ferricyanide potassium / carbon cloth composite electrode was pretreated in a 1 mg / L potassium nitrate solution at an oxidation potential of +1.5 V for 30 min to remove potassium ions from the zinc ferricyanide potassium and residual potassium ions from the synthesis process. Subsequently, the zinc ferricyanide potassium / carbon cloth composite electrode was transferred to 50 mL of the metal leaching solution, and a constant voltage of -0.6 V was applied to the working electrode for 2 h to reach adsorption equilibrium. During the reaction, 0.5 mL of solution was taken from the reaction vessel at predetermined time intervals, and its metal ion concentration was analyzed. After the reaction, the zinc ferricyanide potassium / carbon cloth composite electrode material was washed with deionized water and transferred to a 1 mg / L potassium nitrate solution for cobalt ion desorption and electrode regeneration. The concentration of desorbed cobalt ions in the solution was then measured. After applying an oxidation potential of +1.5V to the zinc potassium ferricyanide / carbon cloth composite electrode for 30 min, it was washed with deionized water and dried overnight in a 60°C oven for use in the next cobalt recovery experiment.

[0065] The zinc ferricyanide potassium / carbon cloth composite electrode materials prepared in Examples 1-3 were subjected to Co-processing as described above. 2+ Electroadsorption kinetics performance test; Comparative Example 1: Co adsorption was tested according to the above application. 2+ Electroadsorption kinetics performance testing was conducted, with the only difference being that the zinc ferrocyanide potassium / carbon cloth composite electrode material was replaced with the hydrophilic carbon cloth electrode material CC obtained in Comparative Example 1; Comparative Example 2 was tested according to the above application for Co... 2+ Electroadsorption kinetics performance testing was conducted, with the only difference being that the zinc potassium ferrocyanide / carbon cloth composite electrode material was replaced with the elemental zinc / carbon cloth composite electrode material Zn / CC obtained in Comparative Example 2; the test results are as follows. Figure 5 As shown.

[0066] The electrode materials prepared in the examples and comparative examples were tested using scanning electron microscopy. The test results are as follows: Figures 1-2 As shown. Figure 1 As shown, Figure 1 Image a is a scanning electron microscope (SEM) image of the potassium zinc ferricyanide / carbon cloth composite material prepared in Example 1 of this invention. After hydrothermal reaction, a dense and uniform layer of potassium zinc ferricyanide nanocubes is uniformly loaded on the entire surface of the carbon cloth substrate, with the size of the cubic blocks being approximately 1 μm. 3 And it is well dispersed throughout the carbon fiber skeleton; Figure 1 b is a scanning electron microscope image of the zinc potassium ferrocyanide / carbon cloth composite material prepared in Example 2 of this invention. As the electrodeposition time increases, the volume of the cubic block increases to 8 μm. 3 Left and right, the cubes begin to cluster together; Figure 1 c is a scanning electron microscope image of the potassium zinc ferrocyanide / carbon cloth composite material prepared in Example 3 of this invention. As the electrodeposition time continues to increase, the volume of the cubic block increases to 12 μm. 3 Left and right, the cubes are tightly packed together. Figure 2 Scanning electron microscope (SEM) images of the hydrophilic carbon cloth electrode material and the elemental zinc / carbon cloth composite electrode material prepared for comparison. Figure 2 a represents the hydrophilic carbon cloth electrode material prepared in Comparative Example 1 of this invention. The carbon fiber surface is smooth and free of impurities after hydrothermal reaction with nitric acid solution, which is beneficial for the subsequent deposition of elemental zinc. Figure 2 b represents the elemental zinc / carbon cloth composite electrode material prepared in Comparative Example 2 of this invention. After electrochemical deposition, a dense layer of nanosheets with lateral dimensions of 1–2 μm is uniformly loaded onto the entire surface of the carbon cloth substrate. X-ray diffraction tests were performed on the electrode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2. The test results are as follows: Figure 3 As shown, the diffraction peak of the hydrophilic carbon cloth electrode material CC at 24.0° corresponds to the (0 0 2) crystal plane of graphite; the diffraction peaks of the elemental zinc / carbon cloth composite electrode material Zn / CC at 36.3° and 39.0° are from the reflection of the (0 0 2) and (1 0 0) crystal planes of zinc nanosheets, respectively, indicating the successful deposition of elemental zinc on the carbon cloth surface; the main characteristic diffraction peaks of the zinc potassium ferrocyanide / carbon cloth composite material KZHCF / CC-1 at 16.4°, 19.7°, 21.8°, 24.3°, 24.5° and 28.7° correspond to the (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 0 0) and (1 1 9) crystal planes of K2Zn3[Fe(CN)6]2·9H2O, respectively, indicating the successful preparation of the zinc potassium ferrocyanide / carbon cloth composite electrode material. Figure 4 The zinc ferricyanide potassium / carbon cloth composite electrode material prepared for the embodiments of the present invention is subjected to 50mM Co 2+Cyclic voltammetry curves in solution; A set of significant redox peaks appeared on the cyclic voltammetry curves of the zinc potassium ferrocyanide / carbon cloth composite electrode materials in Examples 1-3, indicating that the Co in the zinc potassium ferrocyanide / carbon cloth composite electrode material can be controlled by electrochemical reaction. 2+ The possibility of adsorption and desorption is considered, and the fact that the KZHCF / CC-1 composite electrode material prepared in Example 1 has a larger specific capacitance than the KZHCF / CC-2 composite electrode material prepared in Example 2 and the KZHCF / CC-3 composite electrode material prepared in Example 3 indicates that its electroadsorption of Co is significantly improved. 2+ Their capabilities are stronger. Figure 5 Co of the electrode materials prepared for the embodiments and comparative examples of the present invention 2+ Schematic diagram of electroadsorption kinetics; Co(NH3)6 under weakly alkaline conditions at pH 9. 3+ The hydration radius is Less than Co 2+ hydration radius The small hydration radius of Co(NH3)6 makes it advantageous. 3+ It is easier for it to enter the molecular framework of potassium zinc ferricyanide, thereby improving the cobalt recovery rate; the KZHCF / CC-1 composite electrode material prepared in Example 1 of this invention can achieve a cobalt recovery rate of 50 mL of 30 mg·g⁻¹ within 2 h. -1 Cobalt ions and 1.5 mg·g -1 The leachate from waste lithium cobalt oxide batteries achieved highly efficient and selective electrochemical adsorption of cobalt (98.6%), which is higher than that of the KZHCF / CC-2 composite electrode material prepared in Example 2 (74.0%), the KZHCF / CC-3 composite electrode material prepared in Example 3 (66.0%), the CC electrode material prepared in Comparative Example 1 (3.7%), and the Zn / CC composite electrode material prepared in Comparative Example 2 (4.0%). This indicates that the Co content of the zinc potassium ferrocyanide / carbon cloth composite electrode material prepared under conditions of shorter electrodeposition time is significantly improved. 2+ It exhibits the best adsorption performance while eliminating the influence of carbon cloth substrate and zinc nanosheets on Co. 2+ The effect of adsorption. Figure 6 The Co content of the zinc potassium ferrocyanide / carbon cloth composite electrode material in Example 1 of this invention is... 2+ A schematic diagram of the adsorption / desorption cycle performance; After five cycles, the adsorption and desorption efficiencies of cobalt ions in the zinc potassium ferrocyanide / carbon cloth composite electrode material prepared in Example 1 of this invention decreased by 16.6% and 16.0%, respectively, indicating that most of the adsorbed cobalt ions can be desorbed from the electrode, and the electrode material itself can be successfully regenerated and recycled by electrochemical reaction to be converted to the oxidation state.

[0067] In summary, the zinc potassium ferrocyanide / carbon cloth composite electrode material provided by this invention can achieve efficient and selective electrochemical adsorption (98.6%) of cobalt in the leachate of waste lithium cobalt oxide batteries and desorb cobalt ions by applying a reverse potential; it can cycle the adsorption / desorption of cobalt ions multiple times.

[0068] 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. The application of a zinc ferrocyanide potassium / carbon cloth composite electrode material in the electrochemical recovery of cobalt from waste lithium cobalt oxide batteries, characterized in that, The zinc ferricyanide potassium / carbon cloth composite electrode material is used as the working electrode, the hydrophilic carbon cloth as the counter electrode, and the silver / silver chloride electrode as the reference electrode. The preparation method of the zinc potassium ferrocyanide / carbon cloth composite electrode material includes the following steps: S1. Hydrophilic treatment is applied to the carbon cloth to obtain hydrophilic carbon cloth; S2. Using hydrophilic carbon cloth as the working electrode and zinc salt solution as the electrodeposition precursor solution, elemental zinc is electrochemically deposited on the surface of hydrophilic carbon cloth under constant current conditions. S3. After the reaction is complete, the carbon cloth is taken out, washed with deionized water and vacuum dried to obtain elemental zinc / carbon cloth composite material; S4. The elemental zinc / carbon cloth composite material is placed in an aqueous solution of potassium ferricyanide, and after a constant temperature hydrothermal reaction, it is washed with deionized water and vacuum dried to obtain the potassium ferricyanide / carbon cloth composite electrode material.

2. The application according to claim 1, characterized in that, In S1, the hydrophilic treatment includes: immersing carbon cloth in a 1-5 mol / L nitric acid solution in a polytetrafluoroethylene reactor, heating at 60-120°C for 6-8 hours, cooling to room temperature, washing with deionized water until neutral, and then storing in deionized water.

3. The application according to claim 1, characterized in that, In S2, the constant current used for electrochemical deposition is -100 to -20 mA·cm. -2 The duration is 500-1000 seconds.

4. The application according to claim 1, characterized in that, In step S3, the vacuum drying temperature is 40–80°C, and the time is 6–18 hours.

5. The application according to claim 1, characterized in that, The method for preparing potassium ferricyanide aqueous solution in S4 includes the following steps: dissolving potassium ferricyanide in water to obtain potassium ferricyanide solution; the mass ratio of potassium ferricyanide to water is (5-20):

50.

6. The application according to claim 1, characterized in that, In S4, the temperature of the constant-temperature hydrothermal reaction is 60–100°C, and the time is 5–11 h; the temperature of the vacuum drying is 40–80°C, and the time is 6–18 h.

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