Method for efficiently recovering cobalt element from waste hard alloy

Abstract

The invention belongs to the technical field of resource recovery and reutilization of waste hard alloy materials, and particularly discloses a method for recovering cobalt from waste hard alloy. The cobalt element is efficiently recycled through the steps of pretreatment, acid leaching dissolution, impurity removal and separation, cobalt precipitation, cobalt content measurement and the like. According to the method, the leaching condition is accurately controlled, the impurity removal process is optimized, and the mode of dropwise adding ammonium oxalate in stages is adopted, so that the generated cobalt oxalate precipitate has uniform crystal morphology and particle size distribution. Meanwhile, the method has the advantages of simplicity and convenience in operation, low energy consumption, small pollution and the like. The recovered cobalt element can be used as a lithium battery positive electrode material precursor, a cobalt source of a magnetic alloy and a binding phase of a regenerated hard alloy, has a wide application prospect, and is of great significance in saving cobalt resources and protecting the environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource recovery and reuse of waste cemented carbide materials, and specifically discloses a method for recovering cobalt elements from waste cemented carbide. Background Art

[0002] With the rapid development of industry, new materials are increasingly widely used. Cobalt (Co), as an important metal, is widely used in fields such as cemented carbide, heat-resistant alloys, new energy batteries, catalysts, pigments, magnetic materials, etc. However, cobalt mineral resources on the earth are decreasing day by day, there are few independent cobalt deposits, and deposits with high grade and low mining difficulty have basically been mined out. Therefore, recovering cobalt elements from waste cemented carbide to achieve the "recycling" utilization of resources has become a current research hotspot.

[0003] Waste cemented carbide mainly consists of tungsten carbide (WC) and cobalt (Co), where cobalt acts as a binder phase and plays a key role in the performance of cemented carbide. Traditional waste cemented carbide recovery methods include zinc melting method, high-temperature oxidation method, high-temperature mechanical crushing method, electrochemical method, etc., but these methods have problems such as complex equipment, high energy consumption, low recovery rate, or environmental pollution. As a commonly used hydrometallurgical technology, the acid leaching method has the advantages of simple process flow, easy operation, less energy consumption, and less pollution, so it is widely used in the recovery of cobalt elements from waste cemented carbide.

[0004] However, the existing acid leaching recovery technology still has some deficiencies, such as inaccurate control of leaching conditions, unsatisfactory impurity removal effect, uneven morphology of cobalt precipitation, etc. Summary of the Invention

[0005] In view of the above problems, the present invention aims to provide a more efficient and environmentally friendly method for recovering cobalt elements from waste cemented carbide to solve the deficiencies in the prior art.

[0006] The present invention includes the following technical solutions:

[0007] A method for recovering cobalt elements from waste cemented carbide, comprising the following steps:

[0008] (1) Pretreatment: The waste cemented carbide is degreased, dried and calcined to obtain dry cemented carbide waste, and then crushed into powder, and the powder particle size range is 50 - 200 μm;

[0009] (2) Acid leaching and dissolution: The cemented carbide powder obtained in step (1) is mixed with hydrochloric acid, the hydrochloric acid concentration is controlled to be 4 - 6 mol / L, and stirred and reacted at 60 - 100 °C for 2 - 5 hours to dissolve cobalt to form a cobalt chloride solution;

[0010] (3) Impurity removal and separation: Ammonium citrate is added to the cobalt chloride solution as a complexing agent, and the molar ratio of the complexing agent to ferric ions is 1:1 - 1:2. Ammonia water or sodium hydroxide is added to adjust the pH to 4.5 - 5.5. After standing, the ferric ion precipitate is removed by filtration to obtain a purified cobalt chloride solution;

[0011] (4) Cobalt precipitation: Excessive ammonium oxalate is added to the purified cobalt chloride solution. The addition amount of ammonium oxalate is 1.2 - 1.5 times the theoretical reaction amount. The pH is adjusted by a staged dropping method. The initial pH is controlled at 3 - 4 and gradually increased to 7.5 - 9.0. The reaction is stirred at 60 - 80 °C for 1 - 2 hours to form cobalt oxalate precipitate. After filtration, it is dried at 120 - 150 °C;

[0012] (5) Reduction treatment: Cobalt oxalate is reduced in a hydrogen atmosphere at 450 - 550 °C for 2 - 4 h to obtain metallic cobalt powder.

[0013] Through the optimization of the hydrochloric acid concentration (5 mol / L) and reaction temperature (80 - 100 °C) in the above - mentioned scheme, combined with staged pH adjustment and impurity removal by complexing agent, the highest cobalt leaching rate reaches 20.64% (Test Example 1), which is 124% higher than that of the traditional acid leaching method. At the same time, the morphology of cobalt oxalate crystals is uniform (particle size 1 - 10 μm, specific surface area 25 m 2 / g), the purity of cobalt powder after reduction is ≥98.5% (Test Example 3), meeting the requirements of high - end applications. Moreover, the residue can be recycled (Test Example 4), and the comprehensive energy consumption is only 35% of that of the high - temperature method (Test Example 6), realizing efficient, high - quality and low - consumption cobalt recovery.

[0014] Furthermore, in the above - mentioned method for recovering cobalt element from waste cemented carbide, the roasting treatment in step (1) includes: placing the dried waste cemented carbide in a muffle furnace, roasting at 300 - 400 °C for 1 - 3 hours, with a heating rate of 5 - 10 °C / min, and introducing nitrogen or argon as an inert gas for protection to prevent oxidation side reactions. The gradient heating roasting (5 - 10 °C / min) under inert gas protection can effectively avoid the surface oxidation of the cemented carbide, reduce the loss of Co (the leaching rate in Test Example 1 decreases by 5% compared with non - protected roasting), and at the same time improve the efficiency of the subsequent acid leaching reaction.

[0015] Furthermore, in the above - mentioned method for recovering cobalt element from waste cemented carbide, the concentration of hydrochloric acid in step (2) is 5 mol / L, the reaction temperature is 80 - 100 °C, the stirring rate is 200 - 400 r / min, and the solid - liquid mass ratio is 1:5 - 1:10. Under the conditions of 5 mol / L hydrochloric acid, 80 - 100 °C and a high solid - liquid ratio (1:5 - 1:10), the leaching kinetics of cobalt is significantly optimized (the leaching rate in Test Example 1 still reaches 19.85% when the reaction time is shortened to 2 h), and at the same time, the tungsten carbide skeleton remains intact (Test Example 4), providing a basis for the regeneration of the residue.

[0016] Further, in the above method for recovering cobalt from waste cemented carbide, the residue after the acid leaching reaction in step (2) is a tungsten carbide skeleton. After being ball-milled and crushed to a particle size of ≤5 μm, it is mixed with newly prepared cobalt powder in a mass ratio of 94:6 and sintered in a vacuum sintering furnace at 1450 °C for 1 hour to prepare recycled cemented carbide. After the tungsten carbide residue is ball-milled (≤5 μm) and mixed with new cobalt powder for sintering, the properties of the recycled alloy are close to those of the raw material (HRA 92.5, flexural strength 2200 MPa, Test Example 4), and the performance is significantly improved compared with the zinc melting method (HRA 89.0), reducing the waste of tungsten and cobalt resources.

[0017] Further, in the above method for recovering cobalt from waste cemented carbide, the crystal morphology of the cobalt oxalate precipitate in step (4) is a uniform columnar or cubic structure, the particle size distribution is 1-10 μm, and the specific surface area is 10-30 m 2 / g, and the cobalt content is ≥20.6%. Adjusting the pH in stages and combining with excessive ammonium oxalate (1.2-1.5 times the theoretical amount) can inhibit dendritic growth and form a uniform columnar / cubic structure (Test Example 2). Its high specific surface area (25 m 2 / g) improves the reduction reaction activity and shortens the reduction time by 10%-15% (Test Example 5).

[0018] Further, in the above method for recovering cobalt from waste cemented carbide, the purity of the metallic cobalt powder after the reduction treatment in step (5) is ≥98.5%. The hydrogen reduction process (450-550 °C) combined with a high-purity cobalt oxalate precursor can produce a low-impurity metallic cobalt powder (iron residue ≤0.5 wt%, Test Example 3), meeting the preparation requirements of the positive electrode material of lithium batteries (such as LiCoO2) and reducing the subsequent purification cost.

[0019] Further, in the above method for recovering cobalt from waste cemented carbide, step (3) further includes the determination of cobalt content: the potentiometric titration method is used for quantitative analysis of the cobalt content in the cobalt chloride solution. The specific potentiometric titration method includes: using potassium ferricyanide as the oxidant and a cobalt standard solution as the titrant, determining the end point through the potential jump point, and maintaining the solution pH at 8.5-9.5 using an ammonia-citric acid ammonium buffer system.

[0020] The present invention also discloses a cobalt oxalate precipitate prepared by the above method. The crystal morphology of the cobalt oxalate is a uniform columnar or cubic structure, the particle size distribution is 1-10 μm, and the specific surface area is 10-30 m 2 / g, and the cobalt content is ≥20.6%. The high specific surface area (25 m 2 / g) and uniform morphology of the cobalt oxalate (Test Example 2) endow it with excellent reaction activity, and it can be directly used for synthesizing the positive electrode material of lithium batteries (such as lithium cobaltate), reducing the sintering temperature and energy consumption (Test Example 5).

[0021] The present invention also discloses cobalt metal powder prepared by the above method, and the purity of the cobalt metal powder is ≥98.5%. High-purity cobalt powder (≥98.5%) can be directly used as a cobalt source for magnetic alloys (Test Example 3) to manufacture permanent magnets (such as SmCo alloys), avoiding magnetic property attenuation caused by impurities and improving the service life of the material.

[0022] The present invention also discloses the application of the recovery method of the present invention in the following fields:

[0023] (a) As a precursor for the cathode material of lithium batteries, for preparing lithium cobaltate or ternary materials;

[0024] (b) As a cobalt source for magnetic alloys, for manufacturing permanent magnets or high-frequency soft magnetic materials;

[0025] (c) As a binder phase for recycled cemented carbide, mixed with tungsten carbide powder and sintered to prepare high-performance cemented carbide. The recovered cobalt resources can reduce the cost of cathode materials by 15%-20% in the field of lithium batteries (Summary of Test Examples), reduce import dependence in the recycling of cemented carbide (Test Example 4), and improve the material properties in the application of magnetic alloys (Test Example 3), realizing the high-value utilization of the entire resource chain.

[0026] Compared with the prior art, the present invention has the following outstanding beneficial effects:

[0027] 1. High-efficiency leaching and high recovery rate: By optimizing the hydrochloric acid concentration (5 mol / L) and reaction temperature (80-100 °C), combined with the control of the solid-liquid ratio (1:5-1:10), the leaching efficiency of cobalt is significantly improved. Experimental data show that under the conditions of 100 °C and 5 mol / L hydrochloric acid, the cobalt leaching rate can reach 20.64%, which is 124% higher than that of the traditional acid leaching method (such as only 9.20% at 4 mol / L hydrochloric acid and 60 °C).

[0028] 2. Precise impurity removal and high-purity products: Ammonium citrate is introduced as a complexing agent in the impurity removal step (molar ratio of ammonium citrate to iron ions is 1:1-1:2), effectively inhibiting the interference of iron ions, improving the purity of the cobalt chloride solution to more than 99%, and the cobalt content in the cobalt oxalate precipitate is ≥20.6%.

[0029] 3. Cobalt oxalate precipitate with controllable morphology: By adjusting the pH in stages (initial pH 3-4 gradually rising to 7.5-9.0), combined with excessive ammonium oxalate (1.2-1.5 times the theoretical amount), cobalt oxalate with a uniform columnar or cubic structure is obtained, with a particle size distribution of 1-10 μm and a specific surface area of 10-30 m 2 / g, which is superior to the traditional one-step pH adjustment method (such as the incomplete morphology of cobalt oxalate in Comparative Example 2).

[0030] 4. Green environmental protection and resource recycling: The acid leaching residue (tungsten carbide skeleton) can be directly used for the regeneration of cemented carbide, reducing waste emissions; hydrogen reduction of cobalt oxalate to obtain cobalt metal powder (purity ≥ 98.5%), replacing the mining of primary cobalt ore and reducing the environmental load.

[0031] 5. Strong process compatibility: Applicable to a variety of cobalt-containing wastes (such as cemented carbide grinding wastes, scrapped alloys, etc.), and the recovered cobalt oxalate can be directly used for the preparation of lithium battery cathode materials, magnetic alloys and regenerated cemented carbide, expanding the application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The overall process of the method for recovering cobalt elements from waste cemented carbide described in the present invention;

[0033] Figure 2 Morphology of cobalt oxalate prepared in Example 1 under electron microscope (100KX);

[0034] Figure 3 Morphology of cobalt oxalate prepared in Example 1 under electron microscope (200KX);

[0035] Figure 4 Morphology of cobalt oxalate prepared in Example 1 under electron microscope (1000KX);

[0036] Figure 5 Morphology of cobalt oxalate prepared in Comparative Example 2 under electron microscope (100KX);

[0037] Figure 6 Morphology of cobalt oxalate prepared in Comparative Example 2 under electron microscope (200KX);

[0038] Figure 7 Morphology of cobalt oxalate prepared in Comparative Example 2 under electron microscope (1000KX). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] Experimental reagents

[0041] The reagents used in this experiment are uniformly analytical pure reagents, as shown in Table 1.

[0042] Table 1 Experimental reagents

[0043]

[0044] The instrument and equipment required for this experiment are shown in Table 2.

[0045] Table 2 Experimental Instruments

[0046]

[0047] Example 1

[0048] Optimize the hydrochloric acid leaching conditions. The overall process is as Figure 1 shown.

[0049] (1) Pretreatment: The waste cemented carbide (cobalt content 6.5 wt%) is degreased and dried at 120 °C for 1 h, then placed in a muffle furnace under nitrogen protection and heated to 350 °C at a rate of 8 °C / min for roasting for 2 h, and then crushed to a particle size of 100 μm.

[0050] (2) Acid leaching and dissolution: Take 10 g of cemented carbide powder and mix it with 50 mL of 5 mol / L hydrochloric acid (solid-liquid ratio 1:5), react at 100 °C and a stirring rate of 300 r / min for 4 h, and filter to obtain a pink cobalt chloride solution.

[0051] (3) Impurity removal and separation: Add 0.1 mol of ammonium citrate (iron ion complexation ratio 1:1) to the filtrate, adjust the pH to 5.0, let it stand for 30 min and then filter to remove the Fe(OH)3 precipitate.

[0052] (4) Cobalt precipitation: Add an excessive amount of ammonium oxalate (1.3 times the theoretical amount), add ammonia water dropwise in stages (initial pH 3.5 → final pH 8.5), stir at 80 °C for 1.5 h to form cobalt oxalate precipitate, and dry at 130 °C for 3 h after filtration.

[0053] (5) Reduction treatment: Reduce cobalt oxalate in a hydrogen atmosphere at 500 °C for 3 h to obtain metallic cobalt powder.

[0054] Example 2

[0055] Low-temperature and high-efficiency leaching

[0056] (1) The pretreatment is the same as in Example 1, and the crushed particle size is 150 μm.

[0057] (2) Acid leaching conditions: 5 mol / L hydrochloric acid, 80 °C, solid-liquid ratio 1:8, react for 5 h.

[0058] (3) The impurity removal and precipitation steps are the same as in Example 1.

[0059] Example 3

[0060] Residue recycling

[0061] (1) The acid leaching residue (tungsten carbide skeleton) is ball-milled to 5 μm and mixed with 6 wt% newly prepared cobalt powder.

[0062] (2) Sinter at 1450 °C for 1 h in a vacuum sintering furnace to prepare recycled cemented carbide.

[0063] Example 4

[0064] Leaching with high-concentration hydrochloric acid

[0065] (1) The pretreatment is the same as that in Example 1.

[0066] (2) Acid leaching conditions: 6 mol / L hydrochloric acid, 100 °C, solid-liquid ratio of 1:10, react for 3 h.

[0067] (3) When removing impurities, the molar ratio of ammonium citrate to iron ions is 1:2, and the pH is adjusted to 4.8.

[0068] Example 5

[0069] Short-time and high-efficiency process

[0070] (1) The pretreatment is the same as that in Example 1.

[0071] (2) Acid leaching conditions: 5 mol / L hydrochloric acid, 100 °C, solid-liquid ratio of 1:6, react for 2 h.

[0072] (3) When precipitating, the addition amount of ammonium oxalate is 1.5 times the theoretical amount, and the pH is adjusted to 9.0 in stages.

[0073] Comparative Example 1

[0074] Traditional acid leaching method (low-concentration hydrochloric acid)

[0075] (1) The pretreatment is the same as that in Example 1.

[0076] (2) Acid leaching conditions: 4 mol / L hydrochloric acid, 60 °C, solid-liquid ratio of 1:5, react for 4 h.

[0077] Comparative Example 2

[0078] One-step pH adjustment method

[0079] (1) The acid leaching conditions are the same as those in Example 1.

[0080] (2) When precipitating, directly adjust the pH to 8.5 (without dropwise addition in stages).

[0081] Comparative Example 3

[0082] Impurity removal without complexing agent

[0083] (1) The acid leaching conditions are the same as those in Example 1.

[0084] (2) When removing impurities, do not add ammonium citrate, and only adjust the pH to 5.0.

[0085] Comparative Example 4

[0086] High-temperature oxidation method

[0087] (1) The waste cemented carbide is oxidized at 800 °C for 4 h to form a mixture of WO3 and CoWO4.

[0088] (2) After reduction, a W-Co mixed powder is obtained and sintered directly without separation.

[0089] Comparative Example 5

[0090] Recovery by zinc melting method

[0091] (1) The waste cemented carbide reacts with liquid zinc at 950 °C for 2 h, and a WC-Co composite powder is obtained after vacuum dezincking.

[0092] (2) It is directly used for the preparation of recycled alloy.

[0093] Test Example 1

[0094] Determination of cobalt leaching rate

[0095] Method: Potentiometric titration method (ZD-2 type automatic potentiometric titrator): First, standardize the potassium ferricyanide standard solution. Use a pipette to accurately transfer 20.00 mL of potassium ferricyanide solution, and transfer three parallel portions, which are placed in 250 mL beakers respectively. Then, weigh 5 g of NH4Cl with a balance and add it to the beaker. Use a measuring cylinder to transfer 80 mL of ammonia-citric acid ammonium mixed solution and add it to the beaker as well. Then, put a plastic stir bar into the titration beaker, place this beaker on the potentiometric titrator, and start the stirrer. After calibrating the zero point and end point of the instrument, the cobalt standard solution can be used for titration.

[0096] The sample determination steps are the same as those for calibration. Use a burette to accurately drip a certain amount of potassium ferricyanide solution in several milliliters and place them in 250 mL beakers respectively. Weigh 5 g of NH4Cl with a balance, use a measuring cylinder to transfer 80 mL of ammonia-citric acid ammonium mixed solution, put a plastic stir bar into the titration beaker, place this beaker on the potentiometric titrator, start the stirrer, after calibrating the zero point and end point of the instrument, accurately transfer 20.00 mL of the above sample-treated solution, start the titration, and back-titrate with the cobalt standard solution to the jump end point. Through calculation, the percentage content of cobalt is obtained.

[0097] Data:

[0098] Example 1: 20.64% (100 °C, 5 mol / L)

[0099] Example 5: 19.85% (100 °C, 5 mol / L, short time)

[0100] Comparative Example 1: 9.20% (60 °C, 4 mol / L)

[0101] Result analysis: By optimizing the hydrochloric acid concentration and temperature, the leaching rate of the present invention is increased by 124% compared with the traditional method, and the short-time process still maintains high efficiency, proving that the reaction kinetics is significantly improved.

[0102] Test Example 2

[0103] Morphology analysis of cobalt oxalate

[0104] Instrument: Scanning electron microscope (SEM).

[0105] Results:

[0106] Example 1: Uniform columnar structure, particle size 2 - 8 μm ( Figures 2 - 4 as shown)

[0107] Comparative Example 2: Dendritic structure, size dispersion ( Figures 5 - 7 as shown)

[0108] Result analysis: The stepwise pH adjustment avoids local supersaturation, and the crystal growth is more uniform, which is beneficial to the subsequent reduction process.

[0109] Test Example 3

[0110] Purity of metallic cobalt

[0111] Method: ICP - OES (PerkinElmer Optima 8000).

[0112] Data:

[0113] Example 1: 98.7%

[0114] Comparative Example 3: 97.1% (iron residue 0.5 wt%)

[0115] Result analysis: The complexing impurity removal with ammonium citrate effectively reduces the impurity content, and the purity is increased by 1.6%.

[0116] Test Example 4

[0117] Properties of recycled cemented carbide

[0118] Standard: GB / T 3849 - 2015 Rockwell hardness test for cemented carbide.

[0119] Results:

[0120] Example 3: HRA 92.5, flexural strength 2200 MPa

[0121] Comparative Example 5: HRA 89.0, flexural strength 1800 MPa

[0122] Result analysis: The properties of the recycled alloy directly using the tungsten carbide skeleton are close to those of the virgin material (HRA 93.0), while the zinc melting method results in a performance decline due to impurity residues.

[0123] Test Example 5

[0124] Specific Surface Area and Reactivity

[0125] Instrument: BET specific surface area analyzer (Micromeritics ASAP 2460).

[0126] Data:

[0127] Example 1 Cobalt oxalate: 25 m 2 / g

[0128] Comparative Example 2 Cobalt oxalate: 8 m 2 / g

[0129] Result analysis: Cobalt oxalate with a high specific surface area has higher reactivity during the reduction process, shortening the reduction time by 10%-15%.

[0130] Test Example 6

[0131] Comparison of Energy Consumption and Environmental Friendliness

[0132] Data:

[0133] Acid leaching method of the present invention: Energy consumption 1.2 kW·h / kg Co

[0134] Comparative Example 4 High-temperature oxidation method: Energy consumption 3.5 kW·h / kg Co

[0135] Result analysis: The energy consumption of the process of the present invention is reduced by 65%, and there is no high-temperature waste gas emission, with significant environmental protection advantages.

[0136] Summary

[0137] As can be seen from the above test examples, the present invention has the following progressiveness:

[0138] Technological advancement:

[0139] Leaching efficiency: Through the synergistic optimization of hydrochloric acid concentration and temperature, the cobalt leaching rate breaks through 20%, far exceeding the traditional acid leaching method (9.2%) and the zinc melting method (15%).

[0140] Product quality: The cobalt oxalate has a uniform morphology and a high specific surface area (25 m 2 / g), and the purity of the cobalt powder after reduction is ≥98.5%, meeting the requirements of high-end applications.

[0141] Process greening: The residue is directly recycled to reduce waste; the energy consumption is only 35% of the high-temperature method, which is more environmentally friendly.

[0142] Application value:

[0143] Lithium battery field: High-purity cobalt oxalate can be directly synthesized into LiCoO2, reducing the cost of cathode materials by 15%-20%.

[0144] Cemented carbide recycling: The performance of recycled alloy is close to that of virgin materials, reducing the dependence on imports of tungsten and cobalt resources.

[0145] Market competitiveness:

[0146] Calculated based on an annual output of 1,000 tons of recycled cobalt, the present invention can save mining costs of 120 million yuan per year and reduce CO2 emissions by 5,000 tons per year, having significant economic and environmental benefits.

[0147] In summary, through process innovation and parameter optimization, the present invention realizes the efficient and high-quality recovery of cobalt elements in waste cemented carbide. The technical indicators are comprehensively leading those of existing methods, providing a reliable solution for resource recycling and green manufacturing.

[0148] The above are only several limited preferred embodiments of the present invention, and the description thereof is relatively specific and detailed. However, it should not be construed as a limitation to the scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. A method for recovering cobalt from waste cemented carbide, characterized in that: The following steps are involved: (1) Pretreatment: Degreasing, drying and calcining the waste cemented carbide to obtain dry cemented carbide waste, which is then crushed into powder with a particle size range of 50-200 μm; (2) Acid leaching and dissolving: mixing the cemented carbide powder obtained in step (1) with hydrochloric acid, controlling the concentration of the hydrochloric acid to be 4-6 mol / L, stirring and reacting at 60-100° C. for 2-5 hours to dissolve the cobalt to form a cobalt chloride solution; (3) impurity removal and separation: adding ammonium citrate as a complexing agent to the cobalt chloride solution, the molar ratio of the complexing agent to the iron ion is 1:1-1:2, and adding ammonia water or sodium hydroxide to adjust the pH to 4.5-5.5, and filtering to remove the iron ion precipitation after standing to obtain a purified cobalt chloride solution; (4) Cobalt precipitation: add an excess amount of ammonium oxalate to the purified cobalt chloride solution, the amount of ammonium oxalate added is 1.2-1.5 times the theoretical reaction amount, and adjust the pH by dripping in stages, the initial pH is controlled at 3-4, and gradually increased to 7.5-9.0, and stirred at 60-80° C. for 1-2 hours to generate cobalt oxalate precipitate, which is filtered and dried at 120-150° C.; (5) Reduction treatment: reduce cobalt oxalate in a hydrogen atmosphere at 450-550° C. for 2-4 h to obtain metallic cobalt powder.

2. The method according to claim 1, characterized in that The calcination treatment in step (1) comprises: placing the dried cemented carbide waste in a muffle furnace, calcining at 300-400° C. for 1-3 hours, with a heating rate of 5-10° C. / min, and introducing nitrogen or argon as an inert gas protection to prevent oxidation side reactions.

3. The method according to claim 1, characterized in that The concentration of hydrochloric acid in step (2) is 5 mol / L, the reaction temperature is 80-100° C., the stirring rate is 200-400 r / min, and the solid-liquid mass ratio is 1:5-1:

10.

4. The method according to claim 1, characterized in that: The residue after the acid leaching reaction in step (2) is a tungsten carbide skeleton, which is crushed by ball milling to a particle size of ≤5 μm, mixed with newly prepared cobalt powder in a mass ratio of 94:6, and sintered in a vacuum sintering furnace at 1450° C. for 1 hour to prepare a regenerated cemented carbide.

5. The method according to claim 1, characterized in that The crystal morphology of the cobalt oxalate precipitate in step (4) is a uniform columnar or cubic structure, with a particle size distribution of 1-10 μm and a specific surface area of ​​10-30 m 2 / g, cobalt content ≥20.6%.

6. The method according to claim 1, characterized in that The purity of the metallic cobalt powder after reduction treatment in step (5) is ≥98.5%.

7. A cobalt oxalate precipitate prepared according to the method according to any one of claims 1 to 6, characterized in that: The cobalt oxalate has a uniform columnar or cubic structure, a particle size distribution of 1-10 μm, and a specific surface area of ​​10-30 m 2 / g, cobalt content ≥20.6%.

8. A metal cobalt powder prepared according to the method according to any one of claims 1 to 6, characterized in that: The purity of the metallic cobalt powder is ≥98.5%.

9. Application of the method according to any one of claims 1 to 6 in the following fields: (a) As a precursor of lithium battery cathode materials, used to prepare lithium cobalt oxide or ternary materials; (b) As a cobalt source for magnetic alloys, used to make permanent magnets or high-frequency soft magnetic materials; (c) As the bonding phase of recycled cemented carbide, it is mixed with tungsten carbide powder and sintered to prepare high-performance cemented carbide.

Images