Preparation method of cobalt carbonate for spherical cobalt powder

Abstract

The invention relates to a preparation method of cobalt carbonate for spherical cobalt powder. A soluble cobalt salt solution reacts with an ammonium bicarbonate solution and an ammonia water solution / sodium hydroxide solution to generate cobalt carbonate. The method comprises the following specific steps: dropwise adding a cobalt solution into an ammonium bicarbonate solution, when the pH value of a synthetic slurry is reduced to 7.9-8.0, releasing a large amount of carbon dioxide generated by reaction, adding a prepared ammonia water solution / sodium hydroxide solution into a reaction kettle at a certain flow rate to react with the generated carbon dioxide, regenerating bicarbonate to react with the cobalt solution, and carrying out solid-liquid separation to obtain the cobalt carbonate. In order to avoid the situation that excessive ammonia water solution / sodium hydroxide solution is added to react with the cobalt solution to generate cobalt hydroxide, through experiments, the amount of substance of the ammonia water solution / sodium hydroxide solution added into the reaction kettle is determined to be 90-95% of the amount of substance of ammonium bicarbonate added into the reaction kettle, so that the prepared substance is pure-phase cobalt carbonate.

Description

Technical Field

[0001] The present invention belongs to the technical field of spherical cobalt powder preparation, and specifically relates to the preparation technology of micro-nano cobalt carbonate for reducing spherical cobalt powder. Background Art

[0002] Due to its unique physical properties, such as smaller particle size, uniform distribution, regular surface morphology, and significantly increased packing density, spherical cobalt powder has significantly improved fluidity and dispersibility, and at the same time reduces the influence of agglomeration. These characteristics make spherical cobalt powder have broad application prospects in many industries such as diamond tool manufacturing, cemented carbide, magnetic fluid, permanent magnet materials, and batteries.

[0003] In recent years, the application of spherical cobalt powder in ultrafine-grained WC-Co cemented carbide has received increasing attention. Among them, sub-micro / micro WC-Co cemented carbide is the most widely used tool material in the metal cutting field. Using spherical cobalt powder with ultrafine / nano-sized particles can reduce the sintering densification temperature of the alloy, thereby inhibiting the abnormal growth of WC grains, improving the cobalt phase distribution in the alloy, and helping to obtain high-performance ultrafine and nanocrystalline WC-Co cemented carbide, thus improving the cutting performance of cemented carbide tools.

[0004] Currently, the main methods for preparing spherical cobalt powder include hydrogen reduction of cobalt carbonate method, DC arc plasma evaporation method, and solvothermal method, etc. And industrial spherical cobalt powder generally adopts the hydrogen reduction of cobalt carbonate method. Therefore, the research on cobalt carbonate for spherical cobalt powder has become a hot topic.

[0005] Currently, the industry mainly prepares cobalt carbonate by reacting soluble cobalt salt with ammonium bicarbonate solution. The reaction equation is as follows: Co 2+ +2HCO3 - =CoCO3+H2O+CO2. However, with the rising price of ammonium bicarbonate, it has become a consensus in the industry to study and reduce the production cost of industrial cobalt carbonate. Summary of the Invention

[0006] To overcome the deficiencies of the existing production process, the purpose of the present invention is to provide a preparation method of cobalt carbonate for spherical cobalt powder with a simple and easy-to-control production process, easy to industrialize, and maximizing the utilization of ammonium bicarbonate raw materials. The purpose of the present invention can be achieved through the following technical solutions: The present invention is a preparation method of cobalt carbonate for spherical cobalt powder, and its steps are as follows: Step (a) Liquid preparation: Using soluble cobalt salt as raw material, prepare a cobalt solution with a cobalt concentration of 1.8 - 2.0 mol / L as solution A; prepare an ammonium bicarbonate solution with a concentration of 2.8 - 3.0 mol / L as solution B, and prepare ammonia water or sodium hydroxide solution as solution C; Step (b) Synthesis reaction: Add solution B, which accounts for 30 - 35% of the volume of the reaction kettle, into the reaction kettle. Then add solution A into the reaction kettle at a preset flow rate for the synthesis reaction. When the pH value of the slurry in the reaction kettle drops to a preset value, start adding a fixed amount of solution C into the reaction kettle at a preset flow rate. After the quantitative solution C is completely added into the reaction kettle, stop adding solution C. When the pH value of the slurry continues to drop to a preset value, stop adding solution A. During the reaction process, strictly control the flow rates of solutions A and C, the reaction temperature, and the stirring intensity. Step (c) Aging: After the synthesis reaction ends, stop adding liquid and start the aging process. Step (d) Washing: After the aging process ends, wash the prepared material. Step (e) Drying: Dry the washed material. Step (f) Crushing: Crush the dried cobalt carbonate to obtain a cobalt carbonate product for reducing spherical cobalt powder.

[0007] Preferably, in step (a), the soluble cobalt salt is one or a mixture of cobalt sulfate, cobalt chloride, and cobalt nitrate; solution C is an ammonia water solution or sodium hydroxide solution with a concentration of 8 - 10 mol / L.

[0008] Preferably, in step (b), the flow rate of solution A is 80 - 100% of the effective volume of the reaction kettle added per hour. When the pH value of the slurry in the reaction kettle drops to 7.9 - 8.0, start adding solution C into the reaction kettle. The flow rate of solution C is 30 - 40% of the flow rate of solution A. When the amount of substance of solution C added into the reaction kettle reaches 90 - 95% of the amount of substance of solution B added into the reaction kettle, stop adding solution C. When the pH value of the slurry in the reaction kettle drops to 7.2 - 7.3, stop adding solution A. During the reaction process, strictly control the reaction temperature at 20 - 25°C and the stirring frequency of the reaction kettle at 45 - 50 Hz.

[0009] Preferably, in step (c), the aging process is that the aging time is 60 - 90 min, the aging temperature is 20 - 25°C, and the stirring frequency during aging is 45 - 50 Hz.

[0010] Preferably, in step (d), the washing equipment is a centrifuge, the filter cloth specification is 8000 - mesh filter cloth, and the washing liquid is deionized water with a temperature of 80 - 90°C.

[0011] Preferably, in step (e), the drying equipment is a vacuum drying oven, the drying temperature is 100 - 120°C, and the moisture content of the dried material is ≤0.5%.

[0012] Preferably, in step (f), the crushing equipment is a jet mill, and the crushing pressure is 0.6 - 0.8 MPa.

[0013] Preferably, in step (f), the indicators of cobalt carbonate for the spherical cobalt powder are as follows: D 50 ≤1.0 μm, Co% ≥ 48%, and AD is 0.2 - 0.3 g / cm 3 , and the microscopic morphology is spherical granular.

[0014] The beneficial effects of the present invention are as follows: A cobalt carbonate is formed by reacting a soluble cobalt salt solution with an ammonium bicarbonate solution and an ammonia water / sodium hydroxide solution. The specific steps are to drop the cobalt solution into the ammonium bicarbonate solution. When the pH of the synthesis slurry decreases to 7.9 - 8.0, a large amount of carbon dioxide generated by the reaction starts to be released outward. At this time, the prepared ammonia water / sodium hydroxide solution is added to the reaction kettle at a certain flow rate to react with the generated carbon dioxide, and bicarbonate is regenerated to react with the cobalt solution. To avoid adding an excessive amount of ammonia water / sodium hydroxide solution to react with the cobalt solution to form cobalt hydroxide, through experiments, the amount of substance of the ammonia water / sodium hydroxide solution added to the reaction kettle is set to 90 - 95% of the amount of substance of ammonium bicarbonate added to the reaction kettle, so that the prepared substance is pure-phase cobalt carbonate.

[0015] Using this process, the carbonate ions in ammonium bicarbonate can be utilized to the maximum extent, and nano-scale, pure-phase spherical cobalt carbonate can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figures 1 to 2 FIG. is the microscopic morphology diagram of cobalt carbonate for the spherical cobalt powder prepared in Example 1, Figures 3 to 4 FIG. is the microscopic morphology diagram of cobalt carbonate for the spherical cobalt powder prepared in Example 2, Figures 5 to 6 FIG. is the microscopic morphology diagram of cobalt carbonate for the spherical cobalt powder prepared in Example 3, Figure 7 FIG. is the XRD diagram of cobalt carbonate prepared in Example 1. Figure 8 is the process flow chart. DETAILED DESCRIPTION OF THE INVENTION

[0017] As Figure 8 shown, the present invention is a preparation method of cobalt carbonate for spherical cobalt powder, and its steps are as follows: Step (a) Solution preparation: Using a soluble cobalt salt as a raw material, prepare a cobalt solution with a cobalt concentration of 1.8 - 2.0 mol / L as solution A; prepare an ammonium bicarbonate solution with a concentration of 2.8 - 3.0 mol / L as solution B, and prepare an ammonia water or sodium hydroxide solution as solution C; Step (b) Synthesis reaction: Add solution B, which accounts for 30 - 35% of the volume of the reaction kettle, into the reaction kettle. Then add solution A into the reaction kettle at a preset flow rate for the synthesis reaction. When the pH value of the slurry in the reaction kettle drops to the preset value, start adding a fixed amount of solution C into the reaction kettle at a preset flow rate. After the quantitative solution C is completely added into the reaction kettle, stop adding solution C. When the pH value of the slurry continues to drop to the preset value, stop adding solution A. During the reaction process, strictly control the flow rates of solutions A and C, the reaction temperature, and the stirring intensity. Step (c) Aging: After the synthesis reaction ends, stop adding liquid and start aging. Step (d) Washing: After aging, wash the prepared material. Step (e) Drying: Dry the washed material. Step (f) Crushing: Crush the dried cobalt carbonate to obtain the cobalt carbonate product for reducing spherical cobalt powder.

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Example 1:

[0019] The production steps are the same as above and will not be repeated here. The specific parameters in each step are as follows: Using cobalt sulfate as the raw material, prepare a cobalt solution with a cobalt concentration of 1.8 mol / L as solution A; prepare an ammonium bicarbonate solution with a concentration of 2.8 mol / L as solution B, and prepare an ammonia water solution with a concentration of 8 mol / L as solution C.

[0020] The synthesis reaction is carried out in a 5 L reaction kettle. Add 1.5 L of solution B into the reaction kettle, and then add solution A into the reaction kettle at a flow rate of 4 L / h to react with solution B. When the reaction lasts for about 7 min, the pH value of the slurry in the reaction kettle drops to 7.9 - 8.0. Start adding 0.48 L of solution C into the reaction kettle at a flow rate of 1.6 L / h. The amount of substance of solution C added into the reaction kettle is about 91% of the amount of substance of B added into the reaction kettle. After 0.48 L of solution C is completely added into the reaction kettle, stop adding solution C. When the synthesis lasts for about 30 min, the pH value of the synthesis slurry drops to 7.2 - 7.3, and stop adding liquid. During the synthesis process, strictly control the reaction temperature at 24 - 25 °C and the stirring frequency of the reaction kettle at 50 Hz.

[0021] After the synthesis reaction ends, stop adding liquid and start aging. The aging time is 90 min, the aging temperature is 24 - 25 °C, and the stirring frequency during aging is 50 Hz.

[0022] After aging, the slurry is washed using a centrifuge and a filter cloth with a mesh size of 8000. The washing liquid is hot pure water at 80 °C. The washing is ended when the S content of the washed material is ≤ 0.02%.

[0023] The washed cobalt carbonate is dried in a vacuum drying oven at a drying temperature of 100 °C. The drying is ended when the water content in the cobalt carbonate is ≤ 0.5%.

[0024] The dried material is crushed on a jet mill with a crushing pressure of 0.6 MPa.

[0025] The physical and chemical indexes of the prepared spherical cobalt powder using cobalt carbonate are as follows: D 50 : 0.83 µm, AD: 0.26 g / cm 3 , Co%: 48.07%, microscopic morphology Figures 1 to 2 . Example 2:

[0026] The production steps are the same as above and will not be elaborated here. The specific parameters in each step are as follows: Using cobalt chloride as the raw material, a cobalt solution with a cobalt concentration of 1.9 mol / L is prepared as solution A; a ammonium bicarbonate solution with a concentration of 2.9 mol / L is prepared as solution B, and an ammonia water solution with a concentration of 9 mol / L is prepared as solution C.

[0027] The synthesis reaction is carried out in a 5 L reaction kettle. 1.6 L of solution B is added to the reaction kettle, and then solution A is added to the reaction kettle at a flow rate of 4.5 L / h to react with solution B. When the reaction lasts for about 6 min, the pH value of the slurry in the reaction kettle drops to 7.9 - 8.0. Then, 0.48 L of solution C is added to the reaction kettle at a flow rate of 1.6 L / h. The amount of substance of solution C added to the reaction kettle is about 93% of the amount of substance of solution B added to the reaction kettle. After 0.48 L of solution C is completely added to the reaction kettle, the addition of solution C is stopped. When the synthesis lasts for about 30 min, the pH value of the synthesis slurry drops to 7.2 - 7.3, and the addition of liquid is stopped. During the synthesis process, the reaction temperature is strictly controlled at 22 - 23 °C, and the stirring frequency of the reaction kettle is 48 Hz.

[0028] After the synthesis reaction ends, the addition of liquid is stopped, and aging starts. The aging time is 75 min, the aging temperature is 22 - 23 °C, and the stirring frequency during aging is 48 Hz.

[0029] After aging, the slurry is washed using a centrifuge and a filter cloth with a mesh size of 8000. The washing liquid is hot pure water at 85 °C. The washing is ended when the chlorine content in the washed material is ≤ 0.02%.

[0030] The washed cobalt carbonate is dried in a vacuum drying oven at a drying temperature of 110 °C. The drying is ended when the water content in the cobalt carbonate is ≤ 0.5%.

[0031] The dried material is crushed on a jet mill, and the crushing pressure is 0.7 MPa.

[0032] The physical and chemical indexes of the spherical cobalt powder prepared with cobalt carbonate are as follows: D 50 : 0.91 µm, AD: 0.22 g / cm 3 , Co%: 48.89%, and the microscopic morphology is shown in Figures 3 to 4 . Example 3:

[0033] The production steps are the same as above and will not be elaborated here. The specific parameters in each step are as follows: Using cobalt nitrate as the raw material, a cobalt solution with a cobalt concentration of 2.0 mol / L is prepared as solution A; an ammonium bicarbonate solution with a concentration of 3.0 mol / L is prepared as solution B, and a sodium hydroxide solution with a concentration of 10 mol / L is prepared as solution C.

[0034] The synthesis reaction is carried out in a 5 L reaction kettle. Add 1.75 L of solution B into the reaction kettle, and then add solution A into the reaction kettle at a flow rate of 5.0 L / h to react with solution B. When the reaction lasts for about 5 min, the pH value of the slurry in the reaction kettle drops to 7.9 - 8.0. Then, start to add 0.48 L of solution C into the reaction kettle at a flow rate of 2 L / h. The amount of substance of solution C added into the reaction kettle is about 91.5% of the amount of substance of B added into the reaction kettle. After 0.48 L of solution C is completely added into the reaction kettle, stop adding solution C. When the synthesis lasts for about 28 min, the pH value of the synthesis slurry drops to 7.2 - 7.3, and stop adding liquid. During the synthesis process, strictly control the reaction temperature at 20 - 21 °C, and the stirring frequency of the reaction kettle is 45 Hz.

[0035] After the synthesis reaction is completed, stop adding liquid and start aging. The aging time is 60 min, the aging temperature is 20 - 21 °C, and the stirring frequency during aging is 45 Hz.

[0036] After aging, the slurry is washed with a centrifuge and a filter cloth with 8000 meshes. The washing liquid is hot pure water at 90 °C. When the sodium content of the washed material ≤ 0.02%, the washing ends.

[0037] The washed cobalt carbonate is dried in a vacuum drying oven at a drying temperature of 120 °C. When the water content in the cobalt carbonate ≤ 0.5%, the drying ends.

[0038] The dried material is crushed on a jet mill, and the crushing pressure is 0.8 MPa.

[0039] The physical and chemical indexes of the spherical cobalt powder prepared with cobalt carbonate are as follows: D 50 : 0.48 µm, AD: 0.28 g / cm 3, Co%: 48.94%, the microscopic morphology is shown in Figures 5 to 6 .

Claims

1. A preparation method of cobalt carbonate for spherical cobalt powder, characterized in that, The steps are as follows: Step (a) Solution preparation: Using soluble cobalt salt as raw material, prepare a cobalt solution with a cobalt concentration of 1.8 - 2.0 mol / L as Solution A; prepare an ammonium bicarbonate solution with a concentration of 2.8 - 3.0 mol / L as Solution B, and prepare an ammonia water or sodium hydroxide solution as Solution C. Step (b) Synthesis reaction: Add Solution B accounting for 30 - 35% of the reaction kettle volume into the reaction kettle, then add Solution A into the reaction kettle at a preset flow rate for synthesis reaction. When the pH value of the slurry in the reaction kettle drops to a preset value, start adding a fixed amount of Solution C into the reaction kettle at a preset flow rate. After the quantitative Solution C is completely added into the reaction kettle, stop adding Solution C. When the pH value of the slurry continues to drop to the preset value, stop adding Solution A. During the reaction process, strictly control the flow rates of Solutions A and C, reaction temperature, and stirring intensity. Step (c) Aging: After the synthesis reaction ends, stop adding liquid and start aging. Step (d) Washing: After aging ends, wash the prepared material. Step (e) Drying: Dry the washed material. Step (f) Crushing: Crush the dried cobalt carbonate to obtain a cobalt carbonate product for reducing spherical cobalt powder.

2. The preparation method of cobalt carbonate for spherical cobalt powder according to claim 1, characterized in that: In the step (a), the soluble cobalt salt is cobalt sulfate, or cobalt chloride, or cobalt nitrate, or a mixture of several; Solution C is an ammonia water solution or sodium hydroxide solution with a concentration of 8 - 10 mol / L.

3. The preparation method of cobalt carbonate for spherical cobalt powder according to claim 1, characterized in that: In the step (b), the flow rate of Solution A is 80 - 100% of the effective volume of the reaction kettle added per hour. When the pH value of the slurry in the reaction kettle drops to 7.9 - 8.0, start adding Solution C into the reaction kettle. The flow rate of Solution C is 30 - 40% of the flow rate of Solution A. When the amount of substance of Solution C added into the reaction kettle reaches 90 - 95% of the amount of substance of Solution B added into the reaction kettle, stop adding Solution C. When the pH value of the slurry in the reaction kettle drops to 7.2 - 7.3, stop adding Solution A. During the reaction process, strictly control the reaction temperature at 20 - 25 °C and the stirring frequency of the reaction kettle at 45 - 50 Hz.

4. The preparation method of cobalt carbonate for spherical cobalt powder according to claim 1, characterized in that: In the step (c), the aging process is that the aging time is: 60 - 90 min, the aging temperature is: 20 - 25 °C, and the stirring frequency during aging is: 45 - 50 Hz.

5. The preparation method of cobalt carbonate for spherical cobalt powder according to claim 1, characterized in that: In the step (d), the washing equipment is a centrifuge, the filter cloth specification is 8000 - mesh filter cloth, and the washing liquid is deionized water with a temperature of 80 - 90 °C.

6. The preparation method of cobalt carbonate for spherical cobalt powder according to claim 1, characterized in that: In the step (e), the drying equipment is a vacuum drying oven, the drying temperature is 100 - 120 °C, and the moisture content of the dried material is ≤ 0.5%.

7. The preparation method of cobalt carbonate for spherical cobalt powder according to claim 1, characterized in that: In the step (f), the crushing equipment is a jet mill, and the crushing pressure is 0.6 - 0.8 MPa.

8. The preparation method of cobalt carbonate for spherical cobalt powder according to claim 1, characterized in that: In the step (f), the indexes of the spherical cobalt powder with cobalt carbonate are: D 50 ≤1.0 μm, Co% ≥ 48%, the apparent density (AD) is: 0.2 - 0.3 g / cm 3 , and the microscopic morphology is spherical granular.

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