A method for recovering cobalt from tungsten carbide waste containing cobalt

Abstract

The application provides a method for recovering cobalt from cobalt-containing tungsten carbide waste, and belongs to the technical field of smelting and recovery.The powder of the cobalt-containing tungsten carbide waste and sulfuric acid are calcined under a protective atmosphere, so that cobalt forms water-soluble cobalt sulfate, tungsten carbide does not react and remains tungsten carbide phase without loss; the reaction of tungsten carbide, oxygen and cobalt to form cobalt tungstate in an air atmosphere or an oxygen atmosphere can be avoided, thereby reducing the loss of tungsten and cobalt. The application adopts microwave calcination, and compared with the conventional wet acid leaching process, the microwave calcination has a higher reaction temperature, can promote the reaction of cobalt in the cobalt-containing tungsten carbide waste and acid to generate cobalt sulfate, and can heat from inside to outside, reduce the calcination temperature and shorten the calcination time; the microwave calcination uniformly heats the inside and the surface of the cobalt-containing tungsten carbide waste, reduces the calcination temperature and avoids the decomposition of surface sulfuric acid caused by uneven heating.

Description

Technical Field

[0001] This invention belongs to the field of smelting and recycling technology, specifically relating to a method for recovering cobalt from cobalt-containing tungsten carbide waste. Background Technology

[0002] Cobalt-containing tungsten carbide waste is rich in tungsten and cobalt, both of which are valuable strategic reserve resources. Comprehensive recycling of cobalt-containing tungsten carbide waste can not only save energy, reduce costs, and decrease environmental pollution, but also further reduce dependence on primary mineral resources, which is of great significance for promoting the stable and sustainable development of the industry.

[0003] Currently, the method for preparing ammonium paratungstate from cobalt-containing tungsten carbide waste is as follows: oxidize and roast the cobalt-containing tungsten carbide waste, dissolve it in ammonia, mix the ammonia solution with phosphoric acid and hydrochloric acid to obtain ammonium phosphotungstate, then dissolve the solid ammonium phosphotungstate in ammonia to remove impurities, and finally evaporate and crystallize the solution to obtain ammonium paratungstate.

[0004] However, the oxidation roasting in this method is carried out at high temperatures of 500–900°C, which generates cobalt tungstate phase. As a result, when the roasted material containing cobalt tungstate phase is dissolved in ammonia, tungsten cannot be effectively dissolved and instead enters the slag in the form of cobalt tungstate. At the same time, this method does not recover cobalt, resulting in a high loss rate of tungsten and cobalt and a low yield (oxidation roasting forms tungsten trioxide. When cobalt is present in the raw material, cobalt tungstate will be formed during oxidation roasting. Cobalt tungstate is more difficult to dissolve than tungsten trioxide, so it enters the slag and carries away tungsten and cobalt, affecting the yield of tungsten and cobalt). Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for recovering cobalt from cobalt-containing tungsten carbide waste. The method provided by the present invention can avoid the formation of cobalt tungstate phase during roasting, thereby reducing the loss rate of tungsten and cobalt and increasing the yield.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a method for recovering cobalt from cobalt-containing tungsten carbide waste, comprising the following steps:

[0008] The powder of cobalt-containing tungsten carbide waste was mixed with sulfuric acid and microwave roasted under a protective atmosphere to obtain roasted residue containing cobalt sulfate and tungsten carbide.

[0009] The roasted residue was ball-milled and water-leached to separate the solid and liquid components, yielding tungsten carbide slag and a cobalt sulfate aqueous solution containing iron and aluminum impurities.

[0010] The iron and aluminum impurities in the cobalt sulfate aqueous solution containing iron and aluminum impurities are removed to obtain a cobalt sulfate aqueous solution with low impurity content.

[0011] The low-impurity cobalt sulfate aqueous solution is mixed with the cobalt extraction organic phase to extract cobalt ions, thereby obtaining an organic phase containing cobalt ions.

[0012] The organic phase containing cobalt ions was back-extracted with sulfuric acid to obtain a solution containing cobalt sulfate.

[0013] Preferably, the powder particle size of the cobalt-containing tungsten carbide waste is ≤75μm.

[0014] Preferably, the sulfuric acid has a mass concentration of 60-70%; the mass of the sulfuric acid is 40-60% of the mass of the cobalt-containing tungsten carbide waste.

[0015] Preferably, the microwave roasting temperature is 200-260°C, the time is 60-180 min, and the power is 1-1.5 kW.

[0016] Preferably, in the ball milling water immersion, the liquid-to-solid ratio is (3-6) mL: 1 g.

[0017] Preferably, the removal of iron and aluminum impurities from the cobalt sulfate aqueous solution includes the following steps:

[0018] The cobalt sulfate aqueous solution containing iron and aluminum impurities is mixed with an oxidant, and the pH of the resulting mixed solution is adjusted to 3.5-4.0. Iron and aluminum ions form precipitates, and solid-liquid separation is achieved to obtain a purified solution.

[0019] The purified liquid and the extraction organic phase were mixed and extracted to obtain a cobalt sulfate aqueous solution with low impurity content.

[0020] Preferably, the cobalt extraction organic phase comprises kerosene, and P507 and / or C272 extractant.

[0021] Preferably, the extractable organic phase comprises P204 extractant and kerosene.

[0022] Preferably, the oxidant includes hydrogen peroxide or sodium chlorate.

[0023] Preferably, the protective atmosphere includes nitrogen or argon.

[0024] This invention provides a method for recovering cobalt from cobalt-containing tungsten carbide waste, comprising the following steps: mixing powdered cobalt-containing tungsten carbide waste with sulfuric acid, and calcining it under a protective atmosphere using microwave to obtain calcined slag containing cobalt sulfate and tungsten carbide; ball milling and water leaching the calcined slag to separate the solid and liquid phases, obtaining tungsten carbide slag and an aqueous solution of cobalt sulfate containing iron and aluminum impurities; removing the iron and aluminum impurities from the aqueous solution of cobalt sulfate containing iron and aluminum impurities to obtain an aqueous solution of cobalt sulfate with low impurity content; mixing the aqueous solution of cobalt sulfate with low impurity content with a cobalt extraction organic phase to extract cobalt ions, obtaining an organic phase containing cobalt ions; and back-extracting the organic phase containing cobalt ions with sulfuric acid to obtain a solution containing cobalt sulfate.

[0025] This invention involves calcining cobalt-containing tungsten carbide waste powder with sulfuric acid under a protective atmosphere, causing cobalt to form cobalt sulfate, which is easily soluble in water, while tungsten carbide does not react and retains its tungsten carbide phase without loss. This invention can avoid the reaction of tungsten carbide, oxygen, and cobalt to form cobalt tungstate in an air or oxygen atmosphere, thereby reducing the loss of tungsten and cobalt.

[0026] This invention employs microwave roasting, which, compared to conventional wet acid leaching processes, results in a higher reaction temperature. This promotes the full reaction of cobalt with acid in cobalt-containing tungsten carbide waste to generate cobalt sulfate, raising the temperature from the inside out, thus reducing the roasting temperature and shortening the roasting time. Microwave roasting also ensures that the interior and surface of the cobalt-containing tungsten carbide waste are heated evenly, further reducing the roasting temperature and preventing uneven heating that could lead to surface sulfuric acid decomposition.

[0027] Furthermore, the present invention uses powder with a particle size of ≤75μm for the cobalt-containing tungsten carbide waste, which can increase the surface area of ​​the cobalt-containing tungsten carbide waste reacting with sulfuric acid, improve the conversion rate of elemental cobalt in the cobalt-containing tungsten carbide waste into cobalt sulfate by reacting with sulfuric acid, and at the same time improve the leaching rate of cobalt ions during the ball milling and water leaching process of the roasted slag. Detailed Implementation

[0028] This invention provides a method for recovering cobalt from cobalt-containing tungsten carbide waste, comprising the following steps:

[0029] The powder of cobalt-containing tungsten carbide waste was mixed with sulfuric acid and microwave roasted under a protective atmosphere to obtain roasted residue containing cobalt sulfate and tungsten carbide.

[0030] The roasted residue was ball-milled and water-leached to separate the solid and liquid components, yielding tungsten carbide slag and a cobalt sulfate aqueous solution containing iron and aluminum impurities.

[0031] The iron and aluminum impurities in the cobalt sulfate aqueous solution containing iron and aluminum impurities are removed to obtain a cobalt sulfate aqueous solution with low impurity content.

[0032] The low-impurity cobalt sulfate aqueous solution is mixed with the cobalt extraction organic phase to extract cobalt ions, thereby obtaining an organic phase containing cobalt ions.

[0033] The organic phase containing cobalt ions was back-extracted with sulfuric acid to obtain a solution containing cobalt sulfate.

[0034] Unless otherwise specified, all materials and equipment used in this invention are commercially available products.

[0035] This invention involves mixing cobalt-containing tungsten carbide waste powder with sulfuric acid and then microwave-roasting it under a protective atmosphere to obtain roasted residue containing cobalt sulfate and tungsten carbide.

[0036] In this invention, the powder particle size of the cobalt-containing tungsten carbide waste is ≤75μm. In this invention, the powder of the cobalt-containing tungsten carbide waste is obtained by ball milling the cobalt-containing tungsten carbide waste; the cobalt-containing tungsten carbide waste preferably originates from waste generated during the production and processing of cemented carbide.

[0037] In this invention, the composition of the cobalt-containing tungsten carbide waste preferably includes: 80-90 wt% tungsten carbide, 5-7 wt% cobalt, and the balance being other impurity elements. In an embodiment of this invention, specifically, it comprises 80-90 wt% tungsten carbide, 5-7 wt% cobalt, 0.5-1.0 wt% aluminum oxide, 0.3-5 wt% iron oxide (Fe2O3), 0.1-0.4 wt% calcium oxide, and the balance being other impurity elements.

[0038] In this invention, the ball milling is preferably wet ball milling; the ball milling medium preferably includes water or ethanol; the solid-liquid ratio of the cobalt-containing tungsten carbide waste and the medium in the ball milling is preferably (0.7-1.5) g:(1-1.5) mL, and in the embodiments of this invention, it can specifically be 0.7 g:1 mL, 0.7 g:1.5 mL, 1 g:1.0 mL, or 1 g:1.5 mL; the ball milling speed is preferably 200-400 r / min, and in the embodiments of this invention, it can specifically be 200 r / min, 300 r / min, 350 r / min, or 400 r / min; the ball milling time is preferably 20-90 min, and in the embodiments of this invention, it can specifically be 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, or 90 min.

[0039] This invention mechanically activates (ball mills) cobalt-containing tungsten carbide waste, controlling the powder particle size of the cobalt-containing tungsten carbide waste to ≤75μm. This increases the surface area of ​​the cobalt-containing tungsten carbide waste in reaction with sulfuric acid, improves the conversion rate of elemental cobalt in the cobalt-containing tungsten carbide waste into cobalt sulfate by reaction with sulfuric acid, and also improves the leaching rate of cobalt ions during the ball milling and water leaching process of the roasted slag.

[0040] In this invention, the mass concentration of the sulfuric acid is preferably 60-70%, and in the embodiments of this invention, it can be 60%, 65% or 70%; the mass of the sulfuric acid is 40-60% of the mass of the cobalt-containing tungsten carbide waste, and in the embodiments of this invention, it can be 40%, 50% or 60%.

[0041] In this invention, the protective atmosphere preferably includes nitrogen or argon; the microwave roasting temperature is preferably 200–260°C, and in embodiments of this invention, it can specifically be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, or 260°C; the microwave roasting time is preferably 60–180 min, and in embodiments of this invention, it can specifically be 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, or 180 min; the microwave roasting power is preferably 1–1.5 kW, and in embodiments of this invention, it can specifically be 1 kW, 1.2 kW, 1.4 kW, or 1.5 kW.

[0042] This invention involves calcining cobalt-containing tungsten carbide waste powder with sulfuric acid under a protective atmosphere, causing cobalt to form cobalt sulfate, which is easily soluble in water, while tungsten carbide does not react and retains its tungsten carbide phase without loss. This invention can avoid the reaction of tungsten carbide, oxygen, and cobalt to form cobalt tungstate in an air or oxygen atmosphere, thereby reducing the loss of tungsten and cobalt.

[0043] This invention employs microwave roasting, which, compared to conventional wet acid leaching processes, results in a higher reaction temperature. This promotes the full reaction of cobalt with acid in cobalt-containing tungsten carbide waste to generate cobalt sulfate, raising the temperature from the inside out, thus reducing the roasting temperature and shortening the roasting time. Microwave roasting also ensures that the interior and surface of the cobalt-containing tungsten carbide waste are heated evenly, further reducing the roasting temperature and preventing uneven heating that could lead to surface sulfuric acid decomposition.

[0044] After obtaining the roasted slag containing cobalt sulfate and tungsten carbide, the present invention ball-mills and leaches the roasted slag with water to separate the solid and liquid phases, thereby obtaining tungsten carbide slag and an aqueous solution of cobalt sulfate containing iron and aluminum impurities.

[0045] In this invention, the liquid-to-solid ratio during ball milling and water immersion is preferably (3-6) mL:1g. In embodiments of this invention, it can specifically be 3 mL:1g, 4 mL:1g, or 6 mL:1g. The rotational speed of the ball milling and water immersion is preferably 200-400 r / min. In embodiments of this invention, it can specifically be 200 r / min, 300 r / min, 350 r / min, or 400 r / min. The ball milling time is preferably 30-120 min. In embodiments of this invention, it can specifically be 30 min, 40 min, 50 min, 60 min, 80 min, 90 min, 100 min, or 120 min.

[0046] In this invention, the solid-liquid separation preferably includes filtration. The leaching of cobalt sulfate can be enhanced by ball milling and water leaching.

[0047] After obtaining the cobalt sulfate aqueous solution containing iron and aluminum impurities, the present invention removes the iron and aluminum impurities from the cobalt sulfate aqueous solution to obtain a cobalt sulfate aqueous solution with low impurity content. In the present invention, the removal of iron and aluminum impurities from the cobalt sulfate aqueous solution preferably includes the following steps:

[0048] The cobalt sulfate aqueous solution containing iron and aluminum impurities is mixed with an oxidant, and the pH of the resulting mixed solution is adjusted to 3.5-4.0. Iron and aluminum ions form precipitates, and solid-liquid separation is performed (referred to as the first solid-liquid separation) to obtain a purified solution.

[0049] The purified liquid and the extraction organic phase were mixed and extracted to obtain a cobalt sulfate aqueous solution with low impurity content.

[0050] In this invention, the oxidant preferably includes hydrogen peroxide or sodium chlorate; the mass concentration of the hydrogen peroxide is preferably 30%. In this invention, when the oxidant is sodium chlorate, the following chemical reaction occurs:

[0051] 6Fe 2+ +ClO3 - +6H + =6Fe 3+ +Cl - +3H2O Formula 1;

[0052] Fe 3+ +2H₂O=FeOOH↓+3H + Formula 2;

[0053] In this invention, when the oxidant is hydrogen peroxide, the following chemical reaction occurs:

[0054] 6Fe 2+ +H₂O₂ + 2H₂ + =2Fe 3+2H2O (Formula 3);

[0055] Fe 3+ +2H₂O=FeOOH↓+3H + Equation 4;

[0056] In this invention, the amount of oxidant is calculated according to the ratio in the above reaction equation, and is preferably 1.5 to 2.0 times the theoretical amount.

[0057] In this invention, the first solid-liquid separation preferably includes filtration; the extracted organic phase preferably includes P204 extractant and kerosene.

[0058] In this invention, the mass of the P204 extractant is preferably 20-35% of the total mass of the extracted organic phase. In specific embodiments of this invention, it can be 20%, 25%, 30%, or 35%. In this invention, the volume of the extracted organic phase is preferably 0.3-0.5 times the volume of the purified liquid.

[0059] This invention involves mixing an aqueous solution of cobalt sulfate containing iron and aluminum impurities with an oxidant, and adjusting the pH of the resulting mixed solution to 3.5–4.0. This process effectively removes most of the iron and aluminum ions. Specifically, ferric iron is converted into FeOOH precipitate, and aluminum ions are converted into aluminum hydroxide precipitate, which is then removed by filtration. Furthermore, this invention involves mixing the purified solution with an extraction organic phase for extraction, which further removes iron and aluminum ions, as well as most other impurities (such as calcium ions).

[0060] After obtaining the low-impurity cobalt sulfate aqueous solution, the present invention mixes the low-impurity cobalt sulfate aqueous solution with the cobalt extraction organic phase to extract cobalt ions, thereby obtaining an organic phase containing cobalt ions.

[0061] In this invention, the cobalt extraction organic phase preferably includes kerosene, as well as P507 and / or C272; the mass of the kerosene is preferably 65-80% of the total mass of the cobalt extractant, and in the embodiments of this invention, it can specifically be 65%, 70%, 75% or 80%; the volume of the cobalt extraction organic phase is preferably 0.5 to 1 times the volume of the low-impurity cobalt sulfate aqueous solution.

[0062] The present invention does not have special requirements for removing iron and aluminum impurities from cobalt sulfate aqueous solution containing iron and aluminum impurities and for extracting cobalt ions; steps well known in the art can be used.

[0063] After obtaining the organic phase containing cobalt ions, the present invention back-extracts the organic phase containing cobalt ions with sulfuric acid to obtain a solution containing cobalt sulfate.

[0064] In this invention, the concentration of sulfuric acid in the back-extraction is preferably 1.0 to 2 mol / L. In the embodiments of this invention, it can be 1 mol / L, 1.5 mol / L or 2 mol / L. The volume ratio of the sulfuric acid to the volume of the organic phase containing cobalt ions is 1:(8 to 9). In the embodiments of this invention, it can be 1:8 or 1:9.

[0065] After the back-extraction is completed, the present invention preferably removes the organic matter from the cobalt sulfate-containing solution, and then obtains cobalt sulfate by evaporation and crystallization.

[0066] The present invention preferably uses activated carbon to remove organic matter from the back-extraction solution (i.e., a solution containing cobalt sulfate). The present invention does not have particular requirements for the evaporation and crystallization method; any method well-known in the art can be used.

[0067] To further illustrate the present invention, the following detailed description of a method for recovering cobalt from cobalt-containing tungsten carbide waste is provided by the present invention in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0068] Example 1

[0069] Cobalt-containing tungsten carbide waste was mixed with water at a solid-liquid ratio of 1g:1.5mL and ball-milled at a speed of 300r / min for 60min. The ball-to-material ratio was 15:1. Solid-liquid separation was performed to obtain cobalt-containing tungsten carbide waste powder. The particle size of the cobalt-containing tungsten carbide waste powder was ≤75μm. The cobalt-containing tungsten carbide waste contained 88.7wt% tungsten carbide, 6.5wt% cobalt, 0.5wt% aluminum oxide, 0.3wt% iron oxide (Fe2O3), 0.1wt% calcium oxide, and the balance being other impurity elements.

[0070] Sulfuric acid was added to the cobalt-containing tungsten carbide waste powder and mixed evenly. The amount of sulfuric acid added was 50% of the mass of the cobalt-containing tungsten carbide waste powder, and the mass concentration of sulfuric acid was 70%. After mixing, the mixture was calcined in a microwave sintering furnace under an argon atmosphere at a temperature of 200°C for 180 min and a power of 1 kW to obtain calcined slag containing cobalt sulfate and tungsten carbide.

[0071] The roasted slag was ball-milled and water-leached at a liquid-to-solid ratio of 4 mL:1 g, a ball milling speed of 300 r / min, a ball-to-material ratio of 10:1, and a time of 60 min. After ball milling, the solid and liquid were separated to obtain tungsten carbide slag and a cobalt sulfate aqueous solution containing iron and aluminum impurities. The cobalt sulfate aqueous solution containing iron and aluminum impurities contained 0.4 g / L of iron, 0.4 g / L of aluminum, and 0.2 g / L of calcium.

[0072] Add sodium chlorate at 2.0 times the theoretical amount to the cobalt sulfate aqueous solution containing iron and aluminum impurities, and then adjust the pH to 4.0. The iron and aluminum impurities precipitate, with iron ions forming hydrated iron oxide and aluminum ions forming aluminum hydroxide, which are then removed by filtration to obtain a purified solution. The purified solution is then subjected to extraction of an organic phase to remove impurities. The extracted organic phase consists of 30wt% P2O4 + 70wt% kerosene, and its volume is 0.5 times that of the purified solution, resulting in a cobalt sulfate aqueous solution with low impurity content. The cobalt sulfate aqueous solution with low impurity content contains 0.1 mg / L of iron, 2.2 mg / L of aluminum, and 1.1 mg / L of calcium.

[0073] A low-impurity cobalt sulfate aqueous solution is separated from cobalt by cobalt extraction organic phase. The cobalt extraction organic phase is composed of 35wt% P507 + 65wt% kerosene. The volume of the cobalt extraction organic phase is the same as that of the low-impurity cobalt sulfate aqueous solution, thus obtaining an organic phase containing cobalt ions.

[0074] The organic phase containing cobalt ions is back-extracted with sulfuric acid at a concentration of 1 mol / L, and the volume ratio of the sulfuric acid to the organic phase containing cobalt ions is 1:9. Cobalt sulfate is then obtained by evaporation and crystallization.

[0075] Results: The cobalt removal rate was 96.4%, and the overall yield of cobalt sulfate preparation was 95.1%.

[0076] Example 2

[0077] The preparation steps are the same as in Example 1, except that the microwave roasting temperature is 250°C.

[0078] The cobalt sulfate aqueous solution containing iron and aluminum impurities has an iron content of 0.5 g / L, an aluminum content of 0.6 g / L, and a calcium content of 0.2 g / L.

[0079] A low-impurity cobalt sulfate aqueous solution was obtained, containing 0.2 mg / L iron, 2.4 mg / L aluminum, and 1.5 mg / L calcium.

[0080] Results: Tungsten carbide slag was obtained by cobalt removal, with a cobalt removal rate of 99.6% and an overall yield of 98.1% for the preparation of cobalt sulfate.

[0081] Example 3

[0082] Cobalt-containing tungsten carbide waste was mixed with water at a solid-liquid ratio of 1g:1.0mL and ball-milled at a speed of 350r / min for 90min with a ball-to-material ratio of 20:1. Solid-liquid separation was performed to obtain cobalt-containing tungsten carbide waste powder. The particle size of the cobalt-containing tungsten carbide waste powder was ≤75μm. The composition of the cobalt-containing tungsten carbide waste was the same as that in Example 1.

[0083] Sulfuric acid was added to cobalt-containing tungsten carbide waste powder and mixed evenly. The amount of sulfuric acid added was 50% of the mass of cobalt-containing tungsten carbide waste, and the mass concentration of sulfuric acid was 70%. After mixing, the mixture was calcined in a microwave sintering furnace under an argon atmosphere at a temperature of 200℃ for 180 min and a power of 1.5 kW to obtain calcined slag containing cobalt sulfate and tungsten carbide.

[0084] The roasted slag was ball-milled and water-leached at a liquid-to-solid ratio of 4 mL:1 g, a ball milling speed of 200 r / min, a ball-to-material ratio of 15:1, and a time of 60 min. Solid-liquid separation was then performed to obtain tungsten carbide slag and a cobalt sulfate aqueous solution containing iron and aluminum impurities.

[0085] A cobalt sulfate aqueous solution containing iron and aluminum impurities has an iron content of 0.4 g / L, an aluminum content of 0.5 g / L, and a calcium content of 0.1 g / L. Sodium chlorate (1.5 times the theoretical amount) is added to the solution to adjust the pH to 4.0. After filtration, the iron and aluminum impurities precipitate and are removed, yielding a purified solution. The purified solution is then subjected to extraction of an organic phase to remove impurities. The organic phase consists of 25% P2O4 + 75% kerosene, and its volume is 0.5 times that of the purified solution, resulting in a cobalt sulfate aqueous solution with low impurity content. The low impurity content cobalt sulfate aqueous solution contains an iron content of 0.6 mg / L, an aluminum content of 3.5 mg / L, and a calcium content of 6.1 mg / L.

[0086] A low-impurity cobalt sulfate aqueous solution is separated from cobalt by cobalt extraction organic phase. The cobalt extraction organic phase is composed of 30% P507 + 70% kerosene. The volume of the cobalt extraction organic phase is the same as that of the low-impurity cobalt sulfate aqueous solution, thus obtaining an organic phase containing cobalt ions.

[0087] The organic phase containing cobalt ions is back-extracted with sulfuric acid at a concentration of 2 mol / L, and the volume ratio of the sulfuric acid to the organic phase containing cobalt ions is 1:8. Cobalt sulfate is then obtained by evaporation and crystallization.

[0088] Results: Tungsten carbide slag was obtained by removing cobalt, with a cobalt removal rate of 97.2% and an overall yield of 95.8% for preparing cobalt sulfate.

[0089] Comparative Example 1

[0090] The preparation steps are the same as in Example 1, except that the microwave calcination is carried out in an air atmosphere.

[0091] The cobalt sulfate aqueous solution containing iron and aluminum impurities has an iron content of 0.3 g / L, an aluminum content of 0.4 g / L, and a calcium content of 0.2 g / L.

[0092] A cobalt sulfate aqueous solution with low impurity content was obtained, containing 0.1 mg / L iron, 2.3 mg / L aluminum, and 1.6 mg / L calcium.

[0093] Results: Tungsten carbide slag was obtained by cobalt removal, with a cobalt removal rate of 63.7% and an overall yield of 62.5% for the preparation of cobalt sulfate.

[0094] Comparative Example 2

[0095] The preparation steps are the same as in Example 1, except that the calcination is carried out in a conventional sintering furnace.

[0096] The cobalt sulfate aqueous solution containing iron and aluminum impurities has an iron content of 0.3 g / L, an aluminum content of 0.3 g / L, and a calcium content of 0.1 g / L.

[0097] A cobalt sulfate aqueous solution with low impurity content was obtained, containing 0.2 mg / L iron, 2.4 mg / L aluminum, and 1.7 mg / L calcium.

[0098] Results: Tungsten carbide slag was obtained by cobalt removal, with a cobalt removal rate of 90.7% and an overall yield of 89.2% for preparing cobalt sulfate.

[0099] Comparative Example 3

[0100] The preparation steps are the same as in Example 1, except that the ball milling and water leaching step of the calcined slag is replaced by: crushing the calcined slag through a 100-mesh sieve, leaching it in water for 60 minutes at a liquid-to-solid ratio of 4 mL:1 g, and separating the solid and liquid to obtain tungsten carbide slag and a cobalt sulfate aqueous solution containing iron and aluminum impurities. The cobalt sulfate aqueous solution containing iron and aluminum impurities contains 0.2 g / L of iron, 0.3 g / L of aluminum, and 0.1 g / L of calcium.

[0101] A cobalt sulfate aqueous solution with low impurity content was obtained, containing 0.1 mg / L iron, 2.3 mg / L aluminum, and 1.6 mg / L calcium.

[0102] Results: Tungsten carbide slag was obtained by removing cobalt, with a cobalt removal rate of 93.2% and an overall yield of 91.7% for preparing cobalt sulfate.

[0103] As can be seen from the embodiments and comparative examples of the present invention, the method provided by the present invention has a high overall yield for preparing cobalt sulfate and a high cobalt removal rate in cobalt-containing tungsten carbide waste.

[0104] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for recovering cobalt from cobalt-containing tungsten carbide waste, comprising the following steps: Cobalt-containing tungsten carbide waste powder is mixed with sulfuric acid and microwave roasted under a protective atmosphere to obtain roasted slag containing cobalt sulfate and tungsten carbide; the particle size of the cobalt-containing tungsten carbide waste powder is ≤75μm. The roasted residue was ball-milled and water-leached to separate the solid and liquid components, yielding tungsten carbide slag and a cobalt sulfate aqueous solution containing iron and aluminum impurities. The iron and aluminum impurities in the cobalt sulfate aqueous solution containing iron and aluminum impurities are removed to obtain a cobalt sulfate aqueous solution with low impurity content. The low-impurity cobalt sulfate aqueous solution is mixed with the cobalt extraction organic phase to extract cobalt ions, thereby obtaining an organic phase containing cobalt ions. The organic phase containing cobalt ions was back-extracted with sulfuric acid to obtain a solution containing cobalt sulfate; The microwave roasting temperature is 200–260°C, the time is 60–180 min, and the power is 1–1.5 kW.

2. The method according to claim 1, characterized in that, The sulfuric acid has a mass concentration of 60-70%; the mass of the sulfuric acid is 40-60% of the mass of the cobalt-containing tungsten carbide waste.

3. The method according to claim 1, characterized in that, During the ball milling and water immersion, the liquid-to-solid ratio was (3-6) mL:1 g.

4. The method according to claim 1, characterized in that, The removal of iron and aluminum impurities from a cobalt sulfate aqueous solution includes the following steps: The cobalt sulfate aqueous solution containing iron and aluminum impurities is mixed with an oxidant, and the pH of the resulting mixed solution is adjusted to 3.5-4.

0. Iron and aluminum ions form precipitates, and solid-liquid separation is achieved to obtain a purified solution. The purified liquid and the extraction organic phase were mixed and extracted to obtain a cobalt sulfate aqueous solution with low impurity content.

5. The method according to claim 1, characterized in that, The cobalt extraction organic phase includes kerosene, and P507 and / or C272 extractants.

6. The method according to claim 4, characterized in that, The extracted organic phase includes P204 extractant and kerosene.

7. The method according to claim 4 or 6, characterized in that, The oxidizing agent includes hydrogen peroxide or sodium chlorate.

8. The method according to claim 1, characterized in that, The protective atmosphere includes nitrogen or argon.