A method for recovering cobalt from cobalt-based superalloy scrap

Abstract

The application provides a method for recovering cobalt from cobalt-based high-temperature alloy waste. After the cobalt-based high-temperature alloy waste is effectively destroyed by high-strength mechanical activation, the dense passivation layer of the high-temperature alloy is destroyed, and through three-stage gradient leaching, the cobalt with different leaching difficulties in the waste is separated, and after enrichment and oxidation precipitation, the recovery rate of cobalt in the cobalt-based high-temperature alloy waste is greatly improved; after the obtained cobalt precipitate is dissolved and then extracted and impurities are removed, a high-purity cobalt salt solution can be efficiently prepared, and the recovery of cobalt in the cobalt-based high-temperature alloy waste is realized.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology and relates to a method for recovering cobalt from cobalt-based superalloy waste. Background Technology

[0002] Cobalt-based superalloys, with their excellent high-temperature strength, creep resistance, corrosion resistance, and oxidation resistance, are indispensable core structural materials in high-end fields such as aerospace, gas turbines, energy and power, and precision manufacturing. They are widely used in key components such as turbine blades for aero-engines, combustion chambers, and industrial high-temperature furnace components. During the casting, processing, and decommissioning of cobalt-based superalloy products, a large amount of industrial waste, including scrap, defective products, and scrapped components, is generated. This waste has a high cobalt content and is often accompanied by other precious metals such as tungsten, chromium, nickel, and molybdenum, possessing extremely high resource recycling and reuse value. Cobalt, as a strategic rare metal, faces scarce primary mineral reserves, high mining costs, and a persistent supply-demand gap. Superalloy waste, however, represents high-quality secondary cobalt resources. Efficiently recovering the cobalt from these resources can not only alleviate the industry's pain point of primary cobalt resource shortage and reduce raw material costs in high-end alloy production, but also reduce environmental pollution from mining and waste landfilling. This aligns with the industry's development trend of industrial solid waste resource utilization and green, low-carbon production, possessing significant economic and environmental value.

[0003] Currently, the industry's cobalt recovery processes for cobalt-based superalloy waste mainly rely on traditional hydrometallurgy, pyrometallurgy, and single leaching purification technologies. Pyrometallurgy suffers from high energy consumption at high temperatures, high metal loss rates, poor cobalt recovery selectivity, and the generation of smoke and exhaust pollution, making it difficult to achieve efficient and accurate cobalt recovery. Conventional hydrometallurgical processes often employ a single strong acid direct leaching mode, which is simple but has extremely poor adaptability. The core challenge lies in the fact that cobalt-based superalloys are formed and used under high temperature and complex conditions for extended periods. This results in a dense and highly stable passivation oxide layer forming on the surface and inside the matrix of the waste. This passivation layer has high chemical inertness and effectively prevents the leaching agent from contacting the cobalt element in the matrix, leading to the defects of slow leaching rate, incomplete leaching, and low cobalt dissolution rate in traditional direct leaching processes.

[0004] Existing recycling processes all employ a uniform leaching system, which cannot adapt to the diverse leaching requirements of cobalt. This easily leads to problems such as excessive leaching of easily leached cobalt and large residual amounts of difficult-to-leach cobalt, ultimately resulting in a low overall cobalt recovery rate and significant resource waste. Furthermore, the existing process leachates contain low purity cobalt ions and complex impurity components, making subsequent impurity removal and purification processes cumbersome and prone to secondary cobalt ion loss. This makes it difficult to efficiently prepare high-purity cobalt salt solutions, failing to meet the application requirements of high-end industries for high-purity cobalt raw materials and severely limiting the industrial application of cobalt-based high-temperature alloy waste resource recycling. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for recovering cobalt from cobalt-based superalloy waste. This invention involves using high-intensity mechanical activation to effectively break down the dense passivation layer of the superalloy, followed by three-stage gradient leaching to separate cobalt from the waste at different leaching difficulties. After enrichment and oxidation precipitation, the cobalt recovery rate from the cobalt-based superalloy waste is significantly improved. The obtained cobalt precipitate is then dissolved and extracted and impurities removed to efficiently obtain a high-purity cobalt salt solution, thus achieving the recovery of cobalt from the cobalt-based superalloy waste.

[0006] To achieve this objective, the present invention employs the following technical solution: This invention provides a method for recovering cobalt from cobalt-based superalloy waste, the method comprising the following steps: Activated material was obtained by mechanical grinding and activation of cobalt-based superalloy waste. The activated material is pulped to obtain an activated slurry. The activated slurry is mixed with an oxidant and subjected to oxidative leaching treatment to obtain an oxidative leaching solution and a first leaching residue. The first leaching residue, the first acid solution, and the first oxidant are mixed and subjected to pressure acid leaching to obtain a pressure acid leaching solution and a second leaching residue. The second leaching residue, the second acid solution, and the second oxidant are mixed and subjected to high acid leaching treatment to obtain a high acid leaching solution and a third leaching residue. The oxidizing leachate is mixed with the third oxidant, and after stirring and reaction, alkaline material is added to carry out precipitation reaction to obtain cobalt hydroxide precipitate. The cobalt hydroxide precipitate is mixed with the third acid solution to obtain primary cobalt salt solution. The primary cobalt salt solution is then subjected to extraction and impurity removal treatment to obtain high-purity cobalt salt solution. The slurrying agent used to slurry the activated material includes pressurized acid leaching solution and / or high-acid acid leaching solution.

[0007] The slurrying agent used in the pulping of activated materials described in this invention includes pressurized acid leaching solution and / or high-acid acid leaching solution. The initial slurrying agent is water. The leachate obtained from the initial oxidation leaching is mixed with the leachate obtained from the subsequent oxidation leaching of activated slurry using pressurized acid leaching solution and / or high-acid acid leaching solution as slurrying agent to form an oxidizing leachate for subsequent "mixing with a third oxidizing agent, stirring and reacting, adding alkaline material to carry out a precipitation reaction to obtain cobalt hydroxide precipitate". The oxidizing leachate obtained in the initial step can also be directly subjected to oxidation and precipitation reactions to obtain cobalt hydroxide, but the cobalt yield is low.

[0008] This invention pre-activates cobalt-based superalloy waste through mechanical ball milling, destroying the passivation film on the waste surface and pre-oxidizing insoluble metal carbides, nitrides, and intermetallic compounds, transforming the inert insoluble cobalt phase into an easily leached active cobalt phase. Then, oxidative leaching preferentially leaches out most of the free and active cobalt, yielding an oxidative leachate. Next, pressure acid leaching utilizes a high-temperature, high-pressure environment to break down the semi-stable alloy phase and leach encapsulated cobalt components. Finally, high-acid acid leaching thoroughly decomposes the residual insoluble metal solid solution and alloy framework phase in a high-acidity, strongly corrosive system, deeply recovering residual cobalt (since the leachates obtained from pressure acid leaching and high-acid acid leaching contain a small amount of impurity metal ions, they need to be reused as a slurrying agent, rather than directly mixing the pressure acid leaching solution and high-acid acid leaching solution with the oxidative leachate for oxidation precipitation). The resulting cobalt-rich solution undergoes oxidation and precipitation reactions to obtain cobalt hydroxide precipitate. After acid dissolution, extraction, and impurity removal treatment of the obtained cobalt hydroxide precipitate, a high-purity cobalt salt solution can be obtained.

[0009] Preferably, before the mechanical grinding and activation, the cobalt-based superalloy waste is subjected to turning and crushing treatment; Preferably, the mechanical grinding activation time is 3h~4h.

[0010] Preferably, the mechanical grinding and activation treatment is followed by magnetic separation treatment.

[0011] Preferably, the mechanical grinding activation time is 3h to 4h, for example: 3h, 3.2h, 3.5h, 3.8h or 4h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] Preferably, the solid content of the activated slurry is 10% to 20%, for example: 10%, 12%, 15%, 18% or 20%, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] Preferably, the oxidant includes NaClO3 and / or Na2S2O8.

[0014] Preferably, the mass ratio of cobalt-based superalloy waste to oxidant in the activated slurry is 1:(0.05~0.2), for example: 1:0.05, 1:0.1, 1:0.15, 1:0.2, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] Preferably, the temperature of the oxidative leaching treatment is 50℃~65℃, for example: 50℃, 52℃, 55℃, 60℃ or 65℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, the oxidative leaching treatment time is 2h to 3h, for example: 2h, 2.2h, 2.5h, 2.8h or 3h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Preferably, the first acid solution comprises a sulfuric acid solution.

[0018] Preferably, the solid-liquid mass ratio of the first leaching residue to the first acid solution is 1:(4~5), for example: 1:4, 1:4.2, 1:4.5, 1:4.8 or 1:5, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Preferably, the first oxidant includes hydrogen peroxide.

[0020] Preferably, during the pressurized acid leaching process, oxygen is introduced to apply pressure.

[0021] Preferably, the temperature of the pressure acid leaching treatment is 150℃~180℃, for example: 150℃, 155℃, 160℃, 170℃ or 180℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the pressure of the pressurized acid leaching treatment is 1.5MPa to 2.5MPa, for example: 1.5 MPa, 1.8MPa, 2MPa, 2.2MPa or 2.5MPa, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] Preferably, the pH of the pressurized acid leaching treatment is 1 to 1.5, for example: 1, 1.1, 1.2, 1.4 or 1.5, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the time for the pressurized acid leaching treatment is 3h to 4h, for example: 3h, 3.2h, 3.5h, 3.8h or 4h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the second acid solution comprises a sulfuric acid solution.

[0026] Preferably, the solid-liquid mass ratio of the second leaching residue to the second acid solution is 1:(3~4.5), for example: 1:3, 1:3.2, 1:3.5, 1:4 or 1:4.5, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the second oxidant includes hydrogen peroxide.

[0028] Preferably, the pH of the high-acid leaching treatment is 0.3 to 0.5, for example: 0.3, 0.35, 0.4, 0.45 or 0.5, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the temperature of the high-acid pickling treatment is 85℃~95℃, for example: 85℃, 88℃, 90℃, 92℃ or 95℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the high-acid pickling treatment time is 4h to 5h, for example: 4h, 4.2h, 4.5h, 4.8h or 5h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the third oxidant comprises sodium hypochlorite.

[0032] This invention uses sodium hypochlorite as an oxidant to oxidize low-valence cobalt in the solution into high-valence cobalt ions, while oxidizing low-valence impurity ions such as iron and manganese. Then, alkaline materials are added to precisely control the pH, selectively precipitating cobalt hydroxide, thus achieving preliminary and efficient separation of cobalt from most alkaline earth metals and light metal impurities.

[0033] Preferably, the molar ratio of cobalt ions to the third oxidant in the high-acid leaching solution is 1:(1.2~1.5), for example: 1:1.2, 1:1.25, 1:1.3, 1:1.4 or 1:1.5, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the temperature of the stirring reaction is 45℃~55℃, for example: 45℃, 48℃, 50℃, 52℃ or 55℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the stirring reaction time is 0.5h to 1h, for example: 0.5h, 0.6h, 0.8h, 0.9h or 1h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the alkaline material includes a sodium hydroxide solution.

[0037] Preferably, the pH of the precipitation reaction is 3 to 4.5, for example: 3, 3.2, 3.5, 4 or 4.5, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, the precipitation reaction time is 0.5h to 1h, for example: 0.5h, 0.6h, 0.8h, 0.9h or 1h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the third acid solution comprises sulfuric acid.

[0040] Preferably, the pH of the primary cobalt salt solution is adjusted to 3.5~4 before extraction, for example: 3.5, 3.6, 3.8, 3.9 or 4, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0041] Preferably, the extractant used in the extraction includes P507.

[0042] Preferably, the impurity removal method includes resin impurity removal.

[0043] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0044] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for recovering cobalt from cobalt-based high-temperature alloy waste provided by the present invention is specifically designed for the complex phases and dense structure of waste cobalt-based high-temperature alloys. After the cobalt-based high-temperature alloy waste is mechanically activated with high strength to effectively destroy the dense passivation layer of the high-temperature alloy, the cobalt with different leaching difficulties in the waste is separated by three-stage gradient leaching. After enrichment and oxidation precipitation, the recovery rate of cobalt in cobalt-based high-temperature alloy waste is greatly improved. After dissolving the obtained cobalt precipitate, it can be extracted and impurities removed to efficiently obtain a high-purity cobalt salt solution, thus realizing the recovery of cobalt in cobalt-based high-temperature alloy waste.

[0045] (2) The method for recovering cobalt from cobalt-based high-temperature alloy waste provided by the present invention can obtain a cobalt salt solution with a purity of over 99% and a cobalt recovery rate of over 90.8%. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the process for recovering cobalt from cobalt-based high-temperature alloy waste according to an embodiment of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0048] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0049] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0050] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0051] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined according to its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order in which they are written or in any order that does not conflict with the technology.

[0052] The mass content of each metal element in the cobalt-based superalloy waste used in the embodiments and comparative examples of this invention is as follows: Co:36%, Cr:18%, Ni:29%, Fe:8%, Mo:6%, Ti:2.5%; The cobalt-based high-temperature alloy scrap is first machined, with the spindle speed controlled at 160 rpm and the feed rate at 0.3 mm, to obtain alloy chips. The alloy chips are then ultrasonically cleaned in a 95% ethanol solution, vacuum dried, and non-magnetic impurities are removed by magnetic separation.

[0053] The sulfuric acid used in the embodiments and comparative examples of this invention has a mass percentage concentration of 15%.

[0054] Example 1 This embodiment provides a method for recovering cobalt from cobalt-based superalloy waste. A schematic diagram of the process flow is shown below. Figure 1 As shown, the method includes the following steps: After high-intensity mechanical grinding and activation of cobalt-based high-temperature alloy waste for 3.5 hours, the activated material was obtained through magnetic separation. The activated material was pulped to obtain an activated slurry with a solid content of 15% (the initial pulping agent was water; after obtaining pressurized acid leaching solution and high-acid acid leaching solution, subsequent pulping used pressurized acid leaching solution and high-acid acid leaching solution). The activated slurry was mixed with NaClO3 at a mass ratio of 1:0.1 between the cobalt-based high-temperature alloy waste in the activated slurry and NaClO3. The mixture was then subjected to oxidative leaching treatment at 58°C for 2.5 hours. The mixture was filtered to obtain an oxidative leaching solution and a first leaching residue. The first leaching residue was mixed with sulfuric acid solution at a solid-liquid mass ratio of 1:4.5, hydrogen peroxide was added, the pH was controlled at 1.2, the temperature was 160℃, and the oxygen was pressurized to 2MPa for 3.5h for pressurized acid leaching treatment. The pressurized acid leaching solution and the second leaching residue were obtained by filtration. The second leaching residue was mixed with sulfuric acid solution at a solid-liquid mass ratio of 1:3.5, hydrogen peroxide was added, and the mixture was subjected to high acid leaching treatment for 4.5 hours under the conditions of pH 0.4 and temperature 90℃. The high acid leaching solution and the third leaching residue were obtained by filtration. The oxidative leachate was mixed with sodium hypochlorite (molar ratio of sodium hypochlorite to cobalt ions was 1.4:1), and stirred at 50°C for 0.8 h. Sodium hydroxide solution was added to adjust the pH to 3.8 to carry out the precipitation reaction. The precipitate of cobalt hydroxide was obtained by filtration. The cobalt hydroxide precipitate was mixed with sulfuric acid solution to obtain a primary cobalt salt solution. The primary cobalt salt solution was extracted with P507 extractant, and then back-extracted with sulfuric acid. The back-extracted solution was treated with M-4195 chelating ion exchange resin to remove impurities and obtain a high-purity cobalt salt solution.

[0055] Example 2 This embodiment provides a method for recovering cobalt from cobalt-based superalloy waste. A schematic diagram of the process flow is shown below. Figure 1 As shown, the method includes the following steps: Cobalt-based high-temperature alloy waste was activated by high-intensity mechanical grinding for 4 hours, and then the activated material was obtained by magnetic separation. The activated material was pulped to obtain an activated slurry with a solid content of 10% (the initial pulping agent was water, and after obtaining pressurized acid leaching solution and high acid leaching solution, subsequent pulping used pressurized acid leaching solution and high acid leaching solution). The activated slurry was mixed with NaClO3 at a mass ratio of cobalt-based high-temperature alloy waste to NaClO3 of 1:0.15. The mixture was oxidized and leached at 65°C for 2 hours, and filtered to obtain oxidized leaching solution and first leaching residue. The first leaching residue was mixed with sulfuric acid solution at a solid-liquid mass ratio of 1:4, hydrogen peroxide was added, the pH was controlled at 1, the temperature was 150℃, and the oxygen was pressurized to 2.5MPa for 4 hours for pressurized acid leaching treatment. The pressurized acid leaching solution and the second leaching residue were obtained by filtration. The second leaching residue was mixed with sulfuric acid solution at a solid-liquid mass ratio of 1:3, hydrogen peroxide was added, and the mixture was subjected to high acid leaching treatment for 4 hours under the conditions of pH 0.3 and temperature 90℃. The high acid leaching solution and the third leaching residue were obtained by filtration. The oxidative leachate was mixed with sodium hypochlorite (molar ratio of sodium hypochlorite to cobalt ions was 1.2:1), and stirred at 45°C for 1 hour. Sodium hydroxide solution was added to adjust the pH to 3.5 to carry out the precipitation reaction. The precipitate of cobalt hydroxide was obtained by filtration. The cobalt hydroxide precipitate was mixed with sulfuric acid solution to obtain a primary cobalt salt solution. The primary cobalt salt solution was extracted with P507 extractant, and then back-extracted with sulfuric acid. The back-extracted solution was treated with M-4195 chelating ion exchange resin to remove impurities and obtain a high-purity cobalt salt solution.

[0056] Example 3 This embodiment provides a method for recovering cobalt from cobalt-based superalloy waste. A schematic diagram of the process flow is shown below. Figure 1 As shown, the method includes the following steps: The cobalt-based high-temperature alloy waste was activated by high-intensity mechanical grinding for 3 hours, and then subjected to magnetic separation to obtain activated material. The activated material was pulped to obtain an activated slurry with a solid content of 20% (the initial pulping agent was water, and after obtaining pressurized acid leaching solution and high acid leaching solution, subsequent pulping used pressurized acid leaching solution and high acid leaching solution). The activated slurry was mixed with Na2S2O8 at a mass ratio of cobalt-based high-temperature alloy waste to Na2S2O8 of 1:0.2. The mixture was oxidized and leached at 50°C for 3 hours, and filtered to obtain oxidized leaching solution and first leaching residue. The first leaching residue was mixed with sulfuric acid solution at a solid-liquid mass ratio of 1:5, hydrogen peroxide was added, the pH was controlled at 1.5, the temperature was 180℃, and the oxygen was pressurized to 1.5MPa for 3 hours for pressurized acid leaching treatment. The pressurized acid leaching solution and the second leaching residue were obtained by filtration. The second leaching residue was mixed with sulfuric acid solution at a solid-liquid mass ratio of 1:4.5, hydrogen peroxide was added, and the mixture was subjected to high acid leaching treatment for 5 hours under the conditions of pH 0.5 and temperature 95℃. The high acid leaching solution and the third leaching residue were obtained by filtration. The oxidative leachate was mixed with sodium hypochlorite (molar ratio of sodium hypochlorite to cobalt ions was 1.5:1), and stirred at 55°C for 0.5 h. Sodium hydroxide solution was added to adjust the pH to 4.5 to carry out the precipitation reaction. The precipitate of cobalt hydroxide was obtained by filtration. The cobalt hydroxide precipitate was mixed with sulfuric acid solution to obtain a primary cobalt salt solution. The primary cobalt salt solution was extracted with P507 extractant, and then back-extracted with sulfuric acid. The back-extracted solution was treated with M-4195 chelating ion exchange resin to remove impurities and obtain a high-purity cobalt salt solution.

[0057] Example 4 The only difference between this embodiment and Embodiment 1 is that the mass ratio of cobalt-based superalloy waste to NaClO3 is 1:0.01, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0058] Example 5 The only difference between this embodiment and Embodiment 1 is that the pressure of the pressurized acid leaching treatment is 1 MPa, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0059] Comparative Example 1 The only difference between this comparative example and Example 1 is that no activation is performed; all other conditions and parameters are exactly the same as in Example 1.

[0060] Comparative Example 2 The only difference between this comparative example and Example 1 is that no pressure acid leaching treatment is performed; all other conditions and parameters are exactly the same as in Example 1.

[0061] Comparative Example 3 The only difference between this comparative example and Example 1 is that the high-acid pickling treatment is not performed; all other conditions and parameters are exactly the same as in Example 1.

[0062] Performance testing: The purity of the cobalt salt solution and the cobalt recovery rate were determined, and the test results are shown in Table 1. Table 1 As can be seen from Table 1, the method for recovering cobalt from cobalt-based high-temperature alloy waste provided by the present invention can achieve a cobalt salt solution purity of over 99% and a cobalt recovery rate of over 90.8%.

[0063] A comparison of Examples 1 and 4 shows that in the method for recovering cobalt from cobalt-based superalloy waste provided by the present invention, the amount of oxidant added affects the recovery effect. When the mass ratio of cobalt-based superalloy waste to composite solid oxidant is controlled at 1:(0.05~0.2), the recovery effect is better; if the amount of oxidant added is too low, the oxidation precipitation is incomplete and the recovery rate is low.

[0064] A comparison of Examples 1 and 5 shows that in the method for recovering cobalt from cobalt-based high-temperature alloy waste provided by the present invention, the pressure of the pressurized acid leaching treatment affects the recovery effect. Controlling the pressure of the pressurized acid leaching treatment at 1.5MPa~2.5MPa results in a better recovery effect; if the pressure of the pressurized acid leaching treatment is too low, the leaching is incomplete and the recovery rate is low.

[0065] As can be seen from the comparison between Example 1 and Comparative Example 1, the present invention pre-activates the cobalt-based high-temperature alloy waste by mechanical ball milling, destroys the passivation film on the surface of the waste, pre-oxidizes the insoluble metal carbides, nitrides and intermetallic compounds, and transforms the inert insoluble cobalt phase into an easily leached active cobalt phase, which can significantly improve the leaching rate of cobalt in the subsequent leaching.

[0066] As can be seen from the comparison between Example 1 and Comparative Examples 2-3, the present invention uses pressurized acid leaching to break the semi-stable alloy phase in a high temperature and high pressure environment, leach out the encapsulated cobalt component, and then uses high acid leaching to completely decompose the residual refractory metal solid solution and alloy framework phase in a high acidity and strong erosion system, thereby deeply recovering the residual cobalt and significantly improving the cobalt recovery rate.

[0067] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for recovering cobalt from cobalt-based superalloy waste, characterized in that, The method includes the following steps: Activated material was obtained by mechanical grinding and activation of cobalt-based superalloy waste. The activated material is pulped to obtain an activated slurry. The activated slurry is mixed with an oxidant and subjected to oxidative leaching treatment to obtain an oxidative leaching solution and a first leaching residue. The first leaching residue, the first acid solution, and the first oxidant are mixed and subjected to pressure acid leaching to obtain a pressure acid leaching solution and a second leaching residue. The second leaching residue, the second acid solution, and the second oxidant are mixed and subjected to high acid leaching treatment to obtain a high acid leaching solution and a third leaching residue. The oxidizing leachate is mixed with the third oxidant, and after stirring and reaction, alkaline material is added to carry out precipitation reaction to obtain cobalt hydroxide precipitate. The cobalt hydroxide precipitate is mixed with the third acid solution to obtain primary cobalt salt solution. The primary cobalt salt solution is then subjected to extraction and impurity removal treatment to obtain high-purity cobalt salt solution. The slurrying agent used to slurry the activated material includes pressurized acid leaching solution and / or high-acid acid leaching solution.

2. The method as described in claim 1, characterized in that, Before mechanical grinding and activation, the cobalt-based high-temperature alloy waste is subjected to turning and crushing treatment. Preferably, the mechanical grinding activation time is 3h~4h; Preferably, the mechanical grinding and activation treatment is followed by magnetic separation treatment.

3. The method as described in claim 1 or 2, characterized in that, The solid content of the activated slurry is 10%~20%; Preferably, the oxidant includes NaClO3 and / or Na2S2O8; Preferably, the mass ratio of cobalt-based superalloy waste to oxidant in the activated slurry is 1:(0.05~0.2).

4. The method according to any one of claims 1-3, characterized in that, The temperature for the oxidative leaching treatment is 50℃~65℃; Preferably, the oxidative leaching treatment time is 2h to 3h.

5. The method according to any one of claims 1-4, characterized in that, The first acid solution includes a sulfuric acid solution; Preferably, the solid-liquid mass ratio of the first leaching residue to the first acid solution is 1:(4~5); Preferably, the first oxidant includes hydrogen peroxide.

6. The method according to any one of claims 1-5, characterized in that, During the pressurized acid leaching process, oxygen is introduced to apply pressure; Preferably, the temperature of the pressure acid leaching treatment is 150℃~180℃; Preferably, the pressure of the pressurized acid leaching treatment is 1.5 MPa to 2.5 MPa; Preferably, the pH of the pressurized acid leaching treatment is 1~1.5; Preferably, the pressurized acid leaching treatment lasts for 3 to 4 hours.

7. The method according to any one of claims 1-6, characterized in that, The second acid solution includes a sulfuric acid solution; Preferably, the solid-liquid mass ratio of the second leaching residue to the second acid solution is 1:(3~4.5); Preferably, the second oxidant includes hydrogen peroxide.

8. The method according to any one of claims 1-7, characterized in that, The pH of the high-acid leaching treatment is 0.3~0.5; Preferably, the temperature of the high-acid leaching treatment is 85℃~95℃; Preferably, the high-acid leaching treatment time is 4h to 5h.

9. The method according to any one of claims 1-8, characterized in that, The third oxidant includes sodium hypochlorite; Preferably, the molar ratio of cobalt ions to the third oxidant in the high-acid leaching solution is 1:(1.2~1.5); Preferably, the temperature of the stirring reaction is 45℃~55℃; Preferably, the stirring reaction time is 0.5 h to 1 h; Preferably, the alkaline material includes a sodium hydroxide solution; Preferably, the pH of the precipitation reaction is 3 to 4.5; Preferably, the precipitation reaction takes 0.5 h to 1 h.

10. The method according to any one of claims 1-9, characterized in that, The third acid solution includes sulfuric acid; Preferably, the pH of the primary cobalt salt solution is adjusted to 3.5-4 before extraction; Preferably, the extractant used in the extraction includes P507; Preferably, the impurity removal method includes resin impurity removal.

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