A process for the recovery of nickel from a superalloy

Abstract

This invention provides a method for recovering nickel from high-temperature alloys. The method includes the following steps: electrochemically dissolving the high-temperature alloy to obtain a nickel-containing electrolyte and anode mud; adjusting the pH of the nickel-containing electrolyte until impurity metal ions form a precipitate, separating the precipitate to obtain a purified solution; mixing the purified solution, a chloride-containing solution, and an extractant for extraction to separate a cobalt-supported organic phase and a nickel-containing raffinate; adjusting the pH of the nickel-containing raffinate until nickel ions are converted into nickel precipitate, and then reducing the nickel precipitate with hydrogen plasma to obtain metallic nickel powder. The recovery process provided by this invention achieves high purity nickel recovery from high-temperature alloys, significantly shortens the single-batch operation cycle, improves recovery efficiency, and can meet the needs of large-scale, high-load continuous production.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for recovering nickel from high-temperature alloys. Background Technology

[0002] High-temperature alloys are metallic materials with nickel, cobalt, iron, etc., as the base material, capable of long-term operation at temperatures above 600℃ and under certain stress. They are widely used in aviation, aerospace, energy, and other fields. In recent years, the annual output of high-temperature alloys has been increasing year by year. At the same time, the amount of high-temperature alloy waste generated during the manufacturing process is also increasing. The accumulation of waste has caused serious resource waste. Therefore, the efficient recovery of nickel from high-temperature alloy waste has significant economic value and resource significance.

[0003] Currently, nickel recovery technologies from high-temperature alloys are mainly divided into two categories: hydrometallurgy and pyrometallurgy. Hydrometallurgical processes typically employ steps such as acid leaching, solvent extraction, ion exchange, and precipitation separation to selectively separate nickel from other metallic elements. Pyrometallurgical processes utilize high-temperature smelting, sulfide roasting, or chlorination roasting to enrich and purify nickel. However, existing technologies generally have significant shortcomings: 1) The single-batch operation cycle is too long. For example, the multi-stage extraction and back-extraction processes in hydrometallurgical processes are cumbersome and time-consuming, while pyrometallurgical processes require slow heating and long-term holding, resulting in low production efficiency; 2) Existing methods are mostly intermittent operations, making continuous production difficult. In batch production scenarios, capacity is limited and cannot meet the demands of high-load industrial production. Furthermore, due to insufficient separation selectivity or impurity entrainment during the process, the purity of nickel recovered by existing processes is low, making it difficult to directly apply to the remanufacturing of high-end alloys, thus hindering the high-value utilization of recovered resources. Therefore, how to further improve the purity of recovered nickel in high-temperature alloys while increasing the recovery efficiency to meet the needs of large-scale, high-efficiency, and high-purity industrial production is an urgent technical problem to be solved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for recovering nickel from high-temperature alloys. This invention first performs an electrochemical dissolution treatment on the high-temperature alloy, which can rapidly and selectively dissolve nickel and reduce the introduction of impurities. Then, by adjusting the pH value of the nickel-containing electrolyte, impurity metal ions are precipitated and removed, effectively reducing the impurity load for subsequent extraction. Following this, an extraction process is performed, utilizing the assisted complexation effect of chloride ions to achieve efficient extraction of cobalt and selective retention of nickel. Finally, the pH value of the nickel-containing raffinate is adjusted to convert nickel ions into nickel precipitate, which is then reduced using hydrogen plasma reduction technology. Leveraging the high activity and strong reducing power of hydrogen plasma, the reduction reaction can be rapidly completed at relatively low temperatures, yielding high-purity nickel powder. In summary, this method achieves high purity nickel recovery from high-temperature alloys, significantly shortens the single-batch operation cycle, and significantly improves recovery efficiency, meeting the needs of large-scale, high-load continuous production.

[0005] To achieve this objective, the present invention employs the following technical solution: This invention provides a method for recovering nickel from high-temperature alloys, the method comprising the following steps: Electrochemical dissolution treatment of high-temperature alloys yields nickel-containing electrolyte and anode mud.

[0006] The pH value of the nickel-containing electrolyte is adjusted until impurity metal ions form a precipitate, and the precipitate is separated to obtain a purified solution.

[0007] The impurity removal solution, the chloride-containing solution, and the extractant are mixed and extracted to separate the cobalt-supported organic phase and the nickel-containing raffinate.

[0008] The pH of the nickel-containing raffinate is adjusted until nickel ions are converted into nickel precipitate, and then the nickel precipitate is reduced by hydrogen plasma to obtain metallic nickel powder.

[0009] This invention employs a step-by-step synergistic recycling process, specifically as follows: First, the high-temperature alloy waste undergoes electrochemical dissolution treatment, achieving rapid and selective dissolution of nickel while significantly reducing the introduction of impurities. Then, by adjusting the pH of the nickel-containing electrolyte, impurity metal ions in the system are oriented to form precipitates and are separated and removed, greatly reducing the impurity treatment load in subsequent extraction processes. Based on this, extraction treatment is performed, utilizing the assisted complexation effect of chloride ions to achieve efficient separation and extraction of cobalt and selective retention of nickel, further enhancing the nickel enrichment. Finally, the pH of the nickel-containing raffinate is adjusted to promote the conversion of nickel ions into nickel-based precipitates, which are then reduced using hydrogen plasma reduction technology. Utilizing the high activity and strong reducing power of hydrogen plasma, the reduction reaction can be rapidly completed under relatively low temperature conditions, ultimately obtaining high-purity metallic nickel powder.

[0010] In summary, the recycling method of the present invention can not only achieve high-purity recovery of nickel from high-temperature alloys, but also significantly shorten the single-batch operation cycle and significantly improve the recycling efficiency, which can stably meet the industrial needs of large-scale, high-load continuous production.

[0011] Preferably, the electrochemical dissolution treatment method includes: A high-temperature alloy was placed in an electrolytic cell as the anode and an inert cathode. Acid and composite additives were added as the electrolyte, and the current density was controlled at 10-20 A / dm³. 2 For example, it could be 10A / dm 2 12.5A / dm 2 15A / dm 2 17.5A / dm 2 Or 20A / dm 2 Electrolysis is carried out for 2-4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, to obtain nickel-containing electrolyte and anode mud.

[0012] The composite additives include citric acid and ferrous sulfate.

[0013] For example, an inert cathode may be a stainless steel plate or a graphite plate.

[0014] In the electrochemical dissolution process of high-temperature alloys, this invention introduces a combination of citric acid and ferrous sulfate as a composite additive into the electrolyte. Citric acid, through its complexing effect on metal ions, inhibits the formation of a passivation film on the anode surface, maintaining the stability of the electrolysis process. Simultaneously, ferrous sulfate, as a redox medium, promotes electron transfer between the anode and the electrolyte, improving current efficiency and dissolution rate. The synergistic effect of these two additives significantly improves the electrochemical dissolution effect of the high-temperature alloys, enabling nickel to dissolve rapidly and uniformly into the electrolyte while reducing impurity entrainment, thus facilitating the smooth progress of subsequent purification steps.

[0015] Preferably, the concentration of the acid solution is 1-3 mol / L, for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, etc.

[0016] Preferably, the mass concentration of the composite additive in the electrolyte is 3-10 g / L, for example, it can be 3 g / L, 4.75 g / L, 6.5 g / L, 8.25 g / L or 10 g / L.

[0017] In this invention, the composite additive of appropriate mass concentration can fully complex the nickel ions dissolved from the anode, maintain the stability of the electrolyte and prevent anode passivation. Too much or too little will reduce the current efficiency, accelerate the occurrence of side reactions, and lead to uneven dissolution.

[0018] Preferably, the mass ratio of citric acid to ferrous sulfate is (1.5-2.5):1, for example, it can be 1.5:1, 1.75:1, 2:1, 2.25:1 or 2.5:1, etc.

[0019] By controlling the mass ratio of citric acid and ferrous sulfate within the above-mentioned range, this invention can promote the efficient and selective dissolution of nickel while inhibiting the excessive dissolution of impurity metals, thus laying a good foundation for subsequent impurity removal and nickel extraction.

[0020] Preferably, the pH value of the nickel-containing electrolyte is adjusted to 4.2-4.8, for example, it can be 4.2, 4.3, 4.4, 4.5, 4.6, 4.7 or 4.8, so that iron ions, aluminum ions and chromium ions form hydroxide precipitates.

[0021] Within the aforementioned acidic range, the complexing ability of nickel ions with citric acid is stronger than that of cobalt ions, and the complex is more stable. This helps prevent nickel precipitation during pH adjustment and inhibits the extraction of nickel during subsequent extraction with acidic phosphorus extractants and the co-extraction of nickel during extraction with amine extractants.

[0022] Preferably, the chloride-containing solution includes sodium chloride and / or hydrochloric acid.

[0023] Preferably, the concentration of chloride ions in the solution after mixing the impurity removal solution, the chloride-containing solution, and the extractant is 0.5-1 mol / L, for example, it can be 0.5 mol / L, 0.625 mol / L, 0.75 mol / L, 0.875 mol / L, or 1 mol / L, etc.

[0024] Preferably, the extractant includes acidic phosphorus extractants and / or amine extractants.

[0025] This invention utilizes the coordination of chloride ions in sodium chloride and / or hydrochloric acid with metal ions to form easily extractable chloride complexes. Further extraction using acidic phosphorus extractants and amine extractants for Co exhibits a synergistic effect, significantly improving cobalt extraction efficiency. The combined effect of these two steps greatly enhances cobalt extraction efficiency and effectively suppresses nickel co-extraction loss, laying the foundation for obtaining high-purity metallic nickel.

[0026] Preferably, during the extraction process, the volume ratio of the organic phase to the aqueous phase is 1:(1.5-2.5), for example, it can be 1:1.5, 1:1.75, 1:2, 1:2.25 or 1:2.5, etc.

[0027] Preferably, the extraction temperature is 28-32℃, for example, 28℃, 29℃, 30℃, 31℃ or 32℃.

[0028] Preferably, the cobalt-supported organic phase is further post-processed, and the post-processing steps include back-extraction.

[0029] Preferably, the pH of the nickel-containing raffinate is adjusted to 7-8, for example, 7, 7.25, 7.5, 7.75 or 8, so that nickel ions are converted into nickel hydroxide precipitate.

[0030] Preferably, the method for hydrogen plasma reduction includes: The nickel hydroxide precipitate was placed in a hydrogen plasma reduction furnace, a vacuum was drawn, hydrogen gas was introduced, and then the plasma generator was started for reduction treatment.

[0031] This invention utilizes the high-energy active hydrogen ions in hydrogen plasma to reduce nickel hydroxide precipitate, resulting in a high reduction rate. Furthermore, due to the low reaction temperature of the plasma, the particle size growth and re-contamination of the obtained nickel powder particles can be effectively avoided, resulting in well-dispersed spherical or near-spherical particles of nickel powder. This simplifies the process and further improves the recovery efficiency and product quality.

[0032] Preferably, the vacuum level inside the furnace after vacuuming is ≤5×10⁻⁶. -2 Pa, for example, could be 5 × 10 -2 Pa, 4×10 - 2 Pa, 3×10 -2 Pa, 2×10 -2 Pa, 1×10 -2 Pa or 0.5×10 -2 Pa, etc.

[0033] Preferably, the temperature of the reduction treatment is 280-350℃, for example, it can be 280℃, 300℃, 310℃, 320℃ or 350℃.

[0034] Preferably, the reduction process takes 1-1.5 hours, for example, 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, or 1.5 hours.

[0035] Preferably, during the hydrogen plasma reduction process, the hydrogen flow rate is 100-500 mL / min, for example, it can be 100 mL / min, 200 mL / min, 300 mL / min, 400 mL / min or 500 mL / min.

[0036] Preferably, during the hydrogen plasma reduction process, the output power of the plasma generator is 5-15kW, for example, it can be 5kW, 7.5kW, 10kW, 12.5kW or 15kW.

[0037] Preferably, the method includes the following steps: (1) Electrolytic treatment of high-temperature alloys to obtain nickel-containing electrolyte and anode mud.

[0038] The electrolytic treatment method includes: placing a high-temperature alloy as the anode and stainless steel as the inert cathode in an electrolytic cell; adding an acid solution with a concentration of 1-3 mol / L and composite additives as the electrolyte; and controlling the current density to be 10-20 A / dm³. 2 Electrolysis for 2-4 hours yields a nickel-containing electrolyte and anode mud; the acid solution includes a sulfuric acid solution; the electrolyte contains a composite additive with a mass concentration of 3-10 g / L; the composite additive includes citric acid and ferrous sulfate, and the mass ratio of citric acid to ferrous sulfate is (1.5-2.5):1.

[0039] (2) Under stirring conditions, add an alkaline solution (such as sodium hydroxide solution) to the nickel-containing electrolyte to adjust the pH to 4.2-4.8 so that iron ions, aluminum ions and chromium ions form hydroxide precipitates, which are then filtered and separated to obtain a purified solution.

[0040] The impurity removal solution and a chloride-containing solution are mixed to achieve a chloride ion concentration of 0.5-1 mol / L in the impurity removal solution. Then, an acidic phosphorus extractant is added for extraction, followed by extraction of Co using an amine extractant. The volume ratio of the organic phase to the aqueous phase is controlled at 1:(1.5-2.5). The extraction process is carried out at 28-32°C. After separation, a cobalt-supported organic phase and a nickel-containing raffinate are obtained. The chloride-containing solution includes sodium chloride and hydrochloric acid. The acidic phosphorus extractant includes P204 or P507, and the amine extractant includes N235 and / or a quaternary ammonium salt, wherein the quaternary ammonium salt includes trioctylmethylammonium chloride.

[0041] The cobalt-supported organic phase is back-extracted using an acid solution to obtain a cobalt salt solution; wherein the acid solution includes a sulfuric acid solution.

[0042] (3) Under stirring conditions, add an alkaline solution (e.g., sodium hydroxide solution) to the nickel-containing raffinate to adjust the pH to 7-8, so that the nickel ions are converted into nickel hydroxide precipitate. After filtration, wash with water and dry. Then, place the dried nickel hydroxide precipitate into a hydrogen plasma reduction furnace and evacuate the furnace to a vacuum degree ≤ 5 × 10⁻⁶. -2 Pa is introduced with hydrogen gas at a flow rate of 100-500 mL / min, and then the plasma generator is started with an output power of 5-15 kW. The reduction process is carried out at 280-350℃ for 1-1.5 h. After the process is completed, the plasma is cooled to room temperature under hydrogen protection to obtain nickel powder with a purity ≥99.6% (e.g., 99.6%, 99.7%, 99.8%, 99.9%, or 99.95%).

[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: This invention employs a step-by-step synergistic recycling process, specifically as follows: First, the high-temperature alloy waste undergoes electrochemical dissolution treatment, achieving rapid and selective dissolution of nickel while significantly reducing the introduction of impurities. Then, by adjusting the pH of the nickel-containing electrolyte, impurity metal ions in the system are oriented to form precipitates and are separated and removed, greatly reducing the impurity treatment load in subsequent extraction processes. Based on this, extraction treatment is performed, utilizing the assisted complexation effect of chloride ions to achieve efficient separation and extraction of cobalt and selective retention of nickel, further enhancing the nickel enrichment. Finally, the pH of the nickel-containing raffinate is adjusted to promote the conversion of nickel ions into nickel-based precipitates, which are then reduced using hydrogen plasma reduction technology. Utilizing the high activity and strong reducing power of hydrogen plasma, the reduction reaction can be rapidly completed under relatively low temperature conditions, ultimately obtaining high-purity metallic nickel powder.

[0045] In summary, the recycling method of the present invention can not only achieve high-purity recovery of nickel from high-temperature alloys, but also significantly shorten the single-batch operation cycle and significantly improve the recycling efficiency, which can stably meet the industrial needs of large-scale, high-load continuous production. Detailed Implementation

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0051] It should be noted that the main components and contents of the high-temperature alloys used in the following embodiments are shown in Table 1.

[0052] Table 1 It should be noted that in the following implementation methods, room temperature refers to 25°C.

[0053] Example 1 This embodiment provides a method for recovering nickel from high-temperature alloys, the method comprising the following steps: (1) Electrolytic treatment of high-temperature alloys to obtain nickel-containing electrolyte and anode mud.

[0054] The electrolytic treatment method includes: placing a high-temperature alloy as the anode and stainless steel as the inert cathode in an electrolytic cell; adding a 2 mol / L sulfuric acid solution and composite additives as the electrolyte; and controlling the current density to 15 A / dm³. 2 Electrolysis for 3 hours yields a nickel-containing electrolyte and anode mud; the electrolyte contains a composite additive with a mass concentration of 6 g / L; the composite additive includes citric acid and ferrous sulfate, with a mass ratio of citric acid to ferrous sulfate of 2:1.

[0055] (2) Under stirring conditions, sodium hydroxide solution is added to the nickel-containing electrolyte to adjust the pH to 4.5, so that iron ions, aluminum ions and chromium ions form hydroxide precipitates, which are then filtered and separated to obtain the purified solution.

[0056] The impurity removal solution and the chloride ion-containing solution were mixed to achieve a chloride ion concentration of 0.8 mol / L in the impurity removal solution. Then, P2O4 was added for extraction. Subsequently, Co was extracted using N235 and trioctylmethylammonium chloride at a volume ratio of 1:1, while controlling the volume ratio of the organic phase to the aqueous phase to be 1:2. The extraction was carried out at 30°C, and after separation, a cobalt-supported organic phase and a nickel-containing raffinate were obtained. The chloride ion-containing solution consisted of sodium chloride and hydrochloric acid at a mass concentration ratio of 1:1.

[0057] The cobalt-supported organic phase was back-extracted using sulfuric acid solution to obtain a cobalt salt solution.

[0058] (3) Under stirring conditions, sodium hydroxide solution is added to the nickel-containing raffinate to adjust the pH to 7.5, so that nickel ions are converted into nickel hydroxide precipitate. After filtration, the precipitate is washed four times with pure water and dried. Then, the dried nickel hydroxide precipitate is placed in a hydrogen plasma reduction furnace and evacuated until the vacuum degree inside the furnace is <5×10⁻⁶. -2 Pa was introduced with hydrogen gas at a flow rate of 300 mL / min, and then the plasma generator was started with an output power of 10 kW. The reduction process was carried out at 310 °C for 1.2 h. After the process was completed, the plasma was cooled to room temperature under hydrogen protection to obtain metallic nickel powder.

[0059] Example 2 This embodiment provides a method for recovering nickel from high-temperature alloys, the method comprising the following steps: (1) Electrolytic treatment of high-temperature alloys to obtain nickel-containing electrolyte and anode mud.

[0060] The electrolytic treatment method includes: placing a high-temperature alloy as the anode and stainless steel as the inert cathode in an electrolytic cell; adding a 1 mol / L sulfuric acid solution and composite additives as the electrolyte; and controlling the current density to 10 A / dm³. 2 Electrolysis for 4 hours yields a nickel-containing electrolyte and anode mud; the acid solution includes a sulfuric acid solution; the mass concentration of the composite additive in the electrolyte is 3 g / L; the composite additive includes citric acid and ferrous sulfate, and the mass ratio of citric acid to ferrous sulfate is 1.5:1.

[0061] (2) Under stirring conditions, sodium hydroxide solution is added to the nickel-containing electrolyte to adjust the pH to 4.2, so that iron ions, aluminum ions and chromium ions form hydroxide precipitates, which are then filtered and separated to obtain the purified solution.

[0062] The impurity removal solution and the chloride ion-containing solution were mixed to achieve a chloride ion concentration of 0.5 mol / L in the impurity removal solution. Then, P2O4 was added for extraction. Subsequently, Co was extracted using N235 and trioctylmethylammonium chloride at a volume ratio of 1:1, while controlling the volume ratio of the organic phase to the aqueous phase to be 1:1.5. The extraction was carried out at 28°C, and after separation, a cobalt-supported organic phase and a nickel-containing raffinate were obtained. The chloride ion-containing solution consisted of sodium chloride and hydrochloric acid at a mass concentration ratio of 1:1.

[0063] The cobalt-supported organic phase was back-extracted using sulfuric acid solution to obtain a cobalt salt solution.

[0064] (3) Under stirring conditions, sodium hydroxide solution is added to the nickel-containing raffinate to adjust the pH to 7, so that nickel ions are converted into nickel hydroxide precipitate. After filtration, the precipitate is washed four times with pure water and dried. Then, the dried nickel hydroxide precipitate is placed in a hydrogen plasma reduction furnace and evacuated until the vacuum degree inside the furnace is <5×10⁻⁶. -2 Pa was introduced with hydrogen gas at a flow rate of 100 mL / min, and then the plasma generator was started with an output power of 5 kW. The reduction process was carried out at 280 °C for 1.5 h. After the process was completed, the plasma was cooled to room temperature under hydrogen protection to obtain metallic nickel powder.

[0065] Example 3 This embodiment provides a method for recovering nickel from high-temperature alloys, the method comprising the following steps: (1) Electrolytic treatment of high-temperature alloys to obtain nickel-containing electrolyte and anode mud.

[0066] The electrolytic treatment method includes: placing a high-temperature alloy as the anode and stainless steel as the inert cathode in an electrolytic cell; adding a 3 mol / L sulfuric acid solution and composite additives as the electrolyte; and controlling the current density to 20 A / dm³. 2 Electrolysis for 2 hours yields a nickel-containing electrolyte and anode mud; the acid solution includes a sulfuric acid solution; the mass concentration of the composite additive in the electrolyte is 10 g / L; the composite additive includes citric acid and ferrous sulfate, and the mass ratio of citric acid to ferrous sulfate is 2.5:1.

[0067] (2) Under stirring conditions, sodium hydroxide solution is added to the nickel-containing electrolyte to adjust the pH to 4.8, so that iron ions, aluminum ions and chromium ions form hydroxide precipitates, which are then filtered and separated to obtain the purified solution.

[0068] The impurity removal solution and the chloride ion-containing solution were mixed to achieve a chloride ion concentration of 1 mol / L in the impurity removal solution. Then, P2O4 was added for extraction. Subsequently, Co was extracted using N235 and trioctylmethylammonium chloride at a volume ratio of 1:1, while controlling the weight ratio of the organic phase to the aqueous phase to be 1:2.5. The extraction was carried out at 32°C, and after separation, a cobalt-supported organic phase and a nickel-containing raffinate were obtained. The chloride ion-containing solution consisted of sodium chloride and hydrochloric acid at a mass concentration ratio of 1:1.

[0069] The cobalt-supported organic phase was back-extracted using sulfuric acid solution to obtain a cobalt salt solution.

[0070] (3) Under stirring conditions, sodium hydroxide solution is added to the nickel-containing raffinate to adjust the pH to 8, so that nickel ions are converted into nickel hydroxide precipitate. After filtration, the precipitate is washed four times with pure water and dried. Then, the dried nickel hydroxide precipitate is placed in a hydrogen plasma reduction furnace and evacuated to a vacuum degree of <5×10⁻⁶. -2 Pa was introduced with hydrogen gas at a flow rate of 500 mL / min, and then the plasma generator was started with an output power of 15 kW. The reduction process was carried out at 350 °C for 1 hour. After the process was completed, the plasma was cooled to room temperature under hydrogen protection to obtain metallic nickel powder.

[0071] Example 4 The difference between this embodiment and Embodiment 1 is that the mass concentration of the composite additive in the electrolyte is 0 g / L.

[0072] The remaining methods and parameters are consistent with those in Example 1.

[0073] Example 5 The difference between this embodiment and Embodiment 1 is that the mass concentration of the composite additive in the electrolyte is 15 g / L.

[0074] The remaining methods and parameters are consistent with those in Example 1.

[0075] Example 6 The difference between this embodiment and Embodiment 1 is that the mass ratio of citric acid to ferrous sulfate is 1:1.

[0076] The remaining methods and parameters are consistent with those in Example 1.

[0077] Example 7 The difference between this embodiment and Embodiment 1 is that the mass ratio of citric acid to ferrous sulfate is 3:1.

[0078] The remaining methods and parameters are consistent with those in Example 1.

[0079] Example 8 The difference between this embodiment and Embodiment 1 is that the chloride ion concentration in the impurity removal solution is 2 mol / L.

[0080] The remaining methods and parameters are consistent with those in Example 1.

[0081] Example 9 The difference between this embodiment and Embodiment 1 is that, during the extraction process, trioctylmethylammonium chloride is replaced with an equal volume of N235.

[0082] The remaining methods and parameters are consistent with those in Example 1.

[0083] Example 10 The difference between this embodiment and Embodiment 1 is that the reduction treatment temperature is 250°C.

[0084] The remaining methods and parameters are consistent with those in Example 1.

[0085] Example 11 The difference between this embodiment and Embodiment 1 is that the reduction treatment temperature is 400°C.

[0086] The remaining methods and parameters are consistent with those in Example 1.

[0087] Comparative Example 1 The difference between this comparative example and Example 1 is that, in step (2), no solution containing chloride ions is added.

[0088] The remaining methods and parameters are consistent with those in Example 1.

[0089] Comparative Example 2 The difference between this comparative example and Example 1 is that in step (3), the hydrogen plasma reduction method is replaced by hydrogen gas reduction. The specific steps are as follows: the dried nickel hydroxide precipitate is placed in a tube furnace, and the furnace is evacuated to a vacuum degree of <5×10 - 2Pa was introduced with hydrogen gas at a flow rate of 300 mL / min, the temperature was raised to 800 °C and kept at that temperature for 4 hours for reduction. After the reduction was completed, the mixture was cooled to room temperature under hydrogen protection to obtain metallic nickel powder.

[0090] The remaining methods and parameters are consistent with those in Example 1.

[0091] Performance testing The purity of the nickel powder provided in the above examples and comparative examples was tested using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0092] The test results are shown in Table 2.

[0093] Table 2 analyze: As shown in Table 2, this invention first performs an electrochemical dissolution treatment on the high-temperature alloy, which can rapidly and selectively dissolve nickel and reduce the introduction of impurities. Then, by adjusting the pH value of the nickel-containing electrolyte, the impurity metal ions are precipitated and removed, effectively reducing the impurity load of subsequent extraction. Following this, an extraction process is performed, utilizing the assisted complexation effect of chloride ions to achieve efficient extraction of cobalt and selective retention of nickel. Finally, the pH value of the nickel-containing raffinate is adjusted to convert nickel ions into nickel precipitate, and the precipitate is reduced using hydrogen plasma reduction technology. Utilizing the high activity and strong reducing power of hydrogen plasma, the reduction reaction can be rapidly completed at a relatively low temperature, yielding high-purity nickel powder. In summary, this method achieves high purity nickel recovery from high-temperature alloys, significantly shortens the single-batch operation cycle, and significantly improves recovery efficiency, meeting the needs of large-scale, high-load continuous production.

[0094] A comparison of Examples 1 and 4-5 shows that if the mass concentration of the composite additive in the electrolyte is 0, i.e., there is no composite additive, a dense passivation film is easily formed on the anode surface during electrochemical dissolution, resulting in a significant decrease in current efficiency, a reduced dissolution rate, incomplete nickel dissolution, and poor dissolution selectivity. Impurities such as iron and chromium are excessively dissolved and enter subsequent processes, leading to a decrease in the purity of the nickel powder. If the mass concentration of the composite additive in the electrolyte is too high, some of the dissolved nickel will form stable complexes, resulting in a decrease in the impurity removal rate during subsequent pH purification, an increase in the residue of impurities such as iron and aluminum, and ultimately a decrease in the purity of the nickel powder.

[0095] A comparison of Examples 1 and 6-7 shows that if the mass ratio of citric acid to ferrous sulfate is too low, it can easily lead to uneven anodic dissolution, resulting in a large number of suspended particles. This leads to an increase in the impurity content in the nickel powder after precipitation and reduction, and a decrease in product purity. If the mass ratio of citric acid to ferrous sulfate is too high, the excess citric acid will inhibit the promoting effect of ferrous sulfate, resulting in a decrease in anodic dissolution selectivity. At the same time, a large amount of citric acid remaining in the electrolyte will partially compete with the subsequent extractant for complexation, resulting in a small amount of iron and chromium being co-extracted into the final product, and a decrease in product purity.

[0096] As can be seen from the comparison between Example 1 and Example 8, if the concentration of chloride ions in the impurity removal solution is too high, nickel will be extracted along with cobalt, resulting in incomplete separation of cobalt and nickel, which reduces the nickel recovery rate and the purity of nickel powder.

[0097] As can be seen from the comparison between Example 1 and Example 9, if the extractant does not contain trioctylmethylammonium chloride during the extraction process, the extractant system will have a lower selectivity for cobalt extraction. Cobalt ions will remain in the nickel-containing raffinate, and during subsequent precipitation and reduction, cobalt will be mixed into the nickel powder, resulting in an increase in the cobalt impurity content and a decrease in purity in the nickel powder.

[0098] A comparison of Example 1 and Examples 10-11 shows that if the reduction treatment temperature is too low, the activation degree of the hydrogen plasma is insufficient, the reduction efficiency is low, and the product contains a large amount of unreduced nickel hydroxide precipitate, resulting in a decrease in the purity of the nickel powder. If the reduction treatment temperature is too high, the plasma energy is too large, the nickel particles are violently sintered, and the surface of the nickel powder is easily oxidized at high temperatures, leading to a decrease in purity.

[0099] As can be seen from the comparison between Example 1 and Comparative Example 1, if a solution containing chloride ions is not added in step (2), a stable chloride complex cannot be formed, the synergistic effect between extractants is difficult to exert, the cobalt extraction rate is low, and a large number of cobalt ions enter the raffinate, which co-precipitate with nickel hydroxide during subsequent precipitation. The reduced nickel powder has a high cobalt impurity content and its purity decreases.

[0100] As can be seen from the comparison between Example 1 and Comparative Example 2, if the hydrogen plasma reduction method in step (3) is replaced by hydrogen gas reduction, the cycle is long, the energy consumption is high, and it is easy to cause nickel powder particles to sinter and agglomerate, making it difficult to avoid trace oxidation and carbon pollution, resulting in low purity of the obtained metallic nickel powder.

[0101] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recovering nickel from high-temperature alloys, characterized in that, The method includes the following steps: Electrochemical dissolution treatment of high-temperature alloys yields nickel-containing electrolyte and anode mud; The pH value of the nickel-containing electrolyte is adjusted until impurity metal ions form a precipitate, and the precipitate is separated to obtain a purified solution. The impurity removal solution, the chloride-containing solution, and the extractant are mixed and extracted to separate the cobalt-supported organic phase and the nickel-containing raffinate. The pH of the nickel-containing raffinate is adjusted until nickel ions are converted into nickel precipitate, and then the nickel precipitate is reduced by hydrogen plasma to obtain metallic nickel powder.

2. The method according to claim 1, characterized in that, The electrochemical dissolution treatment method includes: A high-temperature alloy was placed in an electrolytic cell as the anode and an inert cathode. Acid and composite additives were added as the electrolyte, and the current density was controlled at 10-20 A / dm³. 2 Electrolysis for 2-4 hours yields nickel-containing electrolyte and anode mud; The composite additives include citric acid and ferrous sulfate.

3. The method according to claim 2, characterized in that, The concentration of the acid solution is 1-3 mol / L; And / or, in the electrolyte, the mass concentration of the composite additive is 3-10 g / L; And / or, the mass ratio of citric acid to ferrous sulfate is (1.5-2.5):

1.

4. The method according to any one of claims 1-3, characterized in that, The pH of the nickel-containing electrolyte is adjusted to 4.2-4.8 so that iron, aluminum and chromium ions form hydroxide precipitates.

5. The method according to any one of claims 1-4, characterized in that, The chloride-containing solution includes sodium chloride and / or hydrochloric acid; And / or, in the solution after mixing the impurity removal solution, the chloride-containing solution and the extractant, the concentration of chloride ions is 0.5-1 mol / L; And / or, the extractant includes acidic phosphorus extractants and / or amine extractants.

6. The method according to any one of claims 1-5, characterized in that, During the extraction process, the volume ratio of the organic phase to the aqueous phase is 1:(1.5-2.5); And / or, the extraction treatment temperature is 28-32°C; And / or, the cobalt-supported organic phase is further post-processed, the post-processing steps including back-extraction.

7. The method according to any one of claims 1-6, characterized in that, Adjust the pH of the nickel-containing raffinate to 7-8 so that nickel ions are converted into nickel hydroxide precipitate; And / or, the method of hydrogen plasma reduction includes: The nickel hydroxide precipitate was placed in a hydrogen plasma reduction furnace, a vacuum was drawn, hydrogen gas was introduced, and then the plasma generator was started for reduction treatment.

8. The method according to claim 7, characterized in that, The vacuum level inside the furnace after vacuuming is ≤5×10⁻⁶. -2 Pa; And / or, the temperature of the reduction treatment is 280-350℃; And / or, the reduction process takes 1-1.5 hours.

9. The method according to any one of claims 1-8, characterized in that, During the hydrogen plasma reduction process, the hydrogen flow rate is 100-500 mL / min; And / or, during the hydrogen plasma reduction process, the output power of the plasma generator is 5-15kW.

10. The method according to any one of claims 1-9, characterized in that, The method includes the following steps: (1) Electrolytic treatment of high-temperature alloys yields nickel-containing electrolyte and anode mud; The electrolytic treatment method includes: placing a high-temperature alloy as the anode and stainless steel as the inert cathode in an electrolytic cell; adding an acid solution with a concentration of 1-3 mol / L and composite additives as the electrolyte; and controlling the current density to be 10-20 A / dm³. 2 Electrolysis for 2-4 hours yields a nickel-containing electrolyte and anode mud; the acid solution includes a sulfuric acid solution; the mass concentration of the composite additive in the electrolyte is 3-10 g / L; the composite additive includes citric acid and ferrous sulfate, and the mass ratio of citric acid to ferrous sulfate is (1.5-2.5):1; (2) Under stirring conditions, add alkaline solution to the nickel-containing electrolyte to adjust the pH to 4.2-4.8 so that iron ions, aluminum ions and chromium ions form hydroxide precipitates, filter and separate to obtain impurity-removed solution; The impurity-removing solution and a chloride-containing solution are mixed to achieve a chloride ion concentration of 0.5-1 mol / L in the impurity-removing solution. Then, an acidic phosphorus extractant is added for extraction, followed by extraction of Co using an amine extractant. The volume ratio of the organic phase to the aqueous phase is controlled at 1:(1.5-2.5). The extraction process is carried out at 28-32°C. After separation, a cobalt-supported organic phase and a nickel-containing raffinate are obtained. The chloride-containing solution includes sodium chloride and hydrochloric acid. The acidic phosphorus extractant includes P204 or P507, and the amine extractant includes N235 and / or a quaternary ammonium salt, wherein the quaternary ammonium salt includes trioctylmethylammonium chloride. The cobalt-supported organic phase is back-extracted using an acid solution to obtain a cobalt salt solution; wherein the acid solution includes a sulfuric acid solution. (3) Under stirring conditions, add alkaline solution to the nickel-containing raffinate to adjust the pH to 7-8, so that the nickel ions are converted into nickel hydroxide precipitate. After filtration, wash with water and dry. Then, place the dried nickel hydroxide precipitate into a hydrogen plasma reduction furnace and evacuate the furnace to a vacuum degree ≤ 5 × 10⁻⁶. -2 Pa, hydrogen gas is introduced at a flow rate of 100-500 mL / min, and then the plasma generator is started with an output power of 5-15 kW. The reduction treatment is carried out at 280-350℃ for 1-1.5 h. After the treatment, the powder is cooled to room temperature under hydrogen protection to obtain nickel powder with a purity of ≥99.6%.

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