Method for efficient separation and high-value utilization of nickel-cobalt-magnesium in magnesium sulfate solution

Abstract

The application belongs to the technical field of hydrometallurgy, and particularly relates to a method for efficient separation and high-value utilization of nickel-cobalt-magnesium in a magnesium sulfate solution, comprising the following steps: S1, obtaining an impurity-containing magnesium sulfate solution, adding magnesium sulfite into the impurity-containing magnesium sulfate solution to perform a first reaction, and performing solid-liquid separation to obtain cobalt sulfite and a cobalt-removed solution; S2, adding magnesium powder into the cobalt-removed solution to perform a second reaction, performing solid-liquid separation to obtain nickel powder and a nickel-removed solution, calcining the cobalt sulfite to obtain tricobalt tetroxide and sulfur dioxide, and passing the sulfur dioxide into the nickel powder to perform a third reaction to obtain functionalized composite nickel powder; and S3, evaporating, crystallizing and pyrolyzing the nickel-removed solution to obtain active magnesium oxide. The application constructs two technical keystones of a single magnesium salt system and precise temperature control, and converts cobalt into battery-grade tricobalt tetroxide, upgrades nickel powder into functionalized nickel powder, and converts magnesium from traditional waste into high-value-added active magnesium oxide in the same process.

Description

Technical Field

[0001] This application relates to the field of hydrometallurgical technology, specifically, to a method for the efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution. Background Technology

[0002] In the high-pressure acid leaching process of laterite nickel ore, the recycling of spent lithium-ion batteries, and the hydrometallurgical process of nickel and cobalt, large amounts of magnesium sulfate solutions containing nickel and cobalt are often generated. The magnesium ion concentration in these solutions is typically as high as 20-100 g / L, while the nickel and cobalt concentrations are relatively low. Efficiently separating and recovering nickel and cobalt from these solutions, while simultaneously realizing the resource utilization of magnesium salts, is a pressing technical challenge in the field of hydrometallurgy.

[0003] Currently, the mainstream technical routes for separating nickel and cobalt from magnesium sulfate solution include the following: Solvent extraction method: This method uses acidic phosphorus extractants such as P204 and P507 to separate nickel, cobalt, and magnesium through multi-stage countercurrent extraction. This technology has the following drawbacks: the organic extractant is at risk of leakage, causing environmental pollution; the saponification process introduces a large amount of sodium ions, preventing the direct resource utilization of magnesium sulfate in the raffinate; the process is lengthy; equipment investment is high; and the extractant cost is high.

[0004] Chemical precipitation: Chemical precipitation separates different metals by controlling pH and adding selective precipitants. Common methods include: Sulfide precipitation: Utilizing the difference in solubility product of various metal sulfides, copper, cobalt, and nickel are precipitated stepwise by controlling the amount of sulfide added. However, the use of hydrogen sulfide or sodium sulfide poses safety and environmental risks, and the precipitation products are a mixture of sulfides, making subsequent processing complex; Carbonate precipitation: Cobalt carbonate and nickel carbonate are precipitated stepwise using sodium carbonate or sodium bicarbonate, but the selectivity is insufficient. Magnesium will also partially precipitate as magnesium carbonate or basic magnesium carbonate at higher pH, resulting in limited separation of cobalt and nickel; Hydroxide precipitation: Separation is achieved by utilizing the difference in pH range for the precipitation of various metal hydroxides. However, since the pH ranges for the precipitation of cobalt, nickel, and magnesium hydroxides overlap significantly, efficient separation cannot be achieved by pH control alone.

[0005] Ion exchange and adsorption method: This method utilizes chelating resins or special adsorbents to selectively adsorb nickel or cobalt, followed by acid elution for recovery. While this method offers high separation precision, it suffers from limited resin capacity and small throughput, making it suitable primarily for the advanced treatment of low-concentration solutions or the preparation of high-purity products. It is less effective for large-scale processing of high-concentration solutions.

[0006] In summary, the treatment of nickel-cobalt-containing magnesium sulfate solutions faces the following common technical challenges: 1. Disconnection between nickel-cobalt separation and magnesium utilization: Existing processes focus on nickel-cobalt separation and purification, with magnesium being treated as a "side problem" and discharged into wastewater or waste residue, failing to achieve simultaneous resource utilization of magnesium. 2. Low product added value: Nickel products are mostly nickel sulfate crystals or ordinary metal powder, and cobalt products are mainly in intermediate form, falling short of the product standards for battery material precursors, requiring further processing before entering the industrial chain. 3. Significant reagent consumption and wastewater issues: Whether it's the loss of extractant and saponification wastewater, or the reagent consumption and saline wastewater from precipitation methods, all constitute significant economic and environmental burdens. 4. Lack of a complete value-added solution: There is currently no technical solution that can simultaneously achieve the productization and value-added of nickel, cobalt, and magnesium in a closed-loop process.

[0007] Therefore, there is an urgent need to develop a method that can simultaneously achieve efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution, which has significant industrial application value and environmental benefits. Summary of the Invention

[0008] To solve the above-mentioned technical problems, this application provides a method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution, comprising the following steps: S1, obtaining a magnesium sulfate solution containing impurities, adding magnesium sulfite to the magnesium sulfate solution containing impurities for a first reaction, and separating the solid and liquid to obtain cobalt sulfite and a liquid after cobalt removal; S2, adding magnesium powder to the liquid after cobalt removal for a second reaction, separating the solid and liquid to obtain nickel powder and a liquid after nickel removal, calcining the cobalt sulfite to obtain cobalt tetroxide and sulfur dioxide, and passing the sulfur dioxide into the nickel powder for a third reaction to obtain functionalized composite nickel powder; S3, evaporating, crystallizing, and pyrolyzing the liquid after nickel removal to obtain active magnesium oxide.

[0009] As a preferred embodiment of the method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution as described in this application, in step S1, the composition of the magnesium sulfate solution containing impurities includes: Co: 2-5 g / L, Mg: 40-60 g / L, Ni: 0.5-2 g / L.

[0010] As a preferred embodiment of the method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution as described in this application, in step S1, the temperature of the first reaction is 40-80℃, the pH of the first reaction is 3.5-5.0, the reaction time is 30-90 min, and the amount of magnesium sulfite added is 1.0-1.2 times the theoretical amount.

[0011] As a preferred embodiment of the method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution as described in this application, in step S2, the temperature of the second reaction is 50-80℃, the pH of the second reaction is 4.0-5.5, the reaction time is 30-90 min, and the amount of magnesium powder added is 1.0-1.2 times the theoretical amount.

[0012] As a preferred embodiment of the method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution as described in this application, in step S2, the calcination temperature is 400-600℃ and the calcination time is 60-180min.

[0013] As a preferred embodiment of the method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution as described in this application, in step S2, the temperature of the third reaction is 200-400℃, and the time of the third reaction is 60-180 min.

[0014] As a preferred embodiment of the method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution as described in this application, in step S2, the functionalized composite nickel powder has a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel disulfide and nickel oxide as the outer shell. The functionalized composite nickel powder has antioxidant properties, and the weight gain of the functionalized composite nickel powder in air at room temperature is ≤0.2% after 30 days.

[0015] As a preferred embodiment of the method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution as described in this application, in step S3, the pyrolysis temperature is 800-1100℃ and the pyrolysis time is 60-180min.

[0016] As a preferred embodiment of the method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution as described in this application, the purity of the activated magnesium oxide is ≥99.0%, the purity of the functionalized composite nickel powder is ≥99.0%, the mass fraction of cobalt in the cobalt tetroxide is ≥72.6%, and the specific surface area of ​​the activated magnesium oxide is ≥110 m². 2 / g.

[0017] As a preferred embodiment of the method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution as described in this application, the comprehensive recovery rate of magnesium is ≥97.0%, the comprehensive recovery rate of nickel is ≥99.0%, and the comprehensive recovery rate of cobalt is ≥96.0%.

[0018] The beneficial effects of this application are as follows: This application provides a method for the efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution. This application constructs two major technical cornerstones: "single magnesium salt system" and "precise temperature control". In the same process, cobalt is converted into battery-grade cobalt tetroxide, nickel powder is upgraded into functionalized nickel powder, and magnesium is transformed from traditional waste into high-value-added active magnesium oxide.

[0019] In this application, the cobalt sulfite obtained by precipitation is upgraded to battery-grade cobalt tetroxide by calcination, and sulfur dioxide is simultaneously recovered and introduced into nickel powder. The nickel powder undergoes surface sulfidation functionalization treatment to obtain an antioxidant and highly active battery-specific nickel source, significantly increasing its added value. The highly active magnesium oxide produced by pyrolysis in this application can be directly recycled and sold, or it can be used to prepare the precipitant magnesium sulfite. Nickel, cobalt, and magnesium are all produced in the form of high-value-added products, realizing the high-value utilization of these three metals. The process of this application is simple and environmentally friendly, with no saline wastewater discharge. The sulfur dioxide generated from the calcination of cobalt sulfite is used for the functionalization and value-added of nickel powder, realizing cascade utilization. The entire process introduces no impurities such as sodium and chlorine, and generates no saponification wastewater or high-salt wastewater, meeting the requirements of clean production.

[0020] The specific principles of the technical solution adopted in this application are as follows: S1: Selective Cobalt Precipitation: The purpose of this step is to achieve highly selective precipitation of cobalt from a solution containing nickel, cobalt, and magnesium. The technical challenge lies in the fact that the separation of cobalt from nickel and magnesium relies on the difference in sulfite solubility products, and this difference can only be effectively utilized within a very narrow pH range. If the pH is too low, cobalt precipitation is incomplete; if the pH is too high, magnesium begins to co-precipitate, contaminating the cobalt product and causing magnesium loss. Furthermore, if traditional precipitants such as sodium carbonate are used, the introduced sodium ions will contaminate magnesium oxide during subsequent pyrolysis, preventing it from reaching its high-value potential. The solution in this application is to lock in an extremely narrow pH operating window and add a pre-removal process. Magnesium sulfite must be used as the precipitant to prevent the introduction of external cations at the source. Strict control is required: the pH for cobalt precipitation must be within a specific range; the precipitant must be magnesium sulfite.

[0021] S2: Nickel Powder Replacement and Functionalization: This step involves two closely linked stages: nickel replacement and nickel powder surface functionalization. The technical challenge of the first stage lies in the selection of the replacement agent. While zinc powder and iron powder can replace nickel, they introduce foreign metal ions, generating inseparable mixed oxides during S3 pyrolysis, turning high-value active magnesium oxide into waste slag. The solution in this application is to establish the technical red line that "the replacement agent must and can only be magnesium powder," ensuring the purity of the liquid after nickel removal from the source. The technical challenge of the second stage is that when the sulfur dioxide released from cobalt calcination reacts with nickel powder, sulfur dioxide and oxygen are present in the gas, creating strong competition between sulfidation and oxidation reactions. Too low a temperature results in insufficient sulfidation; too high a temperature intensifies oxidation, causing the protective layer to fail. The solution in this application is to discover an optimal temperature window of "sulfidation priority and controllable oxidation," allowing the functionalized nickel powder to simultaneously achieve the contradictory characteristics of "inert storage and transportation" and "active use." Cobalt calcination and nickel powder functionalization are coupled in this step, achieving resource utilization of sulfur dioxide. Strict control is required: the displacement agent must be magnesium powder; the functionalization reaction temperature must be within a specific window.

[0022] S3: Pyrolysis and Preparation of High-Value Active Magnesium Oxide: The purpose of this step is to convert magnesium sulfate in the nickel-removed solution into high-value-added active magnesium oxide. The technical challenge lies in the fact that the pyrolysis temperature is crucial in determining product quality. If the temperature is too low, decomposition is incomplete, resulting in substandard purity; if the temperature is too high, the magnesium oxide is overburned, causing a sharp decrease in specific surface area, rendering it a low-value product. The solution proposed in this application is to precisely lock in the optimal temperature window under an air atmosphere, ensuring complete decomposition while preserving high activity and a porous structure. Since S2 established the red line for magnesium powder, and the nickel-removed solution is a pure magnesium sulfate solution, a fundamental guarantee is provided for producing high-purity active magnesium oxide. Strict control is essential: the pyrolysis temperature must be within a specific window, and the process must be carried out under an air atmosphere.

[0023] The three steps described above are interconnected: pH control in S1 ensures cobalt purity and prevents magnesium loss; the magnesium powder red line in S2 guarantees the purity of the solution after nickel removal, laying the foundation for the production of high-purity active magnesium oxide in S3; and the precise temperature window in S2 simultaneously achieves cobalt calcination, nickel powder functionalization, and sulfur resource utilization. Any malfunction in any step will lead to a precipitous drop in the value of at least one product. This is precisely the core technological barrier of this application, enabling the efficient separation and high-value utilization of nickel, cobalt, and magnesium in nickel-cobalt-containing magnesium sulfate solutions. Detailed Implementation

[0024] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0025] This application provides a method for the efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution, comprising the following steps: S1. Obtain a magnesium sulfate solution containing impurities, add magnesium sulfite to the magnesium sulfate solution containing impurities to carry out a first reaction, and separate the solid and liquid to obtain cobalt sulfite and the cobalt-removed liquid; The composition of the magnesium sulfate solution containing impurities includes: Co: 2-5 g / L, Mg: 40-60 g / L, Ni: 0.5-2 g / L; the temperature of the first reaction is 40-80℃, the pH of the first reaction is 3.5-5.0, the reaction time is 30-90 min, and the amount of magnesium sulfite added is 1.0-1.2 times the theoretical amount; Specifically, the pH of the first reaction is any one of 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, and 5.0, and a range between any two of them; S2. Add magnesium powder to the cobalt-removed liquid for a second reaction, and separate the solid and liquid to obtain nickel powder and nickel-removed liquid. Calcinate the cobalt sulfite to obtain cobalt tetroxide and sulfur dioxide. Pass the sulfur dioxide into the nickel powder for a third reaction to obtain functionalized composite nickel powder. The second reaction is carried out at a temperature of 50-80℃, a pH of 4.0-5.5, and a time of 30-90 minutes. The amount of magnesium powder added is 1.0-1.2 times the theoretical amount. The calcination temperature is 400-600℃, and the calcination time is 60-180 minutes. The third reaction is carried out at a temperature of 200-400℃, and the third reaction time is 60-180 minutes. The functionalized composite nickel powder has a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel trisulfide and nickel oxide as the outer shell. The functionalized composite nickel powder has antioxidant properties, and its weight gain in air at room temperature is ≤0.2% after 30 days. Specifically, the temperature of the third reaction is any one of 200℃, 220℃, 240℃, 260℃, 280℃, 300℃, 320℃, 340℃, 360℃, 380℃, and 400℃, and a range between any two of them. S3. The nickel-removed liquid is evaporated, crystallized, and pyrolyzed to obtain active magnesium oxide; The pyrolysis temperature is 800-1100℃, and the pyrolysis time is 60-180 min; the purity of the active magnesium oxide is ≥99.0%, the purity of the functionalized composite nickel powder is ≥99.0%, the mass fraction of cobalt in the cobalt tetroxide is ≥72.6%, and the specific surface area of ​​the active magnesium oxide is ≥110 m². 2 / g; the overall recovery rate of magnesium is ≥97.0%, the overall recovery rate of nickel is ≥99.0%, and the overall recovery rate of cobalt is ≥96.0%; Specifically, the pyrolysis temperature is any one of 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, and 1100℃, or any two of them. The technical solution of this application will be further described below with reference to specific embodiments.

[0026] Example 1 This application provides a method for the efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution, comprising the following steps: S1. Obtain a magnesium sulfate solution containing impurities, add magnesium sulfite to the magnesium sulfate solution containing impurities to carry out the first reaction, and separate the solid and liquid to obtain cobalt sulfite and the cobalt-removed liquid. The magnesium sulfate solution containing impurities contains the following components: Co: 3.8 g / L, Mg: 49.5 g / L, Ni: 1.6 g / L; the temperature of the first reaction is 60℃, the pH of the first reaction is 4.4, the time of the first reaction is 60 min, and the amount of magnesium sulfite added is 1.05 times the theoretical amount. S2. Add magnesium powder to the cobalt-removed liquid for a second reaction, and separate the solid and liquid to obtain nickel powder and the nickel-removed liquid. Calcinate cobalt sulfite to obtain cobalt tetroxide and sulfur dioxide. Pass sulfur dioxide into the nickel powder for a third reaction to obtain functionalized composite nickel powder. The second reaction was carried out at a temperature of 65℃, a pH of 5.0, and a time of 60 min, with the amount of magnesium powder added being 1.05 times the theoretical amount; the calcination temperature was 500℃ and the calcination time was 120 min; the third reaction was carried out at a temperature of 300℃ and the third reaction time was 120 min. S3. The nickel-removed liquid is evaporated, crystallized, and pyrolyzed to obtain active magnesium oxide; The pyrolysis temperature was 950℃, and the pyrolysis time was 120 min. Testing revealed that the functionalized composite nickel powder possesses a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel disulfide and nickel oxide. The functionalized composite nickel powder exhibits antioxidant properties, with a weight gain of only 0.12% after 30 days in air at room temperature. The specific surface area of ​​the active magnesium oxide is 132 m². 2 / g, the purity of active magnesium oxide is 99.3%, the purity of functionalized composite nickel powder is 99.5%, and the mass fraction of cobalt in cobalt tetroxide is 73.2%; the comprehensive recovery rate of magnesium is 97.6%, the comprehensive recovery rate of nickel is 99.4%, and the comprehensive recovery rate of cobalt is 96.5%.

[0027] Example 2 This application provides a method for the efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution, comprising the following steps: S1. Obtain a magnesium sulfate solution containing impurities, add magnesium sulfite to the magnesium sulfate solution containing impurities to carry out the first reaction, and separate the solid and liquid to obtain cobalt sulfite and the cobalt-removed liquid. The composition of the magnesium sulfate solution containing impurities includes: Co: 3.8 g / L, Mg: 49.5 g / L, Ni: 1.6 g / L; the temperature of the first reaction is 80℃, the pH of the first reaction is 3.5, the time of the first reaction is 90 min, and the amount of magnesium sulfite added is 1.0 times the theoretical amount; S2. Add magnesium powder to the cobalt-removed liquid for a second reaction, and separate the solid and liquid to obtain nickel powder and the nickel-removed liquid. Calcinate cobalt sulfite to obtain cobalt tetroxide and sulfur dioxide. Pass sulfur dioxide into the nickel powder for a third reaction to obtain functionalized composite nickel powder. The second reaction was carried out at a temperature of 80℃, a pH of 4.0, and a time of 90 min, with the amount of magnesium powder added being 1.0 times the theoretical amount; the calcination temperature was 600℃ and the calcination time was 60 min; the third reaction was carried out at a temperature of 200℃ and a time of 180 min. S3. The nickel-removed liquid is evaporated, crystallized, and pyrolyzed to obtain active magnesium oxide; The pyrolysis temperature was 800℃, and the pyrolysis time was 180 min. Testing revealed that the functionalized composite nickel powder possesses a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel trisulfide and nickel oxide. The functionalized composite nickel powder exhibits antioxidant properties, with a weight gain of only 0.18% after 30 days in air at room temperature. The magnesium oxide has a specific surface area of ​​125 m². 2 / g, the purity of active magnesium oxide is 99.0%, the purity of functionalized composite nickel powder is 99.0%, and the mass fraction of cobalt in cobalt tetroxide is 72.8%; the comprehensive recovery rate of magnesium is 97.4%, the comprehensive recovery rate of nickel is 99.2%, and the comprehensive recovery rate of cobalt is 96.1%.

[0028] Example 3 This application provides a method for the efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution, comprising the following steps: S1. Obtain a magnesium sulfate solution containing impurities, add magnesium sulfite to the magnesium sulfate solution containing impurities to carry out the first reaction, and separate the solid and liquid to obtain cobalt sulfite and the cobalt-removed liquid. The composition of the magnesium sulfate solution containing impurities includes: Co: 3.8 g / L, Mg: 49.5 g / L, Ni: 1.6 g / L; the temperature of the first reaction is 40℃, the pH of the first reaction is 5.0, the time of the first reaction is 30 min, and the amount of magnesium sulfite added is 1.2 times the theoretical amount; S2. Add magnesium powder to the cobalt-removed liquid for a second reaction, and separate the solid and liquid to obtain nickel powder and the nickel-removed liquid. Calcinate cobalt sulfite to obtain cobalt tetroxide and sulfur dioxide. Pass sulfur dioxide into the nickel powder for a third reaction to obtain functionalized composite nickel powder. The second reaction was carried out at a temperature of 50℃, a pH of 5.5, and a time of 30 min, with the amount of magnesium powder added being 1.2 times the theoretical amount; the calcination temperature was 400℃ and the calcination time was 180 min; the third reaction was carried out at a temperature of 400℃ and a time of 60 min. S3. The nickel-removed liquid is evaporated, crystallized, and pyrolyzed to obtain active magnesium oxide; The pyrolysis temperature was 1100℃, and the pyrolysis time was 60 min. Testing revealed that the functionalized composite nickel powder possesses a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel trisulfide and nickel oxide. The functionalized composite nickel powder exhibits antioxidant properties, with a weight gain of only 0.20% after 30 days in air at room temperature. The magnesium oxide has a specific surface area of ​​114 m². 2 / g, the purity of active magnesium oxide is 99.2%, the purity of functionalized composite nickel powder is 99.2%, and the mass fraction of cobalt in cobalt tetroxide is 73.0%; the comprehensive recovery rate of magnesium is 97.2%, the comprehensive recovery rate of nickel is 99.0%, and the comprehensive recovery rate of cobalt is 96.6%.

[0029] Comparative Example 1 The difference between this comparative example and Example 1 is that the pH of the first reaction in step S1 is 3.0.

[0030] Testing revealed that the functionalized composite nickel powder possesses a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel trisulfide and nickel oxide. The functionalized composite nickel powder exhibits antioxidant properties, showing a weight gain of only 0.21% after 30 days in air at room temperature. The specific surface area of ​​the active magnesium oxide is 128 m². 2 / g, the purity of active magnesium oxide is 98.9%, the purity of functionalized composite nickel powder is 96.1%, and the mass fraction of cobalt in cobalt tetroxide is 73.1%; the comprehensive recovery rate of magnesium is 97.1%, the comprehensive recovery rate of nickel is 98.8%, and the comprehensive recovery rate of cobalt is 92.1%.

[0031] Comparative Example 2 The difference between this comparative example and Example 1 is that the pH of the first reaction in step S1 is 5.5.

[0032] Testing revealed that the functionalized composite nickel powder possesses a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel trisulfide and nickel oxide. The functionalized composite nickel powder exhibits antioxidant properties, showing a weight gain of only 0.16% after 30 days in air at room temperature. The magnesium oxide has a specific surface area of ​​130 m². 2 / g, the purity of active magnesium oxide is 99.0%, the purity of functionalized composite nickel powder is 99.4%, and the mass fraction of cobalt in cobalt tetroxide is 70.3%; the comprehensive recovery rate of magnesium is 96.1%, the comprehensive recovery rate of nickel is 99.1%, and the comprehensive recovery rate of cobalt is 96.6%.

[0033] Comparative Example 3 The difference between this comparative example and Example 1 is that the temperature of the third reaction in step S2 is 150°C.

[0034] Testing revealed that the functionalized composite nickel powder possesses a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel disulfide and nickel oxide as the outer shell. The functionalized composite nickel powder exhibits antioxidant properties, but the resulting coating layer is thin and incomplete, resulting in a weight gain of only 0.45% after 30 days in air at room temperature. The specific surface area of ​​the active magnesium oxide is 130 m². 2 / g, the purity of active magnesium oxide is 99.0%, the purity of functionalized composite nickel powder is 99.4%, and the mass fraction of cobalt in cobalt tetroxide is 73.0%; the comprehensive recovery rate of magnesium is 97.1%, the comprehensive recovery rate of nickel is 99.4%, and the comprehensive recovery rate of cobalt is 96.3%.

[0035] Comparative Example 4 The difference between this comparative example and Example 1 is that the temperature of the third reaction in step S2 is 450°C.

[0036] Testing revealed that the functionalized composite nickel powder possesses a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel trisulfide and nickel oxide as the outer shell. The functionalized composite nickel powder exhibits antioxidant properties, but the coating layer is porous, resulting in a weight gain of only 0.36% after 30 days in air at room temperature. The specific surface area of ​​the active magnesium oxide is 129 m². 2 / g, the purity of active magnesium oxide is 99.1%, the purity of functionalized composite nickel powder is 99.3%, and the mass fraction of cobalt in cobalt tetroxide is 73.1%; the comprehensive recovery rate of magnesium is 97.0%, the comprehensive recovery rate of nickel is 99.3%, and the comprehensive recovery rate of cobalt is 96.4%.

[0037] Comparative Example 5 The difference between this comparative example and Example 1 is that the pyrolysis temperature in step S3 is 750°C.

[0038] Testing revealed that the functionalized composite nickel powder possesses a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel trisulfide and nickel oxide as the outer shell. The functionalized composite nickel powder exhibits antioxidant properties, with a weight gain of only 0.17% after 30 days in air at room temperature. The magnesium oxide has a specific surface area of ​​131 m². 2 / g, the purity of active magnesium oxide is 96.1%, the purity of functionalized composite nickel powder is 99.3%, and the mass fraction of cobalt in cobalt tetroxide is 73.0%; the comprehensive recovery rate of magnesium is 95.3%, the comprehensive recovery rate of nickel is 99.1%, and the comprehensive recovery rate of cobalt is 96.4%.

[0039] Comparative Example 6 The difference between this comparative example and Example 1 is that the pyrolysis temperature in step S3 is 1150°C.

[0040] Testing revealed that the functionalized composite nickel powder possesses a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel trisulfide and nickel oxide. The functionalized composite nickel powder exhibits antioxidant properties, showing a weight gain of only 0.18% after 30 days in air at room temperature. The magnesium oxide has a specific surface area of ​​91 m². 2 / g, the purity of active magnesium oxide is 99.0%, the purity of functionalized composite nickel powder is 99.4%, and the mass fraction of cobalt in cobalt tetroxide is 73.1%; the comprehensive recovery rate of magnesium is 97.1%, the comprehensive recovery rate of nickel is 99.2%, and the comprehensive recovery rate of cobalt is 96.3%.

[0041] As can be seen from the above embodiments and comparative examples: Example 1, in conjunction with Comparative Example 1, shows that when the pH of the first reaction in S1 is reduced from 4.4 to 3.0, the cobalt recovery rate and the purity of the nickel powder are significantly reduced. This is because the low pH leads to incomplete cobalt precipitation, and the residual cobalt is replaced by magnesium powder in the subsequent steps, resulting in a decrease in the purity of the nickel powder.

[0042] Example 1, in conjunction with Comparative Example 2, shows that when the pH of the first reaction in S1 increases from 4.4 to 5.5, the mass fraction of cobalt in cobalt tetroxide decreases significantly. This is because the excessively high pH causes magnesium to co-precipitate into the cobalt slag, contaminating the cobalt product.

[0043] Example 1, combined with Comparative Example 3, shows that when the third reaction temperature in S2 is reduced from 300°C to 150°C, the oxidation resistance of nickel powder is significantly reduced. Due to the low temperature, the sulfidation reaction rate is insufficient, and the resulting coating layer is thin and incomplete, failing to effectively block air.

[0044] Example 1, combined with Comparative Example 4, shows that when the third reaction temperature in S2 is increased from 300°C to 450°C, the oxidation resistance of nickel powder is significantly reduced. This is because the competition between the oxidation reaction and the sulfidation reaction intensifies due to the excessively high temperature, resulting in a loose coating layer.

[0045] Example 1, combined with Comparative Example 5, shows that when the pyrolysis temperature in S3 is reduced from 950℃ to 750℃, the purity of active magnesium oxide and the magnesium recovery rate are significantly reduced. Due to the low pyrolysis temperature, magnesium sulfate is not completely decomposed, and the residual sulfate reduces the purity of the magnesium oxide product.

[0046] Example 1, combined with Comparative Example 6, shows that when the pyrolysis temperature in S3 is increased from 950℃ to 1150℃, the specific surface area of ​​active magnesium oxide decreases significantly. This is because the excessively high temperature leads to overheating of magnesium oxide, resulting in grain growth and fusion, a significant decrease in specific surface area, and reduced activity.

[0047] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for the efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution, characterized in that, Includes the following steps: S1. Obtain a magnesium sulfate solution containing impurities, add magnesium sulfite to the magnesium sulfate solution containing impurities to carry out a first reaction, and separate the solid and liquid to obtain cobalt sulfite and the cobalt-removed liquid; S2. Add magnesium powder to the cobalt-removed liquid for a second reaction, and separate the solid and liquid to obtain nickel powder and nickel-removed liquid. Calcinate the cobalt sulfite to obtain cobalt tetroxide and sulfur dioxide. Pass the sulfur dioxide into the nickel powder for a third reaction to obtain functionalized composite nickel powder. S3. The nickel-removed liquid is evaporated, crystallized, and pyrolyzed to obtain active magnesium oxide; In step S1, the pH of the first reaction is 3.5-5.0; In step S2, the calcination temperature is 400-600℃, and the temperature of the third reaction is 200-400℃. In step S3, the pyrolysis temperature is 800-1100℃.

2. The method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution according to claim 1, characterized in that, In step S1, the composition of the magnesium sulfate solution containing impurities includes: Co: 2-5 g / L, Mg: 40-60 g / L, Ni: 0.5-2 g / L.

3. The method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution according to claim 1, characterized in that, In step S1, the temperature of the first reaction is 40-80℃, the reaction time is 30-90 min, and the amount of magnesium sulfite added is 1.0-1.2 times the theoretical amount.

4. The method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution according to claim 1, characterized in that, In step S2, the temperature of the second reaction is 50-80℃, the pH of the second reaction is 4.0-5.5, the reaction time is 30-90 min, and the amount of magnesium powder added is 1.0-1.2 times the theoretical amount.

5. The method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution according to claim 1, characterized in that, In step S2, the calcination time is 60-180 min.

6. The method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution according to claim 1, characterized in that, In step S2, the time for the third reaction is 60-180 min.

7. The method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution according to claim 1, characterized in that, In step S2, the functionalized composite nickel powder has a core-shell structure, with metallic nickel as the core and a coating structure composed of nickel disulfide and nickel oxide as the outer shell. The functionalized composite nickel powder has antioxidant properties, and its weight gain in air at room temperature is ≤0.2% after 30 days.

8. The method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution according to claim 1, characterized in that, In step S3, the pyrolysis time is 60-180 min.

9. The method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution according to claim 1, characterized in that, The purity of the active magnesium oxide is ≥99.0%, the purity of the functionalized composite nickel powder is ≥99.0%, the mass fraction of cobalt in the cobalt tetroxide is ≥72.6%, and the specific surface area of ​​the active magnesium oxide is ≥110 m². 2 / g.

10. The method for efficient separation and high-value utilization of nickel, cobalt, and magnesium in magnesium sulfate solution according to claim 1, characterized in that, The overall recovery rate of magnesium is ≥97.0%, the overall recovery rate of nickel is ≥99.0%, and the overall recovery rate of cobalt is ≥96.0%.