Method for separating and enriching nickel and iron in ferronickel alloy and nickel-based recovery product

Abstract

This invention discloses a method for separating and enriching nickel and iron in nickel-iron alloys, as well as nickel-based recovery products. Ferric chloride, containing inherent nickel impurities, obtained from the chlorination roasting of nickel-iron alloys, is used as raw material to prepare a solution. Under ammonium-free conditions, a first iron precipitation agent is added to conduct a first iron precipitation reaction, controlling the pH at 1.5-1.8, resulting in solid-liquid separation to obtain ferric phosphate and a nickel-iron-containing filtrate. The pH of the filtrate is adjusted to 5.2-5.7 to conduct a second iron precipitation reaction, yielding an iron-containing precipitate and a nickel-containing filtrate. The pH of the nickel-containing filtrate is adjusted to 9.5-10.5 to conduct a nickel precipitation reaction, yielding a nickel-containing precipitate. This invention eliminates nickel-ammonia complexation at the source, achieving complete nickel recovery, and simultaneously producing high-purity ferric phosphate and resource-recoverable intermediate products.

Description

Technical Field

[0001] This invention belongs to the field of separation technology, specifically relating to a method for separating and enriching nickel and iron in nickel-iron alloys, as well as nickel-based recycled products. Background Technology

[0002] Lateritic nickel ore is smelted to obtain ferronickel alloy, and then the iron is selectively chlorinated and volatilized through high-temperature chlorination roasting to produce a roasted product mainly composed of ferric chloride. This process has the advantages of short process and high iron separation efficiency, and has become one of the important directions for the resource utilization of lateritic nickel ore. However, the obtained ferric chloride inherently contains 0.3%-0.5% nickel in the form of physical inclusions or solid solution, which cannot be removed by simple physical sorting. Therefore, this material is not only a high-quality iron source, but also an important secondary nickel source. Achieving efficient separation and separate enrichment of the two has significant dual benefits in terms of resources and the environment.

[0003] Currently, research on nickel-iron separation from nickel-containing ferric chloride materials mainly follows the ammonia process route. This route uses ammonia or ammonium salts as pH adjusters, utilizing the difference in coordination behavior between ammonium ions and iron and nickel to achieve separation. Specifically, during the iron precipitation stage, acidic conditions are controlled to precipitate iron as ferric phosphate, while nickel remains in solution as an ammonium-nickel complex or in a free state. However, this route has an inherent thermodynamic bottleneck: the nickel-ammonium complex ion ([Ni(NH3)2]2)... n ] 2+ The stability constant of nickel is extremely high. In industrial practice, due to limitations such as the amount of precipitant, reaction time, and interference from impurities, the direct recovery rate of nickel in the nickel immersion process can usually only reach about 60%. About 35%-40% of the nickel remains in the nickel immersion tail liquid as dissolved nickel-ammonia complex, which not only causes the invisible loss of strategic metal resources, but also increases the burden of wastewater treatment.

[0004] Therefore, there is an urgent need for a method to separate and enrich nickel and iron in nickel-iron alloys in order to alleviate or solve the above problems. Summary of the Invention

[0005] To address the technical problem of limited nickel recovery rate when separating nickel and iron in nickel-iron alloys using the aforementioned commonly used techniques, this invention provides a method for separating and enriching nickel and iron in nickel-iron alloys, comprising the following steps: The nickel-iron alloy was subjected to chlorination roasting to obtain ferric chloride containing inherent nickel impurities. The ferric chloride containing inherent nickel impurities is prepared into a nickel-containing ferric chloride solution; Under conditions without the addition of ammonium ions, a first iron precipitation agent is added to the nickel-containing ferric chloride solution to carry out the first iron precipitation reaction, followed by solid-liquid separation to obtain ferric phosphate product and nickel- and iron-containing filtrate. The nickel- and iron-containing filtrate is subjected to a second iron precipitation reaction to achieve solid-liquid separation, yielding an iron-containing precipitate and a nickel-containing filtrate. The nickel-containing filtrate was subjected to a nickel precipitation reaction to obtain a nickel-containing precipitate.

[0006] Furthermore, the chemical composition of the nickel-iron alloy includes: 80%-85% iron, 10%-15% nickel, and 0.4%-0.6% cobalt; the composition of the ferric chloride containing inherent nickel impurities includes: ≥98% ferric chloride, 0.3-0.5% nickel, and 0.03-0.05% cobalt.

[0007] Furthermore, a first iron precipitation agent is added to the nickel-containing ferric chloride solution to induce a first iron precipitation reaction, followed by solid-liquid separation to obtain ferric phosphate and a nickel-containing filtrate. The first iron-sinking agent includes a phosphorus agent and an alkaline agent; The phosphate agent includes at least one of sodium dihydrogen phosphate solution and phosphoric acid solution, and the alkali agent includes at least one of sodium hydroxide, nickel hydroxide, and iron hydroxide. The molar ratio of phosphorus in the phosphorus agent to iron in the nickel-containing ferric chloride solution is 1.3-1.5, and the temperature of the first iron precipitation reaction is 80-90℃; the pH during the first iron precipitation reaction is controlled to be 1.5-1.8 by the alkali agent.

[0008] Furthermore, the sources of the nickel- and iron-containing filtrate also include cleaning fluid; The ferric phosphate product is washed for 0.5-1 h at a liquid-to-solid ratio of 5-10:1 to obtain wet ferric phosphate material; the liquid phase is collected to obtain the washing solution.

[0009] Furthermore, the second iron precipitation reaction includes adding a second iron precipitation agent to the nickel- and iron-containing filtrate, wherein the second iron precipitation agent includes at least one of sodium hydroxide and potassium hydroxide.

[0010] Furthermore, the second iron precipitation agent controls the pH during the second iron precipitation reaction process to be 5.2-5.7.

[0011] Furthermore, the nickel precipitation reaction includes adding a nickel precipitant to the nickel-containing filtrate, wherein the nickel precipitant includes at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide.

[0012] Furthermore, the nickel precipitant controls the pH of the nickel precipitation reaction to be 9.5-10.5.

[0013] Furthermore, the wet-based iron phosphate material is dried to obtain an iron-based recovery product, the chemical composition of which is iron phosphate dihydrate. The drying process is carried out at a temperature of 75-80℃ for 2-4 hours.

[0014] This invention provides a nickel-based recycled product, prepared by the method for separating and enriching nickel and iron in nickel-iron alloys as described in any of the above claims.

[0015] Compared with the prior art, the present invention has at least the following advantages: This invention uses anhydrous ferric chloride, which contains 0.3%-0.5% nickel after chlorination roasting of nickel-iron alloy, as raw material. Nickel in this material exists as physical inclusions or in solid solution, making it impossible to remove through simple sorting. However, this invention considers it a dual-resource carrier for nickel and iron: iron is the main component in the preparation of ferric phosphate, while nickel is a strategic metal requiring maximal recovery. This raw material positioning dictates that subsequent processes must simultaneously ensure the high-purity precipitation of iron and the complete retention of nickel, rather than a crude separation of a single element.

[0016] This invention strictly limits the introduction of ammonium ions in the first iron precipitation reaction, thus eliminating the prerequisite for the formation of nickel-ammonia complexes through reagent selection. Nickel in solution always exists as free Ni. 2+ The presence of this substance, along with the reaction driving force of subsequently added hydroxide or carbonate sources, allows the nickel precipitation reaction to proceed until the liquid phase nickel concentration approaches zero. This combination of characteristics is the fundamental reason for the qualitative breakthrough in nickel recovery achieved in this invention, and also the most essential technical difference between it and the ammonia process.

[0017] In the first iron precipitation reaction of this invention, sodium hydroxide is used as an alkaline agent to control the pH of the system within a strongly acidic range of 1.5-1.8 (this parameter is the key process window of this invention). At this pH, on the one hand, the solubility of iron phosphate is extremely low, and more than 98% of the iron is quantitatively precipitated in the form of iron phosphate dihydrate crystals. After washing and drying, the iron-phosphorus molar ratio of the precipitate is close to the theoretical value, and the content of the key impurity nickel can be stably lower than the battery-grade standard limit, realizing the efficient preparation of battery-grade iron phosphate. On the other hand, because the pH is much lower than the precipitation starting point of its hydroxide (about 6.5) and phosphate, nickel ions are completely retained in the liquid phase in a free state, without co-precipitation loss or complexation risk.

[0018] In this invention, the filtrate after the first iron precipitation still contains a small amount of residual iron. This invention adjusts the pH of the filtrate to a narrow, weakly acidic window of 5.2-5.7 for a second iron precipitation reaction, ensuring that the residual iron is completely precipitated as ferric hydroxide, thus preventing iron contamination of the nickel products. Furthermore, this pH range is lower than the initial pH for nickel ion hydrolysis precipitation; more than 90% of the nickel remains in a free state in the liquid phase, while a small portion of nickel co-precipitates with iron to form nickel-iron slag, which is then returned to the first iron precipitation reaction as an alkali for pH adjustment.

[0019] The nickel-containing filtrate after the first and second iron precipitation reactions described above possesses an ideal chemical environment for nickel precipitation. In this invention, nickel precipitants such as sodium hydroxide, sodium carbonate, or sodium bicarbonate are directly added at this stage to release free Ni. 2+ It rapidly generates a low-solubility precipitate, with sufficient reaction driving force, resulting in a nickel recovery rate of up to 100%. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a photograph of the battery-grade iron phosphate product obtained in Example 1 of the present invention. Figure 2 This is a flowchart of a method for separating and enriching nickel and iron in a nickel-iron alloy according to an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0024] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0025] like Figure 2 As shown, the present invention provides a method for separating and enriching nickel and iron in a nickel-iron alloy, comprising the following steps: S1. The nickel-iron alloy is subjected to chlorination roasting treatment to obtain ferric chloride containing inherent nickel impurities.

[0026] In this invention, the chemical composition of the nickel-iron alloy includes: 80%-85% iron, 10%-15% nickel, and 0.4%-0.6% cobalt; the composition of the ferric chloride containing inherent nickel impurities includes: ≥98% ferric chloride, 0.3-0.5% nickel, and 0.03-0.05% cobalt.

[0027] In this invention, the chlorination roasting temperature is 650-850℃, the mass ratio of nickel-iron alloy to chlorine is 1:1.66-2.5, the chlorine flow rate is 1.45kg / min-2.2kg / min, and the chlorination reaction time is 2.5h-3h.

[0028] For example, the temperature of the chlorination roasting treatment can be 650°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 850°C, and any value between such a minimum and maximum value, or a range of any two values.

[0029] For example, the mass ratio of the nickel-iron alloy to chlorine gas can be 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4, and any value between such a minimum and maximum value, or a range of any two values.

[0030] S2. Prepare the ferric chloride containing inherent nickel impurities into a nickel-containing ferric chloride solution.

[0031] In some embodiments, the concentration of the nickel-containing ferric chloride solution can be 0.8-1.2 mol / L.

[0032] For example, the concentration of the nickel-containing ferric chloride solution can be 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, or any value between such a minimum and maximum value, or a range of any two values.

[0033] S3. Under conditions without the addition of ammonium ions, a first iron precipitation agent is added to the nickel-containing ferric chloride solution to carry out the first iron precipitation reaction, followed by solid-liquid separation to obtain ferric phosphate product and nickel- and iron-containing filtrate.

[0034] In this invention, the first iron-sinking agent includes a phosphorus agent and an alkaline agent; The phosphoric acid agent includes at least one of sodium dihydrogen phosphate solution and phosphoric acid solution, and the alkaline agent includes at least one of sodium hydroxide, nickel hydroxide, and iron hydroxide.

[0035] In this invention, during the first iron precipitation reaction, the molar ratio of phosphorus in the phosphorus agent to iron in the nickel-containing ferric chloride solution is 1.3-1.5, and the temperature of the first iron precipitation reaction is 80-90℃; the pH during the first iron precipitation reaction is controlled to be 1.5-1.8 by the alkali agent.

[0036] For example, the molar ratio of phosphorus in the phosphorus agent to iron in the nickel-containing ferric chloride solution can be 1.3, 1.40, 1.54, 1.50, or any value between such a minimum and maximum value, or a range of any two values.

[0037] For example, the pH in the first iron deposition reaction process can be 1.5, 1.6, 1.7, 1.8, and any value between such a minimum and maximum value, or a range of any two values.

[0038] In some embodiments, the duration of the first iron deposition reaction can be 3-6 hours; and, by another example, the duration of the first iron deposition reaction can be 3-5 hours.

[0039] In this invention, the source of the nickel- and iron-containing filtrate also includes a cleaning solution; The ferric phosphate product is washed for 0.5-1 h at a liquid-to-solid ratio of 5-10:1 to obtain wet ferric phosphate material; the liquid phase is collected to obtain the washing solution.

[0040] In some embodiments, the cleaning solution is combined with the nickel- and iron-containing filtrate and participates in the second iron precipitation reaction in step S4.

[0041] In this invention, the wet-based iron phosphate material is dried to obtain an iron-based recycled product, the chemical composition of which is iron phosphate dihydrate. The drying process is carried out at a temperature of 75-80℃ for 2-4 hours.

[0042] S4. The nickel- and iron-containing filtrate undergoes a second iron precipitation reaction to separate the solid and liquid components, yielding an iron-containing precipitate and a nickel-containing filtrate.

[0043] In this invention, the second iron precipitation reaction includes adding a second iron precipitation agent to the nickel- and iron-containing filtrate, wherein the second iron precipitation agent includes at least one of sodium hydroxide and potassium hydroxide.

[0044] In this invention, the second iron precipitation agent controls the pH of the second iron precipitation reaction to be 5.2-5.7. For example, the duration of the second precipitation reaction can be 0.5-1.5 hours.

[0045] It should be noted that the amount of the second iron precipitation agent should be based on the required pH value of the system to ensure complete precipitation of iron and minimize the co-precipitation of nickel.

[0046] In this invention, the iron-containing precipitate can be returned to the first iron precipitation reaction as an alkaline agent to reduce iron loss in the process.

[0047] S5. The nickel-containing filtrate is subjected to a nickel precipitation reaction to obtain a nickel-containing precipitate.

[0048] In this invention, the nickel precipitation reaction includes adding a nickel precipitant to the nickel-containing filtrate, wherein the nickel precipitant includes at least one of sodium carbonate, ammonium bicarbonate, and sodium hydroxide.

[0049] In this invention, the nickel precipitant controls the pH of the nickel precipitation reaction to be 9.5-10.5. For example, the duration of the nickel precipitation reaction can be 0.5-2 hours to ensure complete precipitation of nickel ions.

[0050] For example, the pH of the nickel plating reaction can be 9.5, 9.8, 10.0, 10.5, or any value between such a minimum and maximum value, or a range of any two values.

[0051] In this invention, the formula for calculating the yield of battery-grade iron phosphate is as follows: Yield (%) = (Mass of iron in battery-grade ferric phosphate ÷ Total mass of iron in nickel-containing ferric chloride solution) × 100%.

[0052] The formula for calculating nickel recovery rate is: Nickel recovery rate (%) = (mass of nickel in nickel-based recovered products ÷ total mass of nickel in nickel-containing ferric chloride solution) × 100%.

[0053] The present invention also provides a nickel-based recycled product, which is prepared by the method for separating and enriching nickel and iron in nickel-iron alloys as described in any of the above claims.

[0054] In this invention, the main chemical components of the nickel-based recycled products are nickel hydroxide or nickel carbonate. After purification, they can be used in high-end fields such as ternary lithium battery precursors and electroplating, which is the core embodiment of the high-value utilization of nickel resources.

[0055] To facilitate a further understanding of the present invention by those skilled in the art, the following examples are provided: Example 1 S1. The nickel-iron alloy is subjected to chlorination roasting to obtain ferric chloride containing inherent nickel impurities; wherein, the chlorination roasting temperature is 700℃, the mass ratio of nickel-iron alloy to chlorine gas is 1:2.0, the chlorine gas flow rate is 1.8 kg / min, and the chlorination roasting reaction time is 2.5 h; the chemical composition of the nickel-iron alloy, by mass fraction, includes: 83.44% iron, 13.24% nickel, 0.526% cobalt, and the remainder being unavoidable impurities; the chemical composition of the ferric chloride containing inherent nickel impurities includes: 98.5% ferric chloride, 0.37% nickel, 0.034% cobalt, and the remainder being unavoidable impurities.

[0056] S2. Weigh 162.5g of ferric chloride containing inherent nickel impurities, dissolve it in 1L of water until fully dissolved, and prepare a nickel-containing ferric chloride solution with a concentration of 1mol / L for later use.

[0057] S3. A nickel-containing ferric chloride solution and a sodium phosphate solution are mixed at a P / Fe molar ratio of 1.35. The mixture is stirred uniformly at 80°C (stirring speed 400 r / min), and an alkaline agent (sodium hydroxide solution) is slowly added dropwise. The pH of the system is precisely controlled at 1.8. After the first iron precipitation reaction, ferric phosphate slurry is obtained after 3 hours. The ferric phosphate slurry is then filtered to separate the ferric phosphate product and the nickel- and iron-containing filtrate. The ferric phosphate product is washed to obtain a wet-based ferric phosphate material. The washing liquid is collected (the liquid-to-solid ratio during washing is 5:1, and the washing time is 0.5-1 h). The wet-based ferric phosphate material is dried to obtain a battery-grade ferric phosphate product, the actual product of which is as follows: Figure 1 As shown in Table 1, the nickel- and iron-containing filtrate and washing solution are combined to obtain a mixture. This mixture participates in step S4. The composition of the mixture is shown in Table 1.

[0058] Table 1. Composition content of the mixture S4. Slowly add the second iron precipitation agent (sodium hydroxide) to the nickel- and iron-containing filtrate and washing solution, while stirring (stirring speed 200 r / min) to adjust the pH of the system to 5.5, and carry out the second iron precipitation reaction for 1 hour to ensure that the iron ions are completely converted into ferric hydroxide precipitate. After the reaction is complete, perform solid-liquid separation by pressure filtration to obtain the iron-containing precipitate (ferric hydroxide) and the nickel-containing filtrate. The amount of the second iron precipitation agent is determined by ensuring that the pH value of the system reaches the required value. The iron content in the nickel-containing filtrate is 0 mg / L, and the nickel content is 283.54 mg / L.

[0059] The iron-containing precipitate is returned to the first iron precipitation reaction as an alkaline agent.

[0060] S5. Add sodium hydroxide to the nickel-containing filtrate, stir (stirring speed 350 r / min) to adjust the pH of the system to 10.5, and react for 1 hour to carry out the nickel precipitation reaction, so that the nickel ions are completely precipitated, and a nickel-containing precipitate is obtained (the main chemical composition is nickel hydroxide, i.e., nickel-based recycled product); the amount of nickel precipitant (sodium hydroxide) added is based on maintaining the pH at 10.5. The obtained nickel-based recycled product can be used in battery materials, electroplating, and other fields.

[0061] Results: The battery-grade iron phosphate yield obtained in this embodiment was 98.2%, with Fe: 28.9%, P: 16.5%, iron-phosphorus ratio: 0.97, Ni: 0.0039%, and Co: 0.0034%. The product meets the technical requirements of "Iron Phosphate for Batteries" (HG / T4701-2021); the nickel recovery rate was 100%.

[0062] It should be noted that the technical requirements for "Iron Phosphate for Batteries" (HG / T4701-2021) specify that the iron content in iron phosphate for batteries should be 28.5-30.0% by mass, the phosphorus content should be 16.2-17.2% by mass, the iron-phosphorus molar ratio should be 0.96-1.02, and the cobalt content should not exceed 0.005%; and to ensure the quality of iron phosphate for batteries, the nickel content should not exceed 0.005%.

[0063] Example 2 Compared to Example 1, steps S1-S2 remain unchanged in this example.

[0064] S3. A nickel-containing ferric chloride solution (chemical composition same as in Example 1) and a sodium phosphate solution are mixed at a P / Fe molar ratio of 1.4. The mixture is stirred at a constant speed (400 r / min) at a reaction temperature of 85°C. Sodium hydroxide solution is slowly added dropwise to precisely control the pH of the system at 1.8. After 4 hours of the first iron precipitation reaction, ferric phosphate slurry is obtained. The ferric phosphate slurry is then filtered to separate the ferric phosphate product and the nickel- and iron-containing filtrate. The ferric phosphate product is washed to obtain a wet-based ferric phosphate material, and the washing liquid is collected. The wet-based ferric phosphate material is dried to obtain a battery-grade ferric phosphate product. The nickel- and iron-containing filtrate and the washing liquid are combined to form a mixture, which participates in step S4. The composition of the mixture is shown in Table 2.

[0065] Table 2. Composition content of the mixture S4. Slowly add the second iron-precipitating agent (sodium hydroxide) to the nickel- and iron-containing filtrate and washing solution, while stirring (stirring speed 200 r / min) to adjust the pH of the system to 5.5. The reaction time is 1 hour to allow the iron ions to be completely converted into ferric hydroxide precipitate. After the reaction is complete, perform solid-liquid separation by pressure filtration to obtain ferric hydroxide and nickel-containing filtrate. The amount of the second iron-precipitating agent is determined by achieving a system pH of 5.5. The nickel-containing filtrate has an iron content of 0 mg / L and a nickel content of 271.22 mg / L.

[0066] The iron-containing precipitate is returned to the first iron precipitation reaction as an alkali agent.

[0067] S5. Add sodium carbonate to the nickel-containing filtrate, stir (stirring speed 350 r / min) to adjust the pH of the system to 9.5, and react for 1 hour to completely precipitate nickel ions, obtaining a nickel-containing precipitate (the main chemical composition is nickel carbonate, i.e., a nickel-based recycled product); the amount of nickel precipitant (sodium carbonate) added should be adjusted to achieve a pH of 9.5. The obtained nickel-based recycled product can be used in battery materials, electroplating, and other fields.

[0068] Results: The battery-grade iron phosphate yield obtained in this embodiment was 99.1%, with Fe: 29.5%, P: 17.0%, iron-phosphorus ratio: 0.96, Ni: 0.0032%, and Co: 0.0039%. The product meets the technical requirements of "Iron Phosphate for Batteries" (HG / T4701-2021); the nickel recovery rate was 100%.

[0069] Comparative Example 1 Compared to Example 1, all other conditions in this comparative example remain unchanged, except that the pH of the first iron precipitation reaction in step S3 is adjusted to 1.38.

[0070] Results: The yield of battery-grade iron phosphate obtained in this comparative example was 85.1%, which is too low.

[0071] Comparative Example 2 Compared to Example 1, the other conditions in this comparative example remain unchanged, except that the pH of the first iron precipitation reaction in step S3 is adjusted to 1.92.

[0072] Results: The yield of battery-grade iron phosphate obtained in this comparative example was 98.7%, Ni: 0.012%, Co: 0.007%, and the product did not meet the technical requirements of "Iron Phosphate for Batteries" (HG / T4701-2021).

[0073] Comparative Example 3 Compared to Example 1, the other conditions in this comparative example remain unchanged, except that the temperature of the first iron deposition reaction in step S3 is adjusted to 70°C.

[0074] Results: The Fe content in the battery-grade iron phosphate product obtained in this comparative example was 31.28%, which did not meet the product standard, and the product was reddish-brown.

[0075] Comparative Example 4 Compared to Example 1, the other conditions in this comparative example remain unchanged, except that the iron-phosphorus ratio in the first iron precipitation reaction in step S3 is adjusted to 1:1.2.

[0076] Results: The battery-grade iron phosphate product obtained in this comparative example had a phosphorus content of 15.8%, which does not meet the product standard, and the product was reddish-brown.

[0077] Comparative Example 5 Compared to Example 1, the other conditions in this comparative example remain unchanged, except that the iron-phosphorus ratio in the first iron precipitation reaction in step S3 is adjusted to 1:1.6.

[0078] Result: The phosphorus content in the battery-grade iron phosphate product obtained in this comparative example was 17.7%, which does not meet the product standard.

[0079] Comparative Example 6 Compared to Example 1, the other conditions in this comparative example remain unchanged, except that the reaction time of the first iron deposition reaction in step S3 is adjusted to 2 hours.

[0080] Results: The battery-grade iron phosphate product obtained in this comparative example had an Fe content of 30.6%, a Ni content of 0.0052%, and a Co content of 0.0017%, which did not meet the product standards.

[0081] Comparative Example 7 Compared to Example 1, all other conditions in this comparative example remain unchanged, except that the pH of the second iron precipitation reaction in step S4 is adjusted to 4.5.

[0082] Results: In this embodiment, the yield of battery-grade iron phosphate was 98.2%, with Fe: 28.9%, P: 16.5%, iron-to-phosphorus ratio: 0.97, Ni: 0.0039%, and Co: 0.0034%. The product met the technical requirements of "Iron Phosphate for Batteries" (HG / T4701-2021). However, the nickel-containing filtrate still contained 15.31 mg / L of unprecipitated iron, and the final nickel hydroxide contained 6.1% iron hydroxide, indicating incomplete separation of nickel and iron.

[0083] Comparative Example 8 Compared to Example 1, the other conditions in this comparative example remain unchanged, except that the pH value of the nickel immersion reaction in step S5 is adjusted to 8.5.

[0084] Results: In this embodiment, the yield of battery-grade iron phosphate was 98.2%, with Fe: 28.9%, P: 16.5%, iron-to-phosphorus ratio: 0.97, Ni: 0.0039%, and Co: 0.0034%. The product met the technical requirements of "Iron Phosphate for Batteries" (HG / T4701-2021). However, the nickel-containing filtrate still contained 28.76 mg / L of nickel, and the nickel recovery rate was 91.6%, indicating incomplete recovery.

Claims

1. A method for separating and enriching nickel and iron in a nickel-iron alloy, characterized in that, Including the following steps: The nickel-iron alloy was subjected to chlorination roasting to obtain ferric chloride containing inherent nickel impurities. The ferric chloride containing inherent nickel impurities is prepared into a nickel-containing ferric chloride solution; Under conditions without the addition of ammonium ions, a first iron precipitation agent is added to the nickel-containing ferric chloride solution to carry out the first iron precipitation reaction, followed by solid-liquid separation to obtain ferric phosphate product and nickel- and iron-containing filtrate. The nickel- and iron-containing filtrate is subjected to a second iron precipitation reaction to achieve solid-liquid separation, yielding an iron-containing precipitate and a nickel-containing filtrate. The nickel-containing filtrate was subjected to a nickel precipitation reaction to obtain a nickel-containing precipitate.

2. The method for separating and enriching nickel and iron in a nickel-iron alloy according to claim 1, characterized in that, The chemical composition of the nickel-iron alloy includes: 80%-85% iron, 10%-15% nickel, and 0.4%-0.6% cobalt; the composition of the ferric chloride containing inherent nickel impurities includes: ≥98% ferric chloride, 0.3-0.5% nickel, 0.03-0.05% cobalt, with the remainder being unavoidable impurities.

3. The method for separating and enriching nickel and iron in a nickel-iron alloy according to claim 1, characterized in that, The first iron-sinking agent includes a phosphorus agent and an alkaline agent; The phosphate agent includes at least one of sodium dihydrogen phosphate solution and phosphoric acid solution, and the alkali agent includes at least one of sodium hydroxide, nickel hydroxide, and iron hydroxide. The molar ratio of phosphorus in the phosphorus agent to iron in the nickel-containing ferric chloride solution is 1.3-1.5, and the temperature of the first iron precipitation reaction is 80-90℃; the pH during the first iron precipitation reaction is controlled to be 1.5-1.8 by the alkali agent.

4. The method for separating and enriching nickel and iron in a nickel-iron alloy according to claim 1, characterized in that, The sources of the nickel- and iron-containing filtrate also include cleaning fluid; The cleaning solution is obtained by washing the ferric phosphate product for 0.5-1h under a liquid-to-solid ratio of 5-10:1 to obtain a wet-based ferric phosphate material; collecting the liquid phase to obtain the cleaning solution.

5. The method for separating and enriching nickel and iron in a nickel-iron alloy according to claim 1, characterized in that, The second iron precipitation reaction includes: adding a second iron precipitation agent to the nickel- and iron-containing filtrate; the second iron precipitation agent includes at least one of sodium hydroxide and potassium hydroxide.

6. The method for separating and enriching nickel and iron in a nickel-iron alloy according to claim 5, characterized in that, The pH during the second iron precipitation reaction is controlled to be 5.2-5.7 by the second iron precipitation agent.

7. The method for separating and enriching nickel and iron in a nickel-iron alloy according to claim 1, characterized in that, The nickel precipitation reaction includes adding a nickel precipitant to the nickel-containing filtrate, wherein the nickel precipitant includes at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide.

8. The method for separating and enriching nickel and iron in a nickel-iron alloy according to claim 7, characterized in that, The pH of the nickel precipitation reaction is controlled to be 9.5-10.5 by the nickel precipitant.

9. The method for separating and enriching nickel and iron in a nickel-iron alloy according to claim 4, characterized in that, The wet-based iron phosphate material is dried to obtain an iron-based recovery product, the chemical composition of which is iron phosphate dihydrate. The drying process is carried out at a temperature of 75-80℃ for 2-4 hours.

10. A nickel-based recycling product, characterized in that, The chemical composition includes nickel hydroxide or nickel carbonate, and is prepared by the method for separating and enriching nickel and iron in the nickel-iron alloy as described in any one of claims 1-9.

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