A process for the co-production of battery grade nickel sulfate and battery grade iron phosphate

Abstract

The application provides a method for co-production of battery-grade nickel sulfate and battery-grade iron phosphate, comprising the following steps: 1) performing first acid leaching treatment on a nickel-iron alloy pair by using an acid liquor to obtain a first acid leaching liquor and a first acid leaching residue; 2) performing second acid leaching treatment on the first acid leaching residue by using an oxidizing agent and an acid liquor to obtain a second acid leaching liquor and a second acid leaching residue; 3) performing extraction treatment on a mixed liquor comprising the first acid leaching liquor and the second acid leaching liquor by using an ion exchange resin to obtain a raffinate comprising ferrous ions; performing oxidation treatment on a system comprising the raffinate and a phosphorus source to obtain iron phosphate; 4) performing cleaning treatment on the ion exchange resin after the extraction treatment by using an acid liquor, then performing stripping treatment on the ion exchange resin by using an acid liquor and performing cooling crystallization treatment on a stripping liquor comprising nickel ions to obtain nickel sulfate. The method provided by the application has high nickel leaching rate and iron leaching rate, the prepared nickel sulfate and iron phosphate have high purity, and the process flow is simple.

Description

Technical Field

[0001] This invention relates to a method for preparing nickel sulfate and iron phosphate, and more particularly to a method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate. Background Technology

[0002] Lithium-ion batteries are widely used in various fields such as electric vehicles, smart home products, computers, power banks, and portable electronic products due to their advantages such as high energy density, no memory effect, low pollution, and small size. Therefore, the demand for positive and negative electrode materials for lithium-ion batteries has increased linearly.

[0003] Nickel sulfate and iron phosphate are important raw materials in the battery industry. Nickel sulfate is mainly used in the production of ternary cathode materials, while iron phosphate can be used in the preparation of lithium iron phosphate. Nickel sulfate and iron phosphate can be prepared by nickel-iron alloys. However, the process of preparing battery-grade nickel sulfate and battery-grade iron phosphate from nickel-iron alloys is complicated, requires high control of the impurity removal process, and results in low yield, poor quality, and high production cost of the prepared nickel sulfate and iron phosphate.

[0004] Therefore, there is an urgent need to develop a method for the co-production of battery-grade nickel sulfate and battery-grade iron phosphate with high nickel leaching rate, high iron leaching rate, simple process flow and low cost. Summary of the Invention

[0005] This invention provides a method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate. This method can achieve high nickel leaching rate and iron leaching rate, and the prepared nickel sulfate and iron phosphate have high purity. It also has the advantages of simple process and low cost.

[0006] This invention provides a method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate, comprising the following steps:

[0007] 1) The nickel-iron alloy pair is subjected to a first acid leaching treatment using an acid solution with a mass percentage of 1% to 30% to obtain a first acid leaching solution and a first acid leaching residue;

[0008] 2) The first acid leaching residue is subjected to a second acid leaching treatment using an oxidant and an acid solution with a mass percentage of 1% to 15% to obtain a second acid leaching solution and a second acid leaching residue.

[0009] 3) The mixture of the first and second acid leaching solutions is extracted using an ion exchange resin to obtain a raffinate containing ferrous ions; the system comprising the raffinate and a phosphorus source is oxidized to obtain ferric phosphate.

[0010] 4) After cleaning the ion exchange resin after extraction with acid, the ion exchange resin is then back-extracted with acid of 20% by mass, and the back-extraction solution containing nickel ions is cooled and crystallized to obtain nickel sulfate.

[0011] The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate as described above, wherein in step 1), the first acid leaching treatment includes: performing a first acid leaching treatment on the nickel-iron alloy using an acid solution with a mass percentage of 1% to 10% to obtain a first acid leaching solution and a first acid leaching residue; and performing a second acid leaching treatment on the first acid leaching residue using an acid solution with a mass percentage of 10% to 30% to obtain a second acid leaching solution and a first acid leaching residue.

[0012] The first acid leaching solution includes the primary acid leaching solution and the secondary acid leaching solution.

[0013] In the method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate as described above, the ratio of the mass content of nickel ions in the primary acid leaching solution to the mass content of nickel metal in the nickel-iron alloy is 0.55 to 0.65, and the ratio of the mass content of ferrous ions in the primary acid leaching solution to the mass content of iron metal in the nickel-iron alloy is 0.65 to 0.75.

[0014] The ratio of the mass content of nickel ions in the secondary acid leaching solution to the mass content of nickel metal in the nickel-iron alloy is 0.15 to 0.25, and the ratio of the mass content of ferrous ions in the secondary acid leaching solution to the mass content of iron metal in the nickel-iron alloy is 0.05 to 0.15.

[0015] The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate as described above, wherein in the primary acid leaching treatment, the solid-liquid ratio of the nickel-iron alloy to the acid solution is 1:4 to 1:12, and the temperature of the primary acid leaching treatment is 50 to 90°C.

[0016] In the secondary acid leaching treatment, the solid-liquid ratio of the primary acid leaching residue to the acid solution is 1:4 to 1:12, and the temperature of the secondary acid leaching treatment is 50 to 90°C.

[0017] The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate as described above, wherein the oxidant includes at least one of hydrogen peroxide, sodium chlorate, oxygen, ozone, and sodium nitrite.

[0018] In the method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate as described above, the amount of oxidant added is 1 to 1.8 times the molar equivalent required for the reaction of nickel and iron metals in the first acid leaching residue.

[0019] In the method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate as described above, in step 2), the solid-liquid ratio of the first acid leaching residue and the acid solution is 1:4 to 1:12, and the temperature of the second acid leaching treatment is 50 to 90°C.

[0020] In the method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate as described above, step 4) includes washing the ion exchange resin with a 1% to 10% acid solution for a time of 10 to 60 minutes.

[0021] The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate as described above, wherein, in step 3), before the oxidation treatment, sodium carbonate is added to the raffinate to adjust the pH of the raffinate to 4-6.

[0022] The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate as described above, wherein the nickel-iron alloy further includes other metals, including at least one of calcium, magnesium, zinc and aluminum;

[0023] The nickel-iron alloy contains 5% to 30% nickel by mass, 50% to 85% iron by mass, and 1% to 20% other metals by mass.

[0024] This invention utilizes a multi-stage acid leaching process on nickel-iron alloys to efficiently convert nickel and iron metals into nickel and ferrous ions, achieving high nickel and iron leaching rates. Subsequently, an ion exchange resin is used to achieve a high degree of separation between nickel and ferrous ions, thereby producing high-purity nickel sulfate and iron phosphate. The ion exchange resin is then cleaned to partially remove impurities, preventing them from affecting the purity of the nickel sulfate. Furthermore, this method features a simple process, low cost, and material savings. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] This invention provides a method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate, comprising the following steps:

[0027] 1) The nickel-iron alloy pair is subjected to a first acid leaching treatment using an acid solution with a mass percentage of 1% to 30% to obtain a first acid leaching solution and a first acid leaching residue;

[0028] 2) The first acid leaching residue is subjected to a second acid leaching treatment using an oxidant and an acid solution with a mass percentage of 1% to 15% to obtain a second acid leaching solution and a second acid leaching residue.

[0029] 3) The mixture of the first and second acid leaching solutions is extracted using an ion exchange resin to obtain a raffinate containing ferrous ions; the system including the raffinate and a phosphorus source is oxidized to obtain ferric phosphate.

[0030] 4) After cleaning the ion exchange resin after extraction with acid, the ion exchange resin is then back-extracted with 20% by mass acid and the back-extraction solution containing nickel ions is cooled and crystallized to obtain nickel sulfate.

[0031] In this invention, battery-grade nickel sulfate refers to nickel sulfate with a purity higher than 99% and high conductivity, and battery-grade iron phosphate refers to iron phosphate with a purity higher than 99%.

[0032] In step 1), an acidic solution with a mass percentage of 1% to 30% is prepared. Under an inert protective atmosphere, the acidic solution is mixed with the nickel-iron alloy and subjected to a first acid leaching treatment under stirring conditions. After solid-liquid separation, a first acid leaching solution and a first acid leaching residue are obtained.

[0033] The present invention does not impose any special limitation on the selection of acidic solutions, as long as they can convert nickel and iron metals in nickel-iron alloys into nickel ions and ferrous ions. For example, common acidic solutions such as sulfuric acid and hydrochloric acid can be used, with sulfuric acid being preferred.

[0034] The present invention does not impose any special limitation on the inert atmosphere; for example, the inert atmosphere is nitrogen.

[0035] This invention does not limit the purity of the nickel-iron alloy, as long as its main components are nickel metal and iron metal.

[0036] The present invention does not limit the appearance of the nickel-iron alloy. For example, a block nickel-iron alloy or a powdered nickel-iron alloy can be selected, with a powdered nickel-iron alloy being preferred.

[0037] The present invention does not limit the stirring method and stirring rate. For example, mechanical stirring can be used with a stirring rate of 250 r / min.

[0038] This invention does not specifically limit the method of solid-liquid separation. For example, filtration, centrifugation, or gravity sedimentation can be used.

[0039] In step 2), an acidic solution with a mass percentage of 1% to 15% is prepared. Under an inert atmosphere, the acidic solution, oxidant and the first acid leaching residue prepared in step 1) are mixed and subjected to a second acid leaching treatment under stirring conditions. After solid-liquid separation, a second acid leaching solution and a second acid leaching residue are obtained.

[0040] The acidic solution in step 2) is subject to the same limitations as described above, and will not be repeated here.

[0041] The inert atmosphere in step 2) is the same as the aforementioned limitation, and will not be repeated here.

[0042] The present invention does not limit the choice of oxidant, such as hydrogen peroxide, sodium chlorate, oxygen, ozone, sodium nitrite, nitric acid, bromine water, etc.

[0043] The stirring method and stirring rate in step 2) are the same as those specified above, and will not be repeated here.

[0044] The solid-liquid separation method in step 2) is the same as the aforementioned limitation, and will not be repeated here.

[0045] In step 3), the first and second acid leaching solutions are mixed to obtain a mixture. This mixture is then extracted using an ion exchange resin to obtain a raffinate containing ferrous ions. The raffinate is then mixed with a system containing a phosphorus source and subjected to oxidation to obtain ferric phosphate.

[0046] The present invention does not limit the mixing method of the first acid leaching solution and the second acid leaching solution; for example, mechanical stirring, magnetic stirring, or other methods can be used.

[0047] This invention does not specifically limit the selection of ion exchange resin, as long as it can exchange nickel ions into the ion exchange resin and leave ferrous ions in the remaining mixture after extraction, i.e., the raffinate.

[0048] This invention does not limit the selection of the phosphorus source system or the oxidation treatment method, as long as phosphorus can be provided and can react with ferrous ions to generate ferric phosphate. For example, phosphoric acid, potassium dihydrogen phosphate, potassium trihydrogen phosphate, calcium phosphate, etc. can be selected as phosphoric acid sources. Oxidation treatment can be carried out using oxidants such as hydrogen peroxide and sodium chlorate. Preferably, phosphoric acid and sulfuric acid can be added to the raffinate to adjust the pH to 1.6, and then hydrogen peroxide can be added to react and obtain ferric phosphate.

[0049] In step 4), the ion exchange resin after extraction is first cleaned with acid to ensure that there are no ferrous ions or other impurities on the surface of the ion exchange resin. The waste liquid after cleaning is returned to step 1) for repeated acid leaching. Then, an acid solution with a mass percentage of 10% to 30% is prepared and used to back-extract the cleaned ion exchange resin to back-extract the nickel ions in the ion exchange resin into the back-extraction solution. The back-extraction solution is then cooled and crystallized. The crystals are then cleaned and dried to obtain nickel sulfate.

[0050] This invention does not limit the acid solution used for cleaning, as long as it can clean the ferrous ions and other impurities on the surface of the ion exchange resin without causing the nickel ions in the ion exchange resin to be back-extracted. For example, an acid solution with a mass percentage of 1% to 10% can be used to clean the ion exchange resin after extraction until there are no ferrous ions or other impurities on the surface of the ion exchange resin. The waste liquid after cleaning is then returned to the acid leaching treatment in step 1) for use, thereby achieving the purpose of saving costs.

[0051] The present invention does not limit the cleaning treatment method of ion exchange resin. For example, ultrasonic cleaning, soaking cleaning or stirring cleaning can be selected.

[0052] The acid solution used in the back-extraction process in step 4) is the same as the aforementioned limitation, and will not be repeated here.

[0053] The present invention does not limit the method of cooling crystallization; for example, natural cooling crystallization or cooling crystallization in a cooling medium may be used.

[0054] The present invention does not limit the method of cleaning and drying. For example, water can be used to rinse the crystals to remove surface acid and other impurities, and then the crystals can be dried in a vacuum atmosphere to obtain nickel sulfate.

[0055] The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate of the present invention involves first subjecting a nickel-iron alloy to a first acid leaching treatment to obtain a first acid leaching solution and a first acid leaching residue containing nickel ions and ferrous ions. Then, the first acid leaching residue, oxidant, and acid solution are subjected to a second acid leaching treatment to further convert nickel and iron metals into nickel and ferrous ions, resulting in a second acid leaching solution and a second acid leaching residue containing nickel and ferrous ions. Compared to a one-step acid leaching treatment, the nickel and iron leaching rates of the nickel-iron alloy of the present invention are higher. Subsequently, nickel ions in the first and second acid leaching solutions are adsorbed by an ion exchange resin, leaving ferrous ions in the raffinate for oxidation with the phosphorus source system. Ferric phosphate is obtained, and then the extracted ion exchange resin is washed with acid. The washing waste liquid is returned to the first acid leaching process, and the washed ion exchange resin is back-extracted with acid to obtain a back-extract containing nickel ions. Cooling and crystallization yields nickel sulfate. The use of ion exchange resin to separate nickel and ferrous ions achieves a high degree of separation. Furthermore, the washing of the ion exchange resin partially removes other impurities from the acid leaching solution. Oxidation is then performed by adding a phosphorus source system to the raffinate, followed by cooling and crystallization of the back-extract, ultimately achieving the co-production of ferric phosphate and nickel sulfate. This invention, through a two-step acid leaching process combined with ion exchange resin, achieves high nickel and ferric leaching rates and a high degree of separation between nickel and ferric ions, thus preparing high-purity battery-grade nickel sulfate and ferric phosphate. The process is simple, using common chemical substances such as acids and oxidants, and the acid used in the washing process can be reused, making the method low-cost and resource-saving.

[0056] In one specific embodiment, step 1) includes: performing a first acid leaching treatment on the nickel-iron alloy using a 1% to 10% acid solution to obtain a first acid leaching solution and a first acid leaching residue; performing a second acid leaching treatment on the first acid leaching residue using a 10% to 30% acid solution to obtain a second acid leaching solution and a first acid leaching residue; the first acid leaching solution includes the first acid leaching solution and the second acid leaching solution.

[0057] Specifically, the acid leaching process consists of two steps. First, under an inert gas atmosphere, an acidic solution with a mass percentage of 1% to 10% is prepared. The acidic solution is mixed with the nickel-iron alloy and subjected to a first acid leaching treatment under stirring conditions. After solid-liquid separation, a first acid leaching solution containing nickel ions and ferrous ions and a first acid leaching residue are obtained. Then, an acidic solution with a mass percentage of 10% to 30% is prepared. The acidic solution is mixed with the first acid leaching residue and subjected to a second acid leaching treatment under stirring conditions. After solid-liquid separation, a second acid leaching solution and a first acid leaching residue are obtained. The first acid leaching solution is composed of the first acid leaching solution and the second acid leaching solution.

[0058] This invention divides the first acid leaching treatment into two steps. First, a low-concentration acidic solution is used to leach the nickel-iron alloy, and then a higher-concentration acidic solution is used to continue the acid leaching treatment. This not only allows for a greater conversion of nickel and iron metals in the nickel-iron alloy into nickel and ferrous ions, increasing the nickel and iron leaching rates, but also reduces the use of higher-concentration acidic solutions, thus saving acid. At the same time, it avoids the generation of side reactions due to violent reactions during the acid leaching process, providing a foundation for the subsequent preparation of battery-grade nickel sulfate and iron phosphate, and increasing the safety of the reaction.

[0059] In one specific embodiment, the mass content of nickel ions in the primary pickling solution is 0.55–0.65 to the mass content of nickel metal in the ferroalloy, and the mass content of ferrous ions in the primary pickling solution is 0.65–0.75 to the mass content of iron metal in the ferroalloy; the mass content of nickel ions in the secondary pickling solution is 0.15–0.25 to the mass content of nickel metal in the ferroalloy, and the mass content of ferrous ions in the secondary pickling solution is 0.05–0.15 to the mass content of iron metal in the ferroalloy.

[0060] When the ratios of nickel ions, ferrous ions, and nickel and iron metals in the primary acid leaching solution, and the ratios of nickel ions, ferrous ions, and nickel and iron metals in the secondary acid leaching solution, are within the aforementioned ranges, the amount of nickel and ferrous ions leached is more suitable. At the same time, excessive leaching of other impurity metal ions in the nickel-iron alloy during the acid leaching process is avoided. This prevents problems such as the ion exchange resin's exchange channels being blocked by impurity ions during subsequent extraction, or impurity ions being simultaneously extracted and adsorbed. Such problems would lead to a decrease in the extraction efficiency of the ion exchange resin, or the preparation of nickel sulfate and iron phosphate containing too many impurities and having low purity, failing to meet battery-grade standards. If the ratio of nickel ions to nickel metal and the ratio of ferrous ions to iron metal are higher than the above ranges, it indicates that the leaching amount of nickel ions and ferrous ions is too high. Similarly, the leaching amount of impurity metals in the nickel-iron alloy is also too high, which may lead to low purity of the prepared nickel sulfate and iron phosphate. If the ratio of nickel ions to nickel metal and the ratio of ferrous ions to iron metal are lower than the above ranges, the leaching amount of nickel ions and ferrous ions is too low, resulting in low nickel leaching rate and iron leaching rate, low yield of nickel sulfate and iron phosphate, and waste of raw materials.

[0061] Specifically, the mass percentages of nickel ions and ferrous ions in the primary and secondary acid leaching solutions of the present invention can be obtained by ICP testing; the mass percentages of nickel metal and iron metal in the nickel-iron alloy of the present invention can be obtained by ICP testing.

[0062] In one specific embodiment, during the primary acid leaching treatment, the solid-liquid ratio of the nickel-iron alloy to the acid solution is 1:4 to 1:12, and the temperature of the primary acid leaching treatment is 50 to 90°C. During the secondary acid leaching treatment, the solid-liquid ratio of the primary acid leaching residue to the acid solution is 1:4 to 1:12, and the temperature of the secondary acid leaching treatment is 50 to 90°C. When the solid-liquid ratio of the nickel-iron alloy to the acid solution and the temperature of the acid leaching treatment are within the above ranges, under suitable temperature conditions, the acid solution can fully convert nickel and iron metals into nickel ions and ferrous ions, thereby increasing the nickel leaching rate and iron leaching rate, while avoiding excessive leaching of impurity metals. Furthermore, it can reduce the use of acid solution, avoid raw material waste, and reduce costs. If the solid-liquid ratio of the nickel-iron alloy and the acid solution is below the above range, excessive acid usage leads to excessive leaching of impurity metals and waste of raw materials. If the solid-liquid ratio is above the above range, excessive nickel-iron alloy is added while insufficient acid is used, resulting in excessive nickel and iron metals in the nickel-iron alloy failing to be converted into nickel and ferrous ions, thus wasting the nickel-iron alloy. If the acid leaching temperature is below the above range, the acid leaching efficiency is low, and only by increasing the amount of acid added can a high nickel and iron leaching rate be achieved, leading to acid waste. If the acid leaching temperature is above the above range, the acid leaching reaction is violent, leading to the generation of side reactions during the acid leaching process, reducing the nickel and iron leaching rates, and also resulting in energy waste and loss.

[0063] In one specific embodiment, the oxidant includes at least one selected from hydrogen peroxide, sodium chlorate, oxygen, ozone, and sodium nitrite. These oxidants are all common oxidants that can efficiently convert nickel and iron metals into nickel ions and ferrous ions, improving nickel and iron leaching rates. They are also inexpensive and readily available. Furthermore, the use of these oxidants does not introduce excessive impurity ions, reducing subsequent impurity removal processes and saving production costs. Preferably, the oxidant is hydrogen peroxide, which can more efficiently convert nickel and iron metals into nickel ions and ferrous ions, and hydrogen peroxide reacts to form water, without introducing impurity ions.

[0064] In one specific embodiment, the amount of oxidant added is 1 to 1.8 times the molar equivalent required for the reaction of nickel and iron in the first acid leaching residue. When the amount of oxidant added is within the above range, the oxidant can efficiently help nickel and iron transform into nickel ions and ferrous ions, increasing the nickel leaching rate and iron leaching rate, and avoiding excessive leaching of impurity ions, which would reduce the purity of nickel sulfate and ferric phosphate. If the ratio of oxidant to nickel content is higher than the above range, the amount of oxidant used is excessive, resulting in excessive leaching of impurity ions. At the same time, the acid leaching reaction is violent, causing side reactions and reducing the purity of nickel sulfate and ferric phosphate. If the ratio of oxidant to nickel content is lower than the above range, the proportion of nickel and iron transformed into nickel ions and ferrous ions is low, resulting in low nickel and iron leaching rates, low yields of nickel sulfate and ferric phosphate, and excessive unreacted nickel and iron in the second acid leaching residue, leading to waste of raw materials.

[0065] In one specific embodiment, in step 2), the solid-liquid ratio of the first acid leaching residue to the acid solution is 1:4 to 1:12, and the temperature of the second acid leaching treatment is 50 to 90°C. When the solid-liquid ratio of the first acid leaching residue to the acid solution and the temperature of the second acid leaching treatment are within the above ranges, the acid solution, with the help of a suitable temperature, can more efficiently convert nickel and iron metals in the first acid leaching residue into nickel ions and ferrous ions, thereby increasing the nickel leaching rate and iron leaching rate, while ensuring a low leaching rate of impurity ions and improving the purity of nickel sulfate and iron phosphate.

[0066] In one specific embodiment, step 4) includes washing the ion exchange resin with an acid solution of 1% to 10% by mass for 10 to 60 minutes. When the concentration of the acid solution is within the above range, the acid solution can efficiently and quickly remove ferrous ions and impurity ions from the surface of the ion exchange resin, which helps to back-extract the nickel ions adsorbed by the resin into the back-extraction solution, and reduces the amount of acid used, thus saving costs.

[0067] In one specific embodiment, step 3) further includes adding sodium carbonate to the raffinate to adjust its pH to 4-6 before oxidation treatment. Specifically, before oxidizing the raffinate and the phosphorus source system, sodium carbonate is added to the raffinate until its pH reaches 4-6. The aluminum ions in the raffinate react with the sodium carbonate to form aluminum hydroxide precipitate. After solid-liquid separation, the aluminum ion impurities in the raffinate are separated, further improving the purity of ferric phosphate.

[0068] In one specific embodiment, the nickel-iron alloy further includes other metals, including at least one of calcium, magnesium, zinc, and aluminum; the nickel metal content in the nickel-iron alloy is 5%–30% by mass, the iron metal content is 50%–85% by mass, and the other metal content is 1%–20% by mass. In addition to nickel and iron, the nickel-iron alloy also includes at least one of calcium, magnesium, zinc, and aluminum. When the nickel, iron, and other metals are within the above ranges, the method provided by this invention can still achieve excellent nickel and iron leaching rates, and produce high-purity nickel sulfate and iron phosphate, realizing the co-production of battery-grade nickel sulfate and battery-grade iron phosphate.

[0069] The present invention will be further described in detail below through specific embodiments.

[0070] Example 1

[0071] The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate in this embodiment includes the following steps:

[0072] 1. A primary acid leaching treatment was performed on a nickel-iron alloy using 8% sulfuric acid to obtain a primary acid leaching solution and a primary acid leaching residue. The solid-liquid ratio of the nickel-iron alloy to the sulfuric acid was 1:10. The temperature of the primary acid leaching treatment was 90℃, and the stirring rate was 250 r / min. The mass content of nickel ions in the primary acid leaching solution was 0.65 to the mass content of nickel metal in the nickel-iron alloy, and the mass content of ferrous ions in the primary acid leaching solution was 0.75 to the mass content of iron metal in the nickel-iron alloy.

[0073] 2. The primary acid leaching residue is subjected to a secondary acid leaching treatment using sulfuric acid with a mass percentage of 15%, resulting in a secondary acid leaching solution and a primary acid leaching residue. The solid-liquid ratio of the primary acid leaching residue to sulfuric acid is 1:10. The temperature of the secondary acid leaching treatment is 90℃, and the stirring rate is 250 r / min. The mass content of nickel ions in the secondary acid leaching solution is 0.25 to the mass content of nickel metal in the nickel-iron alloy, and the mass content of ferrous ions in the secondary acid leaching solution is 0.15 to the mass content of iron metal in the nickel-iron alloy.

[0074] 3. The first acid leaching residue is subjected to a second acid leaching treatment using 27% hydrogen peroxide and 5% sulfuric acid to obtain a second acid leaching solution and a second acid leaching residue. The solid-liquid ratio of the first acid leaching residue to sulfuric acid is 1:10, the temperature of the second acid leaching treatment is 60℃, and the amount of hydrogen peroxide is 1.1 times the molar equivalent required for the reaction of nickel and iron metals in the first acid leaching residue.

[0075] 4. The mixture of primary acid leaching solution, secondary acid leaching solution and second acid leaching solution is extracted using ion exchange resin to obtain an extract containing ferrous ions. Sodium carbonate is then added to the extract to adjust the pH of the raffinate to 5.2. After solid-liquid separation, phosphoric acid and sulfuric acid are added to the remaining raffinate to adjust the pH to 1.6, and then hydrogen peroxide is added to prepare ferric phosphate.

[0076] 5. Wash the ion exchange resin with a 5% (w / w) acid solution for 30 minutes to obtain a clean ion exchange resin. Then, back-extract the ion exchange resin with 20% sulfuric acid to obtain a back-extraction solution containing nickel ions. After cooling and crystallization, wash and dry the crystals to obtain nickel sulfate.

[0077] Example 2

[0078] It is largely the same as Example 1, except that the acid leaching temperature in step 1 is 70°C.

[0079] Example 3

[0080] The process is largely the same as in Example 1, except that the secondary acid leaching temperature in step 2 is 70°C.

[0081] Example 4

[0082] It is largely the same as Example 1, except that the solid-liquid ratio in step 1 is 1:8.

[0083] Example 5

[0084] The process is largely the same as in Example 1, except that the solid-liquid ratio for the second acid leaching in step 2 is 1:8.

[0085] Example 6

[0086] It is generally the same as Example 1, except that the solid-liquid ratio of the acid leaching in step 1 is 1:12.

[0087] Example 7

[0088] The process is largely the same as in Example 1, except that the solid-liquid ratio for the second acid leaching in step 2 is 1:12.

[0089] Example 8

[0090] The process is largely the same as in Example 1, except that the solid-liquid ratio for the first acid leaching step is 1:15, and the solid-liquid ratio for the second acid leaching step is also 1:15.

[0091] Example 9

[0092] It is largely the same as Example 1, except that step 1 uses 5% sulfuric acid for a single acid leaching.

[0093] Example 10

[0094] The process is largely the same as in Example 1, except that step 1 involves a single acid leaching with 10% sulfuric acid.

[0095] Example 11

[0096] The process is largely the same as in Example 1, except that step 2 involves a second acid leaching with 5% sulfuric acid.

[0097] Example 12

[0098] The process is largely the same as in Example 1, except that step 2 involves a second acid leaching with 10% sulfuric acid.

[0099] Example 13

[0100] The process is largely the same as in Example 1, except that step 2 involves a second acid leaching with 20% sulfuric acid.

[0101] Example 14

[0102] The process is largely the same as in Example 1, except that step 2 involves a second acid leaching with 1% sulfuric acid.

[0103] Example 15

[0104] The process is largely the same as in Example 1, except that step 2 involves a second acid leaching with 15% sulfuric acid.

[0105] Example 16

[0106] The process is largely the same as in Example 1, except that step 2 involves a second acid leaching with 20% sulfuric acid.

[0107] Example 17

[0108] The process is largely the same as in Example 1, except that step 3 uses one molar equivalent of hydrogen peroxide.

[0109] Example 18

[0110] The method is largely the same as in Example 1, except that step 3 uses 1.8 molar equivalents of hydrogen peroxide.

[0111] Example 19

[0112] The method is largely the same as in Example 1, except that step 3 uses 0.8 molar equivalents of hydrogen peroxide.

[0113] Example 20

[0114] It is largely the same as Example 1, except that the solid-liquid ratio of the second acid leaching in step 3 is 1:6.

[0115] Example 21

[0116] The process is largely the same as in Example 1, except that the solid-liquid ratio in the second acid leaching step 3 is 1:12.

[0117] Example 22

[0118] It is largely the same as Example 1, except that the solid-liquid ratio of the second acid leaching in step 3 is 1:15.

[0119] Example 23

[0120] It is largely the same as Example 1, except that the second acid leaching temperature in step 3 is 50°C.

[0121] Example 24

[0122] It is largely the same as Example 1, except that the second acid leaching temperature in step 3 is 90°C.

[0123] Example 25

[0124] It is largely the same as Example 1, except that the second acid leaching temperature in step 3 is 45°C.

[0125] Example 26

[0126] It is largely the same as Example 1, except that the acid leaching temperature in step 1 is 45°C.

[0127] Example 27

[0128] The process is largely the same as in Example 1, except that the secondary acid leaching temperature in step 2 is 45°C.

[0129] Example 28

[0130] The process is largely the same as in Example 1, except that step 1 uses 20% sulfuric acid for a first acid leaching, while step 2 uses 5% sulfuric acid for a second acid leaching.

[0131] Example 29

[0132] The process is largely the same as in Example 1, except that step 5 involves washing the resin with 1% sulfuric acid.

[0133] Example 30

[0134] The process is largely the same as in Example 1, except that step 5 involves washing the resin with 3% sulfuric acid.

[0135] Example 31

[0136] The process is largely the same as in Example 1, except that in step 5, the resin is washed with 10% sulfuric acid.

[0137] Example 32

[0138] The process is largely the same as in Example 1, except that step 5 involves washing the resin with 15% sulfuric acid.

[0139] Example 33

[0140] The process is largely the same as in Example 1, except that the washing time in step 5 is 10 minutes.

[0141] Example 34

[0142] The process is largely the same as in Example 1, except that the washing time in step 5 is 60 minutes.

[0143] Example 35

[0144] The process is largely the same as in Example 1, except that the washing time in step 5 is 90 minutes.

[0145] Example 36

[0146] The process is largely the same as in Example 1, except that in step 4, sodium carbonate is used to adjust the pH to 3.5.

[0147] Example 37

[0148] The process is largely the same as in Example 1, except that in step 4, sodium carbonate is used to adjust the pH to 4.

[0149] Example 38

[0150] The process is largely the same as in Example 1, except that in step 4, sodium carbonate is used to adjust the pH to 4.5.

[0151] Example 39

[0152] The process is largely the same as in Example 1, except that in step 4, sodium carbonate is used to adjust the pH to 5.5.

[0153] Example 40

[0154] The process is largely the same as in Example 1, except that in step 4, sodium carbonate is used to adjust the pH to 6.5.

[0155] Comparative Example 1

[0156] The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate in this comparative example is basically the same as that in Example 1, except that the primary acid leaching treatment and the secondary acid leaching treatment are combined, and a 23% concentration acid is used.

[0157] Comparative Example 2

[0158] The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate in this comparative example is basically the same as that in Example 1, except that step 3 is omitted.

[0159] Test case

[0160] ICP tests were performed on the primary, secondary, and second acid leaching solutions to obtain the mass content of nickel ions and ferrous ions in the primary, secondary, and second acid leaching solutions.

[0161] ICP testing was performed on the nickel-iron alloy, the primary acid leaching residue, and the first acid leaching residue to obtain the mass content of nickel and iron metals in the nickel-iron alloy, the primary acid leaching residue, and the first acid leaching residue.

[0162] Nickel leaching rate = mass content of nickel ions in total leachate / mass content of nickel metal in nickel-iron alloy; Iron leaching rate = mass content of iron ions in total leachate / mass content of iron metal in nickel-iron alloy;

[0163] The purity of nickel sulfate and ferrous sulfate was determined by ICP testing.

[0164] Table 1. Leaching rates and product purity of the method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate.

[0165]

[0166]

[0167]

[0168] As shown in Table 1:

[0169] A comparison of Examples 1-40 and Comparative Examples 1-2 shows that the method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate of the present invention has high nickel leaching rate and iron leaching rate, with the highest nickel leaching rate reaching 99.9% and the highest iron leaching rate reaching 99.9%. The purity of the prepared nickel sulfate can reach 99.9%, and the purity of the iron phosphate can reach 99.9%. Therefore, the method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate of the present invention achieves high nickel leaching rate and iron leaching rate, produces high-purity nickel sulfate and iron phosphate, and has advantages such as simple process and low cost.

[0170] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate, characterized in that, Includes the following steps: 1) The nickel-iron alloy is subjected to a first acid leaching treatment using an acid solution with a mass percentage of 1% to 30% to obtain a first acid leaching solution and a first acid leaching residue; 2) The first acid leaching residue is subjected to a second acid leaching treatment using an oxidant and an acid solution with a mass percentage of 1% to 15% to obtain a second acid leaching solution and a second acid leaching residue. 3) Extract the first and second acid leaching solutions using an ion exchange resin to obtain a raffinate containing ferrous ions; oxidize the system containing the raffinate and a phosphorus source to obtain ferric phosphate. 4) The ion exchange resin after extraction is cleaned with acid, and the waste liquid after cleaning is returned to step 1) for repeated acid leaching. Then, the cleaned ion exchange resin is back-extracted with acid with a mass percentage of 20%, and the back-extraction liquid containing nickel ions is cooled and crystallized to obtain nickel sulfate. In step 1), the first acid leaching treatment includes: performing a first acid leaching treatment on the nickel-iron alloy using an acid solution with a mass percentage of 1% to 10% to obtain a first acid leaching solution and a first acid leaching residue; and performing a second acid leaching treatment on the first acid leaching residue using an acid solution with a mass percentage of 10% to 30% to obtain a second acid leaching solution and a first acid leaching residue, wherein the mass percentage of the acid solution in the second acid leaching treatment is higher than the mass percentage of the acid solution in the first acid leaching treatment. The first acid leaching solution includes the primary acid leaching solution and the secondary acid leaching solution; The ratio of the mass content of nickel ions in the primary pickling solution to the mass content of nickel metal in the nickel-iron alloy is 0.55~0.65, and the ratio of the mass content of ferrous ions in the primary pickling solution to the mass content of iron metal in the nickel-iron alloy is 0.65~0.

75. The ratio of the mass content of nickel ions in the secondary acid leaching solution to the mass content of nickel metal in the nickel-iron alloy is 0.15~0.25; the ratio of the mass content of ferrous ions in the secondary acid leaching solution to the mass content of iron metal in the nickel-iron alloy is 0.05~0.

15.

2. The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate according to claim 1, characterized in that, In the first acid leaching treatment, the solid-liquid ratio of the nickel-iron alloy to the acid solution is 1:4 to 1:12, and the temperature of the first acid leaching treatment is 50 to 90°C. In the secondary acid leaching treatment, the solid-liquid ratio of the primary acid leaching residue to the acid solution is 1:4 to 1:12, and the temperature of the secondary acid leaching treatment is 50 to 90°C.

3. The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate according to claim 1, characterized in that, The oxidant includes at least one of hydrogen peroxide, sodium chlorate, oxygen, ozone, and sodium nitrite.

4. The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate according to claim 1, characterized in that, The amount of oxidant added is 1 to 1.8 times the molar equivalent required for the reaction of nickel and iron metals in the first acid leaching residue.

5. The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate according to claim 1, characterized in that, In step 2), the solid-liquid ratio of the first acid leaching residue and the acid solution is 1:4 to 1:12, and the temperature of the second acid leaching treatment is 50 to 90°C.

6. The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate according to claim 1, characterized in that, In step 4), the cleaning process includes washing the ion exchange resin with an acid solution of 1% to 10% by mass for 10 to 60 minutes.

7. The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate according to claim 1, characterized in that, In step 3), before the oxidation treatment, sodium carbonate is added to the raffinate to adjust the pH of the raffinate to 4-6.

8. The method for co-producing battery-grade nickel sulfate and battery-grade iron phosphate according to claim 1, characterized in that, The nickel-iron alloy also includes other metals, including at least one of calcium, magnesium, zinc and aluminum; The nickel-iron alloy contains 5% to 30% nickel by mass, 50% to 85% iron by mass, and 1% to 20% other metals by mass.

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