Method for comprehensive utilization of iron phosphate waste and nickel-iron alloy

Abstract

The application discloses a method for comprehensively utilizing iron phosphate waste and nickel-iron alloy, and belongs to the technical field of battery material recycling. The method comprises the following steps: low-temperature acid leaching of the iron phosphate waste and the chromium-containing nickel-iron alloy in a first solution comprising acid and sulfur dioxide to obtain a first leaching solution; high-temperature acid leaching of the first leaching solution by adding a first oxidizing agent to obtain a second leaching solution; removal of chromium in the second leaching solution to obtain a chromium-removed solution; iron precipitation reaction of at least part of the chromium-removed solution with supplemented phosphoric acid and a second oxidizing agent to obtain iron phosphate and an iron phosphate mother liquor; removal of phosphorus in the iron phosphate mother liquor to obtain a phosphorus-removed mother liquor; and nickel precipitation reaction of at least part of the phosphorus-removed mother liquor to prepare nickel sulfate. The method is simple in operation, realizes effective recycling of phosphorus and iron in the iron phosphate waste and nickel and iron in the nickel-iron alloy, and reduces the production cost of preparing battery-grade nickel sulfate and iron phosphate.

Description

Technical Field

[0001] This invention relates to the field of battery material recycling technology, and more specifically, to a method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy. Background Technology

[0002] In recent years, China's iron phosphate shipments have maintained growth. The large volume of iron phosphate shipments means that the output of waste iron phosphate and substandard iron phosphate has also increased year-on-year, indicating a huge prospect for the recycling, processing and utilization of waste iron phosphate.

[0003] Currently, most recycling and processing solutions for waste iron phosphate are complex, costly, and have low element utilization rates. Furthermore, some recycling and processing solutions also generate odorous exhaust gases.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows:

[0007] In a first aspect, the present invention provides a method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy, comprising the following steps:

[0008] The ferric phosphate waste and chromium-containing nickel-iron alloy to be treated are subjected to low-temperature acid leaching in a first solution containing acid and a reducing agent to obtain a first leachate containing ferrous iron, nickel, phosphorus, and chromium; wherein the reducing agent includes thiourea dioxide, the low-temperature acid leaching temperature is 50℃~70℃, and the Fe in the first leachate is... 3+ The content does not exceed 1g / L;

[0009] A first oxidant is added to the first leachate for high-temperature acid leaching to obtain a second leachate; wherein the high-temperature acid leaching temperature is 80℃~95℃.

[0010] Remove chromium from the second leachate to obtain the chromium-removed solution;

[0011] At least a portion of the chromium-removed liquid was reacted with supplemented phosphoric acid and a second oxidant to induce an iron precipitation reaction, followed by solid-liquid separation to obtain ferric phosphate and ferric phosphate mother liquor.

[0012] Phosphorus is removed from the ferric phosphate mother liquor to obtain a phosphorus-removed mother liquor;

[0013] At least a portion of the dephosphorization mother liquor is subjected to a nickel precipitation reaction before being prepared into nickel sulfate.

[0014] In an optional embodiment, low-temperature acid leaching includes at least one of the following features:

[0015] Feature 1: The mass ratio of iron phosphate waste to nickel-iron alloy is 1:1.5 to 1:2;

[0016] Feature 2: The acid includes at least one of sulfuric acid and phosphoric acid;

[0017] Feature 3: The concentration of acid in the first solution is 90 g / L to 120 g / L;

[0018] Feature 4: The concentration of thiourea dioxide in the first solution is 5.5 g / L to 7.5 g / L;

[0019] Feature 5: In iron phosphate waste, the mass fraction of phosphorus is 12% to 20.5%, and the mass fraction of iron is 25% to 37%.

[0020] Feature 6: In nickel-iron alloys, the mass fraction of nickel is 10%–30%, and the mass fraction of iron is 60%–75%.

[0021] Feature 7: In the first leachate, the Ni content is 5 g / L to 12 g / L, and the Fe content is... 2+ The content of Cr is 20g / L to 40g / L, the content of Cr is 0.02g / L to 0.1g / L, and the content of P is 2.5g / L to 7.5g / L.

[0022] In an optional embodiment, high-temperature acid leaching includes at least one of the following features:

[0023] Feature 8: The primary oxidizing agent includes hydrogen peroxide;

[0024] Feature 9: The amount of the first oxidant added is 20 g / L to 60 g / L;

[0025] Feature 10: The high-temperature acid leaching time is 3 to 5 hours;

[0026] Feature 11: The pH value of the second leachate is 1.4 to 2.3;

[0027] Feature 12: The Ni content in the second leachate is 10 g / L to 20 g / L, and the Fe content is... 2+ The content of Cr is 40g / L to 60g / L, the content of Cr is 0.04g / L to 0.12g / L, and the content of P is 2.5g / L to 7.5g / L.

[0028] In an optional embodiment, removing chromium from the second leaching solution includes: adding seed crystals to the second leaching solution to perform a seed crystal reaction, and then adding a modifier to perform a chromium removal reaction.

[0029] Among them, the seed crystals include at least one of anhydrous ferric phosphate, ferric phosphate dihydrate, amorphous ferric phosphate, and ferrous hydrogen phosphate;

[0030] The modifier includes at least one of nickel carbonate, chromium slag, and nickel hydroxide.

[0031] In an optional embodiment, the seed reaction includes at least one of the following features:

[0032] Feature 13: The amount of seed crystals added is 1 g / L to 1.5 g / L;

[0033] Feature 14: The temperature of the seed crystal reaction is 50℃~70℃, and the reaction time is 0.5h~1.5h.

[0034] In an optional embodiment, the chromium removal reaction includes at least one of the following characteristics:

[0035] Feature 15: A pH adjuster is added to control the pH of the reaction system corresponding to the chromium removal reaction to be 2.5–3.5;

[0036] Feature 16: The temperature for the chromium removal reaction is 50℃~70℃, and the reaction time is 1h~3h;

[0037] Feature 17: The Ni content in the solution after chromium removal is 15 g / L to 25 g / L, and the Fe content is... 2+ The content of Cr is 35g / L to 60g / L, the content of Cr is 0.002g / L to 0.008g / L, and the content of P is 2.5g / L to 7.5g / L.

[0038] In an optional embodiment, the iron precipitation reaction includes: first adding supplemented phosphoric acid to at least part of the chromium removal solution to carry out a first reaction, and then adding a second oxidant to carry out a second reaction;

[0039] The ratio of the total number of moles of P in the supplemented phosphoric acid to the total number of moles of P in the chromium-removed solution to the total number of moles of Fe in the chromium-removed solution is 1:0.8 to 1:0.98.

[0040] The temperature of the first reaction is 40℃~55℃, and the reaction time is 1h~3h;

[0041] Adding a second oxidizing agent to reduce the Fe content in the ferric phosphate mother liquor 2+ The concentration is 0.8 g / L to 1.6 g / L;

[0042] The temperature of the second reaction is 30℃~60℃, and the reaction time is 0.5h~1.5h.

[0043] In an optional embodiment, the Ni content in the ferric phosphate mother liquor is 15 g / L to 25 g / L, and the Fe content is... 2+ The content of is 0.8g / L to 1.6g / L, and the content of P is 2g / L to 4g / L.

[0044] In an optional embodiment, the pH value of the ferric phosphate mother liquor is 0.1 to 1.2.

[0045] In an optional embodiment, removing phosphorus from the ferric phosphate mother liquor includes: adding an iron source to the ferric phosphate mother liquor and adding a third oxidant to carry out a phosphorus removal reaction, followed by solid-liquid separation to obtain ferric phosphate dihydrate and the phosphorus removal mother liquor.

[0046] In an optional embodiment, the phosphorus removal reaction includes at least one of the following features:

[0047] Feature 18: The ratio of the total number of moles of Fe in the mother liquor of ferric phosphate and Fe in the supplementary iron source to the number of moles of P in the mother liquor of ferric phosphate is 1.05:1 to 1.2:1;

[0048] Feature 19: The third oxidizing agent includes at least one of hydrogen peroxide, ozone, air, oxygen and nickel trioxide;

[0049] Feature 20: The temperature of the phosphorus removal reaction is 85℃~95℃, and the reaction time is 3h~8h;

[0050] Feature 21: The Ni content in the phosphorus removal mother liquor is 15 g / L to 25 g / L; and / or, the pH value of the phosphorus removal mother liquor is 0.1 to 1.2.

[0051] In an optional embodiment, the nickel precipitation reaction includes: reacting the dephosphorization mother liquor with soda ash, separating the solid and liquid, and obtaining nickel carbonate.

[0052] In an optional embodiment, the nickel plating reaction includes at least one of the following characteristics:

[0053] Feature 22: The amount of soda ash added is 1 to 1.5 times the nickel content in the dephosphorization mother liquor;

[0054] Feature 23: The temperature of the nickel plating reaction is 40℃~60℃, and the reaction time is 2h~6h.

[0055] In an optional embodiment, when the first solution contains sulfuric acid, the preparation of nickel sulfate includes: mixing and reacting a portion of the dephosphorization mother liquor with nickel carbonate.

[0056] In an optional implementation, the mixing reaction includes at least one of the following features:

[0057] Feature 24: The mixed reaction is carried out under conditions of pH 4.0–5.5;

[0058] Feature 25: The temperature of the mixed reaction is 60℃~80℃, and the time of the mixed reaction is 2h~4h.

[0059] The beneficial effects of this invention include:

[0060] This invention involves acid leaching of iron phosphate waste and nickel-iron alloy to extract elemental iron and Fe. 3+ Ion reaction to produce Fe 2+ Ions can promote the dissolution of ferric phosphate and ferronickel alloys, and are more efficient than leaching ferric phosphate and ferronickel alloys separately.

[0061] When nickel-iron metal is leached, some odorous substances are produced, such as sulfide ions and organic sulfur compounds. Thiourea dioxide has strong reducing properties and can chemically react with these odor-producing substances. For example, thiourea dioxide reacts with sulfide ions, converting them into other relatively odorless or mildly odorous substances, such as elemental sulfur or polysulfides, thereby reducing or eliminating the odor to some extent. During the reaction, thiourea dioxide itself may also decompose to produce some gases. These gases can interact with or dilute the odorous substances, thus contributing to the deodorization effect.

[0062] Furthermore, thiourea dioxide exhibits good stability and strong reducing power in acidic solutions, maintaining the stability of its molecular structure. Simultaneously, the presence of hydrogen ions helps promote the reduction reaction and accelerates the reduction of Fe. 3+ Ions reduced to Fe 2+ Ions. In Fe 2+ After ion conversion, when further dissolving the nickel-iron alloy, adding a primary oxidizing agent can oxidize the elemental nickel-iron, accelerating the dissolution rate. Furthermore, due to the presence of thiourea dioxide and excess nickel-iron alloy, the leaching system is a reducing system, avoiding the formation of Fe. 3+ ion.

[0063] The method provided by this invention is simple to operate and achieves effective recycling of phosphorus and iron in iron phosphate waste and nickel and iron in nickel-iron alloys. It reduces the production cost of preparing battery-grade nickel sulfate and iron phosphate, and has a high recovery rate of Ni, Fe and P elements. Moreover, the entire process does not produce any obvious odor. Attached Figure Description

[0064] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1 A process flow diagram for the comprehensive utilization of iron phosphate waste and nickel-iron alloy provided by the present invention;

[0066] Figure 2 This is a schematic diagram illustrating the mechanism of action of thiourea dioxide.

[0067] Figure 3 This is a SEM image of the filter residue obtained after low-temperature acid leaching in Example 1 of Experiment 2;

[0068] Figure 4 The image shows the SEM image of the filter residue obtained after low-temperature acid leaching, corresponding to Comparative Example 1 in Experimental Example 2. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0070] The method for comprehensive utilization of iron phosphate waste and nickel-iron alloy provided by the present invention will be described in detail below.

[0071] This invention provides a method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy. Please refer to [the relevant documentation]. Figure 1 It mainly includes the following steps S1 to S6.

[0072] S1: The ferric phosphate waste and chromium-containing nickel-iron alloy to be treated are subjected to low-temperature acid leaching in a first solution containing acid and a reducing agent to obtain a first leachate containing ferrous iron, nickel, phosphorus, and chromium; wherein the reducing agent includes thiourea dioxide, the low-temperature acid leaching temperature is 50℃~70℃, and the Fe in the first leachate is... 3+ The content does not exceed 1g / L.

[0073] This process is mainly used to leach Fe, Ni, P, and Cr from the ferrophosphate waste and nickel-iron alloy to be treated, and to ensure that Fe... 3+ Reduced to Fe 2+ .

[0074] The above process first mixes the ferric phosphate waste to be treated with nickel-iron alloy to obtain a mixed raw material, and then performs low-temperature acid leaching of the mixed raw material in the first solution.

[0075] Compared to the reactions of elemental iron with sulfuric acid and ferric phosphate with sulfuric acid, the reaction of elemental iron with Fe... 3+ Ions have a higher reaction priority. This invention involves mixing iron phosphate waste and nickel-iron alloy, followed by acid leaching to extract elemental iron and Fe. 3+ Ion reaction to produce Fe 2+ Ions can promote the dissolution of ferric phosphate and ferronickel alloys, and are more efficient than leaching ferric phosphate and ferronickel alloys separately.

[0076] When nickel-iron metal is leached, some odorous substances are produced, such as sulfide ions and organic sulfur compounds. Thiourea dioxide has strong reducing properties and can chemically react with these odor-producing substances. For example, thiourea dioxide reacts with sulfide ions, converting them into other relatively odorless or mildly odorous substances, such as elemental sulfur or polysulfides, thereby reducing or eliminating the odor to some extent. During the reaction, thiourea dioxide itself may also decompose to produce some gases. These gases can interact with or dilute the odorous substances, thus contributing to the deodorization effect.

[0077] For more specific details, please refer to Figure 2 Adding thiourea dioxide during the leaching process can facilitate the leaching of ferric phosphate. Specifically, under acidic conditions, hydrogen ions first combine with nitrogen or oxygen atoms in the thiourea dioxide molecule, causing a certain degree of change in the molecular structure. This leads to a decrease in the stability of the carbon-sulfur bond, causing it to break, thereby producing sulfinic acid (H2SO2) and urea. H2SO2 promotes the leaching of nickel-iron alloy (exemplarily in the form of nickel-iron atomized material), and urea adsorbs and coordinates with the nickel-iron surface, promoting the formation of a porous adsorption structure. The organic gases such as methanethiol and diethyl sulfide produced during the acid leaching process fully react with Ni... 0 -Fe 0 The catalytic site combines with in-situ autocatalytic decomposition to reduce the content of organic odors (such as methanethiol and ethyl sulfide) in the exhaust gas (which can also be understood as waste gas).

[0078] The principle behind the organic gases such as methanethiol and ethyl sulfide generated during the above-mentioned acid leaching process includes: During acid leaching, the acid reacts with the sulfides in the nickel-iron alloy to generate hydrogen sulfide. The generated hydrogen sulfide further reacts with methanol or other methyl-containing substances in the system to generate methanethiol. The methanethiol and other thiols generated during acid leaching can undergo oxidative coupling reactions under certain conditions. The sulfur atoms and methyl groups in the two methanethiol molecules combine to generate ethyl sulfide. The sulfur ions in the nickel-iron alloy can also react directly with ethyl-containing substances such as ethanol under the action of acid to generate ethyl sulfide.

[0079] In some alternative implementations, the mass ratio of iron phosphate waste to ferronickel alloy is 1:1.5 to 1:2, such as 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, or other values ​​within the range of 1:1.5 to 1:2.

[0080] In the iron phosphate waste, the mass fraction of phosphorus can be 12% to 20.5%, such as 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or 20.5%, or other values ​​within the range of 12% to 20.5%. The mass fraction of iron can be 25% to 37%, such as 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, or 37%, or other values ​​within the range of 25% to 37%.

[0081] In nickel-iron alloys, the mass fraction of nickel can range from 10% to 30%, such as 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, or 30%, or other values ​​within the range of 10% to 30%. The mass fraction of iron can range from 60% to 75%, such as 60%, 62%, 65%, 68%, 70%, 72%, or 75%, or other values ​​within the range of 60% to 75%.

[0082] By mixing the aforementioned iron phosphate waste and nickel-iron alloy at a mass ratio of 1:1.5 to 1:2, elements such as Ni, Fe, Cr, and P can achieve better leaching effects, and the concentration of leached phosphorus can be ensured to be within a suitable range, so as to facilitate subsequent impurity removal.

[0083] In some alternative implementations, the first solution is formed from water, acid, and a reducing agent.

[0084] The acid may include at least one of sulfuric acid and phosphoric acid, for example, it may be sulfuric acid or phosphoric acid, or it may be a mixture of phosphoric acid and sulfuric acid.

[0085] The concentration of acid in the first solution can be 90 g / L to 120 g / L, such as 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L, 115 g / L or 120 g / L, or other values ​​within the range of 90 g / L to 120 g / L.

[0086] The concentration of thiourea dioxide in the first solution can be 5.5 g / L to 7.5 g / L, such as 5.5 g / L, 6 g / L, 6.5 g / L, 7 g / L or 7.5 g / L, or other values ​​within the range of 5.5 g / L to 7.5 g / L.

[0087] If the concentration of thiourea dioxide is too low, the reduction reaction will be insufficient and the deodorization effect will be poor; if the concentration of thiourea dioxide is too high, its utilization rate will be low.

[0088] In some alternative embodiments, the temperature of the low-temperature acid leaching can be 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, or 70°C, or other values ​​within the range of 50°C to 70°C.

[0089] In some alternative embodiments, Fe in the first leachate 3+ The content of Fe does not exceed 1 g / L, and can be 1 g / L, 0.9 g / L, 0.8 g / L, 0.7 g / L, 0.6 g / L, 0.5 g / L, 0.4 g / L, 0.3 g / L, 0.2 g / L, 0.1 g / L, 0.05 g / L, 0.02 g / L, 0.01 g / L, or 0 g / L, or other values ​​within the range not exceeding 1 g / L. In other words, low-temperature acid leaching uses Fe in the first leachate... 3+ The endpoint is defined as a content not exceeding 1 g / L.

[0090] In addition, the Ni content in the first leachate can be 5 g / L to 12 g / L, and the Fe content can be 10 g / L. 2+ The content of Cr can be 20g / L to 40g / L, the content of Cr can be 0.02g / L to 0.1g / L, and the content of P can be 2.5g / L to 7.5g / L.

[0091] S2: Add a first oxidant to the first leachate and perform high-temperature acid leaching to separate the solid and liquid, thereby obtaining a second leachate and leaching residue; wherein, the temperature of the high-temperature acid leaching is 80℃~95℃.

[0092] This process can further promote the dissolution of nickel-iron alloys.

[0093] In acidic solutions, thiourea dioxide exhibits good stability and strong reducing power, maintaining the stability of its molecular structure. Furthermore, the presence of hydrogen ions helps promote the reduction reaction and accelerates the reduction of Fe. 3+ Ions reduced to Fe 2+ Ions. In Fe 2+ After ion conversion, when further dissolving the nickel-iron alloy, adding a primary oxidizing agent can oxidize the elemental nickel-iron, accelerating the dissolution rate. Furthermore, due to the presence of thiourea dioxide and excess nickel-iron alloy, the leaching system is a reducing system, avoiding the formation of Fe. 3+ ion.

[0094] In some alternative embodiments, the high-temperature acid leaching temperature can be 80°C, 82°C, 85°C, 88°C, 90°C, 92°C or 95°C, or other values ​​within the range of 80°C to 95°C.

[0095] The high-temperature acid leaching time can be 3h to 5h, such as 3h, 3.5h, 4h, 4.5h or 5h, or other values ​​within the range of 3h to 5h.

[0096] The first oxidizing agent may, by way of example but not limitation, include hydrogen peroxide.

[0097] The amount of the first oxidant added can be 20 g / L to 60 g / L, such as 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L or 60 g / L, or other values ​​within the range of 20 g / L to 60 g / L.

[0098] At the end of the high-temperature acid leaching, the pH value of the second leachate is 1.4 to 2.3 (e.g., 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2 or 2.3, etc.).

[0099] In some optional embodiments, the Ni content in the second leachate can be 10 g / L to 20 g / L, and the Fe content can be [missing information]. 2+ The content of Cr can be 40g / L to 60g / L, the content of Cr can be 0.04g / L to 0.12g / L, and the content of P can be 2.5g / L to 7.5g / L.

[0100] The leaching residue can be subjected to acid leaching again with acid solution as needed to improve the recovery rate.

[0101] Continuing from above, in phosphorus-containing solutions, Fe 3+ Due to its poor ionic stability, ferric phosphate dihydrate is easily precipitated during actual production due to material transfer and temperature increases. When ferric phosphate waste is mixed with nickel-iron alloy for leaching, the entire reaction system is a reduction system, generating Fe... 2+ It exhibits higher ionic stability, is less prone to precipitation, and is more suitable for mass production. Furthermore, in this invention, by dividing the leaching process into two stages (low-temperature acid leaching + high-temperature acid leaching), Fe is achieved during the low-temperature acid leaching process. 3+ ions to Fe 2+ The ion conversion, followed by high-temperature acid leaching, further accelerates the dissolution of the nickel-iron alloy.

[0102] S3: Remove chromium from the second leachate to obtain the chromium-removed solution.

[0103] In some alternative embodiments, removing chromium from the second leachate may include: adding seed crystals to the second leachate to perform a seed crystal reaction, and then adding a modifier to perform a chromium removal reaction.

[0104] The seed crystals may, by way of example but not by way of limitation, include at least one of anhydrous ferric phosphate, ferric phosphate dihydrate, amorphous ferric phosphate and ferrous hydrogen phosphate.

[0105] Value adjusters may include, by way of example but not by way of limitation, at least one of nickel carbonate, chromium slag and nickel hydroxide.

[0106] The above seed crystal reaction is mainly used to form chromium phosphate products, while the chromium removal reaction mainly involves removing Cr. 3+ Cr(OH)3 precipitate is generated, and then solid-liquid separation is performed to obtain the chromium-removed liquid and chromium slag. The chromium slag can be recycled and used as a value-regulating agent.

[0107] In some alternative embodiments, the amount of seed crystals added can be 1 g / L to 1.5 g / L, such as 1 g / L, 1.1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L or 1.5 g / L, etc., or other values ​​within the range of 1 g / L to 1.5 g / L.

[0108] The temperature for the seed crystal reaction can be between 50℃ and 70℃, such as 50℃, 55℃, 60℃, 65℃ or 70℃, or other values ​​within the range of 50℃ to 70℃.

[0109] The seed reaction time can be 0.5h to 1.5h, such as 0.5h, 0.8h, 1h, 1.2h or 1.5h, or other values ​​within the range of 0.5h to 1.5h.

[0110] In some optional embodiments, a pH adjuster is added to control the pH of the reaction system corresponding to the chromium removal reaction to be 2.5 to 3.5, such as 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4 or 3.5, or other values ​​in the range of 2.5 to 3.5.

[0111] The temperature for the chromium removal reaction can be between 50℃ and 70℃, such as 50℃, 55℃, 60℃, 65℃ or 70℃, or other values ​​within the range of 50℃ to 70℃.

[0112] The chromium removal reaction time can be from 1 hour to 3 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, or other values ​​within the range of 1 hour to 3 hours.

[0113] In some optional embodiments, the Ni content in the chromium removal solution can be 15 g / L to 25 g / L, and the Fe content can be [missing information]. 2+ The content of Cr can be 35g / L to 60g / L, the content of Cr can be 0.002g / L to 0.008g / L, and the content of P can be 2.5g / L to 7.5g / L.

[0114] S4: At least a portion of the chromium-removed liquid is reacted with supplemented phosphoric acid and a second oxidant to induce iron precipitation, followed by solid-liquid separation to obtain ferric phosphate and ferric phosphate mother liquor.

[0115] In some alternative implementations, the second oxidant may be hydrogen peroxide.

[0116] In some alternative embodiments, the iron precipitation reaction includes: first adding supplemental phosphoric acid to at least a portion of the chromium-removed liquid to carry out a first reaction, and then adding a second oxidant to carry out a second reaction.

[0117] During operation, the chromium-removed solution can be divided into two parts. One part is treated with supplemental phosphoric acid for the first reaction, followed by the addition of a second oxidant for the second reaction. The other part serves as a supplementary iron source for subsequent stages. Alternatively, supplemental phosphoric acid can be added to all the chromium-removed solution for the first reaction, followed by the addition of a second oxidant for the second reaction.

[0118] The first reaction described above is a physical mixing reaction, and the second reaction is a redox reaction.

[0119] The ratio of the total number of moles of P in the supplemented phosphoric acid to the total number of moles of P in the chromium-removed solution to the total number of moles of Fe in the chromium-removed solution can be from 1:0.8 to 1:0.98, such as 1:0.8, 1:0.85, 1:0.88, 1:0.9, 1:0.92, 1:0.95 or 1:0.98, or other values ​​within the range of 1:0.8 to 1:0.98.

[0120] The temperature of the first reaction can be between 40℃ and 55℃, such as 40℃, 42℃, 45℃, 48℃, 50℃, 52℃ or 55℃, or other values ​​within the range of 40℃ to 55℃.

[0121] The time for the first reaction can be 1 to 3 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, or other values ​​within the range of 1 hour to 3 hours.

[0122] In some alternative embodiments, a second oxidant is added to reduce the Fe content in the ferric phosphate mother liquor. 2+ The concentration is 0.8 g / L to 1.6 g / L, such as 0.8 g / L, 1.0 g / L, 1.2 g / L, 1.4 g / L or 1.6 g / L, or other values ​​within the range of 0.8 g / L to 1.6 g / L.

[0123] The temperature of the second reaction can be between 30℃ and 60℃, such as 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃, or other values ​​within the range of 30℃ to 60℃.

[0124] The second reaction time can be 0.5h to 1.5h, such as 0.5h, 0.8h, 1h, 1.2h or 1.5h, or other values ​​within the range of 0.5h to 1.5h.

[0125] In some optional embodiments, the Ni content in the ferric phosphate mother liquor can be 15 g / L to 25 g / L, and the Fe content can be... 2+The content of [a] can be 0.8 g / L to 1.6 g / L, and the content of [P] can be 2 g / L to 4 g / L.

[0126] In some alternative embodiments, the pH value of the ferric phosphate mother liquor can be 0.1 to 1.2, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 or 1.2, or other values ​​within the range of 0.1 to 1.2.

[0127] Depending on the requirements, the obtained iron phosphate can be aged, filtered, washed, and calcined to obtain battery-grade iron phosphate.

[0128] S5: Remove phosphorus from the ferric phosphate mother liquor to obtain a phosphorus-removed mother liquor.

[0129] In some alternative embodiments, removing phosphorus from the ferric phosphate mother liquor includes: adding an iron source to the ferric phosphate mother liquor and adding a third oxidant to carry out a phosphorus removal reaction, followed by solid-liquid separation to obtain ferric phosphate dihydrate and the phosphorus removal mother liquor.

[0130] In some alternative embodiments, the ratio of the total moles of Fe in the ferric phosphate mother liquor and Fe in the supplementary iron source to the moles of P in the ferric phosphate mother liquor can be from 1.05:1 to 1.2:1, such as 1.05:1, 1.08:1, 1.1:1, 1.12:1, 1.15:1, 1.18:1, or 1.2:1, or other values ​​within the range of 1.05:1 to 1.2:1. The excess P is neutralized by supplementing the iron source.

[0131] In some alternative embodiments, the third oxidizing agent may, by way of example but not limitation, include at least one of hydrogen peroxide, ozone, air, oxygen, and nickel trioxide. The third oxidizing agent is used to oxidize Fe... 2+ Oxidized to Fe 3+ .

[0132] In some alternative embodiments, the temperature of the phosphorus removal reaction can be 85°C to 95°C, such as 85°C, 88°C, 90°C, 92°C or 95°C, or other values ​​within the range of 85°C to 95°C.

[0133] The phosphorus removal reaction time can be 3h to 8h, such as 3h, 4h, 5h, 6h, 7h or 8h, or other values ​​within the range of 3h to 8h.

[0134] In some optional embodiments, the Ni content in the dephosphorization mother liquor can be 15 g / L to 25 g / L.

[0135] In some alternative embodiments, the pH value of the phosphorus removal mother liquor can be 0.1 to 1.2, such as 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 or 1.2, or other values ​​in the range of 0.1 to 1.2.

[0136] The ferric phosphate dihydrate obtained above can be reused as a seed crystal in the seed crystal reaction process.

[0137] S6: At least a portion of the dephosphorization mother liquor is subjected to a nickel precipitation reaction before being prepared into nickel sulfate.

[0138] During operation, the dephosphorization mother liquor can be divided into two parts: one part is used for nickel precipitation, and the other part is used to adjust the acid content of the nickel precipitate obtained from the nickel precipitation reaction to obtain nickel sulfate. Alternatively, all the dephosphorization mother liquor can be used for nickel precipitation, and then nickel sulfate can be obtained by adding sulfate source.

[0139] In some alternative embodiments, the nickel precipitation reaction includes: reacting the dephosphorization mother liquor with soda ash, separating the solid and liquid phases, and obtaining nickel carbonate.

[0140] In some optional embodiments, the amount of soda ash added is 1 to 1.5 times the nickel content in the dephosphorization mother liquor, such as 1, 1.1, 1.2, 1.3, 1.4, or 1.5 times, or other values ​​within the range of 1 to 1.5 times.

[0141] In some alternative embodiments, the temperature of the nickel plating reaction can be 40°C to 60°C, such as 40°C, 45°C, 50°C, 55°C or 60°C, or other values ​​within the range of 40°C to 60°C.

[0142] The nickel plating reaction time can be 2h to 6h, such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, or other values ​​within the range of 2h to 6h.

[0143] When the first solution contains sulfuric acid, the preparation of nickel sulfate includes: mixing and reacting a dephosphorization mother liquor (used for purposes other than nickel precipitation) with nickel carbonate.

[0144] The mixed reaction can be carried out under conditions with a pH value of 4.0 to 5.5 (such as 4.0, 4.2, 4.5, 4.8, 5.0, 5.2 or 5.5).

[0145] The temperature of the mixed reaction can be 60℃~80℃, such as 60℃, 65℃, 70℃, 75℃ or 80℃, or other values ​​within the range of 60℃~80℃.

[0146] The reaction time can be 2h to 4h, such as 2h, 2.5h, 3h, 3.5h or 4h, or other values ​​within the range of 2h to 4h.

[0147] Battery-grade nickel sulfate can be obtained through the above reaction.

[0148] In addition, the nickel carbonate obtained from the above nickel precipitation reaction can also be reused as a value modifier in the chromium removal reaction process.

[0149] Continuing from the above, the commonly used process of directly dissolving iron phosphate waste with sulfuric acid, then adding phosphoric acid to prepare a solution with a certain iron-to-phosphorus ratio before preparing battery-grade iron phosphate often results in high acidity and sulfur content, leading to defects such as high sulfur content and small specific surface area in the prepared iron phosphate products. This invention addresses these issues by removing Fe from iron phosphate waste... 3+ Reduced to Fe 2+ After undergoing a pH adjustment and impurity removal process, the acidity is reduced compared to direct leaching, thus decreasing the amount of Fe. 3+ The precipitation of ions improves the utilization rate of iron and phosphorus.

[0150] Throughout the recycling process, the ferric phosphate dihydrate produced by oxidation and heating can be reused as seed crystals in the nickel-iron leaching process and the chromium removal process, recovering phosphorus and iron elements from the slag. The main process that produces ferric phosphate dihydrate is the mother liquor dephosphorization stage. Since there is excess phosphorus in the ferric phosphate mother liquor, in order to obtain a high-purity nickel sulfate solution, the chromium removal solution in the system can be supplemented to utilize the iron in the system for phosphorus removal, without the need to introduce an additional iron source, thus reducing costs. Furthermore, the phosphorus in the mother liquor and the iron in the chromium removal solution are recovered in the form of phosphorus-iron slag, reducing the loss of phosphorus and iron.

[0151] Using nickel carbonate to consume residual acid in the dephosphorization mother liquor can increase the nickel concentration. Compared with adding other nickel sources (such as MHP), it can reduce the calcium and magnesium removal steps in the extraction stage, thereby reducing the process flow. By adjusting the pH value, impurities such as iron, aluminum, and phosphorus in the dephosphorization mother liquor can be further removed, avoiding the introduction of sodium ions by directly adding sodium carbonate, thus improving product purity.

[0152] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0153] Example 1

[0154] This embodiment provides a method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy to prepare battery-grade iron phosphate and nickel sulfate. The operation steps are as follows:

[0155] S1: The ferric phosphate waste and nickel-iron alloy to be treated are subjected to low-temperature acid leaching in a first solution containing acid and reducing agent to obtain a first leachate containing ferrous iron, nickel, phosphorus and chromium.

[0156] The iron phosphate waste contains 20.5% phosphorus and 37% iron by mass; the nickel-iron alloy contains 26% nickel and 70% iron by mass; the mass ratio of iron phosphate waste to nickel-iron alloy is 1:1.5.

[0157] The first solution is a mixture of sulfuric acid, thiourea dioxide, and water, wherein the concentration of sulfuric acid in the first solution is 100 g / L, and the concentration of thiourea dioxide in the first solution is 5.5 g / L.

[0158] The low-temperature acid leaching temperature is 50℃, and the Fe in the first leaching solution is leached out. 3+ The concentration was reduced to 0.8 g / L. The concentration of Ni in the first leachate was 5.5 g / L, and the concentration of Fe... 2+ The concentrations of Cr, P, and Cr were 20 g / L, 0.02 g / L, and 5.77 g / L, respectively.

[0159] S2: Add the first oxidant to the first leachate, heat it for high-temperature acid leaching, and after pressure filtration, obtain the second leachate and leachate residue.

[0160] The first oxidant was hydrogen peroxide, added at a concentration of 20 g / L. The high-temperature acid leaching was performed at 80°C for 3 hours, resulting in a second leachate with a pH of 1.4. The second leachate contained 11 g / L of Ni and Fe... 2+ The content of 40 g / L, Cr is 0.04 g / L, and P is 5.77 g / L.

[0161] S3: Remove chromium from the second leachate to obtain the chromium-removed solution.

[0162] Specifically: seed crystals are added to the second leachate to carry out a seed crystal reaction, then a value adjuster is added to carry out a chromium removal reaction (which can be understood as precipitation and impurity removal), and the solution is filtered to obtain the chromium-removed liquid and chromium slag.

[0163] The seed crystals were anhydrous ferric phosphate, with an addition amount of 1 g / L. The seed crystal reaction temperature was 50℃, and the reaction time was 0.5 h. The pH adjuster was nickel carbonate, which controlled the pH of the reaction solution system to 2.5. The chromium removal reaction temperature was 50℃, and the chromium removal reaction time was 1 h.

[0164] The Ni content in the solution after chromium removal is 15 g / L, and the Fe content is... 2+ The content of Mg was 38 g / L, the content of Cr was 0.008 g / L, and the content of P was 4.8 g / L.

[0165] S4: At least a portion of the chromium-removed liquid is reacted with supplemented phosphoric acid and a second oxidant to induce iron precipitation, followed by solid-liquid separation to obtain ferric phosphate and ferric phosphate mother liquor.

[0166] Specifically: First, supplementary phosphoric acid is added to a portion of the chromium-removed solution to initiate the first reaction, followed by the addition of a second oxidant to initiate the second reaction (the first and second reactions can be understood as phosphorus precipitation of iron). The mixture is then filtered to obtain ferric phosphate and ferric phosphate mother liquor. After aging, filtration, washing, and calcination, battery-grade ferric phosphate is obtained.

[0167] The second oxidant was hydrogen peroxide. The ratio of the total moles of phosphoric acid (P) in the supplemented phosphoric acid to the total moles of phosphoric acid (P) in the chromium-removed solution to the total moles of iron (Fe) in the chromium-removed solution was 1:0.8. The temperature of the first reaction was 40℃, and the reaction time was 1 hour. The second oxidant was added to reduce the iron content in the ferric phosphate mother liquor. 2+ The concentration was 0.8 g / L, the temperature of the second reaction was 30 °C, and the time of the second reaction was 0.5 h.

[0168] The Ni content in the ferric phosphate mother liquor is 15 g / L, and the Fe content is... 2+ The content of ferric phosphate was 0.8 g / L, the content of phosphoric acid was 4 g / L, and the pH value of the ferric phosphate mother liquor was 0.1.

[0169] S5: Remove phosphorus from the ferric phosphate mother liquor to obtain a phosphorus-removed mother liquor.

[0170] Specifically, an iron source is added to the ferric phosphate mother liquor, and a third oxidant is added to carry out a phosphorus removal reaction. After pressure filtration, ferric phosphate dihydrate and phosphorus removal mother liquor are obtained.

[0171] The supplementary iron source was the remaining chromium-removed solution after removing the chromium-removed solution used for S4. The ratio of the total molar amount of Fe in the ferric phosphate mother liquor to the total molar amount of Fe in the supplementary iron source to the total molar amount of P in the ferric phosphate mother liquor was 1.05:1. The third oxidant was hydrogen peroxide. The phosphorus removal reaction was carried out at 85℃ for 3 hours.

[0172] The Ni content in the phosphorus removal mother liquor is 15 g / L; the pH value of the phosphorus removal mother liquor is 0.1.

[0173] S6: Part of the dephosphorization mother liquor is subjected to a nickel precipitation reaction and then prepared into nickel sulfate.

[0174] Specifically, a portion of the dephosphorization mother liquor was reacted with soda ash to undergo a nickel precipitation reaction, followed by pressure filtration to obtain nickel carbonate and wastewater. The amount of soda ash used was equal to the nickel content in the dephosphorization mother liquor, the nickel precipitation reaction temperature was 40℃, and the reaction time was 2 hours.

[0175] S7: The remaining dephosphorization mother liquor is adjusted with the nickel carbonate obtained in S6 to increase the nickel concentration (which can also be understood as the reaction of nickel carbonate and dephosphorization mother liquor) to obtain battery-grade nickel sulfate.

[0176] The pH of the solution was adjusted to 4.0 with nickel carbonate, the mixing reaction temperature was 60℃, and the mixing reaction time was 2h.

[0177] Example 2

[0178] This embodiment provides a method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy to prepare battery-grade iron phosphate and nickel sulfate. The operation steps are as follows:

[0179] S1: The ferric phosphate waste and nickel-iron alloy to be treated are subjected to low-temperature acid leaching in a first solution containing acid and reducing agent to obtain a first leachate containing ferrous iron, nickel, phosphorus and chromium.

[0180] The iron phosphate waste contains 20.5% phosphorus and 37% iron by mass; the nickel-iron alloy contains 26% nickel and 70% iron by mass; the mass ratio of iron phosphate waste to nickel-iron alloy is 1:1.6.

[0181] The first solution is a mixture of sulfuric acid, thiourea dioxide, and water, wherein the concentration of sulfuric acid in the first solution is 105 g / L, and the concentration of thiourea dioxide in the first solution is 6 g / L.

[0182] The low-temperature acid leaching temperature is 55℃, and the Fe in the first leaching solution is leached out. 3+ The concentration was reduced to 0.6 g / L. The concentration of Ni in the first leachate was 6.8 g / L, and the concentration of Fe... 2+ The concentrations of Cr, P, and Cr were 25 g / L, 0.04 g / L, and 6.1 g / L, respectively.

[0183] S2: Add the first oxidant to the first leachate, heat it for high-temperature acid leaching, and after pressure filtration, obtain the second leachate and leachate residue.

[0184] The first oxidant was hydrogen peroxide, added at a concentration of 30 g / L. The high-temperature acid leaching temperature was 83℃, and the leaching time was 3.5 hours. During this process, the pH of the second leachate was 1.6. The second leachate contained 12.5 g / L of Ni and Fe. 2+ The content of 45 g / L, Cr is 0.06 g / L, and P is 6.1 g / L.

[0185] S3: Remove chromium from the second leachate to obtain the chromium-removed solution.

[0186] Specifically: seed crystals are added to the second leachate to carry out a seed crystal reaction, then a value adjuster is added to carry out a chromium removal reaction (which can be understood as precipitation and impurity removal), and the solution is filtered to obtain the chromium-removed liquid and chromium slag.

[0187] The seed crystals were anhydrous ferric phosphate, with an addition amount of 1.15 g / L. The seed crystal reaction temperature was 55℃, and the reaction time was 0.7 h. The pH adjuster was nickel carbonate, which controlled the pH of the reaction solution system to 2.7. The chromium removal reaction temperature was 55℃, and the chromium removal reaction time was 1.5 h.

[0188] The Ni content in the solution after chromium removal was 16.5 g / L, and the Fe content was... 2+ The content of 43 g / L, Cr was 0.007 g / L, and P was 5.3 g / L.

[0189] S4: At least a portion of the chromium-removed liquid is reacted with supplemented phosphoric acid and a second oxidant to induce iron precipitation, followed by solid-liquid separation to obtain ferric phosphate and ferric phosphate mother liquor.

[0190] Specifically: First, supplementary phosphoric acid is added to a portion of the chromium-removed solution to initiate the first reaction, followed by the addition of a second oxidant to initiate the second reaction (the first and second reactions can be understood as phosphorus precipitation of iron). The mixture is then filtered to obtain ferric phosphate and ferric phosphate mother liquor. After aging, filtration, washing, and calcination, battery-grade ferric phosphate is obtained.

[0191] The second oxidant was hydrogen peroxide. The ratio of the total moles of phosphoric acid (P) in the supplemented phosphoric acid to the total moles of phosphoric acid (P) in the chromium-removed solution to the total moles of iron (Fe) in the chromium-removed solution was 1:0.85. The temperature of the first reaction was 44℃, and the reaction time was 1.5 h. The second oxidant was added to reduce the iron content in the ferric phosphate mother liquor. 2+ The concentration was 1 g / L, the temperature of the second reaction was 35℃, and the time of the second reaction was 0.7 h.

[0192] The Ni content in the ferric phosphate mother liquor was 16.5 g / L, and the Fe content was... 2+ The content of Mg is 1.0 g / L, the content of P is 3.5 g / L, and the pH value of the ferric phosphate mother liquor is 0.4.

[0193] S5: Remove phosphorus from the ferric phosphate mother liquor to obtain a phosphorus-removed mother liquor.

[0194] Specifically, an iron source is added to the ferric phosphate mother liquor, and a third oxidant is added to carry out a phosphorus removal reaction. After pressure filtration, ferric phosphate dihydrate and phosphorus removal mother liquor are obtained.

[0195] The supplementary iron source was the remaining chromium-removed solution after removing the chromium-removed solution used for S4. The ratio of the total molar amount of Fe in the ferric phosphate mother liquor to the total molar amount of Fe in the supplementary iron source to the total molar amount of P in the ferric phosphate mother liquor was 1.08:1. The third oxidant was hydrogen peroxide. The phosphorus removal reaction was carried out at a temperature of 87℃ for 4 hours.

[0196] The Ni content in the phosphorus removal mother liquor was 16.5 g / L; the pH value of the phosphorus removal mother liquor was 0.4.

[0197] S6: Part of the dephosphorization mother liquor is subjected to a nickel precipitation reaction and then prepared into nickel sulfate.

[0198] Specifically, a portion of the dephosphorization mother liquor was reacted with soda ash to undergo a nickel precipitation reaction, followed by pressure filtration to obtain nickel carbonate and wastewater. The amount of soda ash used was 1.1 times the nickel content in the dephosphorization mother liquor, the nickel precipitation reaction temperature was 45℃, and the reaction time was 3 hours.

[0199] S7: The remaining dephosphorization mother liquor is adjusted with the nickel carbonate obtained in S6 to increase the nickel concentration (which can also be understood as the reaction of nickel carbonate and dephosphorization mother liquor) to obtain battery-grade nickel sulfate.

[0200] The pH of the solution was adjusted to 4.2 with nickel carbonate, the mixing reaction temperature was 65℃, and the mixing reaction time was 2.5h.

[0201] Example 3

[0202] This embodiment provides a method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy to prepare battery-grade iron phosphate and nickel sulfate. The operation steps are as follows:

[0203] S1: The ferric phosphate waste and nickel-iron alloy to be treated are subjected to low-temperature acid leaching in a first solution containing acid and reducing agent to obtain a first leachate containing ferrous iron, nickel, phosphorus and chromium.

[0204] The iron phosphate waste contains 20.5% phosphorus and 37% iron by mass; the nickel-iron alloy contains 26% nickel and 70% iron by mass; the mass ratio of iron phosphate waste to nickel-iron alloy is 1:1.7.

[0205] The first solution is a mixture of sulfuric acid, thiourea dioxide, and water, wherein the concentration of sulfuric acid in the first solution is 110 g / L, and the concentration of thiourea dioxide in the first solution is 6.5 g / L.

[0206] The low-temperature acid leaching temperature is 60℃, and the Fe in the first leaching solution is leached out. 3+ The concentration was reduced to 0.4 g / L. The concentration of Ni in the first leachate was 8.5 g / L, and the concentration of Fe... 2+ The concentrations of Cr, P, and Cr were 30 g / L, 0.06 g / L, and 6.57 g / L, respectively.

[0207] S2: Add the first oxidant to the first leachate, heat it for high-temperature acid leaching, and after pressure filtration, obtain the second leachate and leachate residue.

[0208] The first oxidant was hydrogen peroxide, added at a concentration of 40 g / L. The high-temperature acid leaching was performed at 86°C for 4 hours, during which time the pH of the second leachate was 1.8. The second leachate contained 14 g / L of Ni and Fe... 2+ The content of Mg is 50 g / L, the content of Cr is 0.08 g / L, and the content of P is 6.57 g / L.

[0209] S3: Remove chromium from the second leachate to obtain the chromium-removed solution.

[0210] Specifically: seed crystals are added to the second leachate to carry out a seed crystal reaction, then a value adjuster is added to carry out a chromium removal reaction (which can be understood as precipitation and impurity removal), and the solution is filtered to obtain the chromium-removed liquid and chromium slag.

[0211] The seed crystals were anhydrous ferric phosphate, with an addition amount of 1.25 g / L. The seed crystal reaction temperature was 60℃, and the reaction time was 0.9 h. The pH adjuster was nickel carbonate, which controlled the pH of the reaction solution system to 2.9. The chromium removal reaction temperature was 60℃, and the chromium removal reaction time was 2 h.

[0212] The Ni content in the solution after chromium removal was 18.3 g / L, and the Fe content was... 2+ The content of 48 g / L, Cr is 0.005 g / L, and P is 5.5 g / L.

[0213] S4: At least a portion of the chromium-removed liquid is reacted with supplemented phosphoric acid and a second oxidant to induce iron precipitation, followed by solid-liquid separation to obtain ferric phosphate and ferric phosphate mother liquor.

[0214] Specifically: First, supplementary phosphoric acid is added to a portion of the chromium-removed solution to initiate the first reaction, followed by the addition of a second oxidant to initiate the second reaction (the first and second reactions can be understood as phosphorus precipitation of iron). The mixture is then filtered to obtain ferric phosphate and ferric phosphate mother liquor. After aging, filtration, washing, and calcination, battery-grade ferric phosphate is obtained.

[0215] The second oxidant was hydrogen peroxide. The ratio of the total moles of phosphoric acid (P) in the supplemented phosphoric acid to the total moles of phosphoric acid (P) in the chromium-removed solution to the total moles of iron (Fe) in the chromium-removed solution was 1:0.9. The temperature of the first reaction was 48℃, and the reaction time was 2 hours. The second oxidant was added to reduce the amount of iron (Fe) in the ferric phosphate mother liquor. 2+ The concentration was 1.2 g / L, the temperature of the second reaction was 40 °C, and the time of the second reaction was 0.9 h.

[0216] The Ni content in the ferric phosphate mother liquor was 18.3 g / L, and the Fe content was... 2+ The content of ferric phosphate was 1.2 g / L, the content of phosphoric acid was 3 g / L, and the pH value of the ferric phosphate mother liquor was 0.7.

[0217] S5: Remove phosphorus from the ferric phosphate mother liquor to obtain a phosphorus-removed mother liquor.

[0218] Specifically, an iron source is added to the ferric phosphate mother liquor, and a third oxidant is added to carry out a phosphorus removal reaction. After pressure filtration, ferric phosphate dihydrate and phosphorus removal mother liquor are obtained.

[0219] The supplementary iron source was the remaining chromium-removed solution after removing the chromium-removed solution used for S4. The ratio of the total molar amount of Fe in the ferric phosphate mother liquor to the total molar amount of Fe in the supplementary iron source to the total molar amount of P in the ferric phosphate mother liquor was 1.1:1. The third oxidant was hydrogen peroxide. The phosphorus removal reaction was carried out at a temperature of 89℃ for 5 hours.

[0220] The Ni content in the phosphorus removal mother liquor was 18.3 g / L; the pH value of the phosphorus removal mother liquor was 0.8.

[0221] S6: Part of the dephosphorization mother liquor is subjected to a nickel precipitation reaction and then prepared into nickel sulfate.

[0222] Specifically, a portion of the dephosphorization mother liquor was reacted with soda ash to undergo a nickel precipitation reaction, followed by pressure filtration to obtain nickel carbonate and wastewater. The amount of soda ash used was 1.2 times the nickel content in the dephosphorization mother liquor, the nickel precipitation reaction temperature was 50℃, and the reaction time was 4 hours.

[0223] S7: The remaining dephosphorization mother liquor is adjusted with the nickel carbonate obtained in S6 to increase the nickel concentration (which can also be understood as the reaction of nickel carbonate and dephosphorization mother liquor) to obtain battery-grade nickel sulfate.

[0224] The pH of the solution was adjusted to 4.5 with nickel carbonate, the mixing reaction temperature was 70℃, and the mixing reaction time was 3h.

[0225] Example 4

[0226] This embodiment provides a method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy to prepare battery-grade iron phosphate and nickel sulfate. The operation steps are as follows:

[0227] S1: The ferric phosphate waste and nickel-iron alloy to be treated are subjected to low-temperature acid leaching in a first solution containing acid and reducing agent to obtain a first leachate containing ferrous iron, nickel, phosphorus and chromium.

[0228] The iron phosphate waste contains 20.5% phosphorus and 37% iron by mass; the nickel-iron alloy contains 26% nickel and 70% iron by mass; the mass ratio of iron phosphate waste to nickel-iron alloy is 1:1.8.

[0229] The first solution is a mixture of sulfuric acid, thiourea dioxide, and water, wherein the concentration of sulfuric acid in the first solution is 115 g / L, and the concentration of thiourea dioxide in the first solution is 7 g / L.

[0230] The low-temperature acid leaching temperature is 65℃, and the Fe in the first leaching solution is leached out. 3+ The concentration was reduced to 0.2 g / L. The concentration of Ni in the first leachate was 10 g / L, and the concentration of Fe... 2+ The concentrations of Cr, P, and Cr were 35 g / L, 0.08 g / L, and 6.9 g / L, respectively.

[0231] S2: Add the first oxidant to the first leachate, heat it for high-temperature acid leaching, and after pressure filtration, obtain the second leachate and leachate residue.

[0232] The first oxidant was hydrogen peroxide, added at a concentration of 50 g / L. The high-temperature acid leaching temperature was 89°C, and the leaching time was 4.5 hours. During this process, the pH of the second leachate was 2.0. The second leachate contained 15.5 g / L of Ni and Fe... 2+ The content of Cr is 55 g / L, the content of P is 0.1 g / L, and the content of P is 6.9 g / L.

[0233] S3: Remove chromium from the second leachate to obtain the chromium-removed solution.

[0234] Specifically: seed crystals are added to the second leachate to carry out a seed crystal reaction, then a value adjuster is added to carry out a chromium removal reaction (which can be understood as precipitation and impurity removal), and the solution is filtered to obtain the chromium-removed liquid and chromium slag.

[0235] The seed crystals were anhydrous ferric phosphate, with an addition amount of 1.35 g / L. The seed crystal reaction temperature was 65℃, and the reaction time was 1.1 h. The pH adjuster was nickel carbonate, which controlled the pH of the reaction solution system to 3.1. The chromium removal reaction temperature was 65℃, and the chromium removal reaction time was 2.5 h.

[0236] The Ni content in the solution after chromium removal was 20.1 g / L, and the Fe content was... 2+ The content of Mg was 52 g / L, the content of Cr was 0.003 g / L, and the content of P was 5.7 g / L.

[0237] S4: At least a portion of the chromium-removed liquid is reacted with supplemented phosphoric acid and a second oxidant to induce iron precipitation, followed by solid-liquid separation to obtain ferric phosphate and ferric phosphate mother liquor.

[0238] Specifically: First, supplementary phosphoric acid is added to a portion of the chromium-removed solution to initiate the first reaction, followed by the addition of a second oxidant to initiate the second reaction (the first and second reactions can be understood as phosphorus precipitation of iron). The mixture is then filtered to obtain ferric phosphate and ferric phosphate mother liquor. After aging, filtration, washing, and calcination, battery-grade ferric phosphate is obtained.

[0239] The second oxidant was hydrogen peroxide. The ratio of the total moles of phosphoric acid (P) in the supplemented phosphoric acid to the total moles of phosphoric acid (P) in the chromium-removed solution to the total moles of iron (Fe) in the chromium-removed solution was 1:0.94. The temperature of the first reaction was 52℃, and the reaction time was 2.5 h. The second oxidant was added to reduce the amount of iron (Fe) in the ferric phosphate mother liquor. 2+ The concentration was 1.4 g / L, the temperature of the second reaction was 50 °C, and the time of the second reaction was 1.2 h.

[0240] The Ni content in the ferric phosphate mother liquor was 20.1 g / L, and the Fe content was... 2+ The content of Mg was 1.4 g / L, the content of P was 2.5 g / L, and the pH value of the ferric phosphate mother liquor was 1.

[0241] S5: Remove phosphorus from the ferric phosphate mother liquor to obtain a phosphorus-removed mother liquor.

[0242] Specifically, an iron source is added to the ferric phosphate mother liquor, and a third oxidant is added to carry out a phosphorus removal reaction. After pressure filtration, ferric phosphate dihydrate and phosphorus removal mother liquor are obtained.

[0243] The supplementary iron source was the remaining chromium-removed solution after removing the chromium-removed solution used for S4. The ratio of the total molar amount of Fe in the ferric phosphate mother liquor to the total molar amount of Fe in the supplementary iron source to the total molar amount of P in the ferric phosphate mother liquor was 1.14:1. The third oxidant was hydrogen peroxide. The phosphorus removal reaction was carried out at a temperature of 92℃ for 6 hours.

[0244] The Ni content in the phosphorus removal mother liquor was 20.1 g / L; the pH value of the phosphorus removal mother liquor was 1.

[0245] S6: Part of the dephosphorization mother liquor is subjected to a nickel precipitation reaction and then prepared into nickel sulfate.

[0246] Specifically, a portion of the dephosphorization mother liquor was reacted with soda ash to undergo a nickel precipitation reaction, followed by pressure filtration to obtain nickel carbonate and wastewater. The amount of soda ash used was 1.3 times the nickel content in the dephosphorization mother liquor, the nickel precipitation reaction temperature was 55℃, and the reaction time was 5 hours.

[0247] S7: The remaining dephosphorization mother liquor is adjusted with the nickel carbonate obtained in S6 to increase the nickel concentration (which can also be understood as the reaction of nickel carbonate and dephosphorization mother liquor) to obtain battery-grade nickel sulfate.

[0248] The pH of the solution was controlled to be 5 by adjusting the nickel carbonate content, the mixing reaction temperature was 75℃, and the mixing reaction time was 3.5h.

[0249] Example 5

[0250] This embodiment provides a method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy to prepare battery-grade iron phosphate and nickel sulfate. The operation steps are as follows:

[0251] S1: The ferric phosphate waste and nickel-iron alloy to be treated are subjected to low-temperature acid leaching in a first solution containing acid and reducing agent to obtain a first leachate containing ferrous iron, nickel, phosphorus and chromium.

[0252] The iron phosphate waste contains 20.5% phosphorus and 37% iron by mass; the nickel-iron alloy contains 26% nickel and 70% iron by mass; the mass ratio of iron phosphate waste to nickel-iron alloy is 1:1.9.

[0253] The first solution is a mixture of sulfuric acid, thiourea dioxide, and water, wherein the concentration of sulfuric acid in the first solution is 120 g / L, and the concentration of thiourea dioxide in the first solution is 7.5 g / L.

[0254] The low-temperature acid leaching temperature is 70℃, and the Fe in the first leaching solution is leached out. 3+ The concentration was reduced to 0 g / L. The concentration of Ni in the first leachate was 11.5 g / L, and the concentration of Fe was... 2+ The concentrations of Cr, P, and Cr were 40 g / L, 0.1 g / L, and 7.2 g / L, respectively.

[0255] S2: Add the first oxidant to the first leachate, heat it for high-temperature acid leaching, and after pressure filtration, obtain the second leachate and leachate residue.

[0256] The first oxidant was hydrogen peroxide, added at a concentration of 60 g / L. The high-temperature acid leaching was performed at 92°C for 5 hours, resulting in a second leachate with a pH of 2.2. The second leachate contained 17.4 g / L of Ni and Fe... 2+ The content of Cr is 60 g / L, the content of P is 0.12 g / L, and the content of P is 7.2 g / L.

[0257] S3: Remove chromium from the second leachate to obtain the chromium-removed solution.

[0258] Specifically: seed crystals are added to the second leachate to carry out a seed crystal reaction, then a value adjuster is added to carry out a chromium removal reaction (which can be understood as precipitation and impurity removal), and the solution is filtered to obtain the chromium-removed liquid and chromium slag.

[0259] The seed crystals were anhydrous ferric phosphate, with an addition amount of 1.45 g / L. The seed crystal reaction temperature was 70℃, and the reaction time was 1.3 h. The pH adjuster was nickel carbonate, which controlled the pH of the reaction solution system to 3.3. The chromium removal reaction temperature was 70℃, and the chromium removal reaction time was 3 h.

[0260] The Ni content in the solution after chromium removal was 22 g / L, and the Fe content was... 2+ The content of Cr was 57 g / L, the content of P was 0.002 g / L, and the content of P was 6 g / L.

[0261] S4: At least a portion of the chromium-removed liquid is reacted with supplemented phosphoric acid and a second oxidant to induce iron precipitation, followed by solid-liquid separation to obtain ferric phosphate and ferric phosphate mother liquor.

[0262] Specifically: First, supplementary phosphoric acid is added to a portion of the chromium-removed solution to initiate the first reaction, followed by the addition of a second oxidant to initiate the second reaction (the first and second reactions can be understood as phosphorus precipitation of iron). The mixture is then filtered to obtain ferric phosphate and ferric phosphate mother liquor. After aging, filtration, washing, and calcination, battery-grade ferric phosphate is obtained.

[0263] The second oxidant was hydrogen peroxide. The ratio of the total moles of phosphoric acid (P) in the supplemented phosphoric acid to the total moles of phosphoric acid (P) in the chromium-removed solution to the total moles of iron (Fe) in the chromium-removed solution was 1:0.98. The temperature of the first reaction was 55℃, and the reaction time was 3 hours. The second oxidant was added to reduce the iron content in the ferric phosphate mother liquor. 2+ The concentration was 1.6 g / L, the temperature of the second reaction was 60 °C, and the time of the second reaction was 1.5 h.

[0264] The Ni content in the ferric phosphate mother liquor is 22 g / L, and the Fe content is... 2+ The content of ferric phosphate was 1.6 g / L, the content of phosphoric acid was 2 g / L, and the pH value of the ferric phosphate mother liquor was 1.2.

[0265] S5: Remove phosphorus from the ferric phosphate mother liquor to obtain a phosphorus-removed mother liquor.

[0266] Specifically, an iron source is added to the ferric phosphate mother liquor, and a third oxidant is added to carry out a phosphorus removal reaction. After pressure filtration, ferric phosphate dihydrate and phosphorus removal mother liquor are obtained.

[0267] The supplementary iron source was the remaining chromium-removed solution after removing the chromium-removed solution used for S4. The ratio of the total molar amount of Fe in the ferric phosphate mother liquor to the total molar amount of Fe in the supplementary iron source to the total molar amount of P in the ferric phosphate mother liquor was 1.17:1. The third oxidant was hydrogen peroxide. The phosphorus removal reaction was carried out at a temperature of 95℃ for 7 hours.

[0268] The Ni content in the phosphorus removal mother liquor was 22 g / L; the pH value of the phosphorus removal mother liquor was 1.2.

[0269] S6: Part of the dephosphorization mother liquor is subjected to a nickel precipitation reaction and then prepared into nickel sulfate.

[0270] Specifically, a portion of the dephosphorization mother liquor was reacted with soda ash to undergo a nickel precipitation reaction, followed by pressure filtration to obtain nickel carbonate and wastewater. The amount of soda ash used was 1.4 times the nickel content in the dephosphorization mother liquor, the nickel precipitation reaction temperature was 60℃, and the reaction time was 6 hours.

[0271] S7: The remaining dephosphorization mother liquor is adjusted with the nickel carbonate obtained in S6 to increase the nickel concentration (which can also be understood as the reaction of nickel carbonate and dephosphorization mother liquor) to obtain battery-grade nickel sulfate.

[0272] The pH of the solution was adjusted to 5.5 with nickel carbonate, the mixing reaction temperature was 80℃, and the mixing reaction time was 4h.

[0273] Example 6

[0274] The difference between this embodiment and Embodiment 1 is that the concentration of thiourea dioxide in the first solution is 5 g / L.

[0275] Example 7

[0276] The difference between this embodiment and Embodiment 1 is that the concentration of thiourea dioxide in the first solution is 8 g / L.

[0277] Comparative Example 1

[0278] The difference between this comparative example and Example 1 is that no reducing agent (thiourea dioxide) was added in S1.

[0279] Comparative Example 2

[0280] The difference between this comparative example and Example 1 is that S1 is a one-step leaching, that is, the ferric phosphate waste to be treated and the chromium-containing nickel-iron alloy are directly subjected to high-temperature acid leaching in a solution including acid, reducing agent and first oxidant.

[0281] Comparative Example 3

[0282] The difference between this comparative example and Example 1 is that sodium sulfite is used instead of thiourea dioxide as the reducing agent.

[0283] Experimental Example 1

[0284] Examples 1-7 and Comparative Examples 1-3 were compared, and the comparison items and results are shown in Table 1.

[0285] In the table below, "Tail Gas Detection" refers to the detection of methanethiol and diethyl sulfide; "Element Utilization Rate" refers to the overall element utilization rate, which is calculated by determining the weight and metal content of the slag ultimately discharged from the system (elements recycled within the system are still utilized and are not considered a loss). The nickel sulfate solution corresponds to the solution obtained from the mixed reaction in step S7.

[0286] Table 1 Comparison Results

[0287]

[0288]

[0289]

[0290] As can be seen from Table 1, the solution provided by the embodiments of the present invention can effectively leach Fe, Ni, P and Cr elements from ferric phosphate waste and chromium-containing nickel-iron alloys, with high element utilization and no obvious odor in the exhaust gas.

[0291] Among them, by comparing Example 1 with Comparative Examples 1 and 2, it can be seen that: without the addition of thiourea dioxide, the reduction effect of ferric phosphate is insufficient, resulting in poor recycling effect of ferric phosphate waste; while direct high-temperature leaching will cause ferric phosphate dihydrate precipitate to form before the trivalent iron in the system is completely reduced, which is not conducive to the dissolution of ferric phosphate waste.

[0292] Experimental Example 2

[0293] Taking Example 1 and Comparative Example 1 as examples, after low-temperature acid leaching in S1 of both Example 1 and Comparative Example 1, the filter residues were filtered, and the SEM images of the resulting filter residues are shown below. Figure 3 and Figure 4 As shown.

[0294] Depend on Figure 3 and Figure 4 The comparison shows that: without thiourea dioxide, the filter residue has insufficient reducing power, resulting in the formation of ferric phosphate dihydrate. The presence of water of crystallization makes the crystal structure more stable, and the chemical bonds in the structure are more tightly connected. This tight structure makes it difficult for the leaching agent to penetrate into the crystal and react with the ferric phosphate, thus hindering the leaching process. In the leaching system with thiourea dioxide, ferric iron is reduced, and the filter residue contains ferrous phosphate. The crystal structure of ferrous phosphate is relatively loose, and its crystal morphology has more defects and pores, which makes it easier for the leaching agent to enter the crystal and react, thus making it easier to be leached.

[0295] In summary, the method provided by this invention is simple to operate, realizes the effective recycling of phosphorus and iron in ferric phosphate waste and nickel and iron in nickel-iron alloy, reduces the production cost of battery-grade nickel sulfate and ferric phosphate, and produces virtually no odor throughout the process.

[0296] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for the comprehensive utilization of iron phosphate waste and nickel-iron alloy, characterized in that, Includes the following steps: The ferric phosphate waste and chromium-containing nickel-iron alloy to be treated are subjected to low-temperature acid leaching in a first solution containing acid and a reducing agent to obtain a first leachate containing ferrous iron, nickel, phosphorus, and chromium; wherein the reducing agent includes thiourea dioxide, the low-temperature acid leaching temperature is 50℃~70℃, and the first leachate contains Fe 3+ The content does not exceed 1g / L; A first oxidant is added to the first leachate for high-temperature acid leaching to obtain a second leachate; wherein the high-temperature acid leaching temperature is 80℃~95℃. Remove chromium from the second leachate to obtain the chromium-removed solution; At least a portion of the chromium-removed liquid is reacted with supplemented phosphoric acid and a second oxidant to induce an iron precipitation reaction, followed by solid-liquid separation to obtain ferric phosphate and ferric phosphate mother liquor. Phosphorus is removed from the ferric phosphate mother liquor to obtain a phosphorus-removed mother liquor; At least a portion of the dephosphorization mother liquor is subjected to a nickel precipitation reaction before being prepared into nickel sulfate.

2. The method according to claim 1, characterized in that, Low-temperature acid leaching includes at least one of the following characteristics: Feature 1: The mass ratio of the iron phosphate waste to the nickel-iron alloy is 1:1.5 to 1:2; Feature 2: The acid includes at least one of sulfuric acid and phosphoric acid; Feature 3: The concentration of the acid in the first solution is 90 g / L to 120 g / L; Feature 4: The concentration of thiourea dioxide in the first solution is 5.5 g / L to 7.5 g / L; Feature 5: In the iron phosphate waste, the mass fraction of phosphorus is 12%~20.5% and the mass fraction of iron is 25%~37%; Feature 6: In the nickel-iron alloy, the mass fraction of nickel is 10%~30%, and the mass fraction of iron is 60%~75%; Feature 7: In the first leachate, the content of Ni is 5 g / L~12 g / L, and the content of Fe is... 2+ The content of Cr is 20g / L~40g / L, the content of Cr is 0.02g / L~0.1g / L, and the content of P is 2.5g / L~7.5g / L.

3. The method according to claim 1, characterized in that, High-temperature acid leaching includes at least one of the following characteristics: Feature 8: The first oxidant includes hydrogen peroxide; Feature 9: The amount of the first oxidant added is 20 g / L to 60 g / L; feature 10: The high-temperature acid leaching time is 3h~5h; Feature 11: The pH value of the second leachate is 1.4~2.3; Feature 12: The Ni content in the second leachate is 10 g / L~20 g / L, and the Fe content is... 2+ The content of Cr is 40g / L~60g / L, the content of Cr is 0.04g / L~0.12g / L, and the content of P is 2.5g / L~7.5g / L.

4. The method according to claim 1, characterized in that, Removing chromium from the second leaching solution includes: adding seed crystals to the second leaching solution to carry out a seed crystal reaction, and then adding a value adjuster to carry out a chromium removal reaction; The seed crystals include at least one of anhydrous ferric phosphate, ferric phosphate dihydrate, amorphous ferric phosphate, and ferrous hydrogen phosphate. The adjusting agent includes at least one of nickel carbonate, chromium slag, and nickel hydroxide.

5. The method according to claim 4, characterized in that, The seed reaction includes at least one of the following characteristics: Feature 13: The amount of seed crystals added is 1 g / L to 1.5 g / L; Feature 14: The temperature of the seed crystal reaction is 50℃~70℃, and the reaction time is 0.5h~1.5h.

6. The method according to claim 4, characterized in that, The chromium removal reaction includes at least one of the following characteristics: Feature 15: The pH adjuster is added to control the pH of the reaction system corresponding to the chromium removal reaction to be 2.5~3.5; Feature 16: The temperature of the chromium removal reaction is 50℃~70℃, and the time of the chromium removal reaction is 1h~3h; feature 17: The Ni content in the chromium removal solution is 15 g / L~25 g / L, and the Fe content is... 2+ The content of Cr is 35g / L~60g / L, the content of Cr is 0.002g / L~0.008g / L, and the content of P is 2.5g / L~7.5g / L.

7. The method according to claim 1, characterized in that, The iron precipitation reaction includes: first, adding supplemented phosphoric acid to at least a portion of the chromium removal solution to carry out a first reaction, and then adding a second oxidant to carry out a second reaction; The ratio of the total number of moles of P in the supplemented phosphoric acid to the total number of moles of P in the chromium-removed solution to the total number of moles of Fe in the chromium-removed solution is 1:0.8 to 1:0.

98. The temperature of the first reaction is 40℃~55℃, and the reaction time is 1h~3h; The second oxidant is added to reduce the Fe content in the iron phosphate mother liquor. 2+ The concentration is 0.8 g / L to 1.6 g / L; The temperature of the second reaction is 30℃~60℃, and the reaction time is 0.5h~1.5h.

8. The method according to claim 7, characterized in that, The Ni content in the ferric phosphate mother liquor is 15 g / L~25 g / L, and the Fe content is... 2+ The content of is 0.8g / L~1.6g / L, and the content of P is 2g / L~4g / L.

9. The method according to claim 7, characterized in that, The pH value of the ferric phosphate mother liquor is 0.1~1.

2.

10. The method according to claim 1, characterized in that, Removing phosphorus from the ferric phosphate mother liquor includes: adding an iron source to the ferric phosphate mother liquor and adding a third oxidant to carry out a phosphorus removal reaction, followed by solid-liquid separation to obtain ferric phosphate dihydrate and phosphorus removal mother liquor.

11. The method according to claim 10, characterized in that, The phosphorus removal reaction includes at least one of the following characteristics: Feature 18: The ratio of the total number of moles of Fe in the iron phosphate mother liquor and Fe in the supplementary iron source to the number of moles of P in the iron phosphate mother liquor is 1.05:1 to 1.2:1; Feature 19: The third oxidant includes at least one of hydrogen peroxide, ozone, air, oxygen, and nickel trioxide; Feature 20: The temperature of the phosphorus removal reaction is 85℃~95℃, and the reaction time is 3h~8h; Feature 21: The Ni content in the phosphorus removal mother liquor is 15 g / L to 25 g / L; and / or, the pH value of the phosphorus removal mother liquor is 0.1 to 1.

2.

12. The method according to claim 1, characterized in that, The nickel precipitation reaction includes: reacting the dephosphorization mother liquor with soda ash, separating the solid and liquid phases, and obtaining nickel carbonate.

13. The method according to claim 12, characterized in that, The nickel plating reaction includes at least one of the following characteristics: Feature 22: The amount of soda ash added is 1 to 1.5 times the nickel content in the dephosphorization mother liquor; Feature 23: The temperature of the nickel plating reaction is 40℃~60℃, and the reaction time is 2h~6h.

14. The method according to claim 12, characterized in that, When the first solution contains sulfuric acid, the preparation of nickel sulfate includes: mixing and reacting a portion of the dephosphorization mother liquor with the nickel carbonate.

15. The method according to claim 14, characterized in that, The mixing reaction includes at least one of the following characteristics: Feature 24: The mixed reaction is carried out under conditions of pH 4.0–5.5; Feature 25: The temperature of the mixed reaction is 60℃~80℃, and the reaction time is 2h~4h.

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