Method for comprehensively utilizing iron phosphate waste and ferro-nickel alloy

Abstract

The invention discloses a comprehensive utilization method of iron phosphate waste and nickel-iron alloy, and belongs to the technical field of battery material recycling. The method comprises the following steps: carrying out low-temperature acid leaching on the iron phosphate waste and the chromium-containing ferro-nickel alloy in a first solution containing acid and thiourea dioxide to obtain a first leaching solution; a first oxidizing agent is added into the first leaching solution for high-temperature acid leaching, and a second leaching solution is obtained; chromium in the second leaching solution is removed, and a chromium-removed solution is obtained; at least part of the chromium-removed liquid, supplemented phosphoric acid and a second oxidizing agent are subjected to an iron precipitation reaction, and iron phosphate and an iron phosphate mother solution are obtained; removing phosphorus in the iron phosphate mother liquor to obtain phosphorus-removed mother liquor; and at least part of the dephosphorized mother liquor is subjected to a nickel precipitation reaction and then prepared into nickel sulfate. The method is easy to operate, phosphorus and iron in the iron phosphate waste and nickel and iron in the nickel-iron alloy are effectively recycled, and the production cost for preparing battery-grade nickel sulfate and iron phosphate is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of battery material recycling, and in particular to a method for comprehensive utilization of ferric phosphate waste and nickel-iron alloy. Background Art

[0002] In recent years, China's iron phosphate shipments have continued to grow. The large amount of iron phosphate shipments means that the output of waste iron phosphate and inferior iron phosphate has also increased year-on-year, and the prospects for the recycling, processing and utilization of waste iron phosphate are huge.

[0003] At present, most of the recycling and treatment solutions for waste iron phosphate have complicated processes, high costs, low element utilization rates, and some recycling and treatment solutions also produce smelly exhaust gas.

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

[0005] The object of the present invention is to provide a method for comprehensive utilization of ferrophosphate waste and nickel-iron alloy to solve or improve the above technical problems.

[0006] The present invention can be implemented like this:

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

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

[0009] Adding a first oxidant to the first leachate for high temperature acid leaching to obtain a second leachate; wherein the temperature of the high temperature acid leaching is 80° C. to 95° C.;

[0010] removing chromium from the second leaching solution to obtain a chromium-removed solution;

[0011] The chromium-free solution is reacted with at least a portion of the solution with supplemented phosphoric acid and a second oxidant to precipitate iron, and the solid and liquid are separated to obtain iron phosphate and an iron phosphate mother liquor;

[0012] removing phosphorus from the ferric phosphate mother liquor to obtain a dephosphorized mother liquor;

[0013] At least part of the dephosphorization mother liquor is subjected to nickel precipitation reaction and then prepared into nickel sulfate.

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

[0015] Feature 1: The mass ratio of ferrophosphate 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 the 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 the 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 alloy, the mass fraction of nickel is 10% to 30%, and the mass fraction of iron is 60% to 75%;

[0021] Feature 7: In the first leaching solution, the content of Ni is 5g / L to 12g / L, and the content of Fe is 2+ The content of Ni 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.

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

[0023] Feature 8: The first oxidant 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 3h to 5h;

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

[0027] Feature 12: The content of Ni in the second leaching solution is 10g / L to 20g / L, and the content of Fe 2+ The content of Ni 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.

[0028] In an optional embodiment, removing chromium from the second leaching solution comprises: adding seed crystals to the second leaching solution to perform a seed crystal reaction, and then adding a value adjusting agent to perform a chromium removal reaction;

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

[0030] The adjusting agent 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 crystal added is 1 g / L to 1.5 g / L;

[0033] Feature 14: The temperature of the seed reaction is 50°C to 70°C, and the time of the seed reaction is 0.5h to 1.5h.

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

[0035] Feature 15: Adding a value adjusting agent to control the pH value of the reaction system corresponding to the chromium removal reaction to be 2.5 to 3.5;

[0036] Feature 16: The temperature of the chromium removal reaction is 50°C to 70°C, and the time of the chromium removal reaction is 1h to 3h;

[0037] Feature 17: The content of Ni in the solution after chromium removal is 15g / L to 25g / L, and Fe 2+ The content of Ni 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.

[0038] In an optional embodiment, the iron precipitation reaction includes: firstly adding supplemented phosphoric acid to at least a portion of the chromium-removed liquid to perform a first reaction, and then adding a second oxidant to perform a second reaction;

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

[0040] The temperature of the first reaction is 40°C to 55°C, and the time of the first reaction is 1h to 3h;

[0041] Add the second oxidant to reduce the Fe 2+ Concentration: 0.8g / L~1.6g / L;

[0042] The temperature of the second reaction is 30° C. to 60° C., and the time of the second reaction is 0.5 h to 1.5 h.

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

[0044] In an optional embodiment, the pH value of the iron phosphate mother solution is 0.1-1.2.

[0045] In an optional embodiment, removing phosphorus from the ferric phosphate mother liquor comprises: adding an iron source to the ferric phosphate mother liquor and adding a third oxidant to perform a dephosphorization reaction, and performing solid-liquid separation to obtain ferric phosphate dihydrate and a dephosphorization mother liquor.

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

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

[0048] Feature 19: The third oxidant 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°C to 95°C, and the time of the phosphorus removal reaction is 3h to 8h;

[0050] Feature 21: The Ni content in the dephosphorization mother liquor is 15 g / L to 25 g / L; and / or the pH value of the dephosphorization 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 the liquid, and obtaining nickel carbonate.

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

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

[0054] Feature 23: The temperature of the nickel precipitation reaction is 40°C to 60°C, and the time of the nickel precipitation reaction is 2h to 6h.

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

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

[0057] Feature 24: The mixed reaction is carried out at a pH value of 4.0 to 5.5;

[0058] Feature 25: The temperature of the mixing reaction is 60°C to 80°C, and the time of the mixing reaction is 2h to 4h.

[0059] The beneficial effects of the present invention include:

[0060] The present invention performs acid leaching on ferrophosphate waste and nickel-iron alloy to extract elemental iron and Fe 3+ Ion reaction produces Fe 2+ Ions can promote the dissolution of iron phosphate and nickel-iron alloy, which is more efficient than leaching iron phosphate and nickel-iron alloy separately.

[0061] When nickel-iron metal is leached, some odorous substances are produced, such as sulfur ions and organic sulfur. Sulfurea dioxide has strong reducing properties and can react chemically with these odorous substances. For example, sulfurea dioxide reacts with sulfur ions and can convert them into other relatively odorless or lightly odorous substances, such as elemental sulfur or polysulfides, thereby reducing or eliminating the odor to a certain extent. Sulfurea dioxide may also decompose itself to produce some gases during the reaction process. These gases can interact with or dilute the odorous substances, thereby playing an auxiliary deodorizing effect.

[0062] Moreover, in acidic solution, thiourea dioxide has good stability and strong reducing ability, which can maintain the stability of its molecular structure. At the same time, the presence of hydrogen ions helps to promote the reduction reaction and accelerate the Fe 3+ ions are reduced to Fe 2+ ions. In Fe 2+ After the ion conversion is completed, when further dissolving the nickel-iron alloy, the first oxidant is added to oxidize the nickel-iron element and accelerate the dissolution rate of nickel-iron. In addition, due to the presence of thiourea dioxide and excess nickel-iron alloy, the leaching system is a reduction system, which avoids the generation of Fe 3+ ion.

[0063] The method provided by the present invention is simple to operate, realizes the effective recovery and utilization of phosphorus and iron in ferrophosphate waste and nickel and iron in nickel-iron alloy, reduces the production cost of preparing battery-grade nickel sulfate and ferrophosphate, has a high recovery rate of Ni, Fe and P elements, and basically does not generate obvious odor during the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

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

[0066] Figure 2 Schematic diagram of 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 corresponding to Example 1 in Experimental Example 2;

[0068] Figure 4 This is the SEM image of the filter residue obtained after low-temperature acid leaching corresponding to Comparative Example 1 in Experimental Example 2. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0070] The method for comprehensive utilization of ferric phosphate waste and nickel-iron alloy provided by the present invention is specifically described below.

[0071] The present invention provides a method for comprehensive utilization of ferrophosphate waste and nickel-iron alloy, please refer to Figure 1 , mainly including the following steps S1 to S6.

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

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

[0074] In the above process, the ferric phosphate waste to be treated and the nickel-iron alloy are first mixed to obtain a mixed raw material, and then the mixed raw material is subjected to low-temperature acid leaching in a first solution.

[0075] Compared with the reaction of elemental iron with sulfuric acid and iron phosphate with sulfuric acid, the reaction of elemental iron with Fe 3+ The reaction priority of ions is higher. In the present invention, the iron phosphate waste and nickel-iron alloy are mixed and then acid leached to obtain elemental iron and Fe 3+ Ion reaction produces Fe 2+ Ions can promote the dissolution of iron phosphate and nickel-iron alloy, which is more efficient than leaching iron phosphate and nickel-iron alloy separately.

[0076] When nickel-iron metal is leached, some odorous substances are produced, such as sulfur ions and organic sulfur. Sulfurea dioxide has strong reducing properties and can react chemically with these odorous substances. For example, sulfurea dioxide reacts with sulfur ions and can convert them into other relatively odorless or lightly odorous substances, such as elemental sulfur or polysulfides, thereby reducing or eliminating the odor to a certain extent. Sulfurea dioxide may also decompose itself to produce some gases during the reaction process. These gases can interact with or dilute the odorous substances, thereby playing an auxiliary deodorizing effect.

[0077] For more details, please refer to Figure 2 , adding thiourea dioxide during the leaching process can help the leaching of iron phosphate. Specifically, under acidic conditions, hydrogen ions first form a combination with nitrogen atoms or oxygen atoms in the thiourea dioxide molecules, causing a certain degree of change in the molecular structure, which in turn leads to a decrease in the stability of the carbon-sulfur bond and a break, thereby generating sulfinic acid H2SO2 and urea. H2SO2 promotes the leaching of nickel-iron alloy (exemplarily in the form of nickel-iron atomized material), and urea is adsorbed and coordinated with the surface of nickel-iron to promote the formation of a porous adsorption structure. Organic gases such as methyl mercaptan and ethyl sulfide generated during the acid leaching process fully react with Ni 0 -Fe 0 The catalytic sites are combined with in-situ autocatalytic decomposition to reduce the content of organic odors (such as methyl mercaptan and ethyl sulfide) in the tail gas (which can also be understood as waste gas).

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

[0079] In some optional embodiments, the mass ratio of ferric phosphate waste to nickel-iron 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, etc., or other values ​​within the range of 1:1.5 to 1:2.

[0080] Wherein, 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%, etc., 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%, etc., or other values ​​within the range of 25% to 37%.

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

[0082] By mixing the above-mentioned ferric phosphate waste and nickel-iron alloy in a mass ratio of 1:1.5 to 1:2, elements such as Ni, Fe, Cr, and P can be better dissolved, and the concentration of dissolved phosphorus can be ensured to be within an appropriate range to facilitate subsequent impurity removal.

[0083] In some optional embodiments, the first solution is formed from water, an acid and a reducing agent.

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

[0085] The concentration of the 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 incomplete and the deodorization effect will be poor; if the concentration of thiourea dioxide is too high, it will easily lead to low utilization rate.

[0088] In some optional embodiments, the temperature of 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, etc., or other values ​​within the range of 50°C to 70°C.

[0089] In some optional embodiments, Fe in the first leachate 3+ The content of Fe in the first leachate is not more than 1 g / L, such as 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, etc., or other values ​​within the range of not more than 1 g / L. 3+ The end point is when the content does not exceed 1g / L.

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

[0091] S2: adding the first oxidant to the first leachate for high temperature acid leaching, and separating the solid and the liquid to obtain a second leachate and a leach residue; wherein the temperature of the high temperature acid leaching is 80°C to 95°C.

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

[0093] In acidic solution, thiourea dioxide has good stability and strong reducing ability, which can maintain the stability of its molecular structure. At the same time, the presence of hydrogen ions helps to promote the reduction reaction and accelerate the Fe 3+ ions are reduced to Fe 2+ ions. In Fe 2+ After the ion conversion is completed, when further dissolving the nickel-iron alloy, the first oxidant is added to oxidize the nickel-iron element and accelerate the dissolution rate of nickel-iron. In addition, due to the presence of thiourea dioxide and excess nickel-iron alloy, the leaching system is a reduction system, which avoids the generation of Fe 3+ ion.

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

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

[0096] The first oxidant may illustratively but not limitedly include hydrogen peroxide.

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

[0098] At the end of the high-temperature acid leaching, the pH value of the second leaching solution is 1.4 to 2.3 (such as 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 content of Ni in the second leaching solution may be 10 g / L to 20 g / L, and the content of Fe 2+ The content of 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 leached residue can be acid-leached again with an acid solution as needed to increase the recovery rate.

[0101] As mentioned above, in phosphorus-containing solutions, Fe 3+ The ion stability is poor. In actual production, due to the influence of material transfer and temperature rise, it is easy to generate ferric phosphate dihydrate precipitation. The ferric phosphate waste is mixed with nickel-iron alloy for leaching. The entire reaction system is a reduction system. The generated Fe 2+ The ion stability is higher, precipitation is not easy to form, and it is more suitable for mass production on the production line; and in the present invention, by dividing the leaching into two stages (low-temperature acid leaching + high-temperature acid leaching), during the low-temperature acid leaching process, Fe 3+ ions to Fe 2+ The ions are converted and then high-temperature acid leaching is performed to further accelerate the dissolution of the nickel-iron alloy.

[0102] S3: removing chromium from the second leaching solution to obtain a chromium-removed solution.

[0103] In some optional embodiments, removing chromium from the second leaching solution may include: adding seed crystals to the second leaching solution to perform a seed reaction, and then adding a value adjusting agent to perform a chromium removal reaction.

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

[0105] The adjusting agent may illustratively but not limitatively include at least one of nickel carbonate, chromium slag and nickel hydroxide.

[0106] The above seed reaction is mainly used to form chromium phosphate products, and the chromium removal reaction is mainly to remove Cr 3+ Cr(OH)3 precipitation is generated, and then solid-liquid separation is performed to obtain chromium-free liquid and chromium slag. Among them, the chromium slag can be recycled and used as a value-adjusting agent.

[0107] In some optional 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 of the seed reaction can be 50°C to 70°C, such as 50°C, 55°C, 60°C, 65°C or 70°C, etc., or other values ​​within the range of 50°C to 70°C.

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

[0110] In some optional embodiments, a value adjusting agent is added to control the pH value of the reaction system corresponding to the chromium removal reaction to 2.5-3.5, 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, etc., or other values ​​within the range of 2.5-3.5.

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

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

[0113] In some optional embodiments, the content of Ni in the chromium-removed solution can be 15 g / L to 25 g / L, and the content of Fe 2+ The content of 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: reacting at least a portion of the chromium-removed liquid with supplemented phosphoric acid and a second oxidant to precipitate iron, and separating the solid from the liquid to obtain iron phosphate and an iron phosphate mother liquor.

[0115] In some optional embodiments, the second oxidant may be hydrogen peroxide.

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

[0117] During operation, the chromium-removed liquid can be divided into two parts, one of which is added with supplementary phosphoric acid for the first reaction, and then the second oxidant is added for the second reaction; the other part is used as a supplementary iron source in the subsequent stage. In addition, the supplementary phosphoric acid can be added to all the chromium-removed liquid for the first reaction, and then the second oxidant is added for the second reaction.

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

[0119] Among them, the ratio of the total molar number of P in the supplemented phosphoric acid and the P in the chromium-removed liquid to the molar number of Fe in the chromium-removed liquid can be 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 40°C to 55°C, such as 40°C, 42°C, 45°C, 48°C, 50°C, 52°C or 55°C, or other values ​​within the range of 40°C to 55°C.

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

[0122] In some optional embodiments, a second oxidant is added to reduce Fe in the ferric phosphate mother solution. 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, etc., and can also be other values ​​within the range of 0.8 g / L to 1.6 g / L.

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

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

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

[0126] In some optional embodiments, the pH value of the ferric phosphate mother solution can be 0.1-1.2, 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 0.1-1.2.

[0127] As required, the obtained iron phosphate is aged, filtered, washed and roasted to obtain battery-grade iron phosphate.

[0128] S5: removing phosphorus from the ferric phosphate mother liquor to obtain a dephosphorized mother liquor.

[0129] In some optional 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 perform a dephosphorization reaction, and performing solid-liquid separation to obtain ferric phosphate dihydrate and a dephosphorization mother liquor.

[0130] In some optional embodiments, the ratio of the total molar number of Fe in the ferric phosphate mother solution and the Fe in the supplementary iron source to the molar number of P in the ferric phosphate mother solution can be 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 optional embodiments, the third oxidant may exemplarily but not limitatively include at least one of hydrogen peroxide, ozone, air, oxygen and nickel trioxide. The third oxidant is used to convert Fe 2+ Oxidized to Fe 3+ .

[0132] In some optional 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, etc., or other values ​​within the range of 85°C to 95°C.

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

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

[0135] In some optional embodiments, the pH value of the phosphorus removal mother solution may 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 ​​within the range of 0.1 to 1.2.

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

[0137] S6: subjecting at least a portion of the dephosphorization mother liquor to nickel precipitation reaction to prepare nickel sulfate.

[0138] During operation, the dephosphorization mother liquor can be divided into two parts, one part is used for nickel precipitation reaction, and the other part is used for adjusting the value of the nickel precipitate obtained by the nickel precipitation reaction to consume acid to obtain nickel sulfate. In addition, all the dephosphorization mother liquor can also be subjected to nickel precipitation reaction, and then a sulfate source is added to obtain nickel sulfate.

[0139] In some optional embodiments, the nickel precipitation reaction includes: reacting the dephosphorization mother liquor with soda ash, separating the solid and the liquid, 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, etc., or other values ​​within the range of 1 to 1.5 times.

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

[0142] The nickel precipitation 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 the phosphorus removal mother solution other than that used for nickel precipitation reaction with nickel carbonate for reaction.

[0144] The mixing reaction can be carried out at a pH value of 4.0 to 5.5 (eg, 4.0, 4.2, 4.5, 4.8, 5.0, 5.2 or 5.5, etc.).

[0145] The temperature of the mixing reaction can be 60°C to 80°C, such as 60°C, 65°C, 70°C, 75°C or 80°C, etc., or other values ​​within the range of 60°C to 80°C.

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

[0147] Through the above reaction, battery-grade nickel sulfate can be obtained.

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

[0149] In the process of preparing battery-grade iron phosphate, the iron phosphate waste is directly dissolved by adding sulfuric acid, and then phosphoric acid is added to prepare a solution with a certain iron-phosphorus ratio. Due to the high acidity and sulfur content, the prepared iron phosphate product usually has the defects of high sulfur content and small specific surface area. 3+ Reduction to Fe 2+ After the process of adjusting the value and removing impurities, the acidity is reduced compared with direct leaching, and the Fe 3+ The precipitation of ions improves the utilization rate of iron and phosphorus.

[0150] During the entire recovery process, ferric phosphate dihydrate produced by oxidation and heating can be reused in the nickel-iron leaching process and the chromium removal process as seeds to recycle the phosphorus and iron elements in the slag. The main process for producing ferric phosphate dihydrate is the mother liquor phosphorus removal stage. Since there is an excess of phosphorus in the ferric phosphate mother liquor, in order to obtain a nickel sulfate solution with a higher purity, the chromium-removed liquid in the system can be supplemented to remove phosphorus using the iron in the system. There is no need to introduce an additional iron source, which reduces costs. The phosphorus in the mother liquor and the iron in the chromium-removed liquid are recovered in the form of ferrophosphorus slag, reducing the loss of phosphorus and iron.

[0151] The use of nickel carbonate to consume the residual acid in the dephosphorization mother liquor can increase the nickel concentration. Compared with the addition of other nickel sources (such as MHP, etc.), it can reduce the calcium and magnesium removal steps in the extraction section, 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 direct addition of sodium carbonate to introduce sodium ions, thereby improving product purity.

[0152] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0153] Example 1

[0154] This embodiment provides a processing method for preparing battery-grade iron phosphate and nickel sulfate by comprehensive utilization of iron phosphate waste and nickel-iron alloy, and the operating steps are as follows:

[0155] S1: low-temperature acid leaching is performed on the ferrophosphate waste and nickel-iron alloy to be treated in a first solution including an acid and a reducing agent to obtain a first leaching solution containing ferrous iron, nickel, phosphorus and chromium.

[0156] Among them, the mass fraction of phosphorus in the ferrophosphate waste is 20.5%, and the mass fraction of iron is 37%; in the nickel-iron alloy, the mass fraction of nickel is 26%, and the mass fraction of iron is 70%; the mass ratio of the ferrophosphate waste to the 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 temperature of low-temperature acid leaching is 50°C, and the Fe in the first leaching solution is leached. 3+ The concentration of Ni in the first leaching solution is 5.5 g / L, Fe 2+ The concentration of is 20g / L, the concentration of Cr is 0.02g / L, and the concentration of P is 5.77g / L.

[0159] S2: adding the first oxidant to the first leachate, raising the temperature to perform high-temperature acid leaching, and filtering to obtain the second leachate and leach residue.

[0160] The first oxidant is hydrogen peroxide, and the amount of hydrogen peroxide added is 20g / L. The temperature of high temperature acid leaching is 80℃, and the time of high temperature acid leaching is 3h. At this time, the pH value of the second leaching solution is 1.4. The content of Ni in the second leaching solution is 11g / L, Fe 2+ The content of Ni is 40g / L, the content of Cr is 0.04g / L, and the content of P is 5.77g / L.

[0161] S3: removing chromium from the second leaching solution to obtain a chromium-removed solution.

[0162] Specifically, seed crystals are added to the second leaching solution to carry out seed crystal reaction, and then a value adjusting agent is added to carry out chromium removal reaction (which can be understood as precipitation and impurity removal), and filter pressing is performed to obtain chromium-removed liquid and chromium slag.

[0163] Among them, the seed is anhydrous ferric phosphate, the seed addition amount is 1g / L, the seed reaction temperature is 50°C, and the seed reaction time is 0.5h; the adjusting agent is nickel carbonate, the adjusting agent controls the pH value of the reaction solution system to 2.5, the chromium removal reaction temperature is 50°C, and the chromium removal reaction time is 1h.

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

[0165] S4: reacting at least a portion of the chromium-removed liquid with supplemented phosphoric acid and a second oxidant to precipitate iron, and separating the solid from the liquid to obtain iron phosphate and an iron phosphate mother liquor.

[0166] Specifically, firstly, phosphoric acid is added to part of the chromium-removed liquid to carry out the first reaction, and then the second oxidant is added to carry out the second reaction (the first reaction and the second reaction can be understood as phosphorus precipitation of iron as a whole), and then the iron phosphate and iron phosphate mother liquor are obtained by filtration. The iron phosphate is aged, filtered, washed, and roasted to obtain battery-grade iron phosphate.

[0167] The second oxidant is hydrogen peroxide. The ratio of the total molar number of P in the supplemented phosphoric acid and the molar number of P in the chromium-removed solution to the molar number of Fe in the chromium-removed solution is 1:0.8. The temperature of the first reaction is 40°C and the time of the first reaction is 1h. The second oxidant is added to reduce the Fe in the iron phosphate mother solution. 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 content of Ni in the iron phosphate mother liquor is 15g / L, Fe 2+ The content of is 0.8g / L, the content of P is 4g / L, and the pH value of the iron phosphate mother liquor is 0.1.

[0169] S5: removing phosphorus from the ferric phosphate mother liquor to obtain a dephosphorized 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 dephosphorization reaction, and the reaction is filtered to obtain ferric phosphate dihydrate and a dephosphorization mother liquor.

[0171] The supplemented iron source is the remaining chromium-removed liquid after removing the chromium-removed liquid used for S4. The ratio of the total molar number of Fe in the iron phosphate mother liquor and the Fe in the supplemented iron source to the molar number of P in the iron phosphate mother liquor is 1.05:1. The third oxidant is hydrogen peroxide. The temperature of the dephosphorization reaction is 85°C, and the time of the dephosphorization reaction is 3 hours.

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

[0173] S6: subjecting part of the dephosphorization mother liquor to nickel precipitation reaction and then preparing nickel sulfate.

[0174] Specifically, part of the phosphorus removal mother liquor is reacted with soda ash to precipitate nickel, and filtered to obtain nickel carbonate and wastewater. The amount of soda ash used is 1 times the nickel content in the phosphorus removal mother liquor, the temperature of the nickel precipitation reaction is 40°C, and the time of the nickel precipitation reaction is 2 hours.

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

[0176] The solution pH was controlled to be 4.0 by adjusting the nickel carbonate, the mixed reaction temperature was 60°C, and the mixed reaction time was 2h.

[0177] Example 2

[0178] This embodiment provides a processing method for preparing battery-grade iron phosphate and nickel sulfate by comprehensive utilization of iron phosphate waste and nickel-iron alloy, and the operating steps are as follows:

[0179] S1: low-temperature acid leaching is performed on the ferrophosphate waste and nickel-iron alloy to be treated in a first solution including an acid and a reducing agent to obtain a first leaching solution containing ferrous iron, nickel, phosphorus and chromium.

[0180] Among them, the mass fraction of phosphorus in the ferrophosphate waste is 20.5%, and the mass fraction of iron is 37%; in the nickel-iron alloy, the mass fraction of nickel is 26%, and the mass fraction of iron is 70%; the mass ratio of the ferrophosphate waste to the 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 temperature of low-temperature acid leaching is 55°C, and the Fe 3+ The concentration of Ni in the first leaching solution is 6.8 g / L, and the concentration of Fe 2+ The concentration of is 25g / L, the concentration of Cr is 0.04g / L, and the concentration of P is 6.1g / L.

[0183] S2: adding the first oxidant to the first leachate, raising the temperature to perform high-temperature acid leaching, and filtering to obtain the second leachate and leach residue.

[0184] The first oxidant is hydrogen peroxide, and the amount of hydrogen peroxide added is 30g / L. The temperature of high temperature acid leaching is 83°C, and the time of high temperature acid leaching is 3.5h. At this time, the pH value of the second leaching solution is 1.6. The content of Ni in the second leaching solution is 12.5g / L, Fe 2+ The content of Ni is 45g / L, the content of Cr is 0.06g / L, and the content of P is 6.1g / L.

[0185] S3: removing chromium from the second leaching solution to obtain a chromium-removed solution.

[0186] Specifically, seed crystals are added to the second leaching solution to carry out seed crystal reaction, and then a value adjusting agent is added to carry out chromium removal reaction (which can be understood as precipitation and impurity removal), and filter pressing is performed to obtain chromium-removed liquid and chromium slag.

[0187] Among them, the seed is anhydrous ferric phosphate, the seed addition amount is 1.15g / L, the temperature of the seed reaction is 55°C, and the time of the seed reaction is 0.7h; the adjusting agent is nickel carbonate, the adjusting agent controls the pH value of the reaction solution system to 2.7, the temperature of the chromium removal reaction is 55°C, and the time of the chromium removal reaction is 1.5h.

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

[0189] S4: reacting at least a portion of the chromium-removed liquid with supplemented phosphoric acid and a second oxidant to precipitate iron, and separating the solid from the liquid to obtain iron phosphate and an iron phosphate mother liquor.

[0190] Specifically, firstly, phosphoric acid is added to part of the chromium-removed liquid to carry out the first reaction, and then the second oxidant is added to carry out the second reaction (the first reaction and the second reaction can be understood as phosphorus precipitation of iron as a whole), and then the iron phosphate and iron phosphate mother liquor are obtained by filtration. The iron phosphate is aged, filtered, washed, and roasted to obtain battery-grade iron phosphate.

[0191] The second oxidant is hydrogen peroxide. The ratio of the total molar number of P in the supplemented phosphoric acid to the molar number of P in the chromium-removed solution to the molar number of Fe in the chromium-removed solution is 1:0.85. The temperature of the first reaction is 44°C and the time of the first reaction is 1.5 hours. The second oxidant is added to reduce the Fe in the iron phosphate mother solution. 2+ The concentration was 1 g / L, the temperature of the second reaction was 35° C., and the time of the second reaction was 0.7 h.

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

[0193] S5: removing phosphorus from the ferric phosphate mother liquor to obtain a dephosphorized 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 dephosphorization reaction, and the reaction is filtered to obtain ferric phosphate dihydrate and a dephosphorization mother liquor.

[0195] The supplemented iron source is the remaining chromium-removed liquid after removing the chromium-removed liquid used for S4. The ratio of the total molar number of Fe in the ferric phosphate mother liquor and the Fe in the supplemented iron source to the molar number of P in the ferric phosphate mother liquor is 1.08:1. The third oxidant is hydrogen peroxide. The temperature of the dephosphorization reaction is 87°C, and the time of the dephosphorization reaction is 4 hours.

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

[0197] S6: subjecting part of the dephosphorization mother liquor to nickel precipitation reaction and then preparing nickel sulfate.

[0198] Specifically, part of the dephosphorization mother liquor is reacted with soda ash to precipitate nickel, and filtered to obtain nickel carbonate and wastewater. The amount of soda ash used is 1.1 times the nickel content in the dephosphorization mother liquor, the temperature of the nickel precipitation reaction is 45°C, and the time of the nickel precipitation reaction is 3 hours.

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

[0200] The solution pH was controlled to be 4.2 by adjusting the nickel carbonate, the mixed reaction temperature was 65°C, and the mixed reaction time was 2.5h.

[0201] Example 3

[0202] This embodiment provides a processing method for preparing battery-grade iron phosphate and nickel sulfate by comprehensive utilization of iron phosphate waste and nickel-iron alloy, and the operating steps are as follows:

[0203] S1: low-temperature acid leaching is performed on the ferrophosphate waste and nickel-iron alloy to be treated in a first solution including an acid and a reducing agent to obtain a first leaching solution containing ferrous iron, nickel, phosphorus and chromium.

[0204] Among them, the mass fraction of phosphorus in the ferrophosphate waste is 20.5%, and the mass fraction of iron is 37%; in the nickel-iron alloy, the mass fraction of nickel is 26%, and the mass fraction of iron is 70%; the mass ratio of the ferrophosphate waste to the 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 temperature of low temperature acid leaching is 60℃, and the Fe 3+ The concentration of Ni in the first leaching solution is 8.5 g / L, Fe 2+ The concentration of is 30g / L, the concentration of Cr is 0.06g / L, and the concentration of P is 6.57g / L.

[0207] S2: adding the first oxidant to the first leachate, raising the temperature to perform high-temperature acid leaching, and filtering to obtain the second leachate and leach residue.

[0208] The first oxidant is hydrogen peroxide, and the amount of hydrogen peroxide added is 40g / L. The temperature of high temperature acid leaching is 86℃, and the time of high temperature acid leaching is 4h. At this time, the pH value of the second leaching solution is 1.8. The content of Ni in the second leaching solution is 14g / L, Fe 2+ The content of is 50g / L, the content of Cr is 0.08g / L, and the content of P is 6.57g / L.

[0209] S3: removing chromium from the second leaching solution to obtain a chromium-removed solution.

[0210] Specifically, seed crystals are added to the second leaching solution to carry out seed crystal reaction, and then a value adjusting agent is added to carry out chromium removal reaction (which can be understood as precipitation and impurity removal), and filter pressing is performed to obtain chromium-removed liquid and chromium slag.

[0211] Among them, the seed is anhydrous ferric phosphate, the seed addition amount is 1.25g / L, the temperature of the seed reaction is 60°C, and the time of the seed reaction is 0.9h; the adjusting agent is nickel carbonate, the adjusting agent controls the pH value of the reaction solution system to 2.9, the temperature of the chromium removal reaction is 60°C, and the time of the chromium removal reaction is 2h.

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

[0213] S4: reacting at least a portion of the chromium-removed liquid with supplemented phosphoric acid and a second oxidant to precipitate iron, and separating the solid from the liquid to obtain iron phosphate and an iron phosphate mother liquor.

[0214] Specifically, firstly, phosphoric acid is added to part of the chromium-removed liquid to carry out the first reaction, and then the second oxidant is added to carry out the second reaction (the first reaction and the second reaction can be understood as phosphorus precipitation of iron as a whole), and then the iron phosphate and iron phosphate mother liquor are obtained by filtration. The iron phosphate is aged, filtered, washed, and roasted to obtain battery-grade iron phosphate.

[0215] The second oxidant is hydrogen peroxide. The ratio of the total molar number of P in the supplemented phosphoric acid to the molar number of P in the chromium-removed solution to the molar number of Fe in the chromium-removed solution is 1:0.9. The temperature of the first reaction is 48°C and the time of the first reaction is 2 hours. The second oxidant is added to reduce the Fe in the iron 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 content of Ni in the iron phosphate mother liquor is 18.3g / L, Fe 2+ The content of is 1.2g / L, the content of P is 3g / L, and the pH value of the iron phosphate mother liquor is 0.7.

[0217] S5: removing phosphorus from the ferric phosphate mother liquor to obtain a dephosphorized 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 dephosphorization reaction, and the reaction is filtered to obtain ferric phosphate dihydrate and a dephosphorization mother liquor.

[0219] The supplemented iron source is the remaining chromium-removed liquid after removing the chromium-removed liquid used for S4. The ratio of the total molar number of Fe in the ferric phosphate mother liquor and the Fe in the supplemented iron source to the molar number of P in the ferric phosphate mother liquor is 1.1:1. The third oxidant is hydrogen peroxide. The temperature of the dephosphorization reaction is 89°C, and the time of the dephosphorization reaction is 5h.

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

[0221] S6: subjecting part of the dephosphorization mother liquor to nickel precipitation reaction and then preparing nickel sulfate.

[0222] Specifically, part of the dephosphorization mother liquor is reacted with soda ash to precipitate nickel, and filtered to obtain nickel carbonate and wastewater. The amount of soda ash used is 1.2 times the nickel content in the dephosphorization mother liquor, the temperature of the nickel precipitation reaction is 50°C, and the time of the nickel precipitation reaction is 4 hours.

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

[0224] The solution pH was controlled to be 4.5 by adjusting the nickel carbonate, the mixed reaction temperature was 70°C, and the mixed reaction time was 3h.

[0225] Example 4

[0226] This embodiment provides a processing method for preparing battery-grade iron phosphate and nickel sulfate by comprehensive utilization of iron phosphate waste and nickel-iron alloy, and the operating steps are as follows:

[0227] S1: low-temperature acid leaching is performed on the ferrophosphate waste and nickel-iron alloy to be treated in a first solution including an acid and a reducing agent to obtain a first leaching solution containing ferrous iron, nickel, phosphorus and chromium.

[0228] Among them, the mass fraction of phosphorus in the ferrophosphate waste is 20.5%, and the mass fraction of iron is 37%; in the nickel-iron alloy, the mass fraction of nickel is 26%, and the mass fraction of iron is 70%; the mass ratio of the ferrophosphate waste to the 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 temperature of low temperature acid leaching is 65℃, and the Fe 3+ The concentration of Ni in the first leaching solution is 10 g / L, Fe 2+ The concentration of is 35g / L, the concentration of Cr is 0.08g / L, and the concentration of P is 6.9g / L.

[0231] S2: adding the first oxidant to the first leachate, raising the temperature to perform high-temperature acid leaching, and filtering to obtain the second leachate and leach residue.

[0232] The first oxidant is hydrogen peroxide, and the amount of hydrogen peroxide added is 50g / L. The temperature of high temperature acid leaching is 89°C, and the time of high temperature acid leaching is 4.5h. At this time, the pH value of the second leaching solution is 2.0. The content of Ni in the second leaching solution is 15.5g / L, Fe 2+ The content of Ni is 55g / L, the content of Cr is 0.1g / L, and the content of P is 6.9g / L.

[0233] S3: removing chromium from the second leaching solution to obtain a chromium-removed solution.

[0234] Specifically, seed crystals are added to the second leaching solution to carry out seed crystal reaction, and then a value adjusting agent is added to carry out chromium removal reaction (which can be understood as precipitation and impurity removal), and filter pressing is performed to obtain chromium-removed liquid and chromium slag.

[0235] Among them, the seed crystal is anhydrous ferric phosphate, the seed crystal addition amount is 1.35g / L, the seed crystal reaction temperature is 65°C, and the seed crystal reaction time is 1.1h; the adjusting agent is nickel carbonate, the adjusting agent controls the pH value of the reaction solution system to 3.1, the chromium removal reaction temperature is 65°C, and the chromium removal reaction time is 2.5h.

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

[0237] S4: reacting at least a portion of the chromium-removed liquid with supplemented phosphoric acid and a second oxidant to precipitate iron, and separating the solid from the liquid to obtain iron phosphate and an iron phosphate mother liquor.

[0238] Specifically, firstly, phosphoric acid is added to part of the chromium-removed liquid to carry out the first reaction, and then the second oxidant is added to carry out the second reaction (the first reaction and the second reaction can be understood as phosphorus precipitation of iron as a whole), and then the iron phosphate and iron phosphate mother liquor are obtained by filtration. The iron phosphate is aged, filtered, washed, and roasted to obtain battery-grade iron phosphate.

[0239] The second oxidant is hydrogen peroxide. The ratio of the total molar number of P in the supplemented phosphoric acid to the molar number of P in the chromium-removed solution to the molar number of Fe in the chromium-removed solution is 1:0.94. The temperature of the first reaction is 52°C and the time of the first reaction is 2.5 hours. The second oxidant is added to reduce the Fe in the iron 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 content of Ni in the iron phosphate mother liquor is 20.1g / L, Fe 2+ The content of is 1.4g / L, the content of P is 2.5g / L, and the pH value of the iron phosphate mother liquor is 1.

[0241] S5: removing phosphorus from the ferric phosphate mother liquor to obtain a dephosphorized 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 dephosphorization reaction, and the reaction is filtered to obtain ferric phosphate dihydrate and a dephosphorization mother liquor.

[0243] The supplemented iron source is the remaining chromium-removed liquid after removing the chromium-removed liquid used for S4. The ratio of the total molar number of Fe in the iron phosphate mother liquor and the Fe in the supplemented iron source to the molar number of P in the iron phosphate mother liquor is 1.14:1. The third oxidant is hydrogen peroxide. The temperature of the dephosphorization reaction is 92°C, and the time of the dephosphorization reaction is 6 hours.

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

[0245] S6: subjecting part of the dephosphorization mother liquor to nickel precipitation reaction and then preparing nickel sulfate.

[0246] Specifically, part of the dephosphorization mother liquor is reacted with soda ash to precipitate nickel, and filtered to obtain nickel carbonate and wastewater. The amount of soda ash used is 1.3 times the nickel content in the dephosphorization mother liquor, the temperature of the nickel precipitation reaction is 55°C, and the time of the nickel precipitation reaction is 5h.

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

[0248] The solution pH was controlled to be 5 by adjusting the nickel carbonate, the mixed reaction temperature was 75°C, and the mixed reaction time was 3.5h.

[0249] Example 5

[0250] This embodiment provides a processing method for preparing battery-grade iron phosphate and nickel sulfate by comprehensive utilization of iron phosphate waste and nickel-iron alloy, and the operating steps are as follows:

[0251] S1: low-temperature acid leaching is performed on the ferrophosphate waste and nickel-iron alloy to be treated in a first solution including an acid and a reducing agent to obtain a first leaching solution containing ferrous iron, nickel, phosphorus and chromium.

[0252] Among them, the mass fraction of phosphorus in the ferrophosphate waste is 20.5%, and the mass fraction of iron is 37%; in the nickel-iron alloy, the mass fraction of nickel is 26%, and the mass fraction of iron is 70%; the mass ratio of the ferrophosphate waste to the 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 temperature of low temperature acid leaching is 70℃, and the Fe 3+ The concentration of Ni in the first leaching solution is 11.5 g / L, Fe 2+ The concentration of is 40g / L, the concentration of Cr is 0.1g / L, and the concentration of P is 7.2g / L.

[0255] S2: adding the first oxidant to the first leachate, raising the temperature to perform high-temperature acid leaching, and filtering to obtain the second leachate and leach residue.

[0256] The first oxidant is hydrogen peroxide, and the amount of hydrogen peroxide added is 60g / L. The temperature of high temperature acid leaching is 92°C, and the time of high temperature acid leaching is 5h. At this time, the pH value of the second leaching solution is 2.2. The content of Ni in the second leaching solution is 17.4g / L, Fe 2+ The content of Ni is 60g / L, the content of Cr is 0.12g / L, and the content of P is 7.2g / L.

[0257] S3: removing chromium from the second leaching solution to obtain a chromium-removed solution.

[0258] Specifically, seed crystals are added to the second leaching solution to carry out seed crystal reaction, and then a value adjusting agent is added to carry out chromium removal reaction (which can be understood as precipitation and impurity removal), and filter pressing is performed to obtain chromium-removed liquid and chromium slag.

[0259] Among them, the seed crystal is anhydrous ferric phosphate, the seed crystal addition amount is 1.45g / L, the seed crystal reaction temperature is 70°C, and the seed crystal reaction time is 1.3h; the adjusting agent is nickel carbonate, the adjusting agent controls the pH value of the reaction solution system to 3.3, the chromium removal reaction temperature is 70°C, and the chromium removal reaction time is 3h.

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

[0261] S4: reacting at least a portion of the chromium-removed liquid with supplemented phosphoric acid and a second oxidant to precipitate iron, and separating the solid from the liquid to obtain iron phosphate and an iron phosphate mother liquor.

[0262] Specifically, firstly, phosphoric acid is added to part of the chromium-removed liquid to carry out the first reaction, and then the second oxidant is added to carry out the second reaction (the first reaction and the second reaction can be understood as phosphorus precipitation of iron as a whole), and then the iron phosphate and iron phosphate mother liquor are obtained by filtration. The iron phosphate is aged, filtered, washed, and roasted to obtain battery-grade iron phosphate.

[0263] The second oxidant is hydrogen peroxide. The ratio of the total molar number of P in the supplemented phosphoric acid to the molar number of P in the chromium-removed solution to the molar number of Fe in the chromium-removed solution is 1:0.98. The temperature of the first reaction is 55°C and the time of the first reaction is 3 hours. The second oxidant is added to reduce the Fe in the iron 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 content of Ni in the iron phosphate mother liquor is 22g / L, and the content of Fe 2+ The content of is 1.6g / L, the content of P is 2g / L, and the pH value of the iron phosphate mother liquor is 1.2.

[0265] S5: removing phosphorus from the ferric phosphate mother liquor to obtain a dephosphorized 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 dephosphorization reaction, and the reaction is filtered to obtain ferric phosphate dihydrate and a dephosphorization mother liquor.

[0267] The supplemented iron source is the remaining chromium-removed liquid after removing the chromium-removed liquid used for S4. The ratio of the total molar number of Fe in the ferric phosphate mother liquor and the Fe in the supplemented iron source to the molar number of P in the ferric phosphate mother liquor is 1.17:1. The third oxidant is hydrogen peroxide. The temperature of the dephosphorization reaction is 95°C, and the time of the dephosphorization reaction is 7h.

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

[0269] S6: subjecting part of the dephosphorization mother liquor to nickel precipitation reaction and then preparing nickel sulfate.

[0270] Specifically, part of the dephosphorization mother liquor is reacted with soda ash to precipitate nickel, and filtered to obtain nickel carbonate and wastewater. The amount of soda ash used is 1.4 times the nickel content in the dephosphorization mother liquor, the temperature of the nickel precipitation reaction is 60°C, and the time of the nickel precipitation reaction is 6 hours.

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

[0272] The solution pH was controlled to be 5.5 by adjusting the nickel carbonate, the mixed reaction temperature was 80°C, and the mixed 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) is added to 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 an acid, a reducing agent and a 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] Test Example 1

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

[0285] The "tail gas detection" in the table below refers to the detection of methyl mercaptan and ethyl sulfide; the "element utilization rate" refers to the total element utilization rate, which is calculated by calculating the weight and metal content of the slag finally discharged from the system (the remaining elements recycled in the system are still utilized and are not considered losses). The nickel sulfate solution corresponds to the solution obtained by the mixed reaction in step S7.

[0286] Table 1 Comparison results

[0287]

[0288]

[0289]

[0290] It can be seen from Table 1 that the solution provided in the embodiment of the present invention can effectively leach Fe, Ni, P and Cr elements in ferrophosphate waste and chromium-containing nickel-iron alloy, with a high element utilization rate and no obvious tail gas odor.

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

[0292] Test Example 2

[0293] Taking Example 1 and Comparative Example 1 as examples, the low-temperature acid leaching of S1 in Example 1 and Comparative Example 1 was followed by filtration, and the SEM images of the obtained filter residues were as follows: Figure 3 and Figure 4 shown.

[0294] Depend on Figure 3 and Figure 4 By comparison, it can be seen that: for the filter residue without adding thiourea dioxide, the system's reducing ability is insufficient, and dihydrated ferric phosphate is generated. The presence of crystal water will make the crystal structure more stable and the chemical bonds in the structure more tightly connected. This tight structure makes it difficult for the leaching agent to penetrate into the crystal to react with ferric phosphate, thus hindering the leaching process. In the leaching system with thiourea dioxide added, the trivalent 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, pores and other structures, which makes it easier for the leaching agent to enter the crystal to contact and react, making it easier to be leached.

[0295] In summary, the method provided by the present invention is simple to operate, realizes the effective recovery and utilization of phosphorus and iron in ferrophosphate waste and nickel and iron in nickel-iron alloy, reduces the production cost of preparing battery-grade nickel sulfate and ferrophosphate, and basically does not generate obvious odor during the entire process.

[0296] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for comprehensive utilization of ferrophosphate waste and nickel-iron alloy, characterized in that: The following steps are involved: The waste ferric phosphate to be treated and the nickel-iron alloy containing chromium are subjected to low-temperature acid leaching in a first solution comprising an acid and a reducing agent to obtain a first leaching solution containing ferrous iron, nickel, phosphorus and chromium; wherein the reducing agent comprises thiourea dioxide, the temperature of the low-temperature acid leaching is 50°C to 70°C, and the Fe 3+ The content does not exceed 1g / L; Adding a first oxidant to the first leachate for high temperature acid leaching to obtain a second leachate; wherein the temperature of the high temperature acid leaching is 80° C. to 95° C.; removing chromium from the second leaching solution to obtain a chromium-removed solution; subjecting at least a portion of the chromium-removed liquid to an iron precipitation reaction with supplemented phosphoric acid and a second oxidant, and performing solid-liquid separation to obtain iron phosphate and an iron phosphate mother liquor; Removing phosphorus from the ferric phosphate mother liquor to obtain a dephosphorized mother liquor; At least a portion of the dephosphorization mother liquor is subjected to nickel precipitation reaction to prepare nickel sulfate.

2. The method according to claim 1, characterized in that Low temperature pickling includes at least one of the following features: Feature 1: The mass ratio of the ferrophosphate 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 the 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% to 20.5%, and the mass fraction of iron is 25% to 37%; Feature 6: In the nickel-iron alloy, the mass fraction of nickel is 10% to 30%, and the mass fraction of iron is 60% to 75%; Feature 7: In the first leaching solution, the content of Ni is 5g / L to 12g / L, and the content of Fe is 2+ The content of Ni 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 pickling includes at least one of the following features: 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 to 5h; Feature 11: The pH value of the second leachate is 1.4-2.3; Feature 12: The content of Ni in the second leaching solution is 10g / L to 20g / L, and the content of Fe 2+ The content of Ni 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 perform a seed crystal reaction, and then adding a value adjusting agent to perform a chromium removal reaction; Wherein, the seed crystals include at least one of anhydrous ferric phosphate, dihydrate ferric phosphate, 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 seeding reaction includes at least one of the following features: Feature 13: The amount of the seed crystal added is 1 g / L to 1.5 g / L; Feature 14: The temperature of the seed crystal reaction is 50°C to 70°C, and the time of the seed crystal reaction is 0.5h to 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 adjusting agent is added to control the pH value of the reaction system corresponding to the chromium removal reaction to be 2.5 to 3.5; Feature 16: The temperature of the chromium removal reaction is 50°C to 70°C, and the time of the chromium removal reaction is 1h to 3h; Feature 17: The content of Ni in the chromium-removed solution is 15 g / L to 25 g / L, and the content of Fe 2+ The content of Ni 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 comprises: firstly adding supplementary phosphoric acid to at least a portion of the chromium-removed liquid to perform a first reaction, and then adding a second oxidant to perform a second reaction; wherein the ratio of the total molar number of P in the supplemented phosphoric acid and the P in the chromium-removed solution to the molar number of Fe in the chromium-removed solution is 1:0.8 to 1:0.98; The temperature of the first reaction is 40°C to 55°C, and the time of the first reaction is 1h to 3h; The second oxidant is added to make Fe 2+ Concentration: 0.8g / L~1.6g / L; The temperature of the second reaction is 30°C to 60°C, and the time of the second reaction is 0.5h to 1.5h; Preferably, the content of Ni in the iron phosphate mother liquor is 15 g / L to 25 g / L, and the content of Fe 2+ The content of is 0.8g / L~1.6g / L, and the content of P is 2g / L~4g / L; Preferably, the pH value of the iron phosphate mother solution is 0.1-1.

2.

8. The method according to claim 1, characterized in that: Removing phosphorus from the ferric phosphate mother liquor comprises: adding an iron source to the ferric phosphate mother liquor and adding a third oxidant to perform a dephosphorization reaction, and performing solid-liquid separation to obtain ferric phosphate dihydrate and a dephosphorization mother liquor; Preferably, the phosphorus removal reaction includes at least one of the following characteristics: Feature 18: The ratio of the total molar number of Fe in the ferric phosphate mother solution and the Fe in the supplementary iron source to the molar number of P in the ferric phosphate mother solution 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°C to 95°C, and the time of the phosphorus removal reaction is 3h to 8h; Feature 21: The Ni content in the dephosphorization mother solution is 15 g / L to 25 g / L; and / or the pH value of the dephosphorization mother solution is 0.1 to 1.

2.

9. The method according to claim 1, characterized in that: The nickel precipitation reaction comprises: reacting the dephosphorization mother liquor with soda ash, separating the solid from the liquid, and obtaining nickel carbonate; Preferably, the nickel deposition 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 solution; Feature 23: The temperature of the nickel precipitation reaction is 40°C to 60°C, and the time of the nickel precipitation reaction is 2h to 6h.

10. The method according to claim 9, characterized in that When the first solution contains sulfuric acid, preparing nickel sulfate includes: mixing a portion of the dephosphorization mother solution with the nickel carbonate for reaction; Preferably, the mixing reaction comprises at least one of the following features: Feature 24: The mixed reaction is carried out at a pH value of 4.0 to 5.5; Feature 25: The temperature of the mixing reaction is 60°C to 80°C, and the time of the mixing reaction is 2h to 4h.

Images