Method for preparing battery-grade iron phosphate and battery-grade nickel sulfate from ferro-nickel alloy

Abstract

The invention discloses a method for preparing battery-grade iron phosphate and battery-grade nickel sulfate from a nickel-iron alloy, and relates to the technical field of lithium ion battery materials. The invention provides a method for preparing battery-grade iron phosphate and battery-grade nickel sulfate by using a nickel-iron alloy, which comprises the following steps of: further removing impurities from a nickel-iron mother solution generated in the production of the battery-grade iron phosphate to obtain the battery-grade nickel sulfate. The iron-containing slag generated in the midway can be returned to the front end to be reused, the leaching efficiency of the nickel-iron alloy is high, and the consumption cost of auxiliary materials is low.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery materials, in particular to a method for preparing battery-grade iron phosphate and battery-grade nickel sulfate by using nickel-iron alloy. Background Art

[0002] At present, the process flow of preparing ferric phosphate from nickel iron has high impurity content in the mother liquor, large amount of impurity removal auxiliary materials, large extraction flux in the extraction stage, and many types of slag produced by refining and removing impurities in the mother liquor. Related technology discloses a selective leaching method of nickel-iron alloy and a method for preparing high-purity nickel salt, including: using nickel-iron alloy powder to configure into slurry, adding a combination of reagents to the slurry to form a system to be leached, and obtaining a leachate after leaching the system at above 30°C and solid-liquid separation. While ensuring the dissolution of nickel, the dissolution of iron in the nickel-iron alloy powder can be avoided as much as possible, the iron leaching rate can be reduced, and the neutralizing reagent required for subsequent nickel-iron separation can be effectively reduced. However, the process of selective leaching to produce nickel sulfate has low iron removal efficiency, difficult process control, slow capacity improvement, and in the process of preparing ferric phosphate from nickel-iron alloy, iron resources cannot be fully utilized, reducing the economic efficiency of the leaching process of nickel-iron alloy. Summary of the invention

[0003] Based on this, the object of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. The present invention first prepares battery-grade iron phosphate. The residual iron content in the nickel-iron mother liquor obtained after preparing battery-grade iron phosphate is relatively high. After primary and secondary iron removal, the primary iron removal slag can be returned to step (2) for co-precipitation and impurity removal, and iron precipitation is increased to prepare battery-grade iron phosphate. After the nickel-iron mother liquor obtained after preparing battery-grade iron phosphate by the present invention undergoes specific primary and secondary iron removal processes, the iron removal efficiency is high and the auxiliary material consumption cost is low.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy, comprising the following steps:

[0005] (1) adding acid solution into the nickel-iron alloy, heating acid dissolving, and solid-liquid separation to obtain nickel-iron leaching solution and leaching residue;

[0006] (2) adding a precipitation agent to the ferronickel leachate to remove impurities, and separating the solid from the liquid to obtain a ferronickel liquid and chromium slag;

[0007] (3) adding phosphoric acid and an oxidant to the chromium-removing ferronickel liquid to carry out an iron precipitation reaction, and separating the solid and liquid to obtain ferric phosphate and ferronickel mother liquor, and aging, filtering, washing, drying and roasting the ferric phosphate to obtain battery-grade ferric phosphate;

[0008] (4) adding ferronickel powder to ferronickel mother liquor to react, and obtaining ferronickel adjustment liquid after filtering;

[0009] (5) adding mixture A to the nickel-iron adjustment liquid to remove iron, and performing solid-liquid separation to obtain iron-containing slag and iron-removing liquid A; returning the iron-containing slag to step (2) to jointly precipitate and remove impurities; the mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte;

[0010] (6) Adding mixture B to the iron removal liquid A for secondary iron removal to obtain iron removal liquid B, and extracting and removing impurities to obtain battery-grade nickel sulfate; the mixture B is a mixture of value-adjusting nickel and iron removal nickel, the value-adjusting nickel is at least one of nickel carbonate and nickel hydroxide, and the iron removal nickel is at least one of nickel oxalate and nickel sulfide; the weight ratio of the value-adjusting nickel to the iron removal nickel is greater than 1.

[0011] The present invention provides a method for preparing battery-grade iron phosphate and battery-grade nickel sulfate simultaneously using nickel-iron alloy. The present invention uses nickel-iron alloy to prepare battery-grade nickel sulfate from nickel-iron mother liquor after preparing battery-grade iron phosphate. A specific primary and secondary iron removal process is used, wherein the primary iron removal uses mixture A, and mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte. The combination of the specific mixture is selected. On the one hand, high-temperature oxidation and chemical precipitation adsorption iron removal are used for iron removal, which can produce iron-containing slag precipitation containing iron phosphate (Ni and sulfate content are low), and achieve efficient phosphorus and acid removal operations on the nickel-iron mother liquor, which is convenient for subsequent impurity removal and purification of nickel sulfate liquid. A variety of methods can be selected to purify the nickel sulfate liquid, and the process optimization is more selective. On the other hand, the introduction of pyrite powder and high-grade nickel matte can provide ferrihydrite generation points, reduce the number of ferrihydrite microparticles generated, and increase the particle size of the generated precipitation particles. And the S element in high-grade nickel matte can be adsorbed with O in the iron-containing slag crystals, strengthen the adsorption and aggregation of Fe in the solution, and can make the Ni in the crystal replaced by Fe, reducing the entrainment of Ni in the slag. The inventors found in the actual experimental process that the surface of pyrite powder contains two functional groups, SH (thiol group) and Fe-OH (hydroxyl group). In the process of primary oxidation and iron removal, it is easier to form S-Fe bonds to form adsorption centers, so that some O atoms in the iron oxide slag lattice in the iron-containing slag are replaced by S. Later, in the process of returning to the front end to adjust the value and remove chromium, S-Fe consumes H and removes Fe, forming S-Cr bonds at the same time. Part of the sulfur-nickel compound composed of high nickel matte is adsorbed on the surface of the iron-containing slag, which can enhance the acid reaction performance of the iron-containing slag and enhance the adsorption performance of Cr, reduce the amount of precipitant used in chromium removal in step (2), and increase the iron recycling rate.

[0012] The secondary iron removal of the present invention uses a mixture B, which is a mixture of value-adjusting nickel and iron-removing nickel. On the one hand, iron is hydrolyzed to precipitate during the value-adjusting process. The present invention uses a mixture of value-adjusting nickel and iron-removing nickel to reduce the introduction of impurities. On the other hand, the present invention uses a mixture of value-adjusting nickel and iron-removing nickel to further reduce the Fe content, so that the operating conditions of the extraction and impurity removal stage are wider, such as the water-oil flow ratio of the extraction and the saponification rate process range are wider.

[0013] The invention uses nickel-iron mother liquor obtained by preparing battery-grade iron phosphate with nickel-iron alloy to prepare battery-grade nickel sulfate, adopts specific primary and secondary iron removal processes, has high iron removal efficiency and low auxiliary material consumption cost.

[0014] Preferably, in the step (1), the mass percentage of nickel in the nickel-iron alloy is greater than 7%, and the mass percentage of iron is less than 85%, the acid solution is at least one of a sulfuric acid solution, a phosphoric acid solution, and a hydrochloric acid solution; the pH value of the nickel-iron leaching solution is 1-2.5; the heating temperature of the heated acid dissolution is 80-95° C., and the heating time is 2-10 h.

[0015] Preferably, in step (2), the precipitant is at least one of ammonia water, nickel hydroxide, nickel carbonate, ferric hydroxide, ferric carbonate and ferric oxide, the impurity removal temperature is 60-95°C, the impurity removal time is 2-8h, and the pH of the chromium-nickel-iron liquid is 3-4.5.

[0016] Preferably, in the step (3), the iron / phosphorus molar ratio in the chromium-removing ferronickel liquid is 0.6-1.2; the oxidant is at least one of hydrogen peroxide, air, oxygen, and ozone, the amount of the oxidant added is based on the end point of the divalent iron concentration in the ferronickel mother liquor being 1-5 g / L, the iron precipitation reaction temperature is 70-95°C, and the iron precipitation reaction time is 4-10h; wherein the pH of the ferronickel mother liquor is 0.5-1, the aging temperature is 80-95°C, and the aging time is 4-14h.

[0017] Preferably, in step (4), the D50 of the nickel-iron powder is 5-100 μm, the reaction temperature is 70-95° C., the reaction time is 4-10 h, and the pH of the nickel-iron adjustment solution is 1.5-3.5.

[0018] The inventors found in actual experiments that the addition of nickel iron powder can consume the acid in the nickel iron mother liquor and promote the dissolution of nickel iron. And the particle size D50 of the nickel iron powder will affect the Ni / Fe content in the nickel iron adjustment solution. When the particle size D50 of the nickel iron powder is 5-100 μm, there are more exposed sites, which can better dissolve nickel iron.

[0019] Preferably, in step (5), the reaction temperature for primary iron removal is 160-220° C., and the reaction time is 2-6 h.

[0020] Preferably, in step (5), the weight ratio of hydrogen peroxide, pyrite powder and nickel matte in mixture A is hydrogen peroxide: pyrite powder: nickel matte = 1: (0.3-0.6): (0.2-0.4).

[0021] Preferably, in step (5), the weight volume ratio of the mixture A to the nickel-iron adjustment solution is 17-34 g:1 L;

[0022] Preferably, in step (6), mixture B is added to the iron removal liquid A to adjust the pH to 4.8-5.8.

[0023] Preferably, in step (6), the weight ratio of the value-adjusting nickel to the iron-removing nickel is value-adjusting nickel:iron-removing nickel=(6-7):(3-4).

[0024] The inventors found in actual experiments that when the mixture B is a mixture of value-adjusting nickel and iron-removing nickel and is within a specific ratio range, on the one hand, iron is hydrolyzed and precipitated during the value-adjusting process. The present invention uses a mixture of value-adjusting nickel and iron-removing nickel to reduce the introduction of impurities; on the other hand, the present invention uses a mixture of value-adjusting nickel and iron-removing nickel to further reduce the Fe content, so that the operating conditions of the extraction and impurity removal stage are wider, such as the water-to-oil flow ratio of the extraction, and the saponification rate process range is wider.

[0025] Preferably, in step (6), the extractant used for extraction and impurity removal is at least one of di(2-ethylhexyl) phosphate P204, 2-ethylhexyl phosphate mono-2-ethylhexyl ester P507, tributyl phosphate tributyl ester TBP, and polyethylene glycol octylphenyl ether TritonX-100.

[0026] The present invention provides battery-grade iron phosphate and battery-grade nickel sulfate prepared by the above method. The present invention first prepares battery-grade iron phosphate, and the residual iron content in the nickel-iron mother liquor obtained after preparing the battery-grade iron phosphate is relatively high. After primary and secondary iron removal, the primary iron removal slag can be returned to step (2) for co-precipitation and impurity removal, and iron precipitation is increased to prepare battery-grade iron phosphate. After the nickel-iron mother liquor obtained after preparing the battery-grade iron phosphate of the present invention undergoes specific primary and secondary iron removal processes, the iron removal efficiency is high and the auxiliary material consumption cost is low.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) The present invention first prepares battery-grade iron phosphate, and the residual amount of iron in the nickel-iron mother liquor obtained after preparing battery-grade iron phosphate is relatively high. After primary and secondary iron removal, the primary iron removal slag can be returned to step (2) for co-precipitation and impurity removal, and iron precipitation is increased to prepare battery-grade iron phosphate. The nickel-iron mother liquor obtained after the present invention prepares battery-grade iron phosphate has high iron removal efficiency and low auxiliary material consumption cost after specific primary and secondary iron removal processes. The present invention adds nickel-iron powder to the nickel-iron mother liquor for reaction, and uses the nickel-iron powder to adjust the nickel-iron mother liquor, which can consume the acid produced in the process of preparing iron phosphate precipitation in the nickel-iron mother liquor, and will not introduce impurity metal ions, thereby shortening the subsequent nickel sulfate treatment process.

[0029] (2) The present invention provides a method for preparing battery-grade iron phosphate and battery-grade nickel sulfate simultaneously using nickel-iron alloy. The present invention uses nickel-iron mother liquor after preparing battery-grade iron phosphate with nickel-iron alloy to prepare battery-grade nickel sulfate, and adopts specific primary and secondary iron removal processes, wherein the primary iron removal uses mixture A, which is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte. The combination of specific mixtures is selected. On the one hand, the hematite method is used for iron removal, which can produce iron-containing slag precipitation containing iron phosphate (low Ni and sulfate content), realize efficient phosphorus and acid removal operations on the nickel-iron mother liquor, facilitate the subsequent impurity removal and purification of nickel sulfate liquid, and can select a variety of methods to purify the nickel sulfate liquid, with multiple process optimization selectivity. On the other hand, the introduction of pyrite powder and high-grade nickel matte can provide ferrihydrite generation points, reduce the number of ferrihydrite microparticles generated, and increase the particle size of the generated precipitation particles. In addition, the S element in high-grade nickel matte can be adsorbed with O in hematite crystals, strengthen the adsorption and aggregation of Fe in the solution, and can make the Ni adsorbed on the surface of hematite or replaced by Fe in the crystal, reducing the entrainment of Ni in the slag. The mixture B used in the secondary iron removal of the present invention is a mixture of value-adjusting nickel and iron-removing nickel. On the one hand, iron is hydrolyzed to precipitate during the value-adjusting process. The present invention uses a mixture of value-adjusting nickel and iron-removing nickel to reduce the introduction of impurities. On the other hand, the present invention uses a mixture of value-adjusting nickel and iron-removing nickel to further reduce the Fe content, so that the operating conditions of the extraction and impurity removal stage are wider, such as the water-oil flow ratio of the extraction and the saponification rate process range is wider.

[0030] (3) The iron-containing slag obtained by the present invention can be returned to the front end for reuse and chromium removal. The iron-containing slag contains phosphate and iron oxide slag, which are returned to the front end for value adjustment and chromium removal, so that phosphate and iron can be dissolved again, which can not only improve the utilization rate of phosphate and iron in the nickel-iron mother liquor, but also reduce the consumption of precipitant (value adjustment and chromium removal) auxiliary materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the process of preparing iron-containing slag precipitation for adjusting the value of nickel-iron mother liquor and removing iron;

[0032] Figure 2Schematic diagram for optimizing the high-temperature iron removal crystal conversion process;

[0033] Figure 3 This is the mechanism pathway diagram of iron removal by the reaction of iron sulfide powder and high nickel matte in the high temperature iron removal process;

[0034] Figure 4 Schematic diagram of the process of adjusting the value of chromium removal and strengthening precipitation of the iron-containing slag returning step (2);

[0035] Figure 5 This is a SEM image of the iron-containing slag obtained by solid-liquid separation after one-time iron removal in Example 1;

[0036] Figure 6 This is a SEM image of the chromium slag after the iron-containing slag is returned to step (2) in Example 1 and the chromium is removed;

[0037] Figure 7 This is the EDS analysis diagram of the chromium slag after the iron-containing slag is returned to step (2) in Example 1 to adjust the value and remove chromium. DETAILED DESCRIPTION

[0038] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0039] In the present invention, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0040] The reagents or instruments used in the present invention without indicating the manufacturer are all conventional products that can be obtained commercially. The raw materials are listed below, but are not limited to the following raw materials:

[0041] The mass percentage of nickel in the nickel-iron alloy used in the present invention is greater than 7%, and the mass percentage of iron is less than 85%. Specifically, the mass percentage of nickel in the nickel-iron alloy used in this batch of experimental examples and comparative examples is 13%, and the mass percentage of iron is 80%.

[0042] Nickel iron powder-1: D50 is 50μm, Yichang Bangpu circulating nickel iron atomized material product;

[0043] Nickel iron powder-2: D50 is 65μm, nickel iron atomized material product of Jiangsu Delong Nickel Industry;

[0044] Nickel iron powder-3: D50 is 80μm, Anglo American nickel iron product;

[0045] Pyrite powder: S>48%, Fe>42%, As<0.1%, SiO2<3%, Zn<0.1%, Pb<0.1%, H2O<0.5%, source: Ma'anshan Guanxu Mining Technology;

[0046] High-grade nickel matte: Ni55-65%, Cu<15%, Co 0.5-1.2%, Fe<4%, S21-24%, Huake Nickel Industry pyrometallurgical high-grade nickel matte project;

[0047] Nickel sulfide: product purity NiS 99.6%, Hubei Xinhongli Chemical Co., Ltd.;

[0048] Siderite: composition is FeO 53.01%, CO2 31.99%, MnO 3.21%, CaO 1.24%, Shaanxi Iron and Steel Group Co., Ltd.

[0049] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy comprises the following steps:

[0050] (1) adding acid solution to the nickel-iron alloy, heating the acid solution, and performing solid-liquid separation to obtain a nickel-iron leaching solution and a leaching residue; the acid solution is at least one of a sulfuric acid solution, a phosphoric acid solution, and a hydrochloric acid solution; the pH value of the nickel-iron leaching solution is 1-2.5; the heating temperature of the heating acid solution is 80-95° C., and the heating time is 2-10 h;

[0051] (2) adding a precipitant to the nickel-iron leaching solution to remove impurities, and separating the solid and liquid to obtain a chromium-removed nickel-iron liquid and a chromium slag; the precipitant is at least one of ammonia water, nickel hydroxide, nickel carbonate, ferric hydroxide, ferric carbonate, and ferric oxide; the impurity removal temperature is 60-95° C., the impurity removal time is 2-8 hours, and the pH of the chromium-removed nickel-iron liquid is 3-4.5;

[0052] (3) adding phosphoric acid and an oxidant to the chromium-removing ferronickel liquid to carry out an iron precipitation reaction, and separating the solid and liquid to obtain iron phosphate and ferronickel mother liquor, and aging, filtering, washing, drying and roasting the ferronickel phosphate to obtain battery-grade iron phosphate; the iron / phosphorus molar ratio in the chromium-removing ferronickel liquid is 0.6-1.2; the oxidant is at least one of hydrogen peroxide, air, oxygen and ozone, and the amount of the oxidant added is based on the end point of the divalent iron concentration in the ferronickel mother liquor of 1-5g / L, the iron precipitation reaction temperature is 70-95°C, and the iron precipitation reaction time is 4-10h; wherein the pH of the ferronickel mother liquor is 0.5-1, the aging temperature is 80-95°C, and the aging time is 4-14h;

[0053] (4) adding nickel iron powder to the nickel iron mother liquor to react, and filtering to obtain a nickel iron adjustment solution; the D50 of the nickel iron powder is 5-100 μm, the reaction temperature is 70-95° C., the reaction time is 4-10 h, and the pH of the nickel iron adjustment solution is 1.5-3.5;

[0054] (5) Adding mixture A to the nickel-iron adjustment liquid to perform a primary iron removal, and performing solid-liquid separation to obtain iron-containing slag and iron removal liquid A; returning the iron-containing slag to step (2) for co-precipitation and impurity removal; the mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte; the reaction temperature for primary iron removal is 160-220° C., and the reaction time is 2-6 hours, wherein the weight ratio of hydrogen peroxide, pyrite powder, and high-grade nickel matte is hydrogen peroxide: pyrite powder: high-grade nickel matte = 1: (0.3-0.6): (0.2-0.4); the weight volume ratio of the mixture A to the nickel-iron adjustment liquid is 17-34 g: 1 L;

[0055] (6) Adding mixture B to the iron removal liquid A to adjust the pH to 4.8-5.8 for secondary iron removal to obtain iron removal liquid B, and extracting and removing impurities to obtain battery-grade nickel sulfate; the mixture B is a mixture of value-adjusting nickel and iron removal nickel, the value-adjusting nickel is at least one of nickel carbonate and nickel hydroxide, and the iron removal nickel is at least one of nickel oxalate and nickel sulfide; the weight ratio of the value-adjusting nickel to the iron removal nickel is greater than 1, and the extractant used for extraction and impurity removal is at least one of P204, P507, TBP, and TritonX-100.

[0056] Further preferably, the weight ratio of the value-adjusting nickel to the iron-removing nickel is value-adjusting nickel:iron-removing nickel=(6-7):(3-4).

[0057] in, Figure 1 Schematic diagram of the process of preparing iron-containing slag precipitation for adjusting the value of nickel-iron mother liquor and removing iron; Figure 2 Schematic diagram for optimizing the high-temperature iron removal crystal conversion process; Figure 3 This is the mechanism pathway diagram of iron removal by the reaction of iron sulfide powder and high nickel matte in the high temperature iron removal process; Figure 4 Schematic diagram of the process of adjusting the value of chromium removal and strengthening precipitation of the iron-containing slag returning step (2);

[0058] Example 1

[0059] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy comprises the following steps:

[0060] (1) adding acid solution to the nickel-iron alloy, heating the acid solution, and performing solid-liquid separation to obtain a nickel-iron leaching solution and a leaching residue; the acid solution is a sulfuric acid solution; the pH value of the nickel-iron leaching solution is 2.5; the heating temperature of the heating acid solution is 80° C., and the heating time is 10 h;

[0061] (2) adding a precipitant to the nickel-iron leaching solution to remove impurities, and separating the solid and liquid to obtain a chromium-removed nickel-iron liquid and a chromium slag; the precipitant is nickel carbonate, the impurity removal temperature is 60° C., the impurity removal time is 8 hours, and the pH value of the chromium-removed nickel-iron liquid is 4.5;

[0062] (3) adding phosphoric acid and an oxidant to the chromium-removing ferronickel liquid to carry out an iron precipitation reaction, separating the solid and liquid to obtain iron phosphate and ferronickel mother liquor, and aging, filtering, washing, drying and roasting the ferronickel phosphate to obtain battery-grade iron phosphate; the iron / phosphorus molar ratio in the chromium-removing ferronickel liquid is 0.6; the oxidant is hydrogen peroxide, the amount of the oxidant added is based on the end point of the divalent iron concentration in the ferronickel mother liquor being 1 g / L, the reaction temperature is 70° C., and the reaction time is 4 hours; wherein the pH of the ferronickel mother liquor is 0.6, the aging temperature is 80° C., and the aging time is 4 hours;

[0063] (4) adding nickel iron powder-1 to the nickel iron mother liquor to react, and filtering to obtain a nickel iron adjustment solution; the D50 of the nickel iron powder-1 is 50 μm, the reaction temperature is 70° C., the reaction time is 10 h, and the pH of the nickel iron adjustment solution is 3.5;

[0064] (5) Adding mixture A to the nickel-iron adjustment liquid to perform a primary iron removal, and performing solid-liquid separation to obtain iron-containing slag and iron removal liquid A; returning the iron-containing slag to step (2) for co-precipitation and impurity removal; the mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte; the reaction temperature for primary iron removal is 160° C., the reaction time is 6 h, the weight ratio of the hydrogen peroxide, pyrite powder, and high-grade nickel matte is hydrogen peroxide: pyrite powder: high-grade nickel matte = 1:0.3:0.2; the weight volume ratio of the mixture A to the nickel-iron adjustment liquid is 25 g:1 L;

[0065] (6) Adding mixture B to the iron removal liquid A to adjust the pH to 5.0 for secondary iron removal to obtain iron removal liquid B, and obtaining battery-grade nickel sulfate after extraction and impurity removal; the mixture B is a mixture of value-adjusting nickel and iron removal nickel, the value-adjusting nickel is nickel carbonate, and the iron removal nickel is nickel oxalate; the weight ratio of the value-adjusting nickel to the iron removal nickel is 6:4, and the extractant used for extraction and impurity removal is P204.

[0066] Example 2

[0067] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy comprises the following steps:

[0068] (1) adding acid solution to the nickel-iron alloy, heating the acid solution, and performing solid-liquid separation to obtain a nickel-iron leaching solution and a leaching residue; the acid solution is at least one of a sulfuric acid solution, a phosphoric acid solution, and a hydrochloric acid solution; the pH value of the nickel-iron leaching solution is 1.5; the heating temperature of the heating acid solution is 95° C., and the heating time is 2 h;

[0069] (2) adding a precipitant to the nickel-iron leaching solution to remove impurities, and separating the solid and liquid to obtain a chromium-removed nickel-iron liquid and a chromium slag; the precipitant is nickel hydroxide, the impurity removal temperature is 85° C., the impurity removal time is 6 hours, and the pH value of the chromium-removed nickel-iron liquid is 3;

[0070] (3) phosphoric acid and an oxidant are added to the chromium-removing ferronickel liquid to precipitate iron, solid-liquid separation is performed to obtain ferric phosphate and ferronickel mother liquor, and the ferric phosphate is aged, filtered, washed, dried and roasted to obtain battery-grade ferric phosphate; the iron / phosphorus molar ratio in the chromium-removing ferronickel liquid is 1.2; the oxidant is hydrogen peroxide, the amount of the oxidant added is based on the end point of the divalent iron concentration in the ferronickel mother liquor being 3 g / L, the reaction temperature is 85° C., and the reaction time is 6 h; wherein the pH of the ferronickel mother liquor is 1, the aging temperature is 85° C., and the aging time is 10 h;

[0071] (4) adding nickel iron powder-1 to the nickel iron mother liquor to react, and filtering to obtain a nickel iron adjustment solution; the D50 of the nickel iron powder-1 is 50 μm, the reaction temperature is 85° C., the reaction time is 6 h, and the pH of the nickel iron adjustment solution is 1.5;

[0072] (5) Adding mixture A to the nickel-iron adjustment liquid to perform a primary iron removal, and performing solid-liquid separation to obtain iron-containing slag and iron removal liquid A; returning the iron-containing slag to step (2) for co-precipitation and impurity removal; the mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte; the reaction temperature for primary iron removal is 220° C., the reaction time is 6 h, the weight ratio of the hydrogen peroxide, pyrite powder, and high-grade nickel matte is hydrogen peroxide: pyrite powder: high-grade nickel matte = 1:0.3:0.2; the weight-volume ratio of the mixture A to the nickel-iron adjustment liquid is 25 g:1 L;

[0073] (6) Adding mixture B to the iron removal liquid A to adjust the pH to 5.8 for secondary iron removal to obtain iron removal liquid B, and obtaining battery-grade nickel sulfate after extraction and impurity removal; the mixture B is a mixture of value-adjusting nickel and iron removal nickel, the value-adjusting nickel is nickel carbonate, and the iron removal nickel is nickel oxalate; the weight ratio of the value-adjusting nickel to the iron removal nickel is 6:4, and the extractant used for extraction and impurity removal is P507.

[0074] Example 3

[0075] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy comprises the following steps:

[0076] (1) adding acid solution to the nickel-iron alloy, heating the acid solution, and performing solid-liquid separation to obtain a nickel-iron leaching solution and a leaching residue; the acid solution is a phosphoric acid solution; the pH value of the nickel-iron leaching solution is 1; the heating temperature of the heating acid solution is 95° C., and the heating time is 2 h;

[0077] (2) adding a precipitant to the nickel-iron leaching solution to remove impurities, and separating the solid and liquid to obtain a chromium-removed nickel-iron liquid and a chromium slag; the precipitant is iron carbonate, the impurity removal temperature is 95° C., the impurity removal time is 2 h, and the pH value of the chromium-removed nickel-iron liquid is 3;

[0078] (3) adding phosphoric acid and an oxidant to the chromium-removing ferronickel liquid to precipitate iron, separating the solid and liquid to obtain ferric phosphate and ferronickel mother liquor, and aging, filtering, washing, drying and roasting the ferric phosphate to obtain battery-grade ferric phosphate; the iron / phosphorus molar ratio in the chromium-removing ferronickel liquid is 1; the oxidant is hydrogen peroxide, the amount of the oxidant added is based on the end point of the divalent iron concentration in the ferronickel mother liquor being 5 g / L, the reaction temperature is 95° C., and the reaction time is 4 hours; wherein the pH of the ferronickel mother liquor is 0.5, the aging temperature is 80° C., and the aging time is 14 hours;

[0079] (4) adding nickel iron powder-1 to the nickel iron mother liquor to react, and filtering to obtain a nickel iron adjustment solution; the D50 of the nickel iron powder-1 is 50 μm, the reaction temperature is 95° C., the reaction time is 4 h, and the pH of the nickel iron adjustment solution is 2;

[0080] (5) Adding mixture A to the nickel-iron adjustment liquid to perform a primary iron removal, and performing solid-liquid separation to obtain iron-containing slag and iron removal liquid A; returning the iron-containing slag to step (2) for co-precipitation and impurity removal; the mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte; the reaction temperature for primary iron removal is 200° C., the reaction time is 4 hours, the weight ratio of the hydrogen peroxide, pyrite powder, and high-grade nickel matte is hydrogen peroxide: pyrite powder: high-grade nickel matte = 1:0.3:0.2; the weight volume ratio of the mixture A to the nickel-iron adjustment liquid is 25 g:1 L;

[0081] (6) Adding mixture B to the iron removal liquid A to adjust the pH to 4.8 for secondary iron removal to obtain iron removal liquid B, and obtaining battery-grade nickel sulfate after extraction and impurity removal; the mixture B is a mixture of value-adjusting nickel and iron removal nickel, the value-adjusting nickel is nickel carbonate, and the iron removal nickel is nickel oxalate; the weight ratio of the value-adjusting nickel to the iron removal nickel is 6:4, and the extractant used for extraction and impurity removal is TritonX-100.

[0082] Example 4

[0083] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the type of nickel-iron powder used in step (4) is different, and the nickel-iron powder-2D50 is 65 μm. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0084] Example 5

[0085] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the type of nickel-iron powder used in step (4) is different, and the nickel-iron powder-3D50 with a particle size of 80 μm is selected. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0086] Example 6

[0087] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture A used in step (5) is different. The mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte, wherein the weight ratio of hydrogen peroxide, pyrite powder, and high-grade nickel matte is hydrogen peroxide: pyrite powder: high-grade nickel matte = 1:0.6:0.4, and the remaining components, weight parts and preparation method are exactly the same as in Example 1.

[0088] Example 7

[0089] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture A used in step (5) is different. The mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte, wherein the weight ratio of hydrogen peroxide, pyrite powder, and high-grade nickel matte is hydrogen peroxide: pyrite powder: high-grade nickel matte = 1:0.9:0.1, and the remaining components, weight parts and preparation method are exactly the same as in Example 1.

[0090] Example 8

[0091] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture A used in step (5) is different. The mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte, wherein the weight ratio of hydrogen peroxide, pyrite powder, and high-grade nickel matte is hydrogen peroxide: pyrite powder: high-grade nickel matte = 1:0.2:0.6, and the remaining components, weight parts and preparation method are exactly the same as in Example 1.

[0092] Example 9

[0093] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture B used in step (6) is different. The mixture B is a mixture of value-adjusting nickel and iron-removing nickel. The value-adjusting nickel is nickel carbonate, and the iron-removing nickel is nickel oxalate. The weight ratio of the value-adjusting nickel to the iron-removing nickel is 7:3. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0094] Example 10

[0095] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture B used in step (6) is different. The mixture B is a mixture of value-adjusting nickel and iron-removing nickel. The value-adjusting nickel is nickel hydroxide, and the iron-removing nickel is nickel sulfide. The weight ratio of the value-adjusting nickel to the iron-removing nickel is 6:4. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0096] Embodiment 11

[0097] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture B used in step (6) is different. The mixture B is a mixture of value-adjusting nickel and iron-removing nickel. The value-adjusting nickel is nickel carbonate, and the iron-removing nickel is nickel oxalate. The weight ratio of the value-adjusting nickel to the iron-removing nickel is 8:2. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0098] Example 12

[0099] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the weight-to-volume ratio of the mixture A to the nickel-iron adjustment liquid in step (5) is different, and the weight-to-volume ratio of the mixture A to the nickel-iron adjustment liquid is 17g:1L. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0100] Example 13

[0101] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the weight-to-volume ratio of the mixture A to the nickel-iron adjustment liquid in step (5) is different, and the weight-to-volume ratio of the mixture A to the nickel-iron adjustment liquid is 34g:1L. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0102] Comparative Example 1

[0103] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture B used in step (6) is different. The mixture B is a mixture of value-adjusting nickel and iron-removing nickel. The value-adjusting nickel is nickel carbonate, and the iron-removing nickel is nickel oxalate. The weight ratio of the value-adjusting nickel to the iron-removing nickel is 5:5. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0104] Comparative Example 2

[0105] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture B used in step (6) is different. The mixture B is a mixture of value-adjusting nickel and iron-removing nickel. The value-adjusting nickel is nickel carbonate, and the iron-removing nickel is nickel oxalate. The weight ratio of the value-adjusting nickel to the iron-removing nickel is 4:6. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0106] Comparative Example 3

[0107] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture B used in step (6) is different. The mixture B is nickel carbonate. The remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0108] Comparative Example 4

[0109] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture A used in step (5) is different. The mixture A is a mixture of hydrogen peroxide, siderite, and nickel matte; wherein the weight ratio of hydrogen peroxide, siderite, and nickel matte is hydrogen peroxide: siderite: nickel matte = 1:0.3:0.2, and the remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0110] Comparative Example 5

[0111] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture A used in step (5) is different. The mixture A is a mixture of hydrogen peroxide, pyrite powder, and nickel sulfide; wherein the weight ratio of hydrogen peroxide, pyrite powder, and nickel sulfide is hydrogen peroxide: pyrite powder: nickel sulfide = 1:0.3:0.2, and the remaining components, weight parts, and preparation method are exactly the same as those in Example 1.

[0112] Comparative Example 6

[0113] A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy. Compared with Example 1, only the mixture A used in step (5) is different. The mixture A is a mixture of hydrogen peroxide and pyrite powder; the weight ratio of hydrogen peroxide to pyrite powder is hydrogen peroxide: pyrite powder = 1:0.5, and the remaining components, weight parts and preparation method are exactly the same as those in Example 1.

[0114] Performance Testing

[0115] Test process: After the iron removal liquid A in step (5), the iron removal liquid B in step (6) and the iron-containing slag returned to step (2) for co-precipitation and impurity removal in each embodiment and comparative example, the chromium-nickel-iron removal liquid obtained was subjected to ICP testing for its metal concentration. The effect of the implementation of each scheme can be judged by the metal concentration data. The results are shown in Table 1.

[0116] The contents of the elements in the nickel-iron leaching solution obtained by step (1) of the original nickel-iron alloy used in the embodiment and the comparative example are as follows: Ni: 38 g / L; Fe: 40 g / L; Cr 300 mg / L;

[0117] The iron-containing slag obtained in step (5) of Example 1 and the chromium slag after the iron-containing slag obtained in step (5) is returned to step (2) for chromium removal are subjected to SEM characterization analysis. The specific morphology is as follows: Figure 5 and Figure 6 .

[0118] Figure 5 There are more hematite-type slags in the medium-iron slag, and some crystal forms are distorted due to the presence of pyrite and high nickel matte powder. Figure 6 SEM shows that the crystals in the distorted hematite slag are dissolved, and the surface adsorbs chromium hydroxide indeterminate slag. Figure 7 The EDS spectrum also shows the existence of Fe-Cr and S-Cr binding energy, and the return of nickel-iron leaching solution has an obvious effect on chromium removal.

[0119] Table 1

[0120]

[0121]

[0122] As can be seen from the above table, the method for simultaneously preparing battery-grade ferric phosphate and battery-grade nickel sulfate using nickel-iron alloy in Examples 1-13 of the present invention adopts mixture A for primary iron removal and mixture B for secondary iron removal, and the iron removal efficiency is high. The iron-containing slag in the operation of the present invention can be returned to the front end for reuse to perform chromium removal operation, which can not only improve the utilization rate of phosphate and iron in the nickel-iron mother liquor, but also reduce the consumption of auxiliary materials of the precipitant (adjustment and chromium removal), and the auxiliary material consumption cost is low.

[0123] Comparison of Example 1 and Examples 4-5 shows that the particle size D50 of nickel iron powder affects the Ni / Fe content. The smaller the particle size D50 of nickel iron powder, the higher the iron removal efficiency.

[0124] From the comparison of Example 1, Example 6-8, and Comparative Example 4-6, it can be seen that the mixture A used in step (5) will affect the iron removal efficiency. When the mixture A is a mixture of hydrogen peroxide, pyrite powder, and high matte nickel, wherein the weight ratio of hydrogen peroxide, pyrite powder, and high matte nickel is hydrogen peroxide: pyrite powder: high matte nickel = 1: (0.3-0.6): (0.2-0.4), the iron removal efficiency is higher. At the same time, the selection of the mixture A used in step (5) will have a greater impact on the Cr element content in the chromium-nickel iron liquid after being reused in step (2) for co-precipitation and impurity removal. When the mixture A is a mixture of hydrogen peroxide, pyrite powder, and high matte nickel, wherein the weight ratio of hydrogen peroxide, pyrite powder, and high matte nickel is hydrogen peroxide: pyrite powder: high matte nickel = 1: (0.3-0.6): (0.2-0.4), the Cr removal effect is better.

[0125] From the comparison between Example 1, Examples 9-11, and Comparative Examples 1-3, it can be seen that the mixture B is a mixture of value-adjusting nickel and iron-removing nickel, and the weight ratio of the value-adjusting nickel and the iron-removing nickel is value-adjusting nickel:iron-removing nickel = (6-7): (3-4), which reduces the introduction of impurities during the value-adjusting process and has a higher iron removal efficiency.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy, characterized in that: The following steps are involved: (1) adding acid solution into the nickel-iron alloy, heating acid dissolving, and solid-liquid separation to obtain nickel-iron leaching solution and leaching residue; (2) adding a precipitation agent to the ferronickel leachate to remove impurities, and separating the solid from the liquid to obtain a ferronickel liquid and chromium slag; (3) adding phosphoric acid and an oxidant to the chromium-removing ferronickel liquid to carry out an iron precipitation reaction, and separating the solid and liquid to obtain ferric phosphate and ferronickel mother liquor, and aging, filtering, washing, drying and roasting the ferric phosphate to obtain battery-grade ferric phosphate; (4) adding ferronickel powder to ferronickel mother liquor to react, and obtaining ferronickel adjustment liquid after filtering; (5) adding mixture A to the nickel-iron adjustment liquid to remove iron, and performing solid-liquid separation to obtain iron-containing slag and iron-removing liquid A; returning the iron-containing slag to step (2) to jointly precipitate and remove impurities; the mixture A is a mixture of hydrogen peroxide, pyrite powder, and high-grade nickel matte; (6) Adding mixture B to the iron removal liquid A for secondary iron removal to obtain iron removal liquid B, and extracting and removing impurities to obtain battery-grade nickel sulfate; the mixture B is a mixture of value-adjusting nickel and iron removal nickel, the value-adjusting nickel is at least one of nickel carbonate and nickel hydroxide, and the iron removal nickel is at least one of nickel oxalate and nickel sulfide; the weight ratio of the value-adjusting nickel to the iron removal nickel is greater than 1.

2. The method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy as claimed in claim 1, characterized in that: In the step (1), the acid solution is at least one of a sulfuric acid solution, a phosphoric acid solution, and a hydrochloric acid solution; and the pH value of the nickel-iron leaching solution is 1-2.

5.

3. The method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy as claimed in claim 1, characterized in that: In the step (2), the precipitant is at least one of ammonia water, nickel hydroxide, nickel carbonate, ferric hydroxide, ferric carbonate and ferric oxide, the impurity removal temperature is 60-95°C, the impurity removal time is 2-8h, and the pH of the chromium-removing nickel-iron liquid is 3-4.

5.

4. The method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy as claimed in claim 1, characterized in that: In the step (3), the iron / phosphorus molar ratio in the chromium-removing ferronickel liquid is 0.6-1.2; the oxidant is at least one of hydrogen peroxide, air, oxygen, and ozone, the amount of the oxidant added is based on the end point of the divalent iron concentration in the ferronickel mother liquor being 1-5 g / L, the iron precipitation reaction temperature is 70-95°C, and the iron precipitation reaction time is 4-10 h; wherein the pH of the ferronickel mother liquor is 0.5-1, the aging temperature is 80-95°C, and the aging time is 4-14 h.

5. The method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy as claimed in claim 1, characterized in that: In the step (4), the D50 of the nickel-iron powder is 5-100 μm, the reaction temperature is 70-95° C., the reaction time is 4-10 h, and the pH of the nickel-iron adjustment solution is 1.5-3.

5.

6. The method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy according to claim 1, characterized in that: In the step (5), the reaction temperature for the primary iron removal is 160-220° C., and the reaction time is 2-6 hours.

7. The method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy according to claim 1, characterized in that: In the step (5), the weight ratio of the hydrogen peroxide, pyrite powder and nickel matte is hydrogen peroxide: pyrite powder: nickel matte = 1: (0.3-0.6): (0.2-0.4).

8. The method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy according to claim 1, characterized in that: In the step (6), the weight ratio of the value-adjusting nickel to the iron-removing nickel is value-adjusting nickel:iron-removing nickel=(6-7):(3-4).

9. The method for preparing battery-grade iron phosphate and battery-grade nickel sulfate using nickel-iron alloy according to claim 1, characterized in that: In the step (6), the extractant used for the extraction and impurity removal is at least one of di(2-ethylhexyl) phosphate, 2-ethylhexyl mono-2-ethylhexyl phosphate, tributyl tributyl phosphate, and polyethylene glycol octylphenyl ether.

10. Battery-grade iron phosphate and battery-grade nickel sulfate prepared by the method according to any one of claims 1 to 9.

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