Method for separating nickel and iron from nickel-containing ferronickel raw materials

Abstract

The present disclosure discloses a method for separating nickel and iron from a nickel-containing iron raw material. Oxalic acid is used as a leaching and precipitation agent. While precipitating nickel and iron, most of the impurities of calcium, chromium, copper, zinc, and silicon are left in the solution, which plays a certain role in removing impurities. The precipitate is then aerobically roasted to generate ferric oxide and nickel oxide. After magnetic separation, nickel oxide and ferric oxide with high purity can be separated. The nickel oxide is used as a raw material for ion battery production, and ferric oxide can also be directly sold as a by-product. The method for separating nickel and iron from a nickel-containing iron raw material in this embodiment is simple in process, the by-product ferric oxide is easy to use, and the waste residue output is low.

Description

Technical Field

[0001] The present disclosure relates to the technical field of hydrometallurgy, and in particular to a method for separating nickel and iron from nickel-containing iron raw materials. Background Art

[0002] Nickel metal is an important element of ternary lithium batteries. As the market demand for lithium battery capacity becomes higher and higher, ternary positive electrode materials are gradually developing towards high nickel content, and the demand for nickel sulfate is increasing.

[0003] Low-grade nickel matte and nickel-iron alloy contain rich nickel resources. Taking the utilization of low-grade nickel matte as an example, compared with the pyrometallurgical extraction of nickel from low-grade nickel matte, the hydrometallurgical extraction of nickel has the advantages of low energy consumption, simple process, simple equipment and low investment cost. In modern industry, the separation and recovery of high-concentration nickel and iron elements in the wet leaching solution of low-grade nickel matte generally adopts the method of removing iron impurities first and then treating the nickel elements in the solution. The general iron removal methods include the goethite method, the hematite method, and the sodium iron alum precipitation method. Although these methods can effectively remove the iron elements in the solution, they all need to oxidize the ferrous iron into trivalent iron before removal; and the sodium iron alum precipitation method produces a large amount of slag, the slag has a low iron content, and the impurity sodium ions are introduced, which is difficult to use directly; the goethite method is only suitable for working conditions with an iron concentration below 2g / L, and the filterability of the iron removal precipitate is poor and it is easy to be mixed with nickel precipitate, resulting in the loss of nickel elements; the hematite method has a high operating temperature and high capital expenditure.

[0004] In view of this, there is an urgent need for a method for utilizing low-matte nickel with simple process, convenient utilization of by-products and low waste slag output. Summary of the invention

[0005] The purpose of the present disclosure is to provide a method for separating nickel and iron from nickel-containing iron raw materials, which has a simple process, convenient utilization of by-products and low waste residue output.

[0006] The present disclosure is implemented as follows:

[0007] In a first aspect, the present disclosure provides a method for separating nickel and iron from a nickel-containing iron raw material, comprising:

[0008] The nickel-iron raw material is mixed with the oxalic acid solution and reacted and solid-liquid separated to obtain nickel-rich and iron-rich slag and nickel-poor and iron-poor liquid;

[0009] The nickel-rich and iron-rich slag is subjected to oxygen roasting and magnetic separation in sequence to obtain nickel oxide and ferric oxide.

[0010] In an optional embodiment, the nickel-iron-containing raw material includes at least one of low-grade nickel matte and nickel-iron alloy.

[0011] In an optional embodiment, the initial concentration of the oxalic acid solution is 1 mol / L-4 mol / L.

[0012] In an optional embodiment, the initial concentration of the oxalic acid solution is 1 mol / L-2 mol / L.

[0013] In an optional embodiment, the nickel-iron raw material is added to the oxalic acid solution at 0.8-1.1 times the stoichiometric ratio and mixed.

[0014] In an optional embodiment, the temperature of the reaction step is 50°C-100°C, and the time is 30min-120min.

[0015] In an optional embodiment, the temperature of the reaction step is 70°C-80°C, and the time is 90min-120min.

[0016] In an optional embodiment, the pH value of the nickel-poor iron-poor liquid is 1.5-3.

[0017] In an optional embodiment, the iron content in the nickel-depleted iron-depleted liquid is less than 0.05 g / L, and / or the nickel content in the nickel-depleted iron-depleted liquid is less than 0.045 g / L.

[0018] In an optional embodiment, the temperature of the oxygen calcination step is 200° C.-450° C., and the time is 1 h-4 h.

[0019] In an optional embodiment, the temperature of the oxygen calcination step is 300°C-350°C, and the time is 2h-3h.

[0020] In an optional embodiment, the magnetic field strength of the magnetic separation step is 200Gs-2000Gs, and the magnetic separation time is 0.1h-1h.

[0021] In an optional embodiment, the magnetic field strength of the magnetic separation step is 500Gs-1500Gs, and the magnetic separation time is 0.5h-1h.

[0022] In an optional embodiment, the mass fraction of nickel in the nickel-containing iron raw material is 20wt%-35wt%, and / or the mass fraction of iron in the nickel-containing iron raw material is 60wt%-70wt%.

[0023] In an optional embodiment, the particle size of the nickel-iron raw material is 60 mesh-300 mesh.

[0024] In an optional embodiment, the particle size of the nickel-iron raw material is 200 mesh-300 mesh.

[0025] In an optional embodiment, the nickel-poor iron-poor liquid is used to prepare oxalic acid solution.

[0026] In an optional embodiment, the mass fraction of iron in the ferric oxide is greater than 67wt%, the mass fraction of nickel is less than 0.06wt%, and the content of cobalt is less than 0.03wt%.

[0027] In an optional embodiment, the mass fraction of iron in the nickel oxide is less than 0.04wt%, the mass fraction of nickel is greater than 77wt%, and the content of cobalt is less than 0.05wt%.

[0028] The present disclosure has the following beneficial effects:

[0029] The present invention uses oxalic acid as a leaching and precipitation agent, and while precipitating nickel and iron, most of the impurities of calcium, chromium, copper, zinc, and silicon are left in the solution, which plays a certain role in removing impurities. The precipitate is then aerobically roasted to generate ferric oxide and nickel oxide, which can be separated into nickel oxide and ferric oxide with high purity after magnetic separation, wherein the nickel oxide is used as a raw material for the production of ion batteries, and the ferric oxide can also be directly sold as a by-product. The method for separating nickel and iron from nickel-containing iron raw materials disclosed in the present invention is simple in process, the by-product ferric oxide is easy to use, and the waste residue output is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure 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 paying creative work.

[0031] Figure 1 The process flow chart of the embodiment of the present disclosure is shown in FIG. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the present disclosure clearer, the technical scheme in the embodiments of the present disclosure 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.

[0033] This embodiment provides a method for separating nickel and iron from a nickel-containing iron raw material, comprising:

[0034] The nickel-iron raw material is mixed with the oxalic acid solution and reacted and solid-liquid separated to obtain nickel-rich and iron-rich slag and nickel-poor and iron-poor liquid;

[0035] The nickel-rich and iron-rich slag is subjected to oxygen roasting and magnetic separation in sequence to obtain nickel oxide and ferric oxide.

[0036] In this embodiment, the reactions of formula (1) to formula (3) mainly occur, wherein the nickel-iron raw material reacts with oxalic acid in the reaction shown in formula (1), and during oxygen roasting, the reactions shown in formula (2) and formula (3) occur.

[0037] Ni 2+ +Fe 2+ +2C 2 O 4 2- +4H 2 O=NiC 2 O 4 ·2H 2 O↓+FeC 2 O 4 ·2H 2 O↓ (1)

[0038] NeC 2 O 4 ·H 2 O=NiO+2CO 2 +H 2 O (2)

[0039] 2FeC 2 O 4 ·2H 2 O=Fe 2 O 3 +4CO 2 +H 2 O (3)

[0040] In this embodiment, the oxalic acid solution is acidic, and can be leached with nickel and iron in the nickel-iron raw material to generate nickel oxalate and ferrous oxalate precipitation, thereby precipitating the nickel and iron elements. At the same time, impurity elements such as calcium, chromium, copper, zinc, and silicon in the nickel-iron raw material react with oxalic acid to generate soluble components that are transferred to the nickel-poor and iron-poor liquid, and some impurity elements such as carbon and sulfur react with oxalic acid to generate gas. Only a few elements such as Co will generate precipitation and affect the precipitation composition. The content of nickel oxalate and ferrous oxalate in the obtained precipitation is high, which is convenient for the subsequent separation of nickel and iron.

[0041] The precipitated nickel oxalate and ferrous oxalate are roasted in an oxygen atmosphere to obtain nickel oxide and ferric oxide. The nickel oxide has magnetism, while the ferric oxide has no magnetism. The nickel oxide and the ferric oxide can be effectively separated after magnetic separation. The atmosphere in the oxygen roasting step can be an oxygen atmosphere, or other atmospheres containing oxygen, such as air, or a mixed gas of oxygen and nitrogen.

[0042] This embodiment uses oxalic acid as a leaching and precipitation agent. While precipitating nickel and iron, most of the impurities of calcium, chromium, copper, zinc, and silicon are left in the solution, which plays a certain role in removing impurities. The precipitate is then aerobically roasted to generate ferric oxide and nickel oxide. After magnetic separation, nickel oxide and ferric oxide with high purity can be separated, wherein the nickel oxide is used as a raw material for the production of ion batteries, and ferric oxide can also be directly sold as a by-product. The method for separating nickel and iron from nickel-containing iron raw materials in this embodiment is simple in process, the by-product ferric oxide is easy to use, and the waste residue output is low.

[0043] In some embodiments, the nickel-iron-containing raw material includes at least one of low-grade nickel matte and nickel-iron alloy, both of which contain a large amount of nickel and iron elements.

[0044] In some embodiments, the initial concentration of the oxalic acid solution is 1 mol / L-4 mol / L, specifically 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L or any value between 1 mol / L and 4 mol / L.

[0045] Normally, the oxalic acid concentration is high, and the reaction rate of oxalic acid and the elements in the nickel-iron raw material is relatively faster, but in the present embodiment, since nickel and iron are leached, nickel oxalate and ferrous oxalate precipitation will be generated with oxalate, if the oxalic acid concentration is too high, the rate of precipitation generation is too fast, and the generated precipitation may be wrapped in the surface of the nickel-iron raw material particles, not only will not increase the precipitation rate, but may reduce the contact area of ​​oxalic acid and the internal elements of the nickel-iron raw material particles, and then the leaching of elements such as nickel and iron will be suppressed, therefore, the concentration of oxalic acid solution should not be too large. In some embodiments, the initial concentration of the oxalic acid solution is 1mol / L-3mol / L, and in some embodiments, the initial concentration of the oxalic acid solution is 1mol / L-2mol / L, while ensuring the leaching precipitation effect, maintaining a higher reaction rate. In order to improve the reaction rate, in some embodiments, the reaction solution is also stirred as needed.

[0046] In some embodiments, the nickel-iron raw material is added to the oxalic acid solution at 0.8-1.1 times the stoichiometric ratio, specifically 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1 times or any value between 0.8 and 1.1 times.

[0047] Among them, the utilization rate of the nickel-iron raw material and oxalic acid in the stoichiometric reaction raw material is higher, but in order to allow the elements in the nickel-iron raw material to be fully leached, oxalic acid can be slightly excessive. For example, in some embodiments, the amount of nickel-iron raw material added is 0.8-1.0 times the stoichiometric ratio. In this embodiment, the content of each component in the nickel-iron raw material can be determined first, and then the stoichiometric ratio of the reaction of the nickel-iron raw material and oxalic acid can be calculated according to the reaction formula, and then the amount of oxalic acid and the nickel-iron raw material can be determined; for example, in theory, each component in the nickel-iron raw material ag completely reacts with oxalic acid and requires oxalic acid bg, then in the leaching step, (0.8-1.1)×ag nickel-iron raw material is added to the oxalic acid solution containing bg oxalic acid to carry out the leaching reaction.

[0048] In some embodiments, the temperature of the reaction step is 50°C-100°C, specifically 50°C, 60°C, 70°C, 80°C, 90°C, 100°C or any value between 50°C and 100°C; the time is 30min-120min, specifically 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min or any value between 30min-120min.

[0049] Generally, lower temperatures are conducive to the precipitation of ferrous oxalate, and higher temperatures are conducive to the precipitation of nickel oxalate. In order to balance the residual amounts of ferrous oxalate and nickel oxalate, the reaction temperature needs to be reasonably set. In addition, the reaction temperature also affects the reaction rate of the nickel-containing iron raw material with oxalic acid, which in turn affects the precipitation efficiency. In some embodiments, the temperature of the reaction step is 70°C-80°C, and the time is 90min-120min, taking into account the precipitation effect and reaction efficiency of ferrous oxalate and nickel oxalate.

[0050] In some embodiments, the pH value of the nickel-depleted and iron-depleted liquid is 1.5-3, specifically, it can be 1.5, 1.8, 2.1, 2.4, 2.7, 3 or any value between 1.5 and 3.

[0051] Oxalic acid is used to leach nickel and iron in nickel-iron containing raw materials, and excess oxalic acid remains in the nickel-depleted and iron-depleted leachate. On the one hand, excess oxalic acid is beneficial to the full leaching of elements in the nickel-iron containing raw materials, and reduces the residual nickel and iron in the nickel-depleted and iron-depleted leachate. On the other hand, under acidic conditions, the solubility of ferrous oxalate is greatly reduced, and the presence of oxalic acid also reduces the solubility of nickel oxalate. At the same time, other elements in the nickel-iron containing raw materials, such as magnesium oxalate, are more soluble under acidic conditions. Therefore, maintaining acidic conditions in the nickel-depleted and iron-depleted liquid is more conducive to the separation of nickel and iron from other elements.

[0052] In some embodiments, the iron content in the nickel-poor iron-poor liquid is less than 0.05 g / L, and / or the nickel content in the nickel-poor iron-poor liquid is less than 0.045 g / L. The nickel and iron elements in the nickel-containing iron raw material are leached and precipitated with oxalic acid, and the residual amounts of nickel and iron in the nickel-poor iron-poor liquid are very low. In some embodiments, the iron content in the nickel-poor iron-poor liquid can reach 0.032 g / L, and the nickel content can reach 0.026 g / L.

[0053] In some embodiments, the temperature of the oxygen roasting step is 200°C-450°C, specifically 200°C, 230°C, 270°C, 300°C, 330°C, 360°C, 390°C, 420°C, 450°C or any value between 200°C and 450°C; the time is 1h-4h, specifically 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h or any value between 1h-4h.

[0054] The purpose of aerobic roasting is to fully oxidize the elements in the nickel-rich and iron-rich slag, especially to oxidize the non-magnetic nickel oxalate into magnetic nickel oxide. At this time, the non-magnetic ferrous oxalate is oxidized into non-magnetic ferric oxide, and the difference in magnetism is used to separate the nickel oxide from other components. It should be noted that in order to ensure that ferrous oxalate is oxidized into non-magnetic ferric oxide rather than magnetic ferric oxide, etc., the temperature and time of the aerobic roasting step need to be reasonably set. In some embodiments, the temperature of the aerobic roasting step is 300°C-350°C, and the time is 2h-3h, which ensures that the nickel oxalate and ferrous oxalate can be fully oxidized into nickel oxide and ferric oxide.

[0055] In some embodiments, the magnetic field strength of the magnetic separation step is 200Gs-2000Gs, specifically 200Gs, 400Gs, 600Gs, 800Gs, 1000Gs, 1200Gs, 1400Gs, 1600Gs, 1800Gs, 2000Gs or any value between 200Gs and 2000Gs; the magnetic separation time is 0.1h-1h, specifically 0.1h, 0.2h, 0.4h, 0.6h, 0.8h, 1h or any value between 0.1h-1h.

[0056] The increase in magnetic field strength is conducive to reducing the residual nickel oxide in ferric oxide, which is conducive to the complete separation of nickel oxide, but it will also cause the content of ferric oxide mixed in the separated nickel oxide to increase, resulting in excessive impurity content in nickel oxide, but the recovery rate of nickel element is relatively high, considering the purity and recovery rate of the separated nickel oxide, the magnetic field strength should not be too large, but the magnetic field strength is too small, which will also cause incomplete separation of nickel oxide, and the recovery rate is relatively low, and the magnetic separation efficiency will also be reduced, so the magnetic field strength and magnetic separation time need to be reasonably set. In some embodiments, the magnetic field strength of the magnetic separation step is 500Gs-1500Gs, and the magnetic separation time is 0.5h-1h, taking into account the purity and recovery rate of nickel oxide.

[0057] In some embodiments, the mass fraction of nickel in the nickel-containing iron raw material is 20wt%-35wt%, specifically 20wt%, 23wt%, 26wt%, 29wt%, 32wt%, 35wt% or any value between 20wt% and 35wt%; and / or the mass fraction of iron in the nickel-containing iron raw material is 60wt%-70wt%, specifically 60wt%, 62wt%, 64wt%, 66wt%, 68wt%, 70wt% or any value between 60wt% and 70wt%.

[0058] The total content of nickel and iron in nickel-containing iron raw materials such as low-grade nickel matte is about 90wt%, and the content of other impurities is relatively small. However, for some other systems with similar contents, the method disclosed in the present invention can also be applied.

[0059] In some embodiments, the particle size of the nickel-iron raw material is 60 mesh-300 mesh, specifically, it can be 60 mesh, 100 mesh, 150 mesh, 200 mesh, 250 mesh, 300 mesh or any value between 60 mesh and 300 mesh.

[0060] Crushing the nickel-iron raw material is beneficial to increase the contact area between the nickel-iron raw material and oxalic acid, which is beneficial to the leaching of elements in the nickel-iron raw material. In particular, in the present disclosure, precipitation will be generated while the nickel-iron is leached. If the particle size of the nickel-iron raw material is too large, the reaction difficulty and reaction time will be increased. If the particle size is too small, the crushing difficulty is large, the equipment requirements are high, and the energy consumption is high. In some embodiments, the particle size of the nickel-iron raw material is 200 mesh-300 mesh, which ensures the leaching effect while controlling the cost.

[0061] In some embodiments, the nickel-depleted and iron-depleted liquid is used to prepare an oxalic acid solution, and excess oxalic acid that is not combined with nickel and iron is transferred to the nickel-depleted and iron-depleted solution, which contains only a small amount of soluble impurity components. Using it for the preparation of the oxalic acid solution is beneficial to improving the utilization efficiency of raw materials and reducing raw material costs and waste liquid emissions.

[0062] In some embodiments, the mass fraction of iron in the ferric oxide is greater than 67wt%, the mass fraction of nickel is less than 0.06wt%, and the content of cobalt is less than 0.03wt%. The purity of the ferric oxide obtained after magnetic separation (assuming that the contents of ferrous oxide and ferroferric oxide are negligible, and iron exists in the form of ferric oxide) is greater than 96.6%, and can reach up to 98.9%, which can be directly used as a by-product, or further purified according to the needs.

[0063] In some embodiments, the mass fraction of iron in the nickel oxide is less than 0.04wt%, the mass fraction of nickel is greater than 77wt%, and the content of cobalt is less than 0.05wt%. The purity of the nickel oxide obtained after magnetic separation is greater than 98.25%, and can reach up to 98.7% at most. The impurity content is low, and it can be used directly, and it is also convenient to further purify according to the needs.

[0064] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0065] Example 1

[0066] A method for separating nickel and iron from a nickel-containing ferronickel raw material, such as Figure 1 As shown, the specific process is:

[0067] (1) Weighing 200-300 mesh low-grade nickel matte powder (Fe: 65.87wt%, Ni: 23.82wt%), adding the low-grade nickel matte to a 2mol / L oxalic acid solution according to a stoichiometric ratio, and then leaching and precipitating at 80°C, reacting for 2 hours, and filtering to obtain an iron-depleted and nickel-depleted solution with iron and nickel concentrations of 0.035g / L and 0.026g / L, respectively; supplementing the iron-depleted and nickel-depleted solution with acid to prepare a 2mol / L oxalic acid solution, and then repeating the leaching;

[0068] (2) calcining the solid oxalic acid precipitate obtained by filtering in step (1) at 300° C. for 3 h;

[0069] (3) The powder obtained by calcining step (2) is magnetically separated at a magnetic separation intensity of 1500 Gs for 0.5 h to obtain separated nickel oxide and ferric oxide.

[0070] Example 2

[0071] A method for separating nickel and iron from nickel-containing iron raw materials, the specific process is:

[0072] (1) Weighing and grinding 200-300 mesh low-grade nickel matte powder (Fe: 68.87wt%, Ni: 21.82wt%), adding the low-grade nickel matte to a 1.5 mol / L oxalic acid solution at 0.9 times the stoichiometric ratio, and then dissolving it at 70°C, reacting for 2 hours, and filtering to obtain an iron-depleted and nickel-depleted solution with iron and nickel concentrations of 0.032 g / L and 0.036 g / L, respectively; supplementing the iron-depleted and nickel-depleted solution with acid to prepare a 1.5 mol / L oxalic acid solution, and then repeating the leaching;

[0073] (2) calcining the solid oxalic acid precipitate obtained by filtering in step (1) at 350° C. for 3 h;

[0074] (3) The powder obtained by calcining step (2) is magnetically separated at a magnetic separation intensity of 1000 Gs for 0.5 h to obtain separated nickel oxide and ferric oxide.

[0075] Example 3

[0076] A method for separating nickel and iron from nickel-containing iron raw materials, the specific process is:

[0077] (1) Weighing and grinding 200-300 mesh low-grade nickel matte powder (Fe: 75wt%, Ni: 22.6wt%), adding the low-grade nickel matte to a 1 mol / L oxalic acid solution at 0.8 times the stoichiometric ratio, and then dissolving it at 70°C, reacting for 2 hours, and filtering to obtain an iron-depleted and nickel-depleted solution with iron and nickel concentrations of 0.045g / L and 0.041g / L, respectively; supplementing the iron-depleted and nickel-depleted solution with acid to prepare a 1 mol / L oxalic acid solution, and then repeating the leaching;

[0078] (2) calcining the solid oxalic acid precipitate obtained by filtering in step (1) at 300° C. for 3 h;

[0079] (3) The powder obtained by calcining step (2) is magnetically separated at a magnetic separation intensity of 500 Gs for 1 hour to obtain separated nickel oxide and ferric oxide.

[0080] The iron-poor nickel solution obtained in step 1 of the above embodiment 1-3 was analyzed for element content, and the results are shown in Table 1.

[0081] Table 1 Content of each element in the oxalic acid precipitated solution obtained in Examples 1-3 (g / L)

[0082] Fe g / L Ni g / L Example 1 0.035 0.026 Example 2 0.032 0.036 Example 3 0.045 0.041

[0083] From the results in Table 1, it can be seen that after low-grade nickel matte is leached and precipitated with oxalic acid, the contents of nickel, iron and cobalt in the leaching solution are very low.

[0084] The element content of the ferric oxide obtained in step 3 of the above embodiment 1-3 was analyzed, and the results are shown in Table 2:

[0085] Table 2 Element content of ferric oxide powder obtained in Examples 1-3 wt%

[0086] Fe wt% Ni wt% Co wt% Example 1 67.6 0.058 0.031 Example 2 68.26 0.039 0.015 Example 3 69.2 0.01 0.01

[0087] From the results in Table 2, it can be seen that the ferric oxide powder obtained after magnetic separation contains low nickel and cobalt content and is mainly iron, which can be further processed into iron products.

[0088] The nickel oxide obtained in step 3 of the above embodiment 1-3 was analyzed for element content, and the results are shown in the following table:

[0089] Table 3 Element content in nickel oxide powder obtained in Examples 1-3 wt%

[0090] Fe wt% Ni wt% Co wt% Example 1 0.041 77.2 0.05 Example 2 0.023 77.56 0.03 Example 3 0.01 77.45 0.01

[0091] From the results in Table 3, it can be seen that the impurity iron content in the nickel oxide powder obtained after magnetic separation is low, and it is mainly nickel element.

[0092] Example 4

[0093] A method for separating nickel and iron from nickel-containing iron raw materials, which differs from Example 1 only in that: the roasting is carried out in a nitrogen atmosphere, the roasting temperature is 500°C, and the slag phase after roasting and magnetic separation is black, which is different from the black and red mixed phase in Example 1.

[0094] Example 5

[0095] A method for separating nickel and iron from nickel-containing iron raw materials, which differs from Example 1 only in that the calcination is carried out in an argon atmosphere, the calcination temperature is 520° C., and the slag phase after calcination and magnetic separation is black.

[0096] The components of the nickel oxide powders obtained in Example 4 and Example 5 were analyzed. The results are shown in Table 4.

[0097] Table 4 Element content in nickel oxide powder obtained in Example 4-5 wt%

[0098] Fe wt% Ni wt% Co wt% Example 4 8.65 70.5 0.08 Example 5 5.32 71.3 0.06

[0099] From the results in Table 4, it can be seen that the impurity iron content in the nickel oxide powder obtained after magnetic separation under inert gas is relatively high. The main reason is that the formation of ferroferric oxide leads to incomplete magnetic separation.

[0100] Example 6

[0101] A method for separating nickel and iron from a nickel-containing iron raw material, which differs from Example 1 only in that: 1.5 mol / L of oxalic acid is used, and the reaction is carried out after 1 hour of filtration to obtain an iron-depleted and nickel-depleted solution in which the iron and nickel concentrations are 0.025 g / L and 0.046 g / L, respectively.

[0102] Example 7

[0103] A method for separating nickel and iron from a nickel-containing iron raw material, the difference from Example 1 is that the oxalic acid used is 1 mol / L, and the reaction is carried out for 4 hours before filtration to obtain an iron-poor and nickel-poor solution with iron and nickel concentrations of 0.065 g / L and 0.025 g / L, respectively.

[0104] From the comparison between Examples 6 and 7 and Example 1, the nickel-iron concentrations in the nickel-poor iron-poor liquids are all trace amounts, but their reaction times are different. The nickel oxalate concentration in Example 7 is relatively low, and its leaching + precipitation time is relatively long. The reaction time in Example 6 is shortened, and when the oxalic acid concentration in Example 1 is increased to 2 mol / L, the time is extended. This may be because the concentration is low and the reaction rate is slow, while the concentration increases, generating a large amount of precipitation hinders the leaching and precipitation of the raw materials.

[0105] Comparative Example 1

[0106] The present disclosure provides a method for separating nickel and iron from a nickel-iron alloy, comprising:

[0107] Step 1:

[0108] Take 250g of sulfuric acid to make 1L nickel-iron sulfate solution in a beaker, and add 400g of nickel-iron alloy. Under the condition of 95°C, stir continuously and react for 3h. When the pH is 2, stop the reaction. Filter to obtain a nickel-iron sulfate solution containing nickel sulfate and ferrous sulfate, and the nickel-iron alloy that has not reacted completely. Add water to the nickel-iron sulfate solution and dilute it to a volume of 2L. The nickel-iron alloy that has not reacted completely can be used as the nickel-iron alloy to be reacted and continue to repeat this step. The composition of the nickel-iron alloy and the composition of the nickel-iron sulfate solution are shown in Table 4.

[0109] Table 4 Nickel-iron alloy and nickel-iron sulfate solution composition wt%

[0110] Ni Fe Co Mn Cu Ca Mg Zn Na Cr Nickel-iron alloy 37.39 60.01 0.88 0.37 0.323 0.101 0.024 0.1174 0.052 0.027 Nickel iron sulfate solution 26.21 42.67 0.64 0.034 0.033 0.031 0.006 0.0047 0.031 0.01

[0111] Step 2:

[0112] Add the diluted nickel-iron sulfate solution in step 1 to an autoclave and heat to 100°C with continuous stirring. Oxygen is introduced to exclude the air in the reactor, and the oxygen pressure is controlled to be 0.3MPa. Subsequently, a crude nickel carbonate intermediate is continuously added to the reaction system, and the feeding rate is controlled at 1.4-1.45g / min (a total amount of 257g, which is the amount of nickel per 98% of the total iron molar amount in the mixed solution) to control the reaction pH value to not exceed 2.5. When all the crude nickel carbonate intermediates have been added, continue the reaction for 30 minutes to ensure that the reaction is completely carried out. Stop the reaction and filter to obtain a crude nickel sulfate solution and goethite slag. The components of the crude nickel carbonate intermediate and the crude nickel sulfate solution are shown in Table 5.

[0113] Table 5 Content of each element in the crude nickel sulfate solution prepared in Comparative Example 1 g / L

[0114]

[0115] In the embodiment of the invention, an oxidant ferrous oxide is added and then a nickel-cobalt intermediate is used to control the pH to remove iron from the leachate in the form of goethite. This will cause the goethite slag to be mixed with a certain amount of nickel, resulting in nickel loss, and the iron element with the largest metal content in nickel iron is not effectively utilized.

[0116] Industrial Applicability

[0117] The present invention uses oxalic acid as a leaching and precipitation agent, and while precipitating nickel and iron, most of the impurities of calcium, chromium, copper, zinc, and silicon are left in the solution, which plays a certain role in removing impurities. The precipitate is then aerobically roasted to generate ferric oxide and nickel oxide, which can be separated into nickel oxide and ferric oxide with high purity after magnetic separation, wherein the nickel oxide is used as a raw material for the production of ion batteries, and the ferric oxide can also be directly sold as a by-product. The method for separating nickel and iron from nickel-containing iron raw materials in this embodiment is simple in process, the by-product ferric oxide is easy to use, and the waste residue output is low.

Claims

1. A method for separating nickel and iron from a nickel-containing ferronickel raw material, characterized in that: include: The nickel-iron raw material is mixed with the oxalic acid solution and reacted and solid-liquid separated to obtain nickel-rich and iron-rich slag and nickel-poor and iron-poor liquid; The nickel-iron raw material includes at least one of low-matte nickel and nickel-iron alloy; the initial concentration of the oxalic acid solution is 1 mol / L-4 mol / L; the temperature of the reaction step is 50° C.-100° C., and the time is 30 min-120 min; The nickel-rich and iron-rich slag is subjected to oxygen roasting and magnetic separation in sequence to obtain nickel oxide and ferric oxide. The temperature of the oxygen roasting step is 200° C.-450° C., and the time is 1 h-4 h.

2. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: The initial concentration of the oxalic acid solution is 1 mol / L-2 mol / L.

3. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: Add nickel-iron raw materials into the oxalic acid solution at 0.8-1.1 times the stoichiometric ratio and mix.

4. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: The temperature of the reaction step is 70°C-80°C, and the time is 90min-120min.

5. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: The pH value of the nickel-poor and iron-poor liquid is 1.5-3.

6. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: The iron content in the nickel-depleted iron-depleted liquid is less than 0.05 g / L, and / or the nickel content in the nickel-depleted iron-depleted liquid is less than 0.045 g / L.

7. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: The temperature of the oxygen roasting step is 300° C.-350° C., and the time is 2 h-3 h.

8. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: The magnetic field strength of the magnetic separation step is 200Gs-2000Gs, and the magnetic separation time is 0.1h-1h.

9. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: The magnetic field strength of the magnetic separation step is 500Gs-1500Gs, and the magnetic separation time is 0.5h-1h.

10. The method for separating nickel and iron from nickel-containing ferronickel raw materials according to claim 1, characterized in that: The mass fraction of nickel in the nickel-containing iron raw material is 20wt%-35wt%, and / or the mass fraction of iron in the nickel-containing iron raw material is 60wt%-70wt%.

11. The method for separating nickel and iron from nickel-containing ferronickel raw materials according to claim 1, characterized in that: The particle size of the nickel-iron raw material is 60 meshes to 300 meshes.

12. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: The particle size of the nickel-iron raw material is 200 meshes to 300 meshes.

13. The method for separating nickel and iron from nickel-containing ferronickel raw materials according to claim 1, characterized in that: The nickel-poor iron-poor liquid is used to prepare oxalic acid solution.

14. The method for separating nickel and iron from a nickel-containing ferronickel raw material according to claim 1, characterized in that: The mass fraction of iron in the ferric oxide is greater than 67wt%, the mass fraction of nickel is less than 0.06wt%, and the content of cobalt is less than 0.03wt%.

15. The method for separating nickel and iron from nickel-containing ferronickel raw materials according to claim 1, characterized in that: The nickel oxide has an iron content of less than 0.04 wt%, a nickel content of more than 77 wt%, and a cobalt content of less than 0.05 wt%.

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