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

Abstract

A method for separating nickel and iron from a ferronickel-containing raw material, comprising: using oxalic acid as a leaching agent and a precipitating agent, leaving most of impurities such as calcium, chromium, copper, zinc, and silicon in a solution while precipitating nickel and iron, so as to achieve a certain impurity removal effect; then performing aerobic roasting on precipitates to produce ferric oxide and nickel oxide; and performing magnetic separation to obtain nickel oxide and ferric oxide with high purity, wherein the nickel oxide is used as a raw material for ion battery production, and the ferric oxide, as a by-product, can also be directly sold. The method has the advantages of a simple process, convenient utilization of the by-product ferric oxide, and a low yield of waste residues.

Description

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

[0002] Nickel metal is an important element of ternary lithium batteries. As the market's demand for lithium battery capacity becomes increasingly 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 abundant nickel resources. Taking the utilization of low-grade nickel matte as an example, compared with the extraction of nickel from low-grade nickel matte by pyrometallurgy, the extraction of nickel by hydrometallurgy 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 low-grade nickel matte wet leaching solution generally adopts the method of first removing iron impurities and then treating the nickel elements in the solution. Common iron removal methods include the goethite method, the hematite method, and the sodium ferroalloy precipitation method. Although these methods can effectively remove iron elements from the solution, they all require the oxidation of ferrous iron to trivalent iron before removal. In addition, the sodium ferroalloy precipitation method produces a large amount of slag with a low iron content and introduces impurity sodium ions, making it difficult to directly utilize. The goethite method is only suitable for working conditions with iron concentrations below 2g / L, and the filterability of the iron removal precipitate is poor, which is easily mixed with nickel precipitates, resulting in nickel loss. The hematite method has a high operating temperature and high capital expenditure.

[0004] In view of this, there is an urgent need for a low-matte nickel utilization method with simple process, convenient by-product utilization and low waste slag production.

[0005] Summary of the Invention

[0006] 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 production.

[0007] The present disclosure is achieved as follows:

[0008] In a first aspect, the present disclosure provides a method for separating nickel and iron from a nickel-containing ferronickel raw material, comprising:

[0009] The nickel-containing 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;

[0010] The nickel-rich and iron-rich slag is subjected to oxygen roasting and magnetic separation in sequence to obtain nickel oxide and ferric oxide.

[0011] In an optional embodiment, the nickel-iron-containing raw material includes at least one of low-grade nickel matte and nickel-iron alloy.

[0012] In an optional embodiment, the initial concentration of the oxalic acid solution is 1 mol / L-4 mol / L.

[0013] In an optional embodiment, the initial concentration of the oxalic acid solution is 1 mol / L-2 mol / L.

[0014] In an optional embodiment, the nickel-containing iron raw material is added to the oxalic acid solution at a stoichiometric ratio of 0.8-1.1 times.

[0015] In an optional embodiment, the temperature of the reaction step is 50°C-100°C, and the time is 30min-120min.

[0016] In an optional embodiment, the temperature of the reaction step is 70°C-80°C, and the time is 90min-120min.

[0017] In an optional embodiment, the pH of the nickel-poor iron-poor liquid is 1.5-3.

[0018] 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.

[0019] In an optional embodiment, the temperature of the oxygen calcination step is 200° C.-450° C., and the time is 1 hour-4 hours.

[0020] In an optional embodiment, the temperature of the oxygen roasting step is 300° C.-350° C., and the time is 2 h-3 h.

[0021] 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.

[0022] 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.

[0023] In an optional embodiment, the mass fraction of nickel in the nickel-containing ferro-raw material is 20 wt%-35 wt%, and / or the mass fraction of iron in the nickel-containing ferro-raw material is 60 wt%-70 wt%.

[0024] In an optional embodiment, the particle size of the nickel-ferro raw material is 60 mesh-300 mesh.

[0025] In an optional embodiment, the particle size of the nickel-ferro raw material is 200 mesh to 300 mesh.

[0026] In an optional embodiment, the nickel-poor iron-poor liquid is used to prepare oxalic acid solution.

[0027] In an optional embodiment, the mass fraction of iron in the ferric oxide is greater than 67 wt%, the mass fraction of nickel is less than 0.06 wt%, and the content of cobalt is less than 0.03 wt%.

[0028] In an optional embodiment, the mass fraction of iron in the nickel oxide is less than 0.04 wt%, the mass fraction of nickel is greater than 77 wt%, and the content of cobalt is less than 0.05 wt%.

[0029] The present disclosure has the following beneficial effects:

[0030] The present invention utilizes oxalic acid as a leaching and precipitation agent, precipitating nickel and iron while leaving most of the impurities, such as calcium, chromium, copper, zinc, and silicon, in solution, thus achieving a certain degree of impurity removal. The precipitate is then subjected to oxygen roasting to produce ferric oxide and nickel oxide. After magnetic separation, the nickel oxide and ferric oxide can be separated to obtain high-purity nickel oxide and ferric oxide. The nickel oxide is used as a raw material for ion battery production, and the ferric oxide, as a byproduct, can also be sold directly. The method for separating nickel and iron from nickel-iron-containing raw materials disclosed in the present invention is simple in process, the byproduct ferric oxide is easily usable, and the waste residue output is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0032] FIG1 is a process flow chart of an embodiment of the present disclosure. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0034] This embodiment provides a method for separating nickel and iron from a nickel-containing ferronickel raw material, comprising:

[0035] The nickel-containing 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;

[0036] The nickel-rich and iron-rich slag is subjected to oxygen roasting and magnetic separation in sequence to obtain nickel oxide and ferric oxide.

[0037] In this embodiment, the reactions of formula (1) to formula (3) mainly occur, wherein the nickel-containing iron raw material reacts with oxalic acid to react as shown in formula (1), and during oxygen roasting, reactions as shown in formula (2) and formula (3) occur. 2+ +Fe 2+ +2C2O4 2- +4H2O=NiC2O4·2H2O↓+FeC2O4·2H2O↓ (1) NiC2O4·H2O=NiO+2CO2+H2O (2) 2FeC2O4·2H2O=Fe2O3+4CO2+H2O (3)

[0038] In this embodiment, the oxalic acid solution is acidic and can be leached with nickel and iron in the nickel-containing iron raw material to simultaneously generate nickel oxalate and ferrous oxalate precipitates, thereby precipitating the nickel and iron elements. At the same time, impurity elements in the nickel-containing iron raw material, such as calcium, chromium, copper, zinc, and silicon, react with oxalic acid to generate soluble components that are transferred to the nickel-depleted and iron-depleted liquid. Some impurity elements, such as carbon and sulfur, react with oxalic acid to generate gas. Only a few elements, such as Co, will generate precipitates that affect the composition of the precipitate. The resulting precipitate has a high content of nickel oxalate and ferrous oxalate, which facilitates the subsequent separation of nickel and iron.

[0039] The precipitated nickel oxalate and ferrous oxalate are calcined in an oxygen atmosphere to obtain nickel oxide and ferrous oxide. Nickel oxide is magnetic, while ferrous oxide is non-magnetic. After magnetic separation, the nickel oxide and ferrous oxide can be effectively separated. The atmosphere in the oxygen calcination step can be an oxygen atmosphere or another oxygen-containing atmosphere, such as air or a mixture of oxygen and nitrogen.

[0040] This embodiment uses oxalic acid as a leaching and precipitation agent. While precipitating nickel and iron, most of the impurities such as calcium, chromium, copper, zinc, and silicon remain in the solution, which plays a certain role in removing impurities. The precipitate is then subjected to oxygen roasting to produce ferric oxide and nickel oxide. After magnetic separation, high-purity nickel oxide and ferric oxide can be separated. The nickel oxide is used as a raw material for ion battery production, and the ferric oxide, as a byproduct, can also be sold directly. The method for separating nickel and iron from nickel-containing iron raw materials in this embodiment is simple, the byproduct ferric oxide is easy to utilize, and the waste residue output is low.

[0041] 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.

[0042] 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.

[0043] Normally, oxalic acid concentration is high, and the reaction rate of oxalic acid and the element in nickel-containing ferronickel raw material is relatively faster, but in the present embodiment, because nickel and iron are leached, nickel oxalate and ferrous oxalate precipitation can be generated with oxalate radical, if oxalic acid concentration is too high, the rate of precipitation generation is too fast, the precipitation generated may be wrapped in the surface of nickel-containing ferronickel raw material particles, not only can not improve precipitation rate, but may reduce oxalic acid and the contact area of ​​the internal element of nickel-containing ferronickel raw material particles, and then can suppress the leaching of elements such as ferronickel, 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 leaching precipitation effect, maintains higher reaction rate. In order to improve reaction rate, in some embodiments, reaction solution is also stirred as needed.

[0044] In some embodiments, the nickel-iron raw material is added to the oxalic acid solution at a stoichiometric ratio of 0.8-1.1 times, specifically 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1 times or any value between 0.8-1.1 times.

[0045] Among them, the utilization rate of nickel-containing iron raw material and oxalic acid according to the stoichiometric ratio reaction raw material is higher, but in order to make the elements in nickel-containing iron raw material can be fully leached, oxalic acid can be slightly excessive. For example, in some embodiments, the addition amount of nickel-containing iron raw material is 0.8-1.0 times of the stoichiometric ratio. In this embodiment, the content of each component in nickel-containing iron raw material can be determined first, and then the stoichiometric ratio of the reaction of nickel-containing iron raw material and oxalic acid is calculated according to the reaction formula, and then the amount of oxalic acid and nickel-containing iron raw material is determined; For example, in theory, each component in ag nickel-containing iron raw material is completely reacted with oxalic acid and needs oxalic acid bg, then in the leaching step, (0.8-1.1) × ag nickel-containing iron raw material is added to the oxalic acid solution containing bg oxalic acid, and leaching reaction is carried out.

[0046] 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.

[0047] Under normal circumstances, 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, it is necessary to reasonably set the reaction temperature. In addition, the reaction temperature also affects the reaction speed of nickel-containing ferro-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.

[0048] In some embodiments, the pH value of the nickel-depleted and iron-depleted liquid is 1.5-3, specifically 1.5, 1.8, 2.1, 2.4, 2.7, 3 or any value between 1.5 and 3.

[0049] Oxalic acid is used to leach nickel and iron from nickel-containing iron 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-containing iron raw materials, reducing 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-containing iron 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.

[0050] In some embodiments, the nickel-depleted iron-depleted liquid has an iron content of less than 0.05 g / L, and / or the nickel content of the nickel-depleted iron-depleted liquid is less than 0.045 g / L. Oxalic acid is used to leach and precipitate the nickel and iron elements in the nickel-containing ferro-raw material, resulting in a nickel-depleted iron-depleted liquid having very low residual nickel and iron. In some embodiments, the nickel-depleted iron-depleted liquid can have an iron content of up to 0.032 g / L and a nickel content of up to 0.026 g / L.

[0051] 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.

[0052] 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.

[0053] 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-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.

[0054] The rise of magnetic field intensity is conducive to reducing the residual of nickel oxide in ferric oxide, is conducive to the complete separation of nickel oxide, but also can cause the content of ferric oxide mixed in the isolated nickel oxide to increase, cause obtaining nickel oxide in impurity content too high, but the recovery rate of nickel element is relatively high, consider the purity and recovery rate of the isolated nickel oxide, magnetic field intensity should not be too large, but magnetic field intensity is too small, also can cause nickel oxide to be separated incompletely, recovery rate is relatively low, and also can reduce magnetic separation efficiency, therefore magnetic field intensity and magnetic separation time need to be reasonably arranged. In some embodiments, the magnetic field intensity of the magnetic separation step is 500Gs-1500Gs, and magnetic separation time is 0.5h-1h, takes into account the purity and recovery rate of nickel oxide.

[0055] 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%.

[0056] 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, the method disclosed in this disclosure can also be applied to some other systems with similar content.

[0057] In some embodiments, the particle size of the nickel-iron raw material is 60 mesh-300 mesh, specifically 60 mesh, 100 mesh, 150 mesh, 200 mesh, 250 mesh, 300 mesh or any value between 60 mesh and 300 mesh.

[0058] Crushing the nickel-containing ferronickel raw material is beneficial to increasing the contact area between the nickel-containing ferronickel raw material and oxalic acid, which is beneficial to the leaching of elements in the nickel-containing ferronickel raw material. In particular, in the present disclosure, a precipitate is generated while the nickel-containing ferronickel is leached. If the particle size of the nickel-containing ferronickel 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-containing ferronickel raw material is 200 mesh to 300 mesh, which ensures the leaching effect while controlling the cost.

[0059] 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 to prepare the oxalic acid solution is beneficial to improving the utilization efficiency of raw materials, reducing raw material costs and waste liquid emissions.

[0060] In some embodiments, the iron content of the ferric oxide is greater than 67 wt %, the nickel content is less than 0.06 wt %, and the cobalt content is less than 0.03 wt %. The purity of the ferric oxide obtained after magnetic separation (assuming that the contents of ferrous oxide and ferroferric oxide are negligible and all iron exists in the form of ferric oxide) is greater than 96.6%, and can reach a maximum of 98.9%. It can be directly used as a by-product or further purified as needed.

[0061] In some embodiments, the nickel oxide has an iron content of less than 0.04% by weight, a nickel content of greater than 77% by weight, and a cobalt content of less than 0.05% by weight. The nickel oxide obtained after magnetic separation has a purity greater than 98.25%, and can reach a maximum of 98.7%. The low impurity content allows for direct use and facilitates further purification as needed.

[0062] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0063] Example 1

[0064] A method for separating nickel and iron from nickel-containing ferronickel raw materials, as shown in FIG1 , includes the following steps:

[0065] (1) Weighing 200-300 mesh low-grade nickel matte powder (Fe: 65.87 wt%, Ni: 23.82 wt%), adding the low-grade nickel matte to a 2 mol / L oxalic acid solution in a stoichiometric ratio, and then leaching and precipitating at 80°C. After reacting for 2 hours, filtering to obtain an iron-depleted and nickel-depleted solution with iron and nickel concentrations of 0.035 g / L and 0.026 g / L, respectively; the iron-depleted and nickel-depleted solution is supplemented with acid to prepare a 2 mol / L oxalic acid solution and then leaching is repeated;

[0066] (2) calcining the solid oxalic acid precipitate obtained by filtering in step (1) at 300° C. for 3 h;

[0067] (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.

[0068] Example 2

[0069] A method for separating nickel and iron from nickel-containing ferronickel raw materials, the specific process is as follows:

[0070] (1) Weighing and grinding 200-300 mesh low-grade nickel matte powder (Fe: 68.87 wt%, Ni: 21.82 wt%), 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. After reacting for 2 hours, 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; the iron-depleted and nickel-depleted solution was supplemented with acid to prepare a 1.5 mol / L oxalic acid solution, and then leaching was repeated;

[0071] (2) calcining the solid oxalic acid precipitate obtained by filtering in step (1) at 350° C. for 3 h;

[0072] (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.

[0073] Example 3

[0074] A method for separating nickel and iron from nickel-containing ferronickel raw materials, the specific process is as follows:

[0075] (1) Weighing ground 200-300 mesh nickel matte powder (Fe: 75wt%, Ni: 22.6wt%), adding the nickel matte to a 1 mol / L oxalic acid solution at 0.8 times the stoichiometric ratio, and then dissolving it at 70°C. After reacting for 2 hours, filtering to obtain an iron-depleted and nickel-depleted solution with iron and nickel concentrations of 0.045g / L and 0.041g / L, respectively; the iron-depleted and nickel-depleted solution was supplemented with acid to prepare a 1 mol / L oxalic acid solution, and then leaching was repeated;

[0076] (2) calcining the solid oxalic acid precipitate obtained by filtering in step (1) at 300° C. for 3 h;

[0077] (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.

[0078] The iron-poor nickel-poor solution obtained in step 1 of the above Examples 1-3 was analyzed for element content. The results are shown in Table 1.

[0079] Table 1 Content of each element in the oxalic acid precipitated solution obtained in Examples 1-3 (g / L)

[0080] From the results in Table 1, we can see that after the 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.

[0081] The element content of the ferric oxide obtained in step 3 of the above embodiment 1-3 was analyzed. The results are shown in Table 2:

[0082] Table 2 Element contents in the ferric oxide powder obtained in Examples 1-3 (wt%)

[0083] From the results in Table 2, we can see 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.

[0084] The nickel oxide obtained in step 3 of the above examples 1-3 was analyzed for element content. The results are shown in the following table:

[0085] Table 3 Element contents (wt%) of nickel oxide powders obtained in Examples 1-3

[0086] From the results in Table 3, it can be seen that the nickel oxide powder obtained after magnetic separation has a low content of impurity iron and is mainly nickel.

[0087] Example 4

[0088] 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.

[0089] Example 5

[0090] 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 an argon atmosphere, the roasting temperature is 520°C, and the slag phase after roasting and magnetic separation is black.

[0091] The components of the nickel oxide powders obtained in Examples 4 and 5 were analyzed, and the results are shown in Table 4.

[0092] Table 4 Element contents (wt%) of nickel oxide powders obtained in Examples 4-5

[0093] From the results in Table 4, it can be seen that the nickel oxide powder obtained after magnetic separation under inert gas has a high content of impurity iron. The main reason is that the formation of ferroferric oxide leads to incomplete magnetic separation.

[0094] Example 6

[0095] 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 after reacting for 1 hour, filtration is performed to obtain an iron-depleted and nickel-depleted solution with iron and nickel concentrations of 0.025 g / L and 0.046 g / L, respectively.

[0096] Example 7

[0097] A method for separating nickel and iron from a nickel-containing iron raw material, which differs from Example 1 only in that: 1 mol / L oxalic acid is used, and after reacting for 4 hours, filtration is performed to obtain an iron-depleted and nickel-depleted solution with iron and nickel concentrations of 0.065 g / L and 0.025 g / L, respectively.

[0098] Comparing Examples 6 and 7 with Example 1, the nickel-iron concentrations in the nickel-depleted and iron-depleted solutions are all trace, while their reaction times differ. The nickel oxalate concentration in Example 7 is relatively low, resulting in a relatively long leaching and precipitation time. The reaction time in Example 6 is somewhat shortened, while the reaction time in Example 1 is prolonged when the oxalic acid concentration is increased to 2 mol / L. This may be because the reaction rate is slow at low concentrations, while increasing the concentration generates a large amount of precipitate, which hinders the leaching and precipitation of the raw materials.

[0099] Comparative Example 1

[0100] The present disclosure provides a method for separating nickel and iron from a nickel-iron alloy, comprising:

[0101] Step 1:

[0102] Take 250g of sulfuric acid to make 1L nickel-iron sulfate solution in a beaker, and add 400g of nickel-iron alloy thereto. Under the condition of 95℃, stir continuously and react for 3h. When the pH is 2, stop the reaction. Filter to obtain the 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.

[0103] Table 4 Nickel-iron alloy and nickel-iron sulfate solution composition wt%

[0104] Step 2:

[0105] The diluted nickel iron sulfate solution in step 1 is added to an autoclave and heated to 100°C with continuous stirring. Oxygen is introduced to exclude the air in the reactor and the oxygen pressure is controlled to 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 based on the total iron molar amount in 98% of the mixed solution) to control the reaction pH value to be no more than 2.5. After all the crude nickel carbonate intermediates have been added, the reaction is continued for 30min to ensure that the reaction is completely carried out. The reaction is stopped and filtered to obtain a crude nickel sulfate solution and goethite slag. The compositions of the crude nickel carbonate intermediate and the crude nickel sulfate solution are shown in Table 5.

[0106] Table 5 Content of each element in the crude nickel sulfate solution prepared in Comparative Example 1 g / L

[0107] In the embodiment of the invention, an oxidizing agent, 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. Industrial Applicability

[0108] The present invention utilizes oxalic acid as a leaching and precipitation agent, and while precipitating nickel and iron, most of the impurities such as calcium, chromium, copper, zinc, and silicon remain in the solution, playing a certain role in removing impurities. The precipitate is then subjected to oxygen roasting to produce ferric oxide and nickel oxide. After magnetic separation, nickel oxide and ferric oxide of higher purity can be separated. The nickel oxide is used as a raw material for the production of ion batteries, and the ferric oxide as a byproduct can also be directly sold. The method for separating nickel and iron from nickel-containing iron raw materials in this embodiment is simple in process, the byproduct ferric oxide is easy to utilize, and the waste residue output is low.

Claims

1. A method for separating nickel and iron from nickel - containing iron raw materials, characterized in that, it includes: Mixing the nickel - containing iron raw materials with an oxalic acid solution, reacting and performing solid - liquid separation to obtain a nickel - rich and iron - rich slag and a nickel - poor and iron - poor liquid; Performing aerobic roasting and magnetic separation on the nickel - rich and iron - rich slag in sequence to obtain nickel oxide and iron(III) oxide.

2. The method for separating nickel and iron from nickel - containing iron raw materials according to claim 1, characterized in that, the nickel - containing iron raw materials include at least one of matte nickel and nickel - iron alloy.

3. The method for separating nickel and iron from nickel - containing iron raw materials according to claim 1 or 2, characterized in that, the initial concentration of the oxalic acid solution is 1 mol / L - 4 mol / L.

4. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 3, characterized in that, the initial concentration of the oxalic acid solution is 1 mol / L - 2 mol / L.

5. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 4, characterized in that, adding the nickel - containing iron raw materials to the oxalic acid solution for mixing according to 0.8 - 1.1 times of the stoichiometric ratio.

6. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 5, characterized in that, the temperature of the reaction step is 50°C - 100°C, and the time is 30 min - 120 min.

7. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 6, characterized in that, the temperature of the reaction step is 70°C - 80°C, and the time is 90 min - 120 min.

8. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 7, characterized in that, the pH of the nickel - poor and iron - poor liquid is 1.5 - 3.

9. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 8, characterized in that, the iron content in the nickel - poor and iron - poor liquid is less than 0.05 g / L, and / or the nickel content in the nickel - poor and iron - poor liquid is less than 0.045 g / L.

10. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 9, characterized in that, the temperature of the aerobic roasting step is 200°C - 450°C, and the time is 1 h - 4 h.

11. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 10, characterized in that, the temperature of the aerobic roasting step is 300°C - 350°C, and the time is 2 h - 3 h.

12. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 11, characterized in that, the magnetic field intensity of the magnetic separation step is 200 Gs - 2000 Gs, and the magnetic separation time is 0.1 h - 1 h.

13. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 12, characterized in that, the magnetic field intensity of the magnetic separation step is 500 Gs - 1500 Gs, and the magnetic separation time is 0.5 h - 1 h.

14. The method for separating nickel and iron from nickel - containing iron raw materials according to any one of claims 1 - 13, 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%.

15. The method for separating nickel and iron from a nickel-containing iron raw material according to any one of claims 1-14, characterized in that, the particle size of the nickel-containing iron raw material is 60 mesh - 300 mesh.

16. The method for separating nickel and iron from a nickel-containing iron raw material according to any one of claims 1-15, characterized in that, the particle size of the nickel-containing iron raw material is 200 mesh - 300 mesh.

17. The method for separating nickel and iron from a nickel-containing iron raw material according to any one of claims 1-16, characterized in that, the nickel- and iron-depleted liquid is used to prepare an oxalic acid solution.

18. The method for separating nickel and iron from a nickel-containing iron raw material according to any one of claims 1-17, characterized in that, the mass fraction of iron element in the iron(III) oxide is greater than 67wt%, the mass fraction of nickel element is less than 0.06wt%, and the cobalt element content is less than 0.03wt%.

19. The method for separating nickel and iron from a nickel-containing iron raw material according to any one of claims 1-18, characterized in that, the mass fraction of iron element in the nickel oxide is less than 0.04wt%, the mass fraction of nickel element is greater than 77wt%, and the cobalt element content is less than 0.05wt%.

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