Iron removal process and its application

Abstract

This invention discloses an iron removal process and its application, belonging to the field of non-ferrous metal hydrometallurgy. This process removes Fe from iron-containing solutions. 3+ Reduced to Fe 2+ A reduced iron-containing solution was obtained; after adjusting the pH of the reduced iron-containing solution, an oxidant was added to maintain the Fe content. 3+ The concentration of the ferrous sulfate is 2.0–8.2 g / L. Sulfate is then added to carry out the pyrite removal reaction. After solid-liquid separation, pyrite slag and the first iron-removed liquid are obtained. This method can control the formation rate of the pyrite slag, which is beneficial to reducing the loss rate of valuable metals. This invention further combines the goethite method and hydrothermal method for iron removal, resulting in high iron removal efficiency and low loss rate of valuable metals.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgy of non-ferrous metals, specifically to an iron removal process and its application. Background Technology

[0002] Currently, there are many methods for removing iron in rare earth hydrometallurgy, mainly including neutralization hydrolysis, pyrite process, goethite process, and hematite process.

[0003] Among these methods, the iron content in the liquid after iron removal using the pyrite or goethite process does not meet the requirements for deep iron removal, increasing the cost of subsequent recovery of valuable metals; the hematite process requires high temperature and pressure conditions, and the equipment is expensive and maintenance costs are high, making it difficult to achieve industrial production; the simple use of hydrolysis will result in a high content of other metal ions in the slag, which cannot achieve effective recovery of valuable metals; the neutralization hydrolysis method will generate Fe(OH)3 colloidal precipitate, which will lead to filtration difficulties, and the precipitate will contain a high content of valuable metals, which cannot achieve effective recovery of valuable metals.

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

[0005] The purpose of this invention is to provide an iron removal process and its application, and to provide a recycling process with high iron removal rate and low loss rate of valuable metals.

[0006] To achieve the above objectives, the present invention provides an iron removal process in a first aspect, comprising:

[0007] Fe in iron-containing solution 3+ Reduced to Fe by a reducing agent 2+ A reduced iron-containing solution was obtained;

[0008] After adjusting the pH of the reduced iron-containing solution, an oxidant is added to maintain Fe. 3+ The concentration of the solution is 2.0-8.2 g / L. Sulfate is then added to carry out the iron removal reaction of ferrous sulfate. After solid-liquid separation, ferrous sulfate residue and the first iron removal liquid are obtained.

[0009] In some embodiments, the reducing agent includes at least one of SO2, sodium sulfite, ammonium sulfite, and iron powder;

[0010] And / or, adjust the pH of the reduced iron-containing solution to 1.0-1.5;

[0011] And / or, the oxidant includes at least one of H2O2, sodium hypochlorite, potassium permanganate, and sodium chlorate;

[0012] And / or, the sulfate includes at least one of sodium sulfate, ammonium sulfate, and potassium sulfate.

[0013] In some embodiments, the iron removal reaction of the ferrous sulfate process is carried out at a temperature of 75-105°C, and a neutralizing agent is added to maintain the pH of the reaction solution at 1.0-2.5.

[0014] In some embodiments, the first iron-removed liquid is subjected to goethite removal to obtain a second iron-removed liquid and goethite.

[0015] After removing iron from the second iron-removed liquid, a pure liquid and goethite are obtained by removing iron through a hydrothermal method.

[0016] In some embodiments, the goethite iron removal process includes adding the first iron-removed liquid to an acidic solution with a pH of 2.0-3.5 to reduce Fe... 3+ The concentration of the reagent is 1.0-2.0 g / L, and a neutralizing agent is added to maintain the pH of the solution at 2.0-3.5 during the reaction process, and the reaction temperature is maintained at 50-70℃.

[0017] In some embodiments, the hydrothermal iron removal method includes adding an alkali to the second iron-removed liquid to carry out a precipitation reaction, then adding an acid to adjust the pH of the reaction solution to 3.0-4.0 and carrying out a hydrothermal reaction, followed by solid-liquid separation to obtain the goethite and the pure liquid; wherein the hydrothermal reaction temperature is 100-200℃ and the pressure is 0.1-10MPa.

[0018] In some embodiments, the iron alum slag is roasted, washed with water, dried, ground, and sieved to obtain iron oxide powder.

[0019] In some embodiments, the calcination temperature is 450-550℃, and the calcination time is 2-3 hours;

[0020] The water washing includes a primary water washing and a secondary water washing; the primary water washing has a solid-liquid mass ratio of 2-4:1, a temperature of 60-70℃, and a stirring time of 1-2 hours; the secondary water washing has a solid-liquid mass ratio of 3-5:1, a temperature of 50-70℃, and a stirring time of 0.5-1.2 hours.

[0021] In some embodiments, the neutralizing agent is at least one selected from sodium carbonate, ammonium carbonate, potassium carbonate, ammonium bicarbonate, and sodium bicarbonate.

[0022] The second aspect of the present invention also provides the application of the iron removal process of the first aspect in the recycling of waste lithium-ion batteries.

[0023] The beneficial effects of this invention include:

[0024] This invention provides an iron removal process and its application, wherein the iron removal process removes Fe from an iron-containing solution. 3+ Reduced to Fe 2 + Then, by controlling the degree of oxidation, Fe3+ Maintaining the concentration of iron ore at an appropriate level controls the formation rate of ferrous sulfate slag, which is beneficial for improving the purity of the slag and reducing the loss rate of valuable metals. This invention further combines the goethite method and the hydrothermal method for iron removal, further improving the iron removal rate while also reducing the loss of valuable metals. Specifically, the ferrous sulfate method does not introduce new impurities during iron removal, reducing the difficulty and cost of subsequent impurity removal and improving overall recovery efficiency; furthermore, the goethite method reduces the Fe content in the liquid after the second iron removal process. 3+ The concentration of Fe in the purified solution was reduced by hydrothermal iron removal, and the resulting goethite had a crystalline structure and good filtration performance. 3+ Concentration. Meanwhile, iron oxide slag is processed through roasting and washing to obtain iron oxide powder, improving iron utilization and increasing economic benefits. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The process flow diagram is provided for the iron removal process in the embodiments of the present invention. Detailed Implementation

[0027] The following detailed description, with appropriate reference to the accompanying drawings, discloses a process and application for removing iron according to the present invention. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0028] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Specifically, "(", ")", "[", and "]" represent intervals, where "(" or ")" represents an open interval, meaning the endpoints of the interval are not included; and "[" and "]" represent a closed interval, meaning the endpoints of the interval are included. A range defined in this way can include endpoints or not, and can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range.

[0029] Specifically, for example, if the ranges 60-120 and 80-110 are listed for a specific parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Furthermore, if the minimum range values ​​are listed as 1 and 2, and if the maximum range values ​​are listed as 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range “ab” represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range “0-5” means that all real numbers between “0-5” have been listed herein, and “0-5” is merely a shortened representation of these numerical combinations. Additionally, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. If (10, 20) is listed, it is understood as any value in the interval 10-20 excluding 10 and 20; (10, 20] is understood as any value in the interval 10-20 excluding 10 but including 20.

[0030] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0031] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0032] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0033] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0034] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0035] The first aspect of this invention provides an iron removal process, comprising:

[0036] Fe in iron-containing solution 3+ Reduced to Fe by a reducing agent 2+ A reduced iron-containing solution was obtained;

[0037] After adjusting the pH of the reduced iron-containing solution, the rate at which the oxidant is added to the reduced iron-containing solution is controlled to maintain Fe 3+ The concentration of the ferrous sulfate was 2.0-8.2 g / L, and sulfate was added to carry out the iron removal reaction of ferrous sulfate. After solid-liquid separation, ferrous sulfate residue and the first iron removal liquid were obtained.

[0038] In some embodiments, the reducing agent includes at least one selected from SO2, sodium sulfite, ammonium sulfite, and iron powder. All ferric iron in the solution is reduced to ferrous iron, and the amount of Fe in the iron removal reaction of the ferrous sulfate process is further controlled by adjusting the amount of oxidant introduced. 3+ The concentration was 2.0-8.2 g / L, Fe 3+ When the concentration of Fe is too high, some of the ferric iron forms ferric hydroxide precipitate, which adsorbs valuable metals from the solution; 3+ The concentration of Fe is too low, reducing the formation rate of iron ore slag. The selected reducing agent will not introduce new impurity ions into the solution. This invention controls the Fe content by completely reducing the iron ions and then controlling the degree of oxidation. 3+ The concentration of the slag can control the sedimentation rate of iron ore slag and reduce the loss rate of valuable metals.

[0039] In some embodiments, the oxidant is added after adjusting the pH of the reduced iron-containing solution to 1.0-1.5. If the pH of the solution before oxidation is too low, the alum formation rate will be slowed down, the reaction time will be too long, and the iron removal efficiency will be low. If the pH of the solution before oxidation is too high, a large amount of colloidal ferric hydroxide will be generated, which will adsorb more valuable metals, affecting the purity of the iron alum and causing the loss of valuable metals.

[0040] In some embodiments, the oxidant includes at least one selected from H₂O₂, sodium hypochlorite, potassium permanganate, and sodium chlorate. Specifically, when the oxidant is H₂O₂, the flow rate of H₂O₂ added is 0.6-2.5 mL / min, so that the Fe in the iron removal reaction of the ferrous sulfate process is reduced. 3+ The concentration is 2.0-8.2 g / L. Adding at too high a flow rate will cause Fe...3+ Too high a concentration or too low a flow rate will cause Fe to... 3 + If the concentration is too low, it will affect the iron removal effect.

[0041] In some embodiments, the sulfate includes at least one of sodium sulfate, potassium sulfate, and ammonium sulfate. If there are insufficient alkali metal cations or ammonium ions in the solution, then Fe... 3+ It may react with hydrogen ions or hydrated hydrogen ions (H3O) + The formation of ferrous sulfate has poor sedimentation, filtration, and washing properties, and also results in a high residual iron content in the solution.

[0042] In some embodiments, during the iron removal process using the ferrous sulfate method, the concentration of alkali metal cations or ammonium ions in the reaction is maintained at 3-7 g / L.

[0043] In some embodiments, the first iron-removed liquid is subjected to goethite removal to obtain a second iron-removed liquid and goethite.

[0044] After removing iron from the second iron-removed liquid, a pure liquid and goethite are obtained by removing iron through a hydrothermal method.

[0045] This invention employs a combination of three methods to remove iron from iron-containing solutions. The resulting second iron-removed solution exhibits a significantly reduced iron content. The iron-containing slag obtained from the three methods has high purity and can be reused through simple post-processing. The reason for using the pyrite method—goethite method—hydrothermal method in this invention is due to the high Fe content... 3+ In iron-containing solutions with high iron concentrations, direct use of the goethite process for iron removal will form a large amount of ferric hydroxide colloid, which adsorbs a significant amount of valuable metals, resulting in the loss of valuable metals. However, if the Fe concentration in the reaction solution is reduced... 3+ Concentration leads to low iron removal efficiency; at higher Fe concentrations... 3+ For iron-containing solutions of varying concentrations, the pyrite process can remove iron by forming ferrous sulfate slag, which is easily removed by filtration due to its large particle size. In the hydrothermal iron removal process, ferric ions are first reacted to form ferric hydroxide intermediates, followed by the addition of acid for adjustment. Under hydrothermal action, dehydration produces goethite. If the solution contains Fe... 3+ If the concentration is too high, basic ferric sulfate and hydrated pyrite will be produced during the hydrothermal process along with goethite, which is detrimental to the application of iron oxide powder formed from subsequent goethite processing in iron smelting and inorganic pigments. Therefore, the pyrite process should be used to treat the high-Fe content first. 3+ A high concentration of iron-containing solution is then treated with the goethite process to obtain lower Fe content. 3+ The first iron removal solution of high concentration was then treated with a hydrothermal method to remove low-Fe iron. 3+ The concentration of the second iron-removed solution.

[0046] In some embodiments, the goethite iron removal method includes adding the first iron-removed liquid to an acidic solution with a pH of 2.0-3.5 to allow Fe to be removed. 3+ The concentration of the reagent is 1.0-2.0 g / L, and a neutralizing agent is added to maintain the pH of the reaction process at 2.0-3.5. The reaction temperature of the goethite method for removing iron is 50-70℃.

[0047] In some embodiments, the rate at which the first iron-removed liquid is added to the acid solution is 1.6-3.5 m / s. 3 / h, making Fe 3+ The concentration is kept stable at 1.0-2.0 g / L to ensure the smooth iron removal process of goethite while preventing the formation of amorphous ferric hydroxide colloids.

[0048] In some embodiments, the hydrothermal iron removal process includes adding an alkali to the second iron-removed liquid to initiate a precipitation reaction, then adding acid to adjust the pH of the reaction solution to 3.0-4.0 and continuing the hydrothermal reaction to obtain the goethite and the purified liquid; wherein the hydrothermal reaction temperature is 100-200℃ and the pressure is 0.1-10 MPa. First, an alkali is added to the second iron-removed liquid to initiate a precipitation reaction, then acid is added to adjust the pH of the reaction solution to 3.0-4.0, and hydrothermal iron removal is performed at this pH value. After hydrothermal iron removal, almost all residual iron in the solution precipitates out, and the iron slag has a crystalline structure and good filtration performance, and can be used as a raw material for iron smelting after treatment.

[0049] In some embodiments, the neutralizing agent is at least one selected from sodium carbonate, ammonium carbonate, potassium carbonate, ammonium bicarbonate, and sodium bicarbonate. This replenishes the monovalent cations needed in the solution while simultaneously adjusting the pH, without introducing new impurities, thus reducing the difficulty and cost of subsequent impurity removal.

[0050] In some embodiments, the iron oxide slag is roasted, washed, dried, ground, and sieved to obtain iron oxide red powder. The washing process includes primary and secondary washing, in which soluble salts (such as sodium sulfate) in the roasted slag are dissolved in water and reused in the iron-containing solution. The obtained iron oxide red powder can subsequently be used in iron smelting or as an inorganic pigment, etc.

[0051] In some embodiments, the iron removal process is applied in the recycling of waste lithium-ion batteries. For example, it is applied to the recycling of ternary lithium-ion batteries. In the recycling process of ternary lithium-ion batteries, after coarse treatment to remove iron and aluminum, the method provided by this invention further removes iron from the mixture, while recovering valuable metal elements such as nickel, cobalt, and manganese.

[0052] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0053] Please refer to the process flow diagram. Figure 1 The features and performance of the present invention will be further described in detail below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0054] Example 1

[0055] (1) Iron ion reduction

[0056] Add 500 ml of an iron-containing solution to a reaction vessel. The concentrations of nickel, cobalt, manganese, and iron ions in the iron-containing solution are 24.69 g / L, 30.28 g / L, 28.6 g / L, and 25.24 g / L, respectively. Open the gas inlet valve at the bottom of the reaction vessel and introduce SO2 gas. Control the temperature inside the vessel during the reaction process to 85-95℃ until the Fe in the solution... 3+ Reduced to Fe 2+ .

[0057] (2) Iron removal by ferrous sulfate method

[0058] Add concentrated sulfuric acid to adjust the pH of the solution to 1.0-1.5. After the pH stabilizes, add H₂O₂ at a flow rate of 1.2-1.9 mL / min and detect the Fe content in the solution. 3+ The concentration is 4-6.3 g / L. Saturated sodium sulfate solution is added to bring the concentration to 4-6 g / L. During the reaction, 10% sodium carbonate solution is slowly added to maintain the pH of the solution at 1.5-2.0. After reacting for 2 hours, the solution is filtered to obtain yellow sodium ferrous sulfate and the first iron-removed liquid.

[0059] (3) Iron removal by goethite method

[0060] First, prepare a sulfuric acid solution with a pH of 2.5-3.0 and add it to the reaction vessel. Then, slowly and evenly add the first iron-removed liquid to the reaction base liquid, controlling the feed rate of the first iron-removed liquid to ensure Fe... 3+ The concentration is 1.0-2.0 g / L, and the feed rate is 1.6-3.5 m / s. 3 The reaction was carried out at a constant temperature of 60°C. Saturated sodium carbonate solution was added to maintain the pH of the solution at 2.5-3.0 during the reaction. After 60 minutes of reaction, solid and liquid were separated to obtain goethite and the second iron-removed liquid.

[0061] (4) Hydrothermal iron removal

[0062] The liquid after the second iron removal was transferred to a reaction vessel, and sodium hydroxide solution was added to generate colloidal ferric hydroxide precursor until no more precipitate was formed. Dilute sulfuric acid was slowly added to adjust the pH value to 3.0-4.0, and then the liquid was transferred to a hydrothermal reaction vessel for 60 minutes (temperature 150℃, pressure 2.0MPa). After solid-liquid separation, goethite and pure liquid were obtained.

[0063] (5) Treatment of iron ore slag

[0064] The sodium ferrous sulfate obtained from the ferrous sulfate process was calcined at 500℃ for 2 hours to obtain calcined residue. The sulfur trioxide produced during calcination was used to prepare sodium sulfate. The calcined residue was then subjected to a second water washing and stirring process to obtain washed residue. The first water washing had a solid-liquid mass ratio of 3:1 and was stirred at 65℃ for 1 hour; the second water washing had a solid-liquid mass ratio of 4:1 and was stirred at 60℃ for 0.8 hours. The washed residue was then dried, ground, and sieved to obtain iron oxide powder.

[0065] The preparation methods of Examples 2-7 and Comparative Examples 1-6 differ from the iron removal process of Example 1 only in the difference of the technical parameters in step (2) iron removal by ferrous sulfate method, as shown in Table 1.

[0066] Table 1. Process parameters and results of iron removal by pyrite method

[0067]

[0068] As can be seen from Table 1, controlling the H2O2 feed flow rate controls the Fe... 3+ The concentration of Fe increases with the increase of H2O2 feed flow rate. 3+ The higher the concentration, the better. Compared with the iron removal process provided in Example 1 of this invention, the excessively high H2O2 feed flow rate in Comparative Example 1 will cause Fe... 3+ The concentration is too high, and the Fe in the feed solution is locally high. 3+ The formation of ferric hydroxide colloid slows down the filtration rate of the feed solution and increases the nickel content in the iron oxide slag. Similarly, in Comparative Example 2, the insufficient H2O2 feed flow rate will cause Fe... 3+ If the concentration is too low, the reaction rate will be too slow, resulting in low efficiency of the process.

[0069] The pH value of the reaction is controlled by adjusting the amount of sodium carbonate added during the iron removal process using the ferrous sulfate method. Compared with the iron removal method provided by this invention, the pH value in Comparative Example 3 is too low, affecting the yield of sodium ferrous sulfate and reducing the efficiency of the process; the pH value in Comparative Example 4 is too high, causing Fe... 3+ Hydrolysis forms ferric hydroxide colloids, which slows down the filtration rate of the feed liquid and increases the nickel content in the iron ore slag, thus increasing the loss rate of valuable metal ions in the recovery system.

[0070] Compared with the iron removal method provided by the present invention, the reaction temperature of the iron removal process of ferrous sulfate in Comparative Example 5 is reduced, which slows down the formation rate of sodium ferrous sulfate and thus reduces the efficiency of the process. In Comparative Example 6, the reaction temperature of the iron removal process of ferrous sulfate is increased, the iron ion concentration in the liquid after the first iron removal is reduced, but the nickel content in the ferrous sulfate residue is increased significantly, which increases the loss rate of valuable metal ions in the recovery system.

[0071] The preparation methods of Comparative Examples 7-8 differ from the iron removal process of Example 1 only in the difference in technical parameters during the iron slag treatment process in step (5), as shown in Table 2.

[0072] Table 2. Parameter settings and results for iron ore slag treatment

[0073]

[0074] As shown in Table 2, sodium sulfate in iron ore slag does not decompose when roasted at 500℃, thus enabling effective recovery after further water washing. Compared with Comparative Example 7 (no water washing) and Comparative Example 8 (one-time water washing), the iron removal method provided by this invention, after two water washing treatments, significantly reduces the sodium content in the washed slag, enriches and recovers soluble sodium salts, and improves the purity of the washed slag, which is beneficial for subsequent utilization.

[0075] The preparation methods of Examples 8-11 and Comparative Examples 9-12 differ from the iron removal process of Example 1 only in the technical parameters of step (3) goethite iron removal process, as shown in Table 3.

[0076] Table 3. Parameter settings and results for iron removal by goethite method

[0077]

[0078] Table 3 shows that the Fe content in the second iron removal solution obtained under different pH conditions for iron removal from goethite varies. 3+ The concentration differs from the nickel and cobalt content in goethite. As can be seen from Comparative Example 9, at pH ranges lower than those provided by this invention, the Fe content in the second iron-removed solution... 3+ The concentration is too high to effectively remove iron; as can be seen from Comparative Example 10, at pH ranges higher than those provided by this invention, the content of nickel and cobalt in goethite increases, resulting in the loss of nickel and cobalt.

[0079] Fe in the second iron removal solution obtained by goethite iron removal at different reaction temperatures 3+ The concentrations are different. As can be seen from Comparative Example 11, the reaction temperature in the goethite iron removal process is lower than the temperature range provided in this invention, which leads to a decrease in Fe in the liquid after the second iron removal. 3+The high concentration of iron in the goethite method is insufficient for effective iron removal. As shown in Comparative Example 12, the reaction temperature during iron removal using the goethite method is higher than the temperature range provided in this invention, resulting in increased Fe concentration. 3+ Increased hydrolysis rate leads to a faster decrease in solution pH, making it difficult to control pH and increasing costs. At the same time, the increased nickel and cobalt content in goethite results in the loss of nickel and cobalt.

[0080] Compared with the iron removal process of Comparative Example 13 and Example 1, the only difference is the difference in the technical parameters of the hydrothermal iron removal process in step (4), as shown in Table 4.

[0081] Table 4. Parameter settings and results of hydrothermal iron removal.

[0082] parameter Second method for treating liquid after iron removal <![CDATA[Fe in the third post-iron-removal liquid (pure liquid) 3+ , g / L]]> Example 1 Hydrothermal iron removal 0.004 Comparative Example 13 none 0.036

[0083] As can be seen from Table 4, compared with Comparative Example 13, the iron content in the solution after the second iron removal liquid in the iron removal method provided by the present invention is significantly reduced after iron removal by hydrothermal method.

[0084] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An iron removal process, characterized in that, Includes the following steps: Fe in iron-containing solution 3+ Reduced to Fe by a reducing agent 2+ A reduced iron-containing solution was obtained; After adjusting the pH of the reduced iron-containing solution, an oxidant is added to maintain Fe. 3+ The concentration of the solution is 2.0-8.2 g / L. Sulfate is then added to carry out the iron removal reaction of ferrous sulfate. After solid-liquid separation, ferrous sulfate residue and the first iron removal liquid are obtained. The first iron-removed liquid is subjected to goethite removal to obtain the second iron-removed liquid and goethite. After removing iron from the second iron-removed liquid, a pure liquid and goethite are obtained by removing iron through a hydrothermal method.

2. The iron removal process according to claim 1, characterized in that, The reducing agent includes at least one of SO2, sodium sulfite, ammonium sulfite, and iron powder; And / or, adjust the pH of the reduced iron-containing solution to 1.0-1.5; And / or, the oxidant includes at least one of H2O2, sodium hypochlorite, potassium permanganate, and sodium chlorate; And / or, the sulfate includes at least one of sodium sulfate, ammonium sulfate, and potassium sulfate.

3. The iron removal process according to claim 1, characterized in that, The iron removal reaction temperature of the ferrous sulfate process is 75-105℃, and a neutralizing agent is added to maintain the pH of the reaction solution at 1.0-2.

5.

4. The iron removal process according to claim 1, characterized in that, The goethite iron removal method includes adding the first iron-removed liquid to an acidic solution with a pH of 2.0-3.5 to reduce Fe content. 3+ The concentration of the reagent is 1.0-2.0 g / L, and a neutralizing agent is added to maintain the pH of the solution at 2.0-3.5 and the reaction temperature at 50-70℃.

5. The iron removal process according to claim 1, characterized in that, The hydrothermal iron removal method includes adding alkali to the second iron removal solution to carry out a precipitation reaction, then adding acid to adjust the pH of the reaction solution to 3.0-4.0 and carrying out a hydrothermal reaction, followed by solid-liquid separation to obtain the goethite and the pure solution; wherein the hydrothermal reaction temperature is 100-200℃ and the pressure is 0.1-10MPa.

6. The iron removal process according to claim 1, characterized in that, The iron oxide slag is roasted, washed, dried, ground, and sieved to obtain iron oxide red powder.

7. The iron removal process according to claim 6, characterized in that, The calcination temperature is 450-550℃, and the calcination time is 2-3 hours. The water washing includes a primary water washing and a secondary water washing; the primary water washing has a solid-liquid mass ratio of 2-4:1, a temperature of 60-70℃, and a stirring time of 1-2 hours; the secondary water washing has a solid-liquid mass ratio of 3-5:1, a temperature of 50-70℃, and a stirring time of 0.5-1.2 hours.

8. The iron removal process according to any one of claims 3 or 4, characterized in that, The neutralizing agent is at least one of sodium carbonate, ammonium carbonate, potassium carbonate, ammonium bicarbonate, and sodium bicarbonate.

9. The application of the iron removal process according to any one of claims 1-8 in the recycling of waste lithium-ion batteries.

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