Method for removing iron and aluminum from mixed solution and liquid with iron and aluminum removed

Abstract

The invention provides a method for removing iron and aluminum from a mixed solution and an iron and aluminum removed solution. The method comprises the following steps: S1, mixing a mixed solution and a first precipitator in an opposite adding manner, adding a first oxidant, carrying out a first-stage iron and aluminum removal reaction, and after the first-stage iron and aluminum removal reaction is finished, filtering to obtain a first-stage iron and aluminum slag product and a first-stage iron and aluminum removed liquid; and S2, mixing the first-stage iron and aluminum removed liquid with a second precipitator in an opposite adding manner, adding a second oxidant, carrying out second-stage iron and aluminum removal reaction, and after the second-stage iron and aluminum removal reaction is finished, filtering to obtain second-stage iron and aluminum slag and second-stage iron and aluminum removed liquid. According to the technical scheme, the iron and aluminum impurities in the leaching filtrate can be effectively removed, formed precipitate particles are large, solid-liquid separation is easy, a large amount of waste gas, waste liquid and waste residues are not generated in the preparation process, the production period is short, and the recovery rate of iron and aluminum elements is high.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrometallurgy, and in particular, to a method for removing iron and aluminum from a mixed solution and a solution after iron and aluminum removal. Background Art

[0002] The wet smelting process of serpentine widely adopts the technological process of raw material leaching, impurity removal, and precipitation. In the impurity removal process, the most important is to remove iron and aluminum impurities. Industrially, usually, sodium hydroxide, soda ash or magnesium oxide is added to adjust the pH value to a certain value to obtain jarosite or iron hydroxide precipitate and aluminum hydroxide precipitate. The slag produced by the precipitation is the hazardous solid waste in the industrial production process - iron and aluminum slag after filtration and washing. The composition of this slag is complex and not single, and its economic value is low; and valuable metals such as nickel and cobalt are often entrained in the impurity removal process, which not only causes great pollution to the environment but also brings losses of nickel and cobalt resources. Therefore, it is very necessary to develop a process technology with simple operation and effective iron and aluminum removal. On the one hand, it can solve the problems of stacking and treatment of a large amount of iron and aluminum slag, and on the other hand, it avoids waste of high-value nickel and cobalt resources and improves the comprehensive utilization value of serpentine ore.

[0003] The current technology mainly first removes impurities from the serpentine leaching solution in one step to obtain iron and aluminum slag, and then performs post-treatment on the iron and aluminum slag, which prolongs the process flow, increases the overall equipment and capital investment, and at the same time increases the difficulty of process operation controllability, which is not conducive to safe production; in addition, new elements are easily introduced during the post-treatment process of iron and aluminum slag, and the composition of the final product is not easy to control, which is not conducive to industrial production and industrial application. Summary of the Invention

[0004] The main object of the present invention is to provide a method for removing iron and aluminum from a mixed solution and a solution after iron and aluminum removal to solve the problems of difficult solid-liquid separation and large amount of iron and aluminum slag during the process of removing iron and aluminum from the mixed solution in the prior art.

[0005] To achieve the above object, according to one aspect of the present invention, a method for removing iron and aluminum from a mixed solution is provided. The method includes: Step S1, mixing the mixed solution and a first precipitant in a countercurrent addition manner, adding a first oxidant, and performing a first-stage iron and aluminum removal reaction. After the first-stage iron and aluminum removal reaction ends, a first-stage iron and aluminum slag product and a first-stage solution after iron and aluminum removal are obtained through filtration; Step S2, mixing the first-stage solution after iron and aluminum removal and a second precipitant in a countercurrent addition manner, adding a second oxidant, and performing a second-stage iron and aluminum removal reaction. After the second-stage iron and aluminum removal reaction ends, a second-stage iron and aluminum slag and a second-stage solution after iron and aluminum removal are obtained through filtration.

[0006] Further, the cations in the mixed solution include Fe 3+ 、Fe 2+ 、Al 3+ 、Ni 2+ and Co2+ Preferably, the mixed solution is a serpentine leaching solution.

[0007] Further, the first precipitant and the second precipitant are each independently selected from any one or more of magnesia slurry, magnesium hydroxide slurry, basic magnesium carbonate slurry, and limestone slurry; preferably, the slurry concentrations of the first precipitant and the second precipitant are 5-30 wt.%.

[0008] Further, the first oxidant and the second oxidant are each independently selected from any one or more of air, oxygen, hydrogen peroxide, and SO2.

[0009] Further, the flow rate ratio of the mixed solution to the first precipitant is 5-20:1; preferably, the reaction temperature of the first iron and aluminum removal reaction is 40-90 °C; preferably, the reaction time of the first iron and aluminum removal reaction is 3-8 h; preferably, the end point pH value of the first iron and aluminum removal reaction is 3.6-4.0.

[0010] Further, the flow rate ratio of the solution after the first iron and aluminum removal to the second precipitant is 5-20:1;

[0011] Preferably, the reaction temperature of the second iron and aluminum removal reaction is 40-90 °C;

[0012] Preferably, the reaction time of the second iron and aluminum removal reaction is 4-6 h;

[0013] Preferably, the end point pH value of the second iron and aluminum removal reaction is 4.8-5.2.

[0014] Further, in the first iron and aluminum slag product, the iron content is 40-60 wt.%, the aluminum content is 3-5 wt.%, the nickel content is less than 0.15 wt.%, and the cobalt content is less than 0.02 wt.%;

[0015] Preferably, in the solution after the second iron and aluminum removal, the iron ion concentration is less than 10 mg / L and the aluminum ion concentration is less than 5 mg / L.

[0016] Further, before step S1, the above method further includes: step S01, leaching serpentine to obtain a serpentine leaching solution;

[0017] Preferably, after step S2, the method further includes: step S3, returning the second iron and aluminum slag to step S01 for leaching treatment.

[0018] Further, the acid used for the leaching treatment is any one or more of sulfuric acid, hydrochloric acid, and nitric acid;

[0019] Optionally, the leaching treatment adopts a high-pressure leaching method, and the temperature of the high-pressure leaching is 170-220 °C and the pressure is 0.2-0.8 MPa.

[0020] According to another aspect of the present invention, there is provided a post-iron-aluminum removal liquid, which is a two-stage post-iron-aluminum removal liquid prepared by any of the above methods.

[0021] By applying the technical solution of the present invention, by adding the mixed solution and the precipitant in a countercurrent manner and adding an oxidant at the same time, the iron and aluminum impurities in the leaching filtrate can be effectively removed, and the formed precipitate particles are relatively large and easy to separate solid from liquid. There is no large amount of waste gas, waste liquid, and waste residue generated during the preparation process, the production cycle is short, and the recovery rates of iron and aluminum elements are high. The iron-aluminum slag obtained by this process has high purity, low moisture content, and small slag volume, significantly reducing the production cost, eliminating the secondary treatment process, reducing the moisture content of the iron-aluminum slag, significantly reducing the slag volume, and significantly reducing the transportation investment and stacking management costs. Further, the iron content in the obtained iron-aluminum slag is high and can be directly used as a product for the market. Especially for the leaching filtrate, the iron-aluminum removal method of the present application solves the problem of difficult solid-liquid separation during the iron-aluminum removal process and reduces the iron-aluminum removal cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0023] Figure 1 It shows a schematic flow diagram of preparing a post-iron-aluminum removal liquid from a serpentine ore according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0025] As analyzed in the background art of this application, in the prior art, there are problems of difficult solid-liquid separation and large amount of iron-aluminum slag during the iron-aluminum removal of the mixed solution. To solve this problem, this application provides a method for removing iron and aluminum from a mixed solution and a post-iron-aluminum removal liquid.

[0026] According to a typical embodiment of this application, there is provided a method for removing iron and aluminum from a mixed solution, the method comprising: Step S1, mixing the mixed solution and a first precipitant in a countercurrent manner, adding a first oxidant, and performing a first-stage iron-aluminum removal reaction. After the first-stage iron-aluminum removal reaction is completed, a first-stage iron-aluminum slag product and a first-stage post-iron-aluminum removal liquid are obtained by filtration; Step S2, mixing the first-stage post-iron-aluminum removal liquid and a second precipitant in a countercurrent manner, adding a second oxidant, and performing a second-stage iron-aluminum removal reaction. After the second-stage iron-aluminum removal reaction is completed, a second-stage iron-aluminum slag and a post-iron-aluminum removal liquid are obtained by filtration.

[0027] In this application, by adding the mixed solution and the precipitant in a countercurrent manner and adding an oxidant simultaneously, iron and aluminum impurities in the leaching filtrate can be effectively removed. Moreover, the formed precipitate particles are relatively large, making solid-liquid separation easy. There is no generation of a large amount of waste gas, waste liquid, or waste residue during the preparation process, the production cycle is short, and the recovery rates of iron and aluminum elements are high. The iron-aluminum slag obtained by this process has high purity, low moisture content, and small slag volume, significantly reducing the production cost, eliminating the secondary treatment process, reducing the moisture content of the iron-aluminum slag, significantly reducing the slag volume, and significantly reducing the transportation investment and stacking management costs. Further, the iron content in the obtained iron-aluminum slag is high, and it can be directly used as a product in the market. Especially for the leaching filtrate, the iron and aluminum removal method of this application solves the problem of difficult solid-liquid separation during the iron and aluminum removal process and reduces the iron and aluminum removal cost.

[0028] In this application, the mixed solution is acidic, and the anions are mainly SO4 2- , Cl - , NO3 - or any one or more of them. In some embodiments of this application, the cations in the above mixed solution include Fe 3+ , Fe 2+ , Al 3+ , Ni 2+ and Co 2+ . In some embodiments of this application, the concentration of Fe 3+ in the above mixed solution is 2-10 g / L, the concentration of Fe 2+ is 0.5-2 g / L, the concentration of Al 3 + is 0.5-3 g / L, the concentration of Ni 2+ is 0.3-3 g / L, and the concentration of Co 2+ is 30-500 mg / L. The improvement effect of the above iron and aluminum removal method is particularly significant. In some embodiments of this application, the pH value of the mixed solution to be treated is 1.0-1.8.

[0029] As a preferred technical solution of this application, the above mixed solution is a serpentine leaching solution. The iron-aluminum slag is directly prepared from the leaching filtrate of serpentine raw ore by the above method without the need for post-treatment, significantly shortening the process flow of iron and aluminum removal and the post-treatment of iron-aluminum slag. Moreover, the composition is single, the iron content in the slag is high, turning the iron-aluminum slag into a useful resource, and avoiding the problems of large stockpiles of iron-aluminum slag and environmental pollution during the impurity removal process, significantly improving the economic and social benefits of serpentine development.

[0030] The types of the first precipitating agent and the second precipitating agent described above may be the same or different, and both can be selected from the prior art. In some embodiments of the present application, the first precipitating agent and the second precipitating agent are each independently selected from slurries containing any one or more of magnesia slurry, magnesium hydroxide slurry, basic magnesium carbonate slurry, and limestone slurry. When the above-mentioned precipitating agent is mixed with the mixed solution or the liquid after the first-stage iron and aluminum removal in a countercurrent addition manner, the formed solid precipitate has good filtration performance, which is more convenient for solid-liquid separation. As a preferred technical solution of the present application, the slurry concentrations of the first precipitating agent and the second precipitating agent are 5-30 wt.%.

[0031] The types of the first oxidizing agent and the second oxidizing agent described above may be the same or different, and both can be selected from the prior art. Passing the oxidizing agent into the first-stage iron and aluminum removal reaction and the second-stage iron and aluminum removal reaction can oxidize the divalent iron therein into trivalent iron, which is convenient for removal at a lower pH value. In some embodiments of the present application, the first oxidizing agent and the second oxidizing agent are each independently selected from any one or more of air, oxygen, hydrogen peroxide, and SO2, and the effect is better. Preferably, starting from the countercurrent addition of the first oxidizing agent and the second oxidizing agent, they are continuously passed in during the corresponding iron and aluminum removal reaction process, which can further improve the removal efficiency of iron ions.

[0032] The countercurrent addition method in step S1 and step S2 described above means that the mixed solution or the liquid after the first-stage iron and aluminum removal and the precipitating agent are simultaneously added to the mixing device at a certain flow rate. In some embodiments of the present application, in step S1, the flow rate ratio of the leaching solution to the first precipitating agent is 5-20:1, and the formed solid crystal form is more easily filtered. Exemplarily, the flow rate ratio of the leaching solution to the first precipitating agent can be 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1 or any range between any two of them. Preferably, the reaction temperature of the first-stage iron and aluminum removal reaction is 40-90 °C, and the reaction time is 3-8 h. The iron and aluminum are more fully precipitated, and the formed solid is more easily filtered. Among them, the reaction time is from the start of countercurrent addition of materials to the stop of the reaction.

[0033] In some preferred embodiments of the present application, the end-point pH value of the first-stage iron and aluminum removal reaction is 3.6-4.0, that is, as the reaction progresses, when the pH value rises to this range, the first-stage iron and aluminum removal reaction is stopped, and this pH value is used as the reaction end-point, which is beneficial to further increasing the iron content in the iron and aluminum slag product, improving its utilization value, and reducing the amount of iron and aluminum slag.

[0034] In some exemplary embodiments of the present application, the flow rate ratio of the post-iron-aluminum removal liquid in the first stage to the second precipitant is 5-20:1. When the mixed device is fed with such a flow rate ratio, the filtration performance of the solid slag formed by the post-iron-aluminum removal reaction in the second stage can be further improved, facilitating separation from the post-iron-aluminum removal liquid. Exemplarily, the flow rate ratio of the post-iron-aluminum removal liquid in the first stage to the second precipitant can be 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1 or any range between any two of them. Preferably, the reaction temperature of the post-iron-aluminum removal reaction in the second stage is 40-90 °C, and the reaction time is 4-6 h, which helps to further improve the reaction efficiency of the post-iron-aluminum removal reaction in the second stage and the filtration performance of the generated precipitate. In some preferred embodiments of the present application, the end-point pH value of the above post-iron-aluminum removal reaction in the second stage is 4.8-5.2. Controlling this end-point pH value not only helps to further reduce the iron and aluminum contents in the post-iron-aluminum removal liquid, but also helps to improve the filtration performance of the product.

[0035] In some preferred embodiments of the present application, in the iron-aluminum slag product in the first stage, the iron content is 40-60 wt.%, the aluminum content is 3-5 wt.%, the nickel content is less than 0.15 wt.%, the cobalt content is less than 0.02 wt.%, and the moisture content is 50-75 wt.%. This iron-aluminum slag product in the first stage has high iron-aluminum slag purity, low moisture content, and small slag volume, avoiding the costs of secondary treatment, transportation, and stacking of the slag, and significantly reducing the production cost. In some embodiments of the present application, in the post-iron-aluminum removal liquid in the second stage, the concentration of iron ions is less than 10 mg / L and the concentration of aluminum ions is less than 5 mg / L.

[0036] In some embodiments of the present application, before step S1, the above method further includes: step S01, subjecting serpentine to leaching treatment to obtain a serpentine leaching solution. In some preferred embodiments of the present application, in order to further recover high-value metals such as nickel and cobalt in the mixed solution, the method for removing iron and aluminum from the mixed solution in the present application further includes step S3 after step S2, returning the iron-aluminum slag in the second stage to the step S01 process for leaching treatment.

[0037] The process of the leaching treatment can refer to the prior art, and atmospheric pressure leaching or high-pressure leaching can be used. There are no special requirements in the present application. In some embodiments of the present application, the acid used for the leaching treatment is any one or more of sulfuric acid, hydrochloric acid, and nitric acid; in some embodiments of the present application, the high-pressure leaching method is adopted for the leaching treatment. The temperature of the high-pressure leaching is 170-220 °C, and the pressure is 0.2-0.8 MPa, which is beneficial to further improving the leaching efficiency of nickel-cobalt-magnesium products, especially has a good leaching effect on the iron-aluminum slag in the second stage, and is beneficial to further improving the development benefit of serpentine.

[0038] In some exemplary embodiments of the present application, the method of the present application is carried out according to the process as Figure 1 shown: The serpentine ore is subjected to conventional leaching or pressure leaching to obtain a leaching filtrate; the obtained leaching filtrate and a first precipitant are added in a countercurrent manner for first-stage iron and aluminum removal, and a first oxidant is added during the process, and the end-point pH value of the filtrate is adjusted. After filtration, a first-stage iron and aluminum slag product and a first-stage iron and aluminum removal post-liquid are obtained; the first-stage iron and aluminum removal post-liquid and a second precipitant are added in a countercurrent manner for second-stage iron and aluminum removal, and a second oxidant is added during the process, and the pH value of the filtrate is adjusted. After filtration, a second-stage iron and aluminum slag and a second-stage iron and aluminum removal post-liquid are obtained; the obtained second-stage iron and aluminum removal post-liquid is subjected to subsequent development of nickel, cobalt, and magnesium products, and the obtained second-stage iron and aluminum slag is returned to the leaching process.

[0039] According to a typical embodiment of the present application, an iron and aluminum removal post-liquid is provided, which is an iron and aluminum removal post-liquid prepared by any of the above methods. By adding the mixed solution and the precipitant in a countercurrent manner and adding an oxidant at the same time, the present application can effectively remove iron and aluminum impurities in the leaching filtrate, and the solid-liquid separation is easy. There is no large amount of waste gas, waste liquid, and waste residue generated during the preparation process, the production cycle is short, and the recovery rates of iron and aluminum elements are high. The iron and aluminum content in the iron and aluminum removal post-liquid prepared by this process is low, which is convenient for further separation and purification of subsequent elements.

[0040] The beneficial effects that the present application can achieve will be further described below in conjunction with examples and comparative examples.

[0041] Example 1

[0042] (1) The serpentine is leached with sulfuric acid under normal pressure to obtain a leaching filtrate. The cations in the leaching filtrate include Mg: 35 g / L, Fe 3+ : 5 g / L, Fe 2+ : 0.5 g / L, Al 3+ : 1 g / L, Ni 2+ : 0.3 g / L, Co 2+ : 30 mg / L.

[0043] (2) The leaching filtrate and a 10 wt.% concentration of magnesia slurry are added simultaneously at a flow rate of 10:1 for the first-stage iron and aluminum removal reaction. Compressed air is introduced during the process, and the reaction temperature is 80 °C. Starting from the addition of the leaching filtrate and the magnesia slurry in a countercurrent manner, the reaction lasts for 3 h, and the end-point pH value of the solution reaches 3.8. After the reaction is complete, filtration is carried out to obtain a first-stage iron and aluminum slag (Fe content 50 wt.%, Al content 3 wt.%, Ni content 0.14 wt.%, cobalt content 0.015 wt.%, water content 55 wt.%) and a first-stage iron removal post-liquid. During filtration, the time taken to obtain 1 kg of filter cake per unit area is 2 min.

[0044] (3) Add a post-first-stage iron and aluminum removal solution and a 5 wt.% magnesium hydroxide slurry simultaneously at a flow rate of 15:1 for the second-stage iron and aluminum removal reaction. Oxygen is introduced during the process. The reaction temperature is 70 °C. Starting from the addition of the post-first-stage iron and aluminum removal solution and the magnesium hydroxide slurry, the reaction time is 5 h, and the pH value of the reaction end solution reaches 5.0. After the reaction is complete, filter to obtain the second-stage iron and aluminum slag and the post-second-stage iron and aluminum removal solution (Fe ion concentration 8 mg / L, Al ion concentration 4 mg / L, where Fe ions include Fe 3+ and Fe 2+ , the same below). During filtration, the time taken to obtain 1 kg of filter cake per unit area is 2.5 min. The second-stage iron and aluminum slag can be returned to the leaching process, and the post-second-stage iron and aluminum removal solution is used for the subsequent development of nickel, cobalt, and magnesium products.

[0045] Example 2

[0046] (1) Serpentine is leached with hydrochloric acid under normal pressure to obtain a leaching filtrate. The cations in the leaching filtrate include Mg: 45 g / L, Fe 3+ : 2 g / L, Fe 2+ : 1 g / L, Al 3+ : 0.5 g / L, Ni 2+ : 1 g / L, Co 2+ : 100 mg / L.

[0047] (2) The leaching filtrate and a 5 wt.% magnesium hydroxide slurry are added simultaneously at a flow rate of 5:1 for the first-stage iron and aluminum removal reaction. Oxygen is introduced during the process. The reaction temperature is 90 °C. Starting from the addition of the leaching filtrate and the magnesium oxide slurry, the reaction time is 6 h, and the pH value of the reaction end solution reaches 3.6. After the reaction is complete, filter to obtain the first-stage iron and aluminum slag (Fe content 40 wt.%, Al content 5 wt.%, Ni content 0.13 wt.%, cobalt content 0.012 wt.%, water content 50 wt.%) and the post-first-stage iron removal solution. During filtration, the time taken to obtain 1 kg of filter cake per unit area is 1.8 min.

[0048] (3) Add the post-first-stage iron and aluminum removal solution and a 20 wt.% basic magnesium carbonate slurry simultaneously at a flow rate of 20:1 for the second-stage iron and aluminum removal reaction. Hydrogen peroxide with a concentration of 30 wt.% is introduced during the process. The reaction temperature is 40 °C. Starting from the addition of the post-first-stage iron and aluminum removal solution and the magnesium hydroxide slurry, the reaction time is 6 h, and the pH value of the reaction end solution reaches 4.8. After the reaction is complete, filter to obtain the second-stage iron and aluminum slag and the post-second-stage iron and aluminum removal solution (Fe ion concentration 5 mg / L, Al ion concentration 3 mg / L). During filtration, the time taken to obtain 1 kg of filter cake per unit area is 2.2 min. The second-stage iron and aluminum slag can be returned to the leaching process, and the post-second-stage iron and aluminum removal solution is used for the subsequent development of nickel, cobalt, and magnesium products.

[0049] Example 3

[0050] (1) The serpentine is leached under normal pressure with nitric acid to obtain a leaching filtrate. The cations in the leaching filtrate include Mg: 55 g / L, Fe 3+ : 10 g / L, Fe 2+ : 2 g / L, Al 3+ : 3 g / L, Ni 2+ : 2 g / L, Co 2+ : 200 mg / L.

[0051] (2) The leaching filtrate and the basic magnesium carbonate slurry with a concentration of 30 wt% are added simultaneously at a flow rate of 20:1 to carry out a first-stage iron and aluminum removal reaction. Hydrogen peroxide is introduced during the process. The reaction temperature is 40 °C. Starting from the time when the leaching filtrate and the magnesium oxide slurry are added in opposite directions, the reaction time is 8 h. The pH value of the reaction end solution reaches 4.0. After the reaction is complete, it is filtered to obtain a first-stage iron and aluminum slag (Fe content 60 wt.%, Al content 4 wt.%, Ni content 0.12 wt.%, cobalt content 0.013 wt.%, water content 60 wt.%) and a first-stage post-iron-removal solution. During filtration, the time taken to obtain 1 kg of filter cake per unit area is 2.5 min.

[0052] (3) Subsequently, the first-stage post-iron and aluminum removal solution and the magnesium hydroxide slurry with a concentration of 30 wt.% are added simultaneously at a flow rate of 5:1 to carry out a second-stage iron and aluminum removal reaction. Air is introduced during the process. The reaction temperature is 90 °C. Starting from the time when the first-stage post-iron and aluminum removal solution and the magnesium hydroxide slurry are added, the reaction time is 4 h. The pH value of the reaction end solution reaches 5.2. After the reaction is complete, it is filtered to obtain a second-stage iron and aluminum slag and a second-stage post-iron and aluminum removal solution (Fe ion concentration 4 mg / L, Al ion concentration 2 mg / L). During filtration, the time taken to obtain 1 kg of filter cake per unit area is 2.8 min. The second-stage iron and aluminum slag can be returned to the leaching process, and the second-stage post-iron and aluminum removal solution is used for the development of subsequent nickel, cobalt, and magnesium products.

[0053] Example 4

[0054] (1) The serpentine is subjected to high-pressure sulfuric acid leaching at a temperature of 200 °C and a pressure of 0.5 MPa to obtain a leaching filtrate. The cations in the leaching filtrate include Mg: 60 g / L, Fe 3+ : 6 g / L, Fe 2+ : 1.5 g / L, Al 3+ : 2 g / L, Ni 2+ : 3 g / L, Co 2+ : 500 mg / L.

[0055] (2) The leaching filtrate and the limestone pulp with a concentration of 20 wt% are added simultaneously at a flow rate of 15:1 to carry out the first-stage iron and aluminum removal reaction. Oxygen is introduced during the process. The reaction temperature is 70 °C. Starting from the time when the leaching filtrate and the magnesium oxide pulp are added in opposite directions, the reaction time is 5 h. The end-point pH value of the reaction solution reaches 3.9. After the reaction is complete, it is filtered to obtain the first-stage iron and aluminum slag (Fe content 55 wt%, Al content 3.5 wt.%, Ni content 0.14 wt.%, cobalt content 0.016 wt.%, water content 75 wt.%) and the first-stage post-iron-removal solution. During filtration, the time taken to obtain 1 kg of filter cake per unit area is 2.4 min.

[0056] (3) The first-stage post-iron and aluminum removal solution and the magnesium hydroxide pulp with a concentration of 10 wt.% are added simultaneously at a flow rate of 10:1 to carry out the second-stage iron and aluminum removal reaction. SO2 gas is introduced during the process. The reaction temperature is 80 °C. Starting from the time when the first-stage post-iron and aluminum removal solution and the magnesium hydroxide pulp are added, the reaction time is 5 h. The end-point pH value of the reaction solution reaches 5.1. After the reaction is complete, it is filtered to obtain the second-stage iron and aluminum slag and the second-stage post-iron and aluminum removal solution (Fe ion concentration 7 mg / L, Al ion concentration 3 mg / L). During filtration, the time taken to obtain 1 kg of filter cake per unit area is 3.0 min. The second-stage iron and aluminum slag can be returned to the leaching process, and the second-stage post-iron and aluminum removal solution is used for the development of subsequent nickel, cobalt, and magnesium products.

[0057] Example 5

[0058] (1) Serpentine is subjected to high-pressure sulfuric acid leaching at a temperature of 220 °C and a pressure of 0.2 MPa to obtain a leaching filtrate. The cations in the leaching filtrate include Mg: 50 g / L, Fe 3+ : 8 g / L, Fe 2+ : 2 g / L, Al 3+ : 1.5 g / L, Ni 2+ : 1.5 g / L, Co 2+ : 300 mg / L.

[0059] (2) The leaching filtrate and the limestone pulp with a concentration of 10 wt.% are added simultaneously at a flow rate of 5:1 to carry out the first-stage iron and aluminum removal reaction. SO2 gas is introduced during the process. The reaction temperature is 60 °C. Starting from the time when the leaching filtrate and the magnesium oxide pulp are added in opposite directions, the reaction time is 7 h. The end-point pH value of the reaction solution reaches 4.0. After the reaction is complete, it is filtered to obtain the first-stage iron and aluminum slag (Fe content 45 wt.%, Al content 4.5 wt.%, Ni content 0.12 wt.%, cobalt content 0.017 wt.%, water content 65 wt.%) and the first-stage post-iron-removal solution. During filtration, the time taken to obtain 1 kg of filter cake per unit area is 2.6 min.

[0060] (3) Add a post-iron and aluminum removal solution and a limestone slurry with a concentration of 20 wt.% simultaneously at a flow rate of 10:1 to conduct a secondary iron and aluminum removal reaction. Compressed air is introduced during the process. The reaction temperature is 85 °C, the reaction time is 6 h, and the pH value at the end of the reaction solution reaches 5.0. After the reaction is complete, filter to obtain secondary iron and aluminum slag and a post-secondary iron and aluminum removal solution (Fe ion concentration 5 mg / L, Al ion concentration 2 mg / L). During filtration, the time taken to obtain 1 kg of filter cake per unit area is 2.7 min. The secondary iron and aluminum slag can be returned to the leaching process, and the post-secondary iron and aluminum removal solution is used for the subsequent development of nickel, cobalt, and magnesium products.

[0061] Example 6

[0062] (1) Mix the secondary iron and aluminum slag obtained in Example 1 with serpentine for leaching treatment. The weight ratio of the secondary iron and aluminum slag to serpentine is 1:10 to obtain a leaching filtrate. The cations in the leaching filtrate include Mg: 40 g / L, Fe 3+ : 9 g / L, Fe 2+ : 1.8 g / L, Al 3+ : 2.5 g / L, Ni 2+ : 1.2 g / L, Co 2+ : 120 mg / L.

[0063] The implementation method of step (2) is the same as that of Example 1. In the primary iron and aluminum slag obtained by filtration after the reaction is complete, the Fe content is 48 wt.%, the Al content is 2.7 wt.%, the Ni content is 0.12 wt.%, the cobalt content is 0.012 wt.%, and the moisture content is 58 wt.%. During filtration, the time taken to obtain 1 kg of filter cake per unit area is 1.9 min.

[0064] The implementation method of step (3) is the same as that of Example 1. In the post-secondary iron and aluminum removal solution obtained by filtration after the reaction is complete, the Fe ion concentration is 7 mg / L, the Al ion concentration is 3 mg / L, and the time taken to obtain 1 kg of filter cake per unit area is 2.3 min.

[0065] Example 7

[0066] (1) The same as the leaching filtrate of Example 1.

[0067] (2) The leaching filtrate and the magnesia slurry with a concentration of 10 wt.% are added simultaneously at a flow rate of 15:1 to carry out the first-stage iron and aluminum removal reaction. Compressed air is introduced during the process, and the reaction temperature is 30 °C. Starting from the time when the leaching filtrate and the magnesia slurry are added in opposite directions, the reaction time is 3 h, and the final pH value of the reaction solution reaches 3.2. After the reaction is complete, the first-stage iron and aluminum slag (Fe content 35 wt.%, Al content 2 wt.%, Mg content 3 wt.%, Ni content 0.04 wt.%, cobalt content 0.02 wt.%, water content 80 wt.%) and the first-stage post-iron-removal solution are obtained by filtration. During filtration, the time taken to obtain 1 kg of filter cake per unit area is 10 min.

[0068] (3) Subsequently, the first-stage post-iron and aluminum removal solution and the magnesia slurry with a concentration of 10 wt.% are added simultaneously at a flow rate of 10:1 to carry out the second-stage iron and aluminum removal reaction. Compressed air is introduced during the process, and the reaction temperature is 80 °C. Starting from the time when the first-stage post-iron and aluminum removal solution and the magnesium hydroxide slurry are added, the reaction time is 3 h, and the final pH value of the reaction solution reaches 4.6. After the reaction is complete, the second-stage iron and aluminum slag and the second-stage post-iron and aluminum removal solution (Fe ion concentration 54 mg / L, Al ion concentration 23 mg / L) are obtained by filtration. During filtration, the time taken to obtain 1 kg of filter cake per unit area is 9.5 min. The second-stage iron and aluminum slag can be returned to the leaching process, and the Fe and Al ion concentrations in the second-stage post-iron and aluminum removal solution are relatively high.

[0069] Example 8

[0070] Steps (1) and (2) are the same as those in Example 7. The implementation method of step (3) is as follows: The first-stage post-iron and aluminum removal solution and the magnesium hydroxide slurry with a concentration of 5 wt.% are added simultaneously at a flow rate of 15:1 to carry out the second-stage iron and aluminum removal reaction. Oxygen is introduced during the process, and the reaction temperature is 70 °C. Starting from the time when the first-stage post-iron and aluminum removal solution and the magnesium hydroxide slurry are added, the reaction time is 5 h, and the final pH value of the reaction endpoint is adjusted to 5.0. After the reaction is complete, the second-stage iron and aluminum slag and the second-stage post-iron and aluminum removal solution (Fe ion concentration 10 mg / L, Al ion concentration 6 mg / L) are obtained by filtration. During filtration, the time taken to obtain 1 kg of filter cake per unit area is 15 min.

[0071] Example 9

[0072] (1) It is the same as the leaching filtrate in Example 1.

[0073] (2) The leaching filtrate and the magnesium oxide slurry with a concentration of 30 wt.% are added simultaneously at a flow rate of 5:1 to carry out the first-stage iron and aluminum removal reaction. Compressed air is introduced during the process. The reaction temperature is 80 °C, the reaction time is 8 h, the final pH value of the solution is adjusted to 4.2. After the reaction is complete, it is filtered to obtain the first-stage iron and aluminum slag (Fe content 35 wt.%, Al content 2.1 wt.%, Ni content 0.6 wt.%, cobalt content 0.02 wt.%, water content 83 wt.%) and the first-stage post-iron-removal solution. When filtering, the time taken to obtain 1 kg of filter cake per unit area is 32 min.

[0074] (3) Subsequently, the first-stage post-iron and aluminum removal solution and the magnesium oxide slurry with a concentration of 20 wt.% are added simultaneously at a flow rate of 10:1 to carry out the second-stage iron and aluminum removal reaction. Compressed air is introduced during the process. The reaction temperature is 80 °C, the reaction time is 3 h, the final pH value of the solution is adjusted to 5.4. After the reaction is complete, it is filtered to obtain the second-stage iron and aluminum slag and the second-stage post-iron and aluminum removal solution (Fe ion concentration 8 mg / L, Al ion concentration 3 mg / L). When filtering, the time taken to obtain 1 kg of filter cake per unit area is 8.5 min. The second-stage iron and aluminum slag can be returned to the leaching process. The Fe and Al ion concentrations in the second-stage post-iron and aluminum removal solution are relatively high.

[0075] Example 10

[0076] The difference from Example 1 is that in steps (2) and (3), the magnesium oxide slurry with a concentration of 10 wt% and the magnesium hydroxide slurry with a concentration of 5 wt.% are respectively replaced with sodium carbonate aqueous solutions with the same concentration.

[0077] In the first-stage iron and aluminum slag obtained by filtering after the reaction in step (2), the Fe content is 30 wt.%, the Al content is 1.5 wt.%, the Ni content is 0.23 wt.%, the cobalt content is 0.03 wt.%, and the water content is 85 wt.%. When filtering, the time taken to obtain 1 kg of filter cake per unit area is 25 min.

[0078] In the second-stage post-iron and aluminum removal solution obtained by filtering after the reaction in step (3), the Fe ion concentration is 35 mg / L and the Al ion concentration is 25 mg / L. When filtering, the time taken to obtain 1 kg of filter cake per unit area is 23 min.

[0079] Comparative Example 1

[0080] Steps (1) and (2) are the same as those in Example 1. The implementation method of step (3) is as follows: A section of the iron- and aluminum-removed liquid is added simultaneously with a 5 wt.% concentration of magnesium hydroxide slurry at a flow rate ratio of 15:1 to carry out the second-stage iron and aluminum removal reaction. During the process, no oxygen is introduced, and no other oxidants are added. The reaction temperature is 70 °C, the reaction time is 5 h, the pH value at the end of the reaction solution reaches 5. After the reaction is complete, the second-stage iron and aluminum slag and the second-stage iron- and aluminum-removed liquid (Fe ion concentration 180 mg / L, Al ion concentration 50 mg / L) are obtained by filtration. When filtering, the time taken to obtain 1 kg of filter cake per unit area is 12 min.

[0081] Comparative Example 2

[0082] (1) is the same as the leaching filtrate in Example 1.

[0083] (2) The leaching filtrate is added to the reaction tank at one time as the bottom liquid. A 10 wt.% concentration of magnesium oxide slurry and hydrogen peroxide are continuously fed into the reaction tank in parallel flow. The weight ratio of the leaching filtrate, magnesium oxide slurry, and hydrogen peroxide is 200:12:1. The first-stage iron and aluminum removal reaction is carried out. During the process, compressed air is introduced. The reaction temperature is 80 °C. After starting to feed the materials, the reaction lasts for 3 h. The pH value at the end of the reaction solution reaches 3.8. After the reaction is complete, the first-stage iron and aluminum slag (Fe content 28 wt.%, Al content 1.5 wt.%, Ni content 0.25 wt.%, cobalt content 0.05 wt.%, magnesium content 10 wt.%, water content 87 wt.%) and the first-stage iron-removed liquid are obtained by filtration. When filtering, the time taken to obtain 1 kg of filter cake per unit area is 8.4 min.

[0084] (3) The first-stage iron- and aluminum-removed liquid is added to the reaction tank at one time as the bottom liquid. A 5 wt.% concentration of magnesium hydroxide slurry and hydrogen peroxide are continuously fed into the reaction tank in parallel flow. The weight ratio of the first-stage iron- and aluminum-removed liquid, magnesium hydroxide slurry, and hydrogen peroxide is 500:10:1. The second-stage iron and aluminum removal reaction is carried out. The reaction temperature is 70 °C, the reaction time is 5 h, the pH value at the end of the reaction solution reaches 5.0. After the reaction is complete, the second-stage iron and aluminum slag and the second-stage iron- and aluminum-removed liquid (Fe ion concentration 80 mg / L, Al ion concentration 55 mg / L) are obtained by filtration. When filtering, the time taken to obtain 1 kg of filter cake per unit area is 10.2 min.

[0085] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: By adding the mixed solution and the precipitant in a countercurrent manner and adding an oxidant simultaneously, the present application can effectively remove iron and aluminum impurities in the leaching filtrate. Moreover, solid-liquid separation is easy, and no large amounts of waste gas, waste liquid, and waste residue are generated during the preparation process. The production cycle is short, and the recovery rates of iron and aluminum elements are high. The iron-aluminum slag prepared by this process has high purity, low moisture content, and small slag volume, significantly reducing the production cost, eliminating the secondary treatment process, reducing the moisture content of the iron-aluminum slag, significantly reducing the slag volume, and significantly reducing the transportation investment and stacking management costs. Further, the iron content in the obtained iron-aluminum slag is high and can be directly used as a product in the market. In particular, for the leaching filtrate, the iron and aluminum removal method of the present application solves the problem of difficult solid-liquid separation during the iron and aluminum removal process and reduces the iron and aluminum removal cost.

[0086] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for removing iron and aluminum from a mixed solution, characterized in that, Including: Step S1: Mix the mixed solution and the first precipitant in a countercurrent addition manner, add the first oxidant, and carry out a first-stage iron and aluminum removal reaction. After the first-stage iron and aluminum removal reaction is completed, filter to obtain a first-stage iron and aluminum slag product and a first-stage post-iron and aluminum removal solution. Step S2: Mix the first-stage post-iron and aluminum removal solution and the second precipitant in a countercurrent addition manner, add the second oxidant, and carry out a second-stage iron and aluminum removal reaction. After the second-stage iron and aluminum removal reaction is completed, filter to obtain a second-stage iron and aluminum slag and a second-stage post-iron and aluminum removal solution.

2. The method according to claim 1, characterized in that The cations in the mixed solution include Fe 3+ , Fe 2+ , Al 3+ , Ni 2+ and Co 2+ ; Preferably, the mixed solution is a serpentine leaching solution.

3. The method according to claim 1, wherein The first precipitant and the second precipitant are each independently selected from any one or more of magnesia slurry, magnesium hydroxide slurry, basic magnesium carbonate slurry, and limestone slurry. Preferably, the slurry concentrations of the first precipitant and the second precipitant are 5 - 30 wt.%.

4. The method according to claim 1, characterized in that, The first oxidant and the second oxidant are each independently selected from any one or more of air, oxygen, hydrogen peroxide, and SO2.

5. The method according to any one of claims 1 to 4, characterized in that The flow rate ratio of the mixed solution to the first precipitant is 5 - 20:

1. Preferably, the reaction temperature of the first-stage iron and aluminum removal reaction is 40 - 90 °C. Preferably, the reaction time of the first-stage iron and aluminum removal reaction is 3 - 8 h. Preferably, the end-point pH value of the first-stage iron and aluminum removal reaction is 3.6 - 4.

0.

6. The method according to any one of claims 1 to 4, characterized in that The flow rate ratio of the first-stage post-iron and aluminum removal solution to the second precipitant is 5 - 20:

1. Preferably, the reaction temperature of the second-stage iron and aluminum removal reaction is 40 - 90 °C. Preferably, the reaction time of the second-stage iron and aluminum removal reaction is 4 - 6 h. Preferably, the end-point pH value of the second-stage iron and aluminum removal reaction is 4.8 - 5.

2.

7. The method according to any one of claims 1 to 4, characterized in that, In the first-stage iron and aluminum slag product, the iron content is 40 - 60 wt.%, the aluminum content is 3 - 5 wt.%, the nickel content is less than 0.15 wt.%, and the cobalt content is less than 0.02 wt.%. Preferably, in the second-stage post-iron and aluminum removal solution, the iron ion concentration is less than 10 mg / L, and the aluminum ion concentration is less than 5 mg / L.

8. The method according to any one of claims 2 to 4, characterized in that, Before step S1, the method further includes: Step S01: Leach the serpentine to obtain a serpentine leaching solution. Preferably, after step S2, the method further includes: Step S3: Return the second-stage iron and aluminum slag to the process of step S01 for the leaching treatment.

9. The method according to claim 8, characterized in that, The acid used for the leaching treatment is any one or more of sulfuric acid, hydrochloric acid, and nitric acid. Optionally, the leaching treatment adopts a high-pressure leaching method, and the temperature of the high-pressure leaching is 170 - 220 °C, and the pressure is 0.2 - 0.8 MPa.

10. A post - iron - and - aluminum - removal liquid, characterized in that, It is a second-stage post-iron and aluminum removal solution prepared by the method according to any one of claims 1 to 9.

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