A method for recovering iron and aluminum from red mud by acid leaching and recovering acid

Abstract

The present invention belongs to the technical field of solid resource utilization, and relates to a method for recovering iron and aluminum from red mud by acid leaching and recovering acid, which comprises the following steps: (1) strongly acid leaching red mud to obtain red mud residue and an iron-aluminum solution; (2) mixing the red mud residue with demineralized water to obtain acid radical-removed red mud residue and a sodium salt solution; (3) stirring, heating and evaporating the iron-aluminum solution to obtain an iron-aluminum mixed solid and a recovered strong acid solution; (4) adjusting the pH of the iron-aluminum mixed solid to obtain an iron-aluminum hydroxide solid and a sodium salt solution; (5) mixing the iron-aluminum mixed solid with demineralized water to obtain acid radical-removed iron-aluminum mixed solid and a sodium salt solution; (6) adjusting the pH of the acid radical-removed iron-aluminum mixed solid to obtain an iron hydroxide solid and a sodium aluminate solution. The present invention realizes the recovery of iron and aluminum in red mud under the conditions of low acid consumption and low alkali consumption; on the basis of recovering iron and aluminum, strong acid is recovered with less energy consumption; the obtained red mud residue, iron hydroxide and sodium aluminate solution contain less impurities, which is convenient for subsequent processes.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid resource utilization, and relates to a method for recovering iron and aluminum from red mud by acid leaching and recovering acid. Background Art

[0002] Red mud is a strongly alkaline by-product discharged during the production of alumina, and is a typical large-volume solid waste in the non-ferrous metallurgy industry. Metallic aluminum is mainly extracted from alumina. Approximately 2 tons of alumina are required to produce 1 ton of electrolytic aluminum, and 2 - 3 tons of bauxite are required to produce 1 ton of alumina. A large amount of red mud will be generated during this process.

[0003] Red mud contains a large amount of valuable components such as iron oxide and alumina. The proportion of iron and aluminum reaches more than 50%, making it a good raw material for extracting iron and aluminum. At present, there have been many studies on the recovery of valuable metal elements in red mud. The acid leaching method is a relatively simple method for recovering valuable elements in red mud. Commonly used acids include organic acids such as oxalic acid and citric acid, and inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid. Due to the high alkalinity of red mud, the acid leaching method often consumes a large amount of acid and alkali, and the obtained product contains a large amount of residual acid solution, resulting in secondary pollution.

[0004] Therefore, how to develop a sustainable large-scale solid waste treatment technology that combines waste reduction and resource recovery, reduces acid and alkali consumption, or recovers the used acid, and achieves high-purity products is an effective way to practice circular economy and promote sustainable development, and has positive significance in solving environmental pollution problems. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for recovering iron and aluminum from red mud by acid leaching and recovering acid, so as to realize the harmlessness and resource utilization of red mud and recover strong acid. The specific technical solutions are as follows:

[0006] A method for recovering iron and aluminum from red mud by acid leaching and recovering acid, comprising the following steps:

[0007] (1) After crushing the red mud, it is mixed with a strong acid solution, and the iron and aluminum solution is leached out by continuously stirring under heating conditions. After solid-liquid separation, red mud residue and iron and aluminum solution are obtained;

[0008] (2) The red mud residue obtained in step (1) is mixed with demineralized water, stirred, and then solid-liquid separated to obtain acid root-removed red mud residue and sodium salt solution;

[0009] (3) The iron and aluminum solution obtained in step (1) is stirred and heated for evaporation to obtain an iron and aluminum mixed solid and gas, and the generated gas is collected and vacuum cooled to obtain a strong acid solution;

[0010] (4) Mix the iron-aluminum mixed solid obtained in step (3) with an NaOH solution, adjust the pH to 5 - 6, stir, and then separate the solid from the liquid to obtain an iron-aluminum hydroxide solid and a sodium salt solution;

[0011] (5) Mix the iron-aluminum hydroxide solid obtained in step (4) with demineralized water, stir, and then separate the solid from the liquid to obtain an iron-aluminum hydroxide solid without acid radicals and a sodium salt solution;

[0012] (6) Mix the iron-aluminum hydroxide solid without acid radicals obtained in step (5) with an NaOH solution, adjust the pH to 10 - 14, stir, and then separate the solid from the liquid to obtain a ferric hydroxide solid and a sodium aluminate solution.

[0013] Further, in the above step (1), the red mud includes Bayer red mud, sintering red mud or combined-process red mud.

[0014] Further, the particle size of the crushed red mud is 60 - 200 mesh.

[0015] Further, in the above step (1), the mass concentration of the strong acid is 15% - 36%; the iron-aluminum solution is recycled for leaching 3 - 6 times. The iron-aluminum solution recycling leaching means that after the red mud and the strong acid solution are heated and stirred and then the solid is separated from the liquid to obtain red mud residue and an iron-aluminum solution, the red mud residue is then mixed with the strong acid solution, heated and stirred, and then the solid is separated from the liquid to obtain red mud residue and an iron-aluminum solution. Each time, the mass-to-volume ratio of the red mud or red mud residue to the strong acid solution is 1 kg:(1 L - 5 L), the stirring time is 30 min - 12 h, the stirring temperature is 50 - 95 °C, and finally red mud residue and a mixed iron-aluminum solution are obtained.

[0016] Further, the above step (1) specifically includes: (1-1) Mix the red mud with a strong acid with a mass concentration of 31%, place it in a water bath thermostatic shaker and react at 80 °C for 30 min. The mass-to-volume ratio of the red mud to the strong acid is 1 kg:1 L. After the reaction, filter by suction to obtain red mud residue and an iron-aluminum solution; (1-2) Mix the red mud residue with a strong acid with a mass concentration of 20%, place it in a water bath thermostatic shaker and react at 90 °C for 30 min. The mass-to-volume ratio of the red mud to the strong acid is 1 kg:1 L. After the reaction, filter by suction to obtain red mud residue and an iron-aluminum solution; (1-3) Repeat step (1-2) for the red mud residue obtained each time 2 more times; (1-4) Combine all the iron-aluminum solutions.

[0017] Further, the strong acid is an organic acid or an inorganic acid; the organic acid is oxalic acid or citric acid, and the inorganic acid is hydrochloric acid, nitric acid or sulfuric acid.

[0018] Further, in the step (2), the mass-to-volume ratio of the red mud residue to the demineralized water is 1 kg:(500 mL - 5 L); in the step (3), the heating and evaporation method includes steam heating, electric heating, and coal heating, and the heating and evaporation temperature is 100 - 200 °C; the gas cooling method includes natural cooling and condensate cooling.

[0019] Further, in the step (4), the stirring time is 15 min - 6 h.

[0020] Further, in the step (5), the mass-to-volume ratio of the iron-aluminum mixed solid to the demineralized water is 1 kg:(500 mL - 5 L).

[0021] Further, in the step (6), the stirring time is 15 min - 6 h.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) The present invention adopts a strong acid leaching and enrichment and concentration process to achieve the recovery of iron and aluminum in red mud with low acid consumption and low alkali consumption; the treatment process is simple, the cost is reduced, and there is no discharge of waste residue and sewage.

[0024] (2) On the basis of recovering iron and aluminum, the present invention also recovers strong acid, and promotes the hydrolysis process of iron and aluminum during evaporation, generating Fe(OH) 3 and Al(OH) 3 reducing the subsequent alkali consumption and having low energy consumption during the recovery of strong acid.

[0025] (3) The red mud residue, iron hydroxide, and sodium metaaluminate solution obtained by the present invention contain fewer impurities, especially acid radicals, facilitating the subsequent resource utilization of the red mud residue and the use of sodium metaaluminate in the electrolytic aluminum process. Description of the Drawings

[0026] Figure 1 is the process flow diagram of the method for recovering iron and aluminum from red mud by acid leaching and recovering acid of the present invention;

[0027] Figure 2 is the photo of the original red mud used in Example 1;

[0028] Figure 3 is the photo of the red mud residue obtained in step (2) of Example 1;

[0029] Figure 4 is the SEM and EDS diagram of the red mud residue obtained in step (2) of Example 1;

[0030] Figure 5 is the XRD diagram of the red mud used in Example 1 and the red mud residue obtained in step (2);

[0031] Figure 6 Photograph of the iron hydroxide solid obtained in Example 1;

[0032] Figure 7 Photograph of the sodium aluminate solution obtained in Example 1. Detailed implementation manners

[0033] For the instruments, reagents, materials, etc. involved in the following examples, unless otherwise specified, they are all conventional instruments, reagents, materials, etc. existing in the prior art and can be obtained through regular commercial channels. For the experimental methods, detection methods, etc. involved in the following examples, unless otherwise specified, they are all conventional experimental methods, detection methods, etc. existing in the prior art.

[0034] In the following examples and comparative examples of the present invention, the source of the red mud used is the Bayer red mud from Shandong Xinfa Group, and the percentage contents of iron and aluminum elements are 20.29% and 9.67% respectively; the particle size of the red mud after crushing is 60 - 200 mesh. The main raw materials, strong acid and sodium hydroxide, come from an electrolytic aluminum plant.

[0035] Example 1

[0036] As Figure 1 shown, a method for recovering iron, aluminum and acid from red mud by acid leaching includes the following steps:

[0037] (1) After being crushed, the red mud is mixed with a strong acid solution with a mass concentration of 31%, placed in a water bath thermostatic shaker and reacted at 80°C for 2 h. The mass - to - volume ratio of the red mud to the strong acid is 1 kg:5 L. After the reaction, filtration is carried out to obtain red mud residue and an iron - aluminum solution; the Bayer red mud is leached by high - concentration strong acid to make Fe and Al in the red mud enter the leaching solution as much as possible;

[0038] (2) The red mud residue obtained in step (1) is mixed with demineralized water. The mass - to - volume ratio of the red mud residue to the demineralized water is 1 kg:1 L. After stirring for 30 min, solid - liquid separation is carried out to obtain acid - root - removed red mud residue and a sodium salt solution;

[0039] (3) The iron - aluminum solution obtained in step (1) is placed in a heating mantle at 180°C and stirred and heated for evaporation to obtain an iron - aluminum mixed solid and a gas. The generated gas is collected and vacuumed with a vacuum pump, and cooled with 20°C cooling water to obtain a strong acid solution;

[0040] (4) The iron - aluminum mixed solid obtained in step (3) is mixed with a NaOH solution with a concentration of 130 mg / L, the pH is adjusted to 5.5, and after stirring for 30 min, solid - liquid separation is carried out to obtain an iron - aluminum hydroxide solid and a sodium salt solution;

[0041] (5) Mix the iron-aluminum hydroxide solid obtained in step (4) with demineralized water. The mass-volume ratio of the iron-aluminum hydroxide solid to demineralized water is 1 kg: 1 L. After stirring for 30 min, perform solid-liquid separation to obtain an acid radical-removed iron-aluminum hydroxide solid and a sodium salt solution;

[0042] (6) Mix the acid radical-removed iron-aluminum hydroxide solid obtained in step (5) with a NaOH solution having a concentration of 130 mg / L, adjust the pH to 13, stir for 30 min, and then perform solid-liquid separation to obtain a ferric hydroxide solid and a sodium aluminate solution.

[0043] In this example, the photo of the red mud residue obtained in step (1) is as Figure 3 shown. Compared with the original red mud (as Figure 2 shown), the color is gray, indicating that iron is leached and recovered. Perform a digestion test on the red mud residue obtained in step (2) to measure the contents of iron and aluminum, and obtain the recovery rates of iron and aluminum. The results are shown in Table 1. Perform SEM and EDS tests on the red mud and the red mud residue respectively. The results are as Figure 4 shown. The colors of iron and aluminum are significantly lighter, indicating that iron and aluminum are leached and recovered. The XRD patterns of the used red mud and the red mud residue are as Figure 5 shown. Measure the mass concentration of the strong acid solution obtained in step (3). The results are shown in Table 1. The mass concentration of the recovered strong acid solution can reach 12.86%. The volume of NaOH consumed in step (5) is shown in Table 1. The digital photo of the ferric hydroxide solid obtained in step (6) is as Figure 6 shown, which is a red powder. The sodium aluminate solution obtained is as Figure 7 shown.

[0044] Example 2

[0045] A method for acid leaching red mud to recover iron and aluminum and recover acid, comprising the following steps:

[0046] (1) After the red mud is crushed, mix it with a strong acid solution having a mass concentration of 20%. Place it in a water bath constant temperature shaker and react at 80 °C for 2 h. The mass-volume ratio of the red mud to the strong acid is 1 kg: 5 L. After the reaction, perform suction filtration to obtain a red mud residue and an iron-aluminum solution;

[0047] (2) Mix the red mud residue obtained in step (1) with demineralized water. The mass-volume ratio of the red mud residue to demineralized water is 1 kg: 1 L. After stirring for 30 min, perform solid-liquid separation to obtain an acid radical-removed red mud residue and a sodium salt solution;

[0048] (3) Place the iron-aluminum solution obtained in step (1) in a heating mantle at 180 °C and stir and heat to evaporate to obtain an iron-aluminum mixed solid and a gas. Collect the generated gas, use a vacuum pump to evacuate, and cool it with cooling water at 20 °C to obtain a strong acid solution;

[0049] (4) Mix the iron-aluminum mixed solid obtained in step (3) with a NaOH solution having a concentration of 130 mg / L, adjust the pH to 5.5, stir for 30 min, and then perform solid-liquid separation to obtain an iron-aluminum hydroxide solid and a sodium salt solution;

[0050] (5) Mix the iron-aluminum hydroxide solid obtained in step (4) with demineralized water. The mass-volume ratio of the iron-aluminum hydroxide solid to demineralized water is 1 kg:1 L. Stir for 30 min and then perform solid-liquid separation to obtain an acid root-removed iron-aluminum hydroxide solid and a sodium salt solution;

[0051] (6) Mix the acid root-removed iron-aluminum hydroxide solid obtained in step (5) with a NaOH solution having a concentration of 130 mg / L, adjust the pH to 13, stir for 30 min, and then perform solid-liquid separation to obtain an iron hydroxide solid and a sodium aluminate solution.

[0052] In this example, the red mud residue obtained in step (2) was digested to test the iron and aluminum contents, and the iron and aluminum recovery rates were obtained. The results are shown in Table 1; the mass concentration of the strong acid solution obtained in step (3) of the test is shown in Table 1. The mass concentration of the recovered strong acid solution can reach 5.78%; the volume of NaOH consumed in step (4) is shown in Table 1.

[0053] Example 3

[0054] A method for recovering iron, aluminum and acid from red mud by acid leaching includes the following steps:

[0055] (1) Separate the red mud residue and the iron-aluminum solution; specifically, it includes (1-1) mixing the red mud with a strong acid having a mass concentration of 31%, placing it in a water bath constant temperature shaker and reacting at 80 °C for 30 min. The mass-volume ratio of the red mud to the strong acid is 1 kg:1 L. After the reaction, perform suction filtration to obtain a red mud residue and an iron-aluminum solution; (1-2) mix the red mud residue with a strong acid having a mass concentration of 20%, place it in a water bath constant temperature shaker and react at 90 °C for 30 min. The mass-volume ratio of the red mud to the strong acid is 1 kg:1 L. After the reaction, perform suction filtration to obtain a red mud residue and an iron-aluminum solution; (1-3) perform step (1-2) on the red mud residue obtained each time for another 2 times; (1-4) combine all the iron-aluminum solutions.

[0056] (2) Mix the red mud residue obtained in step (1) with demineralized water. The mass-volume ratio of the red mud residue to demineralized water is 1 kg:1 L. Stir for 30 min and then perform solid-liquid separation to obtain an acid root-removed red mud residue and a sodium salt solution;

[0057] (3) Place the iron-aluminum solution obtained in step (1) in a heating jacket at 180 °C and stir and heat to evaporate to obtain an iron-aluminum mixed solid and a gas. Collect the generated gas, use a vacuum pump to evacuate, and use cooling water at 20 °C to cool to obtain a strong acid solution;

[0058] (4) Mix the iron-aluminum mixed solid obtained in step (3) with a NaOH solution having a concentration of 130 mg / L, adjust the pH to 5.5, stir for 30 min, and then perform solid-liquid separation to obtain an iron-aluminum hydroxide solid and a sodium salt solution;

[0059] (5) Mix the iron-aluminum hydroxide solid obtained in step (4) with demineralized water, and the mass-volume ratio of the iron-aluminum hydroxide solid to demineralized water is 1 kg: 1 L. Stir for 30 min and then perform solid-liquid separation to obtain an acid radical-removed iron-aluminum hydroxide solid and a sodium salt solution;

[0060] (6) Mix the acid radical-removed iron-aluminum hydroxide solid obtained in step (5) with a NaOH solution having a concentration of 130 mg / L, adjust the pH to 13, stir for 30 min, and then perform solid-liquid separation to obtain an iron hydroxide solid and a sodium aluminate solution.

[0061] In this example, the red mud residue obtained in step (2) was digested to test the contents of iron and aluminum, and the recovery rates of iron and aluminum were obtained. The results are shown in Table 1; the mass concentration of the strong acid solution obtained in step (3) of the test is shown in Table 1, and the mass concentration of the recovered strong acid solution can reach 6.08%; the volume of NaOH consumed in step (4) is shown in Table 1.

[0062] In the above examples, hydrochloric acid is used as the strong acid. Therefore, in step (2), a chlorine-removed red mud residue and a sodium chloride solution are obtained; in step (4), an iron-aluminum hydroxide solid and a sodium chloride solution are obtained; in step (5), a chlorine-removed iron-aluminum hydroxide solid and a sodium chloride solution are obtained.

[0063] Comparative Example 1

[0064] (1) After the red mud is crushed, it is mixed with a hydrochloric acid solution having a mass concentration of 31%, and reacted at 80 °C for 2 h in a water bath constant temperature shaker. The mass-volume ratio of the red mud to the strong acid is 1 kg: 5 L. After the reaction, suction filtration is performed to obtain a red mud residue and an iron-aluminum solution, and hydrochloric acid is used as the strong acid.

[0065] (2) Mix the red mud residue obtained in step (1) with demineralized water, and the mass-volume ratio of the red mud residue to demineralized water is 1 kg: 1 L. Stir for 30 min and then perform solid-liquid separation to obtain a chlorine-removed red mud residue and a sodium chloride solution;

[0066] (3) Mix the iron-aluminum solution obtained in step (1) with a NaOH solution having a concentration of 130 mg / L, adjust the pH to 5.5, stir for 30 min, and then perform solid-liquid separation to obtain an iron-aluminum hydroxide solid and a sodium chloride solution;

[0067] (4) Mix the iron-aluminum hydroxide solid obtained in step (3) with demineralized water. The mass-volume ratio of the iron-aluminum hydroxide solid to demineralized water is 1 kg: 1 L. After stirring for 30 min, perform solid-liquid separation to obtain a chlorine-removed iron-aluminum hydroxide solid and a sodium chloride solution;

[0068] (5) Mix the acid radical-removed iron-aluminum hydroxide solid obtained in step (4) with a NaOH solution having a concentration of 130 mg / L, adjust the pH to 13, stir for 30 min, and then perform solid-liquid separation to obtain a ferric hydroxide solid and a sodium aluminate solution.

[0069] In this comparative example, the red mud residue obtained in step (2) was digested to test the contents of iron and aluminum, and the recovery rates of iron and aluminum were obtained. The results are shown in Table 1; the volume of NaOH consumed in step (3) is shown in Table 1.

[0070] Table 1 Relevant data of Examples 1-3 and Comparative Example 1

[0071]

[0072] From the results in Table 1, it can be seen that the method for recovering iron, aluminum and acid from red mud in the present invention has relatively high Fe and Al recovery rates, providing a feasible solution for the resource utilization of red mud; and by recovering strong acid, the alkali consumption is greatly reduced, and the recovered strong acid also has a relatively high concentration and high utilization value; the sodium aluminate (solution) and sodium salt (solution) in the product can also be reused in the electrolytic aluminum plant to achieve the economic treatment of red mud.

[0073] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirits of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering iron, aluminum and acid by acid leaching of red mud, characterized in that: The following steps are involved: (1) crushing the red mud and mixing it with a strong acid solution, stirring it continuously under heating conditions to leach out the iron and aluminum solution, and obtaining red mud residue and the iron and aluminum solution after solid-liquid separation; (2) mixing the red mud residue obtained in step (1) with desalted water, stirring and separating the solid and liquid to obtain the acid-free red mud residue and sodium salt solution; (3) stirring, heating and evaporating the iron-aluminum solution obtained in step (1) to obtain an iron-aluminum mixed solid and gas, collecting the generated gas and vacuum cooling to obtain a strong acid solution; (4) mixing the iron-aluminum mixed solid obtained in step (3) with a NaOH solution, adjusting the pH to 5 to 6, stirring and separating the solid and the liquid to obtain an iron-aluminum hydroxide solid and a sodium salt solution; (5) mixing the iron aluminum hydroxide solid obtained in step (4) with desalted water, stirring and separating the solid and the liquid to obtain the iron aluminum hydroxide solid with the acid radical removed and a sodium salt solution; (6) The deacidified iron aluminum hydroxide solid obtained in step (5) is mixed with a NaOH solution, the pH value is adjusted to 10 to 14, and the solid-liquid separation is performed after stirring to obtain an iron hydroxide solid and a sodium aluminate solution.

2. The method for recovering iron, aluminum and acid by acid leaching of red mud according to claim 1, characterized in that: In the step (1), the red mud includes Bayer process red mud, sintering process red mud or combined process red mud.

3. The method for recovering iron, aluminum and acid by acid leaching of red mud according to claim 1, characterized in that: The red mud is crushed into particles of 60 to 200 meshes.

4. The method for recovering iron, aluminum and acid by acid leaching of red mud according to claim 1, characterized in that: In the step (1), the mass concentration of the strong acid is 15% to 36%; the iron-aluminum solution is leached in a cycle for 3 to 6 times, and the iron-aluminum solution is leached in a cycle, which means that red mud and a strong acid solution are heated and stirred, solid-liquid separation is performed, and red mud residue and an iron-aluminum solution are obtained; the red mud residue is heated and stirred with a strong acid solution, solid-liquid separation is performed, and red mud residue and an iron-aluminum solution are obtained; the mass volume ratio of the red mud or red mud residue to the strong acid solution is 1kg: (1L to 5L) each time, the stirring time is 30min to 12h, and the stirring temperature is 50 to 95°C, and finally red mud residue and a mixed iron-aluminum solution are obtained.

5. The method for recovering iron, aluminum and acid by acid leaching of red mud according to claim 1, characterized in that: The step (1) specifically includes (1-1) mixing red mud with a strong acid having a mass concentration of 31%, placing the mixture in a water constant temperature oscillator at 80°C for reaction for 30 minutes, wherein the mass volume ratio of the red mud to the strong acid is 1kg:1L, and filtering after the reaction to obtain red mud residue and an iron-aluminum solution; (1-2) mixing the red mud residue with a strong acid having a mass concentration of 20%, placing the mixture in a water constant temperature oscillator at 90°C for reaction for 30 minutes, wherein the mass volume ratio of the red mud to the strong acid is 1kg:1L, and filtering after the reaction to obtain red mud residue and an iron-aluminum solution; (1-3) performing step (1-2) twice on the red mud residue obtained each time; and (1-4) combining all the iron-aluminum solutions.

6. The method for recovering iron, aluminum and acid by acid leaching of red mud according to claim 1, characterized in that: The strong acid is an organic acid or an inorganic acid; the organic acid is oxalic acid or citric acid, and the inorganic acid is hydrochloric acid, nitric acid or sulfuric acid.

7. The method for recovering iron, aluminum and acid by acid leaching of red mud according to claim 1, characterized in that: In the step (2), the mass volume ratio of red mud slag to desalted water is 1 kg: (500 mL-5 L); in the step (3), the heating and evaporation methods include steam heating, electric heating and coal heating, and the heating and evaporation temperature is 100-200° C.; the gas cooling methods include natural cooling and condensed water cooling.

8. The method for recovering iron, aluminum and acid by acid leaching of red mud according to claim 1, characterized in that: In the step (4), the stirring time is 15 min to 6 h.

9. The method for recovering iron, aluminum and acid by acid leaching of red mud according to claim 1, characterized in that: In the step (5), the mass volume ratio of the iron-aluminum mixed solid to the desalted water is 1 kg: (500 mL-5 L).

10. The method for recovering iron, aluminum and acid by acid leaching of red mud according to claim 1, characterized in that: In the step (6), the stirring time is 15 min to 6 h.

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