A method for dealkalization of red mud
By pretreating, roasting, physically separating iron, and leaching the red mud, combined with adjusting the pH value with a buffer solution to precipitate aluminum, the problems of low red mud dealkali removal efficiency and waste residue generation were solved, achieving a highly efficient and rapid dealkali removal process and producing dealkali-removed samples that can be used as cement raw materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2023-12-05
- Publication Date
- 2026-05-19
AI Technical Summary
Existing red mud dealkali removal methods suffer from low dealkali removal efficiency, long cycle time, waste residue generation, and difficulty in large-scale treatment, which affects their application in the building materials field.
Red mud is pretreated, mixed with additives, and roasted. Then, it undergoes physical iron selection and alkali leaching. The pH value is adjusted using a buffer solution to precipitate aluminum. Finally, it is washed with water to obtain a dealkali-treated sample, which is suitable as a cement raw material.
It achieves an efficient and rapid red mud dealkali removal process, producing dealkali-removed samples that can be used as cement raw materials, avoiding the generation of waste residue, and is suitable for batch processing.
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Figure CN117699835B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of chemical engineering, metallurgy and iron beneficiation technology, and more specifically to a method for dealkalizing red mud. Background Technology
[0002] Red mud is a highly alkaline solid waste generated during alumina production. As a major alumina producer, my country discharges as much as 120 million tons of red mud annually, with accumulated stockpiles exceeding 1 billion tons. However, annual usage is less than 7 million tons, resulting in a comprehensive utilization rate of less than 6%. To achieve the goal of a 60% comprehensive utilization rate for newly added bulk solid waste and an orderly reduction in existing bulk solid waste by 2025, the annual comprehensive utilization of red mud needs to reach over 60 million tons. Currently, the scale and rate of red mud utilization in my country are still far from meeting the target.
[0003] In the 1970s, red mud was dumped into the ocean. In recent years, the main treatment of red mud has been landfilling. However, this method not only occupies land resources but also causes harmful chemical components in the red mud to seep into the soil and groundwater, potentially leading to ecological and environmental problems such as soil alkalization, marshland formation, and groundwater pollution. Another treatment method is stockpiling, but because red mud particles have a low natural density, after the surface dries, a large number of extremely fine red mud particles will form dust in windy weather, which will fall into the air and cause serious pollution to the surrounding environment and atmosphere.
[0004] The application of red mud in building materials is an important means of realizing red mud utilization. my country has conducted extensive research on the preparation of (geopolymer) cementitious materials from red mud. The application of red mud in building materials has also demonstrated its advantages in low carbon and energy conservation. Its large-scale promotion should be one of the important paths to help the non-ferrous metals industry achieve carbon peak and carbon neutrality. In addition, traditional technologies for preparing sintered bricks, silicate cement, and sulfoaluminate cement by co-firing red mud are also mature, but the amount of red mud that can be co-fired is very limited due to the alkali content in the red mud.
[0005] Currently, the main methods for red mud dealkali removal include water washing, acid leaching, pyrometallurgical dealkali removal, and biological dealkali removal. Water washing dealkali removal utilizes water soaking or rinsing to dissolve the free alkaline components contained in the red mud. However, this method generates a large amount of alkaline wastewater during the experiment, requiring subsequent treatment. Acid leaching dealkali removal uses inorganic or organic acids to neutralize the free alkali contained in the red mud, achieving a dealkali removal rate of up to 95%, and is also one of the research hotspots in red mud dealkali removal. The drawback of this method lies in the treatment of the waste acid after dealkali removal. Pyrometallurgical dealkali removal involves adding lime to the red mud for roasting. By adjusting the roasting temperature, roasting time, and calcium oxide addition, under optimal process conditions, the residue dissolved after washing has an alkali content of less than 1%. However, it has disadvantages such as high calcium oxide dosage, large residue, and substandard alkali content. For example, Chinese patent (patent number: CN107915386A); patent title: A biological dealkalization method for red mud. This patented method involves inoculating a suspension of Aspergillus niger spores into a culture medium and fermenting it in a fermenter to produce acid. The resulting fermentation broth enters a bacterial separation tank, and the separated fermentation broth enters a coagulation sedimentation tank to further remove the tiny mycelia and suspended matter. Then, the cleaned fermentation broth is sent to a dealkalization tank to undergo an acid-base neutralization reaction and solid-liquid separation process with red mud powder. The upper clear liquid after separation is the dealkalized liquid, and the lower part is the dealkalized red mud. This method is still in the laboratory stage due to its long cycle and the difficulty in selecting and culturing bacteria.
[0006] Therefore, it is still necessary to study a dealkali removal method that is highly efficient, has a short cycle, and can be processed in batches. Summary of the Invention
[0007] To solve the above-mentioned technical problems, the present invention provides a method for dealkalizing red mud, characterized by comprising the following steps:
[0008] S1. Red mud pretreatment: The red mud raw material is put into a crusher for crushing. After crushing, it is put into an oven at 105℃ for 24 hours to dry. The dried red mud sample is passed through a 200-mesh sieve and then dried.
[0009] S2. Based on S1, the dried red mud sample and the additive are mixed evenly according to a certain mass ratio and then placed in a high-temperature muffle furnace for roasting. After roasting, the sample is naturally cooled to obtain roasted residue.
[0010] S3. Based on S2, the roasted slag is placed into the magnetic separator and then enters the physical iron separation process. The product after physical iron separation is divided into iron-containing coarse slag and iron-separated tail slag.
[0011] S4.1 Based on S3, the iron-containing coarse slag is refined and sold as a product;
[0012] S4.2 Based on S3, the iron tailings are added to sodium hydroxide solution in a certain proportion for alkaline leaching. After alkaline leaching, solid-liquid separation is performed to obtain alkaline leaching solution and alkaline leaching tailings.
[0013] S5.1, Based on S4.2, a buffer solvent is added to the alkaline leaching solution to adjust the pH to 8-9.5, thereby removing Al from the alkaline leaching solution. 3+ It precipitates out in the form of Al(OH)3, and then undergoes solid-liquid separation to obtain aluminum mother liquor and alumina product;
[0014] S5.2 Based on S4.2, a buffer solution is added to the alkaline leaching tailings to adjust the pH of the leachate to 8-8.5. After solid-liquid separation, solid residue and filtrate are obtained.
[0015] S6.1, based on S5.1 and S5.2, the filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product;
[0016] S6.2 Based on S5.2, the solid slag is washed three times with high-purity water in a countercurrent manner. After washing, it is dried to obtain a dealkali sample, which can be used as a cement raw material.
[0017] Preferably, the additive in step S2 is one or more of CaO, CaCO3, Ca(OH)2, CaCl2, Na2CO3, NaHCO3, NaCl, and CaSO4.
[0018] Preferably, the mass ratio of red mud sample to additive in step S2 is 5:4 to 10.
[0019] Preferably, the calcination temperature in step S2 is 900℃~1100℃, and the calcination time is 1.5~2.5h.
[0020] Preferably, the magnetic separation intensity of the magnetic separator in step S3 is 4000 to 6000 Gauss.
[0021] Preferably, in step S4.2, the concentration of the sodium hydroxide solution is 25% to 50%, and the solid-liquid ratio of the selected iron tailings to the sodium hydroxide solution is 1:3 to 7.
[0022] Preferably, the reaction temperature of the alkaline leaching in step S4.2 is 50-90°C, and the reaction time is 1-3 hours.
[0023] Preferably, the buffer solutions used in steps S5.1 and S5.2 are both carbonate solvents.
[0024] Compared with the prior art, the present invention has the following beneficial effects:
[0025] (1) This invention involves crushing red mud raw materials in a crusher, drying them after crushing and passing them through a 200-mesh sieve, and then further drying them. The dried red mud sample is then mixed evenly with additives at a certain mass ratio and placed in a high-temperature muffle furnace for roasting. After roasting, the mixture is cooled to obtain roasted slag. The roasted slag is then placed in a magnetic separator and enters the physical iron separation process. The products after physical iron separation are divided into iron-containing coarse slag and iron-selection tail slag. The iron-containing coarse slag is refined and sold as a product. The iron-selection tail slag is added to a sodium hydroxide solution in a certain proportion for alkaline leaching. After alkaline leaching, solid-liquid separation is performed to obtain alkaline leaching solution and alkaline leaching tailings. A buffer solvent is added to the alkaline leaching solution to adjust the pH, and the solution is subjected to aluminum precipitation treatment, followed by solid-liquid separation to obtain aluminum precipitation mother liquor and alumina product. A buffer solution is added to the alkaline leaching tailings to adjust the pH of the leachate, and solid-liquid separation is performed to obtain solid slag and filtrate. The filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product. The solid slag is washed three times countercurrently with high-purity water, and then dried to obtain a dealkalized sample, which can be used as cement raw material. This process for dealkalizing red mud is simple, highly efficient, has a short cycle time, allows for batch processing of red mud raw materials, and produces no waste residue, making it suitable for widespread application. Attached Figure Description
[0026] Figure 1 This is a process flow diagram of the present invention.
[0027] Figure 2 This is a SEM image of the red mud raw material of this invention.
[0028] Figure 3 This is a SEM image of the roasting residue of this invention.
[0029] Figure 4 This is a SEM image of the dealkali-treated sample of the present invention. Detailed Implementation
[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0031] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0033] Example 1
[0034] This embodiment provides a method for dealkalizing red mud, including the following steps:
[0035] S1. Red mud pretreatment: The red mud raw material is put into a crusher for crushing. After crushing, it is put into an oven at 105℃ for 24 hours to dry. The dried red mud sample is passed through a 200-mesh sieve and then dried.
[0036] S2. Based on S1, the dried red mud sample and the additive are mixed evenly in a mass ratio of 5:4 to 10 and then placed in a high-temperature muffle furnace. The roasting temperature is selected as 900℃ to 1100℃ and the roasting time is 1.5 to 2.5h. Specifically, the additive is one or more of CaO, CaCO3, Ca(OH)2, CaCl2, Na2CO3, NaHCO3, NaCl, and CaSO4. After roasting, the mixture is naturally cooled to obtain roasted residue.
[0037] S3. Based on S2, the roasted slag is placed into a magnetic separator and then enters the physical iron separation process. The magnetic separation intensity of the magnetic separator is 4000-6000 Gauss. The product after physical iron separation is divided into iron-containing coarse slag and iron-separated tailings.
[0038] S4.1 Based on S3, the iron-containing coarse slag is refined and sold as a product;
[0039] S4.2 Based on S3, the iron tailings are added to a sodium hydroxide solution with a concentration of 25% to 50% for alkaline leaching at a solid-liquid ratio of 1:3 to 7. The reaction temperature of alkaline leaching is 50 to 90°C and the reaction time is 1 to 3 hours. After alkaline leaching is completed, solid-liquid separation is performed to obtain alkaline leaching solution and alkaline leaching tailings.
[0040] S5.1, Based on S4.2, a buffer solvent is added to the alkaline leaching solution to adjust the pH to 8-9.5, thereby removing Al from the alkaline leaching solution. 3+ It precipitates out in the form of Al(OH)3, and then undergoes solid-liquid separation to obtain aluminum mother liquor and alumina product;
[0041] S5.2 Based on S4.2, a buffer solution is added to the alkaline leaching tailings to adjust the pH of the leachate to 8-8.5. After solid-liquid separation, solid residue and filtrate are obtained.
[0042] In this embodiment, the buffer solutions used in steps S5.1 and S5.2 are both carbonate solvents.
[0043] S6.1, based on S5.1 and S5.2, the filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product;
[0044] S6.2 Based on S5.2, the solid slag is washed three times with high-purity water in a countercurrent manner. After washing, it is dried to obtain a dealkali sample, which can be used as a cement raw material.
[0045] Example 2
[0046] This embodiment provides a method for dealkalizing red mud, including the following steps:
[0047] S1. Red mud pretreatment: The red mud raw material is put into a crusher for crushing. After crushing, it is put into an oven at 105℃ for 24 hours to dry. The dried red mud sample is passed through a 200-mesh sieve and then dried.
[0048] S2. Based on S1, the dried red mud sample, CaO and Na2CO3 were mixed evenly in a mass ratio of 5:4:2 and placed in a muffle furnace for calcination at 900℃ for 2.5h. After calcination, the mixture was cooled to obtain calcined residue.
[0049] S3. Based on S2, the roasted slag is placed into the magnetic separator and then enters the physical iron separation process. The magnetic separation intensity of the magnetic separator is 4000 Gauss. The product after physical iron separation is divided into iron-containing coarse slag and iron-separated tailings.
[0050] S4.1 Based on S3, the iron-containing coarse slag is refined and sold as a product;
[0051] S4.2 Based on S3, the iron tailings were added to a 30% sodium hydroxide solution at a solid-liquid ratio of 1:5 for alkaline leaching. The reaction temperature of the alkaline leaching was 50℃ and the reaction time was 2.5h. After the alkaline leaching was completed, solid-liquid separation was performed to obtain alkaline leaching solution and alkaline leaching tailings.
[0052] S5.1, Based on S4.2, add 30% ammonium bicarbonate buffer solution to the alkaline leaching solution to adjust the pH to 8-9.5, thereby removing Al from the alkaline leaching solution. 3+ It precipitates out in the form of Al(OH)3, and then undergoes solid-liquid separation to obtain aluminum mother liquor and alumina product;
[0053] S5.2 Based on S4.2, add 30% ammonium bicarbonate buffer solution to the alkaline leaching tailings to adjust the pH of the leachate to 8-8.5, and obtain solid residue and filtrate after solid-liquid separation;
[0054] S6.1, based on S5.1 and S5.2, the filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product;
[0055] S6.2, based on S5.2, the solid slag is washed three times countercurrently with high-purity water, and then dried to obtain a dealkali-treated sample. The dealkali-treated sample can be used as a cement raw material. The relevant data of the dealkali-treated sample are as follows:
[0056] Table 2.1 shows the XRF data of the alkaline leaching tailings produced in Example 2.
[0057] element Na K Si Fe Al Ca content(%) 4.075 0.009 5.569 6.473 5.406 22.272
[0058] Table 2.2 shows the XRF data of the alkaline leaching tailings produced in Example 2.
[0059] oxides <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> CaO content(%) 6.053 0.013 13.428 10.572 11.395 36.82
[0060] Example 3
[0061] This embodiment provides a method for dealkalizing red mud, including the following steps:
[0062] S1. Red mud pretreatment: The red mud raw material is put into a crusher for crushing. After crushing, it is put into an oven at 105℃ for 24 hours to dry. The dried red mud sample is passed through a 200-mesh sieve and then dried.
[0063] S2. Based on S1, the dried red mud sample, CaCO3 and NaCl were mixed evenly in a mass ratio of 5:5:3 and placed in a muffle furnace for calcination at 900℃ for 3 hours. After calcination, the mixture was cooled to obtain calcined residue.
[0064] S3. Based on S2, the roasted slag is placed into the magnetic separator and then enters the physical iron separation process. The magnetic separation intensity of the magnetic separator is 4500 Gauss. The product after physical iron separation is divided into iron-containing coarse slag and iron-separated tailings.
[0065] S4.1 Based on S3, the iron-containing coarse slag is refined and sold as a product;
[0066] S4.2 Based on S3, the iron tailings were added to a 40% sodium hydroxide solution at a solid-liquid ratio of 1:6 for alkaline leaching. The reaction temperature of the alkaline leaching was 60℃ and the reaction time was 2h. After the alkaline leaching was completed, solid-liquid separation was performed to obtain alkaline leaching solution and alkaline leaching tailings.
[0067] S5.1, Based on S4.2, add 35% ammonium bicarbonate buffer solution to the alkaline leaching solution to adjust the pH to 8-9.5, thereby removing Al from the alkaline leaching solution. 3+ It precipitates out in the form of Al(OH)3, and then undergoes solid-liquid separation to obtain aluminum mother liquor and alumina product;
[0068] S5.2 Based on S4.2, add 35% ammonium bicarbonate buffer solution to the alkaline leaching tailings to adjust the pH of the leachate to 8-8.5, and obtain solid residue and filtrate after solid-liquid separation;
[0069] S6.1, based on S5.1 and S5.2, the filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product;
[0070] S6.2, based on S5.2, the solid slag is washed three times countercurrently with high-purity water, and then dried to obtain a dealkali-treated sample. The dealkali-treated sample can be used as a cement raw material. The relevant data of the dealkali-treated sample are as follows:
[0071] Table 3.1 shows the XRF data of the alkaline leaching tailings produced in Example 3.
[0072] element Na K Si Fe Al Ca content(%) 0.543 0.0117 4.285 5.216 5.156 27.324
[0073] Table 3.2 shows the XRF data of the alkaline leaching tailings produced in Example 3.
[0074] oxides <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> CaO content(%) 0.829 0.015 10.631 9.31 11.154 47.406
[0075] Example 4
[0076] This embodiment provides a method for dealkalizing red mud, including the following steps:
[0077] S1. Red mud pretreatment: The red mud raw material is put into a crusher for crushing. After crushing, it is put into an oven at 105℃ for 24 hours to dry. The dried red mud sample is passed through a 200-mesh sieve and then dried.
[0078] S2. Based on S1, the dried red mud sample, CaCO3 and Na2CO3 were mixed evenly in a mass ratio of 5:5.5:3, and then placed in a muffle furnace and calcined at 1000℃ for 2 hours. After calcination, the mixture was cooled to obtain calcined residue.
[0079] S3. Based on S2, the roasted slag is placed into the magnetic separator and then enters the physical iron separation process. The magnetic separation intensity of the magnetic separator is 4500 Gauss. The product after physical iron separation is divided into iron-containing coarse slag and iron-separated tailings.
[0080] S4.1 Based on S3, the iron-containing coarse slag is refined and sold as a product;
[0081] S4.2 Based on S3, the iron tailings were added to a 40% sodium hydroxide solution at a solid-liquid ratio of 1:6 for alkaline leaching. The reaction temperature of the alkaline leaching was 80℃ and the reaction time was 1.5h. After the alkaline leaching was completed, solid-liquid separation was performed to obtain alkaline leaching solution and alkaline leaching tailings.
[0082] S5.1, Based on S4.2, add 36% ammonium bicarbonate buffer solution to the alkaline leaching solution to adjust the pH to 8-9.5, thereby removing Al from the alkaline leaching solution. 3+ It precipitates out in the form of Al(OH)3, and then undergoes solid-liquid separation to obtain aluminum mother liquor and alumina product;
[0083] S5.2 Based on S4.2, add 36% ammonium bicarbonate buffer solution to the alkaline leaching tailings to adjust the pH of the leachate to 8-8.5, and obtain solid residue and filtrate after solid-liquid separation;
[0084] S6.1, based on S5.1 and S5.2, the filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product;
[0085] S6.2, based on S5.2, the solid slag is washed three times countercurrently with high-purity water, and then dried to obtain a dealkali-treated sample. The dealkali-treated sample can be used as a cement raw material. The relevant data of the dealkali-treated sample are as follows:
[0086] Table 4.1 shows the XRF data of the alkaline leaching tailings produced in Example 4.
[0087] element Na K Si Fe Al Ca content(%) 0.401 0 3.476 4.431 4.747 29.116
[0088] Table 4.2 shows the XRF data of the alkaline leaching tailings produced in Example 4.
[0089] oxides <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> CaO content(%) 0.631 0 8.924 10.791 10.592 53.454
[0090] Example 5
[0091] This embodiment provides a method for dealkalizing red mud, including the following steps:
[0092] S1. Red mud pretreatment: The red mud raw material is put into a crusher for crushing. After crushing, it is put into an oven at 105℃ for 24 hours to dry. The dried red mud sample is passed through a 200-mesh sieve and then dried.
[0093] S2. Based on S1, the dried red mud sample, CaCl2 and Na2CO3 were mixed evenly in a mass ratio of 5:5:2.5 and placed in a muffle furnace for calcination at 900℃ for 2.5h. After calcination, the mixture was cooled to obtain calcined residue.
[0094] S3. Based on S2, the roasted slag is placed into the magnetic separator and then enters the physical iron separation process. The magnetic separation intensity of the magnetic separator is 4500 Gauss. The product after physical iron separation is divided into iron-containing coarse slag and iron-separated tailings.
[0095] S4.1 Based on S3, the iron-containing coarse slag is refined and sold as a product;
[0096] S4.2 Based on S3, the iron tailings were added to a 45% sodium hydroxide solution at a solid-liquid ratio of 1:5 for alkaline leaching. The reaction temperature of the alkaline leaching was 90℃ and the reaction time was 1h. After the alkaline leaching was completed, solid-liquid separation was performed to obtain alkaline leaching solution and alkaline leaching tailings.
[0097] S5.1, Based on S4.2, add 36% ammonium bicarbonate buffer solution to the alkaline leaching solution to adjust the pH to 8-9.5, thereby removing Al from the alkaline leaching solution. 3+ It precipitates out in the form of Al(OH)3, and then undergoes solid-liquid separation to obtain aluminum mother liquor and alumina product;
[0098] S5.2 Based on S4.2, add 36% ammonium bicarbonate buffer solution to the alkaline leaching tailings to adjust the pH of the leachate to 8-8.5, and obtain solid residue and filtrate after solid-liquid separation;
[0099] S6.1, based on S5.1 and S5.2, the filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product;
[0100] S6.2, based on S5.2, the solid slag is washed three times countercurrently with high-purity water, and then dried to obtain a dealkali-treated sample. The dealkali-treated sample can be used as a cement raw material. The relevant data of the dealkali-treated sample are as follows:
[0101] Table 5.1 shows the XRF data of the alkaline leaching tailings produced in Example 5.
[0102] element Na K Si Fe Al Ca content(%) 0.565 0 1.912 5.472 3.02 34.976
[0103] Table 5.2 shows the XRF data of the alkaline leaching tailings produced in Example 5.
[0104] oxides <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> CaO content(%) 0.926 0 5.111 12.459 7.023 69.453
[0105] Example 6
[0106] This embodiment provides a method for dealkalizing red mud, including the following steps:
[0107] S1. Red mud pretreatment: The red mud raw material is put into a crusher for crushing. After crushing, it is put into an oven at 105℃ for 24 hours to dry. The dried red mud sample is passed through a 200-mesh sieve and then dried.
[0108] S2. Based on S1, the dried red mud sample, CaCl2 and NaHCO3 were mixed evenly in a mass ratio of 5:5:2.5 and placed in a muffle furnace for calcination at 1000℃ for 1.5h. After calcination, the mixture was cooled to obtain calcined residue.
[0109] S3. Based on S2, the roasted slag is placed into the magnetic separator and then enters the physical iron separation process. The magnetic separation intensity of the magnetic separator is 4500 Gauss. The product after physical iron separation is divided into iron-containing coarse slag and iron-separated tailings.
[0110] S4.1 Based on S3, the iron-containing coarse slag is refined and sold as a product;
[0111] S4.2 Based on S3, the iron tailings were added to a 45% sodium hydroxide solution at a solid-liquid ratio of 1:6 for alkaline leaching. The reaction temperature of the alkaline leaching was 90℃ and the reaction time was 1.5h. After the alkaline leaching was completed, solid-liquid separation was performed to obtain alkaline leaching solution and alkaline leaching tailings.
[0112] S5.1, Based on S4.2, add 36% ammonium bicarbonate buffer solution to the alkaline leaching solution to adjust the pH to 8-9.5, thereby removing Al from the alkaline leaching solution. 3+ It precipitates out in the form of Al(OH)3, and then undergoes solid-liquid separation to obtain aluminum mother liquor and alumina product;
[0113] S5.2 Based on S4.2, add 36% ammonium bicarbonate buffer solution to the alkaline leaching tailings to adjust the pH of the leachate to 8-8.5, and obtain solid residue and filtrate after solid-liquid separation;
[0114] S6.1, based on S5.1 and S5.2, the filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product;
[0115] S6.2, based on S5.2, the solid slag is washed three times countercurrently with high-purity water, and then dried to obtain a dealkali-treated sample. The dealkali-treated sample can be used as a cement raw material. The relevant data of the dealkali-treated sample are as follows:
[0116] Table 6.1 shows the XRF data of the alkaline leaching tailings produced in Example 6.
[0117] element Na K Si Fe Al Ca content(%) 0.341 0.005 3.248 4.346 4.954 29.335
[0118] Table 6.2 shows the XRF data of the alkaline leaching tailings produced in Example 6.
[0119] oxides <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> CaO content(%) 0.504 0.009 7.284 10.135 10.263 58.236
[0120] CaO, CaCO3, Ca(OH)2, CaCl2, Na2CO3, NaHCO3, NaCl, CaSO4
[0121] Example 7
[0122] This embodiment provides a method for dealkalizing red mud, including the following steps:
[0123] S1. Red mud pretreatment: The red mud raw material is put into a crusher for crushing. After crushing, it is put into an oven at 105℃ for 24 hours to dry. The dried red mud sample is passed through a 200-mesh sieve and then dried.
[0124] S2. Based on S1, the dried red mud sample, Ca(OH)2 and Na2CO3 were mixed evenly in a mass ratio of 5:6:3 and placed in a muffle furnace for calcination at 1000℃ for 1.5h. After calcination, the mixture was cooled to obtain calcined residue.
[0125] S3. Based on S2, the roasted slag is placed into the magnetic separator and then enters the physical iron separation process. The magnetic separation intensity of the magnetic separator is 4500 Gauss. The product after physical iron separation is divided into iron-containing coarse slag and iron-separated tailings.
[0126] S4.1 Based on S3, the iron-containing coarse slag is refined and sold as a product;
[0127] S4.2 Based on S3, the iron tailings were added to a 45% sodium hydroxide solution at a solid-liquid ratio of 1:6 for alkaline leaching. The reaction temperature of the alkaline leaching was 90℃ and the reaction time was 1.5h. After the alkaline leaching was completed, solid-liquid separation was performed to obtain alkaline leaching solution and alkaline leaching tailings.
[0128] S5.1, Based on S4.2, add 36% ammonium bicarbonate buffer solution to the alkaline leaching solution to adjust the pH to 8-9.5, thereby removing Al from the alkaline leaching solution. 3+ It precipitates out in the form of Al(OH)3, and then undergoes solid-liquid separation to obtain aluminum mother liquor and alumina product;
[0129] S5.2 Based on S4.2, add 36% ammonium bicarbonate buffer solution to the alkaline leaching tailings to adjust the pH of the leachate to 8-8.5, and obtain solid residue and filtrate after solid-liquid separation;
[0130] S6.1, based on S5.1 and S5.2, the filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product;
[0131] S6.2, based on S5.2, the solid slag is washed three times countercurrently with high-purity water, and then dried to obtain a dealkali-treated sample. The dealkali-treated sample can be used as a cement raw material. The relevant data of the dealkali-treated sample are as follows:
[0132] Table 7.1 shows the XRF data of the alkaline leaching tailings produced in Example 7.
[0133] element Na K Si Fe Al Ca content(%) 0.306 0.009 3.676 4.335 5.289 32.565
[0134] Table 7.2 shows the XRF data of the alkaline leaching tailings produced in Example 7.
[0135] oxides <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> CaO content(%) 0.428 0.013 9.334 10.086 9.957 55.234
[0136] The XRF data of the red mud raw materials used in Examples 1-7 are shown in the table below:
[0137] element Na K Si Fe Al Ca content(%) 4.46 0.916 8.205 15 11.625 13.77
[0138] The XRF data tables for the oxide forms of the red mud raw material and the dealkali-treated samples in Examples 2-7 are shown below:
[0139] <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> CaO Original Red Mud 6.32 1.68 18.32 18.17 21.71 20.49 Example 2 6.053 0.013 13.428 10.572 11.395 36.82 Example 3 0.829 0.015 10.631 9.31 11.154 47.406 Example 4 0.631 0 8.924 10.791 10.592 53.454 Example 5 0.926 0 5.111 12.459 7.023 69.453 Example 6 0.504 0.009 7.284 10.135 10.263 58.236 Example 7 0.428 0.013 9.334 10.086 9.957 55.234
[0140] As shown in the table above, after roasting, some non-magnetic iron is converted into magnetic iron, which is very beneficial for physical iron removal. The products obtained after dealkalization treatment of red mud raw materials using the methods in Examples 2-7 have calcium-silicon ratios, iron and aluminum contents, etc., that meet the requirements for red mud as a cement raw material. The XRF data tables of the alkali leaching tailings from Examples 6 and 7 show that even before reaching the final dealkalized sample, the alkali leaching tailings generated in the intermediate steps of dealkalization treatment of red mud raw materials using the methods in Examples 6 and 7 can meet the requirements for cement raw materials and be effectively utilized, increasing economic benefits.
[0141] It should be noted that the various equipment, instruments, and raw materials used in this invention are all commercially available and can be purchased independently. They are not the innovative aspects of this invention, therefore, no specific brand or model is specified in this invention.
[0142] As can be seen from the above embodiments of the present invention, the process of dealkalizing red mud using this method is simple, has high dealkalization efficiency, short cycle, can process red mud raw materials in batches, does not produce waste residue, and can be widely used.
[0143] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any modifications, equivalent changes, improvements, etc., made in accordance with the claims of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for dealkalizing red mud, characterized in that, Includes the following steps: S1. Red mud pretreatment: The red mud raw material is put into a crusher for crushing. After crushing, it is put into an oven at 105℃ for 24 hours to dry. The dried red mud sample is passed through a 200-mesh sieve and then dried. S2. Based on S1, the dried red mud sample and the additive are mixed evenly according to a certain mass ratio and then placed in a high-temperature muffle furnace for roasting. After roasting, the sample is naturally cooled to obtain roasted residue. S3. Based on S2, the roasted slag is placed into the magnetic separator and then enters the physical iron separation process. The product after physical iron separation is divided into iron-containing coarse slag and iron-separated tail slag. S4.1 Based on S3, iron-containing coarse slag is refined and sold as a product; S4.2 Based on S3, the iron tailings are added to sodium hydroxide solution in a certain proportion for alkaline leaching. After alkaline leaching, solid-liquid separation is performed to obtain alkaline leaching solution and alkaline leaching tailings. S5.1, Based on S4.2, a buffer solvent is added to the alkaline leaching solution to adjust the pH to 8-9.5, thereby removing Al from the alkaline leaching solution. 3+ It precipitates out in the form of Al(OH)3, and then undergoes solid-liquid separation to obtain aluminum mother liquor and alumina product; S5.2 Based on S4.2, a buffer solution is added to the alkaline leaching tailings to adjust the pH of the leachate to 8-8.
5. After solid-liquid separation, solid residue and filtrate are obtained. S6.1, based on S5.1 and S5.2, the filtrate is mixed with the aluminum precipitation mother liquor to recover sodium carbonate product; S6.2 Based on S5.2, the solid slag is washed three times with high-purity water in a countercurrent manner. After washing, it is dried to obtain a dealkali sample, which can be used as a cement raw material. The additive in step S2 is one or more of CaO, CaCO3, Ca(OH)2, CaCl2, Na2CO3, NaHCO3, NaCl, and CaSO4. In step S2, the mass ratio of red mud sample to additive is 5:4~10; In step S4.2, the concentration of sodium hydroxide solution is 25%~50%, and the solid-liquid ratio of iron tailings to sodium hydroxide solution is 1:3~7. The reaction temperature for the alkaline leaching in step S4.2 is 50~90℃, and the reaction time is 1~3h.
2. The method for dealkalizing red mud according to claim 1, characterized in that: The roasting temperature in step S2 is 900℃~1100℃, and the roasting time is 1.5~2.5h.
3. The method for dealkalizing red mud according to claim 2, characterized in that: In step S3, the magnetic separation intensity of the magnetic separator is 4000~6000 Gauss.
4. The method for dealkalizing red mud according to claim 3, characterized in that: The buffer solutions used in steps S5.1 and S5.2 are both ammonium bicarbonate buffer solutions.