Red mud roadbed filler based on industrial tail gas regulation and control acidification and preparation method of red mud roadbed filler

Abstract

The invention discloses a red mud roadbed filler based on industrial tail gas regulation acidification and a preparation method of the red mud roadbed filler, and belongs to the technical field of industrial solid waste recycling and road engineering materials. According to the method, after red mud, calcium-based solid waste and a pollution component curing agent are mixed, industrial tail gas at 300-500 DEG C is utilized for gradient acidification under the conditions of specific pressure (0.5-2.0 MPa) and time (1-4 h), and active design of particle size grading of an acidified product is achieved by accurately regulating and controlling acidifying process parameters, so that the acidified product meets the optimal grading curve of roadbed filler. Acidic components such as CO2, SO2 and NOx in the industrial tail gas react with the calcium-based solid waste, so that gelation products such as calcium sulfate and calcium nitrate are generated while desulfurization and denitrification are realized, and the performance of the material is synergistically improved. The introduced pollution component curing agent can specifically adsorb and fix soluble sodium ions and heavy metal ions remaining in the red mud in the acidification process and the later service stage, migration of alkali and heavy metal is effectively inhibited, and meanwhile the pollution component curing agent serves as a nano reinforced phase to improve the compactness and mechanical property of the material. According to the obtained acidified red mud roadbed filler, the optimal water content range is 12-18%, the maximum dry density can reach 1.8-2.1 g / cm < 3 >, the CBR value is larger than 80%, the water stability is larger than 0.8, and the unconfined compressive strength gt is achieved; and the leaching concentration of sodium / heavy metal meets the III water standard of Quality Standard for Underground Water. The requirements of highway subgrade filler technology and environmental protection are completely met, and three targets of red mud harmlessness, tail gas purification and subgrade material production are achieved.

Description

Technical Field

[0001] This invention belongs to the field of industrial solid waste resource utilization and road engineering, and relates to a roadbed filler that utilizes industrial exhaust gas to acidify red mud and regulate its engineering properties, while simultaneously providing long-term stability against harmful ions, and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Red mud is a large amount of solid waste generated during the alumina industrial production process. Its strong alkalinity poses a potential threat to the environment, with global annual emissions exceeding 150 million tons.

[0004] The main reason restricting the utilization of red mud resources is its strong alkalinity. Carbonation is an effective method for modifying red mud. By reacting CO2 with alkaline substances in red mud, stable carbonates are generated, reducing its pH value and improving its engineering properties. However, existing carbonation technologies have the following shortcomings: (1) pure CO2 gas is mostly used, which is costly; (2) the carbonation temperature is mostly at room temperature or low temperature, resulting in low reaction efficiency; (3) the particle size distribution of the carbonation products is not effectively controlled, making it difficult to meet the strict requirements of roadbed materials.

[0005] In addition to CO2, industrial exhaust gases often contain acidic pollutants such as SO2 and NOx. Current technologies primarily focus on the carbonation and utilization of CO2, while research on the synergistic resource-based treatment of SO2 and NOx in exhaust gases is insufficient. If these acidic components could also be used to modify red mud, it would not only more thoroughly reduce the pH value of the red mud but also improve material properties by generating new cementitious phases (such as calcium sulfate), achieving low-cost desulfurization and denitrification of exhaust gases, resulting in significant environmental and economic benefits. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a roadbed material and its preparation method that utilizes industrial tail gas containing multiple acidic components to synergistically acidify red mud, precisely control product properties, and provide long-term stability of harmful ions.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a method for preparing red mud roadbed filler based on industrial tail gas acidification, comprising: Red mud, calcium-based solid waste, and pollutant solidifying agent are mixed evenly at a mass ratio of 100: (5-15): (0.1-3) to obtain a mixture. The mixture is subjected to an acidification reaction with industrial exhaust gas at 300-500°C to obtain an acidification product; the industrial exhaust gas contains CO2, SO2 and NOx. The acidification products are crushed and screened, and their moisture content is adjusted to 12-18% to obtain red mud roadbed material.

[0008] In a second aspect, the present invention provides a red mud roadbed filler prepared by the above-described method based on industrial exhaust gas acidification.

[0009] First, the abundant calcium source in calcium-based solid waste reacts with CO2 in the exhaust gas to generate calcium carbonate, while simultaneously reacting efficiently with SO2 and NOx to produce calcium sulfate, calcium nitrate, and other products. The generation of calcium sulfate not only consumes sulfur oxides in the exhaust gas but also acts as a cementing material, further reacting with aluminum, silicon, and other components in the system to generate strong phases such as ettringite. This significantly enhances the mechanical properties of the roadbed material while simultaneously achieving desulfurization and denitrification of the exhaust gas.

[0010] Secondly, a contaminant solidifying agent with specific functions was innovatively introduced. This solidifying agent possesses an ultra-high specific surface area and designable functional groups, enabling it to strongly adsorb and fix Na released from red mud. + And heavy metal ions. More importantly, its highly ordered crystal framework and regular nanopores can serve as an excellent heterogeneous nucleation matrix, providing a large number of nucleation sites for the precipitation and crystallization of reaction products such as calcium carbonate, promoting the formation of finer and more uniformly distributed crystals, thereby optimizing the microstructure of the material and improving its density and early strength.

[0011] Finally, by using the heat of the industrial exhaust gas at 300-500℃ as the heat source for the reaction, and by designing a pressure-time gradient process, the mass transfer and reaction conditions of different acidic gases are optimized in sequence to achieve precise control of the reaction process and product composition, and finally regulate the particle size distribution of the resulting mixed product to meet the requirements of roadbed filler.

[0012] Finally, the acidified red mud subgrade material prepared by the above process has a gradation curve that falls within the optimal range for highway subgrade materials. It has a suitable optimal moisture content (12-18%), a high maximum dry density (1.8-2.1 g / cm³), and a CBR value (>80%), which fully meets the technical requirements for highway subgrade fillers. Furthermore, the alkalinity and heavy metal ions of the contaminated components are effectively fixed by the curing agent, resulting in excellent environmental safety.

[0013] Beneficial effects of the present invention (1) Waste treatment with waste, low cost: At the same time, deep treatment of red mud and industrial tail gas containing sulfur and nitrogen oxides is carried out to realize the dual resource utilization of "solid waste" and "waste gas"; (2) Controllable gradation and excellent performance: The active design of the particle size distribution of the product is achieved through precise control of the acidification process parameters, ensuring that the material meets the requirements of roadbed engineering; (3) High energy efficiency and thorough reaction: The waste heat of industrial exhaust gas is used to promote the acidification reaction, thereby improving the reaction efficiency and depth; (4) Long-lasting stability and environmental safety: The introduced functionalized pollutant component curing agent can target and adsorb and fix alkali metal and heavy metal ions, giving the material excellent environmental friendliness; (5) Multiple performance enhancements: The calcium carbonate, calcium sulfate and ettringite products generated by the reaction work together to bind the materials, and the contaminant curing agent has both adsorption curing and nano-reinforcement effects, enabling the material to obtain excellent mechanical properties and water stability.

[0014] (6) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 XRD patterns of optimal embodiment 1 and comparative example 1. Detailed Implementation

[0017] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they are used in accordance with conventional methods in the art or product instructions. Similarly, unless otherwise specified, the test methods of this invention are performed in accordance with conventional methods in the art or industry-standard methods or practices. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0019] This invention provides a method for preparing red mud roadbed filler based on industrial exhaust gas acidification, comprising: Red mud, calcium-based solid waste, and pollutant solidifying agent are mixed evenly at a mass ratio of 100: (5-15): (0.1-3) to obtain a mixture. The mixture is subjected to an acidification reaction with industrial exhaust gas at 300-500°C to obtain an acidification product; the industrial exhaust gas contains CO2, SO2 and NOx. The acidification products are crushed and screened, and their moisture content is adjusted to 12-18% to obtain red mud roadbed material.

[0020] This invention utilizes the abundant calcium source in calcium-based solid waste to react with CO2 in the exhaust gas to generate calcium carbonate, and at the same time, it efficiently reacts with SO2 and NOx to generate products such as calcium sulfate and calcium nitrate. Therefore, this invention studies the types of calcium-based solid waste. Preferably, the calcium-based solid waste is carbide slag or granulated blast furnace slag to obtain better performance.

[0021] Preferably, the contaminant curing agent is prepared with iron, aluminum, or zirconium as the metal center and terephthalic acid, trimesic acid, or 2-methylimidazole as the organic ligand. This invention effectively increases the strength of the roadbed filler and adsorbs pollutants by introducing the contaminant curing agent, while also providing new nucleation sites.

[0022] Preferably, the specific surface area of ​​the contaminant solidifying agent is greater than 1000 m² / g. Its functional groups include at least one of amino, carboxyl, or sulfonic acid groups, which enhance the adsorption capacity for sodium ions and heavy metal ions, and also provide crystallization nucleation sites for calcium carbonate in the acidification reaction, thus promoting the acidification reaction.

[0023] The contaminant solidifying agent in this invention has a highly ordered porous structure and functional groups (such as -NH2, -SO3H) on its surface, which can efficiently capture free Na that may be released from red mud due to incomplete acidification or long-term hydration through ion exchange, coordination, or electrostatic interaction. + K + Ions, as well as heavy metal ions such as Pb, Cd, Cr, and As, are firmly locked within the crystal lattice channels, fundamentally inhibiting the risk of leaching and migration of alkali and heavy metals. Simultaneously, the solidifying agent particles, typically in the nanometer to micrometer range, can fully fill the micropores of the red mud-calcium carbonate gel system, optimizing particle size distribution and increasing the material's maximum dry density. Its rigid crystal framework serves as a micro / nano reinforcing phase, interlocking with acid-generated CSH gel and ettringite, improving the microstructural integrity of the composite material and thus significantly enhancing its macroscopic mechanical strength and water stability.

[0024] Acidification effectively solves the problem of alkali pollution in red mud and changes the particle size distribution of the red mud. Preferably, the industrial exhaust gas is the exhaust gas from the industrial kiln of an alumina power plant, with a CO2 volume concentration of 12%-20%, an SO2 concentration of 100-4000 ppm, and a NOx concentration of 100-600 ppm, in order to save costs.

[0025] Preferably, the acidification reaction pressure is 0.8-1.2 MPa and the reaction time is 2-3 hours, or the pressure is 1.5-2.0 MPa and the reaction time is 1-2 hours. More preferably, the acidification reaction is carried out using a staged pressure-time gradient process, including at least two consecutive pressure-time stages combined. Further preferably, the first stage of the acidification reaction is carried out at a pressure of 0.5-1.0 MPa for 1-2 hours, and the second stage increases the pressure to 1.5-2.0 MPa and continues the reaction for 0.5-2 hours to obtain better mechanical properties.

[0026] In this invention, the solubility and mass transfer rate of CO2 are controlled by adjusting the acidification pressure. Under low-pressure conditions (e.g., 0.1-0.3 MPa), CO2 solubility is low, the reaction is mild, and the nucleation rate and growth rate of calcium carbonate are relatively balanced. The product tends to form thermodynamically stable calcite, with larger crystal size and more complete crystal form, resulting in higher structural strength of the material in the later stages, but with a smaller specific surface area. Under medium-high pressure conditions (e.g., 0.5-2.0 MPa), CO2 solubility increases sharply, and the supersaturation of the system increases rapidly, leading to explosive nucleation, with the nucleation rate much greater than the growth rate. The product tends to form metastable aragonite or amorphous calcium carbonate, with small, numerous, and uniformly distributed crystals. The material easily forms a denser microstructure, significantly improving early strength.

[0027] In this invention, the acidification reaction time controls the reaction process and the degree of crystal maturation. With a short time (0.5-1 h), the reaction is incomplete, the acidification efficiency is low, and the generated calcium carbonate is mostly in its initial form. The product may be a mixture of amorphous calcium carbonate and a small amount of aragonite, resulting in incomplete crystal development and incomplete structural strength development in the later stages, possibly containing unreacted alkaline cores. With a moderate time (2-4 h), the reaction is relatively complete, allowing sufficient time for crystal growth. The product may begin to transform from aragonite to more stable calcite, increasing crystal size, and the material can obtain a product with excellent strength and stability. With a long time (>4 h), small crystals dissolve, large crystals grow, and the metastable phase is almost completely transformed into stable calcite. The product is mainly calcite, with coarse crystals, resulting in the best long-term chemical stability of the material. However, the strength growth may plateau or even slightly decrease due to structural coarsening.

[0028] More specifically, including: (1) Raw material preparation: Mix red mud, calcium-based solid waste and pollutant component solidifying agent in a mass ratio of 100:(5-15):(0.1-3) until uniform; (2) Acidification reaction: The mixture is placed in an acidification reaction apparatus, and industrial tail gas at 300-500℃ is introduced. The reaction pressure is controlled at 0.5-2.0 MPa, and the reaction time is 1-4 hours. The industrial tail gas contains CO2, SO2, and NO. x ; (3) Gradation control: The acidification reaction is carried out in stages using a pressure-time gradient process. By combining at least two consecutive pressure-time stages, the nucleation, growth and particle breakage of carbonate crystals are precisely controlled, thereby actively designing and optimizing the final particle size distribution of the product.

[0029] (4) Performance adjustment: The acidification products are crushed and screened, and their moisture content is adjusted to 12-18% to obtain red mud roadbed material.

[0030] The present invention also provides a red mud roadbed filler based on industrial tail gas acidification prepared by the above method, preferably with the following optimal gradation range: 90-100% pass rate through 4.75mm sieve, 40-70% pass rate through 0.6mm sieve, and 10-35% pass rate through 0.075mm sieve.

[0031] Preferably, the maximum dry density is 1.8-2.1 g / cm³, the CBR value is greater than 80%, and the water swelling rate is less than 1.5%.

[0032] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0033] In the following examples, the calcium-based solid waste is carbide slag, and the pollutant solidifying agent is MIL-101(Fe), a commercially available product.

[0034] Maximum dry density and moisture content were tested using the compaction test method (T0131-2019) in the People's Republic of China industry standard "Specifications for Geotechnical Testing of Highways" (JTG 3430-2020). The bearing ratio (CBR) test method (T0134-2019) was used to measure the CBR value. The immersion swelling rate was determined according to T0124-2019. The prepared CBR specimens were immersed in water for 4 days and nights, and the change in height was measured as a percentage of the original height.

[0035] Example 1: Take 100g of red mud from an aluminum plant, add 8g of calcium-based solid waste and 1.5g of pollutant solidification agent, and mix thoroughly. Place in a reaction apparatus and introduce tail gas (approximately 15% CO2, approximately 800ppm SO2, NO3) from an alumina-supporting power plant at 350℃. xApproximately 200 ppm). A gradient process was employed: the reaction was first carried out at 0.8 MPa for 1.5 hours, then increased to 1.8 MPa for 1 hour. The product was crushed and sieved after the reaction, and the gradation was found to be excellent (95% passing through a 4.75 mm sieve, 55% through a 0.6 mm sieve, and 20% through a 0.075 mm sieve), with a maximum dry density of 2.02 g / cm³, a CBR value of 88%, and a water swelling rate of 0.3%. XRD analysis showed that the product contained calcite (CaCO3), calcium sulfate dihydrate (CaSO4·2H2O), and trace amounts of ettringite. Water stability was greater than 0.8, and unconfined compressive strength was >1.2 MPa. The concentrations of sodium and heavy metals in the leachate were tested using ICP-OES. The sodium ion concentration was 85 mg / L, with a limit of <200 mg / L according to the "Identification Standard for Hazardous Waste - Leaching Toxicity Identification" (GB 5085.3); the Pb concentration was 0.08 mg / L, with a limit of 5 mg / L; the Cr concentration was 0.15 mg / L, with a limit of 15 mg / L; and the As concentration was 0.02 mg / L, with a limit of 5 mg / L.

[0036] Example 2: Based on Example 1, the acidification parameters were adjusted to react at 1.8 MPa for 1.5 hours, then reduced to 0.8 MPa for 1 hour, with other conditions remaining unchanged. The measured particle size distribution of the product was: 98% passing through a 4.75 mm sieve, 62% passing through a 0.6 mm sieve, and 18% passing through a 0.075 mm sieve. The moisture content was adjusted to 14%, and the maximum dry density was measured to be 2.05 g / cm³, the CBR value was 60%, and the water swelling rate was 0.5%.

[0037] Example 3: The calcium-based solid waste was increased to 12g, and the acidification parameters were the same as in Example 1. The product performance was further improved, with a CBR value reaching 90% and a water swelling rate decreasing to 0.2%.

[0038] Comparative Example 1: Without adding calcium-based solid waste, and under the same conditions as in Example 1, the product had a CBR value of only 18% and a water immersion swelling rate of 2.5%, which did not meet the requirements for roadbed materials.

[0039] Comparative Example 2: Acidification with pure CO2 at 350℃ was performed under the same conditions as in Example 1. The reaction efficiency was low, and the product CBR value was 22%, indicating poor performance.

[0040] Comparative Example 3: The conditions were the same as in Example 1, but without the addition of the contaminating curing agent. The maximum dry density of the product was measured to be 1.95 g / cm³, the CBR value was 45%, the leaching concentration of heavy metal Pb was close to but slightly higher than the standard limit of 80%, and SEM showed that the calcium carbonate crystals were large in size and unevenly distributed.

[0041] Comparative Example 4: Using an equal mass of solid waste gypsum to replace calcium-based solid waste resulted in an increase in the calcium sulfate phase and a decrease in the calcium carbonate phase in the reaction products. This led to slower early strength development in the material and reduced NO content in the exhaust gas. x The fixation effect is not obvious.

[0042] Comparative Example 5: The conditions were the same as in Example 1, but the acidification pressure remained constant at 1.8 MPa. The same industrial exhaust gas at 350°C was introduced, and the reaction continued for 2.5 hours. The product particles were coarse, poorly graded, and only 5% passed through a 0.075 mm sieve. The maximum dry density was measured to be 1.78 g / cm³, the optimum moisture content was 17%, the CBR value was only 38%, and the unconfined compressive strength was 0.7 MPa.

[0043] Comparative Example 6: The conditions were the same as in Example 1, but the contaminant curing agent, MIL-101(Fe), was replaced by an equal mass of zeolite imidazole ester framework material ZIF-8 (centered on Zn and with 2-methylimidazole as a ligand). The measured CBR value of the material was 52%, and the unconfined compressive strength was 0.9 MPa.

[0044] Comparative Example 7: Under the same conditions as in Example 1, the contaminant curing agent was replaced with an equal mass of amino-functionalized UIO-66 (UiO-66-NH2, centered on Zr and with terephthalic acid as a ligand). The measured CBR value of the material was 65%, the unconfined compressive strength was 1.0 MPa, and the alkali removal rate was approximately 75%.

[0045] As can be seen from the comparison of Examples 1-3, the acidification parameters and the amount of calcium-based solid waste will affect the performance of the packing.

[0046] A comparison of Example 1 and Comparative Example 1 shows that calcium-based solid waste can react with CO2 in the exhaust gas to produce calcium carbonate, while also efficiently reacting with SO2 and NO. x The reaction produces products such as calcium sulfate and calcium nitrate, which significantly improves the mechanical properties of the packing.

[0047] Depend on Figure 1It can be seen that the diffraction peak intensity of the structural alkali calcium nepheline in the product of optimal Example 1 is reduced, indicating that a displacement reaction occurred between the calcium-based solid waste and the structural alkali in the red mud, improving the dealkali removal efficiency. In addition, the diffraction peaks of calcite and calcium sulfate prove that the abundant calcium source in the calcium-based solid waste reacts with CO2 in the tail gas to form calcium carbonate, and at the same time reacts efficiently with SO2 to form calcium sulfate. Meanwhile, acidification generates a small amount of ettringite, which can fill the micropores of the red mud-calcium carbonate gel system with the pollutant component solidifying agent, optimize the particle size distribution, and increase the maximum dry density of the material. As can be seen from the XRD pattern of the acidification treatment in Comparative Example 1, there is still a lot of calcium nepheline in the red mud, and the diffraction peaks of calcite and calcium sulfate are less, indicating that the dealkali removal efficiency of acidification treatment alone is low and the amount of product generated is small, which is not conducive to the subsequent adsorption of pollutant component solidifying agent.

[0048] As can be seen from the comparison between Example 1 and Comparative Example 2, compared with simple CO2 acidification, the use of industrial tail gas containing a variety of acidic gases can better react with calcium-based solid waste and improve the mechanical properties of the packing.

[0049] As can be seen from the comparison between Example 1 and Comparative Example 3, the addition of the contaminant curing agent not only significantly enhances the adsorption capacity for heavy metal ions, but also effectively improves the mechanical properties of the filler.

[0050] A comparison of Example 1 and Comparative Example 4 shows that, compared with industrial gypsum, calcium-based solid waste can better improve the early strength of materials and reduce NO in exhaust gas. x The fixation effect is better.

[0051] As can be seen from the comparison between Example 1 and Comparative Example 5, gradient acidification can better improve the mechanical strength of the packing and obtain a better gradation range compared with constant pressure acidification.

[0052] As can be seen from the comparison of Example 1 and Comparative Examples 6 and 7, the type of curing agent material for the pollutant component affects the mechanical properties of the filler and the adsorption effect on heavy metals. Using MIL-101(Fe) can better adsorb heavy metals and improve mechanical strength.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing red mud roadbed filler based on industrial tail gas acidification, characterized in that, include: Red mud, calcium-based solid waste, and pollutant solidifying agent are mixed evenly at a mass ratio of 100: (5-15): (0.1-3) to obtain a mixture. The mixture is subjected to an acidification reaction with industrial exhaust gas at 300-500°C to obtain an acidification product; the industrial exhaust gas contains CO2, SO2 and NO. x ; The acidification products are crushed and screened, and their moisture content is adjusted to 12-18% to obtain red mud roadbed material.

2. The method for preparing red mud roadbed filler based on industrial tail gas acidification as described in claim 1, characterized in that, The calcium-based solid waste is carbide slag or granulated blast furnace slag.

3. The method for preparing red mud roadbed filler based on industrial tail gas acidification as described in claim 1, characterized in that, The contaminant curing agent is prepared by using iron, aluminum or zirconium as the metal center and terephthalic acid, trimesic acid or 2-methylimidazole as the organic ligand.

4. The method for preparing red mud roadbed filler based on industrial tail gas acidification as described in claim 1, characterized in that, The specific surface area of ​​the contaminant curing agent is greater than 1000 m² / g.

5. The method for preparing red mud roadbed filler based on industrial tail gas acidification as described in claim 1, characterized in that, The industrial exhaust gas is from the industrial kiln exhaust gas of an alumina power plant, with a CO2 volume concentration of 12%-20%, SO2 concentration of 100-4000 ppm, and NO... x The concentration is 100-600 ppm.

6. The method for preparing red mud roadbed filler based on industrial tail gas acidification as described in claim 1, characterized in that, The acidification reaction is carried out at a pressure of 0.5-2.0 MPa for 1-4 hours.

7. The method for preparing red mud roadbed filler based on industrial tail gas acidification as described in claim 1, characterized in that, The acidification reaction is carried out using a staged pressure-time gradient process, including at least two consecutive pressure-time stages combined.

8. The method for preparing red mud roadbed filler based on industrial tail gas acidification as described in claim 1, characterized in that, The first stage of the acidification reaction is carried out at a pressure of 0.5-1.0 MPa for 1-2 hours, and the second stage involves increasing the pressure to 1.5-2.0 MPa and continuing the reaction for another 0.5-2 hours.

9. The red mud roadbed filler based on industrial tail gas acidification prepared by the method according to any one of claims 1-8, characterized in that, The optimal gradation range is: 90-100% pass rate for 4.75mm sieve, 40-70% pass rate for 0.6mm sieve, and 10-35% pass rate for 0.075mm sieve.

10. The red mud roadbed filler based on industrial tail gas acidification as described in claim 9, characterized in that, The maximum dry density is 1.8-2.1 g / cm³, the CBR value is greater than 80%, and the water swelling rate is less than 1.5%.

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