Preparation method of red mud active material and application thereof

Abstract

The application belongs to the technical field of solid waste treatment, and discloses a preparation method of red mud active material.The preparation method comprises the following steps: mixing red mud, sodium tetraphenylborate and silica acid gel to obtain a mixture, performing powder grinding treatment on the mixture, heating the mixture to 90-100 DEG C, then adding a mixed solution of water and butyl titanate ethanol solution with a temperature of 90-100 DEG C into the mixture, uniformly mixing, and then performing reaction at 190-250 DEG C in a closed environment, drying and cooling the reaction product after the reaction, and finally mixing and grinding the cooled product and dihydrate gypsum to obtain the red mud active material.The application further discloses the red mud active material and application thereof in building materials, catalysts, adsorbents and / or soil improvers.The preparation method of the red mud active material provided by the application effectively eliminates the adverse effects of alkaline substances in the red mud, significantly improves the activity of the red mud, and realizes the resource utilization of the red mud.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, specifically to a method for preparing red mud active materials and their applications. Background Technology

[0002] Red mud is a solid waste generated during the alumina refining process from bauxite. Its main chemical components are alumina, iron oxide, silicon dioxide, calcium oxide, sodium oxide, and titanium dioxide, and it also contains small amounts of rare earth elements and trace amounts of radioactive elements. Each year, aluminum plants in my country discharge over ten million tons of red mud. Most of this waste is either wet-stored in dammed areas or dried and dehydrated before being dry-stored. This method not only occupies a large amount of land and farmland, but the dust generated by the dried red mud also causes serious environmental pollution. Furthermore, many usable components in the red mud are not effectively utilized, resulting in a waste of resources.

[0003] With the development of the aluminum industry and the decline in bauxite quality, the production of red mud will continue to increase. Therefore, how to effectively utilize red mud has become an important research area attracting global attention. Current methods for utilizing red mud mainly include recovering valuable metals, preparing silicon fertilizers, and developing new building materials, with particular potential in the latter area. Using red mud to prepare cementitious materials has become a major utilization method; however, due to its high alkalinity and sodium content, red mud easily causes alkali-aggregate reactions, thereby damaging the concrete structure, causing efflorescence, and corroding steel components. Furthermore, the low activity of red mud reduces the strength of concrete. These characteristics limit the use of red mud in the production process. Summary of the Invention

[0004] In view of the problems and shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing red mud active materials and their applications.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of this invention provides a method for preparing red mud active materials, characterized in that the method includes the following steps:

[0007] (1) The dried red mud was mixed with sodium tetraphenylborate and silica gel to obtain a mixture. The mixture was ground and heated to 90-100°C. Then, a mixture of water and tetrabutyl titanate ethanol solution was added to the mixture. After mixing, it was placed in a sealed environment and reacted at 190-250°C. After the reaction was completed, the reaction product was dried and cooled to obtain product A.

[0008] (2) The product A is mixed with gypsum dihydrate and ground to obtain red mud active material.

[0009] Preferably, the mass ratio of the red mud to sodium tetraphenylborate is 100:(0.8-1).

[0010] Preferably, the mass ratio of the red mud to the tetrabutyl titanate ethanol solution is 100:(10-15).

[0011] Preferably, the mass fraction of the tetrabutyl titanate ethanol solution is 8-12%.

[0012] Preferably, the mass ratio of the red mud to the silica gel is 100:(5-8).

[0013] Preferably, the mass ratio of the red mud to dihydrate gypsum is 100:(2-3).

[0014] Preferably, the mass ratio of water to tetrabutyl titanate ethanol solution is (1.3-1.5):1.

[0015] Preferably, the temperature of the water in step (1) is 90 to 100°C.

[0016] Preferably, the reaction time in step (1) is 10 to 12 hours.

[0017] Preferably, the grinding in step (1) is grinding to a specific surface area > 400 m². 2 / kg.

[0018] Preferably, the grinding in step (2) is grinding to a specific surface area > 400m². 2 / kg.

[0019] Preferably, the red mud in step (1) is dried red mud.

[0020] Preferably, the drying temperature in step (1) is 190–250°C.

[0021] The second aspect of the present invention provides a red mud active material prepared by the preparation method described in the first aspect above.

[0022] The third aspect of the present invention provides the application of the red mud active material described in the second aspect above in building materials, catalysts, adsorbents and / or soil conditioners.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] Red mud contains a large amount of soluble alkalis, such as NaOH, Na₂CO₃, NaHCO₃, K₂CO₃, NaAl(OH)₄, KOH, and Ca(OH)₂. Eliminating these alkalis and soluble metal ions is crucial for increasing the utilization rate of red mud. Among these soluble alkalis, except for Ca(OH)₂, the solubility of the others increases with increasing temperature. Therefore, controlling the temperature between 190 and 250℃ and maintaining a specific surface area greater than 400 m² is essential. 2 The addition of sodium tetraphenylborate and butyl titanate ethanol per kg of potassium hydroxide allows for the reaction of potassium hydroxide with sodium tetraphenylborate to form potassium tetraphenylborate precipitate and sodium hydroxide, and the reaction of butyl titanate ethanol with sodium hydroxide to form sodium titanate precipitate and ester compounds. These reactions consume potassium hydroxide and sodium hydroxide, thereby improving the stability of red mud. Furthermore, the generated ester compounds possess certain surface activity, which can improve the dispersibility of red mud and increase the fluidity of the slurry.

[0025] Meanwhile, since the solubility of calcium hydroxide decreases rapidly with increasing temperature, raising the water and material temperatures can minimize the dissolution of calcium hydroxide and prevent it from reacting with butyl titanate ethanol or sodium tetraphenylborate to form a precipitate, thus avoiding incomplete reaction of the sodium-potassium alkali solution. This preserves the calcium hydroxide content, allowing it to play a positive role in the cement hydration process.

[0026] Silicate gel is a porous structure with strong adsorption properties, capable of reacting with alkaline substances. Its incorporation enriches soluble alkalis, promoting the precipitation of potassium tetraphenylborate and sodium titanate ethanol around the silicate gel. The resulting potassium tetraphenylborate particles and sodium titanate microparticles are adsorbed by the porous structure of the silicate gel, preventing microparticle crystal growth. Furthermore, the microparticle structure acts as a filler and nucleation site in concrete, promoting the hydration reaction of red mud cementitious materials and improving early strength. Simultaneously, the silicate gel can acidify the surface of red mud under high-temperature conditions, effectively enhancing its activity. The method for preparing red mud active materials provided by this invention significantly improves the activity of red mud by effectively eliminating the adverse effects of alkaline substances, thereby realizing the resource utilization of red mud. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Example 1

[0029] This embodiment provides a method for preparing red mud active materials, the specific method of which is as follows:

[0030] (1) Mix 100 parts of dried red mud, 0.8 parts of sodium tetraphenylborate and 8 parts of silica gel to obtain a mixture, and grind the mixture to a specific surface area of ​​645 m². 2 / kg, heated to 90℃, then added 20 parts of hot water at 90℃ and 15 parts of tetrabutyl titanate ethanol solution (mass fraction of 10%), and stirred in a closed environment for 10 min. Then, the pressure was increased to 10 MPa and the temperature was raised to 190℃, and the reaction was carried out for 12 h. After the reaction was completed, the reaction product was placed in an open space to dry and cool at 190℃ to obtain product B.

[0031] (2) Mix product B obtained in step (1) with 2 parts of gypsum dihydrate and grind until the specific surface area is 650 m². 2 / kg, to obtain red mud active material.

[0032] Example 2

[0033] This embodiment provides a method for preparing red mud active materials, the specific method of which is as follows:

[0034] (1) Mix 100 parts of dried red mud, 1.0 part of sodium tetraphenylborate and 5 parts of silica gel to obtain a mixture. Grind the mixture to a specific surface area of ​​720 m². 2 / kg, heated to 98℃, then added 15 parts of hot water at 96℃ and 10 parts of tetrabutyl titanate ethanol solution (mass fraction of 10%), and stirred in a closed environment for 20 min. Then, the pressure was increased to 1.5 MPa, the temperature was raised to 200℃, and the reaction was carried out for 10 h. After the reaction was completed, the reaction product was placed in an open space to dry and cool at 200℃ to obtain product C.

[0035] (2) Mix product C obtained in step (1) with 3 parts of gypsum dihydrate and grind until the specific surface area is 720 m². 2 / kg, to obtain red mud active material.

[0036] Example 3

[0037] This embodiment provides a method for preparing red mud active materials, the specific method of which is as follows:

[0038] (1) Mix 100 parts of dried red mud, 0.9 parts of sodium tetraphenylborate and 6 parts of silica gel to obtain a mixture, and grind the mixture to a specific surface area of ​​680 m². 2 / kg, heated to 100℃, then added 18 parts of hot water at 100℃ and 13 parts of tetrabutyl titanate ethanol solution (mass fraction of 10%), and stirred in a closed environment for 15 min. Then, the pressure was increased to 2 MPa, the temperature was raised to 195℃, and the reaction was carried out for 11 h. After the reaction was completed, the reaction product was placed in an open space to dry and cool at 195℃ to obtain product D.

[0039] (2) Mix product D obtained in step (1) with 2.5 parts of gypsum dihydrate and grind until the specific surface area is 680 m². 2 / kg, to obtain red mud active material.

[0040] Comparative Example 1

[0041] Comparative Example 1 is basically the same as Example 3, except that step (1) of Comparative Example 1 does not include titanium tetrabutyl ethanol solution.

[0042] Comparative Example 2

[0043] Comparative Example 2 is basically the same as Example 3, except that sodium tetraphenylborate is not added in step (1) of Comparative Example 2.

[0044] Comparative Example 3

[0045] Comparative Example 3 is basically the same as Example 3, except that silica gel is not added in step (1) of Comparative Example 3.

[0046] Comparative Example 4

[0047] Comparative Example 4 is basically the same as Example 3, except that in step (1) of Comparative Example 4, silica gel is not added, while in step (2), the material cooled in step (1), gypsum dihydrate and silica gel are mixed and ground.

[0048] Comparative Example 5

[0049] Comparative Example 5 is basically the same as Example 3, except that step (1) of Comparative Example 5 does not involve stirring.

[0050] Comparative Example 6

[0051] Comparative Example 6 is basically the same as Example 3, except that step (1) of Comparative Example 6 does not involve heating to 100°C, and hot water is replaced with room temperature water.

[0052] Comparative Example 7

[0053] Comparative Example 7 is basically the same as Example 3, except that the gypsum dihydrate in Comparative Example 7 is mixed and ground with red mud, sodium tetraphenylborate and silica gel in step (1), but step (2) is omitted.

[0054] Comparative Example 8

[0055] In this comparative example, red mud was ground to 680 μm. 2 / kg, using this material as a control for subsequent evaluation of red mud performance.

[0056] In accordance with the provisions of TCMFB 194-2022 "Ultrafine Composite Mineral Admixtures", the performance of the red mud materials obtained in Examples 1 to 3 and Comparative Examples 1 to 8 was tested. The results are shown in Table 1.

[0057] Table 1 Performance Indicators of Activated Red Mud

[0058]

[0059] As shown in Table 1, compared with Example 3, the red mud material obtained in Comparative Example 1 failed to meet the stability requirements and exhibited decreased fluidity. The activity index of the red mud material also decreased at 7 days and 28 days. This is because tetrabutyl titanate mainly reacts with sodium hydroxide to form sodium titanate microparticles and ester compounds. This reaction consumes sodium hydroxide, thereby improving the stability of the red mud. Simultaneously, the generated ester compounds have a certain surface activity, which can improve the dispersibility of the red mud and increase the fluidity of the slurry. In the absence of tetrabutyl titanate ethanol, the alkalinity of sodium hydroxide remains, affecting the stability of the red mud and preventing the formation of sodium titanate microparticles. Consequently, these microparticles cannot function as nuclei and fillers, ultimately leading to a decrease in the strength of the red mud.

[0060] Compared to Example 3, the red mud material obtained in Comparative Example 2 exhibited unsatisfactory stability and decreased fluidity. The activity index of the red mud material decreased at 7 and 28 days. This is because sodium tetraphenylborate primarily reacts with potassium hydroxide to form potassium tetraphenylborate microparticles and sodium hydroxide. Subsequently, tetrabutyl titanate reacts with sodium hydroxide to form sodium titanate microparticles and ester compounds. These reactions consume potassium hydroxide and sodium hydroxide, thus improving the stability of the red mud. Simultaneously, the generated ester compounds possess certain surface activity, improving the dispersibility of the red mud and increasing the fluidity of the slurry. In the absence of sodium tetraphenylborate, the alkalinity of potassium hydroxide remains, affecting the stability of the red mud and preventing the formation of potassium tetraphenylborate microparticles, which thus cannot exert their nucleation and filling effects, ultimately leading to a decrease in the activity of the red mud.

[0061] Compared to Example 3, although the stability of the red mud material obtained in Comparative Example 3 was satisfactory, its activity index decreased significantly at 7 days and 28 days. The results indicate that adding silica gel enhances the activity of red mud. This is because silica gel is a porous structure with extremely strong adsorption properties, capable of reacting with alkaline substances. Its incorporation enriches soluble alkali, promoting the potassium salt precipitation reaction of sodium tetraphenylborate and the sodium salt precipitation reaction of tetrabutyl titanate around the silica gel. This generates potassium tetraphenylborate microparticles and sodium titanate microparticles, which are adsorbed by the porous structure of the silica gel, thus preventing the growth of microparticle crystals. These microparticle structures act as fillers and nuclei in concrete, promoting the hydration reaction of the red mud cementitious material and improving early strength. Simultaneously, silica gel can acidify the surface of the red mud under high-temperature conditions, further enhancing its activity.

[0062] Compared with Example 3, although the stability of the red mud material obtained in Comparative Example 4 was acceptable, its activity index decreased significantly at 7d and 28d. This is because silica gel was not incorporated in step (1), but was incorporated in step (2), which caused the generated sodium titanate microparticles and potassium tetraphenylborate microparticles to crystallize into large particles, losing their nucleation effect, thus limiting the activation of red mud activity by the silica gel.

[0063] Compared to Example 3, although the stability of the red mud material obtained in Comparative Example 5 was satisfactory, its activity index decreased significantly at 7 days and 28 days; compared to Comparative Example 4, the performance of the red mud material obtained in Comparative Example 5 was not significantly different. This is because the stirring in step (1) is to allow the silica gel to uniformly enrich the soluble alkali. If this stirring step is missing, the potassium salt precipitation reaction of sodium tetraphenylborate and the sodium salt precipitation reaction of tetrabutyl titanate cannot occur uniformly around the silica gel, and the generated potassium tetraphenylborate microparticles and sodium titanate microparticles cannot be adsorbed by the porous structure of the silica gel, thus crystallizing into large particles. Therefore, the effect of not stirring and later incorporating silica gel is not significantly different.

[0064] Compared with Example 3, the stability of the red mud material obtained in Comparative Example 6 was unqualified, and its activity decreased at 7d and 28d. This is because red mud contains a large amount of soluble alkalis, such as NaOH, Na2CO3, NaHCO3, K2CO3, NaAl(OH)4, KOH, Ca(OH)2, etc. Eliminating these alkalis and soluble metal ions is crucial for increasing the amount of red mud used. Under hot water conditions, the solubility of calcium hydroxide decreases, thereby delaying its reaction with tetrabutyl titanate and sodium tetraphenylborate; while the solubility of the other alkalis increases with increasing temperature. If step (1) is not heated to 100°C and hot water is replaced with room temperature water, calcium hydroxide will react with tetrabutyl titanate and sodium tetraphenylborate in advance, resulting in limited precipitation reactions of potassium and sodium salts. In addition, the calcium salt in the red mud admixture decreases during the hydration process in the later stage, affecting its reaction with silicate to form hydrated calcium silicate, thereby affecting the activity of red mud.

[0065] Compared to Example 3, the red mud material obtained in Comparative Example 7 exhibited unsatisfactory stability, decreased fluidity, and reduced activity at 7 and 28 days. This is because gypsum dihydrate mainly participates in the reaction to form ettringite; premature addition would cause calcium ions to react with tetraphenylboron salts, limiting the precipitation reaction of sodium and potassium salts. Simultaneously, gypsum dihydrate readily reacts with silicate ions to form precipitates, affecting the activating effect of silicate ions on red mud activity and losing its activating effect on enhancing red mud activity in later stages. Therefore, gypsum dihydrate should be added during step (2).

[0066] Compared with Comparative Example 8, the red mud material obtained in Example 3 had satisfactory stability, significantly increased fluidity, and significantly increased activity at 7d and 28d.

[0067] In summary, this invention improves the stability and slurry fluidity of red mud by controlling temperature and specific surface area, and by adding sodium tetraphenylborate and butyl titanate ethanol. At the same time, it utilizes the adsorption properties of silica gel to promote precipitation reaction, thereby enhancing the activity and early strength of red mud.

[0068] The above description illustrates the embodiments of the present invention. By describing the disclosed embodiments, those skilled in the art are able to implement or use the present invention, and it is not intended to limit the present invention. The various aspects of the present invention cannot be fully embodied in the above embodiments. Any equivalent changes or modifications made by those skilled in the art without departing from the spirit or scope of the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing red mud active material, characterized in that, The method includes the following steps: (1) The dried red mud was mixed with sodium tetraphenylborate and silica gel to obtain a mixture. The mixture was ground and heated to 90-100°C. Then, a mixture of water and tetrabutyl titanate ethanol solution was added to the mixture. After mixing, it was placed in a sealed environment and reacted at 190-250°C. After the reaction was completed, the reaction product was dried and cooled to obtain product A. (2) The product A is mixed with gypsum dihydrate and ground to obtain red mud active material.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the red mud to sodium tetraphenylborate is 100:(0.8-1).

3. The preparation method according to claim 1, characterized in that, The mass ratio of the red mud to the tetrabutyl titanate ethanol solution is 100:(10-15); the mass fraction of the tetrabutyl titanate ethanol solution is 8-12%.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the red mud to the silica gel is 100:(5-8).

5. The preparation method according to claim 1, characterized in that, The mass ratio of the red mud to dihydrate gypsum is 100:(2-3).

6. The preparation method according to claim 1, characterized in that, The mass ratio of the water to the tetrabutyl titanate ethanol solution is (1.3–1.5):

1.

7. The preparation method according to any one of claims 1 to 6, characterized in that, In step (1), the temperature of the water is 90-100℃, and the reaction time is 10-12h.

8. The preparation method according to claim 1, characterized in that, In step (1), the grinding process involves grinding the mixture to a specific surface area > 400 m². 2 / kg; The grinding in step (2) involves grinding the mixture of product A and gypsum dihydrate to a specific surface area >400m². 2 / kg.

9. A red mud active material prepared by any one of the preparation methods described in claims 1 to 8.

10. The application of the red mud active material according to claim 9 in building materials, catalysts, adsorbents and / or soil conditioners.

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