Preparation method and application of red mud active material

Abstract

The invention belongs to the technical field of solid waste treatment, and discloses a preparation method of a red mud active material. The preparation method comprises the following steps: mixing red mud, sodium tetraphenylborate and silicic acid gel to obtain a mixture, grinding the mixture, heating to 90-100 DEG C, adding a mixed solution of water with the temperature of 90-100 DEG C and a butyl titanate ethanol solution into the mixture, uniformly mixing, reacting in a closed environment at the temperature of 190-250 DEG C, filtering, washing, and drying to obtain the red mud-sodium tetraphenylborate-silicic acid composite material. And after the reaction is finished, drying and cooling a reaction product, finally mixing the cooled product with dihydrate gypsum, and grinding to obtain the red mud active material. The invention also discloses a red mud active material and application thereof in building materials, catalysts, adsorbents and / or soil conditioners. According to the preparation method of the red mud active material provided by the invention, by effectively eliminating adverse effects of alkaline substances in the red mud, the activity of the red mud is remarkably improved, so that resource utilization of the red mud is realized.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste treatment, and in particular to a preparation method of a red mud active material and application thereof. Background Art

[0002] Red mud is a solid waste produced in the process of refining alumina from bauxite. The main chemical components of red mud are aluminum oxide, iron oxide, silicon dioxide, calcium oxide, sodium oxide and titanium dioxide, and it contains a small amount of rare earth elements and trace radioactive elements. Every year, aluminum plants in my country discharge more than 10 million tons of red mud. Most of these wastes are stored in damming areas by wet methods or dry piled after drying and dehydrating the red mud. This treatment method not only occupies a large amount of land resources and farmland, but also the dust generated by the dried red mud has caused serious pollution to the ecological environment. At the same time, the various usable components in red mud have not been effectively utilized, resulting in a waste of resources.

[0003] With the development of the aluminum industry and the decline in the quality of bauxite ore, the output of red mud will continue to increase. Therefore, how to effectively utilize red mud has become an important research field that has attracted the attention of researchers around the world. The current methods of utilizing red mud mainly include recovering valuable metals, preparing silicon fertilizers, and developing new building materials, especially in the field of new building materials. The use of red mud to prepare cementitious materials has become a major utilization method. However, due to the high alkalinity and sodium content of red mud, it is easy to cause alkali-aggregate reaction, thereby destroying the concrete structure, causing frost and corroding steel parts. In addition, red mud has low activity and will reduce 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 in the prior art, the purpose of the present invention is to provide a method for preparing red mud active material and its application.

[0005] Based on the above purpose, the present invention adopts the following technical solution:

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

[0007] (1) Mixing the dried red mud with sodium tetraphenylborate and silica gel to obtain a mixture, grinding the mixture and heating it to 90-100° C., then adding a mixture of water and butyl titanate ethanol solution to the mixture, mixing well and placing the mixture in a closed environment at 190-250° C. to react, and drying and cooling the reaction product after the reaction is completed to obtain product A;

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

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

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

[0011] Preferably, the mass fraction of the butyl 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 butyl titanate ethanol solution is (1.3-1.5):1.

[0015] Preferably, the temperature of the water in step (1) is 90-100°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 of ​​400m 2 / kg.

[0018] Preferably, the grinding in step (2) is grinding to a specific surface area of ​​400m 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.

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

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] Red mud contains a large amount of soluble alkali, such as NaOH, Na 2 CO 3 、NaHCO 3 , K 2 CO 3 、NaAl(OH) 4 , KOH, Ca(OH) 2Eliminating these alkalis and soluble metal ions is crucial to increasing the use of red mud. Among these soluble alkalis, except for Ca(OH) 2 The solubility of other alkalis increases with increasing temperature. Therefore, by controlling the temperature at 190-250°C and the specific surface area greater than 400m 2 / kg, and adding sodium tetraphenylborate and butyl titanate ethanol, potassium hydroxide and sodium tetraphenylborate react to generate potassium tetraphenylborate precipitate and sodium hydroxide, and butyl titanate ethanol reacts with sodium hydroxide to generate sodium titanate precipitate and ester compounds. These reactions can consume potassium hydroxide and sodium hydroxide, thereby improving the stability of red mud. In addition, the generated ester compounds have certain surface activity, which can improve the dispersibility of red mud and improve the fluidity of slurry.

[0025] At the same time, since the solubility of calcium hydroxide decreases rapidly with increasing temperature, by increasing the water temperature and material temperature, the dissolution of calcium hydroxide can be minimized to avoid its reaction with butyl titanate ethanol or sodium tetraphenylborate to form precipitation, resulting in incomplete reaction of sodium potassium alkali solution. In this way, the content of calcium hydroxide can be retained, allowing it to play a positive role in the cement hydration process.

[0026] Silicic acid gel is a porous structure with extremely strong adsorption and can react with alkaline substances. After being added, it can enrich soluble alkali, and promote the precipitation reaction of potassium salt of sodium tetraphenylborate and sodium salt of butyl titanate ethanol to occur around the silica gel. The generated potassium tetraphenylborate particles and sodium titanate microparticles are adsorbed by the porous structure of silica gel, which can prevent the microparticles from crystallizing and growing. In addition, the microparticle structure can play a filling and nucleation role in concrete, promote the hydration reaction of red mud cementitious materials, and improve the early strength. At the same time, silica gel can acidify the surface of red mud under high temperature conditions, effectively improving the activity of red mud. The preparation method of red mud active material provided by the present invention significantly improves the activity of red mud by effectively eliminating the adverse effects of alkaline substances in red mud, thereby realizing the resource utilization of red mud. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail by way of embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] Example 1

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

[0030] (1) 100 parts of dried red mud, 0.8 parts of sodium tetraphenylborate and 8 parts of silica gel were mixed to obtain a mixture, and the mixture was ground to a specific surface area of ​​645 m 2 / kg, heated to 90°C, then added with 20 parts of 90°C hot water and 15 parts of butyl titanate ethanol solution (mass fraction of 10%), and placed in a closed environment and stirred for 10 minutes, then pressurized to 10MPa, heated to 190°C, reacted for 12 hours, and after the reaction was completed, the reaction product was placed in an open space at 190°C for drying and cooling to obtain product B;

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

[0032] Example 2

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

[0034] (1) 100 parts of dried red mud, 1.0 part of sodium tetraphenylborate and 5 parts of silica gel were mixed to obtain a mixture, and the mixture was ground to a specific surface area of ​​720 m 2 / kg, heated to 98°C, then added with a mixture of 15 parts of 96°C hot water and 10 parts of butyl titanate ethanol solution (mass fraction of 10%), and placed in a closed environment and stirred for 20 minutes, and then pressurized to 1.5MPa, heated to 200°C, reacted for 10 hours, and after the reaction was completed, the reaction product was placed in an open space at 200°C for drying and cooling to obtain product C;

[0035] (2) The product C obtained in step (1) was mixed with 3 parts of dihydrate gypsum and ground to a specific surface area of ​​720 m 2 / kg, and obtain red mud active material.

[0036] Example 3

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

[0038] (1) 100 parts of dried red mud, 0.9 parts of sodium tetraphenylborate and 6 parts of silica gel were mixed to obtain a mixture, and the mixture was ground to a specific surface area of ​​680 m 2 / kg, heated to 100°C, then added a mixture of 18 parts of 100°C hot water and 13 parts of butyl titanate ethanol solution (mass fraction of 10%), and placed in a closed environment and stirred for 15 minutes, then pressurized to 2MPa, heated to 195°C, reacted for 11 hours, and after the reaction was completed, placed the reaction product in an open space at 195°C for drying and cooling to obtain product D;

[0039] (2) The product D obtained in step (1) was mixed with 2.5 parts of dihydrate gypsum and ground to a specific surface area of ​​680 m 2 / kg, and obtain red mud active material.

[0040] Comparative Example 1

[0041] Comparative Example 1 is basically the same as Example 3, except that no butyl titanate ethanol solution is added in step (1) of Comparative Example 1.

[0042] Comparative Example 2

[0043] Comparative Example 2 is substantially 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 no silica gel is 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, no silica gel is added, and in step (2), the cooled material in step (1), dihydrate gypsum and silica gel are mixed and ground.

[0048] Comparative Example 5

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

[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 the hot water is replaced by water at room temperature.

[0052] Comparative Example 7

[0053] Comparative Example 7 is basically the same as Example 3, except that the dihydrate gypsum in Comparative Example 7 is mixed and ground with red mud, sodium tetraphenylborate and silica gel in step (1), and there is no step (2).

[0054] Comparative Example 8

[0055] In this comparative example, red mud is ground to 680m 2 / kg, and this material was used as a control for the subsequent evaluation of red mud performance.

[0056] According to the provisions of TCMBF 194-2022 "Ultrafine Composite Mineral Admixtures", the properties of the red mud materials obtained in Examples 1 to 3 and Comparative Examples 1 to 8 were tested. The results are shown in Table 1.

[0057] Table 1 Performance indexes of activated red mud

[0058]

[0059] As can be seen from Table 1, compared with Example 3, the stability of the red mud material obtained in Comparative Example 1 is unqualified, the fluidity decreases, and the activity index of the red mud material also decreases at 7d and 28d. This is because butyl titanate mainly reacts with sodium hydroxide to generate sodium titanate microparticles and ester compounds, and the reaction consumes sodium hydroxide, thereby improving the stability of the red mud. At the same time, the generated ester compounds have a certain surface activity, which can improve the dispersibility of red mud and increase the fluidity of the slurry. In the absence of butyl titanate ethanol, the alkalinity of sodium hydroxide still exists, resulting in the stability of the red mud being affected, and the sodium titanate microparticles cannot be formed, so that its nucleation and filling functions cannot be exerted, and finally the strength of the red mud is reduced.

[0060] Compared with Example 3, the stability of the red mud material obtained in Comparative Example 2 is unqualified, the fluidity decreases, and the activity index of the red mud material decreases at 7d and 28d. This is because sodium tetraphenylborate mainly reacts with potassium hydroxide to generate potassium tetraphenylborate microparticles and sodium hydroxide, and then butyl titanate reacts with sodium hydroxide to generate sodium titanate microparticles and ester compounds. These reactions consume potassium hydroxide and sodium hydroxide to improve the stability of red mud. At the same time, the generated ester compounds have a certain surface activity, which can improve the dispersibility of red mud and increase the fluidity of slurry. In the absence of sodium tetraphenylborate, the alkalinity of potassium hydroxide still exists, resulting in the stability of red mud being affected, and potassium tetraphenylborate microparticles cannot be formed, so that its nucleation and filling effects cannot be exerted, and ultimately the activity of red mud is reduced.

[0061] Compared with Example 3, although the stability of the red mud material obtained in Comparative Example 3 is qualified, its activity index is significantly reduced at 7d and 28d. The results show that the addition of silica gel will enhance the activity of red mud. This is because silica gel is a porous structure with extremely strong adsorption and can react with alkaline substances. After its incorporation, it can enrich soluble alkali, prompting the potassium salt precipitation reaction of sodium tetraphenylborate and the sodium salt precipitation reaction of butyl titanate to occur around the silica gel. Potassium tetraphenylborate microparticles and sodium titanate microparticles are generated and adsorbed by the porous structure of the silica gel, thereby avoiding the crystallization and growth of the microparticles. These microparticle structures play a filling and nucleation role in concrete, promote the hydration reaction of red mud cementitious materials, and improve the early strength. At the same time, silica gel can acidify the surface of red mud under high temperature conditions, further enhancing the activity of red mud.

[0062] Compared with Example 3, although the stability of the red mud material obtained in Comparative Example 4 is qualified, its activity index is significantly reduced at 7d and 28d. This is because the silica gel is not added in step (1), but is added in step (2), which will cause the generated sodium titanate microparticles and potassium tetraphenylborate microparticles to crystallize into large particles, lose the crystal nucleus effect, and thus limit the activation of the red mud activity by the silica gel.

[0063] Compared with Example 3, although the stability of the red mud material obtained in Comparative Example 5 is qualified, its activity index decreases significantly at 7d and 28d; compared with Comparative Example 4, the performance of the red mud material obtained in Comparative Example 5 is not much different. This is because the stirring in step (1) is to allow the silica gel to evenly enrich the soluble alkali. If the stirring step is missing, the potassium salt precipitation reaction of sodium tetraphenylborate and the sodium salt precipitation reaction of butyl titanate cannot occur evenly 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, thereby crystallizing to form large particles. Therefore, there is little difference in the effect of not stirring and adding silica gel later.

[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 the red mud contains a large amount of soluble alkali, such as NaOH, Na 2 CO 3 、NaHCO 3 , K 2 CO 3 、NaAl(OH) 4 , KOH, Ca(OH) 2 The elimination of these alkalis and soluble metal ions is crucial to increasing the amount of red mud used. Under hot water conditions, the solubility of calcium hydroxide decreases, thereby delaying its reaction with butyl titanate and sodium tetraphenylborate; while the solubility of the remaining alkalis increases with increasing temperature. If step (1) is not heated to 100°C, and the hot water is replaced with room temperature water, calcium hydroxide will react with butyl titanate and sodium tetraphenylborate in advance, resulting in limited precipitation reactions of potassium and sodium salts. In addition, the calcium salt of the red mud admixture is reduced during the hydration process in the later stage, affecting its reaction with silicate to form hydrated calcium silicate, thereby affecting the activity of the red mud.

[0065] Compared with Example 3, the stability of the red mud material obtained in Comparative Example 7 is unqualified, the fluidity decreases, and its activity decreases at 7d and 28d. This is because dihydrate gypsum mainly participates in the reaction to form calcium sulfonate, and premature addition will cause calcium ions to react with tetraphenylborate, limiting the precipitation reaction of sodium salt and potassium salt. At the same time, dihydrate gypsum easily reacts with silicate to form a precipitate, affecting the stimulating effect of silicate on the activity of red mud, and losing the activation effect on the later red mud activity. Therefore, dihydrate gypsum should be added during step (2).

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

[0067] In summary, the present invention can improve the stability and slurry fluidity of red mud by controlling temperature and specific surface area and adding sodium tetraphenylborate and butyl titanate ethanol, while utilizing the adsorption of silica gel to promote precipitation reaction and enhance the activity and early strength of red mud.

[0068] The above is an explanation of the embodiments of the present invention. By describing the disclosed embodiments, professionals in the field can implement or use the present invention, but it is not used to limit the present invention. It is impossible to fully reflect the various contents involved in the present invention in the above embodiments. Any equivalent changes or modifications made by any professional familiar with this technology without departing from the spirit or scope of the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing red mud active material, characterized in that: The method comprises the following steps: (1) Mixing the dried red mud with sodium tetraphenylborate and silica gel to obtain a mixture, grinding the mixture and heating it to 90-100° C., then adding a mixture of water and butyl titanate ethanol solution to the mixture, mixing well and placing the mixture in a closed environment at 190-250° C. to react, and drying and cooling the reaction product after the reaction is completed to obtain product A; (2) The product A is mixed with dihydrate gypsum 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 butyl titanate ethanol solution is 100:(10-15); the mass fraction of the butyl 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 butyl 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° C., and the reaction time of the reaction is 10-12 hours.

8. The preparation method according to claim 1, characterized in that: In step (1), the grinding is to grind the mixture to a specific surface area of ​​400m 2 / kg; the grinding in step (2) is to grind the mixture of product A and dihydrate gypsum to a specific surface area of ​​400m 2 / kg.

9. A red mud active material prepared by the preparation method according to any one of claims 1 to 8.

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

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