A low-carbon admixture based on red mud and its preparation method

Abstract

This invention belongs to the field of building materials and discloses a low-carbon admixture based on red mud and its preparation method. The low-carbon admixture comprises the following raw materials in parts by weight: 100 parts red mud, 5-10 parts sodium ammonium hydrogen phosphate, 20-30 parts modified plant fiber powder, and 20-40 parts water. The preparation method includes: mixing red mud, sodium ammonium hydrogen phosphate, modified plant fiber powder, and water; wet ball milling followed by calcination; cooling to room temperature; and then milling again to obtain the red mud admixture. This invention utilizes red mud as a raw material, and the prepared low-carbon admixture has the advantages of high compressive strength and high activity index, and effectively solves the pollution problem of red mud.

Description

Technical Field

[0001] This invention relates to the field of building material recycling, and in particular to a low-carbon admixture based on red mud and its preparation method. Background Technology

[0002] Red mud is an industrial solid waste discharged during the extraction of alumina in the aluminum industry. Because of its high iron oxide content and appearance resembling reddish soil, it is called red mud. Depending on the ore grade, production methods, and technological level, approximately 1.0 to 1.8 tons of red mud are discharged for every ton of alumina produced.

[0003] Due to the difficulty in removing and the high content of chemical alkalis bound to red mud, as well as the presence of fluorine, aluminum, and other impurities, the harmless utilization of red mud has been challenging. Red mud contains a large amount of strongly alkaline chemicals; even after a 10-fold dilution, its pH value remains 11.25–11.50 (compared to above 12 in the original soil). This extremely high pH value determines the strong corrosiveness of red mud to biological materials, metals, and siliceous materials. However, red mud also contains components such as SiO2, Al2O3, CaO, and Fe2O3, and possesses sub-clay characteristics, making it suitable for use in cement, bricks, ceramics, concrete, road materials, trace amounts of glass, and plastics. Extensive research and practical experience have shown that red mud can be used to produce various types of cement.

[0004] Compared to the enormous amount of red mud emitted, limited utilization still cannot alleviate the heavy burden that red mud places on society and the environment. Especially under the dual-carbon policy, the low-carbon utilization of red mud is imminent. Therefore, a more comprehensive and in-depth study of the characteristics of red mud, how to develop new materials based on industrial waste residue, and the full and effective recycling and utilization of red mud have become urgent tasks at this stage. Summary of the Invention

[0005] To address the problems and shortcomings of existing technologies, this invention provides a low-carbon admixture based on red mud and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a low-carbon admixture based on red mud, comprising the following raw materials: red mud, sodium ammonium hydrogen phosphate, modified plant fiber powder, and water.

[0008] Preferably, the raw materials, by weight, are: 100 parts red mud, 5-10 parts sodium ammonium hydrogen phosphate, 20-30 parts modified plant fiber powder, and 20-40 parts water.

[0009] Preferably, the modified plant fiber powder comprises the following raw materials in parts by weight: 20-30 parts plant fiber, 0.1-0.5 parts LIP bacteria, 1-2 parts phosphoric acid, 3-5 parts sodium ammonium hydrogen phosphate, 0.5-1 parts iron manganese oxide, 5-10 parts water, and 10-15 parts quicklime powder.

[0010] More preferably, the plant fiber is succulent plant fiber.

[0011] More preferably, the LIP fungus is one or more of the following: *Procambarus chrysospora*, *Procambarus variegata*, *Procambarus versicolor*, *Procambarus cibarius*, *Procambarus radiata*, *Procambarus spp.*, and *Procambarus versicolor*.

[0012] Secondly, the present invention provides a method for preparing a low-carbon admixture based on red mud, comprising the following steps:

[0013] (1) After mixing and grinding plant fiber, LIP bacteria, phosphoric acid, sodium ammonium hydrogen phosphate, iron manganese oxide and water into a homogenate, a hydrothermal reaction is carried out. Then quicklime powder is added, mixed, dried and ground to obtain modified plant fiber powder.

[0014] (2) Mix red mud, sodium ammonium hydrogen phosphate, modified plant fiber powder and water, and perform wet ball milling;

[0015] (3) Calcine the mixture obtained in step (2), cool it to room temperature, and then grind it again to obtain the red mud admixture.

[0016] Furthermore, the hydrothermal reaction temperature in step (1) is 25–40°C and the duration is 24–48 h.

[0017] Furthermore, the wet ball milling temperature in step (2) is 78-80°C and the time is 6-8h.

[0018] Furthermore, the calcination temperature in step (3) is 200–300°C.

[0019] Furthermore, the specific surface area of ​​the red mud admixture mentioned in step (3) is 400-600 m². 2 / kg.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. This invention modifies plant fibers by: dissolving lignin in plant fibers using LIP bacteria, phosphoric acid, and sodium ammonium hydrogen phosphate to eliminate the adverse effects of lignin; using iron-manganese oxides to catalyze the structural transformation of organic acids and biopolysaccharides in plant fibers to reduce their retarding effect; accelerating the reaction of the above substances through hydrothermal reaction at a certain temperature; and adding quicklime to promote water loss in plant fibers, lock in protein active substances, and kill bacteria.

[0022] 2. This invention utilizes the grinding-aiding effect of modified plant fibers and relies on the melting action of sodium ammonium hydrogen phosphate to dissolve and react metal oxides such as aluminum and magnesium in red mud to generate phosphates, thereby disrupting the mixed structure formed by various oxides in the red mud. The modified plant fibers themselves provide adhesion, lubrication, and grinding assistance, as well as the adhesion and bonding effect on the generated silicates, reducing the migration rate of the silicate products and preventing the agglomeration and deactivation of the generated active substances. Calcination at 200–300℃ removes organic components such as organic carbon, sugars, and proteins from the modified red mud, thereby enhancing the final activity of the red mud.

[0023] 3. This invention selects red mud, an industrial solid waste, as raw material, and effectively utilizes its components such as SiO2, Al2O3, CaO, and Fe2O3, as well as its sub-clay properties. Combined with biomaterial-modified plant fiber powder, it prepares a low-carbon admixture based on red mud, which has the advantages of high compressive strength and high activity index. It not only effectively solves the pollution problem of red mud and achieves the purpose of energy conservation and environmental protection, but also enables the reuse of waste and creates economic benefits. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the invention is further described in detail below through embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0025] Example 1

[0026] A low-carbon admixture based on red mud, wherein the raw materials of the low-carbon admixture based on red mud are, by weight: 100 parts red mud, 5 parts sodium ammonium hydrogen phosphate, 20 parts modified snake plant fiber powder, and 40 parts water.

[0027] The above-mentioned method for preparing low-carbon admixtures based on red mud includes the following steps:

[0028] (1) Mix 20 parts of snake plant fiber powder, 0.5 parts of Phanerochaete chrysospora, 1 part of phosphoric acid, 3 parts of sodium ammonium hydrogen phosphate, 1 part of iron manganese oxide and 5 parts of water, grind into a homogenate, and then perform a hydrothermal reaction at 40°C for 24 hours. Then add 15 parts of quicklime powder, mix, dry and grind to obtain modified snake plant fiber powder.

[0029] (2) Mix red mud, sodium ammonium hydrogen phosphate, modified snake skin orchid leaf plant fiber powder and water, and perform wet ball milling at 78°C for 8 hours.

[0030] (3) Take out the mixture obtained from grinding in step (2), calcine it further at 200°C, cool it to room temperature, and then grind it again until the specific surface area is 600 m². 2 / kg yields the red mud admixture.

[0031] Example 2

[0032] A low-carbon admixture based on red mud, whose composition and preparation method are basically the same as those in Example 1, except that the modified plant fiber is aloe vera leaf plant fiber.

[0033] Example 3

[0034] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 1, except that the modified plant fiber is a mixture of snake plant fiber and aloe vera leaf fiber in a mass ratio of 1:1.

[0035] According to Appendix A of GB / T 18046 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", the red mud admixtures in Examples 1-3 were tested for activity. The activity index is the ratio of the compressive strength of mortar prepared by replacing 30% of cement with the admixture and cured to the compressive strength of mortar prepared by not replacing cement with the admixture and cured to the corresponding age. A higher ratio indicates higher activity and better performance of the admixture. The test results are shown in Table 1.

[0036]

[0037] As can be seen from Table 1, the activity indices of Examples 1 to 3 are all relatively high, with Example 1 using snake plant leaf fiber being superior.

[0038] Example 4

[0039] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 1, except that 1.5 parts of phosphoric acid and 4 parts of sodium ammonium hydrogen phosphate are added in step (1).

[0040] Example 5

[0041] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 1, except that 2 parts of phosphoric acid and 5 parts of sodium ammonium hydrogen phosphate are added in step (1).

[0042] Comparative Example 1

[0043] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 1, except that phosphoric acid and sodium ammonium hydrogen phosphate are not added in step (1).

[0044] Comparative Example 2

[0045] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 1, except that sodium ammonium hydrogen phosphate is not added in step (1).

[0046] Comparative Example 3

[0047] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 1, except that phosphoric acid is not added in step (1).

[0048] Comparative Example 4

[0049] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 1, except that 4 parts of phosphoric acid and 6 parts of sodium ammonium hydrogen phosphate are added in step (1).

[0050] In accordance with Appendix A of GB / T 18046 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", the red mud admixture activity of Examples 4-5 and Comparative Examples 1-4 was tested. The test results are shown in Table 2.

[0051]

[0052] As shown in Table 2, the activity indices of Examples 1 and 4-5 are all relatively high, with Example 4 exhibiting the best dosage of phosphate and sodium ammonium hydrogen phosphate. In contrast, the activity indices of Comparative Examples 1-4 are all lower than those of the Examples. Comparative Examples 1-3, in the modification of plant fibers, either did not add phosphate or sodium hydrogen phosphate, or only added one of them, resulting in less lignin decomposition and affecting activity. Comparative Example 4, with its excessive addition of phosphate and sodium hydrogen phosphate, caused severe retardation of the mortar, leading to a decrease in the mortar's mechanical properties and activity. In conclusion, the synergistic use of appropriate amounts of phosphate and sodium hydrogen phosphate can significantly improve the activity index of the admixture.

[0053] Example 6

[0054] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 4, except that 0.5 parts of iron-manganese oxide are added in step (1).

[0055] Example 7

[0056] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 4, except that 0.8 parts of iron-manganese oxide are added in step (1).

[0057] Comparative Example 5

[0058] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 4, except that iron and manganese oxides are not added in step (1).

[0059] In accordance with Appendix A of GB / T 18046 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", the red mud admixture activity of Examples 6-7 and Comparative Example 5 was tested. The test results are shown in Table 3.

[0060]

[0061] As can be seen from Table 3, the activity indices of Examples 4, 6-7 are all relatively high, with Example 7 showing a better dosage of phosphorus, iron, and manganese oxides. The activity indices of Comparative Example 5 are all lower than those of the Examples, indicating that the addition of iron and manganese oxides can effectively catalyze the dissolution of lignin in plant fibers, reduce the adverse effects of lignin, and promote the activation of the admixture's activity.

[0062] Example 8

[0063] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 7, except that 8 parts of sodium ammonium hydrogen phosphate are added in step (2).

[0064] Example 9

[0065] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 7, except that 10 parts of sodium ammonium hydrogen phosphate are added in step (2).

[0066] Comparative Example 6

[0067] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 7, except that sodium ammonium hydrogen phosphate is not added in step (2).

[0068] Comparative Example 7

[0069] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 7, except that 15 parts of sodium ammonium hydrogen phosphate are added in step (2).

[0070] In accordance with Appendix A of GB / T 18046 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", the red mud admixture activity of Examples 8-9 and Comparative Examples 6-7 was tested. The test results are shown in Table 4.

[0071]

[0072] As can be seen from Table 4, the activity indices of Examples 7-9 are all relatively high, with Example 8 showing the best dosage of sodium hydrogen phosphate. The activity indices of Comparative Examples 6-7 are all lower than those of the Examples. Comparative Example 6 did not add sodium hydrogen phosphate, resulting in insufficient dissolution of metal oxides in the red mud and limited generation of active substances. Comparative Example 7 added excessive sodium hydrogen phosphate, causing its retarding effect to gradually become apparent, leading to a decrease in the activity of the admixture.

[0073] Comparative Example 8

[0074] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 8, except that the temperature of the hydrothermal reaction in step (1) is 60°C.

[0075] Comparative Example 9

[0076] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 8, except that the hydrothermal reaction time in step (1) is 12h.

[0077] In accordance with Appendix A of GB / T 18046 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", the red mud admixtures of Comparative Examples 8 and 9 were tested for activity. The test results are shown in Table 5.

[0078]

[0079] As shown in Table 5, the activity indices of Comparative Examples 8-9 were all lower than those of Example 8. Specifically, Comparative Example 8 increased the hydrothermal reaction temperature during plant fiber modification, leading to the inactivation of LIP bacteria and their inability to form enzymes, thus failing to achieve complete lignin decomposition. Comparative Example 9 shortened the hydrothermal reaction time during plant fiber modification, resulting in incomplete lignin dissolution and poor polysaccharide isomerization. In conclusion, plant fiber modification involves the synergistic effect of multiple substances and conditions, which can act on the chemical components of red mud during the grinding process, improving its grinding effect and increasing its post-grinding activity.

[0080] Comparative Example 10

[0081] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 8, except that the temperature of wet ball milling in step (2) is 60°C.

[0082] Comparative Example 11

[0083] A low-carbon admixture based on red mud has the same composition and preparation method as in Example 8, except that the temperature of wet ball milling in step (2) is 90°C.

[0084] In accordance with Appendix A of GB / T 18046 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", the red mud admixtures of Comparative Examples 10 and 11 were tested for activity. The test results are shown in Table 6.

[0085]

[0086] As can be seen from Table 6, the activity indices of Comparative Examples 10-11 are all lower than those of Example 8. In Comparative Example 10, the wet ball milling temperature was lowered during the red mud grinding process, which resulted in sodium hydrogen phosphate not being able to react effectively with the metal oxides, and the generation of active substances was limited. In Comparative Example 11, the wet ball milling temperature was increased during the red mud grinding process, which caused the sodium hydrogen phosphate to react too quickly, as well as react with the oxides, resulting in adhesion and excessive reaction with the oxide particles in the red mud, and a decrease in activity.

[0087] In conclusion, by utilizing the synergistic effect of modified plant fibers and other components with reaction conditions, it is highly feasible to apply red mud to admixtures. This not only reduces red mud pollution but also develops a low-carbon admixture based on red mud, achieving good economic, social, and environmental benefits.

[0088] The foregoing has described preferred embodiments of the present invention. However, it should be understood that the invention is not limited to the content disclosed herein. Any non-substantial improvements made using the inventive concept and technical solution, or any application of the inventive concept and technical solution to other situations, are within the protection scope of the present invention.

Claims

1. A low carbon red mud based blend, characterised in that, The low-carbon admixture comprises the following raw materials by weight: 100 parts of red mud, 5-10 parts of ammonium sodium hydrogen phosphate, 20-30 parts of modified plant fiber powder, and 20-40 parts of water; The modified plant fiber powder is made of the following raw materials by weight: 20-30 parts of plant fiber, 0.1-0.5 parts of LIP bacteria, 1-2 parts of phosphoric acid, 3-5 parts of ammonium sodium hydrogen phosphate, 0.5-1 parts of iron-manganese oxide, 5-10 parts of water, and 10-15 parts of quicklime powder; The following method is used for preparation, comprising the following steps: (1) mixing and grinding the plant fiber, LIP bacteria, phosphoric acid, ammonium sodium hydrogen phosphate, iron-manganese oxide and water into a homogenate, then performing a hydrothermal reaction, and then adding quicklime powder, mixing, drying and grinding to obtain the modified plant fiber powder; (2) mixing the red mud, ammonium sodium hydrogen phosphate, modified plant fiber powder and water, and performing wet ball milling at 78-80℃; (3) calcining the mixture obtained in step (2), cooling to room temperature, and then powdering to obtain the red mud admixture.

2. A low carbon red mud based blend as claimed in claim 1 wherein, The plant fiber is a succulent plant fiber.

3. The low carbon red mud based blend of claim 1, wherein, The LIP bacteria are one or more of Phanerochaete chrysosporium, Coriolopsis suberosa, Ramaria spiciformis, Bjerkandera adusta, Phlebia radiata, Volvariella volvacea and Neodolabratia fimbriata.

4. The low carbon red mud based blend of claim 1, wherein, The hydrothermal reaction temperature in step (1) is 25-40℃, and the time length is 24-48h.

5. The low carbon red mud based blend of claim 1, wherein, The calcination temperature in step (3) is 200-300℃.

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