A method for preparing a soil conditioner using red mud and a soil conditioner

Abstract

This application relates to the field of red mud solid waste recycling technology, and particularly to a method for preparing a soil conditioner using red mud and the soil conditioner itself. The red mud comprises alkaline components. The method includes: mixing an activator, a modifier, cellulose-containing waste biomass, water, and red mud to obtain a red mud slurry containing alkaline components and cellulose; performing a co-hydrothermal reaction on the red mud slurry containing alkaline components and cellulose using a reaction gas containing carbon dioxide to obtain a mixed product; and post-processing the mixed product to obtain a soil conditioner. This method, under the combined reaction of carbon dioxide and the red mud slurry, exposes fine fibers on the surface of the waste biomass. These fine fibers form a three-dimensional fused copolymer structure with the red mud, with a specific surface area of ​​63.25 m². 2 / g~70.85m 2 / g and porosity of 82.17%–90.79%.

Description

Technical Field

[0001] This application relates to the field of red mud solid waste recycling technology, and in particular to a method for preparing soil conditioners using red mud and the soil conditioners themselves. Background Technology

[0002] Red mud is a highly alkaline general industrial solid waste generated during the alumina production process from bauxite. Depending on its iron oxide content, red mud can appear red, reddish-brown, dark red, or gray. It also has a high water content and contains harmful components such as heavy metals. Currently, the comprehensive utilization rate of red mud is less than 10%, making its large-scale treatment a global challenge. At present, using red mud in the production of building materials is an effective way to dispose of it on a large scale. However, due to its high alkali content, fine particle size, and complex composition, these defects significantly impact production processes and product quality. Therefore, most red mud is currently stored in the open. This open storage consumes vast amounts of land resources, and the maintenance costs of these sites are high. Furthermore, large-scale open storage poses risks of dam failure and the leakage of toxic and harmful substances. Therefore, the resource utilization of red mud has significant practical, economic, and ecological benefits. In response to this situation, most current solutions rely on soil conditioners to improve the physical, chemical, and biological properties of the soil, making it more suitable for plant growth. However, existing soil conditioners are mostly synthesized from organic extracts, natural minerals, or artificial polymers, resulting in high production costs and making them difficult to mass-produce industrially.

[0003] To address the shortcomings of the aforementioned soil conditioners, red mud can be used as a raw material to prepare soil conditioners. However, the addition of red mud will reduce the number of pore structures in the soil conditioner and decrease its specific surface area and porosity. Summary of the Invention

[0004] This application provides a method for preparing a soil conditioner using red mud and the soil conditioner itself, in order to solve the following technical problem: how to increase the number of pore structures in a soil conditioner mixed with red mud.

[0005] In a first aspect, this application provides a method for preparing a soil conditioner using red mud, wherein the red mud comprises alkaline components, and the method includes:

[0006] The activator, modifier, cellulose-containing waste biomass and the red mud are mixed to obtain a red mud mixture slurry;

[0007] The reaction raw gas containing carbon dioxide is subjected to a co-hydrothermal reaction with the red mud mixture slurry to generate carbonates and form a three-dimensional fused copolymer structure to obtain a mixed product.

[0008] The mixture is then post-processed to obtain a soil conditioner.

[0009] Optionally, the temperature of the co-hydrothermal reaction is 80℃~200℃, and the time of the co-hydrothermal reaction is 4h~20h.

[0010] Optionally, the volume V1 of carbon dioxide introduced into the reaction raw material gas and the volume V2 of the red mud mixture slurry satisfy the relationship: V1:V2≥10:1.

[0011] Optionally, the weight m1 of the activator, the weight m2 of the modifier, the weight m3 of the waste biomass containing cellulose, and the weight m4 of the dry basis of the red mud satisfy the following relationship: m1:m2:m3:m4=(1~5):(0.5~2):(5~10):100.

[0012] Optionally, the cellulose content of the waste biomass is ≥ 35% of the weight of the waste biomass.

[0013] Optionally, the red mud includes Bayer process red mud; and / or

[0014] The waste biomass includes at least one of the following: corn stalks, wheat stalks, rice stalks, biogas residue, sugarcane bagasse, distiller's grains residue, and tree leaves; and / or

[0015] The activator includes at least one of the following: sodium silicate, silica fume, and nano-silica; and / or

[0016] The modifier includes at least one of the following: polyacrylic acid, polystyrene sulfonic acid, and polylactic acid.

[0017] Optionally, the particle size of the waste biomass containing cellulose is <0.1 mm.

[0018] Optionally, the step of post-processing the mixed product to obtain a soil conditioner includes the following steps:

[0019] The mixture is cooled and filtered to obtain filter residue;

[0020] The filter residue is dried and finely ground to obtain a soil conditioner.

[0021] Optionally, the final particle size of the fine grinding process is <0.1 mm.

[0022] Secondly, this application provides a soil conditioner, which is prepared by the method described in the first aspect.

[0023] The technical solutions provided in this application have the following advantages compared with the prior art:

[0024] This application provides a method for preparing a soil conditioner using red mud. The method involves first mixing an activator, a modifier, cellulose-containing waste biomass, and red mud. Sodium hydroxide and sodium aluminate from the red mud are thoroughly mixed with the cellulose from the waste biomass to obtain a red mud slurry containing alkaline components and cellulose. Then, a reaction gas containing carbon dioxide is introduced into the red mud slurry. During the hydrothermal reaction, the carbon dioxide in the reaction gas reacts with the alkaline components of the red mud at the liquid phase interface of the red mud slurry, generating carbonates. These carbonates catalyze and destroy the long-chain molecular structure of the cellulose in the waste biomass during the hydrothermal reaction, causing the cellulose to swell and aggregate, thus exposing fine fibers on the surface of the waste biomass. Therefore, under the combined reaction of carbon dioxide, the solid phase of the red mud slurry, and the liquid phase, fine fibers are exposed on the surface of the waste biomass, and these exposed fine fibers can encapsulate… A large amount of red mud forms a three-dimensional fused copolymer structure. Furthermore, the reactant gas enters this three-dimensional fused copolymer structure, creating numerous pores. These pores, combined with the support of fine fibers, promote a solidification reaction between the red mud in the mixture and the carbon dioxide in the reactant gas. This alters the mineral phase and microstructure of the red mud, thereby improving the pore structure of the three-dimensional fused copolymer structure. This increases the specific surface area and porosity of the three-dimensional fused copolymer structure, thus increasing the number of pores in the soil conditioner containing red mud. Additionally, the addition of activators and modifiers further improves the bonding strength between the red mud and the three-dimensional fused copolymer structure, further increasing the specific surface area and porosity of the three-dimensional fused copolymer structure, thereby further increasing the number of pores in the soil conditioner containing red mud. Therefore, this method can increase the number of pores in soil conditioners containing red mud. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This application provides a schematic flowchart of a method for preparing a soil conditioner using red mud, as shown in the embodiments of this application.

[0028] Figure 2This application provides a detailed flowchart illustrating a method for preparing a soil conditioner using red mud, as illustrated in the embodiments of this application.

[0029] Figure 3 This is a scanning electron microscope (SEM) schematic diagram of red mud provided in an embodiment of this application;

[0030] Figure 4 This is a scanning electron microscope (SEM) schematic diagram of a soil conditioner provided in Embodiment 1 of this application. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range such as 1, 2, 3, 4, 5, and 6, regardless of the range; in addition, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0033] In this document, terms such as “comprising” mean “including but not limited to”. Relational terms such as “first” and “second” are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. “And / or” describes the relationship between related objects, indicating that there can be three relationships, for example, A and / or B can mean: A alone, A and B simultaneously, or B alone; where A and B can be singular or plural. “At least one” means one or more, “more” means two or more; “at least one,” “at least one of the following,” or similar expressions refer to any combination of these items, including any combination of single or plural items; for example, “at least one of a, b, or c,” or “at least one of a, b, and c,” can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation" such as parts by weight or parts by mass indicates the proportional relationship between components. In the proportional relationships discussed in this article, the parameters that need to be described by proportion should be understood as the first term of the proportion in the order of description, and the proportion figures should be understood as the second term of the proportion. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figures in the proportion in the order of description, that is, the mass of substance A : the mass of substance B : the mass of substance C = 1:2:3.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0035] Figure 1 An exemplary schematic diagram of a method for preparing a soil conditioner using red mud, provided in an embodiment of this application, is shown.

[0036] like Figure 1 As shown in the embodiments of this application, a method for preparing a soil conditioner using red mud is provided, wherein the red mud comprises alkaline components, and the method includes:

[0037] S1. The activator, modifier, waste biomass containing cellulose and the red mud are mixed to obtain a red mud mixture slurry;

[0038] S2. The reaction raw gas containing carbon dioxide is subjected to a co-hydrothermal reaction with the red mud mixture slurry to generate carbonates and form a three-dimensional fused copolymer structure to obtain a mixed product;

[0039] S3. The mixture is post-processed to obtain a soil conditioner.

[0040] It should be noted that the mixing method can be stirring, and the mixing process can also involve slurry preparation to ensure that the alkaline components of the red mud are fully mixed with the cellulose of the waste biomass.

[0041] It should be noted that the reactant gas can be carbon dioxide gas alone, or it can be a mixture of carbon dioxide gas and inert gas.

[0042] It should be noted that the alkaline component can be sodium hydroxide, sodium aluminate, and sodalite. Sodium hydroxide and sodium aluminate are generally the main free alkali components of red mud, while sodalite is generally the combined alkali of red mud. These free alkalis and combined alkalis will react with carbon dioxide at the liquid interface to produce carbonates. The generated carbonates can catalyze and destroy the long-chain molecular structure of cellulose in waste biomass during the subsequent hydrothermal reaction, so that the cellulose in waste biomass will expand and aggregate, thereby exposing fine fibers on the surface of waste biomass.

[0043] It should be noted that the mixture of activator, modifier, cellulose-containing waste biomass, and red mud...

[0044] It should be noted that the amount of water added is 2 to 10 times the sum of the weights of the activator, modifier, cellulose-containing waste biomass, and red mud, so as to ensure that the red mud mixture slurry has sufficient moisture and to ensure that enough carbonates are generated during the subsequent hydrothermal reaction.

[0045] In some optional embodiments, the temperature of the co-hydrothermal reaction is 80°C to 200°C, and the time of the co-hydrothermal reaction is 4h to 20h;

[0046] In these embodiments, the temperature of the co-hydrothermal reaction can be 80℃ to 200℃, and the reaction time can be 4h to 20h. Through the co-hydrothermal reaction, under the combined reaction of the solid matter and liquid phase of the carbon dioxide and red mud mixture slurry, microfibers are exposed on the surface of the waste biomass. These microfibers can encapsulate a large amount of red mud and form a three-dimensional fused copolymer structure with the red mud. In addition, the co-hydrothermal reaction can promote the formation of a large number of pores in the three-dimensional fused copolymer structure by the reaction raw material gas. These pores, together with the supporting effect of the microfibers, can improve the pore structure of the three-dimensional fused copolymer structure, thereby increasing the specific surface area and porosity of the three-dimensional fused copolymer structure, and thus increasing the number of pores in the soil conditioner doped with red mud.

[0047] The temperature of the hydrothermal reaction can be 80℃, 100℃, 120℃, 140℃, 160℃, 180℃ or 200℃.

[0048] The hydrothermal reaction time can be 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h or 20h.

[0049] In some optional embodiments, the volume V1 of carbon dioxide introduced into the reaction feed gas and the volume V2 of the red mud mixture slurry satisfy the relationship: V1:V2≥10:1;

[0050] In these embodiments, the volume V1 of carbon dioxide introduced into the reaction raw material gas and the volume V2 of the red mud mixture slurry can satisfy the relationship: V1:V2≥10:1, ensuring that the reaction raw material gas contains sufficient carbon dioxide. Sufficient carbon dioxide can promote acid-base reactions with the alkaline components of red mud at the liquid phase interface of the red mud mixture slurry to generate sufficient carbonates, causing the cellulose of the waste biomass to expand and coagulate. This exposes the fine fibers from the surface of the waste biomass, encapsulating a large amount of red mud. Sufficient carbon dioxide will enter the three-dimensional fused copolymer structure formed by the fine fibers and red mud, forming a large number of pores in the three-dimensional fused copolymer structure, thereby improving the pore structure of the three-dimensional fused copolymer structure, increasing the specific surface area and porosity of the three-dimensional fused copolymer structure, and thus increasing the number of pores in the soil conditioner doped with red mud.

[0051] In some optional embodiments, the weight m1 of the activator, the weight m2 of the modifier, the weight m3 of the waste biomass containing cellulose, and the weight m4 of the dry basis of the red mud satisfy the following relationship: m1:m2:m3:m4=(1~5):(0.5~2):(5~10):100;

[0052] In these embodiments, the weights of the activator (m1), modifier (m2), cellulose-containing waste biomass (m3), and dry red mud (m4) satisfy the following relationship: m1:m2:m3:m4 = (1-5):(0.5-2):(5-10):100. This ensures that the red mud mixture contains sufficient activator and modifier. Sufficient activator not only promotes the decomposition and conversion of waste biomass into cellulose, but also fully colloidalizes the oxygen-containing functional groups such as hydroxyl and carboxyl groups on the cellulose surface, improving the stability of the three-dimensional fused copolymer structure. This, in turn, promotes the conversion of cellulose into cellulose. The red mud is adsorbed more tightly, thus increasing the red mud content in the soil conditioner. In addition, sufficient modifiers can adsorb onto the surface of waste biomass, causing the surface of waste biomass to carry a sufficient amount of negative charge. Sufficient negative charge will form active sites on the surface of waste biomass. These surface active sites can promote the formation of chelate structures between the cellulose of waste biomass and red mud. Furthermore, since modifiers generally contain a large number of hydrophilic groups, these hydrophilic groups will further promote the adsorption of red mud by the cellulose of waste biomass, so as to promote the gelation of red mud on the surface of cellulose, thereby facilitating the formation of a multi-layered cross-linked stable three-dimensional fused copolymer structure between red mud and cellulose.

[0053] The weight m1 of the activator can be 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8 or 2.0; the weight m2 of the modifier can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4 or 5; and the weight m3 of the cellulose-containing waste biomass can be 5, 6, 7, 8, 9 or 10.

[0054] In some optional embodiments, the cellulose content of the waste biomass is ≥ 35% by weight of the waste biomass;

[0055] In these embodiments, the cellulose content of the waste biomass is ≥35% of the weight of the waste biomass, ensuring that the waste biomass contains sufficient cellulose. Under the combined reaction of carbon dioxide, solid matter of red mud mixture and liquid phase, the surface of the waste biomass will expose fine fibers. The exposed fine fibers can encapsulate a large amount of red mud and form a three-dimensional fused copolymer structure with the red mud. This three-dimensional fused copolymer structure can increase the number of pore structures in the soil conditioner that is doped with red mud.

[0056] In some alternative embodiments, the red mud includes Bayer process red mud; and / or

[0057] The waste biomass includes at least one of the following:

[0058] Corn stalks, wheat stalks, rice stalks, biogas residue, sugarcane bagasse, distiller's grains residue, and leaves; and / or

[0059] The activator includes at least one of the following:

[0060] Sodium silicate, silica, and nano-silica; and / or

[0061] The modifier includes at least one of the following:

[0062] Polyacrylic acid, polystyrene sulfonic acid, and polylactic acid;

[0063] In these embodiments, the red mud may include Bayer process red mud, which can promote the inclusion of sufficient alkaline components. During the co-hydrothermal reaction, the carbon dioxide from the reactant gas reacts with the alkaline components of the red mud at the liquid phase interface of the red mud mixture to generate sufficient carbonates, facilitating the subsequent expansion and coagulation of cellulose from the waste biomass. Additionally, the waste biomass may include at least one of corn stalks, wheat stalks, rice stalks, biogas residue, bagasse, distiller's grains residue, and leaves, ensuring sufficient cellulose content. This sufficient cellulose, under the hydrothermal reaction of carbon dioxide, the solid phase of the red mud mixture, and the liquid phase, can fully expose a large number of fine fibers on the surface of the waste biomass. These fine fibers can encapsulate a large amount of red mud and form a three-dimensional fused copolymer structure with it, thereby improving the red mud content of the soil conditioner. The doping amount; in addition, the activator may include at least one of sodium silicate, silica, and nano-silica, which can cover most types of activators. The activator can improve the stability of the three-dimensional fused copolymer structure, thereby promoting the adsorption of red mud by cellulose more tightly, so as to increase the red mud doping amount of the soil conditioner; in addition, the modifier may include at least one of polyacrylic acid, polystyrene sulfonic acid, and polylactic acid, which can cover most types of modifiers. The modifier can be adsorbed on the surface of waste biomass, so as to promote the surface of waste biomass to carry a sufficient amount of negative charge. The sufficient amount of negative charge will form active sites on the surface of waste biomass. These surface active sites can promote the formation of chelate structure between cellulose of waste biomass and red mud, thereby preventing red mud from invading into the pore structure, thereby increasing the number of pore structures in the soil conditioner doped with red mud.

[0064] It should be noted that, based on the characteristic that this activator can promote the adsorption of red mud by cellulose more tightly, the soil conditioner can effectively adsorb elements such as nitrogen, phosphorus, and potassium from fertilizers during the soil conditioning process, and slow down the release rate of these elements, thereby improving the utilization efficiency of fertilizers.

[0065] It should be noted that, based on the characteristic of this modifier that it can promote the formation of chelate structures between cellulose from waste biomass and red mud, the soil conditioner can adsorb metal ions in the soil through these chelate structures, thereby avoiding the toxic effects of metal ions on the soil. In addition, based on the modifier's effect of promoting the formation of multi-layer cross-linked stable three-dimensional fused copolymer structures between red mud and cellulose, these three-dimensional fused copolymer structures can be used to increase the number of pore structures in the soil conditioner that has been mixed with red mud. Sufficient pore structures can improve the soil conditioner's ability to store water and fertilizer, thereby further enhancing the soil conditioner's effect on improving the soil.

[0066] In some alternative embodiments, the particle size of the waste biomass containing cellulose is <0.1 mm;

[0067] In these embodiments, the particle size of the cellulose-containing waste biomass is <0.1 mm, which promotes the particle size of the waste biomass to be within a relatively fine range. This allows the cellulose to form sufficiently fine microfibers during the hydrothermal reaction. These sufficiently fine microfibers can encapsulate a large amount of red mud and form a three-dimensional fused copolymer structure with the red mud. In addition, the cellulose in this relatively fine particle size range has a good supporting effect. When combined with the reaction raw material gas, it enters the formed three-dimensional fused copolymer structure to form a large number of pores, which can increase the specific surface area and porosity of the three-dimensional fused copolymer structure, thereby increasing the number of pore structures in the soil conditioner mixed with red mud.

[0068] Figure 2 An exemplary schematic diagram illustrates a detailed process flow diagram of a method for preparing a soil conditioner using red mud, provided in an embodiment of this application.

[0069] In some alternative implementations, such as Figure 2 As shown, the step of post-processing the mixed product to obtain a soil conditioner includes the following steps:

[0070] S301. Cool and filter the mixture to obtain filter residue;

[0071] S302. The filter residue is dried and finely ground to obtain a soil conditioner;

[0072] In these embodiments, the mixture is sequentially cooled, filtered, dried and finely ground to remove impurities and obtain a soil conditioner with a finer particle size.

[0073] In some alternative embodiments, the final particle size of the fine grinding process is <0.1 mm;

[0074] In these embodiments, the final particle size of the fine grinding process is <0.1 mm, which results in a soil conditioner with a smaller particle size. The sufficiently small soil conditioner can better exert the characteristics of its three-dimensional fused copolymer structure, effectively adsorbing metal ions, fertilizers and water in the soil, thereby improving the soil conditioner's conditioning effect on the soil.

[0075] Based on a general inventive concept, embodiments of this application provide a soil conditioner prepared by the method described above.

[0076] The soil conditioner is implemented based on the above method. The specific steps of the method can be referred to the above embodiments. Since the soil conditioner adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0077] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0078] Example 1

[0079] like Figure 2 As shown, a method for preparing a soil conditioner using red mud is described. The red mud comprises alkaline components, including:

[0080] S1. The activator, modifier, waste biomass containing cellulose and red mud are mixed to obtain a red mud mixture slurry containing alkaline components and cellulose;

[0081] S2. A red mud mixture containing alkaline components and cellulose is subjected to a hydrothermal reaction using a reaction feed gas containing carbon dioxide to generate carbonates and form a three-dimensional fused copolymer structure to obtain a mixed product.

[0082] S301. Cool and filter the mixture to obtain filter residue;

[0083] S302. The filter residue is dried and finely ground to obtain a soil conditioner;

[0084] The amount of water added is five times the sum of the weights of the activator, modifier, cellulose-containing waste biomass, and red mud.

[0085] The hydrothermal reaction was carried out at a temperature of 120℃ for 10 hours.

[0086] The volume of carbon dioxide introduced into the reaction raw material gas, V1, and the volume of the red mud mixture slurry, V2, satisfy the relationship: V1:V2=20:1.

[0087] The weights of the activator (m1), the modifier (m2), the waste biomass containing cellulose (m3), and the dry weight of the red mud (m4) satisfy the relationship: m1:m2:m3:m4=1:0.8:8:100.

[0088] Cellulose content in waste biomass is ≥ 35% of the weight of waste biomass.

[0089] The red clay is Bayer process red clay;

[0090] The waste biomass is corn stalks;

[0091] The activator is nano-silica;

[0092] The modifier is polyacrylic acid.

[0093] The particle size of waste biomass containing cellulose is <0.1mm.

[0094] The final particle size after fine grinding is <0.1mm.

[0095] Example 2

[0096] Based on the content disclosed in Example 1, the following modifications are made:

[0097] The amount of water added is twice the sum of the weights of the activator, modifier, cellulose-containing waste biomass, and red mud.

[0098] The hydrothermal reaction was carried out at a temperature of 180℃ for 15 hours.

[0099] The weights of the activator (m1), modifier (m2), cellulose-containing waste biomass (m3), and dry red mud (m4) satisfy the following relationship: m1:m2:m3:m4=5:1.5:6.5:100.

[0100] Waste biomass is rice straw;

[0101] The activator is silica;

[0102] The modifier is polyacrylic acid.

[0103] Example 3

[0104] Based on the content disclosed in Example 1, the following modifications are made:

[0105] The amount of water added is 10 times the sum of the weights of the activator, modifier, cellulose-containing waste biomass, and red mud.

[0106] The temperature of the hydrothermal reaction was 160℃, and the reaction time was 8 hours.

[0107] The weights of the activator (m1), the modifier (m2), the waste biomass containing cellulose (m3), and the dry weight of the red mud (m4) satisfy the following relationship: m1:m2:m3:m4=4:2:5:100.

[0108] Waste biomass is sugarcane bagasse;

[0109] The activator is sodium silicate;

[0110] The modifier is polylactic acid.

[0111] Example 4

[0112] Based on the content disclosed in Example 1, the following modifications are made:

[0113] The amount of water added is eight times the sum of the weights of the activator, modifier, cellulose-containing waste biomass, and red mud.

[0114] The temperature of the hydrothermal reaction was 200℃, and the reaction time was 4 hours.

[0115] The weights of the activator (m1), the modifier (m2), the waste biomass containing cellulose (m3), and the dry weight of the red mud (m4) satisfy the following relationship: m1:m2:m3:m4=3:0.5:9:100.

[0116] Waste biomass is converted into biogas residue;

[0117] The activator is sodium silicate;

[0118] The modifier is polystyrene sulfonic acid.

[0119] Example 5

[0120] Based on the content disclosed in Example 1, the following modifications are made:

[0121] The amount of water added is 6 times the sum of the weights of the activator, modifier, cellulose-containing waste biomass, and red mud.

[0122] The hydrothermal reaction was carried out at a temperature of 80℃ for 20 hours.

[0123] The weights of the activator (m1), the modifier (m2), the waste biomass containing cellulose (m3), and the dry weight of the red mud (m4) satisfy the following relationship: m1:m2:m3:m4 = 2.5:1.2:10:100.

[0124] Waste biomass is wheat straw;

[0125] The activator is silica;

[0126] The modifier is polystyrene sulfonic acid.

[0127] Comparative Example 1

[0128] Based on the content disclosed in Example 1, the following modifications are made:

[0129] The volume of carbon dioxide introduced into the reaction raw material gas, V1, and the volume of the red mud mixture slurry, V2, satisfy the relationship: V1:V2=8:1.

[0130] Comparative Example 2

[0131] Based on the content disclosed in Example 1, the following modifications are made:

[0132] The hydrothermal reaction temperature was 60℃, and the hydrothermal reaction time was 30h.

[0133] Comparative Example 3

[0134] Based on the content disclosed in Example 1, the following modifications are made:

[0135] The temperature of the hydrothermal reaction was 250℃, and the reaction time was 2 hours.

[0136] Comparative Example 4

[0137] Based on the content disclosed in Example 1, the following modifications are made:

[0138] The weights of the activator (m1), the modifier (m2), the waste biomass containing cellulose (m3), and the dry weight of the red mud (m4) satisfy the following relationship: m1:m2:m3:m4 = 0.5:0.1:3:100.

[0139] Comparative Example 5

[0140] Based on the content disclosed in Example 1, the following modifications are made:

[0141] The weights of the activator (m1), the modifier (m2), the waste biomass containing cellulose (m3), and the dry weight of the red mud (m4) satisfy the following relationship: m1:m2:m3:m4=10:5:15:100.

[0142] Relevant experimental and effect data:

[0143] 1. The red mud doping amount, specific surface area and porosity of the soil conditioners obtained in each comparative example and embodiment were statistically analyzed, and the results are shown in Table 1.

[0144] Table 1. Results of red mud doping amount, specific surface area, and porosity of soil conditioners in each comparative example and embodiment.

[0145]

[0146] As shown in Table 1, the method for preparing a soil conditioner using red mud provided in this application involves the exposure of fine fibers on the surface of waste biomass under the combined reaction of solid matter and liquid phases of a carbon dioxide and red mud mixture slurry. These exposed fine fibers can encapsulate a large amount of red mud and form a three-dimensional fused copolymer structure. Furthermore, the reactant gas enters the formed three-dimensional fused copolymer structure, increasing its specific surface area to 63.25 m². 2 / g~70.85 m 2 / g and porosity up to 82.17% to 90.79%, indicating that this method significantly increases the number of pore structures in soil conditioners doped with red mud. A sufficient number of pore structures can further increase the adsorption amount of red mud in the three-dimensional fused copolymer structure adsorbing red mud mixture slurry, thereby increasing the red mud doping amount of the soil conditioner to 88.50% to 91.07%. Comparative Example 1 reduced the ratio of the volume of carbon dioxide introduced into the reaction raw material gas V1 to the volume of the red mud mixture V2 to 9:1 based on Example 1. Comparative Example 2 reduced the temperature of the co-hydrothermal reaction to 60°C based on Example 1. Comparative Example 2 increased the temperature of the co-hydrothermal reaction to 250°C based on Example 1. Comparative Example 4 changed the raw material ratio based on Example 1 (the weights of the activator m1, modifier m2, cellulose-containing waste biomass m3, and dry red mud m4 satisfy the relationship: m1:m2:m3:m4=0.5:0.1:3:100). Comparative Example 5 changed the raw material ratio based on Example 1 (the weights of the activator m1, modifier m2, cellulose-containing waste biomass m3, and dry red mud m4 satisfy the relationship: m1:m2:m3:m4=10:5:15:100). Although the amount of red mud doping in Comparative Examples 1-4 did not change much, the specific surface area and porosity of the soil conditioners prepared in Comparative Examples 1-5 were significantly worse than those prepared in Examples 1-5. This indicates that the poor process conditions in the comparative examples significantly affected the pore structure distribution and quantity of the soil conditioners.

[0147] 2. The soil conditioners from each embodiment and comparative example were applied to infertile soil for experiments: The soil conditioners prepared in each embodiment were added to the top 30cm of infertile soil at a dosage of 5% of the soil mass. The soil and soil conditioner were then mixed evenly using a tillage machine and watered. After 7 days of stable cultivation, samples were taken to test changes in soil porosity, field water holding capacity, specific surface area, and organic matter content. Ryegrass was planted uniformly during the stable cultivation period, and the germination rate of the ryegrass after 10 days and the plant height after 30 days were recorded. Additionally, blank and control group experiments were conducted following the same steps. The blank group consisted of infertile soil without soil conditioner, replaced by the same mass of water; the control group consisted of infertile soil with only 5% (by weight) dry red mud added. The results are shown in Table 2.

[0148] Table 2. Soil test results of soil conditioners in each embodiment and comparative example.

[0149]

[0150] As shown in Table 2, compared with the control group where dry red mud was added to barren soil at a dosage of 5%, the porosity, field water holding capacity, specific surface area, and organic matter content of the soil in the control group increased by only 3.2%, 4.7%, 0.56%, and 0.22%, respectively. However, the soil conditioner provided in this application embodiment, when added to barren soil at a dosage of 5%, can increase the soil porosity, field water holding capacity, specific surface area, and organic matter content by more than 11%, more than 12%, more than 7%, and more than 15%, respectively. Furthermore, a comparison of the growth of ryegrass crops revealed that the germination rates of the blank group (without soil conditioner) and the control group (with only dry red mud) were only 55.25% and 57.46% after 10 days, respectively, and the average plant height after 30 days was only 13.38 cm and 14.32 cm, respectively. However, after treatment with the various soil conditioners provided in the embodiments of this application, the germination rate of ryegrass crops could be increased to over 80% after 10 days, and the average plant height after 30 days could be over 25 cm. Comparative Example 1, based on Example 1, reduced the ratio of the volume of carbon dioxide introduced into the reaction raw material gas (V1) to the volume of the red mud mixture slurry (V2) to 9:1. Comparative Example 2, based on Example 1, reduced the temperature of the co-hydrothermal reaction to 60°C. Comparative Example 2, based on Example 1, increased the temperature of the co-hydrothermal reaction to 250°C. Comparative Example 4, based on Example 1, changed the raw material ratio (weight m1 of activator, weight m2 of modifier, weight m3 of waste biomass containing cellulose, and weight m3 of dry red mud). 4. The ratio of raw materials in Comparative Example 5 is changed based on Example 1 (the weight of activator m1, the weight of modifier m2, the weight of waste biomass containing cellulose m3, and the weight of dry red mud m4 satisfy the ratio of m1:m2:m3:m4=10:5:15:100). The experimental results of the soil conditioners prepared in Comparative Examples 1 to 5 in the soil test were significantly worse than those in Examples 1 to 5. This shows that the soil conditioner provided in this application can significantly improve the soil porosity, field water holding capacity, and specific surface area of ​​barren soil. In addition, it can increase the organic matter content of barren soil, and the soil conditioner also has the beneficial effects of water retention, fertilizer retention, and promoting crop growth.

[0151] In summary, the present application provides a method for preparing a soil conditioner using red mud. Under the combined reaction of carbon dioxide, solid matter in a red mud mixture, and liquid phase, the surface of waste biomass exposes fine fibers. These fine fibers form a three-dimensional fused copolymer structure with the red mud. Furthermore, the reaction gas enters the formed three-dimensional fused copolymer structure, increasing its specific surface area and porosity. This significantly increases the number of pores in the soil conditioner containing red mud, thereby increasing the amount of red mud adsorbed by the three-dimensional fused copolymer structure, and ultimately increasing the amount of red mud in the soil conditioner to 88.50%–91.07%.

[0152] Another embodiment of this application provides a method for preparing a soil conditioner using red mud. This method uses carbon dioxide, waste biomass containing cellulose, and red mud as raw materials, which can achieve the synergistic treatment of red mud, waste biomass resources, and carbon dioxide, thereby increasing the red mud content in the soil conditioner and reducing production costs, so as to achieve the purpose of "treating waste with waste" through synergistic utilization.

[0153] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A method for preparing a soil conditioner using red mud, wherein the red mud comprises alkaline components, the method comprising: The activator, modifier, cellulose-containing waste biomass and the red mud are mixed to obtain a red mud slurry; The reaction raw gas containing carbon dioxide is subjected to a co-hydrothermal reaction with the red mud mixture slurry to generate carbonates and form a three-dimensional fused copolymer structure to obtain a mixed product. The mixture is then post-processed to obtain a soil conditioner; The temperature of the co-hydrothermal reaction is 80℃~200℃, and the time of the co-hydrothermal reaction is 4h~20h; The volume V1 of carbon dioxide in the reaction feed gas and the volume V2 of the red mud mixture slurry satisfy the following relationship: V1:V2≥10:1; The weights m1 of the activator, m2 of the modifier, m3 of the waste biomass containing cellulose, and m4 of the dry basis of the red mud satisfy the following relationship: m1:m2:m3:m4 = (1~5):(0.5~2):(5~10):100; The cellulose content of the waste biomass is ≥ 35% of the weight of the waste biomass; The activator includes at least one of the following: sodium silicate, silica fume, and nano-silica; The modifier includes at least one of the following: polyacrylic acid, polystyrene sulfonic acid, and polylactic acid; The specific surface area of ​​the three-dimensional fused copolymer structure is 63.25 m². 2 / g~70.85 m 2 / g, with a porosity of 82.17%–90.79%.

2. The method according to claim 1, wherein the red mud comprises Bayer process red mud; and / or The waste biomass includes at least one of the following: corn stalks, wheat stalks, rice stalks, biogas residue, sugarcane bagasse, distiller's grains residue, and tree leaves.

3. The method according to claim 1, wherein the particle size of the waste biomass containing cellulose is <0.1 mm.

4. The method according to claim 1, wherein post-processing the mixed product to obtain a soil conditioner includes the following steps: The mixture is cooled and filtered to obtain filter residue; The filter residue is dried and finely ground to obtain a soil conditioner.

5. The method according to claim 4, wherein the final particle size of the fine grinding process is <0.1 mm.

6. A soil conditioner, said soil conditioner being prepared by the method according to any one of claims 1 to 5.

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