Geopolymer based on industrial waste and preparation method thereof

Abstract

The invention belongs to the field of comprehensive utilization of wastes, and relates to a geopolymer based on industrial wastes and a preparation method thereof. The preparation raw materials of the geopolymer based on the industrial waste comprise a precursor material, an alkali-activated solution, zirconium silicate and zirconium phosphate. The precursor material comprises any two of fly ash, red mud and kaolin, and the alkali-activated solution comprises sodium hydroxide, water glass, sodium borate, sodium fluoride and water. The solid-to-liquid ratio w: v of the precursor material to the alkali-activated solution is 1: 1-2: 1, zirconium silicate accounts for 2-5% of the mass of the precursor material, and zirconium phosphate accounts for 2-3% of the mass of the precursor material. After the geopolymer is soaked in a dilute sulfuric acid solution, the mass loss rate of the geopolymer is only 1.7-2.2%, the geopolymer has good acid corrosion resistance, the structural integrity can still be kept after the geopolymer is exposed in an acid environment for a long time, and the chemical stability and durability of the geopolymer serving as a building material are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of wastes, and in particular to a geopolymer based on industrial waste and a preparation method thereof. Background Art

[0002] With the acceleration of industrialization, large amounts of industrial waste, such as fly ash and red mud, are placing tremendous pressure on the environment. Furthermore, the production of traditional building materials also involves resource waste and environmental pollution. The development of high-performance geopolymer materials using industrial waste as raw materials not only enables the resource utilization of waste but also provides environmentally friendly, high-performance building materials, which is of great significance for promoting green buildings and sustainable development.

[0003] Red mud is a by-product of bauxite aluminum smelting, mainly consisting of bauxite and iron oxides, of which the iron oxide content is relatively high and appears reddish-brown. Due to the large output of red mud, it must be properly handled to avoid environmental pollution. Fly ash is the ash produced during the combustion of coal in thermal power plants, mainly consisting of minerals such as iron, silicon, and aluminum. Fly ash usually exists in the form of fine particles, with a particle size generally ranging from 1 to 100 μm and a color of gray or black. Kaolin is a common non-metallic layered silicate mineral with the chemical formula Al2Si2O5(OH)4, containing elements such as silicon, oxygen, and aluminum. Kaolin is a white powder with fine particle size and good refractory properties. It is widely used in ceramics, coatings, papermaking, medicine and other fields.

[0004] Patent application CN113735515A discloses a fly ash and red mud-based geopolymer curing material and its preparation method. The raw materials consist of solid and liquid raw materials. The solid raw materials include, by mass, 2-4% cement, 2-4% red mud, 3-5% fly ash, and 87-93% polymetallic contaminated soil. The liquid raw materials include an aqueous solution containing an alkali activator and a water reducer. The solid and liquid raw materials are mixed at a water-cement ratio of 0.30-0.40. The water reducer is an anionic surfactant polycarboxylate water reducer, and the alkali activator is sodium silicate. The sodium silicate has a Na2O to SiO2 ratio of 1.03 and a modulus of 1. This technical solution focuses on heavy metal curing and improving short-term mechanical properties, but the resulting geopolymer material exhibits poor acid corrosion resistance.

[0005] Therefore, although some studies have attempted to prepare geopolymers using industrial waste materials such as red mud and fly ash, in actual engineering applications, the acid resistance of existing geopolymers is poor. Most studies only focus on basic physical properties such as compressive strength and setting time, but ignore the chemical stability of geopolymers in acidic environments, such as rainwater erosion and acid mist corrosion in industrial plants. As a result, geopolymers may suffer from structural damage and strength loss during long-term use.

[0006] Therefore, it is necessary to effectively improve the acid corrosion resistance of geopolymers. Summary of the Invention

[0007] (1) Technical issues to be resolved

[0008] In view of the above technical problems, in order to solve the problem of poor acid corrosion resistance of geopolymers in the prior art, the present invention provides a geopolymer based on industrial waste and a preparation method thereof.

[0009] (2) Technical solution

[0010] In order to achieve the above objectives, the main technical solutions adopted by the present invention include:

[0011] The present invention provides a geopolymer based on industrial waste, wherein the raw materials for preparing the geopolymer include a precursor material, an alkali-activated solution, zirconium silicate and zirconium phosphate;

[0012] The precursor materials include any two of fly ash, red mud and kaolin;

[0013] The alkaline excitation solution comprises sodium hydroxide, water glass, sodium borate, sodium fluoride and water;

[0014] The solid-liquid ratio w:v of the precursor material and the alkaline excited solution is 1:1-2:1;

[0015] The zirconium silicate accounts for 2-5% of the mass of the precursor material, and the zirconium phosphate accounts for 2-3% of the mass of the precursor material.

[0016] The industrial waste-based geopolymer as described above, preferably, when the precursor materials are red mud and fly ash, the mass ratio of red mud to fly ash is (30-40): (70-60);

[0017] When the current drive materials are kaolin and red mud, the mass ratio of kaolin to red mud is (60-50):(40-50);

[0018] When the current driving material is fly ash and kaolin, the mass ratio of fly ash to kaolin is (60-50):(40-50).

[0019] In the above-mentioned geopolymer based on industrial waste, preferably, in the alkali-activated solution, the concentration of sodium hydroxide is 5-7.5 mol / L, the concentration of water glass is 0.45-1.31 mol / L, the amount of sodium borate added is 1-5% of the mass of the sodium hydroxide, and the amount of sodium fluoride added is 0.5-3% of the mass of the sodium hydroxide.

[0020] The present invention also provides a method for preparing the above-mentioned industrial waste-based geopolymer, comprising the following steps:

[0021] S1: uniformly mixing the precursor material, zirconium silicate and zirconium phosphate to obtain a mixed material;

[0022] S2: adding the alkali-activated solution to the mixed material and mixing them uniformly to obtain a slurry;

[0023] S3: injecting the slurry into the mold and vibrating it to obtain a preform;

[0024] S4: The rough blank is cured and then solidified, and the geopolymer is obtained after demoulding.

[0025] In the above-mentioned method for preparing geopolymers based on industrial waste, preferably, in step S1, the particle size of the precursor material, zirconium silicate and zirconium phosphate is 450-550 mesh.

[0026] In the above-mentioned method for preparing geopolymers based on industrial waste, preferably, in step S2, the preparation method of the alkali-activated solution is as follows:

[0027] Sodium borate and sodium fluoride are added to a sodium hydroxide solution having a concentration of 8-12 mol / L, mixed evenly, and then mixed with a water glass solution having a concentration of 1.2-3.5 mol / L, and allowed to stand to obtain an alkali-activated solution;

[0028] The volume ratio of sodium hydroxide solution to water glass solution is 5:3.

[0029] In the above-mentioned method for preparing geopolymer based on industrial waste, preferably, in step S2, the alkali-activated solution is added to the mixed material, and stirred at a stirring rate of 500-800 rpm for 30-60 minutes to obtain a slurry.

[0030] In the above-mentioned method for preparing geopolymers based on industrial waste, preferably, in step S3, the vibration speed is 100-150 times / min, and the vibration treatment time is 2-5 minutes.

[0031] In the above-mentioned method for preparing geopolymer based on industrial waste, preferably, in step S4, the preform is placed at room temperature for curing for 5-7 days.

[0032] In the above-mentioned method for preparing geopolymer based on industrial waste, preferably, in step S4, the temperature of the curing treatment is 60-80° C., and the curing treatment time is 20-22 days.

[0033] (3) Beneficial effects

[0034] The present invention uses any two of fly ash, red mud, and kaolin as silicon-aluminum source precursors, and undergoes a geopolymerization reaction in an alkaline-activated solution system, forming a three-dimensional network structure with excellent chemical stability and mechanical properties. Zirconium silicate and zirconium phosphate are introduced as functional acid-resistant fillers. These zirconium silicate and zirconium phosphate can form a stable, physically inert barrier within the matrix, effectively blocking the penetration path of acidic media, thereby significantly improving the corrosion resistance of the geopolymer in acidic environments.

[0035] The alkali-activated solution of the present invention can activate the active ingredients in the precursor material, causing it to undergo dissolution, reorganization and polymerization reactions under alkaline conditions, thereby forming a new building material with high strength and good stability. The solution also contains sodium borate and sodium fluoride. Sodium borate can form stable BO bonds and enhance the intrinsic acid resistance of the geopolymer network structure. Sodium fluoride can also promote the formation of a denser and more uniform microstructure, further improving the overall corrosion resistance of the material.

[0036] Experimental results show that after the geopolymer of the present invention is immersed in a dilute sulfuric acid solution, its mass loss rate is only 1.7-2.2%, indicating that the geopolymer of the present invention has good acid corrosion resistance and can still maintain structural integrity after long-term exposure to acidic environments, significantly improving its chemical stability and durability as a building material. In addition, the geopolymer bricks of the present invention also have excellent compressive properties, with a compressive strength of more than 20MPa, fully meeting the basic mechanical requirements of building materials. Its water absorption rate is moderate, at 3.7-10%, indicating that the material has good waterproof properties and can effectively prevent structural damage caused by water penetration. At the same time, the geopolymer bricks also exhibit a certain degree of tolerance to high-temperature environments, ensuring their structural integrity and functional stability under extreme conditions. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 Schematic diagram of the process for preparing geopolymers based on industrial waste according to the present invention; Figure 2 The XRD patterns of the geopolymer products prepared in Examples 1-3 are shown. DETAILED DESCRIPTION

[0037] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The present invention provides a geopolymer based on industrial waste. The raw materials for preparing the geopolymer include a precursor material, an alkali-activated solution, zirconium silicate and zirconium phosphate.

[0039] The precursor materials include any two of fly ash, red mud, and kaolin, and the alkaline activation solution includes sodium hydroxide, water glass, sodium borate, sodium fluoride, and water. The solid-to-liquid ratio (w:v) of the precursor materials to the alkaline activation solution is 1:1-2:1, where the solid-to-liquid ratio is a mass-to-volume ratio expressed in g:ml. The zirconium silicate accounts for 2-5% of the precursor material's mass, and the zirconium phosphate accounts for 2-3% of the precursor material's mass.

[0040] The red mud used in this invention is the residue left after alumina extraction from bauxite. Its main components include metal oxides such as iron, aluminum, and titanium, as well as small amounts of silicates. Fly ash is the fine ash discharged from coal-fired power plants. It is mainly composed of silicon (SiO2) and aluminum oxide (Al2O3), and also contains small amounts of elements such as calcium (CaO) and iron.

[0041] The main component of kaolin is aluminum silicate (Al2Si2O5(OH)4), which has a layered structure. It can undergo dissolution and recombination reactions in an alkaline environment to produce products with gelling properties. Alkaline conditions help to destroy the layered structure of kaolin, releasing soluble silicates and aluminates, thereby increasing its reactivity. In an alkaline environment, the layered structure of aluminum silicate in kaolin is destroyed, releasing soluble silicate ions (SiO4 4- ) and aluminate ions (AlO2 - These ions further dissolve in the presence of sodium hydroxide and combine with the silicate ions in the water glass. Active components in fly ash, such as silica and alumina, also dissolve under alkaline conditions and react with these ions to form aluminosilicate compounds with gelling properties. These compounds polymerize to form a stable three-dimensional network structure, imparting high strength and excellent durability to the material.

[0042] The basic raw materials of the present invention are any two of fly ash, red mud and kaolin. Under an alkaline environment (provided by NaOH), the silicates and aluminates in the fly ash, red mud and kaolin can be dissolved and recombined to form complex aluminosilicate structures. These structures are further polymerized in the presence of water glass to form a stable three-dimensional network structure. This polymerization process can not only enhance the integrity and stability of the material, but also improve its mechanical properties, such as compressive strength, wear resistance and chemical corrosion resistance. After activation treatment, the harmful substances in the fly ash, red mud and kaolin are effectively fixed, reducing the impact on the environment. At the same time, by adjusting the formula ratio and process parameters, high-polymer bricks with different performance can be obtained to meet different engineering needs.

[0043] In this invention, sodium hydroxide provides a strongly alkaline environment, promoting the reaction. It dissolves certain minerals, such as silicates and aluminates, making them more reactive with other components. Water glass (Na2SiO3), a silicate source, promotes the formation of a silicon-oxygen (Si-O-Si) bond network under alkaline conditions, helping to improve the material's mechanical strength and durability. It also reacts with active ingredients in red mud and fly ash to produce a product with gelling properties.

[0044] The method for preparing high-polymer bricks provided by this invention uses NaOH and water glass to activate the active ingredients in red mud, kaolin, and fly ash, prompting a chemical reaction between them to form a new building material with high strength and excellent stability. This method is not only environmentally friendly but also cost-effective and highly efficient, demonstrating the huge potential of waste resource utilization.

[0045] Based on the above basic components and principles, the present invention further introduces zirconium silicate and zirconium phosphate as functional acid-resistant fillers. Zirconium silicate and zirconium phosphate can construct a stable physical inert barrier in the matrix, effectively blocking the penetration path of acidic media, thereby significantly improving the corrosion resistance of geopolymers in acidic environments.

[0046] The sodium borate in the alkali-activated solution of the present invention can form a stable BO bond, thereby enhancing the intrinsic acid resistance of the geopolymer network structure; the sodium fluoride can promote the formation of a denser and more uniform microstructure, thereby further improving the overall erosion resistance of the geopolymer.

[0047] Testing has shown that after the geopolymer of the present invention is immersed in a dilute sulfuric acid solution, its mass loss rate is only 1.7-2.2%, indicating that the geopolymer of the present invention has good acid corrosion resistance and can still maintain structural integrity after long-term exposure to an acidic environment, significantly improving its chemical stability and durability as a building material.

[0048] Furthermore, the geopolymer bricks of this invention possess excellent compressive strength, exceeding 20 MPa, fully meeting the basic mechanical requirements of building materials. Their moderate water absorption rate, ranging from 3.7% to 10%, demonstrates excellent waterproofing, effectively preventing structural damage from water penetration. Furthermore, the geopolymer bricks exhibit a high degree of tolerance to high-temperature environments, ensuring their structural integrity and functional stability under extreme conditions.

[0049] Therefore, the geopolymer of the present invention can be widely used in the fields of building materials, engineering structures, etc., and has good market prospects and application value.

[0050] Preferably, when the precursor materials are red mud and fly ash, the mass ratio of red mud and fly ash is (30-40):(70-60); when the precursor materials are kaolin and red mud, the mass ratio of kaolin and red mud is (60-50):(40-50); when the precursor materials are fly ash and kaolin, the mass ratio of fly ash and kaolin is (60-50):(40-50).

[0051] Preferably, in the alkali excitation solution, the concentration of sodium hydroxide is 5-7.5 mol / L, the concentration of water glass is 0.45-1.31 mol / L, the addition amount of sodium borate is 1-5% of the mass of sodium hydroxide, and the addition amount of sodium fluoride is 0.5-3% of the mass of sodium hydroxide.

[0052] Extensive experimental research has found that when the sodium hydroxide concentration is higher than 7.5 mol / L and the water glass solution is higher than 1.31 mol / L, the reaction is very violent, easily forming a porous structure, resulting in a decrease in the strength of the geopolymer, rapid evaporation of water, and cracks that affect the product's appearance and durability. Unreacted alkali easily seeps out, polluting the environment and endangering the health of users. When the sodium hydroxide concentration is lower than 5 mol / L and the water glass solution is lower than 0.45 mol / L, the reaction speed is too slow, the Si-O and Al-O bonds in the raw materials cannot be fully broken, the dissolution rate is reduced, the polymerization reaction is incomplete, and the setting time is increased, making geopolymer bricks more difficult to form.

[0053] like Figure 1 As shown, the present invention also provides a method for preparing the above-mentioned industrial waste-based geopolymer, comprising the following steps:

[0054] S1: uniformly mixing the precursor material, zirconium silicate and zirconium phosphate to obtain a mixed material.

[0055] S2: adding the alkali excitation solution to the mixed material and mixing them evenly to obtain a slurry.

[0056] S3: The slurry is injected into the mold and vibrated to obtain a preform.

[0057] S4: The rough blank is cured and then solidified, and the geopolymer is obtained after demoulding.

[0058] Preferably, in the above step S1, the particle size of the precursor material, zirconium silicate and zirconium phosphate is 450-550 mesh.

[0059] The fly ash used in the present invention is fly ash from thermal power plants, with a particle size of less than 100 μm; the red mud is red mud produced during bauxite smelting, with a particle size of less than 150 μm; and the kaolin is crushed kaolin ore, with a particle size of less than 200 μm. These raw materials can be ground in a grinder and then sieved through a 450-550 mesh sieve to obtain a precursor material.

[0060] Preferably, in the above step S2, the preparation method of the alkaline excitation solution is as follows:

[0061] Sodium borate and sodium fluoride are added to a sodium hydroxide solution with a concentration of 8-12 mol / L, mixed evenly, and then mixed with a water glass solution with a concentration of 1.2-3.5 mol / L. After standing for 24 hours, an alkali-activated solution is obtained, wherein the volume ratio of the sodium hydroxide solution to the water glass solution is 5:3.

[0062] Further preferably, in step S2, the alkali excitation solution is added to the mixed material, and stirred at a stirring rate of 500-800 rpm for 30-60 min to obtain a slurry.

[0063] Preferably, in the above step S3, the vibration speed is 100-150 times / min, the vibration treatment time is 2-5 minutes, and the purpose of the vibration treatment is to remove surface bubbles.

[0064] Preferably, in the above step S4, the preform is placed at room temperature for curing for 5-7 days, the curing temperature is 60-80° C., and the curing time is 20-22 days.

[0065] In order to further clarify the solution of the present invention and its technical advancement, the following description is made in conjunction with specific embodiments and technical effects.

[0066] Example 1

[0067] This embodiment provides a method for preparing geopolymers based on industrial waste, comprising the following steps:

[0068] S1: Grind the precursor material, zirconium silicate, and zirconium phosphate in a grinder, pass through a 500-mesh sieve, and mix them evenly to obtain a mixed material. The precursor material includes fly ash and red mud in a mass ratio of 70:30, with zirconium silicate accounting for 3% of the precursor material by mass and zirconium phosphate accounting for 2.5% of the precursor material by mass.

[0069] S2: Sodium borate and sodium fluoride are added to a sodium hydroxide solution with a concentration of 10 mol / L, and after mixing evenly, the mixture is continued to be mixed with a water glass solution with a concentration of 3.5 mol / L. After standing for 24 hours, an alkali-excited solution is obtained, and the volume ratio of the sodium hydroxide solution to the water glass solution is 5:3. In the alkali-excited solution of this embodiment, the concentration of sodium hydroxide is 6.25 mol / L, the concentration of water glass is 1.31 mol / L, the amount of sodium borate added is 3% of the mass of sodium hydroxide, and the amount of sodium fluoride added is 1.5% of the mass of sodium hydroxide. After the alkali-excited solution is prepared, the alkali-excited solution is added to the mixed material, the solid-liquid ratio w:v of the precursor material and the alkali-excited solution is 3 g:2 mL, and the mixture is stirred at a stirring rate of 600 rpm for 40 minutes to obtain a slurry.

[0070] S3: The slurry is injected into the mold, and then placed on a vibration table at a vibration speed of 120 times / min for 3 minutes to obtain a preform.

[0071] S4: The preform is placed at room temperature for curing for 7 days, then placed in an oven and cured at 70°C for 22 days, and demoulded to obtain the geopolymer.

[0072] After curing, the compressive and flexural strengths of the geopolymer prepared in each example and comparative example (denoted as R1) were tested according to the national standard GB / T4111-2013. The compressive strength of R1 was 24.7 MPa, which meets the requirements for standard building bricks.

[0073] The mineral composition of geopolymers was analyzed by XRD and their crystal phases were detected to obtain Figure 2 ,XRD analysis showed that the main mineral phase in R1 was aluminosilicate minerals.

[0074] Acid Resistance Test: Weigh R1 and record its exact mass. Immerse it in a 10% sulfuric acid solution and allow it to stand for 48 hours. Remove R1 from the solution, place it in an oven, and dry it at 70°C for 7 days. Weigh R1 again and calculate its mass loss. The calculated mass loss is 1.7%. See Table 1.

[0075] Water absorption test: Weigh R1 and record its exact mass. Soak it in deionized water and let it stand for 7 days before taking it out. Remove the surface moisture and accurately weigh R1. The calculated mass change rate (i.e., water absorption rate) of R1 is 8.3%.

[0076] Physiological saline test: Weigh R1 and record its exact mass. Immerse it in 0.9% physiological saline. After standing for 7 days, take it out, remove the surface liquid, accurately weigh the mass, and calculate the mass change rate. The mass growth rate is 10.0%.

[0077] High-temperature mass-volume change test: R1 was placed in an oven at 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, and 1000°C. The temperature was adjusted from low to high for 2 hours. The R1 was then removed and the mass change ratio was calculated. The results are shown in Table 2.

[0078] Example 2

[0079] This embodiment provides a method for preparing geopolymers based on industrial waste, comprising the following steps:

[0080] S1: Grind the precursor material, zirconium silicate, and zirconium phosphate using a grinder, pass through a 450-mesh sieve, and mix them evenly to obtain a mixed material. The precursor material includes fly ash and kaolin in a mass ratio of 60:40, with zirconium silicate accounting for 2% of the precursor material by mass and zirconium phosphate accounting for 2% of the precursor material by mass.

[0081] S2: Sodium borate and sodium fluoride are added to a sodium hydroxide solution with a concentration of 8 mol / L, and after mixing evenly, the mixture is continued to be mixed with a water glass solution with a concentration of 1.2 mol / L. After standing for 24 hours, an alkali-excited solution is obtained, and the volume ratio of the sodium hydroxide solution to the water glass solution is 5:3. In the alkali-excited solution of this embodiment, the concentration of sodium hydroxide is 5 mol / L, the concentration of water glass is 0.45 mol / L, the amount of sodium borate added is 5% of the mass of sodium hydroxide, and the amount of sodium fluoride added is 3% of the mass of sodium hydroxide. After the alkali-excited solution is prepared, the alkali-excited solution is added to the mixed material, the solid-liquid ratio w:v of the precursor material and the alkali-excited solution is 1 g:1 mL, and the mixture is stirred at a stirring rate of 500 rpm for 60 minutes to obtain a slurry.

[0082] S3: The slurry is injected into the mold, and then placed on a vibration table at a vibration speed of 100 times / min and processed for 5 minutes to obtain a preform.

[0083] S4: The preform is placed at room temperature for curing for 5 days, then placed in an oven and cured at 60° C. for 20 days, and demoulded to obtain the geopolymer.

[0084] The compressive strength and flexural strength of the geopolymer prepared in this example (denoted as R2) were tested according to the national standard GB / T 4111-2013. The compressive strength of R2 was 22.9 MPa, which meets the requirements of standard building bricks.

[0085] The mineral composition of geopolymers was analyzed by XRD and their crystal phases were detected to obtain Figure 2 ,XRD analysis showed that the main mineral phase in R2 was aluminosilicate minerals.

[0086] Acid resistance test: Weigh R2 and record its exact mass. Immerse it in a 10% sulfuric acid solution and let it sit for 48 hours. Remove R2 from the solution, place it in an oven, and dry it at 70°C for 7 days. Weigh R2 again and calculate its mass loss. The calculated mass loss is 2.5%. See Table 1.

[0087] Water absorption test: Weigh R2 and record its exact mass. Soak it in deionized water and let it stand for 7 days before taking it out. Remove the surface moisture and accurately weigh R2. The calculated mass change rate (i.e., water absorption rate) of R2 is 6.4%.

[0088] Physiological saline test: Weigh R2 and record its exact mass. Soak it in 0.9% physiological saline. After standing for 7 days, take it out, remove the surface liquid, accurately weigh the mass, and calculate the mass change rate. The mass growth rate is 3.9%.

[0089] High-temperature mass-volume change test: R2 was placed in an oven at 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, and 1000°C. The temperature was adjusted from low to high for 2 hours at each temperature. The R2 was then removed and the mass change ratio was calculated. The results are shown in Table 3.

[0090] Example 3

[0091] This embodiment provides a method for preparing geopolymers based on industrial waste, comprising the following steps:

[0092] S1: Grind the precursor material, zirconium silicate, and zirconium phosphate in a grinder, pass through a 550-mesh sieve, and mix them evenly to obtain a mixed material. The precursor material includes red mud and kaolin in a mass ratio of 40:60, with zirconium silicate accounting for 5% of the precursor material by mass and zirconium phosphate accounting for 3% of the precursor material by mass.

[0093] S2: Sodium borate and sodium fluoride are added to a sodium hydroxide solution with a concentration of 12 mol / L, and after mixing evenly, the mixture is continued to be mixed with a water glass solution with a concentration of 2 mol / L. After standing for 24 hours, an alkali-excited solution is obtained, and the volume ratio of the sodium hydroxide solution to the water glass solution is 5:3. In the alkali-excited solution of this embodiment, the concentration of sodium hydroxide is 7.5 mol / L, the concentration of water glass is 0.75 mol / L, the amount of sodium borate added is 1% of the mass of sodium hydroxide, and the amount of sodium fluoride added is 0.5% of the mass of sodium hydroxide. After the alkali-excited solution is prepared, the alkali-excited solution is added to the mixed material, the solid-liquid ratio w:v of the precursor material and the alkali-excited solution is 2 g:1 mL, and the mixture is stirred at a stirring rate of 800 rpm for 30 min to obtain a slurry.

[0094] S3: The slurry is injected into the mold, and then placed on a vibration table at a vibration speed of 150 times / min and processed for 2 minutes to obtain a preform.

[0095] S4: The preform is placed at room temperature for curing for 6 days, then placed in an oven and cured at 80°C for 21 days, and demoulded to obtain the geopolymer.

[0096] The compressive strength and flexural strength of the geopolymer prepared in this example (denoted as R3) were tested according to the national standard GB / T 4111-2013. The compressive strength of R3 was 21.4 MPa, which meets the requirements of standard building bricks.

[0097] The mineral composition of geopolymers was analyzed by XRD and their crystal phases were detected to obtain Figure 2 ,XRD analysis showed that the main mineral phase in R3 was aluminosilicate minerals. Figure 2 XRD analysis of R1-R3 revealed broad, asymmetric peaks between 25° and 45°, indicating that the geopolymer bricks contain a certain amount of amorphous material, including amorphous silicon and bauxite. The narrower peaks indicate that the geopolymer bricks contain crystalline phases, including calcium sulfate and calcium sulfate dihydrate. Silicon exists in both crystalline and amorphous phases within the geopolymers. All three geopolymers exhibit sharp peaks at 26.77°, 33.64°, 35.62°, and 41.1°, which can be attributed to the characteristic peaks of the geopolymers.

[0098] Acid resistance test: Weigh R3 and record its exact mass. Immerse it in a 10% sulfuric acid solution and let it sit for 48 hours. Remove R3 from the solution, place it in an oven, and dry it at 70°C for 7 days. Weigh R3 again and calculate its mass loss. The calculated mass loss of R3 is 2.2%. See Table 1.

[0099] Water absorption test: Weigh R3 and record its exact mass. Soak it in deionized water and let it stand for 7 days before taking it out. Remove the surface moisture and accurately weigh R3. The calculated mass change rate (i.e., water absorption rate) of R3 is 8.2%.

[0100] Physiological saline test: Weigh R3 and record its exact mass. Soak it in 0.9% physiological saline and let it stand for 7 days. Then take it out and remove the surface liquid. Then accurately weigh the mass and calculate the mass change rate. The mass growth rate is 8.8%.

[0101] High-temperature mass-volume change test: R3 was placed in an oven at 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, and 1000°C. The temperature was adjusted from low to high for 2 hours. The R3 was then removed and the mass change ratio was calculated. Its high-temperature tolerance was similar to that of Example 1.

[0102] Table 1 Acid resistance test results of geopolymers of Examples 1-3

[0103]

[0104]

[0105] Table 2 Mass changes of geopolymers in Example 1 under high temperature conditions

[0106]

[0107] Table 3 Mass changes of geopolymers under high temperature conditions in Example 2

[0108]

[0109] At temperatures between 200 and 300°C, the mass loss of the geopolymer may be due to water volatilization. At temperatures between 300 and 400°C, the mass loss may be due to the hydroxylation of magnetite. At temperatures between 400 and 500°C, the mass loss of the geopolymer may be due to the conversion of calcium hydroxide to calcium carbonate. At temperatures between 500 and 600°C, the mass loss of the geopolymer may be due to the degradation of bauxite. Above 700°C, the mass change rate decreases significantly, likely due to the mass loss caused by the degradation of organic compounds. However, the geopolymer bricks of Examples 1 and 2 maintained their structural integrity throughout the high-temperature stability testing.

[0110] Example 4

[0111] This embodiment provides a method for preparing geopolymers based on industrial waste. The difference from Example 1 is that in the precursor material, the mass ratio of fly ash to red mud is 60:40.

[0112] The properties of the geopolymer prepared in this example (denoted as R4) were tested using the same testing methods as in Example 1. The results showed that R4 had a compressive strength of 23.3 MPa, meeting the requirements for standard building bricks. The primary mineral phase in R4 was aluminosilicate minerals. After immersion in the same sulfuric acid solution for the same period of time, R4 experienced a mass loss of 1.9%, a water absorption of 7.4%, and a mass gain of 7.7% after immersion in saline.

[0113] Example 5

[0114] This embodiment provides a method for preparing geopolymers based on industrial waste. The difference from Example 1 is that in the precursor material, the mass ratio of fly ash to red mud is 65:35.

[0115] The properties of the geopolymer prepared in this example (denoted as R5) were tested using the same testing methods as in Example 1. The results showed that R5 had a compressive strength of 20.9 MPa, meeting the requirements for standard building bricks. The primary mineral phase in R5 was aluminosilicate minerals. After immersion in the same sulfuric acid solution for the same period of time, R5 experienced a mass loss of 2.3%, a water absorption of 5.6%, and a mass gain of 6.7% after immersion in saline.

[0116] Example 6

[0117] This embodiment provides a method for preparing geopolymers based on industrial waste. The difference from Example 2 is that in the precursor material, the mass ratio of fly ash to kaolin is 50:50.

[0118] The properties of the geopolymer prepared in this example (denoted as R6) were tested using the same testing methods as in Example 1. The results showed that R6 had a compressive strength of 24.2 MPa, meeting the requirements for standard building bricks. The primary mineral phase in R6 was aluminosilicate minerals. After immersion in the same sulfuric acid solution for the same period of time, R6 experienced a mass loss of 2.1%, a water absorption of 5.8%, and a mass gain of 6.9% after immersion in saline.

[0119] Example 7

[0120] This embodiment provides a method for preparing geopolymers based on industrial waste. The difference from Example 2 is that in the precursor material, the mass ratio of fly ash to kaolin is 55:45.

[0121] The properties of the geopolymer prepared in this example (denoted as R7) were tested using the same testing methods as in Example 1. The results showed that R7 had a compressive strength of 25.1 MPa, meeting the requirements for standard building bricks. The primary mineral phase in R7 was aluminosilicate minerals. After immersion in the same sulfuric acid solution for the same period of time, R7 experienced a mass loss of 2.4%, a water absorption of 8.1%, and a mass gain of 9.0% after immersion in saline.

[0122] Example 8

[0123] This embodiment provides a method for preparing geopolymers based on industrial waste. The difference from Example 3 is that in the precursor material, the mass ratio of red mud to kaolin is 50:50.

[0124] The properties of the geopolymer prepared in this example (denoted as R8) were tested using the same testing methods as in Example 1. The results showed that R8 had a compressive strength of 24.4 MPa, meeting the requirements for standard building bricks. The primary mineral phase in R8 was aluminosilicate minerals. After immersion in the same sulfuric acid solution for the same period of time, R8 experienced a mass loss of 2.0%, a water absorption of 6.3%, and a mass gain of 7.2% after immersion in saline.

[0125] Example 9

[0126] This embodiment provides a method for preparing geopolymers based on industrial waste. The difference from Example 3 is that in the precursor material, the mass ratio of red mud to kaolin is 45:55.

[0127] The properties of the geopolymer prepared in this example (denoted as R9) were tested using the same testing methods as in Example 1. The results showed that R9 had a compressive strength of 21.8 MPa, meeting the requirements for standard building bricks. The primary mineral phase in R9 was aluminosilicate minerals. After immersion in the same sulfuric acid solution for the same time, R9 experienced a mass loss of 2.2%, a water absorption of 7.8%, and an 8.3% mass gain after immersion in saline.

[0128] In addition, the tolerance of the geopolymers prepared in Examples 4-9 under high temperature environment is substantially the same as that of Examples 1-3.

[0129] Comparative Example 1

[0130] This comparative example provides a method for preparing a geopolymer based on industrial waste. The method differs from Example 1 in that the mass ratio of fly ash to red mud is 30:70. The finished geopolymer produced in Comparative Example 1, designated D1, exhibited a compressive strength of only 8.6 MPa, significantly lower than R1's 24.7 MPa. Its water absorption rate of 12.5% ​​was significantly higher than R1's 8.3%. These results indicate that the excessively high red mud content results in a loose geopolymer structure and reduced performance.

[0131] Comparative Example 2

[0132] This comparative example provides a method for preparing a geopolymer based on industrial waste. Unlike Example 1, the red mud was not ground, resulting in a particle size of approximately 150 μm. The finished geopolymer produced in Comparative Example 2, designated D2, exhibited a compressive strength of only 3.1 MPa, significantly lower than the 24.7 MPa of R1. Furthermore, cracks were observed, demonstrating that the red mud particle size improves the geopolymer's formability and mechanical properties.

[0133] Comparative Example 3

[0134] This comparative example provides a method for preparing a geopolymer based on industrial waste. Unlike Example 1, zirconium phosphate and zirconium silicate were not added. The finished geopolymer produced in Comparative Example 3, designated D3, exhibited a compressive strength of 15.1 MPa. After immersion in the same sulfuric acid solution for the same period of time, D3 exhibited a mass loss of 9.7%. Its water absorption rate was 16.4%, significantly lowering its resistance to high-temperature environments compared to Example 1.

[0135] Comparative Example 4

[0136] This comparative example provides a method for preparing a geopolymer based on industrial waste. Unlike Example 1, no sodium fluoride or sodium borate was added. The finished geopolymer produced in Comparative Example 4, designated D4, exhibited a compressive strength of 13.6 MPa. After immersion in the same sulfuric acid solution for the same period of time, the mass loss was 7.8%. D3's water absorption was 14.8%, significantly lowering its resistance to high-temperature environments compared to Example 1.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A geopolymer based on industrial waste, characterized in that The raw materials for preparing the geopolymer include precursor materials, alkali-activated solution, zirconium silicate and zirconium phosphate; The precursor materials include any two of fly ash, red mud and kaolin; The alkaline excitation solution comprises sodium hydroxide, water glass, sodium borate, sodium fluoride and water; The solid-liquid ratio w:v of the precursor material and the alkaline excited solution is 1:1-2:1; Zirconium silicate accounts for 2-5% of the mass of the precursor material, and zirconium phosphate accounts for 2-3% of the mass of the precursor material.

2. The industrial waste-based geopolymer according to claim 1, characterized in that When the precursor materials are red mud and fly ash, the mass ratio of red mud to fly ash is (30-40):(70-60); When the current drive materials are kaolin and red mud, the mass ratio of kaolin to red mud is (60-50):(40-50); When the current driving material is fly ash and kaolin, the mass ratio of fly ash to kaolin is (60-50):(40-50).

3. The industrial waste-based geopolymer according to claim 1, characterized in that In the alkali excitation solution, the concentration of sodium hydroxide is 5-7.5 mol / L, the concentration of water glass is 0.45-1.31 mol / L, the added amount of sodium borate is 1-5% of the mass of the sodium hydroxide, and the added amount of sodium fluoride is 0.5-3% of the mass of the sodium hydroxide.

4. A method for preparing geopolymers based on industrial waste according to any one of claims 1 to 3, characterized in that: The steps include: S1: uniformly mixing the precursor material, zirconium silicate and zirconium phosphate to obtain a mixed material; S2: adding the alkali-activated solution to the mixed material and mixing them uniformly to obtain a slurry; S3: injecting the slurry into the mold and vibrating it to obtain a preform; S4: The rough blank is cured and then solidified, and the geopolymer is obtained after demoulding.

5. The method for preparing geopolymers based on industrial waste according to claim 4, characterized in that In step S1 , the particle sizes of the precursor material, zirconium silicate and zirconium phosphate are 450-550 meshes.

6. The method for preparing geopolymers based on industrial waste according to claim 4, characterized in that In step S2, the preparation method of the alkaline excitation solution is as follows: Sodium borate and sodium fluoride are added to a sodium hydroxide solution having a concentration of 8-12 mol / L, mixed evenly, and then mixed with a water glass solution having a concentration of 1.2-3.5 mol / L, and allowed to stand to obtain an alkali-activated solution; The volume ratio of sodium hydroxide solution to water glass solution is 5:

3.

7. The method for preparing geopolymers based on industrial waste according to claim 4, characterized in that In step S2, the alkaline excitation solution is added to the mixed material, and stirred at a stirring rate of 500-800 rpm for 30-60 minutes to obtain a slurry.

8. The method for preparing geopolymers based on industrial waste according to claim 4, characterized in that In step S3, the vibration speed is 100-150 times / min, and the vibration treatment time is 2-5 minutes.

9. The method for preparing geopolymers based on industrial waste according to claim 4, characterized in that In step S4, the preform is placed at room temperature for curing for 5-7 days.

10. The method for preparing geopolymers based on industrial waste according to claim 4, characterized in that In step S4, the curing temperature is 60-80° C., and the curing time is 20-22 days.

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