Porous microcrystalline glass based on composite tailings and preparation method thereof

Abstract

The invention discloses porous microcrystalline glass based on composite tailings and a preparation method thereof, and relates to the technical field of industrial solid waste resource utilization, the preparation method comprises the following steps: weighing stone coal vanadium extraction tailings, quartz sand tailings, rutile tailings, aluminum ash and tunnel waste slag in a predetermined amount, and carrying out heating, heat preservation and water quenching to obtain glass particles; drying and grinding to obtain basic glass powder; adding a composite pore-forming agent, a fluxing agent and a nucleating agent into the basic glass powder, and mixing by adopting a magnetic field-assisted mixing technology to obtain a uniform mixture; putting the mixture into a mold, and carrying out dry pressing molding to obtain a biscuit; and heating the biscuit to a target temperature by stages, and preserving heat for a preset time to form the porous microcrystalline glass. According to the invention, the porous glass ceramic is prepared by taking the composite tailings as the main raw material, so that synergistic resource utilization of various solid wastes is realized, and the problems of land occupation, environmental pollution and potential safety hazards caused by tailings stockpiling are effectively relieved.

Description

Technical Field

[0001] This invention belongs to the field of industrial solid waste resource utilization technology, specifically relating to a porous microcrystalline glass based on composite tailings and its preparation method. Background Technology

[0002] my country is rich in mineral resources, but the ore composition is complex, resulting in large tailings accumulations after mining. These tailings not only encroach on land resources but also pollute the ecological environment. Tailings are mainly composed of metal oxides such as silicon dioxide, iron oxide, aluminum oxide, and potassium oxide, and can be comprehensively utilized based on their different characteristics. Therefore, seeking ways to utilize tailings resources and increase their added value has become a current research hotspot in tailings pollution control.

[0003] Porous microcrystalline glass is a novel functional material composed of three parts: a glass phase, crystals, and pores. The crystals are distributed within a porous glass matrix, forming an interwoven structure of glass and crystals. Therefore, porous microcrystalline glass has advantages such as being lighter than regular microcrystalline glass and having higher compressive strength than foamed glass. It also possesses excellent properties such as low density, high strength, low thermal conductivity, and strong chemical stability, making it widely used in chemical, thermal insulation, and building materials industries. Utilizing composite tailings to prepare porous microcrystalline glass transforms waste into valuable resources, reflecting the commitment to building an environmentally friendly society.

[0004] Existing technologies have proposed some methods for preparing porous microcrystalline glass using composite tailings, but the existing methods have the following problems: (1) Strong dependence on raw materials. Existing technologies mostly rely on single tailings (such as iron tailings or molybdenum tailings) as the main raw materials, and a large amount of clay (15-25%) or chemical raw materials (such as analytical grade CaO / Al2O3) need to be added to adjust the composition, which violates the principle of full utilization of solid waste. (2) Traditional sintering methods (such as one-step / two-step methods) are difficult to optimize performance. When the porosity is high (20-35%), the compressive strength is only 15-25MPa, and there is a situation of strength-porosity inversion, which cannot meet the needs of building materials; the melting temperature generally needs to be 1300-1450℃, which consumes a lot of energy, and the two-step method requires nucleation / crystallization in stages, which is complicated. (3) Existing technologies mostly use expensive nucleating agents such as analytical grade TiO2 or AlN, with raw material costs accounting for more than 30%; the pore structure control is insufficient, the pore size distribution of the self-propagating method is uneven (17-60μm), and CaCO3 as a single pore-forming agent can easily lead to an excessively high pore closure rate (>80%), affecting the filtration or sound absorption function. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a porous microcrystalline glass based on composite tailings and its preparation method. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a method for preparing porous microcrystalline glass based on composite tailings, comprising: S1: Weigh out a predetermined amount of vanadium extraction tailings from coal shale, quartz sand tailings, rutile tailings, aluminum ash and tunnel waste, heat and keep warm and quench in water to obtain glass particles, dry and grind to obtain basic glass powder. S2: A composite pore-forming agent, flux, and nucleating agent are added to the base glass powder, and the mixture is mixed using magnetic field-assisted mixing technology to obtain a homogeneous mixture; S3: The mixture is placed in a mold and dry-pressed to obtain a raw blank; S4: The green blank is heated to the target temperature in stages and held at that temperature for a predetermined time to form the porous microcrystalline glass.

[0006] Another aspect of the present invention provides a porous microcrystalline glass based on composite tailings, prepared using the preparation method described in any one of the above embodiments.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention uses composite tailings as the main raw material to achieve the synergistic resource utilization of various solid wastes, significantly reducing the consumption of natural mineral raw materials (such as quartz sand, feldspar, soda ash, etc.), and effectively alleviating the problems of land occupation, environmental pollution (such as heavy metal leaching and dust) and potential safety hazards caused by tailings storage.

[0008] 2. This invention utilizes graded activation treatment (planetary ball milling + low-temperature liquid nitrogen activation) and elemental gradation (five-element synergy of SiO2 / Al2O3 / TiO2 / CaO / MgO) to form a quaternary eutectic of CaO-Al2O3-SiO2-TiO2. This reduces the melting temperature by 120-150℃ and energy consumption by over 40%, effectively improving raw material utilization and the amorphization rate of glass powder, providing a uniform nucleation basis for subsequent crystallization. It also achieves the directional conversion of low-value-added components such as Fe2O3 and TiO2 in tailings (e.g., Fe2O3 reduces crystallization activation energy by 23%), significantly improving the resource utilization rate of tailings.

[0009] 3. This invention employs a three-stage gradient heating + magnetic field-assisted sintering process, which enables the decomposition and exothermic separation of PMMA and CaCO3 during the pore-forming stage, achieving a porosity control precision of ±1.2%. During the crystallization stage, the activation of the borax flux and the synergistic directional growth of anorthite significantly improve the crystalline phase ratio and Vickers hardness of the resulting porous microcrystalline glass. This achieves an ultimate balance between high porosity and compressive strength, breaking through the boundaries of material performance.

[0010] 4. The porous microcrystalline glass prepared by this invention has high porosity, high mechanical strength, good chemical corrosion resistance (especially acid and alkali resistance), excellent thermal stability, and long service life. Furthermore, the pore structure and matrix properties can be flexibly controlled by adjusting the composite tailings ratio, the type / dosage of the pore-forming agent, and the heat treatment regime to meet the specific needs of different application scenarios. This invention transforms industrial solid waste, which was originally of low or even negative value, into high-performance porous functional materials with broad application prospects and high economic value, realizing "turning waste into treasure" and providing an efficient and sustainable technical path for tailings treatment in mining and metallurgical enterprises. This invention successfully transforms tailings into products that meet the performance requirements of these fields, and their value far exceeds that of simple landfilling or low-end utilization (such as road paving).

[0011] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0012] Figure 1 This is a flowchart of a method for preparing porous microcrystalline glass based on composite tailings provided in an embodiment of the present invention. Detailed Implementation

[0013] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a detailed explanation of the porous microcrystalline glass based on composite tailings and its preparation method proposed in accordance with the present invention.

[0014] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0015] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes said element.

[0016] Please see Figure 1 , Figure 1This is a flowchart illustrating a method for preparing porous microcrystalline glass based on composite tailings, provided in an embodiment of the present invention. The preparation method includes: S1: Weigh a predetermined amount of vanadium extraction tailings from coal shale, quartz sand tailings, rutile tailings, aluminum ash, and tunnel waste, heat and keep warm, and then quench in water to obtain glass particles. After drying, grind to obtain basic glass powder.

[0017] Step S1 specifically includes: S1.1: Weigh 40-60 parts by weight of vanadium extraction tailings from coal shale, 3-7 parts by weight of quartz sand tailings, 3-7 parts by weight of rutile tailings, 7-13 parts by weight of aluminum ash, and 27-33 parts by weight of tunnel waste, mix them, and then perform graded activation treatment to obtain mixed raw materials with a particle size of less than 500 mesh.

[0018] In this embodiment, the mass percentage of SiO2 in vanadium extraction tailings from coal shale is 63%-73%; the mass percentage of SiO2 in quartz sand tailings is 91%-97%; the mass percentage of SiO2 in rutile tailings is 47%-53%; the mass percentage of CaO in tunnel waste is 5%-10%; and the mass percentage of Al2O3 in aluminum ash is 60%-80%. In the process of preparing porous microcrystalline glass from composite tailings, the mechanical activation treatment of raw materials induces changes in the physicochemical properties of the raw materials through mechanical forces (such as impact, friction, shearing, and extrusion), thereby optimizing the subsequent vitrification, crystallization processes, and the final product performance.

[0019] Specifically, this embodiment employs a planetary ball mill for a three-stage activation treatment: the first stage is dry grinding, where the mixed composite tailings are ground at 400 rpm for 30 minutes to reduce the particle size to 300 mesh; the second stage is wet grinding, where 0.5 wt% of a dispersant is added, the speed is adjusted to 300 rpm, and the grinding time is 45 minutes to reduce the particle size to 500 mesh. The dispersant is ammonium polyacrylate. Subsequently, the third stage is low-temperature activation, where the mixture is ball-milled for 15 minutes under liquid nitrogen cooling to achieve an activation index ≥0.8 for the mixed raw materials.

[0020] S1.2: The mixed raw materials after graded activation treatment are loaded into a crucible and placed in a muffle furnace. The temperature is raised to 1450-1500℃ in stages and held for 60-120 minutes. Then the crucible is removed and subjected to segmented water quenching to obtain amorphous glass particles.

[0021] Specifically, the mixed raw materials after graded activation are loaded into a crucible and placed in a muffle furnace for staged heating. The staged heating process includes: the first stage, heating to 840-860℃ (glass softening point) at a rate of 45-55℃ / min; the second stage, heating to 1330-1370℃ (viscosity peak point) at a rate of 8-12℃ / min; and the third stage, heating to 1450-1500℃ at a rate of 4-6℃ / min and holding at that temperature for 60min-120min, ultimately forming a CaO-Al2O3-SiO2-TiO2 quaternary eutectic.

[0022] The crucible was then removed and subjected to segmented water quenching. In the first stage, the melt at 1450-1500℃ was cooled to 1150-1250℃ at a rate of 100℃ / s to form β-nepheline crystal nuclei. In the second stage, the melt was cooled to 750-850℃ at a rate of 50℃ / s to induce the precipitation of anorthite crystal phase. In the third stage, the melt was quenched in ice water to obtain amorphous glass particles with an average particle size of about 85μm.

[0023] S1.3: The obtained glass particles are ground into glass powder using a vibratory ball milling combined with airflow pulverization process to form a basic glass powder. The basic glass powder comprises 45%-55% SiO2, 2.5%-3.5% Fe2O3, 20%-26% Al2O3, 1.3%-1.7% K2O, 0.8%-1.2% Na2O, 1.2%-1.8% MgO, 14%-24% CaO, and 0.8%-1.2% TiO2 by mass. Furthermore, this basic glass powder is amorphous.

[0024] In this step, a preliminary grinding process is first carried out using a vibratory ball milling process, specifically using zirconia balls for 20 hours, so that the D50 (median diameter) of the particles is about 15μm. Then, air jet milling is carried out under nitrogen protection and a pressure of 0.8MPa to make the D90 (90% of the particle size) of the particles ≤5μm. Finally, the surface is modified using 3%wt of silane coupling agent KH-570, so that the contact angle of the formed glass powder is reduced to about 38°.

[0025] In this embodiment, the five raw materials—vanadium extraction tailings from coal shale, quartz sand tailings, rutile tailings, aluminum ash, and tunnel waste—are formulated based on the principles of "elemental complementarity" and "functional coupling." Specifically, the vanadium extraction tailings from coal shale serve as the primary silicon-aluminum source, providing 45-55 wt% (wt% represents mass percentage) of SiO2 and 20-26% of aluminum oxide. wt% Al2O3 is used to construct the glass network, and its trace vanadium element can reduce the crystallization activation energy in step S4 below; quartz sand tailings are precisely supplemented with 91-97wt% high-purity SiO2 to maintain network stability; rutile tailings are introduced with 0.8-1.2wt% TiO2, which can be transformed into the rutile crystal phase during sintering in step S4 to improve hardness; aluminum ash provides 60-80wt% highly active Al2O3 to regulate the aluminum-silicon ratio and promote the formation of the mullite crystal phase; tunnel waste provides 14-24wt% CaO in the form of calcareous shale, which can reduce the melting temperature during sintering in step S4 to avoid calcite decomposition defects. This embodiment achieves elemental-level resource utilization of solid waste through the combination of five raw materials, forming a CaO-Al2O3-SiO2-TiO2 quaternary eutectic system, which reduces the melting temperature and energy consumption.

[0026] Aluminum ash accounts for 7-13% of the total weight of the five raw materials, and tunnel waste accounts for 27-33% of the total weight of the five raw materials, so that the molar ratio of Al2O3 / CaO is ≈1.1, ensuring the formation of anorthite (CaAl2Si2O8) rather than brittle wollastonite.

[0027] Preferably, the mass ratio of vanadium extraction tailings from coal shale, quartz sand tailings, rutile tailings, aluminum ash, and tunnel waste is 50:5:5:10:30, which can achieve the ideal composition of 50% SiO2 + 23% Al2O3 + 19% CaO, resulting in porous microcrystalline glass with high compressive strength.

[0028] S2: A composite pore-forming agent, flux, and nucleating agent are added to the base glass powder, and the mixture is mixed using magnetic field-assisted mixing technology to obtain a homogeneous mixture.

[0029] A predetermined amount of composite pore-forming agent, flux, and nucleating agent are added to the base glass powder, and then poured into a mixing tank. A rotating magnetic field of 50 mT is applied in the mixing tank, and the mixture is mixed for 15 min to 35 min to form a homogeneous mixture. In this mixture, the Fe2O3 particles are oriented to form a conductive network, which increases the resistivity of the mixture from 10... 8 Ω·cm decreased to 10 3 Ω·cm.

[0030] In this embodiment, the composite pore-forming agent includes calcium carbonate and polymethyl methacrylate (PMMA), wherein the mass ratio of calcium carbonate to base glass powder is (0.05-0.15):1, and the mass ratio of PMMA to base glass powder is (0.05-0.15):1. The flux includes one or more of anhydrous sodium carbonate or borax, wherein the mass ratio of anhydrous sodium carbonate or borax to base glass powder is (0.01-0.02):1; or the mass ratio of a mixture of anhydrous sodium carbonate and borax to base glass powder is (0.01-0.02):1. The nucleating agent includes one or more of boron oxide, phosphorus pentoxide, or zinc oxide, and the mass ratio of the nucleating agent to base glass powder is (0.01-0.02):1.

[0031] Specifically, the composite pore-forming agent is a combination of calcium carbonate and polymethyl methacrylate (PMMA). Based on the complementary temperature range and synergistic pore structure, calcium carbonate can decompose and release CO2 at 600-800℃, forming a closed-pore structure and contributing CaO to strengthen the pore walls. PMMA completely pyrolyzes at 350-450℃ to produce hydrocarbon gases, constructing through-pore channels. The decomposition temperature ranges of the two do not overlap, avoiding explosive defects caused by concentrated gas release.

[0032] Preferably, the mass ratio of calcium carbonate to base glass powder is 0.1:1, and the mass ratio of PMMA to base glass powder is 0.1:1. By mixing calcium carbonate and PMMA in equal proportions, a bi-level pore structure of "micron-level through pores (PMMA effect) + submicron-level closed pores (CaCO3 effect)" is formed to enhance the compressive strength of the generated porous microcrystalline glass.

[0033] The flux in this embodiment includes anhydrous sodium carbonate (Na₂CO₃) and borax (Na₂B₄O₇). The mass ratio of the mixture of anhydrous sodium carbonate and borax to the base glass powder is (0.01-0.02):1, and the mass ratio of anhydrous sodium carbonate to borax is 2:1. Anhydrous sodium carbonate can provide Na₂CO₃. + Breaking the Si-O-Si network (sodium ions breaking silicon-oxygen bonds) reduces the melt viscosity from 10 during subsequent sintering. 5 Pa·s decreased to 10 3 Pa·s; B2O3 in borax forms a flexible [BO3] structure, which can lower the glass transition temperature. The combination of the two can achieve dual low-temperature activation of network modification (sodium) + structural reconstruction (boron).

[0034] Furthermore, in this embodiment, the mass ratio of the nucleating agent to the base glass powder is (0.01-0.02):1. The nucleating agent comprises boron oxide (B₂O₃), phosphorus pentoxide (P₂O₅), and zinc oxide (ZnO), wherein boron oxide, phosphorus pentoxide, and zinc oxide have approximately the same mass percentage. Among the three nucleating agent raw materials, boron oxide can lower the phase transition energy barrier of the high-silicon system, promoting metastable phase separation nucleation; phosphorus pentoxide can form [PO₄] tetrahedra in a high-calcium environment, serving as a template for apatite crystal nuclei; and zinc oxide can inhibit abnormal grain growth (grain size ≤ 1 μm) at high titanium content. The nucleating agent in this embodiment, through the ternary compounding of the three raw materials, can lower the crystallization initiation temperature and increase the crystallization rate during subsequent sintering, resulting in a crystalline phase ratio of 68% and a Vickers hardness of 1.18 GPa.

[0035] Furthermore, this embodiment employs magnetic field-assisted mixing technology, causing the Fe2O3 particles in the mixture to oriented and form a conductive network. This oriented Fe2O3 conductive network can generate Joule heating under an applied electric field or during sintering, forming an endogenous heat source. This uniform heating can compensate for the defect of rapid heat dissipation at the edges in traditional sintering, reduce the sintering temperature gradient, and avoid local over- or under-sintering. After the resistivity is reduced, the material becomes more sensitive to electromagnetic fields, and the sintering temperature can be adjusted in real time through a closed-loop feedback system, controlling temperature fluctuations within ±5℃ and significantly improving crystallization uniformity.

[0036] S3: The mixture of base glass powder, composite pore-forming agent, flux and nucleating agent is placed in a mold and dry-pressed to obtain a green blank.

[0037] Specifically, the mixture obtained after thorough mixing in step S2 is placed in a mold and dry-pressed under a pressure of 5MPa-10MPa to obtain a green blank. The mold specifications in this embodiment are: 10mm×10mm×50mm.

[0038] S4: The green blank is heated to the target temperature in stages and held at that temperature for a predetermined time to obtain porous microcrystalline glass.

[0039] The green blank obtained in step S3 is placed in a box and heated in a muffle furnace in stages to the target temperature (i.e., the sintering temperature) and held for 60 min-120 min to obtain porous microcrystalline glass. The sintering temperature is 800℃-980℃. The staged heating includes: the first stage: heating from room temperature to 280℃ at a heating rate of 5℃ / min; the second stage: heating from 280℃ to 550℃ at a heating rate of 3℃ / min; the third stage: heating from 550℃ to the target temperature at a heating rate of 2℃ / min. At the same time, a gradient magnetic field of 0.1-1 Tesla and microwave-assisted heating of 2.45 GHz are superimposed in the third stage.

[0040] It should be noted that the purpose of the three-stage heating method (i.e., phased heating) in this embodiment is to match the kinetic requirements of the multi-stage reaction of the material and resolve the temporal conflict between pore formation, pore stabilization, and crystallization. In the actual sintering process, the green blank is placed in a box, which is then placed in a muffle furnace. In the first stage, the temperature in the muffle furnace is raised from room temperature to 280°C at a heating rate of 5°C / min. 280°C is the critical point for the complete decomposition of PMMA; below this temperature, the retention of gaseous products can be avoided. The rapid heating rate of 5°C / min ensures that the zone of intense PMMA decomposition is crossed within 5 minutes, preventing excessive expansion that could cause cracking of the green blank. The purpose of the first stage is to efficiently remove hydrocarbon gases and construct the initial open-pore framework, laying the foundation for subsequent pore formation.

[0041] In the second stage, the temperature in the muffle furnace is increased from 280℃ to 550℃ at a heating rate of 3℃ / min. 280℃ marks the end of organic decomposition, while 550℃ corresponds to the initiation temperature of the glass transition, at which point the glass phase has not yet softened. In this stage, the heating rate is reduced to 3℃ / min to match the CaCO3 decomposition kinetics and prevent the concentrated release of CO2 from breaking through the pore walls. The purpose of the second stage is to control the uniform growth of bubbles while simultaneously releasing the thermal stress from the first stage and eliminating the potential for microcracks.

[0042] In the third stage, the temperature in the muffle furnace was increased from 550℃ to the target temperature at a heating rate of 2℃ / min. Above 500℃, the glass viscosity dropped sharply (10). 12 Pa·s to 10 6 The heating rate of 2℃ / min precisely matches the pore wall shrinkage rate (0.3μm / min) with the crystal nucleation rate (5nm / min). When the temperature rises to 800℃-900℃, the borax flux is activated, and the pore structure is permanently fixed; when the temperature rises to 900℃-980℃, the anorthite main crystal phase grows, and the strength jumps to more than 30MPa. Holding at the target temperature for 70 min-130 min achieves a crystallinity of 60%-70%. Too short a holding time will lead to uneven grains, while too long a holding time will cause pore coarsening. At the same time, in the third stage, a gradient magnetic field of 0.1-1 Tesla and microwave-assisted heating of 2.45 GHz are superimposed. The magnetic field induces the Fe2O3 particles to oriented and form conductive channels, reducing the resistivity to 10² Ω·cm; the microwave selectively heats the glass phase (dielectric loss tangent tanδ=0.3), making the local temperature gradient ΔT≤20℃. This results in preferential grain growth along the magnetic field direction (length-to-diameter ratio ≥10), increased bending strength to 58.3 MPa, reduced porosity uniformity index (Span value) from 1.2 to 0.8, and achieved a through-hole ratio ≥92%.

[0043] This step separates the three conflicting processes of pore formation (first stage), pore stabilization (second stage), and crystallization (third stage), and sets three anchoring temperatures of 280℃ (decomposition endpoint), 550℃ (structural relaxation point), and 980℃ (crystallization peak) according to the intrinsic properties of the material. Finally, it achieves precise control of the multi-scale structure by decreasing the rate of change. This not only makes the performance of tailings-based glass ceramics surpass that of traditional materials, but also provides a reusable process template for industrial scale-up.

[0044] In summary, this embodiment utilizes a pore-forming agent to construct a multi-level porous framework, a flux to optimize the melting behavior of the pore walls, and a nucleating agent to strengthen the crystal support network. When these three components are combined in a critical ratio, the contradictory relationship between compressive strength and porosity can be broken, resulting in a corrosion resistance improvement of over 30%.

[0045] Example 1 This embodiment provides a detailed method for preparing porous microcrystalline glass based on composite tailings, the method comprising: Step 1: Weigh appropriate amounts of vanadium extraction tailings from coal shale, quartz sand tailings, rutile tailings, aluminum ash, and tunnel waste, heat and keep warm, and quench in water to obtain glass particles. After drying, grind to obtain basic glass powder.

[0046] First, weigh 50 parts by weight of vanadium extraction tailings from coal shale, 5 parts by weight of quartz sand tailings, 5 parts by weight of rutile tailings, 10 parts by weight of aluminum ash, and 30 parts by weight of tunnel waste. Mix them and then perform a graded activation treatment to obtain a mixed raw material with a particle size of less than 500 mesh. Next, load the mixed raw material into a mixing tank and mix for 25 minutes until homogeneous. Then, load the homogeneous raw material into a crucible and place it in a muffle furnace, holding it at 1300℃-1400℃ for 60-120 minutes. Preferably, the holding temperature is 1350℃ and the holding time is 90 minutes.

[0047] Next, the crucible is removed and quenched in water to obtain glass particles; the glass particles are ground into powder to form basic glass powder. In this embodiment, the basic glass powder includes 50 wt% SiO2, 3.0 wt% Fe2O3, 23 wt% Al2O3, 1.5 wt% K2O, 1.0 wt% Na2O, 1.5 wt% MgO, 19 wt% CaO, and 1.0 wt% TiO2.

[0048] Step 2: Add composite pore-forming agent, flux and nucleating agent to the base glass powder, and mix using magnetic field-assisted mixing technology to obtain a homogeneous mixture.

[0049] In this embodiment, a predetermined amount of composite pore-forming agent, flux, and nucleating agent are added to the base glass powder, then poured into a mixing tank. A rotating magnetic field of 50 mT is applied in the mixing tank, and the mixture is stirred for 20 minutes to form a homogeneous mixture. The composite pore-forming agent includes calcium carbonate and polymethyl methacrylate, wherein the mass ratio of calcium carbonate to base glass powder is 0.15:1, and the mass ratio of polymethyl methacrylate to base glass powder is 0.05:1. The flux includes anhydrous sodium carbonate and borax, wherein the mass ratio of anhydrous sodium carbonate to base glass powder is 0.0134:1, and the mass ratio of borax to base glass powder is 0.0067:1. The nucleating agent includes boron oxide, phosphorus pentoxide, and zinc oxide, each with a mass ratio of 0.0067:1 to the base glass powder.

[0050] Step 3: Place the mixture into a mold and dry press it to obtain a raw blank.

[0051] Specifically, the mixture of basic glass powder, pore-forming agent, flux and nucleating agent obtained in step 2 is placed into a 10mm×10mm×50mm mold and dry-pressed under a pressing pressure of 10MPa to obtain a green blank.

[0052] Step 4: Heat the green blank to the target temperature in stages and hold it at that temperature for a predetermined time to obtain porous microcrystalline glass.

[0053] Specifically, the green blank is placed in a box and heated in a muffle furnace to 980℃ (sintering temperature) in stages and held for 100 min to obtain porous microcrystalline glass. The staged heating includes: the first stage: heating from room temperature to 280℃ at a heating rate of 5℃ / min; the second stage: heating from 280℃ to 550℃ at a heating rate of 3℃ / min; and the third stage: heating from 550℃ to 980℃ at a heating rate of 2℃ / min. At the same time, a gradient magnetic field of 0.5 Tesla and microwave-assisted heating of 2.45 GHz are superimposed in the third stage.

[0054] Example 2 This embodiment provides a detailed method for preparing porous microcrystalline glass based on composite tailings, the method comprising: Step 1: Weigh 40 parts by weight of vanadium extraction tailings from coal shale, 7 parts by weight of quartz sand tailings, 7 parts by weight of rutile tailings, 13 parts by weight of aluminum ash, and 33 parts by weight of tunnel waste, and grind them separately to below 500 mesh. Then, place the ground components into a mixing tank and mix for 25 minutes until homogeneous. Next, place the homogeneous mixture into a crucible and place it in a muffle furnace, holding it at 1300℃ for 60 minutes. Afterward, remove the crucible and water quench it to obtain glass particles; grind the glass particles into powder to form basic glass powder.

[0055] Step 2: Add composite pore-forming agent, flux and nucleating agent to the base glass powder, and mix using magnetic field-assisted mixing technology to obtain a homogeneous mixture.

[0056] In this embodiment, a predetermined amount of composite pore-forming agent, flux, and nucleating agent are added to the base glass powder, and then poured into a mixing tank. A rotating magnetic field of 50 mT is applied in the mixing tank, and the mixture is mixed for 20 minutes to form a homogeneous mixture. The composite pore-forming agent includes calcium carbonate and polymethyl methacrylate, wherein the mass ratio of calcium carbonate to base glass powder is 0.1:1, and the mass ratio of polymethyl methacrylate to base glass powder is 0.1:1. The flux includes anhydrous sodium carbonate and borax, wherein the mass ratio of anhydrous sodium carbonate to base glass powder is 0.01:1, and the mass ratio of borax to base glass powder is 0.01:1. The nucleating agent includes boron oxide, phosphorus pentoxide, and zinc oxide, wherein the mass ratio of boron oxide to base glass powder is 0.01:1, the mass ratio of phosphorus pentoxide to base glass powder is 0.005:1, and the mass ratio of zinc oxide to base glass powder is 0.005:1.

[0057] Step 3: Place the mixture of basic glass powder, pore-forming agent, flux and nucleating agent obtained in Step 2 into a 10mm×10mm×50mm mold and dry press it under a pressure of 7MPa to obtain a green blank.

[0058] Step 4: Heat the green blank to the target temperature in stages and hold it at that temperature for a predetermined time to obtain porous microcrystalline glass.

[0059] Specifically, the green blank is placed in a box and heated to 980°C in stages in a muffle furnace and held for 100 min to obtain porous microcrystalline glass. The staged heating includes: the first stage: heating from room temperature to 280°C at a heating rate of 5°C / min; the second stage: heating from 280°C to 550°C at a heating rate of 3°C / min; and the third stage: heating from 550°C to 980°C at a heating rate of 2°C / min. At the same time, a gradient magnetic field of 0.5 Tesla and microwave-assisted heating of 2.45 GHz are superimposed in the third stage.

[0060] Example 3 This embodiment provides a detailed method for preparing porous microcrystalline glass based on composite tailings, the method comprising: Step 1: Weigh 60 parts by weight of vanadium extraction tailings from shale coal, 3 parts by weight of quartz sand tailings, 3 parts by weight of rutile tailings, 7 parts by weight of aluminum ash, and 27 parts by weight of tunnel waste, and grind them separately to below 500 mesh. In this embodiment, the mass percentage of SiO2 in the vanadium extraction tailings from shale coal is 63%-73%; the mass percentage of SiO2 in the quartz sand tailings is 91%-97%; the mass percentage of SiO2 in the rutile tailings is 47%-53%; the mass percentage of CaO in the tunnel waste is 5%-10%; and the mass percentage of Al2O3 in the aluminum ash is 60%-80%.

[0061] Subsequently, the ground components are placed into a mixing tank and mixed for 25 minutes until homogeneous. Then, the homogeneous raw materials are placed into a crucible and placed in a muffle furnace and held at 1400℃ for 60 minutes. After that, the crucible is removed and water quenched to obtain glass particles. The glass particles are then ground into powder to form basic glass powder.

[0062] Step 2: Add composite pore-forming agent, flux and nucleating agent to the base glass powder, and mix using magnetic field-assisted mixing technology to obtain a homogeneous mixture.

[0063] In this embodiment, a predetermined amount of composite pore-forming agent, flux, and nucleating agent are added to the base glass powder, and then poured into a mixing tank. A rotating magnetic field of 50 mT is applied in the mixing tank, and the mixture is mixed for 20 minutes to form a homogeneous mixture. The composite pore-forming agent includes calcium carbonate and polymethyl methacrylate, wherein the mass ratio of calcium carbonate to base glass powder is 0.13:1, and the mass ratio of polymethyl methacrylate to base glass powder is 0.07:1. The flux includes anhydrous sodium carbonate and borax, wherein the mass ratio of anhydrous sodium carbonate to base glass powder is 0.0067:1, and the mass ratio of borax to base glass powder is 0.0134:1. The nucleating agent includes boron oxide, phosphorus pentoxide, and zinc oxide, wherein the mass ratio of boron oxide to base glass powder is 0.005:1, the mass ratio of phosphorus pentoxide to base glass powder is 0.005:1, and the mass ratio of zinc oxide to base glass powder is 0.01:1.

[0064] Step 3: Place the mixture of basic glass powder, pore-forming agent, flux and nucleating agent obtained in Step 2 into a 10mm×10mm×50mm mold and dry press it under 8MPa pressure to obtain a green blank.

[0065] Step 4: Heat the green blank to the target temperature in stages and hold it at that temperature for a predetermined time to obtain porous microcrystalline glass.

[0066] Specifically, the green blank is placed in a box and heated to 980°C in a muffle furnace in stages and held for 120 min to obtain porous microcrystalline glass. The staged heating includes: the first stage: heating from room temperature to 280°C at a heating rate of 5°C / min; the second stage: heating from 280°C to 550°C at a heating rate of 3°C / min; and the third stage: heating from 550°C to 980°C at a heating rate of 2°C / min. At the same time, a gradient magnetic field of 0.5 Tesla and microwave-assisted heating of 2.45 GHz are superimposed in the third stage.

[0067] Example 4 This embodiment provides a detailed method for preparing porous microcrystalline glass based on composite tailings, the method comprising: Step 1: Weigh 45 parts by weight of vanadium extraction tailings from coal shale, 5 parts by weight of quartz sand tailings, 5 parts by weight of rutile tailings, 15 parts by weight of aluminum ash, and 30 parts by weight of tunnel waste, and grind them to below 500 mesh.

[0068] The ground components were placed in a mixing tank and mixed for 25 minutes until homogeneous. Then, the homogeneous raw material was placed in a crucible and placed in a muffle furnace, where it was held at 1300℃ for 60 minutes. Subsequently, the crucible was removed and water-quenched to obtain glass particles. The glass particles were then ground into powder to form basic glass powder.

[0069] Step 2: Add composite pore-forming agent, flux and nucleating agent to the base glass powder, and mix using magnetic field-assisted mixing technology to obtain a homogeneous mixture.

[0070] In this embodiment, a predetermined amount of composite pore-forming agent, flux, and nucleating agent are added to the base glass powder, and then poured into a mixing tank. A rotating magnetic field of 50 mT is applied in the mixing tank, and the mixture is mixed for 20 minutes to form a homogeneous mixture. The composite pore-forming agent includes calcium carbonate and polymethyl methacrylate, wherein the mass ratio of calcium carbonate to base glass powder is 0.05:1, and the mass ratio of polymethyl methacrylate to base glass powder is 0.15:1. The flux includes anhydrous sodium carbonate and borax, wherein the mass ratio of anhydrous sodium carbonate to base glass powder is 0.005:1, and the mass ratio of borax to base glass powder is 0.015:1. The nucleating agent includes boron oxide, phosphorus pentoxide, and zinc oxide, wherein the mass ratio of boron oxide to base glass powder is 0.005:1, the mass ratio of phosphorus pentoxide to base glass powder is 0.01:1, and the mass ratio of zinc oxide to base glass powder is 0.005:1.

[0071] Step 3: Place the mixture of base glass powder, pore-forming agent, flux and nucleating agent obtained in Step 2 into a 10mm×10mm×50mm mold and dry press it under a pressure of 5MPa to obtain a green blank.

[0072] Step 4: Heat the green blank to the target temperature in stages and hold it at that temperature for a predetermined time to obtain porous microcrystalline glass.

[0073] Specifically, the green blank is placed in a box and heated to 980°C in a muffle furnace in stages and held for 120 min to obtain porous microcrystalline glass. The staged heating includes: the first stage: heating from room temperature to 280°C at a heating rate of 5°C / min; the second stage: heating from 280°C to 550°C at a heating rate of 3°C / min; and the third stage: heating from 550°C to 980°C at a heating rate of 2°C / min. At the same time, a gradient magnetic field of 0.5 Tesla and microwave-assisted heating of 2.45 GHz are superimposed in the third stage.

[0074] The following tests were conducted on various properties of the porous microcrystalline glass obtained using the methods of Examples 1 to 4, and the results are shown in Table 1.

[0075] Table 1. Performance Comparison of Various Embodiments

[0076] As can be seen from Table 1, Example 1 maintained the highest compressive strength (36.2 MPa) and the lowest density (2.0 g / cm³) despite having the highest porosity (23.2%). 3 This demonstrates that the formulation achieves a combination of lightweight and high strength through optimized tailings composition and sintering process. This characteristic has significant advantages in building insulation materials or aerospace applications. The porosity (19.3%) of Example 4 is similar to that of Examples 2 and 3, but the compressive strength (23.3 MPa) is significantly lower, possibly due to uneven distribution of the pore-forming agent or defects in the crystal structure (such as broken pore edges or excessive glass phase), highlighting the process stability of Examples 1 to 3.

[0077] All examples exhibited acid / alkali resistance mass loss rates below 0.21%, especially Example 1 (0.14% acid resistance, 0.16% alkali resistance), demonstrating excellent chemical stability of the material in acidic or alkaline environments. This property is suitable for thermal insulation components in chemical filtration or corrosive environments. Example 4 had the highest density (2.3 g / cm³). 3 However, its corrosion resistance is relatively poor, which may be related to the low closed-pore ratio or uneven distribution of crystalline phases (such as wollastonite). This further verifies the effect of low-density, high-closed-pore structure on improving corrosion resistance. The hardness of Examples 1 to 4 (1.18 GPa → 1.03 GPa) decreases with decreasing density, which is consistent with the law of mechanical properties of porous materials in the Gibson-Ashby model (hardness is proportional to the square root of relative density). However, Example 1 still maintains high hardness at low density, indicating that its microstructure (such as pore wall crystallinity or crystalline phase content) is superior.

[0078] This invention achieves an optimal match between porosity and strength through the component design of composite tailings, outperforming traditional porous glass (typically with compressive strength <20MPa and density >2.5g / cm³). 3 High corrosion resistance: The low mass loss rate indicates that a stable silicate network is formed on the material surface, which can resist acid and alkali corrosion, superior to ordinary microcrystalline glass (acid loss rate is usually >0.3%). High process stability: The performance fluctuations of Examples 1 to 3 are small, indicating that the formulation and sintering process (such as the two-step foaming method) are highly controllable and suitable for industrial production.

[0079] In summary, this invention uses composite tailings as the main raw material to achieve the synergistic resource utilization of multiple solid wastes, significantly reducing the consumption of natural mineral raw materials (such as quartz sand, feldspar, and soda ash), and effectively alleviating the land occupation, environmental pollution (such as heavy metal leaching and dust), and potential safety hazards caused by tailings storage. This invention, through graded activation treatment (planetary ball milling + low-temperature liquid nitrogen activation) and elemental gradation (five-element synergy of SiO2 / Al2O3 / TiO2 / CaO / MgO), forms a quaternary eutectic of CaO-Al2O3-SiO2-TiO2, reducing the melting temperature by 120-150℃ and energy consumption by more than 40%. This effectively improves the raw material utilization rate and the amorphization rate of glass powder, providing a uniform nucleation basis for subsequent crystallization. It also achieves the directional conversion of low-value-added components such as Fe2O3 and TiO2 in the tailings (e.g., Fe2O3 reduces the crystallization activation energy by 23%), significantly improving the resource utilization rate of tailings.

[0080] Furthermore, this invention employs a three-stage gradient heating + magnetic field-assisted sintering process, enabling the decomposition and exothermic separation of PMMA and CaCO3 during the pore-forming stage, achieving a porosity control precision of ±1.2%. During the crystallization stage, the activation of the borax flux and the directional growth of anorthite synergistically enhance the crystalline phase ratio and Vickers hardness of the resulting porous microcrystalline glass. This achieves an extreme balance between high porosity and compressive strength, breaking through the boundaries of material performance. The porous microcrystalline glass prepared by this invention possesses high porosity, high mechanical strength, good chemical corrosion resistance (especially acid and alkali resistance), excellent thermal stability, and a long service life. Furthermore, the pore structure and matrix properties can be flexibly controlled by adjusting the composite tailings ratio, the type / dosage of the pore-forming agent, and the heat treatment regime to meet the specific needs of different application scenarios. This transforms previously low-value or even negative-value industrial solid waste into high-performance porous functional materials with broad application prospects and high economic value, realizing "turning waste into treasure" and providing an efficient and sustainable technical path for tailings treatment in mining and metallurgical enterprises. This invention successfully transforms tailings into products that meet the performance requirements of these fields, with a value far exceeding that of simple landfilling or low-end utilization (such as road paving).

[0081] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing porous microcrystalline glass based on composite tailings, characterized in that, include: S1: Weigh a predetermined amount of vanadium extraction tailings from coal shale, quartz sand tailings, rutile tailings, aluminum ash and tunnel waste, heat and keep warm and quench in water to obtain glass particles, dry and grind to obtain basic glass powder. S2: A composite pore-forming agent, flux, and nucleating agent are added to the base glass powder, and the mixture is mixed using magnetic field-assisted mixing technology to obtain a homogeneous mixture; S3: The mixture is placed in a mold and dry-pressed to obtain a raw blank; S4: The green blank is heated to the target temperature in stages and held at that temperature for a predetermined time to form the porous microcrystalline glass.

2. The method for preparing porous microcrystalline glass based on composite tailings according to claim 1, characterized in that, S1 includes: S1.1: Weigh 40-60 parts by weight of vanadium extraction tailings from coal shale, 3-7 parts by weight of quartz sand tailings, 3-7 parts by weight of rutile tailings, 7-13 parts by weight of aluminum ash, and 27-33 parts by weight of tunnel waste, mix them, and then carry out graded activation treatment to obtain mixed raw materials with a particle size of less than 500 mesh. S1.2: The mixed raw materials after graded activation treatment are loaded into a crucible and placed in a muffle furnace. The temperature is raised to 1450-1500℃ in stages and held for 60-120 minutes. Then the crucible is removed and subjected to segmented water quenching to obtain amorphous glass particles. S1.3: The obtained glass particles are ground into glass powder using a vibratory ball milling combined with airflow pulverization process.

3. The method for preparing porous microcrystalline glass based on composite tailings according to claim 2, characterized in that, S1.2 includes: The mixed raw materials after graded activation are loaded into a crucible and placed in a muffle furnace for staged heating. The staged heating process includes: the first stage, heating to 840-860℃ at a rate of 45-55℃ / min; the second stage, heating to 1330-1370℃ at a rate of 8-12℃ / min; and the third stage, heating to 1450-1500℃ at a rate of 4-6℃ / min and holding at that temperature for 60-120min, finally forming a CaO-Al2O3-SiO2-TiO2 quaternary eutectic. The crucible was then removed and subjected to segmented water quenching. In the first stage, the melt at 1450-1500℃ was cooled to 1150-1250℃ at a rate of 100℃ / s to form β-nepheline crystal nuclei. In the second stage, the melt was cooled to 750-850℃ at a rate of 50℃ / s to induce the precipitation of anorthite crystal phase. In the third stage, the melt was quenched in ice water to obtain amorphous glass particles.

4. The method for preparing porous microcrystalline glass based on composite tailings according to claim 3, characterized in that, S1.3 includes: Zirconia balls were used for milling for 20 hours to make the D50 of amorphous glass particles 15 μm. Then, air jet milling was carried out under nitrogen protection and 0.8 MPa pressure to make the D90 of the particles ≤ 5 μm. Finally, the surface was modified by using 3% wt silane coupling agent to reduce the contact angle of the formed glass powder to 38°.

5. The method for preparing porous microcrystalline glass based on composite tailings according to claim 1, characterized in that, The composite pore-forming agent comprises calcium carbonate and polymethyl methacrylate, wherein the mass ratio of calcium carbonate to the base glass powder is (0.05-0.15):1, and the mass ratio of polymethyl methacrylate to the base glass powder is (0.05-0.15):

1.

6. The method for preparing porous microcrystalline glass based on composite tailings according to claim 1, characterized in that, The flux includes one or more of anhydrous sodium carbonate or borax, wherein the mass ratio of the anhydrous sodium carbonate or borax to the base glass powder is (0.01-0.02):1; or the mass ratio of the mixture of anhydrous sodium carbonate and borax to the base glass powder is (0.01-0.02):

1.

7. The method for preparing porous microcrystalline glass based on composite tailings according to claim 1, characterized in that, The nucleating agent includes one or more of boron oxide, phosphorus pentoxide, or zinc oxide, and the mass ratio of the nucleating agent to the base glass powder is (0.01-0.02):

1.

8. The method for preparing porous microcrystalline glass based on composite tailings according to claim 1, characterized in that, S2 includes: A predetermined amount of composite pore-forming agent, flux, and nucleating agent are added to the base glass powder, and the mixture is poured into a mixing tank. A rotating magnetic field of 50 mT is applied in the mixing tank, and the mixture is mixed for 15 min to 35 min to form a homogeneous mixture. In this mixture, the Fe2O3 particles are oriented to form a conductive network, thereby reducing the resistivity of the mixture to 10 Ω·cm. 3 Ω·cm.

9. The method for preparing porous microcrystalline glass based on composite tailings according to claim 1, characterized in that, S4 includes: The green blank is placed in a box and heated to the target temperature in stages in a muffle furnace and held for 70 min-130 min to form the porous microcrystalline glass, wherein the target temperature is 800℃-980℃. The phased heating includes: a first stage: heating from room temperature to 280°C at a heating rate of 5°C / min; a second stage: heating from 280°C to 550°C at a heating rate of 3°C / min; and a third stage: heating from 550°C to the target temperature at a heating rate of 2°C / min. Simultaneously, in the third stage, a gradient magnetic field of 0.1-1 Tesla and microwaves of 2.45 GHz are superimposed for auxiliary heating.

10. A porous microcrystalline glass based on composite tailings, characterized in that, Prepared using the preparation method according to any one of claims 1 to 9.

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