A preparation method for improving performance of high-sulfur tailings filling body by industrial magnesium slag

Abstract

The present application relates to the field of filling mining, and particularly relates to a preparation method for improving the performance of high-sulfur tailings filling body by using industrial magnesium slag. In order to reduce the filling cost and realize low-cost green filling mining, the present application uses high-sulfur tailings and gobi aggregate as mixed filling aggregate, uses magnesium slag, quicklime, desulfurization gypsum and other multi-element solid waste and a composite activation solution to activate the potential activity of slag powder, and introduces three-dimensional rod-shaped high-entropy alloy nanoparticles to prepare a filling body with excellent mechanical properties. Compared with using traditional portland cement, the compressive strength and the sulfuric acid corrosion resistance of the high-sulfur tailings filling body are improved, the resource utilization of high-sulfur tailings in the filling field is promoted, and the economic cost and safety risk of the mine are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of filling mining, and particularly relates to a preparation method for improving the performance of high-sulfur tailings filling body by using industrial magnesium slag. BACKGROUND

[0002] The main components of magnesium slag are similar to the composition of silicate cement clinker, and the magnesium slag can generate hydration products with cementitious properties when meeting water, and has a certain hydration activity. Among them, the main component β-C2S has the characteristics of low early reactivity and slow hydration rate. Therefore, the magnesium slag is usually used as an auxiliary cementitious material and mixed with other waste residues or additives for modification or activation to achieve better cementitious effect, and is applied to the research of mining filling process. The combination of comprehensive utilization of solid waste magnesium slag and mine filling not only solves the environmental pollution problem of magnesium slag, but also effectively controls the cost of mine filling and improves the stability of the strength of the filling body.

[0003] High-sulfur tailings are solid waste generated during mining operations, with high sulfur content typically present as sulfates. A key characteristic of high-sulfur tailings is the high proportion of sulfide minerals, such as pyrite, which often exist in a free or associated state within the tailings. During surface stockpiling, the sulfides in high-sulfur tailings react with oxygen and water, producing acidic substances and releasing large amounts of sulfuric acid and heavy metals, causing severe environmental pollution. Therefore, the stockpiling of high-sulfur tailings not only occupies significant land resources, but its potential acidic leachate also poses a significant threat to groundwater, soil, and surrounding ecosystems. Using tailings as backfill aggregate in mined-out areas can alleviate storage pressure, reduce backfilling costs, and mitigate environmental pollution. Therefore, full tailings backfilling technology is a relatively mature method for the utilization of tailings resources. Studies have shown that sulfides in high-sulfur tailings affect the compressive strength of backfill materials. These sulfides can react with calcium hydroxide in cement to form sulfate minerals, which not only affect the strength of the backfill but may also lead to long-term expansion and cracking. Therefore, this invention utilizes alkaline substances (CaO / MgO) in magnesium slag to react with sulfides to generate stable sulfates, reducing the risk of acid leaching. Currently, mines primarily use mixed aggregates formed from high-sulfur tailings and Gobi aggregates, with cementing materials consisting of M37.5 cement and slag powder; the backfill slurry concentration is below 80%, typically around 77%. However, the later-stage strength of cemented backfill materials containing high-sulfur tailings is affected by sulfate erosion. Therefore, exploring the mechanical properties of high-sulfur tailings backfill materials to reduce the overall cost of composite backfill materials while meeting the long-term strength requirements for mine backfill stability is an urgent issue for mines. To reduce backfilling costs and achieve low-cost, green backfilling mining, this invention uses high-sulfur tailings and Gobi aggregate as mixed backfilling aggregates, and magnesium slag, quicklime, slag powder, and desulfurized gypsum as cementing materials. Furthermore, three-dimensional rod-shaped high-entropy alloy nanoparticles are introduced to prepare a backfill body with excellent mechanical properties. In addition, the composite alkaline activator prepared in this invention improves the compressive strength and sulfate resistance of the magnesium slag-activated high-sulfur tailings-based backfill body. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a method for preparing high-sulfur tailings backfill bodies using industrial magnesium slag. This is achieved through the following technical solution:

[0005] S1. Dry the industrial magnesium slag at 90-120℃ to constant weight, crush it, and then put it into a ball mill for ball milling for 6-8 hours; high sulfur tailings and Gobi aggregate need to be dried for later use.

[0006] S2. Dissolve sodium hydroxide and cesium hydroxide in deionized water in a certain proportion, treat with ultrasound at 40kHz for 5-10 minutes, and then heat the solution to 43-47℃ while stirring to obtain the composite activator solution.

[0007] S3. Dissolve phosphotungstic acid, rhenium chloride, ferric nitrate, copper sulfate, zirconium chloride, manganese sulfate, nickel nitrate, tungsten chloride, and ascorbic acid in a mixed solvent of ethanol, oleylamine, ethylene glycol, and oleic acid in a certain proportion. Then transfer the solution to a microwave reactor, set the temperature to 143-155℃, the heating time to 5 min, and the holding time to 80-110 min. After the reaction is completed, centrifuge to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles.

[0008] S4. Weigh out 527.67-879.45g of high-sulfur tailings, 879.45-1231.23g of Gobi aggregate, 29.31-58.62g of industrial magnesia slag, 175.86-205.17g of slag powder, 11.73-23.45g of quicklime, and 35.17-52.76g of desulfurized gypsum, 1.8-3.8g of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in S3, and 85mL of... The composite activator solution prepared by S2 and 548-656 mL of water are put into a cement mortar mixer and stirred for 5-8 minutes to form a mixed filling slurry. Then, the filling slurry is poured into a standard mold and compacted by vibration table to remove air bubbles. Then, the filling slurry exceeding the mold is scraped off with a metal ruler to smooth the surface of the cemented filling sample. At the same time, the mold is numbered and placed in a standard constant temperature and humidity curing chamber for curing.

[0009] S5. Curing and performance regulation: Early curing: Curing for 7 days at 20±2℃ and humidity ≥95% to promote the slow hydration of MgO in magnesium slag and avoid expansion and cracking; Long-term stability treatment: Spraying 5% Na2CO3 solution on the surface of the filling body to form an alkaline barrier to inhibit sulfur oxidation.

[0010] The specific operation steps of this invention are as follows:

[0011] S1. Dry the industrial magnesium slag at 90-120℃ to constant weight, crush it, and then ball mill it for 6-8 hours. The high-sulfur tailings and Gobi aggregate need to be dried for later use. In this step, the high-sulfur tailings contain approximately 70% fine particles smaller than 38μm, classifying them as fine-grained tailings. The mineral phases of the high-sulfur tailings mainly consist of quartz, mica, gypsum, and chlorite, with a calcination weight of 17.03%. The Gobi aggregate is mainly composed of inert components, with particles smaller than 1mm accounting for 39.12%. The purpose of drying is to avoid the influence of moisture content on the concentration of the filling slurry.

[0012] S2. Preparation of the composite activator: Dissolve 1.47-2.94 g of sodium hydroxide and 0.48-0.96 g of cesium hydroxide in 100 mL of deionized water. After sonicating at 40 kHz for 5-10 min, heat the solution to 43-47 °C while stirring to obtain the composite activator solution. The CsOH added in this step is far more alkaline than conventional alkali metal hydroxides, enabling it to more efficiently break the Si-O and Al-O bonds in the raw materials, release the active components, and shorten the induction period. Even at 5-15 °C, CsOH maintains high reactivity, avoiding the delayed coagulation caused by low temperatures in traditional activators. Furthermore, Cs... + The ionic radius is significantly larger than that of Na. + This creates a looser ion coordination structure within the gel network, reducing shrinkage stress and inhibiting microcrack propagation. (Cs) + It can adsorb onto the surface of gel pores, reducing porosity and improving material density and impermeability. (Cs) + The resulting silicate network is more stable and has a lower dissolution rate than Na in acidic environments. + Low basicity and extended material lifespan. Cs-based polymers maintain structural stability even at temperatures above 800°C. The application of CsOH in this step balances high basicity activation with silicate network construction, thereby improving compressive strength.

[0013] S3. Preparation of three-dimensional rod-shaped high-entropy alloy nanoparticles: 1.4-1.9 g of phosphotungstic acid (PTA), 0.7-1.2 g of rhenium chloride, 1.1-2.3 g of ferric nitrate, 1.6-3.3 g of copper sulfate, 1.5-1.9 g of zirconium chloride, 3.2-4.1 g of manganese sulfate, 0.9-2.1 g of nickel nitrate, 0.6-0.9 g of tungsten chloride, and 0.5-0.8 g of ascorbic acid were dissolved in 20 mL of ethanol and 15 mL of oleylamine. The mixture of 8 mL ethylene glycol and 5 mL oleic acid was transferred to a 100 mL microwave reactor. The temperature was set at 143-155 °C for 5 min, followed by a holding time of 80-110 min. After the reaction, the mixture was centrifuged to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles. In this step, under the influence of phosphotungstic acid clusters, these three-dimensional rod-shaped high-entropy alloy nanoparticles can form and remain stable under the drive of Coulomb forces and van der Waals forces. A multi-element synergistic effect and unique nanostructure (three-dimensional rod morphology) exist among Re, Fe, Cu, Zr, Mn, W, and Ni, significantly improving the compressive strength and ductility of the filler. Multiple metal elements among Re, Fe, Cu, Zr, Mn, W, and Ni form a solid solution, generating solid solution strengthening through atomic size differences and lattice distortion, further optimizing the microstructural stability of the filler. These three-dimensional rod-shaped high-entropy alloy nanoparticles exhibit excellent corrosion resistance and thermal stability, resisting the oxidative erosion of active sulfides in high-sulfur tailings. These three-dimensional rod-shaped nanoparticles can be uniformly dispersed in the backfill matrix, enhancing the interfacial bonding force between magnesium slag and the backfill through mechanical interlocking and chemical bonding, reducing porosity, improving compactness, and optimizing the rheological properties of the backfill slurry.

[0014] S4. Weigh out 527.67-879.45g of high-sulfur tailings, 879.45-1231.23g of Gobi aggregate, 29.31-58.62g of industrial magnesia slag, 175.86-205.17g of slag powder, 11.73-23.45g of quicklime, and 35.17-52.76g of desulfurized gypsum, 1.8-3.8g of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in S3, and 78-96mL of... The composite activator solution prepared by S2 and 548-656 mL of water were placed together in a JJ-5 cement mortar mixer and stirred for 5-8 minutes to form a mixed filling slurry. The filling slurry was then poured into a standard mold and compacted using a vibratory compaction table to remove air bubbles. The excess filling slurry beyond the mold was then scraped off with a metal ruler to smooth the surface of the cemented filling sample. The mold was then numbered and placed in a YH-40B standard constant temperature and humidity curing chamber at a temperature of 20±1℃ and a relative humidity of over 90% for curing. In this step, the magnesium slag reacts with sulfides in the tailings to form gypsum (CaSO4·2H2O), and CaO / MgO reacts with sulfides to form stable sulfates, reducing the risk of acid leaching. The composite activator prepared using this invention possesses both strong alkali activation and silicate network formation capabilities. Three-dimensional rod-shaped high-entropy alloy nanoparticles, through multi-dimensional synergistic effects such as mechanical reinforcement, sulfur solidification, and microstructure optimization, provide a new solution for industrial magnesium slag-based high-sulfur tailings filling bodies. In this step, the CaO contained in the magnesium slag reacts with sulfides (such as FeS2) in the high-sulfur tailings to generate CaSO4·2H2O (gypsum) and CaCO3, effectively solidifying sulfur and inhibiting sulfate corrosion and acid leaching. On the other hand, the slow hydration characteristics of MgO can compensate for the volume shrinkage caused by sulfide oxidation, reducing microcracks. In addition, the active SiO2 and Al2O3 in the magnesium slag participate in the geological polymerization reaction, forming a three-dimensional network structure, ensuring the backfill meets downhole filling requirements. Furthermore, the MgO in the magnesium slag forms a gel during long-term hydration, improving impermeability and sulfate corrosion resistance. In this step, high-sulfur tailings, Gobi aggregate, industrial magnesium slag, slag powder, quicklime, and desulfurized gypsum are weighed as composite high-sulfur tailings backfill materials.

[0015] S5. Curing and Performance Control: Early Curing: Curing for 7 days at 20±2℃ and ≥90% humidity promotes the slow hydration of MgO in magnesium slag and avoids expansion and cracking; Long-term Stability Treatment: Curing for 28 days at 20±2℃ and ≥90% humidity, due to the addition of three-dimensional rod-shaped high-entropy alloy nanoparticles and composite activator solution, the strength of the 28-day cemented filling body is significantly improved, and the strength value is much greater than that of the filling body using 100% cement.

[0016] When 100% cement is used for activation, and the ratio of high-sulfur tailings to Gobi aggregate is set at 3:7, the strength value of the high-sulfur tailings backfill body R7 = 0.61 MPa.28 =1.53MPa; When the ratio of high-sulfur tailings to Gobi aggregate is set at 4:6, the strength value of the high-sulfur tailings backfill body R7 = 0.66MPa, R 28 =1.61MPa; When the ratio of high-sulfur tailings to Gobi aggregate is set at 5:5, the strength value of the high-sulfur tailings backfill body R7 = 0.80MPa, R 28 =1.85MPa.

[0017] Preferably, the proportion of fine particles smaller than 38μm in the high-sulfur tailings of the present invention is about 70%, which belongs to fine-grained tailings.

[0018] Preferably, the mineral phase of the high-sulfur tailings of the present invention is mainly composed of quartz, mica, gypsum and chlorite, with a calcination vector of 17.03%;

[0019] Preferably, the Gobi aggregate of the present invention is mainly composed of inert components, with particles smaller than 1 mm accounting for 39.12%;

[0020] Preferably: In S1 of the present invention, the industrial magnesium slag is dried to constant weight at 90°C, crushed and then ball-milled in a ball mill for 6-8 hours; the high-sulfur tailings and Gobi aggregate need to be dried for later use.

[0021] Preferably: In S1 of the present invention, the industrial magnesium slag is dried to constant weight at 120°C, crushed and then ball-milled in a ball mill for 6-8 hours; the high-sulfur tailings and Gobi aggregate need to be dried for later use.

[0022] Preferably, in step S3 of this invention, 1.4 g of phosphotungstic acid (PTA), 0.7 g of rhenium chloride, 1.1 g of ferric nitrate, 1.6 g of copper sulfate, 1.5 g of zirconium chloride, 3.2 g of manganese sulfate, 0.9 g of nickel nitrate, 0.6 g of tungsten chloride, and 0.5 g of ascorbic acid are dissolved in a mixed solvent of 20 mL of ethanol, 15 mL of oleylamine, 8 mL of ethylene glycol, and 5 mL of oleic acid. The solution is then transferred to a 100 mL microwave reactor, and the temperature is set to 143 °C for 5 min, followed by a holding time of 80 min. After the reaction is completed, the mixture is centrifuged to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles.

[0023] Preferably, in step S3 of this invention, 1.9 g of phosphotungstic acid (PTA), 1.2 g of rhenium chloride, 2.3 g of ferric nitrate, 3.3 g of copper sulfate, 1.9 g of zirconium chloride, 4.1 g of manganese sulfate, 2.1 g of nickel nitrate, 0.9 g of tungsten chloride, and 0.8 g of ascorbic acid are dissolved in a mixed solvent of 20 mL of ethanol, 15 mL of oleylamine, 8 mL of ethylene glycol, and 5 mL of oleic acid. This solution is then transferred to a 100 mL microwave reactor, and the temperature is set to 155 °C for 5 min, followed by a holding time of 110 min. After the reaction is complete, centrifugation is performed to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles.

[0024] Preferably: In step S4 of the present invention, 879.45g of high-sulfur tailings, 1231.23g of Gobi aggregate, 58.62g of industrial magnesium slag, 205.17g of slag powder, 23.45g of quicklime, 52.76g of desulfurized gypsum, 3.8g of three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in step S3, 85mL of composite activator solution prepared in step S2, and 656mL of water are weighed and placed into a JJ-5 cement mortar mixer. After stirring for 5 minutes, a mixed filling slurry is formed. Then, the filling slurry is injected into a standard mold and compacted by vibration table to remove air bubbles. Then, the excess filling slurry beyond the mold is scraped off with a metal ruler to smooth the surface of the cemented filling sample. At the same time, the mold is numbered and placed in a standard constant temperature and humidity curing chamber for curing.

[0025] Preferably: In step S4 of the present invention, 527.67g of high-sulfur tailings, 879.45g of Gobi aggregate, 29.31g of industrial magnesium slag, 175.86g of slag powder, 11.73g of quicklime, 35.17g of desulfurized gypsum, 1.8g of three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in step S3, 95mL of composite activator solution prepared in step S2, and 548mL of water are weighed and placed into a JJ-5 cement mortar mixer. After stirring for 8 minutes, a mixed filling slurry is formed. Then, the filling slurry is injected into a standard mold and compacted using a vibrating table to remove air bubbles. Then, the excess filling slurry beyond the mold is scraped off with a metal ruler to smooth the surface of the cemented filling sample. At the same time, the mold is numbered and placed in a standard constant temperature and humidity curing chamber for curing.

[0026] Preferably, the present invention uses a JA2003 electronic scale, which can be accurate to 0.001g. Figure 1 ).

[0027] Preferably, the mold used in this invention is a three-piece mold with dimensions of 7.07cm × 7.07cm × 7.07cm.

[0028] Preferably, the present invention uses a standard mold.

[0029] Advantages of this invention:

[0030] 1. In this invention, the sulfide content in the aggregate is reduced by adding Gobi aggregate. The alkaline substances (CaO / MgO) in magnesium slag and slag powder react with sulfides to generate stable sulfates and silicate hydrates, thereby reducing the risk of acid leaching.

[0031] 2. This invention utilizes the differences in chemical composition of multi-component solid waste and its acid-base neutralization properties to regulate the phase composition of the filling composite material, and develops a low-cost and high-performance multi-component solid waste high-sulfur tailings filling material that can replace silicate cement, meeting the early and long-term mechanical strength requirements of cemented backfill bodies in mines.

[0032] 3. The solid waste comprehensive utilization rate of this invention is >90%, which reduces heavy metal pollution in tailings ponds and the land occupied by magnesium slag storage, and has good environmental benefits.

[0033] 4. This invention is simple to operate, has low production costs, and is conducive to mass production.

[0034] 5. The CsOH added in this invention has a much higher alkalinity than conventional alkali metal hydroxides, enabling it to more efficiently break Si-O and Al-O bonds in the raw materials, release active components, and shorten the induction period. Even at 5-15℃, CsOH can maintain high reactivity, avoiding the condensation delay caused by low temperatures in traditional activators. Furthermore, Cs... + The ionic radius is significantly larger than that of Na. + This creates a looser ion coordination structure within the gel network, reducing shrinkage stress and inhibiting microcrack propagation. (Cs) + It can adsorb onto the surface of gel pores, reducing porosity and improving material density and impermeability. (Cs) + The resulting silicate network is more stable and has a lower dissolution rate than Na in acidic environments. + The low alkalinity of the base extends the material's lifespan. Cs-based polymers maintain structural stability even at temperatures above 800°C. The application of CsOH in this invention balances high alkalinity activation with silicate network construction, thereby improving compressive strength. Attached Figure Description

[0035] Figure 1 The JA2003 electronic balance used in this invention.

[0036] Figure 2 The raw materials used in this invention.

[0037] Figure 3 XRD patterns of magnesium slag used in the embodiments of the present invention.

[0038] Figure 4 Scanning electron microscope image of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Example 3 of this invention.

[0039] Figure 5 Transmission electron microscope image of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Example 3 of the present invention.

[0040] Figure 6Transmission electron microscope image of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Comparative Example 6 of this invention.

[0041] Figure 7 The pore size distribution curve of the N2 adsorption-desorption isotherm of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Example 3 of this invention.

[0042] Figure 8 Transmission electron microscope image of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Comparative Example 7 of this invention. Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0044] Example 1

[0045] S1. Dry the industrial magnesium slag at 90℃ to constant weight, crush it, and then ball mill it for 6 hours. The high-sulfur tailings and Gobi aggregate need to be dried for later use. In this step, the high-sulfur tailings contain approximately 70% fine particles smaller than 38μm, classifying them as fine-grained tailings. The mineral phases of the high-sulfur tailings mainly consist of quartz, mica, gypsum, and chlorite, with a calcination weight of 17.03%. The Gobi aggregate is mainly composed of inert components, with particles smaller than 1mm accounting for 39.12%. The purpose of drying is to avoid the influence of moisture content on the concentration of the filling slurry.

[0046] S2. Preparation of the composite activator: Dissolve 1.47g of sodium hydroxide and 0.48g of cesium hydroxide in 100mL of deionized water. After sonicating at 40kHz for 5-10min, heat the solution to 43℃ while stirring to obtain the composite activator solution. The CsOH added in this step is far more alkaline than conventional alkali metal hydroxides, enabling it to more efficiently break the Si-O and Al-O bonds in the raw materials, release the active components, and shorten the induction period. Even at 5℃, CsOH maintains high reactivity, avoiding the delayed coagulation caused by low temperatures in traditional activators. Furthermore, Cs... + The ionic radius is significantly larger than that of Na. + This creates a looser ion coordination structure within the gel network, reducing shrinkage stress and inhibiting microcrack propagation. (Cs) + It can adsorb onto the surface of gel pores, reducing porosity and improving material density and impermeability. (Cs) +The resulting silicate network is more stable and has a lower dissolution rate than Na in acidic environments. + Low basicity and extended material lifespan. Cs-based polymers maintain structural stability even at temperatures above 800°C. The application of CsOH in this step balances high basicity activation with silicate network construction, thereby improving compressive strength.

[0047] S3. Preparation of three-dimensional rod-shaped high-entropy alloy nanoparticles: 1.4 g of phosphotungstic acid (PTA), 0.7 g of rhenium chloride, 1.1 g of ferric nitrate, 1.6 g of copper sulfate, 1.5 g of zirconium chloride, 3.2 g of manganese sulfate, 0.9 g of nickel nitrate, 0.6 g of tungsten chloride, and 0.5 g of ascorbic acid were dissolved in a mixed solvent of 20 mL ethanol, 15 mL oleylamine, 8 mL ethylene glycol, and 5 mL oleic acid. The solution was then transferred to a 100 mL microwave reactor, and the temperature was set to 143 °C for 5 min, followed by a holding time of 80 min. After the reaction, the nanoparticles were centrifuged to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles. In this step, under the influence of phosphotungstic acid clusters, these three-dimensional rod-shaped high-entropy alloy nanoparticles can be formed and remain stable under the drive of Coulomb forces and van der Waals forces. The presence of multi-element synergistic effects and a unique nanostructure (three-dimensional rod-like morphology) among Re, Fe, Cu, Zr, Mn, W, and Ni significantly improves the compressive strength and ductility of the backfill. The formation of a solid solution among these elements, through atomic size differences and lattice distortion, generates solid solution strengthening, further optimizing the microstructural stability of the backfill. These three-dimensional rod-shaped high-entropy alloy nanoparticles exhibit excellent corrosion resistance and thermal stability, resisting the oxidative erosion of active sulfides in high-sulfur tailings. These nanoparticles can be uniformly dispersed within the backfill matrix, enhancing the interfacial bonding between magnesium slag and the backfill through mechanical interlocking and chemical bonding, reducing porosity, improving density, and optimizing the rheological properties of the backfill slurry.

[0048] S4. Weigh out 527.67g of high-sulfur tailings, 879.45g of Gobi aggregate, 29.31g of industrial magnesia slag, 175.86g of slag powder, 11.73g of quicklime, 35.17g of desulfurized gypsum, 1.8g of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in S3, and 78mL of... The composite activator solution prepared by S2 and 548 mL of water were placed together in a JJ-5 cement mortar mixer and stirred for 5 minutes to form a mixed filling slurry. The filling slurry was then poured into a standard mold and compacted using a vibratory compaction table to remove air bubbles. The excess filling slurry beyond the mold was then scraped off with a metal ruler to smooth the surface of the cemented filling sample. The mold was then numbered and placed in a YH-40B standard constant temperature and humidity curing chamber at a temperature of 20±1℃ and a relative humidity of over 90% for curing. In this step, the magnesium slag reacts with sulfides in the tailings to form gypsum (CaSO4·2H2O), and CaO / MgO reacts with sulfides to form stable sulfates, reducing the risk of acid leaching. The composite activator prepared using this invention possesses both strong alkali activation and silicate network formation capabilities. Three-dimensional rod-shaped high-entropy alloy nanoparticles, through multi-dimensional synergistic effects such as mechanical reinforcement, sulfur solidification, and microstructure optimization, provide a new solution for industrial magnesium slag-based high-sulfur tailings filling bodies. In this step, the CaO contained in the magnesium slag reacts with sulfides (such as FeS2) in the high-sulfur tailings to generate CaSO4·2H2O (gypsum) and CaCO3, effectively solidifying sulfur and inhibiting sulfate corrosion and acid leaching. On the other hand, the slow hydration characteristics of MgO can compensate for the volume shrinkage caused by sulfide oxidation, reducing microcracks. In addition, the active SiO2 and Al2O3 in the magnesium slag participate in the geological polymerization reaction, forming a three-dimensional network structure, ensuring the backfill meets downhole filling requirements. Furthermore, the MgO in the magnesium slag forms a gel during long-term hydration, improving impermeability and sulfate corrosion resistance. In this step, high-sulfur tailings, Gobi aggregate, industrial magnesium slag, slag powder, quicklime, and desulfurized gypsum are weighed as composite high-sulfur tailings backfill materials.

[0049] S5. Curing and Performance Control: Early Curing: Curing for 7 days at 20±2℃ and ≥90% humidity promotes the slow hydration of MgO in magnesium slag and avoids expansion and cracking; Long-term Stability Treatment: Curing for 28 days at 20±2℃ and ≥90% humidity, due to the addition of three-dimensional rod-shaped high-entropy alloy nanoparticles and composite activator solution, the strength of the 28-day cemented filling body is significantly improved, and the strength value is much greater than that of the filling body using 100% cement.

[0050] Table 1 Chemical composition of magnesium slag and slag powder

[0051]

[0052] Figure 1 The JA2003 electronic balance used in this invention.Figure 2 Images of the raw materials used in the experiments of this invention are shown. Table 1 shows the chemical composition of the magnesium slag and slag powder used in the embodiments of this invention. Analysis of Table 1 shows that the magnesium slag used is similar in chemical composition to the slag powder currently used in mines, with main components including CaO, SiO2, MgO, Al2O3, and Fe2O3. The magnesium slag has higher calcium oxide and silicon dioxide content than the slag powder, but lower magnesium oxide and aluminum oxide content. The CaO content is >40%, indicating good cementitious activity. Figure 3 The XRD pattern of the magnesium slag used in this embodiment of the invention shows that the main minerals are γ-C2S and β-C2S, with small amounts of C3S and calcium magnesium olivine (CaO·MgO·SiO2). Magnesium slag has a chemical composition similar to cement and slag, and contains minerals with cementing properties such as β-C2S and C3S, indicating that magnesium slag has excellent application prospects.

[0053] Example 2

[0054] S1. Dry the industrial magnesium slag at 120℃ to constant weight, crush it, and then ball mill it for 8 hours. The high-sulfur tailings and Gobi aggregate need to be dried for later use. In this step, the high-sulfur tailings contain approximately 70% fine particles smaller than 38μm, classifying them as fine-grained tailings. The mineral phases of the high-sulfur tailings mainly consist of quartz, mica, gypsum, and chlorite, with a calcination weight of 17.03%. The Gobi aggregate is mainly composed of inert components, with particles smaller than 1mm accounting for 39.12%. The purpose of drying is to avoid the influence of moisture content on the concentration of the filling slurry.

[0055] S2. Preparation of the composite activator: Dissolve 2.94 g of sodium hydroxide and 0.96 g of cesium hydroxide in 100 mL of deionized water. After sonicating at 40 kHz for 10 min, heat the solution to 47 °C while stirring to obtain the composite activator solution. The CsOH added in this step has a much higher alkalinity than conventional alkali metal hydroxides, enabling it to more efficiently break the Si-O and Al-O bonds in the raw materials, release the active components, and shorten the induction period. Even at 15 °C, CsOH maintains high reactivity, avoiding the delayed coagulation caused by low temperatures in traditional activators. Furthermore, Cs... + The ionic radius is significantly larger than that of Na. + This creates a looser ion coordination structure within the gel network, reducing shrinkage stress and inhibiting microcrack propagation. (Cs) + It can adsorb onto the surface of gel pores, reducing porosity and improving material density and impermeability. (Cs) + The resulting silicate network is more stable and has a lower dissolution rate than Na in acidic environments. +Low basicity and extended material lifespan. Cs-based polymers maintain structural stability even at temperatures above 800°C. The application of CsOH in this step balances high basicity activation with silicate network construction, thereby improving compressive strength.

[0056] S3. Preparation of three-dimensional rod-shaped high-entropy alloy nanoparticles: 1.9 g of phosphotungstic acid (PTA), 1.2 g of rhenium chloride, 2.3 g of ferric nitrate, 3.3 g of copper sulfate, 1.9 g of zirconium chloride, 4.1 g of manganese sulfate, 2.1 g of nickel nitrate, 0.9 g of tungsten chloride, and 0.8 g of ascorbic acid were dissolved in a mixed solvent of 20 mL ethanol, 15 mL oleylamine, 8 mL ethylene glycol, and 5 mL oleic acid. The solution was then transferred to a 100 mL microwave reactor, and the temperature was set to 155 °C for 5 min, followed by a holding time of 110 min. After the reaction, the nanoparticles were centrifuged to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles. In this step, under the influence of phosphotungstic acid clusters, these three-dimensional rod-shaped high-entropy alloy nanoparticles can be formed and remain stable under the drive of Coulomb forces and van der Waals forces. The presence of multi-element synergistic effects and a unique nanostructure (three-dimensional rod-like morphology) among Re, Fe, Cu, Zr, Mn, W, and Ni significantly improves the compressive strength and ductility of the backfill. The formation of a solid solution among these elements, through atomic size differences and lattice distortion, generates solid solution strengthening, further optimizing the microstructural stability of the backfill. These three-dimensional rod-shaped high-entropy alloy nanoparticles exhibit excellent corrosion resistance and thermal stability, resisting the oxidative erosion of active sulfides in high-sulfur tailings. These nanoparticles can be uniformly dispersed within the backfill matrix, enhancing the interfacial bonding between magnesium slag and the backfill through mechanical interlocking and chemical bonding, reducing porosity, improving density, and optimizing the rheological properties of the backfill slurry.

[0057] S4. Weigh out 879.45g of high-sulfur tailings, 1231.23g of Gobi aggregate, 58.62g of industrial magnesium slag, 205.17g of slag powder, 23.45g of quicklime, 52.76g of desulfurized gypsum, 3.8g of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in S3, and 96mL of... The composite activator solution prepared by S2 and 656 mL of water were placed together in a JJ-5 cement mortar mixer and stirred for 8 minutes to form a mixed filling slurry. The filling slurry was then poured into a standard mold and compacted using a vibratory compaction table to remove air bubbles. The excess filling slurry beyond the mold was then scraped off with a metal ruler to smooth the surface of the cemented filling sample. The mold was then numbered and placed in a YH-40B standard constant temperature and humidity curing chamber at a temperature of 20±1℃ and a relative humidity of over 90% for curing. In this step, the magnesium slag reacts with sulfides in the tailings to form gypsum (CaSO4·2H2O), and CaO / MgO reacts with sulfides to form stable sulfates, reducing the risk of acid leaching. The composite activator prepared using this invention possesses both strong alkali activation and silicate network formation capabilities. Three-dimensional rod-shaped high-entropy alloy nanoparticles, through multi-dimensional synergistic effects such as mechanical reinforcement, sulfur solidification, and microstructure optimization, provide a new solution for industrial magnesium slag-based high-sulfur tailings filling bodies. In this step, the CaO contained in the magnesium slag reacts with sulfides (such as FeS2) in the high-sulfur tailings to generate CaSO4·2H2O (gypsum) and CaCO3, effectively solidifying sulfur and inhibiting sulfate corrosion and acid leaching. On the other hand, the slow hydration characteristics of MgO can compensate for the volume shrinkage caused by sulfide oxidation, reducing microcracks. In addition, the active SiO2 and Al2O3 in the magnesium slag participate in the geological polymerization reaction, forming a three-dimensional network structure, ensuring the backfill meets downhole filling requirements. Furthermore, the MgO in the magnesium slag forms a gel during long-term hydration, improving impermeability and sulfate corrosion resistance. In this step, high-sulfur tailings, Gobi aggregate, industrial magnesium slag, slag powder, quicklime, and desulfurized gypsum are weighed as composite high-sulfur tailings backfill materials.

[0058] S5. Curing and Performance Control: Early Curing: Curing for 7 days at 20±2℃ and ≥90% humidity promotes the slow hydration of MgO in magnesium slag and avoids expansion and cracking; Long-term Stability Treatment: Curing for 28 days at 20±2℃ and ≥90% humidity, due to the addition of three-dimensional rod-shaped high-entropy alloy nanoparticles and composite activator solution, the strength of the 28-day cemented filling body is significantly improved, and the strength value is much greater than that of the filling body using 100% cement.

[0059] Comparative Example 1: Except for step S2, where cesium hydroxide is not added, all other steps are the same as in Example 2.

[0060] Comparative Example 2: Except for step S3, which does not include ascorbic acid, all other steps are the same as in Example 2.

[0061] Comparative Example 3: Except for step S3, which does not involve the addition of oleic acid, all other steps are the same as in Example 2.

[0062] Comparative Example 4: Except for step S2, in which sodium hydroxide is not added, all other steps are the same as in Example 2.

[0063] Comparative Example 5: Except for step S4, in which the composite activator solution is not added, all other steps are the same as in Example 2.

[0064] In the experimental process of this invention, step S2 involves preparing a composite activator solution to activate the high-sulfur tailings backfill material. The reason for this is that an alkaline environment not only helps inhibit the precipitation of sulfate ions but also facilitates the activation of active components in backfill materials such as magnesium slag and slag powder. Therefore, the composition, type, and dosage of the alkaline activator are crucial to the experimental results. Insufficient composite activator solution will not achieve the desired activation effect, while excessive dosage will result in efflorescence. Secondly, before conducting the mechanical strength test of the high-sulfur tailings backfill, to reduce errors in the experimental operation, the top and bottom of the backfill sample are smoothed with fine sandpaper, and the dimensions of the sample are measured with vernier calipers to an accuracy of 0.02 mm. This invention conducts uniaxial compressive strength tests on the backfill sample according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999). This invention uses a standard mold. Uniaxial compressive strength tests (7d and 28d) were conducted using an INSTRON5969 electronic universal testing machine (load range 100kN), with a constant displacement loading rate of 0.5mm / min. Simultaneously, the computer system collected load and displacement data in real time. Table 2 shows the uniaxial compressive strength test results of the fillers prepared in Examples 1-2 and Comparative Examples 1-4 of this invention. To avoid randomness in the experimental data, the tests were performed five times. Based on the compressive strength values ​​at 7d and 28d, the results show that the incorporation of the composite activator prepared in this invention has a significant activating effect on the strength of the filler. Sodium hydroxide and cesium hydroxide have a synergistic effect in the composite activator solution, influencing each other. In particular, the alkalinity of CsOH is far greater than that of conventional alkali metal hydroxides, which can more efficiently break the Si-O and Al-O bonds in the raw materials, release active components, shorten the induction period, and CsOH can still maintain high reactivity, avoiding the solidification delay caused by low temperature in traditional activators. Furthermore, Cs... + The ionic radius is significantly larger than that of Na. + This creates a looser ion coordination structure within the gel network, reducing shrinkage stress and inhibiting microcrack propagation. (Cs) + It can adsorb onto the surface of gel pores, reducing porosity and improving material density and impermeability. (Cs) + The resulting silicate network is more stable and has a lower dissolution rate than Na in acidic environments. +The low gel content extends the material's lifespan. The application of CsOH can balance high alkalinity activation and silicate network construction, improving compressive strength. The uniaxial compressive strength test results of the fillers prepared in Examples 1-2 and Comparative Examples 1-4 further demonstrate that the composite alkaline activator prepared in this invention improves the compressive strength and mechanical properties of magnesium slag-activated high-sulfur tailings-based fillers. In addition, ascorbic acid and oleic acid are essential reagents for preparing the three-dimensional rod-shaped high-entropy alloy nanoparticles described in this invention. The absence of either one will prevent the acquisition of the required three-dimensional rod-shaped high-entropy alloy nanoparticles, thus affecting the uniaxial compressive strength test results of the final product.

[0065] Table 2 Results of uniaxial compressive strength test

[0066] Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 7d (MPa) 3.53±0.03 2.65±0.04 3.01±0.05 2.95±0.01 2.85±0.03 2.03±0.01 28d (MPa) 5.68±0.01 3.42±0.03 3.89±0.02 3.76±0.03 3.49±0.02 3.11±0.02

[0067] Example 3

[0068] S1. Dry the industrial magnesium slag at 99℃ to constant weight, crush it, and then ball mill it for 7 hours. The high-sulfur tailings and Gobi aggregate need to be dried for later use. In this step, the high-sulfur tailings contain approximately 70% fine particles smaller than 38μm, classifying them as fine-grained tailings. The mineral phases of the high-sulfur tailings mainly consist of quartz, mica, gypsum, and chlorite, with a calcination weight of 17.03%. The Gobi aggregate is primarily composed of inert components, with particles smaller than 1mm accounting for 39.12%. The purpose of drying is to avoid the influence of moisture content on the concentration of the filling slurry.

[0069] S2. Preparation of the composite activator: Dissolve 2.47g of sodium hydroxide and 0.56g of cesium hydroxide in 100mL of deionized water. After sonicating at 40kHz for 5-10min, heat the solution to 45℃ while stirring to obtain the composite activator solution. The CsOH added in this step is far more alkaline than conventional alkali metal hydroxides, enabling it to more efficiently break the Si-O and Al-O bonds in the raw materials, release the active components, and shorten the induction period. Even at 9℃, CsOH maintains high reactivity, avoiding the delayed coagulation caused by low temperatures in traditional activators. Furthermore, Cs... + The ionic radius is significantly larger than that of Na. + This creates a looser ion coordination structure within the gel network, reducing shrinkage stress and inhibiting microcrack propagation. (Cs) + It can adsorb onto the surface of gel pores, reducing porosity and improving material density and impermeability. (Cs) + The resulting silicate network is more stable and has a lower dissolution rate than Na in acidic environments. + Low basicity and extended material lifespan. Cs-based polymers maintain structural stability even at temperatures above 800°C. The application of CsOH in this step balances high basicity activation with silicate network construction, thereby improving compressive strength.

[0070] S3. Preparation of three-dimensional rod-shaped high-entropy alloy nanoparticles: 1.5 g of phosphotungstic acid (PTA), 0.9 g of rhenium chloride, 1.9 g of ferric nitrate, 1.8 g of copper sulfate, 1.6 g of zirconium chloride, 3.5 g of manganese sulfate, 1.1 g of nickel nitrate, 0.7 g of tungsten chloride, and 0.6 g of ascorbic acid were dissolved in a mixed solvent of 20 mL ethanol, 15 mL oleylamine, 8 mL ethylene glycol, and 5 mL oleic acid. The solution was then transferred to a 100 mL microwave reactor, and the temperature was set to 149 °C for 5 min, followed by a holding time of 99 min. After the reaction, the nanoparticles were centrifuged to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles. In this step, under the influence of phosphotungstic acid clusters, these three-dimensional rod-shaped high-entropy alloy nanoparticles can be formed and remain stable under the drive of Coulomb forces and van der Waals forces. The presence of multi-element synergistic effects and a unique nanostructure (three-dimensional rod-like morphology) among Re, Fe, Cu, Zr, Mn, W, and Ni significantly improves the compressive strength and ductility of the backfill. The formation of a solid solution among these elements, through atomic size differences and lattice distortion, generates solid solution strengthening, further optimizing the microstructural stability of the backfill. These three-dimensional rod-shaped high-entropy alloy nanoparticles exhibit excellent corrosion resistance and thermal stability, resisting the oxidative erosion of active sulfides in high-sulfur tailings. These nanoparticles can be uniformly dispersed within the backfill matrix, enhancing the interfacial bonding between magnesium slag and the backfill through mechanical interlocking and chemical bonding, reducing porosity, improving density, and optimizing the rheological properties of the backfill slurry.

[0071] S4. Weigh out 599.45g of high-sulfur tailings, 899.23g of Gobi aggregate, 49.62g of industrial magnesium slag, 195.17g of slag powder, 13.45g of quicklime, 45.17g of desulfurized gypsum, 2.8g of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in S3, and 88mL of... The composite activator solution prepared by S2 and 556 mL of water were placed together in a JJ-5 cement mortar mixer and stirred for 7 minutes to form a mixed filling slurry. The filling slurry was then poured into a standard mold and compacted using a vibratory table to remove air bubbles. The excess filling slurry beyond the mold was then scraped off with a metal ruler to smooth the surface of the cemented filling sample. The mold was then numbered and placed in a YH-40B standard constant temperature and humidity curing chamber at a temperature of 20±1℃ and a relative humidity of over 90% for curing. In this step, the magnesium slag reacts with sulfides in the tailings to form gypsum (CaSO4·2H2O), and CaO / MgO reacts with sulfides to form stable sulfates, reducing the risk of acid leaching. The composite activator prepared using this invention possesses both strong alkali activation and silicate network formation capabilities. Three-dimensional rod-shaped high-entropy alloy nanoparticles, through multi-dimensional synergistic effects such as mechanical reinforcement, sulfur solidification, and microstructure optimization, provide a new solution for industrial magnesium slag-based high-sulfur tailings filling bodies. In this step, the CaO contained in the magnesium slag reacts with sulfides (such as FeS2) in the high-sulfur tailings to generate CaSO4·2H2O (gypsum) and CaCO3, effectively solidifying sulfur and inhibiting sulfate corrosion and acid leaching. On the other hand, the slow hydration characteristics of MgO can compensate for the volume shrinkage caused by sulfide oxidation, reducing microcracks. In addition, the active SiO2 and Al2O3 in the magnesium slag participate in the geological polymerization reaction, forming a three-dimensional network structure, ensuring the backfill meets downhole filling requirements. Furthermore, the MgO in the magnesium slag forms a gel during long-term hydration, improving impermeability and sulfate corrosion resistance. In this step, high-sulfur tailings, Gobi aggregate, industrial magnesium slag, slag powder, quicklime, and desulfurized gypsum are weighed as composite high-sulfur tailings backfill materials.

[0072] S5. Curing and Performance Control: Early Curing: Curing for 7 days at 20±2℃ and ≥90% humidity promotes the slow hydration of MgO in magnesium slag and avoids expansion and cracking; Long-term Stability Treatment: Curing for 28 days at 20±2℃ and ≥90% humidity, due to the addition of three-dimensional rod-shaped high-entropy alloy nanoparticles and composite activator solution, the strength of the 28-day cemented filling body is significantly improved, and the strength value is much greater than that of the filling body using 100% cement.

[0073] Comparative Example 6: Except for step S2, in which 1.6g of phosphotungstic acid (PTA) was not added, all other steps were the same as in Example 3.

[0074] Figure 4This is a scanning electron microscope image of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Example 3 of the present invention. Figure 5 This is a transmission electron microscope image of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Example 3 of the present invention. As can be seen from the image, the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared by the present invention are uniform in shape and size. When the size of the material decreases to the nanoscale, more atoms are exposed, which greatly increases the number of active sites. Figure 6 This is a transmission electron microscope image of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Comparative Example 6 of this invention. A comparison between the high-entropy alloy nanoparticles prepared in Example 3 and Comparative Example 6 shows that phosphotungstic acid (PTA) clusters promote the formation of three-dimensional rod-shaped high-entropy alloy nanoparticles. Under the influence of phosphotungstic acid (PTA) clusters, these three-dimensional rod-shaped high-entropy alloy nanoparticles can form and remain stable under the drive of Coulomb forces and van der Waals forces. In this invention, due to the oxygen-rich surface, phosphotungstic acid (PTA) can act as a connector to achieve the aggregation of various metal oxides under covalent or non-covalent interactions. When phosphotungstic acid (PTA) clusters are not introduced into the multi-metal oxide system, only small nanoparticles can be obtained, and three-dimensional nanorods cannot be obtained. Figure 7 The pore size distribution curve of the N2 adsorption-desorption isotherm of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Example 3 of this invention confirms the mesoporous structure of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in this invention. The exposed active sites and anisotropic structure of the three-dimensional nanorods increase the contact area between the high-entropy alloy nanoparticles and the filling slurry, allowing them to be uniformly dispersed in the filling matrix. Through mechanical interlocking and chemical bonding, they enhance the interfacial bonding force between magnesium slag and tailings, reduce porosity, improve compactness, and optimize the rheological properties of the filling slurry.

[0075] Example 4

[0076] S1. Dry the industrial magnesium slag at 110℃ to constant weight, crush it, and then ball mill it for 7 hours. The high-sulfur tailings and Gobi aggregate need to be dried for later use. In this step, the high-sulfur tailings contain approximately 70% fine particles smaller than 38μm, classifying them as fine-grained tailings. The mineral phases of the high-sulfur tailings mainly consist of quartz, mica, gypsum, and chlorite, with a calcination weight of 17.03%. The Gobi aggregate is mainly composed of inert components, with particles smaller than 1mm accounting for 39.12%. The purpose of drying is to avoid the influence of moisture content on the concentration of the filling slurry.

[0077] S2. Preparation of the composite activator: Dissolve 1.66g of sodium hydroxide and 0.86g of cesium hydroxide in 100mL of deionized water. After sonication at 40kHz for 7min, heat the solution to 45℃ while stirring to obtain the composite activator solution. The CsOH added in this step has a much higher alkalinity than conventional alkali metal hydroxides, enabling it to more efficiently break the Si-O and Al-O bonds in the raw materials, release the active components, and shorten the induction period. Even at 11℃, CsOH maintains high reactivity, avoiding the delayed coagulation caused by low temperatures in traditional activators. Furthermore, Cs... + The ionic radius is significantly larger than that of Na. + This creates a looser ion coordination structure within the gel network, reducing shrinkage stress and inhibiting microcrack propagation. (Cs) + It can adsorb onto the surface of gel pores, reducing porosity and improving material density and impermeability. (Cs) + The resulting silicate network is more stable and has a lower dissolution rate than Na in acidic environments. + Low basicity and extended material lifespan. Cs-based polymers maintain structural stability even at temperatures above 800°C. The application of CsOH in this step balances high basicity activation with silicate network construction, thereby improving compressive strength.

[0078] S3. Preparation of three-dimensional rod-shaped high-entropy alloy nanoparticles: 1.6 g of phosphotungstic acid (PTA), 0.9 g of rhenium chloride, 1.6 g of ferric nitrate, 2.3 g of copper sulfate, 1.7 g of zirconium chloride, 3.8 g of manganese sulfate, 1.6 g of nickel nitrate, 0.8 g of tungsten chloride, and 0.7 g of ascorbic acid were dissolved in a mixed solvent of 20 mL ethanol, 15 mL oleylamine, 8 mL ethylene glycol, and 5 mL oleic acid. The solution was then transferred to a 100 mL microwave reactor, and the temperature was set to 149 °C for 5 min, followed by a holding time of 95 min. After the reaction, the nanoparticles were centrifuged to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles. In this step, under the influence of phosphotungstic acid clusters, these three-dimensional rod-shaped high-entropy alloy nanoparticles can be formed and remain stable under the drive of Coulomb forces and van der Waals forces. The presence of multi-element synergistic effects and a unique nanostructure (three-dimensional rod-like morphology) among Re, Fe, Cu, Zr, Mn, W, and Ni significantly improves the compressive strength and ductility of the backfill. The formation of a solid solution among these elements, through atomic size differences and lattice distortion, generates solid solution strengthening, further optimizing the microstructural stability of the backfill. These three-dimensional rod-shaped high-entropy alloy nanoparticles exhibit excellent corrosion resistance and thermal stability, resisting the oxidative erosion of active sulfides in high-sulfur tailings. These nanoparticles can be uniformly dispersed within the backfill matrix, enhancing the interfacial bonding between magnesium slag and the backfill through mechanical interlocking and chemical bonding, reducing porosity, improving density, and optimizing the rheological properties of the backfill slurry.

[0079] S4. Weigh out 779.45g of high-sulfur tailings, 931.23g of Gobi aggregate, 38.62g of industrial magnesia slag, 185.17g of slag powder, 22.45g of quicklime, 50.76g of desulfurized gypsum, 2.8g of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in S3, and 88mL of... The composite activator solution prepared by S2 and 595 mL of water were placed together in a JJ-5 cement mortar mixer and stirred for 6 minutes to form a mixed filling slurry. The filling slurry was then poured into a standard mold and compacted using a vibratory compaction table to remove air bubbles. The excess filling slurry beyond the mold was then scraped off with a metal ruler to smooth the surface of the cemented filling sample. The mold was then numbered and placed in a YH-40B standard constant temperature and humidity curing chamber at a temperature of 20±1℃ and a relative humidity of over 90% for curing. In this step, the magnesium slag reacts with sulfides in the tailings to form gypsum (CaSO4·2H2O), and CaO / MgO reacts with sulfides to form stable sulfates, reducing the risk of acid leaching. The composite activator prepared using this invention possesses both strong alkali activation and silicate network formation capabilities. Three-dimensional rod-shaped high-entropy alloy nanoparticles, through multi-dimensional synergistic effects such as mechanical reinforcement, sulfur solidification, and microstructure optimization, provide a new solution for industrial magnesium slag-based high-sulfur tailings filling bodies. In this step, the CaO contained in the magnesium slag reacts with sulfides (such as FeS2) in the high-sulfur tailings to generate CaSO4·2H2O (gypsum) and CaCO3, effectively solidifying sulfur and inhibiting sulfate corrosion and acid leaching. On the other hand, the slow hydration characteristics of MgO can compensate for the volume shrinkage caused by sulfide oxidation, reducing microcracks. In addition, the active SiO2 and Al2O3 in the magnesium slag participate in the geological polymerization reaction, forming a three-dimensional network structure, ensuring the backfill meets downhole filling requirements. Furthermore, the MgO in the magnesium slag forms a gel during long-term hydration, improving impermeability and sulfate corrosion resistance. In this step, high-sulfur tailings, Gobi aggregate, industrial magnesium slag, slag powder, quicklime, and desulfurized gypsum are weighed as composite high-sulfur tailings backfill materials.

[0080] S5. Curing and Performance Control: Early Curing: Curing for 7 days at 20±2℃ and ≥90% humidity promotes the slow hydration of MgO in magnesium slag and avoids expansion and cracking; Long-term Stability Treatment: Curing for 28 days at 20±2℃ and ≥90% humidity, due to the addition of three-dimensional rod-shaped high-entropy alloy nanoparticles and composite activator solution, the strength of the 28-day cemented filling body is significantly improved, and the strength value is much greater than that of the filling body using 100% cement.

[0081] Comparative Example 7 was identical to Example 4 except that 1.1g of ammonium perrylate and 1.9g of sodium tungstate were not added in step S3.

[0082] Comparative Example 8: Except for step S3, in which 2.1g of cobalt nitrate was not added, all other steps were the same as in Example 4.

[0083] Comparative Example 9: Except for step S3, in which 3.8g of copper sulfate was not added, all other steps were the same as in Example 4.

[0084] Comparative Example 10: Except for step S4, in which three-dimensional rod-shaped high-entropy alloy nanoparticles are not added, all other steps are the same as in Example 4.

[0085] Figure 8 This is a transmission electron microscope image of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in Comparative Example 7 of this invention. Figure 8 and Figure 4 In contrast, as can be seen from the figure, without the participation of rhenium and tungsten metals, the three-dimensional rod-shaped nanoparticles are prone to agglomeration, which is not conducive to their application in filling slurries. The slump of this invention is measured using a slump cone, commonly used in concrete experiments. The filling slurries prepared in Example 4 and Comparative Examples 7-10 of this invention are loaded into the slump cone, vibrated according to standards, and then the slump cone is lifted vertically and steadily. The difference between the final slump height under the self-weight of the filling slurry and the top of the slump cone is measured and recorded as the slump. The spread diameter of the filling slurry in the horizontal plane is also measured and recorded as the spread. Slump and spread are manifestations of the flow properties of filling slurries; generally, the larger the slump and spread, the better the flow properties of the filling slurry. According to Table 3, the addition of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in this invention can improve the flow properties of high-sulfur tailings filling slurries, enabling them to meet the requirements of horizontal gravity flow and pipeline transportation. The reason is speculated to be that multiple metallic elements such as Re, Fe, Cu, Zr, Mn, W and Ni form a solid solution, which strengthens the solid solution through differences in atomic size and lattice distortion, further optimizing the microstructure stability of the filling.

[0086] Table 3

[0087] Example 4 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Slump / cm 28.5 27.5 26.5 26.0 25.0 Spread / cm 84.5×85.0 70.0×66.5 63.0×67.5 62.0×65.0 60.0×58.0

[0088] The above-described embodiments are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of protection of the present invention. It should be noted that for those skilled in the art, any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the scope of protection of the present invention.

Claims

1. A method for preparing high-sulfur tailings backfill using industrial magnesium slag, characterized in that: The specific operating steps are as follows: S1. Dry the industrial magnesium slag at 90-120 ℃ to constant weight, crush it, and then put it into a ball mill for ball milling for 6-8 hours; high sulfur tailings and Gobi aggregate need to be dried for later use. S2. Dissolve 1.47-2.94 g of sodium hydroxide and 0.48-0.96 g of cesium hydroxide in 100 mL of deionized water, sonicate at 40 kHz for 5-10 min, and then heat the solution to 43-47 ℃ while stirring to obtain the composite activator solution. S3. Dissolve 1.4-1.9 g of phosphotungstic acid, 0.7-1.2 g of rhenium chloride, 1.1-2.3 g of ferric nitrate, 1.6-3.3 g of copper sulfate, 1.5-1.9 g of zirconium chloride, 3.2-4.1 g of manganese sulfate, 0.9-2.1 g of nickel nitrate, 0.6-0.9 g of tungsten chloride, and 0.5-0.8 g of ascorbic acid in a mixed solvent of 20 mL ethanol, 15 mL oleylamine, 8 mL ethylene glycol, and 5 mL oleic acid. Then transfer the solution to a 100 mL microwave reactor, set the temperature to 143-155 ℃, the heating time to 5 min, and the holding time to 80-110 min. After the reaction is complete, centrifuge to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles. S4. Weigh out 527.67-879.45 g of high-sulfur tailings, 879.45-1231.23 g of Gobi aggregate, 29.31-58.62 g of industrial magnesium slag, 175.86-205.17 g of slag powder, 11.73-23.45 g of quicklime, 35.17-52.76 g of desulfurized gypsum, 1.8-3.8 g of the three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in step S3, 78-96 mL of the composite activator solution prepared in step S2, and 548-656 mL of water, and place them together in a JJ-5 cement mortar mixer. Stir for 5-8 hours. After min, a mixed filling slurry is formed; then the filling slurry is injected into a standard mold and compacted by vibration table to remove air bubbles; then a metal ruler is used to scrape off the filling slurry that exceeds the mold, so that the surface of the cemented filling sample is smoothed, and the mold is numbered and placed in a standard constant temperature and humidity curing chamber for curing.

2. The preparation method for improving the performance of high-sulfur tailings backfill using industrial magnesium slag according to claim 1, characterized in that: The high-sulfur tailings contain 70% fine-grained tailings.

3. A method for preparing a high-sulfur tailings backfill body using industrial magnesium slag according to claim 1 or 2, characterized in that: The mineral phases of the high-sulfur tailings are mainly composed of quartz, mica, gypsum and chlorite, with a calcination vector of 17.03%.

4. The preparation method for improving the performance of high-sulfur tailings backfill using industrial magnesium slag according to claim 1, characterized in that: In step S1, industrial magnesium slag is dried to constant weight at 90 °C, crushed, and then ball-milled for 8 h.

5. A method for preparing a high-sulfur tailings backfill body using industrial magnesium slag according to claim 1 or 4, characterized in that: In step S1, industrial magnesium slag is dried to constant weight at 120 °C, crushed, and then ball-milled for 6 hours.

6. The preparation method for improving the performance of high-sulfur tailings backfill using industrial magnesium slag according to claim 1, characterized in that: In step S3, 1.4 g of phosphotungstic acid, 0.7 g of rhenium chloride, 1.1 g of ferric nitrate, 1.6 g of copper sulfate, 1.5 g of zirconium chloride, 3.2 g of manganese sulfate, 0.9 g of nickel nitrate, 0.6 g of tungsten chloride, and 0.5 g of ascorbic acid are dissolved in a mixed solvent of 20 mL of ethanol, 15 mL of oleylamine, 8 mL of ethylene glycol, and 5 mL of oleic acid. The solution is then transferred to a 100 mL microwave reactor, and the temperature is set to 143 °C for 5 min, followed by a holding time of 80 min. After the reaction is completed, the mixture is centrifuged to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles.

7. A method for preparing a high-sulfur tailings backfill body using industrial magnesium slag according to claim 1 or 6, characterized in that: In step S3, 1.9 g of phosphotungstic acid, 1.2 g of rhenium chloride, 2.3 g of ferric nitrate, 3.3 g of copper sulfate, 1.9 g of zirconium chloride, 4.1 g of manganese sulfate, 2.1 g of nickel nitrate, 0.9 g of tungsten chloride, and 0.8 g of ascorbic acid are dissolved in a mixed solvent of 20 mL of ethanol, 15 mL of oleylamine, 8 mL of ethylene glycol, and 5 mL of oleic acid. The solution is then transferred to a 100 mL microwave reactor, and the temperature is set to 155 °C for 5 min, followed by a holding time of 110 min. After the reaction is completed, the mixture is centrifuged to obtain three-dimensional rod-shaped high-entropy alloy nanoparticles.

8. The preparation method for improving the performance of high-sulfur tailings backfill using industrial magnesium slag according to claim 1, characterized in that: In step S4, 879.45 g of high-sulfur tailings, 1231.23 g of Gobi aggregate, 58.62 g of industrial magnesium slag, 205.17 g of slag powder, 23.45 g of quicklime, 52.76 g of desulfurized gypsum, 3.8 g of three-dimensional rod-shaped high-entropy alloy nanoparticles prepared in step S3, 85 mL of composite activator solution prepared in step S2, and 656 mL of water are weighed and placed into a JJ-5 cement mortar mixer. After stirring for 5 minutes, a mixed filling slurry is formed. The filling slurry is then injected into a standard mold and compacted using a vibrating table to remove air bubbles. The excess filling slurry beyond the mold is then scraped off with a metal ruler to smooth the surface of the cemented filling sample. The mold is then numbered and placed in a standard constant temperature and humidity curing chamber for curing.

9. Three-dimensional rod-shaped high-entropy alloy nanoparticles prepared by the preparation method according to any one of claims 1-8.

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