Mine filling material and preparation method thereof

Abstract

The invention relates to the technical field of comprehensive utilization of building materials and solid waste resources, and particularly discloses a mine filling material and a preparation method thereof. The mine filling material provided by the invention comprises the following raw material components in percentage by mass: 75%-80% of lithium tailings, 8%-10% of smelting slag, 5%-8% of cement, 5%-8% of yellow phosphorus slag, 1%-2% of waste silicon slag, 0.4%-1% of an alkali activator and 0.02%-0.05% of vinyl terephthalic acid. The alkali activator comprises caustic soda, gypsum and a water reducing agent. According to the mine filling material provided by the invention, the components and the proportion of the mine filling material are optimized, the solid waste utilization rate is increased, the problem that the existing lithium tailings are difficult to fully utilize is solved, the low-temperature strength of the mine filling material is remarkably improved, and meanwhile, the negative influence of the mine filling material on the environment is reduced.

Description

Technical Field

[0001] This invention relates to the field of building materials and comprehensive utilization of solid waste resources, and in particular to a mine filling material and its preparation method. Background Technology

[0002] Industrial solid waste emissions continue to rise, with huge stockpiles of various solid wastes such as lithium tailings and smelting slag. These wastes not only occupy a large amount of land resources, but also contain heavy metals such as lead, cadmium, and chromium, as well as harmful chemical components that can easily pollute groundwater and soil through rainwater leaching and soil infiltration, causing serious environmental safety hazards and threatening the surrounding ecological environment and human health. The harmless disposal and resource utilization of solid waste has become a major environmental problem that urgently needs to be solved.

[0003] Currently, while there are attempts to use industrial solid waste to replace cement or river sand in the preparation of backfill materials, these are mostly limited to simple addition and replacement of single or small amounts of solid waste, failing to achieve large-scale synergistic disposal of multi-source solid waste. Such technologies not only have limited solid waste disposal capacity, making it difficult to fundamentally solve the problem of solid waste accumulation, but also suffer from poor backfill performance, especially insufficient toughness and poor crack resistance, which cannot meet the bearing requirements of complex mine goaf areas. At the same time, the complex composition of multi-source solid waste and the weak synergistic effect between components can easily lead to uneven backfill structure and unstable strength, as well as poor solidification of heavy metals, posing secondary environmental risks. These technical bottlenecks severely limit the large-scale application of industrial solid waste in the field of mine backfilling.

[0004] Therefore, developing a new type of filling material system that can efficiently absorb multi-source industrial solid waste on a large scale, while endowing the filling body with excellent mechanical properties and good environmental stability, can not only effectively reduce the cost of filling materials and reduce energy consumption and carbon emissions, but also realize the resource utilization and harmless disposal of industrial solid waste, taking into account mine safety production, ecological environmental protection and resource recycling. Summary of the Invention

[0005] In view of this, the present invention provides a mine backfill material and its preparation method. The mine backfill material provided by the present invention uses lithium tailings as the main material, supplemented by smelting slag, yellow phosphorus slag, cement, waste silica slag and vinyl terephthalic acid, which significantly improves the activity index of lithium tailings, enhances the early strength of the mine backfill material under low temperature conditions, solves the pain point of the inability to utilize lithium tailings as a resource, and has low preparation cost and excellent strength under low temperature conditions.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: This invention provides a mine backfill material comprising the following raw material components in the following mass percentages: lithium tailings 75%~80%, smelting slag 8%~10%, cement 5%~8%, yellow phosphorus slag 5%~8%, waste silicon slag 1%~2%, alkali activator 0.4%~1%, and vinyl terephthalic acid 0.02%~0.05%; The alkaline activator includes caustic soda, gypsum, and water-reducing agent.

[0007] Lithium ore processing generates a large amount of lithium tailings, whose mineral phase is glassy silicate. These tailings are stable in physicochemical properties but have a low activity index, making them difficult to hydrate with cementing materials and thus unable to provide a binding effect; they can only be used as inert aggregates. Currently, the highest proportion of lithium tailings added to backfill materials is only 50%, which is insufficient for full utilization and increases engineering costs. Furthermore, the low-temperature environment in mines in high-altitude and cold regions delays the hydration reaction, leading to insufficient strength of the backfill and posing safety hazards. Therefore, the purpose of this study is to provide a novel mine backfill material that improves the utilization rate of lithium tailings and enhances the early strength of the backfill material under low-temperature conditions, thus addressing the aforementioned problems.

[0008] In the mine backfill material provided by this invention, a specific alkali activator can dissolve rapidly, creating a strongly alkaline environment that disrupts the Si-O-Al framework of the glassy phase in lithium tailings, smelting slag, and yellow phosphorus slag minerals, releasing active silica-alumina monomers. This specific alkali activator can also rapidly activate the active silica-alumina phase in smelting slag, yellow phosphorus slag, and lithium tailings, forming a three-dimensional aluminosilicate geopolymer network, thus improving the low-temperature strength of the mine backfill material. Cement hydration and the dissolution of yellow phosphorus slag provide sufficient calcium ions, which react with sulfate ions in the alkali activator to form ettringite, significantly enhancing the low-temperature early strength of the mine backfill material. Simultaneously, subsequent Na… + or Ca 2+ Under the effect of charge balance, the active silica-alumina phase reacts with the phosphate ions released by the yellow phosphorus slag, and recombines into a highly durable gel through a condensation reaction, generating stable minerals such as hydroxyapatite. This achieves in-situ chemical bonding and fixation of heavy metals in the slag, reducing the environmental pollution of mine backfill materials.

[0009] The carboxyl groups in vinyl terephthalic acid (VTI) can coordinate and ionize with metal ions such as calcium and aluminum ions in cement and smelting slag hydration products. Furthermore, the vinyl groups in VTI can polymerize under alkaline conditions to form an organic polymer network, giving mine backfill materials certain toughness, crack resistance, and deformation capacity, thus preventing solidification shrinkage cracking and improving the low-temperature strength of the backfill materials. Simultaneously, because the carboxyl groups in VTI have a strong chelating effect on certain metal ions, they can chemically fix easily leached trace amounts of harmful substances in solid waste. Vinyl terephthalic acid (VTI) can effectively encapsulate lithium tailings, smelting slag, yellow phosphorus slag, and waste silica slag cementitious material particles, preventing material agglomeration and thus greatly improving the fluidity and workability of the slurry. It also significantly enhances the early and long-term strength of mine backfill materials under low-temperature conditions. Furthermore, VTI can adsorb onto the surface of mineral materials, slowing down the early hydration rate and preventing increased internal defects in the mine backfill material due to premature hydration, local agglomeration, or bleeding segregation. Simultaneously, it makes the hydration products more uniform, significantly improving the density and low-temperature strength of the mine backfill material. Waste silica slag can further fill the microscopic voids in the mine backfill material, making the structure more compact and further enhancing the mechanical properties of the mine backfill material.

[0010] The mine filling material provided by this invention has a solid waste content of >95% and low raw material cost. Furthermore, through the rational design of the components and proportions of the mine filling material, this invention significantly improves the low-temperature strength of the mine filling material through synergistic effects, fixes the heavy metals in the mine filling material, and has leaching toxicity far below the national standard, thus solving the disposal problem of hazardous wastes such as yellow phosphorus slag. In addition, the raw materials of the mine filling material provided by this invention are readily available, the process is simple, and it is easy to promote industrialization.

[0011] Preferably, the lithium tailings have a particle size of 70-120 mesh.

[0012] Preferably, the water content of the lithium tailings is 15wt%~20wt%.

[0013] Preferably, the lithium tailings contain ≥80% SiO2 and >9% total content of Al2O3, Li2O and CaO.

[0014] Preferably, the total content of SiO2, Al2O3, Li2O and CaO in the lithium tailings is ≥95%.

[0015] This invention improves the utilization rate of lithium tailings and significantly enhances the mechanical properties of mine backfill materials by further limiting the content of chemical components in lithium tailings.

[0016] It should be noted that all the contents mentioned above refer to mass percentages.

[0017] Preferably, the particle size of the smelting slag is 120-200 mesh.

[0018] Preferably, the content of CaO in the smelting slag is 30%~40%, and the content of SiO2 is 60%~70%.

[0019] Preferably, the smelting slag includes at least one of lead-zinc smelting slag, nickel-cobalt smelting slag, tin smelting slag, magnesium smelting slag, silicon smelting slag, or steel slag.

[0020] It should be further noted that when selecting at least two components from the smelting slag, using any proportion can achieve a comparable effect, and there is no need to further limit the proportion used.

[0021] In a preferred embodiment, the cement is PF cement, and the mass percentage of fly ash in the cement is 30% to 40%.

[0022] Preferably, the particle size of the yellow phosphorus slag is 80-120 mesh.

[0023] Preferably, the P2O5 content in the yellow phosphorus slag is 2% to 3.5%.

[0024] Preferably, the particle size of the waste silicon slag is 5~30μm, and the activity index after 7 days is not less than 85%.

[0025] Preferably, the alkali activator comprises the following components by mass percentage: caustic soda 2-12%, gypsum 85%-95%, and water-reducing agent 2%-8%.

[0026] The preferred alkali activator can improve the early strength of mine backfill materials under low temperature conditions. By limiting the composition and specific ratio of the water-reducing agent, the water-material ratio of the backfill material can also be reduced. Gypsum regulates the setting and participates in the early formation of ettringite. Caustic soda activates the hydration reaction balance of the backfill material, so that the strength increases rapidly in the early stage.

[0027] More preferably, the gypsum includes at least one of phosphogypsum, titanium gypsum, fluorogypsum, citric acid gypsum, salt gypsum, mirabilite gypsum, or copper gypsum.

[0028] More preferably, the gypsum contains two bound water molecules and has a particle size of 200 mesh.

[0029] It should be further noted that when selecting at least two components in plaster, using any ratio can achieve a comparable effect, and there is no need to further limit the ratio used.

[0030] More preferably, the water-reducing agent is a polycarboxylate high-performance water-reducing agent.

[0031] More preferably, the water-reducing agent is purchased from Shanghai Yingshan New Material Technology Co., Ltd., and the model is PC-100.

[0032] This invention provides a method for preparing the above-mentioned mine backfill material, comprising the following steps: Weigh each component according to the mass ratio, mix the weighed components evenly, and then add water to obtain the mine filling material.

[0033] Preferably, the water-to-material ratio is (0.14~0.17):1.

[0034] It should be further explained that the water-to-material ratio in this invention refers to the mass ratio of water to the mixed dry material in the mine backfill material excluding water. The mixed dry material refers to the substances other than the water content in the lithium tailings in the mine backfill material.

[0035] The raw materials for the mine backfill material provided by this invention are readily available and have low production costs, making it an ideal choice for mine backfill materials. Furthermore, most mines are deep and operate in low-temperature environments year-round, where ordinary cementitious materials are prone to freezing and failure to solidify. The mine backfill material provided by this invention can adapt to backfill environments of 0-5℃ and maintains excellent compressive strength after 28 days. In this invention, the synergistic effect of the components results in a mine backfill material with good fluidity, facilitating transport and conveying. It also exhibits higher strength after 28 days of final setting and shows no shrinkage after solidification, providing a new approach to mine backfill material systems. In addition, the mine backfill material provided by this invention improves the comprehensive utilization level of lithium tailings resources and has broad application prospects in the field of solid waste resource utilization. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] In the embodiments and comparative examples provided by this invention, unless otherwise specified, the lithium tailings have a particle size of 70-120 mesh, a water content of 15 wt%, a SiO2 content of 89%, and a total content of Al2O3, Li2O, and CaO of 10%; the cement is PF cement, and the fly ash content is 40% by mass; the yellow phosphorus slag has a particle size of 80-120 mesh, and a P2O5 content of 2%; the waste silicon slag has a particle size of 5-30 μm, and a 7-day activity index of not less than 85%; the water-reducing agent is a polycarboxylate high-performance water-reducing agent, purchased from Shanghai Yingshan New Material Technology Co., Ltd., model PC-100.

[0038] Unless otherwise specified, the raw materials and reagents used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0039] Example 1 This embodiment provides a mine backfill material comprising the following raw material components by mass percentage: 75% lithium tailings, 8.5% smelting slag, 8% cement, 6% yellow phosphorus slag, 2% waste silicon slag, 0.45% alkali activator, and 0.05% vinyl terephthalic acid; The alkali activator comprises the following components by mass percentage: 10% caustic soda, 85% gypsum, and 5% water-reducing agent; The gypsum is a mixture of citric acid gypsum, salt gypsum, and copper gypsum in a mass ratio of 2:5:3; The smelting slag has a particle size of 120-200 mesh, a CaO content of 35%, a SiO2 content of 60%, and includes a mixture of lead-zinc smelting slag and nickel-cobalt smelting slag in a mass ratio of 3:7. This embodiment provides a method for preparing the above-mentioned mine backfill material, including the following steps: Weigh each component according to the mass ratio, mix the weighed components evenly, and then add water to obtain the mine filling material; The water-to-material ratio is 0.14:1. The water-to-material ratio refers to the mass ratio of water to the mixed dry material in the mine backfill material excluding water. The mixed dry material refers to the substances other than the water content in the lithium tailings in the mine backfill material.

[0040] Example 2 This embodiment provides a mine backfill material comprising the following raw material components by mass percentage: 80% lithium tailings, 8% smelting slag, 5% cement, 5% yellow phosphorus slag, 1% waste silicon slag, 0.95% alkali activator, and 0.05% vinyl terephthalic acid; The alkali activator comprises the following components by mass percentage: caustic soda 12%, gypsum 85%, and water-reducing agent 3%; The gypsum is a mixture of phosphogypsum, titanium gypsum, fluorogypsum and mirabilite in a mass ratio of 2:4:1:3. The smelting slag has a particle size of 120-200 mesh, a CaO content of 35%, a SiO2 content of 60%, and includes a mixture of lead-zinc smelting slag and nickel-cobalt smelting slag in a mass ratio of 3:7. This embodiment provides a method for preparing the above-mentioned mine backfill material, including the following steps: Weigh each component according to the mass ratio, mix the weighed components evenly, and then add water to obtain the mine filling material; The water-to-material ratio is 0.14:1. The water-to-material ratio refers to the mass ratio of water to the mixed dry material in the mine backfill material excluding water. The mixed dry material refers to the substances other than the water content in the lithium tailings in the mine backfill material.

[0041] Example 3 This embodiment provides a mine backfill material comprising the following raw material components by mass percentage: 77% lithium tailings, 10% smelting slag, 5% cement, 5% yellow phosphorus slag, 1.95% waste silicon slag, 1% alkali activator, and 0.05% vinyl terephthalic acid; The alkali activator comprises the following components by mass percentage: 2% caustic soda, 95% gypsum, and 3% water-reducing agent; The gypsum is a mixture of citric acid gypsum, salt gypsum, and copper gypsum in a mass ratio of 2:5:3; The particle size of the smelting slag is 120~200 mesh, the CaO content in the smelting slag is 35%, the SiO2 content is 60%, and the smelting slag includes a mixture of tin smelting slag, magnesium smelting slag, silicon smelting slag and steel slag in a mass ratio of 2:3:3:2. This embodiment provides a method for preparing the above-mentioned mine backfill material, including the following steps: Weigh each component according to the mass ratio, mix the weighed components evenly, and then add water to obtain the mine filling material; The water-to-material ratio is 0.14:1. The water-to-material ratio refers to the mass ratio of water to the mixed dry material in the mine backfill material excluding water. The mixed dry material refers to the substances other than the water content in the lithium tailings in the mine backfill material.

[0042] Comparative Example 1 This comparative example provides a mine filling material, which differs from Example 1 in that: the caustic soda in the alkali activator is replaced with an equal amount of sodium bicarbonate; The other components and preparation methods remain unchanged, and will not be repeated here.

[0043] Comparative Example 2 This comparative example provides a mine filling material that differs from Example 1 in that vinyl terephthalic acid is replaced with an equal amount of acrylic acid. The other components and preparation methods remain unchanged, and will not be repeated here.

[0044] Comparative Example 3 This comparative example provides a mine filling material, which differs from Example 1 in that: the smelting slag and yellow phosphorus slag are replaced with an equal amount of 200 mesh fly ash, and the fly ash is secondary fly ash. The other components and preparation methods remain unchanged, and will not be repeated here.

[0045] Comparative Example 4 This comparative example provides a mine backfill material comprising the following raw material components by mass percentage: 90% lithium mica ultrafine tailings and 10% composite activated solid waste-based cementitious material; The mixed raw materials and PO42.5 cement are mixed at a mass ratio of 3:2 to form a composite activated solid waste-based cementitious material; The mixed raw materials consist of the following raw material components in the indicated mass percentages: The composition is as follows: lithium tailings 40%, steel slag 20%, desulfurized gypsum 20%, wollastonite powder 10%, and sodium silicate 10%. The average particle sizes of lithium tailings, steel slag, desulfurized gypsum, wollastonite powder, and sodium silicate are 270 mesh, 50-70 mesh, 230-400 mesh, 230-500 mesh, and 170-230 mesh, respectively. The chemical composition of lithium slag, based on oxides, is as follows: SiO2 content is 20t%~30wt%, CaO content is 30t%~40wt%, Al2O3 content is 15t%~25wt%, SO3 content is 5t%~15wt%, and loss on ignition is 5t%~10wt%. The chemical composition of steel slag, based on oxides, is as follows: SiO2 content is 15t%~25wt%, CaO content is 40t%~50wt%, Al2O3 content is 5t%~15wt%, Fe2O3 content is 5t%~15wt%, SO3 content is 1t%~5wt%, and loss on ignition is 10t%~15wt%. The purity of CaSO4·2H2O in the desulfurized gypsum is greater than 95 wt%. The purity of CaO in the wollastonite powder is greater than 45 wt%, and the purity of SiO2 is greater than 50 wt%. The purity of Na2SiO3 in the sodium silicate is greater than 90 wt%. After classification, the average characteristic particle sizes of the ultrafine lepidolite tailings obtained are 5.31 μm, 16.92 μm, 40.83 μm and 145.86 μm, respectively. 600-mesh ultrafine particles shall account for no less than 50%; The above raw materials were mixed and steamed in saturated steam at 250℃ and 1.2MPa for 4 hours; then dried in a drying oven at 85℃ for 16 hours, turning the mixture every 8 hours during the drying process; finally, the mixture was ground in a planetary ball mill and the resulting powder was screened using an ultrasonic vibrating screen to obtain a specific surface area of ​​550 m². 2 Mixed raw materials of / kg or more; This comparative example provides a method for preparing the above-mentioned mine backfill material, including the following steps: Weigh each component according to the mass ratio, mix the weighed components evenly, and then add water to obtain the mine filling material; the water-to-material ratio is 0.14:1.

[0046] Example of effect The mine filling materials provided in the examples and comparative examples were poured into 70.7mm×70.7mm×70.7mm construction mortar molds. After pouring, they were transferred to a low-temperature curing chamber with an average temperature of 3°C. The performance of the mine backfill materials provided in the above embodiments and comparative examples was tested, and the specific test indicators are as follows: The compressive strength of the prepared mine filling material was tested in accordance with GB / T 17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)". Heavy metal leaching tests were conducted in accordance with GB 5085.3-2007 "Identification Standard for Hazardous Waste - Leaching Toxicity Identification". The specific test results are shown in Table 1.

[0047] Table 1

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A mine filling material, characterized in that, The raw material components include the following percentages by weight: lithium tailings 75%~80%, smelting slag 8%~10%, cement 5%~8%, yellow phosphorus slag 5%~8%, waste silicon slag 1%~2%, alkali activator 0.4%~1%, and vinyl terephthalic acid 0.02%~0.05%; The alkaline activator includes caustic soda, gypsum, and water-reducing agent.

2. The mine filling material as described in claim 1, characterized in that, The lithium tailings have a particle size of 70-120 mesh; The lithium tailings contain ≥80% SiO2 and >9% total content of Al2O3, Li2O and CaO. The total content of SiO2, Al2O3, Li2O and CaO in the lithium tailings is ≥95%.

3. The mine filling material as described in claim 1, characterized in that, The particle size of the smelting slag is 120~200 mesh; The smelting slag contains 30% to 40% CaO and 60% to 70% SiO2.

4. The mine filling material as described in claim 1, characterized in that, The cement is PF cement, and the mass percentage of fly ash in the cement is 30%~40%.

5. The mine filling material as described in claim 1, characterized in that, The particle size of the yellow phosphorus slag is 80-120 mesh.

6. The mine filling material as described in claim 1 or 5, characterized in that, The P2O5 content in the yellow phosphorus slag is 2%~3.5%.

7. The mine filling material as described in claim 1, characterized in that, The waste silicon slag has a particle size of 5~30μm and an activity index of not less than 85% after 7 days.

8. The mine filling material as described in claim 1, characterized in that, The alkali activator comprises the following components by mass percentage: caustic soda 2-12%, gypsum 85%-95%, and water-reducing agent 2%-8%.

9. A method for preparing a mine backfill material according to any one of claims 1 to 8, characterized in that, Includes the following steps: Weigh each component according to the mass ratio, mix the weighed components evenly, and then add water to obtain the mine filling material.

10. The method for preparing mine backfill material as described in claim 9, characterized in that, The water-to-material ratio is (0.14~0.17):1.

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