Green low-carbon preparation method of iron-rich tailing heavy metal stabilization and waterproof mortar

Abstract

The invention provides a green low-carbon preparation method of iron-rich tailing heavy metal stabilization and waterproof mortar, and belongs to the field of resource utilization. After the prepared slurry is cured, a nano hierarchical structure of framework supporting, interface bridging and gel bonding is formed, the performance is excellent when the mixing amount of tailings reaches 75 wt%, and the compressive strength reaches 15.5 MPa after the slurry is cured for one day and is increased to 20.0 MPa after the slurry is cured for 28 days. After the mortar is cured for 1 day, the fixing rates of the heavy metals Mn, Zn and Pb which can be leached from the tailings respectively reach 99.74%, 98.10% and 99.55%, the GB / T30760-2014 requirements are met, and the harmlessness of toxic solid wastes is realized; the compact nanometer hierarchical structure endows the mortar with excellent waterproofness, and the waterproofness is far better than that of ordinary mortar. The method has both low carbon and economic values, the CO2 emission amount is about 285.6 to 292.1 kg / t, and the production cost is about 293.5 to 583.3 CNY / t.

Description

Technical Field

[0001] This invention relates to the field of resource utilization, specifically to a green and low-carbon method for stabilizing heavy metals in iron-rich tailings and preparing waterproof mortar. Background Technology

[0002] Tailings are rich in valuable elements such as silicon, aluminum, and calcium, making them a potentially ideal raw material for mortar. Utilizing tailings to prepare mortar not only contributes to the sustainable development of low-carbon cement and concrete but also promotes sustainable mine management. However, due to the high crystallinity of raw tailings, these elements typically exist in an inert form, resulting in low cementitious reactivity and low strength in the prepared mortar, thus limiting the application of tailings in mortar. Summary of the Invention

[0003] This invention provides a green and low-carbon preparation method for heavy metal stabilization and waterproof mortar made from iron-rich tailings. The mortar prepared by this invention has the strength requirement to meet that of M15 cement mortar and has good waterproof performance.

[0004] This invention provides a method for rapidly preparing waterproof mortar from iron-rich tailings based on mechanochemistry, comprising the following steps: Tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent are mixed and then ball-milled. The silane coupling agent undergoes hydrolysis and polymerization, and self-assembly to generate a cementitious material with a multi-level ordered structure, thus obtaining a slurry. The tailings sand includes one or both of iron tailings sand and copper tailings sand. The slurry is cured to obtain the iron-rich tailings waterproof mortar; The iron-rich tailings waterproof mortar includes several nano-units, and each nano-unit includes silica and calcium iron aluminum silicate hydrate coated on the surface of the silica. The silicon dioxide and calcium iron aluminum silicate hydrate are linked by a silanol compound; The interconnected nanounits are bonded together by calcium iron aluminum silicate hydrate.

[0005] Preferably, by mass fraction, the iron tailings sand comprises 0.395% Na2O, 2.315% MgO, 8.256% Al2O3, 38.959% SiO2, 0.129% P2O5, 10.591% SO3, 0.048% Cl, 0.655% K2O, 12.887% CaO, 0.367% TiO2, 3.926% MnO, 20.462% Fe2O3, 0.041% Co3O4, 0.078% CuO, 0.46% ZnO, 0.01% Rb2O, 0.01% SrO, 0.015% ZrO2, 0.395% PbO, and the balance being impurities.

[0006] Preferably, the copper tailings sand, by mass fraction, comprises 0.538% Na2O, 1.949% MgO, 8.211% Al2O3, 46.697% SiO2, 0.33% P2O5, 0.39% SO3, 0.037% Cl, 1.03% K2O, 0.89% CaO, 0.311% TiO2, 0.427% MnO, 8.924% Fe2O3, 0.169% CuO, 0.016% ZnO, 0.008% Rb2O, 0.014% SrO, 0.011% ZrO2, 0.047% PbO, and the balance being impurities.

[0007] Preferably, the mass of the quicklime is 18-22.48% of the total mass of tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent; The mass of the tailings sand is 50-55% of the total mass of tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent; The mass of the water is 25.36-25.8% of the total mass of tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent; The mass of the silane coupling agent is 0.55~1.28% of the total mass of tailings sand, quicklime, water, glacial acetic acid and silane coupling agent.

[0008] Preferably, the silane coupling agent includes one or both of 3-aminopropyltriethoxysilane and allyltriethoxysilane.

[0009] Preferably, the mass of the glacial acetic acid is 0.4 to 0.87% of the total mass of tailings sand, quicklime, water, glacial acetic acid and silane coupling agent.

[0010] Preferably, the ball milling is carried out in a high-energy oscillating impact ball mill, and the ball milling uses steel grinding balls with a radius of 10 mm, and the slurry volume accounts for 1 / 8 to 1 / 7 of the ball mill container volume.

[0011] The ball milling speed is 800~900 r / min, and the time is 2~11 min.

[0012] Preferably, the curing temperature is 20~30℃, the relative humidity is 50~60%, and the time is 1~28 days.

[0013] The present invention also provides a waterproof mortar for iron-rich tailings prepared by the method described in the above technical solution, characterized in that it comprises a plurality of nanounits, wherein each nanounit comprises silica and calcium iron aluminum silicate hydrate coated on the surface of the silica. The silicon dioxide and calcium iron aluminum silicate hydrate are linked by a silanol compound; The interconnected nanounits are bonded together by calcium iron aluminum silicate hydrate.

[0014] The present invention also provides the application of the iron-rich tailings waterproof mortar described above in waterproof wall bricks or road filling.

[0015] This invention revolutionizes the process of tailings resource utilization through an integrated synergy of "physical crushing-chemical transformation-structural reconstruction." This integrated process is the fundamental reason why the material can be prepared rapidly, with low energy consumption and high efficiency: This invention releases active ions such as calcium, silicon, and iron from the inert lattice of the mortar through ball milling, improving the utilization rate of active ions and thus increasing the strength of the mortar. Subsequently, the local high temperature and pressure caused by mechanical force during ball milling drive the condensation of free silicon-oxygen units, while simultaneously driving the Si-OH generated by the hydrolysis of the silane coupling agent to hydrolyze and condense with the Si-OH on the surface of the reconstructed silicon-oxygen network to construct a siloxane network containing C=C bonds. The oxygen-containing groups on the surface of the siloxane network preferentially adsorb Ca. 2+ A double electric layer is formed, and under mechanical force, it hydrates to form an amorphous calcium gel. Finally, during ball milling, it self-assembles into a nano-layered mortar with a silicon crystal core, organic groups as bridges, and calcium-based gel as a shell. The tight nano-layered structure improves the strength and waterproofness of the mortar.

[0016] This invention directly synthesizes mortar in situ using mechanically driven tailings sand, completely eliminating the high-energy-consuming thermal activation and long-term mechanical grinding pretreatment steps required in traditional processes. This avoids additional energy consumption during raw material pretreatment, saves energy, and reduces carbon emissions.

[0017] A high-performance waterproof mortar for iron-rich tailings was prepared by mechanical synthesis over an 8-minute time. This mortar exhibits both excellent early strength and stable later-stage properties. Its compressive strength after 1 day of curing is ≥15 MPa, and after 28 days of curing… The post-compressive strength is ≥20 MPa (after curing and drying to constant weight), which meets the strength grade of M15 mortar in the "Standard for Test Methods of Basic Performance of Building Mortar" JGJ / T70-2009, indicating that the nano-layer structure gives the material excellent stability.

[0018] To assess the environmental safety of the material, the leaching heavy metal content in the tailings was determined according to the "Leaching Toxicity Method for Solid Waste - Sulfuric Acid and Nitric Acid Method" (HJ / T 299-2007), and the leaching heavy metal content in the iron-rich tailings waterproof mortar was determined according to the "Determination of Leachable Heavy Metals in Cement Mortar" (GB / T 30810-2014). The results showed that the leaching concentrations of Mn, Zn, and Pb in the original tailings were 47.8198 mg / L, 3.6358 mg / L, and 1.0872 mg / L, respectively. After mortar curing, the concentrations of these three metals decreased to 123.753 μg / L, 69.093 μg / L, and 4.848 μg / L, respectively, all meeting the requirements for heavy metal leaching concentrations in the "Technical Specification for Co-processing Solid Waste in Cement Kilns" (GB / T 30760-2014), confirming that the material has good environmental safety. In addition, its high compressive modulus (1d, 266.52 MPa; 28d, 528.7 MPa) ensures its excellent resistance to deformation, making it suitable for engineering scenarios with stringent requirements for resistance to deformation, such as airports and ground subgrades. Furthermore, following the methods described in the literature (Fabrication of all-dimensional superhydrophobic mortar with enhanced waterproof ability and freeze-thaw resistance), two key waterproofing indicators—water absorption rate and permeability—were evaluated. The results showed that the 28-day curing material exhibited excellent hydrophobicity and impermeability: under immersion conditions, its 6-day water absorption rate was 1%, primarily attributed to the strong hydrophobic effect imparted to the pore surface by the silane coupling agent and the ultra-low surface energy imparted to the material surface by the nano-layer structure; under a certain hydrostatic pressure, its 5-day permeability rate was 7.2%, indicating the existence of a small number of permeation pathways within the material that can be driven by higher water pressure. Its waterproofing performance far exceeds the 6-day water absorption rate of 17.2% and the 5-day permeability rate of 12.7% for ordinary mortar in the literature, and is close to the 6-day water absorption rate of 3.7% and the 5-day permeability rate of 2.1% for enhanced waterproof superhydrophobic mortar.

[0019] The above characteristics demonstrate that this material performs excellently in normal moisture-proof environments.

[0020] This invention uses glacial acetic acid and a silane coupling agent (3-aminopropyltriethoxysilane) as chemical accelerators, which reduces secondary pollution to the environment compared to the traditional use of inorganic strong acids or bases as activators. The waterproof mortar of this invention can be widely used in the manufacture of waterproof wall bricks or for road filling, etc.

[0021] Economic and environmental assessments show that this method combines low carbon emissions with economic value. The production of one ton of product emits approximately 285.6 to 292.1 kg of CO2, with an estimated cost of approximately 293.5 to 583.3 CNY. This significantly reduces the carbon emissions of traditional mortar production (approximately 560 kg of CO2 per ton of product) (Source: Projecting future carbon emissions from cement production in developing countries). Compared to commercially available waterproof mortar (approximately 2000 CNY per ton of product), it has a cost advantage (Source: https: / / mp.weixin.qq.com / s / N8oHNS94njUD8Jbu-vzfNQ).

[0022] This invention provides a green and low-carbon preparation method for heavy metal stabilization and waterproof mortar based on iron-rich tailings. Attached Figure Description

[0023] Figure 1 The XRD patterns are of the products obtained in Examples 1-4; Figure 2 The FTIR spectra of the products obtained in Examples 1-4 are shown below. Figure 3 Thermogravimetric curve of the product obtained in Example 3 Figure 4 The images show SEM images and structural simulation diagrams of the products obtained in Examples 1-4, and TEM images of the product obtained in Example 3. Figure 5 This is an elemental distribution diagram of the product obtained in Example 3; Figure 6 The reaction mechanism of the product obtained from DFT calculation; Figure 7 The contact angle test results are for the product obtained in Example 3. Detailed Implementation

[0024] This invention provides a method for rapidly preparing waterproof mortar from iron-rich tailings based on mechanochemistry, comprising the following steps: Tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent are mixed and then ball-milled. The silane coupling agent undergoes hydrolysis and polymerization, and self-assembly to generate a cementitious material with a multi-level ordered structure, thus obtaining a slurry. The tailings sand includes one or both of iron tailings sand and copper tailings sand. The slurry is cured to obtain the iron-rich tailings waterproof mortar; The iron-rich tailings waterproof mortar includes several nano-units, and each nano-unit includes silica and calcium iron aluminum silicate hydrate coated on the surface of the silica. The silicon dioxide and calcium iron aluminum silicate hydrate are linked by a silanol compound; The interconnected nanounits are bonded together by calcium iron aluminum silicate hydrate.

[0025] This invention involves mixing tailings sand, quicklime, water, glacial acetic acid, and a silane coupling agent, and then ball milling the resulting mixture. This process causes the silane coupling agent to hydrolyze and polymerize, and then self-assembles to form a cementitious material with a multi-level ordered structure, thus obtaining a slurry.

[0026] In this invention, the mixing method is preferably stirring, and the stirring speed is preferably 500-800 r / min, more preferably 550 r / min, 600 r / min, 650 r / min, 700 r / min or 750 r / min. This invention does not have a specific limitation on the stirring time; stirring until homogeneous is achieved is sufficient.

[0027] In this invention, the preferred mass of the quicklime is 18% to 22.48% of the total mass of tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent. In specific embodiments of this invention, it can be 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.27%, 21.50%, 21.80%, 22.00%, 22.20%, 22.30%, or 22.48%. The role of the quicklime is to chemically regulate (OH-) - Promotes hydrolysis and bonding), ion balance (Ca 2+ The triple effect of stabilizing the calcium-silicon ratio and structural reinforcement (building a complete silicon-oxygen network) optimizes material properties.

[0028] In this invention, the tailings sand includes one or more of iron tailings sand and copper tailings sand. The mass of the tailings sand is preferably 50.00% to 55.00% of the total mass of tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent. In specific embodiments of this invention, it can be 50.00%, 50.20%, 50.50%, 50.80%, 51.00%, 51.30%, 51.50%, 51.80%, 52.00%, 52.20%, 52.50%, 52.80%, 53.00%, 53.30%, 53.50%, 53.80%, 54.00%, 54.20%, 54.50%, or 54.80%.

[0029] In this invention, the iron tailings sand preferably comprises, by mass fraction, 0.395% Na2O, 2.315% MgO, 8.256% Al2O3, 38.959% SiO2, 0.129% P2O5, 10.591% SO3, 0.048% Cl, 0.655% K2O, 12.887% CaO, 0.367% TiO2, 3.926% MnO, 20.462% Fe2O3, 0.041% Co3O4, 0.078% CuO, 0.46% ZnO, 0.01% Rb2O, 0.01% SrO, 0.015% ZrO2, 0.395% PbO, and the balance being impurities; In this invention, the copper tailings sand preferably comprises, by mass fraction, 0.538% Na2O, 1.949% MgO, 8.211% Al2O3, 46.697% SiO2, 0.33% P2O5, 0.39% SO3, 0.037% Cl, 1.03% K2O, 0.89% CaO, 0.311% TiO2, 0.427% MnO, 8.924% Fe2O3, 0.169% CuO, 0.016% ZnO, 0.008% Rb2O, 0.014% SrO, 0.011% ZrO2, 0.047% PbO, and the balance being impurities.

[0030] In this invention, the water is preferably 25.36% to 25.8% of the total mass of tailings sand, quicklime, water, glacial acetic acid and silane coupling agent. In specific embodiments of this invention, it can be 25.36%, 25.40%, 25.50%, 25.55%, 25.58%, 25.60% or 25.64%.

[0031] In this invention, the mass of the glacial acetic acid is preferably 0.4% to 0.87% of the total mass of tailings sand, quicklime, water, glacial acetic acid and silane coupling agent. In specific embodiments of this invention, it can be 0.44%, 0.50%, 0.60%, 0.70%, 0.75%, 0.80%, 0.85% or 0.87%.

[0032] In this invention, the mass of the silane coupling agent is preferably 0.55% to 1.28% of the total mass of tailings sand, quicklime, water, glacial acetic acid, and the silane coupling agent. In specific embodiments of this invention, it can be 0.6%, 0.65%, 0.80%, 0.90%, 1.00%, 1.10%, 1.15%, 1.20%, or 1.28%. The silane coupling agent preferably includes one or more of 3-aminopropyltriethoxysilane and allyltriethoxysilane.

[0033] In this invention, the ball milling is preferably carried out in a planetary ball mill, and the grinding balls used in the ball milling are preferably steel grinding balls with a radius of 10 mm; the rotational speed of the ball milling is preferably 800~900 r / min, and the time is preferably 2~8 min, more preferably 3 min, 4 min, 5 min, 6 min or 7 min.

[0034] After obtaining the slurry, the present invention cures the slurry to obtain the iron-rich tailings waterproof mortar.

[0035] In this invention, the curing is preferably carried out in a mold.

[0036] In this invention, the temperature for curing is preferably 25~30℃, more preferably 25℃, 26℃, 27℃ or 28℃, the relative humidity is preferably 50~60%, more preferably 50%, 52%, 54%, 56% or 58%, and the time is preferably 1~28 days.

[0037] This invention employs a rapid mechanochemical method, using iron and copper tailings sand as raw materials, and employs minute-level ball milling processing involving "physical crushing-chemical transformation-structural reconstruction" to construct a novel waterproof mortar with a nano-layered structure. The material's structural hierarchy is clearly defined: First, ball milling breaks the quartz phase in the tailings into nano-quartz crystals, forming a rigid support; second, under mechanochemical action, vinyl silanol derived from the silane coupling agent APTES acts as a flexible interfacial bridge, chemically anchoring to the quartz surface through covalent bonds, forming a cross-linked network; the vinyl ends of the vinyl silanol strongly adsorb calcium ions, promoting heterogeneous nucleation of calcium ions, ultimately developing into calcium-iron-aluminum silicate hydrate as a binder phase, tightly cementing each unit into a complete and dense whole.

[0038] This nano-layered structure achieves a synergistic effect between organic and inorganic components, endowing the material with superior performance: quartz bears the main load, ensuring early strength; the vinyl silanol flexible bridge effectively dissipates energy through its inherent flexibility, significantly enhancing toughness and imparting a certain degree of hydrophobicity; and calcium iron aluminum silicate hydrate maintains the integrity of the microstructure through bonding. The synergy of these three components enables efficient cross-scale mechanical transfer from the nanoscale to the macroscale, allowing the material to achieve a compressive strength exceeding 15 MPa after just one day of curing. Furthermore, after 28 days of curing, the material's strength increases to 20 MPa. The material exhibits excellent heavy metal fixation capabilities, with fixation rates of Mn, Zn, and Pb reaching 99.74%, 98.10%, and 99.55%, respectively, and the leaching concentration after curing meets the requirements of GB / T30760-2014. The material demonstrates excellent water resistance: after 28 days of curing, the water absorption rate is approximately 1% after 6 days (ultra-low surface energy effect), and the water penetration rate is 7.2% after 5 days. Economic and environmental assessments show that this method combines low carbon emissions with economic value. The production of one ton of product emits approximately 285.6 to 292.1 kg of CO2, with an estimated cost of approximately 293.5 to 583.3 CNY. This significantly reduces carbon emissions from traditional mortar production (approximately 560 kg of CO2 per ton of product) (Source: Projecting future carbon emissions from cement production in developing countries). Compared to commercially available waterproof mortar (approximately 2000 CNY per ton of product), it has a cost advantage (Source: https: / / mp.weixin.qq.com / s / N8oHNS94njUD8Jbu-vzfNQ). This method provides a low-carbon pathway for the large-scale, high-value, and low-cost resource utilization of mining solid waste.

[0039] The present invention also provides a waterproof mortar for iron-rich tailings prepared by the method described above, comprising several nano-units, wherein each individual unit comprises silica and calcium iron aluminum silicate hydrate coated on the surface of the silica; The silicon dioxide and calcium iron aluminum silicate hydrate are linked by a silanol compound; The connected units are bonded together using calcium iron aluminum silicate hydrate.

[0040] The nanounits have a hierarchical structure: silicon dioxide is the inner layer, silanol compounds serve as intermediate connecting bridges, and calcium iron aluminum silicate hydrates are the outer layer.

[0041] The present invention also provides the application of the mortar described in the above technical solution in waterproof wall bricks or road filling.

[0042] The following detailed description of the green and low-carbon preparation method of heavy metal stabilization and waterproof mortar for iron-rich tailings provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0043] In the embodiments, the composition of the iron tailings and the copper tailings are shown in Tables 1-2.

[0044] Table 1 Composition of iron tailings

[0045] Table 2 Composition of copper tailings

[0046] This invention evaluates water absorption and permeability according to the method described in Fabrication of all-dimensional superhydrophobic mortar with enhanced waterproof ability and freeze-thaw resistance.

[0047] Example 1 15g of iron tailings sand (average particle size 267.9 nm), 5g of quicklime powder, 7mL of water, 0.002mol of glacial acetic acid, and 0.0008mol of 3-aminopropyltriethoxysilane were mixed and stirred evenly. The mixture was then placed in a high-energy vibrating impact ball mill (containing one 10mm diameter steel ball, loading rate 0.5mm / min), and cured for 1 day at 800rpm for 2min, 25±5℃, and 50-60% relative humidity. After curing, the mixture was dried to constant weight. Three parallel tests were conducted on the compressive strength of the product, yielding an average compressive strength of 12.59MPa and an average compression modulus of 266.52MPa. Three parallel tests were also conducted on the water resistance of the product, showing a 6-day water absorption rate of 2.4% and a 5-day water penetration rate of 11.5%.

[0048] Example 2 15g of iron tailings sand (average particle size 267.9 nm), 5g of quicklime powder, 7mL of water, 0.002mol of glacial acetic acid, and 0.0008mol of 3-aminopropyltriethoxysilane were mixed and stirred evenly. The mixture was then placed in a high-energy vibrating impact ball mill (containing one 10mm diameter steel ball, loading rate 0.5mm / min), and cured for 1 day at 800rpm for 5min, 25±5℃, and 50-60% relative humidity. After curing, the mixture was dried to constant weight. Three parallel tests were conducted on the compressive strength of the product, yielding an average compressive strength of 13.78MPa and an average compression modulus of 246.31MPa. Three parallel tests were also conducted on the water resistance of the product, showing a water absorption rate of 1.8% after 6 days and a water penetration rate of 9.2% after 5 days.

[0049] Example 3 15g of iron tailings sand (average particle size 267.9 nm), 5g of quicklime powder, 7mL of water, 0.002mol of glacial acetic acid, and 0.0008mol of 3-aminopropyltriethoxysilane were mixed and stirred evenly. The mixture was then placed in a high-energy vibrating impact ball mill (containing one 10mm diameter steel ball, loading rate 0.5mm / min), and cured for 1 day at 800rpm for 8min, 25±5℃, and 50-60% relative humidity. After curing, the mixture was dried to constant weight. Three parallel tests were conducted on the compressive strength of the product, yielding an average compressive strength of 15.45MPa and an average compression modulus of 252.98MPa. Three parallel tests were also conducted on the water resistance of the product, showing a 6-day water absorption rate of 1.2% and a 5-day water penetration rate of 8.9%.

[0050] Example 4 15g of iron tailings sand (average particle size 267.9 nm), 5g of quicklime powder, 7mL of water, 0.002mol of glacial acetic acid, and 0.0008mol of 3-aminopropyltriethoxysilane were mixed and stirred evenly. The mixture was then placed in a high-energy vibrating impact ball mill (containing one 10mm diameter steel ball, loading rate 0.5mm / min), and cured for 1 day at 800rpm for 11min, at a temperature of 25±5℃ and a relative humidity of 50-60%. After curing, the mixture was dried to constant weight. Three parallel tests were conducted on the compressive strength of the product, yielding an average compressive strength of 10.49MPa and an average compression modulus of 230.37MPa. Three parallel tests were also conducted on the water resistance of the product, showing a water absorption rate of 1.5% after 6 days and a water penetration rate of 10.9% after 5 days.

[0051] Example 5 15g of iron tailings sand (average particle size 267.9 nm), 5g of quicklime powder, 7mL of water, 0.002mol of glacial acetic acid, and 0.0008mol of allyltriethoxysilane were mixed and stirred evenly. The mixture was then placed in a high-energy vibrating impact ball mill (containing one 10mm diameter steel ball, loading rate 0.5mm / min), and cured for 1 day at 800rpm for 8min, 25±5℃, and 50-60% relative humidity. After curing, the mixture was dried to constant weight. Three parallel tests were conducted on the compressive strength of the product, yielding an average compressive strength of 4.45MPa and an average compression modulus of 141.31MPa. Three parallel tests were also conducted on the water resistance of the product, showing a 6-day water absorption rate of 2.4% and a 5-day water penetration rate of 13.5%.

[0052] Example 6 15g of copper tailings sand (average particle size 174.3 nm), 5g of quicklime powder, 7mL of water, 0.002mol of glacial acetic acid, and 0.0008mol of 3-aminopropyltriethoxysilane were mixed and stirred evenly. The mixture was then placed in a high-energy vibrating impact ball mill (containing one 10mm diameter steel ball, loading rate 0.5mm / min), and cured for 1 day at 800rpm for 8min, 25±5℃, and 50-60% relative humidity. After curing, the mixture was dried to constant weight. Three parallel tests were conducted on the compressive strength of the product, yielding an average compressive strength of 5.80MPa and an average compression modulus of 86.6MPa. Three parallel tests were also conducted on the water resistance of the product, showing a 6-day water absorption rate of 2.7% and a 5-day water penetration rate of 12.0%.

[0053] Example 7 15g of iron tailings sand (average particle size 267.9 nm), 5g of quicklime powder, 7mL of water, 0.002mol of glacial acetic acid, and 0.0008mol of 3-aminopropyltriethoxysilane were mixed and stirred evenly. The mixture was then placed in a high-energy oscillating impact ball mill (containing one 10mm diameter steel ball, loading rate 0.5mm / min) at 800rpm for 8min, and cured for 28 days under natural environmental conditions (temperature approximately 10-25℃). After curing, the mixture was dried to constant weight. Three parallel tests were conducted on the compressive strength of the product, yielding an average compressive strength of 19.98MPa and an average compression modulus of 528.70MPa. Three parallel tests were also conducted on the water resistance of the product, showing a 1% water absorption rate after 6 days and a 7.2% water seepage rate after 5 days.

[0054] Comparative Example 1 (without mechanical activation) 15g of iron tailings sand (average particle size 267.9 nm), 5g of quicklime powder, 7mL of water, 0.002mol of glacial acetic acid, and 0.0008mol of 3-aminopropyltriethoxysilane were manually mixed and stirred until homogeneous. The mixture was then cured for 7 days at 25±5℃ and 50-60% relative humidity. After curing, the mixture was dried to constant weight. The compressive strength of the product was tested in three parallel samples. The average compressive strength was 1.19 MPa, and the average compression modulus was 49.21 MPa.

[0055] Comparative Example 2 15g of iron tailings sand (average particle size 267.9 nm), 5g of quicklime powder, 7mL of water, 0.002mol of oxalic acid, and 0.0008mol of 3-aminopropyltriethoxysilane were mixed thoroughly and then placed in a high-energy oscillating impact ball mill (containing one 10mm diameter steel ball, model [model missing], loading rate 0.5mm / min), at a speed of 800rpm for 8min, a temperature of 25±5℃, and a relative humidity of 50-60% for 1 day. After curing, the mixture was dried to constant weight, and the compressive strength of the product was tested in three parallel samples. The average compressive strength was 1.48 MPa, and the average compression modulus was 31.68 MPa.

[0056] Comparative Example 3 15g of iron tailings sand (average particle size 267.9 nm), 5g of quicklime powder, 7mL of water, 0.002mol of citric acid, and 0.0008mol of tetrapropoxysilane were mixed thoroughly and then placed in a high-energy oscillating impact ball mill (containing one 10mm diameter steel ball, with a loading rate of 0.5mm / min). The mixture was cured for 1 day at a speed of 800rpm for 8min, a temperature of 25±5℃, and a relative humidity of 50-60%. After curing, the mixture was dried to constant weight. The compressive strength of the product was tested in three parallel samples. The average compressive strength was 1.81 MPa, and the average compression modulus was 151.79 MPa.

[0057] The heavy metal toxicity leaching test was performed on the product obtained in Example 3 (best results), and the results are as follows: The leaching concentration of manganese (Mn) decreased from 47.8198 mg / L in the original tailings to 123.753 μg / L, with a fixation rate of 99.74%; the leaching concentration of zinc (Zn) decreased from 3.6358 mg / L to 69.093 μg / L, corresponding to a fixation rate of 98.10%; and the leaching concentration of lead (Pb) decreased from 1.0872 mg / L to 4.848 μg / L, with a fixation rate of 99.55%. This indicates that the material has excellent immobilization effects on manganese, zinc, and lead metals.

[0058] Note: Based on the activation mechanism and strength test, this invention is mainly effective for iron tailings or iron-containing waste.

[0059] Figure 1 The images shown are XRD patterns of the products obtained in Examples 1-4.

[0060] Depend on Figure 1 XRD pattern analysis revealed that the material is mainly composed of SiO2, Ca(OH)2, CaCO3, and hydrated calcium aluminosilicate (CFASH). The diffraction peaks at 20.9° (100), 26.6° (101), 36.5° (110), 39.5° (102), and 60° (211) are attributed to SiO2; those at 34.1° (101) and 51.0° (110) are attributed to Ca(OH)2; and those at 29.4° (104) and 47.5° (018) correspond to CaCO3. Furthermore, the diffraction peak near 18° can be attributed to the iron-aluminosilicate hydrate (CFASH) phase.

[0061] Figure 2 The images are FTIR diagrams of the products obtained in Examples 1-4.

[0062] Depend on Figure 2 It can be seen that the product is at 1081 cm. -1 and 778 cm -1 The characteristic peaks correspond to Si-O Q respectively 2 -Q 4 Tensile vibration and Si-O Q 3 Tensile vibration indicates the formation of a silicon-oxygen network. 1630 cm -1 and 880 cm -1 The characteristic peaks correspond to C=C and COC, respectively, indicating that the unsaturated groups in the organic monomer may have undergone polymerization. Furthermore, under the combined action of glacial acetic acid and mechanical force, the ethoxy group of 3-aminopropyltriethoxysilane (APTES) hydrolyzes to generate silanol (Si-OH), which subsequently condenses with Si-OH on the quartz crystal surface to form a siloxane network containing C=C bonds. These reactions lead to the formation of a mixed organic-inorganic network structure containing unsaturated groups. Combined with SEM and TEM characterization... Figure 3 Based on relevant references, it is speculated that subsequently, the strong electrostatic attraction of the C=C bonds on the surface of the siloxane network will preferentially adsorb Ca. 2+ A double electric layer is formed, followed by Ca 2+ Under high temperature and pressure induced by mechanical force, a hydration reaction is accelerated, generating a calcium-based gel that assembles into a nanoscale layered structure with a 5-7 nm crystalline SiO2 core and a 2-3 nm amorphous calcium gel shell. 462 cm⁻¹ -1 The Fe / Mn-O bond vibration peak at the location confirms the microscopic mechanism by which heavy metals (Fe, Mn) are stabilized and fixed by participating in the construction of a bonding network.

[0063] Physical properties: The characteristic peaks in the XRD pattern accurately identify each phase. The crystalline phases include SiO2 (20.9° (100), 26.6° (101), 36.5° (110), 39.5° (102) and 60° (211)), CaCO3 (29.4° (104) and 47.5° (018)) and Ca(OH)2 (34.1° (101) and 51.0° (110)); while the gel phase is CFASH at 18°.

[0064] Figure 3 The thermogravimetric curve (TG-DTA) of the product obtained in Example 3 shows that the material exhibits a characteristic decomposition stage during heating: a significant endothermic peak at approximately 406–408 °C corresponds to the dehydration and decomposition of Ca(OH)₂, while the main endothermic peak at approximately 707–730 °C corresponds to the decomposition of the amorphous calcium iron aluminum silicate hydrate gel. This confirms the coexistence of the Ca(OH)₂ phase and the amorphous calcium iron aluminum silicate hydrate gel phase in the material.

[0065] Figure 4 The images shown are SEM images and structural simulation diagrams of the products obtained in Examples 1-4, and TEM images of the product obtained in Example 3.

[0066] Figure 4 In the image: (a) is the SEM image of the product obtained in Example 1, (b) is the SEM image of the product obtained in Example 2, (c) is the SEM image of the product obtained in Example 3, (d) is the SEM image of the product obtained in Example 4, (e) is the TEM image of the product obtained in Example 3, and (f) is the structural simulation diagram.

[0067] By combining scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis, the temporal evolution of material structure during ball milling was systematically revealed: Macroscopic scale (SEM): At 2 min, the sample surface is rough and has obvious pores, corresponding to irregular particle morphology and wide size distribution at the nanoscale, reflecting insufficient mechanical energy input; at 5 min, the surface is smoother (discrete blocks appear), and the nanoparticles tend to be uniform spherical (50~80 nm), reflecting mechanical energy-driven plastic deformation; at the critical 8 min, the sample forms a dense surface through the self-assembly of spherical nanoparticles (about 20 nm); while at 11 min, the roughness and porosity of the sample increase sharply, and the nanoparticles coarsen (spherical → plate-like), indicating that excessive ball milling causes agglomeration.

[0068] Nanoscale (TEM): At the 100 nm scale, the flocculent multilayer stacking leads to differences in electron transmission, showing that the central region tends to be dense; at the 5 nm resolution, the nanoscale structure of crystalline nuclei (multi-directional lattice fringes) and amorphous gel shells is clearly visible. The gel is calcium iron aluminum silicate hydrate, and the crystalline phase is the crystal remaining after the original tailings crystals are broken (based on the tailings composition, it is speculated that it is mainly silicon crystals).

[0069] In summary, appropriate mechanical energy (≤8 min) promotes particle assembly and phase distribution optimization, while excessive ball milling (11 min) disrupts dynamic equilibrium and leads to structural degradation.

[0070] Figure 5 The image shows the elemental distribution of the product obtained in Example 3. The main elements such as Fe, Mn, Ca, and Si are evenly distributed in the product obtained in Example 3, and no obvious elemental segregation was observed, indicating that the material has formed a composite structure with uniform composition.

[0071] Figure 6 To understand the product reaction mechanism obtained from DFT calculations, the DFT results indicate that the high-energy environment provided by mechanical ball milling promotes the formation of the key intermediate silanol. Figure 6 (a) This molecule has a dual function: its silanol end is covalently anchored to the SiO2 surface (silicon core), which can significantly enhance the Ca2+ oxidative stress. 2+ Adsorption on the surface (adsorption energy increases from -6.28 eV to -7.11 eV) Figure 6 (b) and (c) show how calcium iron aluminum silicate hydrate gel phases (calcium gel shells) are directionally guided to grow on their periphery. This explains and verifies the formation of the coating morphology in TEM.

[0072] Figure 7 The contact angle test results of the product obtained in Example 3 show that the average water contact angle of the material surface is as high as 112.6°, which confirms its surface hydrophobicity.

[0073] The product obtained in Example 3 has a low total surface free energy of 26.8 mN / m, with extremely low polar forces (only 0.07 mN / m) and relatively high dispersion forces (26.7 mN / m). This indicates that the material surface is essentially a highly nonpolar, chemically inert interface. It is this microscopic, ultra-low-energy surface structure that effectively blocks the wetting and adsorption of water molecules on the material surface, thereby endowing the material with excellent waterproof properties on a macroscopic scale.

[0074] Economic and environmental assessments show that this method combines low carbon emissions with economic value. The production of one ton of product emits approximately 285.6 to 292.1 kg of CO2, with an estimated cost of approximately 293.5 to 583.3 CNY. This significantly reduces the carbon emissions of traditional mortar production (approximately 560 kg of CO2 per ton of product) (Source: Projecting future carbon emissions from cement production in developing countries). Compared to commercially available waterproof mortar (approximately 2000 CNY per ton of product), it has a cost advantage (Source: https: / / mp.weixin.qq.com / s / N8oHNS94njUD8Jbu-vzfNQ).

[0075] Table 3 Estimated Carbon Emissions of Waterproof Mortar Based on Iron-Rich Tailings

[0076] Calculation instructions: Ball mill energy consumption (kWh / t) = grinding time (h) Power (kW) / Processing capacity (t) Ball mill CO2 emissions (kg / t) = Energy consumption (kWh / t) Average carbon emission factor of China's power grid (kg / kWh) CO2 emissions from quicklime production (kg / t) = Quicklime input (t) Emission coefficient of quicklime production (kg CO2e / t) Data settings and sources: The carbon footprint factor is taken from the national average carbon footprint factor of electricity in 2024 (0.5777 kgCO2e / kWh) released by the Ministry of Ecology and Environment of China in November 2025. The power (kW) of a small-to-medium-sized ball mill processing 1 ton of solid waste is estimated to be 75 kW. The emission coefficient of the quicklime production process (1136.82 kg CO2e / t) is based on the industry average (data reference source: Study on carbon emission characteristics and emission reduction measures of lime production—A case of enterprise in the Yangtze River Basin).

[0077] Table 4. Cost Estimate of Raw Materials for Iron-Rich Tailings-Based Waterproof Mortar

[0078] The electricity cost for the ball mill activation step is calculated as follows: Running a 75 kW ball mill for 8 minutes consumes approximately 10 kWh of electricity. Based on an industrial electricity price of 0.7 CNY / kWh, the corresponding electricity cost is approximately 7 CNY.

[0079] The total production cost of iron-rich tailings-based waterproof mortar is approximately CNY 293.5 ~ 583.3.

[0080] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for rapid preparation of waterproof mortar from iron-rich tailings based on mechanochemistry, characterized in that, Includes the following steps: Tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent are mixed and then ball-milled. The silane coupling agent undergoes hydrolysis and polymerization, and self-assembly to generate a cementitious material with a multi-level ordered structure, thus obtaining a slurry. The tailings sand includes one or both of iron tailings sand and copper tailings sand. The slurry is cured to obtain the iron-rich tailings waterproof mortar; The iron-rich tailings waterproof mortar includes several nano-units, and each nano-unit includes silica and calcium iron aluminum silicate hydrate coated on the surface of the silica. The silicon dioxide and calcium iron aluminum silicate hydrate are linked by a silanol compound; The interconnected nanounits are bonded together by calcium iron aluminum silicate hydrate.

2. The method according to claim 1, characterized in that, The iron tailings sand, by mass fraction, comprises 0.395% Na2O, 2.315% MgO, 8.256% Al2O3, 38.959% SiO2, 0.129% P2O5, 10.591% SO3, 0.048% Cl, 0.655% K2O, 12.887% CaO, 0.367% TiO2, 3.926% MnO, 20.462% Fe2O3, 0.041% Co3O4, 0.078% CuO, 0.46% ZnO, 0.01% Rb2O, 0.01% SrO, 0.015% ZrO2, 0.395% PbO, and the balance being impurities.

3. The method according to claim 1, characterized in that, The copper tailings sand, by mass fraction, comprises 0.538% Na2O, 1.949% MgO, 8.211% Al2O3, 46.697% SiO2, 0.33% P2O5, 0.39% SO3, 0.037% Cl, 1.03% K2O, 30.89% CaO, 0.311% TiO2, 0.427% MnO, 8.924% Fe2O3, 0.169% CuO, 0.016% ZnO, 0.008% Rb2O, 0.014% SrO, 0.011% ZrO2, 0.047% PbO, and the balance being impurities.

4. The method according to claim 1, characterized in that, The mass of the quicklime is 18-22.48% of the total mass of tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent; The mass of the tailings sand is 50-55% of the total mass of tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent; The mass of the water is 25.36-25.8% of the total mass of tailings sand, quicklime, water, glacial acetic acid, and silane coupling agent; The mass of the silane coupling agent is 0.55~1.28% of the total mass of tailings sand, quicklime, water, glacial acetic acid and silane coupling agent.

5. The method according to claim 1, characterized in that, The silane coupling agent includes one or both of 3-aminopropyltriethoxysilane and allyltriethoxysilane.

6. The method according to claim 1, characterized in that, The mass of the glacial acetic acid is 0.4-0.87% of the total mass of tailings sand, quicklime, water, glacial acetic acid and silane coupling agent.

7. The method according to claim 1, characterized in that, The ball milling is carried out in a high-energy oscillating impact ball mill, and the ball milling uses steel grinding balls with a radius of 10 mm. The slurry volume accounts for 1 / 8 to 1 / 7 of the ball mill container volume. The ball milling speed is 800~900 r / min, and the time is 2~11 min.

8. The method according to claim 1, characterized in that, The curing temperature is 20~30℃, the relative humidity is 50~60%, and the time is 1~28 days.

9. The iron-rich tailings waterproof mortar prepared by the method according to any one of claims 1 to 8, characterized in that, It includes several nanounits, wherein each nanounit includes silicon dioxide and calcium iron aluminum silicate hydrate coated on the surface of the silicon dioxide; The silicon dioxide and calcium iron aluminum silicate hydrate are linked by a silanol compound; The interconnected nanounits are bonded together by calcium iron aluminum silicate hydrate.

10. The application of the iron-rich tailings waterproof mortar of claim 9 in waterproof wall bricks or road filling.

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