A cementitious composite targeted activator for consolidation of tailings and method of making same

Abstract

The application belongs to the technical field of mine engineering materials, and particularly relates to a cementitious material composite targeted activator for consolidating tailings and a preparation method thereof. The cementitious material composite targeted activator for consolidating tailings comprises the following raw materials in parts by weight: 10-30 parts of an alkaline excitation source, 5-10 parts of a core-shell structure agent, 20-50 parts of a nanocrystal seed, 4-10 parts of an organic template agent, and 1-5 parts of a heavy metal solidification agent. The composite targeted activator realizes targeted activation through multi-component cooperation, is suitable for tailings with different properties, and has excellent performance such as compressive strength and heavy metal solidification rate. The composite targeted activator not only significantly improves the utilization rate of industrial solid waste, but also is environmentally friendly and economical, and is suitable for mine tailings filling engineering.

Description

Technical Field

[0001] This invention belongs to the field of mining engineering materials technology, specifically relating to a composite targeted activator for cementing materials used in solid tailings and its preparation method. Background Technology

[0002] With the continuous development of global mineral resources, the land occupation and environmental pollution problems caused by tailings storage are becoming increasingly serious. Underground tailings backfilling is the main method for disposing of tailings. Meanwhile, tailings contain 60%-85% siliceous, ferrous, and aluminous minerals, making them significant industrial solid waste with considerable resource potential. Traditionally, cement is used to bind tailings, but with improved mineral processing capabilities, the fine particle size and high mud content of tailings make cement bonding difficult. New types of mine backfill cementing powders are gradually being developed, and more and more mines are using cementing powders to replace cement, achieving the required backfilling technical indicators. Most of these new mine backfill cementing powders use industrial solid waste as raw materials, which can be transformed into cementing materials through mechanical activation (ball milling to d50 < 20μm), chemical activation (NaOH / Na2SiO3 alkali activation), and thermal activation (calcination at 800-1200℃).

[0003] Although this type of solid waste cementitious material has been used to replace cement, the current alkali-activated system is extremely sensitive to fluctuations in tailings composition, so the system still faces the following key bottlenecks: (i) Changes in tailings properties lead to poor adaptability of the system. High-silica tailings (SiO2>70%) lack sufficient Al... 3+ (ii) Crosslinking sites make it difficult to form a stable three-dimensional aluminosilicate network, resulting in low 28-day compressive strength, which is insufficient to meet the safety requirements for mine backfilling; (iii) Heavy metal tailings (such as lead-zinc tailings with Pb / Zn > 0.1%) experience increased ion migration in alkaline environments, requiring an additional 3-5% of traditional solidifying agents (sodium silicate), which also leads to deterioration of the slurry's rheological properties; (iv) Low activation efficiency. High alkalinity (pH > 13) depolymerizes the aluminosilicate network, but strong alkali inhibits the formation of ettringite (AFt), causing later shrinkage cracking (the traditional alkali-activated system experiences a 30% reduction in strength after 28 days). (v) High economic costs, difficulty in controlling the quality of industrial solid waste, and difficulty in activating the activity of solid waste.

[0004] Therefore, there is an urgent need to develop an activator system that combines efficient and stable activation with heavy metal stabilization in order to overcome the aforementioned technical bottlenecks. Summary of the Invention

[0005] To address the synergistic failure of solid waste-based cementitious materials and tailings aggregates, this invention improves the chemical bonding between the cementitious phase and tailings particles through targeted regulation, reducing weak zones in low-strength minerals; it also solidifies tailings with different properties, enhancing the adaptability and activation efficiency of the solid waste-based cementitious material system, thus ensuring stable strength development of the filling body. Simultaneously, it optimizes flow properties, reduces the yield stress of the tailings slurry, and saves economic costs.

[0006] The present invention provides a composite targeted activator for cementing materials used in solidified tailings, comprising the following raw materials in parts by weight: 10-30 parts of alkaline activator, 5-10 parts of core-shell structure agent, 20-50 parts of nanocrystal seed, 4-10 parts of organic template agent, and 1-5 parts of heavy metal curing agent.

[0007] Preferably, the composite targeted activator for solidifying tailings comprises the following raw materials in parts by weight: 30 parts of alkaline activator, 10 parts of core-shell structure agent, 30 parts of nanocrystal seed, 4 parts of organic template agent, and 3 parts of heavy metal curing agent.

[0008] Preferably, the alkaline excitation source is one or a combination of two or more of industrial-grade sodium hydroxide powder, solid sodium silicate powder, and solid potassium silicate powder; wherein: The modulus of the solid sodium silicate powder is 1.0-1.8; The modulus of the solid potassium silicate powder is 1.0-1.5.

[0009] Preferably, the core layer of the core-shell structure agent is iron oxide, and the shell layer is a sulfate compound; wherein: The mass ratio of sulfate compounds to iron oxide is 3-6:1.

[0010] Preferably, the nanocrystal seed is one or a combination of two of nano-silica powder and nano-calcium oxide powder; the size of the nanocrystal seed is 10-50 nm.

[0011] Preferably, the organic template agent is sodium alginate powder.

[0012] Preferably, the heavy metal curing agent is an LDHs precursor powder; the LDHs precursor is Mg6Al2(OH). 16 CO3·4H2O.

[0013] Based on the same technical concept, another aspect of the present invention is to provide a method for preparing a composite targeted activator for cementitious materials used in solid tailings ore, the preparation method comprising the following steps: (1) The alkaline excitation source and nanocrystal seeds are mixed and then homogenized under high pressure to obtain a homogeneous mixture; (2) The homogeneous mixture is mixed and stirred with the core-shell structural agent, organic template agent and heavy metal curing agent to obtain the composite targeted activator for solidifying tailings.

[0014] Preferably, in step (1), the specific surface area of ​​the homogeneous mixture is ≥800 m². 2 / kg.

[0015] Preferably, in step (2), the mixing and stirring time is 20-30 minutes.

[0016] In practical use, the composite targeted activator powder is mixed with industrial solid waste of aluminosilicate minerals, and then mixed with water and tailings in a certain proportion to achieve solidification of the tailings.

[0017] The beneficial effects of this invention are as follows: The composite targeted activator of this invention systematically solves the technical bottleneck of traditional solid waste-based cementitious materials in tailings backfilling applications through multi-component synergistic design and targeted regulation mechanism, and has the following significant beneficial effects: 1. Significantly improves system adaptability, suitable for tailings with different properties such as high silicon (SiO2>70%) and heavy metal content (Pb / Zn>0.1%). Through dual-mode excitation of core-shell structural agents and nucleation regulation of nanocrystal seeds, it compensates for the low Al content in high silicon tailings. 3+ The defect of insufficient crosslinking sites is overcome to form a stable three-dimensional aluminosilicate network, avoiding performance failure caused by fluctuations in tailings composition.

[0018] 2. Enhanced heavy metal curing effect: The interlayer adsorption of LDH precursors synergistically combines with the chelation and hydrophobic film formation functions of sodium alginate to achieve the curing of Pb. 2+ Zn 2+ The efficient curing of heavy metal ions eliminates the need for additional curing agent, thus avoiding deterioration of the slurry's rheological properties.

[0019] 3. Achieving stable strength enhancement: Nanocrystal seeds precisely control the gelation reaction process; nano-SiO2 provides nucleation sites to accelerate CSH gel growth; nano-CaO regulates the liquid phase Ca... 2+ The concentration, combined with the continuous supply of OH- from the alkaline activating source, effectively inhibits the problem of hindered formation of ettringite, prevents the later strength reduction, and ensures that the mortar has a 3-day compressive strength >20MPa and a 28-day compressive strength >42.5MPa, and the strength of the filling body meets the safety requirements of the mine.

[0020] 4. Optimize construction and economic performance: The organic template agent and other components work together to reduce the yield stress of the tailings slurry, improve flowability, and simplify construction operations; the activator can efficiently activate the activity of industrial solid waste, increase the utilization rate of industrial solid waste, reduce the pressure of industrial solid waste storage, and replace traditional cement and high-cost activation systems, significantly reducing the economic cost of backfilling projects.

[0021] 5. It has both environmental protection and resource utilization value. By utilizing a high proportion of industrial solid waste for resource utilization, it reduces the land occupation and environmental pollution caused by mineral development, which is in line with the national policies on tailings disposal and solid waste resource utilization, and has significant ecological and social benefits. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] Example 1 This embodiment provides a method for preparing a composite targeted activator for cementitious materials used in solid tailings ore, the preparation method comprising the following steps: (1) Preparation of core-shell structure agent: Take 8 kg of calcium sulfate and 2 kg of iron oxide (mass ratio 4:1), add them to deionized water containing 0.5% polycarboxylate dispersant (based on the total mass of calcium sulfate and iron oxide), control the stirring speed to 800 r / min, and stir for 15 min to obtain a uniform suspension; pass the suspension into a spray dryer, set the inlet air temperature to 180℃ and the outlet air temperature to 80℃, and collect the core-shell structure agent after spray drying. The polycarboxylate dispersant can prevent the aggregation of calcium sulfate and iron oxide particles, ensuring that the two are uniformly dispersed to form a stable suspension; specific spray drying parameters can accurately control the morphology and integrity of the core-shell structure, so that the calcium sulfate in the shell can quickly release sulfate ions, and the iron oxide in the core can release and catalyze the depolymerization of the silicon-aluminum network in the later stage of hydration, realizing dual-mode excitation.

[0024] (2) Raw material pretreatment: 30 kg of solid sodium silicate powder (modulus 1.2), 20 kg of nano silica powder, 10 kg of nano calcium oxide powder (seed size 30-50 nm), 4 kg of sodium alginate powder, and 3 kg of LDHs precursor powder were sieved through a sieve to remove larger particles. Sieving can remove large particles and clumps from the raw materials, avoiding their impact on the uniformity of subsequent mixing and reactivity, and ensuring the stable function of each component of the activator.

[0025] (3) Preparation of homogenized mixture: The sieved solid sodium silicate powder, nano silica powder, and nano calcium oxide powder were fed into a high-pressure homogenizer, the working pressure was set to 150 MPa, and the homogenization was repeated 3 times to prepare a mixture with a specific surface area >800 m². 2 / kg of homogeneous mixture. The mechanical force of high-pressure homogenization can break the agglomeration structure between raw material particles, significantly increase the specific surface area, and enhance the contact area and reactivity between the alkaline excitation source and the nanocrystal seeds, laying the foundation for subsequent efficient activation of industrial solid waste.

[0026] (4) Preparation of composite activator: The homogeneous mixture, 10 kg of the core-shell structural agent obtained in step (1), 4 kg of sieved sodium alginate powder, and 3 kg of LDHs precursor powder are sequentially added to a mixer. The mixing speed is set to 600 r / min and the mixing time is 20 min. After mixing evenly, the mixture is discharged to obtain the composite targeted activator for cementitious materials used in solid tailings. The strong shearing and mixing capabilities of the mixer can ensure that the multiple components are fully contacted and evenly dispersed to form a synergistic system. The specific speed and time parameters ensure the interfacial bonding effect of each functional component and avoid performance fluctuations caused by local component enrichment.

[0027] The obtained composite targeted activator for solidifying tailings was applied (mortar strength test), and the specific method was as follows: (S1) Preparation of filling cementitious material: Weigh 50 kg of S95 grade slag powder (specific surface area 450 m²) according to the mass ratio. 2 25 kg of primary fly ash and 15 kg of the above-mentioned composite targeted activator were added to a mixer and stirred at 300 r / min for 10 min until uniformly mixed to obtain the filling cementitious material. The uniform stirring in the mixer ensures that the activator is fully integrated with the industrial solid waste, guaranteeing that the activator acts evenly on the solid waste particles and ensuring the overall performance consistency of the cementitious material.

[0028] (S2) Preparation and Testing of Mortar Specimens: Deionized water was added to the filling cementitious material at a water-cement ratio of 1:2. Mortar specimens were prepared using a planetary ball mill according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671). The specimens were cured for 3 days and 28 days respectively in a standard curing chamber at a temperature of (20±1)℃ and a relative humidity ≥90%. The compressive strength was tested using a pressure testing machine. Strict adherence to the standard preparation and curing procedures ensured the accuracy and comparability of the test results, directly reflecting the activating effect of the composite targeted activator on the strength of the cementitious material.

[0029] The final test results showed a 3-day compressive strength of 20.4 MPa and a 28-day compressive strength of 54.1 MPa, verifying its efficient excitation performance.

[0030] Example 2

[0031] This embodiment provides a method for preparing a composite targeted activator for cementitious materials used in solid tailings ore, the preparation method comprising the following steps: (1) Preparation of core-shell structure agent: Take 8 kg of calcium sulfate and 2 kg of iron oxide (mass ratio 4:1), add them to deionized water containing 0.4% naphthalene-based dispersant (based on the total mass of calcium sulfate and iron oxide), control the stirring speed at 750 r / min, and stir for 12 min to obtain a uniform suspension; pass the suspension into a spray dryer, set the inlet air temperature to 180℃ and the outlet air temperature to 75℃, and collect the core-shell structure agent after spray drying. The naphthalene-based dispersant can effectively reduce the viscosity of the suspension and promote the uniform dispersion of calcium sulfate and iron oxide; the precise control of the spray drying parameters ensures the integrity of the core-shell structure and ensures the orderly release of sulfate ions and the catalytic effect of iron oxide during the subsequent excitation process.

[0032] (2) Raw material pretreatment: 30 kg of solid sodium silicate powder (modulus 1.2), 20 kg of nano silica powder, 10 kg of nano calcium oxide powder (seed size 30-50 nm), 4 kg of sodium alginate powder, and 3 kg of LDHs precursor powder were sieved through a sieve to remove larger particles. Sieving can remove large particles and clumps from the raw materials, avoiding their impact on the uniformity of subsequent mixing and reactivity, and ensuring the stable function of each component of the activator.

[0033] (3) Preparation of homogenized mixture: The sieved solid sodium silicate powder, nano silica powder, and nano calcium oxide powder were fed into a high-pressure homogenizer, the working pressure was set to 140 MPa, and the homogenization was repeated 4 times to prepare a mixture with a specific surface area >800 m². 2 / kg of homogeneous mixture. The mechanical force of high-pressure homogenization can break the agglomeration structure between raw material particles, significantly increase the specific surface area, and enhance the contact area and reactivity between the alkaline excitation source and the nanocrystal seeds, laying the foundation for subsequent efficient activation of industrial solid waste.

[0034] (4) Preparation of composite activator: The homogeneous mixture, 10 kg of the core-shell structural agent obtained in step (1), 4 kg of sieved sodium alginate powder, and 3 kg of LDHs precursor powder are sequentially added to a mixer. The stirring speed is set to 600 r / min and the stirring time is 20 min. After mixing evenly, the mixture is discharged to obtain the composite targeted activator for tailings cementitious materials. The strong shearing and mixing capabilities of the mixer can ensure that the multiple components are fully contacted and evenly dispersed to form a synergistic system. The specific speed and time parameters ensure the interfacial bonding effect of each functional component and avoid performance fluctuations caused by local component enrichment.

[0035] The obtained cementitious composite targeted activator for solidifying tailings is applied (filling strength), specifically through the following method: (S1) Preparation of filling cementitious material: Weigh 50 kg of S95 grade slag powder (specific surface area 450 m²) according to the mass ratio. 2 25 kg of primary fly ash and 15 kg of the above-mentioned composite targeted activator were added to a mixer and stirred at 300 r / min for 10 min until uniformly mixed to obtain the filling cementitious material. The uniform stirring in the mixer ensures that the activator is fully integrated with the industrial solid waste, guaranteeing that the activator acts evenly on the solid waste particles and ensuring the overall performance consistency of the cementitious material.

[0036] (S2) Preparation and Testing of Tailings Backfill: Lithium tailings slurry was taken, and backfill cementitious material was added to the slurry at a ratio of 1:6 (cementite to tailings mass ratio). The slurry mass concentration was adjusted to 65%, and the mixture was stirred at 400 r / min for 5 min to ensure uniform mixing. The slurry was poured into a test mold and cured for 7 days and 28 days in an environment with a temperature of (20±2)℃ and a relative humidity of ≥90%. The compressive strength was tested using a pressure testing machine. By controlling the ash-sand ratio and slurry concentration, the actual mine backfilling conditions were simulated. The application effect of the activator in the actual backfilling system was verified through standard curing and strength testing. The performance test results are shown in Table 1.

[0037] Table 1

[0038] As shown in Table 1, the 7-day compressive strength is 2.89 MPa, the 28-day compressive strength is 5.44 MPa, and the 60-day compressive strength is 5.86 MPa, which are significantly better than cement and traditional activated cementitious materials.

[0039] Example 3 This embodiment provides a method for preparing a composite targeted activator for cementitious materials used in solid tailings ore, the preparation method comprising the following steps: (1) Preparation of core-shell structure agent: Take 7.5 kg of calcium sulfate and 2.5 kg of iron oxide (mass ratio 3:1), add them to deionized water containing 0.6% polyether dispersant (based on the total mass of calcium sulfate and iron oxide), control the stirring speed at 850 r / min, and stir for 18 min to obtain a uniform suspension; pass the suspension into a spray dryer, set the inlet air temperature to 160℃ and the outlet air temperature to 70℃, and collect the core-shell structure agent after spray drying. Polyether dispersant has good dispersion stability, which can ensure that calcium sulfate and iron oxide form a uniform suspension; the appropriate spray drying temperature avoids the destruction of the core-shell structure, and ensures the efficient excitation of sulfate ions in the shell and the catalytic function of iron oxide in the core.

[0040] (2) Raw material pretreatment: 25 kg of solid sodium silicate powder (modulus 1.3), 15 kg of nano silica powder, 15 kg of nano calcium oxide powder (seed size 30-50 nm), 7 kg of sodium alginate powder, and 5 kg of LDHs precursor powder were sieved through a screen to remove larger impurity particles. Sieving ensures the purity and dispersibility of the raw materials, avoids impurities affecting the curing effect of heavy metals and the gelation reaction efficiency, and ensures that each functional component plays its full role.

[0041] (3) Preparation of homogenized mixture: The sieved solid sodium silicate powder, nano silica powder, and nano calcium oxide powder were fed into a high-pressure homogenizer, the working pressure was set to 160 MPa, and the homogenization was repeated 3 times to prepare a mixture with a specific surface area >800 m². 2 / kg of homogeneous mixture. High-pressure homogenization increases the specific surface area of ​​the raw materials, enhances the activity of the alkaline excitation source and nanocrystal seeds, and promotes the synergistic process of gelation reaction and heavy metal solidification reaction.

[0042] (4) Preparation of composite activator: Homogeneous mixture, 10 kg of core-shell structure agent, 7 kg of sodium alginate powder, and 5 kg of LDHs precursor powder were sequentially added to a double planetary mixer. The stirring speed was set to 650 r / min and the stirring time was 30 min. After uniform mixing, the mixture was discharged to obtain the composite targeted activator. Extending the stirring time and increasing the speed ensured the deep integration of multiple components, especially the uniform dispersion of the heavy metal curing agent and other components, laying the foundation for subsequent efficient adsorption and chelation of heavy metal ions.

[0043] The obtained cementitious composite targeted activator for solidifying tailings is applied (heavy metal solidification) using the following method: (S1) Preparation of filling cementitious material: Weigh 50 kg of S95 grade slag powder (specific surface area 450 m² / kg), 22 kg of grade I fly ash, and 17 kg of composite targeted activator, put them into a horizontal mixer, and stir at 320 r / min for 12 min until uniformly mixed to obtain the filling cementitious material. Thorough stirring ensures that the activator and industrial solid waste are uniformly mixed, ensuring that the activator can fully cover the tailings particles in the tailings slurry, while ensuring that the heavy metal solidifier is evenly distributed, thereby improving the solidification effect.

[0044] (S2) Preparation of heavy metal tailings backfill: Lead-zinc tailings slurry was taken, and backfill cementitious material was added to the slurry at a ratio of 1:6 (cementite to tailings mass ratio). The slurry mass concentration was adjusted to 70%, and the mixture was stirred at 500 r / min for 6 min using a high-speed mixer to ensure uniform mixing. The slurry was then poured into a test mold and cured in an environment with a temperature of (20±2)℃ and a relative humidity of ≥90% to prepare the heavy metal tailings backfill. The actual backfilling conditions of heavy metal tailings were simulated. High-speed stirring ensured that the cementitious material and tailings slurry were fully integrated, ensuring that heavy metal ions and curing agents were in full contact, thus improving curing efficiency. The performance test results are shown in Table 2.

[0045] Table 2

[0046] Table 2 shows that the 7-day compressive strength is 3.01 MPa, the 28-day compressive strength is 5.23 MPa, and the Pb leaching concentration is 0.011 mg·L⁻¹. -1 Zn leaching concentration 0.009 mg·L -1 This achieves dual optimization of strength and heavy metal curing.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A cementitious composite targeted activator for consolidation of tailings, characterized in that, The raw materials include the following parts by weight: 10-30 parts of alkaline excitation source, 5-10 parts of core-shell structure agent, 20-50 parts of nanocrystal seed, 4-10 parts of organic template agent, and 1-5 parts of heavy metal curing agent. The core layer of the core-shell structured agent is iron oxide, and the shell layer is a sulfate compound; the mass ratio of sulfate compound to iron oxide is 3-6:

1. The nanocrystal seed is one or a combination of two of nano-silica powder and nano-calcium oxide powder; the size of the nanocrystal seed is 10-50 nm. The organic template agent is sodium alginate powder; The heavy metal solidifying agent is a LDHs precursor powder; the LDHs precursor is Mg6Al2(OH) 16 CO3·4H2O; The preparation method of the core-shell structure agent is as follows: Calcium sulfate and iron oxide were added to deionized water containing a polycarboxylate dispersant, with a mass ratio of calcium sulfate to iron oxide of 4:1 and an amount of polycarboxylate dispersant of 0.5% of the total mass of calcium sulfate and iron oxide. The stirring speed was controlled at 800 r / min, and the mixture was stirred for 15 min to obtain a uniform suspension. The suspension was then passed into a spray dryer with an inlet air temperature of 180℃ and an outlet air temperature of 80℃. After spray drying, the core-shell structure agent was collected.

2. The cementitious composite targeted activator for consolidation of tailings according to claim 1, wherein, The raw materials include the following parts by weight: 30 parts alkaline excitation source, 10 parts core-shell structure agent, 30 parts nanocrystal seed, 4 parts organic template agent, and 3 parts heavy metal curing agent.

3. The cementitious composite targeted activator for consolidation of tailings according to claim 1, wherein, The alkaline excitation source is one or a combination of two or more of industrial-grade sodium hydroxide powder, solid sodium silicate powder, and solid potassium silicate powder; wherein: The modulus of the solid sodium silicate powder is 1.0-1.8; The modulus of the solid potassium silicate powder is 1.0-1.

5.

4. A process for the preparation of cementitious composite targeted activator for consolidation of tailings as claimed in any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: (1) The alkaline excitation source and nanocrystal seeds are mixed and then homogenized under high pressure to obtain a homogeneous mixture; (2) The homogeneous mixture is mixed and stirred with the core-shell structural agent, organic template agent and heavy metal curing agent to obtain the composite targeted activator for solidifying the tailings.

5. A method of preparing a cementitious composite targeted activator for consolidation of tailings as claimed in claim 4, wherein, In step (1), the specific surface area of the homogenized mixture is > 800 m 2 / kg.

6. A process for the preparation of cementitious composite targeting activator for consolidation of mine tailings as claimed in claim 4 wherein, In step (2), the mixing and stirring time is 20-30 minutes.

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