Heavy metal solidified non-fired brick based on copper mine tailings and preparation method thereof

Abstract

The application discloses a heavy metal solidified non-burned brick based on copper mine tailings and a preparation method thereof, and belongs to the technical field of solid waste resource utilization, and comprises the following raw materials in parts by weight: lime 2-3 parts, slag 7-9 parts, cement 6-11 parts, copper mine tailings 65-75 parts, nano silicon dioxide 0.5-1.5 parts and modified metakaolin 3-5 parts. The application can not only effectively treat copper mine tailings, solidify heavy metal elements in the tailings, but also reduce environmental pollution and resource waste, and can further prepare the non-burned brick with good performance, meet the use requirements in the field of building and the like, has remarkable economic and environmental benefits, and provides a feasible and effective way for comprehensive utilization of the copper mine tailings. In addition, the preparation method is simple and convenient to popularize and apply.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, and in particular relates to a heavy metal solidified non-fired brick based on copper mine tailings and its preparation method. Background Technology

[0002] Long-term mining and smelting activities have resulted in a significant accumulation of mineral solid waste, with massive tailings ponds leading to increasingly prominent environmental and safety issues. Tailings ponds not only occupy land resources but also cause heavy metal pollution of soil and water bodies. Research data shows that copper mine tailings contain harmful trace elements such as Pb, Cr, Ni, Cu, Cd, As, and Zn. Compared with background values ​​in Tongling soil, the contents of Cd, Cu, Pb, and Zn are all higher than the background values. Therefore, long-term accumulation of tailings in tailings ponds easily leads to heavy metal pollution of the surrounding soil environment and even groundwater.

[0003] Copper mine tailings (WS) can be used as a mineral admixture to prepare non-fired bricks. By adjusting the proportions of each component and mixing them with cement, the bricks can be pressed into shape. This not only solves the problem of large-scale solid waste accumulation polluting the environment and saves land resources, but also realizes the resource utilization of solid waste and creates economic benefits, which is of great significance to environmental protection.

[0004] Therefore, how to provide a method for the resource utilization of copper mine tailings is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a heavy metal solidification non-fired brick based on copper mine tailings and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A heavy metal-cured, non-fired brick based on copper ore tailings comprises the following raw materials in parts by weight:

[0008] 2-3 parts lime, 7-9 parts slag, 6-11 parts cement, 65-75 parts copper mine tailings, 0.5-1.5 parts nano silica, and 3-5 parts modified metakaolin.

[0009] Beneficial Effects: This invention uses copper mine tailings as the main material, realizing the resource utilization of waste, reducing costs, and being environmentally friendly. A specific ratio of M42.5 and M32.5 cement is used to optimize performance. The addition of lime enhances reactivity. Furthermore, the invention also incorporates nano-silica and modified metakaolin, strengthening the brick's strength and other properties. Nano-silica can fill the pores of cement stone and modified metakaolin hydration products, further refining the pore structure, improving the brick's density and impermeability, and reducing the migration channels for heavy metal ions. Simultaneously, the nucleation effect and chemical reactivity of nano-silica enhance the solidification ability of cement and modified metakaolin for heavy metals. The combined effect of these three factors effectively improves the solidification efficiency of heavy metals in copper mine tailings.

[0010] Preferably, the cement is M42.5 cement and M32.5 cement in a mass ratio of (3.5-6.6):(2.5-4.4).

[0011] Beneficial effects: This invention uses M42.5 and M32.5 cement mixed in a specific mass ratio, which can combine the advantages of both and optimize the cement performance, so that the prepared heavy metal solidified non-fired bricks have better strength and other indicators, and meet the use requirements.

[0012] Preferably, the lime is slaked lime.

[0013] Beneficial effects: Quicklime is alkaline and has high chemical activity. It can fully react with other components in the system, promote the formation of cementitious substances, enhance the bonding force of the internal structure of the brick, effectively improve the strength and stability of heavy metal-cured non-fired bricks, and ensure the quality performance of non-fired bricks.

[0014] Preferably, the preparation method of the modified metakaolin includes the following steps:

[0015] Kaolin is ball-milled and then calcined to obtain metakaolin. Metakaolin is then mixed with an organic modifier and ball-milled to obtain modified metakaolin.

[0016] Beneficial effects: The above modification methods can improve the surface properties of metakaolin, enhance its compatibility with other raw materials, increase its reactivity in the brick body, and thus improve the strength and durability of the unfired bricks.

[0017] Preferably, the organic modifier includes one of γ-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, sodium polyacrylate, and polymethacrylic acid.

[0018] Beneficial Effects: The above-mentioned modifiers can effectively combine with metakaolin, improving its dispersibility and interfacial properties, enhancing its adhesion to other components in the brick body, and increasing the density of the brick structure, thereby improving the strength and durability of the heavy metal-cured non-fired bricks. Furthermore, by using the above-mentioned organic modifiers to modify metakaolin, the active groups generated on its surface can chemically bond with heavy metal ions, fixing them within the brick structure. Moreover, the secondary hydration reaction of the modified metakaolin consumes the calcium hydroxide produced during cement hydration, promoting further cement hydration and generating more hydration products beneficial for curing heavy metals. In addition, the high specific surface area and active groups of the modified metakaolin increase its adsorption and fixation capacity for heavy metal ions, complementing the curing effect of cement and improving the overall curing effect of heavy metals in copper mine tailings.

[0019] Preferably, the calcination temperature is 500-900℃ and the time is 1-4h.

[0020] Preferably, the mass ratio of metakaolin to organic modifier is (200-400):1.

[0021] Beneficial effects: The specific calcination temperature and time mentioned above can fully transform kaolin into metakaolin, ensuring its activity; and the appropriate mass ratio allows the organic modifier to play a better role, improving the performance of metakaolin. The two work together to enhance the strength of the unfired bricks, optimize the internal structure of the bricks, and enhance stability and durability.

[0022] Preferably, the particle size distribution of the copper ore tailings is as follows: 36-42% by mass of particles with a diameter of 0.5-2mm, 29-38% by mass of particles with a diameter of 0.1-0.5mm, and 22-28% by mass of particles with a diameter <0.1mm.

[0023] Beneficial effects: This invention utilizes copper ore tailings of different particle sizes to fill each other, which can effectively improve the density of the brick body, reduce internal pores, enhance the structural stability of the brick body, and thus improve the strength, impermeability and other properties of the unfired bricks, making them of better quality and more durable.

[0024] A method for preparing heavy metal-cured non-fired bricks based on copper ore tailings includes the following steps:

[0025] (1) The copper tailings are dried, ground and vibrated to obtain copper tailings with different particle size distributions.

[0026] (2) The copper tailings with different particle sizes, modified metakaolin, slag, cement, nano silica and lime are mixed and dry-mixed, and then water is added and mixed evenly to obtain a mixed slurry. The obtained mixed slurry is hydraulically molded, demolded and cured to obtain the heavy metal solidified non-fired brick based on copper tailings.

[0027] Preferably, the water is added at a water-cement ratio of 0.5-0.9.

[0028] Compared with the prior art, the present invention has the following advantages and technical effects:

[0029] This invention utilizes a large amount of copper mine tailings as the main raw material, achieving resource utilization of waste, reducing costs, and being environmentally friendly. It optimizes performance by mixing M42.5 and M32.5 cement in a specific ratio; simultaneously, it adds nano-silica and modified metakaolin to enhance the strength and other properties of the bricks. Furthermore, this invention optimizes the particle size distribution of the copper mine tailings, which helps improve the density of the bricks. This invention not only effectively treats copper mine tailings, reducing environmental pollution and resource waste, but also produces high-performance, non-fired bricks that meet the needs of construction and other fields, demonstrating significant economic and environmental benefits and providing a feasible and effective way for the comprehensive utilization of copper mine tailings. Moreover, the preparation method provided by this invention is simple and easy to promote and apply. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0032] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels;

[0033] The copper tailings originate from the Tongling Shuimuchong tailings pond. The main chemical components of the copper tailings are Cu, Tfe, S, Au, and Ag. The Cu grade is concentrated between 0.04% and 0.16%, the Tfe grade between 6.55% and 12.85%, the S grade between 0.74% and 2.99%, the Au grade between 0.1% and 0.25 g / t, and the Ag grade between 1.81% and 11.59 g / t. The SiO2 content in the tailings is generally 35% to 45%, which is lower than that of high-silica quartz sandstone. The CaO content is generally 18% to 20%, the MgO content is generally around 2%, the TFe2O3+Al2O3 content is generally 20% to 25%, and the alkaline oxide K2O+Na2O content is generally 1.5% to 2%.

[0034] The slag is S105 grade blast furnace slag, a byproduct of ironmaking, and was purchased from Fuyang Xinyuan Building Materials Co., Ltd. in China.

[0035] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0036] Example 1

[0037] A heavy metal-cured, non-fired brick based on copper ore tailings comprises the following raw materials in parts by weight:

[0038] 2.24 parts quicklime, 7.36 parts slag, 6.4 parts cement (M42.5 cement to M32.5 cement mass ratio of 3.84:2.56), 71 parts copper mine tailings (40% mass fraction of particles with a diameter of 0.5-2mm, 35% mass fraction of particles with a diameter of 0.1-0.5mm, and 25% mass fraction of particles with a diameter <0.1mm), 0.53 parts nano silica, and 4.87 parts modified metakaolin.

[0039] The preparation method of modified metakaolin includes the following steps:

[0040] Kaolin was ball-milled and then calcined at 700℃ for 3 hours to obtain metakaolin. Metakaolin was then mixed with an organic modifier (γ-aminopropyltriethoxysilane) at a mass ratio of 300:1 and ball-milled for 15 minutes to obtain modified metakaolin.

[0041] A method for preparing heavy metal-cured non-fired bricks based on copper ore tailings includes the following steps:

[0042] (1) The copper tailings are dried, ground and vibrated to obtain copper tailings with different particle size distributions.

[0043] (2) Copper tailings with different particle size distribution, modified metakaolin, slag, cement, nano silica and quicklime are mixed and dry-mixed. Water is then added at a water-cement ratio of 0.81 and mixed evenly to obtain a mixed slurry. The obtained mixed slurry is formed by hydraulic molding at 10MPa for 45s using a hydraulic brick press. After demolding, it is left to stand at room temperature for 12h and then naturally cured for 28d to obtain heavy metal solidified non-fired bricks based on copper tailings.

[0044] Example 2

[0045] A heavy metal-cured, non-fired brick based on copper ore tailings comprises the following raw materials in parts by weight:

[0046] 2.52 parts quicklime, 8.28 parts slag, 7.2 parts cement (M42.5 cement to M32.5 cement mass ratio of 4.32:2.88), 69 parts copper mine tailings (mass fraction of 0.5-2mm particle size is 36%, mass fraction of 0.1-0.5mm particle size is 38%, mass fraction of <0.1mm particle size is 26%), 1.12 parts nano silica, and 3.08 parts modified metakaolin.

[0047] The preparation method of modified metakaolin includes the following steps:

[0048] Kaolin was ball-milled and then calcined at 500℃ for 4 hours to obtain metakaolin. Metakaolin was then mixed with an organic modifier (sodium polyacrylate) at a mass ratio of 200:1 and ball-milled for 10 minutes to obtain modified metakaolin.

[0049] A method for preparing heavy metal-cured non-fired bricks based on copper ore tailings includes the following steps:

[0050] (1) The copper tailings are dried, ground and vibrated to obtain copper tailings with different particle size distributions.

[0051] (2) Copper tailings with different particle size distribution, modified metakaolin, slag, cement, nano silica and quicklime are mixed and dry-mixed. Water is then added at a water-cement ratio of 0.73 and mixed evenly to obtain a mixed slurry. The obtained mixed slurry is hydraulically molded at 20MPa for 60s using a hydraulic brick press. After demolding, it is left to stand at room temperature for 6 hours and then naturally cured for 28 days to obtain heavy metal solidified non-fired bricks based on copper tailings.

[0052] Example 3

[0053] A heavy metal-cured, non-fired brick based on copper ore tailings comprises the following raw materials in parts by weight:

[0054] 2.64 parts quicklime, 8.36 parts slag, 11 parts cement (M42.5 cement to M32.5 cement in a mass ratio of 6.6:4.4), 67 parts copper mine tailings (42% by mass of particles with a diameter of 0.5-2mm, 30% by mass of particles with a diameter of 0.1-0.5mm, and 28% by mass of particles with a diameter <0.1mm), 1.37 parts nano-silica, and 4.68 parts modified metakaolin.

[0055] The preparation method of modified metakaolin includes the following steps:

[0056] Kaolin was ball-milled and then calcined at 900℃ for 1 hour to obtain metakaolin. Metakaolin was then mixed with an organic modifier (polymethyl methacrylate) at a mass ratio of 400:1 and ball-milled for 20 minutes to obtain modified metakaolin.

[0057] A method for preparing heavy metal-cured non-fired bricks based on copper ore tailings includes the following steps:

[0058] (1) The copper tailings are dried, ground and vibrated to obtain copper tailings with different particle size distributions.

[0059] (2) Copper tailings with different particle size distribution, modified metakaolin, slag, cement, nano silica and quicklime are mixed and dry-mixed. Water is then added at a water-cement ratio of 0.59 and mixed evenly to obtain a mixed slurry. The mixed slurry is then hydraulically molded at 30MPa for 30s using a hydraulic brick press. After demolding, it is left to stand at room temperature for 12h and then naturally cured for 28d to obtain heavy metal solidified non-fired bricks based on copper tailings.

[0060] Comparative Example 1

[0061] The only difference from Example 1 is that the copper ore tailings consist of particles with a diameter of 0.5-2 mm. All other process steps and parameters are the same as in Example 1.

[0062] Comparative Example 2

[0063] The only difference from Example 1 is that only M42.5 cement is used, that is, M32.5 cement is replaced with an equal mass of M42.5 cement. All other process steps and parameters are the same as in Example 1.

[0064] Comparative Example 3

[0065] The only difference from Example 1 is that only M32.5 cement is used, that is, M42.5 cement is replaced with an equal mass of M32.5 cement. All other process steps and parameters are the same as in Example 1.

[0066] Comparative Example 4

[0067] The only difference from Example 1 is that the cement is replaced with an equal mass of copper ore tailings. All other process steps and parameters are the same as in Example 1.

[0068] Comparative Example 5

[0069] The only difference from Example 1 is that the modified metakaolin is replaced with an equal mass of metakaolin. All other process steps and parameters are the same as in Example 1.

[0070] Comparative Example 6

[0071] The only difference from Example 1 is that no nano-silica is added. All other process steps and parameters are the same as in Example 1.

[0072] Technical effects:

[0073] 1. Mechanical properties

[0074] The flexural strength and compressive strength of the cement mortar materials obtained in Examples 1-3 and Comparative Examples 1-6 were tested. The test methods were based on GB / T4741-1999 Test Method for Flexural Strength of Ceramic Materials and GB / T21144-2007 Test Method for Compressive Strength. The results are shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] As shown in Table 1, the heavy metal-cured non-fired bricks based on copper mine tailings prepared in Examples 1-3 exhibited high 28-day compressive and flexural strengths, indicating that the non-fired bricks prepared according to the given raw material ratio and process have good mechanical properties. Comparative Example 1, which only changed the particle size distribution of the copper mine tailings, showed a significant decrease in strength, indicating that a reasonable particle size distribution plays a crucial role in strength. Comparative Examples 2-3, which changed the type of cement, also showed a decrease in strength, demonstrating the advantages of mixing two types of cement in a specific ratio. Comparative Example 4, which removed cement, showed a sharp drop in strength, highlighting the important role of cement. Comparative Example 5, which replaced modified metakaolin with kaolin, and Comparative Example 6, which did not add nano-silica, both showed a decrease in strength, indicating that the two materials have a certain synergistic effect, jointly improving the mechanical properties of the brick.

[0079] 2. Heavy metal content test of non-fired bricks

[0080] 2.1 Table 2 shows the occurrence of heavy metals in copper mine tailings and the unfired bricks of Examples 1-3 and Comparative Examples 1-6.

[0081] Table 2. Average total amount of heavy metal elements (mg / kg)

[0082]

[0083]

[0084] In the unfired bricks of Examples 1-3, the total amounts of the four heavy metal elements exceeded the background values ​​for soil environmental conditions in Tongling City. Cd exceeded the standard by 1.45–2.33 times, Cu by 7.35–10.30 times, As by 1.69–2.09 times, Pb by 0.98–1.37 times, and Zn by 1.92–2.44 times. Furthermore, the total amounts of the four heavy metal elements in the unfired bricks obtained in Comparative Examples 1-6 also significantly exceeded the background values ​​for soil environmental conditions in Tongling City.

[0085] 2.2 Heavy metal solidification effect of non-fired bricks based on copper mine tailings

[0086] The experiment on the leaching toxicity of heavy metal-concentrated non-fired bricks based on copper mine tailings employed three solid waste leaching methods as specified in the Environmental Protection Industry Standards of the People's Republic of China. The leaching procedures were strictly followed in the standard methods to determine the heavy metal toxicity of the copper mine tailings. The heavy metal elements in the leachate were determined using the method recommended in the standard—inductively coupled plasma atomic emission spectrometry (ICP-AES). The concentration values ​​of hazardous components in the leachate from the three methods are shown in Table 3.

[0087] The sulfuric acid-nitric acid method uses a nitric acid / sulfuric acid mixed solution as the leaching agent to simulate the process by which harmful components of waste leach out of the waste and enter the environment under the influence of acidic precipitation during improper landfill disposal, stockpiling, or land application of waste after harmless treatment. According to the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" (GB 5085.3-2007), the concentrations of Cd, Cu, Pb, and Zn in the leachate of heavy metal-solidified non-fired bricks based on copper mine tailings prepared using the sulfuric acid-nitric acid method (HJ / T 299-2007) did not exceed the concentration limits listed in the standard. Therefore, it was determined that the heavy metal-solidified non-fired bricks based on copper mine tailings do not exhibit leaching toxicity characteristics.

[0088] The horizontal oscillation method (HJ 557-2010) uses pure water as the leaching agent to simulate the process by which harmful components of solid waste are leached into the environment under specific conditions by surface water or groundwater. In the horizontal oscillation method for the production of heavy metal-solidified non-fired bricks based on copper mine tailings, the concentrations of Cd, Cu, Pb, and Zn in the leachate did not exceed the concentration limits listed in the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification".

[0089] The acetic acid buffer solution method (HJ / T300-2007) uses acetic acid buffer solution as the leaching agent to simulate the leaching process of hazardous components from industrial waste after it enters a sanitary landfill, under the influence of landfill leachate. In the acetic acid buffer solution leaching solution for heavy metal solidification of copper mine tailings-based non-fired bricks, the concentrations of Cd, Cu, Pb, and Zn did not exceed the concentration limits listed in the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification".

[0090] In addition, according to the "Surface Water Environmental Quality Standard" (GB3838-2002), among the three toxicity leaching methods for heavy metal solidification non-fired bricks based on copper mine tailings, the Cd concentration in the leachate meets the Class I water quality standard, the Cu and Pb concentrations meet the Class II water quality standard, and the Zn concentration meets the Class I-II water quality standard.

[0091] According to the "Groundwater Quality Standard" (GB / T 14848-2017), among the three toxicity leaching methods for heavy metal solidification non-fired bricks based on copper mine tailings, the Cd concentration in the leachate meets the Class I water quality standard, the Cu concentration meets the Class II water quality standard, the Pb concentration meets the Class IV water quality standard, and the Zn concentration meets the Class I-II water quality standard.

[0092] Table 3 Concentration values ​​of hazardous components in toxic leachates (mg / L)

[0093]

[0094]

[0095] Note: ND means Not Detected.

[0096] In the sulfuric acid-nitric acid method, the acidity of the leaching agent is pH 3.20 ± 0.05, and in the acetic acid buffer solution method, the acidity of the leaching agent is 4.93 ± 0.05. Compared with the pure water leaching agent (pH = 7.0 ± 0.05) in the horizontal oscillation method, the first two methods are relatively extreme, simulating the leaching of heavy metals under the influence of acidic precipitation and landfill leachate. Therefore, the non-fired bricks prepared from copper mine tailings have good curing effects on four heavy metals (Cd, Cu, Pb, and Zn) under extreme acidic or neutral conditions. Among them, the heavy metal curing non-fired bricks based on copper mine tailings in Example 3 have better curing effects than those in Examples 2 and 1. In addition, the experimental data from the comparative examples show that the nano-silica, the particle size distribution of copper mine tailings, and the modification of kaolin in this invention can effectively inhibit the precipitation of heavy metals, achieving a good effect of curing heavy metals.

[0097] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A heavy metal-cured, non-fired brick based on copper mine tailings, characterized in that, The ingredients include the following parts by weight: 2-3 parts lime, 7-9 parts slag, 6-11 parts cement, 65-75 parts copper mine tailings, 0.5-1.5 parts nano silica, and 3-5 parts modified metakaolin. The preparation method of the modified metakaolin includes the following steps: Kaolin is ball-milled and then calcined to obtain metakaolin. Metakaolin is then mixed with an organic modifier and ball-milled to obtain modified metakaolin. The organic modifier includes one of γ-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, sodium polyacrylate, and polymethacrylic acid; The mass ratio of metakaolin to organic modifier is (200-400):1; The cement is M42.5 cement in a mass ratio of (3.5-6.6):(2.5-4.4) to M32.5 cement. The particle size distribution of the copper mine tailings is as follows: 36-42% by mass of particles with a diameter of 0.5-2mm, 29-38% by mass of particles with a diameter of 0.1-0.5mm, and 22-28% by mass of particles with a diameter <0.1mm.

2. The heavy metal solidification non-fired brick based on copper mine tailings according to claim 1, characterized in that, The lime is slaked lime.

3. The heavy metal solidification non-fired brick based on copper mine tailings according to claim 1, characterized in that, The calcination temperature is 500-900℃, and the time is 1-4 hours.

4. A method for preparing heavy metal-cured, non-fired bricks based on copper ore tailings according to any one of claims 1-3, characterized in that, Includes the following steps: (1) After drying, copper tailings are ground and vibrated and screened to obtain copper tailings with different particle sizes; (2) The copper tailings with different particle size distribution, modified metakaolin, slag, cement, nano silica and lime are mixed and dry-mixed, and then water is added and mixed evenly to obtain a mixed slurry. The obtained mixed slurry is hydraulically molded, demolded and cured to obtain the heavy metal solidified non-fired brick based on copper tailings.

5. The method for preparing heavy metal-cured non-fired bricks based on copper ore tailings according to claim 4, characterized in that, The water is added at a water-cement ratio of 0.5-0.9.

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