Preparation method of composite soil heavy metal pollution remediation agent

Abstract

This invention discloses a method for preparing a composite soil heavy metal pollution remediation agent, comprising the following steps: (1) granulating the wet material obtained by mixing carbide slag powder, sodium alginate powder, and sodium silicate solution, and then drying the obtained particles to obtain core particles for later use. (2) mixing waste red brick powder, silica sol, and rubber powder evenly to form a slurry, then placing the core particles in the slurry for coating, removing them, allowing them to stand at room temperature, steam curing them, and then drying them to obtain the remediation agent. The composite soil heavy metal pollution remediation agent prepared by this invention can not only efficiently and quickly reduce the content of heavy metal ions in the soil, but also play a long-term role, helping to prevent pollution from recurring later.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, and in particular to a method for preparing a composite soil heavy metal pollution remediation agent. Background Technology

[0002] Heavy metals are widely used in many products and daily life, leading to the dumping and landfilling of large amounts of industrial waste. Rainfall then washes these wastes into the soil, causing heavy metal pollution. Mining, ore processing, and industrial wastewater discharge are also significant sources of heavy metal pollution in soil. Because heavy metal ions are difficult to degrade in soil like organic matter, they accumulate, leading to increasingly higher levels. This not only damages the soil's physical and chemical properties and microbial community structure, affecting crop growth, but more seriously, they can also transfer to the human body through water sources and the food chain (for example, rice has a strong ability to absorb cadmium), causing health problems and even collective health issues. Therefore, timely remediation and restoration of soil contaminated with heavy metals is crucial.

[0003] Currently, the main methods for removing heavy metal ions from soil include deep tillage, soil replacement, soil leaching, and bioremediation (such as plants and microorganisms). While the first two methods are relatively effective, they involve large-scale engineering projects, high costs, and can easily lead to the loss of other nutrients in the soil, resulting in decreased soil fertility. Bioremediation, although environmentally friendly and cost-effective, suffers from long remediation cycles and unstable remediation results due to environmental conditions. Therefore, exploring faster, more effective, and long-term remediation technologies for heavy metal ion-contaminated soils is of significant practical importance. Summary of the Invention

[0004] This invention provides a method for preparing a composite soil heavy metal pollution remediation agent. This remediation agent can not only efficiently and rapidly reduce the content of heavy metal ions in the soil, but also has a long-term effect, helping to prevent recurrence of pollution. The specific technical solution of this invention is as follows.

[0005] A method for preparing a composite soil heavy metal pollution remediation agent includes the following steps:

[0006] (1) The wet material obtained by mixing carbide slag powder, sodium alginate powder and sodium silicate solution is granulated, and then the obtained particles are dried to obtain core particles for later use.

[0007] (2) Mix waste red brick powder, silica sol and rubber powder evenly to form a slurry, then place the core particles in the slurry, remove them, let them stand at room temperature and then steam them, and finally dry them to obtain the repair agent.

[0008] Further, in step (1), the ratio of the carbide slag powder, sodium alginate powder, and sodium silicate solution is 25~38g: 6~7.5g: 7~10ml. Optionally, the mass fraction of the sodium silicate solution is 30~35%.

[0009] Furthermore, in step (1), the fineness of the carbide slag powder and sodium alginate powder is 200-400 mesh.

[0010] Furthermore, in step (1), the drying temperature is 50~70℃ and the drying time is 1~1.5 hours.

[0011] Furthermore, in step (1), the particle size of the core particles is 5~20mm.

[0012] Further, in step (2), the mass ratio of the waste red brick powder, silica sol, and rubber powder is 1~2:2.4~3.1:0.15~0.23. Optionally, the content of nano-SiO2 in the silica sol is 30~40 wt.%.

[0013] Further, in step (2), the fineness of the waste red brick powder is 200-400 mesh. Optionally, the fineness of the rubber powder is 300-400 mesh.

[0014] Furthermore, in step (2), the time for standing at room temperature is 2 to 3 hours, so as to reduce the moisture in the slurry wrapped on the surface of the core particles to facilitate structural shaping.

[0015] Further, in step (2), the steam curing method is as follows: first, heat the temperature to 60-80℃ at a heating rate of 5-10℃ / h and maintain it for 8-12 hours, while keeping the humidity between 92-95%. After completion, cool the temperature to room temperature at a cooling rate of 5-10℃ / h.

[0016] Furthermore, in step (2), the drying time is 24-36 hours to remove residual moisture from the obtained repair agent.

[0017] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0018] The composite soil heavy metal pollution remediation agent of this invention can not only efficiently and rapidly reduce the content of heavy metal ions in soil, but also has a long-term effect, helping to prevent recurrence of pollution. To this end, this invention uses particles formed from carbide slag powder, sodium alginate powder, and sodium silicate as the core, and coats the surface with a slurry formed from waste red brick powder, silica sol, and rubber powder, followed by steam curing to form a porous outer shell. During this process, on the one hand, the carbide slag gradually releases calcium ions through its slightly soluble properties, causing the sodium alginate to gradually cross-link into a film, thus constructing a slow-release structure for the core. On the other hand, while utilizing the excellent bonding properties of silica sol to coat the slurry on the core surface, the calcium hydroxide released from the carbide slag reacts with the nano-silica in the silica sol during steam curing to form hydrated calcium silicate gel. This not only makes the outer shell more firmly fixed to the core, preventing detachment, but also provides the hydrated calcium silicate with excellent adsorption properties for heavy metal ions. When the remediation agent of this invention is mixed with soil contaminated with heavy metal ions, the heavy metal ions entering the core react rapidly with sodium silicate to form insoluble silicates, thus solidifying them and rapidly reducing the concentration of free heavy metal ions in the soil. Furthermore, the hydroxide ions gradually released from the core not only solidify the heavy metal ions, preventing recurrence of heavy metal ion contamination and maintaining the long-term remediation ability of the remediation agent, but also prevent soil alkalization. Simultaneously, the calcium ions gradually released from the core contribute to improving soil fertility. Additionally, the rubber powder in the outer shell effectively enhances its deformability, reducing damage during loading, transportation, and application to the soil, and accommodating changes in shell volume caused by the solidified heavy metal ion compounds, thus reducing cracking later. Attached Figure Description

[0019] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings, wherein:

[0020] Figure 1 The image shows a sample of the composite soil heavy metal pollution remediation agent from Example 1 below.

[0021] Figure 2 The image shows a sample of the composite soil heavy metal pollution remediation agent from Example 2 below. Detailed Implementation

[0022] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. All reagents and materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0024] Furthermore, any methods and materials similar to or equivalent to those described herein can be applied to the methods of this invention. The invention will now be further described in conjunction with the accompanying drawings and specific embodiments. The preferred embodiments and materials described herein are for illustrative purposes only.

[0025] Example 1:

[0026] A method for preparing a composite soil heavy metal pollution remediation agent includes the following steps:

[0027] (1) Mix 200-mesh carbide slag powder, 250-mesh sodium alginate powder, and 35% sodium silicate solution in a ratio of 32g:7g:8ml and stir evenly. Then granulate the wet material and dry the resulting particles at 60℃ for 1 hour to obtain core particles with a particle size distribution between 10 and 15mm for later use.

[0028] (2) Waste red brick powder with a fineness of 200 mesh, silica sol (SiO2 mass fraction of 30wt.%), and rubber powder with a fineness of 400 mesh are mixed in a ratio of 1.55g:2.8g:0.17g and stirred evenly to form a slurry. The core particles are then placed in this slurry for coating, and then removed and left to stand at room temperature for 2.5 hours. After completion, the obtained particles are placed in a curing chamber and heated to 60℃ at a heating rate of 5℃ / h and held for 12 hours, during which the humidity is maintained between 92% and 95%. After completion, the temperature is lowered to room temperature at a cooling rate of 5℃ / h, and then the obtained particles are air-dried at room temperature for 24 hours to obtain the following: Figure 1 The repair agent shown.

[0029] Heavy metal ion removal capacity test: (1) Mix simulated wastewater containing heavy metal ions (including lead, chromium, copper, chromium, and nickel) with soil, dry the soil, and grind it to obtain initial contaminated soil. Then add 30% by mass of the remediation agent prepared in this embodiment to the soil, and then sprinkle water at a moisture content of 25%. After 7 days, test the total heavy metal ion content in the soil and calculate the removal rate a. (2) Separate the remediation agent from the contaminated soil in (1), mix it with the new simulated contaminated soil in the above proportion, and sprinkle water at a moisture content of 25%. After 20 days, test the total heavy metal ion content in the soil and calculate the removal rate b. (3) Separate the remediation agent from the contaminated soil in (2), mix it with the new simulated contaminated soil in the above proportion, and sprinkle water at a moisture content of 25%. After 20 days, test the total heavy metal ion content in the soil and calculate the removal rate c. During the above process, water was sprayed in a timely manner to maintain the soil moisture in the above state. (4) 30% by mass of the remediation agent prepared in this embodiment was added to the initially contaminated soil, and then water was sprayed at a ratio of 25% moisture content. The pH of the soil at this time was tested (referred to as the initial pH). The rate of change of the soil pH relative to the initial pH was tested after 30 days, and the results are shown in the table below.

[0030]

[0031] Example 2:

[0032] A method for preparing a composite soil heavy metal pollution remediation agent includes the following steps:

[0033] (1) Mix 300-mesh carbide slag powder, 400-mesh sodium alginate powder, and 32% sodium silicate solution in a ratio of 25g:6g:7ml and stir evenly. Then granulate the wet material and dry the resulting particles at 50℃ for 1.5 hours to obtain core particles with a particle size distribution between 15 and 20 mm for later use.

[0034] (2) Waste red brick powder with a fineness of 300 mesh, silica sol (SiO2 mass fraction of 36wt.%), and rubber powder with a fineness of 350 mesh are mixed in a ratio of 1.0g:2.4g:0.15g and stirred evenly to form a slurry. The core particles are then placed in this slurry for coating, and then removed and left to stand at room temperature for 2 hours. After completion, the obtained particles are placed in a curing chamber and heated to 80℃ at a heating rate of 10℃ / h and held for 10 hours, during which the humidity is maintained between 92% and 95%. After completion, the temperature is lowered to room temperature at a cooling rate of 5℃ / h, and then the obtained particles are air-dried at room temperature for 24 hours to obtain the following: Figure 1 The repair agent shown.

[0035] The remediation agent prepared in this embodiment was tested for its ability to remove heavy metal ions from the soil and the rate of pH change in the soil using the same method as in Example 1 above. The results are shown in the table below.

[0036]

[0037] Example 3:

[0038] A method for preparing a composite soil heavy metal pollution remediation agent includes the following steps:

[0039] (1) Mix 350-mesh carbide slag powder, 400-mesh sodium alginate powder, and 30% sodium silicate solution in a ratio of 38g:7.5g:10ml and stir evenly. Then granulate the wet material and dry the resulting particles at 50℃ for 1.5 hours to obtain core particles with a particle size distribution between 5 and 10 mm for later use.

[0040] (2) Waste red brick powder with a fineness of 400 mesh, silica sol (SiO2 mass fraction of 40wt.%), and rubber powder with a fineness of 300 mesh are mixed in a ratio of 2.0g:3.1g:0.23g and stirred evenly to form a slurry. The core particles are then placed in the slurry and coated, and then removed and left to stand at room temperature for 3 hours. After completion, the obtained particles are placed in a curing chamber and heated to 70°C at a heating rate of 5°C / h and maintained for 8 hours, during which the humidity is maintained between 92% and 95%. After completion, the temperature is lowered to room temperature at a cooling rate of 5°C / h, and then the obtained particles are air-dried at room temperature for 36 hours to obtain the repair agent.

[0041] The remediation agent prepared in this embodiment was tested for its ability to remove heavy metal ions from the soil and the rate of pH change in the soil using the same method as in Example 1 above. The results are shown in the table below.

[0042]

[0043] Example 4:

[0044] A method for preparing a composite soil heavy metal pollution remediation agent includes the following steps:

[0045] (1) Mix calcium carbide slag powder with a fineness of 200 mesh with sodium silicate solution with a mass fraction of 35% in a ratio of 32g:7ml and stir evenly. Then granulate the wet material and dry the resulting particles at 60℃ for 1 hour to obtain core particles with a particle size distribution between 10 and 15mm for later use.

[0046] (2) Waste red brick powder with a fineness of 200 mesh, silica sol (SiO2 mass fraction of 30wt.%), and rubber powder with a fineness of 400 mesh are mixed in a ratio of 1.55g:2.8g:0.17g and stirred evenly to form a slurry. The core particles are then placed in the slurry and coated, and then removed and left to stand at room temperature for 2.5 hours. After completion, the obtained particles are placed in a curing chamber and heated to 60°C at a heating rate of 5°C / h and maintained for 12 hours, during which the humidity is maintained between 92% and 95%. After completion, the temperature is lowered to room temperature at a cooling rate of 5°C / h, and then the obtained particles are air-dried at room temperature for 24 hours to obtain the repair agent.

[0047] The remediation agent prepared in this embodiment was tested for its ability to remove heavy metal ions from the soil and the rate of pH change in the soil using the same method as in Example 1 above. The results are shown in the table below.

[0048]

[0049] Example 5:

[0050] A method for preparing a composite soil heavy metal pollution remediation agent includes the following steps:

[0051] (1) Mix 300-mesh carbide slag powder, 400-mesh sodium alginate powder and water in a ratio of 25g:6g:7ml and stir evenly. Then granulate the wet material and dry the resulting particles at 50℃ for 1.5 hours to obtain core particles with a particle size distribution between 15 and 20 mm for later use.

[0052] (2) Waste red brick powder with a fineness of 300 mesh, silica sol (SiO2 mass fraction of 36wt.%), and rubber powder with a fineness of 350 mesh are mixed in a ratio of 1.0g:2.4g:0.15g and stirred evenly to form a slurry. The core particles are then placed in the slurry and coated, and then removed and left to stand at room temperature for 2 hours. After completion, the obtained particles are placed in a curing chamber and heated to 80°C at a heating rate of 10°C / h and maintained for 10 hours, during which the humidity is maintained between 92% and 95%. After completion, the temperature is lowered to room temperature at a cooling rate of 5°C / h, and then the obtained particles are air-dried at room temperature for 24 hours to obtain the repair agent.

[0053] The remediation agent prepared in this embodiment was tested for its ability to remove heavy metal ions from the soil and the rate of pH change in the soil using the same method as in Example 1 above. The results are shown in the table below.

[0054]

[0055] Example 6:

[0056] A method for preparing a composite soil heavy metal pollution remediation agent includes the following steps:

[0057] (1) Mix 200 mesh slag powder, 250 mesh sodium alginate powder and 35% sodium silicate solution in a ratio of 32g:7g:8ml and stir evenly. Then granulate the wet material and dry the resulting particles at 60℃ for 1 hour to obtain core particles with a particle size distribution between 10 and 15mm for later use.

[0058] (2) Waste red brick powder with a fineness of 200 mesh, silica sol (SiO2 mass fraction of 30wt.%), and rubber powder with a fineness of 400 mesh are mixed in a ratio of 1.55g:2.8g:0.17g and stirred evenly to form a slurry. The core particles are then placed in the slurry and coated, and then removed and left to stand at room temperature for 2.5 hours. After completion, the obtained particles are placed in a curing chamber and heated to 60°C at a heating rate of 5°C / h and maintained for 12 hours, during which the humidity is maintained between 92% and 95%. After completion, the temperature is lowered to room temperature at a cooling rate of 5°C / h, and then the obtained particles are air-dried at room temperature for 24 hours to obtain the repair agent.

[0059] The remediation agent prepared in this embodiment was tested for its ability to remove heavy metal ions from the soil and the rate of pH change in the soil using the same method as in Example 1 above. The results are shown in the table below.

[0060]

[0061] Example 7:

[0062] A method for preparing a composite soil heavy metal pollution remediation agent includes the following steps:

[0063] (1) Mix 350-mesh carbide slag powder, 400-mesh sodium alginate powder, and 30% sodium silicate solution in a ratio of 38g:7.5g:10ml and stir evenly. Then granulate the wet material and dry the resulting particles at 50℃ for 1.5 hours to obtain core particles with a particle size distribution between 5 and 10 mm for later use.

[0064] (2) Mix waste red brick powder with a fineness of 400 mesh, silica sol (SiO2 mass fraction of 40wt.%), and rubber powder with a fineness of 300 mesh in a ratio of 2.0g:3.1g:0.23g and stir evenly to form a slurry. Then, place the core particles in the slurry to coat them, and then take them out and dry them at room temperature for 36 hours to obtain the repair agent.

[0065] The remediation agent prepared in this embodiment was tested for its ability to remove heavy metal ions from the soil and the rate of pH change in the soil using the same method as in Example 1 above. The results are shown in the table below.

[0066]

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite soil heavy metal pollution remediation agent, characterized in that, The steps include: (1) The wet material obtained by mixing carbide slag powder, sodium alginate powder and sodium silicate solution is granulated, and then the obtained particles are dried to obtain core particles for later use. (2) Mix waste red brick powder, silica sol rubber powder and water evenly to form a slurry. Then place the core particles in the slurry, coat them with the slurry, remove them, let them stand at room temperature, and then steam them. After completion, dry them to obtain the repair agent.

2. The preparation method of the composite soil heavy metal pollution remediation agent according to claim 1, characterized in that, In step (1), the ratio of carbide slag powder, sodium alginate powder, and sodium silicate solution is 25~38g: 6~7.5g: 7~10ml; optionally, the mass fraction of the sodium silicate solution is 30~35%.

3. The preparation method of the composite soil heavy metal pollution remediation agent according to claim 1, characterized in that, In step (1), the fineness of the carbide slag powder and sodium alginate powder is 200~400 mesh.

4. The preparation method of the composite soil heavy metal pollution remediation agent according to claim 1, characterized in that, In step (1), the drying temperature is 50~70℃ and the drying time is 1~1.5 hours.

5. The preparation method of the composite soil heavy metal pollution remediation agent according to claim 1, characterized in that, In step (1), the particle size of the core particles is 5~20mm.

6. The preparation method of the composite soil heavy metal pollution remediation agent according to claim 1, characterized in that, In step (2), the mass ratio of the waste red brick powder, silica sol, and rubber powder is 1~2:2.4~3.1:0.15~0.23; optionally, the content of nano-SiO2 in the silica sol is 30~40 wt.%.

7. The preparation method of the composite soil heavy metal pollution remediation agent according to claim 1, characterized in that, In step (2), the fineness of the waste red brick powder is 200-400 mesh; optionally, in step (2), the content of nano-SiO2 in the silica sol is 30-40 wt.%.

8. The preparation method of the composite soil heavy metal pollution remediation agent according to claim 1, characterized in that, In step (2), the time for standing at room temperature is 2 to 3 hours.

9. The preparation method of the composite soil heavy metal pollution remediation agent according to any one of claims 1-8, characterized in that, In step (2), the steam curing method is as follows: first, heat the temperature to 60-80℃ at a heating rate of 5-10℃ / h and keep it for 8-12 hours, while maintaining the humidity between 92-95%; after completion, cool the temperature to room temperature at a cooling rate of 5-10℃ / h.

10. The method for preparing the composite soil heavy metal pollution remediation agent according to any one of claims 1-8, characterized in that, In step (2), the drying time is 24~36 hours.

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