Preparation method of composite soil heavy metal pollution repairing agent

Abstract

The invention discloses a preparation method of a composite soil heavy metal pollution repairing agent, which comprises the following steps: (1) uniformly mixing carbide slag powder, sodium alginate powder and a sodium silicate solution to obtain a wet material, granulating, and drying the obtained particles to obtain core particles for later use; and (2) uniformly mixing waste red brick micro powder, silica sol and rubber powder to form slurry, then putting the core particles into the slurry, hanging the slurry, taking out the core particles, standing at room temperature, carrying out steam curing, and airing after the steam curing is completed, so as to obtain the repairing agent. The composite soil heavy metal pollution repairing agent prepared by the invention not only can efficiently and quickly reduce the content of heavy metal ions in soil, but also can play a role for a long time, and is beneficial to preventing pollution occurring again in the later period.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a method for preparing a composite soil heavy metal pollution remediation agent. Background Art

[0002] Heavy metal elements have been widely used in many products of human production and life, which also leads to a large amount of industrial waste dumping, landfill and then washing by rainfall, and heavy metal ions enter the soil to cause heavy metal pollution. In addition, industrial mining, mineral processing, industrial wastewater discharge, etc. are also important sources of heavy metal pollution in the soil. Since heavy metal ions are difficult to degrade in the soil like organic matter, they will continue to accumulate, resulting in an increasing content of heavy metal ions in the soil, which not only damages the physical and chemical properties of the soil, the structure of the microbial community, etc., and affects the growth of crops, but more seriously, it will also be transferred to the human body through water sources, food chains (for example, rice has a strong adsorption capacity for cadmium), etc., causing health problems, and even collective health problems. Therefore, it is very important to timely manage and repair the soil contaminated by heavy metals.

[0003] At present, the main methods for removing heavy metal ions from the soil include deep tillage, soil replacement, soil leaching, biological remediation (such as plants, microorganisms), etc. Among them, although the first two methods are relatively effective, they have large engineering workloads and high costs, and are prone to cause the loss of other nutrients in the soil, leading to a decrease in soil fertility. Although biological remediation has the advantages of being environmentally friendly and low cost, it has problems such as a long remediation cycle and unstable remediation effects due to environmental conditions. Therefore, it is of great practical significance to explore faster, more effective, and long-term remediation technologies for heavy metal ion-contaminated soils. Summary of the invention

[0004] The present invention provides a method for preparing a composite soil heavy metal pollution repair agent, which can not only efficiently and quickly reduce the content of heavy metal ions in the soil, but also can play a role for a long time, helping to prevent the recurrence of pollution in the later period. The technical solution of the present invention is as follows.

[0005] A method for preparing a composite soil heavy metal pollution remediation agent comprises the following steps: (1) The wet material obtained by mixing carbide slag powder, sodium alginate powder and sodium silicate solution is granulated, and then the obtained granules are dried to obtain core granules for later use.

[0006] (2) Mixing the waste red brick powder, silica sol and rubber powder evenly to form a slurry, then placing the core particles in the slurry to coat the slurry and then taking them out, leaving them to stand at room temperature and then steam curing them, and then air-drying them to obtain the repair agent.

[0007] Furthermore, in step (1), the ratio of the carbide slag powder, sodium alginate powder and sodium silicate solution is 25-38 g: 6-7.5 g: 7-10 ml. Optionally, the mass fraction of the sodium silicate solution is 30-35%.

[0008] Furthermore, in step (1), the fineness of the carbide slag powder and the sodium alginate powder is 200-400 mesh. Furthermore, in step (1), the drying temperature is 50-70° C., and the drying time is 1-1.5 hours.

[0009] Furthermore, in step (1), the particle size of the inner core particles is 5 to 20 mm.

[0010] Furthermore, 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. 2 The content is 30~40wt.%.

[0011] Furthermore, 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.

[0012] Furthermore, in step (2), the standing time at room temperature is 2 to 3 hours to reduce the moisture in the slurry coated on the surface of the core particles to facilitate structural shaping.

[0013] Furthermore, in step (2), the steam curing method is: first, the temperature is raised to 60-80°C at a heating rate of 5-10°C / h and maintained for 8-12 hours, and the humidity is maintained between 92-95%. After completion, the temperature is lowered to room temperature at a cooling rate of 5-10°C / h.

[0014] Furthermore, in step (2), the drying time is 24 to 36 hours to remove the residual moisture in the obtained repair agent.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects: The composite soil heavy metal pollution remediation agent of the present invention can not only reduce the content of heavy metal ions in the soil efficiently and quickly, but also play a role for a long time, which is helpful to prevent pollution from occurring again in the later period. To this end, the present invention uses granules formed by carbide slag powder, sodium alginate powder and sodium silicate as the core, and forms a porous shell after wrapping the slurry formed by waste red brick micropowder, silica sol and rubber powder on the surface for steam curing. In this process, on the one hand, the carbide slag gradually releases calcium ions through its slightly soluble characteristics to promote the sodium alginate to gradually cross-link into a film, thereby constructing the core into a slow-release structure. On the other hand, while the slurry is wrapped on the surface of the core by using the good bonding characteristics of silica sol, the calcium hydroxide released by the carbide slag reacts with the nano-silicon dioxide in the silica sol during the steam curing process to form a hydrated calcium silicate gel, thereby not only making the shell more firmly fixed to the core to prevent falling off, but also the hydrated calcium silicate has good adsorption performance for heavy metal ions. After the repair agent of the present invention is mixed with soil contaminated by heavy metal ions, the heavy metal ions entering the inner core first react rapidly with sodium silicate to form insoluble silicates and then solidify, thereby quickly reducing the concentration of free heavy metal ions in the soil. On the other hand, the hydroxide ions gradually released from the inner core can not only play a role in solidifying heavy metal ions, thereby preventing heavy metal ion pollution from occurring again in the later soil, so that the repair agent of the present invention can maintain the ability to repair the soil for a long time, but also prevent soil alkalization. At the same time, the calcium ions gradually released from the inner core can also help improve soil fertility after entering the soil. In addition, the rubber powder in the shell can effectively improve the deformation capacity of the shell, which helps to reduce shell damage during loading, transportation, and application to the soil on the one hand, and helps to adapt to the changes in the volume of the shell caused by the solidified heavy metal ion compounds on the other hand, and reduces the cracking of the shell in the later stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein: Figure 1 This is a sample picture of the composite soil heavy metal pollution remediation agent of the following Example 1.

[0017] Figure 2 This is a sample picture of the composite soil heavy metal pollution remediation agent of the following Example 2. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0019] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions.

[0020] In addition, any method and material similar or equivalent to the content described above can be applied to the method of the present invention. The present invention is further described in conjunction with the accompanying drawings and specific implementation methods. The preferred implementation methods and materials described in the present invention are only for demonstration purposes.

[0021] Embodiment 1: A method for preparing a composite soil heavy metal pollution remediation agent comprises the following steps: (1) Calcium carbide slag powder with a fineness of 200 mesh, sodium alginate powder with a fineness of 250 mesh, and 35% sodium silicate solution by mass fraction are mixed in a ratio of 32 g: 7 g: 8 ml and stirred evenly. The obtained wet material is then granulated and the obtained granules are dried at 60° C. for 1 hour to obtain core granules with a particle size distribution between 10 and 15 mm, which are set aside.

[0022] (2) The waste red brick powder with a fineness of 200 mesh, silica sol (SiO 2 The mass fraction is 30wt.%), and the rubber powder with a fineness of 400 mesh is mixed in a ratio of 1.55g:2.8g:0.17g and stirred evenly to form a slurry. Then the core particles are placed in the slurry and taken out to stand at room temperature for 2.5 hours. After completion, the obtained particles are placed in a curing box and heated to 60°C at a heating rate of 5°C / h for 12 hours. During this process, 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 the obtained particles are dried at room temperature for 24 hours to obtain the following Figure 1 Restoratives shown.

[0023] Heavy metal ion removal ability test: (1) Mix simulated wastewater containing heavy metal ions (including lead, galvanneal, copper, chromium, and nickel) with soil, dry and grind the soil to obtain initial contaminated soil. Then add 30% of the mass of the remediation agent prepared in this embodiment to the soil, then sprinkle water at a moisture content of 25%, and then test the total heavy metal ion content in the soil after 7 days and calculate the removal rate a. (2) Separate the remediation agent from the contaminated soil described in (1), mix it with the new simulated contaminated soil according to the above ratio, sprinkle water at a moisture content of 25%, and test the total heavy metal ion content in the soil after 20 days and calculate the removal rate b. (3) Separate the remediation agent from the contaminated soil described in (2), mix it with the new simulated contaminated soil according to the above ratio, sprinkle water at a moisture content of 25%, and test the total heavy metal ion content in the soil after 20 days and calculate the removal rate c. During the above process, water was sprinkled at appropriate times to keep the soil moisture at the above state. (4) 30% of the mass of the remediation agent prepared in this example was added to the initial contaminated soil, and then water was sprinkled at a ratio of 25% of the moisture content. The pH of the soil at this time was tested (recorded as the initial pH). After 30 days, the change rate of the soil pH relative to the initial pH was tested, and the results are shown in the following table.

[0024]

[0025] Embodiment 2: A method for preparing a composite soil heavy metal pollution remediation agent comprises the following steps: (1) Calcium carbide slag powder with a fineness of 300 mesh, sodium alginate powder with a fineness of 400 mesh, and sodium silicate solution with a mass fraction of 32% are mixed in a ratio of 25 g: 6 g: 7 ml and stirred evenly. The obtained wet material is then granulated and the obtained granules are dried at 50° C. for 1.5 hours to obtain core granules with a particle size distribution between 15 and 20 mm, which are set aside.

[0026] (2) The waste red brick powder with a fineness of 300 mesh and silica sol (SiO 2 The rubber powder with a mass fraction of 36wt.%) and a fineness of 350 mesh are mixed in a ratio of 1.0g:2.4g:0.15g and stirred to form a slurry. Then the core particles are placed in the slurry and taken out to stand at room temperature for 2 hours. After completion, the obtained particles are placed in a curing box and heated to 80°C at a heating rate of 10°C / h for 10 hours. During this process, 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 dried at room temperature for 24 hours to obtain the following Figure 1 Restoratives shown.

[0027] The same method as in Example 1 was used to test the ability of the repair agent prepared in this example to remove heavy metal ions in the soil and the pH change rate of the soil. The results are shown in the following table.

[0028]

[0029] Embodiment 3: A method for preparing a composite soil heavy metal pollution remediation agent comprises the following steps: (1) Calcium carbide slag powder with a fineness of 350 mesh, sodium alginate powder with a fineness of 400 mesh, and 30% sodium silicate solution by mass fraction are mixed in a ratio of 38 g:7.5 g:10 ml and stirred evenly. The obtained wet material is then granulated and the obtained granules are dried at 50°C for 1.5 hours to obtain core granules with a particle size distribution between 5 and 10 mm for later use.

[0030] (2) The waste red brick powder with a fineness of 400 mesh and silica sol (SiO 2 The rubber powder with a mass fraction of 40wt.%) and a fineness of 300 mesh is mixed in a ratio of 2.0g:3.1g:0.23g and stirred to form a slurry, and then the core particles are placed in the slurry and taken out and left to stand at room temperature for 3 hours. After completion, the obtained particles are placed in a curing box and heated to 70°C at a heating rate of 5°C / h for 8 hours. During this process, the humidity is maintained between 92 and 95%. After completion, the temperature is cooled to room temperature at a cooling rate of 5°C / h, and then the obtained particles are dried at room temperature for 36 hours to obtain the repair agent.

[0031] The same method as in Example 1 was used to test the ability of the repair agent prepared in this example to remove heavy metal ions in the soil and the pH change rate of the soil. The results are shown in the following table.

[0032]

[0033] Embodiment 4: A method for preparing a composite soil heavy metal pollution remediation agent comprises the following steps: (1) Calcium carbide slag powder with a fineness of 200 mesh and sodium silicate solution with a mass fraction of 35% are mixed in a ratio of 32 g:7 ml and stirred evenly. The obtained wet material is then granulated and the obtained granules are dried at 60°C for 1 hour to obtain core granules with a particle size distribution between 10 and 15 mm, which are set aside.

[0034] (2) The waste red brick powder with a fineness of 200 mesh, silica sol (SiO 2The rubber powder with a mass fraction of 30wt.%) and a fineness of 400 mesh is mixed in a ratio of 1.55g:2.8g:0.17g and stirred to form a slurry, and then the core particles are placed in the slurry and taken out to stand at room temperature for 2.5 hours. After completion, the obtained particles are placed in a curing box and heated to 60°C at a heating rate of 5°C / h for 12 hours. During this process, the humidity is maintained between 92 and 95%. After completion, the temperature is cooled to room temperature at a cooling rate of 5°C / h, and then the obtained particles are dried at room temperature for 24 hours to obtain the repair agent.

[0035] The same method as in Example 1 was used to test the ability of the repair agent prepared in this example to remove heavy metal ions in the soil and the pH change rate of the soil. The results are shown in the following table.

[0036]

[0037] Embodiment 5: A method for preparing a composite soil heavy metal pollution remediation agent comprises the following steps: (1) Calcium carbide slag powder with a fineness of 300 mesh, sodium alginate powder with a fineness of 400 mesh, and clean water are mixed in a ratio of 25 g: 6 g: 7 ml and stirred evenly. The obtained wet material is then granulated and the obtained granules are dried at 50° C. for 1.5 hours to obtain core granules with a particle size distribution between 15 and 20 mm, which are set aside.

[0038] (2) The waste red brick powder with a fineness of 300 mesh and silica sol (SiO 2 The rubber powder with a mass fraction of 36wt.%) and a fineness of 350 mesh is mixed in a ratio of 1.0g:2.4g:0.15g and stirred evenly to form a slurry, and then the core particles are placed in the slurry and taken out and left to stand at room temperature for 2 hours. After completion, the obtained particles are placed in a curing box and heated to 80°C at a heating rate of 10°C / h for 10 hours. During this process, the humidity is maintained between 92 and 95%. After completion, the temperature is cooled to room temperature at a cooling rate of 5°C / h, and then the obtained particles are dried at room temperature for 24 hours to obtain the repair agent.

[0039] The same method as in Example 1 was used to test the ability of the repair agent prepared in this example to remove heavy metal ions in the soil and the pH change rate of the soil. The results are shown in the following table.

[0040]

[0041] Embodiment 6: A method for preparing a composite soil heavy metal pollution remediation agent comprises the following steps: (1) Mix 200-mesh slag powder, 250-mesh sodium alginate powder, and 35% sodium silicate solution in a ratio of 32 g: 7 g: 8 ml and stir evenly. Then granulate the obtained wet material and dry the obtained granules at 60° C. for 1 hour to obtain core granules with a particle size distribution between 10 and 15 mm for later use.

[0042] (2) The waste red brick powder with a fineness of 200 mesh, silica sol (SiO 2 The rubber powder with a mass fraction of 30wt.%) and a fineness of 400 mesh is mixed in a ratio of 1.55g:2.8g:0.17g and stirred to form a slurry, and then the core particles are placed in the slurry and taken out to stand at room temperature for 2.5 hours. After completion, the obtained particles are placed in a curing box and heated to 60°C at a heating rate of 5°C / h for 12 hours. During this process, the humidity is maintained between 92 and 95%. After completion, the temperature is cooled to room temperature at a cooling rate of 5°C / h, and then the obtained particles are dried at room temperature for 24 hours to obtain the repair agent.

[0043] The same method as in Example 1 was used to test the ability of the repair agent prepared in this example to remove heavy metal ions in the soil and the pH change rate of the soil. The results are shown in the following table.

[0044]

[0045] Embodiment 7: A method for preparing a composite soil heavy metal pollution remediation agent comprises the following steps: (1) Calcium carbide slag powder with a fineness of 350 mesh, sodium alginate powder with a fineness of 400 mesh, and 30% sodium silicate solution by mass fraction are mixed in a ratio of 38 g:7.5 g:10 ml and stirred evenly. The obtained wet material is then granulated and the obtained granules are dried at 50°C for 1.5 hours to obtain core granules with a particle size distribution between 5 and 10 mm for later use.

[0046] (2) The waste red brick powder with a fineness of 400 mesh and silica sol (SiO 2 The rubber powder with a mass fraction of 40wt.%) and a fineness of 300 mesh are mixed in a ratio of 2.0g:3.1g:0.23g and stirred evenly to form a slurry, and then the core particles are placed in the slurry and taken out and dried at room temperature for 36 hours to obtain the repair agent.

[0047] The same method as in Example 1 was used to test the ability of the repair agent prepared in this example to remove heavy metal ions in the soil and the pH change rate of the soil. The results are shown in the following table.

[0048]

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope 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) granulating the wet material obtained by mixing carbide slag powder, sodium alginate powder and sodium silicate solution, and then drying the obtained granules to obtain core granules for standby use; (2) Mixing waste red brick powder, silica sol rubber powder and water to form a slurry, then placing the core particles in the slurry to coat the slurry and then taking them out, leaving them to stand at room temperature and then steam curing them, and then air-drying them to obtain the repair agent.

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

3. The method for preparing 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 the sodium alginate powder is 200-400 mesh.

4. The method for preparing the composite soil heavy metal pollution remediation agent according to claim 1, characterized in that: In step (1), the drying temperature is 50-70° C. and the drying time is 1-1.5 hours.

5. The method for preparing 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 5-20 mm.

6. The method for preparing 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 30-40wt.%.

7. The method for preparing 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 30-40wt.%.

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

9. The method for preparing the composite soil heavy metal pollution remediation agent according to any one of claims 1 to 8, characterized in that: In step (2), the steam curing method is: first, the temperature is raised to 60-80°C at a heating rate of 5-10°C / h and maintained for 8-12 hours, and the humidity is maintained between 92-95%; after completion, the temperature is lowered to room temperature at a cooling rate of 5-10°C / h.

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

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