Humus solidifying agent, its preparation method and application

Abstract

The application belongs to the technical field of solid waste treatment, and particularly relates to a humus soil solidifying agent and a preparation method and application thereof. The humus soil solidifying agent comprises, in mass fraction, 50-80 parts of blast furnace slag, 5-30 parts of carbide slag, 5-10 parts of phosphogypsum and 0-10 parts of biochar. The humus soil solidifying agent and the preparation method and application thereof provided by the application solve the problem of reuse of humus soil, the solidified body formed can meet the requirements of pollutant leaching and mechanical properties, can be used as in-situ or ex-situ backfilling material, a large amount of transportation cost and secondary landfill cost can be saved, and excellent environmental and economic benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, and in particular to a humus solidification agent, its preparation method, and its application. Background Technology

[0002] Landfill extraction and differentiated reuse are considered important pathways to achieve ecological restoration of aging, simple landfills and resource utilization of landfill waste. The main components of landfill soil after screening include: building materials, combustibles, recyclables, and fine particles. The fine particles, also known as humus, are primarily mixed particulate matter produced from the daily soil cover of simple landfills and the degradation of biodegradable substances in municipal solid waste. Currently, humus is not widely reused, despite its content exceeding 50%. As is well known, humus contains high concentrations of organic matter, heavy metals, and soluble salts, so in addition to meeting basic mechanical properties, reuse must also consider the properties of the leachate as a key parameter for evaluating the reliability of direct backfilling with humus.

[0003] Solidification and stabilization is a commonly used method for improving mechanical strength and controlling pollutants. Traditional inorganic solidification materials mainly consist of cementitious materials such as cement and lime, but their large-scale use inevitably increases disposal costs and leads to unavoidable energy consumption and environmental pollution. Therefore, finding a potential low-carbon, low-cost material to replace traditional inorganic solidification materials is of great significance for reducing carbon emissions and achieving the sustainable development goal of "waste-to-waste". Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a humus solidifying agent, its preparation method and application. This solidifying agent solves the problem of humus reuse, and the solidified body formed can meet the requirements of pollutant leaching and mechanical properties. It can be used as an in-situ or ex-situ backfill material, saving a lot of transportation costs and secondary landfill fees, and has excellent environmental and economic benefits.

[0005] To address the aforementioned technical problems, this invention provides a humus-based solidifying agent. Preparation method and application are also described.

[0006] In a first aspect of this application, this application provides a humus solidifying agent, which, by weight, comprises 50-80 parts blast furnace slag, 5-30 parts carbide slag, 5-10 parts phosphogypsum, and 0-10 parts biochar.

[0007] In some embodiments, the particle size of the blast furnace slag, the carbide slag, the phosphogypsum, and the biochar is less than or equal to 200 mesh.

[0008] In a second aspect, this application also provides a method for preparing the above-mentioned humus solidifying agent, the method comprising:

[0009] Provide raw materials, by weight, including: 50-80 parts blast furnace slag, 5-30 parts calcium carbide slag, 5-10 parts phosphogypsum, and 0-10 parts biochar;

[0010] The provided raw materials are mixed and stirred evenly to obtain humus soil solidification agent.

[0011] In some embodiments, the mixing and stirring of the provided raw materials is carried out at a stirring rate of ≥150 r / min and a stirring time of 3 to 5 min.

[0012] In a third aspect of this application, this application also provides an application of the above-mentioned humus solidifying agent, characterized in that the humus solidifying agent is incorporated into wet humus.

[0013] Mix the wet humus soil containing the humus soil stabilizer evenly.

[0014] Mix the well-stirred humus solidifier and wet humus, add the remaining water according to the optimal moisture content, and then mix well again.

[0015] Samples were prepared using the maximum dry density static pressing method, and the solidified body was obtained after curing.

[0016] In some embodiments, the incorporation of the humus solidifying agent into the wet humus specifically includes:

[0017] According to the total mass ratio, the humus soil is 70-90 parts and the solidifying agent is 10-30 parts.

[0018] In some embodiments, the step of uniformly mixing the wet humus mixed with the humus solidifying agent specifically includes:

[0019] The stirring rate is ≥150 r / min, and the stirring time is 5 to 10 min.

[0020] In some implementations, the step of adding the remaining mass of water according to the optimal moisture content and then stirring again to ensure uniformity specifically includes:

[0021] Add 60-80 parts water according to the optimal moisture content, stir well, seal and let stand for more than 12 hours.

[0022] In some implementation schemes, the stirring rate is ≥150 r / min and the stirring time is 5 to 10 min.

[0023] In some embodiments, the curing conditions for the cured body are as follows:

[0024] Temperature 20±2℃, humidity 95±3%, curing time 7~90 days.

[0025] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0026] This application provides a novel humus solidifier, its preparation method, and its application. It fully utilizes the volcanic ash activity of blast furnace slag, carbide slag and phosphogypsum as activators and supplements for various active components, and biochar as an adsorbent that also effectively fixes carbon and nitrogen. By leveraging the strengths of different materials, a novel humus solidifier is prepared. Specifically, carbide slag and phosphogypsum jointly stimulate the potential activity of blast furnace slag, promoting the reaction of volcanic ash to generate hydraulic gels such as hydrated calcium silicate / hydrated calcium aluminate, improving the adhesion between humus particles. The abundant growth of ettringite crystals fills the micropores between humus particles, forming a stable and dense soil structure, thus significantly improving subsequent mechanical properties. Furthermore, the novel solidifier reduces the organic matter content in the sample by influencing the mineralization of organic matter through the presence of some active oxides (e.g., iron oxides and aluminum oxides) in the organic matter solidifier. Organic matter can be adsorbed through electrostatic interactions and ligand exchange, particularly on iron and aluminum oxides. Direct fixation of organic matter on oxides, especially iron and aluminum oxides, is also an important pathway for reducing its content. The encapsulation and chemical stabilization of amorphous gel products can passivate heavy metals, rendering them immobile. Biochar, with its abundant pore structure and large specific surface area, can adsorb heavy metals and organic pollutants from humus, thereby reducing the risk of environmental pollution. Detailed Implementation

[0027] The following will illustrate this through specific examples.

[0028]

[0029]

[0030] Example 1

[0031] This embodiment provides a humus solidification agent, its preparation method, and its application, including the following steps:

[0032] S01. Pass the blast furnace slag through a 200-mesh sieve. The blast furnace slag described in this example was taken from a mineral processing plant. The chemical composition of the blast furnace slag is shown in Table 1.

[0033] Table 1. Main Chemical Composition of Blast Furnace Slag (mass percentage %)

[0034] MgO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> High <![CDATA[Fe2O3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[P2O5]]> <![CDATA[SO3]]> 8.73 13.25 35.86 38.52 0.31 1.08 0.85 0.06 -

[0035] S02. Pass the calcium carbide slag and phosphogypsum through a 200-mesh sieve. The calcium carbide slag in this embodiment was obtained from a chemical company, and its chemical composition is shown in Table 2. The phosphogypsum in this embodiment was obtained from a chemical company, and its chemical composition is shown in Table 3.

[0036] Table 2. Main chemical composition of calcium carbide slag (mass percentage %)

[0037] MgO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> High <![CDATA[Fe2O3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[P2O5]]> <![CDATA[SO3]]> 0.26 1.29 3.65 90.75 0.30 - 0.95 0.03 2.63

[0038] Table 3. Main chemical composition of phosphogypsum (mass percentage %)

[0039] MgO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> High <![CDATA[Fe2O3]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[P2O5]]> <![CDATA[SO3]]> 0.11 0.83 8.27 37.25 0.63 0.53 0.17 0.88 50.11

[0040] S03. Pass the biochar through a 200-mesh sieve. The biochar described in this embodiment is produced by high-temperature pyrolysis of straw. The bulk density of the biochar is 400-450 g / L, and the specific surface area is 1000-1300 m². 2 / g, C content greater than 95%.

[0041] S04. The blast furnace slag, carbide slag, phosphogypsum and biochar are mixed evenly to form a novel inorganic curing agent. The mass ratio of the blast furnace slag, carbide slag, phosphogypsum and biochar is 50 parts of blast furnace slag, 30 parts of carbide slag, 10 parts of phosphogypsum and 10 parts of biochar.

[0042] In step S04 of this embodiment, the main purpose is to mix blast furnace slag, carbide slag, phosphogypsum and biochar evenly. Specifically, blast furnace slag, carbide slag, phosphogypsum and biochar are added to a mixing device in the mass ratio and stirred at a low speed of 150 rpm for 5 to 10 minutes to mix the blast furnace slag, carbide slag, phosphogypsum and biochar evenly to obtain a new type of inorganic curing agent.

[0043] S05. The humus obtained by screening, drying, crushing and passing through a 10-mesh sieve after the components mined from the landfill are dried again in an oven at a temperature of about 60°C for 24 hours before solidification treatment.

[0044] S06. The novel inorganic curing agent is mixed evenly with humus to form a mixture, wherein the mass ratio of the novel inorganic curing agent to humus is 15 parts of the novel inorganic curing agent and 85 parts of the humus.

[0045] S07. Conduct compaction tests according to the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" (JTG E51-2009), and then determine the maximum dry density and optimum moisture content of the mixture according to the standard method of the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" (JTG E51-2009).

[0046] S08. After mixing the new inorganic curing agent with humus soil evenly, and according to the optimal moisture content of the cured soil mixture being 1% to 2% higher, a solidified body with a compaction degree of 95% is formed by static pressure method. The total operation time from adding water, mixing, and compaction is within 0.5 to 2 hours.

[0047] Example 2

[0048] In another embodiment of the present invention, unlike embodiment one, in step S04, the mass ratio of the blast furnace slag, carbide slag, phosphogypsum and biochar is 55 parts of the blast furnace slag, 30 parts of the carbide slag, 10 parts of the phosphogypsum and 5 parts of the biochar.

[0049] Example 3

[0050] In another embodiment of the present invention, unlike embodiment one, in step S04, the mass ratio of the blast furnace slag, carbide slag, phosphogypsum and biochar is 60 parts of the blast furnace slag, 20 parts of the carbide slag, 10 parts of the phosphogypsum and 10 parts of the biochar.

[0051] Example 4

[0052] In another embodiment of the present invention, unlike embodiment one, in step S04, the mass ratio of the blast furnace slag, carbide slag, phosphogypsum and biochar is 65 parts of the blast furnace slag, 20 parts of the carbide slag, 10 parts of the phosphogypsum and 5 parts of the biochar.

[0053] Example 5

[0054] In another embodiment of the present invention, unlike Embodiment 1, in step S04, the mass ratio of the blast furnace slag, carbide slag, phosphogypsum, and biochar is 70 parts of the blast furnace slag, 15 parts of the carbide slag, 5 parts of the phosphogypsum, and 10 parts of the biochar; in step S06, the mass ratio of the novel inorganic curing agent to humus is 10 parts of the novel inorganic curing agent and 90 parts of the humus.

[0055] Example 6

[0056] In another embodiment of the present invention, unlike embodiment one, in step S04, the mass ratio of the blast furnace slag, carbide slag, phosphogypsum and biochar is 70 parts of the blast furnace slag, 15 parts of the carbide slag, 5 parts of the phosphogypsum and 10 parts of the biochar.

[0057] Example 7

[0058] In another embodiment of the present invention, unlike embodiment one, in step S04, the mass ratio of the blast furnace slag, carbide slag, phosphogypsum and biochar is 75 parts of the blast furnace slag, 15 parts of the carbide slag, 5 parts of the phosphogypsum and 5 parts of the biochar.

[0059] Example 8

[0060] In another embodiment of the present invention, unlike embodiment one, in step S04, the mass ratio of the blast furnace slag, carbide slag, phosphogypsum and biochar is 80 parts of the blast furnace slag, 5 parts of the carbide, 5 parts of the phosphogypsum and 10 parts of the biochar.

[0061] Example 9

[0062] In another embodiment of the present invention, unlike embodiment one, in step S04, the mass ratio of the blast furnace slag, carbide slag, phosphogypsum and biochar is 80 parts of the blast furnace slag, 15 parts of the carbide, 5 parts of the phosphogypsum and 0 parts of the biochar.

[0063] The solidified humus soils prepared in each embodiment were tested for solid waste leaching toxicity according to the "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The organic matter content of the samples was tested using the potassium dichromate titration method according to the "Standard for Geotechnical Testing Methods" (GB / T 50123-1999). The 7-day unconfined compressive strength and California bearing capacity ratio of the samples were also tested according to the "Standard for Geotechnical Testing Methods" (GB / T 50123-1999). The test results are shown in the table below:

[0064]

[0065] The table shows that the leaching concentrations of heavy metals (Cr, Pb, Zn, Cu, Ni, Cd) in the solidified humus soil meet the requirements for Class I and Class II land use in the "Soil Environmental Quality Standard for Construction Land Soil Pollution Risk Control (Trial)" (GB36600-2018). The organic matter content of the solidified humus soil in all examples meets the requirements for solidified soil (≤5%) in the Chinese standards "Technical Standard for Application of Soil Stabilizers" (CJJ / T286-2018) and "General Specifications for Building and Municipal Foundations" (GB55003-2021). The 7-day unconfined compressive strength of the samples in all examples meets the design requirements for composite foundation materials (≥300 kPa) in the "General Specifications for Building and Municipal Foundations" (GB55003-2021). The solidified humus soil in all examples meets the California bearing capacity limit requirements for subgrade and embankment fill materials of all levels of highways in the "Specifications for Highway Subgrade Design" (JTG D30-2015).

[0066] In summary, the road subbase layers in all embodiments exhibit excellent heavy metal stabilization effects, mechanical properties, and safety in use. This curing agent not only achieves large-scale consumption of industrial solid waste but also eliminates the need for traditional cement, reducing cement usage. It is environmentally friendly, has a simple preparation process, provides excellent curing results that meet national requirements, and is cost-effective, making it suitable for widespread application.

Claims

1. A humus soil stabilizer, characterized in that, By weight, the humus solidifying agent comprises 50-80 parts blast furnace slag, 5-30 parts carbide slag, 5-10 parts phosphogypsum, and 0-10 parts biochar.

2. The humus-stabilizing agent according to claim 1, characterized in that, The particle size of the blast furnace slag, the carbide slag, the phosphogypsum, and the biochar is less than or equal to 200 mesh.

3. A method for preparing the humus solidifying agent according to claim 1 or 2, characterized in that, The preparation method includes: Provide raw materials, by weight, including: 50-80 parts blast furnace slag, 5-30 parts calcium carbide slag, 5-10 parts phosphogypsum, and 0-10 parts biochar; Mix the provided raw materials thoroughly to obtain a humus solidifier.

4. The method for preparing the humus solidifying agent according to claim 3, characterized in that, In the process of mixing and stirring the provided raw materials evenly, the stirring speed is ≥150r / min and the stirring time is 3-5min.

5. The application of the humus solidifying agent according to claim 1 or 2, characterized in that, The humus solidifying agent is mixed into the wet humus; Mix the wet humus soil containing the humus soil stabilizer evenly. Mix the well-stirred humus solidifier and wet humus, add the remaining water according to the optimal moisture content, and then mix well again. Samples were prepared using the maximum dry density static pressing method, and the solidified body was obtained after curing.

6. The application of the humus solidifying agent according to claim 5, characterized in that, The process of adding the humus solidifying agent to wet humus specifically includes: According to the total mass ratio, the humus soil is 70-90 parts and the solidifying agent is 10-30 parts.

7. The application of the humus solidifying agent according to claim 5, characterized in that, The step of mixing the wet humus mixed with the humus solidifying agent evenly specifically includes: The stirring rate is ≥150 r / min, and the stirring time is 5 to 10 min.

8. The application of the humus solidifying agent according to claim 5, characterized in that, The step of adding the remaining water at the optimal moisture content and then stirring again until homogeneous specifically includes: Add 60-80 parts water according to the optimal moisture content, stir well, seal and let stand for more than 12 hours.

9. The application of the humus solidifying agent according to claim 8, characterized in that, The stirring rate is ≥150 r / min, and the stirring time is 5 to 10 min.

10. The application of the humus solidifying agent according to claim 5, characterized in that, The curing conditions for the solidified body are as follows: Temperature 20±2℃, humidity 95±3%, curing time 7~90 days.

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