River channel sediment solidifying agent, preparation method and application thereof

Abstract

The application discloses a river channel sediment solidifying agent and a preparation method and application thereof, and comprises the following components in parts by weight: 25-32 parts of steel slag micro powder, 16-22 parts of metakaolin, 8-10 parts of modified activated carbon, 3-5 parts of modified straw ash, 3-5 parts of nano calcium carbonate, 5-8 parts of an activator, 3-5 parts of sinking beads, 2-4 parts of nano iron particles, 3-6 parts of chitosan quaternary ammonium salt and 10-15 parts of sulphoaluminate cement clinker. The components of the solidifying agent are synergized in multiple dimensions through 'gelation enhancement-structure densification-pollution fixation-performance adaptation', so that the river channel sediment is efficiently solidified, the mechanical strength, durability and water resistance of the solidified body are ensured, the pollutants in the sediment are stabilized, and the construction feasibility and environmental safety are considered.

Description

Technical Field

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

[0002] Riverbed sediment is a silty material formed by long-term river deposition. Its composition is affected by soil erosion, industrial wastewater, domestic sewage, and agricultural non-point source pollution within the watershed. It contains a large amount of inorganic particles such as clay and silt, as well as organic matter such as humus, animal and plant remains, and persistent pollutants. It also contains some heavy metals (such as cadmium, lead, and mercury), pathogens (bacteria and viruses), and microplastics, resulting in a highly mixed composition of sediment. If the sediment is not cleaned for a long time, it will continue to cause water pollution. Therefore, riverbed sediment needs to be treated periodically.

[0003] Because riverbed sediment has a high water content, typically 60%-90% in natural sediments, it is in a fluid or soft plastic state with high porosity, poor air permeability, and extremely low mechanical strength (shear strength mostly <10kPa), making it difficult to transport or utilize directly. Therefore, riverbed sediment treatment methods mainly include physical dewatering, chemical treatment using solidifying agents / stabilizers, biological treatment using aerobic composting, and high-temperature thermal treatment. Among these, treatment using solidifying agents is the most widely used method due to its simple process, low energy consumption, and ability to recycle resources.

[0004] The solidifying agent used for riverbed sediment is also called sludge solidifying agent. It mainly includes inorganic materials such as cement for solidification, combined with coagulants, water-reducing agents and heavy metal adsorbents to achieve solidification treatment of sludge.

[0005] However, some riverbed sediments contain black and odorous water, with an organic matter content often exceeding 6%. Existing inorganic solidifying agents are difficult to bind with macromolecules such as proteins and oils, resulting in poor compressive strength, water resistance, and volume stability of the treated sludge. Therefore, it is necessary to provide a sediment solidifying agent that can treat sediments with a high organic matter content. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a riverbed sediment solidification agent, its preparation method, and its application, which solves the problem that when the organic matter content in the sediment is high, the treated sludge has poor compressive strength, water resistance, and volume stability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a riverbed sediment solidifying agent, comprising, by weight: 25-32 parts steel slag powder, 16-22 parts metakaolin, 8-10 parts modified activated carbon, 3-5 parts modified straw ash, 3-5 parts nano-calcium carbonate, 5-8 parts activator, 3-5 parts sediment beads, 2-4 parts nano-iron particles, 3-6 parts chitosan quaternary ammonium salt, and 10-15 parts sulfoaluminate cement clinker.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] 1. In this invention, steel slag powder is used to replace cement, which can realize the recycling of industrial solid waste. At the same time, the approximately 40-50% CaO and 10-15% Al2O3 contained in the steel slag powder can be activated with the large amount of SiO2 in metakaolin under the action of an activator to generate CSH (calcium silicate hydrate) and CAH (calcium aluminate hydrate) gels. Meanwhile, the porous structure of modified straw ash and modified activated carbon can quickly adsorb free water in sludge, increasing the dewatering rate by 20-30%. Its silicon-oxygen bonds crosslink with the gel network, reducing later cracking.

[0010] 2. Nano-calcium carbonate, through its pre-filling and post-bridging effect, can refine the pores of the solidified body, achieving an early (14d) compressive strength of over 4MPa, significantly higher than the 2.0MPa of traditional cement-based formulations. The amino and hydroxyl groups of chitosan quaternary ammonium salt can stabilize heavy metals through chelation, reducing the leaching rate of heavy metals to below 0.1mg / L, far below the national standard GB5085.3-2007. At the same time, its cationic flocculated sludge exhibits a significantly improved organic matter degradation rate, reducing solidified body shrinkage.

[0011] 3. Compared with traditional high-alkali curing agents, this formula adjusts the alkalinity through sulfoaluminate cement clinker to avoid the rebound of heavy metal leaching, so that the cured sludge can be directly used for roadbed backfilling or land reclamation.

[0012] 4. The added sediment beads in this invention are hollow glass microspheres with a spherical shape, which makes the combination of each component with the sludge more uniform. At the same time, the sediment beads are oleophilic, and together with the porous modified straw ash and modified activated carbon, they can fix the organic matter in the whole solidified body, reduce the leaching rate of oil, and thus increase the water resistance and volume stability of the solidified body.

[0013] 5. The addition of nano-iron particles can, through the synergistic effect of reduction and adsorption, reduce Cr... 6+ Reduced to Cr 3+ It is fixed and, in conjunction with the adsorption of other heavy metals, reduces the leaching rate of heavy metals, ensuring the treatment effect of sludge.

[0014] Preferably, by weight, it includes: 25-30 parts steel slag powder, 16-18 parts metakaolin, 8-10 parts modified activated carbon, 3-5 parts modified straw ash, 3-5 parts nano calcium carbonate, 6-8 parts activator, 4-5 parts precipitated beads, 3-4 parts nano iron particles, 5-6 parts chitosan quaternary ammonium salt, and 12-15 parts sulfoaluminate cement clinker.

[0015] Preferably, by weight, it includes: 30 parts steel slag powder, 18 parts metakaolin, 10 parts modified activated carbon, 5 parts modified straw ash, 5 parts nano calcium carbonate, 8 parts activator, 5 parts precipitated beads, 3 parts nano iron particles, 5 parts chitosan quaternary ammonium salt, and 15 parts sulfoaluminate cement clinker.

[0016] Preferably, the particle size range of the steel slag powder is 800 mesh to 600 mesh.

[0017] Preferably, the particle size range of nano-calcium carbonate is 50-60 nm.

[0018] Preferably, the activator includes Na2SO4 and NaOH.

[0019] Preferably, the mass ratio of Na2SO4 to NaOH is 1-1.2:1.

[0020] Preferably, the particle size of the iron nanoparticles is in the range of 50-100 nm.

[0021] Secondly, the present invention provides a method for preparing a curing agent, comprising the following steps:

[0022] Weigh out the following raw materials according to the specified weight proportions: 25-32 parts steel slag powder, 16-22 parts metakaolin, 8-10 parts modified activated carbon, 3-5 parts modified straw ash, 3-5 parts nano calcium carbonate, 5-8 parts activator, 3-5 parts precipitated beads, 2-4 parts nano iron particles, 3-6 parts chitosan quaternary ammonium salt, and 10-15 parts sulfoaluminate cement clinker. Set aside for later use.

[0023] The weighed raw materials are mixed and stirred to obtain the target product.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The curing agent preparation method of the present invention is simple and easy to operate, and convenient to prepare and use.

[0026] Thirdly, this application also provides an application of a riverbed sediment solidifier, wherein the solidifier and sediment are mixed and stirred at a weight ratio of (0.6-0.15):1, and then solidified and shaped.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The curing agent of this invention is suitable for treating sediments with high water content and high organic matter content. In particular, it has a better effect on the degradation and curing of oils in sediments with a high content of grease in organic matter, resulting in better water resistance, compressive strength and volume stability of the cured sludge. Furthermore, during the curing process after mixing sediments and curing agents, a film covering method can be selectively used in the early curing process, depending on the specific use environment (humidity, temperature, etc.). Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] The chemical composition of the steel slag powder involved in this invention includes: 40%-50% CaO, 10%-15% SiO2, 20%-25% Fe2O3, 10%-15% Al2O3, and 8%-10% MgO; the specific surface area of ​​the steel slag powder is greater than 600 m². 2 / kg, with a particle size of around 800 mesh.

[0031] Metakaolin: 40%-55% silicon dioxide, 30%-45% aluminum oxide, 1%-3% iron oxide, 0.5%-2% carbon dioxide, and also contains trace amounts of CaO, MgO, K2O, and Na2O.

[0032] Modified activated carbon: This refers to activated carbon treated with ion modification. The modification methods for activated carbon are as follows:

[0033] Activated carbon was impregnated in a 1 mol / L magnesium chloride solution and ultrasonically vibrated at 60°C for 3 hours to allow Mg to embed into the carbon layer structure. After filtration, it was dried at 120°C and then calcined at 600°C under nitrogen protection for 1 hour to form MgO-MgCl2 composite active sites. Surface oxidation: The calcined activated carbon was oxidized with a 30% hydrogen peroxide solution at 70°C for 1 hour to obtain modified activated carbon.

[0034] In addition to its porous structure, which allows it to be used in conjunction with precipitated beads, the modified activated carbon also contains added Mg. 2+ Magnesium ion exchange can adsorb phosphates in organic matter. Oxygen-containing functional groups (such as -COOH, -C=O) on the surface of oxidized activated carbon adsorb organic matter (DOM) through hydrogen bonding and π-π interaction, which can increase the degradation effect of organic matter.

[0035] Modified straw ash is produced by high-temperature calcination (600℃) to remove organic impurities from straw, converting it into inorganic ash, and then activating it with NaOH (a strong alkali) to improve its surface activity. This is a mature existing processing technology. Modified straw ash mainly includes 30%-60% silicon dioxide, 5%-20% potassium oxide, 5%-15% calcium oxide, and small amounts of magnesium oxide, aluminum oxide, iron oxide, and phosphorus pentoxide.

[0036] Activator: A composite activator, consisting of Na2SO4 and NaOH; the mass ratio of Na2SO4 to NaOH is 1-1.2:1.

[0037] This invention provides a riverbed sediment solidification agent, comprising, by weight: 25-32 parts steel slag powder, 16-22 parts metakaolin, 8-10 parts modified activated carbon, 3-5 parts modified straw ash, 3-5 parts nano-calcium carbonate, 5-8 parts activator, 3-5 parts sediment beads, 2-4 parts nano-iron particles, 3-6 parts chitosan quaternary ammonium salt, and 10-15 parts sulfoaluminate cement clinker. The nano-calcium carbonate has a particle size range of 50-60 nm. The nano-iron particles have a particle size range of 50-100 nm. The steel slag powder has a particle size range of 800 mesh-600 mesh. The activator comprises Na₂SO₄ and NaOH, with a mass ratio of Na₂SO₄ to NaOH of 1:1.

[0038] In this invention, steel slag powder provides a calcium-aluminum source, which hydrates to form CAH gel, thus realizing the resource utilization of industrial solid waste and exhibiting superior activity compared to fly ash. Metakaolin supplements the active components of silicon and aluminum, promoting the pozzolanic reaction and replacing traditional silica fume cement, significantly reducing the overall cost of the solidifying agent by up to 30%. Modified activated carbon, a porous material, can adsorb moisture and provide a framework for the effective components such as sediment beads, allowing them to combine with the target components in the sediment to form a more stable solidification system and increase the water resistance of the solidified sediment. Modified straw ash, a porous material, can adsorb moisture and supplement the silicon-oxygen tetrahedral structure, activating the carbonization of biomass waste and enhancing its water retention. Nano-calcium carbonate (50-60nm) can fill micropores, accelerating the densification of the gel, and its large specific surface area promotes early strength growth, resulting in higher compressive strength of the solidified sludge. Chitosan quaternary ammonium salt is used to flocculate organic matter and chelate heavy metals (Cu). 2+ / Pb 2+This invention utilizes a bio-based material that can replace toxic chelating agents, making the curing agent more environmentally friendly. Sulfoaluminate cement clinker is used to regulate setting time, improve mid-term strength, and synergistically reinforce with ettringite formed by steel slag powder. The activator is a composite activator composed of Na₂SO₄ and NaOH, which can activate the activity of steel slag powder and metakaolin, accelerate hydration, and reduce secondary pollution. Nano-iron particles have strong reducing properties, reducing highly toxic heavy metals to less toxic forms through electron transfer; simultaneously, their surface can chemically adsorb heavy metals to form stable complexes. The spherical beads (lightweight hollow microspheres) reduce stress concentration within the solidified body, improve workability, and reduce shrinkage cracking through their smooth surface and spherical shape.

[0039] In this invention, sulfoaluminate cement clinker is used as the core cementitious material. The ettringite (AFt) and CSH gel generated by its rapid hydration provide early strength. Steel slag powder and metakaolin are used as active admixtures. Under the action of an activator, they react with Ca(OH)2 generated by cement hydration to produce pozzolanic reaction, generating additional CSH and CAH gels, which make up for the deficiencies of cement hydration products and significantly improve the later strength and structural density of the solidified body.

[0040] Modified straw ash can further participate in the reaction, forming a "multi-element active system" with steel slag powder and metakaolin. Under the synergistic effect of activators, it can increase the amount of cementitious products generated. At the same time, the porous structure of straw ash provides sites for gel growth, strengthens the interfacial bonding of each phase, and jointly constructs a continuous strength skeleton with cement clinker.

[0041] Furthermore, nano-calcium carbonate, with its nano-size effect, acts as a "crystal nucleus" to promote the directional growth of cement hydration products (ettringite, CSH), while simultaneously filling the tiny pores in the cementitious system and refining the pore structure. Meanwhile, the submerged beads, through their smooth surface and spherical shape, reduce stress concentration inside the solidified body, improve the workability of the slurry, and reduce shrinkage cracking. Together with nano-calcium carbonate, they form a "macro-micro" pore synergistic filling effect, significantly improving the impermeability and crack resistance of the solidified body.

[0042] In addition, chitosan quaternary ammonium salt enhances the interfacial compatibility of inorganic particles (steel slag, metakaolin, nano-calcium carbonate, etc.) through the binding effect of molecular chains, reduces defects caused by uneven component dispersion, and further optimizes the integrity of the microstructure.

[0043] Modified activated carbon enriches organic matter and heavy metal ions in sediment through physical adsorption; nano-iron particles reduce highly toxic heavy metals to less toxic forms through electron transfer, while their surface can chemically adsorb heavy metals to form stable complexes; the cationic groups of chitosan quaternary ammonium salt interact electrostatically with clay particles and anionic pollutants in the sediment, promoting pollutant flocculation and sedimentation. These three elements form a synergistic "adsorption-reduction-flocculation" mechanism: modified activated carbon expands the adsorption range, nano-iron enhances deep detoxification, and chitosan improves the overall pollutant aggregation and fixation efficiency, significantly reducing the leaching risk of pollutants from the solidified material.

[0044] The rapid hardening properties of sulfoaluminate cement, combined with the retarding effects of steel slag powder and metakaolin, form a "rapid hardening-stable strength" balance, avoiding structural looseness caused by excessively rapid solidification. The flexible chain structure of chitosan quaternary ammonium salt can alleviate the rigid shrinkage of inorganic cementitious materials, and works synergistically with the crack resistance of the sediment to reduce late-stage cracking of the solidified body. The porosity of modified straw ash combined with the lightweight properties of the sediment reduces the dry density of the solidified body, avoiding additional loads on the riverbed and meeting the lightweight requirements of river engineering.

[0045] In summary, the components of the curing agent in this invention achieve efficient curing of riverbed sediment through multi-dimensional synergy of "gelation enhancement - structural densification - pollution fixation - performance adaptation". This ensures the mechanical strength, durability and water resistance of the cured body, stabilizes pollutants in the sediment, and takes into account both construction feasibility and environmental safety.

[0046] To verify the effectiveness of the curing agent of the present invention, the present invention will be verified through the following examples and comparative examples.

[0047] Example 1

[0048] This embodiment provides a curing agent, comprising the following raw materials by weight: 30 parts steel slag powder, 18 parts metakaolin, 10 parts modified activated carbon, 5 parts modified straw ash, 5 parts nano-calcium carbonate, 8 parts activator, 5 parts precipitated beads, 3 parts nano-iron particles, 5 parts chitosan quaternary ammonium salt, and 15 parts sulfoaluminate cement clinker. The curing agent in this embodiment is obtained by weighing and mixing the raw materials according to the specified proportions.

[0049] Example 2

[0050] This embodiment provides a curing agent, comprising the following raw materials by weight: 25 parts steel slag powder, 22 parts metakaolin, 8 parts modified activated carbon, 5 parts modified straw ash, 3 parts nano-calcium carbonate, 8 parts activator, 5 parts precipitated beads, 2 parts nano-iron particles, 3 parts chitosan quaternary ammonium salt, and 15 parts sulfoaluminate cement clinker. The curing agent in this embodiment is obtained by weighing and mixing the raw materials according to the specified proportions.

[0051] Example 3

[0052] This embodiment provides a curing agent, comprising the following raw materials by weight: 32 parts steel slag powder, 16 parts metakaolin, 10 parts modified activated carbon, 3 parts modified straw ash, 5 parts nano-calcium carbonate, 5 parts activator, 3 parts precipitated beads, 4 parts nano-iron particles, 6 parts chitosan quaternary ammonium salt, and 10 parts sulfoaluminate cement clinker. The curing agent in this embodiment is prepared by weighing and mixing the raw materials according to the specified proportions.

[0053] Example 4

[0054] This embodiment provides a curing agent, comprising the following raw materials by weight: 25 parts steel slag powder, 20 parts metakaolin, 9 parts modified activated carbon, 4 parts modified straw ash, 5 parts nano-calcium carbonate, 6 parts activator, 4 parts precipitated beads, 3 parts nano-iron particles, 5 parts chitosan quaternary ammonium salt, and 12 parts sulfoaluminate cement clinker. The curing agent in this embodiment is obtained by weighing and mixing the raw materials according to the specified proportions.

[0055] Example 5

[0056] This embodiment provides a curing agent, comprising the following raw materials by weight: 28 parts steel slag powder, 18 parts metakaolin, 8 parts modified activated carbon, 3 parts modified straw ash, 4 parts nano-calcium carbonate, 6 parts activator, 5 parts precipitated beads, 3 parts nano-iron particles, 5 parts chitosan quaternary ammonium salt, and 10 parts sulfoaluminate cement clinker. The curing agent in this embodiment is obtained by weighing and mixing the raw materials according to the specified proportions.

[0057] Example 6

[0058] This embodiment provides a curing agent, comprising the following raw materials by weight: 26 parts steel slag powder, 16 parts metakaolin, 8 parts modified activated carbon, 5 parts modified straw ash, 4 parts nano-calcium carbonate, 6 parts activator, 4 parts precipitated beads, 4 parts nano-iron particles, 5 parts chitosan quaternary ammonium salt, and 15 parts sulfoaluminate cement clinker. The curing agent in this embodiment is obtained by weighing and mixing the raw materials according to the specified proportions.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 1 is that the raw materials do not contain modified activated carbon, but instead use the same amount of modified straw ash. The weight proportions of the remaining raw materials are the same as in Example 1. The specific proportions of each raw material are as follows: 30 parts steel slag powder, 18 parts metakaolin, 15 parts modified straw ash, 5 parts nano-calcium carbonate, 8 parts activator, 5 parts precipitated beads, 3 parts nano-iron particles, 5 parts chitosan quaternary ammonium salt, and 15 parts sulfoaluminate cement clinker. The curing agent in this example is obtained by weighing and mixing each raw material according to the specified proportions.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that the raw materials do not contain modified activated carbon and modified straw ash, while the weight proportions of the other raw materials are the same as those in Example 1.

[0063] Comparative Example 3

[0064] The difference between this comparative example and Example 1 is that the raw materials do not contain sediment beads, and the weight proportions of the other raw materials are the same as those in Example 1.

[0065] Comparative Example 4

[0066] The difference between this comparative example and Example 1 is that the raw materials do not contain nano-calcium carbonate, while the weight parts of the other raw materials are the same as those in Example 1.

[0067] Comparative Example 5

[0068] The difference between this comparative example and Example 1 is that the raw materials do not contain chitosan quaternary ammonium salt, while the weight parts of the other raw materials are the same as those in Example 1.

[0069] Effect verification:

[0070] Examples 1-6 and Comparative Examples 1-5 were mixed with the bottom mud according to the proportions in Table 1. The moisture content and compressive strength of the cured bodies after curing are shown in Table 1 below.

[0071] Table 1:

[0072] Example 1 0.12:1 14 24 4.7 0.04 0.04 0.75 Example 2 0.6:1 14 28 4.3 0.06 0.05 0.82 Example 3 0.8:1 14 30 4.0 0.06 0.06 0.93 Example 4 0.1:1 14 28 4.2 0.08 0.08 0.84 Example 5 0.15:1 14 30 4.1 0.05 0.05 0.89 Example 6 0.13:1 14 31 4.0 0.08 0.08 0.96 Comparative Example 1 0.12:1 14 35 3.6 0.56 0.77 1.46 Comparative Example 2 0.12:1 14 45 2.7 0.64 0.84 1.56 Comparative Example 3 0.12:1 14 27 3.9 0.31 0.36 4.32 Comparative Example 4 0.12:1 14 38 3.2 0.32 0.26 3.02 Comparative Example 5 0.12:1 14 28 4.2 0.89 0.92 2.56

[0073] The moisture content of the sediment is 70%-85%; the dry matter content is 15%-30% (including inorganic minerals, organic matter, heavy metals and other soluble substances).

[0074] Of the dry matter, inorganic minerals (clay minerals, quartz, feldspar, etc.) account for 60%-80% of the dry weight; organic matter accounts for 20%-25% of the dry weight. Within the organic matter, humic substances (6%-15%) include humic acid and fulvic acid, formed by the anaerobic decomposition of aquatic plant remains, algae, and microbial metabolites. These substances possess complex aromatic ring structures and functional groups (carboxyl groups, phenolic hydroxyl groups), and can bind to heavy metals through complexation. Undegraded organic matter (3%-8%) includes animal and plant debris, oils, cellulose, and small amounts of synthetic organic matter (such as detergent and pesticide residues). Due to the anaerobic environment of the sediment, the degradation rate is slow, resulting in a high accumulation. Microbial biomass (1%-2%), mainly composed of anaerobic bacteria (such as methanogens and sulfate-reducing bacteria), participates in the decomposition of organic matter and the transformation of heavy metal forms. The main heavy metals include cadmium, lead, copper, zinc, chromium, and nickel.

[0075] The curing process for each of the above-mentioned solidified bodies was carried out in the laboratory under normal temperature and humidity conditions.

[0076] The compressive strength of the above-mentioned solidified bodies was tested in accordance with the content of the "Standard for Geotechnical Testing Methods" (GB / T50123-2019).

[0077] The heavy metal leaching rates of the aforementioned solidified bodies were tested according to the criteria outlined in the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" (GB5085.3-2007). The standard requires that the nickel leaching rate be ≤1 mg / L and the chromium leaching rate be ≤1 mg / L.

[0078] The leaching rates of heavy oils in the above-mentioned solidified bodies are referenced in HJ / T299-2007 "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method":

[0079] Extraction solvent: a mixture of 0.05 mol / L sulfuric acid and 0.025 mol / L nitric acid (pH=2.88±0.05);

[0080] Liquid-to-solid ratio: 10:1 (L / kg dry mud);

[0081] Shaking conditions: 20±5℃, shake at 110±10r / min for 18 hours, and collect the supernatant after standing for 30 minutes.

[0082] The oils in the supernatant need to be separated by solvent extraction, following the method described in "Determination of Petroleum and Animal Oils in Water - Infrared Spectrophotometry" (HJ637-2018).

[0083] Extractant: Tetrachloroethylene (C2Cl4, a substitute for traditional carbon tetrachloride, with low toxicity);

[0084] Extraction steps:

[0085] Take 100 mL of leachate (filtered through a 0.45 μm filter membrane to remove particulate matter), add 20 mL of tetrachloroethylene, shake in a separatory funnel for 5 minutes (releasing gas 3 times during the process), and let stand to separate the layers;

[0086] Collect the lower organic phase, repeat the extraction twice, and combine the organic phases;

[0087] The oil extract was obtained by dehydration with anhydrous sodium sulfate (to remove moisture) and purification by magnesium silicate column (to remove polar impurities).

[0088] Oil Concentration Determination

[0089] Main method: Infrared spectrophotometry (HJ637-2018):

[0090] Principle: The CH2 and CH3 groups in oils and fats are at 2930 cm⁻¹ -12960cm -1 3030cm -1 The concentration is calculated by measuring the absorbance, as there is a characteristic absorption peak at a certain point.

[0091] Scope of application: Simultaneous determination of petroleum (mineral oil) and animal and vegetable oils, detection range 0.04-200 mg / L.

[0092] Among them, the backfilling of solidified body requires an oil leaching rate of ≤5mg / L.

[0093] According to the data recorded in Table 1, after the curing agent prepared in Examples 1-6 of this invention is mixed with riverbed sediment, the solidified body meets the relevant requirements. It has a significant effect on treating sediment with high water content and high organic matter content. The oil leaching rate and heavy metal leaching rate are far lower than the standard values. At the same time, the early compressive strength is also better than that of traditional curing agents. Therefore, the curing agent of this invention has the characteristics of high compressive strength, good durability and excellent crack resistance.

[0094] The data recorded in Table 1, comparing the test data of the solidified bodies in Example 1, Comparative Example 1, and Comparative Example 2, shows that porous materials can easily absorb moisture from the sediment. The moisture content of the solidified body in Comparative Example 2 is much higher than that in Example 1, indicating that porous materials can quickly adsorb free water from the sludge and reduce the moisture content of the solidified body. Combining the data of the solidified bodies in Comparative Example 1 and Comparative Example 2, it can be seen that using a combination of two porous materials, compared to using a single porous material, can provide different particle size ranges for the entire system. Through the interpenetration and cross-linking of large and small pores, the compressive strength and durability of the solidified body are further improved.

[0095] Based on the data recorded in Table 1, and the comparison of the test data of the cured body in Example 1 and Comparative Example 3, it can be seen that the addition of sediment beads is beneficial to the stability of the grease in the cured body, can significantly reduce the precipitation of grease, and thus increase the stability and durability of the cured body.

[0096] Based on the data recorded in Table 1, and the comparison of the test data of the solidified body in Example 1 and Comparative Example 4, it can be seen that nano-calcium carbonate has a promoting effect on the construction of the solidified body system, can significantly improve the compressive strength of the solidified body, and expand the application range of the solidified body.

[0097] The data recorded in Table 1 shows that, based on the comparison of the test data of the cured body in Example 1 and Comparative Example 5, chitosan quaternary ammonium salt can significantly reduce the leaching rate of heavy metals in the cured body. Combined with the use of nano iron particles, it can greatly reduce the leaching rate of heavy metals, making the curing agent of the present invention environmentally friendly.

[0098] In summary:

[0099] 1. In this invention, steel slag is used instead of cement, which can realize the recycling of industrial solid waste. At the same time, the approximately 40-50% CaO and 10-15% Al2O3 contained in steel slag can be activated with the large amount of SiO2 in metakaolin under the action of an activator to generate CSH (calcium silicate hydrate) and CAH (calcium aluminate hydrate) gels. Meanwhile, the porous structure of modified straw ash and modified activated carbon can quickly adsorb free water in sludge, increasing the dewatering rate by 20-30%. Its silicon-oxygen bonds crosslink with the gel network, reducing later cracking.

[0100] 2. Nano-calcium carbonate, through its pre-filling and post-bridging effect, can refine the pores of the solidified body, achieving an early (14d) compressive strength of over 4MPa, significantly higher than the 2.0MPa of traditional cement-based formulations. The amino and hydroxyl groups of chitosan quaternary ammonium salt can stabilize heavy metals through chelation, reducing the leaching rate of heavy metals to below 0.1mg / L, far below the national standard GB5085.3-2007. At the same time, its cationic flocculated sludge exhibits a significantly improved organic matter degradation rate, reducing solidified body shrinkage.

[0101] 3. Compared with traditional high-alkali curing agents, this formula adjusts the alkalinity through sulfoaluminate cement clinker to avoid the rebound of heavy metal leaching, so that the cured sludge can be directly used for roadbed backfilling or land reclamation.

[0102] 4. The added sediment beads in this invention are hollow glass microspheres with a spherical shape, which makes the combination of each component with the sludge more uniform. At the same time, the sediment beads are oleophilic, and together with the porous modified straw ash and modified activated carbon, they can fix the organic matter in the whole solidified body, reduce the leaching rate of oil, and thus increase the water resistance and volume stability of the solidified body.

[0103] 5. The addition of nano-iron particles can, through the synergistic effect of reduction and adsorption, reduce Cr... 6+ Reduced to Cr 3+ It is fixed and, in conjunction with the adsorption of other heavy metals, reduces the leaching rate of heavy metals, ensuring the treatment effect of sludge.

[0104] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A riverbed sediment solidifying agent, characterized in that: By weight parts Includes: 25-32 parts steel slag powder, 16-22 parts metakaolin, 8-10 parts modified activated carbon, 3-5 parts modified straw ash, 3-5 parts nano calcium carbonate, 5-8 parts activator, 3-5 parts precipitated beads, 2-4 parts nano iron particles, 3-6 parts chitosan quaternary ammonium salt, and 10-15 parts sulfoaluminate cement clinker; The particle size range of steel slag powder is 800 mesh to 600 mesh; The particle size range of nano-calcium carbonate is 50-60 nm; The activator includes Na2SO4 and NaOH, wherein the mass ratio of Na2SO4 to NaOH is 1-1.2:1; The particle size range of the iron nanoparticles is 50-100 nm; The activated carbon was impregnated in a 1 mol / L magnesium chloride solution and ultrasonically vibrated at 60°C for 3 hours to allow Mg to embed into the carbon layer structure. After filtration, it was dried at 120°C and then calcined at 600°C under nitrogen protection for 1 hour to form MgO-MgCl2 composite active sites. The calcined activated carbon was then oxidized with a 30% hydrogen peroxide solution at 70°C for 1 hour to obtain modified activated carbon. Modified straw ash is obtained by high-temperature calcination to remove organic impurities from straw, converting it into inorganic ash, and then activating it with strong alkali to improve its surface activity.

2. The riverbed sediment solidifying agent according to claim 1, characterized in that: By weight parts It includes: 25-30 parts steel slag powder, 16-18 parts metakaolin, 8-10 parts modified activated carbon, 3-5 parts modified straw ash, 3-5 parts nano calcium carbonate, 6-8 parts activator, 4-5 parts precipitated beads, 3-4 parts nano iron particles, 5-6 parts chitosan quaternary ammonium salt, and 12-15 parts sulfoaluminate cement clinker.

3. The riverbed sediment solidifying agent according to claim 1, characterized in that: By weight parts It includes: 30 parts steel slag powder, 18 parts metakaolin, 10 parts modified activated carbon, 5 parts modified straw ash, 5 parts nano calcium carbonate, 8 parts activator, 5 parts precipitated beads, 3 parts nano iron particles, 5 parts chitosan quaternary ammonium salt, and 15 parts sulfoaluminate cement clinker.

4. A method for preparing the riverbed sediment solidifying agent as described in claim 1, characterized in that: Includes the following steps: Weigh out the following raw materials according to the specified weight proportions: 25-32 parts steel slag powder, 16-22 parts metakaolin, 8-10 parts modified activated carbon, 3-5 parts modified straw ash, 3-5 parts nano calcium carbonate, 5-8 parts activator, 3-5 parts precipitated beads, 2-4 parts nano iron particles, 3-6 parts chitosan quaternary ammonium salt, and 10-15 parts sulfoaluminate cement clinker. Set aside for later use. The weighed raw materials are mixed and stirred to obtain the target product.

5. The application of the riverbed sediment solidification agent according to any one of claims 1-3, characterized in that: The curing agent and the bottom mud are mixed and stirred at a weight ratio of (0.6-0.15):1, and then cured and shaped.