Method for preparing multifunctional ecological soil by modifying fly ash and coal gangue in a synergistic degradation manner

Abstract

The application discloses a method for preparing multifunctional ecological soil by modifying fly ash and coal gangue through synergistic degradation, comprising the following steps: S1, adding a degradation agent to the fly ash in an aerobic environment at a temperature of greater than or equal to 20 DEG C for pretreatment; S2, adding a degradation agent to the coal gangue in an aerobic environment at a temperature of greater than or equal to 20 DEG C for pretreatment; S3, mixing the fly ash and the coal gangue obtained in steps S1 and S2 according to a mass ratio of 1:9 to 9:1, grinding and heating at a temperature of 50 DEG C to 300 DEG C; S4, realizing step-by-step separation of nutrient elements by selectively decomposing and activating the coal gangue through chemistry; S5, adding a passivation agent for treatment for 1 h to 60 h, and carrying out acidic complexation and chelation reactions with metal ions in the coal gangue; S6, adding a modifier for treatment for 1 h to 12 h to obtain the ecological soil. The method realizes efficient resource utilization of coal-based solid waste through synergistic degradation, chemical activation and modification of the fly ash and the coal gangue, and solves the problems of low activity of silicon and aluminum, high risk of heavy metals and poor adaptability to acid soil in traditional technologies.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, and in particular to a method for preparing multifunctional eco-soil through the synergistic degradation and modification of fly ash and coal gangue. Background Technology

[0002] Fly ash and coal gangue are the main solid wastes generated by the coal industry, and traditional treatment methods easily cause environmental pollution. While existing technologies can use coal gangue alone to degrade and modify it to prepare eco-soil, they suffer from low silicon and aluminum utilization rates and limited nutrient adjustment ranges. Furthermore, coal gangue used directly without high-temperature calcination is acidic due to its sulfide content, making it more suitable for alkaline soil improvement; without specific treatment, it cannot meet the needs of acidic soil improvement. Moreover, coal gangue typically contains a complex variety and high levels of heavy metals, increasing the difficulty of processing it as a primary raw material for eco-soil preparation. Summary of the Invention

[0003] To address the aforementioned problems, the purpose of this invention is to provide a method for preparing multifunctional eco-soil through the synergistic degradation and modification of fly ash and coal gangue. This method involves the synergistic degradation, chemical activation, and modification of fly ash and coal gangue to prepare multifunctional eco-soil. The fly ash-coal gangue system undergoes synergistic degradation with simultaneous heavy metal passivation, grinding with simultaneous activation, chemical step-by-step activation, chelation heavy metal passivation, and organic modification. Through multi-step activation and heavy metal passivation, efficient resource utilization of coal-based solid waste is achieved. Simultaneously, it solves the core problems of traditional coal gangue eco-soil preparation technologies, such as low silica-alumina activity, high heavy metal risk, and poor compatibility with acidic soils. Its low-carbon, low-cost, and multifunctional characteristics provide a feasible solution for large-scale ecological restoration and soil remediation, agricultural planting, and engineering greening.

[0004] To address the problems in the existing technology, the technical solution adopted by this invention is as follows:

[0005] A method for preparing multifunctional eco-soil through the synergistic degradation and modification of fly ash and coal gangue includes the following steps:

[0006] S1: In an aerobic environment with a temperature ≥20℃, add a degradation agent to the fly ash for pretreatment;

[0007] S2: In an aerobic environment with a temperature ≥20℃, a degradation agent is added to the coal gangue for pretreatment;

[0008] S3: Mix the fly ash obtained in steps S1 and S2 with coal gangue at a mass ratio of 1:9-9:1 to obtain a mixture of fly ash and coal gangue, and heat it to 50-300℃ while grinding.

[0009] S4: Achieve graded separation of nutrients by chemically selectively decomposing and activating the ground mixture.

[0010] S5: Add passivating agent and treat for 1-60 hours to undergo acidic complexation and chelation reactions with metal ions in coal gangue;

[0011] S6: Add modifier and treat for 1-12 hours to obtain ecological soil.

[0012] Further, in step S2, the coal gangue is mechanically crushed to 60-1000 mesh; in step S3, the fly ash and coal gangue are mixed and then uniformly ground to 60-1000 mesh, preferably 325-1000 mesh.

[0013] Further, in step S1, the mass ratio of the degrading agent to fly ash is less than 1:30000, and the pretreatment time is 0.1-12h; in step S2, the mass ratio of the degrading agent to coal gangue is less than 1:30000, and the pretreatment time is 0.1-12h.

[0014] Furthermore, in step S3, the mass ratio of fly ash to coal gangue is 1:4 to 4:1, and the grinding heating temperature is 100-250℃.

[0015] Furthermore, the chemically selective decomposition method is acid decomposition, wherein organic acids are used to selectively dissolve and separate Fe / Al / silicon-potassium; and inorganic acids and salts are used to selectively dissolve and separate Si.

[0016] Furthermore, the organic acid is one or more of fulvic acid, acetic acid, fruit acid or oxalic acid, and the amount added is 5-10 wt% of the coal gangue mass; the inorganic acid is one or more of sodium dihydrogen phosphate or sodium sulfide, and the amount added is 3-5% of the coal gangue mass; the salt is sodium carbonate, and the amount added is 2-4% of the coal gangue mass.

[0017] Furthermore, the degradation agent is water rich in ozone and carbon dioxide, wherein the ozone concentration is 60-100 mg / L and the carbon dioxide concentration is 1000-1200 mg / L.

[0018] Furthermore, the passivating agent is a high-temperature catalytic oxygenation product of a mixture of seaweed sludge and the bottom layer of duck farm manure, and the amount of passivating agent added is 0.3-1.2% of the mass of the mixture of fly ash and coal gangue.

[0019] Furthermore, the modifier composition includes lignin degradation product sulfonate, tea polyphenol-iron complex and red wine lees fermentation product, and the amount of modifier added is 0.05-0.6% of the mass of the fly ash and coal gangue mixture.

[0020] Furthermore, the ecological soil contains 25-260 g / kg of organic phase, 0.5-5.0 g / kg of total nitrogen (TN), 0.4-3 g / kg of total phosphorus (TP), 2-30 g / kg of total potassium (TK), a pH value of 6.0-9.0, a total silicon (TSi) content of 10-60%, and a total iron / aluminum (TFe / Al) content of 0.1-45%.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention promotes synergistic resource utilization and reduces disposal costs. By co-treating two wastes, fly ash and coal gangue, and optimizing the degradation-activation-passivation process, disposal costs can be reduced, achieving efficient resource utilization and simultaneous risk control. Fly ash is rich in elements such as silicon, aluminum, and calcium, which can compensate for the nutrient deficiencies in coal gangue. Furthermore, because it is generally alkaline, especially circulating fluidized bed fly ash with a CaO content higher than 15%, it is particularly suitable for use in combination with coal gangue (especially high-calcium circulating fluidized bed fly ash, CaO > 15%). This neutralizes the acidity of coal gangue, making the final product pH suitable for the large areas of acidic soil in my country, avoiding the need for additional treatment of traditional coal gangue. The invention addresses the issue of adding lime, and the fact that fly ash's large specific surface area, porous structure, and high pH value can passivate some heavy metals in coal gangue. Therefore, this invention co-processes fly ash and coal gangue in a ratio of 1:9-9:1, fully utilizing the alkalinity, high silica-alumina content, and porous structure of fly ash to compensate for the deficiencies of coal gangue, such as insufficient nutrients and strong acidity. Simultaneously, it reduces the energy consumption and cost of treating fly ash or coal gangue separately. The two wastes complement each other, achieving "waste treatment of waste" and significantly improving resource utilization. 2. This invention achieves efficient degradation and activation, improving silica-alumina utilization. The degrading agent used is inexpensive, low-carbon, and environmentally friendly, achieving efficient degradation with extremely low addition amounts (<0.0033%). Furthermore, since fly ash is in powder form, the coal gangue is first crushed before adding the degrading agent, pre-treating the powdered raw materials under aerobic conditions at room temperature.

[0023] 3. This invention features a short reaction time and high processing efficiency. Grinding and heating increase the active sites, and subsequent grinding (60-1000)

[0024] The synergistic effect of grinding and heating (50-300℃) significantly shortens the degradation time (0.1-12 hours), greatly reducing the pretreatment time. At the same time, it can further destroy the crystal structure, increase the specific surface area and active sites, making the silicon and aluminum components more easily utilized by plants or soil microorganisms. The ecological soil optimized by grinding and heating fly ash has low bulk density and high aggregate structure, significantly improving soil permeability and water retention, and solving the problem of low utilization rate of silicon and aluminum modified by traditional coal gangue.

[0025] 4. This invention features multi-stage simultaneous passivation of heavy metals, reducing environmental risks. In addition to its own highly efficient degradation capabilities, the degrading agent reacts with heavy metals such as Cd and Pb during pretreatment to form carbonate insolubles, initially immobilizing the heavy metals. During grinding and activation, the large specific surface area, high pH (alkaline), porous structure, and surface hydroxyl groups (-OH) of fly ash can adsorb heavy metals from coal gangue, reducing the risk of leaching. During passivation, the passivating agent further reduces the bioavailability of heavy metals through acidic complexation and chelation reactions, ensuring the safe use of the eco-soil.

[0026] 5. This invention achieves tiered separation and activation, optimizing nutrients and enhancing functionality. Through selective chemical decomposition, it enables the tiered release of elements such as Si, Fe, and Al, optimizing the slow-release effect of nutrients; the modifier contains amphoteric organic small molecules with functional groups such as amine and carboxyl groups, which can enhance soil microbial activity, promote plant root development, and improve the long-term fertility of ecological soil.

[0027] 6. The process of this invention is highly efficient and low-carbon environmentally friendly. The pretreatment, passivation, and curing steps all adopt continuous processes, which greatly improves the processing efficiency and is suitable for large-scale production; low-temperature heating (50-300℃) reduces energy consumption by more than 50% compared with traditional high-temperature calcination (>800℃), meeting the requirements of low-carbon and environmental protection.

[0028] 7. This invention has a wide range of applications. The resulting ecological soil products can be used for land improvement, ecological restoration, environmental management, and planting applications in various environmental scenarios such as forestry, animal husbandry, agriculture, greening, tidal flats, river and lakeside land, abandoned mines, coal mining subsidence areas, and solid waste dumps. It can also be used for the remediation of acidified and saline-alkali soils. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The degradation agent involved in Examples 1-3 below is water rich in ozone and carbon dioxide, wherein the ozone concentration is 80 mg / L and the carbon dioxide concentration is 1000 mg / L.

[0031] The passivating agent involved in Examples 1-3 below is a high-temperature catalytic oxygenation product of a mixture of seaweed sludge and the bottom layer of duck farm manure, with an addition ratio of 2:1. The high-temperature catalytic conditions are 190°C, 0.5MPa O2, and 2h.

[0032] The modifiers involved in Examples 1-3 below are composed of: lignin degradation product sulfonate + tea polyphenol-iron complex + Cabernet Sauvignon wine lees fermentation product, with a mass ratio of 2:1:1.

[0033] In each embodiment, by selecting different acid / salt combinations and conditions based on the characteristics of the raw materials and the requirements of the target product, selective activation, dissolution, and fixation of specific nutrients (Si, K, Fe, Al) can be achieved.

[0034] Example 1

[0035] This embodiment discloses a method for preparing multifunctional eco-soil through the synergistic degradation and modification of fly ash and coal gangue. Raw materials: coal gangue (SiO2 42%, Fe2O3 18%, Al2O3 10%, Cd 1.0 mg / kg), fly ash (CaO 18%).

[0036] 1. Under an aerobic and ventilated environment at 25℃, add the degradation agent to the fly ash at a mass ratio of 1:30000 and react for 0.1 hours;

[0037] 2. Mechanically crush the coal gangue to 60 mesh, and add the degradation agent to the coal gangue at a mass ratio of 1:30000 in an aerobic and ventilated environment at 25℃, and react for 0.1h;

[0038] 3. Mix the fly ash obtained in steps 1 and 2 with coal gangue at a mass ratio of 4:1 to obtain a mixture of fly ash and coal gangue. Homogenize and grind the mixture to 325 mesh while heating it at 150°C.

[0039] 4. Add the organic weak acids citric acid and malic acid to the ground mixture to selectively dissolve and separate Fe / Al while retaining the silicon component;

[0040] 5. Add 0.5% by weight of a metal passivating agent to the mixture of fly ash and coal gangue, and react for 6 hours;

[0041] 6. Add 0.3% (by weight) of a modifier to the mixture of fly ash and coal gangue, and react for 1 hour;

[0042] 7. Prepare 2-4mm granules for packaging.

[0043] Obtained ecological soil performance data:

[0044] Organic phase 30 g / kg, pH 8.5, Tclp-Cd not detected (GB5085.3 limit 1.0 mg / L);

[0045] TN 2g / kg, TP 0.4g / kg, TK: 6g / kg; TFe / Al 20%;

[0046] The leaching values ​​of Pb, Cr, and As are all below the limits specified in GB15618 for Class I agricultural land.

[0047] Example 2:

[0048] This embodiment discloses a method for preparing multifunctional eco-soil through the synergistic degradation and modification of fly ash and coal gangue. Raw materials: low-organic-matter coal gangue (TOC 1.2%), fly ash (CaO 15%).

[0049] 1. Under an aerobic and ventilated environment at 28℃, add a degradation agent to fly ash at a mass ratio of 1:40000 and react for 12 hours;

[0050] 2. Mechanically crush the coal gangue to 60 mesh, and add the degradation agent to the coal gangue at a mass ratio of 1:40000 in an aerobic and ventilated environment at 28℃, and react for 12 hours;

[0051] 3. Mix the fly ash obtained in steps 1 and 2 with coal gangue at a mass ratio of 2:1 to obtain a mixture of fly ash and coal gangue. Homogenize and grind the mixture to 500 mesh while heating it to 250°C.

[0052] 4. Add the organic weak acids oxalic acid and fulvic acid to the ground mixture to activate the silicon and potassium nutrients and dissolve the silicon and potassium;

[0053] 5. Add 0.7% by weight of a metal passivating agent to the mixture of fly ash and coal gangue, and react for 24 hours;

[0054] 6. Add 0.6% (by weight) of a modifier to the mixture of fly ash and coal gangue, and react for 2 hours;

[0055] 7. Prepare 2-4mm granules for packaging.

[0056] Obtained ecological soil performance data:

[0057] Organic phase 40 g / kg, pH 8.0, Tclp-Cd not detected (GB5085.3 limit 1.0 mg / L), Tclp-Pb: 0.6 mg / L (GB5085.3 limit 5 mg / L);

[0058] TN 3.1g / kg, TP 0.5g / kg, TK: 10g / kg

[0059] Example 3:

[0060] This embodiment discloses a method for preparing multifunctional eco-soil through the synergistic degradation and modification of fly ash and coal gangue. The raw materials are high-environmental-risk coal gangue (Cd 8.2 mg / kg, Pb 300 mg / kg, arsenic 3.7 mg / kg) and fly ash (CaO 22%).

[0061] 1. Under an aerobic and ventilated environment at 28℃, add the degradation agent to the fly ash at a mass ratio of 1:30000 and react for 6 hours;

[0062] 2. Mechanically crush the coal gangue to 60 mesh, and add the degradation agent to the coal gangue at a mass ratio of 1:30000 in an aerobic and ventilated environment at 30℃, and react for 6 hours;

[0063] 3. Mix the fly ash obtained in steps 1 and 2 with coal gangue at a mass ratio of 1:4 to obtain a mixture of fly ash and coal gangue. Homogenize and grind the mixture to 1000 mesh while heating it to 250°C.

[0064] 4. Add inorganic acid, sodium dihydrogen phosphate, to the ground mixture to selectively fix Pb; add sodium carbonate to activate Si;

[0065] 5. Add 1.0% by weight of a metal passivating agent to the mixture of fly ash and coal gangue, and react for 36 hours;

[0066] 6. Add 0.4% (by weight) of a modifier to the mixture of fly ash and coal gangue, and react for 12 hours;

[0067] 7. Prepare 2-4mm granules for packaging.

[0068] Obtained ecological soil performance data:

[0069] TSi 38.5%;

[0070] Tclp-Pb: 1.2 mg / L (GB5085.3 limit 5 mg / L);

[0071] Tclp-Cd: 0.6 mg / L (GB5085.3 limit 1 mg / L);

[0072] Tclp-As: 0.5 mg / L (GB5085.3 limit 5 mg / L).

[0073] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing multifunctional eco-soil through the synergistic degradation and modification of fly ash and coal gangue, characterized in that, Includes the following steps: S1: In an aerobic environment with a temperature ≥20℃, add a degradation agent to the fly ash for pretreatment; S2: In an aerobic environment with a temperature ≥20℃, a degradation agent is added to the coal gangue for pretreatment; S3: Mix the fly ash obtained in steps S1 and S2 with coal gangue at a mass ratio of 1:9-9:1 to obtain a mixture of fly ash and coal gangue, and heat it to 50-300℃ while grinding. S4: Achieve graded separation of nutrients by chemically selectively decomposing and activating the ground mixture. S5: Add passivating agent and treat for 1-60 h to undergo acidic complexation and chelation reactions with metal ions in coal gangue; S6: Add modifier and treat for 1-12 hours to obtain ecological soil; In step S1, the degradation agent is water rich in ozone and carbon dioxide, wherein the ozone concentration is 60-100 mg / L and the carbon dioxide concentration is 1000-1200 mg / L; In step S4, the chemically selective decomposition method is acid decomposition, wherein organic acids are used to selectively dissolve and separate Fe / Al / silicon-potassium; and inorganic acids and salts are used to selectively dissolve and separate Si. The organic acid is one or more selected from fulvic acid, acetic acid, fruit acid, or oxalic acid, and the amount added is 5-10 wt% of the coal gangue mass; the inorganic acid is one or more selected from sodium dihydrogen phosphate or sodium sulfide, and the amount added is 3-5% of the coal gangue mass; the salt is sodium carbonate, and the amount added is 2-4% of the coal gangue mass. The passivating agent is a high-temperature catalytic oxygenation product of a mixture of seaweed sludge and the bottom layer of duck farm manure. The amount of passivating agent added is 0.3-1.2% of the mass of the mixture of fly ash and coal gangue. The modifier consists of lignin degradation product sulfonate, tea polyphenol-iron complex and red wine lees fermentation product, with a mass ratio of 4-6:2-3:2-3. The amount of modifier added is 0.05-0.6% of the mass of the fly ash and coal gangue mixture.

2. The method for preparing multifunctional ecological soil by synergistic degradation and modification of fly ash and coal gangue as described in claim 1, characterized in that, In step S2, the coal gangue is mechanically crushed to 60-1000 mesh; in step S3, the fly ash and coal gangue are mixed and then uniformly ground to 60-1000 mesh.

3. The method for preparing multifunctional ecological soil by synergistic degradation and modification of fly ash and coal gangue as described in claim 1, characterized in that, In step S1, the mass ratio of the degrading agent to fly ash is less than 1:30000, and the pretreatment time is 0.1-12 h; in step S2, the mass ratio of the degrading agent to coal gangue is less than 1:30000, and the pretreatment time is 0.1-12 h.

4. The method for preparing multifunctional ecological soil by synergistic degradation and modification of fly ash and coal gangue as described in claim 1, characterized in that, In step S3, the mass ratio of fly ash to coal gangue is 1:4 to 4:1, and the grinding heating temperature is 50-300℃.

5. The method for preparing multifunctional ecological soil by synergistic degradation and modification of fly ash and coal gangue as described in claim 1, characterized in that, The organic phase content in the ecological soil is 25-260 g / Kg, and the total organic matter content (TN) is 0.5-5.0 g / Kg. TP: 0.4-3 g / Kg; TK: 2-30 g / Kg; pH value: 6.0-9.0; Total silicon TSi content: 10-60%; Total iron and aluminum TFe / Al content: 0.1-45%.