Method for preparing ecological soil by modifying coal gangue degradation

Abstract

The application discloses a method for preparing ecological soil by coal gangue degradation and modification, which comprises the following steps: S1, degradation pretreatment: adding a degradation agent to the coal gangue in an aerobic environment at a temperature of greater than or equal to 20 DEG C; S2, crushing and screening: mechanically crushing the pretreated coal gangue to a target particle size; S3, chemical activation and gradient separation: realizing gradient separation of nutrient elements by selectively decomposing and activating the coal gangue; S4, heavy metal passivation: adding a passivation agent to the coal gangue for not more than 72 hours to generate an acidic complexation and chelation reaction with metal ions in the coal gangue; and S5, curing and modification: adding a modifier to the coal gangue for not more than 12 hours to obtain the ecological soil. The method adopts a chemical selective decomposition and activation, gradient separation and synergistic modification process, solves the problems of high migration risk of heavy metals in the coal gangue and difficult utilization of organic matter and nutrients, breaks through the bottleneck of high energy consumption and long processing period of the traditional process, and provides an efficient and low-cost ecological soil preparation method.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and soil remediation technology, and in particular to a method for preparing eco-soil by degrading and modifying coal gangue. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing. Its massive stockpiling not only occupies land but also poses serious environmental risks such as dust pollution, leaching contamination of soil and water, and heavy metal migration. Resource-based treatment of coal gangue can effectively address the problem of its large-scale accumulation and transform it into high-quality ecological soil matrix for use in agriculture, forestry, animal husbandry, mine ecological restoration, comprehensive management of tidal flats, covering of solid waste landfills, and remediation of contaminated soil. However, traditional disposal methods (such as landfill and open-air dumping) are unsustainable and do not meet the requirements of sustainable development. There is an urgent need to explore large-scale, high-value, and safe resource utilization pathways.

[0003] Existing coal gangue treatment technologies (such as landfill and simple soil covering) generally suffer from problems such as insufficient passivation of heavy metals, low nutrient utilization, and high costs, making it difficult to meet the stringent standards for ecological soil (agricultural / engineering use). Specifically: Patent CN118947491 A does not consider the environmental risks of heavy metals and toxic substances in coal gangue, and requires a reaction cycle of more than 30 days to complete the ecological soil conversion, which is long and inefficient; Patent CN 117243086A obtains improved ecological soil by crushing coal gangue and mixing it with sand, but the activity of mineral elements is not improved, and nutrients are difficult to dissolve and release; Patent CN 116114568 A adds a large amount of nitric acid, microbial agents, and chemical additives during the preparation of ecological soil, which increases costs and brings new environmental pollution.

[0004] There is an urgent need for a new method for treating coal gangue to achieve the efficient transformation of coal gangue into a harmless and resource-efficient form. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a method for preparing eco-soil by degrading and modifying coal gangue. This method employs a chemical selective decomposition and activation, stepwise separation, and synergistic modification process to solve the problems of high heavy metal migration risk and difficulty in utilizing organic matter and nutrients in coal gangue. It also breaks through the bottlenecks of high energy consumption and long processing cycles in traditional processes, providing a high-efficiency and low-cost method for preparing eco-soil.

[0006] To address the problems in the existing technology, the technical solution adopted by this invention is as follows:

[0007] A method for preparing eco-soil by degrading and modifying coal gangue includes the following steps:

[0008] S1 degradation pretreatment: Add degradation agent to coal gangue in an aerobic environment at a temperature ≥20℃;

[0009] S2 crushing and screening: mechanically crushes the pretreated coal gangue to the target particle size;

[0010] S3 Chemical Activation and Cascade Separation: Activating coal gangue through selective chemical decomposition;

[0011] S4 heavy metal passivation: Add passivating agent and treat for no more than 72 hours to undergo acidic complexation and chelation reactions with metal ions in coal gangue;

[0012] S5 maturation and modification: Add modifier and treat for no more than 12 hours to obtain ecological soil.

[0013] Furthermore, the chemically selective decomposition method is acid decomposition, wherein organic acids are used to selectively dissolve and separate Fe / Al / Si / K; and inorganic acids and salts are used to selectively separate Si.

[0014] 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.

[0015] Furthermore, the inorganic acid is one or more of sodium dihydrogen phosphate or sodium sulfide, and the amount added is 3-5% of the mass of coal gangue; the salt is sodium carbonate, and the amount added is 2-4% of the mass of coal gangue.

[0016] Furthermore, the degrading agent is water rich in ozone and carbon dioxide, and the mass ratio of the degrading agent to coal gangue is less than 1:30000, with a pretreatment time of 0.1-36 hours.

[0017] Furthermore, 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 coal gangue.

[0019] Furthermore, the modifier composition includes lignin degradation product sulfonate, tea polyphenol-iron complex and red wine lees fermentation products, and the amount of modifier added is 0.05-0.30% of the coal gangue mass.

[0020] Furthermore, in step S2, the target particle size is 60-1000 mesh.

[0021] The ecological soil contains an organic phase content of no more than 260 g / kg, a total nitrogen (TN) content of 0.1-3.5 g / kg, a total phosphorus (TP) content of 3-600 mg / kg, and a total phosphorus (TK) content of 3-400 mg / kg; a pH value of 5.0-9.0; a total total phosphorus (TSi) content of 0.3-55%; and a total total phosphorus (TFe) / alcohol content of 0.1-45%.

[0022] Performance of the resulting eco-soil products:

[0023] (1) Organic phase content: not exceeding 260 g / kg;

[0024] (2) pH value: 5.0-9.0;

[0025] (3) Heavy metal safety: The leaching toxicity of Tclp-Cd meets the requirements of the "Identification Standard for Hazardous Waste" (GB5085.3);

[0026] (4) Nutrient content: Total nitrogen (TN) 0.1-3.5 g / Kg, total phosphorus (TP) 3-600 mg / Kg, total potassium (TK) 3-400 mg / Kg;

[0027] (5) Environmental standard compliance: Agricultural ecological soil: electrical conductivity (EC) and heavy metal content meet or exceed the requirements of the "Soil Environmental Quality Standard" (GB15618); Engineering ecological soil: meets the requirements of "Greening Planting Soil" (CJ / T340);

[0028] (6) Total silicon (TSi) 0.3-55%, total iron / aluminum (TFe / Al) 0.1-45%;

[0029] (7) The leaching toxicity test complies with the "Leaching Toxicity Method for Solid Waste" (HJ / T299-2007).

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This invention achieves a breakthrough in reducing production costs and energy consumption, with a short production cycle and high efficiency. Specifically, the passivating agent and modifier are recyclable, reducing reagent costs; the reaction does not require high-temperature conversion, resulting in low heat consumption; the entire process has a short processing time, making the process short and efficient; the resulting eco-soil product can be used for land improvement, ecological restoration, environmental management, and planting applications in forestry, animal husbandry, agriculture, greening, tidal flats, river and lake shores, abandoned mines, coal mining subsidence areas, solid waste dumps, and other environmental scenarios. It can also be used for the remediation of acidified land, saline-alkali land, and environmentally polluted land.

[0032] 2. This invention enables on-demand and efficient activation of nutrients and improvement of soil structure. By adding different weak acid or salt activators, it chemically selectively activates nutrients such as Si, Al, Fe, and K, converting inert components in coal gangue into active components as needed, providing nutrients that plants can absorb. Through the synergistic effect of degradation agents and modifiers, it simultaneously optimizes soil structure, increases organic matter, and significantly improves soil fertility.

[0033] 3. The metal passivating agent involved in this invention, through the dual action of acid complexation and chelation, converts free heavy metals (such as Cd and Pb) in coal gangue into stable residual state. The leaching toxicity of Tclp-Cd meets GB5085.3, and the risk of heavy metal migration is reduced by more than 95% (verified by HJ / T299-2007).

[0034] 4. The degradation agent involved in this invention is inexpensive, low-carbon, and environmentally friendly, with ultra-low addition amount. It is a chemically selective decomposition activator with mild properties and no environmental risk. Detailed Implementation

[0035] 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.

[0036] The degradation agent involved in Examples 1-3 below is water rich in ozone and carbon dioxide, wherein the ozone concentration is 60 mg / L and the carbon dioxide concentration is 1100 mg / L.

[0037] 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 7:3. The high-temperature catalytic conditions are 180°C, 0.5MPa O2, and 1h.

[0038] 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 3:1:1.

[0039] 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.

[0040] Example 1

[0041] This embodiment discloses a method for preparing eco-soil by degrading and modifying coal gangue, using ordinary coal gangue as the raw material. The specific steps are as follows:

[0042] 1. Under an aerobic and ventilated environment at 25℃, add a degradation agent to coal gangue at a mass ratio of 1:30000 and react for 0.1 hours;

[0043] 2. Crush the coal gangue treated with the degradation agent to 200 mesh;

[0044] 3. Add 5wt% organic weak acid citric acid + malic acid to the crushed coal gangue to selectively dissolve and separate Fe / Al while retaining the silicon component;

[0045] 4. Add 0.5% metal passivating agent and react for 12 hours;

[0046] 5. Add 0.3% modifier to the coal gangue for aging modification, and react for 1 hour;

[0047] 6. Pack into 2-4mm granules.

[0048] Obtained ecological soil performance data:

[0049] Organic phase 35 g / kg, pH 7.5, Tclp-Cd not detected (GB5085.3 limit 1.0 mg / L);

[0050] TN 1.2g / kg, TP 85mg / kg, TK 120mg / kg; TFe / Al 18%;

[0051] The leaching values ​​of Pb, Cr, and As are all below the limits specified in GB15618 for Class I agricultural land.

[0052] Example 2:

[0053] This embodiment discloses a method for preparing eco-soil by degrading and modifying coal gangue, using low-organic-matter coal gangue (TOC 0.8%) as the raw material. The specific steps are as follows:

[0054] 1. Under an aerobic and ventilated environment at 35℃, add a degradation agent to coal gangue at a mass ratio of 1:30000 and react for 12 hours;

[0055] 2. Crush the coal gangue treated with the degradation agent to 300 mesh;

[0056] 3. Add 10wt% of the organic weak acids oxalic acid and fulvic acid to the crushed coal gangue to activate the silicon and potassium nutrients;

[0057] 4. Add 0.3% metal passivating agent and react for 24 hours;

[0058] 5. Add 0.6% modifier to the coal gangue for aging modification, and react for 3 hours;

[0059] 6. Produce agricultural pellets no larger than 2mm in size and package them.

[0060] Obtained ecological soil performance data:

[0061] Organic phase 210 g / kg, pH 7.2;

[0062] TN 2.8g / kg, TP 480mg / kg, TK 350mg / kg.

[0063] Example 3:

[0064] This embodiment discloses a method for preparing eco-soil by degrading and modifying coal gangue, using polymetallic contaminated coal gangue (Cd 5.2 mg / kg, Pb 280 mg / kg) as the raw material. The specific steps are as follows:

[0065] 1. Under an aerobic and ventilated environment at 40℃, add a degradation agent to coal gangue at a mass ratio of 1:40000 and react for 4 hours;

[0066] 2. Crush the coal gangue treated with the degradation agent to 500 mesh;

[0067] 3. Add 5% sodium dihydrogen phosphate (by weight of coal gangue) to the crushed coal gangue to selectively fix Pb; add 2% Na2CO3 salt to activate Si.

[0068] 4. Add 1.2% metal passivating agent and react for 6 hours;

[0069] 5. Add 0.2% modifier to the coal gangue for aging modification, and react for 2 hours;

[0070] 6. Powder packaging.

[0071] Obtained ecological soil performance data:

[0072] TSi 42.5%;

[0073] Tclp-Pb: 0.8 mg / L (GB5085.3 limit 5 mg / L);

[0074] Passivation efficiency: Cd / Pb fixation rate > 99%;

[0075] Cost: 180 yuan per ton (60% lower than conventional methods).

[0076] 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 eco-friendly soil by degrading and modifying coal gangue, characterized in that, Includes the following steps: S1 degradation pretreatment: Add degradation agent to coal gangue in an aerobic environment at a temperature ≥20℃; S2 crushing and screening: mechanically crushes the pretreated coal gangue to the target particle size; S3 Chemical Activation and Cascade Separation: Through the chemical selective decomposition and activation of coal gangue, the cascade separation of nutrients is achieved; S4 heavy metal passivation: Add passivating agent and treat for no more than 72 hours to undergo acidic complexation and chelation reactions with metal ions in coal gangue; S5 curing and modification: Add modifier, treat for no more than 12 hours; obtain ecological soil; The chemically selective decomposition method is acid decomposition, wherein Fe, Al, silicon, and potassium are selectively dissolved and separated using organic acids; the organic acids are 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; Si is selectively dissolved and separated using inorganic acids and salts; the inorganic acids are 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 degradation agent is water rich in ozone and carbon dioxide; The passivating agent is a high-temperature catalytic oxygen decomposition product of a mixture of seaweed sludge and the bottom layer of duck farm manure; The modifier comprises lignin degradation product sulfonate, tea polyphenol-iron complex, and red wine lees fermentation products.

2. The method for preparing eco-soil by degradation and modification of coal gangue as described in claim 1, characterized in that, The mass ratio of the degrading agent to coal gangue is no greater than 1:30000, and the pretreatment time is no more than 36 hours.

3. The method for preparing eco-soil by degradation and modification of coal gangue as described in claim 1, characterized in that, The ozone concentration is 60-100 mg / L, and the carbon dioxide concentration is 1000-1200 mg / L.

4. The method for preparing eco-soil by degradation and modification of coal gangue as described in claim 1, characterized in that, The amount of passivating agent added is 0.3-1.2% of the mass of coal gangue.

5. The method for preparing eco-soil by degradation and modification of coal gangue as described in claim 1, characterized in that, The lignin degradation products sulfonate, tea polyphenol-iron complex and red wine lees fermentation products are in a mass ratio of 4-6:2-3:2-3, and the amount of modifier added is 0.05-0.30% of the mass of coal gangue.

6. The method for preparing eco-soil by degradation and modification of coal gangue as described in claim 1, characterized in that, In step S2, the target particle size is 60-1000 mesh.

7. The method for preparing eco-soil by degradation and modification of coal gangue as described in claim 1, characterized in that, The ecological soil contains an organic phase content of no more than 260 g / kg, a total nitrogen (TN) content of 0.1-3.5 g / kg, a total phosphorus (TP) content of 3-600 mg / kg, a total phosphorus (TK) content of 3-400 mg / kg, a pH value of 5.0-9.0, a total total phosphorus (TSi) content of 0.3-55%, and a total total phosphorus (TFe / Al) content of 0.1-45%.