Method for preparing ecological soil by degrading and modifying coal gangue

Abstract

The invention discloses a method for preparing ecological soil by degrading and modifying coal gangue, which comprises the following steps: S1, degrading pretreatment: adding a degrading agent into the coal gangue in an aerobic environment at the temperature of more 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 stepped separation: decomposing and activating the coal gangue through chemical selectivity to realize stepped separation of nutrient elements; s4, heavy metal passivation: adding a passivator for treatment for not more than 72 hours, and carrying out acidic complexation and chelation reaction with metal ions in the coal gangue; and S5, curing modification: adding a modifier, and treating for not more than 12 hours to obtain the ecological soil. According to the method, chemical selective decomposition and activation, gradient separation and synergistic modification processes are adopted, the problems that the migration risk of heavy metal in coal gangue is high, and organic matter and nutrients are difficult to utilize are solved, the bottlenecks that a traditional process is large in energy consumption and long in treatment period are broken through, and the ecological soil preparation method is high in efficiency and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization and soil remediation, and in particular to a method for preparing ecological soil by degrading and modifying coal gangue. Background Art

[0002] Gangue is a solid waste generated during coal mining and washing. Its massive storage not only occupies land, but also poses serious environmental risks such as dust, leaching pollution of water and soil, and migration of heavy metals. Resource processing of gangue can not only effectively deal with the problem of its large-scale accumulation, but also transform it into a 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 stacking) 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 methods.

[0003] Existing gangue treatment technologies (such as landfill and simple covering) generally suffer from insufficient heavy metal passivation, poor nutrient utilization, and high costs, making them difficult to meet the stringent standards for ecological soil (for agricultural and engineering use). Specifically, patent CN118947491 A fails to consider the environmental risks of heavy metals and toxic and hazardous substances in gangue, and requires a reaction cycle of over 30 days to complete the ecological soil conversion, resulting in a long and inefficient process. Patent CN 117243086A crushes gangue and mixes it with sandy soil to produce improved ecological soil, but this does not enhance the activity of mineral elements and makes it difficult for nutrients to be dissolved and released. Patent CN 116114568 A adds large amounts of nitric acid, microbial agents, and chemical additives during the ecological soil preparation process, increasing costs and introducing new environmental pollution.

[0004] There is an urgent need for a new method for treating coal gangue to achieve the harmlessness and efficient resource conversion of coal gangue. Summary of the Invention

[0005] In response to the above-mentioned problems, the purpose of the present invention is to provide a method for preparing ecological soil by degrading and modifying coal gangue. The method adopts chemical selective decomposition and activation, cascade separation + synergistic modification process to solve the problems of high risk of heavy metal migration and difficulty in utilizing organic matter and nutrients in coal gangue, breaking through the bottleneck of high energy consumption and long processing cycle of traditional processes, and providing a high-efficiency and low-cost method for preparing ecological soil.

[0006] In order to solve the problems of the prior art, the technical solution adopted by the present invention is:

[0007] A method for preparing ecological soil by degrading and modifying coal gangue comprises the following steps:

[0008] S1 Degradation pretreatment: Add degradation agent to coal gangue in an aerobic environment with a temperature ≥20°C;

[0009] S2 Crushing and Screening: Mechanically crush the pre-treated gangue to the target particle size;

[0010] S3 chemical activation and cascade separation: Activate coal gangue through chemical selective decomposition;

[0011] S4 heavy metal passivation: add passivation agent and treat for no more than 72 hours to produce acidic complexation and chelation reaction with metal ions in coal gangue;

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

[0013] Furthermore, the chemical selective decomposition method is acid decomposition, wherein organic acid is used to selectively dissolve and separate Fe / Al / Si / K; and inorganic acid and salt 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 added amount is 5-10wt% of the mass of the coal gangue.

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

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

[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 oxidation decomposition product of a mixture of seaweed sludge and a bottom layer of duck farm manure, and the amount of the passivating agent added is 0.3-1.2% of the mass of the coal gangue.

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

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

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

[0022] The properties of the obtained ecological soil products:

[0023] (1) Organic phase content: not more than 260g / Kg;

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

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

[0026] (4) Nutrient content: total nitrogen (TN) 0..1-3.5g / Kg, total phosphorus (TP) 3-600mg / Kg, total potassium (TK) 3-400mg / Kg;

[0027] (5) Compliance with environmental standards: Agricultural ecological soil: electrical conductivity (EC) and heavy metal content meet or exceed the "Soil Environmental Quality Standard" (GB15618); Engineering ecological soil: meet the requirements of "Green Planting Soil" (CJ / T340);

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

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

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention significantly reduces production costs and energy consumption, resulting in a short production cycle and high efficiency. Specifically, the passivating agent and modifier can be recycled, reducing reagent costs. The reaction does not require high-temperature conversion, resulting in low heat consumption. The entire process takes a short time, resulting in a short and efficient process. The resulting ecological soil products can be used for land improvement, ecological restoration, environmental management, and crop production in forestry, animal husbandry, agriculture, greening, tidal flats, river and lakeside land, abandoned mines, coal mining subsidence areas, solid waste storage sites, and other environmental scenarios. They can also be used for the management of acidified land, saline-alkali land, and environmentally polluted land.

[0032] 2. The present invention efficiently activates nutrients and improves soil structure on demand. By adding different weak acid or salt activators, it chemically and selectively activates nutrients such as Si, Al, Fe, and K, converting inert components in coal gangue into active components on demand, providing nutrients that can be absorbed by plants. Through the synergistic effect of degraders and modifiers, it simultaneously optimizes soil structure, increases organic matter, and significantly improves soil fertility.

[0033] 3. The metal passivator of the present invention converts free heavy metals (such as Cd and Pb) in coal gangue into a stable residual state through the dual effects of acidic complexation and chelation. The leaching toxicity of Tclp-Cd complies with 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 the present invention is cheap, low-carbon and environmentally friendly, with ultra-low addition amount, and the chemical selective decomposition activator is mild in nature and has no environmental risks. DETAILED DESCRIPTION

[0035] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

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

[0037] The passivating agent involved in the following Examples 1-3 is a high-temperature catalytic oxidation product of a mixture of seaweed sludge and a bottom layer of duck farm manure, with the addition ratio of the two being 7:3. The high-temperature catalytic conditions are 180°C, 0.5MPa O2, and 1h.

[0038] The composition of the modifier involved in the following Examples 1-3 is: lignin degradation product sulfonate + tea polyphenol-iron complex + Cabernet Sauvignon red wine lees fermentation product, and the mass ratio of each component is 3:1:1.

[0039] In each embodiment, according to the raw material characteristics and target product requirements, by selecting different acid / salt combinations and conditions, selective activation, dissolution and selective fixation of specific nutrient elements (Si, K, Fe, Al) can be achieved.

[0040] Example 1

[0041] This embodiment discloses a method for preparing ecological soil by degrading and modifying coal gangue, wherein the raw material is ordinary coal gangue, and the specific steps are as follows:

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

[0043] 2. Crushing the coal gangue treated with the degradation agent into 200 mesh;

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

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

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

[0047] 6. Make into 2-4mm granules and pack.

[0048] The 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 of Pb / Cr / As is all lower than the standard limit of Class I agricultural land in GB15618.

[0052] Example 2:

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

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

[0055] 2. Crushing the coal gangue treated with the degradation agent into 300 mesh;

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

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

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

[0059] 6. Packed into agricultural granules no larger than 2mm.

[0060] The 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 ecological soil by degrading and modifying coal gangue. The raw material is multi-metal contaminated coal gangue (Cd 5.2 mg / kg, Pb 280 mg / kg). The specific steps are as follows:

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

[0066] 2. Crushing the coal gangue treated with the degradation agent into 500 mesh;

[0067] 3. Add 5% of the mass of the coal gangue as inorganic acid sodium dihydrogen phosphate to the crushed coal gangue to selectively fix Pb; add 2% of the salt Na2CO3 to activate Si;

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

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

[0070] 6. Powder packaging.

[0071] The 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 of processing fee (60% lower than the conventional method).

[0076] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing ecological soil by degrading and modifying coal gangue, characterized in that: The steps include: S1 Degradation pretreatment: Add degradation agent to coal gangue in an aerobic environment with a temperature ≥20°C; S2 Crushing and Screening: Mechanically crush the pre-treated gangue to the target particle size; S3 chemical activation and cascade separation: through chemical selective decomposition and activation of coal gangue, cascade separation of nutrient elements is achieved; S4 heavy metal passivation: add passivation agent and treat for no more than 72 hours to produce acidic complexation and chelation reaction with metal ions in coal gangue; S5 Ripening modification: Add modifiers and treat for no more than 12 hours to obtain ecological soil.

2. The method for preparing ecological soil by degrading and modifying coal gangue according to claim 1, characterized in that: The chemical selective decomposition method is acid decomposition, wherein organic acid is used to selectively dissolve and separate Fe / Al / potassium silicon; and inorganic acid and salt are used to selectively dissolve and separate Si.

3. The method for preparing ecological soil by degrading and modifying coal gangue according to claim 2, characterized in that: The organic acid is one or more of fulvic acid, acetic acid, fruit acid or oxalic acid, and the added amount is 5-10 wt% of the mass of the coal gangue.

4. The method for preparing ecological soil by degrading and modifying coal gangue according to claim 2, characterized in that: The inorganic acid is one or more of sodium dihydrogen phosphate and sodium sulfide, and the addition amount is 3-5% of the mass of the coal gangue; the salt is sodium carbonate, and the addition amount is 2-4% of the mass of the coal gangue.

5. The method for preparing ecological soil by degrading and modifying coal gangue according to claim 1, characterized in that: The degradation agent is water rich in ozone and carbon dioxide, the mass ratio of the degradation agent to coal gangue is not greater than 1:30000, and the pretreatment time is not more than 36 hours.

6. The method for preparing ecological soil by degrading and modifying coal gangue according to claim 5, characterized in that: The ozone concentration is 60-100 mg / L, and the carbon dioxide concentration is 1000-1200 mg / L.

7. The method for preparing ecological soil by degrading and modifying coal gangue according to claim 1, characterized in that: The passivating agent is a high-temperature catalytic oxidation decomposition product of a mixture of seaweed sludge and a bottom layer of duck farm feces. The added amount of the passivating agent is 0.3-1.2% of the mass of the coal gangue.

8. The method for preparing ecological soil by degrading and modifying coal gangue according to claim 1, characterized in that: The modifier comprises lignin degradation product sulfonate, tea polyphenol-iron complex and red wine lees fermentation product, with the mass ratio of each component being 4-6:2-3:2-3. The addition amount of the modifier is 0.05-0.30% of the mass of the coal gangue.

9. The method for preparing ecological soil by degrading and modifying coal gangue according to claim 1, characterized in that: In step S2, the target particle size is 60-1000 mesh.

10. The method for preparing ecological soil by degrading and modifying coal gangue according to claim 1, characterized in that: The ecological soil has an organic phase content of no more than 260 g / kg, TN of 0.1-3.5 g / kg, TP of 3-600 mg / kg, and TK of 3-400 mg / kg; a pH value of 5.0-9.0; TSi of 0.3-55%; and a total TFe / Al content of 0.1-45%.