Heavy metal polluted farmland remediation process based on coal gangue activation and peat soil water retention

Abstract

The invention relates to the technical field of farmland remediation processes, in particular to a heavy metal polluted farmland remediation process based on coal gangue activation and peat soil water retention, which comprises the following steps: SI, coal gangue pretreatment; s2, coal gangue acid activation; s3, mixing and stirring; s4, on-site repair construction; according to the farmland remediation process, a large amount of solid waste, namely the coal gangue, generated in the coal mining and washing process is activated, the heavy metal adsorption capacity is given to the solid waste, resource utilization of the industrial solid waste is achieved, and land resource occupation and environmental pollution caused by coal gangue accumulation are reduced; the coal gangue is matched with imported peat soil, the advantages of high organic matter content and high humic acid content of the imported peat soil are fully exerted, and after the coal gangue is activated by acid, rich pore structures are formed on the surface, so that the specific surface area and active sites are increased, and the adsorption capacity on heavy metal ions is greatly improved; the water retention characteristic of the peat soil enables active sites on the surface of the coal gangue to be always in a wet state, and the continuous adsorption capacity is maintained.

Description

Technical Field

[0001] The present invention relates to the technical field of farmland restoration technology, and in particular to a heavy metal-contaminated farmland restoration technology based on gangue activation and peat soil water conservation. Background Art

[0002] Traditional physical remediation techniques for farmland generally use the imported soil method, which achieves remediation by directly replacing contaminated soil; one part of the chemical remediation process uses curing agents, including cement, lime, etc., and another part uses the leaching method, which consumes a large amount of water resources to flush the soil; one part of the biological remediation process relies on hyperaccumulator plants to absorb heavy metals, and another part introduces exogenous microorganisms for remediation.

[0003] In the physical remediation process, a large amount of uncontaminated soil needs to be mined and transported, accompanied by high excavation, transportation and labor costs, which makes large-scale remediation cost unaffordable; in the chemical remediation process, some solidifiers are used, which can fix heavy metals, but may change the pH value and physical and chemical properties of the soil, affect the activity of soil microorganisms and plant growth, and the long-term use of some solidifiers may also lead to the secondary release of heavy metals, causing new pollution; when the leaching method is used, while removing heavy metals, a large amount of leaching will also take away the organic matter, minerals and nutrients in the soil, seriously damaging the soil fertility, and a large amount of fertilizer will be needed to restore the soil fertility; in the biological remediation process, different plants have different absorption capacities for specific heavy metals, and a single plant is difficult to cope with the combined pollution of multiple heavy metals; and it is significantly affected by climate and soil conditions, and the remediation efficiency is low in harsh environments. The introduction of exogenous microorganisms may disrupt the balance of the original microbial community in the soil, affecting the stability and biodiversity of the soil ecosystem.

[0004] Therefore, in view of the problems of the above-mentioned farmland restoration technology, such as high cost, large resource consumption, long restoration cycle, easy to cause secondary pollution, unsustainable restoration effect, limited scope of application, and destruction of soil structure and ecological balance, a heavy metal contaminated farmland restoration technology based on coal gangue activation and peat soil water conservation can be designed. Summary of the Invention

[0005] In order to overcome the problems of traditional farmland restoration technology, such as high cost, large resource consumption, long restoration cycle, easy to cause secondary pollution, unsustainable restoration effect, limited scope of application, and destruction of soil structure and ecological balance.

[0006] The technical solution of the present invention is: a heavy metal contaminated farmland restoration process based on coal gangue activation and peat soil water conservation, the steps of which are as follows:

[0007] S1: Gangue pretreatment

[0008] S11: The raw gangue is conveyed to a jaw crusher, where it is coarsely crushed to a particle size of 5-10 cm. The crushed material then enters a vibrating screening machine to remove impurities and oversized particles.

[0009] S12: The screened gangue is fed into a ball mill. Steel balls are used as grinding media. By controlling the grinding time and speed, the gangue is ground to a particle size of less than 0.15 mm.

[0010] S2: Acid activation of coal gangue

[0011] S21: The above-mentioned gangue is put into an enameled reactor in an amount of 1-2 tons per batch, and sulfuric acid solution is added to the reactor via a metering pump according to a mass ratio of 1:2.5 between gangue and 18% sulfuric acid. A frame stirrer is used to stir the reaction at 85°C and a speed of 60-80 rpm for 2.5 hours;

[0012] S22: After the reaction is completed, the acid-leached coal gangue is repeatedly washed, and then lime is prepared into lime milk, which is added to the reactor through a pipeline for neutralization. The neutralized material is passed through a chamber filter press for solid-liquid separation to obtain an activated coal gangue filter cake;

[0013] S3: Mixing

[0014] S31: Use an electronic belt scale to weigh 0.6 cubic meters of activated coal gangue, 0.4 cubic meters of peat soil, 6 kilograms of lime, and 1.5 kilograms of microbial agent. The weighed raw materials are fed into a double-shaft horizontal mixer. The mixing time is controlled within 18 minutes to form a soil remediation material with good performance.

[0015] S4: On-site repair construction

[0016] S41: Use a rotary tiller and tractor to plow the contaminated farmland to a depth of 28 cm to break up the original soil compaction layer and loosen the soil;

[0017] S42: Use a fertilizer spreader and tractor to evenly spread the mixed restoration material on the surface of the plowed field, ensuring that the restoration material is evenly distributed in each area;

[0018] S43: The rotary tiller was used again and tillage was performed according to the same parameters to fully mix the repair material with the original soil, with the depth also being 28 cm;

[0019] S44: Finally, use a grader to compact and level the farmland.

[0020] Preferably, in step S11, the maximum feed particle size of the jaw crusher is ≤500mm, and the discharge opening adjustment range is 65-160mm; the number of screen layers of the vibrating screening machine is 3, and the processing capacity is 50-500t / h.

[0021] Preferably, in step S12, the rotation speed of the ball mill is 28-32 r / min.

[0022] As a preference, in step S21, the volume of the enamel reactor is 5-10m 3 The reactor has strong acid resistance and can withstand temperatures ranging from -20°C to 200°C; the power of the frame agitator is 15-22kW.

[0023] Preferably, in step S22, a high-pressure water gun with a pressure of 0.8-1.2 MPa is started to repeatedly rinse the acid-leached coal gangue for 30 minutes to remove residual acid; a pH meter is used for real-time monitoring during neutralization to adjust the soil pH to 6.5-7.5; the filtration area of ​​the chamber filter press is 100 m2, the filter plate size is 1000×1000 mm, and the working pressure is 0.6-1.2 MPa.

[0024] Preferably, in step S31, the amount of activated gangue is 1.2-1.5 tons, the amount of peat soil is 0.4-0.6 tons, and the volume ratio of gangue to peat soil is 3:2.

[0025] Preferably, in step S31, the measuring range of the electronic belt scale is 0-5000kg, with an accuracy of ±0.5kg; the discharge capacity of the twin-shaft horizontal mixer is 500L, the stirring power is 18.5kW, and the linear speed of the stirring blade is 1.2-1.5m / s.

[0026] Preferably, in step S41, a 55-75kW tractor is used, a rotary tiller has a tillage width of 250 cm, and a tillage depth adjustment range of 12-30 cm.

[0027] Preferably, in step S42, a 30-50kW tractor is used, a fertilizer spreading width of 6-12m, and a fertilizer application amount adjustment range of 50-500kg / mu.

[0028] Preferably, in step S44, the engine power of the grader is 120 kW, the scraper length is 3048 mm, and the flatness error of the farmland surface is controlled within ±3 cm, creating good conditions for subsequent planting.

[0029] Beneficial effects of the present invention:

[0030] The farmland restoration process of the present invention activates gangue, a large amount of solid waste generated during coal mining and washing, giving it heavy metal adsorption capacity, thereby realizing resource utilization of industrial solid waste. This not only reduces the occupation of land resources and environmental pollution caused by gangue accumulation, but also reduces the procurement cost of restoration materials. The process is combined with imported peat soil to give full play to its advantages of high organic matter and humic acid. The combination of the two not only solves the problem of solid waste disposal, but also optimizes the selection of soil improvement materials and promotes the recycling of resources.

[0031] After acid activation, the gangue forms a rich pore structure on its surface, increasing the specific surface area and active sites, significantly improving its adsorption capacity for heavy metal ions. After mixing with peat soil, the water-retaining properties of the peat soil keep the active sites on the gangue surface moist, maintaining its continuous adsorption capacity. The synergistic effect of the two can reduce the effective content of heavy metals in farmland soil by 60%-80%, quickly and effectively reducing the bioavailability of heavy metals, reducing the absorption of heavy metals by crops, and ensuring the safety of agricultural products.

[0032] Peat soil is rich in organic matter and humic acid, which can promote the formation of soil aggregate structure and enhance soil aeration and water permeability. After coal gangue is mixed with peat soil, the soil particle composition is further optimized and the soil physical properties are improved. At the same time, the synergistic effect of the two enhances the soil's water and fertilizer retention capacity, reduces water evaporation and nutrient loss, creates a good soil environment for crop growth, improves the efficiency of crops in absorbing soil nutrients, and helps farmland achieve high and stable yields.

[0033] Using industrial solid waste gangue as the primary raw material significantly reduces the cost of restoration materials compared to the large amounts of foreign soil and chemical agents used in traditional restoration processes. Reasonable equipment selection and process design improve restoration efficiency, reduce construction time and manpower, and further reduce overall restoration costs. Furthermore, restored farmland can be quickly put back into agricultural production, shortening the return cycle and delivering excellent economic benefits.

[0034] This process avoids the secondary pollution problems that may occur in traditional chemical remediation processes, does not use large amounts of chemical agents, and reduces damage to soil microorganisms and the ecological environment. By adding microbial agents, it promotes the virtuous cycle of the soil ecosystem and protects soil biodiversity. At the same time, under reasonable management, the physical and chemical properties and ecological functions of the restored farmland can be maintained at high-standard farmland levels for 8-10 years, achieving sustainable development of farmland remediation.

[0035] The process flow is clearly designed and standardized, with clear parameters for each step, making it easy to operate and manage; the equipment used are common industrial and agricultural machinery, which are easy to obtain and maintain; whether it is small-scale farmland restoration or large-scale polluted area governance, this process can be effectively applied and is not overly restricted by geographical, climatic and other conditions, and has broad promotion and application value. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the embodiments.

[0037] Example 1

[0038] When using the process of this technical solution, the steps are as follows:

[0039] S1: Gangue pretreatment

[0040] S11: The raw gangue is conveyed to a jaw crusher with a maximum feed size of ≤500mm and a discharge opening adjustment range of 65-160mm. The gangue is coarsely crushed to a particle size of 5-10cm. The crushed material then enters a vibrating screen to remove impurities and oversized particles. The vibrating screen has three screen layers and a processing capacity of 50-500t / h.

[0041] S12: The screened gangue is fed into a ball mill. Steel balls are used as grinding media. The grinding time and speed are controlled to grind the gangue to a particle size of less than 0.15 mm. The speed of the ball mill is 28-32 r / min.

[0042] S2: Acid activation of coal gangue

[0043] S21: Put the above-mentioned gangue into the enameled reactor in batches of 1 ton. The volume of the enameled reactor is 5-10m 3 The reactor has strong acid resistance and can withstand temperatures between -20°C and 200°C. Sulfuric acid solution is added to the reactor via a metering pump in a mass ratio of 1:2.5 between gangue and 18% sulfuric acid. A frame stirrer is used to stir the reaction at 85°C at a speed of 60r / min for 2.5 hours. The power of the frame stirrer is 15kW.

[0044] S22: After the reaction is completed, a high-pressure water gun with a pressure of 0.8-1.2 MPa is started to repeatedly rinse the acid-leached coal gangue for 30 minutes to remove residual acid. Then, lime is prepared into lime milk, which is added to the reactor through a pipeline for neutralization. A pH meter is used for real-time monitoring to adjust the soil pH value to 6.5-7.5. The neutralized material is passed through a chamber filter press for solid-liquid separation. The chamber filter press has a filtration area of ​​100 m2, a filter plate size of 1000×1000 mm, and a working pressure of 0.6-1.2 MPa to obtain an activated coal gangue filter cake;

[0045] S3: Mixing

[0046] S31: 0.6 cubic meters of activated coal gangue, 0.4 cubic meters of peat soil, 6 kilograms of lime, and 1.5 kilograms of microbial agent were weighed using an electronic belt scale with a range of 0-5000 kg and an accuracy of ±0.5 kg. The weighed raw materials were fed into a twin-shaft horizontal mixer with a discharge capacity of 500 L, a stirring power of 18.5 kW, a stirring blade linear speed of 1.2 m / s, and a stirring time of 18 minutes to form a soil remediation material with good performance. The activated coal gangue was 1.2-1.5 tons, the peat soil was 0.4-0.6 tons, and the volume ratio of coal gangue to peat soil was 3:2;

[0047] S4: On-site repair construction

[0048] S41: Using a rotary tiller and a 55kW tractor, with a tillage width of 250cm and an adjustable tillage depth of 12cm, the contaminated farmland was plowed to a depth of 28cm to break up the original soil compaction layer and loosen the soil.

[0049] S42: Use a fertilizer spreader and a 30kW tractor to spread the mixed restoration material evenly on the surface of the plowed farmland with a 6m spreading width and a fertilizer rate adjustment range of 50-500kg / mu, ensuring that the restoration material is evenly distributed in each area;

[0050] S43: The rotary tiller was used again and tillage was performed according to the same parameters to fully mix the repair material with the original soil, with the depth also being 28 cm;

[0051] S44: Finally, a grader is used to compact and level the farmland. The engine power of the grader is 120kW, the scraper length is 3048mm, and the surface flatness error of the farmland is controlled within ±3cm, creating good conditions for subsequent planting.

[0052] Example 2

[0053] When using the process of this technical solution, the steps are as follows:

[0054] S1: Gangue pretreatment

[0055] S11: The raw gangue is conveyed to a jaw crusher with a maximum feed size of ≤500mm and a discharge opening adjustment range of 65-160mm. The gangue is coarsely crushed to a particle size of 5-10cm. The crushed material then enters a vibrating screen to remove impurities and oversized particles. The vibrating screen has three screen layers and a processing capacity of 50-500t / h.

[0056] S12: The screened gangue is fed into a ball mill. Steel balls are used as grinding media. The grinding time and speed are controlled to grind the gangue to a particle size of less than 0.15 mm. The speed of the ball mill is 28-32 r / min.

[0057] S2: Acid activation of coal gangue

[0058] S21: Put the above-mentioned gangue into the enameled reactor in batches of 2 tons. The volume of the enameled reactor is 5-10m 3 The reactor has strong acid resistance and can withstand temperatures between -20°C and 200°C. Sulfuric acid solution is added to the reactor via a metering pump in a mass ratio of 1:2.5 between gangue and 18% sulfuric acid. A frame stirrer is used to stir the reaction at 85°C at a speed of 80r / min for 2.5 hours. The power of the frame stirrer is 22kW.

[0059] S22: After the reaction is completed, a high-pressure water gun with a pressure of 0.8-1.2 MPa is started to repeatedly rinse the acid-leached coal gangue for 30 minutes to remove residual acid. Then, lime is prepared into lime milk, which is added to the reactor through a pipeline for neutralization. A pH meter is used for real-time monitoring to adjust the soil pH value to 6.5-7.5. The neutralized material is passed through a chamber filter press for solid-liquid separation. The chamber filter press has a filtration area of ​​100 m2, a filter plate size of 1000×1000 mm, and a working pressure of 0.6-1.2 MPa to obtain an activated coal gangue filter cake;

[0060] S3: Mixing

[0061] S31: 0.6 cubic meters of activated coal gangue, 0.4 cubic meters of peat soil, 6 kilograms of lime, and 1.5 kilograms of microbial agent were weighed using an electronic belt scale with a range of 0-5000 kg and an accuracy of ±0.5 kg. The weighed raw materials were fed into a twin-shaft horizontal mixer with a discharge capacity of 500 L, a stirring power of 18.5 kW, a stirring blade linear speed of 1.5 m / s, and a stirring time of 18 minutes to form a soil remediation material with good performance. The activated coal gangue was 1.2-1.5 tons, the peat soil was 0.4-0.6 tons, and the volume ratio of coal gangue to peat soil was 3:2;

[0062] S4: On-site repair construction

[0063] S41: Using a rotary tiller and a 75kW tractor, with a tillage width of 250cm and an adjustable tillage depth of 12-30cm, the contaminated farmland was plowed to a depth of 28cm to break up the original soil compaction layer and loosen the soil;

[0064] S42: Use a fertilizer spreader and a 50kW tractor to spread the mixed restoration material evenly on the surface of the plowed farmland with a spreading width of 12m and a fertilizer rate adjustment range of 50-500kg / mu, ensuring that the restoration material is evenly distributed in each area;

[0065] S43: The rotary tiller was used again and tillage was performed according to the same parameters to fully mix the repair material with the original soil, with the depth also being 28 cm;

[0066] S44: Finally, a grader is used to compact and level the farmland. The engine power of the grader is 120kW, the scraper length is 3048mm, and the surface flatness error of the farmland is controlled within ±3cm, creating good conditions for subsequent planting.

[0067] Experimental example

[0068] Five plots of farmland, each with an area of ​​1 mu and similar levels of heavy metal pollution, including cadmium, lead, and zinc, were selected and marked as Area A, Area B, Area C, Area D, and Area E respectively;

[0069] Area A was used as Experimental Example 1 using the process of Example 1;

[0070] Area B is used as Experimental Example 2 using the process of Example 2;

[0071] Area C was used as a control experiment in Experiment 3 using the imported soil method. This involved using excavation equipment to remove the top 20-30 cm of contaminated soil, transporting uncontaminated imported soil to the site and evenly covering it. The soil was then plowed using tillage equipment at the same depth as in Area A to ensure that the imported soil was fully mixed with the original soil.

[0072] Area D was used as a control experiment for Experiment 4 using the chemical curing method. The amount of chemical curing agent was calculated based on the heavy metal content in the soil, the curing agent was evenly spread on the soil surface, and tillage equipment was used to fully mix the curing agent with the soil.

[0073] Area E was used as a control experiment in Experiment 5 using the phytoremediation method, that is, hyperaccumulator plant seedlings were planted in the farmland according to the planned planting density, and regular watering, fertilization and other maintenance work were carried out to ensure the normal growth of the plants;

[0074] Soil sampling was carried out 1 month, 3 months, 6 months, and 12 months after restoration, and crop yield data were recorded during the harvest period. Atomic absorption spectrophotometry was used to determine the available content of heavy metals in the soil, including cadmium, lead, and zinc. The potassium dichromate oxidation method was used to determine the soil organic matter content. A pH meter was used to determine the soil pH value. The ring knife method was used to determine the soil water retention rate. After the crops matured, the crops in each area were harvested and weighed, and the crop yield was recorded. The experimental data are shown in the following table:

[0075]

[0076]

[0077]

[0078]

Claims

1. A heavy metal contaminated farmland restoration process based on coal gangue activation and peat soil water conservation, characterized in that: The steps are as follows: S1: Gangue pretreatment S11: The raw gangue is conveyed to a jaw crusher, where it is coarsely crushed to a particle size of 5-10 cm. The crushed material then enters a vibrating screening machine to remove impurities and oversized particles. S12: The screened gangue is fed into a ball mill. Steel balls are used as grinding media. By controlling the grinding time and speed, the gangue is ground to a particle size of less than 0.15 mm. S2: Acid activation of coal gangue S21: The above-mentioned gangue is put into an enameled reactor in an amount of 1-2 tons per batch, and sulfuric acid solution is added to the reactor via a metering pump according to a mass ratio of 1:2.5 between gangue and 18% sulfuric acid. A frame stirrer is used to stir the reaction at 85°C and a speed of 60-80 rpm for 2.5 hours; S22: After the reaction is completed, the acid-leached coal gangue is repeatedly washed, and then lime is prepared into lime milk, which is added to the reactor through a pipeline for neutralization. The neutralized material is passed through a chamber filter press for solid-liquid separation to obtain an activated coal gangue filter cake; S3: Mixing S31: Use an electronic belt scale to weigh 0.6 cubic meters of activated coal gangue, 0.4 cubic meters of peat soil, 6 kilograms of lime, and 1.5 kilograms of microbial agent. The weighed raw materials are fed into a double-shaft horizontal mixer. The mixing time is controlled within 18 minutes to form a soil remediation material with good performance. S4: On-site repair construction S41: Use a rotary tiller and tractor to plow the contaminated farmland to a depth of 28 cm to break up the original soil compaction layer and loosen the soil; S42: Use a fertilizer spreader and tractor to evenly spread the mixed restoration material on the surface of the plowed field, ensuring that the restoration material is evenly distributed in each area; S43: The rotary tiller was used again and tillage was performed according to the same parameters to fully mix the repair material with the original soil, with the depth also being 28 cm; S44: Finally, use a grader to compact and level the farmland.

2. The heavy metal contaminated farmland restoration process based on gangue activation and peat soil water conservation according to claim 1 is characterized in that: In step S11, the maximum feed particle size of the jaw crusher is ≤500mm, and the discharge opening adjustment range is 65-160mm; the number of screen layers of the vibrating screening machine is 3, and the processing capacity is 50-500t / h.

3. The heavy metal contaminated farmland restoration process based on gangue activation and peat soil water conservation according to claim 1 is characterized in that: In step S12, the rotation speed of the ball mill is 28-32 r / min.

4. The heavy metal contaminated farmland restoration process based on gangue activation and peat soil water conservation according to claim 1 is characterized in that: In step S21, the volume of the enamel reactor is 5-10m 3 The reactor has strong acid resistance and can withstand temperatures ranging from -20°C to 200°C; the power of the frame agitator is 15-22kW.

5. The heavy metal contaminated farmland restoration process based on gangue activation and peat soil water conservation according to claim 1 is characterized in that: In step S22, a high-pressure water gun with a pressure of 0.8-1.2 MPa is started to repeatedly rinse the acid-leached coal gangue for 30 minutes to remove residual acid. During neutralization, a pH meter is used for real-time monitoring to adjust the soil pH value to 6.5-7.

5. The filtration area of ​​the chamber filter press is 100 m2, the filter plate size is 1000×1000 mm, and the working pressure is 0.6-1.2 MPa.

6. The heavy metal contaminated farmland restoration process based on gangue activation and peat soil water conservation according to claim 1 is characterized in that: In step S31, the amount of activated coal gangue is 1.2-1.5 tons, the amount of peat soil is 0.4-0.6 tons, and the volume ratio of coal gangue to peat soil is 3:

2.

7. The heavy metal contaminated farmland restoration process based on gangue activation and peat soil water conservation according to claim 1 is characterized in that: In step S31, the range of the electronic belt scale is 0-5000kg, with an accuracy of ±0.5kg; the discharge capacity of the twin-shaft horizontal mixer is 500L, the stirring power is 18.5kW, and the linear speed of the stirring blade is 1.2-1.5m / s.

8. The heavy metal contaminated farmland restoration process based on gangue activation and peat soil water conservation according to claim 1 is characterized in that: In step S41, a 55-75kW tractor is used, a rotary tiller has a tillage width of 250 cm, and a tillage depth adjustment range of 12-30 cm.

9. The heavy metal contaminated farmland restoration process based on gangue activation and peat soil water conservation according to claim 1, characterized in that: In step S42, a 30-50kW tractor is used, a fertilizer spreading width of 6-12m, and a fertilizer application amount adjustment range of 50-500kg / mu.

10. The heavy metal contaminated farmland restoration process based on gangue activation and peat soil water conservation according to claim 9, characterized in that: In step S44, the engine power of the grader is 120kW, the scraper length is 3048mm, and the flatness error of the farmland surface is controlled within ±3cm, creating good conditions for subsequent planting.

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