Soil improvement method for coupling oil shale waste residue with microorganisms through microwave activation

Abstract

The invention discloses an oil shale waste residue microwave activation and microorganism coupling soil improvement method which comprises the following steps: crushing and screening oil shale dry distillation residues, and adding ground phosphate rock when necessary; then carrying out two-stage microwave activation treatment to obtain an activated waste residue carrier with high specific surface area and low content of harmful substances; mixing the activated carrier with a compound microbial agent (containing azotobacter chroococcum, silicate bacteria and cellulose degrading bacteria) and straws according to a specific ratio, and carrying out stack retting to prepare a harmless activated waste residue modifier; finally, the application amount is determined according to the soil type, and the fertilizer is applied to soil. According to the invention, harmlessness and high-value recycling of the oil shale waste residues are realized, and the prepared modifier can significantly increase the soil nutrient content, improve the soil structure, adjust the pH value and promote crop growth, is suitable for improvement of various degraded soil, has the advantages of efficient process, low cost, environmental friendliness and the like, and has a relatively high popularization value.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and soil improvement technology, and in particular to a soil improvement method using microwave activation coupled with microorganisms from oil shale waste. Background Technology

[0002] Oil shale is an important energy mineral, and its dry distillation process generates a large amount of waste residue (called oil shale dry distillation residue). This waste residue is usually dumped in the open, occupying a large amount of land and potentially causing secondary pollution due to the presence of phenols, polycyclic aromatic hydrocarbons (PAHs), and some heavy metals (such as cadmium and lead) that can seep into water bodies or soil under rainwater runoff. How to safely and efficiently utilize this waste residue has become an important issue in the fields of environmental protection and resource recycling. On the other hand, acidified soils, infertile soils, and soils in mine reclamation areas are widespread, generally suffering from poor soil structure, nutrient deficiency, and low microbial activity. Traditional soil improvement methods, such as applying lime and organic fertilizers, have drawbacks such as high cost, unstable effects, and a tendency to cause soil compaction or secondary salinization.

[0003] In existing technologies, the resource utilization of oil shale waste residue is mostly concentrated on the preparation of building materials or simple landfill, failing to fully realize its potential in soil improvement. Some studies have also attempted to apply the waste residue directly to the soil, but untreated waste residue has problems such as residual organic pollutants, minerals that are difficult for crops to absorb, and poor aggregation with the soil, resulting in limited improvement effects. Although microwave activation technology can be used for solid waste modification and microbial technology can also be used for soil improvement, the integration of the two to construct an integrated synergistic improvement system of "microwave activated waste residue carrier - functional microbial agent - soil-adapted application" has not yet been mass-produced.

[0004] Therefore, developing a method that can simultaneously achieve the harmlessness, resource utilization, and efficient activation of oil shale waste, and can synergistically enhance soil fertility with microorganisms, has significant environmental and economic value. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a soil improvement method for oil shale waste residue by microwave activation coupled with microorganisms, which has a comprehensive and lasting soil improvement effect, high efficiency, low cost, stable effect and environmental protection.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] A method for soil improvement using microwave activation coupled with microorganisms from oil shale waste residue includes the following steps: S1. Waste residue pretreatment: The oil shale dry distillation residue is crushed to a particle size of 2-5 mm, and impurities with a particle size greater than 10 mm are sieved out to obtain pretreated waste residue. The content of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in the pretreated waste residue is detected. If the cadmium content is greater than 0.3 mg / kg, 3%-8% by weight of phosphate rock powder is added to the pretreated waste residue and mixed evenly; S2. Microwave activation treatment: The material obtained in step S1 is placed in a microwave device and subjected to two-stage heating treatment at a frequency of 915 MHz or 2450 MHz and a power of 400-1200 W. The first stage heating power is 400-800 W, and the temperature is controlled at 500-700℃ for 30-90 minutes to remove volatile harmful components. The second stage heating power is 800-1200 W. W. Control the temperature to 800-1000℃ and maintain it for 60-180 minutes to optimize the pore structure. After cooling, an activated waste residue carrier is obtained. The surface area of ​​the activated waste residue carrier is ≥5 m² / g, the carbon content is ≥30 wt%, and the removal rate of harmful components is ≥90%. S3. Preparation of compound microbial agent: Azotobacter chrysotile, silicate bacteria and cellulose degrading bacteria are compounded in a weight ratio of (2-4):(1-3):(0.5-1.5). The compound of quartz sand, sorghum powder and fern residue is used as the carrier. It is statically cultured for 2-3 weeks at 28-32℃ and 50-60% water content to obtain an effective viable count ≥10. 9 S4. Microbial compound treatment: Mix the obtained activated waste residue carrier, compound microbial agent and straw in a mass ratio of (65-75):(0.05-0.15):(25-35), adjust the moisture content of the mixture to 50-60%, place it in a fermentation device, and compost at 25-32℃ for 18-20 days, turning the pile every 5-7 days during the period to obtain a harmless activated waste residue conditioner; S5. Soil improvement application: Determine the application rate according to the type and properties of the soil to be improved; For acidic soil with a pH value of 4.5-6.0, apply the harmless activated waste residue conditioner evenly on the soil surface at an application rate of 1200-1800 kg per mu, and till it to a depth of 25-30 cm with a rotary tiller to fully mix the harmless activated waste residue conditioner with the soil. Water thoroughly once within 7 days after application. During the crop seedling stage, apply 400-600 kg per mu. Apply fertilizer at a rate of kg.

[0008] In the above embodiments, in step S1, the particle size of the phosphate rock powder is 100-200 mesh.

[0009] In the above embodiments, in step S2, the microwave equipment is a continuous microwave processor with a total processing time of 3-5 minutes and a power of 700-900 W. The specific surface area of ​​the activated waste residue carrier is ≥5 m² / g, and the carbon content is ≥30 wt%.

[0010] In the above embodiment, in step S3, the mass ratio of the quartz sand, sorghum powder and fern residue is (1-2):(1-2):(0.5-1), and the cultivation conditions are: temperature 28-32℃, moisture content 50-60%, and static cultivation for 2-3 weeks.

[0011] In the above embodiment, in step S4, the straw is crushed to a particle size of 1-2 cm before use, and during the composting and fermentation period, the straw is turned over once every 5-7 days.

[0012] In the above embodiments, in step S4, if it is used for improving sandy and barren soil, the activated waste residue carrier is added to the mixture, and the activated waste residue carrier is 10%-20% decomposed sheep manure by mass.

[0013] In the above implementation method, in step S5, for acidic soil with a pH value of 4.5-6.0, the soil is applied as a base fertilizer at a rate of 1200-1800 kg per mu. The soil conditioner is mixed with the soil by deep tilling 25-30 cm with a rotary tiller, and the soil is thoroughly watered within 7 days after application.

[0014] In the above embodiment, in step S5, topdressing is applied at a rate of 400-600 kg per mu during the seedling stage of the crop.

[0015] In the above embodiments, in step S5, if it is used for soil improvement in mine reclamation areas, the application rate is 2000-2500 kg per mu, and pioneer plants are planted in combination.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention achieves the harmlessness and high-value resource utilization of solid waste: through the synergistic effect of microwave activation and microbial composting, PAHs in the waste residue are effectively degraded (degradation rate ≥80%) and the bioavailability of heavy metals is reduced (by more than 40%), transforming industrial waste residue into a safe and efficient soil amendment material, thus solving the environmental pressure caused by waste residue dumping. The soil amendment effect is comprehensive and long-lasting: microwave activation significantly increases the activation rate of minerals (such as calcium, magnesium, and potassium) in the waste residue (by 15%-20%); the compound microbial agent plays a role in nitrogen fixation, phosphorus solubilization, potassium solubilization, and cellulose degradation, working synergistically with the activated waste residue to significantly increase the content of available nutrients in the soil (30%-65%), increase soil porosity (10%-14%), enhance water and fertilizer retention capacity, and adjust the pH value of acidic soil to a suitable range for crop growth (5.5-6.5). Microwave activation treatment has a short processing time (only 3-5 minutes) and a moderate microbial composting cycle (18-20 days), resulting in an overall process efficiency that is more than 30% higher than traditional methods. The raw materials are mainly oil shale waste, which has extremely low cost (about 50-60 yuan / ton). The finished soil conditioner has high economic value (400-500 yuan / ton), is easy to scale up and apply, has wide applicability, and is environmentally friendly. This method is applicable to various types of degraded soil (such as acidic soil, sandy barren soil, and mine reclamation soil), and has significant yield-increasing and quality-improving effects on various crops (corn, wheat, forage grass, etc.). The improved soil and agricultural products meet relevant national safety standards and have no risk of secondary pollution. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating an implementation method for soil improvement using microwave activation coupled with microorganisms from oil shale waste, as described in this invention. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] like Figure 1As shown, in a preferred embodiment (first embodiment) of the present invention, a method for soil improvement using microwave activation coupled with microorganisms from oil shale waste residue specifically includes the following steps: S1. Waste residue pretreatment: The oil shale dry distillation residue is crushed to a particle size of 2-5 mm, and impurities with a particle size greater than 10 mm are sieved out to obtain pretreated waste residue. The content of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in the pretreated waste residue is detected. If the cadmium content is greater than 0.3 mg / kg, 3%-8% of its mass of phosphate rock powder is added to the pretreated waste residue and mixed evenly; S2. Microwave activation treatment: The material obtained in step S1 is placed in a microwave device and subjected to two-stage heating treatment at a frequency of 915 MHz or 2450 MHz and a power of 400-1200 W. The first stage heating power is 400-800 W, and the temperature is controlled at 500-700℃ for 30-90 minutes to remove volatile harmful components. The second stage heating power is 800-1200 W. W. Control the temperature to 800-1000℃ and maintain it for 60-180 minutes to optimize the pore structure. After cooling, the activated waste residue carrier is obtained. The surface area of ​​the activated waste residue carrier is ≥5 m² / g, the carbon content is ≥30 wt%, and the removal rate of harmful components is ≥90%. S3. Preparation of compound microbial agent: Azotobacter chrysotile, silicate bacteria and cellulose degrading bacteria are compounded in a weight ratio of (2-4):(1-3):(0.5-1.5). The compound of quartz sand, sorghum powder and fern residue is used as the carrier. It is statically cultured for 2-3 weeks at 28-32℃ and 50-60% water content to obtain an effective viable count ≥10. 9 S4. Microbial compound treatment: Mix the obtained activated waste residue carrier, compound microbial agent and straw in a mass ratio of (65-75):(0.05-0.15):(25-35), adjust the moisture content of the mixture to 50-60%, place it in a fermentation device, and compost at 25-32℃ for 18-20 days, turning the pile every 5-7 days during the period to obtain a harmless activated waste residue conditioner; S5. Soil improvement application: Determine the application rate according to the type and properties of the soil to be improved; For acidic soil with a pH value of 4.5-6.0, apply the harmless activated waste residue conditioner evenly on the soil surface at an application rate of 1200-1800 kg per mu, and till it to a depth of 25-30 cm with a rotary tiller to fully mix the harmless activated waste residue conditioner with the soil. Water thoroughly once within 7 days after application. During the crop seedling stage, apply 400-600 kg per mu. Apply fertilizer at a rate of kg.

[0021] In a preferred embodiment of the present invention, in step S1, the particle size of the phosphate rock powder is 100-200 mesh.

[0022] In step S2, the microwave equipment is a continuous microwave processor with a total processing time of 3-5 minutes and a power of 700-900 W. The specific surface area of ​​the activated waste residue carrier is ≥5 m² / g, and the carbon content is ≥30 wt%.

[0023] In step S3, the mass ratio of the quartz sand, sorghum powder and bracken residue is (1-2):(1-2):(0.5-1), and the cultivation conditions are: temperature 28-32℃, moisture content 50-60%, and static cultivation for 2-3 weeks.

[0024] In step S4, the straw is crushed to a particle size of 1-2 cm before use. During the composting and fermentation process, the straw is turned over every 5-7 days.

[0025] In step S4, if it is used for improving sandy and barren soil, the activated waste residue carrier is added to the mixture, and the activated waste residue carrier is 10%-20% decomposed sheep manure by mass.

[0026] In step S5, for acidic soil with a pH of 4.5-6.0, apply basal fertilizer at a rate of 1200-1800 kg per acre, and mix the conditioner with the soil by deep tilling to a depth of 25-30 cm using a rotary tiller. Water thoroughly within 7 days after application.

[0027] In step S5, topdressing is applied at a rate of 400-600 kg per mu during the seedling stage of the crop.

[0028] In step S5, if it is used for soil improvement in mine reclamation areas, the application rate is 2000-2500 kg per mu, and pioneer plants are planted in combination.

[0029] In the second embodiment of the present invention, acidic farmland soil improvement:

[0030] S21 Raw material preparation: Oil shale dry distillation residue from a certain region was selected. Testing revealed that its PAHs content was 85 μg / kg and cadmium content was 0.25 mg / kg, meeting the risk screening values ​​of the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)" (GB 15618-2018). The straw was crushed to 1-2 cm for later use.

[0031] S22 pretreatment involves crushing the dry distillation residue to a particle size of 2-5 mm using a jaw crusher and sieving out particles larger than 10 mm. Since the cadmium content is within acceptable limits, no phosphate rock powder needs to be added.

[0032] S23 microwave activation was performed using a 2450 MHz microwave device at a power of 800 W for 4 minutes, with a maximum material temperature of approximately 650℃. After cooling, activated waste residue was obtained with a specific surface area of ​​approximately 6.2 m² / g.

[0033] S24 microbial compound treatment involves mixing activated waste residue, compound microbial agent, and straw at a mass ratio of 70:0.1:30. The compound microbial agent is prepared by culturing Azotobacter chrysophagus, silicate bacteria, and cellulose-degrading bacteria in a weight ratio of 3:2:1, with an effective viable count of 2.5 × 10⁻⁶. 9 CFU / g. Adjust the moisture content of the mixture to 55%, place it in a fermentation tank, and compost at 30℃ for 19 days, turning the pile 3 times during the period.

[0034] For S25 soil application, select an acidic cornfield with a pH of 5.2. Apply the soil conditioner obtained in step 4 evenly at a rate of 1500 kg per acre, then till the soil to a depth of 28 cm using a rotary tiller to mix it thoroughly, followed by thorough watering. Twenty days after corn emergence, dig shallow furrows 5 cm deep between rows, apply 500 kg of soil conditioner per acre, and then cover with soil.

[0035] The S26 effect test showed that 30 days after the application of the soil conditioner, the soil pH value rose to 6.3, the soil porosity increased from 38% to 52%, and the available potassium content increased by 65%. At corn harvest, the yield per mu was 38% higher than that of the control group without the conditioner, and the cadmium content in the corn kernels met the requirements of the National Food Safety Standard for Limits of Contaminants in Food (GB 2762-2022).

[0036] In the third embodiment of the present invention, soil improvement is addressed for waste residue with excessive heavy metal content:

[0037] S31 raw material preparation: Analysis of oil shale waste residue showed a cadmium content of 0.42 mg / kg and a PAH content of 92 μg / kg. Prepare 150-mesh phosphate rock powder.

[0038] S32 pretreatment involves crushing the waste residue to 2-5 mm, then adding 5% of its mass of phosphate rock powder and mixing thoroughly.

[0039] S33 was activated by microwave treatment with a power of 750 W for 5 minutes.

[0040] S34 Microbial composite treatment, the same as step S4 in Implementation Method 1.

[0041] For S35 soil application, select acidic soil with a pH of 4.8 for wheat planting. Apply 1600 kg of soil conditioner per mu as basal soil, plow to a depth of 30 cm, mix thoroughly, and water thoroughly. Apply 550 kg of soil conditioner per mu as top dressing during the wheat seedling stage.

[0042] S36 efficacy testing showed that soil pH increased to 6.1, cadmium bioavailability decreased by 42%, and PAHs degradation rate reached 83%. Wheat yield per mu increased by 32%, and grain cadmium content was ≤0.05 mg / kg, meeting national standards.

[0043] In the fourth embodiment of the present invention, soil improvement in the mine reclamation area:

[0044] S41 Raw material preparation: Crush oil shale waste to 3-5 mm and pass inspection. Prepare well-rotted sheep manure (organic matter content ≥30%).

[0045] S42 pretreatment eliminates the need for adding phosphate rock powder.

[0046] S43 was activated by microwave treatment with 850 W power for 3.5 minutes.

[0047] S44 microbial compound treatment involves mixing activated waste residue, compound microbial agent, straw, and decomposed sheep manure in a mass ratio of 65:0.1:25:10, adjusting the moisture content to 56%, composting for 18 days, and turning the compost pile 3 times.

[0048] For S45 soil application, the soil pH value in the mine reclamation area is 5.5, and the organic matter content is 0.8%. Apply 2200 kg of soil conditioner per mu, mix it with 30% topsoil, and then plow to a depth of 30 cm before sowing alfalfa.

[0049] The S45 effect test showed that after 6 months of planting, the soil organic matter content increased to 1.6%, the porosity reached 48%, and the alfalfa survival rate reached 89%, which was 45% higher than the unimproved control group.

[0050] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0051] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0052] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for soil improvement using microwave activation coupled with microorganisms from oil shale waste, characterized in that: Specifically, the steps are as follows: S1. Waste residue pretreatment: The oil shale dry distillation residue is crushed to a particle size of 2-5 mm, and impurities with a particle size greater than 10 mm are screened out to obtain pretreated waste residue. The content of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in the pretreated waste residue is tested. If the cadmium content is greater than 0.3 mg / kg, 3%-8% of its mass of phosphate rock powder is added to the pretreated waste residue and mixed evenly. S2. Microwave activation treatment: The material obtained in step S1 is placed in a microwave device and subjected to a two-stage heating treatment at a frequency of 915 MHz or 2450 MHz and a power of 400-1200 W. The first stage heating power is 400-800 W, the temperature is controlled at 500-700℃, and the treatment lasts for 30-90 minutes to remove volatile harmful components. The second stage heating power is 800-1200 W, the temperature is controlled to rise to 800-1000℃, and the treatment lasts for 60-180 minutes to optimize the pore structure. After cooling, an activated waste residue carrier is obtained. The activated waste residue carrier has a surface area ≥5 m² / g, a carbon content ≥30 wt%, and a harmful component removal rate ≥90%. S3. Preparation of compound microbial inoculant: Azotobacter chrysophyte, silicate bacteria, and cellulose-degrading bacteria are compounded at a weight ratio of (2-4):(1-3):(0.5-1.5). Using a complex of quartz sand, sorghum flour, and bracken residue as a carrier, the mixture is statically cultured for 2-3 weeks at 28-32℃ and a moisture content of 50-60% to obtain an effective viable count ≥10. 9 CFU / g compound microbial inoculant; S4. Microbial compound treatment: The obtained activated waste residue carrier, compound microbial agent and straw are mixed in a mass ratio of (65-75):(0.05-0.15):(25-35), the moisture content of the mixture is adjusted to 50-60%, and it is placed in a fermentation device and composted at 25-32℃ for 18-20 days. During this period, the pile is turned over every 5-7 days to obtain a harmless activated waste residue conditioner. S5. Soil improvement application: The application rate is determined according to the type and properties of the soil to be improved. For acidic soil with a pH value of 4.5-6.0, the harmless activated waste residue conditioner is evenly spread on the soil surface at an application rate of 1200-1800 kg per mu. The soil is then deeply tilled to a depth of 25-30 cm using a rotary tiller to fully mix the harmless activated waste residue conditioner with the soil. The soil is thoroughly watered once within 7 days after application. During the seedling stage of the crop, topdressing is applied at an application rate of 400-600 kg per mu.

2. The soil improvement method for microwave activation coupled with microorganisms of oil shale waste residue according to claim 1, characterized in that, In step S1, the particle size of the phosphate rock powder is 100-200 mesh.

3. The soil improvement method for microwave activation and coupling of microorganisms in oil shale waste as described in claim 1, characterized in that, In step S2, the microwave equipment is a continuous microwave processor with a total processing time of 3-5 minutes and a power of 700-900 W. The specific surface area of ​​the activated waste carrier is ≥5 m² / g and the carbon content is ≥30 wt%.

4. The soil improvement method for microwave activation and coupling of microorganisms in oil shale waste as described in claim 2, characterized in that, In step S3, the mass ratio of the quartz sand, sorghum powder and bracken residue is (1-2):(1-2):(0.5-1), and the cultivation conditions are: temperature 28-32℃, moisture content 50-60%, and static cultivation for 2-3 weeks.

5. The soil improvement method for microwave activation and coupling of microorganisms in oil shale waste as described in claim 1, characterized in that, In step S4, the straw is crushed to a particle size of 1-2 cm before use. During the composting and fermentation process, the straw is turned over every 5-7 days.

6. The soil improvement method for microwave-activated coupled microorganisms from oil shale waste as described in claim 2, characterized in that, In step S4, if it is used for improving sandy and barren soil, the activated waste residue carrier is added to the mixture, wherein the activated waste residue carrier is 10%-20% by mass of decomposed sheep manure.

7. The soil improvement method for microwave activation and coupling of microorganisms in oil shale waste as described in claim 1, characterized in that, In step S5, for acidic soil with a pH of 4.5-6.0, apply basal fertilizer at a rate of 1200-1800 kg per acre, and mix the conditioner with the soil by deep tilling to a depth of 25-30 cm using a rotary tiller. Water thoroughly within 7 days after application.

8. The soil improvement method for microwave activation and coupling of microorganisms in oil shale waste as described in claim 2, characterized in that, In step S5, topdressing is applied at a rate of 400-600 kg per mu during the seedling stage of the crop.

9. The soil improvement method for microwave-activated coupled microorganisms from oil shale waste as described in claim 1, characterized in that, In step S5, if it is used for soil improvement in mine reclamation areas, the application rate is 2000-2500 kg per mu, and pioneer plants are planted in combination.

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