Heavy metal tailing area pollution in-situ prevention and control and efficient biological coverage remediation method

Abstract

The invention relates to the technical field of tailing heavy metal pollution restoration and mine ecological restoration, and discloses a heavy metal tailing area pollution in-situ resistance control and efficient biological coverage restoration method which is an ecological restoration technology integrating solidification / stabilization restoration, barrier landfill and vegetation restoration. The method can solve the problem of simultaneous treatment of heavy metal polluted soil ecological restoration, mine pollution restoration and obstruction, can be used for restoration and ecological restoration of different heavy metal polluted soil and waste residue sites, and especially has a good effect on heavy metal restoration and ecological restoration of mine and smelting polluted sites.

Description

Technical Field

[0001] The present invention relates to the technical field of tailings heavy metal pollution remediation and mine ecological restoration, and in particular to a heavy metal tailings area pollution on-site prevention and control and efficient biological covering restoration method. Background Art

[0002] The Southwest region is rich in mineral resources. It has the largest lead-zinc mine in Asia, the Lanping lead-zinc mine. At the same time, Guizhou accounts for 70% of the country's mercury reserves, Tibet's Luobusa chromite reserves rank first in the country, and antimony reserves are second only to the central and southern regions. Overall, there are both single deposits and symbiotic deposits, with more poor mines and fewer rich mines. The number of tailings ponds is large, the distribution is wide, and the accumulation is large. Due to historical reasons, there are a large number of non-standard construction and disused ponds, which are highly dangerous and have great environmental risks. The heavy metals in the ultra-fine, poor, and acidified tailings accumulated in the ponds are prone to migration and transformation.

[0003] The special geological conditions and fragile ecological environment in the karst area determine the complexity and necessity of heavy metal pollution control in tailings ponds in the southwest region. At the same time, there are differences in the history and accumulation process of heavy metal pollution, and it is difficult to clarify the source of pollution. On the one hand, heavy metals in the mining environment infiltrate into the bottom soil through the pores of waste rock and tailings piles or enter the surrounding environmental soil through surface runoff. On the other hand, they enter the downstream hydrological system through surface runoff or infiltrate into groundwater, connecting surface water and groundwater, causing water pollution in the entire mining area and even in the nearby large area, and affecting the entire ecosystem.

[0004] Soil is the most biodiverse and active life layer in the earth's surface system, with the most active energy exchange and material cycle. It is a buffer zone and filter for toxic pollutants, and also a gathering place for toxic metal pollutants. Based on the relevant soil use targets and standards, adding passivation / stabilization materials to the tailings after heavy metal removal can further stabilize the heavy metals and improve the physical and chemical properties to achieve soil utilization, which is of great significance for managing the mining environment, alleviating the pressure of mine soil sources, and absorbing a large amount of tailings.

[0005] Secondly, during the operation of the tailings pond, the original vegetation in the reservoir area was destroyed. It is difficult to restore vegetation naturally under fragile ecological conditions, and the cycle is long. Therefore, it is necessary to select suitable pioneer plants as species for land reclamation to improve the reclaimed land. At the same time, pioneer plants can grow in the harsh environment of the newly reclaimed land, have strong resistance, can resist cold, drought, wind, waterlogging, barrenness, salinity, etc., grow fast, can fix nitrogen in the atmosphere, are easier to sow and plant, and have a high survival rate. The introduction of pioneer plants can improve the living environment of plants in abandoned mining areas and provide the necessary prerequisites for the growth of suitable plants and other trees, cash crops, and even crops.

[0006] Therefore, for the Sb / As and other heavy non-ferrous metal tailings ponds in the southwest region, through field investigation and analysis of the environmental pollution characteristics of the tailings ponds and the tailings storage forms, the hydrogeological, environmental geological and engineering geological conditions are clarified, and appropriate remediation technologies are selected to control the diffusion and migration of pollution factors in heavy non-ferrous metal tailings ponds from the source, which is of great significance to achieve heavy metal stabilization in tailings ponds, mine soil reclamation and reconstruction, and ecological reconstruction. Summary of the invention

[0007] The purpose of the present invention is to provide a method for in-situ prevention and control of pollution in heavy metal tailings areas and efficient biological coverage restoration. Through the method of the present invention, the passivation / stabilization of heavy metal tailings is combined with the landform remodeling, soil reconstruction, and vegetation reconstruction of abandoned mine land, forming a technical model for soil pollution prevention and ecological restoration of mines and mineral processing sites, achieving pollution prevention and control and ecological function restoration.

[0008] The scheme of the present invention is:

[0009] A method for on-site prevention and control of heavy metal tailings pollution and efficient biological coverage restoration, comprising the following steps:

[0010] S1. Identify the contaminated site and conduct sampling;

[0011] S2. Test the mine soil and the types and concentrations of pollutants in the soil tailings;

[0012] S3. Determine the pollution degree of tailings and determine the phosphorus-based stabilization materials and dosage;

[0013] S4. Clean the surface of the tailings pond or tailings yard, use machinery to excavate the heavy metal-containing waste slag and heavy metal tailings in the site, place the excavated waste slag and tailings in the disposal site, break the consolidated body evenly, and treat the depth of 25 to 30 cm; set up flood diversion ditches outside the restoration area to ensure the stability of soil and water conservation in the restoration area;

[0014] S5. Use phosphorus-based stabilization materials to stabilize and repair heavy metal tailings:

[0015] S6. Curing the mixture of heavy metal tailings and phosphorus-based stabilization materials to allow the phosphorus-based stabilization materials and heavy metal tailings to fully react, and the curing time is 7 to 15 days;

[0016] S7. After the soil stabilization layer is constructed, plants will be planted on the surface to restore the plant ecosystem. Combined with the geological environment around the tailings pond and the tailings yard, plants that are adapted to the site environment will be selected for planting;

[0017] S8. Maintenance and management, including regular watering, top dressing, and pest and disease control.

[0018] As a preferred technical solution, the phosphorus-based stabilizing material in step S3 includes the following raw materials:

[0019] The mass ratio of ferrous sulfate, phosphate tailings, bentonite and organic fertilizer is 3:2:2:2.

[0020] As a preferred technical solution, the dosage of the phosphorus-based stabilizing material in S3 is 3-9% of the mass of the heavy metal tailings to be treated.

[0021] As a preferred technical solution, the stabilization repair method in step S5 is:

[0022] After pre-treatment of the tailings, the phosphorus-based stabilization material is evenly spread on the surface of the tailings area to be repaired. The phosphorus-based stabilization material is added in an amount of 6%. Special repair equipment is used to fully stir the material and tailings until they are evenly mixed. The repair depth is not less than 10cm.

[0023] As a preferred technical solution, the plants planted in S7 include one or more of trees, shrubs and herbs.

[0024] As a preferred technical solution, the tree is one or more of Lemongrass, Salix matsudana and Pinus massoniana.

[0025] As a preferred technical solution, the shrub is one or more of sea buckthorn, magnolia and pyracantha.

[0026] As a preferred technical solution, the herb is one or more of Bermuda grass, Goosegrass, rapeseed, alfalfa, and clover.

[0027] A method for on-site control and efficient biological coverage restoration of heavy metal tailings pollution is adopted, including the following steps: S1. Determine the contaminated site and take samples; S2. Detect the mine soil, detect the types and concentrations of pollutants in the soil tailings; S3. Determine the degree of pollution of the tailings, determine the phosphorus-based stabilization materials and the dosage to be used; S4. Clean the surface of the tailings pond or tailings yard, use machinery to excavate the heavy metal-containing waste slag and heavy metal tailings in the site, place the excavated waste slag and tailings in the disposal site, crush and homogenize the consolidated body, and treat it at a depth of 25 to 30 cm; set up a Flood diversion ditches are built to ensure the stability of water and soil conservation in the restoration area; S5. Use phosphorus-based stabilization materials to stabilize and repair heavy metal tailings: S6. The mixture of heavy metal tailings and phosphorus-based stabilization materials is maintained to allow the phosphorus-based stabilization materials to fully react with the heavy metal tailings. The maintenance time is 7 to 15 days; S7. After the soil stabilization layer is constructed, plants will be planted on the surface to restore the plant ecosystem. Combined with the geological environment around the tailings pond and the tailings yard, plants that are adapted to the site environment will be selected for planting; S8. Maintenance management, regular watering, topdressing, pest and disease control and maintenance management.

[0028] The invention provides a method for the combined restoration of heavy metal tailings heavy metal pollution on-site blocking and vegetation consolidation, which is an ecological restoration technology integrating consolidation / stabilization restoration, barrier landfill and vegetation restoration. It can solve the problem of simultaneous treatment of ecological restoration of heavy metal contaminated soil and mine pollution restoration and blocking, and can be used for the restoration and ecological restoration of different heavy metal contaminated soils and waste residue sites, especially for the restoration and ecological restoration of heavy metals in mines and smelting pollution sites.

[0029] Advantages of the present invention:

[0030] The method for in-situ control and vegetation consolidation combined restoration of tailings heavy metal pollution provided by the present invention has the following characteristics:

[0031] First, strengthen soil and water conservation measures at each tailings waste dump site to prevent rainwater from eroding the waste dump and cut off the pollution diffusion path of water and soil media;

[0032] Second, the soil covering and greening of waste residue piles can reduce rainwater erosion and greatly reduce the amount of waste residue leachate generated. The present invention integrates restoration technologies such as solidification / stabilization restoration and vegetation restoration, uses green and efficient heavy metal stabilizers for on-site solidification and stabilization restoration, and combines vegetation heavy-solidification technology based on the planting of native pioneer plants. Its application in heavy metal contaminated sites of mines and smelters can prevent heavy metals from continuously contaminating the soil and surrounding water bodies and farmland, improve crop safety quality and agricultural economic benefits, and comprehensively improve soil environmental quality and achieve a virtuous cycle of the ecosystem.

[0033] The present invention uses trees, shrubs and herbs to restore the ecology of the restoration site, which is beneficial to the construction of the site ecosystem, and the vegetation coverage rate is more than 90%; after restoration by the method of the present invention, the leaching concentration of heavy metals such as antimony, arsenic, lead, zinc, chromium, and mercury in the contaminated soil and waste residue can be lower than the Class III standard limit of the "Surface Water Environmental Quality Standard" (GB 3838-2002), and the antimony and arsenic solidification rate is more than 95%;

[0034] The phosphorus-based material in the present invention is an important material in the heavy metal solidification / stabilization material, and has the advantages of high efficiency, greenness, and low cost. Its organic solid waste is easy to obtain, low in cost, simple to operate, and suitable for large-scale promotion and application; and the repair effect is stable, environmentally friendly, and will not cause secondary pollution. At the same time, it can realize the resource utilization of solid waste, effectively reduce the treatment cost of industrial and agricultural waste, achieve the purpose of "waste treatment", and save repair funds.

[0035] In addition, the application of phosphorus-based stable passivation materials in mine ecological restoration can effectively prevent the risk of heavy metal pollution in severely polluted tailings ponds, while reducing the cost of tailings pollution control; the application of high-efficiency biomaterials in demonstration projects can prevent the spread of pollution and erode the surrounding environment, while repairing the damage caused by tailings accumulation to the surface and rebuilding a green ecosystem, which has considerable economic, social and ecological benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of stabilizing and repairing antimony-arsenic tailings using phosphorus-based stabilization materials in Example 1 of the present invention;

[0037] Figure 2 A flow chart of constructing a plant ecosystem for Example 1 of the present invention;

[0038] Figure 3 This is a real-life picture of vegetation growth before and after restoration of the heavy metal tailings area in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0040] Embodiment 1:

[0041] The abandoned tailings dump of an antimony ore dressing plant was repaired. The specific steps are as follows:

[0042] S1. Identify the contaminated site - the tailings and tailings pond of a certain antimony-arsenic tailings dump, and conduct sampling;

[0043] S2. Test the soil in the mines, and test the types and concentrations of pollutants in the soil and tailings: Based on the heavy metal leaching concentrations of the tailings in a certain antimony-arsenic tailings dump and tailings pond, refer to the special emission limits of water pollutants in "GB 31574-201531574-2015 Pollutant Emission Standard for Recycled Copper, Aluminum, Lead and Zinc Industries" to determine the remediation targets, and use the standard limits of various heavy metals specified in Class IV water bodies in "GB 3838-2002 Surface Water Environmental Quality Standard" as the remediation limits and target values ​​for other heavy metals. According to the test, Sb and As in the heavy metal tailings need to be stabilized.

[0044] Table 1 Statistics of heavy metal leaching results of tailings from an antimony tailings area using sulfuric acid and nitric acid method

[0045]

[0046]

[0047] S3. According to the pollution degree of tailings, the compatibility and dosage of phosphorus-based stabilization materials are determined. The compatibility of phosphorus-based stabilization materials is ferrous sulfate: phosphorus tailings: bentonite: organic fertilizer = 3:2:2:2, and the dosage is 6% of the mass of heavy metal tailings to be treated;

[0048] S4. Clean the surface of the tailings pond or tailings yard, use machinery to excavate the heavy metal waste residue and antimony and arsenic tailings in the site, place the excavated waste residue and tailings in the disposal site, break the solidified body evenly, and treat it to a depth of 25 to 30 cm; set up flood diversion ditches outside the restoration area to ensure the stability of soil and water conservation in the restoration area;

[0049] S5. Use phosphorus-based stabilization materials to stabilize and repair antimony-arsenic tailings: After pre-treated tailings, evenly spread the phosphorus-based stabilization materials on the surface of the antimony-arsenic tailings area to be repaired, and use special repair equipment to fully stir the materials and tailings until they are evenly mixed. The repair depth is not less than 10cm;

[0050] S6. Curing the mixture of tailings and materials to allow the phosphorus-based stabilization material to fully react with the tailings. The curing time is 10 days, and the antimony and arsenic stabilization rate is greater than 90%;

[0051] S7. After the soil stabilization layer is constructed, plants will be planted on the surface to restore the plant ecosystem. Combined with the geological environment of the tailings pond and the surrounding area of ​​the tailings yard, tree species with good fast-growing ability, strong adaptability, well-developed root system, good stress resistance and excellent heavy metal adsorption performance will be selected. Plants that are adapted to the surrounding environment and plant varieties with good symbiotic relationships between plant species will be selected. Local native varieties will be given priority to build a three-dimensional ecosystem with multi-layered plants. In terms of species matching, a combination of trees, shrubs and grasses should be selected, and evergreen and deciduous plants, fast-growing plants and slow-growing plants should be matched with each other to build a good species distribution for ecological restoration and achieve the optimal effect of ecological restoration.

[0052] S8 maintenance and management, regular watering, top dressing, pest and disease control and maintenance management.

[0053] The samples were commissioned to be tested by a third party, and the results showed that the leaching toxicity of the tailings solidification body was lower than the standard limits of various heavy metals specified in the "Surface Water Environmental Quality Standard" GB3838-2002 Class IV water bodies. The heavy metal stabilization rate exceeded 95%. Compared with the tailings pond of the original antimony ore concentrator, the demonstration base showed good soil reconstruction and excellent ecological restoration effects.

[0054] In the tailings ponds and tailings yards that have completed heavy metal solidification treatment, native pioneer plants such as fragrant lemon, willow, masson pine, sea buckthorn, magnolia, pyracantha, dogtooth grass, goosegrass, rapeseed, and alfalfa that are tolerant to heavy metals are planted for ecological restoration. The ecological restoration rate is over 90% and the ecological restoration effect is good.

[0055] The content of organic matter, total nitrogen, available phosphorus and available potassium in the soil of the restoration area basically reached the soil fertility level 4 standard recommended by the second national soil survey; the ground cover plant coverage reached more than 90%, which significantly reduced dust in the reservoir area and reduced soil erosion by more than 80%; and based on the calculation of covering the compacted soil layer of 0.5m, 5000m3 of soil can be saved per hectare 3 , with significant ecological and economic benefits.

[0056] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for in-situ prevention and control of heavy metal tailings pollution and efficient biological coverage restoration, characterized in that: The following steps are involved: S1. Identify the contaminated site and conduct sampling; S2. Test the mine soil and the types and concentrations of pollutants in the soil tailings; S3. Determine the pollution degree of tailings and determine the phosphorus-based stabilization materials and dosage; S4. Clean the surface of the tailings pond or tailings yard, use machinery to excavate the heavy metal-containing waste slag and heavy metal tailings in the site, place the excavated waste slag and tailings in the disposal site, break the consolidated body evenly, and treat the depth of 25 to 30 cm; set up flood diversion ditches outside the restoration area to ensure the stability of soil and water conservation in the restoration area; S5. Use phosphorus-based stabilization materials to stabilize and repair heavy metal tailings: S6. Curing the mixture of heavy metal tailings and phosphorus-based stabilization materials to allow the phosphorus-based stabilization materials and heavy metal tailings to fully react, and the curing time is 7 to 15 days; S7. After the soil stabilization layer is constructed, plants will be planted on the surface to restore the plant ecosystem. Combined with the geological environment around the tailings pond and the tailings yard, plants that are adapted to the site environment will be selected for planting; S8. Maintenance and management, regular watering, top dressing, pest and disease control and maintenance management.

2. A method for in-situ prevention and control of heavy metal tailings pollution and efficient biological coverage restoration as claimed in claim 1, characterized in that: The phosphorus-based stabilizing material in step S3 includes the following raw materials: The mass ratio of ferrous sulfate, phosphate tailings, bentonite and organic fertilizer is 3:2:2:

2.

3. The method for in-situ prevention and control of heavy metal tailings pollution and efficient biological coverage and restoration as claimed in claim 1, characterized in that: The dosage of the phosphorus-based stabilizing material in S3 is 3-9% of the mass of the heavy metal tailings to be treated.

4. The method for in-situ prevention and control of heavy metal tailings pollution and efficient biological coverage and restoration as claimed in claim 1, characterized in that: The stabilization repair method in step S5: After pre-treatment of the tailings, the phosphorus-based stabilization material is evenly spread on the surface of the tailings area to be repaired. The phosphorus-based stabilization material is added in an amount of 6%. Special repair equipment is used to fully stir the material and tailings until they are evenly mixed. The repair depth is not less than 10cm.

5. The method for in-situ prevention and control of heavy metal tailings pollution and efficient biological coverage and restoration as claimed in claim 1, characterized in that: The plants planted in S7 include one or more of trees, shrubs and herbs.

6. A method for in-situ prevention and control of heavy metal tailings pollution and efficient biological coverage and restoration as claimed in claim 5, characterized in that: The tree is one or more of lemongrass, willow of matsudana and masson pine.

7. A method for in-situ prevention and control of heavy metal tailings pollution and efficient biological coverage and restoration as claimed in claim 5, characterized in that: The shrubs are one or more of seabuckthorn, magnolia multiflora and pyracantha.

8. The method for in-situ prevention and control of heavy metal tailings pollution and efficient biological coverage and restoration as claimed in claim 5, characterized in that: The herb is one or more of bermudagrass, goosegrass, rapeseed, alfalfa and clover.

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