Copper ore tailing pond in-situ soil construction method

Abstract

The invention provides a copper mine tailing pond in-situ soil construction method. According to the in-situ soil construction method for the copper mine tailing pond, a water retention layer is arranged on the copper mine tailing pond, then a planting layer is arranged on the water retention layer, finally vegetation is planted on the planting layer for regreening, and the water retention layer and the planting layer both comprise two kinds of biogas residues with different water contents. On one hand, by adjusting the content of biogas residues with different water contents and particle sizes in the water retention layer and the planting layer, the water retention capacity of reconstructed soil is improved, the soil hardening phenomenon of the planting layer can be effectively prevented, the survival rate and the growth speed of vegetation are improved, and long-term regreening of the copper mine tailings pond is guaranteed; the characteristics that the organic solid waste biogas residues are rich in organic matter, high in water content and the like are fully utilized, the organic solid waste biogas residues are combined with the inorganic solid waste tailings to conduct in-situ soil construction on the copper mine tailing pond, large-scale utilization of solid waste resources is achieved, and the repairing cost of the copper mine tailing pond is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of ecological restoration of abandoned mines and relates to an in-situ soil construction method for a copper mine tailings pond. Background Art

[0002] Copper tailings refer to the waste discharged by the beneficiation plant after grinding copper ore and selecting useful components under specific economic and technical conditions. They are generally stored in tailings ponds. After the tailings pond is closed, surface ecological restoration is generally required. Copper tailings are generally highly acidic, with extremely low organic matter content, fine particle size, rich in heavy metals, poor soil texture, and severe compaction. In addition, acidic substances and heavy metals are easily dissolved during rainfall, which will inhibit plant growth and are extremely unsuitable for plant survival.

[0003] At present, the ecological restoration of copper mine tailings ponds generally adopts the guest soil restoration method, that is, covering a certain amount of guest soil and then planting plants. Patent CN116967276A discloses an isolation material, an isolation layer and its application, and a mine restoration method. The invention can form a reducing barrier and a heavy metal solidification barrier at the contact surface between the mine and the isolation material, effectively reducing the activity of acidophilic bacteria, greatly reducing the generation of acidic leaching water and heavy metal dissolution, but this method requires a large amount of off-site soil or soil purchase, which will not only cause secondary damage to the environment, but also the cost of soil extraction and transportation will cause the restoration cost to increase significantly. In addition, because copper mine tailings have poor water and fertilizer retention effects and strong toxic effects on plant roots, after using guest soil for restoration, plants have weak resistance to high temperature or heavy rainfall weather, resulting in high plant mortality and poor long-term restoration effects.

[0004] Therefore, it is of great significance to develop an in-situ soil construction method for copper mine tailings ponds that can not only improve water and fertilizer retention effects and meet the needs of plant growth, but also reduce biological toxicity and ensure long-term regreening. Summary of the invention

[0005] In view of the defects existing in the prior art, the present invention provides a method for constructing in-situ soil for a copper mine tailings pond, firstly, a water-retaining layer is set on the copper mine tailings pond, then a planting layer is set on the water-retaining layer, and finally vegetation is planted on the planting layer for regreening, wherein both the water-retaining layer and the planting layer contain two kinds of biogas residues with different moisture contents and particle sizes. On the one hand, the present invention improves the water-retaining capacity of the reconstructed soil by adjusting the content of biogas residues with different moisture contents and particle sizes in the water-retaining layer and the planting layer, can effectively prevent the soil compaction phenomenon in the planting layer, improve the survival rate and growth rate of vegetation, and is conducive to ensuring the long-term regreening of the tailings pond. On the other hand, the present invention makes full use of the characteristics of organic solid waste biogas residues such as rich organic matter and high moisture content, and combines them with inorganic solid waste tailings to construct in-situ soil for the tailings pond, thereby realizing large-scale utilization of solid waste resources and greatly reducing the repair cost of the tailings pond.

[0006] The present invention provides an in-situ soil construction method for a copper mine tailings pond, comprising the following steps: arranging a water-retaining layer on the copper mine tailings pond, arranging a planting layer on the water-retaining layer, and finally planting vegetation on the planting layer for regreening;

[0007] The water-retaining layer comprises the following components in parts by mass: 40-60 parts of copper ore tailings, 15-30 parts of biogas residue A, 3-5 parts of biogas residue B, 0.5-2 parts of slaked lime, 2-5 parts of alkaline buffer, and 0.1-0.5 parts of microbial agent;

[0008] The planting layer includes the following components by weight: 30-50 parts of copper ore tailings, 5-10 parts of biogas residue A, 10-20 parts of biogas residue B, 5-10 parts of fly ash, 0.5-2 parts of slaked lime, and 1-3 parts of alkaline buffer;

[0009] The water content of the biogas residue A is 35% to 45%, and the particle size is less than 200 μm;

[0010] The water content of the sludge B is 20%-35%, and the particle size is 0.3-1 cm.

[0011] In an optional embodiment, the pH of the sludge A is 6-8, and the dry weight of organic matter accounts for 30%-50%.

[0012] In an optional embodiment, the pH of the biogas residue B is 7.5-9.5, and the mass proportion of dry weight of organic matter is 30%-50%.

[0013] In an optional embodiment, the preparation of the biogas residue A comprises the following steps: anaerobically digesting the municipal sludge, adjusting the pH, drying it, and finally grinding and screening it to obtain the biogas residue A;

[0014] And / or, the preparation of the biogas residue B comprises the following steps: anaerobically digesting the municipal sludge, adjusting the pH, drying it, and finally granulating it to obtain the biogas residue B.

[0015] In an optional embodiment, the municipal sludge has an initial moisture content of >90%, a saturated moisture content of >98%, an organic matter dry weight percentage of 40% to 60%, and a pH value of 6 to 8.

[0016] In an optional embodiment, the copper mine tailings have a particle size of 50 μm to 1000 μm, an organic matter dry weight ratio of <1%, a total nitrogen content of <0.2%, a total phosphorus content of <0.2%, a pH value of 3 to 6, and a moisture content of <40%.

[0017] In an optional embodiment, the alkaline buffer is one or more of calcium carbonate, magnesium carbonate, and dolomite;

[0018] and / or, the particle size of the alkaline buffer is <100 μm;

[0019] And / or, the microbial agent comprises Bacillus subtilis, actinomycetes, and nitrogen-fixing bacteria in a mass ratio of (1-2):(1-2):(1-2);

[0020] And / or, the fly ash particle size is 10 μm to 100 μm.

[0021] In an optional embodiment, the initial moisture content of the water-retaining layer is 20%~40%, and the saturated moisture content is greater than 60%; the initial moisture content of the planting layer is 15%~30%, and the saturated moisture content is greater than 40%; and the saturated moisture content of the water-retaining layer is higher than the saturated moisture content of the planting layer.

[0022] In an optional embodiment, the thickness of the water-retaining layer is 20-30 cm, and the pH is 7-9;

[0023] And / or, the bulk density of the water-retaining layer is 0.8 g / cm 3 ~1.3g / cm 3 ;

[0024] And / or, the planting layer has a thickness of 20-40 cm and a pH of 7-9;

[0025] And / or, the organic matter dry weight ratio of the planting layer is greater than 5%, the total nitrogen content is greater than 0.5%, the total phosphorus content is greater than 0.5%, and the bulk density is 0.7 g / cm 3 ~1.1g / cm 3 , seed germination index>90%.

[0026] In an optional embodiment, the vegetation includes one or both of herbaceous plants and shrubs.

[0027] The implementation of the present invention has at least the following advantages:

[0028] 1) The present invention aims to solve the problems of large particle size of copper mine tailings, poor water and fertilizer retention, and easy compaction, and constructs a water-retention layer and a planting layer. Among them, the water-retention layer contains more fine-grained biogas residue A with a higher water content, which is beneficial to improving the water retention capacity of the soil. With a certain proportion of coarse-grained biogas residue B with a lower water content, it can provide sufficient growth space and oxygen for plant roots. The planting layer contains more coarse-grained biogas residue B with a lower water content, which can effectively prevent compaction. With a certain proportion of fine-grained biogas residue A with a higher water content, it can meet the demand for water and nutrients during the growth of vegetation, thereby improving the survival rate and growth rate of vegetation.

[0029] 2) The raw materials used in the present invention are municipal sludge anaerobic digestion residue, copper mine tailings, fly ash and other solid wastes. The characteristics of organic solid waste residues, which are rich in organic matter and have a high saturated moisture content, are fully utilized, and combined with inorganic solid waste tailings to construct in-situ soil for the tailings pond, which not only realizes the large-scale utilization of solid waste resources, but also greatly reduces the restoration cost.

[0030] 3) The present invention uses slaked lime to rapidly alkalize copper tailings, and then utilizes alkaline buffers and the acid-base buffering capacity of the sludge itself to maintain the pH value of the reconstructed soil within a weakly alkaline range, which can solidify heavy metals and thereby reduce ecotoxicity and prevent leaching pollution. It can also effectively prevent the copper tailings from returning to acid, thereby forming a virtuous cycle of continuous soil improvement - rapid plant growth - leaching pollution blocking, thereby achieving the purpose of long-term regreening of the copper tailings pond. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0032] After the copper mine tailings pond is closed, the surface ecological restoration needs to be carried out. Copper mine tailings are generally highly acidic, and have extremely low organic matter content, fine particle size, rich in heavy metals, poor soil texture, and severe compaction. The current mainstream foreign soil restoration method has problems such as high cost and poor long-term restoration effect. In order to reduce the use of foreign soil, save restoration costs, and improve long-term greening effects, using copper mine tailings as raw materials and combining them with other improved matrices to construct in situ soil, improve the water and fertilizer retention effect of the "soil", and reduce the toxic effects of pollutants, will be an effective way to reduce the restoration cost of copper mine tailings ponds and realize the resource utilization of tailings.

[0033] With the development of urbanization in my country, the annual output of municipal sludge has exceeded 80 million tons, and the resource utilization of sludge is also imminent. Because it is rich in organic matter and nutrients, stabilizing it to form sludge for land use is a better way of resource utilization. Therefore, combining the sludge stabilization product sludge with copper mine tailings for in-situ soil construction of tailings ponds will achieve effective synergy between organic and inorganic wastes and further reduce the cost of remediation. However, due to the different properties of copper mine tailings and sludge stabilization product sludge, how to effectively construct soil that can not only improve water and fertilizer retention effects and meet the needs of plant growth, but also reduce biological toxicity and ensure long-term greening is still a difficult problem that needs to be solved.

[0034] Based on this, the present invention provides a method for constructing in-situ soil of a tailings pond, comprising the following steps: setting a water-retaining layer on the copper mine tailings pond, then setting a planting layer on the water-retaining layer, and finally planting vegetation on the planting layer for regreening;

[0035] The water-retaining layer comprises the following components in parts by mass: 40-60 parts of copper ore tailings, 15-30 parts of biogas residue A, 3-5 parts of biogas residue B, 0.5-2 parts of slaked lime, 2-5 parts of alkaline buffer, and 0.1-0.5 parts of microbial agent;

[0036] The planting layer includes the following components by weight: 30-50 parts of copper ore tailings, 5-10 parts of biogas residue A, 10-20 parts of biogas residue B, 5-10 parts of fly ash, 0.5-2 parts of slaked lime, and 1-3 parts of alkaline buffer;

[0037] The water content of the biogas residue A is 35% to 45% and the particle size is less than 200 μm;

[0038] The water content of the sludge B is 20%-35%, and the particle size is 0.3-1 cm.

[0039] Among them, the water-retaining layer and the planting layer both include copper mine tailings, sludge A, sludge B, slaked lime, and alkaline buffers. Microbial agents are the unique components in the water-retaining layer, and fly ash is the unique component in the planting layer.

[0040] The compositions of sludge A and sludge B are basically the same, and they only differ in water content and particle size. The rich organic matter and nutrients in sludge A and B can improve the composition structure of reconstructed soil, and enhance the aeration and water retention capacity of reconstructed soil, which is particularly important for the usually poor and poorly structured soil in copper mine tailings areas. The organic matter also provides a rich source of nutrients for microorganisms in the reconstructed soil, which can promote the reproduction and activity of microorganisms, thereby accelerating the ecological recovery of the reconstructed soil. At the same time, using sludge for in-situ soil remediation of tailings ponds is also a way of resource utilization, which can reduce the waste treatment pressure of sludge, reduce dependence on chemical fertilizers, and reduce maintenance costs.

[0041] Among them, biogas residue A has a smaller particle size and is in powder form. The smaller particle size means a larger specific surface area, which can promote the rapid release and effective utilization of nutrients, quickly improve the fertility of reconstructed soil, and the fine particles can fill the pores in the reconstructed soil, improve the structure and texture of the soil, and improve the water retention of the reconstructed soil. The fine particles of biogas residue can also provide more attachment and growth space for microorganisms, promote the activity of microorganisms and the decomposition of organic matter. Biogas residue B has a larger particle size and is in granular form. The larger particle size means that the biogas residue decomposes and releases nutrients more slowly in the reconstructed soil, which can provide a more lasting soil improvement effect, and the larger particles help to increase the looseness of the soil, improve drainage, and prevent the soil from being too compact.

[0042] Adding more fine-grained biogas residue A with high water content and easy water absorption to the water-retention layer is conducive to improving the water-retention capacity of the reconstructed soil. With a certain proportion of coarse-grained biogas residue B, it can provide sufficient growth space and oxygen for plant roots. The planting layer contains more coarse-grained biogas residue B, which can effectively prevent compaction and increase the oxygen content of the reconstructed soil. With a certain proportion of fine-grained biogas residue A, it can provide sufficient nutrients in the early stage of plant growth, and further improve the survival rate and growth rate of vegetation on the basis of ensuring the water required for vegetation growth.

[0043] Since there are more metal ions and sulfides in the tailings of copper mines, sulfides will undergo oxidation reactions to generate sulfuric acid when exposed to air and water, resulting in the tailings having strong acidity. The addition of slaked lime can quickly neutralize the acidity of the tailings. At the same time, the addition of alkaline buffers can keep the pH value of the reconstructed soil within the weak alkaline range, which can solidify more than 60% of heavy metals, reduce ecological toxicity and prevent leaching pollution, and can effectively prevent the tailings from returning to acid.

[0044] In addition, adding microbial agents to the water-retaining layer can make the microbial structure of the soil in the water-retaining layer closer to that of natural soil. Microbial agents can continuously improve the soil microbial community structure at the roots and promote rapid plant growth. In addition, a large number of beneficial microorganisms in the water-retaining layer can also inhibit the growth of acidophilic thiobacillus in the bottom tailings and form an oxygen-consuming layer to prevent the bottom tailings from returning to acid. Adding fly ash to the planting layer can adjust the soil particle size composition and provide a variety of trace elements required for plant growth, such as potassium, calcium, magnesium, etc. These elements can supplement and reconstruct soil nutrients, improve soil fertility, and support plant growth.

[0045] In summary, the present invention constructs a water-retaining layer and a planting layer in situ on the copper mine tailings pond to achieve the modification of the in-situ soil of the copper mine tailings pond. On the one hand, by adjusting the content of sludge A and sludge B with different water content and particle size in the water-retaining layer and the planting layer, and then adjusting the looseness, water storage capacity and nutrient supply capacity of the water-retaining layer and the planting layer, not only can the water-retaining capacity of the reconstructed soil be improved, but also the soil compaction phenomenon in the planting layer can be effectively prevented, the survival rate and growth rate of vegetation can be improved, and it is beneficial to ensure the long-term greening of the tailings pond; on the other hand, slaked lime is added to the reconstructed soil to quickly neutralize the acid and alkali of the strongly acidic tailings, and an alkaline buffer is added to prevent possible acid reflux, so as to provide a soil environment more suitable for vegetation growth.

[0046] If the average particle size of sludge A is too large or the average particle size of sludge B is too small, it will be unfavorable for the compounding of the two. Therefore, it is preferred to control the average particle size of sludge A to be less than 100 μm and the average particle size of sludge B to be greater than 0.5 cm.

[0047] In a specific embodiment, the pH of the sludge A is 6-8, and the dry weight percentage of organic matter is 30%-50%.

[0048] Biogas residue A is neutral to weakly alkaline, which is suitable for the growth needs of most plants. It can neutralize weakly acidic soils and increase the pH value of reconstructed soils to a range more suitable for plant growth. It is also beneficial to the growth and activity of most soil microorganisms, thereby promoting the decomposition of organic matter and nutrient cycling.

[0049] In a specific embodiment, the pH of the sludge B is 7.5-9.5, and the dry weight percentage of organic matter is 30%-50%.

[0050] Compared with sludge A, sludge B has relatively stronger alkalinity and can be used to neutralize the acidity of reconstructed soil, especially in areas with a large impact of acid mine drainage (AMD). It can effectively increase the pH value of reconstructed soil and reduce the negative impact of acidity on plants and the environment. In addition, the relatively strong alkalinity can precipitate heavy metal ions and reduce their mobility and bioavailability.

[0051] The present invention can achieve fine adjustment of the pH of reconstructed soil by combining the use of biogas residues with different pH values ​​to adapt to different soil conditions and restoration needs. This strategy not only helps to improve the chemical properties of reconstructed soil, but also promotes plant growth and ecosystem recovery.

[0052] The dry weight percentage of organic matter refers to the percentage of organic matter in the soil to the dry weight of the soil, and is one of the important indicators for measuring soil fertility. Tailings lack the basic nutrients required for plant growth, such as organic matter, nitrogen, phosphorus, potassium, etc. A high content of organic matter can significantly improve the soil structure of the water-retaining layer and the planting layer, and help promote the healthy growth of plant roots. In addition, organic-rich biogas residues help promote the activity of beneficial microorganisms in the reconstructed soil. These microorganisms play an important role in decomposing organic matter and fixing nitrogen, thereby improving the fertility and health of the reconstructed soil. Based on the above considerations, controlling the dry weight percentage of organic matter in biogas residue A and biogas residue B within the above range can improve the reconstructed soil conditions in many aspects, promote plant growth, and have good environmental and economic benefits.

[0053] In a specific embodiment, the preparation of the biogas residue A comprises the following steps: anaerobic digestion of municipal sludge, adjusting the pH, drying, and finally grinding and screening to obtain the biogas residue A;

[0054] The preparation of biogas residue B comprises the following steps: anaerobically digesting municipal sludge, adjusting the pH, drying it, and finally granulating it to obtain the biogas residue B.

[0055] Untreated sludge is rich in undecomposed perishable organic matter, which will consume oxygen when continuing to decompose in reconstructed soil, resulting in a decrease in the oxygen content in the soil. The anaerobic environment is not conducive to the respiration and healthy growth of plant roots. In addition, the ammonia nitrogen content in untreated sludge is too high, and applying it to reconstructed soil will cause the "root burn" phenomenon of plants and inhibit plant growth. Based on the above considerations, the present invention performs anaerobic digestion treatment on municipal sludge to remove or reduce perishable organic matter in the sludge, inhibit or kill harmful microorganisms, and is conducive to the subsequent stable provision of nutrients for plant growth.

[0056] The present invention does not limit the drying method, as long as the moisture content of the biogas residue can be reduced to a desired value. In some specific embodiments, the drying method can be one or more of natural drying, mechanical dehydration, thermal drying, vacuum drying, and microwave drying.

[0057] The particle size of sludge A is relatively small, so it is ground and screened to reach the desired particle size; while the particle size of sludge B is relatively large, so it is granulated to obtain the desired particle size.

[0058] In a specific embodiment, the initial moisture content of the municipal sludge is >90%, the saturated moisture content is >98%, the dry weight percentage of organic matter is 40%~60%, and the pH value is 6~8.

[0059] Among them, sludge with high organic matter content is a potential source of organic fertilizer. The decomposition of organic matter helps to stabilize the sludge, reduce odor and pathogens, and improve the safety and applicability of the sludge. The pH value of 6-8 indicates that municipal sludge has a certain acid-base buffering capacity, which, together with alkaline buffers, is conducive to reconstructing the soil pH value to remain in the weak alkaline range and effectively prevent the acid return of tailings.

[0060] In a specific embodiment, the particle size of the copper mine tailings is 50 μm~1000 μm, the dry weight ratio of organic matter is <1%, the total nitrogen content is <0.2%, the total phosphorus content is <0.2%, and the pH value is 3~6.

[0061] Copper mine tailings contain a large amount of sulfide minerals. When these minerals are exposed to the surface, they will produce acidic wastewater after oxidation and leaching. Most plants are usually adapted to a neutral to weakly acidic or weakly alkaline soil. Excessive acidity is very unfavorable for vegetation growth. Therefore, it is necessary to add slaked lime to quickly neutralize the acid and alkali, and add alkaline buffers to create a soil environment suitable for vegetation growth. In addition, the larger particle size of copper mine tailings will lead to a larger pore space in the soil, which makes it easy for water to penetrate and lose, making the soil's water retention capacity poor, and larger particles usually have a lower specific surface area, which means that they have a weaker ability to adsorb and retain nutrients, and nutrients are easily carried away by water, resulting in plants unable to obtain sufficient nutrition. In addition, sandy soils are usually loose and lack sticky substances to stabilize the soil structure. This may make the soil susceptible to erosion, especially under the action of rainfall or wind, affecting the stability and growth of vegetation.

[0062] In addition, the low organic matter dry weight percentage, low phosphorus content, and low total nitrogen content indicate that the nutrients provided by copper mine tailings are limited and cannot meet the basic nutritional needs for normal plant growth. In this environment, plants may show symptoms such as poor growth, stunted development, and yellowing leaves. In order to promote the growth of vegetation on tailings, it is usually necessary to increase the nutrient content and water retention capacity of the soil by adding organic matter. A pH value of 3 to 6 means that the tailings are highly acidic. In an acidic environment, nutrient availability is reduced, the solubility of heavy metals is increased, and the activity of beneficial microorganisms is inhibited, which is not conducive to vegetation growth, so its pH needs to be adjusted.

[0063] In a specific embodiment, the alkaline buffer is one or more of calcium carbonate, magnesium carbonate, and dolomite;

[0064] and / or, the particle size of the alkaline buffer is <100 μm;

[0065] and / or, the microbial agent includes Bacillus subtilis, actinomycetes, and nitrogen-fixing bacteria in a mass ratio of (1-2):(1-2):(1-2);

[0066] And / or, the fly ash particle size is 10μm~100μm.

[0067] Since the microbial flora in copper mine tailings and sludge is different from that in natural soil, in order to create a good growth environment for the roots of vegetation, microbial agents mixed with Bacillus subtilis, actinomycetes and nitrogen-fixing bacteria in a specific mass ratio are added to the reconstructed soil of the water-retaining layer. Among them, Bacillus subtilis can inhibit pathogens in the reconstructed soil, reduce the occurrence of plant diseases, decompose organic matter, and improve soil fertility; actinomycetes have antibacterial effects in reconstructed soil, which can inhibit the growth of harmful microorganisms, participate in the decomposition of organic matter, and promote the improvement of soil structure. Nitrogen-fixing bacteria can fix nitrogen in the atmosphere into a form of nitrogen that can be used by plants, increase the effective nitrogen content in the reconstructed soil, and reduce dependence on chemical nitrogen fertilizers. By adding microbial agents to the water-retaining layer, the microbial flora structure of the reconstructed soil can be made closer to natural soil, which is conducive to vegetation growth.

[0068] Among them, the particle size of fly ash is 10μm~100μm. In the planting layer, it is configured in the form of particle size grading. The overall particle sizes of fly ash, sludge A, copper mine tailings and sludge B increase successively. After being matched in proportion, the soil structure can be reconstructed to make it closer to natural soil and increase the water and fertilizer retention effect.

[0069] In a specific embodiment, the initial moisture content of the water-retaining layer is 20%-40%, and the saturated moisture content is greater than 60%; the initial moisture content of the planting layer is 15%-30%, and the saturated moisture content is greater than 40%; and the saturated moisture content of the water-retaining layer is higher than that of the planting layer.

[0070] The present invention does not limit the method for adjusting the initial moisture content of the reconstructed soil, as long as the moisture content can be adjusted to a desired range. In some specific embodiments, the moisture content can be increased by sprinkling water or rain.

[0071] In addition, since the water-retaining layer is located between the tailings pond and the planting layer, the water loss rate is slow, while the planting layer is in direct contact with the external environment and has a faster water loss rate. Therefore, by making the saturated water content of the water-retaining layer higher than that of the planting layer, not only can more rainwater be retained, but water loss can also be reduced. In addition, the water in the water-retaining layer can also replenish the planting layer, supplying the needs of plant growth and ensuring the water demand of vegetation during the long-term greening process.

[0072] In a specific embodiment, the thickness of the water-retaining layer is 20-30 cm, and the pH is 7-9; the thickness of the planting layer is 20-40 cm, and the pH is 7-9.

[0073] Sufficient thickness is conducive to the water retention layer to store a large amount of water, reduce the rapid loss of water, especially in drought conditions, and provide a continuous water supply for the planting layer. In addition, sufficient thickness of the planting layer provides a good growth space for plant roots, supporting the stability and healthy development of plants.

[0074] In addition, a neutral to slightly alkaline pH value is beneficial to the availability of most plant nutrients, reduces the solubility of heavy metals and reduces their toxicity to plants, and a suitable pH value supports the growth and activity of beneficial microorganisms, promoting the decomposition of organic matter and nutrient cycling.

[0075] In a specific embodiment, the bulk density of the water-retaining layer is 0.8 g / cm 3 ~1.3g / cm 3 Bulk density, also known as gravity, refers to the weight of an object per unit volume. It reflects the physical properties of the soil, such as compactness, structural condition, and air permeability. The bulk density of the water-retaining layer is 0.8g / cm 3 ~1.3g / cm 3 When the soil is filled with water, it can effectively store water and gradually release it to the planting layer. This helps to maintain the water supply of the planting layer under drought conditions, and can provide sufficient structural stability to prevent soil compaction while maintaining good air permeability and drainage. Compared with the bulk density of the water-retaining layer, the lower bulk density of the planting layer provides a looser soil structure, which is conducive to the expansion and penetration of plant roots, improves the root system's ability to absorb water and nutrients, and improves the soil's air permeability and drainage, preventing root hypoxia and water accumulation problems, and promoting healthy plant growth.

[0076] In a specific embodiment, the mass ratio of organic matter dry weight of the planting layer is greater than 5%, the total nitrogen content is greater than 0.5%, the total phosphorus content is greater than 0.5%, and the bulk density is 0.7 g / cm 3 ~1.1g / cm 3 , seed germination index>90%.

[0077] Compared with copper mine tailings, the dry weight percentage of organic matter, total nitrogen content and total phosphorus content in the planting layer have all been significantly improved. The rich organic matter and nutrient content support a wider range of plant and microbial communities, helping to improve the diversity and stability of the ecosystem and enhance the resilience and function of the ecosystem.

[0078] In a specific embodiment, the vegetation includes one or both of herbaceous plants and shrubs.

[0079] Specifically, the herbaceous plants include but are not limited to one or more of Setaria viridis, ryegrass, Humulus foetida, Bermuda grass, Cosmos, Rumex sylvestris, and Latifolia; the shrubs include but are not limited to one or more of Leucaena leucaena, Lespedeza, and Amorpha fruticosa.

[0080] Herbs such as Setaria, ryegrass and Bermuda grass have well-developed root systems that can effectively fix the soil, reduce soil loss and wind erosion, and their roots can quickly cover the surface to provide initial soil protection. The roots of shrubs such as Leucaena leucophylla and Amorpha fruticosa penetrate deep into the soil, further enhancing soil stability and preventing rain erosion.

[0081] Furthermore, by planting a variety of herbs and shrubs in a mixed manner, the diversity of vegetation can be increased, and the stability and resilience of the ecosystem can be enhanced. This diversity helps to establish a more complex and stable ecological network.

[0082] In summary, the present invention sets a water storage layer with a higher saturated water content to ensure the vegetation's demand for water during the regreening of the copper mine tailings pond, increases the organic matter content in the tailings by adding sludge to meet the vegetation's demand for nutrients, improves the strong acidic environment of the copper mine tailings pond by adding slaked lime and alkaline buffers to the reconstructed soil to meet the vegetation's demand for the acidity and alkalinity of the reconstructed soil, and optimizes the microbial colony structure in the reconstructed soil by adding microbial agents to accelerate vegetation growth. The present invention is an in-situ soil construction method for a copper mine tailings pond that can not only improve the water and fertilizer retention effects and meet the needs of plant growth, but also reduce biological toxicity and ensure long-term regreening.

[0083] Hereinafter, the in-situ soil construction method for the copper mine tailings pond provided by the present invention will be further introduced in conjunction with specific embodiments.

[0084] In the following examples, the experimental methods used, unless otherwise specified, can be conventional methods in the art.

[0085] In the following examples, unless otherwise specified, all raw materials can be obtained by commercial purchase or conventional methods.

[0086] In the following embodiments, the municipal sludge used has a moisture content of 96.4%, a saturated moisture content of 99.7%, an organic matter dry weight ratio of 52.4%, and a pH value of 6.56; the copper mine tailings used have a particle size range of 300-1000 μm, an average particle size of 545 μm, an organic matter dry weight ratio of 0.37%, a total nitrogen content of 0.14%, a total phosphorus content of 0.17%, and a pH value of 4.36; the alkaline buffer calcium carbonate used has a particle size of <100 μm and an average particle size of 42 μm; the microbial agent is composed of a mixture of Bacillus subtilis, actinomycetes, and nitrogen-fixing bacteria in a mass ratio of 1:1:2; the particle size of the fly ash used is 10-100 μm, and the average particle size is 49 μm.

[0087] In the following embodiments and comparative examples, the vegetation coverage after 3 months and 2 years is calculated by dividing the greening vertical projection area of ​​the planting layer by the total area of ​​the planting layer. After 3 months, a 1m×1m sample plot is set at an interval of 10m in each regreening area, and the average plant height (the distance from the ground to the highest point of all leaves when naturally extended) of the same plant in all the sample plots is taken as the average height of the plant.

[0088] Example 1

[0089] This embodiment provides a method for constructing an in-situ soil for a copper mine tailings pond, comprising the following steps:

[0090] (1) The municipal sludge was divided into two parts, one of which was subjected to anaerobically digested treatment, the pH value was adjusted to 7.52, and then dried. After drying to a moisture content of 42.3%, the sludge was ground and sieved to obtain a powdery sludge A with a particle size of less than 200 μm and an average particle size of 86 μm;

[0091] Another portion of municipal sludge was anaerobically digested, the pH was adjusted to 8.59 and then dried. After drying to a moisture content of 31.6%, granulation was performed to obtain sludge B with a particle size of 0.3-1 cm and an average particle size of 0.65 cm.

[0092] Among them, the dry weight percentage of organic matter in sludge A and sludge B was 36.3%.

[0093] (2) After aging the biogas residue B for at least two months, 50 parts of copper tailings, 25 parts of biogas residue A, 5 parts of biogas residue B, 0.7 parts of slaked lime, 3 parts of alkaline buffer calcium carbonate, and 0.4 parts of microbial agent were fully mixed by weight, spread on the surface of the tailings pond, and sprinkled with water to form a water-retaining layer;

[0094] The initial moisture content of the water-retaining layer was 36.7%, the saturated moisture content was 79.4%, the thickness was 25.8 cm, the pH was 7.42, and the bulk density was 1.15 g / cm 3 .

[0095] (3) After aging the sludge A for at least two months, 45 parts of copper tailings, 10 parts of sludge A, 15 parts of sludge B, 10 parts of fly ash, 0.7 parts of slaked lime, and 2 parts of alkaline buffer calcium carbonate are fully mixed by weight, and then spread on the water-retaining layer. After sprinkling water or letting it rain, let it stand for 2 to 3 weeks to form a planting layer.

[0096] The initial moisture content of the planted layer was 22.6%, the saturated moisture content was 57.9%, the thickness was 35.4 cm, the pH was 7.71, the dry weight of organic matter accounted for 13.9%, the total nitrogen content was 0.66%, the total phosphorus content was 0.91%, and the bulk density was 0.97 g / cm 3 , the seed germination index is 93.2%.

[0097] (4) After rotary tilling the planting layer to a depth of 20 cm, sow ryegrass and bermudagrass for regreening. The sowing depth is about 2-3 cm. After sowing, the soil is fertilized at a rate of about 10 kg / m 2 Just sprinkle water once. The vegetation coverage and average plant height after 3 months and the vegetation coverage after 2 years are shown in Tables 1 and 2 below.

[0098] Example 2

[0099] This embodiment provides a method for constructing an in-situ soil for a copper mine tailings pond, which is basically the same as that of Embodiment 1, except that:

[0100] In step (2), the water-retaining layer includes, by weight, 60 parts of copper tailings, 20 parts of biogas sludge A, 3 parts of biogas sludge B, 0.8 parts of slaked lime, 2 parts of alkaline buffer magnesium carbonate, and 0.2 parts of microbial agent.

[0101] In step (3), the planting layer includes, by weight, 50 parts of copper mine tailings, 7 parts of biogas sludge A, 10 parts of biogas sludge B, 8 parts of fly ash, 0.9 parts of slaked lime, and 2.5 parts of alkaline buffer magnesium carbonate.

[0102] In step (4), the vegetation cover and average plant height after 3 months and the vegetation cover after 2 years are shown in Table 1 below.

[0103] Example 3

[0104] This embodiment provides a method for constructing an in-situ soil for a copper mine tailings pond, which is basically the same as that of Embodiment 1, except that:

[0105] In step (2), the water-retaining layer includes, by weight, 45 parts of copper tailings, 30 parts of biogas sludge A, 5 parts of biogas sludge B, 0.7 parts of slaked lime, 2.5 parts of alkaline buffer calcium carbonate, and 0.5 parts of microbial agent.

[0106] In step (3), the planting layer includes, by weight, 35 parts of copper mine tailings, 10 parts of biogas residue A, 15 parts of biogas residue B, 10 parts of fly ash, 0.6 parts of slaked lime, and 1.5 parts of alkaline buffer calcium carbonate.

[0107] In step (4), the vegetation cover and average plant height after 3 months and the vegetation cover after 2 years are shown in Table 1 below.

[0108] Comparative Example 1

[0109] This embodiment provides a method for constructing an in-situ soil for a copper mine tailings pond, which is basically the same as that of Embodiment 1, except that:

[0110] In steps (2) to (3), all of the sludge A is replaced with an equal mass of sludge B.

[0111] In step (4), the vegetation cover and average plant height after 3 months and the vegetation cover after 2 years are shown in Table 1 below.

[0112] Comparative Example 2

[0113] This embodiment provides a method for constructing an in-situ soil for a copper mine tailings pond, which is basically the same as that of Embodiment 1, except that:

[0114] In steps (2) to (3), replace all of the biogas residue B with an equal amount of biogas residue A.

[0115] In step (4), the vegetation cover and average plant height after 3 months and the vegetation cover after 2 years are shown in Table 1 below.

[0116] Comparative Example 3

[0117] This comparative example provides a method for constructing an in-situ soil for a copper mine tailings pond, which is basically the same as Example 1, except that:

[0118] In step (1), the particle size of the biogas sludge A is 200-400 μm, and the average particle size is 263 μm.

[0119] In step (4), the vegetation cover and average plant height after 3 months and the vegetation cover after 2 years are shown in Table 2 below.

[0120] Comparative Example 4

[0121] This comparative example provides a method for constructing an in-situ soil for a copper mine tailings pond, which is basically the same as Example 1, except that:

[0122] In step (1), the particle size of the biogas residue B is 1.5-3 cm, and the average particle size is 2.41 cm.

[0123] In step (4), the vegetation cover and average plant height after 3 months and the vegetation cover after 2 years are shown in Table 2 below.

[0124] In order to compare the structures of the water-retaining layer and the planting layer of the above embodiments and comparative examples, the types and contents of the water-retaining layer and the planting layer of embodiments 1-3 and comparative examples 1-2 are shown in Table 1 below:

[0125] Table 1

[0126]

[0127] It can be seen from Table 1 above:

[0128] The greening effect of using sludge A and sludge B together to repair the water-retaining layer and the planting layer is more obvious than the effect of using sludge A or sludge B alone.

[0129] In order to compare the effects of the particle sizes of biogas residue A and biogas residue B on the in-situ soil regreening of the copper mine tailings pond, the relevant component information of the water retention layer and the planting layer in Example 1 and Comparative Examples 3-4 are listed in Table 2 for comparison:

[0130] Table 2

[0131]

[0132] It can be seen from Table 2 above:

[0133] Controlling the particle size of sludge A and sludge B within a certain range is more conducive to plant growth and long-term regreening. Particle sizes that are too large or too small are not conducive to plant growth and long-term regreening.

[0134] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing in-situ soil of a copper mine tailings pond, characterized in that: The following steps are involved: A water-retaining layer is set on the copper mine tailings pond, a planting layer is set on the water-retaining layer, and finally vegetation is planted on the planting layer for regreening; The water-retaining layer comprises the following components in parts by mass: 40-60 parts of copper ore tailings, 15-30 parts of biogas residue A, 3-5 parts of biogas residue B, 0.5-2 parts of slaked lime, 2-5 parts of alkaline buffer, and 0.1-0.5 parts of microbial agent; The planting layer includes the following components by weight: 30-50 parts of copper ore tailings, 5-10 parts of biogas residue A, 10-20 parts of biogas residue B, 5-10 parts of fly ash, 0.5-2 parts of slaked lime, and 1-3 parts of alkaline buffer; The water content of the biogas residue A is 35% to 45%, and the particle size is less than 200 μm; The water content of the biogas residue B is 20%-35%, and the particle size is 0.3-1 cm.

2. The construction method according to claim 1, characterized in that: The pH of the sludge A is 6-8, and the mass proportion of organic matter dry weight is 30%-50%.

3. The construction method according to claim 1 or 2, characterized in that: The pH of the sludge B is 7.5-9.5, and the dry weight proportion of organic matter is 30%-50%.

4. The construction method according to claim 1, characterized in that: The preparation of the biogas residue A comprises the following steps: anaerobic digestion of municipal sludge, pH adjustment, drying, and finally grinding and screening to obtain the biogas residue A; And / or, the preparation of the biogas residue B comprises the following steps: anaerobically digesting the municipal sludge, adjusting the pH, drying it, and finally granulating it to obtain the biogas residue B.

5. The construction method according to claim 4, characterized in that: The municipal sludge has an initial moisture content of >90%, a saturated moisture content of >98%, an organic matter dry weight percentage of 40% to 60%, and a pH value of 6 to 8.

6. The construction method according to claim 1, characterized in that: The particle size of the copper mine tailings is 50μm~1000μm, the dry weight ratio of organic matter is <1%, the total nitrogen content is <0.2%, the total phosphorus content is <0.2%, the pH value is 3~6, ​​and the water content is <40%.

7. The construction method according to claim 1, characterized in that: The alkaline buffer is one or more of calcium carbonate, magnesium carbonate and dolomite; and / or, the particle size of the alkaline buffer is <100 μm; And / or, the microbial agent comprises Bacillus subtilis, actinomycetes, and nitrogen-fixing bacteria in a mass ratio of (1-2):(1-2):(1-2); And / or, the fly ash particle size is 10 μm to 100 μm.

8. The construction method according to claim 1, characterized in that: The initial moisture content of the water-retaining layer is 20%-40%, and the saturated moisture content is greater than 60%; the initial moisture content of the planting layer is 15%-30%, and the saturated moisture content is greater than 40%; and the saturated moisture content of the water-retaining layer is higher than the saturated moisture content of the planting layer.

9. The construction method according to claim 1 or 8, characterized in that: The thickness of the water-retaining layer is 20-30 cm, and the pH is 7-9; And / or, the bulk density of the water-retaining layer is 0.8 g / cm 3 ~1.3g / cm 3 ; And / or, the planting layer has a thickness of 20-40 cm and a pH of 7-9; And / or, the organic matter dry weight ratio of the planting layer is greater than 5%, the total nitrogen content is greater than 0.5%, the total phosphorus content is greater than 0.5%, and the bulk density is 0.7 g / cm 3 ~1.1g / cm 3 , seed germination index>90%.

10. The construction method according to claim 1, characterized in that: The vegetation includes one or both of herbaceous plants and shrubs.

Images