Matrix improvement and pioneer plant combined tungsten tailing ecological restoration method

Abstract

The invention discloses a matrix improvement and pioneer plant combined tungsten tailing ecological restoration method which comprises the following steps: (1) matrix improvement: on the basis of the mass of tungsten tailings, adding 2-6% of organic fertilizer, 1-6% of heavy metal passivator, 0.2-1% of water-retaining agent and 0.5-4% of structure conditioner according to the mass of the tungsten tailings into the tungsten tailings, and uniformly mixing; (2) pioneer plant field planting, wherein pioneer plant seeds are sown on the surface of the improved tailings at the density of 40-80 g / m < 2 >, a small amount of tailings are covered, and sprinkling irrigation is conducted; (3) vegetation covering culture: controlling the temperature to be 20 DEG C after field planting, illuminating for 12 hours every day, and performing regular sprinkling irrigation to maintain the water content. By selecting proper pioneer plants and developing a special tailing matrix improvement scheme for the pioneer plants, phytoremediation of tungsten tailings is achieved, and tungsten tailing vegetation is effectively established and ecologically restored.

Description

Technical Field

[0001] The present invention relates to the technical field of mine ecological restoration, and in particular to a tungsten tailings ecological restoration method using a combination of substrate improvement and pioneer plants. Background Art

[0002] my country is rich in mineral resources, but soil pollution caused by mining development is widespread and extensive, causing increasing damage and pollution to the natural ecological environment. This poses a critical challenge to soil contamination remediation in my country. Tungsten, a transitional heavy metal, is abundant in China, concentrated in provinces like Jiangxi and Hunan. Nearly a century of tungsten mining has resulted in a significant accumulation of tailings. Tailings are the solid particles remaining after ore is crushed, finely ground, and beneficiated. Tailings are small in size and low in bulk density, resulting in a loose matrix when stored, making them prone to flow and potentially leading to geological disasters. The current inventory of tungsten tailings is approximately 16 million tons. The large accumulation of tailings from metal resource mining has negatively impacted the environment, necessitating urgent remediation to mitigate these environmental risks.

[0003] Current tailings management methods often involve sealing tailings ponds with soil and then planting vegetation on top of the soil, which consumes significant soil resources and incurs significant economic costs. In recent years, the non-soil-covered phytoremediation of tailings has gained attention. This approach improves the physical and chemical environment of tailings by planting pioneer plants, thereby achieving sustainable vegetation cover. The goal is to enhance the soil function of the tailings while reducing the consumption of soil cover. However, due to the limited nutrient content of tailings, direct vegetation restoration on tailings is difficult.

[0004] In summary, when remediating acidic soils contaminated by heavy metals, it is necessary to develop a new environmental governance technology that can overcome the shortcomings of plant and chemical remediation, while taking into account economic and social benefits, and can be applied commercially on a large scale and promoted over a large area. Summary of the Invention

[0005] Given the aforementioned deficiencies or shortcomings in existing technologies, it is desirable to provide a method for ecological restoration of tungsten tailings that combines substrate modification with pioneer plant cultivation. By selecting suitable pioneer plants and developing a tailings substrate modification solution specifically tailings-specific for these pioneer plants, phytoremediation of tungsten tailings can be achieved, effectively addressing the current challenges of establishing vegetation and ecological restoration at tungsten tailings.

[0006] A method for ecological restoration of tungsten tailings using substrate modification and pioneer plants comprises the following steps:

[0007] (1) Matrix improvement: Based on the mass of tungsten tailings, add 2-6% of organic fertilizer, 1-6% of heavy metal passivator, 0.2%-1% of water retaining agent, and 0.5-4% of structure conditioner to the tungsten tailings and mix them evenly;

[0008] (2) Pioneer plant planting: Pioneer plant seeds are planted at a rate of 40-80g / m 2 The density of the seeds is sown on the surface of the modified tailings, covered with a small amount of tailings and sprinkled;

[0009] (3) Vegetation cover cultivation: After planting, the temperature is controlled at 20℃, the sunlight is 12 hours per day, and regular sprinkler irrigation is used to maintain the moisture content.

[0010] Furthermore, organic fertilizer at a concentration of 3% of the tungsten tailings mass is added to the tungsten tailings.

[0011] Furthermore, a heavy metal passivator is added to the tungsten tailings at a concentration of 2.5-5% of the mass of the tungsten tailings.

[0012] Furthermore, 0.25-0.5% of the mass of the tungsten tailings water retaining agent and 1% of the structure conditioning agent are added to the tungsten tailings.

[0013] Furthermore, the pioneer plant is selected from tall fescue or alfalfa.

[0014] Furthermore, the heavy metal passivator is composed of a mixture of zeolite and biochar in a mass ratio of 1:1; the biochar is prepared by pyrolyzing rice husks at 400°C for 2 hours in an N2 environment.

[0015] Furthermore, the water-retaining agent is composed of polyacrylic acid and bentonite mixed in a mass ratio of 1:9.

[0016] Furthermore, the structure conditioning agent is polyacrylamide.

[0017] Furthermore, the organic fertilizer is prepared by composting and fermenting chicken manure, and is air-dried to a constant weight.

[0018] Furthermore, the sprinkler irrigation cycle is once every three days to maintain the moisture content of the tailings at 30%.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] By optimizing the composition and ratio of organic fertilizer, heavy metal passivator, water retaining agent and structure conditioner, the physical and chemical properties of tungsten tailings are comprehensively improved, and the success rate of plant colonization is significantly improved; the sowing density is 40-80g / m 2Combined with temperature and humidity control, the vegetation coverage period is shortened to 1 month, and the biomass reaches a peak in 4-6 months, solving the problems of high resource consumption and difficulty in direct plant restoration in traditional soil covering methods. Through the selection of pioneer plants, the tailings aggregates are optimally formed and the soil multifunctionality index is the highest, synergistically achieving rapid coverage and heavy metal tolerance. Zeolite and rice husk biochar are compounded, and the synergistic effect of cation exchange and surface adsorption increases the fixation efficiency of characteristic heavy metals such as tungsten, cadmium, and lead by 1.2-1.5 times. The present invention realizes the plant restoration of tungsten tailings by selecting suitable pioneer plants and developing a special tailings matrix improvement plan for pioneer plants, effectively solving the current problems of tungsten tailings vegetation establishment and ecological restoration.

[0021] It should be understood that the contents described in the summary of the invention are not intended to limit the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0023] Figure 1 It is the effect of the growth of different plants on tailings on the agglomeration structure of tailings.

[0024] Figure 2 The effect of the growth of different plants on tailings on the multifunctionality of tailings soil. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the invention are shown in the accompanying drawings.

[0026] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0027] The steps for improving the matrix of tungsten tailings are as follows:

[0028] The tungsten tailings, sourced from a tailings pond in Ganzhou City, Jiangxi Province, are fine-grained tailings. Derived from quartz vein-type tungsten ore, they are a type of wolframite. The tailings are primarily composed of silica and contain high levels of heavy metals such as tungsten, cadmium, lead, arsenic, and zinc.

[0029] Organic fertilizer: The organic matter source is obtained from composted chicken manure, which is then air-dried to a constant weight. The heavy metal content of the fertilizer complies with the "Organic Fertilizer Industry Standard" (NY / T 525□2021).

[0030] Tailings water-retaining agent: It is a mixture of polyacrylic acid and bentonite, mixed in a mass ratio of 1:9. Its heavy metal content complies with the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB 15618□2018)

[0031] Heavy metal passivator: A mixture of zeolite and biochar, mixed in a 1:1 mass ratio. The biochar is obtained by thermally degrading rice husks at 400°C for 2 hours in an N2 environment. The rice husk, biochar, and zeolite mixture has a strong immobilization / adsorption effect on the characteristic heavy metals found in tungsten tailings. The heavy metal content in the heavy metal passivator complies with the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB 15618-2018).

[0032] Structural conditioner: It is a chemical product polyacrylamide, which acts as a binder and improves the loose physical structure of tailings.

[0033] Add organic fertilizer at a ratio of 3% of the mass ratio of the tailings, add heavy metal passivator at a ratio of 2.5-5%, add water retaining agent at a ratio of 0.25-0.5%, and add structure conditioner at a ratio of 1%, and mix them evenly with the tailings to achieve tailings matrix improvement.

[0034] The seeds of pioneer plants are sown on the surface of the tailings with a sowing density of 60g / m2. The surface is covered with a small amount of tailings and sprinkled regularly. The tailings can be completely covered with vegetation after one month of planting, and the plant biomass reaches its maximum in 4-6 months.

[0035] Some notes on the above materials:

[0036] Zeolite: pH = 8.95, cation exchange capacity is 137.68 cmol / kg, specific surface area is 178.24 m2 / g.

[0037] Rice husk biochar: pH = 7.71, cation exchange capacity of 35.32 cmol / kg, specific surface area of ​​89.06 m2 / g, organic matter content of 485.77 g / kg.

[0038] Chicken manure fermentation compost: pH-7.03, available nitrogen 440.07 mg / kg, total nitrogen 5655 mg / kg, available phosphorus 162.66 mg / kg, total phosphorus 1352.75 mg / kg, organic matter 186.21 g / kg, moisture content <3%.

[0039] Example 1: The colonization effect of different pioneer plants on tailings, the steps are as follows:

[0040] Tailings were added to flower pots, 1 kg per pot. Seedlings of alfalfa, sedge, ryegrass (Lolium perenne), tall fescue, Brassica rapa, and white clover were transplanted into the pots. The seedlings of these six plants were pre-germinated and transplanted into the pots, with a planting density of 60 plants per pot. A control group (CK) with no plants was also established. The flower pots were incubated in a greenhouse for 90 days at 20°C, with 12 hours of light per day and watering every three days to maintain a 30% moisture content. The effects of the different plants growing on the tailings were investigated.

[0041] The results are as follows Figure 1 As shown in the figure, the selected plants promoted the formation of tailings aggregates to different degrees, and the average weight diameter size was as follows: tall fescue > ryegrass > alfalfa > white clover > Cynanchum wilfordii > rapeseed > control group. Figure 2 It can be seen that among the six plant treatments, tall fescue increased the soil multifunctionality of the tailings and was proposed as the preferred pioneer plant, followed by alfalfa with greater soil multifunctionality.

[0042] Figure 1 In the soil multifunctionality index (SMI), 2000-250 μm, 250-53 μm, and <53 μm represent aggregates of different sizes, which can also be expressed as macroaggregates, microaggregates, and silt, respectively. The average weight diameter is an indicator of aggregate structure, calculated based on the content of macroaggregates, microaggregates, and silt. A larger value indicates a more stable soil aggregate structure. The soil multifunctionality index is a comprehensive index reflecting soil functions, encompassing indicators of available nitrogen, available phosphorus, available potassium, urease activity, phosphatase activity, and glucosidase activity.

[0043] Example 2: Effect of Tailings Substrate Improvement on Pioneer Plant Growth

[0044] Tailings were added to flower pots at a rate of 1 kg per pot. Modifiers (organic fertilizer, water-retaining agent, heavy metal passivator, and structural conditioner) were added to the tailings to improve the substrate according to different schemes. The pots were then cultured in a greenhouse for 60 days. Tall fescue seeds were seeded at a density of 1.5 g per pot, the temperature was set at 20°C, and the light intensity was 12 hours per day. Every 10 days, 30 mL of deionized water was added to the pots. The effects of different tailings substrate amendment schemes on the fresh weight of pioneer plants were investigated.

[0045] The specific improvement plan and plant fresh weight measurement results are shown in Table 1:

[0046] Table 1 Specific improvement scheme and plant fresh weight measurement results

[0047]

[0048] The results showed that different tailings substrate improvement schemes had quite different effects on the growth of pioneer plants.

[0049] The best improvement plan is to add 3% organic fertilizer, 2.5-5% heavy metal passivator, 0.25-0.5% water retaining agent, and 1% structural conditioner. This improver formula can be used in conjunction with the pioneer plant tall fescue to achieve vegetation coverage and repair of tungsten tailings.

[0050] Throughout this specification, terms such as "one embodiment" or "some embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0051] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for ecological restoration of tungsten tailings using matrix improvement and pioneer plants, characterized in that: The following steps are involved: (1) Matrix improvement: Based on the mass of tungsten tailings, add 2-6% of organic fertilizer, 1-6% of heavy metal passivator, 0.2%-1% of water retaining agent, and 0.5-4% of structure conditioner to the tungsten tailings and mix them evenly; (2) Pioneer plant planting: Pioneer plant seeds are planted at a rate of 40-80g / m 2 The density of the seeds is sown on the surface of the modified tailings, covered with a small amount of tailings and sprinkled; (3) Vegetation cover cultivation: After planting, the temperature is controlled at 20℃, the sunlight is 12 hours per day, and regular sprinkler irrigation is used to maintain the moisture content.

2. The method according to claim 1, wherein Add 3% organic fertilizer by weight of the tungsten tailings to the tungsten tailings.

3. The method according to claim 2, wherein Add 2.5-5% of the mass of the tungsten tailings to the tungsten tailings as a heavy metal passivator.

4. The method according to claim 3, wherein Add 0.25-0.5% of the mass of the tungsten tailings to the tungsten tailings as a water retaining agent and 1% of a structure conditioner.

5. The method according to claim 4, wherein The pioneer plant is selected from tall fescue or alfalfa.

6. The method according to any one of claims 1 to 5, characterized in that The heavy metal passivator is composed of a mixture of zeolite and biochar in a mass ratio of 1:1; the biochar is prepared by pyrolyzing rice husks at 400° C. for 2 hours in an N2 environment.

7. The method according to claim 6, wherein The water-retaining agent is composed of polyacrylic acid and bentonite mixed in a mass ratio of 1:

9.

8. The method according to claim 7, wherein The structure conditioning agent is polyacrylamide.

9. The method according to claim 8, wherein The organic fertilizer is prepared by composting and fermenting chicken manure, and is air-dried to a constant weight.

10. The method according to claim 9, wherein The sprinkler irrigation cycle is once every three days to maintain the moisture content of the tailings at 30%.

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