Mine tail mud soil improvement method using modifier, microbial agent and vermiculite

Abstract

The invention discloses a mine tail mud soil improvement method using an improver, a microbial agent and vermiculite. The method comprises the following steps: adding an improvement matrix and an improvement agent into to-be-improved mine tail mud, sequentially adding a microbial agent and an improvement fertilizer into the turned-over mine tail mud, leveling the mine tail mud, watering, and finally placing and activating the mine tail mud added with the improvement matrix, the improvement agent and the microbial agent under natural conditions for 4-6 months. And turning over at proper time to obtain the improved soil. Aiming at the problem that a large amount of waste tailings generated by mining are difficult to utilize, the used microbial strains are common agricultural microbial agents and have adaptability, the used modifying agents are green and pollution-free materials and are low in price, soil utilization of the tailings can be realized, and secondary pollution possibly generated in the utilization process of the tailings can be eliminated.

Description

Technical Field

[0001] The invention belongs to the improvement of mine tailings, and specifically relates to a method for improving mine tailings by soilification using an improver, a microbial agent and vermiculite. Background Art

[0002] my country is a mining country, and accordingly, it is also a tailings storage country. Tailings usually refer to the solid waste of mines that are not suitable for sorting and recycling under the conditions at that time after the mine is selected. The stock is huge. There are more than 2,700 tailings ponds in my country, with a tailings stock of about 6 billion tons, and the amount increases by 300 million tons each year. The accumulation of open-pit tailings not only occupies land resources, but also easily causes dust pollution. The tailings pond has the risk of dam collapse and leakage. At present, the utilization of tailings has become a research hotspot, such as the research on using them as building materials such as cement admixtures. However, for some tailings that do not contain heavy metal components, a low-cost, pollution-free and ecological utilization method should be sought. For example, siliceous tailings, high-calcium tailings, clay tailings, etc. can be fully utilized in soil because of their above characteristics in theory. However, because the tailings have been selected and sorted, they have problems such as high density, small particle size, poor air permeability, and excessive stickiness, which are not conducive to plant growth, greatly increasing the difficulty of their soil utilization. Soil structure improvement methods have become the premise and key to the ecological reconstruction of tailings mud fields. The prior art lacks a method for improving both the tailing mud structure and the fertility conditions at the same time. Summary of the invention

[0003] In order to solve the problems existing in the background technology, the purpose of the present invention is to provide a method for soil improvement of mine tailings using modifiers, microbial agents and vermiculite, which has the advantages of effectively improving the structure of tailings mud and improving soil fertility.

[0004] The technical solution adopted by the present invention comprises the following steps:

[0005] Step S1, mixing the improved matrix and the improver according to a preset ratio to prepare an improved material;

[0006] Step S2, then adding the improved material to the mine tailings to be improved;

[0007] Step S3: Then, microorganisms and improved fertilizers are added to the mine tailings in sequence, and then the mine tailings are leveled and watered to make the water holding rate of the mine tailings reach a preset value;

[0008] Step S4: Finally, the mine tailings added with the improved substrate, improver, microbial agent and improved fertilizer are placed under natural conditions for 4-6 months to obtain improved soil.

[0009] In the step S1, the mass ratio of the modified matrix to the modifier is 1-5:3-5, and the particle sizes of the modified matrix and the modifier are both <2 mm.

[0010] In the step S1, the improved substrate is one or more of vermiculite and sandstone.

[0011] In step S2, the improver includes one of organic fertilizer, straw and biochar, the organic fertilizer is one of sheep manure and pig manure, the straw is one of bamboo chips and corn straw, and the biochar is one of corn straw charcoal and rice straw charcoal.

[0012] In step S3, the microbial agent is bacteria or fungi, the effective viable count of the microbial agent is ≥ 200 million / g, the bacteria is Bacillus subtilis, and the fungi is Trichoderma harzianum.

[0013] The improved fertilizer in step S3 is mainly prepared by mixing nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer, and the ratio of nitrogen element, phosphorus element and potassium element in the improved fertilizer is 1-1.2:0.5-0.8:0.8-1.

[0014] The nitrogen fertilizer in the improved fertilizer is one of urea, ammonium sulfate and ammonium chloride, the phosphate fertilizer is one of potassium dihydrogen phosphate and calcium magnesium phosphate, and the potash fertilizer is one of potassium chloride and potassium sulfate.

[0015] In step S3, the water holding rate of the mine tailings is maintained at 40%±5% of the maximum field water holding capacity.

[0016] The mass ratio of the improved material to the mine tailings is 2 to 5:5, and the mass ratio of the microbial agent to the mine tailings is 5×10 -6 ~1×10 -5 :1, the mass ratio of the improved fertilizer to the mine tailings is 0.0003-0.001:1.

[0017] The main component of vermiculite / sand is silicate, and its basic characteristics are light weight, high porosity, good water absorption, stable chemical properties, and good cation exchange and adsorption. After mixing with mine tailings, it can help improve the problem of excessive stickiness of tailings, promote ventilation and better root respiration, and prevent water accumulation and soil compaction. At the same time, the water absorption, cation exchange and chemical composition characteristics of vermiculite / sand make it play multiple roles such as fertilizer retention, water retention, water storage, air permeability and mineral fertilizer, and it is a good soil conditioner. In addition, vermiculite / sand will not decompose over time, and can maintain its stable structure and performance for a long time, which is suitable for long-term soil improvement of mine tailings.

[0018] The improver includes sheep manure, straw and straw charcoal. Sheep manure is a widely used animal feces. After fermentation, it can effectively improve soil quality and prevent soil compaction; returning crop straw to the field can effectively improve soil fertility, increase soil organic matter, improve soil structure, make the soil loose, increase porosity, reduce capacity, promote microbial activity and the development of crop roots. The present invention selects corn straw, which contains more than 30% carbohydrates. Corn straw contains rich nutrients and available chemical components and is an important production resource for industrial and agricultural production; biochar is produced by pyrolysis of corn straw carbonized under high temperature and low oxygen conditions. Biochar has a higher carbon content than ordinary charcoal, and its state is more stable. Biochar has a strong pore structure and can be added to the soil to reduce soil leakage and surface loss. It is often used as a soil improver.

[0019] Selection of strains: Bacillus subtilis is selected to represent bacteria, and Trichoderma harzianum is selected to represent fungi, with the effective viable count ≥ 200 million / g. Bacillus subtilis is a bacterium belonging to the genus Bacillus, which has the characteristics of fast growth and strong reproduction ability. It is widely distributed in the soil and effectively degrades the residual fertilizers and organic pesticides in the soil, thereby improving crop yield and quality. Trichoderma harzianum is a fungus belonging to the genus Trichoderma, which has an antagonistic effect on a variety of plant pathogens, prevents and controls soil-borne fungal diseases, promotes the transformation of nutrients in the soil, and improves the absorption rate of nutrients by crops, thereby improving crop yield and quality.

[0020] The present invention aims to solve the problem that a large amount of waste tailings generated by mining are difficult to utilize. The microbial strains used are all commonly used agricultural microbial agents with adaptability, and the improvers used are all green and pollution-free materials with low prices. Not only can the soil utilization of tailings be realized, but also the secondary pollution that may be generated in the process of tailings utilization can be eliminated.

[0021] In addition, the tailings used in the present invention mainly consist of quartz and feldspar, and the secondary phases are calcite and clay minerals. The tailings are mainly composed of silicon and aluminum oxides, and the main minerals include quartz, microcline (orthoclase), zeolite, calcium feldspar and albite. The proportion of the particle size of ≤40μm is more than 95%, which has the characteristics of fine particle size. Theoretically, when used as a raw material, it has the advantages of no heavy metal pollution, heavy texture, good reaction activity, etc.

[0022] The beneficial effects of the present invention are:

[0023] 1. Aiming at the problem that a large amount of waste tailings generated by mining are difficult to utilize, the present invention provides a method for soil improvement of mine tailings by adding vermiculite, improvers (sheep manure, corn stalks, straw charcoal) and microbial agents (Bacillus subtilis and Trichoderma harzianum). The microbial agents used are widely distributed in the soil and have the effects of disease resistance and prevention of pests and diseases. The improvers used are green and pollution-free with low price. Not only can the soil utilization of tailings be realized, but also the resource utilization of improver materials can be realized.

[0024] 2. The present invention adopts vermiculite, which has the basic characteristics of light weight, many pores, good water absorption, stable chemical properties, good cation exchange and adsorption, etc. The vermiculite is mixed with tailings for use, which can increase the porosity of the tailings and improve the physical properties of the tailings, and play multiple roles such as fertilizer retention, water retention, and air permeability. In addition, vermiculite will not decompose over time, and can maintain its structure and performance stable for a long time, and is more suitable for long-term soil improvement of mine tailings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The particle size distribution of tailing mud aggregates under the treatment of modifier and Bacillus subtilis;

[0026] Figure 2 The particle size distribution of tailing mud aggregates under the treatment of vermiculite, amendment and Bacillus subtilis;

[0027] Figure 3 The particle size distribution of tailing mud aggregates under the treatment of modifier and Trichoderma harzianum;

[0028] Figure 4 The particle size distribution of tailing mud aggregates under the treatment of vermiculite, amendment and Trichoderma harzianum;

[0029] Figure 5 Vermiculite, amendments and microorganisms are used to treat tailings ammonium nitrogen (NH4 + -N) content map;

[0030] Figure 6 This is a graph of dissolved organic carbon (DOC) content in tailings mud under vermiculite, amendment and microbial treatment. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The soil particle composition of the mine tailings mud of the method of the present invention is mainly clay particles, without heavy metal pollution, and the organic matter content of the tailings is extremely low. The main phases of the tailings mud are quartz and feldspar, and the secondary phases are calcite and clay minerals. It is mainly silicon and aluminum oxides, has a weak alkaline pH of 7.90, and has low comprehensive fertility.

[0033] Example 1: Effect of vermiculite on improving tailings mud structure

[0034] Vermiculite is selected for tailing mud soil improvement, and the improvement process is as follows:

[0035] Step S1, mixing 10 parts by weight of vermiculite and 30 parts by weight of an improver (corn stalks) to prepare an improved material;

[0036] Step S2, then adding the modified material to 100 parts by weight of the mine tailings to be modified;

[0037] Step S3: Then, 5.5×10 -4 parts by weight of microorganisms (Trichoderma harzianum) and 0.06 parts by weight of improved fertilizers (0.03 g of urea, 0.02 g of potassium dihydrogen phosphate and 0.01 g of potassium chloride), and then leveling the mine tailings and watering them to keep the water holding rate of the mine tailings at 40% ± 5% of the maximum field water holding capacity;

[0038] Step S4, stack the mixed materials, keep the temperature at 30℃~50℃, and the humidity at 40%±5%. Turn the materials over every 3-5 days during the stacking period to avoid anaerobic environment and help the bacteria agent and the added improver to be fully evenly distributed. After 6 months, the improved soil can be obtained.

[0039] Embodiments 2 to 6: The steps of Embodiments 2 to 6 are the same as those of Embodiment 1, except that:

[0040] In Example 2 and Example 3, sheep manure and biochar (corn straw charcoal) were used as improvers respectively, and the other conditions were the same as in Example 1.

[0041] Example 4: Bacillus subtilis was selected as the microorganism, and the other conditions were the same as those in Example 1;

[0042] Example 5: Bacillus subtilis was selected as the microorganism, sheep manure was selected as the improver, and the other conditions were the same as those in Example 1;

[0043] Example 6: Bacillus subtilis was selected as the microorganism, and biochar (corn straw charcoal) was selected as the improver. The other conditions were the same as those in Example 1.

[0044] Comparative Examples 1 to 6:

[0045] Comparative Examples 1 to 6 Except that no vermiculite is added in step S1, the other conditions are the same as those of Examples 1 to 6.

[0046] Experimental Results

[0047] Figure 1 to Figure 4The particle size distribution of soil aggregates treated with modified materials and microorganisms is shown in the figure. The blank control in the figure represents the in-situ tailings mud sample without the addition of modified materials and microorganisms. The distribution of soil aggregates reflects the distribution law of soil particle size. It not only helps to evaluate the structure and dispersion of the soil, but also can judge the potential performance of forming structure. It is the direct evidence of the improvement of tailings mud structure. Figure 1 to Figure 4 As shown in the figure, the addition of inputs significantly increased the content of large aggregates in tailings (>0.25 mm), which is a beneficial effect of tailings improvement. In the process of decomposing organic matter (sheep manure, straw, biochar), microorganisms produce a variety of cementing substances required for the formation of aggregates. Through cementation and adsorption, microaggregates are transformed into large aggregates, which increases the aggregation degree of soil aggregates. Figure 3 and Figure 4 As shown in the figure, the agglomeration effect of the Trichoderma harzianum treatment is more significant, because the formation of fungal hyphae further promotes the agglomeration between soil particles with larger pores in the soil structure, promotes the formation of large aggregates, and makes the improved tailings have good ability to regulate water and air. At the same time, the soil with large aggregate structure is loose, easy to cultivate, has a long farming period and good farming quality. Such soil is conducive to seed germination and root extension, thereby increasing crop yields. In addition, microaggregates are also an ideal soil structure, which can effectively reduce water evaporation, improve soil erosion resistance, and provide a good growth environment for plants. Microaggregates can significantly improve the aeration, water permeability, adhesion, viscosity and swelling and shrinkage of clay soils, and have a good effect on soil physical properties and plant growth. Figure 1 , Figure 3 and Figure 2 , Figure 4 As shown in the comparison, the addition of vermiculite can effectively regulate the proportion of macroaggregates and microaggregates, promote the formation of a multi-level structure, and is beneficial to the stability of the soil structure and the improvement of tillage performance after the tailings have been turned into soil.

[0048] Figure 5 This is a graph of soil dissolved organic carbon (DOC) content under treatment with improved materials and microorganisms. Dissolved organic carbon (DOC) refers to the carbon content in the form of organic matter in the soil solution. It characterizes the solubility, biological activity and interaction between organic matter and other soil components in the soil. Biological agents grow and multiply in tailings, and release a large amount of dissolved organic matter by decomposing organic substrates. Figure 5As shown, the addition of bacteria and fungi can significantly increase the DOC content of tailings, and the effect of Trichoderma harzianum is better, which is a beneficial effect of tailings soil improvement. Although Bacillus subtilis also has the ability to decompose organic matter, the speed and effect are relatively low. Fungi have diverse metabolic pathways and can adapt to different environmental conditions and substrate types, thereby decomposing various difficult-to-degrade organic matter, such as lignocellulose, and converting it into a form that can be used by other organisms. Therefore, the treatment of Trichoderma harzianum and organic matter addition has a better effect on increasing soluble organic carbon, converting difficult-to-degrade substrates into a form that is more easily used by organisms, thereby improving the microecology of tailings.

[0049] Figure 6 Soil ammonium nitrogen (NH4 + -N) content chart. Nitrogen in the soil is the energy and nutrient provider for microbial life activities. Microorganisms decompose organic nitrogen in organic matter and convert it into ammonium nitrogen and nitrate nitrogen. The generation rate of ammonium nitrogen is faster than that of nitrate nitrogen. At the same time, ammonium nitrogen is in the form of ammonium ions (NH4 + ) exists in the form of nitrogen. This form of nitrogen has high solubility and is easily absorbed by plants, promoting plant growth and development. It is a fast-acting nutrient necessary for plant growth. Figure 6 As shown in the results, the addition of bacteria and fungi can significantly increase the content of ammonium nitrogen in tail mud, and the sheep manure has the best improvement effect, which is a beneficial effect of tail mud soil improvement. Microorganisms can secrete enzymes such as proteases, peptidases and ureases, which help decompose organic nitrogen in the soil and release inorganic nitrogen that can be used by plants. Among them, Bacillus subtilis has a high protease activity and can decompose proteins into peptides and amino acids. Peptidases further decompose peptides into amino acids, while ureases participate in the decomposition of urea. As a fungus, the enzyme system secreted by Trichoderma harzianum is more inclined to decompose the main components of plant cell walls, such as cellulose, lignin and hemicellulose. Although Trichoderma harzianum has a strong ability in cellulose decomposition, it may not be as active as Bacillus subtilis in the secretion of proteases, peptidases and ureases. Therefore, under the treatment of bacterial agents, such as Bacillus subtilis, the effect of improving ammonium nitrogen is better. At the same time, the nitrogen contained in sheep manure mainly exists in the form of organic nitrogen, including urea nitrogen, which can be gradually converted into ammonium nitrogen that can be absorbed by plants through the action of microbial urease.

[0050] Table 1 Soil pH under different treatments

[0051]

[0052] Table 1 shows the pH changes of tailings under the treatment of improved materials and microorganisms. Soil pH has an important influence on microbial activity, nutrient availability and plant growth in the soil. Generally, soil pH between 6.5 and 7.5 is considered neutral and most suitable for the growth of most plants. Soils below 6.5 are considered acidic, while those above 7.5 are alkaline. In the study, after adding different substrates, the soil pH remained in a constant range of 6.5-7.5, which is a beneficial effect of tailings soil improvement. It is worth noting that the soil pH was significantly higher in the treatment with the addition of sheep manure. This may be attributed to the sheep manure as a slightly alkaline fertilizer, in which the organic matter consumes acidic substances in the soil during decomposition, thereby improving the acidity and alkalinity of the tailings.

[0053] In summary, adding vermiculite promotes structural improvement in the soil formation process of mine tailings, and the soil formation process of mine tailings is effectively promoted in the process of Bacillus subtilis and Trichoderma harzianum as well as in the process of co-action with different substrates (sheep manure, straw, biochar), and the improvement of tailings structure and nutrient content can be achieved simultaneously, and the experimental materials are easy to obtain, which is a common modifier, secondary resource utilization, low cost, strong adaptability of strains, good stability, making it possible to widely use the method of promoting soil formation of mine tailings using microbial agents and modifiers. The above embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited to the above embodiment, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be equivalent replacement methods, which are included in the protection scope of the present invention.

Claims

1. A method for improving soil of mine tailings using an improver, a microbial agent and vermiculite, characterized in that: The following steps are involved: Step S1, mixing the improved matrix and the improver according to a preset ratio to prepare an improved material; Step S2, then adding the improved material to the mine tailings to be improved; Step S3, then, microorganisms and improved fertilizers are added to the mine tailings in sequence, and then the mine tailings are leveled and watered so that the water holding rate of the mine tailings reaches a preset value; Step S4: Finally, the mine tailings added with the improved substrate, improver, microbial agent and improved fertilizer are placed under natural conditions for 4-6 months to obtain improved soil.

2. The method for improving mine tailings soil by using an improver, a microbial agent and vermiculite according to claim 1, characterized in that: In the step S1, the mass ratio of the modified matrix to the modifier is 1-5:3-5, and the particle sizes of the modified matrix and the modifier are both less than 2 mm.

3. The method for improving mine tailings soil by using an improver, a microbial agent and vermiculite according to claim 1, characterized in that: In the step S1, the improved substrate is one or more of vermiculite and sand.

4. The method for improving mine tailings soil by using an improver, a microbial agent and vermiculite according to claim 1, characterized in that: In step S2, the improver includes one of organic fertilizer, straw and biochar, the organic fertilizer is one of sheep manure and pig manure, the straw is one of bamboo chips and corn straw, and the biochar is one of corn straw charcoal and rice straw charcoal.

5. The method for improving mine tailings soil by using an improver, a microbial agent and vermiculite according to claim 1, characterized in that: In step S3, the microbial agent is bacteria or fungi, the effective viable count of the microbial agent is greater than or equal to 200 million / g, the bacteria is Bacillus subtilis, and the fungi is Trichoderma harzianum.

6. The method for improving mine tailings soil by using an improver, a microbial agent and vermiculite according to claim 1, characterized in that: The improved fertilizer in step S3 is mainly prepared by mixing nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer, and the ratio of nitrogen element, phosphorus element and potassium element in the improved fertilizer is 1-1.2:0.5-0.8:0.8-1.

7. The method for improving mine tailings soil by using an improver, a microbial agent and vermiculite according to claim 6, characterized in that: The nitrogen fertilizer in the improved fertilizer is one of urea, ammonium sulfate and ammonium chloride, the phosphate fertilizer is one of potassium dihydrogen phosphate and calcium magnesium phosphate, and the potash fertilizer is one of potassium chloride and potassium sulfate.

8. The method for improving mine tailings soil by using an improver, a microbial agent and vermiculite according to claim 1, characterized in that: In step S3, the water holding rate of the mine tailings is maintained at 40%±5% of the maximum field water holding capacity.

9. The method for improving mine tailings soil by using an improver, a microbial agent and vermiculite according to claim 1, characterized in that: The mass ratio of the improved material to the mine tailings is 2 to 5:5, and the mass ratio of the microbial agent to the mine tailings is 5×10 -6 ~1×10 -5 :1, the mass ratio of the improved fertilizer to the mine tailings is 0.0003-0.001:1.

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