Saline-alkali soil improver, improved saline-alkali soil and preparation method thereof

Abstract

The application provides a saline-alkali soil modifier, an improved saline-alkali soil and a preparation method thereof, and belongs to the technical field of soil improvement.The modifier comprises tail coal and river mud, and the tail coal is modified tail coal treated by ultrasonic electrochemistry.The improved saline-alkali soil comprises the above saline-alkali soil modifier and saline-alkali soil.The modified tail coal treated by ultrasonic electrochemistry is mixed with the river mud to prepare the saline-alkali soil modifier, so that the solid waste resource utilization and the saline-alkali soil improvement are coordinated.The pH value and the conductivity of the saline-alkali soil can be significantly reduced, the germination rate is improved, the raw material is solid waste, the cost is greatly reduced compared with a traditional method, and the resource circulation of "waste treatment by waste" is realized.

Description

Technical Field

[0001] This invention relates to the field of soil improvement technology, and in particular to saline-alkali soil conditioners, improved saline-alkali soil, and their preparation methods. Background Technology

[0002] The formation of saline-alkali soils is related to multiple factors, including climatic conditions, geographical conditions, and the influence of rivers and seawater. In arid and semi-arid regions, low rainfall and high evaporation rates lead to salt accumulation in the soil surface. Although summer rains leach salts, strong evaporation in spring causes salts to rise to the soil surface again via capillary water, resulting in a phenomenon known as "salinization." Soil texture, groundwater level, and mineralization also influence saline-alkali soil formation. For example, loamy soils experience rapid and high capillary water rise, which facilitates salt accumulation; high groundwater levels and high mineralization also contribute to soil salt accumulation. Furthermore, lateral seepage from rivers and canals, as well as seawater infiltration, promote saline-alkali soil formation. The main soil-forming processes for saline-alkali soils are salinization and alkalization. In saline soils, the accumulation of neutral salts leads to a neutral soil pH, while in alkaline soils, the proportion of sodium ions in soil colloids increases under alkaline aqueous solutions, resulting in a pH value greater than 9.0. This deteriorates soil physical properties and hinders plant growth.

[0003] Meanwhile, the coal industry generates a large amount of flotation tailings during production. Flotation tailings are solid waste produced during coal washing and processing, and their output increases with rising coal mining volumes. The accumulation of large amounts of flotation tailings not only occupies significant land resources but also potentially pollutes surrounding soil, water bodies, and the atmosphere. According to relevant research, flotation tailings contain a certain amount of organic matter, minerals, and trace elements, such as substantial amounts of soluble SiO2 and Al2O3. These components give them potential properties for improving saline-alkali soils. In recent years, some studies have begun to focus on the application potential of flotation tailings in improving saline-alkali soils, providing a foundation for research in this field. However, further in-depth exploration of its mechanism of action and optimal application conditions is still needed to promote the practical application and widespread adoption of this technology.

[0004] Different coal types have significantly different effects on improving saline-alkali soils. The core difference lies in the degree of coalification (metamorphism). Lignite is a typical young coal, bituminous coal is a medium-coalification coal, and anthracite is a typical old coal. Young coals have a lower carbon content, approximately 60%–77%, while anthracite has a higher carbon content, approximately 90%–98%. Current research focuses on this area because young coals (lignite, peat) have low primary salinity (ash content <20%), no additional salt damage, and there is also the issue of solid waste accumulation from coal gangue. Currently, the effectiveness of coal and its byproducts in improving saline-alkali soils is influenced by factors such as organic matter content, pH value, salinity level, and nutrient release capacity. For these reasons, the research community generally agrees that coals with a high degree of humification (such as lignite and weathered coal) have a better improvement effect. Furthermore, lignite and weathered coal have high humic acid content (30%-70%), which can improve soil structure and enhance water and fertilizer retention. Bituminous coal and anthracite have low humic acid content (<10%), mainly playing a physical role in soil improvement (such as loosening the soil). This experiment used bituminous coal from various regions of Xinjiang as a conditioner. It has a high carbon content and decomposes more slowly than young coal. When placed in the soil, it does not cause drastic pH fluctuations and can continuously provide organic matter to the soil, offering a sustainable advantage.

[0005] Ultrasonic electrochemical treatment is a commonly used technique for processing coal. When ultrasound propagates in a liquid, it periodically generates cavitation bubbles (forming low-pressure zones and rupturing in high-pressure zones). The instantaneous bursting of these bubbles generates localized high temperatures (up to 5000K), high pressures (up to 100MPa), strong shock waves, and microjets, directly altering the reaction microenvironment: disrupting the diffusion layer on the electrode surface (in traditional electrochemistry, reactants / products near the electrode tend to accumulate to form a diffusion layer, hindering mass transfer), accelerating the migration of reactants to the electrode surface and the diffusion of products into the solution, significantly improving mass transfer efficiency (by 10-100 times). The reactive species such as hydroxyl radicals and hydrogen radicals generated by the bursting of cavitation bubbles can assist electrochemical redox reactions, enhancing pollutant degradation or material modification.

[0006] River silt (referred to as "river mud"), a byproduct of water conservancy projects, is rich in humus, clay, and microorganisms, possessing a natural advantage in improving saline-alkali soil. Combining modified tailings with the resource characteristics of river mud can achieve a significant modification effect. The organic matter content in river mud is typically 15%-30%, far higher than that of saline-alkali soil (generally <1%). Components such as humic acid and humic acid can regulate soil pH and improve soil aggregate structure. River mud is rich in nutrients and microorganisms: it carries nitrogen, phosphorus, potassium, and trace elements such as calcium, magnesium, and iron, while also containing a large number of bacteria and fungi, which can activate soil nutrient cycling and enhance soil fertility. The clay content in river mud is 20%-40%, which can fill the large pores of saline-alkali soil, reduce soil bulk density, enhance water and fertilizer retention capacity, and inhibit salt accumulation on the surface.

[0007] Currently, there are various methods for improving saline-alkali soil, such as drainage, irrigation for salt leaching, siltation, rice cultivation, fertilization, land leveling, and chemical modification. However, these traditional methods have certain limitations. For example, drainage requires sophisticated water conservancy facilities and is costly; irrigation for salt leaching consumes large amounts of water resources and is difficult to implement in water-scarce areas; the use of chemical modifiers such as calcium chloride and gypsum may cause secondary pollution, and their long-term effects are unstable. Therefore, developing new, efficient, environmentally friendly, and sustainable methods for improving saline-alkali soil is urgently needed. Summary of the Invention

[0008] In view of this, to address the aforementioned limitations of traditional methods for improving saline-alkali soil, this invention provides a saline-alkali soil conditioner, improved saline-alkali soil, and its preparation method. The conditioner is prepared by mixing modified tailings treated with ultrasonic electrochemical processes with river mud, achieving synergistic effects of solid waste resource utilization and saline-alkali soil improvement. It can significantly reduce the pH value and electrical conductivity of saline-alkali soil, increase the germination rate, and, since the raw material is solid waste, the cost is significantly lower than traditional methods, realizing a resource cycle of "treating waste with waste."

[0009] To achieve the above objectives, the present invention provides the following technical solution: Firstly, this invention employs a concentration gradient screening method to determine the optimal concentration ratio of saline-alkali soil to river mud, identifying 1:1 as the best ratio. This invention provides a saline-alkali soil conditioner, comprising tailings and river mud in a 1:1 mass ratio, wherein the tailings are modified tailings that have undergone ultrasonic electrochemical treatment.

[0010] Preferably, the concentration of the tailings is 5% to 20%, and the concentration of the river mud is 10% to 70%.

[0011] Secondly, this invention uses a concentration gradient screening method to select saline-alkali soil and modified tailings coal, and determines that 1:10 is the optimal concentration ratio.

[0012] This invention provides an improved saline-alkali soil, comprising the above-mentioned saline-alkali soil conditioner and saline-alkali soil; The mass ratio of the modified tailings, river mud, and saline-alkali soil is 1:1:10.

[0013] Preferably, the pH value of the saline-alkali soil is ≥8.3.

[0014] Thirdly, the present invention also provides a method for preparing the above-mentioned improved saline-alkali soil, comprising the following steps: Step (1): Mix the coal sample with the electrolyte to form a coal-water slurry, and perform ultrasonic electrochemical treatment and flotation treatment to obtain modified tailings. For example, mix the required coal sample with the electrolyte to form a coal-water slurry and perform electrochemical treatment. Perform flotation treatment on the ultrasonically electrochemically treated coal sample using a single-cell flotation machine. After flotation, collect the tailings in the flotation cell and perform vacuum filtration and drying treatment to obtain modified tailings.

[0015] Step (2): Mix the modified tailings, river mud and saline-alkali soil evenly to obtain the improved saline-alkali soil.

[0016] Preferably, in step (2), the soil ionic composition of saline-alkali soil includes Na... + K + It accounts for 90% or more of the total cations, Cl - It accounts for 95% or more of the total anions.

[0017] Preferably, in step (1), the ultrasonic electrochemical treatment includes the following steps: The pulverized and sieved coal sample was mixed with electrolyte and anhydrous ethanol to form a coal-water slurry, which was then placed in an ultrasonic water bath. The electrolysis temperature was 30℃ and the current intensity was 78×10⁻⁶. -3 A / cm 2 The electrolysis time was 30 minutes, and the ultrasonic cleaner had a frequency of 50 kHz and a power of 100 W.

[0018] Preferably, in step (1), the electrolyte has a concentration of 5.5 × 10⁻⁶. -3 Dilute sulfuric acid at a concentration of mol / L. Anhydrous ethanol, preferably 20 ml.

[0019] Preferably, in step (1), the flotation process includes the following steps: The ultrasonically electrochemically treated coal-water slurry is transferred to a flotation cell, aerated, and a collector and frother are added for flotation. Modified tailings are collected after flotation. The preferred collector is kerosene, and the dosage is 1 kg to 1.5 kg per ton of bituminous coal mixture. The preferred frother is 2-octanol, and the dosage is 100 g to 150 g per ton of bituminous coal mixture.

[0020] Preferably, in step (1), the particle size of the coal sample is less than or equal to 0.2 mm. The finer tailings particles (0.2 mm) mixed into saline-alkali soil can fill large pores in the soil, increasing its porosity and permeability, thereby mitigating the problem of sodium ions (Na+) in saline-alkali soil to some extent. + Excessive coal residue can lead to compaction and poor permeability. Adding tailings can break up the dense structure, promoting water infiltration and root growth. The coal powder (carbonaceous material) and clay minerals in tailings have a porous structure, which can physically adsorb soluble salt ions (such as Na+) in saline-alkali soil. + Cl - SO4 2- This reduces the concentration of free salts in the soil solution. The porous carbon particles in tailings can absorb moisture, and the appropriate concentration of tailings can alleviate the "salinization" phenomenon where salt rises to the topsoil with the moisture. Tailings contain calcium (Ca). 2+ ), magnesium (Mg) 2+ ), aluminum (Al) 3+ Cations such as sodium (Na+) can react with sodium (Na+) on soil colloids. + The ions undergo a displacement reaction, reducing the sodium adsorption ratio (SAR) in the soil and mitigating the harm of sodium alkalization.

[0021] River mud has a high proportion of clay particles, which can fill the large pores of saline-alkali soil, reduce soil bulk density, enhance water and fertilizer retention capacity, and inhibit the surface accumulation of salt.

[0022] As shown in the following chemical formulas (1)-(12), in the displacement reaction process (1), sodium ions (Na) in the soil colloids + ) by calcium (Ca) in tailings 2+ The ions are replaced, and the sodium (Na) that is replaced is displaced. + ) Ions can be leached into deeper soil layers or discharged from the soil body by irrigation water or rainwater. Calcium ions in the soil can also form solid precipitates as shown in reactions (2) and (3). As shown in reaction (4), some tailings contain alkaline substances (such as CaO and MgO) or aluminosilicate minerals that can be decomposed. As shown in reactions (5) and (6), pyrite (FeS2) and other minerals in the tailings are oxidized to sulfuric acid (acidic) under aerobic and aqueous conditions, neutralizing the alkalinity of the soil. The generated H2SO4 reacts with carbonates in saline-alkali soil as shown in reactions (7) and (8). As shown in reaction (9), a small amount of organic matter (such as unburned hydrocarbons) in the tailings decomposes under the action of microorganisms, producing organic acids such as humic acid and acetic acid, which neutralize OH-. - As shown in reaction formulas (10) and (11), Pb in tailings 2+ Cd 2+ Cu 2+ Equal to OH - CO3 2-The reaction, as shown in reaction formula (12), buffers pH changes by slowly dissolving and neutralizing saline-alkali soil. Simultaneously, the activated carbon, organic matter, and clay minerals in the tailings have a large specific surface area and can adsorb Na... + Cl - Salt separation molecules reduce its bioavailability. Tailings contain a small amount of organic carbon, which can slowly mineralize and release nitrogen, phosphorus, potassium, and trace elements, improving the infertility problem of saline-alkali soil. Organic matter can promote the formation of soil aggregates and enhance fertilizer retention capacity.

[0023]

[0024]

[0025] 2+ 3 2- 3 (3)

[0026]

[0027]

[0028] This invention utilizes ultrasonic electrochemical treatment to modify coal samples. Ultrasonic electrochemical treatment breaks down the dense structure of coal, increasing its specific surface area, while electrolysis generates more charged active sites on the coal surface. The treated coal particles exhibit a significantly increased adsorption capacity for sodium and chloride ions in the soil, rapidly reducing the salinity of the topsoil. During electrolysis, alkaline minerals in the coal (such as sodium carbonate and calcium carbonate) decompose or transform through electrode reactions, lowering the coal's pH from 8.0-9.5 to 7.0-8.0 (close to neutral). This change addresses the problem of raw coal easily exacerbating soil alkalization, making it suitable for use in moderately alkaline saline soils with a pH below 8.5, preventing further soil compaction, and simultaneously helping to neutralize some of the soil's alkalinity. The treated coal particles have richer and more uniform porosity, resulting in stronger binding force with soil clay particles and the formation of a more stable aggregate structure. Soil bulk density can be further reduced by 20%-25%, and the duration of air permeability and water retention is extended by 1-2 years compared to raw coal, avoiding the limitations of raw coal, which can only improve soil structure in the short term, and the high cost and low reserves of young coal. Compared with existing technologies, it has the following beneficial effects: (1) Extremely low raw material cost and solid waste resource utilization: using coal tailings (industrial solid waste) from coal preparation plants as core raw materials, the raw material cost is significantly reduced compared to traditional gypsum, organic fertilizer and other modifiers; at the same time, the tailings solid waste is disposed of, reducing the land occupation and heavy metal leakage risk, and realizing "waste treatment".

[0029] (2) Simple and efficient operation: The amendment can take effect after being mixed with saline-alkali soil in one proportion. There is no need to deep plow the soil or apply it multiple times. It is suitable for large-scale mechanized improvement and reduces labor costs.

[0030] (3) It takes effect quickly and has a significant improvement effect: the germination rate of mung beans after improvement by unmodified tailings reached 68%, and the germination rate after ultrasonic electrochemical modification + river mud compounding was 96.5% on average (100% in some examples, exceeding the blank group); it can quickly reduce the pH value of saline-alkali soil (a maximum decrease of 1.55) and electrical conductivity (a maximum decrease of 1802.68 μs / cm), overcoming the defect of seedling death caused by direct planting in saline-alkali soil.

[0031] (4) The improvement effect is long-lasting and stable: the minerals and organic matter in the tailings have a slow-release effect, the porous structure inhibits the surface accumulation of salt, reduces the risk of complex salt alkalization, and avoids the short-term problems of traditional methods (such as fertilizer loss and alkalization rebound).

[0032] (5) Environmentally friendly and resource-recycling: avoid the ecological damage caused by traditional gypsum mining and fertilizer use; promote the closed-loop sustainable model of "industrial solid waste-saline-alkali soil improvement-crop planting" and reduce the consumption of non-renewable resources. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and thoroughly described below with reference to specific embodiments.

[0034] Different coals have different pH and electrical conductivity (EC), and their performance in improving saline-alkali soil also varies. This invention uses five different types of coal: Kashgar Huxiaer coal (No. 1 coal), Baicheng coal (No. 2 coal), Kuqa bituminous coal (No. 3 coal), Kuqa Yushutian coal (No. 4 coal), and Korla Qin'an coal (No. 5 coal). The tailings are collected after ultrasonic electrolytic flotation.

[0035] The pH and electrical conductivity (EC) of different saline-alkali soils can vary significantly, resulting in different effects of the same type of coal on improving different saline-alkali soils. This invention uses saline-alkali soils collected from five different locations in Alar City, Xinjiang Uygur Autonomous Region: saline-alkali soil from Tahe Bridge (No. 1), saline-alkali soil from Boya Academy construction site (No. 2), saline-alkali soil from Xingye Xiangheli (No. 3), saline-alkali soil from Tarim University main campus (No. 4), and saline-alkali soil from Huyanghe Park (No. 5).

[0036] The river mud required for the experiment was collected from the Populus euphratica River Waterfront Park in Alar City. After removing large particles of impurities and drying, the pH and conductivity (EC) were measured.

[0037] The five types of coal used in this experiment were all high-rank coals from various regions of Xinjiang. The composition of the five types of coal is shown in Table 1 below: Table 1. Composition of five types of coal

[0038] Note: Cad represents the carbon content on an air-dried basis, which is the percentage by mass of carbon in the combustible portion of an air-dried coal sample. Cdaf is an important indicator in coal quality analysis, representing the carbon content on a dry, ash-free basis, which is the percentage by mass of carbon measured based solely on organic matter after a hypothetical coal sample has been completely dehydrated and ash removed. Cad ranges from 78.69% to 85.59%, and Cdaf ranges from 8.45% to 18.74%.

[0039] The river mud used in this experiment came from the Populus euphratica River Waterfront Park in Alar City. Its main components are carbonate and sulfate minerals (CaCO3, MgCO3) and humus. The humus includes humic acid and fulvic acid, and is rich in functional groups such as carboxyl and hydroxyl groups, which can regulate soil pH, chelate trace elements, and promote the formation of soil aggregates. After the decomposition of non-humus (aquatic plant remains, animal remains, and microbial cells), organic acids are released to neutralize soil alkalinity, and soluble salts separate cations as Ca. 2+ Mg 2+ Mainly, Na + The content is low; the anion is mainly HCO3- - SO4 2- Mainly, Cl - It has a low content and overall low salt content, so it will not cause additional salt damage to saline-alkali soil. Small molecule organic acids (acetic acid, oxalic acid), amino acids, sugars, etc., can directly participate in soil chemical reactions and improve the nutrient availability of saline-alkali soil. Contains NH4. 2+ NO3 - PO4 3- K + Equally fast-acting nutrients can be directly absorbed and utilized by crops.

[0040] This experiment used tailings obtained from flotation of five different coals as modifiers. The coal samples used were Kashgar Huoxiaer coal (No. 1), Baicheng coal (No. 2), Kuqa bituminous coal (No. 3), Kuqa Yushutian coal (No. 4), and Korla Qin'an coal (No. 5). The saline-alkali soils used were Tahe Bridge saline-alkali soil (No. 1), Boya Academy construction site saline-alkali soil (No. 2), Xingye Xiangheli saline-alkali soil (No. 3), Tarim University main campus saline-alkali soil (No. 4), and Huyanghe Park saline-alkali soil (No. 5). The pH and electrical conductivity (EC) of the five saline-alkali soils are shown in Table 2 below.

[0041] Table 2. pH and electrical conductivity (EC) of five types of saline-alkali soils

[0042] To determine the optimal ratio of saline-alkali soil to tailings, this invention mixed five types of tailings with five types of saline-alkali soil, and planted 20 mung bean seeds in each mixture. A concentration gradient screening was conducted from 5% to 35%, based on the average germination rate. The experimental results are shown in Table 3 below. Table 3. Effects of different tailings concentrations on the germination rate of mung bean plants.

[0043] If the tailings concentration is too low, the improvement effect will be insignificant. If the tailings concentration is too high, the salt in the saline-alkali soil will precipitate from the surface of the mixed soil after watering, thus harming plant growth.

[0044] To determine the optimal ratio of the mixture of saline-alkali soil and tailings to river mud, this invention mixes the above mixture with river mud and plants 20 mung bean seeds separately. A concentration gradient screening from 10% to 60% is used, based on the average germination rate. The experimental results are shown in Table 4 below. Table 4. Effects of different river mud concentrations on the germination rate of mung bean plants.

[0045] If the concentration of river mud is too low, the soil improvement effect will be insignificant. If the concentration of river mud is too high, the soil will become more clayey and will introduce too much nitrogen, phosphorus, potassium, and other elements, which will also affect plant growth.

[0046] The coal sample processing procedure is as follows: Prepare a coal-water slurry by mixing 12g of tailings coal sample with 300ml of distilled water and 20ml of anhydrous ethanol. Place the coal-water slurry into the flotation cell of a flotation machine, start the machine, and adjust the unit aeration rate to 0.25m³. 3 / (m 2 • min); After stirring for 2 min with the flotation machine switch on, add 1000 g / t of kerosene (kerosene: bituminous coal mixture) below the surface of the bituminous coal mixture; after 1 min, add 120 g / t of frother octanol (kerosene: bituminous coal mixture) below the surface of the bituminous coal mixture; after stirring, collect the tailings particles deposited at the bottom of the flotation cell and filter them to obtain filter residue. Place the filter residue in an 80℃ oven to dry, and you will get flotation waste tailings. Repeat the flotation operation to obtain sufficient tailings.

[0047] The seed treatment process is as follows: Place the washed mung beans in a container, spread them out in a single layer, and pour in distilled water to submerge the mung beans for 5 hours. Remove the seeds that float on the surface, the cracked seeds, the seeds without germs, and the unhealthy seeds. Divide the remaining mung bean seeds into groups of 20 each, and then divide them into 35 groups.

[0048] The soil treatment process is as follows: 200g of each of the five types of saline-alkali soil were placed in 25 plastic flower pots. 20g of each of the five types of coal samples were mixed into each flower pot at a ratio of 1:10 and stirred evenly. Three groups of flower pots were prepared with 220g of ordinary soil (collected 5m south of the Yifu Experimental Building of Tarim University) as the control group, and five groups of flower pots were prepared with 220g of each of the five types of saline-alkali soil as the stress group. 200ml of tap water was poured into all the flower pots and the soil was allowed to dry naturally for 24 hours to obtain relatively moist soil samples.

[0049] The grouping is as follows: The soaked mung bean seeds were planted into a total of 35 plastic flowerpot samples, including five blank replicates, five untreated stress groups, and twenty-five improved groups (five types of coal used to improve five types of saline-alkali soil). Each flowerpot contained 20 healthy mung bean seeds planted evenly with a certain spacing. The seeds were cultured for five days, and the germination rate was recorded. The germination rates of the blank and stress groups are shown in Tables 5 and 6 below.

[0050] Table 5 Germination rate of the blank group

[0051] Table 6 Germination rate of the stress group

[0052] Example 1 The coal samples used in this embodiment are data from Kashgar Huoxiaer coal (No. 1 coal) as a conditioner. The saline-alkali soils used are saline-alkali soil from the Tarim River Bridge (No. 1 saline-alkali soil), saline-alkali soil from the Boya Academy construction site (No. 2 saline-alkali soil), saline-alkali soil from Xingye Xiangheli (No. 3 saline-alkali soil), saline-alkali soil from the main campus of Tarim University (No. 4 saline-alkali soil), and saline-alkali soil from Huyanghe Park (No. 5 saline-alkali soil). The pH and electrical conductivity (EC) of the saline-alkali soils improved with No. 1 coal are shown in Table 7.

[0053] Table 7. pH and electrical conductivity (EC) of the improved saline-alkali soil.

[0054] The improvement data for No. 1 coal (Kashgar Khoxiaer coal) is summarized in Table 8 below: Table 8 Improvement data for coal sample 1 (Kashgar Khoxiaer coal)

[0055] In this embodiment, after the No. 1 coal (Kashgar Huoxiaer coal) was used to improve the five types of saline-alkali soil, the germination rate was significantly higher than that of the stress group (germination rate was 0), with an average germination rate of 66%, showing a significant improvement effect.

[0056] Example 2: The coal sample used in this embodiment is data from Baicheng Coal (No. 2 Coal) as a conditioner. The saline-alkali soils used are saline-alkali soil from Tahe Bridge (No. 1 Saline-alkali Soil), saline-alkali soil from Boya Academy construction site (No. 2 Saline-alkali Soil), saline-alkali soil from Xingye Xiangheli (No. 3 Saline-alkali Soil), saline-alkali soil from Tarim University main campus (No. 4 Saline-alkali Soil), and saline-alkali soil from Huyanghe Park (No. 5 Saline-alkali Soil). The pH and electrical conductivity (EC) of the saline-alkali soils improved with No. 2 Coal are shown in Table 9.

[0057] Table 9. pH and electrical conductivity (EC) of saline-alkali soil improved by No. 2 coal.

[0058] The improvement data for No. 2 coal (Baicheng coal) is summarized in Table 10 below: Table 10 Improvement data for No. 2 coal (Baicheng coal)

[0059] In this embodiment, after the No. 2 coal (Baicheng coal) was used to improve the five types of saline-alkali soil, the germination rate was significantly higher than that of the stress group (germination rate was 0), with an average germination rate of 73%, showing a significant improvement effect.

[0060] Example 3 The coal samples used in this embodiment are data from Kuqa bituminous coal (No. 3 coal) as a conditioner. The saline-alkali soils used are saline-alkali soil from Tahe Bridge (No. 1 saline-alkali soil), saline-alkali soil from Boya Academy construction site (No. 2 saline-alkali soil), saline-alkali soil from Xingye Xiangheli (No. 3 saline-alkali soil), saline-alkali soil from Tarim University main campus (No. 4 saline-alkali soil), and saline-alkali soil from Huyanghe Park (No. 5 saline-alkali soil). The pH and electrical conductivity (EC) of the saline-alkali soils improved with No. 3 coal are shown in Table 11.

[0061] Table 11. pH and electrical conductivity (EC) of saline-alkali soil improved by No. 3 coal.

[0062] The improvement data for No. 3 coal (Kuqa bituminous coal) is summarized in Table 12 below: Table 12 Improvement data for No. 3 coal (Kuqa bituminous coal)

[0063] In this embodiment, after the No. 3 coal (Kuqa bituminous coal) was used to improve the five types of saline-alkali soil, the germination rate was significantly higher than that of the stress group (germination rate was 0), with an average germination rate of 72%, showing a significant improvement effect.

[0064] Example 4 The coal samples used in this embodiment are data from Kuqa Yushutian coal (No. 4 coal) as a conditioner. The saline-alkali soils used are Tahe Bridge saline-alkali soil (No. 1 saline-alkali soil), Boya Academy construction site saline-alkali soil (No. 2 saline-alkali soil), Xingye Xiangheli saline-alkali soil (No. 3 saline-alkali soil), Tarim University main campus saline-alkali soil (No. 4 saline-alkali soil), and Huyanghe Park saline-alkali soil (No. 5 saline-alkali soil). The pH and electrical conductivity (EC) of the saline-alkali soils improved with No. 4 coal are shown in Table 13.

[0065] Table 13. pH and electrical conductivity (EC) of saline-alkali soil improved by No. 4 coal.

[0066] The improvement data for No. 4 coal (Kuqa Yushu field coal) is summarized in Table 14 below: Table 14 Improvement data for No. 4 coal (Kuqa Yushu field coal)

[0067] In this embodiment, after the No. 4 coal (Kuqa Yushutian coal) was used to improve the five types of saline-alkali soil, the germination rate was significantly higher than that of the stress group (germination rate was 0), with an average germination rate of 65%, showing a significant improvement effect.

[0068] Example 5 The coal sample used in this embodiment is data from Korla Qin'an Coal (No. 5 Coal) as a conditioner. The saline-alkali soils used are Tahe Bridge saline-alkali soil (No. 1 Saline-alkali Soil), Boya Academy construction site saline-alkali soil (No. 2 Saline-alkali Soil), Xingye Xiangheli saline-alkali soil (No. 3 Saline-alkali Soil), Tarim University main campus saline-alkali soil (No. 4 Saline-alkali Soil), and Huyanghe Park saline-alkali soil (No. 5 Saline-alkali Soil). The pH and electrical conductivity (EC) of the saline-alkali soils improved with No. 5 Coal are shown in Table 15.

[0069] Table 15. pH and electrical conductivity (EC) of saline-alkali soil improved by No. 5 coal.

[0070] The improvement data for No. 5 coal (Korla Qin'an coal) is summarized in Table 16 below: Table 16 Improvement data for No. 5 coal (Korla Qin'an coal)

[0071] In this embodiment, after the Korla Qin'an coal improved the five types of saline-alkali soil, the germination rate was significantly higher than that of the stress group (germination rate was 0), with an average germination rate of 64%, showing a significant improvement effect.

[0072] The above examples demonstrate that tailings have a significant effect on reducing the electrical conductivity (EC) and pH of saline-alkali soil. The improvement effect is summarized in Table 17 below. Table 17 Summary of Experimental Data

[0073] Examples 6-10 below are experimental data on the use of modified high-rank tailings mixed with river mud as a conditioner. This experiment used a mixture of tailings from five different types of coal, obtained through flotation and ultrasonic electrolysis to modify the mixed river mud, as data for the improver. The coal samples used were Kashgar Huoxiaer coal (No. 1), Baicheng coal (No. 2), Kuqa bituminous coal (No. 3), Kuqa Yushutian coal (No. 4), and Korla Qin'an coal (No. 5). The saline-alkali soils used were: Tahe Bridge saline-alkali soil (No. 1), Boya Academy construction site saline-alkali soil (No. 2), Xingye Xiangheli saline-alkali soil (No. 3), Tarim University main campus saline-alkali soil (No. 4), and Huyanghe Park saline-alkali soil (No. 5). The river mud used was from Huyanghe Riverside Park. The pH and electrical conductivity (EC) of the five saline-alkali soils are shown in Table 18 below.

[0074] Table 18. pH and electrical conductivity (EC) of five types of saline-alkali soils

[0075] The coal sample processing procedure is as follows: Mix 12g of coal sample with 300ml of distilled water, add 20ml of anhydrous ethanol and a solution of 5.5×10⁻⁶ ppm. -3 A coal-water slurry was prepared using dilute sulfuric acid at a concentration of mol / L and placed in an ultrasonic cleaning agent bath. A platinum electrode was then immersed in the slurry and stirred. The electrolysis temperature was 30℃, and the current intensity was 78 × 10⁻⁶. -3 A / cm 2 Electrolysis time: 30 min. Ultrasonic cleaning machine frequency: 50 kHz, power: 100 W. After electrolysis, collect the ultrasonically electrochemically treated coal-water slurry. Place the coal-water slurry into the flotation cell of the flotation machine, start and adjust the unit aeration rate to 0.25 m³ / h. 3 / (m 2 • min); After stirring for 2 min with the flotation machine on, add 1000 g / t of kerosene (kerosene: bituminous coal mixture) to the surface of the bituminous coal mixture; after 1 min, add 120 g / t of frother octanol (kerosene: bituminous coal mixture) to the surface of the bituminous coal mixture; after stirring, collect the tailings particles deposited at the bottom of the flotation cell and filter them to obtain filter residue. Place the filter residue in an 80℃ oven to dry, and you will get flotation waste tailings. Repeat the flotation operation to obtain sufficient modified tailings.

[0076] The seed treatment process is as follows: Place the washed mung beans in a container, spread them out in a single layer, and pour in distilled water to submerge the mung beans for 5 hours. Remove the seeds that float on the surface, the cracked seeds, the seeds without germs, and the unhealthy seeds. Divide the remaining mung bean seeds into groups of 20 each, and then divide them into 35 groups.

[0077] The soil treatment process is as follows: 200g of each of the five types of saline-alkali soil were placed in 25 plastic flower pots. 20g of each of the five types of coal samples and river mud from the waterfront park were mixed into the five flower pots in a 1:1:10 ratio and stirred evenly. Three groups of flower pots were prepared with 220g of ordinary soil (collected 5m south of the Yifu Experimental Building of Tarim University) as a control group, and five groups of flower pots were prepared with 220g of each of the five types of saline-alkali soil as a stress group. 200ml of tap water was poured into all the flower pots and the soil was allowed to dry naturally for 24 hours to obtain relatively moist soil samples.

[0078] The grouping is as follows: The soaked mung bean seeds were planted into a total of 35 plastic flowerpot samples, including five blank replicates, five untreated stress groups, and twenty-five improved groups (five types of modified coal mixed with river mud to improve five types of saline-alkali soil). Each flowerpot contained 20 healthy mung bean seeds planted evenly with a certain spacing. The seeds were cultured for five days, and the germination rate was recorded. The germination rates of the blank and stress groups are shown in Tables 19 and 20 below.

[0079] Table 19 Germination rate of the blank group

[0080] Table 20 Germination rate of the stress group

[0081] Example 6 In this embodiment, the coal sample used was modified Kashgar Huoxiaer coal (No. 1 coal) mixed with river mud (1:1 mixture) as No. 6 coal. The saline-alkali soil used was saline-alkali soil from Tahe Bridge (No. 1 saline-alkali soil), saline-alkali soil from Boya Academy construction site (No. 2 saline-alkali soil), saline-alkali soil from Xingye Xiangheli (No. 3 saline-alkali soil), saline-alkali soil from Tarim University main campus (No. 4 saline-alkali soil), and saline-alkali soil from Huyanghe Park (No. 5 saline-alkali soil). The pH and electrical conductivity (EC) of the saline-alkali soil improved by coal sample 6 are shown in Table 21.

[0082] Table 21. pH and electrical conductivity (EC) of saline-alkali soil improved by No. 6 coal.

[0083] The improvement data for No. 6 coal (Kashgar Khoxiaer coal modified and mixed with river mud) are summarized in Table 22 below: Table 22 Improvement data for No. 6 coal (Kashgar Khoxiaer coal modified and mixed with river mud)

[0084] In this embodiment, after the modified Kashgar Gorge coal was mixed with river mud in a 1:1 ratio to improve five kinds of saline-alkali soil, the germination rate was significantly greater than that of the stress group (germination rate was 0%), and significantly greater than the average germination rate of 65% of the tailings obtained by flotation treatment in Example 1. The average germination rate of this embodiment was 96%, which was much greater than the average value of the blank group (80%) and the average value of the stress group (0%), and the improvement effect was very obvious.

[0085] Example 7 In this embodiment, the coal sample used was modified Baicheng coal (No. 2 coal) mixed with river mud (1:1 mixture) as No. 7 coal. The saline-alkali soil used was saline-alkali soil from Tahe Bridge (No. 1 saline-alkali soil), saline-alkali soil from Boya Academy construction site (No. 2 saline-alkali soil), saline-alkali soil from Xingye Xiangheli (No. 3 saline-alkali soil), saline-alkali soil from Tarim University main campus (No. 4 saline-alkali soil), and saline-alkali soil from Huyanghe Park (No. 5 saline-alkali soil). The pH and electrical conductivity (EC) of the saline-alkali soil improved by No. 7 coal are shown in Table 23.

[0086] Table 23. pH and electrical conductivity (EC) of saline-alkali soil improved by No. 7 coal.

[0087] The improvement data for No. 7 coal (modified Baicheng coal mixed with river mud) are summarized in Table 24 below: Table 24 Improvement data for No. 7 coal (modified Baicheng coal mixed with river mud)

[0088] In this embodiment, after the modified Baicheng coal mixed with river mud improved the five kinds of saline-alkali soil, the germination rate was significantly greater than that of the stress group (germination rate was 0%), and significantly greater than the average germination rate of 65% of Example 2 (tailings obtained only by flotation treatment). The average germination rate of this embodiment was 98%, which was much greater than the average value of the blank group (80%) and the average value of the stress group (0%), and the improvement effect was very obvious.

[0089] Example 8 In this embodiment, the coal sample used was modified Kuqa bituminous coal (No. 3 coal) mixed with river mud (1:1 mixture) as No. 8 coal. The saline-alkali soil used was saline-alkali soil from the Tarim River Bridge (No. 1 saline-alkali soil), saline-alkali soil from the Boya Academy construction site (No. 2 saline-alkali soil), saline-alkali soil from Xingye Xiangheli (No. 3 saline-alkali soil), saline-alkali soil from the main campus of Tarim University (No. 4 saline-alkali soil), and saline-alkali soil from Huyanghe Park (No. 5 saline-alkali soil). The pH and electrical conductivity (EC) of the saline-alkali soil improved by No. 8 coal are shown in Table 25.

[0090] Table 25. pH and electrical conductivity (EC) of saline-alkali soil improved by No. 8 coal.

[0091] The improvement data for No. 8 coal (modified Kuqa bituminous coal mixed with river mud) are summarized in Table 26 below: Table 26 Improvement data for No. 8 coal (Kuqa bituminous coal modified and mixed with river mud)

[0092] In this embodiment, after the modified Kuqa bituminous coal mixed with river mud improved the five kinds of saline-alkali soil, the germination rate was significantly greater than that of the stress group (germination rate was 0) and significantly greater than that of Example 3 (tailings obtained by flotation treatment only). The average germination rate of this embodiment was 96%, which was much greater than the average value of the blank group (80%) and the average value of the stress group (0%), and the improvement effect was very obvious.

[0093] Example 9 In this embodiment, the coal sample used was modified Kuqa Yushutian coal (No. 4 coal) mixed with river mud (1:1 mixture) as No. 9 coal. The saline-alkali soil used was saline-alkali soil from Tahe Bridge (No. 1 saline-alkali soil), saline-alkali soil from Boya Academy construction site (No. 2 saline-alkali soil), saline-alkali soil from Xingye Xiangheli (No. 3 saline-alkali soil), saline-alkali soil from Tarim University main campus (No. 4 saline-alkali soil), and saline-alkali soil from Huyanghe Park (No. 5 saline-alkali soil). The pH and electrical conductivity (EC) of the saline-alkali soil improved by No. 9 coal are shown in Table 27.

[0094] Table 27. pH and electrical conductivity (EC) of saline-alkali soil improved by No. 9 coal.

[0095] The improvement data for No. 9 coal (Kuqa Yushu field coal modified and mixed with river mud) are summarized in Table 28 below: Table 28 Improvement data for No. 9 coal (Kuqa Yushu field coal modified and mixed with river mud)

[0096] In this embodiment, after the modified Kuqa Yushutian coal mixed river mud improved the five kinds of saline-alkali soil, the germination rate was significantly greater than that of the stress group (germination rate was 0%), and significantly greater than the average germination rate of 65% of Example 4 (tailings obtained only by flotation treatment). The average germination rate of this embodiment was 97%, which was much greater than the average value of the blank group (80%) and the average value of the stress group (0%), and the improvement effect was very obvious.

[0097] Example 10 In this embodiment, the coal sample used was modified Korla Qin'an coal (No. 5 coal) mixed with river mud (1:1 mixture) as No. 10 coal. The saline-alkali soil used was saline-alkali soil from the Tahe Bridge (No. 1 saline-alkali soil), saline-alkali soil from the Boya Academy construction site (No. 2 saline-alkali soil), saline-alkali soil from Xingye Xiangheli (No. 3 saline-alkali soil), saline-alkali soil from the main campus of Tarim University (No. 4 saline-alkali soil), and saline-alkali soil from Huyanghe Park (No. 5 saline-alkali soil). The pH and electrical conductivity (EC) of the saline-alkali soil improved by No. 10 coal are shown in Table 29.

[0098] Table 29. pH and electrical conductivity (EC) of saline-alkali soil improved by No. 10 coal.

[0099] The improvement data for No. 10 coal (modified Korla Qin'an Gorge coal mixed with river mud) is summarized in Table 30 below: Table 30 Improvement data for No. 10 coal (Korla Qin'an Gorge coal modified and mixed with river mud)

[0100] In this embodiment, after the modified Korla Qin'an Gorge coal mixed river mud improved the five kinds of saline-alkali soil, the germination rate was significantly greater than that of the stress group (germination rate was 0%), and significantly greater than the average germination rate of 65% of Example 5 (tailings obtained only by flotation treatment). The average germination rate of this embodiment was 96%, which was much greater than the average value of the blank group (80%) and the average value of the stress group (0%), and the improvement effect was very obvious.

[0101] The above examples demonstrate that tailings have a significant effect on reducing the electrical conductivity (EC) and pH of saline-alkali soil. The improvement effect is summarized in Table 31 below.

[0102] Table 31 Summary of Experimental Data

[0103] As can be seen from the data in Examples 1-10 above, high-rank tailings have a certain effect on improving saline-alkali soil. The pH and electrical conductivity of the soil have decreased significantly. The tailings mixed with river mud after ultrasonic electrolysis modification further removes harmful substances from the tailings on the basis of high-rank tailings improvement, enhances soil fertility, and further improves the survival rate of plants, even exceeding that of ordinary soil that has not been salinized.

[0104] Comparative Example 1 This comparative example uses coal gangue from Yangquan Mine and Alar Mine in Shanxi Province. The main components of coal gangue are clay minerals, primarily kaolinite, montmorillonite, illite, and quartz (SiO2). It also contains small amounts of carbonates, mainly calcite (CaCO3), dolomite (CaMg(CO3)2), sulfate gypsum (CaSO4·2H2O), and pyrite (FeS2), as well as small amounts of Fe2O3, Al2O3, K2O, and Na2O. It also contains trace elements such as cobalt, copper, and zinc, which can replenish mineral nutrients to the soil. The organic components in coal gangue are mainly unsorted residual coal, humic acid, and small amounts of plant residues.

[0105] The soil conditioner used in this comparative example is based on data from coal gangue from Yangquan Mine in Shanxi Province. The saline-alkali soils used were from the Tahe Bridge, Boya Academy construction site, Xingye Xiangheli, Tarim University main campus, and Huyanghe Park. The pH and electrical conductivity (EC) of the five saline-alkali soils are shown in Table 1 above. The pH and electrical conductivity (EC) of the saline-alkali soils improved with coal gangue are shown in Table 32.

[0106] Table 32 pH and electrical conductivity (EC) of saline-alkali soil improved with coal gangue

[0107] Mix 12g of coal gangue from Yangquan Mine in Shanxi Province with 300ml of distilled water, then add 20ml of anhydrous ethanol and a solution with a concentration of 5.5×10⁻⁶. - 3 A coal-water slurry was prepared using dilute sulfuric acid at a concentration of mol / L and placed in an ultrasonic cleaning agent bath. A platinum electrode was then immersed in the slurry and stirred. The electrolysis temperature was 30℃, and the current intensity was 78 × 10⁻⁶. -3 A / cm 2 Electrolysis time was 30 minutes. After electrolysis, the ultrasonically electrochemically treated coal-water slurry was collected. Then, it was filtered and dried to obtain the final electrolyzed coal gangue sample.

[0108] Place the washed mung beans in a container, spread them out in a single layer, and pour in distilled water to submerge the mung beans for 5 hours. Remove the seeds that float on the surface, the cracked seeds, the seeds without germs, and the unhealthy seeds. Divide the remaining mung bean seeds into groups of 20 each, and then divide them into 35 groups.

[0109] 200g of each of the five types of saline-alkali soil were placed in five plastic flower pots. 20g of electrolyzed Yangquan coal gangue was mixed into each pot at a ratio of 1:10 and stirred evenly. Three sets of flower pots were prepared with 220g of ordinary soil (collected 5m south of the Yifu Experimental Building of Tarim University) as a control group. Five sets of flower pots were prepared with 220g of each of the five types of saline-alkali soil as stress groups. 200ml of tap water was poured into all the flower pots and the soil was dried for 24 hours to obtain relatively moist soil samples.

[0110] The soaked mung bean seeds were planted into a total of 35 plastic flowerpot samples. 20 healthy mung bean seeds were planted evenly in each flowerpot with a certain number of holes. The seeds were cultured for five days and the germination rate was recorded.

[0111] The improvement data for coal gangue (Yangquan Mine coal gangue) are summarized in Table 33 below: Table 33 Improvement data for coal gangue (Yangquan Mine coal gangue)

[0112] In this embodiment, after the coal gangue from Yangquan Mine in Shanxi Province was used to improve five types of saline-alkali soil, the germination rate was still 0, indicating that the coal gangue after ultrasonic electrolysis had no effect on improving the saline-alkali soil. Comparative Example 2 The soil conditioner used in this comparative example is based on data from coal gangue from the Alar Mine. The saline-alkali soils used are from the Tahe Bridge, Boya Academy construction site, Xingye Xiangheli, Tarim University main campus, and Huyanghe Park. The pH and electrical conductivity (EC) of the five saline-alkali soils are shown in Table 1 above. The pH and electrical conductivity (EC) of the saline-alkali soils improved with coal gangue are shown in Table 34.

[0113] Table 34 pH and electrical conductivity (EC) of saline-alkali soil improved with coal gangue

[0114] Mix 12g of Alar coal gangue with 300ml of distilled water, add 20ml of anhydrous ethanol, and then add a solution of 5.5×10⁻⁶ ppm. - 3 A coal-water slurry was prepared using dilute sulfuric acid at a concentration of mol / L and placed in an ultrasonic cleaning agent bath. A platinum electrode was then immersed in the slurry and stirred. The electrolysis temperature was 30℃, and the current intensity was 78 × 10⁻⁶. -3 A / cm 2 Electrolysis time was 30 minutes. After electrolysis, the ultrasonically electrochemically treated coal-water slurry was collected. Then, it was filtered and dried to obtain the final electrolyzed coal gangue sample.

[0115] Place the washed mung beans in a container, spread them out in a single layer, and pour in distilled water to submerge the mung beans for 5 hours. Remove the seeds that float on the surface, the cracked seeds, the seeds without germs, and the unhealthy seeds. Divide the remaining mung bean seeds into groups of 20 each, and then divide them into 35 groups.

[0116] 200g of each of the five types of saline-alkali soil were placed in five plastic flower pots. 20g of electrolyzed Alar coal gangue was mixed into each pot at a ratio of 1:10 and stirred evenly. Three sets of flower pots were prepared with 220g of ordinary soil (collected 5m south of the Yifu Experimental Building of Tarim University) as a control group. Five sets of flower pots were prepared with 220g of each of the five types of saline-alkali soil as stress groups. 200ml of tap water was poured into all the flower pots and the soil was dried for 24 hours to obtain relatively moist soil samples.

[0117] The soaked mung bean seeds were planted into a total of 35 plastic flowerpot samples. 20 healthy mung bean seeds were planted evenly in each flowerpot with a certain number of holes. The seeds were cultured for five days and the germination rate was recorded.

[0118] The improvement data for coal gangue (Alar coal gangue) is summarized in Table 35 below: Table 35 Improvement data for coal gangue (Alar coal gangue)

[0119] In this embodiment, after the coal gangue from Alar Mine was used to improve five types of saline-alkali soil, the germination rate was still 0, indicating that the coal gangue after ultrasonic electrolysis had no effect on improving the saline-alkali soil.

[0120] Comparative Example 3 In 2023, He Xianbo et al. from the School of Chemistry and Chemical Engineering at Datong University in Shanxi Province conducted a study on the effects of coal gangue-improved saline-alkali soil on potato growth (He Xianbo, Qiao Jun, Li Ziwei, Bai Xiuli, Zhang Xiaohui, Zhao Jianguo, Xing Baoyan. Effects of coal gangue-improved saline-alkali soil on potato growth [J]. Transactions of the Chinese Society of Agricultural Engineering, 2023, 39(14):145-154. doi:10.11975 / j.issn.1002-6819.202303140.http: / / www.tcsae.org). In this study, they demonstrated that coal gangue has a significant impact on the physical properties of saline-alkali soil, including soil bulk density, saturated water content, field water holding capacity, and aggregate composition. With the increase of coal gangue usage, the content of components <0.25mm in the soil aggregates of all treatments showed a decreasing trend, while the content of components 0.25–2mm and >2mm increased with the increase of coal gangue usage. The proportion of micro-aggregates in CL30 and CL50 decreased to 17.93% and 15.54%, respectively, while the proportion of small aggregates increased to 38.95% and 41.66%, respectively, and the proportion of large aggregates increased to 43.12% and 42.85%, respectively, indicating that the soil aggregate structure was improved. Coal gangue has a high organic matter content, and after being crushed into fine particles, it has a large specific surface area. Applying it to saline-alkali soil can increase the organic cementing material in the soil and participate in the formation of soil aggregates. [1](Zhang Yuhang, Song Ziling, Kong Tao, et al. Effects of coal gangue on the improvement of physicochemical properties of saline-alkali soil [J]. Journal of Ecology and Environment, 2021, 30(1):195-204). In this study, the tested saline-alkali soil conditions were poor, leading to the death of all potatoes. The addition of coal gangue improved the physicochemical properties of the soil, such as pH, bulk density, salinity, and nutrient content, to varying degrees. The potatoes were able to complete their growth cycle, indicating that coal gangue can be used as a soil conditioner for saline-alkali soil, improving soil fertility to a certain extent and making it suitable for crop growth. [2] ([2] Xu Yu, Yang Yan, Jiang Lihua, et al. Effects of soil improvement measures on soybean yield and quality in saline-alkali land [J]. Shandong Agricultural Sciences, 2020, 52(11): 86-89. [3] Qu Zhongyi, Sun Huihui, Yang Bo, et al. Effects of different soil conditioners on soil microorganisms and processing tomato yield in saline-alkali land [J]. Transactions of the Chinese Society for Agricultural Machinery, 2021, 52(4): 311-318, 350.)

[0121] Adding coal gangue can improve the physicochemical properties of saline-alkali soil. After being crushed, coal gangue added to saline-alkali soil can reduce soil pH, salinity, and bulk density, promoting the formation of large soil aggregates and increasing nutrient content. Compared with the control (CK), among the treatments CL15 (15% coal gangue), CL30 (30% coal gangue), and CL50 (50% coal gangue), CL30 had the lowest soil bulk density (1.30 g / cm³), a decrease of 15.6%; the highest mean mass diameter (MWD) of soil aggregates (2.14 mm), an increase of 20.2%; soil pH and salinity decreased by 12.0% and 30.0%, respectively; and the contents of soil organic matter, total nitrogen, total phosphorus, total potassium, hydrolyzable nitrogen, and available potassium increased, creating a more favorable soil environment for plant growth. [4] (He Xianbo, Qiao Jun, Li Ziwei, Bai Xiuli, Zhang Xiaohui, Zhao Jianguo, Xing Baoyan. Effects of coal gangue on the improvement of saline-alkali soil on potato growth [J]. Transactions of the Chinese Society of Agricultural Engineering, 2023, 39(14):145-154. doi:10.11975 / j.issn.1002-6819.202303140.http: / / www.tcsae.org).

[0122] However, this experiment only explains the effect of coal gangue on saline-alkali soil from the perspective of physical properties. Furthermore, the potato yield (number of tubers per plant) of the improved saline-alkali soil does not reach the level of ordinary soil, and the difference is more than 30%. It also has regional characteristics and is not applicable to saline-alkali soil in Xinjiang.

[0123] Comparative Example 4 In 2012, Zhong Shixia et al. from the College of Resources and Environment of Shandong Agricultural University demonstrated the effects of ultrasonic activation of weathered coal on Chinese cabbage and soil coal activity under the influence of weathered coal humic acid on soil urease, catalase, and sucrase, without involving saline-alkali soil experiments.

[0124] Weathered coal humic acid is a mixture of various condensed aromatic hydrocarbon and carboxylic acid compounds formed from coal-forming materials through complex biochemical processes or oxidation (including weathering). These compounds are soluble in dilute caustic alkali solutions (KOH, NaOH). Humic acid has an exceptionally large specific surface area and a highly complex structure, leading to a wide range of applications. It can not only improve soil but also remediate heavy metal and organic pollution in soil. Humic acid contains many important complexing and chelating functional groups, which can undergo complexation reactions with heavy metal ions or adsorb heavy metal ions, thereby affecting the speciation of heavy metals in the soil and further influencing their fixation and migration. [5] ([5] Zhong Shixia, Xu Yuxin, Luo Hongyi, Zhao Yue, Li Jiajia. Effects of ultrasonic activation of weathered coal humic acid on Pb, Cd absorption and soil enzyme activity in Chinese cabbage[J]. Journal of Soil and Water Conservation, 2012, 26(6):185-189. Article number: 1009-2242(2012)06-0185-05.).

[0125] The experiment has not yet proven that weathered coal has a significant impact on the yield of bok choy.

[0126] Comparative Example 5 In a 2023 study by Lü Keyan et al. on the improvement of saline-alkali soil and sunflower yield by the combined application of lignite organic fertilizer and desulfurized gypsum, they used a 2 t / hm² lignite organic fertilizer treatment (LBF) and four treatments combining lignite organic fertilizer and desulfurized gypsum. Specifically, in addition to the 2 t / hm² lignite organic fertilizer application, 5 (LBF+F5), 10 (LBF+F10), 15 (LBF+F15), and 20 (LBF+F20) t / hm² desulfurized gypsum were applied, with each treatment replicated three times. A randomized block design was used, resulting in 18 plots, each 64 m² (8 m × 8 m), for a total area of ​​0.15 hm². 2 The nitrogen, phosphorus, and potassium application rates for each treatment were 135, 180, and 75 kg / hm² (based on pure N, P, and K elements). Nitrogen fertilizer was applied twice, as basal fertilizer and topdressing. 50% of the nitrogen fertilizer was applied as basal fertilizer, and the remaining 50% was applied as topdressing during the sunflower budding stage. Phosphorus and potassium fertilizers were applied entirely to the sunflower field before sowing. When chemical fertilizers and lignite organic fertilizers were applied together, while ensuring a consistent total nitrogen application rate, the lignite organic fertilizer provided 20% of the nitrogen, and the chemical fertilizer provided 80% of the nitrogen. Therefore, the lignite organic fertilizer application rate was determined to be 2 t / hm². 2Before sowing sunflowers, lignite organic fertilizer and desulfurized gypsum were evenly spread on the soil surface, and then a rotary tiller was used to mix the amendment materials evenly with the top 20cm of soil. All irrigation regimes and field management practices were consistent with local practices. Sunflowers were irrigated once during their entire growth period using surface irrigation with a quota of 100mm, on July 27, 2021 and July 24, 2022, respectively.

[0127] In 2021, all improved treatments significantly increased sunflower yield compared to the control (CK) treatment (P < 0.05). Compared to the CK treatment, the LBF, LBF+F5, LBF+F10, LBF+F15, and LBF+F20 treatments increased yield by 17.65%, 66.47%, 67.01%, 49.71%, and 18.93%, respectively. However, in 2022, only the LBF+F10 and LBF+F15 treatments significantly increased sunflower yield compared to the CK treatment. [6] ([6] Lü Keyan, Chen Zhijun, Li Yue, Hu Min, Xiong Yunwu, Huang Guanhua. Effects of combined application of lignite organic fertilizer and desulfurized gypsum on improvement of saline-alkali soil and sunflower yield [J]. Transactions of the Chinese Society of Agricultural Engineering, 2023, 39(11):77-86. doi:10.11975 / j.issn.1002-6819.202301073.http: / / www.tcsae.org).

[0128] In this embodiment, the yield of sunflowers was significantly increased, but it still relied on the combined effect of lignite and organic fertilizer, and could not be compared with improvement by one method alone.

[0129] This invention verifies through experiments that flotation tailings, as an effective material for improving saline-alkali soil, can significantly improve the soil's pH and salinization level (specifically manifested as a significant decrease in pH and EC) when mixed with saline-alkali soil at a ratio of 1:10.

[0130] The plant growth of five types of saline-alkali soil improved by tailings is shown in Table 36 below.

[0131] Table 36. Plant growth in five types of saline-alkali soil improved by tailings.

[0132] This invention, through Examples 1, 2, 3, 4, and 5, demonstrates that this improvement directly translates into excellent mung bean cultivation results: the germination rate of mung beans after planting is high (68%), and growth indicators (stem height, leaf diameter) are excellent, overcoming the fatal defect of rapid seedling death caused by direct planting in saline-alkali soil. Through Examples 6, 7, 8, 9, and 10, by ultrasonically electrochemically modifying tailings and mixing them with river mud, the average plant survival rate was further improved (96.5%) based on tailings improvement, and the survival rate was even higher compared to non-saline soil. Tailings improvement of saline-alkali soil is significant, simple to operate, low-cost, and environmentally friendly. Compared with existing technologies, it not only saves resources but also achieves the resource utilization and harmless treatment of solid waste, creating a suitable soil environment for plant growth and achieving a win-win situation for resource recycling and environmental protection.

[0133] Compared with traditional methods (such as gypsum, organic fertilizer, irrigation), the advantages of this invention are: (1) Raw material cost: Traditional methods require the purchase of expensive materials such as gypsum and organic fertilizer. This invention utilizes solid waste for improvement, which has a near-zero cost and reduces raw material costs by more than 90%, thus solving the problem of unsustainable economics of traditional methods.

[0134] (2) Environmental burden: Traditional methods may cause ecological damage due to gypsum mining, soil compaction due to chemical fertilizers, and potential secondary pollution due to water waste. This invention uses "waste to treat waste" to dispose of solid waste from coal preparation plants, reduce tailings pollution, restore saline-alkali soil, and reduce the land occupation of solid waste and the risk of heavy metal leakage.

[0135] (3) Ease of operation: Traditional methods are complicated to operate, require deep plowing and mixing, and multiple applications of amendments, resulting in high labor costs. This method only requires mixing in proportion once, making it suitable for large-scale mechanized and rapid improvement of saline-alkali land.

[0136] (4) Onset speed: Traditional organic fertilizers require several months to mineralize, and gypsum leaching requires irrigation. This invention has a high germination rate (68%), which is very close to the blank group (73.3%), ensuring crop survival and shortening the production cycle.

[0137] (5) Improved durability: Traditional methods have instability problems such as easy loss of chemical fertilizers and alkalization rebound after decomposition of organic matter. In this method, the minerals and organic matter in the tailings play a slow-release role, and the empty structure inhibits the rise of salt and reduces the risk of soil resalinization and alkalization.

[0138] (6) Resource recycling: Traditional methods consume water resources and non-renewable resources such as gypsum and phosphate. This invention utilizes an economic cycle model to promote the sustainable development of the industrial-agricultural closed loop.

[0139] The above description is merely a preferred embodiment of the present invention. However, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. A soil conditioner for saline-alkali soil, characterized in that, It includes tailings and river mud in a 1:1 mass ratio, wherein the tailings are modified tailings that have undergone ultrasonic electrochemical treatment.

2. The saline-alkali soil conditioner according to claim 1, characterized in that, The concentration of the tailings is 5% to 20%, and the concentration of the river mud is 10% to 70%.

3. An improved saline-alkali soil, characterized in that, Includes the saline-alkali soil conditioner and saline-alkali soil as described in claim 1 or 2; The mass ratio of the modified tailings, river mud, and saline-alkali soil is 1:1:

10.

4. The improved saline-alkali soil according to claim 3, characterized in that, The pH value of the saline-alkali soil is ≥8.

3.

5. A method for preparing improved saline-alkali soil according to claim 3 or 4, characterized in that, Includes the following steps: Step (1): Mix the coal sample with the electrolyte to make a coal-water slurry, and then perform ultrasonic electrochemical treatment and flotation treatment to obtain modified tailings. Step (2): Mix the modified tailings, river mud and saline-alkali soil evenly to obtain the improved saline-alkali soil.

6. The method for preparing improved saline-alkali soil according to claim 5, characterized in that, In step (2), the soil ionic composition of saline-alkali soil includes Na... + K + It accounts for 90% or more of the total cations, Cl - It accounts for 95% or more of the total anions.

7. The method for preparing improved saline-alkali soil according to claim 5, characterized in that, In step (1), the ultrasonic electrochemical treatment includes the following steps: The crushed and sieved coal sample was mixed with electrolyte and anhydrous ethanol to form a coal-water slurry, which was then placed in an ultrasonic water bath. The electrolysis temperature was 30℃ and the current intensity was 78×10⁻⁶. -3 A / cm 2 The electrolysis time was 30 minutes, and the ultrasonic cleaner had a frequency of 50 kHz and a power of 100 W.

8. The method for preparing improved saline-alkali soil according to claim 5, characterized in that, In step (1), the electrolyte has a concentration of 5.5 × 10⁻⁶. -3 dilute sulfuric acid at mol / L.

9. The method for preparing improved saline-alkali soil according to claim 5, characterized in that, In step (1), the flotation process includes the following steps: The ultrasonically electrochemically treated coal-water slurry is transferred to a flotation cell, aerated, and a collector and frother are added for flotation. Modified tailings are then collected after flotation.

10. A method for preparing improved saline-alkali soil according to any one of claims 5-9, characterized in that, In step (1), the particle size of the coal sample is less than or equal to 0.2 mm.

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