A coal gangue-based soil conditioner and its preparation method and application

Abstract

The present invention relates to the technical field of solid waste resource utilization, and specifically to a gangue-based soil conditioner, a preparation method thereof, and an application thereof. A method for preparing a gangue-based soil conditioner comprises: (a) soaking the gangue raw material in an organic acid solution to obtain acid-treated gangue; (b) calcining dolomite, and then mixing it with quicklime to obtain an alkaline activator; (c) roasting the mixed system formed by the acid-treated gangue, the alkaline activator, and humic acid, wherein the roasting treatment includes a first roasting and a second roasting, and the temperature of the second roasting is greater than the temperature of the first roasting. The preparation method of the gangue-based soil conditioner of the present invention is conducive to improving the physical and chemical properties of the gangue-based soil conditioner through the coordinated cooperation of various raw materials and steps, thereby enhancing the conditioning effect of the gangue-based soil conditioner on the soil and increasing crop yields.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization and environmental restoration, and in particular to a gangue-based soil conditioner and a preparation method and application thereof. Background Art

[0002] With the rapid development of industrialization and urbanization, coal mining activities are increasing, and the emission of coal gangue, a solid waste generated during the coal mining process, has also increased accordingly. Gangue, a mixture of minerals, rock fragments, and fine-grained coal, is typically stored in open-pits or landfills, not only consuming significant land resources but also causing significant environmental pollution. Gangue contains a certain amount of hazardous substances, such as heavy metals and radioactive elements. These substances are released into the environment through rainwater erosion and weathering, polluting the soil, water, and air, posing a threat to ecosystems and human health. During gangue storage, fine gangue particles can be blown away by the wind, forming dust pollution. This dust negatively affects air quality and increases the risk of respiratory diseases. Large-scale gangue storage can lead to geological disasters such as landslides and mudslides. The unstable structure of gangue dumps is particularly vulnerable to disasters during extreme weather conditions, posing a threat to the surrounding environment and human safety.

[0003] In recent years, researchers have begun exploring the potential use of coal gangue as a silicon fertilizer because it contains a certain amount of soluble silicon (Si), which is believed to have positive effects on plant growth and environmental remediation. However, existing technologies for preparing fertilizers from coal gangue have limited ability to improve soil quality and have limited effects on increasing crop yields.

[0004] Therefore, how to use coal gangue to obtain an environmentally friendly and efficient coal gangue-based soil conditioner to effectively improve soil structure and fertility, promote plant growth and increase yield is crucial to the development of agriculture.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] One object of the present invention is to provide a method for preparing a gangue-based soil conditioner. By combining the various steps, the obtained gangue-based soil conditioner has excellent physical and chemical properties, is environmentally friendly and highly efficient, can improve soil structure and fertility, promote plant growth, and increase crop yields.

[0007] Another object of the present invention is to provide a gangue-based soil conditioner.

[0008] Another object of the present invention is to provide a use of a coal gangue-based soil conditioner in soil conditioning.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0010] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0011] (a) The gangue raw material is soaked in an organic acid solution to obtain acid-treated gangue.

[0012] (b) Dolomite is calcined and then mixed with quicklime to obtain an alkaline activator.

[0013] (c) calcining a mixture of the acid-treated gangue, the alkaline activator, and humic acid, wherein the calcination process includes a first calcination and a second calcination, wherein the temperature of the second calcination is higher than the temperature of the first calcination, to obtain a gangue-based soil conditioner.

[0014] There is no particular order in which step (a) and step (b) are performed. In some embodiments, the organic acid solution comprises a citric acid solution, and the concentration of the organic acid solution is 0.1-0.5 mol / L.

[0015] In some embodiments, the soaking treatment time is 2 to 4 hours.

[0016] In some embodiments, the mass ratio of the coal gangue raw material to the organic acid solution is 1:(5-10).

[0017] In some embodiments, the acid-treated coal gangue has a cadmium content of less than or equal to 5 mg / kg and a silicon dioxide content of greater than or equal to 50%.

[0018] In some embodiments, the calcination temperature is 400-500° C., and the calcination time is 1-2 hours.

[0019] In some embodiments, the mass ratio of the dolomite to the quicklime is (1-3):1.

[0020] In some embodiments, the mass of the acid-treated coal gangue accounts for 70% to 80% of the total mass of the acid-treated coal gangue and the alkaline activator.

[0021] In some embodiments, the humic acid has a humification index HIX ≥ 1.8, an ash content less than or equal to 5%, and a particle size less than or equal to 0.075 mm.

[0022] In some embodiments, the mass of the humic acid accounts for 1% to 3% of the total mass of the acid-treated coal gangue and the alkaline activator.

[0023] In some embodiments, the temperature of the first calcination is 600-700° C., and the holding time is 0.5-1 hour; the temperature of the second calcination is 800-900° C., and the holding time is 1-2 hours.

[0024] In some embodiments, the first calcination atmosphere is a protective gas, and the second calcination atmosphere is air.

[0025] In some embodiments, the heating rate of the calcination treatment is 5-12° C. / min.

[0026] In some embodiments, the method further comprises grinding and screening the calcined material.

[0027] In some embodiments, the gangue raw material is obtained by crushing gangue, and the average particle size of the gangue raw material is 0.5-1 mm.

[0028] A gangue-based soil conditioner is prepared by the method for preparing the gangue-based soil conditioner.

[0029] In some embodiments, the mass content of effective silicon in the gangue-based soil conditioner is greater than or equal to 10%.

[0030] In some embodiments, the specific surface area of ​​the gangue-based soil conditioner is 20 to 30 m 2 / g, pH is 8.5~10.5.

[0031] In some embodiments, the gangue-based soil conditioner has an average particle size of 0.5 to 1 mm.

[0032] In some embodiments, the gangue-based soil conditioner is applied to acidic soil with a pH of ≤6.0, thereby increasing the soil pH by 0.2-1.5.

[0033] In some embodiments, when the application amount is 500-800 kg / mu, the crop yield can be increased by 6%-20%.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The preparation method of the coal gangue-based soil conditioner of the present invention comprises the following steps: soaking the coal gangue raw material with an organic acid solution, removing surface impurities and heavy metals through chelation, retaining effective components such as silicon dioxide, and forming a porous structure, thereby increasing the specific surface area of ​​the coal gangue raw material and improving its reaction activity; calcining dolomite, decomposing products including magnesium oxide and calcium oxide, providing a source of calcium and magnesium and enhancing the subsequent solid-phase reaction activity, and then mixing with quicklime to obtain an alkaline activator; and further Acid-treated coal gangue, alkaline activator and humic acid are mixed. Humic acid can be used as a binder to improve the formability of the mixture and delay the release of alkaline components. Through the coordination of various components and the two-stage roasting treatment, silicate minerals and alkaline components (CaO, MgO) are promoted to undergo solid-phase reaction to generate calcium magnesium silicate gel, which is beneficial to improve the physical and chemical properties of coal gangue-based soil conditioners, enhance the conditioning effect of coal gangue-based soil conditioners on the soil, significantly improve the stability of soil aggregates, and increase crop yields.

[0036] (2) The gangue-based soil conditioner of the present invention contains calcium magnesium silicate gel, which has a high content of effective silicon and simultaneously supplements soil nutrients; the heavy metal leaching concentration is extremely low, far below the agricultural land risk management standard; the gangue-based soil conditioner has excellent soil conditioning ability, which is beneficial to increasing crop yields. DETAILED DESCRIPTION

[0037] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0038] According to one aspect of the present invention, the present invention relates to a method for preparing a coal gangue-based soil conditioner, comprising the following steps:

[0039] (a) soaking the gangue raw material in an organic acid solution to obtain acid-treated gangue;

[0040] (b) calcining dolomite and mixing it with quicklime to obtain an alkaline activator;

[0041] (c) calcining a mixture of the acid-treated gangue, the alkaline activator, and humic acid, wherein the calcination process includes a first calcination and a second calcination, wherein the temperature of the second calcination is higher than the temperature of the first calcination, to obtain a gangue-based soil conditioner.

[0042] There is no specific order for steps (a) and (b). The acid-treated coal gangue can be prepared first, followed by the alkaline activator; or the alkaline activator can be prepared first, followed by the acid-treated coal gangue; or the preparations can be performed simultaneously.

[0043] The preparation method of the coal gangue-based soil conditioner of the present invention comprises the following steps: soaking the coal gangue raw material with an organic acid solution, removing surface impurities and heavy metals through chelation, retaining effective components such as silicon dioxide, and forming a porous structure, thereby increasing the specific surface area of ​​the coal gangue raw material and improving its reaction activity; calcining dolomite, decomposing products including magnesium oxide and calcium oxide, providing a calcium and magnesium source and enhancing the subsequent solid-phase reaction activity, and then mixing with quicklime to obtain an alkaline activator; and further treating the dolomite with a calcined dolomite. Acid-treated coal gangue, alkaline activator and humic acid are mixed. Humic acid can be used as a binder to improve the formability of the mixture and delay the release of alkaline components. Through the coordination of various components and the two-stage roasting treatment, the silicate minerals and alkaline components (CaO, MgO) are promoted to undergo solid-phase reaction to generate calcium magnesium silicate gel, which is beneficial to improve the physical and chemical properties of the coal gangue-based soil conditioner, enhance the conditioning effect of the coal gangue-based soil conditioner on the soil, significantly improve the stability of soil aggregates, and increase crop yields.

[0044] In some embodiments, the organic acid solution comprises a citric acid solution, and the concentration of the organic acid solution is 0.1 to 0.5 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc. In some embodiments, the soaking treatment time is 2 to 4 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours. In some embodiments, the mass ratio of the gangue raw material to the organic acid solution is 1:(5-10), such as 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. The present invention utilizes citric acid at an appropriate concentration and dosage ratio, and soaks the gangue raw material for an appropriate time, which helps improve the leaching rate of heavy metal ions (such as lead, cadmium, and chromium), reduces the toxicity of the gangue, and increases the reactivity of the gangue. Furthermore, citric acid has low corrosion to equipment, mild reaction conditions, and more environmentally friendly subsequent wastewater treatment.

[0045] In some embodiments, the acid-treated gangue has a cadmium content of less than or equal to 5 mg / kg and a silicon dioxide content of greater than or equal to 50%. The acid-treated gangue treated with organic acid according to the present invention has a low heavy metal content and a high silicon dioxide content.

[0046] In some embodiments, the calcination temperature is 400-500° C., for example, 400° C., 410° C., 420° C., 450° C., 480° C., 500° C., etc., and the calcination time is 1-2 hours, for example, 1 hour, 1.5 hours, or 2 hours. The present invention ensures that the dolomite is better decomposed into magnesium oxide and calcium oxide through appropriate calcination conditions.

[0047] In some embodiments, the mass ratio of dolomite to quicklime is (1-3):1, such as 1:1, 1.5:1, 2:1, 2.5:1, or 3:1. The dolomite and quicklime of the present invention are combined in an appropriate mass ratio to better ensure the performance of the alkaline activator.

[0048] In some embodiments, the mass of the acid-treated coal gangue accounts for 70% to 80% of the total mass of the acid-treated coal gangue and the alkaline activator, for example, 70%, 71%, 72%, 75%, 78% or 80%, that is, the mass ratio of the two is (7~8):(2~3).

[0049] In some embodiments, the humic acid has a humification index (HIX) of 1.8 or greater, such as 1.9, 2, 2.1, 2.5, etc., an ash content of 5% or less, such as 2%, 3%, 4%, 5%, etc., a particle size of 0.075 mm or less, and an average particle size of 0.05 mm, 0.06 mm, 0.07 mm, etc. In some embodiments, the mass of the humic acid accounts for 1% to 3% of the total mass of the acid-treated gangue and the alkaline activator, such as 1%, 1.5%, 2%, 2.5%, or 3%. The present invention utilizes humic acid in an appropriate dosage ratio, which facilitates synergistic cooperation with other components, improves the roasting effect, and enhances the soil conditioning ability of the soil conditioner.

[0050] In some embodiments, the temperature of the first calcination is 600-700°C, such as 600°C, 610°C, 630°C, 650°C, 660°C, 680°C, 700°C, etc., and the holding time is 0.5-1h, such as 0.5h, 0.8h or 1h; the temperature of the second calcination is 800-900°C, such as 800°C, 810°C, 830°C, 850°C, 860°C, 880°C, 900°C, etc., and the holding time is 1-2h, such as 1h, 1.5h or 2h; the atmosphere of the first calcination is a protective gas to prevent oxidation; the atmosphere of the second calcination is air to promote mineral activation. In some embodiments, the heating rate of the calcination process is 5-12°C / min, such as 5°C / min, 6°C / min, 8°C / min, 10°C / min or 12°C / min. The present invention adopts appropriate two-stage roasting treatment conditions, which is more conducive to ensuring the roasting effect, improving the physical and chemical properties of the coal gangue soil conditioner, ensuring that it has excellent soil conditioning ability, and thus increasing crop yields.

[0051] In some embodiments, the calcined material is ground and sieved to obtain a gangue-based soil conditioner with a particle size of 0.5 to 1 mm.

[0052] In some embodiments, the gangue raw material is obtained by crushing gangue, and the average particle size of the gangue raw material is 0.5-1 mm, for example, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm.

[0053] According to another aspect of the present invention, the present invention also relates to a gangue-based soil conditioner, which is prepared by the above-mentioned method for preparing the gangue-based soil conditioner.

[0054] The gangue-based soil conditioner of the present invention contains calcium magnesium silicate gel, which has a high content of effective silicon and effective calcium and magnesium, and simultaneously replenishes soil nutrients; the heavy metal leaching concentration is extremely low, far below the agricultural land risk management standard; the gangue-based soil conditioner has excellent soil conditioning ability, which is conducive to increasing crop yields.

[0055] In some embodiments, the mass content of effective silicon in the gangue-based soil conditioner is greater than or equal to 10% (as a proportion of total silicon dioxide), for example, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc.

[0056] In some embodiments, the effective calcium and magnesium content calculated as CaO and MgO is greater than or equal to 25%, for example, 25%, 30%, 35%, etc.

[0057] In some embodiments, the specific surface area of ​​the gangue-based soil conditioner is 20 to 30 m 2 / g, for example 20m 2 / g、22m 2 / g, 25m 2 / g, 26m 2 / g、28m 2 / g or 30m 2 / g, etc.; pH is 8.5~10.5, such as 8.5, 9, 9.5, 10, etc.

[0058] In some embodiments, the effective heavy metal content in the gangue-based soil conditioner includes: cadmium less than or equal to 0.02 mg / L; lead less than or equal to 1.2 mg / L; arsenic less than or equal to 0.04 mg / L; and chromium less than or equal to 0.06 mg / L.

[0059] In some embodiments, the average particle size of the gangue-based soil conditioner is 0.5-1 mm, for example, 0.5 mm, 0.6 mm, 0.7 mm, 0.9 mm, 1 mm, etc.

[0060] In some embodiments, the gangue-based soil conditioner is applied to acidic soil with a pH of ≤ 6.0, and the soil pH is increased by 0.2 to 1.5.

[0061] In some embodiments, the exchangeable aluminum content is reduced by 30% to 50%. Exchangeable aluminum content is determined by potassium chloride extraction-atomic absorption spectrometry.

[0062] In some embodiments, when the application amount is 500-800 kg / mu, the crop yield can be increased by 6%-20%.

[0063] The following is a further explanation with reference to specific embodiments and comparative examples.

[0064] Example 1

[0065] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0066] (a) The average particle size of the crushed gangue was 0.6 mm. It was soaked in 0.3 mol / L citric acid for 3 h with a solid-liquid ratio of 1:8 to obtain acid-treated gangue.

[0067] (b) Dolomite was calcined at 450°C for 1.5 h and then mixed with quicklime in a mass ratio of 2:1 to prepare an alkaline activator.

[0068] (c) Acid-treated gangue and alkaline activator were mixed in a mass ratio of 7.5:2.5, and 2% humic acid (HIX = 2.3, ash content of 2.5%, average particle size of 0.068 mm) was added to obtain a mixed system.

[0069] (d) The mixed system was calcined: the first calcination temperature was 650° C., the holding time was 0.75 h, and the second calcination temperature was 850° C., the holding time was 1.5 h, and the air atmosphere was used to obtain a gangue-based soil conditioner.

[0070] Example 2

[0071] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0072] (a) The average particle size of the crushed gangue was 0.8 mm. It was soaked in 0.2 mol / L citric acid for 4 h with a solid-liquid ratio of 1:6 to obtain acid-treated gangue.

[0073] (b) Dolomite was calcined at 480°C for 1 hour and then mixed with quicklime at a mass ratio of 2.5:1 to form an alkaline activator.

[0074] (c) Acid-treated coal gangue and alkaline activator were mixed in a mass ratio of 7:3, and 1.5% humic acid (HIX = 2.3, ash content of 2.5%, average particle size of 0.068 mm) was added to obtain a mixed system.

[0075] (d) The mixed system was calcined: the first calcination temperature was 680°C, the holding time was 1 h, and the nitrogen atmosphere was used; the second calcination temperature was 820°C, the holding time was 2 h, and the air atmosphere was used to obtain a gangue-based soil conditioner.

[0076] Example 3

[0077] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0078] (a) The average particle size of the crushed gangue was 0.5 mm. The gangue was soaked in 0.4 mol / L citric acid for 2.5 h at a solid-liquid ratio of 1:10 to obtain acid-treated gangue.

[0079] (b) Dolomite was calcined at 420°C for 2 h and then mixed with quicklime at a mass ratio of 1.8:1 to form an alkaline activator.

[0080] (c) Acid-treated coal gangue and alkaline activator were mixed in a mass ratio of 8:2, and 3% humic acid (HIX = 2.3, ash content of 2.5%, average particle size of 0.068 mm) was added to obtain a mixed system.

[0081] (d) The mixed system was calcined: the first calcination temperature was 700°C, the holding time was 0.5 h, and the nitrogen atmosphere; the second calcination temperature was 880°C, the holding time was 1.25 h, and the air atmosphere, to obtain a gangue-based soil conditioner.

[0082] Example 4

[0083] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0084] (a) The average particle size of the crushed gangue was 1.0 mm. The gangue was soaked in 0.25 mol / L citric acid for 3.5 h at a solid-liquid ratio of 1:7 to obtain acid-treated gangue.

[0085] (b) Dolomite was calcined at 500°C for 1.25 h and then mixed with quicklime in a mass ratio of 3:1 to form an alkaline activator.

[0086] (c) Acid-treated gangue and alkaline activator were mixed in a mass ratio of 7.2:2.8, and 2.2% humic acid (HIX = 2.3, ash content of 2.5%, average particle size of 0.068 mm) was added to obtain a mixed system.

[0087] (d) The mixed system was calcined: the first calcination temperature was 620°C, the holding time was 1 hour, and the nitrogen atmosphere was used; the second calcination temperature was 800°C, the holding time was 1.75 hours, and the air atmosphere was used to obtain a gangue-based soil conditioner.

[0088] Example 5

[0089] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0090] (a) The average particle size of the crushed gangue was 0.7 mm. It was soaked in 0.35 mol / L citric acid for 2 h at a solid-liquid ratio of 1:9 to obtain acid-treated gangue.

[0091] (b) Dolomite was calcined at 460°C for 1.8 h and then mixed with quicklime at a mass ratio of 2.2:1 to prepare an alkaline activator.

[0092] (c) Acid-treated gangue and alkaline activator were mixed in a mass ratio of 7.8:2.2, and 1.8% humic acid (HIX = 2.3, ash content of 2.5%, average particle size of 0.068 mm) was added to obtain a mixed system.

[0093] (d) The mixed system was calcined: the first calcination temperature was 630°C, the holding time was 0.8 h, and the second calcination temperature was 860°C, the holding time was 1.2 h, and the air atmosphere was used to obtain a gangue-based soil conditioner.

[0094] Example 6

[0095] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0096] (a) The average particle size of the crushed gangue was 0.9 mm. The gangue was soaked in 0.45 mol / L citric acid for 4 h at a solid-liquid ratio of 1:5 to obtain acid-treated gangue.

[0097] (b) Dolomite was calcined at 440°C for 1.6 h and then mixed with quicklime at a mass ratio of 2.8:1 to prepare an alkaline activator.

[0098] (c) Acid-treated gangue and alkaline activator were mixed in a mass ratio of 7.3:2.7, and 2.5% humic acid (HIX = 2.3, ash content of 2.5%, average particle size of 0.068 mm) was added to obtain a mixed system.

[0099] (d) The mixed system was calcined: the first calcination temperature was 670°C, the holding time was 0.6 h, and the nitrogen atmosphere; the second calcination temperature was 830°C, the holding time was 1.6 h, and the air atmosphere, to obtain a gangue-based soil conditioner.

[0100] Example 7

[0101] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0102] (a) The average particle size of the crushed gangue was 0.55 mm. The gangue was soaked in 0.15 mol / L citric acid for 3.2 h at a solid-liquid ratio of 1:8 to obtain acid-treated gangue.

[0103] (b) Dolomite was calcined at 490°C for 1.4 h and then mixed with quicklime in a mass ratio of 2.4:1 to form an alkaline activator.

[0104] (c) Acid-treated gangue and alkaline activator were mixed in a mass ratio of 7.6:2.4, and 2.8% humic acid (HIX = 2.3, ash content of 2.5%, average particle size of 0.068 mm) was added to obtain a mixed system.

[0105] (d) The mixed system was calcined: the first calcination temperature was 690°C, the holding time was 0.9 h, and the nitrogen atmosphere; the second calcination temperature was 810°C, the holding time was 1.8 h, and the air atmosphere, to obtain a gangue-based soil conditioner.

[0106] Example 8

[0107] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0108] (a) The average particle size of the crushed gangue was 0.65 mm. The gangue was soaked in 0.5 mol / L citric acid for 2.8 h at a solid-liquid ratio of 1:6 to obtain acid-treated gangue.

[0109] (b) Dolomite was calcined at 430°C for 1.7 h and then mixed with quicklime at a mass ratio of 1.5:1 to prepare an alkaline activator.

[0110] (c) Acid-treated gangue and alkaline activator were mixed in a mass ratio of 8:2, and 1.2% humic acid (HIX = 2.3, ash content of 2.5%, average particle size of 0.068 mm) was added to obtain a mixed system.

[0111] (d) The mixed system was calcined: the first calcination temperature was 640°C, the holding time was 1.1 h, and the nitrogen atmosphere; the second calcination temperature was 870°C, the holding time was 1.3 h, and the air atmosphere, to obtain a gangue-based soil conditioner.

[0112] Example 9

[0113] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0114] (a) The average particle size of the crushed gangue was 0.75 mm. The gangue was soaked in 0.18 mol / L citric acid for 3.8 h at a solid-liquid ratio of 1:9 to obtain acid-treated gangue.

[0115] (b) Dolomite was calcined at 470°C for 1.3 h and then mixed with quicklime in a mass ratio of 2.6:1 to prepare an alkaline activator.

[0116] (c) Acid-treated gangue and alkaline activator were mixed in a mass ratio of 7.4:2.6, and 2.6% humic acid (HIX = 2.3, ash content of 2.5%, average particle size of 0.068 mm) was added to obtain a mixed system.

[0117] (d) The mixed system was calcined: the first calcination temperature was 660°C, the holding time was 0.7 h, and the second calcination temperature was 840°C, the holding time was 1.4 h, and the air atmosphere was used to obtain a gangue-based soil conditioner.

[0118] Example 10

[0119] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0120] (a) The average particle size of the crushed gangue was 0.85 mm. The gangue was soaked in 0.22 mol / L sulfuric acid for 2.2 h at a solid-liquid ratio of 1:7 to obtain acid-treated gangue.

[0121] (b) Dolomite was calcined at 410°C for 1.9 h and then mixed with quicklime in a mass ratio of 3:1 to form an alkaline activator.

[0122] (c) Acid-treated gangue and alkaline activator were mixed in a mass ratio of 7.7:2.3, and 1.5% humic acid (HIX = 1.9, average particle size 0.07 mm) was added to obtain a mixed system.

[0123] (d) The mixed system was calcined: the first calcination temperature was 710°C, the holding time was 0.85 h, and the second calcination temperature was 890°C, the holding time was 1.15 h, and the air atmosphere was used to obtain a gangue-based soil conditioner.

[0124] Comparative Example 1

[0125] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0126] (a) The average particle size of coal gangue after crushing is 1.2 mm.

[0127] (b) Calcine dolomite at 300°C for 0.5 h and then mix it with quicklime in a mass ratio of 1:4.

[0128] (c) The gangue of step (a) and the mixed material of step (b) are mixed in a mass ratio of 6:4 to obtain a mixed system.

[0129] (d) The mixed system was calcined at 750°C for 3 h in a nitrogen atmosphere to obtain a gangue-based soil conditioner.

[0130] Comparative Example 2

[0131] A method for preparing a gangue-based soil conditioner comprises the following steps:

[0132] (a) The average particle size of the crushed gangue is 0.3 mm. It is soaked in 0.3 mol / L sulfuric acid for 3 h with a solid-liquid ratio of 1:8 to obtain acid-treated gangue.

[0133] (b) Dolomite was calcined at 600°C for 3 h and then mixed with quicklime in a mass ratio of 4:1 to form an alkaline activator.

[0134] (c) Acid-treated coal gangue and alkaline activator were mixed in a mass ratio of 5:5, and 5% of a common binder was added to obtain a mixed system.

[0135] (d) The mixed system was calcined: the first calcination temperature was 550°C, the holding time was 0.75 h, and the second calcination temperature was 950°C, the holding time was 1.5 h, and the air atmosphere was used to obtain a gangue-based soil conditioner.

[0136] Comparative Example 3

[0137] A method for preparing a gangue-based soil conditioner differs from Example 10 in that:

[0138] No acid soaking treatment is performed in step (a).

[0139] Comparative Example 4

[0140] A method for preparing a gangue-based soil conditioner differs from Example 10 in that:

[0141] In step (b), the dolomite is not calcined.

[0142] Comparative Example 5

[0143] A method for preparing a gangue-based soil conditioner differs from Example 10 in that:

[0144] No humic acid was added in step (c).

[0145] Comparative Example 6

[0146] A method for preparing a gangue-based soil conditioner differs from Example 10 in that:

[0147] In step (d), a single-stage calcination is adopted, the temperature is 750° C., the holding time is 3 h, and the nitrogen atmosphere is used.

[0148] Experimental example

[0149] 1. Performance test of coal gangue-based soil conditioner

[0150] The gangue-based soil conditioners of various examples and comparative examples were subjected to performance tests, including pH, specific surface area, effective silicon content, and the effect on the effective silicon content in the soil.

[0151] pH determination: GB / T 18882-2017 test.

[0152] Determination of effective silicon content: sodium carbonate fusion-molybdenum blue colorimetric method.

[0153] Heavy metal leaching concentration: GB / T 30810-2014 test.

[0154] Specific surface area: determined by BET method.

[0155] The test results are shown in Tables 1 and 2.

[0156] Table 1 Performance test results of coal gangue-based soil conditioner

[0157]

[0158] Table 2 Effective heavy metal content of gangue-based soil conditioners (mg / L)

[0159]

[0160] As can be seen from Table 1 and Table 2, the gangue-based soil conditioner of the present invention has suitable pH and specific surface area, low leaching content of heavy metals, and high effective silicon content.

[0161] 2. Soil Conditioning Effect and Crop Yield

[0162] The gangue-based soil conditioners of the various examples and comparative examples were applied to soil conditioning, and the specific effects are shown in Table 3.

[0163] Soil pH determination: Tested according to NY / T 1121.2-2006.

[0164] Determination of available silicon content in soil: Samples were collected by collecting 10 soil samples from the 0-20 cm topsoil layer in the experimental plots using an "S"-shaped spot method before and after silicon fertilizer application and harvest. The samples were mixed, air-dried, and then passed through a 2 mm sieve for later use. Available silicon was extracted using the citric acid-sodium hydrogen phosphate buffer extraction method (refer to NY / T 1121.15-2006): 5.00 g of air-dried soil sample was weighed and placed in a 150 mL Erlenmeyer flask. 50 mL of pH 4.0 citric acid buffer (0.025 mol / L citric acid + 0.05 mol / L disodium hydrogen phosphate) was added. The mixture was shaken at a constant temperature (25°C, 200 rpm) for 5 h, then centrifuged (4000 rpm, 10 min) and filtered. The silicon content of the filtrate was determined by the molybdenum blue colorimetric method: 5 mL of the filtrate was added to 5 mL of 10% ammonium molybdate solution (pH 1.8). After standing for 10 min, 1 mL of 20% tartaric acid solution and 1 mL of 1% ascorbic acid solution were diluted to 25 mL and allowed to stand for 40 minutes. The absorbance was measured at a wavelength of 700 nm and the effective silicon content was calculated based on the standard curve. In the data calculation, the effective silicon increase rate = [(content after application - content before application) / content before application] × 100%.

[0165] Crop yield determination: The experimental field was located in the southern red soil region (initial soil pH 5.2, available silicon 80 mg / kg), and rice variety "Zhongzao 39" was planted. A control group (CK) and a treatment group (T) were set up with three replicates in a randomized block arrangement (plot area 30 m²). The treatment group was fertilized with the coal gangue-based soil conditioner of the present invention, while the control group was not fertilized and other management was the same. When measuring yield, a 1m×1m area was selected from each plot at maturity, and the rice moisture content was measured by manual harvesting and threshing (GB / T 21305-2017). The actual yield was calculated according to the formula: yield (kg / mu) = actual yield of plot × 666.7 / plot area × (1-moisture content) / 14%. The yield increase rate = [(yield of treatment group - yield of control group) / yield of control group] × 100%.

[0166] Table 3 Soil conditioning effect and crop yield

[0167]

[0168] As can be seen from Table 3, the gangue-based soil conditioners of various embodiments of the present invention have excellent soil conditioning capabilities and can significantly increase crop yields.

[0169] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a gangue-based soil conditioner, characterized in that: The following steps are involved: (a) soaking the gangue raw material in an organic acid solution to obtain acid-treated gangue; (b) calcining dolomite and mixing it with quicklime to obtain an alkaline activator; (c) calcining a mixture of the acid-treated gangue, the alkaline activator, and humic acid, wherein the calcination process includes a first calcination and a second calcination, wherein the temperature of the second calcination is higher than the temperature of the first calcination, to obtain a gangue-based soil conditioner; There is no limitation on the order of step (a) and step (b).

2. The method for preparing the gangue-based soil conditioner according to claim 1, wherein: Contains at least one of the following features (1) to (4): (1) The organic acid solution includes a citric acid solution, and the concentration of the organic acid solution is 0.1-0.5 mol / L; (2) The soaking treatment time is 2 to 4 hours; (3) The mass ratio of the coal gangue raw material to the organic acid solution is 1:(5-10); (4) The acid-treated coal gangue has a cadmium content of less than or equal to 5 mg / kg and a silicon dioxide content of greater than or equal to 50%.

3. The method for preparing the gangue-based soil conditioner according to claim 1, wherein: The calcination temperature is 400-500° C., and the calcination time is 1-2 hours.

4. The method for preparing the gangue-based soil conditioner according to claim 1, wherein: The mass ratio of the dolomite to the quicklime is (1-3):

1.

5. The method for preparing the gangue-based soil conditioner according to claim 1, wherein: Contains at least one of the following features (1) to (3): (1) The mass of the acid-treated coal gangue accounts for 70% to 80% of the total mass of the acid-treated coal gangue and the alkaline activator; (2) The humification index HIX of the humic acid is ≥1.8, the ash content is less than or equal to 5%, and the particle size is less than or equal to 0.075 mm; (3) The mass of the humic acid accounts for 1% to 3% of the total mass of the acid-treated coal gangue and the alkaline activator.

6. The method for preparing the gangue-based soil conditioner according to claim 1, wherein: Contains at least one of the following features (1) to (4): (1) The temperature of the first roasting is 600~700℃, and the holding time is 0.5~1h; the temperature of the second roasting is 800~900℃, and the holding time is 1~2h; (2) The atmosphere of the first roasting is a protective gas, and the atmosphere of the second roasting is air; (3) The heating rate of the calcination treatment is 5-12°C / min; (4) Also included: grinding and screening the material after the roasting treatment.

7. The method for preparing the gangue-based soil conditioner according to claim 1, wherein: The gangue raw material is obtained by crushing gangue, and the average particle size of the gangue raw material is 0.5-1 mm.

8. A gangue-based soil conditioner, characterized in that: The invention is prepared by the preparation method of the gangue-based soil conditioner according to any one of claims 1 to 7.

9. The gangue-based soil conditioner according to claim 8, characterized in that: Contains at least one of the following features (1) to (3): (1) The mass content of effective silicon in the gangue-based soil conditioner is greater than or equal to 10%; (2) The specific surface area of ​​the gangue-based soil conditioner is 20~30m 2 / g, pH 8.5~10.5; (3) The average particle size of the gangue-based soil conditioner is 0.5-1 mm.

10. Use of the gangue-based soil conditioner according to claim 8 in soil conditioning, characterized in that: The gangue-based soil conditioner is applied to acidic soil with a pH of ≤6.0, thereby increasing the soil pH by 0.2-1.5; When the application amount is 500~800kg / mu, the crop yield can be increased by 6%~20%.

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