Coal gangue-based soil conditioner as well as preparation method and application thereof

Abstract

The invention relates to the technical field of solid waste resource utilization, in particular to a coal gangue-based soil conditioner as well as a preparation method and application thereof. The preparation method of the coal gangue-based soil conditioner comprises the following steps: (a) soaking a coal gangue raw material with an organic acid solution to obtain acid-treated coal gangue; (b) calcining dolomite, and mixing the calcined dolomite with quick lime to obtain an alkaline activator; and (c) a mixed system formed by the acid-treated coal gangue, the alkaline activator and the humic acid is subjected to roasting treatment, the roasting treatment comprises first roasting and second roasting, and the temperature of the second roasting is higher than that of the first roasting. According to the preparation method of the coal gangue-based soil conditioner disclosed by the invention, the physical and chemical properties of the coal gangue-based soil conditioner are favorably improved through coordination of all the raw materials and steps, so that the conditioning effect of the coal gangue-based soil conditioner on soil is improved, and the yield of crops is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization and environmental remediation. Specifically, it relates to a coal gangue-based soil conditioner and its preparation method and application. Background Art

[0002] With the rapid development of industrialization and urbanization, coal mining activities have increased day by day. As a solid waste in the process of coal mining, the discharge of coal gangue has also increased accordingly. Coal gangue is a mixture composed of minerals, rock fragments and fine coal, which is usually stacked in the open air or landfills. It not only occupies a large amount of land resources, but also has a certain impact on the environment and causes pollution. Coal gangue contains a certain amount of harmful substances, such as heavy metal elements and radioactive elements. These substances will be released into the environment under the action of rainwashing and weathering, polluting the soil, water body and air, and posing a threat to the ecosystem and human health. During the stacking process of coal gangue, fine coal gangue particles may be blown up by the wind, forming dust pollution. These dusts will have a negative impact on air quality and increase the risk of respiratory diseases. Large-scale stacking of coal gangue may lead to geological disasters, such as landslides and mudslides. The unstable structure of coal gangue yards is particularly prone to disasters under extreme weather conditions, posing a threat to the surrounding environment and the safety of human settlements.

[0003] In recent years, researchers have begun to explore the potential use of coal gangue as a silicon fertilizer because coal gangue contains a certain amount of soluble silicon (Si), and silicon is considered to have a positive effect on plant growth and environmental remediation. The fertilizers prepared from coal gangue by the existing technology have an unsatisfactory ability to improve the soil and have a limited yield increase effect on crops.

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

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

[0006] An object of the present invention is to provide a preparation method of a coal gangue-based soil conditioner. Through the cooperation of each step, the obtained coal gangue-based soil conditioner has excellent physical and chemical properties, is environmentally friendly and efficient, can improve the soil structure and fertility, promote plant growth and increase the yield of crops.

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

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

[0009] To achieve the above object of the present invention, the following technical solutions are specifically adopted: A preparation method of a coal gangue-based soil conditioner, comprising the following steps: (a) Soaking a coal gangue raw material with an organic acid solution to obtain acid-treated coal gangue.

[0010] (b) Calcining dolomite and then mixing it with quicklime to obtain an alkaline activator.

[0011] (c) Roasting a mixed system formed by the acid-treated coal gangue, the alkaline activator, and humic acid. The roasting treatment includes a first roasting and a second roasting, and the temperature of the second roasting is higher than that of the first roasting, to obtain a coal gangue-based soil conditioner.

[0012] Among them, there is no limitation on the order of steps (a) and (b). In some embodiments, the organic acid solution includes a citric acid solution, and the concentration of the organic acid solution is 0.1 - 0.5 mol / L.

[0013] In some embodiments, the soaking time is 2 - 4 h.

[0014] In some embodiments, the mass ratio of the coal gangue raw material to the organic acid solution is 1:(5 - 10).

[0015] In some embodiments, in the acid-treated coal gangue, the cadmium content is less than or equal to 5 mg / kg, and the silicon dioxide content is greater than or equal to 50%.

[0016] In some embodiments, the temperature of the calcining treatment is 400 - 500 °C, and the time of the calcining treatment is 1 - 2 h.

[0017] In some embodiments, the mass ratio of the dolomite to the quicklime is (1 - 3):1.

[0018] In some embodiments, the mass of the acid-treated coal gangue accounts for 70% - 80% of the total mass of the acid-treated coal gangue and the alkaline activator.

[0019] In some embodiments, 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.

[0020] In some embodiments, the mass of the humic acid accounts for 1% - 3% of the total mass of the acid-treated coal gangue and the alkaline activator.

[0021] In some embodiments, the temperature of the first calcination is 600 - 700 °C, and the heat preservation time is 0.5 - 1 h; the temperature of the second calcination is 800 - 900 °C, and the heat preservation time is 1 - 2 h.

[0022] In some embodiments, the atmosphere of the first calcination is a protective gas, and the atmosphere of the second calcination is air.

[0023] In some embodiments, the heating rate of the calcination treatment is 5 - 12 °C / min.

[0024] In some embodiments, it further includes: grinding and screening the material after the calcination treatment.

[0025] In some embodiments, the coal gangue raw material is obtained by crushing coal gangue, and the average particle size of the coal gangue raw material is 0.5 - 1 mm.

[0026] A coal gangue-based soil conditioner is prepared by the preparation method of the coal gangue-based soil conditioner.

[0027] In some embodiments, the mass content of effective silicon in the coal gangue-based soil conditioner is greater than or equal to 10%.

[0028] In some embodiments, the specific surface area of the coal gangue-based soil conditioner is 20 - 30 m 2 / g, and the pH is 8.5 - 10.5.

[0029] In some embodiments, the average particle size of the coal gangue-based soil conditioner is 0.5 - 1 mm.

[0030] In some embodiments, after the coal gangue-based soil conditioner is applied to acidic soil with pH ≤ 6.0, the soil pH is increased by 0.2 - 1.5.

[0031] In some embodiments, when the application amount is 500 - 800 kg / mu, the crop yield can be increased by 6% - 20%.

[0032] Compared with the prior art, the beneficial effects of the present invention are: (1) The preparation method of the coal gangue-based soil conditioner of the present invention uses an organic acid solution to soak the coal gangue raw material. Through chelation, surface impurities and heavy metals can be removed, and effective components such as silica are retained. At the same time, a porous structure is formed, the specific surface area of the coal gangue raw material is increased, and the reaction activity is improved. The dolomite is calcined, and the decomposition products include magnesium oxide and calcium oxide, which provide a calcium and magnesium source and enhance the subsequent solid-phase reaction activity. Then it is mixed with quicklime to obtain an alkaline activator. Further, the acid-treated coal gangue, the alkaline activator and humic acid are mixed. Humic acid can be used as a binder, which can improve the moldability of the mixture and delay the release of alkaline components. Through the cooperation of each component and the two-stage roasting treatment, the silicate minerals react with the alkaline components (CaO, MgO) to generate calcium magnesium silicate gel, which is beneficial to improving the physical and chemical properties of the coal gangue-based soil conditioner, enhancing the conditioning effect of the coal gangue-based soil conditioner on the soil, significantly improving the stability of soil aggregates, and increasing the crop yield.

[0033] (2) The coal gangue-based soil conditioner of the present invention contains calcium magnesium silicate gel, has a high content of effective silicon, and synchronously supplements soil nutrients; the heavy metal leaching concentration is extremely low, far lower than the risk control standard for agricultural land; this coal gangue-based soil conditioner has excellent soil conditioning ability and is beneficial to increasing crop yield. Specific embodiments

[0034] The following will describe the implementation scheme of the present invention in detail in combination with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0035] According to one aspect of the present invention, the present invention relates to a preparation method of a coal gangue-based soil conditioner, including the following steps: (a) Soak the coal gangue raw material with an organic acid solution to obtain acid-treated coal gangue; (b) Calcine the dolomite and then mix it with quicklime to obtain an alkaline activator; (c) Roast the mixed system formed by the acid-treated coal gangue, the alkaline activator and humic acid. The roasting treatment includes a first roasting and a second roasting, and the temperature of the second roasting is higher than that of the first roasting to obtain a coal gangue-based soil conditioner.

[0036] Among them, there is no limitation on the order of steps (a) and (b). The acid-treated coal gangue can be prepared first, and then the alkaline activator can be prepared; or the alkaline activator can be prepared first, and then the acid-treated coal gangue can be prepared; or they can be prepared simultaneously.

[0037] The preparation method of the coal gangue-based soil conditioner of the present invention uses an organic acid solution to soak the coal gangue raw material with an acid solution. Through chelation, surface impurities and heavy metals can be removed, and effective components such as silicon dioxide are retained. At the same time, a porous structure is formed, the specific surface area of the coal gangue raw material is increased, and the reactivity is improved. The dolomite is calcined, and the decomposition products include magnesium oxide and calcium oxide, providing a calcium and magnesium source and enhancing the subsequent solid-phase reaction activity. Then it is mixed with quicklime to obtain an alkaline activator. Further, the acid-treated coal gangue, the alkaline activator, and humic acid are mixed. Humic acid can be used as a binder, which can improve the formability of the mixture and delay the release of alkaline components. Through the cooperation of each component and two-stage roasting treatment, the silicate minerals react with the alkaline components (CaO, MgO) in a solid-phase reaction to generate calcium magnesium silicate gel, which is beneficial to improving the physical and chemical properties of the coal gangue-based soil conditioner, enhancing the conditioning effect of the coal gangue-based soil conditioner on the soil, significantly improving the stability of soil aggregates, and increasing the crop yield.

[0038] In some embodiments, the organic acid solution includes a citric acid solution, and the concentration of the organic acid solution is 0.1 - 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 time is 2 - 4 h, such as 2 h, 2.5 h, 3 h, 3.5 h, or 4 h, etc. In some embodiments, the mass ratio of the coal 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, etc. The present invention uses citric acid with a suitable concentration and dosage ratio to soak the coal gangue raw material for a suitable time, which is beneficial to increasing the leaching rate of heavy metal ions (such as lead, cadmium, chromium, etc.), reducing the toxicity of the coal gangue, and improving the reactivity of the coal gangue. In addition, citric acid has low corrosion to equipment, mild reaction conditions, and more environmentally friendly subsequent waste liquid treatment. In some embodiments, in the acid-treated coal gangue, the cadmium content is less than or equal to 5 mg / kg, and the silicon dioxide content is greater than or equal to 50%. After being treated with an organic acid, the heavy metal content of the acid-treated coal gangue of the present invention is low, and the silicon dioxide content is high.

[0039] In some embodiments, the temperature of the calcination treatment is 400 - 500 °C, such as 400 °C, 410 °C, 420 °C, 450 °C, 480 °C, 500 °C, etc., and the calcination time is 1 - 2 h, such as 1 h, 1.5 h, or 2 h, etc. The present invention ensures better decomposition of dolomite into magnesium oxide and calcium oxide through suitable calcination treatment conditions.

[0040] In some embodiments, the mass ratio of dolomite to quicklime is (1 to 3):1, such as 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, etc. The dolomite and quicklime of the present invention are combined with a suitable mass ratio, which is more conducive to ensuring the performance of the alkaline activator.

[0041] 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, such as 70%, 71%, 72%, 75%, 78% or 80%, etc., that is, the mass ratio of the two is (7 to 8):(2 to 3).

[0042] In some embodiments, the humification index HIX of the humic acid ≥ 1.8, such as 1.9, 2, 2.1, 2.5, etc., the ash content is less than or equal to 5%, such as 2%, 3%, 4%, 5%, etc.; the particle size is less than or equal to 0.075 mm, and the average particle size is, for example, 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 coal gangue and the alkaline activator, such as 1%, 1.5%, 2%, 2.5% or 3%, etc. The present invention uses a humic acid with a suitable dosage ratio, which is conducive to synergistic cooperation with other components, improving the roasting effect, and enhancing the soil conditioning ability of the soil conditioner.

[0043] In some embodiments, the temperature of the first roasting is 600 to 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 to 1 h, such as 0.5 h, 0.8 h or 1 h, etc.; the temperature of the second roasting is 800 to 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 to 2 h, such as 1 h, 1.5 h or 2 h, etc.; the atmosphere of the first roasting is a protective gas to prevent oxidation; the atmosphere of the second roasting is air to promote mineral activation. In some embodiments, the heating rate of the roasting treatment is 5 to 12 °C / min, such as 5 °C / min, 6 °C / min, 8 °C / min, 10 °C / min or 12 °C / min, etc. The present invention adopts suitable two-stage roasting treatment conditions, which are more conducive to ensuring the roasting effect, improving the physical and chemical properties of the coal gangue soil conditioner, ensuring its excellent soil conditioning ability, and increasing crop yields.

[0044] In some embodiments, the roasted material is ground and screened to obtain a coal gangue-based soil conditioner with a particle size of 0.5 to 1 mm.

[0045] In some embodiments, the coal gangue raw material is obtained by crushing coal gangue, and the average particle size of the coal gangue raw material is 0.5 - 1 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm, etc.

[0046] According to another aspect of the present invention, the present invention also relates to a coal gangue-based soil conditioner, which is prepared by the preparation method of the above-mentioned coal gangue-based soil conditioner.

[0047] The coal gangue-based soil conditioner of the present invention contains calcium magnesium silicate gel, has a high content of available silicon and available calcium and magnesium, and synchronously supplements soil nutrients; the heavy metal leaching concentration is extremely low, far lower than the risk control standard for agricultural land; this coal gangue-based soil conditioner has excellent soil regulation ability and is beneficial to increasing crop yields.

[0048] In some embodiments, the mass content of available silicon in the coal gangue-based soil conditioner is greater than or equal to 10% (proportion of total silicon dioxide), such as 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc.

[0049] In some embodiments, the available calcium and magnesium content calculated as CaO and MgO is greater than or equal to 25%, such as 25%, 30%, 35%, etc.

[0050] In some embodiments, the specific surface area of the coal gangue-based soil conditioner is 20 - 30 m 2 / g, such as 20 m 2 / g, 22 m 2 / g, 25 m 2 / g, 26 m 2 / g, 28 m 2 / g or 30 m 2 / g, etc.; the pH is 8.5 - 10.5, such as 8.5, 9, 9.5, 10, etc.

[0051] In some embodiments, the content of available heavy metals in the coal 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; chromium less than or equal to 0.06 mg / L.

[0052] In some embodiments, the average particle size of the coal gangue-based soil conditioner is 0.5 - 1 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.9 mm, 1 mm, etc.

[0053] In some embodiments, after the coal gangue-based soil conditioner is applied to acidic soil with pH ≤ 6.0, the soil pH is increased by 0.2 - 1.5.

[0054] In some embodiments, the exchangeable aluminum content is reduced by 30% to 50%. Determination of exchangeable aluminum content: Determined by potassium chloride extraction - atomic absorption method.

[0055] In some embodiments, when the application rate is 500 - 800 kg / mu, the crop yield can be increased by 6% - 20%.

[0056] The following is further explained and illustrated in conjunction with specific examples and comparative examples.

[0057] Example 1 A preparation method of a coal gangue - based soil conditioner, comprising the following steps: (a) The average particle size of the coal gangue after crushing is 0.6 mm, and it is soaked with 0.3 mol / L citric acid for 3 h, with a solid - liquid ratio of 1:8, to obtain acid - treated coal gangue.

[0058] (b) The dolomite is calcined at 450 °C for 1.5 h, and then an alkaline activator is prepared by mixing it with quicklime at a mass ratio of 2:1.

[0059] (c) The acid - treated coal gangue and the alkaline activator are mixed at a mass ratio of 7.5:2.5, and 2% of humic acid (HIX = 2.3, ash content is 2.5%, average particle size is 0.068 mm) is added to obtain a mixed system.

[0060] (d) The mixed system is subjected to roasting treatment: the temperature of the first roasting is 650 °C, the holding time is 0.75 h, in a nitrogen atmosphere; the temperature of the second roasting is 850 °C, the holding time is 1.5 h, in an air atmosphere, to obtain the coal gangue - based soil conditioner.

[0061] Example 2 A preparation method of a coal gangue - based soil conditioner, comprising the following steps: (a) The average particle size of the coal gangue after crushing is 0.8 mm, and it is soaked with 0.2 mol / L citric acid for 4 h, with a solid - liquid ratio of 1:6, to obtain acid - treated coal gangue.

[0062] (b) The dolomite is calcined at 480 °C for 1 h, and then an alkaline activator is prepared by mixing it with quicklime at a mass ratio of 2.5:1.

[0063] (c) The acid - treated coal gangue and the alkaline activator are mixed at a mass ratio of 7:3, and 1.5% of humic acid (HIX = 2.3, ash content is 2.5%, average particle size is 0.068 mm) is added to obtain a mixed system.

[0064] (d) Calcinate the mixed system: The temperature of the first calcination is 680 °C, the heat preservation time is 1 h, and the nitrogen atmosphere is used; the temperature of the second calcination is 820 °C, the heat preservation time is 2 h, and the air atmosphere is used to obtain the coal gangue-based soil conditioner.

[0065] Example 3 A preparation method of a coal gangue-based soil conditioner includes the following steps: (a) The average particle size of the coal gangue after crushing is 0.5 mm. Soak it with 0.4 mol / L citric acid for 2.5 h, and the solid-liquid ratio is 1:10 to obtain acid-treated coal gangue.

[0066] (b) Calcinate dolomite at 420 °C for 2 h, and then mix it with quicklime according to a mass ratio of 1.8:1 to form an alkaline activator.

[0067] (c) Mix the acid-treated coal gangue and the alkaline activator according to a mass ratio of 8:2, and add 3% of humic acid (HIX = 2.3, ash content is 2.5%, average particle size is 0.068 mm) to obtain a mixed system.

[0068] (d) Calcinate the mixed system: The temperature of the first calcination is 700 °C, the heat preservation time is 0.5 h, and the nitrogen atmosphere is used; the temperature of the second calcination is 880 °C, the heat preservation time is 1.25 h, and the air atmosphere is used to obtain the coal gangue-based soil conditioner.

[0069] Example 4 A preparation method of a coal gangue-based soil conditioner includes the following steps: (a) The average particle size of the coal gangue after crushing is 1.0 mm. Soak it with 0.25 mol / L citric acid for 3.5 h, and the solid-liquid ratio is 1:7 to obtain acid-treated coal gangue.

[0070] (b) Calcinate dolomite at 500 °C for 1.25 h, and then mix it with quicklime according to a mass ratio of 3:1 to form an alkaline activator.

[0071] (c) Mix the acid-treated coal gangue and the alkaline activator according to a mass ratio of 7.2:2.8, and add 2.2% of humic acid (HIX = 2.3, ash content is 2.5%, average particle size is 0.068 mm) to obtain a mixed system.

[0072] (d) Calcinate the mixed system: The temperature of the first calcination is 620 °C, the heat preservation time is 1 h, and the nitrogen atmosphere is used; the temperature of the second calcination is 800 °C, the heat preservation time is 1.75 h, and the air atmosphere is used to obtain the coal gangue-based soil conditioner.

[0073] Example 5 A preparation method of a coal gangue-based soil conditioner, comprising the following steps: (a) The average particle size of the coal gangue after crushing is 0.7 mm, and it is soaked with 0.35 mol / L citric acid for 2 h, with a solid-liquid ratio of 1:9, to obtain acid-treated coal gangue.

[0074] (b) The dolomite is calcined at 460 °C for 1.8 h, and then an alkaline activator is prepared by mixing it with quicklime at a mass ratio of 2.2:1.

[0075] (c) The acid-treated coal gangue and the alkaline activator are mixed at a mass ratio of 7.8:2.2, and 1.8% humic acid (HIX = 2.3, ash content is 2.5%, average particle size is 0.068 mm) is added to obtain a mixed system.

[0076] (d) The mixed system is subjected to roasting treatment: the temperature of the first roasting is 630 °C, the holding time is 0.8 h, in a nitrogen atmosphere; the temperature of the second roasting is 860 °C, the holding time is 1.2 h, in an air atmosphere, to obtain the coal gangue-based soil conditioner.

[0077] Example 6 A preparation method of a coal gangue-based soil conditioner, comprising the following steps: (a) The average particle size of the coal gangue after crushing is 0.9 mm, and it is soaked with 0.45 mol / L citric acid for 4 h, with a solid-liquid ratio of 1:5, to obtain acid-treated coal gangue.

[0078] (b) The dolomite is calcined at 440 °C for 1.6 h, and then an alkaline activator is prepared by mixing it with quicklime at a mass ratio of 2.8:1.

[0079] (c) The acid-treated coal gangue and the alkaline activator are mixed at a mass ratio of 7.3:2.7, and 2.5% humic acid (HIX = 2.3, ash content is 2.5%, average particle size is 0.068 mm) is added to obtain a mixed system.

[0080] (d) The mixed system is subjected to roasting treatment: the temperature of the first roasting is 670 °C, the holding time is 0.6 h, in a nitrogen atmosphere; the temperature of the second roasting is 830 °C, the holding time is 1.6 h, in an air atmosphere, to obtain the coal gangue-based soil conditioner.

[0081] Example 7 A preparation method of a coal gangue-based soil conditioner, comprising the following steps: (a) The average particle size of the coal gangue after crushing is 0.55 mm, and it is soaked with 0.15 mol / L citric acid for 3.2 h, with a solid-liquid ratio of 1:8, to obtain acid-treated coal gangue.

[0082] (b) Calcinate dolomite at 490 °C for 1.4 h, and then prepare an alkaline activator by mixing it with quicklime at a mass ratio of 2.4:1.

[0083] (c) Mix the acid-treated coal gangue and the alkaline activator at a mass ratio of 7.6:2.4, and add 2.8% of humic acid (HIX = 2.3, ash content is 2.5%, average particle size is 0.068 mm) to obtain a mixed system.

[0084] (d) Roast the mixed system: The temperature of the first roasting is 690 °C, the holding time is 0.9 h, in a nitrogen atmosphere; the temperature of the second roasting is 810 °C, the holding time is 1.8 h, in an air atmosphere, to obtain a coal gangue-based soil conditioner.

[0085] Example 8 A preparation method of a coal gangue-based soil conditioner, comprising the following steps: (a) The average particle size of the coal gangue after crushing is 0.65 mm. Soak it with 0.5 mol / L citric acid for 2.8 h, and the solid-liquid ratio is 1:6 to obtain acid-treated coal gangue.

[0086] (b) Calcinate dolomite at 430 °C for 1.7 h, and then prepare an alkaline activator by mixing it with quicklime at a mass ratio of 1.5:1.

[0087] (c) Mix the acid-treated coal gangue and the alkaline activator at a mass ratio of 8:2, and add 1.2% of humic acid (HIX = 2.3, ash content is 2.5%, average particle size is 0.068 mm) to obtain a mixed system.

[0088] (d) Roast the mixed system: The temperature of the first roasting is 640 °C, the holding time is 1.1 h, in a nitrogen atmosphere; the temperature of the second roasting is 870 °C, the holding time is 1.3 h, in an air atmosphere, to obtain a coal gangue-based soil conditioner.

[0089] Example 9 A preparation method of a coal gangue-based soil conditioner, comprising the following steps: (a) The average particle size of the coal gangue after crushing is 0.75 mm. Soak it with 0.18 mol / L citric acid for 3.8 h, and the solid-liquid ratio is 1:9 to obtain acid-treated coal gangue.

[0090] (b) Calcinate dolomite at 470 °C for 1.3 h, and then prepare an alkaline activator by mixing it with quicklime at a mass ratio of 2.6:1.

[0091] (c)Mix the acid-treated coal gangue and the alkaline activator in a mass ratio of 7.4:2.6, and add 2.6% of humic acid (HIX = 2.3, ash content is 2.5%, average particle size is 0.068 mm) to obtain a mixed system.

[0092] (d)Roast the mixed system: the temperature of the first roasting is 660 °C, the heat preservation time is 0.7 h, in a nitrogen atmosphere; the temperature of the second roasting is 840 °C, the heat preservation time is 1.4 h, in an air atmosphere, to obtain a coal gangue-based soil conditioner.

[0093] Example 10 A preparation method of a coal gangue-based soil conditioner includes the following steps: (a)The average particle size of the coal gangue after crushing is 0.85 mm. Soak it with 0.22 mol / L sulfuric acid for 2.2 h, and the solid-liquid ratio is 1:7 to obtain acid-treated coal gangue.

[0094] (b)Calcine dolomite at 410 °C for 1.9 h, and then mix it with quicklime in a mass ratio of 3:1 to form an alkaline activator.

[0095] (c)Mix the acid-treated coal gangue and the alkaline activator in a mass ratio of 7.7:2.3, and add 1.5% of humic acid (HIX = 1.9, average particle size is 0.07 mm) to obtain a mixed system.

[0096] (d)Roast the mixed system: the temperature of the first roasting is 710 °C, the heat preservation time is 0.85 h, in a nitrogen atmosphere; the temperature of the second roasting is 890 °C, the heat preservation time is 1.15 h, in an air atmosphere, to obtain a coal gangue-based soil conditioner.

[0097] Comparative Example 1 A preparation method of a coal gangue-based soil conditioner includes the following steps: (a)The average particle size of the coal gangue after crushing is 1.2 mm.

[0098] (b)Calcine dolomite at 300 °C for 0.5 h, and then mix it with quicklime in a mass ratio of 1:4.

[0099] (c)Mix the coal gangue in step (a) and the mixture in step (b) in a mass ratio of 6:4 to obtain a mixed system.

[0100] (d)Roast the mixed system: the temperature is 750 °C, the heat preservation time is 3 h, in a nitrogen atmosphere, to obtain a coal gangue-based soil conditioner.

[0101] Comparative Example 2 A preparation method of a coal gangue-based soil conditioner includes the following steps: (a) The average particle size of the coal gangue after crushing is 0.3 mm. It is soaked with 0.3 mol / L sulfuric acid for 3 h, and the solid-liquid ratio is 1:8 to obtain acid-treated coal gangue.

[0102] (b) The dolomite is calcined at 600 °C for 3 h, and then an alkaline activator is prepared by mixing it with quicklime at a mass ratio of 4:1.

[0103] (c) The acid-treated coal gangue and the alkaline activator are mixed at a mass ratio of 5:5, and 5% of a common binder is added to obtain a mixed system.

[0104] (d) The mixed system is subjected to roasting treatment: the temperature of the first roasting is 550 °C, the holding time is 0.75 h, and the nitrogen atmosphere; the temperature of the second roasting is 950 °C, the holding time is 1.5 h, and the air atmosphere to obtain a coal gangue-based soil conditioner.

[0105] Comparative Example 3 A preparation method of a coal gangue-based soil conditioner, which is different from Example 10 in that: In step (a), no acid soaking treatment is carried out.

[0106] Comparative Example 4 A preparation method of a coal gangue-based soil conditioner, which is different from Example 10 in that: In step (b), the dolomite is not calcined.

[0107] Comparative Example 5 A preparation method of a coal gangue-based soil conditioner, which is different from Example 10 in that: In step (c), no humic acid is added.

[0108] Comparative Example 6 A preparation method of a coal gangue-based soil conditioner, which is different from Example 10 in that: In step (d), single-stage roasting is adopted, the temperature is 750 °C, the holding time is 3 h, and the nitrogen atmosphere.

[0109] Experimental Example I. Performance test of the coal gangue-based soil conditioner The coal gangue-based soil conditioners of each example and comparative example are subjected to performance tests, including: pH, specific surface area, effective silicon content, and the influence on the available state content of the soil.

[0110] pH determination: Tested according to GB / T 18882-2017.

[0111] Determination of effective silicon content: Determined by sodium carbonate melting-molybdenum blue colorimetry.

[0112] Heavy metal leaching concentration: Tested according to GB / T 30810-2014.

[0113] Specific surface area: Determined by BET method.

[0114] The test results are shown in Table 1 and Table 2.

[0115] Table 1 Performance test results of coal gangue-based soil conditioner

[0116] Table 2 Available heavy metal content (mg / L) of coal gangue-based soil conditioner

[0117] As can be seen from Table 1 and Table 2, the coal gangue-based soil conditioner of the present invention has an appropriate pH, specific surface area, low leachable heavy metal content, and high available silicon content.

[0118] II. Soil conditioning effect and crop yield The coal gangue-based soil conditioners of each example and comparative example were applied to soil conditioning, and the specific effects are shown in Table 3.

[0119] Soil pH determination: Tested according to NY / T 1121.2-2006.

[0120] Determination of soil available silicon content: Samples were collected by the "S" -shaped sampling method at 0-20 cm plough layer of the test field before applying silicon fertilizer and after harvest, and 10 soil samples were collected and mixed, air-dried and passed through a 2 mm sieve for standby; The available silicon was extracted by the citrate-disodium hydrogen phosphate buffer solution extraction method (refer to NY / T 1121.15-2006): Weigh 5.00 g of air-dried soil sample into a 150 mL triangular flask, add 50 mL of citrate buffer solution with pH 4.0 (0.025 mol / L citric acid + 0.05 mol / L disodium hydrogen phosphate), oscillate at a constant temperature (25 °C, 200 rpm) for 5 h, then centrifuge (4000 rpm, 10 min) and filter. The silicon content in the filtrate was determined by the molybdenum blue colorimetric method: Take 5 mL of the filtrate and add 5 mL of 10% ammonium molybdate solution (pH 1.8), let it stand for 10 min, then add 1 mL of 20% tartaric acid solution and 1 mL of 1% ascorbic acid solution in sequence, make up the volume to 25 mL and let it stand for 40 min, measure the absorbance at a wavelength of 700 nm and calculate the available silicon content according to the standard curve. In data calculation, the available silicon increase rate = [(content after application - content before application) / content before application] × 100%.

[0121] Crop Yield Measurement: The experimental field is located in the southern red soil area (initial soil pH 5.2, available silicon 80 mg / kg). The rice variety "Zhongzao 39" is planted. Three replicates of the control group (CK) and the treatment group (T) are arranged in a randomized block design (plot area 30 m²). The treatment group is applied with the coal gangue-based soil conditioner of the present invention, while the control group is not fertilized and other management measures are the same. During yield measurement, a 1 m × 1 m area is selected from each plot at maturity for manual harvesting and threshing, and the moisture content of paddy is measured (GB / T 21305-2017). The actual yield is calculated according to the formula: yield (kg / mu) = actual yield of the plot × 666.7 / plot area × (1 - moisture content) / 14%. The yield increase rate = [(yield of the treatment group - yield of the control group) / yield of the control group] × 100%.

[0122] Table 3 Soil Conditioning Effect and Crop Yield

[0123] As can be seen from Table 3, the coal gangue-based soil conditioners of the embodiments of the present invention have excellent soil conditioning ability and can significantly increase the crop yield.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent substitutions on some or all of the technical features; and these modifications or substitutions 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 preparation method of a coal gangue-based soil conditioner, characterized in that, It includes the following steps: (a)Soak the coal gangue raw material with an organic acid solution to obtain acid-treated coal gangue; (b)Calcine dolomite and then mix it with quicklime to obtain an alkaline activator; (c)Roast the mixed system formed by the acid-treated coal gangue, the alkaline activator and humic acid. The roasting treatment includes a first roasting and a second roasting, and the temperature of the second roasting is higher than that of the first roasting, to obtain a coal gangue-based soil conditioner; Among them, there is no limitation on the sequence of steps (a) and (b).

2. The preparation method of the coal gangue-based soil conditioner according to claim 1, characterized in that It includes 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 0.1~0.5mol / L; (2)The soaking time is 2~4h; (3)The mass ratio of the coal gangue raw material to the organic acid solution is 1:(5~10); (4)In the acid-treated coal gangue, the cadmium content is less than or equal to 5mg / kg, and the silica content is greater than or equal to 50%.

3. The preparation method of the coal gangue-based soil conditioner according to claim 1, characterized in that, The temperature of the calcination treatment is 400~500°C, and the time of the calcination treatment is 1~2h.

4. The preparation method of the coal gangue-based soil conditioner according to claim 1, characterized in that, The mass ratio of the dolomite to the quicklime is (1~3):

1.

5. The preparation method of the coal gangue-based soil conditioner according to claim 1, characterized in that It includes at least one of the following features (1) to (3): (1)The mass of the acid-treated coal gangue accounts for 70%~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 0.075mm; (3)The mass of the humic acid accounts for 1%~3% of the total mass of the acid-treated coal gangue and the alkaline activator.

6. The preparation method of the coal gangue-based soil conditioner according to claim 1, characterized in that, It includes at least one of the following features (1) to (4): (1)The temperature of the first roasting is 600~700°C, and the holding time is 0.5~1h; the temperature of the second roasting is 800~900°C, 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 roasting treatment is 5~12°C / min; (4)It also includes: grinding and screening the material after the roasting treatment.

7. The preparation method of the coal gangue-based soil conditioner according to claim 1, characterized in that, The coal gangue raw material is obtained by crushing coal gangue, and the average particle size of the coal gangue raw material is 0.5~1mm.

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

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

10. Use of the coal gangue-based soil conditioner according to claim 7 or 8 in soil conditioning, characterized in that, After the coal gangue-based soil conditioner is applied to acidic soil with pH≤6.0, the soil pH is increased by 0.2~1.5; When the application rate is 500~800kg / mu, the crop yield can be increased by 6%~20%.

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