Soil conditioner for water and soil conservation and preparation method thereof

Abstract

The invention belongs to the technical field of soil improvement, and particularly relates to a soil conditioner for water and soil conservation and a preparation method of the soil conditioner. The soil conditioner is prepared from the following raw material components: zwitterionic polymer modified coal gangue, biochar, hydroxyapatite and humic acid, the preparation method of the zwitterionic polymer modified coal gangue comprises the following steps: dispersing coal gangue powder in a functionalized silane coupling agent solution for first reaction to obtain silane modified coal gangue; and putting the silane modified coal gangue into a zwitterionic auto-polymer solution, and carrying out a second reaction to obtain the zwitterionic polymer modified coal gangue. The optimal soil conditioner raw material composition is obtained through multiple times of screening. Due to the addition of the modified coal gangue, the water and fertilizer retention capacity of the soil is remarkably enhanced, a porous structure and hydrophilic groups of the modified coal gangue effectively adsorb and retain a large amount of water and nutrients, nutrient loss is reduced, and the soil fertility is remarkably improved through mutual cooperation of the components.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement technology, and more specifically, relates to a soil conditioner for soil and water conservation and its preparation method. Background Technology

[0002] The middle reaches of the Yellow River are a crucial area where ecological barriers and energy corridors converge, bearing the dual mission of ecological and energy security. With the continued westward shift of coal production, the Yellow River basin has become a core coal production area. Conducting research and demonstration of key technologies to improve soil and water conservation rates in large coal bases in the middle reaches of the Yellow River is an urgent need to ensure ecological security. Scientifically understanding the soil and water loss effects of coal mining subsidence and exploring precise control strategies for soil and water loss in coal mining subsidence areas have become major scientific issues and strategic needs supporting ecological environmental protection and high-quality development in the upper and middle reaches of the Yellow River.

[0003] However, the intensification of coal mining has brought about a series of ecological problems, including soil erosion, land desertification, and surface subsidence, making the region ecologically fragile and difficult to restore. Improving the soil and water conservation rate of large coal bases in the middle reaches of the Yellow River is an urgent need to ensure national ecological security, especially in large-scale coal mining areas such as the Shendong mining area, where traditional treatment technologies cannot effectively address the complex erosion problems.

[0004] Therefore, given the current problems of severe wind erosion and low water retention in sandy areas, it is essential to develop and screen a soil conditioner for soil and water conservation, apply it in the field, explore its effects on ecological restoration and soil and water conservation, and ultimately form a low-cost and easily promoted soil remediation technology system for sandy areas. Summary of the Invention

[0005] The purpose of this invention is to provide a soil conditioner for soil and water conservation and its preparation method, which can improve the soil's ability to retain fertilizer and water, and the product has low cost and can be widely used in the process of soil improvement, windbreak and sand fixation, and soil and water conservation.

[0006] Therefore, the present invention provides the following technical solution.

[0007] One aspect of the present invention provides a soil conditioner for soil and water conservation, the soil conditioner comprising the following raw material components: zwitterionic polymer modified coal gangue, biochar, hydroxyapatite and humic acid. The preparation method of the zwitterionic polymer modified coal gangue includes the following steps: Coal gangue powder was dispersed in a functionalized silane coupling agent solution for a first reaction to obtain silane-modified coal gangue; The silane-modified coal gangue was placed in a zwitterionic self-polymer solution for a second reaction to obtain zwitterionic polymer-modified coal gangue.

[0008] In a preferred embodiment of the present invention, the functionalized silane coupling agent solution is composed of a silane coupling agent, an organic alcohol, and water.

[0009] In a preferred embodiment of the present invention, the zwitterionic self-polymer is formed by polymerizing zwitterionic monomers under the action of an initiator.

[0010] In a preferred embodiment of the present invention, the zwitterionic monomer is selected from one or more of N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethylammonium betaine, 2-methacryloyloxyethyl phosphoric acid choline, 3-[(3-acrylamidopropyl)dimethylammonium]propionate, and 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate.

[0011] In a preferred embodiment of the present invention, the volume ratio of the silane coupling agent, the organic alcohol and water is 1:(1-5):(20-60).

[0012] In a preferred embodiment of the present invention, the silane coupling agent is selected from one or more of aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0013] In a preferred embodiment of the present invention, the organic alcohol is methanol and / or ethanol.

[0014] In a preferred embodiment of the present invention, the first reaction conditions are: temperature 50-70°C, time 4-8 hours.

[0015] In a preferred embodiment of the present invention, the zwitterionic self-polymer solution is prepared by the following method: In an inert atmosphere, zwitterionic monomers are added to water to prepare zwitterionic monomer solutions, and then an initiator is added to react and a zwitterionic self-polymer solution is obtained.

[0016] In a preferred embodiment of the present invention, the inert gas is nitrogen or argon.

[0017] In a preferred embodiment of the present invention, the initiator is an oxidant-reducing initiator, wherein the oxidant includes hydrogen peroxide, sodium persulfate, and potassium persulfate, and the reducing agent is ferrous sulfate and / or sodium sulfite.

[0018] In a preferred embodiment of the present invention, the mass ratio of the zwitterionic monomer to water is 1:(10-30).

[0019] In a preferred embodiment of the present invention, the amount of the initiator added is 0.2% to 0.6% of the mass of the zwitterionic monomer.

[0020] In a preferred embodiment of the present invention, the reaction process is as follows: first reacting at 5-10°C for 1-2 hours, and then heating to 30-50°C and reacting for 1-3 hours.

[0021] In a preferred embodiment of the present invention, the second reaction conditions are: temperature 25-35 °C, time 3-5 hours.

[0022] In a preferred embodiment of the present invention, the soil conditioner comprises, by weight, the following raw material components: 20-40 parts of zwitterionic polymer modified coal gangue, 20-30 parts of biochar, 10-20 parts of hydroxyapatite, and 20-30 parts of humic acid.

[0023] In a preferred embodiment of the present invention, the hydroxyapatite may also be replaced by modified hydroxyapatite.

[0024] In a preferred embodiment of the present invention, the method for preparing the modified hydroxyapatite includes the following steps: Hydroxyapatite was ultrasonically dispersed in an organic alcohol solution, and then N-vinylpyrrolidone and an initiator were added and stirred to react. The temperature was then kept constant, and a crosslinking agent was added and stirring was continued for 1 to 3 hours. After the reaction was completed, the mixture was filtered, and the resulting solid product was washed and dried to obtain modified hydroxyapatite.

[0025] In a preferred embodiment of the present invention, the organic alcohol is ethanol and / or ethylene glycol.

[0026] In a preferred embodiment of the present invention, the volume fraction of the organic alcohol solution is 30-50%.

[0027] In a preferred embodiment of the present invention, the amount of N-vinylpyrrolidone added is 0.5 to 1% of the mass of hydroxyapatite.

[0028] In a preferred embodiment of the present invention, the initiator is ammonium persulfate or potassium persulfate.

[0029] In a preferred embodiment of the present invention, the amount of the initiator added is 0.3 to 0.5% of the mass of N-vinylpyrrolidone.

[0030] In a preferred embodiment of the present invention, the stirring reaction conditions are: temperature 50-100°C, time 2-4 hours.

[0031] In a preferred embodiment of the present invention, the crosslinking agent is selected from any one of catechol, hydroquinone, and resorcinol.

[0032] In a preferred embodiment of the present invention, the amount of crosslinking agent added is 0.1 to 0.3% of the mass of N-vinylpyrrolidone.

[0033] A second aspect of the present invention provides a method for preparing a soil conditioner for soil and water conservation, the method comprising the following steps; S1: According to the formula, add zwitterionic polymer modified coal gangue, biochar, hydroxyapatite and humic acid to the mixer, stir and mix to obtain a mixture; S2: Add binder to the obtained mixture, then granulate it in a granulator, and then dry it to obtain soil conditioner.

[0034] In a preferred embodiment of the present invention, in step S2, the adhesive is polyvinyl alcohol, and the amount of adhesive added is 2% to 4% of the mass of the mixture.

[0035] In a preferred embodiment of the present invention, in step S2, the drying conditions are: temperature 40-45°C.

[0036] A third aspect of the present invention provides the application of the soil conditioner for soil and water conservation as described above in the remediation and improvement of soil in mining areas, wherein the method of application is as follows: The soil conditioner was evenly applied to the surface of the soil in the mining area and then tilled, followed by land leveling.

[0037] In a preferred embodiment of the present invention, the tillage depth is 20-30 cm.

[0038] In a preferred embodiment of the present invention, the application rate of the soil conditioner is 100-300 kg / mu.

[0039] By employing the above technical solution, the present invention has at least the following advantages: The soil conditioner of this invention, through the compounding of multiple components, can greatly improve the fertility of poor soil and effectively increase crop yield and quality. The soil conditioner of this invention improves soil physical and chemical properties, enhances soil cultivability, and increases soil water retention capacity, thus helping to promote plant growth and increase crop yield.

[0040] This invention uses coal gangue, a solid waste generated and discharged during coal mining and beneficiation, as one of the raw materials. Through surface modification, the modified coal gangue is endowed with hydrophilicity and adsorption properties, enabling it to improve the water retention of soil conditioners. This also achieves the resource utilization of waste, solving the problems of treating coal gangue and other wastes and preventing secondary pollution, while reducing treatment costs. Furthermore, other components in the conditioner, such as humus and biochar, are rich in carbon and plant nutrients, possessing abundant pore structure and a large specific surface area. When applied to the soil, they can increase soil fertility and improve soil structure.

[0041] To further improve the performance of the soil conditioner, the present invention can also modify the surface of hydroxyapatite to make its surface rich in hydrophilic groups. Through synergistic effect with modified coal gangue, the water retention of the soil conditioner can be further increased.

[0042] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Attached Figure Description

[0043] Figure 1 The diagram shows the soil column leaching test setup; where a is the soil column setup and b is the water leaching setup. Figure 2 A statistical chart showing corn yields from different experimental sites. Detailed Implementation

[0044] To make the technical means, creative features, achieved objectives, and effects of this invention readily understandable, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0045] The raw materials mentioned in the following examples include: coal gangue sourced from the Bulian Tower waste rock disposal area of ​​the Shendong mining district; humic acid purchased from Shanxi Lefeng Tianrun Biotechnology Co., Ltd.; biochar purchased from Shandong Yuyang Activated Carbon Co., Ltd.; and hydroxyapatite purchased from Shaanxi Lantai Bioengineering Co., Ltd. Unless otherwise specified, all other experimental materials used in the examples are conventional experimental materials in the art and can be purchased through commercial channels.

[0046] Soil samples were collected from the mining spoil heap and reclaimed plantations according to the "Soil Agrochemical Analysis" standard. Sampling was conducted along an "S"-shaped route, using a soil auger to collect topsoil from the 0-20 cm depth (as the nutrient distribution and changes in the top 0-20 cm layer are most obvious and representative). The samples were placed in sealed plastic bags, labeled, and brought back to the laboratory for air-drying in a well-ventilated, cool place. After air-drying, large clods were broken up, and plant roots, dead leaves, animal and plant debris, and stones were removed. The samples were then sieved through a 2 mm sieve and sealed in plastic bags for use in determining basic soil physicochemical properties and in soil improvement-related experiments.

[0047] Example 1: Under a nitrogen atmosphere, N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine was added to water at a mass ratio of 1:20 to prepare an N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine solution. Then, a hydrogen peroxide / ferrous sulfate initiator system (0.4 times the mass of N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine) was added to the solution. The reaction was first carried out at 10°C for 1.5 hours, and then the temperature was raised to 40°C and the reaction was carried out for 2 hours to obtain a zwitterionic self-polymer solution.

[0048] Coal gangue was pulverized and passed through an 80-mesh sieve to obtain coal gangue powder. The obtained coal gangue powder was dispersed in a functionalized silane coupling agent solution (prepared by mixing aminopropyltriethoxysilane, ethanol, and water in a volume ratio of 1:3:40) and stirred at 60°C for 6 hours to obtain silane-modified coal gangue. The obtained silane-modified coal gangue was placed in a zwitterionic self-polymer solution and stirred at 30°C for 4 hours. After the reaction was completed, zwitterionic polymer-modified coal gangue was obtained.

[0049] Weigh the following raw materials in parts by weight: 30 parts zwitterionic polymer-modified coal gangue, 25 parts biochar, 20 parts hydroxyapatite, and 25 parts humic acid. Add the zwitterionic polymer-modified coal gangue, biochar, hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 4% polyvinyl alcohol solution (3% of the mixture's mass) to the obtained mixture, then granulate it in a granulator and dry it at 40°C until the moisture content is 5% to obtain soil conditioner granules with a particle size between 1 and 5 mm.

[0050] Example 2: Under a nitrogen atmosphere, 2-methacryloyloxyethyl phosphocholine was added to water at a mass ratio of 1:30 to prepare a 2-methacryloyloxyethyl phosphocholine solution. Then, a hydrogen peroxide / sodium sulfite initiator system (0.6% of the mass of 2-methacryloyloxyethyl phosphocholine) was added to the solution. The reaction was first carried out at 10°C for 1 hour, and then the temperature was raised to 45°C and the reaction was carried out for 1 hour to obtain a zwitterionic self-polymer solution.

[0051] Coal gangue was pulverized and passed through an 80-mesh sieve to obtain coal gangue powder. The obtained coal gangue powder was dispersed in a functionalized silane coupling agent solution (prepared by mixing 3-aminopropyltriethoxysilane, ethanol, and water in a volume ratio of 1:5:60) and stirred at 50°C for 8 hours to obtain silane-modified coal gangue. The obtained silane-modified coal gangue was placed in a zwitterionic self-polymer solution and stirred at 25°C for 5 hours. After the reaction was completed, zwitterionic polymer-modified coal gangue was obtained.

[0052] Weigh the following raw materials in parts by weight: 20 parts zwitterionic polymer-modified coal gangue, 30 parts biochar, 20 parts hydroxyapatite, and 20 parts humic acid. Add the zwitterionic polymer-modified coal gangue, biochar, hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 3% polyvinyl alcohol solution (4% of the mixture's mass) to the obtained mixture, then granulate it in a granulator and dry it at 40℃ until the moisture content is 5% to obtain soil conditioner granules with a particle size between 1 and 5 mm.

[0053] Example 3: Under a nitrogen atmosphere, 3-[(3-acrylamidopropyl)dimethylammonium]propionate was added to water at a mass ratio of 1:10 to prepare a 3-[(3-acrylamidopropyl)dimethylammonium]propionate solution. Then, a sodium persulfate / ferrous sulfite initiator system (0.2% of the mass of 3-[(3-acrylamidopropyl)dimethylammonium]propionate) was added to the solution. The reaction was first carried out at 10°C for 2 hours, and then the temperature was raised to 30°C and the reaction was carried out for 3 hours to obtain a zwitterionic self-polymer solution.

[0054] Coal gangue was pulverized and passed through an 80-mesh sieve to obtain coal gangue powder. The obtained coal gangue powder was dispersed in a functionalized silane coupling agent solution (prepared by mixing 3-aminopropyltrimethoxysilane, ethanol, and water in a volume ratio of 1:1:20) and stirred at 70°C for 4 hours to obtain silane-modified coal gangue. The obtained silane-modified coal gangue was placed in a zwitterionic self-polymer solution and stirred at 35°C for 3 hours. After the reaction was completed, zwitterionic polymer-modified coal gangue was obtained.

[0055] Weigh the following raw materials in parts by weight: 40 parts zwitterionic polymer-modified coal gangue, 20 parts biochar, 20 parts hydroxyapatite, and 20 parts humic acid. Add the zwitterionic polymer-modified coal gangue, biochar, hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 5% polyvinyl alcohol solution (2% of the mixture's mass) to the obtained mixture, then granulate it in a granulator and dry it at 45℃ until the moisture content is 5% to obtain soil conditioner granules with a particle size between 1 and 5 mm.

[0056] Example 4: Under a nitrogen atmosphere, 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate was added to water at a mass ratio of 1:20 to prepare a 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate solution. Then, a potassium persulfate / sodium sulfite initiator system (0.4 times the mass of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate) was added to the solution. The reaction was first carried out at 10°C for 1.5 hours, and then the temperature was raised to 40°C and the reaction was carried out for 2 hours to obtain a zwitterionic self-polymer solution.

[0057] Coal gangue was pulverized and passed through an 80-mesh sieve to obtain coal gangue powder. The obtained coal gangue powder was dispersed in a functionalized silane coupling agent solution (prepared by mixing N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, ethanol, and water in a volume ratio of 1:3:40) and stirred at 60°C for 6 hours to obtain silane-modified coal gangue. The obtained silane-modified coal gangue was placed in a zwitterionic self-polymer solution and stirred at 30°C for 4 hours. After the reaction was completed, zwitterionic polymer-modified coal gangue was obtained.

[0058] Weigh the following raw materials in parts by weight: 30 parts zwitterionic polymer-modified coal gangue, 25 parts biochar, 20 parts hydroxyapatite, and 25 parts humic acid. Add the zwitterionic polymer-modified coal gangue, biochar, hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 4% polyvinyl alcohol solution (3% of the mixture's mass) to the obtained mixture, then granulate it in a granulator and dry it at 40°C until the moisture content is 5% to obtain soil conditioner granules with a particle size between 1 and 5 mm.

[0059] Example 5: The difference between this embodiment and Embodiment 1 is that modified hydroxyapatite is used instead of hydroxyapatite, specifically: Under a nitrogen atmosphere, N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine was added to water at a mass ratio of 1:20 to prepare an N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine solution. Then, a hydrogen peroxide / ferrous sulfate initiator system (0.4 times the mass of N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine) was added to the solution. The reaction was first carried out at 10°C for 1.5 hours, and then the temperature was raised to 40°C and the reaction was carried out for 2 hours to obtain a zwitterionic self-polymer solution.

[0060] Coal gangue was pulverized and passed through an 80-mesh sieve to obtain coal gangue powder. The obtained coal gangue powder was dispersed in a functionalized silane coupling agent solution (prepared by mixing aminopropyltriethoxysilane, ethanol, and water in a volume ratio of 1:3:40) and stirred at 60°C for 6 hours to obtain silane-modified coal gangue. The obtained silane-modified coal gangue was placed in a zwitterionic self-polymer solution and stirred at 30°C for 4 hours. After the reaction was completed, zwitterionic polymer-modified coal gangue was obtained.

[0061] Hydroxyapatite was ultrasonically dispersed in a 40% ethanol solution. Then, N-vinylpyrrolidone (0.75% of the mass of hydroxyapatite) and ammonium persulfate (0.4% of the mass of N-vinylpyrrolidone) were added and the mixture was stirred at 80°C for 2 hours. Subsequently, while maintaining the temperature, catechol (0.2% of the mass of N-vinylpyrrolidone) was added and the mixture was stirred for another 2 hours. After the reaction was completed, the mixture was filtered, and the resulting solid product was washed and dried to obtain modified hydroxyapatite.

[0062] Weigh the following raw materials in parts by weight: 30 parts zwitterionic polymer-modified coal gangue, 25 parts biochar, 20 parts modified hydroxyapatite, and 25 parts humic acid. Add the zwitterionic polymer-modified coal gangue, biochar, modified hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 4% polyvinyl alcohol solution (3% of the mixture's mass) to the obtained mixture, then granulate it in a granulator and dry it at 40℃ until the moisture content is 5% to obtain soil conditioner granules with a particle size between 1 and 5 mm.

[0063] Example 6: The difference between this embodiment and Embodiment 1 is that modified hydroxyapatite is used instead of hydroxyapatite, specifically: Under a nitrogen atmosphere, N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine was added to water at a mass ratio of 1:20 to prepare an N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine solution. Then, a hydrogen peroxide / ferrous sulfate initiator system (0.4 times the mass of N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine) was added to the solution. The reaction was first carried out at 10°C for 1.5 hours, and then the temperature was raised to 40°C and the reaction was carried out for 2 hours to obtain a zwitterionic self-polymer solution.

[0064] Coal gangue was pulverized and passed through an 80-mesh sieve to obtain coal gangue powder. The obtained coal gangue powder was dispersed in a functionalized silane coupling agent solution (prepared by mixing aminopropyltriethoxysilane, ethanol, and water in a volume ratio of 1:3:40) and stirred at 60°C for 6 hours to obtain silane-modified coal gangue. The obtained silane-modified coal gangue was placed in a zwitterionic self-polymer solution and stirred at 30°C for 4 hours. After the reaction was completed, zwitterionic polymer-modified coal gangue was obtained.

[0065] Hydroxyapatite was ultrasonically dispersed in a 40% ethanol solution. Then, N-vinylpyrrolidone (in an amount equal to the mass of hydroxyapatite) and ammonium persulfate (in an amount of 0.5% of the mass of N-vinylpyrrolidone) were added and the mixture was stirred at 80°C for 2 hours. Subsequently, while maintaining the temperature, hydroquinone (in an amount of 0.3% of the mass of N-vinylpyrrolidone) was added and the mixture was stirred for another 3 hours. After the reaction was completed, the mixture was filtered, and the resulting solid product was washed and dried to obtain modified hydroxyapatite.

[0066] Weigh the following raw materials in parts by weight: 30 parts zwitterionic polymer-modified coal gangue, 25 parts biochar, 20 parts modified hydroxyapatite, and 25 parts humic acid. Add the zwitterionic polymer-modified coal gangue, biochar, modified hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 4% polyvinyl alcohol solution (3% of the mixture's mass) to the obtained mixture, then granulate it in a granulator and dry it at 40℃ until the moisture content is 5% to obtain soil conditioner granules with a particle size between 1 and 5 mm.

[0067] Example 7: The difference between this embodiment and Embodiment 1 is that modified hydroxyapatite is used instead of hydroxyapatite, specifically: Under a nitrogen atmosphere, N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine was added to water at a mass ratio of 1:20 to prepare an N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine solution. Then, a hydrogen peroxide / ferrous sulfate initiator system (0.4 times the mass of N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine) was added to the solution. The reaction was first carried out at 10°C for 1.5 hours, and then the temperature was raised to 40°C and the reaction was carried out for 2 hours to obtain a zwitterionic self-polymer solution.

[0068] Coal gangue was pulverized and passed through an 80-mesh sieve to obtain coal gangue powder. The obtained coal gangue powder was dispersed in a functionalized silane coupling agent solution (prepared by mixing aminopropyltriethoxysilane, ethanol, and water in a volume ratio of 1:3:40) and stirred at 60°C for 6 hours to obtain silane-modified coal gangue. The obtained silane-modified coal gangue was placed in a zwitterionic self-polymer solution and stirred at 30°C for 4 hours. After the reaction was completed, zwitterionic polymer-modified coal gangue was obtained.

[0069] Hydroxyapatite was ultrasonically dispersed in a 40% ethanol solution. Then, N-vinylpyrrolidone (0.5% of the mass of hydroxyapatite) and ammonium persulfate (0.3% of the mass of N-vinylpyrrolidone) were added and the mixture was stirred at 80°C for 2 hours. Subsequently, while maintaining the temperature, resorcinol (0.1% of the mass of N-vinylpyrrolidone) was added and the mixture was stirred for another hour. After the reaction was completed, the mixture was filtered, and the resulting solid product was washed and dried to obtain modified hydroxyapatite.

[0070] Weigh the following raw materials in parts by weight: 30 parts zwitterionic polymer-modified coal gangue, 25 parts biochar, 20 parts modified hydroxyapatite, and 25 parts humic acid. Add the zwitterionic polymer-modified coal gangue, biochar, modified hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 4% polyvinyl alcohol solution (3% of the mixture's mass) to the obtained mixture, then granulate it in a granulator and dry it at 40℃ until the moisture content is 5% to obtain soil conditioner granules with a particle size between 1 and 5 mm.

[0071] Comparative Example 1: The difference between this comparative example and Example 1 is that the coal gangue was only modified with silane, specifically: Coal gangue was crushed and passed through an 80-mesh sieve to obtain coal gangue powder. The obtained coal gangue powder was dispersed in a functionalized silane coupling agent solution (prepared by mixing aminopropyltriethoxysilane, ethanol and water in a volume ratio of 1:3:40) and stirred at 60°C for 6 hours to obtain silane-modified coal gangue.

[0072] Weigh the following raw materials in parts by weight: 30 parts silane-modified coal gangue, 25 parts biochar, 20 parts hydroxyapatite, and 25 parts humic acid. Add the silane-modified coal gangue, biochar, hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 4% polyvinyl alcohol solution (3% of the mixture's mass) to the obtained mixture, then granulate it in a granulator and dry it at 40℃ until the moisture content is 5% to obtain soil conditioner granules with a particle size between 1 and 5 mm.

[0073] Comparative Example 2: The difference between this comparative example and Example 1 is that the coal gangue was only modified with zwitterionic self-polymer, specifically: Under a nitrogen atmosphere, N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine was added to water at a mass ratio of 1:20 to prepare an N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine solution. Then, a hydrogen peroxide / ferrous sulfate initiator system (0.4 times the mass of N-(3-sulfopropyl)-N-methylpropenoxyethyl-N,N-dimethylammonium betaine) was added to the solution. The reaction was first carried out at 10°C for 1.5 hours, and then the temperature was raised to 40°C and the reaction was carried out for 2 hours to obtain a zwitterionic self-polymer solution.

[0074] Coal gangue was crushed and passed through an 80-mesh sieve to obtain coal gangue powder. The obtained coal gangue powder was placed in a zwitterionic self-polymer solution and stirred at 30 °C for 4 hours. After the reaction was completed, zwitterionic polymer-modified coal gangue was obtained.

[0075] Weigh the following raw materials in parts by weight: 30 parts zwitterionic polymer-modified coal gangue, 25 parts biochar, 20 parts hydroxyapatite, and 25 parts humic acid. Add the zwitterionic polymer-modified coal gangue, biochar, hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 4% polyvinyl alcohol solution (3% of the mixture's mass) to the obtained mixture, then granulate it in a granulator and dry it at 40°C until the moisture content is 5% to obtain soil conditioner granules with a particle size between 1 and 5 mm.

[0076] Comparative Example 3: The difference between this comparative example and Example 1 is that the zwitterionic polymer-modified coal gangue is replaced with pure coal gangue, specifically: Weigh the following raw materials in parts by weight: 30 parts coal gangue, 25 parts biochar, 20 parts hydroxyapatite, and 25 parts humic acid. Add the coal gangue, biochar, hydroxyapatite, and humic acid to a mixer and stir to obtain a mixture. Add a 4% polyvinyl alcohol solution (3% of the mixture's mass) to the mixture, then granulate it in a granulator and dry it at 40°C until the moisture content is 5%, obtaining soil conditioner granules with a particle size between 1 and 5 mm.

[0077] Experiment 1: Detection of basic physicochemical properties of different improved soils 1. Soil preparation Soil conditioners from Examples 1-7 and Comparative Examples 1-3 were mixed with original topsoil collected from the mining area at a mass ratio of 1:10 to obtain improved soil. The physicochemical properties of the soils improved by different soil conditioners were then tested.

[0078] 2. Nutrient content in each group of improved soil was tested, and the methods for detecting each component were as follows: Moisture content: drying method; pH value: potentiometric method; Organic matter: potassium dichromate oxidation-titration method; Alkaline nitrogen: alkaline diffusion method; Available phosphorus: combined extraction-colorimetric method; Available potassium: combined extraction-colorimetric method.

[0079] The test results are shown in Table 1.

[0080] Table 1. Nutrient composition analysis of improved soil

[0081] As shown in Table 1, compared with the soil conditioners prepared in Comparative Examples 1-3, the soil conditioners obtained by Examples 1-7 of this invention, when used in mining area soils, resulted in improved soils with higher contents of available phosphorus, available potassium, and other nutrients, and all of them can be used as planting soils. Specifically, compared with the soil conditioners in Examples 1-4 that only used a combination of modified coal gangue and hydroxyapatite, the soil conditioners in Examples 5-7 that used a combination of modified coal gangue and modified hydroxyapatite for soil improvement resulted in improved soils with higher contents of available phosphorus, available potassium, and other nutrients. This indicates that modified hydroxyapatite can further improve the nutrient content of improved soils when used for soil improvement. Compared with Example 1, the coal gangue in the soil conditioner of Comparative Example 1 was only modified with silane and not with zwitterionic self-polymer. The coal gangue in the soil conditioner of Comparative Example 2 was only modified with zwitterionic and not with silane. The coal gangue in the soil conditioner of Comparative Example 3 was not modified. The nutrient content of the improved soil obtained by using these methods all decreased. The degree of decrease was as follows: Comparative Example 3 > Comparative Example 1 > Comparative Example 2. This shows that the modified coal gangue of the present invention, after being modified by a combination of silane coupling agent and zwitterionic self-polymer, can improve the performance of the modified coal gangue. Therefore, when used in soil, it can improve the nutrient content of the improved soil and make it more in line with the technical requirements of soil indicators for greening and planting.

[0082] Experiment 2: Testing the water and fertilizer retention properties of different improved soils refer to Figure 1 The apparatus shown was used to test the water and fertilizer retention properties of different groups of improved soil. Leaching test: The intermittent soil column leaching method was used to conduct infiltration tests on different treatments of soil amendments obtained by Example 1, Example 5 and Comparative Examples 1 to 3 in Experiment 1 to study the water and fertilizer retention mechanisms of different soil amendments and to comprehensively compare and analyze the water and fertilizer retention capacity of soils with different soil amendments.

[0083] (1) Select an acrylic glass tube with a length of 40 cm and an inner diameter of 6 cm. A liquid receiver is connected to the bottom of the glass column, and a triangular bottle is placed below the receiver. The bottom of the glass column is a porous water outlet glass plate, with a 200-mesh filter screen on top. A filter cloth is placed above the filter screen, and a 1 cm thick layer of quartz sand is placed above the filter cloth. Different numbers of improved soil are filled into different soil column tubes and compacted using a compactor to ensure that the soil is evenly distributed in the soil column. During this process, the bulk density of the soil column is the same as or close to that of the natural soil. The compaction surface is roughened to ensure rough contact between the interfaces of each soil layer. A layer of 40-mesh quartz sand with a thickness of about 1 cm is laid on top of the surface soil (to prevent the soil layer from being disturbed when water is added).

[0084] (2) Add 200 mL of distilled water beforehand to make the soil moisture nearly saturated, let it stand for 7 days, then add 200 mL of water to the leaching soil column, watering once every 5 days, for a total of 5 waterings; collect the leaching solution after leaching, and after leaching, take out the surface quartz sand and measure the soil moisture content under different treatments. Take another soil sample for air drying. After the soil is air dried, pass the soil sample through a 2 mm sieve and use it to measure the content of available nitrogen, available phosphorus, available potassium, and organic matter in the soil. The water retention and fertilizer retention performance of each group of soils was comprehensively evaluated based on the soil moisture content and nutrient indicators before and after leaching, among which: Nutrient loss rate = (Nutrient content before leaching - Nutrient content after leaching) / Nutrient content before leaching. The lower the nutrient loss rate, the better the nutrient retention effect. The test results of the water and fertilizer retention capacity of different soil amendments are shown in Table 2.

[0085] Table 2 Improved Soil Water and Fertilizer Retention Performance

[0086] As shown in Table 2, compared with the soil conditioners prepared in Comparative Examples 1-3, the soil conditioners obtained by Examples 1-7 of this invention resulted in significantly higher soil moisture content and significantly lower nutrient loss rates, such as alkali-available nitrogen and available phosphorus, when used in mining areas. Specifically, compared with the soil conditioners in Examples 1-4 that used only a combination of modified coal gangue and hydroxyapatite, the soil conditioners in Examples 5-7 that used both modified coal gangue and modified hydroxyapatite resulted in higher soil moisture content and significantly lower nutrient loss rates, such as alkali-available nitrogen and available phosphorus. This indicates that modified hydroxyapatite can further increase the moisture content of the improved soil and reduce the loss of various nutrients when used in soil improvement. Compared with Example 1, the coal gangue in the soil conditioner of Comparative Example 1 was only modified with silane and not with zwitterionic self-polymer. The coal gangue in the soil conditioner of Comparative Example 2 was only modified with zwitterionic and not with silane. The coal gangue in the soil conditioner of Comparative Example 3 was not modified. The loss of various nutrients in the improved soil obtained by using these methods all increased. The degree of increase was: Comparative Example 3 > Comparative Example 1 > Comparative Example 2. This shows that the modified coal gangue of the present invention, after being modified by a combination of silane coupling agent and zwitterionic self-polymer, can improve the performance of the modified coal gangue, thereby reducing the loss of nutrients such as alkaline nitrogen and available phosphorus in the improved soil when used in soil.

[0087] Experiment 3: The effects of soil conditioners on crops Soil from a spoil heap at an open-pit mine in Northwest China was used as the experimental site. The site was divided into 16 independent plots, each with an area of ​​50 m². 2Soil conditioners prepared in Examples 1, 5, and Comparative Examples 1-3 were applied, with three replicates for each conditioner. A blank control group consisted of one experimental plot. The application rate of the soil conditioner was 200 kg / mu. The application method was as follows: each soil conditioner was evenly spread on the surface of the experimental plot, followed by the application of basal fertilizer (7.5 kg / mu of urea, 22 kg / mu of diammonium phosphate, and 9.2 kg / mu of potassium sulfate). The plot was then tilled to a depth of 20 cm. After tilling, the experimental plot was leveled, and corn (Xianyu 335) was sown 15 days later with a row spacing of 45 cm, a plant spacing of 30 cm, and a sowing depth of 5 cm. The blank control group underwent only tilling and the application of the same amount of basal fertilizer (7.50 kg / mu of urea, 22 kg / mu of diammonium phosphate, and 9.2 kg / mu of potassium sulfate) to a tilling depth of 20 cm. The sowing parameters were the same as for the other experimental plots. Sowing began in mid-May, and the same field management was adopted in each experimental site. After the corn matured, it was harvested uniformly, and the weight of the harvested corn is shown in Table 3.

[0088] Table 3. Weight of maize grown in different soil types

[0089] As shown in Table 3, the application of the soil conditioners from Examples 1, 5, and Comparative Examples 1-3 effectively increased the dry weight of corn grains compared to the blank control group, thereby improving the economic benefits of corn yield per mu. Furthermore, compared to the soil conditioners from Comparative Examples 1-3, Examples 1 and 5 showed higher corn yields and more significant effects, indicating that the modified coal gangue and hydroxyapatite of this invention can improve the performance of the modified soil.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the methods and techniques disclosed above without departing from the scope of the present invention to create equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A soil conditioner for soil and water conservation, characterized in that, The soil conditioner comprises the following raw material components: zwitterionic polymer modified coal gangue, biochar, hydroxyapatite, and humic acid; The preparation method of the zwitterionic polymer modified coal gangue includes the following steps: Coal gangue powder was dispersed in a functionalized silane coupling agent solution for a first reaction to obtain silane-modified coal gangue; The silane-modified coal gangue was placed in a zwitterionic self-polymer solution for a second reaction to obtain zwitterionic polymer-modified coal gangue. The functionalized silane coupling agent solution is composed of a mixture of silane coupling agent, organic alcohol, and water; The zwitterionic self-polymer is formed by the polymerization of zwitterionic monomers under the action of an initiator; The zwitterionic monomer is selected from one or more of N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethylammonium betaine, 2-methacryloyloxyethyl phosphoric acid choline, 3-[(3-acrylamidopropyl)dimethylammonium]propionate, and 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate.

2. The soil conditioner according to claim 1, characterized in that, The volume ratio of the silane coupling agent, organic alcohol, and water is 1:(1-5):(20-60). The silane coupling agent is selected from one or more of aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane; The organic alcohol is methanol and / or ethanol.

3. The soil conditioner according to claim 1, characterized in that, The first reaction conditions are: temperature 50-70℃, time 4-8 hours.

4. The soil conditioner according to claim 1, characterized in that, The zwitterionic self-polymer solution was prepared according to the following method: In an inert atmosphere, zwitterionic monomers are added to water to prepare zwitterionic monomer solutions, and then an initiator is added to react and a zwitterionic self-polymer solution is obtained. The initiator is an oxidant-reducing initiator, wherein the oxidant includes hydrogen peroxide, sodium persulfate, and potassium persulfate, and the reducing agent is ferrous sulfate and / or sodium sulfite.

5. The soil conditioner according to claim 4, characterized in that, The mass ratio of the zwitterionic monomer to water is 1:(10-30). The amount of the initiator added is 0.2% to 0.6% of the mass of the zwitterionic monomer; The reaction process is as follows: first react at 5-10℃ for 1-2 hours, then raise the temperature to 30-50℃ and react for 1-3 hours.

6. The soil conditioner according to claim 1, characterized in that, The second reaction conditions are: temperature 25-35℃, time 3-5 hours.

7. The soil conditioner for soil and water conservation according to any one of claims 1 to 6, characterized in that, The soil conditioner comprises, by weight, the following raw material components: 20-40 parts of zwitterionic polymer modified coal gangue, 20-30 parts of biochar, 10-20 parts of hydroxyapatite, and 20-30 parts of humic acid.

8. The method for preparing a soil conditioner for soil and water conservation according to any one of claims 1 to 7, characterized in that, The preparation method includes the following steps; S1: According to the formula, add zwitterionic polymer modified coal gangue, biochar, hydroxyapatite and humic acid to the mixer, stir and mix to obtain a mixture; S2: Add binder to the obtained mixture, then granulate it in a granulator, and then dry it to obtain soil conditioner.

9. The preparation method according to claim 8, characterized in that, In step S2, the adhesive is polyvinyl alcohol, and the amount of adhesive added is 2% to 4% of the mass of the mixture. The drying conditions are: temperature 40-45℃.

10. The application of the soil conditioner for soil and water conservation according to any one of claims 1 to 7 in the remediation and improvement of soil in mining areas, characterized in that, The method of application is as follows: After the soil conditioner is evenly applied to the surface layer of the soil in the mining area, the soil is tilled and then the land is leveled. The tillage depth is 20–30 cm; The application rate of the soil conditioner is 100-300 kg / mu.

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