Soil water-retaining slow-release conditioner as well as preparation method and application thereof

Abstract

The invention relates to the technical field of soil water retention, and particularly provides a soil water-retention slow-release conditioner as well as a preparation method and application thereof. The soil water-retaining slow-release conditioner comprises a porous carrier matrix and a composite nutritional agent, pores of the porous carrier matrix are filled with the composite nutritional agent, the porous carrier matrix is of a three-dimensional network structure, and the porous carrier matrix at least comprises modified fly ash, acrylic acid, acrylamide, starch and urea which are crosslinked together. The modified fly ash has an aluminosilicate net structure. The preparation method of the soil water-retaining slow-release conditioner is used for preparing the soil water-retaining slow-release conditioner. The soil water retention slow-release conditioner is used for soil water absorption and soil water retention. According to the soil water-retaining slow-release conditioner as well as the preparation method and the application thereof, the water-retaining property and the water-absorbing property of soil are improved, and the fertilizer-retaining capacity of the soil is improved.

Description

Technical Field

[0001] This disclosure relates to the field of soil water retention technology, and in particular to a soil water retention slow-release conditioner, its preparation method, and its application. Background Technology

[0002] The primary use of coal is for coal-fired power generation, which produces a large amount of fly ash. Fly ash can be added to the soil as a raw material for soil water-retaining and slow-release conditioners, thus realizing the resource utilization of fly ash. After being added to the soil, fly ash can change the soil particle composition, improve soil storability, pH, and aeration, and also help reduce soil bulk density, increase porosity, raise soil temperature, reduce soil swelling rate, and improve soil water retention capacity.

[0003] However, if fly ash is directly added to the soil as a slow-release soil water-retaining conditioner, the water absorption and retention effect is poor for soils with different textures and environmental conditions. Summary of the Invention

[0004] This disclosure is made in view of the above-mentioned problems. This disclosure provides a soil water-retaining slow-release conditioner, its preparation method, and its application, which improves the water retention and water absorption of soil and enhances its fertilizer retention capacity.

[0005] According to a first aspect of this disclosure, a soil water-retaining slow-release conditioner is provided, comprising: a porous carrier matrix and a composite nutrient agent filling the pores of the porous carrier matrix, wherein the porous carrier matrix has a three-dimensional network structure, and the porous carrier matrix comprises at least cross-linked modified fly ash, acrylic acid, acrylamide, starch and second urea, wherein the modified fly ash has an aluminosilicate network structure.

[0006] According to a second aspect of this disclosure, a method for preparing a soil water-retaining slow-release conditioner is provided, for preparing the soil water-retaining slow-release conditioner described in the first aspect, comprising:

[0007] Modified fly ash is obtained by modifying fly ash.

[0008] Modified fly ash was mixed evenly with acrylic acid, acrylamide, urea, starch, initiator and water. Under heating conditions and with the action of the initiator, a polymerization reaction occurred to obtain the first copolymer.

[0009] A crosslinking agent is added to the first copolymer, and polymerization is continued by heating to obtain the soil water-retaining slow-release conditioner.

[0010] According to a third aspect of this disclosure, an application of a soil water-retaining slow-release conditioner in soil water absorption and soil water retention is provided.

[0011] In one or more technical solutions provided in this disclosure, the soil water-retaining slow-release conditioner firstly includes a porous carrier matrix and a composite nutrient agent filled in the pores of the porous carrier matrix, wherein the porous carrier matrix has a three-dimensional network structure. Therefore, on the one hand, the three-dimensional network structure of the porous carrier matrix can provide a large number of pores for the soil water-retaining slow-release conditioner, significantly increasing its water absorption capacity. On the other hand, compared to direct application of the composite nutrient agent, the three-dimensional network structure of the porous carrier matrix can limit the rapid loss of the composite nutrient agent, improving nutrient utilization. Simultaneously, the water-retaining function provides a moist environment for the slow release of the composite nutrient agent, preventing soil drought from interrupting the slow release. The slowly released composite nutrient agent is soluble in water and migrates with the water to the area around the plant roots, achieving simultaneous supply of water and nutrients.

[0012] Secondly, the porous carrier matrix comprises cross-linked modified fly ash, acrylic acid, acrylamide, starch, and urea. Because the modified fly ash has an aluminosilicate network structure, it exposes a large number of Si-OH and Al-OH active sites. When the modified fly ash undergoes a cross-linking reaction with acrylic acid, acrylamide, starch, and urea, these components react with the Si-OH and Al-OH active sites to form polymers. During this process, the modified fly ash forms a rigid framework, synergistically constructing a three-dimensional network structure with other components, thus obtaining the porous carrier matrix. Therefore, when the soil water-retaining slow-release conditioner absorbs water and swells in the soil, the fly ash framework prevents the network structure from collapsing, ensuring the structural stability of the conditioner. Simultaneously, the porous carrier matrix with its three-dimensional network structure limits the rapid loss of urea molecules, improving the utilization rate of urea nutrients and achieving the goal of improving soil water and fertilizer retention.

[0013] It should be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide further illustration of the claimed technology. Attached Figure Description

[0014] The above and other objects, features, and advantages of this disclosure will become more apparent from the more detailed description of the embodiments thereof in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this disclosure and form part of the specification. They are used together with the embodiments of this disclosure to explain the disclosure and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0015] Figure 1 A flowchart illustrating the preparation process of the soil water-retaining slow-release conditioner according to an embodiment of the present disclosure is shown;

[0016] Figure 2 The diagram shows the water absorption rate curve of the soil water-retaining slow-release conditioner according to an embodiment of the present disclosure;

[0017] Figure 3 A water retention rate curve of the soil water-retaining slow-release conditioner according to an embodiment of the present disclosure is shown. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this disclosure more apparent, exemplary embodiments according to this disclosure will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments of this disclosure. It should be understood that this disclosure is not limited to the exemplary embodiments described herein.

[0019] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "multiple" means two or more, unless otherwise expressly specified. "Several" means one or more, unless otherwise expressly specified.

[0020] In the description of this disclosure, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0021] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this disclosure should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0022] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0023] Coal, as an energy resource, is primarily utilized for power generation, but this process produces large amounts of fly ash. Using fly ash as a raw material to prepare slow-release soil conditioners and applying them to the soil is an important way to realize its resource utilization. Studies have shown that fly ash, when applied to the soil, can alter the soil particle composition, loosening compacted clay and enhancing the cohesion of infertile sandy soil. It significantly improves soil arability, pH, and aeration. Simultaneously, fly ash can reduce soil bulk density, increase porosity, raise soil temperature, reduce soil swelling rate, and significantly enhance the soil's water retention capacity, creating a more favorable environment for crop growth.

[0024] However, if unprocessed fly ash is applied directly as a slow-release soil water-retaining conditioner, its water absorption and retention effects often fall short of expectations under different soil types and environmental conditions. In saline-alkali land, fly ash may exacerbate soil salinization; in rainy and humid areas, its water retention capacity is limited, making it difficult to meet the diverse soil improvement needs.

[0025] To address the aforementioned issues, this disclosure provides a soil water-retaining slow-release conditioner, its preparation method, and its application, which improves the water retention and water absorption of soil and enhances its fertilizer retention capacity.

[0026] This disclosure provides a soil water-retaining slow-release conditioner, comprising a porous carrier matrix and a composite nutrient agent filling the pores of the porous carrier matrix. The porous carrier matrix has a three-dimensional network structure. Therefore, on the one hand, the three-dimensional network structure of the porous carrier matrix can provide a large number of pores for the soil water-retaining slow-release conditioner, significantly increasing its water absorption capacity. On the other hand, compared to direct application of the composite nutrient agent, the three-dimensional network structure of the porous carrier matrix can limit the rapid loss of the composite nutrient agent, improving nutrient utilization. Simultaneously, the water-retaining function provides a moist environment for the slow release of the composite nutrient agent, preventing the slow release from being interrupted due to soil drought. The slow-released composite nutrient agent is soluble in water and migrates with the water to the area around the plant roots, achieving simultaneous supply of water and nutrients, thereby improving soil water and fertilizer retention.

[0027] In one feasible example, the aforementioned porous carrier matrix comprises at least cross-linked modified fly ash, acrylic acid, acrylamide, starch, and urea, with the modified fly ash possessing an aluminosilicate network structure. Since the aluminosilicate network structure exposes a large number of Si-OH and Al-OH active sites, when the modified fly ash undergoes a cross-linking reaction with acrylic acid, acrylamide, starch, and urea, these components can react with the Si-OH and Al-OH active sites to generate polymers. During this process, the modified fly ash forms a rigid framework, synergistically constructing a three-dimensional network structure with other components, thus obtaining the porous carrier matrix. Therefore, when the soil water-retaining slow-release conditioner absorbs water and swells in the soil, the fly ash framework prevents the network structure from collapsing, ensuring the structural stability of the soil water-retaining slow-release conditioner and improving soil water retention. Simultaneously, the porous carrier matrix with its three-dimensional network structure can limit the rapid loss of urea molecules, improving the utilization rate of urea nutrients and achieving the goal of improving soil water and fertilizer retention.

[0028] In one example, the aforementioned porous carrier matrix has mesopores and micropores, and the composite nutrient exists simultaneously in both mesopores and micropores through physical adsorption. The hierarchical pore structure of mesopores and micropores provides abundant adsorption sites for the composite nutrient, significantly increasing the loading capacity of the composite nutrient per unit volume. When the soil water-retaining slow-release conditioner comes into contact with water, the water enters the pores of the mesopores and micropores, wetting the composite nutrient adsorbed on the pore walls, causing it to slowly dissolve and migrate and diffuse with the water, achieving simultaneous supply of water and nutrients.

[0029] For example, the mesopores mentioned above have a pore size of 10 nm to 20 nm, and the micropores have a pore size of 0.2 μm to 1 μm. When the composite nutrient is added to the porous carrier matrix, the 10 nm to 20 nm mesopore size facilitates the rapid adsorption of the composite nutrient. When the soil water-retaining slow-release conditioner absorbs water, it ensures that water quickly enters the mesopores of the porous carrier matrix. At the same time, when the soil water-retaining slow-release conditioner comes into contact with water, it can quickly wet the composite nutrient in the mesopores, allowing the composite nutrient in the mesopores to dissolve rapidly in a short period of time, providing the crops with urgently needed nutrients. The 0.2 μm to 1 μm micropore structure has a larger spatial volume, providing a stable storage space for the composite nutrient, preventing its premature loss, and slowly releasing nutrients when soil moisture changes, ensuring a long-term stable nutrient supply during crop growth. Therefore, through the synergistic effect of mesoporous and microporous structures, soil water-retaining slow-release conditioners can have both a high initial water absorption rate and water retention capacity, and achieve a long-term stable nutrient supply, thereby significantly improving nutrient utilization efficiency and soil improvement effects.

[0030] In one example, the water absorption ratio of the soil water-retaining slow-release conditioner of this disclosure in water is (350g~450g) / g. This is equivalent to each gram of soil water-retaining slow-release conditioner absorbing 350 to 450 times its own weight in water. Therefore, it can continuously supply water to plant roots, significantly reducing irrigation frequency and water consumption, and is especially suitable for crop cultivation in arid and semi-arid regions.

[0031] In one example, the water absorption ratio of the soil water-retaining slow-release conditioner of this disclosure in saline solution is (30g~50g) / g. This means that each gram of the soil water-retaining slow-release conditioner can absorb 30 to 50 times its own weight in saline solution. Therefore, on the one hand, the soil water-retaining slow-release conditioner can absorb a large amount of saline solution, diluting the salt concentration in the soil, reducing the damage of sodium ions to the soil aggregate structure, and gradually improving the problems of soil compaction and poor aeration. On the other hand, the absorbed water can be continuously released during dry periods, providing a stable water supply for plants. Combined with the slow-release effect of the compound nutrient, it alleviates the damage of salt to plant roots, improving the emergence rate and yield of crops in saline-alkali land.

[0032] For example, the above-mentioned water absorption rate test method is as follows: a certain amount of dry soil water-retaining slow-release conditioner sample is placed in a microporous mesh bag, sufficient deionized water or saline solution is added, and it is left to stand for a certain period of time. The formula for calculating the water absorption ratio is:

[0033] Water absorption ratio (g / g) = (mass after liquid absorption - mass of soil water-retaining slow-release conditioner) (g) / mass of soil water-retaining slow-release conditioner (g) × 100%, where the mass after liquid absorption is the mass of the soil water-retaining slow-release conditioner after absorbing deionized water or salt water.

[0034] In one feasible embodiment, the soil water-retaining slow-release conditioner of this disclosure, when dried at 50°C, has an initial water release rate of 15.5% to 18.5% and a cumulative water release rate of 68% to 80% during the continuous release phase. The initial phase can be day 1, and the continuous release phase can be day 20.

[0035] For example: Add 1g of soil water-retaining slow-release conditioner to a depth of 5cm in dry soil, then add water until fully absorbed, weigh the soil, and after a certain period of time, allow the soil water-retaining slow-release conditioner to reach water saturation. After saturation, place the soil in a forced-air drying oven at 50℃ to dry, and then calculate the soil water retention performance. The formula for calculating the water retention rate is:

[0036] Water retention rate (g / g) = Soil mass after drying (g) / Soil mass before drying (g) × 100%.

[0037] The soil water-retaining slow-release conditioner of this disclosure has a water release rate of 15.5% to 18.5% in the soil on day 1 and 68% to 80% on day 20. The initial water release rate of 15.5% to 18.5% quickly replenishes the surface soil moisture lost through evaporation, alleviating short-term water shortages in plants. The sustained water release of 68% to 80% over 20 days ensures that the soil maintains suitable humidity for a longer period, providing a stable water source for plant roots. This avoids waste caused by rapid water loss and meets the water requirements of plants throughout their growth cycle, effectively improving plant survival rate and growth quality in drought conditions while reducing the manpower and water consumption associated with frequent irrigation.

[0038] This disclosure also provides a method for preparing a soil water-retaining slow-release conditioner, which can be used to prepare the soil water-retaining slow-release conditioner of this invention. Figure 1 A flowchart illustrating the preparation process of the soil water-retaining slow-release conditioner according to an embodiment of this disclosure is shown, as follows: Figure 1 As shown, the preparation method of the soil water-retaining slow-release conditioner in this embodiment includes:

[0039] Step 101: Modify the fly ash to obtain modified fly ash. It is understood that fly ash comprises quartz, mullite, a glassy phase, and other oxides.

[0040] In one example, the modification of fly ash according to this disclosure specifically includes: first, pre-treating the fly ash by sieving; then, mixing the pre-treated fly ash with an alkaline solution, heating to 50°C–100°C, and maintaining the temperature for 50–70 minutes to obtain modified fly ash.

[0041] Specifically, firstly, the fly ash is ball-milled for 10 minutes. Then, 1-2 portions of the ball-milled fly ash are soaked in a 2 mol / L sodium hydroxide solution, heated to 50℃-100℃, and maintained for 50-70 minutes to obtain modified fly ash. The heating method can be oil bath heating or other feasible heating methods, which are not limited here.

[0042] In practical applications, fly ash particle size can be refined to 10nm-20nm through ball milling, which can significantly increase the specific surface area of ​​fly ash. As a result, during alkaline treatment, sodium hydroxide reacts with the aluminosilicates in the glass phase of fly ash to form an aluminosilicate network structure, which promotes more Si-OH and Al-OH active groups to be exposed from the inside to the surface, providing crosslinking sites for subsequent polymerization reactions.

[0043] In another example, the modification of fly ash according to this disclosure specifically includes: first, pre-treating the fly ash by sieving; then, mixing the pre-treated fly ash with an activator and a flux, and calcining it at a temperature of 500℃ to 800℃ to obtain modified fly ash.

[0044] Specifically, firstly, the fly ash is ball-milled for 10 minutes. Then, the ball-milled fly ash is mixed with an activator and a flux at a ratio of 1:(0.2~1):(0.1~0.5), and calcined at a temperature of 500℃~800℃ to obtain modified fly ash. The calcination operation can be carried out in a muffle furnace or a rotary kiln.

[0045] In practical applications, ball milling can refine fly ash particle size to 10nm–20nm, significantly increasing its specific surface area. During subsequent calcination, fluxes lower the sintering temperature, causing the crystalline phases such as quartz and mullite in the fly ash to decompose into amorphous silica-alumina oxides. Activators react with aluminosilicates in the glassy phase, exposing more Si-OH and Al-OH active groups. Simultaneously, at high temperatures, the escape of gases from the material's interior forms interconnected pores, generating mesoporous pores, further increasing the specific surface area of ​​the fly ash. Therefore, not only can calcination reconstruct the pore network to enhance water retention, but activators can also introduce alkaline sites, enabling the formation of a denser three-dimensional network during subsequent cross-linking reactions.

[0046] It is understood that the ball milling device used in the above-mentioned screening pretreatment of fly ash can be any ball milling device in the prior art, which will not be described in detail here. The above-mentioned activator includes at least one of kaolin, limestone and montmorillonite. The above-mentioned fluxing agent includes at least one of potassium silicate, calcium silicate and potassium sulfate.

[0047] Step 102: Mix the modified fly ash with acrylic acid, acrylamide, urea, starch, initiator and water evenly, and under heating conditions, a polymerization reaction occurs under the action of the initiator to obtain the first copolymer.

[0048] For example, modified fly ash, water, urea, acrylic acid, acrylamide, and starch are added to a three-necked flask in a certain proportion and stirred until homogeneous. Then, an initiator is added, and the mixture is heated and stirred to obtain a first copolymer. The heating method can include oil bath heating or microwave heating, which is not limited here and is selected according to actual needs. The heating temperature is 50℃~70℃. If oil bath heating is used, the heating reaction time is 60min~120min; if microwave heating is used, the heating reaction time is 10min~30min.

[0049] Under heating conditions of 50℃ to 70℃, the initiator decomposes, generating free radicals. These free radicals first attack the carbon-carbon double bonds of acrylic acid and sodium acrylate, causing the double bonds to open and initiating chain polymerization to form the initial segments of polyacrylic acid and sodium polyacrylamide. Simultaneously, the amino groups in urea, through nucleophilic attacks on the double bonds, can nucleophilically add to unreacted double bonds in the acrylic acid and sodium acrylate segments, incorporating them into the polymer chain. Furthermore, the free radicals also attack the hydroxyl groups in starch, initiating graft polymerization of starch with double bonds in other components.

[0050] Building upon this, the carboxyl groups of acrylic acid and sodium acrylate can condense with the amino groups of urea, removing small water molecules and allowing urea to integrate into the chains formed by acrylic acid and sodium acrylate, creating longer free radical polymer chains and enriching the molecular structure. As the reaction proceeds, these longer free radical polymer chains continue to grow, and the active free radicals collide and combine with each other, forming intermolecular cross-linking points. Since the surface of fly ash after ball milling, alkali treatment, or high-temperature calcination is rich in Si-OH and Al-OH active groups, these active groups also chemically bond with the carboxyl and amino groups on the polymer chains, becoming nodes in the cross-linking network. The branches formed by starch grafting intertwine and overlap in space, further enhancing the intermolecular forces. These multiple interactions synergistically promote the gradual interconnection and interweaving of linear polymer chains. During the cross-linking process, mesoporous and microporous pores are arranged in a cross-linked pattern, forming a multi-level interconnected three-dimensional porous network. Furthermore, water in the polymerization system, acting as a solvent, partially evaporates under heating or microwave action, also forming gas-phase channels and generating microporous pores, ultimately forming the first copolymer with a porous network structure.

[0051] Therefore, when this soil water-retaining slow-release conditioner is used in soil, its three-dimensional porous structure allows urea molecules to be adsorbed and embedded within the network pores, restricting the free diffusion of urea and slowing its dissolution and hydrolysis rates, thus achieving long-term slow release. Furthermore, soil moisture can enter the pores, causing the material to absorb water and swell. While maintaining soil moisture, it slowly releases urea through changes in osmotic pressure, meeting the nutrient requirements of crops throughout their growth cycle. In addition, the modified fly ash and starch-reinforced network structure enhances the material's resistance to degradation, ensuring controlled urea release under different soil conditions and reducing nitrogen loss and environmental pollution.

[0052] The initiator described above may include persulfides or peroxides. Persulfides include at least one of potassium persulfate, sodium persulfate, and ammonium persulfate, and peroxides include hydrogen peroxide.

[0053] Step 103: Add a crosslinking agent to the first copolymer and continue heating and polymerization to obtain a soil water-retaining slow-release conditioner.

[0054] For example, firstly, a crosslinking agent is added to the first copolymer, and polymerization is continued by heating to obtain a second copolymer. Then, the second copolymer is dried, pulverized to 90-110 mesh, and a composite nutrient agent is added to obtain a soil water-retaining slow-release conditioner. The second copolymer is the porous carrier matrix described above.

[0055] During the above process, under the conditions of 50℃~70℃, the active groups in the crosslinking agent molecule react with the unreacted monomers or side groups in the first copolymer to form a bridging structure, which tightly connects the rigid skeleton of modified fly ash with the organic polymer chain, thereby increasing the network crosslinking density and constructing a denser three-dimensional network structure. This effectively inhibits the structural collapse during water absorption and swelling, and significantly improves the mechanical strength and water retention stability of the soil water-retaining slow-release conditioner.

[0056] Drying and pulverizing the second copolymer to 90-110 mesh significantly increases the specific surface area of ​​the composite nutrient, allowing it to uniformly fill the mesopores and micropores of the three-dimensional network. This significantly increases the contact area with the porous carrier matrix, thereby enhancing the physical adsorption effect and ensuring that more composite nutrients are uniformly loaded into the mesopores and micropores of the porous carrier matrix. Furthermore, the pulverized particles mix better with soil particles, improving the uniformity of the conditioner's distribution in the soil, enhancing its adaptability to different soil types, and optimizing the water retention, fertilizer retention, and nutrient supply performance of the soil water-retaining slow-release conditioner.

[0057] The crosslinking agent mentioned above may include N,N-methylenebisacrylamide.

[0058] The aforementioned compound nutrients may include humic acid, farmyard manure, agricultural fertilizers rich in nitrogen, phosphorus and potassium, agricultural potassium fertilizers, etc., without any specific restrictions.

[0059] In one feasible embodiment, the mass ratio of the modified fly ash, acrylic acid, acrylamide, urea, starch, water, initiator, crosslinking agent, and composite nutrient is (1-10):(10-45):(5-10):(5-10):(20-30):(100-200):(0.05-0.3):(0.01-0.1):(1-2), preferably (3-7):(20-30):(6-8):(6-8):(25-28):(100-200):(0.5-0.8):(0.05-0.08):(1.2-1.8). Within this mass ratio range, the modified fly ash, acrylic acid, acrylamide, and other components can synergistically construct a high-strength three-dimensional network structure, achieving multiple functions of water retention, slow release, and soil improvement.

[0060] This disclosure also provides an application of a soil water-retaining slow-release conditioner in soil water absorption and retention. It can enable water conservation and increased yields in arid farmland, improve water and salinity in saline-alkali land, and increase vegetation coverage in mine restoration, achieving multiple benefits of water retention, soil improvement, and nutrient release.

[0061] In summary, the soil water-retaining slow-release conditioner, its preparation method, and its application disclosed herein utilize abundant industrial waste fly ash as raw material. It is prepared by combining fly ash with starch, urea, acrylic acid, and other raw materials to create a fly ash soil water-retaining slow-release conditioner. This fully leverages the tetrahedral network structure of silicon-oxygen and aluminum-oxygen in fly ash. After modification, the surface active groups (Si-OH, Al-OH) of fly ash significantly increase, forming a denser three-dimensional network of water-absorbing resin when polymerized with monomers such as acrylic acid and acrylamide. The resulting soil water-retaining slow-release conditioner, through a multi-level porous network loaded with urea and composite nutrients, achieves slow nutrient release. This avoids excessive fertilizer application, improves utilization efficiency, and reduces irrigation frequency and costs. Therefore, it not only reduces production costs through the resource utilization of industrial solid waste, turning waste into treasure, but also significantly improves the comprehensive performance of water retention, fertilizer release, and soil improvement through component optimization and structural design, providing an economical and efficient solution for sustainable agricultural development in arid regions.

[0062] Example 1

[0063] This disclosure provides a method for preparing a soil water-retaining slow-release conditioner, which specifically includes the following steps:

[0064] The first step is to modify fly ash: After ball milling fly ash for 10 minutes, take one part of fly ash and soak it in a 2 mol / L sodium hydroxide solution, heat it to 80°C and keep it for 60 minutes.

[0065] The second step involves adding 20 parts acrylic acid, 10 parts acrylamide, 3 parts urea, 5 parts starch, and 0.2 parts initiator to the above solution. After reacting for 60 minutes, 0.02 parts crosslinking agent are added dropwise and reacted for 120 minutes. After the reaction is completed, the mixture is dried at 70°C for 24 hours, pulverized to 100 mesh, and 2 parts humic acid are added to obtain the fly ash soil water retention slow-release conditioner.

[0066] The water absorption rate and salt water absorption rate of the soil water retention slow-release conditioner were tested according to the standards. Figure 2 A graph showing the water absorption rate of a soil water-retaining slow-release conditioner according to an embodiment of this disclosure is illustrated. Figure 2 As shown, the dry sample of the soil water-retaining slow-release conditioner prepared in Example 1 was placed in a microporous mesh bag, and sufficient deionized water was added. After standing for 10 hours, the water absorption ratio was 405 g / g. During the water absorption process, the water absorption rate in the soil was higher than that of direct water absorption. The dry sample of the soil water-retaining slow-release conditioner prepared in Example 1 was placed in a microporous mesh bag, and sufficient deionized water was added. After standing for 10 hours, the salt water absorption ratio was 32 g / g (not shown in the figure).

[0067] 1g of the soil water-retaining slow-release conditioner obtained in Example 1 was added to dry soil at a depth of 5cm or less. After water was added and the soil was fully absorbed, it was weighed. After 12 hours, the soil reached water saturation. After saturation, the soil was placed in a forced-air drying oven at a temperature of 50°C to test the water retention rate of the soil water-retaining slow-release conditioner. Figure 3 A water retention rate curve of a soil water-retaining slow-release conditioner according to an embodiment of this disclosure is shown. Figure 3 As shown, the water retention rate of the soil water-retaining slow-release conditioner was 81.5% on day 1 and 20% on day 20, meaning that the water release rate was 18.5% on day 1 and 80% on day 20. The blank sample, however, had already released all its water by day 8, indicating that the soil water-retaining slow-release conditioner of this embodiment can significantly extend the soil water retention period.

[0068] Example 2

[0069] The first step is to modify fly ash: After ball milling fly ash for 10 minutes, fly ash is mixed with limestone and potassium silicate at a ratio of 1:0.5:0.2 and then calcined at 650℃ for modification.

[0070] The second step involves adding 5 parts of modified fly ash to 100 parts of water, ultrasonically dispersing the mixture evenly, stirring and heating it, then adding 20 parts of acrylic acid, 5 parts of acrylamide, 5 parts of urea, 10 parts of starch, and 0.2 parts of initiator. After reacting for 120 minutes, 0.015 parts of crosslinking agent are added dropwise and reacted for another 120 minutes. After the reaction is complete, the mixture is dried at 70℃ for 24 hours and then pulverized to 100 mesh to obtain the fly ash soil water-retaining slow-release conditioner.

[0071] Similar to Example 1, the water absorption ratio and salt water absorption ratio of the soil water-retaining slow-release conditioner were tested according to the standard. The water absorption ratio of the soil water-retaining slow-release conditioner was 402 g / g, and the salt water absorption ratio was 48 g / g.

[0072] Similar to Example 1, 1g of the soil water-retaining slow-release conditioner obtained in Example 1 was added to dry soil at a depth of 5cm. After 12 hours, the soil reached water saturation. After saturation, the soil was placed in a forced-air drying oven at a temperature of 50°C. The water release rate of the soil water-retaining slow-release conditioner was measured to be 15.5% on the first day and 68% on the 20th day.

[0073] Example 3

[0074] The first step is to modify fly ash: After ball milling fly ash for 10 minutes, fly ash is mixed with montmorillonite and potassium sulfate at a ratio of 1:05:0.5 and then calcined at 700℃ for modification.

[0075] The second step involves adding 5 parts of modified fly ash to 100 parts of water, ultrasonically dispersing the mixture evenly, microwaving it, adding 20 parts of acrylic acid, 5 parts of acrylamide, 5 parts of urea, 10 parts of starch, and 0.1 parts of initiator, and microwaving the mixture for 20 minutes. Then, 0.015 parts of crosslinking agent are added and the reaction is continued for 10 minutes. After the reaction is complete, the mixture is dried at 80℃, pulverized to 100 mesh, and 2 parts of agricultural fertilizer are added to obtain the fly ash soil moisture-retaining slow-release conditioner.

[0076] Similar to Example 1, the water absorption ratio and salt water absorption ratio of the soil water retention slow-release conditioner were tested according to the standard. The water absorption ratio of the soil water retention slow-release conditioner was 350g / g, and the salt water absorption ratio was 36g / g.

[0077] Similar to Example 1, 1g of the soil water-retaining slow-release conditioner obtained in Example 1 was added to dry soil at a depth of 5cm. After 12 hours, the soil reached water saturation. After saturation, the soil was placed in a forced-air drying oven at a temperature of 50°C. The water release rate of the soil water-retaining slow-release conditioner was measured to be 18.1% on the first day and 75% on the 20th day.

[0078] As can be seen from Examples 1 to 3 above, the water absorption ratio of the soil water-retaining slow-release conditioner of this disclosure is 350g to 405g / g, the water absorption ratio in salt water is 32g / g to 48g / g, and the water release rate after 20 days is 68% to 80%, which verifies the feasibility and process adjustability of the modified fly ash and polymer crosslinking system in the field of water retention and slow release.

[0079] Example 1 modifies fly ash through alkali treatment, increasing the polar groups on the fly ash surface. The resulting soil water-retaining slow-release conditioner has a water absorption ratio of 405 g / g and a water absorption ratio in brine of 32 g / g. Examples 2 and 3 modify fly ash through high-temperature calcination and synergistic flux modification, optimizing the fly ash's pore structure. The interconnected mesopores formed during calcination enhance salt resistance. In Example 2, the introduction of limestone and potassium silicate during calcination resulted in a brine absorption ratio of 48 g / g, a 50% increase compared to alkali treatment.

[0080] In Example 2, the starch content was increased to 10 parts, forming a more flexible network with 5 parts acrylamide. The water release rate on day 20 was 68%, slower than in Example 1 (80%), indicating that increasing the starch content can slow down the water release rate. In Example 3, although the addition of agricultural fertilizer reduced the water absorption ratio to 350 g / g, microwave polymerization shortened the reaction time to 30 minutes, making it suitable for rapid industrial production.

[0081] The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0082] The block diagrams of devices, apparatuses, devices, and systems disclosed herein are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0083] Additionally, as used herein, the “or” used in a list of items beginning with “at least one” indicates a separate list, such that a list of, for example, “at least one of A, B, or C” means A or B or C, or AB or AC or BC, or ABC (i.e., A and B and C). Furthermore, the word “exemplary” does not imply that the described example is preferred or better than other examples.

[0084] It should also be noted that in the systems and methods of this disclosure, the components or steps can be decomposed and / or recombined. These decompositions and / or recombinations should be considered as equivalent solutions to this disclosure.

[0085] Various changes, substitutions, and modifications can be made to the technology described herein without departing from the teachings defined by the appended claims. Furthermore, the scope of the claims of this disclosure is not limited to the specific aspects of the processes, machines, manufactures, events, means, methods, and actions described above. Currently existing or later-developed processes, machines, manufactures, events, means, methods, or actions that perform substantially the same function or achieve substantially the same result as the corresponding aspects described herein can be utilized. Therefore, the appended claims include such processes, machines, manufactures, events, means, methods, or actions within their scope.

[0086] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0087] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A soil water-retaining slow-release conditioner, characterized in that, The invention includes a porous carrier matrix and a composite nutrient agent filling the pores of the porous carrier matrix. The porous carrier matrix has a three-dimensional network structure and includes at least cross-linked modified fly ash, acrylic acid, acrylamide, starch, and urea. The modified fly ash has an aluminosilicate network structure.

2. The soil water-retaining slow-release conditioner according to claim 1, characterized in that, The porous carrier matrix has mesopores and micropores, and the composite nutrient exists simultaneously in the mesopores and micropores by physical adsorption.

3. The soil water-retaining slow-release conditioner according to claim 2, characterized in that, The mesopores have a pore size of 10 nm to 20 nm, and the micropores have a pore size of 0.2 μm to 1 μm.

4. The soil water-retaining slow-release conditioner according to any one of claims 1 to 3, characterized in that, The water absorption ratio of the soil water-retaining slow-release conditioner in water is (350g~450g) / g, and the water absorption ratio of the soil water-retaining slow-release conditioner in salt water is (30g~50g) / g.

5. The soil water-retaining slow-release conditioner according to any one of claims 1 to 3, characterized in that, When the soil water-retaining slow-release conditioner is dried at 50℃, the initial water release rate is 15.5%-18.5%, and the cumulative water release rate in the continuous release phase is 68%-80%.

6. A method for preparing the soil water-retaining slow-release conditioner according to any one of claims 1 to 5, characterized in that, include: Modified fly ash is obtained by modifying fly ash. Modified fly ash was mixed evenly with acrylic acid, acrylamide, urea, starch, initiator and water. Under heating conditions and with the action of the initiator, a polymerization reaction occurred to obtain the first copolymer. A crosslinking agent is added to the first copolymer, and polymerization is continued by heating to obtain the soil water-retaining slow-release conditioner.

7. The method for preparing the soil water-retaining slow-release conditioner according to claim 6, characterized in that, The modification of fly ash to obtain modified fly ash includes: Fly ash is pretreated by screening; The pre-treated fly ash after screening is mixed with an alkaline solution and heated to 50℃~100℃, and kept at that temperature for 50min~70min to obtain modified fly ash.

8. The method for preparing the soil water-retaining slow-release conditioner according to claim 6, characterized in that, The modification of fly ash to obtain modified fly ash includes: Fly ash is pretreated by screening; The pre-treated fly ash after screening is mixed with activator and flux, and then calcined at 500℃~800℃ to obtain modified fly ash.

9. The method for preparing the soil water-retaining slow-release conditioner according to claim 6, characterized in that, The process of adding a crosslinking agent to the first copolymer and continuing to heat and polymerize yields the soil water-retaining slow-release conditioner, comprising: A crosslinking agent is added to the first copolymer, and polymerization is continued by heating to obtain a second copolymer; The second copolymer is dried and pulverized to 90-110 mesh, and then a composite nutrient is added to obtain the soil water retention slow-release conditioner.

10. The method for preparing the soil water-retaining slow-release conditioner according to any one of claims 6 to 9, characterized in that, The mass ratio of the modified fly ash, acrylic acid, acrylamide, urea, starch, water, initiator, crosslinking agent and compound nutrient is (1-10):(10-45):(5-10):(5-10):(20-30):(100-200):(0.05-0.3):(0.01-0.1):(1-2).

11. The application of a soil water-retaining slow-release conditioner according to any one of claims 1 to 5 in soil water absorption and soil water retention.

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