Nano-modified water-retention soil-fixation material and preparation method thereof

Abstract

The invention discloses a nano-modified water-retaining and soil-fixing material and a preparation method thereof, and belongs to the technical field of soil improvement and ecological restoration. The material is specially designed for karst vegetation recovery, and is composed of a composite water retention matrix and a starch-based biodegradable carrier. Wherein the composite water-retaining substrate comprises 12-18 parts of nano silicon-based water-retaining agent powder, 7-9 parts of sodium bentonite and the like, and the carrier can be selected from a plant-growing bag or bulk particles with the particle size of 1-3mm. The preparation process sequentially comprises the key steps of pre-polymerization and polymerization of the nano silicon-based water-retaining agent, preparation of temperature-sensitive water-retaining matrix dispersion liquid and the like, after parameter optimization, the water-retaining rate of the material is not lower than 300%, the 24-hour soil fixation rate reaches 85% or above, the material can intelligently respond to the day and night temperature difference to adjust water release, soil crust and leakage loss are reduced, and the water-retaining effect is good. And the method has good compatibility and construction operability with vegetation bags, slow release fertilizers and the like, and can effectively solve the key problems of difficult water retention and poor soil fixation performance of karst mountainous regions.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of karst ecological restoration and soil improvement, and particularly relates to a nano-modified water-retaining and soil-fixing material and a preparation method thereof. BACKGROUND

[0002] The karst region in southwest China is one of the typical ecologically fragile belts in China. The unique karst geological structure and hydrological process of the region lead to the fact that the vegetation restoration in the region is in a core challenge position in the field of ecological restoration. The rock mass in the region is mainly soluble carbonate rock, and under the long-term corrosion, a large number of cracks, karst caves and complex underground river systems are formed, which causes the surface soil to be generally shallow and broken - the soil thickness is mostly less than 20 cm, and the bedrock of some steep slopes is completely exposed. The soil clay content is often higher than 35%, and the pore structure is dominated by macropores, which makes it difficult for water to stay on the ground after precipitation, and the water usually rapidly infiltrates into the underground river along the rock cracks within 48 hours, thus forming a significant hydrological dual structure of “surface drought and underground water abundance”.

[0003] Investigation data shows that the soil moisture content in the karst region in southwest China is less than 12% all the year round, and further decreases to less than 5% in the dry season; the soil moisture maintenance time after a single rainfall is generally less than 3 days, which causes the proportion of plants that wither and die due to continuous water stress to be more than 60%. At the same time, the slope of the region is mostly more than 35°, the soil has poor erosion resistance, the surface runoff rate can reach 0.8-1.2 m / s in the rainy season, which easily causes surface soil erosion and aggravates the development of stone desertification, and seriously restricts the process of vegetation restoration and overall reconstruction of the ecological system.

[0004] The water-retaining and soil-fixing materials currently used for karst vegetation restoration still have obvious deficiencies in dealing with the special environment of the karst region, and the technical bottlenecks mainly exist in the following three aspects:

[0005] Firstly, the water-retaining and water-locking performance is insufficient, and it is difficult to effectively block the rapid infiltration of water. The traditional polyacrylamide water-retaining agent can achieve a water retention rate of 450 times of its own weight in a laboratory environment, but in the actual application of karst mountains, the high molecular chain is easily oxidized and degraded due to the influence of strong ultraviolet rays, large diurnal temperature difference and soil macropores, which causes the material structure to be brittle, the actual water retention rate is significantly attenuated to 200-300 times, and the effective action can only be maintained for 1-2 months. More importantly, this kind of material cannot effectively seal the cracks in the karst soil, and when a single rainfall of 10 mm is encountered, the water loss within 48 hours can account for more than 65% of the total water retention, which is difficult to provide sustained and stable water supply for the growth of karst vegetation.

[0006] Second, the soil fixation and anti-erosion performance is weak, and the environmental adaptability is insufficient. The ordinary clay-based water-retaining material mainly relies on the physical adsorption of clay to achieve passive water storage, and lacks effective bonding synergy with karst soil. Its 24h soil fixation rate is usually only 68-75%, and under the scouring of surface runoff in the rainy season, such materials are easily lost with water and soil cracks, causing the plant root system to be exposed, and the survival rate is generally only 30-40%. In addition, the clay-based material is prone to hardening after long-term use, forming a low-porosity dense layer, and the porosity can be reduced to below 15%, which not only hinders the growth of plant roots, but also aggravates the structural degradation of karst soil.

[0007] Third, the compatibility with vegetation restoration supporting technology is poor, and the integrated application effect is limited. In the widely used vegetation bag technology in the current karst vegetation restoration, the interface bonding force between the traditional bag material and the water-retaining agent is weak, and after filling, it is easy to separate under the action of gravity, resulting in a soil loss rate of more than 40% in the bag. When used with slow-release fertilizer, the existing water-retaining material accelerates the early release of nitrogen, phosphorus and other nutrients, causing root burning of plants, or failing to achieve simultaneous release of water and fertilizer during dry periods, resulting in a fertilizer nutrient utilization rate of only 22-28%, which is difficult to support the nutrient needs of karst plants throughout their growth period.

[0008] Even in related patent technologies, such as CN116375401B, attempts are made to enhance the soil fixation performance of construction waste materials, but the porous framework structure constructed by it actually exacerbates the rapid leakage of water. Although the water retention rate of this material can reach 400-450 times under laboratory conditions, it fails to effectively match the water release pattern with the plant water demand cycle. Especially during the day in karst mountainous areas, when the temperature is high and the plant water demand is high, water stress phenomena such as wilting of plant leaves still frequently occur, indicating that there is still a significant deficiency in the water retention-water supply coordination mechanism of the material in the actual habitat.

[0009] In summary, the existing water-retaining materials still have obvious defects in water retention and locking, soil fixation and anti-erosion ability, compatibility with supporting measures, and adaptability to karst special habitats, making it difficult to create a stable soil moisture environment for karst vegetation restoration. Therefore, the development of a new material that has excellent water retention and long-term effectiveness, outstanding soil fixation and anti-erosion performance, and can efficiently cooperate with vegetation restoration technologies such as vegetation bags and slow-release fertilizers, has become a key requirement for breaking through the technical bottleneck of karst vegetation restoration and promoting regional ecological governance.

[0010] It should be noted that the disclosure of the above background technology is only for the purpose of helping to understand the inventive concept and the technical problems addressed by the present application, and it does not necessarily constitute the prior art of the present patent application. In the absence of conclusive evidence that the above content was publicly disclosed before the filing date of the present application, the above content cannot be used as a basis for evaluating the novelty and inventiveness of the present application. SUMMARY

[0011] The present application aims to provide a nano-modified water-retaining soil-fixing material suitable for karst mountain vegetation restoration and a preparation method thereof, so as to solve the problems of insufficient water-retaining capacity, mismatch between water release rule and plant water demand cycle, easy compaction of soil surface layer, low nutrient utilization rate, and unsatisfactory vegetation preservation rate in the prior art.

[0012] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0013] The nano-modified water-retaining soil-fixing material comprises a composite water-retaining matrix and a carrier; the composite water-retaining matrix is made of the following raw materials by weight: nano-silicon-based water-retaining agent powder 12-18 parts, sodium-based bentonite 7-9 parts, citrus peel extract 5-7 parts, polyvinyl alcohol 2.5-3.5 parts, slow-release fertilizer 8-12 parts, and deionized water 65-75 parts; the carrier is a starch-based biodegradable planting bag or starch-based biodegradable granules with a particle size of 1-3 mm. If the carrier is a starch-based biodegradable planting bag, the composite water-retaining matrix is filled in the planting bag in the form of slurry; if the carrier is starch-based biodegradable granules, the composite water-retaining matrix is prepared into granules by spray drying, and then mixed with the granules in a mass ratio of 1:0.5-1.5.

[0014] Preferably, the nano-silicon-based water-retaining agent powder is prepared by polymerization reaction of the following raw materials by weight: nano-silicon dioxide 8-12 parts, hydroxypropyl methylcellulose ether 4-6 parts, acrylamide 1.5-2.5 parts, N,N'-methylene bisacrylamide 0.08-0.12 parts, ammonium persulfate 0.04-0.06 parts, deionized water 70-90 parts, and 10% sodium hydroxide solution, which is used to adjust the pH of the prepolymer solution to 7.2-8.3.

[0015] Preferably, the particle size of the nano-silicon dioxide is 20-50 nm, and the purity is not less than 99.5%; the sodium-based bentonite is nano-clay, in which the content of montmorillonite is not less than 85%.

[0016] Preferably, the content of pectin in the citrus peel extract is not less than 60%, and the citrus peel extract is prepared by water extraction-alcohol precipitation method, which specifically comprises the following steps: drying the citrus peel, extracting it in water at 80-90℃ for 2-3h, filtering to obtain the filtrate, adding 70-80% ethanol solution, and standing for 12-16h to precipitate, collecting the precipitate, and drying and crushing to obtain the citrus peel extract; the slow-release fertilizer has a nitrogen-phosphorus-potassium mass ratio of 15:10:10, and the coating material is polylactic acid.

[0017] Preferably, the starch-based biodegradable planting bag is made of the following raw materials by weight: starch 18-22 parts, polyvinyl alcohol 4-6 parts, and deionized water 45-55 parts, and a film with a thickness of 0.15-0.25 mm is prepared, which is cut and heat-sealed to obtain a finished product with a size of 28-32 cm x 38-42 cm.

[0018] The application also provides a preparation method of the nano-modified water-retaining and soil-fixing material, comprising the following steps:

[0019] Step one: preparing a nano-silicon-based water-retaining agent pre-polymer solution;

[0020] Step two: preparing a nano-silicon-based water-retaining agent powder through a polymerization reaction;

[0021] Step three: preparing a temperature-sensitive water-retaining matrix dispersion solution;

[0022] Step four: preparing a composite water-retaining matrix: mixing the nano-silicon-based water-retaining agent powder obtained in step two and the temperature-sensitive water-retaining matrix dispersion solution obtained in step three, stirring at 30-40°C and 1500-2000 r / min for 30-45 min, then adding a slow-release fertilizer crushed to 100-120 mesh, and continuing to stir at the same temperature and speed for 15-25 min to obtain a composite water-retaining matrix slurry;

[0023] Step five: preparing a starch-based biodegradable plant bag;

[0024] Step six: assembling the water-retaining and soil-fixing material;

[0025] Step seven: performance detection and adjustment: detecting the water-retaining rate and soil-fixing rate of the material, and requiring that the water-retaining rate is not less than 300% and the 24h soil-fixing rate is not less than 85%; if the requirements are not met, the weight ratio of each raw material in the composite water-retaining matrix is adjusted until the performance meets the requirements.

[0026] Preferably, the specific process of step one is as follows: adding nano-silicon dioxide into deionized water, stirring at 2500-3500 r / min for 25-35 min to form a suspension; adding hydroxypropyl methylcellulose ether, heating to 55-65°C and continuing to stir for 50-70 min; adding acrylamide and N,N'-methylene bisacrylamide, and stirring for 15-25 min until completely dissolved; adjusting the pH of the system to 7.2-8.3 with 10% sodium hydroxide solution to obtain a pre-polymer solution.

[0027] Preferably, the specific process of step two is as follows: adding ammonium persulfate into the pre-polymer solution, stirring for 8-12 min, then transferring to a sealed reaction kettle, and reacting at 70-80°C for 3.5-4.5 h; after the reaction product is vacuum dried at 55-65°C for 10-14 h, it is crushed and sieved through an 80-220 mesh sieve to obtain a nano-silicon-based water-retaining agent powder.

[0028] Preferably, the specific process of step three is: sodium bentonite is added into deionized water, stirred at 2000-3000 r / min for 35-45 min to form a suspension; citrus peel extract is added, stirred at 45-55 DEG C for 80-100 min; polyvinyl alcohol is added, and stirring is continued for 40-50 min to obtain a temperature-sensitive water-retaining matrix dispersion; the viscosity of the dispersion is 800-1000 mPa s at 25 DEG C, and the viscosity is 200-300 mPa s at 40 DEG C.

[0029] Preferably, in step six, the assembly method of the plant bag type material is: the composite water-retaining matrix slurry is injected into the starch-based biodegradable plant bag prepared in step five at a filling amount of 450-550 g / bag, and the heat sealing parameters are set to 120-140 DEG C, 0.3-0.5 MPa, and 2-4 s; the preparation method of the bulk material is: the composite water-retaining matrix slurry is treated by spray drying at 65-75 DEG C, the inlet air temperature is controlled at 180-200 DEG C, the outlet air temperature is controlled at 80-90 DEG C, the atomization pressure is controlled at 0.2-0.4 MPa, and the feeding rate is controlled at 5-8 mL / min, to prepare particles with a particle size of 40-110 mu, and then the particles are mixed with the starch-based biodegradable bulk particles according to claim 1 in a certain proportion.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] 1. Significantly improve water retention and water locking capacity, effectively solve the problem of rapid water leakage and poor water retention performance in karst areas

[0032] The present application utilizes the synergistic effect of nano-silicon dioxide and hydroxypropyl methyl cellulose ether to construct a three-dimensional elastic gel network, significantly improving the problems of easy water leakage and easy failure of water-retaining materials in karst mountainous areas. Nano-silicon dioxide can quickly adsorb precipitation and effectively fill rock fissures due to its high specific surface area and abundant surface hydroxyl groups; hydroxypropyl methyl cellulose ether enhances the stability of the gel network through hydrogen bonding, alleviating the aging of the material structure caused by strong ultraviolet radiation and diurnal temperature difference. At the same time, the network structure formed by acrylamide and crosslinking agent further locks water, reducing the rate of water infiltration along the rock fissures to underground rivers. This water-retaining system can significantly prolong the effective water retention time, maintain soil moisture after a rainfall, and provide sustained water supply for plant growth, alleviating the contradiction of "surface drought and underground water abundance" in such areas.

[0033] 2. Realize intelligent water release based on temperature, solve the problem of mismatch between water release rhythm and plant water demand

[0034] The present application realizes the temperature-sensitive release of water by the synergistic cooperation of sodium bentonite and citrus peel extract, effectively adapting to the characteristics of the karst region that water is urgently needed during the day and easily lost at night. The layered structure of sodium bentonite can absorb and store a large amount of water, and the pectin component in the citrus peel extract has a sensitive property: under the condition of low temperature at night, the pectin molecules stretch out, enhancing the binding force with the water held by the bentonite, reducing the ineffective leakage of water at night; during the day, when the temperature rises to the period of vigorous plant transpiration, the pectin molecules shrink, gradually releasing water to meet the water demand peak of plants at high temperature. This mechanism effectively improves the soil water supply during the day, reduces the wilting phenomenon of plant leaves, and at the same time reduces the loss of soil water at night, thereby improving the efficiency of water resource utilization.

[0035] 3. effectively inhibits soil crust and enhances soil fixation effect, improves root growth environment and reduces soil erosion

[0036] The present application alleviates the problem of easy soil hardening and weak anti-erosion ability in karst regions through the synergistic effect of multiple components. Nano-silicon dioxide effectively fills soil pores with its nano-sized particles, destroys the agglomeration tendency of soil particles, and prevents the formation of dense crust on the surface; hydroxypropyl methyl cellulose ether can improve the connection between soil particles, enhance the soil permeability and water permeability; the layered structure of sodium bentonite enhances the soil cohesion, reducing the surface soil erosion. The combined effect of the three effectively inhibits the formation of karst soil crust, maintains the loose state of the soil, and expands the space for plant root growth, while enhancing the soil erosion resistance, avoiding the loss of water-retaining materials and soil from karst slope cracks, and comprehensively improving the soil fixation and conservation effect.

[0037] 4. Optimize the compatibility of supporting materials, solve the problem of low integration application and vegetation preservation rate

[0038] In view of the problem of insufficient compatibility between the plant growth bag, slow-release fertilizer and water-retaining material in the karst region, the present application significantly improves the synergistic adaptability through the optimization design of material components. In terms of combination with the plant growth bag, the biodegradable plant growth bag prepared from starch and polyvinyl alcohol has good film-forming performance and toughness, which can stably wrap the composite water-retaining substrate, enhance the interfacial bonding force, reduce the material peeling caused by rainwater erosion or gravity, and avoid the exposure of plant roots, thereby improving the vegetation preservation rate. In terms of combination with slow-release fertilizer, the fertilizer is evenly dispersed in the water-retaining system, and the water slowly released by the water-retaining gel network gradually penetrates the polylactic acid coating of the fertilizer, promoting the synchronization of nutrient release rhythm and plant water absorption rule, avoiding root burn caused by concentrated nutrient release or pollution caused by infiltration into underground rivers, significantly improving the fertilizer utilization efficiency, and ensuring the nutrient supply of plants throughout the growth cycle.

[0039] 5. has excellent biodegradability, solves the problem of environmental pollution and soil texture destruction of traditional materials

[0040] The present application highlights the environmental-friendly characteristics in material selection, avoiding the long-term pollution of traditional chemical water-retaining agents to karst soils. The starch-based biodegradable plant bags can completely decompose under natural conditions without white pollution residues; the polylactic acid coating used in slow-release fertilizers also has biodegradable characteristics; the natural ingredients such as citrus peel extract in the water-retaining system are harmless to the environment. All materials do not produce toxic substances during the degradation process, and can decompose to generate a certain amount of organic matter, thereby improving the physical structure of the barren and shallow soil in the karst area, meeting the demand for sustainability of ecological restoration.

[0041] 6. Enhance the adaptability of karst special habitats, solve the problem of limited application scene and difficult construction of traditional materials

[0042] The present application optimizes the performance of materials from multiple dimensions to improve their applicability in karst special habitats. In terms of terrain adaptation, the starch-based plant bag has both flexibility and mechanical strength, which can be laid on the rugged rock surface to reduce material sliding; the particle design of the bulk water-retaining material facilitates artificial or mechanical spreading in karst areas, improving construction efficiency. In terms of performance adaptation, the water-retaining system has good high-temperature resistance and ultraviolet resistance, which can resist the strong sunlight in the karst area in summer and maintain stable performance; at the same time, the particle size of the material is matched with the pore structure of the karst soil, which can effectively plug part of the leakage cracks and maintain the soil gas exchange function, suitable for various ecological restoration scenes such as rocky desertification areas and rocky slopes, expanding the use range of the material. DETAILED DESCRIPTION

[0043] The present application will be described in more detail below with reference to specific embodiments. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of protection or actual application of the present application.

[0044] In the embodiment of the present application, a nano-modified water-retaining and soil-fixing material is provided, which comprises a composite water-retaining matrix and a carrier; the composite water-retaining matrix is made of the following raw materials by weight: nano-silicon-based water-retaining agent powder 12-18 parts, sodium-based bentonite 7-9 parts, citrus peel extract 5-7 parts, polyvinyl alcohol 2.5-3.5 parts, slow-release fertilizer 8-12 parts, and deionized water 65-75 parts; the carrier is a starch-based biodegradable plant bag or a starch-based biodegradable bulk granule with a particle size of 1-3 mm. If the carrier is a starch-based biodegradable plant bag, the composite water-retaining matrix is filled in the plant bag in the form of slurry; if the carrier is a starch-based biodegradable bulk granule, the composite water-retaining matrix is granulated by spray drying, and then mixed with the bulk granule in a mass ratio of 1:0.5-1.5.

[0045] Preferably, the nanometer silicon-based water-retaining agent powder is prepared by polymerization reaction of the following raw materials by weight: 8-12 parts of nanometer silicon dioxide, 4-6 parts of hydroxypropyl methyl cellulose ether, 1.5-2.5 parts of acrylamide, 0.08-0.12 parts of N,N'-methylene bisacrylamide, 0.04-0.06 parts of ammonium persulfate, 70-90 parts of deionized water, and a proper amount of 10% sodium hydroxide solution for adjusting the pH of the prepolymer solution to 7.2-8.3.

[0046] Preferably, the particle size of the nanometer silicon dioxide is 20-50 nm, and the purity is not less than 99.5%; the sodium-based bentonite is a nanometer clay, wherein the montmorillonite content is not less than 85%.

[0047] Preferably, the pectin content in the citrus peel extract is not less than 60%, and the water extraction-alcohol precipitation method is used for preparation, which specifically includes the following steps: drying the citrus peel, extracting in water at 80-90℃ for 2-3h, filtering to obtain a filtrate, adding 70-80% ethanol solution, standing for 12-16h for precipitation, collecting the precipitate, and drying and crushing to obtain the product; the nitrogen-phosphorus-potassium mass ratio of the slow-release fertilizer is 15:10:10, and the coating material is polylactic acid.

[0048] Preferably, the starch-based biodegradable plant bag is made of the following raw materials by weight: 18-22 parts of starch, 4-6 parts of polyvinyl alcohol, and 45-55 parts of deionized water, and a film with a thickness of 0.15-0.25mm is prepared, and after cutting and heat sealing, the finished product has a size of 28-32cm x 38-42cm.

[0049] The application also provides a preparation method of a nanometer modified water-retaining and soil-fixing material, which comprises the following steps:

[0050] Step one: preparing a nanometer silicon-based water-retaining agent prepolymer solution;

[0051] Step two: preparing a nanometer silicon-based water-retaining agent powder by polymerization reaction;

[0052] Step three: preparing a temperature-sensitive water-retaining matrix dispersion liquid;

[0053] Step four: preparing a composite water-retaining matrix: mixing the nanometer silicon-based water-retaining agent powder obtained in step two and the temperature-sensitive water-retaining matrix dispersion liquid obtained in step three, stirring at 30-40℃ and 1500-2000r / min for 30-45min, then adding slow-release fertilizer crushed to 100-120 mesh, and continuing to stir at the same temperature and speed for 15-25min to obtain a composite water-retaining matrix slurry;

[0054] Step five: preparing a starch-based biodegradable plant bag;

[0055] Step six: assembling the water-retaining and soil-fixing material;

[0056] Step seven: performance detection and adjustment: detect the water retention rate and soil fixation rate of the material, and the water retention rate should not be less than 300%, and the 24h soil fixation rate should not be less than 85%, if it does not meet the standard, adjust the weight ratio of each raw material in the composite water-retaining matrix until the performance meets the standard.

[0057] Preferably, the specific process of step one is: adding nanosilica into deionized water, stirring at 2500-3500r / min for 25-35min to form a suspension; adding hydroxypropyl methyl cellulose ether, heating to 55-65℃ and continuing to stir for 50-70min; adding acrylamide and N,N'-methylene bisacrylamide, stirring for 15-25min until completely dissolved; adjusting the pH of the system to 7.2-8.3 with 10% sodium hydroxide solution to obtain a prepolymer solution.

[0058] Preferably, the specific process of step 2 is: adding ammonium persulfate to the prepolymer solution, stirring for 8-12min, then transferring to a sealed reaction kettle, and reacting at 70-80℃ for 3.5-4.5h; the reaction product is dried at 55-65℃ under vacuum for 10-14h, then crushed and sieved through an 80-220 mesh sieve to obtain a nanosilicon-based water-retaining agent powder.

[0059] Preferably, the specific process of step 3 is: adding sodium bentonite into deionized water, stirring at 2000-3000r / min for 35-45min to form a suspension; adding citrus peel extract, stirring at 45-55℃ for 80-100min; adding polyvinyl alcohol, continuing to stir for 40-50min to obtain a temperature-sensitive water-retaining matrix dispersion; the viscosity of the dispersion is 800-1000mPa·s at 25℃, and the viscosity is 200-300mPa·s at 40℃.

[0060] Preferably, in step six, the assembly method of the plant bag type material is: filling the composite water-retaining matrix slurry into the starch-based biodegradable plant bag prepared in step five at a filling amount of 450-550g / bag, and setting the heat sealing parameters to 120-140℃, 0.3-0.5MPa, and 2-4s; the preparation method of the loose material is: spraying the composite water-retaining matrix slurry at 65-75℃, controlling the inlet air temperature to 180-200℃, the outlet air temperature to 80-90℃, the atomization pressure to 0.2-0.4MPa, and the feeding rate to 5-8mL / min to prepare particles with a particle size of 40-110μm, and then mixing the particles with the starch-based biodegradable loose particles according to claim 1 in a certain proportion.

[0061] The technical principle of the application is:

[0062] 1. The role of the core raw material in the composite water-retaining matrix

[0063] In the present application, the nano-silicon-based water-retaining agent powder is used as the core framework material in the composite water-retaining matrix, which is prepared by polymerization reaction of nano-silicon dioxide, hydroxypropyl methyl cellulose ether, acrylamide and other components. Among them, the nano-silicon dioxide provides abundant nano-scale pore structure, which constructs the physical skeleton of the water-retaining channel; the hydroxypropyl methyl cellulose ether acts as a thickening agent, effectively enhancing the stability of the system and preventing the sedimentation of the water-retaining components; the acrylamide forms a three-dimensional gel network through polymerization and adsorbs water molecules through hydrogen bonding, which is the key component to achieve a water retention rate of not less than 300%. It should be noted that this component alone can achieve a water retention rate of 250-280%, but its soil solidifying capacity is relatively limited. Sodium-based bentonite, as a binding and auxiliary water-retaining component, belongs to nano-clay material, and its montmorillonite interlayer structure has excellent water absorption and swelling properties. When used alone, it can adsorb 5-8 times its own weight of water. At the same time, it forms a preliminary bond with soil particles through interlayer charge, thereby enhancing the overall soil solidifying capacity of the material, but the long-term effectiveness of the water-retaining effect of this component alone is poor.

[0064] The citrus peel extract plays a role in water retention coordination and dispersion. The pectin molecules contained therein are rich in a large number of hydroxyl, carboxyl and other hydrophilic groups, which can adsorb water molecules through these hydrophilic groups when used alone, thereby assisting in improving the water retention performance of the system. In addition, pectin has good dispersion ability, which can effectively prevent the agglomeration of sodium-based bentonite and nano-silicon-based water-retaining agent powder, thereby improving the uniformity of the matrix; however, this component alone does not have soil solidifying function.

[0065] Polyvinyl alcohol as a film-forming and bonding enhancement component, its molecular chain can form a continuous film structure. When used alone, it can form a protective film on the soil surface to reduce water evaporation; at the same time, it can enhance the bonding force between soil particles and other water-retaining components due to its stickiness, and the addition of polyvinyl alcohol alone can increase the soil solidifying rate by 8-12%, but its water-retaining capacity is weak.

[0066] Slow-release fertilizer bears the functions of soil solidifying anchoring and nutrient supply. The polylactic acid coating can achieve slow release of nutrients, effectively avoiding nutrient loss; at the same time, the granular slow-release fertilizer can be embedded between soil particles and water-retaining components as a physical anchor point, which can help to improve the soil solidifying rate when used alone, and promote soil microbial activity through nutrient supply, creating favorable conditions for subsequent material degradation, but this component itself does not have water-retaining effect.

[0067] 2. Role of starch-based carrier

[0068] The starch-based biodegradable planting bag as a forming and slow-release carrier is composed of a film made of starch and polyvinyl alcohol. When used alone, it can effectively wrap the water-retaining matrix and prevent the loss of effective ingredients. At the same time, the starch component can be naturally degraded in the soil environment. It should be noted that the planting bag itself does not have water-retaining or soil-fixing ability, and its main function is physical wrapping.

[0069] The starch-based biodegradable loose granule serves as a dispersion and mixing carrier. Its particle shape structure can be uniformly mixed with the water-retaining matrix particles after spray drying, thereby increasing the contact area with the soil and promoting water exchange. When used alone, the granule helps to improve the dispersibility of the water-retaining component in the soil, but does not play a core role in water retention or soil fixation.

[0070] The synergistic mechanism between the raw materials of the present application:

[0071] The core of the present application is that the components are not simply combined, but are systematically synergized in three dimensions of water retention, soil fixation, and degradation, effectively solving the technical bottlenecks of single raw material, such as strong water retention but weak soil fixation, good soil fixation but poor water retention performance, and effective function but difficult degradation. The specific synergistic mechanism is as follows:

[0072] 1. Synergy in the water retention dimension: building a multi-level water retention network

[0073] The three-dimensional gel network formed by the nano-silicon-based water-retaining agent powder serves as the main water-retaining layer, which can adsorb a large amount of free water; the interlayer swelling structure of sodium-based bentonite serves as the auxiliary water-retaining layer, which can further capture the interstitial water that the water-retaining layer cannot fix, and the expanded clay particles can also fill the pores of the gel network, thereby inhibiting water evaporation; the pectin molecules in citrus peel extract serve as the coordination layer, which forms hydrogen bonds with the gel network and the interlayer water of bentonite through its hydrophilic groups, enhancing the adsorption stability of water molecules, and preventing the agglomeration of bentonite and water-retaining powder, ensuring the continuity and smoothness of the water-retaining channel.

[0074] 2. Synergy in the soil fixation dimension: forming a three-dimensional soil fixation structure

[0075] The sodium-based bentonite forms a basic cohesive layer through interlayer cohesion and charge effect, achieving preliminary fixation of soil particles; the polyvinyl alcohol forms a wrapping layer through film formation, covering a continuous film on the surface of the soil and water-retaining ingredients, enhancing the stability of the cohesive particles; the particles of slow-release fertilizer serve as an anchoring layer, embedded between the film and the soil particles, further improving the mechanical strength of the overall structure; the gel network of the nano-silicon-based water-retaining agent powder serves as a filling layer, effectively filling the gaps between soil particles to prevent loose structure.

[0076] 3. Synergy in the degradation dimension: achieving balanced design of the degradable system

[0077] The starch component of the starch-based carrier can be rapidly decomposed by soil microorganisms to create a degradation environment for other degradable components; the slow-release fertilizer polylactic acid coating and starch degradation products play a synergistic degradation role, and the degradation rate of polylactic acid is significantly higher than that of single polylactic acid under the catalysis of organic acids generated by starch decomposition; at the same time, the pectin molecules in the citrus peel extract can be used as a carbon source for microorganisms to promote the reproduction of microorganisms, thereby accelerating the degradation process of starch and polylactic acid and avoiding the environmental load caused by degradation residues.

[0078] 4. Synergy between process and raw materials: parameter optimization enhances synergistic effect

[0079] The optimized process parameters determined by single-factor experiments can further enhance the synergistic effect between raw materials. For example, a stirring speed of 3000 r / min can ensure the uniform dispersion of nano-silicon-based water-retaining agent powder and sodium-based bentonite, preventing a decrease in synergistic effect due to agglomeration; a polymerization temperature of 75°C helps to form a water-retaining gel network pore size that matches the particle size of bentonite, thereby maximizing the synergistic performance of water retention and soil consolidation. If the above-mentioned optimized parameters are deviated, the synergistic effect will decrease by 20-30%, which further proves the non-obviousness of the raw material combination of the present application from the process.

[0080] In order to make the present disclosure more complete, the following will be described by more specific examples.

[0081] Example 1 (geobag type)

[0082] This example provides a nano-modified water-retaining and soil-consolidating material, which is composed of a composite water-retaining matrix and a carrier. The composite water-retaining matrix includes the following raw materials by weight: nano-silicon-based water-retaining agent powder 15 parts, sodium-based bentonite 8 parts, citrus peel extract 6 parts, polyvinyl alcohol 3.2 parts, slow-release fertilizer 11 parts, and deionized water 72 parts. The carrier is a starch-based biodegradable geobag; when the carrier is a starch-based biodegradable geobag, the composite water-retaining matrix is injected into the bag in the form of slurry.

[0083] The nano-silicon-based water-retaining agent powder is prepared from the following raw materials by polymerization reaction: 10 parts of nano-silicon dioxide, 5 parts of hydroxypropyl methyl cellulose ether, 2.2 parts of acrylamide, 0.11 parts of N,N'-methylene bisacrylamide, 0.05 parts of ammonium persulfate, 85 parts of deionized water, and an appropriate amount of 10% sodium hydroxide solution (for adjusting the pH of the prepolymer solution to 7.9). The particle size of the nano-silicon dioxide is 38 nm, and the purity is not less than 99.5%. The sodium-based bentonite is a nano-sized clay with a montmorillonite content of not less than 85%. The citrus peel extract is prepared by water extraction-alcohol precipitation method, and the pectin content is not less than 60%. The specific process is as follows: dry the citrus peel at 88°C in water for 2.2 h, filter to obtain the filtrate, add 76% ethanol solution and stand for 15 h, then collect the precipitate, dry and crush to obtain the product. The slow-release fertilizer contains nitrogen, phosphorus and potassium in a mass ratio of 15:10:10, and the coating material is polylactic acid. The starch-based biodegradable plant bag is made from 21 parts of starch, 5 parts of polyvinyl alcohol and 52 parts of deionized water, with a film thickness of 0.22 mm. After cutting and heat sealing, the plant bag with a size of 31 cm x 41 cm is obtained.

[0084] A preparation method of a nano-modified water-retaining and soil-fixing material, comprising the following steps:

[0085] Step one: preparing a nano-silicon-based water-retaining agent prepolymer solution;

[0086] Step two: preparing a nano-silicon-based water-retaining agent powder by polymerization reaction;

[0087] Step three: preparing a temperature-sensitive water-retaining matrix dispersion;

[0088] Step four: preparing a composite water-retaining matrix: mixing the nano-silicon-based water-retaining agent powder obtained in step two with the temperature-sensitive water-retaining matrix dispersion obtained in step three, stirring at 36°C and 1700 r / min for 42 min, then adding the slow-release fertilizer crushed to 115 mesh, and continuing to stir under the same temperature and speed conditions for 23 min to obtain a composite water-retaining matrix slurry;

[0089] Step five: preparing a starch-based biodegradable plant bag;

[0090] Step six: assembling the water-retaining and soil-fixing material;

[0091] Step seven: performance testing and adjustment: testing the water-retaining rate and soil-fixing rate of the material, wherein the water-retaining rate should be not less than 300%, and the 24 h soil-fixing rate should be not less than 85%. If the performance does not meet the requirements, the weight ratio of each raw material in the composite water-retaining matrix is adjusted until the performance meets the requirements.

[0092] The step one specifically comprises: adding nano-silica into deionized water, stirring at a speed of 3400 r / min for 27 min to form a suspension; adding hydroxypropyl methyl cellulose ether, and continuously stirring at a temperature of 64℃ for 58 min; adding acrylamide and N,N'-methylene bisacrylamide, and stirring for 22 min until completely dissolved; finally, adjusting the pH of the system to 7.9 by using 10% sodium hydroxide solution to obtain a prepolymer solution.

[0093] The step two specifically comprises: adding ammonium persulfate into the prepolymer solution, stirring for 11 min, and then transferring to a sealed reaction kettle, and reacting at 79℃ for 3.7 h; after the reaction product is vacuum dried at 64℃ for 12 h, it is crushed and passed through a 200 mesh sieve to obtain a nano-silicon-based water-retaining agent powder.

[0094] The step three specifically comprises: adding sodium bentonite into deionized water, stirring at a speed of 2900 r / min for 37 min to form a suspension; then adding citrus peel extract, and continuously stirring at a temperature of 54℃ for 88 min; adding polyvinyl alcohol, and continuously stirring for 47 min to obtain a temperature-sensitive water-retaining matrix dispersion liquid; the viscosity of the temperature-sensitive water-retaining matrix dispersion liquid is 950 mPa·s at 25℃, and the viscosity is 280 mPa·s at 40℃.

[0095] In the step six, the assembly method of the plant bag type material is: the composite water-retaining matrix slurry is injected into the starch-based biodegradable plant bag prepared in the step five at a filling amount of 520 g / bag, and the heat sealing condition is 135℃, 0.45 MPa, and 3 s.

[0096] Example 2 (scattered granular type)

[0097] The embodiment provides a nano-modified water-retaining and soil-fixing material which is composed of a composite water-retaining matrix and a carrier. The composite water-retaining matrix comprises the following raw materials in parts by weight: 12 parts of nano-silicon-based water-retaining agent powder, 7 parts of sodium bentonite, 5 parts of citrus peel extract, 2.5 parts of polyvinyl alcohol, 8 parts of slow-release fertilizer, and 65 parts of deionized water. The carrier is starch-based biodegradable scattered granules with a particle size of 1 mm; when the scattered granules are used as the carrier, the composite water-retaining matrix is first made into granules by spray drying, and then compounded with the scattered granules at a mass ratio of 1:0.5.

[0098] The nano-silicon-based water-retaining agent powder is prepared from the following raw materials by polymerization: 8 parts of nano-silicon dioxide, 4 parts of hydroxypropyl methyl cellulose ether, 1.5 parts of acrylamide, 0.08 parts of N,N'-methylene bisacrylamide, 0.04 parts of ammonium persulfate, 70 parts of deionized water, and an appropriate amount of 10% sodium hydroxide solution (for adjusting the pH of the prepolymer solution to 7.2). The particle size of the nano-silicon dioxide is 20 nm, and the purity is not less than 99.5%. The sodium-based bentonite is a nano-sized clay with a montmorillonite content of not less than 85%. The citrus peel extract is prepared by water extraction-alcohol precipitation method, and the pectin content is not less than 60%. The specific steps are as follows: dry the citrus peel at 90°C in water for 2h, filter to obtain the filtrate, add 70% ethanol solution and stand for precipitation for 12h, collect the precipitate, dry and crush to obtain the product. The mass ratio of nitrogen, phosphorus and potassium in the slow-release fertilizer is 15:10:10, and the coating material is polylactic acid. The particle size of the starch-based biodegradable granular material is 1mm.

[0099] A preparation method of a nano-modified water-retaining and soil-fixing material, comprising the following steps:

[0100] Step one: preparing a nano-silicon-based water-retaining agent prepolymer solution;

[0101] Step two: preparing a nano-silicon-based water-retaining agent powder by polymerization;

[0102] Step three: preparing a temperature-sensitive water-retaining matrix dispersion;

[0103] Step four: preparing a composite water-retaining matrix: mixing the nano-silicon-based water-retaining agent powder obtained in step two with the temperature-sensitive water-retaining matrix dispersion obtained in step three, stirring at 40°C and 2000r / min for 30min, then adding slow-release fertilizer crushed to 100 mesh, maintaining the temperature and speed conditions and continuing to stir for 15min to obtain a composite water-retaining matrix slurry;

[0104] Step five: preparing a starch-based biodegradable plant bag; (this example is a granular material, this step is omitted)

[0105] Step six: assembling the water-retaining and soil-fixing material;

[0106] Step seven: performance testing and adjustment: testing the water retention rate and soil fixation rate of the material, wherein the water retention rate is not less than 300%, and the 24h soil fixation rate is not less than 85%, if not up to standard, adjusting the weight ratio of each raw material in the composite water-retaining matrix until the performance meets the requirements.

[0107] The step one specifically comprises: adding nano-silica into deionized water, stirring at a speed of 3500 r / min for 25 min to form a suspension; adding hydroxypropyl methyl cellulose ether, and continuing to stir at a temperature of 65℃ for 50 min; adding acrylamide and N,N'-methylene bisacrylamide, and stirring for 15 min until completely dissolved; finally, adjusting the pH of the system to 7.2 by using 10% sodium hydroxide solution to obtain a prepolymer solution.

[0108] The step two specifically comprises: adding ammonium persulfate into the prepolymer solution, stirring for 8 min, and then transferring to a sealed reaction kettle, and reacting at 80℃ for 3.5 h; after the reaction product is vacuum dried at 65℃ for 10 h, it is crushed and passed through an 80-mesh sieve to obtain a nano-silicon-based water-retaining agent powder.

[0109] The step three specifically comprises: adding sodium bentonite into deionized water, stirring at a speed of 3000 r / min for 35 min to form a suspension; then adding citrus peel extract, and continuing to stir at 55℃ for 80 min; adding polyvinyl alcohol, and continuing to stir for 40 min to obtain a temperature-sensitive water-retaining matrix dispersion liquid; the viscosity of the temperature-sensitive water-retaining matrix dispersion liquid is 800 mPa·s at 25℃, and the viscosity is 200 mPa·s at 40℃.

[0110] In the step six, the preparation method of the bulk material is: the composite water-retaining matrix slurry is spray dried at 65℃, the inlet air temperature is controlled at 180℃, the outlet air temperature is controlled at 80℃, the atomization pressure is controlled at 0.2 MPa, the feeding rate is controlled at 5 mL / min, particles with a particle size of 40 μm are prepared, and the particles are mixed with the starch-based biodegradable bulk particles in a ratio of 1:0.8.

[0111] Example 3 (geobag type)

[0112] The embodiment provides a nano-modified water-retaining and soil-fixing material, which is composed of a composite water-retaining matrix and a carrier. The composite water-retaining matrix comprises the following raw materials in parts by weight: nano-silicon-based water-retaining agent powder 17 parts, sodium bentonite 9 parts, citrus peel extract 7 parts, polyvinyl alcohol 3.5 parts, slow-release fertilizer 12 parts, and deionized water 75 parts. The carrier is a starch-based biodegradable geobag; in this configuration, the composite water-retaining matrix is injected into the bag in the form of slurry.

[0113] The nanometer silicon-based water-retaining agent powder is prepared from the following raw materials by polymerization reaction: 12 parts of nanometer silicon dioxide, 6 parts of hydroxypropyl methyl cellulose ether, 2.5 parts of acrylamide, 0.12 parts of N,N'-methylene bisacrylamide, 0.06 parts of ammonium persulfate, 90 parts of deionized water, and an appropriate amount of 10% sodium hydroxide solution (for adjusting the pH of the prepolymer solution to 8.3). The particle size of the nanometer silicon dioxide is 45 nm, and the purity is not less than 99.5%. The sodium-based bentonite is a nanoscale clay with a montmorillonite content of not less than 85%. The citrus peel extract is prepared by water extraction-alcohol precipitation method, and the pectin content is not less than 60%. The specific steps are as follows: dry the citrus peel at 85°C in water for 2.5 h, filter to obtain the filtrate, add 78% ethanol solution and stand for precipitation for 14 h, collect the precipitate, dry and crush to obtain the product. The slow-release fertilizer contains nitrogen, phosphorus and potassium in a mass ratio of 15:10:10, and the coating material is polylactic acid. The starch-based biodegradable plant bag is made from 22 parts of starch, 6 parts of polyvinyl alcohol and 55 parts of deionized water, with a film thickness of 0.25 mm. After cutting and heat sealing, a plant bag with a size of 32 cm x 42 cm is obtained.

[0114] A preparation method of a nanometer modified water-retaining and soil-fixing material, comprising the following steps:

[0115] Step one: preparing a nanometer silicon-based water-retaining agent prepolymer solution;

[0116] Step two: preparing a nanometer silicon-based water-retaining agent powder by polymerization reaction;

[0117] Step three: preparing a temperature-sensitive water-retaining matrix dispersion;

[0118] Step four: preparing a composite water-retaining matrix: mixing the nanometer silicon-based water-retaining agent powder obtained in step two with the temperature-sensitive water-retaining matrix dispersion obtained in step three, stirring at 35°C and 1800 r / min for 38 min, then adding slow-release fertilizer crushed to 120 mesh, maintaining the temperature and speed conditions and continuing to stir for 20 min to obtain a composite water-retaining matrix slurry;

[0119] Step five: preparing a starch-based biodegradable plant bag;

[0120] Step six: assembling the water-retaining and soil-fixing material;

[0121] Step seven: performance testing and adjustment: testing the water-retaining rate and soil-fixing rate of the material, wherein the water-retaining rate should be not less than 300%, and the 24h soil-fixing rate should be not less than 85%. If the performance does not meet the requirements, the weight ratio of each raw material in the composite water-retaining matrix is adjusted until the performance meets the requirements.

[0122] The step one specifically comprises: adding nano-silica into deionized water, stirring at a speed of 3000 r / min for 30 min to form a suspension; adding hydroxypropyl methyl cellulose ether, and continuing to stir at a temperature of 60℃ for 60 min; adding acrylamide and N,N'-methylene bisacrylamide, and stirring for 20 min until completely dissolved; finally, adjusting the pH of the system to 8.3 by using 10% sodium hydroxide solution to obtain a prepolymer solution.

[0123] The step two specifically comprises: adding ammonium persulfate into the prepolymer solution, stirring for 10 min, and then transferring to a sealed reaction kettle, and reacting at 75℃ for 4 h; after vacuum drying at 60℃ for 12 h, the reaction product is crushed and passed through a 220 mesh sieve to obtain a nano-silicon-based water-retaining agent powder.

[0124] The step three specifically comprises: adding sodium bentonite into deionized water, stirring at a speed of 2500 r / min for 40 min to form a suspension; then adding citrus peel extract, and continuing to stir at 50℃ for 90 min; adding polyvinyl alcohol, and continuing to stir for 45 min to obtain a temperature-sensitive water-retaining matrix dispersion; the viscosity of the temperature-sensitive water-retaining matrix dispersion is 1000 mPa·s at 25℃, and the viscosity is 300 mPa·s at 40℃.

[0125] In the step six, the assembly method of the plant bag type material is: injecting the composite water-retaining matrix slurry into the starch-based biodegradable plant bag prepared in the step five at a filling amount of 550 g / bag, and the heat sealing conditions are 140℃, 0.5 MPa, and 2 s.

[0126] Example 4 (scattered granular type)

[0127] The embodiment provides a nano-modified water-retaining and soil-fixing material, which is composed of a composite water-retaining matrix and a carrier. The composite water-retaining matrix comprises the following raw materials in parts by weight: nano-silicon-based water-retaining agent powder 16 parts, sodium bentonite 8 parts, citrus peel extract 6 parts, polyvinyl alcohol 3.3 parts, slow-release fertilizer 9 parts, and deionized water 70 parts. The carrier is starch-based biodegradable scattered granules with a particle size of 3 mm; when used, the composite water-retaining matrix is compounded with the scattered granules at a mass ratio of 1:1.5.

[0128] The nanometer silicon-based water-retaining agent powder is prepared from the following raw materials by polymerization reaction: 11 parts of nanometer silicon dioxide, 5 parts of hydroxypropyl methyl cellulose ether, 2.0 parts of acrylamide, 0.09 parts of N,N'-methylene bisacrylamide, 0.05 parts of ammonium persulfate, 80 parts of deionized water, and an appropriate amount of 10% sodium hydroxide solution (for adjusting the pH of the polymerization solution to 8.0). The particle size of the nanometer silicon dioxide is 40 nm, and the purity is not less than 99.5%. The sodium-based bentonite is a nanoscale clay, and the montmorillonite content is not less than 85%. The citrus peel extract is prepared by water extraction-alcohol precipitation method, and the pectin content is not less than 60%. The specific steps are as follows: dry the citrus peel at 82°C in water for 2.8h, filter to obtain the filtrate, add 74% ethanol solution and stand for 16h, then collect the precipitate, dry and crush to obtain the product. The mass ratio of nitrogen, phosphorus and potassium in the slow-release fertilizer is 15:10:10, and the coating material is polylactic acid. The starch-based biodegradable granular particle size is 3mm.

[0129] A preparation method of a nanometer modified water-retaining and soil-fixing material, comprising the following steps:

[0130] Step one: preparing a nanometer silicon-based water-retaining agent pre-polymerization solution;

[0131] Step two: preparing a nanometer silicon-based water-retaining agent powder by polymerization reaction;

[0132] Step three: preparing a temperature-sensitive water-retaining matrix dispersion;

[0133] Step four: preparing a composite water-retaining matrix: mixing the nanometer silicon-based water-retaining agent powder obtained in step two with the temperature-sensitive water-retaining matrix dispersion obtained in step three, stirring at 32°C and 1600r / min for 45min, then adding the slow-release fertilizer crushed to 110 mesh, maintaining the temperature and speed conditions to continue stirring for 25min, to obtain a composite water-retaining matrix slurry;

[0134] Step five: preparing a starch-based biodegradable plant bag; (this example is a granular type, this step is omitted)

[0135] Step six: assembling the water-retaining and soil-fixing material;

[0136] Step seven: performance testing and adjustment: testing the water-retaining rate and soil-fixing rate of the material, wherein the water-retaining rate is not less than 300%, and the 24h soil-fixing rate is not less than 85%, if not up to standard, then adjusting the weight ratio of each raw material in the composite water-retaining matrix until the performance meets the requirements.

[0137] The step one specifically comprises: adding nano-silica into deionized water, stirring at a speed of 2800 r / min for 32 min to form a suspension; adding hydroxypropyl methyl cellulose ether, and continuously stirring at a temperature of 58℃ for 65 min; adding acrylamide and N,N'-methylene bisacrylamide, and stirring for 24 min until completely dissolved; finally, adjusting the pH of the system to 8.0 by using 10% sodium hydroxide solution, to obtain a prepolymer solution.

[0138] The step two specifically comprises: adding ammonium persulfate into the prepolymer solution, stirring for 12 min, and then transferring into a sealed reaction kettle, and reacting at 72℃ for 4.3 h; after vacuum drying at 58℃ for 13 h, the reaction product is crushed and passed through a 150-mesh sieve to obtain a nano-silicon-based water-retaining agent powder.

[0139] The step three specifically comprises: adding sodium bentonite into deionized water, stirring at a speed of 2200 r / min for 43 min to form a suspension; then adding citrus peel extract, and continuously stirring at a temperature of 48℃ for 95 min; adding polyvinyl alcohol, and continuously stirring for 48 min to obtain a temperature-sensitive water-retaining matrix dispersion liquid; the viscosity of the temperature-sensitive water-retaining matrix dispersion liquid is 900 mPa·s at 25℃, and the viscosity is 250 mPa·s at 40℃.

[0140] In the step six, the preparation method of the bulk material is: spray drying the composite water-retaining matrix slurry at 75℃, controlling the inlet air temperature to be 200℃, the outlet air temperature to be 90℃, the atomization pressure to be 0.4 MPa, and the feeding rate to be 8 mL / min, to obtain particles with a particle size of 110 μm, and mixing the particles with the starch-based biodegradable bulk particles in a ratio of 1:1.2.

[0141] Example 5 (geobag type)

[0142] The embodiment provides a nano-modified water-retaining and soil-fixing material, which is composed of a composite water-retaining matrix and a carrier. The composite water-retaining matrix comprises the following raw materials in parts by weight: nano-silicon-based water-retaining agent powder 13 parts, sodium bentonite 7 parts, citrus peel extract 5 parts, polyvinyl alcohol 2.7 parts, slow-release fertilizer 10 parts, and deionized water 69 parts. The carrier is a starch-based biodegradable geobag; when the geobag is used as the carrier, the composite water-retaining matrix is filled in the bag in the form of slurry.

[0143] The nanometer silicon-based water-retaining agent powder is prepared from the following raw materials by polymerization reaction: 9 parts of nanometer silicon dioxide, 4 parts of hydroxypropyl methyl cellulose ether, 1.7 parts of acrylamide, 0.10 part of N,N'-methylene bisacrylamide, 0.04 part of ammonium persulfate, and 78 parts of deionized water; and an appropriate amount of 10% sodium hydroxide solution (for adjusting the pH of the prepolymer solution to 7.4). The particle size of the nanometer silicon dioxide is 30 nm, and the purity is not less than 99.5%. The sodium-based bentonite is a nanoscale clay, and the montmorillonite content is not less than 85%. The citrus peel extract is prepared by water extraction-alcohol precipitation method, and the pectin content is not less than 60%. The specific steps are as follows: dry the citrus peel at 86°C in water for 2.4h, filter to obtain the filtrate, add 73% ethanol solution and stand for precipitation for 14h, then collect the precipitate, dry and crush to obtain the product. The mass ratio of nitrogen, phosphorus and potassium in the slow-release fertilizer is 15:10:10, and the coating material is polylactic acid. The starch-based biodegradable plant bag is prepared from 20 parts of starch, 4 parts of polyvinyl alcohol and 50 parts of deionized water; the film thickness is 0.20mm, and the plant bag with a size of 30cm×40cm is prepared after cutting and heat sealing.

[0144] A preparation method of a nanometer modified water-retaining and soil-fixing material, comprising the following steps:

[0145] Step one: preparing a nanometer silicon-based water-retaining agent prepolymer solution;

[0146] Step two: preparing a nanometer silicon-based water-retaining agent powder by polymerization reaction;

[0147] Step three: preparing a temperature-sensitive water-retaining matrix dispersion;

[0148] Step four: preparing a composite water-retaining matrix: mixing the nanometer silicon-based water-retaining agent powder obtained in step two with the temperature-sensitive water-retaining matrix dispersion obtained in step three, stirring at 34°C and 1800r / min for 40min, then adding the slow-release fertilizer crushed to 108 mesh, and continuing to stir under the same temperature and speed conditions for 22min to obtain a composite water-retaining matrix slurry;

[0149] Step five: preparing a starch-based biodegradable plant bag;

[0150] Step six: assembling the water-retaining and soil-fixing material;

[0151] Step seven: performance testing and adjustment: testing the water-retaining rate and soil-fixing rate of the material, the water-retaining rate should be not less than 300%, and the 24h soil-fixing rate should be not less than 85%; if the performance does not meet the requirements, the weight ratio of each raw material in the composite water-retaining matrix is adjusted until the performance meets the requirements.

[0152] The step one specifically comprises: adding nano-silica into deionized water, stirring at a speed of 3100 r / min for 30 min to form a suspension; adding hydroxypropyl methylcellulose ether, and continuing to stir at a temperature of 62℃ for 62 min; adding acrylamide and N,N'-methylene bisacrylamide, and stirring for 20 min until completely dissolved; finally, adjusting the pH of the system to 7.4 by using 10% sodium hydroxide solution to obtain a prepolymer solution.

[0153] The step two specifically comprises: adding ammonium persulfate into the prepolymer solution, stirring for 9 min, and then transferring into a sealed reaction kettle, and reacting at 77℃ for 3.9 h; after the reaction product is vacuum dried at 61℃ for 11 h, it is crushed and passed through a 120 mesh sieve to obtain a nano-silicon-based water-retaining agent powder.

[0154] The step three specifically comprises: adding sodium bentonite into deionized water, stirring at a speed of 2600 r / min for 40 min to form a suspension; then adding citrus peel extract, and continuing to stir at a temperature of 52℃ for 92 min; adding polyvinyl alcohol, and continuing to stir for 44 min to obtain a temperature-sensitive water-retaining matrix dispersion; the viscosity of the temperature-sensitive water-retaining matrix dispersion is 880 mPa·s at 25℃, and the viscosity is 240 mPa·s at 40℃.

[0155] In the step six, the assembly method of the plant bag type material is: injecting the composite water-retaining matrix slurry into the starch-based biodegradable plant bag prepared in step five at a filling amount of 500 g / bag, and the heat sealing conditions are 132℃, 0.4 MPa, and 3 s.

[0156] Comparative Example 1: missing nano-silicon-based water-retaining agent powder

[0157] Raw material difference: the water-retaining matrix only contains sodium bentonite 8 parts, citrus peel extract 6 parts, polyvinyl alcohol 3.2 parts, slow-release fertilizer 11 parts, and deionized water 72 parts, without nano-silicon-based water-retaining agent powder, and the carrier is a starch-based biodegradable plant bag, with the same specifications as Example 1.

[0158] Preparation difference: omitting the preparation steps of the nano-silicon-based water-retaining agent prepolymer and powder (steps 1 and 2), directly mixing the temperature-sensitive water-retaining matrix dispersion (prepared in the same way as Example 1) with the slow-release fertilizer, stirring at a temperature of 36℃ and a speed of 1700 r / min for 45 min to obtain a slurry, and the subsequent assembly steps are the same as Example 1.

[0159] The test results show that the water-retaining capacity and soil-fixing effect of the product are not ideal: the water-retaining rate is only 180%, and the 24h soil-fixing rate is 72%, far from meeting the standard requirements of ≥300% and ≥85%. The poor performance is mainly due to the absence of the core water-retaining component.

[0160] Comparative Example 2: missing sodium bentonite

[0161] Raw material difference: the composite water-retaining matrix contains 15 parts of nano-silicon-based water-retaining agent powder, 6 parts of citrus peel extract, 3.2 parts of polyvinyl alcohol, 11 parts of slow-release fertilizer, and 72 parts of deionized water (without sodium-based bentonite), and the carrier is a starch-based biodegradable planting bag with the same specifications as Example 1.

[0162] Preparation difference: when preparing the temperature-sensitive water-retaining matrix dispersion, the citrus peel extract is directly added to the deionized water without sodium-based bentonite, and stirred at a speed of 2900 r / min for 37 min, then heated to 54°C. The subsequent steps are the same as in Example 1. The final slurry is prone to stratification, and the viscosity is abnormal (only 300 mPa·s at 25°C and 80 mPa·s at 40°C).

[0163] Test results show that the water retention rate is 220%, and the 24h soil fixation rate is 68%. This result is attributed to the absence of sodium-based bentonite, which lacks the unique binding and water-retaining auxiliary effect, directly leading to a significant reduction in the stability of the slurry and the soil fixation capacity.

[0164] Comparative Example 3: absence of citrus peel extract

[0165] Raw material difference: the composite water-retaining matrix contains 15 parts of nano-silicon-based water-retaining agent powder, 8 parts of sodium-based bentonite, 3.2 parts of polyvinyl alcohol, 11 parts of slow-release fertilizer, and 72 parts of deionized water, without citrus peel extract, and the carrier is a starch-based biodegradable planting bag with the same specifications as Example 1.

[0166] Preparation difference: when preparing the temperature-sensitive water-retaining matrix dispersion, the sodium-based bentonite suspension is directly added to the polyvinyl alcohol without citrus peel extract, and stirred at 54°C for 135 min. The prepared dispersion has an abnormally high viscosity (1200 mPa·s at 25°C and 350 mPa·s at 40°C), and subsequent stirring is difficult and filling is prone to blockage.

[0167] Test results show that the water retention rate is 250% and the 24h soil fixation rate is 75%, both of which are lower than the standard requirements. This result is attributed to the lack of pectin regulation provided by the citrus peel extract, which adversely affects the flowability and water-retaining coordination of the slurry.

[0168] Comparative Example 4: absence of polyvinyl alcohol

[0169] Raw material difference: the composite water-retaining matrix contains 15 parts of nano-silicon-based water-retaining agent powder, 8 parts of sodium-based bentonite, 6 parts of citrus peel extract, 11 parts of slow-release fertilizer, and 72 parts of deionized water (without polyvinyl alcohol), and the carrier is a starch-based biodegradable granular particle with a particle size of 2 mm (with the same specifications as Example 6).

[0170] Preparation difference: when preparing the temperature-sensitive water-retaining matrix dispersion, the sodium-based bentonite is mixed with the citrus peel extract without adding polyvinyl alcohol, and the dispersion is directly prepared. During subsequent spray drying, the particles are easily broken, and the particle size is only 20-50 μm, which does not meet the standard of 40-110 μm. After mixing with the bulk particles, the particles are easily detached.

[0171] The test results show that the water retention rate of 230% and the 24h soil fixation rate of 70% are lower than the standard requirements. The results are attributed to the lack of the binding and film-forming effects provided by polyvinyl alcohol, which affects the particle stability and long-term water retention.

[0172] Single-factor experiment for screening key process parameters:

[0173] Core process parameter benchmark of the optimal embodiment 3: stirring speed of the nanometer silicon-based water-retaining agent pre-polymer solution is 3000 r / min, polymerization reaction temperature is 75°C, stirring temperature of the temperature-sensitive dispersion is 50°C, stirring time of the composite water-retaining matrix is 38 min, and the inlet air temperature of spray drying is 190°C (bulk type). The following single-factor experiments are basically the same as the process of the optimal embodiment 3, only the target process parameters are changed, five levels are set, and the test indexes are the water retention rate (%) and the 24h soil fixation rate (%). The results are as follows:

[0174] Experiment 1: stirring speed screening experiment of the nanometer silicon-based water-retaining agent pre-polymer solution

[0175] The process is basically the same as that of the optimal embodiment 3, except that the stirring speed of the nanometer silicon-based water-retaining agent pre-polymer solution is set to 2000 r / min, 2500 r / min, 3000 r / min, 3500 r / min, and 4000 r / min. The results are shown in Table 1.

[0176]

[0177] As shown in Table 1, when the stirring speed is 3000 r / min, the water retention rate reaches the highest value of 345.6%, and the 24h soil fixation rate is also the highest of 92.3%. When the stirring speed is lower than 2500 r / min, the nanometer silicon dioxide cannot be fully dispersed due to the low stirring speed, forming agglomerates to block the water-retaining channels, and the subsequent polymerization reaction is not sufficient, which leads to the weakened combination of the product with the soil, and thus the water retention rate and the soil fixation rate are both lower than the standard (water retention rate ≥ 300%, soil fixation rate ≥ 85%). When the stirring speed is higher than 3500 r / min, the strong shear force generated by the high stirring speed can damage the molecular chain of the hydroxypropyl methyl cellulose ether, causing the stability of the pre-polymer solution to decrease, the water retention capacity of the polymerization product to decrease, and part of the raw materials to adhere to the container wall, resulting in the loss of effective ingredients and the decrease of the soil fixation rate with the increase of the stirring speed. Therefore, the preferred stirring speed range is determined to be 2500-3500 r / min.

[0178] Experiment 2: Nanosilicon-based water-retaining agent polymerization reaction temperature screening experiment

[0179] The process is basically the same as that of the optimal embodiment 3, except that the nanosilicon-based water-retaining agent polymerization reaction temperature is set to 65°C, 70°C, 75°C, 80°C, and 85°C, respectively. The results are shown in Table 2.

[0180]

[0181] As can be seen from Table 2, when the polymerization reaction temperature is 75°C, the water retention rate and the 24h soil fixation rate both reach the highest level. When the temperature is lower than 70°C, the initiation efficiency of ammonium persulfate is significantly reduced due to the low temperature, resulting in incomplete polymerization of acrylamide, insufficient cross-linking degree of the product, sparse network structure of the water-retaining gel formed, weak water-retaining ability, and not firm combination with soil, so that the final soil fixation rate is at a low level. When the temperature is higher than 80°C, high temperature can accelerate the initiation reaction process, causing the cross-linking degree of the polymerization product to be too high, the gel network pore size to be reduced, the water molecule penetration resistance to be increased, the product brittleness to be increased, and the product to be easily broken, resulting in the water retention rate and the soil fixation rate both to decrease. In summary, the optimal temperature range for polymerization reaction is 70-80°C.

[0182] Experiment 3: Temperature-sensitive water-retaining matrix dispersion liquid stirring temperature screening experiment

[0183] The process is basically the same as that of the optimal embodiment 3, except that the temperature-sensitive water-retaining matrix dispersion liquid stirring temperature is set to 40°C, 45°C, 50°C, 55°C, and 60°C, respectively. The results are shown in Table 3.

[0184]

[0185] As can be seen from Table 3, when the stirring temperature is 50°C, the water retention rate and the 24h soil fixation rate both reach the highest level. When the temperature is lower than 45°C, low temperature can significantly reduce the activity of pectin molecules in citrus peel extract, making it unable to fully combine with sodium-based bentonite and polyvinyl alcohol, resulting in poor uniformity of the dispersion liquid; subsequent mixing with the nanosilicon-based water-retaining agent can easily cause stratification, ultimately causing damage to the water-retaining and soil-fixing performance. When the temperature is higher than 55°C, high temperature can cause thermal denaturation of pectin molecules and loss of adhesion, and also cause local gelatinization of polyvinyl alcohol, resulting in precipitation or agglomeration of the dispersion liquid, blocking of the water-retaining channel, and thus significant decrease in the water retention rate and the soil fixation rate. In summary, the optimal temperature range for the stirring process is 45-55°C.

[0186] Experiment 4: Compound water-retaining matrix stirring time screening experiment

[0187] The process is basically the same as that of the optimal embodiment 3, except that the stirring time of the composite water-retaining matrix is set to 30 min, 34 min, 38 min, 42 min and 46 min respectively, and the results are shown in Table 4.

[0188]

[0189] As shown in Table 4, when the stirring time is 38 min, the water retention rate and the 24 h soil fixation rate both reach the highest level. When the stirring time is less than 34 min, the nano-silicon-based water-retaining agent powder and the temperature-sensitive dispersion liquid cannot be fully mixed due to insufficient mixing time, resulting in the aggregation of slow-release fertilizer and the formation of local clumps, which not only makes the water-retaining channel discontinuous, but also makes the soil fixation force unevenly distributed, ultimately causing the water-retaining and soil-fixing performance to not meet the expectations. When the stirring time is higher than 42 min, excessive stirring will destroy the network structure of the water-retaining gel, and at the same time, it will cause the damage of the coating of slow-release fertilizer, leading to the early release of nutrients, resulting in the loss of effective ingredients, and making the water-retaining capacity and soil fixation force both decrease. In summary, the optimal time range of the stirring process is 34-42 min.

[0190] Experiment 5: Screening experiment of spray drying inlet temperature of bulk material

[0191] The process is basically the same as that of the optimal embodiment 3 (bulk parameter adaptation), except that the spray drying inlet temperature is set to 170℃, 180℃, 190℃, 200℃ and 210℃ respectively, and the results are shown in Table 5.

[0192]

[0193] As shown in Table 5, when the inlet temperature is 190℃, the water retention rate and the 24 h soil fixation rate both reach the highest level, and the particle size formed is within the optimal range of 40-110 μm. When the inlet temperature is lower than 180℃, the slurry is not fully dried due to the insufficient temperature, the particles are prone to stick together and the particle size is large, and the residual moisture inside will increase the risk of mold of the water-retaining gel, and unevenness will also occur when mixed with bulk carriers in the subsequent process, ultimately resulting in low water-retaining and soil-fixing rates. When the inlet temperature is higher than 200℃, high temperature will make the particles dry too fast, not only the surface is easy to form a hard shell and the internal pores collapse, making it difficult for water molecules to penetrate, but also the particles become brittle and easy to break, thus causing the water-retaining capacity and carrier binding force to decrease. In summary, the optimal temperature range of the inlet is 180-200℃.

[0194] Performance index detection test and data comparison analysis:

[0195] 1. Performance detection method

[0196] Water retention rate: 5g material (dry weight) was taken, soaked in deionized water for 24h, filtered, and the wet weight was taken. The water retention rate = (wet weight-dry weight) / dry weight x 100%;

[0197] 24h soil fixation rate: the material was mixed with sandy soil at a mass ratio of 1:10 to make a 10cm x 10cm x 5cm sample. After watering to saturation, the sample was left to stand for 24h. The compressive strength of the sample was tested using a compressive strength tester. The soil fixation rate = (sample compressive strength / standard sample compressive strength) x 100% (the standard sample was sandy soil without the material);

[0198] Degradation rate: the material was buried in soil, and the residual mass was taken after 6 months. The degradation rate = (initial mass-residual mass) / initial mass x 100%;

[0199] pH stability: the material was soaked in solutions with pH = 4, 7, and 10 for 24h. The change rate of water retention rate was tested. The change rate = (water retention rate after soaking-initial water retention rate) / initial water retention rate x 100%.

[0200] 2. Performance test results of examples and comparative examples

[0201] The performance test method was basically the same as that of the optimal example 3. The test samples included 5 examples (1-5) and 4 comparative examples (1-4, which respectively lacked nano-silicon-based water retention agent, sodium-based bentonite, citrus peel extract, and polyvinyl alcohol). The results are shown in Table 6.

[0202]

[0203] 3. Data comparison and theoretical analysis

[0204] From Table 6, it can be seen that:

[0205] I. Water retention rate comparison

[0206] The water retention rates of all examples were significantly higher than those of the comparative examples. Among them, the water retention rate of example 3 was the best, and the improvement effect was significant compared with comparative example 1. The water retention rates of the comparative examples were lower than the standard level. The core reason was that the absence of key ingredients caused the water retention system to break down. For example, the absence of nano-silicon-based water retention agent would lose the support of the three-dimensional gel network, and the absence of sodium-based bentonite would lose the interlayer water absorption auxiliary effect, ultimately causing a significant decrease in water retention capacity. Through the coordination of the gel network of nano-silicon-based water retention agent, the interlayer adsorption of sodium-based bentonite, and the hydrophilic of citrus peel extract, a multi-level water retention system was constructed. Not only did the water retention rates of the examples meet the standard, but the performance was also excellent. The water retention core performance of example 3 was still the best, which met the priority requirement of the optimal example for key indicators.

[0207] II. 24h soil fixation rate comparison

[0208] The soil fixation rate of the embodiments is higher than that of the comparative examples, and the soil fixation rate of the optimal embodiment 3 is significantly improved compared with the comparative example 2. The soil fixation rate of the comparative examples is lower than the standard level, mainly because the core binding or film-forming component is missing, for example, the lack of sodium bentonite will lose the charge binding effect, and the lack of polyvinyl alcohol will lose the film wrapping effect, resulting in loose soil fixation structure; the embodiments rely on the binding property of sodium bentonite, the film-forming property of polyvinyl alcohol, and the anchoring effect of slow-release fertilizer particles to form a three-dimensional soil fixation structure, effectively enhancing the binding force between soil particles, and the soil fixation rate meets the standard and has strong stability, and the soil fixation performance of embodiment 3 is still optimal, further consolidating its overall optimal position.

[0209] III. Comparison of degradation rate and pH stability

[0210] The degradation rate of the embodiments is higher than that of the comparative examples, wherein the degradation rate of embodiment 4 is optimal, and the degradation rate of embodiment 3 is slightly lower, and this difference is due to the uniformity of the mixed water-retaining matrix, the stirring time of embodiment 4 and the raw material ratio are more optimal, so that the nano-silicon-based water-retaining agent is more fully contacted with the starch-based carrier, and the microbial decomposition efficiency is slightly higher; although the degradation rate of embodiment 3 is not optimal, it is still higher than that of all comparative examples, and there is no component residue during the degradation process. At the same time, the absolute value of the pH change rate of the embodiments is much lower than that of the comparative examples, and the pH buffering capacity of the comparative examples is imbalanced due to the lack of components (such as the lack of sodium bentonite in comparative example 2, which cannot adjust the pH through the clay interlayer ion); the embodiments rely on the acid-base synergistic effect of each component (such as the weak acidity of citrus peel extract and the weak alkalinity of sodium bentonite), to ensure the pH stability, which can adapt to the complex soil acid-base environment in karst areas.

[0211] In summary, through the optimization of key process parameters and the synergistic design of raw materials, the overall performance of the embodiments is comprehensively improved. Although the optimal embodiment 3 ranks second in the non-core degradation rate index, its core water-retaining and soil-fixing performance is still significantly better than that of other embodiments and all comparative examples, and the overall performance exceeds that of the comparative examples. This achievement effectively solves the technical problems of water retention difficulty, weak soil fixation ability, and low environmental adaptability in karst areas, and fully demonstrates that the present application has outstanding substantial features and significant technical progress.

[0212] The above content is a further detailed description of the present application in combination with the preferred embodiments, and cannot be regarded as limiting the specific implementation of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, they can make a number of substitutions or modifications to the described embodiments without departing from the concept of the present application, and these substitutions or modifications should be regarded as belonging to the protection scope of the present application.

[0213] While the application and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods or steps.

Claims

1. A nanomodified water retaining soil binding material characterized in that, The composite water-retaining matrix comprises the following raw materials in parts by weight: nano-silicon-based water-retaining agent powder 12-18 parts, sodium-based bentonite 7-9 parts, citrus peel extract 5-7 parts, polyvinyl alcohol 2.5-3.5 parts, slow-release fertilizer 8-12 parts, and deionized water 65-75 parts; the carrier is a starch-based biodegradable plant bag or a starch-based biodegradable granular particle with a particle size of 1-3 mm; when the carrier is a plant bag, the composite water-retaining matrix is filled in the form of slurry in the bag; when the carrier is a granular particle, the composite water-retaining matrix is granulated by spray drying, and then compounded with the granular particle at a mass ratio of 1:0.5-1.

5.

2. The nanoscale modified water retaining soil consolidating material as claimed in claim 1 wherein, The nano-silicon-based water-retaining agent powder is prepared by polymerization reaction of the following raw materials in parts by weight: nano-silicon dioxide 8-12 parts, hydroxypropyl methyl cellulose ether 4-6 parts, acrylamide 1.5-2.5 parts, N,N'-methylene bisacrylamide 0.08-0.12 parts, ammonium persulfate 0.04-0.06 parts, deionized water 70-90 parts, and 10% sodium hydroxide solution in an amount required to adjust the pH of the prepolymer solution to 7.2-8.

3.

3. The nanoscale modified water retaining soil consolidating material according to claim 1 or 2, characterized in that, The nano-silicon dioxide has a particle size range of 20-50 nm and a purity of not less than 99.5%; the sodium-based bentonite is a nano-sized clay, and the montmorillonite content is not less than 85%.

4. The nanoscale modified water retaining soil consolidating material as claimed in claim 1 wherein, The citrus peel extract has a pectin content of not less than 60%, and is prepared by water extraction-alcohol precipitation method. The specific steps are as follows: dry citrus peel is extracted in water at 80-90°C for 2-3 h, the filtrate is obtained by filtration, 70-80% ethanol solution is added to the filtrate, and the precipitate is collected after 12-16 h of standing and precipitation, and then dried and crushed to obtain the citrus peel extract; the slow-release fertilizer has a nitrogen, phosphorus, and potassium mass ratio of 15:10:10, and the coating material is polylactic acid.

5. The nano-modified water retaining soil stabilizing material as claimed in claim 1 wherein, The starch-based biodegradable plant bag is made of the following raw materials in parts by weight: starch 18-22 parts, polyvinyl alcohol 4-6 parts, and deionized water 45-55 parts; the raw materials are made into a film with a thickness of 0.15-0.25 mm, and the obtained plant bag has a size of 28-32 cm×38-42 cm after cutting and heat sealing.

6. A method for preparing a nano-modified water-retention and soil-conservation material according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: Step one: preparing a nano-silicon-based water-retaining agent prepolymer solution; Step two: preparing a nano-silicon-based water-retaining agent powder by polymerization reaction; Step three: preparing a temperature-sensitive water-retaining matrix dispersion; Step four: preparing a composite water-retaining matrix: mixing the nano-silicon-based water-retaining agent powder obtained in step two with the temperature-sensitive water-retaining matrix dispersion obtained in step three, stirring at 30-40°C and 1500-2000 r / min for 30-45 min, then adding slow-release fertilizer crushed to 100-120 mesh, and continuing to stir under the same temperature and speed conditions for 15-25 min to obtain a composite water-retaining matrix slurry; Step five: preparing a starch-based biodegradable plant bag; Step six: assembling the water-retaining and soil-fixing material. Step seven: performance testing and adjustment: test the water retention rate and soil retention rate of the material, wherein the water retention rate is not less than 300%, and the 24h soil retention rate is not less than 85%; if it does not meet the standard, adjust the weight ratio of each raw material in the composite water-retaining substrate until the performance meets the requirements.

7. The preparation method of the nano-modified water-retaining and soil-stabilizing material according to claim 6, characterized in that, The step one specifically comprises: adding nano-silicon dioxide into deionized water, stirring at a speed of 2500-3500 r / min for 25-35 min to form a suspension; adding hydroxypropyl methylcellulose ether, and continuing to stir at a temperature of 55-65℃ for 50-70 min; then adding acrylamide and N,N'-methylene bisacrylamide, and stirring for 15-25 min until completely dissolved; finally, adjusting the pH of the system to 7.2-8.3 with 10% sodium hydroxide solution to obtain a pre-polymer solution.

8. The method for preparing the nano-modified water-retaining and soil-stabilizing material according to claim 6, characterized in that, The step two specifically comprises: adding ammonium persulfate into the pre-polymer solution, stirring for 8-12 min, and then transferring to a sealed reaction kettle, and reacting at 70-80℃ for 3.5-4.5 h; the reaction product is vacuum dried at 55-65℃ for 10-14 h, then crushed and sieved through an 80-220 mesh sieve to obtain a nano-silicon-based water-retaining agent powder.

9. The preparation method of the nano-modified water-retaining and soil-stabilizing material according to claim 6, characterized in that, The step three specifically comprises: adding sodium-based bentonite into deionized water, stirring at a speed of 2000-3000 r / min for 35-45 min to form a suspension; then adding citrus peel extract, and continuing to stir at 45-55℃ for 80-100 min; then adding polyvinyl alcohol, and continuing to stir for 40-50 min to obtain a temperature-sensitive water-retaining substrate dispersion; the viscosity of the dispersion is 800-1000 mPa·s at 25℃, and the viscosity is 200-300 mPa·s at 40℃.

10. The method for preparing the nano-modified water-retaining and soil-stabilizing material according to claim 6, characterized in that, In the step six, the assembly method of the plant bag type material is: filling the composite water-retaining substrate slurry into the starch-based biodegradable plant bag prepared in step five at a filling amount of 450-550 g / bag, and the heat sealing conditions are 120-140℃, 0.3-0.5 MPa, and pressure maintaining for 2-4 s; the preparation method of the bulk material is: spray drying the composite water-retaining substrate slurry at 65-75℃, controlling the inlet air temperature at 180-200℃, the outlet air temperature at 80-90℃, the atomization pressure at 0.2-0.4 MPa, and the feeding rate at 5-8 mL / min to obtain particles with a particle size of 40-110 μm, and mixing the particles with the starch-based biodegradable bulk particles according to claim 1 at a ratio of 1:0.5-1.5.

Images