Self-filling slow-release gel material as well as preparation method and application thereof

Abstract

The invention discloses a self-filling slow-release gel material as well as a preparation method and application thereof, and the self-filling slow-release gel material provided by the invention comprises a gel base material and a moisture absorption compound loaded on the gel base material, wherein the gel base material contains a hydrophilic polymer, lignosulfonate and an optional photo-thermal conversion material. The self-irrigation slow-release type gel material can effectively collect moisture in the atmosphere, has the characteristic of high water absorption rate, shows the characteristic of rapid adsorption kinetics and the characteristic of relatively high water absorption rate, can load nutritional ingredients on the gel base material, and can be applied to the process of clean water production or soil layer construction in an arid region, so that the soil layer construction efficiency is improved, and the soil layer construction efficiency is improved. The device can continuously provide irrigation for plants by taking air as a water source, realizes the functions of self-water supply and slow-release fertilization, solves the problems of water resources and difficult plant survival in arid, semi-arid and seasonal lacking areas, and has potential commercial value and application prospect.

Description

Technical Field

[0001] The present invention relates to the technical fields of atmospheric water collection and soil fertility slow-release materials. Specifically, it relates to a self-irrigation slow-release gel material, its preparation method and application. Background Art

[0002] In arid, semi-arid and seasonally water-scarce regions, the shortage of water resources poses a severe environmental challenge to plant growth. Traditional methods for restoring soil moisture mainly involve using modern machinery for irrigation such as drip irrigation, sprinkler irrigation or micro-irrigation to ensure that crops obtain sufficient water. However, restricted by the region, for arid, semi-arid and seasonally water-scarce regions, the water shortage problem has not been fundamentally solved, and the energy consumption is high. In addition, under water-deficient environments, the poor solubility of fertilizers affects the absorption by plant roots, or the utilization rate is reduced due to the loss of fertilizer nutrients under concentrated precipitation conditions, thus affecting the absorption and utilization effects of fertilizers.

[0003] Recently, some studies have shown that an atmospheric water collection material prepared by loading hygroscopic metal salts inside a hydrogel with a photothermal conversion effect can absorb water molecules in the air and desorb them using solar energy to obtain fresh water. However, the current atmospheric water collection materials have a low water absorption capacity and unstable release performance, and cannot provide sufficient water for plants in arid, semi-arid and seasonally water-scarce regions to maintain their growth requirements, resulting in low efficiency of atmospheric water collection for producing clean water or directly using it for air-water irrigation and low sustainability. In addition, most gel materials have problems of poor dispersibility and single function. Therefore, developing an atmospheric water collection material that can supply water by itself, slow-release fertilizers, and achieve coordinated management of water and fertilizers can simultaneously improve the insufficient soil moisture and fertility loss in arid, semi-arid and seasonally water-scarce regions, and more effectively improve the survival rate of plants. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above deficiencies of the prior art and provide a self-irrigation slow-release gel material, its preparation method and application.

[0005] The present invention solves its technical problems by adopting the following technical solutions.

[0006] The present invention provides a self-irrigation slow-release gel material, including a gel substrate and a hygroscopic compound loaded on the gel substrate; wherein, the gel substrate contains a hydrophilic polymer, lignosulfonate, and optionally a photothermal conversion material.

[0007] The present invention provides a preparation method of the above self-irrigation slow-release gel material, including: preparing the gel substrate containing a hydrophilic polymer, lignosulfonate, and optionally a photothermal conversion material, and loading the hygroscopic compound on the gel substrate.

[0008] The present invention provides an application of the above self-irrigating and slow-release gel composite material in the production of clean water and the construction of soil layers in arid regions.

[0009] The present invention has the following beneficial effects:

[0010] The present invention provides a self-irrigating and slow-release gel material, its preparation method and application. The self-irrigating and slow-release gel material provided by the present invention includes a gel substrate and a hygroscopic compound loaded on the gel substrate; wherein, the gel substrate contains a hydrophilic polymer, lignosulfonate, and optionally a photothermal conversion material. The above self-irrigating and slow-release gel material can quickly adsorb moisture in the air. In addition to showing the characteristics of rapid water absorption and high water absorption rate, it can also utilize the high-efficiency adsorption characteristics of porous gels for inorganic ions and organic functional groups in fertilizers, and apply it in the process of clean water production or the construction of soil layers in arid regions, so as to continuously provide irrigation for plants and slowly release fertility from the air, that is, the purpose of self-irrigating and slow-release can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0012] Figure 1 It is a schematic diagram of the manufacturing process of hygroscopic microspheres;

[0013] Figure 2 In (a), it is the formation of microspheres at different CaLS concentrations; (b) is the influence of CaLS concentration on the size of microspheres; (c) is the zeta potential diagram of the precursor solution (formed by dropping SA (or SA and CNTs) solution into CaLS solution) at different CaLS concentrations;

[0014] Figure 3 It is a scanning electron microscope (SEM) image of hygroscopic microspheres;

[0015] Figure 4 In (a), it is the water vapor adsorption behavior of LiCl / SA / CaLS / CNTs microspheres at relative humidities of 20%, 60% and 90% provided in Example 4; (b) is the adsorption kinetic curves of SA / CaLS / CNTs and LiCl / SA / CaLS / CNTs microspheres; (c) is the water absorption capacity of AWH reported in other papers; (d) is the adsorption-release cycle curve summarizing LiCl / SA / CaLS / CNTs microspheres;

[0016] Figure 5In (a), it shows the surface temperature change of the moisture-absorbing microbeads provided in Example 4 under different light intensities; (b) is the water desorption curve of LiCl / SA / CaLS / CNTs microbeads under different light intensities; (c) is the water desorption rate of LiCl / SA / CaLS / CNTs microbeads under different light intensities; (d) is the production of solar clean water outdoors.

[0017] Figure 6 In (a), it is a schematic diagram of LiCl / SA / CaLS / CNTs microbeads for the production of AWH and clean water; (b) is the water absorption rate of the moisture-absorbing microbeads provided in Example 4 under experimental condition temperature and humidity; (c) is the primary ion concentration in the clean water collected after solar evaporation.

[0018] Figure 7 In (a), it shows the comparison of water absorption isotherms of the moisture-absorbing microbeads SA / CaLS and CaCl2 / SA / CaLS provided in Example 4 at 25 °C and 90% relative humidity; (b) is the water vapor adsorption behavior of CaCl2 / SA / CaLS under relative humidities of 40%, 60% and 90%; (c) is the summary of AWH capabilities in other reports; (d) is the soil moisture content of microbeads doped with different concentrations of CaCl2 / SA / CaLS.

[0019] Figure 8 In (a), it is the seed germination rate when the moisture-absorbing microbeads provided in Example 4 are used to modify the soil; (b) is the plant height of the plants in the modified soil; (c) is the biomass of ryegrass in the modified soil; (d) is the environmental temperature and humidity; (e) is the wilting time of ryegrass in the modified soil; (f) is a photo of the growth of ryegrass.

[0020] Figure 9 In (a), it shows the comparison of moisture absorption isotherms of the gel microbeads CaCl2 / SA / CaLS and NPK / CaCl2 / SA / CaLS provided in Example 4 at 25 °C and 90% relative humidity; under the influence of the gel microbeads, (b) is the slow-release behavior of urea (N); (c) is the slow-release behavior of phosphorus (P); (d) is the slow-release behavior of potassium (K). Detailed implementation manners

[0021] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0022] The following specifically describes a self-irrigation slow-release bead material provided by the embodiments of the present invention, its preparation method and application.

[0023] In a first aspect, an embodiment of the present invention provides a self-filling and slow-release gel material, comprising a gel substrate and a hygroscopic compound loaded on the gel substrate; wherein, the gel substrate contains a hydrophilic polymer, lignosulfonate, and optionally a photothermal conversion material.

[0024] The self-filling and slow-release gel material provided by the embodiment of the present invention comprises a gel substrate and a hygroscopic compound loaded on the gel substrate, wherein: the gel substrate contains a hydrophilic polymer which contains a large number of hydrophilic groups and can efficiently adsorb water molecules in the atmosphere through hydrogen bonds with hydrophilic functional groups. The swelling behavior of natural polymers can dynamically adjust the hygroscopic capacity with humidity changes, achieving efficient capture and release of water. The sulfonic acid group of lignosulfonate endows it with stronger hydrophilicity and ion exchange ability, which can improve the hygroscopic rate and capacity. The amphiphilicity (hydrophilic-hydrophobic balance) of lignosulfonate enables it to maintain stable adsorption performance in complex environments. At the same time, natural polymers can form interconnected porous structures through processes such as freeze-drying and foaming, significantly increasing the specific surface area to improve the efficiency of water molecule capture. After modification, lignosulfonate can form nano-scale pores, enhancing the water locking ability through capillary action. The combination of lignosulfonate and natural polymers can not only utilize the rigid skeleton of lignin to improve mechanical strength but also optimize the water diffusion path through the flexible network of natural polymers. The biodegradability and environmental friendliness of hydrophilic polymers and lignosulfonates are beneficial for practical applications, and lignosulfonate, as an organic substance, can also provide fertilizers for plant growth.

[0025] In addition, as a solar-driven atmospheric water harvesting material, adding a photothermal conversion material to the self-filling and slow-release gel material can not only provide a skeleton support role to increase the condensate adsorption capacity but also endow high solar-thermal conversion efficiency, contributing to water vapor absorption and transmission. As an atmospheric water harvesting material used in soil, there is no need to add a photothermal conversion material to the self-filling and slow-release gel material, and water vapor absorption and transmission are mainly achieved through physical adsorption-humidity diffusion.

[0026] In some optional embodiments, the gel substrate is spherical microbeads with a hollow porous structure;

[0027] Preferably, the particle size of the gel substrate is 0.45 - 0.52 mm.

[0028] The self-irrigation and slow-release gel material provided by the embodiments of the present invention, the gel substrate is spherical microbeads with a hollow porous structure. The hollow structure, high specific surface area and three-dimensional interconnected porous gel structure of the spherical microbeads with a hollow porous structure provide favorable conditions for the loading of high-capacity hygroscopic compounds. Moreover, the gradient pores can reduce the burst release phenomenon and extend the release period. In addition, compared with the traditional bulk gel water-collecting material, the gel water-collecting material in the form of microbeads in the present invention has a larger contact area with the soil and is more evenly mixed, enabling the gel material provided by the present invention to continuously provide irrigation for plants with air as the water source, reducing the demand for centralized water supply and power supply, exerting the effect of self-irrigation and slow release, and effectively fundamentally solving the problems of soil water shortage and slow release of fertility in arid, semi-arid and seasonally water-deficient areas.

[0029] In some alternative embodiments, the mass ratio of the hydrophilic polymer and lignosulfonate in the gel substrate is 10:(1 - 10), or the mass ratio of the hydrophilic polymer, lignosulfonate and photothermal conversion material in the gel substrate is 10:(1 - 10):1;

[0030] Preferably, the hydrophilic polymer is selected from one or more of chitosan, starch or sodium alginate, and preferably sodium alginate;

[0031] Preferably, the lignosulfonate includes one or more of calcium lignosulfonate and magnesium lignosulfonate, and preferably calcium lignosulfonate;

[0032] Preferably, the photothermal conversion material includes one or more of carbon nanotubes, carbon black, activated carbon, graphene or graphyne, and preferably carbon nanotubes.

[0033] In some alternative embodiments, the hygroscopic compound includes one or more of LiCl, CaCl2, MgSO4 and CuSO4; preferably LiCl and CaCl2.

[0034] In some alternative embodiments, the self-irrigation and slow-release gel material has a water absorption rate of up to 1.37 g / g at a relative humidity of 20% RH; and a water absorption rate of up to 11.7 g / g at a relative humidity of 90% RH.

[0035] In some alternative embodiments, nutrients are also loaded on the gel substrate;

[0036] Preferably, the nutrients are selected from fertilizers, and the fertilizers include one or more of macronutrient fertilizers, secondary nutrient fertilizers and micronutrient fertilizers;

[0037] Preferably, the irrigation and slow-release gel material has a water absorption rate of 2.6 g / g at a relative humidity of 90%.

[0038] The key to restoring the ecology of arid and semi-arid regions is to restore soil moisture and reduce the loss of fertility. An important way to restore soil moisture and fertility is soil water and fertilizer conservation technology. Traditional water and fertilizer conservation technologies mainly include methods such as integrated water and fertilizer measures and soil improvement. Through the use of modern machinery, irrigation is carried out by combining drip irrigation, sprinkler irrigation or micro-irrigation with fertilizers. However, due to regional limitations, most of the above methods are difficult to implement, have high energy consumption and low efficiency.

[0039] In order to improve the above problems existing in the prior art, an embodiment of the present invention provides a new soil water and fertilizer conservation technology. An atmospheric water collection material is prepared by simultaneously loading a hygroscopic compound and a nutrient (preferably a fertilizer) on a gel substrate, so that the prepared atmospheric water collection material simultaneously realizes the water and fertilizer synergistic control functions of self-supplying water and slow-release fertilization, providing a favorable guarantee for improving the water use efficiency of plants in arid, semi-arid and seasonally water-deficient regions, reducing the loss of fertility, and improving the survival rate of plants.

[0040] In a second aspect, an embodiment of the present invention provides a preparation method of the above self-irrigation and slow-release gel material, including: preparing the gel substrate containing a hydrophilic polymer, lignosulfonate, and optionally a photothermal conversion material, and loading the hygroscopic compound on the gel substrate.

[0041] In some optional embodiments, the preparation process of the gel substrate includes: dropping the hydrophilic polymer aqueous solution into the lignosulfonate solution, or dropping the mixed solution of the hydrophilic polymer aqueous solution and the photothermal conversion material dispersion into the lignosulfonate solution to carry out polymerization to obtain spherical microbeads, and then soaking the spherical microbeads in water for swelling and removing the excess lignosulfonate. After freeze-drying, a gel substrate is obtained. During the preparation of the gel substrate, the polymer aqueous solution dropped reacts with calcium ions in the lignosulfonate solution, and the liquid film formed by physical cross-linking wraps the internal solution. As the degree of cross-linking reaction increases, the thickness of the outer liquid film increases, and then it is freeze-dried to obtain spherical microbeads with a hollow porous structure.

[0042] In some optional embodiments, the mass fraction of the hydrophilic polymer in the hydrophilic polymer aqueous solution is 1%; the concentration of the photothermal conversion material dispersion is 1 mg / mL, the concentration of the lignosulfonate solution is 1-10 mg / mL, the dropping rate is 8-12 mL / min, and the diameter of the microbeads is 0.45-0.52 mm.

[0043] In some optional embodiments, the process of loading the hygroscopic compound on the gel substrate includes: soaking the obtained gel substrate in an aqueous solution formed by the hygroscopic compound, and drying it after taking it out; wherein, the mass percentage of the hygroscopic compound in the hygroscopic compound is 5-30 wt%.

[0044] Preferably, the soaking time is 12 - 24 h, the drying temperature is 75 - 85 °C, and the drying time is 24 - 48 h.

[0045] In some alternative embodiments, the process of loading the hygroscopic compound and nutrients onto the gel substrate includes: soaking the obtained gel substrate in an aqueous solution formed by the hygroscopic compound, taking it out and drying; then immersing it again in a solution containing nutrients, taking it out and drying; wherein, the mass percentage of the hygroscopic compound in the hygroscopic compound is 5 - 30 wt%.

[0046] Preferably, the soaking time for both times is 12 - 24 h, the drying temperature is 75 - 85 °C, and the drying time is 24 - 48 h.

[0047] The preparation method of the self - irrigation and slow - release gel material provided by the embodiments of the present invention does not require cross - linkers and initiators, and the method is simple and easy to operate. By controlling the preparation parameters, the particle size, porosity, specific surface area, etc. of the microspheres can be controlled, so as to effectively control the release of the absorbed water. Through the slow - release effect of the microspheres, the required water for plants can be continuously provided, achieving the purpose of self - irrigation and slow - release. In some embodiments, by introducing nitrogen, phosphorus, and potassium elements required for plant growth, while realizing uninterrupted self - water supply, slow - release fertilization is achieved, realizing the integrated management and control of soil water and fertilizer, and greatly improving the survival rate of plants in arid and semi - arid regions.

[0048] It should be noted that during the process of loading the hygroscopic compound and nutrients onto the gel substrate, the quantity of the hygroscopic compound and nutrient components loaded on the gel substrate can be increased by soaking the gel substrate in the aqueous solution of the hygroscopic compound or the aqueous solution of nutrients for a long time, and reaching the saturation state as much as possible, thereby improving the water - collecting and fertilizer - releasing ability of the atmospheric water - collecting material.

[0049] In the third aspect, the embodiments of the present invention provide an application of the above - mentioned self - irrigation and slow - release gel material in sand soil solidification or the construction of soil layers in arid regions.

[0050] The present invention will be further described below with reference to embodiments.

[0051] Example 1

[0052] 0.1 g of carbon nanotubes (CNTs) was added to 100 mL of deionized water, shaken and ultrasonicated for 1 hour to obtain a CNTs suspension. At 60 °C, 1.0 g of sodium alginate (SA) was added to the CNTs suspension, and continuously stirred for 2 hours until completely dissolved, and then cooled to room temperature. Then, 100 mL of the mixed solution was dropped into 500 mL of calcium lignosulfonate (CaLS) solution (6 mg / mL) at a rate of 10 mL / min by a peristaltic pump. The non-dripping polymerization process was very fast, and spherical microbeads with a uniform diameter of about 0.5 mm were formed. The precursor microbeads were immersed in 1 L of deionized water for 24 hours to remove the excess CaLS, and SA / CaLS / CNTs microbeads were obtained.

[0053] After freeze-drying the precursor microbeads, they were immersed in a 10 wt% lithium chloride (LiCl) solution for 24 hours. Finally, the microbeads were dried at 75 - 85 °C for 24 h to obtain LiCl / SA / CaLS / CNTs microbeads.

[0054] Example 2

[0055] 0.1 g of carbon nanotubes (CNTs) was added to 100 mL of deionized water, shaken and ultrasonicated for 1 hour to obtain a CNTs suspension. At 60 °C, 1.0 g of sodium alginate (SA) was added to the CNTs suspension, and continuously stirred for 2 hours until completely dissolved, and then cooled to room temperature to obtain a mixed solution. Then, 100 mL of the mixed solution was dropped into 500 mL of calcium lignosulfonate (CaLS) solution (5 mg / mL) at a rate of 10 mL / min by a peristaltic pump. The non-dripping polymerization process was very fast, and spherical microbeads with a uniform diameter of about 0.5 mm were formed. The precursor microbeads were immersed in 1 L of deionized water for 24 hours to remove the excess CaLS, and SA / CaLS / CNTs microbeads were obtained.

[0056] After freeze-drying the precursor microbeads, they were immersed in a 10 wt% lithium chloride (LiCl) solution for 24 hours. Finally, the microbeads were dried at 75 - 85 °C for 24 h to obtain LiCl / SA / CaLS / CNTs microbeads.

[0057] Example 3

[0058] 0.1 g of carbon nanotubes (CNTs) was added to 100 mL of deionized water, shaken and ultrasonically treated for 1 hour to obtain a CNT suspension. 1.0 g of sodium alginate (SA) was added to the CNT suspension at 60 °C and continuously stirred for 2 hours until completely dissolved, and then cooled to room temperature to obtain a mixed solution. Then 100 mL of the mixed solution was dropped into 500 mL of calcium lignosulfonate (CaLS) solution (7 mg / mL) at a rate of 10 mL / min by a peristaltic pump. The non-dripping polymerization process was very fast, and spherical microbeads with a uniform diameter of about 0.5 mm were formed. The precursor microbeads were soaked in 1 L of deionized water for 24 hours to remove the excess CaLS, and SA / CaLS / CNTs microbeads were obtained.

[0059] After the precursor microbeads were freeze-dried, they were immersed in a 10 wt% lithium chloride (LiCl) solution for 24 hours. Finally, the microbeads were dried at 75 - 85 °C for 24 h to obtain LiCl / SA / CaLS / CNTs microbeads.

[0060] Example 4

[0061] Synthesis of LiCl / SA / CaLS / CNTs microbeads: First, 0.1 g of carbon nanotubes (CNTs) was added to 100 mL of deionized water, shaken and ultrasonically treated for 1 hour to obtain a CNT suspension. 1.0 g of sodium alginate (SA) was added to the CNT suspension at 60 °C and continuously stirred for 2 hours until completely dissolved, and then cooled to room temperature to obtain a mixed solution. Then 100 mL of the mixed solution was dropped into 500 mL of calcium lignosulfonate (CaLS) solution (6 mg / mL) at a rate of 10 mL / min by a peristaltic pump. The non-dripping polymerization process was very fast, and spherical microbeads with a uniform diameter of about 0.45 - 0.52 mm were formed. The precursor microbeads were soaked in 1 L of deionized water for 24 hours to remove the excess CaLS. After the precursor microbeads were freeze-dried (the specific surface area of the microbeads was detected to be 23.3390 m 2 / g, and the micropore volume was 6.643×10 -2 cm 3 / g), the freeze-dried microbeads were immersed in a 10 wt% lithium chloride (LiCl) solution for 24 hours. Finally, the microbeads were dried at 85 °C for 24 h to obtain LiCl / SA / CaLS / CNTs microbeads.

[0062] Synthesis of CaCl2 / SA / CaLS microbeads: CaCl2 / SA / CaLS microbeads without CNTs were prepared by the same method and immersed in a 10 wt% calcium chloride (CaCl2) solution ( Figure 1)。The prepared CaCl2 / SA / CaLS microspheres were immersed in a 10 wt% lithium chloride (LiCl) solution by impregnation for 24 hours. Finally, the microspheres were dried at 85 °C for 24 h to obtain CaCl2 / SA / CaLS microspheres.

[0063] Loading of NPK fertilizer: To achieve the performance of slow-release fertilizer of the hygroscopic polymer microspheres, a two-step method was used for the loading of NPK. The completely dried CaCl2 / SA / CaLS microspheres were immersed in a mixed solution composed of 10% potassium dihydrogen phosphate and urea for 12 hours. Finally, the microspheres were dried at 85 °C for 24 hours to obtain NPK / CaCl2 / SA / CaLS composite microspheres.

[0064] A 1% SA (or SA and CNTs) solution was preferably dropped into a 6 mg / mL CaLS solution, and SA / CaLS (or SA / CaLS / CNTs) microsphere precursors were prepared by the dripping polymerization method, and then hygroscopic microspheres were prepared by loading with LiCl and CaCl2. It should be noted that Ca 2+ is an important component for forming the three-dimensional network structure of the microspheres, and the concentration of the CaLS solution determines the shape and size of the microspheres. When the concentration ratio of CaLS to SA is (1 - 4):10, due to insufficient cross-linking, microspheres with uniform size cannot be formed (Figure Figure 2 a). On the contrary, when the concentration ratio of CaLS to SA is (8 - 10):10, over-cross-linking and rapid gelation will occur, forming dense spheres that hinder the entry and diffusion of water molecules ( Figure 2 Figure b). By testing the zeta potential of the precursor solution at different CaLS concentrations, it was found that the Ca 2+ ions in CaLS neutralized the negative charge of SA (zeta potential is -63 mV). When the concentration ratio of CaLS to SA is (5 - 7):10, the prepared hygroscopic microspheres have a porous hollow structure, and when the concentration of CaLS reaches 0.6 wt%, the zeta potential tends to be stable, indicating that Ca 2+ and the carboxyl group (-COO - ) of SA have reached chemical equilibrium, forming a stable cross-linked network ( Figure 2 Figure c). With the saturation of the carboxyl group, the Zeta potential no longer changes with the concentration, and excessive Ca 2+ will cause local over-cross-linking, resulting in a decrease in the microsphere size.

[0065] The internal micro-morphology of the LiCl / SA / CaLS / CNTs microspheres was characterized by scanning electron microscopy (SEM). Figure 3a-f show the morphologies of SA / CaLS, SA / CaLS / CNTs, LiCl / SA / CaLS / CNTs, and CaCl2 / SA / CaLS microspheres, and all samples have interconnected porous and hollow features. The formation of the hollow structure is considered to be related to the dripping polymerization during the preparation process. When the SA droplets are dropped into the CaSL solution, Ca 2+ ions are released and ionically cross-linked with the carboxyl groups (-COO - ) of SA through the "egg-box model" to form egg-box dimers, which polymerize into a stable three-dimensional network, initiate the polymerization reaction, and form an eggshell-like structure. Subsequently, Ca 2+ in the CaSL solution gradually penetrates into the droplets to form a polymer network structure, which further increases the penetration difficulty of Ca 2+ . When there is not enough Ca 2+ participating in the polymerization at the center of the SA solution sphere, a hollow structure is formed. The penetration direction of calcium ions is also affected by the formed polymer network, so it can be seen that the pores formed inside are interconnected ( Figure 3 c and f). Figure 3 Compared with Figure 3 d, the pore structure of SA / CaLS / CNTs microspheres is more ordered than that of SA / CaLS and is arranged in layers, which accelerates the adsorption kinetics of the microspheres.

[0066] Water absorption performance test of the hygroscopic microspheres: The adsorption performance of the microspheres was tested in a constant temperature and humidity chamber (LHS-HC-II, Shanghai Yiheng Scientific Instruments Co., Ltd.). At a constant temperature of 25 °C and different humidity conditions, the mass of the microspheres was monitored in real time until a constant weight was reached. Finally, the adsorption kinetic curve was plotted according to the moisture absorption rate.

[0067] Desorption performance test of the hygroscopic microspheres: A solar xenon light source system (CBL-S500, Beijing Zhongjiao Jinyuan Technology Co., Ltd.) was used to simulate sunlight to test the desorption performance of the microspheres. The light intensity was recorded by a solar power meter (SM206-SOLAR, Xinbao Technology), and the changes in the mass and surface temperature of the microspheres during the experiment were recorded in real time by an electronic balance and an infrared thermal imager.

[0068] Performance evaluation of the hygroscopic microspheres for producing clean water: The clean water production experiment was carried out in a real outdoor environment. The dried microspheres were placed in a solar water collection device, and the water adsorption experiment was carried out when the light intensity was weak (200 - 600 W / m 2 ), and the water collection amount was calculated. Then the released water amount was continuously recorded. The ambient humidity, ambient temperature, and light intensity were recorded every half hour. Finally, the collected water was weighed.

[0069] Performance Evaluation of Hygroscopic Microbeads for Promoting Plant Growth under Atmospheric Water Irrigation: Calcium is a more common element in soil than lithium, and it plays a crucial role in strengthening plant roots in plants. In addition, calcium chloride (CaCl2) is also a hygroscopic salt. Therefore, the hygroscopic microbeads SA / CaLS loaded with CaCl2 can be used for atmospheric water irrigation. Ryegrass was selected as the experimental plant, and the seeds were evenly distributed in the improved sandy soil. A blank control group (CK) was set up, and the initial water content of the experimental group and the blank control group (CK) was ensured to be the same. Subsequently, all samples were subjected to drought stress without adding extra nutrients and water, and the germination rate, plant height, survival time, and biomass of ryegrass were measured. The experiment was repeated three times and the average value was taken.

[0070] Feasibility Evaluation of the Fertility Slow-Release Efficiency of Gel Microbeads: Since the test results of the direct fertility release test in soil had no significant difference and the test period was relatively long, in this study, a blank control group was set up for comparison in the research idea of the adsorption effect of microbeads on fertilizer components in still water to evaluate the gel fertility slow-release. The feasibility of the gel microbeads' fertility slow-release was tested by the static water dissolution test. 0.3 g of microbead material wrapped with a 200-mesh filter cloth was added to 300 mL of deionized water. Samples were taken at different times. When sampling, gently stir and suck 10 mL of the liquid and simultaneously supplement 10 mL of deionized water to prevent partial water evaporation and interference from external substances. Sealing treatment was required. The extracted liquid was placed in a 10-mL centrifuge tube and stored at -24 °C.

[0071] The test of urea was carried out by the method of p-dimethylaminobenzaldehyde; the test of potassium ions was carried out by flame atomic absorption spectrometry; the determination of phosphorus was carried out by ammonium molybdate spectrophotometry.

[0072] Performance Evaluation of the Air Water Collection Adsorption-Desorption of LiCl / SA / CaLS / CNTs Microbeads: The water vapor adsorption experiment was carried out in a constant temperature and humidity chamber to study the adsorption capacity under different relative humidities to systematically evaluate the AWH ability of LiCl / SA / CaLS / CNTs microbeads. As shown in a) of the kinetic curve ( Figure 4 ), even at a relative humidity of 20%, the water absorption rate of LiCl / SA / CaLS / CNTs microbeads was as high as 1.37 g / g. At 60% and 90% relative humidity, the adsorption capacities were 3.1 g / g and 11.7 g / g respectively. The water absorption was significantly higher than that of similar materials reported in the current literature ( Figure 4 c). The excellent hygroscopic performance of the microbeads was attributed to its rich hydrophilic functional groups and the loading of strong hygroscopic salts ( Figure 4In b). In addition, the porous structure of the microbeads is conducive to the loading of hygroscopic salts, thereby improving the ability to adsorb water vapor. The hollow structure promotes the penetration and storage of microporous capillary water, while the interconnected channels facilitate the transmission of seepage water. These physical and chemical properties together contribute to efficient water collection. At 60% RH and a temperature of 25 °C, after five adsorption-desorption cycles, the adsorption performance is hardly affected ( Figure 4 In d).

[0073] In addition to the adsorption performance, the desorption performance also determines the atmospheric water collection performance of the adsorbent. In order to simulate the moisture release in different regions, LiCl / SA / CaLS / CNTs microbeads with an adsorption capacity of 3.1 g / g were placed under four different light intensity conditions for solar-driven moisture release experiments. In the first 90 min, the surface temperature of the LiCl / SA / CaLS / CNTs microbeads increased rapidly and the moisture was released quickly. As the moisture content of the LiCl / SA / CaLS / CNTs microbeads decreased, the release rate slowed down. Higher light intensity increased both the moisture release rate and the release rate of the hydrogel ( Figure 5 In b-c). After 2.5 h of simulated sunlight irradiation (light intensities of 0.5, 1, 1.5, 2 kW / m 2 ²), 74%, 89%, 97%, and 99.9% of the moisture was released. The microbeads without added CNTs had weak light absorption performance. By introducing CNTs, the light energy conversion performance can be significantly improved to achieve rapid moisture release. The LiCl / SA / CaLS / CNTs microbeads can reach 32.5, 47, 51.1, and 54.3 °C within 10 min at light intensities of 0.5, 1, 1.5, 2 kW / m 2 ² ( Figure 5 In a). This indicates that the LiCl / SA / CaLS / CNTs microbeads can perform solar-driven water adsorption-desorption cycles under different light intensities.

[0074] We further carried out outdoor experiments using a self-made solar water collector to achieve rapid capture and collection of water. The dry LiCl / SA / CaLS / CNTs microbeads were placed on a perforated mesh bracket and exposed to the atmosphere to collect water. Subsequently, the LiCl / SA / CaLS / CNTs microbeads used solar energy to drive the conversion of liquid water into gaseous water, which condensed on the surface of the device, and then the condensed water flowed to the bottom water storage area for collection. This indicates that the LiCl / SA / CaLS / CNTs microbeads can effectively collect atmospheric moisture and continuously release it under the drive of the sun.

[0075] The AWH outdoor experiment was carried out at an average outdoor temperature of 18 °C and a humidity of 55%. At a light intensity of 200 - 600 W / m 2The water release experiment was carried out under sunlight, and the environmental humidity, environmental temperature, and the water absorption of LiCl / SA / CaLS / CNTs microbeads were monitored in real time. Figure 6 In b) of. After 3 hours, the amount of water collected can increase to 2.1 g / g, and the average water absorption rate is 0.7 g / (g·h), showing a significant improvement compared with previous studies. Then, under sunlight (about 300 W / m 2 ), after 12 minutes, the surface temperature of the LiCl / SA / CaLS / CNTs microbeads rises to 39 °C and water vapor is released.

[0076] After being exposed to natural light for 3.5 hours, about 1.39 g / g of water was collected, the AWH efficiency of the outdoor collector remained at 85%, and the lost water was 1.63 g / g. In addition, to ensure the safety of the collected water, the contents of several important ions (Na + , K + , Mg 2+ , Ca 2+ , Zn 2+ and Cl - ) in the collected water were detected, and the results showed that they met the quality standards stipulated by the World Health Organization (WHO) Figure 6 in c). These results indicate that LiCl / SA / CaLS / CNTs microbeads can effectively collect clean water under outdoor conditions.

[0077] Hygroscopic microbeads are used for soil atmospheric water irrigation: Due to its hollow porous structure, the SA / CaLS matrix without loaded hygroscopic salt can still achieve a water vapor adsorption capacity of 0.5 g / g at 25 °C and 90% RH Figure 7 in a). After introducing the hygroscopic salt CaCl2, the water absorption rates of CaCl2 / SA / CaLS microbeads are 1.5 g / g and 3.7 g / g at 60% and 90% RH respectively Figure 7 in b), which are higher than most reported CaCl2-loaded AWH materials Figure 7 in c). Adding these microbeads to completely dry sandy soil can increase the water content of the soil and provide necessary water for plant growth. The experimental results show that the water content of the blank control group (CK) is 0.61%, and when different concentrations (0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.% and 0.5 wt.%) of CaCl2 / SA / CaLS microbeads are doped in the sandy soil, the water contents of the improved soil can reach 0.8%, 0.98%, 1.48%, 1.88% and 2.13% respectively Figure 7 in d).

[0078] To prove the feasibility of atmospheric water irrigation, seed germination and plant growth experiments were conducted. Without adding extra nutrients and water, all seeds germinated ( Figure 8 as shown in a) of Figure 8 and grew into ryegrass plants after 11 days, with heights ranging from 12 cm (control group) to 18 cm ( Figure 8 as shown in b) of Figure 8 . Statistical analysis of the survival rate of ryegrass under the conditions of an outdoor average temperature of 26 °C and a relative humidity of 60% RH ( Figure 8 as shown in d) of

[0079] showed that atmospheric water irrigation extended the survival time of ryegrass in sandy soil with added CaCl2 / SA / CaLS microspheres by 13 days ( Figure 9 as shown in e - f) of

[0080] . The biomass after plant harvest showed ( Figure 9 as shown in c) of Figure 9 that CaCl2 / SA / CaLS microspheres were non - toxic to plants and could provide calcium ions required for plant growth through slow - release, promoting plant growth. Therefore, CaCl2 / SA / CaLS microsphere - modified soil can achieve passive atmospheric water irrigation, extend the growth and survival period of plants in sandy soil without artificial irrigation, and has a friendly environmental compatibility for plant growth.

[0081] Hygroscopic microspheres for slow - release of fertility: Research shows that after loading NPK fertilizers, hygroscopic microspheres still possess good water vapor adsorption performance, thus providing a feasible solution for slow - release of fertility. To verify their water vapor adsorption ability, researchers placed the microspheres in a constant temperature and humidity chamber for water vapor adsorption tests. The results showed that under environmental conditions of 25 °C and 90% RH, the NPK / CaCl2 / SA / CaLS composite microspheres could still maintain a water vapor adsorption capacity of 2.6 g / g (

[0082] Figure 9 as shown in a) of

[0080] . In addition, the research also used static water dissolution tests to test the slow - release effect of the microspheres on fertility. The results found that pure urea completely dissolved in only 10 minutes without stirring, while the microspheres could slowly release fertilizers within 24 hours ( Figure 9 as shown in b) of Figure 9 . In contrast, pure potassium dihydrogen phosphate completely dissolved within 30 minutes without stirring, while the microspheres could achieve slow - release of phosphorus for up to 48 hours and the slow - release time of potassium was extended to 96 hours ( Figure 9 as shown in c, d) of

[0081] These experimental results show that the microspheres not only possess significant water vapor adsorption ability but also can effectively achieve the slow - release function of fertilizers, fully proving their feasibility as carriers for slow - release of fertility.

[0082] As can be seen above, the embodiments of the present invention provide a self-priming and slow-release atmospheric water collection material, its preparation method and application, and successfully synthesized LiCl / SA / CaLS / CNTs spherical microbeads and CaCl2 / SA / CaLS spherical microbeads, which can effectively collect water. The LiCl / SA / CaLS / CNTs microbeads showed fast adsorption kinetics at 90% relative humidity (RH), with a high water absorption rate of 11.7 g / g. Under the conditions of atmospheric water irrigation at 26°C and 60% RH, in simulated drought conditions, the sandy soil modified with CaCl2 / SA / CaLS microbeads significantly extended the survival time of ryegrass by 13 days. In addition, by introducing the nitrogen, phosphorus, and potassium elements required for plant growth, slow-release fertilization was achieved while realizing uninterrupted self-water supply, and the coordinated management and control of soil water and fertilizer were realized.

[0083] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A self-priming and sustained-release gel material, characterized in that, It includes a gel substrate and a hygroscopic compound loaded on the gel substrate; wherein, the gel substrate contains a hydrophilic polymer, lignosulfonate, and optionally a photothermal conversion material.

2. The self-priming and sustained-release gel material according to claim 1, wherein The gel substrate is a spherical microbead with a hollow porous structure; Preferably, the particle size is 0.45 mm - 0.52 mm.

3. The self-priming and sustained-release gel material according to claim 1, wherein The mass ratio of the hydrophilic polymer to lignosulfonate in the gel substrate is 10:(1 - 10), or the mass ratio of the hydrophilic polymer, lignosulfonate, and photothermal conversion material in the gel substrate is 10:(1 - 10):1; Preferably, the hydrophilic polymer includes one or more of chitosan, starch, or sodium alginate, and preferably sodium alginate; Preferably, the lignosulfonate includes one or more of calcium lignosulfonate and magnesium lignosulfonate, and preferably calcium lignosulfonate; Preferably, the photothermal conversion material includes one or more of carbon nanotubes, carbon black, activated carbon, graphene, or graphyne, and preferably carbon nanotubes.

4. The self-priming and sustained-release gel material according to claim 1, characterized in that, The hygroscopic compound includes one or more of LiCl, CaCl2, MgSO4, and CuSO4; preferably LiCl and CaCl2.

5. The self-priming and sustained-release gel material according to any one of claims 1-4, characterized in that The self-filling and slow-release atmospheric water collection material can achieve a water absorption rate of 1.37 g / g at a relative humidity of 20% RH; and a water absorption rate as high as 11.7 g / g at a relative humidity of 90% RH.

6. The self-priming and sustained-release gel material according to claim 5, wherein, The gel substrate is also loaded with nutrients; Preferably, the nutrients are selected from fertilizers, and the fertilizers include one or more of macronutrient fertilizers, secondary nutrient fertilizers, and micronutrient fertilizers; Preferably, the filling and slow-release gel material has a water absorption rate of 2.6 g / g at a relative humidity of 90%.

7. A preparation method of the self-priming and sustained-release gel material according to any one of claims 1-6, characterized in that, It includes: Preparing the gel substrate containing a hydrophilic polymer, lignosulfonate, and optionally a photothermal conversion material, and loading the hygroscopic compound on the gel substrate.

8. The preparation method according to claim 7, characterized in that, The preparation process of the gel substrate includes: dropping the hydrophilic polymer aqueous solution into the lignosulfonate solution, or dropping the mixed solution of the hydrophilic polymer aqueous solution and the photothermal conversion material dispersion into the lignosulfonate solution to carry out polymerization to obtain spherical microbeads, then soaking the spherical microbeads in water for swelling and removing the excessive lignosulfonate, and after freeze-drying, obtaining the gel substrate; Preferably, the mass fraction of the hydrophilic polymer in the hydrophilic polymer aqueous solution is 1%; the concentration of the photothermal conversion material dispersion is 1 mg / mL, the concentration of the lignosulfonate solution is 1 - 10 mg / mL, the dropping rate is 8 - 12 mL / min, and the microbead diameter is 0.45 - 0.52 mm.

9. The preparation method according to claim 8, characterized in that, The process of loading the hygroscopic compound on the gel substrate includes: soaking the obtained gel substrate in the aqueous solution formed by the hygroscopic compound, and taking it out for drying; wherein, the mass percentage of the hygroscopic compound in the hygroscopic compound is 5 - 30 wt%, the soaking time is 12 - 24 h, the drying temperature is 75 - 85 °C, and the drying time is 24 - 48 h; Preferably, the process of loading the hygroscopic compound and the nutrient on the gel substrate includes: soaking the obtained gel substrate in an aqueous solution formed by the hygroscopic compound, taking it out and drying; then immersing it again in a solution containing the nutrient, taking it out and drying; wherein, the mass percentage of the hygroscopic compound in the hygroscopic compound is 5-30 wt%, the soaking time for both times is 12-24 h, the drying temperature is 75-85 °C, and the drying time is 24-48 h.

10. Application of the self-irrigation and slow-release gel material according to any one of claims 1-6 or the self-irrigation and slow-release gel material prepared by the preparation method according to any one of claims 7-9 in the production of clean water and the construction of soil layers in arid regions.

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