A hygroscopic material and a method for preparing and using the same

Abstract

The present application relates to a kind of hygroscopic material and its preparation method and application, belong to artificial weather modification catalyst technical field, to solve at least one of the problems such as poor hygroscopicity, poor catalytic performance, low dispersion performance of the hygroscopic material prepared by existing method.The present application forms composite structure by coating nanomaterial on the surface of hygroscopic core.Nanoparticle coating layer can not only effectively inhibit the caking behavior of hygroscopic core in storage and transportation environment, but also promote the hygroscopicity of hygroscopic core to absorb moisture and deliquesce in advance.In addition, the presence of oxide coating layer enhances the chemical stability and durability of the material, so that the hygroscopic material of the present application can maintain high catalytic activity under different climate conditions, and the stability of traditional catalyst in long-term use is improved.The hygroscopic material of this composite structure can be flexibly adjusted according to the type, thickness and interaction of nanomaterial and hygroscopic core, so as to realize the precise control of catalytic performance, and significantly improve the catalytic effect.

Description

Technical Field

[0001] This invention relates to the field of weather modification catalysts, and in particular to a hygroscopic material, its preparation method, and its application. Background Technology

[0002] Against the backdrop of global climate change, increased greenhouse gas emissions have led to global warming, more frequent climate anomalies, increased uneven distribution of precipitation, and a rise in extreme weather events, significantly impacting people's lives and livelihoods and social harmony. Furthermore, there are also problems related to water resources, including a growing global water shortage, uneven distribution of freshwater resources, prominent regional water scarcity, and intensified water supply-demand imbalances. These pose serious challenges to agricultural production and urban water supply, such as water shortages during the wheat growing season, irrigation water shortages for cotton, severe water scarcity, and seasonal water shortages.

[0003] Atmospheric water vapor, as a natural resource, accounts for approximately 10% of the freshwater in all rivers and lakes on Earth. Utilizing weather modification catalysts as cloud condensation nuclei (CCNs) is an effective method to accelerate water droplet formation, which is then collected through rainfall. Therefore, artificial rainmaking is of significant practical importance for ensuring agricultural production, maintaining favorable weather conditions for large-scale international events, and preventing extreme weather events. Currently, weather modification catalysts are mainly classified into three categories: refrigerants, artificial ice nuclei, and hygroscopic nuclei. Refrigerants sublimate or vaporize within clouds, absorbing heat in the process and significantly lowering the surrounding air temperature, causing the air humidity to reach a supersaturated state. This promotes water vapor sublimation to form ice crystals and simultaneously disrupts the metastable state of supercooled water droplets in the cloud, triggering their spontaneous nucleation and freezing. This activates naturally existing ice nuclei within the cloud into ice. Commonly used refrigerants include dry ice (solid CO2), liquid carbon dioxide (LC), liquid nitrogen (LN), and liquid propane (LP). Artificial ice nuclei are weather-modifying catalysts used for cold clouds, i.e., clouds with temperatures below 0°C. Currently, the most commonly used artificial ice nuclei are silver iodide (AgI) and modified doped materials based on AgI. The main reason AgI can exert its ice-nucleating activity is believed to be its hexagonal crystal lattice structure, which is very similar to ice crystals, making it easier for ice crystals to form on its surface, thus catalyzing the cold cloud precipitation process. Hygroscopic nuclei are generally used for warm clouds, i.e., clouds with temperatures above 0°C. Hygroscopic nuclei can adsorb water vapor in warm clouds, eventually converting it completely into water droplets. These droplets grow through collisions and aggregation until they become large enough to fall like rain. Commonly used materials for warm cloud catalysis include sodium chloride (NaCl), calcium chloride (CaCl2), urea (NH2CONH2), and ammonium nitrate (NH4NO3).

[0004] However, currently available hygroscopic materials suffer from problems such as poor hygroscopicity, poor catalytic performance, and low dispersion performance. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a hygroscopic material, its preparation method and application, to solve at least one of the problems of poor hygroscopicity, poor catalytic performance, low dispersion performance and high relative humidity at which hygroscopic materials prepared by existing methods begin to absorb moisture.

[0006] In a first aspect, the present invention provides a hygroscopic material, wherein the hygroscopic material has a hygroscopic core at its center and a surface coated with nanomaterials modified by surfactants.

[0007] Furthermore, the hygroscopic core includes one or more of sodium chloride, calcium chloride, potassium chloride, ammonium sulfate, sodium sulfate, and sodium carbonate;

[0008] The nanomaterials mentioned include one or more of the following: aluminum oxide, zinc oxide, magnesium oxide, iron oxide, copper oxide, indium oxide, carbon nanotubes, and graphene.

[0009] The surfactants mentioned include one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, cocamidopropyl betaine, hexadecyltrimethylammonium bromide, dodecylammonium bromide, Tween-80, polyacryl alcohol, and polyethylene glycol-200.

[0010] Furthermore, the particle size of the nanomaterial is 30-500 nm.

[0011] Secondly, the present invention provides a method for preparing the above-mentioned hygroscopic material, comprising the following steps:

[0012] (1) The nanomaterials were washed in ethanol, filtered, and dried to obtain the purified nanomaterials;

[0013] (2) Dissolve the surfactant in water, add ethanol to obtain a mixed solution, add the nanomaterial to the mixed solution, sonicate, heat to react, and obtain the modified nanomaterial.

[0014] (3) The modified nanomaterials are added to a poor solvent to obtain a poor solvent-nanomaterial phase;

[0015] The hygroscopic nucleus is dissolved in water to obtain a hygroscopic nucleus solution;

[0016] (4) The poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 7:3-9:1, precipitated, and filtered to obtain the hygroscopic material.

[0017] Furthermore, in step (2), the mass-volume ratio of the surfactant, water, and ethanol is 0.1-0.3g:40-60mL:5-15mL, and the mass ratio of the surfactant to the modified nanomaterial is 0.1-0.3:1-3.

[0018] Furthermore, in step (2), the temperature for heating the reaction is 40-60℃, and the reaction time is ≥2h.

[0019] Furthermore, in step (3), the undesirable solvent includes one or more of ethanol, isopropanol, cyclohexane, and acetone.

[0020] Furthermore, in step (3), the concentration of the modified nanomaterial in the poor solvent is 10-100 mg / mL, and the concentration of the hygroscopic core in the hygroscopic core solution is 0.5-3 mol / L.

[0021] Furthermore, in step (4), the total flow rate of the poor solvent-nanomaterial phase and the hygroscopic core solution is 1-10 mL / min.

[0022] Thirdly, the present invention provides an application of the above-mentioned hygroscopic material in weather modification catalysts.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] (1) This invention forms a composite structure by coating the surface of a hygroscopic core with nanomaterials. The nanoparticle coating layer not only effectively inhibits the agglomeration behavior of the hygroscopic core under storage and transportation conditions, but also promotes the early hygroscopic deliquescence of the hygroscopic core. In addition, the presence of the oxide coating layer enhances the chemical stability and durability of the material, enabling the hygroscopic material of this invention to maintain high catalytic activity under different climatic conditions, and improving the stability of traditional catalysts in long-term use. This composite structure of hygroscopic material can be flexibly adjusted according to the type, thickness, and interaction of the nanomaterials with the hygroscopic core, thereby achieving precise control of catalytic performance and significantly improving the catalytic effect;

[0025] (2) The present invention uses a continuous flow method to generate crystal precipitation to prepare micron-sized hygroscopic core-nanomaterial crystals, which can recycle poor solvents and save costs;

[0026] (3) The hygroscopic material of the present invention forms a single-layer coated modified nanomaterial, and the prepared modified nanomaterial can form hydrogen bonds with water, thereby more easily adsorbing water vapor and forming local high humidity on the surface of the hygroscopic core, promoting the hygroscopic growth of the hygroscopic core. Moreover, the particle size of the hygroscopic material meets the requirements of 1-10 μm for warm cloud artificial weather modification catalyst materials, which is the basis for being a good warm cloud artificial weather modification catalyst.

[0027] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0028] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0029] Figure 1 This is a schematic diagram of a cloud chamber and testing device in Experimental Example 2 of the present invention;

[0030] Figure 2 This is a graph showing the change in median particle size of cloud chamber droplets over time in Experiment Example 2 of this invention;

[0031] Figure 3 This is a number concentration diagram of the hygroscopic material and pure NaCl prepared in Example 1 of Experimental Example 2 of this invention before the humidity reaches supersaturation. Detailed Implementation

[0032] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0033] In one specific embodiment of the present invention, a hygroscopic material is disclosed, wherein the hygroscopic material has a hygroscopic core at its center and a surface coated with nanomaterials modified by surfactants.

[0034] Specifically, the hygroscopic core includes one or more of sodium chloride, calcium chloride, potassium chloride, ammonium sulfate, sodium sulfate, and sodium carbonate;

[0035] The nanomaterials mentioned include one or more of the following: aluminum oxide, zinc oxide, magnesium oxide, iron oxide, copper oxide, indium oxide, carbon nanotubes, and graphene.

[0036] The surfactants mentioned include one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, cocamidopropyl betaine, hexadecyltrimethylammonium bromide, dodecylammonium bromide, Tween-80, polyacryl alcohol, and polyethylene glycol-200.

[0037] Specifically, the particle size of the nanomaterial is 30-500nm, for example, 50nm, 70nm, 90nm, 110nm, 130nm, 150nm, 170nm, 190nm, 210nm, 230nm, 250nm, 270nm, 290nm, 310nm, 330nm, 350nm, 370nm, 390nm, 410nm, 430nm, 450nm, 470nm, and 490nm.

[0038] It should be noted that research has found that when the particle size of nanomaterials is too small, their effect on the deliquescence ability of the hygroscopic core is too small, making it difficult to exert their performance in promoting early moisture absorption and deliquescence; when the particle size of nanomaterials is too large, their effect on coating the hygroscopic core is poor, making it difficult to form an effective coating structure.

[0039] The hygroscopic material of this invention differs significantly from materials in the prior art. Traditional hygroscopic materials typically rely on a single hygroscopic salt (such as NaCl, CaCl2, etc.) or a water-retaining material (such as diatomaceous earth, polyacrylamide, etc.) as the catalytic core. However, hygroscopic salts are prone to agglomeration in high-humidity environments, leading to a decline in their catalytic performance, while water-retaining materials exhibit poor hygroscopicity and high water loss rates. In contrast, this invention forms a composite structure by coating the surface of the hygroscopic core with nanomaterials. The nanoparticle coating layer not only effectively inhibits the agglomeration behavior of hygroscopic salts under storage and transportation conditions but also promotes the premature deliquescence of the hygroscopic core. Furthermore, the presence of the oxide coating layer enhances the chemical stability and durability of the material, enabling the hygroscopic material of this invention to maintain high catalytic activity under different climatic conditions, showing improved stability in long-term use compared to traditional catalysts. This composite structure of the hygroscopic material can be flexibly adjusted according to the type, thickness, and interaction with the salt core of the nanomaterials, thereby achieving precise control over catalytic performance and significantly improving the catalytic effect.

[0040] The hygroscopic material of this invention can serve as an effective warm cloud catalyst, primarily by providing effective condensation nuclei to promote the formation and growth of cloud droplets, thereby initiating and accelerating precipitation processes. Within clouds, the hygroscopic material combines with water vapor through hygroscopic action, forming growing water droplets. The nanomaterial coating not only protects the hygroscopic material but also enhances its catalytic efficiency by increasing its surface hydrophilicity and improving its interaction with water vapor in the cloud. Furthermore, the structural design of the oxide coating significantly improves the adaptability of the hygroscopic material under different humidity conditions, enabling it to operate effectively over a wide humidity range and solving the problem of poor humidity adaptability in traditional catalysts. Therefore, the hygroscopic material of this invention not only exhibits highly efficient catalytic activity under various meteorological conditions but also maintains long-term stability, possessing broad application potential, especially in the context of increased extreme weather events due to climate change, providing a feasible solution for artificial rainmaking.

[0041] Another specific embodiment of the present invention discloses a method for preparing a hygroscopic material, comprising the following steps:

[0042] (1) The nanomaterials were washed in ethanol, filtered, and dried to obtain the purified nanomaterials;

[0043] (2) Dissolve the surfactant in water, add ethanol to obtain a mixed solution, add the nanomaterial to the mixed solution, sonicate, heat to react, and obtain the modified nanomaterial.

[0044] (3) The modified nanomaterials are added to a poor solvent to obtain a poor solvent-nanomaterial phase;

[0045] The hygroscopic nucleus is dissolved in water to obtain a hygroscopic nucleus solution;

[0046] (4) The poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 7:3-9:1, precipitated, and filtered to obtain the hygroscopic material.

[0047] Specifically, in step (2), the mass-to-volume ratio of the surfactant, water, and ethanol is 0.1-0.3g (e.g., 0.12g, 0.14g, 0.16g, 0.2g, 0.22g, 0.24g, 0.26g, 0.28g): 40-60mL (e.g., 42mL, 44mL, 46mL, 48mL, 50mL, 52mL, 54mL, 56mL, 58mL): 5-15mL (e.g., 6mL). The surfactant is expressed in the form of 7 mL, 8 mL, 9 mL, 10 mL, 11 mL, 12 mL, 13 mL, or 14 mL, and the mass ratio of the surfactant to the modified nanomaterial is 0.1-0.3 (e.g., 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28):1-3 (1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8).

[0048] It should be noted that when the surfactant content is too low, it is difficult to completely modify the nanomaterials; when the content is too high, it exceeds the critical supersaturation concentration, making it difficult to dissolve. Water, as the reaction medium, needs to dissolve the surfactant and disperse the nanomaterials. When the content is too low, it will reduce the solubility of the surfactant and the dispersibility of the nanomaterials. When the content is too high, the solution concentration is too low, resulting in poor surfactant coating effect. Ethanol can promote the solubility of surfactants. When the content is too low, it is difficult to play a role. When the content is too high, it will reduce the surfactant coating ability.

[0049] Specifically, in step (2), the ultrasonic power is 50-100kHz, for example, 55kHz, 60kHz, 65kHz, 70kHz, 75kHz, 80kHz, 85kHz, 90kHz, 95kHz, and the ultrasonic time is 20-40min, for example, 25min, 30min, 35min.

[0050] It should be noted that the above-mentioned ultrasonic conditions can enable the surfactant to be uniformly adsorbed on the surface of the nanomaterial.

[0051] Specifically, in step (2), the temperature for heating the reaction is 40-60℃, for example, 42℃, 44℃, 46℃, 48℃, 50℃, 52℃, 54℃, 56℃, 58℃, and the reaction time is ≥2h, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h.

[0052] It should be noted that heating the temperature too low will result in insufficient surfactant coating, while heating the temperature too high will cause the ethanol to evaporate too quickly, resulting in reduced surfactant solubility and crystallization; and reaction time too short will result in insufficient surfactant coating.

[0053] Specifically, in step (3), the undesirable solvent includes one or more of ethanol, isopropanol, cyclohexane, and acetone.

[0054] Specifically, in step (3), the concentration of the modified nanomaterial in the unsuitable solvent is 10-100 mg / mL, for example, 20 mg / mL, 25 mg / mL, 30 mg / mL, 35 mg / mL, 40 mg / mL, 45 mg / mL, 50 mg / mL, 55 mg / mL, 60 mg / mL, 65 mg / mL, 70 mg / mL, 75 mg / mL, 80 mg / mL, 85 mg / mL, 90 mg / mL, 95 mg / mL, and the concentration of the hygroscopic core in the hygroscopic core solution is 0.5-3 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L.

[0055] It should be noted that within this range, the modified nanomaterials can form a good structure in which a single layer of nanomaterials is coated on the hygroscopic core. When the relative concentration of the hygroscopic core is high, the coating will be incomplete, resulting in a decrease in hygroscopicity and catalytic ability. When the relative concentration of the hygroscopic core is low, an over-coated structure will be formed, and the outer nanomaterials will easily fall off or form clusters, resulting in a decrease in the material's warm cloud catalytic performance.

[0056] If the concentration of hygroscopic nuclei is too low, the resulting hygroscopic material particles will be too small; if the concentration is too high, the resulting hygroscopic material particles will be too large.

[0057] Specifically, in step (4), the total flow rate of the poor solvent-nanomaterial phase and the hygroscopic core solution is 1-10 mL / min, for example, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L.

[0058] It should be noted that in step (4), the poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 7:3-9:1 (e.g., 3:1, 4:1, 5:1, 6:1, 7:1, 8:1). This is because below this range, the proportion of hygroscopic cores in the resulting product is too high, making it difficult to achieve complete coating of the hygroscopic cores by the nanomaterials, resulting in a decrease in the hygroscopicity and cloud catalytic activity of the material; above this range, the nanomaterials are prone to self-aggregation, that is, some nanomaterials are not coated on the hygroscopic cores, but form clusters of nanomaterials, resulting in a decrease in the overall hygroscopic performance of the product and waste of materials.

[0059] Specifically, in step (4), the filtrate is obtained by filtration, and the filtrate is distilled under reduced pressure to obtain a poor solvent and water, which can be returned to step (3) for recycling.

[0060] Antisolvent precipitation is based on the principle that nanomaterials dissolved in a good solvent immediately precipitate as they are introduced into a large amount of poor solvent. However, conventional antisolvent precipitation methods often suffer from drawbacks such as excessive solvent consumption, low crystal yield, and high time costs. This invention uses a continuous flow method to generate crystal precipitation and prepare micron-sized hygroscopic core-nanomaterial crystals. The poor solvent can be recycled, saving costs.

[0061] Another specific embodiment of the present invention discloses the application of the above-mentioned hygroscopic material in weather modification catalysts.

[0062] The method of this invention prepares a monolayer-coated modified nanomaterial of hygroscopic material. This modified nanomaterial can form hydrogen bonds with water, thus more easily adsorbing water vapor and creating localized high humidity on the surface of the hygroscopic core, promoting the hygroscopic growth of the core. Furthermore, the particle size of the hygroscopic material meets the requirements of 1-10 μm for warm cloud weather modification catalysts, which is the foundation for its use as a good warm cloud weather modification catalyst.

[0063] It should be noted that the central particle size of the hygroscopic material prepared by the present invention is 1-10 μm, the thickness of the coating layer is 80-500 nm, the relative humidity at which it begins to absorb moisture is 31-41%, and the relative humidity at which it completely deliquesces is 66-71%.

[0064] The technical solution of the present invention will be further explained below with reference to specific embodiments.

[0065] Example 1

[0066] This embodiment provides a hygroscopic material, wherein the hygroscopic material has a hygroscopic core at its center and is coated with nanomaterials modified by surfactants on its surface.

[0067] In this embodiment, the hygroscopic core is sodium chloride, the nanomaterial is aluminum oxide with a particle size of 100 nm, the surfactant is sodium dodecyl sulfate, and the unsuitable solvent is ethanol.

[0068] The method for preparing a hygroscopic material according to this embodiment includes the following steps:

[0069] (1) The nanomaterials were ultrasonically cleaned in ethanol for 15 min to remove surface impurities. They were then washed with deionized water multiple times and filtered until the washing solution was odorless. After drying, the nanomaterials were obtained after impurity removal.

[0070] (2) Add 0.2g of surfactant to 50mL of deionized water and stir at 50°C until the surfactant is completely dissolved. Add 10mL of ethanol to obtain a mixed solution. Add 5g of the nanomaterial to the mixed solution and sonicate at 80KHz for 30min. Then heat at 50°C for 2h to obtain the modified nanomaterial.

[0071] (3) The modified nanomaterial is added to a poor solvent to obtain a poor solvent-nanomaterial phase; the hygroscopic core is dissolved in water to obtain a hygroscopic core solution; the concentration of the modified nanomaterial in the poor solvent is 55 mg / mL, and the concentration of the hygroscopic core in the hygroscopic core solution is 1.75 mol / L;

[0072] (4) The poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 7:3, and the total flow rate of the poor solvent-nanomaterial phase and the hygroscopic core solution is 2 mL / min. After precipitation and filtration, the hygroscopic material is obtained.

[0073] Example 2

[0074] This embodiment provides a hygroscopic material, wherein the hygroscopic material has a hygroscopic core at its center and is coated with nanomaterials modified by surfactants on its surface.

[0075] In this embodiment, the hygroscopic core is ammonium sulfate, the nanomaterial is carbon nanotubes with a particle size of 200 nm, the surfactant is cocamidopropyl betaine, and the unsuitable solvent is cyclohexane.

[0076] The method for preparing a hygroscopic material according to this embodiment includes the following steps:

[0077] (1) The nanomaterials were ultrasonically cleaned in ethanol for 15 min to remove surface impurities. They were then washed with deionized water multiple times and filtered until the washing solution was odorless. After drying, the nanomaterials were obtained after impurity removal.

[0078] (2) Add 0.1g of surfactant to 40mL of deionized water and stir at 50°C until the surfactant is completely dissolved. Add 5mL of ethanol to obtain a mixed solution. Add 1g of the nanomaterial to the mixed solution and sonicate at 50kHz for 40min. Then heat at 40°C for 4h to obtain the modified nanomaterial.

[0079] (3) The modified nanomaterial is added to a poor solvent to obtain a poor solvent-nanomaterial phase; the hygroscopic core is dissolved in water to obtain a hygroscopic core solution; the concentration of the modified nanomaterial in the poor solvent is 10 mg / mL, and the concentration of the hygroscopic core in the hygroscopic core solution is 0.5 mol / L;

[0080] (4) The poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 4:1, and the total flow rate of the poor solvent-nanomaterial phase and the hygroscopic core solution is 4 mL / min. After precipitation and filtration, the hygroscopic material is obtained.

[0081] Example 3

[0082] This embodiment provides a hygroscopic material, wherein the hygroscopic material has a hygroscopic core at its center and is coated with nanomaterials modified by surfactants on its surface.

[0083] In this embodiment, the hygroscopic core is sodium sulfate, the nanomaterial is graphene with a particle size of 500 nm, the surfactant is hexadecyltrimethylammonium bromide, and the unsuitable solvent is acetone.

[0084] The method for preparing a hygroscopic material according to this embodiment includes the following steps:

[0085] (1) The nanomaterials were ultrasonically cleaned in ethanol for 15 min to remove surface impurities. They were then washed with deionized water multiple times and filtered until the washing solution was odorless. After drying, the nanomaterials were obtained after impurity removal.

[0086] (2) Add 0.3g of surfactant to 60mL of deionized water and stir at 50°C until the surfactant is completely dissolved. Add 15mL of ethanol to obtain a mixed solution. Add 3g of the nanomaterial to the mixed solution and sonicate at 100kHz for 40min. Then heat at 60°C for 2h to obtain the modified nanomaterial.

[0087] (3) The modified nanomaterial is added to a poor solvent to obtain a poor solvent-nanomaterial phase; the hygroscopic core is dissolved in water to obtain a hygroscopic core solution; the concentration of the modified nanomaterial in the poor solvent is 60 mg / mL, and the concentration of the hygroscopic core in the hygroscopic core solution is 2.5 mol / L;

[0088] (4) The poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 5:1, and the total flow rate of the poor solvent-nanomaterial phase and the hygroscopic core solution is 8 mL / min. After precipitation and filtration, the hygroscopic material is obtained.

[0089] Example 4

[0090] This embodiment provides a hygroscopic material, wherein the hygroscopic material has a hygroscopic core at its center and is coated with nanomaterials modified by surfactants on its surface.

[0091] In this embodiment, the hygroscopic core is potassium chloride, the nanomaterial is iron oxide with a particle size of 80 nm, the surfactant is polyethylene glycol-200, and the unsuitable solvent is ethanol.

[0092] The method for preparing a hygroscopic material according to this embodiment includes the following steps:

[0093] (1) The nanomaterials were ultrasonically cleaned in ethanol for 15 min to remove surface impurities. They were then washed with deionized water multiple times and filtered until the washing solution was odorless. After drying, the nanomaterials were obtained after impurity removal.

[0094] (2) Add 0.3g of surfactant to 50mL of deionized water and stir at 50°C until the surfactant is completely dissolved. Add 10mL of ethanol to obtain a mixed solution. Add 3g of the nanomaterial to the mixed solution and sonicate at 50kHz for 30min. Then heat at 50°C for 2h to obtain the modified nanomaterial.

[0095] (3) The modified nanomaterial is added to a poor solvent to obtain a poor solvent-nanomaterial phase; the hygroscopic core is dissolved in water to obtain a hygroscopic core solution; the concentration of the modified nanomaterial in the poor solvent is 100 mg / mL, and the concentration of the hygroscopic core in the hygroscopic core solution is 3 mol / L.

[0096] (4) The poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 9:1, and the total flow rate of the poor solvent-nanomaterial phase and the hygroscopic core solution is 10 mL / min. After precipitation and filtration, the hygroscopic material is obtained.

[0097] Example 5

[0098] This embodiment provides a hygroscopic material, wherein the hygroscopic material has a hygroscopic core at its center and is coated with nanomaterials modified by surfactants on its surface.

[0099] In this embodiment, the hygroscopic core is calcium chloride, the nanomaterial is copper oxide with a particle size of 100 nm, the surfactant is Tween-80, and the unsuitable solvent is ethanol.

[0100] The method for preparing a hygroscopic material according to this embodiment includes the following steps:

[0101] (1) The nanomaterials were ultrasonically cleaned in ethanol for 15 min to remove surface impurities. They were then washed with deionized water multiple times and filtered until the washing solution was odorless. After drying, the nanomaterials were obtained after impurity removal.

[0102] (2) Add 0.2g of surfactant to 50mL of deionized water and stir at 50°C until the surfactant is completely dissolved. Add 10mL of ethanol to obtain a mixed solution. Add 5g of the nanomaterial to the mixed solution and sonicate at 60kHz for 30min. Then heat at 50°C for 2h to obtain the modified nanomaterial.

[0103] (3) The modified nanomaterial is added to a poor solvent to obtain a poor solvent-nanomaterial phase; the hygroscopic core is dissolved in water to obtain a hygroscopic core solution; the concentration of the modified nanomaterial in the poor solvent is 25 mg / mL, and the concentration of the hygroscopic core in the hygroscopic core solution is 1.5 mol / L;

[0104] (4) The poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 6:1, and the total flow rate of the poor solvent-nanomaterial phase and the hygroscopic core solution is 3.5 mL / min. After precipitation and filtration, the hygroscopic material is obtained.

[0105] Comparative Example 1

[0106] The hygroscopic material and its preparation method in this comparative example are the same as those in Example 1, except that the particle size of the alumina is 10 nm.

[0107] Comparative Example 2

[0108] The hygroscopic material and its preparation method in this comparative example are the same as those in Example 1, except that no surfactant is added in step (2).

[0109] Comparative Example 3

[0110] The hygroscopic material and its preparation method in this comparative example are the same as those in Example 1, except that in step (3), the concentration of the modified nanomaterial in the unsuitable solvent is 1 mg / mL.

[0111] Comparative Example 4

[0112] The hygroscopic material and its preparation method in this comparative example are the same as those in Example 1, except that in step (3), the concentration of the hygroscopic core in the hygroscopic core solution is 12 mol / L.

[0113] Comparative Example 5

[0114] The hygroscopic material and its preparation method in this comparative example are the same as those in Example 1, except that in step (4), the poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 2:1.

[0115] Experimental Example 1

[0116] (1) The center particle size of the hygroscopic materials prepared in Examples 1-5 and Comparative Examples 1-5, and the thickness of the surface-coated nanomaterial modified with surfactant, i.e., the coating layer thickness, were tested respectively. The results are shown in Table 1.

[0117] Among them, the center particle size test is the particle size distribution measured by an aerodynamic particle size spectrometer (APS) when the catalyst material is dispersed in an 800L smoke chamber.

[0118] The thickness of the coating layer was measured using transmission electron microscopy (TEM).

[0119] Table 1

[0120]

[0121] (2) Hygroscopicity test

[0122] The hygroscopicity of this invention was tested using a dynamic water vapor adsorption instrument.

[0123] The hygroscopic properties of the hygroscopic materials prepared in Examples 1-5 and Comparative Examples 1-5 were tested, and the results are shown in Table 2.

[0124] Table 2

[0125] Group Relative humidity at which moisture absorption begins / % Relative humidity at complete deliquescence / % Example 1 31.6 66.8 Example 2 36.2 67.2 Example 3 43.8 70.3 Example 4 37.9 67.3 Example 5 40.6 68.9 Comparative Example 1 72.5 74.3 Comparative Example 2 71.5 73.8 Comparative Example 3 71.6 74.0 Comparative Example 4 73.5 74.9 Comparative Example 5 72.8 74.2

[0126] According to Tables 1 and 2, the nanoparticles in Comparative Example 1 have too small a particle size. Although they can form a coating material, the nanoparticles with too small a particle size have a poor effect on improving hygroscopicity, and their effect is close to that of the uncoated pure hygroscopic core alone.

[0127] In Comparative Example 2, the nanomaterials were not coated with surfactants, which reduced their ability to coat the hygroscopic core, resulting in a low coating thickness of the hygroscopic material. This indicates that the synthesized hygroscopic material was not successfully coated.

[0128] In Comparative Example 3, the concentration of nanomaterials in the unsuitable solvent was too low, resulting in a low proportion of nanomaterials in the obtained product, which caused incomplete coating and a smaller measured coating thickness. Consequently, the prepared warm cloud catalyst had poor performance.

[0129] In Comparative Example 4, the concentration of hygroscopic nuclei in the hygroscopic nuclei solution was too high, resulting in excessively large particle size of the formed hygroscopic material, while the concentration of nanomaterials was relatively low, and the coating layer thickness was too small.

[0130] In Comparative Example 5, the flow rate of the undesirable solvent phase of the nanomaterial was too high, meaning that the nanomaterial accounted for a high proportion of the obtained product, resulting in an excessively thick coating layer instead of a single-layer coating, which led to poor material performance.

[0131] The inventors also conducted the above experiments on catalysts prepared in other embodiments, and the results were basically the same. Due to space limitations, they will not be listed one by one.

[0132] Experimental Example 2

[0133] The hygroscopic material prepared in Example 1 was subjected to a simulated warm cloud-condition catalytic precipitation process in the Beijing Aerosol and Cloud Interaction Chamber (BACIC) at the Beijing Artificial Weather Modification Scientific Experiment Base. The BACIC was 70m thick. 3 Cloud room diagram as shown Figure 1 As shown.

[0134] The volume of the cloud chamber for aerosol-cloud interaction in Beijing is 70m. 3 The cloud chamber can be approximated as a cylinder with a diameter of 2.6m and a height of 14m. The controllable temperature range is -45℃ to room temperature, and the controllable pressure range is 1hPa to atmospheric pressure. It simulates the actual cloud environment by expanding into a cloud. The cloud chamber is equipped with a 3772 particle counter (CPC), a 3938 scanning electromobility particle size spectrometer (SMPS), and a 3321 aerodynamic particle size spectrometer (APS) manufactured by TSI Corporation (USA) to measure the aerosol number concentration spectrum of particles with a diameter of 0.5-20μm. These instruments are used to measure the aerosol number concentration of particles larger than 3nm, the aerosol number concentration spectrum of particles with a diameter of 0.02-0.7μm, and the aerosol number concentration spectrum of particles with a diameter of 0.5-20μm, respectively, achieving a wide range of aerosol number spectrum measurements from small to large particle sizes before expanding into a cloud. After adiabatic expansion into clouds, the pressure inside the cloud chamber decreases, and the particle size spectrometer cannot work properly when the pressure is below the standard atmospheric pressure. Therefore, the warm cloud artificial weather modification catalyst after cloud formation acts as a condensation nucleus and undergoes a hygroscopic growth process. The FM-120 fog droplet spectrometer is needed to measure the raindrop particle size in the range of 2-50μm.

[0135] like Figure 2 As shown, by comparing the aerodynamic median particle size (MVD) in the cloud chamber experiment droplet spectrum, it can be clearly seen that the median particle size of the water droplets produced by the hygroscopic material prepared in Example 1 is about 65 μm, while the median particle size of the water droplets formed by pure NaCl is only about 30 μm. That is, the hygroscopic material of Example 1 has stronger catalytic warm cloud artificial rainmaking performance.

[0136] like Figure 3As shown in the cloud chamber CPC data, when 0.5g of NaCl and 0.5g of the hygroscopic material prepared in Example 1 are added in the same amount, the number concentration of the warm cloud weather modification catalyst corresponding to Example 1 before the humidity reaches supersaturation is approximately 220 ions / cm³. 3 The number concentration of pure NaCl is only 70 ions / cm³. 3 This indicates that the weather modification catalyst material corresponding to Example 1 has better dispersibility, which is related to the fact that after the nanomaterial surface is coated, the micron particles in the hygroscopic core are separated, reducing the electrostatic effect between the hygroscopic micron particles.

[0137] The inventors also conducted the above experiments on catalysts prepared in other embodiments, and the results were basically the same. Due to space limitations, they will not be listed one by one.

[0138] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A hygroscopic material, characterized in that, The hygroscopic material is centered on a hygroscopic core and its surface is coated with nanomaterials modified by surfactants.

2. The hygroscopic material according to claim 1, characterized in that, The hygroscopic core includes one or more of sodium chloride, calcium chloride, potassium chloride, ammonium sulfate, sodium sulfate, and sodium carbonate; The nanomaterials mentioned include one or more of the following: aluminum oxide, zinc oxide, magnesium oxide, iron oxide, copper oxide, indium oxide, carbon nanotubes, and graphene. The surfactants mentioned include one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, cocamidopropyl betaine, hexadecyltrimethylammonium bromide, dodecylammonium bromide, Tween-80, polyacryl alcohol, and polyethylene glycol-200.

3. The hygroscopic material according to claim 2, characterized in that, The particle size of the nanomaterial is 30-500 nm.

4. A method for preparing the hygroscopic material according to any one of claims 1-3, characterized in that, Includes the following steps: (1) The nanomaterials were washed in ethanol, filtered, and dried to obtain the purified nanomaterials; (2) Dissolve the surfactant in water, add ethanol to obtain a mixed solution, add the nanomaterial to the mixed solution, sonicate, heat to react, and obtain the modified nanomaterial. (3) The modified nanomaterials are added to a poor solvent to obtain a poor solvent-nanomaterial phase; The hygroscopic nucleus is dissolved in water to obtain a hygroscopic nucleus solution; (4) The poor solvent-nanomaterial phase and the hygroscopic core solution are mixed at a flow rate ratio of 7:3-9:1, precipitated, and filtered to obtain the hygroscopic material.

5. The preparation method according to claim 4, characterized in that, In step (2), the mass-volume ratio of the surfactant, water and ethanol is 0.1-0.3g:40-60mL:5-15mL, and the mass ratio of the surfactant to the modified nanomaterial is 0.1-0.3:1-3.

6. The preparation method according to claim 4, characterized in that, In step (2), the temperature for heating the reaction is 40-60℃ and the reaction time is ≥2h.

7. The preparation method according to claim 4, characterized in that, In step (3), the undesirable solvent includes one or more of ethanol, isopropanol, cyclohexane, and acetone.

8. The preparation method according to claim 4, characterized in that, In step (3), the concentration of the modified nanomaterial in the poor solvent is 10-100 mg / mL, and the concentration of the hygroscopic core in the hygroscopic core solution is 0.5-3 mol / L.

9. The preparation method according to claim 4, characterized in that, In step (4), the total flow rate of the poor solvent-nanomaterial phase and the hygroscopic core solution is 1-10 mL / min.

10. The use of a hygroscopic material according to any one of claims 1-3 or a hygroscopic material prepared by any one of claims 4-9 in a weather modification catalyst.

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