Biomass-source-based temperature-sensitive core-shell moisture absorption microsphere and preparation method thereof

Abstract

The invention belongs to the field of functional polymer materials, and particularly relates to a temperature-sensitive core-shell moisture absorption microsphere based on a biomass source and a preparation method. The preparation method comprises the following steps: dissolving methyl cellulose in water to prepare a solution A; dissolving calcium lactate and LiCl in water according to a mass ratio of 1: (2-14) to prepare a solution B; uniformly mixing the two to obtain functionalized core liquid; and dropwise adding the core liquid into a sodium alginate coagulating bath to carry out ionic cross-linking reaction to form gel microspheres, and washing and freeze-drying to obtain the product. According to the invention, a stable structure with moisture absorption salt / temperature-sensitive methyl cellulose as a core and calcium alginate gel as a shell is constructed in one step through a reverse instillation molding technology. The structure can effectively prevent moisture absorption salt from leaking, efficient release of moisture can be achieved at the low temperature by means of the temperature-sensitive characteristic of methyl cellulose, and desorption energy consumption for taking water from air is remarkably reduced. The raw materials are green, the process is simple, and the prepared microspheres are good in moisture absorption performance, high in cycling stability and suitable for atmospheric moisture collection.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer materials, specifically relating to a thermosensitive core-shell hygroscopic microsphere based on biomass and its preparation method. Background Technology

[0002] The atmosphere contains abundant water resources, equivalent to six times the total freshwater volume of all rivers and lakes on Earth. Widely distributed and possessing a strong capacity for recycling, it represents a highly promising alternative water source. Directly extracting freshwater from the atmosphere could provide low-cost, low-energy clean water for water-scarce regions. Atmospheric water extraction technology aims to convert gaseous water in the atmosphere into liquid freshwater, providing a sustainable water source for production, daily life, and agricultural development, with significant application value, especially in arid regions and extreme water-scarce scenarios.

[0003] Adsorbent-assisted water extraction is one of the most commonly used methods in existing air-to-water extraction technologies. It utilizes air-to-water materials to capture and enrich atmospheric moisture, which is then released as liquid water through desorption. This method offers advantages such as low cost and minimal equipment requirements. The adsorbent in high-performance air-to-water materials is the core of this technology, determining the freshwater production capacity. Among various adsorbents, hygroscopic salts (such as CaCl2 and LiCl) are favored due to their low cost, environmental friendliness, and high hygroscopic capacity over a wide humidity range. However, hygroscopic salts suffer from deliquescence and aggregation in practical applications, significantly reducing their hygroscopic capacity and rate, and causing equipment corrosion and salt loss.

[0004] To overcome this deficiency, existing technologies generally employ a "porous matrix loading" strategy, dispersing hygroscopic salts into porous materials such as silica gel, zeolites, metal-organic frameworks (MOFs), and aerogels. While this alleviates hygroscopic salt leakage to some extent, it still has the following limitations. There is a lack of strong interaction between the porous matrix and the hygroscopic salt, relying mainly on physical adsorption and capillary action. During long-term operation, salt leakage still occurs, leading to performance degradation and severely limiting the long-term stability and water extraction efficiency of the material. Simultaneously, most porous matrices (such as MOFs) have limited water storage capacity, are expensive, and have complex synthesis processes, making large-scale applications difficult. Inexpensive matrices (such as silica gel) suffer from insufficient water storage capacity and difficulty in releasing adsorbed water, making them unsuitable for efficient air water extraction. Furthermore, the desorption process of existing composite adsorbents heavily relies on external heat sources to drive water evaporation, typically requiring high energy consumption and desorption temperatures as high as 65–80 °C, making it difficult to achieve rapid desorption rates at lower temperatures.

[0005] Therefore, developing a composite desiccant with raw materials derived entirely from biomass, long-term stable storage of hygroscopic salts, and low-energy desorption by liquid water is of significant practical importance and application value. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing composite desiccant technologies, such as limited adsorption capacity, easy leakage of hygroscopic salts, and high desorption energy consumption, and to provide a temperature-sensitive core-shell hygroscopic microsphere based on biomass and its preparation method. The microsphere uses green raw materials, has a stable structure, and can achieve low-temperature, low-energy desorption.

[0007] This invention utilizes sodium alginate's reverse spheroidization technique to achieve one-step coating of hygroscopic salts, and synergistically leverages the temperature-responsiveness of methylcellulose to construct a biomass-derived temperature-sensitive core-shell hygroscopic microsphere, providing a specific preparation method. The temperature-sensitive core-shell hygroscopic microspheres prepared by this method exhibit high hygroscopic efficiency, stable performance during hygroscopic absorption, low desorption temperature, and the method is simple and highly operable.

[0008] Specifically, the present invention adopts the following technical solution: A method for preparing thermosensitive core-shell hygroscopic microspheres based on biomass, the preparation method specifically includes the following steps: (1) Raw material preparation: Dissolve methylcellulose in deionized water to prepare solution A; dissolve calcium lactate and LiCl in deionized water at a mass ratio of 1:(2-14) to prepare solution B; (2) Preparation of functionalized core fluid: Slowly add solution B to solution A and stir at room temperature until the mixture is homogeneous to obtain functionalized core fluid; (3) Preparation of temperature-sensitive core-shell hygroscopic microspheres: First, sodium alginate was dissolved in deionized water to obtain a sodium alginate coagulation bath; then, the functionalized core liquid from step (2) was added dropwise to the sodium alginate coagulation bath through a needle; the mixture was stirred to carry out an ion crosslinking reaction to form gel microspheres; then the sample was collected, washed with deionized water and freeze-dried to obtain temperature-sensitive core-shell hygroscopic microspheres.

[0009] Furthermore, in step (1), the mass fraction of solution A is 0.5-2.5 wt%.

[0010] Furthermore, in step (1), the mass fraction of solution B is 20-70 wt%.

[0011] Furthermore, in step (1), the mass ratio of solution A to solution B is 3:1.

[0012] Furthermore, in step (3), the mass fraction of the sodium alginate coagulation bath is 1.0-3.0 wt%.

[0013] Furthermore, in step (3), the stirring time for the ionic crosslinking reaction is 1-3 h.

[0014] Furthermore, in step (3), the inner diameter of the needle is 20 G, and the extrusion rate of the functionalized core liquid is 60 mL / h.

[0015] Furthermore, the equilibrium moisture content of the temperature-sensitive core-shell hygroscopic microspheres is greater than 1.00 g / g under the conditions of 25°C and 60% relative humidity.

[0016] A thermosensitive core-shell hygroscopic microsphere based on biomass was prepared using the method described above.

[0017] This invention employs a unique reverse spheroidization technique, uniformly blending a crosslinking agent (calcium lactate), a functional core (hygroscopic salt LiCl), and methylcellulose to obtain a core solution. When the core solution is dropwise added to a sodium alginate solution, Ca... 2+ It diffuses outward and undergoes ionic cross-linking with the carboxylic acid groups (-COO⁻) on the sodium alginate molecular chain. The microspheres are formed and the functional components are coated simultaneously in one step, making the process efficient and simple.

[0018] This invention constructs a stable "core-shell" water storage structure, with a hygroscopic salt / MC thermosensitive solution as the "core" and a dense calcium alginate network as the "shell." The outer shell provides a robust physical barrier to prevent leakage of internal components and maintains the structural integrity of the microspheres during hygroscopic / desorption cycles. The hydrophilic network of the core binds the liquid water captured by the hygroscopic salt within the three-dimensional network through hydrogen bonds and capillary forces, effectively avoiding leakage and corrosion problems caused by free flow of water, and achieving integrated "capture-fixation" of water.

[0019] This invention utilizes the temperature-sensitive properties of methylcellulose. During the desorption process, when heated above its phase transition temperature, the MC molecular chains undergo dehydration condensation, actively squeezing out the internally stored liquid water in liquid form. This transforms the desorption process from high-energy-consuming "vaporization" to low-energy-consuming "liquid-solid separation," significantly reducing energy consumption.

[0020] In summary, this invention successfully solves the three key problems raised in the background art: Hygroscopic salts are prone to deliquescence and leakage during the hygroscopic / desorption cycle, leading to performance degradation. The desorption process relies on high temperatures and consumes a lot of energy; High material costs or insufficient environmental friendliness.

[0021] Compared with existing technologies, the present invention has the following advantages: This invention utilizes the temperature-sensitive properties of methylcellulose to enable the hygroscopic microspheres to rapidly and completely release liquid water at low temperatures (45°C), achieving a low-energy-consumption and high-efficiency water extraction process. This invention ensures the regularity of microsphere morphology through the synergistic effect of reverse spheroidization and biomass gelation. The core-shell structure achieves efficient coating of hygroscopic salts, overcoming the problems of easy deliquescence and leakage of hygroscopic salts. The raw materials required for this invention are all biomass-based, which are low-cost and environmentally friendly, laying a material foundation for large-scale air-to-water extraction applications. The reverse spheroidization preparation method provided by this invention completes the molding of gel microspheres and the coating of hygroscopic salts simultaneously through one-step droplet addition. The process is simple and easy to operate, and the post-processing of the product is simple and easy to scale up. Detailed Implementation

[0022] Representative embodiments will now be further refined. It should be understood that the following description is not intended to limit the embodiments to a single preferred embodiment. Rather, it is intended to cover alternatives, modifications, and equivalents that may be included within the substance and scope of the embodiments defined by the appended claims.

[0023] Example 1: The present invention provides a thermosensitive core-shell hygroscopic microsphere based on biomass source. The specific preparation steps are as follows: (1) Raw material preparation: 0.50 g of methylcellulose is dissolved in 74.50 g of deionized water, stirred in a water bath at 70 ℃ for 30 min to make it fully dispersed, and then transferred to room temperature and stirred for 2 h until completely dissolved to obtain 75.00 g of solution A; Dissolve 1.25 g of calcium lactate and 10.00 g of LiCl in 13.75 g of deionized water and stir for 2 h until completely dissolved to obtain 25.00 g of solution B; (2) Preparation of functionalized core liquid: 25.00 g of solution B was slowly added to 75.00 g of solution A and stirred at room temperature for 2 h until the mixture was homogeneous, to obtain 100.00 g of functionalized core liquid; (3) Preparation of thermosensitive core-shell hygroscopic microspheres: First, 6.00 g of sodium alginate was dissolved in 294.00 g of deionized water and stirred in a water bath at 70 ℃ for 30 min until completely dissolved, to obtain 300.00 g of sodium alginate coagulation bath; The functionalized core solution was added dropwise to the sodium alginate coagulation bath at a rate of 60 mL / h using a 20 G needle. After stirring for 1 h, an ionic cross-linking reaction was carried out to form gel microspheres. The sample was then collected, washed with deionized water to remove excess coagulation bath from the surface of the microspheres, and finally freeze-dried in a freeze dryer for 72 h to obtain thermosensitive core-shell hygroscopic microspheres.

[0024] Example 2: This invention provides a thermosensitive core-shell hygroscopic microsphere based on biomass, and the specific preparation steps are as follows: (1) Raw material preparation: 1.00 g of methylcellulose was dissolved in 74.00 g of deionized water and stirred in a water bath at 70 °C for 30 min to disperse it fully. Then, it was transferred to room temperature and stirred for another 2 h until it was completely dissolved to obtain 75.00 g of solution A; Dissolve 1.25 g of calcium lactate and 10.00 g of LiCl in 13.75 g of deionized water and stir for 2 h until completely dissolved to obtain 25.00 g of solution B; (2) Preparation of functionalized core liquid: 25.00 g of solution B was slowly added to 75.00 g of solution A and stirred at room temperature for 2 h until the mixture was homogeneous, to obtain 100.00 g of functionalized core liquid; (3) Preparation of thermosensitive core-shell hygroscopic microspheres: First, 6.00 g of sodium alginate was dissolved in 294.00 g of deionized water and stirred in a water bath at 70 ℃ for 30 min until completely dissolved, to obtain 300.00 g of sodium alginate coagulation bath; The functionalized core solution was added dropwise to the sodium alginate coagulation bath at a rate of 60 mL / h using a 20 G needle. After stirring for 1 h, an ionic cross-linking reaction was carried out to form gel microspheres. The sample was then collected, washed with deionized water to remove excess coagulation bath from the surface of the microspheres, and finally freeze-dried in a freeze dryer for 72 h to obtain thermosensitive core-shell hygroscopic microspheres.

[0025] Example 3: This invention provides a thermosensitive core-shell hygroscopic microsphere based on biomass, and the specific preparation steps are as follows: (1) Raw material preparation: 1.50 g of methylcellulose was dissolved in 73.50 g of deionized water and stirred in a water bath at 70 °C for 30 min to disperse it fully. Then it was transferred to room temperature and stirred for 2 h until completely dissolved to obtain 75.00 g of solution A; Dissolve 1.25 g of calcium lactate and 10.00 g of LiCl in 13.75 g of deionized water and stir for 2 h until completely dissolved to obtain 25.00 g of solution B; (2) Preparation of functionalized core liquid: 25.00 g of solution B was slowly added to 75.00 g of solution A and stirred at room temperature for 2 h until the mixture was homogeneous, to obtain 100.00 g of functionalized core liquid; (3) Preparation of thermosensitive core-shell hygroscopic microspheres: First, 6.00 g of sodium alginate was dissolved in 294.00 g of deionized water and stirred in a water bath at 70 ℃ for 30 min until completely dissolved, to obtain 300.00 g of sodium alginate coagulation bath; The functionalized core solution was added dropwise to the sodium alginate coagulation bath at a rate of 60 mL / h using a 20 G needle. After stirring for 1 h, an ionic cross-linking reaction was carried out to form gel microspheres. The sample was then collected, washed with deionized water to remove excess coagulation bath from the surface of the microspheres, and finally freeze-dried in a freeze dryer for 72 h to obtain thermosensitive core-shell hygroscopic microspheres.

[0026] Example 4: This invention provides a thermosensitive core-shell hygroscopic microsphere based on biomass, and the specific preparation steps are as follows: (1) Raw material preparation: 1.00 g of methylcellulose was dissolved in 74.00 g of deionized water and stirred in a water bath at 70 °C for 30 min to disperse it fully. Then, it was transferred to room temperature and stirred for another 2 h until it was completely dissolved to obtain 75.00 g of solution A; 1.25 g of calcium lactate and 5.00 g of LiCl were dissolved in 18.75 g of deionized water and stirred for 2 h until completely dissolved to obtain 25.00 g of solution B. (2) Preparation of functionalized core liquid: 25.00 g of solution B was slowly added to 75.00 g of solution A and stirred at room temperature for 2 h until the mixture was homogeneous, to obtain 100.00 g of functionalized core liquid; (3) Preparation of thermosensitive core-shell hygroscopic microspheres: First, 6.00 g of sodium alginate was dissolved in 294.00 g of deionized water and stirred in a water bath at 70 ℃ for 30 min until completely dissolved, to obtain 300.00 g of sodium alginate coagulation bath; The functionalized core solution was added dropwise to the sodium alginate coagulation bath at a rate of 60 mL / h using a 20 G needle. After stirring for 1 h, an ionic cross-linking reaction was carried out to form gel microspheres. The sample was then collected, washed with deionized water to remove excess coagulation bath from the surface of the microspheres, and finally freeze-dried in a freeze dryer for 72 h to obtain thermosensitive core-shell hygroscopic microspheres.

[0027] Example 5: This invention provides a thermosensitive core-shell hygroscopic microsphere based on biomass, and the specific preparation steps are as follows: (1) Raw material preparation: 1.00 g of methylcellulose was dissolved in 74.00 g of deionized water and stirred in a water bath at 70 °C for 30 min to disperse it fully. Then, it was transferred to room temperature and stirred for another 2 h until it was completely dissolved to obtain 75.00 g of solution A; 1.25 g of calcium lactate and 15.00 g of LiCl were dissolved in 8.75 g of deionized water and stirred for 2 h until completely dissolved to obtain 25.00 g of solution B. (2) Preparation of functionalized core liquid: 25.00 g of solution B was slowly added to 75.00 g of solution A and stirred at room temperature for 2 h until the mixture was homogeneous, to obtain 100.00 g of functionalized core liquid; (3) Preparation of thermosensitive core-shell hygroscopic microspheres: First, 6.00 g of sodium alginate was dissolved in 294.00 g of deionized water and stirred in a water bath at 70 ℃ for 30 min until completely dissolved, to obtain 300.00 g of sodium alginate coagulation bath; The functionalized core solution was added dropwise to the sodium alginate coagulation bath at a rate of 60 mL / h using a 20 G needle. After stirring for 1 h, an ionic cross-linking reaction was carried out to form gel microspheres. The sample was then collected, washed with deionized water to remove excess coagulation bath from the surface of the microspheres, and finally freeze-dried in a freeze dryer for 72 h to obtain thermosensitive core-shell hygroscopic microspheres.

[0028] Comparative Example 1: The main difference in this comparison is the absence of methylcellulose (MC): The comparative material was prepared according to the following steps: First, 1.25 g of calcium lactate and 10.00 g of LiCl were dissolved in 88.75 g of deionized water and stirred for 2 h until completely dissolved to obtain 100.00 g of functionalized core solution (without MC). The subsequent preparation steps (preparing the SA coagulation bath, adding dropwise to form spheres, washing, and freeze-drying) are the same as in Example 2.

[0029] Comparative Example 2: This comparative example was prepared using a forward spheroidization process; specifically, this material was prepared according to the following steps: First, 1.00 g of methylcellulose and 2.00 g of sodium alginate were dissolved in 72.00 g of deionized water and stirred in a water bath at 70 °C for 30 min to ensure full dispersion. Then, the solution was transferred to room temperature and stirred for another 2 h until completely dissolved, yielding 75.00 g of solution A. Dissolve 10.00 g LiCl in 15.00 g deionized water and stir for 2 h until completely dissolved to obtain 25.00 g solution B; 25.00 g of solution B was slowly added to 75.00 g of solution A and stirred at room temperature for 2 h until the mixture was homogeneous, yielding 100.00 g of core solution. Dissolve 3.75 g of calcium lactate in 296.25 g of deionized water and stir in a 70 ℃ water bath for 30 min until completely dissolved to obtain a 300.00 g calcium lactate coagulation bath. The core solution was added dropwise to the calcium lactate coagulation bath at a rate of 60 mL / h using a 20 G needle to form positively oriented microspheres. The sample was collected, washed with deionized water to remove excess coagulation bath from the surface of the microspheres, and finally freeze-dried in a freeze dryer for 72 h to obtain positively oriented microspheres.

[0030] The samples prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to moisture absorption performance tests. The specific testing procedures are as follows: The freeze-dried samples were placed in a high and low temperature alternating constant temperature and humidity test chamber and subjected to continuous moisture absorption tests at 25 ℃ and constant relative humidity. The upper limit of the moisture absorption equilibrium time was 48 hours, and the mass change of the samples was recorded using an electronic precision balance.

[0031] The moisture absorption properties of the samples prepared in each embodiment and comparative example at 25 °C and 90% RH (hygroscopic) are shown in the table below.

[0032] Moisture absorption time Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 0 h 0 0 0 0 0 0 0 12 h 3.16 3.51 2.92 2.59 3.96 0.61 1.32 24 h 3.45 3.86 3.41 2.96 4.26 0.74 N / A 36 h 3.89 4.02 3.79 3.24 4.35 0.78 N / A 48 h 3.92 4.09 3.81 3.28 4.40 0.81 N / A The moisture absorption (R) of the samples in the table is calculated using the following formula: ; Where R is the moisture absorption of the sample, in grams per gram (g / g); M1 is the mass of the sample after moisture absorption, in grams (g); and M0 is the original mass of the dried sample, in grams (g).

[0033] The moisture absorption data in the table shows that the moisture absorption of Examples 1-5 all showed an upward trend within 48 hours. However, the moisture absorption performance of Examples 1-5 was significantly better than that of Comparative Example 1 and Comparative Example 2.

[0034] The standard data also show that as the content of methylcellulose increases, the saturated moisture absorption of the sample first increases and then decreases. An appropriate amount of methylcellulose is conducive to the formation of a more complete and stable "core-shell" structure. At the same time, the shell has a certain degree of moisture permeability, allowing water molecules to enter and combine with LiCl, thereby increasing the moisture absorption. However, excessive methylcellulose will lead to an overly thick and dense shell, which will hinder the penetration and diffusion of water molecules, thus reducing the moisture absorption.

[0035] As the content of the hygroscopic salt LiCl increases, the saturated moisture absorption gradually increases. When the content is 15 wt%, no moisture leakage occurs after 48 h of moisture absorption, indicating that the "core-shell" structure of the present invention can effectively coat high content LiCl and effectively avoid the leakage of moisture and hygroscopic salt LiCl.

[0036] The data in the table show that Comparative Example 1 (excluding MC) had extremely low saturated hygroscopic capacity and could not form a stable spherical structure. This confirms that methylcellulose can act as a thickener to ensure droplet spheroidization, providing the necessary support framework and water storage space for the hygroscopic salt, thus achieving efficient moisture capture and fixation. Comparative Example 2 (using the traditional forward spheroidization process) showed significant moisture leakage within 24 hours, confirming that the forward spheroidized sample could not efficiently coat the hygroscopic salt, resulting in moisture loss due to leakage.

[0037] The desorption performance of the samples prepared in Examples 1-5 and Comparative Examples 1-2 was tested. The specific testing process is as follows: Samples that have reached saturation moisture absorption at 25 ℃ and 90% RH relative humidity are placed in an electric thermostatic drying oven. The change in sample mass over time is measured at 45 ℃, and the change in sample mass is recorded using an electronic precision balance.

[0038] The desorption properties of the samples prepared in each embodiment and comparative example at 45 °C are shown in the table below.

[0039] Desorption time Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 0 min 3.89 3.97 3.95 4.01 4.10 0.58 N / A 10 min 3.16 3.14 3.02 3.25 3.31 0.32 N / A 20 min 2.53 2.43 2.14 2.31 2.25 0.21 N / A 30 min 1.79 1.49 1.29 1.42 1.75 0.14 N / A 40 min 0.98 0.84 0.70 0.78 1.23 0.12 N / A 50 min 0.65 0.40 0.34 0.55 0.81 0.09 N / A 60 min 0.38 0.22 0.18 0.26 0.59 0.05 N / A The moisture retention (L) of the samples in the table is calculated using the following formula: ; Where L is the moisture retention of the sample, in grams per gram (g / g); M2 is the mass of the dried sample, in grams (g); and M0 is the original mass of the dried sample, in grams (g).

[0040] Table 2 shows the moisture retention of the absorbent materials prepared in Examples 1-5 and Comparative Examples 1-2 at 45 °C for 60 min. Examples 1-5 released most of the moisture (>50%) within 10 minutes, achieving rapid release, and the desorption performance of each example was significantly better than that of Comparative Example 1. Comparative Example 2 suffered from structural instability due to the forward spheroidizing process, resulting in leakage during desorption, making it impossible to obtain valid data.

[0041] As the methylcellulose content increased, the moisture retention of the samples decreased. Example 3 (MC mass fraction of 1.5 wt%) showed the best performance, with the lowest moisture retention (0.18 g / g) after 60 min. This indicates that a higher methylcellulose concentration can enhance the "active extrusion" effect of the temperature-sensitive network, providing a stronger driving force for moisture release. This significantly reduces the time and energy input required to achieve the same dehydration rate, ultimately achieving rapid and deep desorption at a lower temperature (45 ℃).

[0042] As shown in Table 2, the results show that Example 5 of the present invention (LiCl mass fraction of 15.0 wt%) has a higher moisture retention (0.59 g / g), indicating that when the LiCl concentration is too high, its strong hydrophilicity partially offsets the "squeezing out" effect of the temperature-sensitive network, resulting in a higher final moisture retention, which reflects the controllable balance between hygroscopic and desorption properties.

[0043] This invention successfully prepared a temperature-sensitive core-shell hygroscopic microsphere based on biomass. Through a one-step reverse spheroidization process, efficient coating of high-performance hygroscopic salt (LiCl) was successfully achieved. Methylcellulose not only ensured shapeability but also, by utilizing its temperature-sensitive properties and unique core-shell structure, solved the difficulties of traditional adsorbents in terms of moisture absorption capacity, stability, and desorption energy consumption, providing a key technical solution for the development of a new generation of high-efficiency and energy-saving air-to-water materials.

[0044] The process employed in this invention is simple, the post-processing of the product is convenient, and the raw material cost is low, laying a solid foundation for its large-scale industrial production and practical application in the field of air-to-water extraction.

[0045] In summary, at the technical level, this invention utilizes thermosensitive hydrogel (MC), hygroscopic salt (LiCl), and ion-crosslinked gel (SA-Ca). 2+ The combination of these three elements, and the construction of the structure through a specific process called "reverse balling," is not common knowledge or a routine experimental choice in the field. Furthermore, the failure (severe leakage) of Comparative Example 2 (forward balling) demonstrates the crucial but not obvious role of this specific process in achieving "stable core-shell packaging."

[0046] This invention does not simply list the temperature sensitivity of MC, the gelling properties of SA, and the hygroscopic properties of LiCl. Instead, through a unique core-shell design, the "shell" is responsible for mechanical strength and sealing, while the MC in the "core" drives low-temperature desorption, and LiCl efficiently captures water. These three components work synergistically to achieve the comprehensive effect of "highly efficient hygroscopic absorption, zero salt leakage, and rapid low-temperature desorption." The comparative data (hygroscopicity, desorption rate, and structural stability) of the above embodiments with Comparative Example 1 (without MC) and Comparative Example 2 (forward spherical formation) fully demonstrate that this synergistic effect far exceeds the simple sum of the functions of each component, representing an unexpected technical effect.

[0047] Based on the above technical solutions, this invention provides a novel and effective solution based on green materials to address the two well-known problems in the field of air water extraction using adsorption methods: leakage of hygroscopic salts and high energy consumption of desorption.

[0048] Furthermore, compared with existing technologies, the present invention has achieved significant improvements in hygroscopic performance (equilibrium moisture content >1.00 g / g @25℃, 60%RH), cycle stability (salt is sealed), desorption energy consumption (rapid desorption at 45℃), and environmental friendliness of raw materials (all biomass).

[0049] It will be apparent to those skilled in the art that modifications, combinations, and variations can be made to the teachings described above.

Claims

1. A method for preparing thermosensitive core-shell hygroscopic microspheres based on biomass, characterized in that: The preparation method specifically includes the following steps: (1) Raw material preparation: Dissolve methylcellulose in deionized water to prepare solution A; dissolve calcium lactate and LiCl in deionized water at a mass ratio of 1:(2-14) to prepare solution B; (2) Preparation of functionalized core fluid: Slowly add solution B to solution A and stir at room temperature until the mixture is homogeneous to obtain functionalized core fluid; (3) Preparation of temperature-sensitive core-shell hygroscopic microspheres: First, sodium alginate was dissolved in deionized water to obtain a sodium alginate coagulation bath; then, the functionalized core liquid from step (2) was added dropwise to the sodium alginate coagulation bath through a needle; the mixture was stirred to carry out an ion crosslinking reaction to form gel microspheres; then the sample was collected, washed with deionized water and freeze-dried to obtain temperature-sensitive core-shell hygroscopic microspheres.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass fraction of solution A is 0.5-2.5 wt%.

3. The preparation method according to claim 1, characterized in that: In step (1), the mass fraction of solution B is 20-70 wt%.

4. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of solution A to solution B is 3:

1.

5. The preparation method according to claim 1, characterized in that: In step (3), the mass fraction of the sodium alginate coagulation bath is 2.0 wt%.

6. The preparation method according to claim 1, characterized in that: In step (3), the stirring time for the ionic crosslinking reaction is 1-3 h.

7. The preparation method according to claim 1, characterized in that: In step (3), the inner diameter of the needle is 20G and the extrusion rate of the functionalized core liquid is 60 mL / h.

8. The preparation method according to claim 1, characterized in that: The equilibrium moisture content of the temperature-sensitive core-shell hygroscopic microspheres is greater than 1.00 g / g under the conditions of 25℃ and 60% relative humidity.

9. A thermosensitive core-shell hygroscopic microsphere based on biomass, characterized in that: It is prepared by the preparation method described in any one of claims 1-8.