Preparation and application of natural biomass water-retaining gel for collecting and preserving water in arid soil

Abstract

This invention discloses the preparation and application of a natural biomass water-retaining gel for water collection and retention in arid soils. The process includes: dissolving sodium alginate and carboxymethyl cellulose in deionized water, then adding lithium chloride, N-isopropylacrylamide monomer, and N,N'-dimethylacrylamide to obtain a mixture; bubbling the mixture with Ar gas, then adding N,N,N',N'-tetramethylethylenediamine, a polymerization accelerator, and ammonium peroxide as an initiator to polymerize and obtain a mixed gel; and using a microfluidic method to drop the mixed gel into a calcium chloride aqueous solution to obtain hydrogel beads, which are then washed and dried to obtain the natural biomass water-retaining gel. The natural biomass water-retaining gel of this invention contains a three-dimensional porous structure, which enhances adsorption-desorption kinetics and effectively inhibits the aggregation of hygroscopic salt-LiCl particles during hydration, thereby achieving good water absorption performance and cycle stability. This is beneficial for extracting water vapor from arid climates and can effectively capture moisture from the atmosphere.

Description

Technical Field

[0001] This invention belongs to the field of hydrogel technology, specifically relating to the preparation and application of a natural biomass water-retaining gel for water collection and retention in arid soils. Background Technology

[0002] As is well known, water resources play an indispensable role in vegetation restoration. Traditional irrigation methods, such as sprinkler, spray, and drip irrigation systems, face certain limitations when implemented on slopes and other areas. Therefore, the development of new water harvesting systems aims to meet the hydraulic needs of electronic vegetation restoration on railway slopes more effectively and sustainably. Atmospheric water harvesting (AWH) is considered a promising approach to address global water scarcity by extracting water from the atmosphere, particularly suitable for arid and water-scarce regions. Biomass-based porous hydrogel materials are considered ideal absorbent materials and have been used in AWH over a wide humidity range, especially at low relative humidity (≥30%). However, biomass-based porous hydrogel materials are generally limited by their low water harvesting capacity and incomplete water desorption. Therefore, there is a need to develop an absorbent material that can be used in arid soils, improving soil water absorption and addressing the problems of poor water absorption and incomplete water release inherent in traditional water harvesting materials. Summary of the Invention

[0003] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0004] To achieve these objectives and other advantages according to the present invention, a method for preparing a natural biomass water-retaining gel for water collection and retention in arid soils is provided, comprising the following steps:

[0005] Step 1: Dissolve sodium alginate (SC) and carboxymethyl cellulose (CMC) in deionized water and stir until homogeneous. Then add lithium chloride (LiCl), and under stirring conditions, continue to add N-isopropylacrylamide monomer (NIPAM) and N,N'-dimethylacrylamide to obtain a mixture.

[0006] Step 2: The mixture is bubbled with Ar gas, and then N,N,N',N'-tetramethylethylenediamine, polymerization accelerator and ammonium peroxide disulfate are added in sequence as initiators. Polymerization is completed at room temperature to obtain a mixed gel.

[0007] Step 3: Using a microfluidic method, the mixed gel is dropped into a calcium chloride aqueous solution at 60°C and reacted for a period of time to obtain hydrogel beads. Then, the hydrogel beads are washed with deionized water and finally freeze-dried under vacuum to obtain SC-LiCl / PNIPAM (SCLP) gel beads, which are natural biomass water-retaining gels. PNIPAM represents the product of NIPAM polymerization.

[0008] Preferably, in step one, the mass ratio of sodium alginate, carboxymethyl cellulose, deionized water, lithium chloride, N-isopropylacrylamide monomer, and N,N'-dimethylacrylamide is 2:1:100:0.56:5-20:0.006.

[0009] Preferably, in step two, the Ar gas bubbling time is 60 min, the amount of N,N,N',N'-tetramethylethylenediamine added is 12-60 μL, the polymerization accelerator is N,N'-methylenebisacrylamide crosslinking agent (MBA) added at 6-24 mg, the amount of ammonium peroxide added is 20-80 mg, and the polymerization time is 24 h.

[0010] Preferably, in step three, the concentration of the calcium chloride aqueous solution is 0.34 g / mL, the reaction time is 12 h, the vacuum freeze-drying temperature is -60 °C, and the freezing time is 48 h.

[0011] Preferably, lithium chloride is first modified, by means of:

[0012] S1. Dissolve lithium chloride in ethanol, heat and stir until the lithium chloride is completely dissolved to prepare a lithium chloride solution, then add dopamine to it, keep it warm and react for a period of time to obtain polydopamine-lithium chloride gel.

[0013] S2. The polydopamine-lithium chloride gel is carbonized at high temperature, and then argon plasma etching is performed after carbonization to obtain modified lithium chloride.

[0014] Preferably, in step S1, the concentration of the prepared lithium chloride solution is 50-80 wt%, the mass ratio of lithium chloride to dopamine is 1:0.2-0.5, the reaction temperature is 75-110°C, and the reaction is maintained at this temperature for 6-12 hours.

[0015] Preferably, in step S2, the high-temperature carbonization temperature is 500–800°C, the carbonization time is 0.5–2 h, the argon plasma etching time is 5–500 s, the power is 60–120 W, and the pressure is 20–80 Pa.

[0016] The present invention also provides an application of natural biomass water-retaining gel in water collection and retention in arid soil. The natural biomass water-retaining gel is used in arid soil to improve the water absorption and temperature sensitivity of arid soil.

[0017] The present invention has at least the following beneficial effects: The matrix of the natural biomass hydrogel prepared by the present invention is composed of inexpensive, scalable, and non-toxic biomaterials sodium alginate (SA) and carboxymethyl cellulose (CMC), which endow the hydrogel with a three-dimensional porous structure, thereby enhancing the adsorption-desorption kinetics. At the same time, the SA / CMC network effectively inhibits the aggregation of hygroscopic salt-LiCl particles during hydration, thereby achieving good water absorption performance and cycle stability. It is beneficial to extract water vapor from arid climates, can effectively capture moisture from the atmosphere, change the distribution of dominant species in soil communities, and enhance the activity of defense enzymes, thereby mitigating the widespread impact of drought stress on plant growth. It provides a feasible prospect for large-scale production of hygroscopic hydrogels and ecological restoration of barren slope areas.

[0018] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 This is a diagram illustrating the synthesis process of the natural biomass water-retaining gel of the present invention.

[0020] Figure 2 SEM images of SCLP gel beads prepared in Example 1 of this invention at different magnifications;

[0021] Figure 3 Energy dispersive X-ray spectroscopy (EDS) of the SCLP gel beads prepared in Example 1 of this invention;

[0022] Figure 4 The FTIR spectra of SCLP gel beads prepared in Example 1 of the present invention, SCL gel beads prepared in Comparative Example 1, SC gel beads prepared in Comparative Example 3, and PNIPAM are shown.

[0023] Figure 5 XRD patterns of SCLP gel beads prepared in Example 1 of the present invention, SCL gel beads prepared in Comparative Example 1, SC gel beads prepared in Comparative Example 3, and PNIPAM.

[0024] Figure 6 The total XPS spectrum of the SCLP gel beads prepared in Example 1 of this invention;

[0025] Figure 7 High-resolution XPS spectrum of SCLP gel beads prepared in Example 1 of this invention;

[0026] Figure 8 The swelling properties of Examples 1-4 of the present invention at different temperatures are shown in the graphs.

[0027] Figure 9The diagram shows the water contact angle of the SCLP gel beads prepared in Example 1 of this invention at different temperatures.

[0028] Figure 10 The TG curves of Embodiment 1 and Comparative Examples 1 and 3 of the present invention and PNIPAM are shown.

[0029] Figure 11 These are the compressive stress-strain curves of Embodiment 1 and Comparative Examples 1 and 3 of the present invention;

[0030] Figure 12 The graph shows the water absorption performance of the SCLP gel beads prepared in Example 1 of this invention under different humidity levels.

[0031] Figure 13 The image shows the weight change of the SCLP gel beads prepared in Example 1 of this invention during the water vapor adsorption-release cycle, and a digital photograph of the SCLP beads during the water vapor adsorption-desorption cycle.

[0032] Figure 14 This is a graph showing the atmospheric water collection and water release of the SCLP gel beads prepared in Example 1 of the present invention during nighttime circulation;

[0033] Figure 15 The graph shows the water vapor adsorption performance of the SCLP gel beads prepared in Example 1 of this invention under constant humidity flow conditions.

[0034] Figure 16 Figures showing the growth of ryegrass plants in Examples 1-3 and Comparative Examples 4-5 during drought stress treatment.

[0035] Figure 17 The graph shows the changes in soil and leaf water content of ryegrass plants in Examples 1-3 and Comparative Examples 4-5 during drought stress treatment.

[0036] Figure 18 The graph shows the changes in qN and Fv / Fm of ryegrass plants in Examples 1-3 and Comparative Examples 4-5 under drought stress.

[0037] Figure 19 The graphs show the changes in qP and ETR of ryegrass plants under drought stress in Examples 1-3 and Comparative Examples 4-5.

[0038] Figure 20 The diagram shows the enzyme activity in the leaves of ryegrass plants used in Examples 1-3 and Comparative Examples 4-5.

[0039] Figure 21 A graph showing the rhizosphere soil enzyme activity in the soils of Application Example 3 and Comparative Example 5.

[0040] Figure 22The graph shows the water absorption performance of the SCLP gel beads prepared in Example 1 of this invention under different humidity levels. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0042] Example 1

[0043] A method for preparing a natural biomass water-retaining gel for water collection and retention in arid soils, characterized by comprising the following steps:

[0044] Step 1: Dissolve 2g sodium alginate and 1g carboxymethyl cellulose in 100g deionized water and stir until well mixed. Then add 0.56g lithium chloride. Under stirring, add 10g N-isopropylacrylamide monomer (NIPAM) and 6mg N,N'-dimethylacrylamide to obtain a mixture.

[0045] Step 2: Bubble the mixture with Ar gas for 60 min to remove residual oxygen, then add 12 μL of N,N,N',N'-tetramethylethylenediamine, 6 mg of polymerization accelerator MBA, and 20 mg of ammonium peroxide as initiators in sequence, and complete the polymerization in a beaker at room temperature for 24 h to obtain a mixed gel;

[0046] Step 3: Using a microfluidic method, the mixed gel is dropped into a calcium chloride aqueous solution with a concentration of 0.34 g / mL at 60 °C and reacted for 12 h to obtain hydrogel beads. The hydrogel beads are then washed with deionized water and finally freeze-dried under vacuum at -60 °C for 48 h to obtain SCLP gel beads, which are natural biomass water-retaining gels.

[0047] Figure 1 The synthesis process of natural biomass hydrogels. Figure 2 Scanning electron microscopy images of SCLP gel beads at different magnifications reveal a loose, porous internal structure, which is beneficial for capturing more water molecules from the air later. Figure 3 It can be seen that C, N, O, and Cl are uniformly distributed throughout the porous structure, confirming the uniform polymerization of various polymer monomers in the hydrogel beads; from Figure 4 It can be seen that the FT-IR spectra of SCLP gel beads are at 3340 and 2890 cm⁻¹. -1 Absorption bands are present at both 1640 and 1060 cm⁻¹, corresponding to the -OH group of the methyl group and CH, respectively. Simultaneously, absorption bands are observed at 1640 and 1060 cm⁻¹. -1Several characteristic peaks were further observed, corresponding to the CO stretching vibrations of SA and CMC and the symmetric stretching vibrations of the COC bond in the C carboxyl group, respectively. Notably, the SCLP gel beads exhibited two new characteristic peaks, attributed to the CH stretching vibration (2930 cm⁻¹). -1 ) and amide I (1640cm) -1 This further confirms the successful modification of SCL hydrogel beads with NIPAM; from Figure 5 It can be seen that the XRD pattern of the original SC exhibits a broad band at 23 due to its amorphous nature. Compared with the original SC, the SCLP gel beads show a broader diffraction peak at 22, indicating that the hydrophilic framework (SA and CMC) has good miscibility with PNIPAM. After integrating lithium chloride into the SC+PNIPAM gel network, no diffraction peak of crystalline lithium chloride was detected due to the relatively low concentration of crystalline lithium chloride in the hydrophilic framework; from Figures 6-7 It can be seen that the main components on the surface of SCLP gel beads are O1s, N1s, Ca2p, C1s, and Cl2p, with binding energies of 532.08, 399.07, 347.38, 285.08, and 198.05 eV, respectively. The C1s XPS spectrum of the SCLP gel beads conforms to three components: CC at 248.80 eV, CN at 286.38 eV, and NC=O at 287.78 eV. Figure 7 (Left), further confirming the successful grafting of PNIPAM onto SC; major characteristic peaks at 399.28 eV and 401.38 eV were found in the high-resolution N1s spectrum of the SCLP gel beads, corresponding to -NC and NO( Figure 7 (in Chinese); furthermore, the O1s spectrum of the SCLP hydrogel beads further confirmed that the hydrogel beads are rich in oxygen-containing functional groups (in Chinese). Figure 7 right).

[0048] Example 2

[0049] The difference between this embodiment and Embodiment 1 is that the amount of NIPAM added is 5g, while all other aspects are the same as in Embodiment 1.

[0050] Example 3

[0051] The difference between this embodiment and Embodiment 1 is that the amount of NIPAM added is 15g, while all other aspects are the same as in Embodiment 1.

[0052] Example 4

[0053] The difference between this embodiment and Embodiment 1 is that the amount of NIPAM added is 20g, while all other aspects are the same as in Embodiment 1.

[0054] The swelling properties of the SCLP gel beads prepared in Examples 1-4 were tested at different temperatures, and the results are as follows: Figure 8 As shown, the results indicate that when the NIPAM concentration is 10 wt% (i.e., the addition amount is 10 g) (corresponding to Example 1), the maximum swelling ratio of the SCLP gel beads at room temperature can reach 993%. When the temperature exceeds the lower critical solution temperature (LCST, 33°C), the SCLP gel beads can release more than 50% of the water captured from the air, and at 70°C, the SCLP gel beads can release more than 95% of the water. Figure 9 As can be seen, SCLP hydrogel beads have good hydrophilicity at 25℃; when the temperature is increased to 80℃, SCLP hydrogel beads have obvious hydrophobicity, indicating that the introduction of PNIPAM can effectively achieve the hydrophilic-hydrophobic transformation of gel beads by adjusting the temperature.

[0055] Example 5

[0056] A method for preparing a natural biomass water-retaining gel for water collection and retention in arid soils, characterized by comprising the following steps:

[0057] First, lithium chloride is modified using the following method:

[0058] S1. Dissolve 10g of lithium chloride in ethanol, heat and stir until the lithium chloride is completely dissolved to prepare a lithium chloride solution with a concentration of 60wt%, then add 3g of dopamine to it, and keep it at 80℃ for 8h to obtain polydopamine-lithium chloride gel.

[0059] S2. The polydopamine-lithium chloride gel was carbonized at 600℃ for 1 hour. After carbonization, argon plasma etching was performed for 120 seconds, with a power of 100W and a pressure of 40Pa to obtain modified lithium chloride.

[0060] Step 1: Dissolve 2g sodium alginate and 1g carboxymethyl cellulose in 100g deionized water and stir until well mixed. Then add 0.56g modified lithium chloride. Under stirring, add 10g N-isopropylacrylamide monomer (NIPAM) and 6mg N,N'-dimethylacrylamide to obtain a mixture.

[0061] Step 2: Bubble the mixture with Ar gas for 60 min to remove residual oxygen, then add 12 μL of N,N,N',N'-tetramethylethylenediamine, 6 mg of polymerization accelerator MBA, and 20 mg of ammonium peroxide as initiators in sequence, and complete the polymerization in a beaker at room temperature for 24 h to obtain a mixed gel;

[0062] Step 3: Using a microfluidic method, the mixed gel is dropped into a calcium chloride aqueous solution with a concentration of 0.34 g / mL at 60 °C and reacted for 12 h to obtain hydrogel beads. The hydrogel beads are then washed with deionized water and finally freeze-dried under vacuum at -60 °C for 48 h to obtain SCLP gel beads, which are natural biomass water-retaining gels.

[0063] The water absorption properties of the SCLP gel beads prepared in this embodiment were tested at different humidity levels, and the results are as follows: Figure 22 As shown in the figure, it can be seen that the addition of modified lithium chloride in this embodiment improves the ability of the SCLP gel beads to absorb water from the atmosphere under different humidity levels. In particular, the water absorption is greatly improved in short time and low humidity. This is because the polydopamine-lithium chloride gel formed by lithium chloride and dopamine is carbonized and treated with argon plasma to form a porous structure, which greatly increases the specific surface area. This helps to increase the contact area between lithium chloride and moisture in the atmosphere, thereby improving its water absorption capacity.

[0064] Comparative Example 1:

[0065] The difference between this comparative example and Example 1 is that NIPAM is not added. All other steps are the same as in Example 1, and a gel bead without NIPAM, namely SCL, is finally obtained. The moisture absorption capacity of SCL is the same as that of the SCLP gel bead obtained in Example 1 of this invention. However, due to the absence of NIPAM, it is difficult to desorb the adsorbed water or the desorption is incomplete.

[0066] Comparative Example 2:

[0067] The difference between this comparative example and Example 1 is that lithium chloride (LiCl) is not introduced in the preparation process. All other steps are the same as in Example 1. Finally, gel beads without LiCl are obtained. Without the introduction of LiCl, the adsorption capacity of the hydrogel is significantly reduced.

[0068] Comparative Example 3:

[0069] The difference between this comparative example and Example 1 is that lithium chloride (LiCl) and NIPAM are not introduced in the preparation process. All other steps are the same as in Example 1. Finally, SC gel beads without LiCl and NIPAM are obtained, which have basically no water absorption or no significant adsorption capacity.

[0070] Figure 10 The TG curves for Example 1, Comparative Examples 1 and 3, and PNIPAM are shown below. Figure 10As can be seen, for SC gel, the second weight loss stage occurs at 200-700℃, due to the thermal decomposition of the biomass material. The second weight loss initiation temperature for SCL is higher than that for SC, mainly due to its binding with hygroscopic salts. For PNIPAM, the second weight loss at 350-430℃ corresponds to the decomposition of the PNIPAM polymer chains, while for SCLP gel beads, the second weight loss at 270-420℃ corresponds to the rapid decomposition of PNIPAM and the gradual decomposition of SCL. Figure 11 The compressive stress-strain curves for Example 1 and Comparative Examples 1 and 3 are shown below. Figure 11 As can be seen, SCLP gel beads have superior mechanical properties compared to SC and SCL.

[0071] After preparing SCLP gel beads using the method in Example 1, the water absorption performance of the SCLP gel beads under different humidity levels was tested, as follows:

[0072] Indoor measurements: Water vapor adsorption and relative humidity (RH) of all samples were evaluated at room temperature (25°C) in a greenhouse, with the total humidity controlled at 30-90%. During the moisture absorption process, the hydrogel was weighed once per hour to record its mass change.

[0073] Outdoor measurement: At night, SCLP gel beads are placed on a windowsill to collect water from the atmosphere; during the day, saturated SCLP beads are heated under the real sky for solar evaporation; the mass change of SCLP beads is recorded in real time using a high-precision electronic balance; temperature and relative humidity are automatically monitored using a thermometer and hygrometer; water absorption rate and release amount are calculated based on mass change and initial weight.

[0074] The method for calculating the water absorption capacity of hydrogels is as follows:

[0075] Water vapor adsorption capacity = m i -m0 / m0*100%

[0076] Where, m i The values ​​represent the weights of the SCLP gel beads after moisture absorption at different times, and m0 represents the original dry weight of the SCLP gel beads.

[0077] Test results are as follows Figure 12 As shown, the results indicate that the saturated adsorption capacity is 990% within a 600-minute range at 90% humidity.

[0078] Then, the water vapor adsorption-desorption cycle of the SCLP gel beads was tested to evaluate the performance stability of the material. The test results are as follows: Figure 13 As shown, the results indicate that the water absorption rate of the SCLP gel beads did not decrease significantly after 10 adsorption-desorption cycles.

[0079] Since atmospheric water collection typically occurs outdoors, the moisture collection and release performance of the SCLP gel beads under natural conditions was further tested. At night (when air humidity is high), the pre-dried SCLP absorbed moisture from the atmosphere. The test results are as follows: Figure 14 As shown, from Figure 14 As can be seen, around 9 AM on the second day, the SCLP gel beads reached saturation, with a maximum absorption rate of 700%. On a sunny day with mild temperatures, the relative humidity gradually decreased from 71% at 7 AM to a minimum of 30% at 3 PM. Simultaneously, the outdoor temperature rose from 15°C at 7 AM to 30°C at 3 PM. During this phase, due to the increased temperature and decreased humidity, the pre-adsorbed saturated SCLP gel beads began to release water. The water content of the SCLP gel beads gradually decreased from 596% (7 AM) to 310% (3 PM), indicating that the SCLP gel beads have good water release capacity in the presence of the temperature-sensitive material PNIPAM. When the sun set and the relative humidity (RH) rose again, the SCLP gel beads began a new round of water collection from the atmosphere. During the 36-hour outdoor atmospheric water collection period, two water absorption processes and one water release process were recorded, demonstrating the significant potential of SCLP gel beads in atmospheric water collection in natural environments.

[0080] Furthermore, the water vapor adsorption performance of SCLP gel beads under constant humidity conditions was further tested using a dynamic attraction system. The test results are shown in the figure below. Figure 15 As shown, from Figure 15 It can be seen that the adsorption rate of SCLP gel beads with porous mesh structure increases significantly with increasing humidity, reaching 0.252 g / g at 90% RH.

[0081] Application Example 1

[0082] The SCLP gel beads prepared in Example 1 were added to the arid soil at a rate of 0.5g / 5g of soil. The SCLP gel beads were applied to the topsoil, and then ryegrass seeds were planted in the soil. After germination, the seedlings were thoroughly watered once to ensure their survival. After the first thorough watering, the ryegrass seedlings were subjected to drought stress treatment for 10 days, and the growth of the seedlings was observed.

[0083] Application Example 2

[0084] The SCLP gel beads prepared in Example 1 were added to the arid soil at a ratio of 1g / 5g of soil. The SCLP gel beads were applied to the topsoil, and then ryegrass seeds were planted in the soil. After germination, the seedlings were thoroughly watered once to ensure their survival. After the first thorough watering, the ryegrass seedlings were subjected to drought stress treatment for 10 days, and the growth of the seedlings was observed.

[0085] Application Example 3

[0086] The SCLP gel beads prepared in Example 1 were added to the arid soil at a ratio of 2g / 5g of soil. The SCLP gel beads were applied to the topsoil, and then ryegrass seeds were planted in the soil. After germination, the seedlings were thoroughly watered once to ensure their survival. After the first thorough watering, the ryegrass seedlings were subjected to drought stress treatment for 10 days, and the growth of the seedlings was observed.

[0087] Comparative Example 4

[0088] Add the SC gel beads prepared in Comparative Example 3 to the arid soil at a ratio of 2g / 5g of soil. The addition method is to apply the SCLP gel beads to the topsoil, then plant ryegrass seeds in the soil. After germination, water thoroughly once to ensure the survival of the seedlings. After the first thorough watering, subject the ryegrass seedlings to drought stress for 10 days and observe the growth of the seedlings.

[0089] Comparative Example 5

[0090] Ryegrass seeds were planted in normal soil. After germination, the seeds were thoroughly watered once to ensure seedling survival. After the first thorough watering, the ryegrass seedlings were subjected to drought stress treatment for 10 days, and the seedling growth was observed (CK treatment).

[0091] During the drought stress treatments applied in Examples 1-3 and Comparative Examples 4-5, relevant parameters were measured every 2 days using the following method, with each group measuring the above indicators 3 times.

[0092] Soil moisture content determination: A drying method was used. Approximately 5 grams of soil were taken for each treatment, placed in an aluminum box, dried in an oven at 105℃, and then naturally cooled to room temperature before weighing. The calculation formula is as follows:

[0093] Soil moisture content % = (m1 - m2) / m2 * 100%

[0094] Where m1 represents the mass of wet soil, in g; and m2 represents the mass of dry soil, in g.

[0095] Leaf moisture content determination: A drying method was used. Leaf samples were collected at 9:00 AM on a sunny day. At each sampling point, the fresh needles were washed as thoroughly as possible and weighed in distilled water. After 24 hours of storage in the dark, the needles were removed, the water on the leaves was absorbed with filter paper, and then the leaves were weighed at saturation. The green material was deoxidized at 105℃ for 15 min, and then dried in an explosion oven at 90℃ for 8 h. After cooling to room temperature, the dry matter was weighed, and the process was repeated three times. The calculation formula is as follows:

[0096] Leaf water content % = (W1-W0) / (W2-W0)*100%

[0097] Where W0 represents dry weight (g), W1 represents fresh weight (g), and W2 represents saturated weight after absorption (g).

[0098] Determination of plant enzyme activity: Leaf samples (0.1 g) were placed in pre-cooled mortar and homogenized with 0.5 mL of pre-cooled phosphate buffer to obtain a tissue homogenate. The homogenate was then centrifuged at 10,000 rpm for 10 min at 4 °C, and the antioxidant enzyme activity was determined using the supernatant. The activities of three antioxidant enzymes—superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)—were determined using a kit (Soleibor Biotechnology Co., Ltd., China).

[0099] Soil enzyme activity assay: The soil was air-dried before measuring enzyme activity. Catalase activity (S-CAT) was expressed as 0.1 mol / L potassium permanganate / (hg). Phosphatase activity (S-ACP) was determined colorimetrically, and soil urease (S-UE) was detected using a kit (Subo Biotech Co., Ltd., China).

[0100] Chlorophyll fluorescence parameters were measured every two days at 8:30 AM, with each treatment repeated three times. Before measurement, plants were placed in darkness for one hour, and chlorophyll fluorescence parameters were measured using a DUAL-PAM-100 dual-channel modulated chlorophyll fluorescence spectrometer (Heinz, Germany). The non-photochemical quenching coefficient (qN), photochemical quenching coefficient (qP), PSII maximum photochemical efficiency (Fv / Fm), and electron transport efficiency (ETR) were recorded in the system. All parameters were completed on the same day.

[0101] Determination of rhizosphere soil bacterial community structure: High-throughput sequencing analysis was performed on the collected rhizosphere soil samples. 1 g of rhizosphere soil was collected from each treatment group and immediately frozen in liquid nitrogen for subsequent studies. Total genomic DNA was extracted using a DNA extraction kit following the DNA extraction instructions. DNA concentration was verified using NanoDrop and agarose gel electrophoresis. PCR amplification was performed using genomic DNA as a template, employing barcoding primers and Tks Gflex DNA polymerase (Takara).

[0102] Figure 16 The graph shows the growth of ryegrass plants in Examples 1-3 and Comparative Examples 4-5 during drought stress treatment. Figure 16 It can be seen that after 10 days of drought stress, the ryegrass seedlings in the CK group showed signs of wilting and collapse. In contrast, the ryegrass in the different SCLP gel bead treatment groups grew normally, with the SCLP gel bead treatment group (2g) showing the best growth.

[0103] Figure 17The graph shows the changes in soil and leaf water content of ryegrass plants in Examples 1-3 and Comparative Examples 4-5 during drought stress treatment. Figure 17 As can be seen, the soil moisture content and leaf moisture content of the SCLP treatment group (2g) were the highest, at 28% and 40% respectively, which also confirms that the addition of SCLP provided the necessary water for plant growth, which is conducive to the normal development and growth of plants. Therefore, the ryegrass in the SCLP gel bead treatment group (2g) grew the best.

[0104] Figure 18 The graph shows the changes in qN and Fv / Fm in ryegrass plants of Examples 1-3 and Comparative Examples 4-5 under drought stress. Figure 19 The graphs show the changes in qP and ETR of ryegrass plants under drought stress in Examples 1-3 and Comparative Examples 4-5. Figure 18-19 As can be seen, the values ​​of qP and ETR show a decreasing trend with the increase in the duration of drought stress. This is mainly due to the impact of water shortage on plant photosynthesis, which reduces the participation of water molecules in the light reaction, leading to a decrease in qP and ETR values. With the intensification of drought stress, the values ​​of qN and Fv / Fm show a trend of first increasing and then decreasing. This phenomenon is because plants activate photoprotective mechanisms in the early stages of drought to increase qN and Fv / Fm in response to stress. Compared with the CK group, the addition of 2g of SCLP gel beads did not significantly decrease the values ​​of qP, qN, ETR, and Fv / Fm, indicating that the introduction of SCLP gel beads can capture moisture from the atmosphere and alleviate the weakening of photosynthesis caused by drought.

[0105] Figure 20 The diagram shows the enzyme activity in the leaves of ryegrass plants used in Examples 1-3 and Comparative Examples 4-5 (SOD is superoxide dismutase, POD is peroxidase, and CAT is catalase). Figure 21 The diagram shows the rhizosphere soil enzyme activities in the soils of Application Example 3 and Comparative Example 5 (S-UE represents soil urease, S-NP represents soil neutral phosphatase, and S-CAT represents soil dehydrogenase). From Figure 20-21 It can be seen that the activities of POD, SOD, and CAT in plant leaves and soil treated with SCLP gel beads were all higher than those in the control group, with the SCLP treatment group (2g) showing the highest activity. Therefore, an appropriate amount of SCLP gel beads can regulate soil moisture, improve the plant growth environment, thereby increasing the activity of defense enzymes and maintaining normal plant metabolism.

[0106] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a natural biomass water-retaining gel for water collection and retention in arid soils, characterized in that, Includes the following steps: Step 1: Dissolve sodium alginate and carboxymethyl cellulose in deionized water and stir until homogeneous. Then add lithium chloride and, under stirring, continue to add N-isopropylacrylamide monomer and N,N'-dimethylacrylamide to obtain a mixture. Step 2: The mixture is bubbled with Ar gas, and then N,N,N',N'-tetramethylethylenediamine, polymerization accelerator and ammonium peroxide disulfate are added in sequence as initiators. Polymerization is completed at room temperature to obtain a mixed gel. Step 3: Using a microfluidic method, the mixed gel is dropped into a calcium chloride aqueous solution at 60°C and reacted for a period of time to obtain hydrogel beads. Then, the hydrogel beads are washed with deionized water and finally freeze-dried under vacuum to obtain a natural biomass water-retaining gel.

2. The method for preparing the natural biomass water-retaining gel for water collection and retention in arid soil according to claim 1, characterized in that, In step one, the mass ratio of sodium alginate, carboxymethyl cellulose, deionized water, lithium chloride, N-isopropylacrylamide monomer, and N,N'-dimethylacrylamide is 2:1:100:0.56:5 to 20:0.

006.

3. The method for preparing the natural biomass water-retaining gel for water collection and retention in arid soil according to claim 1, characterized in that, In step two, the Ar gas bubbling time is 60 min, the amount of N,N,N',N'-tetramethylethylenediamine added is 12-60 μL, the polymerization accelerator is N,N'-methylenebisacrylamide crosslinking agent added is 6-24 mg, the amount of ammonium peroxide added is 20-80 mg, and the polymerization time is 24 h.

4. The method for preparing the natural biomass water-retaining gel for water collection and retention in arid soil according to claim 1, characterized in that, In step three, the concentration of calcium chloride aqueous solution is 0.34 g / mL, the reaction time is 12 h, the vacuum freeze-drying temperature is -60 °C, and the freezing time is 48 h.

5. The method for preparing the natural biomass water-retaining gel for water collection and retention in arid soil according to claim 1, characterized in that, First, lithium chloride is modified using the following method: S1. Dissolve lithium chloride in ethanol, heat and stir until the lithium chloride is completely dissolved to prepare a lithium chloride solution, then add dopamine to it, keep it warm and react for a period of time to obtain polydopamine-lithium chloride gel. S2. The polydopamine-lithium chloride gel is carbonized at high temperature, and then argon plasma etching is performed after carbonization to obtain modified lithium chloride.

6. The method for preparing the natural biomass water-retaining gel for water collection and retention in arid soil according to claim 5, characterized in that, In step S1, the concentration of the prepared lithium chloride solution is 50-80 wt%, the mass ratio of lithium chloride to dopamine is 1:0.2-0.5, the reaction temperature is 75-110℃, and the reaction is maintained at this temperature for 6-12 hours.

7. The method for preparing the natural biomass water-retaining gel for water collection and retention in arid soil according to claim 5, characterized in that, In S2, the high-temperature carbonization temperature is 500-800℃, the carbonization time is 0.5-2h, the argon plasma etching time is 5-500s, the power is 60-120W, and the pressure is 20-80Pa.

8. The application of a natural biomass water-retaining gel prepared by the preparation method according to any one of claims 1-7 in water collection and retention in arid soil, characterized in that, The natural biomass water-retaining gel was used in arid soils to improve the water absorption and temperature sensitivity of the arid soils.

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