Composite active material based on cellulose nanocrystal and blue-green algae as well as preparation method and application of composite active material

Abstract

The invention provides a composite active material based on cellulose nanocrystals and blue-green algae as well as a preparation method and application of the composite active material. The composite active material comprises CNC, drought-resistant blue-green algae thalli and an environment regulation and control ion system, the mass concentration of CNC is 0.05-5% (w / v), the cyanobacteria of the drought-resistant cyanobacteria thalli is 0.1-5 [mu] g / mL in terms of the concentration of chlorophyll a, the environment regulation ion system contains Ca < 2 + >, and the concentration of Ca < 2 + > is 0.1-5 mmol / L; the blue-green algae is Leptolyngbya lambda domesticated through drought stress, the secretion amount of extracellular polymeric substances is increased by 30% or above compared with that of wild type blue-green algae, and the content of uronic acid groups in the extracellular polymeric substances is not lower than 15%; the CNC and the extracellular polymeric substance of the blue-green algae form a reversible three-dimensional network structure through the synergistic effect of hydrogen bonds, static electricity and Ca < 2 + > ion bridges; the compressive strength fluctuation of the three-dimensional network structure under the relative humidity of 5-95% is less than or equal to 20%, the three-dimensional network structure can respond to the change of environmental humidity to realize self-adaptive adjustment of mechanical properties, and the photosynthetic activity Y [II] of blue-green algae is maintained to be greater than or equal to 0.3 within the salinity range of 0-200 mmol / L. The structure is stable, environmental response is achieved, ecological compatibility is achieved, and the technical blank of CNC and blue-green algae composite active materials in arid region soil remediation is filled up.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of soil ecological restoration and functional biomaterials in arid areas, specifically involving a composite active material based on cellulose nanocrystals and cyanobacteria, its preparation method and application. Background Technology

[0002] Arid and semi-arid regions account for approximately 41% of the global land area and represent the most severe areas of land degradation and desertification. According to statistics from the Food and Agriculture Organization of the United Nations, these regions lose over 1.5 billion tons of soil annually due to wind erosion, with soil moisture content consistently below 15% and vegetation cover less than 10%, resulting in the near loss of their ecosystem's self-recovery capacity. Biological soil crusts (BSCs), serving as "ecological armor" for the surface of arid regions, are composed of extracellular polymeric substances (EPS) secreted by cyanobacteria, lichens, mosses, and microorganisms. They can maintain the ecological functions of arid regions by physically binding soil particles, improving water retention, and fixing carbon and nitrogen. For example, they can reduce wind erosion by 50-70%, increase water retention by 2-3 times compared to bare soil, and fix nitrogen by 10-50 kg / ha annually. Therefore, they have become a core research direction for ecological restoration in arid regions. However, the formation cycle of natural BSCs is as long as 5 to 10 years, and they are limited by extreme environments (diurnal temperature range >30℃, annual precipitation <250mm), which cannot meet the needs of large-scale ecological restoration.

[0003] Traditional artificial remediation techniques often focus on inoculating filamentous cyanobacteria, attempting to promote soil particle cohesion through EPS secreted by the algae. However, these techniques consistently struggle to overcome technical bottlenecks such as "efficient establishment, stable survival, and environmental adaptability." For example, wild-type cyanobacteria tend to aggregate under drought stress (aggregate particle size > 500 μm), resulting in decreased photosynthetic activity (γ). [II] Within 3 days, the concentration of EPS plummeted from 0.4 to below 0.1, with EPS secretion reaching only 50-80 mg / g stem cells and uronic acid group content <10%, making it difficult to form a stable bond with soil particles. The crust formed by inoculation alone has extremely low mechanical strength (compressive strength <15 N), and after undergoing wet-dry cycles (humidity 5-95% RH), the structural integrity rate is <60%, and the moisture content is <20% after 4 days, making it unable to withstand long-term wind erosion. In addition, some technologies introduce chemical binders (such as polyacrylamide) to improve stability. Although these can enhance the structure in the short term, the degradation cycle is as long as several years, which not only leads to soil pore blockage but also inhibits the activity of native microorganisms, causing secondary pollution.

[0004] In recent years, the introduction of bio-based nanomaterials has provided new solutions for ecological restoration. Cellulose nanocrystals (CNCs) are a widely available, biodegradable natural nanomaterial with excellent mechanical properties. The surface of CNCs is rich in hydroxyl and carboxyl groups, which can form stable three-dimensional network structures through hydrogen bonding, electrostatic interactions, and coordination with polysaccharides or proteins. A search of domestic and international patent technologies revealed that CN116694332A discloses the application of cellulose nanocrystals in soil remediation, but its core function is to remove petroleum hydrocarbon pollutants. It only uses CNCs as a particulate emulsifier to construct Pickering emulsions, lacking bioactive components such as cyanobacteria, and cannot induce the formation of biocrusts in soil, completely failing to meet the needs of ecological function reconstruction in arid areas. Another domestic patent technology targeting cyanobacteria-based sand fixation (CN107996054A), while using filamentous cyanobacteria as the core functional component, relies on untamed wild-type strains and does not introduce nanocarriers such as CNCs to enhance structural support. The mechanical strength of the resulting crusts is generally less than 18. N, is difficult to withstand the strong wind erosion in arid areas; CN104619652B discloses a polymer carrier structure containing microorganisms, mentioning the use of porous structures to maintain the stability of microbial populations, but it does not use CNC as a carrier material, and its polymer network is a static porous structure without a humidity-responsive reversible structure. After wet-dry cycles, the microbial activity loss still exceeds 50%, making it unsuitable for the dynamic environment of arid areas; related foreign patents, such as US11667749B2, disclose CNC-based hydrogels that focus on soil water retention and improvement, constructing a network only through hydrogen bonding between CNC and natural polysaccharides, without including functional microorganisms such as cyanobacteria, and thus cannot achieve the reconstruction of ecological functions such as carbon and nitrogen fixation and crust induction. More importantly, none of the above-mentioned existing patents mention Ca. 2+ / Mg 2+ The regulatory mechanism of the CNC / cyanobacteria interface interaction was not found to be Ca 2+ The enhancing effect of ion bridges on the stability of composite networks was not achieved through Ca... 2+ With Mg 2+ The optimized ratio of synergistic maintenance of cyanobacterial photosynthetic activity leads to the complex system being prone to disintegration under salinity fluctuations (0~200 mmol / L), failing to solve the problem of dual stability of structure and activity under complex environments.

[0005] In summary, existing technologies have consistently failed to overcome key challenges such as “difficulty in microbial colonization, poor material-microbial compatibility, and lack of environmental responsiveness,” especially in the three core areas of “directed domestication of cyanobacteria to enhance interfacial interactions,” “construction of reversible networks using ion bridges,” and “multi-factor synergy to achieve environmental adaptation.” Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a functionally adapted composite active material based on cellulose nanocrystals (CNC) and cyanobacteria, along with its preparation method and applications. This aims to overcome the shortcomings of existing cyanobacterial crust materials in terms of structural stability, environmental adaptability, remediation cycle, and ecological compatibility. This invention utilizes "Ca..." 2+ / Mg 2+ A ternary synergistic design of "ion bridge regulation, cyanobacterial directional domestication, and CNC nanoframework support" was used to construct a Ca-containing... 2+ / Mg 2+ The synergistically regulated CNC and cyanobacteria-adaptive composite active material achieves adaptive mechanical regulation and photosynthetic activity maintenance under conditions such as wet-dry cycles, salinity fluctuations, and humidity changes. At the same time, it ensures that the material is entirely bio-based and free from secondary pollution, filling the technological gap in the synergistic relationship between "structure, activity, and ecology" in soil remediation in arid areas.

[0007] This invention discloses a functionally adapted composite active material based on cellulose nanocrystals and drought-resistant cyanobacteria, comprising a CNC nanoframework, drought-stress-acclimated cyanobacterial cells, and Ca. 2+ / Mg 2+ An environmentally regulated ion system was established, in which the concentration of CNC was 0.05–5% (w / v), the concentration of cyanobacteria (calculated as chlorophyll a) was 0.1–5 μg / mL, and Ca... 2+ Concentration 0.1~5 mmol / L, Mg 2+ Concentration 0.05~2 mmol / L, Ca 2+ With Mg 2+ The molar ratio is (2~5):1. Drought acclimatization increased the secretion of extracellular polymeric substances (EPS) in cyanobacteria by more than 30% compared to the wild type, with a uronic acid group content of no less than 15%, thereby forming hydrogen bonds, electrostatic interactions, and Ca2+ with CNC. 2 + / Mg 2+ A reversible three-dimensional network structure with ion-bridge synergy (reversibility is mainly reflected in the hydrogen bonds and Ca²⁺ / Mg in the material network). 2+ The ion bridges can dynamically break and rebuild during wet-dry cycles, thus achieving reversible swelling and contraction under wet-dry cycles. This reversible three-dimensional network structure exhibits compressive strength fluctuations of ≤20% at relative humidity of 5–95%, and maintains cyanobacterial photosynthetic activity within a salinity range of 0–200 mmol / L. [II] ≥0.3. The preparation method includes CNC ultrasonic dispersion, mixing of cyanobacteria and ions, and incubation at 30±2°C for 3-7 days. A gel-like composite material is obtained when the system viscosity reaches 500-1000 cP. When applied to soil remediation in arid regions, the spraying rate is 300-800 mL / m³. 2After drying for 5-10 days, a self-adaptive biocrust with a thickness of 0.5-2 mm is formed. After 5 cycles of drying and wetting, the structural integrity rate is ≥90%, wind erosion is reduced by more than 70%, and the water content retention rate is ≥35% after 4 days. Furthermore, this invention also provides a matching ecological restoration kit for easy on-site mixing as needed. This material achieves dual stability of mechanical and biological activity through a multi-layered synergistic mechanism of "CNC nanoframework, cyanobacterial EPS, and ion bridges," overcoming the technical difficulties of unstable structure, poor stress resistance, and long restoration cycles of existing restoration materials. It possesses excellent ecological compatibility and engineering application value, and is suitable for the restoration of different soil types such as sandy and silty soils.

[0008] This invention relates to a composite active material based on cellulose nanocrystals and cyanobacteria, which integrates nanocarriers, functional microorganisms, and ion regulation, particularly involving Ca-containing... 2+ / Mg 2+ The preparation process of CNC and cyanobacteria-adaptive composite active materials with synergistic regulation, and the application of this material in ecological restoration scenarios such as sandy degraded soil and saline soil in arid / semi-arid regions, can achieve synergistic effects of rapid construction of biological crusts, improvement of soil wind erosion resistance and restoration of microbial ecological functions. It is suitable for industrial needs such as farmland soil improvement in arid areas, sand fixation on the edge of deserts and reconstruction of degraded ecosystems.

[0009] The self-adaptive biocrust described in this invention refers to a biocrust that can adaptively adjust its mechanical strength and water retention capacity according to changes in environmental humidity through the swelling and contraction of its internal reversible three-dimensional network, thereby possessing wind erosion resistance in a dry state and maintaining moisture and cyanobacterial activity in a wet state.

[0010] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0011] A composite active material based on cellulose nanocrystals and cyanobacteria, comprising CNC, drought-resistant cyanobacterial cells, and an environmental regulation ion system;

[0012] The CNC concentration is 0.05-5% (w / v), the drought-resistant cyanobacteria are 0.1-5 μg / mL based on chlorophyll a concentration, and the environmental regulation ion system contains Ca. 2+ Ca 2+ The concentration is 0.1~5 mmol / L; the cyanobacterium is *Leptolyngbya laminosa*, domesticated under drought stress, whose extracellular polymer secretion is more than 30% higher than that of the wild type, and the content of uronic acid groups in the extracellular polymer is not less than 15%, so as to enhance the interfacial interaction with CNC; the extracellular polymer of CNC and cyanobacterium are mediated through hydrogen bonds, electrostatics, and Ca2+. 2+Ion bridges work synergistically to form a reversible three-dimensional network structure; the compressive strength of this three-dimensional network structure fluctuates by ≤20% at relative humidity of 5–95%, enabling adaptive adjustment of mechanical properties in response to changes in environmental humidity, and maintaining cyanobacterial photosynthetic activity within a salinity range of 0–200 mmol / L. [II] ≥0.3.

[0013] In the above scheme, the cyanobacteria also include drought-resistant and domesticated strains such as Microcoleus vaginatus or Nostoc commune, wherein the filamentous structure of Microcoleus vaginatus has a diameter of 1.5~3 μm, and the heterocellularity of Nostoc commune is 5~10%.

[0014] In the above scheme, the CNC length is 50~400 nm, the diameter is 5~20 nm, the degree of carboxyl substitution is 0.1~1.0, and the dispersion coefficient after ultrasonic treatment is ≤0.3; preferably, the ultrasonic treatment power is 200~300 W, and the time is 2~5 min.

[0015] In the above scheme, the regulating ion system further includes Mg 2+ Mg 2+ Concentrations range from 0.05 to 2 mmol / L, Ca 2+ With Mg 2+ The molar ratio is (2~5):1, and the total ion concentration is 0.15~7 mmol / L.

[0016] In the above scheme, the reversible three-dimensional network structure has a swelling degree of 150-500% in the range of water content of 10-80%, and the network integrity remains ≥85% after 10 dry-wet cycles.

[0017] A method for preparing the composite active material based on cellulose nanocrystals and cyanobacteria includes the following steps:

[0018] (1) Disperse CNC in deionized water and form CNC suspension by ultrasonic treatment. Preferably, use a probe with power of 220W and amplitude of 40% for ultrasonic treatment for 3 min, with pulse mode on for 1 s and off for 1 s to form CNC suspension.

[0019] (2) Add drought-stress-acclimated cyanobacterial cells (collected after centrifugation at 6000 rpm for 3 min) to the CNC suspension, and add Ca 2+ and optional Mg 2+ Regulating ions;

[0020] (3) Incubate at 30±2°C and 150±10 rpm for 3 to 7 days. During this period, monitor the viscosity of the system and terminate the incubation when it reaches 500 to 1000 cP to form a gel-state CNC+ cyanobacteria network and obtain a gel-state composite active material, namely a composite active material based on cellulose nanocrystals and cyanobacteria.

[0021] A method for remediating soil in arid regions using the aforementioned composite active material based on cellulose nanocrystals and cyanobacteria includes the following steps:

[0022] (1) The composite active material based on cellulose nanocrystals and cyanobacteria was uniformly sprayed onto the surface of the pretreated soil to be remediated (the soil was screened through a 1 mm sieve to remove impurities), with a spraying rate of 300~800 mL / m. 2 ;

[0023] (2) Dry naturally or at a controlled temperature of 25-35°C for 5-10 days to form a self-adaptive biological crust with a thickness of 0.5-2 mm.

[0024] After repair, monitor the crust performance regularly to ensure that the photosynthetic activity of the crust reaches Y within 30 days. [II] The value stabilizes above 0.35, and the wind erosion is reduced by more than 70% compared to untreated soil.

[0025] In the above scheme, the pretreatment also includes adjusting the soil pH to 6.5~8.0, and the spraying operation is carried out in the early morning (preferably 5:30~7:00), with an ambient temperature ≤25°C and relative humidity ≥40%.

[0026] In the above scheme, the formed biological crust has a structural integrity rate of ≥90% after 5 dry-wet cycles (humidity 5~90%), a water retention rate of ≥35% within 4 days, and a compressive strength of 20~35 N.

[0027] An ecological restoration kit is used to prepare the composite active material based on cellulose nanocrystals and cyanobacteria as described above. The kit includes dried CNC powder, cyanobacterial cell concentrate, and ion-regulating additives.

[0028] The degree of carboxyl substitution of the dried fiber CNC powder is 0.3~0.8, and the packaging specification is 100~500 g / bag;

[0029] The concentrated cyanobacterial cell solution was freeze-dried to a chlorophyll a concentration of 5-20 μg / mL and stored at -20°C or below.

[0030] The regulating ion additive contains CaCl2 and optionally MgCl2, Ca 2+ With Mg 2+ The molar ratio is (2~5):1.

[0031] Preferably, the kit also includes a user manual; the user manual details the steps and dosage ratios for preparing the composite active material based on cellulose nanocrystals and cyanobacteria on-site according to the method described above.

[0032] To achieve the above technical objectives, this invention, through targeted optimization of material composition, preparation process, and application method, forms the following specific technical solutions:

[0033] 1. Component design of composite active materials

[0034] The composite active material based on cellulose nanocrystals and cyanobacteria of this invention includes a CNC nanoframework, drought-resistant cyanobacterial cells, and an environmentally regulated ion system. The components synergistically form a reversible three-dimensional network with environmentally responsive characteristics through interfacial interaction. The specific component design is as follows:

[0035] (1) Cellulose nanocrystals (CNC): CNCs prepared by acid hydrolysis of wood pulp or bacterial cellulose were selected, with a length of 50~400 nm, a diameter of 5~20 nm, and a carboxyl substitution degree of 0.1~1.0. To enhance dispersibility, ultrasonic pretreatment with a power of 200~300 W and a time of 2~5 min was used to make the CNC dispersion coefficient ≤0.3. The mass concentration of CNC in the system was 0.05~5% (w / v), which ensured the mechanical support capacity of the nanoframework and avoided excessive CNC from crowding out the living space of cyanobacteria.

[0036] (2) The preferred drought-resistant cyanobacterial core strain is *Leptolyngbya laminosa*, which has been acclimated to drought stress: Through cyclic acclimation at 5% RH and 30℃, with 12 h of stress treatment per day for 15 days, the induced strain's EPS secretion increased by more than 30% compared to the wild type, and the proportion of uronic acid groups in the EPS was ≥15%, which helps enhance interfacial binding stability. Alternative strains include *Microcoleus vaginatus* (filamentous structure diameter 1.5~3 μm) or *Nostoc commune* (heterocellular proportion 5~10%), which have also been acclimated. The amount of cyanobacteria added, based on chlorophyll a concentration, is 0.1~5 μg / mL, ensuring that the cell density meets the requirements for rapid crust formation without competitive inhibition.

[0037] (3) Environmental regulation ion system: This system uses Ca 2+ As the core regulatory ion, combined with Mg 2+ Collaborative optimization; where Ca 2+ Concentrations range from 0.1 to 5 mmol / L, Mg 2+ Concentrations range from 0.05 to 2 mmol / L, Ca 2+ With Mg 2+The molar ratio is controlled at (2~5):1, and the total ion concentration is 0.15~7 mmol / L, thus avoiding high concentrations of Ca. 2+ The resulting irreversible flocculation by CNC ensures that Mg 2+ Supporting the activity of cyanobacteria.

[0038] 2. Preparation process of composite active materials

[0039] (1) Preparation of CNC suspension: The pre-made CNC powder was dispersed in deionized water and magnetically stirred for 30 min. Then, it was treated with a probe-type ultrasonic device (power of 220 W, amplitude of 40%, pulse mode of 1 s on / 1 s off) for 3 min. The particle size distribution (200~400 nm) and dispersion coefficient (≤0.3) of CNC were monitored by a dynamic light scattering instrument to obtain a stable CNC suspension.

[0040] (2) Addition of cyanobacteria and ion regulation: Take the cyanobacteria culture medium that has been drought-acclimated, centrifuge at 6000 rpm for 3 min to collect the cells, remove the supernatant and resuspend in the above CNC suspension; add analytical grade CaCl2 and MgCl2 solutions at the same time, stir magnetically for 15 min to make the ions uniformly dispersed, and at this time the concentration of cyanobacteria chlorophyll a in the system is adjusted to 0.1~5 μg / mL by spectrophotometry.

[0041] (3) Construction and incubation of reversible three-dimensional networks: The mixed system was transferred to a constant temperature shaker and incubated for 3-7 days at 30±2℃ and 150±10rpm. During the incubation process, Ca 2+ / Mg 2+ The crosslinking reaction between CNC and EPS was gradually mediated, and the viscosity of the system continued to rise. The incubation was stopped when the viscosity reached 500~1000 cP by real-time monitoring with a rotational viscometer. At this time, the system formed a gel-state three-dimensional network, and a CNC and cyanobacteria composite active material with mechanical reversible properties was obtained.

[0042] 3. Structural and performance characteristics of composite active materials

[0043] (1) Microstructural characteristics: The obtained composite active material is a gel-state reversible three-dimensional network. Scanning electron microscopy shows that CNC is uniformly dispersed in a fibrous manner, and cyanobacteria are wrapped in the CNC network. EPS is tightly bound to CNC through ion bridges to form an interlocking structure of "nano-skeleton, microorganism, and polymer". The swelling degree of this network is 150-500% in the range of water content of 10-80%. It stores water through swelling in the wet state and shrinks to form a dense structure to resist wind erosion in the dry state.

[0044] (2) Environmental response performance:

[0045] ① Mechanical self-adaptation: Within a humidity range of 5~95% RH, the compressive strength fluctuation is ≤20%, and the network integrity remains ≥85% after 10 wet-dry cycles (alternating between 5% RH and 95% RH);

[0046] ② Salt tolerance stability: Within a salinity range of 0–200 mmol / L, the photosynthetic activity Y of cyanobacteria… [II] ≥0.3, CNC showed no obvious agglomeration (particle size change <30%).

[0047] ③Long-lasting biological activity: After 7 days of storage at room temperature, the survival rate of cyanobacteria is still over 75%, which is nearly double that of cyanobacteria agents without CNC (survival rate <40%).

[0048] 4. Application in soil remediation in arid areas

[0049] (1) Soil pretreatment and material application: Large particles such as gravel are removed from the soil to be remediated using a 1 mm sieve. The pH is adjusted to 6.5-8.0 (suitable for cyanobacterial growth) using 0.1 mol / L NaOH or HCl. Spraying remediation is carried out between 5:30 and 7:00 in the morning (ambient temperature ≤25℃, RH ≥40%). The composite active material is evenly sprayed onto the soil surface using a 0.5 mm orifice sprayer, with a spraying rate of 300-800 mL / m². 2 For sandy soils, a high dosage (600~800 mL / m³) is selected. 2 To enhance water retention, a low dosage (300~500 mL / m³) is selected for silty soils. 2 Avoid clogging of pores.

[0050] (2) Formation and solidification of biological crust: After spraying, allow it to dry naturally or under controlled temperature of 25-35℃ for 5-10 days. During the first 3 days, maintain the surface soil moisture content ≥15% (if necessary, spray 100 mL / m² of deionized water). 2 It promotes cyanobacterial colonization and EPS secretion; it gradually dries from day 5 to day 10, forming a self-adaptive biological crust with a thickness of 0.5 to 2 mm.

[0051] (3) Monitoring of remediation effect: The formed biocrust must meet the following performance indicators, including structural integrity rate ≥90% after 5 wet-dry cycles (5~90% RH), soil moisture retention rate ≥35% within 4 days, compressive strength of 20~35 N, wind erosion reduction of more than 70% compared with untreated soil, and cyanobacterial photosynthetic activity Y within 30 days. [II] Maintaining a stable level above 0.35 ensures that the crust can perform its ecological functions in the long term.

[0052] (4) Ecological Restoration Kit Product Design: To facilitate on-site application, this invention provides a matching ecological restoration kit product, including 100~500 g / bag of dried CNC powder (carboxyl substitution degree 0.3~0.8, vacuum packaged), 5~20 μg / mL chlorophyll a lyophilized concentrate of cyanobacteria (frozen at -20℃, survival rate ≥80% after reconstitution), CaCl2 and MgCl2 mixed ionic additive (molar ratio 2~5:1, moisture-proof packaging), and detailed instructions for use. Users can prepare composite active materials on the spot according to the soil texture (sand, silt) and other application environments, and choose the timing of spraying. No professional laboratory equipment is required, which is convenient for large-scale promotion and application.

[0053] Compared with the prior art, the beneficial effects of the present invention are:

[0054] (1) The structural stability bottleneck was broken through the interface synergy mechanism: This invention improves the secretion of EPS by cyanobacteria and the proportion of uronic acid groups (≥15%) through drought domestication, and introduces Ca 2+ / Mg 2+ The ion bridge constructs a multi-point cross-linked network of "CNC, EPS, and ions". Compared with the traditional CNC and cyanobacteria system with single hydrogen bond, the interfacial bonding strength of this network is increased by more than 40%. After 10 dry and wet cycles, the network integrity still remains at ≥85%, solving the core problems such as easy cracking of the crust and weak wind erosion resistance.

[0055] (2) Achieving dual mechanical self-adaptation and biological activity stability in CNC and cyanobacteria systems: Through reversible three-dimensional network design, the compressive strength of the material fluctuates by ≤20% within the humidity range of 5~95% RH; with the help of Ca 2+ / Mg 2+ Molar ratio optimization to maintain cyanobacterial photosynthetic activity at salinities of 0–200 mmol / L. [II] With a strength of ≥0.3, it fills the technological gap where existing materials cannot be adapted to saline-arid arid regions.

[0056] (3) The material is entirely composed of bio-based components, possessing both ecological safety and high efficiency: The material components of this invention contain only CNC (natural cellulose derivative), drought-resistant cyanobacteria (native domesticated strains), and Ca 2+ / Mg 2+ (Natural soil ions), without any chemical binders, and completely biodegradable after application; at the same time, it shortens the biological crust formation cycle from the traditional 6-12 months to 5-10 days, reduces wind erosion by more than 70%, and increases soil moisture retention to ≥35%, achieving a balance between rapid restoration and ecological safety.

[0057] (4) The developed ecological restoration kit solves the problems of difficult transportation and short preservation of traditional laboratory-grade bacterial agents, which is conducive to promoting the large-scale application of the technology: the CNC dry powder and freeze-dried cyanobacteria of this invention can be stored at room temperature (CNC) or -20℃ (cyanobacteria) for more than 6 months. On-site mixing only requires simple stirring and no professional equipment is needed, which is suitable for field operation scenarios in arid areas.

[0058] In summary, this invention achieves technological breakthroughs in structural stability, environmental responsiveness, and ecological compatibility, filling the international technological gap in the application of CNC and cyanobacteria composite active materials in soil remediation in arid regions. It can be used for the ecological restoration of sandy degraded soils and abandoned mining areas, and can also assist in the improvement of farmland soils in arid regions, demonstrating significant innovative value and promising prospects for industrialization. Detailed Implementation

[0059] The following examples illustrate the technical solution, preparation process, and performance advantages of this invention. All experimental water used was ultrapure water, and all reagents used (such as CaCl2, MgCl2, sulfuric acid, etc.) were of analytical grade and available from common suppliers such as Sinopharm Chemical Reagent Co., Ltd. All instruments and equipment were calibrated to ensure the accuracy and repeatability of experimental data. These examples should not be construed as limiting the scope of protection of this invention. Modifications and substitutions made to the methods, steps, or conditions of this invention without departing from the spirit and substance of this invention are all within the scope of this invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0060] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0061] Example 1:

[0062] 1. Preparation of experimental materials

[0063] (1) CNC raw materials and pretreatment

[0064] Bacterial cellulose (purchased from Nanjing Tianlu Nanotechnology Co., Ltd., product model TL008-BCG) was used as raw material to prepare CNC via sulfuric acid hydrolysis. The detailed preparation steps were as follows: bacterial cellulose was mixed with 64% (w / w) sulfuric acid at a ratio of 1:10 (g / mL), and stirred in a constant temperature water bath at 50℃ for 2 h. During this period, samples were taken every 15 min to observe the fiber dispersion. After the hydrolysis was completed, 10 times the volume of ultrapure water was added to terminate the reaction. Dialysis was performed using a dialysis bag (molecular weight cutoff 14000 Da) until the pH of the dialysate stabilized at 6.5~7.0. The solution was then freeze-dried (-50℃, 0.1 Pa) to obtain white CNC powder. X-ray diffraction analysis showed that the crystallinity of CNC was 82%, and the Fourier transform infrared spectrum was within the range of 3340 cm⁻¹.-1 (Hydroxy stretching vibration), 1630 cm -1 (Adsorbed water bending vibration), 1050 cm -1 The presence of a characteristic peak at the (COC stretching vibration) point confirms the structural integrity of cellulose.

[0065] (2) Cyanobacterial strains and culture media

[0066] The cyanobacterium *Leptolyngbya laminosa* (purchased from the Freshwater Algae Culture Collection, Chinese Academy of Sciences, species number FACHB-1404) was cultured on BG-11 medium, the formulation of which was: 1.5 g / L NaNO3, 40 mg / L K2HPO4, 75 mg / L MgSO4·7H2O, 36 mg / L CaCl2·2H2O, 6 mg / L citric acid, 6 mg / L ferric ammonium citrate, 1 mg / L disodium ethylenediaminetetraacetate, 20 mg / L Na2CO3, 2.86 mg / L H3BO3, 1.86 mg / L MnCl2·4H2O, 0.22 mg / L ZnSO4·7H2O, 0.39 mg / L Na2MoO4·2H2O, 0.08 mg / L CuSO4·5H2O, 0.05 mg / L Na2MoO4·2H2O, 0.05 ... mg / L Co(NO3)2·6H2O, pH 7.1.

[0067] 2. Preparation and stability verification of CNC suspension

[0068] (1) Optimization of CNC dispersion process

[0069] Weigh 0.5 g of CNC powder, add 100 mL of ultrapure water, and magnetically stir (500 rpm) for 30 min. After initial dispersion, transfer to a probe-type ultrasonic instrument. Set the power to 220 W, amplitude to 40%, and pulse mode to 1 s on / 1 s off. Ultrasonicate for 2 min, 3 min, and 4 min respectively. Measure the particle size distribution and polydispersity index (PDI) of CNC at different ultrasonic times using a dynamic light scattering instrument. The results are shown in Table 1.

[0070] Table 1. Particle size distribution and dispersion coefficient of CNC at different ultrasonic times

[0071]

[0072] (2) Final CNC suspension preparation: The ultrasonic time was determined to be 3 min. A 0.5% (w / v) CNC suspension was prepared and its Zeta potential was measured to be -41 mV (strong negative charge repulsion, system stability). It was stored at 4℃ in the dark for later use. Within 7 days of storage, the particle size and PDI did not change significantly (PDI≤0.3), confirming that the stability of the suspension met the requirements of subsequent experiments.

[0073] 3. Targeted domestication and physiological characteristic characterization of drought-resistant cyanobacteria

[0074] (1) Domestication program design: Domestication programs designed for individuals in the exponential growth phase (OD) 680 Leptolyngbya laminosa bacterial suspension (BG-11 medium) with a concentration of 0.8 g / mL was divided into two groups, with each group having three replicates:

[0075] ① Drought stress acclimatization group: placed in a custom-designed low-humidity incubator (humidity control accuracy ±2%), initially at 5% RH, 30℃, and 80 μmol photons / m 2 The cells were treated under light for 12 hours (simulating drought), then transferred to 70% RH and recovered under the same temperature and light conditions for 12 hours. This cycle was repeated for 15 days, with daily sampling to measure cell density (OD). 680 ).

[0076] ② Control group: maintained at 70% RH, 30℃, and 80 μmol photons / m throughout the process. 2 / s light, continuously cultured for 15 days.

[0077] (2) Measurement of physiological indicators of cyanobacteria after domestication:

[0078] ① EPS extraction and quantification: EPS was extracted using a hot extraction method: 100 mL of bacterial culture was centrifuged at 6000 rpm for 3 min to collect the bacterial cells, washed 3 times with ultrapure water, 50 mL of ultrapure water was added, and the mixture was incubated in an 80℃ water bath for 3 h. After centrifugation (12000 rpm, 10 min), the supernatant was collected, and the EPS content was determined by the phenol-sulfuric acid method. The results showed that the EPS secretion of the acclimatization group was 73 mg / g stem cells, which was 30.4% higher than that of the control group (56 mg / g).

[0079] ② Determination of uronic acid groups in EPS: The m-hydroxybiphenyl method was used. 1 mL of EPS extract was taken and 0.5 mL of 0.5% m-hydroxybiphenyl solution (purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S30798) (dissolved in 0.5% NaOH) was added. The mixture was incubated in a 95℃ water bath for 5 min. After cooling, the absorbance was measured at 520 nm. The results showed that the uronic acid group content in the acclimatized EPS was 16.5%, which was 47.3% higher than that in the control group (11.2%), providing more chemical anchors (-COOH groups) for subsequent interfacial bonding with CNC.

[0080] ③ Photosynthetic activity assay: Y-chromosome activity was measured using a PAM chlorophyll fluorometer. [II] The results showed that: the domestication group Y [II] The value was 0.42, while the control group was 0.40, confirming that the domestication process improved EPS secretion while maintaining the basic photosynthetic activity of cyanobacteria.

[0081] 4. Construction and incubation of a CNC, cyanobacteria, and ion composite system

[0082] (1) Preparation of the mixing system: Take 50 mL of 0.5% (w / v) CNC suspension (taken out at 4℃ and restored to room temperature), add the domesticated cyanobacteria cells collected by centrifugation at 6000 rpm for 3 min and washed 3 times, and measure the absorbance at 665 nm by spectrophotometry according to formula C Chla (μg / mL)=OD 665 (Calculate chlorophyll a content using ×1000 / 74.5), adjust the chlorophyll a concentration in the system to 2 μg / mL; then add 1 mol / L CaCl2 solution (final concentration 1 mmol / L) and 1 mol / L MgCl2 solution (final concentration 0.3 mmol / L), and magnetically stir (300 rpm) for 15 min to ensure uniform ion dispersion. At this point, the system Ca... 2+ / Mg 2+ The molar ratio was 3.3:1, and the total ion concentration was 1.3 mmol / L.

[0083] (2) Constant temperature incubation and viscosity monitoring: The mixed system was transferred to a 50 mL Erlenmeyer flask, sealed with a breathable sealing film (to ensure gas exchange), and incubated in a constant temperature shaker (30±0.5℃, 150±5 rpm). The viscosity of the system was measured at the same time every day using a rotational viscometer, and the trend of change was recorded. The results are as follows: At the beginning of incubation, the viscosity was 120 cP (dilute suspension state); after 2 days of incubation, the viscosity was 420 cP (weak gel formation began); after 5 days of incubation, the viscosity was 720 cP (gel state stable, viscosity change ≤5% / 24h); after 7 days of incubation, the viscosity was 730 cP (given that the viscosity reached a plateau after 5 days of incubation, and that extending the incubation time did not significantly increase the viscosity, 5 days was determined to be the optimal incubation time that balances efficiency and effect). After incubation, the system was a light green uniform gel state, without layering or precipitation, and was stored at 4℃ for later use.

[0084] 5. Characterization of the microstructure and interfacial interactions of composite active materials

[0085] (1) Scanning electron microscopy observation: A small amount of gel-state composite material was taken, freeze-dried and sputtered with gold (thickness 5 nm). The microstructure was observed by field emission scanning electron microscopy. It was found that: CNC was distributed in a continuous fibrous manner, forming a support grid with a diameter of 50~100 nm; Leptolyngbya laminosa filaments (diameter 1.2~1.5 μm) were uniformly embedded in the CNC grid without obvious aggregation; EPS was coated on the surface of CNC in the form of a thin film, forming an interwoven structure of CNC nanoskeleton, cyanobacterial filaments and EPS polymer, confirming the successful construction of the three-dimensional network.

[0086] (2) FTIR spectral analysis: FTIR comparisons were performed on the freeze-dried composite material, pure CNC, and domesticated cyanobacteria EPS. The results showed that: pure CNC: 3340 cm⁻¹ -1 (Hydroxy stretching), 1050 cm -1 (COC stretching) is the characteristic peak; EPS: 3400 cm⁻¹ -1 (Hydroxy and amino stretching), 1620 cm -1 (Amide I band), 1410 cm -1 (Carboxyl group bending) is a characteristic peak; composite material: 3340 cm⁻¹ -1 The hydroxyl stretching peak is broadened (due to hydrogen bonding), at 1725 cm⁻¹. -1 A C=O stretching enhancement peak appears at 1580 cm⁻¹ (synergistic effect of CNC carboxyl group and EPS uronic acid carboxyl group). -1 A new peak appears at (Ca) 2+ (Coordination with carboxyl groups), confirming that CNC and EPS communicate via hydrogen bonds and Ca... 2+ Ion bridges form stable interface bonds.

[0087] (3) X-ray photoelectron spectroscopy analysis: XPS was used to determine the elemental composition of the composite material surface. It was found that the O element content was 8.2% higher than that of pure CNC, the Ca element content was 0.5%, and the Mg element content was 0.15%. Binding energy analysis showed that a new component (coordinated oxygen of carboxyl group and metal ion) appeared at the O 1s peak at 531.8 eV, which further confirmed the existence of ion bridging effect.

[0088] 6. Environmental response and mechanical property testing of composite active materials

[0089] (1) Humidity responsiveness test: The composite material was made into cylindrical samples with a diameter of 10 mm and a thickness of 2 mm. They were placed in constant temperature and humidity chambers (accuracy ±1% RH, ±0.5℃) at 5%, 35%, 65% RH and 95% RH respectively for 24 h to equilibrate. The compressive strength was tested using a universal testing machine (loading rate 1 mm / min, displacement control). Each group was repeated 3 times. The results are shown in Table 2:

[0090] Table 2. Environmental response and mechanical property test results of composite active materials

[0091]

[0092] The above results show that when the humidity increases from 5% to 95%, the compressive strength fluctuates by only 18%, which is much lower than that of traditional CNC and cyanobacteria systems (fluctuation >40%). This confirms that the material has excellent mechanical adaptive properties, which can be attributed to the environmental response behavior of the reversible three-dimensional network in shrinking and densifying under low humidity and moderately swelling under high humidity.

[0093] (2) Dry-wet cycle stability test: The above cylindrical samples were placed in 5% RH and 95% RH environments and cycled alternately (each cycle lasts 24 hours for equilibration) for a total of 10 cycles. The structural integrity (weighing method: integrity = mass of sample after cycle / initial mass × 100%) and compressive strength of the samples after cycling were measured. The structural integrity was 87%, with no obvious cracks or breakage; the compressive strength was 27.2 ± 1.5 N (only 3.4% lower than the initial value), which confirmed that the network structure has good reversible recovery ability.

[0094] (3) Salt tolerance test: The composite material was immersed in NaCl solutions of 0, 50, 100, 150, and 200 mmol / L (simulating the soil environment of saline-arid arid areas), and removed after 24 h. The photosynthetic activity Y of cyanobacteria was then measured. [II] The results, based on CNC particle size analysis, confirmed that the photosynthetic activity of cyanobacteria, Y... [II]The concentrations were between 0.33 and 0.35, with no significant difference, confirming that the ion system can alleviate the damage of high salt to the photosynthetic system of cyanobacteria; and the CNC particle size remained stable at 280-300 nm (PDI≤0.32) at all salinities, with no obvious aggregation, confirming that Ca 2+ / Mg 2+ CNC and Na can be inhibited through competitive adsorption. + Unfavorable interactions.

[0095] 7. Application and Effect Evaluation of Sandy Soil Remediation

[0096] (1) Soil pretreatment: Sandy soil from Ordos, Inner Mongolia (sampling depth 0~10 cm) was taken, and gravel and plant residues were removed by passing it through a 1 mm sieve. The pH was adjusted to 7.0 with 0.1 mol / L HCl or NaOH (suitable for cyanobacterial growth). The basic properties of the soil were: sand content 85%, silt content 12%, clay content 3%, initial moisture content 5%, organic matter content 0.8 g / kg, and total nitrogen content 0.32 g / kg.

[0097] (2) Application of composite material: The prepared composite active material (viscosity 720 cP) was loaded into a backpack sprayer (nozzle orifice diameter 0.5 mm, spray uniformity ±5%) and sprayed evenly on the soil surface from 6:00 to 6:30 in the morning (ambient temperature 22±2℃, RH 45±3%, wind speed <1m / s), with an application rate of 600 mL / m. 2 Three 1 m × 1 m experimental plots were set up, and a blank control group (sprayed with an equal amount of ultrapure water) was also set up.

[0098] (3) Formation and solidification of biological crust: For the first 3 days after application, spray 100 mL / m every morning. 2 Ultrapure water was used to maintain the surface soil moisture content at 15-20% (to promote cyanobacterial colonization and EPS secretion); the soil was then naturally dried from day 4 to day 7 (average daily temperature 25-30℃, RH 35-40%). After 7 days, a continuous biocrust was formed, and the thickness of the biocrust was measured to be 1.1 mm.

[0099] (4) Monitoring of repair effect: Wind erosion was measured using a small wind tunnel device (wind speed 3.5 m / s, continuous for 10 min). The results showed that the wind erosion of the experimental group was 6.9 ± 1.3 g / m. 2 Compared with the control group (25.8±2.5 g / m²), 2The soil moisture content decreased by 73.2%. The change in soil moisture content over 4 days was measured using the weighing method. The results showed that the moisture content of the experimental group remained at 38±2% over 4 days, while that of the control group was only 12±1%, representing a 216.7% improvement in water retention. The compressive strength of the crust was measured using a universal testing machine. The results showed that the compressive strength of the experimental group was 28±2 N, while that of the control group (natural soil) was only 5±1 N, representing a 460% increase in strength. The compressive strength (γ) of the crust was measured weekly during the experimental period. [II] The results showed that: experimental group Y [II] The concentration remained stable at 0.33–0.34, without significant decrease, confirming the continued survival and ecological function of cyanobacteria. Soil total nitrogen content was measured after 30 days, showing an increase to 0.65 g / kg in the experimental group, a 103.1% increase from the initial level (0.32 g / kg), attributed to nitrogen fixation by cyanobacteria and EPS decomposition.

[0100] Example 2:

[0101] 1. Experimental Design

[0102] To address the remediation needs of silty soils (high silt content, prone to compaction), the concentration of CNC and Ca is increased. 2+ The content enhances the air permeability and mechanical strength of the composite network. Microcoleus vaginatus, which has been drought-acclimated, is selected (its filamentous structure is more developed, which is conducive to the physical entanglement of soil particles). The rest of the basic processes are the same as in Example 1.

[0103] 2. Key parameter adjustment

[0104] (1) The concentration of CNC suspension is 5% (w / v), that is, 5 g of CNC powder is weighed and 100 mL of ultrapure water is added (10 times higher than in Example 1, which enhances the support capacity of the skeleton).

[0105] (2) The cyanobacterial strain was Microcoleus vaginatus after drought domestication (purchased from the Freshwater Algae Culture Bank of the Chinese Academy of Sciences, strain number FACHB-2003). After domestication, the EPS secretion amount was 82 mg / g stem cells and the uronic acid group content was 17.2%.

[0106] (3) Ca concentration in the ion system 2+ The final concentration was 5 mmol / L, Mg 2+ The final concentration was 1 mmol / L (molar ratio 5:1, total ion concentration 6 mmol / L).

[0107] (4) Incubation time: 6 days (due to the increased CNC concentration, the incubation needs to be extended to ensure that the network is fully formed).

[0108] 3. Material properties and repair effects

[0109] (1) Material characterization: After 6 days of incubation, the viscosity of the system was 980 cP, and the gel state was more compact; the swelling degree at 80% RH was 420% (350% in Example 1), and the water retention was stronger; the diameter of the Microcoleus vaginatus filaments was 2.1±0.2 μm, which formed a denser interwoven structure through the CNC grid, reducing the risk of compaction of silty soil; the compressive strength was 31±2 N (10.7% higher than that in Example 1).

[0110] (2) Remediation of silty soil: Take silty soil from Yulin, Shaanxi (60% silt content, 35% sand content, 5% clay content, pH 6.8), pass it through a 1 mm sieve, and adjust the pH to 6.8; apply 500 mL / m 2 The active material (low dosage for silty soils to avoid pore blockage) forms a 0.9 mm thick crust in 7 days; the soil remediation effect is: wind erosion reduced by 76%, moisture content maintained at 40% for 4 days, and Y... [II] The pH value was stabilized at 0.34, and the soil organic matter content increased from 0.9 g / kg to 1.8 g / kg, confirming that parameter optimization can adapt to the remediation needs of soils with different textures.

[0111] Example 3:

[0112] 1. Experimental Design

[0113] To verify whether low-concentration CNC can synergistically form a stable network with domesticated cyanobacteria through ion bridging and adapt to the remediation scenario of silty soil (porosity is easily blocked, requiring low CNC dosage), the core process is referenced in Example 1, with only the CNC concentration and adaptation parameters adjusted.

[0114] 2. Key parameter adjustment

[0115] (1) The concentration of CNC suspension is 0.05% (w / v), that is, weigh 0.05 g of CNC powder and add 100 mL of ultrapure water.

[0116] (2) The cyanobacterial strain was Microcoleus vaginatus after drought domestication. After domestication, the EPS secretion amount was 78 mg / g stem cells and the uronic acid group content was 18.3%.

[0117] (3) Ca concentration in the ion system 2+ The final concentration was 0.1 mmol / L, Mg 2+ The final concentration was 0.05 mmol / L (molar ratio 2:1, total ion concentration 0.15 mmol / L).

[0118] (4) Incubation time: 7 days.

[0119] 3. Material properties and repair effects

[0120] Material characterization: After 7 days of incubation, the system viscosity reached 510 cP (meeting the gel state requirements); the compressive strength fluctuated by 19% within the 5–95% RH range, and the structural integrity was 85% after 10 wet-dry cycles; the photosynthetic activity of cyanobacteria at 200 mmol / L salinity was [missing information]. [II] It is 0.30.

[0121] Soil remediation application: Silty sandy soil (pH 6.9) from Yulin, Shaanxi Province was selected, and the spraying rate was 300 mL / m². 2 (Low dosage is suitable for silty soil); a 0.5 mm thick biological crust is formed in 7 days; monitoring of the remediation effect shows that wind erosion is reduced by 70%, water content is retained at 35% in 4 days, compressive strength is 20 N, and total nitrogen is increased by 90% in 30 days, confirming that low concentration CNC can still achieve stable remediation function.

[0122] Example 4

[0123] 1. Set Design and Composition

[0124] To address the lack of laboratory equipment for field operations in arid regions, a convenient ecological restoration kit has been designed. Each kit can prepare 10 L of composite active materials, including:

[0125] (1) Component A (CNC dry powder): 200 g / bag, vacuum aluminum foil packaging, carboxyl substitution degree 0.3~0.8, pre-treated by ultrasonication (dispersion coefficient 0.28), and can be dispersed on site with simple stirring.

[0126] (2) Component B (lyophilized cyanobacteria concentrate): 10 mL / vial, frozen at -20℃, containing domesticated Leptolyngbyalaminosa cells, chlorophyll a concentration of 15 μg / mL after reconstitution, survival rate ≥85% (verified by plate counting method).

[0127] (3) Component C (ion regulator): 10 mL / vial, containing CaCl2 (2 mol / L) and MgCl2 (0.4 mol / L), molar ratio 5:1, ready to use immediately after opening.

[0128] (4) Instructions for use: The application amount, mixing steps and spraying time (5:30-7:00 am, temperature ≤25℃, RH≥40%) for different soil textures (sand, silt).

[0129] 2. On-site mixing and application

[0130] In the arid region of Changji, Xinjiang (39°N, 87°E), a 10 m × 10 m experimental plot (sandy soil, pH 7.2) was selected and divided into 3 subplots (3 m × 3 m). The field operation was carried out as follows:

[0131] (1) Mixing process: Take 8 L of ultrapure water (or local well water, filtered through a 0.45 μm filter membrane), add component A (200 g CNC dry powder), and magnetically stir (portable stirrer, speed 500 rpm) for 30 min. After evenly dispersing, add component B (10 mL of cyanobacterial freeze-dried liquid) and component C (10 mL of ion regulator), and continue stirring for 15 min. The chlorophyll a concentration is 1.5 μg / mL and the viscosity is 650 cP, which meets the spraying requirements.

[0132] (2) Spraying and monitoring: Application rate 700 mL / m 2 A 1.0 mm thick crust was formed in 5 days; 30-day monitoring results showed that the crust integrity rate was 90%, the compressive strength was 26±2 N, the wind erosion was reduced by 69%, and the total nitrogen content of the soil increased by 93%, confirming that the kit can achieve efficient remediation under field conditions without the need for professional laboratory equipment.

[0133] Comparative Example 1

[0134] 1. Experimental design: Except for not adding CaCl2 and MgCl2, the other steps are the same as in Example 1.

[0135] 2. Experimental Results: After 5 days of incubation, the viscosity of the system was only 210 cP, and a stable gel could not be formed. Scanning electron microscopy revealed that the CNC separated from the cyanobacteria, EPS did not coat the surface of the CNC, and there was no interwoven structure. After 10 wet-dry cycles, the structural integrity was only 54%, the compressive strength was 11±1 N, and the Y content in 150 mmol / L NaCl solution was... [II] The value is 0.19, and the wind erosion decreases by only 28%. Therefore, the lack of Ca... 2+ / Mg 2+ When using ion bridges, CNC and EPS are only bonded by a single hydrogen bond, resulting in weak interfacial interaction and an inability to form a stable three-dimensional network, thus exhibiting significantly inferior performance compared to this invention.

[0136] Comparative Example 2

[0137] 1. Experimental design: Undomesticated wild-type Leptolyngbya laminosa was used, and the remaining steps were the same as in Example 1;

[0138] 2. Experimental Results: The EPS secretion amount was 55 mg / g, and the uronic acid group content was 10.8%. After 7 days of incubation, the system viscosity was only 300 cP, failing to form a stable gel. After 10 wet-dry cycles, the structural integrity was 61%, the compressive strength was 14±1 N, the wind erosion was reduced by 35%, and the cyanobacterial survival rate after 7 days was 42% (compared to 78% in Example 1). Therefore, the EPS and uronic acid content of unacclimated cyanobacteria are low, making it unable to form an effective bond with CNC, and the stress resistance is poor, confirming that acclimation is a key step in improving material performance.

[0139] Comparative Example 3

[0140] 1. Experimental Design

[0141] (1) Single CNC group: Spray 600 mL / m of 0.5% (w / v) CNC solution 2 ;

[0142] (2) Single cyanobacteria group: Spraying unacclimated cyanobacteria solution (chlorophyll a concentration of 2 μg / mL) at 600 mL / m 2 ;

[0143] 2. Experimental Results

[0144] (1) Single CNC group: only a fragile film is formed in 7 days, with no skinning characteristics, compressive strength of 7±1 N, wind erosion reduced by 18%, and no ecological function (no carbon and nitrogen fixation).

[0145] (2) Single cyanobacteria group: No dense crust formed after 7 days, surface cracked, wind erosion decreased by 25%, water content was 15% after 4 days, Y [II] Only 0.18;

[0146] Based on the above experimental results, it can be concluded that neither CNC nor cyanobacteria alone can achieve the dual goals of structural stability and biological activity. An effective repair system can only be constructed through the synergistic effect of CNC, EPS, and ions.

[0147] Comprehensive performance comparison of the embodiments and comparative examples: To clearly present the performance gap between the present invention and the prior art, the core indicators of embodiments 1-3 and comparative examples 1-3 are summarized in the following table. All data are the mean ± standard deviation of three repeated experiments. The results are shown in Table 3:

[0148] Table 3 Performance Comparison Analysis of Examples and Comparative Examples

[0149]

[0150] Note: Comparative Examples 3-1 and 3-2 in Table 3 are two parallel experimental groups of Comparative Example 3.

[0151] Based on the experimental results of the above embodiments and comparative examples, the inventiveness of this invention is mainly reflected in the following four technical breakthroughs, which are significantly different from the prior art:

[0152] (1) Increase the content of uronic acid groups in cyanobacteria EPS through drought domestication, combined with Ca 2+ / Mg 2+Ion bridges construct a multi-point cross-linked network of "hydrogen bonds, electrostatics, and ion bridges," innovating the interface synergy mechanism. Compared with a single hydrogen bond system (Comparative Example 1), the structural integrity is improved by 61.1%, and the compressive strength is improved by 154.5%, solving the technical bottleneck of weak interface bonding in traditional systems.

[0153] (2) The reversible three-dimensional network constructed in the example exhibits an intensity fluctuation of only 18% at 5-95% RH, achieving mechanical self-adaptation compared to existing CNC and cyanobacteria systems (fluctuation >40%), while maintaining Y at a salinity of 200 mmol / L. [II] ≥0.33, filling the technological gap in the remediation of saline-alkali arid areas.

[0154] (3) Compared with the two subgroups of Comparative Example 3, a single CNC has no biological activity and a single cyanobacterium cannot form a stable crust. However, the present invention achieves the effect of reducing wind erosion rate by more than 70% and increasing total nitrogen by more than 90% through the ternary synergistic technology of CNC skeleton support, acclimation of cyanobacterial activity and ion interface enhancement, which fully demonstrates the uniqueness and inventiveness of the technical solution of the present invention.

[0155] (4) The ecological restoration kit designed in this invention solves the problem of field operations. On-site mixing only takes 30 minutes, which is 80% more efficient than laboratory preparation. It has a shelf life of up to 6 months (stored at 4℃), no change in CNC dispersibility, and a resolution survival rate of cyanobacteria ≥85%. The restoration effect after 30 days is consistent with that of laboratory preparation, providing a feasible solution for industrialization and promotion.

[0156] This invention involves drought stress acclimatization of *Leptolyngbya laminosa* (5% RH, 30℃ cyclic treatment), resulting in an increase of over 30% in EPS secretion and a uronic acid group content ≥15%, combined with Ca... 2+ (0.1~5 mmol / L) and Mg 2 + The molar ratio of (0.05~2 mmol / L) was optimized to (2~5):1. An ion bridge was used to connect the CNC and EPS to form a reversible three-dimensional network, achieving adaptive adjustment of "wet-state swelling and water retention (swelling degree 150~500%) and dry-state shrinkage and wind erosion resistance (compressive strength 20~35 N)". Simultaneously, the composite system maintained Y within the salinity range of 0~200 mmol / L. [II]The photosynthetic activity is ≥0.3, and the structural integrity rate is ≥85% after 10 wet-dry cycles. Furthermore, this invention also develops a kit product consisting of dried CNC powder, freeze-dried cyanobacteria, and ionic additives, which can be mixed and used on-site and has a shelf life of up to 6 months, completely solving the practical application problems of existing technologies. This design achieves a technological leap from "passive enhancement" to "active adaptation," filling the research gap in "functionally adaptable composite active materials" in the field of arid zone ecological restoration. It provides an innovative system for arid zone ecological restoration that combines high stability, environmental responsiveness, and ecological safety, possessing significant creative and industrial application value.

[0157] In summary, this invention, through component optimization, process innovation, and product design, overcomes multiple limitations of existing technologies and achieves the four objectives of "structural stability, environmental adaptability, ecological safety, and convenient application" for soil remediation in arid regions. It is significantly superior to existing technologies and possesses outstanding creativity and industrialization value.

[0158] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0159] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite active material based on cellulose nanocrystals and cyanobacteria, characterized in that, This includes cellulose nano-crystals (CNC), drought-resistant cyanobacteria, and environmental regulation ion systems. The CNC concentration is 0.05-5% (w / v), the drought-resistant cyanobacteria are 0.1-5 μg / mL based on chlorophyll a concentration, and the environmental regulation ion system contains Ca. 2+ Ca 2+ The concentration is 0.1~5 mmol / L; the cyanobacteria is *Leptolyngbya laminosa* acclimated under drought stress. After drought stress acclimation, the extracellular polymer secretion of *Leptolyngbya laminosa* is more than 30% higher than that of the wild type, and the content of uronic acid groups in the extracellular polymers is not less than 15%; the CNC and the extracellular polymers of the cyanobacteria are bonded by hydrogen bonds, electrostatics, and Ca2+. 2+ Ion bridges work synergistically to form a reversible three-dimensional network structure; the compressive strength of this three-dimensional network structure fluctuates by ≤20% at relative humidity of 5–95%, and maintains cyanobacterial photosynthetic activity within a salinity range of 0–200 mmol / L. [II] ≥0.

3.

2. The composite active material based on cellulose nanocrystals and cyanobacteria according to claim 1, characterized in that, The cyanobacteria also include Microcoleus vaginatus or Nostoc commune, wherein the filamentous structure of Microcoleus vaginatus has a diameter of 1.5 to 3 μm, and the heterocellular proportion of Nostoc commune is 5 to 10%.

3. The composite active material based on cellulose nanocrystals and cyanobacteria according to claim 1, characterized in that, The CNC has a length of 50~400 nm, a diameter of 5~20 nm, a carboxyl substitution degree of 0.1~1.0, and a dispersion coefficient ≤0.3 after ultrasonic treatment.

4. The composite active material based on cellulose nanocrystals and cyanobacteria according to claim 1, characterized in that, The regulating ion system also contains Mg 2+ Mg 2+ Concentrations range from 0.05 to 2 mmol / L, Ca 2+ With Mg 2+ The molar ratio is (2~5):1, and the total ion concentration is 0.15~7 mmol / L.

5. The composite active material based on cellulose nanocrystals and cyanobacteria according to claim 1, characterized in that, The reversible three-dimensional network structure has a swelling degree of 150-500% in the range of water content of 10-80%, and the network integrity remains ≥85% after 10 dry-wet cycles.

6. A method for preparing the composite active material based on cellulose nanocrystals and cyanobacteria as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) CNC is dispersed in deionized water and ultrasonically treated to form a CNC suspension; (2) Add drought-stress-acclimated cyanobacteria to the CNC suspension and add Ca 2+ and optional Mg 2+ Regulating ions; (3) Incubate at 30±2°C and 150±10 rpm for 3 to 7 days. During this period, monitor the viscosity of the system and terminate the incubation when it reaches 500 to 1000 cP to form a gel-state CNC+ cyanobacteria network and obtain a gel-state composite active material, namely a composite active material based on cellulose nanocrystals and cyanobacteria.

7. A method for remediating soil in arid regions using the composite active material based on cellulose nanocrystals and cyanobacteria as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) The composite active material based on CNC and cyanobacteria was uniformly sprayed onto the pretreated soil surface to be remediated at a rate of 300-800 mL / m². 2 ; (2) Dry naturally or at a controlled temperature of 25-35°C for 5-10 days to form a self-adaptive biological crust with a thickness of 0.5-2 mm.

8. The method for remediating soil in arid areas according to claim 7, characterized in that, The pretreatment also includes adjusting the soil pH to 6.5-8.0, and the spraying operation is carried out in the early morning with an ambient temperature ≤25°C and relative humidity ≥40%.

9. The method for remediating soil in arid areas according to claim 7, characterized in that, The resulting biological crust exhibits a structural integrity rate of ≥90% after 5 wet-dry cycles, a water retention rate of ≥35% within 4 days, and a compressive strength of 20~35 N.

10. An ecological restoration kit product, used to prepare the composite active material based on cellulose nanocrystals and cyanobacteria as described in any one of claims 1-5, characterized in that, The kit includes dried CNC powder, concentrated blue-green algae cell solution, and ion-regulating additives. The degree of carboxyl substitution of the dried CNC powder is 0.3~0.8; The concentrated cyanobacterial cell solution was freeze-dried, and the chlorophyll a concentration was 5~20 μg / mL. The regulating ion additive contains CaCl2, or contains both CaCl2 and MgCl2, wherein Ca... 2+ With Mg 2+ The molar ratio is (2~5):1.

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