Seaweed composition for sandy soil improvement and preparation method thereof

Abstract

The invention belongs to the technical field of soil conditioning, and particularly discloses a seaweed composition for sandy soil improvement and a preparation method thereof. The seaweed composition for sandy soil improvement is prepared from the following raw materials in parts by weight: 20 to 24 parts of sodium alginate, 14 to 18 parts of seaweed nano cellulose, 10 to 13 parts of attapulgite, 8 to 12 parts of carboxymethyl cellulose, 6 to 9 parts of montmorillonite and 12 to 15 parts of fulvic acid. The sodium alginate is prepared by performing cleaning, digestion extraction, acidification precipitation and conversion on brown algae, and the seaweed nanocellulose is prepared by performing water washing, dispersion, enzymolysis, homogenization and drying on seaweed residues. A plurality of components are matched to form a composite network, so that sand grains on the surface layer are effectively fixed, wind erosion and water erosion are prevented, rapid loss of the fertilizer is avoided, and nutrients are continuously provided for plants.

Description

A seaweed composition for improving desertified soil and its preparation method Technical Field

[0001] This application relates to the technical field of soil conditioning, and in particular to a seaweed composition for improving desertified soil and a method for preparing the same. Background Technology

[0002] Globally, especially in arid and semi-arid regions of northern China, such as Hotan in Xinjiang, the Horqin Sandy Land in Inner Mongolia, Dingbian in Shaanxi, and the Mu Us Desert, the remediation of desertified soils has become an urgent priority. Desertified areas typically suffer from drought, high evaporation rates, infertile soil (lacking organic matter and nutrient loss), and salinization, making it difficult for plants to survive and establish communities. The remediation model for desertified soils is increasingly emphasizing integrated management.

[0003] Soil conditioners are fundamental and crucial for improving desertified soils, aiming to increase soil organic matter and clay content, improve soil structure, and enhance water and fertilizer retention capacity. Existing conditioners include organic, inorganic, biological, and polymeric types. Sodium alginate, in particular, offers unique advantages in improving desertified soils, including sand fixation and topsoil stabilization, excellent water retention, improved soil structure and fertility retention, promotion of soil biological community development, and environmental friendliness and sustainability.

[0004] Existing technologies disclose the use of sodium alginate in combination with acidic raw materials, plant-derived organic matter, animal-derived organic matter, compound probiotics, and trace elements as a soil conditioner. However, the focus of this type of patent is on the combination of various nutrient-containing components to form a soil conditioner, which has a single regulatory mechanism and is not suitable for harsh environments such as drought. Summary of the Invention

[0005] To address the issue of limited regulation mechanisms in soil conditioners, this application provides a seaweed composition for improving desertified soil and its preparation method.

[0006] This application provides a seaweed composition for improving desertified soil, using the following technical solution: A seaweed composition for improving desertified soil, comprising, by weight, the following raw materials: 20-24 parts sodium alginate, 14-18 parts seaweed nanocellulose, 10-13 parts attapulgite, 8-12 parts carboxymethyl cellulose, 6-9 parts montmorillonite, and 12-15 parts humic acid; the sodium alginate is obtained by washing, digesting, extracting, acidifying, precipitating, and converting brown algae.

[0007] By employing the above-mentioned technical solution, sodium alginate, when dissolved in water, forms a viscous sol that can bind loose sand particles together, facilitating the formation of soil aggregates. Its molecular chains contain numerous hydrophilic groups, absorbing and retaining tens or even hundreds of times its own weight in water, forming a "miniature reservoir" in the soil, improving the water-holding capacity of sandy soil, and reducing water evaporation and seepage. Furthermore, its gel network structure loads fulvic acid and releases it slowly, improving fertilizer utilization. Fulvic acid can be directly absorbed and utilized by plants, providing organic matter and bioactive substances, improving soil fertility and biological activity, promoting microbial reproduction, accelerating soil organic matter cycling, and improving soil fertility in the long term.

[0008] Seaweed nanocellulose is derived from seaweed residue, achieving comprehensive resource utilization. Furthermore, seaweed nanocellulose synergistically forms a high-strength three-dimensional network structure with sodium alginate. This fiber network, while fixing sand, retains a certain degree of porosity, preventing excessive soil compaction, maintaining good aeration, and promoting plant root respiration and microbial activity. The combination of carboxymethyl cellulose and sodium alginate allows its linear molecular chains to interweave within the sodium alginate gel network, further enhancing the stability of the water-retaining layer and increasing the solution viscosity, preventing water-retaining components from being lost with rainwater.

[0009] Attapulgite has a surface rich in hydroxyl groups and charges, which can bind loose sand particles into small aggregates through electrostatic adsorption. At the same time, its interlayer structure can lock in sand particles and reduce soil loss caused by wind and water erosion. Montmorillonite has high expansibility, which can fill the large pores between sand particles after expansion, reducing water infiltration and loss. At the same time, its plate-like structure interweaves with the layered chain structure of attapulgite to form a dense bonding network, which further enhances the stability of soil aggregates and prevents the aggregates from disintegrating under the erosion of rainwater.

[0010] In this application, multiple components of the seaweed composition work synergistically. The hydrophilic components together construct a water-retaining network that can significantly reduce the permeability of sandy soil, firmly locking water and fertilizer around the plant roots and creating a microenvironment suitable for seed germination and seedling growth. Moreover, the composite network formed by multiple components can dry quickly and form a biological crust or covering film with a certain strength and toughness, effectively fixing surface sand particles and preventing wind and water erosion. Fulvic acid and adsorbent minerals work together to form a long-lasting nutrient supply system, preventing rapid fertilizer loss and continuously providing nutrients to plants.

[0011] Preferably, the method for preparing sodium alginate includes the following steps: (1) crushing Sargassum, Laminaria japonica, giant kelp, and kelp, washing them with water, then dispersing them in a washing solution, sonicating them for 1-2 hours, washing them with water to obtain mixture one, dispersing mixture one in deionized water, shearing them to obtain a slurry; (2) adding a compound enzyme to the slurry for enzymatic hydrolysis, adding a phosphate buffer solution, controlling the pH of the system between 6 and 7, and enzymatically hydrolyzing it at 40-45℃ for 3-4 hours to obtain an enzymatic hydrolysate; (3) adding a Na2CO3 aqueous solution to the enzymatic hydrolysate from step (2), digesting it, and then adding ethanol. (3) A mixture of aqueous solution is obtained, filtered to obtain filtrate and seaweed residue; (4) Hydrochloric acid aqueous solution is added to the filtrate of step (3) to adjust the pH to 2-3, kept warm at 40-45℃, cooled down, filtered to obtain alginic acid; (5) The alginic acid of step (4) is dispersed in Na2CO3 aqueous solution, stirred for 20 min, ethanol is added dropwise, and when the system becomes turbid, the addition is stopped, the temperature is raised to 48-50℃ to clarify the system, and then the temperature is kept at 48-50℃ and stirred. After cooling down to 25℃, a large amount of solid precipitates out. After filtration, washing with ethanol and drying, sodium alginate is obtained.

[0012] By employing the above-mentioned technical solution, pulverizing the brown algae raw material facilitates cleaning. The cleaning solution removes salt from seawater, silt adhering to the algal surface, soluble impurities, and some pigments. Further breaking down the fragments into a slurry fully exposes the cell structure, significantly improving the efficiency of subsequent enzymatic hydrolysis and alkaline extraction. The complex enzyme disrupts the algal cell wall structure, releasing calcium alginate and degrading intracellular proteins, lipids, and other impurities.

[0013] Adding Na2CO3 solution, sodium carbonate in With calcium in calcium alginate 2+ An ion exchange reaction occurs, producing calcium carbonate precipitate and soluble sodium alginate, which then enter the solution. Adding an aqueous ethanol solution disrupts the hydration layer of the sodium alginate, causing it to flocculate. This destabilizes and coagulates colloidal impurities and some pigments in the solution, facilitating subsequent filtration and removal.

[0014] When hydrochloric acid is added, the sodium carboxylate group (-COONa) of sodium alginate is converted into a carboxyl group (-COOH), which enhances intermolecular hydrogen bonding and drastically reduces solubility, causing it to precipitate as a gel-like alginate. Cooling allows the alginate molecules to precipitate and aggregate, forming larger, denser precipitates, which aids in subsequent filtration and improves product yield and purity.

[0015] Alginic acid is converted back into sodium alginate. Alginic acid is mixed with Na₂CO₃ solution, and a neutralization reaction regenerates sodium alginate. Ethanol is added until the system becomes turbid, indicating that sodium alginate has begun to precipitate from the solution. Increasing the temperature increases the solubility of sodium alginate, causing the newly formed tiny crystal nuclei to dissolve again, returning the system to a homogeneous state. Further cooling promotes the formation of sodium alginate crystals with uniform particle size, concentrated molecular weight distribution, and higher purity. Sodium alginate prepared using this method has high purity and yield. In subsequent applications in desertified soils, it forms stronger and more durable biocrusts and soil aggregates, absorbing and locking in more water, forming a more stable hydrogel.

[0016] In addition, a large amount of Sargassum resources are currently undeveloped and underutilized due to the natural disaster of "golden tide". Using Sargassum for sodium alginate extraction has problems such as dark color. This patent can solve this problem, realize the high-value application of Sargassum, and at the same time solve resource waste and provide targeted treatment in desertified soil.

[0017] Preferably, the cleaning solution comprises, by weight, 5-6 parts sucrose fatty acid ester, 8-10 parts sodium hypochlorite, 15-17 parts acetic acid, 22-25 parts ethanol, 80-85 parts deionized water, 15-17 parts modified bamboo charcoal powder, 3-5 parts xanthan gum, 2-3 parts cocoyl glucoside, 1-2 parts sodium sulfite, and 2-3 parts disodium EDTA.

[0018] By employing the above technical solutions, sucrose fatty acid esters effectively reduce the interfacial tension between water and oil and impurities on the algal surface, helping to peel off organic dirt adhering to the raw material surface. Simultaneously, they possess a certain emulsifying effect, preventing dirt from re-adhering. The combination of cocoyl glucoside and sucrose fatty acid esters synergistically enhances the cleaning effect, avoiding damage to the effective components in the algal material. Sodium hypochlorite disrupts microbial cell membranes and oxidase systems, killing bacteria, fungi, and other microorganisms adhering to the algal surface, removing some pigments, and improving the cleanliness of the raw material.

[0019] Acetic acid adjusts the pH of the system. In this acidic environment, sodium hypochlorite exhibits higher stability and bactericidal efficiency, while also neutralizing any alkaline impurities that may be present on the algae surface. Modified bamboo charcoal powder possesses a large specific surface area and abundant pore structure, adsorbing tiny particles, pigment molecules, odor molecules, and some heavy metal ions that detach from the algae during the cleaning process. It can also adjust the viscosity of the cleaning solution, improve adhesion, and prevent detached impurities from re-attaching to the algae.

[0020] Disodium EDTA binds to heavy metal ions on the algal surface, forming stable water-soluble complexes to remove them. It also chelates calcium and magnesium ions in the water, preventing them from reacting with cleaning agent components to form insoluble scale and affecting cleaning effectiveness. Sodium sulfite inhibits excessive oxidation of the effective components in the algae by sodium hypochlorite, reducing nutrient loss; it also prevents browning of the algae due to oxidation during cleaning, preserving the natural color of the raw material. Xanthan gum increases the viscosity of the cleaning solution, allowing the modified bamboo charcoal powder to remain uniformly suspended in the liquid, preventing it from settling to the bottom. This ensures that all components are evenly contacted on the algal surface during cleaning, and the viscous liquid adheres to the algal surface for a longer period, improving cleaning efficiency.

[0021] The cleaning solution removes impurities from the raw materials, improving the purity and yield of sodium alginate. The resulting sodium alginate forms a stronger and more durable biocrust and soil aggregate, absorbing and locking in more water to form a more stable hydrogel.

[0022] Preferably, the preparation method of the cleaning solution includes the following steps: heating deionized water to 33-35℃, adding xanthan gum and stirring until dissolved, then adding disodium EDTA, sucrose fatty acid ester, and cocoyl glucoside in sequence, stirring for 10-15 minutes, then adding modified bamboo charcoal powder, stirring for 20-25 minutes, cooling the temperature to room temperature, adding acetic acid, sodium hypochlorite, sodium sulfite, and ethanol, and stirring evenly to obtain the cleaning solution.

[0023] By employing the above technical solution, xanthan gum exhibits thickening properties and, under heating conditions, can hydrate and expand its molecular chains more rapidly, forming a stable three-dimensional network structure. This provides a suspending carrier for the subsequently added modified bamboo charcoal powder, preventing its precipitation. When the components are added sequentially, the resulting cleaning solution exhibits good stability and is less prone to stratification.

[0024] Preferably, the preparation method of the modified bamboo charcoal powder includes the following steps: crushing bamboo, sieving, dispersing in sodium hydroxide solution and soaking for 20-24 hours, washing with water, then dispersing in sodium carbonate aqueous solution, stirring for 3-4 hours, drying, and vacuum heating at 900-920℃ for 40-45 minutes to obtain carbonized bamboo charcoal powder; dispersing hydroxypropyl starch in deionized water, adding nano-silica, tannic acid, and sodium dodecylbenzene sulfonate, stirring at 60-65℃ for 30-35 minutes to obtain a mixed solution; immersing the carbonized bamboo charcoal powder in the mixed solution, immersing 1-2 times, and drying to obtain modified bamboo charcoal powder.

[0025] By employing the above technical solution, sodium hydroxide solution disrupts the hydrogen bond network of cellulose, hemicellulose, and lignin in the bamboo structure, dissolving some of the hemicellulose and lignin, thus loosening the bamboo structure and laying the foundation for the formation of a porous structure during subsequent carbonization. Sodium carbonate further cleans the fiber surface, introducing some sodium carboxylate groups to increase hydrophilicity and ion exchange capacity. During high-temperature carbonization, sodium carbonate decomposes, creating more and more complex pores. Simultaneously, the carboxyl groups in its molecules may be retained, increasing the surface chemical activity and hydrophilicity of the carbonized bamboo charcoal powder.

[0026] Hydroxypropyl starch dissolves in water to form a viscous solution that firmly adheres other components to the surface of bamboo charcoal powder. After drying, it forms a coating film. Nano-silica is embedded in the starch film, increasing the mechanical strength and wear resistance of the coating layer. During subsequent cleaning of raw materials, it can scrape and peel off stubborn dirt, biofilms, and other impurities attached to the algae surface, helping to increase the network strength of the system and form a more stable system, so that the modified bamboo charcoal powder and other solid particles are stably suspended in the solution.

[0027] Tannic acid contains a large number of phenolic hydroxyl groups, which adsorb onto hydroxypropyl starch molecular chains and nano-silica, forming a complex ternary compound. In subsequent raw material cleaning processes, tannic acid exhibits a strong complexing and adsorption capacity for heavy metal ions, dyes, and organic matter, increasing the adsorption capacity of bamboo charcoal powder. Sodium dodecylbenzenesulfonate prevents the agglomeration of nano-SiO2 and tannic acid in the mixture, ensuring their uniform and stable dispersion and guaranteeing the uniformity of the final coating effect.

[0028] By impregnating, the mixed liquid is coated on the surface of the bamboo charcoal powder, resulting in modified bamboo charcoal powder with a bamboo charcoal core, a nano-SiO2-reinforced intermediate layer, and a tannic acid-rich outer layer, forming a multi-level, multi-functional adsorption system. This system has high cleaning efficiency for subsequent algae cleaning.

[0029] Preferably, the method for preparing the seaweed nanocellulose includes the following steps: washing seaweed residue with water, drying it, dispersing it in NaOH solution, stirring for 2-4 hours, washing it with water, dispersing it in deionized water, adding xylanase, adjusting the pH of the system to 4.5-5.5 with acetate-sodium acetate buffer, completing the enzymatic hydrolysis, incubating at 80-85℃ for 10-12 minutes to inactivate the enzyme, drying it, homogenizing it under high pressure, and freeze-drying it to obtain seaweed nanocellulose.

[0030] By employing the above technical solution, NaOH solution treatment removes residual hemicellulose from seaweed residue, causing the fibers to swell, disrupting the cellulose crystal structure, and increasing its specific surface area, creating favorable conditions for subsequent enzymatic hydrolysis and mechanical processing. Xylanase further degrades and removes residual hemicellulose, weakening the hydrogen bonding between microfibrils and significantly reducing the energy required for subsequent mechanical exfoliation. High-pressure homogenization decomposes the purified cellulose fibers from the micron level to the nanoscale, yielding a gel-like seaweed nanocellulose suspension. Freeze-drying yields solid dry powder seaweed nanocellulose. The obtained seaweed nanocellulose, when combined with matrix materials such as sodium alginate, enhances the mechanical strength and toughness of the water-retaining gel, preventing it from breaking under external forces.

[0031] Preferably, the complex enzyme consists of endoglucanase, pectinase, and protease in a mass ratio of 1:1:3-4.

[0032] By employing the above-mentioned technical solution, protein impurities can severely affect the purity and color of sodium alginate. Proteases can efficiently degrade these proteins, converting them into soluble short peptides or amino acids, which are easily removed during subsequent washing and filtration. Endoglucanase cleaves the amorphous regions in the cellulose network, weakening the physical strength of the cell wall and making it porous. This facilitates the processing of algae by other enzymes, while preserving most of the intact cellulose framework for the subsequent preparation of algal nanocellulose from algal residue, significantly reducing the energy consumption of subsequent mechanical processing.

[0033] Pectinase effectively dissolves pectin-like substances, promotes cell separation, and works synergistically with endoglucanase to completely dismantle cell wall defenses. The combined effect of these three agents improves the purity and yield of sodium alginate, which is beneficial for the subsequent preparation of seaweed nanocellulose from seaweed residue.

[0034] Preferably, the attapulgite is pretreated by the following steps: (1) Dispersing the attapulgite in deionized water, calcining at 580-600℃ for 4-5 hours, then dispersing it in hydrochloric acid solution, soaking for 1-2 hours, washing with water, and drying to obtain treated attapulgite; (2) Stirring humic acid, sodium polyacrylate, polyethylene glycol 400, deionized water, and gum arabic evenly, spray drying to obtain powder; (3) Dispersing chitosan in citric acid solution, adding genipin and mixing, reacting at 60-62℃ for 1-1.5 hours to obtain a mixture, adding the treated attapulgite from step (1) and the powder from step (2), stirring for 2-3 hours, and drying to obtain pretreated attapulgite.

[0035] The above technical solution removes the water of crystallization from attapulgite through high-temperature calcination, creating more pores and cracks, increasing the specific surface area of ​​the attapulgite, and exposing more active sites. Hydrochloric acid can dissolve inorganic impurities in the attapulgite, remove impurities clogging the pores, expand the pore size, and facilitate the subsequent entry and loading of macromolecules.

[0036] Humic acid provides abundant organic matter and functional groups, stimulating plant growth, improving soil structure, and chelating trace elements. Sodium polyacrylate can absorb hundreds of times its own weight in water, acting as a water-retaining agent and gel skeleton. Polyethylene glycol 400 makes the mixture more uniform and improves the flowability of the final powder. Gum arabic, as a film-forming agent and binder, helps form uniform microspheres during spray drying; polyethylene glycol 400 also reduces the brittleness of film-forming substances such as gum arabic, making the final powder particles more resilient and less prone to breakage. Spray drying yields humic acid-rich, water-retaining organic powder particles.

[0037] Chitosan possesses excellent film-forming properties, biocompatibility, and adsorption capacity. Genipin undergoes a highly efficient nucleophilic reaction with the amino groups of chitosan, forming a stable three-dimensional network gel. Attapulgite soil and powder are added to this gel and stirred thoroughly, allowing the gel network to fully encapsulate and embed itself into the pores of the attapulgite soil, firmly fixing the organic powder particles within its network. After drying, the chitosan-genipin gel network shrinks and tightly encapsulates all components, ensuring a stable powder load within the pores of the treated attapulgite soil, forming a robust composite. The resulting pretreated attapulgite soil can absorb and lock in a large amount of moisture, gradually releasing internal humic acid for long-term nutrient supply, enhanced aggregation, and promotion of soil aggregate formation.

[0038] Preferably, the mass ratio of attapulgite, sodium polyacrylate and chitosan is 1:0.4-0.5:0.1-0.2.

[0039] By adopting the above technical solution and further limiting the ratio of attapulgite, sodium polyacrylate, and chitosan within a certain range, the pretreated attapulgite obtained exhibits excellent comprehensive performance. Attapulgite's large specific surface area and pores make it an excellent adsorption carrier. Sodium polyacrylate can absorb hundreds or even thousands of times its own weight in water and rapidly form a gel, converting free water into bound water. Chitosan can form a semi-permeable membrane on the surface of other substances, coating attapulgite and sodium polyacrylate. The resulting pretreated attapulgite provides long-lasting water retention and slow-release fertilizer, promoting soil aggregation and nutrient retention.

[0040] Secondly, this application also provides a method for preparing a seaweed composition for improving desertified soil, comprising the following steps: heating deionized water to 52-55℃, adding sodium alginate and carboxymethyl cellulose, stirring evenly, then adding attapulgite, montmorillonite, and humic acid, dispersing continuously at 3000-5000 rpm for 30-45 min, then adding seaweed nanocellulose, dispersing at 2000-3000 rpm for 20-30 min, drying, and sieving to obtain the seaweed composition.

[0041] By adopting the above technical solution, this method is simple to operate, and the resulting seaweed composition has high water retention, excellent sand fixation, slow-release fertilizer effect, and improves soil structure.

[0042] In summary, this application has the following beneficial effects: 1. In this application, seaweed nanocellulose and sodium alginate synergistically form a high-strength three-dimensional network structure. While fixing sand, the fiber network can retain a certain amount of porosity, avoid excessive soil compaction, maintain good air permeability, and is conducive to plant root respiration and microbial activity.

[0043] 2. In this application, carboxymethyl cellulose is combined with sodium alginate, and its linear molecular chains can be interwoven in the sodium alginate gel network, which further improves the stability of the water-retaining layer, further increases the viscosity of the solution, and prevents the water-retaining components from being lost with rainwater.

[0044] 3. In this application, multiple components of the seaweed composition work together to form a water-retaining network, which can significantly reduce the permeability of sandy soil, lock water and fertilizer firmly around the plant roots, and create a microenvironment suitable for seed germination and seedling growth. Detailed Implementation

[0045] The present application will be further described in detail below with reference to the embodiments.

[0046] The raw materials used in the examples and comparative examples are all commercially available.

[0047] Preparation Example of Sodium Alginate Preparation Example 1-1 The preparation method of sodium alginate includes the following steps: (1) Crush 50kg of Sargassum, 15kg of Laminaria japonica, and 10kg of Kelp into brown algae with an area of ​​1.5-2cm 2The fragments were washed with water and then dispersed in the washing solution. The mixture was sonicated for 1.5 hours and then washed with water to obtain mixture one. Mixture one was dispersed in 6 times the amount of deionized water and sheared at 1200 rpm to obtain a slurry. (2) A compound enzyme was added to the slurry for enzymatic hydrolysis. A phosphate buffer solution (a mixture of 0.2 mol / L sodium dihydrogen phosphate and 0.2 mol / L disodium hydrogen phosphate in a volume ratio of 1:1) was added to control the pH of the system to 6. The mixture was enzymatically hydrolyzed at 45°C for 3 hours to obtain an enzymatic hydrolysate (the total weight of the enzyme was 0.2% of the total weight of kelp, giant kelp, and Sargassum fusiforme). (3) 1 times the weight of 6.0% wt Na2CO3 aqueous solution was added to the enzymatic hydrolysate from step (2). The mixture was digested at 45°C for 2 hours and then 1 / 5 volume of 3% wt Na2CO3 aqueous solution was added. The ethanol aqueous solution yields mixture two, which is filtered (through a 0.5 μm microporous membrane) to obtain filtrate and seaweed residue; (4) 4 mol / L hydrochloric acid aqueous solution is added to the filtrate of step (3) to adjust the pH to 3, and the solution is kept at 45°C for 2 h (cooling rate of 10°C / h), cooled, filtered, and alginic acid is obtained; (5) The alginic acid of step (4) is dispersed in 1.5 times its weight of 10% wt Na2CO3 aqueous solution, stirred at 36°C for 20 min, ethanol is added dropwise, and the addition is stopped when the system becomes turbid. The temperature is raised to 50°C to clarify the system, and then the temperature is maintained at 50°C and stirred for 2 h. The temperature is then lowered to 25°C at a cooling rate of 10°C / h, and a large amount of solid is precipitated. After filtration, washing with ethanol and drying, sodium alginate is obtained.

[0048] The cleaning solution, by weight, includes: 6 kg of sucrose fatty acid ester, 9 kg of sodium hypochlorite, 16 kg of acetic acid, 22 kg of ethanol, 83 kg of deionized water, 16 kg of modified bamboo charcoal powder, 4 kg of xanthan gum, 3 kg of cocoyl glucoside, 2 kg of sodium sulfite, and 2 kg of disodium EDTA.

[0049] The preparation method of the cleaning solution includes the following steps: heating deionized water to 34°C, adding xanthan gum and stirring until dissolved, then adding disodium EDTA, sucrose fatty acid ester, and cocoyl glucoside in sequence, stirring for 15 minutes, then adding modified bamboo charcoal powder and stirring for 23 minutes, cooling the temperature to room temperature, adding acetic acid, sodium hypochlorite, sodium sulfite, and ethanol, and stirring evenly to obtain the cleaning solution.

[0050] Cleaning parameters: The total weight of Sargassum, Laminaria japonica, and Giant Kelp and the solid-liquid ratio of the cleaning solution are controlled at 1:10 (g / mL). Ultrasonic cleaning is performed for 2 hours (300W power). After cleaning, the solution is rinsed 3 times with deionized water until the pH of the rinse water is 7 (no acidic residue).

[0051] The preparation method of modified bamboo charcoal powder includes the following steps: 50 kg of bamboo is crushed, passed through an 80-mesh sieve, dispersed in 70 L of 5% sodium hydroxide solution and soaked for 23 h, washed with water, then dispersed in 80 L of 20% sodium carbonate aqueous solution, stirred for 4 h, dried, and vacuum heated at 910 °C for 42 min to obtain carbonized bamboo charcoal powder; 10 kg of hydroxypropyl starch is dispersed in 30 L of deionized water, 6 kg of nano-silica, 4 kg of tannic acid, and 1 kg of sodium dodecylbenzenesulfonate are added, and stirred at 62 °C for 32 min to obtain a mixed solution; 10 kg of carbonized bamboo charcoal powder is immersed in the mixed solution twice, dried, and the modified bamboo charcoal powder is obtained.

[0052] The preparation method of seaweed nanocellulose includes the following steps: 30 kg of seaweed residue is washed with water, dried, and dispersed in 55 L of 1 mol / L NaOH solution. The mixture is stirred and reacted in an 80℃ water bath for 4 h. After washing with water, the mixture is dispersed in 100 L of deionized water. Xylanase (1000 U / g activity enzyme, 1 g enzyme per 10 g seaweed residue) is added. The pH of the system is adjusted to 4.5 with 0.1 mol / L acetate-sodium acetate buffer. After enzymatic hydrolysis, the mixture is kept at 85℃ for 10 min to inactivate the enzyme. The mixture is dried, homogenized under high pressure, and freeze-dried to obtain seaweed nanocellulose. The pressure of the high-pressure homogenization is 80 MPa, and the temperature is controlled at 35℃.

[0053] The complex enzyme consists of endoglucanase, pectinase, and protease in a mass ratio of 1:1:3.5.

[0054] The difference between Preparation Example 1-2 and Preparation Example 1-1 is that no cleaning solution is added in step (1).

[0055] The difference between Preparation Example 1-3 and Preparation Example 1-1 is that modified bamboo charcoal powder is not added to the cleaning solution.

[0056] The difference between Preparation Example 1-4 and Preparation Example 1-1 is that hydroxypropyl starch is not added in the preparation method of modified bamboo charcoal powder.

[0057] The difference between Preparation Example 1-5 and Preparation Example 1-1 is that nano-silica is not added in the preparation method of modified bamboo charcoal powder.

[0058] The difference between Preparation Example 1-6 and Preparation Example 1-1 is that tannic acid is not added in the preparation method of modified bamboo charcoal powder.

[0059] Preparation Example 2-1: Attapulgite is pretreated by the following steps: (1) 25 kg of attapulgite is dispersed in 60 L of deionized water, calcined at 600 °C for 5 h, then dispersed in 50 L of 3% hydrochloric acid solution, soaked for 1.5 h, washed with water, and dried to obtain treated attapulgite; (2) 8 kg of humic acid, sodium polyacrylate, 2 kg of polyethylene glycol 400, 60 kg of deionized water, and 5 kg of gum arabic are stirred evenly and spray-dried to obtain powder; (3) Chitosan is dispersed in 20 L of 3% citric acid solution, 0.5 kg of genipin is added and mixed, reacted at 60 °C for 1 h to obtain a mixture, the treated attapulgite from step (1) and the powder from step (2) are added, stirred for 2.5 h, and dried to obtain pretreated attapulgite.

[0060] The mass ratio of attapulgite, sodium polyacrylate, and chitosan is 1:0.4:0.2.

[0061] The difference between Preparation Example 2-2 and Preparation Example 2-1 is that sodium polyacrylate is not added in step (2).

[0062] The difference between Preparation Example 2-3 and Preparation Example 2-1 is that chitosan is not added in step (3).

[0063] The difference between Preparation Example 2-4 and Preparation Example 2-1 is that the mass ratio of attapulgite, sodium polyacrylate and chitosan is 1:0.5:0.1.

[0064] The difference between Preparation Example 2-5 and Preparation Example 2-1 is that the mass ratio of attapulgite, sodium polyacrylate, and chitosan is 1:0.2:0.5. Examples

[0065] Example 1: A seaweed composition for improving desertified soil, comprising the following raw materials by weight: 24 kg sodium alginate, 14 kg seaweed nanocellulose, 13 kg attapulgite, 12 kg carboxymethyl cellulose, 9 kg montmorillonite, and 15 kg humic acid; the preparation method of the above seaweed composition for improving desertified soil includes the following steps: heating deionized water to 55°C, adding sodium alginate and carboxymethyl cellulose, stirring evenly, then adding attapulgite, montmorillonite, and humic acid, dispersing continuously at 4000 rpm for 40 min, then adding seaweed nanocellulose, dispersing at 2500 rpm for 25 min, drying, and passing through a 60-mesh sieve to obtain the seaweed composition.

[0066] Sodium alginate was prepared using Preparation Example 1-1, and attapulgite was purchased from Hebei McMini Mineral Products Co., Ltd.

[0067] Example 2: A seaweed composition for improving desertified soil, which differs from Example 1 in that, by weight, it includes the following raw materials: 20 kg sodium alginate, 18 kg seaweed nanocellulose, 10 kg attapulgite, 8 kg carboxymethyl cellulose, 6 kg montmorillonite, and 12 kg humic acid.

[0068] Example 3: A seaweed composition for improving desertified soil, which differs from Example 1 in that the sodium alginate is prepared using Preparation Examples 1-2.

[0069] Example 4: A seaweed composition for improving desertified soil, which differs from Example 1 in that sodium alginate is prepared using Preparation Examples 1-3.

[0070] Example 5: A seaweed composition for improving desertified soil, which differs from Example 1 in that sodium alginate is prepared using Preparation Examples 1-4.

[0071] Example 6: A seaweed composition for improving desertified soil, which differs from Example 1 in that sodium alginate is prepared using Preparation Examples 1-5.

[0072] Example 7: A seaweed composition for improving desertified soil, which differs from Example 1 in that sodium alginate is prepared using Preparation Examples 1-6.

[0073] Example 8: A seaweed composition for improving desertified soil, which differs from Example 1 in that the attapulgite soil is prepared using Preparation Example 2-1.

[0074] Example 9: A seaweed composition for improving desertified soil, which differs from Example 8 in that the attapulgite soil is prepared using Preparation Example 2-2.

[0075] Example 10: A seaweed composition for improving desertified soil, which differs from Example 8 in that the attapulgite soil is prepared using Preparation Examples 2-3.

[0076] Example 11: A seaweed composition for improving desertified soil, which differs from Example 8 in that the attapulgite soil is prepared using Preparation Examples 2-4.

[0077] Example 12: A seaweed composition for improving desertified soil, which differs from Example 8 in that the attapulgite soil is prepared using Preparation Examples 2-5.

[0078] Comparative Example 1: A seaweed composition for improving desertified soil, which differs from Example 1 in that it does not contain seaweed nanocellulose.

[0079] Comparative Example 2: A seaweed composition for improving desertified soil, which differs from Example 1 in that it does not contain attapulgite.

[0080] Performance testing was conducted on the seaweed compositions prepared in Examples 1-12 and Comparative Examples 1-2 for improving desertified soil. The total porosity of the soil was determined using the ring cutter method. Water absorption: 30g of dried sand and 7g of the test sample were weighed, mixed thoroughly, and recorded as m1. The mixture was placed in a mesh bag (weighing m0) and immersed in 300mL of deionized water. After absorbing water for 24 hours, the mixture was hung up to drain. When no water dripped out, the weight was recorded as m2. The water absorption multiple (times) was calculated using the following formula: Water absorption multiple (times) = (m2 - m1 - m0) / m1. Moisture content: 300g of dried sand and 50g of the test sample were weighed, mixed thoroughly, and recorded as M1. The mixture was placed in a PVC pipe (weighing M0). 1 50 mL of deionized water was allowed to stand until no water leakage occurred. The weight was recorded as M2. The moisture content (%) was calculated using the following formula: Moisture content (%) = (M2 - M1 - M0) / M1 × 100%. A ceramic basin with holes at the bottom (5 cm in diameter and 8 cm in height) was used. 250 g of air-dried sandy soil was placed in each basin, and 3 g of the test sample was added and mixed thoroughly. Water was added to the soil sample using the mass difference method to maintain the relative moisture content at 60%. After standing indoors for 20 days, the soil aggregate structure was tested. A 50 g soil sample was taken and sieved dry using a 0.25 mm mesh sieve. The percentage (%) of aggregates at each level in the soil was determined. Aggregates >0.25 mm were considered large aggregates, and those <0.25 mm were considered microaggregates. The test results are shown in Table 1.

[0081] Table 1 Test data for the examples and comparative examples As shown in Table 1, the seaweed compositions prepared in Examples 1-2 of this application for improving desertified soil have good porosity, water absorption, and sand-fixing properties. Specifically, the soil in Example 1 has a porosity of 45.5%, a water absorption ratio of 2.12 times, a moisture content of 34%, a sand content of 50% (>0.25 mm), and a sand content of 38% (<0.25 mm). It is evident that the multiple components in the seaweed compositions prepared in this application work synergistically to effectively fix surface sand particles, expand pores, and construct a water-retaining network. The seaweed compositions extracted in this application have high purity, good water absorption and retention properties, and are suitable for arid environments.

[0082] The purity and yield of sodium alginate were tested in Examples 1-7. The yield of Example 1 was 32.9%, the yield of Example 2 was 32.5%, the yield of Example 3 was 26.9%, the yield of Example 4 was 28.6%, the yield of Example 5 was 29.8%, the yield of Example 6 was 30.5%, and the yield of Example 7 was 31.1%.

[0083] Therefore, it can be seen that the sodium alginate prepared in this application has high purity and yield. The addition of cleaning agent and the change of the raw material components in the cleaning agent have a great impact on the cleaning of algae raw materials, which in turn affects the yield and purity of sodium alginate, and thus affects the overall effect of subsequent desertification soil improvement.

[0084] In Example 3, no cleaning solution was added to the preparation method of sodium alginate. As can be seen from Table 1, the test results of soil porosity, water absorption multiple, moisture content, and sand content (>0.25mm) in Example 3 were significantly worse than those in Examples 1-2. This indicates that the cleaning solution treated the raw materials, removed the mud, soluble impurities, and some pigments attached to the surface of the algae, and improved the purity and yield of sodium alginate. The resulting sodium alginate formed a stronger and more durable biological crust and soil aggregate, which absorbed and locked in more water, forming a hydrogel with better stability.

[0085] In Example 4, no modified bamboo charcoal powder was added to the cleaning solution. As can be seen from Table 1, the test results of soil porosity, water absorption multiple, moisture content, and sand content (>0.25mm) in Example 3 were significantly worse than those in Examples 1-2, but better than those in Example 3. This indicates that the modified bamboo charcoal powder has a huge specific surface area and rich pore structure, which can adsorb the tiny particles, pigment molecules, odor molecules, and some heavy metal ions that fall off from the algae during the cleaning process. It can also adjust the viscosity of the cleaning solution, improve adhesion, and prevent the impurities that have fallen off from reattaching to the algae, thereby significantly improving the cleaning efficiency of the cleaning solution.

[0086] In the preparation methods of modified bamboo charcoal powder in Examples 5-7, hydroxypropyl starch, nano-silica, and tannic acid were not added respectively. As can be seen from Table 1, the test results of soil porosity, water absorption multiple, moisture content, and sand content (>0.25mm) in Examples 5-7 were significantly worse than those in Examples 1-2, but better than those in Examples 3-4. This indicates that after hydroxypropyl starch dissolves in water, it forms a viscous solution that firmly adheres other components to the surface of the bamboo charcoal powder. After drying, it forms a coating film. Nano-silica is embedded in the starch film, increasing the mechanical strength and wear resistance of the coating layer. During subsequent cleaning of raw materials, it can scrape and peel off stubborn dirt, biofilm, and other impurities attached to the surface of the algae. Tannic acid contains a large number of phenolic hydroxyl groups, which are adsorbed on the hydroxypropyl starch molecular chains and nano-silica to form a complex ternary complex. During subsequent cleaning of raw materials, tannic acid has a strong complexing and adsorption capacity for heavy metal ions, dyes, organic matter, etc., which increases the adsorption capacity of bamboo charcoal powder. This improves the cleaning efficiency of subsequent cleaning solutions, thereby increasing the purity of raw materials.

[0087] Examples 8 and 11 pretreated attapulgite soil. Table 1 shows that the soil in Example 8 had a porosity of 56.8%, a water absorption ratio of 2.98 times, a moisture content of 46%, a sand content of 62% (>0.25mm), and a sand content of 28% (<0.25mm). This demonstrates that the attapulgite soil pretreated in this application can absorb and lock in a large amount of water, gradually release internal humic acid, achieve long-term nutrient supply, enhance aggregation, and promote the formation of soil aggregates.

[0088] In Examples 9-10, sodium polyacrylate and chitosan were not added to the pretreatment methods for attapulgite soil, respectively. In Example 12, the mass ratio of attapulgite soil, sodium polyacrylate, and chitosan was changed. Table 1 shows that the test results for soil porosity, water absorption multiple, moisture content, and sand content (>0.25mm) in Examples 9-10 were significantly better than those in Examples 1-2, but worse than those in Example 8. The corresponding performance test results in Example 12 were better than those in Examples 9-10, but worse than those in Example 8. This indicates that sodium polyacrylate can absorb hundreds of times its own weight in water, acting as a water-retaining agent and gel framework. Chitosan has good film-forming properties, biocompatibility, and adsorption properties, subsequently improving the overall performance of attapulgite soil. The pretreated attapulgite soil obtained by the combination of these components provides long-lasting water retention and slow-release fertilizer, resulting in soil aggregation and fertilizer retention.

[0089] In Comparative Examples 1-2, neither seaweed nanocellulose nor attapulgite was added. As shown in Table 1, the test results of soil porosity, water absorption multiple, moisture content, and sand content (>0.25mm) in Comparative Examples 1-2 were significantly worse than those in Examples 1-2. This indicates that seaweed nanocellulose and sodium alginate synergistically form a high-strength three-dimensional network structure. Its fiber network can retain a certain amount of porosity while fixing sand. Attapulgite can bind loose sand particles into small aggregates through electrostatic adsorption. At the same time, its interlayer structure can lock sand particles and reduce soil loss caused by wind and water erosion. Its plate-like structure and the layer chain structure of attapulgite interweave to form a dense bonded network, which further enhances the stability of soil aggregates.

[0090] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A seaweed composition for improving desertified soil, characterized in that, By weight, it includes the following raw materials: 20-24 parts sodium alginate, 14-18 parts seaweed nanocellulose, 10-13 parts attapulgite, 8-12 parts carboxymethyl cellulose, 6-9 parts montmorillonite, and 12-15 parts fulvic acid; sodium alginate is obtained by washing, digesting, extracting, acidifying, precipitating, and converting brown algae.

2. The seaweed composition for improving desertified soil according to claim 1, characterized in that, The method for preparing sodium alginate includes the following steps: (1) crushing Sargassum, Laminaria japonica, giant kelp, and kelp, washing them with water, then dispersing them in a washing solution, sonicating them for 1-2 hours, washing them with water to obtain mixture one, dispersing mixture one in deionized water, shearing them to obtain a slurry; (2) adding a compound enzyme to the slurry for enzymatic hydrolysis, adding a phosphate buffer solution, controlling the pH of the system between 6 and 7, and enzymatically hydrolyzing it at 40-45℃ for 3-4 hours to obtain an enzymatic hydrolysate; (3) adding a Na2CO3 aqueous solution to the enzymatic hydrolysate from step (2), digesting it, and then adding an ethanol aqueous solution. (3) Mixture 2 is obtained by filtration to obtain filtrate and seaweed residue; (4) Hydrochloric acid aqueous solution is added to the filtrate of step (3) to adjust the pH to 2-3, keep warm at 40-45℃, cool down, filter to obtain alginic acid; (5) The alginic acid of step (4) is dispersed in Na2CO3 aqueous solution, stirred for 20 min, ethanol is added dropwise, and when the system becomes turbid, the addition is stopped, the temperature is raised to 48-50℃ to clarify the system, and then the temperature is kept at 48-50℃ and stirred. After cooling down to 25℃, a large amount of solid precipitates out. After filtration, washing with ethanol and drying, sodium alginate is obtained.

3. The seaweed composition for improving desertified soil according to claim 2, characterized in that, The cleaning solution, by weight, comprises: 5-6 parts sucrose fatty acid ester, 8-10 parts sodium hypochlorite, 15-17 parts acetic acid, 22-25 parts ethanol, 80-85 parts deionized water, 15-17 parts modified bamboo charcoal powder, 3-5 parts xanthan gum, 2-3 parts cocoyl glucoside, 1-2 parts sodium sulfite, and 2-3 parts disodium EDTA.

4. The seaweed composition for improving desertified soil according to claim 3, characterized in that, The preparation method of the cleaning solution includes the following steps: heating deionized water to 33-35℃, adding xanthan gum and stirring until dissolved, then adding disodium EDTA, sucrose fatty acid ester, and cocoyl glucoside in sequence, stirring for 10-15 minutes, then adding modified bamboo charcoal powder and stirring for 20-25 minutes, cooling the temperature to room temperature, adding acetic acid, sodium hypochlorite, sodium sulfite, and ethanol, and stirring evenly to obtain the cleaning solution.

5. The seaweed composition for improving desertified soil according to claim 3, characterized in that, The method for preparing the modified bamboo charcoal powder includes the following steps: crushing bamboo, sieving, dispersing it in sodium hydroxide solution and soaking for 20-24 hours, washing with water, then dispersing it in sodium carbonate aqueous solution, stirring for 3-4 hours, drying, and vacuum heating at 900-920℃ for 40-45 minutes to obtain carbonized bamboo charcoal powder; dispersing hydroxypropyl starch in deionized water, adding nano-silica, tannic acid, and sodium dodecylbenzenesulfonate, stirring at 60-65℃ for 30-35 minutes to obtain a mixed solution; immersing the carbonized bamboo charcoal powder in the mixed solution 1-2 times, drying, and obtaining modified bamboo charcoal powder.

6. The seaweed composition for improving desertified soil according to claim 2, characterized in that, The method for preparing seaweed nanocellulose includes the following steps: washing seaweed residue with water, drying it, dispersing it in NaOH solution, stirring for 2-4 hours, washing it with water, dispersing it in deionized water, adding xylanase, adjusting the pH of the system to 4.5-5.5 with acetate-sodium acetate buffer, completing the enzymatic hydrolysis, incubating at 80-85℃ for 10-12 minutes to inactivate the enzyme, drying it, homogenizing it under high pressure, and freeze-drying it to obtain seaweed nanocellulose.

7. The seaweed composition for improving desertified soil according to claim 2, characterized in that, The complex enzyme consists of endoglucanase, pectinase, and protease in a mass ratio of 1:1:3-4.

8. The seaweed composition for improving desertified soil according to claim 1, characterized in that, The pretreatment of the attapulgite includes the following steps: (1) Disperse the attapulgite in deionized water, calcine at 580-600℃ for 4-5 hours, then disperse it in hydrochloric acid solution, soak for 1-2 hours, wash with water, and dry to obtain treated attapulgite; (2) Stir humic acid, sodium polyacrylate, polyethylene glycol 400, deionized water, and gum arabic evenly, spray dry to obtain powder; (3) Disperse chitosan in citric acid solution, add genipin and mix, react at 60-62℃ for 1-1.5 hours to obtain a mixture, add the treated attapulgite from step (1) and the powder from step (2), stir for 2-3 hours, and dry to obtain pretreated attapulgite.

9. A seaweed composition for improving desertified soil according to claim 8, characterized in that, The mass ratio of attapulgite, sodium polyacrylate and chitosan is 1:0.4-0.5:0.1-0.

2.

10. A method for preparing a seaweed composition for improving desertified soil according to claim 1, characterized in that, The process includes the following steps: heating deionized water to 52-55℃, adding sodium alginate and carboxymethyl cellulose, stirring until homogeneous, then adding attapulgite, montmorillonite, and humic acid, dispersing at 3000-5000 rpm for 30-45 minutes, then adding seaweed nanocellulose, dispersing at 2000-3000 rpm for 20-30 minutes, drying, and sieving to obtain the seaweed composition.

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