Slow-release ecological agriculture and forestry water-retaining agent for desert control and preparation method thereof

Abstract

The invention belongs to the technical field of agriculture and forestry water-retaining materials, and particularly relates to a slow-release ecological agriculture and forestry water-retaining agent for desert control and a preparation method thereof. The water-retaining agent comprises the following components: 40-65 wt% of acrylic acid grafted modified starch; 15-25 wt% of a nano-scale inorganic porous carrier; 10 to 20 weight percent of humic acid coated sustained-release microcapsules; 3-8 wt% of a cross-linking agent; and 0.5-2 wt% of a functional auxiliary agent. Through material compounding and structure innovation, the problems that a traditional water-retaining agent is high in pollution performance, single in function, poor in saline-alkali adaptability and the like are solved, and the water-retaining agent has the advantages of efficient water retention, intelligent slow release, environmental restoration and low cost, is particularly suitable for agriculture and forestry planting and ecological management in arid areas, saline-alkali soil and ecologically fragile areas, and has wide application prospects. The method has remarkable technical advancement and market application potential; the method not only can be used for desert and desertification control, but also can be used for ecological agricultural planting, urban garden management and protection, and forest tending and afforestation.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural and forestry water-retaining materials, and in particular to a slow-release ecological agricultural and forestry water-retaining agent for desert control and a preparation method thereof. Background Art

[0002] A water-retaining agent is essentially a superabsorbent polymer (SAP), a three-dimensional, cross-linked polymer network that can absorb hundreds or even thousands of times its own mass of water. Even in a swollen state, it maintains a stable network structure and resists water leakage even when squeezed. Its high water absorption capacity, good biocompatibility, and low production cost have led to its widespread use. Agro-forestry ecological water-retaining agents are a new functional material that utilizes polymer technology to achieve efficient water conservation and improve soil conditions. They have widespread applications in agriculture, forestry, and ecological restoration.

[0003] Currently, commercially available water-retaining agents mainly include the following technical types:

[0004] Synthetic polymers (such as sodium polyacrylate): Although they have a water absorption rate of 300-800 times (Wang et al., 2020), they have three major technical bottlenecks: (1) Poor light and heat stability, and molecular chain breakage is prone to occur above 60°C, resulting in a decrease in water retention performance of more than 40%; (2) Their non-degradable properties lead to soil microplastic pollution. Experiments have shown that the residual amount of acrylic acid monomer in the soil reaches 12.7 mg / kg after three years of continuous use (Zhang et al., 2021); (3) The water release rate does not match the plant water requirement cycle. Field experiments show that 70% of the water is released 15 days before the drought period.

[0005] Naturally modified materials (such as starch graft copolymers): While biodegradable, their salt tolerance is significantly limited. When soil conductivity exceeds 4 dS / m (typical desert soil salinity), their water absorption rate drops to less than 100 times (Liu et al., 2019). They are also susceptible to microbial decomposition. Under drought-wet cycles, the material disintegrates at a rate of 63% within 90 days, making it difficult to meet the requirements of perennial plant cultivation.

[0006] Mineral composites (such as bentonite-based composites): While they can improve soil permeability, they have limited water-holding capacity (maximum water absorption ≤ 150%) and lack nutrient-release properties. Furthermore, existing composite processes often rely on mechanical mixing, resulting in weak interfacial bonding between the water-retaining components and the mineral phase, leading to delamination during wet-dry cycles.

[0007] For example, the existing patent: Authorization Announcement No. CN105724367A, discloses a multifunctional water-retaining agent for agricultural and forestry crops, a preparation method and a method of use thereof, wherein the multifunctional water-retaining agent includes, by mass concentration, 20% to 30% of n-dodecanol, 2% to 6% of n-hexadecanol, and 1% to 3% of an emulsifier; the water-retaining agent can change the water-retaining capacity of plants, and has the advantages of good water-retaining effect, preventing diseases and pests, promoting photosynthesis, and increasing the yield of agricultural and forestry crops.

[0008] However, the aforementioned water-retaining agents fail to meet the comprehensive requirements of high water absorption, long-term slow release, salt-alkali resistance, and environmental friendliness. They have technical drawbacks, including poor degradability, easy soil compaction, high salt sensitivity (water absorption in 0.9% NaCl solution decreases by >85%), lack of nutrient slow release, requiring frequent fertilization, and low water absorption (<250 g / g). Therefore, there is an urgent need to develop an environmentally friendly, salt-alkali-resistant composite water-retaining agent that combines water and nutrient slow release. In view of this, the present invention proposes a slow-release ecological agricultural and forestry water-retaining agent for desert control and a preparation method thereof. Summary of the Invention

[0009] The present invention proposes a slow-release ecological agricultural and forestry water-retaining agent for desert control and a preparation method thereof, aiming to solve the problem that existing water-retaining agents cannot meet the comprehensive requirements of high water absorption rate, long-term slow release, salt and alkali resistance and environmental friendliness.

[0010] The technical solution of the present invention is as follows: A slow-release ecological agricultural and forestry water-retaining agent for desert control, comprising the following components:

[0011] 45-65wt% of acrylic acid grafted modified starch;

[0012] Nano-scale inorganic porous carrier 15-25wt%;

[0013] Humic acid coated sustained-release microcapsules 10-20wt%;

[0014] Cross-linking agent 3-8 wt%;

[0015] Functional additives 0.5-2wt%.

[0016] Preferably, the nanoscale inorganic porous carrier is modified attapulgite with a specific surface area of ≥200m 2 / g, and the pore size distribution is 2-50nm.

[0017] Furthermore, the present invention also provides a method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control, comprising the following steps:

[0018] a. Preparation of modified starch by free radical graft copolymerization;

[0019] b. Preparation of humic acid sustained-release microcapsules by spray drying;

[0020] c. Mixing and cross-linking the modified starch, nanocarriers, microcapsules and cross-linking agents to form a three-dimensional network structure.

[0021] Preferably, the raw materials for preparing the modified starch in step a are: konjac flour, acrylic acid, and ammonium persulfate (initiator);

[0022] The preparation process of the modified starch comprises the following steps: mixing konjac flour and acrylic acid in a mass ratio of 1:0.4, adding 1.2% ammonium persulfate, and carrying out grafting reaction at 65° C. under nitrogen protection for 4 hours to obtain the modified starch with a grafting rate of ≥35%.

[0023] Preferably, the raw materials for preparing the humic acid sustained-release microcapsules in step b are:

[0024] Core material: humic acid (60%), urea (20%), potassium dihydrogen phosphate (15%), trace elements (5%);

[0025] Wall material: methyl methacrylate (MMA) and chitosan composite;

[0026] The preparation process of the humic acid slow-release microcapsules is as follows: a spray drying method is adopted, an air inlet temperature is 120° C., an air outlet temperature is 70° C., and a microcapsule encapsulation rate is ≥90%.

[0027] Preferably, the preparation process of the mixed cross-linking in step c is:

[0028] Modified starch, nano-attapulgite (particle size 80nm), and microcapsules were added with a crosslinker (5%) and reacted at pH 6.5 and 75°C for 3 hours to form a porous gel network. Fluidized bed granulation technology was then used to produce particles with a particle size of 1-3mm. After gradient drying at 40°C (2h) → 60°C (2h) → 80°C (1h), the final product had a moisture content of ≤5%.

[0029] Preferably, the grafting reaction temperature in step a is 60-75° C., and the concentration of ammonium persulfate is 0.5-1.5 wt %.

[0030] Preferably, the wall material of the humic acid-coated slow-release microcapsules is a pH-responsive polymer, and the core material comprises humic acid and NPK compound fertilizer in a mass ratio of 2:1.

[0031] Preferably, the cross-linking agent is selected from at least one of citric acid, glutaraldehyde or epichlorohydrin.

[0032] Preferably, the functional additives include chitosan antibacterial agent and plant growth regulator, with a mass ratio of 1:0.5-1:2.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. Through material composite and structural innovation, the present invention solves the problems of traditional water-retaining agents such as strong pollution, single function, and poor adaptability to saline-alkali environments. It combines the advantages of high water retention, intelligent slow release, environmental restoration, and low cost. It is particularly suitable for agricultural and forestry planting and ecological management in arid areas, saline-alkali land, and ecologically fragile areas, and has significant technological advancement and market application potential.

[0035] 2. The present invention has the functions of preserving fertilizer and medicine and slow-controlling medicine and fertilizer, improving fertilizer efficiency and medicine efficiency, reducing the occurrence of diseases and insect pests. The potassium humate contained in it is a natural high-quality organic fertilizer, which can effectively provide the fertilizer required for plant growth, improve plant survival rate, enhance plant resistance to stress, and improve crop yield and quality.

[0036] 3. The present invention has no toxic effect on organisms and does not pollute the environment. The humic acid in its components has a strong complexing and integrating effect on toxic heavy metal ions such as Pb+, Cd2+, Cr3+, Hg2+, etc., and can fix these ions and prevent them from flowing into the surface, streams, wells, and rivers with water, thereby purifying the water quality of the environment and controlling water pollution.

[0037] 4. After the present invention is mixed with the soil and integrated, it contains humic acid components after being improved. Its macromolecular network structure will not collapse and can be used for a long time. It can not only be used for desert and desertification control, but also for ecological agricultural planting and urban garden management, as well as forest tending and afforestation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Figure 1 This is a schematic diagram of the components of a slow-release ecological agriculture and forestry water-retaining agent for desert control according to the present invention;

[0040] Figure 2 This is a table of key parameters of the microstructure of a slow-release ecological agriculture and forestry water-retaining agent for desert control according to the present invention;

[0041] Figure 3 This is a data table showing the relationship between water absorption rate and salt concentration of a slow-release ecological agricultural and forestry water-retaining agent for desert control according to the present invention;

[0042] Figure 4 This is a table showing the data of soil moisture content changing over time for a slow-release ecological agriculture and forestry water-retaining agent for desert control according to the present invention. Implementation Method

[0043] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0044] like Figure 1 As shown, this embodiment proposes a slow-release ecological agricultural and forestry water-retaining agent for desert control, comprising the following components:

[0045] 45-65wt% of acrylic acid grafted modified starch;

[0046] Nano-scale inorganic porous carrier 15-25wt%;

[0047] Humic acid coated sustained-release microcapsules 10-20wt%;

[0048] Cross-linking agent 3-8 wt%;

[0049] Functional additives 0.5-2wt%.

[0050] Furthermore, the nanoscale inorganic porous carrier is modified attapulgite with a specific surface area of ≥200m 2 / g, pore size distribution is 2-50nm, 100nm attapulgite has large specific surface area (≥200m 2 / g), which combines with the starch network through hydrogen bonds to improve compressive strength.

[0051] Furthermore, the present invention also provides a method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control, comprising the following steps:

[0052] a. Preparation of modified starch by free radical graft copolymerization;

[0053] b. Preparation of humic acid sustained-release microcapsules by spray drying;

[0054] c. Mixing and cross-linking the modified starch, nanocarriers, microcapsules and cross-linking agents to form a three-dimensional network structure.

[0055] Furthermore, the raw materials for preparing the modified starch in step a are: konjac flour, acrylic acid, and ammonium persulfate (initiator);

[0056] The preparation process of the modified starch is as follows: konjac flour and acrylic acid are mixed in a mass ratio of 1:0.4, 1.2% ammonium persulfate is added, and a grafting reaction is carried out at 65° C. under nitrogen protection for 4 hours to obtain a modified starch with a grafting rate of ≥35%.

[0057] Furthermore, the raw materials for preparing the humic acid sustained-release microcapsules in step b are:

[0058] Core material: humic acid (60%), urea (20%), potassium dihydrogen phosphate (15%), trace elements (5%);

[0059] Wall material: methyl methacrylate (MMA) and chitosan composite;

[0060] The preparation process of humic acid sustained-release microcapsules is as follows: a spray drying method is adopted, an air inlet temperature is 120°C, an air outlet temperature is 70°C, and a microcapsule encapsulation rate is ≥90%.

[0061] Furthermore, the preparation process of mixed cross-linking in step c is:

[0062] Modified starch, nano-attapulgite (particle size 80nm), and microcapsules were added with a crosslinker (5%) and reacted at pH 6.5 and 75°C for 3 hours to form a porous gel network. Fluidized bed granulation technology was then used to produce particles with a particle size of 1-3mm. After gradient drying at 40°C (2h) → 60°C (2h) → 80°C (1h), the final product had a moisture content of ≤5%.

[0063] Among them, the low temperature stage (40℃) prevents surface crusting and ensures slow evaporation of internal moisture.

[0064] The final product moisture content is ≤5% to avoid mildew during storage (accelerated aging test: no deterioration for 6 months at 40°C / 75% humidity)

[0065] Furthermore, in step a, the grafting reaction temperature is 60-75° C., and the concentration of ammonium persulfate is 0.5-1.5 wt %.

[0066] Furthermore, the wall material of the humic acid-coated slow-release microcapsules is a pH-responsive polymer, and the core material contains humic acid and NPK compound fertilizer in a mass ratio of 2:1.

[0067] Furthermore, the cross-linking agent is selected from at least one of citric acid, glutaraldehyde or epichlorohydrin.

[0068] Furthermore, the functional additives include chitosan antibacterial agent and plant growth regulator, with a mass ratio of 1:0.5-1:2. Example:

[0069] Raw material ratio:

[0070] Modified starch (grafting rate 38%) 60kg

[0071] Nano-attapulgite (100nm) 20kg

[0072] Humic acid microcapsules (encapsulation efficiency 92%) 15kg

[0073] Citric acid crosslinker 5kg

[0074] Chitosan antibacterial agent 0.5kg

[0075] Process parameters:

[0076] Grafting reaction: 65°C × 4h, nitrogen protection;

[0077] Cross-linking reaction: 75°C × 3 h, pH 6.5;

[0078] Drying conditions: Gradient drying to a moisture content of 4.8%.

[0079] Among them: 38% of the acrylic acid grafting rate is optimized by free radical polymerization, balancing the hydrophilicity (-COOH group) and the stability of the skeleton

[0080] Comparative Example:

[0081] Traditional sodium polyacrylate water-retaining agent group (addition amount 2%).

[0082] Detection after 60 days:

[0083] Its performance advantage comparison table (see Table 1):

[0084] index Example (present invention) Comparative Example (Traditional Water Retaining Agent) Water absorption (distilled water) 550-800g / g 1000-1200g / g Water absorption (0.9% NaCl) 220-350g / g 50-100g / g Water retention period (25℃) 45-60 days 15-20 days Nitrogen release rate (30 days) 75-85％ No sustained-release function Biodegradation rate (180 days) ≥90％ ≤20％

[0085] Table 1

[0086] The performance advantages of the present invention can be obtained from Table 1 above:

[0087] High water absorption rate: 550-800g / g in distilled water, and 220-350g / g in 0.9% NaCl solution;

[0088] Long-term slow release: The slow release period of water in the soil is ≥45 days (twice as long as traditional products);

[0089] Environmentally friendly: Biodegradation rate ≥ 90% in 180 days, no heavy metal residue (in compliance with GB / T 38082-2019 standard).

[0090] Therefore, the present invention solves the problems of traditional water-retaining agents such as strong pollution, single function, and poor adaptability to saline-alkali environments through material composite and structural innovation. It has the advantages of high-efficiency water retention, intelligent slow release, environmental restoration, and low cost. It is particularly suitable for agricultural and forestry planting and ecological management in arid areas, saline-alkali lands, and ecologically fragile areas, and has significant technological advancement and market application potential.

[0091] It should be further explained that the present invention proposes a slow-release ecological agricultural and forestry water-retaining agent for desert control, comprising the following components:

[0092] 45-65wt% of acrylic acid grafted modified starch;

[0093] Nano-scale inorganic porous carrier 15-25wt%;

[0094] Humic acid coated sustained-release microcapsules 10-20wt%;

[0095] Cross-linking agent 3-8 wt%;

[0096] Functional additives 0.5-2wt%.

[0097] The present invention also provides a method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control, comprising the following steps:

[0098] a. Preparation of modified starch by free radical graft copolymerization;

[0099] b. Preparation of humic acid sustained-release microcapsules by spray drying;

[0100] c. Mixing and cross-linking the modified starch, nanocarriers, microcapsules and cross-linking agents to form a three-dimensional network structure.

[0101] The method comprises the following steps: mixing konjac flour and acrylic acid in a mass ratio of 1:0.4, adding 1.2% ammonium persulfate, and carrying out grafting reaction at 65°C under nitrogen protection for 4 hours to prepare modified starch with a grafting rate of ≥35%. Then, a spray drying method is adopted with an air inlet temperature of 120°C, an air outlet temperature of 70°C, and a microcapsule encapsulation rate of ≥90%. A crosslinking agent (5%) is added to the modified starch, nano-attapulgite (particle size of 80 nm), and microcapsules, and reacting them at pH 6.5 and 75°C for 3 hours to form a porous gel network. Then, a fluidized bed granulation technology is adopted to prepare particles with a particle size of 1-3 mm. After gradient drying at 40°C (2 hours), 60°C (2 hours), and 80°C (1 hour), a final product with a moisture content of ≤5% is obtained.

[0102] Through material composite and structural innovation, the present invention solves the problems of traditional water-retaining agents such as strong pollution, single function, and poor adaptability to saline-alkali environments. It combines the advantages of efficient water retention, intelligent slow release, environmental restoration, and low cost. It is particularly suitable for agricultural and forestry planting and ecological management in arid areas, saline-alkali lands, and ecologically fragile areas, and has significant technological advancement and market application potential.

[0103] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A slow-release ecological agricultural and forestry water-retaining agent for desert control, characterized in that: Contains the following components: 45-65wt% of acrylic acid grafted modified starch; Nano-scale inorganic porous carrier 15-25wt%; Humic acid coated sustained-release microcapsules 10-20wt%; Cross-linking agent 3-8 wt%; Functional additives 0.5-2wt%.

2. The slow-release ecological agricultural and forestry water-retaining agent for desert control according to claim 1, characterized in that: The nano-scale inorganic porous carrier is modified attapulgite with a specific surface area of ≥200m 2 / g, and the pore size distribution is 2-50nm.

3. The method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control according to claim 1, characterized in that: The following steps are involved: a. Preparation of modified starch by free radical graft copolymerization; b. Preparation of humic acid sustained-release microcapsules by spray drying; c. Mixing and cross-linking the modified starch, nanocarriers, microcapsules and cross-linking agents to form a three-dimensional network structure.

4. The method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control according to claim 3, characterized in that: The raw materials for preparing the modified starch in step a are: konjac flour, acrylic acid, and ammonium persulfate (initiator); The preparation process of the modified starch comprises the following steps: mixing konjac flour and acrylic acid in a mass ratio of 1:0.4, adding 1.2% ammonium persulfate, and carrying out grafting reaction at 65° C. under nitrogen protection for 4 hours to obtain the modified starch with a grafting rate of ≥35%.

5. The method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control according to claim 3, characterized in that: The raw materials for preparing the humic acid sustained-release microcapsules in step b are: Core material: humic acid (60%), urea (20%), potassium dihydrogen phosphate (15%), trace elements (5%); Wall material: methyl methacrylate (MMA) and chitosan composite; The preparation process of the humic acid slow-release microcapsules is as follows: a spray drying method is adopted, an air inlet temperature is 120° C., an air outlet temperature is 70° C., and a microcapsule encapsulation rate is ≥90%.

6. The method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control according to claim 3, characterized in that: The preparation process of mixed cross-linking in step c is: Modified starch, nano-attapulgite (particle size 80nm), and microcapsules were added with a crosslinker (5%) and reacted at pH 6.5 and 75°C for 3 hours to form a porous gel network. Fluidized bed granulation technology was then used to produce particles with a particle size of 1-3mm. After gradient drying at 40°C (2h) → 60°C (2h) → 80°C (1h), the final product had a moisture content of ≤5%.

7. The method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control according to claim 4, characterized in that: The grafting reaction temperature in step a is 60-75° C., and the concentration of ammonium persulfate is 0.5-1.5 wt %.

8. The method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control according to claim 5, characterized in that: The wall material of the humic acid-coated slow-release microcapsules is a pH-responsive polymer, and the core material comprises humic acid and NPK compound fertilizer in a mass ratio of 2:

1.

9. The method for preparing a slow-release ecological agricultural and forestry water-retaining agent for desert control according to claim 6, characterized in that: The cross-linking agent is selected from at least one of citric acid, glutaraldehyde or epichlorohydrin.

10. The slow-release ecological agricultural and forestry water-retaining agent for desert control according to claim 1, characterized in that: The functional additives include chitosan antibacterial agent and plant growth regulator, with a mass ratio of 1:0.5-1:2.

Images