Preparation method of soil conditioner with double functions of water retention and adhesion

Abstract

The invention discloses a preparation method of a soil conditioner with double functions of water retention and adhesion, and belongs to the technical field of soil improvement. The preparation method comprises the following steps: dissolving sodium alginate (SA), acrylamide (AM) and diacetone acrylamide (DAAM) in an aqueous solution; adding an initiator ammonium persulfate (APS) and a cross-linking agent N, N-methylene bisacrylamide (MBA) into the mixed solution, and stirring and mixing; performing thermal polymerization on the mixed solution to obtain a polymer; soaking the obtained polymer in a soluble magnesium salt aqueous solution to obtain a magnesium ion cross-linked polymer; and carrying out drying treatment on the magnesium ion cross-linked polymer to obtain the soil conditioner. The soil conditioner shows good water retention performance and adhesion performance, not only has excellent water absorption and water retention capacity, but also promotes the formation of soil aggregates due to the adhesion of the soil conditioner to soil particles. The double functions can cooperatively maintain water supply in soil, and normal growth of plants under drought stress is effectively promoted.

Description

Technical Field

[0001] The present invention relates to the field of agricultural soil improvement, and particularly to a preparation method of a soil conditioner with dual functions of water retention and adhesion. Background Art

[0002] Drought, as a common and highly destructive adverse weather condition, on the one hand, causes a global water shortage crisis and agricultural economic losses, and on the other hand, brings ecological negative impacts such as soil erosion and land degradation. The loose soil structure caused by drought severely weakens the water-holding and water-retention capacity of the soil, allowing water to directly runoff through soil pores and carry away root nutrients. Agriculture, being a water-intensive industry, the water shortage caused by drought seriously disrupts the soil's nutrient supply to crops, affects the normal growth and metabolic processes of crops, and thus leads to a decline in crop quality and yield. Therefore, it is of great significance to develop efficient agricultural water use technologies that can effectively improve soil structure and enhance drought resistance.

[0003] Superabsorbent hydrogel soil conditioners exhibit excellent water absorption and water retention capabilities due to their hydrophilic groups and porous structures, becoming an important technical means to alleviate the negative impacts of drought on the soil. Superabsorbent hydrogel soil conditioners can slowly release the water in the network into the soil, thereby maintaining soil humidity, and their adhesion performance can promote the formation of soil aggregates and improve the soil's erosion resistance. The hydrogel prepared by Cui et al. (Carbohydrate Polymers, 2024, 337: 122188) exhibits excellent soil water retention and adhesion performance under the combined action of hydrophilic groups such as quaternary ammonium groups, hydroxyl groups, carboxyl groups, and carbonyl groups, promoting the development and growth of mung beans. Patent CN106398698B discloses a soil conditioner and its preparation method. The soil conditioner synthesized from polyacrylamide, water-soluble organic carbon, polyaspartic acid, and polyglutamic acid not only promotes the formation of soil aggregates but also improves the soil's water retention capacity. The natural raw material alginate has advantages such as biosafety and wide sources and can be used to prepare superabsorbent hydrogel soil conditioners. Due to the weak physical cross-linking and uneven structure of alginate hydrogels, their water absorption and water retention capabilities are poor. Patent CN119639028A discloses a preparation method, obtained product, and application of a sodium alginate / chitosan / calcium ion double-network hydrogel. The physical cross-linking double network of sodium alginate / calcium ion and chitosan / calcium ion effectively improves the structural stability, but under the condition of relying solely on the physical cross-linking network, the swelling performance of the hydrogel is less than 25%. To promote the sustainable development of agriculture, it is urgent to develop soil conditioners that can improve soil structure and provide excellent soil water retention capacity.

[0004] The present invention aims to prepare a soil conditioner with dual functions of water retention and adhesion to meet the technical requirements of efficient agricultural water use. In this material, magnesium ions are physically cross-linked with sodium alginate through non-covalent interactions, and hydrophilic monomer acrylamide and diacetone acrylamide are chemically cross-linked and copolymerized. The introduction of the chemical network makes the polymer network more prone to relaxation and water absorption, thus helping to improve the water absorption capacity of the soil conditioner and the water retention capacity of the soil, thereby reducing water evaporation and loss and improving the water use efficiency of the soil. Magnesium element, as an essential element for plant metabolism, is beneficial to promoting plant growth and development. The methyl and methylene groups of diacetone acrylamide endow the soil conditioner with hydrophobic aggregation, which helps to further improve the water absorption capacity and structural stability. This preparation method has mild conditions and simple operation, and has significant application prospects in the field of agricultural soil improvement. Summary of the Invention

[0005] In view of the water shortage environmental conditions and soil conditions in arid regions, the present invention overcomes the application limitation of poor water retention capacity of a single physically cross-linked network soil conditioner, and develops a soil conditioner with dual functions of water retention and adhesion, which promotes the formation of soil aggregates while releasing water, and is used to maintain the normal growth of crops in arid environments.

[0006] A preparation method of a soil conditioner with dual functions of water retention and adhesion, comprising the following steps:

[0007] Step (1): Dissolve a certain amount of sodium alginate (SA), acrylamide (AM), and diacetone acrylamide (DAAM) in an aqueous solution to obtain a mixed solution;

[0008] Step (2): Add initiator ammonium persulfate (APS) and cross-linking agent N,N'-methylenebisacrylamide (MBA) to the mixed solution obtained in step (1), and mix under stirring;

[0009] Step (3): Subject the mixed solution obtained in step (2) to thermal polymerization to obtain a polymer;

[0010] Step (4): Immerse the polymer obtained in step (3) in an aqueous solution of soluble magnesium salt with a certain concentration to obtain a magnesium ion-cross-linked polymer;

[0011] Step (5): Dry the magnesium ion-cross-linked polymer obtained in step (4) to obtain the dual-functional soil conditioner.

[0012] Preferably, in step (1), the concentration of SA is 0.10 - 3.00%, the M:G ratio of SA is one or any combination of M:G = 1:1, M:G = 1:2, and M:G = 2:1, the concentration of AM is 5.00 - 25.00%, and the concentration of DAAM is 1.00 - 15.00%.

[0013] Preferably, in step (2), the concentration of APS is 0.01-0.30%, and the concentration of MBA is 0.01-0.20%.

[0014] Preferably, in step (3), the thermal polymerization temperature is controlled to be 40-80° C., and the polymerization time is controlled to be 2-12 h.

[0015] Preferably, the soluble magnesium salt in step (4) is one or more of magnesium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium formate, etc. The concentration of the soluble magnesium salt aqueous solution is 0.1-3 mol / L, and the immersion cross-linking time is 0.5-3 h.

[0016] Preferably, the drying time in step (5) is 12-48 hours.

[0017] The present invention discloses a method for preparing a soil conditioner having dual functions of water retention and adhesion, and the present invention has the following advantages:

[0018] (1) The soil conditioner provided by the present invention can effectively improve the water retention capacity of the soil and improve the soil structure. The soil conditioner showed a water absorption capacity of 0.93g / g and 1636% in a humid atmosphere (RH=84%) and a deionized water solution, respectively. The soil conditioner showed a water absorption capacity of 1620% in 0.9wt% NaCl, which reflects that the soil conditioner has a certain degree of salt tolerance. The water retention time of the improved soil with the addition of the soil conditioner is 31d, which is 14d longer than that of the unimproved soil. With its excellent adhesion properties, the soil conditioner can adhere to soil particles and promote the formation of root soil aggregates, thereby improving the soil's anti-erosion ability.

[0019] (2) The soil conditioner provided by the present invention can effectively promote plant growth. Crop planting experiments showed that after adding the soil conditioner, the germination rate of corn was 93.3%, which was 1.47 times that of the test group without adding the soil conditioner.

[0020] (3) Aiming at the problem of soil and water conservation in arid areas, the soil improver prepared by the present invention has strong pertinence, can continuously provide moisture to the soil, maintain the soil moisture at the roots of plants to ensure the normal growth of crops, and has promotion and application value.

[0021] In summary, the soil conditioner prepared using the above method significantly improved the water absorption capacity and soil water retention capacity, and improved the soil structure by adhering to soil particles, thereby overcoming the application limitations of single physical cross-linked hydrogels and providing effective guarantees for the normal growth of crops in arid areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the purpose and technical solution of the present invention, the following drawings are provided for illustration:

[0023] Figure 1 It is the adhesion performance of Example 1 in the present invention and its adhesion effect in soil.

[0024] Figure 2 It is the water absorption performance of Example 1, Comparative Example 1, and Comparative Example 2 in deionized water in the present invention.

[0025] Figure 3 It is the water absorption performance of Example 1 in different solutions in the present invention.

[0026] Figure 4 It is the water absorption performance of Example 1 and Comparative Example 3 in an atmospheric environment (RH = 84%) in the present invention.

[0027] Figure 5 It is the soil water retention performance of Example 1 in the present invention.

[0028] Figure 6 It is the effect of Example 1 in the present invention in crop planting and resistance to drought stress. Specific Embodiments

[0029] The present invention will be further described in detail below through implementation cases. The described implementation cases are only a part of the implementation cases of the present invention, rather than all implementation cases. All other implementation cases obtained by those of ordinary skill in the art based on the implementation cases in the present invention without creative efforts belong to the scope of protection of the present invention.

[0030] Example 1

[0031] A preparation method of a soil conditioner with dual functions of water retention and adhesion, the method specifically includes the following steps:

[0032] Step (1): Dissolve 2.00% sodium alginate (SA, M:G = 1:1), 18.00% acrylamide (AM), and 5.00% diacetone acrylamide (DAAM) in an aqueous solution to obtain a mixed solution;

[0033] Step (2): Add 0.14% initiator ammonium persulfate (APS) and 0.11% crosslinking agent N,N'-methylenebisacrylamide (MBA) to the mixed solution obtained in step (1), and mix under stirring;

[0034] Step (3): Thermally polymerize the mixed solution obtained in step (2) at 60°C for 4 h to obtain a polymer;

[0035] Step (4): soaking the polymer obtained in step (3) in a 2 mol / L magnesium chloride (MgCl2) aqueous solution for 0.5 h to obtain a magnesium ion cross-linked polymer;

[0036] Step (5): Dry the magnesium ion cross-linked polymer obtained in step (4) for 24 hours.

[0037] Examples 2-4

[0038] The difference between Examples 2-4 and Example 1 is that the concentrations of sodium alginate (SA, M:G=1:1) in step (1) are 0.80%, 1.50%, and 3.00%, respectively. The rest are the same as in Example 1.

[0039] Examples 5-6

[0040] The difference between Examples 5-6 and Example 1 is that the M:G ratios of sodium alginate (SA) in step (1) are M:G=1:2 and M:G=2:1, respectively, and the rest are the same as Example 1.

[0041] Examples 7-13

[0042] The difference between Examples 7-13 and Example 1 is that the concentrations of acrylamide (AM) in step (1) are 21.00%, 15.00%, 14.00%, 12.00%, 11.00%, 10.00%, and 9.00%, respectively, and the concentrations of diacetone acrylamide (DAAM) are 2.00%, 8.00%, 9.00%, 10.00%, 11.00%, 12.00%, and 14.00%, respectively. Other processes are the same as in Example 1.

[0043] Examples 14-16

[0044] The difference between Examples 14-16 and Example 1 is that the concentrations of the magnesium chloride (MgCl2) aqueous solution in step (4) are 0.25 mol / L, 0.50 mol / L, and 1.00 mol / L, respectively, and the others are the same as Example 1.

[0045] Examples 17-20

[0046] The difference between Examples 17-20 and Example 1 is that the soluble magnesium salts in step (4) are magnesium sulfate, magnesium nitrate, magnesium acetate, and magnesium formate, respectively, and the rest are the same as Example 1.

[0047] Comparative Example 1

[0048] Step (1): dissolving 2.00% sodium alginate (SA, M:G=1:1) in an aqueous solution to obtain a sodium alginate aqueous solution;

[0049] Step (2): Spray a 2 mol / L aqueous solution of magnesium chloride (MgCl₂) onto the surface of the sodium alginate aqueous solution obtained in step (1) to obtain a magnesium alginate hydrogel;

[0050] Step (3): Dry the magnesium alginate hydrogel obtained in step (2) for 24 h.

[0051] From Figure 2 The results show that physical crosslinking network alone in Comparative Example 1 is not sufficient to have good water absorption capacity. The introduction of chemical crosslinking network can endow the soil conditioner with excellent water absorption capacity.

[0052] Comparative Example 2

[0053] Step (1): Dissolve 2.00% sodium alginate (SA, M:G = 1:1) and 18.00% acrylamide (AM) in an aqueous solution to obtain a mixed solution;

[0054] Step (2): Add 0.14% initiator ammonium persulfate (APS) and 0.11% crosslinking agent N,N'-methylenebisacrylamide (MBA) to the mixed solution obtained in step (1), and mix under stirring;

[0055] Step (3): Carry out thermal polymerization of the mixed solution obtained in step (2) at 60 °C for 4 h to obtain a polymer;

[0056] Step (4): Immerse the polymer obtained in step (3) in a 2 mol / L aqueous solution of magnesium chloride (MgCl₂) for 0.5 h to obtain a magnesium ion-crosslinked polymer;

[0057] Step (5): Dry the magnesium ion-crosslinked polymer obtained in step (4) for 24 h.

[0058] From Figure 2 The results show that Comparative Example 2 without the introduction of the diacetone acrylamide (DAAM) crosslinking network exhibits lower water absorption capacity. The hydrophobic aggregation of methyl and methylene groups of diacetone acrylamide can endow the soil conditioner with more excellent water absorption capacity.

[0059] Comparative Example 3

[0060] The difference between Comparative Example 3 and Example 1 is that the salt solution in step (4) is a 2 mol / L aqueous solution of calcium chloride (CaCl₂), and the others are the same as in Example 1.

[0061] From Figure 3 The results show that Comparative Example 3 crosslinked with calcium ions has lower water absorption capacity in the atmosphere. Hygroscopic magnesium salts can provide good water absorption capacity for the soil conditioner.

Claims

1. A preparation method of a soil conditioner with dual functions of water retention and adhesion, characterized in that, It includes the following steps: (1) Dissolve a certain amount of sodium alginate (SA), acrylamide (AM), and diacetone acrylamide (DAAM) in an aqueous solution to obtain a mixed solution; (2) Add ammonium persulfate (APS) as an initiator and N,N'-methylenebisacrylamide (MBA) as a crosslinking agent to the mixed solution obtained in step (1), and mix under stirring; (3) Subject the mixed solution obtained in step (2) to thermal polymerization to obtain a polymer; (4) Immerse the polymer obtained in step (3) in an aqueous solution of soluble magnesium salt with a certain concentration to obtain a magnesium ion-crosslinked polymer; (5) Dry the magnesium ion-crosslinked polymer obtained in step (4) to prepare the bifunctional soil conditioner.

2. The preparation method of a soil conditioner with both water retention and adhesion functions according to claim 1, characterized in that: In step (1), the concentration of SA is 0.10 - 3.00%, the M:G ratio of SA is one or any combination of M:G = 1:1, M:G = 1:2, M:G = 2:1, the concentration of AM is 5.00 - 25.00%, and the concentration of DAAM is 1.00 - 15.00%.

3. The preparation method of a soil conditioner with dual functions of water retention and adhesion according to claim 1, characterized in that: In step (2), the concentration of APS is 0.01 - 0.30%, and the concentration of MBA is 0.01 - 0.20%.

4. The preparation method of a soil conditioner with dual functions of water retention and adhesion according to claim 1, characterized in that: In step (3), control the thermal polymerization temperature to be 40 - 80 °C and the polymerization time to be 2 - 12 h.

5. The preparation method of a soil conditioner with dual functions of water retention and adhesion according to claim 1, characterized in that: In step (4), the soluble magnesium salt is one or any combination of magnesium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium formate, etc. The concentration of the aqueous solution of soluble magnesium salt is 0.1 - 3 mol / L, and the immersion crosslinking time is 0.5 - 3 h.

6. The preparation method of a soil conditioner with dual functions of water retention and adhesion according to claim 1, characterized in that: In step (5), the drying time is 12 - 48 h.

7. The preparation method of a soil conditioner with both water retention and adhesion functions according to claim 1, characterized in that: The soil conditioner prepared by the method has both water retention performance and adhesion performance, and can be applied to the improvement of arid soil and crop planting.

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