Modified anionic polyacrylamide polymer and application thereof in soil improvement

Abstract

The invention discloses a modified anionic polyacrylamide polymer and application thereof in soil improvement, and relates to the technical field of soil improvement. The preparation method of the modified anionic polyacrylamide polymer comprises the following steps: (1) mixing sodium formate, PEG, ethyl trichlorosilane, KH570 and a solvent, stirring and heating to 40-60 DEG C to obtain a mixture 1; and (2) mixing acrylamide, acrylic acid and a solvent to obtain a mixture 2, then mixing the mixture 2 with the mixture 1, adding an initiator, reacting for 4-6 hours in a nitrogen atmosphere, and drying, crushing and grinding the product to obtain the modified anionic polyacrylamide polymer. According to the invention, organic silicon is introduced for modification, so that specific HPAM with a large-space net structure is obtained, and the soil strength and the water retention capacity are improved.

Description

Technical Field

[0001] The invention relates to the technical field of soil improvement, and in particular to a modified anionic polyacrylamide polymer and application thereof in soil improvement. Background Art

[0002] All kinds of saline-alkali soils are formed under certain natural conditions. The essence of their formation is mainly the horizontal and vertical redistribution of various soluble salts on the ground, so that salt gradually accumulates on the soil surface. The main factors affecting the formation of saline-alkali soil are: climate conditions, terrain conditions, the influence of rivers and seawater, etc.

[0003] Specifically, in the arid and semi-arid areas of Northeast my country, Northwest China, and North China, the precipitation is small and the evaporation is large, so the salt dissolved in the water tends to accumulate on the soil surface. In summer, the rainfall is abundant and concentrated, and a large amount of soluble salts infiltrate into the lower layer or flow away with the water. This is the "desalination" season; in spring, the surface water evaporates strongly, and the salt in the groundwater gathers on the soil surface with the rise of capillary water. This is the main "re-salting" season. The saline-alkali soil in Northeast China, North China, and semi-arid areas has an obvious "re-salting" season. The height of the terrain also has a great influence on the formation of saline-alkali soil. The height of the terrain directly affects the movement of surface water and groundwater, which is closely related to the movement and accumulation of salt. From the perspective of the terrain, water-soluble salts move from high to low with water and accumulate in low-lying areas. Saline-alkali soil is mainly distributed in inland basins, mountain depressions, and flat plains with poor drainage, such as the Songliao Plain. From the perspective of small terrain (local scope), the accumulation of salt in soil is the opposite of that in large terrain, and salt tends to accumulate in small convex parts of the soil. The coarseness and fineness of the texture can affect the speed and height of the movement of soil capillary water. Generally speaking, the capillary water of loamy soil rises faster and higher, while sandy soil and clay accumulate salt more slowly. The key issues affecting soil salinity and alkalinity are the height of the groundwater level and the degree of groundwater mineralization. A high groundwater level and high mineralization make it easy for salt to accumulate. In addition, the land on both sides of rivers and channels has its groundwater level raised due to lateral infiltration of river water, which promotes salt accumulation. Coastal saline-alkali soil can be formed in coastal areas due to seawater infiltration.

[0004] Polyacrylamide (PAM) is a synthetic linear high molecular polymer with multiple properties such as flocculation, viscosity increasing, and adsorption. PAM can be divided into four types according to its ionic type: anionic, cationic, zwitterionic, and non-ionic. Anionic PAM (HPAM) is a polymer with a linear long molecular chain structure. Its effect gradually increases with the increase of molecular weight. Therefore, it has been widely used in the fields of soil structure improvement, erosion prevention and control, and agricultural production.

[0005] Chinese patent CN117887471 A discloses a polyacrylamide composite microparticle for improving oil recovery and a preparation method thereof, wherein the preparation method of the polyacrylamide composite microparticle comprises the following steps: step 1, preparing raw materials for preparing microparticles, including polyacrylamide, crosslinking agent, surfactant, and functional additive; step 2, adding a certain amount of polyacrylamide powder to an appropriate amount of water to form a solution, and adding a crosslinking agent and surfactant to improve the stability and performance of the microparticles; step 3, stirring the solution and providing reaction time to allow the polyacrylamide to undergo a crosslinking reaction. By optimizing the raw material components, the ratio of polyacrylamide, crosslinking agent, surfactant and functional additive, and adding a functional additive with the function of adjusting pH value and inhibiting the deposition of calcium and magnesium ions, the stability and fluidity of the polyacrylamide composite microparticles can be improved, thereby achieving the effect of improving oil recovery.

[0006] Currently, there is a lack of polyacrylamide for improving saline-alkali land. In view of this, the present invention provides a modified anionic polyacrylamide polymer and its application in soil improvement. Summary of the invention

[0007] The purpose of the present invention is to provide a modified anionic polyacrylamide polymer and its application in soil improvement. By introducing organic silicon modification, a HPAM with a specific large-space network structure is obtained. On the one hand, the properties of the HPAM itself are utilized to make the originally loose soil particles stick together, thereby improving the soil strength; on the other hand, the HPAM with a specific large-space network structure induces water molecules in the soil to enter the polymer under the action of osmotic pressure, thereby reducing the evaporation of soil water molecules, improving the water retention capacity of the soil, reducing the surface accumulation of salt and nutrient loss caused by soil evaporation, and promoting crop growth.

[0008] To achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0009] In one aspect, the present invention provides a modified anionic polyacrylamide polymer, the preparation method of which comprises the following steps:

[0010] (1) Sodium formate, PEG, ethyltrichlorosilane, KH570 and a solvent are mixed, stirred and heated to 40-60° C. to obtain a mixture 1;

[0011] (2) acrylamide, acrylic acid and a solvent are mixed to obtain a mixture 2, which is then mixed with the mixture 1, an initiator is added, and the mixture is reacted for 4-6 hours under a nitrogen atmosphere. The product is dried, crushed and ground to obtain the modified anionic polyacrylamide polymer.

[0012] Preferably, in step (1), the amount of sodium formate added relative to the solvent is 1-2 g / 75 mL, more preferably 1.5 g / 75 mL.

[0013] Preferably, in step (1), the amount of PEG added relative to the solvent is 0.1-0.5 g / 75 mL, more preferably 0.3 g / 75 mL.

[0014] Preferably, in step (1), the amount of ethyltrichlorosilane added to the solvent is 0.05-0.15 g / 75 mL, more preferably 0.11 g / 75 mL; the amount of KH570 added to the solvent is 0.8-1.2 g / 75 mL, more preferably 1.1 g / 75 mL.

[0015] Preferably, in step (1), the solvent is a NaCl solution, more preferably a NaCl solution with a mass fraction of 10-50%, and most preferably a NaCl solution with a mass fraction of 20%.

[0016] Preferably, the solvent in step (2) is water.

[0017] Preferably, the volumes of solvents in step (1) and step (2) are equal.

[0018] Preferably, in step (2), the amount of acrylamide added relative to the solvent is 1-2 g / 75 mL, more preferably 1.52 g / 75 mL; the amount of acrylic acid added relative to the solvent is 1.2-1.4 g / 75 mL, more preferably 1.3 g / 75 mL.

[0019] Preferably, in step (2), the initiator is a combination of TMEDA (tetramethylethylenediamine) and potassium persulfate. Further preferably, the mass ratio of TMEDA to potassium persulfate is 1:3-5, most preferably 1:4.

[0020] Preferably, the molecular weight of the modified anionic polyacrylamide polymer is 1.3-1.8 million, more preferably 1.48-1.54 million.

[0021] As a specific example of the present invention, the preparation method of the modified anionic polyacrylamide polymer comprises the following steps:

[0022] (1) Slowly add 1.5 g of sodium formate into a three-necked flask, then add 0.3 g of PEG, 0.11 g of ethyltrichlorosilane, 1.1 g of KH570 and 75 mL of 20% NaCl solution, and heat to 45° C. with stirring;

[0023] (2) Mix 1.52 g acrylamide, 1.3 g acrylic acid and 75 mL water in a 100 mL beaker, stir and heat to 45 °C; transfer to a three-necked flask and pass N 2The mixture was deoxygenated for 15 min, 0.045 g of (a combination of TMEDA and potassium persulfate in a ratio of 1:4) was added, and N 2 After 10 minutes, the reaction device was sealed with a gas. After 5 hours of reaction, the product was transferred out for drying and crushing to obtain a modified anionic polyacrylamide polymer.

[0024] In another aspect, the present invention provides use of the modified anionic polyacrylamide polymer in soil improvement.

[0025] Preferably, the soil is saline-alkali soil.

[0026] Preferably, in the application, the modified anionic polyacrylamide polymer is used in the form of dry spreading or spraying, and more preferably in the form of spraying.

[0027] The beneficial effects of the present invention are:

[0028] By introducing a certain proportion of ethyltrichlorosilane and KH570 for modification, a specific large-space network structure of HPAM is obtained, which can not only make the originally loose soil particles stick together to improve soil strength, but also induce water molecules in the soil to enter the polymer under the action of osmotic pressure, thereby reducing the evaporation of soil water molecules, improving the soil's water retention capacity, and reducing salt surface aggregation and nutrient loss caused by soil evaporation, and has a good salt reduction effect. DETAILED DESCRIPTION

[0029] In order to make the technical means, creative features, purpose and efficacy of the present invention easy to understand, the present invention is further explained in conjunction with specific embodiments below, but the following embodiments are only preferred embodiments of the present invention, not all. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without creative work all belong to the protection scope of the present invention. In the following embodiments, unless otherwise specified, the operating methods used are conventional operating methods, the equipment used are conventional equipment, and the equipment materials used in each embodiment are the same.

[0030] Example 1

[0031] (1) Slowly add 1.5 g of sodium formate into a three-necked flask, then add 0.3 g of PEG, 0.11 g of ethyltrichlorosilane, 1.1 g of KH570 and 75 mL of 20% NaCl solution, and heat to 45° C. with stirring;

[0032] (2) Mix 1.52 g acrylamide, 1.3 g acrylic acid and 75 mL water in a 100 mL beaker, stir and heat to 45 °C; transfer to a three-necked flask and pass N 2The mixture was deoxygenated for 15 min, and 0.045 g of a 1:4 combination of TMEDA and potassium persulfate was added. N 2 After 10 minutes, the reaction device was sealed with a gas, and after the reaction was kept warm for 5 hours, the product was transferred out for drying and crushing to obtain a modified anionic polyacrylamide polymer with a molecular weight of 1.5 million.

[0033] Example 2

[0034] (1) Slowly add 1 g of sodium formate into a three-necked flask, then add 0.1 g of PEG, 0.15 g of ethyltrichlorosilane, 1.2 g of KH570 and 75 mL of 20% NaCl solution, and heat to 40° C. with stirring;

[0035] (2) Mix 1 g acrylamide, 1.4 g acrylic acid and 75 mL water in a 100 mL beaker, stir and heat to 40 °C; transfer to a three-necked flask and pass N 2 The mixture was deoxygenated for 15 min, and 0.045 g of a 1:3 combination of TMEDA and potassium persulfate was added. N 2 After 10 minutes, the reaction device was sealed with a gas, and after the reaction was kept warm for 4 hours, the product was transferred out for drying and crushing to obtain a modified anionic polyacrylamide polymer with a molecular weight of 1.54 million.

[0036] Example 3

[0037] (1) Slowly add 1.2 g of sodium formate into a three-necked flask, then add 0.5 g of PEG, 0.05 g of ethyltrichlorosilane, 0.8 g of KH570 and 75 mL of 20% NaCl solution, and heat to 60° C. with stirring;

[0038] (2) Mix 2 g acrylamide, 1.2 g acrylic acid and 75 mL water in a 100 mL beaker, stir and heat to 60 °C; transfer to a three-necked flask and pass N 2 The mixture was deoxygenated for 15 min, and 0.045 g of a 1:5 combination of TMEDA and potassium persulfate was added. N 2 After 10 minutes, the reaction device was sealed with a gas, and after the reaction was kept warm for 6 hours, the product was transferred out for drying and crushing to obtain a modified anionic polyacrylamide polymer with a molecular weight of 1.48 million.

[0039] Comparative Example 1

[0040] The difference from Example 1 is that ethyltrichlorosilane and KH570 are not added. The rest is the same as Example 1, and a modified anionic polyacrylamide polymer with a molecular weight of 880,000 is obtained.

[0041] Comparative Example 2

[0042] (1) Slowly add 1.5 g of sodium formate into a three-necked flask, then add 0.3 g of PEG, 0.5 g of ethyltrichlorosilane, 0.3 g of KH570 and 75 mL of 20% NaCl solution, and heat to 45° C. with stirring;

[0043] (2) Mix 1.52 g acrylamide, 1.3 g acrylic acid and 75 mL water in a 100 mL beaker, stir and heat to 45 °C; transfer to a three-necked flask and pass N 2 The mixture was deoxygenated for 15 min, and 0.045 g of a 1:4 combination of TMEDA and potassium persulfate was added. N 2 After 10 minutes, the reaction device was sealed with a gas, and after the reaction was kept warm for 5 hours, the product was transferred out for drying and crushing to obtain a modified anionic polyacrylamide polymer with a molecular weight of 1.45 million.

[0044] Comparative Example 3

[0045] (1) Slowly add 1.5 g of sodium formate into a three-necked flask, then add 0.3 g of PEG, 0.05 g of ethyltrichlorosilane, 2 g of KH570 and 75 mL of 20% NaCl solution, and heat to 45° C. with stirring;

[0046] (2) Mix 1.52 g acrylamide, 1.3 g acrylic acid and 75 mL water in a 100 mL beaker, stir and heat to 45 °C; transfer to a three-necked flask and pass N 2 The mixture was deoxygenated for 15 min, and 0.045 g of a 1:4 combination of TMEDA and potassium persulfate was added. N 2 After 10 minutes, the reaction device was

[0047] After sealing and keeping warm for 5 hours, the product was transferred out for drying and crushing to obtain a modified anionic polyacrylamide polymer with a molecular weight of 1.47 million.

[0048] Comparative Example 4

[0049] The difference from Example 1 is that the mass ratio of TMEDA to potassium persulfate is 1:1, and the rest is the same as Example 1, to obtain a modified anionic polyacrylamide polymer with a molecular weight of 1.19 million.

[0050] Results

[0051] Experiment on improving saline-alkali land

[0052] We selected a saline-alkali land in Shandong Province for the experiment and dug up samples with a thickness of 30 cm and an area of ​​0.25 m 2The saline-alkali soil to be improved is mixed with the modified anionic polyacrylamide polymer prepared in each embodiment and comparative example and the commercially available anionic polyacrylamide at a mass ratio of 50:1 (the polymer is configured into an aqueous solution with a mass concentration of 10%, and then mixed with the soil) to obtain improved soil; the improved soil is backfilled, the backfill position is marked, and the soil moisture content of the backfilled system is controlled to be above 20%. After 30 days, the sample is taken again to measure the conductivity, pH value and water retention.

[0053] 1. Conductivity measurement

[0054] Take 20g of soil and place it in a beaker, add 100mL of ultrapure water, mix thoroughly and let it stand, and measure the conductivity of the soil solution with a digital conductivity meter.

[0055] 2. Water retention determination

[0056] Take 100g of soil and place it in a beaker. Add 20mL of water and weigh it, which is recorded as m1. Leave it open at room temperature for 24 hours and measure the mass of the sample in each beaker, m2. The water retention rate is calculated as follows:

[0057] Water retention rate (%) = (m2-100) / m1×100%.

[0058] 3. Test results

[0059] (1) Physical and chemical properties of unmodified soil samples

[0060] Conductivity (%) Water retention rate (%) Day 0 2.60 4.14 30 days 2.62 4.16

[0061] (2) Physical and chemical properties of soil samples after 30 days of improvement with different polymers

[0062]

[0063]

[0064] It can be seen from the experimental results that the modified anionic polyacrylamide polymers prepared in Examples 1-3 of the present invention have better effects in improving water retention and reducing conductivity than commercially available anionic polyacrylamide, and are more suitable for saline-alkali land improvement. Comparative Example 1 did not introduce organosilicon modification, and its improvement ability was significantly reduced. Comparative Examples 2-3 adjusted the monomer ratio, and the results were not as good as Examples 1-3. The results of Comparative Example 4 showed that a polymer with a higher molecular weight can be formed under a specific initiation system.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A modified anionic polyacrylamide polymer, characterized in that: The preparation method comprises the following steps: (1) Sodium formate, PEG, ethyltrichlorosilane, KH570 and a solvent are mixed, stirred and heated to 40-60° C. to obtain a mixture 1; (2) acrylamide, acrylic acid and a solvent are mixed to obtain a mixture 2, which is then mixed with the mixture 1, an initiator is added, and the mixture is reacted for 4-6 hours under a nitrogen atmosphere. The product is dried, crushed and ground to obtain the modified anionic polyacrylamide polymer.

2. The modified anionic polyacrylamide polymer according to claim 1, characterized in that In step (1), the amount of sodium formate added relative to the solvent is 1-2 g / 75 mL, preferably 1.5 g / 75 mL.

3. The modified anionic polyacrylamide polymer according to claim 1, characterized in that In step (1), the amount of PEG added relative to the solvent is 0.1-0.5 g / 75 mL.

4. The modified anionic polyacrylamide polymer according to claim 1, characterized in that In step (1), the amount of ethyltrichlorosilane added to the solvent is 0.05-0.15 g / 75 mL; the amount of KH570 added to the solvent is 0.8-1.2 g / 75 mL.

5. The modified anionic polyacrylamide polymer according to claim 4, characterized in that In step (1), the amount of ethyltrichlorosilane added to the solvent is 0.11 g / 75 mL; the amount of KH570 added to the solvent is 1.1 g / 75 mL.

6. The modified anionic polyacrylamide polymer according to claim 1, characterized in that In step (2), the amount of acrylamide added relative to the solvent is 1-2 g / 75 mL; the amount of acrylic acid added relative to the solvent is 1.2-1.4 g / 75 mL.

7. The modified anionic polyacrylamide polymer according to claim 1, characterized in that In step (2), the initiator is a combination of TMEDA (tetramethylethylenediamine) and potassium persulfate, and the mass ratio of TMEDA to potassium persulfate is 1:3-5.

8. The modified anionic polyacrylamide polymer according to claim 1, characterized in that The molecular weight of the modified anionic polyacrylamide polymer is 1.3-1.8 million, preferably 1.48-1.54 million.

9. Use of the modified anionic polyacrylamide polymer according to any one of claims 1 to 8 in soil improvement.

10. The use according to claim 9, characterized in that: The soil is saline-alkali soil.

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