Preparation method and application of fulvic acid-based saline alkali soil conditioner

Abstract

The invention discloses a preparation method and application of a fulvic acid-based saline-alkali soil conditioner, and relates to the field of super absorbent polymer technology and saline-alkali soil remediation. The saline-alkali soil improvement agent is prepared by a method comprising the following steps: dispersing fulvic acid serving as a raw material in water, then adding neutralized acrylic acid and anionic monomer 3-sulfonic acid propyl methyl propyl potassium acrylate, and finally sequentially adding a cross-linking agent and an initiator for graft polymerization reaction to obtain the saline-alkali soil improvement agent. The fulvic acid serving as the raw material contains active groups with relatively strong ion exchange and complexing capabilities, and can exchange with Na < + > and K < + > in the saline-alkali soil, so that the pH value of the soil is adjusted, and the water absorption and salt tolerance effects of the saline-alkali soil are improved. Experiments prove that the saline-alkali soil conditioner prepared by the invention can absorb 0.9% sodium chloride which is more than 120 times of the weight of the soil conditioner, 0.9% potassium chloride which is more than 130 times of the weight of the soil conditioner, tap water which is more than 300 times of the weight of the soil conditioner and deionized water which is nearly 2300 times of the weight of the soil conditioner, so that the water holding capacity of saline-alkali soil can be improved, and the salinity and alkalinity of the soil can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a preparation method and application of a fulvic acid-based saline-alkali soil conditioner. Background Art

[0002] Soil salinization is a serious ecological problem facing the world, severely impacting the effective utilization of land resources and sustainable agricultural development. According to relevant statistics, over one billion hectares of land worldwide are threatened by salinization. This not only renders large tracts of land unusable for agricultural production but also exacerbates food shortages and ecological degradation. In my country, the area of saline-alkali land is also considerable, particularly in northern China, where it is more widespread and hinders the high-quality development of local agriculture.

[0003] With the continuous growth of population and the acceleration of urbanization, the demand for land resources is increasing. How to effectively control and improve saline-alkali soil and improve its productivity has become a scientific problem and practical need that needs to be solved urgently. Traditional methods for improving saline-alkali soil mainly include water conservancy engineering measures (such as drainage, salt washing, etc.) and chemical improvement measures (such as the application of chemical improvers such as gypsum and ferrous sulfate). However, these methods often have problems such as high cost, unstable effect, and possible negative impact on the environment. For example, water conservancy engineering measures require a large amount of water resources and infrastructure investment, and are difficult to implement in areas with water shortages; the long-term use of chemical improvers may lead to problems such as soil acidification and compaction, and even cause groundwater pollution.

[0004] In recent years, superabsorbent polymers (SAPs), a new functional material, have demonstrated promising potential in soil improvement. With their exceptional water absorption and retention capabilities, SAPs can effectively improve soil physical properties, enhancing its water-holding capacity and drought resistance. However, most commonly available SAPs suffer from poor salt tolerance and biodegradability, limiting their widespread application in saline-alkali soil improvement.

[0005] Fulvic acid is an important component of humus, with a low molecular weight and containing a large number of active functional groups such as carboxyl (-COOH), phenolic hydroxyl (-OH), carbonyl (-C=O) and methoxy (-OCH3). These active functional groups give fulvic acid strong ion exchange and chelating abilities, enabling it to chelate with metal ions in the soil, promote the migration of mineral elements and the formation of soil aggregates, thereby improving the soil's aeration and water and fertilizer retention capacity. In addition, fulvic acid also has good biocompatibility and environmental friendliness, making it an ideal soil improvement material. However, there are currently no reports of using fulvic acid directly as a raw material to prepare highly absorbent polymers to control desertification and saline-alkali soils.

[0006] Potassium 3-sulfopropyl methacrylate (SPMA) is an anionic monomer with a large number of sulfonic acid groups on its surface, exhibiting excellent hydrophilicity and cationic selectivity. Its high charge density allows the coordination of metal ions with its functional groups to enhance the conductivity of hydrogels. Furthermore, the sulfonate metal coordination compound also has a certain toughening effect. These properties make SPMA a promising candidate for the preparation of high-performance, highly absorbent polymers. However, there are currently no reports of its application in the preparation of highly absorbent polymers, particularly in the field of saline-alkali soil improvement.

[0007] Therefore, developing a highly absorbent polymer based on fulvic acid and combined with monomers such as SPMA for saline-alkali soil improvement not only has important theoretical significance but also significant practical application value. This new saline-alkali soil conditioner is expected to overcome the shortcomings of traditional soil improvement methods, achieving efficient and stable soil improvement, and providing a new technical approach for saline-alkali land management in my country and around the world. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for preparing a fulvic acid-based saline-alkali soil conditioner, by compounding fulvic acid with 3-sulfonate propyl potassium methacrylate to prepare a highly efficient, stable and salt-tolerant saline-alkali soil conditioner, so as to solve the problems existing in the above-mentioned prior art.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A method for preparing a fulvic acid-based saline-alkali soil conditioner comprises the following steps: firstly dispersing the raw material fulvic acid in water, then adding an acrylic acid solution and 3-sulfopropyl methacrylate potassium after a neutralizer reaction to the fulvic acid solution, and after uniform dispersion, sequentially adding a crosslinker solution and an initiator solution to carry out a graft polymerization reaction to obtain the saline-alkali soil conditioner.

[0011] Preferably, the mass ratio of the total mass of acrylic acid and potassium 3-sulfonate propyl methacrylate to fulvic acid, crosslinker, and initiator is 100:(0.1-1):(0.01-0.12):(0.1-0.8); the mass ratio of potassium 3-sulfonate propyl methacrylate to acrylic acid is 1:3-10.

[0012] Preferably, the specific conditions of the graft polymerization reaction are: carried out in a nitrogen atmosphere, the polymerization reaction temperature is 60-80°C, the graft polymerization reaction time is 60-120min, and the graft polymerization reaction is carried out under stirring conditions, and the stirring speed is 200-300r / min.

[0013] Preferably, after the graft polymerization reaction, the reaction product is soaked in anhydrous ethanol, and then chopped, dried, crushed, and sieved to obtain a saline-alkali soil conditioner.

[0014] Preferably, the neutralization degree of acrylic acid in the acrylic acid solution after the reaction of the neutralizing agent is 45% to 85%; the neutralizing agent is sodium hydroxide or potassium hydroxide. The term "neutralization degree" refers to the extent of the neutralization reaction, usually expressed as the molar ratio of the reaction product.

[0015] Preferably, the cross-linking agent is one or more of N,N-methylenebisacrylamide, glutaraldehyde and ethylene glycol; and the initiator is one or both of ammonium sulfate and potassium persulfate.

[0016] More preferably, the cross-linking agent is N,N-methylenebisacrylamide, and the initiator is ammonium persulfate.

[0017] Further preferably, the mass ratio of the total mass of the acrylic acid and 3-sulfonate propyl methacrylate potassium to the fulvic acid, crosslinker, and initiator is 100:(0.1-0.5):(0.02-0.04):(0.1-0.3); the mass ratio of the 3-sulfonate propyl methacrylate potassium to acrylic acid is 1:5-6.

[0018] Further preferably, the mass ratio of the total mass of acrylic acid and potassium 3-sulfonate propyl methacrylate to fulvic acid, crosslinker, and initiator is 100:0.2:0.03:0.2; and the mass ratio of potassium 3-sulfonate propyl methacrylate to acrylic acid is 1:6.

[0019] More preferably, the neutralization degree of acrylic acid in the acrylic acid solution after the reaction of the neutralizer is 55% to 75%.

[0020] More preferably, the neutralization degree of acrylic acid in the acrylic acid solution after the reaction of the neutralizer is 60%.

[0021] An application of a fulvic acid-based saline-alkali soil conditioner, characterized in that the fulvic acid-based saline-alkali soil conditioner is used for desertification control and improving soil structure, reducing soil salinity and alkalinity, and promoting plant growth.

[0022] The present invention discloses the following technical effects:

[0023] (1) The present invention prepares a highly water-absorbing polymer by graft polymerization of fulvic acid, acrylic acid and 3-sulfopropyl methacrylate potassium, which is used as a saline-alkali soil improver. The raw material fulvic acid has active groups with strong ion exchange and complexing abilities. The carboxyl group (-COOH) in fulvic acid can react with Na + , K +The monovalent metal ions undergo complexation to form sodium fulvic acid and potassium fulvic acid, thereby forming a buffer system for the mutual conversion of fulvic acid and fulvic acid salts, regulating the pH value of the soil and alleviating saline-alkali stress; fulvic acid is polymerized with acrylic acid and 3-sulfopropyl methacrylate potassium, that is, hydrophilic groups such as sulfonic acid groups (-SO3H) and carboxyl groups (-COOH) are introduced into the polymer. These two groups can also adsorb Na+ and K+ through ion exchange, effectively improving the water retention and salt-alkali resistance of the soil improver.

[0024] (2) The highly absorbent polymer prepared by the present invention can interact with soil particles through electrostatic interaction and hydrogen bonding, promoting the agglomeration of soil particles, thereby improving soil structure and preventing soil desertification.

[0025] (3) The super absorbent polymer of the present invention serves as a soil conditioner, contains nitrogen and potassium elements, and provides nutrients for plant growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a process flow chart for preparing a fulvic acid-based saline-alkali soil conditioner;

[0028] Figure 2 FTIR and XRD patterns of the fulvic acid-based saline-alkali soil conditioner prepared in Example 2;

[0029] Figure 3 This is a scanning electron microscope image of fulvic acid;

[0030] Figure 4 This is a scanning electron microscope image of the saline-alkali soil conditioner prepared in Example 2;

[0031] Figure 5 These are photos of fulvic acid, the super absorbent polymer obtained in Example 2, and the super absorbent polymer after swelling after absorbing tap water, 0.9% sodium chloride solution, 0.9% potassium chloride solution, and deionized water. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms used in the present invention are only used to describe particular embodiments and are not intended to limit the present invention.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0036] An embodiment of the present invention provides a method for preparing a fulvic acid-based saline-alkali soil conditioner, comprising the following steps: first, dispersing the raw material fulvic acid in water; then, adding an acrylic acid solution and 3-sulfopropyl methacrylate potassium after a neutralizer reaction to the fulvic acid solution; and after uniform dispersion, sequentially adding a crosslinker solution and an initiator solution to carry out a graft polymerization reaction; and finally, soaking the reaction product in anhydrous ethanol, shredding, drying, crushing, and sieving to obtain the saline-alkali soil conditioner.

[0037] In some embodiments of the present invention, the mass ratio of the total mass of acrylic acid and potassium 3-sulfonate propyl methacrylate to fulvic acid, crosslinker, and initiator is 100:0.2:0.03:0.2; the mass ratio of potassium 3-sulfonate propyl methacrylate to acrylic acid is 1:6.

[0038] In some embodiments of the present invention, the specific conditions of the graft polymerization reaction are: carried out in a nitrogen atmosphere, the polymerization reaction temperature is 60-80°C, the graft polymerization reaction time is 60-120min, and the graft polymerization reaction is carried out under stirring conditions, and the stirring speed is 200-300r / min.

[0039] In some embodiments of the present invention, the graft polymerization reaction temperature is 75°C.

[0040] Too high a reaction temperature will lead to excessive free radical activity, which is easy to cause chain transfer with the solvent or monomer and excessive consumption of the cross-linker, resulting in uneven cross-linking and reduced water absorption performance; when the temperature is too low, the decomposition of the initiator is slow, and the free radical concentration is insufficient, resulting in incomplete polymerization (a lot of residual monomers) and affecting performance; too short a time will lead to low monomer conversion and insufficient cross-linking density; too long a time will lead to an overly dense network structure or side reactions; the shear force generated by high-speed stirring may cut off the formed polymer chains, destroy the network structure, lead to a decrease in molecular weight, and affect the gel strength; the system cannot be fully mixed under low-speed stirring, resulting in excessively high local monomer concentration or initiator enrichment.

[0041] In some embodiments of the present invention, the neutralization degree of acrylic acid in the acrylic acid solution after the reaction of the neutralizing agent is 60%; and the neutralizing agent is potassium hydroxide.

[0042] In some embodiments of the present invention, the cross-linking agent is one or more of N,N-methylenebisacrylamide, glutaraldehyde and ethylene glycol; and the initiator is one or both of ammonium sulfate and potassium persulfate.

[0043] The present invention prepares a highly water-absorbing polymer by graft polymerization of fulvic acid, acrylic acid and potassium 3-sulfopropyl methacrylate, which is used as a saline-alkali soil improver. The raw material fulvic acid has active groups with strong ion exchange and complexing capabilities. The scanning electron microscope image of fulvic acid is as follows: Figure 3 As shown. The carboxyl group (-COOH) in fulvic acid can react with Na + , K + The monovalent metal ions are complexed to form sodium fulvic acid and potassium fulvic acid, thereby forming a buffer system for the mutual conversion of fulvic acid and fulvic acid salts, regulating the pH value of the soil and alleviating the salt-alkali stress; fulvic acid is polymerized with acrylic acid and 3-sulfopropyl methacrylate potassium, that is, hydrophilic groups such as sulfonic acid group (-SO3H) and carboxyl group (-COOH) are introduced into the polymer. These two groups can also absorb Na through ion exchange. + , K + , effectively improving the water retention and salt-alkali resistance of soil conditioners.

[0044] In the following examples and comparative examples of the present invention, the raw materials used were obtained through conventional commercial routes.

[0045] It should be noted that the technical means not described in detail in the following examples and comparative examples of the present invention are all conventional technical means in the art.

[0046] Example 1

[0047] like Figure 1 As shown, a method for preparing a fulvic acid-based saline-alkali soil conditioner comprises the following steps:

[0048] Add 0.0139 g of fulvic acid to 10 mL of deionized water and stir on a magnetic stirrer for 20 min to evenly disperse the fulvic acid.

[0049] Dissolve 1.9797 g of sodium hydroxide in 10 mL of deionized water to obtain a sodium hydroxide solution;

[0050] Mix 5.945 g of acrylic acid and sodium hydroxide solution to obtain a neutralized acrylic acid solution (neutralization degree 60%), which is set aside;

[0051] Add 0.0014 g of N,N-methylenebisacrylamide (MBA) to 2 ml of deionized water and ultrasonicate to dissolve it completely to obtain a crosslinker solution for later use.

[0052] Dissolve 0.069 g of ammonium persulfate (APS) in 2 ml of deionized water and ultrasonically vibrate to obtain an initiator solution for later use.

[0053] An aqueous solution polymerization method was adopted. In a water bath at 75°C, the mixture was stirred at a speed of 300 r / min. The neutralized acrylic acid solution and 0.9898 g of 3-sulfopropyl methacrylate (SPMA) were added to the fulvic acid dispersion in sequence. After reacting for 10 minutes, a crosslinker solution was added. After 15 minutes, an initiator solution was added to carry out a graft copolymerization reaction. The reaction was carried out in a nitrogen atmosphere. The graft polymerization reaction time was 70 minutes. The mixture was removed from the water bath to obtain a copolymer product. The product was washed with anhydrous ethanol, dried at 60°C for 24 hours, and crushed to 20-40 mesh to obtain highly absorbent polymer particles as a saline-alkali soil conditioner.

[0054] Example 2

[0055] A preparation method of a fulvic acid-based saline-alkali soil conditioner, wherein the remaining steps are the same as those in Example 1, except that the amount of N,N-methylenebisacrylamide added is adjusted to 0.0021 g, and the amount of ammonium persulfate added is adjusted to 0.0139 g.

[0056] The FTIR and XRD patterns of the prepared soil conditioner are shown in Figure 2. Figure 2 As shown, Figure 2 a is the FTIR graph of the material, including infrared spectra of four components (a), (b), (c), and (d), among which the 3421 cm -1 、2931cm -1 、1720cm -1 、3415cm -1The peaks at 1203 cm-1 correspond to the stretching vibration of OH, the asymmetric stretching vibration of -CH2-, the stretching vibration of C=O, and the asymmetric stretching vibration of -CH2- of PAA. Compared with (d), the FTIR spectrum of P(AA-co-SPMA) in (c) has a peak at 1203 cm-1. -1 、1061cm -1 The peak at 3415 cm shows the S=O symmetric stretching vibration and the S=O asymmetric stretching vibration, indicating that the polymerization reaction occurred between SPMA and AA. (a) is the FTIR spectrum of FA, 3415 cm -1 The peak at 2927 cm is attributed to the stretching vibration of OH in the FA structural unit. -1 The peak at 1602 cm is attributed to the asymmetric stretching vibration of -CH2-. -1 The peak at 1411 cm is attributed to the stretching vibration of C=C on the benzene ring skeleton. -1 The peak at 661 cm is attributed to the asymmetric stretching vibration of -CH2- of the benzene ring skeleton. -1 The peak is attributed to the out-of-plane bending vibration of -CH2- on the benzene ring. Compared with (a) and (c), the FTIR spectrum of (b) FA-gP (AA-co-SPMA) has a peak at 1602 cm -1 and 661cm -1 The stretching vibration of C=C on the benzene ring skeleton and the out-of-plane bending vibration of -CH2- are shown, proving that FA participates in the reaction during the polymerization process.

[0057] Figure 2 b XRD spectra of the three components: FA, P(AA-co-SPMA), and FA-gP(AA-co-SPMA). FA exhibits two distinct diffraction peaks at 2θ = 27.7° and 39.8°, indicating the presence of an ordered crystalline structure. No new diffraction peaks were observed in the XRD spectrum of P(AA-co-SPMA), but the intensity of its diffraction peaks decreased significantly. Compared with P(AA-co-SPMA), the addition of FA reduced the crystallinity of the polymer. This is because the long-range order of the material's internal crystal structure decreases after the graft copolymerization reaction between the natural component FA and the polymer P(AA-co-SPMA), indicating that the existing intramolecular and intermolecular hydrogen bonds in the material significantly interact with other ions after the graft copolymerization reaction. Furthermore, the reduced crystallinity of the material indicates that its crystal structure tends to be amorphous, a property that can improve the water absorption and water retention capacity of the copolymer, helping the polymer to better absorb and release water.

[0058] The scanning electron microscopy image of the prepared soil conditioner is as follows Figure 4 As shown, it can be seen that the soil conditioner has uniform and dense pores and has a strong adsorption effect on water.

[0059] The swelling picture of the prepared soil conditioner is as follows Figure 5 As shown in the figure, the swelling effect is as follows: distilled water > tap water > 0.9% KCl > 0.9% NaCl. In distilled water, the hydrophilic groups in the superabsorbent polymer, such as carboxyl and sulfonic acid groups, are completely ionized, the electrostatic repulsion is the largest, the network is fully diffused, and the swelling rate is the highest; in tap water, there may be some divalent ions, such as Ca 2+ , will undergo ionic cross-linking with -COO-, further inhibiting swelling, and the swelling rate is between distilled water and saline; in salt solution, Na + / K + Shield-COO - The negative charge of Na + Hydration radius ratio K + Smaller, more accessible - COO - , the charge shielding is stronger, so the swelling rate in 0.9% NaCl is slightly lower than that in 0.9% KCl.

[0060] Example 3

[0061] A method for preparing a fulvic acid-based saline-alkali soil conditioner, wherein the remaining steps are the same as those in Example 1, and the amount of N,N-methylenebisacrylamide added is adjusted to 0.0028 g.

[0062] Example 4

[0063] Add 0.0346 g of fulvic acid to 10 mL of deionized water and stir on a magnetic stirrer for 20 min to evenly disperse the fulvic acid. Set aside.

[0064] 1.9797 g of sodium hydroxide was dissolved in 10 mL of deionized water to obtain a sodium hydroxide solution.

[0065] 5.945 g of acrylic acid and sodium hydroxide solution were mixed to obtain a neutralized acrylic acid solution for later use.

[0066] 0.0021 g of N,N-methylenebisacrylamide (MBA) was added to 2 ml of deionized water and ultrasonically vibrated to completely dissolve it to obtain a crosslinker solution for later use.

[0067] Dissolve 0.0139 g of ammonium persulfate (APS) in 2 ml of deionized water and ultrasonically vibrate to obtain an initiator solution for later use.

[0068] An aqueous solution polymerization method was adopted. In a water bath at 75°C, the mixture was stirred at a speed of 300 r / min. The neutralized acrylic acid solution and 0.9898 g of 3-sulfopropyl methacrylate (SPMA) were added to the fulvic acid dispersion in sequence. After reacting for 10 minutes, a crosslinker solution was added. After 15 minutes, an initiator solution was added to carry out a graft copolymerization reaction. The reaction was carried out in a nitrogen atmosphere. The graft polymerization reaction time was 70 minutes. The mixture was removed from the water bath to obtain a copolymer product. The product was washed with anhydrous ethanol, dried at 60°C for 24 hours, and crushed to 20-40 mesh to obtain highly absorbent polymer particles as a saline-alkali soil conditioner.

[0069] Example 5

[0070] Add 0.0139 g of fulvic acid to 10 mL of deionized water and stir on a magnetic stirrer for 20 min to evenly disperse the fulvic acid. Set aside.

[0071] 1.9797 g of sodium hydroxide was dissolved in 10 mL of deionized water to obtain a sodium hydroxide solution.

[0072] 3.77 g of acrylic acid and sodium hydroxide solution were mixed to obtain a neutralized acrylic acid solution for later use.

[0073] 0.0021 g of N,N-methylenebisacrylamide (MBA) was added to 2 ml of deionized water and ultrasonically vibrated to completely dissolve it to obtain a crosslinker solution for later use.

[0074] Dissolve 0.0139 g of ammonium persulfate (APS) in 2 ml of deionized water and ultrasonically vibrate to obtain an initiator solution for later use.

[0075] An aqueous solution polymerization method was adopted. In a water bath at 75°C, the mixture was stirred at a speed of 300 r / min. A neutralized acrylic acid solution and 0.9898 g of 3-sulfopropyl methacrylate (SPMA) were added to the fulvic acid dispersion in sequence. After reacting for 10 minutes, a crosslinker solution was added. After 15 minutes, an initiator solution was added to carry out a graft copolymerization reaction. The reaction was carried out in a nitrogen atmosphere. The graft polymerization reaction time was 70 minutes. The mixture was removed from the water bath to obtain a copolymer product. The product was washed with anhydrous ethanol, dried at 60°C for 24 hours, and crushed to 20-40 mesh to obtain highly absorbent polymer particles as a saline-alkali soil conditioner.

[0076] Example 6

[0077] Add 0.0139 g of fulvic acid to 10 mL of deionized water and stir on a magnetic stirrer for 20 min to evenly disperse the fulvic acid. Set aside.

[0078] 1.9797 g of sodium hydroxide was dissolved in 10 mL of deionized water to obtain a sodium hydroxide solution.

[0079] Mix 6.93 g of acrylic acid and sodium hydroxide solution to obtain a neutralized acrylic acid solution for later use.

[0080] 0.0021 g of N,N-methylenebisacrylamide (MBA) was added to 2 ml of deionized water and ultrasonically vibrated to completely dissolve it to obtain a crosslinker solution for later use.

[0081] Dissolve 0.0139 g of ammonium persulfate (APS) in 2 ml of deionized water and ultrasonically vibrate to obtain an initiator solution for later use.

[0082] An aqueous solution polymerization method was adopted. In a water bath at 75°C, the mixture was stirred at a speed of 300 r / min. A neutralized acrylic acid solution and 0.9898 g of 3-sulfopropyl methacrylate (SPMA) were added to the fulvic acid dispersion in sequence. After reacting for 10 minutes, a crosslinker solution was added. After 15 minutes, an initiator solution was added to carry out a graft copolymerization reaction. The reaction was carried out in a nitrogen atmosphere. The graft polymerization reaction time was 70 minutes. The mixture was removed from the water bath to obtain a copolymer product. The product was washed with anhydrous ethanol, dried at 60°C for 24 hours, and crushed to 20-40 mesh to obtain highly absorbent polymer particles as a saline-alkali soil conditioner.

[0083] Example 7

[0084] Add 0.0277 g of fulvic acid to 10 mL of deionized water and stir on a magnetic stirrer for 20 min to evenly disperse the fulvic acid. Set aside.

[0085] 1.9797 g of sodium hydroxide was dissolved in 10 mL of deionized water to obtain a sodium hydroxide solution.

[0086] Mix 6.93 g of acrylic acid and sodium hydroxide solution to obtain a neutralized acrylic acid solution for later use.

[0087] 0.0021 g of N,N-methylenebisacrylamide (MBA) was added to 2 ml of deionized water and ultrasonically vibrated to completely dissolve it to obtain a crosslinker solution for later use.

[0088] Dissolve 0.0139 g of ammonium persulfate (APS) in 2 ml of deionized water and ultrasonically vibrate to obtain an initiator solution for later use.

[0089] An aqueous solution polymerization method was adopted. In a water bath at 75°C, the mixture was stirred at a speed of 300 r / min, and acrylic acid solution and 0.9898 g of 3-sulfopropyl methacrylate potassium (SPMA) were added to the fulvic acid dispersion in sequence. After reacting for 10 minutes, a crosslinker solution was added, and after 15 minutes, an initiator solution was added to carry out a graft copolymerization reaction. The reaction was carried out in a nitrogen atmosphere. The graft polymerization reaction time was 70 minutes. The mixture was removed from the water bath to obtain a copolymer product. The product was washed with anhydrous ethanol, dried at 60°C for 24 hours, and crushed to 20-40 mesh to obtain highly absorbent polymer particles as a saline-alkali soil conditioner.

[0090] Comparative Example 1

[0091] The preparation method is basically the same as that in Example 1, except that the raw material fulvic acid is not added.

[0092] Comparative Example 2

[0093] The preparation method is basically the same as that in Example 1, except that the raw material 3-sulfonate propyl potassium methacrylate is not added.

[0094] Table 1 Water absorption of water-absorbing polymer particles prepared in Examples 1-7 and Comparative Examples 1-2

[0095]

[0096] It can be seen from the data in the above table that: as shown in the data of Example 2: when the added mass ratio of acrylic acid and SPMA is 6:1, the mass ratio of the total mass of acrylic acid and 3-sulfopropyl methacrylate potassium to fulvic acid, crosslinker, and initiator is 100:0.2:0.03:0.2, the saline-alkali soil conditioner has the best salt tolerance and water absorption. As shown in the data of Example 1, when the amount of initiator added is too much, the content of SPMA participating in the graft polymerization is relatively small, which limits the performance of its strong hydrophilic function, and ultimately causes the saline-alkali soil conditioner to absorb salt. The effect is reduced; as shown in the data of Examples 4 and 7, the addition of fulvic acid by mass ratio is too much, and the salt absorption effect of the saline-alkali soil improver is reduced. As shown in the data of Examples 5 and 6, the addition of acrylic acid by mass is too much, and the salt absorption effect of the saline-alkali soil improver is reduced. As shown in the data of Comparative Examples 1 and 2, the water absorption and salt-alkali resistance of the saline-alkali soil improver without the addition of fulvic acid or 3-sulfonate propyl methacrylate potassium are greatly reduced, indicating that fulvic acid and 3-sulfonate propyl methacrylate synergistically greatly improve the salt tolerance and water absorption of the saline-alkali soil improver. The saline-alkali soil improver prepared by the present invention has good salt tolerance and water absorption, and has good application prospects in desertification control, improving saline-alkali soil, and promoting plant growth.

[0097] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a fulvic acid-based saline-alkali soil conditioner, characterized in that: It is prepared by graft polymerization reaction using fulvic acid, acrylic acid and 3-sulfopropyl methacrylate potassium as monomer raw materials.

2. The preparation method of the fulvic acid-based saline-alkali soil conditioner according to claim 1, wherein The following steps are involved: First, the raw material fulvic acid is dispersed in water, and then the acrylic acid solution and 3-sulfopropyl methacrylate potassium after the neutralizer reaction are added to the fulvic acid solution. After uniform dispersion, the crosslinker solution and the initiator solution are added in sequence to carry out graft polymerization reaction to obtain a saline-alkali soil conditioner.

3. The preparation method of the fulvic acid-based saline-alkali soil conditioner according to claim 2, characterized in that: The mass ratio of the total mass of the acrylic acid and potassium 3-sulfonate propyl methacrylate to fulvic acid, crosslinking agent, and initiator is 100:(0.1-1):(0.01-0.12):(0.1-0.8); and / or, the mass ratio of the potassium 3-sulfonate propyl methacrylate to acrylic acid is 1:(3-10).

4. The preparation method of the fulvic acid-based saline-alkali soil conditioner according to claim 2, wherein: The specific conditions of the graft polymerization reaction are: carried out in a nitrogen atmosphere, the polymerization reaction temperature is 60-80° C., the graft polymerization reaction time is 60-120 min, and the graft polymerization reaction is carried out under stirring conditions, and the stirring speed is 200-300 r / min.

5. The preparation method of the fulvic acid-based saline-alkali soil conditioner according to claim 2, characterized in that: After the graft polymerization reaction, the reaction product is washed with anhydrous ethanol, and then chopped, dried, crushed, and sieved to obtain a saline-alkali soil conditioner.

6. The preparation method of the fulvic acid-based saline-alkali soil conditioner according to claim 2, wherein: The neutralization degree of acrylic acid in the acrylic acid solution after the reaction of the neutralizer is 45% to 85%; the neutralizer is sodium hydroxide or potassium hydroxide.

7. The preparation method of the fulvic acid-based saline-alkali soil conditioner according to claim 2, characterized in that: The cross-linking agent is one or more of N,N-methylenebisacrylamide, glutaraldehyde and ethylene glycol; and / or the initiator is one or both of ammonium sulfate and potassium persulfate.

8. The preparation method of the fulvic acid-based saline-alkali soil conditioner according to claim 3, characterized in that: The mass ratio of the total mass of the acrylic acid and potassium 3-sulfonate propyl methacrylate to the fulvic acid, the crosslinking agent, and the initiator is 100:(0.1-0.5):(0.02-0.04):(0.1-0.3); and / or, the mass ratio of the potassium 3-sulfonate propyl methacrylate to acrylic acid is 1:5-6.

9. The method for preparing the fulvic acid-based saline-alkali soil conditioner according to claim 8, wherein: The mass ratio of the total mass of acrylic acid and potassium 3-sulfonate propyl methacrylate to fulvic acid, crosslinker and initiator is 100:0.2:0.03:0.2; and / or the mass ratio of potassium 3-sulfonate propyl methacrylate to acrylic acid is 1:

6.

10. An application of a fulvic acid-based saline-alkali soil conditioner, characterized in that: The fulvic acid-based saline-alkali soil conditioner is used for desertification control and soil structure improvement, soil salinity reduction, and plant growth promotion.

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