Humic substance-based water-retaining agent and method for preparing the same

Abstract

This application relates to the field of water-retaining agent technology, and particularly to a humicin-based water-retaining agent and its preparation method. The preparation method of the humicin-based water-retaining agent includes the following steps: S1, preparing lignocellulose-based biomass-derived humicin; S2, preparing sodium polyacrylate water-absorbing resin; S3, surface crosslinking and composite modification: adding lignocellulose-based biomass-derived humicin to the sodium polyacrylate water-absorbing resin, adding an interface-modified emulsion, stirring, adding methanol and deionized water, heating and maintaining the temperature for reaction, cooling to room temperature after the reaction is complete, filtering, pulverizing and drying to obtain the humicin-based water-retaining agent. This application solves the problems of traditional humic acid being non-renewable, difficult to apply in water-retaining agent preparation, and having poor salt resistance in saline-alkali environments by providing a humicin-based water-retaining agent and its preparation method.

Description

Technical Field

[0001] This application relates to the field of water-retaining agent technology, and in particular to a humicin-based water-retaining agent and its preparation method. Background Technology

[0002] Water-retaining agents refer to water-swellable polymers composed of strongly hydrophilic groups such as carboxyl and hydroxyl groups, and possessing a certain degree of cross-linking. Their unique three-dimensional network structure allows for repeated absorption and release of large amounts of water, and they retain good water retention even under pressure, making them widely used in agricultural production. Currently, the most widely used water-retaining agents on the market are superabsorbent polymers, which can be further divided into starch-based, cellulose-based, and synthetic polymer-based types. Among these, synthetic polymer superabsorbent polymers mainly include polyacrylates and polyvinyl alcohols. These materials are the most commonly used due to their high water absorption rate, excellent water retention performance, and wide applicability. However, these materials are not only expensive to produce, but synthetic resins are also not environmentally friendly; after being released into nature, they degrade into microplastics after several years, posing potential ecological risks.

[0003] Humic acid (HA), as one of the organic components of soil, not only stimulates plant growth and development, increases crop resistance to stress, and improves plant nutrition, but also enhances the soil's ability to retain fertilizer and water. It is now widely used in agricultural production. Furthermore, the humic acid molecule contains abundant functional groups such as carboxyl and hydroxyl groups, enabling it to participate in cross-linking polymerization reactions to form a three-dimensional network structure. It also possesses good hydrophilicity and ion adsorption capacity, thus being applied in the field of water-retaining agents to improve the water absorption, salt tolerance, and ecological compatibility of materials. However, on the one hand, natural humic acid mainly comes from non-renewable resources such as peat, lignite, and weathered coal. Not only are its reserves limited, but its extraction process may also damage the ecological environment. Its natural formation cycle is also as long as hundreds to thousands of years, making it difficult to meet the ever-increasing market demand. On the other hand, when water-retaining agents are in a high-salt environment, the osmotic pressure of salt ions is higher than the osmotic pressure inside the water-retaining agent, causing it to lose water and shrink, failing to effectively maintain the soil's moisture balance. This limits its application in saline-alkali land improvement and agricultural production in saline-alkali environments. Summary of the Invention

[0004] This application provides a humic acid-based water-retaining agent and its preparation method to solve the problems in related technologies, such as the non-renewable nature of traditional humic acid, its difficulty in being used in the preparation of water-retaining agents, and its poor salt resistance in saline-alkali environments.

[0005] In a first aspect, a method for preparing a humicin-based water-retaining agent is provided, comprising the following steps: S1. Preparation of lignocellulose biomass-derived humin: After pulverizing the lignocellulose matrix, it is mixed with sulfuric acid solution, heated to 100~110℃ under stirring and kept at the temperature for 4~5h. After the reaction is completed, it is cooled to room temperature, washed until the pH of the filtrate is 4~5, filtered, and the filter cake is vacuum dried and pulverized to obtain lignocellulose biomass-derived humin. S2. Preparation of sodium polyacrylate water-absorbing resin: S201. Add sodium hydroxide solution dropwise to acrylic acid, stir the reaction until the pH is 6.5-7, add triisopropanolamine to obtain monomer solution; S202. Add a composite modifier to the monomer solution, stir and then ultrasonically disperse, heat to 55~60℃, add an initiator and a reducing agent under nitrogen protection, stir and then obtain a gel. S203. Add a crosslinking agent to the gel, heat to 70~75℃, and stir while maintaining the temperature to obtain sodium polyacrylate water-absorbing resin. The amount of crosslinking agent added is 0.5~1.5% of the gel mass. S3. Surface crosslinking and composite modification: The lignocellulose biomass-derived humin is added to sodium polyacrylate water-absorbing resin, and an interface-modified emulsion is added. After stirring, methanol and deionized water are added, the temperature is raised to 80~85℃, and the reaction is maintained for 1.5~2h. After the reaction is completed, the mixture is cooled to room temperature, filtered, pulverized and dried to obtain humin-based water-retaining agent. The mass ratio of the lignocellulose biomass-derived humin, sodium polyacrylate water-absorbing resin, and interface-modified emulsion is 1:(2~3):(0.4~0.5); The method for preparing the composite modifier includes: Sepiolite, hydroxyethyl cellulose, and cyclodextrin were dispersed in deionized water and stirred at 45-50°C for 10-15 minutes. After ultrasonic dispersion, a composite modifier was obtained. The mass ratio of sepiolite, hydroxyethyl cellulose, and cyclodextrin was 1:(0.5-0.8):(0.4-0.5).

[0006] Preferably, in S1, the lignocellulose matrix comprises agricultural and forestry waste biomass cellulose matrix and furfural residue in a mass ratio of 10:(1~2); The agricultural and forestry waste biomass cellulose matrix includes at least one of corn cob lignocellulose, straw lignocellulose, rice husk lignocellulose, and sawdust lignocellulose.

[0007] Preferably, in step S1, the conditions for vacuum drying and pulverizing the filter cake are: vacuum drying at 55~60℃ for 7~8 hours, and pulverizing through a 100-mesh sieve.

[0008] Preferably, in step S1, the mass ratio of the pulverized lignocellulose matrix to the sulfuric acid solution is 1:(1.2~2), and the concentration of the sulfuric acid solution is 3mol / L.

[0009] Preferably, in S201, the mass of triisopropanolamine is 2 to 5% of the mass of acrylic acid.

[0010] Preferably, in S202, the amount of composite modifier added is 4-6% of the mass of the monomer solution; The amount of initiator added is 0.5-1% of the mass of the monomer solution, and the mass ratio of the reducing agent to the initiator is 1:3; The initiator is selected from ammonium persulfate or potassium persulfate, and the reducing agent is selected from vitamin C.

[0011] Preferably, in S203, the crosslinking agent is selected from N,N'-methylenebisacrylamide; Alternatively, the crosslinking agent is selected from a mixture of N,N'-methylenebisacrylamide and gellan gum, and the mass ratio of N,N'-methylenebisacrylamide to gellan gum is (0.5~1):1.

[0012] Preferably, the method for preparing the interface-modified emulsion includes: dissolving lignin in sodium hydroxide solution at a mass ratio of (0.2~0.3):1, adding tea saponin, and stirring at 35~40℃ for 20~25 min to obtain the interface-modified emulsion; The amount of tea saponin added is 50% of the lignin content, and the concentration of the sodium hydroxide solution is 5 wt%.

[0013] Preferably, in step S3, the total mass of methanol and deionized water is 3 to 5 times the mass of the lignocellulosic biomass-derived humic acid, and the mass ratio of methanol to deionized water is 1:4.

[0014] Secondly, a humicin-based water-retaining agent is provided, which is prepared by any of the above-described methods for preparing humicin-based water-retaining agents.

[0015] The beneficial effects of the technical solution provided in this application include: This application provides a humic acid-based water-retaining agent and its preparation method. It uses a lignocellulose matrix as raw material and prepares biomass humic acid through acid hydrolysis, replacing non-renewable humic acid resources such as peat and lignite. The raw materials are inexpensive and readily available. The chemical structure of humic acid is highly similar to that of natural humic acid. It is also rich in functional groups such as carboxyl and hydroxyl groups and has multiple functions such as promoting plant growth, improving soil structure, and adsorbing heavy metals. From the perspective of raw materials, it can effectively reduce production costs. Sepiolite, hydroxyethyl cellulose, and cyclodextrin are combined as a composite modifier. Layered sepiolite blocks the penetration of soil salt ions, while hydroxyethyl cellulose optimizes the rigidity and toughness of the polymer cross-linking network. Its hydroxyl groups can form a hydration layer with salt ions, buffering the damage of salt ions to the polymer network. The cyclodextrin cavity structure directionally adsorbs salt ions, alleviating the problems of network pore collapse and chain segment breakage under salt stress. Triisopropanolamine effectively inhibits the ineffective self-polymerization side reaction of acrylic acid, improves the monomer graft copolymerization efficiency, and optimizes the regularity of polymer chain segments. The resulting water-absorbing resin, combined with the interface-modified emulsion and humulin, results in a water-retaining agent with simultaneously improved hydrophilicity and ion adsorption capacity. The interface-modified emulsion optimizes the interfacial compatibility between humulin and sodium polyacrylate resin, avoiding the two-phase layering and aggregation, making it suitable for various farmland application scenarios such as dry land, saline-alkali land, and field crops. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating the preparation method of the humicin-based water-retaining agent provided in this application; Figure 2 Infrared characterization images of humulin and humulin-based water-retaining agents provided in Example 1 of this application. Figure 2 Image (a) is the infrared characterization image of humin obtained in Example 1. Figure 2 (b) is the infrared characterization diagram of the humicin-based water-retaining agent prepared in Example 1; Figure 3 These are scanning electron microscope (SEM) images of humulin and humulin-based water-retaining agents provided in Example 1 of this application at different magnifications. Figure 3 Image (a) is a scanning electron microscope image of humin prepared in Example 1. Figure 3 (b) is a scanning electron microscope image of the humicin-based water-retaining agent prepared in Example 1. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] See Figures 1-3 As shown, this application provides a humicin-based water-retaining agent and its preparation method.

[0020] In the following examples and comparative examples, the corn cobs, straw, rice husks, and sawdust used all had a lignocellulose purity of ≥95%, a lignin content of 18%~22%, and a cellulose content of 42%~48%; furfural residue was industrial by-product furfural purification residue with a lignocellulose content of ≥88% and a pH of 5.5~6.5; acrylic acid was analytical grade with a purity of ≥99.0%; triisopropanolamine had a purity of ≥98.5%; ammonium persulfate, potassium persulfate, N,N'-methylenebisacrylamide, and methanol were all analytical grade; and vitamin C was food grade.

[0021] Sepiolite with a specific surface area ≥80m² 2 / g; hydroxyethyl cellulose molecular weight 9.5×10 4 The degree of substitution is 1.0; the cyclodextrin is β-cyclodextrin with a purity ≥98%; the lignin is alkali lignin, a by-product of the papermaking industry, with a weight-average molecular weight of about 4200; the tea saponin has a molecular weight of 1300 and a purity ≥95%.

[0022] Example 1 The preparation method of the humin-based water-retaining agent provided in this embodiment includes the following steps: S1. Preparation of lignocellulose-derived humin: 120g of agricultural and forestry waste biomass cellulose matrix (corn cob lignocellulose and rice husk lignocellulose in a mass ratio of 2:1) was mixed with 24g of furfural residue, pulverized through an 80-mesh sieve, placed in a reaction vessel, and 216g of 3mol / L sulfuric acid solution was added. The mixture was heated to 110℃ under stirring at 60r / min and kept at that temperature for 4h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water until the pH of the filtrate was 4.5, filtered, and the filter cake was placed in a 60℃ vacuum drying oven for 7h and pulverized through a 100-mesh sieve to obtain lignocellulose biomass-derived humin. S2. Preparation of sodium polyacrylate water-absorbing resin: S201. Add 20wt% sodium hydroxide solution dropwise to 200g acrylic acid at 25℃, stir the reaction until pH is 6.5, add 8g triisopropanolamine, and stir to obtain monomer solution; S202. Add 10g of composite modifier to 200g of monomer solution, stir at 100r / min for 30min, then sonicate at 300W for 20min to disperse the composite modifier. Then heat to 55℃, add 1g of potassium persulfate and 0.33g of vitamin C under nitrogen protection, and stir to obtain gel. The preparation method of the composite modifier is as follows: 6g sepiolite, 3g hydroxyethyl cellulose, and 3g cyclodextrin were dispersed in 30g deionized water, stirred at 45℃ for 15min, and then ultrasonically dispersed at 200W for 15min to obtain a composite modifier. S203. Add 0.8g N,N'-methylenebisacrylamide and 1g gellan gum to 180g gel, heat to 70℃, keep warm and stir for 1h to obtain sodium polyacrylate water-absorbing resin. S3. Surface crosslinking and composite modification: 80g of lignocellulose biomass-derived humin was added to 160g of sodium polyacrylate water-absorbing resin prepared in S2, and 40g of interface-modified emulsion was added. After stirring at 80r / min for 40min, 64g of methanol (volume concentration of 64.3%) and 256g of deionized water were added. The temperature was raised to 80℃ and the reaction was maintained for 2h. After the reaction was completed, the mixture was cooled to room temperature, filtered, pulverized through a 60-mesh sieve, and dried in a vacuum drying oven at 50℃ to obtain humin-based water-retaining agent.

[0023] The method for preparing the interface-modified emulsion is as follows: 12g of lignin is dissolved in 40g of 5wt% sodium hydroxide solution, 6g of tea saponin is added, and the mixture is stirred at 35℃ for 20min to obtain the interface-modified emulsion.

[0024] Example 2 The difference between this embodiment and Embodiment 1 is that, in this embodiment, the amount of sulfuric acid solution used in step S1 is 172.8g, the crosslinking agent used in step S203 is N,N'-methylenebisacrylamide, and the preparation method of the composite modifier in S202 is as follows: 6g sepiolite, 4.8g hydroxyethyl cellulose, and 3g cyclodextrin were dispersed in 30g deionized water, stirred at 45℃ for 15min, and then ultrasonically dispersed at 200W for 15min to obtain a composite modifier.

[0025] Example 3 The preparation method of the humin-based water-retaining agent provided in this embodiment includes the following steps: S1. Preparation of lignocellulose-derived humin: 120g of corn cob lignocellulose and 24g of furfural residue were mixed, pulverized and passed through an 80-mesh sieve, placed in a reaction vessel, and 288g of 3mol / L sulfuric acid solution was added. The mixture was heated to 100℃ and kept at that temperature for 5h under stirring at 60r / min. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water until the pH of the filtrate was 4, filtered, and the filter cake was placed in a vacuum drying oven at 55℃ for 8h and pulverized and passed through a 100-mesh sieve to obtain lignocellulose biomass-derived humin. S2. Preparation of sodium polyacrylate water-absorbing resin: S201. Add 20wt% sodium hydroxide solution dropwise to 200g acrylic acid at 25℃, stir the reaction until pH is 7, add 4g triisopropanolamine, and stir to obtain monomer solution; S202. Add 8g of composite modifier to 200g of monomer solution, stir at 100r / min for 30min, then sonicate at 300W for 20min to disperse the composite modifier. Then heat to 60℃, add 1.5g of ammonium persulfate and 0.5g of vitamin C under nitrogen protection, and stir to obtain gel. The preparation method of the composite modifier is as follows: 6g sepiolite, 4.8g hydroxyethyl cellulose, and 2.4g cyclodextrin were dispersed in 30g deionized water, stirred at 50℃ for 10min, and then ultrasonically dispersed at 200W for 15min to obtain a composite modifier. S203. Add 0.3g N,N'-methylenebisacrylamide and 0.6g gellan gum to 180g gel, heat to 70℃, keep warm and stir for 1h to obtain sodium polyacrylate water-absorbing resin. S3. Surface crosslinking and composite modification: 50g of lignocellulose biomass-derived humin was added to 150g of sodium polyacrylate water-absorbing resin prepared in S2, and 25g of interface-modified emulsion was added. After stirring at 80r / min for 40min, 50g of methanol (volume concentration of 64.3%) and 200g of deionized water were added. The temperature was raised to 85℃ and the reaction was maintained for 1.5h. After the reaction was completed, the mixture was cooled to room temperature, filtered, pulverized through a 60-mesh sieve, and dried in a vacuum drying oven at 50℃ to obtain humin-based water-retaining agent.

[0026] The method for preparing the interface-modified emulsion is as follows: 10g of lignin is dissolved in 50g of 5wt% sodium hydroxide solution, 5g of tea saponin is added, and the mixture is stirred at 40℃ for 20min to obtain the interface-modified emulsion.

[0027] Example 4 The preparation method of the humin-based water-retaining agent provided in this embodiment includes the following steps: S1. Preparation of lignocellulose-derived humin: 120g of agricultural and forestry waste biomass cellulose matrix (corn cob lignocellulose, straw lignocellulose, and sawdust lignocellulose in a mass ratio of 1:1:1) was mixed with 12g of furfural residue, pulverized and passed through an 80-mesh sieve, placed in a reaction vessel, and 198g of 3mol / L sulfuric acid solution was added. The mixture was heated to 110℃ under stirring at 60r / min and kept at that temperature for 4h. After the reaction was completed, the mixture was cooled to room temperature, washed with deionized water until the pH of the filtrate was 5, filtered, and the filter cake was placed in a 60℃ vacuum drying oven for 7h and pulverized and passed through a 100-mesh sieve to obtain lignocellulose biomass-derived humin. S2. Preparation of sodium polyacrylate water-absorbing resin: S201. Add 20wt% sodium hydroxide solution dropwise to 200g acrylic acid at 25℃, stir the reaction until pH is 6.5, add 10g triisopropanolamine, and stir to obtain monomer solution; S202. Add 12g of composite modifier to 200g of monomer solution, stir at 100r / min for 30min, then sonicate at 300W for 20min to disperse the composite modifier. Then heat to 55℃, add 2g of potassium persulfate and 0.67g of vitamin C under nitrogen protection, and stir to obtain gel. The preparation method of the composite modifier is as follows: 8g sepiolite, 4g hydroxyethyl cellulose, and 3.2g cyclodextrin were dispersed in 40g deionized water, stirred at 45℃ for 15min, and then ultrasonically dispersed at 200W for 15min to obtain a composite modifier. S203. Add 1.35g N,N'-methylenebisacrylamide and 1.35g gellan gum to 180g gel, heat to 75℃, keep warm and stir for 1h to obtain sodium polyacrylate water-absorbing resin. S3. Surface crosslinking and composite modification: 80g of lignocellulose biomass-derived humin was added to 160g of sodium polyacrylate water-absorbing resin prepared in S2, and 32g of interface-modified emulsion was added. After stirring at 80r / min for 40min, 48g of methanol (volume concentration of 64.3%) and 182g of deionized water were added. The temperature was raised to 80℃ and kept at that temperature for 2h. After the reaction was completed, the mixture was cooled to room temperature, filtered, pulverized through a 60-mesh sieve, and dried in a vacuum drying oven at 50℃ to obtain humin-based water-retaining agent.

[0028] The method for preparing the interface-modified emulsion is as follows: 12g of lignin is dissolved in 40g of 5wt% sodium hydroxide solution, 6g of tea saponin is added, and the mixture is stirred at 35℃ for 25min to obtain the interface-modified emulsion.

[0029] Comparative Example 1 The difference from Example 1 is that in this comparative example, the lignocellulose matrix in S1 is replaced with an equal amount of corn cob lignocellulose, and no composite modifier is added in S202.

[0030] Comparative Example 2 The difference from Example 1 is that in this comparative example, triisopropanolamine is not added in step S201, and no composite modifier is added in S202.

[0031] Comparative Example 3 The difference from Example 1 is that no interface-modified emulsion is added in S3 in this comparative example.

[0032] The humicin-based water-retaining agents prepared in the examples and comparative examples were tested.

[0033] Absorption rate test: Weigh 0.5g of humulin-based water-retaining agent and place it in a 200-mesh nylon mesh bag. Seal the bag and immerse it in 500mL of deionized water (25℃). Let it stand for 24 hours until it reaches water absorption equilibrium. Remove the bag and hang it for 10 minutes to drain the surface free water. Accurately weigh the total mass m1 after water absorption. Calculate the water absorption ratio. In the formula, m0 = 0.5g.

[0034] Weigh 0.5g of humulin-based water-retaining agent and place it in a 200-mesh nylon mesh bag. Seal the bag and immerse it in 500mL of salt solution (NaCl concentration 0.9wt%). Let it stand for 24 hours until it reaches water absorption equilibrium. Remove the mesh bag and hang it for 10 minutes to drain the free water on the surface. Accurately weigh the total mass m2 after water absorption. Calculate the salt tolerance water absorption ratio and salt tolerance rate. In the formula, m0 = 0.5g.

[0035] The results are shown in Table 1.

[0036] Table 1 In Example 1, humulin, combined with sodium polyacrylate superabsorbent resin, introduces a large number of carboxyl and hydroxyl groups, which adsorb water through ion osmotic pressure and capillary action. A composite modifier (sepiolite and hydroxyethyl cellulose) optimizes the network pore size, while gellan gum and N,N'-methylenebisacrylamide synergistically regulate the crosslinking density, preventing excessive crosslinking leading to pore collapse or insufficient crosslinking leading to swelling and disintegration. The physical barrier of sepiolite combined with the chemical adsorption of cyclodextrin effectively reduces sodium... +Impact on the network: In Example 2, the amount of sulfuric acid solution used for acid hydrolysis was reduced, resulting in a lower yield of humin. Furthermore, the use of only N,N'-methylenebisacrylamide as a crosslinking agent led to poor pore uniformity, decreased water absorption ratio, and reduced salt tolerance. In Example 3, the reduced proportion of triisopropanolamine triggered monomer self-polymerization, and the resulting oligomers and irregular molecular chain structures reduced the water absorption rate and water retention capacity. In Example 4, the higher amounts of composite modifier and crosslinking agent resulted in a slightly higher network density, and the water retention capacity was close to, but lower than, that of Example 1. Comparative Example 1 lacked a composite modifier, resulting in insufficient network skeleton strength, easy disintegration, and a decreased water absorption ratio. Comparative Example 2 lacked triisopropanolamine, leading to severe self-polymerization. The absence of a composite modifier further reduced the water retention capacity. Comparative Example 3 lacked an interface-modified emulsion, resulting in poor compatibility between humin and the superabsorbent resin, and a decrease in both water absorption ratio and salt tolerance.

[0037] See Figure 2 As shown, it is an infrared characterization diagram of humulin and humulin-based water-retaining agent prepared in Example 1, wherein... Figure 2 (a) is the infrared characterization image of humulin obtained in Example 1. Figure 2 (b) is the infrared characterization diagram of the humicin-based water-retaining agent prepared in Example 1. Compared to Figure 2 (a) Hu Minsu, Figure 2 (b) The infrared characterization image of the prepared humin-based water-retaining agent showed the following characteristic absorption peak: 1383 cm⁻¹ -1 The contents belong to the carboxylate ion (-COO) in sodium polyacrylate. - The stretching vibration of 1024 cm -1 The peaks are attributed to the stretching vibrations of the CO bond, and the peak shape is stable with no free impurity peaks; that is, in the humin-based water-retaining agent, humin and sodium polyacrylate water-absorbing resin have been successfully cross-linked.

[0038] See Figure 3 The images shown are scanning electron microscope (SEM) images of humulin and humulin-based water-retaining agent prepared in Example 1, respectively. Figure 3 As can be seen in (a), the humin prepared in Example 1 has a relatively rough morphology and fewer pores. Figure 3 (b) is the humicin-based water-retaining agent prepared in Example 1, which has a complete three-dimensional porous network, abundant pores, clear fibrous skeleton, and no obvious agglomeration.

[0039] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a humulin-based water-retaining agent, characterized in that, It includes the following steps: S1. Preparation of lignocellulose biomass-derived humin: After pulverizing the lignocellulose matrix, it is mixed with sulfuric acid solution, heated to 100~110℃ under stirring and kept at the temperature for 4~5h. After the reaction is completed, it is cooled to room temperature, washed until the pH of the filtrate is 4~5, filtered, and the filter cake is vacuum dried and pulverized to obtain lignocellulose biomass-derived humin. S2. Preparation of sodium polyacrylate water-absorbing resin: S201. Add sodium hydroxide solution dropwise to acrylic acid, stir the reaction until the pH is 6.5-7, add triisopropanolamine to obtain monomer solution; S202. Add a composite modifier to the monomer solution, stir and then ultrasonically disperse, heat to 55~60℃, add an initiator and a reducing agent under nitrogen protection, stir and then obtain a gel. S203. Add a crosslinking agent to the gel, heat to 70~75℃, and stir while maintaining the temperature to obtain sodium polyacrylate water-absorbing resin. The amount of crosslinking agent added is 0.5~1.5% of the gel mass. S3. Surface crosslinking and composite modification: The lignocellulose biomass-derived humin is added to sodium polyacrylate water-absorbing resin, and an interface-modified emulsion is added. After stirring, methanol and deionized water are added, the temperature is raised to 80~85℃, and the reaction is maintained for 1.5~2h. After the reaction is completed, the mixture is cooled to room temperature, filtered, pulverized and dried to obtain humin-based water-retaining agent. The mass ratio of the lignocellulose biomass-derived humin, sodium polyacrylate water-absorbing resin, and interface-modified emulsion is 1:(2~3):(0.4~0.5). The method for preparing the composite modifier includes: Sepiolite, hydroxyethyl cellulose, and cyclodextrin were dispersed in deionized water and stirred at 45-50°C for 10-15 minutes. After ultrasonic dispersion, a composite modifier was obtained. The mass ratio of sepiolite, hydroxyethyl cellulose, and cyclodextrin was 1:(0.5-0.8):(0.4-0.5).

2. The preparation method of the humulin-based water-retaining agent as described in claim 1, characterized in that: In S1, the lignocellulose matrix includes agricultural and forestry waste biomass cellulose matrix and furfural residue in a mass ratio of 10:(1~2); The agricultural and forestry waste biomass cellulose matrix includes at least one of corn cob lignocellulose, straw lignocellulose, rice husk lignocellulose, and sawdust lignocellulose.

3. The preparation method of the humulin-based water-retaining agent as described in claim 1, characterized in that: In step S1, the conditions for vacuum drying and pulverizing the filter cake are: vacuum drying at 55~60℃ for 7~8 hours, and pulverizing through a 100-mesh sieve.

4. The preparation method of the humulin-based water-retaining agent as described in claim 1, characterized in that: In step S1, the mass ratio of the pulverized lignocellulose matrix to the sulfuric acid solution is 1:(1.2~2), and the concentration of the sulfuric acid solution is 3mol / L.

5. The preparation method of the humin-based water-retaining agent as described in claim 1, characterized in that: In S201, the mass of triisopropanolamine is 2 to 5% of the mass of acrylic acid.

6. The preparation method of the humin-based water-retaining agent as described in claim 1, characterized in that: In S202, the amount of composite modifier added is 4-6% of the mass of the monomer solution; The amount of initiator added is 0.5-1% of the mass of the monomer solution, and the mass ratio of the reducing agent to the initiator is 1:3; The initiator is selected from ammonium persulfate or potassium persulfate, and the reducing agent is selected from vitamin C.

7. The preparation method of the humulin-based water-retaining agent as described in claim 1, characterized in that: In S203, the crosslinking agent is selected from N,N'-methylenebisacrylamide; Alternatively, the crosslinking agent is selected from a mixture of N,N'-methylenebisacrylamide and gellan gum, and the mass ratio of N,N'-methylenebisacrylamide to gellan gum is (0.5~1):

1.

8. The preparation method of the humulin-based water-retaining agent as described in claim 1, characterized in that: The method for preparing the interface-modified emulsion includes: dissolving lignin in sodium hydroxide solution at a mass ratio of (0.2~0.3):1, adding tea saponin, and stirring at 35~40℃ for 20~25 min to obtain the interface-modified emulsion; The amount of tea saponin added is 50% of the lignin content, and the concentration of the sodium hydroxide solution is 5 wt%.

9. The preparation method of the humulin-based water-retaining agent as described in claim 1, characterized in that: In step S3, the total mass of methanol and deionized water is 3 to 5 times the mass of the lignocellulosic biomass-derived humic acid, and the mass ratio of methanol to deionized water is 1:

4.

10. A humin-based water-retaining agent, characterized in that, It is prepared by the preparation method of the humicin-based water-retaining agent according to any one of claims 1 to 9.

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