Humic acid hydrogel soil conditioner and preparation method thereof

Abstract

The invention provides a humic acid hydrogel soil conditioner and a preparation method thereof, and belongs to the technical field of soil conditioners. The humic acid hydrogel soil conditioner provided by the invention can effectively improve the sandy soil structure, improve the soil organic carbon immobilization capability, realize structure optimization and carbon sequestration, water storage and soil moisture conservation, and improve the utilization efficiency of nitrogen, phosphorus and potassium nutrients in farmland. According to the preparation method disclosed by the invention, the humic acid is extracted from the soy sauce waste residues, so that resource utilization is realized, and the extracted humic acid also has the advantages of being natural and low in environmental threat, particularly, the threat of heavy metal pollution is relatively small, and the humic acid hydrogel has an excellent agricultural application prospect. The humic acid hydrogel prepared by the preparation method disclosed by the invention is relatively excellent in slow release performance, and can be slowly released for a relatively long time, so that the soil environment is continuously regulated, the impact on the environment is reduced, the soil regulating effect is more durable and stable, and the circulation of N, P and K nutrients is continuously promoted.

Description

Technical Field

[0001] The invention relates to the technical field of soil conditioners, and in particular to a humic acid hydrogel soil conditioner and a preparation method thereof. Background Art

[0002] Soil conditioner is a material mainly used to improve the physical, chemical and biological properties of soil to make it more suitable for plant growth, rather than mainly providing plant nutrients. Soil conditioner has the functions of retaining moisture and increasing temperature. It can effectively improve soil moisture, increase the ground temperature of the cultivated layer, improve soil structure, coordinate the relationship between soil water, fertilizer, air, heat and organisms, prevent soil erosion, enhance the anti-seepage capacity of channels, inhibit secondary salinization of soil, and improve the development and utilization of sandy wasteland. It is suitable for arid, semi-arid areas and areas with insufficient accumulated temperature during the crop growth period, as well as soils with poor soil structure, especially dry land and sloping sandy land and saline-alkali land with severe water shortage. The soil structure improvers commonly used in the current prior art are mainly polyacrylamide, gypsum, a byproduct of sulfur removal in coal-fired power plants, etc.

[0003] Humus is produced by the degradation of dead biological matter such as lignin by microorganisms. It is difficult to degrade further, and its specific properties and structure depend on the specific conditions when a given sample is extracted. However, although the sources of humus are different, the properties are very similar. Humus in soil and sediment can be divided into three main parts: humic acid (HA), fulvic acid (FA) and humin (HM). Among them, HA is soluble in alkali but insoluble in water and acid; FA is soluble in alkali, water and acid; while HM is soluble in dilute alkali and insoluble in water and acid. Humic acid (HA) is a type of macromolecular organic matter in humus (HS) that is insoluble in acidic media. It is widely present in nature and is widely used in various fields such as agriculture, forestry, animal husbandry, petroleum, chemical industry, building materials, medicine and health, and environmental protection. Especially now that ecological agriculture construction, pollution-free agricultural production, green food, pollution-free environmental protection, etc. are advocated, humic acid is highly respected. The basic structure of humic acid macromolecules is an aromatic ring and an aliphatic ring, with functional groups such as carboxyl, hydroxyl, carbonyl, quinone, and methoxy groups attached to the ring. In the process of HA formation, the matrix organic matter undergoes three stages: hydrolysis of organic products, initial conversion, and humification of lignin structure. Its properties tend to be stable after completing aromatic structure copolymerization, HS core densification, and HS "maturation" in sequence. At present, the HA formation theory includes the lignin hypothesis of lignin-protein synthesis condensation, the polyphenol hypothesis of lignin polyphenols oxidized to quinones and condensed with nitrogen-containing substances, the microbial synthesis hypothesis, and the sugar-amine condensation hypothesis. Among them, the polyphenol hypothesis has a higher degree of recognition. Some studies believe that oxygen-bonded non-protonated carbon (such as aromatic ketones), non-protonated alkyl CO, and abundant COOH groups are the characteristics of HA and FA, while the corresponding characteristics are not observed in plant biopolymers. HA is an important intermediate product in the degradation process of biological residues.

[0004] Chinese patent CN111171237A discloses a humic acid high-strength self-healing hydrogel and a preparation method thereof, comprising the following steps: 1) dissolving polyvinyl alcohol in water to obtain solution A; dissolving an initiator and a cross-linking agent in water to obtain solution B; 2) dissolving a humate and a hydrophilic monomer in water, and adding solution A at the same time to obtain solution C; the hydrophilic monomers are acrylic acid and acrylamide; 3) stirring and heating solution C continuously, and when the temperature rises to 50-70°C, adding solution B dropwise to solution C, and continuing the reaction for 4-8h to obtain a hydrogel; 4) freezing and preserving the hydrogel in step 3) and placing it at room temperature to complete the freeze-thaw cycle; 5) placing the hydrogel in step 4) in a Fe 3+ The humic acid high-strength self-healing hydrogel is obtained by soaking in the solution for 6 to 12 hours. The humic acid high-strength self-healing hydrogel described in the invention has high strength and self-healing ability, overcoming the constraints of insufficient mechanical strength and self-healing ability of hydrogel.

[0005] There is no humic acid hydrogel soil conditioner with excellent effect in the prior art. Summary of the invention

[0006] The purpose of the present invention is to provide a humic acid hydrogel soil conditioner, which can effectively improve the sandy soil structure, improve the soil organic carbon fixation capacity, achieve structural optimization and carbon fixation, store water and conserve moisture, and improve the utilization efficiency of nitrogen, phosphorus and potassium nutrients in farmland.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a humic acid hydrogel, comprising the following steps:

[0009] S1, mixing the soy sauce waste residue with KOH solution, dissolving and centrifuging to obtain a supernatant;

[0010] S2, ultrafiltration treatment of the supernatant to obtain a retained component;

[0011] S3, mixing the retained components with HCl solution to obtain humic acid;

[0012] S4, mixing humic acid, polyvinyl alcohol, acrylamide, chitosan and water, adding a crosslinking agent and an initiator, and performing a polymerization reaction to obtain a humic acid hydrogel.

[0013] Preferably, the soy sauce waste residue is dried before being mixed with the KOH solution.

[0014] Preferably, the dissolution time is 20 to 50 minutes;

[0015] The dissolving temperature is 40 to 80°C;

[0016] The weight ratio of the soy sauce waste residue to the volume of the KOH solution is 1 g: 10-30 mL;

[0017] The centrifugal speed is 1000-3000 rpm;

[0018] The centrifugation time is 20 to 40 minutes.

[0019] Preferably, the molecular weight cut-off of the ultrafiltration treatment is 1000Da;

[0020] The pH of the system after the intercepted component is mixed with the HCl solution is 1-2.

[0021] Preferably, the humic acid participates in the reaction in the form of a humic acid solution;

[0022] The solvent used in the humic acid solution is KOH solution;

[0023] The concentration of the KOH solution is 2-3 mol / L;

[0024] The weight ratio of humic acid to solvent in the humic acid solution is 1:8-10.

[0025] Preferably, the weight ratio of humic acid, polyvinyl alcohol, acrylamide and chitosan is 0.5-1.5:0.5-1.5:1.5-2.5:0.5-1.5;

[0026] The weight ratio of humic acid to cross-linking agent is 1:0.01-0.03;

[0027] The weight ratio of the humic acid to the initiator is 1:0.05-0.15.

[0028] Preferably, the cross-linking agent is N,N-methylenebisacryloyl;

[0029] The initiator is potassium persulfate;

[0030] The weight ratio of humic acid to water is 1:80-120;

[0031] The polymerization reaction temperature is 70 to 90°C;

[0032] The polymerization reaction time is 12 to 40 hours.

[0033] The invention also provides humic acid hydrogel prepared by the preparation method.

[0034] The present invention also provides application of the humic acid hydrogel as a soil conditioner.

[0035] Preferably, the field application amount of the humic acid hydrogel is 1 to 5 g / m 2.

[0036] The present invention also provides application of the humic acid hydrogel as a fertilizer synergist.

[0037] Technical effects and advantages of the present invention:

[0038] In the present invention, since humic acid is extracted from soy sauce waste residue, not only resource utilization is achieved, but the extracted humic acid also has the advantages of natural low environmental threat, especially low threat of heavy metal pollution, and has excellent agricultural application prospects.

[0039] The humic acid hydrogel provided by the present invention can be used for sandy soil improvement and effectively improves soil water retention. The humic acid hydrogel prepared by the present invention has excellent sustained release performance and is slowly released over a long period of time, thereby continuously regulating the soil environment, reducing the impact on the environment, improving the use effect, making the soil conditioning effect more durable and stable, and continuously promoting the N, P, K nutrient cycle. DETAILED DESCRIPTION

[0040] The present invention provides a method for preparing a humic acid hydrogel, comprising the following steps:

[0041] S1, mixing the soy sauce waste residue with KOH solution, dissolving and centrifuging to obtain a supernatant;

[0042] S2, ultrafiltration treatment of the supernatant to obtain a retained component;

[0043] S3, mixing the retained components with HCl solution to obtain humic acid;

[0044] S4, mixing humic acid, polyvinyl alcohol, acrylamide, chitosan and water, adding a crosslinking agent and an initiator, and performing a polymerization reaction to obtain a humic acid hydrogel.

[0045] In the present invention, preferably, the soy sauce waste residue is dried before being mixed with the KOH solution; preferably, the dissolution time is 20 to 50 minutes; the dissolution temperature is 40 to 80°C; the weight ratio of the soy sauce waste residue to the volume of the KOH solution is 1g:10 to 30mL; the centrifugal speed is 1000 to 3000rpm; the centrifugal time is 20 to 40min; preferably, the retention molecular weight of the ultrafiltration treatment is 1000Da; the pH of the system after the retained component is mixed with the HCl solution is 1 to 2.

[0046] In the present invention, preferably, the humic acid participates in the reaction in the form of a humic acid solution; the solvent used in the humic acid solution is a KOH solution; the concentration of the KOH solution is 2-3 mol / L; the weight ratio of humic acid to solvent in the humic acid solution is 1:8-10; preferably, the weight ratio of humic acid, polyvinyl alcohol, acrylamide and chitosan is 0.5-1.5:0.5-1.5:1.5-2.5:0.5-1.5; the weight ratio of humic acid to crosslinking agent is 1:0.01-0.03; the weight ratio of humic acid to initiator is 1:0.05-0.15. Preferably, the crosslinking agent is N,N-methylenebisacryl; the initiator is potassium persulfate; the weight ratio of humic acid to water is 1:80-120; the temperature of the polymerization reaction is 70-90; the time of the polymerization reaction is 12-40h.

[0047] The invention also provides humic acid hydrogel prepared by the preparation method.

[0048] The present invention also provides the use of the humic acid hydrogel as a soil conditioner, wherein the field application amount of the humic acid hydrogel is preferably 1 to 5 g / m 2 .

[0049] The present invention also provides the use of the humic acid hydrogel as a fertilizer synergist; the humic acid hydrogel can be mixed with other conventional fertilizers for application.

[0050] The soy sauce waste residue used in the specific embodiment of the present invention is a by-product of soy sauce processing using soybeans as raw materials, and mainly contains water, crude protein, crude fat, oil, fiber, sugar, phospholipids, etc.

[0051] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1

[0053] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 200 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 40 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0054] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.5, and a brown precipitate was humic acid prepared by the present invention.

[0055] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0056] Example 2

[0057] 10 g of the dried and crushed soy sauce waste residue was placed in a conical flask, 200 mL of 1 mol / L KOH solution was added, dissolved in a 55°C water bath for 40 min, and then cooled. After cooling, the supernatant was separated by centrifugation at 2000 rpm for 30 min.

[0058] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.5, and a brown precipitate was humic acid prepared by the present invention.

[0059] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0060] Example 3

[0061] 10 g of the dried and crushed soy sauce waste residue was placed in a conical flask, 200 mL of 1 mol / L KOH solution was added, dissolved in a 65°C water bath for 40 min, and then cooled. After cooling, the supernatant was separated by centrifugation at 2000 rpm for 40 min.

[0062] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 2, and a brown precipitate was precipitated, which was the humic acid prepared by the present invention.

[0063] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0064] Example 4

[0065] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 150 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 50 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0066] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.5, and a brown precipitate was humic acid prepared by the present invention.

[0067] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0068] Example 5

[0069] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 250 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 30 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0070] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.2, and a brown precipitate was humic acid prepared by the present invention.

[0071] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0072] Example 6

[0073] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 200 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 40 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0074] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 2, and a brown precipitate was precipitated, which was the humic acid prepared by the present invention.

[0075] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (3 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0076] Example 7

[0077] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 200 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 40 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0078] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.5, and a brown precipitate was humic acid prepared by the present invention.

[0079] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1.5 g of polyvinyl alcohol powder, 2.5 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0080] Example 8

[0081] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 200 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 40 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0082] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.5, and a brown precipitate was humic acid prepared by the present invention.

[0083] Accurately weigh 1.5 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1.5 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0084] Example 9

[0085] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 200 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 40 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0086] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.5, and a brown precipitate was humic acid prepared by the present invention.

[0087] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.01 g of cross-linking agent N,N-methylenebisacrylamide and 0.08 g of potassium persulfate, stir to mix evenly, and polymerize at 75°C for 20 h to obtain a humic acid hydrogel.

[0088] Example 10

[0089] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 200 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 40 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0090] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.5, and a brown precipitate was humic acid prepared by the present invention.

[0091] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.03 g of cross-linking agent N,N-methylenebisacrylamide and 0.12 g of potassium persulfate, stir to mix evenly, and polymerize at 85°C for 36 h to obtain a humic acid hydrogel.

[0092] Comparative Example 1

[0093] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 200 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 40 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0094] HCl solution was added to the obtained supernatant to adjust the pH to 1.5, and the precipitate was the humic acid prepared in this comparative example.

[0095] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 1 g of polyvinyl alcohol powder, 2 g of acrylamide powder, 1 g of chitosan powder, and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0096] Comparative Example 2

[0097] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 200 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 40 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0098] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.5, and a brown precipitate was humic acid prepared by the present invention.

[0099] Accurately weigh 1 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 4 g of polyvinyl alcohol powder and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir to mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0100] Comparative Example 3

[0101] Take 10 g of the dried and crushed soy sauce waste residue and place it in a conical flask, add 200 mL of 1 mol / L KOH solution, dissolve it in a 60°C water bath for 40 min, and then cool it. After cooling, centrifuge it at 2000 rpm for 30 min to separate the supernatant;

[0102] The obtained supernatant was passed through an ultrafiltration membrane (molecular weight cutoff: 1000Da), the membrane was washed with 50 mL of pure water to obtain the components retained on the membrane, HCl solution was added to adjust the pH to 1.5, and a brown precipitate was humic acid prepared by the present invention.

[0103] Accurately weigh 3 g of humic acid and add it to 9 g of KOH solution (2.5 mol / L), and stir magnetically to dissolve evenly to obtain a humic acid solution; add 2 g of acrylamide powder and 100 mL of distilled water into a reactor, heat to 70°C, add 0.02 g of cross-linking agent N,N-methylenebisacrylamide and 0.1 g of potassium persulfate, stir and mix evenly, and polymerize at 80°C for 24 h to obtain a humic acid hydrogel.

[0104] Experimental example

[0105] The humic acid hydrogels in Example 1 and Comparative Examples 1 to 3 were dried at 80° C. and crushed to obtain humic acid hydrogel soil conditioner products for easy application.

[0106] The experimental field was divided into five blocks, including one control group and four experimental groups. The experimental groups were treated with 2 g / m2 Apply the humic acid hydrogel soil conditioner in Example 1 and Comparative Examples 1 to 3, and till and mix evenly after application;

[0107] Peanuts were planted in each block. Conventional field water and fertilizer management measures were adopted during the experiment. The planting parameters and water and fertilizer application amounts of each group remained consistent.

[0108] After planting, random sampling was performed at a soil depth of 20 to 30 cm every 30 days (0, 30, 60, and 90 days) to test soil moisture content, organic matter (SOM) content, total nitrogen (TN) content, ammonium nitrogen (SN) content, available phosphorus (AP) content, and available potassium (AK) content. The test method is as follows:

[0109] Soil moisture content: calculated according to the following formula:

[0110] Soil moisture content = (original soil weight - oven-dried soil weight) / oven-dried soil weight × 100% = water weight / oven-dried soil weight × 100%.

[0111] After the soil to be tested is air-dried, the soil nutrient content is determined using the following test method:

[0112] Organic matter (SOM) content: potassium dichromate external heating method;

[0113] Total nitrogen (TN) content: Kjeldahl method;

[0114] Ammonium nitrogen (SN) content: 0.1 mol / LCaCl2 solution extraction-flow injection analyzer;

[0115] Available phosphorus (AP) content: sodium bicarbonate extraction-molybdenum antimony anti-absorption photometry;

[0116] Available potassium (AK) content: ammonium acetate extraction-flame photometer method.

[0117] The results are shown in Tables 1 to 6 below:

[0118] Table 1 Determination results of moisture content of sandy soil improvement (%)

[0119]

[0120] Table 2 Determination results of organic matter content in sandy soil improvement (g / kg)

[0121]

[0122] Table 3 Determination results of total nitrogen content in sandy soil improvement (g / kg)

[0123]

[0124] Table 4 Determination results of ammonium nitrogen content in sandy soil improvement (mg / kg)

[0125]

[0126]

[0127] Table 5 Determination results of available phosphorus content in sandy soil improvement (mg / kg)

[0128]

[0129] Table 6 Sandy soil improvement available potassium content determination results (mg / kg)

[0130]

[0131] The soil quality test results show that the humic acid hydrogel soil conditioner provided by the present invention can effectively improve the moisture content and nutrient content of sandy soil, quickly meet the standards for crop planting, and in the product of the present invention, a better sustained release effect can be achieved through the multi-component cross-linked network of humic acid hydrogel. During the entire growth period of the crop, it only needs to be applied before sowing, and a long-term soil improvement effect can be achieved without secondary supplementation. Compared with the comparative example and the control group, it has excellent use prospects in the agricultural field.

[0132] Peanuts were harvested 120 days after sowing, and the yield of each block was counted. The results are shown in Table 7 below:

[0133] Table 7 Peanut yield statistics (catties / m 2 )

[0134] Control group 0.62 Example 1 3.23 Comparative Example 1 1.09 Comparative Example 2 1.57 Comparative Example 3 1.94

[0135] Peanut planting experiments show that soil with high sand content without soil improvement is not conducive to crop growth due to poor water holding capacity. During the planting experiment, some plants died or had no yield. The humic acid hydrogel soil conditioner provided by the embodiment of the present invention can be slowly released over a long period of time, thereby continuously regulating the soil environment, reducing the impact on the environment, being more suitable for crop cultivation, improving the use effect, making the soil conditioning effect more lasting and stable, and continuously promoting the N, P, and K nutrient cycles to meet the growth needs of crops and obtain higher yields.

[0136] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing humic acid hydrogel, characterized in that: The following steps are involved: S1, mixing the soy sauce waste residue with KOH solution, dissolving and centrifuging to obtain a supernatant; S2, ultrafiltration treatment of the supernatant to obtain a retained component; S3, mixing the retained components with HCl solution to obtain humic acid; S4, mixing humic acid, polyvinyl alcohol, acrylamide, chitosan and water, adding a crosslinking agent and an initiator, and performing a polymerization reaction to obtain a humic acid hydrogel.

2. The method for preparing humic acid hydrogel according to claim 1, characterized in that: The soy sauce waste residue is dried before being mixed with the KOH solution.

3. The method for preparing humic acid hydrogel according to claim 1, characterized in that: The dissolution time is 20 to 50 minutes; The dissolving temperature is 40 to 80°C; The weight ratio of the soy sauce waste residue to the volume of the KOH solution is 1 g: 10-30 mL; The centrifugal speed is 1000-3000 rpm; The centrifugation time is 20 to 40 minutes.

4. The method for preparing humic acid hydrogel according to claim 1, characterized in that: The molecular weight cut-off of the ultrafiltration treatment is 1000Da; The pH of the system after the intercepted component is mixed with the HCl solution is 1-2.

5. The method for preparing humic acid hydrogel according to claim 1, characterized in that: In S4, the humic acid participates in the reaction in the form of a humic acid solution; The solvent used in the humic acid solution is KOH solution; The concentration of the KOH solution is 2-3 mol / L; The weight ratio of humic acid to solvent in the humic acid solution is 1:8-10.

6. The method for preparing humic acid hydrogel according to claim 1, characterized in that: The weight ratio of humic acid, polyvinyl alcohol, acrylamide and chitosan is 0.5-1.5:0.5-1.5:1.5-2.5:0.5-1.5; The weight ratio of humic acid to cross-linking agent is 1:0.01-0.03; The weight ratio of humic acid to initiator is 1:0.05-0.15; The cross-linking agent is N,N-methylenebisacryloyl; The initiator is potassium persulfate; The weight ratio of humic acid to water is 1:80-120; The polymerization reaction temperature is 70 to 90°C; The polymerization reaction time is 12 to 40 hours.

7. Humic acid hydrogel prepared by the preparation method according to any one of claims 1 to 7.

8. Use of the humic acid hydrogel according to claim 7 as a soil conditioner.

9. The field application rate of the humic acid hydrogel is 1-5 g / m 2 .

10. Use of the humic acid hydrogel according to claim 7 as a fertilizer synergist.

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