Preparation method and application of soda saline-alkali soil modifier of sulfate radical intercalated dolomite
By subjecting dolomite to acidification pretreatment, hydrothermal reaction, and sulfonation, a soda saline-alkali soil conditioner with sulfate-intercalated dolomite was prepared. This solved the solubility problem of natural dolomite and addressed the technical issues that were not effectively addressed in existing technologies. The acidification technique was adopted, and this highly efficient soda saline-alkali soil conditioner, utilizing existing conditioners, was developed. This highly efficient conditioner significantly reduced the pH value of the soil, increased the ion exchange capacity, and achieved a long-term improvement effect on soda saline-alkali soil.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-16
- Publication Date
- 2026-04-10
AI Technical Summary
Natural dolomite has extremely low solubility, making direct application almost ineffective. Existing amendments are costly or pose a risk of secondary pollution, making it difficult to effectively improve soda saline-alkali soil.
Sulfate-intercalated dolomite is prepared by acidification pretreatment, hydrothermal reaction and sulfonation treatment of dolomite, forming a soil conditioner with strong acidity and continuous sulfate release capacity, which is used to replace sodium ions in soil and neutralize alkalinity.
It significantly reduces soil pH, increases ion exchange capacity, achieves long-term improvement effect, synergistically enhances the improvement effect on soda saline-alkali soil, reduces costs and avoids short-term failure.
Smart Images
Figure CN121825554A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of soil improvement and environmental protection technology, specifically relating to a method for preparing a soda saline-alkali soil conditioner and its application. Background Technology
[0002] Soda-saline-alkali soil is a major type of low- to medium-yield farmland soil in arid and semi-arid regions of northern my country. It is characterized by a high soil pH (reaching above 9.0), high levels of sodium carbonate and sodium bicarbonate, and a large amount of exchangeable sodium ions adsorbed on soil colloids. The high pH and sodium ion toxicity severely inhibit crop absorption of nutrients and water, leading to stunted crop growth.
[0003] Currently, the common method for improving soda-alkali soil is to apply gypsum (CaSO4·2H2O), which, through the action of Ca... 2+ Replace Na in the soil + and utilize SO4 2- Reducing soil alkalinity is important. However, natural gypsum has low solubility, resulting in slow improvement and requiring large-scale application, leading to high costs. Other chemical amendments, such as aluminum sulfate and ferrous sulfate, are faster-acting but also expensive, and long-term, large-scale use may pose a risk of secondary pollution.
[0004] Dolomite is a naturally abundant carbonate mineral (CaMg(CO3)2) with advantages such as wide availability and low cost. It contains calcium and magnesium, theoretically making it a potential calcium source for improving saline-alkali soils. However, natural dolomite has extremely low solubility, rendering direct application almost ineffective. Therefore, a low-cost, high-efficiency activation modification of dolomite to rapidly release calcium is needed. 2+ Mg 2+ Neutralizing soil alkalinity is key to its application in saline-alkali soil improvement. Summary of the Invention
[0005] The purpose of this invention is to solve the technical problem that natural dolomite has extremely low solubility and is almost ineffective when applied directly. This invention provides a method for preparing a soda saline-alkali soil conditioner based on sulfate-intercalated dolomite and its application.
[0006] The preparation method of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner is as follows:
[0007] I. Acidification Pretreatment of Dolomite
[0008] Take 0.1g-2g of dolomite powder, soak it in 60 mL of 1 mol / L dilute sulfuric acid solution, let it stand for 12 hours to obtain acidic mother liquor;
[0009] II. Hydrothermal Reaction
[0010] Add 0.1g-4g of aluminum sulfate to the acidic mother liquor obtained in step one, stir until completely dissolved, add 1g of thiourea, stir until completely dissolved, and obtain a mixture. Transfer the mixture to a hydrothermal reactor lined with polytetrafluoroethylene, place it in an explosion-proof oven, react at 180°C for 20 hours, cool to room temperature, separate the precipitate, wash and dry to obtain the hydrothermal product.
[0011] Under these conditions, thiourea slowly hydrolyzes to produce ammonium sulfate and carbon dioxide, while aluminum salts hydrolyze in the acidic mother liquor to produce hydroxyaluminum sulfate ions with polymeric structures. These ions can be inserted into the layered structure of the pretreated dolomite or form a coating on its surface, achieving "sulfate intercalation".
[0012] III. Sulfonation treatment (surface functionalization and acid site reinforcement):
[0013] The hydrothermal product obtained in step two was immersed in 20 mL of p-toluenesulfonic acid-ethanol solution and refluxed at 60 °C for 6 hours.
[0014] The p-toluenesulfonic acid-ethanol solution has a p-toluenesulfonic acid mass concentration of 10%.
[0015] This process involves esterification or direct coordination of sulfonic acid groups with hydroxyl groups on the material surface, fixing the strongly acidic sulfonic acid groups on the material surface and between layers, thereby significantly enhancing its surface acidity, ion exchange capacity, and continuous supply of sulfate ions.
[0016] IV. After the reflux in step three is completed, the solid product is separated and washed with ethanol 2-3 times to remove unreacted sulfonic acid agent. It is then dried at 60-80℃ to finally obtain continuously acidified sulfate-intercalated dolomite, i.e., sulfate-intercalated dolomite as a soda saline-alkali soil conditioner.
[0017] The sulfate-intercalated dolomite-based soda saline-alkali soil conditioner is used for soil improvement of soda saline-alkali soil.
[0018] This invention addresses the impact of soda saline-alkali soil on crop growth by preparing a simple, low-cost, and highly effective sulfate-intercalated dolomite-based soil conditioner. The invention synthesizes a sulfate-intercalated dolomite composite material through sequential acidification, hydrothermal reaction, and sulfonation treatments, effectively improving soda saline-alkali soil, reducing soil pH, and enriching its microbial community structure.
[0019] This invention primarily utilizes sulfate intercalation in dolomite to regulate the carbonate and sodium ion concentrations in soda-alkali soil through sulfate release. Furthermore, the introduction of sulfonation treatment enhances the sustained sulfate release performance of the composite material, resulting in the following significant advantages:
[0020] (1) Increased ion exchange capacity: The surface sulfonic acid groups provide a large amount of exchangeable H+.+ It can more efficiently replace Na on soil colloids. + This will accelerate the soil improvement process.
[0021] (2) Structural stability and long-term effectiveness: The sulfate and sulfonic acid groups on the chemically bonded surface and intercalated layer are not easily leached, which allows the amendment to play a longer-term role in the soil environment and avoids short-term failure.
[0022] (3) Synergistic effect: This invention achieves the synergy of "interlayer intercalation modification" and "surface functionalization". The sulfate groups in the interlayer and the sulfonic acid groups on the surface jointly construct a multi-functional system from the inside to the outside, realizing the synergistic enhancement effect of pH reduction, sodium ion replacement and structural improvement of soda saline-alkali soil. Attached Figure Description
[0023] Figure 1 The images show SEM images of the sulfate-intercalated dolomite-based soda-alkali soil conditioners prepared in Examples 1-6. In the images, a represents the SEM image of the sulfate-intercalated dolomite-based soda-alkali soil conditioner prepared in Example 6; b represents the SEM image of the sulfate-intercalated dolomite-based soda-alkali soil conditioner prepared in Example 1; c represents the SEM image of the sulfate-intercalated dolomite-based soda-alkali soil conditioner prepared in Example 2; d represents the SEM image of the sulfate-intercalated dolomite-based soda-alkali soil conditioner prepared in Example 3; e represents the SEM image of the sulfate-intercalated dolomite-based soda-alkali soil conditioner prepared in Example 4; and f represents the SEM image of the sulfate-intercalated dolomite-based soda-alkali soil conditioner prepared in Example 5.
[0024] Figure 2 The XRD patterns of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioners prepared in Examples 4-5 are shown in the figures. 1g of dolomite represents the XRD pattern of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner prepared in Example 4, and 2g of dolomite represents the XRD pattern of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner prepared in Example 5.
[0025] Figure 3 FT-IR images of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner from Examples 1, 4, and 5;
[0026] Figure 4 The graph shows the change in soil pH after improvement with the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner prepared in Example 4.
[0027] Figure 5 Comparison of soil pH changes after improvement with the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner prepared in Examples 4 and 5. Detailed Implementation
[0028] Example 1:
[0029] The preparation method of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner is as follows:
[0030] I. Acidification Pretreatment of Dolomite
[0031] Take 0.1 g of dolomite powder, soak it in 60 mL of 1 mol / L dilute sulfuric acid solution, let it stand for 12 hours to obtain acidic mother liquor;
[0032] II. Hydrothermal Reaction
[0033] Add 0.1g of aluminum sulfate to the acidic mother liquor obtained in step one, stir until completely dissolved, add 1g of thiourea, stir until completely dissolved, and obtain a mixture. Transfer the mixture to a hydrothermal reactor lined with polytetrafluoroethylene, place it in an explosion-proof oven, react at 180°C for 20 hours, cool to room temperature, separate the precipitate, wash and dry to obtain the hydrothermal product.
[0034] III. Sulfonation treatment (surface functionalization and acid site reinforcement):
[0035] The hydrothermal product obtained in step two was immersed in 20 mL of p-toluenesulfonic acid-ethanol solution and refluxed at 60 °C for 6 hours.
[0036] The p-toluenesulfonic acid-ethanol solution has a p-toluenesulfonic acid mass concentration of 10%.
[0037] IV. After the reflux in step three is completed, the solid product is separated and washed with ethanol 2-3 times to remove unreacted sulfonic acid agent. It is then dried at 60°C to finally obtain continuously acidified sulfate-intercalated dolomite, namely, the soda saline-alkali soil conditioner of sulfate-intercalated dolomite (Al2(SO4)3 0.1g-HCl).
[0038] Example 2:
[0039] The preparation method of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner is as follows:
[0040] I. Acidification Pretreatment of Dolomite
[0041] Take 2 g of dolomite powder, soak it in 60 mL of 1 mol / L dilute sulfuric acid solution, let it stand for 12 hours to obtain acidic mother liquor;
[0042] II. Hydrothermal Reaction
[0043] Add 0.25 g of aluminum sulfate to the acidic mother liquor obtained in step one, stir until completely dissolved, add 1 g of thiourea, stir until completely dissolved, and obtain a mixture. Transfer the mixture to a hydrothermal reactor lined with polytetrafluoroethylene, place it in an explosion-proof oven, react at 180°C for 20 hours, cool to room temperature, separate the precipitate, wash and dry to obtain the hydrothermal product.
[0044] III. Sulfonation treatment (surface functionalization and acid site reinforcement):
[0045] The hydrothermal product obtained in step two was immersed in 20 mL of p-toluenesulfonic acid-ethanol solution and refluxed at 60 °C for 6 hours.
[0046] The p-toluenesulfonic acid-ethanol solution has a p-toluenesulfonic acid mass concentration of 10%.
[0047] IV. After the reflux in step three is completed, the solid product is separated and washed with ethanol 2-3 times to remove unreacted sulfonic acid agent. It is then dried at 70°C to finally obtain continuously acidified sulfate-intercalated dolomite, which is a soda saline-alkali soil conditioner for sulfate-intercalated dolomite.
[0048] Example 3:
[0049] The preparation method of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner is as follows:
[0050] I. Acidification Pretreatment of Dolomite
[0051] Take 2 g of dolomite powder, soak it in 60 mL of 1 mol / L dilute sulfuric acid solution, let it stand for 12 hours to obtain acidic mother liquor;
[0052] II. Hydrothermal Reaction
[0053] Add 0.5g of aluminum sulfate to the acidic mother liquor obtained in step one, stir until completely dissolved, add 1g of thiourea, stir until completely dissolved, and obtain a mixture. Transfer the mixture to a hydrothermal reactor lined with polytetrafluoroethylene, place it in an explosion-proof oven, react at 180°C for 20 hours, cool to room temperature, separate the precipitate, wash and dry to obtain the hydrothermal product.
[0054] III. Sulfonation treatment (surface functionalization and acid site reinforcement):
[0055] The hydrothermal product obtained in step two was immersed in 20 mL of p-toluenesulfonic acid-ethanol solution and refluxed at 60 °C for 6 hours.
[0056] The p-toluenesulfonic acid-ethanol solution has a p-toluenesulfonic acid mass concentration of 10%.
[0057] IV. After the reflux in step three is completed, the solid product is separated and washed with ethanol 2-3 times to remove unreacted sulfonic acid agent. It is then dried at 80°C to finally obtain continuously acidified sulfate-intercalated dolomite, which is a soda saline-alkali soil conditioner for sulfate-intercalated dolomite.
[0058] Example 4:
[0059] The preparation method of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner is as follows:
[0060] I. Acidification Pretreatment of Dolomite
[0061] Take 1g of dolomite powder and soak it in 60 mL of 1 mol / L dilute sulfuric acid solution. Let it stand for 12 hours to obtain an acidic mother liquor.
[0062] II. Hydrothermal Reaction
[0063] Add 1g of aluminum sulfate to the acidic mother liquor obtained in step one and stir until completely dissolved. Add 1g of thiourea and stir until completely dissolved to obtain a mixture. Transfer the mixture to a hydrothermal reactor lined with polytetrafluoroethylene and place it in an explosion-proof oven. React at 180°C for 20 hours and then cool to room temperature. Separate the precipitate, wash and dry it to obtain the hydrothermal product.
[0064] III. Sulfonation treatment (surface functionalization and acid site reinforcement):
[0065] The hydrothermal product obtained in step two was immersed in 20 mL of p-toluenesulfonic acid-ethanol solution and refluxed at 60 °C for 6 hours.
[0066] The p-toluenesulfonic acid-ethanol solution has a p-toluenesulfonic acid mass concentration of 10%.
[0067] IV. After the reflux in step three is completed, the solid product is separated and washed with ethanol 2-3 times to remove unreacted sulfonic acid agent. It is then dried at 60°C to finally obtain continuously acidified sulfate-intercalated dolomite, namely, the soda saline-alkali soil conditioner of sulfate-intercalated dolomite (Al2(SO4)3 1.0g-HCl).
[0068] Example 5:
[0069] The preparation method of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner is as follows:
[0070] I. Acidification Pretreatment of Dolomite
[0071] Take 2 g of dolomite powder, soak it in 60 mL of 1 mol / L dilute sulfuric acid solution, let it stand for 12 hours to obtain acidic mother liquor;
[0072] II. Hydrothermal Reaction
[0073] Add 2g of aluminum sulfate to the acidic mother liquor obtained in step one and stir until completely dissolved. Add 1g of thiourea and stir until completely dissolved to obtain a mixture. Transfer the mixture to a hydrothermal reactor lined with polytetrafluoroethylene and place it in an explosion-proof oven. React at 180°C for 20 hours and then cool to room temperature. Separate the precipitate, wash and dry it to obtain the hydrothermal product.
[0074] III. Sulfonation treatment (surface functionalization and acid site reinforcement):
[0075] The hydrothermal product obtained in step two was immersed in 20 mL of p-toluenesulfonic acid-ethanol solution and refluxed at 60 °C for 6 hours.
[0076] The p-toluenesulfonic acid-ethanol solution has a p-toluenesulfonic acid mass concentration of 10%.
[0077] IV. After the reflux in step three is completed, the solid product is separated and washed with ethanol 2-3 times to remove unreacted sulfonic acid agent. It is then dried at 70°C to finally obtain continuously acidified sulfate-intercalated dolomite, namely, the soda saline-alkali soil conditioner of sulfate-intercalated dolomite (Al2(SO4)32.0g-HCl).
[0078] Through SEM images ( Figure 1 It can be observed that the composite material formed by the hydrothermal reaction of acidified dolomite and aluminum sulfate exhibits a nano-sized two-dimensional morphology, with a thin, lamellar structure attached to the surface. This is due to the formation of new phases inside and on the surface of the dolomite. XRD results ( Figure 2 Further confirmation revealed that after acidification and the hydrothermal reaction of aluminum sulfate, well-crystallized calcium sulfate precipitate formed in the composite material. Compared with the characteristic diffraction peaks of dolomite, the diffraction peaks of calcium sulfate were dominant, indicating that anion exchange occurred in the dolomite during the modification process, and sulfate ions successfully intercalated into the dolomite structure, thereby forming a new mineral precipitate. This provides a material basis for the slow release of sulfate ions during soil improvement.
[0079] In addition, FT-IR spectroscopy ( Figure 3 The data showed that there was a distinct sulfate characteristic absorption peak on the surface of the composite material, and the absorption peak intensity shifted significantly with the increase of aluminum sulfate addition, indicating that sulfate ions had inserted into the dolomite interlayer during the hydrothermal reaction, causing changes in its original mineral structure.
[0080] Example 6:
[0081] The preparation method of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner is as follows:
[0082] I. Acidification Pretreatment of Dolomite
[0083] Take 2 g of dolomite powder, soak it in 60 mL of 1 mol / L dilute sulfuric acid solution, let it stand for 12 hours to obtain acidic mother liquor;
[0084] II. Hydrothermal Reaction
[0085] Add 4g of aluminum sulfate to the acidic mother liquor obtained in step one and stir until completely dissolved. Add 1g of thiourea and stir until completely dissolved to obtain a mixture. Transfer the mixture to a hydrothermal reactor lined with polytetrafluoroethylene and place it in an explosion-proof oven. React at 180°C for 20 hours and then cool to room temperature. Separate the precipitate, wash and dry it to obtain the hydrothermal product.
[0086] III. Sulfonation treatment (surface functionalization and acid site reinforcement):
[0087] The hydrothermal product obtained in step two was immersed in 20 mL of p-toluenesulfonic acid-ethanol solution and refluxed at 60 °C for 6 hours.
[0088] The p-toluenesulfonic acid-ethanol solution has a p-toluenesulfonic acid mass concentration of 10%.
[0089] IV. After the reflux in step three is completed, the solid product is separated and washed with ethanol 2-3 times to remove unreacted sulfonic acid agent. It is then dried at 80°C to finally obtain continuously acidified sulfate-intercalated dolomite, which is a soda saline-alkali soil conditioner for sulfate-intercalated dolomite.
[0090] Example 7:
[0091] Experiments were conducted using sulfate-intercalated dolomite as a soda saline-alkali soil conditioner, biochar, and iron tailings to improve soil, prepared according to Examples 1, 4, and 5.
[0092] Soil conditioner is added to each acre of land at a ratio of 0.5% (by weight).
[0093] Soil improvement experiments showed that adding a sodium bicarbonate-intercalated dolomite soil conditioner could significantly reduce soil pH. Figure 4 Compared to the control group, the soil pH decreased by 1.31 after treatment with the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner. Meanwhile, the amount of aluminum sulfate added during the preparation of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner had a significant impact on the treatment effect. Figure 5The optimal effect on soda-alkali soil improvement was observed when the aluminum sulfate dosage was 1 g (corresponding to 1 g of modified dolomite), with a soil pH decrease of up to 2.51. Notably, as the aluminum sulfate dosage increased, the pH of the soda-alkali soil conditioner with sulfate-intercalated dolomite gradually decreased (Table 1). This phenomenon further illustrates that the soil-improving effect of modified dolomite stems not only from its inherent acidity but also from the continuous release of intercalated sulfate ions in the soil, thus achieving a long-term improvement effect on saline-alkali soil.
[0094] Table 1
[0095]
[0096]
[0097] The biological agent fertilizer, produced by Shandong Future Biotechnology Co., Ltd., contains Bacillus lateralis, Bacillus subtilis and Bacillus mucilaginosa, with a total number of beneficial live bacteria ≥10×10⁹ CFU / mL.
[0098] The novel composite modifier is composed of bacterial bran, gypsum, and aluminum sulfate in a mass ratio of 15:15:9.
[0099] The tuff rock amendment is tuff rock, whose main component is quartz (i.e., SiO2), and also contains albite [Na(AlSi3O8)], orthoclase [K(AlSi3O8)] and clinoptilolite (CaAl2Si2O8·4H2O).
Claims
1. A method for preparing a soda-based saline-alkali soil conditioner using sulfate-intercalated dolomite, characterized in that... The preparation method of the sulfate-intercalated dolomite soda saline-alkali soil conditioner is as follows: I. Acidification Pretreatment of Dolomite Take 0.1g-2g of dolomite powder, soak it in 60 mL of 1 mol / L dilute sulfuric acid solution, let it stand for 12 hours to obtain acidic mother liquor; II. Hydrothermal Reaction Add 0.1g-4g of aluminum sulfate to the acidic mother liquor obtained in step one, stir until completely dissolved, add 1g of thiourea, stir until completely dissolved, and obtain a mixture. Transfer the mixture to a hydrothermal reactor lined with polytetrafluoroethylene, place it in an explosion-proof oven, react at 180°C for 20 hours, cool to room temperature, separate the precipitate, wash and dry to obtain the hydrothermal product. III. Sulfonation treatment: The hydrothermal product obtained in step two was immersed in 20 mL of p-toluenesulfonic acid-ethanol solution and refluxed at 60 °C for 6 hours. The p-toluenesulfonic acid-ethanol solution has a p-toluenesulfonic acid mass concentration of 10%. IV. After the reflux in step three is completed, the solid product is separated, washed with ethanol 2-3 times, and dried at 60-80℃ to finally obtain continuously acidified sulfate-intercalated dolomite, that is, sulfate-intercalated dolomite as a soda saline-alkali soil conditioner.
2. The method for preparing the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner according to claim 1, characterized in that... Add 0.1g of aluminum sulfate in step two.
3. The method for preparing the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner according to claim 1, characterized in that... Add 0.25g of aluminum sulfate in step two.
4. The method for preparing the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner according to claim 1, characterized in that... Add 0.5g of aluminum sulfate in step two.
5. The method for preparing the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner according to claim 1, characterized in that... Add 1g of aluminum sulfate in step two.
6. The method for preparing the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner according to claim 1, characterized in that... Add 2g of aluminum sulfate in step two.
7. The method for preparing the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner according to claim 1, characterized in that... Add 4 g of aluminum sulfate in step two.
8. The application of the sulfate-intercalated dolomite-based soda saline-alkali soil conditioner according to claim 1, characterized in that... The sulfate-intercalated dolomite-based soda saline-alkali soil conditioner is used for soil improvement of soda saline-alkali soil.