A phosphogypsum-based water-locking and temperature-regulating modifier for saline-alkali land, its preparation method and application
The integrated core-shell-bridge soil conditioner solves the compatibility and adaptability issues of phosphogypsum in saline-alkali land improvement, realizes the high-value utilization of phosphogypsum and the long-term improvement of saline-alkali land, improves soil water retention and bacterial agent survival rate, and reduces improvement costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA MINMETALS CHANGSHA MINING RES INST
- Filing Date
- 2026-02-10
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies for treating phosphogypsum and improving saline-alkali land are difficult to balance scalability, functionality, and economy. Phosphogypsum has low activity, long improvement cycles, short-lived effects, and lacks adaptability to different scenarios. Existing amendments are prone to leakage and loss, microbial agents have low survival rates, and the improvement effect is prone to rebound.
A core-shell-bridge integrated modifier is adopted, which achieves targeted alkali adjustment, long-term water retention and temperature-sensitive adaptation by targeting and activating the three-layer composite structure of phosphogypsum, phase change wax and compound microbial agent. The core-shell-bridge integrated modifier is constructed by using modified paraffin, bentonite, sodium alginate and other materials to form a stable structure, thereby enhancing the activity of phosphogypsum and the survival rate of microbial agent.
It has realized the high-value utilization of phosphogypsum. The water retention rate of the soil conditioner in arid saline-alkali land has increased by 45%, the survival rate of the microbial agent has increased to 75%, the soil pH is stable after improvement, the salt return rate has been reduced to below 5%, and the cost has been reduced by 50%.
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Abstract
Description
Technical Field
[0001] This invention relates to the fields of phosphogypsum solid waste utilization and saline-alkali land improvement technology, and in particular to a phosphogypsum-based saline-alkali land water-locking and temperature-regulating improver, its preparation method and application. Background Technology
[0002] The current treatment of phosphogypsum and the improvement of saline-alkali land face a dual technical dilemma, and existing solutions are difficult to balance scalability, functionality and economy.
[0003] On the one hand, the disposal of phosphogypsum presents significant challenges. my country's annual phosphogypsum emissions exceed 80 million tons, with a cumulative stockpile of over 600 million tons, occupying more than 50,000 mu of land. Its natural acidity (pH 1.5-3.5) makes open-air stockpiling prone to soil acidification and groundwater pollution, and single neutralization treatment requires an additional investment of 50-80 yuan per ton; the comprehensive utilization rate is less than 40%, lower than the required target of 60%, and existing disposal methods are mostly landfill or low-value building material utilization, failing to achieve deep integration with the function of saline-alkali land improvement.
[0004] On the other hand, existing saline-alkali land improvement technologies have core flaws. Related technologies involve simple compounding without synergy, merely mechanically mixing phosphogypsum, phase change materials, and microbial agents. This fails to address the contradictions between the acidity of phosphogypsum and the survival of microbial agents, the hydrophobicity and leakage of phase change materials, and the speed of alkali adjustment and long-term effectiveness. The functions are fragmented, and the effects are prone to rebound after 1-2 years. Furthermore, phosphogypsum has low activity, often being directly crushed or simply steam-pressurized, resulting in low Ca... 2+ It has a slow release rate, with an improvement cycle of 3-6 months, and is prone to precipitation by combining with soil ions, resulting in a short-lived alkalinity adjustment effect. It also has poor adaptability to different scenarios; general-purpose soil conditioners do not consider the combined problems of "water shortage + large temperature difference + wind erosion" in arid saline-alkali land, only addressing the salinity issue and failing to address water loss and soil desertification. Furthermore, it lacks a core structural design; the phase change material and phosphogypsum are not chemically bonded, leading to easy leakage and loss, rapid decline in water retention and temperature regulation effects, and a survival rate of ≤30% for the microbial agent in acidic environments after 30 days.
[0005] The National Territorial Spatial Planning Outline calls for the large-scale utilization of phosphogypsum and emphasizes the comprehensive improvement of saline-alkali land. Currently, there is a lack of technology that can address the issues of "component incompatibility, fragmented effects, insufficient long-term effectiveness, and poor adaptability to various scenarios" through structural restructuring and mechanism innovation. Therefore, there is an urgent need to develop new technologies for the utilization of phosphogypsum solid waste and the improvement of saline-alkali land to fill this technological gap. Summary of the Invention
[0006] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention provides a phosphogypsum-based water-locking and temperature-regulating amendment for saline-alkali land. The purpose of this invention is to overcome the limitations of simple compound formulations in existing technologies, and through structural reconstruction, mechanism innovation, and scenario adaptation, provide a core-shell-bridge integrated amendment that achieves four synergistic functions: targeted alkali regulation, long-lasting water locking, temperature-sensitive adaptation, and biological synergistic effect. This solves the core technical problems of poor compatibility, easy salinization, and weak adaptability in saline-alkali land improvement.
[0007] The present invention also provides a method for preparing the modifier and its application.
[0008] In a first aspect, the present invention provides a phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver, the raw material components of which, by mass fraction, include: 70-80 parts of dihydrate phosphogypsum, 5-8 parts of potassium magnesium sulfate composite salt, 6-10 parts of modified paraffin, 3-5 parts of bentonite, 2-4 parts of modified humic acid, 1-2 parts of sodium alginate, 0.5-1 part of modified water-retaining agent, 0.5-1.5 parts of composite bacterial agent, and 8-12 parts of water;
[0009] The modifier has a core-shell-bridge three-layer composite structure, with the core layer containing targeted activated phosphogypsum, the shell layer containing phase change wax, and the bridge layer containing bridging composite bacterial agents.
[0010] The phosphogypsum-based water-locking and temperature-regulating amendment for saline-alkali land provided by this invention is suitable for severely saline-alkali land in arid / semi-arid regions (soil pH 9.5~10.5, salinity 2.5~3.5g / kg, moisture content ≤8%, wind speed ≥3m / s). This invention targets dihydrate phosphogypsum collected from phosphate chemical enterprises and constructs a core-shell-bridge three-layer composite structure through a targeted activation-structural composite-synergistic enhancement process, achieving organic compatibility and functional progression of each component.
[0011] According to some embodiments of the present invention, the modified paraffin is a carboxyl-modified paraffin, wherein the content of grafted carboxyl groups is 3wt% to 10wt%.
[0012] According to some embodiments of the present invention, the phase change wax loading rate of the shell layer is ≥90%.
[0013] According to some embodiments of the present invention, the compound microbial agent comprises phosphate-solubilizing bacteria and nitrogen-fixing bacteria, wherein the mass ratio of phosphate-solubilizing bacteria to nitrogen-fixing bacteria is (1~2):1, and the effective viable count is ≥2×10⁻⁶. 8 CFU / g.
[0014] According to some embodiments of the present invention, the pH of the dihydrate phosphogypsum is 1.5 to 3.5.
[0015] According to some embodiments of the present invention, the bentonite contains ≥85% montmorillonite and has an expansion ratio ≥20 times.
[0016] According to some embodiments of the present invention, the modified humic acid contains ≥70wt% humic acid.
[0017] According to some embodiments of the present invention, the viscosity of the sodium alginate is ≥200 mPa·s.
[0018] A second aspect of the present invention provides a method for preparing a phosphogypsum-based saline-alkali soil water-locking and temperature-regulating modifier as described in the first aspect of the present invention, comprising the following steps:
[0019] S1. Mix dihydrate phosphogypsum with potassium magnesium sulfate, steam-activate, cool and then pulverize to a particle size ≤0.15mm to obtain targeted activated phosphogypsum cores;
[0020] S2. Modified paraffin is heated and melted, bentonite is added, and the mixture is stirred to obtain a composite phase change slurry. Targeted activated phosphogypsum core is added, and the mixture is stirred to obtain a core-shell intermediate.
[0021] S3. Mix modified humic acid, sodium alginate and water, stir at 70~90℃ to obtain bridging slurry, add compound bacterial agent and modified water-retaining agent and mix, then add core-shell intermediate and stir to obtain core-shell-bridge structure modifier, which is phosphogypsum-based saline-alkali soil water-locking and temperature-regulating modifier.
[0022] According to some embodiments of the present invention, in step S1, the steam activation treatment is performed at 100~120℃ and 0.1~0.2MPa for 1~2 hours.
[0023] According to some embodiments of the present invention, the specific surface area of the targeted activated phosphogypsum core is ≥45 m². 2 / g.
[0024] According to some embodiments of the present invention, in step S2, the temperature of the composite phase change slurry is 80~90°C.
[0025] According to some embodiments of the present invention, in step S2, the stirring to obtain the core-shell intermediate is carried out by stirring at a speed of 150~250 rpm for 30~50 min.
[0026] According to some embodiments of the present invention, in step S3, the pH of the bridging slurry is adjusted to 6.8~7.2 after it is obtained.
[0027] According to some embodiments of the present invention, in step S3, after obtaining the modifier with a core-shell-bridge structure, a drying treatment is performed at 50~60°C.
[0028] The third invention provides the application of the phosphogypsum-based saline-alkali soil water-locking and temperature-regulating amendment as described in the first aspect of the invention in the improvement of saline-alkali soil, wherein the application involves spreading the amendment on the saline-alkali soil, tilling and watering.
[0029] According to some embodiments of the present invention, the pH of the saline-alkali soil is 9.5~10.5, the salinity is 2.5~3.5g / kg, and the wind speed is 3~5m / s.
[0030] According to some embodiments of the present invention, the dosage of the amendment is 300-600 kg / mu, and the tillage depth is 15-25 cm.
[0031] According to some embodiments of the present invention, the application also includes planting salt-tolerant crops in 10 days; the salt-tolerant crops include sunflower and Suaeda salsa.
[0032] According to some embodiments of the present invention, in the application, the survival rate of the microbial agent is ≥75% after 30 days, the pH of the improved soil is 7.5~8.5, and the salinity return rate is ≤5% after 1 year.
[0033] The beneficial effects of this invention are:
[0034] (1) This invention breaks through the compatibility problem through structural innovation. Specifically, it utilizes a three-layer structure of "core-shell-bridge" to fundamentally solve the core contradiction of "acidity of phosphogypsum-survival of bacterial agent-leakage of phase change wax", achieving a phase change wax loading rate of ≥90% and a 30-day survival rate of bacterial agent of ≥75%. This effect of the organic whole of this invention cannot be achieved by existing technologies.
[0035] (2) This invention utilizes mechanism innovation to achieve progressive synergy. This invention pioneers a triple progressive mechanism of "alkalinity adjustment → water retention → efficiency enhancement" to achieve Ca 2+ Rapid replacement of Na + (Salinity reaches standard in 15 days), phase change wax + water-retaining agent locks in moisture (water retention rate increases by 40%), and bacterial agent inhibits salt return for a long time (salt return rate ≤5% in 1 year), achieving an unexpected effect of 1+1+1>3;
[0036] (3) The present invention has strong scene adaptability and specifically solves the technical problems of "water shortage + wind and sand + large temperature difference" in arid areas, achieving a 45% increase in soil water holding capacity. The modifier of the present invention can form wind erosion resistant aggregates, and the temperature-sensitive response stabilizes the soil temperature. Its adaptability is far superior to that of general-purpose modifiers.
[0037] (4) This invention also has the effect of economic and environmental protection win-win. It can realize 100% high-value disposal of phosphogypsum and modification and recycling of industrial waste wax. The improvement cost per mu is only 320-380 yuan, which is more than 50% lower than chemical improvers, and there is no secondary pollution problem.
[0038] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description
[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:
[0040] Figure 1 This is a schematic diagram of the preparation process of the core-shell-bridge integrated modifier according to an embodiment of the present invention. Detailed Implementation
[0041] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.
[0042] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0043] The raw material components and their related information in the examples are shown in Table 1 below:
[0044] Example 1
[0045] This embodiment provides a phosphogypsum-based saline-alkali soil water-locking and temperature-regulating modifier—a core-shell-bridge integrated modifier—and its preparation method.
[0046] The raw material ratio of the core-shell-bridge integrated modifier in this embodiment is as follows by mass: 75 parts phosphogypsum dihydrate, 6 parts potassium magnesium sulfate compound salt, 8 parts modified paraffin, 4 parts bentonite, 3 parts modified humic acid, 1.5 parts sodium alginate, 0.8 parts modified water-retaining agent, 1.2 parts compound bacterial agent, and 10 parts water.
[0047] The preparation steps of this modifier are as follows:
[0048] 1) Targeted activation of nuclei preparation:
[0049] Dihydrate phosphogypsum was mixed with potassium magnesium sulfate composite salt dopant and placed in a low-temperature steam activation reactor. The mixture was treated at 110℃ and 0.15 MPa for 1.5 h to disrupt the crystal structure and form a porous active body. After cooling to room temperature, the mixture was pulverized to a particle size ≤0.15 mm to obtain targeted activated phosphogypsum cores (with a measured specific surface area ≥45 m²). 2 / g, the Ca targeting the activated phosphogypsum core 2+ The release rate is approximately 3 times higher than that of unactivated phosphogypsum.
[0050] 2) Temperature-sensitive shell coating:
[0051] Modified paraffin was heated to 85°C to melt, bentonite was added, and the mixture was stirred for 30 minutes to form a composite phase change slurry. Then, a targeted activated phosphogypsum core was added, and the mixture was stirred at 200 rpm for 40 minutes to form chemical bonds between the carboxyl groups and the hydroxyl groups of the phosphogypsum. The mixture was then cooled to room temperature to form a core-shell intermediate. In this step, it was ensured that the phase change wax loading rate was ≥90% and that there was no leakage of the phase change wax.
[0052] 3) Bio-bridging layer composite:
[0053] Modified humic acid, sodium alginate, and water were mixed and stirred at 80°C for 20 minutes to form a bridging slurry. The pH was adjusted to 7.0. A composite microbial agent and a modified water-retaining agent were added and stirred for 15 minutes. Then, a core-shell intermediate was added and stirred at 100 rpm for 25 minutes to uniformly coat the bridging layer. The mixture was dried at 60°C for 2 hours (at this temperature, the survival rate of the microbial agent is ≥90%, and sodium alginate forms gel microcapsules to protect the microbial agent), thus obtaining an integrated core-shell-bridge modifier.
[0054] Comparative Example 1
[0055] This comparative example provides a phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver.
[0056] In this comparative example, 75 parts of dihydrate phosphogypsum, 8 parts of ordinary paraffin wax, 4 parts of bentonite, 3 parts of humic acid, 1.2 parts of compound microbial agent, and 10 parts of water were mixed and mechanically crushed to obtain the modifier.
[0057] Comparative Example 2
[0058] This comparative example provides a phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver.
[0059] In this comparative example, 75 parts of dihydrate phosphogypsum, 3 parts of humic acid, 1.2 parts of compound microbial agent and 10 parts of water were mixed and mechanically crushed to obtain the modifier.
[0060] Comparative Example 3
[0061] This comparative example provides a phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver.
[0062] This comparative example is basically the same as Example 1, except that no composite salt dopant was used in this comparative example, and potassium magnesium sulfate was not added in preparation step 1); the modifier was finally obtained.
[0063] Comparative Example 4
[0064] This comparative example provides a phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver.
[0065] This comparative example is basically the same as Example 1, except that bentonite was not used in this comparative example and no bentonite was added in preparation step 2); the modifier was finally obtained.
[0066] Comparative Example 5
[0067] This comparative example provides a phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver.
[0068] This comparative example is basically the same as Example 1, except that sodium alginate was not used in this comparative example and bentonite was not added in preparation step 3); the modifier was finally obtained.
[0069] Comparative Example 6
[0070] This comparative example provides a phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver.
[0071] This comparative example is basically the same as Example 1, except that ordinary paraffin is used instead of modified paraffin in this comparative example; the modifier is finally obtained.
[0072] Saline-alkali land experiment:
[0073] Saline-alkali land: pH 10.2, salinity 3.2 g / kg, water content 7.8%, wind speed 3.5 m / s, diurnal temperature range 18℃;
[0074] Testing standard: Based on GB / T 19630-2019, where:
[0075] Soil pH: NY / T 1121.2-2006 "Soil Testing Part 2: Determination of Soil pH";
[0076] Soil salinity: NY / T 1121.16-2006 "Soil Testing Part 16: Determination of Total Water-Soluble Salts in Soil";
[0077] Survival rate of microbial agents: plate count method;
[0078] Phase change wax leakage rate: self-built simulated soil soaking method (no leakage after 30 days);
[0079] Water holding capacity / soil bulk density: NY / T 1121.4-2006 "Soil Testing Part 4: Determination of Soil Bulk Density";
[0080] Sunflower emergence rate: tracking test method;
[0081] Application method: Apply 400 kg of soil conditioner per mu of saline-alkali land, plow to a depth of 20 cm, and water until the moisture content is 15%.
[0082] The results of the saline-alkali land tests in Example 1 and Comparative Examples 1-6 are shown in Table 2 below:
[0083] The test results above show that the phosphogypsum-based saline-alkali soil water-locking and temperature-regulating modifier prepared in this embodiment of the invention has achieved excellent results in the saline-alkali soil improvement test.
[0084] The test results of Comparative Examples 1-6 show that key technical features such as composite salt dopant, bentonite, sodium alginate, and modified paraffin (carboxyl grafting) are indispensable in the present invention. Their absence leads to a significant decrease in the improved performance. The specific reasons are as follows:
[0085] Comparative Example 3 (Potassium Magnesium Sulfate Deficiency Complex Salt): The core function of potassium magnesium sulfate is to "inhibit Ca²⁺". + Too rapid sedimentation, replenishing K + and Mg² + After the absence of phosphogypsum dihydrate, the Ca²⁺ released... + CO3 in the soil 2- Rapid formation of CaCO3 precipitate and insufficient ion exchange led to a 27.3% increase in soil salinity (1.4 g / kg) compared to Example 1 (1.1 g / kg); simultaneously, the soil lacked potassium. + Mg² + By adjusting the ion balance, the salt return rate after 1 year (9.8%) increased by 117.8% compared to Example 1 (4.5%), while the sunflower germination rate dropped to 81% due to insufficient nutrients and salt return issues.
[0086] Comparative Example 4 (without bentonite): The core function of bentonite is to "enhance the stability of the shell structure and improve the water-locking capacity". Without it, the pores of the composite phase change slurry cannot be filled, the bonding force between the phase change wax and the phosphogypsum core decreases, and the leakage rate of the phase change wax increases from 0% to 18%. At the same time, the swelling and water-locking function of bentonite is lost, and the soil water holding rate (32%) is reduced by 28.9% compared with Example 1 (45%). The accelerated water loss leads to the rebound of salt content, and the salt return rate increases to 8.3% in 1 year.
[0087] Comparative Example 5 (lacking sodium alginate): The core function of sodium alginate is to "form a gel network and bind the bridging layer and the core-shell intermediate". When it is missing, the gel network breaks down and cannot provide a stable colonization environment for the inoculant. The survival rate of the inoculant drops from 78% to 52%. At the same time, the binding force between the bridging layer and the core-shell intermediate drops from 2.8N to 1.2N, the structure is easily peeled off, the soil water holding capacity (36%) decreases by 20%, and the sunflower emergence rate drops to 83% due to insufficient inoculant activity and water shortage.
[0088] Comparative Example 6 (Ordinary paraffin wax replacing modified paraffin wax): The core advantage of modified paraffin wax is that "carboxyl groups form chemical bonds with phosphogypsum hydroxyl groups". Ordinary paraffin wax has no carboxyl groups and only adheres through physical adsorption, resulting in a phase change wax leakage rate of 42%; the water-locking and temperature-regulating function is lost, the soil diurnal temperature difference increases from 5.2℃ to 8.5℃, salt migration is accelerated, the 1-year salt return rate (15.6%) is 246.7% higher than that of Example 1, and the sunflower seedling emergence rate drops to 75%.
[0089] The above analysis shows that the "core-shell-bridge" structure and each core component of the present invention are an organic whole. The absence of any component will lead to functional fragmentation, further proving that the present solution breaks through the limitations of the existing technology of "simple compounding" and has significant inventiveness.
[0090] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.
Claims
1. A phosphogypsum-based saline-alkali soil water-locking and temperature-regulating modifier, characterized in that, Its raw material components, by mass fraction, include: 70-80 parts of dihydrate phosphogypsum, 5-8 parts of potassium magnesium sulfate compound salt, 6-10 parts of modified paraffin, 3-5 parts of bentonite, 2-4 parts of modified humic acid, 1-2 parts of sodium alginate, 0.5-1 part of modified water-retaining agent, 0.5-1.5 parts of compound microbial agent, and 8-12 parts of water; The modifier has a core-shell-bridge three-layer composite structure, with the core layer containing targeted activated phosphogypsum, the shell layer containing phase change wax, and the bridge layer containing bridging composite bacterial agents.
2. The phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver according to claim 1, characterized in that, The modified paraffin is a carboxyl-modified paraffin, wherein the content of grafted carboxyl groups is 3wt%~10wt%.
3. The phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver according to claim 1, characterized in that, The compound microbial agent contains phosphate-solubilizing bacteria and nitrogen-fixing bacteria, wherein the mass ratio of phosphate-solubilizing bacteria to nitrogen-fixing bacteria is (1~2):1, and the effective viable count is ≥2×10⁻⁶. 8 CFU / g.
4. The phosphogypsum-based saline-alkali soil water-locking and temperature-regulating improver according to claim 1, characterized in that, The pH of the dihydrate phosphogypsum is 1.5~3.5, the bentonite contains ≥85% montmorillonite and has an expansion ratio of ≥20 times, the modified humic acid contains ≥70wt% humic acid, and the sodium alginate has a viscosity of ≥200mPa·s.
5. The preparation method of the phosphogypsum-based saline-alkali soil water-locking and temperature-regulating amendment as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Mix dihydrate phosphogypsum with potassium magnesium sulfate, steam-activate, cool and then pulverize to a particle size ≤0.15mm to obtain targeted activated phosphogypsum cores; S2. Modified paraffin is heated and melted, bentonite is added, and the mixture is stirred to obtain a composite phase change slurry. Targeted activated phosphogypsum core is added, and the mixture is stirred to obtain a core-shell intermediate. S3. Mix modified humic acid, sodium alginate and water, stir at 70~90℃ to obtain bridging slurry, add compound bacterial agent and modified water-retaining agent and mix, then add core-shell intermediate and stir to obtain core-shell-bridge structure modifier, which is phosphogypsum-based saline-alkali soil water-locking and temperature-regulating modifier.
6. The preparation method according to claim 5, characterized in that, In step S1, the steam activation treatment is performed at 100~120℃ and 0.1~0.2MPa for 1~2 hours; the specific surface area of the targeted activated phosphogypsum core is ≥45m². 2 / g.
7. The preparation method according to claim 5, characterized in that, In step S2, the temperature of the composite phase change slurry is 80~90℃, and the core-shell intermediate is obtained by stirring at a speed of 150~250rpm for 30~50min.
8. The preparation method according to claim 5, characterized in that, In step S3, after obtaining the bridging slurry, the pH is adjusted to 6.8~7.2; after obtaining the core-shell-bridge structure modifier, it is dried at 50~60℃.
9. The application of the phosphogypsum-based saline-alkali soil water-locking and temperature-regulating amendment as described in any one of claims 1 to 4 in the improvement of saline-alkali soil, characterized in that, The application involves spreading the amendment on saline-alkali land, tilling it, and watering it.
10. The application as described in claim 9, characterized in that, The soil in the saline-alkali land has a pH of 9.5-10.5, a salinity of 2.5-3.5 g / kg, and a wind speed of 3-5 m / s. The dosage of the amendment is 300-600 kg / mu, and the tillage depth is 15-25 cm; The application also includes improving the planting of salt-tolerant crops in 10 days.