Phosphogypsum-based saline-alkali soil conditioner, preparation method and application method

Abstract

The present invention relates to the field of solid waste resource utilization, and discloses a phosphogypsum-based saline-alkali soil conditioner, a preparation method and an application method thereof, wherein the conditioner comprises the following raw materials in parts by weight: 235-330 parts of phosphogypsum, 40-100 parts of sepiolite, 20-70 parts of lignocellulose, 15-30 parts of epichlorohydrin, and 8-20 parts of urea. In the solution, sepiolite and phosphogypsum are compounded, and the phosphogypsum is hydrated and dissolved to produce Ca 2+ Replacement of Na in soil + , sepiolite fixes Na in soil through magnesium ion exchange + The magnesium ions react with the water-soluble phosphorus in the phosphogypsum to reduce the effect of soluble phosphorus on the hydration of the phosphogypsum and dissolve Ca 2+ It can further promote the hydration of phosphogypsum, thereby improving the improvement and management effect of phosphogypsum on saline-alkali land.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization, and in particular to a phosphogypsum-based saline-alkali soil conditioner, and a preparation and application method thereof. Background Art

[0002] As a solid waste in the process of phosphate fertilizer production, the effective utilization rate of phosphogypsum is less than 20%. A large amount of phosphogypsum is still stored in the form of direct stacking. The random discharge and storage not only occupies a large amount of land resources, but also causes serious environmental pollution due to water leaching and wind drifting, and also creates a great burden on phosphate fertilizer enterprises. However, phosphogypsum has the characteristics of improving soil structure, reducing salt content, regulating soil pH, and activating soil nutrients. Through the technical test research and demonstration of applying agricultural waste phosphogypsum to improve saline-alkali land, the effect of phosphogypsum application on soil salinity and the mechanism of increasing production are explored to achieve the purpose of efficient utilization of agricultural waste resources. The main components of phosphogypsum are calcium and sulfur, which are essential medium-amount nutrients for plants. Sulfur has become the fourth nutrient element after nitrogen, phosphorus and potassium. Improving saline-alkali land with phosphogypsum is an important part of farmland protection and quality improvement. It is an urgent need to improve farmland quality and enhance agricultural comprehensive production capacity. It is also an effective way to increase crop yields and ensure sustained income growth.

[0003] Saline-alkali land refers to land with excessive soluble salt accumulated on the soil surface, which is harmful to the growth of crops. Factors such as climate conditions, geographical conditions, soil texture, unreasonable farming techniques, and rising groundwater levels can all lead to soil salinization. The main characteristics of saline-alkali land are high alkalinity, high salt content, and serious loss of soil humus. Excessive salt content in the soil will harm plant photosynthesis, cell metabolism, and plant nutrition, making it difficult for most plants to survive in saline-alkali land. Therefore, saline-alkali land has become an important factor restricting the development of agriculture and animal husbandry.

[0004] By applying phosphogypsum to the soil, phosphogypsum reacts chemically with substances in the soil under the influence of external factors such as rainwater scouring or soaking, which is called the effective conversion part and is an important part of improving saline-alkali soil. 2+ To replace the exchangeable Na on soil colloids + , dissolved Ca 2+ With CO3 2- and HCO3 - This reaction occurs, thereby reducing the salinity of the soil, which is partly called the conversion of salts. 2+ When the replaced water-soluble ions accumulate in the soil in large quantities, the high concentration of salt ions in the soil directly affects the solubility of gypsum and may even cause a reverse reaction, resulting in poor effect of phosphogypsum in treating saline-alkali land. Summary of the invention

[0005] The purpose of the present invention is to overcome the Ca2+ dissolution problem of phosphogypsum in the prior art. 2+ The replaced water-soluble ions accumulate in the soil in large quantities, resulting in poor effect of phosphogypsum in treating saline-alkali land. Provided are a phosphogypsum-based saline-alkali land soil conditioner, a preparation method and an application method. The conditioner can promote the hydration of phosphogypsum and improve the improvement effect of saline-alkali land.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a phosphogypsum-based saline-alkali land soil conditioner on the one hand, comprising the following raw materials in parts by weight: 235-330 parts of phosphogypsum, 40-100 parts of sepiolite, 20-70 parts of lignocellulose, 15-30 parts of epichlorohydrin, and 8-20 parts of urea.

[0007] Preferably, the raw materials include the following parts by weight: 275 parts of phosphogypsum, 70 parts of sepiolite, 40 parts of lignocellulose, 20 parts of epichlorohydrin, and 17 parts of urea.

[0008] A second aspect of the present invention provides a method for preparing a phosphogypsum-based saline-alkali soil conditioner, comprising the following steps:

[0009] S1, treating the wood cellulose with alkali, washing and drying to obtain cellulose with high solubility;

[0010] S2, grinding phosphogypsum and sepiolite in a ball mill to obtain a mixture;

[0011] S3, uniformly mixing the cellulose treated in step S1, water, urea and epichlorohydrin, adding the mixture to the mixture, stirring at 40-90° C. for 2-100 hours to obtain the improver.

[0012] Preferably, in the grinding of step S2, the ball-to-material mass ratio is 4-15, the grinding time is 30-250 min, and the grinding temperature is 1-50°C.

[0013] Preferably, in step S3, the mass ratio of the mixture to water is 0.01-0.5.

[0014] Preferably, the method further comprises:

[0015] S4. Add humic acid, wood ash, superphosphate, polyacrylamide, animal and plant residues, microbial fermentation agent and water to the improver, mix evenly and perform closed fermentation, let stand at 15-25° C. for 7-20 days, spray dry, and granulate when the moisture content is 1%-9%.

[0016] Preferably, in step S4, the added weight portions of each component are as follows: 0.1-1 parts of humic acid, 5-30 parts of wood ash, 2-5 parts of superphosphate, 0.01-0.5 parts of polyacrylamide, 150-200 parts of animal and plant residues, 0.1-10 parts of microbial fermentation agent and 200-300 parts of water.

[0017] A third aspect of the present invention provides a method for applying a phosphogypsum-based saline-alkali land soil conditioner, wherein the conditioner is prepared by the above-mentioned method for preparing the phosphogypsum-based saline-alkali land soil conditioner, and the method comprises the following steps:

[0018] (1) Sprinkling the improver evenly on the surface of the saline-alkali land, turning the ground and leaving it to stand for 4-7 days;

[0019] (2) Water injection irrigation, the water injection volume is 10-40 cubic meters per mu;

[0020] (3) Wait until the soil moisture is suitable for sowing before sowing;

[0021] (4) 3-8 weeks after the seedlings sprout, add the above-mentioned improver next to the sprouting seedlings.

[0022] Preferably, in step (1), the amount of the improver used is 500-1000 kg / mu.

[0023] Preferably, in step (4), the dosage of the improver is 100-200 kg / mu, and the improver is spread in a pit dug next to the root system of the seedlings, and then 1-5 kg ​​of water is injected into the pit and the pit is sealed.

[0024] Due to its large specific surface area and unique pore structure, sepiolite has abundant water channels, pore structure and adsorption characteristics. The phosphogypsum and sepiolite are ground and mixed evenly to make the phosphogypsum adsorbed on the surface and in the pores. Furthermore, highly soluble wood cellulose, epichlorohydrin, urea and water are mixed and added to the mixture of phosphogypsum and sepiolite to generate cellulose hydrogel in situ on the composite particles of phosphogypsum and sepiolite, thereby achieving the compounding of phosphogypsum and sepiolite, and then strengthening the compounding of phosphogypsum and sepiolite to obtain a phosphogypsum-based saline-alkali land soil conditioner. When the phosphogypsum-based conditioner is applied to saline-alkali land, the Ca dissolved in the phosphogypsum 2+ With CO3 2- and HCO3 - The reaction generates insoluble calcium salts (Ca 2+ Reacts with soluble sodium salts to form insoluble calcium salts and Na + ), thereby replacing the soil including Na + However, as water-soluble ions accumulate in the soil, they will hinder the 2+Sepiolite is a hydrated magnesium silicate clay mineral in which Mg is highly enriched. The surface of the sepiolite is weakly acidic and magnesium ions are easily replaced by other ions. 2+ Replacement of Na in soil + After that, sepiolite replaces part of Na by magnesium ions. + On the other hand, part of Na is adsorbed through the pore structure + In addition, the phosphorus content in phosphogypsum is usually relatively high. Soluble phosphorus has the greatest impact on the performance of phosphogypsum. The main component of soluble phosphorus is phosphoric acid, which is ionized in the solution. Water-soluble phosphorus is mainly in the form of H3PO4 and H2PO4. - 、HPO4 2- PO4 3- The soluble phosphorus easily reacts with calcium ions to form insoluble calcium salts, which hinder the hydrolysis of dihydrate gypsum and seriously affect the further hydration of phosphogypsum. By using the modifier of the present invention, the magnesium ions exchanged by sepiolite react with water-soluble phosphorus to form inorganic substances such as magnesium phosphate and magnesium hydrogen phosphate, which can be used as a soil nutrient supplement to provide magnesium and phosphorus to the soil and promote the further hydration of phosphogypsum.

[0025] Through the above technical scheme, cellulose hydrogel is generated in situ to solidify phosphogypsum and sepiolite, and a composite of phosphogypsum and sepiolite is synthesized as a modifier. The preparation method is simple, and through the compounding of sepiolite and phosphogypsum, phosphogypsum is hydrated and dissolved to produce Ca 2+ Replacement of Na in soil + , sepiolite fixes Na in soil through magnesium ion exchange + The magnesium ions react with the water-soluble phosphorus in the phosphogypsum to reduce the effect of soluble phosphorus on the hydration of the phosphogypsum and dissolve Ca 2+ The phosphogypsum-based saline-alkali land soil conditioner of the present invention can effectively reduce the content of soluble salts and pH value in saline-alkali soil, increase the phosphorus content and the content of the major element magnesium, improve the physical and chemical properties of the soil, make the soil more fertile, and be beneficial to the normal growth of crops. DETAILED DESCRIPTION

[0026] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0027] The present invention will be described in detail below through examples. In the following examples, the reagents used are all commercially available products. In the following examples, in addition to the improver, appropriate amounts of urea, phosphate fertilizer and potash fertilizer are applied. The conventional application methods and dosages are consistent in each example and test example, which are not the research focus of this application and are not specifically introduced here.

[0028] Embodiment 1:

[0029] A phosphogypsum-based saline-alkali soil conditioner comprises the following raw materials in parts by weight: 275 parts of phosphogypsum, 40 parts of sepiolite, 70 parts of lignocellulose, 30 parts of epichlorohydrin, and 20 parts of urea; and a preparation method comprises the following steps:

[0030] S1, treating the wood cellulose with alkali, washing and drying to obtain cellulose with high solubility;

[0031] S2, grinding phosphogypsum and sepiolite in a ball mill, with a ball-to-material mass ratio of 15, a grinding time of 250 min, and a grinding temperature of 50° C. to obtain a mixture;

[0032] S3, uniformly mixing the cellulose treated in step S1, water, urea and epichlorohydrin, and then adding the mixture to the mixture, the mass ratio of the mixture to water being 0.5, stirring at 90° C. for 100 hours to obtain the improver.

[0033] Embodiment 2:

[0034] A phosphogypsum-based saline-alkali soil conditioner comprises the following raw materials in parts by weight: 330 parts of phosphogypsum, 100 parts of sepiolite, 20 parts of lignocellulose, 15 parts of epichlorohydrin, and 8 parts of urea; and a preparation method comprises the following steps:

[0035] S1, treating the wood cellulose with alkali, washing and drying to obtain cellulose with high solubility;

[0036] S2, grinding phosphogypsum and sepiolite in a ball mill, with a ball-to-material mass ratio of 4, a grinding time of 30 min, and a grinding temperature of 1° C. to obtain a mixture;

[0037] S3, uniformly mixing the cellulose treated in step S1, water, urea and epichlorohydrin, and then adding the mixture to the mixture, the mass ratio of the mixture to water being 0.01, stirring at 40° C. for 2 hours to obtain the improver.

[0038] Embodiment 3:

[0039] A phosphogypsum-based saline-alkali soil conditioner comprises the following raw materials in parts by weight: 235 parts of phosphogypsum, 70 parts of sepiolite, 40 parts of lignocellulose, 20 parts of epichlorohydrin, and 17 parts of urea; and a preparation method comprises the following steps:

[0040] S1, treating the wood cellulose with alkali, washing and drying to obtain cellulose with high solubility;

[0041] S2, grinding phosphogypsum and sepiolite in a ball mill, with a ball-to-material mass ratio of 9, a grinding time of 150 min, and a grinding temperature of 25° C. to obtain a mixture;

[0042] S3, uniformly mixing the cellulose treated in step S1, water, urea and epichlorohydrin, and then adding the mixture to the mixture, the mass ratio of the mixture to water being 0.25, stirring at 60° C. for 50 hours to obtain the improver.

[0043] Highly soluble lignocellulose, epichlorohydrin, urea and water are mixed and added to a mixture of phosphogypsum and sepiolite. Epichlorohydrin acts as a cross-linking agent to generate cellulose hydrogel in situ on the composite particles of phosphogypsum and sepiolite, thereby achieving the compounding of phosphogypsum and sepiolite, and further strengthening and solidifying the composite of phosphogypsum and sepiolite to obtain a phosphogypsum-based saline-alkali land soil conditioner. The preparation method is simple and can be completed in one step.

[0044] Due to its large specific surface area and unique internal pore structure, sepiolite has abundant water channels and pore structures and adsorption characteristics. By grinding and mixing phosphogypsum and sepiolite evenly, phosphogypsum is adsorbed on the surface and in the pores. Sepiolite is a hydrated magnesium silicate clay mineral in which Mg is highly enriched. The surface of sepiolite is weakly acidic and magnesium ions are easily replaced by other ions, which can cooperate with phosphogypsum to reduce the pH value of the soil. When the modifier of the present invention is used, the Ca2+ dissolved from phosphogypsum can be absorbed by the surface of the soil. 2+ Replacement of Na in soil + After that, sepiolite replaces part of Na by magnesium ions. + On the other hand, part of Na is adsorbed through the pore structure + In addition, the phosphorus content in phosphogypsum is usually relatively high. Soluble phosphorus has the greatest impact on the performance of phosphogypsum. The main component of soluble phosphorus is phosphoric acid, which is ionized in the solution. Water-soluble phosphorus is mainly in the form of H3PO4 and H2PO4. - 、HPO4 2- PO4 3- The soluble phosphorus easily reacts with calcium ions to form insoluble calcium salts, which hinder the hydrolysis of dihydrate gypsum and seriously affect the further hydration of phosphogypsum. By using the modifier of the present invention, the magnesium ions exchanged by sepiolite react with water-soluble phosphorus to form inorganic substances such as magnesium phosphate and magnesium hydrogen phosphate, which can be used as a soil nutrient supplement to provide magnesium and phosphorus to the soil and promote the further hydration of phosphogypsum.

[0045] Embodiment 4:

[0046] A phosphogypsum-based saline-alkali soil conditioner comprises the following raw materials in parts by weight: 235 parts of phosphogypsum, 70 parts of sepiolite, 40 parts of lignocellulose, 20 parts of epichlorohydrin, and 17 parts of urea; the preparation method is carried out according to the method of Example 3, and further comprises:

[0047] S4. Add humic acid, wood ash, superphosphate, polyacrylamide, animal and plant residues, microbial fermentation agent and water to the improver, mix evenly and perform closed fermentation, let stand at 15-25° C. for 7-20 days, spray dry, and granulate when the moisture content is 1%-9%; the reaction conditions are preferably let stand at 20° C. for 12 days, spray dry, and granulate when the moisture content is 5%.

[0048] After adding humic acid, wood ash, superphosphate, polyacrylamide, animal and plant residues, and microbial fermentation agents to the improver for fermentation, it contains essential nutrients and trace elements for plants, which can reduce the pH value of the soil, increase the organic matter content of the soil, and improve the physical and chemical properties of the soil. In addition, organic matter and exchangeable calcium ions form organic colloids, which can also absorb heavy metal ions in the soil.

[0049] Example 5

[0050] A method for applying a phosphogypsum-based saline-alkali soil conditioner, wherein the conditioner is prepared by the preparation method of Example 2, comprising the following steps:

[0051] (1) Sprinkle the improver evenly on the surface of saline-alkali land at a rate of 500 kg / mu, till the ground and leave it to stand for 4 days;

[0052] (2) Water injection irrigation, the water injection volume is 10 cubic meters per mu;

[0053] (3) Wait until the soil moisture is suitable for sowing before sowing;

[0054] (4) Three weeks after the seedlings sprout, add the above-mentioned improver once beside the sprouting seedlings at a dosage of 100 kg / mu. Dig a hole next to the root system of the seedlings and spread the improver in the hole. Then, add 1 kg of water into the hole and seal it.

[0055] Example 6

[0056] A method for applying a phosphogypsum-based saline-alkali soil conditioner, wherein the conditioner is prepared by the preparation method of Example 3, comprising the following steps:

[0057] (1) Sprinkle the improver evenly on the surface of saline-alkali land at a rate of 1000 kg / mu, till the ground and leave it to stand for 7 days;

[0058] (2) Water injection irrigation, the water injection volume is 40 cubic meters per mu;

[0059] (3) Wait until the soil moisture is suitable for sowing before sowing;

[0060] (4) After 8 weeks of germination, add the above-mentioned amendment once beside the germinating seedlings at a dosage of 200 kg / mu. Dig a hole next to the root system of the seedlings and spread the amendment in the hole. Then, add 5 kg of water into the hole and seal it.

[0061] Example 7

[0062] A method for applying a phosphogypsum-based saline-alkali soil conditioner, wherein the conditioner is prepared by the preparation method of Example 4, comprising the following steps:

[0063] (1) Sprinkle the improver evenly on the surface of saline-alkali land at a rate of 750 kg / mu, till the ground and leave it to stand for 5 days;

[0064] (2) Water injection irrigation, the water injection volume is 25 cubic meters per mu;

[0065] (3) Wait until the soil moisture is suitable for sowing before sowing;

[0066] (4) After 5 weeks of germination, add the above-mentioned improver once beside the germinating seedlings at a dosage of 150 kg / mu. Dig a hole next to the root system of the seedlings and spread the improver in the hole. Then, add 3 kg of water into the hole and seal it.

[0067] Comparative Example 1: As a blank control group, the method of Example 6 was used, except that no improver was used.

[0068] Comparative Example 2: The method of Example 6 was used, but unlike Example 6, no sepiolite was added to the improver.

[0069] Comparative Example 3: The application was carried out according to the method of Example 7, except that the application method did not include step (4).

[0070] Comparative Example 4: The method of Example 6 was used, but the difference from Example 6 was that no lignocellulose was added to the improver.

[0071] Test Case

[0072] The experimental effect test selected the experimental field of Derisu Village, Wudan Town, Wengniute Banner, Chifeng City, Inner Mongolia, and took corn planting as an example. It is worth noting that the improver and application method of the present invention are not limited to corn planting, and can be used for planting crops such as wheat, soybeans, cotton, and sesame.

[0073] A test field was divided into seven parts, numbered as Field 1, Field 2, Field 3, Field 4, Field 5, Field 6 and Field 7. Field 1 was treated by the method of Example 5, Field 2 was treated by the method of Example 6, Field 3 was treated by the method of Example 7, Field 4 was treated by the method of Comparative Example 1, Field 5 was treated by the method of Comparative Example 2, Field 6 was treated by the method of Comparative Example 3, and Field 7 was treated by the method of Comparative Example 4. The seven plots were treated at the same time, and the soil before and after treatment was sampled. The salt concentration EC value (EC value is used to measure the soluble salt concentration in the solution) and pH value in the soil at a depth of 20 cm were tested on the 0th, 15th, 30th and 60th day of treatment, respectively. The test results are shown in Tables 1 and 2, and each test result is the result value of taking the average value of multiple tests. Planting density of corn: 4800 plants per mu, cultivation specifications: plant spacing 25cm×40cm. The statistical results of corn yield in seven test fields are shown in Table 3.

[0074] Table 1 Soluble salt index

[0075]

[0076] It can be seen from the test data of sites 1-3 that the EC value of the saline-alkali land treated by the modifier of the embodiment of the present invention can be reduced from 4.88-4.92ms / cm to 0.69-0.72ms / cm within 30 days, which can effectively reduce soluble salts and avoid soil compaction. Site 4 did not use modifiers, and the EC value hardly changed. Site 5 used phosphogypsum that did not contain sepiolite as a modifier. Within 30-60 days after the addition of phosphogypsum, the EC value increased slightly. It can be seen that when phosphogypsum reduces the alkalinity of the soil, the dissolved calcium ions replace the sodium ions and then enrich them, resulting in an increase in the soluble salts in the soil. By comparing the test data of sites 1-3, it can be seen that sepiolite can overcome the problem of an increase in soluble salts in the soil caused by phosphogypsum as a modifier.

[0077] The amendments used in Plot 6 were the same as those in Plot 3, except that there was no second additional application in the application method. It can be seen that the EC value change in Plot 6 within 30 days had the same trend as that in Plot 3, but there was no obvious change after 30 days, indicating that the additional application method is beneficial to reducing soil soluble salts.

[0078] The modifier used in plot 7 did not contain lignocellulose, and the EC value change was improved compared with the blank group plot 4, but the effect was far less than that of plots 1-3, indicating that lignocellulose promoted the recombination of sepiolite and phosphogypsum, further improving the improvement effect of the modifier on saline-alkali land.

[0079] Table 2 Soil pH value

[0080]

[0081] It can be seen from the test data of sites 1-3 that the pH value of the saline-alkali land treated by the modifier of the embodiment of the present invention can be reduced from 8.96 to 7.13, which can effectively reduce the alkalinity of the soil. By comparing the data of site 5, it can be seen that the modifier that does not contain sepiolite and is mainly composed of phosphogypsum has a certain effect on improving the alkalinity of the soil. After the sepiolite is compounded with phosphogypsum, the pH value of the soil alkali can be further reduced. By comparing the data of site 7, it can be seen that the modifier that does not contain lignocellulose and is mainly composed of sepiolite and phosphogypsum has a certain effect on improving the alkalinity of the soil, indicating that lignocellulose promotes the compounding of sepiolite and phosphogypsum, which can further reduce the pH value of the soil alkali.

[0082] Table 3 Corn yield

[0083]

[0084] From the results in Table 3, it can be seen that compared with the per-acre yield of 660 kg in Plot 4 without the use of the modifier, the per-acre yield of Plots 1-3 can reach up to 1000 kg after the modifier of the present invention is used, which effectively increases the yield of crops. The per-acre yield of Plot 5, where phosphogypsum is used as the modifier alone, is 700 kg, which is significantly lower than that of Plots 1-3, indicating that the use of the modifier of the present invention not only plays the role of phosphogypsum in improving soil and promoting yield increase, but also reacts with water-soluble phosphorus through the exchange of magnesium ions after the compounding of sepiolite to generate inorganic substances such as magnesium phosphate and magnesium hydrogen phosphate, which provide nutrients such as magnesium and phosphorus to the soil as a nutrient supplement for the soil, further promoting crop yield increase. Compared with Plot 6, the per-acre yield of Plot 3 using the additional application method of the present invention is significantly improved.

[0085] The modifier combined with the application method of the present invention is used. After the modifier is applied to the soil and turned over, the modifier continuously hydrates and absorbs the alkali and soluble salts in the soil, and the soil begins to be enriched with soluble salts. After water injection and irrigation, the sepiolite in the modifier absorbs water and expands rapidly. On the one hand, the pores expand and enter the aqueous solution. The aqueous solution replaces the soluble salts in the soil into the sepiolite to fix sodium, further promoting the hydration of phosphogypsum. At the same time, the replaced magnesium ions participate in the reaction to generate magnesium phosphate and magnesium hydrogen phosphate, etc. to provide magnesium and phosphate fertilizers for the soil; on the one hand, the pores are filled with a large amount of water to avoid rapid loss of soil moisture, and gradually release slowly to provide moisture for the soil. After the seedlings sprout, the system digs pits beside the system to sow in the pits and inject water, which not only further promotes the improvement of saline-alkali land, effectively fixes water to avoid soil loss, reduces the amount of irrigation water, but also can absorb heavy metal ions near the seedlings to avoid the enrichment of metal ions in crops.

[0086] In summary, through the above technical scheme, cellulose hydrogel is generated in situ to solidify phosphogypsum and sepiolite, and a composite of phosphogypsum and sepiolite is synthesized as a modifier. The preparation method is simple, and through the compounding of sepiolite and phosphogypsum, phosphogypsum is hydrated and dissolved to produce Ca 2+Replacement of Na in soil + , sepiolite fixes Na in soil through magnesium ion exchange + The magnesium ions react with the water-soluble phosphorus in the phosphogypsum to reduce the effect of soluble phosphorus on the hydration of the phosphogypsum and dissolve Ca 2+ The phosphogypsum-based saline-alkali land soil conditioner of the present invention can effectively reduce the content of soluble salts and pH value in saline-alkali soil, increase the phosphorus content and the content of the major element magnesium, improve the physical and chemical properties of the soil to make the soil more fertile, and be conducive to the normal growth of crops; the conditioner can fix water and release it slowly, avoid the loss of water and nutrients, save water resources, and can also adsorb heavy metal ions.

[0087] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A phosphogypsum-based saline-alkali soil conditioner, characterized in that: The preparation method of the phosphogypsum-based saline-alkali soil conditioner comprises the following raw materials in parts by weight: 235-330 parts of phosphogypsum, 40-100 parts of sepiolite, 20-70 parts of lignocellulose, 15-30 parts of epichlorohydrin, and 8-20 parts of urea. The preparation method of the phosphogypsum-based saline-alkali soil conditioner comprises the following steps: S1, treating the wood cellulose with alkali, washing and drying to obtain cellulose with high solubility; S2, grinding phosphogypsum and sepiolite in a ball mill to obtain a mixture; S3, uniformly mixing the cellulose treated in step S1, water, urea and epichlorohydrin, adding the mixture to the mixture, stirring at 40-90° C. for 2-100 hours to obtain the improver.

2. The phosphogypsum-based saline-alkali soil conditioner according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 275 parts of phosphogypsum, 70 parts of sepiolite, 40 parts of wood cellulose, 20 parts of epichlorohydrin and 17 parts of urea.

3. A method for preparing the phosphogypsum-based saline-alkali soil conditioner according to claim 1, characterized in that: The following steps are involved: S1, treating the wood cellulose with alkali, washing and drying to obtain cellulose with high solubility; S2, grinding phosphogypsum and sepiolite in a ball mill to obtain a mixture; S3, uniformly mixing the cellulose treated in step S1, water, urea and epichlorohydrin, adding the mixture to the mixture, stirring at 40-90° C. for 2-100 hours to obtain the improver.

4. The preparation method according to claim 3, characterized in that: In the grinding of step S2, the ball-to-material mass ratio is 4-15, the grinding time is 30-250 min, and the grinding temperature is 1-50°C.

5. The preparation method according to claim 3, characterized in that: In step S3, the mass ratio of the mixture to water is 0.01-0.

5.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The method further comprises: S4. Add humic acid, wood ash, superphosphate, polyacrylamide, animal and plant residues, microbial fermentation agent and water to the improver, mix evenly and perform closed fermentation, let stand at 15-25° C. for 7-20 days, spray dry, and granulate when the moisture content is 1%-9%.

7. The preparation method according to claim 6, characterized in that: In step S4, the added weight portions of the components are as follows: 0.1-1 parts of humic acid, 5-30 parts of wood ash, 2-5 parts of superphosphate, 0.01-0.5 parts of polyacrylamide, 150-200 parts of animal and plant residues, 0.1-10 parts of microbial fermentation agent and 200-300 parts of water.

8. A method for applying a phosphogypsum-based saline-alkali soil conditioner, characterized in that: The improver is prepared by the preparation method as described in any one of claims 3 to 6, comprising the following steps: (1) Sprinkling the improver evenly on the surface of the saline-alkali land, turning the ground and leaving it to stand for 4-7 days; (2) Water injection irrigation, the water injection volume is 10-40 cubic meters per mu; (3) Let the soil sit until the moisture level is suitable for sowing before sowing; (4) 3-8 weeks after the seedlings sprout, add the improver once beside the sprouted seedlings.

9. The application method according to claim 8, characterized in that In step (1), the dosage of the improver is 500-1000 kg / mu.

10. The application method according to claim 9, characterized in that In step (4), the dosage of the improver is 100-200 kg / mu, and the improver is spread in a pit dug next to the root system of the seedlings, and then 1-5 kg ​​of water is injected into the pit and the pit is sealed.

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