A saline-alkali soil conditioner and a preparation method thereof

Abstract

The application discloses a saline-alkali soil conditioner and a preparation method thereof, and belongs to the technical field of soil improvement. The soil conditioner is prepared from the following raw materials in parts by weight: modified phosphogypsum 100-200 parts, microbial agent 5-10 parts, and activator 10-20 parts; the modified phosphogypsum is prepared from phosphogypsum and modified coal gangue after compounding and rare earth modification; the microbial agent is prepared from Bacillus subtilis, Streptomyces cellulans and Bacillus mycoides. The chemical-physical-biological improvement technology is combined, the physical and chemical properties of the saline-alkali soil are effectively improved, the soil biological activity is increased, the growth of crops is promoted, the yield and disease resistance of crops are improved, and the resource utilization rate of phosphogypsum is improved.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement technology, specifically relating to a saline-alkali soil conditioner and its preparation method. Background Technology

[0002] Studies show that producing 1 ton of phosphoric acid using the sulfuric acid process generates nearly 5 tons of phosphogypsum. Statistics indicate that the global stockpile of phosphogypsum has reached 6 billion tons, and is still increasing at a rate of 150 million tons annually, but the global comprehensive utilization rate of phosphogypsum is only about 25%. my country is the world's largest producer of phosphate fertilizer and also the largest producer of phosphogypsum by-products, with a stockpile of 400 million tons, still increasing at a rate of approximately 50 million tons annually. Phosphogypsum's main component is calcium sulfate dihydrate (CaSO4·2H2O), and it also contains small amounts of free acid, phosphates, fluorides, organic matter, and trace elements. In my country, phosphogypsum production is mainly concentrated in Hubei, Yunnan, Guizhou, Shandong, and Anhui provinces, accounting for about 85% of the country's total phosphogypsum production, but the comprehensive utilization rate is less than 50%. Compared with other countries, my country's comprehensive utilization of phosphogypsum is insufficient and requires further exploration.

[0003] Currently, scholars have conducted extensive research on the comprehensive utilization of phosphogypsum, mainly focusing on three aspects: building materials, chemical products, and its application as a soil conditioner in agriculture. In recent years, the comprehensive utilization rate of phosphogypsum has shown a gradual upward trend; however, significant stockpiling pressure and environmental risks remain. While phosphogypsum has significant effects on soil improvement in some aspects, it also has some undeniable drawbacks, such as the introduction of harmful substances like heavy metals (Cd, Pb, As) and excessive fluoride (F), which can damage soil ecosystems. In particular, the fluorides in phosphogypsum have a direct toxic effect on plant growth; when the fluoride content in the soil is too high, it can inhibit plant growth and even lead to plant death. If the fluorides in phosphogypsum are discharged or stockpiled without treatment, they will pollute the soil environment. Long-term stockpiled phosphogypsum, under the influence of rainwater, will allow the fluorides to seep into the soil, leading to soil pollution. This pollution may persist for years or even decades, causing long-term impacts on soil ecosystems and agricultural production. Fluorides, once in the soil, can enter the human body through the food chain, posing a health hazard. Therefore, seeking comprehensive and safe utilization methods and technologies for phosphogypsum is of great importance. Summary of the Invention

[0004] The purpose of this invention is to provide a soil conditioner for saline-alkali soil. This conditioner is made by using modified phosphogypsum as the main raw material, mixing it with microorganisms, and then adding a suitable activator. By combining chemical-physical-biological improvement technologies, this method effectively improves the physical and chemical properties of saline-alkali soil, increases soil biological activity, promotes crop growth, enhances crop yield and disease resistance, and improves the resource utilization rate of phosphogypsum.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] A soil conditioner for saline-alkali soil is made from the following raw materials in parts by weight: 100-200 parts modified phosphogypsum, 5-10 parts microbial inoculant, and 10-20 parts activator; wherein the modified phosphogypsum is prepared by compounding phosphogypsum with modified coal gangue and then modifying it with rare earth elements; wherein the microbial inoculant is made by mixing Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus.

[0007] Preferably, the activator is composed of bamboo shoot shell and sodium lignosulfonate in a mass ratio of 2:1.

[0008] Preferably, the modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed and ball-milled at 600 r / min for 1-2 h. The mixture is then immersed in a 0.1 mol / L NdCl3 solution and magnetically stirred at room temperature for 4-6 h. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, dried, and ground into powder to obtain the modified phosphogypsum.

[0009] Preferably, the mass ratio of the phosphogypsum to the modified coal gangue is 1:0.25-0.5; and the material-to-liquid ratio of the ball-milled mixture to the NdCl3 solution is 1g:30ml.

[0010] Preferably, the modified coal gangue is prepared by the following method:

[0011] (1) The raw coal gangue is crushed, ground, and passed through a 200-mesh sieve, and then heat-treated at 500℃ for 2 hours to obtain pretreated coal gangue powder;

[0012] (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically at room temperature for 30-45 min, add pretreated coal gangue powder, heat to 40-45℃, react for 2-3 h, filter and wash the product until neutral, and dry to obtain modified coal gangue.

[0013] Preferably, in step (2), the mass ratio of silane coupling agent KH570 to pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; and the material-liquid ratio of pretreated coal gangue powder to mixed solution is 1g:20ml.

[0014] This invention also provides a method for preparing the above-mentioned saline-alkali soil conditioner, which includes the following steps:

[0015] a. Inoculate Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus into LB liquid medium, respectively, and incubate with shaking at 28°C until the bacterial count reaches OD200. 600 ≈2.0, then mixed in a volume ratio of 1:1:1 and dried to obtain microbial inoculant;

[0016] The LB liquid culture medium consists of: 5g yeast extract, 10g tryptone, 10g sodium chloride, 1000mL distilled water, pH adjusted to 7.0, and sterilized by steam at 121℃ for 20min.

[0017] b. After crushing the bamboo shoot shells, pass them through a 100-mesh sieve and mix them with sodium lignosulfonate in a certain mass ratio to prepare an activator;

[0018] c. Preparation of modified phosphogypsum;

[0019] d. Mix the modified phosphogypsum, microbial inoculant, and activator evenly according to the weight ratio, and package to obtain the final product.

[0020] The dosage of the soil conditioner of this invention is 20-30 kg / mu, and the application rate should be adjusted according to the actual land conditions.

[0021] The *Bacillus subtilis* used in this invention were purchased from the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 1.7740 and accession date July 24, 2008; *Streptomyces cellulose* were purchased from the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 4.6365 and accession date September 3, 2008; and *Bacillus mucilaginosus* were purchased from the China Center for Type Culture Collection, located at Luojia Mountain, Bayi Road, Wuchang District, Wuhan City, Hubei Province, with accession number CCTCC No. KB 20082790 and accession date September 25, 2004. All of the above strains can be purchased through the collection center's strain catalog without additional preservation.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] (1) Using phosphogypsum and coal gangue as solid wastes to prepare saline-alkali soil conditioner improves the comprehensive utilization rate of solid waste and has significant environmental benefits.

[0024] (2) The modified phosphogypsum in this invention is made by compounding phosphogypsum and coal gangue, and then modifying it with the rare earth element neodymium. The modified phosphogypsum has a significantly rough and loose microstructure with increased porosity (see Figure 1 With increased specific surface area and enhanced surface functional group activity, it has a good adsorption effect on harmful substances such as heavy metals (such as Cd, Pb, As, etc.) and fluoride (F) ions in soil and original phosphogypsum. At the same time, it also promotes the formation of soil aggregate structure and increases the infiltration rate of salt, thereby achieving the purpose of reducing salinity, lowering pH and reducing soil compaction.

[0025] (3) Phosphogypsum modified with rare earth neodymium can more effectively exchange with sodium ions in saline-alkali soil and reduce soil alkalinity. This is because the ionic radius of rare earth neodymium is similar to that of calcium ions, which can replace some sodium ions in the soil to form more stable compounds, thereby reducing the sodium ion content in the soil.

[0026] (4) The activator prepared in this invention can produce soluble ions and small molecule organic acids after the decomposition of bamboo shoot shells, which can reduce the soil pH value and promote the dissolution and release of heavy metal ions in the soil. Sodium lignosulfonate can improve the activity of functional groups on the surface of modified phosphogypsum and improve the adsorption of harmful heavy metal ions in the soil. The combination of the two can significantly improve the soil conditioner's effect on improving saline-alkali soil.

[0027] (5) The modified phosphogypsum prepared by the present invention provides a suitable ecological environment for microorganisms, promotes the growth of beneficial microorganisms, increases soil enzyme activity, promotes crop growth, increases crop yield and disease resistance, and truly realizes the improvement of saline-alkali soil. Attached Figure Description

[0028] Figure 1 The images shown are SEM images of the microstructure of the modified phosphogypsum prepared in Example 3 of this invention before and after modification, where a is unmodified phosphogypsum, b is unmodified coal gangue, and c is modified phosphogypsum. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0030] Example 1

[0031] A soil conditioner for saline-alkali soil is made from the following raw materials in parts by weight: 100 parts modified phosphogypsum, 5 parts microbial inoculant, and 10 parts activator; wherein the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying it with rare earth elements; wherein the microbial inoculant is made by mixing Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus.

[0032] The activator is composed of bamboo shoot shells and sodium lignosulfonate in a mass ratio of 2:1.

[0033] The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed at a mass ratio of 1:0.25 and ball-milled at 600 r / min for 1-2 h. The mixture is then immersed in a 0.1 mol / L NdCl3 solution and magnetically stirred at room temperature for 4-6 h. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, dried, and ground into powder to obtain the modified phosphogypsum. The material-to-liquid ratio of the ball-milled mixture to the NdCl3 solution is 1 g: 30 ml.

[0034] The modified coal gangue was prepared using the following method:

[0035] (1) The raw coal gangue is crushed, ground, and passed through a 200-mesh sieve, and then heat-treated at 500℃ for 2 hours to obtain pretreated coal gangue powder;

[0036] (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically at room temperature for 30-45 min, add pretreated coal gangue powder, heat to 40-45℃, react for 2-3 h, filter and wash the product until neutral, and dry to obtain modified coal gangue; the mass ratio of silane coupling agent KH570 to pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the material-liquid ratio of pretreated coal gangue powder to mixed solution is 1g:20ml.

[0037] A method for preparing the above-mentioned saline-alkali soil conditioner includes the following steps:

[0038] a. Inoculate Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus into LB liquid medium, respectively, and incubate with shaking at 28°C until the bacterial count reaches OD200. 600 ≈2.0, then mixed in a volume ratio of 1:1:1 and dried to obtain microbial inoculant;

[0039] The LB liquid culture medium consists of: 5g yeast extract, 10g tryptone, 10g sodium chloride, 1000mL distilled water, pH adjusted to 7.0, and sterilized by steam at 121℃ for 20min.

[0040] b. After crushing the bamboo shoot shells, pass them through a 100-mesh sieve and mix them with sodium lignosulfonate in a certain mass ratio to prepare an activator;

[0041] c. Preparation of modified phosphogypsum;

[0042] d. Mix the modified phosphogypsum, microbial inoculant, and activator evenly according to the weight ratio, and package to obtain the final product.

[0043] Example 2

[0044] A soil conditioner for saline-alkali soil is made from the following raw materials in parts by weight: 200 parts modified phosphogypsum, 10 parts microbial inoculant, and 20 parts activator; wherein the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying it with rare earth elements; wherein the microbial inoculant is made by mixing Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus.

[0045] The activator is composed of bamboo shoot shells and sodium lignosulfonate in a mass ratio of 2:1.

[0046] The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed at a mass ratio of 1:0.4 and ball-milled at 600 r / min for 1-2 h. The mixture is then immersed in a 0.1 mol / L NdCl3 solution and magnetically stirred at room temperature for 4-6 h. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, dried, and ground into powder to obtain the modified phosphogypsum. The material-to-liquid ratio of the ball-milled mixture to the NdCl3 solution is 1 g: 30 ml.

[0047] The modified coal gangue was prepared using the following method:

[0048] (1) The raw coal gangue is crushed, ground, and passed through a 200-mesh sieve, and then heat-treated at 500℃ for 2 hours to obtain pretreated coal gangue powder;

[0049] (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically at room temperature for 30-45 min, add pretreated coal gangue powder, heat to 40-45℃, react for 2-3 h, filter and wash the product until neutral, and dry to obtain modified coal gangue; the mass ratio of silane coupling agent KH570 to pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the material-liquid ratio of pretreated coal gangue powder to mixed solution is 1g:20ml.

[0050] A method for preparing the above-mentioned saline-alkali soil conditioner includes the following steps:

[0051] a. Inoculate Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus into LB liquid medium, respectively, and incubate with shaking at 28°C until the bacterial count reaches OD200. 600 ≈2.0, then mixed in a volume ratio of 1:1:1 and dried to obtain microbial inoculant;

[0052] The LB liquid culture medium consists of: 5g yeast extract, 10g tryptone, 10g sodium chloride, 1000mL distilled water, pH adjusted to 7.0, and sterilized by steam at 121℃ for 20min.

[0053] b. After crushing the bamboo shoot shells, pass them through a 100-mesh sieve and mix them with sodium lignosulfonate in a certain mass ratio to prepare an activator;

[0054] c. Preparation of modified phosphogypsum;

[0055] d. Mix the modified phosphogypsum, microbial inoculant, and activator evenly according to the weight ratio, and package to obtain the final product.

[0056] Example 3

[0057] A soil conditioner for saline-alkali soil is made from the following raw materials in parts by weight: 150 parts modified phosphogypsum, 8 parts microbial inoculant, and 15 parts activator; wherein the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying it with rare earth elements; wherein the microbial inoculant is made by mixing Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus.

[0058] The activator is composed of bamboo shoot shells and sodium lignosulfonate in a mass ratio of 2:1.

[0059] The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed at a mass ratio of 1:0.5 and ball-milled at 600 r / min for 1-2 h. The mixture is then immersed in a 0.1 mol / L NdCl3 solution and magnetically stirred at room temperature for 4-6 h. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, dried, and ground into powder to obtain the modified phosphogypsum. The material-to-liquid ratio of the ball-milled mixture to the NdCl3 solution is 1 g: 30 ml.

[0060] The modified coal gangue was prepared using the following method:

[0061] (1) The raw coal gangue is crushed, ground, and passed through a 200-mesh sieve, and then heat-treated at 500℃ for 2 hours to obtain pretreated coal gangue powder;

[0062] (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically at room temperature for 30-45 min, add pretreated coal gangue powder, heat to 40-45℃, react for 2-3 h, filter and wash the product until neutral, and dry to obtain modified coal gangue; the mass ratio of silane coupling agent KH570 to pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the material-liquid ratio of pretreated coal gangue powder to mixed solution is 1g:20ml.

[0063] A method for preparing the above-mentioned saline-alkali soil conditioner includes the following steps:

[0064] a. Inoculate Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus into LB liquid medium, respectively, and incubate with shaking at 28°C until the bacterial count reaches OD200. 600 ≈2.0, then mixed in a volume ratio of 1:1:1 and dried to obtain microbial inoculant;

[0065] The LB liquid culture medium consists of: 5g yeast extract, 10g tryptone, 10g sodium chloride, 1000mL distilled water, pH adjusted to 7.0, and sterilized by steam at 121℃ for 20min.

[0066] b. After crushing the bamboo shoot shells, pass them through a 100-mesh sieve and mix them with sodium lignosulfonate in a certain mass ratio to prepare an activator;

[0067] c. Preparation of modified phosphogypsum;

[0068] d. Mix the modified phosphogypsum, microbial inoculant, and activator evenly according to the weight ratio, and package to obtain the final product.

[0069] Comparative Example 1

[0070] A soil conditioner for saline-alkali soil is made from the following raw materials in parts by weight: 150 parts phosphogypsum, 8 parts microbial inoculant, and 15 parts activator. The microbial inoculant is a mixture of Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus. The activator is composed of bamboo shoot shell and sodium lignin sulfonate in a 2:1 mass ratio.

[0071] This comparative example is basically the same as Example 3, except that the phosphogypsum is unmodified phosphogypsum, which is a common byproduct of wet-process phosphoric acid production in the market.

[0072] Comparative Example 2

[0073] A soil conditioner for saline-alkali soil is made from the following raw materials in parts by weight: 150 parts modified phosphogypsum, 8 parts microbial inoculant, and 15 parts activator; wherein the modified phosphogypsum is prepared by compounding phosphogypsum and coal gangue and then modifying it with rare earth elements; wherein the microbial inoculant is made by mixing Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus.

[0074] The activator is composed of bamboo shoot shells and sodium lignosulfonate in a mass ratio of 2:1.

[0075] The modified phosphogypsum is prepared by the following method: phosphogypsum and coal gangue are mixed at a mass ratio of 1:0.5 and ball-milled at 600 r / min for 1-2 h. The mixture is then immersed in a 0.1 mol / L NdCl3 solution and magnetically stirred at room temperature for 4-6 h. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, dried, and ground into powder to obtain the modified phosphogypsum. The material-to-liquid ratio of the ball-milled mixture to the NdCl3 solution is 1 g: 30 ml.

[0076] A method for preparing the above-mentioned saline-alkali soil conditioner includes the following steps:

[0077] a. Inoculate Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus into LB liquid medium, respectively, and incubate with shaking at 28°C until the bacterial count reaches OD200. 600 ≈2.0, then mixed in a volume ratio of 1:1:1 and dried to obtain microbial inoculant;

[0078] The LB liquid culture medium consists of: 5g yeast extract, 10g tryptone, 10g sodium chloride, 1000mL distilled water, pH adjusted to 7.0, and sterilized by steam at 121℃ for 20min.

[0079] b. After crushing the bamboo shoot shells, pass them through a 100-mesh sieve and mix them with sodium lignosulfonate in a certain mass ratio to prepare an activator;

[0080] c. Preparation of modified phosphogypsum;

[0081] d. Mix the modified phosphogypsum, microbial inoculant, and activator evenly according to the weight ratio, and package to obtain the final product.

[0082] This comparative example is basically the same as Example 3, except that the modified phosphogypsum is made by mixing phosphogypsum and coal gangue as raw materials and then modifying them with rare earth elements.

[0083] Comparative Example 3

[0084] A soil conditioner for saline-alkali soil is made from the following raw materials in parts by weight: 150 parts modified phosphogypsum and 8 parts microbial inoculant; wherein the modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying it with rare earth elements; wherein the microbial inoculant is made by mixing Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus.

[0085] The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed at a mass ratio of 1:0.5 and ball-milled at 600 r / min for 1-2 h. The mixture is then immersed in a 0.1 mol / L NdCl3 solution and magnetically stirred at room temperature for 4-6 h. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, dried, and ground into powder to obtain the modified phosphogypsum. The material-to-liquid ratio of the ball-milled mixture to the NdCl3 solution is 1 g: 30 ml.

[0086] The modified coal gangue was prepared using the following method:

[0087] (1) The raw coal gangue is crushed, ground, and passed through a 200-mesh sieve, and then heat-treated at 500℃ for 2 hours to obtain pretreated coal gangue powder;

[0088] (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically at room temperature for 30-45 min, add pretreated coal gangue powder, heat to 40-45℃, react for 2-3 h, filter and wash the product until neutral, and dry to obtain modified coal gangue; the mass ratio of silane coupling agent KH570 to pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; the material-liquid ratio of pretreated coal gangue powder to mixed solution is 1g:20ml.

[0089] A method for preparing the above-mentioned saline-alkali soil conditioner includes the following steps:

[0090] a. Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus were inoculated into LB liquid medium and cultured at 28°C with shaking until the bacterial count reached 0.D600≈2.0. Then, they were mixed in a volume ratio of 1:1:1 and dried to obtain the microbial inoculum.

[0091] The LB liquid culture medium consists of: 5g yeast extract, 10g tryptone, 10g sodium chloride, 1000mL distilled water, pH adjusted to 7.0, and sterilized by steam at 121℃ for 20min.

[0092] b. Preparation of modified phosphogypsum;

[0093] c. Mix the modified phosphogypsum and microbial inoculant according to the weight ratio, and package to obtain the final product.

[0094] This comparative example is basically the same as Example 3, except that it does not contain an activator.

[0095] Performance testing

[0096] The safety of the products prepared in Examples 1-3 and Comparative Examples 1-3 of this invention was tested. 10g of each test sample was added to 100ml of deionized water to prepare a mixed solution. The solution was sealed and protected from light, then placed in a constant temperature shaking oven at 120 r / min and 25℃ for 8 hours. After standing for 16 hours, samples were taken for analysis. Before testing, the mixed solution was first filtered through a 0.45 μm glass fiber membrane. The filtered water samples were tested according to the method in "Identification Standard for Hazardous Toxic Substances: Leaching Toxicity Identification" (GB 5085.3-2007). Specific test results are shown in Table 1.

[0097] Table 1 Test Results

[0098]

[0099] As can be seen from the results in Table 1 above, the saline-alkali soil conditioner prepared by this invention is safer than conventional phosphogypsum. The content of heavy metal elements and fluoride ions in the conditioner is significantly reduced. This is because the modified phosphogypsum has a loose and porous structure, which has a good adsorption effect on harmful substances such as heavy metals (such as Cd, Pb, As, etc.) and fluoride (F) ions, thus reducing the cumulative harm of fluoride ions and heavy metals to the soil caused by the application of the conditioner.

[0100] Field application trials

[0101] The experiment was conducted in a farmland in Huaguan Village, Huaguan Town, Guangrao County, Shandong Province. Soil samples were collected from the top 0-30 cm layer and immediately sent back to the laboratory, where they were frozen during transport. Upon arrival at the laboratory, the physicochemical properties, heavy metal content, and fluoride ion levels of the collected soil samples were immediately tested. The results are shown in Tables 2-3.

[0102] Table 2 Basic physicochemical properties of the tested soils

[0103]

[0104] Table 3. Heavy metal and fluoride ion content in the original soil

[0105]

[0106] Wheat was planted as the crop, and the tested variety was Jimai 60. The experimental field was divided into three groups: Examples 1-3, Comparative Examples 1-3, and a blank control group, totaling seven treatments. Each treatment group covered an area of ​​2 mu (approximately 0.13 hectares), and the wheat planting density was the same in each group, 80 plants / m². Different soil conditioners were applied to each group at a rate of 30 kg / mu (approximately 20 kg / mu). The blank control group received no soil conditioner. All other procedures were performed using conventional field management. At harvest, the number of wilted and dead seedlings per mu (approximately 0.067 hectares), plant height (average of 50 randomly selected plants), thousand-grain weight, and yield per mu were recorded. Specific experimental results are shown in Table 4.

[0107] Table 4 Results of wheat planting experiment in experimental fields

[0108]

[0109] As can be seen from the data in Table 4 above, compared with the blank control group, wheat yield was significantly increased after using the soil conditioner of this invention, and the plant height, thousand-grain weight, and yield per acre were all superior to those of comparative examples 1-3 and the blank control. This is because the saline-alkali soil conditioner prepared by this invention can effectively improve the physical and chemical properties of saline-alkali soil through the synergistic effect of multiple components, thereby significantly improving soil fertility and health. This helps to promote plant growth and development, and improve crop yield and quality.

[0110] To further test the soil conditioner's effect on improving saline-alkali soil, the physicochemical properties, heavy metal content, and fluoride ion content of the soil in each treatment group were measured after planting. Soil samples were taken and tested from a depth of 0-30 cm in the experimental area. Soil samples were collected from each treatment group using the S-shaped sampling method. During sampling, the soil auger was drilled to a depth of 30 cm in one pass. Three replicates were collected from each treatment group, and the three replicate samples from the same treatment group were combined into one sample. Visible debris such as gravel and plant roots were removed, and the sample was divided into two equal parts. One part was used to determine the basic physicochemical properties of the soil; the other part was used to determine the heavy metal content and fluoride ion content. The test results are shown in Tables 5-6.

[0111] Table 5 Test Results

[0112]

[0113] Table 6 Test Results

[0114]

[0115] As can be seen from the results in Tables 5-6 above, after using the soil conditioner prepared according to the present invention, the soil pH, bulk density, total salt content, and contents of various heavy metals and fluoride ions were significantly reduced, while the soil organic matter content increased. The soil improvement effects of Comparative Examples 1, 2, and 3 were poor. This is because the modified phosphogypsum obtained by treating phosphogypsum and modified coal gangue using a specific modification method has a significantly rough and loose microstructure with increased pores (see...). Figure 1The modified phosphogypsum exhibits an increased specific surface area and enhanced surface functional group activity, resulting in excellent adsorption of heavy metals (such as Cd, Pb, and As) and harmful substances like fluoride (F) ions in the soil. It also promotes soil aggregate formation, increases salt infiltration rate, and enhances sodium ion exchange capacity, thereby reducing salinity, pH, and soil compaction. Furthermore, the activator used promotes the dissolution and release of heavy metal ions in the soil and enhances the adsorption of harmful heavy metal ions by increasing the activity of the surface functional groups, significantly improving the soil conditioner's effect on saline-alkali soils.

[0116] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A soil conditioner for saline-alkali soil, characterized in that, It is made from the following raw materials in parts by weight: 100-200 parts modified phosphogypsum, 5-10 parts microbial inoculant, and 10-20 parts activator; The modified phosphogypsum is prepared by compounding phosphogypsum and modified coal gangue and then modifying it with rare earth elements; the microbial agent is prepared by mixing Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus; the activator is composed of bamboo shoot shell and sodium lignosulfonate in a mass ratio of 2:

1. The modified phosphogypsum is prepared by the following method: phosphogypsum and modified coal gangue are mixed and ball-milled at 600 r / min for 1-2 h. The mixture is then immersed in a 0.1 mol / L NdCl3 solution and magnetically stirred at room temperature for 4-6 h. After the reaction is completed, the mixture is centrifuged, washed with anhydrous ethanol, dried, and ground into powder to obtain the modified phosphogypsum. The modified coal gangue was prepared using the following method: (1) The raw coal gangue is crushed, ground, and passed through a 200-mesh sieve, and then heat-treated at 500℃ for 2 hours to obtain pretreated coal gangue powder; (2) Add silane coupling agent KH570 to the mixed solution, adjust the pH value to 6.0 with sodium hydroxide and hydrochloric acid, stir magnetically for 30-45 min at room temperature, add pretreated coal gangue powder, heat to 40-45℃, react for 2-3 h, filter and wash the product until neutral, and dry to obtain modified coal gangue.

2. The saline-alkali soil conditioner according to claim 1, characterized in that, The mass ratio of the phosphogypsum to the modified coal gangue is 1:0.25-0.5; the material-to-liquid ratio of the mixture to the NdCl3 solution is 1g:30ml.

3. The saline-alkali soil conditioner according to claim 1, characterized in that, In step (2), the mass ratio of silane coupling agent KH570 to pretreated coal gangue powder is 1:30; the mixed solution is composed of anhydrous ethanol and deionized water in a volume ratio of 3:1; and the material-liquid ratio of pretreated coal gangue powder to mixed solution is 1g:20ml.

4. A method for preparing a saline-alkali soil conditioner according to any one of claims 1-3, characterized in that, It includes the following steps: a. Inoculate Bacillus subtilis, Streptomyces cellulose, and Bacillus mucilaginosus into LB liquid medium, respectively, and incubate with shaking at 28°C until the bacterial count reaches OD200. 600 ≈2.0, then mixed in a volume ratio of 1:1:1 and dried to obtain microbial inoculant; b. After crushing the bamboo shoot shells, pass them through a 100-mesh sieve and mix them with sodium lignosulfonate in a certain mass ratio to prepare an activator; c. Preparation of modified phosphogypsum; d. Mix the modified phosphogypsum, microbial inoculant, and activator evenly according to the weight ratio, and package to obtain the final product.

Images