Method for preparing soil conditioner from ardealite and application of soil conditioner

Abstract

The invention discloses a method for preparing a soil conditioner from ardealite and application of the soil conditioner, and belongs to the field of solid waste resource utilization. According to the method, the preparation process is simple, effective utilization of the phosphogypsum can be achieved, and effective resource utilization of the phosphogypsum is achieved through calcination pre-activation, reasonable burdening and functional mixed bacteria fermentation. The prepared product is high in activity when being used as a liquid biological phosphate fertilizer, the yield of lettuce can be obviously increased only through a leaf surface spraying mode, thallium and beryllium pollutants in polluted soil can be effectively passivated when the product is used as a soil conditioner, the thallium leaching concentration is lower than 2.11 * 10 <-3 > mg / L, and the beryllium leaching concentration is lower than 3.02 * 10 <-3 > mg / L.

Description

Technical Field

[0001] The present invention belongs to the field of resource utilization of solid waste, and particularly relates to a method for preparing a soil conditioner from phosphogypsum and its application. Background Art

[0002] Phosphogypsum is a by-product of the wet-process phosphoric acid process, and its main component is calcium sulfate dihydrate. The accumulation of phosphogypsum is not only a quantitative problem but also an environmental problem that urgently needs to be solved. The harms it brings are mainly reflected in three aspects: ecological risk, resource waste, and space occupation. From the perspective of ecological risk, phosphogypsum contains various substances that may harm the environment and human health. For example, the presence of fluoride and heavy metal elements (such as cadmium and lead) makes the acidic substances in phosphogypsum gradually seep into the soil and water bodies during long-term stacking. This will not only cause soil acidification, destroy the ecological balance of the soil, but also lead to groundwater pollution, posing a serious threat to the drinking water safety of surrounding residents. In addition, phosphogypsum may also contain radioactive elements, and the long-term exposure to these elements will also have an immeasurable impact on the environment and human health. In terms of resource waste, the content of calcium sulfate in phosphogypsum is extremely high, and both sulfur and calcium are important chemical raw materials. However, due to the limitations of current technical levels, the utilization rate of these resources is seriously insufficient, resulting in a large amount of potential resources being wasted. This is not only a great waste of natural resources but also restricts the development of related industries. Space occupation is another serious problem brought by phosphogypsum. Due to the large volume of phosphogypsum, the stacking yard needs to occupy a large amount of land resources. This not only wastes precious land resources but also may lead to the deterioration of the ecological environment around the stacking yard. In addition, there is a risk of dam break in the phosphogypsum stacking yard. Once a dam break accident occurs, it will pose a serious threat to the health and ecological safety of surrounding residents.

[0003] Regarding the problem of resource utilization of phosphogypsum, current technologies mainly focus on three major fields: building materials, chemical engineering, and agriculture. However, these technologies all have significant deficiencies. In the field of building materials applications, due to the large amount of impurities in phosphogypsum, it needs to be removed through high-temperature calcination or complex pretreatment processes. This not only has high energy consumption but also poor process stability, making it difficult to be widely promoted and applied on a large scale. In the chemical engineering field, the process of producing sulfuric acid and co-producing cement from phosphogypsum has certain feasibility, but it also requires high-temperature decomposition, with large equipment investment and high carbon emissions, and poor economic efficiency. In the agricultural field, directly applying phosphogypsum has the risk of heavy metal migration, and the phosphorus element in phosphogypsum exists in a poorly soluble state, with low plant absorption rate, making it difficult to meet the needs of agricultural production.

[0004] To overcome these challenges, after in-depth research, researchers have proposed an innovative solution - the bio-directed conversion technology. Through the action of microorganisms, this technology achieves the efficient conversion and utilization of phosphorus in phosphogypsum, while effectively reducing the pollution risk of heavy metals. More importantly, this technology realizes the efficient delivery of nutrients in liquid form, highly matching the requirements of precise agricultural fertilization. Compared with traditional technologies, the bio-directed conversion technology combines environmental friendliness, resource efficiency, and economic feasibility, providing a brand-new path for the resource utilization of phosphogypsum. The successful application of this technology not only promises to solve the environmental problems caused by the accumulation of phosphogypsum but also injects new vitality into the development of related industries. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a method for preparing a soil conditioner using phosphogypsum and its application.

[0006] Technical Solution: The present invention provides a method for preparing a soil conditioner using phosphogypsum, comprising the following steps: (1) Calcining and pulverizing the phosphogypsum to obtain calcined gypsum powder; (2) Mixing semen cassiae, semen hoveniae, and straw powder, and stirring evenly to obtain a phosphorus-release auxiliary material; (3) Mixing the phosphorus-release auxiliary material, plant ash, and calcined gypsum powder evenly to obtain a plant ash-phosphorus-release gypsum powder mixture; (4) Mixing water and the plant ash-phosphorus-release gypsum powder mixture, stirring evenly, and performing a hydrothermal reaction to obtain a hydrothermal phosphorus-release slurry; (5) Adding a composite microorganism to the hydrothermal phosphorus-release slurry for fermentation, and performing solid-liquid separation to obtain a soil conditioner.

[0007] Further, in step (1), the calcination time is 0.5 - 5.5 hours, and the calcination temperature is 450 - 850 °C.

[0008] Further, in step (2), the mass ratio of semen cassiae, semen hoveniae, and straw powder is 2 - 8:1.5 - 7.5:100.

[0009] Further, in step (3), the mass ratio of the phosphorus-release auxiliary material, plant ash, and calcined gypsum powder is 2.5 - 22.5:5 - 15:100.

[0010] Further, in step (4), the liquid-solid ratio of water and the plant ash-phosphorus-release gypsum powder mixture is 10 - 50:1 mL / g, the hydrothermal time is 0.5 - 4.5 hours, and the hydrothermal temperature is 120 - 360 °C.

[0011] Further, in step (5), the fermentation time is 4 - 24 days.

[0012] Further, the mass ratio of the composite microorganism to the hydrothermal phosphorus-releasing slurry in step (5) is 0.25-4.75:1000.

[0013] Further, the composite microorganism described in step (5) is composed of Serratia, Rhizobium, Streptomyces, and Aspergillus.

[0014] Further, the mass ratio of Serratia, Rhizobium, Streptomyces, and Aspergillus is 0.25-1.75:0.25-1.75:0.25-1.75:0.25-1.75.

[0015] Among them, the Serratia is any one of Serratia marcescens, Serratia rubidaea, and Serratia nematodiphila; the Rhizobium is any one of Cellulolytic rhizobium, Sophora japonica root nodule bacteria, Tropical rhizobium, Sunflower root nodule bacteria, Pea root nodule bacteria, Radiobacter, Gallic rhizobium, Laguerre rhizobium, Broad bean root nodule bacteria, Pusha rhizobium, Sludge rhizobium, Rice rhizobium, Grape root nodule bacteria, Fred rhizobium, Kidney bean root nodule bacteria, Sesbania rostrata rhizobium; the Streptomyces is any one of Streptomyces avermitilis, Streptomyces pactum, Streptomyces flavidofuscus, Streptomyces luteoverticillatus, Streptomyces thermoalkalophilus, Streptomyces albidoflavus, Streptomyces vinaceusdrappus, Streptomyces herbicola, Streptomyces thermophilus, Streptomyces hiroshimensis, Streptomyces cinnamoneus; the Aspergillus is any one of Aspergillus niger, Aspergillus sydowii, Aspergillus terreus, Aspergillus wentii, Aspergillus japonicus, Aspergillus ruber, Aspergillus usamii, Aspergillus oryzae, Aspergillus carbonarius, Aspergillus purpureus.

[0016] The present invention also provides a soil conditioner prepared according to the above method.

[0017] The present invention also provides the application of the above soil conditioner in conditioning heavy metal-contaminated soil or as a phosphate fertilizer in promoting crop growth.

[0018] Further, the heavy metals include thallium and beryllium.

[0019] Reaction mechanism: Under the high-temperature calcination environment, complex physical and chemical changes occur in phosphogypsum. First, it undergoes dehydration reactions, gradually removing free water and crystal water to form β-type hemihydrate gypsum and anhydrous gypsum, accompanied by crystal form transformation. At high temperatures, part of the fluorine in phosphogypsum volatilizes in the form of HF, and the organic phosphorus and sulfides contained are oxidized and decomposed into gases such as CO2 and SO2. The soluble phosphate is converted into pyrophosphate or metaphosphate, reducing the interference with the hydration activity of gypsum. In the hydrothermal system, the high-temperature and high-pressure conditions significantly enhance the solubility and reaction activity of the materials. In this environment, the ion migration rate accelerates, the hydrolysis energy barrier of organic matter decreases, and the activation energy of mineral phase transformation decreases, forming a multi-scale synergistic reaction system. The cellulose / hemicellulose in the mixture undergoes hydrolysis and cleavage to generate monosaccharides such as glucose and xylose. Lignin undergoes demethylation in an alkaline medium (the role of plant ash) to produce phenolic hydroxyl compounds. The anthraquinone substances (such as emodin) contained in Cassia obtusifolia and the flavonoid glycosides of Hovenia dulcis undergo a synergistic antioxidant reaction to form stable polycyclic aromatic hydrocarbon derivatives. The phosphorus-containing organic matter in the mixture is released, and calcium magnesium phytate is gradually hydrolyzed under high temperature and high pressure to release phosphate ions and Ca 2+ and Mg 2+ ions. At the same time, phospholipids undergo a β-elimination reaction to generate phosphatidylglycerol and free fatty acids. The residual carbon-based substances undergo a polycondensation reaction to form carbon materials. K2CO3 (the main component of plant ash) hydrolyzes to produce OH⁻, promoting the cleavage of organic phosphorus ester bonds. At the same time, K⁺ acts as a charge compensator to inhibit the premature precipitation of Ca 2 ⁺ and PO4 3 ⁻. Amorphous SiO2 reacts with OH⁻ to form [SiO(OH)3]⁻, which forms a C-S-H gel precursor with Ca 2 ⁺ in the system. Anhydrous gypsum reacts with phosphate ions to form a Ca5(PO4)3(OH) precursor. Ca(PO3)2 hydrolyzes in a high-temperature hydrothermal environment to generate CaHPO4, releasing H +Balance the alkalinity of the system to form a pH buffer system. The phosphate ions produced by the hydrolysis of organic phosphorus react with calcium ions and dehydrate to form brushite and hydroxyapatite. The silicate provided by plant ash forms calcium silicophosphate with calcium ions and phosphate ions through the ripening process. Through material circulation in the hydrothermal reaction system, the directional regulation of phosphorus is achieved, making the product have the functions of both a soil conditioner and a slow-release fertilizer. Serratia uses the monosaccharides in the hydrothermal phosphorus-releasing slurry as a carbon source and energy source, decomposes the monosaccharides into pyruvate through the glycolytic pathway, and pyruvate further enters the tricarboxylic acid cycle to produce energy (ATP), carbon dioxide and water. Serratia can also use the amino acids in the hydrothermal phosphorus-releasing slurry for protein synthesis and metabolism. It secretes extracellular enzymes, such as proteases and amylases, to decompose macromolecular organic substances into small-molecular substances. Its metabolites include organic acids, antibiotics and some extracellular polysaccharides. These organic acids can lower the pH value of the surrounding environment, which is beneficial to the dissolution of certain minerals and the release of phosphorus; antibiotics can inhibit the growth of other harmful microorganisms and create a good living environment for itself and other beneficial microorganisms; extracellular polysaccharides can enhance the attachment ability of microorganisms in the soil. Rhizobium uses the sugars and nitrogen-containing compounds in the hydrothermal phosphorus-releasing slurry, and reduces nitrogen in the air to ammonia through the action of nitrogenase, providing a nitrogen source for itself and other microorganisms. At the same time, Rhizobium can use monosaccharides for growth and reproduction, synthesize its own cell substances, and its metabolites are mainly ammonia and some growth hormones, such as indole acetic acid, etc. Ammonia can provide nitrogen nutrition for other microorganisms and promote the growth of the microbial community; growth hormones can stimulate the growth and development of plant roots and improve the nutrient absorption ability of plants. Streptomyces uses macromolecular substances such as polysaccharides and proteins in the hydrothermal phosphorus-releasing slurry. It secretes a variety of extracellular enzymes, such as cellulase, protease, amylase, etc., to decompose macromolecular substances into small-molecular sugars, amino acids, etc. Streptomyces uses these small-molecular substances for growth and metabolism, and synthesizes a variety of antibiotics, vitamins and enzymes through secondary metabolic pathways. The antibiotics produced by it can inhibit the growth of other microorganisms and maintain the balance of the microbial community; vitamins can provide nutrition for other microorganisms and promote the growth and reproduction of microorganisms; enzymes can further decompose the organic substances in the hydrothermal phosphorus-releasing slurry and improve the availability of nutrients. Aspergillus secretes a variety of hydrolases, such as cellulase, hemicellulase, pectinase, etc., to decompose polysaccharide substances such as cellulose, hemicellulose and pectin in the hydrothermal phosphorus-releasing slurry into monosaccharides. Aspergillus can also use substances such as amino acids and fatty acids for growth and metabolism. Its metabolites include organic acids, enzymes and some secondary metabolites. Organic acids can regulate the pH value of the environment, promote the dissolution of minerals and the release of phosphorus; enzymes can accelerate the decomposition of organic substances; secondary metabolites may have functions such as antibacterial and antioxidant. Serratia, Rhizobium, Streptomyces and Aspergillus have different nutritional requirements and metabolic abilities in the hydrothermal phosphorus-releasing slurry.Rhizobia can fix nitrogen and provide a nitrogen source for other microorganisms; while substances such as sugars and amino acids produced by the decomposition of organic matter by other microorganisms can provide a carbon source and energy for rhizobia. Extracellular enzymes secreted by Serratia and Aspergillus can decompose macromolecular organic matter into small-molecule substances, providing easily absorbable nutrients for microorganisms such as Streptomyces. This nutritional complementary relationship enables the microbial community to more efficiently utilize various nutrient components in the hydrothermal phosphorus-releasing slurry, promoting the growth and reproduction of microorganisms. The metabolites produced by each microorganism also have a synergistic effect. The organic acids produced by Serratia and Aspergillus can lower the pH value of the environment, which is beneficial for the antibiotics produced by Streptomyces to play a role, and at the same time promotes mineral dissolution and phosphorus release. The ammonia produced by rhizobia can provide a nitrogen source for other microorganisms, promoting the synthesis of biological macromolecules such as proteins and nucleic acids by microorganisms. In addition, the extracellular polysaccharides produced by microorganisms can form biofilms, aggregating microorganisms together and enhancing the interaction and synergistic effect between microorganisms. The organic acids produced by microorganisms can react with minerals in the hydrothermal phosphorus-releasing slurry to dissolve the minerals and release nutrient elements such as phosphorus and calcium. The antibiotics produced by microorganisms can inhibit the growth of harmful microorganisms in the hydrothermal phosphorus-releasing slurry, reducing the damage to beneficial microorganisms and the original components. Enzymes secreted by microorganisms (such as cellulase, protease, amylase, etc.) can react with macromolecular organic matter in the hydrothermal phosphorus-releasing slurry and decompose it into small-molecule substances. Cellulase can decompose cellulose into glucose, protease can decompose proteins into amino acids, and amylase can decompose starch into maltose and glucose. These small-molecule substances can be absorbed and utilized by microorganisms, and at the same time increase the effectiveness of nutrients in the hydrothermal phosphorus-releasing slurry. In addition, enzymes can also promote the progress of some chemical reactions, such as the hydrolysis of organic phosphorus, improving the phosphorus release efficiency. Serratia, rhizobia, Streptomyces, and Aspergillus effectively utilize the components in the hydrothermal phosphorus-releasing slurry through their respective unique metabolic pathways and synergistic effects among them, producing a variety of metabolites and enzymes.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: The preparation process of the method of the present invention is simple, and the effective utilization of phosphogypsum can be realized. Through calcination pre-activation, reasonable batching, and functional mixed bacteria fermentation, the effective resource utilization of phosphogypsum is realized. The prepared product has high activity when used as a liquid biological phosphate fertilizer, and significant yield increase of lettuce can be achieved only by foliar spraying. When used as a soil conditioner, it can also effectively passivate thallium and beryllium pollutants in polluted soil, with the thallium leaching concentration lower than 2.11×10 -3 mg / L and the beryllium leaching concentration lower than 3.02×10 -3 mg / L. Description of the Drawings

[0021] Figure 1 is a flowchart of the present invention. Detailed Embodiments

[0022] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

[0023] Preparation of heavy metal contaminated soil: Weigh 1 kg of uncontaminated soil sample, then add 10 mg of thallium and 10 mg of beryllium to the soil sample, add water to the soil according to the liquid-solid ratio of 1:1 ml / mg, stir evenly, and obtain the tested heavy metal contaminated soil sample after aging for 24 hours; Plant ash: Purchased from Xinghua Sannong Plant Ash Co., Ltd., with soluble K content of 9.35% and soluble P content of 1.36%; Straw powder: Purchased from Shaanxi Jinhe Agricultural Technology Co., Ltd., type: wheat straw powder, brand: Shanjinhe; Phosphogypsum: Phosphogypsum is taken from Guizhou Xifeng Phosphate Mine Co., Ltd. The phosphogypsum sample mainly contains 52.70% SO3, 37.01% CaO, 4.37% SiO2, 2.07% Al2O3, 1.63% P2O5 and other components (inevitable impurities and loss on ignition).

[0024] Example 1 Influence of phosphogypsum calcination time on the performance of the prepared liquid soil conditioner (bio-phosphate fertilizer) Put the phosphogypsum into a calcination furnace, calcine and then grind it to obtain calcined paste powder, where the calcination time is 0.35 hours, 0.4 hours, 0.45 hours, 0.5 hours, 3 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, and the calcination temperature is 450 °C. Mix semen cassiae, fructus hoveniae, and straw powder according to the mass ratio of 2:1.5:100, stir evenly to obtain the phosphorus-release auxiliary material. Mix the phosphorus-release auxiliary material, plant ash, and calcined paste powder according to the mass ratio of 2.5:5:100, stir evenly to obtain the plant ash phosphorus-release paste powder mixture. Mix water and the plant ash phosphorus-release paste powder mixture according to the liquid-solid ratio of 10:1 mL / g, stir evenly, and carry out hydrothermal reaction to obtain hydrothermal phosphorus-release slurry, where the hydrothermal time is 0.5 hours and the hydrothermal temperature is 120 °C. Add composite microorganisms to the hydrothermal phosphorus-release slurry for fermentation, and perform solid-liquid separation to obtain the liquid, which is the liquid soil conditioner (bio-phosphate fertilizer). The mass ratio of the composite microorganisms to the hydrothermal phosphorus-release slurry is 0.25:1000, the fermentation time of the composite microorganisms is 4 days, the composite microorganisms are composed of Serratia, Rhizobium, Streptomyces, and Aspergillus, where the powder of Serratia, Rhizobium, Streptomyces, and Aspergillus is composed according to the mass ratio of 0.25:0.25:0.25:1. The Serratia is Serratia marcescens (CGMCC 1.12941); the Rhizobium is Rhizobium cellulolyticum (CGMCC 1.15995); the Streptomyces is Streptomyces avermitilis (CGMCC 4.7296); the Aspergillus is Aspergillus niger (CGMCC 3.15663).

[0025] Comparative Experiment on Lettuce Cultivation: Select two identical plots of land for lettuce cultivation, namely No .1 and No .2 plots. The processes of lettuce seedling selection, planting, and plant protection are the same. During the entire growth cycle No .1 plot is not sprayed with liquid biological phosphate fertilizer, No .2 plot is sprayed with liquid biological phosphate fertilizer once every week after transplanting (2 kg per mu, diluted 200 times before use). After the planting period ends, harvest the lettuce, wash it, drain the water, and weigh it.

[0026] Lettuce Yield Increase Rate: No The weight difference between the lettuce harvested from plot No .2 and the lettuce harvested from plot No .1 is divided by the weight of the lettuce harvested from plot

[0027] to obtain the lettuce yield increase rate.

[0027] Preparation of Remediated Heavy Metal-Contaminated Soil: Different groups of liquid soil conditioners prepared in this example are respectively mixed with heavy metal-contaminated agricultural land soil according to a mass ratio of 2.5:100, stirred evenly, evenly sprinkled with water, and aged for 7 days to obtain remediated heavy metal-contaminated agricultural land soil.

[0028] Heavy Metal Toxicity Leaching Test: Toxicity leaching tests are carried out on heavy metal-contaminated soil samples before and after remediation in accordance with "Solid Waste - Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJ / T 299-2007).

[0029] Detection of Thallium and Beryllium Ion Concentrations: The thallium concentration in the leachate is determined in accordance with "Water Quality - Determination of Thallium - Graphite Furnace Atomic Absorption Spectrophotometry" (HJ 748-2015); the beryllium concentration in the leachate is determined in accordance with "Water Quality - Determination of 65 Elements - Inductively Coupled Plasma Mass Spectrometry" (HJ 700-2014).

[0030] The test results of this example are shown in Table 1.

[0031] Table 1 Influence of Phosphogypsum Calcination Time on the Performance of the Prepared Liquid Soil Conditioner (Biological Phosphate Fertilizer)

[0032] As can be seen from Table 1, when the calcination time of phosphogypsum is less than 0.5 hours (as shown in Table 1, when the calcination time of phosphogypsum = 0.45 hours, 0.4 hours, 0.35 hours and lower values not listed in Table 1), the calcination time of phosphogypsum is short and the pre-activation of phosphogypsum is insufficient, resulting in a decrease in the fertilizer efficiency of the prepared liquid bio-fertilizer. As a result, the leaching concentration rates of thallium and beryllium both increase significantly with the decrease of the phosphogypsum calcination time, and the lettuce yield increase rate decreases significantly with the decrease of the phosphogypsum calcination time. When the calcination time of phosphogypsum is equal to 0.5 - 5.5 hours (as shown in Table 1, when the calcination time of phosphogypsum = 0.5 hours, 3 hours, 5.5 hours), in a high-temperature calcination environment, complex physical and chemical changes occur in phosphogypsum. First, dehydration reactions occur, gradually removing free water and crystal water to form β-type hemihydrate gypsum and anhydrous gypsum, accompanied by crystal form transformation. At high temperatures, part of the fluorine in phosphogypsum volatilizes in the form of HF, and the organic phosphorus and sulfides contained are oxidized and decomposed into gases such as CO2 and SO2, and the soluble phosphate is converted into pyrophosphate or metaphosphate, reducing the interference with the hydration activity of gypsum. Finally, the lettuce yield increase rate is higher than 124%, the thallium leaching concentration in the soil is lower than 0.05 mg / L, and the beryllium leaching concentration is lower than 0.05 mg / L. When the calcination time of phosphogypsum is higher than 5.5 hours (as shown in Table 1, when the calcination time of phosphogypsum = 6 hours, 6.5 hours, 7 hours and higher values not listed in Table 1), the phosphogypsum is overcalcined and the heat treatment activity of phosphogypsum decreases, resulting in a decrease in the fertilizer efficiency of the prepared liquid bio-fertilizer. It also leads to a significant increase in the leaching concentration rates of thallium and beryllium in the soil with the further increase of the phosphogypsum calcination time, and a significant decrease in the lettuce yield increase rate with the further increase of the phosphogypsum calcination time.

[0033] Therefore, generally speaking, considering the benefits and costs, when the calcination time of phosphogypsum is equal to 0.5 - 5.5 hours, it is most beneficial to improve the fertilizer efficiency of the prepared liquid bio-fertilizer and the performance of the soil conditioner.

[0034] Example 2 Influence of the mass ratio of cassia seed,hovenia seed and straw powder on the performance of the prepared liquid soil conditioner (bio-fertilizer) The phosphogypsum is placed in a calcining furnace, calcined and ground into powder to obtain calcined paste powder, wherein the calcination time is 5.5 hours and the calcination temperature is 650°C. Mix cassia seed, hovenia dulcis fruit and straw powder in a mass ratio of 0.5:1.5:100, 1:1.5:100, 1.5:1.5:100, 2:0.5:100, 2:1:100, 2:1.25:100, 2:1.5:100, 5:1.5:100, 8:1.5:100, 2:4.5:100, 5:4.5:100, 8:4.5:100, 2:7.5:100, 5:7.5:100, 8:7.5:100, 8:8.5:100, 8:9.5:100, 8:10:100, 8.5:7.5:100, 9:7.5:100 and 9.5:7.5:100 and stir well to obtain a phosphorus-releasing auxiliary material. The phosphorus-releasing auxiliary material, plant ash and calcined paste powder were mixed in a mass ratio of 12.5:10:100, stirred evenly, and a plant phosphorus-releasing paste powder mixture was obtained. Water and the plant phosphorus-releasing paste powder mixture were mixed in a liquid-solid ratio of 30:1 mL / g, stirred evenly, and subjected to a hydrothermal reaction to obtain a hydrothermal phosphorus-releasing slurry, wherein the hydrothermal time was 2.5 hours and the hydrothermal temperature was 240°C. Composite microorganisms are added to the hydrothermal phosphorus slurry for fermentation, and the solid-liquid separation is performed to obtain a liquid, which is a liquid soil conditioner (biophosphate fertilizer). The mass ratio of the composite microorganism to the hydrothermal phosphorus slurry is 2.5:1000, and the fermentation time of the composite microorganism is 14 days. The composite microorganisms are composed of Serratia, Rhizobium, Streptomyces, and Aspergillus. The Serratia, Rhizobium, Streptomyces, and Aspergillus powders are composed of a mass ratio of 1:1:1:1. The Serratia is Serratia rubrum (CGMCC 1.10839); the Rhizobium is Rhizobium chinense (CGMCC 1.15555); the Streptomyces is Streptomyces condensus (CGMCC 4.6287); and the Aspergillus is Aspergillus polydorum (CGMCC 3.13944).

[0035] The comparative test of lettuce planting, the yield increase rate of lettuce, the preparation method of heavy metal contaminated soil after restoration, the heavy metal toxicity leaching test and the detection of thallium and beryllium ion concentrations are all the same as in Example 1. The test results of this example are shown in Table 2.

[0036] Table 2 Effect of mass ratio of Cassia seed, Hovenia dulcis, and straw powder on the performance of prepared liquid soil conditioner (biophosphate fertilizer)

[0037] As can be seen from Table 2, when the mass ratio of cassia seed,hovenia fruit, and straw powder is less than 2:1.5:100 (as in Table 2, the mass ratio of cassia seed, hovenia fruit, and straw powder = 1.5:1.5:100, 1:1.5:100, 0.5:1.5:100, 2:1.25:100, 2:1:100, 2:0.5:100 and lower ratios not listed in Table 2), the addition of cassia seed and hovenia fruit is less, and the reaction of the materials is insufficient during the later hydrothermal reaction process, resulting in a decrease in the fertilizer efficiency of the prepared liquid bio-phosphate fertilizer. It also causes the leaching concentration rates of thallium and beryllium in the soil to increase significantly with the decrease in the mass ratio of cassia seed, hovenia fruit, and straw powder, and the lettuce yield increase rate to decrease significantly with the decrease in the mass ratio of cassia seed, hovenia fruit, and straw powder. When the mass ratio of cassia seed, hovenia fruit, and straw powder is equal to 2 - 8:1.5 - 7.5:100 hours (as in Table 2, the mass ratio of cassia seed, hovenia fruit, and straw powder = 2:1.5:100, 5:1.5:100, 8:1.5:100, 2:4.5:100, 5:4.5:100, 8:4.5:100, 2:7.5:100, 5:7.5:100, 8:7.5:100), in the hydrothermal system, the high-temperature and high-pressure conditions significantly improve the solubility and reaction activity of the materials. In this environment, the ion migration rate accelerates, the hydrolysis energy barrier of organic matter decreases, the activation energy of mineral phase transformation decreases, and a multi-scale synergistic reaction system is formed. The cellulose / hemicellulose in the mixture undergoes hydrolysis cleavage to generate monosaccharides such as glucose and xylose. Lignin undergoes demethylation in an alkaline medium (the role of plant ash) to produce phenolic hydroxyl compounds. The anthraquinone substances (such as emodin) contained in cassia seed and the flavonoid glycosides of hovenia fruit undergo a synergistic antioxidant reaction to generate stable polycyclic aromatic hydrocarbon derivatives. The release of phosphorus organic matter in the mixture, and the gradual hydrolysis of calcium magnesium phytate under high temperature and high pressure to release phosphate and Ca 2+ and Mg 2+ ions. At the same time, phospholipids undergo a β-elimination reaction to generate phosphatidylglycerol and free fatty acids. The residual carbon-based substances undergo a polycondensation reaction to form carbon materials. K2CO3 (the main component of plant ash) hydrolyzes to produce OH⁻, promoting the cleavage of organic phosphorus ester bonds. At the same time, K⁺ acts as a charge compensator to inhibit the premature precipitation of Ca 2 ⁺ and PO4 3 ⁻. Amorphous SiO2 reacts with OH⁻ to generate [SiO(OH)3]⁻, forming a C-S-H gel precursor with Ca 2 ⁺ in the system. Anhydrous gypsum reacts with phosphate to generate a Ca5(PO4)3(OH) precursor. Ca(PO3)2 hydrolyzes in a high-temperature hydrothermal environment to generate CaHPO4, releasing H +Balance the alkalinity of the system to form a pH buffer system. The phosphate ions produced by the hydrolysis of organic phosphorus react with calcium ions and dehydrate to form brushite and hydroxyapatite. The silicate provided by plant ash forms calcium silicophosphate with calcium ions and phosphate ions through the curing process. Through material circulation in the hydrothermal reaction system, the directional regulation of phosphorus is achieved, making the product have the functions of both a soil conditioner and a slow-release fertilizer. Finally, the lettuce yield increase rate is higher than 136%, and the thallium leaching concentration in the soil is lower than 0.01 mg / L, and the beryllium leaching concentration is lower than 0.01 mg / L. When the mass ratio of cassia seed,hovenia dulcis fruit, and straw powder is higher than 8:7.5:100 (as shown in Table 2, the mass ratio of cassia seed, hovenia dulcis fruit, and straw powder = 8:8.5:100, 8:9.5:100, 8:10:100, 8.5:7.5:100, 9:7.5:100, 9.5:7.5:100 and higher ratios not listed in Table 2), the addition of cassia seed and hovenia dulcis fruit is excessive, and the reaction of the materials during the hydrothermal and fermentation processes is unbalanced, resulting in a decrease in the fertilizer efficiency of the prepared liquid bio-fertilizer, and the leaching concentration rates of thallium and beryllium increase significantly with the further increase of the mass ratio of cassia seed, hovenia dulcis fruit, and straw powder, while the lettuce yield increase rate decreases significantly with the further increase of the mass ratio of cassia seed, hovenia dulcis fruit, and straw powder.

[0038] Therefore, generally speaking, considering the benefits and costs, when the mass ratio of cassia seed, hovenia dulcis fruit, and straw powder is equal to 2 - 8:1.5 - 7.5:100, it is most beneficial to improve the fertilizer efficiency of the prepared liquid bio-fertilizer and the performance of the soil conditioner.

[0039] Example 3 Influence of the mass ratio of phosphorus-release adjuvant, plant ash, and calcined paste powder on the performance of the prepared liquid soil conditioner (bio-fertilizer) Put phosphogypsum into a calcination furnace, calcine it and then grind it into powder to obtain calcined gypsum powder. The calcination time is 5.5 hours and the calcination temperature is 850 °C. Mix semen cassiae, fructushoveniae and straw powder according to the mass ratio of 8:7.5:100, and stir evenly to obtain a phosphorus-release auxiliary material. Mix the phosphorus-release auxiliary material, plant ash and calcined gypsum powder according to the mass ratios of 1:5:100, 1.5:5:100, 2:5:100, 2.5:2.5:100, 2.5:3:100, 2.5:4:100, 2.5:5:100, 12.5:5:100, 22.5:5:100, 2.5:10:100, 12.5:10:100, 22.5:10:100, 2.5:15:100, 12.5:15:100, 22.5:15:100, 22.5:17.5:100, 22.5:20:100, 22.5:22.5:100, 25:15:100, 27.5:15:100, 30:15:100, stir evenly to obtain a plant ash phosphorus-release gypsum powder mixture. Mix water and the plant ash phosphorus-release gypsum powder mixture according to the liquid-solid ratio of 50:1 mL / g, stir evenly, and carry out a hydrothermal reaction to obtain a hydrothermal phosphorus-release slurry. The hydrothermal time is 4.5 hours and the hydrothermal temperature is 360 °C. Add composite microorganisms to the hydrothermal phosphorus-release slurry for fermentation, carry out solid-liquid separation, and the obtained liquid is the liquid soil conditioner (bio-phosphate fertilizer). The mass ratio of the composite microorganisms to the hydrothermal phosphorus-release slurry is 4.75:1000. The fermentation time of the composite microorganisms is 24 days. The composite microorganisms are composed of Serratia, Rhizobium, Streptomyces and Aspergillus. The powder of Serratia, Rhizobium, Streptomyces and Aspergillus is composed according to the mass ratio of 1.75:1.75:1.75:1. The Serratia is Serratia nematodiphila (CGMCC 1.6853); the Rhizobium is Rhizobium tropici (CGMCC1.15554); the Streptomyces is Streptomyces flavogriseus (CGMCC 4.6391); the Aspergillus is Aspergillus terreus (CGMCC 3.15736).

[0040] The comparative experiment on lettuce cultivation, the lettuce yield increase rate, the preparation method of the heavy metal-polluted soil after remediation, the heavy metal toxicity leaching test and the detection of thallium and beryllium ion concentrations are the same as those in Example 1. The test results of this example are shown in Table 3.

[0041] Table 3 Influence of the mass ratio of phosphorus-release auxiliary material, plant ash and calcined gypsum powder on the performance of the prepared liquid soil conditioner (bio-phosphate fertilizer)

[0042] As can be seen from Table 3, when the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder is less than 2.5:5:100 (as in Table 3, when the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder = 2:5:100, 1.5:5:100, 1:5:100, 2.5:4:100, 2.5:3:100, 2.5:2.5:100 and lower ratios not listed in Table 3), the addition of phosphorus-releasing auxiliary materials and plant ash is less, and the material reaction is insufficient during the later hydrothermal reaction and mixed bacteria fermentation process, resulting in a decrease in the fertilizer efficiency of the prepared liquid bio-fertilizer. As a result, the leaching concentration rates of thallium and beryllium in the soil both increase significantly with the decrease in the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder, and the lettuce yield increase rate decreases significantly with the decrease in the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder. When the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder is equal to 2.5 - 22.5:5 - 15:100 hours (as in Table 3, when the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder = 2.5:5:100, 12.5:5:100, 22.5:5:100, 2.5:10:100, 12.5:10:100, 22.5:10:100, 2.5:15:100, 12.5:15:100, 22.5:15:100), in the hydrothermal system, the high temperature and high pressure conditions significantly improve the solubility and reaction activity of the materials. In this environment, the ion migration rate accelerates, the hydrolysis energy barrier of organic matter decreases, and the activation energy of mineral phase transformation decreases, forming a multi-scale synergistic reaction system. The cellulose / hemicellulose in the mixture undergoes hydrolysis and cleavage to generate monosaccharides such as glucose and xylose. Lignin undergoes demethylation in an alkaline medium (the role of plant ash) to produce phenolic hydroxyl compounds. The anthraquinone substances (such as emodin) contained in Cassia obtusifolia and the flavonoid glycosides of Hovenia dulcis undergo a synergistic antioxidant reaction to generate stable polycyclic aromatic hydrocarbon derivatives. Phospholipid substances undergo a β-elimination reaction to generate phosphoglycerides and free fatty acids. The residual carbon-based substances undergo a polycondensation reaction to form carbon materials. Serratia marcescens uses the monosaccharides in the hydrothermal phosphorus-releasing slurry as a carbon source and energy source, and decomposes the monosaccharides into pyruvate through the glycolysis pathway. Pyruvate further enters the tricarboxylic acid cycle to produce energy (ATP), carbon dioxide, and water. Serratia marcescens can also use the amino acids in the hydrothermal phosphorus-releasing slurry for protein synthesis and metabolism. It secretes extracellular enzymes such as proteases and amylases to decompose macromolecular organic matter into small molecule substances. Its metabolites include organic acids, antibiotics, and some extracellular polysaccharides. These organic acids can lower the pH value of the surrounding environment, which is beneficial to the dissolution of certain minerals and the release of phosphorus; antibiotics can inhibit the growth of other harmful microorganisms and create a good living environment for itself and other beneficial microorganisms; extracellular polysaccharides can enhance the attachment ability of microorganisms in the soil. Rhizobium uses the sugars and nitrogen-containing compounds in the hydrothermal phosphorus-releasing slurry, and reduces nitrogen in the air to ammonia through the action of nitrogenase, providing a nitrogen source for itself and other microorganisms.Meanwhile, rhizobia can utilize monosaccharides for growth and reproduction, synthesizing their own cellular substances. Their metabolic products are mainly ammonia and some growth hormones, such as indole acetic acid, etc. Ammonia can provide nitrogen nutrition for other microorganisms, promoting the growth of the microbial community; growth hormones can stimulate the growth and development of plant roots, enhancing the plant's ability to absorb nutrients. Streptomyces utilizes macromolecular substances such as polysaccharides and proteins in the hydrothermal phosphorus-releasing slurry. It secretes various extracellular enzymes, such as cellulase, protease, amylase, etc., to decompose macromolecular substances into small-molecule sugars, amino acids, etc. Streptomyces uses these small-molecule substances for growth and metabolism, synthesizing various antibiotics, vitamins, and enzymes through secondary metabolic pathways. The antibiotics it produces can inhibit the growth of other microorganisms, maintaining the balance of the microbial community; vitamins can provide nutrition for other microorganisms, promoting their growth and reproduction; enzymes can further decompose the organic matter in the hydrothermal phosphorus-releasing slurry, improving the availability of nutrients. Aspergillus secretes various hydrolases, such as cellulase, hemicellulase, pectinase, etc., to decompose polysaccharide substances such as cellulose, hemicellulose, and pectin in the hydrothermal phosphorus-releasing slurry into monosaccharides. Aspergillus can also utilize substances such as amino acids and fatty acids for growth and metabolism. Its metabolic products include organic acids, enzymes, and some secondary metabolites. Organic acids can regulate the pH value of the environment, promoting the dissolution of minerals and the release of phosphorus; enzymes can accelerate the decomposition of organic matter; secondary metabolites may have functions such as antibacterial and antioxidant. Serratia, rhizobia, Streptomyces, and Aspergillus have different nutritional requirements and metabolic capabilities in the hydrothermal phosphorus-releasing slurry. Rhizobia can fix nitrogen, providing a nitrogen source for other microorganisms; while the sugars, amino acids, etc. produced by other microorganisms through the decomposition of organic matter can provide a carbon source and energy source for rhizobia. The extracellular enzymes secreted by Serratia and Aspergillus can decompose macromolecular organic matter into small-molecule substances, providing easily absorbable nutrients for microorganisms such as Streptomyces. This nutritional complementary relationship enables the microbial community to more efficiently utilize various nutrient components in the hydrothermal phosphorus-releasing slurry, promoting the growth and reproduction of microorganisms. The metabolic products produced by each microorganism also have a synergistic effect. The organic acids produced by Serratia and Aspergillus can lower the pH value of the environment, which is beneficial for the antibiotics produced by Streptomyces to play a role, and at the same time promotes the dissolution of minerals and the release of phosphorus. The ammonia produced by rhizobia can provide a nitrogen source for other microorganisms, promoting the synthesis of biological macromolecules such as proteins and nucleic acids by microorganisms. In addition, the extracellular polysaccharides produced by microorganisms can form biofilms, aggregating microorganisms together and enhancing the interaction and synergistic effect among microorganisms. The organic acids produced by microorganisms can react with the minerals in the hydrothermal phosphorus-releasing slurry, dissolving the minerals and releasing nutrient elements such as phosphorus and calcium. The antibiotics produced by microorganisms can inhibit the growth of harmful microorganisms in the hydrothermal phosphorus-releasing slurry, reducing the damage to beneficial microorganisms and the original components. The enzymes secreted by microorganisms (such as cellulase, protease, amylase, etc.) can react with the macromolecular organic matter in the hydrothermal phosphorus-releasing slurry, decomposing it into small-molecule substances.Cellulase can decompose cellulose into glucose, protease can decompose proteins into amino acids, and amylase can decompose starch into maltose and glucose. These small molecule substances can be absorbed and utilized by microorganisms, and at the same time, the effectiveness of nutrients in the hydrothermal phosphorus-releasing slurry is increased. In addition, enzymes can also promote some chemical reactions, such as the hydrolysis of organic phosphorus, and improve the phosphorus release efficiency. Serratia, Rhizobium, Streptomyces, and Aspergillus effectively utilize the components in the hydrothermal phosphorus-releasing slurry through their respective unique metabolic pathways and synergistic effects among them, producing a variety of metabolites and enzymes. Complex reactions occur between these metabolites and enzymes and the original components, improving the phosphorus effectiveness and enhancing the functions of the product as a soil conditioner and slow-release fertilizer. Finally, the lettuce yield increase rate is higher than 156%, and the thallium leaching concentration in the soil is lower than 0.005 mg / L, and the beryllium leaching concentration is lower than 0.005 mg / L. When the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder is higher than 22.5:15:100 (as shown in Table 3, when the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder = 22.5:17.5:100, 22.5:20:100, 22.5:22.5:100, 25:15:100, 27.5:15:100, 30:15:100 and higher ratios not listed in Table 3), the addition of phosphorus-releasing auxiliary materials and plant ash is excessive, and the material reaction is unbalanced during the hydrothermal and fermentation processes, resulting in a decrease in the fertilizer properties of the prepared liquid bio-fertilizer, and the thallium and beryllium leaching concentration rates in the soil increase significantly with the further increase of the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder, and the lettuce yield increase rate decreases significantly with the further increase of the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder.

[0043] Therefore, generally speaking, considering the benefits and costs, when the mass ratio of phosphorus-releasing auxiliary materials, plant ash, and calcined paste powder is equal to 2.5 - 22.5:5 - 15:100, it is most beneficial to improve the fertilizer properties of the prepared liquid bio-fertilizer and the performance of the soil conditioner.

[0044] Example 4 Influence of Rhizobium on the Performance of the Prepared Liquid Soil Conditioner (Bio-Fertilizer) Put phosphogypsum into a calcination furnace, calcine it and then grind it to obtain calcined gypsum powder. The calcination time is 5.5 hours and the calcination temperature is 850 °C. Mix semen cassiae, fructus hoveniae and straw powder according to a mass ratio of 8:7.5:100, and stir evenly to obtain a phosphorus-release auxiliary material. Mix the phosphorus-release auxiliary material, plant ash and calcined gypsum powder according to a mass ratio of 22.5:15:100, and stir evenly to obtain a plant ash phosphorus-release gypsum powder mixture. Mix water and the plant ash phosphorus-release gypsum powder mixture according to a liquid-solid ratio of 50:1 mL / g, stir evenly, and carry out a hydrothermal reaction to obtain a hydrothermal phosphorus-release slurry. The hydrothermal time is 4.5 hours and the hydrothermal temperature is 360 °C. Add composite microorganisms to the hydrothermal phosphorus-release slurry for fermentation, and carry out solid-liquid separation to obtain a liquid, which is a liquid soil conditioner (bio-phosphate fertilizer). The mass ratio of the composite microorganisms to the hydrothermal phosphorus-release slurry is 2.5:1000. The fermentation time of the composite microorganisms is 24 days. The composite microorganisms are composed of Serratia, Rhizobium, Streptomyces and Aspergillus. The powder of Serratia, Rhizobium, Streptomyces and Aspergillus is composed according to a mass ratio of 1:1:1:0.25. The Serratia is Serratia nematodiphila (CGMCC 1.6853); the Rhizobium is Rhizobium cellulolyticum (CGMCC1.15995), Rhizobium sophorae (CGMCC 1.15555), Rhizobium tropici (CGMCC 1.15554), Rhizobium helianthi (CGMCC 1.12192), Rhizobium leguminosarum (CGMCC 1.11035), Rhizobium radiobacter (CGMCC 1.1702), Rhizobium gallicum (CGMCC 1.15596), Rhizobium laguerreae (CGMCC 1.15588), Rhizobium viciae (CGMCC 1.8542), Rhizobium pusense (CGMCC 1.8513), Rhizobium limnium (CGMCC 1.5318), Rhizobium oryzae (CGMCC 1.7048), Rhizobium vitis (CGMCC 1.7033), Rhizobium fredii (CGMCC 1.4354), Rhizobium phaseoli (CGMCC 1.4348), Rhizobium sesbaniae (CGMCC 1.4317), any one of them; the Streptomyces is Streptomyces gilvosporeus (CGMCC 4.6973); the Aspergillus is Aspergillus wentii (CGMCC 3.15268).

[0045] The comparative experiment of lettuce planting, the lettuce yield increase rate, the preparation method of the heavy metal-polluted soil after remediation, the heavy metal toxicity leaching test and the detection of thallium and beryllium ion concentrations are the same as those in Example 1. The test results of this example are shown in Table 4.

[0046] Table 4 Influence of Rhizobium on the performance of the prepared liquid soil conditioner (bio-phosphate fertilizer)

[0047] As can be seen from Table 4, when the rhizobia are any one of Cellulolytic rhizobium, Sophora japonica root nodule bacteria, Tropical rhizobium, Sunflower root nodule bacteria, Pea root nodule bacteria, Radiobacter rhizobium, Gallic rhizobium, Laguerrella rhizobium, Broad bean root nodule bacteria, Pusha rhizobium, Sludge rhizobium, Rice rhizobium, Grape root nodule bacteria, Fred rhizobium, Kidney bean root nodule bacteria, Sesbania rostrata root nodule bacteria, the performance of the prepared liquid bio - phosphate fertilizer is similar, and there are no significant differences in the leaching concentrations of thallium and beryllium and the lettuce yield increase rate achieved.

[0048] Example 5 Effect of Streptomyces on the performance of the prepared liquid soil conditioner (bio - phosphate fertilizer) Put the phosphogypsum into a calcining furnace, calcine it and then grind it to obtain calcined paste powder, where the calcining time is 5.5 hours and the calcining temperature is 850 °C. Mix cassia seed, raisin tree seed and straw powder according to a mass ratio of 8:7.5:100, and stir evenly to obtain a phosphorus - releasing auxiliary material. Mix the phosphorus - releasing auxiliary material, plant ash and calcined paste powder according to a mass ratio of 22.5:15:100, and stir evenly to obtain a plant ash - phosphorus - releasing paste powder mixture. Mix water and the plant ash - phosphorus - releasing paste powder mixture according to a liquid - solid ratio of 50:1 mL / g, stir evenly, and carry out a hydrothermal reaction to obtain a hydrothermal phosphorus - releasing slurry, where the hydrothermal time is 4.5 hours and the hydrothermal temperature is 360 °C. Add composite microorganisms to the hydrothermal phosphorus - releasing slurry for fermentation, and carry out solid - liquid separation to obtain the liquid, which is the liquid soil conditioner (bio - phosphate fertilizer). Among them, the mass ratio of the composite microorganisms to the hydrothermal phosphorus - releasing slurry is 2.5:1000, the fermentation time of the composite microorganisms is 24 days, the composite microorganisms are composed of Serratia, Rhizobium, Streptomyces, and Aspergillus. Among them, the powder of Serratia, Rhizobium, Streptomyces, and Aspergillus is composed according to a mass ratio of 1:1:1:1.75. The Serratia is Serratia nematodiphila (CGMCC 1.6853); the Rhizobium is Sesbania rostrata root nodule bacteria (CGMCC1.4317); the Streptomyces is any one of Streptomyces avermitilis (CGMCC 4.7296), Streptomyces pactum (CGMCC 4.6287), Streptomyces flavogriseus (CGMCC 4.6391), Streptomyces luteolus (CGMCC 4.6973), Streptomyces thermoalkalophilus (CGMCC 4.6961), Streptomyces albidoflavus (CGMCC 4.7292), Streptomyces vinaceusdrappus (CGMCC 4.7294), Streptomyces herbicola (CGMCC4.6835), Streptomyces thermophilus (CGMCC 4.3573), Streptomyces hiroshimensis (CGMCC 4.6966), Streptomyces cinnamoneus (CGMCC 4.6972); the Aspergillus is Aspergillus japonicus (CGMCC 3.11442).

[0049] The lettuce planting comparison test, the lettuce yield increase rate, the preparation method of the heavy - metal - contaminated soil after remediation, the heavy - metal toxicity leaching test, and the detection of thallium and beryllium ion concentrations are the same as in Example 1. The test results of this example are shown in Table 5.

[0050] Table 5 Influence of Streptomyces on the Performance of the Prepared Liquid Soil Conditioner (Bio - phosphate Fertilizer)

[0051] As can be seen from Table 5, when the Streptomyces is any one of Streptomyces avermitilis, Streptomyces pactum, Streptomyces flavidofuscus, Streptomyces luteoverticillatus, Streptomyces thermoalkalophilus, Streptomyces albidoflavus, Streptomyces vinaceusdrappus, Streptomyces herbarum, Streptomyces thermophilus yogyakartensis, Streptomyces hiroshimensis, Streptomyces cinnamoneus, the performance of the prepared liquid bio - phosphate fertilizer is similar, and there is no significant difference in the leaching concentrations of thallium and beryllium and the lettuce yield increase rate achieved.

[0052] Example 6 Influence of Aspergillus on the Performance of the Prepared Liquid Soil Conditioner (Bio - phosphate Fertilizer) Put the phosphogypsum into a calcination furnace, calcine it and then grind it to obtain calcined paste powder, where the calcination time is 3 hours and the calcination temperature is 650 °C. Mix semen cassiae, fruit of Japanese raisin tree and straw powder according to a mass ratio of 8:7.5:100, and stir evenly to obtain a phosphorus - releasing auxiliary material. Mix the phosphorus - releasing auxiliary material, plant ash and calcined paste powder according to a mass ratio of 22.5:15:100, and stir evenly to obtain a plant ash - phosphorus - releasing paste powder mixture. Mix water and the plant ash - phosphorus - releasing paste powder mixture according to a liquid - to - solid ratio of 30:1 mL / g, stir evenly, and carry out a hydrothermal reaction to obtain a hydrothermal phosphorus - releasing slurry, where the hydrothermal time is 2.5 hours and the hydrothermal temperature is 240 °C. Add composite microorganisms to the hydrothermal phosphorus - releasing slurry for fermentation, and carry out solid - liquid separation to obtain a liquid, which is the liquid soil conditioner (bio - phosphate fertilizer). Among them, the mass ratio of the composite microorganisms to the hydrothermal phosphorus - releasing slurry is 2.5:1000, the fermentation time of the composite microorganisms is 24 days, the composite microorganisms are composed of Serratia, Rhizobium, Streptomyces and Aspergillus, and the powder of Serratia, Rhizobium, Streptomyces and Aspergillus is composed according to a mass ratio of 0.25:1.75:0.25:1.75. The Serratia is Serratia nematodiphila (CGMCC 1.6853); the Rhizobium is Rhizobium sesbania (CGMCC 1.4317); the Streptomyces is Streptomyces cinnamoneus (CGMCC 4.6972); the Aspergillus is any one of Aspergillus niger (CGMCC3.15663), Aspergillus sydowii (CGMCC 3.13944), Aspergillus terreus (CGMCC 3.15736), Aspergillus wentii (CGMCC3.15268), Aspergillus japonicus (CGMCC 3.11442), Aspergillus ruber (CGMCC 3.7882), Aspergillus usamii (CGMCC3.7010), Aspergillus oryzae (CGMCC 3.13905), Aspergillus carbonarius (CGMCC 3.7132), Aspergillus purpureus (CGMCC 3.15548).

[0053] The comparative test of lettuce cultivation, the method for preparing the heavy metal - polluted soil after remediation with increased lettuce yield rate, the heavy metal toxicity leaching test, and the detection of thallium and beryllium ion concentrations are the same as those in Example 1. The test results of this example are shown in Table 6.

[0054] Table 6 Influence of Aspergillus on the performance of the prepared liquid soil conditioner (bio - phosphate fertilizer)

[0055] As can be seen from Table 6, when Aspergillus is any one of Aspergillus niger, Aspergillus sydowii, Aspergillus terreus, Aspergillus wentii, Aspergillus japonicus, Monascus ruber, Aspergillus usamii, Aspergillus oryzae, Aspergillus carbonarius, Monascus purpureus, the performance of the prepared liquid bio - phosphate fertilizer is similar, and there is no significant difference in the leaching concentrations of thallium and beryllium and the lettuce yield - increasing rate.

Claims

1. A method for preparing a soil conditioner using phosphogypsum, characterized in that, It includes the following steps: (1) Calcining and grinding phosphogypsum to obtain calcined paste powder; (2) Mixing semen cassiae, fruit of Japanese raisin tree, and straw powder, and stirring evenly to obtain phosphorus-release auxiliary materials; (3) Mixing the phosphorus-release auxiliary materials, plant ash, and calcined paste powder evenly to obtain a plant ash phosphorus-release paste powder mixture; (4) Mixing water and the plant ash phosphorus-release paste powder mixture evenly, and performing a hydrothermal reaction to obtain a hydrothermal phosphorus-release slurry; (5) Adding composite microorganisms to the hydrothermal phosphorus-release slurry for fermentation, and performing solid-liquid separation to obtain a soil conditioner.

2. The method for preparing a soil conditioner using phosphogypsum according to claim 1, wherein In step (1), the calcining time is 0.5 - 5.5 hours, and the calcining temperature is 450 - 850 °C.

3. The method for preparing a soil conditioner using phosphogypsum according to claim 1, wherein In step (2), the mass ratio of semen cassiae, fruit of Japanese raisin tree, and straw powder is 2 - 8:1.5 - 7.5:

100.

4. The method for preparing a soil conditioner using phosphogypsum according to claim 1, characterized in that, In step (3), the mass ratio of the phosphorus-release auxiliary materials, plant ash, and calcined paste powder is 2.5 - 22.5:5 - 15:

100.

5. The method for preparing a soil conditioner using phosphogypsum according to claim 1, characterized in that, In step (4), the liquid-solid ratio of water and the plant ash phosphorus-release paste powder mixture is 10 - 50:1 mL / g, the hydrothermal time is 0.5 - 4.5 hours, and the hydrothermal temperature is 120 - 360 °C.

6. The method for preparing a soil conditioner using phosphogypsum according to claim 1, characterized in that, In step (5), the fermentation time is 4 - 24 days.

7. The method for preparing a soil conditioner using phosphogypsum according to claim 1, wherein, The composite microorganisms in step (5) are composed of serratia, rhizobium, streptomyces, and aspergillus.

8. A soil conditioner prepared by the method according to any one of claims 1 - 7.

9. Use of the soil conditioner according to claim 8 in conditioning heavy metal-contaminated soil or as a phosphate fertilizer in promoting crop growth.

10. The application according to claim 9, characterized in that, The heavy metals include thallium and beryllium.

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