A high-efficiency phosphate fertilizer for inhibiting cadmium absorption and preparation method thereof

Abstract

The present invention relates to the technical field of high-efficiency phosphate fertilizers, and specifically discloses a high-efficiency phosphate fertilizer for inhibiting cadmium absorption and a preparation method thereof. The method comprises the following steps: S1: a click chemical reaction occurs between thiolated nano-hydroxyapatite and 1-vinyl imidazole under ultraviolet irradiation to obtain modified nano-hydroxyapatite; S2: the modified nano-hydroxyapatite is added to deionized water to obtain a mixed solution A; diammonium citrate, ferrous sulfate heptahydrate, manganese phosphate, and zinc phosphate are added to deionized water and uniformly mixed to obtain a mixed solution B; at a rotation speed of 500 to 600 rpm, the mixed solution A is added dropwise to the mixed solution B, the stirring is continued, the mixture is allowed to stand at room temperature, and the mixture is purified to obtain a composite material; S3: the composite material and the passivator are used as a high-efficiency phosphate fertilizer for inhibiting cadmium absorption; when used, the mixture is sequentially used in the soil.

Description

Technical Field

[0001] The invention relates to the technical field of high-efficiency phosphate fertilizers, in particular to a high-efficiency phosphate fertilizer capable of inhibiting cadmium absorption and a preparation method thereof. Background Art

[0002] Cadmium pollution has affected a large area of ​​farmland soil and crops. In order to reduce the activity of cadmium in the soil and reduce the absorption of cadmium by crops, adding lime and calcium silicate mixture in situ is an effective and economical method. However, the application of conventional phosphate fertilizers during crop growth may bring some adverse effects. First, the application of conventional phosphate fertilizers may reduce the utilization efficiency of phosphate fertilizers, resulting in phosphorus waste. Second, the use of conventional phosphate fertilizers will also affect the passivation effect of heavy metal passivation materials, thereby affecting plant photosynthesis and growth. Therefore, it is particularly important to find a new type of phosphate fertilizer that can provide phosphate fertilizer without affecting the solidification effect of heavy metals in the soil. Summary of the invention

[0003] The object of the present invention is to provide a high-efficiency phosphate fertilizer for inhibiting cadmium absorption and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0004] A high-efficiency phosphate fertilizer for inhibiting cadmium absorption, wherein the high-efficiency phosphate fertilizer for inhibiting cadmium absorption comprises the following components, calculated in terms of usage per mu: 28 to 35 kilograms of negatively charged nano-hydroxyapatite and 170 to 180 kilograms of a passivator.

[0005] More optimally, the passivating agent includes lime and calcium silicate in a mass ratio of 1:1.

[0006] A method for preparing a high-efficiency phosphate fertilizer for inhibiting cadmium absorption comprises the following steps:

[0007] S1: uniformly mixing a calcium nitrate aqueous solution and a diammonium citrate aqueous solution in a mass ratio of 1:1 to obtain a solution A; adding (NH4)2HPO4 to deionized water to obtain a solution B; adjusting the pH of the solutions A and B with an NH3·H2O aqueous solution; heating the solution A to 85-95°C, adding the solution B, reacting for 11-14 hours, and then performing an aging treatment and purification to obtain negatively charged nano-hydroxyapatite;

[0008] S2: Use negatively charged nano-hydroxyapatite and passivating agent as high-efficiency phosphate fertilizer to inhibit cadmium absorption; when using, apply them to the soil in sequence.

[0009] More optimally, in the solution A, the concentration of calcium nitrate is 0.07-0.09 g / mL, and the concentration of diammonium citrate is 0.092-0.15 g / mL; in the solution B, the concentration of (NH4)2HPO4 is 0.04-0.08 g / mL; and the pH of the solutions A and B is adjusted to 9.5-10.5.

[0010] More optimally, the negatively charged nano-hydroxyapatite is further modified to obtain a composite material; the high-efficiency phosphate fertilizer for inhibiting cadmium absorption includes the following components, calculated on a usage basis per mu: 28 to 35 kg of the composite material and 170 to 180 kg of the passivator.

[0011] The preparation method of the composite material is more optimized as follows: (1) ultrasonically dispersing negatively charged nano-hydroxyapatite in anhydrous ethanol, adding an ethanol aqueous solution of 3-mercaptopropyltrimethoxysilane at 75-85° C., reacting for 10-14 hours, and purifying to obtain thiolated nano-hydroxyapatite; (2) adding thiolated nano-hydroxyapatite to tetrahydrofuran for ultrasonic dispersion, adding AIBN and 1-vinylimidazole, stirring for 20-30 minutes, and placing under ultraviolet light for 1.8-2.5 hours to obtain modified nano-hydroxyapatite;

[0012] (3) adding modified nano-hydroxyapatite to deionized water to obtain a mixed solution A; adding diammonium citrate, ferrous sulfate heptahydrate, manganese phosphate, and zinc phosphate to deionized water and uniformly mixing to obtain a mixed solution B; adding the mixed solution A dropwise to the mixed solution B at a rotation speed of 500 to 600 rpm, continuing to stir for 25 to 35 minutes, standing at room temperature for 12 to 16 hours, and purifying to obtain a composite material.

[0013] In a more optimized method, the ratio of 3-mercaptopropyltrimethoxysilane to negatively charged nano-hydroxyapatite is 1 mL: (0.035-0.05) g; the concentration of the ethanol aqueous solution is 80-90 wt %; the raw materials of the modified nano-hydroxyapatite include the following components: 2-5 parts of thiolated nano-hydroxyapatite, 3-4 parts of 1-vinylimidazole, 0.02-0.022 parts of AIBN, and 30-50 parts of tetrahydrofuran by weight; the process conditions of ultraviolet irradiation are: the emission light is 350 nm, and the light intensity is 90-110 mW / cm 2 .

[0014] More optimally, the raw materials of the mixed solution B include the following components: 0.05-0.06 g / mL diammonium citrate, 0.03-0.035 g / mL ferrous sulfate heptahydrate, 0.002-0.005 g / mL manganese phosphate, and 0.04-0.08 g / mL zinc phosphate; in the mixed solution A, the concentration of modified nano-hydroxyapatite is 0.82-1.4 g / mL; and the mass ratio of the mixed solution A to the mixed solution B is 1:1.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: in the present invention, lime (CaO) and calcium silicate (CaSiO3) are mixed in equal proportions as a passivating agent. This mixture is widely available and cheap. Silicate ions can combine with cadmium ions in the soil to form insoluble silicate precipitation, while increasing the pH value of the soil, prompting the cadmium form to change to an insoluble inert form. This process also increases the negative charge on the soil surface, strengthens the adsorption of cadmium ions, and thus reduces the activity of cadmium ions in the soil. At the same time, the calcium ions in the mixture can inhibit the absorption of cadmium ions by crops and promote the growth of crops.

[0016] Compared with adding conventional passivators, such as sodium silicate, potassium silicate, lime, etc., although conventional passivators can effectively reduce the activity of cadmium in the soil and reduce the absorption of plants, they often cause soil compaction and affect the normal growth of crops; therefore, adding lime and calcium silicate can not only effectively reduce the absorption of cadmium ions by crops, but also will not have adverse effects on the original structure of the soil, but can promote plant growth.

[0017] Although the addition of passivators will reduce the absorption of cadmium by plants, it will also passivate the trace elements required by plants, such as copper, zinc, iron, manganese, etc., leading to problems such as yellowing of plant leaves, short plants, reduced photosynthetic rate, and weakened resistance to heavy metals.

[0018] In order to solve this problem, the present invention utilizes 3-mercaptopropyltrimethoxysilane to modify negatively charged nano-hydroxyapatite to obtain mercapto nano-hydroxyapatite; reacts with 1-vinylimidazole under ultraviolet light to obtain modified nano-hydroxyapatite; and coordinates the imidazole groups on the modified nano-hydroxyapatite with zinc ions in zinc phosphate to obtain a composite material of ZIF-8 and nano-hydroxyapatite.

[0019] Nano-hydroxyapatite, as a slow-release phosphate fertilizer, can alleviate the problem of soil eutrophication; it has the characteristics of small size, low loss rate and slow release, so it can effectively coordinate the dissolution and release of fertilizers with the absorption of crops, and will not inhibit the effect of passivators; compared with conventional large-particle phosphate fertilizers, nano-hydroxyapatite has better specific surface area and phosphorus availability. In addition, due to its stability, this type of nano-phosphate fertilizer can also reduce the risk of soil acidification and phosphorus leaching.

[0020] ZIF-8 has good biocompatibility, large specific surface area and pore volume; ZIF-8 is based on zinc ions, which is a trace nutrient required by plants. Combining it with nano-hydroxyapatite can increase the specific surface area and bioavailability of nano-hydroxyapatite, and can also control the release of multiple trace nutrients to provide nutrition for plants.

[0021] Cadmium in the soil will inhibit plant photosynthesis, thereby inhibiting plant growth and yield; iron is essential for the establishment of light systems, light-harvesting complexes, ferredoxin, etc., and manganese is a cofactor of the oxygen-evolving complex; the introduction of iron on nanohydroxyapatite not only reduces the toxicity of cadmium, but also effectively prevents cadmium from damaging plant root growth and inhibiting photosynthesis. The addition of manganese can assist iron, thereby improving the inhibition of cadmium on plant photosynthesis.

[0022] However, composite materials are prone to agglomeration, which reduces the utilization of active sites and leads to reduced effectiveness of the composite materials, thus affecting the plant's absorption of nutrients.

[0023] In order to alleviate the agglomeration of the composite material, the present invention adds diammonium citrate therein to make its surface charge negative, improve the dispersion of particles, and the dispersed particles can effectively improve the utilization of adsorption sites, while also being able to more flexibly adjust their migration and transformation behaviors and improve the structure of the root microbial community. Therefore, we can customize this type of fertilizer as a dual-action fertilizer, which can provide nutrients and fix heavy metals according to soil characteristics and crop types, thereby achieving a more comprehensive soil remediation effect. DETAILED DESCRIPTION

[0024] The following is a preferred implementation of the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. For ordinary technicians in this technical field, all other embodiments obtained by ordinary technicians in this field without creative work without departing from the principle of the embodiment of the present invention are within the scope of protection of the present invention.

[0025] In the following specific implementation manner, parts are parts by weight; it should be noted that the purchasing manufacturers of all raw materials involved in the present invention do not have any special restrictions, and illustratively include: the CAS number of calcium nitrate is 10124-37-5, the CAS number of diammonium citrate is, the CAS number of (NH4)2HPO4 is 7783-28-0, the CAS number of 3-mercaptopropyltrimethoxysilane is 4420-74-0, the CAS number of AIBN is 78-67-1, the CAS number of 1-vinylimidazole is 1072-63-5, the CAS number of ferrous sulfate heptahydrate is 7782-63-0, the CAS number of manganese phosphate is 10236-39-2, the CAS number of zinc phosphate is 7779-90-0, the CAS number of lime is 73018-51-6, and the item number of calcium silicate is S42157.

[0026] The preparation method of negatively charged nano-hydroxyapatite is as follows: a calcium nitrate aqueous solution and a diammonium citrate aqueous solution are uniformly mixed at a mass ratio of 1:1 to obtain a solution A; (NH4)2HPO4 is added to deionized water to obtain a solution B; the pH of the solution A and the solution B is adjusted to 10 with an NH3·H2O aqueous solution; after the solution A is heated to 90°C, the solution B is added, reacted for 12 hours, and then aged and purified to obtain the negatively charged nano-hydroxyapatite;

[0027] Among them, in solution A, the concentration of calcium nitrate aqueous solution is 0.08 g / mL; the concentration of diammonium citrate aqueous solution is 0.1 g / mL; in solution B, the concentration of (NH4)2HPO4 is 0.06 g / mL.

[0028] The preparation method of the composite material is as follows: (1) ultrasonically dispersing negatively charged nano-hydroxyapatite in anhydrous ethanol, adding an ethanol aqueous solution of 3-mercaptopropyltrimethoxysilane at 80° C., reacting for 10 hours, and purifying to obtain thiolated nano-hydroxyapatite; (2) adding 4 parts of thiolated nano-hydroxyapatite to 30 parts of tetrahydrofuran and ultrasonically dispersing, adding 0.02 parts of AIBN and 3 parts of 1-vinylimidazole, stirring for 25 minutes, and placing under ultraviolet light for 2 hours to obtain modified nano-hydroxyapatite;

[0029] The ratio of 3-mercaptopropyltrimethoxysilane to negatively charged nanohydroxyapatite is 1 mL: 0.032 g; the concentration of the ethanol aqueous solution is 80 wt %; the process conditions of ultraviolet irradiation are: the emission light is 350 nm, the light intensity is 90 mW / cm 2 ;

[0030] (3) 0.85 g / mL modified nano-hydroxyapatite was added to deionized water to obtain a mixed solution A; 0.055 g / mL diammonium citrate, 0.032 g / mL ferrous sulfate heptahydrate, 0.0032 g / mL manganese phosphate, and 0.062 g / mL zinc phosphate were added to deionized water and uniformly mixed to obtain a mixed solution B; the mixed solution A was added dropwise to the mixed solution B at a rotation speed of 550 rpm, and the stirring was continued for 30 minutes. The mixture was allowed to stand at room temperature for 12 hours, and purified to obtain a composite material; the mass ratio of the mixed solution A to the mixed solution B was 1:1.

[0031] Example 1: A high-efficiency phosphate fertilizer for inhibiting cadmium absorption, comprising calcium dihydrogen phosphate and a passivator (the mass ratio of lime to calcium silicate is 1:1);

[0032] Farmland soil contaminated by cadmium was collected, 1 cm of the soil was air-dried and sieved, 3 kg of cadmium-contaminated farmland soil was taken and fully mixed with 0.6 g of calcium dihydrogen phosphate, and placed in a flower pot with a diameter of 23 cm and a height of 15 cm, and then a passivator was added to the soil to obtain sample soil 1.

[0033] Example 2: A high-efficiency phosphate fertilizer for inhibiting cadmium absorption, comprising negatively charged nano-hydroxyapatite and a passivating agent (the mass ratio of lime to calcium silicate is 1:1);

[0034] Farmland soil contaminated by cadmium was collected, 1 cm of the soil was air-dried and sieved, 3 kg of cadmium-contaminated farmland soil was taken and mixed with 0.6 g of negatively charged nanohydroxyapatite, respectively, and placed in a flower pot with a diameter of 23 cm and a height of 15 cm, and then a passivator was added to the soil to obtain sample soil 2.

[0035] Example 3: A high-efficiency phosphate fertilizer for inhibiting cadmium absorption, comprising a composite material and a passivating agent (the mass ratio of lime to calcium silicate is 1:1);

[0036] The farmland soil contaminated by cadmium was collected, 1 cm of the soil was air-dried and sieved, 3 kg of the cadmium-contaminated farmland soil was taken and fully mixed with 0.5 g of the composite material, respectively, and placed in a flower pot with a diameter of 23 cm and a height of 15 cm, and then the passivator was added to the soil to obtain sample soil 3.

[0037] Example 4: A high-efficiency phosphate fertilizer for inhibiting cadmium absorption, comprising a composite material and a passivating agent (the mass ratio of lime to calcium silicate is 1:1);

[0038] Farmland soil contaminated by cadmium was collected, 1 cm of the soil was air-dried and sieved, 3 kg of cadmium-contaminated farmland soil was taken and fully mixed with 0.4 g of the composite material, respectively, and placed in a flowerpot with a diameter of 23 cm and a height of 15 cm, and then a passivator was added to the soil to obtain sample soil 4.

[0039] Example 5: A high-efficiency phosphate fertilizer for inhibiting cadmium absorption, comprising a composite material and a passivating agent (the mass ratio of lime to calcium silicate is 1:1);

[0040] Farmland soil contaminated by cadmium was collected, air-dried and 1 cm was sieved, 3 kg of cadmium-contaminated farmland soil was taken and fully mixed with 0.6 g of the composite material, respectively, and placed in a flowerpot with a diameter of 23 cm and a height of 15 cm, and then a passivator was added to the soil to obtain sample soil 5.

[0041] Comparative Example 1 Based on Example 5, without adding manganese and iron, a method for preparing a high-efficiency phosphate fertilizer for inhibiting cadmium absorption comprises the following steps:

[0042] 0.85 g / mL modified nano-hydroxyapatite was added to deionized water to obtain a mixed solution A; 0.055 g / mL diammonium citrate and 0.062 g / mL zinc phosphate were added to deionized water and uniformly mixed to obtain a mixed solution B; the mixed solution A was added dropwise to the mixed solution B at a speed of 550 rpm, and the mixture was stirred for 30 minutes, and allowed to stand at room temperature for 12 hours, and purified to obtain a composite material; the mass ratio of the mixed solution A to the mixed solution B was 1:1;

[0043] Farmland soil contaminated by cadmium was collected, 1 cm of the soil was air-dried and sieved, 3 kg of cadmium-contaminated farmland soil was taken and fully mixed with 0.6 g of the composite material, respectively, and placed in a flowerpot with a diameter of 23 cm and a height of 15 cm, and then a passivator was added to the soil to obtain sample soil 6.

[0044] Comparative Example 2 is based on Example 5, without introducing diammonium citrate, and a method for preparing a high-efficiency phosphate fertilizer for inhibiting cadmium absorption comprises the following steps:

[0045] (1) adding calcium nitrate to deionized water to obtain solution A; adding (NH4)2HPO4 to deionized water to obtain solution B; adjusting the pH of solution A and solution B to 10 with an NH3·H2O aqueous solution; heating solution A to 90° C., adding solution B, reacting for 12 hours, and then performing aging treatment and purification to obtain negatively charged nano-hydroxyapatite;

[0046] In solution A, the concentration of calcium nitrate aqueous solution is 0.08 g / mL; in solution B, the concentration of (NH4)2HPO4 is 0.06 g / mL;

[0047] (2) ultrasonically dispersing negatively charged nano-hydroxyapatite in anhydrous ethanol, adding an ethanol aqueous solution of 3-mercaptopropyltrimethoxysilane at 80° C., reacting for 10 hours, and purifying to obtain thiolated nano-hydroxyapatite; (2) adding 4 parts of thiolated nano-hydroxyapatite to 30 parts of tetrahydrofuran and ultrasonically dispersing, adding 0.02 parts of AIBN and 3 parts of 1-vinylimidazole, stirring for 25 minutes, and placing under ultraviolet light for 2 hours to obtain modified nano-hydroxyapatite;

[0048] (3) adding 0.85 g / mL modified nano-hydroxyapatite to deionized water to obtain a mixed solution A; adding 0.032 g / mL ferrous sulfate heptahydrate, 0.0032 g / mL manganese phosphate, and 0.062 g / mL zinc phosphate to deionized water and uniformly mixing to obtain a mixed solution B; adding the mixed solution A dropwise to the mixed solution B at a rotation speed of 550 rpm, continuing to stir for 30 minutes, standing at room temperature for 12 hours, and purifying to obtain a composite material; the mass ratio of the mixed solution A to the mixed solution B is 1:1;

[0049] Farmland soil contaminated by cadmium was collected, 1 cm of the soil was air-dried and sieved, 3 kg of cadmium-contaminated farmland soil was taken and fully mixed with 0.6 g of the composite material, respectively, and placed in a flowerpot with a diameter of 23 cm and a height of 15 cm, and then a passivator was added to the soil to obtain sample soil 7.

[0050] Comparative Example 3 is based on Example 5, without adding a passivating agent, a high-efficiency phosphate fertilizer for inhibiting cadmium absorption, which includes a composite material;

[0051] The farmland soil contaminated by cadmium was collected, air-dried and 1 cm thick, and 3 kg of the farmland soil contaminated by cadmium was taken and mixed with 0.6 g of the composite material respectively, and then placed in a flower pot with a diameter of 23 cm and a height of 15 cm to obtain sample soil 8.

[0052] Detection experiment 1: Determine the concentration of available cadmium and available phosphorus in the soil samples of Examples 1 to 5 and Comparative Examples 1 to 3; the total cadmium content in the soil is 2.2 mg / kg; as shown in Table 1, the concentrations of available cadmium and phosphorus in the soil under the use of lime\calcium silicate and different phosphate fertilizers.

[0053]

[0054]

[0055] Table 1 Concentrations of available cadmium and phosphorus in soil under the application of lime, calcium silicate and different phosphate fertilizers

[0056] The numbers in the table are the averages of 4 replicates. The same letters after the numbers indicate that there is no significant difference in the same column by LSD test (P=0.05).

[0057] Conclusion: From Table 1, it can be seen that in Examples 3 to 5 of the composite materials with different addition amounts, it is found that as the concentration of the composite materials increases, the concentration of effective cadmium decreases; compared with the conventional phosphate fertilizer Example 1 and the negatively charged nano-hydroxyapatite Example 2, it can more effectively inhibit;

[0058] For the available phosphorus in the soil, the addition of lime and calcium silicate mixture slightly reduced its concentration, while the application of calcium dihydrogen phosphate significantly increased the concentration of available phosphorus, increasing the risk of phosphorus loss. However, the treatment of lime and calcium silicate and negatively charged nanohydroxyapatite in Example 2, and the treatment of lime and calcium silicate and composite materials in Examples 3 to 5 can keep the available phosphorus in the soil at a lower concentration for sustainable use of phosphorus by plants; Comparative Example 1 is based on Example 5, and iron and manganese are not added, resulting in an increase in effective cadmium. Comparative Example 2 is based on Example 5, and diammonium citrate is not added, resulting in agglomeration between the composite materials, thereby affecting the effect of the composite materials on cadmium. Comparative Example 3 is based on Example 5, and no passivator is added, resulting in an increase in effective cadmium; however, compared with the blank control group, its cadmium content decreased by 19.6%. The results show that when the composite material is used alone, it also has a certain inhibitory effect on cadmium; however, the concentration of available phosphorus is increased, thereby increasing the risk of phosphorus loss.

[0059] Detection Experiment 2: The soil in this example is farmland soil that has been contaminated by cadmium for many years, and the total cadmium content is 2.2 mg / kg.

[0060] Before sowing, the passivator (the mass of lime and calcium silicate is 1:1) is applied to the cadmium-contaminated farmland soil at an application rate of 175 kg / mu, and after being fully mixed with the 20 cm cultivated layer, water is added to maintain the conventional field water holding capacity. After balancing for one week, 30 kg / mu of the phosphate fertilizer of Examples 1 to 5 and Comparative Examples 1 to 3 are applied; maintaining the conventional field water holding capacity, after balancing for 3 days, red amaranth is sown and conventional management is carried out; as shown in Table 2, the crop yield, plant height and leaf chlorophyll content (the crop is red amaranth) under each treatment.

[0061]

[0062] Table 2 Crop yield, plant height and leaf chlorophyll content under each treatment (crop is red amaranth)

[0063] The numbers in the table are the averages of 4 replicates, and the same letters after the numbers represent no significant differences in the same column by LSD test (P=0.05).

[0064] Conclusion: Compared with the blank control group, the application of the combination of lime\calcium silicate and negatively charged nano-hydroxyapatite (Example 2) can increase the total dry weight of red amaranth by 852%, the average plant height by 433%, and the leaf chlorophyll content by 105%; the application of the components of lime\calcium silicate and monocalcium phosphate (Example 1) can increase the total dry weight of red amaranth by 317%, the average plant height by 333%, and the leaf chlorophyll content by 59%; the total dry weight, average plant height, and leaf chlorophyll content of red amaranth in Examples 3 to 5 are better than those in Examples 1 and 2.

[0065] Comparative Example 1 is based on Example 5, but iron and manganese are not added, so that cadmium inhibits plant photosynthesis and damages plant roots, resulting in a decrease in the chlorophyll content of the plant and a decrease in the average plant height and total dry weight biomass. Comparative Example 2 is based on Example 5, but diammonium citrate is not introduced, and agglomeration easily occurs between the composite materials, reducing the utilization of active sites, thereby reducing the inhibition of cadmium toxicity, affecting the plant's absorption of nutrients, and reducing the total dry weight biomass, average plant height, and leaf chlorophyll content of the plant. Comparative Example 3 is based on Example 5, but no passivator is added, resulting in an increase in cadmium content, inhibiting plant photosynthesis, thereby reducing the average plant height, leaf chlorophyll content, and total dry weight biomass of the plant.

[0066] Finally, it should be noted that the above is only a preferred embodiment of the present invention, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the spirit and principle of the present invention and within the technical scope disclosed in this application should be included in the protection scope of this application; in the absence of conflict, the embodiments of this application and the features in the embodiments can be combined with each other. Therefore, the protection scope of this application shall be based on the protection scope of the claims.

Claims

1. A method for preparing a high-efficiency phosphate fertilizer for inhibiting cadmium absorption, characterized in that: The steps include: S1: uniformly mixing a calcium nitrate aqueous solution and a diammonium citrate aqueous solution in a mass ratio of 1:1 to obtain a solution A; adding (NH4)2HPO4 to deionized water to obtain a solution B; adjusting the pH of the solutions A and B with an NH3·H2O aqueous solution; heating the solution A to 85-95°C, adding the solution B, reacting for 11-14 hours, and then performing an aging treatment and purification to obtain negatively charged nano-hydroxyapatite; S2: (1) Ultrasonic dispersion of negatively charged nanohydroxyapatite in anhydrous ethanol, adding an ethanol aqueous solution of 3-mercaptopropyltrimethoxysilane at 75-85°C, reacting for 10-14 hours, purifying, and obtaining thiolated nanohydroxyapatite; (2) Ultrasonic dispersion of thiolated nanohydroxyapatite in tetrahydrofuran, adding AIBN and 1-vinylimidazole, stirring for 20-30 minutes, and placing under ultraviolet light for 1.8-2.5 hours to obtain modified nanohydroxyapatite; (3) Adding modified nanohydroxyapatite to deionized water to obtain a mixed solution A; adding diammonium citrate, ferrous sulfate heptahydrate, manganese phosphate, and zinc phosphate to deionized water and mixing uniformly to obtain a mixed solution B; adding mixed solution A dropwise to mixed solution B at a rotation speed of 500-600 rpm, continuing stirring for 25-35 minutes, standing at room temperature for 12-16 hours, purifying, and obtaining a composite material; S3: The composite material and the passivating agent are used as a highly effective phosphate fertilizer for inhibiting cadmium absorption; when used, they are applied to the soil in sequence; The high-efficiency phosphate fertilizer for inhibiting cadmium absorption includes the following components: 28-35 kg of composite material and 170-180 kg of passivator in an amount per mu; the passivator includes lime and calcium silicate in a mass ratio of 1:

1.

2. The method for preparing a high-efficiency phosphate fertilizer for inhibiting cadmium absorption according to claim 1, characterized in that: In the solution A, the concentration of calcium nitrate is 0.07-0.09 g / mL, and the concentration of diammonium citrate is 0.092-0.15 g / mL; in the solution B, the concentration of (NH4)2HPO4 is 0.04-0.08 g / mL; and the pH of the solutions A and B is adjusted to 9.5-10.

5.

3. The method for preparing a high-efficiency phosphate fertilizer for inhibiting cadmium absorption according to claim 1, characterized in that: The ratio of 3-mercaptopropyltrimethoxysilane to negatively charged nano-hydroxyapatite is 1 mL: (0.035-0.05) g; the concentration of the ethanol aqueous solution is 80-90 wt %; the raw materials of the modified nano-hydroxyapatite include the following components: by weight, 2-5 parts of thiolated nano-hydroxyapatite, 3-4 parts of 1-vinylimidazole, 0.02-0.022 parts of AIBN, and 30-50 parts of tetrahydrofuran; the process conditions of ultraviolet irradiation are: the emission light is 350 nm, and the light intensity is 90-110 mW / cm 2 .

4. The method for preparing a high-efficiency phosphate fertilizer for inhibiting cadmium absorption according to claim 1, characterized in that: The raw materials of the mixed solution B include the following components: 0.05-0.06 g / mL diammonium citrate, 0.03-0.035 g / mL ferrous sulfate heptahydrate, 0.002-0.005 g / mL manganese phosphate, and 0.04-0.08 g / mL zinc phosphate; in the mixed solution A, the concentration of the modified nano-hydroxyapatite is 0.82-1.4 g / mL; and the mass ratio of the mixed solution A to the mixed solution B is 1:

1.

5. The high-efficiency phosphate fertilizer prepared by the method for preparing a high-efficiency phosphate fertilizer for inhibiting cadmium absorption according to claim 1.

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