A copper-doped hydroxyapatite material and its preparation method and application

Abstract

The invention discloses a copper-doped hydroxyapatite material and a preparation method and application thereof, and belongs to the field of nano-agricultural technology. The preparation method of the copper-doped hydroxyapatite material of the invention comprises the following steps: mixing calcium salt, copper salt and phosphoric acid for reaction, collecting solid phase components, crushing, and obtaining a hydroxyapatite precursor; mixing ethyl silicate, acetic acid and ethanol to obtain a treatment liquid, mixing the hydroxyapatite precursor with the treatment liquid, stirring, and crushing to obtain the copper-doped hydroxyapatite material. The preparation process of the invention is simple, the raw materials are cheap and easy to obtain, the sources are wide, and the application prospects are broad. It has the advantages of low amount and high efficiency when used for crop growth, and is suitable for large-scale industrial application.

Description

Technical Field

[0001] The invention relates to the technical field of nano-agriculture, and in particular to a copper-doped hydroxyapatite material and a preparation method and application thereof. Background Art

[0002] At present, with the reduction of arable land, water shortage, climate change and the low efficiency of current agricultural chemicals, it is increasingly difficult to increase the yield of crops. For example, there is a widespread problem of excessive use of traditional phosphate fertilizers in today's agricultural system, and because the utilization efficiency of traditional phosphate fertilizers by vegetation is generally low, it is very easy to cause eutrophication. Supplementing phosphorus in the form of foliar fertilizer has the advantages of high utilization rate, strong targeting, high efficiency and rapidity, and has certain research value; however, the field of foliar fertilizer also faces the problems of easy loss of effective ingredients, short duration and high cost. By applying nanotechnology in the fields of agriculture and food science, a new solution is provided for this; compared with traditional fertilizers, nano-agricultural chemicals have a larger specific surface area, can contact plant cells more effectively, and have the characteristics of precise delivery, so the problem of nutrient loss is smaller, and it has great research value.

[0003] Hydroxyapatite (HAP) is a naturally occurring calcium phosphate mineral with the molecular formula Ca 10 (PO4)6(OH)2, it not only provides calcium and phosphorus, two key nutrients, but also its unique structure makes these elements easier for plants to absorb and utilize. Hydroxyapatite is similar to the main inorganic components of human and animal bones, has excellent biocompatibility and biological activity, and has a hexagonal structure. The Ca 2+ It can be replaced by other metal elements to form hydroxyapatite with different doping. However, the problem of hydroxyapatite being very easy to aggregate and precipitate in foliar fertilizer and its insufficient stability has not been solved, and its biocompatibility still needs to be further improved, so there is still a lot of room for improvement. Summary of the invention

[0004] The purpose of the present invention is to provide a copper-doped hydroxyapatite material and its preparation method and application. The preparation process of the present invention is simple, the raw materials are cheap and easy to obtain, the source is wide, and the application prospect is broad. It has the advantages of low amount and high efficiency when used for crop growth, and is suitable for large-scale industrial application.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a method for preparing a copper-doped hydroxyapatite material, comprising the following steps:

[0007] (1) mixing calcium salt, copper salt and phosphoric acid for reaction, collecting solid phase components, and crushing them to obtain a hydroxyapatite precursor;

[0008] (2) Ethyl silicate, acetic acid and ethanol are mixed to obtain a treatment liquid, and the hydroxyapatite precursor is mixed with the treatment liquid, stirred and crushed to obtain a copper-doped hydroxyapatite material.

[0009] In the preparation process of the present invention, copper ions partially replace calcium ions in the hydroxyapatite lattice to achieve doping of related elements.

[0010] The acetic acid in the treatment liquid system can improve the stability of the reaction system, prevent premature coagulation, and control the structure of the loaded silica to avoid the loading layer being too dense, thereby achieving the technical effect of improving the dispersion of hydroxyapatite in the foliar fertilizer system without excessively affecting the absorption of hydroxyapatite by crops.

[0011] Preferably, in step (1), the calcium salt is calcium hydroxide, and the copper salt is copper nitrate; the molar ratio of the sum of the amounts of the calcium salt and the copper salt to phosphoric acid is 1.67:1, and the amount of the copper salt accounts for 3.5-5% of the sum of the amounts of the calcium salt and the copper salt.

[0012] During the doping process, the amount of copper ions added must be strictly controlled. Too many doping ions may cause instability in the hydroxyapatite structure, while too few doping ions may not achieve the expected doping effect.

[0013] Preferably, in step (1), the reaction is carried out at a pH of 10-11 and a temperature of 45-70° C. for 12-20 hours; and the pulverization is carried out until the product passes through a 120-150 mesh sieve.

[0014] Preferably, after the pulverizing operation in step (1), a drying step is further included; the drying is freeze-drying at a vacuum degree of -300 to -250 mmHg and a temperature of -45 to -30°C for 1 to 2 hours.

[0015] Preferably, in step (2): the mass ratio of ethyl silicate, acetic acid and ethanol is 1:2-5:30-50; the mass ratio of ethyl silicate to hydroxyapatite precursor is 8-15:1.

[0016] Preferably, in step (2), the stirring treatment is carried out at a temperature of 30-50°C, a rotation speed of 50-300 rpm, and a time of 1-1.5 h; and the pulverization is carried out until the product passes through a 120-150 mesh sieve.

[0017] The ratio of ethyl silicate to hydroxyapatite precursor should not be too high, and the rotation speed should not be too fast, otherwise the SiO2 loading layer will be too thick or completely cover the hydroxyapatite precursor, which will affect the final fertilizer effect.

[0018] The second technical solution of the present invention is to provide a copper-doped hydroxyapatite material obtained according to the above preparation method.

[0019] The third technical solution of the present invention is to provide a hydroxyapatite foliar fertilizer, the raw materials of which include the above-mentioned copper-doped hydroxyapatite material.

[0020] Preferably, the raw materials of the hydroxyapatite foliar fertilizer include, by weight:

[0021] 4-7 parts of copper-doped hydroxyapatite material, 0.2-0.5 parts of sodium bisulfite, 0.5-1 parts of surfactant, and 85-100 parts of water.

[0022] The proportion of HAP in the foliar fertilizer system must be within a reasonable range; too low a concentration will result in too little nutrient elements being exposed to crops, and the effect will not be obvious; too high a concentration may affect the dispersion of HAP in the foliar fertilizer and make it easier to cause agglomeration.

[0023] Preferably, the surfactant is one or more of sodium dodecyl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate and potassium laurate.

[0024] The fourth technical solution of the present invention is to provide a method for preparing the above-mentioned hydroxyapatite foliar fertilizer, comprising the following steps:

[0025] The surfactant added in the present invention can reduce the surface tension of the foliar fertilizer system, improve the dispersion effect of copper-doped hydroxyapatite, and prevent its sedimentation and agglomeration.

[0026] After sodium bisulfite and a surfactant are uniformly mixed in water, copper-doped hydroxyapatite material is added to obtain the hydroxyapatite foliar fertilizer.

[0027] The beneficial technical effects of the present invention are as follows:

[0028] After SiO2 is loaded on the surface of copper-doped hydroxyapatite through the preparation process of the present invention, the dispersibility and stability of HAP in the foliar fertilizer system can be greatly improved, the oxidation and agglomeration of HAP can be effectively prevented, and the stability and effectiveness of the foliar fertilizer during storage and use can be ensured. Loading SiO2 can make HAP have better suspension stability in the foliar fertilizer system, so that the nutrient distribution of the foliar fertilizer spray liquid is more uniform, avoiding fertilizer damage caused by burning leaves due to uneven distribution of HAP, and improving the fertilization effect. In addition, the loaded SiO2 can further improve the biocompatibility of HAP, reduce the negative impact on plant leaf cells, and improve the absorption efficiency of crops.

[0029] The copper-doped hydroxyapatite prepared by the present invention has a high specific surface area and a developed pore structure, can exert surface effect and small size effect, is more conducive to attachment to leaves, can enter the interior of leaves through the cuticle, stomata or cell gaps on the surface of leaves, and is gradually decomposed to release nutrients such as calcium and phosphorus.

[0030] The copper ions in the hydroxyapatite of the present invention can promote the metabolism of proteins and the formation of chlorophyll in crops, improve the photosynthesis efficiency to a certain extent, and prevent and treat fungal diseases and bacterial diseases, and protect the healthy growth of crops. In addition, the present invention can also avoid the loss and volatilization of copper ions by loading copper into hydroxyapatite, thereby improving the utilization efficiency.

[0031] The sodium bisulfite added in the present invention can simultaneously play the role of anti-oxidation, pH balance, etc. In the storage stage (sealed environment) of the foliar fertilizer of the present invention, the sodium bisulfite can prevent the copper ions in the hydroxyapatite from undergoing oxidation reaction during storage, prevent it from having adverse reactions or precipitation with other components, and maintain its activity. In the fertilization stage, the foliar fertilizer of the present invention is changed from a sealed state to an oxygen-rich state, and the sodium bisulfite is rapidly oxidized to produce acidic substances and reduce the pH value. This process is more conducive to the dissolution of HAP, which can increase the absorption rate of HAP by plants and improve the initial fertilizer effect.

[0032] The invention has a simple preparation process, low-cost and easily available raw materials, a wide range of sources, and broad application prospects. It has the advantages of low quantity and high efficiency in crop growth, and is suitable for large-scale industrial application. The invention significantly improves the photosynthetic rate and yield of plants and promotes the growth and development of plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 This is the SEM image of the hydroxyapatite precursor in Example 1.

[0035] Figure 2 This is the SEM image of the hydroxyapatite precursor in Comparative Example 1.

[0036] Figure 3 This is the XRD spectrum of the hydroxyapatite precursor in Example 1.

[0037] Figure 4 This is the pore size distribution diagram of copper-doped hydroxyapatite in Example 1.

[0038] Figure 5 This is the pore size distribution diagram of the hydroxyapatite material in Comparative Example 1. DETAILED DESCRIPTION

[0039] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0040] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0041] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0042] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0043] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0044] Example 1

[0045] Preparation of hydroxyapatite foliar fertilizer:

[0046] (1) preparing a calcium hydroxide suspension, a copper nitrate solution, and a phosphoric acid solution with concentrations of 1.67 mol / L, 1.67 mol / L, and 1.0 mol / L, respectively; mixing 100 mL of the phosphoric acid solution with 4 mL of the copper nitrate solution to obtain a premixed solution;

[0047] The premix was added dropwise to 96 mL of calcium hydroxide suspension at a rate of 5 mL / min, and then the pH was adjusted to 10.0 with ammonia water, and the reaction was carried out at 65°C and 300 rpm for 15 h. The solid phase components were collected by filtration, ground to pass through a 150-mesh sieve, washed with deionized water 6 times, and then freeze-dried at -250 mmHg vacuum and -40°C for 2 h to obtain a hydroxyapatite precursor (its SEM image is shown in FIG. Figure 1 As shown in the XRD spectrum Figure 3 shown).

[0048] (2) Ethyl silicate, acetic acid and ethanol were mixed in a mass ratio of 1:3.5:25 to obtain a treatment liquid, and a hydroxyapatite precursor was mixed with the treatment liquid (the mass ratio of ethyl silicate to hydroxyapatite precursor was 8:1), and the mixture was reacted at 35° C. and 200 rpm for 1.5 h. The solid phase components were collected by filtration, ground to pass through a 150-mesh sieve, washed with deionized water for 6 times, and then dried at 60° C. for 20 min to obtain copper-doped hydroxyapatite.

[0049] (3) After 0.4 parts by mass of sodium bisulfite, 1 part by mass of sodium octadecyl sulfate and 90 parts by mass of water are uniformly mixed, 7 parts by mass of the above copper-doped hydroxyapatite are added under rapid stirring, and then poured into a high-pressure homogenizer, homogenized at a pressure of 120 MPa for 30 minutes, and sealed for storage to obtain a hydroxyapatite foliar fertilizer.

[0050] Figure 3 is the XRD spectrum of the hydroxyapatite precursor in Example 1. As can be seen from the figure, the hydroxyapatite precursor prepared by the present invention corresponds to the standard spectrum of hydroxyapatite, proving that the product of the present invention can be successfully synthesized.

[0051] Figure 4 : is the pore size distribution diagram of the copper-doped hydroxyapatite in Example 1. As can be seen from the figure, the copper-doped hydroxyapatite prepared in the present invention has a relatively large pore structure.

[0052] Example 2

[0053] Preparation of hydroxyapatite foliar fertilizer:

[0054] (1) preparing a calcium hydroxide suspension, a copper nitrate solution, and a phosphoric acid solution with concentrations of 1.67 mol / L, 1.67 mol / L, and 1.0 mol / L, respectively; mixing 100 mL of the phosphoric acid solution with 5 mL of the copper nitrate solution to obtain a premixed solution;

[0055] The premixed solution was added dropwise to 95 mL of calcium hydroxide suspension at a rate of 5 mL / min, and then the pH was adjusted to 11.0 with ammonia water, and the reaction was carried out at 45°C and 300 rpm for 20 hours. The solid phase components were collected by filtration, ground to pass through a 120-mesh sieve, washed 6 times with deionized water, and then freeze-dried at -300 mmHg vacuum and -30°C for 1 hour to obtain a hydroxyapatite precursor.

[0056] (2) Ethyl silicate, acetic acid and ethanol are mixed in a mass ratio of 1:5:20 to obtain a treatment liquid, and a hydroxyapatite precursor is mixed with the treatment liquid (the mass ratio of ethyl silicate to hydroxyapatite precursor is 7:1), and the mixture is reacted at 50° C. and 300 rpm for 1 hour. The solid phase components are collected by filtration, ground to pass through a 120-mesh sieve, washed with deionized water for 6 times, and then dried at 60° C. for 20 minutes to obtain copper-doped hydroxyapatite.

[0057] (3) After 0.2 parts by mass of sodium bisulfite, 0.5 parts by mass of sodium octadecyl sulfate and 100 parts by mass of water are uniformly mixed, 4 parts by mass of the above copper-doped hydroxyapatite are added under rapid stirring, and then poured into a high-pressure homogenizer, homogenized at a pressure of 120 MPa for 30 minutes, and sealed for storage to obtain a hydroxyapatite foliar fertilizer.

[0058] Comparative Example 1 (omit copper doping and directly add copper sulfate to foliar fertilizer)

[0059] The only difference from Example 1 is that step (1) is modified to:

[0060] (1) A calcium hydroxide suspension and a phosphoric acid solution with concentrations of 1.67 mol / L and 1.0 mol / L were prepared respectively; 100 mL of the phosphoric acid solution was added dropwise to 100 mL of the calcium hydroxide suspension at a rate of 5 mL / min, and then the pH was adjusted to 10.0 with aqueous ammonia, and the mixture was reacted at 65° C. and 300 rpm for 15 h. The solid phase components were collected by filtration, ground to pass through a 150-mesh sieve, washed with deionized water for 6 times, and then freeze-dried at a vacuum degree of -250 mmHg and -40° C. for 2 h to obtain a hydroxyapatite precursor (the SEM image of which is shown in FIG. 1 ). Figure 2 shown).

[0061] (2) Ethyl silicate, acetic acid and ethanol are mixed in a mass ratio of 1:3.5:25 to obtain a treatment liquid, and a hydroxyapatite precursor is mixed with the treatment liquid (the mass ratio of ethyl silicate to hydroxyapatite precursor is 8:1), and the mixture is reacted at 35°C and 200 rpm for 1.5 h. The solid phase components are collected by filtration, ground to pass through a 150-mesh sieve, washed 6 times with deionized water, and then dried at 60°C for 20 min to obtain a hydroxyapatite material.

[0062] (3) After 0.4 parts by mass of sodium bisulfite, 0.3 parts by mass of copper sulfate, 1 part by mass of sodium octadecyl sulfate and 90 parts by mass of water are uniformly mixed, 7 parts by mass of the above-mentioned hydroxyapatite material are added under rapid stirring, and then poured into a high-pressure homogenizer, homogenized at a pressure of 120 MPa for 30 minutes, and sealed for storage to obtain a hydroxyapatite foliar fertilizer.

[0063] Figure 5 is the pore size distribution diagram of the hydroxyapatite material in Comparative Example 1. Figure 4 and Figure 5 It can be seen from the comparison that the operation of doping copper ions in the present invention does not lead to a decrease in the porosity of hydroxyapatite.

[0064] Comparative Example 2

[0065] The only difference from Example 1 is that step (2) is omitted, and the copper-doped hydroxyapatite added in step (3) is directly replaced by an equal mass of hydroxyapatite precursor in step (1).

[0066] Comparative Example 3

[0067] The only difference from Example 1 is that the amount of copper-doped hydroxyapatite added in step (3) is changed to 9 parts by mass.

[0068] Comparative Example 4

[0069] The only difference from Example 1 is that the addition of sodium bisulfite is omitted and an equal mass of ascorbic acid is supplemented.

[0070] Comparative Example 5 (Adjusting Catalyst Type)

[0071] The only difference from Example 1 is that acetic acid is replaced by an equal mass of aqueous ammonia.

[0072] Comparative Example 6

[0073] The only difference from Example 1 is that the mass ratio of ethyl silicate, acetic acid and ethanol is modified to 3:3.5:25.

[0074] Effect verification

[0075] (1) Test the change in crop growth after applying the above-mentioned foliar fertilizer. The specific test method is: take 400 healthy millennium tomato seedlings with a plant height of 15-20 cm and a similar growth range, transplant them in the same test field, and apply the foliar fertilizers of Example 1 and Comparative Examples 1-6 (experimental group) in each group, and compare them with the group without foliar fertilizer; apply the conventional amount of inorganic transplanting fertilizer 7 days after transplanting, and spray the same mass of foliar fertilizer with a sprayer every 30 days during the test (after the foliar fertilizer is diluted 200 times, each tomato is sprayed with about 15 mL), spray 3 times in total, and keep the same management methods in other aspects. After 60 days of transplanting tomatoes, randomly select 3 tomatoes in each group, cut the aboveground parts, measure their fresh weight, and calculate the fresh weight growth rate; the calculation formula for the fresh weight growth rate is:

[0076]

[0077] When the tomato fruiting period (110 days after transplanting), the plant height and total fruit yield of the tomato plants were measured. The average value of the measurement results was taken. The test results are shown in Table 1.

[0078] Table 1

[0079] Fresh weight growth rate (%) Plant height (cm / plant) Total yield (kg / plant) Example 1 11.8 175 8.5 Comparative Example 1 7.2 151 6.9 Comparative Example 2 8.3 158 7.2 Comparative Example 3 8.1 164 6.6 Comparative Example 4 7.6 160 7.1 Comparative Example 5 8.1 162 7.0 Comparative Example 6 7.9 159 6.7 Control group / 143 5.3

[0080] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A hydroxyapatite foliar fertilizer, characterized in that: The raw materials of the hydroxyapatite foliar fertilizer include, by weight: 4-7 parts of copper-doped hydroxyapatite material, 0.2-0.5 parts of sodium bisulfite, 0.5-1 parts of surfactant and 85-100 parts of water; The method for preparing the copper-doped hydroxyapatite material comprises the following steps: (1) mixing calcium hydroxide, copper salt and phosphoric acid for reaction, collecting solid phase components, and crushing them to obtain a hydroxyapatite precursor; (2) mixing ethyl silicate, acetic acid and ethanol to obtain a treatment liquid, mixing the hydroxyapatite precursor with the treatment liquid, stirring and crushing, and obtaining a copper-doped hydroxyapatite material; Among them, the surface of copper-doped hydroxyapatite is loaded with SiO2.

2. The hydroxyapatite foliar fertilizer according to claim 1, characterized in that In step (1), the copper salt is copper nitrate; the molar ratio of the sum of the amounts of calcium hydroxide and the copper salt to phosphoric acid is 1.67:1, and the amount of the copper salt accounts for 3.5-5% of the sum of the amounts of calcium hydroxide and the copper salt.

3. The hydroxyapatite foliar fertilizer according to claim 1, characterized in that In step (1), the reaction is carried out at a pH of 10-11 and a temperature of 45-70° C. for 12-20 hours; and the pulverization is carried out until the product passes through a 120-150 mesh sieve.

4. The hydroxyapatite foliar fertilizer according to claim 1, characterized in that In step (2): the mass ratio of the ethyl silicate, acetic acid and ethanol is 1:2-5:30-50; the mass ratio of the ethyl silicate to the hydroxyapatite precursor is 8-15:

1.

5. The hydroxyapatite foliar fertilizer according to claim 1, characterized in that In step (2), the stirring treatment temperature is 30-50°C, the rotation speed is 50-300 rpm, and the time is 1-1.5 hours; and the crushing is crushing until it passes through a 120-150 mesh sieve.

6. The hydroxyapatite foliar fertilizer according to claim 1, characterized in that: The surfactant is one or more of sodium dodecyl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate and potassium laurate.

7. A method for preparing the hydroxyapatite foliar fertilizer according to any one of claims 1 to 6, characterized in that: The following steps are involved: After sodium bisulfite and a surfactant are uniformly mixed in water, copper-doped hydroxyapatite material is added to obtain the hydroxyapatite foliar fertilizer.

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