CN113896180A

CN113896180A - Hydroxyapatite and preparation method thereof

Info

Publication number: CN113896180A
Application number: CN202111392393.1A
Authority: CN
Inventors: 詹志豪
Original assignee: Shenzhen Jirong New Energy Technology Co ltd
Current assignee: Shenzhen Jirong New Energy Technology Co ltd
Priority date: 2021-11-23
Filing date: 2021-11-23
Publication date: 2022-01-07

Abstract

The application provides hydroxyapatite and a preparation method thereof, and the method comprises the following steps: providing biogas residues, and carrying out hydrothermal reaction on the biogas residues in the presence of water to obtain hydroxyapatite; biogas residue is solid waste remaining after anaerobic fermentation of organic waste substances, which are usually organic waste such as kitchen waste, garden waste and municipal sludge. The method utilizes the organic waste material to carry out anaerobic fermentation to generate the biogas residue remained after the biogas, and after water is added into the biogas residue, phosphate radicals and calcium ions in the solution can form substances such as calcium hydrophosphate and the like under the hydrothermal condition, and further gradually convert, crystallize and grow to hydroxyapatite under the high-temperature calcination condition to form the hydroxyapatite.

Description

Hydroxyapatite and preparation method thereof

Technical Field

The application relates to the field of preparation of biological materials, in particular to hydroxyapatite and a preparation method thereof.

Background

Hydroxyapatite, as a calcium phosphate salt with good biocompatibility and stability, has wide application in the fields of medical treatment, environmental remediation and treatment and the like. The global market of the compound fertilizer presents a growing situation, the market scale exceeds 8 million yuan in 2019, the annual growth rate of 6.5 percent is expected to reach about 11.5 million yuan in the next five years, and the growth space is huge.

The implant is mainly used for orthopedic implants and dental implants at present, and as the application technology of the implant in the environmental field is continuously developed, particularly the implant is applied to the aspects of sewage treatment and soil remediation, the market of the implant is expected to increase in a well-jet manner.

The main preparation method of the hydroxyapatite is a coprecipitation method, and calcium hydroxide, namely Ca (OH) is adopted₂And phosphoric acid, i.e. H₃PO₄Adjusting the pH value of the solution by ammonia water as a raw material, and finally calcining the obtained precipitate to obtain hydroxyapatite. In the process, a large amount of calcium oxide, phosphoric acid and ammonia water are consumed, the cost of raw materials is high, and the product is easy to agglomerate.

On the other hand, one of the main treatment modes of organic waste such as kitchen waste is anaerobic fermentation, and although a part of biogas can be generated in the process to be used as energy for subsequent application, only partial reduction of organic solid waste can be realized, and then a large amount of biogas residues still exist and need to be further treated. Because the water content of the biogas residues is high and the salt content is high, the currently adopted methods such as landfill or incineration and the like face a plurality of problems due to the environmental risk or high energy consumption.

Disclosure of Invention

In order to solve the problems, the invention provides a hydroxyapatite and a preparation method thereof, and a method for reasonably utilizing biogas residues is urgently needed to be found.

The method utilizes organic garbage for anaerobic fermentation to generate biogas, the biogas is used as energy for subsequent application, residue after the biogas is biogas residue, and the biogas residue contains calcium, phosphorus, zinc, iron, potassium and other trace metal elements; after the biogas residues are added with water, phosphate radicals and calcium ions in the solution can form substances such as calcium hydrophosphate and the like, and further gradually convert to hydroxyapatite, crystallize and grow under the hydrothermal condition. Meanwhile, the organic matters in the solution undergo hydrolysis and other reactions to further release calcium and phosphorus elements in the solution, so that the calcium and phosphorus in the biogas residues can be efficiently recycled. The hydroxyapatite is generated by drying and calcining after hydrothermal reaction.

The invention relates to a method for preparing hydroxyapatite.

In a first aspect, a method of making hydroxyapatite comprises the steps of:

providing biogas residues, and carrying out hydrothermal reaction on the biogas residues in the presence of water to obtain hydroxyapatite.

The biogas residues are residual solid wastes after organic waste fermentation, and the raw materials currently used for the anaerobic fermentation of organic substances are kitchen waste, garden waste, municipal sludge and the like. The biogas residue is preferably selected from biogas residues generated after anaerobic fermentation of the kitchen waste.

Kitchen waste is the most common waste produced in daily life and belongs to household waste. The food processing leftover (kitchen leftover) and the food residue (kitchen waste) generated in the industries of families, hotels, schools, canteens, restaurants, organs, enterprises, public institutions and the like and comprising leftovers, vegetable leaves, tea residue starch type real objects, plant fibers, animal proteins, fats and the like are complex in components, and mainly comprise oil, water, peels, vegetables, rice noodles, fish, meat, bones and the like and a mixture of a plurality of substances such as waste tableware, plastics, paper towels and the like.

It is noted that pretreatment is required before anaerobic fermentation, and the pretreatment comprises sorting, impurity removal, oil extraction, pulping and other processes, so that the obtained kitchen waste slurry is required to meet the requirement of anaerobic digestion.

The garden garbage refers to dead branches, fallen leaves, withered flowers, tree and shrub pruning and other plant residues generated by natural withering or artificial trimming of garden plants.

-municipal sludge is sludge from municipal sewage plants, by-products from the sludge treatment process in sewage plants, the main components of which are large amounts of microorganisms, extracellular polymers, organic matter and other components; the amount of the biogas produced in the anaerobic digestion process is small, and the amount of the biogas residues produced is high.

Although the rural areas are remote, the food mixture and the cellulosic organic solid wastes such as agricultural straws exist, and meanwhile, a special transport vehicle is used for transporting the wastes such as kitchen wastes and garden wastes to an anaerobic fermentation treatment plant for fermentation treatment. The steps are the same as above, and are not described herein again.

According to the preferred technical solution provided by the embodiment of the present application,

carrying out hydrothermal reaction on the biogas residues and water;

preferably, the solid-to-liquid ratio of the biogas residue to the water is 1 kg: 3L-6L.

For the purposes of the present description and claims that follow, the biogas residue is in kg and the water is in L.

The hydrothermal reaction needs a certain amount of water, the biogas residue has a water content of about 80%, but the biogas residue still cannot form a liquid state, the repeated mixing and mass transfer of reactants are not facilitated in the reaction, therefore, water needs to be added, and meanwhile, in order to improve the efficiency, too much water cannot be added, and the biogas residue can form a liquid state, so that the solid-to-liquid ratio of the biogas residue to the water is preferably 1 kg: 3L-6L.

According to the preferable technical scheme provided by the embodiment of the application, a calcium source is also added when the biogas residue and water are subjected to hydrothermal reaction.

The method does not add an external calcium source, and utilizes the biogas residues obtained after the fermentation of the organic garbage to carry out hydrothermal reaction, thereby obtaining the hydroxyapatite and reducing the environmental pollution. Meanwhile, calcium sources such as calcium nitrate, calcium chloride, calcium oxide, calcium carbonate and the like are reasonably added in the hydrothermal process, so that more phosphorus in the biogas residues can be recycled, the acid-base strength of the hydroxyapatite can be adjusted, and the hydroxyapatite prepared by the method has wider application prospect, such as: and (5) restoring acid soil.

According to a preferred embodiment provided by the embodiments of the present application, the exogenous source of calcium comprises: any one or combination of calcium nitrate, calcium chloride, calcium oxide and calcium carbonate. In order to change the acidity and alkalinity of the hydroxyapatite, calcium chloride can be added in the early stage, and chloride ions are not removed well in the subsequent calcining process and may remain to influence the quality of the hydroxyapatite. In addition, calcium carbonate may be added in the early stage in order to change the acid-base property of hydroxyapatite, and eggshell may be used as calcium carbonate, but when calcium carbonate is used as a calcium source, calcium carbonate is poor in solubility and easily remains in finally obtained hydroxyapatite, so that the effect of calcium carbonate affects the quality of hydroxyapatite. Therefore, according to the present invention, any one or a combination of calcium nitrate and calcium oxide is particularly preferable.

According to the preferred technical scheme provided by the embodiment of the application, the calcium nitrate can be any one or combination of calcium nitrate powder or a calcium nitrate solution, preferably, the calcium nitrate solution; therefore, the calcium nitrate powder is converted into the calcium nitrate solution in advance, so that the biogas residues can be subjected to hydrothermal reaction with the calcium nitrate solution more fully.

Carrying out hydrothermal reaction on the biogas residues and a calcium nitrate solution;

preferably, the solid-to-liquid ratio of the biogas residue to the calcium nitrate solution is 1 kg: 3L-6L, and the concentration of the calcium nitrate solution is 0.01mol/L-0.02 mol/L.

Similarly, in order to further explain the technical scheme of the invention, the biogas residue is in kg unit, and the calcium nitrate solution is in L unit.

the calcium oxide can be calcium oxide powder;

mixing the biogas residues with water, and adding calcium oxide powder;

preferably, the ratio of the biogas residue to the water to the calcium oxide powder is 1 kg: 5L-10L: 0.003kg-0.01 kg.

In order to further explain the technical scheme of the invention, the biogas residue is in kg, the water is in L, and the calcium oxide powder is in kg;

according to the technical scheme provided by the embodiment of the application, the method further comprises the step of calcining after the hydrothermal reaction is finished;

carrying out hydro-thermal synthesis reaction on biogas residues obtained after organic garbage fermentation to generate a first product of hydroxyapatite; the first product hydroxyapatite contains hydrothermal carbon, the first product hydroxyapatite is calcined, the hydrothermal carbon in the first product hydroxyapatite can be removed by the calcination, and the calcination step is simultaneously an impurity removal step, so that stable hydroxyapatite crystals are further obtained. Preferably, the hydrothermal reaction temperature is 150-200 ℃ and the time is 4-10 h; the hydrothermal reaction temperature is a system temperature obtained from the pressure of the hydrothermal reactor, and the boiling point of water is increased at a high pressure, so that the reaction temperature can be reached.

Preferably, the method further comprises the steps of drying and then calcining after the hydrothermal reaction is finished;

preferably, the drying temperature is 60 ℃. The optimal temperature of the hydrothermal reaction is 160-180 ℃, and the reaction time is 6 h.

The hydrothermal reaction needs a certain temperature and time, so the hydrothermal reaction temperature in the application is preferably 150 ℃ to 200 ℃, and the reaction time can be 4h to 10 h; the higher the hydrothermal reaction temperature and the longer the hydrothermal reaction time, the larger the product particles obtained. Through experiments, the reaction temperature is 160-180 ℃, and the reaction time is 6 h.

In order to obtain hydroxyapatite more quickly and cleanly, drying is needed before the calcining step after the hydrothermal reaction is finished, and the drying mode of the invention is drying, but the drying is not limited to drying mode. Preferably, the drying temperature is 60 ℃.

According to the technical scheme provided by the embodiment of the application, in the calcining step, the reaction temperature is 500-900 ℃, and the treatment time is 1-5 h.

Preferably, in the step of calcining, the reaction temperature is 700-800 ℃, and the calcining time is 2 h.

The calcination also needs a certain temperature and time, so that the calcination reaction temperature can be 500-900 ℃, and the reaction time can be 1-5 h; if the calcining reaction temperature is higher and the time is too long, the prepared product is sintered and becomes calcium phosphate; the reaction temperature is low, the reaction time is short, and partial residues are remained. Through experiments, the reaction temperature is 700-800 ℃, and the reaction time is 2 h.

According to the technical scheme provided by the embodiment of the application, 3L-6L of water is added into every 1kg of biogas residues, the mixture is uniformly stirred and then put into a hydrothermal kettle, the temperature is kept at 160-180 ℃ for 6h, and after cooling, filtering and drying at 60 ℃, a first product is obtained; then calcining the first product at 700-800 ℃ for 2h to obtain hydroxyapatite; the pH value of the hydroxyapatite is 8-8.5; or the like, or, alternatively,

adding 3-6L of calcium nitrate solution into every 1kg of biogas residues, wherein the concentration of the calcium nitrate solution is 0.01-0.02 mol/L, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6 hours at 160-180 ℃, cooling, filtering, and drying at 60 ℃ to obtain a first product; then calcining the first product at 700-800 ℃ for 2h to obtain hydroxyapatite; the pH value range of the hydroxyapatite is 10-11; or the like, or, alternatively,

adding 5L-10L of water into every 1kg of biogas residues, then adding 0.003kg-0.01kg of calcium oxide powder into the biogas residues, uniformly stirring the mixture, then putting the mixture into a hydrothermal kettle, preserving the heat at 160-180 ℃ for 6h, cooling the mixture, filtering the mixture, and drying the mixture at 60 ℃ to obtain a first product; then calcining the first product at 700-800 ℃ for 2h to obtain hydroxyapatite; the pH value of the hydroxyapatite is 9-10.

The preferable temperature of the hydrothermal reaction in the invention is 160-180 ℃, the reaction time is 6h, and then the mixture is cooled, the cooling can be not limited to normal temperature cooling, but also can be other cooling methods, as long as the product obtained by the hydrothermal reaction is cooled down, the filtration is only a method for separating the solid product (first product) from the solid-liquid mixture obtained after the hydrothermal reaction, the filtration can be a conventional filtration method, a filtration method such as reduced pressure filtration, a centrifugal method and the like, or a solid product (first product) can be separated out by a centrifugal method and then dried, and the drying step is not limited to drying and drying, or other drying methods can be adopted.

In order to more clearly illustrate the technical scheme of the invention, the first product is a hydroxyapatite and hydrothermal carbon composite obtained after hydrothermal reaction; since the first product, hydroxyapatite, contains hydrothermal carbon complex and is calcined as a decontamination step, the second product is hydroxyapatite which is more clean and stable in crystal after decontamination.

The application also provides hydroxyapatite prepared by the method for preparing hydroxyapatite.

Furthermore, the present application discloses the use of a hydroxyapatite prepared according to the method of the first aspect, primarily for environmental remediation.

The beneficial effect of this application: biogas residue is solid waste remaining after anaerobic fermentation of organic waste substances, which are usually organic waste such as kitchen waste, garden waste and municipal sludge. According to the method, organic waste materials are subjected to anaerobic fermentation to generate biogas residues, after water is added into the biogas residues, phosphate radicals and calcium ions in a solution can form substances such as calcium hydrophosphate and the like, and the substances are further gradually converted, crystallized and grown to hydroxyapatite under a hydrothermal condition to form a first product of hydroxyapatite.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:

FIG. 1 is an X-ray diffraction analysis chart of a hydroxyapatite standard;

FIG. 2 is an X-ray diffraction test chart of hydroxyapatite of the present application;

FIG. 3 is a photograph of a field emission scanning electron microscope of example 1 of the present application;

FIG. 4 is a photograph of a field emission scanning electron microscope of parallel example 1, parallel example 2 and parallel example 3 in the present application;

FIG. 5 is a photograph of a field emission scanning electron microscope of example 4 of the present application;

FIG. 6 is a photograph of a field emission scanning electron microscope of example 3, example 4, example 5 and example 6 in this application;

FIG. 7 is a photograph of a field emission scanning electron microscope of example 7 of the present application;

FIG. 8 is a photograph of a field emission scanning electron microscope of example 5, example 6, example 8 and example 9.

Detailed Description

The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

The invention ensures that the synthesized hydroxyapatite is beneficial to the adsorption of heavy metal in sewage and the soil remediation in the environmental treatment by adjusting reasonable process parameters. The preparation of hydroxyapatite from biogas residues can be realized by the following specific implementation mode through reasonable adjustment of process parameters.

The specific implementation mode is as follows:

parallel example 1:

1) adding 1L of water into every 1kg of biogas residues, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6h at 160 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

2) And placing the dried first product in a calcining furnace for calcining, wherein the calcining temperature is set to be below 700 ℃, and the calcining treatment time is 2 hours, so that a second product is obtained.

3) And the second product obtained in the parallel example 1 is subjected to an X-ray diffraction test, and the characteristic peak of the test is compared with the characteristic peak of the hydroxyapatite, so that whether the second product is the hydroxyapatite or not is determined.

4) The second product obtained in parallel example 1 was weighed to 18g by an electronic balance, and an image was scanned with a field emission scanning electron microscope to obtain a second product obtained in parallel example 1.

5) The second product obtained in parallel example 1 was taken to have a mass of 30mg, placed in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium of the second product obtained in the parallel example 1 by using an inductively coupled plasma mass spectrometry method.

Parallel example 2:

1) adding 8L of water into every 1kg of biogas residues, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6h at 180 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

2) And placing the dried first product in a calcining furnace for calcining at 800 ℃ for 2h to obtain a second product.

3) And the second product calcined in the parallel example 2 is tested by an X-ray diffraction test, and the characteristic peak of the second product is compared with the characteristic peak of the hydroxyapatite, so that whether the second product is the hydroxyapatite is determined.

4) The second product obtained in parallel example 2 was weighed to 18g by an electronic balance, and an image of the second product obtained in parallel example 2 was scanned by a field emission scanning electron microscope.

5) The second product obtained in parallel example 2 was taken to have a mass of 30mg, placed in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium in the second product obtained in the parallel example 2 by using an inductively coupled plasma mass spectrometry method.

Example 1:

1) adding 3L of water into every 1kg of biogas residues, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6h at 170 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) The second product calcined according to example 1 was subjected to an X-ray diffraction test, and its characteristic peak was compared with that of hydroxyapatite, thereby determining whether the second product was hydroxyapatite.

4) The second product obtained in example 1 was weighed to 18g by an electronic balance, and images of each of the parallel examples and examples were scanned by a field emission scanning electron microscope.

5) The second product obtained in example 1 was taken to have a mass of 30mg, placed in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium of the metals by using an inductively coupled plasma mass spectrometry method on the second product obtained in example 1.

Example 2:

1) adding 4.5L of water into every 1kg of biogas residues, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6h at 160 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) The second product calcined in example 2 was subjected to an X-ray diffraction test, and its characteristic peak was compared with that of hydroxyapatite, thereby determining whether the second product was hydroxyapatite.

4) The second product obtained in example 2 was weighed to have a mass of 18g by an electronic balance, and an image of the second product obtained in example 2 was scanned by a field emission scanning electron microscope.

5) The second product obtained in example 2 was taken to have a mass of 30mg, placed in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium of the second product obtained in example 2 by using an inductively coupled plasma mass spectrometry method.

Example 3:

1) adding 6L of water into every 1kg of biogas residues, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6h at 180 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) The second product obtained by calcining in example 3 was subjected to an X-ray diffraction test, and its characteristic peak was compared with that of hydroxyapatite, thereby determining whether the second product was hydroxyapatite.

4) The second product obtained in example 3 was weighed to have a mass of 18g by an electronic balance, and scanned with a field emission scanning electron microscope to obtain a scanning image of the second product obtained in example 3.

5) The second product obtained in example 3 was taken to have a mass of 30mg, placed in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium of the metals by using an inductively coupled plasma mass spectrometry method on the second product obtained in the example 3.

Parallel example 3:

1) adding 1L of calcium nitrate aqueous solution into every 1kg of biogas residues, wherein the solubility of the calcium nitrate aqueous solution is 0.02mol/L, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6 hours at 160 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) And the second product calcined in the parallel example 3 is subjected to an X-ray diffraction test, and the characteristic peak of the test is compared with the characteristic peak of the hydroxyapatite, so that whether the second product is the hydroxyapatite is determined.

4) The second product obtained in parallel example 3 was scanned with a field emission scanning electron microscope to obtain an image, taking the mass of the second product obtained in parallel example 3 as 18g by an electronic scale.

5) The second product obtained in parallel example 3 was taken to have a mass of 30mg, placed in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium in the second product obtained in the parallel example 3 by using an inductively coupled plasma mass spectrometry method.

Parallel example 4:

1) adding 8L of calcium nitrate aqueous solution into every 1kg of biogas residues, wherein the solubility of the calcium nitrate aqueous solution is 0.02mol/L, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6 hours at 180 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) And the second product calcined in the parallel example 4 is subjected to an X-ray diffraction test, and the characteristic peak of the test is compared with the characteristic peak of the hydroxyapatite, so that whether the second product is the hydroxyapatite is determined.

4) The second product obtained in parallel example 4 was scanned with a field emission scanning electron microscope to obtain an image of 18g of the second product obtained in parallel example 4 by using an electronic balance.

5) The second product obtained in parallel example 4 was taken to have a mass of 30mg, placed in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium in the second product obtained in the parallel example 4 by using an inductively coupled plasma mass spectrometry method.

Example 4:

1) adding 3L of calcium nitrate aqueous solution into every 1kg of biogas residues, wherein the solubility of the calcium nitrate aqueous solution is 0.01mol/L, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6h at 170 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) The second product obtained by calcining in example 4 was subjected to an X-ray diffraction test, and its characteristic peak was compared with that of hydroxyapatite, thereby determining whether the second product was hydroxyapatite.

4) The second product obtained in example 4 was weighed to have a mass of 18g by an electronic balance, and scanned with a field emission scanning electron microscope to obtain a scanning image of the second product obtained in example 4.

5) A sample of the second product obtained in example 4 was taken to have a mass of 30mg, and was placed in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium of the metals by using an inductively coupled plasma mass spectrometry method on the second product obtained in example 4.

Example 5:

1) adding 4.5L of calcium nitrate aqueous solution into every 1kg of biogas residues, wherein the solubility of the calcium nitrate aqueous solution is 0.02mol/L, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6h at 160 ℃, cooling, filtering by using a 200-mesh filter screen, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) And the second product obtained in the example 5 is subjected to an X-ray diffraction test, and the characteristic peak of the test is compared with the characteristic peak of hydroxyapatite, so that whether the second product is the hydroxyapatite or not is determined.

4) The second product obtained in example 5 was weighed to a mass of 15g to 20g by an electronic balance, and an image of the second product obtained in example 5 was scanned by a field emission scanning electron microscope.

5) A sample of the second product obtained in example 5, which had a mass of 30mg, was placed in 10mL of deionized water, stirred for 10 hours and then allowed to stand for 2 hours, and the pH of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium of the metals by using an inductively coupled plasma mass spectrometry method on the second product obtained in example 5.

Example 6:

1) adding 6L of calcium nitrate aqueous solution into every 1kg of biogas residues, wherein the solubility of the calcium nitrate aqueous solution is 0.015mol/L, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6h at 180 ℃, cooling, filtering by using a 200-mesh filter screen, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) And the second product obtained in the example 6 is subjected to an X-ray diffraction test, and the characteristic peak of the test is compared with the characteristic peak of hydroxyapatite, so that whether the second product is the hydroxyapatite or not is determined.

4) The second product obtained in example 6 was weighed to a mass of 15g to 20g by an electronic balance, and an image of the second product obtained in example 6 was scanned by a field emission scanning electron microscope.

5) A sample of the second product obtained in example 6 was taken to have a mass of 30mg, and was placed in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium of the metals by using an inductively coupled plasma mass spectrometry method on the second product obtained in example 6.

Parallel example 5:

1) adding 3L of water into every 1kg of biogas residues, then adding 0.003kg of calcium oxide solid powder, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6 hours at 160 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) And the second product obtained in the parallel example 5 is subjected to an X-ray diffraction test, and the characteristic peak of the test is compared with the characteristic peak of the hydroxyapatite, so that whether the second product is the hydroxyapatite or not is determined.

4) The second product obtained in parallel example 5 was taken by an electronic balance, and an image was scanned with a field emission scanning electron microscope using a mass of 18g for the second product obtained in parallel example 5.

5) 30mg of the second product obtained in parallel example 5 was put in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: the second product obtained in the parallel example 5 is used for detecting the contents of metal zinc, iron, potassium, lead, magnesium and chromium by using an inductively coupled plasma mass spectrometry method.

Parallel example 6:

1) adding 12L of water into every 1kg of biogas residues, then adding 0.01kg of calcium oxide solid powder, uniformly stirring, then putting into a hydrothermal kettle, preserving heat for 6 hours at 180 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and obtaining a first product after drying for later use.

3) And the second product obtained in the parallel example 6 is subjected to an X-ray diffraction test, and the characteristic peak of the test is compared with the characteristic peak of the hydroxyapatite, so that whether the second product is the hydroxyapatite or not is determined.

4) The second product obtained in parallel example 6 was taken by an electronic balance, and an image was scanned with a field emission scanning electron microscope using a mass of 18g for the second product obtained in parallel example 6.

5) 30mg of the second product obtained in parallel example 6 was put in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: the second product obtained in parallel example 6 was analyzed by inductively coupled plasma mass spectrometry for the contents of zinc, iron, potassium, lead, magnesium and chromium.

Example 7:

1) adding 5L of water into every 1kg of biogas residues, then adding 0.003kg of calcium oxide solid powder, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6 hours at 170 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) The second product obtained in example 7 was subjected to an X-ray diffraction test, and its characteristic peak was compared with that of hydroxyapatite, thereby determining whether the second product was hydroxyapatite.

4) The second product obtained in example 7 was weighed with an electronic balance to obtain a mass of 18g, and an image of the second product obtained in example 7 was scanned with a field emission scanning electron microscope.

5) 30mg of the second product obtained in example 7 was put in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium of the metals by using an inductively coupled plasma mass spectrometry method on the second product obtained in example 7.

Example 8:

1) adding 7.5L of water into every 1kg of biogas residues, adding 0.007kg of calcium oxide solid powder, uniformly stirring, putting into a hydrothermal kettle, preserving heat at 160 ℃ for 6h, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) And the second product obtained in the example 8 is subjected to an X-ray diffraction test, and the characteristic peak of the test is compared with the characteristic peak of hydroxyapatite, so that whether the second product is the hydroxyapatite or not is determined.

4) The second product obtained in example 8 was weighed with an electronic balance to obtain a mass of 18g, and an image of the second product obtained in example 8 was scanned with a field emission scanning electron microscope.

5) 30mg of the second product obtained in example 8 was put in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: and detecting the contents of zinc, iron, potassium, lead, magnesium and chromium of the metals by using an inductively coupled plasma mass spectrometry method on the second product obtained in the example 8.

Example 9:

1) adding 10L of water into every 1kg of biogas residues, then adding 0.01kg of calcium oxide solid powder, uniformly stirring, then putting into a hydrothermal kettle, preserving heat for 6 hours at 180 ℃, cooling, filtering by using a 200-mesh filter sieve, drying at 60 ℃ in a drying box, and drying to obtain a first product for later use.

3) The second product obtained in example 9 was subjected to an X-ray diffraction test, and its characteristic peak was compared with that of hydroxyapatite, thereby determining whether the second product was hydroxyapatite.

4) The second product obtained in example 9 was weighed with an electronic balance, and an image of the second product obtained in example 9 was scanned with a field emission scanning electron microscope, taking a mass of 18 g.

5) 30mg of the second product obtained in example 9 was put in 10mL of deionized water, stirred for 10 hours, and then allowed to stand for 2 hours, and the pH value of the solution was measured by a pH meter.

6) And detecting the metal content: the second product obtained in example 9 was subjected to inductively coupled plasma mass spectrometry to detect the contents of zinc, iron, potassium, lead, magnesium and chromium.

TABLE 1 technological parameters of hydroxyapatite preparation from biogas residues and final hydroxyapatite detection results

X-ray diffraction testing: the white powders of the second product after being calcined in the above parallel example and example are respectively subjected to an X-ray diffraction test, and the characteristic peaks of the product obtained by the method are found to accord with the characteristic peaks of hydroxyapatite, and the characteristic peaks exist at positions with 2 theta of 25.92 degrees, 31.88 degrees, 32.18 degrees, 32.96 degrees and the like, as shown in fig. 1 and fig. 2, so that the second product is determined to be hydroxyapatite.

Field emission scanning electron microscope: a white powder of the second product was weighed by an electronic balance to give a mass of 15g to 20g for each of parallel example 1, parallel example 2 and example 1 to example 3, and a field emission scanning electron microscope picture was taken, wherein example 1 is shown in detail in FIG. 3, parallel example 1 is shown in detail in the upper left of FIG. 4, parallel example 2 is shown in detail in the upper right of FIG. 4, example 2 is shown in detail in the lower left of FIG. 4, and example 3 is shown in detail in the lower right of FIG. 4. Along with the increase of the proportion of water, the agglomeration degree of the hydroxyapatite particles is reduced, and the dispersity is improved.

A white powder of the second product was weighed by an electronic balance to give 15g to 20g in mass, respectively, of each of replicate 3, replicate 4, and replicate 4 to replicate 6, respectively, and a field emission scanning electron microscope photograph was taken, respectively, in which replicate 4 is shown in detail in FIG. 5, replicate 3 is shown in detail in the upper left of FIG. 6, replicate 4 is shown in detail in the upper right of FIG. 6, replicate 5 is shown in detail in the lower left of FIG. 6, and replicate 6 is shown in detail in the lower right of FIG. 6. The use of calcium nitrate promotes the adhesion of hydroxyapatite particles, forming aggregated hydroxyapatite material.

A white powder of the second product was weighed by an electronic balance to give 15g to 20g in mass, respectively, of each of parallel example 5, parallel example 6, and example 7 to example 9, and a field emission scanning electron microscope photograph was taken, respectively, in which example 7 is shown in detail in FIG. 7, parallel example 5 is shown in detail in the upper left of FIG. 8, parallel example 6 is shown in detail in the upper right of FIG. 8, example 8 is shown in detail in the lower left of FIG. 8, and example 9 is shown in detail in the lower right of FIG. 8. It can be seen that there is a tendency for the size of the hydroxyapatite to decrease as the proportion of water increases.

Detecting the content of metal in the product: the determination refers to the agricultural industry standard organic fertilizer (NY525-2012) of the people's republic of China, and the requirement of the limit index of heavy metal in the organic fertilizer can be known according to the table 1;

the content of other metals than calcium in the hydroxyapatite depends on the step of the hydrothermal treatment. In principle, the content of other metals decreases as the volume of the solution increases during the hydrothermal treatment, but in the hydroxyapatite preparation process, the hydrothermal treatment time and energy consumption increase as the volume of the solution increases, so that the hydrothermal reaction cannot be performed by using too much water in order to reduce the content of other metals. Meanwhile, when the content of the heavy metal is considered, the preparation process of the hydroxyapatite and the specific type of the heavy metal are considered; meanwhile, the metal content increases with the increase of exogenous calcium and with the increase of treatment time. This is because the increase of exogenous calcium will cause the pH change of the whole hydrothermal environment, and most metal ions are sensitive to the pH change, and the metal hydroxide will precipitate together with hydroxyapatite. For those metals with better solubility of metal hydroxides, the pH change is not affected or is less affected. The increase in the volume of the whole solution, however, helps to dilute the concentration of the non-calcium metal ions, thus reducing the residues in the hydroxyapatite.

In summary, in the hydroxyapatite prepared in the parallel examples 1-2 and the examples 1-3 of the present application, each of the parallel examples and examples contains elements such as zinc, iron, potassium, magnesium and the like required for the growth of crops; from the viewpoint of comprehensive preparation process and effect of heavy metal elements of lead and chromium, the control effect of heavy metals containing lead and chromium in example 1 is the best.

Meanwhile, in the hydroxyapatite prepared in parallel examples 3-4 and examples 4-6 of the present application, each of the parallel examples and examples contains elements such as zinc, iron, potassium, magnesium and the like required for crop growth; from the viewpoint of comprehensive preparation process and effect of heavy metal elements of lead and chromium, the control effect of heavy metals containing lead and chromium in example 4 is the best.

Meanwhile, in the hydroxyapatite prepared in parallel examples 5-6 and examples 7-9 of the present application, each of the parallel examples and examples contains elements such as zinc, iron, potassium, magnesium and the like required for crop growth; from the viewpoint of comprehensive preparation process and effect of heavy metal elements of lead and chromium, the control effect of heavy metals containing lead and chromium in example 7 is the best.

The foregoing description is only exemplary of the preferred embodiments of the application and is provided for the purpose of illustrating the general principles of the technology and the like. Meanwhile, the scope of the invention according to the present application is not limited to the technical solutions in which the above-described technical features are combined in a specific manner, and also covers other technical solutions in which the above-described technical features or their equivalent are combined arbitrarily without departing from the inventive concept described above. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.

Claims

1. A method for preparing hydroxyapatite is characterized in that: the method comprises the following steps:

2. The method for preparing hydroxyapatite according to claim 1, wherein the biogas residue and water are subjected to hydrothermal reaction;

the solid-liquid ratio of the biogas residue to the water is 1 kg: 3L-6L of the mixture is added,

the biogas residues are generated after the organic garbage is subjected to anaerobic fermentation.

3. The method for preparing hydroxyapatite according to claim 1, wherein a calcium source is further added when the biogas residue and water are subjected to hydrothermal reaction.

4. A method according to claim 3, wherein the calcium source comprises: any one or combination of calcium nitrate and calcium oxide.

5. The method for preparing hydroxyapatite according to claim 4, wherein the calcium nitrate is any one or a combination of calcium nitrate powder and calcium nitrate solution;

the solid-liquid ratio of the biogas residues to the calcium nitrate solution is 1 kg: 3L-6L, and the concentration of the calcium nitrate solution is 0.01mol/L-0.02 mol/L.

6. The method for preparing hydroxyapatite according to claim 4, characterized in that the calcium oxide is calcium oxide powder;

mixing the biogas residues with water, and adding calcium oxide powder;

the ratio of the biogas residue to the water to the calcium oxide powder is 1 kg: 5L-10L: 0.003kg-0.01 kg.

7. The method for preparing hydroxyapatite according to any one of claims 1 to 6, characterized in that it further comprises a step of calcination after the hydrothermal reaction is completed;

the hydrothermal reaction temperature is 150-200 ℃, and the time is 4-10 h;

or the hydrothermal reaction temperature is 160-180 ℃ and the time is 6 h;

the method also comprises the steps of drying after the hydrothermal reaction is finished, and then calcining; the temperature of the drying was 60 ℃.

8. The method for preparing hydroxyapatite according to claim 7, wherein the calcining step is carried out at a reaction temperature of 500 ℃ to 900 ℃ for 1h to 5 h;

or, in the calcining step, the reaction temperature is 700-800 ℃, and the calcining time is 2 h.

9. A method for preparing hydroxyapatite according to any one of claims 1 to 6,

adding 3-6L of water into every 1kg of biogas residues, uniformly stirring, putting into a hydrothermal kettle, preserving heat for 6 hours at 160-180 ℃, cooling, filtering, and drying at 60 ℃ to obtain a first product; then calcining the first product at 700-800 ℃ for 2h to obtain hydroxyapatite; the pH value of the hydroxyapatite is 8-8.5; or the like, or, alternatively,

adding 3-6L of calcium nitrate solution into every 1kg of biogas residues, wherein the concentration of the calcium nitrate solution is 0.01-0.02 mol/L, uniformly stirring, putting into a hydrothermal kettle, keeping the temperature at 160-180 ℃ for 6h, cooling, filtering, and drying at 60 ℃ to obtain a first product; then calcining the first product at 700-800 ℃ for 2h to obtain hydroxyapatite; the pH value range of the hydroxyapatite is 10-11; or the like, or, alternatively,

10. Hydroxyapatite, characterized in that it is obtained by preparation according to the method of any one of claims 1 to 9.