A method for preparing hydroxyapatite with different morphologies from solid waste by ammonia-alkali method

Abstract

The application provides a method for preparing hydroxyapatite with different morphologies from solid waste by using ammonia alkali method, and belongs to the field of comprehensive utilization of solid waste resources and synthesis of inorganic materials. First, ammonia distillation waste supernatant, alkali residue, acidification aid and functional non-imidazole liquid of the solid waste of ammonia alkali method are mixed, then concentrated hydrochloric acid is added, then calcium-containing alkaline solid material is added to adjust pH, remove impurities and concentrate, then hydroxyapatite crystal formation inducer is added, finally, the hydroxyapatite is obtained after reaction with trisalt phosphate solution and cleaning and purification, and the hydroxyapatite has high yield, high purity and different morphologies, including flaky, tubular and spherical morphologies. The utilization rate of the alkali residue reaches 79.05-82.45%, the extraction of effective components reaches more than 93%, the yield of the hydroxyapatite is as high as more than 99.9%, and the purity is more than 99%, so that not only the emission of the alkali residue is reduced, but also the ammonia distillation waste supernatant is reused.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization of solid waste resources and synthesis of inorganic materials, specifically involving a method for preparing hydroxyapatite with different morphologies using ammonia-soda process solid waste. Background Technology

[0002] The domestic ammonia-soda process has a production capacity of approximately 14 million tons per year, resulting in the annual discharge of about 126 million tons of ammonia stripping waste liquid and 3.78 million tons of alkali residue. These large quantities of waste liquid and residue have become a major problem for enterprises. Furthermore, the surge in natural soda ash production has significantly impacted chemical soda ash manufacturers. Therefore, achieving comprehensive utilization of ammonia stripping waste liquid and alkali residue to reduce operating costs and enhance enterprise competitiveness is urgently needed.

[0003] Because ammonia stripping waste liquid and alkali residue contain a large amount of calcium resources, their value-added utilization can help chemical soda ash production enterprises reduce costs and increase efficiency. The main components of ammonia stripping waste liquid are CaCl2 (8-10%) and NaCl (4-6%); the main components of alkali residue are CaCO3 (46-48%), Mg(OH)2 (9-11%), NaCl (10-17%), CaCl2 (7-13%), Fe2O3 (0.5-1.5%), and acid-insoluble matter (11-15%, mainly SiO2 and CaSO4, with SiO2 being the primary component). The main components of ammonia stripping waste liquid are shown in the table below:

[0004]

[0005] Currently, the mainstream process for the resource utilization of ammonia stripping waste liquid from the ammonia-soda process, both domestically and internationally, is the evaporation and crystallization process to produce calcium chloride. The traditional method involves introducing the liquid into salt fields for natural evaporation, and then using it in production once the concentration reaches approximately 20°Bé. This process is inefficient, time-consuming, and requires a large area. Furthermore, the instability of natural evaporation makes it difficult to guarantee the quality and supply of concentrated calcium chloride, leading to significant fluctuations in production costs. For the alkaline residue generated during the ammonia-soda process, the common treatment methods are direct discharge or its use as a filler material in the construction industry. Overall, neither domestic nor international efforts have achieved ideal results in the resource utilization of ammonia stripping waste liquid and alkaline residue.

[0006] The molecular formula of hydroxyapatite is Ca. 10(PO4)6(OH)2 can be prepared by solid-state reaction, sol-gel method, microemulsion method, and solvothermal method. Among these, the solid-state reaction method requires high-temperature blending, resulting in high energy consumption and long processing time, limiting its widespread application. The sol-gel method offers milder reaction conditions, simpler equipment, and produces products with good crystallinity and high dispersion, but suffers from drawbacks such as expensive alkoxide raw materials, highly toxic organic solvents, and low yield. The microemulsion method for preparing hydroxyapatite mainly involves microemulsion preparation, precipitation reaction, separation and washing, drying, and calcination. This process is complex and requires high-temperature calcination, leading to high energy consumption and low product yield. The solvothermal method utilizes high temperature and high pressure to induce a chemical reaction, easily obtaining particles with uniform morphology. However, this method is prone to side reactions, has a long reaction time, low yield, and requires sophisticated equipment, making it unsuitable for large-scale production.

[0007] To regulate the morphology of hydroxyapatite, researchers typically add surfactants, organic solvents, and template agents. The resulting morphologies are mostly spherical, rod-shaped, and linear, with platy and tubular morphologies being less common. Among these, surfactants such as hexadecyltrimethylammonium bromide are often expensive and highly toxic. During the reaction, the addition of surfactants easily causes foaming, requiring multiple cleanings of the product after the reaction, generating large amounts of waste liquid and resulting in poor environmental performance. The addition of organic solvents can alter the polarity of the reaction solution or the hydrolysis rate of the phosphorus source, thereby inducing changes in the morphology of hydroxyapatite. However, the large amount of organic solvent added as a reaction solvent requires evaporation and recovery, increasing process costs; failure to recover it also impacts the environment. Template agents first mix with and combine with the calcium source to form a complex, influencing the crystal morphology of hydroxyapatite by regulating the reaction rate between calcium and phosphorus. However, removing the template agent requires high-temperature calcination, increasing energy consumption and resulting in poor economic efficiency.

[0008] Chinese invention patent document CN111115599A discloses a method for preparing ionic liquid-induced hydroxyapatite hierarchical nanorods. This method involves adding an imidazole ionic liquid to an alkaline solution of a phosphorus source, followed by a reaction with a calcium salt solution under high temperature and pressure for 12-36 hours. After standing at room temperature for 0-3 days, the mixture is centrifuged, washed, and dried to obtain nanorod-shaped hydroxyapatite. This patent changes the reaction solution system from pure water to a system of imidazole ionic liquid and water, with a ratio of imidazole ionic liquid to water of 0.5-2:1. Although imidazole ionic liquids are non-toxic to the environment, the recovery of large quantities of imidazole ionic liquid increases the process operating cost. Furthermore, this method requires high temperature and pressure reaction conditions, further increasing energy consumption and operational difficulty.

[0009] Chinese invention patent document CN100441503C discloses a method for ionothermal synthesis of nano-hydroxyapatite. This method uses an imidazole-based ionic liquid as the reaction solvent, then adds a calcium and phosphorus source, adjusting the pH of the reaction solution to 8-9 (or not), and reacting at 100-200℃ for 24-72 hours to obtain nano-sized hydroxyapatite. This method only uses an imidazole-based ionic liquid as the reaction solvent to obtain nano-sized hydroxyapatite and does not involve any change in the morphology of the hydroxyapatite. Because the reaction solvent is an imidazole-based ionic liquid, the production of nano-sized hydroxyapatite is costly and economically inefficient. Summary of the Invention

[0010] The technical problem this invention aims to solve is to provide a method for preparing hydroxyapatite with different morphologies using solid waste from the ammonia-soda process. This method can produce a high-concentration calcium ion solution without evaporation and concentration, and can simply and rapidly prepare hydroxyapatite with high yield, high purity, and controllable morphology. Furthermore, this method not only eliminates the risk of reaction solution overflow during the acidification process of ammonia-soda solid waste, but also overcomes the shortcomings of traditional solvothermal methods for preparing hydroxyapatite, such as long reaction time, high energy consumption at medium and high temperatures, and low yield.

[0011] To address the above problems, the present invention provides a method for preparing hydroxyapatite from ammonia-soda solid waste, specifically comprising the following steps:

[0012] (1) The alkali residue is crushed / ground into fine particles, and the ammonia stripping waste liquid is added to adjust the slurry to obtain alkali residue slurry. Non-imidazolium functionalized ionic liquid and acidification aid are added to the slurry to obtain the first mixed solution. The non-imidazolium functionalized ionic liquid is diethylmethyl-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide salt or tetrabutylphosphonium β-alanine salt or tetraethylammonium-alanine salt.

[0013] (2) Add concentrated hydrochloric acid to the first mixed solution and react at 40-60℃ for 1-2 hours. After filtration / centrifugation, the first residue and the second mixed solution are obtained.

[0014] (3) Add calcium-containing alkaline solid to the second mixed solution to adjust the pH to 10-12, stir the reaction for 0.3-0.5 h, filter / centrifuge to obtain the second residue and the third mixed solution, and recycle the second residue;

[0015] (4) Add hydroxyapatite seed crystals, adipic acid or succinic acid to the third mixed solution, stir and mix evenly to obtain the fourth mixed solution; add the triphosphate aqueous solution to the fourth mixed solution, and adjust the pH to 10-12 with alkaline solution, stir and react at room temperature for 2-4 hours. After the reaction is completed, filter / centrifuge to obtain crude hydroxyapatite and the fifth mixed solution, and recycle the fifth mixed solution.

[0016] (5) The crude hydroxyapatite is washed and dried with a cleaning solution composed of pure water and proton organic solvent to obtain hydroxyapatite with a flaky, tubular or spherical morphology.

[0017] Furthermore, in step (1), the particle size of the alkali residue is 100-300 mesh; the ratio of alkali residue to ammonia stripping waste liquid in the alkali residue slurry is 1g:2-4mL.

[0018] Further, in step (1), the acidification aid is one of allyl polyoxyalkyl epoxy ether, allyl alcohol polyoxyalkyl ether, or nonylphenol polyoxyethylene ether.

[0019] Furthermore, the ratio of the amount of the non-imidazolium functionalized ionic liquid added to the amount of ammonia-removed waste liquid added to the first mixed solution is 0.05-0.1 g: 1 mL; the ratio of the amount of the acidifying agent added to the amount of ammonia-removed waste liquid added to the first mixed solution is 0.001-0.005 g: 1 mL.

[0020] Furthermore, in step (2), the mass concentration of concentrated hydrochloric acid is 31-37%; the ratio of the amount of concentrated hydrochloric acid used to the amount of alkaline residue added in the first mixed solution is 0.02-0.024 mol: 1g.

[0021] Furthermore, in step (3), the calcium-containing alkaline solid substance is calcium oxide or calcium hydroxide; the particle size of the calcium-containing alkaline solid substance is 200-300 mesh.

[0022] Furthermore, in step (3), the second residue can be recycled by using it in cement production.

[0023] Further, in step (4), the ratio of the amount of hydroxyapatite seed crystals added to the amount of the third mixed solution in the fourth mixed solution is 0.01-0.05 g: 1 mL; the ratio of the amount of adipic acid or succinic acid added to the amount of the third mixed solution is 0.03-0.08 g: 1 mL.

[0024] Furthermore, in step (4), the triphosphate is trisodium phosphate, tripotassium phosphate, or triammonium phosphate; the alkaline solution is saturated sodium hydroxide solution, saturated potassium hydroxide solution, or ammonia.

[0025] Furthermore, in step (4), the molar ratio of calcium ions in the triphosphate and the third mixed solution is 0.581-0.599:1; the volume ratio of water content in the triphosphate aqueous solution to that in the third mixed solution is 0.5-1:1.

[0026] Furthermore, in step (4), the fifth mixed solution is recycled by returning it to step (1) to be used as ammonia stripping waste liquid.

[0027] Further, in step (5), the proton organic solvent is methanol, ethanol, or isopropanol; the volume ratio of pure water to proton organic solvent in the cleaning solution is 1 mL: 0.5-1.0 mL; the cleaning conditions are: two to four cleanings; the drying conditions are: drying temperature 40-60℃ and drying time 1-3 h.

[0028] The first residue obtained by the inventors in step (2) is solid waste such as silicon dioxide and calcium sulfate. The first residue is mainly silicon dioxide and is used for road paving.

[0029] The second residue obtained by the inventors in step (3) is a solid waste of magnesium hydroxide and iron hydroxide. The second residue is mainly composed of magnesium hydroxide and is used as a raw material for cement preparation.

[0030] During the experiment in step (4), the inventors discovered that when the pH was below 10, the reaction conditions did not yield pure hydroxyapatite, and the product was mainly calcium hydrogen phosphate; when the pH was above 12, the reaction conditions did not yield pure hydroxyapatite, and the product was mainly calcium hydroxide. Therefore, to obtain pure hydroxyapatite, the pH of the reaction system needs to be appropriately controlled.

[0031] The beneficial effects of this invention are as follows:

[0032] (1) This invention provides a comprehensive utilization method for the treatment of ammonia stripping waste liquid and alkali residue solid waste in the ammonia-soda process soda ash industry. By introducing ammonia stripping waste liquid as a reaction solvent and adding non-imidazolium ionic liquid and acidification aid as reaction aids, controlling the mesh size of the alkali residue and the amount of concentrated hydrochloric acid added, the total acidification reaction time is controlled within 2 hours, the utilization rate of alkali residue reaches 79.05-82.45%, and the extraction rate of effective components in alkali residue reaches 93-97%. The entire process generates virtually no waste, saving energy and reducing emissions, turning waste into treasure, and guiding the healthy development of the soda ash industry. In addition, concentrated hydrochloric acid is a product of the chlor-alkali industry, but the price of concentrated hydrochloric acid has long been inverted, seriously hindering the development of the chlor-alkali industry. This method can consume a large amount of concentrated hydrochloric acid from chlor-alkali, promoting the coordinated development of the chlor-alkali and soda ash industries. By realizing the comprehensive utilization of ammonia stripping waste liquid and alkali residue, this invention significantly improves the resource value and product added value of waste, showing broad industrial application prospects.

[0033] (2) The addition of a small amount of non-imidazolium functionalized ionic liquid in this invention not only improves the dispersibility of alkaline residue in solution and reduces surface tension, but also absorbs carbon dioxide generated during the acidification reaction, which can suppress large carbon dioxide bubbles during the acidification reaction. Different types of non-imidazolium functionalized ionic liquids are used as morphology-regulating induction agents for in-situ reactions. They synergistically induce morphological changes in hydroxyapatite with succinic acid or adipic acid. The mechanism is that the carboxyl group in succinic acid or adipic acid, together with the amino group provided by the non-imidazolium functionalized ionic liquid, causes hydroxyapatite to change from rod-shaped to other morphologies. Specifically, diethylmethyl-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide salt produces a plate-like morphology, tetrabutylphosphonium β-alanine salt produces a tubular morphology, and tetraethylammonium-alanine produces a spherical morphology.

[0034] (3) The acidification aid of the present invention can suppress the large bubbles generated by carbon dioxide gas during the acidification process, prevent the overflow of the reaction solution, reduce the danger of the acidification reaction, and has a synergistic effect with non-imidazolium functionalized ionic liquids to jointly suppress large carbon dioxide bubbles. Concentrated hydrochloric acid can be safely added, laying the foundation for industrial continuous acidification reaction.

[0035] (4) The calcium-containing alkaline solid material CaO / Ca(OH)2 in this invention uses smaller particles of 200-300 mesh, which can save the amount of calcium-containing alkaline solid material used, improve the effective utilization rate of resources and the dissolution rate in water, reduce the time required for impurity removal, and improve the efficiency of calcium-containing alkaline solid material in removing iron and magnesium. Moreover, the waste residue after impurity removal can be used for cement production or road paving, which helps to realize the circular economy. In addition, the calcium-containing alkaline solid material CaO / Ca(OH)2 can not only neutralize excess hydrochloric acid to adjust the pH, but also introduce calcium source, thereby increasing the concentration of calcium ions in the solution to 3.75-4.25 mol / L. Unlike traditional ammonia stripping waste liquid, it does not require evaporation, sun-drying, or high-temperature concentration to obtain a high-concentration calcium ion solution, thus saving time and energy.

[0036] (5) In this invention, hydroxyapatite seed crystals, adipic acid or succinic acid are used as crystallization inducers, and alkaline solution is used as a pH adjuster. Among them, hydroxyapatite seed crystals, adipic acid or succinic acid can all improve the nucleation rate of hydroxyapatite. The addition of both can synergistically improve the nucleation rate of hydroxyapatite, thereby increasing the reaction rate and shortening the preparation time of hydroxyapatite to less than 4 hours. Maintaining the pH of the alkaline solution at 10-12 is the key to obtaining hydroxyapatite.

[0037] (6) This invention purifies crude hydroxyapatite using a cleaning solution composed of pure water and a proton-based organic solvent. The cleaning solution not only effectively removes impurities but also reduces the drying conditions, allowing the drying process to be carried out at a lower temperature, thereby reducing energy consumption. In addition, the wastewater generated after cleaning can be used to recover the proton-based organic solvent through evaporation. The residual wastewater after distillation contains sodium chloride, which can be discharged to the salt field for salt production, thus achieving a circular economy.

[0038] (7) The present invention provides a method for preparing hydroxyapatite with different morphologies using ammonia-soda solid waste. This method is a simple and rapid way to prepare hydroxyapatite with high yield, high purity, and different morphologies, with a yield of over 99.9% and a purity of over 99%. This method utilizes a specific triphosphate salt, which has a synergistic effect with hydroxyapatite seed crystals, adipic acid, or succinic acid, allowing the reaction time to be controlled within 4 hours. Furthermore, the non-imidazolium functionalized ionic liquid in the in-situ reaction can synergistically induce the formation of plate-like, tubular, and spherical morphologies with adipic acid or succinic acid. This eliminates the need for traditional methods involving long aging reactions, high temperature and pressure, and the introduction of large amounts of other solvents or surfactants to prepare hydroxyapatite with different morphologies. It features simple preparation, fast reaction rate, low energy consumption, and controllable morphology. The plate-like and tubular hydroxyapatite products can be applied in the field of water treatment adsorption, while the spherical hydroxyapatite products are mainly used in the field of bone repair. Attached Figure Description

[0039] Figure 1 The image shows the scanning electron microscope (SEM) morphology of the flaky hydroxyapatite obtained in step (5) of Example 1;

[0040] Figure 2 The X-ray diffraction (XRD) structure diagram of the hydroxyapatite obtained in step (5) of Examples 1-4;

[0041] Figure 3 The image shows the SEM morphology of the tubular hydroxyapatite obtained in step (5) of Example 2.

[0042] Figure 4 The image shows the SEM morphology of the spherical hydroxyapatite obtained in step (5) of Example 3;

[0043] Figure 5 The image shows the SEM morphology of the flaky hydroxyapatite obtained in step (5) of Example 4.

[0044] Figure 6 The image shows the SEM morphology of the hydroxyapatite obtained in step (5) of Comparative Example 1.

[0045] Figure 7 The image shows the SEM morphology of the hydroxyapatite obtained in step (5) of Comparative Example 2.

[0046] Figure 8 The XRD structure diagram of the hydroxyapatite obtained in step (5) of Comparative Example 4 is shown.

[0047] Figure 9 The XRD structure diagram of the product obtained in step (5) of Comparative Examples 6-8 is shown.

[0048] Figure 10 The image shows the SEM morphology of the product obtained in step (5) of Comparative Example 6.

[0049] Figure 11 The image shows the SEM morphology of the product obtained in step (5) of Comparative Example 7.

[0050] Figure 12 The image shows the SEM morphology of the hydroxyapatite obtained in step (5) of Comparative Example 9.

[0051] Figure 13 The XRD structure diagram of the hydroxyapatite obtained in step (5) of Comparative Example 10 is shown.

[0052] Figure 14 The XRD structure diagram of the product obtained in step (5) of Comparative Example 11-12 is shown. Detailed Implementation

[0053] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, but the scope of protection of the present invention is not limited thereto.

[0054] Example 1

[0055] (1) Grind the dried alkali residue using a ball mill and pass it through a 200-mesh sieve to obtain 200-mesh alkali residue particles. Take 50g of the ground alkali residue particles and add 150mL of ammonia stripping waste liquid, i.e., control the ratio of alkali residue to ammonia stripping waste liquid to be 1g:3mL. Stir to prepare alkali residue slurry. Then add 12.0g of diethylmethyl-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide salt and 0.45g of allyl polyoxyalkyl epoxy ether to the alkali residue slurry to obtain the first mixed solution.

[0056] (2) Add 1.1 mol of 37wt% concentrated hydrochloric acid to the first mixed solution, stir and react at 50°C for 1.5 h, filter and obtain the first residue and the second mixed solution, and discharge the first residue.

[0057] (3) Add calcium hydroxide with a particle size of 250 mesh to the second mixed solution to adjust the pH to 12. After stirring the reaction for 0.4 h, filter the solution to obtain the second residue and the third mixed solution.

[0058] (4) Take 100 mL of the third mixed solution and add 3.0 g of hydroxyapatite seed crystals and 5.0 g of adipic acid to it. Stir and mix evenly to obtain the fourth mixed solution. Add 0.2516 mol of trisodium phosphate to 70 mL of pure water to prepare a trisodium phosphate aqueous solution. Add the trisodium phosphate aqueous solution to the fourth mixed solution and adjust the pH to 11 with saturated sodium hydroxide solution. Stir and react at room temperature for 3 h. After the reaction is completed, filter to obtain crude hydroxyapatite and the fifth mixed solution. Return the fifth mixed solution to step (1) as a recycled ammonia stripping waste liquid.

[0059] (5) The crude hydroxyapatite was washed three times with a washing solution composed of pure water and ethanol in a volume ratio of 20:14, and then dried at 50°C for 1.5 h to obtain flaky hydroxyapatite. The washing wastewater was distilled to recover ethanol.

[0060] In step (2), the utilization rate of alkali residue and the extraction rate of effective components in alkali residue were tested. The test results are shown in Table 1.

[0061] In step (3), the third mixed solution was subjected to inductively coupled plasma atomic emission spectrometry (ICP) for Ca... 2+ Concentration test results are shown in Table 1.

[0062] The morphology, X-ray diffraction (XRD) structure, yield, and purity of the platy hydroxyapatite in step (5) were measured by scanning electron microscopy (SEM), and the results are shown in the figure below. Figure 1 , Figure 2 Table 1.

[0063] The utilization rate test procedure for alkali residue is as follows: Place the first residue in an oven at 80℃ or higher, and after drying, weigh its mass. The calculation formula is: Y 总 = (m0-m1) / m0×100%, Y 总 The alkali residue utilization rate is %; m0 is the amount of alkali residue added (g); m1 is the mass of the first residue after drying (g). Where m0 is 50g.

[0064] The procedure for testing the extraction rate of effective components in alkali residue is as follows: Place the first residue in an oven at 80℃ or higher and dry for 12 hours. After drying, weigh its mass. The calculation formula is: Y 有效 = (m0-m1) / (m0×(1-X)) 酸性不溶物 ))×100%, Y 有效 X represents the extraction rate of effective components from the alkali residue, %; m0 represents the amount of alkali residue added, g; 酸性不溶物 The content of acid-insoluble matter is %; m1 is the mass of the first residue after drying, in g. Wherein, X 酸性不溶物 It is 15%.

[0065] Ca 2+ Concentration testing method: Standard curves of calcium chloride solutions of different concentrations were prepared using calcium chloride and deionized water, with an average error ≥0.999. The Ca content of the test sample was determined based on the standard curve of the calcium chloride solution. 2+ Concentration. Among them, the mass fraction of calcium chloride is related to Ca... 2+ The concentration relationship is: W = C × M / (1000 × ρ) × 100%, where W is the mass fraction of CaCl2, and %; C is the mass fraction of CaCl2. 2+ Concentration, mol / L; M is the relative molecular mass of CaCl2, g / mol; ρ is the density of the calcium chloride solution at this concentration, g / L.

[0066] The yield test of flaky hydroxyapatite is performed as follows: Weigh the flaky hydroxyapatite from step (5) to obtain m2; based on the Ca in the third mixed solution from step (4) 2+ The concentration and dosage were used to calculate the corresponding amount (mol) of hydroxyapatite (HAP), and then the theoretical mass (m) of HAP was obtained. max The formula is: Y HAP =(m2-m 晶种 ) / m max ×100%, Y HAP m is the yield of HAP, %; m2 is the total mass of HAP, g; m 晶种 The mass of hydroxyapatite seed crystals in the fourth mixed solution is given in g; m max For the third mixed solution, Ca 2+ The entire theory is converted into the mass of HAP, g.

[0067] The purity test procedure for flaky hydroxyapatite is as follows: Weigh 1g of the product, dissolve it in hydrochloric acid, and dilute to 100mL in a volumetric flask. Measure the Ca content in the solution using ICP. 2+ Concentration, from Ca 2+ The concentration of flaky hydroxyapatite was calculated from the concentration of Ca. 2+ The relationship between concentration and purity is: X 纯度 =C Ca 2+ ×a×M HAP / 10b×100%, X 纯度 denoted as hydroxyapatite (HAP), %; a is the volume of the solution, 0.1 L; M HAP It is hydroxyapatite (molecular formula Ca) 10 The relative molecular mass of (PO4)6(OH)2 is 1004; b is the mass of the product when dissolved in hydrochloric acid, 1g.

[0068] As shown in Table 1, in step (2), the mass of the first residue after drying is 8.99g. Calculations and in conjunction with Table 1 show that the utilization rate of the alkali residue and the extraction rate of the effective components in the alkali residue are 82.03% and 96.50%, respectively; in step (3), the third mixed solution Ca... 2+ The concentration was 4.25 mol / L; the mass of HAP obtained in step (5) was 45.67 g. According to calculation and combined with Table 1, the yield of flaky hydroxyapatite reached 99.99%.

[0069] Depend on Figure 1 and Figure 2 It can be seen that hydroxyapatite has a platy morphology and corresponds to the standard card 09-0432 for hydroxyapatite, indicating that the substance contains only the diffraction peaks of hydroxyapatite and does not contain other phases.

[0070] As shown in Table 1, the hydroxyapatite content in the flaky hydroxyapatite (HAP) product is 99.5%, that is, the purity of the product is 99.5%. Example 2

[0071] (1) Grind the dried alkali residue using a ball mill and pass it through a 100-mesh sieve to obtain 100-mesh alkali residue particles. Take 50g of the ground alkali residue particles and add 100mL of ammonia stripping waste liquid. Stir to prepare an alkali residue slurry. Control the ratio of alkali residue to ammonia stripping waste liquid to be 1g:2mL. Then add 5.0g of tetrabutylphosphonium β-alanine salt and 0.1g of allyl alcohol polyoxyalkylene ether to the alkali residue slurry to obtain the first mixed solution.

[0072] (2) Add 1.0 mol of 31wt% concentrated hydrochloric acid to the first mixed solution, stir and react at 40℃ for 2.0 h, centrifuge to obtain the first residue and the second mixed solution, and discharge the first residue.

[0073] (3) Add calcium oxide with a particle size of 200 mesh to the second mixed solution to adjust the pH to 10. After stirring the reaction for 0.5 h, centrifuge to obtain the second residue and the third mixed solution.

[0074] (4) Take 100 mL of the third mixed solution and add 1.0 g of hydroxyapatite seed crystals and 3.0 g of succinic acid to it. Stir and mix evenly to obtain the fourth mixed solution. Add 0.2246 mol of tripotassium phosphate to 50 mL of pure water to prepare a tripotassium phosphate aqueous solution. Add the tripotassium phosphate aqueous solution to the fourth mixed solution and adjust the pH to 12 with saturated potassium hydroxide solution. Stir and react at room temperature for 2 h. After the reaction is completed, centrifuge to obtain crude hydroxyapatite and the fifth mixed solution. Return the fifth mixed solution to step (1) as a recycled ammonia stripping waste liquid.

[0075] (5) The crude hydroxyapatite was washed twice with a washing solution composed of pure water and methanol in a volume ratio of 20:10, and then dried at 40°C for 3.0 h to obtain tubular hydroxyapatite. The washing wastewater was distilled to recover methanol.

[0076] In step (2), the utilization rate of alkali residue and the extraction rate of effective components in alkali residue were tested. The test methods were the same as in Example 1, and the test results are shown in Table 1.

[0077] In step (3), the third mixed solution is subjected to ICP Ca2+. 2+ Concentration testing was conducted using the same method as in Example 1, and the results are shown in Table 1.

[0078] In step (5), the tubular hydroxyapatite was subjected to SEM morphology, XRD structure, yield, and purity tests. The test methods were the same as in Example 1, and the test results are shown in [reference needed]. Figure 3 , Figure 2 Table 1.

[0079] As shown in Table 1, in step (2), the mass of the first residue after drying is 10.48g. Calculations and in conjunction with Table 1 show that the utilization rate of the alkali residue and the extraction rate of the effective components in the alkali residue are 79.05% and 93.00%, respectively; in step (3), the third mixed solution Ca... 2+ The concentration was 3.75 mol / L; the mass of HAP obtained in step (5) was 38.64 g. According to calculation and combined with Table 1, the yield of tubular hydroxyapatite reached 99.97%; the purity of hydroxyapatite was 99.0%.

[0080] Depend on Figure 2 and Figure 3 It can be seen that hydroxyapatite has a tubular morphology and corresponds to the standard card 09-0432 for hydroxyapatite, indicating that the substance contains only the diffraction peaks of hydroxyapatite and does not contain other phases.

[0081] As shown in Table 1, the hydroxyapatite content in the tubular hydroxyapatite (HAP) product is 99.0%, that is, the product purity is 99.0%. Example 3

[0082] (1) Grind the dried alkali residue using a ball mill and pass it through a 300-mesh sieve to obtain 300-mesh alkali residue particles. Take 50g of the ground alkali residue particles and add 200mL of ammonia stripping waste liquid, i.e., control the ratio of alkali residue to ammonia stripping waste liquid to be 1g:4mL. Stir to prepare alkali residue slurry. Then add 20.0g of tetraethylammonium-alanine salt and 1.0g of nonylphenol polyoxyethylene ether to the alkali residue slurry to obtain the first mixed solution.

[0083] (2) Add 1.2 mol of 35wt% concentrated hydrochloric acid to the first mixed solution, stir and react at 60℃ for 1.0 h, centrifuge to obtain the first residue and the second mixed solution, and discharge the first residue.

[0084] (3) Add calcium oxide with a particle size of 300 mesh to the second mixed solution to adjust the pH to 12. After stirring the reaction for 0.3 h, centrifuge to obtain the second residue and the third mixed solution.

[0085] (4) Take 100 mL of the third mixed solution and add 5.0 g of hydroxyapatite seed crystals and 8.0 g of adipic acid to it. Stir and mix evenly to obtain the fourth mixed solution. Add 0.2353 mol of triammonium phosphate to 100 mL of pure water to prepare a triammonium phosphate aqueous solution. Add the triammonium phosphate aqueous solution to the fourth mixed solution and adjust the pH to 10 with ammonia water. Stir and react at room temperature for 4 h. After the reaction is completed, centrifuge to obtain crude hydroxyapatite and the fifth mixed solution. Return the fifth mixed solution to step (1) as a waste liquid for ammonia stripping and recycling.

[0086] (5) The crude hydroxyapatite was washed twice with a washing solution composed of pure water and isopropanol in a volume ratio of 20:20, and then dried at 60°C for 1.0 h to obtain spherical hydroxyapatite. The washing wastewater was distilled to recover isopropanol.

[0087] In step (2), the utilization rate of alkali residue and the extraction rate of effective components in alkali residue were tested. The test methods were the same as in Example 1, and the test results are shown in Table 1.

[0088] In step (3), the third mixed solution is subjected to ICP Ca2+. 2+ Concentration testing was conducted using the same method as in Example 1, and the results are shown in Table 1.

[0089] In step (5), the spherical hydroxyapatite was subjected to SEM morphology, XRD structure, yield, and purity tests. The test methods were the same as in Example 1, and the test results are shown in [the table below]. Figure 4 , Figure 2 Table 1.

[0090] In step (2), the mass of the first residue after drying is 8.78g. Calculations and Table 1 show that the utilization rate of the alkali residue and the extraction rate of the effective components in the alkali residue are 82.45% and 97.00%, respectively. Table 1 shows that in step (3), the third mixed solution Ca... 2+ The concentration was 4.05 mol / L; the mass of HAP obtained in step (5) was 45.66 g. According to calculation and Table 1, the yield of spherical hydroxyapatite reached 99.99%.

[0091] Depend on Figure 2 and Figure 4It can be seen that hydroxyapatite has a spherical morphology and corresponds to the standard card 09-0432 for hydroxyapatite, indicating that the substance contains only the diffraction peaks of hydroxyapatite and does not contain other phases.

[0092] As shown in Table 1, the hydroxyapatite content in the spherical hydroxyapatite product is 99.5%, that is, the purity of the product is 99.5%. Example 4

[0093] (1) The dried alkali residue was ground using a ball mill and passed through a 200-mesh sieve to obtain 200-mesh alkali residue particles. 50g of the ground alkali residue particles were added to 180mL of ammonia stripping waste liquid, i.e., the ratio of alkali residue to ammonia stripping waste liquid was controlled to be 1g:3.6mL. The mixture was stirred to prepare an alkali residue slurry. Then, 16.2g of diethylmethyl-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide salt and 0.72g of allyl polyoxyalkyl epoxy ether were added to the alkali residue slurry to obtain the first mixed solution.

[0094] (2) Add 1.1 mol of 37wt% concentrated hydrochloric acid to the first mixed solution, stir and react at 45℃ for 1.5h, filter and obtain the first residue and the second mixed solution, and discharge the first residue.

[0095] (3) Add calcium hydroxide with a particle size of 250 mesh to the second mixed solution to adjust the pH to 11.5. After stirring the reaction for 0.4 h, filter the solution to obtain the second residue and the third mixed solution.

[0096] (4) Take 100 mL of the third mixed solution and add 2.5 g of hydroxyapatite seed crystals and 7.0 g of adipic acid to it. Stir and mix evenly to obtain the fourth mixed solution. Add 0.2370 mol of trisodium phosphate to 80 mL of pure water to prepare a trisodium phosphate aqueous solution. Add the trisodium phosphate aqueous solution to the fourth mixed solution and adjust the pH to 11 with saturated sodium hydroxide solution. Stir the reaction at room temperature for 2.5 h. After the reaction is completed, filter to obtain crude hydroxyapatite and the fifth mixed solution. Return the fifth mixed solution to step (1) as a waste liquid for ammonia stripping and recycling.

[0097] (5) The crude hydroxyapatite was washed three times with a washing solution composed of pure water and ethanol in a volume ratio of 20:18, and then dried at 50°C for 1.5 h to obtain flaky hydroxyapatite. The washing wastewater was distilled to recover ethanol.

[0098] In step (2), the utilization rate of alkali residue and the extraction rate of effective components in alkali residue were tested. The test methods were the same as in Example 1, and the test results are shown in Table 1.

[0099] In step (3), the third mixed solution is subjected to ICP Ca2+. 2+Concentration testing was conducted using the same method as in Example 1, and the results are shown in Table 1.

[0100] In step (5), the flaky hydroxyapatite was subjected to SEM morphology, XRD structure, yield, and purity tests. The test methods were the same as in Example 1, and the test results are shown in [reference needed]. Figure 5 , Figure 2 Table 1.

[0101] In step (2), the mass of the first residue after drying is 9.12g. Calculations and Table 1 show that the utilization rate of the alkali residue and the extraction rate of the effective components in the alkali residue are 81.77% and 96.20%, respectively. Table 1 shows that in step (3), the third mixed solution Ca... 2+ The concentration was 4.03 mol / L; the mass of HAP obtained in step (5) was 42.96 g. According to calculation and Table 1, the yield of flaky hydroxyapatite reached 99.99%.

[0102] Depend on Figure 2 and Figure 5 It can be seen that hydroxyapatite has a platy morphology and corresponds to the standard card 09-0432 for hydroxyapatite, indicating that the substance contains only the diffraction peaks of hydroxyapatite and does not contain other phases.

[0103] As shown in Table 1, the hydroxyapatite content in the flaky hydroxyapatite product is 99.4%, that is, the purity of the product is 99.4%. Comparative Example 1

[0104] The difference between Comparative Example 1 and Example 1 is that the amount of ammonia waste liquid added in step (1) is different. 150 mL of ammonia waste liquid is replaced with 300 mL of ammonia waste liquid, while the other steps remain unchanged.

[0105] In step (3), the third mixed solution is subjected to ICP Ca2+. 2+ Concentration testing was conducted using the same method as in Example 1, and the results are shown in Table 1.

[0106] In step (5), the yield and SEM morphology of hydroxyapatite were tested using the same methods as in Example 1. The test results are shown in Table 1. Figure 6 .

[0107] As shown in Table 1, the third mixed solution Ca in step (3) 2+ The concentration was 2.97 mol / L, and the mass of HAP obtained in step (5) was 28.24 g. It can be calculated that the yield of HAP was 84.50%. This is because when the amount of ammonia stripping waste liquid added was increased, the concentration of calcium chloride solution obtained was low, which led to a decrease in the yield of hydroxyapatite.

[0108] Depend on Figure 6It is known that hydroxyapatite has a rod-like morphology. This may be because the excessive addition of ammonia stripping waste liquid reduced the concentration of non-imidazolium functionalized ionic liquid and adipic acid in the solution, thus failing to induce morphological transformation of hydroxyapatite. Therefore, appropriately controlling the amount of ammonia stripping waste liquid added can not only obtain a high concentration of calcium chloride solution to improve the yield of HAP, but also regulate the morphology of hydroxyapatite. Comparative Example 2

[0109] The difference between Comparative Example 2 and Example 1 is that the non-imidazolium functionalized ionic liquid added in step (1) is different. The non-imidazolium functionalized ionic liquid is replaced with an imidazolium functionalized ionic liquid of 1-aminopropyl-3-methylimidazolium bromide. The other steps remain unchanged.

[0110] In step (3), the third mixed solution is subjected to ICP Ca2+. 2+ Concentration testing was conducted using the same method as in Example 1, and the results are shown in Table 1.

[0111] In step (5), the yield and SEM morphology of hydroxyapatite were tested using the same methods as in Example 1. The test results are shown in Table 1. Figure 7 .

[0112] As shown in Table 1, the utilization rate of the alkali residue was 43.18%, and the extraction rate of effective components from the alkali residue was 50.80%, which was far lower than the treatment effect of Example 1, resulting in a large loss of effective components; in step (3), the third mixed solution Ca 2+ With a concentration of 3.20 mol / L, the obtained HAP mass was 31.75 g. Calculations showed that the HAP yield was 89.50%, which is significantly lower than the yield in Example 1. This is because 1-aminopropyl-3-methylimidazolium bromide has a weaker adsorption capacity for carbon dioxide than the non-imidazolium functionalized ionic liquid in Example 1. During the reaction, a large amount of carbon dioxide bubbles were generated, causing the alkaline residue to adhere to the walls. This resulted in incomplete reaction between a large amount of alkaline residue and acid, reducing the concentration of the calcium chloride solution and consequently decreasing the hydroxyapatite yield.

[0113] Depend on Figure 7 It can be seen that hydroxyapatite has a rod-like morphology, and combined with Comparative Example 1... Figure 6 It is known that the initial morphology of hydroxyapatite is rod-shaped. Imidazole-based functionalized ionic liquids cannot change the morphology of hydroxyapatite. This may be because, in the in-situ synthesis of hydroxyapatite, the imidazole and amino groups (both nitrogen-active sites) in the imidazole-based functionalized ionic liquids competitively induce the carboxyl group in adipic acid, resulting in the hydroxyapatite morphology remaining rod-shaped, thus failing to achieve the goal of morphology regulation. In summary, selecting a suitable ionic liquid is key to improving the utilization rate of alkaline residue, the yield of hydroxyapatite, and morphology regulation. Comparative Example 3

[0114] The difference between Comparative Example 3 and Example 1 is that no acidifying agent was added in step (1), while the other steps remained the same.

[0115] During the experiment, it was found that without the addition of an acidifying agent, the acidification reaction was violent, producing a large amount of carbon dioxide gas bubbles that caused the solution to overflow, making the reaction dangerous. Therefore, the acidifying agent is a key factor in ensuring the safe and mild conduct of the acidification reaction, and it has a synergistic effect with non-imidazolium functionalized ionic liquids. Comparative Example 4

[0116] The difference between Comparative Example 4 and Example 1 is that the pH adjusted by calcium hydroxide in step (3) is different. The pH is changed from 12 to 9, while the other steps remain the same.

[0117] During the experiment, it was found that no precipitate appeared when the pH was less than 10, meaning that the purification of the reaction solution was not completed.

[0118] In step (3), the third mixed solution is subjected to Ca... 2+ Concentration testing was conducted using the same method as in Example 1, and the results are shown in Table 1.

[0119] In step (5), the hydroxyapatite was subjected to XRD structure and yield tests, using the same methods as in Example 1. The test results are shown in [reference needed]. Figure 8 Table 1.

[0120] As shown in Table 1, the Ca in the third mixed solution in step (3) 2+ The concentration was 3.35 mol / L, and the mass of HAP obtained in step (5) was 33.44 g. Calculations showed that the HAP yield was 90.50%. This is because the concentration of the obtained calcium chloride solution was low, resulting in a yield far lower than that of Example 1.

[0121] Depend on Figure 8 It is known that hydroxyapatite contains impurities, with the impurity peak being magnesium hydroxyphosphate (Mg2(PO4)OH), corresponding to standard card 97-004-0828. This is because magnesium impurities in the calcium chloride solution were not completely removed, resulting in magnesium-related impurity peaks in the product. Therefore, calcium oxide can not only adjust pH to remove impurities but also act as a calcium source, thereby increasing the concentration of the calcium chloride solution and thus improving the yield of hydroxyapatite. Comparative Example 5

[0122] The difference between Comparative Example 5 and Example 2 is that the mesh size of calcium oxide in step (3) is different. 200 mesh is replaced with 50 mesh, while the other steps remain the same.

[0123] During the experiment, it was found that when the mesh size of calcium oxide was below 200 mesh, the large particle size made it difficult to dissolve in water, and the particles tended to agglomerate upon contact with water, further increasing in size and resulting in a very slow dissolution rate, making it difficult to remove impurities from the reaction system. Therefore, selecting a calcium-containing alkaline solid with an appropriate particle size can help improve the impurity removal efficiency. Comparative Example 6

[0124] The difference between Comparative Example 6 and Example 1 is that no hydroxyapatite seed crystals were added in step (4), while the other steps remained the same.

[0125] In step (5), the product was subjected to XRD structure and SEM morphology tests. The test results are shown in the figure below. Figure 9 , Figure 10 .

[0126] Depend on Figure 9 It is known that the product is a mixed phase of hydroxyapatite and calcium hydrogen phosphate dihydrate, with the standard card for calcium hydrogen phosphate dihydrate being 97-001-6132. This is because, without the addition of hydroxyapatite, a pure phase of hydroxyapatite cannot be obtained within a short reaction time. Therefore, hydroxyapatite acts as a crystallization inducer, accelerating the reaction rate.

[0127] Depend on Figure 10 It can be seen that the main morphology of the product is flake-like. Under the action of non-imidazolium functionalized ionic liquid and adipic acid, the morphology of hydroxyapatite changes from rod-like to flake-like. Comparative Example 7

[0128] The difference between Comparative Example 7 and Example 1 is that adipic acid and hydroxyapatite seed crystals are not added in step (4), while the other steps remain unchanged.

[0129] In step (5), the product was subjected to XRD structure and SEM morphology tests. The test results are shown in the figure below. Figure 9 , Figure 11 .

[0130] Depend on Figure 9 It is known that the product is a miscible phase of hydroxyapatite and calcium hydrogen phosphate dihydrate. This is because, without the addition of adipic acid, pure hydroxyapatite cannot be obtained within a short reaction time. Therefore, adipic acid and hydroxyapatite, as crystallization inducers, have the effect of accelerating the reaction rate, and the two have a synergistic effect.

[0131] Depend on Figure 10 and Figure 11 It can be seen that the product morphology of Comparative Example 8 is rod-shaped, while the product morphology of Comparative Example 7 is flake-shaped. In summary, the role of adipic acid is to synergistically induce the morphological transformation of hydroxyapatite with non-imidazolium functionalized ionic liquids. Comparative Example 8

[0132] The difference between Comparative Example 8 and Example 1 is that there is no alkaline solution to adjust the pH in step (4), while the other steps remain the same.

[0133] The product from step (5) underwent XRD structural testing, and the test results are shown in [the table below]. Figure 9 .

[0134] Depend on Figure 9 It is known that the product is pure-phase calcium hydrogen phosphate dihydrate, corresponding to standard card PDF#97-001-6132. Hydroxyapatite cannot be obtained in a short reaction time without pH adjustment. Therefore, pH is another important factor in the formation of hydroxyapatite. Comparative Example 9

[0135] The difference between Comparative Example 9 and Example 1 is that the amount of pure water used for phosphorus source in step (4) is different, with 70 ml replaced by 200 ml, while the other steps remain unchanged.

[0136] In step (5), the yield and SEM morphology of hydroxyapatite were tested using the same methods as in Example 1. The test results are shown in Table 1. Figure 12 .

[0137] As shown in Table 1, the mass of HAP is 39.06 g. Calculations show that the yield of HAP is 84.50%, which is much lower than the effect of Example 1. This is because the amount of pure water used as the phosphorus source was increased, which led to a decrease in the concentration of calcium chloride solution in the reaction system and a decrease in the yield of hydroxyapatite.

[0138] Depend on Figure 12 It is known that hydroxyapatite has a rod-like morphology, which may be due to the excessive addition of pure water as the phosphorus source, which reduces the concentration of non-imidazolium functionalized ionic liquid and adipic acid in the solution. Therefore, appropriately controlling the volume ratio of pure water in the fifth mixed solution to that in the third mixed solution can not only improve the yield of HAP but also regulate the morphology of hydroxyapatite. Comparative Example 10

[0139] The difference between Comparative Example 10 and Example 1 is that no protonated organic solvent ethanol is added in step (5), while the other steps remain unchanged. The operation method of step (5) is as follows:

[0140] The crude hydroxyapatite was washed three times with 5 mL of pure water and then dried at 70 °C for 8 hours to obtain hydroxyapatite. The washing wastewater was discharged to the salt field for salt production.

[0141] The XRD structure of hydroxyapatite in step (5) was analyzed, and the results are shown in [the table below]. Figure 13 .

[0142] Depend on Figure 13 and Figure 2The comparison shows that the product is mainly hydroxyapatite, but it contains some impurity peaks located at 14.2°, 35.5°, and 55.7°. This is because the addition of the protonated organic solvent ethanol cannot completely remove the impurities, resulting in the presence of impurity phases in the hydroxyapatite. Furthermore, the addition of the protonated organic solvent ethanol can reduce the drying time. Comparative Example 11

[0143] The difference between Comparative Example 11 and Example 1 is that in step (4), trisodium phosphate is replaced with disodium hydrogen phosphate, while the other steps remain unchanged.

[0144] The product from step (5) underwent XRD structural testing, and the test results are shown in [the table below]. Figure 14 .

[0145] Depend on Figure 14 and Figure 2 as well as Figure 9 The comparison shows that the product is mainly a mixed phase of calcium hydrogen phosphate dihydrate and hydroxyapatite, but calcium hydrogen phosphate dihydrate is dominant. This is because the hydrolysis rate of triphosphate is greater than that of diphosphate, allowing it to quickly combine with calcium ions to obtain the target product, hydroxyapatite. Therefore, triphosphate is another necessary condition for the rapid preparation of hydroxyapatite; diphosphate cannot be used to rapidly prepare hydroxyapatite. Comparative Example 12

[0146] The difference between Comparative Example 12 and Example 1 is that in step (4), trisodium phosphate is replaced with sodium dihydrogen phosphate, while the other steps remain unchanged.

[0147] The product from step (5) underwent XRD structural testing, and the test results are shown in [the table below]. Figure 14 .

[0148] Depend on Figure 14 and Figure 2 as well as Figure 9 The comparison shows that the product is mainly a mixed phase of calcium hydrogen phosphate dihydrate and hydroxyapatite, but calcium hydrogen phosphate dihydrate is dominant. This is because the hydrolysis rate of triphosphate is greater than that of dihydrogen phosphate, allowing it to quickly combine with calcium ions. After a period of reaction, the target product, hydroxyapatite, is finally obtained. Therefore, triphosphate is another necessary condition for the rapid preparation of hydroxyapatite; dihydrogen phosphate cannot rapidly prepare hydroxyapatite.

[0149]

[0150] As can be seen from the above, compared with Comparative Example 1, Example 1 shows that controlling the amount of ammonia stripping waste liquid added is more appropriate. This not only yields a high concentration of calcium chloride solution, increasing the HAP yield, but also regulates the morphology of hydroxyapatite. Compared with Comparative Example 2, Example 1 shows that a suitable ionic liquid can not only improve the utilization rate of alkaline residue during acidification, but also induce morphological changes in hydroxyapatite. This is because non-imidazolium functionalized ionic liquids have a stronger adsorption capacity for carbon dioxide, while imidazolium functionalized ionic liquids have a weaker adsorption capacity for carbon dioxide. Non-imidazolium functionalized ionic liquids can better promote the acidification reaction, thereby obtaining a high concentration of calcium chloride solution and increasing the yield of hydroxyapatite. Compared with Comparative Example 3, the acidification aid in Example 1 is a key factor in the mild acidification reaction, inhibiting the generation of a large number of carbon dioxide bubbles. It has a synergistic effect with the non-imidazolium functionalized ionic liquid, jointly promoting the acidification reaction. Compared to Comparative Example 4, in Example 1, the calcium-containing alkaline solid calcium oxide not only adjusts the pH for impurity removal but also acts as a calcium source to supplement calcium, increasing the concentration of the calcium chloride solution and thus improving the yield of hydroxyapatite. This is another key factor in the preparation of pure-phase hydroxyapatite. In Example 2, compared to Comparative Example 5, the mesh size of the calcium-containing alkaline solid affects the impurity removal efficiency. This is because larger-sized calcium oxide particles have limited solubility in water, and the surface of calcium oxide easily absorbs water, leading to calcium oxide agglomeration and further increasing the particle size, making impurity removal difficult. Selecting an appropriate particle size for the calcium-containing alkaline solid helps improve the impurity removal efficiency. In Example 1, compared to Comparative Examples 6-7, both hydroxyapatite and adipic acid accelerate the reaction rate, and the two work synergistically to accelerate the reaction rate and promote the conversion of calcium hydrogen phosphate to hydroxyapatite. Adipic acid also synergistically induces the morphology of hydroxyapatite with non-imidazolium functionalized ionic liquids. Compared to Comparative Example 8, adjusting the pH of the reaction system to 10-12 is a necessary condition for obtaining hydroxyapatite in Example 1, indicating that pH has a significant impact on hydroxyapatite production. Compared to Comparative Example 9, appropriately controlling the volume ratio of pure water to the third mixed solution in Example 1 not only improves the yield of HAP but also regulates the morphology of hydroxyapatite. The morphology is mainly affected by the concentrations of non-imidazolium functionalized ionic liquids and adipic acid in the solution, while the yield is mainly affected by the concentration of calcium chloride solution. Compared to Comparative Example 10, the protonated organic solvent ethanol in Example 1 can both purify the target product and reduce drying requirements. Compared to Comparative Examples 11-12, the triphosphate in Example 1 exhibits a faster reaction rate compared to dihydrogen phosphate and dihydrogen phosphate, which is a necessary condition for the rapid preparation of hydroxyapatite.

Claims

1. A method for preparing hydroxyapatite with different morphologies using solid waste from the ammonia-soda process, characterized in that, Includes the following steps: (1) The alkali residue is crushed or ground into fine particles, and then mixed with ammonia stripping waste liquid to obtain alkali residue slurry; non-imidazolium functionalized ionic liquid and acidification aid are added to the slurry to obtain the first mixed solution; the non-imidazolium functionalized ionic liquid is diethylmethyl-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide salt or tetrabutylphosphonium β-alanine salt or tetraethylammonium-alanine salt; (2) Add concentrated hydrochloric acid to the first mixed solution and react at 40-60℃ for 1-2 hours. After filtration or centrifugation, obtain the first residue and the second mixed solution. Dispose of the first residue. (3) Add calcium-containing alkaline solid to the second mixed solution to adjust the pH to 10-12, stir the reaction for 0.3-0.5 h, filter or centrifuge to obtain the second residue and the third mixed solution, and recycle the second residue. (4) Add hydroxyapatite seed crystals and adipic acid or succinic acid to the third mixed solution, stir and mix evenly to obtain the fourth mixed solution; Aqueous solution of triphosphate was added to the fourth mixed solution, and the pH was adjusted to 10-12 with alkaline solution. The mixture was stirred at room temperature for 2-4 hours. After filtration or centrifugation, crude hydroxyapatite and the fifth mixed solution were obtained. The fifth mixed solution was then recycled. (5) The crude hydroxyapatite is washed and dried with a cleaning solution composed of pure water and proton organic solvent to obtain hydroxyapatite with a flaky, tubular or spherical morphology. In step (1), the ratio of the amount of alkali residue to the amount of ammonia stripping waste liquid in the alkali residue slurry is 1g:2-4mL; the acidification aid is one of allyl polyoxyalkyl epoxy ether, allyl alcohol polyoxyalkyl ether, or nonylphenol polyoxyethylene ether. In step (4), the volume ratio of water content in the triphosphate aqueous solution to that in the third mixed solution is 0.5-1:

1.

2. The method for preparing hydroxyapatite with different morphologies using solid waste from the ammonia-soda process according to claim 1, characterized in that, In step (1), the particle size of the alkali residue is 100-300 mesh.

3. The method for preparing hydroxyapatite with different morphologies using ammonia-soda process solid waste according to claim 1, characterized in that, In step (1), the ratio of the amount of non-imidazolium functionalized ionic liquid added to the amount of ammonia-steamed waste liquid added to the first mixed solution is 0.05-0.1g:1mL; the ratio of the amount of acidifying agent added to the amount of ammonia-steamed waste liquid added to the first mixed solution is 0.001-0.005g:1mL.

4. The method for preparing hydroxyapatite with different morphologies using ammonia-soda process solid waste according to claim 1, characterized in that, In step (2), the mass concentration of concentrated hydrochloric acid is 31-37%; the ratio of the amount of concentrated hydrochloric acid used to the amount of alkaline residue added in the first mixed solution is 0.02-0.024 mol: 1g.

5. The method for preparing hydroxyapatite with different morphologies using ammonia-soda process solid waste according to claim 1, characterized in that, In step (3), the calcium-containing alkaline solid substance is calcium oxide or calcium hydroxide; the particle size of the calcium-containing alkaline solid substance is 200-300 mesh.

6. The method for preparing hydroxyapatite with different morphologies using solid waste from the ammonia-soda process according to claim 1, characterized in that, In step (4), the ratio of the amount of hydroxyapatite seed crystals added to the amount of the third mixed solution in the fourth mixed solution is 0.01-0.05 g: 1 mL; the ratio of the amount of adipic acid or succinic acid added to the amount of the third mixed solution is 0.03-0.08 g: 1 mL.

7. The method for preparing hydroxyapatite with different morphologies using solid waste from the ammonia-soda process according to claim 1, characterized in that, In step (4), the triphosphate is trisodium phosphate, tripotassium phosphate, or triammonium phosphate; the alkaline solution is saturated sodium hydroxide solution, saturated potassium hydroxide solution, or ammonia.

8. The method for preparing hydroxyapatite with different morphologies using solid waste from the ammonia-soda process according to claim 1, characterized in that, In step (4), the molar ratio of calcium ions in the triphosphate and the third mixed solution is 0.581-0.599:

1.

9. The method for preparing hydroxyapatite with different morphologies using solid waste from the ammonia-soda process according to claim 1, characterized in that, In step (5), the proton organic solvent is methanol, ethanol, or isopropanol; the volume ratio of pure water to proton organic solvent in the cleaning solution is 1:0.5-1.0; the cleaning conditions are: two to four cleanings; the drying conditions are: temperature 40-60℃, time 1-3h.

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