Method for preparing nano beta-tricalcium phosphate by comprehensively utilizing phosphogypsum

Abstract

The invention discloses a method for preparing nano beta-tricalcium phosphate by comprehensive utilization of ardealite, which comprises the following preparation steps: grinding and washing industrial by-product ardealite to remove soluble impurities in the ardealite; adding an L-sodium lactate solution into the pretreated phosphogypsum as a calcium ion transfer agent, so that insoluble impurities in the phosphogypsum can be effectively separated from calcium ions, and reacting a calcium ion solution with disodium hydrogen phosphate to obtain a tricalcium phosphate precursor; and washing, drying and roasting the tricalcium phosphate to obtain the nano beta-tricalcium phosphate powder. The method is easy to operate, L-sodium lactate is adopted as a calcium ion transfer agent, the ardealite solid waste is converted into high-grade nano beta-tricalcium phosphate, the problem of environmental pollution caused by large-area accumulation of ardealite can be solved, and meanwhile the prepared beta-tricalcium phosphate has the advantages of being high in purity, good in particle dispersity, high in crystallinity and the like.

Description

Technical Field

[0001] The present invention belongs to the field of “the technical field of comprehensive utilization of phosphogypsum” and “the technical field of nanomaterial preparation”, and relates to a method for preparing high-grade β-tricalcium phosphate by comprehensive utilization of phosphogypsum. Background Art

[0002] Background introduction of related technologies: Phosphogypsum is a solid waste generated in industrial production, mainly from phosphate fertilizer, phosphoric acid, phosphorus chemical industry and other industries. According to statistics, about five tons of phosphogypsum are produced for every ton of phosphoric acid produced. Due to its complex impurity composition, such as phosphides (H3PO4, Ca3(PO4)2, CaHPO4·2H2O and P2O5, etc.), fluorides (NaF, KF, Na3AlF6, CaSiF6 and CaF2, etc.), organic impurities and undecomposed apatite, the application of phosphogypsum in building materials, agriculture and other fields is limited. The existing phosphogypsum resource technology mainly includes landfill, stacking and comprehensive utilization. Among them, landfill and stacking are more common treatment methods, but these methods not only occupy a lot of land, but also may cause secondary pollution to the environment. The comprehensive utilization is mainly to convert phosphogypsum into useful products, such as cement, building materials, etc., but these products have low added value and limited consumption of phosphogypsum. Therefore, how to effectively utilize phosphogypsum, a solid waste, and realize the high-value utilization of its resources is an important research topic in the current fields of environmental protection and materials science.

[0003] The main component of phosphogypsum is calcium sulfate dihydrate, which contains about 70% to 90%. Using phosphogypsum as raw material to prepare high-quality nano-β-tricalcium phosphate can not only solve the pollution problem caused by the accumulation of phosphogypsum solid waste, but also provide a new and cheap method for preparing nano-β-tricalcium phosphate. β-tricalcium phosphate is an important inorganic biomaterial. It is widely used in bone tissue repair and support materials because of its good biocompatibility and biodegradability. The methods for preparing nano-β-tricalcium phosphate are mainly divided into wet process and dry process. The wet process includes chemical precipitation, sonochemical method, sol-gel method, hydrothermal method, microemulsion method, etc. The dry process includes solid phase synthesis method and mechanochemical synthesis method. The dry process usually uses CaHPO4·2H2O and Ca(OH)2 or CaCO3 as raw materials to react and prepare β-TCP powder at a temperature above 900 ℃. The crystal structure obtained by this method is complete, but the particle size is large and there are impurities. The chemical precipitation method is to react a calcium ion solution with a phosphate ion solution to obtain a tricalcium phosphate precipitation precursor, and then calcine at a high temperature to obtain β-tricalcium phosphate. This method is simple to operate, but the particles are prone to agglomeration. Problems with the prior art: The existing β-tricalcium phosphate preparation method has many problems and disadvantages, such as slow reaction rate, particle agglomeration, high experimental equipment requirements, complex process, long preparation time, toxic organic solvents, environmental pollution, coarse grains, uneven composition, presence of impurities, uneven powder particle size distribution, easy agglomeration, etc. These problems and disadvantages limit the large-scale application and development of β-tricalcium phosphate. Therefore, it is of great significance to develop a new, environmentally friendly, and efficient method for preparing nano β-tricalcium phosphate. Summary of the invention

[0004] The purpose of the present invention is to provide a simple method for preparing nano-β-tricalcium phosphate by resource utilization of phosphogypsum solid waste, which provides a new path for the high-value utilization of phosphogypsum. The traditional high-value utilization of phosphogypsum is a "two-step double decomposition" method, and the reaction equation is as follows: CaSO4+ Na2CO3= CaCO3+ Na2SO4, CaCO3+ 2HCl = CaCl2+ H2O + CO2↑. The method first reacts phosphogypsum with a sodium carbonate solution to obtain a crude calcium carbonate product, and then dissolves it with hydrochloric acid to obtain a calcium chloride solution. The typical disadvantage of this method is that the extraction of calcium ions in phosphogypsum requires the consumption of a large amount of acid and alkali, which is costly and complicated, and is not conducive to the large-scale promotion and utilization of phosphogypsum.

[0005] The present invention is based on the assumption that calcium sulfate dihydrate, the main component of phosphogypsum solid waste, can be used as a raw material for synthesizing high-grade nanometer β-tricalcium phosphate. The phosphogypsum is placed in a calcium ion transfer agent L-sodium lactate solution for dissociation, filtration, removal of insoluble impurities, concentration of the calcium ion solution, recrystallization, and then reacted with phosphate to prepare a tricalcium phosphate precursor, and finally β-tricalcium phosphate is obtained after filtration, washing, drying, and roasting. The reaction process is as follows: CaSO4+ 2NaC3H5O3= Na2SO4+ Ca(C3H5O3)2; 3Ca(C3H5O3)2+ 2Na3PO4= Ca3(PO4)2+ 6NaC3H5O3. The method uses L-sodium lactate as a phase transfer agent to transfer calcium ions in the phosphogypsum to the liquid phase, and filter to remove insoluble solid impurities in the phosphogypsum. The obtained calcium lactate is easily soluble in boiling water and slightly soluble in cold water, and the calcium lactate can be extracted from the sodium sulfate solution by physical recrystallization. Traditional synthesis of β-tricalcium phosphate usually uses soluble inorganic calcium salts and inorganic phosphates. Due to the high ion concentration in the reaction system and the rapid reaction, the obtained β-tricalcium phosphate is easy to agglomerate, and it is necessary to introduce additional surfactants as nanoparticle dispersants. In the present invention, calcium lactate extracted from phosphogypsum is used as a calcium source for synthesizing β-tricalcium phosphate. During the reaction process, calcium lactate can slowly release calcium ions into the aqueous solution, thereby effectively avoiding the high ion concentration in the solution and the rapid reaction, resulting in uneven distribution of the generated β-tricalcium phosphate particles and the phenomenon of easy formation of agglomerates. In addition, compared with the traditional "two-step double decomposition method", the "phase transfer-precipitation method" only uses L-sodium lactate, and it has obvious advantages that calcium ions can be extracted from phosphogypsum without using a large amount of acid and alkali. At the same time, L-sodium lactate can be recycled as a calcium ion transfer agent, thereby reducing production costs. In summary, the β-tricalcium phosphate prepared according to the present method not only has cost advantages, but also has the advantages of high purity, good particle dispersibility, and high crystallinity.

[0006] The technical solution of the present invention relates to the preparation of nano-β-tricalcium phosphate by comprehensive utilization of phosphogypsum, which is characterized by comprising the following steps: First, the phosphogypsum solid waste is preliminarily treated by grinding, washing, filtering and drying to remove soluble impurities. The phosphogypsum is fully salted with L-sodium lactate solution to obtain soluble sodium sulfate solution, calcium lactate solution and insoluble solid impurities. The solid and the filtrate are separated by filtration. The calcium lactate in the filtrate is easily soluble in boiling water and slightly soluble in cold water. Calcium lactate can be obtained from the solution mixture by recrystallization, which lays the foundation for the preparation of high-grade β-tricalcium phosphate.

[0007] Ca in phosphogypsum 2+The molar ratio of sodium lactate to L-lactate is 1:1.5~3.5. The salt leaching reaction temperature is 60~100 °C, and the reaction time is 2~8 h. In some embodiments, the salt leaching reaction is carried out under stirring. After the reaction is completed, the reaction mixture is filtered to separate insoluble impurities to obtain a solution containing calcium ions, and the pH value of the solution is adjusted to 7~8 with sodium hydroxide or ammonia water, and finally the filtrate is concentrated and recrystallized to obtain calcium lactate.

[0008] Phosphate is slowly added dropwise to the calcium lactate solution obtained above again, and the pH value of the solution is adjusted to 7-9 for reaction. After the reaction is completed, the solution is allowed to stand for aging, filtered, washed, and dried to obtain tricalcium phosphate precursor powder.

[0009] The concentration of calcium lactate solution is 0.3-0.9 mol / L, the concentration of phosphate is 0.2-0.6 mol / L, the molar ratio of calcium lactate to phosphate is 1.0-2.5:1, and ammonia water needs to be slowly added to the reaction solution to adjust the pH value of the solution during the reaction, wherein the pH value ranges from 7 to 9, the reaction temperature is 25-90°C, the reaction time is 6-12 h, and the stirring is stopped after the reaction is complete, and the solution is allowed to stand for 6-12 h. The precipitate is filtered, washed three times with water and ethanol in turn, and then dried in an oven at 60-110°C overnight to obtain a white tricalcium phosphate precursor powder.

[0010] The filtrate is an ion solution containing lactate, which can be used for phosphogypsum dissociation cycle experiments.

[0011] The phosphate can be one or more mixtures of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate. The obtained tricalcium phosphate is calcined at 750-900° C. for 2-4 h to obtain high-purity β-tricalcium phosphate powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a flow chart of the nano β-tricalcium phosphate prepared in Example 1 of the present invention.

[0013] Figure 2 This is a scanning electron microscope image of the nano-β-tricalcium phosphate prepared in Example 1 of the present invention.

[0014] Figure 3 This is the X-ray diffraction pattern of the nano-β-tricalcium phosphate prepared in Example 1 of the present invention.

[0015] Figure 4 This is the particle size distribution diagram of the nano β-tricalcium phosphate prepared in Example 1 of the present invention.

[0016] Figure 5This is a scanning electron microscope image of the nano-β-tricalcium phosphate prepared in Example 1 of the present invention after being placed for 3 months. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0018] Example 1 According to the attached Figure 1 In the technical process, the phosphogypsum is first ground and washed three times with water to remove soluble impurities. 2+ The molar ratio of sodium lactate to L-lactate is 1:1.5) and stirred in a constant temperature water bath at 85 °C for 3 h to completely convert the reaction into calcium lactate and sodium sulfate solution, and filter to remove insoluble impurities in phosphogypsum. The pH value of the above filtrate is adjusted to 7.5, and then concentrated, recrystallized, and filtered to obtain calcium lactate. The calcium lactate obtained above is dissolved in deionized water to obtain a solution A with a volume of 2 L and a concentration of 0.3 mol / L. 2 L of diammonium hydrogen phosphate solution B with a concentration of 0.2 mol / L is prepared. Solution B is slowly added dropwise to solution A and stirred evenly. During the reaction, ammonia water is added dropwise to adjust the pH value of the solution to 7. Under room temperature, the reaction is stirred for 8 h, and then allowed to stand for 6 h. The solid obtained by suction is washed three times with water and three times with ethanol, and then dried in an oven at 90 °C overnight to obtain a β-tricalcium phosphate precursor. Finally, the β-tricalcium phosphate precursor was heated to 900 ℃ at a heating rate of 10 ℃ / min and calcined for 2 h to obtain nano β-tricalcium phosphate powder. Figure 2 The scanning electron microscope image of the nanometer β-tricalcium phosphate in the embodiment of the present invention is shown in the figure. It can be seen from the figure that the nanometer β-tricalcium phosphate nanoparticles in the present embodiment have good dispersibility and the particle size range is: 180~400 nm. Figure 3 : This is an X-ray diffraction diagram of the nano β-tricalcium phosphate in an embodiment of the present invention. It can be seen from the diagram that the nano β-tricalcium phosphate in this embodiment has high nanocrystallinity. Figure 4 The particle size distribution of the nano-β-tricalcium phosphate nanoparticles in this embodiment measured by a laser particle size distribution instrument shows that the particles are symmetrically normally distributed, with D90 = 26.60 μm and D50 = 11.77 μm, indicating that the obtained nano-β-tricalcium phosphate nanoparticles are uniformly dispersed. Under normal temperature and common conditions, the nano-β-tricalcium phosphate is sealed and packaged in units of 1KG. After being placed for 3 months, D90 = 27.13 μm and D50 = 11.89 μm.

[0019] Example 2 According to the attached Figure 1The overall technical process is to grind the phosphogypsum and add an appropriate amount of water to wash it three times to remove the soluble impurities in it, and obtain the pretreated phosphogypsum. 2+ The molar ratio of sodium phosphate to L-lactate is 1:2.0) and mixed evenly, heated in a constant temperature water bath at 80 °C, and stirred for 4 hours. After the reaction is completed, filter to remove insoluble impurities in phosphogypsum. The pH value of the solution is adjusted to 7, and then the filtrate is concentrated and recrystallized to obtain calcium lactate. The calcium lactate obtained above is dissolved in deionized water, and the pH value of the solution is adjusted to 7 to obtain a solution A with a volume of 2 L and a concentration of 0.3 mol / L. Prepare 2 L of disodium hydrogen phosphate solution B with a concentration of 0.2 mol / L. Solution B is slowly added dropwise to solution A and stirred evenly to ensure that the molar ratio of calcium ions to phosphate ions in the reactants is 1.5:1. During the reaction, ammonia water is added dropwise to adjust the pH value of the solution to 8, stirred for 6 hours, and allowed to stand for 8 hours. Finally, the solid is obtained by suction filtration, and then the solid is washed three times with water and three times with ethanol, and then placed in an oven, set at 80 °C, and dried overnight to obtain a β-tricalcium phosphate precursor. Finally, the β-tricalcium phosphate precursor was heated to 800°C at a heating rate of 5°C / min and calcined for 2 h to obtain nano β-tricalcium phosphate powder. According to SEM, XRD and test, the nano β-tricalcium phosphate of this embodiment has high purity, high crystallinity and good particle dispersion, D90=26.51 μm, D50=13.87 μm; under normal temperature and common conditions, it was sealed and packaged in units of 1KG. After being placed for 3 months, D90=26.96 μm, D50=14.15 μm.

[0020] Example 3 According to the attached Figure 1 The overall technical process is to grind the phosphogypsum and wash it three times with water to remove the soluble impurities in it, and obtain the preliminarily treated phosphogypsum. Then the phosphogypsum is mixed with L-sodium lactate solution (Ca in phosphogypsum) 2+The molar ratio of sodium phosphate to L-lactate is 1:2.5) and reacted in a constant temperature water bath at 75 °C for 5 hours under stirring. After stopping the reaction, filter to remove insoluble impurities in phosphogypsum. The above filtrate is concentrated, the pH value of the solution is adjusted to 7, and then the filtrate is concentrated and recrystallized to obtain calcium lactate. The above calcium lactate is dissolved in 2 L of deionized water to obtain a solution A with a concentration of 0.3 mol / L. Prepare 2 L of trisodium phosphate solution B with a concentration of 0.2 mol / L. Solution B is slowly added dropwise to solution A and stirred evenly. During the reaction, ammonia water is added dropwise to adjust the pH value of the solution to 7, the reaction is stirred for 7 hours, and it is allowed to stand for 7 hours. After the reaction solution is layered, it is filtered to obtain a white solid, and then the solid is washed with water three times, washed with ethanol three times, and then placed in an oven, set at 80 °C, and dried overnight to obtain a β-tricalcium phosphate precursor. Finally, the β-tricalcium phosphate precursor was heated to 900°C at a heating rate of 5°C / min and calcined for 2 h to obtain nano β-tricalcium phosphate powder. According to SEM, XRD and particle size distribution tests, the nano β-tricalcium phosphate of this embodiment has high purity, high particle crystallinity and good dispersibility, D90=28.44 μm, D50=12.04 μm; under normal temperature and common conditions, it was sealed and packaged in units of 1KG. After being placed for 3 months, D90=28.70 μm and D50=12.62 μm.

[0021] Example 4 According to the attached Figure 1The overall technical process in the process is to grind the phosphogypsum and wash it three times with water to remove soluble impurities. Stir the phosphogypsum and sodium gluconate solution (i.e. replace the L-sodium lactate solution with sodium gluconate) in a constant temperature water bath at 85 °C for 6 h under stirring to completely convert the reaction into calcium gluconate and sodium sulfate solution, and filter to remove insoluble impurities in the phosphogypsum. The filtrate is concentrated, recrystallized, and filtered to obtain calcium gluconate. The calcium gluconate obtained above is dissolved in deionized water to obtain a solution A with a volume of 2 L and a concentration of 0.3 mol / L. Prepare 2 L of diammonium hydrogen phosphate solution B with a concentration of 0.2 mol / L, slowly add solution B to solution A, stir evenly, and drip ammonia water to adjust the pH value of the solution to 7~8 during the reaction. Stir the reaction for 10 h at room temperature, let it stand for 8 h, and wash the solid obtained by suction three times with water and three times with ethanol, and then dry it in an oven at 90 °C overnight to obtain a β-tricalcium phosphate precursor. Finally, the β-tricalcium phosphate precursor was placed in a muffle furnace at 900 ° C and calcined for 2-3 h, with a heating rate of 5-10 ° C / min, to obtain nano β-tricalcium phosphate powder. The nano β-tricalcium phosphate of this embodiment has high purity, high particle crystallinity, and good dispersibility, D90=46.86 μm, D50=26.26 μm; under normal temperature and common conditions, it was sealed and packaged in units of 1KG. After being placed for 2 months, D90=49.60 μm, D50=28.63 μm. It can be seen that the use of sodium gluconate can actually obtain a product with very high purity, but after being placed for 2 months, there was a relatively large fluctuation in particle size, a certain amount of aggregation, and fluctuations in product performance stability.

Claims

1. A method for preparing nano β-tricalcium phosphate by comprehensive utilization of phosphogypsum, characterized in that: The steps include: a) Pretreatment: crush or grind the phosphogypsum, wash it with water, and dry it to preliminarily remove the soluble impurities in it; b) Dissociation of phosphogypsum: Add sodium L-lactate solution to the pretreated phosphogypsum for salt leaching reaction, filter the reaction product to obtain a solution containing calcium ions, adjust the pH value of the solution to 7-8, and finally concentrate and recrystallize the filtrate to obtain calcium lactate; c) Preparation of tricalcium phosphate precursor: slowly dropwise adding phosphate into the calcium lactate solution, adjusting the pH value of the solution to 7-9 for reaction, and after the reaction is completed, aging, filtering, washing, and drying to obtain tricalcium phosphate precursor powder; d) Preparation of nano-β-tricalcium phosphate: The temperature of the tricalcium phosphate precursor powder is raised to 750-900°C and kept at this temperature for 2-4 h to obtain nano-β-tricalcium phosphate.

2. The method for preparing nano β-tricalcium phosphate by comprehensive utilization of phosphogypsum according to claim 1, characterized in that: In step b), Ca in phosphogypsum 2+ The molar ratio with sodium L-lactate is 1:1.5~3.

5.

3. The method for preparing nano β-tricalcium phosphate by comprehensive utilization of phosphogypsum according to claim 2, characterized in that: In step b), the salt leaching reaction temperature is 60-100°C and the reaction time is 2-8 h.

4. The method for preparing nano β-tricalcium phosphate by comprehensive utilization of phosphogypsum according to claim 1, characterized in that: In step c), the concentration of the calcium lactate solution is 0.3 to 0.9 mol / L, the concentration of the phosphate is 0.2 to 0.6 mol / L, and the molar ratio of calcium lactate to phosphate is 1.0-2.5:

1.

5. The method for preparing nano β-tricalcium phosphate by comprehensive utilization of phosphogypsum according to claim 4, characterized in that: In step c), the phosphate is selected from diammonium hydrogen phosphate, ammonium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, or one or more mixtures of potassium dihydrogen phosphate.

6. The method for preparing nano-β-tricalcium phosphate by comprehensive utilization of phosphogypsum according to claim 4, characterized in that: In step c), after stirring at room temperature for 6-8 hours, the mixture is allowed to stand for aging for 4-12 hours.

7. The method for preparing nano-β-tricalcium phosphate by comprehensive utilization of phosphogypsum according to claim 1, characterized in that: In step d), the temperature is raised to 900° C. at a heating rate of 2-5° C. / min and the reaction is kept warm for 2 hours to obtain nano β-tricalcium phosphate.

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