Preparation method of water-soluble calcium phosphate

Abstract

The invention discloses a preparation method of water-soluble calcium phosphate, which comprises the following steps: S1, respectively preparing a phosphoric acid solution and a calcium carbonate suspension, and adding citric acid and hexametaphosphate into the phosphoric acid solution; s2, mixing the phosphoric acid solution and the calcium carbonate suspension, and reacting until the solution is clear; s3, performing spray drying to obtain a water-soluble calcium phosphate product. The whole reaction is simple, no redundant waste exists in the reaction process, and the production concept of green chemistry is met; the product is good in solubility, the calcium-phosphorus ratio is 2: 1, the solubility reaches 9g / 100ml water or above, calcium is not easy to separate out after the solution is placed, the product is relatively stable, the application field is wider, and the application effect is better.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and specifically relates to a method for preparing water-soluble calcium phosphate. Background Technology

[0002] Calcium promotes bone growth and development, maintains electrolyte balance, and supports normal heart pumping function, also affecting muscles. Phosphorus is the second most abundant element in the human body after calcium, with 85.7% concentrated in bones and teeth, and the remainder distributed throughout tissues and fluids, half of which is found in muscle tissue. It not only constitutes a part of the human body but also participates in crucial metabolic processes, making it a vital element. Calcium and phosphorus are abundant in the human body, forming bones and teeth in forms such as hydroxyapatite, and playing key roles in physiological processes such as metabolism, signal transduction, and energy conversion.

[0003] Currently, most calcium phosphate salts in China are insoluble or only slightly soluble in water. Water-soluble calcium phosphate salts are unstable and easily precipitate after a short period of storage. This application presents a method for synthesizing water-soluble calcium phosphate, which is of great significance for promoting the large-scale production, industrial synthesis and application of water-soluble calcium phosphate. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing water-soluble calcium phosphate.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing water-soluble calcium phosphate includes the following steps: S1. Prepare a phosphoric acid solution and a calcium carbonate suspension, wherein the phosphoric acid solution also contains citric acid and hexametaphosphate; the amount of citric acid added is 1.5 to 2 times the molar amount of phosphoric acid in the phosphoric acid solution; the amount of hexametaphosphate added is 0.1 to 0.3% of the molar amount of phosphoric acid in the phosphoric acid solution. S2. Mix the phosphoric acid solution and calcium carbonate suspension and react until the solution is clear; the molar ratio of phosphoric acid to calcium carbonate is 1:(1~1.3); S3. Spray drying to obtain water-soluble calcium phosphate product.

[0006] Preferably, the hexametaphosphate is selected from at least one of potassium hexametaphosphate or sodium hexametaphosphate.

[0007] Preferably, the concentration of phosphoric acid in the phosphoric acid solution is 0.3~0.7 mol / L; The concentration of calcium carbonate in the calcium carbonate suspension is 2~4 mol / L.

[0008] Preferably, the phosphoric acid solution is prepared by the following steps: First, the citric acid and phosphoric acid are dissolved in water, and then the hexametaphosphate is added. After dissolving, the phosphoric acid solution is obtained.

[0009] Preferably, in step S2, the calcium carbonate suspension is slowly added to the phosphoric acid solution.

[0010] Preferably, the calcium carbonate suspension is added at a rate of 2-5 ml / min.

[0011] Preferably, the reaction time in step S2 is 20-40 min.

[0012] Preferably, the inlet air temperature of the spray drying in step S3 is 140~150℃, and the outlet air temperature is 90~100℃.

[0013] The reaction process in this application is relatively simple, with no excess waste, which aligns with the production philosophy of green chemistry. The product has good solubility, with a calcium-to-phosphorus ratio of 2:1 and a solubility of over 9g / 100ml water. Calcium does not easily precipitate out after the solution is left to stand, making the product relatively stable. It has a wider range of applications and better application effects. Detailed Implementation

[0014] This application provides a method for preparing water-soluble calcium phosphate, comprising the following steps: S1. Prepare a phosphoric acid solution and a calcium carbonate suspension separately. Citric acid and hexametaphosphate are added to the phosphoric acid solution. The amount of citric acid added is 1.5 to 2 times the molar amount of phosphoric acid in the phosphoric acid solution. The amount of hexametaphosphate added is 0.1 to 0.3% of the molar amount of phosphoric acid in the phosphoric acid solution. Calcium carbonate is poorly soluble in water. First, the calcium carbonate is dispersed evenly in water so that the reaction with the phosphoric acid solution is more complete and faster.

[0015] S2. Mix the phosphoric acid solution and calcium carbonate suspension and react until the solution becomes clear, proving that the calcium carbonate has reacted completely; the molar ratio of phosphoric acid to calcium carbonate is 1:(1~1.3). Phosphoric acid and calcium carbonate can react at room temperature. If the reaction is carried out at high temperature, calcium is easily precipitated after heating, forming insoluble calcium salts.

[0016] Under these reaction ratio conditions, phosphoric acid and calcium carbonate can ensure that the calcium-to-phosphorus ratio of the product is 2:1, preventing the formation of other by-products.

[0017] S3. Spray drying to obtain water-soluble calcium phosphate product.

[0018] Other heating and drying methods can lead to calcium precipitation and the formation of insoluble calcium salts. Spray drying prevents calcium precipitation, resulting in water-soluble calcium phosphate that is more easily absorbed. Currently, there is limited research on water-soluble calcium phosphate salts in China. Some water-soluble calcium salts are uncommon and unstable, and tend to precipitate after standing. The water-soluble calcium phosphate obtained in this application is calcium that can dissolve in water or other solutions as a soluble compound. It has an optimal biomimetic calcium-to-phosphorus ratio (2:1), with a solubility of up to 9 g / 100 ml water. Under these conditions, it remains fully water-soluble, does not easily precipitate even after prolonged standing, and its bioabsorption rate is more than twice that of calcium carbonate.

[0019] This application uses phosphoric acid and calcium carbonate as raw materials to prepare water-soluble calcium phosphate. First, a phosphoric acid solution and a calcium carbonate suspension are prepared separately. Citric acid is added to the phosphoric acid solution to form a stable acidic solution. Hexametaphosphate is added to form a stable complex with calcium ions, preventing calcium ions from precipitating out during product reconstitution. Then, it reacts with moistened calcium carbonate, and the mixture is spray-dried to obtain water-soluble calcium phosphate.

[0020] Both citric acid and hexametaphosphate bind calcium ions through chelation. Together, they form a multi-layered calcium ion stabilization mechanism, preventing calcium ion precipitation and forming stable water-soluble calcium. Citric acid's chelating effect is relatively weak; as an organic acid, it can promote calcium absorption. Hexametaphosphate's chelating effect is stronger and more efficient; therefore, it is important to control the amount of hexametaphosphate added.

[0021] Hexametaphosphate is a chain-like polyphosphate with a long molecular structure and a large number of negative charges. It can bind calcium ions like crab claws, forming a stable chelate ring with good chelation effect, making it easier to form stable water-soluble compounds. Experiments have shown that hexametaphosphate has a better complexation effect with calcium ions than similar compounds such as sodium pyrophosphate, disodium dihydrogen pyrophosphate, and sodium lactate, effectively preventing calcium precipitation during the resolution of water-soluble calcium phosphate products. Using calcium carbonate, compared to other calcium sources such as calcium hydroxide, is more conducive to a thorough and uniform reaction with phosphoric acid to produce calcium phosphate. Furthermore, the generation of carbon dioxide gas when using calcium carbonate allows for more direct observation of the reaction process.

[0022] The reaction process in this application is relatively simple, with no excess waste, which aligns with the production philosophy of green chemistry. The product has good solubility, with a calcium-to-phosphorus ratio of 2:1 and a solubility of over 9g / 100ml water. Calcium does not easily precipitate out after the solution is left to stand, making the product relatively stable. It has a wider range of applications and better application effects.

[0023] Preferably, the hexametaphosphate is selected from at least one of potassium hexametaphosphate or sodium hexametaphosphate.

[0024] Preferably, the concentration of phosphoric acid in the phosphoric acid solution is 0.3~0.7 mol / L; and the concentration of calcium carbonate in the calcium carbonate suspension is 2~4 mol / L. Suitable concentrations facilitate sufficient contact and reaction between phosphoric acid and calcium carbonate.

[0025] Preferably, the phosphoric acid solution is prepared by the following steps: First, citric acid and phosphoric acid are dissolved in water to form a stable acidic solution. Then, hexametaphosphate is added, and after dissolution, a stable phosphoric acid solution is obtained. Adding citric acid first to establish an acidic environment can slow down or prevent hydrolysis of hexametaphosphate during the preparation process, ensuring its long-term stability. The two functions work synergistically to form a multi-layered calcium ion stabilization mechanism, allowing it to be stored for a longer period of time and preventing calcium precipitation.

[0026] Preferably, in step S2, the calcium carbonate suspension is slowly added to the phosphoric acid solution to allow the two to react fully.

[0027] Adding phosphoric acid solution to calcium carbonate suspension will cause a violent reaction, resulting in a large amount of bubbling, which will cause the solution to overflow, affecting the reaction and reducing the product yield.

[0028] Preferably, the calcium carbonate suspension is added at a rate of 2-5 ml / min within 10-20 minutes.

[0029] Preferably, the reaction time in step S2 is 20-40 min.

[0030] Preferably, in step S3, the inlet air temperature for spray drying is 140~150℃, and the outlet air temperature is 90~100℃.

[0031] Example 1 Add 40 parts citric acid and 12 parts phosphoric acid to 250 parts water, stir to dissolve, then add 0.1 parts sodium hexametaphosphate and dissolve completely to obtain a phosphoric acid solution. In another beaker, add 50 parts water and 14 parts calcium carbonate, stir well, and slowly add this mixture (at a rate of 3 ml / min) to the phosphoric acid solution. After reacting for 30 minutes, the solution becomes clear, is filtered, and the filtrate is spray-dried (inlet air temperature 145℃, outlet air temperature 95℃) to obtain a water-soluble calcium phosphate product. Testing shows that the product contains 11.36% calcium, 5.55% phosphorus, has a solubility of over 9g, and remains stable for 3-4 days without calcium precipitation.

[0032] All parts mentioned in the examples and comparative examples are parts by weight.

[0033] Comparative Example 1 (blank group, without any stabilizer) Add 40 parts citric acid and 12 parts phosphoric acid to 250 parts water, stir and dissolve to obtain a phosphoric acid solution. In another beaker, add 50 parts water and 14 parts calcium carbonate, stir well, and slowly add this mixture (at an addition rate of 3 ml / min) to the phosphoric acid solution. After reacting for about 30 minutes, the solution becomes clear. Filter the solution, and spray dry the filtrate (inlet air temperature 145℃, outlet air temperature 95℃) to obtain a water-soluble calcium phosphate product. Testing shows that the product contains 12.89% calcium and 7.48% phosphorus, with a solubility of over 9g. However, after standing for 2-3 hours, calcium precipitation occurs.

[0034] Comparative Example 2 (Choice of Stabilizer: Sodium Pyrophosphate) Add 40 parts citric acid and 12 parts phosphoric acid to 250 parts water, stir to dissolve, then add 5 parts sodium pyrophosphate and dissolve completely to obtain a phosphoric acid solution. In another beaker, add 50 parts water and 14 parts calcium carbonate, stir well, and slowly add this mixture (at a rate of 3 ml / min) to the phosphoric acid solution. After reacting for about 30 minutes, the solution becomes clear. Filter the solution and spray-dry the filtrate (inlet air temperature 145℃, outlet air temperature 95℃) to obtain a water-soluble calcium phosphate product. Testing shows that the product contains 12.12% calcium and 5.15% phosphorus, with a solubility of over 9g. However, after standing for 5-6 hours, calcium precipitation occurs.

[0035] Comparative Example 3 (Choice of stabilizer: disodium dihydrogen pyrophosphate) Add 40 parts citric acid and 12 parts phosphoric acid to 250 parts water, stir to dissolve, then add 5 parts disodium dihydrogen pyrophosphate and dissolve completely to obtain a phosphoric acid solution. In another beaker, add 50 parts water and 14 parts calcium carbonate, stir well, and slowly add this mixture (at a rate of 3 ml / min) to the acid solution. After reacting for about 30 minutes, the solution becomes clear. Filter the solution and spray-dry the filtrate (inlet air temperature 145℃, outlet air temperature 95℃) to obtain a water-soluble calcium phosphate product. Testing shows that the product contains 11.37% calcium and 5.82% phosphorus, with a solubility of over 9g. However, it does not stand for long; calcium precipitation occurs after approximately 36 hours.

[0036] Comparative Example 4 (Choice of stabilizer: sodium lactate) Add 40 parts citric acid and 12 parts phosphoric acid to 250 parts water, stir to dissolve, then add 5 parts sodium lactate and dissolve completely to obtain a phosphoric acid solution. In another beaker, add 50 parts water and 14 parts calcium carbonate, stir well, and slowly add this mixture (at a rate of 3 ml / min) to the phosphoric acid solution. After reacting for about 30 minutes, the solution becomes clear. Filter the solution and spray-dry the filtrate (inlet air temperature 145℃, outlet air temperature 95℃) to obtain a water-soluble calcium phosphate product. Testing shows that the product contains 12.13% calcium and 5.08% phosphorus, with a solubility of over 9g. However, after standing for 2-3 hours, calcium precipitation occurs.

[0037] Comparative Example 5 (Calcium hydroxide was used instead of calcium carbonate) Add 40 parts citric acid and 12 parts phosphoric acid to 250 parts water, stir to dissolve, then add 0.1 parts sodium hexametaphosphate and dissolve completely to obtain a phosphoric acid solution. In another beaker, add 50 parts water and 10.4 parts calcium hydroxide and stir well. Slowly add this mixture (at a rate of 3 ml / min) to the phosphoric acid solution. After reacting for about 30 minutes, if the solution is not clear, filter it. Spray dry the filtrate (inlet air temperature 145℃, outlet air temperature 95℃) to obtain a calcium phosphate product with a calcium content of 10.09% and a phosphorus content of 6.05%.

[0038] Table 1. Effects of different experimental conditions on the water solubility stability and content of the product.

[0039]

[0040] Comparing Table 1, it can be seen that different stabilizers lead to poor solubility stability due to calcium complexation. Sodium hexametaphosphate has better complexation ability, and its water solubility stability can reach 3-4 days without calcium precipitation.

[0041] Example 2 Add 40 parts citric acid and 11 parts phosphoric acid to 250 parts water, stir to dissolve, then add 0.15 parts sodium hexametaphosphate and dissolve completely to obtain a phosphoric acid solution. In another beaker, add 50 parts water and 14 parts calcium carbonate and stir well. Slowly add this mixture (at a rate of 3 ml / min) to the phosphoric acid solution. After reacting for about 40 minutes, the solution becomes clear. Filter the solution and spray-dry the filtrate (inlet air temperature 145℃, outlet air temperature 95℃) to obtain a water-soluble calcium phosphate product with a calcium content of 11.06%, a phosphorus content of 5.62%, a solubility of over 9g, and stable storage for 3-4 days without calcium precipitation.

[0042] Example 3 Add 40 parts citric acid and 11.5 parts phosphoric acid to 250 parts water, stir to dissolve, then add 0.15 parts potassium hexametaphosphate and dissolve completely to obtain a phosphoric acid solution. In another beaker, add 50 parts water and 14 parts calcium carbonate and stir well. Slowly add this mixture (at a rate of 3 ml / min) to the phosphoric acid solution. After reacting for about 30 minutes, the solution becomes clear. Filter the solution and spray-dry the filtrate (inlet air temperature 150℃, outlet air temperature 100℃) to obtain a water-soluble calcium phosphate product with a calcium content of 11.20%, a phosphorus content of 5.69%, a solubility of over 9g, and stable storage for 3-4 days without calcium precipitation.

[0043] Example 4 Add 40 parts citric acid and 12 parts phosphoric acid to 250 parts water, stir to dissolve, then add 0.2 parts sodium hexametaphosphate and dissolve completely to obtain a phosphoric acid solution. In another beaker, add 50 parts water and 14 parts calcium carbonate and stir well. Slowly add this mixture (at a rate of 5 ml / min) to the phosphoric acid solution. After reacting for about 20 minutes, the solution becomes clear. Filter the solution and spray-dry the filtrate (inlet air temperature 140℃, outlet air temperature 90℃) to obtain a water-soluble calcium phosphate product with a calcium content of 11.19%, a phosphorus content of 5.63%, a solubility of over 9g, and stable storage for 3-4 days without calcium precipitation.

[0044] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for preparing water-soluble calcium phosphate, characterized in that, Includes the following steps: S1. Prepare a phosphoric acid solution and a calcium carbonate suspension, wherein the phosphoric acid solution also contains citric acid and hexametaphosphate; the amount of citric acid added is 1.5 to 2 times the molar amount of phosphoric acid in the phosphoric acid solution; the amount of hexametaphosphate added is 0.1 to 0.3% of the molar amount of phosphoric acid in the phosphoric acid solution. S2. Mix the phosphoric acid solution and the calcium carbonate suspension and react until the solution is clear; the molar ratio of phosphoric acid to calcium carbonate is 1:(1~1.3); S3. Spray drying to obtain water-soluble calcium phosphate product.

2. The method for preparing water-soluble calcium phosphate as described in claim 1, characterized in that, The hexametaphosphate is selected from at least one of potassium hexametaphosphate or sodium hexametaphosphate.

3. The method for preparing water-soluble calcium phosphate as described in claim 1, characterized in that, The concentration of phosphoric acid in the phosphoric acid solution is 0.3~0.7 mol / L; The concentration of calcium carbonate in the calcium carbonate suspension is 2~4 mol / L.

4. The method for preparing water-soluble calcium phosphate as described in claim 1, characterized in that, The phosphoric acid solution is prepared by the following steps: First, the citric acid and phosphoric acid are dissolved in water, and then the hexametaphosphate is added. After dissolving, the phosphoric acid solution is obtained.

5. The method for preparing water-soluble calcium phosphate as described in claim 1, characterized in that, Step S2 involves slowly adding the calcium carbonate suspension to the phosphoric acid solution.

6. The method for preparing water-soluble calcium phosphate as described in claim 5, characterized in that, The calcium carbonate suspension is added at a rate of 2-5 ml / min.

7. The method for preparing water-soluble calcium phosphate as described in claim 1, characterized in that, The reaction time for step S2 is 20-40 minutes.

8. The method for preparing water-soluble calcium phosphate as described in claim 1, characterized in that, The inlet air temperature of the spray dryer in step S3 is 140~150℃, and the outlet air temperature is 90~100℃.

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