Method for preparing flaky nano hydroxyl calcium phosphate in clarification system by compounding additive in cooperation with cavitation jet flow

Abstract

The invention discloses a method for preparing flaky nano hydroxyl calcium phosphate in a clarification system by cooperating a compound additive with cavitation jet flow, which is characterized in that an SDBS / AEO9 / citrate ternary compound additive system is created for the first time, and oriented growth of hydroxyl calcium phosphate flaky crystals is realized through a molecular-level synergistic effect; an anionic sulfonic acid group of sodium dodecyl benzene sulfonate is specifically adsorbed to a 001 crystal face calcium site of HAP, growth in the c-axis direction is inhibited, and a crystal is forced to expand along an ab face to form a flaky element; through the synergistic effect of the three components, the contradiction that flaky HAP high diameter-thickness ratio growth and dispersion stability cannot be achieved at the same time is solved, a high-pressure cavitation jet flow technology is adopted in a breakthrough mode, and through the synergistic effect of cavitation bubble collapse microjet flow 300-1000 m / s and an instantaneous extreme physical field, crystal nanocrystallization crushing and flaky structure recombination are synchronously achieved; the ultrathin lamellar crystal with the average thickness is obtained on the premise that the crystallinity reaches up to 95.3%, and the energy consumption is reduced by 76% compared with that of a traditional process.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic chemistry, and in particular to preparing flaky nano-calcium hydroxyphosphate by combining compound additives with cavitation jet in a clarification system. Background Art

[0002] Calcium and phosphorus are essential elements for living organisms, and calcium phosphate products have long been used extensively as nutritional supplements for animal husbandry. However, the low bioavailability of calcium phosphates has not been effectively addressed. The gradual depletion of high-grade phosphate rock has led to increased production costs, and product homogeneity among phosphate rock processors has become increasingly severe. Driven by the contemporary trend of environmental protection and ecological innovation, more efficient and bioactive calcium and phosphate nutrients, as well as further processing and new applications of these products, are the inevitable direction of development now and in the future.

[0003] Hydroxyapatite (HAP, chemical formula Ca 10 (PO4)6(OH)2) is the primary inorganic component of human and animal bones and teeth, exhibiting excellent biocompatibility, bioactivity, and osteoconductivity. Therefore, nano-hydroxy calcium phosphate (HAP) exhibits enormous potential for application in biomedical applications, such as bone tissue engineering scaffolds, bone defect filling materials, sustained-release drug carriers, dental repair, and bio-coatings. In particular, sheet-like nano-hydroxy calcium phosphate, due to its unique two-dimensional structure, large specific surface area, and specific crystal orientation, offers significant advantages in enhancing the mechanical properties of composite materials, promoting cell adhesion and directional growth, and improving drug loading efficiency. It is also an important inorganic dispersant material used in current suspension polymerization.

[0004] Currently, the commonly used methods for preparing nano-hydroxy calcium phosphate mainly include chemical precipitation, hydrothermal method, sol-gel method, microemulsion method, and biomimetic mineralization method. However, the hydrothermal method can produce flaky HAP, but it is relatively thick. The high temperature and high pressure reaction conditions will also cause the surfactant to deactivate and decompose, resulting in uneven mass transfer and stacking. In the microemulsion method, the oil-water interfacial tension disturbs crystal growth, the emulsion is poorly stable, and the particle size distribution is too wide. Therefore, the development of a new method that can effectively combine the precise morphology control ability of compound additives with the enhanced mass transfer / energy input advantages of cavitation jets in a clear and uniform reaction system environment, thereby achieving efficient, stable, and controllable preparation of flaky nano-hydroxy calcium phosphate with uniform size, good dispersion, and controllable thickness has become a key technical problem that needs to be solved in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing flaky nano-calcium hydroxyphosphate in a clarification system by using a compound additive in conjunction with a cavitation jet.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] The present invention discloses a method for preparing flaky nano-calcium hydroxyphosphate in a clarification system by using a composite additive in conjunction with a cavitation jet, comprising the following steps:

[0008] 1) preparing a 10-20% sodium hydroxide solution in a reaction kettle, then adding a composite additive of sodium dodecylbenzenesulfonate: AEO9: citrate in a ratio of 1:1-4:4-10, starting stirring, and preparing a phosphoric acid solution and a 15-30% calcium chloride solution;

[0009] 2) using a cavitation jet device to spray a mixed solution of phosphoric acid and calcium chloride into a sodium hydroxide solution, controlling the pH value after the addition of the mixed solution, and then increasing the reaction temperature and aging for 2 to 4 hours;

[0010] 3) After the reaction is completed, the temperature is lowered to room temperature to obtain a suspension system containing flaky crystals, which is then washed after solid-liquid separation and dried to obtain product-grade calcium hydroxyphosphate, and the mother liquor is separated and recycled.

[0011] As a further improvement, the citrate in step 1) of the present invention is sodium citrate or potassium citrate.

[0012] As a further improvement, the compounded additive in step 1) of the present invention is 0.5-2% of the mass of calcium chloride.

[0013] As a further improvement, the concentration of the phosphoric acid solution in step 1) of the present invention is 15-45%.

[0014] As a further improvement, in step 2) of the present invention, the reaction temperature is 30-50°C, and the aging temperature is 60-80°C.

[0015] As a further improvement, the nozzle diameter of the jet device in step 2) of the present invention is 0.05 to 0.3 mm.

[0016] As a further improvement, the pH value in step 2) of the present invention is 8.5-11.5.

[0017] As a further improvement, the yield of calcium hydroxyphosphate prepared by the present invention can reach 97.8%, and the specific surface area can reach 140m 2 / g, and the particle size distribution is 25-35nm.

[0018] The beneficial effects of the present invention are as follows:

[0019] The reaction system of the present invention initially forms a clear solution, which facilitates slow precipitation of ions and facilitates the formation of a well-crystalline structure. In a homogeneous solution, nucleation and crystal growth can occur under more controlled conditions. By precisely controlling the reaction parameters, it is easier to induce the formation of highly crystalline, structurally regular calcium hydroxyphosphate crystals. This is crucial for obtaining materials with specific biological activities.

[0020] The present invention pioneered a ternary composite additive system of SDBS / AEO9 / citrate, which achieves the directional growth of hydroxy calcium phosphate platelet crystals through molecular-level synergy. Its core mechanism is that the anionic sulfonic acid group of SDBS (sodium dodecylbenzenesulfonate) specifically adsorbs on the calcium site of the (001) crystal plane of HAP, inhibiting growth along the c-axis and forcing the crystal to expand along the ab plane to form platelet units; the long polyoxyethylene chain (EO=9) of AEO9 (fatty alcohol polyoxyethylene ether) forms a hydration layer with a thickness of 8.2nm, which prevents the stacking of the plates through steric hindrance, while reducing the interfacial tension of the solution and promoting the separation of the plates; and citrate chelates the free Ca 2+ , prolonging the nucleation induction period by 3-5 times to control the number of crystal nuclei, and competitively adsorbing on the crystal surface, synergistically enhancing the growth advantage of the surface. The synergistic effect of the three solves the contradiction between the high aspect ratio growth of flake HAP and dispersion stability.

[0021] The present invention uses breakthrough high-pressure cavitation jet technology, through the synergistic effect of cavitation collapse micro jet (300-1000m / s) and instantaneous extreme physical field, to achieve crystal nano-fragmentation and lamellar structure reorganization simultaneously: micro jet generation> 10 7 s -1 The ultra-high shear rate precisely crushes the crystals to the submicron level and selectively retains the integrity of the (001) crystal plane. At the same time, the high-energy field of cavitation collapse not only allows the particles to precipitate at the nanometer level, but also drives the broken wafers to be reorganized in situ along the (001) plane, thereby increasing the aspect ratio by 40-60% (reorganization time <10ms). Ultra-thin flakes of average thickness are obtained with a crystallinity of up to 95.3%, reducing energy consumption by 76% compared with traditional processes. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments, but the scope of the present invention is not limited to the embodiments.

[0023] Example 1

[0024] (1) 900 g of 30% sodium hydroxide solution and 1800 g of water were added to a reaction apparatus and stirred to obtain a 10% concentration solution. 1.5 g of a composite additive (sodium dodecylbenzenesulfonate: AEO9: sodium citrate = 1:1:4) was added and stirred evenly. 1059.4 g of a 15% phosphoric acid solution and 2000 g of a 15% calcium chloride solution were prepared for standby use.

[0025] (2) The temperature was set at 30°C. A mixed solution of calcium chloride and phosphoric acid was sprayed into the sodium hydroxide solution through a cavitation jet device (nozzle = 0.05 mm). After the addition of the mixed solution, the pH was controlled to 8.5. After the addition, the reaction temperature was raised to 60°C and aged for 2 hours.

[0026] (3) After the reaction, the temperature was lowered to room temperature to obtain a suspension system containing flaky crystals. The solid-liquid separation, washing, and drying were performed to obtain product-grade hydroxy calcium phosphate with a yield of 97.2%, a particle size range of 70 to 90 nm, and a specific surface area of ​​113.3 m 2 / g, separate the mother liquor for recycling.

[0027] Example 2

[0028] (1) 900 g of 30% sodium hydroxide solution and 900 g of water were added to a reaction apparatus and stirred to obtain a 15% concentration solution. 3 g of a composite additive (sodium dodecylbenzenesulfonate: AEO9: potassium citrate = 1:2:6) was added and stirred evenly. 635.64 g of 25% phosphoric acid solution and 1500 g of 20% calcium chloride solution were prepared for later use.

[0029] (2) The temperature was set at 40°C. A mixed solution of calcium chloride and phosphoric acid was sprayed into the sodium hydroxide solution through a cavitation jet device (nozzle = 0.1 mm). After the addition of the mixed solution, the pH value was controlled to 10.5. After the addition, the reaction temperature was raised to 70°C and aged for 3 hours.

[0030] (3) After the reaction, the temperature was lowered to room temperature to obtain a suspension system containing flaky crystals. The solid-liquid separation, washing, and drying were performed to obtain product-grade hydroxy calcium phosphate with a yield of 97.8%, a particle size range of 30 to 40 nm, and a specific surface area of ​​133.5 m 2 / g, separate the mother liquor for recycling.

[0031] Example 3

[0032] (1) 900 g of 30% sodium hydroxide solution and 900 g of water were added to a reaction apparatus and stirred to obtain a 15% concentration solution. 3 g of a composite additive (sodium dodecylbenzenesulfonate: AEO9: sodium citrate = 1:2:6) was added and stirred evenly. 635.64 g of 25% phosphoric acid solution and 1500 g of 20% calcium chloride solution were prepared for standby use.

[0033] (2) The temperature was set at 40°C. A mixed solution of calcium chloride and phosphoric acid was sprayed into the sodium hydroxide solution through a cavitation jet device (nozzle = 0.1 mm). After the addition of the mixed solution, the pH value was controlled to 10.5. After the addition, the reaction temperature was raised to 70°C and aged for 3 hours.

[0034] (3) After the reaction, the temperature was lowered to room temperature to obtain a suspension system containing flaky crystals. The solid-liquid separation, washing, and drying were performed to obtain product-grade calcium hydroxyphosphate with a yield of 97.8%, a particle size range of 25 to 35 nm, and a specific surface area of ​​140 m 2 / g, separate the mother liquor for recycling.

[0035] Example 4

[0036] (1) 900 g of 30% sodium hydroxide solution and 450 g of water were added to a reaction apparatus and stirred to obtain a 20% concentration solution. 6 g of a composite additive (sodium dodecylbenzenesulfonate: AEO9: sodium citrate = 1:4:10) was added and stirred evenly. 353.13 g of 45% phosphoric acid solution and 1000 g of 30% calcium chloride solution were prepared for later use.

[0037] (2) The temperature was set at 50°C. A mixed solution of calcium chloride and phosphoric acid was sprayed into the sodium hydroxide solution through a cavitation jet device (nozzle = 0.3 mm). After the addition of the mixed solution, the pH was controlled to 11.5. After the addition, the reaction temperature was raised to 80°C and aged for 4 hours.

[0038] (3) After the reaction, the temperature was lowered to room temperature to obtain a suspension system containing flaky crystals. The solid-liquid separation, washing, and drying were performed to obtain product-grade calcium hydroxyphosphate with a yield of 94.6%, a particle size range of 60 to 80 nm, and a specific surface area of ​​108.8 m 2 / g, separate the mother liquor for recycling.

[0039] Comparative Example 1

[0040] The additive added was 3g of sodium dodecylbenzenesulfonate, and other conditions remained unchanged. The yield was 96.5%, the particle size range was 80-110nm, and the specific surface area was 80m 2 / g.

[0041] Comparative Example 2

[0042] The additive added was 3g of AEO9, and the other conditions remained unchanged. The yield was 96.3%, the particle size range was 80-110nm, and the specific surface area was 78m 2 / g.

[0043] Comparative Example 3

[0044] The compound additive added was 3g of sodium citrate, and the other conditions remained unchanged. The yield was 97.4%, the particle size range was 80-110nm, and the specific surface area was 82m 2 / g.

[0045] Comparative Example 4

[0046] The compound additive added was 3g sodium dodecylbenzenesulfonate: AEO9 = 1:2, and other conditions remained unchanged. The yield was 97.4%, the particle size range was 70-90nm, and the specific surface area was 93m 2 / g.

[0047] Comparative Example 5

[0048] The added compound additive was 3g sodium dodecylbenzenesulfonate: sodium citrate = 1:6, and other conditions remained unchanged. The yield was 97.2%, the particle size range was 70-90nm, and the specific surface area was 92m 2 / g.

[0049] Comparative Example 6

[0050] The added compound additive is 3g of AEO9: sodium citrate = 1:3, and other conditions remain unchanged. The yield is 97.5%, the particle size range is 70-90nm, and the specific surface area is 95m 2 / g.

[0051] It can be seen that, compared with Example 3, Control Examples 1-6 use traditional single surfactants or additives mixed in pairs, and the synergistic effect of the three is not achieved, resulting in slightly poor crystallization uniformity, and the crystals cannot form flaky calcium hydroxyphosphate. The particle size distribution range is wide, and the particle size is large, the specific surface area is small, and the dispersant effect is greatly reduced.

[0052] Comparative Example 7

[0053] (1) Take 300g of calcium oxide uniform powder and mix it with a small amount of water to make a wet solid. The obtained wet solid and 45g of maltodextrin are added alternately in batches to 1200ml of water, and stirred to obtain a white emulsion. 5g of glacial acetic acid is added dropwise and stirred evenly.

[0054] (2) Dilute 235.5 g of the obtained 25% phosphoric acid solution for later use, and add the phosphoric acid solution dropwise to the stabilized calcium source emulsion within 20 minutes. Continue to react under the radiation atmosphere with temperature control for 120 minutes. During the entire reaction process, the system pH is controlled to be greater than 10.5 with ammonia water. The temperature is controlled by circulating chilled water to keep the reaction temperature at 15-35°C.

[0055] (3) After the reaction is completed, a suspension containing solid particles is obtained. The solid-liquid separation and drying process yield nanoscale calcium hydrogen hydroxyphosphate. The mother liquor is separated and returned for use in the calcium source emulsion and base liquid preparation. The dried product is a white powdery solid with a yield of 96.35%, a product content of 99.2%, good fluidity, and a particle size range of 70 to 130 nm.

[0056] It can be seen that, compared with Example 3, in Control Example 7, the traditional dropwise addition method is used to obtain calcium hydroxyphosphate, and the resulting crystals are mostly rod-shaped and granular, which greatly reduces the specific surface area. The preparation process has high energy consumption, and the obtained particle size range is large, resulting in uneven dispersion effect, which greatly increases its limitations in dispersant applications.

[0057] Finally, it should be noted that the above examples are merely specific implementation examples of the present invention. Obviously, the present invention is not limited to the above examples and is subject to numerous variations. All variations that can be directly derived or conceived by a person of ordinary skill in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. Preparation of flaky nano-calcium hydroxyphosphate in a clarification system by using compound additives in conjunction with cavitation jet, characterized in that: The following steps are involved: 1) preparing a 10-20% sodium hydroxide solution in a reaction kettle, then adding a composite additive of sodium dodecylbenzenesulfonate: AEO9: citrate in a ratio of 1:1-4:4-10, starting stirring, and preparing a phosphoric acid solution and a 15-30% calcium chloride solution; 2) using a cavitation jet device to spray a mixed solution of phosphoric acid and calcium chloride into a sodium hydroxide solution, controlling the pH value after the addition of the mixed solution, and then increasing the reaction temperature and aging for 2 to 4 hours; 3) After the reaction is completed, the temperature is lowered to room temperature to obtain a suspension system containing flaky crystals, which is then washed after solid-liquid separation and dried to obtain product-grade calcium hydroxyphosphate, and the mother liquor is separated and recycled.

2. The composite additive according to claim 1 is used in conjunction with cavitation jet to prepare flaky nano-calcium hydroxyphosphate in a clarification system, characterized in that: The citrate in step 1) is sodium citrate or potassium citrate.

3. The composite additive according to claim 1 is used in conjunction with cavitation jet to prepare flaky nano-calcium hydroxyphosphate in a clarification system, characterized in that: The compounded additive in step 1) is 0.5-2% of the mass of calcium chloride.

4. The composite additive according to claim 1, 2 or 3 is used in conjunction with cavitation jet to prepare flaky nano-calcium hydroxyphosphate in a clarification system, characterized in that: The concentration of the phosphoric acid solution in step 1) is 15-45%.

5. The composite additive according to claim 4 is used in conjunction with cavitation jet to prepare flaky nano-calcium hydroxyphosphate in a clarification system, characterized in that: In the step 2), the reaction temperature is 30-50°C, and the aging temperature is 60-80°C.

6. The composite additive according to claim 5 is used in conjunction with cavitation jet to prepare flaky nano-calcium hydroxyphosphate in a clarification system, characterized in that: The nozzle diameter of the jet device in step 2) is 0.05-0.3 mm.

7. The composite additive according to claim 6 is used to prepare flaky nano-calcium hydroxyphosphate in a clarification system in cooperation with a cavitation jet, characterized in that: The pH value in the step 2) is 8.5 to 11.

5.

8. The composite additive according to claim 1 or 2 or 3 or 5 or 6 or 7 is used in conjunction with cavitation jet to prepare flaky nano-calcium hydroxyphosphate in a clarification system, characterized in that: The yield of the prepared calcium hydroxyphosphate can reach 97.8%, and the specific surface area can reach 140m 2 / g, and the particle size distribution is 25-35nm.