Preparation method of flaky nano hydroxyl calcium phosphate based on compound additive coupling cavitation jet flow

Abstract

The invention discloses a preparation method of flaky nano hydroxyl calcium phosphate based on compound additive coupling cavitation jet. An SDBS / AEO9 / citrate ternary compound additive system is created for the first time, and oriented growth of the hydroxyl calcium phosphate lamellar crystals is achieved through a molecular-level synergistic effect. A high-pressure cavitation jet flow technology is adopted in a breakthrough mode, crystal nanocrystallization crushing and sheet structure recombination are synchronously achieved through the synergistic effect of cavitation bubble collapse micro jet flow 300-1000 m / s and an instantaneous extreme physical field, the ultra-high shear rate generated by the micro jet flow is larger than 107 s <-1 >, crystals are accurately crushed to the submicron level, and 001 crystal face integrity is selectively reserved; meanwhile, particles can be separated out at the nanoscale by utilizing a cavitation collapse high-energy field, and the crushed wafer is driven to be subjected to in-situ recombination along the 001 surface, so that the radius-thickness ratio is increased by 40-60%, an ultrathin lamellar crystal with the average thickness is obtained on the premise that the crystallinity is as high as 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 a method for preparing flaky nano-calcium hydroxyphosphate based on compound additives coupled with cavitation jets. 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] Calcium hydroxyphosphate (also known as hydroxyapatite) is a major component of active bone in animals and exhibits excellent biological activity and absorption efficiency. Nanoscale calcium phosphate salts offer improved dispersibility and elemental utilization. Due to their selective permeability within the body, they can be used as special nutrients or drug carriers to improve their utilization, reduce dosage, and reduce side effects. Currently, after extensive research and testing, this technology has been widely explored in areas such as artificial bones, medicine, food, daily chemicals, and new industrial materials. Numerous research reports have been published on the production methods and application directions of calcium hydroxyphosphate and nanoscale calcium phosphate salts.

[0004] Traditional chemical precipitation methods often produce rod-shaped or granular products. Flake-shaped structures require the addition of a template, but template residue can lead to biotoxicity. Hydrothermal methods can produce flake HAP, but the product is relatively thick, and the high-temperature and high-pressure reaction conditions can deactivate and decompose the surfactant, resulting in uneven mass transfer and stacking. In microemulsion methods, oil-water interfacial tension disrupts crystal growth, resulting in poor emulsion stability and a wide particle size distribution. Therefore, research into preparation methods is urgently needed to obtain flake-shaped nanoscale calcium hydroxyphosphate. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing sheet-like nano-hydroxy calcium phosphate based on compound additives coupled with cavitation jets.

[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 based on compound additive coupled with cavitation jet, comprising the following steps:

[0008] 1) Calcium hydroxide is added to an aqueous solution and stirred to obtain a white emulsion, which is placed in a reaction kettle. A composite additive of sodium dodecylbenzenesulfonate: AEO9: citrate in a ratio of 1:1-4:4-10 is then added and stirred evenly. This is the calcium source emulsion, and a phosphoric acid solution with a concentration of 15-45% is prepared for use.

[0009] 2) At a reaction temperature of 30 to 50° C., a phosphoric acid solution is sprayed into the calcium source emulsion using a cavitation jet device. After the addition of the phosphoric acid solution, the pH value is controlled. After the addition, the reaction temperature is increased and aging is performed 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, and the solid-liquid separation and drying are performed to obtain product-grade calcium hydroxyphosphate. The mother liquor is separated and returned to be used for the preparation of calcium source emulsion and base liquid.

[0011] As a further improvement, in step 1) of the present invention, the mass ratio of calcium hydroxide to water is 1:2-4.

[0012] As a further improvement, in step 1) of the present invention, the citrate is sodium citrate or potassium citrate.

[0013] As a further improvement, the compounded additive in step 1) of the present invention is 0.5-2% of the mass of calcium hydroxide.

[0014] As a further improvement, in step 2) of the present invention, 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 the calcium hydroxyphosphate prepared by the present invention can reach 98.5%, and the specific surface area can reach 135m 2 / g, and the particle size distribution is 30-50nm.

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

[0019] 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.

[0020] 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

[0021] The present invention discloses a method for preparing flaky nano-calcium hydroxyphosphate based on compound additives coupled with cavitation jets. 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.

[0022] Example 1

[0023] (1) 300 g of calcium hydroxide and 600 g of water were added to a reaction apparatus and stirred to obtain a white emulsion. 1.5 g of a composite additive (sodium dodecylbenzenesulfonate: AEO9: sodium citrate = 1:1:4) was added and stirred evenly. 1589 g of a 15% phosphoric acid solution was prepared for later use.

[0024] (2) Set the temperature to 30°C and inject 15% phosphoric acid solution into the calcium source emulsion through a cavitation jet device (nozzle = 0.05 mm). After the addition of the phosphoric acid solution, control the pH value to 8.5. After the addition, increase the reaction temperature to 60°C and age for 2 hours.

[0025] (3) After the reaction is completed, the temperature is lowered to room temperature to obtain a suspension system containing flaky crystals. The solid-liquid separation and drying are performed to obtain product-grade calcium hydroxyphosphate with a yield of 95.8%, a particle size range of 70 to 100 nm, and a specific surface area of ​​105.3 m 2 / g, the separated mother liquor is returned for use as calcium source emulsion and base liquid preparation.

[0026] Example 2

[0027] (1) 300 g of calcium hydroxide and 900 g of water were added to a reaction apparatus and stirred to obtain a white emulsion. 3 g of a composite additive (sodium dodecylbenzenesulfonate: AEO9: potassium citrate = 1:2:6) was added and stirred evenly. 953.5 g of a 25% phosphoric acid solution was prepared for later use.

[0028] (2) Set the temperature to 40°C and inject 25% phosphoric acid solution into the calcium source emulsion through a cavitation jet device (nozzle = 0.1 mm). After the addition of the phosphoric acid solution, control the pH value to 10.5. After the addition, increase the reaction temperature to 70°C and age for 3 hours.

[0029] (3) After the reaction, the temperature was lowered to room temperature to obtain a suspension system containing flaky crystals. The solid-liquid separation and drying were performed to obtain product-grade calcium hydroxyphosphate with a yield of 98.5%, a particle size range of 50 to 70 nm, and a specific surface area of ​​135 m 2 / g, the separated mother liquor is returned for use as calcium source emulsion and base liquid preparation.

[0030] Example 3

[0031] (1) 300 g of calcium hydroxide and 900 g of water were added to a reaction apparatus and stirred to obtain a white emulsion. 3 g of a composite additive (sodium dodecylbenzenesulfonate: AEO9: sodium citrate = 1:2:6) was added and stirred evenly. 953.5 g of a 25% phosphoric acid solution was prepared for later use.

[0032] (2) Set the temperature to 40°C and inject 25% phosphoric acid solution into the calcium source emulsion through a cavitation jet device (nozzle = 0.1 mm). After the addition of the phosphoric acid solution, control the pH value to 10.5. After the addition, increase the reaction temperature to 70°C and age for 3 hours.

[0033] (3) After the reaction, the temperature was lowered to room temperature to obtain a suspension system containing flaky crystals. The solid-liquid separation and drying were performed to obtain product-grade calcium hydroxyphosphate with a yield of 98.5%, a particle size range of 30 to 50 nm, and a specific surface area of ​​135 m 2 / g, the separated mother liquor is returned for use as calcium source emulsion and base liquid preparation.

[0034] Example 4

[0035] (1) 300 g of calcium hydroxide and 1200 g of water were added to a reaction apparatus and stirred to obtain a white emulsion. 6 g of a composite additive (sodium dodecylbenzenesulfonate: AEO9: citrate = 1:4:10) was added and stirred evenly. 529.7 g of a 45% phosphoric acid solution was prepared for standby use.

[0036] (2) Set the temperature to 50°C and inject 45% phosphoric acid solution into the calcium source emulsion through a cavitation jet device (nozzle = 0.3 mm). After the addition of the phosphoric acid solution, the pH value was controlled to 11.5. After the addition, the reaction temperature was raised to 80°C and aged for 4 hours.

[0037] (3) After the reaction, the temperature was lowered to room temperature to obtain a suspension system containing flaky crystals. The solid-liquid separation and drying were performed to obtain product-grade calcium hydroxyphosphate with a yield of 92.8%, a particle size range of 60 to 80 nm, and a specific surface area of ​​108.3 m 2 / g, the separated mother liquor is returned for use as calcium source emulsion and base liquid preparation.

[0038] Comparative Example 1

[0039] The additive added was 3g of sodium dodecylbenzenesulfonate, and other conditions remained unchanged. The yield was 97.5% and the specific surface area was 55.8m 2 / g.

[0040] Comparative Example 2

[0041] The additive added was 3g of AEO9. The yield was 96.8% under other conditions unchanged. The particle size range was 58.6m 2 / g.

[0042] Comparative Example 3

[0043] The compound additive added was 3g of sodium citrate, and the other conditions remained unchanged. The yield was 97.2% and the specific surface area was 56.2m 2 / g.

[0044] Comparative Example 4

[0045] The compound additive added was 3g sodium dodecylbenzenesulfonate: AEO9 = 1:2, and the other conditions remained unchanged. The yield was 97.4% and the specific surface area was 83m 2 / g.

[0046] Comparative Example 5

[0047] The compound additive added was 3g sodium dodecylbenzenesulfonate: sodium citrate = 1:6, and the other conditions remained unchanged. The yield was 97.2% and the specific surface area was 80m 2 / g.

[0048] Comparative Example 6

[0049] The added compound additive is 3g of AEO9: sodium citrate = 1:3, and the other conditions remain unchanged. The yield is 97.5% and the specific surface area is 82m 2 / g.

[0050] It can be seen that compared with Example 3, Control Examples 1-6 use traditional single surfactants or compound additives mixed in pairs, and the synergistic effect of the three is not achieved, resulting in the inability of the crystals to form flaky calcium hydroxyphosphate, and the particle size distribution range is wide, and the particle size is large, the specific surface area is small, and its effect as a dispersant is greatly reduced.

[0051] Comparative Example 7

[0052] The feeding method was changed to a common jet device instead of a cavitation jet, and other conditions remained unchanged. The yield was 98.2%, the particle size range was 60-80 nm, and the specific surface area was 95 m 2 / g.

[0053] It can be seen that, compared with Example 3, Control Example 7 uses only a conventional jet device without ultrasonic cavitation assistance, and the two do not achieve a synergistic effect, resulting in the prepared calcium hydroxyphosphate having a wide particle size distribution range and a small specific surface area, and cannot form ultra-thin flake crystals, and its effect as a dispersant is greatly reduced.

[0054] Comparative Example 8

[0055] (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.

[0056] (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.

[0057] (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.

[0058] It can be seen that, compared with Example 3, in Control Example 2, 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.

[0059] 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. A method for preparing sheet-like nano-hydroxy calcium phosphate based on compound additives coupled with cavitation jets, characterized in that: The following steps are involved: 1) Calcium hydroxide is added to an aqueous solution and stirred to obtain a white emulsion, which is placed in a reaction kettle. A composite additive of sodium dodecylbenzenesulfonate: AEO9: citrate in a ratio of 1:1-4:4-10 is then added and stirred evenly. This is the calcium source emulsion, and a phosphoric acid solution with a concentration of 15-45% is prepared for use. 2) At a reaction temperature of 30 to 50° C., a phosphoric acid solution is sprayed into the calcium source emulsion using a cavitation jet device. After the addition of the phosphoric acid solution, the pH value is controlled. After the addition, the reaction temperature is increased and aging is performed 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, and the solid-liquid separation and drying are performed to obtain product-grade calcium hydroxyphosphate. The mother liquor is separated and returned to be used for the preparation of calcium source emulsion and base liquid.

2. The method for preparing sheet-like nano-hydroxy calcium phosphate based on compound additive coupled cavitation jet according to claim 1, characterized in that: In the step 1), the mass ratio of calcium hydroxide to water is 1:2-4.

3. The method for preparing sheet-like nano-hydroxy calcium phosphate based on compound additive coupled cavitation jet according to claim 2, characterized in that: In step 1), the citrate is sodium citrate or potassium citrate.

4. The method for preparing sheet-like nano-hydroxy calcium phosphate based on compound additive coupled cavitation jet according to claim 3, characterized in that: The compounded additive in step 1) is 0.5-2% of the mass of calcium hydroxide.

5. The method for preparing sheet-like nano-hydroxy calcium phosphate based on compound additive coupled cavitation jet according to claim 1, 2, 3 or 4, characterized in that: In the step 2), the aging temperature is 60-80°C.

6. The method for preparing sheet-like nano-hydroxy calcium phosphate based on compound additive coupled cavitation jet according to claim 5, characterized in that: The nozzle diameter of the jet device in step 2) is 0.05-0.3 mm.

7. The method for preparing sheet-like nano-hydroxy calcium phosphate based on compound additive coupled with cavitation jet according to claim 6, characterized in that: The pH value in the step 2) is 8.5 to 11.

5.

8. The method for preparing sheet-like nano-hydroxy calcium phosphate based on compound additive coupled cavitation jet according to claim 1 or 2 or 3 or 4 or 6 or 7, characterized in that: The yield of the prepared calcium hydroxyphosphate can reach 98.5%, and the specific surface area can reach 135m 2 / g, and the particle size distribution is 30-50nm.