Normal-temperature normal-pressure acid-free alkali-free preparation method of nanoscale alpha semi-hydrated gypsum

Abstract

The invention belongs to the technical field of gypsum production, and particularly relates to a normal-temperature normal-pressure acid-free alkali-free preparation method of nanoscale alpha semi-hydrated gypsum. A normal-temperature normal-pressure acid-free alkali-free preparation method of nanoscale alpha semi-hydrated gypsum comprises the following steps: respectively preparing a CuSO4 solution and a CaCl2 ethanol solution, dropwise adding the CuSO4 solution into the CaCl2 ethanol solution, respectively carrying out centrifugation, separation and washing treatment, and collecting a solid product; and drying the solid product to obtain the alpha-semi-hydrated gypsum nanocrystal. According to the preparation method disclosed by the invention, a CuSO4 aqueous solution is dropped into a stirred or ultrasonic CaCl2 ethanol solution to synthesize the alpha-hemihydrate gypsum nanocrystal by utilizing a high-concentration ethanol environment under the process conditions of normal temperature, normal pressure, acid-free and alkali-free, the alpha-hemihydrate gypsum nanocrystal is separated out in a precipitation form, and the CuCl2 is dissolved in ethanol, so that the alpha-hemihydrate gypsum nanocrystal is separated out. The purity of the alpha-semi-hydrated gypsum nanocrystal precipitate is ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gypsum production, and particularly relates to a normal-temperature and normal-pressure acid-free and alkali-free preparation method of nanoscale alpha hemihydrate gypsum. BACKGROUND

[0002] As a high-performance biomedical material and industrial filler, the morphology-controllable synthesis of alpha hemihydrate gypsum nanocrystals (α-CaSO4·0.5H2O) is of great importance. The current mainstream methods have significant limitations: the hydrothermal synthesis method requires high-temperature and high-pressure conditions above 120℃ (Journal of Applied Chemistry. 18 (1968) 307-312; Processes. 11 (2023) 1809.), which has high energy consumption and equipment cost; the microemulsion method (such as W / O system) relies on expensive surfactants such as cetyltrimethylammonium bromide (Langmuir. 15 (1999) 1993-2002; Langmuir. 28 (2012) 14137-14142.), and the organic residues lead to a decrease in product purity; the acid and alkali medium method needs to add strong acid / alkali (such as HCl / NaOH) to regulate the crystallization environment (Journal of Materials Chemistry. 13 (2003) 1817-1821.), which produces corrosive waste liquid and has high requirements for production equipment; the template-directed method uses expensive organic templates, which not only increases the production cost but also needs a complex template removal process (Ultrasonics Sonochemistry. 21 (2014) 1117-1131.), making it difficult to be applied on a large scale. Therefore, it is an urgent need to develop a green process for precisely synthesizing pure alpha hemihydrate gypsum nanocrystals under room temperature and normal pressure without adding acid and alkali, which is low in cost and can break through the technical bottleneck. SUMMARY

[0003] To solve the above-mentioned prior art, a normal-temperature and normal-pressure acid-free and alkali-free preparation method of nanoscale alpha hemihydrate gypsum is provided.

[0004] A normal-temperature and normal-pressure acid-free and alkali-free preparation method of nanoscale alpha hemihydrate gypsum, comprising the following steps: preparing CuSO4 solution and CaCl2 ethanol solution respectively, adding the CuSO4 solution into the CaCl2 ethanol solution, and then performing centrifugation, separation and washing treatment respectively, and collecting the solid product; drying the solid product to obtain alpha hemihydrate gypsum nanocrystals.

[0005] Further, the concentration of the CuSO4 solution is 40-120 g / L.

[0006] Furthermore, the method for preparing CaCl2 ethanol solution is as follows: CaCl2 is dissolved in anhydrous ethanol, and after uniform dissolution, CaCl2 ethanol solution is obtained; wherein, based on the molar ratio, CuSO4:CaCl2=1:1, and the concentration of CaCl2 ethanol solution is 0.8~2.4 g / L.

[0007] Furthermore, the dropping rate is 0.01~0.05 mL / s.

[0008] Furthermore, the centrifugation process was carried out at a speed of 6000 r / min for 5 min; the washing solvent was anhydrous ethanol.

[0009] Furthermore, the drying temperature conditions are 40~60℃, and the time conditions are 12~16 h.

[0010] The nano-sized α-hemihydrate gypsum prepared above.

[0011] Furthermore, the diameter of the nanoscale α-hemihydrate gypsum is 30-210 nm, and the aspect ratio is 3.5-10.0.

[0012] Furthermore, the diameter of the nano-sized α-hemihydrate gypsum is 30-80 nm, and the aspect ratio is 3.5-4.5.

[0013] The beneficial effects of this invention are as follows: (1) The preparation method described in this invention uses a process under normal temperature and pressure, without acid or alkali, and utilizes a high concentration of ethanol environment (ethanol concentration higher than 90%) to synthesize α-hemihydrate gypsum nanocrystals by dropping CuSO4 aqueous solution into a CaCl2 ethanol solution under stirring or sonication. The α-hemihydrate gypsum nanocrystals are separated in the form of precipitation. Since CuCl2 is soluble in ethanol, the purity of the α-hemihydrate gypsum nanocrystal precipitate is guaranteed.

[0014] (2) Compared with the hydrothermal method (reaction conditions of 120℃ and 0.2 MPa), the preparation method of the present invention is carried out at room temperature and atmospheric pressure, saving 92% of energy. Compared with the microemulsion method, the amount of organic reagents is reduced by 100%, which significantly reduces the synthesis cost. In addition, the present invention does not require complex steps such as pH adjustment and template removal, and the process time is shortened to 10 minutes (traditional method > 2 h). (3) The preparation method described in this invention does not require the use of equipment adapted to high temperature and high pressure, strong acid and strong alkali, which can reduce equipment investment costs; (4) The preparation method described in this invention does not require expensive template reagents. Furthermore, ethanol and copper chloride can be recovered by distillation. The former is used to repeatedly prepare α-hemihydrate gypsum nanocrystals, while the latter is used as a co-product to further reduce production costs. Attached Figure Description

[0015] Figure 1 This is a SEM image of the trigonal α-hemihydrate gypsum obtained in Example 2 of this invention; Figure 2 This is the XRD pattern of trigonal α-hemihydrate gypsum obtained in Example 2 of this invention; Figure 3 The TG-DSC of the trigonal α-hemihydrate gypsum obtained in Example 2 of this invention; Figure 4 This is a SEM image of the α-hemihydrate gypsum prepared in the comparative example of this invention. Figure 5 This is the XRD pattern of α-hemihydrate gypsum prepared according to the comparative example of this invention. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the equipment and reagents used in the present invention are commercially available products conventional in this technical field.

[0017] The first aspect of this invention is to protect a method for preparing nano-sized α-hemihydrate gypsum at room temperature and pressure without acid or alkali, comprising the following steps: S1. Preparation of CuSO4 solution: Weigh a certain amount of CuSO4 and place it in a beaker, add 5-10 mL of water to form CuSO4 solution, wherein the concentration of CuSO4 solution is 40-120 g / L, specifically 40 g / L, 60 g / L, 80 g / L, 100 g / L or 120 g / L. S2. Preparation of CaCl2 ethanol solution: Weigh CaCl2 with a molar ratio of 1:1 to CuSO4 and place it in a beaker. Add 100 mL of anhydrous ethanol to form a CaCl2 ethanol solution. Place the beaker containing the CaCl2 ethanol solution in a mechanical stirrer or ultrasonic oscillator and shake it thoroughly until homogeneous. Finally, the concentration of the CaCl2 ethanol solution is 0.8~2.4 g / L, specifically 0.8 g / L, 1.2 g / L, 1.6 g / L, 2.0 g / L, and 2.4 g / L.

[0018] S3. Add CuSO4 aqueous solution dropwise to CaCl2 ethanol solution; after the addition is complete, wait 60 s, remove the beaker, and transfer it to a centrifuge tube; place the centrifuge tube in a centrifuge and run at 6000 r / min for 5 min to separate the liquid and solid products; wash the solid product three times with anhydrous ethanol by centrifugation, collect the solid product, and vacuum dry it at 40℃ for 6 h to obtain nano-sized α-hemihydrate gypsum. Simultaneously, collect and distill the centrifuged liquid to obtain ethanol as the vapor condensate, which can be recycled for the preparation of α-hemihydrate gypsum nanocrystals; the distillation residue is copper chloride, an economically valuable compound.

[0019] The second aspect of this invention is to protect the nanoscale α-hemihydrate gypsum obtained by the above preparation method. This nanoscale α-hemihydrate gypsum is a micro-nano-sized trigonal α-hemihydrate gypsum with a diameter of 30-210 nm and an aspect ratio of 3.5-10.0. Preferably, the diameter is 30-80 nm and the aspect ratio is 3.5-4.5.

[0020] <Example 1> A method for preparing nano-sized α-hemihydrate gypsum at room temperature and pressure without acid or alkali includes the following steps: The concentration of CuSO4 aqueous solution was controlled at 40 g / L, and the concentration of CaCl2 ethanol solution was controlled at 1.6 g / L. The beaker containing CaCl2 ethanol solution was placed in a mechanical stirrer and stirred at 400 r / min. At the same time, CuSO4 aqueous solution was added dropwise to CaCl2 ethanol solution at a rate of 0.05 mL / s. After the addition was completed, wait for 60 s, stop stirring, and transfer to a centrifuge tube. The centrifuge tube was placed in a centrifuge and run at 6000 r / min for 5 min to separate the liquid and solid products. The solid product was washed three times with anhydrous ethanol by centrifugation, and the solid product was collected and vacuum dried at 40℃ for 6 h to obtain pure trigonal α-hemihydrate gypsum.

[0021] Testing revealed that the trigonal α-hemihydrate gypsum prepared in this embodiment has a diameter of 40-150 nm and an aspect ratio of 4.0-10.0.

[0022] <Example 2> A method for preparing nano-sized α-hemihydrate gypsum at room temperature and pressure without acid or alkali includes the following steps: The concentration of CuSO4 aqueous solution was controlled at 40 g / L, and the concentration of CaCl2 ethanol solution was controlled at 1.6 g / L. The beaker containing CaCl2 ethanol solution was placed in an ultrasonic oscillator and oscillated at a frequency of 40 kHz. At the same time, CuSO4 aqueous solution was added dropwise to CaCl2 ethanol solution at a rate of 0.05 mL / s. After the addition was completed, the oscillation was stopped after 60 s, and the solution was transferred to a centrifuge tube. The centrifuge tube was placed in a centrifuge and run at 6000 r / min for 5 min to separate the liquid and solid products. The solid product was washed three times with anhydrous ethanol by centrifugation, and the solid product was collected and vacuum dried at 40 °C for 6 h to obtain pure trigonal α-hemihydrate gypsum.

[0023] Testing revealed that the trigonal α-hemihydrate gypsum prepared in this embodiment has a diameter of 30-80 nm and an aspect ratio of 3.5-4.5.

[0024] The SEM, XRD, and TG-DSC images of the trigonal α-hemihydrate gypsum prepared in this embodiment were obtained, and the results are as follows: Figures 1-3 As shown.

[0025] Depend on Figure 1 It can be seen that the trigonal α-hemihydrate gypsum prepared by the method is a short rod-shaped nanoparticle with a uniform and stable morphology.

[0026] Depend on Figure 2 It can be seen that the characteristic peaks of the trigonal α-hemihydrate gypsum prepared by the method are highly consistent with the standard spectrum of trigonal hemihydrate gypsum (PDF NO. 01-81-1848). In addition, no other impurity peaks were found, indicating that the purity is high.

[0027] Depend on Figure 3 It can be seen that the samples prepared by the method for trigonal α-hemihydrate gypsum exhibit a mass decrease after endothermic heating between 97-130℃, and the mass decreases to 6.34% of the initial total mass, which is consistent with the characteristics of hemihydrate gypsum. In addition, DSC shows a continuous exothermic peak after endothermic heating, which is consistent with the characteristics of α-hemihydrate gypsum.

[0028] <Example 3> A method for preparing nano-sized α-hemihydrate gypsum at room temperature and pressure without acid or alkali includes the following steps: The concentration of CuSO4 aqueous solution was controlled at 120 g / L, and the concentration of CaCl2 ethanol solution was controlled at 2.4 g / L. The beaker containing CaCl2 ethanol solution was placed in an ultrasonic oscillator and oscillated at a frequency of 40 kHz. At the same time, CuSO4 aqueous solution was added dropwise to CaCl2 ethanol solution at a rate of 0.05 mL / s. After the addition was completed, the oscillation was stopped after 60 s, and the solution was transferred to a centrifuge tube. The centrifuge tube was placed in a centrifuge and run at 6000 r / min for 5 min to separate the liquid and solid products. The solid product was washed three times with anhydrous ethanol by centrifugation, and the solid product was collected and vacuum dried at 40 °C for 6 h to obtain pure trigonal α-hemihydrate gypsum.

[0029] The diameter of the trigonal α-hemihydrate gypsum prepared in this embodiment is 30-210 nm, and the aspect ratio is 3.5-7.0.

[0030] <Comparative Example> The concentration of CuSO4 aqueous solution was controlled at 120 g / L and the concentration of CaCl2 ethanol solution was controlled at 2.4 g / L. The CuSO4 aqueous solution was slowly poured into the CaCl2 ethanol solution. After the CuSO4 aqueous solution was completely poured in, wait for 60 s and then transfer it to a centrifuge tube. The centrifuge tube was placed in a centrifuge and run at 6000 r / min for 5 min to separate the liquid and solid products. The solid product was washed three times with anhydrous ethanol by centrifugation, and the solid product was collected and vacuum dried at 40℃ for 6 h to obtain α-hemihydrate gypsum.

[0031] The SEM and XRD images of the α-hemihydrate gypsum prepared in this comparative example are shown below. Figures 4-5 As shown.

[0032] Depend on Figure 4 It can be seen that the α-hemihydrate gypsum prepared by this method contains only a small amount of nano-hemihydrate gypsum structure, while the rest are plate-like interlocking block structures.

[0033] Depend on Figure 5 It can be seen that the α-hemihydrate gypsum prepared by the method has characteristic peaks corresponding to the standard spectra of hemihydrate gypsum (PDF NO.01-81-1848) and dihydrate gypsum (PDF NO.01-70-1848), indicating that the control sample is a mixture of hemihydrate gypsum and dihydrate gypsum and has no practical value.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing nano-sized α-hemihydrate gypsum at room temperature and pressure without acid or alkali, characterized in that, Includes the following steps: CuSO4 solution and CaCl2 ethanol solution were prepared separately. After adding CuSO4 solution dropwise to CaCl2 ethanol solution, the solid products were collected after centrifugation, separation and washing. Nanoscale α-hemihydrate gypsum can be obtained by drying the solid product.

2. The method for preparing nano-scale α-hemihydrate gypsum at room temperature and pressure without acid or alkali, according to claim 1, is characterized in that, The concentration of the CuSO4 solution is 40~120 g / L.

3. The method for preparing nano-sized α-hemihydrate gypsum at room temperature and pressure without acid or alkali, according to claim 1, is characterized in that... The method for preparing CaCl2 ethanol solution is as follows: CaCl2 is uniformly dissolved in anhydrous ethanol to obtain CaCl2 ethanol solution; In terms of molar ratio, CuSO4:CaCl2 = 1:1; The concentration of CaCl2 ethanol solution is 0.8~2.4 g / L.

4. The method for preparing nano-sized α-hemihydrate gypsum at room temperature and pressure without acid or alkali, according to claim 1, is characterized in that... The dropping rate is 0.01~0.05 mL / s.

5. The method for preparing nano-scale α-hemihydrate gypsum at room temperature and pressure without acid or alkali, according to claim 1, is characterized in that... The centrifugation conditions were 6000 r / min and 5 min; the washing solvent was anhydrous ethanol.

6. The method for preparing nano-sized α-hemihydrate gypsum at room temperature and pressure without acid or alkali, according to claim 1, is characterized in that, The drying temperature conditions are 40~60℃, and the time conditions are 12~16 h.

7. Nanoscale α-hemihydrate gypsum prepared according to any one of claims 1-6.

8. The nanoscale α-hemihydrate gypsum according to claim 7, characterized in that, The diameter of nanoscale α-hemihydrate gypsum is 30-210 nm, and the aspect ratio is 3.5-10.

0.

9. The nanoscale α-hemihydrate gypsum according to claim 8, characterized in that, The diameter of nanoscale α-hemihydrate gypsum is 30-80 nm, and the aspect ratio is 3.5-4.5.

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