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Microwave preparation method of alpha-calcium sulfate hemihydrate

A technology of calcium sulfate hemihydrate and calcium sulfate dihydrate, which is applied in the field of preparation of α-calcium sulfate hemihydrate, can solve the problems of multiple impurities, low added value, high free water, etc., and achieve the effect of shortening the reaction time

Active Publication Date: 2017-02-22
SOUTH CHINA UNIV OF TECH +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The main component of this salt gypsum is the same as natural gypsum, which is calcium sulfate dihydrate, but it has relatively high free water and more impurities. Its comprehensive utilization methods mainly include: ① Used in the cement industry, that is, pressing chemical gypsum into balls It can be used as a cement retarder instead of natural gypsum, which has the advantages of simple process and large processing capacity, but low added value

Method used

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  • Microwave preparation method of alpha-calcium sulfate hemihydrate
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Examples

Experimental program
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Effect test

Embodiment 1

[0029] Add 5.0g calcium sulfate dihydrate and 100mL mixed salt solution (calcium chloride 100g / L, sodium chloride 50g / L) into the reaction vessel, put it into the CW-2000 ultrasonic / microwave collaborative extraction / reaction instrument, set the program: Under the combined action of ultrasonic waves and microwaves, the temperature of the reaction system was raised to 105°C at a heating rate of 4°C / min, and then kept at a constant temperature for 2 hours; immediately after the reaction, the reaction mixture was filtered and washed, and the solid product was dried in an oven at 60°C After 19 hours, α-calcium sulfate hemihydrate was obtained.

[0030] figure 2 It is the scanning electron micrograph of the prepared α-calcium sulfate hemihydrate, by figure 2 It can be seen that the prepared α-calcium sulfate hemihydrate has a uniform fibrous structure with an average length of 112.9 μm and an average diameter of 7.37 μm.

Embodiment 2

[0032] Add 5.0g calcium sulfate dihydrate and 100mL mixed salt solution (calcium chloride 100g / L, sodium chloride 50g / L) into the reaction vessel, put it into the CW-2000 ultrasonic / microwave collaborative extraction / reaction instrument, set the program: Under the combined action of ultrasonic waves and microwaves, the temperature of the reaction system was raised to 105°C at a heating rate of 8°C / min, and then kept at a constant temperature for 3 hours; immediately after the reaction, the reaction mixture was filtered and washed, and the solid product was placed in an oven at 60°C Dry for 12 hours to obtain α-calcium sulfate hemihydrate.

[0033] image 3 is the scanning electron micrograph of the prepared α-calcium sulfate hemihydrate, by image 3 It can be seen that the prepared α-calcium sulfate hemihydrate has a uniform fibrous structure with an average length of 113.78 μm and an average diameter of 8.31 μm.

[0034] Figure 4 is the XRD pattern of the prepared α-calcium...

Embodiment 3

[0040] Add 8.0g calcium sulfate dihydrate and 100mL mixed salt solution (calcium chloride 80g / L, sodium chloride 50g / L) into the reaction vessel, put it into the CW-2000 ultrasonic / microwave collaborative extraction / reaction instrument, set the program: Under the combined action of ultrasonic waves and microwaves, the temperature of the reaction system was raised to 105°C at a heating rate of 2°C / min, and then kept at a constant temperature for 3 hours; immediately after the reaction, the reaction mixture was filtered and washed, and the solid product was placed in an oven at 60°C Dry for 18 hours to obtain α-calcium sulfate hemihydrate. The crystal morphology of the obtained α-calcium sulfate hemihydrate was a uniform fibrous structure, the average crystal length was 110.78 μm, and the average diameter was 7.31 μm.

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Abstract

The invention discloses a microwave preparation method of alpha-calcium sulfate hemihydrate. The method includes the steps of: adding calcium sulphate dehydrate into an aqueous solution containing calcium chloride and sodium chloride, carrying out microwave heating reaction under the action of ultrasound, and conducting filtering, washing and drying to obtain alpha-calcium sulfate hemihydrates. The method provided by the invention is characterized in that it utilizes the synergistic effect of microwave and ultrasonic wave to accelerate the reaction rate and reduce the reaction time, and the prepared alpha-calcium sulfate hemihydrates crystal is a fibrous structure, and has uniform shape and size and high crystallinity.

Description

technical field [0001] The invention belongs to the field of preparation of α-calcium sulfate hemihydrate, in particular to a microwave preparation method of α-calcium sulfate hemihydrate. Background technique [0002] Calcium sulfate dihydrate (DH) can be heated and dehydrated to obtain calcium sulfate hemihydrate (HH), and there are two types of α-type and β-type according to different preparation processes. β-HH (that is, building gypsum, or ordinary gypsum powder) usually has a loose structure and low physical strength, and is mainly used to produce plasterboard, gypsum blocks, ceilings, gypsum composite cementitious materials, etc.; α-HH is a kind of It is a type of gypsum with excellent performance and high added value. Its products have the advantages of complete crystal form, large crystal grains, high hardness, high strength, and good wear resistance. They are widely used in molds, models, coatings, papermaking, arts and crafts, and architecture. , medicine and oth...

Claims

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Application Information

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IPC IPC(8): C04B11/02
CPCC04B11/02
Inventor 彭峰朱明丽谢谦曹正伟李俊杰
Owner SOUTH CHINA UNIV OF TECH
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