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Method for preparing calcium sulfate crystal whiskers by using impurity-containing gypsum as raw material

A technology of calcium sulfate whisker, calcium sulfate hemihydrate, applied in chemical instruments and methods, calcium/strontium/barium sulfate, single crystal growth, etc. Calcium sulfate is difficult to dissolve and transform, and the comprehensive utilization rate is less than 10%, so as to achieve the effects of high added value, regular morphology and large aspect ratio.

Inactive Publication Date: 2010-06-16
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, my country's phosphorus chemical industry discharges nearly 40 million tons of phosphogypsum every year, and the cumulative stockpiles have exceeded hundreds of millions of tons, but the comprehensive utilization rate is still less than 10%.
The shortcomings of the existing method are that the impurities in the impurity-containing gypsum are not removed, and the fineness of the raw materials is also lack of control, resulting in irregular appearance of the formed whisker products, small length, and low aspect ratio
Calcium sulfate dihydrate with coarse particle size and complete crystallization is difficult to dissolve and transform, and it is impossible to prepare calcium sulfate whiskers with regular shape and high aspect ratio

Method used

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  • Method for preparing calcium sulfate crystal whiskers by using impurity-containing gypsum as raw material
  • Method for preparing calcium sulfate crystal whiskers by using impurity-containing gypsum as raw material
  • Method for preparing calcium sulfate crystal whiskers by using impurity-containing gypsum as raw material

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Experimental program
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Effect test

Embodiment 1

[0045] Take by weighing natural gypsum (main composition: CaSO 4 2H 2 O: 99wt%, SiO 2 : 0.5wt%, Al 2 o 3 : 0, Fe 2 o 3 :0, MgO:0, P 2 o 5 :0,F:0,CO 3 : 0) 100g, sodium chloride 1g, the two are mixed and roasted at 300°C for 1h to obtain calcined sand. Add calcined sand to an aqueous solution containing 0.1mol / L hydrochloric acid and 0.1mol / L ethylenediaminetetraacetic acid to prepare a suspension with a solid content of 1 wt%, and react for 5 hours at 20°C with stirring (500 rpm) After filtering and washing the above slurry, add a sodium hydroxide solution with a concentration of 0.1mol / L to make a suspension with a solid content rate of 1wt%, react at 20°C for 5h under stirring (500 rpm), and filter 1. After washing, the calcium sulfate dihydrate precursor is obtained.

[0046] Put the calcium sulfate dihydrate precursor into the autoclave, add 0.005mol / L sodium chloride solution to adjust the solid content to 0.1wt%, and perform a hydrothermal reaction at 100°C for...

Embodiment 2

[0048] Take by weighing phosphogypsum (main composition: CaSO 4 2H 2 O: 70wt%, SiO 2 : 2wt%, Al 2 o 3 : 5wt%, Fe 2 o 3 : 5wt%, P 2 o 5 : 5wt%, F: 2wt%, CO 3 : 2wt%) 100g, potassium chloride 20g, after the two are mixed, roast at 800°C for 5h to obtain calcined sand. Add calcined sand to an aqueous solution containing 5mol / L hydrochloric acid and 0.5mol / L succinic acid to make a suspension with a solid content of 30wt%, and react for 1 hour at 100°C under stirring (50 rpm); After the slurry is filtered and washed, a potassium hydroxide solution with a concentration of 5 mol / L is added to make a suspension with a solid content rate of 30 wt%, and reacted at 100° C. for 1 hour under stirring (50 rpm) conditions, filtered and washed to obtain Precursor of calcium sulfate dihydrate.

[0049] Put the precursor of calcium sulfate dihydrate into a high-pressure reactor, add 5mol / L potassium chloride solution to adjust the solid content to 25wt%, react hydrothermally at 250°C...

Embodiment 3

[0051] Weigh desulfurized gypsum (main composition: CaSO 4 2H 2 O: 80wt%, SiO 2 : 2.5wt%, Al 2 o 3 : 2.5wt%, Fe 2 o 3 : 2wt%, CO 3 : 10wt%) 100g, ammonium chloride 10g, the two are mixed and roasted at 500°C for 2.5h to obtain calcined sand. Add calcined sand to an aqueous solution containing 2mol / L hydrochloric acid and 1mol / L citric acid to make a suspension with a solid content of 10wt%, and react for 2 hours at 40°C under stirring (250 rpm); filter the above slurry After washing, add ammonia solution with a concentration of 2.5mol / L to make a suspension with a solid content of 10wt%, react at 40°C and stir (250 rpm) for 2.5h, filter and wash to obtain dihydrate Calcium sulfate precursor.

[0052]Put the calcium sulfate dihydrate precursor into the autoclave, add 2mol / L sodium sulfate solution to adjust the solid content to 5wt%, react hydrothermally at 150°C for 2h under stirring (250 rpm), cool, filter, and wash , Drying (105°C, 4h), the intermediate product of c...

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Abstract

The invention relates to a method for preparing calcium sulfate crystal whiskers (CaSO4) by using impurity-containing gypsum as a raw material. The method comprises the following steps of: removing main impurities in the raw material which is the low-priced impurity-containing gypsum resource in a mode of roasting, acid-complex leaching and alkaline leaching and simultaneously thinning crystal grains to obtain a superfine dihydrate calcium sulfate precursor which is high in purity and dispersibility; and preparing the anhydrous calcium sulfate crystal whiskers with a length of 20 to 2,000mu m, a diameter of 0.5 to 20 mu m, a length-diameter ratio of 40 to 1,000 and a weight percent content of over 95 percent in a mode of hydrothermal conversion-roasting of a fluxing agent. The method has the advantages of low-priced and easily bought raw materials, simple process, wide application range, and high added value. The calcium sulfate crystal whiskers prepared by the method have a big length-diameter ratio and regular shape, and can be used as reinforcing, heat insulating or flame retardant materials in industries of plastics, rubbers, coatings, papermaking, building materials and the like.

Description

technical field [0001] The invention relates to a method for preparing calcium sulfate whiskers by using gypsum containing impurities as a raw material, and belongs to the technical field of preparation of inorganic chemical materials. Background technique [0002] my country is a country with a large amount of gypsum resources. Natural gypsum, phosphogypsum, desulfurized gypsum and other resources are very rich, which provides good conditions for the development of calcium sulfate whisker materials. [0003] my country is rich in natural gypsum resources, with reserves of tens of billions of tons, mainly distributed in East China, North China, Central South, Southwest, Northwest and other places. The proven natural ore reserves are nearly 60 billion tons, ranking first in the world, including 53.4 billion tons of prospective reserves and nearly 5 billion tons of industrial reserves. At present, about 20 million tons of gypsum mines are mined in my country every year, 80% o...

Claims

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Application Information

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IPC IPC(8): C30B29/62C30B29/10C01F11/46
Inventor 罗康碧向兰李沪萍李春梅宁平谭艳霞陈锐
Owner KUNMING UNIV OF SCI & TECH
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