What Are the Industrial Uses of Calcium Sulfate?

White monoclinic crystal or crystalline powder. No smell. Hygroscopic. One molecule of crystal water was lost at 128 ° C, and all water was lost at 163 ° C. Slightly soluble in acid, sodium thiosulfate and ammonium salt solution, soluble in 400 parts of water, less soluble in hot water, very slowly soluble in glycerin, insoluble in ethanol and most organic solvents. The relative density is 2.32. Irritating. It usually contains 2 crystal waters, and exists in nature as gypsum ore.

CAS number: 10101-41-4

MDL number: MFCD00149625

EINECS number: 231-2900-3

RTECS number: EW4150000

PubChem number: 24892640 ^[1]

Properties: Colorless monoclinic crystalline powder. Glass gloss.

Density (g / mL, 20 ° C): 2.32

Melting point (ºC): 128

Boiling point (ºC, atmospheric pressure): 163

Flash point (ºC): 163

Solubility: slightly soluble in water. Soluble in hydrochloric acid.

Solubility of calcium sulfate (dihydrate): 0 ° C 0.233; 10 ° C 0.244; 18 ° C 0.255; 30 ° C 0.264; 40 ° C 0.265; 65 ° C 0.244; 75 ° C 0.234.

Calcium sulfate colorless orthogonal or

Can react with carbon at high temperature

It is generally slightly harmful to water bodies. Do not expose undiluted or large quantities of products to groundwater, waterways or sewage systems. Do not discharge materials into the surrounding environment without government permission. ^[1]

1. Hydrophobic parameter calculation reference value (XlogP): None

2.Number of hydrogen-bonded donors: 2

3.Number of hydrogen bond acceptors: 6

4.Number of rotatable chemical bonds: 0

5.Number of tautomers: none

6. Topological molecular polar surface area 90.6

7.Number of heavy atoms: 8

8.Surface charge: 0

9.Complexity: 62.2

10.Number of isotope atoms: 0

11. Determine the number of atomic stereocenters: 0

12. Uncertain number of atomic stereocenters: 0

13. Determine the number of chemical bond stereocenters: 0

14. Uncertain number of chemical bond stereocenters: 0

15.Number of covalent bond units: 4 ^[1]

Avoid light, open flames and high temperatures. Insoluble in water, soluble in acid, ammonium salt, sodium thiosulfate and glycerol. Slightly soluble in water. Soluble in hydrochloric acid. The gypsum deposit is mainly caused by evaporative deposition, which is the product of chemical deposition. It is in lime specifications and quality requirements. ^[1]

Store in a dry, clean warehouse. Food-grade products must be prevented from being contaminated by toxic substances and not allowed to be stored and transported together with toxic substances. Pay attention to moisture and moisture. ^[1]

1. There are open-pit mining and underground mining. The former is mostly hillside open-air, step mining; most of the latter mining methods use vertical shaft or inclined shaft development, and the main method is room and pillar mining, followed by comprehensive mining. For the mining process, see "Phosphorite Rock". Most gypsum mines in China use the manual beneficiation method. Some mines produce ore without any sorting, and the ore mined is the mineral product. The natural gypsum ore is removed from the impurities and the soil is calcined and ground.

2. Sodium sulfate is added to the byproduct (calcium chloride) of alkali production by ammonia-alkali method, and the reactant is purified to obtain calcium sulfate dihydrate.

3. By-products in the production of organic acids. For example, calcium oxalate, a by-product of oxalic acid production, is decomposed with sulfuric acid, and then refined to obtain calcium sulfate dihydrate.

4. Add reagent grade calcium sulfate to the ammonium sulfate aqueous solution (excess of calcium chloride), and carry out the reaction.

When the precipitation is complete, stand still and clarify. Wash the precipitate 5-6 times with water. After suction filtration, wash with water until the NH4 + ion content of the solution is qualified (tested with Nessler's reagent). Dry at 60-70 ° C to obtain chemically pure calcium sulfate. To prepare anhydrous calcium sulfate, the dihydrate can be heated to constant weight at 200 ° C.

5. The hydrothermal method adds a dihydrate gypsum suspension with a mass fraction of less than 2% to a hydraulic autoclave. Under saturated steam pressure, the dihydrate gypsum becomes a small needle-like hemihydrate gypsum, and then passes through the crystal form. Stabilization treatment yielded calcium sulfate hemihydrate whiskers.

6. Atmospheric acidification method At a certain temperature, a high-concentration calcium sulfate dihydrate suspension can be transformed into needle-like or fibrous calcium sulfate hemihydrate whiskers in an acidic solution. There are also patent reports on the use of ammonia-alkaline waste liquor plants and brine to make calcium sulfate whiskers. The specific method is to mix the steamed ammonia waste liquor of the ammonia-alkali plant with the brine to prepare calcium sulfate dihydrate, and then use calcium sulfate dihydrate to obtain calcium sulfate hemihydrate whiskers through normal pressure acidification method. ^[1]

1. Raw materials for manufacturing cement, calcium sulfate hemihydrate and sulfuric acid. Used as a filler in the paint and paper industry. Used as fertilizer in agriculture, it can reduce soil alkalinity and improve soil performance.

2. Food grade can be used as nutritional supplement (calcium fortification), coagulant, yeast food, dough conditioner, chelating agent, and also used as a tissue strengthening agent in tomatoes and canned potatoes, a hardener for brewing water, wine Flavor enhancer and so on.

3. Gypsum is widely used in rubber, plastics, fertilizers, pesticides, paints, textiles, food, medicine, papermaking, daily chemicals, arts and crafts, culture and education, in addition to a large number of construction materials and cement raw materials. It can be used to produce sulfuric acid and ammonium sulfate in areas lacking sulfur resources. Colorless and transparent gypsum can be used as optical material.

4. Used as a filler for epoxy resin, it can prepare epoxy resin adhesive with high strength, high temperature resistance and good wear resistance. It can also replace non-asbestos friction materials. ^[1]

Calcium sulfate safety term

S22 Do not breathe dust. Do not breathe dust.

S24 / 25 Avoid contact with skin and eyes. Avoid contact with skin and eyes.

Calcium sulfate risk term

R49 May cause cancer by inhalation. ^[3]