Calcium carbonate overview

Calcium carbonate is an inorganic chemical compound with the formula CaCO3. It is widely present in nature, and is commonly found in rocks, in the shells of snails and other marine organisms, pearls, eggshells, etc. The raw material used to manufacture Calcium Carbonate is extracted by mining or quarrying. Based on the purity of Calcium Carbonate desired, the quarry source can be selected. For example, for high purity Calcium Carbonate used by the food and pharmaceutical industry, the quarry source will usually be marble, which is a pure source rock. The common geological sources are calcite, aragonite and vaterite and they are pure Calcium Carbonate minerals. Industrially important source rocks are limestone, chalk, marble and travertine.

Properties of Calcium Carbonate:

  • Odourless
  • Tasteless
  • Can exist as a powder or a crystal
  • It is usually white in colour when it is a powder, or colourless when it is a crystal
  • It is a stable compound.
Production of Calcium Carbonate:

Calcium Carbonate is prepared from calcium oxide. Water is added to calcium oxide, which results in the formation of calcium hydroxide. Carbon dioxide is passed through the calcium hydroxide solution and the calcium carbonate formed is precipitated. The reaction can be written as:
CaO + H2O → Ca(OH)2
Ca(OH)2 + CO2 → CaCO3 + H2O

Calcium Carbonate has various applications in a number of industries. Some of the major applications are discussed below:

Metallurgy Industry
Around 60% of the calcium carbonate produce is used in metallurgy industry, mainly in the manufacturing of steel, for the formation of slag and for the purification of iron from iron ore in blast furnace.

Construction industry
Calcium Carbonate is mainly used in the construction industry as a building material or limestone aggregate. It is added to numerous building materials such as ready-made mortars, interior and exterior plaster mixes, paving, coatings, etc. It is also integrated into construction sealants and flooring, because of its rheological and finishing properties.

Thermoplastic industry
It is used as an important reinforcing filler in thermoplastic industry to enhance the mechanical, thermal and structural properties such as impact strength, modulus, toughness, etc. Sealants, adhesives and stained glass windows are some of the applications of uncoated calcium carbonate as a filler in the thermoplastic industry.

Paint industry
It is used in the paint industry as an extender that provides the hiding power and high brightness to the paint. This is due to its pigmentation property. Also, the addition of Calcium Carbonate lowers the carbon foot-print for architectural indoor paints, hence being environmentally friendly.

Paper industry
It is used in the papermaking industry as both filler and pigment as it provides an increased whiteness in papers and reduces brittleness of paper as it ages. It also gives the paper a high opacity, thus increasing the quality.

Environmental Uses
It is used to soften water and also in the treatment of sewage to remove colloidal particles. It is even used in desulphurisation of flue gas.

Food industry
Calcium Carbonate food grade is used as a food additive, for example in snacks or bakery items, it is used as an anticaking agent, a food preservative and as a colour retainer. Calcium carbonate is also used as a firming agent in canned food.

Pharmaceutical industry
In the pharmaceutical industry, it is used in manufacturing of antibiotics through fermentation, and also as an excipient in pharmaceutical tablets. It is used as a supplement for calcium, in the treatment of osteoporosis, for growing children and pregnant women. It is also used as an antacid.

CAS No. : 471-34-1
Formula : CaCO3
Mol Wt. : 100.087
Synonyms : Limestone, calcite, aragonite, chalk, marble

Physical state : White, powdered solid, odourless
Melting point : 1339°C
Boiling point : Decomposes
Solubility in water : 0.0013 g/100mL (25°C)
Density and phase : 2.711 g/cm3, Solid

Content : 65.0% min
Total Nitrogen : 20% min
Calcium Carbide : 0.1% max
Sieve analysis : 97.0% min (850µm)