Calcium Carbonate
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Calcium carbonate is prepared through the calcination of limestone to produce calcium oxide and carbon dioxide, followed by slaking the calcium oxide with water and carbonating the resulting milk of lime with carbon dioxide. It has various applications including use in the paper, plastics, paint and coatings industries as a filler and pigment, as an acid neutralizer in antacids, and in the construction industry. Prolonged exposure to calcium carbonate dust can cause irritation to eyes and respiratory tract.
Calcium Carbonate
- 1. A R T I C L E W R I T T E N A N D P U B L I S H E D B Y W W W . W O R L D O F C H E M I C A L S . C O M Calcium carbonate – Preparation and Applications
- 2. Calcium carbonate - Chemical properties - Acidity 9.0 Appearance White powder CAS Number 471-34-1 ChEBI 3311 Crystal Structure Trigonal Density 2.93 g/cm3 IUPAC Name Calcium Carbonate Melting Point 825 °C Molar Mass 100.09 g/mol RTECS Number FF9335000 Refractive 1.59 Solubility 0.00015 mol/l
- 3. Calcium carbonate - Methods of preparation Precipitated calcium carbonate is produced using the most economic process existing today. Limestone is converted into calcium oxide and carbon dioxide by means of calcination at temperatures in excess of 900°C. To ensure a high level of purity, the calcination process is carried out using natural gas. After the calcined lime has been slaked with water, the resulting milk of lime is purified and carbonated with the carbon dioxide obtained from the calcination process
- 4. Calcium carbonate - Methods of preparation Burning of limestone CaCO3 --> CaO+CO2 Slacking of quicklime CaO + H2O --> Ca(OH)2 Precipitaion Ca(OH)2 + CO2 --> CaCO3 + H20 (precipitated calcium carbonate)
- 5. Calcium carbonate - Methods of preparation Following total carbonation, a suspension of CaCO3 results. A cake comprising 40 per cent – 60 per cent solid matter (depending on particle diameter) is then obtained by filtration. This filter cake is then dried and subsequently deagglomerated in grinders. Ultrafine precipitated calcium carbonate grades are reacted with fatty acids prior to filtration (ie) when still in the suspension stage. The fineness of the grain, as well as the crystal form (aragonite, calcite), is controlled by temperature, concentration of reactants and time. Depending on the chemical composition of the milk of lime used and on the purifying stages during production, both technical as well as foodstuff and pharmaceutical grades can be produced. © SpecialChem
- 6. Calcium carbonate - Applications i) Calcium carbonate is the common natural form of chalk, limestone, and marble, produced by the sedimentation of the shells of small fossilized snails, shellfish, and coral over millions of years. ii) Precipitated calcium carbonate is used in paper industry. It enhances optical properties and print characteristics of paper products, improves paper machine productivity, and can reduce papermaking costs through the replacement of more expensive pulp fiber and optical brightening agents. iii) Calcium carbonate is the most widely used mineral in the paper, plastics, paints and coatings industries both as a filler – and due to its special white colour - as a coating pigment.
- 7. Calcium carbonate - Applications iv) Precipitated calcium carbonate is an effective acid neutralizer, often used in calcium-based antacid tablets and liquids. Being high in calcium content, precipitated calcium carbonte enables the formulation of high dosage calcium supplements and multi- vitamin/mineral tablets. The small particle sizes and special particle shapes contribute to the development of good tasting calcium fortified foods and beverages. v) Calcium carbonate is critical to the construction industry, both as a building material in its own right (e.g. marble), and as an ingredient of cement. It contributes to the making of mortar used in bonding bricks, concrete blocks, stones, roofing shingles, rubber compounds, and tiles. Calcium carbonate decomposes to form carbon dioxide and lime, an important material in making steel, glass, and paper. Because of its antacid properties, calcium carbonate is used in industrial settings to neutralize acidic conditions in both soil and water.
- 8. Calcium carbonate - Toxicity Calcium carbonate dust is a physical irritant to eyes, nose, mucous membrane and skin. Contact of calcium carbonate dust with eyes causes redness, pain and inflammation of the eyelids while contact to skin causes local irritation. Exposure of large amount of dust causes coughing, sneezing and nasal irritation. Calcium carbonate is an ingredient in most antacids and taken as a dietary supplement. Overdose of calcium carbonate may lead to abdominal pain, bone pain, coma, confusion, constipation, depression, diarrhea, headache, irregular heartbeat, muscle twitching, nausea and vomiting.
- 9. More Info On Calcium carbonate Safety Tips for handling – Calcium carbonate should be used with adequate ventilation, minimized dust generation and accumulation. Contact with eyes, skin, clothing and breathing of dust should be avoided. Calcium carbonate should be stored in a cool, dry place with a tightly closed container. Manufacturers – Omya, Solvay, Imerys, Minerals Technologies, Carmeuse. Largest manufacturing country/consuming country - The total production of world’s ground calcium carbonate is contributed by Europe with six countries - Austria, France, Germany, Norway, Italy and Spain.