Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a ternary compound, which falls into the category of oxosalts. It is a very abundant substance in nature, forming rocks, as a main component, in all parts of the world and is the main component of shells and skeletons of many organisms (eg molluscs, corals) or eggshells. It is the main cause of hard water. In medicine it is commonly used as a calcium supplement, as an antacid and adsorbing agent. It is essential in the production of glass and cement, among other products. Like sodium bicarbonate, in the presence of any acid it gives off carbon dioxide by effervescence.
Minerals and Rocks
It is the main component of minerals such as calcite or aragonite and carbonate rocks such as limestone and its varieties (travertine, chalk, carniola) or marble, from limestone metamorphism. It is also a main part of the composition of sedimentary structures of organic origin such as calcareous tuffs, speleothems, stromatolites, oncolithes, etc.
Presence in living organisms
Calcium carbonate is the main component of many structures present in living organisms, such as the thallus of some algae, for example Padina pavonica, sponges of the Calcareous class, shells of mollusks, skeletons of corals or the eggshells of reptiles and birds.
Uses
Construction
The main use of calcium carbonate is in the construction industry, either as a construction material, or as an aggregate for road construction, as an ingredient in cement, or as a starting material for the preparation of lime for builders by burning it in a furnace. However, due to weathering caused mainly by acid rain, calcium carbonate (in the form of limestone) is no longer used for construction purposes by itself, but only as a raw material for building materials.
Calcium carbonate is also used in the purification of iron from iron ore in a blast furnace. The carbonate is calcined in situ to give calcium oxide, which forms a slag with various impurities present, and is separated from the purified iron.
In the oil industry, calcium carbonate is added to drilling fluids as a formation bridging and filter cake sealing agent; It is also a weighting material that increases the density of drilling fluids to control downhole pressure. Calcium carbonate is added to swimming pools as a pH corrector to maintain alkalinity and offset the acidic properties of the sanitizing agent.
It is also used as a raw material in refining sugar from sugar beets; it is calcined in a furnace with anthracite to produce calcium oxide and carbon dioxide. This burnt lime is quenched in fresh water to produce a calcium hydroxide slurry for the precipitation of impurities from the raw juice during carbonation.
Calcium carbonate in the form of chalk has traditionally been a major component of blackboard chalk. However, modern manufactured chalk is mostly gypsum, hydrated calcium sulfate CaSO
4 2H2O. Calcium carbonate is a primary source for biorock cultivation. Precipitated calcium carbonate (PCC), predisposed as a slurry, is a common filler material for latex gloves with the aim of achieving maximum material and production cost savings.
Finely ground calcium carbonate (GCC) is an essential ingredient in microporous film used in diapers and some construction films, as pores nucleate around calcium carbonate particles during film manufacturing. biaxial stretch film. GCC and PCC are used as fillers in paper because they are cheaper than wood fiber. In terms of market volume, GCCs are the most important filler types currently in use. Printing and writing paper may contain 10–20% calcium carbonate. In North America, calcium carbonate has begun to replace kaolin in the production of glossy paper. In Europe, the manufacture of alkaline or acid-free paper has been practiced for some decades. PCC used for paper fillers and paper coatings is precipitated and prepared in a variety of shapes and sizes having characteristic narrow particle size distributions and equivalent spherical diameters of 0.4 to 3 microns.
Calcium carbonate is widely used as an extender in paints, particularly emulsion flat paint where typically 30% by weight of the paint is chalk or marble. It is also a popular filler in plastics. Typical examples include around 15-20% chalk loading in unplasticized polyvinyl chloride (uPVC) drain pipes, 5-15% chalk loading or coated marble. of stearic acid|stearate]] in the uPVC window profile. PVC cables can use calcium carbonate at loadings up to 70 phr (parts per hundred parts of resin) to improve mechanical (tensile strength and elongation) and electrical (volume resistivity) properties. Polypropylene compounds are often filled with calcium carbonate to increase stiffness, a requirement that becomes important at high temperatures of use. Here the percentage is usually 20-40%. It is also routinely used as a filler in thermosetting resins (sheet and bulk molding compounds) and has also been mixed with ABS, and other ingredients, to form some types of compression molded poker chips. Calcium carbonate precipitate, made by dropping calcium oxide into water, is used by itself or with additives such as white paint, known as whitewash.
Calcium carbonate is added to a wide range of commercial and do-it-yourself adhesives, sealants and decorative fillers. Ceramic tile adhesives typically contain between 70% and 80% limestone. Decorative crack fillers contain similar levels of marble or dolomite. It is also mixed with the putty in the placement of stained glass windows, and as a resistance to prevent the glass from sticking to the oven shelves when enamels and paints are fired at high temperatures.
In ceramic glaze applications, calcium carbonate is known as whiting, and is a common ingredient for many glazes in its white powder form. When a glaze containing this material is fired in a kiln, the whiting acts as a flux material in the glaze. Ground calcium carbonate is an abrasive (both as a scouring powder and as an ingredient in household cream cleaners), particularly in its calcite form, which has the relatively low hardness level of 3 on the Mohs Scale, so it will not scratch glass and most ceramics, enamel, bronze, iron and steel, and has a moderate effect on softer metals such as aluminum and copper. A paste made from calcium carbonate and deionized water can be used to clean tarnish from silver.
Health and diet
Calcium carbonate is widely used in medicine as a cheap calcium dietary supplement for gastric antacid (such as Tums and Eno). It can be used as a phosphate binder for the treatment of hyperphosphatemia (mainly in patients with chronic renal failure). It is used in the pharmaceutical industry as an inert filler for tablets and other pharmaceutical products.
Calcium carbonate is used in the production of calcium oxide, as well as in toothpaste, and has seen a resurgence as a food preservative and color retainer, when used in or with products such as organic apples.
Calcium carbonate is used therapeutically as a phosphate binder in patients on maintenance hemodialysis. It is the most common form of phosphate binder prescribed, especially in non-dialysis-related chronic kidney disease. Calcium carbonate is the most widely used phosphate binder, but physicians are increasingly prescribing the more expensive, non-calcium-based phosphate binders, especially sevelamer.
Excess calcium from supplements, fortified foods, and diets high in calcium can cause milk-alkali syndrome, which has severe toxicity and can be fatal. In 1915, Bertram Sippy introduced the 'Sippy diet', consisting of hourly intake of milk and cream, and the gradual addition of eggs and boiled cereals, for 10 days, in combination with alkaline powders, which provided symptomatic relief for peptic ulcer disease. Over the next few decades, the Sippy regimen caused renal failure, alkalosis, and hypercalcemia, especially in men with peptic ulcer disease. These adverse effects were reversed on discontinuation of the regimen, but it was fatal in some patients with prolonged vomiting. Milky-alkali syndrome decreased in men after effective treatments for peptic ulcer disease emerged. Since the 1990s, it has been reported more frequently in women taking calcium supplements above the recommended range of 1.2 to 1.5 grams daily, for the prevention and treatment of osteoporosis, and is aggravated by dehydration. Calcium has been added to over-the-counter products, contributing to inadvertent excessive intake. Excessive calcium intake can lead to hypercalcemia, the complications of which include vomiting, abdominal pain, and altered mental status.
As a food additive it is designated E170, and has an INS number of 170. Used as an acidity regulator, anti-caking agent, stabilizer, or colorant it is approved for use in the EU, the United States, and Australia and New Zealand. It is "added by law to all UK bread-ground flour except whole wheat". It is used in some soya milk and almond milk products as a source of dietary calcium; at least one study suggests that calcium carbonate could be as bioavailable as the calcium in cow's milk. Calcium carbonate is also used as a firming agent in many canned and bottled vegetable products.
Several calcium supplement formulations have been documented to contain the chemical element lead, which is a public health concern. Lead is commonly found in natural sources of calcium.
Agriculture and Aquaculture
Agricultural lime, chalk or powdered limestone, is used as a cheap method to neutralize acid soil, making it suitable for planting, it is also used in the aquaculture industry for pH regulation of the pond floor before starting the culture.
Domestic cleaning
Calcium carbonate is a key ingredient in many household cleaning powders like Comet and is used as a scouring agent.
Pollution Mitigation
In 1989, a researcher, Ken Simmons, introduced CaCO
3 in Whetstone Creek, Massachusetts. His hope was that carbonate of calcium to counteract the acid from acid rain in the creek and save the trout that had stopped spawning. Although his experiment was successful, he increased the amount of aluminum ions in the area of the stream that was not treated with the limestone. This shows that you can add CaCO
3 to neutralize the effects of acid rain on river ecosystems. Today, calcium carbonate is used to neutralize acidic conditions in both soil and water. Since the 1970s, this liming has been practiced on a large scale in Sweden to mitigate acidification and several thousand lakes and streams are repeatedly silted.
Calcium carbonate is also used in flue gas desulfurization applications that remove harmful SO emissions
2 and NO
2 from coal and other fossil fuels burned in large fossil fuel power plants.