Calcium carbonate

Production Methods

Calcium carbonate is obtained from natural limestone deposits. The purified compound, known as precipitated calcium carbonate, is synthesized from limestone. Limestone is calcined to calcium oxide and carbon dioxide in a kiln. The products are recombined after purification. Calcium oxide is hydrated with water to give a slurry called milk of lime, which is then carbonated by bubbling CO2 through it. The reactions involved in the process are as follows: CaCO3 CaO + CO2 CaO + H2O Ca(OH)2 Ca(OH)2+ CO2→CaCO3+ H2O The crystal sizes required for various commercial applications may be controlled by temperature, pH, concentrations, and mixing rate. Calcium carbonate also may be precipitated by mixing solutions of calcium chloride and sodium carbonate.

Preparation

Calcium carbonate may also be produced by mixing solutions of calcium chloride and sodium carbonate. In some cases, the presence of sodium is objectionable so that the ammonium carbonate salt is preferable.

Reactions

Calcium carbonate decomposes to calcium oxide and CO2 on heating. Treatment with dilute mineral acids produces corresponding calcium salts with liberation of CO2: CaCO3+ 2HCl →CaCl2+ H2O + CO2 In the presence of CO2 it dissolves in water with the formation of bicarbonate: CaCO3+ H2O + CO2→Ca2++ 2HCO3 ˉ It is reduced to calcium carbide when heated with coke or anthracite in an electric furnace: 2CaCO3+ 5C→(high temperature)→2CaC2+ 3CO2

Flammability and Explosibility

Notclassified

Pharmaceutical Applications

Calcium carbonate (CaCO3) can be found in clinical applications such as antacids, but not that an excessive intake can be hazardous. A variety of calcium salts are used for clinical application, including calcium carbonate, calcium chloride, calcium phosphate, calcium lactate, calcium aspartate and calcium gluconate. Calcium carbonate is the most common and least expensive calcium supplement. It can be difficult to digest and may cause gas in some people because of the reaction of stomach HCl with the carbonate and the subsequent production of CO2. Calcium carbonate is recommended to be taken with food, and the absorption rate in the intestine depends on the pH levels. Taking magnesium salts with it can help prevent constipation. Calcium carbonate consists of 40% Ca2+, which means that 1000 mg of the salt contains around 400 mg of Ca2+. Often, labels will only indicate the amount of Ca2+ present in each tablet and not the amount of calcium carbonate.

Biochem/physiol Actions

Calcium carbonate is a naturally occurring compound that reduces T4 absorption and enhancess serum thyrotropin levels. It also precludes osteoporosis induced by thyrotropin-suppressive doses of levothyroxine in postmenopausal women. Additionally, it reduces diarrhea in individuals with protease inhibitor-induced HIV-infection.

Safety

Calcium carbonate is mainly used in oral pharmaceutical formulations and is generally regarded as a nontoxic material. However, calcium carbonate administered orally may cause constipation and flatulence. Consumption of large quantities (4–60 g daily) may also result in hypercalcemia or renal impairment. Therapeutically, oral doses of up to about 1.5 g are employed as an antacid. In the treatment of hyperphosphatemia in patients with chronic renal failure, oral daily doses of 2.5–17 g have been used. Calcium carbonate may interfere with the absorption of other drugs from the gastrointestinal tract if administered concomitantly. LD50 (rat, oral): 6.45 g/kg

Metabolism

Under the influence of gastric acid, any residual carbonate will be converted to carbon dioxide and water. Any unbound calcium not involved in the binding of phosphate will be variable and may be absorbed. Calcium is absorbed mainly from the small intestine by active transport and passive diffusion. About one-third of ingested calcium is absorbed although this can vary depending upon dietary factors and the state of the small intestine. 1,25-Dihydroxycholecalciferol (calcitriol), a metabolite of vitamin D, enhances the active phase of absorption. Excess calcium is mainly excreted renally. Unabsorbed calcium is eliminated in the faeces, together with that secreted in the bile and pancreatic juice. Minor amounts are lost in the sweat, skin, hair, and nails.

storage

Calcium carbonate is stable and should be stored in a well-closed container in a cool, dry place.

Incompatibilities

Incompatible with acids and ammonium salts.

Regulatory Status

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (buccal chewing gum, oral capsules and tablets; otic solutions; respiratory inhalation solutions). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.

Natural Occurrence and Biological Functions

Calcium carbonate is found in sedimentary rocks such as marble, limestone, and chalk, as well as in marine sediments.
It serves various functions in living organisms, including structural support (e.g., in algae, corals), protection (e.g., shells), buoyancy (e.g., cuttlebone), and in photoreceptor systems.

Polymorphs and Phases

Calcium carbonate exhibits different polymorphs, including vaterite, aragonite, and calcite, with varying thermodynamic stability. Hydrated crystal phases such as monohydrocalcite, ikaite, and hemihydrate have also been identified, along with an amorphous phase (ACC) found in various organisms.

Applications and Research

Calcium carbonate is widely used as a filler material in various industries including paper, plastics, rubber, paints, and foodstuffs.
Synthetic calcium carbonate micro/nanoparticles (MNPs) are tailored for specific applications by controlling their dimensions, polymorphs, morphologies, and surface functionalities. Research focuses on synthesizing calcium carbonate with specific properties such as size, morphology, polymorph, or surface functionality, leading to new applications in biomaterials, biomedicines, and environmental applications.

Biomedical and Therapeutic Applications

Calcium carbonate particles are stable at neutral pH but dissolve under acidic conditions, making them useful for targeted drug delivery.
They are employed in chemotherapy, photothermal therapy (PTT), photodynamic therapy (PDT), wound healing, blood clotting, ultrasound (US), fluorescence, magnetic resonance imaging (MRI), and multimodal imaging and therapy.

Synthesis Methods

Various synthesis methods have been developed for calcium carbonate, including liquid-liquid or solid-liquid-gas routes tailored by adding organic compounds or polymers. The carbonation method is considered eco-friendly and innovative, with potential for CO2 mitigation.

Physical properties

Calcium carbonate is a naturally occurring compound found in organisms and throughout the earth’s crust. After quartz, calcium carbonate, primarily in the form of calcite, is the most common mineral found in the crust. Geologically, calcium carbonate exists in several mineral forms: calcite, aragonite, and vaterite. Calcite is the most common calcium carbonate mineral, whereas vaterite is a very rare form. The different mineral forms of calcium carbonate are based on their crystalline structure. The form of calcium carbonate depends on the conditions at its formation such as temperature and pressure.

Definition

calcium carbonate: A white solid,CaCO3, which is only sparingly solublein water. Calcium carbonatedecomposes on heating to give calciumoxide (quicklime) and carbondioxide. It occurs naturally as theminerals calcite (rhombohedral; r.d.2.71) and aragonite (rhombic; r.d.2.93). Rocks containing calcium carbonatedissolve slowly in acidifiedrainwater (containing dissolved CO2)to cause temporary hardness. In thelaboratory, calcium carbonate is precipitatedfrom limewater by carbondioxide. Calcium carbonate is used inmaking lime (calcium oxide) and isthe main raw material for theSolvay process.

Brand name

Cal-Sup (3M Pharmaceuticals); Children’s Mylanta Upset Stomach Relief (Johnson & Johnson-Merck Consumer); Chooz (Schering- Plough HealthCare); Mylanta Soothing Lozenges (Johnson & Johnson-Merck Consumer).

General Description

Calcium Carbonate (CaCO3) is a naturally found material in chalk, limestone, and marble. It is composed of three elements which include carbon, oxygen, and calcium. It is formed by reacting carbon dioxide with slaked or burnt lime. It can be used for a variety of applications ranging from industrial, food to agriculture.

Agricultural Uses

Calcium carbonate (CaCO3) is a naturally occurring white solid that is sparingly soluble in water. It is most commonly used to neutralize soil acidity to the required level in a process called liming. The major sources of calcium carbonate are calcitic limestone, dolomitic limestone, marl, chalk and marble. Calcium carbonate is made by passing carbon dioxide (CO2) into limewater. Pure calcium carbonate is assumed to have a 100% neutralizing value. The values of other liming materials are measured against the neutralizing value of pure calcium carbonate. Calcium carbonate, on heating, decomposes to give calcium oxide (quick lime) and carbon dioxide. Limestone, which consists mainly of calcium carbonate, is called calcitic limestone or high calcium limestone. Limestone containing more than 10% magnesium carbonate is called dolomitic limestone or dolomite. These forms contain about 12% magnesium. Agricultural dolomitic limestone is a fine, grey to white powder of a double carbonate of calcium and magnesium with 12.8% magnesium and 17% calcium. The double carbonate is much less soluble in water than the individual carbonates.