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MICP can be also applied to achieve sequestration of heavy metals and radionuclides. Microbially induced calcium carbonate precipitation of radionuclide and contaminant metals into calcite is a competitive co-precipitation reaction in which suitable divalent cations are incorporated into the calcite lattice.
Calcite seas existed in Earth's history when the primary inorganic precipitate of calcium carbonate in marine waters was low-magnesium calcite (lmc), as opposed to the aragonite and high-magnesium calcite (hmc) precipitated today. Calcite seas alternated with aragonite seas over the Phanerozoic, being most prominent in the Ordovician and ...
The formation of biogenic calcium carbonate by marine calcifiers is one way to add ballast to sinking particles and enhance transport of carbon to the deep ocean and seafloor. [46] The calcium carbonate counter pump refers to the biological process of precipitation of carbonate and the sinking of particulate inorganic carbon. [47]
Whiting event clouds consist of calcium carbonate polymorphs; aragonite tends to be the dominant precipitate, but some studies in oligotrophic and mesotrophic lakes show calcite is favored. [ 3 ] [ 7 ] Whiting events have been observed in tropical and temperate waters, and they can potentially cover hundreds of meters. [ 3 ]
Limestone forms when calcite or aragonite precipitate out of water containing dissolved calcium, which can take place through both biological and nonbiological processes. [41] The solubility of calcium carbonate (CaCO 3) is controlled largely by the amount of dissolved carbon dioxide (CO 2) in the water. This is summarized in the reaction:
Calcium carbonate is used in the production of calcium oxide as well as toothpaste and has seen a resurgence as a food preservative and color retainer, when used in or with products such as organic apples. [58] Calcium carbonate is used therapeutically as phosphate binder in patients on maintenance haemodialysis. It is the most common form of ...
As the concentration of carbonate increases, calcium carbonate precipitates as the salt: Ca 2+ + CO 2− 3 → CaCO 3. In pipes as limescale and in surface deposits of calcite as travertine or tufa the primary driver of calcite formation is the exsolution of gas.
Evaporite minerals start to precipitate when their concentration in water reaches such a level that they can no longer exist as solutes. The minerals precipitate out of solution in the reverse order of their solubilities, such that the order of precipitation from sea water is: Calcite (CaCO 3) and dolomite (CaMg(CO 3) 2)