Amorphous calcium carbonate

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These deposits of tufa contain amorphous calcium carbonate along remains of algae and moss Moeraskalk Ronde Hoep - Spoelresidu.JPG
These deposits of tufa contain amorphous calcium carbonate along remains of algae and moss

Amorphous calcium carbonate (ACC) is the amorphous and least stable polymorph of calcium carbonate. ACC is extremely unstable under normal conditions and is found naturally in taxa as wide-ranging as sea urchins, corals, mollusks, and foraminifera. [1] [2] [3] It is usually found as a monohydrate, holding the chemical formula CaCO3·H2O; however, it can also exist in a dehydrated state, CaCO3. ACC has been known to science for over 100 years when a non-diffraction pattern of calcium carbonate was discovered by Sturcke Herman, exhibiting its poorly-ordered nature. [4]

Contents

ACC is an example of crystallization by particle attachment (CPA), where crystals form via the addition of particles ranging from multi-ion complexes to fully formed nanocrystals. [5] Research of such systems have diverse application; however, the current lack of unambiguous answers to fundamental questions (i.e. solubility product, interfacial forces, structure, etc.) causes them to be topics of study in fields ranging from chemistry, geology, biology, physics, and materials science engineering. [6] [5]

Stability

ACC is the sixth and least stable polymorph of calcium carbonate. The remaining five polymorphs (in decreasing stability) are: calcite, aragonite, vaterite, monohydrocalcite and ikaite. When mixing two supersaturated solutions of calcium chloride and sodium carbonate (or sodium bicarbonates) these polymorphs will precipitate from solution following Ostwald's step rule, which states that the least stable polymorph will precipitate first. But while ACC is the first product to precipitate, it rapidly transforms into one of the more stable polymorphs within seconds. [7] [8] When in pure CaCO3, ACC transforms within seconds into one of the crystalline calcium carbonate polymorphs. This transformation from amorphous to crystalline is proposed to be a dissolution-reprecipitation mechanism. [3] Despite ACC's highly unstable nature, some organisms are able to produce stable ACC. For example, the American Lobster Homarus americanus, maintains stable ACC throughout its yearly molt cycle. [2] Studies of biogenic ACC have also shown that these stable forms of ACC are hydrated whereas the transient forms are not. From observations of spicule growth in sea urchins, it seems that ACC is deposited at the location of new mineral growth where it then dehydrates and transforms into calcite. [2]

In biology

Several organisms have developed methods to stabilize ACC by using specialized proteins for various purposes. The function of ACC in these species is inferred to be for the storage/transport of materials for biomineralization or enhancement of physical properties, but the validity of such inferences has yet to be determined. Earthworms, some bivalves species, and some gastropods species are known to produce very stable ACC. [2] [9] ACC is widely used by crustaceans to stiffen the exoskeleton as well as to store calcium in gastroliths during the molt cycle. Here, the benefit of utilizing ACC may not be for physical strength, but for its periodic need of the exoskeleton to be dissolved for molting. [2] Sea urchins and their larvae utilize the transient form of ACC when forming spicules. The new material, a hydrated form of ACC, for the spicule is transported and deposited at the outer edges of the spicule. Then the deposited material, ACC·H2O, rapidly dehydrates to ACC. Following the dehydration, within 24 hours, all of the ACC will have transformed into calcite. [10]

Synthetic ACC

Many methods, [9] [7] [11] have been devised for synthetically producing ACC since its discovery at 1989, however, only few syntheses successfully stabilized ACC for more than several weeks. The best effective method to stabilize ACC lifetime is by forming it in the presence of magnesium and/or phosphorus. [12] [13] Also, ACC crystallisation pathways have been observed to depend on its Mg/Ca ratio, transforming to aragonite, [14] Mg-calcite, [15] monohydrocalcite [16] or dolomite [17] with increasing Mg content. Huang et al. managed to stabilize ACC using polyacrylic acid for several months, [18] while Loste et al. showed that magnesium ions can increase ACC stability as well. [19] But only the discovery that aspartic acid, glycine, [20] citrate, [21] and phosphorylated amino acids can produce long term stable ACC [22] have opened the door for production commercialization.

Highly porous ACC

Highly porous ACC has been synthesized using a surfactant-free method. [23] In this method CaO is dispersed in methanol under a pressure of carbon dioxide in a sealed reaction vessel. ACC with surface area over 350 m2/g was synthesized using this method. Highly porous ACC appeared to be made up aggregated nanoparticles with dimensions less than 10 nm in size. Highly porous ACC was also found to be stable in ambient conditions for up to 3 weeks with most of its porosity retained.

Applications and uses

Bioavailability: Since 2013 a company named Amorphical Ltd. sells an ACC dietary supplement. [24] [25] Calcium carbonate is used as a calcium supplement worldwide, however, it is known that its bioavailability is very low, only around 20–30%. ACC is roughly 40% more bioavailable than crystalline calcium carbonate. [26]

Drug delivery: Due to the ability to tune the size and morphology of the amorphous calcium carbonate particles (as well as other calcium carbonate particles), they have huge applications in drug delivery systems.[ citation needed ] Highly porous ACC showed the ability to stabilize poorly soluble drug molecules in its extensive pore system and could also enhance the drug release rates of these drugs. [23]

Paleoclimate reconstruction: A better understanding of the transformation process from amorphous to crystalline calcium carbonate will improve reconstructions of past climates that use chemical and biological proxies. For example, the calibrations of the clumped 13C-18O carbonate paleothermometer and understanding the origins and evolution of skeletal structures. [6] [5]

Environmental remediation: Improving environmental remediation efforts through gaining insight into the roles of earth materials in biogeochemical cycling of nutrients and metals through better understandings of the properties of environmental mineral phases involved in elemental uptake and release [27] [28]

Material science: Improving nanomaterials design and synthesis such as improving photovoltaic, photocatalytic, and thermoelectric materials for energy applications or improving biomedical cementations. Also improving framework material development for CO2 capture, H2 storage, emissions control, biomass conversion, molecular separations, and biofuel purification. [5]

Related Research Articles

<span class="mw-page-title-main">Calcite</span> Calcium carbonate mineral

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scratch hardness comparison. Large calcite crystals are used in optical equipment, and limestone composed mostly of calcite has numerous uses.

<span class="mw-page-title-main">Calcium carbonate</span> Chemical compound

Calcium carbonate is a chemical compound with the chemical formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. Materials containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime and is produced when calcium ions in hard water react with carbonate ions to form limescale. It has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.

<span class="mw-page-title-main">Aragonite</span> Calcium carbonate mineral

Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate, the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation from marine and freshwater environments.

<span class="mw-page-title-main">Vaterite</span> Calcium carbonate mineral

Vaterite is a mineral, a polymorph of calcium carbonate (CaCO3). It was named after the German mineralogist Heinrich Vater. It is also known as mu-calcium carbonate (μ-CaCO3). Vaterite belongs to the hexagonal crystal system, whereas calcite is trigonal and aragonite is orthorhombic.

<span class="mw-page-title-main">Carbonate rock</span> Class of sedimentary rock

Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and dolomite rock (also known as dolostone), which is composed of mineral dolomite (CaMg(CO3)2). They are usually classified based on texture and grain size. Importantly, carbonate rocks can exist as metamorphic and igneous rocks, too. When recrystallized carbonate rocks are metamorphosed, marble is created. Rare igneous carbonate rocks even exist as intrusive carbonatites and, even rarer, there exists volcanic carbonate lava.

<span class="mw-page-title-main">Biomineralization</span> Process by which living organisms produce minerals

Biomineralization, also written biomineralisation, is the process by which living organisms produce minerals, often resulting in hardened or stiffened mineralized tissues. It is an extremely widespread phenomenon: all six taxonomic kingdoms contain members that are able to form minerals, and over 60 different minerals have been identified in organisms. Examples include silicates in algae and diatoms, carbonates in invertebrates, and calcium phosphates and carbonates in vertebrates. These minerals often form structural features such as sea shells and the bone in mammals and birds.

<span class="mw-page-title-main">Monohydrocalcite</span>

Monohydrocalcite is a mineral that is a hydrous form of calcium carbonate, CaCO3·H2O. It was formerly also known by the name hydrocalcite, which is now discredited by the IMA. It is a trigonal mineral which is white when pure. Monohydrocalcite is not a common rock-forming mineral, but is frequently associated with other calcium and magnesium carbonate minerals, such as calcite, aragonite, lansfordite, and nesquehonite.

<span class="mw-page-title-main">Calcite sea</span> Sea chemistry favouring low-magnesium calcite as the inorganic calcium carbonate precipitate

A calcite sea is a sea in which low-magnesium calcite is the primary inorganic marine calcium carbonate precipitate. An aragonite sea is the alternate seawater chemistry in which aragonite and high-magnesium calcite are the primary inorganic carbonate precipitates. The Early Paleozoic and the Middle to Late Mesozoic oceans were predominantly calcite seas, whereas the Middle Paleozoic through the Early Mesozoic and the Cenozoic are characterized by aragonite seas.

<span class="mw-page-title-main">Aragonite sea</span> Chemical conditions of the sea favouring aragonite deposition

An aragonite sea contains aragonite and high-magnesium calcite as the primary inorganic calcium carbonate precipitates. The chemical conditions of the seawater must be notably high in magnesium content relative to calcium for an aragonite sea to form. This is in contrast to a calcite sea in which seawater low in magnesium content relative to calcium favors the formation of low-magnesium calcite as the primary inorganic marine calcium carbonate precipitate.

<span class="mw-page-title-main">Mollusc shell</span> Exoskeleton of an animal in the phylum Mollusca

The molluscshell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater.

<span class="mw-page-title-main">Mineralized tissues</span> Biological tissues incorporating minerals

Mineralized tissues are biological tissues that incorporate minerals into soft matrices. Typically these tissues form a protective shield or structural support. Bone, mollusc shells, deep sea sponge Euplectella species, radiolarians, diatoms, antler bone, tendon, cartilage, tooth enamel and dentin are some examples of mineralized tissues.

Sporosarcina pasteurii formerly known as Bacillus pasteurii from older taxonomies, is a gram positive bacterium with the ability to precipitate calcite and solidify sand given a calcium source and urea; through the process of microbiologically induced calcite precipitation (MICP) or biological cementation. S. pasteurii has been proposed to be used as an ecologically sound biological construction material. Researchers studied the bacteria in conjunction with plastic and hard mineral; forming a material stronger than bone. It is a commonly used for MICP since it is non-pathogenic and is able to produce high amounts of the enzyme urease which hydrolyzes urea to carbonate and ammonia.

<span class="mw-page-title-main">Sponge spicule</span> Structural element of sea sponges

Spicules are structural elements found in most sponges. The meshing of many spicules serves as the sponge's skeleton and thus it provides structural support and potentially defense against predators.

<span class="mw-page-title-main">Stereom</span>

Stereom is a calcium carbonate material that makes up the internal skeletons found in all echinoderms, both living and fossilized forms. It is a sponge-like porous structure which, in a sea urchin may be 50% by volume living cells, and the rest being a matrix of calcite crystals. The size of openings in stereom varies in different species and in different places within the same organism. When an echinoderm becomes a fossil, microscopic examination is used to reveal the structure and such examination is often an important tool to classify the fossil as an echinoderm or related creature.

<i>Pyura pachydermatina</i> Species of sea squirt

Pyura pachydermatina is a sea tulip, a solitary species of tunicate in the suborder Stolidobranchia. It is native to shallow waters around New Zealand.

<span class="mw-page-title-main">Microbiologically induced calcite precipitation</span>

Microbiologically induced calcium carbonate precipitation (MICP) is a bio-geochemical process that induces calcium carbonate precipitation within the soil matrix. Biomineralization in the form of calcium carbonate precipitation can be traced back to the Precambrian period. Calcium carbonate can be precipitated in three polymorphic forms, which in the order of their usual stabilities are calcite, aragonite and vaterite. The main groups of microorganisms that can induce the carbonate precipitation are photosynthetic microorganisms such as cyanobacteria and microalgae; sulfate-reducing bacteria; and some species of microorganisms involved in nitrogen cycle. Several mechanisms have been identified by which bacteria can induce the calcium carbonate precipitation, including urea hydrolysis, denitrification, sulfate production, and iron reduction. Two different pathways, or autotrophic and heterotrophic pathways, through which calcium carbonate is produced have been identified. There are three autotrophic pathways, which all result in depletion of carbon dioxide and favouring calcium carbonate precipitation. In heterotrophic pathway, two metabolic cycles can be involved: the nitrogen cycle and the sulfur cycle. Several applications of this process have been proposed, such as remediation of cracks and corrosion prevention in concrete, biogrout, sequestration of radionuclides and heavy metals.

<span class="mw-page-title-main">Pupa Gilbert</span> Italian-American biophysicist and geobiologist

Pupa Gilbert is an American biophysicist and geobiologist. She has been pioneering synchrotron spectromicroscopy methods since 1989, and she continues to use and develop them today. Since 2004 she has focused on biomineralization in sea urchins, mollusk shells, and tunicates. She and her group are frequent users of the Berkeley-Advanced Light Source.

<span class="mw-page-title-main">Lia Addadi</span> Israeli biochemist

Lia Addadi is a professor of structural biology at the Weizmann Institute of Science. She works on crystallisation in biology, including biomineralization, interactions with cells and crystallisation in cell membranes. She was elected a member of the National Academy of Sciences (NAS) in 2017 for “distinguished and continuing achievements in original research”, and the American Philosophical Society (2020).

<span class="mw-page-title-main">Patricia Dove</span> American geochemist and crystal growth researcher

Patricia Martin Dove is an American geochemist. She is a university distinguished professor and the C.P. Miles Professor of Science at Virginia Tech with appointments in the department of Geosciences, department of Chemistry, and department of Materials Science and Engineering. Her research focuses on the kinetics and thermodynamics of mineral reactions with aqueous solutions in biogeochemical systems. Much of her work is on crystal nucleation and growth during biomineralization and biomaterial interactions with mineralogical systems. She was elected a member of the National Academy of Sciences (NAS) in 2012 and currently serves as chair of Class I, Physical and Mathematical Sciences.

<span class="mw-page-title-main">Particulate inorganic carbon</span>

Particulate inorganic carbon (PIC) can be contrasted with dissolved inorganic carbon (DIC), the other form of inorganic carbon found in the ocean. These distinctions are important in chemical oceanography. Particulate inorganic carbon is sometimes called suspended inorganic carbon. In operational terms, it is defined as the inorganic carbon in particulate form that is too large to pass through the filter used to separate dissolved inorganic carbon.

References

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  16. ↑ Rodriguez-Blanco, J.D.; Shaw, S.; Bots, P.; Roncal-Herrero, T.; Benning, L.G. (2014). "The role of Mg in the crystallisation of monohydrocalcite" (PDF). Geochimica et Cosmochimica Acta. 127: 204–220. Bibcode:2014GeCoA.127..204R. doi:10.1016/j.gca.2013.11.034.
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  20. ↑ Tobler, D.J.; Rodriguez-Blanco, J.D.; Dideriksen, K.; Sand, K.K.; Bovet, N. Benning; Stipp, S.L.S. (2014). "Effect of aspartic acid and glycine on amorphous calcium carbonate (ACC) structure, stability and crystallisation". Procedia Earth and Planetary Science. 10: 143–148. Bibcode:2014PrEPS..10..143T. doi:10.1016/j.proeps.2014.08.047. hdl: 2262/89858 . S2CID   85651837.
  21. ↑ Tobler, D.J.; Rodriguez-Blanco, J.D.; Dideriksen, K.; Bovet, N.; Sand, K.K.; Stipp, S.L.S. (2015). "Citrate Effects on Amorphous Calcium Carbonate (ACC) Structure, Stability, and Crystallization". Advanced Functional Materials. 25 (20): 3081–3090. doi:10.1002/adfm.201500400. hdl: 2262/89861 . S2CID   97248392.
  22. ↑ Bentov, Shmuel; Weil, Simy; Glazer, Lilah; Sagi, Amir; Berman, Amir (2010). "Stabilization of amorphous calcium carbonate by phosphate rich organic matrix proteins and by single phosphoamino acids". Journal of Structural Biology . 171 (2): 207–215. doi:10.1016/j.jsb.2010.04.007. PMID   20416381.
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  24. ↑ The dietary supplement "DENSITY" homepage Archived March 11, 2015, at the Wayback Machine
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  27. ↑ Mehta, Neha; Bougoure, Jeremy; Kocar, Benjamin D.; Duprat, Elodie; Benzerara, Karim (2022-04-08). "Cyanobacteria Accumulate Radium ( 226 Ra) within Intracellular Amorphous Calcium Carbonate Inclusions". ACS ES&T Water. 2 (4): 616–623. doi:10.1021/acsestwater.1c00473. ISSN   2690-0637. S2CID   247456505.
  28. ↑ Cam, Nithavong; Benzerara, Karim; Georgelin, Thomas; Jaber, Maguy; Lambert, Jean-François; Poinsot, Mélanie; Skouri-Panet, Fériel; Cordier, Laure (2016-11-01). "Selective Uptake of Alkaline Earth Metals by Cyanobacteria Forming Intracellular Carbonates". Environmental Science & Technology. 50 (21): 11654–11662. doi:10.1021/acs.est.6b02872. ISSN   0013-936X. PMID   27712057. S2CID   30420839.
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