Diatomaceous earth (pronounced /ˌdaɪ.ətɵˌmeɪʃəs ˈɜrθ/) also known as diatomite or kieselgur, is a naturally occurring, soft, siliceous The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with a chemical formula of Si sedimentary rock Sedimentary rock is a type of rock that is formed by sedimentation of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution. Particles that form a sedimentary rock by accumulating that is easily crumbled into a fine white to off-white powder. It has a particle size ranging from less than 1 micron to more than 1 millimeter, but typically 10 to 200 microns.[1] This powder has an abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away. While finishing a material often means polishing it to gain a smooth, reflective surface it can also involve roughening as in satin, matte or beaded finishes feel, similar to pumice Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid cooling and rapid depressurization. The depressurization powder, and is very light, due to its high porosity Porosity is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%. The term is used in multiple fields including pharmaceutics, ceramics, metallurgy, materials, manufacturing, earth sciences and construction. The typical chemical composition of oven dried diatomaceous earth is 80 to 90% silica The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with a chemical formula of Si , with 2 to 4% alumina Aluminium oxide is the family of inorganic compounds with the chemical formula Al2O3. It is an amphoteric oxide and is commonly referred to as alumina, corundum as well as many other names, reflecting its widespread occurrence in nature and industry. Its most significant use is in the production of aluminium metal, although it is also used as an (attributed mostly to clay minerals Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths and other cations. Clays have structures similar to the micas and therefore form flat hexagonal sheets. Clay minerals are common weathering products and low temperature hydrothermal alteration products. Clay) and 0.5 to 2% iron oxide Iron oxides are chemical compounds composed of iron and oxygen. Altogether, there are sixteen known iron oxides and oxyhydroxides.[1]

Diatomaceous earth consists of fossilized remains of diatoms Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans (e.g. Meridion), zigzags (e.g. Tabellaria), or stellate colonies (e.g. Asterionella). Diatoms are producers within the food chain. A characteristic, a type of hard-shelled algae Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in land plants. It is used as a filtration Filtration is a mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass. Oversize solids in the fluid are retained, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the aid, as a mild abrasive, as a mechanical insecticide An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind the increase in agricultural productivity in the 20, as an absorbent Absorption, in chemistry, is a physical or chemical phenomenon or a process in which atoms, molecules, or ions enter some bulk phase - gas, liquid or solid material. This is a different process from adsorption, since molecules undergoing absorption are taken up by the volume, not by the surface . A more general term is "sorption", which for liquids, as cat litter A litter box, sometimes called a sandbox, sand box, litter tray, litter pan, catbox, or cat box, is an indoor feces and urine disposal box for cats that are permitted free roam of a home but who cannot or do not always go outside to relieve themselves, as an activator in blood clotting Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis , wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel. Disorders of coagulation can lead to an increased risk of bleeding (hemorrhage) or clotting (thrombosis) studies, and as a component of dynamite Dynamite is an explosive material based on the explosive potential of nitroglycerin, initially using diatomaceous earth or another absorbent substance such as sawdust as an absorbent. It was invented by Swedish chemist and engineer Alfred Nobel in Krümmel (Geesthacht, Schleswig-Holstein, Germany), and patented in 1867. As it is also heat-resistant, it can be used as a thermal insulator The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer. Heat energy can be transferred by conduction, convection, radiation or by actual movement of material from one location to another. For the purposes of this discussion only the first three.

Contents

Geology and occurrence

Diatomaceous earth as viewed under bright field illumination on a light microscope The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest and simplest of the microscopes. However, new designs of digital microscopes are now available which use a CCD camera to. Diatomaceous earth is made up of the cell walls A cell wall is a tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to act as a pressure vessel, preventing over-expansion/shells of single cell diatoms Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans (e.g. Meridion), zigzags (e.g. Tabellaria), or stellate colonies (e.g. Asterionella). Diatoms are producers within the food chain. A characteristic and readily crumbles to a fine powder. Diatom cell walls are made up of biogenic silica The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with a chemical formula of Si ; silica synthesised in the diatom cell by the polymerisation In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains. There are many forms of polymerization and different systems exist to categorize them of silicic acid Silicic acid is a general name for a family of chemical compounds of the element silicon, hydrogen, and oxygen, with the general formula [SiOx4-2x]n. Some simple silicic acids have been identified in very dilute aqueous solution, such as metasilicic acid (H2SiO3), orthosilicic acid (H4SiO4, pKa1=9.84, pKa2=13.2 at 25°C), disilicic acid (H2Si2O5),. This image of diatomaceous earth particles in water Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state, water vapor or steam is at a scale of 6.236 pixels/μm A micrometre is one millionth of a metre, or equivalently one thousandth of a millimetre or one thousand nanometres. It can also be written in scientific notation as 1×10−6 m, meaning 1⁄1000000 m, the entire image covers a region of approximately 1.13 by 0.69 mm.

Formation

Diatomite forms by the accumulation of the amorphous An "amorphous solid" is a solid in which there is no long-range order of the positions of the atoms. . Most classes of solid materials can be found or prepared in an amorphous form. For instance, common window glass is an amorphous solid, many polymers (such as polystyrene) are amorphous, and even junkfoods such as cotton candy are silica (opal OPAL is a 20 megawatt (MW) pool-type nuclear research reactor that was officially opened in April 2007 at the Australian Nuclear Science and Technology Organisation (ANSTO) Research Establishment at Lucas Heights, located in South Sydney, Australia, SiO2·nH2O) remains of dead diatoms (microscopic single-celled algae Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in land plants) in lacustrine or marine Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology. As a noun it can be a term for a certain kind of navy, or those enlisted in such a navy sediments Sediment is naturally-occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself. The fossil Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record. The study of fossils across geological time, how remains consist of a pair of symmetrical shells or frustules.[1]

Discovery

In 1836 or 1837, the peasant and goods waggoner, Peter Kasten,[2] discovered kieselgur when sinking a well on the northern slopes of the Haußelberg hill, in the Lüneburg Heath The Lüneburg Heath is a large area of heath, geest and woodland in northeastern part of the state of Lower Saxony in northern Germany. It forms part of the hinterland for the cities of Hamburg, Hanover, and Bremen and is named after the town of Lüneburg. Most of the area is a nature reserve. Northern Low Saxon is still widely spoken in the in north Germany. Initially, it was thought that limestone had been found, which could be used as fertiliser. They even tried baking pancakes with it, because it resembled cornmeal[citation needed]. Alfred Nobel Alfred Bernhard Nobel ( pronunciation ) (Stockholm, Sweden, 21 October 1833 – Sanremo, Italy, 10 December 1896) was a Swedish chemist, engineer, innovator, armaments manufacturer and the inventor of dynamite. He owned Bofors, a major armaments manufacturer, which he had redirected from its previous role as an iron and steel mill. Nobel held 355 used the properties of kieselgur in the manufacture of dynamite Dynamite is an explosive material based on the explosive potential of nitroglycerin, initially using diatomaceous earth or another absorbent substance such as sawdust as an absorbent. It was invented by Swedish chemist and engineer Alfred Nobel in Krümmel (Geesthacht, Schleswig-Holstein, Germany), and patented in 1867. The Celle Celle is a town and capital of the district of Celle, in Lower Saxony, Germany. The town is situated on the banks of the River Aller, a tributary of the Weser and has a population of about 71,000. Celle is the southern gateway to the Lüneburg Heath, has a castle (Schloss Celle) built in the renaissance and baroque style and a picturesque old town engineer, Wilhelm Berkefeld, recognised its ability to filter, and developed 'filter candles' fired from kieselgur.[3] During the cholera epidemic in Hamburg in 1892, these Berkefeld filters were used successfully.

Extraction and storage sites in the Lüneburg Heath

The deposits are up to 28 metres thick and are all of freshwater kieselgur.

ca. 1900–1910 Kieselgur pit at Neuohe

ca.1900–1910 a drying area: one firing pile is being prepared; another is under way

1913 Staff at the Neuohe factory, with workers and a female cook in front of a drying shed

Until the First World War World War I was a military conflict centered on Europe that began in the summer of 1914. The fighting ended in late 1918. This conflict involved most of the world's great powers, assembled in two opposing alliances: the Allies and the Central Powers. More than 70 million military personnel, including 60 million Europeans, were mobilized in one of almost the entire worldwide production of kieselgur was from this region.

Other deposits

In Germany kieselgur was also extracted at Altenschlirf [4] on the Vogelsberg (Upper Hesse) and at Klieken Klieken is a village and a former municipality in the district of Wittenberg, Saxony-Anhalt, Germany. Since 1 March 2009, it is part of the town Coswig [5] (Saxony-Anhalt Saxony-Anhalt is a state of Germany. It has an area of 20,447 square kilometres (7,895 sq mi) and a population of 2.4 million (more than 2.8 million in 1990). Its capital is Magdeburg).

There is a layer of kieselgur up to 4 metres thick in the nature reserve of Soos in the Czech Republic The Czech Republic (pronounced /ˈtʃɛk/ chek; Czech: Česká republika, pronounced [ˈtʃɛskaː ˈrɛpuˌblɪka] ( listen), short form Česko [ˈtʃɛskɔ]) is a country in Central Europe. The country borders Poland to the northeast, Germany to the west and northwest, Austria to the south and Slovakia to the east. The Czech Republic has been a.

In Colorado and in Clark, Nevada Nevada is the seventh-largest state in area, and geographically covers the Mojave Desert in the south to the Great Basin in the north. It is the most arid state in the Union. Approximately 86% of the state's land is owned by the U.S federal government under various jurisdictions both civilian and military. As of 2008, there were about 2.6 million (USA), there are deposits that are up to several hundred metres thick in places.

Sometimes kieselgur is found on the surface in deserts A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Deserts are defined as areas with an average annual precipitation of less than 250 millimetres per year, or as areas where more water is lost by evapotranspiration than falls as precipitation. In the Köppen. Research has shown that the erosion of kieselgur in such areas (such as the Bodélé Depression The Bodélé Depression , located at the southern edge of the Sahara Desert in north central Africa, is the lowest point in Chad. Dust Storms from the Bodélé Depression occur on average about 100 days per year (Washington et al., 2005), one typical example being the massive dust storms that swept over West Africa and the Cape Verde Islands in in the Sahara The Sahara is the world's largest hot desert. At over 9,400,000 square kilometres (3,630,000 sq mi), it covers most of Northern Africa, making it almost as large as Europe or the United States. The only larger desert in the world is Antarctica. The Sahara Desert stretches from the Red Sea, including parts of the Mediterranean coasts, to the) is one of the most important sources of climate-affecting dust in the atmosphere.

The commercial deposits of diatomite are restricted to Tertiary The Tertiary is a term for a geologic period 65 million to 1.8 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Tertiary extinction event, at the start of the Cenozoic era, spanning to the beginning of or Quaternary The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Tertiary Period, spanning 2.588 ± 0.005 million years ago to the present. The Quaternary includes two geologic epochs: the Pleistocene and the Holocene Epochs periods. Older deposits from as early as the Cretaceous The Cretaceous , Latin for "chalky", usually abbreviated K for its German translation Kreide (chalk), is a geologic period and system from circa 145.5 ± 4 to 65.5 ± 0.3 million years (Ma) ago. In the geologic timescale, the Cretaceous follows on the Jurassic Period and is followed by the Paleogene Period of the Cenozoic Era. It is the Period are known, but are of low quality.[6] Marine deposits have been worked in the Lompoc area of Santa Barbara County, California Santa Barbara County is a county located on the Pacific coast of the southern portion of the U.S. state of California, just west of Ventura County. As of 2000 the county had a population of 399,347. The estimated total population of Santa Barbara County as of January 2006 was 421,625, according to The California Department of Finance. The county and along the southern California coast. Additional marine deposits have been worked in Maryland Maryland is a major center for life sciences research and development. With more than 350 biotechnology companies located there, Maryland is the third-largest nexus in this field in the United States, Virginia The area's history begins with several indigenous groups, including the Powhatan. In 1607 the London Company established the Colony of Virginia as the first permanent New World English colony. Land from displaced Native American tribes and slave labor each played significant roles in the colony's early politics and plantation economy. Virginia was, Algeria and the MoClay of Denmark. Fresh water lake deposits occur in Nevada, Oregon, Washington and California. Lake deposits also occur in interglacial lakes in the eastern US and Canada and in Europe in Germany, France, Denmark and the Czech Republic. The worldwide association of diatomite deposits and volcanic deposits suggests that the availability of silica from volcanic ash may be needed for thick diatomite deposits.[6]

Applications

Industrial

In 1866, Alfred Nobel discovered that nitroglycerin could be made much more stable if absorbed in diatomite. This allows much safer transport and handling than nitroglycerin in its raw form. He patented this mixture as dynamite in 1867, and the mixture is also referred to as guhr dynamite.

Filtration

Individual diatom cell walls often maintain their shape even in commercially processed filter media, such as this one for swimming pools

The most common use (68%)[citation needed] of diatomaceous earth is as a filter medium, especially for swimming pools. It has a high porosity, because it is composed of microscopically-small, coffin-like, hollow particles. It is used in chemistry under the brand name Celatom or Celite as a filtration aid, to filter very fine particles that would otherwise pass through or clog filter paper. It is also used to filter water, particularly in the drinking water treatment process and in fish tanks, and other liquids, such as beer and wine. It can also filter syrups and sugar. Other industries such as paper, paints, ceramics, soap and detergents use it as a fulling material.

Abrasive

Live marine diatoms from Antarctica (magnified)

The oldest use of diatomite is as a very mild abrasive and, for this purpose, it has been used both in toothpaste and in metal polishes, as well as in some facial scrubs.

Pest control

Diatomite is also used as an insecticide, due to its physico-sorptive properties. The fine powder absorbs lipids from the waxy outer layer of insects' exoskeletons, causing them to dehydrate[7]. Arthropods die as a result of the water pressure deficiency, based on Fick's law of diffusion. This also works against gastropods and is commonly employed in gardening to defeat slugs. However, since slugs inhabit humid environments, efficacy is very low. It is sometimes mixed with an attractant or other additives to increase its effectiveness. Medical-grade diatomite is sometimes used to de-worm both animals and humans. It is most commonly used in lieu of boric acid, and can be used to help control and eventually eliminate a cockroach infestation. This material has wide application for insect control in grain storage.[8]

Absorbent

Its absorbent qualities make it useful for spill clean-up and the U.S. Centers for Disease Control recommends it to clean up toxic liquid spills. These qualities also lend themselves to use in facial masks to absorb excess oils.

It has been employed as a primary ingredient in a type of cat litter. The type of silica used in cat litter comes from freshwater sources and does not pose a significant health risk to pets or humans.

Thermal

Its thermal properties enable it to be used as the barrier material in some fire resistant safes. It is also used in evacuated powder insulation for use with cryogenics.[9] Diatomaceous earth powder is inserted into the vacuum space to aid in the effectiveness of vacuum insulation.

DNA purification

Diatomite (Celite) can be used for the removal of DNA in the presence of a highly concentrated chaotropic agent such as sodium iodide, guanidinium hydrochloride and guanidinium thiocyanate. As with other silicates, the diatomites will remove double stranded DNA but not RNA or proteins. The DNA can be extracted from the diatomites using low ionic strength buffers, including water, at neutral to slightly alkaline pH. Crude diatomites of a uniform size must first be washed in a heated acid such as 5M HCl[10]. Calcination can further improve consistency of the material, while mild caustic treatment may improve adsorption with lower levels of chaotrophs.

Use in agriculture

Natural freshwater diatomaceous earth is used in agriculture for grain storage as an anticaking agent, as well as an insecticide.[11] It is approved by the US Department of Agriculture as a feed supplement.

It is also used as a neutral anthelmintic (dewormer). Some farmers add it to their livestock and poultry feed to improve the health of animals.[12] "Food Grade Diatomaceous Earth" is widely available in agricultural feed supply stores. It is acceptable as organic feed additive for livestock.

Hydroponics

Freshwater diatomite can be used as a growing medium in hydroponic gardens.

It is also used as a growing medium in potted plants, particularly as bonsai soil. Bonsai enthusiasts use it as a soil additive, or pot a bonsai tree in 100% diatomaceous earth. Like perlite, vermiculite, and expanded clay, it retains water and nutrients, while draining fast and freely, allowing high oxygen circulation within the growing medium.

Marker in livestock nutrition experiments

Natural diatomaceous earth (dried, not calcined) is regularly used in livestock nutrition research as a source of acid insoluble ash (AIA), which is used as an indigestible marker. By measuring the content of AIA relative to nutrients in test diets and feces or digesta sampled from the terminal ileum (last third of the small intestine) the percentage of that nutrient digested can be calculated using the following equation:

% Nutrient Digestibility = (1 - (% Nutrientfeces/digesta / % Nutrientfeed) X (% AIAfeed / % AIAfeces/digesta)) X 100

Natural diatomaceous earth (freshwater) is preferred by many researchers over chromic oxide, which has been widely used for the same purpose, but which is also a known carcinogen and therefore a potential hazard to research personnel.

Specific varieties

Climatologic importance

The Earth's climate is affected by dust in the atmosphere, so locating major sources of atmospheric dust is important for climatology. Recent research indicates that surface deposits of diatomaceous earth play an important role. For instance, the largest single atmospheric dust source is the Bodélé depression in Chad, where storms push diatomite gravel over dunes, generating dust by abrasion.[13]

Safety considerations

The absorbent qualities of diatomite can result in a significant drying of the hands if handled without gloves. The flux-calcined form contains a highly crystalline form of silica, resulting in sharp edges. The sharpness of this version of the material makes it dangerous to breathe and a dust mask is recommended when working with it.

The type of hazard posed by inhalation depends on the form of the silica. Crystalline silica poses a serious inhalation hazard because it can cause silicosis. Amorphous silica can cause dusty lungs, but does not carry the same degree of risk as crystalline silica. Natural or dried diatomite generally contains very low percentages of crystalline silica. Diatomite produced for pool filters is treated with high heat (calcining) and a fluxing agent (soda ash), causing the formerly amorphous silicon dioxide to assume its crystalline form.

The crystalline silica content of the dusts particulate is regulated in the United States by the Occupational Safety and Health Administration (OSHA), and there are guidelines for the maximum amounts allowable in the product and in the air near the breathing zone of workers.[14]

See also

References

  1. ^ a b c Antonides1, Lloyd E., Diatomite, 1997, U.S.G.S. http://minerals.usgs.gov/minerals/pubs/commodity/diatomite/250497.pdf
  2. ^ http://www.humboldt-foundation.de/kosmos/kultur/2001_002.htm + Heinrich Küsel „Der Speicher“ v.1930
  3. ^ ELGA Berkefeld Water Treatment (Wasseraufbereitung)
  4. ^ http://www2.natpa.de/bonifatius/senken/p7.htm Über den früheren Abbau von Kieselgur im Vogelsberg/Hessen
  5. ^ http://homepages.compuserve.de/tmby100/kieselgur.htm Geschichte des Kieselgurabbaus in Klieken
  6. ^ a b Cummins, Arthur B., Diatomite, in Industrial Minerals and Rocks, 3rd ed. 1960, American Institute of Mining, Metallurgical, and Petroleum Engineers, pp. 303 - 319
  7. ^ Staff. "Natural Methods for Controlling Fleas."http://www.xmission.com/~emailbox/fleas.htm
  8. ^ http://www.survival-center.com/foodfaq/ff17-oxy.htm Survival Information Center
  9. ^ Flynn, Thomas M. "Cryogenic Equipment and Cryogenic Systems Analysis." Cryogenic Engineering. Boca Raton [etc.: CRC, 2005. Print.
  10. ^ Goren R, Baykara T, Marsoglu M. A study on the purification of diatomite in hydrochloric acid (2002). Scand. J. of Metallurgy 31:115-119
  11. ^ Manitoba Agriculture, Food and Rural Initiatives
  12. ^ Diatomaceous Earth (DE)
  13. ^ Washington et al., Geophys. Res. Lett. 33 (2006) L09401 doi:10.1029/2006GL025827.
  14. ^ Inert Dusts at Kansas State University

External links

Categories: Sedimentary rocks | Inorganic insecticides | Swimming pools | Water treatment | Soil | Soil improvers | Fodder | Fossils

 

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