Diatomaceous earth facts for kids
Diatomaceous earth, also known as diatomite, kieselguhr, kieselgur, and Celite, is a naturally occurring, soft, chalk-like, sedimentary rock that is easily crumbled into a fine white to off-white powder. This powder has an abrasive feeling similar to pumice powder and is very light-weight due to its high porosity. It is made primarily of silica and consists of fossilized remains of diatoms, a type of hard-shelled algae. It is used as a filtration aid, as a mild abrasive, as a mechanical insecticide, as an absorbent for liquids, as cat litter, and as a component of dynamite. Heat resistant as well, kieselguhr can be used as an insulator.
Contents
Applications
Filtration
The most common use (68%) of diatomaceous earth is a filter medium, especially for swimming pools. Diatomaceous earth has a high porosity because it is made of microscopically small coffin-like hollow particles. It is used in chemistry as a filtration aid to filter very fine particles that would otherwise pass or clog the filter paper. It is also used to filter water and other liquids such as beer. It can also filter syrups and sugar. Other industustries such as paper, paints, ceramics, soap, and detergents use it as a filling material.
Abrasive
The oldest use of diatomite is as a very mild abrasive and for this purpose has been used in toothpaste and metal polishes.
Pest repellent
Diatomaceous earth is also used as an insecticide due to its abrasive properties. The fine powder causes small cuts in the waxy outer layer of insects, causing them to dehydrate. In addition to insects, this also works against gastropods and is commonly employed in gardening to defeat slugs. Beekeepers are apparently experimenting with it to keep small hive beetles from breeding. It is sometimes mixed with an attractant or other additives to increase its effectiveness. Medical grade diatomaceous earth is sometimes used to de-worm both animals and humans.
Absorbent
Its absorbent qualities make it useful for spill cleanup and the U.S. Center for Disease Control recommends it to clean up toxic liquid spills.
More recently, diatomaceous earth 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.
In 1867, Alfred Nobel discovered that nitroglycerin could be made much more stable if absorbed in diatomaceous earth. He patented this mixture as dynamite.
Geology
Because diatomaceous earth forms from the remains of water-borne diatoms, it is found in proximity to either current or former bodies of water. Diatomaceous earth is generally divided into two categories based upon source: freshwater and saltwater. Freshwater diatomaceous earth is mined from dry lakebeds and is characteristically low in crystalline silica content. Saltwater diatomaceous earth, in contrast, contains a high crystalline silica content making it a useful material for filters due to the sieve-like features of the crystals.
Specific varieties
- TripoliteDakine refers to the variety found in Tripoli, Libya.
- Bann clay refers to the variety found in the Lower Bann valley in Northern Ireland.
Safety considerations
The absorbent qualities of diatomaceous earth can result in a significant drying of the hands if handled without gloves. The saltwater form contains the 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 (silicon dioxide) poses a serious inhalation hazard because it can cause silicosis and can eventually lead to cancer. Amorphous silica can cause dusty lungs, but does not carry the same degree of risk as crystalline silica. Food-grade diatomaceous earth generally contains very low percentages of crystalline silica. Diatomaceous earth produced for pool filters is treated with heat, causing the formerly amorphous silicon dioxide to assume crystalline form; so if you want to know the risk you are assuming with exposure to diatomaceous earth, it is important to ascertain its crystalline silica content.
Images for kids
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Diatomaceous earth as viewed with bright-field illumination under an optical microscope. This image of diatomaceous earth particles in water is at a scale of 6.236 pixels/μm, the entire image covering a region of approximately 1.13 by 0.69 mm.
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Scanning electron micrograph of diatomaceous earth -
Individual diatom cell walls often maintain their shape even in commercially processed filter media, such as this one for swimming pools
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Live marine diatoms from Antarctica (magnified)
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c. 1900–1910 Diatomaceous earth pit at Neuohe
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c. 1900–1910 a drying area: one firing pile is being prepared; another is under way
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1913: Staff at the Neuohe factory, with male workers and a female cook in front of a drying shed
See also
In Spanish: Diatomita para niños
