Diatomaceous Earth

Define Diatomaceous Earth - Diatomaceous Earth (DE) is a naturally occurring, soft and sedimentary rock that can be crumbled into a fine white to off white powder. It is also known as the diatomite or Kieselgur/kieselguhr, with the particle size ranging from less than three micrometres to more than one millimetre, but typically it is from 10 to 200  μm. The powder of the diatomaceous earth can have the abrasive feel the same as the pumice powder depending on the granularity and it has a low density as a result of its high porosity. The diatomaceous earth that is dried in the oven, is 80–90% silica, with 2–4% alumina, and 0.5–2% iron oxide.

Diatomaceous Earth Meaning - It is a fine siliceous earth composed chiefly of the cell walls of diatoms. 

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Diatomaceous Earths contains the remaining fossilized diatoms, it is a type of hard-shelled protist. Diatomaceous earth can be used in the filtration aid, mild abrasive products including metal polishes and the toothpaste, mechanical insecticide, matting agent for coatings, absorbent for liquids, thermal insulators, activator in blood clotting studies, cat litter, porous support for the chemical catalysts, anti-block in the plastic films, reinforcing filler in plastics and rubbers, and soil for potted plants and trees like bonsai.

Composition 

The composition of the diatomaceous earth is different for the different deposits, varying with the blend of the pure diatomaceous earth combined with other natural clays and minerals.  The diatoms in each deposit vary in the quantity of the silica, depending on the age of the silica, the species of the diatom can also vary among the deposits. The species of the diatom mainly depends on the age and paleoenvironment of the deposit, in turn, the shape of the diatom is determined by the species.

Many deposits in British Columbia, such as Red Lake Earth are derived from the Miocene epoch, which contains Melosira granulata, a diatom species. These diatoms have a small globular form and are around 12 to 13 million years old. A deposit containing diatoms from this epoch will provide significantly more benefits than a deposit from a previous epoch. For example, diatoms from the Eocene epoch which is approximately 40 to 50 million years old are not more effective in their ability to absorb fluid, because as the diatoms get older it recrystallizes and their smaller pores will be filled with silica. 

Formation 

The formation of the diatomite occurs by the accumulation of the amorphous silica (opal, SiO₂ . nH₂O), which the remaining dead diatoms in lacustrine or marine sediments. A pair of symmetrical shells, or frustules, make up the fossil remains. Marine diatomites can be found in a number of other rock types, but lacustrine diatomites are almost exclusively found with volcanic rock. The diatomite in diatomaceous chert has been cemented with silica.

Diatoms can remove amorphous silica from water with less than 1% amorphous silica saturation. Since they are surrounded by an organic matrix, their frustules do not dissolve. Clay minerals may also form on the frustules, preventing them from dissolving in the seawater. The frustule is stripped of its organic coating and exposed to seawater when the diatom dies. As a result, only 1% to 10% of frustules live long enough to be buried under sediments, and some of this is dissolved. In the sedimentary record, only about 0.05 percent to 0.15 percent of the original amount of silica generated by diatoms is stored.

Discovery 

Diatomaceous earth was discovered by German peasant Peter Kasten In 1836 or 1837, when saw sinking a well on the northern slopes of the Haußelberg hill, in the Lüneburg Heath in North Germany.

Extraction and storage sites in the Lüneburg Heath

• Neuohe – extraction from 1863 to 1994

• Wiechel from 1871 to 1978

• Hützel from 1876 to 1969

• Hösseringen from c.1880 to 1894

• Hammersdorf from c.1880 to 1920

• Oberohe from 1884 to 1970

• Schmarbeck from 1896 to c. 1925

• Steinbeck from 1897 to 1928

• Breloh from 1907 to 1975

• Schwindebeck from 1913 to 1973

• Hetendorf from 1970 to 1994

Commercial Forms 

Diatomaceous earth is found commercially in many forms:

• Diatomaceous earth granulated is a raw material that has been crushed for easy packaging.

• Diatomaceous earth that has been milled or micronized is particularly fine (10 μm to 50 μm) and is used in insecticides.

• For filters, calcined diatomaceous earth is heat-treated and activated.

Usage 

There are several uses of the diatomaceous earth, some of them are explained below:

• Explosives - Alfred Nobel in 1866 discovered that absorbing nitroglycerin in diatomite made it much more stable. This makes transporting and treating nitroglycerin in its raw form much safer. In 1867, he patented this mixture as dynamite, and it is also known as guhr dynamite.

• Filtration - Wilhelm Berkefeld, a Celle engineer, recognised diatomaceous earth's filtering ability and created tubular filters (also known as filter candles) driven by diatomaceous earth. These Berkefeld filters were successfully used during the cholera outbreak in Hamburg in 1892. Diatomaceous earth, in one form, is used as a filter medium, especially in swimming pools.

• Abrasive - Diatomite's oldest application is as a very mild abrasive, and it's been used in toothpaste, metal polishes, and even some facial scrubs for this reason.

• Pest Control - Diatomite's abrasive and physico-sorptive properties make it useful as an insecticide. The fine powder absorbs lipids from the waxy outer layer of several insect exoskeletons, which serves as a shield to prevent water vapour from escaping the insect's body. The evaporation of water from their bodies is increased when the layer is damaged, causing them to become dehydrated, often fatally.

• Thermal - Its thermal properties allow it to be used as a fire-resistant safe's barrier material. It's also used in cryogenic-safe evacuated powder insulation. To improve the efficacy of vacuum insulation, diatomaceous earth powder is injected into the vacuum room. It was used as a thermal heat barrier in traditional AGA cookers.

• Catalyst Support - Diatomaceous earth is often used as catalyst support, primarily to increase the surface area and operation of the catalyst. To boost its operation as a hydrogenation catalyst, nickel can be assisted on the material (the combination is known as Ni–Kieselguhr).

• Agriculture - Natural freshwater diatomaceous earth is used in agriculture as an anti-caking agent and insecticide for grain storage. The Food and Drug Administration has approved it as a feed additive to avoid caking.

• Construction -  The diatomaceous earth spent in the process of brewing can be added to the ceramics for the manufacturing of red bricks with higher open porosity. Diatomaceous earth is considered one of the most prominent inorganic, non-metallic materials. Which can be used for the production of different ceramics, along with the production of porous ceramics under low-temperature hydrothermal technology.