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Palygorskite (Russian: Палыгорскит) or attapulgite is a magnesium aluminium phyllosilicate with the chemical formula ) that occurs in a type of clay soil common to the Southeastern United States. It is one of the types of fuller's earth. Some smaller deposits of this mineral can be found in Mexico, where its use is tied to the manufacture of Maya blue in pre-Columbian times.Arnold 2005
Attapulgite, unlike some bentonite (sodium-rich montmorillonites), can gel in seawater, forming gel structures in salt water and is used in special saltwater drilling mud for drilling formations contaminated with salt. Palygorskite particles can be considered as charged particles with zones of positive and negative charges. The bonding of these alternating charges allows them to form gel suspensions in salt and fresh water.
Attapulgite clays found in the Meigs-Quincy district are bundles of palygorskite clay particles between 2 and 3 μm long and below 3 nm in diameter. The bundles are surrounded by a matrix of smectite clays that are slightly swellable. Dry-process grades contain up to 25% non-attapulgite material in the form of carbonates and other mineral inclusions. Processing of the clays consist of drying and grinding the crude clay to specific particle size distributions with specific ranges of gel viscosity measured by a variety of means depending on the end use.
Gel-grade, dry-processed attapulgites are used in a very wide range of applications for suspension, reinforcement, and binding properties. Paints, sealants, adhesives, tape-joint compound, catalysts, suspension fertilizers, wild-fire suppressants, foundry coatings, animal feed suspensions, and molecular sieve binders are just a few uses of dry-process attapulgite.
7–10% attapulgite clay mixed with the eutectic salt, sodium sulfate decahydrate (mirabilite or Glauber's salt), keeps anhydrous suspended in the solution, where they hydrate during phase transition and hence contribute to the heat absorbed and released when Glaubers salt is used for heat storage.
Stabilization of nanopalygorskite suspensions was improved using mechanical dispersion (magnetic stirring, high-speed shearing and Sonication) and (carboxymethyl cellulose, Alginic acid, sodium polyphosphate, and Acrylate polymer) at different pH. Surface energy and nanoroughness were studied in a palygorskite sample.
Until 2003, Kaopectate marketed in the US also contained attapulgite. However, at that time, the U.S. Food and Drug Administration retroactively rejected medical studies showing its efficacy, calling them insufficient. Kaopectate's U.S. formula was changed to bismuth subsalicylate (pink bismuth). The next year (2004), an additional change in labeling was made; from then on, Kaopectate was no longer recommended for children under 12 years old. Nevertheless, Kaopectate with attapulgite is still available in Canada and elsewhere. Until the early 1990s, Kaopectate used the similar clay product kaolinite with pectin (hence the name).
A Maya region source for palygorskite was unknown until the 1960s, when one was found at a cenote on the Yucatán Peninsula near the modern township of Sacalum, Yucatán. A second possible site was more recently (2005) identified, near Ticul, Yucatán.See abstract of Arnold (2005).
The Maya blue synthetic pigment was also manufactured in other regions and used by other Mesoamerican cultures, such as the of central Mexico. The blue coloration seen on Maya codices and Aztec codices, and early colonial-era manuscripts and maps, is largely produced by the organic-inorganic mixture of añil leaves and palygorskite, with smaller amounts of other mineral additives.Haude (1997). Human sacrificial victims in postclassic Mesoamerica were frequently daubed with this blue pigmentation.Arnold and Bohor (1975), as cited in Haude (1997).
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