Attapulgite Clay

Attapulgite clays are a composite of  smectite and palygorskite. Smectites are expanding lattice clays, of which bentonite is a commonly known generic name for smectite clays. The palygorskite component is an acicular bristle-like crystalline form that does not swell or expand. Attapulgite forms gel structures in fresh and salt water by establishing a lattice structure of particles connected through hydrogen bonds.

Attapulgite, unlike some bentonite (sodium rich montmorillonites), can gel in sea water, 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 (Glaubers salt), keeps anhydrous crystals 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 ultrasonication) and polyelectrolytes (carboxymethylcellulose, alginate, sodium polyphosphate, and poly(sodium acrylate)) at different pH. Surface energy and nanoroughness were studied in a palygorskite sample

Medical use,

Attapulgite is used widely in medicine. Taken by mouth, it physically binds to acids and toxic substances in the stomach and digestive tract. Also, as an antidiarrheal, it was believed to work by adsorbing the diarrheal pathogen. For this reason, it has been used in several antidiarrheal medications, including Diar-Aid.Diarrest, Diasorb, Diatabs, Diatrol, Donnagel, Kaopek, k-pek, Parepectolin and Rheaban.  It has been used for decades to treat diarrhea.

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).