Halloysite

White to gray or brown solid

Crystalline ... an elongated mineral that occurs in a hydrated and a dehydrated form ... the hydrated form consists of curved sheets of kaolin unit layers

Can exist as spheres, tubular elongates, or plygonal tubes ... particle morphology can have significant effects on ceramic forming systems

This chemical does not meet GHS hazard criteria for 37.5% (3 of 8) of reports.

Warning

H373 (62.5%): May causes damage to organs through prolonged or repeated exposure [Warning Specific target organ toxicity, repeated exposure]

P260, P319, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 8 reports by companies from 3 notifications to the ECHA C&L Inventory.

Wear self contained breathing apparatus for fire fighting if necessary.

Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal and plant life; and conformance with environmental and public health regulations.

Chemically, the outer surface of the halloysite nanotubes has properties similar to SiO2 while the inner cylinder core is related to Al2O3. The charge (zeta potential) behavior of halloysite particles can be roughly described by superposition of mostly negative (at pH 6-7) surface potential of SiO2, with a small contribution from the positive Al2O3 inner surface.The positive (below pH 8.5) charge of the inner lumen promotes loading of halloysite nanotubes with negative macromolecules, which are at the same time repelled from the negatively charged outer surfaces. A wide range of active agents, including drugs, nicotinamide adenine dineculeotide (NAD), and marine biocides, can be entrapped within the inner lumen, as well as within void spaces of the multilayered aluminosilicate shells. This entrapment can be followed by retention and release of the agents, making the halloysite a nanomaterial well suited for macromolecular delivery applications.

Both hydrophobic and hydrophilic agents can be entrapped after an appropriate pre-treatment of the halloysite surface. For example, /the authors/ recently demonstrated loading of the halloysite with urease for bio-catalytic CaCO3 synthesis in the tubule lumen. For hydrophilic molecules (like kellin, NAD, tetracycline) a typical release time was 2-5 hours and for molecules with low solubility in water (like dexamethasone, furosemide, nifedipine) release time 5-20 hours was observed . Macromolecular release profiles from the halloysite are well described by a one-dimensional diffusion model through the nanotube lumen opening.

A clay used in refractories and as a catalyst support

Used primarily in whiteware ceramics as an additive where it adds dry and fired strength and makes the dinnerware more translucent ... also used in paper and as a raw material to make synthetic zeolites.

For more Uses (Complete) data for Halloysite (7 total), please visit the HSDB record page.

Halloysite, a naturally occurring aluminosilicate nanotube, has been undeservedly forgotten. Halloysite (Al2Si2O5(OH)4*2H2O) is a two-layered aluminosilicate, with a predominantly hollow tubular structure in the submicron range and chemically similar to kaolin. The neighboring alumina and silica layers, and their waters of hydration, curve and form multilayer tubes due to a packing disorder. Halloysite is an economically viable material that can be mined from the corresponding deposit as a raw mineral. As for most natural materials, the size of halloysite particles varies within 1-15 microns of length and 10-150 nm of inner diameter, depending on the deposits.