Halloysite, Halloysite and Halloysite!!, page-219

Hello poundofflesh,

You certainly pose a number of valid questions. I agree with Rhino’s reply and indepth review of ADN’s historic announcements will likely much of the ground here.

I do not presently have the time to descend in any detail with replies to your queries regarding HNTs and their characteristics, however, was interested in the issue you posed about HNTs and their size, uniformity, etc.

My recollection is that the HNTs at the Great White deposit are exceptionally uniform in their size and characteristics, by reason of
the manner in which the deposit was formed (will have to locate the precise reference to that information later).

In any event, amongst the abundance of academic papers and research on HNTs, this one from July 2020 may be of interest to you entitled: “Purification and Sorting of Halloysite Nanotubes into Homogeneous, Agglomeration-Free Fractions by Polydopamine Functionalization”

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7391362/


The limitations on potential uses arising from differences in the sizes of HNTs is identified discussed:

”Halloysite nanotubes (HNTs) are abundant clay nanoparticles that have been utilized in a variety of scientific and industrial applications because of their intrinsic nanostructure, high thermal stability, acceptable mechanical strength, relatively low cost, and biocompatibility. HNTs present a natural hollow tubular structure composed of tetrahedral silicone dioxide outside and octahedral aluminum oxide inside along with a high aspect ratio and a low hydroxyl group density.1 Their unique structural properties make HNTs notable as reinforcing fillers for polymers and also as containers for active components,2,3 resulting in the utilization of HNTs in specific applications such as water purification,4−6 drug delivery,7,8 cancer cell isolation,9,10 bone regeneration,11,12 dentistry,13,14 and cosmetics.15,16HNTs naturally exist in a wide range of lengths and diameters.17 Furthermore, they tend to agglomerate and cannot be individually dispersed in aqueous solutions and polymers. This inhomogeneity and agglomeration behavior of HNTs constitutes a significant limiting factor in the final properties of their nanocomposites, which prevents their full potential utilization. HNTs have been incorporated into polymeric materials mainly to obtain polymer nanocomposites with enhanced mechanical and thermal properties. As for all polymeric nanocomposites, a homogeneous dispersion of the filler within the polymer matrix is one of the key requirements to achieve significant property improvements.18−20”

Accordingly, here a 3 step method was used to separate HNTs into uniform sizes:


”HNTs were successfully separated into monodisperse, agglomeration-free fractions of different sizes through a facile three-step separation process that includes (i) coating of HNT surfaces with polydopamine, (ii) ultrasonication, and (iii) hydrophilicity-based centrifugation. The polydopamine coating on the surface of HNTs imparted hydrophilicity and aqueous dispersibility, which allowed the sorting of HNTs via centrifugation. Following the separation process, the polydopamine coating was completely removed through a simple heat treatment step. Resulting fractions of HNTs were demonstrated to be uniform in size and shape and preserved their intact nanotubular forms and crystal structures.”

Hope this provides an interesting and useful read. Very best to you.