Separation of Halloysite Nano Tubes (HNTs) by Homogenization of Quartz Contaminated Kaolins Authors: Zhao, Jing Ming 1 ; Chang, Jeong Ho 2 ; Lee, Youn Ki 3 ; Hwang, Kyu Hong 3 ; Lee, Jong Kook 4 ; Source: Journal of Nanoscience and Nanotechnology, Volume 19, Number 2, February 2019, pp. 984-987(4)
Extract: Natural halloysite kaolin contains a lot of impurities such as quartz phases and varies in morphology and size during their formation in the earth. So to utilize as a new type of natural nano material, removing quartz impurities from kaolin clays without scathe the tube morphologies are necessary. So to remove quartz impurities from kaolin by forming a well deflocculated aqueous slip without fracturing the morphology of tubes, the slip of homogenized halloysite clay was recovered by adding polyvalent metallic cations and anionic polyelectrolyte flocculants simultaneously to selectively flocculate the mixture of quartz and halloysite, whereby the halloysite particles form floes and the tubular halloysite remains in suspensions. Then, the uniform size and tubular shape of halloysite was obtained which could be suitably used as a container or a carrier to encapsulate nanomaterials.
....and this one...
Purification of Dunino halloysite by H 2 SO 4 leaching and magnetic separation Authors: P. Sakiewicz (Silesian University of Technology) and Marcin Lutynski (Silesian University of Technology)
Extract: The article presents results of purification and comminution of raw halloysite from the Dunino deposit. The aim of the study was to clean halloysite from Dunino deposit with acid (H2SO4) leaching and to remove iron impurities in order to obtain fine grained fractions smaller than 20 nm, which can be used in future for manufacturing polymer-aluminosilicate composites. The proposed method, where nanotubes (HNT) and nanoplates (HNP) were separated, consisted of several simple stages including crushing, milling magnetic separation and sedimentation. A multi-stage process resulted in three products: heavy iron oxide fraction, HNP and HNT mixture (20nm).
Furthermore, you can even separate the nanotubes into their different lengths....
Purification and Sorting of Halloysite Nanotubes into Homogeneous, Agglomeration-Free Fractions by Polydopamine Functionalization Authors: Cuneyt Erdinc Tas, Emine Billur Sevinis Ozbulut, Omer Faruk Ceven, Buket Alkan Tas, Serkan Unal, and Hayriye Unal*
Extract: 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. The method allowed the sorting of raw polydisperse HNTs into fractions of different quality grades based on the velocity of centrifugation
That took me all of 5 minutes to find and I'm sure there are more.
DYOR!
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