Preparation And Application Of Halloysite Nanotubes-polysaccharide Composites

Halloysite is a natura aluminosilicate nanotube from a clay mineral with a similar structure to kaolinite, which has a pre-dominantly hollow nanotube structure with an inner diameter of5-10nm. Halloysite nanotubes (HNTs) have attracted great attentions and studies in recent years, due to their characteristics, such as large surface area, large pore vol-ume and nanomater size.In views of the deficiency of mechanical properties and poor water resistance of the starch films, this article researched on the enhance role of halloysite nanotubes for glycerol yam starch film. Experiments showed that halloysite nanotubes and the yam starch exhibited a good compatibility, and the addition of halloysite nanotubes could increase the density of the glycerol yam starch film, the tensile strength, the thermal stability of starch films, the paste viscosity, and reduce the water vapor transmission and fracture elongation. These properities expanded the scope of application of the starch films.In order to improve the hydrophily and biocompatibility of HNTs, amylose was isolated from starch-rich yam, Dioscorea opposita Thunb. and used to prepare a halloysite nanotubes (HNTs) supramolecular structure by mechanical force. Transmission electron microscopy and thermogravimetric analysis showed that the walls of the HNTs were wrapped with an amylose component (about44.1wt%). Good dispersion of amylose-HNT in the DMSO/H2O solution also illustrated that an interaction existed between amylose and the HNT outer surface.The magnetic nano-composite Fe3O4-HNTs was prepared by chemical precipitation method, which was explored the adsorption for three dyes, namely methylene blue (MB), neutral red (NR) and methyl orange (MO). Transmission electron microscopy and X-ray analysis showed that the Fe3O4crystal particles on the HNTs were larger and cluster state. The study of kinetics revealed that the pseudo-second-order kinetic adsorption model was suitable for describing the adsorption of MB, NRand MO on the Fe3O4-HNTs. The magnetic Fe3O4-HNTs exhibited better adsorption on MB than NR, while the adsorption of MO was very little. And as the adsorbent, Fe3O4-HNTs nanocomposite exhibited paramagnetic and could be easily separated from the aqueous solution in a magnetic field.Since the Fe3O4nanoparticles had a tendency to aggregate on HNTs, in this paper, iron oxide nanoparticles were synthesized on halloysite nanotubes (HNTs) modified with anionic guar gum (AGG) to form the HNT-AGG-Fe3O4composite for the removal of methylene blue (MB) from aqueous solution.Transmission electron microscopy showed that HNTs were covered with AGG, and Fe3O4nanoparticles were evenly dispersed on the surface of HNT-AGG composite without obvious aggregation. AGG could act as templates for Fe3O4nanoparticle growth in the smaller sizes. Also hydrophilic AGG could result in the good dispersion of HNT-AGG-Fe3O4in aqueous solution, which facilitates the diffusion of MB molecules to the surface of HNTs. The adsorption process of HNT-AGG-Fe3O4for MB could be described well by the pseudo second-order model.