Sunaree Bordeepong, Darunee Bhongsuwan, Thongchai Pungrassami, and Tripob Bhongsuwan

pp. 599 - 607

Abstract

Halloysite obtained from Thung Yai District, Nakhon Si Thammarat Province, Southern Thailand was characterized by
X-Ray fluorescence (XRF), X-Ray diffraction (XRD), Fourier transform infrared (FTIR), a zeta potential analyzer, thermal
analysis (TGA and DTA), scanning (SEM), and transmission (TEM) electron microscopy. SEM and TEM analysis showed
that it consisted mainly of hollow microtubules and plates with typical dimension of 0.08-0.20 μm diameter and lengths of
0.50-4.50 μm. XRF analysis showed that it consisted mainly of Al₂O₃
 and SiO₂
. The SiO₂
/Al₂O₃
 molar ratio of 1.37 indicated
that a 1:1 clay mineral was the dominant component. It had a high Fe₂O₃
 (2.27%) and TiO₂
 (2.72%) content. XRD analysis
showed that the halloysite was mainly in its dehydrated (7Å basal spacing) form with some kaolinite, quartz and anatase.
Semi quantification in clay by XRD after formamide treatment showed that it was approx. 70% halloysite. FTIR was used to
distinguish between the different types of clay minerals and provided information concerning their structure. TGA and DTA
were used to examine the dehydroxylation and other thermally induced caused changes of the halloysite. The charge (zeta
potential) behavior of the halloysite was negative over the relevant pH range (>2) and indicated that the material has a
potential for binding of cationic drugs or could be used as a coating polymer from solution.