Characterization of halloysite from Thung Yai District, Nakhon Si Thammarat Province, in Southern Thailand

Abstract

Halloysite obtained from Thung Yai District, Nakhon Si Thammarat Province, Southern Thailand was characterized byX-Ray fluorescence (XRF), X-Ray diffraction (XRD), Fourier transform infrared (FTIR), a zeta potential analyzer, thermalanalysis (TGA and DTA), scanning (SEM), and transmission (TEM) electron microscopy. SEM and TEM analysis showedthat it consisted mainly of hollow microtubules and plates with typical dimension of 0.08-0.20 m diameter and lengths of0.50-4.50 m. XRF analysis showed that it consisted mainly of Al2O3 and SiO2. The SiO2/Al2O3 molar ratio of 1.37 indicatedthat a 1:1 clay mineral was the dominant component. It had a high Fe2O3 (2.27%) and TiO2 (2.72%) content. XRD analysisshowed 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 todistinguish between the different types of clay minerals and provided information concerning their structure. TGA and DTAwere used to examine the dehydroxylation and other thermally induced caused changes of the halloysite. The charge (zetapotential) behavior of the halloysite was negative over the relevant pH range (>2) and indicated that the material has apotential for binding of cationic drugs or could be used as a coating polymer from solution.

Keywords

• halloysite characterisation
• clay
• southern Thailand