A Mexican kaolin deposit: XANES characterization, mineralogical phase analysis and applications

Abstract

A kaolin obtained from Villa de Reyes, a region near to San Luis Potosí (México) was characterized by means of X-ray powder diffraction (XRD, optical microscopy (OM), scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-Ray Absorption Near Edge Spectroscopy (XANES), thermal analysis (DTA/TGA), dilatometry (DIL), and chemical analysis. Mineralogical and morphological characteristics of the mineral are presented. The kaolin sample was formed mainly by kaolinite, but other minor phases were also detected such as quartz, cristobalite, tridymite, and dolomite. The high content of volcanic glass detected, by optical microscopy, revealed an incomplete kaolinization process of the raw material. The reddish color of the kaolin was associated with the free iron content in the form of limonite [FeO(OH)], which was determined by XANES. The influence of the particle size on the whiteness of kaolin was evaluated. Dilatometric analysis revealed a strong thermal expansion between 110 y 240 °C, which would difficult the use of this material in traditional ceramic applications. On the other hand the presence of glass and high temperature phases of SiO2, such as cristobalite and tridymite will favor its use in the cement industry.

Keywords

• kaolin
• characterization
• minerals
• ceramic
• sem