Synergistic effect of high-energy milling and organic intercalation on the kaolin properties and structural evolution

Abstract

Clays are raw materials with a wide range of applications in modern times. They can be used in various industrial applications, from the simplest to the most technological, such as in the ceramic industry to functionalizing components for the intercalation of organic molecules into polymeric matrices. Kaolinitic clays with a 1:1-layer structure is among the most abundant in the Earth's crust and are relatively easy to extract. Therefore, studies aimed at expanding the range of applications through the modification of the microstructure of these clay minerals have increasingly attracted scientific attention. The microstructural alteration of kaolinite through high-energy mechanical action can be an interesting method for mineral functionalization, as it leads to an increase in specific surface area and, consequently, the reactivity of the inorganic solid component. For this reason, this study investigated the effectiveness of the mechanical transformation process using high-purity kaolin, characterized before and after the high-energy milling process using XRF, XRD, DTA/TG, PSD, FTIR, and SEM techniques. The results showed that the milling process significantly altered the kaolinitic microstructure, demonstrating a reduction in particle size under the established experimental conditions, reaching D₉₀ ≤ 1 μm. By obtaining a reactive solid with a significantly increased specific surface area (18× increase through milling), a 2^k factorial experimental design was applied to study some variables of the intercalation process, such as the type of molecule (diaminomethanal - urea and dimethyl sulfoxide - DMSO), stirring time (from 12 to 24 h), and kaolinite mass (varying from 10 to 50 g) in a 100 mL solution. The microstructural characterization results via XRD revealed that the use of DMSO resulted in better efficacy in increasing basal spacing (from 7.2 Å to 11.3 Å with DMSO) and consequently in a possible application with functional groups.