Organic Intercalation with Dimethyl Sulfoxide and Diaminomethanal in the Kaolin Organophilization Process

Abstract

The intercalation process, which involves the incorporation of organic molecules to increase the basal spacing between the structural layers of clay, also known as organophilization, has been extensively studied over several decades, particularly in clays with higher reactivity, such as montmorillonite, a mineral in the smectite group. In contrast, kaolinite, characterized by lower reactivity, presents significant challenges to the intercalation process due to its inherent mineralogical structure. Despite these challenges, the widespread abundance of kaolinite in the Earth’s crust continues to drive interest in its potential novel applications. The main objective of this study was to investigate the organophilization of kaolin using diaminomethanal (urea) and dimethyl sulfoxide (DMSO), alternating the variables that were studied in isolation previously. Initially, the kaolinite was characterized to determine its physicochemical, mineralogical, thermal, and morphological properties using various analytical techniques, including X-ray fluorescence, X-ray diffraction (XRD), thermogravimetric analysis, Brunauer–Emmett–Teller surface area analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy. A 2^k factorial experimental design was then employed to evaluate several intercalation parameters, including the type of molecule (urea and DMSO), agitation time (ranging from 12 to 24 h), and powder mass (10–50 g) in a 100 mL solution maintained at 60 °C. The experimental results, as determined by XRD analysis, showed that DMSO was more effective in increasing the basal spacing (from 7.2 to 11.3 Å), with an intercalation efficiency of up to 80%.