Ultrasound-assisted green template removal from Al-MCM-41 derived from kaolin: Temperature-dependent structural evolution and thermodynamic insight into CTAB solvation

Al-MCM-41 has attracted significant interest in heterogeneous catalysis, adsorption, and materials engineering due to its high surface area, uniform mesoporous structure, and acid sites arising from aluminum incorporation into the silica framework. However, conventional template removal requires high temperature calcination which may induce framework degradation, partial dealumination and high energy consumption. In this study, a sustainable ultrasound-assisted method was developed for CTAB template removal from Al-MCM-41 derived from Indonesian kaolin under mild operating conditions. The influence of sonication temperature (T = 30, 40, 50, 60, and 70 °C) on mesostructure properties, framework stability and surfactant extraction efficiency was systematically investigated. Low angle XRD analysis confirmed the preservation of the ordered hexagonal mesostructure with characteristic peak (100) at 2θ = 1–2°, with enhanced structural ordering at elevated sonication temperature. The N 2 adsorption-desorption analysis of Al-MCM-41 (30 ℃) exhibit the highest surface area of 645.94 m 2 /g whereas excessive sonication temperature reduced textural properties due to intensified cavitation effects and possible pore wall deterioration. Morphological analysis indicated reduced agglomeration and improved elemental dispersion following sonication treatment. FTIR and TGA analysis confirmed the successful template removal without significant destruction. The integrated experimental and computational analysis further confirmed that higher temperatures enhance CTAB solvation in ethanol through strong electrostatic interactions, hydrogen bonding, and favorable entropy. These results provide insights into optimizing CTAB removal from Al-MCM-41 and could serve as a green and energy-efficient alternative for sustainable mesoporous catalyst production.