Effect of pre-treatments on analcime synthesis from abundant clay-rich illite

Abstract Analcime is an important nanomaterial in: heterogeneous catalysis, selective adsorption, stomatology, sensing, and nanoelectronics. Given its occurrence in limited regions worldwide, achieving low-cost, high-purity synthesis of this zeolite is crucial. The objective of the present study was to synthesize pure analcime from an abundant, naturally occurring clay-rich illite material without the use of an organic template. Various pretreatment methods – NaOH pre-fusion, sonication, and reflux – using 1.5 M NaOH were explored to enhance the material’s reactivity at nanoscale. The resulting samples were annealed hydrothermally at 150°C for 36 h. The effect of the Si/Al mass ratio, ranging from 2 to 4, was examined by incorporating a fumed silica by-product into the optimally pre-treated sample. Characterization using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FT-IR), and Brunauer–Emmett–Teller (BET) surface area measurement confirmed that all pre-treatment routes converted illite (Si/Al≈2) effectively into analcime, demonstrating nanoscale control and synthesis precision. The analcime content achieved 77.8% through hydrothermal synthesis without pre-treatment, while it increased to 80.2%, 83.4%, and 91.7% with sonochemical, reflux, and NaOH pre-fusion pre-treatments, respectively. Notably, high-purity analcime with superior crystallinity was attained using the NaOH pre-fusion pre-treatment of a blend of clay and fumed silica with a Si/Al ratio of 3.71. The zeolite synthesized exhibited a surface area of 23.76 m 2 g –1 and a significant cation exchange capacity of 510 meq 100 g –1 . These results offer valuable insights into the synthesis of organic-template-free zeolites, emphasizing the importance of precise nanoscale methodology in enhancing clay-phase reactivity. Furthermore, this study distinguishes itself as one of the few in the literature to prepare pure analcime by innovatively combining low-cost precursor clay and fumed silica, contributing to the advancement of nanoscale material synthesis and its applications in technology.