Mechanochemical Route and Recrystallization Strategy to Fabricate Mordenite Nanoparticles from Natural Zeolites

For the first time, we fabricated hierarchical mordenite nanoparticles from low-cost natural zeolites through high-energy ball milling followed by recrystallization strategy. The analysis of the as-received natural zeolites revealed that it is comprised of mordenite (MOR) as the main phase and clinoptilolite (HEU) as the impurities phase. The natural zeolites samples were milled by a high-energy ball milling attritor to obtain nano-zeolites within the size of 20-160 nm, which were confirmed by field emission scanning electron microscopy and transmission electron microscopy analysis. The X-ray diffraction study revealed that crystallinity of the milled nano-zeolite has decreased significantly. The high crystallinity of nano-MOR with less phase HEU impurities was recovered after recrystallization of the milled sample in the hydrothermal basic silicate solution. The nitrogen physisorption study showed that the textural properties of recrystallized nano-mordenite were improved with enhancements in the external surface area at 6-fold of the parent. The hierarchical pore system was observed on the recrystallized MOR as the intercrystalline mesopore volume increased to 0.36 cm³/g from only 0.04 cm³/g in the as-received natural zeolites. Recrystallization time, the ratio of the milled sample weight to the solution, and the silica and OH^- concentration were varied to study the effect on the crystallinity of the recrystallized MOR sample. The developed technique has the potential to be applied as an efficient method to prepare better natural mordenite properties for the industrial application.