Preparation of NaA zeolite spheres from geopolymer gels using a one-step method in silicone oil

A simple one-step method for the preparation of NaA zeolite spheres using a nonhydrothermal process is introduced in this article. The mechanism of formation of NaA zeolite spheres was studied by the suspension solidification method in both silicone oil and polyethylene glycol. The crystalline phase, micromorphology, and microstructure of the spheres produced were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET specific surface tests. The results demonstrate that geopolymer spheres can directly transform into NaA zeolite spheres in silicone oil but not in polyethylene glycol (PEG). Since the formation process in PEG cannot retain water in the geopolymer spheres, there is no additional medium that can transport and rearrange the aluminate and silicate groups in the geopolymer gel. Thus, the geopolymer gel cannot crystallize to form zeolite crystals.