This research was focused on the production of zeolites from CFA throughutilizing ultrasound and microwave power. The initial conventional heating process of 6 h prior to microwave irradiation for samples with high solid-to-liquid (S/L) ratio (CFA mass/ NaOH solution volume) led to a higher yield of zeolite and decreased the synthesis time and consumption of energy,while keeping the high quality of the synthesized zeolite intact. The crystal growth of the nuclei generated over 6 h of conventional hydrothermal treatment was enhanced by the post-microwave heating. Ultrasound-assisted zeolitizationCFA was also applied in this research.
When ultrasound energy was applied after hydrothermal treatment, crystal growth of zeolite nuclei was enhanced. However, when ultrasound irradiation was applied in the early stage; non-hydrothermal treated mixture, crystallization of zeolite was prevented. Ultrasound energy increased the pore diameter and surface area of the synthesized product. The ultrasound-assisted hydrothermal system enhanced the rate of nucleation and decreased the crystallization time during the synthesis process. The present technique could be considered an economic, eco-friendly, and fast conversion process.
This study has shown that zeolites were successfully synthesized from CFA by utilizing microwave and ultrasound irradiation. These novel energy sources significantly decreased the zeolitizationprocess time. The single-mode microwave-assisted synthesis at high S/L ratio has been shown to be much more effective in producing the same results at a lower S/L ratio. On the other hand, utilization of an ultrasound probe produced a single-phase zeolite in a very short synthesis time compared to other conventional methods
