Characterization of X-type Zeolite Prepared from Coal Fly Ash

摘要

This study presents experimental results dealing with the possibility of transforming F-class fly ash into a zeolitic material. Two types of synthesis methods were used in the research: hydrothermal and low-temperature synthesis. As a result of alkaline reaction of fly ash with NaOH, all experimental cases yielded zeolitic material that are rich in a Na-X phase. The mineralogical composition (determined by SEM and XRD analysis) as well as the physio-chemical (chemical composition, CEC, textural parameters - BET surface area and PSD) properties of a Na-X phase were determined. The ratio Si/Al in the case of Na-X obtained by hydrothermal reactions was 1.2, but low-temperature reaction resulted in 1.04. CEC values for hydrothermal synthesis (average 240 meq/100g) are higher than low-temperature synthesis (average 200 meq/100 g). The BET surface area of hydrothermal Na-X is almost five times higher (332.5 m~2/g) than low-temperature Na-X (73 m~2/g). Hydrothermal reaction gave the zeolitic phase rich in Na-X that amount in total reaction products was from 55 to 60%, whereas in low-temperature reactions the Na-X phase in zeolitic material ranged from 42 to 55%. This work showed the potential of fly ash to be zeolitic materials through the proposed synthesis methods. An effective reaction turned out to be hydrothermal synthesis, which could form about 60% zeolite phase during a 24-hour reaction.