The effect of alumina addition on the synthesis of zeolite from fly ash by hydrothermal method

Abstract

ZSM-5 and analcime were successfully synthesized from coal fly ash using hydrothermal method in alkaline solution. The fly ash used was taken from the Paiton PLTU, one of the largest steam power plants in Indonesia. The fly ash was purified using sulphuric acid for 30 minutes and it was found that it has 17.7 wt.% of Si content and 2.79 wt.% of Al content. The zeolite synthesis was carried out in a hydrothermal reactor at 160 oC and 3 bar for 48 hours both with and without alumina addition. Subsequently, the zeolite produced was then calcined and characterized using X-ray diffraction (XRD) analysis. The results showed that ZSM-5 crystals were obtained from the hydrothermal process without alumina addition. On the other hand, the addition of alumina has a large impact on the hydrothermal process, which formed analcime crystals as the final product. Furthermore, the ZSM-5 and analcime produced have great correspondence to ICSD (Inorganic Crystal Structure Database) standards (no. 61010 for ZSM-5 and no. 34877 for analcime).