Silica-alumina molar ratio and some factors effect on the synthesis of zeolites from fly ash

摘要

In order to improve the activity and eliminate some impurities, pretreatment wasused before hydrothermal synthesis. The fly ash was mixed with an aqueous NaOH solution, the alkali melted fly ash was also adopted, which is hydrothermally treated at about104^(。)C, and the liquid/solid ratio was controlled at 6:1. In order to control Si/AI molar ratio,SiO_2 or AI_2O_3 powers were added to the fly ash. The results of XRD and SEM show thatthe alkali melted can activate fly ash and eliminate its quartz and mullite, along with theimprovement of Si/AI molar ratio and alkalinity. In addition, zeolite Na-A changes into sodalite gradually, and nepheline is the synthesized intermediateproduct. Those resultswere discussed on the basis of a formation mechanism of zeolite from fly ash.