Abstract
Zeolitic products formed by hydrothermal treatment of coal fly ash (FA) with KOH aqueous solution under various reaction conditions were examined. Only linde F-type zeolite (K2Al2Si2O8·3H2O) was newly formed at atmospheric pressure, except formation of a small amount of kalsilite (KAlSiO4) at longer reaction time. The yield of the linde F zeolite was highest when reaction time, temperature, KOH concentration and (KOH solution / FA) ratio were 48 h, 95°C, 8 mol dm-3 and 25 ml g-1, respectively. In this case, the original FA spheres were almost completely dissolved out, and regular prisms of the linde F zeolite crystal with 0.5 to 1 μm in width and 1 to a few μm in length were formed. The specific surface area and cation exchange capacity of the FA-derived linde F zeolite were 20.2 m2 g-1 and 2.3 meq g-1, respectively.
