Highly crystalline zeolite - a from flyash of bituminous and lignite coal combustion

Flyash is being generated in voluminous amounts by large scale coal combust ion process. It poses a serious threat to thermal power industries specific ally, in India, wherein the percent of utilisation of flyash is very poor ( 3-5%). In view of this problem, newer methods of its disposal and utilisati on are being explored. The synthesis of zeolite from flyash appears to be o ne of the most promising alternatives as it has emphasis on value addition to waste material. Flyashes originating from different sources of coal differ in their charact eristics and have implications in this work on Zeolite-A production. These factors have been thoroughly investigated and the conditions favourable for formation of Zeolite-A have been delineated. The reactivity of flyash towa rds zeolite formation is directly dependent on the SiO2/Al2O3 ratio, Fe2O3 and CaO content. Amongst the flyashes investigated, so far the sub-bitumino us coal based flyash with SiO2/Al2O3 ratio of 3.47 appears to be a suitable substrate for Zeolite-A synthesis. These zeolites have been characterised with respect to XRD crystallinity, calcium binding capacity (CBC) and sorpt ion capacity, wherein the crystallinity ranges from 50 to 100%, the CBC ran ges from 290 to 560 meq/100 g and sorption capacity ranges from 16.6 to 23. 8%. (C) 2001 Elsevier Science B.V All rights reserved.