| Zdroj: |
Journal of Solid Waste Technology & Management; May2003, Vol. 29 Issue 2, p82, 9p, 1 Black and White Photograph, 5 Diagrams, 1 Chart, 1 Graph |
| Abstrakt: |
Devastating effects of flyash on environment have been realized and therefore, regulations for disposal of such waste on land have accordingly been made stringent. It is, therefore, imperative to develop alternate methods of disposal with recourse to resource recovery, and in this context, the utilization of flyash for production of high value added products viz. zeolites is receiving increasing attention. Also, Flyash based zeolite (FAZ) production technology has advantages of value addition, attractive profit margins; with concomitant conservation of raw materials thus offering an edge over other fiyash utilization technologies. The focus of the synthesis program has been to synthesize a wider array of zeolites ranging from highly sorptive material viz. Zeolite-A & X to thermally stable and siliceous zeolites viz. Zeolite-Y, ZSM-5 and Mordenite. The process developed is simple, non-tedious and environmentally benign. The three major steps involved in the synthesis are fusion of fiyash and caustic soda, aging and hydrothermal crystallization. The FAZs have been thoroughly characterized with respect to crystallinity, exchange capacity, surface area, particle and pore size etc. The crystallinity for various zeolites is as follows: Zeolite-A: 100%; Zeolite-X: 99.8%, Zeolite-Y: 97% mordenite: 68% and ZSM-5: 64%. The exchange capacity is significant parameter for assessing use of zeolites as a sorptive material and is as follows: Zeolite-A: 540 meq/100, Zeolite-X: 480 meq/100g, Zeolite-Y: 420 meq/100g, mordenite: 200 meq/100g and ZSM-5: 100 meq/100g. The surface area for Zeolite-A, X, Y, ZSM-5 and mordenite is 580, 560, 480, 320, 200 m²/g respectively. The cost of production for most of the zeolites is 25-40% less than commercial zeolites. [ABSTRACT FROM AUTHOR] |
