EVALUATION OF MODIFIED FLY ASH BASED NAA-ZEOLITE: EFFECT OF CRYSTALLINITY ON CO2 ADSORPTION CAPACITY

NaA zeolite was successfully synthesised from fly ash through hydrothermal process. The synthesised NaA zeolite was modified with Li+, Ca2+ and Mg2+ through ion exchange at a temperature of 60 degrees C and contact times of 1 h and 4 h. In this study the crystallinity of the synthesised NaA as well as its modified (LiA, CaA and MgA) was evaluated towards CO2 adsorption capacity using temperature programmed desorption (TPD) process at low temperature (40-150 degrees C) and high temperature (150-700 degrees C). The mineral phase and structural characteristics of zeolites were examined using XRD and FT-IR. The results from XRD and FT-IR spectra revealed unique structural alterations influenced by the intrinsic characteristic of individual cation incorporated in NaA zeolite. Monovalent cations displayed highest crystallinity compared to divalent cations (downward order: NaA > LiA > MgA > CaA). Low and high temperature CO2-TPD profiles were independent of the degree of crystallinity of the zeolites and a significant amounts of CO2 desorption occur at low temperature indicating that physisorption is the most prominent adsorption mode in NaA, LiA, CaA and MgA zeolite.