Synthesis of zeolite NA-A using single mode microwave irradiation at atmospheric pressure: The effect of microwave power

摘要

This paper investigates the effects of single mode microwave irradiation on the synthesis of zeolite Na-A from sodium aluminate and sodium silicate gel at atmospheric pressure. Microwave irradiation has been shown to accelerate the zeolitization process from several hours to several minutes. The microwave irradiation employed was produced in a single mode lab scale microwave, which enabled control of irradiated power and temperature of the reaction mixture, while the pressure was controlled by affixing a condenser to a Teflon reactor vessel with a working volume of 20mL. Two sets of experiments were conducted, the first with three levels of temperature and reaction time, and the second with three levels of power and reaction time. The characteristics and physical properties of the synthesized samples were analyzed with different instrumental techniques including XRD, Rietveld refinement, SEM, BET, TGA, and by determination of cation exchange capacity (CEC). It was observed that the crystallinity of the product was influenced by both power and time of microwave irradiation; moreover power and time of microwave irradiation influenced the phase selection between Na-A and Na-X. Single phase zeolite Na-A was achieved with a crystallinity of 80% at 300 W using single mode microwave irradiation at atmospheric pressure after 30min of exposure to radiation.