CO₂ adsorption performance of template free zeolite A and X synthesized from rice husk ash as silicon source

In this work, zeolite NaA (RA) and NaX (RX) have been successfully synthesized using rice husk ash and it is a low cost synthesis process and it does not produce environmental hazards. Sodium silicate (SS) is extracted from rice husk ash which is an alternative silica source for zeolite synthesis. The zeolites are prepared by using a SS silica source extracted from the rice husk ash, and it has been used as an adsorbent for the CO₂ adsorption process which may help in controlling the global warming problems. The zeolites are synthesized by a hydrothermal method without using any organic templating agent. FESEM and TEM micrographs revealed that the synthesized zeolites RA and RX have "Ice cube" and octahedral morphology respectively. From the N₂ sorption studies, the BET surface area of the synthesized zeolites have been found and are 106.25 m² g^-1 and 512.79 m² g^-1 respectively. The maximum CO₂ adsorption capacities of zeolite RA and RX are 2.22 and 2.45 mmol g^-1, respectively at a temperature of 297.15 K. The recorded data are fitted by using non-linear adsorption isotherm models of Langmuir, Freundlich and Toth isotherm models. The fitted isotherm models are observed to be a type I adsorption isotherm according to the IUPAC classification criterion.