Low-Temperature and Solvent-Free Synthesis of FAU Zeolite: A Nanosized Platform for CO2 Capture and Ion-Exchange

The synthesis of zeolite at a mild temperature without the use of solvents presents a significant and ongoing challenge within industrial applications. In this work, we describe an approach to the solvent-free synthesis of FAU zeolite at 50 °C, achieving high crystalline yields and forming small crystal sizes ranging from approximately 30 to 100 nm. A study by CO2 isotherms at 273 K demonstrates that the nanosized Na-form FAU zeolite possesses high CO2 adsorption capacity (5.93 mmol g–1) at atmospheric pressure. This capacity is attributed to its elevated Na+ content and the presence of large pore sizes (approximately 0.74 nm), positioning it among the most effective systems reported to date. Furthermore, to assess its potential application in the softening of hard water, ion-exchange experiments involving Ca2+ and Mg2+ are pursued over the Na-form FAU sample at 298 K. The results showcase the ion-exchange capacity of 149.3 mg CaCO3/g zeolite and 82.8 mg MgCO3/g zeolite, which is rivaling that of LTA zeolite. These remarkable adsorption capabilities underscore the potential applications of this material in both domestic and industrial contexts.