Synthesis of swelling micas with stoichiometric amount of fluorine, characterization and ion exchange studies

A stoichiometric fluorine content method for synthesizing high charge density swelling micas is developed by keeping the fluorine content stoichiometric in the precursors. Hydrated mica phase was obtained in all cases. The synthetic mica samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and magic angle spinning nuclear magnetic resonance (MASNMR) spectroscopy. Using the stoichiometric amount of fluorine has yielded micas of small particle size (< 2 μm) as revealed by SEM. Distribution coefficient, K_d values were obtained for the micas by conducting ion exchange studies with solutions containing Sr²⁺ and Ba²⁺ cations separately and these studies show high selectivity for the above metal cations. The present studies show that swelling micas could be obtained without using excessive fluorine in the synthesis procedure, there by minimizing processing steps and perhaps reducing but not eliminating the release of fluorides in to the environment. The confirmation of high selectivity for cations such as Sr²⁺ makes these micas potential remediation agents for cleanup of nuclear waste contaminated sites.