The 65th Annual Meeting of the American Crystallographic Association is happening this July 25-29 in Philadelphia. Let us know if you are going and keep in touch in the comments!
Caleb Chappell submitted an abstract, titled "Modeling the crystal structure and ion exchange mechanisms of rare earth elements into zorite" will be presented in two sessions:
First: Undergraduate and Graduate Student Reception (all are welcome to come by, refreshments are provided!)
Second: SESSION: 2.1.1 Porous and Meso-scale Structures
Nanoporous materials have a long and important history in petroleum and enivronmental sciences. The ion diffusion properties of natural zeolites and their synthetic analogues have been used successfully for catalysis and molecular separation during the petroleum refinement processes, and also for the advancement of heavy metal and radioactive waste seperation technologies. The goal of our research is to understand the processes that direct ion diffusion and allow for specific ion selectivity in nanoporous sodium titanium silicates zorite (Na-ETS-4). Here we detail the synthesis, crystal structure, and cation exchange mechanisms of rare earth element yttrium, with further discussions concerning the sequestration of other REE cations europium, gadolinium, terbium.
Single crystals of zorite where successfully grown using hydrothermal techniques, and the composition and crystal structure were characterized using inductively coupled plasma spectroscopy and X-ray diffraction using both single crystal and powder methods. In order to resolve the diffusion mechanisms, time-resolved Raman spectroscopy experiments were conducted to follow the ion exchange process in situ (see figure). Changes in thermal stability were also measured for the pre- and post- exchanged zorite.
To summarize the results of the ion exchange study, the REE ion exchange processes follow several distinct steps where molecular distortion modifies channel geometry, a transient dynamic disorder event occurs, and guest cations migrate to optimize bond-valence sums. The end results is a more porous channel as the REE moves close to the framework oxygen sites, and there are fewer cations in the channel. Having zorite possessing a more open nanoporous channel structure may have applications in improved gas sensing and catalytic cracking technologies.
IMAGE: Example time-resolved data plotted in 3D for the yttrium exchange into Na-zorite.