(96f) Removal of Hazardous Organics from Water: the Effects of Quadrupole Moments on Separation in Microporous Solids
Zeolites have long been in the focus of waste separation as they have great potential to capture pollutants inside their micropore networks. However, not all molecular interactions within the pore are completely understood. Silicalite-2 (ZSM-11) for example is a highly hydrophobic zeolite structure, yet it allows water to penetrate more readily than certain organic pollutants such as 1,4-dioxane. Our study is to determine if and how 1,4-dioxane's quadrupole moment affects this separation. Quadrupole moments exist in molecules that can change conformation across energy barriers. Water cannot change its relative shape beyond normal oscillation. 1,4-dioxane however can shift between 2 boat and 2 chair conformations. The pore of ZSM-11 acts as an inhomogeneous electric field, so it is believed that as 1,4-dioxane travels through the pore, it needs to change shape to overcome energy barriers. Water on the other hand merely changes its spatial orientation when encountering various positive and negative fields. A Silicalite-2 pore has been modeled based on the work of Fyfe et al. as documented in ?Detailed investigation of the lattice structure of zeolite ZSM-11 by a combination of solid-state NMR and synchrotron x-ray diffraction techniques?. Currently, the position of water and water clusters inside of a zeolite pore are being examined using ab initio methods at HF/6-31G and B3LYP/LANL2DZ levels of theory. Future work involves the examination of 1,4-dioxane within the pore as well as moving to higher levels of theory.