(644a) Environmental Risk-Relevant Molecular Modeling of Adsorbed NDMA In MFI Zeolites

Authors: 
Kamaloo, E., Worcester Polytechnic Institute
Deskins, N. A., Worcester Polytechnic Institute
Thompson, R. W., Worcester Polytechnic Institute


Protecting the water supply is a top environmental concern and of great importance. Zeolites have been widely used to separate harmful molecules from water streams and ensure a safe, clean environment. N-Nitrosodimethylamine (NDMA) is a suspected carcinogenic and toxic chemical. NDMA can be found in water resources as a result of industrial facilities or as a by-product of water or wastewater treatment. Therefore removal of NDMA from drinking water is an important human safety concern. Studying of the adsorption and stability of NDMA inside a zeolite provides useful information about the feasibility and operating conditions of NDMA removal. Computer modeling can play a significant role in the study of NDMA  removal (and other toxics), particularly since experimental studies with NDMA are undesirable. Current work presents quantum mechanical modeling (density functional theory) of NDMA adsorption in purely siliceous MFI, MFI with extra-framework Na and H, and MFI with silanol nests. Stability of NDMA inside the zeolite is investigated by calculating binding energies at various sites and in various configurations. Preliminary results provide a promising prospect on the development of scientifically sound guidelines on the utility of high-silica zeolites for NDMA removal as well as transparent criteria for the determination of key zeolite features (e. g. composition of the zeolite) that need to be incorporated into the synthesis stage.