(666d) Molecular Simulation Studies on Adsorption of Hazardous Air Pollutants –Hydrogen Cyanide and Methyl Ethyl Ketone

In the present research study, the performance of potential adsorbents for the removal of volatile organic compounds such as hydrogen cyanide and methyl ethyl ketone (MEK) from water and air is evaluated using molecular simulation and computational quantum chemistry techniques. Hydrogen cyanide is sometimes discharged from organic chemical and metal processing industries in waste water and also in air. The US EPA has characterized it as a hazardous chemical, when exposure to this chemical is more than 1 milligram per cubic meter [1]. It is also used as a solvent for gums, resins, cellulose nitrate, as well as in consumer products such as lacquers, varnishes, paint remover, and glues [2-3]. Furthermore, it has been demonstrated that MEK emissions above 200 ppm in air are responsible for eye, nose, and throat irritation. Due to its very low concentrations in air, adsorption operations are attractive options for removing MEK from the air effectively. However, the limited availability of experimental data on the adsorption of hydrogen cyanide and MEK on activated carbon and Zeolite –Y pose significant problems in the selection and design of the appropriate adsorbents based on the capacity and selectivity of these organic molecules [4-7]. The aforementioned problem of selecting and designing the appropriate adsorbent for the removal of the above hazardous chemicals provides ample motivation to researchers to enhance their understanding on the adsorption behavior of these molecules through molecular simulation and computational quantum chemistry techniques, where capacity and selectivity can be explicitly quantified and evaluated by appropriately varying the surface characteristics.

In the present research study the primary aim is to understand and characterize the physical adsorption of hydrogen cyanide and MEK, as well as their binary mixtures with nitrogen in zeolite-X, silicalite, mordenite and activated carbon through detailed Monte–Carlo simulations and computational quantum chemistry techniques. The capacity of different zeolites are compared with activated carbon with different acid sites concentration, type of acid site, pore sizes by simulating single component isotherms. The adsorption of a binary mixture with nitrogen is simulated in both types of micro-pore adsorbents at different hydrogen cyanide and MEK concentrations (in the limit of infinite dilution) in the temperature range of 25 to 80 °C. Finally, the selectivity of hydrogen cyanide and MEK with respect to N2 in different zeolites is characterized and analyzed as a function of pore size, acid site concentration as well as their relative positions within the pore in the case of activated carbon.

References: 1. http://www.epa.gov/ttn/atw/hlthef/cyanide.html 2. http://www.spacelab.com/compound/c78933.htm 3. S.H. Yen and F.T. Jeng, J. Env. Sci. Health, A32(8), 2087 (1997) 4. P.J. Reucroft, P.B. Rao and G.B. Freeman, Carbon, 21, 171 (1983) 5. G.B. Freeman and P.J. Reucroft, Carbon, 17, 313 (1979) 6. P. Monneyron, M. Manero and J. Foussard, Env.Sci.Techn., 37, 2410 (2003) 7. M.A. Uguina, J.L. Sotelo, J.A. Delgado, J.M. Gomez and L.I. Celemin, Sep. Pur. Techn, 42, 91(2005)