459781 Adsorption, Structural and Dynamic Properties of Ethanol-Water Mixtures in Graphene and Hexagonal Boron Nitride Slit Pores

Thursday, November 17, 2016: 3:15 PM
Plaza A (Hilton San Francisco Union Square)
Anitha Kommu and Jayant K Singh, Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur, India

The industries discharge a variety of pollutants, such as heavy metals, organic toxins, and oils, in water resources. Exposure of these contaminants in water causes adverse health effects on various forms of life [1-3]. Novel materials are needed for the effective removal of pollutants from industrial wastewater. Graphene and hexagonal boron nitride (hBN) sheets are promising materials for removal of organic pollutants [4]. In this work, the suitability of the sheets for the separation of ethanol-water mixture is investigated by studying the adsorption and structural behavior of ethanol-water mixtures in slit pore with variable width (7 to 13 Å) using molecular dynamics. The simulation results indicate that the selectivity of ethanol varies with pore width and with the nature of the surface. The selectivity of ethanol is highest for 9 Å pore and lowest for 7 Å pore, irrespective of the nature of the substrate. However, selectivity of ethanol is relatively higher for hBN compare to the graphene surface, for all slit-pore widths. At lower pore width, molecular sieving plays an important role for separation of ethanol; whereas at higher pore width separation is governed by the adsorption behavior. The diffusion coefficients of water and ethanol molecules substantially decrease with decrease in pore width for both graphene and hBN surfaces. The resident time of water and ethanol molecules decreases with increase in the slit-width. Furthermore, water and ethanol molecules confined in hBN pores show higher residence time and lower diffusion coefficient values compare to graphene slit pores.

References

[1] M. A. Shannon, P. W. Bohn, M. Elimelech, J. G. Georgiadis, B. J. Mariñas, A. M. Mayes, “Science and technology for water purification in the coming decades” Nature, 2008, 452: 301-310.

[2] M. A. Montgomery and M. Elimelech, “Water and sanitation in developing countries: including health in the equation” Environmental Science and Technology, 2007, 41: 17-24.

[3] F. Zhang, WB. Zhang, Z. Shi, D. Wang, J. Jin, L. Jiang, “Nanowire-haired inorganic membranes with superhydrophilicity and underwater ultralow adhesive superoleophobicity for high-efficiency oil/water separation” Advanced Materials, 2013.

[4] W. Lei, D. Portehault, D. Liu, S. Qin, Y. Chen, “Porous boron nitride nanosheets for effective water cleaning” nature communications, 2013.


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