posted on 2017-03-20, 00:00authored byAnitha Kommu, Jayant K. Singh
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. 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. In this work, the suitability of the sheets for the separation
of the ethanol–water mixture is investigated by studying the
adsorption and structural behavior of ethanol–water mixtures
in slit pores with variable width (7–13 Å) using molecular
dynamics simulations. The selectivity of ethanol is found to depend
on the pore-width and nature of the pore walls. The selectivity of
ethanol is highest for 9 Å pores and lowest for 7 Å pores,
irrespective of the nature of the pore walls. However, selectivity
of ethanol is relatively higher for hBN pores compared to the graphene
pores, for all the considered pore widths. At a lower pore width,
molecular sieving plays an important role for selective adsorption
of ethanol molecules. On the other hand, at a higher pore width, selective
adsorption of ethanol molecules is affected by the nature of the pore
walls. The diffusion coefficients of water and ethanol molecules substantially
decrease with a 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 compared to graphene pores. The adsorption behavior of water
and ethanol molecules in the slit pores are analyzed using the potential
mean forces, for water and ethanol molecules on the graphene and hBN
surfaces, which are determined by umbrella sampling technique.