Preferential Adsorption From Liquid Ethanol-Water Mixtures in Alumina Pores

Equilibrium MD simulations were employed to investigate interfacial liquid ethanol-water mixtures on several alumina slit-shaped pores. The results were quantified in terms of preferential adsorption from the bulk, density profiles, in-plane radial distribution functions, residence times at contact with the substrate, self-diffusion coefficients, orientational distribution functions, hydrogen bonds distributions, and reorientation autocorrelation functions. When pure ethanol is simulated, the results show that ethanol molecules in the first monolayer near a solid surface have a well-organized arrangement, while those in the second layer show bulk-like features. The predicted orientational distribution for ethanol molecules within the first layer is consistent with experimental results. When water is added to the system, our results show that water quickly replaces ethanol molecules from the first adsorbed layer, and preferentially partitions within narrow slit-shaped alumina pores. We will discuss how such results could be useful for the design of separation processes. The results could also be important for better understanding the behavior of fluids in sub-surface environments.