Directional solvent for membrane-free water desalination—A molecular level study

Development of desalination technologies has been identified as vital to fulfilling future water demand. In this paper, we use molecular simulation to demonstrate that decanoic acid can dissolve water but reject salt, and itself is insoluble in water. We have recently demonstrated that the directional properties of decanoic acid together with the temperature dependence of water solubility in decanoic acid can be utilized to design a desalination process which extracts water molecules, using the decanoic acid as a directional solvent, from saline source at a higher-than-ambient temperature, and precipitate out the water from the solvent at a lower temperature to recover pure water. Such a desalination process is membrane-free and can make use of low temperature heat sources. Solubility properties between water and decanoic acid are characterized through free energy calculations, and water-decanoic acid interdiffusion processes are studied by molecular dynamics simulations. This work also exemplifies an approach to characterize other possible directional solvents.National Science Foundation (U.S.) (grant No. CBET-0755825)National Science Foundation (U.S.) (TeraGrid Project, TACC Ranger and SDSC Trestles under grant number TG-CTS100078