Role of Nanoscale Morphology on the Efficiency of Solvent-Based Desalination Method

Brine desalination is important for minimizing the environmental impact of contaminated wastewater, yet current desalination techniques have high energy requirements. Solvent-based desalination (SBD) method, which is the process of extracting fresh water using an organic solvent, has existed for decades, yet has not reached competitive efficiencies. In this work, 10 organic solvents were tested for SBD efficacy via synergetic studies using bench-scale extraction experiments and molecular dynamics (MD) simulations. The SBD effectiveness was correlated to the computationally observed ability of the solvent to form one of the three morphologies in water: ordered, disordered, or partial nanoscale. We correlated that solvents that form ordered and disordered morphologies were not able to clean up the water. Solvents that were able to cause low salinity in water showed computationally observed partial nanoscale phase separation, where nanometer-scale aggregated solvent phases were able to effectively reject salt ions while capturing comparatively large amounts of water molecules. The formation of a partial nanoscale phase is likely driven by the solvent structure with bulky hydrocarbons adjacent to hydrophilic end groups. Our results make a step toward the rational design of solvents that may allow for efficient SBD and thus a low-cost source of fresh water.