Computational Assessment of an Amine-Based Solvent Library for High-Salinity Brine Desalination

Humanpopulation growth has increased the demand for freshwater.Simultaneously, improvements to high-salinity brine desalination technologyare needed to treat wastewater from expanding industrial activities.Temperature-swing solvent extraction (TSSE), initially proposed inthe 1960s for low-salinity brine desalination, has recently been foundto be effective for processing high-salinity brines. Although therehave been several individual investigations performed to test theTSSE performance of various amine-based solvents, the desired molecularproperties of the best solvent candidates remain unknown. Using molecularsimulation data and an unsupervised learning method, the molecularcharacteristics of 60 different amine-based solvents are analyzedand grouped into clusters based on their thermodynamic properties,such as density, heat of vaporization, volumetric thermal expansioncoefficient, solvent-solvent binding free energy, solvationfree energy, and number of hydrogen-bonds. Solvents with featuresmost similar to one of the best current TSSE solvents (diisopropylamine)were analyzed further by simulating brine-water interfacialsystems. Among the 59 amine-based solvents compared to diisopropylamine,we find that secondary amines with a six-carbon branched or linearstructure display the most promising TSSE performance and should beexperimentally investigated in the future.