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

Abstract

Human population growth has increased the demand for freshwater. Simultaneously, improvements to high-salinity brine desalination technology are needed to treat wastewater from expanding industrial activities. Temperature-swing solvent extraction (TSSE), initially proposed in the 1960s for low-salinity brine desalination, has recently been found to be effective for processing high-salinity brines. Although there have been several individual investigations performed to test the TSSE performance of various amine-based solvents, the desired molecular properties of the best solvent candidates remain unknown. Using molecular simulation data and an unsupervised learning method, the molecular characteristics of 60 different amine-based solvents are analyzed and grouped into clusters based on their thermodynamic properties, such as density, heat of vaporization, volumetric thermal expansion coefficient, solvent–solvent binding free energy, solvation free energy, and number of hydrogen-bonds. Solvents with features most similar to one of the best current TSSE solvents (diisopropylamine) were analyzed further by simulating brine–water interfacial systems. Among the 59 amine-based solvents compared to diisopropylamine, we find that secondary amines with a six-carbon branched or linear structure display the most promising TSSE performance and should be experimentally investigated in the future.