(348g) Effect of Amine Location of 6-Carbon Amines on Desalination in Temperature Swing Solvent Extraction

Hypersaline brine solutions are a major issue in industry due to their high levels of total dissolved solids. They are unable to be discharged to the environment and must undergo further treatment to meet EPA standards. Since this water is typically 3 times saltier than seawater, traditional methods do not work or are very energy intensive. Reverse osmosis membranes do not work at these high salt concentrations, while evaporative processes, such as distillation, require large amounts of energy to ensure the water meets EPA guidelines. Temperature Swing Solvent Extraction (TSSE) is a recently re-discovered technique that could achieve desalination of these high salinity brines. TSSE is performed by adding brine water to an amine-based solvent and manipulating the temperature of the mixture. The temperature changes will cause a shift in the solvent’s ability to hydrogen bond with water so that the solvent will selectively extract water but not salt at a low temperature and then phase separate the water out at a higher temperature. Diisopropylamine (DIPA) and dipropylamine (DPA) are the two best-performing amine-based solvents due to their ability to desalinate and release water. However, these solvents cross-over into the product water phase enough to the point where a purification step would be needed after TSSE. The goal of this study is to look at isomers of DIPA to study structure-property-performance relationships to find guiding principles for solvent design. Solvents with six carbons other than DIPA and DPA have yet to be studied in literature; solvents with more carbons have, however these other solvents do not perform as well as DIPA and DPA. TSSE performance evaluation of the solvents will report solvent viscosity and density, mixing temperature and volume changes, and pH, salt concentration, water uptake, and organic cross-over in the brine and product water phases.