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SYSTEMATIC ANALYSIS OF TEMPERATURE SWING SOLVENT EXTRACTION USING VARYING OPERATION AND ANALYSIS BASES**

Abstract

Temperature swing solvent extraction (TSSE) for the energy-efficient and economical desalination of high-salinity brines can be further expanded by using other solvents with varied chemical structures and characteristics. TSSE utilizes a low-polarity solvent with temperature-dependent water solubility for the selective extraction of water over salt from saline feeds. Current water extraction methods involve high heat and pressure for desalination. In this research, two types of amines are used: secondary and tertiary amines, to measure water recovery efficiency. Diispropylamine, N-methylcyclohexylamine, and N-ethylcyclohexylamine represent secondary amines, and Triethylamine, N,N-dimethylcyclohexylamine, N,N-diethylcyclohexylamine and N,N-Diisopropylethylhexylamine represent tertiary amines. The temperature-dependent differential partitioning behavior of saline water in amines was controlled by adjusting the extraction/equilibrium temperature, and the separation of the amine and the raffinate led to the final product water (extraction product). Current literature provides related studies, but those adopted simple volumetric or gravimetric ratios. It was hypothesized that the interaction between solvent and brine would be dependent on the solvent:water ratio as well as the salinity and the type of the solvent. To fully evaluate the water recovery efficiency of the different amines on a molar basis, the experiment consisted of measuring the product water recovery ratios, residual salt content, and residual amine content. Overall, both groups of solvents had a different level of efficiency. As the molar ratio of solvent:water increased, the water recovery efficiency decreased; however, the incremental effect of the ratio was not proportional. It was noted that the extraction efficiency was also dependent on the specific moieties. This observation is being investigated for better understanding of the molecular interactions between water and amines. The isolation of the effects of the molecular structures including the type of substituents and degree of substitution from the apparent extraction efficiency is being performed.

Acknowledgements

The research was funded by the School of Science and Technology's STEC 4500 Research Fund.

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