Exploring Ionic Liquids for Low Temperature and Low Emission Water Desalination

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The availability of clean water has become one of the most critical problems facing society and the global economy in the 21st century. Oceans cover 71% of the planet and store approximately 97% of its water. Therefore, future water shortages could be alleviated through the development and deployment of more efficient and cost-effective technologies to desalinate seawater. Current commercial seawater desalination technologies are energy intensive and their operations require high-grade electricity. Recent studies have shown that a solvent-based desalination process, referred to as directional solvent extraction, can extract and release clean water from high salinity source waters using readily available sources of heat (e.g., solar energy, waste heat, etc.). The goal of this research project is to gain a better understanding of the underlying physical and chemical principles behind the directional solvent extraction process. The investigators will combine state-of-the-art computational modeling with the synthesis, characterization, and bench scale lab evaluation of new materials for the design and development of next-generation methods. Successful outcomes of this project will benefit society through efficient and cost-effective technologies to desalinate seawater. Further benefits to society will be achieved through student education and training including the mentoring of two doctoral students.Current thermal and membrane-based seawater desalination technologies are energy intensive and costly. In contrast, a directional solvent extraction process could be operated using heat sources at temperatures as low 40 ˚C and without the need for a membrane. However, the availability of solvents with the right properties has remained a major impediment to the development and implementation of this technology. The comparatively low volatility, minimal toxicity, and architectural variability of ionic liquids have made them attractive as potential solvents for use in directional solvent extraction-based desalination. The goal of this research project is to better understand the solvation and phase behavior of ionic liquids in high salinity aqueous solutions. By combining molecular simulations with materials synthesis and characterization and bench scale desalination experiments, the investigators will identify the key structure-property relationships that govern the competing solubilities of ionic liquids with water and natural salt ions. Ultimately, the investigators will leverage this new knowledge in developing more energy-efficient and environmentally benign directional solvent extraction processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.