(114c) Using Redox Couples to Enable Energy-Efficient Water Desalination and Nutrient Recovery

Water, energy, and food systems are closely intertwined. Energy is needed for treating and distributing water. Water is needed for cooling in thermoelectric power plants that produce the majority of electricity in the United States. Meeting the growing demand for food requires not only water, but also fertilizer that is being produced using natural gas and energy. While improving efficiencies in these systems is an important task in the near term, building a circular economy is the critical step toward sustainable water, energy, and food infrastructures in the long term. This talk will highlight our recent efforts in the development of a sustainable water-energy-food nexus enabled by electrochemical separations. The use of a redox couple dissolved in an aqueous solution offers a compelling approach that creates new opportunities of enabling energy-efficient water desalination and nutrient recovery. Our recent studies showed that the voltage required for redox couples to drive salt separation or modulate the solution pH was low (<0.5 V) relative to electrolysis of water (>2.5 V). Operating an electrochemical separation process at such a low voltage allows for producing freshwater with low energy demands. Using a proton-mediated redox couple facilitated the conversion of ammonium into ammonia, which was captured by an acid solution for nutrient recovery. In addition to the electrochemical properties and performance metrics, several remaining challenges and future research plans will be highlighted to move beyond the current status.