Global water shortages are upon us. Droughts exacerbated by climate change, exponential population growth and leaky, antiquated water systems are turning clean drinking water into a precious commodity. In South Africa, for instance, Cape Town instituted rationing and narrowly avoided shutting off taps in June due to falling water levels in reservoirs. Other cities are promoting conservation to reduce consumption and considering desalination to generate additional supplies, although that is an energy-intensive, expensive process. Geoffrey Geise, an assistant professor in the University of Virginia's Chemical Engineering Department, has proposed a new approach to desalination that would make it more sensitive, selective and efficient. In addition to tuning a desalination plant's critical polymer membranes to filter organic compounds that existing plants miss, these engineered membranes could be designed to recover valuable contaminants like rare earth metals, thus offsetting some of the costs of desalination. The membranes could also be used to remove nitrogen and phosphorus from agricultural run-off. These nutrients are responsible for dead zones in the Gulf of Mexico, the Great Lakes and the Chesapeake Bay. “Polymer membranes have been used in desalination since the 1960s, and the current state of the art — based primarily on physical sorting — dates back to the 1980s,†said Geise. “If we want to create more selective separations, we need to learn enough about polymer membrane chemistry so that we can tailor membranes to separate specific ions based on their chemical and physical properties.†The National Science Foundation thought enough of Geise's proposal that it presented him with a prestigious CAREER Award to pursue it. NSF CAREER Awards help promising early career faculty build a foundation of lifetime leadership as educators and researchers in their fields. Geise is using the five-year, $550,000 grant to conduct the fundamental scientific investigations needed to make ion-specific membrane separations a practical option. One advantage of Geise's approach is that he is not starting from scratch. Polymer membranes are a well-established, well-accepted platform. They are easy to manufacture in the structures and form factors required for applications requiring separation, and they are more durable and less likely to shatter than ceramic membranes. Currently, polymer membranes for desalination are designed to filter out objects larger than water molecules. Water molecules pass through them, but ions from dissolved salts, which attract clumps of water molecules, do not. For purposes of desalinating ocean water, this nonselective approach is adequate. For finer separations, Geise must devise a way to distinguish among similarly charged ions, which when covered with water molecules are essentially identical in size. In other words, Geise would like to develop a separation process that is much like one that human cells use. “The potassium channels in cell membranes do an exquisite job selecting for potassium ions,†he said. “They employ a protein structure with a geometry that aligns perfectly with potassium ions but not with other ions.†One of Geise's goals is to learn how to use the tools of polymer chemistry to create analogous molecular structures to preferentially select or reject a specific ion. “We want to move away from thinking of size as the prime consideration and instead use chemical interactions between the ion and the polymer to produce preferential transport or rejection of an ion,†he said. A major component of Geise's CAREER Award is for exploring the properties of functional molecular groups that could be integrated into the polymer, the spatial orientation of these groups and the effects of different arrangements on selectivity. In essence, Geise wants to create a toolbox. “In five years, we want to have described relationships between the structure of these groups and the properties of a series of target ions, so that polymer engineers could make rational decisions about the chemistry they should integrate in their membranes,†he said. Even more ambitiously, Geise wants to go beyond separating individual ions in isolation and explore the chemistry of polymers that could select for a target ion in a solution containing many different ions. In other words, he wants to address water issues that an engineer might encounter in the real world. The drive to address big challenges through innovation is something Geise instills in his students, too. In his research group, graduate assistants and undergraduates are working with him to find ways to expand access to clean water and make it economically viable. It's no surprise, then, that he also was selected to receive the 2018 Robert A. Moore Jr. Award in Chemical Engineering. The award, established in 2007 by Bob Moore, recognizes a UVA chemical engineering faculty member whose teaching, research and outreach activities during the previous 12 months best represent the interests of industry and prepare students for industrial careers.