Heavy Metal Recognition and Separation from Aqueous Media with Surface-Embedded Hosts

The goal of this project is to develop a separation system that can effectively extract heavy metals, specifically actinides and lanthanides, from water to address environmental contamination. Removing heavy metals from environmental water sources is a pressing research challenge due to their persistent risk to ecosystems and potential harm to human health. Such a heavy metal separation process requires molecules that can selectively bind actinides. However, designing these molecules is difficult, as the coordination profiles of heavy elements are largely similar. Additionally, liquid-liquid extraction systems are less desirable than solid-phase extractions. The investigators will apply a simpler and more efficient flow-based method that can be easily reused. The research approach involves developing an innovative metal extraction system utilizing flexible cavitand molecules. These molecules are capable of shape-based molecular recognition and high-affinity metal binding, enabling the capture and removal of heavy metals from environmental water. This project also provides graduate and undergraduate students with interdisciplinary research training in areas that bridge organic, environmental, and analytical chemistry with materials engineering. This project aims to develop flexible, small molecule cavity-containing molecules known as cavitands that are embedded at surfaces. The cavitand receptors enable the selective molecular recognition and separation of heavy metal ions directly from the aqueous phase without organic solvents. The flexibility and tunability of the cavitand receptors will provide a unique platform that will allow strong selectivity for binding metals. The selectivity can be tuned by adding external small molecule guests to the cavitand molecule; these guests can be used to trigger the release of the metals from the cavitand. The research approach combines the team’s expertise in surface-based molecular recognition and column separation to (1) incorporate the cavitands in coated capillaries for selective metal ion binding and extractions, (2) study the kinetic and thermodynamic factors behind this selective recognition, and (3) perform actinide and heavy metal separations and triggered release at interfaces with aqueous flow. These studies will be extended to larger-scale applications, whereby packed columns will be exploited for selective metal separation and triggered release. 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.