Functionalized Nano-structured Silicas for Trace Collection from Natural Waters
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Throughout this body of work, three classes of sorbent materials were created and optimized, each designed to selectively capture organics or desired metals from natural water sources. These target species included toxic heavy metals, uranium, rare earths, and simple organics, such as benzene. Each class of sorbent materials is functionalized nanostructured silicas, created by the development of several functionalization methods: utilizing thiol-ene click chemistry, aromatic interactions, and the formation of inclusion complexes. Thiol-ene click surface modification gave rise to sorbent materials with impressive affinities for both soft metals, such as gold, and harder metals, such as uranium and rare earth elements. Applications of these materials for aqueous mining of uranium and rare earth elements from various natural water sources are presented. Two classes of materials based on supramolecular functionalization methods were prepared. In the first class, aromatic interactions allowed for surface functionalization with thiol containing aryl ligands. These materials proved to have an excellent affinity for heavy metals from natural waters, and hold promise for regenerable nanostructured silica sorbents. The second class of materials utilizes the ability of β-cyclodextins to form inclusion complexes with small molecule organics, such as benzene. The formation of inclusion complexes drove both surface functionalization and the capture of small molecule organics from aqueous solutions. This work serves to inspire the development of novel functionalized nanostructured sorbents for trace collection of toxic organics from aqueous streams. These supramolecular methods for surface medication can be expanded to nanomaterials at large. This dissertation includes both previously published/unpublished and co-authored material.