Affiliation: Colorado School of Mines
Title: Innovative Approaches to Minimize the Chemist's Environmental Footprint: From Organic Contaminants to Heavy Elements
Chemical scientists catalyze the technological innovations in many facets of modern society, nonetheless it is evident that our inventions sometimes do more harm than good. A lack of both hindsight and foresight plagues our progress, with ongoing chemical pollution paving a future path to worldwide destruction of the biosphere. Many engineering solutions to mitigating pollution lack the fundamental physiochemical knowledge into the intricacies of chemical speciation and chemical structure, and sometimes only rely on a superficial understanding of reactivity and mechanisms in those specified contexts. To this end, our group focuses on elucidating and contextualizing the vital chemical mechanisms in environmental matrices, from tackling the remediation of recalcitrant persistent organic pollutants such as perfluorinated alkyl acids (PFAS) to the separation of trivalent actinides and lanthanides in used nuclear fuel. A broad use of experimental, computational and spectroscopic techniques facilitates a molecular based approach to these macroscopic problems.
This talk will describe our approach to predicting the redox behavior of PFAS molecules, from oxidation with (in)organic photocatalysts to reduction via Co(I)-catalysts and via photosensitized hydrated electron generation. Density functional theory (DFT) was imperative to understand the redox mechanisms in both cases, providing insight into both substrate and solution level effects, helping to describe previously ignored pathways, and allowing us to develop structure activity relationships for a broad suite of PFAS substrates. Laser flash photolysis studies of UV-photosensitized reduction of PFAS in a variety of conditions provides kinetic rate constants which help us to design new catalytic systems or improve existing practices.
Next, I will describe our efforts to understand and improve f-element separations to close the nuclear fuel cycle, both mitigating the most toxic and long-lived components of nuclear waste and restoring precedent for nuclear power generation. Through ab initio calculations and molecular dynamics simulations we have sought to understand the dominant mechanisms of metal-ligand complexation and separation at the interface during the liquid-liquid extraction process with the goal of improving the kinetics of Actinide-Lanthanide SEParation (ALSEP). Concurrently, time-resolved laser induced fluorescence studies of Europium complexes with the ALSEP ligands in n-dodecane and aqueous solvent give us vital information into the speciation and stoichiometry of nuclear materials throughout the ALSEP process that facilitate our computational work.
Hosted by: Dr. Hadad