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Molly MacInnes, professor of chemistry, is currently on sabbatical at Los Alamos National Laboratory studying oxidation-reduction reactions with uranium. This work is part of a larger project to understand how heavy metals interact with oxide surfaces. When most of us hear ‘heavy metals’ we think of Slipknot or Iron Maiden; those of us who took high school chemistry might think of mercury or lead. But MacInnes is exploring lanthanides and actinides — the elements in the two offset rows at the bottom of the periodic table.  

They are separate from the rest of the table for good reason; they act differently from many other elements. In introductory chemistry classes, we learn that elements in the same column on the periodic table act similarly, but that’s not true for these two rows. MacInnes explains, “that’s why we need to do more studies with them so we can better understand what they do.”  

These elements are also being used increasingly in industrial applications, including in cars, magnets, and renewable energies. "Partly because they have not been used much industrially until recently and partly because half of them (the actinides) are radioactive, they haven’t been studied as much as the rest of the periodic table,” MacInnes says. 

As these materials are used more, it becomes important to understand how they interact with other materials in the environment. MacInnes states, “I’m really interested in understanding these elements better in terms of how we can extract them from the environment or recycle them, how we can detect them and understanding what happens to them in the environment.”

The combination of exposure to negative environmental rhetoric and her interest in the inorganic and materials side of chemistry (rather than the biological/health side) led MacInnes to focus on the environmental applications of chemistry. She solidified this path after an internship where she saw the assembly of solar cells which piqued her interest in environmental electrochemistry.  

Before research can be applied to specific situations, the mechanisms for these understudied elements need to be understood.  In an effort to build foundational knowledge, MacInnes is looking specifically at how the lanthanides and actinides react with oxide surfaces.  

She says, “I am most interested in how these elements interact with solid surfaces when they’re dissolved in water. So, if you find them in waterways and they interact with minerals for example, are they going to stick to the minerals and accumulate on certain types? Are they going to leach other things out into the water?” This exploratory work is the first step in understanding how these elements work and what mechanisms drive the reactions.  

MacInnes is conducting this exploration through electrochemistry. Electrochemistry refers to chemical reactions that are driven by the electron transfer between two oppositely charged electrodes. MacInnes was introduced to electrochemistry in her graduate work and now likes to use the techniques to explore questions people have tried to answer in other ways. She says that some researchers have already looked at heavy metal absorption, but most of the time it requires difficult or expensive techniques that include synchrotrons or high-energy X-rays where you can’t see the reactions happening. 

In contrast, she says, “Electrochemistry is a really nice analysis technique that is easy and cheap. You just need a beaker of water, a couple of electrodes, and a power source.” 

The accessibility of electrochemistry makes it very powerful for this type of research. Additionally, its accessibility makes electrochemistry easy for students to participate in. The students in MacInnes’s lab can make impactful contributions to foundational chemistry knowledge.

MacInnes hopes her work serves as the foundation for other researchers to explore the many applications of these reactions. In fact, there are so many places this research can go that it was hard for MacInnes to write the grant proposal (the research is funded by the National Science Foundation’s Launching Early-Career Academic Pathways in the Mathematical and Physical Sciences program — CHE-2532882). MacInnes’s work is the first step to the more specific applications. 

She says, “At this point it’s very exploratory and fundamental. I’m looking at what the mechanisms are. And if we understand that and build up trends among different elements and different oxide surfaces, then maybe we can predict other interactions. And maybe we can design materials that will be strongly absorbing.”