Chemical mixtures are everywhere, from nuclear waste to power plant emissions to the ocean, and separating them accounts for approximately 15 percent of industrial energy use in the United States. Researchers at Pacific Northwest National Laboratory (PNNL) are working to understand separations in great detail, from fundamental interfacial science to scalable industrially and environmentally relevant processes.

Separations that isolate different critical minerals, including rare earth elements, from non-traditional and secondary sources are of particular interest at PNNL. Rare earth elements are essential for advanced electronics, national security, and clean energy applications. Given their limited domestic production and high importance, identifying new sources, in parallel with effectively isolating and reusing these elements, is essential to enabling the widespread adoption of clean energy technologies. Researchers at PNNL are exploring multiple routes to separating mixtures containing critical elements, including in solid-liquid, electrode-liquid, liquid-liquid, and gas-liquid interface systems.

Separations also play a key role in decarbonization efforts. Separating carbon dioxide from industrial waste streams or even the air itself reduces the amount of harmful greenhouse gas present in the environment. This process is particularly well suited to reactive separations, where waste carbon may be converted into valuable feedstock chemicals or materials in a net-zero process.

Separations Research at PNNL

As a multi-disciplinary national laboratory, PNNL is ideally positioned to transform separations science, the study of separating chemicals and minerals from complex mixtures. With deeply established expertise in areas such as chemical physics, catalysis, geochemistry, energy storage, materials synthesis, and computational modeling, scientists at PNNL continue developing innovative approaches to separations. They are working to both increase the efficiency and selectivity of existing separation processes as well as devise entirely new separation schemes.

Researchers at PNNL take an integrated approach to understanding how separations occur, combining experimental studies with computational modeling. The broad expertise across the Lab allows internal partnerships across separations science. Collaborations between fundamental science teams and applications-focused groups allow researchers at PNNL to accelerate the process of converting scientific knowledge into functional processes.

New Approaches to Separations

Separations may be accomplished through a wide variety of techniques. These methods often take advantage of chemical differences, such as electric charge or solubility, or physical differences, such as size. A growing body of work, including at PNNL, focuses on reactive separations. These processes involve chemically or electrochemically converting different components of the separation mixture. While this approach may seem more complex, it provides additional ways to tune the separation process for increased efficiency and selectivity. Integrating chemical and electrochemical reactions into flow-based processes allows scientists to change the properties of the system for more effective separations. Reactive separations also offer process intensification as methods are scaled to applications.

A priority of separations research at PNNL is understanding interfaces, the regions where two things meet. Interfaces have unique reactivity and, if properly managed, exert substantial control over the behavior of larger systems. However, interfaces are often highly dynamic and complex, making detailed studies challenging to execute. PNNL has specialized instruments (e.g., ion soft landing, scanning electrochemical cell microscopy, nuclear magnetic resonance spectroscopy, imaging X-ray photoelectron spectroscopy, and microfluidics) that enable researchers to better prepare and understand the realities of interfaces at relevant operating conditions.