(Nanowerk News) For many of the materials critical to the supply chain that will help enable America’s decarbonization transition, resources are limited. Traditional mining is fraught with challenges, so advancing clean energy depends on finding new ways to reliably access critical materials.
Promoting national security and economic competitiveness will require American researchers to find new ways to get the materials we need for many technologies. These include batteries, magnets in electric motors, catalysts, nuclear reactors and other important carbon-free energy technologies.
Water represents an unexplored route for obtaining these materials. Scientists at the US Department of Energy’s Argonne National Laboratory recently published a comprehensive review detailing the various mechanisms by which important materials can be extracted from various streams of water.
Different types of water offer different types of material resources, said Seth Darling, head of science and technology directorate at Argonne’s Advanced Energy Technologies. The oceans are an extraordinary resource because the total amount of many valuable and important materials is very large, but it is also very dilute, he said. “Wastewater also needs to be reframed — we want people to see that wastewater isn’t really waste, it’s rich with all kinds of valuables.”
Darling also pointed to groundwater aquifers and geothermal brines as other possible sources of valuable materials. These materials include lithium, which is of increasing interest for electric vehicle batteries and could be used to help decarbonize our economy. “Lithium is in the oceans and in geothermal brines; You will extract it differently from these two sources, but it is important to understand which is cheapest, has the least environmental impact, and enables a secure supply chain,” said Darling. “For many other materials, water is under-explored as a resource, and it’s something we are paying increasing attention to.”
The technologies Darling and his colleagues are currently exploring for extracting key ingredients from different types of water range from the traditional (such as membranes) to the innovative (such as interfacial solar steam generators).
Omar Kazi, Ph.D. Molecular engineering students at the University of Chicago working with Darling, are studying methods for concentrating wastewater streams to recover valuable materials. ”Removing water through evaporation is an energy-intensive and slow process,” says Kazi. “In geothermal brines, it takes years for the water to evaporate to be able to recover the lithium contained within, which creates a huge drag. The question we asked was ’how can we make the water evaporate faster?’”
One way to do this could be through the use of porous photothermal materials, which convert light to heat efficiently. This light absorber acts like a black T-shirt that heats up on a sunny day. That heat is transferred to the water directly at its interface with the surrounding air, speeding up evaporation significantly.
Overall, said Darling, Argonne has rich capabilities in supply chain, life cycle and technoeconomic analysis. In addition, this laboratory specializes in materials, chemistry and process engineering relevant to the extraction of critical materials. This uniquely positions the lab to help achieve safer and circular material savings, especially when it comes to getting more out of water flow.
A paper based on the study appears online at Advanced Materials (“Material Design Strategy for Recovery of Critical Resources from Water”).