There are few things more precious than water, and engineers are making sure these resources stay clean and healthy — using everything from high-tech labs to store-bought sponges. CHEE assistant professor Vicky Karanikola is leading a collaboration between the University of Arizona and Northern Arizona University that is creating a regenerable method for removing toxins from drinking water.
The team, which is focusing on removing a group of chemicals known as PFAS from water, received $1.487 million from the Arizona Board of Regents, with $1.24 million allocated to UA. PFAS is an abbreviation for perfluoroalkyl and polyfluoroalkyl substances, which are used for food packaging, nonstick pans, firefighting foam and more. They have been used for decades, but scientists now know exposure to PFAS can be harmful to humans and animals. And what's worse, they can percolate into groundwater systems.
To draw PFAS out of water, engineers need to use a material that can adsorb PFAS – or, more simply, a material that PFAS will stick to. The first step in this million-dollar effort: Buy off-the-shelf materials from the store.
While simple cellulose sponges are good for initial study of factors such as optimal pore size and density, sponges being developed for removal of PFAS are far more complex. They will soak up PFAS-contaminated water, then squeeze out clean water while the PFAS stay stuck. Then, an extraction solution will remove the PFAS from the sponges so they can be used again.
One common method for removing PFAS from water uses granulated activated carbon, or GAC, another material to which PFAS stick quite well. A little too well, in fact. The tricky part is the unsticking. Getting the PFAS off the GAC so the carbon materials can be reused for another round of removal is expensive and difficult.
"The amount of energy you need to release them from GAC is huge," Karanikola said. "The innovation of this project is that we're focusing on a regenerable method: We want to break that barrier of just using something once and throwing it away. We are trying to find the sweet spot for absorbing it just enough to hold, but that will take the minimum amount of energy to release the PFAS into a controlled environment."