With an increase in the threat of algae blooms and pollution from agricultural runoff and industrial activities in our waterways, innovative ways to eliminate harmful substances like phosphate, copper, and zinc are being developed.
Although some solutions are available, they often come with a high price tag and can only be used once. However, a unique sponge designed by researchers at Northwestern University shows promise as a reusable and cost-effective remedy to address these pollutants.
This sponge is enhanced with nanoparticles that attract pollutants, allowing it to capture metals such as zinc and copper, along with phosphate. Previous versions have successfully removed lead, microplastics, and oil from water bodies. The sponge releases these pollutants when exposed to varying pH levels.
In a paper set for publication on February 5 in the American Chemical Society journal Environmental Science & Technology Water, the researchers present a method for customizing their sponge to address specific pollutants in Chicago, enabling selective release and offering a second life to resources generally extracted through mining.
“This technology can function as a universal sorbent or be adjusted for specific types of contaminants, such as metals, plastics, or nutrients,” explained the lead researcher, Vinayak Dravid.
Dravid, who holds the Abraham Harris Professorship in Materials Science and Engineering at Northwestern’s McCormick School of Engineering, is also a faculty affiliate at the Paula M. Trienens Institute for Sustainability and Energy. Furthermore, he serves as the founding director of both the Northwestern University Atomic and Nanoscale Characterization (NUANCE) Center and the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource and is the associate director for global programs at the International Institute of Nanotechnology.
What’s with the sponge?
The sponge was initially made from polyurethane and had a coating that drew in oil while repelling water. The latest version is a cellulose sponge that loves water and is coated with particles designed to target different pollutants. Its effectiveness is attributed to its porous structure, providing ample surface area for pollutants to adhere.
Dravid has likened the technology to a “Swiss Army knife” for its flexibility and the possibility for repeated use. He established Coral Innovations (previously MFNS-Tech) to advance the commercialization of this sponge-based technology for cleaning up environmental pollutants.
A one-two P(h)unch
Stormwater treatment manufacturer StormTrap, LLC learned about this sponge technology and contacted the research team, inquiring about three specific pollutants that are significantly impacting the Chicago area. They expressed interest in incorporating absorbent materials to their offerings and asked if Dravid could reduce the pollutant concentrations to untraceable levels.
The Environmental Protection Agency (EPA) sets legal limits for certain minerals based on human health, which are sometimes higher than the amounts deemed safe for the environment. Typically, these limits for drinking water are set in parts per million, while preventing issues like algae blooms requires much lower concentrations.
Although developing the sponge to capture copper, zinc, and phosphate was relatively straightforward, Kelly Matuszewski, a Ph.D. student in Dravid’s group and the paper’s primary author, was assigned the challenge of figuring out how to reclaim these resources. With diminishing supplies of phosphate and metals in mines, this step is increasingly necessary.
“We can’t simply keep discarding these minerals carelessly,” Matuszewski remarked. “We need to grasp how these substances behave and identify ways to utilize them properly.”
Matuszewski discovered that by lowering the pH, she could effectively wash the metals from the sponge. Once copper and zinc are removed, raising the pH causes phosphate to be released. Remarkably, after five cycles of extracting and recovering minerals, the sponge maintained its high effectiveness, enabling her to provide water with undetectable levels of pollutants.
Matuszewski is competing as a finalist in the FoundHer Spotlight competition, which promotes early-career women scientists, organized by Northwestern’s Querrey inQbation Lab. She will present her pitch on March 5 against seven other talented researchers.
Taking it to the storm drains
The collaboration with StormTrap, LLC has enabled the team to evaluate the sponge technology’s performance and transition rapidly from laboratory tests to practical applications. Implementing the technology in real-world settings will be crucial since Matuszewski conducted her research in a controlled environment where pollutants were at consistent concentrations. The next stage will help determine the maximum amount of minerals the sponge can hold and facilitate collaboration with other Northwestern researchers focused on developing cleaner waterways.
This research was made possible through funding from Trienens and StormTrap, related to The Great Lakes Water Innovation Engine, which is supported by the National Science Foundation (grant number ITE-2315268).
Note: Vinayak Dravid and Northwestern hold financial stakes (equities, royalties) in Coral Innovations.
