New Sponge Saves Minerals from Stormwater

Reusable Sponge Captures and Reuses Phosphate and Heavy Metals

A breakthrough sponge created by scientists at Northwestern University can clean stormwater while recovering valuable nutrients. Funded by the U.S. National Science Foundation, the project provides an eco-friendly way to filter runoff from farms and cities.

The sponge features iron oxide nanoparticles that target and absorb zinc, copper, and phosphate. These substances often become pollutants through industrial and farm runoff but are important resources for agriculture. Once full, the sponge can be triggered by pH changes to release the collected materials and be reused again.

Lowering the pH releases copper and zinc, while raising the pH releases phosphate. The sponge remains effective after five uses and leaves behind water with untraceable pollution levels.

“The technology can be used as a universal sorbent or 'catch-all,' or it can be tailored to certain groups of contaminants like metals, plastics or nutrients,” said Vinayak Dravid, professor and co-author.

Doctoral student Kelly Matuszewski explained, “We can't just keep flushing these minerals down the toilet. We need to understand how they interact and find ways to actually utilize them.”

The sponge has already been shown to absorb other pollutants like lead, microplastics, and oil in previous tests. The research was published in the journal Environmental Science and Technology Water.

Dravid’s team has launched a startup with help from NSF's Small Business Innovation Research program to make the sponge available for real-world use. Next steps include testing its durability against water flow, clogging, and biofilm buildup.

This innovation offers a smart, low-cost tool to improve water quality and recycle resources vital for agriculture and industry.